JP2013020789A - Electrolyte for dye sensitized solar cell and dye sensitized solar cell manufactured using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an excellent electrolyte for a dye sensitized solar cell, having high durability and capable of obtaining high short circuit current density and conversion efficiency; and a dye sensitized solar cell manufactured using the electrolyte.SOLUTION: There are provided: an electrolyte for a dye sensitized solar cell, containing a boric acid ester as an additive; and a dye sensitized solar cell manufactured using the electrolyte. A dye sensitized solar cell capable of obtaining high short circuit current density and conversion efficiency and also capable of maintaining high durability can be obtained by adding a boric acid ester to an electrolyte for a dye sensitized solar cell.

Description

  The present invention relates to an electrolyte solution for a dye-sensitized solar cell. More specifically, the invention provides a dye-sensitized solar cell that has a high short-circuit current density and conversion efficiency, can be used in a wide temperature range, and has excellent durability. The present invention relates to an electrolytic solution and a dye-sensitized solar cell using the same.

  In recent years, a dye-sensitized solar cell in which a sensitizing dye that absorbs a visible light region is supported on a semiconductor layer has been studied. This dye-sensitized solar cell has advantages such as being inexpensive and capable of being manufactured by a relatively simple process, and is expected to be put to practical use.

  A dye-sensitized solar cell generally includes an anode electrode (semiconductor electrode) in which a porous film of a metal oxide semiconductor is formed on a transparent substrate with a transparent conductive film and a sensitizing dye is adsorbed on the surface, and a conductive substrate. A cathode electrode (counter electrode) on which a catalyst layer is formed is disposed so as to be opposed to each other, and an electrolytic solution is sealed therebetween. When light is incident on the semiconductor electrode, the sensitizing dye absorbs visible light to be in an excited state, electrons are injected from the sensitizing dye into the semiconductor electrode, and current is taken out through the current collector. On the other hand, the oxidized form of the sensitizing dye is reduced and regenerated by the redox pair in the electrolytic solution. The oxidized redox pair is reduced by the catalyst layer on the surface of the counter electrode disposed opposite to the semiconductor electrode, and the cycle goes around.

Conventionally, as an electrolyte for a dye-sensitized solar cell, lithium iodide or an iodide salt and iodine dissolved in methoxyacetonitrile or acetonitrile are generally used (Non-patent Document 1 and Patent Document 1). . Iodide salt and iodine form I ⁻ and I ₃ ⁻ in the electrolyte, and function as charge carriers between the two electrodes as a redox pair. On the other hand, lithium iodide is frequently used as an additive for improving the short-circuit current density.

In recent years, due to the low toxicity and durability of nitriles, dye-sensitized solar cell electrolytes using propylene carbonate or γ-butyrolactone as solvents in place of nitriles have also been disclosed (Patent Documents 1 and 2). However, there is a problem that lithium iodide has low solubility in these solvents. In addition, lithium ions have a feature that they are easily solvated because of their small ion radius. However, when these solvents are solvated with lithium ions, they are solvated more strongly than when nitrile is used as the solvent, resulting in an electrolyte solution. As a result, there is a big problem that the effect of improving the short-circuit current density by lithium ions is canceled.
Furthermore, when lithium iodide is added, titanium oxide, which is the most widely used as an oxide semiconductor, reacts with lithium ions, increasing the electrical resistance of the semiconductor electrode, which significantly reduces long-term stability. There was also a fatal problem.

  In order to obtain practical durability as an electrolyte solution for a dye-sensitized solar cell, it is required to use a solvent having a high boiling point of 200 ° C. or higher. However, as the boiling point increases, the viscosity of the solvent itself increases. Therefore, the electrolytic solution using the high boiling point solvent tends to have a low short circuit current density. Therefore, there is a demand for an electrolytic solution that can obtain a larger short-circuit current density. However, as described above, the electrolytic solution using lithium iodide as an additive has a low durability and a short-circuit current density that is obtained. At the same time, an additive for improving the short-circuit current density that can be used, and an electrolytic solution that can obtain a high short-circuit current density using the additive have not yet been found.

  Accordingly, there is a demand for an excellent dye-sensitized solar cell electrolytic solution that has high durability and provides high short-circuit current density and conversion efficiency, and a dye-sensitized solar cell using the same.

JP 2007-220608 A JP 2000-277182 A

Japan Journal of Applied Physics, Vol. 45, no. 25, 2006, L638-L640

  Accordingly, in view of the above problems, the present invention provides an excellent electrolyte solution for dye-sensitized solar cells that is highly durable and has high short-circuit current density and high conversion efficiency, and a dye-sensitized solar cell using the same. Is the subject.

  As a result of intensive studies, the present inventors have been able to greatly improve the short-circuit current density and conversion efficiency by using an electrolyte containing a borate ester as an additive, and can maintain high durability. As a result, the present invention has been completed.

  That is, the present invention is as follows.

  1st invention is the electrolyte solution for dye-sensitized solar cells characterized by containing the boric acid ester represented by following General formula (1).

（一般式（１）中、Ｒ_１〜Ｒ_３は独立して、ハロゲン、ニトリル、アルコキシ基若しくは芳香環で一部置換されていても良い炭素数１〜２０のアルキル基、またはアリール基を表す。）

(In the general formula (1), R _{1 to} R ₃ independently represent a halogen, nitrile, alkoxy group or an alkyl group having 1 to 20 carbon atoms which may be partially substituted with an aromatic ring, or an aryl group. .)

  In the second invention, the borate ester is trimethyl borate, triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate, triisobutyl borate, triphenyl borate, tris borate (propionitrile). The electrolyte solution for a dye-sensitized solar cell according to the first invention, which is at least one selected from the group consisting of:

  The third invention is the electrolysis for dye-sensitized solar cell according to the first or second invention, wherein the concentration of borate ester in the electrolytic solution is 0.001 to 5.0 mol / l. It is a liquid.

  4th invention contains the boric acid ester and the donor compound whose donor number is 25 or more, Electrolysis for dye-sensitized solar cells in any one of 1st to 3rd invention characterized by the above-mentioned It is a liquid.

  A fifth invention is characterized in that the donor compound is at least one selected from the group consisting of pyridine, pyrazine, pyrimidine, imidazole, pyrazole, triazole, pyrrolidine, piperidine, hydrazine, pyrrolidone, sulfoxide, and amide compounds. The electrolyte solution for a dye-sensitized solar cell according to the fourth invention.

  A sixth invention is characterized in that the solvent contains at least one organic solvent selected from the group consisting of a nitrile, a lactone, a cyclic carbonate, and a chain sulfone represented by the following general formula (2). To an electrolyte solution for a dye-sensitized solar cell according to any one of the fifth to fifth inventions.

（一般式（２）中、Ｒ_４、Ｒ_５は独立して、ハロゲン、アルコキシ基若しくは芳香環で一部置換されていても良い炭素数１〜１２のアルキル基、またはアリール基を表す。）

(In the general formula (2), R ₄ and R ₅ independently represent a halogen, an alkoxy group or an alkyl group having 1 to 12 carbon atoms which may be partially substituted with an aromatic ring, or an aryl group.)

  According to a seventh aspect of the invention, there is provided a dye-sensitized solar as described in any one of the first to sixth aspects, wherein the redox electrolyte contains a halogen compound having a halogen anion as a counter ion and a halogen molecule. It is an electrolyte for batteries.

