JP2010198823A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element capable of sufficiently suppressing decrease in photoelectric conversion efficiency even in use in a place where the change of surrounding environmental temperature is large. <P>SOLUTION: The photoelectric conversion element 100 includes: a first electrode 1 composing a transparent conductive electrode; a second electrode 2 facing the first electrode 1; a sealing portion 4 connecting the first electrode 1 and the second electrode 2; and an electrolyte 3 filled in a cell space surrounded by the first electrode 1, the second electrode 2 and the sealing portion 4. The second electrode 2 includes: a metallic substrate 9 made of at least one metal selected from the group consisting of titanium, platinum and nickel; and a conductive layer 10 arranged on the electrolyte 3 side of the metallic substrate 9. The metallic substrate 9 has a thickness of 5-35 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element.

  As a photoelectric conversion element, a dye-sensitized solar cell has attracted attention because it is inexpensive and can provide high photoelectric conversion efficiency, and various developments have been made on dye-sensitized solar cells.

  In general, a dye-sensitized solar cell includes a working electrode, a counter electrode, a photosensitizing dye supported on the working electrode, a sealing portion that connects the working electrode and the counter electrode, and a working electrode, a counter electrode, and a sealing portion. And an electrolyte disposed in an enclosed space (hereinafter referred to as “cell space”).

  As such a dye-sensitized solar cell, one using a counter electrode in which a catalyst layer such as platinum is provided on a metal substrate such as titanium is known (Patent Document 1 below).

JP 2007-265796 A

  However, the dye-sensitized solar cell described in Patent Document 1 described above has a problem that the electrolyte leaks and the photoelectric conversion efficiency decreases particularly when used in a place where the ambient temperature changes greatly. It was.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a photoelectric conversion element that can sufficiently suppress a decrease in photoelectric conversion efficiency even when used in a place where a change in ambient environmental temperature is large. To do.

  The present inventors examined the cause of the above problem. First, attention was paid to the thickness of the metal substrate used for the counter electrode. The thickness of the metal substrate used for the counter electrode is generally 100 μm to 300 μm. However, the present inventors have thought that when a metal substrate having such a thickness is used as a counter electrode, the metal substrate may have a relatively rigid structure. In this case, the volatile solute and the electrolyte solvent in the electrolyte are volatilized due to a change in the ambient environmental temperature, the internal pressure of the cell space is changed, and the electrolyte expands and contracts. Accordingly, when stress is repeatedly applied to the metal substrate, the stress is concentrated on the interface between the counter electrode and the sealing portion, and the sealing ability of the sealing portion with respect to the counter electrode is considered to be weakened. As a result, it is considered that electrolyte leakage gradually occurs and the photoelectric conversion efficiency decreases.

Here, although it is conceivable to reduce the thickness of the metal substrate, it is generally considered difficult to reduce the thickness of the metal substrate for the following reason.
1. It is considered that when the metal substrate is thinned, the mechanical strength of the metal substrate is weakened. For this reason, when stress is repeatedly applied to the metal substrate, it is considered that the metal substrate is cracked or broken due to metal fatigue.
2. Since the pinhole density in the metal substrate increases as the metal substrate becomes thinner, it is generally considered that electrolyte leakage is likely to occur.

  However, the present inventors have conducted a thermal cycle test on a dye-sensitized solar cell using a metal substrate having a thickness in a predetermined range as a counter electrode, and surprisingly, leakage of the electrolyte is extremely small, Moreover, it turned out that the fall of a photoelectric conversion efficiency is also small. Therefore, as a result of further earnest studies based on the above findings, the present inventors have found that the above-described problems can be solved by the following invention.

  That is, the present invention includes a first electrode that constitutes a transparent conductive electrode, a second electrode provided to face the first electrode, a sealing portion that connects the first electrode and the second electrode, and the first electrode At least one metal selected from the group consisting of titanium, platinum, and nickel, wherein the electrode fills a cell space surrounded by one electrode, the second electrode, and the sealing portion. And a conductive layer provided on the electrolyte side with respect to the metal substrate, wherein the metal substrate has a thickness of 5 to 35 μm.

