JP2009238610A - Material for photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a material for a photoelectric conversion element made by using compounds with a high sensitizing effect and excellent in an absorption property and chronological stability. <P>SOLUTION: The material for the photoelectric conversion element is structured by using compounds of formula [1]. In the formula, R<SB>1</SB>, R<SB>2</SB>and R<SB>3</SB>, R<SB>4</SB>are denote alkylene groups forming 5-membered rings or 6-membered rings by coupling with each other, and Z<SB>1</SB>denotes a bivalent coupling group. R<SB>5</SB>, R<SB>6</SB>, R<SB>7</SB>, R<SB>8</SB>denote a hydrogen atom, alkyl group, aryl group, halogen atom, or cyano group. R<SB>9</SB>and R<SB>10</SB>denotes a hydrogen atom or an alkyl group. R<SB>11</SB>as well as R<SB>12</SB>is a substituent on an aromatic hydrocarbon residual, and denotes a hydrogen atom, alkyl group, alkoxy group, or halogen atom. R<SB>13</SB>is a substituent selected from a carboxyl group, alkyl group, aryl group, aralkyl group, or a heterocyclic substituent; and R<SB>14</SB>is a substituent selected from an alkyl group, aryl group, aralkyl group, or heterocyclic substituent. If both R<SB>13</SB>and R<SB>14</SB>are alkyl groups, aryl groups, aralkyl groups, or heterocyclic substituent, at least either R<SB>13</SB>or R<SB>14</SB>has a carboxyl group as a substituent. Y<SB>1</SB>is a bivalent residual forming a nitrogen-content heterocyclic ring by coupling with carbonyl carbon and methine carbon, and has at least one carboxyl group as a substituent. 'l' and m denote 0 or 1. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element material.

Elements that convert light into electrical energy are used in photodiodes, photosensors, solar cells, and the like. In recent years, global warming due to the increase in CO ₂ concentration caused by the use of a large amount of fossil fuel, and the increase in energy demand accompanying population increase are recognized as problems related to the existence of human beings. Therefore, a solar cell using a photoelectric conversion element has been energetically studied for the purpose of using sunlight that is infinite and does not generate harmful substances.

  Examples of solar cells that have been put into practical use include residential single crystal silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and indium copper selenide. However, silicon-based solar cells require materials with very high purity, have a problem that the purification process is complicated, the number of processes is large, and the manufacturing cost is high. In addition, inorganic solar cells also have a demand for weight reduction, which is disadvantageous in that payback to users is long, and there has been a problem in spreading.

  On the other hand, many organic solar cells using organic materials have been proposed. For organic solar cells, a Schottky photoelectric conversion element that joins a p-type organic semiconductor and a metal having a low work function, a p-type organic semiconductor and an n-type inorganic semiconductor, or a p-type organic semiconductor and an electron-accepting organic compound. A heterojunction photoelectric conversion element or the like is used. Organic semiconductors used are synthetic dyes and pigments such as chlorophyll and perylene, conductive polymer materials such as polyacetylene or composite materials thereof. Although these organic solar cells have advantages such as low cost and easy area enlargement, they often have conversion efficiency as low as 1% or less and also have poor durability.

  Under such circumstances, an organic solar cell exhibiting good conversion efficiency has been reported by Dr. Gretzell of Switzerland, and is called a dye-sensitized solar cell or a Gretzel solar cell (for example, see Non-Patent Document 1). ). In a dye-sensitized solar cell, a photoelectric conversion element using a semiconductor electrode in which a semiconductor layer carrying a sensitizing dye is provided on a conductive substrate is used as a working electrode. Although the semiconductor electrode itself does not have photoelectric conversion ability in the visible light region, by carrying a sensitizing dye having an absorption wavelength in the visible light region, the photoelectric conversion ability of the semiconductor electrode can be expanded to the visible region, Sunlight with many visible light components can be effectively converted into electrical energy.

  The ruthenium complex used by Dr. Gretzell et al. As a sensitizing dye has limited resources, and if this dye-sensitized solar cell is put to practical use, its supply is in danger. This problem can be solved if the sensitizing dye can be changed to an organic dye with less resource constraints. As organic dyes, for example, merocyanine dyes, cyanine dyes, and 9-phenylxanthene dyes have been reported (for example, see Patent Documents 1 to 3). However, these organic dyes have poor adsorptivity to the semiconductor layer, and a high sensitization effect cannot be obtained. Further, since the organic dye supported on the semiconductor layer elutes into the electrolytic solution over time during storage of the photoelectric conversion element, there is a problem that stability with time is low. An organic dye capable of obtaining a higher sensitizing effect is also disclosed, but there is still a problem in stability over time (see, for example, Patent Documents 4 to 5).

