JP2008186669A - Method for producing dye-sensitized solar cell - Google Patents

Abstract

A method for producing a dye-sensitized solar cell with improved photoelectric conversion efficiency is obtained by reducing the disappearance of electrons generated by light absorption of the dye to improve electromotive force and current density.
In a method for producing a dye-sensitized solar cell, comprising a semiconductor electrode, a counter electrode facing the semiconductor electrode, and an electrolyte or an electrolytic solution sandwiched between the semiconductor electrode and the counter electrode, a transparent A semiconductor porous layer and a light scattering layer are sequentially formed on a conductive substrate, and then the semiconductor electrode is produced by immersing at least the semiconductor porous layer in a solution containing a dye and an organic acid. And a method for producing a dye-sensitized solar cell.
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Description

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

A dye-sensitized solar cell includes a semiconductor electrode having a transparent conductive substrate and a semiconductor porous layer on which a dye is adsorbed, a counter electrode facing the semiconductor electrode, and an electrolyte or electrolysis sandwiched between these electrodes. The liquid is at least composed of a liquid and generates electricity by converting light energy absorbed by the pigment into electric energy. Such dye-sensitized solar cells are expected to be put to practical use because raw material costs are low and safety is high.
In such a dye-sensitized solar cell, when an n-type semiconductor such as titanium dioxide is used for the semiconductor porous layer, electrons generated by light absorption of the dye adsorbed on the semiconductor porous layer are injected into the conduction band of the semiconductor. Then, it diffuses in the semiconductor and reaches the transparent conductive substrate to collect current. In such a process, electrons generated in the dye may disappear due to a bond with an oxidant of an adjacent dye or a direct oxidation-reduction reaction with an electrolyte or electrolytic solution on a semiconductor electrode, which may reduce photoelectric conversion efficiency. There is.

  Examples of the dye used in the dye-sensitized solar cell include various dyes such as a chlorophyll derivative and a ruthenium complex. Such a dye can be adsorbed by immersing the semiconductor porous layer in a solution containing the dye. In a method for producing a dye-sensitized solar cell using a chlorophyll derivative as a dye, it is known that photoelectric conversion efficiency is improved by using a solution containing a dye and a derivative such as cholic acid added (for example, Non-Patent Document 1). In addition, in a method for producing a dye-sensitized solar cell using a ruthenium complex as a dye, it is known to use a solution containing a dye containing sodium taurochenodeoxycholic acid sodium salt (for example, see Non-Patent Document 2). .

Andreas Kay, 1 other, "Photosensitization of TiO2 Solar Cells with Chlorophyll Derivatives and Related Natural Porphyrins" using chlorophyll derivatives and homologous natural porphyrins, Journal of • Journal of Physical Chemistry (USA), 1993, Vol. 97, p. 6272-6277 Mohammad K. Nazeeruddin, 13 others, “Engineering of Efficient Panchromatic Sensitizers for Nanocrystalline TiO2-Based Solar Cells” (USA), Journal of American Chemical Society, 2001, Vol. 123, p. 1613-1624

However, even with the method of Non-Patent Document 1, sufficient photoelectric conversion efficiency is still not obtained. Further, in the method of Non-Patent Document 2, the effect of using a solution containing a dye containing taurochenodeoxycholic acid sodium salt is not clear, and even with this method, sufficient photoelectric conversion efficiency is still obtained. Not.
The present invention has been made to solve the above-mentioned problems, and improves photoelectric conversion efficiency by reducing the disappearance of electrons generated by light absorption of the dye and improving electromotive force and current density. It aims at obtaining the manufacturing method of the made dye-sensitized solar cell.

As a result of diligent research to solve the above problems, the present inventors reduced the disappearance of electrons generated by light absorption of the dye by immersing the semiconductor porous layer in a solution containing the dye and the organic acid. Found to get. On the other hand, with the decrease in the amount of adsorbing dye in the semiconductor porous layer, there is a problem that the amount of light absorption decreases, but by providing a light scattering layer on the semiconductor porous layer, the semiconductor porous layer It has been found that since the light transmitted through the light is reflected by the light scattering layer and returns to the semiconductor porous layer again, a decrease in the amount of light absorption in the semiconductor porous layer can be suppressed. Based on these viewpoints, a semiconductor porous layer and a light scattering layer are sequentially formed on a transparent conductive substrate, and then at least the semiconductor porous layer is immersed in a solution containing a dye and an organic acid. With the decrease in the amount of dye adsorbed in the layer, the inventors have conceived that the loss of electrons generated by the light absorption of the dye can be reduced without causing the problem that the light absorption amount decreases, and the present invention has been completed. .
That is, the present invention relates to a method for producing a dye-sensitized solar cell comprising a semiconductor electrode, a counter electrode facing the semiconductor electrode, and an electrolyte or an electrolyte solution sandwiched between the semiconductor electrode and the counter electrode. Forming the semiconductor electrode by immersing at least the semiconductor porous layer in a solution containing a dye and an organic acid after sequentially forming the semiconductor porous layer and the light scattering layer on the transparent conductive substrate. This is a method for producing a dye-sensitized solar cell.

