WO2018056312A1 - Perovskite solar cell - Google Patents

Abstract

The purpose of the present invention is to provide a perovskite solar cell with high photoelectric conversion efficiency. The perovskite solar cell according to the present invention has: a laminate including an electrode, a counter electrode, and a photoelectric conversion layer disposed between the electrode and the counter electrode; and a sealing layer that covers the counter electrode and seals the laminate. The photoelectric conversion layer includes an organic-inorganic perovskite compound represented by general formula R-M-X₃ (here, R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom), and the difference in refractive index between the sealing layer and the counter electrode is 0.4 or less.

Description

Perovskite solar cells

The present invention relates to a perovskite solar cell with high photoelectric conversion efficiency.

Conventionally, a photoelectric conversion element including a stacked body in which an N-type semiconductor layer and a P-type semiconductor layer are arranged between opposing electrodes has been developed. In such a photoelectric conversion element, photocarriers are generated by photoexcitation, and an electric field is generated by electrons moving through an N-type semiconductor and holes moving through a P-type semiconductor.

Currently, most of the photoelectric conversion elements in practical use are inorganic solar cells manufactured using an inorganic semiconductor such as silicon. However, inorganic solar cells are expensive to manufacture and difficult to increase in size, resulting in a limited range of use. Thus, an organic solar cell manufactured using an organic semiconductor instead of an inorganic semiconductor has attracted attention.

In organic solar cells, fullerene is almost always used. Fullerenes are known to work mainly as N-type semiconductors. For example, Patent Document 1 describes a semiconductor heterojunction film formed using an organic compound that becomes a P-type semiconductor and fullerenes. However, in organic solar cells manufactured using fullerenes, it is known that the cause of deterioration is fullerenes (see, for example, Non-Patent Document 1), and materials that replace fullerenes are required.

Therefore, in recent years, an organic inorganic perovskite compound having a perovskite structure using lead, tin, or the like as a central metal has been found as a photoelectric conversion material, and has been shown to have high photoelectric conversion efficiency (for example, Non-Patent Document 2). However, the perovskite solar cell using a conventional organic / inorganic perovskite compound for the photoelectric conversion layer has a problem that it does not exhibit the photoelectric conversion efficiency as expected.

JP 2006-344794 A

Reese et al. , Adv. Funct. Mater. , 20, 3476-3483 (2010) M.M. M.M. Lee et al. , Science, 338, 643-647 (2012)

An object of this invention is to provide the perovskite solar cell with high photoelectric conversion efficiency.

The present invention provides a laminate having an electrode, a counter electrode, and a photoelectric conversion layer disposed between the electrode and the counter electrode, and sealing for covering the counter electrode and sealing the laminate. The photoelectric conversion layer has a general formula R-MX ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom). The perovskite solar cell includes an organic / inorganic perovskite compound and has a refractive index difference of 0.4 or less between the sealing layer and the counter electrode.
The present invention is described in detail below.

The present inventors examined the cause that the photoelectric conversion efficiency of the conventional perovskite solar cell does not increase as expected. As a result, it was found that the light that passed through the sealing layer was reflected at the interface with the upper transparent electrode. Since the photoelectric conversion layer containing the organic / inorganic perovskite compound has a property of being weak against moisture, the laminate of the electrode and the photoelectric conversion layer is sealed with a sealing layer mainly made of a resin or an inorganic material. However, the sealing layer has a lower refractive index than the upper transparent electrode, and the difference in refractive index between the sealing layer and the upper transparent electrode is large. And the photoelectric conversion efficiency was lowered. Therefore, the present inventors have further studied, and the refractive index of the sealing layer is increased by adding an inorganic filler in the sealing layer or selecting a resin constituting the sealing layer. It has been found that the difference in refractive index from the electrode can be reduced. As a result, it has been found that the photoelectric conversion efficiency of the perovskite solar cell can be improved by suppressing the reflection of light at the interface between the sealing layer and the upper transparent electrode, and the present invention has been completed.

The perovskite solar cell of this invention has a laminated body which has an electrode, a counter electrode, and the photoelectric converting layer arrange | positioned between the said electrode and the said counter electrode.
In this specification, the term “layer” means not only a layer having a clear boundary but also a layer having a concentration gradient in which contained elements gradually change. The elemental analysis of the layer can be performed, for example, by performing FE-TEM / EDS line analysis measurement of the cross section of the solar cell and confirming the element distribution of the specific element. In addition, in this specification, a layer means not only a flat thin film-like layer but also a layer that can form a complicated and complicated structure together with other layers.

The material of the said electrode and the said counter electrode is not specifically limited, A conventionally well-known material can be used. The counter electrode is a transparent electrode and is often patterned.
Examples of the electrode material include FTO (fluorine-doped tin oxide), gold, silver, titanium, sodium, sodium-potassium alloy, lithium, magnesium, aluminum, magnesium-silver mixture, magnesium-indium mixture, and aluminum-lithium alloy. , Al / Al ₂ O ₃ mixtures, Al / LiF mixtures, metals such as gold. As the material of the counter electrode, CuI, ITO (indium tin oxide), SnO ₂ , AZO (aluminum zinc oxide), IZO (indium zinc oxide), GZO (gallium zinc oxide), ATO (antimony-doped oxide) Examples thereof include conductive transparent materials such as tin) and conductive transparent polymers. These materials may be used alone or in combination of two or more. Further, the electrode and the counter electrode may be a cathode or an anode, respectively.

The refractive index of the counter electrode is not particularly limited, but is usually about 1.8 to 2.2.

The photoelectric conversion layer includes an organic / inorganic perovskite compound represented by the general formula R-MX ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom).
By using the organic-inorganic perovskite compound for the photoelectric conversion layer, the photoelectric conversion efficiency of the perovskite solar cell can be improved. Moreover, although the said organic inorganic perovskite compound has low moisture resistance, durability of a perovskite solar cell can be improved by arrange | positioning the sealing layer which is mentioned later on the said counter electrode.

