JP2011044318A - Dye-sensitized solar cell and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive dye-sensitized solar cell having improved photoelectric conversion efficiency. <P>SOLUTION: The dye-sensitized solar cell includes a photoelectrode using a stainless steel plate, and a counter electrode using a translucent conductive material. The photoelectrode using the stainless steel plate as a substrate which has a chemical composition containing Cr: 16 mass% or more and Mo: 0.3 mass% or more and whose roughened surface is formed with pitting-corrosive recesses and reconditioned at an arithmetic average roughness Ra of 0.2 μm or more, has a semiconductor layer supporting sensitizing dye on the roughened surface of the substrate. The counter electrode has a catalyst thin film layer formed on the surface of the translucent conductive material and having visible light permeability. The semiconductor layer of the photoelectrode and the catalyst thin film layer of the counter electrode face each other via electrolyte. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a dye-sensitized solar cell using stainless steel as a constituent material of a photoelectrode (negative electrode), and a method for producing the same.

  Currently, solar cells using silicon as the photoelectric conversion element are the mainstream, but the practical application of “dye-sensitized solar cells” is being studied as a more economical next-generation solar cell to replace this. . Dye-sensitized solar cells require light from the outside to reach the sensitizing dye carried inside the “photoelectrode” (inside the cell). It is necessary to comprise a translucent conductive material. On the other hand, since the material constituting the electrode on the side opposite to the light incident side does not have to be translucent, it is advantageous to apply a metal material having good conductivity. Recently, it has been confirmed that stainless steel, which is a relatively inexpensive corrosion-resistant material, can be used as such a metal material, and thereby, cost reduction of the dye-sensitized solar cell is expected. Patent Document 1 discloses a dye-sensitized solar cell using a stainless steel plate as an electrode on the side opposite to the light incident side.

  1 and 2 schematically show the structure of a conventional dye-sensitized solar cell using a stainless steel plate as an electrode. FIG. 1 shows a type in which an electrode on the incident light side is a “counter electrode” for passing electrons to ions in the solution. FIG. 2 shows a “photo electrode” in which the electrode on the incident light side has a semiconductor layer (photoelectric conversion layer). It is a type that is.

  In the type of FIG. 1, a dye-sensitized solar cell 1 is configured by a translucent conductive material 3 formed on the surface of a translucent substrate 2 and a stainless steel plate 4 facing each other.

A semiconductor layer 6 is formed on the surface of the stainless steel plate 4. The semiconductor layer 6 is a porous layer obtained by sintering oxide semiconductor particles made of, for example, TiO ₂ particles having a large specific surface area, and a sensitizing dye 8 such as a ruthenium complex dye is supported on the surface of the oxide semiconductor 7. Has been. In this example, the photoelectrode 40 is constituted by the stainless steel plate 4 and the semiconductor layer 6 existing on the surface thereof. Note that the semiconductor layer 6 in the figure is conceptually drawn from the structure of the oxide semiconductor 7 and the sensitizing dye 8 for convenience of explanation, and does not reflect the actual structure of the semiconductor layer 6 as it is. (Same in FIGS. 2 and 3). On the other hand, a glass plate, a PEN (polyethylene naphthalate) film, or the like is used as the translucent substrate 2. The translucent conductive material 3 is usually composed of a translucent conductive film such as ITO (indium-tin oxide), FTO (fluorine-doped tin oxide), or TO (tin oxide). A catalyst thin film layer 5 such as platinum is formed on the surface of the translucent conductive material 3. In this example, the counter electrode 30 is constituted by the translucent conductive material 3 and the catalyst thin film layer 5 present on the surface thereof. Between the catalyst thin film layer 5 of the counter electrode 30 and the semiconductor layer 6 of the photoelectrode 40, for example, an electrolytic solution 9 containing iodide ions is filled. A load 11 is connected to the outside of the dye-sensitized solar cell 1 between the counter electrode 30 and the photoelectrode 40 with a conductive wire to form a circuit.

