JP2006155938A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the durability of a photoelectric conversion element such as a dye-sensitized solar cell by preventing the liquefaction of a gel-form or solid electrolyte and reducing light absorption loss resulting from yellow discoloration. <P>SOLUTION: The photoelectric conversion element comprises a semiconductor electrode 8, a counter electrode 9, and an electrolyte layer 4 held between those electrodes. The electrolyte layer 4 is made of a gel-form or solid electrolyte that has been gelled or solidified using a compound having a polyoxyalkylene chain, and the electrolyte includes a light stabilizer and further an antioxidant. The light stabilizer is preferably a hindered-amine-based light stabilizer, and the antioxidant is preferably a phenolic antioxidant. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photoelectric conversion element suitably used as a dye-sensitized solar cell.

  Conventionally, various solar cells have been proposed as photoelectric conversion elements that convert light energy into electrical energy. Among such solar cells, a dye-sensitized solar cell was developed by Gretzzel et al. Of the University of Lausanne in Switzerland in 1991. In general, a photoelectric conversion layer made of a semiconductor having a dye adsorbed on a conductive substrate is formed. A semiconductor electrode, a counter electrode made of a conductive base material provided opposite to the semiconductor electrode, and an electrolyte layer (charge transport layer) held between the semiconductor electrode and the counter electrode.

  Since the dye-sensitized solar cell uses an organic substance inside the battery, deterioration of characteristics due to ultraviolet rays or heat becomes a problem. On the other hand, for example, in Patent Document 1 described below, the deterioration of the characteristics of the solar cell can be suppressed by providing a resin having benzophenone or the like as an ultraviolet absorbing member on the light incident surface. However, in such an ultraviolet absorbing member, the wavelength region to be cut cannot be completely prevented, and there is a concern that auto-oxidation occurs inside the battery, and a chain of auto-oxidation that occurs inside the battery due to the light that could not be cut. The cycle cannot be prevented directly.

  Conventionally, the electrolyte layer has been formed by injecting an electrolytic solution containing a redox body between the semiconductor electrode and the counter electrode, but prevents such liquid leakage from the liquid electrolyte layer. For this reason, it has been proposed to form the electrolyte layer with a gel-like or solid electrolyte (see, for example, Patent Documents 2 and 3 below). In such a gel-like or solid electrolyte, not only the problem of performance deterioration due to the absorption of visible light being hindered by yellowing of the electrolyte but also the network structure composed of the gelling agent and the solidifying agent is oxidized. There is also concern about the problem of liquefaction of the electrolyte due to deterioration.

Patent Document 4 listed below proposes adding a stabilizer such as an antioxidant to the electrolyte in order to prevent oxidation of the dye contained in the semiconductor electrode. The document also describes prevention of deterioration of the electrolyte itself as an additional effect of adding an antioxidant to the electrolyte. However, in this document, the electrolyte handled in the actual embodiment is a liquid electrolyte, and there is no disclosure about the problem of liquefaction in a gel or solid electrolyte.
JP-A-11-345991 JP 2002-289271 A JP 2002-289272 A JP 2004-39292 A

  The present invention has been made in view of the above points. A photoelectric conversion element having excellent durability by preventing liquefaction of a gel-like or solid electrolyte and reducing light absorption loss due to yellowing is provided. The purpose is to provide.

  The photoelectric conversion element according to the present invention that solves the above problems includes a semiconductor electrode, a counter electrode, and an electrolyte layer held between the two electrodes, and the electrolyte layer is gelled or solid with a compound having a polyoxyalkylene chain. It is made of a gelled or solid electrolyte, and the electrolyte contains a light stabilizer.

  In the photoelectric conversion element according to the present invention, the electrolyte preferably further contains an antioxidant.

  Moreover, in the photoelectric conversion element which concerns on this invention, it is preferable that the said light stabilizer is a hindered amine type light stabilizer, and the said antioxidant is a phenolic antioxidant.

  According to the present invention, liquefaction of an electrolyte can be suppressed by adding a light stabilizer to the electrolyte in an electrolyte layer made of an alkylene oxide gel or solid electrolyte. In addition, light absorption loss of the photoelectric conversion element due to yellowing of the gel or solid electrolyte can be reduced. Therefore, the long-term stability of the electrolyte layer made of a gel or solid electrolyte can be improved.

  Details of the photoelectric conversion element according to the present invention will be described below.

  The photoelectric conversion element of the present invention comprises a semiconductor electrode, a counter electrode, and an electrolyte layer held between both electrodes. Preferably, a semiconductor electrode having a photoelectric conversion layer made of a semiconductor (for example, an n-type semiconductor) having a dye adsorbed on the conductive base material, and a counter electrode made of a conductive base material provided opposite to the semiconductor electrode A dye-sensitized photoelectric conversion element comprising an electrolyte layer held between these semiconductor electrodes and a counter electrode.