The R is an organic molecule, and is preferably represented by C ₁ N _m H _n (l, m, and n are all positive integers).
Specifically, R is, for example, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, dipentylamine, dihexylamine, trimethylamine, triethylamine, tripropyl. Amine, tributylamine, tripentylamine, trihexylamine, ethylmethylamine, methylpropylamine, butylmethylamine, methylpentylamine, hexylmethylamine, ethylpropylamine, ethylbutylamine, imidazole, azole, pyrrole, aziridine, azirine, Azetidine, azeto, azole, imidazoline, carbazole and their ions (eg, methylammonium (CH ₃ NH ₃ )) and fluorine And enethylammonium. Of these, methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine and their ions and phenethylammonium are preferred, and methylamine, ethylamine, propylamine and these ions are more preferred.

M is a metal atom, for example, lead, tin, zinc, titanium, antimony, bismuth, nickel, iron, cobalt, silver, copper, gallium, germanium, magnesium, calcium, indium, aluminum, manganese, chromium, molybdenum, Europium etc. are mentioned. These metal atoms may be used independently and 2 or more types may be used together.

X is a halogen atom or a chalcogen atom, and examples thereof include chlorine, bromine, iodine, sulfur, and selenium. These halogen atoms or chalcogen atoms may be used alone or in combination of two or more. Among these, the halogen atom is preferable because the organic / inorganic perovskite compound becomes soluble in an organic solvent and can be applied to an inexpensive printing method by containing halogen in the structure. Furthermore, iodine is more preferable because the energy band gap of the organic-inorganic perovskite compound becomes narrow.

The organic / inorganic perovskite compound preferably has a cubic structure in which a metal atom M is disposed at the body center, an organic molecule R is disposed at each vertex, and a halogen atom or a chalcogen atom X is disposed at the face center.
FIG. 1 shows an example of a crystal structure of an organic / inorganic perovskite compound having a cubic structure in which a metal atom M is arranged at the body center, an organic molecule R is arranged at each vertex, and a halogen atom or a chalcogen atom X is arranged at the face center. It is a schematic diagram. Although details are not clear, since the orientation of the octahedron in the crystal lattice can be easily changed by having the above structure, the mobility of electrons in the organic-inorganic perovskite compound is increased, and the perovskite solar cell It is estimated that the photoelectric conversion efficiency is improved.

The organic / inorganic perovskite compound is preferably a crystalline semiconductor. The crystalline semiconductor means a semiconductor capable of measuring the X-ray scattering intensity distribution and detecting a scattering peak. When the organic / inorganic perovskite compound is a crystalline semiconductor, the mobility of electrons in the organic / inorganic perovskite compound is increased, and the photoelectric conversion efficiency of the perovskite solar cell is improved.

In addition, the degree of crystallization can be evaluated as an index of crystallization. The degree of crystallinity is determined by separating the crystalline-derived scattering peak detected by the X-ray scattering intensity distribution measurement and the halo derived from the amorphous part by fitting, obtaining the respective intensity integrals, Can be obtained by calculating the ratio.
A preferable lower limit of the crystallinity of the organic-inorganic perovskite compound is 30%. When the crystallinity is 30% or more, the mobility of electrons in the organic / inorganic perovskite compound is increased, and the photoelectric conversion efficiency of the perovskite solar cell is improved. A more preferred lower limit of the crystallinity is 50%, and a more preferred lower limit is 70%.
Examples of the method for increasing the crystallinity of the organic / inorganic perovskite compound include thermal annealing, irradiation with intense light such as laser, and plasma irradiation.

When the photoelectric conversion layer contains the organic / inorganic perovskite compound, the photoelectric conversion layer further includes an organic semiconductor or an inorganic semiconductor in addition to the organic / inorganic perovskite compound as long as the effect of the present invention is not impaired. May be included. Note that the organic semiconductor or inorganic semiconductor referred to here may serve as an electron transport layer or a hole transport layer described later.
Examples of the organic semiconductor include compounds having a thiophene skeleton such as poly (3-alkylthiophene). In addition, for example, conductive polymers having a polyparaphenylene vinylene skeleton, a polyvinyl carbazole skeleton, a polyaniline skeleton, a polyacetylene skeleton, and the like can be given. Further, for example, compounds having a porphyrin skeleton such as a phthalocyanine skeleton, a naphthalocyanine skeleton, a pentacene skeleton, or a benzoporphyrin skeleton, a spirobifluorene skeleton, etc., and carbon-containing materials such as carbon nanotubes, graphene, and fullerene that may be surface-modified Also mentioned.

Examples of the inorganic semiconductor include titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, CuSCN, Cu ₂ O, CuI, MoO ₃ , V ₂ O ₅ , WO ₃ , _{MoS 2, MoSe 2, Cu 2} S , and the like.

In the case where the photoelectric conversion layer includes the organic-inorganic perovskite compound and the organic semiconductor or the inorganic semiconductor, the photoelectric conversion layer is a laminated body in which a thin-film organic semiconductor or an inorganic semiconductor portion and a thin-film organic-inorganic perovskite compound portion are stacked. Alternatively, a composite film in which an organic semiconductor or inorganic semiconductor part and an organic / inorganic perovskite compound part are combined may be used. A laminated body is preferable in that the production method is simple, and a composite film is preferable in that the charge separation efficiency in the organic semiconductor or the inorganic semiconductor can be improved.

The preferable lower limit of the thickness of the thin-film organic / inorganic perovskite compound site is 5 nm, and the preferable upper limit is 5000 nm. If the thickness is 5 nm or more, light can be sufficiently absorbed, and the photoelectric conversion efficiency is increased. If the said thickness is 5000 nm or less, since it can suppress that the area | region which cannot carry out charge separation generate | occur | produces, it leads to the improvement of photoelectric conversion efficiency. The more preferable lower limit of the thickness is 10 nm, the more preferable upper limit is 1000 nm, the still more preferable lower limit is 20 nm, and the still more preferable upper limit is 500 nm.

When the photoelectric conversion layer is a composite film in which an organic semiconductor or an inorganic semiconductor part and an organic / inorganic perovskite compound part are combined, a preferable lower limit of the thickness of the composite film is 30 nm, and a preferable upper limit is 3000 nm. If the thickness is 30 nm or more, light can be sufficiently absorbed, and the photoelectric conversion efficiency is increased. If the said thickness is 3000 nm or less, since it becomes easy to reach | attain an electrode, a photoelectric conversion efficiency becomes high. The more preferable lower limit of the thickness is 40 nm, the more preferable upper limit is 2000 nm, the still more preferable lower limit is 50 nm, and the still more preferable upper limit is 1000 nm.

