JP2009272198A - Photoelectric conversion material, semiconductor electrode, and photoelectric conversion element using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion material, having superior photoelectric conversion efficiency and superior durability, a semiconductor electrode, and to provide a photoelectric conversion element. <P>SOLUTION: In the photoelectric conversion material, at least one kind of compounds which are indicated in general formula (1) is used as a coloring matter. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion material, a semiconductor electrode, and a photoelectric conversion element using the same.

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. The organic material has advantages such as low cost and easy area enlargement, but 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. In addition, due to this resource limitation, the ruthenium complex itself is expensive, and it is considered that there may be a problem in terms of cost. Therefore, various proposals have heretofore been made for the purpose of changing the ruthenium complex to a cheaper organic dye. Examples thereof include various merocyanine dyes, cyanine dyes, 9-phenylxanthene dyes, coumarin dyes, and the like (see, for example, Patent Documents 1 to 4). Most of them were very inferior and poor in practicality.

On the other hand, recently, organic dyes having high performance comparable to ruthenium complexes and excellent in temporal stability have been disclosed as spectral sensitizing dyes for oxide semiconductors (see, for example, Patent Documents 5 to 7). From the viewpoint of manufacturing a practical solar cell, further improvements are required.
JP 11-238905 A JP 2001-76773 A Japanese Patent Laid-Open No. 10-92477 JP 2002-164089 A JP 2004-200068 A JP 2005-19252 A JP 2007-115673 A Nature, 353, 737 (1991)

  An object of the present invention is to provide a photoelectric conversion material, a semiconductor electrode, and a photoelectric conversion element that have excellent photoelectric conversion efficiency 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 characterized by using at least one compound represented by the general formula (1).

  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 compound represented by the general formula (1) used in the present invention acts as this sensitizing dye.

In the formula, R ₁ , R ₂ and R ₃ represent an aliphatic group, an aromatic group and a heterocyclic group, and R ₂ and R ₃ may be linked to each other to form a ring. R ₄ represents an aliphatic group or an aromatic group having an acidic group of less than pKa6 as a substituent. L ₁ represents a conjugated methine group unit. L ₂ represents an alkylene group having 8 or less carbon atoms, and R ₅ represents an aromatic group or a heterocyclic group. However, when L ₂ is an alkylene group having 1 or 2 carbon atoms, R ₅ represents an aromatic group having at least one substituent other than a hydrogen atom, or a substituted or unsubstituted heterocyclic group. .

  By using at least one compound represented by the general formula (1) used in the present invention, a photoelectric conversion material, a semiconductor electrode and a photoelectric conversion element having excellent photoelectric conversion efficiency and excellent durability Obtainable.

The compounds used in the present invention are described in detail below. In the general formula (1), R ₁ , R ₂ and R ₃ are aliphatic groups (eg, alkyl groups such as methyl, ethyl, propyl and octyl groups, alkenyl groups such as allyl and butenyl groups, propargyl) Alkynyl groups such as aralkyl groups, aralkyl groups such as benzyl groups, etc., aromatic groups (eg phenyl groups, tolyl groups, naphthyl groups, etc.), heterocyclic groups (eg indolyl groups, pyridyl groups, furyl groups, thienyl groups, etc.) ). Among them, preferred as R ₁ is an aromatic group, and this aromatic group may be further substituted with various substituents. Preferred examples thereof include vinyl groups, alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, hydroxy groups, carboxy groups, halogen atoms, etc. in addition to the aliphatic groups, aromatic groups, and heterocyclic groups as described above. These may be further substituted if possible. Preferred as R ₂ and R ₃ are aliphatic groups. Among the combinations of R ₁ , R ₂ , and R ₃ described above, those having more preferable characteristics in photoelectric conversion efficiency are those in which R ₁ is an aromatic group and R ₂ and R ₃ are connected to each other to form 5 or 6 members. A combination of R ₁ , R ₂ , and R ₃ that forms a ring and exhibits particularly preferable characteristics is represented by the following structure.

In the above structure, R ₂₁ represents an aromatic group (note that this aromatic group may be substituted with various substituents). Specific preferred examples thereof include the following, but are not limited thereto.

