JP2012113839A - Thin metallic film for dye-sensitized solar cell and dye-sensitized solar cell element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin metallic film having low electrical resistivity and high corrosion resistance for an electrolyte solution in a dye-sensitized solar cell.SOLUTION: In a dye-sensitized solar cell element in which a gap between a negative electrode and a positive electrode is filled with an electrolyte solution, at least one of a collecting electrode that comes into contact with the electrolyte solution and a thin metallic film constituting a conductive film is composed of at least one selected from the group consisting of metals of Ti and Ta, and nitride of the Ti. In a thin metallic film for a dye-sensitized solar cell, the nitride may include oxygen.

Description

  The present invention relates to a metal thin film used for a dye-sensitized solar cell and a dye-sensitized solar cell element, and more specifically, a low-electric resistance dye-sensitized solar metal thin film excellent in electrolyte solution corrosion resistance, And a dye-sensitized solar cell element including the metal thin film.

  The use of solar energy is attracting attention as one of alternative energy for petroleum energy, and in particular, technological development using solar cells is being performed as a method for converting sunlight into electric power. Silicon solar cells have been put to practical use as solar cells, but silicon solar cells have a problem of high power generation costs. That is, since high-purity silicon is used as a raw material for silicon-based solar cells, the material cost is high, and a high vacuum process and a high-temperature process are required in the manufacturing process, resulting in high capital investment costs, etc. Since silicon-based solar cells are expensive to produce, the power generation cost is high.

  While techniques for reducing the manufacturing cost of silicon-based solar cells have been proposed, various types of solar cells using materials other than silicon have been proposed.

  For example, as a solar cell using a material other than silicon, a dye-sensitized solar cell has recently attracted attention. The manufacturing process of the dye-sensitized solar cell does not require a high vacuum process, so the capital investment cost is low. The basic structure of the dye-sensitized solar cell is a semiconductor electrode (negative electrode) carrying a sensitizing dye, Since it is comprised with the counter electrode (positive electrode) and the electrolyte solution with which it filled between electrodes, and a structure is comparatively simple, mass production is easy and manufacturing cost can be held down. Furthermore, since dye-sensitized solar cells do not use expensive materials such as silicon, there is also an advantage that material costs are low.

  FIG. 1 is a cross-sectional view showing a general configuration of a dye-sensitized solar cell. This dye-sensitized solar cell element 1 is one in which an electrolyte solution 5 is filled between an electrode (negative electrode) 10 that carries a sensitizing dye and an opposite electrode (positive electrode) 20. The negative electrode 10 has a conductive film 3, a collector electrode 7, and an oxide semiconductor layer 6 on a substrate 2, and a sensitizing dye (not shown) is supported on the oxide semiconductor layer 6. The positive electrode 20 facing the negative electrode 10 has a catalyst electrode including the conductive film 3 ′ and the catalyst layer 4 on the substrate 2 ′. As the electrolytic solution 5, for example, an iodine-based electrolytic solution is generally used.

In the dye-sensitized solar cell, when light is incident on the negative electrode 10, the sensitizing dye (not shown) carried on the oxide semiconductor layer 6 is excited and electrons (e ⁻ ) are emitted, and the sensitizing dye is emitted. Becomes a cation. On the other hand, the emitted electrons (e ⁻ ) travel from the oxide semiconductor layer 6 to the positive electrode 20 side through the collector electrode 7 through an external circuit (not shown) such as a conducting wire, and then the catalyst electrode (conductive) on the positive electrode 20 side. Through the membrane 3 ′ and the catalyst layer 4), iodine (triiodide) in the electrolyte solution 5 undergoes a reduction reaction (I ₃ ⁻ + 2e ⁻ → 3I ⁻ ) to generate iodine ions (I ⁻ ). The iodine ion (I ⁻ ) gives electrons again to the sensitizing dye (cation) from which electrons have been released, and returns to triiodide (3I ⁻ → I ₃ ⁻ + 2e ⁻ ). To get back to the original state. By repeating the above cycle, the dye-sensitized solar cell converts light into electric power.