In the perovskite solar cell of this invention, the electron carrying layer may be arrange | positioned between what becomes a cathode among the said electrodes or the said counter electrodes, and the said photoelectric converting layer.
The material of the electron transport layer is not particularly limited. For example, N-type conductive polymer, N-type low molecular organic semiconductor, N-type metal oxide, N-type metal sulfide, alkali metal halide, alkali metal, surface activity Agents and the like. Specific examples include cyano group-containing polyphenylene vinylene, boron-containing polymer, bathocuproine, bathophenanthrene, hydroxyquinolinato aluminum, oxadiazole compound, and benzimidazole compound. Also, naphthalene tetracarboxylic acid compound, perylene derivative, phosphine oxide compound, phosphine sulfide compound, fluoro group-containing phthalocyanine, titanium oxide, zinc oxide, indium oxide, tin oxide, gallium oxide, tin sulfide, indium sulfide, zinc sulfide, etc. It is done.

The electron transport layer may consist of only a thin film electron transport layer, but preferably includes a porous electron transport layer. In particular, when the photoelectric conversion layer is a composite film in which an organic semiconductor or an inorganic semiconductor part and an organic / inorganic perovskite compound part are combined, a more complex composite film (a more complicated and complicated structure) is obtained. In order to increase efficiency, it is preferable that the composite film is formed on the porous electron transport layer.

The preferable lower limit of the thickness of the electron transport layer is 1 nm, and the preferable upper limit is 2000 nm. If the thickness is 1 nm or more, holes can be sufficiently blocked. If the said thickness is 2000 nm or less, it will become difficult to become resistance at the time of electron transport, and photoelectric conversion efficiency will become high. The more preferable lower limit of the thickness of the electron transport layer is 3 nm, the more preferable upper limit is 1000 nm, the still more preferable lower limit is 5 nm, and the still more preferable upper limit is 500 nm.

In the perovskite solar cell of this invention, the hole transport layer may be arrange | positioned between what becomes an anode among the said electrodes or the said counter electrodes, and the said photoelectric converting layer.
The material for the hole transport layer is not particularly limited, and examples thereof include a P-type conductive polymer, a P-type low molecular organic semiconductor, a P-type metal oxide, a P-type metal sulfide, and a surfactant. Specific examples include polyethylene dioxythiophene polystyrene sulfonate adduct, carboxyl group-containing polythiophene, phthalocyanine, porphyrin and the like. In addition, molybdenum oxide, vanadium oxide, tungsten oxide, nickel oxide, copper oxide, tin oxide, molybdenum sulfide, tungsten sulfide, copper sulfide, tin sulfide, etc., fluoro group-containing phosphonic acid, carbonyl group-containing phosphonic acid, CuSCN, CuI, etc. Examples thereof include copper compounds, carbon nanotubes that may be surface-modified, and carbon-containing materials such as graphene.

The preferable lower limit of the thickness of the hole transport layer is 1 nm, and the preferable upper limit is 2000 nm. If the thickness is 1 nm or more, electrons can be sufficiently blocked. If the said thickness is 2000 nm or less, it will become difficult to become resistance at the time of hole transport, and a photoelectric conversion efficiency will become high. The more preferable lower limit of the thickness is 3 nm, the more preferable upper limit is 1000 nm, the still more preferable lower limit is 5 nm, and the still more preferable upper limit is 500 nm.

The perovskite solar cell of the present invention may further have a substrate or the like. The said board | substrate is not specifically limited, For example, transparent glass substrates, such as soda-lime glass and an alkali free glass, a ceramic substrate, a transparent plastic substrate, a metal substrate, etc. are mentioned. Among these, from the viewpoint of imparting flexibility to the perovskite solar cell, a transparent plastic substrate, a metal substrate, or the like is preferable.

The perovskite solar cell of the present invention has a sealing layer that covers the counter electrode and seals the stacked body.
When the sealing layer seals the stacked body, moisture can be prevented from penetrating into the inside, and durability of the perovskite solar cell can be improved. In the present specification, the term “sealing” of the sealing layer means that the sealing layer covers the entire object so as to close its end.

In the perovskite solar cell of the present invention, the refractive index difference between the sealing layer and the counter electrode is 0.4 or less. Since the difference in refractive index between the sealing layer and the counter electrode is 0.4 or less, incident light can be prevented from being reflected at the interface between the sealing layer and the counter electrode. Conversion efficiency can be improved. The refractive index difference between the sealing layer and the counter electrode is preferably 0.3 or less. The refractive index can be measured with a spectroscopic ellipsometer or an automatic thin film measuring device (for example, HORIBA Scientific, product name: UVISEL2, HORIBA Scientific, product name: Auto SE, etc.).

In the perovskite solar cell of the present invention, the refractive index difference between the sealing layer and the counter electrode can be increased by adding an inorganic filler in the sealing layer or selecting a resin constituting the sealing layer. It can be 0.4 or less. In addition to the method of containing an inorganic filler in the sealing layer or selecting the resin constituting the sealing layer, the refractive index difference is set to 0. 0 by combining the method of selecting the material of the counter electrode. 4 or less.

In the perovskite solar cell of the present invention, the sealing layer preferably contains an inorganic filler.
By including an inorganic filler in the sealing layer, the difference in refractive index between the sealing layer and the counter electrode is reduced, so that the difference in refractive index between the sealing layer and the counter electrode is 0.4 or less. Can do.

Is not particularly restricted but includes the inorganic filler, for _{example, TiO 2, ZrO, WO 3} , Nb 2 O 5, Ta 2 O 5, consisting of BaTiO _3, etc. particles. Among them, the inorganic filler preferably has a refractive index of 2 to 3, and particles made of TiO ₂ or ZrO are preferable because the difference in refractive index from the counter electrode can be reduced.