  According to this photoelectric conversion element, even if it is used in a place where the surrounding environmental temperature change is large, a decrease in photoelectric conversion efficiency is sufficiently suppressed. About this reason, the present inventors guess as follows. That is, when the ambient temperature around the photoelectric conversion element changes and the internal pressure of the cell space changes, the cell space expands or contracts, and the electrolyte expands or contracts accordingly. At this time, stress is repeatedly applied to the second electrode. Here, it is considered that the metal substrate has flexibility by setting the thickness of the metal substrate within the above range. Therefore, even if stress is applied to the second electrode, the stress is absorbed at the interface between the second electrode and the electrolyte, and the stress concentration at the interface between the second electrode and the sealing portion is relaxed. For this reason, the fall of the sealing capability of the sealing part with respect to a 2nd electrode is suppressed. Further, since the metal substrate has flexibility, it is possible to prevent the metal substrate from being cracked or damaged. As a result, according to the photoelectric conversion element, even when used in a place where the ambient temperature change is large, leakage of the electrolyte is effectively suppressed, and a decrease in photoelectric conversion efficiency is sufficiently suppressed.

  In the photoelectric conversion element, the first electrode is a working electrode having a transparent substrate, a transparent conductive film provided on the transparent substrate, and a porous oxide semiconductor layer provided on the transparent conductive film. The second electrode is preferably a counter electrode.

  In this case, since the second electrode does not have the porous oxide semiconductor layer included in the first electrode, even if the second electrode bends due to stress applied to the second electrode, the porous oxide semiconductor is accompanied accordingly. There is no need to worry about cracks in the layer.

  In the said photoelectric conversion element, it is preferable that a said 2nd electrode has a resin layer provided in the opposite side to the said electrolyte with respect to the said metal substrate.

  In this case, even if the metal substrate has a pinhole, leakage of the electrolyte through the pinhole is suppressed by the resin layer. For this reason, compared with the case where there is no resin layer, leakage of the electrolyte is more effectively suppressed, and a decrease in photoelectric conversion efficiency can be more sufficiently suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion element which can fully suppress the fall of a photoelectric conversion efficiency is provided even if it is used in the place where the surrounding environmental temperature is large.

It is sectional drawing which shows one Embodiment of the photoelectric conversion element of this invention. It is sectional drawing which shows a photoelectric conversion element when the photoelectric conversion element of FIG. 1 is put under high temperature. It is sectional drawing which shows a photoelectric conversion element when the photoelectric conversion element of FIG. 1 is set | placed under low temperature. It is sectional drawing which shows other embodiment of the photoelectric conversion element of this invention. It is sectional drawing which shows other embodiment of the photoelectric conversion element of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In all the drawings, the same or equivalent components are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a cross-sectional view showing a preferred embodiment of a dye-sensitized solar cell according to the present invention.

  FIG. 1 shows a dye-sensitized solar cell 100 as a photoelectric conversion element. As shown in FIG. 1, the dye-sensitized solar cell 100 includes a working electrode 1 and a counter electrode 2 disposed so as to face the working electrode 1. The working electrode 1 carries a photosensitizing dye. Between the working electrode 1 and the counter electrode 2, a sealing portion 4 that connects the working electrode 1 and the counter electrode 2 is provided. The cell space surrounded by the working electrode 1, the counter electrode 2, and the sealing portion 4 is filled with an electrolyte 3.

  The working electrode 1 includes a transparent substrate 6, a transparent conductive film 7 provided on the counter electrode 2 side of the transparent substrate 6, and a porous oxide semiconductor layer 8 provided on the transparent conductive film 7. It constitutes an electrode. The photosensitizing dye is supported on the porous oxide semiconductor layer 8 in the working electrode 1.