  However, since dye-sensitized solar cells have lower power generation efficiency than silicon-based solar cells, improvement in power generation efficiency has been demanded. It has been pointed out that the electrical resistivity of the conductive film 3 is high as one of the causes of the low power generation efficiency of the dye-sensitized solar cell. As described above, iodine is generally used as an electrolyte solution in a dye-sensitized solar cell. However, since iodine is stabilized by receiving one electron (octet rule), it is contained in a metal thin film constituting an electrode. It is known that when the reaction occurs, the metal thin film is corroded. Therefore, the metal thin film used for the conductive film 3 and the collector electrode 7 must be made of a material that does not corrode against iodine. For example, although FTO (fluorine-doped tin oxide) is widely used as a material having both electrolytic corrosion resistance (corrosion resistance) and translucency for transparent conductive films, FTO has a problem of high electrical resistivity.

  As a technique for reducing the resistivity by preventing the corrosion of the metal thin film, for example, Patent Document 1 proposes a technique of using a low resistivity Ag and forming a protective film on Ag in order to protect it from dissolution by iodine. ing. However, when an electrode such as Ag is used, it is essential to form a protective film, which complicates the production of the solar cell element and increases the production cost.

JP 2008-186692 A

  The present invention has been made paying attention to the circumstances as described above, and the object thereof is a dye-sensitized solar cell having a low electrical resistivity and a high corrosion resistance against an electrolyte solution (iodine). It is to provide a metal thin film.

  The present invention that has solved the above problems is a dye-sensitized solar cell element in which an electrolyte solution is filled between a negative electrode and a positive electrode, and a metal that constitutes a collector electrode that contacts the electrolyte solution and a conductive film At least one of the thin films is composed of at least one selected from the group consisting of Ti and Ta metals and Ti nitrides, and the nitrides may contain oxygen. It is a metal thin film for batteries.

  It is also a preferred embodiment of the present invention that the metal thin film is not coated with a corrosion resistant material.

  In the present invention, a dye-sensitized solar cell element using the metal thin film for dye-sensitized solar cell is also a preferred embodiment.

  According to the present invention, at least one of the collector electrode and the metal thin film constituting the conductive film is at least one of Ti, Ta, and a nitride of Ti (which may contain oxygen). In addition, it was possible to provide a metal thin film for a dye-sensitized solar cell element having not only excellent corrosion resistance to an electrolyte solution but also having an electric resistivity equal to or lower than that of a conventional FTO. Therefore, the dye-sensitized solar cell element using the metal thin film of the present invention has characteristics excellent in corrosion resistance and power generation efficiency as compared with the conventional dye-sensitized solar cell element using FTO.

FIG. 1 is a schematic cross-sectional view showing an example of a dye-sensitized solar cell element. FIG. 5 is an XPS analysis montage spectrum diagram of No. 5. FIG. 5 is a composition distribution diagram in the depth direction of the metal thin film No. 5; FIG. 6 is an XPS analysis montage spectrum diagram of No. 6. FIG. FIG. 6 is a composition distribution diagram in the depth direction of the metal thin film No. 6;

  In order to increase the power generation efficiency of the dye-sensitized solar cell, the present inventors presuppose that the collector electrode used in the dye-sensitized solar cell and the electrical resistivity of the metal thin film constituting the conductive film can be reduced. In addition, earnest research was repeated to provide technology with excellent corrosion resistance.

  First, using Ag or Al, which is widely used as a metal thin film with low electrical resistivity, the corrosion resistance against an electrolyte solution (iodine) was examined, and it was confirmed that Ag and Al would be dissolved by the electrolyte solution. (See Example 1 below). As a result of further investigations on various metals, the present inventors have found that Ti, Ta, and Ti nitride not only have high corrosion resistance to an electrolyte solution (iodine) but also dyes such as electrical resistivity and light transmittance. The present inventors have found that the characteristics required for a metal thin film used for a sensitized solar cell are satisfied, and have reached the present invention.

  First, the metal thin film for dye-sensitized solar cell according to the present invention will be described.

  The metal thin film of the present invention is selected from the group consisting of Ti and Ta metals and Ti nitrides.