The inorganic filler is preferably surface-modified with a surface modifier. By the surface modification of the inorganic filler, the dispersibility of the inorganic filler in the resin constituting the sealing layer can be improved, and a highly transparent sealing layer can be constructed. Thereby, the photoelectric conversion efficiency of a perovskite solar cell can be improved.
The surface modifier includes at least one element selected from the group consisting of P (phosphorus), Ti (titanium), Zr (zirconium), Al (aluminum), and Si (silicon), and a bond to these elements A surface modifier containing a modified organic group is preferred. Among these, a surface modifier containing at least one element selected from the group consisting of P, Ti, Zr, and Si and an organic group bonded to these elements is more preferable. When the surface modifier contains Al, the organic / inorganic perovskite compound may be deteriorated by diffusion of Al into the photoelectric conversion layer, and the photoelectric conversion efficiency of the perovskite solar cell may be reduced.
Specific examples of the surface modifier include, for example, phosphate esters (including P), titanium coupling agents (including Ti), silane coupling agents (including Si), and zirconium coupling agents (including Zr). Etc. These surface modifiers may be used independently and 2 or more types may be used together.

Although the organic group in the said surface modifier is not specifically limited, It is preferable that it is group containing a linear hydrocarbon chain.
Although carbon number of the said organic group is not specifically limited, A preferable minimum is 8 and a preferable upper limit is 22. If the number of carbon atoms is 8 or more, the dispersibility of the inorganic filler in the resin constituting the sealing layer and the organic solvent used in forming the sealing layer is improved, and the transparency of the sealing layer is increased. . When the carbon number is 22 or less, the surface modifier is easily added to the surface of the particles. The more preferable lower limit of the carbon number is 14, and the more preferable upper limit is 20.

The average particle diameter of the inorganic filler is preferably 1 μm or less. By setting the average particle size of the inorganic filler to 1 μm or less, the inorganic filler can be dispersed without impairing the transparency of the sealing layer. A more preferable average particle size of the inorganic filler is 100 nm or less, and a more preferable average particle size is 50 nm or less. The lower limit of the average particle diameter of the inorganic filler is not particularly limited, but is substantially about 1 nm.
Here, the average particle diameter refers to the average primary particle diameter. The average particle diameter can be measured with a transmission electron microscope.

The minimum with preferable content of the said inorganic filler in the said sealing layer is 50 weight%, and a preferable upper limit is 95 weight%. The refractive index of a sealing layer can be improved effectively because the said inorganic filler is 50 weight% or more. When the content of the inorganic filler is 95% by weight or less, the sealing layer can be prevented from significantly exceeding the refractive index of the counter electrode. The minimum with more preferable content of the said inorganic filler in the said sealing layer is 70 weight%, and a more preferable upper limit is 90 weight%.

The sealing agent constituting the sealing layer is preferably a resin, and examples thereof include a thermoplastic resin, a thermosetting resin, and a photocurable resin. The refractive index of these resins is not particularly limited, but is usually about 1.42 to 1.60. Examples of the thermoplastic resin include butyl rubber, polyester, polyurethane, polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyvinyl alcohol, polyvinyl acetate, ABS resin, polybutadiene, polyamide, polycarbonate, polyimide, polyisobutylene, and cycloolefin resin. Can be mentioned. As said thermosetting resin, an epoxy resin, an acrylic resin, a silicone resin, a phenol resin, a melamine resin, a urea resin etc. are mentioned, for example. Examples of the photocurable resin include an epoxy resin, an acrylic resin, an allyl phthalate resin, a vinyl resin, and an ene-thiol resin. Of these, acrylic resins are preferred from the viewpoints of transparency and barrier properties.
In addition, from the viewpoint of improving the dispersibility of the inorganic filler and constructing a highly transparent sealing layer, a resin having a relatively high polarity is preferable. On the other hand, from the viewpoint of suppressing deterioration of the organic / inorganic perovskite compound, a resin having a relatively low polarity is preferable. If the resin has a relatively low polarity, it is possible to suppress the organic component in the organic / inorganic perovskite compound from eluting into the sealing layer at the time of sealing, and as a result, the organic / inorganic perovskite compound is deteriorated. Can be suppressed. An acrylic resin is preferable because it can be adjusted to an appropriate polarity from the viewpoint of achieving both the dispersibility of the inorganic filler and the suppression of deterioration of the organic / inorganic perovskite compound.

Examples of the monomer constituting the acrylic resin include a monomer having a linear skeleton and a monomer having a cyclic skeleton. Among these, from the viewpoint of ease of improving the refractive index, a monomer having a cyclic skeleton is preferable, an alicyclic skeleton and a monomer having an aromatic hydrocarbon skeleton are more preferable, and the alicyclic skeleton contained in the repeating unit of the molecule. A monomer having 6 to 12 carbon atoms in the aromatic hydrocarbon skeleton is more preferable.
Examples of the monomer having 6 to 12 carbon atoms of the aromatic hydrocarbon skeleton contained in the repeating unit of the molecule include benzyl (meth) acrylate, phenyl (meth) acrylate, and bisphenol A di (meth) acrylate. . Examples of the monomer having 6 to 12 carbon atoms in the alicyclic skeleton contained in the repeating unit of the molecule include norbornyl (meth) acrylate, isobornyl (meth) acrylate, adamantyl (meth) acrylate, cyclohexyl (meth) acrylate, Examples include dicyclopentadienyl (meth) acrylate, dicyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, and dicyclopentenyloxyethyl (meth) acrylate.

The acrylic resin preferably has 4 or more C atoms / O atoms in the molecule. If the C atom / O atom is 4 or more, the acrylic resin becomes a resin having a relatively low polarity, and the organic component in the organic / inorganic perovskite compound is eluted into the sealing layer at the time of sealing. It can suppress that a perovskite compound deteriorates. Further, when the C atom / O atom is 4 or more, molecular diffusion over time is suppressed, and the heat resistance durability of the perovskite solar cell is improved. The C atom / O atom is more preferably 5 or more, and still more preferably 6 or more.
From the viewpoint of solvent solubility of the acrylic resin, the C atom / O atom is preferably 30 or less, and more preferably 20 or less.
In addition, the value of C atom / O atom in the molecule | numerator of an acrylic resin is the CHN / O elemental analysis using an organic trace element analyzer (For example, Perkin Elmer 2400II), NMR apparatus (For example, JEOL). It can be measured by solution NMR using ECA II).

