JP2012124297A - Organic photoelectric conversion element and solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic photoelectric conversion element which is excellent in photoelectric conversion efficiency and durability, and to provide a solar cell using the same.SOLUTION: The organic photoelectric conversion element comprises a cathode, a hole block layer, a bulk-heterojunction photoelectric conversion layer containing a p-type semiconductor material and an n-type semiconductor material, and an anode in this order. The hole block layer is adjacent to the photoelectric conversion layer and contains the following compound.

Description

  The present invention relates to an organic photoelectric conversion element and a solar cell using the same, and more particularly to a bulk heterojunction type organic photoelectric conversion element and a solar cell using the same.

  Due to the recent rise in fossil energy, a system that can generate electric power directly from natural energy has been demanded. Solar cells using single-crystal / polycrystal / amorphous Si, GaAs, CIGS (copper (Cu), indium (In) ), Semiconductor materials such as gallium (Ga) and selenium (Se)), and dye-sensitized photoelectric conversion elements (Gretzel cells) have been proposed and put to practical use.

  However, the cost of generating electricity with these solar cells is still higher than the price of electricity generated and transmitted using fossil fuels, which has hindered widespread use. In addition, since heavy glass must be used for the substrate, reinforcement work is required at the time of installation, which is one of the causes that increase the power generation cost.

  In this situation, as a solar cell that can achieve a power generation cost that is lower than that of fossil fuel, an electron donor layer (p-type semiconductor layer) and an electron acceptor are interposed between the transparent electrode and the counter electrode. A bulk heterojunction photoelectric conversion element sandwiching a photoelectric conversion layer mixed with a body layer (n-type semiconductor layer) has been proposed, and an efficiency exceeding 5% has been reported (see Non-Patent Document 1).

  The photoelectric conversion efficiency is calculated by the product of short-circuit current (Jsc) × open-circuit voltage (Voc) × fill factor (FF), but generally includes organic photoelectric conversion elements including the above-described high-efficiency organic thin-film solar cells. The curve factor remains as low as about 0.55, and if these can be improved to values equivalent to silicon solar cells (0.65 to 0.75), it is expected that further photoelectric conversion efficiency can be obtained. .

  The curve factor is closely related to the internal resistance of the photoelectric conversion element, and it is known that lowering the resistance of the organic thin film and improving the charge separation efficiency (improving rectification) are effective for improving the curve factor. Yes.

  As a technique for improving the charge separation efficiency, a technique using a layer made of bathocuproine (BCP) as a hole blocking layer of a photoelectric conversion element is disclosed (see Patent Document 1).

  Further, a layer using TiOx is disclosed as a hole blocking layer that can be produced by a coating process (see Non-Patent Document 2).

  However, since the material such as BCP has high crystallinity and low solubility, there is a problem that it is difficult to apply to a coating method with high productivity.

  In addition, in order to form the TiOx layer, it is necessary to react moisture with titanium alkoxides, which is not a preferable production method for an organic photoelectric conversion element that is deteriorated by moisture, and has a problem in durability. is doing.

  Thus, in the conventional photoelectric conversion element, productivity, photoelectric conversion efficiency, and durability were not sufficient.

US Pat. No. 6,658,0027

A. Heeger: Nature Mat. Vol. 6 (2007), p497 A. Heeger: Science; vol. 317 (2007), p222

  An object of the present invention is to provide an organic photoelectric conversion element having high productivity and excellent photoelectric conversion efficiency and durability, and a solar cell using the same.

  The above object of the present invention is achieved by the following configurations.

  1. An organic photoelectric conversion element having a cathode, a hole blocking layer, a bulk heterojunction type photoelectric conversion layer containing a p-type semiconductor material and an n-type semiconductor material, and an anode in this order, An organic photoelectric conversion element comprising a compound adjacent to the conversion layer and represented by the following general formula (1).

[Wherein R ^{1 to} R ⁴ represent a hydrogen atom, an alkyl group, an aryl group, a heteroaryl group, a hydroxyl group, an alkyloxycarbonyl group, an alkoxy group, an amino group, a halogen atom, or a halogenated alkyl group.

A ¹ represents a hydrogen atom, an aryl group, a heteroaryl group, an acyl group, an alkyloxycarbonyl group or a carbamoyl group.

A ² represents a hydroxyl group, an alkoxy group, an amino group, an acylamino group, a thiol group or an alkylthio group.

X ¹ represents an oxygen atom, a sulfur atom or N—R ⁵ , and R ⁵ represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group.

X ² represents an oxygen atom or N—R ⁶ , and R ⁶ represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group. ]
2. Formula X ² is in (1), an organic photoelectric conversion element according to the 1, characterized in that an oxygen atom.

3. 3. The organic photoelectric conversion device as described in 1 or 2 above, wherein A ¹ in the general formula (1) is an aryl group or a heteroaryl group.

4). Wherein X ¹ in the general formula (1) is an organic photoelectric conversion element of any one of the items 1 to 3, characterized in that an oxygen atom.

  5). 5. A solar cell comprising the organic photoelectric conversion device according to any one of 1 to 4 above.

  According to the present invention, an organic photoelectric conversion element having high productivity and excellent photoelectric conversion efficiency and durability and a solar cell using the same can be provided.

It is a schematic sectional drawing which shows the example of a structure of the organic photoelectric conversion element of this invention. It is a schematic sectional drawing which shows the example of the organic photoelectric conversion element of this invention provided with the tandem type photoelectric conversion layer.

  The present invention is an organic photoelectric conversion element having a cathode, a hole blocking layer, a bulk heterojunction photoelectric conversion layer containing a p-type semiconductor material and an n-type semiconductor material, and an anode in this order, It is adjacent to the photoelectric conversion layer and contains the compound represented by the general formula (1).

