JP2000243134A - Electrolyte, photoelectric transducer, and photoelectric chemical battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce deterioration of photoelectric transducing characteristic with the lapse of time by containing a compound having at least one ether combination and at least two cyanoether groups. SOLUTION: For organic soluvent used for electrolyte, a compound having at least one ether combination and at least two or more cyanoether groups is used. A photoelectric transducer and a photoelectric chemical battery using electrolyte containing such compound are excellent in photoelectric transducing characteristic as an element, and deterioration of characteristic with the lapse of time is particularly small. Such compound is the compound in the formula I (a compound having at least one ether combination and at least cyanoether groups is indicated) or in the formula II (L in the formula indicates n-pieces alcohol residue, and (n) indicates an integer two or more). The residue group of n-valent alcohol is residual substituent removing all hydroxyl groups from n-valent alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel electrolyte. Furthermore, the present invention relates to a photoelectric conversion element and a photoelectrochemical cell using the electrolyte.

[0002]

2. Description of the Related Art Photovoltaic power generation is a single-crystal silicon solar cell,
Polycrystalline silicon solar cells, amorphous silicon solar cells, and compound solar cells such as cadmium telluride and indium copper selenide have been put into practical use or subject to major research and development.
It is necessary to overcome problems such as a long energy payback time. On the other hand, many solar cells using an organic material intended to have a large area and a low price have been proposed so far, but have a problem that conversion efficiency is low and durability is poor. Under these circumstances, Nature (Vol.353, 737-
740, 1991) and U.S. Pat.
No. 644, No. 5463057, JP-A-7-249790
No., Tokuhei 8-15097, Advanced Materials (Vol. 9, No. 11, pp. 904-906, 1997), etc.
A photoelectric conversion element and a solar cell using semiconductor fine particles sensitized by a dye, and a material and a manufacturing technique for producing the same are disclosed. The proposed battery is a wet solar cell using a titanium dioxide porous thin film spectrally sensitized by a ruthenium complex as a working electrode and using an organic solvent as an electrolyte. This method is promising in that it is inexpensive and can achieve high energy conversion efficiency. However,
If a carbonate ester such as ethylene carbonate or propylene carbonate or a nitrile such as acetonitrile, or a mixture thereof, which has been conventionally used as the electrolyte is used, the photoelectric conversion characteristics (particularly, photoelectric conversion efficiency) deteriorate with time. Was found, and the durability was found to be insufficient.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a photoelectric conversion element and a photoelectrochemical cell which have little deterioration in photoelectric conversion characteristics with the passage of time, and to provide a novel electrolyte suitable for this. is there.

[0004]

The above object has been achieved by the following items which specify the present invention and preferred embodiments thereof. (1) An electrolyte containing a compound having at least one ether bond and at least two cyanoethyl groups. (2) The above (1), wherein the compound is a compound of the formula (I)
Electrolyte.

[0005]

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(3) The electrolyte of the above (1), wherein the compound is represented by the formula (II).

[0007]

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[Wherein, L represents an n-valent alcohol residue. n represents an integer of 2 or more. (4) The electrolyte according to the above (3), wherein in the formula (II), n is 2 or more and 4 or less. (5) The electrolyte according to the above (3), wherein in the formula (II), n is 2. (6) The electrolyte according to the above (5), wherein the dihydric alcohol residue is a polyethylene glycol residue. (7) A photoelectric conversion having an electrolyte-containing layer using the electrolyte according to any of (1) to (6), a conductive support, a semiconductor-containing layer coated on the conductive support, and a counter electrode element. (8) The photoelectric conversion device according to (7), wherein the semiconductor is a fine particle semiconductor sensitized by a dye. (9) The photoelectric conversion element according to the above (7) or (8), wherein the semiconductor is a metal chalcogenide. (10) A photoelectrochemical cell using the photoelectric conversion element according to any of (7) to (9).

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The present invention is characterized in that a compound having at least one ether bond and at least two or more cyanoethyl groups is used as the organic solvent used for the electrolyte. A photoelectric conversion element and a photoelectrochemical cell using an electrolyte containing such a compound have excellent photoelectric conversion characteristics as an element, and in particular, characteristic deterioration with time is small.