Recently, an organic dye having a high sensitizing effect and excellent stability over time has been disclosed. From the viewpoint of producing a dye-sensitized solar cell having practical durability, further stability over time is required. However, the disclosed organic dyes still have insufficient temporal stability (see, for example, Patent Documents 6 to 7).
JP 11-238905 A JP 2001-76773 A Japanese Patent Laid-Open No. 10-92477 JP 2002-164089 A JP 2004-95450 A JP 2004-200068 A JP 2005-19252 A Brian O'Regan & Michael Graetzel, "A low-cost, high-efficiency solar cell based on dyed TiO2 films", 1991, 353, p. 737-740

  An object of the present invention is to provide a material for a photoelectric conversion element using a compound having a high sensitizing effect and excellent in adsorptivity and stability over time.

  The problem could be solved by a material for a photoelectric conversion element using at least one of the compounds represented by the general formula [I] or [II].

In the general formula [I], R ₁ and R ₂ , R ₃ and R ₄ are each bonded to form an alkylene residue which forms a 5-membered or 6-membered ring, and Z ₁ represents a divalent linking group. Show. R ₅ , R ₆ , R ₇ and R ₈ represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom or a cyano group. R ₉ and R ₁₀ represent a hydrogen atom or an alkyl group. R ₁₁ and R ₁₂ are substituents on the aromatic hydrocarbon residue and each represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. R ₁₃ is a substituent selected from a carboxyl group, an alkyl group, an aryl group, an aralkyl group or a heterocyclic substituent, and R ₁₄ is selected from an alkyl group, an aryl group, an aralkyl group or a heterocyclic substituent. When R ₁₃ and R ₁₄ are both an alkyl group, an aryl group, an aralkyl group or a heterocyclic substituent, at least one of R ₁₃ and R ₁₄ has a carboxyl group as a substituent. Y ₁ is a divalent residue that forms a nitrogen-containing heterocycle by linking to a carbonyl carbon and a methine carbon, and has at least one carboxyl group as a substituent. l and m each represents 0 or 1;

In the general formula [II], R ₁₅ and R ₁₆ , R ₁₇ and R ₁₈ are linked together to form a 5- or 6-membered alkylene residue, and Z ₂ represents a divalent linking group. Show. R ₁₉ , R ₂₀ , R ₂₁ and R ₂₂ represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom or a cyano group. R ₂₃ and R ₂₄ represent a hydrogen atom or an alkyl group. R ₂₅ and R ₂₆ are substituents on the aromatic hydrocarbon residue and each represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom. R ₂₇ is a substituent selected from a carboxyl group, an alkyl group, an aryl group, an aralkyl group or a heterocyclic substituent, and R ₂₈ is selected from an alkyl group, an aryl group, an aralkyl group or a heterocyclic substituent. When R ₂₇ and R ₂₈ are both alkyl groups, aryl groups, aralkyl groups, or heterocyclic substituents, at least one of R ₂₇ and R ₂₈ has a carboxyl group as a substituent. X ₁ represents an electron-withdrawing substituent. n and p represent 0 or 1.

The compound represented by the general formula [I] or [II] is a compound classified as a merocyanine dye and has a high sensitizing effect. The merocyanine dye has a structure in which a unit having a donor substituent in a molecule and a unit having an acceptor substituent are connected by a conjugated double bond. When a merocyanine dye is used as a sensitizing dye for a semiconductor layer, it is common to introduce an acidic group that promotes adsorption to the semiconductor layer onto the acceptor unit of the merocyanine dye. However, the adsorptivity is insufficient from a practical point of view, and there is a problem that the sensitizing dye is eluted in the electrolytic solution when the photoelectric conversion element is stored over time. As shown in the present invention, sensitization is achieved by using a dye in which two molecules of a merocyanine dye composed of a pair of donor unit / acceptor unit are connected by a divalent linking group (Z ₁ , Z ₂ ). It has been found that the elution of the dye can be effectively prevented. The compound represented by the general formula [I] or [II] has at least two acidic groups that promote the adsorptivity to the semiconductor layer in one molecule, and is efficiently adsorbed on the semiconductor layer. By combining a donor unit having a specific structure and an acidic group, a photoelectric conversion element having both reduced elution of a sensitizing dye during storage with time and high conversion efficiency can be produced.

  Hereinafter, the present invention will be described in detail. The present invention is a photoelectric conversion element material using a compound represented by the general formula [I] or [II] as a sensitizing dye.

In general formula [I] and general formula [II], R ₁ and R ₂ , R ₃ and R ₄ , R ₁₅ and R ₁₆ , R ₁₇ and R ₁₈ are linked to form a 5-membered or 6-membered ring. Is an alkylene residue. Specific examples thereof include a trimethylene group and a tetramethylene group.

Specific examples of Z ₁ and Z ₂ include 1,4-phenylene group, 4,4′-biphenylene group, 1,5-naphthalene group, 1,6-pyrenylene group and other divalent arylene groups, ethylene group, An alkylene group such as 1,3-propylene group, or 1,2-diphenylethylene-4,4′-diyl group, transstilbene-4,4′-diyl group, 1,4-distyrylbenzene-4 ′, 4 A divalent hydrocarbon residue such as a “-diyl group” can be mentioned.

