JP5566082B2 - Counter electrode of dye-sensitized solar cell, method for producing the same, and battery - Google Patents

Description

  The present invention relates to a counter electrode of a dye-sensitized solar cell, which uses stainless steel as a current collecting member, a manufacturing method thereof, and a dye-sensitized solar cell using the counter electrode.

  Conventionally, solar cells using mainly silicon as a photoelectric conversion element have been used, but the practical application of “dye-sensitized solar cells” has been studied as a more economical next-generation solar cell.

  FIG. 1 schematically shows the configuration of a general dye-sensitized solar cell. A translucent conductive film 3 is provided on the surface of the translucent plate-like body 2, and a porous semiconductor layer 4 carrying a sensitizing dye is formed on the surface of the translucent conductive film 3. A photoelectrode 10 is constituted by the translucent conductive film 3 and the porous semiconductor layer 4. The translucent conductive film 3 is composed of an oxide conductive film such as ITO (indium-tin oxide), FTO (fluorine-doped tin oxide), TO (tin oxide), ZnO (zinc oxide), and the like. The plate-like body 2 is made of glass or plastic film. A counter electrode 20 is disposed so as to face the photoelectrode 10, and the dye-sensitized solar cell 1 is configured by the photoelectrode 10, the counter electrode 20, and the electrolytic solution 8 interposed between the two electrodes. The counter electrode 20 is composed of a conductive material 6 and a catalyst layer 7 provided on the surface thereof. A substrate 5 for supporting the counter electrode 20 is provided as necessary.

The porous semiconductor layer 4 constituting the photoelectrode 10 is a porous layer using semiconductor particles such as TiO ₂ having a large specific surface area, and a sensitizing dye such as a ruthenium complex is supported on the surface of the semiconductor particles. In general, an electrolytic solution containing iodine (I ₂ ) and iodide ions is used. When the incident light 30 reaches the sensitizing dye supported on the porous semiconductor layer 4, the sensitizing dye (for example, ruthenium complex) is excited by absorbing light, and the electrons are converted into semiconductor particles (for example, TiO ₂ ). Injected. The sensitizing dye that is in an oxidized state by injecting excited electrons receives electrons from ions (for example, iodide ions I ⁻ ) in the electrolyte 8 and returns to the ground state. At this time, ions (for example, I ⁻ ) in the liquid are oxidized to ions having different valences (for example, I ₃ ⁻ ), diffuse to the counter electrode 20, receive electrons from the counter electrode 20, and receive original ions (for example, I ^−). Return to). As a result, electrons move along the path “porous semiconductor layer 4 → translucent conductive film 3 → load 40 → conductive material 6 → catalyst layer 7 → electrolytic solution 8 → porous semiconductor layer 4”. As a result, a current for operating the load 40 is generated.

  As the conductive material 6 constituting the counter electrode 20, a light-transmitting oxide conductive film such as ITO or FTO may be used in the same manner as the light-transmitting conductive film 3. In this case, when the catalyst layer 7 is a thin film layer having many pinholes, visible light can be transmitted through the counter electrode 20, so that the dye-sensitized solar cell 1 itself can have visible light transmittance. . That is, a so-called “see-through” appearance is obtained in which the opposite side can be seen through the dye-sensitized solar cell 1 to some extent, and this property may be utilized in terms of design. Further, there is an advantage that incident light inserted from the counter electrode side can also be used for power generation.

  However, since a light-transmitting oxide conductive film has lower conductivity than a metal material, use of such a light-transmitting conductive film as a counter electrode improves the photoelectric conversion efficiency of a dye-sensitized solar cell. It was disadvantageous above. In addition, since the catalyst layer 7 covers the surface of the conductive material 6, the visible light transmittance of the counter electrode 20 is weakened, and it is often difficult to obtain a desired see-through appearance.

  On the other hand, there is a dye-sensitized solar cell using a stainless steel plate as a counter electrode (Patent Document 1). In this type of dye-sensitized solar cell, conductivity at the counter electrode is improved compared to the one using an oxide conductive film, and good photoelectric conversion efficiency can be obtained even if the thickness of the platinum catalyst layer is reduced. It has been known. However, see-through appearance cannot be obtained.

