Sealing agent for dye-sensitized solar cell and dye-sensitized solar cell using the same

Abstract

To provide a sealing agent for a dye-sensitized solar cell excellent in electrolyte sealing performance and also excellent in high temperature and high humidity resistance, and to provide a solar cell having the sealing agent.SOLUTION: A sealing agent for a dye-sensitized solar cell includes (A) a polybutadiene compound having a (meth) acrylic group in a molecule, (B) a curable compound, and two or more kinds of (C) photopolymerization initiators, in which a content of the (C) photopolymerization initiators is 1.5 to 4 parts by mass with respect to 100 parts by mass of a total amount of the (A) polybutadiene compound having a (meth) acrylic group in a molecule and the (B) curable compound.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a sealant for dye-sensitized solar cells and a dye-sensitized solar cell using the same, more particularly to a sealant for dye-sensitized solar cells that utilizes ultraviolet curing and / or thermal curing and a dye-sensitized solar cell using the same. [Background technology]

[0002] Solar cells, which have been attracting attention as a clean energy source, have recently begun to be used in ordinary homes. However, they have not yet become widespread. This is due to the fact that the performance of solar cell elements is not sufficiently excellent, which necessitates the use of large modules, and the low productivity of module manufacturing makes them expensive.

[0003] There are several types of solar cells, but the majority of solar cells in practical use are silicon solar cells. However, dye-sensitized solar cells have recently attracted attention and are being researched for practical use. The prototype of today's dye-sensitized solar cells was developed by Grätzel et al. (Switzerland) in 1991 and is also known as the Grätzel cell. Their structure typically consists of a conductive support (oxide semiconductor electrode) bearing a layer of oxide semiconductor particles sensitized by a dye, a second conductive support bearing a counter electrode such as platinum, a charge transfer layer (such as an electrolyte containing a redox substance) sandwiched between the two electrodes, and a sealing agent such as a resin surrounding the charge transfer layer. Furthermore, by adsorbing a ruthenium complex dye onto a porous titanium oxide electrode, for example, their performance has been improved to the point where they have a photoelectric conversion efficiency comparable to that of amorphous silicon solar cells (Non-Patent Document 1). However, many challenges remain before they can be put into practical use. Important challenges to be overcome include improving productivity to accommodate larger cell areas and improving durability for long-term use.

[0004] Dye-sensitized solar cells are typically manufactured by providing a predetermined gap between an oxide semiconductor electrode and a counter electrode, bonding the two electrodes together with a sealant, and then injecting an electrolyte solution that will form a charge transfer layer. Examples of electrolyte injection methods include, for example, a method described in Patent Document 1 in which two through-holes are provided in the counter electrode, one as an injection hole and the other as a vent hole, and then injecting the electrolyte solution by utilizing capillary action. Another method described in Patent Document 2 involves providing a single through-hole in the counter electrode, immersing the through-hole in the electrolyte solution under reduced pressure, and then injecting the electrolyte solution at atmospheric pressure after opening to the atmosphere. However, these electrolyte injection methods suffer from the problem that the takt time (time required for the injection process) of the injection process becomes significantly longer as the area of ​​the manufactured battery increases, significantly reducing productivity. Furthermore, the electrode must be provided with an injection hole in advance, and the injection hole must then be sealed after the electrolyte solution is injected, which increases the number of manufacturing steps. In addition, there is a risk of electrolyte leakage from the sealed injection hole, which may impair durability.

[0005] To solve the above problems, Patent Documents 3, 4, 5, etc. disclose a method for manufacturing a dye-sensitized solar cell (electrolyte dripping method) that includes the steps of arranging a dam of a sealant continuously on one electrode so as to surround the semiconductor-containing layer, dripping a predetermined amount of electrolyte inside the dam of the sealant, then overlaying the other electrode, forming a cell gap, and then curing the sealant. These manufacturing methods significantly shorten the takt time of the electrolyte injection step, and also reduce the number of manufacturing steps because the steps of providing an injection hole in the electrode and sealing the injection hole are not necessary. Furthermore, because the resulting solar cell does not have a sealed injection hole, it is possible to produce a dye-sensitized solar cell with excellent sealing properties.

[0006] In the electrolyte dripping method, the sealant must be cured while in contact with the uncured sealant containing the redox couple used in the dye-sensitized solar cell. Furthermore, the sealant must be durable against external environmental temperatures and humidity to protect the electrolyte in the manufactured cell. Therefore, selecting the right sealant is important for manufacturing highly reliable dye-sensitized solar cells. If an inappropriate sealant is used, the pressure generated during cell gap formation or the internal pressure increase during sealant curing can cause the electrolyte to burst through the sealant barrier and leak. After manufacturing, use in a high-temperature, high-humidity environment can lead to softening of the cured sealant, expansion of the electrolyte, or a decrease in the adhesive strength of the sealant to the oxide semiconductor electrode, resulting in sealant peeling, which can lead to electrolyte leakage from the cell interior or air bubbles entering from the cell exterior. These problems can result in dye-sensitized solar cells with unsatisfactory reliability.

[0007] Generally, to bond an organic material such as a curable compound to an inorganic material such as an oxide semiconductor electrode, methods include adding a compound having a functional group such as a hydroxyl group to increase the polarity of the curable compound and thereby increase the adhesive strength through hydrogen bonding, or adding a coupling agent, such as a silane coupling agent, to chemically bond the organic material to the inorganic material. However, in the electrolyte dripping method, in order to first seal a relatively highly polar electrolyte in an uncured sealant and then cure it, it is preferable to use a curable compound with low polarity. Furthermore, the coupling agent itself tends to be easily dissolved in the electrolyte, making it difficult to achieve both sealing properties for the electrolyte and adhesive strength to the oxide semiconductor electrode. Although the electrolyte dripping method, which includes a step in which the uncured sealant contacts the electrolyte, is likely to realize dye-sensitized solar cells with excellent performance and high productivity, there has been no satisfactory sealant that can be used in this method, and many problems remain. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-348783 [Patent Document 2] Patent No. 4037618 [Patent Document 3] International Publication No. 2007 / 046499 [Patent Document 4] Japanese Patent Application Laid-Open No. 2007-220608 [Patent Document 5] Japanese Patent Application Laid-Open No. 2009-283228 [Non-patent literature]

[0009] [Non-Patent Document 1] Nature, Vol. 353, pp. 737-740, 1991 [Non-patent document 2] CJ Barbe, F Arendse, P Compt and M. Graetzel J. Am. Ceram. Soc., 80, 12, 3157-71 (1997). Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in view of the above-mentioned problems, and aims to provide a sealant for dye-sensitized solar cells that has excellent electrolyte sealing performance and also excellent resistance to high temperatures and high humidity, and a solar cell comprising the sealant. [Means for solving the problem]

