JP2007128750A - Dye-sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a dye-sensitized solar cell preventing separation of an electrolyte layer and a counter electrode interface due to expansion and contraction resulting from temperature changes and superior in photoelectric transfer efficiency and high temperature durability. <P>SOLUTION: A pseudo-solid type or a solid type dye-sensitized solar cell 10 has a counter electrode 9 arranged opposed to a semiconductor electrode through a gelatinous or solid electrolyte layer 5. A separation preventative layer 6 is provided at a jointing interface between the counter electrode 9 and the electrolyte layer 5. As a separation preventative layer 6, it is desirable that it consists of a porous conductive polymer composed of a polymer of aniline derivative. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dye-sensitized solar cell, and more particularly to a dye-sensitized solar cell using a gel electrolyte and a solid electrolyte.

  In recent years, various solar cells have been proposed as photoelectric conversion elements that convert light energy into electrical energy. Among them, dye-sensitized solar cells announced in 1991 by Gretzel et al. At the University of Lausanne in Switzerland in “Nature” 1991, 353, p737-740 etc. are relatively simple in that the materials used are inexpensive. Practical use is expected from the advantages such as being able to be manufactured by the process.

  A dye-sensitized solar cell generally includes a semiconductor electrode having a photoelectric conversion layer made of a semiconductor having a dye adsorbed on a conductive substrate, and a catalyst layer provided on the conductive substrate provided facing the semiconductor electrode. And an electrolyte layer (charge transport layer) held between the semiconductor electrode and the counter electrode.

  In general, the electrolyte of a dye-sensitized solar cell uses an iodine-based redox dissolved in a solvent. However, since it is a liquid, there is a problem in durability deterioration due to leakage, volatilization, etc. of the electrolyte. . On the other hand, it has been proposed that the electrolyte is formed of a gel or solid electrolyte (see, for example, Patent Documents 1 to 3).

  However, in the case of such a conventional dye-sensitized solar cell using a gel-like or solid electrolyte, the electrolyte layer expands and contracts due to repeated heating and cooling, etc. Due to the change in volume, the counter electrode and the electrolyte layer are peeled off, resulting in a problem that the high temperature durability of the device is lowered.

Patent Document 4 discloses a method for manufacturing a photoelectric conversion element, which includes a step of using a conductive resin such as carbon paste or Pt as a counter electrode, and further stacking and sequentially assembling a working electrode layer, a gel electrolyte layer, and a counter electrode layer. Is disclosed. It is described that according to this method, it is possible to prevent a decrease in the adhesion between the counter electrode surface and the electrolyte due to a change in volume or shape of the electrolyte due to gelation.
JP 2002-289271 A JP 2002-289272 A JP 2002-289273 A JP 2003-157914 A

  However, in the solar cell using the conductive resin described in Patent Document 4 as the counter electrode, although the element assembly, that is, the interface peeling between the counter electrode and the electrolyte layer due to gelation can be prevented, the element in actual use There is no description regarding interfacial delamination associated with temperature changes. In particular, in the actual use of solar cells, for example, in the case of amorphous silicon solar cells, thermal durability of 85 ± 2 ° C. × 1000 ± 12 hours is required in the JIS standard (JIS C 8938), and 80 ° C. × 1000 hours in the EU standard. ing. Therefore, even in the case of a dye-sensitized solar cell, heat resistance up to at least 80 ° C. is required. This is only a durability evaluation. Therefore, this patent document 4 does not improve the high-temperature durability of the quasi-solid solar cell element, and a dye-sensitized solar cell having high durability under a high-temperature condition is required.

  In view of the above circumstances, an object of the present invention is to provide a dye-sensitized solar cell that prevents peeling between the electrolyte layer and the counter electrode interface due to a temperature change and is excellent in photoelectric conversion efficiency and high-temperature durability.

  As a result of intensive studies to solve the above problems, the present inventors have provided a peeling prevention layer between the counter electrode and the electrolyte layer on the counter electrode in the dye-sensitized solar cell having a gel electrolyte or a solid electrolyte. The inventors have found that interfacial delamination and deterioration of durability due to temperature changes of the element are prevented while maintaining high element performance, and the present invention has been completed.

  The dye-sensitized solar cell of the present invention includes a light-transmitting semiconductor electrode containing a dye having a photosensitizing action, a gel-like or solid electrolyte layer containing a chemical species that becomes a redox pair, and the electrolyte layer. In a quasi-solid type or solid type dye-sensitized solar cell having a counter electrode disposed opposite to the semiconductor electrode, a separation preventing layer is provided at the bonding interface between the counter electrode and the electrolyte layer.

  In the dye-sensitized solar cell according to the present invention, a porous conductive polymer can be suitably used as the peeling prevention layer.

In this case, the specific surface area of the porous conductive polymer is preferably 5 m ² / g or more.

  In the dye-sensitized solar cell according to the present invention, it is preferable that the peeling prevention layer is a porous conductive polymer composed of at least one polymer selected from the group consisting of aniline and aniline derivatives.

  In the dye-sensitized solar cell according to the present invention, there is also provided a porous conductive polymer composed of a copolymer having at least one monomer component selected from the group consisting of aniline and aniline derivatives in the anti-peeling layer. It can be preferably used.

  In the quasi-solid type solar cell according to the present invention, the substrate on which the organic conductive polymer layer is formed is preferably composed of a substrate with a large surface irregularity having an actual surface area / projected area ratio of 10 or more. .

  By providing the anti-separation layer that also serves as the catalyst layer of the present invention in a quasi-solid type or solid type dye-sensitized solar cell, while having excellent photoelectric conversion efficiency, the high temperature durability of the device can be improved without degrading its performance. Can be improved.

