JP2006127782A - Metal-metal oxide composite electrode, manufacturing method therefor, and photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metal-metal oxide composite electrode having an excellent industrial productivity and a uniform and sufficient surface roughness, and to provide a dye-sensitized photoelectric conversion device having a large photoelectric current by adsorbing the sensitization dye on the metal-metal oxide composite oxide electrode. <P>SOLUTION: A metal selected from among titanium, tantalum, niobium, tungsten and zirconium, or an alloy consisting of mainly the metals, is electrolytically oxidized in an electrolyte solution containing ions including halogen atoms, and thereby the metal-metal oxide composite electrode having the uniform and sufficient roughness can be manufactured and the dye-sensitized photoelectric conversion device having the large photoelectric current is obtained using the composite electrode. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a metal-metal oxide composite electrode, a manufacturing method thereof, and a photoelectric conversion element including the metal-metal oxide composite electrode manufactured by the method.

  Photoelectric conversion elements are used in various sensors, copiers, photovoltaic devices and the like. Various systems such as those using metals, semiconductors, organic pigments and dyes, and combinations thereof have been put to practical use as photoelectric conversion elements.

For example, a dye-sensitized solar cell announced by Gretzell et al. In 1991 is a wet solar cell using a titania porous thin film spectrally sensitized with a ruthenium complex as a working electrode, and can perform as high as a silicon solar cell. Has been reported (see Non-Patent Document 1). According to this technology, inexpensive oxide semiconductor fine particles such as titania are formed on a transparent electrode that is a support, and a film is formed. By simply adsorbing a dye, an excellent photoelectric conversion element is obtained. There is an advantage that a photoelectric conversion element can be provided.
By Oregan et al., “Nature”, 1991, Vol. 353, p. 737-739

  However, the adhesion between the oxide semiconductor fine particles and the transparent electrode is not necessarily high, and there has been a problem in peeling and electrical bonding of the oxide semiconductor fine particles. On the other hand, an electrolytic oxidation method is known in which a metal is used as an anode and an arbitrary conductive material is used as a cathode in various aqueous solutions, and a metal is electrochemically oxidized to form the oxide on the surface. It has been. When electrolytic oxidation is used, the adhesion between the substrate and the oxide is strong, and electrical bonding is excellent. Even when the conductive substrate is large in area, the deposition rate is faster than other oxide film manufacturing methods. There is an advantage that the film can be formed uniformly. However, when this technique is applied to metals such as titanium, tantalum, niobium, tungsten, and zirconium suitable as oxide semiconductor electrodes, a strong oxide film can be obtained, but the ratio of the surface area to the projected area, that is, the surface roughness is small. There was a problem that only a small photocurrent could be taken out.

  The present invention has been made in view of such a situation, and has excellent industrial productivity, uniform and sufficient surface roughness, a metal-metal oxide composite electrode, a method for producing the same, and the metal-metal. Provided is a dye-sensitized photoelectric conversion element having a large photocurrent using an oxide composite electrode.

  That is, the present invention is characterized in that a metal selected from titanium, tantalum, niobium, tungsten and zirconium, or an alloy mainly containing these metals is electrolytically oxidized in an electrolyte solution containing an ion containing a halogen atom. The present invention relates to a method for producing a metal-metal oxide composite electrode.

The present invention also relates to the above-described method for producing a metal-metal oxide composite electrode, wherein the halogen atom is a chlorine atom.
The present invention also relates to the above-described method for producing a metal-metal oxide composite electrode, wherein perchloric acid is contained in the electrolyte solution.

The present invention also relates to the above-described method for producing a metal-metal oxide composite electrode, wherein a titanium-titanium oxide composite electrode is produced by electrolytic oxidation of titanium or an alloy containing titanium.
The present invention also relates to the above-described method for producing a metal-metal oxide composite electrode, wherein the maximum applied voltage during electrolytic oxidation is 14 V or more.

  The present invention also relates to a metal-metal oxide composite electrode produced by the method described above.

  Furthermore, the present invention relates to a dye-sensitized photoelectric conversion element comprising a metal-metal oxide composite electrode produced by the method described above, a dye, and a charge transport material.

Hereinafter, the present invention will be described in detail.
The metal used for the metal-metal oxide composite electrode of the present invention is a metal selected from titanium, tantalum, niobium, tungsten and zirconium. These may be a single metal or an alloy.
In the case of using an alloy, it is preferable to use an element that largely elutes under the conditions of electrolytic oxidation for elements other than titanium, tantalum, niobium, tungsten and zirconia contained in the alloy. The proportion of titanium, tantalum, niobium, tungsten and zirconia in the alloy is preferably 30% by weight or more, more preferably 50% by weight or more, and most preferably 70% by weight or more.