[0011] That is, the present invention relates to the following [1] to [7]. In this application, "(numerical value 1) to (numerical value 2)" indicates that the upper and lower limits are included. Also, the (meth)acrylic group means a methacrylic group and / or an acrylic group, and the (meth)acrylate means a methacrylate and / or an acrylate. [1] A sealing agent for dye-sensitized solar cells, comprising (A) a polybutadiene compound having a (meth)acrylic group in the molecule, (B) a curable compound, and two or more types of (C) photopolymerization initiators, wherein the content of the (C) photopolymerization initiators is 1.5 to 4 parts by mass per 100 parts by mass of the total amount of the (A) polybutadiene compound having a (meth)acrylic group in the molecule and the (B) curable compound. [2] The sealing agent for dye-sensitized solar cells according to the above item [1], wherein the (C) photopolymerization initiator contains a photopolymerization initiator having at least one structure selected from the group consisting of a phenyl sulfide structure, an oxime ester structure, a thioxanthone structure, and a phosphine oxide structure in the molecule. [3] The sealing agent for dye-sensitized solar cells according to the above item [1], wherein the (C) photopolymerization initiator comprises a photopolymerization initiator having an oxime ester structure in the molecule and a photopolymerization initiator having at least one structure selected from the group consisting of a phenyl sulfide structure, a thioxanthone structure, and a phosphine oxide structure. [4] The sealing agent for dye-sensitized solar cells according to any one of items [1] to [3], wherein the content of the polybutadiene compound (A) having a (meth)acrylic group in the molecule is 40 to 80 parts by mass relative to 100 parts by mass of the total amount of the polybutadiene compound (A) having a (meth)acrylic group in the molecule and the curable compound (B). [5] The sealant for a dye-sensitized solar cell according to any one of items [1] to [4] above, further comprising (D) a (meth)acrylate having a phosphate group. [6] The sealant for a dye-sensitized solar cell according to any one of the above items [1] to [5], further comprising (E) an inorganic filler. [7] A solar cell comprising the sealant for a dye-sensitized solar cell according to any one of the above items [1] to [6]. [Effects of the Invention]

[0012] According to the present invention, it is possible to provide a sealant for a dye-sensitized solar cell that has excellent electrolyte sealing performance and also excellent resistance to high temperatures and high humidity, and a solar cell comprising the sealant. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic cross-sectional view of a main part of a dye-sensitized solar cell of the present invention. [Figure 2] 1 shows a substrate for adhesion testing used in Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] The sealing agent for dye-sensitized solar cells of the present invention (also simply referred to as "sealing agent") comprises (A) a polybutadiene compound having a (meth)acrylic group in the molecule, (B) a curable compound, and two or more types of (C) photopolymerization initiators, and the content of the (C) photopolymerization initiators is 1.5 to 4 parts by mass relative to 100 parts by mass of the total amount of the (A) polybutadiene compound having a (meth)acrylic group in the molecule and the (B) curable compound.

[0015] The sealant of the present invention has excellent sealing performance for an electrolyte solution, adhesive strength to an oxide semiconductor electrode, and reliability under high temperature and humidity conditions, and can particularly exhibit excellent performance in an electrolyte dripping method that includes a step in which an uncured sealant comes into contact with an electrolyte solution.

[0016] [(A) Polybutadiene compound having a (meth)acrylic group in the molecule] The sealing agent of the present invention contains, as component (A), a polybutadiene compound having a (meth)acrylic group in the molecule (also simply referred to as "component (A)"). Component (A) has a (meth)acrylic group, which allows it to cure quickly through a photoreaction, and it has excellent sealing properties for electrolytes and low contamination.

[0017] Component (A) is commercially available, for example, as TEAI-1000 or TE-2000 manufactured by Nippon Soda Co., Ltd. The number average molecular weight of these polybutadiene compounds having (meth)acrylic groups in the molecule has a lower limit of 500, more preferably 750, and particularly preferably 1000, from the viewpoint of preventing contamination of the electrolyte. Furthermore, from the viewpoint of handleability, the upper limit of the number average molecular weight is preferably 10000, more preferably 8000, and particularly preferably 6000.

[0018] Component (A) may be used alone or in a mixture of two or more types. Component (A) is preferably contained in an amount of 40 to 80 parts by mass, more preferably 50 to 70 parts by mass, per 100 parts by mass of the total amount of component (A) and component (B) described below. By containing 40 parts by mass or more of component (A), excellent low-contamination properties of the electrolyte can be achieved, and by containing 80 parts by mass or less, performance can be improved by blending with other components.

[0019] [(B) Curable compound] The sealing agent of the present invention contains a curable compound (also simply referred to as "component (B)") as component (B). Component (B) is not particularly limited as long as it is a compound that is cured by light, heat, or the like, but is preferably a compound having a (meth)acrylic group or an epoxy group, and particularly preferably a compound having a (meth)acrylic group, such as (meth)acrylate, epoxy (meth)acrylate, or urethane (meth)acrylate. Note that, in the present invention, component (A) and component (D), which will be described later, are not included in component (B).

[0020] [(Meth)acrylate] Specific examples of (meth)acrylates include N-acryloyloxyethylhexahydrophthalimide, acryloylmorpholine, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, cyclohexane-1,4-dimethanol mono(meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, phenylpolyethoxy (meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, and o-phenylphenol monoethoxy (meth)acrylate. Acrylate, o-phenylphenol polyethoxy (meth)acrylate, p-cumylphenoxyethyl (meth)acrylate, isobornyl (meth)acrylate, tribromophenyloxyethyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,9-nonanediol di(meth)acrylate, tricyclodecanediol Methanol (meth)acrylate, tricyclodecane dimethanol di(meth)acrylate, bisphenol A polyethoxydi(meth)acrylate, bisphenol A polypropoxydi(meth)acrylate, bisphenol F polyethoxydi(meth)acrylate, ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tris(acryloxyethyl)isocyanurate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol Examples of the monomer include tripentaerythritol(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol penta(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane polyethoxytri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ester diacrylate of neopentyl glycol and hydroxypivalic acid, and diacrylate of an ε-caprolactone adduct of an ester of neopentyl glycol and hydroxypivalic acid.Preferred examples include isobornyl(meth)acrylate and tricyclodecane dimethanol di(meth)acrylate.

[0021] [Epoxy (meth)acrylate] Epoxy (meth)acrylates are obtained by known methods by reacting epoxy resins with (meth)acrylic acid. The epoxy resins used as raw materials are not particularly limited, but are preferably bifunctional or higher functional epoxy resins. Examples include resorcinol diglycidyl ether, bisphenol A epoxy resins, bisphenol F epoxy resins, bisphenol S epoxy resins, phenol novolac epoxy resins, cresol novolac epoxy resins, bisphenol A novolac epoxy resins, bisphenol F novolac epoxy resins, alicyclic epoxy resins, aliphatic linear epoxy resins, glycidyl ester epoxy resins, glycidyl amine epoxy resins, hydantoin epoxy resins, isocyanurate epoxy resins, phenol novolac epoxy resins having a triphenolmethane skeleton, and diglycidyl ethers of bifunctional phenols such as catechol and resorcinol, diglycidyl ethers of bifunctional alcohols, and their halides and hydrogenated derivatives. Bisphenol A epoxy resins and resorcinol diglycidyl ethers are preferred. Furthermore, the ratio of epoxy groups to (meth)acryloyl groups is not limited and may be appropriately selected from the viewpoint of process suitability, and may be a partial (meth)acrylate having both epoxy groups and (meth)acryloyl groups.

[0022] Component (B) may be used alone or in combination of two or more. In the sealing agent of the present invention, component (B) is preferably contained in an amount of 20 to 60 parts by mass, more preferably 30 to 50 parts by mass, per 100 parts by mass of the total amount of components (A) and (B).

[0023] The content of the compound having a (meth)acrylic group in 100 parts by mass of the total amount of component (B) is preferably 80 to 100 parts by mass, and particularly preferably 100 parts by mass.

