JP2006165014A - Method of forming metal oxide film and method of manufacturing dye-sensitized solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of forming a metal oxide film having a continuous structure with no boundary between oxides, and to provide a method of manufacturing a dye-sensitized solar cell having high photoelectric conversion efficiency using the metal oxide film. <P>SOLUTION: In this method of forming the metal oxide film 3, the metal oxide film 3 having a dendritic structure is formed on a substrate 1 by vacuum vapor deposition. The vacuum vapor deposition uses a plurality of evaporation sources 9 and lets evaporation particles incident from a plurality of directions. The dye-sensitized solar cell 10 has such a structure that at least a transparent conductive layer 2, a pigment 4-adsorbed metal oxide film 3 and an electrolyte layer 5, and another transparent conductive layer 2 are formed in order on the substrate 1. In the method of manufacturing the dye-sensitized solar cell 10, the metal oxide film 3 has a dendritic structure, and is formed by vacuum vapor deposition wherein the evaporation particles are made to be incident from a plurality of directions. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a porous metal oxide film comprising a dendritic structure, and the metal oxide film is used as an electrode, a dye is adsorbed to the electrode, and an electrolyte is provided between the electrode and the counter electrode. The present invention relates to a method for producing a dye-sensitized solar cell having a structure with a structure interposed therebetween.

  A dye-sensitized solar cell is composed of a photoelectrode in which a porous metal oxide semiconductor having a dye adsorbed on a transparent conductive film, a counter electrode made of a conductive film serving as a catalyst, and a charge transport layer. Manufactured by overlapping the photoelectrode and the counter electrode through the transport layer, the principle is that the presence of a suitable dye on the semiconductor surface, the light response can be obtained from a wavelength region that is not the absorption wavelength of the semiconductor itself, This is an application of the so-called spectral sensitization phenomenon. So far, it has been known that a pigment that absorbs light of 800 to 900 nm and a porous metal oxide semiconductor for adsorbing more of this pigment exhibit photoelectric conversion efficiency comparable to that of an amorphous silicon solar cell. (For example, refer to Patent Document 1). Furthermore, this type of solar cell has the potential to be manufactured at a lower cost than conventional single crystal silicon solar cells, amorphous silicon solar cells, and compound semiconductor solar cells, and has attracted attention as the next-generation solar cell. It is what.

  In the future, in order to put the dye-sensitized solar cell into practical use, it is necessary to further improve the photoelectric conversion efficiency. In order to improve the efficiency, it is possible to increase the light absorption efficiency of the metal oxide semiconductor film and obtain a larger short-circuit current density. In order to increase the light absorption efficiency, the surface area of the film should be increased to increase the amount of adsorption to the film surface, and long wavelength light with a low dye absorption coefficient can be efficiently scattered within the film, resulting in a loss of light absorption. It is necessary to reduce the resistance of the semiconductor film. In order to satisfy these conditions, various porous membranes have been studied so far.

  The porous metal oxide semiconductor has generally been produced by a liquid phase method such as a sol-gel method or a spray method. Films obtained by the liquid phase method generally consist of aggregates of fine particles of about 10 to 50 nm, and by selecting the size of the particles, light in the long wavelength region is efficiently scattered to improve the light absorption efficiency. Various performance enhancements have been made. However, these films have a problem that loss occurs at the oxide fine particle interface and the like due to the existence of charge transfer resistance between the particles. For this reason, after the production of the film, treatments such as necking between particles using a precursor of the same substance have been performed, but no drastic improvement has been achieved.

  On the other hand, as a means for improving the photoelectric conversion efficiency, many studies have been made on oxide composites. By compounding an oxide, for example, by compounding a substance having a large electron diffusion length and an oxide having a low conduction band energy level, an improvement in voltage is expected while maintaining a high current value of the cell. In addition, since electrons once injected into the conduction band of one oxide move to the other oxide, suppression of reverse electron transfer from the oxide to the electrolyte is also expected. Until now, various combinations of oxides have been carried out by the liquid phase method, but no material superior to the conversion efficiency of titanium oxide alone, which has shown the best performance in the past, has been obtained.

Prior art documents are shown below.
Japanese Patent No. 2664194

  Therefore, in order to solve the above-mentioned problems, the problem in the present invention is a method for producing a metal oxide film having a continuous structure without a grain boundary between oxides, and a photoelectric device using this metal oxide film. It aims at providing the manufacturing method of a dye-sensitized solar cell with high conversion efficiency.