  The reason why the high temperature durability of the element can be improved by the peeling preventing layer of the present invention is as follows.

  The above anti-peeling layer is composed of a porous conductive polymer, and when this is used for a quasi-solid or solid solar cell element, the electrolyte layer may penetrate into the porous anti-peeling layer. As a result, delamination between layers can be suppressed by a physical anchor effect. In addition, since the contact interface between the peeling prevention layer having conductivity and the electrolyte layer increases, even if peeling occurs, the influence can be reduced.

  Furthermore, the influence of interfacial peeling can be further reduced by using a material having a catalytic ability for the reduction reaction of the redox couple, particularly a conductive polymer, as the material for forming the peeling prevention layer. With the above action, the high temperature durability can be improved without deteriorating the element performance.

  In general, when the electrolytic solution is gelled or solidified, depending on the gelling agent and solid electrolyte used, the ionic conductivity is lower than when using the electrolytic solution. As a result, the concentration of redox couple in the electrolyte is reduced. Measures such as increasing were taken. However, when a porous conductive polymer layer is used as the peeling prevention layer, the contact area between the peeling prevention layer having a catalytic ability and the electrolyte layer is increased, so that the influence of the reduction in the oxidation-reduction pair movement speed is reduced. be able to. Therefore, it is not necessary to use a high-concentration redox pair, and it is possible to prevent deterioration of the photoelectric conversion performance of the device due to the high concentration of redox, such as reverse electron transfer from the semiconductor electrode to the electrolyte and the influence of light absorption.

  The best mode for carrying out the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view showing an example of the dye-sensitized solar cell 10 of the present invention. In FIG. 1, reference numeral 1 is a transparent substrate, reference numeral 2 is a transparent conductive film, reference numeral 3 is a porous metal oxide semiconductor layer, reference numeral 4 is a sensitizing dye, reference numeral 5 is an electrolyte layer, reference numeral 6 is an anti-peeling layer, reference numeral 7. Denotes an electrode base material carrying the reference numeral 6, reference numeral 8 denotes an electrode substrate, and reference numeral 9 denotes a counter electrode.

  A porous metal oxide semiconductor layer 3 is formed on the surface of the electrode substrate 8 composed of the transparent substrate 1 and the transparent conductive film 2 formed thereon. Further, on the surface of the porous metal oxide semiconductor layer 3, Sensitizing dye 4 is adsorbed. And the counter electrode 9 in which the peeling prevention layer 6 of this invention was formed is opposed and installed on the surface of the electrode base material 7 through the electrolyte layer 5, and the dye-sensitized solar cell 10 is formed.

  Hereinafter, a suitable form is demonstrated about each constituent material of the dye-sensitized solar cell (henceforth abbreviated as a solar cell) 10 of this invention.

[Transparent substrate]
As the transparent substrate 1 constituting the electrode substrate 8, one that transmits visible light can be used, and transparent glass can be suitably used. Moreover, what processed the glass surface and scattered incident light can also be used. Moreover, not only glass but a plastic plate, a plastic film, etc. can be used if it transmits light.

  The thickness of the transparent substrate 1 is not particularly limited because it varies depending on the shape and use conditions of the solar cell. For example, when glass or plastic is used, the thickness is about 1 mm to 1 cm in consideration of durability during actual use. Preferably, flexibility is required, and when a plastic film or the like is used, about 1 μm to 1 mm is preferable.

[Transparent conductive film]
As the transparent conductive film 2, a material that transmits visible light and has conductivity can be used. An example of such a material is a metal oxide. Although not particularly limited, for example, tin oxide doped with fluorine (hereinafter abbreviated as “FTO”) or indium oxide, a mixture of tin oxide and indium oxide (hereinafter abbreviated as “ITO”) antimony. Doped tin oxide, zinc oxide and the like can be suitably used.

  In addition, an opaque conductive material can be used as long as visible light is transmitted through a treatment such as dispersion. Such materials include carbon materials and metals. Although it does not specifically limit as a carbon material, For example, graphite (graphite), carbon black, glassy carbon, a carbon nanotube, fullerene, etc. are mentioned. Further, the metal is not particularly limited, and examples thereof include platinum, gold, silver, ruthenium, copper, aluminum, nickel, cobalt, chromium, iron, molybdenum, titanium, tantalum, and alloys thereof.

  Therefore, the transparent conductive film 2 can be formed by providing a conductive material composed of at least one of the above-described conductive materials on the surface of the transparent substrate 1. Alternatively, it is possible to incorporate the conductive material into the material constituting the transparent substrate 1 and integrate the transparent substrate 1 and the transparent conductive film 2 to form the electrode substrate 8.

  As a method for forming the transparent conductive film 2 on the transparent substrate 1, when a metal oxide is used, there are a liquid layer method such as a sol-gel method, a vapor phase method such as sputtering or CVD, and a coating of a dispersion paste. Moreover, when using an opaque electroconductive material, the method of fixing a powder etc. with a transparent binder etc. is mentioned.

  In order to integrate the transparent substrate 1 and the transparent conductive film 2, the conductive film material is mixed as a conductive filler when the transparent substrate 1 is molded.

  The thickness of the transparent conductive film 2 is not particularly limited because the conductivity varies depending on the material to be used, but is generally 0.01 to 5 μm, preferably 0.1 to 1 μm in commonly used FTO-coated glass. It is. Further, the required conductivity varies depending on the area of the electrode to be used, and a wider electrode is required to have a lower resistance, but is generally 100Ω / □ or less, preferably 10Ω / □ or less, more preferably 5Ω. / □ or less.