[0024] [(C) Photoradical polymerization initiator] The sealing agent of the present invention contains a photoradical polymerization initiator (also simply referred to as "component (C)") as component (C). The photoradical polymerization initiator is not particularly limited as long as it is a compound that generates radicals or acids and initiates a chain polymerization reaction when irradiated with ultraviolet or visible light. Examples of the photoradical polymerization initiator include benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, 2-chlorothioxanthone, 2,4-diisopropylthioxanthone, benzophenone, 2-ethylanthraquinone, 2-hydroxy-2-methylpropiophenone, 2-methyl-[4-(methylthio)phenyl]-2-morpholino-1-propane, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, camphorquinone, 9-fluorenone, and diphenyl disulfide. Specific examples include Omunirad RTM 651, 184, 2959, 127D, 907, 369, 379EG, 819, 784, 754, 500, TPO, IRGACURE RTM OXE01, OXE02, OXE03, OXE04, DAROCURE RTM 1173, LUCIRIN RTM TPO (both manufactured by BASF), Seikuol RTM Z, BZ, BEE, BIP, BBI (all manufactured by Seiko Chemical Co., Ltd.), KAYACURE RTM DETX-S (manufactured by Nippon Kayaku Co., Ltd.) and the like. Among these, preferred are initiators having any of a phenyl sulfide structure, an oxime ester structure, a thioxanthone structure, and a phosphine oxide structure in the molecule. Commercially available products include Omunirad RTM 819, TPO, IRGACURE RTM OXE01, OXE02, OXE03, OXE04, LUCIRIN RTM TPO, CAYACURE RTMExamples include DETX-S. Compounds with these structures have good resistance to contaminating the electrolyte, and having two or more types allows for efficient absorption of light irradiated during photocuring, effectively reducing unreacted materials in the sealant during photocuring. This reduces the amount of components eluted into the electrolyte during high-temperature, high-humidity testing, allowing for the production of cells with excellent high-temperature, high-humidity resistance. A preferred combination of two types of photopolymerization initiators is one with an oxime ester structure in the molecule and one with a phenyl sulfide structure, thioxanthone structure, or phosphine oxide structure.

[0025] The total amount of component (C) is preferably 1.5 to 4 parts by mass, and more preferably 2 to 3 parts by mass, per 100 parts by mass of the total amount of the sealing agent. By including a total amount of component (C) of 1.5 parts by mass or more, unreacted substances in the sealing agent can be reacted efficiently, and by including a total amount of component (C) of 4 parts by mass or less, elution of unreacted substances of component (C) into the electrolyte can be prevented.

[0026] [(D) (Meth)acrylate having a phosphate group] The sealing agent of the present invention may contain, as component (D), (D) a (meth)acrylate having a phosphate group (also simply referred to as "component (D)"). Component (D) is a compound containing one or more, preferably 1 to 5, phosphate groups and one or more, preferably 1 to 3, (meth)acryloyl groups in one molecule. The mass proportion of component (D) in the sealing agent for dye-sensitized solar cells of the present invention is usually 0.0005 to 3 mass%, preferably 0.001 to 2 mass%, and more preferably 0.002 to 1 mass%. If it is more than 3 mass%, the transparency of the cured product of the adhesive composition may be reduced, and if it is less than 0.0005 mass%, sufficient adhesion cannot be obtained. Component (D) can be used alone or in combination of two or more types. In the present invention, by incorporating component (D), the phosphate group bonds with an oxide such as ITO (indium-doped tin oxide) and the acrylate group bonds with a curable resin, thereby increasing the adhesive strength between the sealant and the oxide semiconductor electrode, preventing peeling of the sealant even under high-temperature, high-humidity conditions and enabling the electrolyte solution in the cell to be retained.

[0027] Component (D) in the sealing agent of the present invention is not particularly limited, and examples thereof include 2-(meth)acryloyloxyethyl acid phosphate (for example, "Light Ester P-1M" and "Light Acrylate P-1A" manufactured by Kyoeisha Chemical Co., Ltd.), alkylene (meth)acrylate phosphates such as methylene (meth)acrylate phosphate, ethylene (meth)acrylate phosphate, propylene (meth)acrylate phosphate, and tetramethylene (meth)acrylate phosphate, and phosphate esters of polyethylene glycol monoacrylate. Examples of such an acid ester include phosphate esters of polypropylene glycol monomethacrylate, bis(2-(meth)acryloyloxyethyl) acid phosphate (for example, "Light Ester P-2M" and "Light Acrylate P-2A" manufactured by Kyoeisha Chemical Co., Ltd.), ethylene oxide-modified phosphate di(meth)acrylate, tris(2-acryloyloxyethyl)phosphate, and a mixture of caprolactone-modified phosphate mono(meth)acrylate and caprolactone-modified phosphate di(meth)acrylate (for example, "KAYAMER PM-21" manufactured by Nippon Kayaku Co., Ltd.).

[0028] [(E) Inorganic filler] The sealing agent of the present invention may contain an inorganic filler (also simply referred to as "component (E)") as component (E). Examples of component (E) include silica, silicon carbide, silicon nitride, boron nitride, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, magnesium oxide, zirconium oxide, aluminum hydroxide, magnesium hydroxide, calcium silicate, aluminum silicate, lithium aluminum silicate, zirconium silicate, barium titanate, glass fiber, carbon fiber, molybdenum disulfide, and asbestos. Preferred examples include fused silica, crystalline silica, silicon nitride, boron nitride, calcium carbonate, barium sulfate, calcium sulfate, mica, talc, clay, alumina, aluminum hydroxide, calcium silicate, and aluminum silicate, with silica, alumina, and talc being preferred. Two or more of these inorganic fillers may be used in combination.

[0029] When component (E) is used in the sealant of the present invention, it is preferably contained in an amount of 5 to 60 parts by mass, more preferably 5 to 50 parts by mass, per 100 parts by mass of the total amount of sealant. If the content of inorganic filler is less than 5 parts by mass, the adhesive strength to the glass substrate decreases, and moisture resistance reliability also decreases, which may result in a significant decrease in adhesive strength after moisture absorption. Furthermore, if the content of inorganic filler is more than 60 parts by mass, the filler content is too high, which may cause problems with gap formation when bonding two electrodes together during the production of dye-sensitized solar cells.

[0030] [Silane coupling agents] The sealing agent of the present invention may contain a silane coupling agent. Examples of silane coupling agents include 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)3-aminopropylmethyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, N-(2-(vinylbenzylamino)ethyl)3-aminopropyltrimethoxysilane hydrochloride, 3-methacryloxypropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane, and 3-chloropropyltrimethoxysilane. These silane coupling agents are sold by Shin-Etsu Chemical Co., Ltd. and other companies under the names KBM series and KBE series, and are therefore readily available on the market. When a silane coupling agent is used in the sealing agent of the present invention, it is preferable that the amount contained is 0.05 to 3 parts by mass per 100 parts by mass of the total amount of the sealing agent.