  Other divalent linking groups may include formulas (1) to (17), but are not limited thereto.

Specific examples of R ₅ , R ₆ , R ₇ , R ₈ , R ₁₉ , R ₂₀ , R ₂₁ , R ₂₂ include hydrogen groups, alkyl groups such as methyl, ethyl, and isopropyl groups, phenyl groups , Aryl groups such as 1-naphthyl group, halogen atoms such as chlorine and bromine, and cyano groups.

Specific examples of R ₉ , R ₁₀ , R ₂₃ , and R ₂₄ include a hydrogen atom or an alkyl group such as a methyl group, an ethyl group, and an isopropyl group.

Specific examples of R ₁₁ , R ₁₂ , R ₂₅ , and R ₂₆ include hydrogen atoms, alkyl groups such as methyl, ethyl, and n-butyl groups, methoxy groups, ethoxy groups, and n-butoxy groups. There can be mentioned an alkoxy group or a halogen atom such as chlorine or bromine.

Specific examples of R ₁₃ , R ₁₄ , R ₂₇ and R ₂₈ include a carboxyl group, an alkyl group such as a methyl group, an ethyl group and an isopropyl group, an aryl group such as a phenyl group and a 1-naphthyl group, and a benzyl group. And heterocyclic substituents such as aralkyl groups such as phenethyl group, 2-pyridyl group, 4-pyridyl group and 2-benzothiazolyl group. When R ₁₃ and R ₁₄ , R ₂₇ and R ₂₈ are both alkyl groups, aryl groups, aralkyl groups, and heterocyclic substituents, at least one of R ₁₃ and R ₁₄ , R ₂₇ and R ₂₈ is a carboxyl group As a substituent.

Specific examples of the nitrogen-containing heterocyclic group formed by linking Y ₁ with a carbonyl carbon and a methine carbon include 4-oxo-2-thioxo-3-thiazolidine-5,5-diyl group, 2,4-dioxo Imidazolidine-5,5-diyl group, 4-oxo-2-thioxo-imidazolidine-5,5-diyl group, 5-oxo-2-pyrazolin-4,4-diyl group, etc., and these rings Is substituted with a carboxyl group or carboxyl group-containing residue such as at least one carboxymethyl group, 2-carboxyethyl group, 3-carboxy-1-propyl group.

Specific examples of X ₁ include a cyano group, an acyl group, a perfluoroalkyl group, a nitro group, a trifluoroacetyl group, a substituted sulfonyl group, etc. Among them, a cyano group is particularly preferable.

The two substituted indoline residues linked to Z ₁ and Z ₂ may be the same structure or different structures. l and m each represents 0 or 1; n and p represent 0 or 1. l, m, n, and p may be the same number or different numbers.

  Next, specific examples of the compound of the general formula [I] according to the present invention will be given, but the present invention is not limited thereto.

  Next, specific examples of the compound of the general formula [II] of the present invention will be given, but the present invention is not limited thereto.

  In the present invention, the photoelectric conversion element includes a conductive substrate, a semiconductor layer on which the sensitizing dye provided on the conductive substrate is supported, a charge transfer layer, and a counter electrode. The material for the photoelectric conversion element is a member constituting the photoelectric conversion element. For example, the sensitizing dye, the semiconductor layer carrying the sensitizing dye, and the semiconductor layer carrying the sensitizing dye on the conductive substrate. A semiconductor electrode provided with a semiconductor layer provided with a sensitizing dye and a semiconductor layer provided on a conductive substrate and a charge transfer layer; a laminate obtained by further bonding a counter electrode to the laminate; and a sensitizing dye And a charge transfer layer contained therein.

  As the conductive substrate, a support having a conductive surface on its surface, such as metal, or a glass or plastic support having a surface conductive layer containing a conductive agent on the surface can be used. In the latter case, the conductive agent is a metal oxide such as platinum, gold, silver, copper, aluminum or the like, carbon or indium-tin composite oxide (hereinafter abbreviated as “ITO”), fluorine-doped tin oxide or the like. (Hereinafter abbreviated as “FTO”) and the like. For the purpose of reducing the resistance of the surface conductive layer, a metal lead wire may be used. Examples of the material of the metal lead wire include metals such as aluminum, copper, silver, gold, platinum, and nickel. In the case of using a metal lead wire, even if a surface conductive layer is provided after the metal lead wire is placed on a support such as glass or plastic by vapor deposition, sputtering, crimping, etc., the metal after the surface conductive layer is provided on the support Lead wires may be installed. The conductive substrate preferably has a transparency that transmits light of 10% or more, and more preferably transmits 50% or more. Among these, conductive glass in which a surface conductive layer made of ITO or FTO is deposited on glass is particularly preferable.