  The thickness of the electrode substrate 8 composed of the transparent substrate 1 and the transparent conductive film 2 or the electrode substrate 8 in which the transparent substrate 1 and the transparent conductive film 2 are integrated depends on the shape and use conditions of the solar cell as described above. Since it differs, it is not particularly limited, but is generally about 1 μm to 1 cm.

[Porous metal oxide semiconductor]
Examples of the porous metal oxide semiconductor 3 include, but are not limited to, titanium oxide, zinc oxide, tin oxide, and the like. In particular, titanium dioxide and further anatase type titanium dioxide are suitable. Further, it is desirable that the metal oxide has few grain boundaries in order to reduce the electric resistance value. Further, in order to adsorb more sensitizing dye 4, the semiconductor layer preferably has a large specific surface area, specifically 10 to 200 m ² / g. Further, in order to increase the light absorption amount of the sensitizing dye 4, it is desirable to scatter light by giving a width to the particle diameter of the oxide used.

  Such a porous metal oxide semiconductor 3 is not particularly limited and can be provided on the transparent conductive film 2 by a known method. For example, there are a sol-gel method, dispersion paste application, electrodeposition and electrodeposition.

  The thickness of the semiconductor layer 3 is not particularly limited because the optimum value varies depending on the oxide used, but is 0.1 to 50 μm, preferably 5 to 30 μm.

[Sensitizing dye]
The sensitizing dye layer 4 is not particularly limited as long as it can be excited by sunlight and can inject electrons into the metal oxide semiconductor layer 3, and dyes generally used in dye-sensitized solar cells can be used. However, in order to improve the conversion efficiency, it is desirable that the absorption spectrum overlaps with the sunlight spectrum in a wide wavelength region and the light resistance is high. Although not particularly limited, a ruthenium complex, particularly a ruthenium polypyridine complex is desirable, and a ruthenium complex represented by Ru (L) 2 (X) 2 is more desirable. Here, L is 4,4′-dicarboxy-2,2′-bipyridine, or a quaternary ammonium salt thereof, and a polypyridine ligand into which a carboxyl group is introduced, and X is SCN, Cl, CN It is. Examples thereof include bis (4,4′-dicarboxy-2,2′-bipyridine) diisothiocyanate ruthenium complex.

  Examples of other dyes include metal complex dyes other than ruthenium, such as iron complexes and copper complexes. Further examples include organic dyes such as cyan dyes, porphyrin dyes, polyene dyes, coumarin dyes, cyanine dyes, squaric acid dyes, styryl dyes, and eosin dyes. These dyes preferably have a bonding group with the metal oxide semiconductor layer in order to improve the efficiency of electron injection into the metal oxide semiconductor layer 3. The linking group is not particularly limited, but a carboxyl group, a sulfonic acid group, a hydroxyl group and the like are desirable.

  The method for adsorbing the sensitizing dye 4 to the porous metal oxide semiconductor 3 is not particularly limited. For example, the porous metal is dissolved in a solution in which the dye is dissolved at room temperature and atmospheric pressure. A method of immersing the electrode substrate 8 on which the oxide semiconductor 3 is formed may be mentioned. The immersion time is preferably adjusted as appropriate so that a monomolecular film of the dye is uniformly formed on the semiconductor layer according to the type of semiconductor, dye, solvent, and dye concentration used. In addition, what is necessary is just to perform the immersion under a heating in order to perform adsorption | suction effectively.

Examples of the solvent used for dissolving the sensitizing dye 4 include alcohols such as ethanol, nitrogen compounds such as acetonitrile, ketones such as acetone, ethers such as diethyl ether, and halogenated aliphatic hydrocarbons such as chloroform. And 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 sufficiently adsorb on the semiconductor surface, it is desirable that the concentration is somewhat high. For example, a concentration of 5 × 10 ⁻⁵ mol / L or more is desirable.

[Electrolyte layer]
In the present invention, the electrolyte layer 5 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 network structure formed by a crosslinking reaction of a gelling agent holds a redox couple and a solvent capable of dissolving the redox couple. And the electrolyte solution containing the solvent which can melt | dissolve this is gelatinized using the gelatinizer containing the said compound. Further, after gelling a solvent solution containing a solvent and a gelling agent, the same gel electrolyte can be obtained by liquid exchange in an electrolytic solution having a final composition containing a redox pair.

  The solid electrolyte is obtained by crosslinking reaction of a solidification agent containing the above compound in which a redox couple is dissolved. The solid electrolyte is formed into a network structure formed by crosslinking reaction of the solidification agent. A solid polymer electrolyte in which the oxidation-reduction pair is held.

  The 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, and is 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) It includes a compound A having at least one isocyanate group and a compound B reactive with at least one isocyanate group, and at least one of compound A and compound B has a polyoxyalkylene chain. (See Patent Documents 1 to 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 (1) is, for example, glycerol or trimethylolpropane in the case of trifunctional, diglycerin or pentaerythritol in the case of tetrafunctional, etc. As starting materials, alkylene oxides such as ethylene oxide and propylene oxide are added thereto, and an unsaturated organic acid such as acrylic acid and methacrylic acid is esterified, or acrylic acid chloride, methacrylic acid chloride, etc. It is a compound obtained by carrying out dehydrochlorination reaction of acid chlorides.

  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 subjecting polyoxyalkylene and these isocyanates to a load reaction 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 couple constituting the electrolyte layer 5 is not particularly limited as long as it can be generally used in a battery or a solar battery, for example, a combination of a halogen diatomic molecule and a halide salt, Organic redox such as a combination of thiocyanate anion and bimolecular thiocyanate, polypyridylcobalt complex, hydroquinone, and the like. Of these, a combination of iodine molecules and iodide is particularly preferred. The concentration of the redox couple is usually 0.1 to 10 mol / L, more preferably 0.1 to 5 mol / L.