[0031] [Compounds containing thiol groups] The sealing agent of the present invention may contain a compound having a thiol group, such as methanedithiol, 1,2-dimercaptoethane, 1,2-dimercaptopropane, 2,2-dimercaptopropane, 1,3-dimercaptopropane, 1,2,3-trimercaptopropane, 1,4-dimercaptobutane, 1,6-dimercaptohexane, bis(2-mercaptoethyl)sulfide, 1,2-bis(2-mercaptoethylthio)ethane, 1,5-dimercapto-3-oxapentane, and 1,8-dimercapto-3,6-dioxapentane. saoctane, 2,2-dimethylpropane-1,3-dithiol, 3,4-dimethoxybutane-1,2-dithiol, 2-mercaptomethyl-1,3-dimercaptopropane, 2-mercaptomethyl-1,4-dimercaptobutane, 2-(2-mercaptoethylthio)-1,3-dimercaptopropane, 1,2-bis(2-mercaptoethylthio)-3-mercaptopropane, 1,1,1-tris(mercaptomethyl)propane, tetrakis(mercaptomethyl)methane, ethylene glycol Lithium bis(2-mercaptoacetate), ethylene glycol bis(3-mercaptopropionate), 1,4-butanediol bis(2-mercaptoacetate), 1,4-butanediol bis(3-mercaptopropionate), trimethylolpropane tris(2-mercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), pentaerythritol tetrakis(3-mercaptopropionate) Dipentaerythritol hexakis(3-mercaptopropionate), dipentaerythritol hexakis(2-mercaptoacetate), 1,2-dimercaptobenzene, 1,3-dimercapto-2-propanol, 2,3-dimercapto-1-propanol, 1,2-dimercapto-1,3-butanediol, hydroxyethyl-tris(mercaptoethylthiomethyl)methane, hydroxyethylthiomethyl-tris(mercaptoethylthio)methane, ethylene glycol bis(3-mercaptopropionate), propylene glycol bis(3-mercaptopropionate), butanediol bis(3-mercaptopropionate), octanediol bis(3-mercaptopropionate), tetraethylene glycol bis(3-mercaptopropionate), Ethylene glycol bis(4-mercaptobutyrate), propylene glycol bis(4-mercaptobutyrate), butanediol bis(4-mercaptobutyrate), octanediol bis(4-mercaptobutyrate), trimethylolpropane tris(4-mercaptobutyrate), pentaerythritol tetrakis(4-mercaptobutyrate), ethylene glycol bis(6-mercaptovalerate), propylene glycol bis(6-mercaptovalerate) , butanediol bis(6-mercaptovalerate), octanediol bis(6-mercaptovalerate), trimethylolpropane tris(6-mercaptovalerate), pentaerythritol tetrakis(6-mercaptovalerate), 1,6-hexanedithiol, 1,9-nonanedithiol, 1,10-decanedithiol, 4,4'-bis(mercaptomethyl)phenyl sulfide, 2,4'-bis(mercaptomethyl)phenyl sulfide, 2,4,4'-tri( mercaptomethyl)phenyl sulfide, 2,2',4,4'-tetra(mercaptomethyl)phenyl sulfide, 1,3,5-tris[2-(3-mercaptopropionyloxy)ethyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, polysulfide polymers, etc., which may be used alone or in combination of two or more. Among these, preferred are trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), 1,3,5-tris[2-(3-mercaptopropionyloxy)ethyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3-mercapto Preferred are 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and pentaerythritol tetrakis(3-mercaptobutyrate), and more preferred are 1,3,5-tris(3-mercaptobutyloxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione and pentaerythritol tetrakis(3-mercaptobutyrate), which have a secondary thiol structure.

[0032] The compound having a thiol group may be produced by a known method, or a commercially available compound may be used. RTM PE1, BD1, NR1, trimethylolpropane tris(3-mercaptobutyrate), trimethylolethane tris(3-mercaptobutyrate) (all manufactured by Showa Denko K.K.), polythiol RTM 340M (manufactured by Toray Fine Chemicals Co., Ltd.), pentaerythritol tetrakis(3-mercaptopropionate) (manufactured by SC Organic Chemicals Co., Ltd.), and the like.

[0033] Also preferred are compounds having three or more functional thiol groups in the molecule. Examples include 2,4,4'-tri(mercaptomethyl)phenyl sulfide, 2,2',4,4'-tetra(mercaptomethyl)phenyl sulfide, 1,3,5-tris[2-(3-mercaptopropionyloxy)ethyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 1,3,5-tris(3-mercaptobutyloxyethyl)1,3,5-triazine-2,4,6(1H,3H,5H)-trione, pentaerythritol tetrakis(3-mercaptobutyrate), and 1,4-bis(3-mercaptobutyryloxy)butane. This is because the increased crosslink density can improve heat resistance and other properties.

[0034] When a compound having a thiol group is used in the sealing agent of the present invention, it is preferable that the compound be contained in an amount of 1 to 10 parts by mass per 100 parts by mass of the total amount of the sealing agent.

[0035] [Organic filler] The sealing agent of the present invention may contain an organic filler. Examples of the organic filler include urethane fine particles, acrylic fine particles, styrene fine particles, styrene olefin fine particles, and silicone fine particles. Examples of silicone fine particles include KMP-594, KMP-597, and KMP-598 (manufactured by Shin-Etsu Chemical Co., Ltd.), Trefil RTM E-5500, 9701, and EP-2001 (manufactured by Toray Dow Corning Co., Ltd.) are preferred, JB-800T and HB-800BK (manufactured by Negami Chemical Industries Co., Ltd.) are preferred as urethane fine particles, and Rabalon is preferred as styrene fine particles. RTM T320C, T331C, SJ4400, SJ5400, SJ6400, SJ4300C, SJ5300C, and SJ6300C (manufactured by Mitsubishi Chemical) are preferred, and Septon is the styrene olefin fine particle. RTM SEPS2004 and SEPS2063 are preferred. These organic fillers may be used alone or in combination of two or more. Two or more may be used to form a core-shell structure. Among these, acrylic fine particles and silicone fine particles are preferred.

[0036] [Thermal radical polymerization initiator] The sealing agent of the present invention contains a thermal radical polymerization initiator, which can improve the curing rate and curability. The thermal radical polymerization initiator is not particularly limited as long as it is a compound that generates radicals by heating and initiates a chain polymerization reaction, and examples thereof include organic peroxides, azo compounds, benzoin compounds, benzoin ether compounds, acetophenone compounds, and benzopinacol, with benzopinacol being preferred. For example, an organic peroxide is Kayamec RTM A, M, R, L, LH, SP-30C, Perkadox CH-50L, BC-FF, Kadox B-40ES, Perkadox 14, Trigonox RTM 22-70E, 23-C70, 121, 121-50E, 121-LS50E, 21-LS50E, 42, 42LS, Kayaester RTM P-70, TMPO-70, CND-C70, OO-50E, AN, Kayabutyl RTM B, Percadox 16, Kayacarvone RTM BIC-75, AIC-75 (manufactured by Kayaku Akzo Co., Ltd.), Permec RTM N, H, S, F, D, G, Perhexa RTM H,HC,TMH,C,V,22,MC,Percure RTM AH, AL, HB, Perbutyl RTM H, C, ND, L, Park Mill RTM H., D., Parloyle RTM IB, IPP, Perocta RTM ND (manufactured by NOF Corporation) and other products are available commercially.

[0037] Furthermore, commercially available azo compounds include VA-044, 086, V-070, VPE-0201, and VSP-1001 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.).

[0038] The content of the thermal radical polymerization initiator is preferably 0.0001 to 10 parts by mass, more preferably 0.0005 to 5 parts by mass, and particularly preferably 0.001 to 3 parts by mass, per 100 parts by mass of the total amount of the sealing agent of the present invention.

