JP2013110224A - Photoelectric conversion element, solar cell, and solar cell module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photoelectric conversion element with higher durability, a solar cell, and a solar cell module.SOLUTION: A photoelectric conversion element (107) comprises a pair of electrodes (101, 105), an active layer (103) disposed between the electrodes (101, 105), and an electron extraction layer (104) disposed between at least one of the electrodes and the active layer (103). The electron extraction layer (104) contains a compound represented by general formula (1).

Description

  The present invention relates to a photoelectric conversion element, a solar cell, and a solar cell module.

  In recent years, solar cells have been actively developed. A solar cell has a configuration in which an active layer is sandwiched between a pair of electrodes (anode and cathode). It is known that the performance of a solar cell can be improved by sandwiching a buffer layer between the electrode and the active layer.

  For example, as a material for a buffer layer (electron extraction layer) provided between the cathode and the active layer, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 4,7-diphenyl- Examples using phenanthroline derivatives such as 1,10-phenanthroline (Bphen), 2,9-bis (naphthalen-2-yl) -4,7-diphenyl-1,10-phenanthroline (NBphen), phosphine oxide compounds, etc. It is known (Non-Patent Document 1, Patent Documents 1, 2, and 3).

US Patent Application Publication No. 2010/0147386 JP 2011-077107 A JP 2006-073583 A

Organic Electronics 2008, 9, 656-660.

  However, when phenanthroline derivatives such as BCP, Bphen, and NBphen are used as the material for the electron extraction layer, the durability of the obtained photoelectric conversion element is not sufficient.

  As a result of intensive studies to solve the above problems, the present inventors have found that a photoelectric conversion element with higher durability can be produced by using a specific phenanthroline derivative in the electron extraction layer, and to achieve the present invention. It came. That is, this invention makes the following a summary.

[1] A photoelectric conversion element comprising a pair of electrodes, an active layer disposed between the electrodes, and an electron extraction layer disposed between at least one of the electrodes and the active layer, An electron extraction layer contains a compound represented by the following general formula (1), a photoelectric conversion element.
(In the formula (1), at least one of R ^{1 to} R ⁸ is a substituent represented by the general formula (2). When there are a plurality of substituents represented by the formula (2), they are the same. R ^{1 to} R ⁸ other than the substituents are each independently a hydrogen atom, a halogen atom, an amino group, a hydroxy group, a cyano group, a carboxyl group, a sulfo group, an isocyano group, a formyl group, a mercapto group. Group, nitro group, silyl group, boryl group, or hydrocarbon group optionally having a hetero atom.)
(In the formula (2), R ^{9 to} R ¹⁶ are each independently a hydrogen atom, halogen atom, amino group, hydroxy group, cyano group, carboxyl group, sulfo group, isocyano group, formyl group, mercapto group, nitro group, A silyl group, a boryl group, or a hydrocarbon group which may have a hetero atom.)
[2] The photoelectric conversion element according to [1], wherein the compound represented by the general formula (1) has a glass transition temperature of 120 ° C. or higher.
[3] The photoelectric conversion element according to [1] or [2], wherein the active layer contains fullerene or a fullerene derivative.
[4] A solar cell comprising the photoelectric conversion element according to any one of [1] to [3].
[5] A solar cell module comprising the solar cell according to [4].

  ADVANTAGE OF THE INVENTION According to this invention, a durable photoelectric conversion element, a solar cell, and a solar cell module can be provided.

It is sectional drawing which shows typically the structure of the photoelectric conversion element as one Embodiment of this invention. It is sectional drawing which shows typically the structure of the solar cell as one Embodiment of this invention. It is sectional drawing which shows typically the structure of the solar cell module as one Embodiment of this invention.

  Embodiments of the present invention will be described in detail below, but these descriptions are examples (representative examples) of the embodiments of the present invention, and the present invention is not limited to these contents unless it exceeds the gist. Not.

<Photoelectric conversion element>
A photoelectric conversion element according to the present invention includes a pair of electrodes, an active layer disposed between the electrodes, and an electron extraction layer disposed between one of the electrodes and the active layer. And the said electronic taking-out layer contains the compound represented by following General formula (1).
(In the formula (1), at least one of R ^{1 to} R ⁸ is a substituent represented by the general formula (2). When there are a plurality of substituents represented by the formula (2), they are the same. R ^{1 to} R ⁸ other than the substituents are each independently a hydrogen atom, a halogen atom, an amino group, a hydroxy group, a cyano group, a carboxyl group, a sulfo group, an isocyano group, a formyl group, a mercapto group. Group, nitro group, silyl group, boryl group, or hydrocarbon group optionally having a hetero atom.)
(In the formula (2), R ^{9 to} R ¹⁶ are each independently a hydrogen atom, halogen atom, amino group, hydroxy group, cyano group, carboxyl group, sulfo group, isocyano group, formyl group, mercapto group, nitro group, A silyl group, a boryl group, or a hydrocarbon group which may have a hetero atom.)

  FIG. 1 shows a photoelectric conversion element used in a general organic thin film solar cell as one embodiment of the present invention. A photoelectric conversion element 107 according to an embodiment of the present invention includes a substrate 106, an electrode (anode) 101, a hole extraction layer 102, an organic active layer 103 (a mixed layer of p-type semiconductor compound and n-type semiconductor compound), and an electron extraction layer. 104 and an electrode (cathode) 105 have a layered structure formed in order. However, the structure of the photoelectric conversion element according to the present invention is not limited to that shown in FIG. For example, another layer may be inserted between each layer to the extent that it does not affect the function of each layer described later. Further, the hole extraction layer 102 may not be present, and the anode 101 and the cathode 105 may be arranged in reverse.

<Buffer layer (102, 104)>
The photoelectric conversion element according to the present invention includes an electron extraction layer disposed between one electrode and the active layer. Preferably, the photoelectric conversion element according to the present invention further includes a hole extraction layer disposed between the other electrode and the active layer. Hereinafter, the electron extraction layer and the hole extraction layer are collectively referred to as a buffer layer. Providing the buffer layer has advantages that the mobility of electrons and holes between the active layer and the electrode is increased, and that a short circuit between the electrodes can be prevented.

  The electron extraction layer 104 and the hole extraction layer 102 are disposed so as to sandwich the organic active layer 103 between a pair of electrodes (101, 105). That is, when the photoelectric conversion element 107 according to the present invention includes both the electron extraction layer 104 and the hole extraction layer 102, the electrode 101, the hole extraction layer 102, the organic active layer 103, the electron extraction layer 104, and the electrode 105 Arranged in order. When the photoelectric conversion element 107 according to the present invention includes the electron extraction layer 104 and does not include the hole extraction layer 102, the electrode 101, the organic active layer 103, the electron extraction layer 104, and the electrode 105 are arranged in this order. The stacking order of the electron extraction layer 104 and the hole extraction layer 102 may be reversed, or at least one of the electron extraction layer 104 and the hole extraction layer 102 may be composed of a plurality of different films. .

<Electron extraction layer (104)>
The electron extraction layer 104 is a layer disposed between one electrode and the active layer. Usually, the electron extraction layer is disposed between the cathode 105 and the active layer 103. The electron extraction layer 104 contains a phenanthroline derivative represented by the following formula (1). For example, the electron extraction layer 104 may be a layer of a phenanthroline derivative represented by the following formula (1). The electron extraction layer 104 may be a mixture layer containing a phenanthroline derivative represented by the following formula (1) and another compound such as a metal or a metal oxide. Further, the electron extraction layer 104 may have a structure in which a layer containing a phenanthroline derivative represented by the following formula (1) and a layer containing another compound such as a metal oxide are stacked. Good.

[Phenanthroline derivative]
The electron extraction layer 104 contains a compound represented by the following formula (1) (hereinafter referred to as a phenanthroline derivative according to the present invention).

In the formula (1), at least one of R ^{1 to} R ⁸ is a substituent represented by the general formula (2) (hereinafter referred to as a carbazolyl group). When there are a plurality of substituents represented by the formula (2), they may be the same or different. That is, when two or more of R ^{1 to} R ⁸ are carbazolyl groups, R ^{9 to} R ¹⁶ of each carbazolyl group may be the same or different from each other.

One or more, preferably two or more of R ^{1 to} R ⁸ is a carbazolyl group. Moreover, 8 or less, preferably 4 or less of R ^{1 to} R ⁸ is a carbazolyl group. From the viewpoint of ease of synthesis, the number of carbazolyl groups is preferably an even number, and particularly preferably 2 or 4. From the viewpoint of keeping the LUMO energy level at a suitable value for the electron extraction layer, the number of carbazolyl groups is particularly preferably two.

The substituents other than R ^{1 to} R ⁸ other than the carbazolyl group are not particularly limited as long as the function of the electron extraction layer is not lost when the compound of the formula (1) is included in the electron extraction layer, and is the same as each other. But it can be different. Specifically, it has a hydrogen atom, halogen atom, amino group, hydroxy group, cyano group, carboxyl group, sulfo group, isocyano group, formyl group, mercapto group, nitro group, silyl group, boryl group, or hetero atom. And hydrocarbon groups which may be used. Improving the planarity of the phenanthroline derivative according to the present invention is preferable in that the three-dimensional structure can be stabilized. From this viewpoint, the substituent other than the carbazolyl group is preferably a smaller substituent. Specifically, a hydrogen atom, a halogen atom, an amino group, a hydroxy group, a cyano group, a sulfo group, an isocyano group, a formyl group, a mercapto group, a nitro group, or a methyl group is preferable, and in particular, a hydrogen atom or a halogen atom It is preferable that it is a substituent comprised by 1 atom like. In order to adjust the LUMO energy level of the phenanthroline derivative, it is also preferable that at least one of R ^{1 to} R ^{8 is} a fluoroalkyl group, particularly a fluoromethyl group containing a trifluoromethyl group. Further, adjacent groups of R ^{1 to} R ⁸ may be bonded to each other to form a ring.

  Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. A fluorine atom or a chlorine atom is preferable because the atom is small and the flatness of the phenanthroline derivative is not easily affected, and a fluorine atom is particularly preferable from the viewpoint of stability.

  As silyl group, alkylsilyl group, dialkylsilyl group, trialkylsilyl group, arylsilyl group, diarylsilyl group, triarylsilyl group, aryl-alkyl-silyl group, aryl-dialkyl-silyl group, or diaryl-alkyl- A silyl group etc. are mentioned. The number of carbon atoms of the substituent that the silyl group has is not particularly limited, but is usually 1 or more and 40 or less. When the silyl group has an alkyl group as a substituent, the carbon number of the alkyl group is not particularly limited, but is usually 1 or more and 40 or less. When the silyl group has an aryl group as a substituent, the carbon number of the aryl group is not particularly limited, but is usually 2 or more and 40 or less. In the following, “aryl” represents an aromatic hydrocarbon group or an aromatic heterocyclic group.

  As the alkylsilyl group, those having 1 to 20 carbon atoms are preferable, and examples thereof include a methylsilyl group, an ethylsilyl group, and an n-octylsilyl group.

  As the dialkylsilyl group, those having 2 to 30 carbon atoms are preferable, and examples thereof include a dimethylsilyl group, a diethylsilyl group, a di-n-octylsilyl group, and an ethylmethylsilyl group.

  The trialkylsilyl group is preferably one having 3 to 40 carbon atoms, for example, a trimethylsilyl group, a triethylsilyl group, a triisopropylsilyl group, a tri-n-octylsilyl group, an ethyldimethylsilyl group, or a t-butyldimethylsilyl group. Groups and the like.

  As the arylsilyl group, those having 2 to 20 carbon atoms are preferable, and examples thereof include a phenylsilyl group.

  As the diarylsilyl group, those having 4 to 30 carbon atoms are preferable, and examples thereof include a diphenylsilyl group.

  The triarylsilyl group is preferably a group having 6 to 40 carbon atoms, and examples thereof include a triphenylsilyl group.

  As the aryl-alkyl-silyl group, those having 3 to 30 carbon atoms are preferable, and examples thereof include a methylphenylsilyl group.

  As the aryl-dialkyl-silyl group, those having 4 to 40 carbon atoms are preferable, and examples thereof include a dimethylphenylsilyl group.

  The diaryl-alkyl-silyl group is preferably a group having 5 to 40 carbon atoms, and examples thereof include a dimethylphenylsilyl group and a t-butyldiphenylsilyl group.

  Examples of the boryl group include a dialkylboryl group, an aryl-alkyl-boryl group, and a diarylboryl group. Although the carbon number of the substituent which a boryl group has is not restrict | limited, Usually, it is 1-40. When the boryl group has an alkyl group as a substituent, the carbon number of the alkyl group is not particularly limited, but is usually 1 or more and 40 or less. When the boryl group has an aryl group as a substituent, the carbon number of the aryl group is not particularly limited, but is usually 2 or more and 40 or less.

  As the dialkylboryl group, those having 2 to 30 carbon atoms are preferable, and examples thereof include a dimethylboryl group, a diethylboryl group, and a di-n-octylboryl group.

  As the aryl-alkyl-boryl group, those having 3 to 30 carbon atoms are preferable, and examples thereof include a phenylmethylboryl group.

  As the diarylboryl group, those having 4 to 30 carbon atoms are preferable, and examples thereof include a diphenylboryl group.

  Examples of the hydrocarbon group which may have a hetero atom include a hydrocarbon group which may have a substituent, a heterocyclic group which may have a substituent, a carbonyl group which has a substituent, Or the hydrocarbon group or heterocyclic group couple | bonded through the hetero atom which may have a substituent is mentioned. The hydrocarbon group or heterocyclic group bonded via a hetero atom means a hydrocarbon group or heterocyclic group bonded to a basic skeleton, for example, a phenanthroline ring of the formula (1) via a hetero atom. This hydrocarbon group or heterocyclic group and a hetero atom are collectively referred to as a hydrocarbon group or a heterocyclic group bonded via a hetero atom.

  Although it does not restrict | limit especially as a hetero atom, For example, an oxygen atom, a nitrogen atom, or a sulfur atom etc. are mentioned.

  Examples of the hydrocarbon group include an aliphatic hydrocarbon group and an aromatic hydrocarbon group. Examples of the aliphatic hydrocarbon group include saturated aliphatic hydrocarbon groups such as alkyl groups (including cycloalkyl groups); and unsaturated aliphatic hydrocarbon groups such as alkenyl groups (including cycloalkenyl groups) or alkynyl groups. Can be mentioned. Of these, a saturated aliphatic hydrocarbon group such as an alkyl group is preferable.

  As an alkyl group, a C1-C20 thing is preferable, For example, a methyl group, an ethyl group, i-propyl group, t-butyl group, n-hexyl group etc. are mentioned.

  As the cycloalkyl group, those having 3 to 20 carbon atoms are preferable, and examples thereof include a cyclopropyl group, a cyclopentyl group, and a cyclohexyl group.

  As the alkenyl group, those having 2 to 20 carbon atoms are preferable, and examples thereof include a vinyl group and a styryl group.

  The cycloalkenyl group preferably has 3 to 20 carbon atoms, and examples thereof include a cyclopropenyl group, a cyclopentenyl group, and a cyclohexenyl group.

  As the alkynyl group, those having 2 to 20 carbon atoms are preferable, and examples thereof include a methylethynyl group and a trimethylsilylethynyl group.

  As the aromatic hydrocarbon group, those having 6 to 30 carbon atoms are preferable, for example, phenyl group, naphthyl group, phenanthryl group, biphenylenyl group, triphenylenyl group, anthryl group, pyrenyl group, fluorenyl group, azulenyl group, acenaphthenyl group. Fluoranthenyl group, naphthacenyl group, perylenyl group, pentacenyl group or quarterphenyl group. Of these, a phenyl group, a naphthyl group, a phenanthryl group, a triphenylenyl group, an anthryl group, a pyrenyl group, a fluorenyl group, an acenaphthenyl group, a fluoranthenyl group, or a perylenyl group is preferable.

  Examples of the heterocyclic group include an aliphatic heterocyclic group and an aromatic heterocyclic group. As the aliphatic heterocyclic group, those having 2 to 30 carbon atoms are preferable, and examples thereof include a pyrrolidinyl group, piperidinyl group, piperazinyl group, tetrahydrofuranyl group, dioxanyl group, morpholinyl group, and thiomorpholinyl group. Of these, a pyrrolidinyl group, a piperidinyl group, or a piperazinyl group is preferable. The aromatic heterocyclic group preferably has 2 to 30 carbon atoms. For example, a pyridyl group, thienyl group, furyl group, pyrrolyl group, oxazolyl group, thiazolyl group, oxadiazolyl group, thiadiazolyl group, pyrazinyl group, pyrimidinyl group, Pyrazolyl group, imidazolyl group, benzothienyl group, dibenzofuryl group, dibenzothienyl group, phenoxathiinyl group, xanthenyl group, benzofuranyl group, thianthenyl group, indolizinyl group, phenoxazinyl group, phenothiazinyl group, acridinyl group, phenanthridinyl group Group, phenanthrolinyl group, quinolyl group, isoquinolyl group, indolyl group, quinoxalinyl group and the like. Among them, pyridyl group, pyrazinyl group, pyrimidinyl group, pyrazolyl group, quinolyl group, isoquinolyl group, imidazolyl group, acridinyl group, phenanthridinyl group, phenanthrolinyl group, quinoxalinyl group, dibenzofuryl group, dibenzothienyl group, A xanthenyl group or a phenoxazinyl group is preferred.

  Further, the aromatic hydrocarbon group and the aromatic heterocyclic group may be a condensed polycyclic aromatic group. The ring forming the condensed polycyclic aromatic group may have a cyclic alkyl structure which may have a substituent, an aromatic hydrocarbon ring which may have a substituent, or a substituent. Aromatic heterocycles are preferred. Examples of the cyclic alkyl structure include a cyclopentane structure or a cyclohexane structure. Examples of the aromatic hydrocarbon ring include a benzene ring or a naphthalene ring. Examples of the aromatic heterocycle include a pyridine ring, a thiophene ring, a furan ring, a pyrrole ring, an oxazole ring, a thiazole ring, an oxadiazole ring, a thiadiazole ring, a pyrazine ring, a pyrimidine ring, a biazole ring, and an imidazole ring. It is done. Among these, a pyridine ring or a thiophene ring is preferable.

  Specifically, the condensed polycyclic aromatic group is preferably a condensed polycyclic aromatic hydrocarbon group or a condensed polycyclic aromatic heterocyclic group. Examples of the condensed polycyclic aromatic hydrocarbon group include phenanthryl group, anthryl group, pyrenyl group, fluoranthenyl group, naphthacenyl group, perylenyl group, pentacenyl group, and triphenylenyl group. Examples of the condensed polycyclic aromatic heterocyclic group include a phenoxazinyl group, a phenothiazinyl group, an acridinyl group, a phenanthridinyl group, and a phenanthrolinyl group.

  Examples of the carbonyl group having a substituent include an alkylcarbonyl group, an arylcarbonyl group, an alkyloxycarbonyl group, an aryloxycarbonyl group, an alkylcarbamoyl group, an arylcarbamoyl group, an alkylimide group, and an arylimide group.

  Although the carbon number of the substituent which a carbonyl group has is not specifically limited, Usually, it is 1-40. The alkyl group of the alkylcarbonyl group, alkyloxycarbonyl group, alkylcarbamoyl group or alkylimide group is not particularly limited, but usually has 1 to 40 carbon atoms. The aryl group of the arylcarbonyl group, aryloxycarbonyl group, arylcarbamoyl group or arylimide group is not particularly limited, but usually has 2 to 40 carbon atoms.

  Examples of the alkylcarbonyl group include an acetyl group, an ethylcarbonyl group, a propylcarbonyl group, a pentylcarbonyl group, a cyclohexylcarbonyl group, an octylcarbonyl group, a 2-ethylhexylcarbonyl group, and a dodecylcarbonyl group. Of these, an octylcarbonyl group, a 2-ethylhexylcarbonyl group, or a dodecylcarbonyl group is preferable.

  Examples of the arylcarbonyl group include a benzoyl group, a naphthylcarbonyl group, and a pyridylcarbonyl group. Of these, a benzoyl group is preferable.

  Examples of the alkyloxycarbonyl group include a methoxycarbonyl group, an ethoxycarbonyl group, and an n-butoxycarbonyl group.

  Examples of the aryloxycarbonyl group include a phenoxycarbonyl group and a naphthoxycarbonyl group.

  As the alkylcarbamoyl group, those having 3 to 40 carbon atoms are preferable. For example, methylaminocarbonyl group, dimethylaminocarbonyl group, propylaminocarbonyl group, pentylaminocarbonyl group, cyclohexylaminocarbonyl group, octylaminocarbonyl group, methyl Examples include hexylaminocarbonyl group, octylaminocarbonyl group, 2-ethylhexylaminocarbonyl group, dodecylaminocarbonyl group and the like. Of these, an octylaminocarbonyl group or a 2-ethylhexylaminocarbonyl group is preferable.

  The arylcarbamoyl group preferably has 3 to 40 carbon atoms, and examples thereof include a phenylaminocarbonyl group, a naphthylaminocarbonyl group, and a 2-pyridylaminocarbonyl group. Of these, a phenylaminocarbonyl group is preferred.

  The alkylimide group preferably has 2 to 20 carbon atoms, and examples thereof include a methylcarbonylaminocarbonyl group, an ethylcarbonylaminocarbonyl group, and an n-butylcarbonylaminocarbonyl group.

  As the arylimide group, those having 2 to 20 carbon atoms are preferable, and examples thereof include a phenylcarbonylaminocarbonyl group and a naphthylcarbonylaminocarbonyl group.

  The number of carbon atoms of the hydrocarbon group bonded via a hetero atom is not particularly limited, but is usually 1 or more and 40 or less. When the hydrocarbon group bonded through a heteroatom is an alkyl group, the number of carbons is not particularly limited, but is usually 1 or more and 40 or less. Moreover, when the hydrocarbon group couple | bonded through a hetero atom is aryl, there is no special restriction | limiting in carbon number, Usually, it is 2-40.

  Specific examples of the hydrocarbon group or heterocyclic group bonded through a hetero atom include an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an alkylamino group, an arylamino group, and N-aryl-N-alkyl. An amino group, an alkylsulfonyl group, an arylsulfonyl group, etc. are mentioned. From the viewpoint of improving the electron transport property of the electron extraction layer, an alkoxy group or an aryloxy group is preferable.