  Especially in this invention, the organic photoelectric conversion element excellent in photoelectric conversion efficiency and durability is obtained by providing the layer containing the compound represented by General formula (1) between a cathode and a photoelectric converting layer.

(Configuration of organic photoelectric conversion element)
FIG. 1 is a cross-sectional view showing an example of the organic photoelectric conversion element of the present invention having a bulk heterojunction type photoelectric conversion layer.

  In FIG. 1, the organic photoelectric conversion element 10 is installed on a substrate 11.

  From the substrate 11 side, an anode 12, a hole transport layer 17, a bulk heterojunction photoelectric conversion layer 14, a hole blocking layer 18, and a cathode 13 are sequentially stacked to constitute an organic photoelectric conversion element.

  The substrate 11 is a member that holds the anode 12, the photoelectric conversion layer 14, and the cathode 13 that are sequentially stacked.

  In FIG. 1, the anode 12 is a transparent electrode. In this example, since light used for photoelectric conversion enters from the substrate 11 side, the substrate 11 can transmit the light subjected to photoelectric conversion, that is, with respect to the wavelength of light used for this photoelectric conversion. Transparent member.

  As the substrate 11, for example, a glass substrate or a resin substrate is used.

  The photoelectric conversion layer 14 is a layer that converts light energy into electrical energy, and contains a p-type semiconductor material and an n-type semiconductor material.

  The p-type semiconductor material functions relatively as an electron donor (donor), and the n-type semiconductor material functions relatively as an electron acceptor (acceptor). Here, the electron donor and the electron acceptor are “an electron donor in which, when light is absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ”, which does not simply donate or accept electrons as in the case of an electrode, but donates or accepts electrons by a photoreaction.

  In FIG. 1, light incident from the anode 12 through the substrate 11 is absorbed by the electron acceptor or the electron donor in the bulk heterojunction photoelectric conversion layer 14, and electrons move from the electron donor to the electron acceptor. A hole-electron pair (charge separation state) is formed.

  The generated charge is caused by an internal electric field, for example, a potential difference due to the work function of the anode 12 and the cathode 13 being different, so that electrons pass through the hole blocking layer and holes pass through the hole transporting layer 17 to different electrodes. Carried and photocurrent is detected. In the example of FIG. 1, the work function of the anode 12 is larger than the work function of the cathode 13.

  Although not shown in FIG. 1, other layers such as an electron block layer, an electron injection layer, a hole injection layer, or a smoothing layer may be included.

  Furthermore, it is good also as a tandem-type structure which laminated | stacked such a photoelectric conversion element for the purpose of the improvement of sunlight utilization factor (photoelectric conversion efficiency).

  FIG. 2 is a cross-sectional view showing a solar cell composed of an organic photoelectric conversion element including a tandem type bulk heterojunction layer.

  In the case of the tandem configuration, the anode 12 and the first photoelectric conversion layer 14 ′ are sequentially stacked on the substrate 11, the charge recombination layer 15 is stacked, the second photoelectric conversion layer 16, and then the cathode 13 are stacked. By stacking, a tandem structure can be obtained.

  The second photoelectric conversion layer 16 may be a layer that absorbs the same spectrum as the absorption spectrum of the first photoelectric conversion layer 14 'or may be a layer that absorbs a different spectrum, but is preferably a layer that absorbs a different spectrum. is there.

  Below, the material which comprises these layers is described.

[P-type semiconductor materials]
Examples of the p-type semiconductor material used for the photoelectric conversion layer according to the present invention include various condensed polycyclic aromatic low molecular compounds and conjugated polymers.

  Examples of the condensed polycyclic aromatic low-molecular compound include anthracene, tetracene, pentacene, hexacene, heptacene, chrysene, picene, fluorene, pyrene, peropyrene, perylene, terylene, quaterylene, coronene, ovalene, circumanthracene, bisanthene, zesulene, Compounds such as heptazeslen, pyranthrene, violanthene, isoviolanthene, circobiphenyl, anthradithiophene, porphyrin, copper phthalocyanine, tetrathiafulvalene (TTF) -tetracyanoquinodimethane (TCNQ) complex, bisethylenetetrathiafulvalene (BEDTTTTF ) -Perchloric acid complexes, and derivatives and precursors thereof.

  Examples of the derivative having the above condensed polycycle include WO 03/16599 pamphlet, WO 03/28125 pamphlet, US Pat. No. 6,690,029, JP 2004-107216 A. A pentacene derivative having a substituent as described in U.S. Pat. No. 2003/136964, J. Pat. Amer. Chem. Soc. , Vol127. No. 14.4986, J. MoI. Amer. Chem. Soc. , Vol. 123, p9482; Amer. Chem. Soc. , Vol. 130 (2008), no. 9, acene-based compounds substituted with a trialkylsilylethynyl group described in 2706 and the like.

  As the conjugated polymer, for example, a polythiophene such as poly-3-hexylthiophene (P3HT) and its oligomer, or a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Polythiophene, Nature Material, (2006) vol. 5, p328, a polythiophene-thienothiophene copolymer described in WO2008000664, a polythiophene-diketopyrrolopyrrole copolymer described in WO2008000664, a polythiophene-thiazolothiazole copolymer described in Adv Mater, 2007p4160, Nature Mat. vol. 6 (2007), p497 described in PCPDTBT, etc., polypyrrole and its oligomer, polyaniline, polyphenylene and its oligomer, polyphenylene vinylene and its oligomer, polythienylene vinylene and its oligomer, polyacetylene, polydiacetylene, Examples thereof include polymer materials such as σ-conjugated polymers such as polysilane and polygermane.