The above-mentioned compound is preferably a compound of the formula (I) or a compound of the formula (II). In the formula (II), L represents a residue of an n-valent alcohol. The residue of the n-valent alcohol refers to a remaining substituent obtained by removing all hydroxyl groups from the n-valent alcohol. n is an integer of 2 or more, preferably 2 or more and 4 or less. More preferably, it is 2. Preferred examples of L include an alkylene group which may have a substituent, an arylene group which may have a substituent, and -O-, -S-, -NH-
Or a substituent combined with —N (CH ₃ ) — is exemplified. More preferred specific examples of L include-(C
H ₂ ) _k- (k represents an integer of 2 or more and 10 or less),-(C
_{H 2 CH 2 O) m -} CH 2 CH 2 -, - (C 3 H 7 O) m -C 3 H 7 -
(M represents an integer of 1 or more and 30 or less)

[0011]

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[0012]

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And so on. Most preferably,-(CH ₂ CH ₂
O) _m -CH ₂ CH ₂ - it is. Examples of the substituent that may be substituted on L include an alkyl group (for example, methyl and ethyl),
Halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), hydroxyl group, carboxy group, sulfo group,
Acylamino groups (eg, acetamido, benzamido), sulfonamido groups, carbamoyl groups, acyloxy groups, alkoxycarbonyl groups, acyl groups, alkoxy groups (eg, methoxy, ethoxy, methoxyethoxy),
Examples include an aryloxy group (for example, phenoxy), a nitro group, a formyl group, an alkylsulfonyl group and an arylsulfonyl group, an amino group, an aryl group, and the like.

Specific examples of the compound represented by the formula (II) are shown below, but the present invention is not limited to these.

[0015]

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[0016]

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The compounds of formula (I) are commercially available and are readily available. Further, the compound represented by the formula (II) is described in J.
Am. Chem. Soc., 65, 24 (1943), Bull. C
According to the method described in Chem. Soc. Jpn., vol. 61, p. 2443 (1988), acrylonitrile can be easily synthesized by reacting a compound of the following formula (II-a).

[0018]

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The salt used in the electrolyte of the present invention comprises I ₂ and various iodides (eg, LiI, NaI, KI, Cs
Metal iodides such as I and CaI ₂ , iodine salts of quaternary imidazolium compounds, iodine salts of quaternary pyridinium compounds, iodine salts of tetraalkylammonium compounds, etc., Br ₂ and various bromides (eg, LiBr, Na
Br, KBr, CsBr, metal bromide such as CaBr _2, a bromine salt of a quaternary ammonium compound such as tetraalkylammonium bromide and pyridinium bromide), ferrocyanide - ferricyanide or ferrocene - metal complexes such as ferricinium ion , A combination of sulfur compounds such as sodium polysulfide, alkyl thiol-alkyl disulfide, alkyl viologen (for example, methyl viologen chloride,
Hexyl viologen bromide, benzyl viologen tetrafluoroborate) and its reduced form in combination,
A combination of polyhydroxybenzenes (eg, hydroquinone, naphthohydroquinone, etc.) and oxidized products thereof can be used. Among them, LiI, NaI,
KI, CsI, the metal iodide CaI _2, iodine salt of a quaternary imidazolium compound, a combination of iodine salt and I ₂ of the iodide salt or a tetraalkyl ammonium compound of the quaternary pyridinium compound.

Since the redox couple becomes a carrier of electrons, a certain concentration is required. The concentration in the electrolyte is preferably 0.01 mol / L or more, more preferably 0.1 mol / L or more, and particularly preferably 0.3 mol / L or more. The upper limit in this case is not particularly limited, but is usually about 5 mol / l.

Next, the structure and materials of the photoelectric conversion element and the photoelectrochemical cell of the present invention will be described in detail. In the present invention, the dye-sensitized photoelectric conversion element includes a conductive support, a semiconductor film (photosensitive layer) sensitized by a dye or the like provided on the conductive support, a charge transfer layer, and a counter electrode. A photoelectrochemical cell that can use this photoelectric conversion element for a battery that works in an external circuit is used. The photosensitive layer is designed according to the purpose, and may have a single-layer structure or a multilayer structure. Light incident on the photosensitive layer excites dyes and the like. The excited dye or the like has high-energy electrons, which are transferred from the dye or the like to the conduction band of the semiconductor fine particles and reach the conductive support by diffusion. At this time, molecules such as dyes are oxidized. In a photoelectrochemical cell, electrons on a conductive support return to an oxidant such as a dye via a counter electrode and a charge transfer layer while working in an external circuit, and the dye or the like is regenerated. The semiconductor film functions as a negative electrode of this battery. In the present invention, at the boundaries between the layers (for example, the boundary between the conductive layer and the photosensitive layer of the conductive support, the boundary between the photosensitive layer and the charge transfer layer, the boundary between the charge transfer layer and the counter electrode, etc.) They may be mutually diffused and mixed.