  As a stainless steel material having translucency, a stainless steel mesh is known. However, this is expensive because it is a woven fabric made of fine stainless steel wires, and cannot be easily employed for the spread of dye-sensitized solar cells.

JP 2009-26532 A

  The present invention provides a dye-sensitized solar cell counter electrode having visible light permeability, excellent conductivity, and low cost, and a dye sensitizing exhibiting a see-through appearance using the same. An object is to provide a sensitive solar cell.

  As a result of detailed studies, the inventors have found that the above object can be achieved by using a stainless steel sheet having a large number of through holes as the conductive material of the counter electrode. It was also found that such a stainless steel sheet can be efficiently produced by etching in a ferric chloride aqueous solution.

That is, in the present invention,
A counter electrode of a dye-sensitized solar cell composed of a stainless steel sheet having a through hole and a catalyst layer formed on at least one surface thereof,
The stainless steel sheet contains Cr: 16% by mass or more, Mo: 0.3% by mass or more, and has a chemical composition corresponding to a ferritic steel type defined in JIS G4305: 2005. A counter electrode of a dye-sensitized solar cell having a through hole in which the area ratio of the through portion occupying the projected area viewed in the thickness direction is 5 to 80% and the average diameter of the through portion is 5 to 500 μm. Provided.
The through holes of the stainless steel sheet are preferably formed by immersing the rolled sheet in an aqueous electrolyte solution to grow pitting corrosion pits.

As the steel types of the stainless steel sheet, the following are suitable targets when standard steel types are listed.
(1) Cr: 16 to 32% by mass, Mo: 0.3 to 3% by mass, and corresponding to a ferritic steel type specified in JIS G4305: 2005.
(2) Cr: 16 to 32% by mass, Mo: 0.3 to 7% by mass, and corresponding to the austenitic steel grade specified in JIS G4305: 2005.

When the content range of each element is specifically shown, the following are suitable targets.
(3) By 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%, Ferritic stainless steel consisting of N: 0.025% or less, B: 0-0.01%, balance Fe and inevitable impurities.
(4) 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 : Austenitic stainless steel consisting of 0.3% or less, B: 0 to 0.01%, balance Fe and inevitable impurities.
Here, the element whose lower limit of content is 0% is an optional element.

  As the catalyst layer, those using any one of platinum, nickel, polyaniline, and carbon are suitable targets.

Moreover, as a manufacturing method of said counter electrode,
A stainless steel rolled sheet having a thickness of 0.005 to 0.2 mm is immersed in an aqueous ferric chloride solution having a trivalent iron ion concentration of 30 to 100 g / L and a hydrochloric acid concentration of 0 to 50 g / L, Through the growth of pitting corrosion-like pits, through holes with an area ratio of the penetrating portion occupying the projected area of the sheet in the thickness direction of 5 to 80% and an average diameter of the penetrating portion of 5 to 500 μm are formed. Forming (through hole forming step),
A step of forming a catalyst layer on at least one side of the stainless steel sheet in which the through hole is formed (catalyst layer forming step),
The manufacturing method of the counter electrode of the dye-sensitized solar cell which has is provided.

  Moreover, in this invention, a dye-sensitized solar cell provided with said counter electrode is provided.

According to the present invention, the following advantages can be obtained.
(1) Since the conductive material of the counter electrode is a metal material, the conductivity is better than that of a conventional counter electrode using a translucent conductive film, which is advantageous in improving the photoelectric conversion efficiency.
(2) Since visible light is transmitted through the through-holes provided in the counter electrode without being interrupted by the catalyst layer, a dye-sensitized solar cell with excellent see-through property (visible light transmission property) is constructed. can do.
(3) Since the perforated stainless steel sheet used in the present invention is obtained by etching a stainless steel rolled sheet in an aqueous solution without applying a resist method, the productivity is high and suitable for mass production. For this reason, it is advantageous for the cost reduction of the dye-sensitized solar cell exhibiting a see-through appearance.

The figure which showed typically the structure of the general dye-sensitized solar cell. The figure which illustrated typically the structure of the counter electrode of this invention, and a dye-sensitized solar cell using the same. The figure which illustrated typically the structure of the counter electrode of this invention, and a dye-sensitized solar cell using the same.