  The material which comprises the transparent substrate 6 should just be a transparent material, for example, As such a transparent material, glass, such as borosilicate glass, soda lime glass, white plate glass, quartz glass, polyethylene terephthalate (PET), for example , Polyethylene naphthalate (PEN), polycarbonate (PC), polyethersulfone (PES) and the like. The thickness of the transparent substrate 6 is appropriately determined according to the size of the dye-sensitized solar cell 100 and is not particularly limited, but may be in the range of 50 μm to 10000 μm, for example.

Examples of the material constituting the transparent conductive film 7 include tin-doped indium oxide (Indium-Tin-Oxide: ITO), tin oxide (SnO ₂ ), and fluorine-doped tin oxide (Fluorine-doped-Tin-Oxide: FTO). Examples include conductive metal oxides. The transparent conductive film 7 may be a single layer or a laminate of a plurality of layers made of different conductive metal oxides. When the transparent conductive film 7 is composed of a single layer, the transparent conductive film 7 is preferably composed of FTO because it has high heat resistance and chemical resistance. Moreover, it is preferable to use a laminated body composed of a plurality of layers as the transparent conductive film 7 because the characteristics of each layer can be reflected. Among these, it is preferable to use a laminate of a layer made of ITO and a layer made of FTO. In this case, the transparent conductive film 7 having high conductivity, heat resistance and chemical resistance can be realized. The thickness of the transparent conductive film 7 may be in the range of 0.01 μm to 2 μm, for example.

The porous oxide semiconductor layer 8 is composed of a porous oxide semiconductor. Examples of the porous oxide semiconductor include titanium oxide (TiO ₂ ), zinc oxide (ZnO), tungsten oxide (WO ₃ ), niobium oxide (Nb ₂ O ₅ ), strontium titanate (SrTiO ₃ ), and tin oxide (SnO ₂ ). ), Indium oxide (In ₃ O ₃ ), zirconium oxide (ZrO ₂ ), thallium oxide (Ta ₂ O ₅ ), lanthanum oxide (La ₂ O ₃ ), yttrium oxide (Y ₂ O ₃ ), holmium oxide (Ho ₂₎ O ₃ ), bismuth oxide (Bi ₂ O ₃ ), cerium oxide (CeO ₂ ), aluminum oxide (Al ₂ O ₃ ), or oxide semiconductor particles composed of two or more thereof. The average particle diameter of these oxide semiconductor particles is 1-1000 nm, the surface area of the oxide semiconductor covered with the dye is increased, that is, the field for photoelectric conversion is increased, and more electrons are generated. Is preferable. Here, it is preferable that the porous oxide semiconductor layer 8 is configured by a stacked body in which oxide semiconductor particles having different particle size distributions are stacked. In this case, it becomes possible to cause reflection of light repeatedly in the laminated body, and light can be efficiently converted into electrons without escaping incident light to the outside of the laminated body. The thickness of the porous oxide semiconductor layer 8 may be, for example, 0.5 to 50 μm. In addition, the porous oxide semiconductor layer 8 can also be comprised with the laminated body of the several semiconductor layer which consists of a different material.

  Examples of the photosensitizing dye include a ruthenium complex having a ligand containing a bipyridine structure, a terpyridine structure, and the like, and organic dyes such as porphyrin, eosin, rhodamine, and merocyanine.

  The counter electrode 2 includes a metal substrate 9 and a conductive catalyst film (conductive layer) 10 that is provided on the working electrode 1 side of the metal substrate 9 and promotes a reduction reaction on the surface of the counter electrode 2.

  The metal substrate 9 is made of titanium, nickel, platinum, or an alloy of two or more of these. These can be used regardless of the type of the electrolyte 3, but are particularly suitable when the electrolyte 3 contains iodine because it has corrosion resistance particularly against iodine. Of these, the metal substrate 9 is preferably composed of titanium from the viewpoint of corrosion resistance, cost, and availability. The thickness of the metal substrate 9 is 5-35 micrometers, Preferably it is 10-30 micrometers, More preferably, it is 10-20 micrometers.

  The catalyst film 10 is made of platinum, a carbon-based material, a conductive polymer, or the like.