  When the purpose of using the metal-metal oxide composite electrode is a dye-sensitized photoelectric conversion element, titanium is particularly preferable as the metal, and an alloy containing titanium is particularly preferable as the alloy. As titanium or an alloy thereof, industrial pure titanium prepared with oxygen, iron, nitrogen, or hydrogen, or a low alloy titanium alloy having a certain degree of press formability can be used. JIS (Japanese Industrial Standard) 1 type, 2 types, 3 types, 4 types of various industrial pure titanium, alloys with improved corrosion resistance by adding nickel, ruthenium, tantalum, palladium, etc., aluminum, vanadium, molybdenum, tin, iron, chromium, niobium An example of such an alloy is that an alloy is added. As for the shape, in addition to various shapes such as titanium or its alloy plates, rods, meshes, etc., the plate, rods, meshes, etc. grown on titanium or its alloys as a film on the surface of different types of conductive materials, plates However, the present invention is not limited to these. Examples include, but are not limited to, those obtained by growing titanium or an alloy thereof as a film on the surface of a semiconductor or insulating material such as a rod or mesh. Regarding surface smoothness, titania can be grown in the electrolytic oxidation process even if the surface structure has a complicated shape, and the smoothness is not limited.

In the present invention, electrolytic oxidation is a technique in which a metal or an alloy thereof is used as an anode in an electrolyte solution, an arbitrary conductive material is used as a cathode, and an oxide is formed on the surface of the anode by applying a voltage. In addition, the state in which the metal or its alloy is the anode is sufficient even once, and includes the case where the anode and the cathode are alternately performed.
In the electrolytic oxidation, the applied voltage is usually 5 to 200 V, preferably 10 to 150 V, more preferably 14 V to 110 V. Current density 0.2~500mA / cm ^2, preferably in the range of 0.5~100mA / cm ^2, ~24 hours 1 minute, preferably takes place 5 minutes to 10 hours.
Moreover, 0-50 degreeC is preferable and, as for the temperature of the electrolyte solution at the time of anodizing, More preferably, it is 0-40 degreeC.

  The electrolyte solution used for the electrolytic oxidation needs a dissolving power capable of dissolving the metal or its alloy when the metal or its alloy is subjected to anodic polarization. It is essential that the electrolyte solution used in the present invention contains an ion containing a halogen atom. The ion containing a halogen atom here is an ion containing any atom of fluorine, chlorine, bromine and iodine, specifically, fluoride ion, chloride ion, bromide ion, iodide ion, Examples include perchlorate ion, chlorate ion, bromate ion, iodate ion, chlorite ion, bromite ion, hypochlorite ion, hypobromite ion, hypoiodite ion and the like. These ions may be used alone or as a mixture of two or more.

The electrolyte solution containing these ions can be either aqueous or non-aqueous, but is preferably aqueous. Specifically, an aqueous solution of an acid or salt that forms ions containing a halogen atom is used. The concentration of the acid or salt is preferably 0.0001 to 10% by volume, more preferably 0.0005 to 5% by volume, and still more preferably 0.0005 to 1% by volume.
In the present invention, a chlorine atom is preferable as the halogen atom, and a perchloric acid aqueous solution is particularly preferable as the electrolyte solution.

The electrolyte solution may contain an acidic compound different from the acid or salt that forms ions containing halogen atoms. By containing such different kinds of acidic compounds, the reaction rate can be controlled, such as promoting or suppressing the anodic oxidation rate.
Examples of such acidic compounds include sulfuric acid, nitric acid, acetic acid, hydrogen peroxide, oxalic acid, phosphoric acid, chromic acid, glycerophosphoric acid and the like in addition to the above-mentioned halide or acid of its oxidant ion. Is not to be done. The concentration is preferably 0.001 to 1000, more preferably 0.01 to 50, and still more preferably 0.04 to 5 in terms of molar ratio to the halogen atom-containing ions.

  By the above method, a metal-metal oxide composite electrode having a sufficient surface roughness can be obtained. The shape of the metal oxide to be obtained can be various, such as a sponge shape and a tube shape, depending on the electrolytic oxidation conditions, the type of electrolyte, and the concentration.

  If necessary, the obtained metal-metal oxide composite electrode can be subjected to post-treatment such as heat treatment, water vapor treatment, and ultraviolet irradiation to grow a crystal structure of the metal oxide. For example, in the case of heat treatment, the crystallinity is improved by performing the treatment at a temperature of 100 ° C. to 1200 ° C. for 10 minutes to 500 minutes, preferably at a temperature of 300 ° C. to 800 ° C. for 30 minutes to 160 minutes. Can be expected. By these treatments, the structure does not collapse.