  In FIG. 2, the structure of the counter electrode of this invention and a dye-sensitized solar cell using the same is illustrated typically. The counter electrode 20 includes a stainless steel sheet 9 having a through hole 50 and a catalyst layer 7 formed on one surface thereof. The through hole 50 is not blocked by the catalyst layer 7. In the dye-sensitized solar cell 1 using the counter electrode 20, incident light 30 ′ incident through the through hole 50 can be used for power generation as necessary. That is, one or both of the incident light 30 from the photoelectrode 10 side and the incident light 30 ′ from the counter electrode 20 side can be used for power generation. A translucent plate-like body 2 ′ is provided outside the counter electrode 20 for the purpose of sealing the electrolytic solution 8. As the translucent plate-like body 2 ′, a plate or a film made of a translucent material such as glass or plastic can be applied as in the translucent plate-like body 2 on the photoelectrode 10 side.

  In the example of the battery shown in FIG. 2, electrons pass through “porous semiconductor layer 4 → translucent conductive film 3 → load 40 → stainless steel sheet 9 → catalyst layer 7 → electrolyte solution 8 → porous semiconductor layer 4”. Move with. As a result, a current for operating the load 40 is generated.

The counter electrode 20 of the present invention does not necessarily need to be closely attached to the surface of the translucent plate-like body 2 ′ as long as a gap is secured between the counter electrode 20 and the photoelectrode 10. What is necessary is just to hold | maintain in the optimal position in consideration of design property and productivity.
FIG. 3 illustrates the configuration of a dye-sensitized solar cell of the type in which the counter electrode 20 of the present invention is disposed in a state where it is not in contact with the translucent plate-like body 2 ′. In this case, the catalyst layer 7 may be formed on one side of the stainless steel sheet 9 as illustrated, or may be formed on both sides.

[Steel grade of stainless steel sheet]
An organic solvent containing iodine (I ₂ ) and iodide ions is usually used for the electrolyte solution of the dye-sensitized solar cell. The stainless steel sheet applied to the present invention needs to be made of a material that exhibits stable and excellent corrosion resistance for a long time in such an electrolytic solution. As a result of investigations by the inventors, it has been found that it is extremely effective to apply stainless steel having a property that the corrosion weight loss when immersed in the electrolyte heated to 80 ° C. for 500 hours is 1 g / m ² or less. It was. Stainless steel with a corrosion weight loss of 1 g / m ² or less in the above-mentioned severe test environment in the so-called bare state (in which no coating layer is formed) is a popular dye-sensitized solar mounted on personal use equipment. In constructing a battery, it usually has sufficient durability. In addition, stainless steel having a property that the corrosion weight loss when immersed in the above solution for 1000 hours is 1 g / m ² or less is further advantageous in constructing a highly reliable dye-sensitized solar cell.

As a result of detailed studies, the inventors have found that in stainless steel, by containing a certain amount or more of Cr and Mo, dissolution in an electrolyte solution containing iodine (I ₂ ) and iodide ions using an organic solvent is almost impossible. It has been confirmed that excellent corrosion resistance that does not progress can be imparted. Specifically, in the stainless steel material, when the Cr content is 16% by mass or more and the Mo content is 0.3% by mass or more, iodine (I ₂ ) applied to the dye-sensitized solar cell and It has been found that it exhibits excellent corrosion resistance with little dissolution in an iodide ion-containing electrolyte. When the Cr content is 17% by mass or more and the Mo content is 0.8% by mass or more, a more reliable dye-sensitized solar cell can be constructed. This tendency is not significantly affected by the steel types such as austenite and ferritic, and is less affected by other additive elements.

  In the present invention, stainless steels having the following composition ranges can be applied to ferritic steel types and austenitic steel types. Unless otherwise specified, “%” with respect to the alloy element content means “mass%”.