The electrolyte 3 is usually composed of an electrolytic solution, and this electrolytic solution contains a redox couple such as I ⁻ / I ₃ ⁻ and an organic solvent. As the organic solvent, acetonitrile, methoxyacetonitrile, methoxypropionitrile, propionitrile, ethylene carbonate, propylene carbonate, diethyl carbonate, γ-butyrolactone, and the like can be used. Examples of the redox pair include I ⁻ / I ₃ ⁻ and bromine / bromide ion pairs. The dye-sensitized solar cell 100 is an electrolytic solution that includes a volatile solute such as I ⁻ / I ₃ ⁻ as an oxidation-reduction pair and an organic solvent such as acetonitrile, methoxyacetonitrile, and methoxypropionitrile that easily volatilizes at a high temperature. This is particularly effective when is used as the electrolyte 3. In this case, the change in the internal pressure of the cell space is particularly large due to the change in the ambient temperature around the dye-sensitized solar cell 100, and the interface between the sealing part 20 and the counter electrode 2 and the sealing part 20 and the working electrode 1 This is because the electrolyte 3 easily leaks from the interface. A gelling agent may be added to the volatile solvent. Moreover, the electrolyte 3 may be comprised with the ionic liquid electrolyte which consists of a mixture of an ionic liquid and a volatile component. Also in this case, the change in the internal pressure of the cell space increases due to the change in the ambient temperature around the dye-sensitized solar cell 100. As the ionic liquid, for example, a known iodine salt such as a pyridinium salt, an imidazolium salt, or a triazolium salt, and a room temperature molten salt that is in a molten state near room temperature is used. As such a room temperature molten salt, for example, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide is preferably used. As the volatile component, the above and an organic solvent, 1-methyl-3-methyl imidazolium iodide, _LiI, and the like I 2, 4-t-butylpyridine. Further, as the electrolyte 3, a nanocomposite ionic gel electrolyte which is a pseudo-solid electrolyte formed by kneading nanoparticles such as SiO ₂ , TiO ₂ and carbon nanotubes with the ionic liquid electrolyte may be used. An ionic liquid electrolyte gelled using an organic gelling agent such as vinylidene chloride, polyethylene oxide derivative, or amino acid derivative may be used.

  Examples of the material constituting the sealing portion 4 include inorganic insulating materials such as lead-free transparent low melting point glass frit, ionomers, ethylene-vinyl acetic anhydride copolymers, ethylene-methacrylic acid copolymers, ethylene -Resins such as vinyl alcohol copolymer, ultraviolet curable resin, and vinyl alcohol polymer. In addition, the sealing part 4 may be comprised only with resin, and may be comprised with resin and an inorganic filler.

  According to the dye-sensitized solar cell 100 described above, a decrease in photoelectric conversion efficiency is sufficiently suppressed even when used in a place where the ambient temperature change is large. About this reason, the present inventors guess as follows.

  That is, when the environmental temperature change around the dye-sensitized solar cell 100 is large, the organic solvent and the electrolyte component in the electrolyte 3 are volatilized, and the internal pressure of the cell space surrounded by the working electrode 1, the counter electrode 2, and the sealing portion 4. Also changes significantly. Then, the cell space expands or contracts, and accordingly, the electrolyte 3 expands (see FIG. 2) or contracts (see FIG. 3). At this time, stress is repeatedly applied to the counter electrode 2. Here, it is considered that the metal substrate 9 has flexibility by setting the thickness of the metal substrate 9 in the range of 5 to 35 μm as described above. Therefore, even if stress is applied to the counter electrode 2, the stress is absorbed at the interface A between the counter electrode 2 and the electrolyte 3, and the stress concentration at the interface B between the counter electrode 2 and the sealing portion 4 is relaxed. For this reason, the fall of the sealing capability of the sealing part 4 with respect to the counter electrode 2 is suppressed. Further, since the metal substrate 9 has flexibility, it is possible to prevent the metal substrate 9 from being cracked or damaged. As a result, according to the dye-sensitized solar cell 100, leakage of the electrolyte 3 is effectively suppressed even when the ambient temperature change is large, and a decrease in photoelectric conversion efficiency is sufficiently suppressed. .

