JP2007188809A - Gel electrolyte, photoelectric conversion element and solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gel electrolyte which is prevented from liquid leakage, a photoelectric conversion element, and a solar cell which exhibits high photoelectric conversion efficiency and excellent stability. <P>SOLUTION: The gel electrolyte includes electrolytes containing redox species, and solvents which dissolves the redox species, and this electrolyte contains smectite. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gel electrolyte, a photoelectric conversion element, and a solar cell.

  A photoelectric conversion material is a material that converts light energy into electrical energy using an electrochemical reaction between electrodes. When the photoelectric conversion material is irradiated with light, electrons are generated on one electrode side and move to the counter electrode. The electrons that have moved to the counter electrode move as ions in the electrolyte and return to one electrode.

  That is, the photoelectric conversion material is a material that can continuously extract light energy as electric energy, and is used for, for example, a solar cell. There are several types of solar cells, but most of them are silicon solar cells that have been put to practical use in power generation panels for home installation, desk calculators, watches, portable game machines and the like.

  However, recently, dye-sensitized solar cells have attracted attention and are being studied for practical use. Dye-sensitized solar cells have been studied for a long time, and the basic structure specifically includes a metal oxide semiconductor, a dye adsorbed thereon, an electrolyte solution, and a counter electrode.

  In the conventional dye-sensitized solar cell as described above, a photoelectric conversion material in which a spectral sensitizing dye having absorption in the visible light region is adsorbed on the semiconductor surface is used. For example, a solar cell having a spectral sensitizing dye layer such as a transition metal complex on the surface of a metal oxide semiconductor is described (for example, see Patent Document 1), and a titanium oxide semiconductor doped with metal ions Examples include a solar cell having a spectral sensitizing dye layer such as a transition metal complex on the surface of the layer (for example, see Patent Document 2).

On the other hand, as an oxide semiconductor electrode having photoelectric conversion ability, a semiconductor single crystal electrode has been used in the early days. The types include titanium oxide (TiO ₂ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), and the like.

  However, since the single crystal electrode has a small amount of dye adsorption, the efficiency is very low and the cost is high. Thus, a high surface area semiconductor electrode having a large number of pores formed by sintering fine particles has been devised.

  For example, it has been reported by Tsubomura et al. That a porous zinc oxide electrode adsorbing an organic dye has very high performance (for example, see Non-Patent Document 1).

  After that, the dye has also been improved, and Graetzel et al. Have adsorbed the ruthenium complex dye on the porous titanium oxide electrode, so that it now has the same performance as a silicon solar cell (for example, Non-patent document 2).

However, for practical use to replace silicon solar cells, higher energy conversion efficiency, higher short-circuit current, open-circuit voltage, and form factor are required than ever before. Technological developments using reported materials such as ZnO, TiO ₂ , zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ) and the like have been carried out.

In addition, since dye-sensitized wet solar cells are much cheaper to manufacture than silicon solar cells, in the future, there is a possibility of replacing silicon solar cells used in the above-mentioned various products. In some cases, the characteristics of the solar cell according to each product are important. Among various characteristics of solar cells, the following are shown. Short circuit current 2. Open voltage Form factor 4. 4. Energy conversion efficiency The light absorption spectrum is important. The energy conversion efficiency of the solar cell is the biggest problem for solar cells, and its improvement has been strongly desired. As one of the technical problems affecting the efficiency, there is a demand for a sensitizing dye having the ability to efficiently transfer photoexcited electrons to a semiconductor. Of the various dyes studied so far, the ruthenium complex dyes have been found to have relatively excellent characteristics, but the dyes are expensive and ruthenium, the central metal of the complex, is a rare element. Therefore, organic dyes that can be supplied at a lower cost and more stably are more preferable. Many organic dyes have been studied so far because of such demands, but their photoelectric conversion efficiency is not yet sufficient, and there is a demand for an organic dye that can constitute a photoelectric conversion element with higher conversion efficiency.

  In addition to ruthenium complex dyes, various dyes have been studied (for example, see Patent Documents 3, 4, and 5). Well-known dyes are merocyanine dyes, xanthene dyes, and coumarin dyes. Acridine dyes, phenylmethane dyes, and the like. Further, other new dye nuclei have been developed (see, for example, Patent Document 6), but since none of the dyes has yet satisfactory performance, the adsorptive power is strong and the long wavelength region. Further development of highly efficient dyes is desired.

On the other hand, in order to prevent liquid leakage from the electrolyte layer, which is another problem, a dye-sensitized solar cell in which the electrolyte layer is solidified is described. The porous semiconductor layer used at this time has a specific surface area. those of 100 m ² ～10000M about ² per 1g are described as preferable. Moreover, the following method is described as a solidification method of an electrolyte solution layer (for example, refer patent document 7).

First, a compound represented by the following general formula (I):
Formula (I)

(Wherein R ¹ and R ² are a hydrogen atom or a methyl group, R ³ is a hydrogen atom or a lower alkyl group having 1 or more carbon atoms, n is an integer of 1 or more, and m is an integer of 0 or more. And m / n is in the range of 0-5.)
In a monomer solution obtained by dissolving the monomer represented by ethylene glycol in an ethylene glycol solution, an iodine compound (lithium iodide, etc.) that is a redox species is dissolved and impregnated in the porous semiconductor layer, and then ultraviolet or heat To polymerize the polymer compound. Thereafter, a solid electrolyte solution layer is formed by doping the polymer compound by sublimating iodine, which is another oxidation-reduction species (see, for example, Patent Documents 8 and 9).

The average particle size is produced porous semiconductor layer using particles of about 1Nm～2000nm, the specific surface area of the layer is described as preferably 10 m ² 200 m ² approximately per 1g. Moreover, as a method for solidifying the electrolyte, a compound represented by the following general formula (II);
Formula (II)

(In the formula, R ¹ is a hydrogen atom or a methyl group, A is a residue bonded to an ester group and a carbon atom, and n is 2 to 4.)
In the gel electrolyte using the poly (meth) acrylate monomer unit represented by the formula, it is described that ethylene carbonate (also referred to as EC) or propylene carbonate (also referred to as PC) is used as a solvent (for example, Patent Document 10). reference.).

  In addition, a gel electrolyte characterized in that it contains at least one structural unit having a monovalent organic residue derived from a carbonate group, a heterocyclic ring containing a nitrogen atom or a quaternary ammonium salt (for example, patents) Reference 11).

However, in order to prevent the liquid leakage of the dye-sensitized solar cell, solidification of the electrolyte using a polymer compound has been studied, but the viscosity of a solvent or a mixture of the electrolyte solution and the polymer compound is low. It was difficult to improve and inject into the porous semiconductor layer. Therefore, it is difficult to form a contact interface between the porous semiconductor layer and the gel electrolyte, and there is a problem that the conversion efficiency of the dye-sensitized solar cell using the electrolytic solution is about 70%. A means to solve is desired.
Japanese Patent Laid-Open No. 1-220380 Japanese National Patent Publication No. 5-504023 JP-A-11-167937 Japanese Patent Laid-Open No. 11-214730 Japanese Patent Laid-Open No. 11-214731 JP 2001-76775 A JP 2004-87202 A JP-A-8-236165 JP-A-9-27352 Japanese Patent Laid-Open No. 2001-210390 Japanese Patent Laid-Open No. 11-126917 Nature, 261 (1976) p402. J. et al. Am. Chem. Soc. 115 (1993) 6382

  A first object of the present invention is to provide a gel electrolyte that prevents liquid leakage, and a second object is to provide a photoelectric conversion element and a solar cell that exhibit high photoelectric conversion efficiency and excellent stability.

  The above object of the present invention has been achieved by the following configurations 1 to 7.

  1. A gel electrolyte comprising an electrolyte containing a redox species and a solvent in which the redox species can be dissolved, and the electrolyte contains smectites.

  2. 2. The gel electrolyte according to 1 above, which contains 1 to 30% by mass of the smectites.

  3. 3. The gel electrolyte according to 1 or 2 above, which contains imidazolium or a salt of the imidazolium as a constituent component of the electrolyte.

  4). The photoelectric conversion element containing the porous semiconductor layer which adsorb | sucked the pigment | dye at least, and electrolyte, The gel electrolyte of any one of said 1-3 is included, The photoelectric conversion element characterized by the above-mentioned.

  5. 5. The photoelectric conversion element as described in 4 above, wherein the semiconductor contained in the porous semiconductor layer is a metal oxide or a metal sulfide.

  6). The solar cell characterized by including the porous semiconductor layer which adsorb | sucked the pigment | dye between a pair of conductive substrates, and the gel electrolyte of any one of said 1-3.