Ferritic steel grades;
“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: 0.6% or less, Cr : 16-32%, preferably 17-32%, Mo: 0.3-3%, preferably 0.8-3%, Cu: 0-1%, Nb: 0-1%, Ti: 0-1%, Ferritic stainless steel having a composition of Al: 0 to 0.2%, N: 0.025% or less, B: 0 to 0.01%, balance Fe and inevitable impurities "
When using a standard steel grade, for example, it is a ferritic steel grade specified in JIS G4305: 2005, Cr: 16-32 mass%, preferably 17-32 mass%, Mo: 0.3-3 mass%, preferably 0.3. What is necessary is just to apply the stainless steel containing 8-3 mass%.

Austenitic grades;
“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 to 28%, Cr: 16 to 32%, preferably 17-32%, Mo: 0.3-7%, preferably 0.8-7%, Cu: 0-3.5%, Nb: 0-1%, Ti: 0-1%, Al : 0 to 0.1%, N: 0.3% or less, B: 0 to 0.01%, the balance being Fe and an inevitable impurity composition austenitic stainless steel "
When using a standard steel grade, for example, it is an austenitic steel grade defined in JIS G4305: 2005, Cr: 16-32 mass%, preferably 17-32 mass%, Mo: 0.3-7 mass%, preferably 0.3. What is necessary is just to apply the stainless steel containing 8-7 mass%.

When the Cr content is less than 16% or the Mo content is less than 0.3%, the material is hardly dissolved in the electrolyte solution containing iodine (I ₂ ) and iodide applied to the dye-sensitized solar cell. It becomes difficult to stably obtain excellent corrosion resistance that does not occur. In order to further improve the reliability, in the case of ferrite, it is preferable to contain 17% or more of Cr and 0.8% or more of Mo, and it is more preferable to contain 18% or more of Cr and 1% or more of Mo. In the case of an austenitic system, it is preferable to contain 17% or more of Cr and 0.8% or more of Mo, and more preferably to contain 18% or more of Cr and 2% or more of Mo. However, when the content of Cr or Mo is excessively increased, the adverse effects such as the manufacturability are remarkable. For this reason, the Cr content is desirably 32% or less, and more preferably 30% or less. In addition, the Mo content is preferably 3% or less in the case of ferrite, and is preferably 7% or less in the case of austenite. In addition, the lower limit “0%” of the element content means that the content of the element is equal to or lower than the measurement limit in an analysis method at a normal steelmaking site.

  As elements other than the above, mixing of elements such as V: 0.3% or less, Zr: 0.3% or less, Ca, Mg, Co, and REM (rare earth elements): 0.1% or less in total is allowed. These may be inevitably mixed from raw materials such as scrap, but if mixed within the above range, the effect of the present invention is not hindered.

The stainless steel of various compositions, which illustrate the results of examining the corrosion resistance to a test liquid containing a simulated iodine (I ₂₎ and iodide ion electrolyte of the dye-sensitized solar cell.
Various stainless steels having the compositions shown in Table 1 were melted, and cold rolled annealed steel sheets (2D finishing materials) having a thickness of 0.28 to 0.81 mm were manufactured by a general stainless steel sheet manufacturing process. It was. In Table 1, in the structure column, “α” means ferrite and “γ” means austenite. The hyphen “-” in the table means that it is below the measurement limit by a normal analysis method in the steelmaking field.

A 35 × 35 mm test piece was cut out from each test material, and the surface (including the end face) was finished by # 600 dry emery polishing to obtain a corrosion resistance test piece.
As a test solution simulating an electrolyte solution of a dye-sensitized solar cell, a solution prepared by dissolving iodine I ₂ : 0.05 mol / L and lithium iodide LiI: 0.5 mol / L in an acetonitrile solvent was prepared.

  10 mL of the test solution was placed in a Teflon (registered trademark) container, and the corrosion resistance test piece was immersed in the solution. The container was covered to suppress the volatilization of the solvent. This container was held in a constant temperature bath at 80 ° C., and a test piece was taken out after 500 hours from the start of immersion. For each steel type, the number of samples was n = 3.