The operating principle of the battery will be briefly described by taking as an example the case where the oxide semiconductor 7 is TiO ₂ , the sensitizing dye 8 is a ruthenium complex dye, and the electrolytic solution 9 is a solution containing iodide ions. When the incident light 20 reaches the sensitizing dye (ruthenium complex dye) 8, the sensitizing dye 8 is excited by absorbing light, and its electrons are injected into the oxide semiconductor (TiO ₂ ) 7. The sensitizing dye (ruthenium complex dye) 8 in the excited state receives electrons from the iodide ion I ^{− in the} electrolyte 9 and returns to the ground state. I ⁻ is oxidized to I ₃ ⁻ , diffuses toward the catalyst thin film layer 5 of the counter electrode 30, receives electrons from the counter electrode 30, and returns to I ⁻ . As a result, electrons are sensitized dye (ruthenium complex dye) 8 → oxide semiconductor (TiO ₂ ) 7 → stainless steel plate 4 → load 11 → translucent conductive material 3 → catalytic thin film layer 5 → electrolyte 9 → sensitizing dye. (Ruthenium complex dye) It moves by the route of 8. As a result, a current for operating the load 11 is generated.

In the type of FIG. 2, the stainless steel plate 4 is used for the counter electrode 30, and the translucent conductive material 3 such as ITO, FTO, or TO is used for the photoelectrode 40. The principle of current generation is basically the same as that of the type shown in FIG. In this case, the electrons are sensitizing dye (ruthenium complex dye) 8 → oxide semiconductor (TiO ₂ ) 7 → translucent conductive material 3 → load 11 → stainless steel plate 4 → catalyst thin film layer 5 → electrolytic solution 9 → sensitizing dye. (Ruthenium complex dye) It moves by the route of 8. As a result, a current for operating the load 11 is generated.

JP 2008-34110 A

  In the dye-sensitized solar cell of the type shown in FIGS. 1 and 2, cost reduction and conductivity improvement are realized by using a stainless steel plate for one of the electrodes. However, in order to promote the spread of dye-sensitized solar cells, further improvement in photoelectric conversion efficiency is desired. The present invention is intended to provide a technique for improving the photoelectric conversion efficiency in a dye-sensitized solar cell using a stainless steel plate for one of the electrodes in order to meet such a demand.

  The photoelectrode of the dye-sensitized solar cell has a semiconductor layer as described above. This semiconductor layer is usually formed on a conductive substrate, and current is taken through the substrate. In the type of FIG. 1, the stainless steel plate 4 corresponds to the conductive base material, and in the type of FIG. As a result of various studies, the inventors have found that the adhesion between the semiconductor layer and the conductive base material greatly affects the photoelectric conversion efficiency. When the adhesion between the semiconductor layer and the conductive substrate is increased, the electrical resistance at the joint between the two is reduced, which is considered to contribute to the improvement of the photoelectric conversion efficiency. As a result of examining the configuration of the battery in detail, the inventors applied the roughened stainless steel plate having a specific surface form to the stainless steel plate 4 constituting the photoelectrode 40 in the type of FIG. It has been found that the adhesion between the stainless steel plate 4 and the stainless steel plate 4 is increased, and the photoelectric conversion efficiency can be improved as compared with the prior art.

In Patent Document 1, as a stainless steel to be applied to the electrode material of the dye-sensitized solar cell, a steel type having a Cr content of 17% by mass or more and a Mo content of 0.8% by mass or more should be selected. Teaching. However, the inventors subsequently conducted a study considering practicality, and as a result, stainless steel having a Cr content of 16% by mass or more and a Mo content of 0.3% by mass or more was replaced with a dye-sensitized solar cell. It was found that it can be applied to electrode materials.
The present invention has been completed based on these findings.

That is, in the present invention, a dye-sensitized solar cell having a photoelectrode using a stainless steel plate and a counter electrode using a translucent conductive material,
The photoelectrode is made of a stainless steel species having any one of the following chemical compositions (A) to (D), and has a roughened surface in which a pitting corrosion-like recess is formed and the arithmetic average roughness Ra is adjusted to 0.2 μm or more. With a stainless steel plate having a base material, a semiconductor layer carrying a sensitizing dye is provided on the roughened surface of the base material,
The counter electrode has visible light permeability by forming a catalyst thin film layer on the surface of the translucent conductive material,
Provided is a dye-sensitized solar cell in which a semiconductor layer of a photoelectrode and a catalyst thin film layer of a counter electrode are opposed to each other through an electrolyte.