  The invention according to claim 1 of the present invention is a method for producing a metal oxide film 3 which forms a metal oxide film 3 having a dendritic structure on a substrate 1 by a vacuum vapor deposition method. Is a method for producing a metal oxide film, wherein vapor deposition particles are incident from a plurality of directions using a plurality of vapor deposition sources 9.

  The invention according to claim 2 of the present invention is the method for producing a metal oxide film according to claim 1, wherein at least one of the plurality of vapor deposition sources 9 is a straight line connecting the vapor deposition source 9 and the substrate 8; The metal oxide film manufacturing method is characterized in that the angle formed by the normal line of the substrate 8 is in a position within a range of 10 to 80 °.

  The invention according to claim 3 of the present invention is the method for producing a metal oxide film according to claim 1 or 2, wherein a straight line connecting the evaporation source 9 and the substrate 8 of the plurality of evaporation sources 9 and the substrate 8 are provided. The metal oxide film manufacturing method is characterized in that the angles formed by the normal lines are different from each other.

  The invention according to claim 4 of the present invention is the method of manufacturing a metal oxide film according to any one of claims 1 to 3, wherein the metal oxide film 3 is any one of titanium, niobium, zinc, and tin. It is a manufacturing method of the metal oxide film characterized by including one or more.

  The invention according to claim 5 of the present invention is the method for producing a metal oxide film according to any one of claims 1 to 4, wherein the materials of the plurality of vapor deposition sources 9 are different and are co-deposited to perform composite oxidation. A metal oxide film manufacturing method characterized by forming a physical film.

  The invention according to claim 6 of the present invention is such that at least a transparent conductive layer 2, a metal oxide film 3 adsorbed with a dye 4, an electrolyte layer 5, and a transparent conductive layer 2 are sequentially formed on a substrate 1. It is a manufacturing method of the solar cell 10, characterized in that the metal oxide film 3 has a dendritic structure and is formed by a vacuum deposition method in which vapor deposition particles are incident from a plurality of directions. It is a manufacturing method of a dye-sensitized solar cell.

  The invention according to claim 7 of the present invention is the method for producing a dye-sensitized solar cell according to claim 6, wherein at least one of the plurality of vapor deposition sources 9 is a straight line connecting the vapor deposition source 9 and the substrate 8. The method for producing a dye-sensitized solar cell, characterized in that the angle formed by the normal line of the substrate 8 is in a position within a range of 10 to 80 °.

  The invention according to claim 8 of the present invention is the method for producing a dye-sensitized solar cell according to claim 6 or 7, wherein a straight line connecting the evaporation source 9 and the substrate 8 of the plurality of evaporation sources 9 and the substrate 8 is a method for producing a dye-sensitized solar cell, characterized in that angles formed by normal lines 8 are different from each other.

  The invention according to claim 9 of the present invention is the method for producing a dye-sensitized solar cell according to any one of claims 6 to 8, wherein the metal oxide film 3 is any one of titanium, niobium, zinc, and tin. It is a manufacturing method of the dye-sensitized solar cell characterized by including one or more.

  The invention according to claim 10 of the present invention is the method for producing a dye-sensitized solar cell according to any one of claims 6 to 9, wherein the materials of the plurality of evaporation sources 9 are different and are combined by co-evaporation. An oxide film is formed. A method for producing a dye-sensitized solar cell.

  According to the present invention, a metal oxide film made of a dendritic structure having no grain boundaries and a large surface area is obtained by producing a metal oxide film by a vacuum deposition method using a plurality of deposition sources. be able to. Moreover, the dye-sensitized solar cell which has high conversion efficiency can be provided by using this semiconductor film.

  Embodiments of the present invention will be described below in detail with reference to FIGS.

  FIG. 1 is a side sectional view showing a layer structure in a state in which a metal oxide film 3 is formed on a substrate 1 by the method for producing a metal oxide film 3 according to the present invention, and FIG. 2 according to the present invention. FIG. 3 is a side sectional view showing a layer structure of a dye-sensitized solar cell 10 produced using the metal oxide film 3, and FIG. 3 is a method for producing the metal oxide film 3 according to the present invention, which is based on a vacuum deposition method. It is a schematic diagram which shows the positional relationship of the base material 8 and the vapor deposition source 9 in film-forming.

  In the present invention, a metal oxide film (semiconductor film) 3 can be provided on a substrate 1 as shown in FIG. As the substrate 1, a transparent known material can be used. For example, polymethyl methacrylate, polycarbonate, polystyrene, polyethylene sulfide, polyethersulfone, polyolefin, polyethylene terephthalate, polyethylene naphthalate, triacetyl cellulose, polyimide, and the like. A plastic film or glass can be used.