  In the present invention, the electrolyte layer is composed of an alkylene oxide gel or solid electrolyte gelled or solidified with a compound having a polyoxyalkylene chain. Here, the gel electrolyte is one in which a redox body and a solvent capable of dissolving it are held in a network structure formed by a crosslinking reaction of a gelling agent. And the electrolyte solution containing the solvent which can melt | dissolve this is gelatinized using the gelatinizer containing the said compound. Moreover, after gelatinizing the solvent solution containing a solvent and a gelatinizer, the same gel electrolyte can also be obtained by carrying out liquid exchange in the electrolyte solution of the final composition containing a redox body. The solid electrolyte is obtained by crosslinking reaction of a redox substance dissolved in a solidifying agent containing the above compound. The solid electrolyte is formed into a network structure formed by crosslinking reaction of the solidifying agent. A solid polymer electrolyte in which the redox substance is retained.

Such a gelling agent or solidifying agent is not particularly limited as long as it contains a compound having a polyoxyalkylene chain and can gel or solidify an electrolyte. Usually, a polymer precursor having a polyoxyalkylene chain ( Polymer gelling agent) is used. For example, (1) alkylenes such as trifunctional terminal acryloyl-modified alkylene oxide polymers and tetrafunctional terminal acryloyl-modified alkylene oxide polymers disclosed in JP-A-5-109311 and JP-A-11-176442 Examples include acryloyl-modified polymer compounds having an oxide polymer chain. (2) In addition, it includes compound A having at least one type of isocyanate group and compound B that is reactive with at least one type of isocyanate group, and at least one of compound A and compound B has a polyoxyalkylene chain. (See Patent Documents 2 and 3 above). As the compound having a polyoxyalkylene chain, a compound having a polymer structure having a molecular weight of 500 to 50,000 is preferably used. The trifunctional or tetrafunctional terminal acryloyl-modified alkylene oxide polymer of the above (1) is, for example, In the case of trifunctionality, glycerol, trimethylolpropane, etc., in the case of tetrafunctionality, diglycerin, pentaerythritol, etc. are used as starting materials, respectively, and alkylene oxides such as ethylene oxide and propylene oxide are added thereto, Furthermore, it is a compound obtained by esterifying an unsaturated organic acid such as acrylic acid or methacrylic acid, or by dehydrochlorinating an acid chloride such as acrylic acid chloride or methacrylic acid chloride.

  Examples of the compound A of (2) include aromatic isocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, and xylylene diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; fats such as isophorone diisocyanate and cyclohexyl diisocyanate. Examples thereof include cyclic isocyanates, which may be multimers such as dimers and trimers, or modified products. Further, low molecular alcohols and adducts of these isocyanates, and compounds obtained by addition reaction of polyoxyalkylene and these isocyanates in advance can be mentioned. Examples of the compound B include compounds having an active hydrogen group such as a carboxyl group, a hydroxyl group, and an amino group. More specifically, examples of the compound having a carboxyl group include hexanoic acid, adipic acid, phthalic acid, and azelaic acid. Carboxylic acids such as: hydroxyl group-containing compounds such as ethylene glycol, diethylene glycol, glycerin, pentaerythritol, sorbitol, sucrose alcohols; amino group-containing compounds such as ethylenediamine, tolylenediamine, diphenylmethanediamine, diethylenetriamine, etc. Each of the amines can be mentioned. Compound B also includes a compound having one or more active hydrogen groups as described above in one molecule and a polyoxyalkylene chain.

  The redox compound constituting the electrolyte is not particularly limited as long as it can be generally used in a battery, a solar battery, etc. Among them, a halogen dioxide such as a combination of iodine molecules and iodide, a combination of bromine molecules and bromide, and the like. A combination of atomic molecules and halide salts is preferred. The density | concentration of a redox body is 0.1-10 mol / L normally, More preferably, it is 0.1-5 mol / L.

  The solvent is not particularly limited as long as it is a compound that can dissolve the redox substance. For example, as an organic solvent, nitrile compounds such as methoxypropionitrile and acetonitrile, lactone compounds such as γ-butyrolactone and valerolactone, carbonate compounds such as ethylene carbonate and propylene carbonate, ethers such as dioxane, diethyl ether and ethylene glycol dialkyl ether , Alcohols such as methanol and ethanol, imidazoles, and the like. These may be used alone or in admixture of two or more.

