JP2007200714A - Dye-sensitized solar cell and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of a dye-sensitized solar cell having high photoelectric conversion efficiency by suppressing leak current and internal resistance. <P>SOLUTION: The manufacturing method of the dye-sensitized solar cell contains a process in which a peroxotitanic acid aqueous solution, peroxotitanic acid reforming anatase type titanium oxide water system sol, or a mixture of them is applied to a conductor layer 2 formed on a transparent substrate 1, dried, and then baked to form a leak current suppressing layer 3, and a semiconductor layer 4 is formed on the leak current suppressing layer 3, and then dye is adsorbed in the semiconductor layer 4 to manufacture a semiconductor electrode 7. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a dye-sensitized solar cell and a method for producing the same.

A dye-sensitized solar cell is composed of a semiconductor electrode on which a dye is adsorbed, a counter electrode facing the semiconductor electrode, and an electrolyte sandwiched between the electrodes, and absorbs light energy absorbed by the dye. It generates electricity by converting it into electrical energy. Such dye-sensitized solar cells are expected to be put to practical use because raw material costs are low and safety is high.
A semiconductor electrode used in a dye-sensitized solar cell generally has a semiconductor layer formed by coating and baking a dispersion of semiconductor fine particles on a conductor layer formed on a transparent substrate, and then the dye is applied to the semiconductor layer. It is manufactured by adsorbing. However, in the semiconductor electrode manufactured by such a method, a gap is generated between individual semiconductor fine particles. Therefore, in the dye-sensitized solar cell provided with this semiconductor electrode, the electrolyte and the conductor layer are in direct contact with each other through the gap to cause a leakage current, thereby reducing the photoelectric conversion efficiency.
Therefore, in order to prevent direct contact between the electrolyte and the conductor layer, the conductor layer and the semiconductor layer are formed by forming a titanium dioxide layer on the conductor layer formed on the transparent substrate using a spray pyrolysis method. There is a method of disposing a titanium dioxide layer between them (for example, see Non-Patent Document 1). In addition, a reverse electron injection prevention layer is formed between the conductor layer and the semiconductor layer by applying and baking a titanium alkoxide solution on the conductor layer formed on the transparent substrate to form a reverse electron injection prevention layer. There is a method of arranging (see, for example, Patent Document 1).

U. Bach et al., “Solid-state dye-sensitized mesoporous TiO2 solar cells with high photon-to-electron conversion efficiencies”, Nature 1991, 395, pp. 583-585. JP 2000-151168 A

However, in the dye-sensitized solar cell in which the titanium dioxide layer or the reverse electron injection preventing layer is disposed between the conductor layer and the semiconductor layer by the above-described conventional method, direct contact between the conductor layer and the electrolyte is prevented and leakage current is prevented. However, there is a problem that the internal resistance increases, the fill factor in the current-voltage curve is greatly reduced, and the photoelectric conversion efficiency is lowered.
Therefore, the present invention has been made to solve the above problems, and to obtain a dye-sensitized solar cell with high photoelectric conversion efficiency in which leakage current and internal resistance are suppressed, and a method for producing the same. Objective.

Therefore, as a result of intensive studies to solve the above problems, the present inventors have found that the increase in internal resistance is caused by the thickness of the layer disposed between the conductor layer and the semiconductor layer. Based on this, it was conceived that the leakage current and the internal resistance can be suppressed by forming a thin and dense leakage current suppressing layer between the conductor layer and the semiconductor layer using a specific material. It came to complete.
That is, the present invention is to apply a peroxotitanic acid-based aqueous solution on a conductor layer formed on a transparent substrate, dry it, and fire it to form a leakage current suppression layer, and then on the leakage current suppression layer. A method for producing a dye-sensitized solar cell, comprising the steps of: forming a semiconductor layer, and then preparing a semiconductor electrode by adsorbing the dye to the semiconductor layer.
Moreover, this invention is a dye-sensitized solar cell manufactured by the said method.

  According to the present invention, by using a peroxotitanic acid-based aqueous solution, a thin and dense leakage current suppression layer made of fine particles having a high aspect ratio is formed between the conductor layer and the semiconductor layer, whereby leakage current and internal It is possible to manufacture a dye-sensitized solar cell with high resistance and reduced photoelectric conversion efficiency.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a dye-sensitized solar cell according to an embodiment of the present invention. In FIG. 1, the dye-sensitized solar cell includes a semiconductor electrode 7, a counter electrode 6 facing the semiconductor electrode 7, and an electrolyte 5 sandwiched between these electrodes. The semiconductor electrode 7 includes a transparent substrate 1, a conductor layer 2 formed on the transparent substrate 1, a leakage current suppression layer 3 formed on the conductor layer 2, and the leakage current suppression layer 3. The semiconductor layer 4 is formed and adsorbed with a dye.