  As the alkoxy group, those having 1 to 20 carbon atoms are preferable. For example, methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group and t-butoxy group, benzyl Examples thereof include linear or branched alkoxy groups such as an oxy group and an ethylhexyloxy group.

  As the aryloxy group, those having 2 to 20 carbon atoms are preferable, and examples thereof include a phenoxy group, a naphthyloxy group, a pyridyloxy group, a thiazolyloxy group, an oxazolyloxy group, and an imidazolyloxy group. Of these, a phenoxy group or a pyridyloxy group is preferable.

  As the alkylthio group, those having 1 to 20 carbon atoms are preferred, and examples thereof include a methylthio group, an ethylthio group, a propylthio group, a pentylthio group, a hexylthio group, an octylthio group, a dodecylthio group, a cyclopentylthio group, and a cyclohexylthio group. . Of these, a methylthio group or an octylthio group is preferable.

  The arylthio group is preferably one having 2 to 20 carbon atoms, and examples thereof include a phenylthio group, a naphthylthio group, a pyridylthio group, a thiazolylthio group, an oxazolylthio group, an imidazolylthio group, a furylthio group, and a pyrrolylthio group. Of these, a phenylthio group or a pyridylthio group is preferable.

  The alkylamino group is preferably an alkylamino group having 1 to 20 carbon atoms, for example, methylamino group, ethylamino group, dimethylamino group, diethylamino group, butylamino group, octylamino group, cyclopentylamino group, 2-ethylhexylamino. Group or dodecylamino group. Of these, a dimethylamino group, an octylamino group or a 2-ethylhexylamino group is preferable.

  As the arylamino group, those having 2 to 20 carbon atoms are preferable, and examples thereof include an anilino group, a diphenylamino group, a naphthylamino group, a 2-pyridylamino group, and a naphthylphenylamino group. Of these, a diphenylamino group is preferable.

  As the N-aryl-N-alkylamino group, those having 3 to 40 carbon atoms are preferable, and examples thereof include an N-phenyl-N-methylamino group and an N-naphthyl-N-methylamino group.

  Examples of the alkylsulfonyl group include a methylsulfonyl group, an ethylsulfonyl group, a butylsulfonyl group, an octylsulfonyl group, a cyclohexylsulfonyl group, a 2-ethylhexylsulfonyl group, and a dodecylsulfonyl group. Of these, an octylsulfonyl group or a 2-ethylhexylsulfonyl group is preferable.

  Examples of the arylsulfonyl group include a phenylsulfonyl group, a naphthylsulfonyl group, and a 2-pyridylsulfonyl group. Of these, a phenylsulfonyl group is preferable.

R ^{9 to} R ¹⁶ are not particularly limited as long as the function of the electron extraction layer is not lost when the compound of the formula (1) is included in the electron extraction layer. Examples of R ^{9 to} R ¹⁶ include the same substituents as those described for R ^{1 to} R ⁸ that are not carbazolyl groups.

Improving the planarity of the phenanthroline derivative of the present invention is preferable in that the three-dimensional structure can be stabilized. From this point of view, R ^{9 to} R ¹⁶ are preferably smaller substituents. Specifically, a hydrogen atom, a halogen atom, an amino group, a hydroxy group, a cyano group, a sulfo group, an isocyano group, a formyl group, a mercapto group, a nitro group, or a methyl group is preferable, and in particular, a hydrogen atom or a halogen atom It is preferable that it is a substituent comprised by 1 atom like. In order to adjust the LUMO energy level of the phenanthroline derivative, it is also preferable that at least one of R ^{9 to} R ^{16 is} a fluoroalkyl group, particularly a fluoromethyl group containing a trifluoromethyl group.

The term “which may have a substituent” in the description of R ^{1 to} R ¹⁶ means that it may have one or more substituents. The substituent is not particularly limited, but a halogen atom, alkyl group, alkenyl group, alkynyl group, silyl group, boryl group, alkoxy group, amino group, hydroxy group, cyano group, carboxyl group, sulfo group, isocyano group, Examples include formyl group, mercapto group, nitro group, carbamoyl group, imide group, aromatic hydrocarbon group or aromatic heterocyclic group.

  As the halogen atom, a fluorine atom is preferable.

  As an alkyl group, a C1-C20 thing is preferable, for example, a methyl group, an ethyl group, i-propyl group, t-butyl group, or a cyclohexyl group etc. are mentioned.

  As the alkenyl group, those having 2 to 20 carbon atoms are preferable, and examples thereof include a vinyl group, a styryl group, and a diphenylvinyl group.

  As the alkynyl group, those having 2 to 20 carbon atoms are preferable, and examples thereof include a methylethynyl group, a phenylethynyl group, and a trimethylsilylethynyl group.

  As the silyl group, those having 2 to 20 carbon atoms are preferable, and examples thereof include a trimethylsilyl group and a triphenylsilyl group.

  Examples of the boryl group include an aromatic group-substituted boryl group such as a dimesitylboryl group.

  As the alkoxy group, those having 2 to 20 carbon atoms are preferable. For example, methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, ethylhexyloxy group, benzyloxy And a linear or branched alkoxy group such as a group or a t-butoxy group.

  Examples of the amino group include aromatic substituted amino groups such as a diphenylamino group, a ditolylamino group, and a carbazolyl group.

  As the aromatic hydrocarbon group, those having 6 to 20 carbon atoms are preferable, and these are not limited to monocyclic groups, and are not limited to monocyclic aromatic hydrocarbon groups, condensed polycyclic aromatic hydrocarbon groups or ring-linked aromatic groups. Any of group hydrocarbon groups may be used.

  Examples of the monocyclic aromatic hydrocarbon group include a phenyl group. Examples of the condensed polycyclic aromatic hydrocarbon group include a biphenyl group, a naphthyl group, an anthryl group, a fluorenyl group, a pyrenyl group, and a perylenyl group. Examples of the ring-linked aromatic hydrocarbon group include a biphenyl group and terphenyl. Among these, a phenyl group or a naphthyl group is preferable.

  As the aromatic heterocyclic group, those having 2 to 20 carbon atoms are preferable, for example, pyridyl group, thienyl group, furyl group, oxazolyl group, thiazolyl group, oxadiazolyl group, benzothienyl group, dibenzofuryl group, dibenzothienyl group. A pyrazinyl group, a pyrimidinyl group, a pyrazolyl group, a phenanthrolinyl group, an imidazolyl group, a phenylcarbazolyl group, and the like. Among these, a pyridyl group, a thienyl group, a benzothienyl group, a dibenzofuryl group, a dibenzothienyl group, or a phenanthrolinyl group is preferable.

In order to enhance the durability of the photoelectric conversion element, the phenanthroline derivative of the present invention preferably has high symmetry. If the symmetry is high, it is considered that a more stable three-dimensional structure can be obtained. From this viewpoint, it is preferable that R ¹ = R ⁸ , R ² = R ⁷ , R ³ = R ⁶ , and R ⁴ = R ⁵ .

  Examples of the phenanthroline derivative according to the present invention include the following compounds.

  The lowest unoccupied orbital (LUMO) level of the phenanthroline derivative according to the present invention is not particularly limited, but the value relative to the vacuum level calculated by the cyclic voltammogram measurement method is usually −3.5 eV or more, preferably −3. 0.0 eV or more. On the other hand, it is usually −1.9 eV or less, preferably −2.0 eV or less. It is preferable that it is −1.9 eV or less because charge transfer is promoted. Moreover, it is preferable that it is -3.5 eV or more at the point which can prevent the reverse electron transfer to n-type semiconductor material.

  As a method for calculating the value of LUMO, there are a method of theoretically obtaining a calculated value and a method of actually measuring. Theoretically calculated methods include semi-empirical molecular orbital methods and non-empirical molecular orbital methods. Examples of the actual measurement method include ultraviolet-visible absorption spectrum measurement method and cyclic voltammogram measurement method. Among them, the cyclic voltammogram measurement method is preferable.

  Further, the glass transition temperature (hereinafter sometimes referred to as Tg) of the phenanthroline derivative according to the present invention measured by the DSC method is 120 ° C. or higher, or the glass transition temperature is not observed thermally. It is preferable in that it has high stability. The fact that the glass transition temperature is not observed means that there is no glass transition temperature, and specifically means that there is no glass transition temperature at 400 ° C. or lower.

  Phenanthroline derivatives such as BCP, Bphen, and NBphen, which have been used as an electron extraction layer material, have a relatively low glass transition temperature. For this reason, it is considered that a photoelectric conversion element using these phenanthroline derivatives as an electron extraction layer material has poor heat resistance and durability. On the other hand, when a phenanthroline derivative having a glass transition temperature of 120 ° C. or higher is used, heat resistance or durability can be improved, and heating at a higher temperature can be performed when a photoelectric conversion element is manufactured. For example, heating (annealing) may be performed when a photoelectric conversion element is manufactured as described later, but when a phenanthroline derivative having a glass transition temperature of 120 ° C. or higher is used, annealing can be performed in a wider temperature range. Further, by using a phenanthroline derivative having a glass transition temperature of 120 ° C. or higher, heating in the production process can be performed in a wider temperature range, particularly when a plastic substrate such as polyethylene terephthalate is used.

  The glass transition temperature of the phenanthroline derivative according to the present invention is preferably 130 ° C. or higher, and more preferably 140 ° C. or higher, in that it has high thermal stability. On the other hand, the upper limit of the glass transition temperature is not particularly limited, and is usually 400 ° C. or lower.

  The glass transition temperature in the present specification is defined as a point at which specific heat is changed by a temperature at which local molecular motion is initiated by thermal energy in an amorphous solid of a compound. When the temperature rises further than Tg, the solid structure changes and crystallization occurs (the temperature at this time is defined as the crystallization temperature (Tc)). When the temperature rises further, it generally melts at the melting point (Tm) and changes to a liquid state. However, these phase transitions may not be observed due to molecular decomposition or sublimation at high temperatures.

  The DSC method is a thermophysical property measurement method (differential scanning calorimetry method) defined in JIS K-0129 “General Rules for Thermal Analysis”. The glass transition temperature is a temperature at which molecular motion starts from a glass state, and can be measured by a DSC method as a temperature at which specific heat changes. In order to determine the glass transition temperature more clearly, it is measured after rapidly cooling a sample once heated to a temperature higher than the glass transition temperature. For example, this method can be carried out by a method described in a known document (International Publication No. 2011/016430).

  When the glass transition temperature of the phenanthroline derivative according to the present invention is 120 ° C. or higher, the structure of the phenanthroline derivative is difficult to change with respect to external stress such as applied electric field, flowing current, stress due to bending or temperature change. It is preferable in terms of durability. Furthermore, when the glass transition temperature of the phenanthroline derivative according to the present invention is 120 ° C. or higher, the crystallization of the compound thin film tends not to proceed. For this reason, since the phenanthroline derivative is less likely to change between the amorphous state and the crystalline state in the actual use temperature range, the stability as the electron extraction layer is improved, which is preferable in terms of durability. This effect becomes more prominent as the glass transition temperature of the material is higher.

[Features of phenanthroline derivative according to the present invention]
The phenanthroline derivative according to the present invention has a structure in which the substituent represented by the formula (2) is bonded to the phenanthroline skeleton represented by the formula (1). The photoelectric conversion element using the phenanthroline derivative according to the present invention as an electron extraction layer material can obtain relatively high photoelectric conversion efficiency and can have high durability or heat resistance. Specifically, even when heating is performed at a high temperature, for example, heating is performed at 120 ° C. for 1 minute or 3 minutes, the photoelectric conversion efficiency is unlikely to decrease. Further, even when left for a long period of time, for example, at room temperature for 8 weeks, the photoelectric conversion efficiency is unlikely to decrease.

  The reason why the durability or heat resistance of the photoelectric conversion element using the phenanthroline derivative according to the present invention as the electron extraction layer material can be increased is as follows. For example, the planarity of the phenanthroline derivative can be increased by bonding the substituent represented by the formula (2) to the phenanthroline ring represented by the formula (1). That is, when the nitrogen atom of the substituent represented by the formula (2) is directly bonded to the phenanthroline ring, the planarity of the molecule can be increased due to resonance. In the phenanthroline derivative according to the present invention, since the nitrogen atom of the substituent represented by the formula (2) is directly bonded to the phenanthroline ring, for example, the nitrogen atom of the substituent represented by the formula (2) has a phenylene group. It is considered that the planarity is higher than that in the case where it is bonded to the phenanthroline ring.

From the viewpoint of obtaining a greater resonance effect, it is preferable that at least one of R ¹ , R ³ , R ⁶ , and R ⁸ is a carbazolyl group. Of these, at least one of R ¹ and R ³ is preferably a carbazolyl group, and at least one of R ⁶ and R ⁸ is also preferably a carbazolyl group. Furthermore, it is also preferably at least one of R ³ and R ⁶ are carbazolyl group, and R ³ and R ⁶ are both carbazolyl groups are particularly preferred.

  The higher molecular planarity makes the molecules easier to pack, requiring more energy for the molecules to act freely. For this reason, it is thought that the high planarity of the molecule leads to a higher glass transition temperature. Thus, it is thought that higher glass transition temperature is obtained by the high planarity of the phenanthroline derivative according to the present invention, and the durability or heat resistance of the photoelectric conversion element is improved.

The presence of the carbazolyl group of the phenanthroline derivative according to the present invention is also considered to contribute to the relatively high photoelectric conversion efficiency and durability of the photoelectric conversion element. For example, a carbazolyl group has the following characteristics as compared with a diphenylamino group that does not particularly have a condensed ring structure. For example, a carbazolyl group is a substituent having high planarity. For this reason, it is expected that effects such as high electron donating property, high mobility, high Tg, and reduction of thermal deactivation due to vibration expansion and contraction are obtained. Moreover, since the unshared electron pair on the nitrogen atom contained in the carbazolyl group contributes to resonance, the basicity is small. For this reason, it is expected that damage to other photoelectric conversion element materials is reduced. Furthermore, the triplet energy level of the carbazolyl group is high (that is, the energy difference between S ₁ and T ₁ is small). For this reason, it is expected that triplet electron orbits can be used for charge transfer. Moreover, since the triplet energy level is high, generation of singlet oxygen is suppressed, and it is expected that the durability is improved.

[Method for producing phenanthroline derivative]
As the phenanthroline derivative according to the present invention, a commercially available product can be used, or it can be produced according to a known method.

  As an example of the method for producing a phenanthroline derivative according to the present invention, 1,10-phenanthroline which may have a substituent is halogenated with an appropriate halogenating reagent, and a carbazole which may have a substituent is combined with a cup. The method of making it ring is mentioned.

[Method for Forming Electron Extraction Layer 104]
There is no particular limitation on the method for forming the electron extraction layer 104. In the case of using a sublimable material, it can be formed by a vacuum deposition method or the like. For example, when a material soluble in a solvent is used, it can be formed by a coating method such as spin coating or inkjet.

  When the electron extraction layer 104 containing the phenanthroline derivative according to the present invention is formed by a coating method, a phenanthroline derivative-containing ink can be used. The solvent of the phenanthroline derivative-containing ink is not particularly limited. For example, water; aliphatic hydrocarbons such as hexane, heptane, octane, isooctane, nonane, or decane; aromatic carbonization such as toluene, xylene, chlorobenzene, or orthodichlorobenzene. Hydrogen; alcohols such as methanol, ethanol, isopropanol or 2-butoxyethanol; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; esters such as ethyl acetate, butyl acetate or methyl lactate; chloroform, methylene chloride, Halogen hydrocarbons such as dichloroethane, trichloroethane or trichloroethylene; propylene glycol monomethyl ether acetate (PGMEA), ethyl ether, Ethers such as lahydrofuran or dioxane; amides such as dimethylformamide or dimethylacetamide; aromatic hydrocarbons such as toluene, xylene, chlorobenzene or orthodichlorobenzene; or halogens such as chloroform, methylene chloride, dichloroethane, trichloroethane or trichloroethylene Hydrocarbons; and the like. As a solvent, only 1 type may be used and 2 or more types may be used together by arbitrary combinations and a ratio. Further, since the solvent may remain in the electron extraction layer 104 as long as the function of the electron extraction layer 104 is not impaired, there is no particular limitation on the boiling point of the solvent.

  Further, a binder resin such as polyimine, polyester, polyamide, polyurethane, polyurea or polyethylene glycol may be contained in the phenanthroline derivative-containing ink.

  The concentration of the phenanthroline derivative in the phenanthroline derivative-containing ink is not particularly limited, but is usually 0.02% by weight or more, preferably 0.05% by weight or more, more preferably 0.08% by weight or more. 60% by weight or less, preferably 40% by weight or less, more preferably 20% by weight or less. A concentration of the organic compound in the ink within the above range is preferable in that the phenanthroline derivative can be applied uniformly.

  Application | coating can be performed by arbitrary methods. Examples thereof include spin coating, gravure coating, kiss coating, roll brushing, spray coating, air knife coating, wire barber coating, pipe doctor method, impregnation / coating method, curtain coating method and the like. Coating may be performed using only one of these methods, or coating may be performed by arbitrarily combining two or more.

  The total film thickness of the electron extraction layer 104 is not particularly limited, but is usually 0.2 nm or more, preferably 0.5 nm or more, more preferably 1 nm or more, and particularly preferably 5 nm or more. On the other hand, it is usually 1 μm or less, preferably 700 nm or less, more preferably 400 nm or less, and particularly preferably 200 nm or less. When the film thickness of the electron extraction layer 104 is 0.2 nm or more, it functions as an electron extraction layer. When the film thickness of the electron extraction layer 104 is 1 μm or less, electrons are easily extracted, Conversion efficiency can be improved.

  As described above, the electron extraction layer 104 may further contain a metal or a metal oxide. In particular, the electron extraction layer 104 preferably includes a mixture layer containing a phenanthroline derivative and another compound such as a metal or a metal oxide.

  Mixing a phenanthroline derivative and a metal is preferable in that the metal is doped into the phenanthroline derivative and the energy levels of HOMO and LUMO can be controlled. Although there is no special restriction | limiting as a metal, From this viewpoint, it is preferable to use barium, yttrium, cesium, niobium, etc. In this case, one type of metal may be used alone, or two or more types of metals may be used in combination.

  The concentration of the metal in the mixture layer of the phenanthroline derivative and the metal is not particularly limited, but is usually 0.01% or more, preferably 0.05 or more, more preferably 0.1% or more. On the other hand, it is usually 50% or less, preferably 30% or less, more preferably 10% or less. When the metal concentration is within this range, the energy levels of HOMO and LUMO can be controlled without impairing the function of facilitating extraction of electrons.

  The thickness of the mixture layer of the phenanthroline derivative and the metal is not particularly limited, but may be the same as the thickness described above for the entire electron extraction layer 104.

  Mixing the phenanthroline derivative and the metal oxide is preferable because the phenanthroline derivative is difficult to dissolve when another layer is further formed on the mixture layer using a coating method. There are no particular restrictions on the metal oxide, but metal oxides having n-type semiconductor characteristics such as zinc oxide, titanium oxide, tin oxide, aluminum oxide, silicon oxide, cerium oxide, lead oxide, zirconium oxide or gallium oxide are available. Take as an example. Among these, zinc oxide, titanium oxide or tin oxide is preferable. In this case, one type of metal oxide may be used alone, or two or more types of metal oxides may be used in combination.

  The average primary particle size of the metal oxide is usually 5 nm or more, preferably 10 nm or more, more preferably 20 nm or more, and is usually 100 nm or less, preferably 60 nm or less, more preferably 40 nm or less. When the average primary particle size is 5 nm or more, the metal oxide is less likely to aggregate and a metal oxide having a suitable average secondary particle size can be obtained. Moreover, it is preferable that an average primary particle diameter is 100 nm or less because each secondary particle of the metal oxide has an appropriate size and an electron extraction layer having a uniform film thickness is formed. The average primary particle size of the metal oxide can be measured with a dynamic light scattering particle size measuring device, a transmission electron microscope (TEM), or the like. Specific examples of metal oxides having an average primary particle size of 5 nm to 100 nm (sometimes referred to as metal oxide nanoparticles) include Nanozinc 60 (Honjo Chemical Co., Ltd.) and FINEX-30 (Sakai Chemical) Manufactured by Kogyo Co., Ltd.).

  The concentration of the metal oxide in the mixture layer of the phenanthroline derivative and the metal oxide is not particularly limited, but is usually 0.5% or more, preferably 1% or more, more preferably 3% or more. It is 99.99% or less, preferably 99.9% or less. When the concentration of the metal oxide is within this range, dissolution of the phenanthroline derivative can be prevented while maintaining the ability to transport electrons.

  The thickness of the mixture layer of the phenanthroline derivative and the metal oxide is not particularly limited, but may be the same as the thickness described above for the entire electron extraction layer 104.

<Hole extraction layer (102)>
The material of the hole extraction layer 102 is not particularly limited as long as it can improve the efficiency of extracting holes from the active layer 103 to the anode 101. Specifically, conductive organic compounds such as polythiophene, polypyrrole, polyacetylene, triphenylenediamine polypyrrole or polyaniline doped with sulfonic acid and / or iodine, polythiophene derivatives having a sulfonyl group as a substituent, conductive organic compounds such as arylamine And metal oxides such as copper oxide, nickel oxide, manganese oxide, molybdenum oxide, vanadium oxide, and tungsten oxide, and p-type semiconductors described later. Among them, a conductive polymer doped with sulfonic acid is preferable, and PEDOT: PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid is more preferable. A thin film of metal such as gold, indium, silver or palladium can also be used. Furthermore, a thin film of metal or the like may be formed alone or in combination with the above organic material.

  The thickness of the hole extraction layer 102 is not particularly limited, but is usually 0.2 nm or more. On the other hand, it is usually 400 nm or less, preferably 200 nm or less. When the film thickness of the hole extraction layer 102 is 0.2 nm or more, it functions as a buffer material, and when the film thickness of the hole extraction layer 102 is 400 nm or less, holes are easily extracted. The photoelectric conversion efficiency is improved.