  ADVANTAGE OF THE INVENTION According to this invention, the dye-sensitized solar cell which improved the photoelectric conversion efficiency can be manufactured by reducing the loss | disappearance of the electron generated by the light absorption of a pigment | dye, and improving an electromotive force and a current density. .

Embodiment 1 FIG.
Below, with reference to drawings, the manufacturing method of the dye-sensitized solar cell in this Embodiment is demonstrated.
FIG. 1 is a schematic cross-sectional view of a dye-sensitized solar cell manufactured in the present embodiment. In FIG. 1, the dye-sensitized solar cell includes a semiconductor electrode 1, a counter electrode 2 facing the semiconductor electrode 1, and an electrolyte or electrolyte solution 3 sandwiched between these electrodes. The semiconductor electrode 1 includes a transparent conductive substrate 4, a semiconductor porous layer 5 formed on the transparent conductive substrate 4, and a light scattering layer 6 formed on the semiconductor porous layer 5. Yes.

(Semiconductor electrode 1)
The semiconductor electrode 1 in the present embodiment can be produced by sequentially forming the semiconductor porous layer 5 and the light scattering layer 6 on the transparent conductive substrate 4 and then immersing them in a solution containing a dye and an organic acid. it can.
The transparent conductive substrate 4 in the present embodiment is not particularly limited as long as it can be used as the transparent conductive substrate 4 in the technical field. Specifically, the transparent conductive substrate 4 may be one obtained by imparting conductivity to the surface of the transparent substrate by surface modification, or one provided with a conductor layer on the surface of the transparent substrate.
The transparent substrate is not particularly limited as long as it is a material having insulating properties and transparency. As such a material, plastics such as glass, polymethyl methacrylate, polycarbonate, polystyrene, polyethylene sulfide, polyethersulfone, polyolefin, polyethylene terephthalate, polyethylene naphthalate, and triacetyl cellulose can be used. Among these, it is preferable to use glass having light resistance and heat resistance from the viewpoint of the environment in which the solar cell is used and the life.

The material used for the conductor layer is not particularly limited as long as it has conductivity, has little absorption in the visible light region, and is substantially transparent. Such materials include common metals and conductive oxides known as tin oxide, tantalum oxide, tungsten oxide, strontium titanate, cobalt oxide, nickel oxide, ruthenium oxide, zinc oxide and indium oxide. Examples thereof include metal oxides, and solid solutions or doping treatment bodies thereof.
Here, “substantially transparent” means that the transmittance of light (visible light region of 400 nm or more and 900 nm or less) is 10% or more, more preferably 50% or more, and 70% What has the above transmittance | permeability is especially preferable.
Moreover, it does not restrict | limit especially as a method of forming a conductor layer on a transparent substrate, A conventionally well-known method can be used. Specifically, 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, a sol-gel method, or the like can be used.

  Furthermore, in order to take in incident light effectively, an antireflection layer can be provided on the outer surface (the surface on the side where the conductor layer is not formed) on which light is incident. Such an antireflection layer can be formed by a method of forming a metal oxide using a dipping method or a sputtering method, a method of providing irregularities on the surface by etching, a method of attaching an antireflection film, or the like.

The semiconductor porous layer 5 in the present embodiment is not particularly limited as long as it is a material that can be used as the semiconductor porous layer 5 in this technical field. Such materials 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, strontium titanate, calcium titanate, One or more known semiconductors such as 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.
Here, the titanium oxide may be anatase type titanium oxide, rutile type titanium oxide, amorphous titanium oxide, various titanium oxides such as meta titanium oxide and ortho titanium oxide, titanium hydroxide, and titanium oxide. Among these, from the viewpoint of photoelectric conversion efficiency, those having a high anatase content are preferable, and the content is more preferably 70% or more.

  The semiconductor porous layer 5 has a roughness factor (actual surface area ratio relative to the projected area) of preferably 20 times or more, and more preferably 500 times or more. When the semiconductor porous layer 5 having a large roughness factor is formed as described above, 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 porous layer 5 is obtained by laminating and fusing semiconductor particles having an average particle diameter of about 5 nm to about 500 nm, and is preferably transparent or translucent.

The thickness of the semiconductor porous layer 5 is preferably 0.5 μm or more and 50 μm or less, and more preferably 5 μm or more and 30 μm or less. If the thickness of the semiconductor porous layer 5 is less than 0.5 μm, a surface area sufficient to absorb incident light cannot be obtained, and a desired photoelectric conversion efficiency may not be obtained. On the other hand, if the thickness of the semiconductor porous layer 5 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.
In addition, when the semiconductor porous layer 5 is formed into fine particles, the semiconductor porous layer 5 tends to be difficult to form, for example, cracks occur when the thick film is formed or peeling from the substrate occurs. Therefore, in order to obtain a desired film thickness, a desired film thickness may be obtained by stacking layers having a film thickness within a film forming range. For example, in the case of forming a porous film formed of fine particles of 10 nm or more and 20 nm or less in a thickness of 10 μm or more and 20 μm or less, a desired film thickness is obtained by stacking 2 μm or more and 5 μm or less of layers in a thickness of 2 or more and 10 or less. Can be achieved.