The leakage current suppressing layer 3 can be formed by applying a peroxotitanic acid-based aqueous solution onto the conductor layer 2 formed on the transparent substrate 1, drying it, and baking it. In the present embodiment, examples of the peroxotitanic acid aqueous solution used for forming the leakage current suppressing layer 3 include a peroxotitanic acid aqueous solution and a peroxotitanic acid modified anatase type titanium oxide aqueous sol.
The peroxotitanic acid aqueous solution is composed of a binuclear complex anion Ti ₂ O ₅ (OH) _x ^{(2-x) −} (x> 2) having a basic structure of the following formula and a polyanion ((Ti ₂ O ₅ ) _q (OH). ) _Y ^{(y-2q) −} , (2 <q / y)) and the like, and is characterized by being stabilized with a low concentration of impurity ions.

Such an aqueous peroxotitanic acid solution is not particularly limited, and an aqueous solution prepared by a known method can be used. For example, first, a solution obtained by adding 30 wt% excess H ₂ O ₂ to a low concentration TiCl ₄ aqueous solution (0.1 mol / dm ³ ) and NH ₄ OH are mixed at a weight ratio of 1: 9, By adjusting the pH to 10, peroxohydrate as a precipitate is obtained. The resulting peroxohydrate is washed with distilled water, and impurities NH ₄ ⁺ and Cl ⁻ are removed by an ion exchange resin. Next, an aqueous peroxotitanic acid solution (0.1 mol / dm ³ ) can be produced by mixing and reacting this peroxohydrate with an excess of 30% by weight of H ₂ O ₂ at 7 ° C. The peroxotitanic acid aqueous solution thus produced contains 0.014 mol / dm ³ NH ₄ ⁺ and 0.0085 mol / dm ³ Cl ⁻ .
Moreover, as such a peroxotitanic acid aqueous solution, it is also possible to use commercial products, such as PTA (Tsubaki Corporation).

The peroxotitanate-modified anatase-type titanium oxide aqueous sol contains anatase-type titanium oxide crystals in a peroxotitanate aqueous solution. This anatase-type titanium oxide crystal has a flat shape, a spindle shape, an arrowhead shape, or the like, and has a size of several nm to 30 nm.
Such a peroxotitanic acid-modified anatase-type titanium oxide aqueous sol is obtained by heating the peroxotitanic acid aqueous solution at 65 ° C. to 100 ° C. for 2 to 40 hours, so that part or all of the peroxotitanic acid is converted into an amorphous type. It can be made into a precursor of titanium oxide and further anatase type crystal, and then crystallized into anatase type titanium oxide. In this case, the lower limit of the heating temperature is preferably 80 ° C. or higher, more preferably 90 ° C. or higher, and the upper limit of the heating temperature is preferably 95 ° C. or lower. Furthermore, the heating time is preferably 4 to 15 hours. When the heating temperature is less than 65 ° C., there is a tendency that part or all of peroxotitanic acid cannot be rapidly crystallized into anatase-type titanium oxide, while when it exceeds 100 ° C., side reactions occur, Since water etc. tend to volatilize too much, it is not preferable. Similarly, if the heating temperature is less than 2 hours, a part or all of peroxotitanic acid tends to be insufficiently crystallized in anatase-type titanium oxide. Since it tends to volatilize too much, it is not preferable.
Moreover, as such a peroxotitanate-modified anatase-type titanium oxide aqueous sol, commercially available products such as TOsol and TPX (both are Tsubaki Corporation) can also be used.

The peroxotitanic acid aqueous solution used for forming the leakage current suppressing layer 3 preferably has a solid content concentration of 0.1 to 3.0% by weight, and preferably 0.5 to 2.5% by weight. Is more preferable. If the solid content concentration is less than 0.1% by weight, it is not preferable because it is too thin and needs to be repeatedly applied when the leakage current suppressing layer 3 is formed, resulting in poor production efficiency and impracticality. On the other hand, if the solid content concentration exceeds 3.0% by weight, the storage stability of the peroxotitanic acid-based aqueous solution may be remarkably impaired, and the transparency, hardness, adhesion, and This is not preferable because the wear resistance tends to decrease.
The solid content concentration of the peroxotitanic acid aqueous solution in the present embodiment is the weight ratio of components other than the solvent to the aqueous solution, estimated at the time of preparing the aqueous solution, or the weight of the solid content after drying with respect to the aqueous solution. It means the ratio.

