JP4984440B2 - Metal oxide film and dye-sensitized solar cell - Google Patents

Description

  The present invention relates to a dye-sensitized solar cell having a structure in which a porous metal oxide film and a metal oxide film produced by a vacuum deposition method are used as electrodes, a dye is adsorbed on the electrodes, and an electrolyte is sandwiched between the electrodes. It is about.

  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. ing. (For example, refer to Patent Document 1) Further, 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. It is attracting attention as a generation solar cell.

  In the future, in order to put the dye-sensitized solar cell into practical use, further improvement in photoelectric conversion efficiency is required. 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.

  A 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 are generally composed 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 scattered for efficiency, and the light absorption efficiency is improved. However, various performance enhancements have been attempted. 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 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.

  In recent years, in order to solve these problems, attempts have been made to form a dye-sensitized solar cell by forming a porous film having an oblique columnar structure by vacuum deposition (for example, non-patent literature). 1). However, the conversion efficiency was inferior to that of the conventional liquid phase method.

Patent documents and non-patent documents are described below.
Japanese Patent No. 2664194 G. K. Kiema, et. al. , Solar Energy Materials and Solar Cells

The present invention has been made to solve the above-described problems, and has a metal oxide film having a continuous structure without a grain boundary between oxides, and a structure suitable for electron transfer during photoelectric conversion. The metal oxide film is produced by vacuum deposition, and the size of the structure obtained by changing the pressure during film formation is controlled in the production process. The metal oxide film is used as an electrode, and a dye is applied to the electrode. An object of the present invention is to provide a dye-sensitized solar cell having a high photoelectric conversion efficiency having a structure in which an electrolyte is sandwiched between adsorbed electrodes and a counter electrode.

The invention described in claim 1 is a metal oxide film comprising a dense metal oxide layer (1) and a metal oxide layer (2) having a columnar structure on a substrate, The metal oxide layer (2) has a columnar structure in which the column thickness is larger than 1 μm, and the thickness of the column is 0 to 5 μm, and the column thickness is 0 It is a metal oxide film characterized by comprising a metal oxide layer (2b) having a columnar structure in the range of 0.01 to 1 μm and a film thickness in the range of 5 to 15 μm.
The invention according to claim 2 is characterized in that the metal oxide film has the columnar structure in which the thickness of the metal oxide layer (1) and the column is in a range of 0.01 to 1 μm, and Metal oxide layer (2b) having a thickness in the range of 5 to 15 μm, metal oxide layer having a columnar structure in which the thickness of the column is larger than 1 μm and a thickness in the range of 1 to 5 μm 2. The metal oxide film according to claim 1, wherein the metal oxide film is continuously formed in the order of (2a).

In the invention according to claim 3 , the total light transmittance in a wavelength range of 350 to 900 nm is 20% to 80%, and the ratio of diffuse transmittance to the total light transmittance in a wavelength range of 600 to 900 nm ( 3. The metal oxide film according to claim 1 , wherein the haze is 80% or more.

The invention according to claim 4 is characterized in that the metal oxide layer (1) and the metal oxide layer (2) contain at least one metal of titanium, niobium, zinc and tin. It is a metal oxide film of any one of -3 .

Invention of Claim 5 has a transparent conductive layer between the said base material and a metal oxide layer (1), The metal oxide film of any one of Claims 1-4 characterized by the above-mentioned. It is.

According to a sixth aspect of the present invention, there is provided a dye comprising: a metal oxide film adsorbed with a dye, an electrolyte, a counter electrode, and a transparent conductive layer sequentially formed on the metal oxide film according to the fifth aspect. It is a sensitized solar cell.

  According to the present invention, in a porous metal oxide film produced by vacuum film formation, porous metal oxide films having various structures can be obtained by changing film formation conditions such as pressure during film formation and substrate temperature. The dye-sensitized solar cell having high conversion efficiency can be provided by optimizing the structure.

Hereinafter, an embodiment as an example of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic cross-sectional view showing an example of the layer structure of the metal oxide film of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of the layer structure of the dye-sensitized solar cell of the present invention. In the present invention, as shown in FIG. 1, a metal oxide film 3 having a dense metal oxide layer (1) and a metal oxide layer (2) having a columnar structure on a substrate is used. is there. The metal oxide layer (2) has a columnar structure in which the column thickness is larger than 1 μm, and the thickness of the column is in the range of 1 to 5 μm. It has a columnar structure in the range of 0.01 to 1 μm, and the film thickness is 5 to 1.
The transparent conductive layer 2 can be provided between the base material and the metal oxide film.