  In addition to the polymer material, the following oligomer materials can also be suitably used. For example, α-seccithiophene α, ω-dihexyl-α-sexithiophene, α, ω-dihexyl-α-kinkethiophene, α, ω-bis (3-butoxypropyl) -α-sexithiophene which are thiophene hexamers , Etc.

  Among these compounds, compounds that have high solubility in organic solvents to the extent that solution processing is possible, can form a crystalline thin film after drying, and can achieve high mobility are preferable.

  More preferably, it is a compound (a compound capable of forming an appropriate phase separation structure) having appropriate compatibility with a fullerene derivative preferably used as an n-type organic semiconductor material described below.

  In addition, when an electron transport layer or a hole blocking layer is further formed on the bulk heterojunction layer by a solution process, it can be easily laminated if it can be further coated on the layer once coated, but usually dissolved. When a layer is further laminated by a solution process on a layer made of a good material, there is a problem that the layer cannot be laminated because the underlying layer is dissolved. Therefore, a material that can be insolubilized after application by a solution process is preferable.

  Examples of such materials include materials that can be insolubilized by polymerizing the coating film after coating, such as polythiophene having a polymerizable group described in Technical Digest of the International PVSEC-17, Fukuoka, Japan, 2007, P1225. Or a material in which soluble substituents react and become insoluble (pigmented) by applying energy such as heat, as described in US Patent Application Publication No. 2003/136964, and Japanese Patent Application Laid-Open No. 2008-16834 And so on.

[N-type semiconductor materials]
The n-type semiconductor material used for the bulk heterojunction type photoelectric conversion layer according to the present invention is not particularly limited. For example, perfluoro compounds in which hydrogen atoms of p-type semiconductors are substituted with fluorine atoms, such as fullerene and octaazaporphyrin. (Skeletons such as perfluoropentacene and perfluorophthalocyanine), naphthalenetetracarboxylic anhydride, naphthalenetetracarboxylic acid diimide, perylenetetracarboxylic acid anhydride, perylenetetracarboxylic acid diimide, etc. The polymer compound etc. which are contained as can be mentioned.

  Among these, fullerene derivatives that can efficiently perform charge separation with various p-type semiconductor materials at high speed (˜50 fs) are preferable. Fullerene derivatives include fullerene C60, fullerene C70, fullerene C76, fullerene C78, fullerene C84, fullerene C240, fullerene C540, mixed fullerene, fullerene nanotubes, multi-walled nanotubes, single-walled nanotubes, nanohorns (conical), and the like. Partially by hydrogen atom, halogen atom, substituted or unsubstituted alkyl group, alkenyl group, alkynyl group, aryl group, heteroaryl group, cycloalkyl group, silyl group, ether group, thioether group, amino group, silyl group, etc. Examples thereof include substituted fullerene derivatives.

  Among them, [6,6] -phenyl C61-butyric acid methyl ester (abbreviation PCBM), [6,6] -phenyl C61-butyric acid-nbutyl ester (PCBnB), [6,6] -phenyl C61-buty Rick acid-isobutyl ester (PCBiB), [6,6] -phenyl C61-butyric acid-n hexyl ester (PCBH), Adv. Mater. , Vol. 20 (2008), p2116, etc., aminated fullerenes such as JP-A 2006-199674, metallocene fullerenes such as JP-A 2008-130889, and cyclics such as US Pat. No. 7,329,709. It is preferable to use a fullerene derivative having a substituent and having improved solubility, such as fullerene having an ether group.

[Method for forming photoelectric conversion layer]
Examples of the method for forming a bulk heterojunction type photoelectric conversion layer containing an electron acceptor and an electron donor include a vapor deposition method and a coating method (including a casting method and a spin coating method).

  Among these, the coating method is preferable in order to increase the area of the interface where charges and electrons are separated from each other as described above and to produce a device having high photoelectric conversion efficiency. The coating method is also excellent in production speed.

  After coating, it is preferable to perform heating in order to cause removal of residual solvent, moisture and gas, and improvement of mobility and absorption longwave due to crystallization of the semiconductor material. When annealing is performed at a predetermined temperature during the manufacturing process, a part of the particles is microscopically aggregated or crystallized and the photoelectric conversion layer can have an appropriate phase separation structure.

  As a result, the carrier mobility of the bulk heterojunction photoelectric conversion layer is improved, and high efficiency can be obtained.

  The photoelectric conversion layer may be composed of a single layer in which an electron acceptor and an electron donor are uniformly mixed, or may be composed of a plurality of layers in which the mixing ratio of the electron acceptor and the electron donor is changed. Good. In this case, it can be formed by using a material that can be insolubilized after coating as described above.

  The film thickness of the photoelectric conversion layer is 2 nm to 5 μm, preferably 2 to 200 nm, more preferably 5 to 20 nm.

[Hole blocking layer (electron transport layer)]
In the organic photoelectric conversion element of the present invention, by forming a hole blocking layer between a bulk heterojunction type photoelectric conversion layer and a cathode, it becomes possible to more efficiently extract charges generated in the photoelectric conversion layer. .

  The hole blocking layer according to the present invention is a layer having a rectifying effect that prevents holes generated in the bulk heterojunction layer from flowing to the cathode side, but also functions as electron transport having a function of transporting electrons.

  The hole blocking layer according to the present invention contains the compound represented by the general formula (1) and is adjacent to the photoelectric conversion layer.

  Adjacent means that the hole blocking layer and the photoelectric conversion layer are in contact and laminated.

