JP2008071648A - Photoelectric conversion material, semiconductor electrode, and photoelectric conversion element using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element superior in photoelectric conversion characteristics and durability. <P>SOLUTION: The photoelectric conversion material uses at least one kind of dye as shown by a general formula [I]. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element.

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. For this reason, in recent years, the use of sunlight that is infinite and does not generate harmful substances has been energetically studied. What is currently put into practical use as sunlight, which is a clean energy source, includes residential single crystal silicon, polycrystalline silicon, amorphous silicon, and inorganic solar cells such as cadmium telluride and indium copper selenide.

  However, these inorganic solar cells also have drawbacks. For example, a silicon system is required to have a very high purity. Naturally, the purification process is complicated, the number of processes is large, and the manufacturing cost is high. In addition, there is a demand for weight reduction and the like, and in particular, it is disadvantageous in that payback to the user is long, and there is a problem in the spread.

  On the other hand, many solar cells using organic materials have been proposed. As an organic solar cell, 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 are joined. There are heterojunction photoelectric conversion elements and the like, and organic semiconductors used are synthetic dyes and pigments such as chlorophyll and perylene, conductive polymer materials such as polyacetylene, or composite materials thereof. These are thinned by a vacuum deposition method, a casting method, a dipping method, or the like to form a battery material. Although organic materials have advantages such as low cost and easy area enlargement, there are many problems that the conversion efficiency is as low as 1% or less and the durability is poor.

  Under such circumstances, a solar cell exhibiting good characteristics has been reported by Dr. Gretzell of Switzerland (see Non-Patent Document 1). This document also discloses materials and manufacturing techniques necessary for battery fabrication. The proposed battery is called a dye-sensitized solar cell or a Gretzel solar cell, and is a wet solar cell using a titanium oxide porous thin film spectrally sensitized with a ruthenium complex as a working electrode. The advantage of this method is that it is not necessary to purify an inexpensive oxide semiconductor such as titanium oxide to high purity, and therefore, it is inexpensive and more usable light extends over a wide visible light region, and the solar light with many visible light components. It is that light can be effectively converted into electricity.

  On the other hand, ruthenium complexes with limited resources are used, so when this solar cell is put to practical use, the supply of ruthenium complexes is in danger. Moreover, since this ruthenium complex is expensive, this problem can be solved if it can be changed to an inexpensive organic dye. Merocyanine dyes, cyanine dyes, and 9-phenylxanthene dyes have been reported as dyes for this battery (see, for example, Patent Documents 1 to 3). However, these dyes have poor adsorptivity to titanium oxide, and a high sensitization effect cannot be obtained.

Recently, organic dyes having high performance as an oxide semiconductor spectral sensitizing dye and excellent in stability over time have been disclosed (see, for example, Patent Documents 4 to 5). From this viewpoint, the performance was insufficient in terms of both photoelectric conversion efficiency and durability.
JP 11-238905 A JP 2001-76773 A Japanese Patent Laid-Open No. 10-92477 JP 2004-200068 A JP 2005-19252 A Nature, 353, 737 (1991)

  An object of the present invention is to provide a photoelectric conversion element having high performance and excellent durability.

  As a result of intensive studies to achieve the above-mentioned problems, the present inventors have been able to achieve the target with a photoelectric conversion material using at least one dye represented by the general formula [I].

  The photoelectric conversion material means all members constituting an element that converts light into electric energy, such as a material constituting a conductive support, a material constituting a semiconductor electrode, an electrolyte, and a material constituting a counter electrode. To do. By adsorbing and supporting a dye that absorbs light in the visible region on a semiconductor electrode that does not have photoelectric conversion capability in the visible region, the photoelectric conversion capability of the semiconductor electrode can be expanded to the visible region. The dye used in is called a sensitizing dye. The dye of the present invention means this sensitizing dye.

In the general formula [I], R ₁ represents an alkyl group or alkylthio group having 4 or more carbon atoms, L ₁ and L ₂ represent a divalent linking group, and Ar ₁ and Ar ₂ represent a divalent aromatic carbonization. It represents a hydrogen residue or a divalent aromatic heterocyclic residue, and m and n represent 0 or 1. R ₂ and R _{3 each} represents an alkyl group, an aralkyl group, an aryl group, or a heterocyclic substituent, and may be bonded with R ₂ and R ₃ to form a cyclic structure. R ₄ is a substituent on the aromatic ring and represents a hydrogen atom, an alkyl group, an alkoxy group, an aryl group, a heterocyclic substituent, or a halogen atom. R ₅ represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic substituent. R ₆ represents an alkyl group having an acidic group as a substituent, an aralkyl group, or an aryl group, and R ₇ represents an alkyl group having 1 to 3 carbon atoms.