  Moreover, when producing the solar cell (10) of a structure like FIG. 2, one base material 1 needs to be transparent, but the other does not need to be transparent. Such a base material 1 may have a surface modified by corona treatment, plasma treatment, chemical treatment, or the like, if necessary. At this time, the form of film growth during film formation by vacuum deposition changes depending on the roughness of the surface of the substrate 1, but there is no problem, and the density of the film can be reduced by controlling the roughness. Can be changed. When the metal oxide film 3 is used as an electrode for a dye-sensitized solar cell, by using the base material 1 having an appropriate surface roughness, the surface area per volume is large and the light scattering in the film is large. A film can be produced.

  In the present invention, a protective layer (not shown) may be provided between the substrate 1 and the metal oxide film 3. As the protective layer in the present invention, silicon oxide or aluminum oxide can be used. In addition, iron, cobalt, zirconium, other metal oxides, metal oxynitrides, metal nitrides, metal fluorides can be used. A compound or the like can be used. In addition, a high molecular compound such as a silicon resin or a fluorine-containing organic compound can be used, but at this time, it needs to be not decomposed due to a photocatalytic action that occurs when a specific metal oxide film is used. By providing the protective layer, the substrate 1 can be protected when post-processing described later is performed.

  In the present invention, the transparent conductive layer 2 can be provided between the substrate 1 and the metal oxide film 3. As the transparent conductive layer 2, a known transparent conductive material with little absorption in the visible light region can be used. Indium oxide doped with tin (ITO), tin oxide doped with fluorine, indium, or the like Zinc oxide doped with aluminum, gallium or the like is preferable. Moreover, also about this transparent conductive film, the shape of the metal oxide film 3 can be changed by giving the uneven surface like the above.

The method for forming the transparent conductive layer 2 includes vacuum deposition methods such as vacuum deposition, reactive deposition, ion beam assisted deposition, sputtering, ion plating, plasma CVD, dipping, and spin coating. The film can be produced by a liquid phase coating method such as a roll coating method, a screen printing method, or a spray method, but any film forming method may be used.

In the present invention, various metal oxide films 3 can be used. Specific examples include oxides of zinc, niobium, tin, titanium, vanadium, indium, tungsten, tantalum, zirconium, molybdenum, manganese, iron, copper, nickel, iridium, rhodium, chromium, and ruthenium. In addition, perovskites such as SrTiO ₃ , CaTiO ₃ , BaTiO ₃ , MgTiO ₃ , SrNb ₂ O ₆ , composite oxides or oxide mixtures thereof can also be used.

  When the metal oxide film 3 of the present invention is used as an electrode for a dye-sensitized solar cell, the important factors are the energy level of the conduction band and the conductivity. Since the energy level of the conduction band determines the voltage of the cell, the energy level at the position where the voltage becomes higher is preferable. On the other hand, since electrons are injected from the dye, it is necessary to be at a position higher than the excitation level of the dye. As a substance satisfying these conditions, titanium oxide, niobium oxide, tin oxide, and zinc oxide are suitable. In addition, it is possible to improve performance by combining a material having low conductivity but an advantageous energy level with a material having high conductivity. In this case, in order to reduce the loss of electron transfer in the composite oxide, it is preferable that an oxide having a low energy level of the conduction band exists on the surface and a highly conductive substance exists on the inside thereof. At this time, the conductive substance may or may not be an oxide.

  The structure of the metal oxide film 3 in the present invention is composed of a collection of dendritic structures as shown in FIG. 1, and each structure has no grain boundary and has a continuous structure. It is said. When this film is used as an electrode for a dye-sensitized solar cell, since the metal oxide film 3 generally has a large surface area, it can adsorb a large amount of the dye 4 shown in FIG. Can be increased. Moreover, since each structure does not have a grain boundary, the resistance at the time of charge transfer is very small. For these reasons, when the metal oxide film 3 is used as an electrode for a dye-sensitized solar cell, a large photocurrent can be obtained.

  When the metal oxide film 3 in the present invention is used as an electrode of a dye-sensitized solar cell, if it is 3 μm or less, the amount of dye adsorbed is small and a sufficient photocurrent cannot be obtained. Preferably there is. Further, when the film thickness is 20 μm or more, the resistance value of the metal oxide film 3 increases, and the probability that electrons injected from the dye 4 into the conduction band of the oxide recombine with the dye 4 or the electrolyte is high. Therefore, it is not preferable. Therefore, a film thickness of about 3 to 20 μm is suitable. However, this does not apply when used for applications other than dye-sensitized solar cells.