  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, triacetylcellulose, polyimide, and the like. A plastic film or glass can be used.

  Moreover, when producing the solar cell 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 substrate may have a surface modified by corona treatment, plasma treatment, chemical treatment, or the like, if necessary. At this time, depending on the roughness of the surface of the substrate, the form of film growth during film formation by vacuum deposition changes, but there is no problem, and the density of the film changes conversely by controlling the roughness. Can be made. When a metal oxide film is used as an electrode for a dye-sensitized solar cell, a film having a large surface area per volume and a large amount of light scattering in the film can be obtained by using a substrate having an appropriate surface roughness. Can be made.

  In the present invention, the transparent conductive layer 2 can be provided between the substrate and the metal oxide film. 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 a metal oxide film can be changed by giving the uneven surface like the above.

  The method for forming the transparent conductive layer 2 includes vacuum deposition processes such as vacuum deposition, reactive deposition, ion beam assisted deposition, sputtering, ion plating, plasma CVD, dipping, 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 case of using a vacuum film formation method, it can be formed in-line with a metal oxide layer described later, which is preferable.

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 used as an n-type semiconductor for a dye-sensitized solar cell, if a conduction band exists at a level higher than the excitation level of the dye and a conduction band exists at a position close to the excitation level, Among these substances, TiO ₂ , Nb ₂ O ₅ , ZnO, and SnO ₂ are preferably used because the efficiency of electron injection from the dye is increased.

  The structure of the metal oxide film 3 in the present invention is composed of a collection of columnar structures as shown in FIG. 1, and each structure has no grain boundary and has a continuous structure. Yes. 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, a large amount of the dye 4 shown in FIG. 2 can be adsorbed, and the light absorption efficiency can be increased. 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 3 is used as an electrode for a dye-sensitized solar cell, a large photocurrent can be obtained.

  When used as a dye-sensitized solar cell, the thickness of the metal oxide film 3 in the present invention is more than 3 μm or less because the dye adsorption amount is small and a sufficient photocurrent cannot be obtained. Is preferred. In addition, when the film thickness is 20 μm or more, the resistance value of the metal oxide film is increased, and the electrons injected from the dye into the conduction band of the oxide are more likely to recombine with the dye or the electrolyte. It is not preferable. Therefore, a film thickness of about 3 μm 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 adsorbed per volume increases, and a large current value can be obtained in a smaller area. When the actual surface area value relative to the projected area is used as a guide for the surface area, this value is preferably 500 times or more, and more preferably 700 times or more. Also, by providing a dense layer with a small surface area at the interface between the metal oxide film 3 and the transparent conductive layer 2, electron transfer between the layers can be performed efficiently, and reverse electron transfer between the electrolytic solution and the transparent conductive layer can be performed. Can be suppressed. The actual area value with respect to the projected area of the dense layer is preferably 100 times or less. Moreover, since this dense layer traps electrons if it is too thick, it needs an appropriate film thickness. The thickness is preferably 1 μm or less, more preferably 500 nm or less.

  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 nm to 900 nm. In addition, when the haze value defined by (diffuse transmittance) / (total light transmittance) is large, when used as an electrode for a dye-sensitized solar cell, light absorption when the dye is adsorbed on the surface of the semiconductor film This is preferable because the efficiency is improved. Specifically, it is 60% or more, more preferably 80% or more in the wavelength range of 350 nm to 900 nm. In addition, 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 nm to 900 nm. More preferably, it includes a region. In order to increase light scattering in the long wavelength region, in the case of a columnar structure, a thicker column is required. When the column thickness is 1 μm or more, the haze ratio is high, which is preferable. Further, the thickness of the layer having a thick column is preferably 1 μm or more and 5 μm or less in consideration of the haze ratio and surface area of the film. It is also possible to gradually change the thickness of the column in the film thickness direction.

  As a method for producing a metal oxide film having a columnar structure obtained in the present invention, a method such as chemical etching or self-organization of a film, or a vacuum deposition 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, and the incident angle of the evaporated substance, and therefore can control the surface area and the scattering property of incident light. This is preferable because it is possible. Hereinafter, this condition will be described in detail.