  By using the dye of the general formula [I] used in the present invention, a photoelectric conversion element exhibiting excellent conversion efficiency and excellent durability can be obtained.

  Details of the dye of the general formula [I] will be described.

Specific examples of R ₁ include the substituents shown below. an alkyl group having 4 or more carbon atoms such as n-butyl group, t-butyl group, n-hexyl group, sec-hexyl group, n-octyl group, n-decyl group, n-dodecyl group, n-octadecyl group, Alkylthio groups having 4 or more carbon atoms such as n-butylthio group, sec-butylthio group, n-hexylthio group, n-octylthio group, sec-octylthio group, n-decylthio group, n-dodecyl group, n-octadecylthio group Is mentioned. Among these, a linear alkyl group or a linear alkylthio group is particularly preferable. When the number of carbon atoms is less than 4, the durability of the dye is poor and the effect of the invention is insufficient. The durability of the dye is good if it is an alkyl group or alkylthio group having 4 or more carbon atoms, and among them, an alkyl group or alkylthio group having 4 to 20 carbon atoms is particularly preferable.

Specific examples of Ar ₁ and Ar ₂ are monocyclic or condensed polycyclic aromatics such as 1,4-phenylene group, 4,4′-biphenylene group, 2,6-naphthylene group, 2,7-phenanthrylene group, etc. Examples thereof include divalent aromatic heterocyclic residues such as hydrocarbon, 2,5-thiophenediyl group, and 2,2′-bithiophene-5,5′-diyl group.

Specific examples of L ₁ include divalent linking groups as shown below, and these may further have a substituent.

Specific examples of L ₂ include divalent linking groups as shown below, and these may further have a substituent.

Specific examples of R ₂ and R ₃ include alkyl groups such as methyl group, ethyl group and cyclohexyl, aralkyl groups such as benzyl group and phenethyl group, aryl groups such as phenyl group, biphenyl group and 1-naphthyl group, and furyl group. And heterocyclic substituents such as thienyl group and indolyl group. Among them, preferred are residues that are bonded between R ₂ and R ₃ to form a cyclic structure, and particularly preferred are those bonded between R ₂ and R ₃ to form a cyclopentane ring or cyclohexane. An alkylene group residue that forms a ring.

Specific examples of R ₄ include a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, and a cyclohexyl group, an alkoxy group such as a methoxy group and an ethoxy group, an aryl group such as a phenyl group, a biphenyl group, and a 1-naphthyl group, a furyl group, Heterocycle such as thienyl group and indolyl group, or a halogen atom, which may further have a substituent. Specific examples of the substituent include an alkylthio group, an aryloxy group, an arylthio group, a halogen atom, a disubstituted amino group, an aryl group, and a heterocyclic ring.

Specific examples of R ₅ include a hydrogen atom, an alkyl group such as a methyl group and an ethyl group, an aralkyl group such as a benzyl group and a phenethyl group, an aryl group such as a phenyl group, a biphenyl group, and a 1-naphthyl group, a furyl group, Heterocycles such as thienyl group and indolyl group can be mentioned.

Specific examples of R ₆ include methyl groups having an acidic group as a substituent, alkyl groups such as ethyl group, propyl group and n-butyl group, aralkyl groups such as benzyl group and phenethyl group, phenyl group, 2-naphthyl group and the like. Of the aryl group. Examples of the acidic substituent include a carboxyl group, a sulfo group, a sulfino group, a sulfeno group, a phosphono group, and a phosphinico group, among which a carboxyl group is particularly preferable.

  The dye of the present invention is a dye classified as a merocyanine dye. The merocyanine dye has a structure in which a unit having an electron-donating substituent in a molecule and a unit having an electron-withdrawing substituent are connected by a conjugated double bond. When a merocyanine dye is used as a semiconductor sensitizing dye, it is common to introduce an acidic group that promotes the adsorptivity with the semiconductor onto the unit having an electron-withdrawing substituent of the dye. The dye is adsorbed onto the semiconductor via an acidic group that promotes adsorptivity.