  As the semiconductor, a single semiconductor such as silicon or germanium, a compound semiconductor typified by a metal chalcogenide, a compound having a perovskite structure, or the like can be used. Metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, or tantalum oxide, cadmium, zinc, lead, silver, antimony, Bismuth sulfide, cadmium, lead selenide, cadmium telluride and the like. Other compound semiconductors are preferably phosphides such as zinc, gallium, indium, cadmium, gallium arsenide, copper-indium-selenide, copper-indium-sulfide, and the like. As the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, potassium niobate and the like are preferable.

  The semiconductor used in the present invention may be single crystal or polycrystalline. As the conversion efficiency, a single crystal is preferable, but a polycrystal is preferable in terms of manufacturing cost, securing raw materials, and the like, and the particle size of the semiconductor is preferably 2 nm or more and 1 μm or less.

  As a method for forming a semiconductor layer on a conductive substrate, there are a method of applying a dispersion or colloidal solution of semiconductor fine particles on a conductive substrate, a sol-gel method, and the like. As a method for preparing the dispersion, the above-described sol-gel method, a method of mechanically pulverizing with a mortar, a method of dispersing while pulverizing using a mill, or a fine particle in a solvent when synthesizing a semiconductor is deposited. And a method of using it as it is.

  In the case of a dispersion prepared by mechanical pulverization or pulverization using a mill, it is prepared by dispersing at least semiconductor fine particles alone or a mixture of semiconductor fine particles and a resin in water or an organic solvent. Resins used include polymers and copolymers of vinyl compounds such as styrene, vinyl acetate, acrylic acid esters, methacrylic acid esters, silicone resins, phenoxy resins, polysulfone resins, polyvinyl butyral resins, polyvinyl formal resins, polyester resins. , Cellulose ester resin, cellulose ether resin, urethane resin, phenol resin, epoxy resin, polycarbonate resin, polyarylate resin, polyamide resin, polyimide resin and the like.

  Solvents for dispersing the semiconductor fine particles include alcohol solvents such as water, methanol, ethanol, and isopropyl alcohol, ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, ethyl formate, ethyl acetate, and n-butyl acetate. Ester solvents, diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or ether solvents such as dioxane, N, N-dimethylformamide, N, N-dimethylacetamide, or amide solvents such as N-methyl-2-pyrrolidone , Dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chlorobenzene, o-dichlorobenzene, fluorobenzene, bromobenzene, iodine Halogenated hydrocarbon solvents such as debenzene or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, Examples thereof include hydrocarbon solvents such as m-xylene, p-xylene, ethylbenzene, and cumene. These can be used alone or as a mixed solvent of two or more.

  Examples of a method for applying the obtained dispersion include a roller method, a dip method, an air knife method, a blade method, a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method. .

  Furthermore, the semiconductor layer may be a single layer or a multilayer and is designed according to the purpose. In the case of multiple layers, the particle diameter of semiconductor fine particles, the type of semiconductor, the composition of resins and additives, and the like can be changed in each layer. In addition, when the film thickness is insufficient by a single application, the multilayer application is an effective means. In addition, at the boundary of this element such as the boundary between the surface conductive layer and the semiconductor layer of the conductive substrate and the boundary between the semiconductor layer and the charge transfer layer, the constituent components of each layer may be diffused or mixed with each other.

  In general, as the thickness of the semiconductor layer increases, the amount of supported sensitizing dye per unit projected area increases, so the light capture rate increases, but the diffusion distance of the generated electrons also increases, resulting in charge recombination. Will also increase. Therefore, the film thickness of the semiconductor layer is preferably 0.1 to 100 μm, and more preferably 1 to 30 μm.

After the semiconductor fine particles are applied on the conductive substrate, heat treatment may or may not be performed. However, heat treatment is preferred from the viewpoints of electronic contact between semiconductor fine particles and improvement of coating film strength and adhesion with a conductive substrate. Furthermore, microwave irradiation, press treatment, or electron beam irradiation may be performed, and these treatments may be performed alone or in combination of two or more. In the heat treatment, the heating temperature is preferably 40 to 700 ° C, more preferably 80 to 600 ° C. The heating time is preferably 5 minutes to 50 hours, and more preferably 10 minutes to 20 hours. The microwave irradiation may be performed from the semiconductor layer forming side of the semiconductor electrode or from the back side. Although there is no restriction | limiting in particular in irradiation time, It is preferable to carry out within 1 hour. The press treatment is preferably 9.8 × 10 ⁶ Pa or more, and more preferably 9.8 × 10 ⁷ Pa or more. There is no particular limitation on the pressing time, but it is preferably performed within 1 hour.

  The semiconductor fine particles preferably have a large surface area so that many sensitizing dyes can be adsorbed. For this reason, the surface area of the semiconductor layer coated on the conductive substrate is preferably 10 times or more, more preferably 100 times or more the projected area.