  An oxide semiconductor may be further formed on the obtained metal-metal oxide composite electrode. As a method for forming an oxide semiconductor, a vapor deposition method such as a vacuum deposition method, a chemical deposition method, or a sputtering method, a liquid phase method such as a spin coating method, a dip coating method, or a liquid phase growth method, a thermal spraying method, or a solid phase method. Examples include a solid phase method such as a method using a reaction, a heat treatment method, and a method of applying a semiconductor fine particle colloid.

  The particle size of the semiconductor fine particles is generally on the order of nm to μm, but the particle size of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably 5 to 200 nm, more preferably 8 to 100 nm. The average particle size of the secondary particles in the dispersion is preferably 0.01 to 10 μm.

  Examples of preferred coating methods include roller methods, dip methods, etc. as application systems, air knife methods, blade methods, etc. as metering systems, and wire bar methods, slide hopper methods, etc., as applications and metering can be made the same part. Examples include the extrusion method and the curtain method. Moreover, a spin method and a spray method are also preferable as a general purpose machine. As the wet printing method, intaglio, rubber plate, screen printing and the like are preferred, including the three major printing methods of letterpress, offset and gravure. A film forming method may be selected from these according to the liquid viscosity and the wet thickness.

  After coating the semiconductor fine particles on the metal-metal oxide composite electrode, heating is performed to improve the electrical contact between the semiconductor fine particles and to improve the coating strength and the adhesion with the metal-metal oxide composite electrode. It is preferable to process. In the heat treatment, the treatment is performed at a temperature of 100 ° C. to 1200 ° C. for 10 minutes to 500 minutes, preferably at a temperature of 300 ° C. to 800 ° C. for 30 minutes to 160 minutes.

  After heat treatment, chemical plating treatment using titanium tetrachloride aqueous solution, electrochemical plating treatment using titanium trichloride aqueous solution, or crystal liquid using aqueous solution containing titanium fluoride, ammonium hexafluorotitanate, titanyl sulfate By performing the phase growth, the adhesion between the semiconductor fine particles and between the metal-metal oxide composite electrode and the semiconductor fine particles can be further improved.

  The metal-metal oxide composite electrode produced as described above can be preferably used for a dye-sensitized photoelectric conversion element. The dye-sensitized photoelectric conversion element preferably has a configuration in which a conductive layer 1, a photosensitive layer 2, a charge transport layer 3, and a transparent counter electrode conductive layer 4 are laminated in this order as shown in FIG. In the present invention, the metal portion of the metal-metal oxide composite electrode is used for the conductive layer 1, and the metal oxide portion of the metal-metal oxide composite electrode is used for the photosensitive layer 2. In order to impart strength to the photoelectric conversion element, a transparent substrate 5 may be provided as a base of the transparent conductive layer 4. In the present invention, the layer composed of the counter electrode conductive layer 4 and the optional substrate 5 is called a counter electrode, and the counter electrode needs to be transparent. Among such photoelectric conversion elements, a photovoltaic cell is connected to an external load in order to generate power, and a photoelectric sensor is a sensor made for the purpose of sensing optical information. Among photovoltaic cells, those in which the charge transport material is mainly composed of an ion transport material are called photoelectrochemical cells, and those whose main purpose is power generation by sunlight are called solar cells.

  In the photoelectric conversion element shown in FIG. 1, light incident on the photosensitive layer 2 containing a metal oxide sensitized by a dye excites the dye and the high-energy electrons in the excited dye and the like are conducted by the metal oxide. It is passed to the body and further diffuses to reach the conductive layer 1. At this time, the dye is an oxidant. In the photovoltaic cell, electrons in the conductive layer 1 return to the oxidant of the dye through the transparent counter electrode conductive layer 4 and the charge transport layer 3 while working in the external circuit, and the dye is regenerated. The photosensitive layer 2 serves as an anode, and the transparent counter electrode conductive layer 4 serves as a cathode. The constituent components of each layer may be diffused and mixed with each other at the boundary between the layers.

  In the metal-metal oxide composite electrode, by adsorbing an appropriate sensitizing dye, the metal portion becomes a conductive layer and the metal oxide portion becomes a photosensitive layer. In the photosensitive layer, the dye-sensitized metal oxide acts as a photoconductor, absorbs light, separates charges, and generates electrons and holes. Light absorption and the generation of electrons and holes thereby occur mainly in the dye, and the metal oxide plays a role in receiving and transmitting these electrons. That is, a metal oxide is an n-type semiconductor that provides an anode current due to conductor electrons under photoexcitation.