The value of C atom / O atom in the molecule of the acrylic resin can be easily controlled by adjusting the kind and composition of the monomer constituting the acrylic resin.
Specifically, for example, an acrylic resin having 4 or more C atoms / O atoms can be obtained by homopolymerizing or copolymerizing a monomer having 4 or more C atoms / O atoms in the molecule. .
Examples of the monomer having 4 or more C atoms / O atoms in the molecule include an alkyl group having 8 or more carbon atoms such as ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate (meta) ) Alkyl acrylate. Moreover, (meth) acrylate which has aromatic hydrocarbon frame | skeletons, such as a phenyl (meth) acrylate and a naphthyl (meth) acrylate, is mentioned. Moreover, (meth) acrylates having an alicyclic skeleton such as isobornyl (meth) acrylate, norbornyl (meth) acrylate, adamantyl (meth) acrylate, cyclohexyl (meth) acrylate, and the like can be given. Furthermore, (meth) acrylate etc. which have groups (for example, a hydroxyl group, a carboxyl group, an epoxy group, etc.) which can add reactive functional groups, such as hydroxyl ethyl hexyl (meth) acrylate, are mentioned. These monomers may be used independently and 2 or more types may be used together. Among them, (meth) alkyl acrylate having an alkyl group having 8 or more carbon atoms, (meth) acrylate having an alicyclic skeleton, and a group to which a reactive functional group can be added (for example, a hydroxyl group, a carboxyl group, an epoxy group, etc.) The (meth) acrylate etc. which have are preferable, and the (meth) acrylate which has alicyclic skeleton is suitable.

The acrylic resin may be a resin obtained by forming a copolymer having a reactive functional group and then crosslinking the reactive functional group with a crosslinking agent. In this case, by adjusting the number of the reactive functional groups, deterioration (initial deterioration) at the time of sealing the perovskite solar cell due to curing shrinkage accompanying the crosslinking reaction can be suppressed, and the sputtering resistance can be improved. be able to. As said reactive functional group, an epoxy group, a hydroxyl group, a carboxyl group, an alkenyl group, an isocyanate group etc. are mentioned, for example.
The said crosslinking agent is not specifically limited, The crosslinking reaction of the said reactive functional group can be started using a catalyst etc.
The acrylic resin may be a resin obtained by forming a film of the monomer as it is and then crosslinking or polymerizing the monomer with heat or UV.

The acrylic resin has a preferable lower limit of the solubility parameter (SP value) of 7.0 and a preferable upper limit of 10.0. If the SP value is 7.0 or more, the range of resin options is widened and molding becomes easy. When the SP value is 10.0 or less, it is possible to suppress deterioration of the organic / inorganic perovskite compound by elution of the organic component in the organic / inorganic perovskite compound into the sealing layer at the time of sealing. The more preferable lower limit of the SP value is 7.5, and the more preferable lower limit is 8.0. From the viewpoint of enhancing the high temperature durability of the perovskite solar cell, the upper limit of the SP value is more preferably 9.5, and still more preferably 9.0.

The SP value is called a solubility parameter, and is an index that can express the ease of dissolution. In this specification, the method proposed by Fedors (R. F. Fedors, Polym. Eng. Sci., 14 (2), 147-154 (1974)) is used to calculate the SP value. The SP value can be calculated according to the following formula (1) from the evaporation energy (Δecoh) (cal / mol) and the molar volume (Δv) (cm ³ / mol) for each atomic group in the repeating unit. In formula (1), δ represents an SP value (cal / mol) ^1/2 .

As Δecoh and Δv, J.H. The values described in Brandrup et al., “Polymer Handbook, Fourth Edition”, volume 2 can be used.
When Tg ≧ 25 ° C., the number of main chain skeleton atoms is n, and 2n is calculated when n ≧ 3, and 4n is added to Δv when n <3.

The SP value of the copolymer can be calculated by the following formula (2) by calculating the SP value of each repeating unit alone in the copolymer and using the volume fraction thereof. In the formula (2), δcop represents the SP value of the copolymer, φ1, φ2 represents the volume fraction of the repeating units 1 and 2, and δ1, δ2 represents the SP value of the repeating units 1 and 2 alone.

When the sealing layer does not contain the inorganic filler, as described above, in the perovskite solar cell of the present invention, the refractive index difference between the sealing layer and the counter electrode is 0.4 or less. The refractive index of the resin constituting the sealing layer is preferably 1.6 to 2.0. Examples of the resin having such a refractive index include an epoxy resin, an acrylic resin, a silicone resin, and a phenol resin. Especially, it is preferable that the said sealing layer contains resin which has an aromatic skeleton. That is, the sealing layer preferably contains a resin having an aromatic skeleton, and the refractive index of the resin having an aromatic skeleton is 1.6 to 2.0. Examples of such aromatic skeletons include triazine skeleton resins, fluorene skeleton resins, naphthalene skeleton resins, biphenyl skeleton resins, and fluorene skeleton resins.

The resin constituting the sealing layer preferably has a molecular weight of 100,000 to 1,000,000. When the molecular weight is 100,000 or more, damage during the inorganic layer deposition can be suppressed, and transparency is improved. When the molecular weight is 1000000 or less, the fixability of the inorganic layer is improved.

The preferable lower limit of the thickness of the sealing layer is 100 nm, and the preferable upper limit is 100,000 nm. When the thickness is 100 nm or more, the counter electrode can be sufficiently covered by the sealing layer. When the thickness is 100000 nm or less, water vapor entering from the side surface of the sealing layer can be sufficiently blocked. The more preferable lower limit of the thickness is 500 nm, the more preferable upper limit is 50000 nm, the still more preferable lower limit is 1000 nm, and the still more preferable upper limit is 2000 nm.

The perovskite solar cell of the present invention preferably further has an inorganic layer that seals the outside of the sealing layer. Thereby, since the said inorganic layer exhibits water vapor | steam barrier performance and it can suppress that a water | moisture content osmose | permeates the inside of the said sealing layer, durability of a perovskite solar cell can be improved more. In addition, since the inorganic layer is formed on the sealing layer instead of forming the inorganic layer on the counter electrode, the sealing layer plays a role of filling and flattening the unevenness on the surface of the counter electrode. The inorganic layer can be more easily adhered.

