JP2005044697A - Photoelectric conversion element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element with high performance, especially high durability using a solid electrolyte. <P>SOLUTION: The photoelectric conversion element comprises two conductive substrates whose at least one is transparent and an electrolyte layer installed at least between the conductive substrates and containing a substance showing reversible electrochemical oxidation-reduction characteristics. R<SB>D</SB>obtained by fitting an AC impedance measured result under light illumination with an equivalent circuit shown in the figure is specified to 5 Ω or less. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel photoelectric conversion element.

  A photoelectric conversion element such as a so-called wet solar cell represented by a dye-sensitized solar cell generally has two or more electrodes and a structure in which an electrolyte is stored between the electrodes. In such a photoelectric conversion element, the electrolyte plays an indispensable role in the device function as a charge transfer medium, and its electrochemical characteristics, particularly a reversible electrochemical redox commonly used as a charge transfer medium. The diffusion coefficient of a substance exhibiting characteristics greatly affects solar cell characteristics (see, for example, Non-Patent Document 1). Further, the distance between the electrodes also greatly affects the solar cell characteristics (see, for example, Non-Patent Document 2). However, these factors are often discussed independently and so far they have not been optimized in relation to each other. In particular, liquid electrolytes that have been used in the past have problems such as electrolyte leakage due to damage to the element and evaporation of the electrolyte during long-term use. Therefore, research on solar cells using solid electrolytes has been actively conducted in recent years. However, the actual situation is that only the physical properties of the solid electrolyte are focused on, and the optimization of the entire system has hardly been performed so far.

Japanese Patent Laid-Open No. 2001-338700 Japanese Patent Laid-Open No. 2001-160427 M. Gratzel et.al., Journal of Physical Chemistry B, USA, 1997, 101, p. 2576-2582 Wet solar cell feasibility study, “1999 Consignment Work Results Report”, New Energy and Industrial Technology Development Organization, March 2000, p. 17-18

  The present invention has been made in view of such circumstances, and provides a high-performance photoelectric conversion element by optimizing the electrochemical characteristics of the electrolyte layer and the distance between the electrodes in correlation with each other. Objective. Another object of the present invention is to provide a photoelectric conversion element having high durability by a simple manufacturing method by applying the above association to a solid electrolyte.

That is, the present invention is a photoelectric conversion element comprising two conductive substrates, at least one of which is transparent, and an electrolyte layer containing at least a substance exhibiting reversible electrochemical redox characteristics provided therebetween. Further, the present invention relates to a photoelectric conversion element characterized in that _RD obtained by fitting an AC impedance measurement result under light irradiation with an equivalent circuit shown in FIG. 1 is 5Ω or less.
The present invention also relates to a photoelectric conversion element, wherein the electrolyte layer is a solid electrolyte.
The present invention also relates to a photoelectric conversion element, wherein the solid electrolyte is an ion conductive film containing at least a polymer matrix and a substance exhibiting reversible electrochemical redox characteristics as constituent components.
The present invention also relates to a photoelectric conversion element, wherein the polymer matrix is a polyvinylidene fluoride polymer compound.
The present invention also relates to a photoelectric conversion element, wherein the polyvinylidene fluoride polymer compound contains a carboxyl group.
Furthermore, the present invention relates to a photoelectric conversion element, wherein the substance exhibiting reversible electrochemical redox characteristics is a room temperature molten salt.

Hereinafter, the present invention will be described in detail.
The photoelectric conversion element of the present invention essentially has an electrolyte layer containing a substance exhibiting reversible electrochemical redox characteristics. The electrolyte layer is usually used by being inserted between a pair of electrode substrates, and has a function of transporting electrons by a substance having reversible electrochemical redox characteristics contained in the electrolyte layer. For example, an oxidized form of a substance exhibiting electrochemical redox characteristics is reduced at one electrode to receive an electron to become a reduced form, diffuses to the other electrode, and returns to the oxidized form by delivering electrons to the electrode. The oxidant diffuses again to the original electrode and receives electrons. This process is substantially equivalent to the flow of electrons through the electrolyte layer, and the electrolyte layer functions as an electron transport medium.

The electrolyte layer used in the present invention must contain a substance exhibiting reversible electrochemical redox characteristics. Here, showing reversible electrochemical redox characteristics means that a reversible electrochemical redox reaction can occur in a potential region where the photoelectric conversion element acts. Typically, it is usually desirable to be reversible in the potential region of −1 to +2 V with respect to the hydrogen reference electrode (NHE).
A substance exhibiting reversible electrochemical oxidation-reduction characteristics is usually referred to as a so-called redox material, but the type is not particularly limited. Examples of such substances include ferrocene, p-benzoquinone, 7,7,8,8-tetracyanoquinodimethane, N, N, N ′, N′-tetramethyl-p-phenylenediamine, tetrathiafulvalene, thi Anthracene, p-toluylamine, etc. can be mentioned. Further, LiI, NaI, KI, CsI , CaI 2, 4 quaternary imidazolium iodide salt, iodine tetraalkylammonium Motoshio, Br ₂ and LiBr, NaBr, KBr, CsBr, and metal bromides, such as CaBr ₂ and the like, In addition, Br ₂ and tetraalkylammonium bromide, bipyridinium bromide, bromine salts, complex salts such as ferrocyanic acid-ferricyanate, sodium polysulfide, alkylthiol-alkyldisulfides, hydroquinone-quinones, viologen dyes and the like can be mentioned. .

As the redox material, only one of an oxidant and a reductant may be used, or the oxidant and the reductant may be mixed and added at an appropriate molar ratio. Further, these redox pairs may be added so as to show electrochemical responsiveness. Materials exhibiting such properties include halogen ions, SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N _{^{-, PF 6 -, AsF 6}} -, CH 3 COO -, CH 3 (C 6 H 4) SO 3 -, and _{(C 2 F 5 SO 2)} 3 C - , such as ferrocenium having a counter anion selected from metallocenium of In addition to salts, halogens such as iodine, bromine and chlorine can also be used.

In addition, as another substance exhibiting reversible electrochemical redox characteristics, a salt having a counter anion (X ⁻ ) selected from a halogen ion and SCN ⁻ can be mentioned. As the cation, as a quaternary ammonium salt, specifically, (CH ₃ ) ₄ NX ⁻ , (C ₂ H ₅ ) ₄ NX ⁻ , (n-C ₄ H ₉ ) ₄ NX ⁻ ,

Etc. A phosphonium salt having a counter anion (X ⁻ ), specifically, (CH ₃ ) ₄ PX ⁻ , (C ₂ H ₅ ) ₄ PX ⁻ , (C ₃ H ₇ ) ₄ PX ⁻ , (C ₄ H ₉ ) ₄ PX- ^{and the} like.
Of course, a mixture of these can also be used suitably.