  As a method for supporting the sensitizing dye in the semiconductor layer, a method in which a working electrode containing semiconductor fine particles is immersed in a sensitizing dye solution or a sensitizing dye dispersion, or a sensitizing dye solution or dispersion is applied to the semiconductor layer. Then, a method of adsorbing can be used. In the former case, dipping method, dipping method, roller method, air knife method, etc. can be used, and in the latter case, wire bar method, slide hopper method, extrusion method, curtain method, spin method, spray method, etc. Can be used.

  In carrying the sensitizing dye, a condensing agent may be used in combination. The condensing agent may be either a catalyst that seems to physically or chemically bind the sensitizing dye to the inorganic surface, or a substance that acts stoichiometrically to favorably shift the chemical equilibrium. Good. Furthermore, a thiol or a hydroxy compound may be added as a condensation aid.

  Solvents that dissolve or disperse the sensitizing dye are water, methanol, ethanol, alcohol solvents such as isopropyl alcohol, ketone solvents such as acetone, methyl ethyl ketone, or methyl isobutyl ketone, ethyl formate, ethyl acetate, or n acetate. Ester solvents such as butyl, ether solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran (THF), dioxolane, or dioxane, nitrile solvents such as acetonitrile and propionitrile, N, N-dimethylformamide, N, N -Amide solvents such as dimethylacetamide or N-methyl-2-pyrrolidone, dichloromethane, chloroform, bromoform, methyl iodide, dichloroethane, trichloroethane, trichloroethylene, chloroform Zen, o-dichlorobenzene, fluorobenzene, bromobenzene, iodobenzene, or halogenated hydrocarbon solvents such as 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, Examples include hydrocarbon solvents such as methylcyclohexane, cyclohexadiene, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, and cumene, and these are used alone or as a mixture of two or more. be able to.

  The temperature at which these are used and the sensitizing dye is supported is preferably -50 ° C or higher and 200 ° C or lower. The sensitizing dye may be supported while stirring. Examples of the stirring method include, but are not limited to, a stirrer, a ball mill, a paint conditioner, a sand mill, an attritor, a disperser, and ultrasonic dispersion. The time required for loading is preferably from 5 seconds to 1000 hours, more preferably from 10 seconds to 500 hours, and even more preferably from 1 minute to 150 hours.

  In the present invention, when the compound represented by the general formula [I] or the general formula [II] is adsorbed on the semiconductor layer as a sensitizing dye, a steroidal compound may be used in combination and co-adsorbed. 0.01-1000 mass parts is preferable with respect to 1 mass part of sensitizing dye, and, as for the quantity of a steroid type compound, 0.1-100 mass parts is more preferable.

  In order to improve the performance of the photoelectric conversion element after supporting the sensitizing dye or after co-adsorbing the sensitizing dye and the steroidal compound, 4-t-butylpyridine, 2-picoline, 2,6- It may be dipped in an organic solvent containing a basic compound such as lutidine, or an acidic compound such as phosphoric acid, phosphoric acid ester, alkyl phosphoric acid, acetic acid or propionic acid. When a basic compound is added, in the case of a sensitizing dye having low adsorption stability to the semiconductor layer, elution tends to occur in the electrolytic solution, but the compound represented by the general formula [I] or [II] is added to the semiconductor layer. Therefore, elution is difficult to occur, and the performance of the photoelectric conversion element can be effectively improved.

  As the charge transfer layer, an electrolytic solution in which a redox couple is dissolved in an organic solvent, a gel electrolyte in which a liquid in which a redox couple is dissolved in an organic solvent is impregnated in a polymer matrix, a molten salt containing a redox couple, a solid electrolyte, an inorganic A hole transport material, an organic hole transport material, or the like can be used.

  The electrolytic solution is preferably composed of an electrolyte, a solvent, and an additive. Preferred electrolytes are metal iodide-iodine combinations such as lithium iodide, sodium iodide, potassium iodide, cesium iodide, and calcium iodide, and quaternary compounds such as tetraalkylammonium iodide, pyridinium iodide, and imidazolium iodide. Iodine salt of ammonium compound-iodine combination, metal bromide-bromine combination such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide, quaternary ammonium such as tetraalkylammonium bromide, pyridinium bromide Bromine-bromine combinations of compounds, metal complexes such as ferrocyanate-ferricyanate, ferrocene-ferricinium ion, sulfur compounds such as sodium polysulfide, alkylthiol-alkyldisulfide, viologen Dye, hydroquinone - quinones, and the like. The above-mentioned electrolytes may be a single combination or a mixture. Further, a molten salt in a molten state at room temperature can be used as the electrolyte. When this molten salt is used, it is not necessary to use a solvent.

  The electrolyte concentration in the electrolytic solution is preferably 0.05 to 20M, and more preferably 0.1 to 15M. Solvents used for the electrolyte include carbonate solvents such as ethylene carbonate and propylene carbonate, heterocyclic compounds such as 3-methyl-2-oxazolidinone, ether solvents such as dioxane, diethyl ether and ethylene glycol dialkyl ether, methanol, ethanol Alcohol solvents such as polypropylene glycol monoalkyl ether, nitrile solvents such as acetonitrile and benzonitrile, aprotic polar solvents such as dimethyl sulfoxide and sulfolane are preferred. Further, basic compounds such as 4-t-butylpyridine, 2-picoline, and 2,6-lutidine may be used in combination.