  There is no limitation on the method of forming the hole extraction layer 102. For example, when a material having sublimation property is used, it can be formed by a vacuum deposition method or the like. Further, for example, when a material soluble in a solvent is used, it can be formed by a wet coating method such as spin coating or inkjet. When a semiconductor material is used for the hole extraction layer 102, the precursor may be converted into a semiconductor compound after the layer is formed using the precursor, similarly to the low-molecular organic semiconductor compound of the organic active layer described later.

In particular, when PEDOT: PSS is used as the material of the hole extraction layer 102, it is preferable to form the hole extraction layer 102 by applying a dispersion. PEDOT: The dispersion of PSS, HC Starck, Inc. of CLEVIOS ^TM series and Agfa Corporation of ORGACON ^TM series, and the like.

  When using the coating method, the coating solution may further contain a surfactant. By using the surfactant, generation of dents due to adhesion of fine bubbles, foreign matters, etc., uneven coating in the drying process, and the like are suppressed.

  Known surfactants (cationic surfactants, anionic surfactants, nonionic surfactants) can be used as the surfactant. Among these, it is preferable to use a silicon-based surfactant, an acetylenic diol-based surfactant, or a fluorine-based surfactant. In addition, only 1 type of surfactant may be used and 2 or more types of surfactant may be used together by arbitrary combinations and a ratio.

<Active layer (103)>
In the photoelectric conversion element according to the present invention, the active layer 103 refers to a layer in which photoelectric conversion is performed, and includes a p-type semiconductor compound and an n-type semiconductor compound. When the photoelectric conversion element 107 receives light, the light is absorbed by the active layer 103, electricity is generated at the interface between the p-type semiconductor compound and the n-type semiconductor compound, and the generated electricity is extracted from the electrodes 101 and 105.

  The active layer 103 may use either an inorganic compound or an organic compound, but is preferably a layer that can be formed by a simple coating process. More preferably, the active layer 103 is an organic active layer made of an organic compound. In the following description, it is assumed that the active layer 103 is an organic active layer.

  The layer structure of the organic active layer is a thin film laminated type in which a p-type semiconductor compound and an n-type semiconductor compound are laminated, a bulk heterojunction type in which a p-type semiconductor compound and an n-type semiconductor compound are mixed, and a p-type in an intermediate layer of a thin film laminated type. Examples include a structure having a layer (i layer) in which a semiconductor compound and an n-type semiconductor compound are mixed. Among these, a bulk heterojunction type in which a p-type semiconductor compound and an n-type semiconductor compound are mixed is preferable.

The thickness of the organic active layer 103 is not particularly limited, but is usually 10 nm or more, preferably 50 nm or more, while usually 1.0 × 10 ³ nm or less, preferably 5.0 × 10 ² nm or less, more preferably 2 0.0 × 10 ² nm or less. It is preferable that the thickness of the organic active layer is 10 nm or more because uniformity is maintained and short-circuiting is less likely to occur. Further, it is preferable that the thickness of the organic active layer is 1.0 × 10 ³ nm or less because the internal resistance is reduced and the distance between the electrodes is not increased, and the charge diffusion is improved.

[Thin film type active layer]
The thin film stacked active layer has a structure in which a p-type semiconductor layer containing a p-type semiconductor compound and an n-type semiconductor layer containing an n-type semiconductor compound are stacked. The thin film stacked active layer can be formed by forming a p-type semiconductor layer and an n-type semiconductor layer, respectively. The p-type semiconductor layer and the n-type semiconductor layer may be formed by different methods.

[P-type semiconductor layer]
The p-type semiconductor layer is a layer containing a p-type semiconductor compound described later. There is no limitation on the film thickness of the p-type semiconductor layer. However, it is usually 5 nm or more, preferably 10 nm or more, and usually 500 nm or less, preferably 200 nm or less. When the film thickness of the p-type semiconductor layer is 500 nm or less, it is preferable in that the series resistance is lowered. It is preferable that the thickness of the p-type semiconductor layer is 5 nm or more because more light can be absorbed.

  The p-type semiconductor layer can be formed by any method including a coating method and a vapor deposition method, but the use of the coating method is preferable in that the p-type semiconductor layer can be formed more easily. When a p-type semiconductor layer is produced by a coating method, a coating solution containing a p-type semiconductor compound may be prepared and applied. As an application method, any method can be used. For example, spin coating method, inkjet method, doctor blade method, drop casting method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method , Air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method or curtain coating method. After applying the coating solution, a drying process may be performed by heating or the like. As will be described later, after preparing a coating liquid containing a p-type semiconductor compound precursor and applying the coating liquid, the p-type semiconductor compound precursor is converted into a p-type semiconductor compound, whereby a p-type semiconductor layer is formed. May be formed.

[N-type semiconductor layer]
The n-type semiconductor layer is a layer containing an n-type semiconductor compound described later. However, the thickness of the n-type semiconductor layer is not particularly limited, but is usually 5 nm or more, preferably 10 nm or more, and is usually 500 nm or less, preferably 200 nm or less. When the film thickness of the n-type semiconductor layer is 500 nm or less, it is preferable in that the series resistance is lowered. The thickness of the n-type semiconductor layer is preferably 5 nm or more in that more light can be absorbed.

  The n-type semiconductor layer can be formed by any method including a coating method and a vapor deposition method, but it is preferable to use the coating method because the n-type semiconductor layer can be more easily formed. When an n-type semiconductor layer is formed by a coating method, a coating solution containing an n-type semiconductor compound may be prepared and this coating solution may be applied. As a coating method, any method can be used, and for example, the methods mentioned as the method for forming the p-type semiconductor layer can be used. After applying the coating solution, a drying process may be performed by heating or the like.

[Bulk heterojunction active layer]
The bulk heterojunction active layer has a layer (i layer) in which a p-type semiconductor compound described later and an n-type semiconductor compound described later are mixed. The i layer has a structure in which the p-type semiconductor compound and the n-type semiconductor compound are phase-separated, carrier separation occurs at the phase interface, and the generated carriers (holes and electrons) are transported to the electrode.

  There is no restriction | limiting in the film thickness of i layer. However, it is usually 5 nm or more, preferably 10 nm or more, and usually 500 nm or less, preferably 200 nm or less. When the film thickness of the i layer is 500 nm or less, it is preferable in that the series resistance is lowered. When the film thickness of the i layer is 5 nm or more, it is preferable in that more light can be absorbed.

  The i layer can be formed by any method including a coating method and a vapor deposition method (for example, a co-evaporation method), but it is preferable to use the coating method because the i layer can be formed more easily. When the i layer is produced by a coating method, a coating solution containing a p-type semiconductor compound and an n-type semiconductor compound may be prepared, and this coating solution may be applied. The coating liquid containing the p-type semiconductor compound and the n-type semiconductor compound may be prepared by preparing and mixing a solution containing the p-type semiconductor compound and a solution containing the n-type semiconductor compound, respectively. It may be prepared by dissolving the compound and the n-type semiconductor compound. In addition, as will be described later, after preparing a coating liquid containing a p-type semiconductor compound precursor and an n-type semiconductor compound, and applying this coating liquid, converting the p-type semiconductor compound precursor into a p-type semiconductor compound. Thus, the i layer may be formed. As a coating method, any method can be used, and for example, the methods mentioned as the method for forming the p-type semiconductor layer can be used. After applying the coating solution, a drying process may be performed by heating or the like.

  When the bulk heterojunction active layer is formed by a coating method, an additive may be further added to the coating solution containing the p-type semiconductor compound and the n-type semiconductor compound. The phase separation structure of the p-type semiconductor compound and the n-type semiconductor compound in the bulk heterojunction active layer has an influence on the light absorption process, the exciton diffusion process, the exciton separation (carrier separation) process, the carrier transport process, etc. is there. Therefore, it is considered that good photoelectric conversion efficiency can be realized by optimizing the phase separation structure. When the coating solution contains an additive having volatility different from that of the solvent, a preferable phase separation structure can be obtained at the time of forming the organic active layer, and the photoelectric conversion efficiency can be improved. Therefore, the additive is preferably contained.

  As an example of an additive, the compound etc. which are described in the international publication 2008/066933 are mentioned, for example. More specific examples of the additive include aromatic compounds such as alkane having a substituent or naphthalene having a substituent. Examples of substituents include aldehyde groups, oxo groups, hydroxy groups, alkoxy groups, thiol groups, thioalkyl groups, carboxyl groups, ester groups, amine groups, amide groups, fluoro groups, chloro groups, bromo groups, iodo groups, halogen groups, A nitrile group, an epoxy group, an aromatic group, an arylalkyl group, etc. are mentioned. There may be one or more, for example two, substituents. A preferred substituent for the alkane is a thiol group or an iodo group. Moreover, as a substituent which an aromatic compound like naphthalene has, Preferably, they are a bromo group or a chloro group.

  Since the additive preferably has a high boiling point, the aliphatic hydrocarbon used as the additive preferably has 6 or more carbon atoms, and more preferably 8 or more carbon atoms. Moreover, since it is preferable that an additive is liquid at normal temperature, carbon number of an aliphatic hydrocarbon has preferable 14 or less, and 12 or less is more preferable. For the same reason, the aromatic hydrocarbon used as an additive usually has 6 or more carbon atoms, preferably 8 or more, more preferably 10 or more, and usually 50 or less, preferably 30 or less, more preferably 20 or less. The number of carbon atoms of the aromatic heterocycle used as an additive is usually 2 or more, preferably 3 or more, more preferably 6 or more, and usually 50 or less, preferably 30 or less, more preferably 20 or less.

  The boiling point of the additive is usually 100 ° C. or higher, preferably 200 ° C. or higher, and usually 600 ° C. or lower, preferably 500 ° C. or lower, at normal pressure (one atmospheric pressure).

  The amount of the additive contained in the coating solution containing the p-type semiconductor compound and the n-type semiconductor compound is preferably 0.1% by weight or more, and more preferably 0.5% by weight or more with respect to the entire coating solution. Moreover, 10 weight% or less is preferable with respect to the whole coating liquid, and 3 weight% or less is more preferable. When the amount of the additive is within this range, a preferable phase separation structure can be obtained while reducing the additive remaining in the organic active layer. As described above, a bulk heterojunction active layer can be formed by applying a coating liquid (ink) containing a p-type semiconductor compound, an n-type semiconductor compound, and an additive.

[Solvent of coating solution]
Examples of the solvent for the coating solution containing the p-type semiconductor compound, the coating solution containing the n-type semiconductor compound, and the coating solution containing the p-type semiconductor compound and the n-type semiconductor compound include p-type semiconductor compounds and / or n-type. Although it will not specifically limit if a semiconductor compound can be melt | dissolved uniformly, For example, aliphatic hydrocarbons, such as hexane, heptane, octane, isooctane, nonane, or decane; Toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene, or orthodi Aromatic hydrocarbons such as chlorobenzene; cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin; lower alcohols such as methanol, ethanol or propanol; acetone, methyl ethyl ketone Aliphatic ketones such as cyclohexane, cyclopentanone or cyclohexanone; aromatic ketones such as acetophenone or propiophenone; esters such as ethyl acetate, butyl acetate or methyl lactate; chloroform, methylene chloride, dichloroethane, trichloroethane, or trichloroethylene Halogen ethers of the above; ethers such as ethyl ether, tetrahydrofuran or dioxane; or amides such as dimethylformamide or dimethylacetamide.

  Among them, aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene, chlorobenzene or orthodichlorobenzene; cycloaliphatic carbonization such as cyclopentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin Hydrogens; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; halogen hydrocarbons such as chloroform, methylene chloride, dichloroethane, trichloroethane or trichloroethylene; or ethers such as ethyl ether, tetrahydrofuran or dioxane. More preferably, non-halogen aromatic hydrocarbons such as toluene, xylene, mesitylene or cyclohexylbenzene; non-halogen ketones such as cyclopentanone or cyclohexanone; aromatic ketones such as acetophenone or propiophenone; tetrahydrofuran, cyclohexane Alicyclic hydrocarbons such as pentane, cyclohexane, methylcyclohexane, cycloheptane, cyclooctane, tetralin or decalin; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; or non-halogens such as 1,4-dioxane Aliphatic ethers. Particularly preferred are non-halogen aromatic hydrocarbons such as toluene, xylene, mesitylene or cyclohexylbenzene.

  In addition, 1 type of solvent may be used independently as a solvent, and arbitrary 2 or more types of solvents may be used together by arbitrary ratios. When two or more kinds of solvents are used in combination, it is preferable to combine a low boiling point solvent having a boiling point of 60 to 150 ° C. with a high boiling point solvent having a boiling point of 180 to 250 ° C. Examples of combinations of low and high boiling solvents include non-halogen aromatic hydrocarbons and alicyclic hydrocarbons, non-halogen aromatic hydrocarbons and aromatic ketones, ethers and alicyclic carbonization. Examples thereof include hydrogens, ethers and aromatic ketones, aliphatic ketones and alicyclic hydrocarbons, or aliphatic ketones and aromatic ketones. Specific examples of preferred combinations include toluene and tetralin, xylene and tetralin, toluene and acetophenone, xylene and acetophenone, tetrahydrofuran and tetralin, tetrahydrofuran and acetophenone, methyl ethyl ketone and tetralin, methyl ethyl ketone and acetophenone, and the like.

[P-type semiconductor compound]
Although there is no limitation in particular in the p-type semiconductor compound used by this invention, A low molecular organic semiconductor compound and a high molecular organic-semiconductor compound are mentioned.

(Low molecular organic semiconductor compounds)
The molecular weight of the low-molecular organic semiconductor compound is not particularly limited both at the upper limit and the lower limit, but is usually 5000 or less, preferably 2000 or less, and is usually 100 or more, preferably 200 or more.

  Further, the low molecular organic semiconductor compound preferably has crystallinity. A p-type semiconductor compound having crystallinity has a strong intermolecular interaction, and in the organic active layer 103, holes (holes) generated at the interface between the p-type semiconductor compound and the n-type semiconductor compound are efficiently formed. This is because it is expected that it can be transported to.

The crystallinity in the present invention is a property of a compound that takes a three-dimensional periodic array in which orientation is aligned by intermolecular interaction or the like. Examples of the method for measuring crystallinity include X-ray diffraction (XRD) or field effect mobility measurement. In particular, in the field effect mobility measurement, a crystalline compound having a hole mobility of 1.0 × 10 ⁽⁻⁵⁾ cm ² / (Vs) or more is preferable, and 1.0 × 10 ⁽⁻⁴⁾ cm ² / ( Vs) or more is more preferable. On the other hand, a crystalline compound having a hole mobility of usually 1.0 × 10 ⁽⁴⁾ cm ² / (Vs) or less is preferable, and a crystallinity of 1.0 × 10 ⁽³⁾ cm ² / (Vs) or less. A compound is more preferable, and a crystalline compound of 1.0 × 10 ⁽²⁾ cm ² / (Vs) or less is still more preferable.

  The low-molecular organic semiconductor compound is not particularly limited as long as it satisfies the above-mentioned performance. Specifically, it is a condensed aromatic hydrocarbon such as naphthacene, pentacene or pyrene; four or more thiophene rings such as α-sexithiophene Including oligothiophenes; including at least one of thiophene ring, benzene ring, fluorene ring, naphthalene ring, anthracene ring, thiazole ring, thiadiazole ring and benzothiazole ring, and a total of four or more linked; phthalocyanine compound and The metal complex; or a macrocyclic compound such as a porphyrin compound such as tetrabenzoporphyrin and a metal complex thereof. Preferably, they are a phthalocyanine compound and its metal complex, or a porphyrin compound and its metal complex.

  Examples of the porphyrin compound used as a p-type semiconductor compound and its metal complex (Q in the following formula is Q), the phthalocyanine compound and its metal complex (Q in the following formula is N) are, for example, compounds having the following structures: Is mentioned.

Here, M represents a metal or two hydrogen atoms. As the metal, in addition to a divalent metal such as Cu, Zn, Pb, Mg, Co or Ni, a trivalent or higher metal having an axial ligand. Examples thereof include TiO, VO, SnCl ₂ , AlCl, InCl, and Si.

Y ^{1 to} Y ⁴ are each independently a hydrogen atom or an alkyl group having 1 to 24 carbon atoms. The alkyl group having 1 to 24 carbon atoms is a saturated or unsaturated chain hydrocarbon group having 1 to 24 carbon atoms or a saturated or unsaturated cyclic hydrocarbon having 3 to 24 carbon atoms. . Among these, a saturated or unsaturated chain hydrocarbon group having 1 to 12 carbon atoms or a saturated or unsaturated cyclic hydrocarbon group having 3 to 12 carbon atoms is preferable.

  Among phthalocyanine compounds and metal complexes thereof, 29H, 31H-phthalocyanine, copper phthalocyanine complex, zinc phthalocyanine complex, titanium phthalocyanine oxide complex, magnesium phthalocyanine complex, lead phthalocyanine complex or copper 4 is preferable in order to obtain good photoelectric conversion efficiency. , 4 ′, 4 ″, 4 ′ ″-tetraaza-29H, 31H-phthalocyanine complex, more preferably 29H, 31H-phthalocyanine or copper phthalocyanine complex. In addition, the above kind of compound or a mixture of plural kinds of compounds may be used.

  Among porphyrin compounds and metal complexes thereof, 5,10,15,20-tetraphenyl-21H, 23H-porphine, 5,10,15,20-tetraphenyl-21H are preferable to obtain good photoelectric conversion efficiency. , 23H-porphine cobalt (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine copper (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine zinc (II) 5,10,15,20-tetraphenyl-21H, 23H-porphine nickel (II), 5,10,15,20-tetraphenyl-21H, 23H-porphine vanadium (IV) oxide, 5,10,15, 20-tetra (4-pyridyl) -21H, 23H-porphine, 29H, 31H-tetrabenzo [ , G, l, q] porphine, 29H, 31H-tetrabenzo [b, g, l, q] porphine cobalt (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine copper (II), 29H , 31H-tetrabenzo [b, g, l, q] porphine zinc (II), 29H, 31H-tetrabenzo [b, g, l, q] porphine nickel (II) or 29H, 31H-tetrabenzo [b, g, l , Q] porphine vanadium (IV) oxide, preferably 5,10,15,20-tetraphenyl-21H, 23H-porphine or 29H, 31H-tetrabenzo [b, g, l, q] porphine. In addition, you may use 1 type of compounds among the above, or a mixture of multiple types of compounds.

  As a method for forming a low molecular organic semiconductor compound, there are a method of forming a film by a vacuum deposition method and a method of forming a film by converting a low molecular organic semiconductor compound precursor into a low molecular organic semiconductor compound after coating. The latter is preferred because of the process advantage that coating can be formed.

(Low molecular organic semiconductor compound precursor)
A low molecular organic semiconductor compound precursor is a substance that changes its chemical structure and is converted into a low molecular organic semiconductor compound by applying an external stimulus such as heating or light irradiation. The low molecular organic semiconductor compound precursor is preferably excellent in film forming property. In particular, in order to be able to apply the coating method, it is preferable that the precursor itself can be applied in a liquid state, or the precursor is highly soluble in some solvent and can be applied as a solution. For this reason, the solubility with respect to the solvent of a low molecular organic-semiconductor compound precursor is usually 0.1 weight% or more, Preferably it is 0.5 weight% or more, More preferably, it is 1 weight% or more. On the other hand, the upper limit is not particularly limited, but is usually 50% by weight or less, preferably 40% by weight or less.

  The type of the solvent is not particularly limited as long as it can uniformly dissolve or disperse the semiconductor precursor compound. For example, aliphatic hydrocarbons such as hexane, heptane, octane, isooctane, nonane or decane; toluene, xylene , Aromatic hydrocarbons such as cyclohexylbenzene, chlorobenzene or orthodichlorobenzene; lower alcohols such as methanol, ethanol or propanol; ketones such as acetone, methyl ethyl ketone, cyclopentanone or cyclohexanone; ethyl acetate, butyl acetate or methyl lactate Esters such as: Chloroform, methylene chloride, dichloroethane, trichloroethane, trichloroethylene, and other halogen hydrocarbons; Ethyl ether, tetrahydrofuran, dioxane, and the like Le acids; or amides such as dimethylformamide or dimethylacetamide, and the like. Of these, aromatic hydrocarbons such as toluene, xylene, cyclohexylbenzene, chlorobenzene, or orthodichlorobenzene; ketones such as acetone, methyl ethyl ketone, cyclopentanone, or cyclohexanone; chloroform, methylene chloride, dichloroethane, trichloroethane, or trichloroethylene Halogen ethers; ethers such as ethyl ether, tetrahydrofuran or dioxane. More preferably, non-halogen aromatic hydrocarbons such as toluene, xylene or cyclohexylbenzene; non-halogen ketones such as cyclopentanone or cyclohexanone; or non-halogen aliphatic ethers such as tetrahydrofuran or 1,4-dioxane It is kind. Particularly preferred are non-halogen aromatic hydrocarbons such as toluene, xylene or cyclohexylbenzene. In addition, a solvent may be used individually by 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  Furthermore, it is preferable that the low molecular organic semiconductor compound precursor can be easily converted into a semiconductor compound. In the step of converting a low-molecular organic semiconductor compound precursor to a semiconductor compound, which will be described later, what kind of external stimulus is given to the semiconductor precursor is arbitrary, but usually heat treatment, light treatment, etc. are performed. From the viewpoint of ease of processing, heat treatment is preferable. In this case, it is preferable that a part of the skeleton of the low molecular organic semiconductor compound precursor has a solvophilic group with respect to a predetermined solvent that can be eliminated by a reverse Diels-Alder reaction.

  Moreover, it is preferable that a low molecular organic-semiconductor compound precursor is converted into a semiconductor compound with a high yield through a conversion process. At this time, the yield of the semiconductor compound obtained by conversion from the low molecular organic semiconductor compound precursor is arbitrary as long as the performance of the organic photoelectric conversion element is not impaired, but the low molecular organic obtained from the precursor of the low molecular organic semiconductor compound The yield of the semiconductor compound is usually 90 mol% or more, preferably 95 mol% or more, more preferably 99 mol% or more.

  The low molecular organic semiconductor compound precursor is not particularly limited as long as it has the above characteristics, and specifically, compounds described in JP-A-2007-324587 can be used. Particularly preferred examples include compounds represented by the following formula (A1).