  The eighth invention is the electrolyte solution for a dye-sensitized solar cell according to the seventh invention, wherein the halogen compound is iodide or bromide and the halogen molecule is iodine or bromine.

  A ninth invention is the electrolyte solution for a dye-sensitized solar cell according to any one of the first to sixth inventions, which contains a polypyridylcobalt complex as a redox electrolyte.

According to a tenth aspect of the present invention, there is provided a photoelectrode in which a porous metal oxide semiconductor layer is formed on a conductive layer, and a dye having a photosensitizing action is adsorbed on the metal oxide semiconductor layer, and the photoelectrode A dye-sensitized solar cell having a counter electrode disposed and an electrolyte layer formed between the photoelectrode and the counter electrode and containing an electrolyte solution,
A dye-sensitized solar cell, wherein the electrolyte solution is the electrolyte solution for a dye-sensitized solar cell according to any one of the first to ninth inventions.

  The eleventh invention is for a dye-sensitized solar cell containing at least a boric acid ester represented by the following general formula (1), an organic solvent different from the boric acid ester, and a redox electrolyte. It is a method for producing a dye-sensitized solar cell, wherein an electrolytic solution is filled between a semiconductor electrode and a counter electrode and sealed.

（一般式（１）中、Ｒ_１〜Ｒ_３は独立して、ハロゲン、ニトリル、アルコキシ基若しくは芳香環で一部置換されていても良い炭素数１〜２０のアルキル基、またはアリール基を表す。）

(In the general formula (1), R _{1 to} R ₃ independently represent a halogen, nitrile, alkoxy group or an alkyl group having 1 to 20 carbon atoms which may be partially substituted with an aromatic ring, or an aryl group. .)

  The twelfth invention is that a dye-sensitized solar cell electrolytic solution containing a boric acid ester and a donor compound having a donor number of 25 or more is filled and sealed between a semiconductor electrode and a counter electrode. A method for producing a dye-sensitized solar cell according to the eleventh aspect of the invention.

  The dye-sensitized solar cell using the electrolytic solution of the present invention can obtain a high short-circuit current density, and as a result, can obtain high conversion efficiency and can maintain its performance for a long time.

It is a cross-sectional schematic diagram which shows an example of a structure of the dye-sensitized solar cell of this invention.

  The electrolyte solution for dye-sensitized solar cells of the present invention contains a boric acid ester represented by the following general formula (1), at least one organic solvent different from the boric acid ester, and a redox electrolyte. . By using such a borate ester, a high short-circuit current density can be obtained even with a high-boiling solvent having a high viscosity.

In General Formula (1), R _{1 to} R ₃ independently represent a halogen, a nitrile, an alkoxy group, an alkyl group having 1 to 20 carbon atoms which may be partially substituted with an aromatic ring, or an aryl group.

  Examples of the boric acid ester in the present invention include trimethyl borate, triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate, triisobutyl borate, tripentyl borate, trihexyl borate, triheptyl borate, borate Trimethylbutyl borate, tris (ethylhexyl) borate, triisooctyl borate, tri-n-octyl borate, tridecyl borate, tridodecyl borate, triphenyl borate, tri-o-tolyl borate, tri-borate Examples include m-tolyl, tris borate (propionitrile), tris borate (2-methoxyethyl), tris borate (chloroethyl), and the like.

The boiling point of the boric acid ester is not limited because the optimum value varies depending on the use conditions of the solar cell, but is preferably 60 ° C or higher, more preferably 120 ° C or higher, and 180 ° C or higher. Is particularly preferred.
Moreover, it is desirable that the boric acid ester of the present invention is dissolved in the electrolyte solvent. Further, the optimum value varies depending on the electrolyte solution to be dissolved, but is not limited. However, the viscosity of the borate ester is desirably low so that the conductivity of the electrolyte solution is high, for example, 10 mPa · s or less, more preferably 5 mPa · s. It is desirable that it is s or less.
Among the borate esters described above, borate esters are trimethyl borate, triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate, triisobutyl borate, triphenyl borate, tris borate (pro Pionitrile) is desirable, and triethyl borate, tributyl borate, and tris borate (propionitrile) are particularly desirable.

  The boric acid ester concentration in the electrolytic solution is not necessarily limited because the optimum value varies depending on the electrolytic solution solvent to be used. However, the concentration of the substance is preferably 0.001 to 5.0 mol / l so that the effect of addition sufficiently appears. . Since the solubility of the electrolyte is low in the borate ester itself, if the concentration of the borate ester is too high, the short-circuit current density is reduced. Therefore, it is desirable that the concentration of borate ester is as low as possible within the range where the desired short-circuit current density can be obtained.

By the way, since boric acid ester has fire extinguishing properties, it has been studied to use it as a non-flammable solvent for enhancing safety in use of an electrolyte solution other than a dye-sensitized solar cell such as a lithium ion battery. In order to develop nonflammability, it is necessary to increase the concentration of borate ester as much as possible after dissolving the necessary electrolyte. Specifically, at least 30 vol% of the entire electrolyte solution, and a concentration of 50 vol% or more is necessary to more reliably suppress ignition. On the other hand, in the present invention, as described above, even if a high concentration boric acid ester used as an existing non-flammable electrolyte is used, the improvement addition of the short circuit current density which is the object of the present invention is added. It cannot function as an agent at all, and conversely deteriorates the characteristics of the dye-sensitized solar cell. On the other hand, the effectiveness against nonflammability of the electrolytic solution is not recognized in the concentration range of the boric acid ester in the present invention.
In addition, borate esters have never been used in dye-sensitized solar cells, and the specific mechanism for improving the short-circuit current density of solar cells by adding a small amount of borate ester is still unknown. In addition, the purpose and method of use of the conventional borate ester, which aims to improve safety by making the electrolyte nonflammable, is essentially different from the improvement of the current value in the present invention. Therefore, it is impossible to deduce that there is an effect of improving the short-circuit current density in the dye-sensitized solar cell from the conventional purpose of nonflammability and the conditions and mechanism used.

  Then, the solvent of the electrolyte solution of this invention is demonstrated. The solvent of the electrolytic solution is not particularly limited as long as the electrolyte can be dissolved, and a conventionally known electrolytic solution solvent can be used. For example, nitriles such as acetonitrile, methoxyacetonitrile, methoxypropionitrile, benzonitrile, cyclic carbonates such as ethylene carbonate and propylene carbonate, chain carbonates such as dimethyl carbonate and diethyl carbonate, lactones such as γ-butyrolactone, Amides such as dimethylformamide and N-methylpyrrolidone, ethers such as ethylene glycol dialkyl ether and propylene glycol dialkyl ether, alcohols such as ethylene glycol monoalkyl ether and propylene glycol monoalkyl ether, ethylene glycol and propylene glycol Monohydric alcohols, dimethyl sulfoxide, cyclic sulfones such as sulfolane and methyl sulfolane, N, N′-dimethylimidazolidinone, - it is like methyl oxazolidinone, they may be mixed and used s alone.