  When the thickness of the metal substrate 9 is less than 5 μm, the metal substrate 9 is cracked or damaged, or the pinhole density in the metal substrate 9 is increased, and the electrolyte 3 is likely to leak. As a result, the decrease in photoelectric conversion efficiency cannot be sufficiently suppressed. On the other hand, when the thickness of the metal substrate 9 exceeds 35 μm, the rigidity of the metal substrate 9 increases, and the electrolyte 3 leaks from the interface between the counter electrode 2 and the sealing portion 4 in a place where the ambient temperature change is large. Photoelectric conversion efficiency decreases.

  In the dye-sensitized solar cell 100, the counter electrode 2 is different from the working electrode 1 and does not have the porous oxide semiconductor layer 8 made of a porous oxide semiconductor. Even if the substrate 9 bends, there is no need to worry about the occurrence of cracks or the like in the porous oxide semiconductor layer 8.

  Next, a method for manufacturing the dye-sensitized solar cell 100 will be described.

  First, the working electrode 1 is prepared as follows.

  First, the transparent conductive film 7 is formed on the transparent substrate 6. As a method for forming the transparent conductive film 7, a sputtering method, a vapor deposition method, a spray pyrolysis (SPD) method, a CVD method, or the like is used. Of these, the spray pyrolysis method is preferable from the viewpoint of apparatus cost.

  Next, a paste for forming a porous oxide semiconductor layer is printed on the transparent conductive film 7. The semiconductor layer forming paste includes a resin such as polyethylene glycol and a solvent such as terpineol, in addition to the oxide semiconductor particles described above. As a method for printing the semiconductor layer forming paste, for example, a screen printing method, a doctor blade method, a bar coating method, or the like can be used.

  Next, the semiconductor layer forming paste is baked to form the porous oxide semiconductor layer 8 on the transparent conductive film 7. The firing temperature varies depending on the oxide semiconductor particles, but is usually 350 ° C. to 600 ° C., and the firing time also varies depending on the oxide semiconductor particles, but is usually 1 to 5 hours.

  Next, a photosensitizing dye is supported on the porous oxide semiconductor layer 8 of the working electrode 1. For this purpose, the working electrode 1 is immersed in a solution containing a photosensitizing dye, the dye is adsorbed on the porous oxide semiconductor layer 8, and then the excess dye is washed away with the solvent component of the solution. The photosensitizing dye may be adsorbed on the porous oxide semiconductor layer 8 by drying. However, even if the photosensitizing dye is adsorbed to the porous oxide semiconductor film by applying a solution containing the photosensitizing dye to the porous oxide semiconductor layer 8 and then drying, the photosensitizing dye is porous. It can be supported on the oxide semiconductor layer 8.

  On the other hand, the counter electrode 2 is prepared as follows.

  First, a metal substrate 9 having a thickness of 5 to 35 μm is prepared. Then, the catalyst film 10 is formed on the metal substrate 9. As a method for forming the catalyst film 10, a sputtering method, a vapor deposition method, or the like is used. Of these, sputtering is preferred from the viewpoint of film uniformity.

  Next, for example, a sheet made of a thermoplastic resin is prepared, the sheet is sandwiched between the working electrode 1 carrying the pigment and the counter electrode 2, and the working electrode 1 and the counter electrode 2 are bonded and connected by heating and melting the sheet. To do. Thus, the sealing portion 4 is formed between the working electrode 1 and the counter electrode 2. At this time, a through hole for injecting the electrolyte 3 is formed in the working electrode 1 in advance.

  Then, the electrolyte 3 is injected and filled into the cell space surrounded by the working electrode 1, the counter electrode 2, and the sealing portion 4 through the through hole formed in the working electrode 1.

  After the electrolyte 3 is filled, the through hole is sealed with, for example, a sheet similar to the above sheet. Thus, the dye-sensitized solar cell 100 is obtained, and the manufacture of the dye-sensitized solar cell 100 is completed.