  The method for forming the semiconductor porous layer 5 on the transparent conductive substrate 4 is not particularly limited, and a conventionally known method can be used. As such a method, specifically, a method of oxidizing a co-deposited thin film in which a metal and carbon or an organic compound, or a metal oxide or metal suboxide and an organic compound are simultaneously deposited in a vacuum, Using a wet process such as a dry process such as a sputtering method, a sol-gel method, a method of applying a dispersion of semiconductor fine particles prepared by a chemical method, a method of applying and baking a semiconductor fine particle paste, etc. it can. Among these methods, it is relatively advantageous to use a wet process such as a coating method, a printing method, or a spray method from the viewpoint of mass production, liquid physical properties, and flexibility of the support.

In addition to the sol-gel method, a method for preparing a dispersion of semiconductor fine particles includes a method of grinding with a mortar, a method of dispersing while pulverizing using a mill, or a method of precipitating fine particles in a solvent when synthesizing a semiconductor. The method of 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). During 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 may be prepared by adding a solvent, a thickener, an acid, an alkali, or the like to a semiconductor fine particle or a dispersion of semiconductor fine particles.
As a coating method, 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 are used. be able to.

When the wet process is used, it is necessary to fire the film formed by coating. The firing temperature in this case is preferably 400 ° C. or higher and 550 ° C. or lower, and more preferably 450 ° C. or higher and 500 ° C. or lower. If the firing temperature is less than 400 ° C., there is little fusion between the semiconductor fine particles, 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 conductive substrate 4 made of glass or the like, which is not preferable.
In addition, for example, an aqueous titanium tetrachloride solution is used from the viewpoint 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. A thin titanium oxide layer may be applied by chemical plating or electrochemical plating using a titanium trichloride aqueous solution.

  It is also effective to provide an undercoat layer between the semiconductor porous layer 5 and the transparent conductive substrate 4 from the viewpoint of suppressing leakage current due to direct contact between the electrolyte or the electrolytic solution 3 and the transparent conductive substrate 4. It is. The undercoat layer can be formed by using an alcohol solution of titanium alkoxide, an aqueous solution of titanium tetrachloride, an aqueous solution of peroxotitanic acid, a peroxotitanic acid-modified anatase-type titanium oxide aqueous sol, or an aqueous solution of peroxotitanic acid and an anatase-type oxidation of peroxotitanate. Titanium oxide compound mixture obtained by mixing with titanium aqueous sol, roller method, dipping method, air knife method, blade method, wire bar method, slide hopper method, extrusion method, curtain method, spin method, spray Examples thereof include a method of coating using various printing methods such as a printing method and screen printing, followed by drying and, if necessary, baking.

The light scattering layer 6 in the present embodiment is provided to effectively use incident light by returning incident light that has not been absorbed by the dye adsorbed to the semiconductor porous layer 5 to the semiconductor porous layer 5 again. is there.
The dye adsorbed on the semiconductor porous layer 5 substantially absorbs light in the wavelength range with a high absorption coefficient, but does not sufficiently absorb light in the wavelength range with a low absorption coefficient, and passes through the semiconductor porous layer 5. End up. Therefore, by providing the light scattering layer 6 on the semiconductor porous layer 5, the transmitted light is scattered by the light scattering layer 6 and returned to the semiconductor porous layer 5 again, and again by the dye adsorbed on the semiconductor porous layer 5. It can be absorbed.
As the light scattering layer 6, the same material as that used for the semiconductor porous layer 5 can be used. In particular, from the viewpoint of light scattering properties, the light scattering layer 6 is a porous layer formed from particles having a primary particle diameter of 100 nm to 500 nm, and the primary particle diameter is 30 nm or less. A porous layer having increased scattering properties is preferred.
The thickness of the light scattering layer 6 is preferably as thin as it can sufficiently reflect light and has no transmitted light. Specifically, the thickness of the light scattering layer 6 is preferably 0.5 μm or more and 10 μm or less, and more preferably 2 μm or more and 5 μm or less. If the thickness of the light scattering layer 6 is less than 0.5 μm, it is not preferable because the light cannot be sufficiently reflected and the incident light may be wasted. On the other hand, if the thickness of the light scattering layer 6 exceeds 10 μm, the portion not contributing to photoelectric conversion increases and the internal resistance may increase, which is not preferable.
The method for forming the light scattering layer 6 on the semiconductor porous layer 5 is not particularly limited, and the light scattering layer 6 can be formed using the same method as that for the semiconductor porous layer 5.