  The electrolyte can also be gelled by techniques such as polymer addition, oil gelling agent addition, polymerization including polyfunctional monomers, and polymer crosslinking reaction. Preferable polymers in the case of gelation by polymer addition include polyacrylonitrile, polyvinylidene fluoride and the like. Preferred gelling agents for gelation by adding an oil gelling agent include dibenzylden-D-sorbitol, cholesterol derivatives, amino acid derivatives, trans- (1R, 2R) -1,2-cyclohexanediamyl alkylamide derivatives, alkyls Examples include urea derivatives, N-octyl-D-gluconamide benzoate, double-headed amino acid derivatives, quaternary ammonium derivatives, and the like.

  Preferred monomers for polymerization with a polyfunctional monomer include divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, pentaerythritol triacrylate, trimethylolpropane triacrylate, and the like. be able to. Furthermore, esters and amides derived from acrylic acid such as acrylamide and methyl acrylate and α-alkyl acrylic acid, esters derived from maleic acid and fumaric acid such as dimethyl maleate and diethyl fumarate, butadiene, cyclohexane and the like. Dienes such as pentadiene, aromatic vinyl compounds such as styrene, p-chlorostyrene and sodium styrene sulfonate, vinyl esters, acrylonitrile, methacrylonitrile, vinyl compounds having a nitrogen-containing heterocyclic ring, vinyl having a quaternary ammonium salt A monofunctional monomer such as a compound, N-vinylformamide, vinylsulfonic acid, vinylidene fluoride, vinyl alkyl ethers, N-phenylmaleimide may be contained. 0.5-70 mass% is preferable and the polyfunctional monomer which occupies for the monomer whole quantity has more preferable 1.0-50 mass%.

  The above-mentioned monomers can be polymerized by radical polymerization. The monomer for gel electrolyte that can be used in the present invention can be radically polymerized by heating, light, electron beam or electrochemical. The polymerization initiator used when the crosslinked polymer is formed by heating is 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylvaleronitrile), dimethyl-2 An azo initiator such as 2,2'-azobis (2-methylpropionate) and a peroxide initiator such as benzoyl peroxide are preferable. The addition amount of these polymerization initiators is preferably 0.01 to 20% by mass and more preferably 0.1 to 10% by mass with respect to the total amount of monomers.

  When the electrolyte is gelled by a polymer crosslinking reaction, it is desirable to use a polymer containing a reactive group necessary for the crosslinking reaction and a crosslinking agent in combination. Preferable examples of the crosslinkable reactive group include nitrogen-containing heterocycles such as pyridine, imidazole, thiazole, oxazole, triazole, morpholine, piperidine, piperazine, etc. Preferred crosslinking agents include alkyl halides, halogens Bifunctional or higher functional reagents capable of electrophilic reaction with nitrogen atoms such as aralkyl fluoride, sulfonic acid ester, acid anhydride, acid chloride, and isocyanate can be exemplified.

  When an inorganic hole transport material is used instead of the electrolyte, copper iodide, copper thiocyanide, or the like can be introduced into the electrode by a casting method, a coating method, a spin coating method, a dipping method, electrolytic plating, or the like.

  It is also possible to use an organic charge transport material instead of the electrolyte. Charge transport materials include hole transport materials and electron transport materials. Examples of the former include, for example, oxadiazoles disclosed in Japanese Patent Publication No. 34-5466, triphenylmethanes disclosed in Japanese Patent Publication No. 45-555, and Japanese Patent Publication No. 52-4188. Pyrazolines shown in the above, hydrazones shown in JP-B-55-42380, oxadiazoles shown in JP-A-56-123544, etc., JP-A-54-58445 And tetrasylbenzidines disclosed in JP-A No. 58-65440, and stilbenes disclosed in JP-A No. 60-98437. Among them, examples of the charge transport material used in the present invention are shown in JP-A-60-24553, JP-A-2-96767, JP-A-2-183260, and JP-A-2-226160. Particularly preferred are the hydrazones described, and the stilbenes shown in JP-A-2-51162 and JP-A-3-75660. Moreover, these can be used individually or in mixture of 2 or more types.

  On the other hand, examples of the electron transport material include chloranil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 1,3,7-trinitrodibenzothiophene, 1,3,7-trinitrodibenzothiophene-5,5-dioxide, etc. . These electron transport materials can be used alone or as a mixture of two or more.