[0039] The sealing agent of the present invention may further contain additives such as a radical polymerization inhibitor, a pigment, a leveling agent, an antifoaming agent, a solvent, etc. These additives are preferably those that have little tendency to stain the charge transport layer.

[0040] [Radical polymerization inhibitor] The radical polymerization inhibitor is not particularly limited as long as it is a compound that reacts with radicals generated from a photoradical polymerization initiator, a thermal radical polymerization initiator, or the like to prevent polymerization, and can be a quinone-based, piperidine-based, hindered phenol-based, nitroso-based, etc. Specific examples include naphthoquinone, 2-hydroxynaphthoquinone, 2-methylnaphthoquinone, 2-methoxynaphthoquinone, 2,2,6,6-tetramethylpiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-methoxypiperidine-1-oxyl, 2,2,6,6-tetramethyl-4-phenoxypiperidine-1-oxyl, and hydroquinone. , 2-methylhydroquinone, 2-methoxyhydroquinone, parabenzoquinone, butylated hydroxyanisole, 2,6-di-t-butyl-4-ethylphenol, 2,6-di-t-butylcresol, stearyl β-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 2,2'-methylenebis(4-ethyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-butylphenol) ol), 4,4'-butylidenebis(3-methyl-6-t-butylphenol), 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl], 2,4,8,10-tetraoxaspiro[5,5]undecane, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenylpropionate)methane], 1,3,5-trimethyl- Examples of suitable antibacterial agents include, but are not limited to, this(3',5'-di-t-butyl-4'-hydroxybenzyl)-sec-triazine-2,4,6-(1H,3H,5H)trione, paramethoxyphenol, 4-methoxy-1-naphthol, thiodiphenylamine, aluminum salt of N-nitrosophenylhydroxyamine, and Adeka STAB LA-81 (trade name) and Adeka STAB LA-82 (trade name) (manufactured by Adeka Corporation).Of these, naphthoquinone-based, hydroquinone-based, nitroso-based, and piperazine-based radical polymerization inhibitors are preferred, naphthoquinone, 2-hydroxynaphthoquinone, hydroquinone, 2,6-di-tert-butyl-p-cresol, and Polystop 7300P (manufactured by Hakuto Co., Ltd.) are more preferred, and Polystop 7300P (manufactured by Hakuto Co., Ltd.) is most preferred.

[0041] The content of the radical polymerization inhibitor is preferably 0.0001 to 1 part by mass, more preferably 0.001 to 0.5 parts by mass, and particularly preferably 0.01 to 0.2 parts by mass, per 100 parts by mass of the total amount of the sealing agent of the present invention.

[0042] The following method is one example of a method for obtaining the sealing agent of the present invention. First, components (A), (B), and (C) are heated and dissolved. Next, after cooling to room temperature, components (D), (E), a silane coupling agent, a compound having a thiol group, an antifoaming agent, a leveling agent, a solvent, etc. are added as needed, and the mixture is mixed uniformly using a known mixing device such as a three-roll mill, a sand mill, a ball mill, a planetary mixer, etc., to produce the sealing agent. If necessary, filtration may be performed after mixing to remove impurities.

[0043] The solar cell manufactured using the sealing agent of the present invention will be described in detail below. The following specific embodiments are merely examples, and the present invention is not limited thereto.

[0044] Generally, dye-sensitized solar cells are mainly composed of a first conductive support (oxide semiconductor electrode) having a dye-sensitized semiconductor-containing layer on its surface, a second conductive support as a counter electrode, and a charge transfer layer. The sealant of the present invention is used for the purpose of bonding the first and second conductive supports and maintaining the charge transfer layer between the two supports. Examples of conductive supports include a thin film of a conductive material, such as FTO (fluorine-doped tin oxide), ATO (antimony-doped tin oxide), or ITO (indium-doped tin oxide), formed on the surface of a substrate such as glass, plastic, polymer film, quartz, or silicon. The thickness of the substrate is usually 0.01 to 10 mm, and its shape can vary from film to plate, but at least one of the two substrates is optically transparent. The conductivity of the conductive support is usually 1000 Ω / cm. 2 Less than or equal to 100 Ω / cm, preferably 2 The following is the result.

[0045] The oxide semiconductor used in preparing the semiconductor-containing layer is preferably metal chalkenide fine particles. Specific examples include oxides of transition metals such as Ti, Zn, Sn, Nb, W, In, Zr, Y, La, and Ta; oxides of Al; oxides of Si; and perovskite-type oxides such as SiTiO3, CaTiO3, and BaTiO3. Among these, TiO2, ZnO, and SnO2 are particularly preferred. These may also be used in mixture, with a preferred example being a SnO2-ZnO mixture. In the case of a mixture, the components may be mixed in the form of fine particles, or in the form of a slurry or paste, as described below, or layered. The concentration of the oxide semiconductor in the slurry or paste is typically 1 to 90% by mass, preferably 5 to 80% by mass. The primary particle size of the oxide semiconductor used is typically 1 to 200 nm, preferably 1 to 50 nm.

[0046] Methods for preparing the semiconductor-containing layer include a method of forming a thin film made of an oxide semiconductor directly on a substrate by vapor deposition, a method of applying or coating a slurry or paste onto a substrate and then applying pressure, a method of electrically depositing the layer using the substrate as an electrode, a method of applying or coating a slurry or paste onto a substrate and then drying, curing, or baking the slurry or paste, etc. Examples of the application or coating method include a bar coater method, a dip coating method, a spin coating method, a spray method, a screen printing method, a doctor blade method, and a dispense method.

[0047] These methods can be selected appropriately or used in combination depending on the type and form of the substrate. From the viewpoint of the performance of the oxide semiconductor electrode, a method using a slurry or paste is preferred. The slurry can be obtained, for example, by dispersing secondary agglomerated oxide semiconductor particles in a dispersion medium using a dispersant so that the average primary particle diameter is usually 1 to 200 nm, or by hydrolyzing an alkoxide or the like, which is a precursor of the oxide semiconductor, by a sol-gel method. Furthermore, oxide semiconductor particles with different particle size distributions may be mixed and used.

[0048] The dispersion medium for dispersing the slurry is not particularly limited as long as it can disperse oxide semiconductor particles. Examples of the dispersion medium include water, alcohols such as ethanol and terpineol, ketones such as acetone and acetylacetone, and organic solvents such as hydrocarbons such as hexane. These may also be used in combination. The use of water is preferable in that it minimizes changes in the viscosity of the slurry. A dispersion stabilizer or the like may be added to the slurry in order to obtain stable primary particles. Specific examples of dispersion stabilizers that can be used include polyhydric alcohols such as polyethylene glycol, phenols, monohydric alcohols such as octyl alcohol, and other co-condensates thereof; cellulose derivatives such as hydroxypropylmethylcellulose, hydroxymethylcellulose, hydroxyethylcellulose, and carboxymethylcellulose; polyacrylamide; acrylamide, (meth)acrylic acid or its salts, (meth)acrylic acid esters (methyl (meth)acrylate, ethyl (meth)acrylate, etc.), and other co-condensates thereof; water-soluble polyacrylic acid derivatives that are copolymers of acrylamide, (meth)acrylic acid or its salts, (meth)acrylic acid esters, etc. with hydrophobic monomers such as styrene, ethylene, and propylene; salts of melamine sulfonic acid formaldehyde condensates; salts of naphthalene sulfonic acid formaldehyde condensates; high molecular weight lignin sulfonates; acids such as hydrochloric acid, nitric acid, and acetic acid, but are not limited thereto. These dispersion stabilizers may be used alone or in combination of two or more.