After the semiconductor porous layer 5 and the light scattering layer 6 are sequentially formed on the transparent conductive substrate 4 as described above, at least the semiconductor porous layer 5 (for example, the semiconductor porous layer 5) is added to the solution containing the dye and the organic acid. The semiconductor electrode 1 can be produced by immersing the layer 5 and the light scattering layer 6, or the transparent conductive substrate 4, the semiconductor porous layer 5 and the light scattering layer 6).
Further, in the case where a baking process is not required when forming the light scattering layer 6, after forming the semiconductor porous layer 5 on the transparent conductive substrate 4, at least the semiconductor porous layer is added to the solution containing the dye and the organic acid. The semiconductor electrode 1 is formed by immersing the porous layer 5 (for example, the semiconductor porous layer 5 or the transparent conductive substrate 4 and the semiconductor porous layer 5) and then forming the light scattering layer 6 on the semiconductor porous layer 5. Can also be produced.

  The dye that can be used in the solution containing the dye and the organic acid in the present embodiment is not particularly limited as long as it absorbs light, and various known dyes can be used. Specific examples of such a dye include metal complex salts containing one or more atoms of ruthenium, osmium, iron or zinc; metal-free phthalocyanines; porphyrins; so-called metal chelate complexes such as 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 and Crystal Violet Triphenylmethane dyes such as copper phthalocyanine or titanyl phthalocyanine metal phthalocyanines; 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. The dye is preferably capable of being chemically adsorbed to the semiconductor porous layer 5 and 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. preferable. Further, it is preferable that there are a plurality of such functional groups in the dye molecule.

  Among the above dyes, a ruthenium complex having a wide absorption range in the visible light region and high photoelectric conversion ability is more preferable. Examples of such ruthenium complexes include the following formula (1):

Cis-bis (isothiocyanato) bis (2,2'-bipyridyl-4,4'-dicarboxylate) ruthenium (II) bistetrabutylammonium (commonly referred to as N-719) represented by the following formula (2):

Cis-bis (isothiocyanato) bis (2,2'-bipyridyl-4,4'-dicarboxylate) ruthenium (II) (commonly known as N3) represented by the following formula (3):

Tris (isothiocyanato) -ruthenium (II) -2,2 ′, 6 ′, 2 ″ -terpyridine-4,4 ′, 4 ″ -tricarboxylic acid tristetrabutylammonium salt (commonly known as black dye) And the like. Among these, cis-bis (isothiocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium (II) bistetrabutyl of the formula (1) having the best photoelectric conversion efficiency and reproducibility Ammonium (common name N-719) is preferred.

Examples of organic acids that can be used in a solution containing a dye and an organic acid include carboxylic acids having a steroid skeleton such as cholic acid derivatives; carboxylic acids such as acetic acid, adamantaneacetic acid, cyclohexanecarboxylic acid, quinic acid, cyclohexylhydroxyacetic acid, and fatty acids; Examples thereof include compounds having a hydroxy group such as glucose, sorbitol, and glycerol.
As the carboxylic acid having the steroid skeleton, the following formula (4):

It is a derivative of cyclopentahydrophenanthrene having the basic skeleton. Among these derivatives, from the viewpoint of photoelectric conversion efficiency, the following formula (5):

A chenodeoxycholic acid having the following formula (6):

Deoxycholic acid having the following formula (7):

Cholic acid having the following formula (8):

Lysocholic acid having the following formula (9):

Ursodeoxycholic acid having the following formula (10):

Dehydrocholic acid and the like having is preferred.
The solvent that can be used in the solution containing the dye and the organic acid can be appropriately selected according to the solubility of the dye. Examples of such solvents include water, alcohols (such as methanol, ethanol, t-butanol and benzyl alcohol), nitriles (such as acetonitrile, propionitrile and 3-methoxypropionitrile), nitromethane, and halogenated carbonization. Hydrogen (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N, N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (such as ethyl acetate and butyl acetate), carbonates (such as diethyl carbonate, ethylene carbonate and propylene carbonate), ketones (acetone, 2 Butanone and cyclohexanone), hydrocarbons (hexane, petroleum ether, benzene and toluene, etc.). Such solvents can be used alone or in combination.

Since the optimum concentration of the dye and the organic acid in the solution containing the dye and the organic acid varies depending on the kind and solubility of the dye and the organic acid, the concentration may be appropriately adjusted according to the dye and the organic acid to be used. In a solution containing a dye and an organic acid, generally, the concentration of the organic acid is 0.1 to 100 times the dye concentration of 5 × 10 ⁻⁵ mol / L to 5 × 10 ⁻² mol / L. It is preferable to do. When the dye concentration is less than 5 × 10 ⁻⁵ mol / L, the dye may not be sufficiently adsorbed on the semiconductor porous layer 5. On the other hand, when the dye concentration exceeds 5 × 10 ⁻² mol / L, the dye may not be sufficiently dissolved in the solution. Further, if the concentration of the organic acid is less than 0.1 times, the effect of adding the organic acid may not be sufficiently obtained. On the other hand, when the concentration of the organic acid exceeds 100 times, the adsorption of the dye is excessively inhibited. As a result, the light absorption efficiency may be lowered and the photoelectric conversion efficiency may be lowered.
In particular, when a ruthenium complex is used as the dye and a cholic acid derivative is used as the organic acid, the concentration of the cholic acid derivative with respect to the ruthenium complex concentration of 5 × 10 ⁻⁵ mol / L or more and 5 × 10 ⁻⁴ mol / L or less. Is preferably 1 to 30 times.