In addition, redox room temperature molten salts can also be used as substances exhibiting reversible electrochemical redox properties. Here, the redox ambient temperature molten salt is a salt composed of ion pairs that are melted at room temperature (that is, in a liquid state) consisting only of ion pairs that do not contain a solvent component, and usually has a melting point of 20 ° C. or less. A salt composed of an ion pair that is in a liquid state at a temperature exceeding 20 ° C. and capable of performing a reversible electrochemical redox reaction. When redox room temperature molten salts are used as the substance exhibiting reversible electrochemical redox properties, the solvent may be used or may not be used.
The redox room temperature molten salt can be used alone or in combination of two or more.
Examples of redox room temperature molten salts include the following.

(Here, R represents an alkyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and X ⁻ represents a halogen ion or SCN ⁻ ).

(Wherein R1 and R2 each represent an alkyl group having 1 to 10 carbon atoms (preferably a methyl group or an ethyl group) or an aralkyl group having 7 to 20 carbon atoms, preferably 7 to 13 carbon atoms (preferably a benzyl group). And may be the same as or different from each other, and X ⁻ represents a halogen ion or SCN ⁻ .)

(Here, R1, R2, R3, R4 each represents an alkyl group having 1 or more carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms (such as a phenyl group), or a methoxymethyl group. And may be the same as or different from each other, and X ⁻ represents a halogen ion or SCN ⁻ .)

The electrolyte layer of the present invention may be either a liquid system or a solid system as long as it contains a substance exhibiting the above-described reversible electrochemical redox characteristics, and is not particularly limited. The diffusion coefficient D of the substance exhibiting electrochemical redox characteristics is 1 × 10 ⁻⁹ cm ² / s or more, preferably 1 × 10 ⁻⁸ cm ² / s or more, more preferably 1 × 10 ⁻⁷ cm ² / s. More preferably, 1 × 10 ⁻⁶ cm ² / s is desirable, and the distance L between the two conductive substrates is usually 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and even more preferably 20 μm. These are usually 1 mm or less, preferably 500 μm or less, more preferably 200 μm or less, and still more preferably 100 μm or less.

Further, in the present invention, when the _RD obtained by measuring the AC impedance of the photoelectric conversion element under light irradiation and fitting the result with the equivalent circuit shown in FIG. The photoelectric conversion element shown is obtained. Here, the measurement method of AC impedance measurement under light irradiation is not particularly limited, and a general method is used. For example, a light source such as a solar simulator using a potentiostat / galvanostat and an impedance analyzer is used. When irradiating light with an illuminance of AM 1.5 and 100 mW / cm ² using AC modulation of ± 5 mV with respect to the open-circuit voltage of the photoelectric conversion element and measuring the frequency range from 1 MHz to 0.01 Hz, FIG. An impedance spectrum such as
When this impedance spectrum is fitted by the equivalent circuit shown in FIG. 1, _RD is obtained.
In FIG. 1, Rs, R1, and R2 represent resistance components, and CPE1 and CPE2 are constants represented by CPE = 1 / [T (jω) P] (ω: frequency, T and P are fitting parameters). Phase element (Constant Phase Element), Z _D is Z _D = R _D {[tanh (jωτ) ^1/2 ] / (jωτ) ^1/2 } (ω: frequency, τ, R _D are fitting parameters) It represents the finite diffusion length Warburg impedance.

In the present invention, the R _D obtained as described above needs to be 5Ω or less, preferably 4Ω or less, more preferably 3Ω or less, and particularly preferably 2Ω or less.

  There are no particular limitations on the liquid electrolyte, and usually a solvent, a substance exhibiting the above-described reversible electrochemical oxidation-reduction characteristics (soluble in a solvent), and a supporting electrolyte as necessary are basically used. Configured as an ingredient.

Any solvent can be used as long as it is generally used in electrochemical cells and batteries. Specifically, acetic anhydride, methanol, ethanol, tetrahydrofuran, propylene carbonate, nitromethane, acetonitrile, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide, ethylene carbonate, dimethoxyethane, γ-butyrolactone, γ-valerolactone, sulfolane, dimethoxy Ethane, propiononitrile, glutaronitrile, adiponitrile, methoxyacetonitrile, dimethylacetamide, methylpyrrolidinone, dimethyl sulfoxide, dioxolane, sulfolane, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, ethyldimethyl phosphate, tributyl phosphate, phosphorus Tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, phosphoric acid Tridecyl, tris phosphate (trifluoromethyl), tris phosphate (pentafluoroethyl), triphenyl polyethylene glycol phosphate, polyethylene glycol, and the like can be used. In particular, propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethoxyethane, acetonitrile, γ-butyrolactone, sulfolane, dioxolane, dimethylformamide, dimethoxyethane, tetrahydrofuran, adiponitrile, methoxyacetonitrile, methoxypropionitrile, dimethylacetamide, methylpyrrolidinone, dimethylsulfoxide , Dioxolane, sulfolane, trimethyl phosphate and triethyl phosphate are preferred. Also, room temperature molten salts can be used. Here, the room temperature molten salt is a salt made of an ion pair that is melted at room temperature (that is, in a liquid state) consisting of only an ion pair that does not contain a solvent component, and usually has a melting point of 20 ° C. or less. A salt composed of an ion pair that is in a liquid state at a temperature in excess of ° C.
Examples of the room temperature molten salt include the following.

(Here, R represents an alkyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and X ⁻ represents a halogen ion or SCN ⁻ ).

(Wherein R1 and R2 each represent an alkyl group having 1 to 10 carbon atoms (preferably a methyl group or an ethyl group) or an aralkyl group having 7 to 20 carbon atoms, preferably 7 to 13 carbon atoms (preferably a benzyl group). And may be the same as or different from each other, and X ⁻ represents a halogen ion or SCN ⁻ .)

(Here, R1, R2, R3, R4 each represents an alkyl group having 1 or more carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms (such as a phenyl group), or a methoxymethyl group. And may be the same as or different from each other, and X ⁻ represents a halogen ion or SCN ⁻ .)
The solvent may be used alone or in combination of two or more.

Further, as the supporting electrolyte added as necessary, salts, acids, alkalis, and room temperature molten salts that are usually used in the field of electrochemistry or the field of batteries can be used.
The salt is not particularly limited, and examples thereof include inorganic ion salts such as alkali metal salts and alkaline earth metal salts; quaternary ammonium salts; cyclic quaternary ammonium salts; quaternary phosphonium salts. preferable.
Specific examples of the salts include ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , PF ₆ ⁻ and AsF ₆ ^−. Li salt, Na salt, or K salt having a counter anion selected from CH ₃ COO ⁻ , CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ , and (C ₂ F ₅ SO ₂ ) ₃ C ⁻ .