[0049] Among these, polyhydric alcohols such as polyethylene glycol, self- or mutual co-condensation products of phenol, octyl alcohol, etc., poly(meth)acrylic acid, sodium poly(meth)acrylate, potassium poly(meth)acrylate, lithium poly(meth)acrylate, carboxymethyl cellulose, hydrochloric acid, nitric acid, acetic acid, etc. are preferred.

[0050] After drying the slurry applied to the conductive support, it can be subjected to a firing treatment at a temperature equal to or lower than the melting point (or softening point) of the substrate used for the conductive support. The firing temperature is usually 100 to 900°C, preferably 100 to 600°C. The firing time is not particularly limited, but is generally within 4 hours. The thickness of the semiconductor-containing layer provided on the conductive support is usually 1 to 50 μm.

[0051] To improve the surface smoothness, the semiconductor-containing layer may be subjected to a secondary treatment (see Non-Patent Document 2). For example, the smoothness of the semiconductor-containing layer can be improved by directly immersing the conductive support provided with the thin film of the semiconductor-containing layer prepared by the above-mentioned method in a solution of an alkoxide, chloride, nitrate, sulfide, or the like of the same metal as that used to prepare the semiconductor-containing layer, and then drying the support, or optionally further baking (re-baking) the support in the same manner as above. Here, examples of metal alkoxides include titanium ethoxide, titanium isopropoxide, titanium t-butoxide, n-dibutyl-diacetyltin, etc., and alcohol solutions thereof are used. Examples of chlorides include titanium tetrachloride, tin tetrachloride, zinc chloride, etc., and aqueous solutions thereof are used. The specific surface area of ​​the semiconductor-containing layer made of oxide semiconductor fine particles obtained in this manner is usually 1 to 1,000 m 2 / g, preferably 10 to 500m 2 / g.

[0052] Next, the process of supporting a sensitizing dye on the semiconductor-containing layer will be described. The sensitizing dye is not particularly limited as long as it has the effect of sensitizing light absorption together with the semiconductor fine particles that constitute the semiconductor-containing layer. As the sensitizing dye, a metal complex dye containing a metal element such as ruthenium or a metal-free organic dye may be used alone, or several types may be mixed in any ratio. When mixed, it may be a combination of multiple types of metal complex dyes, multiple types of organic dyes, or a metal complex dye and an organic dye. By mixing multiple types of dyes with different absorption wavelength ranges, a wide range of absorption wavelengths can be used, resulting in a solar cell with high conversion efficiency.

[0053] There is no particular limitation on the metal complex dye that can be supported, but phthalocyanine, porphyrin, etc. are preferred, and ruthenium complexes are more preferred. Furthermore, there is also no particular limitation on the organic dye that can be supported, and examples thereof include metal-free phthalocyanine, porphyrin, cyanine, merocyanine, oxonol, triphenylmethane-based, acrylic acid-based dyes, methine dyes such as pyrazolone-based methine dyes, and xanthene-based, azo-based, anthraquinone-based, and perylene-based dyes. International Publication No. 2002-001667, International Publication No. 2002-011213, International Publication No. 2002-071530, JP 2002-334729A, JP 2003-007358A, JP 2003-017146A, JP 2003-059547A, JP 2003-086257A, JP 2003-115333A, JP 2003-132965A, JP 2003-142172A, JP 2003-151649A, JP 2003-

[0039] Preferred are dyes described in JP-A-157915, JP-A-2003-282165, JP-A-2004-014175, JP-A-2004-022222, JP-A-2004-022387, JP-A-2004-227825, JP-A-2005-005026, JP-A-2005-019130, JP-A-2005-135656, JP-A-2006-079898, JP-A-2006-134649, WO 2006-082061, etc. Merocyanine and methine dyes such as the above-mentioned acrylic acid dyes are more preferred. When a mixture of multiple dyes is used, the ratio of each dye is not particularly limited, but it is generally preferable to use at least 10 mol% of each dye. When a solution or dispersion of two or more dyes is used to support the dyes in the semiconductor-containing layer, the total concentration of the dyes in the solution may be the same as when only one type is supported. When a mixture of multiple dyes is used, the solvents described above for oxide semiconductors can be used, and the solvents used for the dyes may be the same or different.

[0054] A method for supporting the sensitizing dye includes immersing the conductive support provided with the semiconductor-containing layer in a solution in which the dye is dissolved in a solvent or a dispersion in which the dye is dispersed in a solvent. The concentration of the dye in the solution or dispersion may be determined appropriately depending on the type and solubility of the dye. The immersion temperature is generally from room temperature to the boiling point of the solvent, and the immersion time may be about 1 to 72 hours. Specific examples of solvents that can be used to dissolve the sensitizing dye include methanol, ethanol, acetone, acetonitrile, dimethyl sulfoxide, dimethylformamide, t-butanol, and tetrahydrofuran. These may be used alone or in combination in any ratio. The concentration of the sensitizing dye in the solution is usually 1 x 10 -6 M to 1M, preferably 1 × 10 5 M~1×10 -1 In this way, a conductive support having a dye-sensitized semiconductor-containing layer is obtained, which is used as an oxide semiconductor electrode.

[0055] When loading a dye into a semiconductor-containing layer, it is effective to load the dye in the presence of an inclusion compound to prevent dye particle aggregation. Examples of inclusion compounds include steroid compounds such as cholic acid, crown ethers, cyclodextrins, calixarene, and polyethylene oxide. Preferred examples include cholic acids such as cholic acid, deoxycholic acid, chenodeoxycholic acid, cholic acid methyl ester, sodium cholate, and ursodeoxycholic acid, as well as polyethylene oxide. These inclusion compounds may be added to a dye solution, or the inclusion compound may be dissolved in a solvent beforehand, after which the dye is dissolved or dispersed. Two or more types of these inclusion compounds may be used in combination, and the ratio can be selected as desired. After loading the dye, the semiconductor-containing layer may be treated with an amine compound such as 4-t-butylpyridine. For example, the treatment may involve immersing the conductive support having the dye-loaded semiconductor-containing layer in an ethanol solution of the amine compound.

[0056] The counter electrode is made by depositing conductive particles of platinum, carbon, rhodium, ruthenium, etc., which act catalytically in the reduction reaction of the redox electrolyte, on the surface of a conductive support such as FTO conductive glass, or by coating and baking precursors of these conductive particles on the surface.

[0057] Next, the charge transfer layer will be described. The charge transfer layer uses a solution in which a redox electrolyte pair, a hole transport material, etc. are dissolved in a solvent or a room-temperature molten salt (ionic liquid). Examples of the redox electrolyte that can be used include halogen redox electrolytes composed of halogen compounds and halogen molecules with halogen ions as counter ions; metal redox electrolytes such as ferrocyanide-ferricyanide, ferrocene-ferricinium ions, and metal complexes such as cobalt complexes; and organic redox electrolytes such as alkylthiol-alkyl disulfides, viologen dyes, and hydroquinone-quinone. Halogen redox electrolytes are preferred. Examples of halogen molecules in the halogen redox electrolyte include iodine molecules and bromine molecules, with iodine molecules being preferred. Examples of halogen compounds include metal halide salts such as LiI, NaI, KI, CsI, CaI, and CuI, as well as organic quaternary ammonium salts of halogens such as tetraalkylammonium iodide, imidazolium iodide, 1-methyl-3-alkylimidazolium iodide, and pyridinium iodide. Salt compounds with iodide ions as counter ions are preferred. Specific examples include lithium iodide, sodium iodide, and trimethylammonium iodide salts. These compounds may be used alone or in combination of two or more.