  The method for preparing the solution containing the dye and the organic acid is not particularly limited, and the dye and the organic acid may be dissolved in the solvent using a conventionally known method and apparatus.

Since the time for immersing at least the semiconductor porous layer 5 in the solution containing the dye and the organic acid varies depending on the kind of the dye and the organic acid, it is necessary to appropriately set according to the kind of the dye and the organic acid to be used. It suffices if the time is sufficient for adsorption. In general, the immersion time is preferably 6 hours or more and 24 hours or less at 25 ° C.
Although not essential, at least when the semiconductor porous layer 5 is immersed in a solution containing a dye and an organic acid, from the viewpoint of improving the adsorption of the dye, the solution containing the dye and the organic acid is heated, It is also possible to make the solution acidic or basic.

After completion of the immersion, the semiconductor electrode 1 is obtained by pulling up at least the semiconductor porous layer 5 from the solution containing the dye and the organic acid, washing and drying. Here, the washing and drying methods are not particularly limited. For example, after washing the non-adsorbed dye using a solvent containing a solution containing the dye and the organic acid, and drying at room temperature. Good.
In the semiconductor electrode 1 thus manufactured, the dye is adsorbed on the semiconductor porous layer 5. When the light scattering layer 6 is immersed in a solution containing a dye and an organic acid, the light scattering layer 6 may be adsorbed with the dye. In this case, in the light scattering layer 6, the amount of light that has not been absorbed by the adsorbing dye is scattered and returned to the semiconductor porous layer 5.
In addition, it is not clear in what state the organic acid exists in the semiconductor porous layer 5. However, such an organic acid is present between the dye molecules adsorbed on the semiconductor porous layer 5 and is considered to prevent the electrons generated in the dye from being lost by combining with the oxidant of the adjacent dye. It is done. As a result, in the dye-sensitized solar cell using such a semiconductor electrode 1, the photoelectric conversion efficiency can be improved by reducing the disappearance of electrons generated by light absorption of the dye and improving the electromotive force and the current density. Conceivable.

(Counter electrode 2)
As the counter electrode 2 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 conductor layer in the counter electrode 2, the same materials as the transparent substrate and conductor layer used in the semiconductor electrode 1 can be used. In addition to the materials exemplified above, it is effective to use a material having high catalytic activity as 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 and the like, 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 supporting catalytically active materials such as platinum, nanocarbon materials, polythiophene derivatives such as PEDOT-TsO Examples thereof include a polymer material and a polymer complex catalyst. Among these, platinum, a carbon material, a catalyst-supporting nanocarbon material, and the like are preferable in that they are hardly attacked by the electrolyte or the electrolytic solution 3 and have high catalytic activity.

(Electrolyte or electrolyte 3)
The electrolyte or electrolytic solution 3 in the present embodiment is not particularly limited, and various conventionally known ones can be used. Examples of the electrolyte or the electrolytic solution 3 include an electrolyte solution in which ions of a redox couple as an ion transport material are dissolved, a so-called gel electrolyte in which a solution of the redox couple is impregnated in a polymer matrix gel, and the redox couple. Examples include molten salt electrolytes containing ions, and solid electrolytes.
Here, as the ion transport material, a redox agent generally used for an electrolyte of a dye-sensitized solar cell can be arbitrarily used. Specifically, as such an ion transport material, a combination of I ₂ and iodide (as iodide, metal iodide such as LiI, NaI, KI, CsI, CaI ₂ , tetraalkylammonium iodide, pyridinium, etc.) Iodide, iodine salt of quaternary ammonium compound such as imidazolium iodide, etc., combination of Br ₂ and bromide (as bromide, bromide, metal bromide such as LiBr, NaBr, KBr, CsBr, CaBr ₂ or tetraalkyl) Quaternary ammonium compounds such as ammonium bromide and pyridinium bromide), metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ion, sodium polysulfide, alkylthiol-alkyl disulfide, etc. Sulfur compounds of A viologen dye, hydroquinone-quinone, or 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. Such ion transport materials may be used alone or in combination. Among these, a combination of I ₂ and an iodine salt of a quaternary ammonium compound such as LiI, pyridinium iodide or imidazolium iodide is more preferable.