In the present invention, the semiconductor is a so-called photoreceptor, which plays a role of absorbing light to separate electric charges to generate electrons and holes. In a dye-sensitized semiconductor, light absorption and the resulting generation of electrons and holes mainly occur in the dye, and the semiconductor is responsible for receiving and transmitting the electrons. As the semiconductor, besides a simple semiconductor such as silicon or germanium, a so-called compound semiconductor represented by a metal chalcogenide (for example, oxide, sulfide, selenide, or the like) or a compound having a perovskite structure can be used. . Preferably as a metal chalcogenide titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium,
Cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxide, cadmium, zinc,
Lead, silver, antimony, bismuth sulfide, cadmium,
Examples include lead selenide and cadmium telluride. Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, gallium arsenide, copper-indium-selenide, copper-indium-sulfide and the like. Further, as the compound having a perovskite structure, strontium titanate, calcium titanate, sodium titanate, barium titanate, and potassium niobate are preferably exemplified. More preferably, as the semiconductor used in the present invention, specifically, Si, TiO ₂ , SnO ₂ , Fe
₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, ZnS, PbS, Bi ₂ S ₃ , Cd
Se, CdTe, GaP, InP, GaAs, CuInS ₂ , and CuInSe ₂ are mentioned. More preferably _{TiO 2, ZnO, SnO 2,} Fe 2 O 3, WO
_{3, Nb 2 O 5, CdS} , PbS, CdSe, InP, GaAs, CuInS 2, CuI
a nSe _2, particularly preferably TiO ₂ or Nb ₂ O _5, and most preferably TiO _2.

The semiconductor used in the present invention may be single crystal or polycrystal. Although a single crystal is preferable as the conversion efficiency, a polycrystal is preferable in terms of manufacturing cost, securing of raw materials, energy payback time, and the like, and a fine particle semiconductor having a nanometer to micrometer size is particularly preferable. The particle diameter of these semiconductor fine particles is an average particle diameter using the diameter when the projected area is converted into a circle, and is 5% as a primary particle.
It is preferably from 200 to 200 nm, particularly preferably from 8 to 100 nm. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is 0.01 to 100 μm.
It is preferred that Further, two or more kinds of fine particles having different particle size distributions may be mixed and used, and in this case, the average size of the small particles is preferably 5 nm or less. In addition, semiconductor particles having a large particle size, for example, about 300 nm may be mixed for the purpose of improving the light capture rate by scattering incident light.

The method for producing semiconductor fine particles is described in "Sol-Gel Method Science" by Akio Sakuhana, Agne Shofusha (1988), "Thin Film Coating Technology by Sol-Gel Method" by the Technical Information Association (1995), etc. Tadao Sugimoto, "Synthesis of Monodisperse Particles and Size Morphology Control by New Synthetic Gel-Sol Method", Materia, Vol. 35, No. 9, 1012
The gel-sol method described on pages 10 to 1018 (1996) is preferred. Further, a method of producing an oxide by hydrolyzing a chloride in an oxyhydrogen flame at a high temperature developed by Degussa is also preferable. In the case of titanium oxide, the above sol-gel method,
The gel-sol method and the high-temperature hydrolysis method of chloride in an oxyhydrogen flame are both preferable, but the sulfuric acid method and chlorine method described in Manabu Kiyono's "Titanium oxide physical properties and applied technology" Gihodo Shuppan (1997) are also used. You can also. In the case of titanium oxide, among the sol-gel methods described above, in particular, Barb et al., Journal of American Ceramic Society No. 8
Vol. 0, No. 12, pages 3157 to 3171 (1997) "and the method described in Burnside et al.," Chemical Materials Vol. 10, No. 9, pages 2419 to 2425 "are preferred.