Further, the leakage current suppressing layer 3 may be formed using a mixture of a peroxotitanic acid aqueous solution and a peroxotitanic acid modified anatase type titanium oxide aqueous sol as the peroxotitanic acid aqueous solution.
In this mixture, the mixing ratio of the peroxotitanate aqueous solution and the peroxotitanate-modified anatase-type titanium oxide aqueous sol is not particularly limited. When the solid content concentration of the peroxotitanic acid aqueous solution is 0.1 to 3.0% by weight, the peroxotitanic acid aqueous solution is more than 0% by weight and 70% by weight or less, and 30% by weight or more and less than 100% by weight. It is preferable to mix a peroxotitanate-modified anatase-type titanium oxide aqueous sol, and an aqueous peroxotitanate solution of more than 0% by weight and 50% by weight or less and a peroxotitanate-modified anatase of 50% by weight to less than 100% by weight It is more preferable to mix a water-type titanium oxide aqueous sol with a peroxotitanic acid aqueous solution of more than 0% by weight and 30% by weight or less and a peroxotitanic acid-modified anatase-type titanium oxide aqueous sol of 70% by weight to less than 100% by weight. And are most preferably mixed. If the blending ratio of the peroxotitanic acid aqueous solution and the peroxotitanate-modified anatase-type titanium oxide aqueous sol is within the above range, a denser leakage current suppressing layer 3 can be obtained and the leakage current suppressing effect can be improved. .

Since the peroxotitanic acid aqueous solution exhibits neutrality or weak basicity, it can be applied to materials such as metals having no acid resistance. Further, the peroxotitanic acid-based aqueous solution does not gel for a long period of time, so that it can be stably supplied even during mass production over a long period of time, is extremely safe and easy to handle. The film obtained from the peroxotitanic acid aqueous solution is amorphous peroxotitanium hydrate Ti ₂ O ₅ (OH) ₂ , but is crystallized into anatase-type titanium dioxide by heating to 250 ° C. or higher. Can be made. This anatase-type crystal has a characteristic that the peroxotitanium dinuclear complex, which is the basic structure of the peroxotitanic acid aqueous solution, has a planar structure and is thus strongly oriented in the (101) plane. In addition, the peroxo group in the film obtained from the peroxotitanic acid-based aqueous solution is decomposed by heating and ultraviolet rays, and the film becomes denser and gradually changes to amorphous TiO ₂ . The characteristic of going. Further, the peroxotitanic acid-based aqueous solution is easy to form a very smooth film, and the film is excellent in adhesion. Therefore, the leakage current suppressing layer 3 formed from the peroxotitanic acid-based aqueous solution is oriented in the (101) plane and has excellent thin and dense adhesion and transparency.

The method for applying the peroxotitanic acid aqueous solution when forming the leakage current suppressing layer 3 is not particularly limited, and is a roller method, a dipping method, an air knife method, a blade method, a wire bar method, a slide hopper method. Application may be made by various printing methods such as an extrusion method, a curtain method, a spin method, a spray method, and screen printing.
The drying method is not particularly limited, and may be dried at 5 to 150 ° C. for 15 to 60 minutes in an air atmosphere.
As a baking method, it is preferable to bake for 10 to 60 minutes at 250 to 550 ° C., preferably 350 to 500 ° C. in an air or oxygen atmosphere. If the firing temperature is less than 250 ° C., it cannot be crystallized into anatase-type titanium dioxide, and the dense leakage current suppressing layer 3 tends not to be obtained. On the other hand, if it exceeds 550 ° C., it may exceed the heat resistance temperature of the transparent substrate 1 made of glass or the like, which is not preferable.

  The thickness of the leakage current suppressing layer 3 thus obtained is preferably 5 to 500 nm, more preferably 10 to 250 nm. If the thickness is less than 5 nm, the shielding effect of direct contact between the conductor layer 2 and the electrolyte 5 cannot be sufficiently obtained, and the leakage current suppressing effect tends to be lowered, which is not preferable. On the other hand, if the thickness exceeds 500 nm, the contribution to improvement in photoelectric conversion efficiency tends to decrease due to an increase in internal resistance, which is not preferable.

The transparent substrate 1 is not particularly limited as long as it has insulating properties and transparency. Glass, polymethyl methacrylate, polycarbonate, polystyrene, polyethylene sulfide, polyethersulfone, polyolefin, polyethylene terephthalate, polyethylene naphthalate. Plastics such as phthalate and triacetyl cellulose can be used. Among these, it is more preferable to use a glass having light resistance and heat resistance from the viewpoint of the environment in which the solar cell is used and the lifetime.
In order to effectively take in incident light, an antireflection layer may be provided on the surface on which the conductor layer 2 is not formed. The method of forming the antireflection layer is not particularly limited, and a method of forming a metal oxide using a dipping method or a sputtering method, a method of forming irregularities on the surface by etching, or an antireflection film is attached. It may be formed by a method.