Also, ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , CH ₃ COO ⁻ A quaternary ammonium salt having a counter anion selected from CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ , and (C ₂ F ₅ SO ₂ ) ₃ C ⁻ , specifically, (CH ₃ ) ₄ NBF ₄ , (C ₂ H ₅ ) ₄ NBF ₄ , (n-C ₄ H ₉ ) ₄ NBF ₄ , (C ₂ H ₅ ) ₄ NBr, (C ₂ H ₅ ) ₄ NClO ₄ , (n-C ₄ H ₉ ) ₄ NClO ₄ , CH ₃ (C ₂ H ₅ ) ₃ NBF ₄ , (CH ₃ ) ₂ (C ₂ H ₅ ) ₂ NBF ₄ , (CH ₃ ) ₄ NSO ₃ CF ₃ , (C ₂ H ₅ ) ₄ NSO ₃ CF ₃ , (n-C ₄ H ₉ ) ₄ NSO ₃ CF ₃ ,

Etc. Also, ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , CH ₃ COO ⁻ , A phosphonium salt having a counter anion selected from CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ and (C ₂ F ₅ SO ₂ ) ₃ C ⁻ , specifically, (CH ₃ ) ₄ PBF ₄ , (C ₂ H ₅ ) ₄ PBF ₄ , (C ₃ H ₇ ) ₄ PBF ₄ , (C ₄ H ₉ ) ₄ PBF _{4 and the} like.
Moreover, these mixtures can also be used suitably.

The acids are not particularly limited, and inorganic acids and organic acids can be used. Specifically, sulfuric acid, hydrochloric acid, phosphoric acids, sulfonic acids, carboxylic acids and the like can be used.
The alkalis are not particularly limited, and any of sodium hydroxide, potassium hydroxide, lithium hydroxide and the like can be used.

The room temperature molten salt is not particularly limited, but the room temperature molten salt in the present invention is a salt made of an ion pair that is melted at room temperature (that is, a liquid form) consisting of only an ion pair that does not contain a solvent component. In general, it indicates a salt composed of an ion pair having a melting point of 20 ° C. or lower and being liquid at a temperature exceeding 20 ° C.
The room temperature molten salt can be used alone or in combination of two or more.
Examples of the room temperature molten salt include the following.

(Wherein R represents an alkyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms. X ⁻ represents ClO ₄ ⁻ , BF ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) represents a counter anion selected from ₂ N ⁻ , PF ₆ ⁻ , AsF ₆ ⁻ , CH ₃ COO ⁻ , CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ , and (C ₂ F ₅ SO ₂ ) ₃ C ⁻ .)

(Wherein R1 and R2 each represent an alkyl group having 1 to 10 carbon atoms (preferably a methyl group or an ethyl group) or an aralkyl group having 7 to 20 carbon atoms, preferably 7 to 13 carbon atoms (preferably a benzyl group). X ⁻ may be ClO ₄ ⁻ , BF ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , PF ₆ ⁻ , (It represents a counter anion selected from AsF ₆ ⁻ , CH ₃ COO ⁻ , CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ , and (C ₂ F ₅ SO ₂ ) ₃ C ⁻ ).

(Here, R1, R2, R3, R4 each represents an alkyl group having 1 or more carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms (such as a phenyl group), or a methoxymethyl group. X ⁻ may be ClO ₄ ⁻ , BF ₄ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) ₂ N ⁻ , PF ₆ ⁻ , AsF. _This represents a counter anion selected from ₆ ⁻ , CH ₃ COO ⁻ , CH ₃ (C ₆ H ₄ ) SO ₃ ⁻ , and (C ₂ F ₅ SO ₂ ) ₃ C ⁻ .)

  There is no restriction | limiting in particular about the usage-amount of a supporting electrolyte, Although it is arbitrary, Usually, 0.01-10 mol / L, Preferably about 0.05-1 mol / L can be contained as a density | concentration in electrolyte.

  The electrolyte used in the present invention may be a liquid as described above, but a polymer solid electrolyte (ion conductive film) is particularly preferable from the viewpoint that solidification is possible. As the polymer solid electrolyte, it is particularly preferable that (a) the polymer matrix (component (a)) contains at least (c) a substance (component (c)) exhibiting reversible electrochemical redox characteristics. If desired, those further containing (b) a plasticizer (component (b)) may be mentioned. In addition to these, other optional components such as (d) the above-mentioned supporting electrolyte and (e) a room temperature molten salt may be further contained as desired. As an ion conductive film, the said component (b), a component (b) and a component (c), or a further arbitrary component is hold | maintained in a polymer matrix, and a solid state or a gel state is formed.

As a material that can be used as a polymer matrix in the present invention, a solid state or a gel state can be formed by a polymer matrix alone, or by adding a plasticizer, a supporting electrolyte, or a plasticizer and a supporting electrolyte. There is no restriction | limiting in particular and what is called a high molecular compound generally used can be used.
Examples of the polymer compound exhibiting characteristics as the polymer matrix include hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, ethylene, propylene, acrylonitrile, vinylidene chloride, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, methyl Examples thereof include polymer compounds obtained by polymerizing or copolymerizing monomers such as acrylate, ethyl acrylate, methyl methacrylate, styrene, and vinylidene fluoride. These polymer compounds may be used alone or in combination. Among these, a polyvinylidene fluoride polymer compound is particularly preferable. Furthermore, a polyvinylidene fluoride polymer compound containing a carboxyl group is preferable.

  Examples of the polyvinylidene fluoride polymer compound include a homopolymer of vinylidene fluoride, or a copolymer of vinylidene fluoride and another polymerizable monomer, preferably a radical polymerizable monomer. Specific examples of other polymerizable monomers copolymerized with vinylidene fluoride (hereinafter referred to as copolymerizable monomers) include hexafluoropropylene, tetrafluoroethylene, trifluoroethylene, ethylene, propylene, acrylonitrile, and vinylidene chloride. Acrylic acid, methacrylic acid, maleic acid, maleic anhydride, methyl acrylate, ethyl acrylate, methyl methacrylate, styrene and the like can be exemplified. Among these, a copolymer with a monomer having a carboxyl group is particularly preferable.

  These copolymerizable monomers can be used in the range of 0.1 to 50 mol%, preferably 1 to 25 mol%, based on the total amount of monomers.

  As the copolymerizable monomer, hexafluoropropylene is preferably used. In the present invention, in particular, it can be preferably used as an ion conductive film using a vinylidene fluoride-hexafluoropropylene copolymer obtained by copolymerizing 1 to 25 mol% of hexafluoropropylene with vinylidene fluoride as a polymer matrix. Two or more kinds of vinylidene fluoride-hexafluoropropylene copolymers having different copolymerization ratios may be mixed and used.

  Further, two or more of these copolymerizable monomers can be used for copolymerization with vinylidene fluoride. For example, copolymerization with combinations of vinylidene fluoride + hexafluoropropylene + tetrafluoroethylene, vinylidene fluoride + hexafluoropropylene + acrylic acid, vinylidene fluoride + tetrafluoroethylene + ethylene, vinylidene fluoride + tetrafluoroethylene + propylene, etc. The copolymer obtained by making it also can be used.