The concentration of the ion transport material in the electrolyte or the electrolytic solution 3 is preferably 0.1 M or more and 15 M or less, and more preferably 0.2 M or more and 10 M or less. If the concentration of the ion transport material is less than 0.1M, the conductivity tends to decrease, which is not preferable. On the other hand, if the concentration of the ion transport material 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 electrolyte or the electrolyte solution 3, it is preferable that the addition density | concentration of an iodine is 0.01 M or more and 5.0 M or less. 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 in the electrolyte or electrolyte 3 is an organic solvent in which the dye supported on the semiconductor porous layer 5 is difficult to dissolve, is electrochemically stable, and does not generate gas due to an electrochemical reaction. preferable. Examples of such solvents include acetonitrile, methoxypropionitrile, methoxyacetonitrile, propylene carbonate, ethylene carbonate and methyl pyrrolidone, ethyl acetate or tetrahydrofuran, water, alcohol and mixtures thereof.
Moreover, molten salt can also be used as a solvent or electrolyte solution in the electrolyte or electrolyte solution 3. Such a molten salt is more preferable from the viewpoint of achieving both photoelectric conversion efficiency and durability. Examples of such molten salt electrolytes include pyridinium described in WO95 / 18456 pamphlet, JP-A-8-259543, Electrochemical Vol.65, No.11, p.923 (1997), etc. Examples thereof include known iodine salts such as salts, imidazolium salts and triazolium salts.

  In the present embodiment, the electrolyte or electrolytic solution 3 can be used after being gelled. Examples of gelation methods include polymer addition, oil gelling agent addition, polymerization including polyfunctional monomers, addition of a polymer by techniques such as a crosslinking reaction, and addition of nanoparticles. For example, when gelling by adding an oil gelling agent, it is preferable to use a compound having an amide structure in the molecular structure. Moreover, when making it gelatinize by a crosslinking reaction etc., polyacrylonitrile and polyvinylidene fluoride can be used. Further, in the case of gelation by polymerization of polyfunctional monomers, a sol-like electrolyte or electrolytic solution 3 is formed on the light scattering layer 6 from a solution composed of polyfunctional monomers, a polymerization initiator, an ion transport material, and a solvent. Then, a method of gelling by radical polymerization is preferable.

In the present embodiment, instead of the electrolyte or the electrolytic solution 3, a charge transporting material that is organic or inorganic, or a combination of both can be used.
Examples of organic hole transport materials that can be used in the present invention include aromatic amine compounds such as triphenylamine, diphenylamine, and phenylenediamine, condensed polycyclic hydrocarbons such as naphthalene, anthracene, and bilen, azo compounds such as azobenzene, and stilbene. Compounds having a structure in which the aromatic rings are linked by ethylene bonds or acetylene bonds, heteroaromatic compounds substituted by amino groups, porphyrins, phthalocyanines, α-octylthiophene, α, ω-dihexyl-α-octylthiophene Oligothiophene compounds such as hexadodecyl dodecithiophene, polypyrrole, polyacetylene and derivatives thereof, poly (p-phenylene) and derivatives thereof, poly (p-phenylene vinylene) and derivatives thereof, polythienylene vinylene and derivatives thereof, polythiophene and Derivatives, polyaniline and derivatives thereof, conductive polymers such as poly-toluidine and derivatives thereof can be used.
Examples of the organic electron transporting material that can be used in the present invention include quinones, tetracyanoquinodimethanes, dicyanoquinone diimines, tetracyanoethylene, viologens, dithiol metal complexes, and the like.

In addition, in order to control the dopant level, the organic hole transport material may be added with a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate, or the potential of the oxide semiconductor surface. A salt such as Li [(CF ₃ SO ₂ ) ₂ N] can also be added for control (space charge layer compensation). In addition, CuI, AgI, TiI, and other metal iodides, CuBr, CuSCN, and the like can be used as inorganic materials.
In order to improve the performance, basic compounds such as ter-butylpyridine, 2-picoline, and 2,6-lutidine can also be added (J. Am. Ceram. Soc., 80 (12) 3157-). 3171 (1997)). A preferable concentration range when adding the basic compound is 0.05M or more and 2M or less.

(Dye-sensitized solar cell)
The method for producing the dye-sensitized solar cell in the present embodiment is not particularly limited except that the semiconductor electrode 1, the counter electrode 2, and the electrolyte or the electrolytic solution 3 are used, and may be performed according to a conventionally known method. . Specifically, after the semiconductor electrode 1 and the counter electrode 2 are bonded together, a liquid electrolyte or an electrolytic solution 3 is injected into the gap and sealed; the counter electrode having a hole formed on the semiconductor electrode 1 A method of injecting an electrolyte or an electrolytic solution 3 from a hole of the counter electrode 2 and sealing the injection port after the 2 is bonded and sealed with a sealing material; the electrolyte or the electrolytic solution 3 is directly applied on the semiconductor electrode 1 After the application, a method of bonding the counter electrode 2 on the surface can be used.
In addition, when injecting the electrolyte or the electrolytic solution 3, a normal pressure process using a capillary phenomenon due to immersion or the like, or a pressure lower than the normal pressure is used to replace the gas phase between the electrodes or in the porous film with the liquid phase. A vacuum process can also be used.