The conductor layer 2 is formed on the transparent substrate 1. The material used for the conductor layer 2 is not particularly limited as long as it has conductivity, has little absorption in the visible light region, and is substantially transparent. Known as conductive oxides, metal oxides such as tin oxide, tantalum oxide, tungsten oxide, strontium titanate, cobalt oxide, nickel oxide, ruthenium oxide, zinc oxide and indium oxide, or their solid solutions or doping A treatment body can be used. Here, “substantially transparent” means that the transmittance of light (visible light range of 400 to 900 nm) is 10% or more, more preferably 50% or more, more preferably 70% or more. Particularly preferred are those having a transmittance of
The method for forming the conductor layer 2 on the transparent electrode 1 is not particularly limited, and is a vacuum deposition method, a reactive deposition method, an ion beam assisted deposition method, a sputtering method, an ion plating method, a plasma CVD method. And a sol-gel method or the like.

The semiconductor layer 4 is formed on the leakage current suppression layer 3. The semiconductor layer 4 needs to have a roughness factor (a ratio of an actual surface area to a projected area) of 20 times or more, preferably 500 times or more. When the semiconductor layer 4 having a surface with a large surface roughness is formed in this way, the surface area per unit area increases and the amount of adsorbed dye increases, so that the amount of light absorption can be increased sufficiently. Therefore, the semiconductor layer 4 is preferably one in which semiconductor particles having a particle size of about 5 to 500 nm are laminated and fused. Examples of the material used for the semiconductor layer 4 include titanium oxide, zinc oxide, tungsten oxide, niobium oxide, tin oxide, vanadium oxide, indium oxide, tantalum oxide, zirconium oxide, molybdenum oxide, manganese oxide, barium titanate, One or more known semiconductors such as strontium titanate, calcium titanate, magnesium titanate, strontium niobate, silicon carbide, and GaP can be mixed and used. Among these, titanium oxide is preferable from the viewpoints of stability and safety.
The titanium oxide may be various titanium oxides such as anatase type titanium oxide, rutile type titanium oxide, amorphous titanium oxide, meta titanium oxide and ortho titanium oxide, titanium hydroxide, and titanium oxide. Among these, those having a high anatase content are preferable from the viewpoint of photoelectric conversion efficiency, and more preferably 80% or more.

  The thickness of the semiconductor layer 4 varies depending on the application, and may be reduced if transparency is required, and may be increased if high photoelectric conversion efficiency is required. Specifically, the thickness of the semiconductor layer 4 is preferably 0.5 to 50 μm, and more preferably 5 to 30 μm. If the thickness of the semiconductor layer 4 is less than 0.5 μm, a surface area sufficient to absorb incident light cannot be obtained, and the desired photoelectric conversion efficiency may not be obtained. On the other hand, if the thickness of the semiconductor layer 4 exceeds 50 μm, the portion that does not contribute to light absorption increases, the internal resistance increases, and the desired photoelectric conversion efficiency may not be obtained.

  The method for forming the semiconductor layer 4 on the leakage current suppressing layer 3 is not particularly limited, and a known method can be used. Specifically, a method of oxidizing a co-deposited thin film by simultaneously depositing a metal and carbon or an organic compound, or a metal oxide or metal suboxide and an organic compound in a vacuum, a sputtering method, etc. A wet process such as a dry process, a sol-gel method, a method of applying a dispersion of semiconductor fine particles produced by a chemical method, a method of applying and baking a semiconductor fine particle paste, or the like can be used. In consideration of mass production, liquid physical properties, and support flexibility, it is relatively advantageous to use a wet process. As a method used in the wet process, a coating method, a printing method, and a spray method are representative.

In addition to the sol-gel method described above, a method of preparing a dispersion of semiconductor fine particles is a method of grinding in a mortar, a method of dispersing while pulverizing using a mill, or a fine particle in a solvent when synthesizing a semiconductor. The method of depositing and using as it is is mentioned. Examples of the dispersion medium include water or various organic solvents (for example, methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, and the like). At the time of dispersion, a polymer, a surfactant, an acid, a chelating agent, or the like may be used as a dispersion aid as necessary.
The semiconductor fine particle paste is produced by adding a semiconductor fine particle or a dispersion of semiconductor fine particles to a solvent, a thickener, an acid, an alkali, or the like.
As a coating method, use various printing methods such as a roller method, a dip method, an air knife method, a blade method, a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, a spray method and a screen printing. Can do.

The semiconductor layer 4 can be obtained by baking a film formed using a wet process. In this case, the firing temperature is preferably 400 to 550 ° C, and more preferably 450 to 500 ° C. When the firing temperature is less than 400 ° C., fusion between the semiconductor fine particles is reduced, and the current collection efficiency of the generated electrons tends to decrease, which is not preferable. On the other hand, if the firing temperature exceeds 550 ° C., it may exceed the heat resistance temperature of the transparent substrate 1 made of glass or the like, which is not preferable.
In addition, for example, chemical plating using an aqueous solution of titanium tetrachloride for the purpose of increasing the surface area of the semiconductor particles after firing, increasing the purity in the vicinity of the semiconductor particles, and increasing the efficiency of electron injection from the dye to the semiconductor particles. Alternatively, an electrochemical plating process using a titanium trichloride aqueous solution may be performed to coat a thin titanium oxide layer.