As the conductive support, use is made of a support such as metal, which has conductivity, or a glass or plastic support having a conductive layer (conductive agent layer) containing a conductive agent on the surface. Can be. In the latter case, a preferable conductive agent is a metal (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), carbon, or a conductive metal oxide (indium-tin composite oxide, tin oxide doped with fluorine). And the like). The conductive agent layer preferably has a thickness of about 0.02 to 10 μm. The lower the surface resistance of the conductive support, the better.
The preferred range of the surface resistance is 100 Ω / cm ² or less, and more preferably 40 Ω / cm ² or less. The lower limit is not particularly limited, but is usually about 0.1 Ω / cm ² . Preferably, the conductive support is substantially transparent. Substantially transparent means that the light transmittance is 10% or more, preferably 50% or more,
70% or more is particularly preferred. As the transparent conductive support, glass or plastic coated with a conductive metal oxide is preferable. Among them, conductive glass in which a conductive layer made of tin dioxide doped with fluorine is deposited on a transparent substrate made of low-cost soda-lime float glass is particularly preferable. In addition, for a low-cost and flexible photoelectric conversion element or solar cell, a transparent polymer film provided with the above conductive layer is preferably used. For the transparent polymer film, tetraacetyl cellulose (TA
C), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndioctatic polysterene (SPS), polyphenylene sulfide (P
PS), polycarbonate (PC), polyacrylate (PAr), polysulfone (PSF), polyestersulfone (PES), polyetherimide (PE)
I), cyclic polyolefins, brominated phenoxy and the like. When a transparent conductive support is used, it is preferable that light be incident from the support side. In this case, the coating amount of the conductive metal oxide is preferably 0.01 to 100 g per 1 m ² of a glass or plastic support.

It is also preferable to use a metal lead for the purpose of lowering the resistance of the transparent conductive substrate. The material of the metal lead is preferably a metal such as aluminum, copper, silver, gold, platinum and nickel, and particularly preferably aluminum and silver. It is preferable that the metal lead is provided on a transparent substrate by vapor deposition, sputtering, or the like, and a transparent conductive layer made of tin oxide doped with fluorine or an ITO film is provided thereon. It is also preferable to provide a metal lead on the transparent conductive layer after providing the transparent conductive layer on a transparent substrate. The decrease in the amount of incident light due to the installation of metal leads is 1 to 10%, more preferably 1 to 5%.
It is.

Examples of the method of applying the semiconductor fine particles on the conductive support include a method of applying a dispersion or a colloid solution of the semiconductor fine particles on the conductive support, and the above-mentioned sol-gel method. In consideration of mass production of photoelectric conversion elements, liquid physical properties, and flexibility of a support, a wet film forming method is relatively advantageous. As a wet type film applying method, a coating method and a printing method are typical. In addition to the sol-gel method described above, a method of preparing a dispersion of semiconductor fine particles, a method of grinding in a mortar, a method of dispersing while crushing using a mill, or a method of depositing fine particles in a solvent when synthesizing a semiconductor. And a method of using it as it is. Examples of the dispersion medium include water and various organic solvents (eg, methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.). At the time of dispersion, a polymer, a surfactant, an acid, a chelating agent, or the like may be used as a dispersing aid, if necessary. As a coating method, a roller method as an application system,
Dip method, air knife method, blade method and the like as metering system, and wire bar method disclosed in JP-B-58-4589, U.S. Pat.
The slide hopper method, the extrusion method, the curtain method, and the like described in JP-A Nos. 294, 2761419, and 2761791 are preferable. As a general-purpose machine, a spin method or a spray method is also preferably used. As a wet printing method, intaglio, rubber printing, screen printing, and the like are conventionally preferable, including three major printing methods of letterpress, offset, and gravure. From the above methods, a preferable film-forming method is selected according to the liquid viscosity and the wet thickness.

The liquid viscosity largely depends on the type and dispersibility of the semiconductor fine particles, the type of solvent used, and additives such as a surfactant and a binder. High viscosity liquid (for example, 0.01 to 500 Po
In ise), an extrusion method or a casting method is preferable, and in a low-viscosity liquid (for example, 0.1 Poise or less), a slide hopper method, a wire bar method, or a spin method is preferable, and a uniform film can be formed. It should be noted that even in the case of applying a low-viscosity liquid by the extrusion method, the application is possible as long as the application amount is a certain amount. Screen printing is often used for applying a high-viscosity paste of semiconductor fine particles, and this method can also be used. As described above, a method of applying a wet film may be appropriately selected according to parameters such as the liquid viscosity of the coating liquid, the coating amount, the support, and the coating speed.

Further, the semiconductor fine particle layer need not be limited to a single layer. It is also possible to apply a multi-layer coating of dispersions having different particle diameters of fine particles.Also, it is possible to apply a multi-layer coating of different types of semiconductors or different coating compositions of binders and additives. Even when the film thickness is insufficient, the multilayer coating is effective. The extrusion method or slide hopper method is suitable for multi-layer coating. In the case of multi-layer coating, multiple layers may be coated at the same time,
It may be applied several times to several tens of times sequentially. Furthermore, a screen printing method can also be preferably used in the case of successive coating.