  The metal oxide used for the photosensitive layer may be treated with a solution of a metal compound. Examples of the metal compound include scandium, yttrium, lanthanoid, hafnium, niobium, tantalum, gallium, indium, germanium, aluminum, zinc, strontium, tungsten, zirconium, and metal alkoxides and halides. it can. The solution of the metal compound is usually an aqueous solution or an alcohol solution. The treatment refers to an operation of bringing the metal oxide into contact with the solution for a certain period of time before adsorbing the pigment to the metal oxide. The metal compound may or may not be adsorbed on the metal oxide after contact. As a specific method for the treatment, a method in which a metal oxide is immersed in the solution is given as a preferred example. Further, a method in which the solution is sprayed for a predetermined time can be applied. Although the temperature of the solution at the time of immersion is not specifically limited, Typically, it is -10-70 degreeC, Preferably it is 0-40 degreeC. The immersion time is not particularly limited, and is typically 1 minute to 24 hours, preferably 30 minutes to 15 hours. After the immersion, the metal oxide may be washed with a solvent such as water. Moreover, you may heat in order to strengthen the coupling | bonding of the substance adhering to the metal semiconductor by immersion or a spray process. The heating conditions may be set similarly to the above-described conditions.

  The sensitizing dye used in the photosensitive layer is not particularly limited as long as it has absorption characteristics in the visible region and near infrared region and can sensitize the semiconductor, but metal complex dyes, organic dyes, natural dyes, and semiconductors are preferable. Those having a functional group such as carboxyl group, hydroxyl group, sulfonyl group, phosphonyl group, carboxylalkyl group, hydroxyalkyl group, sulfonylalkyl group, phosphonylalkyl group in the molecule of the dye are preferably used. As the metal complex dye, a complex of ruthenium, osmium, iron, cobalt, zinc, mercury (for example, mellicle chromium), metal phthalocyanine, chlorophyll, or the like can be used. Examples of organic dyes include, but are not limited to, cyanine dyes, hemicyanine dyes, merocyanine dyes, xanthene dyes, triphenylmethane dyes, metal-free phthalocyanine dyes, and the like. As a semiconductor that can be used as a dye, an amorphous semiconductor having a large i-type light absorption coefficient, a direct transition semiconductor, or a fine particle semiconductor that exhibits a quantum size effect and efficiently absorbs visible light is preferable. Usually, one of various semiconductors, metal complex dyes and organic dyes, or two or more kinds of dyes can be mixed in order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency. Further, the dye to be mixed and its ratio can be selected so as to match the wavelength range and intensity distribution of the target light source.

  As a method for attaching the dye to the metal oxide, a solution in which the dye is dissolved in a solvent is applied on the metal oxide by spray coating, spin coating, or the like, and then dried. In this case, the substrate may be heated to an appropriate temperature. Alternatively, a method in which a metal oxide is immersed in a solution and adsorbed can be used. The immersion time is not particularly limited as long as the dye is sufficiently adsorbed, but is preferably 10 minutes to 30 hours, more preferably 10 minutes to 20 hours. Moreover, you may heat a solvent and a board | substrate when immersing as needed. The concentration of the dye in the case of a solution is preferably about 1 to 1000 mmol / L, preferably about 10 to 500 mmol / L.

  The solvent to be used is not particularly limited, but water and an organic solvent are preferably used. Examples of the organic solvent include alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and t-butanol, acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, and the like. Nitriles, aromatic hydrocarbons such as benzene, toluene, o-xylene, m-xylene and p-xylene, aliphatic hydrocarbons such as pentane, hexane and heptane, alicyclic hydrocarbons such as cyclohexane, acetone and methyl ethyl ketone , Ketones such as diethyl ketone and 2-butanone, ethers such as diethyl ether and tetrahydrofuran, ethylene carbonate, propylene carbonate, nitromethane, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoa , Dimethoxyethane, γ-butyrolactone, γ-valerolactone, sulfolane, dimethoxyethane, adiponitrile, methoxyacetonitrile, dimethylacetamide, methylpyrrolidinone, dimethyl sulfoxide, dioxolane, sulfolane, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, Ethyl dimethyl phosphate, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, tris phosphate (trifluoromethyl), tris phosphate (pentafluoro) Ethyl), triphenyl polyethylene glycol phosphate, polyethylene glycol and the like.