The inorganic layer preferably contains a metal oxide, a metal nitride, or a metal oxynitride. The metal oxide, metal nitride or metal oxynitride is not particularly limited as long as it has a water vapor barrier property. For example, Si, Al, Zn, Sn, In, Ti, Mg, Zr, Ni, Ta , W, Cu, or an oxide, nitride, or oxynitride of an alloy containing two or more of these. Among these, in order to impart water vapor barrier property and flexibility to the inorganic layer, an oxide, nitride or oxynitride of a metal element containing both metal elements of Zn and Sn is preferable.

Among them, the metal oxide, metal nitride or metal oxynitride is particularly preferably a general formula _Zn a _Sn b _{O c} metal oxide represented by (ZTO). By using the metal oxide represented by the general formula Zn _a Sn _b O _c for the inorganic layer, the metal oxide contains tin (Sn) atoms, and thus gives the inorganic layer appropriate flexibility. Even when the thickness of the inorganic layer is increased, the stress is reduced, so that peeling of the inorganic layer, the electrode, the semiconductor layer, and the like can be suppressed. Thereby, the water vapor | steam barrier property of the said inorganic layer can be improved, and durability of a perovskite solar cell can be improved more.

In the metal oxide represented by the above general formula Zn _a Sn _b O _c , it is preferable that the ratio Xs (wt%) of Sn to the sum of Zn and Sn satisfies 70>Xs> 0.
The element ratio of zinc (Zn), tin (Sn), and oxygen (O) contained in the metal oxide represented by the general formula Zn _a Sn _b O _c in the inorganic layer is determined by X-ray photoelectron spectroscopy ( It can be measured using an XPS) surface analyzer (for example, ESCALAB-200R manufactured by VG Scientific).

The inorganic layer, when containing a metal oxide represented by the general formula _Zn a _Sn b _{O c,} preferably further contains silicon (Si) and / or aluminum (Al).
By adding silicon (Si) and / or aluminum (Al) to the inorganic layer, the transparency of the inorganic layer can be increased and the photoelectric conversion efficiency of the perovskite solar cell can be improved.

The inorganic layer preferably has a refractive index close to that of the counter electrode. When the refractive index of the inorganic layer is close to the refractive index of the counter electrode, not only the refractive index difference between the counter electrode and the sealing layer but also the inorganic layer by adjusting the refractive index of the sealing layer. Since the refractive index difference of the sealing layer is also reduced, reflection of light at the interface between the inorganic layer and the sealing layer can be suppressed, and the photoelectric conversion efficiency can be increased.

The preferable lower limit of the thickness of the inorganic layer is 30 nm, and the preferable upper limit is 3000 nm. If the said thickness is 30 nm or more, the said inorganic layer can have sufficient water vapor | steam barrier property, and durability of a perovskite solar cell will improve. When the thickness is 3000 nm or less, even if the thickness of the inorganic layer is increased, the generated stress is small, and thus the peeling of the inorganic layer, the electrode, the semiconductor layer, and the like can be suppressed. The more preferable lower limit of the thickness is 50 nm, the more preferable upper limit is 1000 nm, the still more preferable lower limit is 100 nm, and the still more preferable upper limit is 500 nm.
The thickness of the inorganic layer can be measured using an optical interference film thickness measuring device (for example, FE-3000 manufactured by Otsuka Electronics Co., Ltd.).

FIG. 2 is a cross-sectional view schematically showing an example of the perovskite solar cell of the present invention.
The perovskite solar cell 1 shown in FIG. 2 has an electrode 2, a counter electrode 3, and a photoelectric conversion layer 4 disposed between the electrode 2 and the counter electrode 3 on a substrate 7. The sealing layer 5 is arrange | positioned by this, and the inorganic layer 6 is arrange | positioned on the sealing layer 5. FIG. In the perovskite solar cell 1 shown in FIG. 2, the counter electrode 3 is a patterned electrode.

The method for producing the perovskite solar cell of the present invention is not particularly limited. For example, after forming the electrode, the photoelectric conversion layer, and the counter electrode in this order on the substrate, the sealing layer is formed on the counter electrode. And a method of arranging the inorganic layer on the sealing layer.

The method for forming the photoelectric conversion layer is not particularly limited, and examples thereof include a vacuum deposition method, a sputtering method, a gas phase reaction method (CVD), an electrochemical deposition method, and a printing method. Especially, the solar cell which can exhibit high photoelectric conversion efficiency can be simply formed in a large area by employ | adopting the printing method. Examples of the printing method include a spin coating method and a casting method, and examples of a method using the printing method include a roll-to-roll method.

The method of disposing the sealing layer on the counter electrode is not particularly limited. For example, a method of sealing the counter electrode using a sheet-shaped sealing layer, and a resin constituting the sealing layer as an organic solvent. The method etc. which apply | coat the dissolved resin solution on the said counter electrode are mentioned. In addition, a method of polymerizing a liquid monomer with heat or UV after applying a liquid monomer to be a sealing layer on the counter electrode, a method of cooling after melting the sealing layer with heat, and the like can be mentioned. .

As a method of disposing the inorganic layer on the sealing layer, a vacuum deposition method, a sputtering method, a gas phase reaction method (CVD), or an ion plating method is preferable. Among these, the sputtering method is more preferable for forming a dense layer, and the DC magnetron sputtering method is more preferable among the sputtering methods. In the sputtering method, an inorganic layer can be formed by using a metal target and oxygen gas or nitrogen gas as raw materials and depositing the raw material on the sealing layer to form a film.

According to the present invention, a perovskite solar cell with high photoelectric conversion efficiency can be provided.