  Although it is unclear about the reason why the dye of the present invention has high photoelectric conversion efficiency and high durability, the following estimation can be made.

  When a dye is adsorbed on a semiconductor, a plurality of dye molecules are adsorbed on the semiconductor while maintaining a specific orientation that is most stable in terms of chemical thermodynamics. In the case of a dye in which a hydrocarbon residue of a specific size is introduced at the end of a unit having an electron-donating substituent, the dye is bonded to the semiconductor due to a large hydrophobic interaction between hydrocarbon residues of a plurality of dye molecules. To form aggregates and adsorb. Since this aggregate has a high molecular weight and holds a large number of acidic groups that promote adsorptivity, it is presumed that the binding force to the semiconductor is improved compared to general dyes that do not form aggregates. The Therefore, the coloring matter of the present invention has high durability.

  In addition, this dye aggregate has a hydrophobic barrier layer on the surface due to the arrangement of a plurality of hydrocarbon residues. This barrier layer reduces direct contact between the semiconductor and the electrolytic solution, and as a result, the reverse electron transfer reaction between the semiconductor and the electrolytic solution can be efficiently prevented during battery operation. Therefore, it is estimated that excellent photoelectric conversion efficiency can be achieved.

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

  The photoelectric conversion element of the present invention comprises a conductive support, a semiconductor layer sensitized by a dye placed on the conductive support, a charge transfer layer, and a counter electrode. The semiconductor layer may be a single layer structure or a stacked structure, and is designed according to the purpose. In addition, at the boundary of this element such as the boundary between the conductive layer and the semiconductor layer of the conductive support, the boundary between the semiconductor layer and the moving layer, the constituent components of each layer may be diffused or mixed with each other.

  As the conductive support, there can be used a support made of glass or plastic having a conductive layer containing a conductive agent on its surface, such as a metal having a conductive property in itself. 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. The conductive support 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 conductive layer made of ITO or FTO is deposited on glass is particularly preferable.

  For the purpose of reducing the resistance of the transparent conductive support, 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. The metal lead wire is installed on the transparent conductive support by vapor deposition, sputtering, pressure bonding, etc., and ITO or FTO is provided thereon, or the metal lead wire is set on the transparent conductive support.

  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 support, there are a method of applying a dispersion or colloidal solution of semiconductor fine particles on a conductive support, a sol-gel method, and the like. The dispersion can be prepared by the above-mentioned sol-gel method, a method of mechanically pulverizing with a mortar, etc., a method of dispersing while pulverizing using a mill, or a fine particle in a solvent when synthesizing a semiconductor. 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 formed 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 the application method of the obtained dispersion include a roller method, a dip method, an air knife method, a blade method, a wire bar, 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 multiple layers. In the case of multiple layers, a dispersion of semiconductor fine particles having different particle diameters can be applied in multiple layers, or different types of semiconductors, and application layers having different compositions of resins and additives can be applied in multiple layers. In addition, when the film thickness is insufficient with a single coating, the multilayer coating is an effective means.

  In general, as the thickness of the semiconductor layer increases, the amount of supported dye increases per unit projected area and the light capture rate increases. However, the diffusion distance of the generated electrons also increases, and the recombination of charges also increases. End up. Therefore, the film thickness of the semiconductor layer is preferably 0.1 to 100 μm, and more preferably 1 to 30 μm.

The semiconductor fine particles may or may not be heat-treated after being coated on the conductive support. However, from the viewpoint of improving the electronic contact between the particles and the strength of the coating film and the adhesion to the support, the heat treatment is performed. Is preferable. 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 9.80665 × 10 ⁶ N / m ² or more, and more preferably 9.80665 × 10 ⁷ N / m ² 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 dyes can be adsorbed. For this reason, it is preferable that the surface area in the state which coated the semiconductor layer on the support body is 10 times or more with respect to a projection area, and it is more preferable that it is 100 times or more.

  As the dye in the photoelectric conversion element of the present invention, any one of the dyes represented by the general formula [I] is used. Moreover, you may use these together.

  As a method of adsorbing the dye to the semiconductor layer, a method of immersing a working electrode containing semiconductor fine particles in a dye solution or a dye dispersion, or a method of applying a dye solution or a dispersion to the semiconductor layer and adsorbing it is used. Can do. 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.

  When adsorbing the dye, a condensing agent may be used in combination. The condensing agent may be either one that has a catalytic action that is supposed to physically or chemically bind the dye to the inorganic surface, or one that acts stoichiometrically to favorably shift the chemical equilibrium. Furthermore, a thiol or a hydroxy compound may be added as a condensation aid.