As a pigment | dye adsorb | sucked to the semiconductor layer 4, if it absorbs light, it can be used without a restriction | limiting in particular. Specific examples of such dyes include so-called metal chelate complexes such as metal complex salts containing at least one atom of ruthenium, osmium, iron or zinc, metal-free phthalocyanines, porphyrins, dithiolate complexes, and acetylacetonate complexes. Cyanine dyes such as NK1194 and NK3422 (manufactured by Nippon Photosensitivity Laboratories), merocyanine dyes such as NK2426 and NK2501 (manufactured by Nippon Photosensitivity Laboratories), xanthene dyes such as rose bengal and rhodamine B, malachite green, crystal violet Triphenylmethane dyes such as copper phthalocyanine or copper phthalocyanine or titanyl phthalocyanine, chlorophyll, hemin, or cyanidin dyes, and oxadiazole derivatives, benzothiazole derivatives, coumarin derivatives, stilbene derivatives Body, and organic compounds having an aromatic ring. These dyes preferably have a large extinction coefficient and are stable against repeated redox. The dye may be a low molecular compound or a polymer having a repeating unit. Further, an aggregate such as a J aggregate may be formed. Of these, metal complexes having excellent spectral sensitization effects and durability, J-aggregates of organic dyes, and pigment dyes are preferable.
The dye is preferably capable of being chemically adsorbed to the semiconductor electrode, and preferably has a functional group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amide group, an amino group, a carbonyl group, or a phosphine group. . Further, it is preferable that there are a plurality of such functional groups in the dye molecule.

In the present embodiment, the dye is adsorbed onto the semiconductor layer 4 by preparing a dye solution in which the dye is dissolved in a solvent, and then immersing the semiconductor layer 4 in the dye solution, and a sufficient time has elapsed for the dye to adsorb. Later, the semiconductor layer 4 can be lifted from the dye solution, washed and dried. If necessary, the semiconductor layer 4 may be heated when immersed in the dye solution, or the dye solution may be acidic or basic.
The solvent for dissolving the dye can be appropriately selected according to the solubility of the dye. For example, water, alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.), nitromethane, halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform) , Chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazo Lidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonate esters (diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.), carbonization Arsenide (hexane, petroleum ether, benzene, toluene, etc.) or mixed solvents thereof.

The electrolyte 5 in the present embodiment contains, as an ion transport material, a solution in which redox couple ions are dissolved, a so-called gel electrolyte in which a polymer matrix gel is impregnated with a redox couple solution, and redox counter ions. Examples include molten salt electrolytes and solid electrolytes.
When an electrolyte solution is used for the electrolyte 5, the electrolyte solution is preferably composed of an electrolyte, a solvent, and other additives, and an oxidation-reduction agent generally used for an electrolyte of a dye-sensitized solar cell is arbitrarily used. Can do. Electrolyte 5 in the present embodiment is a combination of I ₂ and iodide (as iodide, metal iodide such as LiI, NaI, KI, CsI, CaI ₂ , tetraalkylammonium iodide, pyridinium iodide, A quaternary ammonium compound iodine salt such as imidazolium iodide), a combination of Br ₂ and bromide (as bromide, bromide such as LiBr, NaBr, KBr, CsBr, CaBr ₂ or the like, or tetraalkylammonium bromide, In addition to bromine salts of quaternary ammonium compounds such as pyridinium bromide), metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ions, sulfur compounds such as sodium polysulfide and alkylthiol-alkyldisulfides , Viologen color Elemental, hydroquinone-quinone and the like can be used. Furthermore, transition metal complexes such as a quinone complex, a tetracyanoquinone dimethane (TCNQ) complex, and a dicyanoquinone diimine complex that carry unbonded electrons can also be used. The above-described electrolyte 5 may be used as a mixture. Among these, electrolytes that combine iodine salts of quaternary ammonium compounds such as I ₂ and LiI, pyridinium iodide, and imidazolium iodide are more preferable.

The concentration of the electrolyte 5 in the electrolyte solution is preferably 0.1 to 15M, and more preferably 0.2M to 10M. If the concentration of the electrolyte 5 is less than 0.1M, the conductivity tends to decrease, which is not preferable. On the other hand, if the concentration of the electrolyte 5 exceeds 15M, the viscosity of the solution increases and the conductivity decreases, or the solid content tends to precipitate due to temperature fluctuations, which is not preferable.
Moreover, when adding an iodine to the electrolyte 5, it is more preferable that the addition density | concentration of an iodine is 0.01M-5.0M. If the concentration of iodine added is less than 0.01M, the conductivity tends to decrease, such being undesirable. On the other hand, if the concentration of iodine exceeds 5.0M, the viscosity of the solution increases and the conductivity decreases, or the solid content tends to precipitate due to temperature fluctuations, which is not preferable.