  Further, as the solvent, an ionic liquid, that is, a molten salt can be used. Examples of the ionic liquid are disclosed in “Inorg. Chem.” 1996, 35, p1168-1178, “Electrochemistry” 2002.2, p130-136, JP-T-9-507334, JP-A-8-259543, and the like. Although it will not specifically limit if it can generally be used in the well-known battery, solar cell, etc. which have a melting point lower than room temperature (25 degreeC) or higher than room temperature. However, a salt that liquefies at room temperature by dissolving other molten salt or additives other than the molten salt is preferably used.

Specifically, as the cation of the molten salt, ammonium, imidazolium, oxazolium, thiazolium, piperidinium, pyrazolium, isoxazolium, thiadiazolium, oxadiazolium, triazolium, pyrrolidinium, pyridinium, pyrimidinium, pyridazinium, pyrazinium, Triazinium, phosphonium, sulfonium, carbazolium, indolium, and derivatives thereof are preferable, and ammonium, imidazolium, pyridinium, piperidinium, pyrazolium, and sulfonium are particularly preferable. The anion of the molten salt includes metal chlorides such as AlCl ₄ ⁻ and Al ₂ Cl ₇ ^— , PF ₆ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , N (CF ₃ SO ₂ ) ₂ ⁻ , F ( HF) Fluorine-containing materials such as _n ⁻ and CF ₃ COO ⁻ , NO ₃ ⁻ , CH ₃ COO ⁻ , C ₆ H ₁₁ COO ⁻ , CH ₃ OSO ₃ ⁻ , CH ₃ OSO ₂ ⁻ , CH ₃ SO ₃ ⁻ , CH Non-fluorine compounds such as ₃ SO ₂ ⁻ and (CH ₃ O) ₂ PO ₂ ^— , halides such as iodine and bromine, and the like.

  Among these, as the solvent, it is more preferable to use a nitrile compound or a room temperature molten salt.

  In the present invention, a light stabilizer is added to the electrolyte composed of the above. By including the light stabilizer in the electrolyte, it is possible to directly prevent deterioration of the electrolyte, to prevent yellowing of the electrolyte, and to reduce visible light absorption loss.

  The light stabilizer of the present invention is a concept including an ultraviolet absorber, for example, benzophenone, benzotriazole, cyanoacrylate, oxalic acid, hindered amine, salicylic acid ester, hydroxybenzoate, benzoate, Carbamate type | system | group etc. are mentioned, These can also be used individually or in combination with 2 or more types, respectively. Preferably, a hindered amine light stabilizer is used. With this light stabilizer, the autooxidation degradation initiation reaction of the electrolyte can be suppressed, and the autooxidation chain reaction can be stopped. The liquefaction of the alkylene oxide-based gel or solid electrolyte can be particularly effectively suppressed. It is also effective to use a UV absorber such as a salicylic acid ester, benzophenone, benzotriazole, hydroxybenzoate, benzoate, cyanoacrylate, or carbamate together with a hindered amine light stabilizer.

  Examples of the hindered amine light stabilizer include bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, tris (2,2,6,6-tetramethyl-4-piperidyl) nitriloacetate, succinic acid-bis (2,2,6,6- Tetramethyl-4-piperidyl) ester, dimethyl succinate 1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate, N, N′-bis (3- Aminopropyl) ethylenediamine-2,4-bis [N-butyl-N- (1,2,2,6,6-pentamethyl-4-piperidyl) amino] -6-chloro-1,3 Examples include triazine condensate, tetrakis (2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butanetetracarboxylic acid ester, and these may be used alone or in combination of two or more. Can be used.