  7). 7. The solar cell as described in 6 above, wherein the semiconductor contained in the porous semiconductor layer is a metal oxide or a metal sulfide.

  According to the present invention, it was possible to provide a gel electrolyte that prevented liquid leakage, and a second object was to provide a photoelectric conversion element and a solar cell exhibiting high photoelectric conversion efficiency and excellent stability.

  In the gel electrolyte of the present invention, by using the configuration defined in any one of claims 1 to 3, a gel electrolyte that does not leak even when applied to a porous semiconductor layer can be provided. It was. Furthermore, it succeeded also in providing the photoelectric conversion element and solar cell which show high photoelectric conversion efficiency and the outstanding stability by using the said gel electrolyte.

  Hereinafter, details of each component according to the present invention will be sequentially described.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have used the gel electrolyte as represented by any one of claims 1 to 3 to obtain the effect described in the present invention, that is, The present inventors have succeeded in obtaining a photoelectric conversion element and a solar cell that prevent liquid leakage, exhibit high photoelectric conversion efficiency, and exhibit excellent stability.

《Gel electrolyte》
The gel electrolyte of the present invention includes an electrolyte containing a redox species and a solvent in which the redox species can be dissolved, and is characterized by containing smectites.

《Redox species (also called redox electrolyte)》
The redox species according to the gel electrolyte of the present invention will be described.

The redox species according to the present invention (also referred to as a redox electrolyte in the present invention) is not particularly limited as long as it is an electrolyte that can generally be used in a battery, a solar battery, or the like. A combination of metal iodides such as NaI, KI, CaI ₂ and iodine is preferred.

  Further, an imidazolium iodide derivative may be added to the above combination, and imidazolium iodide or the like may be used in place of the metal iodide. Examples of the electrolyte concentration include a range of 0.1 mol / liter to 1.5 mol / liter with respect to the solvent, and a range of 0.5 mol / liter to 1.5 mol / liter is preferable.

  Examples of the imidazolium iodide derivative (also referred to as imidazolium salt) used as one of the redox species according to the present invention include 1-methyl-3-propylimidazolium iodide, 1-methyl-3-isopropylimidazolium. At least one selected from the group consisting of iodide, 1-methyl-3-butylimidazolium iodide, 1-methyl-3-isobutylimidazolium iodide and 1-methyl-3-sbutylimidazolium iodide Examples include imidazolium salts.

  In addition to the above, 1,1-dimethylimidazolium iodide, 1-methyl-3-ethylimidazolium iodide, 1-methyl-3-pentylimidazolium iodide, 1-methyl-3-isopentylimidazolium iodide Dye, 1-methyl-3-hexylimidazolium iodide, 1-methyl-3-isohexyl (branched) imidazolium iodide, 1-methyl-3-ethylimidazolium iodide, 1,2-dimethyl-3-propyl Examples thereof include imidazole iodide, 1-ethyl-3-isopropylimidazolium iodide, 1-propyl-3-propylimidazolium iodide and the like.

  As for the form of the imidazolium iodide derivative, for example, 1-methyl-3-propylimidazolium iodide is a compound that hardly undergoes crystallization up to about -20 ° C and does not decompose up to about 200 ° C. That is, the imidazolium iodide is a compound exhibiting the characteristic of taking a liquid form within a range of −20 ° C. to 200 ° C.

  An electrolyte (electrolyte composition) containing the redox species (redox electrolyte) according to the present invention and a solvent capable of dissolving the redox species described later (specific examples of usable solvents will be described in detail later). Is also in a liquid form, but the gel electrolyte of the present invention having sol-gel conversion characteristics is prepared by using it together with smectites to be described later.

(Reversible redox couple)
The redox species according to the present invention and the electrolyte in which the redox species can be dissolved preferably include a reversible redox pair.

Here, the “reversible redox _couple ” can be supplied from, for example, a mixture of iodine (I ₂ ) and iodide, iodide, bromide, hydroquinone, TCNQ complex or the like. In particular, a redox ^couple consisting of I ⁻ and I ³⁻ supplied from a mixture of iodine and iodide is preferred.

The redox couple is, for example, that a reducing species such as I ⁻ can easily accept holes from an oxidized dye, and the electrolyte containing the redox couple can transport charges between the n-type semiconductor electrode and the conductive film. From the viewpoint of increasing the speed and setting the open end voltage high, it is desirable to exhibit an oxidation-reduction potential that is 0.1 V to 0.6 V smaller than the oxidation potential of the dye described later.

(Other iodides that can be used in combination)
The gel electrolyte according to the present invention may further contain iodide in addition to the various iodides (metal iodide, imidazolium iodide derivative, etc.) used as the above redox species. Examples of the iodide include an iodide of an organic compound, a molten salt of iodide, and the like.

  As the molten salt of the iodide, an iodide of a heterocyclic nitrogen-containing compound such as a pyridinium salt, a quaternary ammonium salt, a pyrrolidinium salt, a pyrazolidium salt, an isothiazolidinium salt, or an isoxazolidinium salt should be used. Can do.

<Solvent capable of dissolving redox species>
The solvent capable of dissolving the redox species according to the present invention is formed from the following group consisting of organic solvent, halogenated compound, N, P and S capable of forming an onium salt with the above redox species. And compounds containing at least one element.

Here, “the redox species can be dissolved” is defined as “a solvent in which the redox species according to the present invention can be dissolved when the solubility of the redox species in the solvent is 5% by mass or more”. ]
(Organic solvent)
Examples of the organic solvent that is one embodiment of the solvent in which the redox species according to the present invention can be dissolved include cyclic carbonates such as ethylene carbonate (EC) and propylene carbonate (PC), dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate. Chain carbonates, γ-butyrolactone, acetonitrile, methoxypropionitrile, methyl propionate, ethyl propionate, cyclic ethers such as tetrahydrofuran and monomethyltetrahydrofuran, and chain ethers such as dimethoxyethane and diethoxyethane.

  Specifically, the solvent used for preparing the gel electrolyte can be injected well into the porous semiconductor layer by using a mixture of a solvent having a low viscosity and a solvent having a high viscosity and a high dielectric constant. In addition, a higher performance gel electrolyte can be prepared.

  For example, examples of the solvent having a high relative dielectric constant include ethylene carbonate (hereinafter referred to as EC). EC shows a high relative dielectric constant of 90, but is in a solid state at 25 ° C. Therefore, mixing with another solvent can realize a state where the relative dielectric constant is high and the viscosity is low.

  Specifically, it is desirable to mix one or more aprotic solvents having a relative dielectric constant of 40 or more with respect to EC (boiling point 238 ° C.). Further, specifically, a mixed solvent of EC and propylene carbonate (hereinafter referred to as PC, relative dielectric constant 65, viscosity 0.0025 Pa · s (2.5 cP), boiling point 242 ° C.), EC and γ-butyrolactone ( Hereinafter, a mixed solvent having a relative dielectric constant of 42, a viscosity of 0.0017 Pa · s (1.7 cP), a boiling point of 204 ° C.), and a mixed solvent of EC, PC, and γ-BL, which are described as γ-BL, are preferable.

  EC has a high relative dielectric constant, and PC and γ-BL have a high relative dielectric constant and a lower viscosity and a higher boiling point than EC. Therefore, a mixture of EC and these solvents is preferable. Among these, a combination of EC and γ-BL is particularly preferable.

  Further, in order to reduce the viscosity, a solvent having a lower viscosity may be added to the above mixed solvent. Specific examples of such an organic solvent include 1,2-diethoxyethane, tetrahydrofuran, 2 -Methyl tetrahydrofuran, methyl acetate, methyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, 3-methoxypropionitrile, acetonitrile, alcohols (for example, methanol, ethanol, etc.), etc. There is no particular limitation as long as it has a lower viscosity than the solvent and is compatible.

  Although these solvents may have a low boiling point, they can be added to an electrolyte that is immersed in order to inject an electrolyte to prevent volatilization of a solvent with a low boiling point, thereby reducing the viscosity of the gel electrolyte. (Low boiling point) The solvent can be retained.

(Content of organic solvent)
The content of the organic solvent in the gel electrolyte of the present invention is set to 65% by mass or less from the viewpoint of suppressing alteration of the gel electrolyte and preventing precipitation of various compounds in the electrolyte into the electrolyte composition. It is preferably 0.5% by mass to 40% by mass, more preferably 1% by mass to 20% by mass.

(Water content)
The gel electrolyte of the present invention preferably contains water. By containing water, for example, the energy conversion efficiency of the photosensitized solar cell described later can be further increased.

  The content of water in the gel electrolyte of the present invention is preferably 10% by mass or less, more preferably 10% by mass or less when the total amount of the redox species (for example, imidazolium salt) and water is 100% by mass. Is in the range of 0.01% by mass to 10% by mass, and particularly preferably in the range of 0.5% by mass to 5% by mass.