  The solvent used for the electrolyte is not particularly limited as long as it is a compound that can dissolve the redox couple, and can be arbitrarily selected from a non-aqueous organic solvent, a room temperature molten salt, water, a protic organic solvent, and the like. For example, as an organic solvent, nitrile compounds such as acetonitrile, methoxyacetonitrile, valeronitrile, methoxypropionitrile, lactone compounds such as γ-butyllactone and valerolactone, carbonate compounds such as ethylene carbonate and propylene carbonate, dioxane, diethyl ether, ethylene Examples include ethers such as glycol dialkyl ether, alcohols such as methanol and ethanol, dimethylformamide and imidazoles, among which acetonitrile, valeronitrile, methoxypropionitrile, propylene carbonate, and the like can be preferably used. In addition, these can be used individually or in mixture of 2 or more types, respectively.

  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, p 1168 to 1178, “Electrochemistry” 2002, 2, p 130 to 136, JP 9-507334 A, JP 8-259543 A, and the like. In the known battery or solar battery, there is no particular limitation as long as it can be generally used, but a salt having a melting point lower than room temperature (25 ° C.) or a melting point 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, the cation of the molten salt includes ammonium, imidazolium, oxazolium, thiazolium, oxadiazolium, triazolium, pyrrolidinium, pyridinium, piperidinium, pyrazolium, pyrimidinium, pyrazinium, triazinium, phosphonium, sulfonium, carbazolium, indolium and These derivatives 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 OS ₂ ⁻ , CH ₃ SO ₃ ⁻ , CH ^{_{3 SO 2 -, (CH 3}} O) 2 PO 2 -, SCN - non-fluorinated compounds such as iodine, and the like halides, such as bromine.

  The electrolyte layer 5 further includes lithium salt, imidazolium salt, quaternary ammonium salt, and the like as supporting electrolyte, bases such as t-butylpyridine and n-methylimidazole, thiocyanates such as guanidinium thiocyanate, water, and the like. Etc. can be added. The concentration of these additives is not particularly limited because the optimum concentration varies depending on the solvent, the semiconductor electrode, the dye, and the like used, but is preferably about 1 to 5 mol / L.

[Counter electrode]
The counter electrode 9 has a structure in which the peeling prevention layer 6 of the present invention is formed on the surface of the electrode substrate 7.

  Since the electrode base material 7 is used as a support and a current collector for the peeling prevention layer 6, and when a porous conductive polymer is electrochemically polymerized as the peeling prevention layer 6 on the surface of the electrode base material In addition, at least the surface portion on which the conductive polymer layer is formed must have conductivity.

  As such a material, for example, a conductive metal or metal oxide, a carbon material, a conductive polymer, or the like is preferably used. Examples of the metal include platinum, gold, silver, ruthenium, copper, aluminum, nickel, cobalt, chromium, iron, molybdenum, titanium, tantalum, and alloys thereof. Although it does not specifically limit as a carbon material, For example, graphite (graphite), carbon black, glassy carbon, a carbon nanotube, fullerene etc. are mentioned. In addition, when a metal oxide such as FTO, ITO, indium oxide, zinc oxide or antimony oxide is used, the amount of incident light to the sensitizing dye layer can be increased because it is transparent or translucent. Can do.

  Also, an insulator such as glass or plastic may be used as long as at least the surface of the electrode substrate 7 is treated. As a treatment method for maintaining conductivity in such an insulator, a method of covering a part or the whole surface of the insulating material with the above-described conductive material, for example, when using a metal, plating, electrodeposition, etc. And a gas phase method such as sputtering or vacuum deposition. When a metal oxide is used, a sol-gel method or the like can be used. Moreover, the method of mixing with an insulating material using the powder of the said electroconductive material etc. using 1 type or multiple, etc. is mentioned.

  Furthermore, in the present invention, even when an insulating material is used as the base material 7 of the counter electrode 9, a conductive polymer layer can be provided directly on the base material as a peeling prevention layer. The molecular layer alone functions as both a current collector and a peeling prevention layer.

  Further, the shape of the electrode substrate 7 is not particularly limited because it can be changed according to the shape of the solar cell, and may be a plate shape or a film shape that can be curved. Further, the electrode substrate 7 may be transparent or opaque, but can be transparent or translucent because the amount of light incident on the sensitizing dye layer can be increased and, in some cases, the design can be improved. Is desirable.

  In general, glass with an FTO film, PET with an ITO film, and a PEN film with an ITO film are used as the electrode substrate 7. However, since the conductivity differs depending on the material used, the thickness of the conductive layer is particularly limited. Not. For example, in FTO-coated glass, the thickness is 0.01 to 5 μm, preferably 0.1 to 1 μm. Further, the required conductivity varies depending on the area of the electrode to be used, and a wider electrode is required to have a lower resistance, but is generally 100Ω / □ or less, preferably 10Ω / □ or less, more preferably 5Ω. / □ or less.

  The thickness of the electrode base material 7 is not particularly limited because it varies depending on the shape and use conditions of the solar cell as described above, but is generally about 1 μm to 1 cm.

  As the electrode substrate 7 on which the porous conductive polymer layer is formed, a conductive substrate having particularly large surface irregularities can be suitably used. The degree of surface roughness is such that the actual surface area / projected area ratio is preferably 10 or more, more preferably 20 or more. The method for enlarging the surface irregularities is not particularly limited as long as it is a known method, and examples thereof include chemical treatment of FTO or ITO conductive film with aqua regia, mechanical treatment with files, and the like. Further, the surface irregularities can be increased by adjusting the formation conditions of the FTO or ITO conductive film. Furthermore, a method of coating a conductive film on a substrate having large surface irregularities such as ground glass can also be mentioned. The actual surface area / projected area ratio was calculated from the actual surface area of a substrate having a certain projected area using a stylus type three-dimensional surface roughness measuring apparatus.