[Stainless steel grade]
(A) Cr: 16% by mass or more, Mo: 0.3% by mass or more, and corresponding to a ferritic stainless steel type specified in JIS G4305: 2005.
(B) A material containing Cr: 16% by mass or more, Mo: 0.3% by mass or more and corresponding to an austenitic stainless steel type specified in JIS G4305: 2005.
(C) In mass%, C: 0.15% or less, Si: 1.2% or less, Mn: 1.2% or less, P: 0.04% or less, S: 0.03% or less, Ni: 0.0 6% or less, Cr: 16 to 32%, Mo: 0.3 to 3%, Cu: 0 to 1%, Nb: 0 to 1%, Ti: 0 to 1%, Al: 0 to 0.2%, N: 0.025% or less, B: 0 to 0.01%, remaining ferritic stainless steel grade consisting of Fe and inevitable impurities.
(D)% by mass C: 0.15% or less, Si: 4% or less, Mn: 2.5% or less, P: 0.045% or less, S: 0.03% or less, Ni: 6-28% Cr: 16 to 32%, Mo: 0.3 to 7%, Cu: 0 to 3.5%, Nb: 0 to 1%, Ti: 0 to 1%, Al: 0 to 0.1%, N : 0.3% or less, B: 0 to 0.01%, balance of Fe and austenitic stainless steel composed of inevitable impurities.

  In the above-described dye-sensitized solar cell, the counter electrode is particularly preferably one having visible light transmittance such that the transmittance of light having a wavelength of 500 nm is 55% or more. Platinum, nickel, or a conductive polymer is mentioned as a catalyst which comprises the catalyst thin film layer of a counter electrode. Here, when the catalyst is platinum or nickel, the thickness of the catalyst thin film layer is preferably 0.5 to 5 nm. When the catalyst is a conductive polymer, the thickness of the catalyst thin film layer is preferably 1 to 10 nm.

  The roughened surface of the base stainless steel plate used for the photoelectrode is particularly preferably one having an edge-like boundary at a portion where adjacent concave portions are in contact with each other.

In the present invention, as a method for producing the dye-sensitized solar cell,
A step of obtaining a base material having a roughened surface having an arithmetic average roughness Ra of 0.2 μm or more by etching a stainless steel plate in an aqueous solution containing trivalent iron ions to form a pitting corrosion-like recess;
Forming a coating film containing oxide semiconductor particles on the roughened surface;
Baking the coating film into a porous semiconductor layer;
A photoelectrode comprising a semiconductor layer having a sensitizing dye supported on the roughened surface of the base stainless steel plate, the sensitizing dye being supported on the semiconductor layer by immersing the semiconductor layer in a solvent in which the sensitizing dye is dispersed; The process of
The photoelectrode and a visible light transmissive counter electrode formed by forming a catalyst thin film layer on the surface of the translucent conductive material are arranged so that the semiconductor layer of the photo electrode and the catalyst thin film layer of the counter electrode face each other, A step of encapsulating an electrolyte between both electrodes,
A method for producing a dye-sensitized solar cell having the following is provided.
An aqueous solution containing trivalent iron ions is, for example, an aqueous solution containing ferric chloride.

  According to the present invention, in a dye-sensitized solar cell using a stainless steel plate as an electrode on one side, it has become possible to improve the photoelectric conversion efficiency as compared with the related art. In addition, in the dye-sensitized solar cell of the present invention, it is possible to use a stainless steel type having a lower Cr content and a lower Mo content for the electrode, and it is expected to be applied to applications where a cheaper steel type is desired. Is done.

The figure which showed typically the structure of the conventional dye-sensitized solar cell which used the stainless steel plate for the photoelectrode. The figure which showed typically the structure of the conventional dye-sensitized solar cell which used the stainless steel plate for the counter electrode. The figure which illustrated typically the composition of the dye sensitizing type solar cell of the present invention. The figure which illustrated typically the cross-section of the roughening surface where the boundary of adjacent recessed parts is gentle. The figure which illustrated typically the cross-section of the roughening surface which has an edge-like boundary in the part which adjacent recessed parts contact | connect. An example of the SEM photograph of the surface of the roughened stainless steel plate which formed the pitting corrosion-like recessed part by etching in a trivalent iron ion containing aqueous solution.

  FIG. 3 schematically illustrates the configuration of the dye-sensitized solar cell of the present invention. The basic configuration of the battery and the principle of current generation are the same as those in FIG. However, the stainless steel plate 4 constituting the photoelectrode 40 is greatly different in that the surface on which the semiconductor layer 6 exists is a roughened surface 10.