  Furthermore, for the purpose of improving the charge transfer efficiency in the charge transfer layer, a certain kind of electron withdrawing compound can be added to the charge transfer layer. Examples of the electron-withdrawing compound include quinones such as 2,3-dichloro-1,4-naphthoquinone, 1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone, 2-chloroanthraquinone, and phenanthrenequinone, 4-nitro Aldehydes such as benzaldehyde, ketones such as 9-benzoylanthracene, indandione, 3,5-dinitrobenzophenone, or 3,3 ', 5,5'-tetranitrobenzophenone, phthalic anhydride, 4-chloronaphthalic anhydride Acid anhydrides such as terephthalalmalononitrile, 9-anthrylmethylidenemalononitrile, 4-nitrobenzalmalononitrile, or cyano compounds such as 4- (p-nitrobenzoyloxy) benzalmalononitrile, 3-benzalphthalide , 3- (α-cyano- - Nitorobenzaru) phthalide, or 3- (alpha-cyano -p- Nitorobenzaru) -4,5,6,7 can be mentioned phthalides such as tetrachloro phthalide like.

  When forming a charge transfer layer using a charge transport material, a resin may be used in combination. When resin is used in combination, polystyrene resin, polyvinyl acetal resin, polysulfone resin, polycarbonate resin, polyester resin, polyphenylene oxide resin, polyarylate resin, acrylic resin, methacrylic resin, phenoxy resin and the like can be mentioned. Among these, polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, and polyarylate resin are preferable. These resins may be used alone or as a copolymer in combination of two or more.

  There are two main methods for forming the charge transfer layer. One is a method in which a counter electrode is first pasted on a semiconductor layer carrying a sensitizing dye, and a liquid charge transfer layer is sandwiched between the two, and the other is a method for forming a semiconductor layer carrying a sensitizing dye. This is a method of directly providing a charge transfer layer thereon. In the latter case, a counter electrode is newly provided on the charge transfer layer.

  In the former case, examples of the method for sandwiching the charge transfer layer include a normal pressure process using a capillary phenomenon due to immersion and a vacuum process in which the gas phase is replaced with a liquid phase at a pressure lower than normal pressure. In the latter case, in the wet charge transfer layer, it is necessary to provide a counter electrode without being dried to prevent liquid leakage at the edge portion. In the case of a gel electrolyte, there is a method in which it is applied in a wet manner and solidified by a method such as polymerization. In that case, you may provide a counter electrode after drying and fixing. In addition to the electrolytic solution, the organic charge transport material solution and gel electrolyte can be applied in the same manner as the semiconductor layer and pigment application, as well as the immersion method, roller method, dipping method, air knife method, extrusion method, slide Examples thereof include a hopper method, a wire bar method, a spin method, a spray method, a casting method, and various printing methods.

  As the counter electrode, a support having a surface conductive layer can be used in the same manner as the conductive substrate described above, but the support is not necessarily required when the surface conductive layer itself has sufficient strength and sealing properties. Specific examples of the material used for the counter electrode include metals such as platinum, gold, silver, copper, aluminum, rhodium and indium, carbon compounds, and conductive metal oxides such as ITO and FTO. There is no particular limitation on the thickness of the counter electrode.

  In the photoelectric conversion element, at least one of the conductive substrate and the counter electrode of the semiconductor electrode must be substantially transparent. In the present invention, it is preferable to use a method in which the conductive substrate of the semiconductor electrode is transparent and sunlight is incident from here. In this case, it is preferable to use a material that reflects light for the counter electrode, and it is preferable to use a metal, glass on which a conductive oxide is deposited, plastic, or a metal thin film.

  As described above, there are two types of counter electrodes: a case where the counter electrode is provided on the charge transfer layer and a case where the counter electrode is provided on the semiconductor layer. In any case, the counter electrode can be formed by a technique such as coating, laminating, vapor deposition, and bonding. When the charge transfer layer is solid, the counter electrode can be directly formed thereon by a technique such as coating, vapor deposition, or CVD.

  EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited to these at all.

Example 1
Paint conditioner (product name: P-25, manufactured by Nippon Aerosil Co., Ltd.) 2 g, acetylacetone 0.2 g, surfactant (trade name: Triton X-100, manufactured by Aldrich) 0.3 g together with water 6.5 g (Red Devil) for 6 hours. Further, 0.2 g of concentrated nitric acid, 0.4 ml of ethanol, and 1.2 g of polyethylene glycol (# 20,000) were added to 4.0 g of this dispersion to prepare a paste. This paste was applied on a conductive substrate (FTO glass substrate) so as to have a film thickness of 12 μm, dried at room temperature, and then baked at 100 ° C. for 1 hour and further at 550 ° C. for 1 hour to produce a semiconductor electrode.

  The sensitizing dye shown by the exemplary compound (A-13) was dissolved in THF to prepare a sensitizing dye solution having a concentration of 0.3 mM. The semiconductor electrode prepared previously was immersed in this sensitizing dye solution at room temperature for 15 hours and subjected to an adsorption treatment to prepare a semiconductor electrode (working electrode) in which the sensitizing dye was supported on the semiconductor layer. As the counter electrode, a titanium plate on which platinum was sputtered was used. Both electrodes were arranged so as to face each other, and an electrolytic solution was injected between them to produce a photoelectric conversion element. As the electrolytic solution, a 3-methoxyacetonitrile solution of lithium iodide 0.1M, iodine 0.05M, 1,2-dimethyl-3-n-propylimidazolium iodide 0.5M was used.