(Compound represented by the general formula (1))
In the general formula (1), R ^{1 to} R ⁴ are a hydrogen atom or an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 8 carbon atoms. For example, methyl , Ethyl, iso-propyl, tert-butyl, n-octyl, n-decyl, n-hexadecyl, etc.), an aryl group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably carbon number) 6-12, for example, phenyl, p-methylphenyl, naphthyl, etc.), heteroaryl groups (preferably having 1-20 carbon atoms, more preferably having 1-12 carbon atoms). Atom, oxygen atom, sulfur atom, specifically, for example, imidazolyl, pyridyl, quinolyl, furyl, oxazolidyl, thiazolyl, benzoxazolyl, benz Midazolyl, benzthiazolyl, etc.), halogen atom (eg, fluorine atom, chlorine atom, bromine atom, iodine atom), alkyloxycarbonyl group (eg, ethyloxycarbonyl group, methyloxycarbonyl group), alkoxy group (eg, methoxy group, Ethoxy group), amino group (for example, amino group, dimethylamino group, diethylamino group) or halogenated alkyl group (for example, trifluoromethyl group, dichloromethyl group, pentafluoroethyl group, pentachloroethyl group, heptafluoropropyl group) Chlorodifluoromethyl group, hexafluoropropyl group, etc.).

R ^{1 to} R ⁴ are preferably a hydrogen atom, an alkyl group, an aryl group, or a halogenated alkyl group.

A ¹ represents a hydrogen atom, an aryl group, a heteroaryl group, an acyl group, an alkyloxycarbonyl group or a carbamoyl group. These groups may further have a substituent.

The aryl group may be the same as those mentioned R ¹ to R ^4.

The heteroaryl group may be the same as those mentioned R ¹ to R ^4.

  Examples of the acyl group include acyl groups having 1 to 16 carbon atoms.

As the alkyloxycarbonyl group, the same groups as those described for R ^{1 to} R ⁴ can be used.

  Examples of the carbamoyl group include an unsubstituted carbamoyl group, a phenyl-substituted carbamoyl group, and an alkyl-substituted carbamoyl group.

A ¹ is preferably an aryl group, heteroaryl group, acyl group, alkyloxycarbonyl group or carbamoyl group, more preferably an aryl group or heteroaryl group.

A ² represents a hydroxyl group, an alkoxy group, an amino group, an acylamino group, a thiol group or an alkylthio group. These groups may further have a substituent.

A ² is preferably an alkoxy group or an amino group.

  As the alkoxy group and amine group, the same groups as mentioned above can be used.

X ¹ represents an oxygen atom, a sulfur atom, or N—R ⁵ , and R ⁵ represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group. These groups may further have a substituent. X ¹ is preferably an oxygen atom.

  As the alkyl group, aryl group, and heteroaryl group, the same groups as described above can be used.

X ² represents an oxygen atom or N—R ⁶ , and R ⁶ represents a hydrogen atom, an alkyl group, an aryl group, or a heteroaryl group. These groups may further have a substituent. X ² is preferably an oxygen atom.

Examples of the group that can be substituted for the group represented by A ¹ include an alkyl group, a cycloalkyl group, an aryl group, a heteroaryl group, a halogen atom, a halogenated alkyl group, and an alkenyl group (preferably having a carbon number of 2 to 20, more preferably 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms, such as vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), alkynyl group (preferably 2 carbon atoms) -20, more preferably 2-12 carbon atoms, particularly preferably 2-8 carbon atoms, including, for example, propargyl, 3-pentenyl, etc.), heterocyclic groups (preferably having 1-20 carbon atoms, more Preferably, it has 1 to 12 carbon atoms, and examples of the hetero atom include a nitrogen atom, an oxygen atom, and a sulfur atom. Peridine, piperazine, morpholine, thiomorpholine, thiomorpholine dioxide, etc.), an alkoxy group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, Methoxy, ethoxy, butoxy, etc.), a cycloalkyloxy group (preferably having 4 to 8 carbon atoms, such as cyclopentyloxy, cyclohexyloxy, etc.), an aryloxy group (preferably having 6 carbon atoms). -20, more preferably 6-16 carbon atoms, particularly preferably 6-12 carbon atoms, for example, phenyloxy, 2-naphthyloxy, etc.), acyl groups (preferably 1-20 carbon atoms, More preferably, it has 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms. Zoyl, formyl, pivaloyl, etc.), alkoxycarbonyl groups (preferably having 2-20 carbon atoms, more preferably 2-16 carbon atoms, particularly preferably 2-12 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, etc. An aryloxycarbonyl group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, and particularly preferably 7 to 10 carbon atoms), for example, phenyloxycarbonyl. ), An acyloxy group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms such as acetoxy and benzoyloxy), an acylamino group (preferably 2-20 carbon atoms, more preferably 2-16 carbon atoms, particularly preferably 2 carbon atoms Is 10, for example, acetylamino or benzoylamino. ), An alkoxycarbonylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms, such as methoxycarbonylamino), aryloxycarbonyl An amino group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonylamino), a sulfonylamino group (preferably C1-C20, More preferably, it is C1-C16, Most preferably, it is C1-C12, For example, methanesulfonylamino, benzenesulfonylamino, etc. are mentioned.), Sulfamoyl group (preferably C0) To 20, more preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, For example, sulfamoyl, methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl, etc.), a carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably carbon number). 1 to 12, for example, carbamoyl, methylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl, etc.), alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably carbon number). 1-12, for example, methylthio, ethylthio, etc.), arylthio groups (preferably having 6-20 carbon atoms, more preferably 6-16 carbon atoms, particularly preferably 6-12 carbon atoms, , Phenylthio, etc.), a sulfonyl group (preferably carbon 1 to 20, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as mesyl, tosyl, etc.), sulfinyl groups (preferably 1 to 20 carbon atoms, more preferably C1-C16, Most preferably, it is C1-C12, for example, methanesulfinyl, benzenesulfinyl etc. are mentioned), a ureido group (preferably C1-C20, more preferably C1-C16 Particularly preferably, it has 1 to 12 carbon atoms, and examples thereof include ureido, methylureido, phenylureido and the like.), Alkylsilyl group (trimethylsilyl group, triethylsilyl group, triisopropylsilyl group, etc.), phosphoric acid amide group (Preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms. Examples thereof include diethyl phosphoric acid amide and phenyl phosphoric acid amide. ), Hydroxy group, mercapto group, cyano group, sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, imino group, and the like.