[0058] Furthermore, when the charge transfer layer is composed of a solution containing a redox electrolyte, an electrochemically inactive solvent is used. Specific examples of the solvent include acetonitrile, valeronitrile, propylene carbonate, ethylene carbonate, 3-methoxypropionitrile, 3-butoxypropionitrile, methoxyacetonitrile, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, dimethoxyethane, diethyl carbonate, diethyl ether, dimethyl carbonate, 1,2-dimethoxyethane, dimethylformamide, dimethyl sulfoxide, 1,3-dioxolane, methyl formate, 2-methyltetrahydrofuran, 3-methyloxazolidin-2-one, γ-butyrolactone, sulfolane, tetrahydrofuran, and water. Among these, acetonitrile, propylene carbonate, ethylene carbonate, 3-methoxypropionitrile, methoxyacetonitrile, ethylene glycol, 3-methyloxazolidin-2-one, γ-butyrolactone, and the like are preferred. These may be used alone or in combination of two or more. The concentration of the redox electrolyte in the solution is usually 0.01 to 99% by mass, preferably 0.1 to 90% by mass.

[0059] Furthermore, when the charge transfer layer is formed in the form of a composition containing a redox electrolyte, a room-temperature melting liquid (ionic liquid) can be used as a solvent. Specific examples of room-temperature melting liquids that can be used include 1-methyl-3-alkylimidazolium iodide, vinylimidazolium tetrafluoride, 1-ethylimidazole sulfonate, alkylimidazolium trifluoromethylsulfonylimide, and 1-methylpyrrolidinium iodide. Furthermore, in order to improve the durability of dye-sensitized solar cells, a gel electrolyte can be prepared by, for example, dissolving a low-molecular-weight gelling agent in the charge transfer layer to thicken it, or by injecting a charge transfer layer containing a reactive component and then reacting it to gel it, or by impregnating the charge transfer layer with a pre-polymerized gel.

[0060] On the other hand, in the case of a completely solid-state charge transfer layer, a hole transport material or a P-type semiconductor can be used instead of a redox electrolyte. Examples of hole transport materials that can be used include amine derivatives and conductive polymers such as polyacetylene, polyaniline, and polythiophene. Examples of P-type semiconductors include CuI and CuSCN.

[0061] A dye-sensitized solar cell can be obtained by injecting a charge transfer layer into the gap between a pair of conductive supports and then sealing the injection port of the charge transfer layer. Examples of a sealing material (sealing agent) that can be used to seal the injection port of the charge transfer layer include isobutylene resin, epoxy resin, and UV-curable acrylic resin.

[0062] Next, a method for fabricating a dye-sensitized solar cell using the sealing agent of the present invention will be described. After adding spacers (gap control materials) such as glass fiber to the sealing agent of the present invention, the sealing agent is applied to one of the pair of substrates using a dispenser or screen printing device, etc., to form a continuous dam surrounding the semiconductor-containing layer. Then, a charge transfer layer, which will become a charge transfer layer, is dropped inside the dam of the sealing agent using a dispenser or the like. The amount of the charge transfer layer dropped is adjusted so that the gap between the electrodes after bonding is a predetermined size. The type of charge transfer layer to be enclosed is not particularly limited. The amount of the charge transfer layer dropped can be calculated from the effective area and cell gap of the solar cell. Then, the first and second conductive supports are placed in a vacuum bonding device so that they face each other, and the two electrodes are overlapped under reduced pressure. The pressure is then returned to atmospheric pressure to form a gap. After the gap is formed, the sealant is irradiated with ultraviolet light using an ultraviolet irradiator to photocure it. The ultraviolet irradiation dose is preferably 500 to 6000 mJ / cm. 2 , more preferably 1000 to 4000 mJ / cm 2 The preferred irradiation dose is 365 nm (measurement wavelength). Thereafter, if necessary, curing is performed at 60 to 120°C for 30 minutes to 2 hours to obtain the electrochemical cell of the present invention. The gap (cell gap) between the first and second conductive supports is usually 1 to 100 μm, preferably 20 to 70 μm.

[0063] Figure 1 is a cross-sectional schematic diagram illustrating the structure of a dye-sensitized solar cell prepared using the sealing agent of the present invention. In the figure, 1 is a conductive support having conductivity on the inside, 2 is a semiconductor-containing layer sensitized by a dye (1 and 2 collectively referred to as the oxide semiconductor electrode), 3 is a counter electrode in which platinum or the like is disposed on the conductive surface inside the conductive support, 4 is a charge transfer layer disposed in the gap between the pair of conductive supports, 5 is the sealing agent of the present invention, and 6 is a glass substrate. Lead wires are disposed on the positive and negative electrodes of the dye-sensitized solar cell thus obtained, and a resistance component is inserted between them to obtain a solar cell of the present invention.

[0064] The sealant of the present invention can also be applied to the production of a large-area dye-sensitized solar cell module in which a plurality of dye-sensitized solar cells arranged in a plane are electrically connected in series. Several types of module structures for large-area dye-sensitized solar cells are known. The sealant of the present invention can be used for any of these types of module structures. For example, it can also be used for a dye-sensitized solar cell module having a series-connection structure as described in International Publication No. 2009 / 057704.

[0065] The sealant of the present invention is excellent in ease of application to substrates, lamination, adhesion, and electrolyte sealing performance in the production process of dye-sensitized solar cells, and is also excellent in adhesive strength to oxide semiconductor electrodes and durability in high-temperature, high-humidity environments. Therefore, the dye-sensitized solar cells of the present invention obtained using the sealant can be efficiently produced by an electrolyte dropping method, have excellent durability, and are low-cost and applicable to a wide range of uses, from indoors to outdoors. [Example]

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0067] [Examples 1 to 2, Comparative Examples 1 to 6] Components (A), (B), and (C) were mixed at 90°C in the proportions shown in Table 1 below, and then cooled to room temperature. Components (D) and (E) were added and stirred, and then dispersed in a planetary mixer to prepare a sealing agent.

[0068] [viscosity] 0.15 mL of sealant was added to the measuring cup of an E-type viscometer (RE105, Toki Sangyo Co., Ltd.). After preheating for 120 seconds at a temperature of 25°C and a cone angle of 3° x R7.7, the value was measured after 120 seconds at a rotation speed of 5 rpm. The results are shown in Table 1.

[0069] [Thixotropy] 0.15 mL of sealing compound was added to the measuring cup of an E-type viscometer (RE105, Toki Sangyo Co., Ltd.). After preheating for 120 seconds at 25°C and a cone angle of 3° x 7.7°C, the viscosity was measured at 5 rpm and 120 seconds at 0.5 rpm. The thixotropy ratio was calculated by dividing the viscosity value at 0.5 rpm by the viscosity value at 5 rpm. The results are shown in Table 1.