[Roughening form of stainless steel sheet]
In this invention, the stainless steel plate roughened by forming a pitting corrosion-like recessed part is used for the electroconductive base material (member which bears electricity while holding a semiconductor layer). The pitting corrosion-like recess is a recess formed by causing “pitting corrosion” which is one form of local corrosion on the surface of the stainless steel plate by chemical etching in an electrolyte aqueous solution. The surface roughened by the formation of a large number of pitting corrosion-like recesses exerts an anchor effect on the semiconductor layer existing thereon, and contributes to improving the adhesion between the stainless steel plate and the semiconductor layer. As a result, the bonding force between the two increases and the contact area also increases, and as a result, the electrical resistance at the bonding interface between the two decreases. As a result of various studies, when a stainless steel plate having an arithmetic average roughness Ra of 0.2 μm or more on the roughened surface on which pitting corrosion-like recesses are formed, a clear increase in photoelectric conversion efficiency is recognized. When Ra is smaller than that, the above-mentioned action tends to be insufficient, and it is difficult to stably improve the photoelectric conversion efficiency. A roughened surface having pitting corrosion-like recesses can be formed by etching in an aqueous electrolyte solution containing trivalent iron ions, as will be described later. Ra grows in the (depth direction) and disappears in the plate thickness direction while reducing the thickness of the adjacent recesses, so Ra does not increase indefinitely. Therefore, the upper limit of Ra does not need to be specified in particular, but in practice, a good photoelectric conversion efficiency improvement effect is likely to be obtained when the range of Ra is approximately 0.2 to 5 μm.

  It is preferable that the area ratio of the pitting-corrugated concave portion occurrence portion on the stainless steel plate surface is 20% or more in the projected area ratio when the roughened surface is viewed from directly above. The pitting corrosion-like recessed part may be formed in the whole surface of the steel plate surface, and the area ratio of the pitting corrosion-like recessed part generating part may be 100%.

  FIG. 4 schematically illustrates a cross-sectional structure of a roughened surface where the boundary between adjacent recesses is gentle. Although the recessed part 60 is formed in the surface of the stainless steel plate 50, the recessed part boundary 70 is exhibiting a gentle form. Such a roughened form is easily obtained when a stainless steel plate is etched in an aqueous electrolyte solution in which trivalent iron ions do not exist, or when the surface is roughened by physical removal means such as polishing or shot blasting. When the recess boundary 70 becomes excessively gentle, the anchor effect on the semiconductor layer is reduced, and the effect of improving the adhesion tends to be insufficient. In this case, the improvement effect of photoelectric conversion efficiency is also reduced.

  FIG. 5 schematically illustrates a cross-sectional structure of a roughened surface having an edge-like boundary at a portion where adjacent concave portions are in contact with each other. This roughened form is particularly suitable as a stainless steel plate applied to the present invention. A concave portion 60 is formed on the surface of the stainless steel plate 50. This concave portion is a pitting corrosion-like concave portion, and the opening diameter of the pitting corrosion gradually increases in the process of growing the pitting corrosion in the depth direction. The 60 wall surfaces collide with each other, and the recess boundary 70 becomes an edge-shaped boundary. Such a roughened form can be obtained by etching in an aqueous electrolyte solution in which trivalent iron ions are present. Due to the presence of the edge-like boundary, an excellent anchor effect for the semiconductor layer is exhibited, and the adhesion between the stainless steel plate and the semiconductor layer is improved. As a result, the electrical resistance at the junction between the stainless steel plate and the semiconductor layer is reduced, and the photoelectric conversion efficiency is significantly improved.

  In FIG. 6, the SEM photograph of the roughening surface suitable as a roughening stainless steel plate applied to the dye-sensitized solar cell of this invention is illustrated. An edge boundary is observed between adjacent pitting-like recesses.

[Chemical composition of stainless steel sheet]
In the present invention, the stainless steel plate applied to the conductive substrate of the photoelectrode needs to employ a stainless steel type exhibiting excellent durability against the electrolyte solution of the dye-sensitized solar cell. As a result of detailed studies by the inventors, it is possible to construct a dye-sensitized solar cell that can withstand practical use by using a stainless steel type containing 16 mass% or more of Cr and 0.3 mass% or more of Mo. I found out that

Generally stainless steel chloride ion Cl ^- is to have a weak point in corrosion resistance to an aqueous solution containing, to improve its corrosion resistance the addition of increasing or Mo and Cr is to be effective. For example, in ferrite type SUS444 suitable for water heaters, Cr: 17% by mass or more and Mo: 1.75% by mass or more are ensured. Even in SUS316, which is a high corrosion resistance austenitic general-purpose steel grade, Cr: 16% by mass. As mentioned above, Mo: Content of 2 mass% or more is ensured. However, there are few reports on the corrosion resistance of stainless steel against iodide ions, and practical studies have not been sufficiently conducted especially for photoelectrode applications of dye-sensitized solar cells. Therefore, the inventors investigated in detail and found that after the cell was left at 65 ° C. for 100 hours with respect to the initial photoelectric conversion efficiency η ₀ (%) measured immediately after the cell of the dye-sensitized solar cell was constructed. Dye-sensitized solar cells that have a measured rate of change in photoelectric conversion efficiency η ₁ (%) (conversion efficiency retention rate according to formula (2) described later) of 80% or more are used in applications incorporated into everyday personal use products. It can be evaluated as having practical durability. It is more preferable that the conversion efficiency retention is 90% or even 95% or more. As a result of further investigation, as described above, if a stainless steel type containing Cr of 16% by mass or more and Mo of 0.3% by mass or more is adopted, the conversion efficiency retention becomes 80% or more. It was revealed that a sensitive solar cell can be sufficiently constructed.