  Among the above-mentioned aromatic groups, those that exhibit more preferable characteristics in photoelectric conversion efficiency are Ar-5, Ar-10 to Ar-13, Ar-20 to Ar-22, and the like, of which particularly preferable characteristics are shown. Are Ar-5, Ar-10 to Ar-12, Ar-21, Ar-22.

R _{4 in the} general formula (1) is an aliphatic group having the acidic group having a pKa of less than 6 as a substituent (synonymous with the above R ₁ , R ₂ , R ₃ ), an aromatic group (the above R ₁ , R ₂ , R ₃ is synonymous). Of these, an aliphatic group having 4 or less carbon atoms is preferred, and an aliphatic group having 2 or less carbon atoms is particularly preferred. Examples of the acidic group having a pKa of less than 6 include a carboxy group, a sulfo group, a sulfino group, a sulfeno group, a phosphono group, and a phosphinico group, among which a carboxy group is particularly preferable. These acidic groups may be free acids, such as salts (for example, ammonium salts such as ammonium salt, trimethylammonium salt, triethylammonium salt, tetra-n-butylammonium salt, lithium salt, sodium salt, potassium salt, etc. Alkali metal salts, etc.).

L ₁ represents a conjugated methine group unit (consisting of an odd number of conjugated methine chains). Among these, a monomethine structure having 1 carbon is preferable.

L ₂ is an alkylene group having 8 or less carbon atoms (for example, methylene group, ethylene group, propylene group, butylene group, hexylene group, octylene group, etc.). Represents good). Of these, those having 6 or less carbon atoms are preferred. R ₅ represents an aromatic group (synonymous with R ₁ , R ₂ , R ₃ ) or a heterocyclic group (synonymous with R ₁ , R ₂ , R ₃ ). However, when L ₂ is an alkylene group having 1 or 2 carbon atoms, R ₅ represents an aromatic group having at least one substituent other than a hydrogen atom, or a substituted or unsubstituted heterocyclic group. . Among the combinations of L ₂ and R ₅ described above, preferred specific examples include the following, but are not limited thereto.

Among the preferable combinations of L ₂ and R ₅ , those having more preferable characteristics in photoelectric conversion efficiency are A-1 to A-5, A-7 to A-10, A-13, and A-18. .

  The dye represented by the general formula (1) 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 sensitizing dye for a semiconductor, 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 details are unknown as to why the dye of the present invention can achieve high photoelectric conversion efficiency, 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. The dye of the present invention has a hydrocarbon residue having a specific size at the position of R ₅ in the general formula (1), which is the terminal of a unit having an electron-withdrawing substituent, and the hydrocarbon residue of a plurality of dyes Aggregates are formed and adsorbed on the semiconductor by the large hydrophobic interaction between the groups. This dye aggregate has a hydrophobic barrier layer on the surface by 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 seems that it was possible to achieve excellent photoelectric conversion efficiency.

  Although it is unclear that the dye of the present invention has high durability, the following estimation can be made.

  The dye aggregate formed on the semiconductor can be regarded as a group of dyes, and thus apparently holds a large number of acidic groups that promote adsorptivity. It is presumed that the bonding force with the semiconductor is improved as compared with the above dye.

Further, the dye of the present invention has a hydrocarbon residue having a specific size at the position of R ₁ in the general formula (1), which is the terminal of the unit having an electron donating substituent of the dye molecule. Therefore, two sites including the above-described R ₅ site are included in the dye molecule, and the thermodynamic stability of the resulting aggregate can be further enhanced. As a result, it seems that the bond strength of the dye to the semiconductor can be greatly improved.

  In the technical field of dye-sensitized solar cells, it is widely known to add a basic substance (for example, 4-t-butylpyridine) to the electrolytic solution for the purpose of improving battery performance. In the case of a dye having low adsorption stability to a semiconductor, re-dissolution of the dye in the electrolyte cannot be ignored if a basic substance coexists in the electrolyte. Since the dye of the present invention has excellent adsorption stability to a semiconductor, it is possible to effectively improve battery performance by adding a basic substance to the electrolytic solution.

  Next, although the specific example of the compound of General formula (1) of this invention is given, it is not limited to these.

  These compounds can be easily synthesized by referring to known synthesis methods described in, for example, JP-A-8-269345 and JP-A-2004-200068. A typical synthesis example is described below.