About each test piece after 500-hour immersion, corrosion weight loss (initial test piece mass-test piece mass after immersion) was measured. The largest value among the corrosion weight loss values of n = 3 (that is, the one with the largest metal elution amount) was adopted as the result of the corrosion weight loss of the steel type. Those having a weight loss of 1 g / m ² or less in this 500 hour immersion test were determined to be acceptable. Further, the surface of the test piece after the 500 hour immersion test was visually observed to examine the appearance. Also in this case, the appearance of the test piece having the most severe degree of corrosion among n = 3 was adopted as the grade of the steel type.
For reference, except for steel types that were found to have full-surface corrosion or end-face corrosion in the appearance after 500 hours of immersion, the specimens after observation were again subjected to the above immersion test, and the corrosion weight loss and appearance in the immersion test for a total of 1000 hours I investigated.
The results are shown in Table 2.

As can be seen from Tables 1 and 2, the steel according to the present invention containing Cr: 16% or more and Mo: 0.3% or more is 80 ° C. × 500 h in the iodide ion-containing electrolyte while being bare. It was confirmed that the corrosion weight loss when immersed under severe conditions was 1 g / m ² or less, there was little occurrence of spot rust, and excellent corrosion resistance was exhibited. Those containing Cr: 17% or more and Mo: 0.8% or more have a corrosion weight loss of 1 g / m ² or less even in a total 1000 hour immersion test, and are further excellent in durability.

[Stainless steel sheet form]
The stainless steel sheet 9 constituting the counter electrode 20 of the present invention must be sufficiently transparent to visible light through the through hole 50. When the area ratio of the penetrating portion is too small, it becomes difficult to impart good see-through property to the dye-sensitized solar cell 1. Further, when the incident light 30 ′ from the counter electrode 20 side is used for power generation, the photoelectric conversion efficiency is lowered, which is not preferable. Here, the area ratio of the penetrating portion can be represented by the area ratio of the penetrating portion (hereinafter sometimes referred to as “penetration ratio”) in the projected image when the stainless steel sheet 9 is viewed in the thickness direction. . The area of the through portion for each through hole 50 is a projected area of a portion where the other side is seen through the hole when the through hole 50 is viewed in the thickness direction of the stainless steel sheet 9. The penetration rate is defined as the area of each penetrating part (the penetrating part partially protruding from the rectangular area is the area of the part in the rectangular area) for a rectangular area in which the penetrating part in at least thirty through holes 50 is completely included. And the total area is divided by the area (projected area) of the rectangular region.

  The through hole 50 can be formed by etching in an aqueous electrolyte solution as will be described later. In that case, pitting corrosion-like pits grow from both surfaces of the stainless steel sheet, so that pits grown from one surface may reach the other surface and a through hole may be formed, or pits grown from both sides It may collide in the middle of the thickness and become a through hole. According to the study by the inventors, it has been found that it is difficult to construct a dye-sensitized solar cell with good see-through property when the penetration rate is less than 5% in any of these through holes. For this reason, the perforated stainless steel sheet used in the present invention needs to have a penetration rate of 5% or more. What is 10% or more is preferable, and what is 20% or more is more preferable. When the through hole 50 is required to transmit the incident light 30 ', the penetration rate is preferably 50% or more, and more preferably 60% or more. On the other hand, if the penetration rate is excessively high, the sheet is easily broken during the manufacturing process due to a decrease in the strength of the stainless steel sheet 9, and the productivity is poor. As a result of various studies, it was found that the penetration rate should be 80% or less. You may manage to 70% or less.

In addition, if the size of each through hole 50 is excessive, the photoelectric conversion efficiency decreases due to an increase in the average moving distance until ions in the electrolyte solution 8 reach the surface of the counter electrode 20. Is likely to occur. As a result of various studies, the average diameter of the penetrating portion needs to be 500 μm or less, and more preferably 200 μm or less, or 100 μm or less. On the other hand, even if the through hole 50 is too fine, it does not lead to improvement in characteristics such as improvement in photoelectric conversion efficiency, and it is difficult to form a large number of such fine through holes 50. May be 5 μm or more. Here, the average diameter of the penetrating part is a penetrating part that is completely included in the rectangular area that satisfies the conditions for obtaining the penetrating ratio (that is, a part of the penetrating part that protrudes from the rectangular area). Excluding) average diameter. An equivalent circle diameter is adopted as the diameter of each penetrating portion. Circle-equivalent diameter refers to the area of the through portion S (μm ^2), when the circular constant [pi, means D ([mu] m) determined by S = πD ^2/4.