The solvent of the electrolyte solution is preferably an organic solvent that does not dissolve the dye supported on the semiconductor electrode, is electrochemically stable, and does not generate gas due to an electrochemical reaction. Examples of such solvents include acetonitrile, methoxypropionitrile, methoxyacetonitrile, propylene carbonate, ethylene carbonate and methyl pyrrolidone, ethyl acetate or tetrahydrofuran, water, alcohol and mixtures thereof. It is not limited.
A molten salt can also be used as the solvent or electrolyte of the electrolyte solution. Molten salt is more preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. Examples of the molten salt electrolyte include, for example, pyridinium salts described in International Publication No. 95/18456, JP-A-8-259543, Electrochemical Vol. 65, No. 11, 923 (1997), etc. Known iodine salts such as imidazolium salts and triazolium salts can be used.

In the present embodiment, the electrolyte 5 can be used by gelation. Examples of gelation methods include polymer addition, oil gelling agent addition, polymerization including polyfunctional monomers, polymer addition by a method such as a crosslinking reaction, and nano fine particle addition. In the case of gelation by a crosslinking reaction or the like, polyacrylonitrile or polyvinylidene fluoride can be used. When gelation is performed by adding an oil gelling agent, it is preferable to use a compound having an amide structure in the molecular structure.
When the gel electrolyte is formed by polymerization of polyfunctional monomers, a sol-like electrolyte layer is formed on the semiconductor layer 4 on which the dye is adsorbed from a solution composed of polyfunctional monomers, a polymerization initiator, an electrolyte, and a solvent. The method of making it gelatinize by radical polymerization after that is preferable.

In the present embodiment, instead of the electrolyte 5, a charge transport material that is organic or inorganic, or a combination of both can be used. Examples of organic hole transport materials applicable in the present embodiment include aromatic amine compounds such as triphenylamine, diphenylamine, and phenylenediamine, condensed polycyclic hydrocarbons such as naphthalene, anthracene, and birene, azo compounds such as azobenzene, Compounds having a structure in which aromatic rings such as stilbene are linked by ethylene bond or acetylene bond, heteroaromatic compounds substituted by amino groups, porphyrins, phthalocyanines, α-octylthiophene, α, ω-dihexyl-α- Oligothiophene compounds such as octylthiophene, hexadodecyldodecithiophene, polypyrrole, polyacetylene and derivatives thereof, poly (p-phenylene) and derivatives thereof, poly (p-phenylene vinylene) and derivatives thereof, polythienylene vinylene and derivatives thereof, Polythiophe And its derivatives, polyaniline and derivatives thereof, conductive polymers such as poly-toluidine and derivatives thereof can be used. Examples of the electron transport material include quinones, tetracyanoquinodimethanes, dicyanoquinone diimines, tetracyanoethylene, viologens, and dithiol metal complexes. In addition, a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate is added to the organic hole transport material in order to control the dopant level, or an oxide semiconductor. In order to perform surface potential control (space charge layer compensation), a salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added. In addition, CuI, AgI, TiI and other metal iodides, CuBr, CuSCN, and the like can be used as inorganic materials.
In order to improve performance, J. Org. Am. Ceram. Soc. , 80 (12) 3157-3171 (1997), and basic compounds such as ter-butylpyridine, 2-picoline, and 2,6-lutidine can also be added. A preferable concentration range when adding the basic compound is 0.05M to 2M.

  As the counter electrode 6 in this Embodiment, it does not restrict | limit in particular, What is comprised from a transparent substrate and a conductor layer can be used. As the transparent substrate and the conductor layer in the counter electrode 6, the same substrates as the transparent substrate 1 and the conductor layer 2 used in the semiconductor electrode 7 can be used. In addition, a material having high catalytic activity can be used for the conductor layer. Here, the material having high catalytic activity means a material having a catalytic action for the oxidation-reduction reaction and electrochemically stable. Examples of the material having high catalytic activity include platinum, palladium, ruthenium, nickel, rhodium, gold, platinum, etc., a multi-component catalyst in which at least one of molybdenum, ruthenium, tin, iron, or tungsten is added, or tin oxide, Conductivity such as metal oxides such as gallium oxide and molybdenum oxide, and mixed materials thereof, carbon materials, nanocarbon materials, carbon materials and nanocarbon materials carrying catalytically active materials such as platinum, and polythiophene derivatives such as PEDOT-TsO Examples thereof include a polymer material and a polymer complex catalyst. Among these, platinum, a carbon material, a nanocarbon material carrying a catalyst, and the like are preferable from the viewpoint of being hardly affected by the electrolyte 5 and having high catalytic activity.