Further, a solvent having a low viscosity, a high boiling point, low volatility, and sufficient ion conductivity is preferable. The boiling point of a specific organic solvent is preferably 150 ° C. or higher, and more preferably 200 ° C. or higher. Among the above organic solvents, examples of the organic solvent satisfying the boiling point include methoxypropionitrile, propylene carbonate, and γ-butyrolactone.
Moreover, even if it is a solid at room temperature alone, it may be a solid alone as long as it causes a freezing point depression by mixing with another organic solvent or a redox couple and is liquid at the operating range temperature.

  Furthermore, it is preferable to use a chain sulfone represented by the following general formula (2) as the electrolyte solution solvent of the present invention.

In General Formula (2), R ₄ and R ₅ independently represent a halogen, an alkoxy group, an alkyl group having 1 to 12 carbon atoms which may be partially substituted with an aromatic ring, or an aryl group.

Specific examples of the chain sulfone compound include dimethyl sulfone, ethyl methyl sulfone, methyl isopropyl sulfone, ethyl isopropyl sulfone, ethyl isobutyl sulfone, isobutyl isopropyl sulfone, methoxyethyl isopropyl sulfone, and fluoroethyl isopropyl sulfone. Among these, a compound in which the total number of carbon atoms of R ₄ and R ₅ such as ethyl isopropyl sulfone, ethyl isobutyl sulfone, isobutyl isopropyl sulfone, methoxyethyl isopropyl sulfone, and fluoroethyl isopropyl sulfone is 5 or more, preferably 5 to 10 It can be used in a wide range of temperatures and is particularly suitable because of its excellent durability.

Other examples of the chain sulfone compound of the general formula (2) include compounds in which at least one of R ₄ and R ₅ is a phenyl group, such as phenyl isopropyl sulfone, phenyl ethyl sulfone, and diphenyl sulfone. It can be illustrated. Among these, there are a wide range of compounds in which one of R ₄ and R ₅ is a phenyl group and one is a C 1-12 alkyl group which may be partially substituted with a halogen, an alkoxy group or an aromatic ring. It is preferably used because it can be used at a temperature and has excellent durability, and more preferably, it is a compound of which one is an unsubstituted alkyl group having 1 to 5 carbon atoms, and in particular, phenylisopropylsulfone can be suitably used.

  In addition to the various organic solvents described above, an ionic liquid can be used for the electrolytic solution of the present invention. As preferable examples of the ionic liquid, for example, the cation is 1-methyl-3-methylimidazolium, 1-butyl-3-methylimidazolium, 1-hexyl-3-methylimidazolium, 1-octyl-3-methyl. Imidazolium, 1-methyl-2,3-dimethylimidazolium, 1-butyl-2,3-dimethylimidazolium, 1-hexyl-2,3-dimethylimidazolium, 1-octyl-2,3-dimethylimidazolium Imidazolium-based, such as 1-methyl-pyridium, 1-butyl-pyridium, 1-hexyl-pyridium and the like, pyrazolium-based, aliphatic amine-based, anion is tetrafluoroborate, hexafluoroborate, Fluorinated sulfonic acids such as trifluoromethanesulfonate, trifluoro Fluorinated carboxylic acids such as acetic acid, thiocyanate, dicyanamide, tetracyanoborate, also can be given like what is sulfonylimide system such as bisfluorosulfonylimide and bistrifluoromethanesulfonylimide. Any one of these substances may be used alone, or a plurality of these substances may be mixed and used.

  The electrolytic solution of the present invention contains a redox electrolyte, that is, a redox couple. Examples of the redox pair include halogen compounds and halogen molecules having a halogen anion as a counter ion. Specific examples include a combination of iodide anion and iodine, a combination of bromide anion and bromine, or a mixture thereof. In particular, a combination of iodide anion and iodine is preferable because of high conversion efficiency.

  Examples of the cation constituting the halogen compound having the halogen anion as a counter ion, specifically, a halide salt such as iodide or bromide, include metal cations such as lithium, sodium, magnesium and calcium. As described above, under high-boiling solvents, it is difficult to obtain good characteristics even when a metal cation is used, and there are cases in which the durability is lowered. More preferred cations include imidazolium, pyridinium, pyrrolidinium. And onium cations such as pyrazolium. In particular, imidazolium-based and spiro-type quaternary ammonium such as spiro- (1,1 ′)-bipyrrolidinium can be preferably used. These 1 type (s) or 2 or more types can also be mixed and used.

  The concentration of halide varies depending on the amount of current generated depending on the amount of incident light when used as a solar cell, and the optimum concentration is not necessarily constant, but is preferably 0.01 to 4.0 mol / l, particularly preferably. 0.5 to 2.5 mol / l. If the concentration is less than 0.01 mol / l, sufficient performance may not be obtained. On the other hand, if the concentration is more than 4.0 mol / l, it may be difficult to dissolve in the solvent.

On the other hand, the halogen molecule for acting as a redox pair is specifically preferably iodine (I ₂ ) or bromine (Br ₂ ). In particular, when an iodide salt is used as the halide, it is desirable to use iodine as the halogen molecule. In this case, it acts as a redox pair of I ⁻ / I ₃ ⁻ together with an iodide salt. The content of halogen molecules in the electrolyte is not necessarily constant because the amount of current generated varies depending on the amount of incident light when used as a solar cell, but from the viewpoint of ion conductivity and light energy conversion efficiency. , Preferably 0.01 mmol to 0.5 mol / l, particularly preferably 0.05 mmol to 0.2 mol / l.

Examples of the redox pair other than the halogen compound in the present invention include tris (2,2′-bipyridine) cobalt complex and tris (4,4′-dimethyl-2) substituted with an alkyl group at the 4,4 ′ position. , 2′-bipyridine) cobalt complex, tris (4,4′-di-t-butyl-2,2′-bipyridine) cobalt complex, and tris (1,10-phenanthroline) cobalt complex. A pyridyl cobalt complex is mentioned.
The content of polypyridylcobalt complex used as a redox couple is not necessarily constant because the amount of current generated varies depending on the amount of incident light when used as a solar cell, but the ionic conductivity and light are not necessarily constant. From the viewpoint of energy conversion efficiency, the divalent complex is preferably 0.05 to 0.5 mol / l, and the trivalent complex is preferably 0.01 to 0.1 mol / l.

  In addition, the electrolyte of the present invention can be prepared by adding a polymer such as polyacrylonitrile or polyvinylidene fluoride or a low molecular gelling agent to the solvent, or polymerizing a polyfunctional monomer having an ethylenically unsaturated group in the solvent. The electrolyte layer 7 may be formed as a gel electrolyte by gelling these solvents by a method such as The polymer for gelling the solvent may have ionicity, but it is desirable that the polymer does not have ionicity when the movement of the electrolyte is hindered.

  Further, instead of polymer, particles may be added to give thixotropy so as to give a solid, paste, or gel when the cell is formed. The material of such particles is not particularly limited, and a known material can be used. For example, indium oxide, a mixture of tin oxide and indium oxide (hereinafter abbreviated as “ITO”), inorganic oxides such as silica, carbon materials such as ketjen black, carbon black, and carbon nanotubes, and kaolinite Or a layered inorganic compound such as montmorillonite, that is, a clay mineral may be used.