  The water content in the gel electrolyte of the present invention can be measured with a commercially available automatic moisture meter (Karl Fischer moisture meter).

  Here, the relationship between the viscosity of the gel electrolyte, the mixed solvent, and the mixing ratio when the mixing ratio of EC and γ-BL is changed will be described with reference to FIGS.

FIG. 1 is a graph showing changes in conductivity and solvent viscosity with respect to the mixing ratio of EC and γ-BL. The electrolyte is lithium iodide, iodine and 1,2-dimethyl-3-propylimidazole iodide, and the polymer compound is R ¹ in the monomer unit represented by the general formula (II). A is a radical polymerized monomer unit composed of a butanetetrayl group with eight polyethylene oxide groups and two polypropylene oxide groups as the central core. As shown in FIG. 1, increasing the EC percentage increases the conductivity but also increases the viscosity. This is because the ratio of EC having a high relative dielectric constant has increased, so that the ion concentration effective for ionic conduction has increased, and the increase in viscosity has made it difficult for ions to move. It is thought that this showed a change in conductivity.

  Moreover, it is preferable from FIG. 1 to mix EC and (gamma) -BL in the ratio of 1.5: 8.5-4.5: 5.5 (mass ratio).

  FIG. 2 shows the conductivity dependence of conversion efficiency when a gel electrolyte using a mixed solvent of EC and γ-BL and a porous semiconductor layer (also referred to as a semiconductor layer for photoelectric conversion material) having a porosity of 62% are used. It is a graph to show. The electrolyte is lithium iodide, iodine and 1,2-dimethyl-3-propylimidazole iodide, the polymer compound is the same as that described in the explanation of FIG. 1, and the semiconductor is titanium oxide. It is used.

The conductivity is varied by changing the mixing ratio of the solvents. As shown in FIG. 2, it can be seen that the conversion efficiency has a peak at a conductivity in the vicinity of 9 × 10 ⁻³ . In view of FIG. 2, when the conductivity is improved, the viscosity is also increased, so that it is difficult to inject the gel electrolyte into the porous semiconductor layer. Therefore, it is considered that the conversion efficiency is lowered when the conductivity is high.

  FIG. 3 shows the viscosity (Pa) of a mixed solvent when a gel electrolyte using a mixed solvent of EC and γ-BL and a porous semiconductor layer having a porosity of 62% (also referred to as a semiconductor layer for photoelectric conversion material) are used. -It is a graph which shows the change of the conversion efficiency with respect to s (cP)). The electrolyte is lithium iodide, iodine and 1,2-dimethyl-3-propylimidazole iodide, the polymer compound is the same as that described in the description of FIG. 1, and titanium oxide is used as the semiconductor. It was. As shown in FIG. 3, it can be seen that the conversion efficiency has a peak when the viscosity is around 0.002 Pa · s (2 cP). This is thought to be due to the fact that the penetration into the porous material becomes difficult due to the increase in the solvent viscosity.

  FIG. 4 shows the conversion efficiency relative to the solvent mixing ratio when a gel electrolyte using a mixed solvent of EC and γ-BL and a porous semiconductor layer having a porosity of 62% (also referred to as a semiconductor layer for photoelectric conversion material) are used. It is a graph which shows a change. The electrolyte used was lithium iodide, iodine and 1,2-dimethyl-3-propylimidazole iodide, the polymer compound was the same as that used in the description of FIG. 1, and the semiconductor was titanium oxide. Was used. As shown in FIG. 4, it can be seen that high conversion efficiency is exhibited when a solvent in which EC and γ-BL are mixed at a specific mixing ratio is used.

  As shown in FIG. 1, the conductivity and the solvent viscosity change depending on the mixing ratio of the solvents. Therefore, it is considered that the maximum conversion efficiency is exhibited due to both effects. FIG. 4 shows that the mixing ratio is preferably EC: γ-BL = 1.5: 8.5 to 4.5: 5.5.

(Compound containing an atom selected from the group consisting of N, P and S as a constituent atom)
The compound containing atoms selected from the group consisting of N, P and S as constituent atoms for use in the present invention will be described.

  In the compound containing the atom as a constituent atom, from the viewpoint of promoting the gelation of the electrolyte composition by reducing the polymerization degree of the polymer of the onium salt formed from the compound containing the element and the redox species, It is preferable to have two or more groups containing an element per molecule. The element-containing groups present in one molecule may be of the same type, but one molecule may have two or more different element-containing groups in one molecule.

  Moreover, the more preferable range of the number of containing groups which have the said element per molecule is 2-1,000,000.

  As the form of the compound containing the atom as a constituent atom, for example, a monomer, an oligomer, a polymer, or the like can be selected.

  Examples of the compound containing an atom as a constituent atom include those having a substituent containing at least one kind of atom selected from the group consisting of N, P and S in the main chain or side chain. The position of the substituent containing the atom is not particularly limited as long as the target polymer is obtained.

  The skeleton of the main chain of the compound containing the atom as a constituent atom is not particularly limited and can be, for example, polyethylene, polyester, polycarbonate, polymethyl methacrylate, polyacrylonitrile, polyamide, polyethylene terephthalate, or the like.

  As the substituent, for example, at least one group selected from the group consisting of a primary amino group, a secondary amino group, a tertiary amino group, a phosphine group, and a group derived from a nitrogen-containing heterocyclic compound is used. Can do. The compound containing the element as a constituent atom may have the same type of substituents present in one molecule, but may have two or more different types of substituents in one molecule. Among these, a primary amino group, a secondary amino group, and a tertiary amino group are preferable.

  Examples of the tertiary nitrogen including the primary amino group, the secondary amino group, and the tertiary amino group include an amino group, an N-methylamino group, an N, N-dimethylamino group, and an N-ethylamino group. Group, N, N-diethylamino group, N-propylamino group, N, N-dipropylamino group, N-butylamino group, N, N-dibutylamino group and the like.

  Examples of the nitrogen-containing heterocyclic substituent include pyridyl group, pyrimidinyl group, furyl group, pyrrolyl group, thienyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, pyrazinyl group, triazolyl group (for example, 1,2,4- Triazol-1-yl group, 1,2,3-triazol-1-yl group, etc.), oxazolyl group, benzoxazolyl group, thiazolyl group, isoxazolyl group, isothiazolyl group, furazanyl group, quinolyl group, benzofuryl group, dibenzo Furyl group, benzothienyl group, dibenzothienyl group, indolyl group, carbazolyl group, carbolinyl group, diazacarbazolyl group (indicating that one of the carbon atoms constituting the carboline ring of the carbolinyl group is replaced by a nitrogen atom) , Quinoxalinyl group, pyridazinyl group, triazini Group, quinazolinyl group, phthalazinyl group, morpholinyl group, 1-methylimidazolyl group, 1-ethyl-imidazolylmethyl group, and a 1-propyl-imidazolylmethyl group.

  In addition, as the substituent, a spiro ring composed of one or more nitrogen-containing heterocyclic substituents selected from the aforementioned types, and two or more nitrogen-containing heterocyclic substitutions selected from the aforementioned types An aggregate of groups (heterocyclic aggregate) or the like may be used.

  Examples of the compound containing N as a constituent atom include polyvinylimidazole, poly (4-vinylpyridine), polybenzimidazole, bipyridyl, terpyridyl, polyvinylpyrrole, 1,3,5-tris (3-dimethylamino) propylhexahydro. -1,3,5 triazine, tris-2aminoethylamine, polydiallylmethylamine, polyallyldimethylamine, polydimethylallylamine, polyallylamine, polydimethylaminoethylmethyl methacrylate, polydimethylaminoethyl methacrylate, and the like. The said compound can use 1 type, or 2 or more types chosen from the types mentioned above. Among these, tris-2aminoethylamine, polydiallylmethylamine, polyallyldimethylamine, polydimethylallylamine, polyallylamine, polydimethylaminoethylmethyl methacrylate, and polydimethylaminoethyl methacrylate are preferable.

  Examples of the compound containing P as a constituent atom include a monomer, oligomer or polymer having a phosphine group. Specific examples include polyvinylphenyl diphenylphosphine, 1,2-phenylenebisphosphine, 1,3-bis (diphenylphosphino) propane, 1,5-bis (diphenylphosphino) pentane, and the like. The said compound can use 1 type, or 2 or more types chosen from the types mentioned above.

  Examples of the compound containing S as a constituent atom include those containing a thioether structure. Specific examples include bis (methylthio) methane, 1,1-bis (methylthio) -2-nitroethylene, (di) ethyl sulfide, polyvinylphenylphenylthioether, and ethyl (bisethylthio) acetate. The said compound can use 1 type, or 2 or more types chosen from the types mentioned above.