  Specifically, the stainless steel types shown in the above (A) to (D) are suitable targets. In addition, when further corrosion resistance is desired, it is preferable that Cr content shall be 17 mass% or more. Further, the Mo content is preferably 0.5% by mass or more, and may be controlled in a range of 0.8% by mass or more, or 1.0% by mass or more. The upper limit of Cr should just be 32 mass%, and you may adjust a component in 25 mass% or less. The upper limit of Mo should just be 3 mass%, and you may adjust a component in the range of 2 mass% or less.

[Roughening of stainless steel sheet]
The above-mentioned specific roughening form is that trivalent iron ions are present on a stainless steel plate having a surface texture that is not roughened, such as normal annealing / pickling finish, BA annealing finish, or skin pass rolling finish. It can be obtained by etching in an existing aqueous solution. As an etching method, a technique of dipping and holding in a liquid, a technique of alternating electrolysis in a liquid, or the like can be employed. In either case, ferric chloride (FeCl ₃ ) can be suitably used as a trivalent iron ion source.

In the case of immersion holding, a method of etching in a mixed aqueous solution of ferric chloride (FeCl ₃ ) and hydrochloric acid (HCl) is extremely effective. Specifically, for example, within the condition ranges of Fe ³⁺ ion concentration: 15 to 100 g / L, HCl concentration: 20 to 200 g / L, temperature: 35 to 70 ° C., immersion time: 3 to 120 sec, pitting corrosion-like recesses And a condition for obtaining a roughened surface with Ra of 0.2 μm or more can be found.

In the case of alternating electrolysis, for example, a ferric chloride aqueous solution is used as an electrolytic solution, Fe ³⁺ ion concentration: 1 to 50 g / L, temperature: 30 to 70 ° C., anode electrolytic current density: 1.0 to 10.0 kA / m ^2. Cathodic electrolysis current density: 0.1 to 3.0 kA / m ² , alternating electrolysis cycle: 1 to 20 Hz, electrolysis time: 10 to 300 sec. It is possible to find a condition for obtaining a roughened surface of 0.2 μm or more. If the alternating electrolysis cycle is made smaller, the energization time per cycle becomes longer, so that the size of the pitting corrosion-like recess can be increased, and conversely, if the alternating electrolysis cycle is made larger, the size of the pitting corrosion-like depression can be made smaller.

[Manufacture of photoelectrodes]
The photoelectrode can be manufactured, for example, by the following method. First, on the roughened surface of the above-mentioned roughened stainless steel plate, a paint (paste or liquid) containing oxide semiconductor particles is applied and dried to form a coating film. Thereafter, the coating film is baked to sinter the oxide particles, thereby forming a porous semiconductor layer. The firing may be performed by inserting the stainless steel plate into a heating furnace and maintaining the temperature at which the sintering proceeds moderately (for example, 400 to 600 ° C.). TiO ₂ is generally used as the oxide semiconductor, but ZnO, SnO ₂ , ZrO _2, or the like can also be used. These oxides may be used in combination. The porous semiconductor layer thus obtained is immersed in an organic solvent in which the sensitizing dye is dispersed, whereby the sensitizing dye is supported on the semiconductor layer. The stainless steel plate may be immersed in the organic solvent. A typical example of the sensitizing dye is a ruthenium complex dye.