  In order to reduce the interaction such as aggregation between the dyes, a colorless compound having properties as a surfactant may be added to the dye adsorbing solution and co-adsorbed on the metal oxide. Examples of such colorless compounds include steroid compounds such as cholic acid having a carboxyl group or sulfo group, deoxycholic acid, chenodeoxycholic acid, taurodeoxycholic acid, sulfonates, and the like.

  It is preferable to remove the unadsorbed dye by washing immediately after the adsorption step. Washing is preferably performed using acetonitrile, an alcohol solvent or the like in a wet washing tank.

  After adsorbing the dye, a metal using an amine, a quaternary ammonium salt, a ureido compound having at least one ureido group, a silyl compound having at least one silyl group, an alkali metal salt, an alkaline earth metal salt, etc. The oxide surface may be treated. Examples of preferred amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like. Examples of preferable quaternary ammonium salts include tetrabutylammonium iodide and tetrahexylammonium iodide. These may be used by dissolving in an organic solvent, or may be used as they are in the case of a liquid.

  The charge transport layer contains a charge transport material having a function of replenishing electrons to the oxidant of the dye. The charge transport material used in the present invention may be a charge transport material related to ions or a charge transport material related to carrier movement in a solid. Examples of the charge transport material in which ions are involved include a solution in which a redox counter ion is dissolved, a gel electrolyte composition in which a polymer matrix gel is impregnated with a solution of a redox pair, a solid electrolyte composition, and the like. Examples of the charge transport material involved in the electron transport material include an electron transport material and a hole transport material. A plurality of these charge transport materials may be used in combination.

The electrolyte solution as a charge transport material involving ions is preferably composed of an electrolyte, a solvent, and an additive. Examples of the electrolyte used in the electrolytic solution, iodine and iodide (LiI, NaI, KI, CsI, metal iodide such as CaI _2, tetraalkylammonium iodide, pyridinium iodide, quaternary ammonium such as imidazolium iodide A combination of bromine and bromide (metal bromide such as LiBr, NaBr, KBr, CsBr, CaBr, CaBr ₂ , quaternary ammonium compound bromide such as tetraalkylammonium bromide, pyridinium bromide, etc.) Examples thereof include metal complexes such as Russianate-ferricyanate and ferrocene-ferricinium ions, sulfur compounds such as sodium polysulfide and alkylthiol-alkyldisulfides, viologen dyes, and hydroquinone-quinone. Among them, an electrolyte obtained by combining I ₂ and a quaternary ammonium compound iodine salt such as LiI or pyridinium iodide, imidazolium iodide or the like is preferable. The electrolyte may be used as a mixture.

  Any solvent can be used as long as it is generally used in electrochemical cells and batteries. Specifically, acetic anhydride, methanol, ethanol, tetrahydrofuran, propylene carbonate, nitromethane, acetonitrile, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide, ethylene carbonate, dimethoxyethane, γ-butyrolactone, γ-valerolactone, sulfolane, dimethoxy Ethane, propiononitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, dimethylacetamide, methylpyrrolidinone, dimethyl sulfoxide, dioxolane, sulfolane, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, ethyldimethyl phosphate, tributyl phosphate, phosphorus Tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, phosphoric acid Tridecyl, tris phosphate (trifluoromethyl), tris phosphate (pentafluoroethyl), triphenyl polyethylene glycol phosphate, polyethylene glycol, and the like can be used. In particular, propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethoxyethane, acetonitrile, γ-butyrolactone, sulfolane, dioxolane, dimethylformamide, dimethoxyethane, tetrahydrofuran, adiponitrile, methoxyacetonitrile, methoxypropionitrile, dimethylacetamide, methylpyrrolidinone, dimethylsulfoxide , Dioxolane, sulfolane, trimethyl phosphate and triethyl phosphate are preferred. Also, room temperature molten salts can be used. Here, the room temperature molten salt is a salt composed of an ion pair that is melted at room temperature (that is, in a liquid state) and usually has a melting point of 20 ° C. or lower and is a liquid at a temperature exceeding 20 ° C. Is a salt. The solvent may be used alone or in combination of two or more.

  Moreover, it is preferable to add basic compounds, such as 4-t-butyl pyridine, 2-picoline, and 2, 6-lutidine, to the above-mentioned molten salt electrolyte composition and electrolyte solution. A preferable concentration range when adding the basic compound to the electrolytic solution is 0.05 to 2 mol / L. When added to the molten salt electrolyte composition, the basic compound preferably has an ionic group. The mass ratio of the basic compound to the entire molten salt electrolyte composition is preferably 1 to 40% by mass, more preferably 5 to 30% by mass.