In the formula (A1), at least one of X ¹ and X ² represents a group that forms a π-conjugated divalent aromatic ring, Z ¹ -Z ² is a group that can be removed by heat or light, The compound represented by the formula (A1) is obtained by elimination of Z ¹ -Z ² . Further, X ¹ and X ² which are not a group that forms a π-conjugated divalent aromatic ring represent a substituted or unsubstituted ethenylene group.

In the compound represented by the formula (A1), Z ¹ -Z ² is eliminated by heat or light as shown in the following chemical reaction formula, and a π-conjugated compound having high planarity is generated. This produced π-conjugated compound is a semiconductor compound that can be used in the present invention. In the present invention, the semiconductor compound preferably exhibits semiconductor characteristics.

  Examples of the compound represented by the formula (A1) include the following. T-Bu represents a t-butyl group. M represents an atomic group in which a divalent metal atom or a trivalent or higher metal and another atom are bonded.

  Specific examples of the conversion of the low molecular organic semiconductor compound precursor into a semiconductor compound include the following.

  The low molecular organic semiconductor compound precursor represented by the formula (A1) may have a structure in which positional isomers exist, and in that case, may consist of a mixture of a plurality of positional isomers. A low-molecular organic semiconductor compound precursor composed of a plurality of positional isomers is preferable because it has a higher solubility in a solvent than a low-molecular organic semiconductor compound precursor composed of a single isomer component, so that coating film formation is easy. The reason why the solubility is improved when a mixture of multiple positional isomers is used is that the detailed mechanism is not clear, but the crystallinity of the compound itself is potentially retained, but the mixture of multiple isomers is mixed in the solution. Therefore, it is assumed that the three-dimensional regular intermolecular interaction becomes difficult. In the present invention, the solubility of the precursor mixture composed of a plurality of isomeric compounds in a non-halogen solvent is usually 0.1% by weight or more, preferably 1% by weight or more, more preferably 5% by weight or more. Although there is no restriction | limiting in an upper limit, Usually, it is 50 weight% or less, More preferably, it is 40 weight% or less.

(High molecular organic semiconductor compounds)
The organic polymer semiconductor compound is not particularly limited, and is a conjugated polymer semiconductor such as polythiophene, polyfluorene, polyphenylene vinylene, polythienylene vinylene, polyacetylene, or polyaniline; or an oligothiophene substituted with an alkyl group or other substituent. Also included are polymer semiconductors. Moreover, the semiconductor polymer which copolymerized 2 or more types of monomer units is also mentioned. One kind of compound may be used alone, or a mixture of plural kinds of compounds may be used.

Examples of the polymer, for ^{example, Handbook of Conducting Polymers, 3 rd} Ed. (2 volumes), 2007, Materials Science and Engineering, 2001, 32, 1-40, Pure Appl. Chem. 2002, 74, 2031-3044, Handbook of THIOPHENE-BASED MATERIALS (2 volumes), 2009, etc. it can.

  The monomer skeleton of the polymer and the substituent of the monomer can be selected to control solubility, crystallinity, film formability, HOMO energy level, LUMO energy level, and the like. Moreover, being soluble in an organic solvent is preferable because a coating method can be used in the manufacturing process of an organic solar cell element.

  Specific examples of the polymer organic semiconductor compound include the following, but are not limited to the following.

  Among them, the p-type semiconductor compound is preferably a low molecular organic semiconductor compound such as condensed aromatic hydrocarbons such as naphthacene, pentacene, and pyrene, phthalocyanine compounds and metal complexes thereof, or porphyrin compounds such as tetrabenzoporphyrin (BP) and The metal complex and the polymer organic semiconductor compound is preferably a conjugated polymer semiconductor such as polythiophene. In addition, the above kind of compound or a mixture of plural kinds of compounds may be used.

  The p-type semiconductor compound layer preparation method is not particularly limited, but a coating method is preferable. The coating method can be performed by any of the following methods. Examples include spin coating method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method or curtain coating method. It is done.

  The low molecular weight organic semiconductor compound and / or the high molecular weight organic semiconductor compound may have some self-organized structure in the film-formed state, or may be in an amorphous state.

  The HOMO energy level of the p-type semiconductor compound is not particularly limited, but can be selected according to the type of the n-type semiconductor described later, and the HOMO energy level of the p-type semiconductor combined with the fullerene derivative is usually −5. 7 eV or more, more preferably −5.5 eV or more, on the other hand, usually −4.6 eV or less and −4.8 eV or less. When the HOMO energy level of the p-type semiconductor compound is −5.7 eV or more, the characteristics as the p-type semiconductor are improved, and when the HOMO energy level of the p-type semiconductor is −4.6 eV or less, the stability of the compound is improved. The open circuit voltage (Voc) can be improved. The LUMO energy level of the p-type semiconductor is not particularly limited, but can be selected depending on the type of the n-type semiconductor described later. In particular, the LUMO energy level of the p-type semiconductor combined with the fullerene derivative is usually − 3.7 eV or more, preferably -3.6 eV or more. On the other hand, it is usually −2.5 eV or less, preferably −2.7 eV or less. When the LUMO energy level of the p-type semiconductor is −2.5 eV or less, the band gap is adjusted and light energy having a long wavelength can be effectively absorbed, and the short-circuit current density can be improved. When the LUMO energy level of the p-type semiconductor is −3.7 eV or more, electron transfer to the n-type semiconductor is likely to occur, and the short-circuit current density can be improved.

[N-type semiconductor compound]
The n-type semiconductor compound is not particularly limited. Specifically, a fullerene derivative; a quinolinol derivative metal complex typified by 8-hydroxyquinoline aluminum; a condensed ring such as naphthalenetetracarboxylic diimide or perylenetetracarboxylic diimide Tetracarboxylic acid diimides; perylene diimide derivatives, terpyridine metal complexes, tropolone metal complexes, flavonol metal complexes, perinone derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazole derivatives, benzthiazole derivatives, benzothiadiazole derivatives, oxadiazole derivatives, thiadiazoles Derivatives, triazole derivatives, aldazine derivatives, bisstyryl derivatives, pyrazine derivatives, phenanthroline derivatives, quinoxaline derivatives, benzoquinoline derivatives Body, bipyridine derivatives, borane derivatives, anthracene, pyrene, total fluoride condensed polycyclic aromatic hydrocarbons such as naphthacene or pentacene; or single-walled carbon nanotubes, and the like.

  Among them, from the viewpoint of obtaining higher photoelectric conversion efficiency, fullerene derivatives, borane derivatives, thiazole derivatives, benzothiazole derivatives, benzothiadiazole derivatives, N-alkyl substituted naphthalene tetracarboxylic acid diimides and N-alkyl substituted perylene diimides Derivatives are preferred, fullerene derivatives, N-alkyl substituted perylene diimide derivatives and N-alkyl substituted naphthalene tetracarboxylic acid diimides are more preferred. One or two or more of these compounds can be used as the n-type semiconductor compound, and the n-type polymers described below may be used alone or in combination of two or more.

  Moreover, an n-type polymer is also mentioned as an n-type semiconductor compound. Specifically, although there is no particular limitation, condensed ring tetracarboxylic acid diimides such as naphthalene tetracarboxylic acid diimide and perylene tetracarboxylic acid diimide, perylene diimide derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazole derivatives, benzothiazoles Examples thereof include n-type polymers having at least one of a derivative, a benzothiadiazole derivative, an oxadiazole derivative, a thiadiazole derivative, a triazole derivative, a pyrazine derivative, a phenanthroline derivative, a quinoxaline derivative, a bipyridine derivative, and a borane derivative. Among them, from the viewpoint of obtaining higher photoelectric conversion efficiency, among borane derivatives, thiazole derivatives, benzthiazole derivatives, benzothiadiazole derivatives, N-alkyl substituted naphthalene tetracarboxylic acid diimides and N-alkyl substituted perylene diimide derivatives A polymer having at least one constituent unit is preferred, and at least one of the n-type polymer having an N-alkyl-substituted perylene diimide derivative and an N-alkyl-substituted naphthalenetetracarboxylic acid diimide as a constituent unit is a constituent unit. More preferred are n-type polymers.

  The active layer 103 preferably contains fullerene or a fullerene derivative as an n-type semiconductor compound in that high photoelectric conversion efficiency can be obtained when combined with the phenanthroline derivative according to the present invention contained in the electron extraction layer 104. . It is particularly preferable that the active layer 103 contains a fullerene derivative having a silylalkyl group.

Fullerene is a carbon cluster having a closed shell structure. The carbon number of fullerene is not particularly limited as long as it is an even number of 60 or more and 130 or less. Examples of fullerenes include C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₂ , C ₈₄ , C ₉₀ , C ₉₄ , C ₉₆ and higher carbon clusters having more carbon than these. . Among these, _C60 or _C70 is preferable. As fullerenes, carbon-carbon bonds on some fullerene rings may be broken. Some carbon atoms may be replaced with other atoms. Furthermore, a metal atom, a nonmetal atom, or an atomic group composed of these may be included in the fullerene cage.

  Below, the preferable example of a fullerene derivative is demonstrated in detail.

(Fullerene derivative)
As the fullerene derivative, those having partial structures represented by the following general formulas (n1), (n2), (n3) and (n4) are preferably used.

In formulas (n1) to (n4), FLN represents the above-mentioned fullerene. a, b, c and d are integers, and the sum of a, b, c and d is usually 1 or more, and usually 5 or less, preferably 3 or less. The partial structures in (n1), (n2), (n3) and (n4) are added to the same 5-membered ring or 6-membered ring in the fullerene skeleton. In the general formula (n1), —R ¹⁷ and — (CH ₂ ) _L — are respectively added to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. . In the general formula (n2), —C (R ²¹ ) (R ²² ) —N (R ²³ ) —C with respect to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. (R ²⁴ ) (R ²⁵ ) — are added to form a 5-membered ring. In the general formula (n3), —C (R ²⁶ ) (R ²⁷ ) —C—C—C (R) with respect to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton. ^{28) (R 29)} - forms an additional six-membered ring. In the general formula (n4), —C (R ³⁰ ) (R ³¹ ) — is added to two adjacent carbon atoms on the same 5-membered ring or 6-membered ring in the fullerene skeleton to form a 3-membered ring. doing. L is an integer of 1 to 8. L is preferably an integer of 1 to 4, more preferably an integer of 1 to 2.

R ¹⁷ in the general formula (n1) is an alkyl group having 1 to 14 carbon atoms which may have a substituent, an alkoxy group having 1 to 14 carbon atoms which may have a substituent, or a substituent. Is an aromatic group which may have

  The alkyl group is preferably an alkyl group having 1 to 10 carbon atoms, more preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group or an isobutyl group, and even more preferably a methyl group or an ethyl group. .

  The alkoxy group is preferably an alkoxy group having 1 to 10 carbon atoms, more preferably an alkoxy group having 1 to 6 carbon atoms, and particularly preferably a methoxy group or an ethoxy group.

  The aromatic group is preferably an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, more preferably a phenyl group, a thienyl group, a furyl group, or a pyridyl group. More preferred are groups or thienyl groups.

  As the substituent that the alkyl group, alkoxy group and aromatic group may have, a halogen atom or a silyl group is preferable. As the halogen atom, a fluorine atom is preferable. The silyl group is preferably a diarylalkylsilyl group, a dialkylarylsilyl group, a triarylsilyl group or a trialkylsilyl group, more preferably a dialkylarylsilyl group, and even more preferably a dimethylarylsilyl group.

R ¹⁸ to R ²⁰ in the general formula (n1) represents each independently a substituent, a hydrogen atom, have an alkyl group or a substituent having 1 to 14 carbon atoms which may have a substituent An aromatic group that may be used.

  As the alkyl group, an alkyl group having 1 to 10 carbon atoms is preferable, and a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, or an n-hexyl group is preferable. . The substituent that the alkyl group may have is preferably a halogen atom. As the halogen atom, a fluorine atom is preferable. The alkyl group substituted with a fluorine atom is preferably a perfluorooctyl group, a perfluorohexyl group or a perfluorobutyl group.

  The aromatic group is preferably an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, more preferably a phenyl group, a thienyl group, a furyl group, or a pyridyl group. Or a thienyl group is more preferable. Examples of the substituent that the aromatic group may have include a fluorine atom, an alkyl group having 1 to 14 carbon atoms, a fluorinated alkyl group having 1 to 14 carbon atoms, an alkoxy group having 1 to 14 carbon atoms, or An aromatic group having 3 to 10 carbon atoms is preferred, a fluorine atom or an alkoxy group having 1 to 14 carbon atoms is more preferred, and a methoxy group, n-butoxy group or 2-ethylhexyloxy group is still more preferred. When the aromatic group has a substituent, the number is not limited, but is preferably 1 or more and 3 or less, and more preferably 1. When the aromatic group has a plurality of substituents, the types of the substituents may be different, but are preferably the same.

R ^{21 to} R ²⁵ in general formula (n2) are each independently a hydrogen atom, an alkyl group having 1 to 14 carbon atoms which may have a substituent, or an aromatic group which may have a substituent. It is a group. The alkyl group is preferably a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, n-hexyl group or n-octyl group, and more preferably a methyl group. As the aromatic group, an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms is preferable, a phenyl group or a pyridyl group is more preferable, and a phenyl group is further preferable.

  The substituent that the alkyl group may have is preferably a halogen atom. As the halogen atom, a fluorine atom is preferable. The alkyl group substituted with a fluorine atom is preferably a perfluorooctyl group, a perfluorohexyl group or a perfluorobutyl group.

  The substituent that the aromatic group may have is not particularly limited, but is preferably a fluorine atom, an alkyl group having 1 to 14 carbon atoms, or an alkoxy group having 1 to 14 carbon atoms. The alkyl group may be substituted with a fluorine atom. More preferably, it is an alkoxy group having 1 to 14 carbon atoms, and more preferably a methoxy group. When it has a substituent, the number is not limited, but it is preferably 1 or more and 3 or less, more preferably 1. The types of substituents may be different, but are preferably the same.

Ar ¹ in the general formula (n3) is an optionally substituted aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms, preferably A phenyl group, a naphthyl group, a biphenyl group, a thienyl group, a furyl group, a pyridyl group, a pyrimidyl group, a quinolyl group or a quinoxalyl group, more preferably a phenyl group, a thienyl group or a furyl group. Although there is no limitation as a substituent which you may have, a fluorine atom, a chlorine atom, a hydroxyl group, a cyano group, a silyl group, a boryl group, an amino group which may be substituted with an alkyl group, an alkyl having 1 to 14 carbon atoms Group, an alkoxy group having 1 to 14 carbon atoms, an alkylcarbonyl group having 1 to 14 carbon atoms, an alkylthio group having 1 to 14 carbon atoms, an alkenyl group having 1 to 14 carbon atoms, and an alkyl group having 1 to 14 carbon atoms. An alkynyl group, an ester group, an arylcarbonyl group, an arylthio group, an aryloxy group, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or a heterocyclic group having 2 to 20 carbon atoms is preferable, a fluorine atom, and one or more carbon atoms An alkyl group having 14 or less, an alkoxy group having 1 to 14 carbon atoms, an ester group, an alkylcarbonyl group having 1 to 14 carbon atoms, or an aryl group Sulfonyl group is more preferable. The alkyl group having 1 to 14 carbon atoms may be substituted with fluorine.

  The alkyl group having 1 to 14 carbon atoms is preferably a methyl group, an ethyl group or a propyl group. The alkoxy group having 1 to 14 carbon atoms is preferably a methoxy group, an ethoxy group, or a propoxyl group. The alkylcarbonyl group having 1 to 14 carbon atoms is preferably an acetyl group. As the ester group, a methyl ester group or an n-butyl ester group is preferable. As the arylcarbonyl group, a benzoyl group is preferable.

  When it has a substituent, the number is not limited, but it is preferably 1 or more and 4 or less, more preferably 1 or more and 3 or less. When there are a plurality of substituents, the types may be different, but are preferably the same.

R ^{26 to} R ²⁹ in the general formula (n3) each independently have a hydrogen atom, an alkyl group which may have a substituent, an amino group which may have a substituent, or a substituent. It is an optionally substituted alkoxy group or an optionally substituted alkylthio group. R ²⁶ or R ²⁷ may form a ring with any one of R ²⁸ or R ²⁹ .

The structure in the case of forming a ring can be represented by, for example, the general formula (n5) which is a bicyclo structure in which an aromatic group is condensed. F in the general formula (n5) is the same as c, and X ³ is an oxygen atom, a sulfur atom, an amino group, an alkylene group or an arylene group. The alkylene group preferably has 1 to 2 carbon atoms. The arylene group preferably has 5 to 12 carbon atoms, such as a phenylene group.

  The amino group may be substituted with an alkyl group having 1 to 6 carbon atoms such as a methyl group or an ethyl group. The alkylene group is an alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or 2 to 20 carbon atoms. The aromatic heterocyclic group may be substituted. The arylene group is an alkoxy group having 1 to 6 carbon atoms such as a methoxy group, an aliphatic hydrocarbon group having 1 to 5 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or 2 to 20 carbon atoms. The aromatic heterocyclic group may be substituted.

R ³⁰ and R ^{31 in} general formula (n4) each independently have a hydrogen atom, an alkoxycarbonyl group, an alkyl group having 1 to 14 carbon atoms which may have a substituent, or a substituent. An aromatic group that may be used.

  The alkoxy group in the alkoxycarbonyl group is preferably an alkoxy group having 1 to 12 carbon atoms or a fluorinated alkoxy group having 1 to 12 carbon atoms, more preferably an alkoxy group having 1 to 12 carbon atoms, a methoxy group, an ethoxy group A group, n-propoxy group, isopropoxy group, n-butoxy group, isobutoxy group, n-hexoxy group, n-octoxy group, 2-propylpentoxy group, 2-ethylhexoxy group, cyclohexylmethoxy group or benzyloxy group A methoxy group, an ethoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group or an n-hexoxy group is particularly preferable.

  As the alkyl group, a linear alkyl group having 1 to 8 carbon atoms is preferable, and an n-propyl group is more preferable. The substituent that the alkyl group may have is not particularly limited, but is preferably an alkoxycarbonyl group. The alkoxy group of the alkoxycarbonyl group is preferably an alkoxy group having 1 to 14 carbon atoms or a fluorinated alkoxy group, more preferably a hydrocarbon group having 1 to 14 carbon atoms, a methoxy group, an ethoxy group, or an n-propoxy group. , Isopropoxy group, n-butoxy group, isobutoxy group, n-hexoxy group, octoxy group, 2-propylpentoxy group, 2-ethylhexoxy group, cyclohexylmethoxy group or benzyloxy group, more preferably methoxy group or n-butoxy group The group is particularly preferred.

  As the aromatic group, an aromatic hydrocarbon group having 6 to 20 carbon atoms or an aromatic heterocyclic group having 2 to 20 carbon atoms is preferable, and a phenyl group, a biphenyl group, a thienyl group, a furyl group, or a pyridyl group is preferable. More preferred are a phenyl group and a thienyl group. The substituent that the aromatic group may have is preferably an alkyl group having 1 to 14 carbon atoms, a fluorinated alkyl group having 1 to 14 carbon atoms, or an alkoxy group having 1 to 14 carbon atoms. An alkoxy group having a number of 1 or more and 14 or less is more preferable, and a methoxy group or 2-ethylhexyloxy group is particularly preferable. When it has a substituent, the number is not limited, but it is preferably 1 or more and 3 or less, more preferably 1. The types of substituents may be different or the same, preferably the same.

As the structure of the general formula (n4), preferably R ³⁰ and R ³¹ are both alkoxycarbonyl groups, R ³⁰ and R ³¹ are both aromatic groups, or R ³⁰ is an aromatic group and R ³¹ is 3- (alkoxycarbonyl) propyl group.

  The n-type semiconductor compound used in the present invention may be a single compound or a mixture of multiple compounds.

  In order for the fullerene derivative to be applicable to a coating method, the fullerene derivative itself can be applied in a liquid state, or the fullerene derivative can be applied as a solution with high solubility in some solvent. preferable. As a preferable range of solubility, the solubility in toluene at 25 ° C. is usually 0.1% by weight or more, preferably 0.4% by weight or more, more preferably 0.7% by weight or more. It is preferable that the solubility of the fullerene derivative is 0.1% by weight or more because the dispersion stability of the fullerene derivative is increased and aggregation, sedimentation, separation, and the like are less likely to occur.

  The solvent for the fullerene derivative is not particularly limited as long as it is a nonpolar organic solvent, but a non-halogen solvent is preferable. A halogen-based solvent such as dichlorobenzene is also possible, but an alternative is required in terms of environmental impact. Examples of non-halogen solvents include non-halogen aromatic hydrocarbons. Of these, toluene, xylene, cyclohexylbenzene, and the like are preferable.

(Method for producing fullerene derivative)
The method for producing the fullerene derivative is not particularly limited. For example, as a method for synthesizing fullerene having the partial structure (n1), International Publication No. 2008/059771 pamphlet and J. Org. Am. Chem. Soc. 2008, 130 (46), 15429-15436.

  As a method for synthesizing fullerene having the partial structure (n2), J. et al. Am. Chem. Soc. 1993, 115, 9798-9799, Chem. Mater. 2007, 19, 5363-5372 and Chem. Mater. The method described in 2007, 19, 5194-5199 can be used.

  As a synthesis method of fullerene having the partial structure (n3), Angew. Chem. Int. Ed. Engl. 1993, 32, 78-80, Tetrahedron Lett. The methods described in 1997, 38, 285-288, WO 2008/018931 and WO 2009/086212 can be used.

  As a method for synthesizing fullerene having a partial structure (n4), J. et al. Chem. Soc. Perkin Trans. 1, 1997 1595, Thin Solid Films 489 (2005) 251-256, Adv. Funct. Mater. 2005, 15, 1979-1987 and J. Org. Org. Chem. The method described in 1995, 60, 532-538 can be used.

(N-alkyl substituted perylene diimide derivatives)
The N-alkyl-substituted perylene diimide derivative is not particularly limited, and specifically, International Publication No. 2008/063609, International Publication No. 2009/115513, International Publication No. 2009/098250, International Publication No. 2009. / 000756 and the compound described in international publication 2009/091670 are mentioned. High electron mobility and absorption in the visible range are preferable because they contribute to both charge transport and power generation.