On the other hand, when a gel electrolyte is used as the electrolyte or the electrolyte solution 3 or when a solution of an organic charge transport material is used instead of the electrolyte or the electrolyte solution 3, a method for forming the semiconductor porous layer 5, or the semiconductor porous layer 5 is used. Similar to the method of adsorbing the dye on the surface, the dipping method, roller method, dipping method, air knife method, extrusion method, slide hopper method, wire bar method, spin method, spray method, casting method, various printing methods, etc. Good.
In addition, when a solid electrolyte is used as the electrolyte or the electrolytic solution 3 or when an organic hole transport material is used instead of the electrolyte or the electrolytic solution 3, a dry film forming process such as a vacuum deposition method or a CVD method, a plating method, The electrolyte or electrolytic solution 3 can be formed on the counter electrode 2 by wet treatment such as electrolytic polymerization, and then bonded to the semiconductor electrode 1.

  Further, from the viewpoint of reducing the resistance of the semiconductor electrode 1 and the counter electrode 2, a collector electrode made of a metal wiring pattern may be formed on each electrode. As the material for the collector electrode, metals such as aluminum, silver, gold, platinum, nickel, tungsten and the like are preferable. The collector electrode is preferably formed on the transparent conductive substrate 4 by vapor deposition, sputtering, plating, or the like, and a conductor layer is formed thereon. Alternatively, the collector electrode may be formed on the conductor layer after the conductor layer is formed on the transparent substrate. From the viewpoint of conductivity, in particular, gold, silver, copper, nickel and tungsten are more preferable, but it is preferable to avoid direct contact with the electrolyte or the electrolytic solution 3, and a collector electrode is provided under the sealing material, It is preferable to provide a corrosion prevention layer made of a metal oxide or polymer.

  Furthermore, it is preferable to seal the gap between the semiconductor electrode 1 and the counter electrode 2 with a sealant. Although it does not restrict | limit especially as a sealing agent, 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)
A titanium oxide paste (Tinanoxide T manufactured by Solaronix) was applied onto a fluorine-doped tin oxide transparent conductive substrate (manufactured by Asahi Glass) by a squeegee method and dried, followed by firing (firing temperature 400 ° C., firing time 30 minutes) did. Next, the above titanium oxide paste is applied again by the squeegee method, dried, and then fired (firing temperature: 400 ° C., calcining time: 30 minutes) by repeating twice the process of semiconductor porous having a thickness of about 10 μm. Layers were formed. Next, a titanium oxide paste (SP-100 manufactured by Showa Denko) that forms an opaque film with high light scattering properties is applied onto the semiconductor porous layer and dried, followed by firing (firing temperature 480 ° C., firing time). 30 minutes), a light scattering layer having a thickness of about 9 μm was formed.
Ruthenium 535-bisTBA (cis-bis (isothiocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium (II) bistetrabutylammonium) 0.3 mmol / L, manufactured by Solaronix A 0.25 to 2.5 mmol / L t-butanol / acetonitrile solution of deoxycholic acid was prepared. The semiconductor porous layer and the light scattering layer were immersed in this dye solution at 25 ° C. for 18 hours, and then washed with acetonitrile and dried to prepare a semiconductor electrode. Further, a semiconductor electrode prepared by immersing the semiconductor porous layer and the light scattering layer in a dye solution not containing deoxycholic acid was prepared as a control for this example. Since the color of the semiconductor porous layer of the prepared semiconductor electrode became thinner as the amount of deoxycholic acid added to the dye solution increased, the amount of dye adsorbed on the semiconductor porous layer of the semiconductor electrode It is believed that it decreases as the amount of deoxycholic acid formulated increases.

(Preparation of dye-sensitized solar cell)
As the counter electrode, a fluorine-doped tin oxide transparent conductive substrate obtained by sputtering platinum with a thickness of about 100 nm was used. Further, as an electrolyte or electrolytic solution, the 1M LiI, _I 2 of 0.05 M, 4-tert-butylpyridine 0.5M, of 0.5M 1,2-dimethyl-1,3-propyl imidazolium iodide An electrolytic solution consisting of a methoxyacetonitrile solution was used.
A dye-sensitized solar cell was produced by laminating a spacer film between the semiconductor electrode and the counter electrode and injecting an electrolyte solution through a gap between the semiconductor electrode and the counter electrode.

[Comparative Example 1]
No light scattering layer is provided on the semiconductor porous layer, the firing temperature of the semiconductor porous layer is 480 ° C., and Ruthenium 535-bisTBA (cis-bis (isothiocyanato) bis (2,2) manufactured by Solaronix '-Bipyridyl-4,4'-dicarboxylate) ruthenium (II) bistetrabutylammonium) except using 0.3 mmol / L, deoxycholic acid 0-3 mmol / L t-butanol / acetonitrile solution Produced a dye-sensitized solar cell in the same manner as in the example.

In the dye-sensitized solar cells obtained in Example 1 and Comparative Example 1, the photoelectric conversion elements were evaluated.
In the evaluation of such a photoelectric conversion element, a solar simulator (Yamashita Denso, YSS-50A, air mass 1.5, light intensity 100 mW / cm ² ) was used as a light source, and a Solartron SI1280B electrochemical measurement device was used as an evaluation device. The evaluation results are shown in FIG.