  Examples of the ultraviolet absorber include 2- (2H-benzotriazol-2-yl) -p-cresol, 2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl-6 (T-butyl) phenol, 2- (2-hydroxy-5-methylphenyl) -2H-benzotriazole, 5-chloro-2- (3,5-di-t-butyl-2-hydroxyphenyl) -2H- Benzotriazole, 2- (3-tert-butyl-2-hydroxy-5-methylphenyl) -5-chloro-2H-benzotriazole, 2- (3,5-di-tert-pentyl-2-hydroxyphenyl)- 2H-benzotriazole, 2- (3,5-di-t-butyl-2-hydroxyphenyl) -2H-benzotriazole, 2- (2H-benzooliazol-2-yl)- -Methyl-6- (3,4,5,6-tetrahydrofasalimidylmethylphenol, 2- (2-di-hydroxy-5-t-octylphenyl) -2H-benzotriazole, 1,4-bis (4 -Benzol-3-hydroxyphenoxy) -butane, 2- (2-hydroxy-4-octylphenyl) -2H-benzotriazole, 5-chloro-2- (3,5-di-sec-butyl-2-hydroxyphenyl) ) -2H-benzotriazole, 2- (2H-benzotriazol-2-yl) -4,6-bis (I-methyl-I-phenylethyl) phenol, 2,4-di-t-6- (5- Chlorobenzotriazol-2-yl) phenol, 2- (2H-benzotriazol-2-yl) -4,6-di-t-pentylphenol, 2- (2H-ben Triazol-2-yl) -4-1,1,3,3-tetramethylbutyl) phenol, 2,2′-methylenebis [6- (2H-benzotriazol-2-yl) -4- (1,1, 3,3-tetramethylbutyl) phenol, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone 5-sulfonic acid trihydrate, 2-hydroxy-4-octyl Oxybenzophenone, 4-dodecyloxy-2-hydrobenzophenone, 4-benzyloxy-2-hydrobenzophenone, 2,2 ', 4,4'-tetrahydrobenzophenone, 2,2'-dihydroxy-4,4'- Dimethoxybenzophenone, phenyl salicylate, 4-t-butylphenyl salicylate Sylate, ethyl 2-cyano-3,3′-diphenyl acrylate, 2′-ethylhexyl 2-cyano-3,3′-diphenyl acrylate, [2,2′-thiobis (4-t-octylphenolate)]-2 -Ethylhexylamine, 2 ', 4'-di-t-butylphenyl 3,5-di-t-butyl-4-hydroxybenzoate, 2- (4,6-diphenyl-1,3,5-triazine-2- Yl) -5-[(hexyl) oxy] -phenol, octabenzene, 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-4-hydroxybenzoate, each of which is used alone Or in combination of two or more.

  It is preferable that an antioxidant is added to the electrolyte together with the light stabilizer. By containing an antioxidant, liquefaction of the gel or solid electrolyte can be more effectively suppressed. As antioxidant, a phenol type, phosphorus type, sulfur type etc. are mentioned, for example, These can also be used individually or in combination of 2 or more types, respectively.

  Examples of phenolic antioxidants include 2,6-di-t-butylphenol, 2,6-di-t-butyl-4-methylphenol, 2-t-butyl-4-methoxyphenol, 2,4- Dimethyl-6-t-butylphenol, 2,6-di-t-butyl-p-cresol, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butyl-4-hydroxy Methylphenol, 2,6-di-t-butyl-4- (N, N′-dimethylaminomethyl) phenol, pentaerythritol tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate , N-octadecyl-β- (4′-hydroxy 3 ′, 5′-di-t-butylphenyl) propionate, 2,4-bis (n-octylthio) -6- (4-hydro Cis-3 ', 5'-di-t-butylanilino) -1,3,5-triazine, styrenated phenol, styrenated cresol, vitamin E, 2-t-butyl-6- (3'-t-butyl- 5′-methyl-2′-hydroxybenzyl) -4-methylphenyl acrylate, 2,2′-methylenebis (4-methyl-6-tert-butylphenol), 2,2′-methylenebis (4-methyl-6-t) -Butylphenol), 2,2′-methylenebis (4-methyl-6-cyclohexylphenol), 2,2′-dihydroxy-3,3′-di (α-methylcyclohexyl) -5,5′-dimethyldiphenylmethane, 2, 2,2′-ethylidene-bis (2,4-di-tert-butylphenol), 2,2′-butylidene-bis (4-methyl-6-tert-butylphenol), 4 , 4′-methylenebis (2,6′-di-tert-butylphenol), 4,4′-butylidenebis (3-methyl-6-tert-butylphenol), 1,6-bis [2- (3,5-diphenol) -T-butyl-hydroxyphenyl) propionate] hexane, triethyleneglycol-bis-3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionate, N, N'-bis [3- (3 5-di-t-butyl-4-hydroxyphenyl) propionitrile] hydrazine, N, N′-hexamethylenebis- (3,5-di-t-butyl-4-hydroxyhydrocinnamide, 2,2 ′ -Thiobis (4-methyl-6-tert-butylphenol), 4,4'-thiobis (3-methyl-6-tert-butylphenol), 2,2-thiodiethylenebis- [3 (3,5 -Di-t-butyl-4-hydroxyphenyl) propionate] and the like.

  Phosphorus antioxidants include tris (nonylphenyl) phosphite, bis [2,4-bis (1,1-dimethylethyl) -6-methylphenyl] ethyl ester phosphorous acid, triphenyl phosphite, diphenyldecyl Examples thereof include phosphite and dicresyl phosphite.

  Examples of the sulfur-based antioxidant include dilauryl 3,3'-thiodipropionate, distearyl thiodipropionate, and the like.

  The blending amounts of these light stabilizer and antioxidant are preferably 50 to 20000 ppm for the light stabilizer and 50 to 20000 ppm for the antioxidant as a ratio to the gelling agent or solidifying agent. Moreover, it is preferable to mix | blend so that the direction of a light stabilizer may increase between a light stabilizer and antioxidant.