  Among these metals, Ti and Ta metals have high corrosion resistance to an electrolyte solution (iodine), and have optical transparency depending on the film thickness, and electrical resistivity of metal thin films using the metal has been widely used. Since it is about the same as or lower than FTO, it is suitable as a metal thin film used for an electrode or the like constituting a dye-sensitized solar cell element.

  The Ti nitride is also excellent in corrosion resistance and has a low electrical resistivity. The nitride of Ti may contain oxygen. As shown in the examples described later, even if oxygen is contained in the nitride, good corrosion resistance to the electrolyte solution can be maintained, but as the amount of oxygen increases, the electrical resistivity tends to increase. It is preferable to use nitride that does not substantially contain oxygen, or oxygen-containing nitride (for example, oxynitride) in which the amount of oxygen in the metal thin film is preferably reduced to 30% or less. Such an oxygen-containing nitride can be inevitably generated in the preferred film formation process of the present invention (details will be described later). That is, when forming the metal nitride film, in the present invention, it is recommended to form a film by a sputtering method under an atmosphere containing a nitrogen-containing gas. In the present invention, it means that an oxygen-containing nitride is also included as long as the electrical resistivity is not adversely affected. Depending on the film formation conditions, elements other than oxygen may inevitably be included, but nitrides containing these elements are also included within the scope of nitrides in the present invention.

  However, since the electrical resistivity increases as the amount of oxygen in the nitride increases, the amount of oxygen should be as small as possible. Specifically, from the viewpoint of reducing electrical resistivity, when the metal thin film is calculated based on an XPS montage spectrum obtained by XPS (X-ray Photoelectron Spectroscopy) analysis, the proportion of oxygen contained in the metal thin film is preferably It is desirable that it is 30% or less, more preferably 10% or less, and still more preferably 0%.

  Among these, Ti, Ta, and TiN (oxygen content is 10% or less) are preferable from the viewpoint of electric resistivity reduction, and TiN (oxygen content is 10% or less, lower than FTO). More preferably, the oxygen content is 0%. The same is preferable from the viewpoint of corrosion resistance.

  Specifically, the metal thin film of the present invention can be used for the collector electrode and / or the conductive film constituting the dye-sensitized solar cell element, thereby reducing the electrical resistivity of the dye-sensitized solar cell element. When the metal thin film is used for a collector electrode and / or a conductive film, while maintaining the properties such as light transmittance required for the metal thin film (however, depending on the film thickness), it exhibits excellent corrosion resistance against an electrolyte solution, It is desirable because it also exhibits a resistivity reduction effect.

  Since the metal thin film of the present invention has excellent corrosion resistance against the electrolyte solution, it is necessary to provide a protective layer by coating with a corrosion resistant material such as resin or metal in order to protect the metal thin film from the electrolyte solution. Absent. Therefore, when the metal thin film of the present invention is used, the film forming process is simplified and the manufacturing cost can be reduced as compared with the case where the protective film is formed.

  Hereinafter, preferred embodiments 1 to 3 of the metal thin film of the present invention will be described with reference to FIG. However, the present invention is not limited to this. Components not particularly mentioned may be appropriately selected with reference to the description of a specific dye-sensitized solar cell element to be described later.

  Preferred Embodiment 1 is a configuration in which the metal thin film of the present invention is used for the collector electrode 7 constituting the negative electrode 10. The collector electrode 7 is a member that is often formed when the solar cell is enlarged, and is not an essential component. As described above, the metal thin film of the present invention not only has excellent corrosion resistance, but also has a low electrical resistivity. Therefore, when used for the collector electrode 7, the power generation efficiency of the dye-sensitized solar cell element can be increased.

  Preferred Embodiment 2 is a configuration in which the metal thin film of the present invention is used for the (transparent) conductive film 3 constituting the negative electrode 10 instead of the conventional FTO. As in the first embodiment, the metal thin film of the present invention is excellent in corrosion resistance and electrical resistivity. Therefore, when the metal thin film of the present invention is used for the (transparent) conductive film 3, the power generation of the dye-sensitized solar cell element is performed. Efficiency can be increased. In particular, the conductive film 3 is required to have high translucency in addition to corrosion resistance. However, the use of TiN or the like having a low electric resistance can reduce the thickness of the conductive film 3, thereby improving the translucency.