(Synthesis of Exemplified Compound D-2)
Intermediate A 1.2 g and Intermediate B 1.2 g were mixed, ammonium acetate 0.05 g and acetic acid 60 ml were mixed, and the mixture was heated at a bath temperature of 120 ° C. for 8 hours. Subsequently, the mixture was cooled to room temperature, and the precipitated solid was collected by filtration, washed with acetone and dried to obtain 1.4 g of a crude product. This was purified by silica gel column chromatography (developing solvent chloroform / methanol = 10/1) to obtain 1.2 g of exemplified compound D-2.
Absorption maximum (N, N-dimethylformamide solution): 531 nm

(Synthesis of Exemplified Compound D-13)
Intermediate A 1.2 g and Intermediate C 1.2 g were mixed, ammonium acetate 0.05 g and acetic acid 60 ml were mixed, and heated at a bath temperature of 120 ° C. for 8 hours. Then, the mixture was cooled to room temperature, and the precipitated solid was collected by filtration, washed with acetone and dried to obtain 1.5 g of a crude product. This was purified by silica gel column chromatography (developing solvent chloroform / methanol = 10/1) to obtain 1.3 g of exemplary compound D-13.
Absorption maximum (N, N-dimethylformamide solution): 530 nm

  The semiconductor electrode of the present invention has a substrate having conductivity on the surface and a semiconductor layer sensitized by a dye placed on the conductive surface, and the photoelectric conversion element of the present invention further comprises a charge transfer layer and Consists of 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 substrate having conductivity on the surface, a substrate having conductivity on the support itself such as metal, or a glass or plastic support having a 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. The substrate having conductivity on the surface preferably has a transparency that transmits 10% or more of light, 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 lowering the resistance of the surface conductive layer in the transparent substrate having conductivity on the surface, 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. A metal lead wire is installed on a transparent conductive support by vapor deposition, sputtering, pressure bonding, etc., and a method of providing ITO or FTO thereon, or a method of installing a metal lead wire on a transparent substrate having conductivity on the surface. is there.

  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. Single crystals are preferable for improving the photoelectric conversion characteristics, but polycrystals are preferable for manufacturing cost and securing raw materials. Further, the particle diameter of the semiconductor is preferably 2 nm or more and 1 μm or less.

  As a method for forming a semiconductor layer on a substrate having conductivity on the surface, 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 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 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 need not be heat-treated after being coated on a substrate having conductivity on the surface, but from the viewpoint of improving the electronic contact between the particles and the strength of the coating film and the adhesion to the support, Heat treatment is preferred. 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 pressing 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 dyes can be adsorbed. The specific surface area in a state of coated with a semiconductor layer on a support is preferably 1 to 1,000 m ² / g, and more preferably 10 to 500 m ² / g.

  The semiconductor electrode and photoelectric conversion element of the present invention use at least one compound represented by the general formula (1) as a sensitizing dye. Two or more kinds may be used in combination.

  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 from −50 ° C. to 200 ° C. 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 to 1000 hours, more preferably 10 seconds to 500 hours, and even more preferably 1 minute to 150 hours.

  In the present invention, when the compound represented by the general formula (1) is adsorbed to the semiconductor layer as a dye, a steroidal compound may be used in combination.

  Specific examples of the steroid compound include those shown in E-1 to E-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 according to the present invention, an electrolytic solution in which a redox couple is dissolved in an organic solvent, a gel electrolyte in which a polymer matrix is impregnated with a liquid in which the redox couple is dissolved in an organic solvent, a molten salt containing the redox couple, A solid electrolyte, an inorganic hole transport material, 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 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 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 dibenzylidene-D-sorbitol, cholesterol derivatives, amino acid derivatives, trans- (1R, 2R) -1,2-cyclohexanediamine alkylamide derivatives, alkyl 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 crosslinking reaction of the polymer, 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.

  Further, for the purpose of improving the charge transfer efficiency in the charge transfer layer, a certain 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 in the gap, and the other is on a semiconductor layer carrying a sensitizing dye. This is a method of directly providing a charge transfer 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 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.

  The counter electrode can be used on a support having a conductive layer in the same manner as the substrate having conductivity on the surface, 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 photosensitive layer, at least one of the conductive substrate and the counter electrode on the surface holding the semiconductor layer must be substantially transparent. In the photoelectric conversion element of the present invention, a method in which the conductive substrate is transparent on the surface holding the semiconductor fine particle layer and sunlight is incident from the conductive substrate side holding the semiconductor layer 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.