  The present invention is not limited to the above embodiment. For example, in the above-described embodiment, the counter electrode 2 includes the metal substrate 9 and the catalyst layer 10, but the counter electrode 202 includes the catalyst layer 10 and the metal substrate as in the dye-sensitized solar cell 200 illustrated in FIG. 9 and a resin layer 201 provided on the side opposite to the catalyst layer 10 and the electrolyte 3 with respect to the metal substrate 9. In this case, even if the metal substrate 9 has a pinhole, leakage of the electrolyte 3 through the pinhole is suppressed by the resin layer 201. For this reason, compared with the case where there is no resin layer 201, the leakage of the electrolyte 3 is suppressed more effectively, and the fall of photoelectric conversion efficiency can be suppressed more fully. In addition, as resin which comprises the resin layer 201, an ionomer, an ethylene-methacrylic acid copolymer, etc. can be mentioned, for example. The counter electrode 2 may be composed of only the metal substrate 9.

  Furthermore, in the said embodiment, although the 1st electrode is comprised by the working electrode 1 and the 2nd electrode is comprised by the counter electrode 2, the 1st electrode is comprised by the counter electrode 302 like the dye-sensitized solar cell 300 shown in FIG. The working electrode 301 may constitute the second electrode. Here, the counter electrode 302 is constituted by the transparent substrate 6 and the transparent catalyst layer 310, and constitutes a transparent conductive electrode. Examples of the material constituting the catalyst layer 310 include a transparent conductive material. Examples of such a transparent conductive material include a material constituting the transparent conductive film 7. The working electrode 301 includes a metal substrate 9, a conductive film (conductive layer) 307 provided on the metal substrate 9, and a porous oxide semiconductor layer 8 provided on the conductive film 307. The conductive film 307 may be any conductive material and is not necessarily transparent. Examples of such a conductive material include a material constituting the transparent conductive film 7 and a material constituting the catalyst layer 10.

  Hereinafter, the content of the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples.

Example 1
First, a 10 cm × 10 cm × 4 mm FTO substrate was prepared. Subsequently, a titanium oxide paste (manufactured by Solaronix, Ti nanoixide T / sp) is applied on the FTO film by a doctor blade method so that its thickness becomes 10 μm, and then placed in a hot air circulation type oven. Baking was performed at 500 ° C. for 3 hours, a porous oxide semiconductor layer was formed on the FTO film, and a 5 cm × 5 cm laminate was obtained. Next, two through holes were formed in the laminate to obtain a working electrode.

  Next, the working electrode was immersed in a dehydrated ethanol solution in which 0.2 mM of N719 dye, which is a photosensitizing dye, was dissolved for 24 hours to support the photosensitizing dye on the working electrode.

  On the other hand, a metal substrate made of a titanium foil of 6 cm × 6 cm × 35 μm was prepared. Then, a platinum catalyst film having a thickness of 10 nm was formed on the metal substrate by sputtering to obtain a counter electrode.

  Then, an annular thermoplastic resin sheet made of Himiran (trade name, manufactured by Mitsui DuPont Polychemical Co., Ltd.), which is an ionomer, was sandwiched between the working electrode and the counter electrode. At this time, the porous oxide semiconductor layer was arranged inside the thermoplastic resin sheet. The thermoplastic resin sheet was heated and melted at 180 ° C. for 5 minutes to bond the working electrode and the counter electrode.

  Next, through the through-hole formed in the working electrode, an electrolyte containing methoxyacetonitrile as the main solvent, 0.1M lithium iodide, 0.05M iodine, and 0.5M 4-tert-butylpyridine is used as the working electrode and the counter electrode. And filled in the cell space surrounded by the sealing portion. And the through-hole formed in the working electrode was sealed using the thermoplastic resin similar to the said sheet | seat. Thus, a dye-sensitized solar cell was obtained.

(Examples 2-7 and Comparative Examples 1-3)
A dye-sensitized solar cell was produced in the same manner as in Example 1 except that the thickness of the metal substrate constituting the counter electrode was set to the value shown in Table 1.