The material that can be used as the polymer matrix is not particularly limited as long as the polymer matrix alone, or the solid state or gel state is formed by the addition of a plasticizer, the addition of a supporting electrolyte, or the addition of a plasticizer and a supporting electrolyte. Generally used so-called polymer compounds can be used.
Examples of the polymer compound exhibiting characteristics as the polymer matrix include hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, ethylene, propylene, acrylonitrile, vinylidene chloride, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, methyl Examples thereof include polymer compounds obtained by polymerizing or copolymerizing monomers such as acrylate, ethyl acrylate, methyl methacrylate, styrene, and vinylidene fluoride. These polymer compounds may be used alone or in combination. Among these, a polyvinylidene fluoride polymer compound is particularly preferable.

  Further, in the present invention, an organic solid hole transport material, an inorganic solid hole transport material, or a material combining both can be used instead of the ion conductive electrolyte.

Examples of organic hole transport materials that can be preferably used in the present invention include triphenylene derivatives, oligothiophene compounds, polypyrrole, polyacetylene and / or derivatives thereof, poly (p-phenylene) and / or derivatives thereof, and poly (p-phenylene). Conductive polymers such as vinylene) and / or derivatives thereof, polythienylene vinylene and / or derivatives thereof, polythiophene and / or derivatives thereof, polyaniline and / or derivatives thereof, polytoluidine and / or derivatives thereof are preferably used. Can do. At that time, a compound containing a cation radical such as tris (4-bromophenyl) aminium hexachloroantimonate may be added to the hole transport material in order to control the dopant level. Further, a salt such as Li [(CF ₃ SO ₂ ) ₂ N] may be added in order to perform potential control (space charge layer compensation) on the surface of the metal oxide semiconductor.

A p-type inorganic compound semiconductor can be used as the inorganic hole transport material, and the band gap is preferably 2 eV or more, more preferably 2.5 eV or more. Further, the ionization potential of the p-type inorganic compound semiconductor needs to be smaller than the ionization potential of the dye adsorption electrode in order to reduce the holes of the dye. Although the preferable range of the ionization potential of the p-type inorganic compound semiconductor varies depending on the dye used, it is generally preferably 4.5 to 5.5 eV, more preferably 4.7 to 5.3 eV. Preferred p-type inorganic compound semiconductor is a compound semiconductor containing monovalent copper, _CuI and examples _{thereof, CuSCN, CuInSe 2, Cu (} In, Ga) Se 2, CuGaSe 2, Cu2O, CuS, CuGaS 2, CuInS 2 CuAlSe _{2 and the} like. Among these, CuI and CuSCN are preferable, and CuI is most preferable. Examples of other p-type inorganic compound semiconductors include GaP, NiO, CoO, FeO, Bi ₂ O ₃ , MoO ₂ , Cr ₂ O _{3 and the} like.

  The charge transport layer can be formed by one of two methods. The first method is a method in which a photosensitive layer and a counter electrode are bonded together, and a liquid charge transport layer is sandwiched between the gaps. The second method is a method in which a charge transport layer is directly provided on the photosensitive layer, and the counter electrode is subsequently provided.

  In the case of the former method, when sandwiching the charge transport layer, a normal pressure process using capillary action by dipping or the like, or a vacuum process in which the gas phase in the gap is replaced with a liquid phase at a pressure lower than normal pressure can be used. .

  When a wet charge transport layer is used in the latter method, a counter electrode is usually applied in an undried state to prevent liquid leakage at the edge. Moreover, when using a gel electrolyte composition, you may solidify by methods, such as superposition | polymerization, after apply | coating this with a wet process. Solidification may be performed before or after applying the counter electrode. In the case of forming a charge transport layer made of an electrolytic solution, a wet organic hole transport material, a gel electrolyte composition, or the like, the same method as the method for forming a semiconductor fine particle layer described above can be used.

  When a solid electrolyte composition or a solid hole transport material is used, a charge transport layer can be formed by a dry film forming process such as a vacuum deposition method or a CVD method, and then a counter electrode can be provided. The organic hole transport material can be introduced into the electrode by a vacuum deposition method, a casting method, a coating method, a spin coating method, a dipping method, an electrolytic polymerization method, a photoelectrolytic polymerization method, or the like. The inorganic solid compound can be introduced into the electrode by a casting method, a coating method, a spin coating method, a dipping method, an electrolytic deposition method, an electroless plating method, or the like.