  Although the thickness of the stainless steel sheet 9 can be selected in a wide range of about 0.005 to 1 mm, it is necessary to make the stainless steel sheet 9 bear most of the strength of the dye-sensitized solar cell 1 as a whole. As long as there is not, generally the thinner one is preferable. However, if it is too thin, it becomes difficult to handle at the time of manufacture due to insufficient strength, so it is desirable to secure a thickness of 0.005 mm or more. Specifically, for example, it is preferable to form the through hole 50 by a method described later using a rolled stainless steel sheet having a thickness of about 0.005 to 0.2 mm as a material. It is more preferable to use a rolled stainless steel sheet having a thickness of 0.005 to 0.1 mm.

(Formation of through holes)
As a method for forming the through hole 50 in the stainless steel sheet 9, etching in a ferric chloride aqueous solution is extremely effective. A method of simply immersing the material of the stainless steel sheet in a ferric chloride aqueous solution or a method of adding anode electrolysis or alternating electrolysis as required can be used. When a ferric chloride aqueous solution is used for the electrolyte aqueous solution, a large number of fine pitting corrosion pits can be formed on the stainless steel surface. Since the pitting corrosion pit has a deep shape with respect to the opening diameter, it is possible to open a hole penetrating the thickness of the sheet by growing the pitting corrosion pit. Specifically, a ferric chloride aqueous solution having a trivalent iron ion concentration of 30 to 100 g / L and a hydrochloric acid concentration of 0 to 50 g / L can be used. The temperature is preferably in the range of 20 to 80 ° C., for example. Since there is a difference in the corrosion resistance level depending on the stainless steel type, the concentration and temperature of the aqueous electrolyte solution corresponding to each steel type should be set within the above ranges, and the treatment time and electrolysis conditions for electrolysis should be set optimally. . The penetration rate and the average diameter of the penetration part can be controlled by changing each of the above conditions according to the plate thickness. What is necessary is just to determine optimal conditions by preliminary experiment according to the steel grade and plate | board thickness of a raw material, the target penetration rate, and the average diameter of a penetration part.

  When the through hole 50 is formed by etching in the above ferric chloride aqueous solution, many pitting corrosion pits are also formed on the surface of the portion where the through hole 50 is not formed. That is, in the stainless steel sheet 9 in which the through holes 50 are formed by the etching, the surface of the portion where the through holes 50 are not generated is roughened by pitting corrosion pits. This roughening increases the surface area and is effective in reducing the internal resistance of the battery.

Below, the experiment example which formed the through-hole on various conditions about the stainless steel rolled sheet (annealed material) with a plate | board thickness of 0.01 mm using the steel H of Table 1 is disclosed.
As an aqueous electrolyte solution, an aqueous ferric chloride solution with various concentrations of trivalent iron ions and hydrochloric acid was prepared, and attempts were made to form through holes by immersing the stainless steel rolled sheet in the aqueous electrolyte solution. . The liquid temperature and treatment time were also varied. The stainless steel sheet after the immersion treatment was observed in the plate thickness direction with an optical microscope (manufactured by KEYENCE Corp .; HV-5500), and the average diameter of the penetration portion and the area ratio (penetration rate) of the penetration portion were obtained.
The processing conditions and results are shown in Table 3.

  As can be seen from Table 3, the average diameter of the penetrating part and the area ratio (penetrating ratio) of the penetrating part can be controlled by changing the concentration of the electrolyte aqueous solution, the liquid temperature, and the treatment time. In Nos. 1 and 2, since the trivalent iron ion concentration was too low, the etching force was weak, and the formation of through holes was insufficient. In No. 3, since the hydrochloric acid concentration was too high, the tendency of dissolution of the entire surface increased and the amount of metal elution was large, but pitting corrosion-like deep pits were difficult to grow. As a result, through holes were sufficiently obtained in 60 seconds. There wasn't. In addition, it was confirmed that all the target materials of the present invention were roughened by pitting pits on the surface of the portion where no through hole was generated.