(Naphthalene tetracarboxylic acid diimide)
The naphthalenetetracarboxylic acid diimide is not particularly limited, and specific examples thereof include compounds described in International Publication No. 2008/063609, International Publication No. 2007/146250 and International Publication No. 2009/000756. . It is preferable from the viewpoint of high electron mobility, high solubility, and excellent coating properties.

(N-type polymer)
The n-type polymer is not particularly limited, but condensed ring tetracarboxylic acid diimides such as naphthalenetetracarboxylic acid diimide and perylenetetracarboxylic acid diimide, perylene diimide derivatives, benzimidazole derivatives, benzoxazole derivatives, thiazole derivatives, benzothiazoles Examples thereof include n-type polymers having at least one of a derivative, a benzothiadiazole derivative, an oxadiazole derivative, a thiadiazole derivative, a triazole derivative, a pyrazine derivative, a phenanthroline derivative, a quinoxaline derivative, a bipyridine derivative, and a borane derivative.

  Among them, a polymer having at least one of a borane derivative, a thiazole derivative, a benzothiazole derivative, a benzothiadiazole derivative, an N-alkyl-substituted naphthalenetetracarboxylic acid diimide and an N-alkyl-substituted perylene diimide derivative as a constituent unit is provided. Preferably, an n-type polymer having at least one of a N-alkyl-substituted perylene diimide derivative and an N-alkyl-substituted naphthalene tetracarboxylic acid diimide as a constituent unit is more preferable. Two or more of these may be configured units. Furthermore, you may use together 2 or more types of polymers as an n-type polymer.

  Specific examples thereof include compounds described in International Publication No. 2009/098253, International Publication No. 2009/098250, International Publication No. 2010/012710, and International Publication No. 2009/098250. Since it has absorption in the visible region, it is preferable from the viewpoint of contributing to power generation, high viscosity, and excellent coating properties.

  Although there is no special restriction | limiting about the n-type semiconductor compound layer preparation method, The application | coating method is preferable. The coating method can be performed by any of the following methods. Examples include spin coating method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method or curtain coating method. It is done.

  The n-type semiconductor compound may have some self-organized structure in a film-formed state, or may be in an amorphous state.

  The energy level of the lowest unoccupied orbital (LUMO) of the n-type semiconductor compound is not particularly limited. For example, the value for the vacuum level calculated by a cyclic voltammogram measurement method is usually −3.85 eV or more, preferably − 3. 80 eV or more. In order to efficiently move electrons from the electron donor layer (p-type semiconductor layer) to the electron acceptor layer (n-type semiconductor layer), the minimum vacancy of the materials used for each electron donor layer and electron acceptor layer is required. The relative relationship between orbital (LUMO) energy levels is important. Specifically, the LUMO energy level of the material of the electron donor layer is higher than the LUMO energy level of the material of the electron acceptor layer by a predetermined energy, in other words, the electron affinity of the electron acceptor is an electron. It is preferable that the predetermined energy is larger than the electron affinity of the donor. Since the open circuit voltage (Voc) is determined by the difference between the highest occupied orbital (HOMO) energy level of the material of the electron donor layer and the LUMO energy level of the material of the electron acceptor layer, the LUMO energy of the electron acceptor layer When the level is increased, Voc tends to increase. On the other hand, the LUMO value is usually −1.0 eV or less, preferably −2.0 eV or less, more preferably −3.0 eV or less, and still more preferably −3.3 eV or less. By lowering the LUMO energy level of the electron acceptor, electrons tend to move and the short circuit current (Jsc) tends to increase.

  As a method for calculating the value of the LUMO energy level of the n-type semiconductor, there are a method of theoretically obtaining a calculated value and a method of actually measuring. Theoretically calculated methods include semi-empirical molecular orbital methods and non-empirical molecular orbital methods. Examples of the actual measurement method include ultraviolet-visible absorption spectrum measurement method and cyclic voltammogram measurement method. Among them, the cyclic voltammogram measurement method is preferable.

<Substrate (106)>
The photoelectric conversion element according to the present invention usually has a substrate 106 that serves as a support. That is, an electrode, an active layer, and a buffer layer are formed on the substrate. The material of the substrate (substrate material) is arbitrary as long as the effects of the present invention are not significantly impaired. Suitable examples of substrate materials include inorganic materials such as quartz, glass, sapphire, and titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluorine A resin film, a polyolefin such as vinyl chloride or polyethylene; an organic material such as cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, polynorbornene or epoxy resin; a paper material such as paper or synthetic paper; or Examples thereof include composite materials such as those obtained by coating or laminating a surface of a metal such as stainless steel, titanium, or aluminum to impart insulation.

  Examples of the glass include soda glass, blue plate glass, and alkali-free glass. As for the glass material, alkali-free glass is preferred because it is better that there are fewer ions eluted from the glass.

  There is no restriction | limiting in the shape of the board | substrate 106, For example, shapes, such as a board, a film, a sheet | seat, can be used. There is no limitation on the film thickness of the substrate 106. However, it is usually 5 μm or more, particularly 20 μm or more. On the other hand, it is usually preferably 20 mm or less, particularly preferably 10 mm or less. It is preferable that the thickness of the substrate is 5 μm or more because the possibility that the strength of the semiconductor device is insufficient is reduced. It is preferable that the film thickness of the substrate is 20 mm or less because the cost is suppressed and the weight is not increased. When the substrate is glass, the film thickness is usually 0.01 mm or more, preferably 0.1 mm or more, while it is usually 1 cm or less, preferably 0.5 cm or less. When the film thickness of the glass substrate is 0.01 mm or more, the mechanical strength increases and it is difficult to break, which is preferable. It is preferable that the thickness of the glass substrate is 0.5 cm or less without increasing the weight.

<Electrodes (101, 105)>
The electrodes (101, 105) according to the present invention have a function of collecting holes and electrons generated by light absorption. Therefore, the pair of electrodes includes an electrode 101 suitable for collecting holes (hereinafter also referred to as an anode) and an electrode 105 suitable for collecting electrons (hereinafter also referred to as a cathode). Are preferably used. Any one of the pair of electrodes may be translucent, and both may be translucent. Translucency means that sunlight passes through 40% or more. In addition, it is preferable that the transparent electrode has a solar ray transmittance of 70% or more in order to allow light to reach the active layer through the transparent electrode. The light transmittance can be measured with a normal spectrophotometer.

  The electrode 101 (anode) suitable for collecting holes is generally an electrode made of a conductive material having a work function higher than that of the cathode and having a function of smoothly extracting holes generated in the organic active layer 103. It is.

  Examples of the material of the anode 101 include conductive metal oxides such as nickel oxide, tin oxide, indium oxide, indium tin oxide (ITO), indium-zirconium oxide (IZO), titanium oxide, indium oxide, and zinc oxide. Or a metal such as gold, platinum, silver, chromium or cobalt, or an alloy thereof. Since these substances have a high work function, they are preferable, and further, a conductive polymer material represented by PEDOT / PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid can be laminated. When laminating such a conductive polymer, the work function of the conductive polymer material is high, so it is suitable for cathodes such as aluminum and magnesium, even if it is not a material with a high work function as described above. It is also possible to use a metal.

  A PEDOT / PSS in which a polythiophene derivative is doped with polystyrene sulfonic acid, or a conductive polymer material in which polypyrrole or polyaniline is doped with iodine or the like can also be used as the anode material.

  When the anode 101 is a transparent electrode, a light-transmitting conductive metal oxide such as ITO, zinc oxide, or tin oxide is preferably used as the material of the anode 101, and ITO is particularly preferable.

  The film thickness of the anode 101 is not particularly limited, but is usually 10 nm or more, preferably 20 nm or more, and more preferably 50 nm or more. On the other hand, it is usually 10 μm or less, preferably 1 μm or less, more preferably 500 nm or less. When the film thickness of the anode 101 is 10 nm or more, the sheet resistance is suppressed, and when the film thickness of the anode 101 is 10 μm or less, light can be efficiently converted into electricity without decreasing the light transmittance. it can. When used for a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance.

  The sheet resistance of the anode 101 is not particularly limited, but is usually 1Ω / □ or more, on the other hand, 1000Ω / □ or less, preferably 500Ω / □ or less, more preferably 100Ω / □ or less.

  As a method for forming the anode 101, there are a vacuum film formation method such as vapor deposition or sputtering, or a method of forming a film by applying an ink containing nanoparticles or a precursor.

  An electrode 105 (cathode) suitable for collecting electrons is generally made of a conductive material having a work function higher than that of the anode, and has a function of smoothly extracting electrons generated in the organic active layer 103. The cathode 105 is adjacent to the electron extraction layer 104.

  Examples of the material of the cathode 105 include metals such as platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, cesium, calcium, and magnesium, and alloys thereof; Examples thereof include inorganic salts such as lithium and cesium fluoride; or metal oxides such as nickel oxide, aluminum oxide, lithium oxide, and cesium oxide. These materials are preferable because they are materials having a low work function. Similarly to the anode 101, the cathode 105 can be made of a material having a high work function suitable for the anode 101 when the electron extraction layer 104 includes an n-type semiconductor such as titania having conductivity. From the viewpoint of electrode protection, the material of the anode 101 is preferably a metal such as platinum, gold, silver, copper, iron, tin, aluminum, calcium or indium and an alloy using these metals.

  The film thickness of the cathode 105 is not particularly limited, but is usually 10 nm or more, preferably 20 nm or less, and more preferably 50 nm or more. On the other hand, it is usually 10 μm or less, preferably 1 μm or less, more preferably 500 nm or less. When used for a transparent electrode, it is necessary to select a film thickness that achieves both light transmittance and sheet resistance. When the film thickness of the cathode 105 is 10 nm or more, sheet resistance is suppressed, and when the film thickness of the cathode 105 is 10 μm or less, light can be efficiently converted into electricity without a decrease in light transmittance. it can.

  The sheet resistance of the cathode 105 is not particularly limited, but is usually 1000Ω / □ or less, preferably 500Ω / □ or less, and more preferably 100Ω / □ or less. Although there is no restriction on the lower limit, it is usually 1Ω / □ or more.

  Examples of the method for forming the cathode 105 include a vacuum film formation method such as vapor deposition or sputtering, or a method in which an ink containing nanoparticles or a precursor is applied to form a film.

  Furthermore, the anode 101 or the cathode 105 may have a laminated structure of two or more layers, and characteristics (electric characteristics, wetting characteristics, etc.) may be improved by surface treatment.

  After laminating anode 101 and cathode 105, the photoelectric conversion element is heated in a temperature range of usually 50 ° C. or higher, preferably 80 ° C. or higher, usually 300 ° C. or lower, preferably 280 ° C. or lower, more preferably 250 ° C. or lower. It is preferable to do this (this step may be referred to as an annealing treatment step). It is preferable to perform the annealing treatment at 50 ° C. or higher because an effect of improving the adhesion between the electron extraction layer 104 and the electrode 105 and / or the electron extraction layer 104 and the active layer 103 can be obtained. It is preferable to set the temperature of the annealing treatment step to 300 ° C. or lower because the possibility that the organic compound contained in the active layer 103 is thermally decomposed is reduced. In addition, it is not necessary to perform heating at a constant temperature. For example, stepwise heating may be performed within the above range.

  The heating time is usually 1 minute or longer, preferably 3 minutes or longer, and usually 3 hours or shorter, preferably 1 hour or shorter. By heating for 1 minute or longer, the effect of the annealing treatment is increased, and the decomposition of the compound can be prevented by setting the heating time to 3 hours or shorter. This annealing process is preferably terminated when the open circuit voltage, the short circuit current, and the fill factor, which are parameters of the solar cell performance, reach a constant value. The annealing treatment is preferably performed under normal pressure and in an inert gas atmosphere.

  As a heating method, the photoelectric conversion element may be placed on a heat source such as a hot plate, or the photoelectric conversion element may be put in a heating atmosphere such as an oven. Moreover, the heating of the photoelectric conversion element may be performed by a batch method or a continuous method.

  By this annealing treatment step, the adhesion between the electron extraction layer 104 and the cathode 105 and / or the electron extraction layer 104 and the organic active layer 103 can be improved. For this reason, the heat resistance and durability of the photoelectric conversion element can be improved, and the self-organization of the organic active layer can be promoted.

<Photoelectric conversion characteristics>
In order to put the photoelectric conversion element into practical use, it is also important that the photoelectric conversion element has high photoelectric conversion efficiency and high durability, in addition to simple manufacture of the photoelectric conversion element. As described above, the photoelectric conversion element using the phenanthroline derivative according to the present invention as the electron extraction layer material can obtain relatively high photoelectric conversion efficiency and can have high durability or heat resistance. Here, high durability means that the photoelectric conversion efficiency after storing under predetermined conditions does not decrease much compared to the photoelectric conversion efficiency immediately after production. In addition, high heat resistance means that the photoelectric conversion efficiency after the annealing treatment is improved or at least does not decrease much compared to the photoelectric conversion efficiency before the annealing treatment.

In the present specification, the photoelectric conversion efficiency is obtained as follows. That is, the current / voltage characteristics are measured by irradiating the photoelectric conversion element with light of AM1.5G at an irradiation intensity of 100 mW / cm ^{2 using a} solar simulator. From this current / voltage curve, photoelectric conversion characteristics such as photoelectric conversion efficiency (PCE), short-circuit current, open-circuit voltage, FF (fill factor), series resistance, and shunt resistance can be obtained.

Moreover, a maintenance factor is defined as follows as a parameter which shows durability or heat resistance of a photoelectric conversion element.
(Maintenance rate) = (Photoelectric conversion efficiency after storage) / (Photoelectric conversion efficiency before storage) or
(Maintenance rate) = (Photoelectric conversion efficiency after annealing) / (Photoelectric conversion efficiency before annealing)

  The photoelectric conversion efficiency of the photoelectric conversion element according to the present invention is not particularly limited, but is usually 1% or more, preferably 1.5% or more, more preferably 2% or more. On the other hand, there is no particular limitation on the upper limit, and the higher the better.

  In particular, the photoelectric conversion element according to the present invention has a photoelectric conversion efficiency after storage for 8 weeks at room temperature in a nitrogen atmosphere, preferably 1% or more, more preferably 1.5% or more, and further preferably 2% or more. Especially preferably, it is 3% or more. On the other hand, there is no particular limitation on the upper limit, and the higher the better.

  The photoelectric conversion element according to the present invention preferably has a maintenance rate of 60% or more, more preferably 80% or more, and 95% or more when an annealing treatment is performed at 120 ° C. for 1 minute. Is more preferable, and 100% or more is particularly preferable. There is no particular upper limit, and the higher the better.

  The photoelectric conversion element according to the present invention preferably has a maintenance rate of 60% or more, more preferably 80% or more, and 90% or more when an annealing process is performed at 120 ° C. for 3 minutes. Is more preferable, and 100% or more is particularly preferable. There is no particular upper limit, and the higher the better.

  The photoelectric conversion element according to the present invention preferably has a maintenance rate of 90% or more, more preferably 95% or more, and 97% or more when stored for 8 weeks at room temperature in a nitrogen atmosphere. More preferably, it is particularly preferably 98% or more. There is no particular upper limit, and the higher the better.

  In addition, the photoelectric conversion element according to the present invention has a retention rate when stored at room temperature in a nitrogen atmosphere for 8 weeks after annealing at 120 ° C. for 3 minutes (in this case, (retention rate) = (photoelectric conversion efficiency after storage) / (Photoelectric conversion efficiency before annealing treatment)) is preferably 60% or more, more preferably 80% or more, further preferably 90% or more, and particularly preferably 100% or more. . There is no particular upper limit, and the higher the better.

<Solar cell module>
[Solar cell module 13]
The photoelectric conversion element 107 according to the present invention is preferably used in a solar cell as a solar cell element, particularly in a thin film solar cell.

  FIG. 2 is a cross-sectional view schematically showing the configuration of a thin film solar cell as one embodiment of the present invention. As shown in FIG. 2, the thin film solar cell 14 of this embodiment includes a weather-resistant protective film 1, an ultraviolet cut film 2, a gas barrier film 3, a getter material film 4, a sealing material 5, and a solar cell element. 6, a sealing material 7, a getter material film 8, a gas barrier film 9, and a back sheet 10 are provided in this order. And light is irradiated from the side (downward in the figure) where the weather-resistant protective film 1 is formed, and the solar cell element 6 generates power. In addition, when using a highly waterproof sheet such as a sheet in which a fluororesin film is bonded to both surfaces of an aluminum foil as the back sheet 10 described later, the getter material film 8 and / or the gas barrier film 9 may not be used depending on the application. Good.

[Weather-resistant protective film 1]
The weather-resistant protective film 1 is a film that protects the solar cell element 6 from weather changes. Some components of the solar cell element 6 are deteriorated by temperature change, humidity change, natural light, and / or erosion caused by wind and rain. Therefore, by covering the solar cell element 6 with the weather-resistant protective film 1, the solar cell element 6 and the like are protected from weather changes and the like, and the power generation capacity is kept high.

  Since the weather resistant protective film 1 is located on the outermost layer of the thin film solar cell 14, the surface covering material of the thin film solar cell 14 such as weather resistance, heat resistance, transparency, water repellency, stain resistance and / or mechanical strength is provided. It is preferable to have a property suitable for the above and to maintain it for a long period of time in outdoor exposure.

  Moreover, the weather-resistant protective film 1 is preferably one that transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the light transmittance of visible light (wavelength 360 or more and 830 nm or less) is preferably 80% or more, more preferably 90% or more, and particularly preferably 95%.

  Furthermore, since the thin-film solar cell 14 is often heated by receiving light, it is preferable that the weather-resistant protective film 1 also has heat resistance. From this viewpoint, the melting point of the constituent material of the weather-resistant protective film 1 is usually 100 ° C. or higher, preferably 120 ° C. or higher, more preferably 130 ° C. or higher, and usually 350 ° C. or lower, preferably 320 ° C. or lower. Preferably it is 300 degrees C or less. By increasing the melting point, it is possible to reduce the possibility that the weather resistant protective film 1 is melted and deteriorated when the thin film solar cell 14 is used.

  The material which comprises the weather-resistant protective film 1 is arbitrary as long as it can protect the solar cell element 6 from a weather change. Examples of such materials are polyethylene resin, polypropylene resin, cyclic polyolefin resin, AS (acrylonitrile-styrene) resin, ABS (acrylonitrile-butadiene-styrene) resin, polyvinyl chloride resin, fluorine resin, polyethylene terephthalate, polyethylene naphthalate. Examples thereof include polyester resins such as phthalates, phenol resins, polyacrylic resins, polyamide resins such as various nylons, polyimide resins, polyamide-imide resins, polyurethane resins, cellulose resins, silicon resins, and polycarbonate resins.

  Among them, fluorine resin is preferable, and specific examples thereof include polytetrafluoroethylene (PTFE), 4-fluoroethylene-perchloroalkoxy copolymer (PFA), 4-fluoroethylene-6-fluoride. Propylene copolymer (FEP), 2-ethylene-4-fluoroethylene copolymer (ETFE), poly-3-fluoroethylene chloride (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), etc. Can be mentioned.

  In addition, the weather-resistant protective film 1 may be formed with 1 type of material, and may be formed with 2 or more types of materials. Moreover, although the weather-resistant protective film 1 may be formed with the single layer film, the laminated | multilayer film provided with the film of two or more layers may be sufficient as it.

  The thickness of the weather-resistant protective film 1 is not particularly specified, but is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and usually 200 μm or less, preferably 180 μm or less, more preferably 150 μm or less. Increasing the thickness tends to increase mechanical strength, and decreasing the thickness tends to increase flexibility.

  Moreover, you may perform surface treatments, such as a corona treatment and / or a plasma treatment, for the weather-resistant protective film 1 in order to improve adhesiveness with another film.

  The weatherproof protective film 1 is preferably provided on the outer side as much as possible in the thin-film solar cell 14. This is because more of the constituent members of the thin-film solar cell 14 can be protected.

[UV cut film 2]
The ultraviolet cut film 2 is a film that prevents the transmission of ultraviolet rays. Some components of the thin film solar cell 14 are deteriorated by ultraviolet rays. Some of the gas barrier films 3, 9 and the like are deteriorated by ultraviolet rays depending on the type. Therefore, the ultraviolet cut film 2 is provided in the light receiving portion of the thin-film solar cell 14, and the ultraviolet cut film 2 covers the light receiving surface 6a of the solar cell element 6, whereby the solar cell element 6 and, if necessary, the gas barrier films 3, 9 and the like. Can be protected from ultraviolet rays and the power generation capacity can be kept high.

  The degree of the ability to suppress the transmission of ultraviolet rays required for the ultraviolet cut film 2 is such that the transmittance of ultraviolet rays (for example, wavelength 300 nm) is preferably 50% or less, more preferably 30% or less, and particularly preferably. 10% or less.

  Further, the ultraviolet cut film 2 is preferably one that transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the transmittance of visible light (wavelength 360 or more and 830 nm or less) is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more.

  Furthermore, since the thin film solar cell 14 is often heated by receiving light, the ultraviolet cut film 2 preferably has heat resistance. From this viewpoint, the melting point of the constituent material of the ultraviolet cut film 2 is usually 100 ° C. or higher, preferably 120 ° C. or higher, more preferably 130 ° C. or higher, and usually 350 ° C. or lower, preferably 320 ° C. or lower, more preferably. Is 300 ° C. or lower. If the melting point is too low, the ultraviolet cut film 2 may melt when the thin film solar cell 14 is used.

  Moreover, the ultraviolet cut film 2 has a high softness | flexibility, its adhesiveness with an adjacent film is favorable, and what can cut water vapor | steam and oxygen is preferable.

  The material which comprises the ultraviolet cut film 2 is arbitrary if the intensity | strength of an ultraviolet-ray can be weakened. Examples of the material include films formed by blending an ultraviolet absorber with an epoxy, acrylic, urethane, or ester resin. Further, a film in which a layer of an ultraviolet absorbent dispersed or dissolved in a resin (hereinafter referred to as “ultraviolet absorbing layer” as appropriate) is formed on a base film may be used.