[Peeling prevention layer]
The peeling prevention layer 6 of the present invention desirably has a porous shape in order to prevent peeling from the counter electrode due to a physical anchor effect with the gel or solid electrolyte layer. Furthermore, it is desirable that the peeling prevention layer has conductivity so as not to hinder the movement of electric charges in the element and to suppress the decrease in conductivity due to peeling.

  Further, as a function required for the counter electrode, there is a catalytic characteristic for a reaction for reducing an oxidant of the redox pair. Therefore, by imparting the catalytic ability together with the conductivity to the peeling prevention layer 6, it is possible to further reduce the deterioration of the element performance due to peeling. Moreover, it is desirable that it is a porous shape also from the surface of catalytic ability similarly to electroconductivity. 5 nm-10 micrometers are suitable for the thickness of the peeling prevention layer of this invention, Especially preferably, they are 50 nm-3 micrometers.

  As a material for forming such an anti-peeling layer, a conductive polymer having conductivity and the above catalytic ability can be suitably used. In particular, the monomer component is at least one selected from the group consisting of aniline or a polymer of aniline derivatives, or a polymer of aniline and aniline derivatives, which has high conductivity and catalytic ability and can be easily made porous. A polymer is desirable.

[Conductive polymer]
The use of the conductive polymer composed of the aniline derivative in the anti-peeling layer is not particularly limited as long as the polymerized polymer has conductivity, but a polymer film with a certain aniline derivative alone has conductivity. Even if it has electroconductivity by making it a copolymer with aniline or another aniline derivative, it does not matter. Two or more kinds of aniline derivatives can be used as the monomer component of the polymer used in the peeling prevention layer 6.

The monomer component used preferably has a conductivity of 10 ⁻⁹ S / cm or more as a polymerized film.

  Examples of the substituent of the aniline derivative include an electron-donating substituent such as an alkyl group, an alkoxy group, an amino group, a benzyl group, a hydroxyl group, and an amide group, or a sulfone group, a nitro group, a trifluoromethyl group, a halogen, Examples include electron-withdrawing substituents such as cyano group, and specific examples include anisidine, phenetidine, toluidine, phenylenediamine, hydroxyaniline, N-methylaniline, trifluoromethaneaniline, nitroaniline, cyanoaniline, halogenated aniline and the like. Is mentioned.

  Furthermore, a copolymer of an aniline derivative and aniline can be preferably used. When aniline and aniline derivatives are used, their ratio is not particularly limited, but it is generally appropriate to polymerize aniline and aniline derivatives in a molar ratio of 100 as one and the other as 3 or more.

  Further, it is desirable to add a dopant to the conductive polymer layer in order to improve conductivity. A dopant is not specifically limited, A well-known material can be used. For example, hexafluoroline, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron, halide anions such as perchloric acid, halogen anions such as iodine, bromine, chlorine, hexafluoroline, hexafluoroarsenic, hexafluoroantimony, tetrafluoroboron , Halide anions such as perchloric acid, alkyl group-substituted organic sulfonic acid anions such as methanesulfonic acid and dodecylsulfonic acid, cyclic sulfonic acid anions such as camphorsulfonic acid, benzenesulfonic acid, paratoluenesulfonic acid, dodecylbenzenesulfonic acid Alkyl having 1 to 3 sulfonic acid groups such as benzene monosulfonic acid, alkyl group-substituted or unsubstituted benzene mono- or disulfonic acid anion, 2-naphthalenesulfonic acid, 1,7-naphthalenedisulfonic acid, etc. Substituted or unsubstituted naphthalene sulfonate anion, anthracene sulfonic acid, anthraquinone sulfonic acid, alkyl biphenyl sulfonic acid, biphenyl disulfonic acid and other alkyl group substituted or unsubstituted biphenyl sulfonic acid ions, polystyrene sulfonic acid, sulfonated polyether, sulfonation Polymer sulfonate anions such as polyester, sulfonated polyimide, naphthalene sulfonate formalin condensate, substituted or unsubstituted aromatic sulfonate anions, boron compound anions such as bissaltylate boron and biscatecholate boron, or molybdophosphoric acid And heteropoly acid anions such as tungstophosphoric acid and tungstomolybdophosphoric acid. These may be used alone or in combination of two or more.

  In order to suppress the desorption of the dopant, it is desirable that it is an organic acid anion rather than an inorganic anion, and it is desirable that thermal decomposition or the like hardly occur.

  The amount of dopant used in the conductive polymer layer is not particularly limited because the optimum value varies depending on the type of dopant used, but is preferably 5 to 60% by mass, more preferably 10 to 45% by mass.

  Such a dopant can be used at an appropriate stage when the conductive polymer layer is formed. For example, it can coexist with a monomer of the conductive polymer.

  The conductive polymer layer is formed on the electrode substrate 7. The formation method is not particularly limited, and examples thereof include a method of forming a film from a solution in which a conductive polymer is in a molten state or dissolved.

  In addition, since it is desirable that the porous state has a larger surface area, the monomer is chemically or electrochemically oxidatively polymerized in a state where the solution containing the conductive polymer monomer and the electrode substrate 7 are in contact with each other. A method is mentioned.

  Also, there is a method in which the conductive polymer powder is formed into a paste form, an emulsion form, or a mixture form containing a polymer solution and a binder, and then formed on the electrode substrate by screen printing, spray coating, brush coating, or the like. Is possible.