[Formation of catalyst layer]
A catalyst layer 7 is formed on the surface of the counter electrode 20 applied in the present invention. As the catalyst material, platinum, nickel, polyaniline, polyethylenedioxythiophene, carbon and the like can be applied. In the case of a metal film such as platinum or nickel, it can be formed by sputtering, for example. Conductive polymer films such as polyaniline and polyethylenedioxythiophene can be formed by, for example, spin coating. In the case of carbon, for example, it can be formed by spin coating using an activated carbon dispersion solvent. According to the study by the inventors, it was confirmed that even when an extremely thin platinum film having an average film thickness of about 1 nm was formed, it functions as a battery. The average film thickness of the catalyst layer 7 may be about 1 to 300 nm, for example. In order to achieve both conversion efficiency stability and economic efficiency, it is more effective to control the range of 10 to 200 nm or 20 to 100 nm.

  A counter electrode was prepared using the stainless steel sheets No. 1, 2, 3, 4, 6, 11, and 13 shown in Table 3, and the dye-sensitized solar cell having the configuration shown in FIG. Prototyped.

[Counter electrode]
A counter electrode was obtained by forming a catalyst layer using one of platinum, nickel, polyaniline, and carbon as a catalyst material on one surface of a stainless steel sheet.
In the case of platinum or nickel, a stainless steel sheet was set in a sputtering apparatus, and a catalyst layer was formed by sputter coating using a metal as a catalyst material as a target. This film thickness was about 20 nm.
In the case of polyaniline, a catalyst layer was formed by a spin coating method in which a toluene solution in which polyaniline was dissolved was dropped onto the surface of a stainless steel sheet. This film thickness is about 30 nm.
In the case of carbon, a catalyst layer was formed by a spin coating method in which a tert-butanol solution in which activated carbon was dispersed was dropped onto the surface of a stainless steel sheet. This film thickness is about 50 nm.

[Photoelectrode]
As a translucent conductive film for a photoelectrode, an ITO film formed on a PEN (polyethylene naphthalate) film substrate (Peccell Technologies, Inc .; PECF-IP) was prepared. As a material for obtaining a porous semiconductor layer, a TiO ₂ paste (Peccell Technologies, Inc .; PECC-01-06) was prepared. A ruthenium complex dye (manufactured by Solaronix) was prepared as a sensitizing dye, and this was dispersed in a mixed solvent of acetonitrile and tert-butanol to obtain a dye solution.

A TiO ₂ paste was applied on the ITO surface of the PEN film substrate by a doctor blade method, and allowed to stand at room temperature and dried to form a porous semiconductor layer. The thickness of the obtained porous semiconductor layer was 10 μm. The plate-like body thus obtained was immersed in the dye solution, whereby a sensitizing dye was supported on the porous semiconductor layer, and a photoelectrode composed of an ITO film and the porous semiconductor layer was obtained. . Here, the PEN film substrate corresponds to the translucent plate 2 in FIG.

[Electrolyte]
As an electrolytic solution, a solution prepared by dissolving iodine I ₂ : 0.05 mol / L and lithium iodide LiI: 0.5 mol / L in an acetonitrile solvent was prepared.

[Production of battery]
These electrodes were arranged so that the surface of the photoelectrode on the stainless steel sheet side and the platinum film of the counter electrode face each other. At that time, a PEN film substrate was disposed at the end in the thickness direction on the counter electrode side. A cell was constructed so that the distance between the ITO surface and the counter electrode was 50 μm by inserting a spacer around the cell portion. Then, an electrolytic solution was injected into the cell using a microcylinder, and the space between both electrodes and the gap of the porous semiconductor layer was filled with the electrolytic solution and then sealed. In this way, a dye-sensitized solar cell having the configuration shown in FIG. 2 was obtained.