FIG. 2 is a graph showing the relationship between the photoelectric conversion efficiency of the dye-sensitized solar cell and the concentration of the organic acid in the solution containing the dye and the organic acid.
As shown in FIG. 2, in the dye-sensitized solar cell of Comparative Example 1, even when an organic acid is added, the photoelectric conversion efficiency is not improved. Conversely, as the concentration of the organic acid increases, the photoelectric conversion efficiency increases. Conversion efficiency decreased. This is considered due to a decrease in the amount of light absorption accompanying a decrease in the amount of adsorbed dye in the semiconductor porous layer.
On the other hand, in the dye-sensitized solar cell of Example 1, the photoelectric conversion efficiency was improved by adding an organic acid. In Example 1, (1) Although the amount of adsorbed dye decreases and the amount of light absorption decreases as in Comparative Example 1, transmitted light that is not absorbed by the semiconductor porous layer is reflected by the light scattering layer. Since it is returned to the semiconductor porous layer again and absorbed, the decrease in the amount of light absorption is suppressed, and (2) the loss due to the leakage current of generated electrons is reduced by the decrease in the amount of adsorbed dye in the semiconductor porous layer. As a result, it is considered that the photoelectric conversion efficiency was improved as a result.

[Example 2]
Except that the thickness of the light scattering layer was adjusted to about 5 μm, the total thickness (semiconductor porous layer and light scattering layer) was about 15 μm, and the deoxycholic acid concentration of the dye solution was 1 mmol / L, A dye-sensitized solar cell was produced in the same manner as in Example 1.
[Example 3]
The optical scattering layer paste (Tinanoxide 300 manufactured by Solaronix) with a primary particle size of 300 nm is used to form the light scattering layer, and the thickness of the light scattering layer is adjusted to about 5 μm (semiconductor porous) The dye-sensitized solar cell was prepared in the same manner as in Example 1 except that the thickness of the layer and the light scattering layer was about 15 μm, and the deoxycholic acid concentration of the dye solution was 1 mmol / L.

[Comparative Example 2]
A dye-sensitized solar cell was produced in the same manner as in Comparative Example 1 except that the thickness of the semiconductor porous layer was about 15 μm and no deoxycholic acid was added to the dye solution.
[Comparative Example 3]
A dye-sensitized solar cell was produced in the same manner as in Comparative Example 1 except that the thickness of the semiconductor porous layer was about 15 μm and the deoxycholic acid concentration in the dye solution was 1 mmol / L.
[Comparative Example 4]
A dye-sensitized solar cell was produced in the same manner as in Example 3 except that deoxycholic acid was not added to the dye solution.
In the dye-sensitized solar cells of Examples 2 and 3 and Comparative Examples 2 to 4, the photoelectric conversion elements were evaluated in the same manner as in Example 1. The results are shown in Table 1.

As shown in Table 1, the dye-sensitized solar cells of Examples 2 and 3 including a semiconductor electrode having a light scattering layer, which was prepared using a dye solution to which deoxycholic acid was added, To the dye-sensitized solar cells of Comparative Examples 2 and 3 that do not have a light scattering layer, and the dye-sensitized solar cell of Comparative Example 4 that is manufactured using a dye solution to which deoxycholic acid is not added Compared with the photoelectric conversion efficiency.
As can be seen from the above results, according to the method for producing a dye-sensitized solar cell of the present invention, there is no problem that the amount of light absorption decreases with a decrease in the amount of adsorbed dye in the semiconductor porous layer. By reducing the disappearance of electrons generated by light absorption of the dye and improving the electromotive force and current density, a dye-sensitized solar cell with improved conversion efficiency can be obtained.

It is a cross-sectional schematic diagram of the dye-sensitized solar cell manufactured in this Embodiment. It is a figure which shows the relationship of the photoelectric conversion efficiency of the dye-sensitized solar cell with respect to the density | concentration of the organic acid in the solution containing a pigment | dye and an organic acid.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Semiconductor electrode, 2 Counter electrode, 3 Electrolyte or electrolyte solution, 4 Transparent conductive substrate, 5 Semiconductor porous layer, 6 Light-scattering layer.

Claims (5)

In a method for producing a dye-sensitized solar cell comprising a semiconductor electrode, a counter electrode facing the semiconductor electrode, and an electrolyte or an electrolyte solution sandwiched between the semiconductor electrode and the counter electrode,
A semiconductor porous layer and a light scattering layer are sequentially formed on a transparent conductive substrate, and then the semiconductor electrode is produced by immersing at least the semiconductor porous layer in a solution containing a dye and an organic acid. A method for producing a dye-sensitized solar cell.   The method for producing a dye-sensitized solar cell according to claim 1, wherein the semiconductor porous layer contains titanium oxide.   The method for producing a dye-sensitized solar cell according to claim 1 or 2, wherein the dye is a ruthenium complex.   4. The ruthenium complex is cis-bis (isothiocyanato) bis (2,2′-bipyridyl-4,4′-dicarboxylate) ruthenium (II) bistetrabutylammonium. A method for producing a dye-sensitized solar cell.   The method for producing a dye-sensitized solar cell according to any one of claims 1 to 4, wherein the organic acid is a carboxylic acid having a steroid skeleton.

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