  In the gel electrolyte of the present invention, the content of a compound containing an atom selected from the group consisting of N, P and S as a constituent atom suppresses gel electrolyte alteration, and electrolytes of various compounds in the electrolyte From the viewpoint of preventing precipitation in the composition, it is preferably 65% by mass or less, more preferably 0.5% by mass to 40% by mass, and particularly preferably 1% by mass to 20% by mass. It is preferable to adjust to the range.

(About preparation and use of mixed electrolyte)
Further, an electrolyte A is prepared by dissolving a compound containing at least one kind of atom selected from the group consisting of N, P, and S as a constituent atom in the electrolyte, and the electrolyte A contains a halogen-containing substance described later. The electrolyte B is prepared by dissolving the compound, and the obtained electrolyte A and electrolyte B are stored. It is possible to mix the stored electrolyte A and electrolyte B when necessary, and use the obtained mixed electrolyte as an electrolyte composition.

(Halogen-containing compounds)
The halogen-containing compound used in the present invention will be described.

  The halogen-containing compound preferably has 2 or more halogen atoms per molecule. In such a compound, different types of halogen atoms may be present in one molecule, and the total number of halogen atoms may be 2 or more, but two or more types of halogen atoms may be present in one molecule. good. If the number of halogen atoms per molecule is one, the degree of polymerization of the polymer obtained from the onium salt and the halogen-containing compound may be low, making it difficult to gel the electrolyte composition. A more preferable range of the number of halogen atoms per molecule is from 2 to 1,000,000.

  Examples of the halogen-containing compound having 2 or more halogen atoms per molecule include dibromomethane, dibromoethane, dibromopropane, dibromobutane, dibromopentane, dibromohexane, dibromoheptane, dibromooctane, dibromononane, dibromodecane, Dibromoundecane, dibromododecane, dibromotridecane, dichloromethane, dichloroethane, dichloropropane, dichlorobutane, dichloropentane, dichlorohexane, dichloroheptane, dichlorooctane, dichlorononane, dichlorodecane, dichloroundecane, dichlorododecane, dichlorotridecane, diiodomethane, Diiodoethane, diiodopropane, diiodobutane, diiodopentane, diiodohexane, diiodoheptane, diiodoocta , Diiodononane, diiododecane, diiodoundecane, diiodododecane, diiodotridecane, 1,2,4,5-tetrakisbromomethylbenzene, epichlorohydrin oligomer, epibromohydrin oligomer, hexabromocyclododecane, tris ( 3,3-dibromo-2-bromopropyl) isocyanuric acid, 1,2,3-tribromopropane, diiodoperfluoroethane, diiodoperfluoropropane, diiodoperfluorohexane, polyepichlorohydrin, polyepichlorohydrin and polyethylene ether And polyfunctional halides such as polyepibromohydrin and polyvinyl chloride. As the halogen-containing compound, one type or two or more types of organic halides selected from the types described above can be used. Of these, organic halides having two halogen atoms per molecule are preferred.

(Content of halogen-containing compound)
The content of the halogen-containing compound in the gel electrolyte of the present invention is 65% by mass or less from the viewpoint of suppressing the deterioration of the gel electrolyte and preventing precipitation of various compounds in the electrolyte into the electrolyte composition. It is preferable to adjust to a range of 1% by mass to 20% by mass.

《Smectite》
The smectite according to the gel electrolyte of the present invention will be described.

  The gel electrolyte of the present invention is characterized in that it contains smectites, but smectite is a clay mineral contained in clay, and it has a tetrahedral structure. The basic crystal structure consists of a layer composed of ions (tetrahedral layer) and a layer composed of divalent and trivalent cations having an octahedral structure (octahedral layer), namely tetrahedral layer, octahedral layer and tetrahedral layer. There are clay minerals such as montmorillonite, beidellite, nontronite, saponite, hectorite, etc., and these are collectively called smectite.

  As its properties, for example, when it is put in water or an aqueous solvent, it is linked to various directions to cause gelation. The bond is weak, and there is a sol-gel conversion property in which the viscosity is lowered and sol is formed by shaking the solution, and is returned to the original gel state by standing.

  This sol-gel conversion can occur repeatedly. The gel electrolyte of this invention can be prepared by adding a redox electrolyte, a solvent, etc. to this. That is, it is possible to reduce the viscosity by applying vibrations, form a charge transfer layer by a method such as injection (immersion), coating, etc., and leave it to gel to cause no liquid leakage.

  The smectite can change the viscosity of the gel depending on its content. From the viewpoint of smoothly performing gelation and solification, the amount of smectite added (also referred to as content) is 1% by mass to 30% by mass. It is preferable to adjust to the range.

  Further, in the case of an organic solvent system other than an aqueous system, the same effect can be obtained by using a smectite modified for a commercially available organic solvent system (for example, S-BEN, ORGANITE series manufactured by Hojun Co., Ltd.).

  Considering the movement of ions, the lower the viscosity of the solvent in the gel electrolyte, the easier the ions move. Therefore, the solvent is preferably 0.003 Pa · s (3.0 cP) or less (viscosity is a conical plate type). It is a value measured with a rotary viscometer). Furthermore, in order to prevent volatilization of the solvent, the boiling point is preferably high. Specifically, a solvent having a temperature of 70 ° C. or higher is preferable, and the boiling point of the mixed solvent is also preferably 70 ° C. or higher.

  In order to improve the performance of a solar cell (also referred to as a dye-sensitized solar cell), which will be described later, it is preferable to increase the ionic conductivity of the electrolytic solution. In order to increase the ionic conductivity, it is preferable that the solvent used has a low viscosity and a high relative dielectric constant. However, a solvent having a high relative dielectric constant has a high viscosity, and a solvent having a low relative dielectric constant tends to have a low viscosity. is there. Therefore, in order to efficiently inject into the porous semiconductor layer, further improve the performance of the gel electrolyte itself, and improve the conversion efficiency of the dye-sensitized solar cell, it is preferable to combine a plurality of solvents. .

《Charge transfer layer》
The charge transfer layer used in the present invention will be described.

  The charge transfer layer used in the present invention is preferably used as a constituent layer of the photoelectric conversion element of the present invention or the solar cell of the present invention.

The charge transfer layer preferably contains the gel electrolyte of the present invention, preferably contains a redox species contained in the gel electrolyte of the present invention, and a reversible redox pair is also preferably used. Examples of the reversible redox couple include redox electrolytes such as I ⁻ / I ³⁻ , Br ⁻ / Br ^{3 −} and quinone / hydroquinone.

Such a redox electrolyte can be obtained by a conventionally known method. For example, an I ⁻ / I ³⁻ type electrolyte can be obtained by mixing an ammonium salt of iodine and iodine.

  The charge transfer layer used in the present invention is composed of a dispersion of these redox electrolytes. The dispersion is a liquid electrolyte when it is a solution, and a solid polymer electrolyte when it is dispersed in a polymer that is solid at room temperature. Any of the gel electrolytes can be applied when dispersed in a gel substance, but the gel electrolyte of the present invention can be used from the viewpoint of preventing liquid leakage when a photoelectric conversion element or a solar cell is formed. Particularly preferred.

  When a liquid electrolyte is used as the charge transfer layer, a solvent capable of dissolving the redox species according to the present invention can be used, or an electrochemically inert solvent such as acetonitrile, propylene carbonate, ethylene carbonate Etc. are used. Examples of the electrolyte composition include electrolytes described in JP-A No. 2001-160427, “Surface Science”, Vol. 21, No. 5, pages 288 to 293, and the like.

<< Photoelectric conversion element >>
The photoelectric conversion element of the present invention will be described with reference to FIG.

  FIG. 5 is a partial cross-sectional view showing an example of the structure of the photoelectric conversion element of the present invention.

  21 represents a conductive support, 22 represents a photosensitive layer, 23 represents a charge transfer layer, and 24 represents a counter electrode. The conductive support 21 and the photosensitive layer 22 are also collectively referred to as a semiconductor electrode.

  Here, the photosensitive layer 22 is a layer having the semiconductor for a photoelectric conversion material of the present invention, and the charge transfer layer 23 contains the gel electrolyte of the present invention (a conventional redox electrolyte may be used in combination) and is conductive. Used in contact with the conductive support 21, the photosensitive layer 22, and the counter electrode 24.

<< Method for Manufacturing Photoelectric Conversion Element >>
The manufacturing method of a photoelectric conversion element is demonstrated using FIG.

  As shown in FIG. 5, the photoelectric conversion element of the present invention is manufactured through a process of adsorbing a sensitizing dye after forming a semiconductor thin film on a conductive support 1 using a conventionally known plasma processing apparatus. Is done.