In addition, it is desirable to use a donor compound having a donor number of 25 or more in addition to a borate ester as an additive in the electrolytic solution of the present invention. Specifically, the mechanism of the synergistic effect that works by combining the borate ester and the donor additive is unclear, but the short circuit current density and the open circuit voltage can be improved at the same time, and the shape factor is also improved. The conversion efficiency can be greatly improved as compared with the case where it is used alone.
Conventionally known materials can be used as such donor additives, but the number of donors of various solvents such as methoxypropionitrile, γ-butyrolactone, and chain sulfone, which are general solvents, is 14 often a 18 order of, addition, I have been most frequently used as a redox pair ^- since it is a donor number of ions 14, it is necessary to have a donor number of predominantly higher than these solvents and electrolytes . Specifically, pyridines having a donor number of 25 or more, more preferably alkylpyridines such as 4-t-butylpyridine, pyrazines, nitrogen-containing 6-membered ring compounds such as pyrimidines and piperidines, Nitrogen-containing 5-membered ring compounds such as imidazoles, pyrazoles, triazoles and pyrrolidines, amides such as dimethylformamide and dimethylacetamide, cyclic amides such as pyrrolidone and N-methylpyrrolidone, dimethyl sulfoxide and diphenyl sulfoxide And sulfoxides. Among these, preferred additives are pyridine substituted with alkyl at the 4-position, imidazole substituted with alkyl at the 2-position and 4-position, pyrazole, triazole, N-methyl substituted with alkyl at the 3-position and / or 5-position. Examples include pyrrolidone, dialkyl sulfoxide, and dialkylacetamide. In the case of pyridines and sulfoxides, the alkyl substituent is a combination of a molecular size such that the viscosity of the electrolyte does not become too high when the donor compound is added, and an effect of improving donor properties by introducing the substituent. In the case where is an alkyl group having 1 to 4 carbon atoms, imidazoles, pyrazoles, or acetamide, an alkyl group having 1 or 2 carbon atoms is desirable.

Here, the number of donors represents the nature of a molecule as a donor as an amount irrelevant to the solvent, and is also called donating property. The number of donors is defined as the molar enthalpy value of the reaction as a donor, selecting 10 ⁻³ M SbCl ₃ in dichloroethane as the reference acceptor.

  The electrolytic solution of the present invention can be obtained by dissolving the boric acid ester of the present invention together with the above-described redox couple such as iodide and iodine in the above-mentioned various solvents according to a conventional method. On the other hand, the dye-sensitized solar cell of the present invention uses this electrolytic solution, but a general dye-sensitized solar cell configuration may be adopted except for the electrolytic solution. FIG. 1 shows an example of the configuration of the dye-sensitized solar cell of the present invention. In FIG. 1, 1 is an electrode substrate, 2 is a transparent substrate, 3 is a transparent conductive film, 4 is a porous metal oxide semiconductor layer, 5 is a sensitizing dye layer, 6 is a semiconductor electrode, and 7 is an electrolytic solution of the present invention. An electrolyte layer to be included, 8 is a counter electrode, 9 is an electrode substrate, 10 is a catalyst active layer, 11 is a spacer, and 12 is a peripheral seal portion.

  The electrode substrate 1 is a transparent electrode substrate such as conductive glass in which a transparent conductive film 3 is formed on a transparent substrate 2. A porous metal oxide semiconductor layer 4 is formed on the transparent conductive film 3 and has a sensitizing dye layer 5 in which a dye is adsorbed on the surface of the metal oxide semiconductor. From these, the semiconductor electrode 6 which is an anode electrode is comprised.

<Transparent substrate>
As the transparent substrate 2 constituting the electrode substrate 1, one that transmits visible light can be used, and transparent glass can be suitably used. Moreover, the thing which processed the glass surface and scattered incident light, and a translucent ground glass-like thing can also be used. Moreover, not only glass but a plastic plate, a plastic film, etc. can be used if it transmits light.

  The thickness of the transparent substrate 2 is not particularly limited because it varies depending on the shape and use conditions of the solar cell. For example, when glass or plastic is used, it is about 1 mm to 1 cm in consideration of durability during use. When flexibility is required and a plastic film or the like is used, the thickness is about 25 μm to 1 mm. Moreover, you may use surface treatments, such as a hard coat which improves a weather resistance as needed.

<Transparent conductive film>
As the transparent conductive film 3, a material that transmits visible light and has conductivity can be used, and examples of such a material include metal oxide. Although not particularly limited, for example, tin oxide doped with fluorine (hereinafter abbreviated as “FTO”), tin oxide doped with indium oxide, ITO, or antimony (hereinafter abbreviated as “ATO”), oxidation. Zinc or the like can be suitably used.

  In addition, it is possible to increase the transmissivity of the electrode as a whole by forming a thin wire-like conductive material such as a mesh shape on a transparent substrate, such as by dispersing and supporting the conductive material. For example, an opaque conductive material can be used. Such materials include carbon materials and metals. Although it does not specifically limit as a carbon material, For example, graphite (graphite), carbon black, glassy carbon, a carbon nanotube, fullerene, etc. are mentioned. Further, the metal is not particularly limited, and examples thereof include platinum, gold, silver, copper, aluminum, nickel, cobalt, chromium, iron, molybdenum, titanium, tantalum, niobium, and alloys thereof.

  Here, in the present invention, it is desirable to use halogen molecules and halides, more specifically iodine and iodide or bromine and bromide as the redox pair contained in the electrolytic solution. It is desirable that the material has high corrosion resistance to the electrolytic solution. Accordingly, metal oxides, particularly FTO and ITO, and copper, aluminum, nickel, alloys thereof, and the like whose surfaces are subjected to conductive corrosion resistance treatment are particularly suitable.

  The transparent conductive film 3 can be formed by providing at least one kind of the above conductive materials on the surface of the transparent substrate 1. Alternatively, it is also possible to incorporate the conductive material into the material constituting the transparent substrate 2 and integrate the transparent substrate and the transparent conductive film into the electrode substrate 1.

  As a method for forming the transparent conductive film 3 on the transparent substrate 2, in the case of forming a metal oxide, there are a sol-gel method, a vapor phase method such as sputtering and CVD, and a coating of a dispersion paste. Moreover, when using an opaque electroconductive material, the method of fixing powder etc. with a transparent binder etc. is mentioned.

  In order to integrate the transparent substrate and the transparent conductive film, the conductive film material may be mixed as a conductive filler at the time of forming the transparent substrate.

  The thickness of the transparent conductive film 3 is not particularly limited because the conductivity varies depending on the material to be used, but is generally 0.01 to 5 μm, preferably 0.1 to 1 μm in the FTO-coated glass. It is. Further, the required conductivity varies depending on the area of the electrode to be used, and a larger area electrode is required to have a lower resistance, but is generally 100Ω / □ or less, preferably 10Ω / □ or less, more preferably 5Ω / □ or less. Exceeding 100Ω / □ is not preferable because the internal resistance of the solar cell increases.

  The thickness of the electrode substrate 1 composed of a transparent substrate and a transparent conductive film, or the electrode substrate 1 in which the transparent substrate and the transparent conductive film are integrated varies depending on the shape and use conditions of the solar cell as described above, and thus is particularly limited. Generally, it is about 1 μm to 1 cm.