[0070] [GBL swelling rate] The hardened sealant was immersed in gamma-butyrolactone (GBL), the main component of the electrolyte, and subjected to the same temperature as in the high-temperature, high-humidity reliability test to check whether the hardened sealant absorbed the GBL and changed shape. The less the shape change, the better the cell durability during the high-temperature, high-humidity reliability test. Specifically, the test was conducted as described below. The sealants produced in the examples and comparative examples were sandwiched between polyethylene terephthalate (PET) films to form thin films with a thickness of 100 μm, and then irradiated with UV light at 3000 mJ / cm 2After irradiation with ultraviolet light (measurement wavelength: 365 nm), the PET film was peeled off to obtain a sample. The prepared sample was cut into 2 cm x 6 cm strips to obtain sample pieces, which were immersed in GBL and left at 60°C for 6 hours. The swelling rate (%) was determined by the change in weight of the sample piece before and after the test (weight of sample piece after test / weight of sample piece before test x 100), and evaluated according to the criteria shown below. The results are shown in Table 1. ○: Swelling rate is less than 110% ×: Swelling rate exceeds 110%

[0071] [Sealant curing rate] The samples obtained in the GBL immersion test were dried, and the weight loss due to the elution of uncured components of the sealant was confirmed. Specifically, the test was carried out as follows. The samples obtained in the GBL immersion test were vacuum dried in a vacuum dryer (temperature 80°C, vacuum 0.1 MPa) for 4 hours, and the sealant cure rate (%) was determined by the change in weight of the sample piece before and after vacuum drying (weight of sample piece after test / weight of sample piece before test x 100), and evaluated according to the following criteria. The results are shown in Table 1. 〇: Sealant curing rate exceeds 98% ×: Sealant cure rate is less than 98%

[0072] [Electrolyte sealing performance] A test was carried out to confirm whether the sealant had the ability to seal the electrolyte. Specifically, the test was carried out according to the following description. The sealant produced in the examples and comparative examples was dispensed onto the ITO film on the ITO-equipped glass substrate in a 1cm x 1cm cell shape so that the line width after lamination would be 1.0mm, and then minute droplets of electrolyte were dropped into the frame of the seal pattern. Furthermore, in-plane spacers (Hayabeads SD-BD-DEA-LT 50μm: manufactured by Hayakawa Rubber Co., Ltd.) were sprayed onto the ITO film of another glass substrate with ITO electrodes, thermally fixed, and then the substrate with the previously dropped electrolyte was laminated in a vacuum using a laminating device. After opening to the atmosphere to form a gap, 3000mJ / cm was applied using a UV irradiator. 2The test cell was then irradiated with ultraviolet light (measurement wavelength: 365 nm) to prepare an electrolyte test cell for evaluation. The resulting evaluation cell was observed under a microscope, and the adhesion state of the sealant was evaluated according to the following criteria. The results are shown in Table 1. 〇: The sealant seals the electrolyte, and the electrolyte is not inserted into the sealant. ×: Electrolyte is leaking from the sealant or has entered the sealant.

[0073] [High temperature and humidity reliability test] The 1cm x 1cm cell sealed with electrolyte prepared in the sealant sealing evaluation was placed in a constant temperature and humidity tester set at 60°C and 90% humidity. The cell was removed from the tester at regular intervals and visually inspected to ensure it was still functioning. The cell was left in the constant temperature and humidity tester for a maximum of 1,500 hours. A cell that was still functioning was defined as one in which the sealant had not peeled off from the ITO-coated glass substrate, and there was no sign of electrolyte leakage outside the cell or air bubbles entering from outside the cell. The cell was evaluated according to the following criteria, depending on the length of time it was maintained. The results are shown in Table 1. 〇: 1500 hours durability △: Cell collapses between 500 and 1500 hours ×: Cell collapses within 500 hours

[0074] [Oxide semiconductor electrode adhesive strength] The sealants produced in the examples and comparative examples were mixed and stirred using a planetary stirrer (EME: VMX-360) and filled into a 5 ml syringe. The filled sealant was applied to the ITO film of a 0.5 mm thick glass substrate with an ITO electrode in a manner that replicated a corner with a radius of 0.5 mm and a length of 3 cm x 3 cm, so that the line width after lamination would be 1.0 mm. Furthermore, in-plane spacers (Hayabeads SD-BD-DEA-LT 4 μm: Hayakawa Rubber Co., Ltd.) were sprayed onto the ITO film of another glass substrate with an ITO electrode, thermally fixed, and then laminated to the previous substrate coated with the sealant in a vacuum using a lamination device. After opening to the atmosphere to form a gap, the substrate was irradiated with 3000 mJ / cm using a UV irradiator. 2The bonded substrate was then irradiated with ultraviolet light (measurement wavelength: 365 nm). The resulting bonded substrate was cut into a shape with only the lower substrate protruding, as shown in Figure 2, and a universal testing machine (Shimadzu Corporation: Autograph AG-Xplus500N) equipped with a 3 mm diameter needle terminal was used to press the lower substrate at a point 4 mm diagonally away from the corner of the applied sealant, and the maximum load when the bonded substrates peeled off was measured to determine the adhesive strength. The results are shown in Table 1.

[0075] [Table 1]

[0076] [Table 2]

[0077] As can be seen from the results in Table 1, the sealant of the present invention has excellent electrolyte sealing performance and high temperature and humidity resistance, and therefore can provide a highly reliable dye-sensitized solar cell. [Industrial Applicability]

[0078] The sealant for dye-sensitized solar cells of the present invention has excellent workability in applying to substrates, excellent lamination properties, excellent adhesion, and excellent electrolyte sealing performance, and is extremely low in contamination, during the production process of dye-sensitized solar cells. Therefore, the dye-sensitized solar cells of the present invention obtained using the sealant can be efficiently produced by an electrolyte dropping method, and also have excellent durability. [Explanation of symbols]

[0079] 1. Conductive support 2. Dye-sensitized semiconductor-containing layer 3 Counter electrode 4. Charge transfer layer 5. Sealant 6. Glass substrate

Claims

1. A sealing agent for dye-sensitized solar cells, comprising: (A) a polybutadiene compound having a (meth)acrylic group in the molecule; (B) a curable compound; and two or more types of (C) photopolymerization initiators, wherein the content of the (C) photopolymerization initiators is 1.5 to 4 parts by mass relative to 100 parts by mass of the total amount of the (A) polybutadiene compound having a (meth)acrylic group in the molecule and the (B) curable compound.

2. 2. The sealing agent for dye-sensitized solar cells according to claim 1, wherein the (C) photopolymerization initiator is a photopolymerization initiator having at least one structure selected from the group consisting of a phenyl sulfide structure, an oxime ester structure, a thioxanthone structure, and a phosphine oxide structure in its molecule.

3. 2. The sealing agent for dye-sensitized solar cells according to claim 1, wherein the (C) photopolymerization initiator comprises a photopolymerization initiator having an oxime ester structure in the molecule and a photopolymerization initiator having at least one structure selected from the group consisting of a phenyl sulfide structure, a thioxanthone structure, and a phosphine oxide structure.

4. 2. The sealing agent for dye-sensitized solar cells according to claim 1, wherein the content of the polybutadiene compound (A) having a (meth)acrylic group in the molecule is 40 to 80 parts by mass relative to 100 parts by mass of the total amount of the polybutadiene compound (A) having a (meth)acrylic group in the molecule and the curable compound (B).

5. The sealant for a dye-sensitized solar cell according to claim 1 , further comprising (D) a (meth)acrylate having a phosphate group.

6. The sealant for a dye-sensitized solar cell according to claim 1 , further comprising (E) an inorganic filler.

7. A solar cell comprising the sealant for a dye-sensitized solar cell according to claim 1 .

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