  When used as an electrode for a dye-sensitized solar cell, the larger the surface area of the metal oxide film 3, the better. As the surface area per volume increases, the amount of dye 4 adsorbed per volume increases, and a large current value can be obtained in a smaller area. When the value of the actual surface area relative to the projected area is used as a guide for the surface area, this value is preferably 300 times or more, preferably 500 times or more.

  The light transmittance of the metal oxide film 3 of the present invention is not particularly limited, but the total light transmittance is preferably 20 to 80% in the wavelength range of 350 to 900 nm. Further, when the haze value defined by (diffuse transmittance) / (total light transmittance) is large, when used as an electrode for a dye-sensitized solar cell, the dye 4 is adsorbed on the surface of the semiconductor film. Since light absorption efficiency improves, it is suitable. Specifically, it is 60% or more, more preferably 80% or more in the wavelength range of 350 to 900 nm. Further, since such a correlation between haze and absorptance is prominently observed in a long wavelength region such as near infrared and infrared, a near infrared and infrared wavelength region having a haze ratio of 80% or more is 600 to 900 nm. More preferably, it includes a region.

  As a method for producing the metal oxide film 3 having a dendritic structure obtained in the present invention, a technique such as chemical etching or self-organization of the film, a CVD method, or a vacuum evaporation method can be considered. Among these, the vacuum deposition method can control the structure of the film by changing the conditions such as the film formation rate, film formation pressure, the incident angle of the evaporating substance, the number of the evaporation sources 9, and therefore the surface area and incident light. It is preferable because the scattering property can be controlled. Hereinafter, this condition will be described in detail.

  FIG. 3 is a model diagram showing the positional relationship between the substrate 8 and the vapor deposition source 9 in the coordinate axes. At this time, the center of the base material 8 is on the Z axis. The distance h between the plane on which the substrate 8 and the evaporation source 9 are located is not particularly limited, but is preferably between 10 and 50 cm in consideration of the film forming rate and the porosity of the dendritic structure. It is known that a film having a large surface area can be produced by changing the incident angle of the evaporation substance and forming the film by so-called oblique vapor deposition, but the same method can be used in this case as well. In FIG. 3, the porosity of the membrane can be controlled by changing the angle α formed between the substrate 8 and the x = 0 plane. The value of α can be varied from 0 to 90 °. The position of the vapor deposition source 9 may be anywhere as long as the evaporated substance can enter the base material 8, but in consideration of the film formation rate, it is in the position of x ≦ 0 and z ≧ 0 in FIG. Is preferred. In particular, when the angle β formed by the straight line connecting the vapor deposition source 9 and the substrate 8 and the normal of the substrate 8 is 10 ° ≦ β ≦ 80 ° or less, a film having a large surface area can be produced by the shadowing effect, which is preferable. . In the case of 10 ° or less, since there is almost no shadowing effect, a dense film with a small surface area can be formed. In the case of 80 ° or more, the film forming rate is lowered or the strength of the film is lowered.

  When a plurality of vapor deposition sources 9 are used, if any one vapor deposition source 9 is also at a position where the shadowing effect occurs, a void is formed and a film having a large surface area is obtained. The ratio of the voids, the surface area of the film, and the structure of the film can be controlled by the position of the vapor deposition source 9. For example, when vapor deposition particles are incident from a certain direction, an oblique columnar structure is obtained. On the other hand, as shown in FIG. 3, when two vapor deposition sources 9 are placed symmetrically with respect to the x-axis and vapor deposition is performed, a dendritic structure with branches growing symmetrically on the left and right is obtained. These structures also have various surface areas depending on the incident angle. As the angle β formed by the straight line connecting the vapor deposition source 9 and the base material 8 and the normal line of the base material 8 increases, the shadowing effect becomes more prominent and the surface area per volume increases, but β further increases. Since the proportion of voids increases, the surface area per volume decreases. Thus, the surface area per volume takes a maximum value with respect to β. A dendritic structure can be obtained even if the number of vapor deposition sources 9 is two or more, and a metal oxide film 3 having a larger surface area can be obtained by optimizing conditions such as an incident angle. At this time, the β values for the respective vapor deposition sources 9 may or may not be the same.

  In addition, a composite oxide film can be easily produced by performing co-evaporation using two or more different substances. In the case of producing a complex oxide film, different materials may be deposited one by one, even by co-evaporation as described above. When the metal oxide film 3 is used as an electrode for a dye-sensitized solar cell, it is preferable to coat a conductive substance with a substance that is advantageous in terms of the conduction band as described above. After the film is deposited, the other material can be deposited.