  Furthermore, in the present invention, a polyacrylic acid-based polymer compound, a polyacrylate-based polymer compound, a polymethacrylic acid-based polymer compound, a polymethacrylate-based polymer compound, One or more polymer compounds selected from acrylonitrile polymer compounds and polyether polymer compounds may be used in combination. Alternatively, one or more kinds of copolymers obtained by copolymerizing two or more kinds of monomers of the above-described polymer compound with a polyvinylidene fluoride polymer compound may be used. In this case, the blending ratio of the homopolymer or copolymer is usually preferably 200 parts by mass or less with respect to 100 parts by mass of the polyvinylidene fluoride polymer compound.

  The weight-average molecular weight of the polyvinylidene fluoride polymer compound used in the present invention is usually 10,000 to 2,000,000, preferably 100,000 to 1,000,000. can do.

The plasticizer (component (b)) acts as a solvent for substances exhibiting reversible electrochemical redox properties. Any plasticizer can be used as long as it can be generally used as an electrolyte solvent in an electrochemical cell or battery, and specific examples thereof include various solvents exemplified in liquid electrolytes. In particular, propylene carbonate, ethylene carbonate, dimethyl sulfoxide, dimethoxyethane, acetonitrile, γ-butyrolactone, sulfolane, dioxolane, dimethylformamide, dimethoxyethane, tetrahydrofuran, adiponitrile, methoxyacetonitrile, dimethylacetamide, methylpyrrolidinone, dimethyl sulfoxide, dioxolane, sulfolane, Trimethyl phosphate and triethyl phosphate are preferred. Also, room temperature molten salts can be used. Here, the room temperature molten salt is a salt made of an ion pair that is melted at room temperature (that is, in a liquid state) consisting of only an ion pair that does not contain a solvent component, and usually has a melting point of 20 ° C. or less. A salt composed of an ion pair that is in a liquid state at a temperature in excess of ° C.
Examples of the room temperature molten salt include the following.

(Here, R represents an alkyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and X ⁻ represents a halogen ion or SCN ⁻ ).

(Wherein R1 and R2 each represent an alkyl group having 1 to 10 carbon atoms (preferably a methyl group or an ethyl group) or an aralkyl group having 7 to 20 carbon atoms, preferably 7 to 13 carbon atoms (preferably a benzyl group). And may be the same as or different from each other, and X ⁻ represents a halogen ion or SCN ⁻ .)

(Here, R1, R2, R3, R4 each represents an alkyl group having 1 or more carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms (such as a phenyl group), or a methoxymethyl group. And may be the same as or different from each other, and X ⁻ represents a halogen ion or SCN ⁻ .)
The solvent may be used alone or in combination of two or more.

  The amount of the plasticizer (component (b)) used is not particularly limited, but is usually 20% by mass or more, preferably 50% by mass or more, more preferably 70% by mass or more, and 98% by mass in the ion conductive material. It can be contained in an amount of not more than mass%, preferably not more than 95 mass%, more preferably not more than 90 mass%.

Next, the substance showing the reversible electrochemical redox characteristics of the component (c) used in the present invention will be described.
Component (c) is a compound capable of performing the reversible electrochemical redox reaction as described above, and is usually referred to as a redox material.
The type of the compound is not particularly limited, and examples thereof include ferrocene, p-benzoquinone, 7,7,8,8-tetracyanoquinodimethane, N, N, N ′, N′-tetramethyl. -P-phenylenediamine, tetrathiafulvalene, anthracene, p-toluylamine and the like can be used. Further, LiI, NaI, KI, CsI, CaI ₂ , quaternary imidazolium iodine salt, tetraalkylammonium iodine salt, Br ₂ and LiBr, NaBr, KBr, CsBr, CaBr ₂ and other metal bromides are listed.

Further, Br ₂ and tetraalkylammonium bromide, bipyridinium bromide, bromine salts, complex salts such as ferrocyanic acid-ferricyanate, sodium polysulfide, alkylthiol-alkyldisulfides, hydroquinone-quinones, viologens, and the like can be used. As the redox material, only one of an oxidant and a reductant may be used, or the oxidant and the reductant may be mixed and added at an appropriate molar ratio.

Further, as the component (c), halogen ions, SCN ^- counter anion selected from (X ^-) include salts having a. As the cation, as a quaternary ammonium salt, specifically, (CH ₃ ) ₄ NX ⁻ , (C ₂ H ₅ ) ₄ NX ⁻ , (n-C ₄ H ₉ ) ₄ NX ⁻ ,

Etc. A phosphonium salt having a counter anion (X ⁻ ), specifically, (CH ₃ ) ₄ PX ⁻ , (C ₂ H ₅ ) ₄ PX ⁻ , (C ₃ H ₇ ) ₄ PX ⁻ , (C ₄ H ₉ ) ₄ PX- ^{and the} like.
Of course, a mixture of these can also be used suitably.
In addition, in the case of these compounds, it is preferable to use together with a normal component (b).

Further, redox room temperature molten salts can also be used as the component (c). Here, the redox ambient temperature molten salt is a salt composed of ion pairs that are melted at room temperature (that is, in a liquid state) consisting only of ion pairs that do not contain a solvent component, and usually has a melting point of 20 ° C. or less. A salt composed of an ion pair that is in a liquid state at a temperature exceeding 20 ° C. and capable of performing a reversible electrochemical redox reaction. When redox room temperature molten salts are used as the component (c), the component (b) may or may not be used in combination.
The redox room temperature molten salt can be used alone or in combination of two or more.
Examples of redox room temperature molten salts include the following.

(Here, R represents an alkyl group having 2 to 20 carbon atoms, preferably 2 to 10 carbon atoms, and X ⁻ represents a halogen ion or SCN ⁻ ).

(Wherein R1 and R2 each represent an alkyl group having 1 to 10 carbon atoms (preferably a methyl group or an ethyl group) or an aralkyl group having 7 to 20 carbon atoms, preferably 7 to 13 carbon atoms (preferably a benzyl group). And may be the same as or different from each other, and X ⁻ represents a halogen ion or SCN ⁻ .)

(Here, R1, R2, R3, R4 each represents an alkyl group having 1 or more carbon atoms, preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms (such as a phenyl group), or a methoxymethyl group. And may be the same as or different from each other, and X ⁻ represents a halogen ion or SCN ⁻ .)

  Moreover, there is no restriction | limiting in particular about the usage-amount of the substance (component (c)) which shows a reversible electrochemical oxidation-reduction characteristic, Usually, 0.1 mass% or more in a polymer solid electrolyte, Preferably it is 1 mass% or more. More preferably, the content is 10% by mass or more and 70% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less.

When component (c) is used in combination with component (b), it is desirable that component (c) has a mixing ratio that dissolves in component (b) and does not cause precipitation even when a polymer solid electrolyte is obtained. Preferably, component (c) / component (b) is in the range of 0.01 to 0.5, more preferably 0.03 to 0.3 in terms of mass ratio.
For component (a), the mass ratio of component (a) / (component (b) + component (c)) is preferably 1/20 to 1/1, more preferably 1/10 to 1/2. It is desirable to be in the range.