  As the ultraviolet absorber, for example, salicylic acid-based, benzophenone-based, benzotriazole-based, and cyanoacrylate-based ones can be used. Of these, benzophenone and benzotriazole are preferable. Examples of this include various aromatic organic compounds such as benzophenone and benzotriazole. In addition, a ultraviolet absorber may use 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  As described above, a film in which an ultraviolet absorbing layer is formed on a base film can also be used as the ultraviolet absorbing film. Such a film can be produced, for example, by applying a coating solution containing an ultraviolet absorber on a substrate film and drying it.

  Although the material of a base film is not specifically limited, For example, polyester is mentioned at the point from which the balance of heat resistance and a softness | flexibility is obtained.

  Application | coating can be performed by arbitrary methods. Examples include spin coating method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe doctor method, impregnation / coating method or curtain coating method. It is done. In addition, one of these methods may be performed alone, or two or more may be arbitrarily combined.

  The solvent used for the coating solution is not particularly limited as long as it can uniformly dissolve or disperse the UV absorber. For example, a liquid resin can be used as a solvent, and examples thereof include various synthetic resins such as polyester, acrylic, polyamide, polyurethane, polyolefin, polycarbonate, or polystyrene. Further, for example, natural polymers such as gelatin and cellulose derivatives; water, alcohol mixed solutions such as water and ethanol, and the like can also be used as the solvent. Further, an organic solvent may be used as the solvent. If an organic solvent is used, it becomes possible to dissolve or disperse the pigment and the resin, and to improve the coatability. In addition, 1 type of solvent may be used independently and 2 or more types may be used together by arbitrary combinations and a ratio.

  The coating solution may further contain a surfactant. Use of the surfactant improves the dispersibility of the ultraviolet absorbing dye in the resin. Thereby, in the ultraviolet absorbing layer, the occurrence of dents due to adhesion of minute bubbles, foreign matters and / or uneven coating in the drying process is suppressed.

  As the surfactant, a known surfactant (cationic surfactant, anionic surfactant or nonionic surfactant) can be used. Among these, a silicon-based surfactant or a fluorine-based surfactant is preferable. In addition, 1 type may be used for surfactant and it may use 2 or more types together by arbitrary combinations and a ratio.

  In addition, the drying after apply | coating a coating liquid to a base film can employ | adopt well-known drying methods, such as hot air drying and drying by an infrared heater, for example. Among these, hot air drying with a high drying speed is preferable.

  Examples of specific products of the ultraviolet cut film 2 include cut ace (MKV Plastic Co., Ltd.).

  In addition, the ultraviolet cut film 2 may be formed with 1 type of material, and may be formed with 2 or more types of materials. Further, the ultraviolet cut film 2 may be formed of a single layer film, but may be a laminated film including two or more layers.

  The thickness of the ultraviolet cut film 2 is not particularly defined, but is usually 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and usually 200 μm or less, preferably 180 μm or less, more preferably 150 μm or less. Increasing the thickness tends to increase the absorption of ultraviolet rays, and decreasing the thickness tends to increase the transmittance of visible light.

Although the ultraviolet cut film 2 should just be provided in the position which covers at least one part of the light-receiving surface 6a of the solar cell element 6, Preferably it is provided in the position which covers all the light-receiving surfaces 6a of the solar cell element 6. FIG.
However, the ultraviolet cut film 2 may be provided at a position other than the position covering the light receiving surface 6 a of the solar cell element 6.

[Gas barrier film 3]
The gas barrier film 3 is a film that prevents permeation of water and oxygen. The solar cell element 6 tends to be vulnerable to moisture and oxygen. In particular, transparent electrodes such as ZnO: Al, compound semiconductor solar cell elements, and organic solar cell elements may be deteriorated by moisture and oxygen. Therefore, by covering the solar cell element 6 with the gas barrier film 3, the solar cell element 6 can be protected from water and oxygen, and the power generation capacity can be kept high.

The degree of moisture resistance required for the gas barrier film 3 varies depending on the type of the solar cell element 6 and the like. For example, when the solar cell element 6 is a compound semiconductor solar cell element, the water vapor permeability per unit area (1 m ² ) per day is 1 × 10 ⁻¹ g / m ² / day or less. Is preferably 1 × 10 ⁻² g / m ² / day or less, more preferably 1 × 10 ⁻³ g / m ² / day or less, and further preferably 1 × 10 ⁻⁴ g / m ^2. / Day or less is particularly preferable, 1 × 10 ⁻⁵ g / m ² / day or less is particularly preferable, and 1 × 10 ⁻⁶ g / m ² / day or less is particularly preferable.

Moreover, when the solar cell element 6 is an organic solar cell element, it is preferable that the water vapor permeability per unit area (1 m ² ) per day is 1 × 10 ⁻¹ g / m ² / day or less. It is more preferably 1 × 10 ⁻² g / m ² / day or less, further preferably 1 × 10 ⁻³ g / m ² / day or less, and further preferably 1 × 10 ⁻⁴ g / m ² / day. Among them, the following is particularly preferable, and it is particularly preferably 1 × 10 ⁻⁵ g / m ² / day or less, and particularly preferably 1 × 10 ⁻⁶ g / m ² / day or less.

  The more water vapor has to pass through, the lower the degradation caused by the reaction of the solar cell element 6 and the transparent electrode such as ZnO: Al of the element 6 with moisture, thus increasing the power generation efficiency and extending the life.

The degree of oxygen permeability required for the gas barrier film 3 varies depending on the type of the solar cell element 6 and the like. For example, when the solar cell element 6 is a compound semiconductor solar cell element, the oxygen permeability per unit area (1 m ² ) per day is 1 × 10 ⁻¹ cc / m ² / day / atm or less. Preferably, it is 1 × 10 ⁻² cc / m ² / day / atm or less, more preferably 1 × 10 ⁻³ cc / m ² / day / atm or less, and further preferably 1 × 10 2. ⁻⁴ cc / m ² / day / atm or less is particularly preferable, and 1 × 10 ⁻⁵ cc / m ² / day / atm or less is particularly preferable, and 1 × 10 ⁻⁶ cc / m ² / day. / Atm or less is particularly preferable.

For example, when the solar cell element 6 is an organic solar cell element, the oxygen permeability per unit area (1 m ² ) per day is 1 × 10 ⁻¹ cc / m ² / day / atm or less. Preferably, it is 1 × 10 ⁻² cc / m ² / day / atm or less, more preferably 1 × 10 ⁻³ cc / m ² / day / atm or less, and further preferably 1 × 10 2. ⁻⁴ cc / m ² / day / atm or less is particularly preferable, and 1 × 10 ⁻⁵ cc / m ² / day / atm or less is particularly preferable, and 1 × 10 ⁻⁶ cc / m ² / day. / Atm or less is particularly preferable. The deterioration due to oxidation of the solar cell element 6 and the transparent electrode such as ZnO: Al of the element 6 is suppressed as the oxygen does not permeate.

  Conventionally, it has been difficult to mount the gas barrier film 3 having such a high moisture-proof and oxygen-blocking capability, so that a solar cell including an excellent solar cell element such as a compound semiconductor solar cell element and an organic solar cell element is realized. Although it was difficult to carry out, implementation of the thin film solar cell 14 which utilized the outstanding properties, such as a compound semiconductor type solar cell element and an organic solar cell element, becomes easy by applying such a gas barrier film 3.

  Further, the gas barrier film 3 is preferably one that transmits visible light from the viewpoint of not preventing the light absorption of the solar cell element 6. For example, the light transmittance of visible light (wavelength 360 or more and 830 nm or less) is usually 60% or more, preferably 70% or more, more preferably 75% or more, still more preferably 80% or more, and particularly preferably 85% or more, Particularly preferably, it is 90% or more, particularly preferably 95% or more, and particularly preferably 97% or more. This is to convert more sunlight into electrical energy.

  Furthermore, since the thin film solar cell 14 is often heated by receiving light, it is preferable that the gas barrier film 3 also has heat resistance. From this viewpoint, the melting point of the constituent material of the gas barrier film 3 is usually 100 ° C. or higher, preferably 120 ° C. or higher, more preferably 130 ° C. or higher, and usually 350 ° C. or lower, preferably 320 ° C. or lower, more preferably. It is 300 degrees C or less. By increasing the melting point, it is possible to reduce the possibility that the gas barrier film 3 is melted and deteriorated when the thin film solar cell 14 is used.

  The specific configuration of the gas barrier film 3 is arbitrary as long as the solar cell element 6 can be protected from water. However, since the manufacturing cost increases as the amount of water vapor or oxygen that can permeate the gas barrier film 3 increases, it is preferable to use an appropriate film considering these points comprehensively.

  Hereinafter, the configuration of the gas barrier film 3 will be described with examples. The following two examples are preferable as the configuration of the gas barrier film 3. The first example is a film in which an inorganic barrier layer is disposed on a plastic film substrate. In this case, the inorganic barrier layer may be formed only on one side of the plastic film substrate, or may be formed on both sides of the plastic film substrate. When forming on both surfaces, the number of inorganic barrier layers formed on both surfaces may be the same or different.

  The second example is a film in which a unit layer composed of two layers in which an inorganic barrier layer and a polymer layer are arranged adjacent to each other is formed on a plastic film substrate. At this time, a unit layer composed of two layers in which the inorganic barrier layer and the polymer layer are arranged adjacent to each other is regarded as one unit, and this unit layer is composed of one unit (one inorganic barrier layer and one polymer layer are combined to form one unit layer). (Meaning of unit) may be formed, but two or more units may be formed. For example, you may laminate | stack 2 units or more and 5 units or less.

  The unit layer may be formed only on one side of the plastic film substrate, or may be formed on both sides of the plastic film substrate. When forming on both surfaces, the numbers of inorganic barrier layers and polymer layers formed on both surfaces may be the same or different. In addition, when forming a unit layer on a plastic film substrate, an inorganic barrier layer may be formed and then a polymer layer may be formed thereon, or after forming a polymer layer and forming an inorganic barrier layer. Also good.

(Plastic film substrate)
The plastic film substrate used for the gas barrier film 3 is not particularly limited as long as it is a film capable of holding the above-described inorganic barrier layer and polymer layer, and can be appropriately selected from the purpose of use of the gas barrier film 3 and the like.

  Examples of the material for the plastic film substrate include polyester resin, polyarylate resin, polyethersulfone resin, fluorene ring-modified polycarbonate resin, alicyclic modified polycarbonate resin, and acryloyl compound. It is also preferable to use a condensation polymer containing spirobiindane or spirobichroman. Among the polyester resins, biaxially stretched polyethylene terephthalate (PET) or biaxially stretched polyethylene naphthalate (PEN) is excellent in thermal dimensional stability, and is preferably used as a plastic film substrate. In addition, as a material of a plastic film base material, 1 type of material may be used independently, and 2 or more types may be used together by arbitrary combinations and ratios.

  The thickness of the plastic film substrate is not particularly defined, but is usually 10 μm or more, preferably 15 μm or more, more preferably 20 μm or more, and usually 200 μm or less, preferably 180 μm or less, more preferably 150 μm or less. Increasing the thickness tends to increase mechanical strength, and decreasing the thickness tends to increase flexibility.

  The plastic film substrate is preferably one that transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the light transmittance of visible light (wavelength 360 or more and 830 nm or less) is usually 60% or more, preferably 70% or more, more preferably 75% or more, still more preferably 80% or more, and particularly preferably 85% or more, Particularly preferably, it is 90% or more, particularly preferably 95% or more, and particularly preferably 97% or more. This is to convert more sunlight into electrical energy.

  An anchor coat agent layer (anchor coat layer) may be formed on the plastic film substrate in order to improve adhesion to the inorganic barrier layer. Usually, the anchor coat layer is formed by applying an anchor coat agent. Examples of the anchor coating agent include polyester resins, urethane resins, acrylic resins, oxazoline group-containing resins, carbodiimide group-containing resins, epoxy group-containing resins, isocyanate-containing resins, and copolymers thereof. Among them, at least one resin selected from polyester resins, urethane resins and acrylic resins, and at least one resin selected from oxazoline group-containing resins, carbodiimide group-containing resins, epoxy group-containing resins and isocyanate group-containing resins. What combined the above resin is preferable. In addition, an anchor coat agent may use 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

  The thickness of the anchor coat layer is usually 0.005 μm or more, preferably 0.01 μm or more, and usually 5 μm or less, preferably 1 μm or less. If the thickness is less than or equal to the upper limit of this range, the slipperiness is good, and there is almost no peeling from the plastic film substrate due to the internal stress of the anchor coat layer itself. Moreover, if it is the thickness more than the lower limit of this range, a uniform thickness can be maintained and it is preferable.

  In addition, in order to improve the applicability and adhesion of the anchor coating agent to the plastic film substrate, the plastic film substrate may be subjected to a surface treatment such as normal chemical treatment or electric discharge treatment before application of the anchor coating agent. Good.

(Inorganic barrier layer)
The inorganic barrier layer is usually a layer formed of a metal oxide, nitride or oxynitride. In addition, 1 type may be used individually as a metal oxide, nitride, and oxynitride which form an inorganic barrier layer, and 2 or more types may be used together by arbitrary combinations and a ratio.

Examples of the metal oxide include oxides such as silicon, aluminum, magnesium, indium, nickel, tin, zinc, titanium, copper, cerium, and tantalum. Among these, in order to achieve both high barrier properties and high transparency, it is preferable to include aluminum oxide or silicon oxide, and it is particularly preferable to include silicon oxide from the viewpoint of moisture permeability and light transmittance. The ratio of each metal atom and oxygen atom is also arbitrary, but in order to improve the transparency of the inorganic barrier layer and prevent coloration, the oxygen atom ratio is extremely small from the stoichiometric ratio of the oxide. It is desirable. On the other hand, in order to improve the denseness of the inorganic barrier layer and increase the barrier property, it is desirable to reduce oxygen atoms. From this viewpoint, for example, when SiO _x is used as the metal oxide, the value of x is particularly preferably 1.5 or more and 1.8 or less. For example, when AlO _x is used as the metal oxide, the value of x is particularly preferably 1.0 or more and 1.4 or less.

  Moreover, when an inorganic barrier layer is comprised with 2 or more types of metal oxides, as a metal oxide, it is desirable to contain aluminum oxide and silicon oxide. When the inorganic barrier layer is made of aluminum oxide and silicon oxide, the ratio of aluminum to silicon in the inorganic barrier layer can be arbitrarily set, but the ratio of silicon / aluminum is usually 1/9 or more, preferably 2 / 8 or more, and usually 9/1 or less, preferably 2/8 or less.

  When the thickness of the inorganic barrier layer is increased, the barrier property tends to be increased. However, it is desirable to reduce the thickness in order to prevent cracking and prevent cracking when bent. Therefore, the appropriate thickness of the inorganic barrier layer is usually 5 nm or more, preferably 10 nm or more, and is usually 1000 nm or less, preferably 200 nm or less.

  Although there is no restriction | limiting in the film-forming method of an inorganic barrier layer, Generally, it can carry out by sputtering method, a vacuum evaporation method, an ion plating method, plasma CVD method etc. For example, the sputtering method can be formed by a reactive sputtering method using plasma using one or more metal targets and oxygen gas as raw materials.

(Polymer layer)
Any polymer can be used for the polymer layer, and for example, a film that can be formed in a vacuum chamber can be used. In addition, as a polymer which comprises a polymer layer, 1 type of polymer may be used and 2 or more types may be used together by arbitrary combinations and ratios.

  A wide variety of compounds can be used as the polymer-providing compound, and examples include the following (i) to (vii). In addition, 1 type of compounds may be used as a monomer and 2 or more types may be used together by arbitrary combinations and a ratio.

(I) Examples include siloxanes such as hexamethyldisiloxane. An example of a method for forming a polymer layer in the case of using hexamethyldisiloxane is to introduce hexamethyldisiloxane as a vapor into a parallel plate type plasma apparatus using an RF electrode, to cause a polymerization reaction in the plasma, The polymer layer can be formed as a polysiloxane thin film by being deposited on a plastic film substrate.

(Ii) Examples include paraxylylene such as diparaxylylene. As an example of a method for forming a polymer layer in the case of using diparaxylylene, first, a vapor of diparaxylylene is heated at 650 ° C. or more and 700 ° C. or less in a high vacuum to generate thermal radicals. Then, the radical monomer vapor is introduced into the chamber and adsorbed to the plastic film substrate, and at the same time, the polymer layer can be formed by causing the radical polymerization reaction to proceed and depositing polyparaxylylene.

(Iii) For example, a monomer capable of alternately repeating addition polymerization of two kinds of monomers can be mentioned. The polymer thus obtained is a polyaddition polymer. Examples of the polyaddition polymer include polyurethane (diisocyanate / glycol), polyurea (diisocyanate / diamine), polythiourea (dithioisocyanate / diamine), polythioether urethane (bisethyleneurethane / dithiol), polyimine ( Bisepoxy / primary amine), polypeptide amide (bisazolactone / diamine) or polyamide (diolefin / diamide).

(Iv) Examples include acrylate monomers. The acrylate monomer includes monofunctional, bifunctional or polyfunctional acrylate monomers, and any of them may be used. However, it is preferable to use two or more acrylate monomers in combination in order to obtain an appropriate evaporation rate, degree of cure, and / or cure rate. Examples of monofunctional acrylate monomers include aliphatic acrylate monomers, alicyclic acrylate monomers, ether acrylate monomers, cyclic ether acrylate monomers, aromatic acrylate monomers, hydroxyl group-containing acrylate monomers, or carboxy group-containing acrylate monomers. There are, but any can be used.

(V) Monomers capable of obtaining a photocationically cured polymer, such as epoxy and oxetane, are exemplified. As an epoxy-type monomer, an alicyclic epoxy-type monomer, a bifunctional monomer, or a polyfunctional oligomer etc. are mentioned, for example. Examples of the oxetane-based monomer include monofunctional oxetane, bifunctional oxetane, and oxetane having a silsesquioxane structure.

(Vi) An example is vinyl acetate. When vinyl acetate is used as a monomer, polyvinyl alcohol is obtained by saponifying the polymer, and this polyvinyl alcohol can be used as a polymer.

(Vii) Examples thereof include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, ethacrylic acid, fumaric acid, maleic acid, itaconic acid, monomethyl maleate, monoethyl maleate, maleic anhydride or itaconic anhydride. These constitute a copolymer with ethylene, and the copolymer can be used as a polymer. Furthermore, a mixture thereof, a mixture obtained by mixing glycidyl ether compounds, and a mixture with an epoxy compound can also be used as the polymer.

  There is no restriction | limiting in the polymerization method of a monomer, when polymerizing the above-mentioned monomer and producing | generating a polymer. However, the polymerization is usually carried out after a composition containing a monomer is applied or vapor deposited to form a film. As an example of the polymerization method, when a thermal polymerization initiator is used, the polymerization is started by contact heating with a heater or the like, or radiation heating such as infrared rays or microwaves. Moreover, when a photoinitiator is used, an active energy ray is irradiated and polymerization is started. Various light sources can be used when irradiating active energy rays, such as mercury arc lamps, xenon arc lamps, fluorescent lamps, carbon arc lamps, tungsten-halogen radiation lamps, or irradiation light from sunlight. Can do. Further, electron beam irradiation or atmospheric pressure plasma treatment can also be performed.

  Examples of the method for forming the polymer layer include a coating method and a vacuum film forming method. When the polymer layer is formed by a coating method, examples of the coating method include spin coating method, reverse roll coating method, gravure coating method, kiss coating method, roll brush method, spray coating method, air knife coating method, wire barber coating method, pipe Examples include a doctor method, an impregnation / coating method, or a curtain coating method. Moreover, you may apply | coat the coating liquid for polymer layer formation as mist form. In this case, the average particle diameter of the droplets may be adjusted to an appropriate range. For example, when forming a coating liquid containing a polymerizable monomer as a mist on a plastic film substrate, the droplets The average particle size of is usually 5 μm or less, preferably 1 μm or less. On the other hand, when forming a polymer layer by a vacuum film-forming method, film-forming methods, such as vapor deposition and plasma CVD, are mentioned, for example.

  The thickness of the polymer layer is not particularly limited, but is usually 10 nm or more, and is usually 5000 nm or less, preferably 2000 nm or less, more preferably 1000 nm or less. By increasing the thickness of the polymer layer, the uniformity of the thickness can be easily obtained, and structural defects of the inorganic barrier layer can be efficiently filled with the polymer layer, and the barrier property tends to be improved. In addition, by reducing the thickness of the polymer layer, the barrier property can be improved because the polymer layer itself is less likely to crack due to an external force such as bending.

Particularly suitable gas barrier film 3 includes, for example, a film obtained by vacuum-depositing SiO _x on a base film such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN).

  In addition, the gas barrier film 3 may be formed with 1 type of material, and may be formed with 2 or more types of materials. The gas barrier film 3 may be formed of a single layer film, but may be a laminated film including two or more layers.

  The thickness of the gas barrier film 3 is not particularly defined, but is usually 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and is usually 200 μm or less, preferably 180 μm or less, more preferably 150 μm or less. Increasing the thickness tends to increase gas barrier properties, and decreasing the thickness tends to increase flexibility and improve visible light transmittance.

  As long as the gas barrier film 3 covers the solar cell element 6 and can be protected from moisture and oxygen, the formation position is not limited. However, the front surface of the solar cell element 6 (surface on the light receiving surface side, lower surface in FIG. 2) and It is preferable to cover the back surface (the surface opposite to the light receiving surface; the upper surface in FIG. 2). This is because the front and back surfaces of the thin film solar cell 14 are often formed in a larger area than the other surfaces. In this embodiment, the gas barrier film 3 covers the front surface of the solar cell element 6, and a gas barrier film 9 described later covers the back surface of the solar cell element 6. In addition, when using a highly waterproof sheet such as a sheet in which a fluororesin film is bonded to both surfaces of an aluminum foil as the back sheet 10 described later, the getter material film 8 and / or the gas barrier film 9 may not be used depending on the application. Good.

[Getter material film 4]
The getter material film 4 is a film that absorbs moisture and / or oxygen. Some components of the solar cell element 6 are deteriorated by moisture as described above, and some are deteriorated by oxygen. Therefore, by covering the solar cell element 6 with the getter material film 4, the solar cell element 6 and the like are protected from moisture and / or oxygen, and the power generation capacity is kept high.