  In a preferred embodiment 3, the metal thin film of the present invention is used for the conductive film 3 ′ constituting the catalyst electrode of the positive electrode 20. In the illustrated example, the catalyst electrode includes a catalyst layer 4 and a conductive film 3 ′ supporting the catalyst (layer) 4, and the metal thin film of the present invention is used for the conductive film 3 ′. When the metal thin film of the present invention is used for the conductive film 3 ′ constituting the catalyst electrode, the loss of electrons supplied to the electrolyte solution from the positive electrode side can be suppressed, so that the power generation efficiency of the dye-sensitized solar cell element can be increased. it can.

  In addition, since the metal thin film of this invention is more excellent in the electrical resistivity reduction effect than conventional FTO, higher power generation efficiency can be obtained by using the said Embodiments 1-3 suitably. For example, a combination of Embodiments 1 and 3, a combination of Embodiments 1 and 2, a combination of Embodiments 2 and 3, and a combination of Embodiments 1 to 3 are also preferred embodiments. By configuring the sensitized solar cell element, the electric resistivity reduction effect can be further enhanced, and the power generation efficiency of the dye-sensitized solar cell element can be further increased.

  Hereinafter, the configuration of the dye-sensitized solar cell element according to the present invention will be described with reference to FIG. 1, but the present invention is not limited to the illustrated examples and can be appropriately changed.

  As already described, the dye-sensitized solar cell 1 has a configuration in which the electrolyte solution 5 is filled between the negative electrode 10 carrying the sensitizing dye and the positive electrode 20 facing the negative electrode. Yes.

  The negative electrode 10 includes a (transparent) conductive film 3, a collector electrode 7, and an oxide semiconductor layer 6 on a substrate 2, and a sensitizing dye (not shown) is supported on the oxide semiconductor layer 6. . Among these, when light is incident from the substrate 2 side of the negative electrode 10, it is desirable to use a material having a high transmittance (light transmittance) in the visible light region. As such a material, for example, glass is preferable, but a colorless and transparent material such as a resin such as PET (polyethylene terephthalate) or PEN (polyethylene naphthalate) may be used. When light is incident from the substrate 2 ′ side of the positive electrode 20, a material that does not transmit light (for example, a metal such as copper or a colored resin) may be used for the substrate 2 on the negative electrode side.

A conductive film 3 is formed on the surface of the substrate 2 on the negative electrode side. The conductive film 3 has a function of conducting electrons (e ⁻ ) emitted when the sensitizing dye is excited by light irradiation, and has a high light transmittance and is excellent in conductivity. Although not limited, FTO can be used as the conductive film 3, but as described in Embodiment 2 above, it is preferable to use the metal thin film of the present invention as the conductive film 3. Note that in the case where light is not incident from the substrate side of the negative electrode, the conductive film 3 may not have translucency.

  The thickness of the conductive film 3 on the negative electrode 10 side is not particularly limited and may be determined according to required characteristics. However, if the thickness of the conductive film 3 is too small, sufficient conductivity may not be obtained. The thickness is preferably 10 nm or more. On the other hand, if the thickness of the conductive film 3 is too large, the light transmission may be reduced or it may be difficult to form a homogeneous conductive film. Therefore, the thickness is preferably 50 nm or less, more preferably 30 nm or less. .

A collector electrode 7 is formed on the conductive film 3 on the negative electrode 10 side. The collector electrode 7 has a function of collecting electrons (e ⁻ ) and taking them out to an external circuit, and is excellent in conductivity and corrosion resistance. However, the electrical resistivity of the collector electrode 7 is lower than the electrical resistivity of the conductive film 3 in order to increase the current collection efficiency and increase the power generation efficiency of the dye-sensitized solar cell. As described in Embodiment 1, it is preferable to use the metal thin film of the present invention. For example, since TiN has a lower electrical resistivity than FTO, if FTO is used as conductive film 3 and TiN is used as a collector electrode, the current collection efficiency can be improved and the power generation efficiency can be increased because the electrical resistivity is also low. . In addition, since the metal thin film of the present invention has high corrosion resistance to the electrolyte solution, it is not necessary to form a protective film such as coating with a corrosion resistant material so as not to contact the electrolyte solution. Therefore, when Ag or Al is used for the collector electrode It has better power generation efficiency. That is, a metal having a low resistivity such as Ag or Al can be used for the collector electrode, but Ag or Al dissolves when it comes into contact with the electrolyte solution. Therefore, the protective film is formed as described above. Therefore, since the power generation efficiency is lowered, it is useful to use the metal thin film of the present invention.