  The substance used as the vapor deposition source 9 in the present invention may be a metal oxide itself, or a metal, a metal suboxide, or the like can be produced by reactive vapor deposition in an oxygen atmosphere. Further, by using a mixture of two or more kinds of metals or metal oxides for the vapor deposition source 9, the film can be doped.

Since the pressure during vapor deposition greatly affects the mean free path of the evaporated particles, it greatly affects the film formation rate and the film porosity. In the case of reactive vapor deposition, the pressure can be adjusted by the flow rate of the introduced oxygen gas. When the pressure is low, the amount of evaporated particles reaching the film increases, so that a dense film is formed. When the pressure is high, a film with many voids is formed. As the density of the film decreases, the surface area per volume increases, but if the number of voids increases, the surface area per volume decreases. In this case as well, as in the case of the aforementioned angle, the surface area per volume takes a maximum value with respect to the pressure during film formation. In addition, the temperature of the base material 8 during vapor deposition affects the diffusion of vapor deposition particles on the base material 8. When the temperature of the base material 8 is high, the average diffusion distance of the particles on the base material 8 increases, and when the temperature of the base material 8 is low, the average diffusion distance of the particles on the base material 8 decreases, More voids. Further, the density of the film can be changed by changing the temperature of the vapor deposition source 9 by heating, the intensity of the electron beam, or the like. By changing various conditions in this way, films having various structures and various surface areas can be obtained. Further, by changing the conditions during film formation, the structure can be gradually changed or the surface area can be changed in the depth direction of the film. Moreover, there is no problem even if the voids of the film produced by vacuum deposition are filled with particles, and a film having a larger surface area can be obtained.

  The metal oxide film 3 produced by the above vacuum deposition method is often amorphous when the substrate is not heated. When used as an electrode for a dye-sensitized solar cell, the metal oxide film 3 is low in conductivity and needs to be crystallized. For this reason, in the case of almost all substances deposited by vacuum deposition, it is necessary to perform a heat treatment at 400 ° C. or higher after the deposition. When the heat treatment is performed, adjacent structures are aggregated, so that the surface area of the film is reduced. For this reason, it is necessary to suppress aggregation as much as possible by optimizing the heat treatment conditions. As a method for crystallization, in addition to heat treatment, any method such as plasma treatment, corona treatment, UV treatment, and chemical treatment can be used. Further, post-processing can be performed using any means such as baking by heat, pressurization using a compressor, or laser annealing.

  Next, the case where the metal oxide film 3 in the present invention is used as an electrode for a dye-sensitized solar cell will be described in detail. The dye-sensitized solar cell 10 of the present invention shown in FIG. 2 includes a substrate 1, a transparent conductive layer 2, a metal oxide film 3, a dye 4 supported on the metal oxide film (semiconductor film) 3, and further It is formed of an electrolyte layer 5, a conductive catalyst layer 6, a transparent conductive layer 2, and a base material 1 that are formed so as to fill a crack in the metal oxide film 3.

  Examples of the dye 4 in the present invention include ruthenium-tris, ruthenium-bis type transition metal complexes, or organic dyes such as phthalocyanine, porphyrin, cyanidin dye, merocyanine dye, rhodamine dye, coumarin dye, and rhodanine dye. These dyes preferably have a large extinction coefficient and are stable against repeated redox. Further, when the dye 4 is chemically adsorbed on the metal oxide film (semiconductor film) 3, electron transfer to the metal oxide film (semiconductor film) 3 is efficiently performed. It preferably has a functional group such as a phosphoric acid group, an amide group, an amino group, a carbonyl group, or a phosphine group.

  As the electrolyte layer 5 in the present invention, iodine, metals, organic compounds and other iodide salts are dissolved in acetonitrile, propionitrile, nitriles such as ethylene carbonate and propylene carbonate, and carbonates as polar solvents. A solution containing a redox system can be used. However, there is a concern that these solutions may deteriorate in performance due to liquid leakage or solvent evaporation when cells are actually produced. In order to avoid the possibility of such deterioration, a solid charge transport layer containing a gel electrolyte in which a solution is supported in a gel or a p-type semiconductor can be used.