  In addition, a collector electrode may be formed on the counter electrode 6 in order to reduce the resistance of the counter electrode 6. As the material for the collector electrode, metals such as aluminum, gold, silver, copper, platinum, nickel, tungsten and the like are preferable. Among these, gold, silver, copper, nickel and tungsten are more preferable from the viewpoint of conductivity. This collector electrode can be formed by a known method, but after forming a grid-like collector electrode on a transparent substrate by vapor deposition, sputtering, plating, etc., a conductor layer is formed on this collector electrode. It is preferable to form. Alternatively, after forming a conductor layer on the transparent substrate, it is also possible to form a grid-like collector electrode on the conductor layer. Further, from the viewpoint of preventing direct contact between the collector electrode and the electrolyte 5 and preventing corrosion of the collector electrode, it is also possible to form a corrosion prevention layer such as a sealing material or a metal oxide on the collector electrode.

The production of the dye-sensitized solar cell including the semiconductor electrode 7, the electrolyte 5 and the counter electrode 6 is not particularly limited, and a known method may be used. Specifically, after the semiconductor electrode 7 and the counter electrode 6 are bonded together, the liquid electrolyte 5 is injected into the gap and sealed, and the counter electrode 6 with a hole is bonded on the semiconductor electrode 7. In addition, after sealing with a sealing material, the electrolyte 5 is injected from the hole of the counter electrode 6 to seal the injection port. After the electrolyte 5 is directly applied on the semiconductor electrode 7, the counter electrode 6 is pasted. A matching method or the like can be used.
In addition, when injecting the electrolyte 5, there are a normal pressure process using a capillary phenomenon due to dipping and the like, and a vacuum process in which the gas phase between the electrodes and the porous film is replaced with a liquid phase at a pressure lower than the normal pressure. Can be used.

When an organic charge transport material solution or gel electrolyte is used in addition to the electrolyte solution, the dipping method, the roller method, the dipping method, as in the method for forming the semiconductor layer 4 and the method for adsorbing the dye to the semiconductor layer 4 , Air knife method, extrusion method, slide hopper method, wire bar method, spin method, spray method, casting method, various printing methods, and the like can be used.
When a solid electrolyte or a solid hole transport material is used, the electrolyte layer is formed on the counter electrode 6 by a dry film forming process such as a vacuum deposition method or a CVD method, or a wet process such as a plating method or an electrolytic polymerization method. After being formed, the semiconductor electrode 7 can be bonded.
A film sheet, a tape-shaped film sheet, a porous sheet, or a spacer such as fine particles of an organic compound or an inorganic compound is sandwiched between the semiconductor electrode 7 and the counter electrode 6, and the desired between the semiconductor electrode 7 and the counter electrode 6. Can also be provided.
Furthermore, in producing the dye-sensitized solar cell, it is preferable to seal the gap between the semiconductor electrode 7 and the counter electrode 6 with a sealing material.
Although it does not restrict | limit especially as a sealing material, The material which has light resistance, insulation, and moisture resistance is preferable, for example, ionomer resin, an epoxy resin, an ultraviolet curable resin, an acrylic adhesive, ethylene vinyl acetate ( Various heat-sealing films such as EVA), silicon rubber, and ceramic can be used.

EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated concretely, this invention is not limited to the following Example.
[Example 1]
(Production of semiconductor electrodes)
Using a solution obtained by diluting a peroxotitanic acid aqueous solution (manufactured by Sakai Corporation, PTA-170, solid concentration 1.70%) twice, spin coater (1000 rpm) on an FTO substrate (manufactured by Nippon Sheet Glass) with a side of 2 cm. 15 seconds), the film was dried at room temperature in the air atmosphere, and baked at 450 ° C. for 30 minutes in the air atmosphere to form a leakage current suppressing layer. The thickness of the leakage current suppressing layer thus obtained was 26 nm. Next, 6 g of titanium oxide powder (P-25 manufactured by Nippon Aerosil Co., Ltd., anatase / rutile = 80/20 titanium oxide, average primary particle size 21 nm), 0.2 g of acetylacetone, 8 g of pure water, and 0.2 g of interface A paste prepared by kneading an activator (manufactured by Wako Pure Chemical Industries, Triton X-100) was applied on the leakage current suppression layer using the squeegee method and dried, and then in an air atmosphere at 500 ° C. for 30 minutes. The semiconductor layer was formed by baking. The thickness of the semiconductor layer thus obtained was 14 to 15 μm. Next, 0.3 mmol / L of ruthenium dye (commonly known as N719, cis-bis (isothiocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylato) -ruthenium (II) bis-tetra-butylammonium) A semiconductor layer was prepared by immersing the semiconductor layer in a t-butanol / acetonitrile solution at 25 ° C. for 12 hours to adsorb the dye to the semiconductor layer.
(Preparation of counter electrode)
A platinum layer (500 nm) was formed on an FTO transparent electrode substrate (manufactured by Nippon Sheet Glass) by sputtering to produce a counter electrode.
(Preparation of dye-sensitized solar cell)
A semiconductor film and a counter electrode obtained as described above were bonded together with a spacer film interposed therebetween. Next, 1M of LiI, _I 2 of 0.05 M, 4-tert-butylpyridine 0.5M, imidazole salts of 0.5M DMPII (1,2dimethyl-1,3-propylimidazolium iodide) and methoxy acetonitrile as a solvent A dye-sensitized solar cell was produced by injecting an electrolyte solution consisting of the above through a gap between the titanium oxide electrode and the counter electrode.