  In FIG. 3, when there is an angle α formed by the normal of the substrate 7 and the normal of the surface on which the vapor deposition source 8 is placed, it is known that an oblique columnar structure can be obtained by the shadowing effect (for example, Non-patent document 1). As the angle α increases, the shadowing effect becomes remarkable and the surface area per volume increases. However, when α increases further, the proportion of voids increases, so the surface area per volume decreases. Thus, the surface area per volume takes a maximum value with respect to α. By controlling the angle, films with various surface areas can be produced.

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 a porous film having a columnar structure is produced, if the pressure is low, the amount of evaporated particles reaching the film increases, so that a dense and thick film is formed. If the pressure is high, a film having many voids and a thin column 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 in the case of the angle, the surface area per volume takes a maximum value with respect to the pressure during film formation. Thus, by changing the pressure during film formation, a columnar structure having various surface areas and columns with various thicknesses can be formed.

  The temperature of the substrate during vapor deposition affects the diffusion of vapor deposition particles on the substrate. When the temperature of the base material is high, the average diffusion distance of the particles on the base material increases, and when the temperature of the base material is low, the average diffusion distance of the particles on the substrate decreases and the voids of the film increase. It is also possible to change the density of the film by changing the temperature of the vapor deposition source by heating or electron beam. 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 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 is amorphous when it is amorphous 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 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 base material 1, a transparent conductive layer 2, a metal oxide film 3, a dye 4 supported on the semiconductor film 3, and a crack in the metal oxide film 3. The electrolyte layer 5, the conductive catalyst layer 6, the transparent conductive layer 2, and the substrate 1 are formed so as to satisfy the above.

  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. In addition, when the above dye is chemically adsorbed on a semiconductor, electron transfer to the semiconductor is efficiently performed, so that a carboxyl group, a sulfonic acid group, a phosphoric acid group, an amide group, an amino group, a carbonyl group, a phosphine group, etc. It preferably has a functional 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, 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, and stilbene. Compounds having a structure in which aromatic rings such as ethylene bonds or acetylene bonds are connected, heteroaromatic compounds substituted with amino groups, porphyrins, phthalocyanines, quinones, tetracyanoquinodimethanes, dicyanoquinone diimines , 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, but the amorphous one has a more uniform interface with the dye than the crystalline one, and charge separation occurs uniformly. Is preferred. 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. In the case of using a solid electrolyte or p-type semiconductor, after forming a solution using an arbitrary solvent, coating is performed using the above method, and the substrate is heated to an arbitrary temperature to evaporate the solvent. .

  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. When these are formed, a vacuum film forming method similar to that of the transparent conductive layer 5 or a method of coating a paste made of fine particles of these materials can be used.

  Moreover, in the dye-sensitized solar cell in this invention, a short circuit prevention layer 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 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, 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 the vacuum film formation process, the transparent conductive layer 2, the short-circuit prevention layer 7, and the metal oxide layer 3 can be formed in-line under vacuum without being exposed to the atmosphere.

  The semiconductor film of the present invention is not limited to application only to dye-sensitized solar cells, and can be used for various applications such as devices using photocatalysts and electrode materials such as electrochromic devices.

  Hereinafter, specific examples will be described with reference to examples in which the semiconductor film of the present invention is applied to a dye-sensitized solar cell.

<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 substrate, titanium oxide was produced as a metal oxide film 3 by a vacuum deposition method. The deposition conditions at this time are as follows: the normal line of the substrate 7 and the deposition source 8 in FIG. The angle α formed by the normal line of the surface is 45 °, the film forming pressure is 0.1 to 0.5 Pa, and the substrate temperature is 25 ° C. When the specific surface area measurement and SEM observation were performed on the obtained film, the film was composed of a columnar structure, the actual surface area with respect to the projected area was 1000, the column thickness was 800 nm, and the film thickness was 11 μm. I understood it. At this time, the total light transmittance in the wavelength range of 350 to 900 nm was 40% to 80%, and the ratio of the diffuse transmittance to the total light transmittance in the wavelength range of 600 to 900 nm was 80% or more. The obtained laminate was fired at 450 ° C. for 30 minutes using an electric furnace. The obtained laminate was immersed in an ethanol solution of bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium to adsorb the dye. After supporting bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium as the dye 4, it was washed with ethanol and dried. The following operations were performed under a dry argon atmosphere. An electrolyte made of 0.4 M TPAI (tetrapropylammonium iodide), 0.05 M I ₂ and methoxyacetonitrile was formed on the titanium oxide film 3 as the charge transport layer 5. 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 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 = 15 mA / cm ² , the open circuit voltage Voc = 0.77 V, the fill factor FF = 0.63, and the photoelectric conversion efficiency is η = 7 3%.