[Production of counter electrode]
The counter electrode is formed by holding a translucent conductive material on the surface of a translucent substrate such as a glass plate or a PEN (polyethylene naphthalate) film, and further forming a catalyst thin film layer on the surface of the translucent conductive material. Can be manufactured. As the translucent conductive material, a conductive film such as ITO (indium-tin oxide), FTO (fluorine-doped tin oxide), or TO (tin oxide) can be used. As the catalyst thin film layer, a metal film such as platinum or nickel, or a conductive polymer film such as polyaniline or polyethylenedioxythiophene is suitable. The metal film can be formed by, for example, a sputtering method. The conductive polymer film can be formed by, for example, a spin coating method. The counter electrode is particularly preferably one having a visible light transmittance with a transmittance of light having a wavelength of 500 nm of 55% or more. In this case, high photoelectric conversion efficiency can be obtained. The light transmittance varies depending on the thickness of the catalyst thin film layer. The thinner the catalyst thin film layer, the higher the transmittance. However, if the catalyst thin film layer is excessively thinned, the photoelectric conversion efficiency decreases due to the decrease in the catalytic action. As a result of various studies, when the catalyst is platinum or nickel, the thickness of the catalyst thin film layer is preferably adjusted in the range of 0.5 to 5 nm. When the catalyst is polyaniline, the thickness of the catalyst thin film layer is preferably adjusted in the range of 1 to 10 nm.

[Battery construction]
The dye-sensitized solar cell of the present invention is constructed by arranging the photoelectrode and the counter electrode so that the semiconductor layer of the photoelectrode and the catalyst thin film layer of the counter electrode face each other through the electrolytic solution.

  Stainless steel having the composition shown in Table 1 was melted, and a cold-rolled annealed steel sheet (No. 2D finish) having a thickness of 0.2 mm was manufactured by a general stainless steel sheet manufacturing process. In Table 1, in the structure column, “α” means ferrite and “γ” means austenite. “-” (Hyphen) in the table means that it is below the measurement limit by a normal analysis method in the steelmaking field.

(Roughening treatment)
A sample cut out from the steel sheet was subjected to a surface roughening treatment by dipping and alternating electrolysis to obtain a test material. Part of the test material was also prepared with a No. 2D finish that had not been roughened. In Table 2, “immersion” indicates the immersion retention, and “electrolysis” indicates the alternating electrolysis.
The roughening treatment by dipping is a method in which the test piece is immersed for 40 seconds in a ferric chloride + hydrochloric acid mixed aqueous solution of Fe ³⁺ ion concentration: 30 g / L, HCl concentration: 30 g / L, temperature: 50 ° C. went.
The roughening treatment by alternating electrolysis is performed using an aqueous ferric chloride solution having an Fe ³⁺ ion concentration of 5 to 50 g / L and a temperature of 35 to 65 ° C., an anode electrolysis current density of 3 kA / m ² , and a cathode electrolysis current. Density: 0.3 kA / m ² , alternating electrolysis cycle: 10 Hz, electrolysis time: 10 to 120 sec.
As a result of SEM observation, pitting corrosion-like recesses are generated at an area ratio of 20% or more on any roughened surface obtained here, and there is an edge-like boundary at a portion where adjacent recesses are in contact with each other. It was confirmed that

[Measurement of Ra]
The arithmetic average roughness Ra of the roughened surface obtained was measured using a fine shape measuring instrument (manufactured by Kosaka Laboratory Ltd .; Surfcorder ET4000A).

[Production of photoelectrode]
A TiO ₂ paste (Peccell Technologies, Inc .; PECC-01-06) was prepared as a material for obtaining a semiconductor layer. A TiO ₂ -containing coating film was formed by applying a TiO ₂ paste to the surface of the test material (roughened surface is a roughened surface) by a doctor blade method and drying. Thereafter, the stainless steel plate as a base material was placed in an oven at 450 ° C. and fired, and the semiconductor layer was formed by sintering the TiO ₂ particles. The average thickness of the obtained semiconductor layer was 10 μm. A ruthenium complex dye (PECD-07 manufactured by the same company) was used as a sensitizing dye, and this was dispersed in a mixed solvent of acetonitrile and tert-butanol to obtain a dye solution. The stainless steel substrate on which the semiconductor layer was formed was immersed in this dye solution to obtain a photoelectrode in which a sensitizing dye was supported on the semiconductor layer.

[Preparation of counter electrode]
An “ITO-PEN film” (Peccell Technologies, Inc .; PECF-IP) in which an ITO film was formed on a PEN film substrate was prepared as a translucent conductive material for the counter electrode. This was set in a sputtering apparatus and sputtered for 1 minute using platinum as a target to form a platinum catalyst thin film layer on the ITO film to obtain a counter electrode. In this case, the film thickness of platinum is about 3 nm.