[Comparative Example 1]
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the leakage current suppressing layer was not formed.
[Comparative Example 2]
Using a titanium isopropoxide solution consisting of 2 g of titanium isopropoxide, 4 g of acetic acid, 16 g of ethanol, and 2 g of water, a spin coater (1000 rpm, 5 seconds), the film was dried at room temperature in the air atmosphere, and baked at 450 ° C. for 30 minutes in the air atmosphere to form a leakage current suppressing layer. The thickness of the leakage current suppressing layer thus obtained was 75 nm. Other than that was carried out similarly to Example 1, and produced the dye-sensitized solar cell.

The photoelectric conversion elements were evaluated for the dye-sensitized solar cells obtained in Example 1 and Comparative Examples 1 and 2.
(Evaluation of photoelectric conversion element)
In the dye-sensitized solar cell obtained above, dark current characteristics and current-voltage characteristics (open electromotive force, short-circuit current density, photoelectric conversion efficiency) during light irradiation were evaluated.
Light irradiation current-voltage characteristics are measured using a solar simulator (Yamashita Denso, YSS-50A), irradiating pseudo-sunlight with air mass 1.5 and light intensity 100 mW / cm ² from the semiconductor electrode side, and measuring current / voltage characteristics. did.

  Regarding the above evaluation, the results of the dark current characteristics are shown in FIG. Table 1 shows the results of current-voltage characteristics (open electromotive force, short-circuit current density, photoelectric conversion efficiency) during light irradiation.

As shown in FIG. 2, the dye-sensitized solar cell of Example 1 had a slower dark current rise and less leakage current than the dye-sensitized solar cells of Comparative Examples 1 and 2.
In addition, Example 1 using a peroxotitanic acid aqueous solution had a thinner leakage current suppression layer and a superior leakage current suppression effect than Comparative Example 2 using a titanium isopropoxide solution. .
Furthermore, as shown in Table 1, the dye-sensitized solar cell of Example 1 has an open electromotive force, a short-circuit current density, and a photoelectric conversion efficiency as compared with the dye-sensitized solar cells of Comparative Examples 1 and 2. It was excellent.
As can be seen from the above results, the present invention can produce a dye-sensitized solar cell with high photoelectric conversion efficiency by suppressing leakage current and internal resistance.

It is a cross-sectional schematic diagram of the dye-sensitized solar cell which concerns on embodiment of this invention. It is a figure which shows the measurement result of the dark current in the dye-sensitized solar cell of Example 1 and Comparative Examples 1 and 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Transparent substrate, 2 Conductor layer, 3 Leakage current suppression layer, 4 Semiconductor layer, 5 Electrolyte, 6 Counter electrode, 7 Semiconductor electrode.

Claims (5)

  After forming a leakage current suppression layer by applying a peroxotitanic acid-based aqueous solution onto a conductor layer formed on a transparent substrate, drying and firing, a semiconductor layer is formed on the leakage current suppression layer. Then, the manufacturing method of the dye-sensitized solar cell characterized by including the process of preparing a semiconductor electrode by making a dye adsorb | suck to the said semiconductor layer.   The said baking is performed at 250 to 550 degreeC, The manufacturing method of the dye-sensitized solar cell of Claim 1 characterized by the above-mentioned.   The dye-sensitized solar cell according to claim 1 or 2, wherein the peroxotitanic acid aqueous solution is a peroxotitanic acid aqueous solution, a peroxotitanic acid-modified anatase-type titanium oxide aqueous sol, or a mixture thereof. Production method.   The method for producing a dye-sensitized solar cell according to any one of claims 1 to 3, wherein a solid content concentration of the peroxotitanic acid-based aqueous solution is 0.1 to 3.0% by weight. .   It manufactures by the method as described in any one of Claims 1-4, The dye-sensitized solar cell characterized by the above-mentioned.

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