From the working electrode side of the thus produced photoelectric conversion element, simulated sunlight (AM1.5G, irradiation intensity 100 mW / cm ² ) using a solar simulator (trade name: YSS-40S, manufactured by Yamashita Denso Co., Ltd.) as a light source. The photoelectric conversion characteristics were evaluated using an electrochemical measurement device (trade name: SI-1280B, manufactured by Solartron). As a result, an open circuit voltage of 0.65 V, a short circuit current density of 9.37 mA / cm ² , a form factor of 0.60, and a conversion efficiency of 3.65% were shown.

  Furthermore, the adsorption stability of the dye to the semiconductor electrode was evaluated. A semiconductor electrode (working electrode) having a sensitizing dye supported on a semiconductor layer was immersed in 3-methoxyacetonitrile, which is a solvent of an electrolytic solution, and stored for 10 days under light shielding, sealing, and room temperature. The loaded state of the sensitizing dye on the semiconductor electrode after storage was visually observed. The results are shown in Table 2.

(Examples 2 to 13)
A photoelectric conversion element was produced in the same manner as in Example 1 except that the exemplary compound (A-13) was changed to the exemplary compound shown in Table 1, and the photoelectric conversion characteristics were evaluated. The results are shown in Table 1. Further, the adsorption stability of the dye to the semiconductor electrode was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

(Comparative Examples 1-4)
A photoelectric conversion element was produced in the same manner as in Example 1 except that the exemplary compound (A-13) was changed to the compounds (R-1) to (R-4), and the photoelectric conversion characteristics were evaluated. The results are shown in Table 1. Further, the adsorption stability of the dye to the semiconductor electrode was evaluated in the same manner as in Example 1, and the results are shown in Table 2.

  As is clear from Tables 1 and 2, it can be seen that the photoelectric conversion elements prepared in Examples 1 to 13 are excellent in both conversion efficiency and adsorption stability to a semiconductor. On the other hand, the photoelectric conversion elements of Comparative Examples 1 to 4 have poor adsorption stability, and the photoelectric conversion elements of Comparative Examples 1 and 3 have low conversion efficiency.

  Examples of utilization of the present invention include optical sensors that are sensitive to light of a specific wavelength, in addition to photoelectric conversion elements used in solar cells and the like.

Claims (1)

A material for a photoelectric conversion element, wherein at least one of the compounds represented by the general formula [I] or the general formula [II] is used.

(In the general formula [I], R ₁ and R ₂ , R ₃ and R ₄ are each linked together to form an alkylene residue which forms a 5-membered or 6-membered ring, and Z ₁ is a divalent linking group. R ₅ , R ₆ , R ₇ and R ₈ represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom or a cyano group, R ₉ and R ₁₀ represent a hydrogen atom or an alkyl group, R ₁₁ , R ₁₂ is a substituent on the aromatic hydrocarbon residue and represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom, and R ₁₃ is a carboxyl group, an alkyl group, an aryl group, an aralkyl group, or a hetero atom. A substituent selected from ring substituents, R ₁₄ is a substituent selected from alkyl groups, aryl groups, aralkyl groups, or heterocyclic substituents, and both R ₁₃ and R ₁₄ are alkyl groups, Aryl, aralkyl, or heterocycle In the case of a substituent, at least one of R ₁₃ and R ₁₄ has a carboxyl group as a substituent, and Y ₁ is a divalent residue that forms a nitrogen-containing heterocycle linked to a carbonyl carbon and a methine carbon. Yes, and has at least one carboxyl group as a substituent. L and m represent 0 or 1.)

(In the general formula [II], R ₁₅ and R ₁₆ , R ₁₇ and R ₁₈ are linked together to form an alkylene residue forming a 5-membered or 6-membered ring, and Z ₂ is a divalent linking group. R ₁₉ , R ₂₀ , R ₂₁ and R ₂₂ represent a hydrogen atom, an alkyl group, an aryl group, a halogen atom, or a cyano group, and R ₂₃ and R ₂₄ represent a hydrogen atom or an alkyl group. ₂₅ and R ₂₆ are substituents on the aromatic hydrocarbon residue and each represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom, and R ₂₇ represents a carboxyl group, an alkyl group, an aryl group, an aralkyl group, or R ₂₈ is a substituent selected from among heterocyclic substituents, R ₂₈ is a substituent selected from an alkyl group, aryl group, aralkyl group, or heterocyclic substituent, and both R ₂₇ and R ₂₈ are alkyl groups. , Aryl group, aralkyl group, or For B ring substituents, the .n and p .X ₁ is showing an electron-withdrawing group having either one of at least R ₂₇ and R ₂₈ are as a substituent a carboxyl group, represents 0 or 1. )