  Among the methods described above, an electrolytic polymerization method or a chemical polymerization method can be suitably used as the method for forming the conductive polymer layer. The chemical polymerization method is a method in which a polymerization monomer is oxidatively polymerized using an oxidizing agent. On the other hand, the electrolytic polymerization method is a method of forming a conductive polymer film on an electrode such as a metal by performing electrolytic oxidation in a solution containing a polymerization monomer.

  The oxidizing agent used in the chemical polymerization method includes iodine, bromine, bromine iodide, chlorine dioxide, iodic acid, periodic acid, chlorous acid and other halides, antimony pentafluoride, phosphorus pentachloride, phosphorus pentafluoride. , Metal halides such as aluminum chloride, molybdenum chloride, permanganate, dichromate, chromic anhydride, ferric salt, cupric salt and other high-valent metal salts, sulfuric acid, nitric acid, trifluoromethanesulfuric acid Protonic acids such as oxygen compounds such as sulfur trioxide and nitrogen dioxide, hydrogen peroxide, ammonium persulfate, peroxo acids such as sodium perborate or salts thereof, molybdophosphoric acid, tungstophosphoric acid, tungstomolybdophosphoric acid, etc. There are heteropolyacids or salts thereof, and at least one of them can be used.

  Although the above chemical polymerization method is suitable for mass production, when the polymer is reacted with an oxidizing agent in a solution containing a conductive polymer monomer component, the resulting polymer is in the form of particles or lumps, and the desired polymer is obtained. It is difficult to develop porosity and mold into an electrode shape. Accordingly, the electrode substrate 7 is immersed in a solution containing either the conductive polymer monomer component or the oxidizing agent, or after the solution is applied to them, the electrode substrate 7 is subsequently immersed in a solution in which the other component is dissolved or It is desirable to form a conductive polymer by applying the polymer so that the polymerization proceeds on the surface of the electrode substrate.

  Further, using a separately prepared conductive polymer particle dispersion or paste, a conductive polymer film is formed on the surface of the electrode substrate 7 or the electrode substrate with the conductive film, and then subjected to the above chemical polymerization to conduct the conductivity. A method of growing polymer particles can also be performed.

  On the other hand, in the electropolymerization method, a conductive polymer having a relatively high conductivity can be obtained in the form of a film, and the synthesis method thereof is also simple and can be suitably used as a method for producing a peeling prevention layer made of a conductive polymer. . The electrolytic polymerization may be performed directly on the electrode substrate 7 or may be bonded to the electrode substrate 7 to be used after the porous conductive polymer film separately prepared by electrolytic polymerization is peeled off.

  The electrolytic polymerization solvent used in the electrolytic polymerization method is not particularly limited as long as it can dissolve an aromatic compound and is stable even in the electrolytic polymerization potential of the aromatic compound. For example, water, acetonitrile or the like nitrile system, Alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, carbonates such as propylene carbonate, tetrahydrofuran and the like can be used. These may be used alone or as a mixed solvent of two or more. Of the above, organic solvents having a certain degree of polarity, such as acetonitrile, methanol, propylene carbonate, tetrahydrofuran and the like, can be suitably used. Furthermore, when adding the said dopant, it is desirable that a dopant can also be melt | dissolved.

As the electrolytic polymerization conditions, the current collector is immersed in an electrolytic polymerization solution in which the aromatic compound is dissolved in advance, and an arbitrary voltage is applied between the counter electrode installed in the same electrolytic solution. Allow polymerization to proceed. The concentration of the aromatic compound at this time is not particularly limited because the optimum value varies depending on the type of the aromatic compound, but generally a range of 0.01 to 10 mol / L is desirable. In the case where a dopant is allowed to coexist, the concentration of the dopant is preferably in the range of 1/10 to 100 times the aromatic compound concentration. The applied current density at the time of polymerization is not particularly limited because the optimum value varies depending on the type of aromatic compound, but it is preferably in the range of 0.01 to 100 mA / cm ² .

  The thickness of the conductive polymer layer in the peeling prevention layer of the present invention is suitably 5 nm to 5 μm, particularly preferably 100 nm to 2 μm.

In addition, the conductive polymer layer in the peel preventing layer of the present invention preferably has a porous structure having a large specific surface area in order to exhibit a peel preventing effect. The specific surface area is preferably 5 m ² / g or more, more preferably 10 m ² / g or more. The upper limit of the specific surface area is not particularly limited, but is preferably 200 m ² / g or less. If the specific surface area is too small, the effect of preventing peeling cannot be obtained, and if the specific surface area is too large, the mechanical strength of the conductive polymer layer itself is lowered and peeling from the electrode substrate 7 is likely to occur, which is not preferable. The specific surface area is a value obtained by nitrogen isothermal adsorption measurement.

  After preparing each constituent material as described above, a dye-sensitized solar cell is completed by assembling the semiconductor electrode and the counter electrode so as to face each other through an electrolyte by a conventionally known method.

EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited at all by these <Example 1>
[Fabrication of semiconductor electrode]
A porous metal oxide semiconductor layer 3 was formed by the following method on a transparent conductive film 2 in which a conductive film made of SnO ₂ was formed by vacuum deposition on a transparent substrate 1 made of glass.

As the transparent substrate 1 on which the transparent conductive film 2 made of SnO ₂ is formed, FTO glass (manufactured by Nippon Sheet Glass) is used, and a commercially available titanium oxide paste (manufactured by Solaronix, trade name Ti-Nanoxide D-SP) is screened on the surface. The film was printed on the transparent conductive film 2 side by a printing method with a film thickness of about 15 μm and an area of about 5 mm × 10 mm, and baked in the air at 450 ° C. for 30 minutes. As a result, a titanium oxide film 3 having a thickness of about 15 μm was obtained.