  In addition, the surface area of the semiconductor thin film is increased, impurities on the surface of the semiconductor thin film are removed, the purity of the semiconductor is increased, and the efficiency of electron injection from the sensitizing dye to the semiconductor for photoelectric conversion material (also simply referred to as semiconductor) is increased. For the purpose, for example, chemical plating using a titanium tetrachloride aqueous solution or electrochemical plating using a titanium trichloride aqueous solution may be performed. In order to obtain the same effect, carboxylic acids (acetic acid, propionic acid, hexanoic acid, benzoic acid, etc.) may be adsorbed on the semiconductor surface after dye adsorption.

  A sensitizing dye is adsorbed on the semiconductor film formed on the conductive support 21, and the photosensitive film 22 is formed by sensitizing the semiconductor film for photoelectric conversion material. Although the details of the sensitization treatment method will be described later, this is also performed by dissolving a dye to be described later in an appropriate solvent and immersing the semiconductor film formed on the conductive support 21 in the solution. In that case, it is preferable that the semiconductor film is preliminarily decompressed or heat-treated to remove bubbles in the film so that the sensitizing dye can enter deep inside the semiconductor film.

  When the sensitizing dye is adsorbed to the photoelectric conversion material semiconductor according to the present invention, it may be used alone or in combination. Furthermore, conventionally known sensitizing dye compounds (for example, U.S. Pat. Nos. 4,684,537, 4,927,721, 5,084,365, 5, 350,644, 5,463,057, 5,525,440, JP-A-7-249790, JP-A-2000-150007, etc.) May be mixed and adsorbed.

  In particular, when the application of the semiconductor for photoelectric conversion material is a solar cell, it is possible to use a mixture of two or more kinds of dyes so that the wavelength range of photoelectric conversion can be widened and sunlight can be used as effectively as possible. preferable.

  The semiconductor for a photoelectric conversion material sensitized by using a combination of a plurality of sensitizing dyes described above may be prepared by immersing in a solution prepared by mixing a dye to be used together (also referred to as a dye compound). It can also be prepared by preparing a solution for the dye and immersing in each solution in turn.

  When preparing a separate solution for each dye and immersing it in each solution in order, this is possible regardless of the order in which the dye or a conventionally known sensitizing dye is adsorbed to the semiconductor for photoelectric conversion material. The effects described in the invention can be obtained.

  The adsorption treatment may be performed at room temperature using a solution in which the dye is dissolved, or may be performed by heating the solution to a temperature that does not affect the dye. Furthermore, it is preferable to remove the dye that has not been adsorbed during the adsorption treatment by washing treatment with a solvent or the like.

  When the photosensitive layer 22 is formed by adsorbing the dye to the semiconductor film for photoelectric conversion material formed on the conductive support 21, the counter electrode 24 is disposed so as to face the photosensitive layer 22. Further, a photoelectric conversion element can be formed by injecting a redox electrolyte as a charge transfer layer between the semiconductor electrode and the counter electrode 24.

<< Semiconductor for photoelectric conversion material >>
As a semiconductor for photoelectric conversion materials (also simply referred to as a semiconductor) used in the photoelectric conversion element of the present invention and the solar cell of the present invention, a simple substance such as silicon or germanium, a periodic table (also referred to as an element periodic table), A compound having a group 3 to group 5 or group 13 to group 15 element, a metal chalcogenide (eg, oxide, sulfide, selenide, etc.), metal nitride, or the like can be used.

  Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxides, cadmium, zinc, lead, silver, antimony or Bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like. Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, gallium-arsenic or copper-indium selenide, copper-indium sulfide, titanium nitride, and the like.

Specific examples of the semiconductor for photoelectric conversion material used in the present invention include metal oxides such as TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, ZnS, PbS, Bi _2. Examples thereof include metal sulfides such as S ₃ , CdSe, CdTe, GaP, InP, GaAs, CuInS ₂ , CuInSe ₂ , Ti ₃ N _4, etc., but TiO ₂ , ZnO, SnO ₂ , Fe ₂ are preferably used. Metal oxides such as O ₃ , WO ₃ , and Nb ₂ O ₅ , and metal sulfides such as CdS and PbS, and more preferably TiO ₂ or Nb ₂ O ₅ , but are preferably used among them. Is TiO ₂ .

The semiconductor for a photoelectric conversion material used in the present invention may be used in combination with a plurality of semiconductors described above. For example, several types of metal oxides or metal sulfides described above can be used in combination, or 20% by mass of titanium nitride (Ti ₃ N ₄ ) may be mixed and used in the titanium oxide semiconductor. In addition, J.H. Chem. Soc. , Chem. Commun. 15 (1999). At this time, when a component is added as a semiconductor in addition to the metal oxide or metal sulfide, the mass ratio of the additional component to the metal oxide or metal sulfide is preferably 30% by mass or less.

(Porous semiconductor layer)
A semiconductor for a photoelectric conversion material (also referred to as a semiconductor film or a semiconductor layer) used in the present invention is a porous semiconductor layer, and the porous semiconductor layer has a porous layer having voids. The formation of the voids is preferably performed by a baking process described later.

(Porosity of porous semiconductor layer (volume%))
A porous semiconductor layer used as a semiconductor layer for a photoelectric conversion material (also referred to as a semiconductor thin film) is a semiconductor layer having voids by firing the semiconductor (the firing treatment will be described in detail later). As a porosity, 10 volume% or less is preferable, More preferably, it is 8 volume% or less, Most preferably, it is 0.01 volume%-5 volume% or less.

(Measurement of porosity and film thickness of porous semiconductor layer)
The porosity of the porous semiconductor layer means a porosity that is penetrable in the thickness direction of the dielectric, and can be measured using a commercially available device such as a mercury porosimeter (Shimadzu porer 9220 type). Further, the film thickness of the porous semiconductor layer according to the present invention, which is a fired product film having a porous structure, is preferably at least 10 nm or more, more preferably 100 nm to 10,000 nm.

<< Sensitivity treatment of semiconductor for photoelectric conversion material >>
By sensitizing the semiconductor for photoelectric conversion material with the dye described below, the present invention further improves high photoelectric conversion efficiency and excellent stability, which is one of the objects described in the present invention. The semiconductor for photoelectric conversion materials which can be preferably applied to the photoelectric conversion element of this, a solar cell, etc. can be obtained.

  The semiconductor for a photoelectric conversion material is sensitized by a dye described below (hereinafter referred to as a sensitizing dye), and the effects described in the present invention can be more preferably achieved. Here, including the dye includes various modes such as adsorption to the semiconductor surface, the semiconductor surface layer, and the like, and the dye entering the porous structure of the semiconductor of the porous semiconductor layer.

The total content of sensitizing dyes described below per 1 m ² of the semiconductor layer (which may be a semiconductor) is preferably in the range of 0.01 to 100 mmol, more preferably 0.1 to 50 mmol. Particularly preferred is 0.5 to 20 mmol.

  In addition, when sensitizing treatment is performed using any one of the sensitizing dyes, the above compounds may be used alone or in combination with other compounds (for example, US Pat. No. 4,684,684). No. 5,537, No. 4,927,721, No. 5,084,365, No. 5,350,644, No. 5,463,057, It is also possible to use a mixture of each of the specifications such as US Pat. No. 5,525,440 and the compounds described in JP-A-7-249790, JP-A-2000-150007 and the like.

  In particular, when the application of the semiconductor for photoelectric conversion material is a solar cell described later, two or more kinds of dyes having different absorption wavelengths so that sunlight can be effectively used by widening the wavelength range of photoelectric conversion as much as possible. It is preferable to mix and use.

  In order to include a sensitizing dye in a semiconductor, a method in which the dye is dissolved in an appropriate solvent (such as ethanol) and a well-dried semiconductor is immersed in the solution for a long time is generally used.

  When preparing a semiconductor for a photoelectric conversion material in which a plurality of sensitizing dyes are used in combination or in combination with other sensitizing dye compounds, a mixed solution of each compound may be prepared and used. A solution can be prepared for a dye (also referred to as a dye compound) and immersed in each solution in order. In the case where a separate solution is prepared for each dye and is prepared by immersing in each solution in order, the effect described in the present invention can be obtained regardless of the order in which the dye is included in the semiconductor. Alternatively, it may be produced by mixing semiconductor fine particles adsorbing the dye alone.

  The adsorption treatment may be performed when the semiconductor is in the form of particles, or may be performed after forming a film on the support. A solution in which a dye (also referred to as a dye compound) used for the adsorption treatment is dissolved may be used at room temperature, or may be used by heating in a temperature range in which the dye does not decompose and the solution does not boil.