It is a schematic diagram which shows an example of the crystal structure of an organic inorganic perovskite compound. It is sectional drawing which shows typically an example of the perovskite solar cell of this invention.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Example 1
(1) Fabrication of laminated body in which electrode / electron transport layer / photoelectric conversion layer / hole transport layer / counter electrode are laminated On a glass substrate, an FTO film having a thickness of 1000 nm is formed as an electrode, and pure water, acetone, and methanol are added. Using this order, each was subjected to ultrasonic cleaning for 10 minutes and then dried.
A titanium isopropoxide ethanol solution adjusted to 2% was applied on the surface of the FTO film by a spin coating method, followed by baking at 400 ° C. for 10 minutes to form a thin-film electron transport layer having a thickness of 20 nm. Further, a titanium oxide paste containing polyisobutyl methacrylate as an organic binder and titanium oxide (a mixture of an average particle size of 10 nm and 30 nm) is applied onto the thin film electron transport layer by a spin coat method, and then heated to 500 ° C. Was fired for 10 minutes to form a porous electron transport layer having a thickness of 500 nm.
Next, CH ₃ NH ₃ I and PbCl ₂ were dissolved at a molar ratio of 3: 1 using N, N-dimethylformamide (DMF) as a solvent as a photoelectric conversion layer forming solution, and the total weight of CH ₃ NH ₃ I and PbCl ₂ The concentration was adjusted to 20%. This solution was laminated on the electron transport layer by spin coating. Further, a 1% by weight chlorobenzene solution of Poly (4-butylphenyl-diphenyl-amine) (manufactured by 1-Material) was laminated as a hole transport layer on the organic / inorganic perovskite compound site to a thickness of 50 nm by spin coating.
On the hole transport layer, an ITO film having a thickness of 100 nm was formed as a counter electrode by vacuum vapor deposition to obtain a laminate in which the electrode / electron transport layer / photoelectric conversion layer / hole transport layer / counter electrode were stacked.

(2) Formation of sealing layer (2-1) Synthesis of acrylic resin and preparation of acrylic resin solution Isobornyl methacrylate (manufactured by Kyoeisha Chemical Co., Ltd.) and hydroxyethyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd.) in a molar ratio of 9: 1 Mixed. Next, AIBN (manufactured by Nippon Finechem Co., Ltd.) as a catalyst was added in an amount of 0.002 equivalent in molar ratio to hydroxyethyl acrylate, cyclohexane (manufactured by Wako Pure Chemical Industries, Ltd.) was added so that the monomer would be 50% by weight, and 70 ° C. The mixture was heated and stirred for 12 hours. After heating and stirring, 2-methacryloyloxyethyl isocyanate (manufactured by Showa Denko KK) in a molar ratio with respect to hydroxyethyl acrylate is 0.002 equivalent, and dibutyltin dilaurate (manufactured by Tokyo Chemical Industry Co., Ltd.) is 2-methacryloyloxyethyl isocyanate. In contrast, 300 ppm was added, and the mixture was heated and stirred at 70 ° C. for 6 hours. The reaction solution was allowed to cool and then added dropwise to methanol. The precipitated solid was collected by filtration and dried under reduced pressure to obtain an acrylic resin having a molecular weight of 200,000.
The obtained acrylic resin was mixed with cyclohexane so that it might become 10 weight%, and the acrylic resin solution was obtained.
(2-2) Synthesis of inorganic filler and preparation of inorganic filler dispersion A methanol dispersion of titanium oxide nanoparticles (manufactured by Sakai Chemical Industry Co., Ltd., SRD-M, average particle diameter: 4 nm) was converted into phosphate ester (oleyl acid phosphate, The titanium oxide nanoparticles were surface-treated by treatment with P containing organic group carbon number = 18, manufactured by SC Organic Chemical Co., Ltd. (Phoslex A-18D), and dried to obtain an inorganic filler powder. The obtained powder was dispersed in cyclohexane so as to be 10% by weight to obtain an inorganic filler dispersion.
(2-3) Formation of sealing layer Acrylic resin solution obtained in “(2-1) Synthesis of acrylic resin and preparation of acrylic resin solution” and “(2-2) Synthesis of inorganic filler and inorganic filler dispersion liquid” The inorganic filler dispersion obtained in “Preparation” was mixed at a volume ratio of 7: 3, and 4% by weight of perhexyl PV was added to the solute weight to obtain a resin solution having an inorganic filler content of 50% by weight. The obtained resin solution was applied onto the counter electrode by the doctor blade method and heated on a hot plate at 100 ° C. for 10 minutes to form a sealing layer containing an inorganic filler.

(3) Formation of inorganic layer The sample on which the sealing layer was formed was attached to the substrate holder of the sputtering apparatus, and a ZnSn alloy (ZTO, Zn: Sn = 95: 5 wt%) target was applied to the cathode A of the sputtering apparatus. A Si target was attached to B. The film formation chamber of the sputtering apparatus was evacuated by a vacuum pump, and the pressure was reduced to 5.0 × 10 ⁻⁴ Pa. Thereafter, sputtering was performed under the conditions shown in the film formation condition A, and a ZnSnO (Si) thin film was formed as an inorganic layer on the sealing layer to a thickness of 100 nm to obtain a perovskite solar cell.
(Film formation condition A)
Argon gas flow rate: 50 sccm, oxygen gas flow rate: 50 sccm
Power output: Cathode A = 500W, Cathode B = 1500W

(Examples 2 to 12, Comparative Example 3)
A perovskite solar cell in the same manner as in Example 1 except that the content of the inorganic filler was changed as shown in Table 1 by changing the type of the inorganic filler and the mixing ratio of the acrylic resin solution and the inorganic filler dispersion. Got.

In the example using zirconium oxide as the inorganic filler, zirconium oxide nanoparticle methanol dispersion (manufactured by Sakai Chemical Industry Co., Ltd., SZR-M, average particle size: 3 nm) and phosphate ester (including P) as a surface modifier. , Organic group carbon number = 18, SC Organic Chemical Co., Ltd., Phoslex A-18D) was used. In the example using tungsten oxide, tungsten oxide nanoparticle isopropanol dispersion (manufactured by Nanograde AG, 6040-W, average particle size: 15 nm) and phosphoric acid ester as a surface modifier (carbon number of organic group including P) = 18, SC Organic Chemical Co., Phoslex A-18D) was used. In an example using silica, a silica nanoparticle methanol dispersion (manufactured by Nissan Chemical Industries, MA-ST-M, average particle size: 20 nm) and a phosphoric acid ester as a surface modifier (the carbon number of the organic group including P = 18, Phoslex A-18D manufactured by SC Organic Chemical Co., Ltd. was used. In the example using titanium oxide of Example 8, titanium oxide nanoparticle methanol dispersion (manufactured by Sakai Chemical Industry Co., Ltd., R-38L, average particle size 400 nm) and phosphate ester (containing P, organic group as surface modifier) Carbon number = 18, manufactured by SC Organic Chemicals, Phoslex A-18D).