  In addition, when using the metal thin film of this invention for both the electrically conductive film 3 and the collector electrode 7, the collector electrode 7 is made by making the amount of oxygen contained in the collector electrode 7 smaller than the amount of oxygen contained in the transparent conductive film 3. The electrical resistivity can be reduced. Of course, the electrical resistivity can be reduced by changing the constituent elements of the metal thin film in addition to the amount of oxygen (for example, Ti and TiN).

  The collector electrode 7 is desirably provided in order to increase the size of the dye-sensitized solar cell while efficiently suppressing the increase in resistivity, and to efficiently extract electrons to the external circuit. Depending on the size and required characteristics of the solar cell, the collector electrode 7 may not be provided.

  The thickness and size of the collector electrode 7 are not particularly limited. However, if the collector electrode 7 is too thin, sufficient conductivity may not be obtained.

  Moreover, since the area which generate | occur | produces electricity will become small if the thickness of the collector electrode 7 is too thick, and the electric power value obtained may fall, Preferably it is 500 nm or less, It is desirable to set it as 300 nm or less more preferably.

An oxide semiconductor layer 6 is formed on the collector electrode 7. The oxide semiconductor layer 6 is a porous layer containing (supporting) a sensitizing dye. In the present invention, the type of the oxide semiconductor layer 6 is not particularly limited, and various known metal oxides such as TiO ₂ , ZnO, SnO ₂ , and WO ₃ can be used. The fine particles of these metal oxides are porous. It is suitable for forming a high quality oxide semiconductor layer 6. Further, TiO ₂ having a high conductivity, excellent stability with respect to an electrolyte solution, and suitable for forming a porous layer is particularly preferable.

  The particle diameter of the metal oxide fine particles is not particularly limited, but the conversion efficiency is improved by adsorbing many dyes on these particles having a surface area. It is desirable to use it.

  The thickness of the oxide semiconductor layer 6 is not particularly limited. However, if the thickness of the oxide semiconductor layer 6 is too small, the sensitizing dye cannot be sufficiently supported, and the photoelectric conversion efficiency may be inferior. It is desirable to be 2 μm or more. On the other hand, if the thickness of the oxide semiconductor layer 6 is too large, the electrical resistivity of the oxide semiconductor layer 6 is increased. Therefore, the thickness is preferably 15 μm or less, more preferably 5 μm or less.

  The sensitizing dye supported on the oxide semiconductor layer 6 is not particularly limited as long as it has an action of emitting electrons when excited by light. For example, various known organic dyes or metal complex dyes are used. be able to. For example, examples of the organic dye include azo dyes, indigo dyes, and coumarin dyes. For example, as the metal complex dye, a ruthenium-based dye can be mentioned, which is desirable because of high photoelectric conversion efficiency.

  The electrolyte solution 5 is filled between the negative electrode 10 and the positive electrode 20 facing the negative electrode 10, and has a property of transporting electrons between the sensitizing dye supported on the oxide semiconductor layer 6 and the catalyst layer 4 formed on the positive electrode 20. It is what you have. The electrolyte solution 5 used in the dye-sensitized solar cell is not particularly limited, but any electrolyte can be used as long as it has a mechanism capable of giving and receiving electrons to the dye by an oxidation-reduction reaction. Therefore, it is considered that the power generation efficiency can be most improved with an electrolyte containing iodine.

  In addition, an oxidation-reduction pair such as an iodine-iodine compound can be used as the electrolytic solution. As the solvent, various solvents such as a mixed solution of acetonitrile and ethylene carbonate can be used.

The positive electrode 20 only needs to have conductivity and have a catalytic function (for example, to reduce I ₃ ⁻ ions to I ⁻ ions) that reduces a redox pair present in the electrolyte. The configuration is not particularly limited, and for example, a configuration in which a catalyst electrode composed of a conductive film 3 ′ and a catalyst layer 4 is provided on the negative electrode side surface of the substrate 2 ′ may be used.