[Production of battery]
Combining the photoelectrode and the counter electrode with a heat-sealing film (Serlin film manufactured by Pexel Technologies Co., Ltd.) arranged so as to surround the cell portion, the photoelectrode stainless steel surface and the counter electrode A cell structure having a distance of 50 μm was obtained. The cell structure was heated and compressed with a hot press to seal the cell, and an epoxy resin was applied around the cell and cured. An electrolytic solution (manufactured by the same company; PECE-K01) was injected into the inside of the cell from the electrolytic solution injection port provided in the counter electrode. Thereafter, the electrolyte solution injection port was sealed with an epoxy resin to obtain a dye-sensitized solar cell.

[Measurement of photoelectric conversion efficiency]
The conversion efficiency of the produced dye-sensitized solar cell was measured according to the following procedure.
Using a solar simulator (Yamashita Denso Co., Ltd .; YSS-100) to the dye-sensitized solar cell, irradiating AM1.5, 100 mW / cm ² pseudo sunlight from the counter electrode side, manufactured by KEITHLEY; 2400 type The IV characteristics were measured with a source meter, and the values of the short circuit current JSC, the open circuit voltage VOC, and the form factor FF were obtained. From these values, the value of photoelectric conversion efficiency η was determined by the following formula (1).
Photoelectric conversion efficiency η (%) = short circuit current JSC (mA / cm ² ) × open circuit voltage VOC (V) × form factor FF / incident light 100 (mW / cm ² ) × 100 (1)

Here, the initial photoelectric conversion efficiency measured immediately after the production of the battery is expressed as η ₀ (%). After the η ₀ measurement, the solar cell was left in a constant temperature bath at 65 ° C. for 100 hours. Thereafter, the photoelectric conversion efficiency was measured in the same manner. Here, the photoelectric conversion efficiency after being left at 65 ° C. for ₁₀₀ hours is expressed as η ₁ (%). The degree of change in photoelectric conversion efficiency due to standing under the above conditions was evaluated by the conversion efficiency retention rate (%) defined by the following formula (2).
Conversion efficiency retention ratio (%) = η ₁ / η ₀ × 100 (2)
The results are shown in Table 2.

As can be seen from Table 2, the examples of the present invention used a roughened stainless steel plate having a Cr content and a Mo content in appropriate ranges, a pitting corrosion-like recess formed, and Ra of 0.2 μm or more. The photoelectric conversion efficiency was high for both η ₀ and η _1, and the conversion efficiency retention was extremely high.

On the other hand, Test Nos. 1 to 5, which are comparative examples, are those using a stainless steel plate having a low Mo content, and the photoelectric conversion efficiency after leaving at 65 ° C. for 100 hours is remarkably lowered, so that the conversion efficiency retention ratio is high. It was bad. This is thought to be due to the fact that the stainless steel components Fe and Cr were eluted in the electrolyte due to the lack of corrosion resistance in the electrolyte. In Test Nos. 6 to 8, it was considered that the adhesion between the stainless steel plate of the photoelectrode and the semiconductor layer was low due to the use of a stainless steel plate that had not been roughened, and the photoelectric conversion efficiency was η ₀ , η ₁ Both were low.

A photoelectrode corresponding to No. 11 (steel G) in Table 2 prepared in the same manner as in Example 1 was prepared.
As the counter electrode, here, the catalyst was made of platinum, nickel or polyaniline, and the thickness of the catalyst thin film layer was variously changed as follows. As in Example 1, an “ITO-PEN film” in which an ITO film was formed on a PEN film substrate was prepared. When platinum or nickel was employed, the catalyst thin film layer was formed by a sputtering apparatus in the same manner as in Example 1, and the film thickness was controlled by changing the sputtering time. When using polyaniline, a solution of polyaniline dissolved in a toluene solvent is dropped onto the ITO film, a catalyst thin film layer is formed by spin coating, and the film thickness is controlled by changing the spin coating rotation speed. did. About the obtained counter electrode, the transmittance | permeability of the light of wavelength 500nm was measured with the spectrophotometer (Hitachi High-Technologies make; U-4100).
Using these photoelectrodes and counter electrode, a dye-sensitized solar cell was produced in the same manner as in Example 1, and the photoelectric conversion efficiency η ₀ was measured. The results are shown in Table 3.

  As can be seen from Table 3, in order to achieve good photoelectric conversion efficiency, it is important to increase the light transmittance of the counter electrode above a certain level.