The counter electrode may have a single layer structure of a counter electrode conductive layer made of a conductive material, or may be composed of a counter electrode conductive layer and a support substrate. In the present invention, since the dye-sensitized photoelectric conversion element irradiates light from the counter electrode side, a highly transparent metal oxide (such as tin or zinc, and other metal elements are used for the counter electrode conductive layer). Micro-doped Indium Tin Oxide (ITO (In ₂ O ₃ : Sn)), Indium Zinc Oxide (IZO (In ₂ O ₃ : Zn)), Fluorine doped Tin Oxide (FTO (SnO ₂ : F)), Aluminum doped A conductive film made of a metal oxide such as Oxide (AZO (ZnO: Al)). A small amount of metal (platinum, gold, silver, copper, aluminum, magnesium, indium, etc.) or carbon may be used in combination with this. The substrate used for the counter electrode is preferably a glass substrate or a plastic substrate, and can be used by applying or vapor-depositing the above-mentioned conductive agent. The thickness of the counter electrode conductive layer is limited by the light transmittance. The light transmittance is preferably 30% or more, and more preferably 50% or more. The surface resistance of the counter electrode conductive layer is preferably as low as possible, preferably 50Ω / □ or less, more preferably 20Ω / □ or less.

  The counter electrode may be installed by directly applying, plating, or vapor-depositing (PVD, CVD) a conductive agent on the charge transport layer, or by attaching the conductive layer side of the substrate having the conductive layer. A metal lead may be used for the purpose of reducing the resistance of the counter electrode. The metal lead is preferably made of a metal such as platinum, gold, nickel, titanium, aluminum, copper, or silver, and particularly preferably made of aluminum or silver. It is preferable that a metal lead is disposed on the transparent substrate by vapor deposition, sputtering, or the like, and a transparent counter electrode conductive layer made of fluorine-doped tin oxide, ITO film or the like is disposed thereon. It is also preferable that a metal lead is provided on the transparent counter electrode conductive layer after the transparent counter electrode conductive layer is provided on the transparent substrate. The decrease in the amount of incident light due to the installation of the metal lead is preferably within 10%, more preferably 1 to 5%.

  As described above, according to the present invention, it is possible to provide a metal-metal oxide composite electrode having excellent industrial productivity, uniform and sufficient surface roughness, and the metal-metal oxide composite electrode. It is possible to provide a dye-sensitized photoelectric conversion element having a large photocurrent by supporting a sensitizing dye.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

<< Production of metal-metal oxide composite electrode >>
[Example 1]
The titanium-titanium oxide composite electrode according to the present invention was manufactured by the following procedure.
First, a titanium plate (purity: 99.7% by weight) having a size of 6 cm × 1.5 cm and a thickness of 1 mm was prepared and subjected to ultrasonic cleaning in ethanol for 5 minutes. Next, titanium oxide was obtained on the titanium surface by subjecting titanium to constant-voltage electrolytic oxidation at 30 V for 1 hour in an aqueous electrolyte solution composed of an aqueous perchloric acid solution having a concentration of 0.01% by volume and a temperature of 16 ° C. When this composite electrode was baked at 450 ° C. for 1 hour, titania having an anatase type crystal structure was obtained. The obtained titania was shaved off from the titanium plate so as to have a size of 0.5 mm × 0.5 mm.

[Example 2]
The titanium-titanium oxide composite electrode according to the present invention was manufactured by the following procedure.
First, a titanium plate (purity: 99.7% by weight) having a size of 6 cm × 1.5 cm and a thickness of 1 mm was prepared and subjected to ultrasonic cleaning in ethanol for 5 minutes. Next, titanium oxide was formed on the titanium surface by subjecting titanium to constant current electrolytic oxidation at 3.5 mA / cm ² for 1 hour in an aqueous electrolyte solution composed of an aqueous perchloric acid solution having a concentration of 0.01% by volume and a temperature of 16 ° C. Got. The maximum voltage in this electrolysis was 29V. When this composite electrode was baked at 450 ° C. for 1 hour, titania having an anatase type crystal structure was obtained. The obtained titania was shaved off from the titanium plate so as to have a size of 0.5 mm × 0.5 mm.

[Example 3]
The titanium-titanium oxide composite electrode according to the present invention was manufactured by the following procedure.
First, a titanium plate (purity: 99.7% by weight) having a size of 6 cm × 1.5 cm and a thickness of 1 mm was prepared and subjected to ultrasonic cleaning in ethanol for 5 minutes. Next, titanium oxide was formed on the titanium surface by subjecting titanium to constant current electrolytic oxidation at 3.5 mA / cm ² for 1 hour in an aqueous electrolyte solution composed of an aqueous perchloric acid solution having a concentration of 0.01% by volume and a temperature of 16 ° C. Got. The maximum voltage in this electrolysis was 29V. On the obtained titanium-titanium oxide composite electrode, a nanosize titania paste (Ti-Nanoxide T manufactured by SOLARONIX) was applied with a gap of about 120 μm using an applicator and dried at 80 ° C. This composite electrode was baked at 450 ° C. for 1 hour, and the obtained titania was scraped from the titanium plate so as to have a size of 0.5 mm × 0.5 mm.