  The substrate 2 ′ used for the positive electrode 20 is not particularly limited, and may be the same as the substrate 2 of the negative electrode 10. Further, when light is not incident from the positive electrode 20 side, it is only necessary to have conductivity even if it is not a transparent material. For example, a copper thin plate or a conductive resin can be used as such a material.

  The conductive film 3 ′ of the positive electrode 20 is not particularly limited as long as it has conductivity. For example, the same conductive film 3 as that of the negative electrode 10 may be used. Further, as long as light is not incident from the positive electrode side, the light-transmitting property is not particularly limited. As such a conductive film 3 ′, a known material such as FTO may be used, but the metal thin film of the present invention is suitable because it is excellent in corrosion resistance to an electrolyte solution and has a low electrical resistivity. is there.

  A catalyst layer 4 is formed on the surface of the conductive film 3 'and has a function of improving the reduction performance. Although it does not specifically limit as the catalyst layer 4, For example, various well-known materials which function as catalysts, such as Pt, carbon, an oxide, can be used.

  In the dye-sensitized solar cell element of the present invention, each of the above constituent members may be sealed in a container made of a resin or the like, or the positive electrode and the negative electrode may be bonded so as to seal the electrolyte solution, A known configuration can be employed. The shape of the dye-sensitized solar cell element is not particularly limited, and may be a desired shape, and examples thereof include polygons such as quadrangles and octagons, and circles such as circles and ellipses.

  A large dye-sensitized solar cell module can be produced by arranging and connecting a plurality of the dye-sensitized solar cell elements of the present invention.

  Hereinafter, after describing the film forming method of the metal thin film of the present invention, the method of manufacturing the dye-sensitized solar cell element of the present invention will be described. However, the present invention is not limited to the following manufacturing method, and appropriate modifications may be made. it can.

  The basic component of the metal thin film of the present invention is at least one selected from the group consisting of Ti, Ta, and Ti nitrides, but these are easily oxidized during the film formation process, and those containing a large amount of oxygen have electrical resistance. Since the rate increases, it is important to control the atmospheric conditions during film formation.

For example, when a pure Ti film and / or a pure Ta film is formed as a metal thin film, the atmosphere is preferably an inert atmosphere such as Ar gas. Further, when a Ti nitride film is formed as the metal wiring film, it is desirable to use a mixed atmosphere of an inert gas and a nitrogen gas. In order to reduce the amount of oxygen contained in the formed metal thin film, it is desirable to increase the nitrogen concentration in the gas necessary for the film formation as much as possible, and preferably the N ₂ partial pressure is 30% or more of the whole, more preferably Is 70% or more.

  By increasing the atmospheric gas flow rate, oxygen present at the time of film formation can be eliminated at a higher level, so that the rate at which Ti, Ta, etc. react with oxygen during the film formation process can be reduced.

  From the viewpoint of easily controlling the atmosphere during film formation as described above and forming a metal thin film having a uniform and uniform film thickness, it is desirable to use a sputtering method. In particular, reactive sputtering using nitrogen gas is desirable to form a nitride thin film such as TiN. As shown in the first embodiment, when the metal thin film of the present invention is used as the collector electrode 7 formed on the negative transparent conductive film 3, a mask corresponding to the wiring pattern of the collector electrode 7 is provided on the transparent conductive film 3. The collector electrode 7 having a desired wiring pattern can be formed on the transparent conductive film 3 by performing sputtering after forming the transparent conductive film 3.

  Further, as shown in the second and third embodiments, the metal thin film of the present invention is applied to the conductive film 3 formed on the substrate 2 constituting the negative electrode 10 and the conductive film 3 ′ formed on the substrate 2 ′ constituting the positive electrode 20. Is used, it is desirable to form a metal thin film having a desired composition on the substrate by sputtering using a pure Ti and / or pure Ta sputtering target.

  Other sputtering conditions when the sputtering method is used are not particularly limited, but the substrate temperature may be, for example, room temperature, and the gas pressure may be, for example, about 2 to 3 mTorr.