Further, the following surface modifier was used.
Titanium coupling agent (including Ti, organic group carbon number = 18, manufactured by Matsumoto Fine Chemical Co., Ltd., ORGATICS TC-800)
Aluminum coupling agent (including Al, carbon number of organic group = 18, manufactured by Ajinomoto Fine Techno Co., Plenact AL-M)
Silane coupling agent (including Si, organic group carbon number = 8, manufactured by Shin-Etsu Silicone, KBM-1083)
Zirconium coupling agent (including Zr, organic group carbon number = 18, manufactured by Matsumoto Fine Chemical Co., Ltd., ORGATIZ ZC-320)

(Example 13)
(1) Production of laminate in which electrode / electron transport layer / photoelectric conversion layer / hole transport layer / counter electrode are laminated In the same manner as in Example 1, electrode / electron transport layer / photoelectric conversion layer / hole transport layer / opposite A laminate in which electrodes were laminated was produced.

(2) Formation of sealing layer A resin having a triazine skeleton (Nissan Chemical Co., Ltd., UR-101) was coated on the counter electrode by the doctor blade method, and heated and sealed on a hot plate at 100 ° C for 10 minutes. A layer was formed.

(3) Formation of inorganic layer An inorganic layer was formed on the sealing layer in the same manner as in Example 1.

(Example 14, comparative example 4)
A perovskite solar cell was obtained in the same manner as in Example 13 except that the type of resin for the sealing layer was changed as shown in Table 1. The following resin was used.
OGSOL EA-0200: fluorene skeleton, Nissan Chemical Co., Ltd. TOPAS6017: cycloolefin polymer, manufactured by Polyplastics

(Comparative Example 1)
(1) Production of laminate in which electrode / electron transport layer / photoelectric conversion layer / hole transport layer / counter electrode are laminated In the same manner as in Example 1, electrode / electron transport layer / photoelectric conversion layer / hole transport layer / opposite A laminate in which electrodes were laminated was produced.

(2) Formation of sealing layer (2-1) Synthesis of acrylic resin and preparation of acrylic resin solution An acrylic resin was synthesized in the same manner as in the examples to prepare an acrylic resin solution.
(2-2) Formation of Sealing Layer 4% by weight of perhexyl PV is added to the solute weight of the acrylic resin solution, and the resulting resin solution is applied onto the counter electrode by the doctor blade method, at 100 ° C. for 10 minutes. And a sealing layer was formed on the counter electrode.

(3) Formation of inorganic layer An inorganic layer was formed on the sealing layer in the same manner as in Example 1.

(Comparative Example 2)
(1) Production of laminate in which electrode / electron transport layer / photoelectric conversion layer / hole transport layer / counter electrode are laminated In the same manner as in Example 1, electrode / electron transport layer / photoelectric conversion layer / hole transport layer / opposite A laminate in which electrodes were laminated was produced.

(2) Formation of sealing layer Magnesium fluoride (manufactured by Wako Pure Chemical Industries, Ltd.) was deposited using a vacuum vapor deposition machine to form a 100 nm sealing layer on the counter electrode.

(3) Formation of inorganic layer An inorganic layer was formed on the sealing layer in the same manner as in Example 1.

<Evaluation>
The following evaluation was performed about the counter electrode obtained by the Example and the comparative example, the sealing layer, the inorganic layer, and the perovskite solar cell. The results are shown in Table 2.

(1) Measurement of refractive index difference Using an automatic thin film measuring apparatus (manufactured by HORIBA Scientific, product name: Auto SE, laser wavelength 632.8 nm), the refractive index of the sealing layer (A), the refractive index of the counter electrode (B ) And the refractive index of the inorganic layer. The refractive index difference B−A was calculated from the obtained refractive index.

(2) Photoelectric conversion efficiency A power source (manufactured by KEITHLEY, 236 model) is connected between the electrodes of the solar cell, and the photoelectric conversion efficiency is measured by using a solar simulation (manufactured by Yamashita Denso Co., Ltd.) having an intensity of 100 mW / cm ^2. The obtained photoelectric conversion efficiency was defined as the initial conversion efficiency. The solar cell obtained in Comparative Example 1 was normalized based on the initial conversion efficiency, and evaluated according to the following criteria.
A: Normalized value is 1.05 or more. O: Normalized value is 1.0 or more and less than 1.05. X: Normalized value is less than 1.0.

According to the present invention, a perovskite solar cell with high photoelectric conversion efficiency can be provided.

1 Perovskite solar cell 2 Electrode 3 Counter electrode (patterned electrode)
4 Photoelectric conversion layer 5 Sealing layer 6 Inorganic layer 7 Substrate

Claims (10)

A laminate including an electrode, a counter electrode, a photoelectric conversion layer disposed between the electrode and the counter electrode, and a sealing layer that covers the counter electrode and seals the stack. A perovskite solar cell,
The photoelectric conversion layer includes an organic / inorganic perovskite compound represented by a general formula RMX ₃ (where R is an organic molecule, M is a metal atom, and X is a halogen atom or a chalcogen atom),
A perovskite solar cell, wherein a refractive index difference between the sealing layer and the counter electrode is 0.4 or less. The perovskite solar cell according to claim 1, wherein the sealing layer contains an inorganic filler. The perovskite solar cell according to claim 2, wherein the inorganic filler has a refractive index of 2 to 3. The perovskite solar cell according to claim 2 or 3, wherein the inorganic filler is particles made of TiO ₂ or ZrO. The inorganic filler is surface-modified with a surface modifier, and the surface modifier includes at least one element selected from the group consisting of P, Ti, Zr and Si, and an organic group bonded to the element. The perovskite solar cell according to claim 2, 3, or 4. 6. The perovskite solar cell according to claim 5, wherein the organic group in the surface modifier has 8 to 22 carbon atoms. 7. The perovskite solar cell according to claim 2, wherein the content of the inorganic filler in the sealing layer is 50 to 95% by weight. The perovskite solar cell according to claim 2, 3, 4, 5, 6 or 7, wherein the inorganic filler has an average particle size of 1 µm or less. The perovskite solar cell according to claim 1, wherein the sealing layer contains a resin having an aromatic skeleton, and the refractive index of the resin having an aromatic skeleton is 1.6 to 2.0. The perovskite solar cell according to claim 1, further comprising an inorganic layer that seals the outside of the sealing layer.

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