  Moreover, you may implement adsorption | suction of a pigment | dye after application | coating of a semiconductor fine particle (after formation of a photosensitive layer) like manufacture of the photoelectric conversion element mentioned later. Moreover, you may implement adsorption | suction of a pigment | dye by apply | coating semiconductor fine particles and a pigment | dye simultaneously. Unadsorbed pigment can be removed by washing.

  The sensitizing treatment of the semiconductor for a photoelectric conversion material used in the present invention is performed by adsorbing a sensitizing dye to the semiconductor. Details of the sensitizing treatment will be described later.

  Further, in the case of a semiconductor for a photoelectric conversion material having a semiconductor thin film with a high porosity, the above compound or sensitization is performed before water is adsorbed on the semiconductor thin film and in the voids inside the semiconductor thin film by moisture, water vapor, etc. It is preferable to complete the adsorption treatment (sensitization treatment of a semiconductor for a photoelectric conversion material) such as a dye compound.

  You may surface-treat the semiconductor for photoelectric conversion materials of this invention using an organic base. Examples of the organic base include diarylamine, triarylamine, pyridine, 4-t-butylpyridine, polyvinylpyridine, quinoline, piperidine, amidine, and the like. Among them, pyridine, 4-t-butylpyridine, and polyvinylpyridine are preferable. preferable.

  When the organic base is a liquid, it can be surface treated by preparing a solution dissolved in an organic solvent as it is, and immersing the semiconductor for a photoelectric conversion material of the present invention in a liquid amine or an amine solution. .

<< Dye (also called dye compound, sensitizing dye) >>
The dyes (also referred to as dye compounds, sensitizing dyes, etc.) according to the present invention will be described.

  The dye according to the present invention is not particularly limited as long as it is adsorbed on the porous semiconductor layer and functions as a photosensitizer and has absorption in various visible light regions and / or infrared light regions. In order to firmly adsorb the dye to the porous semiconductor layer, an interlock group such as a carboxyl group, an alkoxy group, a hydroxyl group, a hydroxyalkyl group, a sulfonic acid group, an ester group, a mercapto group, or a phosphonyl group is included in the dye molecule. What has is preferable and a carboxyl group is especially preferable among these. The interlock group provides an electrical bond that facilitates electron transfer between the excited dye and the conduction band edge of the porous semiconductor layer.

  Examples of the dye having an interlock group include ruthenium bipyridine dyes, azo dyes, quinone dyes, quinone imine dyes, quinacridone dyes, and squarylium dyes, cyanine dyes, merocyanine dyes, and the like. Examples thereof include polymethine dyes, triphenylmethane dyes, xanthene dyes, porphyrin dyes, phthalocyanine dyes, berylene dyes, indigo dyes, and naphthalocyanine dyes.

  As the dye that can be used in combination with the sensitizing dye, any of the above dyes can be used. In order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency, it is also preferable to mix two or more kinds of dyes. Moreover, the pigment | dye to mix and its ratio can be selected so that it may match with the wavelength range and intensity distribution of the target light source.

  Among the dyes according to the present invention, metal complex dyes, phthalocyanine dyes, porphyrin dyes, and polymethine dyes are preferably used from the comprehensive viewpoints such as photoelectron transfer reaction activity, light durability, and photochemical stability.

  Among the metal complex dyes, JP-A Nos. 2001-223037, 2001-226607, U.S. Pat. Nos. 4,927,721, 4,684,537, 5,084. No. 5,365, No. 5,350,644, No. 5,463,057, No. 5,525,440, JP-A-7-249750, JP The ruthenium complex dyes described in JP-A-10-504512, WO 98/50393 pamphlet and the like are preferably used.

  Examples of the porphyrin dye and the phthalocyanine dye include dyes described in JP-A No. 2001-223037 as preferable dyes.

  Examples of the polymethine dye include conventionally known methine dyes, JP-A Nos. 11-35836, 11-158395, 11-163378, 11-214730, and 11-214731. 10-093118, 11-273754, JP-A 2000-106224, 2000-357809, 2001-052766, EP 892,411, 911,841 Specification, Japanese Patent Application Laid-Open Nos. 2004-119099, 2004-207224, 2004-234953, 2004-319202, 2004-319309, 2005-11800, 2005-56697 Gazette, 2005-78888 gazette, 200 -123013, JP same 2005-129329, JP same 2005-129429, JP same 2005-203112 JP, include those described in the 2005-209359 Patent Publication.

  Although the preferable specific example of the pigment | dye (a pigment | dye compound, a sensitizing pigment | dye, etc.) based on this invention is shown below, this invention is not limited to these.

  In the above specific examples, TBA represents a tributylammonium cation.

<< Method for Manufacturing Semiconductor for Photoelectric Conversion Material >>
A method for manufacturing a semiconductor for a photoelectric conversion material used in the present invention will be described.

  As one mode of the semiconductor for a photoelectric conversion material used in the present invention, a method of forming the above semiconductor for a photoelectric conversion material on a conductive support by firing or the like can be mentioned as a preferable mode.

  When the semiconductor for a photoelectric conversion material used in the present invention is produced by firing, sensitization (adsorption, penetration into a porous body, etc.) of the semiconductor using the above dye (dye compound, sensitizing dye, etc.) ) The treatment is preferably carried out after firing. It is particularly preferable to perform the compound adsorption treatment quickly after the firing and before the water is adsorbed to the semiconductor.

  When the semiconductor for a photoelectric conversion material used in the present invention is in the form of particles, the semiconductor electrode is preferably prepared by applying or spraying the semiconductor for a photoelectric conversion material onto a conductive support. Moreover, when the semiconductor for photoelectric conversion materials used for this invention is a film | membrane form, and is not hold | maintained on an electroconductive support body, the semiconductor for photoelectric conversion materials is bonded on an electroconductive support body, and a semiconductor is used. It is preferable to produce an electrode.

  Hereinafter, a process for manufacturing a semiconductor for a photoelectric conversion material used in the present invention will be specifically described.

<< Preparation of coating liquid containing semiconductor fine powder >>
First, a coating solution containing fine semiconductor powder is prepared. The semiconductor fine powder preferably has a fine primary particle diameter, and the primary particle diameter is preferably in the range of 1 nm to 5000 nm, more preferably in the range of 2 nm to 50 nm. Is.

  As an example, the coating liquid containing the semiconductor fine powder can be prepared by dispersing the semiconductor fine powder in a solvent. The semiconductor fine powder dispersed in the solvent is dispersed in the form of primary particles. The solvent is not particularly limited as long as it can disperse the semiconductor fine powder.

  Examples of the solvent include water, an organic solvent, and a mixed solution of water and an organic solvent. As the organic solvent, alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone, acetone and acetyl acetone, hydrocarbons such as hexane and cyclohexane, and the like are used. A surfactant and a viscosity modifier (polyhydric alcohol such as polyethylene glycol) can be added to the coating solution as necessary. The range of the semiconductor fine powder concentration in the solvent is preferably 0.1% by mass to 70% by mass, and more preferably 0.1% by mass to 30% by mass.

<< Application of Semiconductor Fine Powder-Containing Coating Liquid and Firing Process of Formed Semiconductor Layer >>
The semiconductor fine powder-containing coating solution obtained as described above is applied or sprayed onto a conductive support, dried, etc., and then baked in air or an inert gas to form a conductive substrate (conductive A semiconductor layer (semiconductor film) is formed over a conductive support or a conductive substrate.

  The film obtained by applying and drying the coating liquid on the conductive support is composed of an aggregate of semiconductor fine particles, and the particle size of the fine particles corresponds to the primary particle size of the semiconductor fine powder used. is there.

  The semiconductor fine particle aggregate film formed on the substrate such as the conductive support in this way has a low bonding force with the conductive substrate (conductive support) and the bonding force between the fine particles, and has a high mechanical strength. From the viewpoint of increasing mechanical strength, it is preferable that the semiconductor fine particle aggregate film is fired to form a fired material film that is strongly fixed to the substrate.

(Conditions for firing treatment)
From the viewpoint of appropriately adjusting the actual surface area of the fired product film during the firing treatment and obtaining a fired product film having the above porosity, the firing temperature is preferably lower than 1000 ° C, more preferably 200 ° C to 800 ° C. It is the range of 300 degreeC, Most preferably, it is the range of 300 to 800 degreeC.

  Further, the ratio of the actual surface area to the apparent surface area can be controlled by the particle diameter and specific surface area of the semiconductor fine particles, the firing temperature, and the like. In addition, for the purpose of increasing the surface area of the semiconductor particles after heating, increasing the purity in the vicinity of the semiconductor particles, and increasing the efficiency of electron injection from the dye into the semiconductor particles, for example, chemical plating using a titanium tetrachloride aqueous solution or three An electrochemical plating process using a titanium chloride aqueous solution may be performed.