[Adsorption of sensitizing dye]
As sensitizing dye 4, bis (4-carboxy-4′-tetrabutylammoniumcarboxy-2,2′-bipyridine) diisothiocyanate ruthenium complex (manufactured by Solaronix) generally called N719dye was used. The porous titanium oxide semiconductor electrode was immersed in an absolute ethanol solution having a pigment concentration of 0.4 mol / L and allowed to stand overnight under light shielding. Thereafter, excess pigment was washed with absolute ethanol and then air-dried to produce a semiconductor electrode of a solar cell.

[Preparation of counter electrode]
As the electrode substrate 7, FTO-coated glass (Asahi Glass, 10Ω / □) was used. The electrode substrate cleaned ultrasonically in an organic solvent is immersed in an aqueous solution containing aniline 0.1 mol / L and p-toluenesulfonic acid 1 mol / L, and is electrochemically oxidized to form a polyaniline film on the FTO glass surface. Formed. This FTO glass with a polyaniline film was washed with pure water and dried at 100 ° C. in the air to obtain a counter electrode 9 provided with a peeling prevention layer 6.

The specific surface area of this conductive polymer layer 6 was 26 m ² / g.
[Preparation of electrolyte, assembly of solar cell elements]
Next, an electrolytic solution to be held in the gel electrolyte layer 5 was prepared. A trifunctional alkylene oxide acrylate macromonomer having a molecular weight of about 8000 and 95 parts by weight of methoxypropionitrile as a solvent, and a heat-curable polymer cured product precursor (trade name “ELEXEL, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.” TA-140 ") A titanium oxide film on the transparent substrate 1 provided with the transparent conductive film 2 prepared as described above by preparing a solvent solution containing 5 parts by weight of the gelling agent 1 and 20000 ppm of AIBN as a starting material. The semiconductor electrode made of 3 and the counter electrode made of the peeling prevention layer 6 on the electrode substrate 7 were placed so as to face each other, and an electrolyte was impregnated between both electrodes by capillary action.

  Next, after heating and curing at 60 ° C. for 120 minutes, 0.5 mol / L lithium iodide, 0.05 mol / L iodine, 0.6 mol / L 1,2-dimethyl-3- A solar cell provided with the gel electrolyte layer 5 was prepared by performing liquid exchange in a solution of an electrolytic solution having a final composition containing propylimidazolium iodide and 0.5 mol / L of 4-t-butylpyridine. . The liquid exchange conditions were 50 ° C. × 4 hours. After the device was formed, sealing was carried out with an epoxy resin to avoid contact with the outside world.

<Example 2>
In the method for producing a gel electrolyte layer, methoxypropionitrile was used as a solvent, 0.5 mol / L lithium iodide, 0.05 mol / L iodine, 0.6 mol / L 1,2-dimethyl-3-propyl A solution in which imidazolium iodide and 0.5 mol / L of 4-t-butylpyridine were dissolved was used as an electrolytic solution. A solution containing 5% by weight of gelling agent 2 in this electrolytic solution was used as the electrolyte. The working electrode and the counter electrode prepared in the same manner as in Example 1 were installed so as to face each other, the electrolyte was impregnated between both electrodes by capillary action, and then heated at 60 ° C. for 120 minutes to form the gel electrolyte layer 5. The provided solar cell was produced. After forming the battery, sealing was carried out with an epoxy resin to avoid contact with the outside world.

The gelling agent 2 will be described below.
Gelling agent 2: 92 g of glycerin as a starting material and 30 g of potassium hydroxide as a catalyst were charged in a reaction vessel and reacted at 130 ° C. for 10 hours, followed by neutralization and dehydration treatment to obtain ethylene oxide having a molecular weight of 8000. A propylene oxide copolymer was obtained. 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 have a functional group concentration of 1.2: 1 (number of moles of isocyanate functional group of compound A / number of moles of functional group of amine of compound B = 1.2). Mixed one.

<Example 3>
As a gelling agent, instead of compound B shown in Example 2, polyetheramine (trade name Jeffamine JT-3000, manufactured by HUNTSMAN) (gelling agent 3) was used in the same manner as in Example 2 A solar cell was produced.

<Example 4>
As a gelling agent, polytetramethylene glycol (manufactured by Mitsubishi Kasei Kogyo Co., Ltd., trade name “PTMG2000”, 100 g of tolylene diisocyanate and 0.05 g of dibutyltin dilaurate as a catalyst was added and reacted at 80 ° C. , 6 g of the obtained compound A having a molecular weight of 2350, polyether modified polycarbonate diol as compound B (trade name “Placcel CD-221” manufactured by Daicel Chemical Industries, Ltd., and 0.005 g of triethylenediamine as a catalyst) A solar cell was produced in the same manner as in Example 2 except that the gelling agent 4) was used.

<Example 5>
As a gelling agent, 53.4 g of polyester polyol (trade name “Phantol PL-2010” manufactured by Toho Rika Co., Ltd.) and 34.8 g of tolylene diisocyanate are mixed, and 0.05 g of dibutyltin dilaurate is added as a catalyst. Reaction was performed at 80 ° C., 2 g of the obtained compound A, 10 g of a carboxyl group-modified polysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “X-22-16C”) as compound B, and stannous octoate as a catalyst A solar cell was produced in the same manner as in Example 2 except that 0.01 g mixed (gelator 5) was used.

<Example 6>
A solar battery cell was produced in the same manner as in Example 3 except that in the method for producing the counter electrode, the monomer was changed to 0.05 mol / L aniline and 0.05 mol / L anisidine.