  The amount of the supporting electrolyte (component (d)) used in the polymer solid electrolyte is not particularly limited and is arbitrary, but is usually 0.1% by mass or more, preferably 1% by mass or more in the polymer solid electrolyte. More preferably, it is 10% by mass or more and 70% by mass or less, preferably 60% by mass or less, and more preferably 50% by mass or less.

The polymer solid electrolyte may further contain other components. Examples of other components include ultraviolet absorbers and amine compounds. Although it does not specifically limit as a ultraviolet absorber which can be used, Organic UV absorbers, such as a compound which has a benzotriazole skeleton and a compound which has a benzophenone skeleton, are mentioned as a typical thing.
As the compound having a benzotriazole skeleton, for example, a compound represented by the following general formula (1) is preferably exemplified.

In the general formula (1), R ⁸¹ represents a hydrogen atom, a halogen atom or an alkyl group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. Examples of the halogen atom include fluorine, chlorine, bromine and iodine. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an i-propyl group, a butyl group, a t-butyl group, and a cyclohexyl group. The substitution position of R ⁸¹ is the 4-position or 5-position of the benzotriazole skeleton, but the halogen atom and the alkyl group are usually located at the 4-position. R ⁸² represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an i-propyl group, a butyl group, a t-butyl group, and a cyclohexyl group. R ⁸³ represents an alkylene group or alkylidene group having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a trimethylene group, and a propylene group. Examples of the alkylidene group include an ethylidene group and a propylidene group.

  Specific examples of the compound represented by the general formula (1) include 3- (5-chloro-2H-benzotriazol-2-yl) -5- (1,1-dimethylethyl) -4-hydroxy-benzenepropanoic acid. 3- (2H-benzotriazol-2-yl) -5- (1,1-dimethylethyl) -4-hydroxy-benzeneethanoic acid, 3- (2H-benzotriazol-2-yl) -4-hydroxybenzene Ethanoic acid, 3- (5-methyl-2H-benzotriazol-2-yl) -5- (1-methylethyl) -4-hydroxybenzenepropanoic acid, 2- (2′-hydroxy-5′-methylphenyl) Benzotriazole, 2- (2′-hydroxy-3 ′, 5′-bis (α, α-dimethylbenzyl) phenyl) benzotriazole, 2- (2′-hydroxy-3 ′, 5 '-Di-t-butylphenyl) benzotriazole, 2- (2'-hydroxy-3'-t-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 3- (5-chloro-2H-benzo And triazol-2-yl) -5- (1,1-dimethylethyl) -4-hydroxy-benzenepropanoic acid octyl ester.

  Suitable examples of the compound having a benzophenone skeleton include compounds represented by the following general formulas (2) to (4).

In the general formulas (2) to (4), R ⁹² , R ⁹³ , R ⁹⁵ , R ⁹⁶ , R ⁹⁸ , and R ⁹⁹ are the same or different from each other, and are a hydroxyl group, a carbon number of 1 to 10, Preferably 1-6 alkyl groups or alkoxy groups are shown. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an i-propyl group, a butyl group, a t-butyl group, and a cyclohexyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, a propoxy group, an i-propoxy group, and a butoxy group.

R ⁹¹ , R ⁹⁴ , and R ^{97 each} represents an alkylene group or alkylidene group having 1 to 10 carbon atoms, preferably 1 to 3 carbon atoms. Examples of the alkylene group include a methylene group, an ethylene group, a trimethylene group, and a propylene group. Examples of the alkylidene group include an ethylidene group and a propylidene group.
p1, p2, p3, q1, q2, and q3 each independently represent an integer of 0 to 3.

Preferred examples of the compound having a benzophenone skeleton represented by the general formulas (2) to (4) include 2-hydroxy-4-methoxybenzophenone-5-carboxylic acid and 2,2′-dihydroxy-4-methoxybenzophenone. -5-carboxylic acid, 4- (2-hydroxybenzoyl) -3-hydroxybenzenepropanoic acid, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfone Acid, 2-hydroxy-4-n-octoxybenzophenone, 2,2′-dihydroxy-4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone, 2-hydroxy-4-methoxy -2'-carboxybenzophenone and the like.
Of course, two or more of these can be used in combination.

  The use of an ultraviolet absorber is optional, and the amount used is not particularly limited, but when used, it is 0.1% by mass or more, preferably 1% by mass or more in the ion conductive film. It is desirable to make it contain in the quantity of the range of 20 mass% or less, Preferably it is 10 mass% or less.

  The amine compound that can be contained in the ion conductive film is not particularly limited, and various aliphatic amines and aromatic amines are used. For example, pyridine derivatives, bipyridine derivatives, quinoline derivatives and the like are representative examples. Can be mentioned. By adding these amine compounds, an improvement in open circuit voltage is expected. Specific examples of these compounds include 4-t-butyl-pyridine, quinoline, isoquinoline and the like.

  The ion conductive film can be obtained by forming a mixture of the components (a) to (c) and optional components blended as desired into a film by a known method. The molding method in this case is not particularly limited, and examples thereof include extrusion molding, a method obtained in a film state by a casting method, a spin coating method, a dip coating method, an injection method, and an impregnation method.

Extrusion molding can be performed by a conventional method, and after the mixture is melted by heating, film molding is performed.
Regarding the casting method, the mixture can be formed into a film by further adjusting the viscosity with an appropriate diluent, applying the mixture with a normal coater used in the casting method, and drying. As the coater, a doctor coater, a blade coater, a rod coater, a knife coater, a reverse roll coater, a gravure coater, a spray coater, and a curtain coater can be used, and they can be selectively used depending on the viscosity and the film thickness.
As for the spin coating method, the mixture can be formed into a film by further adjusting the viscosity with an appropriate diluent, applying the mixture with a commercially available spin coater, and drying.
As for the dip coating method, a film can be formed by adjusting the viscosity of the mixture with an appropriate diluent to prepare a mixture solution, pulling up an appropriate base from the mixture solution, and drying.

The ion conductive film of the present invention has an ionic conductivity of usually 1 × 10 ⁻⁷ S / cm or more, preferably 1 × 10 ⁻⁶ S / cm or more, more preferably 1 × 10 ⁻⁵ S / cm at room temperature. The above is shown. The ionic conductivity can be obtained by a general method such as a complex impedance method.
In the ion conductive film of the present invention, the diffusion coefficient of the oxidant is 1 × 10 ⁻⁹ cm ² / s or more, preferably 1 × 10 ⁻⁸ cm ² / s or more, more preferably 1 × 10 ⁻⁷ cm. ² / s or more. The diffusion coefficient is an index indicating ion conductivity, and can be obtained by a general method such as constant potential current characteristic measurement or cyclic voltammogram measurement.