  The method for producing a dye-sensitized solar cell element of the present invention is characterized in that the film formation conditions are controlled when the metal thin film of the present invention is used, and the production conditions of other components are particularly limited. What is necessary is just to operate well-known manufacturing conditions.

  For example, the negative electrode 10 may be formed with a transparent conductive film such as FTO on the substrate 2 such as a glass plate, but the film forming method when a known material is used is not particularly limited, for example, spin coating method, screen printing The film may be formed by a known method such as a method. When the metal thin film (conductive film 3) of the present invention is formed on a substrate, it is desirable to use the above sputtering method.

  When a conventional material such as Ag is used for the collector electrode 7, a desired pattern may be formed on the conductive film 3 by screen printing or the like using an Ag paste, and then heat treatment is performed to form a collector electrode. When the metal thin film of the present invention is formed on the conductive film 3, it is desirable to use the above sputtering method.

  In the case where titanium oxide is used as the oxide semiconductor layer 6, a porous oxide semiconductor layer can be formed by performing a heat treatment after screen printing using a titanium oxide paste. Then, the sensitizing dye can be supported on the surface of the oxide semiconductor layer 6 by immersing the porous semiconductor layer 6 in an alcohol solution in which a sensitizing dye such as a Ru metal complex is dissolved.

  In the positive electrode 20, the conductive film 3 ′ constituting the catalyst electrode is formed on the substrate, but the film forming method may be the same as that of the conductive film 3 of the negative electrode 10. Further, the catalyst layer 4 is formed on the surface of the conductive film 3 ′, and a desired catalyst material such as Pt may be formed by, for example, a sputtering method or a vapor deposition method.

  The electrolyte solution 5 may be a commercially available one or may be prepared. For example, an electrolytic solution may be prepared by dissolving copper iodide (CuI) or iodine (I) in a solvent such as acetonitrile.

  A dye-sensitized solar cell element can be prepared by pasting the anode 10 so that the oxide semiconductor layer 6 side of the negative electrode 10 and the catalyst layer 4 side of the positive electrode 20 face each other and filling the electrolyte solution by a known method therebetween. .

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

  Using the sample prepared as follows, the electrical resistivity of the metal thin film and the corrosion resistance against the electrolyte solution were examined.

[Sample preparation]
Various metal thin films shown in Table 1 were formed on a transparent substrate (Corning Corp., EAGLE XG, circular glass with a diameter of 55.3 mm) by sputtering under the following conditions. No. Films 5 to 7 were formed by reactive sputtering with N ₂ .

Sputtering conditions ・ Target composition (including inevitable impurities)
No. 1: Pure Ag
No. 2: Pure Al
No. 3: Pure Ta
No. 4-7: Pure Ti
No. 8: FTO
・ Substrate temperature: room temperature ・ Gas pressure: 2 mTorr
・ Atmosphere No. 1-4: Ar atmosphere 5-7: Ar atmosphere (10 sccm) + N ₂ atmosphere (5-20 sccm)
No. 8: Oxygen partial pressure [O ₂ / (Ar + O ₂ )] = 20% atmosphere 5 Nitrogen flow: 6sccm
No. 6. Nitrogen flow rate: 8sccm
No. 7 Nitrogen flow: 10 sccm

Composition of metal thin film The composition of the metal thin film of each obtained sample was etched by XPS analysis (Physical Electronics: Quantera SXM) and Ar ⁺ sputter from the surface in the depth direction until reaching the substrate, and at constant depth. Table 1 shows the results of analyzing the composition distribution in the depth direction of the metal thin film by measuring a narrow-area photoelectron spectrum. No. 5 and No. 6A and 6B show the montage spectrum diagrams obtained by XPS analysis in FIGS. 2a and 3a, respectively, and the results of examining the composition distribution in the depth direction are shown in FIGS. 2b and 3b, respectively.

  Using the above samples, the electrical resistivity and corrosion resistance were examined by the following methods.

[Electric resistivity (mΩcm)]
The electrical resistivity of each of the above samples was measured by measuring the sheet resistance of the thin film using a commercially available measuring instrument (manufactured by Hioki Electric Co., Ltd .: 3540 mOhm HiTester) according to a commonly used four-point probe method. The electrical resistivity was calculated by multiplying by The measurement results are shown in Table 1.