<Example 2>
A dye-sensitized solar cell 10 having the layer configuration of FIG. 2 was produced. The base material 1 and the transparent conductive layer 2 were produced in the same manner as in Example 1, and titanium oxide was produced as the metal oxide film 3 by a vacuum vapor deposition method. The angle α formed by the normal and the normal of the surface on which the vapor deposition source 8 is placed is 45 °, the film forming pressure is 0.1 to 0.5 Pa, and the substrate temperature is 25 ° C. When the specific surface area measurement and SEM observation were performed on the obtained film, the film was composed of a columnar structure, and the actual surface area with respect to the projected area was 1000, and the thickness of the column was 800 nm. It was found that there was a layer of 7 μm in the direction, an actual surface area with respect to the projected area of 600 μm, and a layer with a column thickness of 1.5 μm of 3 μm. At this time, the total light transmittance in the wavelength range of 350 to 900 nm was 30% to 80%, and the ratio of the diffuse transmittance to the total light transmittance in the wavelength range of 600 to 900 nm was 85% or more. . The obtained laminate was fired at 450 ° C. for 30 minutes using an electric furnace. The obtained laminate was immersed in an ethanol solution of bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium to adsorb the dye. After supporting bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium as the dye 4, it was washed with ethanol and dried. The following operations were performed under a dry argon atmosphere. An electrolyte made of 0.4 M TPAI (tetrapropylammonium iodide), 0.05 M I ₂ and methoxyacetonitrile was formed on the titanium oxide film 3 as the charge transport layer 5. 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 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 Voc = 0.77 V, the fill factor FF = 0.66, and the photoelectric conversion efficiency is η = 8 It was 6%.

<Example 3>
A dye-sensitized solar cell 10 having the layer configuration of FIG. 2 was produced. The base material 1 and the transparent conductive layer 2 were produced in the same manner as in Example 1, and titanium oxide was produced as the metal oxide film 3 by a vacuum vapor deposition method. The angle α formed by the normal and the normal of the surface on which the vapor deposition source 8 is placed is 45 °, the film forming pressure is 0.1 to 0.5 Pa, and the substrate temperature is 25 ° C. When the specific surface area measurement and SEM observation were performed on the obtained film, the film was composed of a columnar structure, and the actual surface area with respect to the projected area was 80 and the thickness of the column was 5 μm from the substrate surface. A layer with an area of 500 nm in the direction and an actual surface area with respect to the projected area of 1000 and a column thickness of 800 nm is 7 μm from the substrate surface in the film thickness direction, and an actual surface area with respect to the projected area of 600 is It was found that a layer having a thickness of 1.5 μm and a layer having a thickness of 3 μm existed. A laminate in which the total light transmittance in a wavelength range of 350 to 900 nm is 30% to 80%, and the ratio of the diffuse transmittance to the total light transmittance in a wavelength range of 600 to 900 nm is 85% or more. Then, it was baked at 450 ° C. for 30 minutes using an electric furnace. The obtained laminate was immersed in an ethanol solution of bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium to adsorb the dye. After supporting bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium as the dye 4, it was washed with ethanol and dried. The following operations were performed under a dry argon atmosphere. An electrolyte made of 0.4 M TPAI (tetrapropylammonium iodide), 0.05 M I ₂ and methoxyacetonitrile was formed on the titanium oxide film 3 as the charge transport layer 5. 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 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 Voc = 0.78 V, the fill factor FF = 0.68, and the photoelectric conversion efficiency is η = 9 %Met.