The thickness of the ion conductive film is not particularly limited, but is usually 1 μm or more, preferably 10 μm or more, and usually 3 mm or less, preferably 1 mm or less.
Moreover, it is desirable that the ion conductive film has self-supporting properties. In that case, the tensile modulus at 25 ° C. is usually 5 × 10 ⁴ N / m ² or more, preferably 1 × 10 ⁵ N / m ² or more, and most preferably 5 × 10 ⁵ N / m ² or more. It is desirable to have In addition, this tensile elasticity modulus is a value at the time of measuring by a 2 cm x 5 cm strip sample with the tensile tester used normally.

  As the photoelectric conversion element in the present invention, for example, it has a layer structure represented by the structure shown in FIG. 3, and at least two conductive substrates are used, at least one of which is substantially transparent, so-called It is a transparent conductive substrate. In addition, as shown in FIG. 3, a semiconductor layer (photosensitive layer) is usually formed on the transparent conductive substrate.

The transparent conductive substrate usually has a transparent electrode layer on the transparent substrate.
The transparent substrate is not particularly limited, and the material, thickness, dimensions, shape, and the like can be appropriately selected according to the purpose. For example, colorless or colored glass, meshed glass, glass block, etc. are used, and colorless. Alternatively, a colored transparent resin may be used. Specifically, polyesters such as polyethylene terephthalate, polyamide, polysulfone, polyether sulfone, polyether ether ketone, polyphenylene sulfide, polycarbonate, polyimide, polymethyl methacrylate, polystyrene, cellulose triacetate, polymethylpentene and the like can be mentioned. The term “transparent” in the present invention means a transmittance of 10 to 100%, preferably a transmittance of 50% or more, and the substrate in the present invention has a smooth surface at room temperature. The surface may be a flat surface or a curved surface, or may be deformed by stress.

Further, the transparent electrode layer acting as an electrode is not particularly limited as long as it fulfills the object of the present invention. For example, a metal thin film such as gold, silver, chromium, copper, and tungsten, a conductive film made of metal oxide, etc. Is mentioned. Examples of the metal oxide include Indium Tin Oxide (ITO (In ₂ O ₃ : Sn)) obtained by doping a metal oxide such as tin or zinc with a small amount of other metal elements, or Fluorine doped Tin Oxide (FTO (SnO ₂ )). : F)), Aluminum doped Zinc Oxide (AZO (ZnO: Al)) and the like are preferably used.
The film thickness is usually 100 to 5000 μm, preferably 500 to 3000 μm. The surface resistance (resistivity) is appropriately selected depending on the use of the substrate of the present invention, but is usually 0.5 to 500 Ω / sq, preferably 2 to 50 Ω / sq.

  The method for forming the transparent electrode layer is not particularly limited, and a known method is appropriately selected and used depending on the kind of the metal or metal oxide used as the electrode layer. Usually, a vacuum deposition method, an ion plating method is used. The method, CVD, sputtering method or the like is used. In any case, it is desirable that the substrate is formed within a range of 20 to 700 ° C.

  The other substrate, that is, the counter substrate, may be any substrate as long as the substrate itself is conductive or at least one surface is conductive, and may be the transparent transparent conductive substrate described above or an opaque conductive substrate. As an opaque conductive substrate, in addition to various metal electrodes, for example, Au, Pt, Cr formed on a glass substrate can be exemplified.

In the photoelectric conversion element of the present invention, the semiconductor layer used is not particularly limited. For example, Bi ₂ S ₃ , CdS, CdSe, CdTe, CuInS ₂ , CuInSe ₂ , Fe ₂ O ₃ , GaP, GaAs, InP, Nb ₂ O ₅ , PbS, Si, SnO ₂ , TiO ₂ , WO ₃ , ZnO, ZnS and the like can be mentioned, preferably CdS, CdSe, CuInS ₂ , CuInSe ₂ , Fe ₂ O ₃ , GaAs, InP, Nb ₂ O ₅ , PbS, SnO ₂ , TiO ₂ , WO ₃ , and ZnO, and a plurality of combinations may be used. Particularly preferred are TiO ₂ , ZnO, SnO ₂ and Nb ₂ O ₅ , and most preferred are TiO ₂ and ZnO.

The semiconductor used in the present invention may be single crystal or polycrystalline. As the crystal system, anatase type, rutile type, brookite type and the like are mainly used, and anatase type is preferable. A known method can be used for forming the semiconductor layer.
As a method for forming the semiconductor layer, the semiconductor nanoparticle dispersion, the sol solution, or the like can be obtained by coating on a substrate by a known method. The coating method in this case is not particularly limited, and examples include a method of obtaining a thin film by a casting method, a spin coating method, a dip coating method, a bar coating method, and various printing methods including a screen printing method. .
Although the thickness of a semiconductor layer is arbitrary, it is 0.5 micrometer or more and 50 micrometers or less, Preferably they are 1 micrometer or more and 20 micrometers or less.

Various dyes can be adsorbed or contained in the semiconductor layer for the purpose of improving the light absorption efficiency of the semiconductor layer.
The dye that can be used in the present invention is not particularly limited as long as it is a dye that improves the light absorption efficiency of the semiconductor layer. Usually, one or more of various metal complex dyes and organic dyes are used. Can be used. In addition, in order to impart adsorptivity to the semiconductor layer, a functional group such as a carboxyl group, a hydroxyl group, a sulfonyl group, a phosphonyl group, a carboxylalkyl group, a hydroxyalkyl group, a sulfonylalkyl group, or a phosphonylalkyl group is included in the dye molecule. Those having a group are preferably used.
As the metal complex dye, ruthenium, osmium, iron, cobalt, zinc complex, metal phthalocyanine, chlorophyll and the like can be used.
Examples of the metal complex dye used in the present invention are as follows.

(Dye 1)

Here, X represents a monovalent anion, but the two Xs may be independent or cross-linked. For example, the following is exemplified.

(Dye 2)

Here, X represents a monovalent anion. For example, the following is exemplified.

Y is a monovalent anion, which is a halogen ion, SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) _{2 ^{N -, PF 6 -, AsF}} 6 -, CH 3 COO -, CH 3 (C 6 H 4) SO 3 -, and _{(C 2 F 5 SO 2)} 3 C - , and the like.

(Dye 3)

  Here, Z is an atomic group having an unshared electron pair, and the two Zs may be independent or bridged. For example, the following is exemplified.

Y is a monovalent anion, which is a halogen ion, SCN ⁻ , ClO ₄ ⁻ , BF ₄ ⁻ , CF ₃ SO ₃ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ , (C ₂ F ₅ SO ₂ ) _{2 ^{N -, PF 6 -, AsF}} 6 -, CH 3 COO -, CH 3 (C 6 H 4) SO 3 -, and _{(C 2 F 5 SO 2)} 3 C - , and the like.

(Dye 4)

As the organic dye, a cyanine dye, a hemicyanine dye, a merocyanine dye, a xanthene dye, a triphenylmethane dye, or a metal-free phthalocyanine dye can be used. Examples of organic dyes that can be used in the present invention include the following.