[Battery characteristics]
Each dye-sensitized solar cell is irradiated with pseudo solar light of AM 1.5, 100 mW / cm ² from the photoelectrode side using a solar simulator (Yamashita Denso Co., Ltd .; YSS-100) “2400” manufactured by KEITHLEY The IV characteristics were measured with a “type source meter” to obtain values of the short circuit current J _SC , the open circuit voltage V _OC , and the form factor FF. From these values, the value of photoelectric conversion efficiency η was determined by the following formula (1).
Photoelectric conversion efficiency η (%) = short circuit current J _SC (mA / cm ² ) × open circuit voltage V _OC (V) × {form factor FF / incident light 100 (mW / cm ² )} × 100 (1)

[See-through]
The produced dye-sensitized solar cell was placed on newspaper, and the see-through property of the battery was evaluated based on whether or not letters on the newspaper could be seen through the battery cell. The case where a newspaper letter could be seen through the cell was judged as ◯ (good), and the other case was judged as x (bad).
These results are shown in Table 4.

  As can be seen from Table 4, in the example of the present invention in which the area ratio (penetration ratio) of the through holes formed in the stainless steel sheet was 5% or more, a battery having a see-through appearance could be constructed. The battery characteristics were also good.

DESCRIPTION OF SYMBOLS 1 Dye-sensitized solar cell 2, 2 'Translucent plate-shaped body 3 Translucent conductive film 4, 4' Porous semiconductor layer 5 Substrate 6 Conductive material 7 Catalyst layer 8 Electrolytic solution 9 Stainless steel sheet 10 Photoelectrode 20 Counter electrode 30, 30 'Incident light 40 Load 50 Through hole

Claims (7)

A counter electrode of a dye-sensitized solar cell composed of a stainless steel sheet having a through hole and a catalyst layer formed on at least one surface thereof,
The stainless steel sheet contains Cr: 16 to 32% by mass, Mo: 0.3 to 3% by mass, and has a chemical composition corresponding to a ferritic steel type defined in JIS G4305: 2005. area ratio 5% to 80% of the penetrating part occupying the projected area viewed sheet in the thickness direction, and the average diameter of the through portion have a through hole is 5 to 500 [mu] m, the through hole electrolytic solution rolled sheet A counter electrode of a dye-sensitized solar cell, which is formed by growing pitting corrosion-like pits by dipping inside . A counter electrode of a dye-sensitized solar cell composed of a stainless steel sheet having a through hole and a catalyst layer formed on at least one surface thereof,
The stainless steel sheet contains Cr: 16 to 32% by mass, Mo: 0.3 to 7% by mass, and has a chemical composition corresponding to an austenitic steel type defined in JIS G4305: 2005, and is a stainless steel sheet. the through portion area ratio of occupied to the projected area when viewed in the thickness direction 5% to 80%, and an average diameter of the through portion have a through hole is 5 to 500 [mu] m, the through hole aqueous electrolyte solution in a rolled sheet A counter electrode of a dye-sensitized solar cell, which is formed by growing pitting corrosion-like pits by dipping in a plutonium .   The chemical composition of the stainless steel sheet is, by 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: 0.6% 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% The opposite of the dye-sensitized solar cell according to claim 1, which is a ferritic stainless steel comprising 0.2%, N: 0.025% or less, B: 0 to 0.01%, the balance Fe and unavoidable impurities. electrode. The chemical composition of the stainless steel sheet 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 counter electrode of a dye-sensitized solar cell according to claim 2 , which is an austenitic stainless steel comprising 0.1%, N: 0.3% or less, B: 0 to 0.01%, the balance Fe and inevitable impurities . Catalyst layer, platinum, nickel, polyaniline, the counter electrode of the dye-sensitized solar cell according to any one of claims 1-4 is obtained by using any of the carbon. A stainless steel rolled sheet having a thickness of 0.005 to 0.2 mm is immersed in an aqueous ferric chloride solution having a trivalent iron ion concentration of 30 to 100 g / L and a hydrochloric acid concentration of 0 to 50 g / L, Through the growth of pitting corrosion-like pits, through holes with an area ratio of the penetrating portion occupying the projected area of the sheet in the thickness direction of 5 to 80% and an average diameter of the penetrating portion of 5 to 500 μm are formed. Forming (through hole forming step),
A step of forming a catalyst layer on at least one side of the stainless steel sheet in which the through hole is formed (catalyst layer forming step),
Method for manufacturing a counter electrode of a dye-sensitized solar cell according to claim 1 having a. Dye-sensitized solar cell including a counter electrode according to any one of claims 1-5.

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