  Solvents for dissolving or dispersing the 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-butyl acetate. Ester solvents such as diethyl ether, dimethoxyethane, tetrahydrofuran, dioxolane, or dioxane, nitrile solvents such as acetonitrile, propionitrile, 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-di Halogenated hydrocarbon solvents such as lolobenzene, fluorobenzene, bromobenzene, iodobenzene, or 1-chloronaphthalene, n-pentane, n-hexane, n-octane, 1,5-hexadiene, cyclohexane, methylcyclohexane, cyclohexadiene , Hydrocarbon solvents such as benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, or cumene, and these can be used alone or as a mixture of two or more.

  The temperature at which these are used and the dye is adsorbed is preferably -50 ° C or higher and 200 ° C or lower. Further, this adsorption may be performed 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 adsorption is preferably 5 seconds or more and 1000 hours or less, more preferably 10 seconds or more and 500 hours or less, and further preferably 1 minute or more and 150 hours or less.

  In the present invention, when adsorbing the dye represented by the general formula [I], a steroidal compound may be used in combination as a coadsorbent.

  Specific examples of the steroid compound include those shown in (B-1) to (B-10). 0.01-1000 mass parts is preferable with respect to 1 mass part of pigment | dyes, and, as for the quantity of a steroid type compound, 0.1-100 mass parts is more preferable.

  After adsorbing the dye, or after co-adsorbing the dye and the steroidal compound, basic compounds such as t-butylpyridine, 2-picoline, 2,6-lutidine, or phosphoric acid, phosphate ester, alkyl phosphoric acid Further, it may be dipped in an organic solvent containing an acidic compound such as acetic acid or propionic acid.

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

  The electrolytic solution used in the present invention is preferably composed of an electrolyte, a solvent, and an additive. Preferred electrolytes include metal iodide-iodine combinations such as lithium iodide, sodium iodide, potassium iodide, cesium iodide, and calcium iodide, tetraalkylammonium iodide, pyridinium iodide, imidazolium iodide, and the like. Iodine salt of quaternary ammonium compound-iodine combination, metal bromide-bromine combination such as lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide, quaternary compound such as tetraalkylammonium bromide, pyridinium bromide Bromine-bromine combinations of ammonium 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 also 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 t-butylpyridine, 2-picoline, and 2,6-lutidine may be used in combination.

  In the present invention, the electrolyte can be gelled by a technique such as addition of a polymer, addition of an oil gelling agent, polymerization including polyfunctional monomers, or a crosslinking reaction of the polymer. 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, alkylamide derivatives of trans- (1R, 2R) -1,2-cyclohexanediamine, alkylureas Derivatives, N-octyl-D-gluconamide benzoate, double-headed amino acid derivatives, quaternary ammonium derivatives and the like can be mentioned.

  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. Azo initiators such as 2,2′-azobis (2-methylpropionate) and peroxide initiators 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 solid compound 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.

  In the present invention, an organic charge transport material can be used 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.

  Further, as a sensitizer that further increases the sensitizing effect, a certain kind of electron-withdrawing compound can be added. 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 these charge transport materials, 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 fine particle-containing layer carrying a sensitizing dye, and a liquid charge transfer layer is sandwiched between the opposite electrodes, and the other is a method in which a charge is directly applied on the semiconductor fine particle-containing layer. This is a method of providing a moving layer. 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 electrolyte solution, the organic charge transport material solution or gel electrolyte can be applied in the same manner as the semiconductor fine particle-containing layer and the dye, as in the immersion method, roller method, dipping method, air knife method, and extrusion method. , Slide hopper method, wire bar method, spin method, spray method, casting method, various printing methods, and the like.

  The counter electrode can be used on a support having a conductive layer in the same manner as the conductive support described above, but the support is not necessarily required when the 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 order for light to reach the semiconductor layer, at least one of the conductive support holding the semiconductor layer and the counter electrode must be substantially transparent. In the photoelectric conversion element of the present invention, a method in which the conductive support holding the semiconductor fine particle layer is transparent and sunlight is incident from the conductive support side is preferable. In this case, a material that reflects light is preferably used for the counter electrode, and a metal, glass, plastic, or metal thin film on which a conductive oxide is deposited is preferable.