Generally, as the thickness of the layer containing semiconductor fine particles increases, the amount of dye carried per unit projected area increases, so that the light capture rate increases. However, the diffusion distance of the generated electrons increases, and the loss due to charge recombination also increases. growing. Therefore, the semiconductor fine particle-containing layer has a preferable thickness, but typically has a thickness of 0.1 to 100 μm. When used as a photoelectrochemical cell, the thickness is preferably 1 to 30 μm, and more preferably 2 to 25 μm. The coating amount of the semiconductor fine particles per 1 m ² of the support is 0.5 to 400.
g, more preferably 5 to 100 g. The semiconductor fine particles are preferably subjected to a heat treatment in order to electronically contact the particles after being applied to the conductive support, and to improve the strength of the coating film and the adhesion to the support. A preferred range of the heat treatment temperature is 40 ° C. or more and less than 700 ° C., and more preferably 100 ° C. or more and 600 ° C. or less. The heat treatment time is about 10 minutes to 10 hours.
When a support having a low melting point or softening point, such as a polymer film, is used, high-temperature treatment is not preferable because the support is deteriorated. Further, it is preferable that the temperature is as low as possible from the viewpoint of cost. The lowering of the temperature can be achieved by the above-mentioned combination of small semiconductor particles having a size of 5 nm or less, heat treatment in the presence of a mineral acid, and the like. Further, after the heat treatment, for example, chemical plating or trichloride using an aqueous solution of titanium tetrachloride for the purpose of increasing the surface area of the semiconductor particles, increasing the purity in the vicinity of the semiconductor particles, and increasing the efficiency of electron injection from the dye into the semiconductor particles. Electrochemical plating using an aqueous titanium solution may be performed. The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. For this reason, the surface area in the state where the semiconductor fine particle layer is coated on the support is preferably at least 10 times, more preferably at least 100 times the projected area. The upper limit is not particularly limited, but is usually about 1000 times.

The dye used in the present invention is preferably a complex dye, particularly a metal complex dye or a polymethine dye. In the present invention, two or more kinds of dyes can be mixed in order to widen the wavelength range of photoelectric conversion as much as possible and to increase the conversion efficiency. Dyes to be mixed and their proportions can be selected so as to match the intended wavelength range and intensity distribution of the light source. Such a dye preferably has an appropriate interlocking group for the surface of the semiconductor fine particles. Preferred linking groups, COOH groups, SO ₃ H group, a cyano group, -P (O) (OH) 2 group, -OP (O) (OH) 2 group, or, oxime, dioxime, hydroxyquinoline, salicylate and Chelating groups having π conductivity, such as α-keto enolate. Among them, COOH group, -P (O) (OH) ₂
The group, -OP (O) (OH) _2, is particularly preferred. These groups may form a salt with an alkali metal or the like, or may form an intramolecular salt. In the case of a polymethine dye, if the methine chain contains an acidic group as in the case of forming a squarylium ring or a croconium ring, this portion may be used as a bonding group.

When the dye used in the present invention is a metal complex dye,
In this case, a ruthenium complex dye is preferable, and the following formula (II)
The dyes represented by I) are preferred. Formula (III) (A₁)_pRuB_aB_bB_c In the formula, p is 0 to 2, preferably 2. Ru is
Represents ruthenium. A ₁Is Cl, SCN, H_TwoO, B
r, I, CN, NCO and SeCN
It is a child. B_a, B_b, B_cAre each independently
It is an organic ligand selected from B-1 to B-8.

[0033]

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[0034]

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Here, _Ra is a hydrogen atom, a halogen atom,
A substituted or unsubstituted alkyl group having 1 to 12 carbon atoms (hereinafter referred to as C number), an aralkyl group substituted or unsubstituted with 7 to 12 carbon atoms, or a substituted or unsubstituted with 6 to 12 carbon atoms Represents an aryl group. The above alkyl group,
The alkyl portion of the aralkyl group may be linear or branched, and the aryl portion of the aralkyl group may be monocyclic or polycyclic (condensed ring, ring assembly). . Examples of the ruthenium complex dye used in the present invention include, for example, U.S. Pat.Nos. 4,492,721, 4,684,537 and 5,084.
And complex dyes described in JP-A Nos. 365, 5350644, 5463057, 5525440 and JP-A-7-249790. Preferred specific examples of the metal complex dye used in the present invention are shown below, but the present invention is not limited thereto.

[0036]

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[0037]

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[0038]

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When the dye used in the present invention is a polymethine dye, a dye represented by the following formula (IV) or (V) is preferable.