<Porous metal oxide semiconductor>
A conventionally well-known thing can be used as the porous metal oxide semiconductor 4. That is, in addition to oxides of transition metals such as Ti, Nb, Zn, Sn, Zr, Y, La, and Ta, perovskite oxides such as SrTiO ₃ and CaTiO ₃ are exemplified. Although not particularly limited, titanium oxide, zinc oxide, tin oxide and the like can be mentioned, and titanium dioxide, and further anatase type titanium dioxide are particularly suitable.

  Such a porous metal oxide semiconductor is not particularly limited and can be provided on the transparent conductive film 3 by a known method. For example, there are a sol-gel method, dispersion paste application, electrodeposition and electrodeposition. Furthermore, in order to lower the electrical resistance value, it is desirable that the metal oxide has few grain boundaries, and it is desirable to sinter the applied metal oxide. Sintering conditions vary depending on the type and formation method of the metal oxide semiconductor to be used and the heat-resistant temperature of the substrate, and may be appropriately changed. However, when titanium dioxide is used, it is desirable to sinter at 450 to 550 ° C.

Further, in order to adsorb more sensitizing dye, the semiconductor layer is desirably porous, and specifically has a specific surface area of 10 to 200 m ² / g. Further, in order to increase the light absorption amount of the sensitizing dye, it is desirable to scatter the light by making the particle diameter of the oxide to be used wide. The thickness of the semiconductor layer is not particularly limited because the optimum value varies depending on the oxide used and its properties, but is 0.1 to 50 μm, preferably 5 to 30 μm.

<Sensitizing dye>
The sensitizing dye layer 5 is not particularly limited as long as it can be excited by sunlight and can inject electrons into the metal oxide semiconductor layer 4, and dyes generally used in dye-sensitized solar cells can be used. However, in order to improve the conversion efficiency, it is desirable that the absorption spectrum overlaps with the sunlight spectrum in a wide wavelength region and the light resistance is high.

  The sensitizing dye is not particularly limited, but is preferably a ruthenium complex, particularly a ruthenium polypyridine-based complex, and more preferably a ruthenium complex represented by Ru (L) (L ′) (X) 2. Here, L is 4,4′-dicarboxy-2,2′-bipyridine, or a polypyridine ligand into which a quaternary ammonium salt and a carboxyl group are introduced, and L ′ is the same as L, or 4, 4'-substituted 2,2'-bipyridine, and examples of the substituent at the 4'-position of L 'include a long-chain alkyl group, an alkyl-substituted vinylthienyl group, an alkyl or alkoxy-substituted styryl group, and a thienyl group derivative. It is done. X is SCN, Cl, or CN. Examples thereof include bis (4,4'-dicarboxy-2,2'-bipyridine) diisothiocyanate ruthenium complex.

  Examples of other dyes include metal complex dyes other than ruthenium, such as iron complexes and copper complexes. Further examples include organic dyes such as cyan dyes, porphyrin dyes, polyene dyes, coumarin dyes, cyanine dyes, squarylium dyes, styryl dyes, and eosin dyes. And a dye (trade name: D149 dye). These dyes preferably have a bonding group with the metal oxide semiconductor layer in order to improve the efficiency of electron injection into the metal oxide semiconductor layer. The linking group is not particularly limited, but is preferably a carboxyl group, a sulfonyl group or the like.

  The method for adsorbing the sensitizing dye to the porous metal oxide semiconductor layer 4 is not particularly limited. For example, it is transparent in a solution in which the dye is dissolved at room temperature and atmospheric pressure. A method of immersing the metal oxide semiconductor layer 4 formed on the conductive film 2 can be given. It is desirable that the immersion time is appropriately adjusted so that a monomolecular film of the dye is uniformly formed on the semiconductor layer depending on the type of the semiconductor, the dye, the solvent, and the concentration of the dye used. In addition, what is necessary is just to perform the immersion under a heating in order to perform adsorption | suction effectively.

  It is desirable that the sensitizing dye does not associate on the surface of the porous metal oxide semiconductor layer. If association occurs when the dye is adsorbed alone, a co-adsorbent may be adsorbed as necessary. Such an adsorbent is not particularly limited because the optimum kind and concentration varies depending on the dye used, and examples thereof include organic carboxylic acids such as deoxycholic acid. The method for adsorbing the co-adsorbent is not particularly limited, but by dissolving the co-adsorbent together with the sensitizing dye in a solvent for dissolving the sensitizing dye, the metal oxide semiconductor layer is immersed in the solvent. The coadsorbent can be adsorbed simultaneously with the adsorption step.

Examples of the solvent used for dissolving the sensitizing dye include alcohols such as ethanol, nitrogen compounds such as acetonitrile, ketones such as acetone, ethers such as diethyl ether, halogenated aliphatic hydrocarbons such as chloroform, Examples thereof include aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene, and esters such as ethyl acetate. It is desirable that the dye concentration in the solution is appropriately adjusted according to the type of dye and solvent used. For example, a concentration of 5 × 10 ⁻⁵ mol / L or more is desirable.

<Counter electrode>
Opposite the semiconductor electrode 6, a counter electrode 8 that is a cathode electrode is disposed via an electrolyte layer 7 and a spacer 11.

<Counter electrode-substrate>
In order to reduce the internal resistance of the solar cell, it is desirable that the counter substrate 9 has high electrical conductivity. In addition, as described above, in the present invention, halogen molecules and halides are used as an oxidation-reduction pair in the electrolyte. Therefore, it is desirable that the conductive electrode substrate 9 has high corrosion resistance against the electrolytic solution.

  Specific examples of such a conductive base material include chromium, nickel, titanium, tantalum, niobium, and stainless steels thereof, which have an oxide film formed on the surface and good corrosion resistance, and a surface thereof. Examples thereof include aluminum having an oxide film formed thereon to improve corrosion resistance.

  Another suitable material is a conductive metal oxide. Although not particularly limited, for example, ITO, FTO, ATO, zinc oxide, titanium oxide, or the like can be suitably used. Among these, FTO and ITO can be preferably used.

  The conductive electrode substrate 9 can also have a support for the purpose of improving durability and handling properties. For example, when transparency is required, glass or a transparent plastic resin plate can be used. Further, a plastic resin plate can be used when lightness is required, and a plastic resin film can be used when flexibility is required. Moreover, a metal plate etc. can also be used when raising intensity | strength.

  The arrangement method of the support is not particularly limited, but the catalytically active layer 10 is formed on the surface of the conductive electrode substrate 9 as a counter electrode working part. Therefore, the support is a part where the catalytically active layer is not supported, particularly It is preferable to arrange on the back surface of the electrode substrate 9. In addition, the conductive electrode substrate and the support can be integrated by supporting the support by a method such as embedding a powder or filler of a conductive material on the support surface.

  The thickness of the support is not particularly limited because it varies depending on the shape of the counter electrode and use conditions, but for example, when glass or plastic is used, it is about 1 mm to 1 cm in consideration of durability during actual use. When flexibility is required and a plastic film or the like is used, it is about 25 μm to 1 mm. Moreover, you may use the process of a hard coat etc. which improve a weather resistance as needed, and a film attachment process. Moreover, when a metal material is used as the support, the thickness is about 10 μm to 1 cm.