  The electrical resistivity of each sample was evaluated according to the following criteria (shown as “resistance value” in Table 1).

As an evaluation standard (）) that the electrical resistivity is particularly excellent, No. An electrical resistivity (mΩcm) of 8 (FTO) was employed (0.140). In addition, a practically preferable level was set as ◯, and a practically usable level was set as △, and these were evaluated as equivalent to FTO. Those that were not suitable for practical use were marked with x.
◎: 0.140 (mΩcm) or less ○: 0.140 (mΩcm) or more, 0.3 (mΩcm) or less △: 0.3 (mΩcm) or more, 0.5 (mΩcm) or less ×: 0.5 (mΩcm) )Super

[Corrosion resistance to electrolyte solution]
Each of the above samples was immersed in an electrolyte solution (100% iodine solution) at room temperature for 10 days, washed, and then visually evaluated for the presence or absence of dissolution of the metal thin film according to the following criteria.
○: The dissolution of the metal thin film could not be confirmed by visual observation. ×: The metal thin film was completely or partially dissolved and disappeared, and the substrate was exposed or the metal thin film was peeled off from the substrate.

  From Table 1, No. which is a metal thin film of the present invention. 3 (Ta), No. 3 4 (Ti), No. 4 5, 6 (TiON), no. All 7 (TiN) did not dissolve in the electrolyte solution and had excellent corrosion resistance. In particular, focusing on the electrical resistivity of the Ti material (Nos. 4 to 7), the nitrogen gas flow rate is increased to form a nitride (No. 7), or the oxygen amount is kept low (No. 6). The electrical resistivity was lower than that of pure Ti (No. 4), and a resistivity evaluation (◎) comparable to that of the standard FTO was obtained. In addition, No. When the amount of oxygen increased as shown in FIG. 5, the electrical resistivity increased (evaluation Δ), but was within the allowable range of this example. From the above results, it was confirmed that the electrical resistivity decreased as the amount of oxygen in the thin film decreased. A tendency similar to that of Ti material was also observed in Ta.

  The electrical resistivity is also No. No. 5 in which the nitrogen gas flow rate was increased compared to No.5. Nos. 6 and 7 have an oxygen content of 10% or less (FIGS. 3a and 3b) (No. 7 is 0%). The electrical resistivity was lower than 8 (FTO). On the other hand, no. No. 5 had an oxygen content as high as 30% (FIGS. 2a and 2b), and the electric resistivity slightly increased, but was within an allowable range (Δ).

  No. 3 (Ta) and No. 3 4 (Ti) is No. Although the electrical resistivity was inferior to 6 and 7, it had an electrical resistivity comparable to that of FTO (◯).

  No. 1 (Ag) and No. 1 2 (Al) is No. An electrical resistivity lower than 8 was shown. No. 1 is dissolved by the electrolyte solution, and No. 1 No. 2 was peeled off from the substrate, and the corrosion resistance of both was lowered.

1 Dye-sensitized solar cell element 2 Substrate (negative electrode side)
2 'substrate (positive electrode side)
3 (Transparent) conductive film (negative electrode side)
3 'conductive film (positive electrode side)
4 Catalyst layer 5 Electrolyte solution 6 Oxide semiconductor layer carrying a sensitizing dye (not shown) 7 Collector 10 Negative electrode 20 Positive electrode

Claims (3)

  In the dye-sensitized solar cell element in which the electrolyte solution is filled between the negative electrode and the positive electrode, at least one of the collector electrode in contact with the electrolyte solution and the metal thin film constituting the conductive film is a metal of Ti and Ta , And at least one selected from the group consisting of the nitrides of Ti, wherein the nitrides may contain oxygen, and have a low electrical resistance excellent in electrolytic solution corrosion resistance Metal thin film for dye-sensitized solar cells.   The metal thin film for a dye-sensitized solar cell according to claim 1, wherein the metal thin film is not coated with a corrosion-resistant material.   A dye-sensitized solar cell element using the metal thin film for a dye-sensitized solar cell according to claim 1 or 2.