[0040]

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In the formula, R _b and R _f each represent a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, and R _{c to} R _e
Represents a hydrogen atom or a substituent. R _{b to} R _f may combine with each other to form a ring. X ₁₁ and X ₁₂ each represent nitrogen, oxygen, sulfur, selenium, or tellurium. m ₁₁ and m
₁₃ represents an integer of 0 to 2, and m ₁₂ represents an integer of 1 to 6. The compound represented by the formula (IV) may have a counter ion depending on the charge of the whole molecule. The alkyl group in the above,
The aryl group and the heterocyclic group may have a substituent.
The alkyl group may be linear or branched, and the aryl group and the heterocyclic group may be monocyclic or polycyclic (condensed ring, ring assembly). The ring formed by R _{b to} R _f may have a substituent and may be a single ring or a condensed ring.

[0042]

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[0043] In the formula, Z _a represents a non-metallic atomic group necessary for forming a nitrogen-containing heterocyclic ring. R _g is an alkyl group or an aryl group. Q represents a methine group or a polymethine group necessary for the compound represented by the formula (V) to form a methine dye. X ₁₃ represents a charge balancing counter ion, and m ₁₄ represents an integer of 0 or more and 10 or less necessary for neutralizing the charge of the molecule. Nitrogen-containing heterocyclic ring formed by the above Z _a may have a substituent, it may be a condensed ring may be a single ring. Further, the alkyl group and the aryl group may have a substituent, the alkyl group may be linear or branched, and the aryl group may be monocyclic or polycyclic (condensed ring, Ring set). The dye represented by the formula (V) is preferably a dye represented by the following formulas (Va) to (Vd).

[0044]

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In the formulas (Va) to (Vd), R _a1 to
R _a5 , R _{b1 to} R _b4 , R _{c1 to} R _c3 , and R _{d1 to} R _d3 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group, and Y ₁₁ , Y ₁₂ , Y ₂₁ , Y _22, Y ₃₁ ~Y
₃₅ and Y ₄₁ to Y ₄₆ each independently represent oxygen, sulfur, selenium, tellurium, -CR _e1 R _e2 - represents a -, or -NR _e3. Y ₂₃ represents O ⁻ , S ⁻ , Se ⁻ , Te ⁻ , or NR _e4 ⁻ . R _{e1 to} R _e4 each independently represent a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. V _11, V _12,
V ₂₁ , V ₂₂ , V ₃₁ and V ₄₁ each independently represent a substituent, and m ₁₅ , m ₃₁ and m ₄₁ each independently represent an integer of 1 to 6. The alkyl group, aryl group and heterocyclic group in the above may have a substituent, the alkyl group may be linear or branched, and the aryl group and heterocyclic group may be monocyclic. Or polycyclic (condensed ring, ring assembly). Specific examples of such polymethine dyes are described in M. Okawar
a, T.Kitao, T.Hirasima, M.Matuoka by Organic Colorants
(Elsevier) and the like. The formula (I
Preferred specific examples of the polymethine dye represented by V) or (V) are shown below, but the present invention is not limited thereto.

[0046]

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[0047]

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[0048]

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[0049]

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[0050]

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[0051]

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[0052]

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[0053]

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[0054]

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[0055]

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[0056]

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The compounds represented by the formulas (IV) and (V) are described in FM Harmer, "Heterocyclic Compounds-Cysteine Soybeans and Related Compounds (Heterocyclic Compounds-Cy)".
anine Dyes and Related Compounds), John Wiley & Sons, New York, London, 1964, DMSturmer, Heterogeneous Cyclic Compounds Special Topics・ In ・ Complex Cyclic Chemistry (Heterocyclic Compounds-Special
topics in heterocyclic chemistry), Chapter 18, Section 14, 482-515, John Wiley & Sons, Inc.-New York,
London, 1977, "Rodd's Chemistry of Car Compounds
bon Compounds) "2nd.Ed.vol.IV, partB, 1977, Chapter 15, Chapters 369-422, Elsevier Scienc Inc.
e Publishing Company Inc.), New York, UK Patent No. 1,077,611, and the like.