DESCRIPTION OF SYMBOLS 1 Dye-sensitized solar cell 2 Translucent substrate 3 Translucent conductive material 4 Stainless steel plate 5 Catalyst thin film layer 6 Semiconductor layer 7 Oxide semiconductor 8 Sensitizing dye 9 Electrolytic solution 10 Roughened surface 11 Load 30 Counter electrode 40 Photoelectrode 50 Stainless steel plate 60 Recess 70 Recess boundary

Claims (11)

A dye-sensitized solar cell having a photoelectrode using a stainless steel plate and a counter electrode using a translucent conductive material,
The photoelectrode contains Cr: 16% by mass or more, Mo: 0.3% by mass or more, and has a chemical composition corresponding to a ferritic stainless steel type specified in JIS G4305: 2005, and a pitting corrosion-like recess is formed. A stainless steel plate having a roughened surface with an arithmetic average roughness Ra adjusted to 0.2 μm or more is used as a base material, and a semiconductor layer carrying a sensitizing dye is provided on the roughened surface of the base material. Yes,
The counter electrode has visible light permeability by forming a catalyst thin film layer on the surface of the translucent conductive material,
A dye-sensitized solar cell in which a semiconductor layer of a photoelectrode and a catalyst thin film layer of a counter electrode face each other through an electrolyte.   The stainless steel used for the photoelectrode contains Cr: 16% by mass or more, Mo: 0.3% by mass or more, and has a chemical composition corresponding to the austenitic stainless steel type specified in JIS G4305: 2005. Item 2. The dye-sensitized solar cell according to Item 1.   Stainless steel used for the photoelectrode is C: 0.15% or less, Si: 1.2% or less, Mn: 1.2% or less, P: 0.04% or less, S: 0.03% or less in mass%. Ni: 0.6% or less, Cr: 16 to 32%, Mo: 0.3 to 3%, Cu: 0 to 1%, Nb: 0 to 1%, Ti: 0 to 1%, Al: 0 to 0% 2. The dye-sensitized solar cell according to claim 1, which is a ferritic stainless steel made of 0.2%, N: 0.025% or less, B: 0 to 0.01%, the balance Fe and unavoidable impurities.   The stainless steel used for the photoelectrode is, by mass%, C: 0.15% or less, Si: 4% or less, Mn: 2.5% or less, P: 0.045% or less, S: 0.03% or less, Ni : 6-28%, Cr: 16-32%, Mo: 0.3-7%, Cu: 0-3.5%, Nb: 0-1%, Ti: 0-1%, Al: 0-0 The dye-sensitized solar cell according to claim 1, which is an austenitic stainless steel comprising 0.1%, N: 0.3% or less, B: 0 to 0.01%, the balance Fe and unavoidable impurities.   The dye-sensitized solar cell according to any one of claims 1 to 4, wherein the counter electrode has visible light transmittance such that the transmittance of light having a wavelength of 500 nm is 55% or more.   The dye-sensitized solar cell according to any one of claims 1 to 5, wherein the catalyst constituting the catalyst thin film layer of the counter electrode is platinum, nickel, or a conductive polymer.   The dye-sensitized solar cell according to claim 6, wherein the catalyst is platinum or nickel, and the thickness of the catalyst thin film layer is 0.5 to 5 nm.   The dye-sensitized solar cell according to claim 6, wherein the catalyst is a conductive polymer, and the thickness of the catalyst thin film layer is 1 to 10 nm.   The dye-sensitized solar according to any one of claims 1 to 8, wherein the roughened surface of the base stainless steel plate used for the photoelectrode has an edge-like boundary at a portion where adjacent concave portions are in contact with each other. battery. A step of obtaining a base material having a roughened surface having an arithmetic average roughness Ra of 0.2 μm or more by etching a stainless steel plate in an aqueous solution containing trivalent iron ions to form a pitting corrosion-like recess;
Forming a coating film containing oxide semiconductor particles on the roughened surface;
Baking the coating film into a porous semiconductor layer;
A photoelectrode comprising a semiconductor layer having a sensitizing dye supported on the roughened surface of the base stainless steel plate, the sensitizing dye being supported on the semiconductor layer by immersing the semiconductor layer in a solvent in which the sensitizing dye is dispersed; The process of
The photoelectrode and a visible light transmissive counter electrode formed by forming a catalyst thin film layer on the surface of the translucent conductive material are arranged so that the semiconductor layer of the photo electrode and the catalyst thin film layer of the counter electrode face each other, A step of encapsulating an electrolyte between both electrodes,
The manufacturing method of the dye-sensitized solar cell in any one of Claims 1-9 which have these.   The method for producing a dye-sensitized solar cell according to claim 10, wherein the aqueous solution containing trivalent iron ions is a ferric chloride-containing aqueous solution.