  These light stabilizers and antioxidants are preferably contained in the gelling agent or the fixing agent itself. As a result, deterioration of the gelling agent and solidifying agent is prevented, the storage stability is excellent, and it is not necessary to separately add a light stabilizer or an antioxidant when preparing the electrolyte. The manufacturing process can be simplified.

  About the said semiconductor electrode, the said photoelectric converting layer can be formed by forming a porous semiconductor layer on a conductive base material, and making a pigment | dye adsorb | suck to this porous semiconductor layer.

As the conductive substrate, a substrate having a transparent conductive film is used. Examples of the substrate include a glass substrate and a plastic substrate. Among them, a glass substrate (transparent with high transparency and low surface resistance). Substrate) is particularly preferred. The transparent conductive film is not particularly limited, but for example, a transparent conductive film such as ITO (indium-tin oxide) or SnO ₂ is preferable. These electrodes can be formed by a method such as vacuum deposition, and the film thickness and the like can be appropriately selected.

  Examples of the porous semiconductor constituting the porous semiconductor layer include known semiconductors such as titanium oxide, zinc oxide, barium titanate, and strontium titanate. These porous semiconductors are a mixture of two or more types. Can also be used. Among these, titanium oxide is particularly preferable in terms of conversion efficiency, stability, and safety. Examples of such titanium oxide include anatase-type titanium oxide, rutile-type titanium oxide, amorphous titanium oxide, various titanium oxides such as metatitanic acid and orthotitanic acid, and titanium-containing titanium oxide complexes. One or more types can be used as appropriate, and anatase-type titanium oxide is particularly preferable.

  The porous semiconductor may be in various forms such as particles and films, but is preferably a film-like porous semiconductor formed on a conductive substrate. As a method for forming such a film-like porous semiconductor on a conductive substrate, various known methods can be used.

  Specifically, (1) a method of applying a suspension containing semiconductor particles on a conductive substrate, drying and firing, and (2) a CVD method using a desired source gas on the conductive substrate. Or a method of forming a semiconductor film by MOCVD method, etc., (3) a method of forming a semiconductor film by PVD method, vapor deposition method, sputtering method or sol-gel method using raw material solids, and (4) electrochemical For example, a method of forming by a redox reaction.

The film thickness of the porous semiconductor film is desirably about 5 to 25 μm. In addition, in order to improve the conversion efficiency, it is necessary to adsorb more dye, which will be described later, to the film-like porous semiconductor. For this reason, it is desirable that the film-like porous semiconductor has a large specific surface area, specifically about 10 to 200 m ² / g.

  As the above-mentioned particulate semiconductor, single or compound semiconductor particles having an appropriate average particle diameter among commercially available ones, for example, an average particle diameter of about 1 nm to 500 nm can be used. Examples of the solvent used for suspending the semiconductor particles include glyme solvents such as ethylene glycol monomethyl ether, alcohols such as isopropyl alcohol, mixed solvents such as isopropyl alcohol / toluene, water, and the like. It is done.

  The above-described porous semiconductor is dried and fired by appropriately adjusting the temperature, time, atmosphere, and the like according to the type of conductive base material and semiconductor particles used. In a general example, it is performed for about 10 seconds to 12 hours in a temperature range of about 50 to 800 ° C. in the air or in an inert gas atmosphere. This drying and baking may be performed only once at a single temperature, or may be performed twice or more by changing the temperature.

  Examples of a method for adsorbing a dye functioning as a photosensitizer on the porous semiconductor layer include a method of immersing a porous semiconductor layer formed on a conductive substrate in a solution in which the dye is dissolved.

  Dyes that can be used here have absorption in various visible light regions and infrared light regions, and in order to adsorb firmly to the semiconductor layer, carboxyl groups, alkoxy groups, hydroxyl groups in the dye molecules. Those having an interlock group such as a group, a hydroxyalkyl group, a sulfonic acid group, an ester group, a mercapto group, and a phosphonyl group are preferred. The interlock group provides an electrical bond that facilitates electron transfer between the excited dye and the semiconductor conductor. Examples of the dye containing an interlock group include ruthenium bipyridine dyes, azo dyes, quinone dyes, quinone imine dyes, quinacridone dyes, squarylium dyes, cyanine dyes, merocyanine dyes, and triphenylmethane dyes. And dyes, xanthene dyes, porphyrin dyes, phthalocyanine dyes, berylene dyes, indigo dyes, naphthalocyanine dyes, and the like.