In general, a method of adsorbing a dye onto semiconductor fine particles is a method of immersing well-dried semiconductor fine particles in a solution of a dye or the like for several hours. The dye may be adsorbed at room temperature or may be heated and refluxed as described in JP-A-7-249790. The dye may be adsorbed before or after coating the semiconductor fine particles on the conductive support, or the semiconductor fine particles and the dye may be simultaneously coated and adsorbed. Is preferably adsorbed on the semiconductor fine particle film. The method of adsorbing the dye on the semiconductor fine particle film coated on the conductive support is performed by immersing the dried semiconductor fine particle film in the dye solution or by applying the dye solution onto the semiconductor fine particle film and adsorbing the dye solution. be able to.
In the former case, a dipping method, a dipping method, a roller method, an air knife method, or the like can be used. As the latter coating method, a wire bar method, a slide hopper method, an extrusion method,
There are a curtain method, a spin method, and a spray method, and examples of the printing method include letterpress, offset, gravure, and screen printing.

As in the case of the formation of the semiconductor fine particle layer, the liquid viscosity is the same as in the formation of the semiconductor fine particle layer. In addition to the extrusion method for a high-viscosity liquid (for example, 0.01 to 500 Poise), various printing methods are used. A slide hopper method, a wire bar method, or a spin method is suitable, and a uniform film can be obtained. As described above, an application method may be appropriately selected in accordance with parameters such as the liquid viscosity of the dye coating liquid, the coating amount, the support, and the coating speed. The time required for dye adsorption after coating should be as short as possible in consideration of mass production.

The total amount of the dye used is preferably 0.01 to 100 mmol per 1 m ² of the support. The amount of the dye adsorbed on the semiconductor fine particles is preferably 0.01 to 1 mmol per 1 g of the semiconductor fine particles. With such an amount of the dye, a sensitizing effect in the semiconductor can be sufficiently obtained. On the other hand, if the amount of the dye is small, the sensitizing effect becomes insufficient, and if the amount of the dye is too large, the dye not adhering to the semiconductor floats and causes a reduction in the sensitizing effect.

Since the presence of unadsorbed dye causes disturbance of device performance, it is preferable to remove the dye by washing immediately after adsorption. It is preferable to perform cleaning with a polar solvent such as acetonitrile and an organic solvent such as an alcohol solvent using a wet cleaning tank. In order to increase the amount of the adsorbed dye, it is preferable to perform the heat treatment before the adsorption. After the heat treatment, in order to avoid adsorption of water on the surface of the semiconductor fine particles, it is also preferable to quickly adsorb the dye at 40 to 80 ° C. without returning to normal temperature.

A colorless compound may be co-adsorbed for the purpose of reducing the interaction between dyes such as association. Examples of the hydrophobic compound to be co-adsorbed include steroid compounds having a carboxyl group (for example, cholic acid). In addition, an ultraviolet absorber can be co-adsorbed for the purpose of preventing light deterioration due to ultraviolet light. For the purpose of accelerating the removal of excess dye, the surface of the semiconductor fine particles may be treated with an amine after adsorbing the dye. Preferred amines include pyridine, 4-tert-butylpyridine, polyvinylpyridine and the like. When these are liquid, they may be used as they are, or may be used by dissolving them in an organic solvent.

Hereinafter, the charge transfer layer and the counter electrode will be described in detail. The charge transfer layer is a layer having a function of replenishing the oxidized dye with electrons. Typical examples are a liquid (electrolytic solution) in which a redox couple is dissolved in an organic solvent, a so-called gel electrolyte in which a liquid in which a redox couple is dissolved in an organic solvent is impregnated in a polymer matrix, and a molten salt containing a redox couple. Is mentioned. In the present invention, the charge transfer layer is an electrolyte-containing layer containing the electrolyte of the present invention. The thickness of the electrolyte-containing layer is preferably 0.001 to 200 μm,
More preferably, it is 0.1 to 100 μm. The electrolyte of the present invention is prepared by preparing a solution from a compound of the present invention in which a salt is dissolved, and forming an electrolyte layer on an electrode supporting a dye by a casting method, a coating method, an immersion method, an impregnation method, or the like. Is preferred.

When the electrolyte layer is formed by a coating method,
Spin coating, dip coating, air knife coating, curtain coating, and roller coating are applied to a uniform solution prepared by adding additives such as a coating agent such as a leveling agent to a coating solution composed of a solvent in which salt is dissolved. , Wire bar coating method, gravure coating method, or US Patent No.
Extrusion coating method using hopper described in 2681294, or U.S. Patent Nos. 2,761,418 and 3,508,947
And the multi-layer simultaneous coating method described in JP-A-2761791 can form the electrolyte layer of the present invention. When a compound such as iodine is introduced into the electrolyte layer, for example, after the formation of the electrolyte layer, a sample including the electrolyte layer may be placed in a closed container together with a compound such as iodine, and the sample may be introduced by a method of diffusing into the electrolyte. Further, a compound such as iodine can be introduced into the device by a method of coating or vapor-depositing on a counter electrode.