[Evaluation of change in photoelectric conversion efficiency by thermal cycle test: Evaluation 1]
About the dye-sensitized solar cell obtained in Examples 1-7 and Comparative Examples 1-3, after measuring photoelectric conversion efficiency, the heat cycle test was done. After the thermal cycle test, the photoelectric conversion efficiency was measured again for the dye-sensitized solar cell, and the decrease rate of the photoelectric conversion efficiency was calculated. Regarding the evaluation, “◯” is displayed when the rate of decrease in photoelectric conversion efficiency is 10% or less, and “X” is displayed when the rate of decrease in photoelectric conversion efficiency is greater than 10% and 20% or less. It was decided to. The results are shown in Table 1.

  The thermal cycle test is a cycle in which the temperature is raised from −40 ° C. to 90 ° C., held at 90 ° C. for 10 minutes, then lowered from 90 ° C. to −40 ° C., and held at −40 ° C. for 10 minutes. A cycle was performed 100 times. At this time, the rate of temperature increase and the rate of temperature decrease were both 10 ° C./min.

[Evaluation of electrolyte remaining rate by thermal cycle test: Evaluation 2]
The dye-sensitized solar cells obtained in Examples 1 to 7 and Comparative Examples 1 to 3 were subjected to the same thermal cycle test as described above, and then the volume of the dye-sensitized solar cell (cell), that is, the working electrode and the counter electrode. The ratio of the remaining amount of electrolyte in the volume of the cell space surrounded by the sealing portion was measured. When the electrolyte remaining ratio is 80% or more, “◯” is displayed, and when it is less than 80%, “×” is displayed. The results are shown in Table 1.

  From the results shown in Table 1, it was found that according to the dye-sensitized solar cells of Examples 1 to 7, the decrease in photoelectric conversion efficiency after the thermal cycle test was sufficiently small. In addition, when the dye-sensitized solar cell of Examples 1-7 was observed after the thermal cycle test, neither a crack nor damage was observed in the counter electrode. In addition, in the dye-sensitized solar cells of Comparative Examples 1 and 2, the performance was abruptly reduced until the number of thermal cycles reached 70. As a result of disassembling after the test, peeling was confirmed at the interface between the titanium metal substrate and the sealing portion. Although peeling was not confirmed in the dye-sensitized solar cell of Comparative Example 3, a decrease in performance was observed.

  Therefore, according to the photoelectric conversion element of this invention, even if it used in the place where the surrounding environmental temperature change is large, it was confirmed that the fall of photoelectric conversion efficiency can fully be suppressed.

  DESCRIPTION OF SYMBOLS 1 ... Working electrode (1st electrode), 2,202 ... Counter electrode (2nd electrode), 3 ... Electrolyte, 4 ... Sealing part, 9 ... Metal substrate, 10 ... Catalyst film (conductive layer), 201 ... Resin layer, DESCRIPTION OF SYMBOLS 100,200,300 ... Dye-sensitized solar cell (photoelectric conversion element), 301 ... Working electrode (second electrode), 302 ... Counter electrode (first electrode), 307 ... Conductive film (conductive layer).

Claims (3)

A first electrode constituting a transparent conductive electrode;
A second electrode provided opposite to the first electrode;
A sealing portion connecting the first electrode and the second electrode;
An electrolyte filled in a cell space surrounded by the first electrode, the second electrode, and the sealing portion;
The second electrode has a metal substrate made of at least one metal selected from the group consisting of titanium, platinum and nickel, and a conductive layer provided on the electrolyte side with respect to the metal substrate;
The metal substrate has a thickness of 5 to 35 μm;
A photoelectric conversion element characterized by the above. The first electrode is a working electrode having a transparent substrate, a transparent conductive film provided on the transparent substrate, and a porous oxide semiconductor layer provided on the transparent conductive film,
The second electrode is a counter electrode;
The photoelectric conversion element according to claim 1. The second electrode has a resin layer provided on a side opposite to the electrolyte with respect to the metal substrate;
The photoelectric conversion element according to claim 1 or 2.

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