  As described above, there are two types of coating of the counter electrode: when applied on the charge transfer layer and when applied on the semiconductor layer. In any case, the counter electrode material can be appropriately formed on the charge transfer layer or the semiconductor layer by a technique such as coating, laminating, vapor deposition, or bonding depending on the type of the counter electrode material or the type of the charge transfer layer. When the charge transfer layer is solid, the counter electrode can be formed directly on the charge transfer layer 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)
2 hours of titanium oxide (P-25 manufactured by Nippon Aerosil Co., Ltd.), 0.2 g of acetylacetone, and 0.3 g of surfactant (Triton X-100 manufactured by Aldrich) together with 6.5 g of water in a paint conditioner (manufactured by Red Devil) for 6 hours. Dispersion treatment was performed. 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 onto an FTO glass substrate so as to have a film thickness of 12 μm, dried at room temperature, and then fired at 100 ° C. for 1 hour and further at 550 ° C. for 1 hour.

  The dye shown in the exemplified dye (A-4) was dissolved in THF to prepare a dye solution having a concentration of 0.3 mM. The semiconductor electrode prepared previously was immersed in this dye solution for 15 hours at room temperature to perform an adsorption treatment, thereby preparing a dye-sensitized semiconductor electrode. 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. The electrolyte was 3-methoxypropionitrile of lithium iodide 0.1M, iodine 0.05M, 1,2-dimethyl-3-n-propylimidazolium iodide 0.5M, 4-t-butylpyridine 0.05M. The solution was used.

Pseudo sunlight (AM1.5G, irradiation intensity: 100 mW / cm ² ) generated from a solar simulator (YSS-40S, manufactured by Yamashita Denso Co., Ltd.) is irradiated as a light source from the working electrode side of the photoelectric conversion element thus manufactured. The photoelectric conversion characteristics were evaluated using an electrochemical measurement device (SI-1280B, manufactured by Solartron). As a result, the open circuit voltage was 0.72 V, the short-circuit current density was 12.0 mA / cm ² , the shape factor was 0.65, and the photoelectric conversion efficiency was 5.62%.

(Example 2)
The dye shown in the exemplified dye (A-4) was dissolved in THF to prepare a dye solution having a concentration of 0.3 mM. In this dye solution, a steroid compound (B-1) as a co-adsorbent was dissolved at a concentration of 0.6 mM. The thus prepared semiconductor electrode was immersed in the dye solution thus prepared at room temperature for 15 hours to perform an adsorption treatment, thereby preparing a working electrode. 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. The electrolyte was 3-methoxypropionitrile of lithium iodide 0.1M, iodine 0.05M, 1,2-dimethyl-3-n-propylimidazolium iodide 0.5M, 4-t-butylpyridine 0.05M. The solution was used.

Pseudo-sunlight (AM1.5G, irradiation intensity 100 mW / cm ² ) generated from a solar simulator (YSS-40S, manufactured by Yamashita Denso Co., Ltd.) is irradiated as a light source from the semiconductor electrode side of the photoelectric conversion element thus manufactured. The photoelectric conversion characteristics were evaluated using an electrochemical measurement device (SI-1280B, manufactured by Solartron). As a result, the open circuit voltage was 0.72 V, the short-circuit current density was 12.3 mA / cm ² , the shape factor was 0.67, and the photoelectric conversion efficiency was 5.93%.

(Examples 3 to 13)
A device was prepared and evaluated in the same manner as in Example 1 except that the exemplified dye (A-4) was changed to the exemplified dye shown in Table 1. The results are shown in Table 1.

(Examples 14 to 24)
Exemplified dye (A-4) was changed to the exemplified dye shown in Table 2, and the steroid compound (B-1) was changed to the exemplified compound shown in Table 2 as a co-adsorbent. Were prepared and evaluated. The results are shown in Table 2.

(Example 25)
Exemplified dye (C-1) was dissolved in THF to prepare a dye solution having a concentration of 0.3 mM. In this dye solution, the steroid compound (B-1) as a co-adsorbent was dissolved at a concentration of 0.6 mM. The semiconductor electrode prepared previously was immersed in the dye solution thus prepared at room temperature for 15 hours to perform an adsorption treatment, thereby preparing a dye-sensitized semiconductor electrode. As the counter electrode, a titanium plate with sputtering platinum 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. The electrolyte was 3-methoxypropionitrile of lithium iodide 0.1M, iodine 0.05M, 1,2-dimethyl-3-n-propylimidazolium iodide 0.5M, 4-t-butylpyridine 0.05M. The solution was used.