  The form and thickness of the conductive electrode substrate 9 are not particularly limited because the conductivity varies depending on the shape and use conditions when used as an electrode, and the material used, and any form can be selected. For example, when practical strength is maintained by using the above-mentioned support, a thickness of about 100 nm may be used as long as electrical conductivity necessary for use as an electrode can be secured. Further, when the strength is ensured only by the conductive electrode substrate 9 without using the support, a thickness of about 1 mm or more is preferable.

  Further, the required conductivity varies depending on the area of the electrode to be used, and a larger area electrode is required to have a lower resistance, but is generally 100Ω / □ or less, preferably 5Ω / □ or less, more preferably 1Ω / □ or less. If it exceeds 100Ω / □, the internal resistance of the solar cell increases, which is not preferable.

<Catalytic active layer>
The catalytically active layer 10 supported on the surface of the conductive electrode substrate 9 reduces the halide contained in the electrolyte layer 7 as an oxidation-reduction pair or an oxidized form of polypyridylcobalt complex to the reductant at a sufficient rate. Specifically, a polypyridylcobalt complex can be prepared by using a triiodide anion (I ₃ ⁻ ) as an iodide anion (I ⁻ ) or a tribromide anion (Br ₃ ⁻ ) as a bromide anion (Br ⁻ ). In this case, there is no particular limitation as long as trivalent cobalt metal ions can be reduced to divalent, and known substances can be used. For example, transition metals, conductive polymer materials, carbon materials, etc. It can be used suitably.
The shape is not particularly limited because it varies depending on the type of catalyst used. A catalyst material composed of at least one of the above-described catalyst materials can be provided on the surface of the electrode substrate 9. Alternatively, the catalyst material can be incorporated into the material constituting the electrode substrate 9.

  Platinum, palladium, ruthenium, rhodium, or the like can be suitably used as the transition metal serving as a catalyst, and these may be used as an alloy. Of these, platinum or a platinum alloy is particularly suitable. As a method for supporting the transition metal on the conductive substrate, it can be produced by a known method. For example, a method of directly forming by sputtering, vapor deposition or electrodeposition, a method of thermally decomposing a precursor such as chloroplatinic acid, or the like can be used.

  As a monomer for the conductive polymer, a conductive polymer obtained by polymerizing at least one monomer among pyrrole, aniline, thiophene, and derivatives thereof can be used as a catalyst. In particular, polyaniline or poly (ethylenedioxythiophene) is desirable. As a method for supporting the conductive polymer electrode substrate 9, a known method can be used. For example, a method of electrochemically polymerizing the conductive substrate by immersing it in a solution containing the monomer, or a solution containing an oxidizing agent such as Fe (III) ion or ammonium persulfate and the monomer, A chemical polymerization method of reacting on an electrode substrate, a method of forming a film from a solution in which a conductive polymer is melted or dissolved, and particles of a conductive polymer in a paste, emulsion, or polymer solution and Examples of the method include forming the mixture on the electrode substrate by screen printing, spray coating, brush coating and the like after processing into a mixture containing a binder.

  The carbon material is not particularly limited, and a conventionally known carbon material having a catalytic ability to reduce an oxidant of a redox pair can be used, and among these, carbon nanotubes, carbon black, activated carbon, and the like are preferable. As a method for supporting the carbon material on the conductive substrate, a known method such as a method of applying and drying a paste using a fluorine-based binder or the like can be used.

  Between the semiconductor electrode 6 and the counter electrode 8, an electrolyte solution is filled to form an electrolyte layer 7, which is sealed by a peripheral seal portion 12.

<Spacer>
The spacer 11 controls and fixes the distance between the electrodes so that the semiconductor electrode and the counter electrode do not come into contact with each other, and is not particularly limited as long as it is a material that does not deteriorate due to an electrolyte solution, heat, light, or the like. Any known material can be used in any shape. Examples of the material include glass and ceramic materials, fluorine-based resins, photo-curing resins, and thermosetting resins. In addition, the peripheral seal portion can also serve as a spacer by a method such as mixing minute glass or ceramic material in the peripheral seal portion 12.

  The peripheral sealing part is not particularly limited as long as the semiconductor electrode and the counter electrode are bonded and sealed so that the electrolytic solution of the present invention does not leak, and the material is not deteriorated by the electrolytic solution or heat / light. Examples thereof include thermoplastic resins, thermosetting resins, ultraviolet curable resins, electron beam curable resins, metals, and rubbers.

  EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated concretely, these do not limit this invention at all.

Example 1
The electrolyte solution and the dye-sensitized solar cell were prepared as follows.

<Preparation of electrolyte>
1-methyl-3-propylimidazolium iodide (abbreviated as “MPImI” in the table) 0.7 mol / l, iodine (abbreviated as “I ₂ ” in the table) 0.05 mol / l, boron An electrolyte was prepared by dissolving in ethyl isopropyl sulfone at a ratio of 0.1 mol / l of trimethyl acid.

<Formation of porous metal oxide semiconductor layer>
As a transparent substrate with a transparent conductive film, FTO glass (25 mm × 50 mm made by Japanese plate glass) is used, and titanium oxide paste (Titania paste PST-18NR made by JGC Catalysts & Chemicals Co., Ltd.) is applied on the surface thereof. After repeatedly applying the drying process at 30 ° C. for 30 minutes three times, the porous titanium oxide layer having a thickness of about 15 μm was formed by baking at 500 ° C. for 60 minutes in the air atmosphere. Further, a titanium oxide paste (Titania paste PST-400C manufactured by JGC Catalysts & Chemicals, Inc.) is applied over the porous titanium oxide layer by screen printing, and then fired in the same manner to obtain a thickness of about 20 μm. The completed porous metal oxide semiconductor layer was completed as a porous titanium oxide semiconductor electrode.

<Adsorption of sensitizing dye>
As the sensitizing dye, bis (4-carboxy-4′-tetrabutylammoniumcarboxy-2,2′-bipyridine) diisothiocyanate ruthenium complex (manufactured by Solaronix) generally called N719dye was used. The porous titanium oxide semiconductor electrode heated to 80 ° C. was immersed for 48 hours under light shielding while slowly shaking in a mixed solution of acetonitrile and t-butyl alcohol (1: 1) having a dye concentration of 0.5 mmol / L. Thereafter, excess pigment was washed with dehydrated acetonitrile and air-dried to complete a solar cell photoelectrode (anode electrode).

<Counter electrode>
As a counter electrode, a platinum counter electrode (manufactured by Geomatec) was formed by depositing Ti (film thickness 50 nm) on a glass substrate by sputtering as an anchor layer and then depositing Pt (film thickness 50 nm) on the Ti layer by sputtering. )It was used.

<Assembly of solar cells>
The photoelectrode produced as described above and a counter electrode provided with two 0.6 mmφ electrolyte injection holes with an electric drill are placed opposite each other, and a 50 μm thick FEP resin sheet as a spacer and a spacer A thermoplastic sheet (DuPont bynel, film thickness of 50 μm) was sandwiched between the outer circumferences of the two and bonded to each other by thermocompression bonding. Next, the electrolytic solution prepared as described above is impregnated between the electrodes by capillary action from the electrolytic solution injection hole, a 1 mm thick glass plate is placed on the electrolytic solution injection hole with a plastic sheet interposed therebetween, and thermocompression bonding is performed again. In this way, sealing was carried out to produce a solar cell element.

(Example 2)
A solar battery cell was produced in the same manner as in Example 1 except that the electrolytic solution was prepared using triethyl borate instead of trimethyl borate.