<< Sensitivity treatment of semiconductor for photoelectric conversion material >>
As described above, the semiconductor sensitization treatment is performed by dissolving the dye in an appropriate solvent and immersing the substrate obtained by firing the semiconductor in the solution. In that case, a substrate on which a semiconductor layer (also referred to as a semiconductor film) is formed by baking is subjected to pressure reduction treatment or heat treatment in advance to remove bubbles in the film, so that a sensitizing dye is a semiconductor layer (semiconductor film). A porous semiconductor layer (porous semiconductor film) is used as the semiconductor layer (semiconductor film) so that it can enter deep inside.

"solvent"
The solvent used for dissolving the sensitizing dye is exceptional as long as it can dissolve the dye (dye compound, sensitizing dye, etc.) and does not dissolve the semiconductor or react with the semiconductor. In order to prevent moisture and gas dissolved in the solvent from entering the semiconductor film and preventing sensitizing treatment such as adsorption of the dye (dye compound, sensitizing dye, etc.) in advance, It is preferable to deaerate and purify by distillation.

  Solvents preferably used for dissolving dyes (dye compounds, sensitizing dyes, etc.) are alcohol solvents such as methanol, ethanol and n-propanol, ketone solvents such as acetone and methyl ethyl ketone, diethyl ether, diisopropyl ether, tetrahydrofuran, 1 Ether solvents such as 1,4-dioxane and halogenated hydrocarbon solvents such as methylene chloride and 1,1,2-trichloroethane, particularly preferably methanol, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran and methylene chloride.

《Solar cell》
The solar cell of the present invention will be described.

  As shown in FIG. 5, the solar cell of the present invention is optimal when sunlight and light are used as a light source as an aspect of the photoelectric conversion element of the present invention. It has a structure in which photoelectric conversion is performed. That is, the semiconductor for photoelectric conversion material has a structure that can be irradiated with sunlight. When constituting the solar cell of the present invention, it is preferable that the semiconductor electrode, the charge transfer layer and the counter electrode are housed in a case and sealed, or the whole is sealed with resin.

  When the solar cell of the present invention is irradiated with sunlight or an electromagnetic wave equivalent to sunlight, a compound (sensitizing dye or the like) adsorbed on the photoelectric conversion material semiconductor absorbs the irradiated light or electromagnetic wave and excites it. Electrons generated by excitation move to the semiconductor, and then move to the counter electrode 4 via the conductive support 1 to reduce the redox electrolyte of the charge transfer layer 3. On the other hand, the compound of the present invention in which electrons are transferred to a semiconductor is an oxidant, but is reduced by the supply of electrons from the counter electrode 4 via the redox electrolyte of the charge transfer layer 3 and is reduced to the original. At the same time, the redox electrolyte of the charge transfer layer 3 is oxidized and returned to a state where it can be reduced again by the electrons supplied from the counter electrode 4. In this way, electrons flow, and a solar cell using the photoelectric conversion element of the present invention can be configured.

<< Conductive support (also referred to as conductive substrate, conductive substrate, etc.) >>
The conductive substrate used in the photoelectric conversion element of the present invention or the solar cell of the present invention is provided with a conductive material such as a conductive material such as a metal plate or a non-conductive material such as a glass plate or a plastic film. A structure can be used. Examples of materials used for the conductive substrate include metals (eg, platinum, gold, silver, copper, aluminum, rhodium, indium) or conductive metal oxides (eg, indium-tin composite oxide, tin oxide doped with fluorine) And carbon). The thickness of the conductive support is not particularly limited, but is preferably 0.3 mm to 5 mm.

  Further, the conductive substrate is preferably substantially transparent, and substantially transparent means that the light transmittance is 10% or more, and the transmittance is 50% or more. Is more preferable and 80% or more is most preferable.

Here, in order to obtain a transparent conductive substrate, it is preferable to provide a conductive layer made of a conductive metal oxide on the surface of a glass plate or a plastic film. In the case of using a transparent conductive substrate, light is preferably incident from the conductive substrate side. The conductive substrate has a surface resistance of preferably 50 Ω / cm ² or less, more preferably 10 Ω / cm ² or less.

《Counter electrode》
The counter electrode used in the present invention will be described.

The counter electrode is not particularly limited as long as it has conductivity, and any conductive material can be used. However, the counter electrode has a catalytic ability to oxidize I ³⁻ ions and other redox ions at a sufficiently high rate. It is preferable to use what you have. Examples of such materials include, but are not limited to, a platinum electrode, a surface of a conductive material subjected to platinum plating or platinum deposition, rhodium metal, ruthenium metal, ruthenium oxide, carbon, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

Example 1
<< Preparation of Gel Electrolyte A >>: The present invention As a solvent, methoxypropionitrile is used and redox concentration is obtained by dissolving lithium iodide at a concentration of 0.5 mol / liter and iodine at a concentration of 0.05 mol / liter. An electrolyte solution was prepared. While stirring with a high-speed stirrer, smectite (manufactured by Co-op Chemical Co., Ltd., trade name: SPN) was added to this solution so as to be 8% by mass to prepare a gel electrolyte (A).

<< Preparation of Gel Electrolyte B >>: The present invention Using methoxypropionitrile as a solvent, lithium iodide at a concentration of 0.5 mol / liter, iodine at a concentration of 0.05 mol / liter, and further a concentration of 0.2 mol / liter Redox electrolyte solution was prepared by dissolving 1-methyl-3-propylimidazole iodide.

  While stirring with a high-speed stirrer, smectite (manufactured by Co-op Chemical Co., Ltd., trade name: SPN) was added to the solution so as to be 8% by mass to prepare a gel electrolyte (B).

<< Preparation of Redox Electrolytic Solution C >>: Comparative Example Using methoxypropionitrile as a solvent, lithium iodide at a concentration of 0.5 mol / liter and iodine at a concentration of 0.05 mol / liter are dissolved to obtain redox properties. An electrolytic solution (C) was produced.

<Evaluation of suitability for preventing liquid leakage>
With respect to each of the obtained gel electrolyte A, gel electrolyte B, and oxidation-reduction electrolyte solution C, the evaluation of the liquid leakage prevention suitability was evaluated as follows.

  The obtained three kinds of electrolyte solutions were put into a sample tube, allowed to stand for 24 hours and then inverted, and the viscosity (viscosity) was visually evaluated as follows, and the liquid obtained when three kinds of samples were used for the porous semiconductor layer. The suitability for leakage prevention was observed. The observation results were as follows.

Gel electrolyte A: gelled and has no dripping, high suitability for liquid leakage Gel electrolyte B: gelled, has no dripping and has great suitability for liquid leakage Redox electrolyte C: fluid and low viscosity Yes, and there is no suitability for preventing liquid leakage Note that the electrochemical stability of the three types of gel electrolyte A, gel electrolyte B and redox electrolyte C was good.

  Here, good electrochemical stability means that, as a result of cyclic voltammetry using a platinum electrode in a 6M-KOH aqueous solution and the electrolyte solution of the present invention, hydrogen generation on a platinum electrode well known to those skilled in the art, Although reaction currents based on hydrogen adsorption and desorption, platinum surface oxide formation and reduction, and oxygen generation are observed, reaction currents due to decomposition and the like are not observed in a wide potential range, and the gel electrolyte of the present invention is electrochemical. Means stable.

Example 2
<< Preparation of dye-sensitized solar cell 101 >>: SC-101
The dye-sensitized solar cell shown in FIG. 7 was produced according to the steps shown in FIGS. 6 (a) to 6 (d) below.

Step 1: Production of Dye-Sensitized Solar Cell Forming Unit 100 On the transparent conductive glass plate 1 having the fluorine-doped tin oxide coating layer 2, the following titanium oxide suspension is applied, and after natural drying, 300 By baking at 60 ° C. for 60 minutes, the semiconductor layer 3 for photoelectric conversion material having a film-like titanium oxide was formed on the support.

Subsequently, cis-bis (thiocyanato) -N, N-bis (2,2′-dipyridyl-4,4′-dicarboxylic acid) -ruthenium (II): (D-1) was 4 × 10 ⁻⁴ mol / L. 200 ml of a dehydrated ethanol solution of the above was prepared, the semiconductor layer 3 for photoelectric conversion material was immersed together with the transparent conductive glass support 1, and 1 g of trifluoroacetic acid was further added, followed by ultrasonic irradiation for 2 hours.

  After the reaction, the semiconductor layer 3 for photoelectric conversion material was washed with chloroform and vacuum-dried to prepare an n-type semiconductor electrode 4 which is a porous semiconductor layer.