The specific surface area of this conductive polymer layer was 17 m ² / g.
<Example 7>
In the method for producing the counter electrode, glass with an FTO coating in which surface irregularities were increased to an actual surface area / projected area ratio of about 27 using an aqua regia treatment or sandpaper (# 600) as the electrode base material 7 was used. A solar battery cell was produced in the same manner as in Example 3 except for the above.

<Example 8>
Instead of the counter electrode 9, the electrode substrate 7 is a 30-minute aqua regia treatment or sandpaper (# 600) on the FTO-coated glass whose surface irregularities are increased to an actual surface area / projected area ratio of about 27. A solar battery cell was produced in the same manner as in Example 3 except that an electrode (platinum film thickness: ~ 0.1 μm) formed by thermal decomposition of chloroplatinic acid according to a previously reported method was used.

<Comparative Examples 1-5>
In Examples 1 to 5, instead of the counter electrode 9, elements using electrodes (made by Geomatic, platinum film thickness of 0.25 μm) formed by sputtering platinum on an ITO conductive substrate were used as Comparative Examples 1 to 5, respectively. As produced.

<Comparative Example 6>
As in Example 3, except that an electrode (platinum film thickness˜0.1 μm) in which a platinum layer was formed by thermal decomposition of chloroplatinic acid according to a previously reported method was used in place of the counter electrode, on a FTO conductive substrate. A battery cell was produced.

[Solar cell durability evaluation]
Evaluation of the solar cells prepared in Examples and Comparative Examples was performed by the following method.

For performance evaluation, a xenon lamp solar simulator XES-502S (manufactured by Kansai Scientific Machinery Co., Ltd.) equipped with an AM filter was used to adjust the AM1.5G spectrum, and then a potentiostat under irradiation conditions of 100 mW / cm ^2. The load characteristics (IV characteristics) were evaluated. The evaluation value of the solar cell includes an open circuit voltage Voc (V), a short circuit current density Jsc (mA / cm ² ), a form factor FF (−), and a conversion efficiency η (%). Was evaluated based on the conversion efficiency η.

  Thermal durability evaluation was performed by measuring the initial conversion efficiency immediately after cell formation and the conversion efficiency of the element cooled to room temperature after being held in a constant temperature bath maintained at 80 ° C., and again holding in the constant temperature bath for 24 hours. This cycle was repeated a total of 10 times. Further, the solar cell performance retention rate before and after heating for a total of 240 hours was also calculated. In addition, the state of the solar cell held in the thermostat was set to an open state. The results are shown in Table 1.

  As shown in Table 1, by providing the anti-separation layer 6 composed of a porous conductive polymer, the solar cell performance is lowered as compared with the conventional quasi-solid type solar cell using the platinum counter electrode shown in the comparative example. It can be seen that the thermal durability is greatly improved. In particular, Example 7 using an anti-peeling layer on a conductive thin film with large irregularities shows the highest performance retention. It is considered that this is because the use of a conductive thin film with large irregularities prevents the interface peeling between the peeling prevention layer 6 and the electrode substrate 7 during heating. In Comparative Example 6, a platinum counter electrode produced by a thermal decomposition method is used, and since these are known to have higher surface irregularity than a platinum counter electrode produced by a sputtering method, Comparative Example 1 Although it shows high thermal durability compared to ˜5, it is still inferior compared to the examples. This is because the adhesion of platinum particles produced by a thermal decomposition method is low.

  Moreover, the performance retention rate of Example 8 is higher than that of Comparative Example 6, and even when a platinum counter electrode is used, the effect of suppressing the interfacial peeling between the electrolyte layer and the counter electrode by increasing the surface irregularities of the electrode substrate is achieved. I can confirm. However, the performance retention is inferior compared with Example 7, and it turns out that the porous conductive polymer layer which is a peeling prevention layer of this invention is more excellent in the point of delamination prevention than a platinum counter electrode.

  From these facts, it can be seen that by using the anti-peeling layer of the present invention, higher durability can be achieved as compared with a solar cell element made of a conventional material.

  The photoelectric conversion element according to the present invention is suitably used as a dye-sensitized solar cell having high temperature durability that can withstand outdoor use, and can be used not only as a solar cell but also as an optical sensor. .

It is a schematic cross section which shows the basic structure of the dye-sensitized solar cell of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Transparent base body 2 ... Transparent electrically conductive film 3 ... Porous metal oxide semiconductor layer 4 ... Sensitizing dye 5 ... Electrolyte layer 6 ... Anti-peeling layer 7 ... Electrode group Material 8 ... Electrode base 9 ... Counter electrode 10 ... Dye-sensitized solar cell

Claims (6)

  A light-transmitting semiconductor electrode containing a dye having a photosensitizing action, a gel-like or solid electrolyte layer containing a chemical species serving as a redox pair, and the semiconductor electrode via the electrolyte layer. A quasi-solid type or solid type dye-sensitized solar cell having a counter electrode, wherein the dye-sensitized solar cell has an anti-peeling layer at a bonding interface between the counter electrode and the electrolyte layer.   2. The dye-sensitized solar cell according to claim 1, wherein the peeling prevention layer is made of a porous conductive polymer. 3. The dye-sensitized solar cell according to claim 2, wherein a specific surface area of the porous conductive polymer is 5 m ² / g or more.   The dye-sensitized solar cell according to any one of claims 1 to 3, wherein the porous conductive polymer is composed of at least one polymer selected from the group consisting of aniline and aniline derivatives.   The dye enhancement according to any one of claims 1 to 3, wherein the porous conductive polymer comprises a copolymer having at least one monomer component selected from the group consisting of aniline and aniline derivatives. Sensitive solar cell. The dye-sensitized solar cell according to any one of claims 1 to 5, wherein the substrate on which the peeling prevention layer is formed comprises a substrate having an actual surface area / projected area ratio of 10 or more.

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