(Example 3)
A solar battery cell was produced in the same manner as in Example 1 except that the electrolyte was prepared using tributyl borate instead of trimethyl borate.

Example 4
A solar cell was produced in the same manner as in Example 1 except that 0.05 mol / l of triphenyl borate was used instead of trimethyl borate to prepare an electrolytic solution.

(Example 5)
A solar battery cell was produced in the same manner as in Example 1 except that the electrolytic solution was prepared using tris borate (propionitrile) instead of trimethyl borate.

(Example 6)
Example except that tributyl borate was used instead of trimethyl borate, and 3-methoxypropionitrile (abbreviated as “MPN” in the table) was used instead of ethyl isopropyl sulfone as a solvent. A solar battery cell was produced in the same manner as in Example 1.

(Example 7)
A solar battery cell was produced in the same manner as in Example 6 except that an electrolyte was prepared using γ-butyrolactone (abbreviated as “GBL” in the table) instead of 3-methoxypropionitrile.

(Example 8)
The same as Example 6 except that an electrolytic solution was prepared using a mixed solvent of ethylene carbonate / propylene carbonate (30 wt%: 70 wt%) (abbreviated as “EC + PC” in the table) instead of 3-methoxypropionitrile. Thus, a solar battery cell was produced.

Example 9
A solar cell was produced in the same manner as in Example 6 except that instead of 3-methoxypropionitrile, an electrolytic solution was prepared using ethyl isobutyl sulfone (abbreviated as “EiBS” in the table).

(Example 10)
A solar battery cell was produced in the same manner as in Example 6 except that 0.05 mol / l trioctyl borate was used instead of 0.1 mol / l tributyl borate to prepare an electrolytic solution.

(Example 11)
A solar battery cell was produced in the same manner as in Example 6 except that 0.05 mol / l tri (dodecyl) borate was used instead of 0.1 mol / l tributyl borate.

(Example 12)
An electrolyte solution was prepared in the same manner as in Example 3 except that 0.5 mol / l of 4-t-butylpyridine was also contained, and a solar battery cell was produced.

(Example 13)
An electrolyte solution was prepared in the same manner as in Example 3 except that 0.5 mol / l imidazole was also contained, and a solar battery cell was produced.

(Example 14)
An electrolyte solution was prepared in the same manner as in Example 3 except that 0.5 mol / l of triazole was also contained, and a solar battery cell was produced.

(Example 15)
An electrolyte solution was prepared in the same manner as in Example 3 except that 0.5 mol / l dimethylpyrazole was also contained, and a solar battery cell was produced.

(Example 16)
An electrolyte solution was prepared in the same manner as in Example 3 except that 30% by volume of dimethyl sulfoxide was also contained, and a solar battery cell was produced.

(Example 17)
An electrolyte solution was prepared in the same manner as in Example 16 except that N-methylpyrrolidone was used in place of dimethyl sulfoxide to prepare a solar battery cell.

(Example 18)
An electrolyte solution was prepared in the same manner as in Example 16 except that N-dimethylacetamide was used in place of dimethyl sulfoxide to prepare a solar battery cell.

(Example 19)
An electrolyte solution was prepared in the same manner as in Example 3 except that 0.5 mol / l of tetrahydrofuran was also contained, and a solar battery cell was produced.

(Example 20)
An electrolyte solution was prepared in the same manner as in Example 3 except that 0.5 mol / l sulfolane was also contained, and a solar battery cell was produced.

(Example 21)
An electrolyte solution was prepared in the same manner as in Example 3 except that 0.5 mol / l of ethyl acetate was also contained, and a solar battery cell was produced.

(Example 22)
In place of 0.1 mol / l tributyl borate, an electrolytic solution was prepared in the same manner as in Example 6 except that 3 mol / l triethyl borate was contained, and a solar battery cell was produced.

(Example 23)
An electrolyte solution was prepared in the same manner as in Example 6 except that 6 mol / l triethyl borate was contained instead of 0.1 mol / l tributyl borate, and a solar battery cell was produced.

(Example 24)
<Preparation of electrolyte>
Spiro- (1,1 ′)-bipyrrolidinium bromide salt (abbreviated as “SBP-Br” in the table) 1.0 mol / l, bromine (abbreviated as “Br ₂ ” in the table) 0.025 mol / l. 1 and triethyl borate at a rate of 0.1 mol / l was dissolved in acetonitrile to prepare an electrolytic solution.
<Assembly of cell>
In the sensitizing dye adsorbing step, the porous titanium oxide semiconductor electrode made of Mitsubishi Paper Industries D141 dye as the sensitizing dye and heated to 80 ° C. was mixed with acetonitrile / t-butyl alcohol (pigment concentration 0.5 mmol / L). 1: 1) It was immersed in a mixed solution for 15 hours while being gently shaken, and then washed with excess acetonitrile and then air-dried to complete a photoelectrode (anode electrode) of a solar cell. A cell was assembled in the same manner as in Example 1 except for the above.

(Example 25)
<Preparation of electrolyte>
0.1 mol / l spiro- (1,1 ′)-bipyrrolidinium tetrafluoroborate (abbreviated as “SBP-BF ₄ ” in the table), cobalt bis (trifluorophosphate) complex (in the table, “Co (bpy) ₃ (PF ₆ ) ₂ ”)) 0.22 mol / l, tris (2,2′-bipyridine) cobalt tris (trifluorophosphate) complex (in the table, “Co (bpy) ₃ (PF ₆ ) ₃ ”.) An electrolyte solution was prepared by dissolving in 0.033 mol / l, triethyl borate 0.1 mol / l, bis- (1,1 ′) in ethyl isopropyl sulfone. .
<Assembly of cell>
In the sensitizing dye adsorption step, a D149 dye made by Mitsubishi Paper Industries Co., Ltd. was used as the sensitizing dye, and the porous titanium oxide semiconductor electrode heated to 80 ° C. was mixed with acetonitrile / t-butyl alcohol (pigment concentration 0.5 mmol / l). 1: 1) It was immersed in a mixed solution for 15 hours while being gently shaken, and then washed with excess acetonitrile and then air-dried to complete a photoelectrode (anode electrode) of a solar cell. A cell was assembled in the same manner as in Example 1 except for the above.

(Comparative Example 1)
An electrolyte solution was prepared in the same manner as in Example 1 except that trimethyl borate was not included, and a solar battery cell was produced.

(Comparative Example 2)
An electrolyte solution was prepared in the same manner as in Comparative Example 1 except that a 3-methoxypropionitrile solvent (abbreviated as “MPN” in the table) was used instead of the ethylisopropylsulfone solvent, and a solar battery cell was produced. .

(Comparative Example 3)
An electrolyte solution was prepared in the same manner as in Comparative Example 1 except that a γ-butyrolactone solvent (abbreviated as “GBL” in the table) was used instead of the ethylisopropylsulfone solvent, and a solar battery cell was produced.

(Comparative Example 4)
An electrolyte solution was prepared in the same manner as in Comparative Example 1 except that a mixed solvent of ethylene carbonate / propylene carbonate (30 wt%: 70 wt%) (abbreviated as “EC + PC” in the table) was used instead of the ethyl isopropyl sulfone solvent. A solar battery cell was produced.