Specific examples of materials that can be used for the solid charge transport layer include aromatic amine compounds such as triphenylamine, diphenylamine, and phenylenediamine, condensed polycyclic hydrocarbons such as naphthalene and anthracene, azo compounds such as azobenzene, Compounds having a structure in which aromatic rings such as stilbene are linked by ethylene bonds or acetylene bonds, heteroaromatic compounds substituted with amino groups, porphyrins, phthalocyanines, quinones, tetracyanoquinodimethanes, dicyanoquinone dii Mines, tetracyanoethylene, viologens, dithiol metal complexes and the like. In addition, conductive polymers such as polypyrrole, polyaniline, and polythiophene can also be used. These organic hole transport materials are crystalline and amorphous. However, the amorphous material has a more uniform interface with the dye 4 than the crystalline material, and charge separation occurs uniformly. Is preferable. Other materials that can be used for the solid charge transport layer include CuI, AgI, TiI, and other metal iodides, CuBr, CuSCN, and the like. Further, an iodide salt, iodine or the like may be included in a polymer gel such as polyalkylene ether. These materials can be used in any combination as required.

  As a method for forming the electrolyte layer 5 in the present invention, microgravure coating, dip coating, screen coating, spin coating, or the like can be used. When a solid electrolyte or p-type semiconductor is used, it is formed by making a solution using an arbitrary solvent, coating by using the above method, and evaporating the solvent by heating the substrate 1 to an arbitrary temperature. To do.

  As the conductive catalyst layer 6 in the present invention, any conductive material can be used, and examples thereof include metals such as platinum, gold, silver, and copper, or carbon. In forming these, a vacuum film forming method similar to that of the transparent conductive layer 2 or a method of coating a paste made of fine particles of these materials can be used.

  In the dye-sensitized solar cell of the present invention, the short-circuit prevention layer 7 can be provided between the transparent conductive layer 2 and the metal oxide film 3. Thereby, the short circuit current of an electrolyte and an anode can be reduced. In particular, this layer is essential when a solid p-type semiconductor is used as the electrolyte. The short-circuit prevention layer 7 is not particularly limited as long as it is an n-type semiconductor that transmits visible light and has a conduction band energy level close to that of the metal oxide film 3.

  As a method for forming the short-circuit prevention layer 7, it can be produced by a vacuum film formation process or a liquid phase coating method as in the case of the transparent conductive layer 2. When using a vacuum film formation process, the transparent conductive layer 2, the short-circuit prevention layer 7, and the metal oxide film 3 can be formed in-line under vacuum without being exposed to the atmosphere.

  The metal oxide film (semiconductor film) 3 of the present invention is not limited to the application of only the dye-sensitized solar cell, and can be used for various applications such as a device using a photocatalyst and an electrode material such as an electrochromic device. Can be used.

  Hereinafter, an example in which the metal oxide film (semiconductor film) of the present invention is applied to a dye-sensitized solar cell will be specifically described.

<Example 1>
The dye-sensitized solar cell 10 having the layer configuration of FIG. 2 was produced as follows. Glass (Corning 7059, 1 mm thickness) was used as the substrate 1, and fluorine-doped tin oxide (FTO) was formed thereon as the transparent conductive layer 2 by the atmospheric pressure plasma CVD method. On the obtained transparent conductive base material, titanium oxide was produced as a metal oxide film 3 by a vacuum vapor deposition method. The vapor deposition conditions at this time were as follows: two vapor deposition sources 9 in FIG. (X, y, z) = (0, 20, 0), (x, y, z) = (0, −20, 0) (unit: cm), height h is 40 cm, base material and x = 0 Angle formed by plane = 45 °, film forming pressure 0.3Pa, substrate temperature 25 ° C, film forming speed 15nm / s. The obtained laminate was fired at 450 ° C. for 30 minutes using an electric furnace. The thickness of the obtained titanium oxide film was 8 μm. The actual surface area with respect to the projected area at this time was about 700 times. When a cross-sectional image of this film was observed by SEM, it was composed of an aggregate of dendritic structures. The obtained laminate was immersed in an ethanol solution of bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium to adsorb the dye 4. After loading the dye 4, washing with ethanol and drying were performed. The following operations were performed under a dry argon atmosphere. An electrolyte composed of 0.4 M-TPAI (tetrapropylammonium iodide), 0.05 M-I ₂ , and methoxyacetonitrile is used as an electrolyte (charge transport layer) 5 on a titanium oxide film that is a metal oxide film (semiconductor film) 3. Formed. Furthermore, by preparing a laminate composed of the base material 1 and the transparent conductive layer 2 formed in the same manner as described above as the counter electrode, and forming platinum as a conductive catalyst layer 6 by depositing platinum thereon by a vacuum deposition method. After preparing the counter electrode and fixing the conductive catalyst layer 6 and the electrolyte (charge transport layer) 5 so as to overlap each other, the side surface was sealed with an adhesive to prepare a dye-sensitized solar cell. The current-voltage characteristics of the dye-sensitized solar cell obtained above were measured. M.M. When using pseudo sunlight of 1.5 and 100 mW / cm ² , the short-circuit current J _SC = 17 mA / cm ² , the open circuit voltage V _OC = 0.77 V, the fill factor FF = 0.66, and the photoelectric conversion efficiency is η = It was 8.6%.