  As a method for adsorbing the dye to the semiconductor layer, a solution in which the dye is dissolved in a solvent is applied on the semiconductor layer by spray coating or spin coating and then dried. In this case, the substrate may be heated to an appropriate temperature. Alternatively, a method in which a semiconductor layer is immersed in a solution and adsorbed can be used. The immersion time is not particularly limited as long as the dye is sufficiently adsorbed, but is preferably 1 to 30 hours, particularly preferably 5 to 20 hours. Moreover, you may heat a solvent and a board | substrate when immersing as needed. Preferably, the concentration of the dye in the case of a solution is about 1 to 1000 mM / L, preferably about 10 to 500 mM / L.

  The solvent to be used is not particularly limited as long as the dye is not dissolved and the semiconductor layer is not dissolved, but methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, t-butanol, etc. Nitrile solvents such as alcohol, acetonitrile, propionitrile, methoxypropionitrile, glutaronitrile, benzene, toluene, o-xylene, m-xylene, p-xylene, pentane, heptane, hexane, cyclohexane, heptane, Acetone, methyl ethyl ketone, diethyl ketone, ketones such as 2-butanone, diethyl ether, tetrahydrofuran, ethylene carbonate, propylene carbonate, nitromethane, dimethylformamide, dimethyl sulfoxide, hexamethylphosphoamide Dimethoxyethane, γ-butyrolactone, γ-valerolactone, sulfolane, dimethoxyethane, adiponitrile, methoxyacetonitrile, dimethylacetamide, methylpyrrolidinone, dimethylsulfoxide, dioxolane, sulfolane, trimethyl phosphate, triethyl phosphate, tripropyl phosphate, phosphoric acid Ethyl dimethyl, tributyl phosphate, tripentyl phosphate, trihexyl phosphate, triheptyl phosphate, trioctyl phosphate, trinonyl phosphate, tridecyl phosphate, tris phosphate (trifluoromethyl), tris phosphate (pentafluoroethyl) In addition, triphenyl polyethylene glycol phosphate, polyethylene glycol, and the like can be used.

  As an example of the photoelectric conversion element of this invention, the element which has the cross section shown in FIG. 3 can be mentioned, for example. This element has a semiconductor layer 3 on which a dye is adsorbed on a transparent conductive substrate 1 (substrate A), a counter electrode substrate 2 (substrate B), and a gap between the semiconductor layer 3 and the counter electrode substrate 2. An ion conductive film 4 is disposed, and the periphery is sealed with a seal member 5. Note that the lead wire is connected to the conductive portions of the substrate A and the substrate B, and power can be taken out.

  The method for producing a solar cell using the photoelectric conversion element of the present invention is not particularly limited. Usually, a substrate A having a semiconductor layer adsorbing a dye, an ion conductive film, and a substrate B are laminated, and a known method is used. It can be easily manufactured by appropriately sealing the peripheral part. As a method of sealing the peripheral part, after placing an ion conductive film on one of the substrates, a sealant is placed on the outside and the other substrate is aligned, and the seal and the ion conductive film are placed on the same substrate. It is possible to use a distribution method.

The photoelectric conversion element of the present invention has a high conversion efficiency by optimizing the diffusion coefficient of the electrolyte layer, the distance between the electrodes of the element, etc. so that _RD obtained by the AC impedance method is below a certain value. . In particular, when a solid electrolyte is used as the electrolyte layer, a high-performance element equivalent to a liquid electrolyte can be produced.

    EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

[Example 1]
Ti-Nanoxide T manufactured by SOLARONIX was bar-coated on SnO ₂ : F glass (transparent conductive glass having a SnO ₂ : F film formed on a glass substrate) having a film resistance of 10Ω / sq and dried. During bar coating, a scotch tape was attached to the side of the transparent conductive glass so that the film thickness was uniform. The coated substrate was baked at 450 ° C. for 1 hour to form a semiconductor layer. This was soaked in a ruthenium dye (Rutenium 535-bisTBA manufactured by SOLARONIX) / ethanol solution (5.0 × 10 ⁻⁴ mol / L) for 15 hours to adsorb the dye.
Next, the semiconductor layer adsorbing the dye and the Pt surface of the glass with the Pt thin film are arranged facing each other with a polyethylene terephthalate film as a spacer, and 0.1 mol / L lithium iodide, 0 Injecting a γ-butyrolactone solution containing 5 mol / L of 1-propyl-2,3-dimethylimidazolium iodide, 0.5 mol / L of 4-t-butylpyridine and 0.05 mol / L of iodine by capillary action Then, the periphery was sealed with an ultraviolet curable sealing material to obtain a photoelectric conversion element. The distance between the electrodes of the photoelectric conversion element when this polyethylene terephthalate film spacer was used was 56 μm. While irradiating light of illuminance of AM 1.5 and 100 mW / cm ² using a solar simulator (YSS-150, manufactured by Yamashita Denso Co., Ltd.) to the produced photoelectric conversion element, an impedance measuring device (potentiometer galvanostat 1287, impedance analyzer) 1260 (manufactured by Solartron Co., Ltd.), AC modulation of ± 5 mV is applied to an open circuit voltage of 0.71 V of the photoelectric conversion element, and measurement is performed in a frequency range of 1 MHz to 0.01 Hz, and the equivalent circuit shown in FIG. 1 is used. Then, fitting was performed with fitting software (Z-View, manufactured by Solartron), and _RD was calculated. This element satisfied R _D of 5Ω or less, which is a requirement of the present invention, and good conversion efficiency (η) was obtained as shown in Table 1.

[Example 2]
When an experiment was performed under the same conditions as in Example 1 except that the distance between the electrodes of the photoelectric conversion element was 96 μm, this element satisfied R _D of 5Ω or less, which is a requirement of the present invention, as shown in Table 2. Good conversion efficiency (η) was obtained.

[Comparative Example 1]
An experiment was conducted under the same conditions as in Example 1 except that the distance between the electrodes of the photoelectric conversion element was 203 μm. As shown in Table 3, this element did not satisfy _RD, which is a requirement of the present invention, of 5Ω or less. Thus, it was found that the conversion efficiency (η) of Example 1 and Example 2 was not reached.

[Example 3]
<Production of ion conductive film>
1 g of a polyvinylidene fluoride polymer containing a carboxyl group (KF9300, Kureha Chemical Co., Ltd.), 0.1 mol / L lithium iodide, 0.5 mol / L 1-propyl-2,3-dimethylimidazolium iodide, 2 g of a γ-butyrolactone solution containing 0.5 mol / L of 4-t-butylpyridine and 0.05 mol / L of iodine was added, diluted with acetone, and heated to obtain a uniform solution. This solution was applied onto a polyethylene terephthalate film substrate by a doctor blade method and dried by heating to obtain an ion conductive film having a uniform thickness.
By changing the gap of the doctor blade in the same manner, four types of ion conductive films (112 μm, 54 μm, 26 μm, and 15 μm) having the same composition and different thicknesses were obtained.