  Here, unlike the gas barrier film 3 as described above, the getter material film 4 does not prevent moisture permeation but absorbs moisture. By using a film that absorbs moisture, the getter material film 4 captures moisture that slightly enters the space formed by the gas barrier films 3 and 9 when the solar cell element 6 is covered with the gas barrier film 3 or the like. The influence of moisture on the solar cell element 6 can be eliminated.

The degree of water absorption capacity of the getter material film 4 is usually 0.1 mg / cm ² or more, preferably 0.5 mg / cm ² or more, more preferably 1 mg / cm ² or more. The higher this value, the higher the water absorption capacity, and the deterioration of the solar cell element 6 can be suppressed. Moreover, although there is no restriction | limiting in an upper limit, it is usually 10 mg / cm < ² > or less.

  In addition, when the solar cell element 6 is covered with the gas barrier films 3, 9, etc. by absorbing the oxygen by the getter material film 4, the getter material absorbs oxygen that slightly enters the space formed by the gas barrier films 3, 9. The film 4 is captured and the influence of oxygen on the solar cell element 6 can be eliminated.

  Furthermore, the getter material film 4 is preferably one that transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the light transmittance of visible light (wavelength 360 or more and 830 nm or less) is usually 60% or more, preferably 70% or more, more preferably 75% or more, still more preferably 80% or more, and particularly preferably 85% or more, Particularly preferably, it is 90% or more, particularly preferably 95% or more, and particularly preferably 97% or more. This is to convert more sunlight into electrical energy.

  Furthermore, since the thin film solar cell 14 is often heated by receiving light, the getter material film 4 preferably has heat resistance. From this viewpoint, the melting point of the constituent material of the getter material film 4 is usually 100 ° C. or higher, preferably 120 ° C. or higher, more preferably 130 ° C. or higher, and usually 350 ° C. or lower, preferably 320 ° C. or lower, more preferably. Is 300 ° C. or lower. By increasing the melting point, it is possible to reduce the possibility that the getter material film 4 melts and deteriorates when the thin-film solar cell 14 is used.

  The material constituting the getter material film 4 is arbitrary as long as it can absorb moisture and / or oxygen. Examples of the materials include alkali metal, alkaline earth metal or alkaline earth metal oxides; alkali metal or alkaline earth metal hydroxides; silica gel, zeolite compounds, magnesium sulfate And sulfates such as sodium sulfate or nickel sulfate; or organometallic compounds such as aluminum metal complexes or aluminum oxide octylates. Specifically, examples of the alkaline earth metal include calcium, strontium, and barium. Examples of the alkaline earth metal oxide include calcium oxide, strontium oxide, and barium oxide. In addition, Zr-Al-BaO and aluminum metal complexes are also included. Specific product names include, for example, OleDry (Futaba Electronics).

  Examples of the substance that absorbs oxygen include activated carbon, silica gel, activated alumina, molecular sieve, magnesium oxide, and iron oxide. In addition, iron, manganese, zinc, and inorganic salts such as sulfates, chlorides, and nitrates of these metals are also included.

  In addition, the getter material film 4 may be formed of one type of material or may be formed of two or more types of materials. The getter material film 4 may be formed of a single layer film, but may be a laminated film including two or more layers.

  The thickness of the getter material film 4 is not particularly specified, but is usually 5 μm or more, preferably 10 μm or more, more preferably 15 μm or more, and usually 200 μm or less, preferably 180 μm or less, more preferably 150 μm or less. Increasing the thickness tends to increase mechanical strength, and decreasing the thickness tends to increase flexibility.

  The formation position of the getter material film 4 is not limited as long as it is in the space formed by the gas barrier films 3 and 9, but the front surface of the solar cell element 6 (the surface on the light receiving surface side, the lower surface in FIG. 2). And it is preferable to cover the back surface (surface opposite to the light receiving surface; upper surface in FIG. 2). This is because, in the thin film solar cell 14, the front and back surfaces are often formed in a larger area than the other surfaces, and therefore moisture and oxygen tend to enter through these surfaces. From this viewpoint, the getter material film 4 is preferably provided between the gas barrier film 3 and the solar cell element 6. In this embodiment, the getter material film 4 covers the front surface of the solar cell element 6, a getter material film 8 described later covers the back surface of the solar cell element 6, and the getter material films 4 and 8 are respectively the solar cell element 6 and the gas barrier film 3. , 9 are located between them. In addition, when using a highly waterproof sheet such as a sheet obtained by bonding a fluororesin film on both surfaces of an aluminum foil as the back sheet 10 described later, the getter material film 8 and / or the gas barrier film 9 may not be used depending on the application. .

  The getter material film 4 can be formed by any method depending on the type of the water-absorbing agent or desiccant. The method of apply | coating this solution with a spin coat method, the inkjet method, or a dispenser method etc. can be used. Further, a film forming method such as a vacuum evaporation method or a sputtering method may be used.

  As a film for a water absorbing agent or a desiccant, for example, polyethylene resin, polypropylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, fluorine resin, poly (meth) acrylic resin, polycarbonate resin, or the like can be used. Among these, a film of polyethylene resin, fluorine resin, cyclic polyolefin resin or polycarbonate resin is preferable. In addition, the said resin may use 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

[Sealing material 5]
The sealing material 5 is a film that reinforces the solar cell element 6. Since the solar cell element 6 is thin, the strength is usually weak, and thus the strength of the thin film solar cell tends to be weak. However, the strength can be maintained high by the sealing material 5.

  Moreover, it is preferable that the sealing material 5 has high strength from the viewpoint of maintaining the strength of the thin-film solar cell 14. The specific strength is related to the strength of the weatherproof protective film 1 other than the sealing material 5 and the strength of the back sheet 10 and is generally difficult to define, but the thin film solar cell 14 as a whole has good bending workability. However, it is desirable to have a strength that does not cause peeling of the bent portion.

  In addition, the sealing material 5 is preferably one that transmits visible light from the viewpoint of not preventing the solar cell element 6 from absorbing light. For example, the light transmittance of visible light (wavelength 360 or more and 830 nm or less) is usually 60% or more, preferably 70% or more, more preferably 75% or more, still more preferably 80% or more, and particularly preferably 85% or more, Particularly preferably, it is 90% or more, particularly preferably 95% or more, and particularly preferably 97% or more. This is to convert more sunlight into electrical energy.

  Furthermore, since the thin film solar cell 14 is often heated by receiving light, it is preferable that the sealing material 5 also has heat resistance. From this viewpoint, the melting point of the constituent material of the sealing material 5 is usually 100 ° C. or higher, preferably 120 ° C. or higher, more preferably 130 ° C. or higher, and usually 350 ° C. or lower, preferably 320 ° C. or lower, more preferably. Is 300 ° C. or lower. By increasing the melting point, it is possible to reduce the possibility that the sealing material 5 melts and deteriorates when the thin film solar cell 14 is used.

  The thickness of the sealing material 5 is not particularly defined, but is usually 100 μm or more, preferably 150 μm or more, more preferably 200 μm or more, and usually 700 μm or less, preferably 600 μm or less, more preferably 500 μm or less. Increasing the thickness tends to increase the strength of the thin-film solar cell 14 as a whole, and decreasing the thickness tends to increase flexibility and improve visible light transmittance.

  As a material which comprises the sealing material 5, what used the ethylene-vinyl acetate copolymer (EVA) resin composition for the film (EVA film) etc. can be used, for example. In order to improve weather resistance, the EVA film is usually blended with a crosslinking agent to form a crosslinked structure. As the crosslinking agent, an organic peroxide that generates radicals at 100 ° C. or higher is generally used. Examples of such organic peroxides include 2,5-dimethylhexane, 2,5-dihydroperoxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, and 3-di- t-Butyl peroxide or the like can be used. The compounding amount of these organic peroxides is usually 5 parts by weight or less, preferably 3 parts by weight or less, and usually 1 part by weight or more with respect to 100 parts by weight of the EVA resin. In addition, 1 type may be used for a crosslinking agent and it may use 2 or more types together by arbitrary combinations and a ratio.

  This EVA resin composition may contain a silane coupling agent for the purpose of improving the adhesive strength. Examples of the silane coupling agent used for this purpose include γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris- (β-methoxyethoxy) silane, γ-methacryloxypropyltri Examples thereof include methoxysilane and β- (3,4-ethoxycyclohexyl) ethyltrimethoxysilane. The compounding amount of these silane coupling agents is usually 5 parts by weight or less, preferably 2 parts by weight or less, and usually 0.1 parts by weight or more with respect to 100 parts by weight of the EVA resin. In addition, 1 type of compounds may be used as a silane coupling agent, and 2 or more types may be used together by arbitrary combinations and a ratio.

  Furthermore, in order to improve the gel fraction of the EVA resin and improve the durability, a crosslinking aid may be included in the EVA resin composition. Examples of the crosslinking aid provided for this purpose include trifunctional crosslinking aids such as triallyl isocyanurate or triallyl isocyanate. The amount of these crosslinking aids is usually 10 parts by weight or less, preferably 5 parts by weight or less, and usually 1 part by weight or more with respect to 100 parts by weight of the EVA resin. In addition, 1 type of compounds may be used as a crosslinking adjuvant, and 2 or more types may be used together by arbitrary combinations and a ratio.

  Furthermore, for the purpose of improving the stability of the EVA resin, the EVA resin composition may contain, for example, hydroquinone, hydroquinone monomethyl ether, p-benzoquinone, or methylhydroquinone. These compounding quantities are normally 5 weight part or less with respect to 100 weight part of EVA resin.

  However, since the EVA resin cross-linking process requires a relatively long time of about 1 to 2 hours, it may cause a reduction in the production rate and production efficiency of the thin-film solar cell 14. In addition, when used for a long time, the decomposition gas (acetic acid gas) of the EVA resin composition or the vinyl acetate group of the EVA resin itself may adversely affect the solar cell element 6 and reduce the power generation efficiency.

Therefore, as the sealing material 5, in addition to the EVA film, a copolymer film made of a propylene / ethylene / α-olefin copolymer can also be used. As this copolymer, the thermoplastic resin composition with which the following component 1 and the component 2 were mix | blended is mentioned, for example.
Component 1: The propylene polymer is usually 0 part by weight or more, preferably 10 parts by weight or more, and usually 70 parts by weight or less, preferably 50 parts by weight or less.
Component 2: The soft propylene copolymer is 30 parts by weight or more, preferably 50 parts by weight or more, and is usually 100 parts by weight or less, preferably 90 parts by weight or less.
The total amount of component 1 and component 2 is 100 parts by weight. As described above, when component 1 and component 2 are in the preferred ranges, the moldability of the encapsulant 5 into a sheet is good, and the resulting encapsulant 5 has good heat resistance, transparency, and flexibility. Therefore, it is suitable for the thin film solar cell 14.

  The thermoplastic resin composition in which the above components 1 and 2 are blended has a melt flow rate (ASTM D 1238, 230 degrees, load 2.16 kg), usually 0.0001 g / 10 min or more. It is 1000 g / 10 min or less, preferably 900 g / 10 min or less, more preferably 800 g / 10 min or less.

  The melting point of the thermoplastic resin composition containing component 1 and component 2 is usually 100 ° C. or higher, preferably 110 ° C. or higher. Moreover, it is 140 degrees C or less normally, Preferably it is 135 degrees C or less.

Density of The thermoplastic resin composition components 1 and 2 is blended is preferably from 0.98 g / cm ³ or less, more preferably 0.95 g / cm ³ or less, more preferably 0.94 g / cm ³ or less .

  In this sealing material 5, it is possible to mix | blend a coupling agent with the said component 1 and component 2 as an adhesion promoter with respect to a plastics. As the coupling agent, silane, titanate, and chromium coupling agents are preferably used, and a silane coupling agent (silane coupling agent) is particularly preferably used.

  As the silane coupling agent, known ones can be used, and are not particularly limited. For example, vinyltriethoxysilane, vinyltrimethoxysilane, vinyltris (β-methoxy-ethoxysilane), γ-glycidoxy Examples thereof include propyl-tripyltri-methoxysilane and γ-aminopropyltriethoxysilane. In addition, 1 type of compounds may be used as a coupling agent and 2 or more types may be used together by arbitrary combinations and a ratio. The silane coupling agent is usually contained in an amount of 0.1 parts by weight or more and usually 5 parts by weight or less, preferably 3 parts per 100 parts by weight of the thermoplastic resin composition (total amount of Component 1 and Component 2). It is desirable to contain not more than parts by weight.

  Further, the coupling agent may be grafted to the thermoplastic resin composition using an organic peroxide. In this case, it is desirable to contain 0.1 to 5 parts by weight of the coupling agent with respect to 100 parts by weight of the thermoplastic resin composition (total amount of Component 1 and Component 2). Even when a silane-grafted thermoplastic resin composition is used, the same or better adhesiveness as that of the silane coupling agent blend can be obtained with respect to glass or plastic.

  When the organic peroxide is used, the organic peroxide is usually 0.001 part by weight or more, preferably 0.01 part by weight with respect to 100 parts by weight of the thermoplastic resin composition (total amount of Component 1 and Component 2). The amount is usually 5 parts by weight or less, preferably 3 parts by weight or less.

Further, a copolymer made of an ethylene / α-olefin copolymer can be used as the sealing material 5. As this copolymer, a laminate film having a hot tack property of 5 ° C. or more and 25 ° C. or less, which is formed by laminating a base material and a resin composition for a sealing material comprising the following components A and B, is exemplified. The
Component A: ethylene resin.
Component B: a copolymer of ethylene and an α-olefin having the following properties (a) to (d).
(A) Density is 0.86 g / cm ³ or more and 0.935 g / cm ³ or less.
(B) Melt flow rate (MFR) is 1 g / 10 min or more and 50 g / 10 min or less.
(C) There is one peak in the elution curve obtained by temperature rising elution fractionation (TREF), and this peak temperature is 100 ° C. or lower.
(D) The integrated elution amount by temperature rising elution fractionation (TREF) is 90% or more at 90 ° C.

  The blending ratio (component A / component B) of component A and component B is usually 50/50 or more, preferably 55/45 or more, more preferably 60/40 or more, and usually 99 / 1 or less, preferably 90/10 or less, more preferably 85/15 or less. Increasing the amount of component B tends to increase transparency and heat sealability, and decreasing the amount of component B tends to increase the workability of the film.

  The melt flow rate (MFR) of the resin composition for a sealing material produced by blending component A and component B is usually 2 g / 10 minutes or more, preferably 3 g / 10 minutes or more, and usually 50 g / 10 minutes. Hereinafter, it is preferably 40 g / 10 min or less. In addition, the measurement and evaluation of MFR can be implemented by the method based on JISK7210 (190 degreeC, 2.16kg load).

  The melting point of the encapsulant resin composition is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, and is usually 300 ° C. or lower, preferably 250 ° C. or lower, more preferably 200 ° C. or lower. By increasing the melting point, the possibility of melting and deterioration during use of the thin-film solar cell 14 can be reduced.

The density of the resin composition for a sealing material is preferably 0.80 g / cm ³ or more, more preferably 0.85 g / cm ³ or more, and preferably 0.98 g / cm ³ or less, 0.95 g / cm ^3. The following is more preferable, and 0.94 g / cm ³ or less is more preferable. The measurement and evaluation of density can be performed by a method based on JIS K7112.

  Further, in the encapsulant 5 using the ethylene / α-olefin copolymer, a coupling agent can be used as in the case of using the propylene / ethylene / α-olefin copolymer.

  Since the sealing material 5 described above does not generate a decomposition gas derived from the material, there is no adverse effect on the solar cell element 6, and good heat resistance, mechanical strength, flexibility (solar cell sealing property) and transparency. Have sex. In addition, since a material cross-linking step is not required, the manufacturing time of the thin film solar cell 14 during sheet molding can be greatly shortened, and the thin film solar cell 14 after use can be easily recycled.

  In addition, the sealing material 5 may be formed with 1 type of material, and may be formed with 2 or more types of materials. Moreover, although the sealing material 5 may be formed with the single layer film, the laminated | multilayer film provided with the film of 2 or more layers may be sufficient as it.

  The thickness of the sealing material 5 is usually 2 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and usually 500 μm or less, preferably 300 μm or less, more preferably 100 μm or less. Increasing the thickness tends to increase mechanical strength, and decreasing the thickness tends to increase flexibility and light transmittance.

  Although there is no restriction | limiting in the position which provides the sealing material 5, Usually, it provides so that the solar cell element 6 may be inserted | pinched. This is for reliably protecting the solar cell element 6. In this embodiment, the sealing material 5 and the sealing material 7 are provided on the front surface and the back surface of the solar cell element 6, respectively.

[Solar cell element 6]
As the solar cell element 6, the above-described photoelectric conversion element according to the present invention can be used.

-Connection between solar cell elements Only one solar cell element 6 may be provided per one thin film solar cell 14, but usually two or more solar cell elements 6 are provided per one thin film solar cell 14. Provide. The specific number of solar cell elements 6 may be set arbitrarily. When a plurality of solar cell elements 6 are provided, the solar cell elements 6 are often arranged in an array.

  When a plurality of solar cell elements 6 are provided, the solar cell elements 6 are usually electrically connected to each other, and electricity generated from the connected group of solar cell elements 6 is taken out from a terminal (not shown). At this time, the solar cell elements are usually connected in series in order to increase the voltage.

  Thus, when connecting the solar cell elements 6, it is preferable that the distance between the solar cell elements 6 is small, and the clearance between the solar cell element 6 and the solar cell element 6 is preferably narrow. This is because the light receiving area of the solar cell element 6 is widened to increase the amount of received light, and the amount of power generated by the thin film solar cell 14 is increased.

[Encapsulant 7]
The sealing material 7 is a film similar to the sealing material 5 described above, and the same material as the sealing material 7 can be used in the same manner except that the arrangement position is different. Moreover, since the constituent member on the back side of the solar cell element 6 does not necessarily need to transmit visible light, a member that does not transmit visible light can be used.

[Getter material film 8]
The getter material film 8 is the same film as the getter material film 4 described above, and the same material as the getter material film 4 can be used as necessary, except for the arrangement position. Moreover, since the constituent member on the back side of the solar cell element 6 does not necessarily need to transmit visible light, a member that does not transmit visible light can be used. It is also possible to use a film containing more water or oxygen absorbent than the getter material film 4. Examples of such absorbents include calcium oxide, barium oxide, Zr-Al-BaO, and the like as moisture absorbents, and activated carbon and molecular sieves as oxygen absorbents.

[Gas barrier film 9]
The gas barrier film 9 is the same film as the gas barrier film 3 described above, and the same material as the gas barrier film 9 can be used as necessary except that the arrangement position is different. Moreover, since the constituent member on the back side of the solar cell element 6 does not necessarily need to transmit visible light, a member that does not transmit visible light can be used.

[Backsheet 10]
The back sheet 10 is the same film as the weather-resistant protective film 1 described above, and the same material as the weather-resistant protective film 1 can be used in the same manner except that the arrangement position is different. In addition, if the back sheet 10 is difficult to permeate water and oxygen, the back sheet 10 can also function as a gas barrier layer. Moreover, since the constituent member on the back side of the solar cell element 6 does not necessarily need to transmit visible light, a member that does not transmit visible light can be used. For this reason, it is particularly preferable to use the following (i) to (iv) as the backsheet 10.

(I) As the back sheet 10, it is possible to use various resin films or sheets having excellent strength and weather resistance, heat resistance, water resistance and / or light resistance. For example, polyethylene resin, polypropylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, fluorine Resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin such as polyethylene terephthalate or polyethylene naphthalate, various polyamide resins such as nylon, polyimide resin, polyamideimide resin, polyaryl phthalate resin , Silicone resin, polysulfone resin, polyphenylene sulfide resin, polyethersulfone resin, polyurethane resin, acetal resin, cellulose resin or other resin It can be used. Among these resin sheets, it is preferable to use a fluorine resin, a cyclic polyolefin resin, a polycarbonate resin, a poly (meth) acrylic resin, a polyamide resin, or a polyester resin sheet. In addition, these may use 1 type and may use 2 or more types together by arbitrary combinations and a ratio.

(Ii) As the back sheet 10, a metal thin film can also be used. For example, corrosion-resistant aluminum metal foil, stainless steel thin film, and the like can be mentioned. In addition, only 1 type of metal may be used and 2 or more types may be used together by arbitrary combinations and a ratio.

(Iii) As the back sheet 10, for example, a highly waterproof sheet in which a fluorine resin film is bonded to both surfaces of an aluminum foil may be used. Examples of the fluorine-based resin include ethylene monofluoride (trade name: Tedlar, manufactured by DuPont), polytetrafluoroethylene (PTFE), a copolymer of tetrafluoroethylene and ethylene or propylene (ETFE), and a vinylidene fluoride resin. (PVDF) or vinyl fluoride resin (PVF). In addition, 1 type of fluororesin may be used and 2 or more types may be used together by arbitrary combinations and ratios.

(Iv) As the back sheet 10, for example, an inorganic oxide vapor-deposited film is provided on one side or both sides of the base film, and furthermore, the base film provided with the inorganic oxide vapor-deposited film has heat resistance on both sides. What laminated | stacked the property polypropylene-type resin film may be used. Usually, when a polypropylene resin film is laminated on the base film, the lamination is performed by laminating with a laminating adhesive. By providing an inorganic oxide vapor-deposited film, it can be used as a back sheet 10 having excellent moisture resistance that prevents intrusion of moisture and / or oxygen.

・ Base film Basically, the base film is excellent in close adhesion with inorganic oxide vapor deposition film, etc., excellent in strength, weather resistance, heat resistance, water resistance and light resistance. Resin films can be used. For example, polyethylene resin, polypropylene resin, cyclic polyolefin resin, polystyrene resin, acrylonitrile-styrene copolymer (AS resin), acrylonitrile-butadiene-styrene copolymer (ABS resin), polyvinyl chloride resin, fluorine Resin, poly (meth) acrylic resin, polycarbonate resin, polyester resin such as polyethylene terephthalate or polyethylene naphthalate, various polyamide resins such as nylon, polyimide resin, polyamideimide resin, polyaryl phthalate resin , Silicone resins, polysulfone resins, polyphenylene sulfide resins, polyethersulfone resins, polyurethane resins, acetal resins, cellulose resins, and other resins. It is possible to use the beam. Among these, it is preferable to use a film of a fluorine resin, a cyclic polyolefin resin, a polycarbonate resin, a poly (meth) acrylic resin, a polyamide resin, or a polyester resin.