<Comparative Example 1>
A dye-sensitized solar cell 10 having the layer configuration of FIG. 2 was produced. The base material 1 and the transparent conductive layer 2 were produced in the same manner as in Example 1, and titanium oxide was produced as the metal oxide film 3 by a vacuum vapor deposition method. The angle α formed by the normal and the normal of the surface on which the vapor deposition source 8 is placed is 45 °, the film forming pressure is 0.1 to 0.5 Pa, and the substrate temperature is 25 ° C. When the specific surface area measurement and SEM observation were performed on the obtained film, the film was composed of a columnar structure, the actual surface area with respect to the projected area was 800, the column thickness was 2 μm, and the film thickness was 11 μm. It was. At this time, the total light transmittance in the wavelength range of 350 to 900 nm is 20% to 80%, and the ratio of the diffuse transmittance to the total light transmittance in the wavelength range of 600 to 900 nm is 50% or more and less than 70%. Met. The obtained laminate was fired at 450 ° C. for 30 minutes using an electric furnace. The obtained laminate was immersed in an ethanol solution of bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium to adsorb the dye. After supporting bis (4,4-dicarboxy-2,2-bipyridyl) dithiocyanate ruthenium as the dye 4, it was washed with ethanol and dried. The following operations were performed under a dry argon atmosphere. An electrolyte made of 0.4 M TPAI (tetrapropylammonium iodide), 0.05 M I ₂ and methoxyacetonitrile was formed on the titanium oxide film 3 as the charge transport layer 5. 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 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, 100 mW / cm ² , the short-circuit current J _SC = 14 mA / cm ² , the open circuit voltage Voc = 0.75 V, the fill factor FF = 0.63, and the photoelectric conversion efficiency is η = 6 .6%
Met.

  From the results of Examples 1 and 2 and Comparative Example 1, in the porous metal oxide film having a columnar structure, the thickness of the column is 1 μm or less, so that the dye-sensitized solar cell manufactured using the film is high. It was found to show conversion efficiency. It was also found that by providing a thick layer of pillars on the film surface side, the haze ratio in the wavelength region of 600 to 900 nm of the film increases and the conversion efficiency improves. Moreover, the improvement of conversion efficiency was confirmed similarly by providing a dense layer on the substrate side of the film.

It is a schematic cross section which shows an example of the laminated constitution of the metal oxide film of this invention. It is a schematic cross section which shows an example of the layer structure of the dye-sensitized solar cell of this invention. It is explanatory drawing which shows the positional relationship of the board | substrate and vapor deposition source in the film-forming by the vacuum evaporation method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Base material (1) ... Dense metal oxide layer 2 ... Transparent conductive layer (2) ... Metal oxide layer which has columnar structure 2a ... Column thickness is from 1 micrometer Metal oxide layer having a large columnar structure and a film thickness in the range of 1 to 5 μm 2b... Having a columnar structure in which the thickness of the column is in the range of 0.01 to 1 μm and the film Metal oxide layer 3 ... metal oxide film 4 ... dye 5 ... electrolyte layer 6 ... conductive catalyst layer 7 ... substrate 8 ...・ Vapor deposition source 10 ... Dye-sensitized solar cell

Claims (6)

A metal oxide film having a dense metal oxide layer (1) and a metal oxide layer (2) having a columnar structure on a substrate, wherein the metal oxide layer (2) is A metal oxide layer (2a) having a columnar structure with a column thickness greater than 1 μm and a film thickness in the range of 1 to 5 μm, and a column thickness in the range of 0.01 to 1 μm. It consists of a metal oxide layer (2b) having a columnar structure and a film thickness in the range of 5 to 15 μm, and the columnar structure (2a) exists on the columnar structure (2b). A metal oxide film. The metal oxide film has a columnar structure in which the thickness of the metal oxide layer (1) and the column is in a range of 0.01 to 1 μm, and a film thickness is in a range of 5 to 15 μm. The metal oxide layer (2b) is continuously formed in the order of the metal oxide layer (2a) having a columnar structure in which the thickness of the column is larger than 1 μm and a film thickness in the range of 1 to 5 μm. The metal oxide film according to claim 1, wherein: The total light transmittance in the wavelength range of 350 to 900 nm is 20% to 80%, and the ratio (haze) of the diffuse transmittance to the total light transmittance in the wavelength range of 600 to 900 nm is 80% or more. The metal oxide film according to any one of claims 1 and 2 . The metal oxide layer (1) and the metal oxide layer (2) contain at least one metal of titanium, niobium, zinc, and tin, according to any one of claims 1 to 3 . Metal oxide film. Metal oxide film according to any one of claims 1 to 4, characterized in that a transparent conductive layer between the substrate and the metal oxide layer (1). 6. A dye-sensitized solar cell, comprising a metal oxide film adsorbed with a dye, an electrolyte, a counter electrode, and a transparent conductive layer formed on the metal oxide film according to claim 5 .