<Example 2>
Titanium oxide was produced as a metal oxide film 3 by vacuum deposition on the same base material 1 as in Example 1 and the same transparent conductive layer 2. The vapor deposition conditions at this time are as follows. In FIG. 3, the number of vapor deposition sources 9 is three, and their positions are coordinate axes (x, y, z) = (0, 20, 0), (x, y, z) = (0, −20, 0), origin (unit: cm), height h: 40 cm, angle α = 45 ° formed by the substrate and x = 0 plane, film forming pressure 0.3 Pa, substrate temperature 25 ° C. The film formation rate was 15 nm / s. The obtained laminate was fired at 450 ° C. for 30 minutes using an electric furnace. The thickness of the obtained titanium oxide film was 8 μm. The actual surface area with respect to the projected area at this time was about 1000 times. When a cross-sectional image of this film was observed by SEM, it was composed of an aggregate of oblique columnar structures. Using the obtained laminate, a dye-sensitized solar cell was produced in the same manner using the same material as in Example 1. The current-voltage characteristics of the obtained dye-sensitized solar cell were measured. M.M. When using pseudo sunlight of 1.5 and 100 mW / cm ² , the short circuit current J _SC = 18 mA / cm ² , the open circuit voltage V _OC = 0.76 V, the fill factor FF = 0.66, and the photoelectric conversion efficiency is η = It was 9.0%.

<Example 3>
Titanium oxide and niobium oxide were produced as a metal oxide film 3 on a substrate 1 similar to that in Example 1 by providing a similar transparent conductive layer 2 by a vacuum deposition method. First, titanium oxide was vapor-deposited, and then the vapor deposition source material was switched to niobium oxide for further vapor deposition. The vapor deposition conditions at this time are as follows. In FIG. 3, the number of vapor deposition sources 9 is three, and their positions are coordinate axes (x, y, z) = (0, 20, 0), (x, y, z) = (0, −20, 0), origin, height h is 40 cm, angle α = 45 ° between substrate and x = 0 plane, film forming pressure 0.3 Pa, substrate temperature 25 ° C. The deposition rate was 15 nm / s. The obtained laminate was baked at 550 ° C. for 30 minutes using an electric furnace. The thickness of the obtained titanium oxide film was 8 μm. The actual surface area with respect to the projected area at this time was about 900 times. When a cross-sectional image of this film was observed by SEM, it was composed of an aggregate of dendritic structures. Using the obtained laminate, a dye-sensitized solar cell was produced in the same manner using the same material as in Example 1. The current-voltage characteristics of the obtained dye-sensitized solar cell were measured. M.M. 1.5 and 100 mW / cm 2 of simulated sunlight, the short-circuit current J _SC = 17 mA / cm 2, the open circuit voltage V _OC = 0.8 V, the fill factor FF = 0.7, and the photoelectric conversion efficiency is η = 9. It was 5%.

  Below, the comparative example of this invention is demonstrated.

<Comparative Example 1>
Titanium oxide was produced as a metal oxide film 3 by vacuum deposition on the same base material 1 as in Example 1 and the same transparent conductive layer 2. The deposition conditions at this time are as follows. In FIG. 3, the number of deposition sources 9 is one, the position is the origin, the height h is 40 cm, the angle between the substrate and the x = 0 plane α = 45 °, and the deposition pressure is 0.3 Pa. The substrate temperature was 25 ° C. The film formation rate was 15 nm / s. The obtained laminate was fired at 450 ° C. for 30 minutes using an electric furnace. The thickness of the obtained titanium oxide film was 8 μm. The actual surface area with respect to the projected area at this time was about 550 times. When a cross-sectional image of this film was observed by SEM, it was composed of an aggregate of oblique columnar structures. Using the obtained laminate, a dye-sensitized solar cell was produced in the same manner using the same material as in Example 1. The current-voltage characteristics of the obtained dye-sensitized solar cell were measured. M.M. When using pseudo sunlight of 1.5 and 100 mW / cm ² , the short-circuit current J _SC = 15 mA / cm ² , the open-circuit voltage V _OC = 0.73 V, the fill factor FF = 0.64, and the photoelectric conversion efficiency is η = It was 7.0%.
<Comparative example 2>
Titanium oxide was produced as a metal oxide film 3 by screen printing on a substrate 1 similar to that in Example 1 and a similar transparent conductive layer 2 provided thereon. The obtained laminate was fired at 450 ° C. for 30 minutes using an electric furnace. The thickness of the obtained titanium oxide film was 15 μm. The actual surface area with respect to the projected area at this time was about 750 times. When the surface image was observed by SEM, the obtained titanium oxide film was composed of particles having a particle diameter of 10 to 30 nm. Using the obtained laminate, a dye-sensitized solar cell was produced in the same manner using the same material as in Example 1. The current-voltage characteristics of the obtained dye-sensitized solar cell were measured. M.M. When using pseudo sunlight of 1.5, 100 mW / cm ² , the short circuit current J _SC = 15 mA / cm ² , the open circuit voltage V _OC = 0.72 V, the fill factor FF = 0.62, and the photoelectric conversion efficiency is η = It was 6.7%. When titanium oxide produced by this method was used, the film thickness of 15 μm showed the highest efficiency.