Pseudo-sunlight (AM1.5G, irradiation intensity 100 mW / cm ² ) generated from a solar simulator (YSS-40S, manufactured by Yamashita Denso Co., Ltd.) is irradiated as a light source from the semiconductor electrode side of the photoelectric conversion element thus manufactured. The photoelectric conversion characteristics were evaluated using an electrochemical measurement device (SI-1280B, manufactured by Solartron). As a result, the open circuit voltage was 0.61 V, the short-circuit current density was 9.3 mA / cm ² , the form factor was 0.55, and the photoelectric conversion efficiency was 3.12%.

(Example 26)
After the photoelectric conversion element produced in Example 2 was stored for 10 days in an environment of 60 ° C., the same photoelectric conversion characteristics as in Example 2 were evaluated. As a result, the open circuit voltage was 0.71 V, the short-circuit current density was 12.0 mA / cm ² , the shape factor was 0.67, and the photoelectric conversion efficiency was 5.71%. Subsequently, the maintenance rate of photoelectric conversion efficiency was calculated | required. The maintenance rate was calculated as a percentage of the photoelectric conversion efficiency after storage with respect to the photoelectric conversion efficiency before storage. As a result, the maintenance rate was 96%.

(Examples 27 to 37)
Evaluation similar to Example 26 was performed using the photoelectric conversion element produced in Examples 14-24. The results are shown in Table 3.

(Example 38)
The adsorption stability of the dye to the semiconductor electrode was evaluated. Exemplified dye (A-4) was dissolved in THF to prepare a dye solution having a concentration of 0.3 mM. A semiconductor electrode produced in the same manner as in Example 1 was immersed in this solution at room temperature for 15 hours and subjected to an adsorption treatment. Next, the dye-adsorbing semiconductor electrode was immersed in 3-methoxypropionitrile, which is an electrolyte solvent, and stored for 10 days under light shielding, sealing, and room temperature. The state of dye support on the semiconductor electrode after storage was visually observed. As a result, no elution of the dye into the solvent was observed.

(Examples 39 to 49)
The exemplified dye (A-4) was changed to the exemplified dye shown in Table 4, and the same evaluation as in Example 38 was performed. The results are shown in Table 4.

(Comparative Example 1)
The exemplified dye (A-4) was changed to the exemplified dye (C-2), and the same evaluation as in Example 38 was performed. As a result, after 10 days, the dye remained on the semiconductor electrode, but elution of the dye into the solvent was also observed.

  Examples of utilization of the present invention include photosensors that are sensitive to light of a specific wavelength, in addition to photoelectric conversion elements such as solar cells.

Claims (4)

A photoelectric conversion material comprising a dye represented by the general formula [I].

(In the general formula [I], R ₁ represents an alkyl group or alkylthio group having 4 or more carbon atoms, L ₁ and L ₂ represent a divalent linking group, and Ar ₁ and Ar ₂ represent a divalent aromatic group. Represents a hydrocarbon residue or a divalent aromatic heterocyclic residue, and m and n represent 0 or 1. R ₂ and R ₃ represent an alkyl group, an aralkyl group, an aryl group, or a heterocyclic substituent, R ₂ and R ₃ may combine to form a cyclic structure, where R ₄ is a substituent on the aromatic ring, which is a hydrogen atom, alkyl group, alkoxy group, aryl group, heterocyclic substituent, or halogen R ₅ represents a hydrogen atom, an alkyl group, an aralkyl group, an aryl group, or a heterocyclic substituent, R ₆ represents an alkyl group, an aralkyl group, or an aryl group having an acidic group as a substituent, R ₇ is an alkyl having 1 to 3 carbon atoms. Represents a sulfur group.)   In a semiconductor electrode comprising a conductive support, a semiconductor layer coated on the surface of the conductive support, and a dye adsorbed on the surface of the semiconductor layer, the dye is represented by the general formula [I] according to claim 1. A semiconductor electrode comprising at least one dye.   The semiconductor is titanium, tin, zinc, iron, copper, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, tantalum, cadmium, lead, silver, antimony, bismuth, molybdenum, aluminum, 3. The semiconductor electrode according to claim 2, comprising at least one metal chalcogenide selected from gallium, chromium, cobalt, and nickel.   A photoelectric conversion element using the semiconductor electrode according to claim 2.