  Among the various resin films as described above, for example, a fluororesin film such as polytetrafluoroethylene (PTFE), vinylidene fluoride resin (PVDF), or vinyl fluoride resin (PVF) is used. It is more preferable. Further, among these fluororesin films, in particular, a fluororesin film made of polyvinyl fluoride resin (PVF) or a copolymer of tetrafluoroethylene and ethylene or propylene (ETFE) is particularly preferable from the viewpoint of strength and the like. preferable. In addition, 1 type of resin may be used and 2 or more types may be used together by arbitrary combinations and a ratio.

  Of the various resin films as described above, it is more preferable to use a film of a cyclic polyolefin resin such as cyclopentadiene and a derivative thereof or cyclohexadiene and a derivative thereof.

  The film thickness of the base film is usually 12 μm or more, preferably 20 μm or more, and is usually 300 μm or less, preferably 200 μm or less.

-Vapor deposition film of an inorganic oxide As a vapor deposition film of an inorganic oxide, basically any thin film on which a metal oxide is deposited can be used. For example, a deposited film of an oxide of silicon (Si) or aluminum (Al) can be used. At this time, for example, SiO _x (x = 1.0 or more and 2.0 or less) can be used as silicon oxide, and AlO _x (x = 0.5 or more and 1.5 or less) can be used as aluminum oxide, for example. Can do. In addition, the kind of metal and inorganic oxide to be used may be 1 type, and may use 2 or more types together by arbitrary combinations and ratios.

  The film thickness of the inorganic oxide vapor deposition film is usually 50 mm or more, preferably 100 mm or more, and is usually 4000 mm or less, preferably 1000 mm or less.

  As a method for forming the deposited film, a chemical vapor deposition method (chemical vapor deposition method, CVD method) such as a plasma chemical vapor deposition method, a thermal chemical vapor deposition method, or a photochemical vapor deposition method can be used. To give a specific example, on one surface of the substrate film, a monomer gas for vapor deposition such as an organosilicon compound is used as a raw material, an inert gas such as argon gas or helium gas is used as a carrier gas, and oxygen is supplied. An oxygen oxide vapor or the like can be used as a gas, and a vapor deposition film of an inorganic oxide such as silicon oxide can be formed by a low temperature plasma chemical vapor deposition method using a low temperature plasma generator or the like.

-Polypropylene-type resin film As a polypropylene-type resin, the homopolymer of propylene or the copolymer of propylene and another monomer (for example, alpha-olefin etc.) can be used, for example. Moreover, an isotactic polymer can also be used as a polypropylene resin.

  The melting point of the polypropylene resin is usually 164 ° C or higher, and is usually 170 ° C or lower. The specific gravity of the polypropylene resin is usually 0.90 or more, and usually 0.91 or less. The molecular weight of the polypropylene resin is usually 100,000 or more, and usually 200,000 or less.

  Polypropylene resins are largely controlled by their crystallinity, but high isotactic polymers have excellent tensile strength and impact strength, good heat resistance and bending fatigue strength, and workability. Is very good.

-Adhesive When laminating a polypropylene resin film on a base film, an adhesive for laminating is usually used. Thereby, a base film and a polypropylene resin film are laminated | stacked via the adhesive bond layer for lamination.

  Examples of the adhesive constituting the adhesive layer for laminating include, for example, a polyvinyl acetate adhesive, a polyacrylate adhesive, a cyanoacrylate adhesive, an ethylene copolymer adhesive, a cellulose adhesive, and a polyester adhesive. Adhesives, polyamide adhesives, polyimide adhesives, amino resin adhesives, phenol resin adhesives, epoxy adhesives, polyurethane adhesives, reactive (meth) acrylic adhesives, silicone adhesives, etc. Is mentioned. In addition, 1 type may be used for an adhesive agent and it may use 2 or more types together by arbitrary combinations and a ratio.

  The composition system of the adhesive may be any composition form such as an aqueous type, a solution type, an emulsion type, or a dispersion type. Further, the property may be any of film / sheet, powder, solid and the like. Furthermore, the bonding mechanism may be any form such as a chemical reaction type, a solvent volatilization type, a hot melt type, or a hot pressure type.

The above adhesive can be applied by, for example, a coating method such as a spin coating method, a roll coating method, a gravure roll coating method, a kiss coating method, or the like, or a printing method. The coating amount is usually preferably 0.1 g / m ² or more in a dry state, and usually 10 g / m ² or less.

[Dimensions]
The thin film solar cell 14 of the present embodiment is usually a thin film member. Thus, by forming the thin film solar cell 14 as a film-like member, the thin film solar cell 14 can be easily installed in a building material, an automobile, an interior, or the like. The thin-film solar cell 14 is light and difficult to break, and thus a highly safe solar cell can be obtained and can be applied to a curved surface, so that it can be used for more applications. Since it is thin and light, it is preferable in terms of distribution such as transportation and storage. Furthermore, since it is in the form of a film, it can be manufactured in a roll-to-roll manner, and a significant cost cut can be achieved.

  Although there is no restriction | limiting in the specific dimension of the thin film solar cell 14, The thickness is 300 micrometers or more normally, Preferably it is 500 micrometers or more, More preferably, it is 700 micrometers or more, Moreover, it is 3000 micrometers or less normally, Preferably it is 2000 micrometers or less, More preferably. It is 1500 micrometers or less.

[Production method]
Although there is no restriction | limiting in the manufacturing method of the thin film solar cell 14 of this embodiment, For example, between the weather-resistant protective film 1 and the back sheet | seat 10, the 1 or 2 or more solar cell element 6 was connected in series or in parallel. The product can be manufactured by laminating with a general vacuum laminating apparatus together with the ultraviolet cut film 2, the gas barrier films 3, 9, the getter material films 4, 8 and the sealing materials 5, 7. At this time, the heating temperature is usually 130 ° C. or higher, preferably 140 ° C. or higher, and is usually 180 ° C. or lower, preferably 170 ° C. or lower. The heating time is usually 10 minutes or longer, preferably 20 minutes or longer, usually 100 minutes or shorter, preferably 90 minutes or shorter. The pressure is usually 0.001 MPa or more, preferably 0.01 MPa or more, and usually 0.2 MPa or less, preferably 0.1 MPa or less. By setting the pressure within this range, sealing can be reliably performed, and the sealing materials 5 and 7 from the end can be prevented from protruding or reduced in film thickness due to over-pressurization, thereby ensuring dimensional stability.

[Usage]
There is no restriction | limiting in the use of the thin film solar cell 14 mentioned above, It is arbitrary. For example, the thin film solar cell 14 can be used as a solar cell module. As schematically shown in FIG. 3, the solar cell module is a solar cell module 13 in which a thin film solar cell 14 is provided on a certain base material 12. The solar cell module 13 may be used by installing it at a place of use. As a specific example, when a building material plate is used as the substrate 12, a thin-film solar cell 14 is provided on the surface of the plate to produce a solar cell panel as the solar cell module 13, and this solar cell panel is attached to the outer wall of the building. It can be installed and used.

  The substrate 12 is a support member that supports the solar cell element 6. Examples of the material for forming the substrate 12 include inorganic materials such as glass, sapphire or titania; polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyimide, nylon, polystyrene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, fluorine. Organic materials such as resin film, vinyl chloride, polyethylene, cellulose, polyvinylidene chloride, aramid, polyphenylene sulfide, polyurethane, polycarbonate, polyarylate, or polynorbornene; paper materials such as paper or synthetic paper; or stainless steel, titanium, or aluminum Examples thereof include composite materials such as those obtained by coating or laminating the surface in order to impart insulating properties to such metals. In addition, 1 type of material may be used as a material of a base material, and 2 or more types may be used together by arbitrary combinations and a ratio. Moreover, carbon fiber may be included in these organic materials or paper materials to reinforce the mechanical strength.

  Examples of fields to which the thin film solar cell of the present invention is applied include solar cells for building materials, solar cells for automobiles, solar cells for interiors, solar cells for railways, solar cells for ships, solar cells for airplanes, solar cells for spacecraft. Examples include batteries, solar cells for home appliances, solar cells for mobile phones, solar cells for toys, and the like. Specific examples include the following.

1. Building use 1.1 Solar cell as house roofing material When a roof plate or the like is used as a base material, a thin film solar cell is provided on the surface of the plate material to produce a solar cell panel as a solar cell unit. Just install on the roof of the house. Moreover, a roof tile can also be used directly as a base material. The solar cell of the present invention is suitable because it can be brought into close contact with the roof tiles by taking advantage of its flexibility.

1.2 Rooftop The thin-film solar cell of the present invention can also be attached to the rooftop of a building. A solar cell unit in which a thin film solar cell is provided on a base material can be prepared and installed on the roof of a building. At this time, it is desirable to use a waterproof sheet together with the base material to have a waterproof action. Furthermore, taking advantage of the property that the thin film solar cell of the present invention has flexibility, it can be brought into close contact with a roof that is not flat, for example, a folded roof. In this case, it is desirable to use a waterproof sheet in combination.

1.3 Toplight The thin film solar cell of the present invention can also be used as an exterior at the entrance or at the atrium. Curves are often used for entrances and the like that have undergone some design processing, and in such a case, the flexibility of the thin film solar cell of the present invention is utilized. In addition, there is a case of see-through in an entrance or the like, and in such a case, a design aesthetics can be obtained in an era when environmental measures are regarded as important due to the green color of the organic solar cell.

1.4 Wall When a building material plate is used as the base material, a thin-film solar cell is provided on the surface of the plate material to produce a solar cell panel as a solar cell unit, and this solar cell panel is installed on the outer wall of the building. Use it. It can also be installed on a curtain wall. In addition, it can be attached to a spandrel or a vertical. In this case, although there is no restriction | limiting in the shape of a base material, Usually, a board | plate material is used. Moreover, what is necessary is just to set the material of a base material, a dimension, etc. arbitrarily according to the use environment. As an example of such a substrate, Alpolic (registered trademark: manufactured by Mitsubishi Plastics) and the like can be mentioned.

1.5 Window The thin-film solar cell of the present invention can also be used for a see-through window. The green color of organic solar cells is suitable because it provides a beautiful design in an era when environmental measures are important.

1.6 Others Can be used for eaves, louvers, handrails, etc. as other architectural exteriors. Even in such a case, the flexibility of the thin film solar cell of the present invention is suitable for these applications.

2. Interior The thin film solar cell of this invention can also be attached to the slat of a blind. Since the thin-film solar cell of the present invention is lightweight and rich in flexibility, such a use is possible. Further, the interior window can also be used taking advantage of the characteristic that the organic solar cell element is see-through.

3. Vegetable factories Although the number of plant factories that utilize illumination light such as fluorescent lamps is increasing, the current situation is that it is difficult to reduce the cultivation cost due to the electricity bill for lighting and the replacement cost of the light source. Then, the thin film solar cell of this invention can be installed in a vegetable factory, and the illumination system combined with LED or the fluorescent lamp can be produced. At this time, it is preferable to use an illumination system that combines an LED having a longer life than a fluorescent lamp and the solar cell of the present invention, because the cost required for illumination can be reduced by about 30% compared to the current situation. Moreover, the solar cell of this invention can also be used for the roof and side wall of the reefer container (reefer container) which conveys vegetables etc. at fixed temperature.

4). Road Material / Civil Engineering The thin film solar cell of the present invention can be used for an outer wall of a parking lot, a sound insulation wall of an expressway, an outer wall of a water purification plant, and the like.

5. Automobile The thin film solar cell of the present invention can be used on the surface of an automobile bonnet, roof, trunk lid, door, front fender, rear fender, pillar, bumper or rearview mirror. The roof includes the roof of the truck bed. The obtained electric power can be supplied to any of a traveling motor, a motor driving battery, an electrical component, and an electrical component battery. By providing control means for selecting the power supply destination according to the power generation status in the solar cell panel and the power usage status in the motor for driving, the battery for driving the motor, the electrical component and the battery for electrical component, the obtained power is It can be used properly and efficiently. In this case, although there is no restriction | limiting in the shape of the base material 12, Usually, a board | plate material is used. Moreover, what is necessary is just to set the material of the base material 12, a dimension, etc. arbitrarily according to the use environment. An example of such a substrate 12 is Alpolic (registered trademark: manufactured by Mitsubishi Plastics).

  Examples The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to the following examples unless it exceeds the gist.

<Measurement of glass transition temperature (Tg)>
About various phenanthroline derivatives, the glass transition temperature was measured by DSC method. Specifically, a sample of about 4mg placed in an aluminum sample container, using a differential thermal scanning calorimeter manufactured by SII Nano Technology Inc., _{N 2} gas 50 ml / min, heating rate 10 ° C. / min Under these conditions, the glass transition temperature was measured. The measurement results are shown in Table 1.

* 1: Lumitech * 2: Tokyo Chemical Industry * 3: Dojin Chemical Laboratory * 4: Lumitech
<Example 1: Photoelectric conversion element using BUPH1>
Poly (3,4) -ethylenedioxythiophene / polystyrene sulfonate aqueous dispersion (manufactured by HC Starck Co., Ltd., trade name “CLEVIOS ^™ PVP” as a hole extraction layer on a glass substrate on which an ITO electrode is patterned. AI4083 ") was applied by spin coating, and the substrate was heated on a hot plate at 120 ° C for 10 minutes in the air. The film thickness of the hole extraction layer was about 30 nm.

A solution in which 0.5% by weight of the following compound CP was dissolved in a 1: 2 mixed solvent (weight ratio) of chloroform / monochlorobenzene was prepared and filtered under a nitrogen atmosphere. Compound CP was synthesized according to the description in JP-A No. 2003-304014. The obtained filtrate was spin-coated at 1500 rpm on a hole extraction layer in a nitrogen atmosphere and heated at 180 ° C. for 20 minutes. The compound CP was converted to a compound BP which is a p-type semiconductor compound by heating. Thus, a tetrabenzoporphyrin (compound BP) layer was formed as a p-type semiconductor layer on the hole extraction layer. The film thickness of the p-type semiconductor layer was about 30 nm.

A solution in which 0.6% by weight of compound CP and 1.4% by weight of fullerene derivative SIMEF2 were dissolved in a 1: 1 mixed solvent (weight ratio) of chloroform / monochlorobenzene was prepared and filtered under a nitrogen atmosphere. The fullerene derivative SIMEF2 was synthesized according to the description in JP-A-2011-98906. The obtained filtrate was spin-coated on a p-type semiconductor layer at 1500 rpm in a nitrogen atmosphere and heated at 180 ° C. for 20 minutes. The compound CP was converted to a compound BP which is a p-type semiconductor compound by heating. Thus, a mixture layer (i layer) containing tetrabenzoporphyrin (compound BP) and the fullerene derivative SIMEF2 was formed on the p-type semiconductor layer.

  A solution in which 1.2% by weight of the fullerene derivative SIMEF2 was dissolved in toluene was prepared and filtered under a nitrogen atmosphere. The obtained filtrate was spin-coated on the i layer at 3000 rpm in a nitrogen atmosphere and heated at 65 ° C. for 5 minutes. Thus, a layer of fullerene derivative SIMEF2 was formed on the i layer as an n-type semiconductor layer.

  The phenanthroline derivative BUPH1 (manufactured by Lumitec) was placed in a metal boat placed in a vacuum deposition apparatus, heated, and deposited on the n-type semiconductor layer. Thus, a layer of the phenanthroline derivative BUPH1 was formed as an electron extraction layer on the n-type semiconductor layer. The thickness of the electron extraction layer was 5 nm.

  Further, an aluminum electrode having a thickness of 80 nm was provided on the electron extraction layer by vacuum deposition. Then, the 5-mm square photoelectric conversion element was produced by heating at 120 degreeC for 2 minute (s).

  About the produced photoelectric conversion element, photoelectric conversion efficiency (%) was measured by the following method (it is set as an initial value). Furthermore, after the produced photoelectric conversion element was heated (annealed) on a hot plate at 120 ° C. for 1 minute, photoelectric conversion efficiency (%) was calculated by the following method (the value after 120 ° C. for 1 minute). Thereafter, the photoelectric conversion element was further heated (annealed) on a hot plate at 120 ° C. for 2 minutes, and the photoelectric conversion efficiency (%) was calculated by the following method (the value after 3 minutes at 120 ° C.). Thereafter, the photoelectric conversion element was allowed to stand at room temperature for 8 weeks in a nitrogen atmosphere, and then the photoelectric conversion efficiency (%) was calculated by the following method (the value after 8 weeks).

The photoelectric conversion efficiency was measured as follows. That is, a 4 mm square metal mask is attached to the photoelectric conversion element, an air mass (AM) 1.5 G as an irradiation light source, a solar simulator with an irradiance of 100 mW / cm ² , and a source meter (type 2400, manufactured by Keithley, Inc.) The current-voltage characteristics between the electrode and the aluminum electrode were measured.

The open-circuit voltage Voc [V], short-circuit current density Jsc [mA / cm ² ], form factor FF, and photoelectric conversion efficiency PCE [%] of the photoelectric conversion element were determined by measuring the current-voltage characteristics. Here, the open circuit voltage Voc is the voltage value (V) when the current value = 0 (mA / cm ² ), and the short circuit current density Jsc is the current density (mA / mA when the voltage value = 0 (V). cm ² ). The form factor (FF) is a factor representing the internal resistance, and is represented by the following expression when the maximum output point is Pmax.
FF = Pmax / (Voc × Jsc)
Further, the photoelectric conversion efficiency PCE is given by the following equation when the incident energy is Pin.
PCE = Pmax / Pin = Voc × Jsc × FF / Pin

Moreover, the ratio of the photoelectric conversion efficiency with respect to the initial value in each condition was made into the maintenance rate (%).
(Maintenance rate) = (Photoelectric conversion efficiency under each condition) / (initial value)

  Table 2 shows the photoelectric conversion efficiency and the maintenance rate under each condition.

<Comparative Example 1: Photoelectric conversion element using Bphen>
A 5 mm square photoelectric conversion element was produced in the same manner as in Example 1 except that the compound Bphen (manufactured by Tokyo Chemical Industry Co., Ltd.) was used instead of the phenanthroline derivative BUPH1 as the material for the electron extraction layer. Similarly, the photoelectric conversion efficiency was measured. Table 2 shows the photoelectric conversion efficiency and the maintenance rate under each condition.

<Comparative Example 2: Photoelectric conversion element using BCP>
A 5 mm square photoelectric conversion device was prepared in the same manner as in Example 1 except that the compound BCP (manufactured by Dojindo Laboratories) was used instead of the phenanthroline derivative BUPH1 as the material for the electron extraction layer. Similarly, the photoelectric conversion efficiency was measured. Table 2 shows the photoelectric conversion efficiency and the maintenance rate under each condition.

<Comparative Example 3: Photoelectric conversion element using NBphen>
A 5 mm square photoelectric conversion device was prepared in the same manner as in Example 1 except that the above compound NBPhen (manufactured by Lumitech) was used in place of the phenanthroline derivative BUPH1 as the material for the electron extraction layer. The photoelectric conversion efficiency was measured. Table 2 shows the photoelectric conversion efficiency and the maintenance rate under each condition.

  As described above, when the phenanthroline derivative according to the present invention is used as the material for the electron extraction layer, the durability is higher than when phenanthroline derivatives conventionally used such as BPhen, BCP, and NBPhen are used. It was. Specifically, when the conventional phenanthroline derivative was used, the photoelectric conversion efficiency was reduced by the annealing treatment, whereas when the phenanthroline derivative according to the present invention was used, the photoelectric conversion efficiency was improved by the annealing treatment. This shows that the heat resistance of the photoelectric conversion element using the phenanthroline derivative according to the present invention is more excellent. Further, even after being left at room temperature, the photoelectric conversion element using the phenanthroline derivative according to the present invention has higher photoelectric conversion efficiency than the photoelectric conversion element using the conventional phenanthroline derivative. In particular, both the decrease in photoelectric conversion efficiency compared to the photoelectric conversion efficiency before annealing treatment and the decrease in photoelectric conversion efficiency compared to the photoelectric conversion efficiency after annealing treatment due to being left at room temperature are both phenanthroline according to the present invention. Fewer photoelectric conversion elements using derivatives were used. This shows that the durability of the photoelectric conversion element using the phenanthroline derivative according to the present invention is more excellent.

DESCRIPTION OF SYMBOLS 1 Weather-resistant protective film 2 UV cut film 3,9 Gas barrier film 4,8 Getter material film 5,7 Sealing material 6 Solar cell element 10 Back sheet 12 Base material 13 Solar cell module 14 Thin film solar cell 101 Anode 102 Hole extraction Layer 103 Active layer 104 Electron extraction layer 105 Cathode 106 Substrate 107 Photoelectric conversion element

Claims (5)

A photoelectric conversion element comprising a pair of electrodes, an active layer disposed between the electrodes, and an electron extraction layer disposed between at least one of the electrodes and the active layer, wherein the electron extraction layer Contains a compound represented by the following general formula (1), a photoelectric conversion element.
(In the formula (1), at least one of R ^{1 to} R ⁸ is a substituent represented by the general formula (2). When there are a plurality of substituents represented by the formula (2), they are the same. R ^{1 to} R ⁸ other than the substituents are each independently a hydrogen atom, a halogen atom, an amino group, a hydroxy group, a cyano group, a carboxyl group, a sulfo group, an isocyano group, a formyl group, a mercapto group. Group, nitro group, silyl group, boryl group, or hydrocarbon group optionally having a hetero atom.)
(In the formula (2), R ^{9 to} R ¹⁶ are each independently a hydrogen atom, halogen atom, amino group, hydroxy group, cyano group, carboxyl group, sulfo group, isocyano group, formyl group, mercapto group, nitro group, A silyl group, a boryl group, or a hydrocarbon group which may have a hetero atom.)   The photoelectric conversion element according to claim 1, wherein the compound represented by the general formula (1) has a glass transition temperature of 120 ° C. or higher.   The photoelectric conversion element according to claim 1, wherein the active layer contains fullerene or a fullerene derivative.   A solar cell comprising the photoelectric conversion element according to claim 1.   A solar cell module comprising the solar cell according to claim 4.