Examples of the group that can be substituted for the group represented by A ² , R ^{1 to} R ⁴ , X ¹ , or X ² include the same substituents as A ¹ .

In the general formula (1), R ³ and A ² , R ⁴ and A ² , X ¹ and X ² may be bonded to each other to form a ring structure.

  The compound represented by the general formula (1) can be easily synthesized by those skilled in the art by, for example, a dehydration condensation reaction between a salicylaldehyde derivative and an acetate derivative, and can be obtained from a reagent manufacturer or a chemical manufacturer. is there.

  Synthesis examples are shown below, but the synthesis method of the compound represented by the general formula (1) of the present invention is not limited thereto.

(Synthesis Example of Compound (16))
15.2 g (0.1 mol) of 4-methoxysalicylaldehyde and 22.1 g (0.1 mol) of ethyl 2- (2-benzothiazolyl) acetate were dissolved in 70 ml of ethanol, and 1 ml of piperidine was slowly added dropwise with stirring. The reaction solution was heated to reflux for 30 minutes, then allowed to cool and filtered, and the solid was washed with a small amount of ethanol and dried to obtain 27.1 g of a white solid compound (yield 88%). The resulting compound was identified by NMR and MS spectra. The maximum absorption wavelength of the methanol solution of the compound (16) was 380 nm.

(Synthesis of Compound (25))
19.32 g (0.1 mol) of 4- (diethylamino) salicylaldehyde and 16.52 g (0.1 mol) of ethyl 2-pyridylacetate were dissolved in 56 ml of 1-propanol, and 1 ml of piperidine was slowly added dropwise with stirring. The reaction solution was heated to reflux for 4 hours, toluene was added and 1-propanol was removed by azeotropic distillation, water was added and the mixture was extracted with ethyl acetate. The ethyl acetate layer was dried over anhydrous magnesium sulfate, filtered, and then concentrated under reduced pressure. . The obtained residue was purified by silica gel column chromatography (eluent: hexane / ethyl acetate = 1: 5) and recrystallized from ethyl acetate to obtain 11.9 g of Compound (25) (yield 40%). The resulting compound was identified by NMR and MS spectra. The maximum absorption wavelength of the methanol solution of the compound (25) was 415 nm.

  (Synthesis of Compound (36))

(1: Synthesis of intermediate (2))
Intermediate (1) 21.73 g (0.1 mol) and 2-cyanoacetamide 8.41 g (0.1 mol) were dissolved in 1-propanol 56 ml, and 1 ml of piperidine was slowly added dropwise with stirring. The reaction mixture was heated to reflux for 5 hours, toluene was added and 1-propanol was removed azeotropically, water was added and the mixture was extracted with ethyl acetate. The ethyl acetate layer was dried over anhydrous magnesium sulfate, filtered, and then concentrated under reduced pressure. . The obtained residue was purified by silica gel column chromatography (eluent: hexane / ethyl acetate = 1: 5) and recrystallized from ethyl acetate to obtain 21.2 g of intermediate (2) (yield 75%). . The resulting compound was identified by NMR and MS spectra.

(2: Synthesis of compound (36))
300 ml of ethanol and 5.00 g (74 mmol) of methylamine hydrochloride were added to 21.0 g (74 mmol) of the intermediate (2), and the mixture was heated to reflux for 30 minutes. The solid precipitated after standing to cool was filtered, washed with ethanol and dried to obtain 18.36 g of Compound (36) (yield 83%). The resulting compound was identified by NMR and MS spectra.

  Although the specific example of a compound represented by General formula (1) below is shown, this invention is not limited to these. When a plurality of positional isomers are present in one kind of compound, the structure is not limited to only one kind of positional isomer described, and other positional isomers can be used in the present invention.

  The means for forming the hole blocking layer of the present invention may be either a vacuum vapor deposition method or a solution coating method, but is preferably a solution coating method.

  That is, in the present invention, as a method for producing the organic photoelectric conversion element of the present invention, an electron transport layer is formed by using an electron transport layer coating liquid containing the components contained in the electron transport layer. A production method having a forming step is preferably applicable.

  Although there is no restriction | limiting in the application | coating method used in this case, For example, a spin coat method, the cast method from a solution, a dip coat method, a wire bar coat method, a gravure coat method, a spray coat method etc. are mentioned. Furthermore, patterning can also be performed by a printing method such as an ink jet method, a screen printing method, a relief printing method, an intaglio printing method, an offset printing method, or a flexographic printing method.

  Examples of the solvent used in the coating solution include alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone, and ethylene glycol derivatives such as ethylene glycol ethyl ether.

  The film thickness of the formed electron transport layer is 5 nm to 5 μm, preferably 5 to 200 nm.

[Hole transport layer (electron blocking layer)]
The organic photoelectric conversion element of the present invention has a hole transport layer between the photoelectric conversion layer and the anode, and it is possible to extract charges generated in the photoelectric conversion layer more efficiently. It is preferable.