(Comparative Example 5)
An electrolyte solution was prepared in the same manner as in Comparative Example 1 except that an ethyl isobutyl sulfone solvent (abbreviated as “EiBS” in the table) was used instead of the ethyl isopropyl sulfone solvent, and a solar battery cell was produced.

(Comparative Example 6)
An electrolyte solution was prepared in the same manner as in Example 24 except that 0.1 mol / l of triethyl borate was not included, and a solar battery cell was produced.

(Comparative Example 7)
An electrolyte solution was prepared in the same manner as in Example 25 except that 0.1 mol / l triethyl borate was not included, and a solar battery cell was produced.

(Test 1)
<Measurement of photoelectric conversion characteristics of solar cells>
To the dye-sensitized solar cells prepared in Examples 1 to 25 and Comparative Examples 1 to 7, a light irradiation area defining mask with a 5 mm square window was attached at 25 ° C. Using a solar simulator, while irradiating simulated sunlight with the light intensity adjusted at a light amount of 100 mW / cm ² and AM 1.5, an open-circuit voltage (hereinafter referred to as “Voc”) is used with an ADC DC current generator. ”, Short circuit current density (hereinafter abbreviated as“ Jsc ”), shape factor (hereinafter abbreviated as“ FF ”), and photoelectric conversion efficiency. About each measured value of "Voc", "Jsc", "FF", and photoelectric conversion efficiency (henceforth abbreviated as "Eff"), it represents that a larger value is preferable as a performance of a photovoltaic cell. The results are shown in Table 1.

In the electrolyte solutions of Examples 1 to 11, it was shown that high Jsc and consequently high conversion efficiency can be obtained by adding various boric acid esters to various solvents as compared with Comparative Examples 1 to 5. . Moreover, in Examples 12-18, it was shown that the characteristic of a solar cell is further improved compared with Example 3 by coexisting a high donor property compound. On the other hand, Examples 19 to 21 are examples in which a compound having a low donor property was coexisted, but the addition of boric acid ester gave a higher conversion efficiency than Comparative Example 1, while the high efficiency as in Examples 12 to 18 was obtained. It was shown that the characteristics of the solar cell were not improved as in the case of coexisting a donor compound.
Examples 22 and 23 are examples in which the concentration of borate ester is high. In Example 22 in which the amount of borate ester was 3.0 mol / l, the property was sufficiently improved as compared with Comparative Example 2, but in Example 23 in which the amount of borate ester was 6.0 mol / l, comparison was made. Compared to Example 2, the performance improvement was shown to be small.
In Examples 24 and 25, bromine and polypyridylcobalt complexes were used as redox pairs, respectively. However, it was shown that the characteristics were improved by the addition of boric acid ester as compared with Comparative Examples 6 and 7. It was.

(Test 2)
<Evaluation of solar cell durability>
Of the cells used in Test 1, a heat resistance test was conducted at 85 ° C. for 1000 hours in the dark on Examples 1 to 5 and Comparative Example 1 produced using a solvent having high durability. After that, the conversion efficiency in the state returned to room temperature was measured. The results are shown in Table 2.

  From Table 2, it was shown that Examples 1-5 and Comparative Example 1 maintained high durability, and even when boric acid ester was added, the durability was not lowered.

  Since the electrolyte solution for dye-sensitized solar cells of the present invention has high durability and has an effect of improving the short-circuit current density even in a solvent other than nitrile, it can be used for various applications.

DESCRIPTION OF SYMBOLS 1 Electrode base | substrate 2 Transparent base | substrate 3 Transparent electrically conductive film 4 Porous metal oxide semiconductor layer 5 Sensitizing dye layer 6 Semiconductor electrode 7 Electrolyte layer 8 Counter electrode 9 Electrode base | substrate 10 Catalytic active layer 11 Spacer 12 Perimeter seal part

Claims (12)

An electrolyte solution for a dye-sensitized solar cell, comprising a boric acid ester represented by the following general formula (1).

(In the general formula (1), R _{1 to} R ₃ independently represent a halogen, nitrile, alkoxy group or an alkyl group having 1 to 20 carbon atoms which may be partially substituted with an aromatic ring, or an aryl group. .)   The borate ester is selected from the group consisting of trimethyl borate, triethyl borate, tripropyl borate, triisopropyl borate, tributyl borate, triisobutyl borate, triphenyl borate, tris borate (propionitrile) The electrolyte solution for a dye-sensitized solar cell according to claim 1, wherein the electrolyte solution is a dye-sensitized solar cell.   3. The dye-sensitized solar cell electrolyte according to claim 1, wherein the concentration of the borate ester in the electrolyte is 0.001 to 5.0 mol / l.   The electrolyte solution for a dye-sensitized solar cell according to any one of claims 1 to 3, comprising a borate ester and a donor compound having a donor number of 25 or more.   5. The donor compound according to claim 4, wherein the donor compound is at least one selected from the group consisting of pyridine, pyrazine, pyrimidine, imidazole, pyrazole, triazole, pyrrolidine, piperidine, hydrazine, pyrrolidone, sulfoxide, and amide. An electrolyte for dye-sensitized solar cells. 6. The solvent according to claim 1, wherein the solvent contains at least one organic solvent selected from the group consisting of nitriles, lactones, cyclic carbonates, and chain sulfones represented by the following general formula (2). The electrolyte solution for dye-sensitized solar cells as described in 2.

(In the general formula (2), R ₄ and R ₅ independently represent a halogen, an alkoxy group or an alkyl group having 1 to 12 carbon atoms which may be partially substituted with an aromatic ring, or an aryl group.)   The electrolyte solution for a dye-sensitized solar cell according to any one of claims 1 to 6, comprising a halogen compound having a halogen anion as a counter ion and a halogen molecule as a redox electrolyte.   The electrolyte solution for a dye-sensitized solar cell according to claim 7, wherein the halogen compound is iodide or bromide, and the halogen molecule is iodine or bromine.   The electrolyte solution for a dye-sensitized solar cell according to any one of claims 1 to 6, comprising a polypyridylcobalt complex as a redox electrolyte. A porous metal oxide semiconductor layer formed on the conductive layer, and a photoelectrode formed by adsorbing a dye having a photosensitizing action on the metal oxide semiconductor layer; a counter electrode disposed opposite to the photoelectrode; and A dye-sensitized solar cell formed between the photoelectrode and a counter electrode and having an electrolyte layer containing an electrolyte solution,
The dye-sensitized solar cell, wherein the electrolyte solution is the electrolyte solution for a dye-sensitized solar cell according to any one of claims 1 to 9. A dye electrode for a dye-sensitized solar cell containing at least a boric acid ester represented by the following general formula (1), an organic solvent different from the boric acid ester, and an oxidation-reduction electrolyte, and a counter electrode A method for producing a dye-sensitized solar cell, which is filled and sealed in between.

(In the general formula (1), R _{1 to} R ₃ independently represent a halogen, nitrile, alkoxy group or an alkyl group having 1 to 20 carbon atoms which may be partially substituted with an aromatic ring, or an aryl group. .)   The electrolyte solution for dye-sensitized solar cells containing a boric acid ester and a donor compound having a donor number of 25 or more is filled between a semiconductor electrode and a counter electrode and sealed. The manufacturing method of the dye-sensitized solar cell of description.

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