  2 hours of titanium dioxide (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 baked at 100 ° C. for 1 hour and further at 550 ° C. for 1 hour to obtain a semiconductor electrode.

  The dye of the present invention shown in Table 1 and the dye of the following comparison were each dissolved in tetrahydrofuran to prepare a dye solution having a concentration of 0.3 mM. A semiconductor electrode prepared previously was immersed in these dye solutions at room temperature for 8 hours to perform an adsorption treatment, thereby producing a dye-adsorbing semiconductor electrode (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.) as a light source is irradiated 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). The results are shown in Table 1.

  Dissolve the dyes of the present invention (D-1, D-2, D-6, D-8, D-12, D-13, D-14) and comparative dyes (C-2, C-3) in tetrahydrofuran Thus, a dye solution having a concentration of 0.3 mM was prepared. The steroid compound (E-1) was dissolved in this dye solution at a concentration of 0.6 mM. Subsequently, the semiconductor electrode produced in Example 1 was immersed in this dye solution for 8 hours at room temperature to perform an adsorption treatment. Hereinafter, photoelectric conversion characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 2.

  As is apparent from the results of Tables 1 and 2, it can be seen that the compound of the present invention has higher photoelectric conversion efficiency than the comparative compound and has excellent photoelectric conversion characteristics.

  After the photoelectric conversion element produced in Example 2 was stored for 10 days in an environment of 65 ° C., photoelectric conversion characteristics were evaluated in the same manner as in Example 2. Moreover, the maintenance rate of photoelectric conversion efficiency was calculated | required. This maintenance rate was calculated as a percentage of the photoelectric conversion efficiency after storage with respect to the photoelectric conversion efficiency before storage. The above results are shown in Table 3.

  Furthermore, the adsorption stability of the dye to the semiconductor electrode was evaluated. Dissolve the dyes of the present invention (D-1, D-2, D-6, D-8, D-12, D-13, D-14) and comparative dyes (C-2, C-3) in tetrahydrofuran Thus, a dye solution having a concentration of 0.3 mM was prepared. The semiconductor electrode prepared previously was immersed in this dye solution at room temperature for 8 hours to perform an adsorption treatment. Next, the dye-adsorbing semiconductor electrode was immersed in 3-methoxyacetonitrile, which is an electrolyte solvent, and stored for 14 days under light shielding, sealing, and room temperature. The state of dye support on the semiconductor electrode after storage was visually observed. The results are shown in Table 4.

  As is clear from the results in Table 3, the compound of the present invention has higher photoelectric conversion efficiency and retention rate than those of the comparative compound after storage for 10 days in a 65 ° C. environment, and has excellent durability. . Further, as is apparent from the results in Table 4, it can be seen that the adsorption stability to the semiconductor electrode is also excellent.

  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 (5)

At least 1 sort (s) of the compound shown by following General formula (1) is used, The photoelectric conversion material characterized by the above-mentioned.

(Wherein R ₁ , R ₂ and R ₃ represent an aliphatic group, an aromatic group and a heterocyclic group, and R ₂ and R ₃ may be linked to each other to form a ring. R ₄ represents An aliphatic group and an aromatic group each having an acidic group of less than pKa6 as a substituent, L ₁ represents a conjugated methine group unit, L ₂ represents an alkylene group having 8 or less carbon atoms, R ₅ represents an aromatic group, Represents a heterocyclic group, provided that when L ₂ is an alkylene group having 1 or 2 carbon atoms, R ₅ is an aromatic group having at least one substituent other than a hydrogen atom, or substituted or unsubstituted. Represents a heterocyclic group of The general formula (1), wherein R ₁ is an aromatic group, and R ₂ and R ₃ are connected to each other to form a saturated 5- or 6-membered ring. Photoelectric conversion material.   A semiconductor electrode comprising a substrate having conductivity on a surface, a semiconductor layer coated on the conductive surface, and a dye adsorbed on the surface of the semiconductor layer, wherein the dye is any one of claims 1 and 2. A semiconductor electrode comprising at least one of the compounds described above.   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, 4. The semiconductor electrode according to claim 3, comprising at least one metal chalcogenide selected from gallium, chromium, cobalt, and nickel.   A photoelectric conversion element using the semiconductor electrode according to claim 3.