  As a material constituting these layers, for example, as a hole transport layer, PEDOT such as trade name BaytronP, polyaniline and its doped material, cyan compounds described in WO2006019270, etc. Can be used.

  Note that the hole transport layer having a LUMO level shallower than the LUMO level of the n-type semiconductor material used for the photoelectric conversion layer has a rectifying effect that prevents electrons generated in the bulk heterojunction layer from flowing to the anode side. It has an electronic block function. Such a hole transport layer is also called an electron block layer, and it is preferable to use a hole transport layer having such a function. As such a material, a triarylamine compound described in JP-A-5-271166 or a metal oxide such as molybdenum oxide, nickel oxide, or tungsten oxide can be used. A layer made of a single p-type semiconductor material used for the bulk heterojunction layer can also be used. The means for forming these layers may be either a vacuum deposition method or a solution coating method, but is preferably a solution coating method. Forming the coating film in the lower layer before forming the bulk heterojunction layer is preferable because it has the effect of leveling the coating surface and reduces the influence of leakage and the like.

[Other layers]
For the purpose of improving energy conversion efficiency and improving the lifetime of the element, a structure having various intermediate layers in the element may be employed. Examples of the intermediate layer include an electron block layer, a hole injection layer, an electron injection layer, an exciton block layer, a UV absorption layer, a light reflection layer, and a wavelength conversion layer.

<Electrode>
The organic photoelectric conversion element of the present invention has at least an anode and a cathode. Further, when a tandem configuration is adopted, the tandem configuration can be achieved by using an intermediate electrode. In the present invention, an electrode through which holes mainly flow is called an anode, and an electrode through which electrons mainly flow is called a cathode.

  Further, because of the function of whether or not there is a light-transmitting property, a light-transmitting electrode may be called a transparent electrode, and a non-light-transmitting electrode may be called a counter electrode. Usually, the anode is a translucent transparent electrode, and the cathode is a non-translucent counter electrode.

〔anode〕
The anode of the present invention is preferably an electrode that transmits light of 380 to 800 nm. As the material, for example, transparent conductive metal oxides such as indium tin oxide (ITO), SnO ₂ and ZnO, metal thin films such as gold, silver and platinum, metal nanowires and carbon nanotubes can be used.

  Further, a conductive material selected from the group consisting of polypyrrole, polyaniline, polythiophene, polythienylene vinylene, polyazulene, polyisothianaphthene, polycarbazole, polyacetylene, polyphenylene, polyphenylene vinylene, polyacene, polyphenylacetylene, polydiacetylene, and polynaphthalene. A functional polymer can also be used. Further, a plurality of these conductive compounds can be combined to form an anode.

[Cathode]
The cathode may be a single layer of a conductive material, but in addition to a conductive material, a resin that holds these may be used in combination. As the conductive material for the cathode, a material having a small work function (4 eV or less) metal, alloy, electrically conductive compound, and a mixture thereof is used. Specific examples of such electrode materials include sodium, sodium-potassium alloy, magnesium, lithium, magnesium / copper mixture, magnesium / silver mixture, magnesium / aluminum mixture, magnesium / indium mixture, aluminum / aluminum oxide (Al ₂ O ₃ ) Mixtures, indium, lithium / aluminum mixtures, rare earth metals and the like. Among these, from the viewpoint of electron extraction performance and durability against oxidation, etc., a mixture of these metals and a second metal which is a stable metal having a larger work function value than this, for example, a magnesium / silver mixture, magnesium / Aluminum mixtures, magnesium / indium mixtures, aluminum / aluminum oxide (Al ₂ O ₃ ) mixtures, lithium / aluminum mixtures, aluminum and the like are preferred. The cathode can be produced by forming a thin film of these electrode materials by a method such as vapor deposition or sputtering. The film thickness is usually selected in the range of 10 nm to 5 μm, preferably 50 to 200 nm.

  If a metal material is used as the conductive material of the cathode, the light coming to the cathode side is reflected and reflected to the anode side, and this light can be reused and is absorbed again by the photoelectric conversion layer, and the photoelectric conversion efficiency is further improved, which is preferable. .

  The cathode may be a metal (for example, gold, silver, copper, platinum, rhodium, ruthenium, aluminum, magnesium, indium, etc.), carbon nanoparticles, nanowires, nanostructures, and nanowire dispersion. If it is a thing, a transparent and highly conductive cathode can be formed by the apply | coating method, and is preferable.

  Further, when the cathode side is made light-transmitting, for example, a conductive material suitable for the cathode such as aluminum and aluminum alloy, silver and silver compound is made thin with a film thickness of about 1 to 20 nm, and then the anode By providing a film of the conductive light-transmitting material mentioned in the description, a light-transmitting cathode can be obtained.

[Intermediate electrode]
In addition, the intermediate electrode material required in the case of the tandem configuration as shown in FIG. 2 is preferably a layer using a compound having both transparency and conductivity. Transparent metal oxides such as ITO, AZO, FTO and titanium oxide, very thin metal layers such as Ag, Al and Au, or layers containing nanoparticles / nanowires, conductive polymer materials such as PEDOT: PSS and polyaniline Etc.) can be used.

  In addition, in the hole transport layer and the electron transport layer (hole block layer) described above, there is also a combination that works as an intermediate electrode (charge recombination layer) by stacking in an appropriate combination. The step of forming one layer is preferable because it can be omitted.

〔substrate〕
As for the organic photoelectric conversion element of this invention, the form provided on a board | substrate is a preferable form.

  When light that is photoelectrically converted enters from the substrate side, the substrate is a member (transparent substrate) that can transmit the light that is photoelectrically converted, that is, transparent to the wavelength of the light to be photoelectrically converted. It is preferable.