<< Production of photoelectric conversion element >>
Ti-Nanoxide T manufactured by SOLARONIX was bar-coated on SnO ₂ : F glass (transparent conductive glass having a SnO ₂ : F film formed on a glass substrate) having a film resistance of 10Ω / sq and dried. During bar coating, a scotch tape was attached to the side of the transparent conductive glass so that the film thickness was uniform. The coated substrate was baked at 450 ° C. for 1 hour to form a semiconductor layer. This was soaked in a ruthenium dye (Rutenium 535-bisTBA manufactured by SOLARONIX) / ethanol solution (5.0 × 10 ⁻⁴ mol / L) for 15 hours to adsorb the dye.
Next, the ion conductive film having a thickness of 15 μm obtained above is placed on the upper side of the semiconductor layer adsorbing the dye, and further sandwiched with the Pt surface of the glass with the Pt thin film on the ion conductive film side. The periphery was sealed with an ultraviolet curable sealing material to obtain a photoelectric conversion element. At this time, the distance between the electrodes of the photoelectric conversion element was 9 μm.
The impedance of the produced photoelectric conversion element was measured in the same manner as in Example 1, and the results shown in Table 4 were obtained. This element satisfied R _D which is a requirement of the present invention of 5Ω or less, and good conversion efficiency (η) was obtained as shown in Table 4.

[Example 4]
When an experiment was performed under the same conditions as in Example 3 except that the distance between the electrodes of the photoelectric conversion element was 24 μm (use of an ion conductive film having a thickness of 26 μm), this element had an R _D of 5Ω which is a requirement of the present invention. The following conditions were satisfied, and as shown in Table 5, a good conversion efficiency (η) was obtained.

[Comparative Example 2]
An experiment was conducted under the same conditions as in Example 3 except that the distance between the electrodes of the photoelectric conversion element was 50 μm (using an ion conductive film having a thickness of 54 μm). It was found that the requirement _RD did not satisfy 5Ω or less, and did not reach the conversion efficiency (η) of Example 3 and Example 4.

[Comparative Example 3]
An experiment was conducted under the same conditions as in Example 3 except that the distance between the electrodes of the photoelectric conversion element was 107 μm (using an ion conductive film having a thickness of 112 μm). As shown in Table 7, this element was obtained according to the present invention. It was found that the requirement _RD did not satisfy 5Ω or less, and did not reach the conversion efficiency (η) of Example 3 and Example 4.

[Example 5]
<Production of ion conductive film>
1 g of a polyvinylidene fluoride polymer containing a carboxyl group (KF9300, Kureha Chemical Co., Ltd.), 0.3 mol / L lithium iodide, 0.5 mol / L 4-t-butylpyridine, 0.1 mol / L iodine And 4 g of 1-methyl-3-propylimidazolium iodide solution containing 0.5 mass% of water was added, diluted with acetone and heated to obtain a uniform solution. This solution was applied onto a polyethylene terephthalate film substrate by a doctor blade method and dried by heating to obtain an ion conductive film having a uniform thickness.
By changing the gap of the doctor blade in the same manner, four types of ion conductive films (115 μm, 60 μm, 30 μm, and 16 μm) having the same composition and different thicknesses were obtained.

<< Production of photoelectric conversion element >>
Ti-Nanoxide T manufactured by SOLARONIX was bar-coated on SnO ₂ : F glass (transparent conductive glass having a SnO ₂ : F film formed on a glass substrate) having a film resistance of 10Ω / sq and dried. During bar coating, a scotch tape was attached to the side of the transparent conductive glass so that the film thickness was uniform. The coated substrate was baked at 450 ° C. for 1 hour to form a semiconductor layer. This was immersed in a ruthenium dye (Ruthenium 620-1H3TBA manufactured by SOLARONIX) / ethanol solution (5.0 × 10 ⁻⁴ mol / L) for 15 hours to adsorb the dye.
Next, the ion conductive film having a thickness of 16 μm obtained above is placed on the upper side of the semiconductor layer to which the dye is adsorbed, and sandwiched with the Pt surface of the glass with the Pt thin film on the ion conductive film side. The periphery was sealed with an ultraviolet curable sealing material to obtain a photoelectric conversion element. At this time, the distance between the electrodes of the photoelectric conversion element was 10 μm.
The impedance of the produced photoelectric conversion element was measured in the same manner as in Example 1, and the results shown in Table 8 were obtained. This element satisfied R _D of 5Ω or less, which is a requirement of the present invention, and good conversion efficiency (η) was obtained as shown in Table 8.

[Comparative Example 4]
An experiment was conducted under the same conditions as in Example 5 except that the distance between the electrodes of the photoelectric conversion element was 25 μm (using an ion conductive film having a thickness of 30 μm). As shown in Table 9, this element was obtained according to the present invention. It was found that the requirement _RD did not satisfy 5Ω or less, and did not reach the conversion efficiency (η) of Example 5.

[Comparative Example 5]
An experiment was conducted under the same conditions as in Example 5 except that the distance between the electrodes of the photoelectric conversion element was 55 μm (use of an ion conductive film having a thickness of 60 μm). As shown in Table 10, this element was obtained according to the present invention. It was found that the requirement _RD did not satisfy 5Ω or less, and did not reach the conversion efficiency (η) of Example 5.

[Comparative Example 6]
An experiment was conducted under the same conditions as in Example 5 except that the distance between the electrodes of the photoelectric conversion element was 110 μm (using an ion conductive film having a thickness of 115 μm). It was found that the requirement _RD did not satisfy 5Ω or less, and did not reach the conversion efficiency (η) of Example 5.

It is an equivalent circuit used for fitting an impedance spectrum. The impedance spectrum under light irradiation is shown. It is an example of the cross section of a photoelectric conversion element.

Explanation of symbols

Rs, R1, R2: resistance component CPE1, CPE2: Constant Phase Element Z _D: Finite diffusion length Warburg impedance 1: transparent conductive substrate 2: counter electrode substrate 3: semiconductor layer 4: ion-conductive film 5: sealing member

Claims (6)

A photoelectric conversion element comprising at least one transparent conductive substrate, and an electrolyte layer containing a substance exhibiting reversible electrochemical oxidation-reduction characteristics provided at least between the two conductive substrates. A photoelectric conversion element characterized in that _RD obtained by fitting an AC impedance measurement result with the equivalent circuit shown in FIG. 1 is 5Ω or less.   The photoelectric conversion element according to claim 1, wherein the electrolyte layer is a solid electrolyte.   3. The photoelectric conversion element according to claim 2, wherein the solid electrolyte is an ion conductive film containing at least a polymer matrix and a substance exhibiting reversible electrochemical redox characteristics as constituent components.   4. The photoelectric conversion element according to claim 3, wherein the polymer matrix is a polyvinylidene fluoride polymer compound.   The photoelectric conversion element according to claim 4, wherein the polyvinylidene fluoride polymer compound contains a carboxyl group. 2. The photoelectric conversion element according to claim 1, wherein the substance exhibiting reversible electrochemical oxidation-reduction characteristics is a room temperature molten salt.

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