  From the results of Examples and Comparative Examples, the photoelectric conversion efficiency of a dye-sensitized solar cell produced using a titanium oxide film having a dendritic structure obtained when there are two deposition sources 9 is titanium oxide having an oblique columnar structure. It was found that the conversion efficiency was superior when the film was used and when a titanium oxide film produced by a conventional coating method was used. This is presumably because the dendritic structure has a large surface area and a continuous structure with no loss of electron transfer. It was also shown that a dendritic structure with a larger surface area can be obtained by changing the number and position of the vapor deposition sources 9. In addition, it was shown that the voltage and the fill factor are improved while maintaining a high current value by combining two or more kinds of oxides.

It is a sectional side view which shows the layer structure of the state which formed the metal oxide film on the base material with the manufacturing method of the metal oxide film which concerns on this invention. It is a sectional side view which shows the layer structure of the dye-sensitized solar cell produced using the metal oxide film which concerns on this invention. It is a manufacturing method of the metal oxide film which concerns on this invention, Comprising: It is a schematic diagram which shows the positional relationship of the base material and vapor deposition source in the film-forming by a vacuum evaporation method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Transparent conductive layer 3 ... Metal oxide film (semiconductor film)
4 ... Dye 5 ... Electrolyte (charge transport layer)
6 ... Conductive catalyst layer 7 ... Short-circuit prevention layer 8 ... Base material 9 ... Deposition source 10 ... Dye-sensitized solar cell

Claims (10)

  A metal oxide film manufacturing method for forming a metal oxide film having a dendritic structure on a substrate by a vacuum evaporation method, wherein the vacuum evaporation method uses a plurality of evaporation sources to perform evaporation from a plurality of directions. A method for producing a metal oxide film, wherein particles are incident.   The at least one of the plurality of vapor deposition sources is at a position where an angle formed by a straight line connecting the vapor deposition source and the substrate and a normal line of the substrate is within a range of 10 to 80 °. 2. A method for producing a metal oxide film according to 1.   The method for producing a metal oxide film according to claim 1 or 2, wherein an angle formed by a straight line connecting the vapor deposition source and the substrate and a normal line of the substrate is different between the plurality of vapor deposition sources.   The method for producing a metal oxide film according to claim 1, wherein the metal oxide film contains at least one of titanium, niobium, zinc, and tin.   5. The method for producing a metal oxide film according to claim 1, wherein materials of the plurality of vapor deposition sources are different and a composite oxide film is formed by co-evaporation.   A method for producing a dye-sensitized solar cell, in which a transparent conductive layer, a metal oxide film and an electrolyte layer on which a dye is adsorbed, and a transparent conductive layer are sequentially formed on at least a substrate, wherein the metal oxide film is A method for producing a dye-sensitized solar cell, characterized in that the dye-sensitized solar cell is formed by a vacuum vapor deposition method in which vapor deposition particles are incident from a plurality of directions.   The at least one of the plurality of vapor deposition sources is at a position where an angle formed by a straight line connecting the vapor deposition source and the substrate and a normal line of the substrate is within a range of 10 to 80 °. 6. A method for producing a dye-sensitized solar cell according to 6.   The method for producing a dye-sensitized solar cell according to claim 6 or 7, wherein an angle formed by a straight line connecting the vapor deposition source and the substrate and a normal line of the substrate is different between the plurality of vapor deposition sources.   The method for producing a dye-sensitized solar cell according to any one of claims 6 to 8, wherein the metal oxide film contains one or more of titanium, niobium, zinc, and tin.   The method for producing a dye-sensitized solar cell according to any one of claims 6 to 9, wherein a material of the plurality of vapor deposition sources is different and a composite oxide film is formed by co-evaporation.

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