  As the substrate, for example, a glass substrate, a resin substrate, and the like are preferably exemplified, but it is desirable to use a transparent resin film from the viewpoint of lightness and flexibility.

  There is no restriction | limiting in particular in the transparent resin film which can be preferably used as a transparent substrate by this invention, The material, a shape, a structure, thickness, etc. can be suitably selected from well-known things.

  For example, polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) modified polyester, polyethylene (PE) resin film, polypropylene (PP) resin film, polystyrene resin film, polyolefin resins such as cyclic olefin resin Film, vinyl resin film such as polyvinyl chloride, polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF) resin film, polyether sulfone (PES) resin film, polycarbonate (PC) resin film, A polyamide resin film, a polyimide resin film, an acrylic resin film, a triacetyl cellulose (TAC) resin film, and the like can be given. If the resin film transmittance of 80% or more at ~800nm), can be preferably applied to a transparent resin film according to the present invention. Among them, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film, and biaxially stretched. More preferred are polyethylene terephthalate films and biaxially stretched polyethylene naphthalate films.

  The transparent substrate that can be used in the present invention can be subjected to a surface treatment or an easy-adhesion layer in order to ensure wettability and adhesion of the coating solution. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer.

  For the purpose of suppressing the permeation of oxygen and water vapor, a barrier coat layer may be formed in advance on the transparent substrate, or a hard coat layer may be formed in advance on the opposite side to which the transparent conductive layer is transferred. Good.

(Optical function layer)
The organic photoelectric conversion element of the present invention may have various optical functional layers for the purpose of more efficient reception of sunlight. As the optical functional layer, for example, a light condensing layer such as an antireflection film or a microlens array, or a light diffusing layer that can scatter light reflected by the cathode and enter the power generation layer again may be provided. .

  Various known antireflection layers can be provided as the antireflection layer. For example, when the transparent resin film is a biaxially stretched polyethylene terephthalate film, the refractive index of the easy adhesion layer adjacent to the film is 1.57. It is more preferable to set it to ˜1.63 because the interface reflection between the film substrate and the easy adhesion layer can be reduced and the transmittance can be improved. The method for adjusting the refractive index can be carried out by appropriately adjusting the ratio of the oxide sol having a relatively high refractive index such as tin oxide sol or cerium oxide sol and the binder resin. The easy adhesion layer may be a single layer, but may be composed of two or more layers in order to improve adhesion.

  As the condensing layer, for example, it is processed so as to provide a structure on the microlens array on the sunlight receiving side of the support substrate, or the amount of light received from a specific direction is increased by combining with a so-called condensing sheet. Conversely, the incident angle dependency of sunlight can be reduced.

  As an example of the microlens array, quadrangular pyramids having a side of 30 μm and an apex angle of 90 degrees are two-dimensionally arranged on the light extraction side of the substrate. One side is preferably 10 to 100 μm. If it becomes smaller than this, the effect of diffraction will generate | occur | produce and color, and if too large, thickness will become thick and is not preferable.

  Examples of the light scattering layer include various antiglare layers, layers in which nanoparticles or nanowires such as metals or various inorganic oxides are dispersed in a colorless and transparent polymer, and the like.

[Patterning]
There are no particular limitations on the patterning method and process for making the anode, cathode, photoelectric conversion layer, hole blocking layer, hole transport layer, and the like according to the present invention into an organic photoelectric conversion element, and a known method is appropriately used. Can be applied.

  In the case of a layer that can be dissolved in a solvent such as a photoelectric conversion layer, a hole blocking layer, or a hole transporting layer, only unnecessary portions may be wiped off after the entire surface of die coating, dip coating, etc. Alternatively, direct patterning may be performed at the time of application using a method such as a method or screen printing.

  In the case of an insoluble material such as an electrode material, the electrode can be patterned by a known method such as mask vapor deposition during vacuum deposition or etching or lift-off. Alternatively, the pattern may be formed by transferring a pattern formed on another substrate.

(Solar cell)
The solar cell of this invention has said organic photoelectric conversion element.

  The solar cell of the present invention comprises the above-described organic photoelectric conversion element, has a structure in which optimum design and circuit design are performed for sunlight, and optimum photoelectric conversion is performed when sunlight is used as a light source. .

  That is, the photoelectric conversion layer can be irradiated with sunlight. When configuring the solar cell of the present invention, it is preferable that the cathode, the electron transport layer, the photoelectric conversion layer, the anode, and the substrate are housed in a case and sealed, or the whole is sealed with a resin.

  As a sealing method, for example, a method of sealing by bonding an aluminum or glass cap with an adhesive, a plastic film on which a gas barrier layer such as aluminum, silicon oxide, or aluminum oxide is formed, and organic photoelectric conversion A method of bonding elements with an adhesive, a method of spin-coating an organic polymer material with high gas barrier properties (polyvinyl alcohol, etc.), an inorganic thin film with high gas barrier properties (silicon oxide, aluminum oxide, etc.) or an organic film (parylene, etc.) And a method of depositing these in a composite manner.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Production of Organic Photoelectric Conversion Element 1 (Comparative Example)>
The transparent electrode patterned on the glass substrate was cleaned in the order of ultrasonic cleaning with surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally UV ozone cleaning. .

  On this transparent substrate (glass substrate), Baytron P4083 (manufactured by Starck Vitec), which is a conductive polymer, was spin-coated with a film thickness of 30 nm, and then dried by heating at 140 ° C. in the atmosphere for 10 minutes.