Examples of the solvent used for dissolving the dye include alcohols such as ethanol, ketones such as acetone, ethers such as diethyl ether and tetrahydrofuran, nitrogen compounds such as acetonitrile, halogenated aliphatic hydrocarbons such as chloroform, Examples thereof include aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, and esters such as ethyl acetate. The concentration of the dye in the solution can be appropriately adjusted depending on the kind of the dye and the solvent to be used. In order to improve the adsorption function, it is preferable that the concentration is somewhat high. For example, a concentration of 5 × 10 ⁻⁵ mol / L or more is preferable.

  The temperature and pressure of the solution and atmosphere when the semiconductor is immersed in the solution in which the dye is dissolved are not particularly limited, and examples include room temperature and atmospheric pressure, and the immersion time is the dye used. It is preferable to adjust appropriately depending on the type of solvent, the concentration of the solution, and the like. In order to effectively perform the adsorption, the immersion may be performed under heating.

  As the conductive substrate constituting the counter electrode, the same conductive substrate as that constituting the semiconductor electrode described above can be used. However, when the semiconductor electrode is transparent, the conductive base material constituting the counter electrode does not need to be a transparent base material. The counter electrode normally carries a noble metal such as platinum on the surface facing the semiconductor electrode in order to reduce the concentration overvoltage of the redox reaction. As a method for supporting platinum, various known methods such as a sputtering method, a spray method, and a dip method can be employed.

  FIG. 1 is a schematic cross-sectional view showing the basic structure of a dye-sensitized solar cell according to an embodiment of the present invention. As shown in the figure, the dye-sensitized solar cell includes a transparent substrate (1) having light transmittance, a transparent conductive film (2) having light transmittance formed on the surface of the transparent substrate (1), and A semiconductor electrode (8) composed of a photoelectric conversion layer (3), which is a porous semiconductor layer adsorbing a dye formed on the transparent conductive film (2), and provided at a position facing the semiconductor electrode (8). The counter electrode (9) and the electrolyte layer (4) held between the semiconductor electrode (8) and the counter electrode (9) are provided. The counter electrode (9) is composed of a transparent substrate or a support substrate (7) on which a conductive film (6) is formed, and a platinum catalyst layer (5) is formed on the surface of the conductive film (6). In this embodiment, the electrolyte layer (4) is made of an alkylene oxide gel or solid electrolyte, and a light stabilizer and preferably an antioxidant are added to the electrolyte.

  In the solar cell having such a structure, when sunlight is irradiated from the transparent substrate (1) side, the sunlight is transmitted through the transparent substrate (1) and the transparent conductive film (2), and the photoelectric conversion layer (3). The dye adsorbed on the substrate is irradiated, and the dye absorbs light and is excited. Electrons generated by this excitation move from the photoelectric conversion layer (3) to the transparent conductive film (2). The electrons that have moved to the transparent conductive film (2) move to the counter electrode (9) through the external circuit, and return from the counter electrode (9) to the dye through the charge transport layer (4). In this way, current flows and a solar cell can be configured.

  Hereinafter, the present invention will be specifically described by way of examples, but the scope of the present invention is not limited thereto.

Example 1
A dye-sensitized solar cell having the laminated structure shown in FIG. 1 was produced as follows.

A transparent conductive film (2) made of SnO ₂ was formed on a transparent substrate (1) made of glass by vacuum deposition, and a photoelectric conversion layer (3) made of a titanium oxide film was formed on the transparent conductive film (2). . The titanium oxide film uses a commercially available titanium oxide suspension (product name: Ti-Nanoxide D-SP, manufactured by Solaronix). The area was printed on the transparent conductive film (2) side and baked in the air at 450 ° C. for 30 minutes, whereby a titanium oxide film having a thickness of about 14 μm was obtained.

Next, ruthenium dye (manufactured by Kojima Chemical Co., Ltd., trade name: ruthenium complex) was dissolved in absolute ethanol at a concentration of 4 × 10 ⁻⁴ mol / liter to prepare an adsorption dye solution. This adsorption dye solution and the transparent substrate (1) provided with the photoelectric conversion layer (3) and the transparent conductive film (2) obtained above are put in a container and allowed to stand for 12 hours to adsorb the dye. It was. Then, it was washed several times with absolute ethanol and allowed to air dry.

  Next, an electrolytic solution to be retained in the gel was prepared. Using methoxypropionitrile as a solvent, electrolysis of 0.5 mol / liter lithium iodide, 0.05 mol / liter iodine and 0.5 mol / liter 4-t-butylpyridine dissolved Liquid. An electrolyte solution was prepared by adding 5% by weight of a gelling agent and a stabilizer shown in Table 1 to this electrolytic solution.