[Comparative Example 1]
A nano-sized titania paste (Ti-Nanoxide T manufactured by SOLARONIX) was applied on a titanium plate (purity 99.7% by weight) having a size of 6 cm × 1.5 cm and a thickness of 1 mm using an applicator with a gap of about 180 μm. And dried at 80 ° C. The coated titanium plate was baked at 450 ° C. for 1 hour, and the obtained titania fine particle film was cut off from the titanium plate so as to have a size of 0.5 mm × 0.5 mm. The thickness of the titania fine particle film was about 9 μm.

<Dye adsorption>
As described above, the titanium-titanium oxide composite electrodes prepared in Examples 1 to 3 and Comparative Example 1 were each converted to a ruthenium dye (Rutenium 535-bisTBA: manufactured by SOLARONIX) / ethanol solution (3.0 × 10 ⁻⁴ mol). / L) for 15 hours to adsorb the dye.

<Production of counter electrode>
Platinum is deposited on the SnO ₂ : F glass (transparent conductive glass having a SnO ₂ : F film formed on a glass substrate) having a surface resistance of 10 Ω / sq to the extent that the transparency of the conductive glass is not lost. Produced. The transmittance of this platinum-deposited conductive glass was 50%.

<< Production and Measurement of Photoelectric Conversion Element >>
Each of the dye-sensitized electrodes prepared as described above and the platinum surface of the glass with a platinum thin film were placed facing each other with a PET film having a thickness of 60 μm as a spacer, and 0.1 mol / L-lithium iodide, 0.5 mol / L 1-propyl-2,3-dimethylimidazolium iodide, 0.5 mol / L 4-tert-butylpyridine, 0.05 mol / L iodine-containing methoxypro The pionitrile solution was soaked by capillary action and the periphery was sealed with an epoxy adhesive.
The cell thus obtained was irradiated with simulated sunlight (1 kW / m ² ), and current-voltage characteristics were measured. The amount of dye adsorbed on titania was determined by desorbing the adsorbed dye with a 0.01 mol / L aqueous sodium hydroxide solution and spectroscopically determining the eluted dye. Table 1 shows the performance of the photoelectric conversion element of the present invention and the comparative photoelectric conversion element.

  From the result of Table 1, the photoelectric conversion element using the titanium-titanium oxide composite electrode according to the method of the present invention has a larger photocurrent and superior to the photoelectric conversion element of Comparative Example 1 using the conventional nano-sized fine particle titania. It can be seen that this is a photoelectric conversion element. Moreover, the photoelectric conversion element of this invention has much pigment | dye adsorption amount compared with a comparative example. This is considered to be because the surface roughness is high, and it can be estimated that this is a cause of a large photocurrent.

It is a cross-sectional schematic diagram which shows an example of the photoelectric conversion element of this invention. It is a cross-sectional schematic diagram which shows an example of the photoelectric conversion element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive layer 2 Photosensitive layer 3 Charge transport layer 4 Transparent counter electrode conductive layer 5 Transparent substrate

Claims (7)

  A metal-metal oxide characterized in that a metal selected from titanium, tantalum, niobium, tungsten and zirconium, or an alloy mainly containing these metals is electrolytically oxidized in an electrolyte solution containing an ion containing a halogen atom. A method for producing a composite electrode.   The method for producing a metal-metal oxide composite electrode according to claim 1, wherein the halogen atom is a chlorine atom.   The method for producing a metal-metal oxide composite electrode according to claim 1, wherein the electrolyte solution contains perchloric acid.   The titanium-titanium oxide composite electrode is manufactured by electrolytic oxidation of titanium or an alloy containing titanium, The manufacture of the metal-metal oxide composite electrode according to any one of claims 1 to 3 Method.   The method for producing a metal-metal oxide composite electrode according to any one of claims 1 to 4, wherein the maximum applied voltage during electrolytic oxidation is 14 V or more.   A metal-metal oxide composite electrode produced by the method according to claim 1. A dye-sensitized photoelectric conversion element comprising a metal-metal oxide composite electrode produced by the method according to claim 1, a dye, and a charge transport material.

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