  After this, the substrate was brought into the glove box and worked under a nitrogen atmosphere. First, the substrate was heat-treated at 140 ° C. for 3 minutes in a nitrogen atmosphere. A solution was prepared by dissolving 1.5 mass% of plexcores OS2100 manufactured by Plextronics as a p-type semiconductor material and 1.5 mass% of E100 (PCBM) manufactured by Frontier Carbon as an n-type semiconductor material in chlorobenzene. While being filtered through a .45 μm filter, spin coating was performed at 500 rpm for 60 seconds, then at 2200 rpm for 1 second, and left at room temperature for 30 minutes.

  Next, a solution in which batocuproine (BCP) manufactured by Aldrich was mixed with 2,2,3,3-tetrafluoro-1-propanol at a ratio of 0.5% by mass was spin-coated at 1200 rpm, and a hole block having a thickness of 15 nm was formed. A layer was formed.

Next, the substrate on which the series of organic layers was formed was placed in a vacuum deposition apparatus without being exposed to the atmosphere. The element was set so that the shadow mask with a width of 2 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 ⁻³ Pa or less, and then 100 nm of Al was deposited. Finally, heating was performed at 120 ° C. for 30 minutes to obtain a comparative organic photoelectric conversion element 1. The vapor deposition rate was 2 nm / second, and the size was 2 mm square.

  The obtained organic photoelectric conversion element 1 was taken out into the atmosphere after sealing using an aluminum cap and a UV curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1) in a nitrogen atmosphere.

<Production of Organic Photoelectric Conversion Element 2 (Comparative Example)>
In the comparative organic photoelectric conversion element 1, instead of a 0.5% 2,2,3,3-tetrafluoro-1-propanol solution of batocuproine as a hole blocking layer, Ti-isopropoxide was added to ethanol at 25 mmol / l. After the electrode portion was masked and spin-coated at 1500 rpm, the solution was taken out into the atmosphere and left for 60 minutes to hydrolyze Ti-isopropoxide to obtain a film thickness of 15 nm. A comparative organic photoelectric conversion element 2 was produced in the same manner except that a TiOx layer was formed and a hole blocking layer was formed.

<Preparation of the organic photoelectric conversion elements 3 to 25 of the present invention>
In the comparative organic photoelectric conversion element 1, the hole blocking layer was changed to the compound of the present invention described in Table 1 below instead of batocuproine, and the organic photoelectric conversion elements 3 to 25 of the present invention were produced. .

  About the obtained organic photoelectric conversion elements 1-25, evaluation of the following conversion efficiency and durability evaluation were performed. The results are shown in Table 1.

(Evaluation of conversion efficiency)
Photoelectric conversion elements prepared above, was irradiated with light having an intensity of 100 mW / cm ² solar simulator (AM1.5G filter), a superposed mask in which the effective area 4.0 mm ² on the light receiving portion, the short circuit current density Jsc ( The four light-receiving portions formed on the same element were measured for mA / cm ² ), the open circuit voltage Voc (V), and the fill factor (fill factor) FF, and the average value was obtained. Further, energy conversion efficiency η (%) was obtained from Jsc, Voc, and FF according to Equation 1.

Formula 1 Jsc (mA / cm ² ) × Voc (V) × FF = η (%)
(Durability evaluation)
A solar simulator (AM1.5G) was irradiated at a light intensity of 100 mW / cm ² and the initial conversion efficiency measured for voltage-current characteristics was set to 100, and a resistance was connected between the anode and cathode, and 100 mW / cm. The conversion efficiency after continuing irradiation for 100 h at the irradiation intensity of ² was evaluated, and the relative efficiency decrease was calculated by the following formula 2 and used as an index of durability.

  Formula 2 Relative efficiency reduction (%) = (1−conversion efficiency after exposure / conversion efficiency before exposure) × 100

  From Table 1, it can be seen that the organic photoelectric conversion element having the hole blocking layer using the compound according to the present invention has improved curve factor, high conversion efficiency, and high durability.

DESCRIPTION OF SYMBOLS 10 Organic photoelectric conversion element 11 Board | substrate 12 Anode 13 Cathode 14 Photoelectric conversion layer 14 '1st photoelectric conversion layer 15 Charge recombination layer 16 2nd photoelectric conversion layer 17 Hole transport layer 18 Hole block layer

Claims (5)

An organic photoelectric conversion element having a cathode, a hole blocking layer, a bulk heterojunction type photoelectric conversion layer containing a p-type semiconductor material and an n-type semiconductor material, and an anode in this order, An organic photoelectric conversion element comprising a compound adjacent to the conversion layer and represented by the following general formula (1).

[Wherein R ^{1 to} R ⁴ represent a hydrogen atom, an alkyl group, an aryl group, a heteroaryl group, a hydroxyl group, an alkyloxycarbonyl group, an alkoxy group, an amino group, a halogen atom, or a halogenated alkyl group.
A ¹ represents a hydrogen atom, an aryl group, a heteroaryl group, an acyl group, an alkyloxycarbonyl group or a carbamoyl group.
A ² represents a hydroxyl group, an alkoxy group, an amino group, an acylamino group, a thiol group or an alkylthio group.
X ¹ represents an oxygen atom, a sulfur atom or N—R ⁵ , and R ⁵ represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group.
X ² represents an oxygen atom or N—R ⁶ , and R ⁶ represents a hydrogen atom, an alkyl group, an aryl group or a heteroaryl group. ] The organic photoelectric conversion device according to claim 1, wherein X ² in the general formula (1) is an oxygen atom. The organic photoelectric conversion device according to claim 1, wherein A ¹ in the general formula (1) is an aryl group or a heteroaryl group. Wherein X ¹ in the general formula (1) is an organic photoelectric conversion device according to any one of claims 1 to 3, characterized in that the oxygen atom.   A solar cell comprising the organic photoelectric conversion element according to any one of claims 1 to 4.

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