  Then, the photoelectric conversion layer (3) on the transparent substrate (1) provided with the transparent conductive film (2) is evacuated with a rotary pump for about 10 minutes, and the electrolyte solution is dropped on the photoelectric conversion layer so that it is sufficiently impregnated. It was. A counter electrode (9) provided with a platinum catalyst layer (5) was installed and fixed with a jig. Then, the solar cell which comprised the gel-like electrolyte layer (7) was created by heating at 80 degreeC for 60 minute (s). After the battery was created, sealing was performed to avoid contact with the outside with an epoxy resin.

  In addition, about the gelatinizer 1, it replaced with the above and produced the gel electrolyte as follows. Namely, a solvent solution containing 95 parts by weight of the solvent methoxypropionitrile, 5 parts by weight of the gelling agent 1 and 20000 ppm of AIBN as an initiator was prepared, and the same method as in the case of the other gelling agents described above After heat-curing with the above, the stabilizer is obtained by performing a liquid exchange in a solution of an electrolytic solution having a final composition containing lithium iodide 0.5 mol / liter, iodine 0.05 mol / liter, and a stabilizer. The containing gel electrolyte was formed. The liquid exchange conditions were 50 ° C. × 4 hours.

  Details of the gelling agent and stabilizer in Table 1 are as follows.

Gelling agent 1: a trifunctional alkylene oxide acrylate macromonomer having a molecular weight of about 8000, and a heat-curable polymer cured product precursor (trade name “ELEXEL TA-140” manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) .

Gelling agent 2: 92 g of glycerin as a starting material and 30 g of potassium hydroxide as a catalyst are charged in a reaction vessel, and 5950 g of ethylene oxide and 3180 g of propylene oxide are further charged and reacted at 130 ° C. for 10 hours, followed by neutralization. A dehydration treatment was performed to obtain an ethylene oxide-propylene oxide copolymer having a molecular weight of 8,000. To 100 g of the obtained compound, 6.6 g of tolylene diisocyanate and 0.05 g of dibutyltin dilaurate as a catalyst were added and reacted at 80 ° C. for 3 hours to obtain a compound having a molecular weight of 8520. This is referred to as Compound A (an alkylene oxide having an isocyanate functional group at the terminal). Compound B is diethyltoluenediamine, and these compounds A and B are mixed in an equal functional group concentration (number of moles of NCO functional group of compound A = number of moles of functional group of amine of compound B).

Gelling agent 3: Compound B is polyetheramine (trade name Jeffamine JD-400, manufactured by HUNTSMAN), and this has the same functional group concentration as Compound A (number of moles of NCO functional group of Compound A = B (Mole functional group of amine).

Gelling agent 4: 2 g of tolylene diisocyanate, 10 g of silicone (trade name “modified silicone oil FM-4411” manufactured by Chisso Corporation), and 0.01 g of triethylenediamine as a catalyst.

Gelling agent 5: Polyester polyol (trade name “Phantol PL-2010” manufactured by Toho Rika Co., Ltd.) 53.4 g and 34.8 g of tolylene diisocyanate are mixed in a reaction vessel, and dibutyltin dilaurate 0 is used as a catalyst. .05 g was added and reacted at 80 ° C. A mixture of 2 g of the obtained compound, 10 g of carboxyl group-modified polysiloxane (trade name “X-22-162C” manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.01 g of stannous octoate as a catalyst.

Light stabilizer a: hindered amine light stabilizer, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (trade name “LA-77” manufactured by Asahi Denka Co., Ltd.).

Light stabilizer b: hindered amine light stabilizer, bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (trade name “Sanol LS765” manufactured by Sankyo Corporation).

Light stabilizer c: UV absorber, 2- (2H-benzotriazol-2-yl) -p-cresol (trade name “TINUVIN P” manufactured by Ciba Specialty Chemicals Co., Ltd.).

-Light stabilizer d: UV absorber, 2- [5-chloro (2H) -benzotriazol-2-yl] -4-methyl-6- (tert-butyl) phenol (manufactured by Ciba Specialty Chemicals Co., Ltd.) Product name “TINUVIN 326”).

Antioxidant e: 2,6-di-tert-butyl-4-methylphenol (trade name “BHT” manufactured by Sumitomo Chemical Co., Ltd.).

Antioxidant f: pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (trade name “Irganox 1010” manufactured by Ciba Specialty Chemicals).

Antioxidant g: Octadecyl-3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate (trade name “Irganox 1076” manufactured by Ciba Specialty Chemicals).

(Stability evaluation of solar cell characteristics)
The produced solar cell is a solar simulator XES-502S (purchased from Kansai Scientific Machinery Co., Ltd.) of a xenon lamp equipped with an AM filter, and after adjusting the spectrum of AM1.5G, under irradiation conditions of 100 mW / cm ² , The load characteristic (IV characteristic) by a potentiostat was evaluated. The evaluation values of the solar cell are the open circuit voltage Voc (V), the short circuit current density Jsc (mA / cm ² ), the form factor FF (−), and the conversion efficiency η (%). Was evaluated based on the conversion efficiency.