  A transparent conductive material in which a glass substrate 7 on which a fluorine-doped tin oxide electrode (conductive film) 6 attached with platinum is formed as a counter electrode 5 is provided with the n-type semiconductor electrode 4 using a spacer having a diameter of 15 μm. Was installed on a porous glass plate, and the periphery was fixed with an epoxy resin 8 leaving an electrolyte injection port 9 to produce a dye-sensitized solar cell forming unit 100 as shown in FIG.

Step 2: Production of Dye-Sensitized Solar Cell 101 As shown in FIGS. 6B and 6C, the viscosity is given to the opening of the dye-sensitized solar cell forming unit 100 through the inlet (9). The gel electrolyte 10 of the present invention is injected in a state where the pH is lowered, and the gel electrolyte 10 is infiltrated into a void region (not particularly shown) of the n-type semiconductor electrode 4 which is a porous semiconductor layer, It injected into the gap | interval of the n-type semiconductor electrode 4 and the fluorine dope tin oxide electrode (conductive film) 6 which attached platinum.

  Subsequently, the opening of the dye-sensitized solar cell forming unit 100 into which the gel electrolyte 10 has been injected is sealed with the epoxy resin 11 and then heated on a hot plate at 60 ° C. for 30 minutes, as shown in FIG. Such a dye-sensitized solar cell 101 was produced.

  FIG. 6D is a schematic view showing a cross section of the dye-sensitized solar cell 101 after the opening is sealed.

(Preparation of titanium oxide suspension)
62.5 ml of titanium tetraisopropoxide (first grade, manufactured by Wako Pure Chemical Industries, Ltd.) was dropped into 375 ml of pure water at room temperature with vigorous stirring over 10 minutes (a white precipitate was formed), and then 70% aqueous nitric acid 2.65 ml of was added, and the reaction system was heated to 80 ° C., and then stirred for 8 hours.

  Furthermore, after concentrating under reduced pressure until the volume of the reaction mixture reached about 200 ml, 125 ml of pure water and 140 g of titanium oxide powder (Super Titania F-6 manufactured by Showa Titanium Co., Ltd.) were added to form a titanium oxide suspension (about 800 ml) was prepared.

(Preparation of gel electrolyte 10);
The gel electrolyte of the present invention was prepared as follows.

Step 1: Preparation of redox electrolyte (also referred to as electrolyte) Using methoxypropionitrile as a solvent, lithium iodide at a concentration of 0.5 mol / liter and iodine at a concentration of 0.05 mol / liter are dissolved. A redox electrolyte was prepared.

Step 2: Preparation of Gel Electrolyte 10 Smectite (manufactured by Co-op Chemical Co., Ltd., trade name: SPN) was added to the redox electrolyte (also referred to as electrolyte) while stirring with a high-speed stirrer. The gel electrolyte (10) of the present invention was prepared.

<< Preparation of dye-sensitized solar cell 102 >>: SC-102
In the production of the dye-sensitized solar cell 101, a dye-sensitized solar cell 102 was similarly produced except that 1-methyl-3-propylimidazole iodide having a concentration of 0.2 mol / liter was further added to the electrolyte. did.

<< Preparation of dye-sensitized solar cells 103-110 >>
In the production of the dye-sensitized solar cell 101, photoelectric conversion elements 103 to 110 were produced in the same manner except that the ruthenium dye (D-1) was changed to the dye described in Table 1.

(Production of Comparative Example 1)
In the production of the dye-sensitized solar cell 101, methoxypropionitrile was used as a solvent, and lithium oxide at a concentration of 0.5 mol / liter and iodine at a concentration of 0.05 mol / liter were dissolved to obtain a redox electrolyte. A comparative dye-sensitized solar cell (SC-R1) was produced in the same manner except that it was prepared and used.

(Production of Comparative Example 2)
A comparative dye-sensitized solar cell SC-R2 was prepared in the same manner as in the preparation of the dye-sensitized solar cell 101 except that the following electrolyte composition was prepared and used.

(Preparation of electrolyte composition)
Lithium iodide 0.5M and iodine 0.05M are dissolved in propylene carbonate to prepare an electrolyte, and 10% by mass (10 g) of poly (4-vinylpyridine) (with a molecular weight of 2000) is added to 90% by mass of the electrolyte. Dissolved. Thereafter, 10 g of 1,6-dibromohexane as an organic bromide was dissolved in the solution to prepare an electrolyte composition as a gel electrolyte precursor.

  For each of the obtained dye-sensitized solar cells SC-101 to SC-110 (present invention) and comparative dye-sensitized solar cells SC-R1 and SC-R2, as shown in FIG. 12 was irradiated so as to be perpendicular to the surface of the transparent conductive glass plate 1, and the photoelectric conversion characteristics of the solar cell and the liquid leakage evaluation of the solar cell were performed as described below.

<< Evaluation of photoelectric conversion characteristics of solar cells >>
Solar cells SC-101 to SC-110 obtained above and solar cells SC-R1 and R2 are each 100 mW / m by a solar simulator (manufactured by JASCO (JASCO), low energy spectral sensitivity measuring device CEP-25). The short-circuit current density Jsc (mA / cm ² ) and the open-circuit voltage value Voc (V) when irradiated with light having an intensity of ² were measured and shown in Table 1. The indicated value was the average value of the measurement results for three solar cells having the same configuration and production method.

<< Evaluation of electrolyte leakage in solar cells >>
After the solar cell obtained above was stored at 77 ° C. for 14 days, the presence or absence of electrolyte leakage was confirmed.

○: No liquid leakage in all three Δ: One or two had liquid leakage ×: All had liquid leakage Table 1 shows the results obtained.

  Table 1 shows that the solar cell of the present invention shows almost the same photoelectric conversion characteristics as compared with the comparison, and an electrolyte containing smectites is effective. Furthermore, further effects could be confirmed by adding imidazolium salts. In addition, it was revealed that the solar cell of the present invention is excellent in liquid leakage and excellent in stability.

It is a graph which shows the conductivity and the viscosity change of a solvent with respect to the mixing ratio of EC and (gamma) -BL. It is a graph which shows the conductivity dependence of the conversion efficiency when using the gel electrolyte using the mixed solvent of EC and (gamma) -BL, and the porous semiconductor layer (it is also called the semiconductor layer for photoelectric conversion materials) of the porosity 62%. . The graph which shows the change of the conversion efficiency with respect to the viscosity of a mixed solvent when the gel electrolyte using the mixed solvent of EC and (gamma) -BL and the porous semiconductor layer (it is also called the semiconductor layer for photoelectric conversion materials) of the porosity 62% are used. It is. The graph which shows the change of the conversion efficiency with respect to the mixture ratio of the solvent when the gel electrolyte using the mixed solvent of EC and (gamma) -BL and the porous semiconductor layer (it is also called the semiconductor layer for photoelectric conversion materials) of the porosity 62% are used. It is. It is a fragmentary sectional view which shows an example of the structure of the photoelectric conversion element of this invention. It is a schematic diagram which shows an example of the manufacturing process of the solar cell of this invention. It is a schematic diagram which shows the one aspect | mode of the solar cell of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transparent conductive glass plate 2 Tin oxide coat layer 3 Semiconductor layer for photoelectric conversion materials having titanium oxide 4 n-type semiconductor electrode 5 Counter electrode 6 Fluorine-doped tin oxide electrode (conductive film) with platinum
7 Glass substrate 8 Epoxy resin 9 Electrolyte inlet 10 Gel electrolyte 11 Epoxy resin 12 Sunlight 100 Dye-sensitized solar cell forming unit 101 Dye-sensitized solar cell 21 Conductive support 22 Photosensitive layer 23 Charge transfer layer 24 Opposite electrode

Claims (7)

A gel electrolyte comprising an electrolyte containing a redox species and a solvent in which the redox species can be dissolved, and the electrolyte contains smectites. The gel electrolyte according to claim 1, wherein the smectite is contained in an amount of 1% by mass to 30% by mass. The gel electrolyte according to claim 1 or 2, which contains imidazolium or a salt of the imidazolium as a constituent component of the electrolyte. The photoelectric conversion element containing the porous semiconductor layer which adsorb | sucked the pigment | dye at least, and electrolyte, The gel electrolyte of any one of Claims 1-3 is included, The photoelectric conversion element characterized by the above-mentioned. The photoelectric conversion element according to claim 4, wherein the semiconductor contained in the porous semiconductor layer is a metal oxide or a metal sulfide. The solar cell characterized by including the porous semiconductor layer which adsorb | sucked the pigment | dye between a pair of electroconductive board | substrates, and the gel electrolyte of any one of Claims 1-3. The solar cell according to claim 6, wherein the semiconductor contained in the porous semiconductor layer is a metal oxide or a metal sulfide.

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