The measurement is performed by measuring the initial conversion efficiency immediately after cell preparation and the conversion efficiency after exposure to an irradiation time of 100 hours (environmental temperature 63 ± 3 ° C.) using an ultraviolet long life carbon arc fade meter (FAL-5H type). The solar cell performance retention rate (after 100 hours / initial value) before and after the light irradiation was also calculated. In addition, the solar cell state at the time of ultraviolet irradiation was made into the open state. The results are shown in Table 1.

  As shown in Table 1, it can be seen that the addition of the light stabilizer significantly improves the retention of cell performance by light irradiation without lowering the initial solar cell performance. In particular, remarkable retention was shown under the conditions where a light stabilizer and an antioxidant were used in combination and the blending amount of both was light stabilizer> antioxidant. In Examples 7 and 8, it can be seen that the initial performance retention is approximately 100%. On the other hand, in Comparative Examples 4 to 7 in which only the antioxidant was added as the stabilizer, the performance retention was lower than that in the case of using the light stabilizer, which was insufficient. In Comparative Examples 9 and 11, which are not alkylene oxide-based gel electrolytes, the addition effect was not recognized at all, although the light stabilizer and the antioxidant were used in combination.

(Stability evaluation of independent film of crosslinked polymer)
The stability of the polymer used for the gel electrolyte was evaluated by the following method.

  40 g of each gelling agent containing the stabilizer shown in Table 1 is weighed on a plate, vacuumed at 80 ° C to remove bubbles in the polymerizing agent solution, and then heated at 100 ° C for 1.5 hours. By doing this, a film made of a crosslinked polymer was produced.

  About each produced film, the light resistance test was done with the ultraviolet-ray long life carbon arc fade meter (FAL-5H type). The light irradiation time was 100 hours, and the environmental temperature was controlled at 63 ± 3 ° C.

  Tensile strength was measured as mechanical properties before and after light irradiation to evaluate the degree of polymer degradation. Tensile strength was measured using an autograph “INSTRON 5581” (manufactured by Instron Corporation), test piece shape: dumbbell piece (thickness 2 mm), chuck width: 2 cm, tensile speed: 300 mm / min, test temperature: 25 ° C. It carried out in.

In addition, the change of the film by visual observation (the presence or absence of liquefaction) and the discoloration measurement of the film by “X-RITE 310” manufactured by SDC Co., Ltd. were performed. Note that “impossible to measure” in the result of the hue measurement means that the discoloration color was too large to be measured. Further, the visual judgment is: ○: no change, Δ: increased tackiness, x: liquefaction. The results are shown in Table 2.

  As shown in Table 2, it can be seen that physical property deterioration, hue deterioration and liquefaction of the gel electrolyte alone are suppressed by the addition of the light stabilizer. In particular, a remarkable retention was exhibited under conditions in which a light stabilizer and an antioxidant were used in combination and the blending amount of both was a light stabilizer> an antioxidant. In Examples 7 and 8, no liquefaction phenomenon was observed in appearance. On the other hand, in Comparative Examples 4 to 7 in which only the antioxidant was added as a stabilizer, physical property deterioration and hue deterioration were large. In Comparative Examples 9 and 11, which are not alkylene oxide-based gel electrolytes, the addition effect was not recognized at all, although the light stabilizer and the antioxidant were used in combination.

  The photoelectric conversion element according to the present invention is suitably used as a dye-sensitized solar cell, and can be used not only as a solar cell but also as an optical sensor.

1 is a schematic cross-sectional view showing a basic structure of a dye-sensitized solar cell according to an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent base material 2 ... Transparent conductive film 3 ... Photoelectric conversion layer 4 ... Electrolyte layer 5 ... Platinum catalyst layer 6 ... Transparent conductive film 7 ... Transparent base material or support base material 8 ... Semiconductor electrode 9 ... Counter electrode

Claims (3)

  A semiconductor electrode; a counter electrode; and an electrolyte layer held between the two electrodes, wherein the electrolyte layer is made of a gel or solid electrolyte gelled or solidified with a compound having a polyoxyalkylene chain. Contains a light stabilizer. The photoelectric conversion element characterized by the above-mentioned.   The photoelectric conversion element according to claim 1, wherein the electrolyte further contains an antioxidant. 3. The photoelectric conversion element according to claim 2, wherein the light stabilizer is a hindered amine light stabilizer, and the antioxidant is a phenolic antioxidant.

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