The water content in the charge transfer layer was 10,
2,000 ppm or less, more preferably 2,0 ppm
It is at most 00 ppm, particularly preferably at most 100 ppm.

The counter electrode functions as a positive electrode of the photoelectrochemical cell when the photoelectric conversion element is a photoelectrochemical cell. As the counter electrode, a support having a conductive layer can be used as in the case of the above-described conductive support. However, the support is not necessarily required in a configuration in which the strength and the sealing property are sufficiently maintained. Specifically, as the conductive material used for the counter electrode, a metal (for example, platinum, gold, silver, copper, aluminum, rhodium,
Indium, etc.), carbon, or a conductive metal oxide (indium-tin composite oxide, tin oxide doped with fluorine, or the like). The thickness of the counter electrode is not particularly limited, but is preferably 3 nm or more and 10 μm or less. If it is a metal material, its thickness is preferably 5 μm.
m, more preferably 5 nm or more and 3 μm or less. In order for light to reach the photosensitive layer, at least one of the conductive support and the counter electrode described above must be substantially transparent. In the photoelectrochemical cell of the present invention, it is preferable that the conductive support is transparent and sunlight is incident from the support side. In this case, it is more preferable that the counter electrode has a property of reflecting light. In the present invention, as the counter electrode, glass or plastic on which a metal or a conductive oxide is deposited, or a metal thin film can be used.

The counter electrode is applied on the charge transfer layer in two ways: first, on the charge transfer layer, and first, on the semiconductor fine particle-containing layer. In any case, depending on the type of the counter electrode material and the type of the charge transfer layer, the counter electrode material can be appropriately formed on the charge transfer layer or the semiconductor fine particle-containing layer by a method such as application, lamination, vapor deposition, or bonding. For example, in the case of attaching a counter electrode, a substrate provided as a conductive layer can be attached by a method such as application, evaporation, or CVD of the above conductive material.

Further, a layer having other necessary functions such as a protective layer and an antireflection film can be provided on the conductive support or the counter electrode of the working electrode. When such layers are separated in function by multiple layers, simultaneous multilayer coating and sequential coating can be performed, but simultaneous multilayer coating is more preferable in terms of productivity. In the simultaneous multi-layer coating, the slide hopper method and the extrusion method are suitable in consideration of productivity and uniformity of film formation. In addition, these functional layers can be provided by a technique such as vapor deposition or pasting depending on the material.

In the photoelectrochemical cell of the present invention, it is preferable to seal the side of the cell with a polymer, an adhesive or the like in order to prevent deterioration of components and volatilization of the contents.

[0070]

The present invention will be described in more detail with reference to specific examples, but the present invention is not limited to the examples unless it exceeds the gist of the invention. 1. Preparation of Coating Solution Containing Titanium Dioxide Particles Barb's Journal of American Ceramic Society except that the autoclave temperature was 230 ° C.
In a manner similar to that described in Vol. 80, p. 3157, a titanium dioxide dispersion having a titanium dioxide concentration of 11% by weight was obtained. The average size of the obtained titanium dioxide particles was about 10 nm. To this dispersion was added 30% by weight of polyethylene glycol (molecular weight: 20,000, manufactured by Wako Pure Chemical Industries) based on titanium dioxide, and mixed to obtain a coating solution.

2. Preparation of titanium dioxide electrode adsorbing dye Transparent conductive glass coated with fluorine-doped tin oxide (manufactured by Nippon Sheet Glass, surface resistance is about 10Ω / cm ² )
This coating solution was applied to the conductive surface side of the sample with a doctor blade to a thickness of 140 μm, dried at 25 ° C. for 30 minutes, and then dried at 450 ° C. for 30 minutes in an electric furnace (Yamato Scientific muffle furnace FP-32).
Bake for a minute. The coating amount of titanium dioxide is 15 g / m ^2,
The film thickness was 10 μm.

After the glass was taken out and cooled, it was immersed in an ethanol solution of the dye shown in Table 1 (3 × 10 ^-4 mol / l) for 3 hours. The glass to which the dye was dyed was immersed in 4-tert-butylpyridine for 15 minutes, washed with ethanol, and air-dried. The coating amount of the dye was appropriately selected from the range of 0.1 to 10 mmol / m ² according to the type of the dye.

[0073]

[Table 1]

3. Preparation of Photoelectrochemical Cell A color-sensitized TiO ₂ electrode substrate (2 cm × 2 cm) prepared as described above was overlaid with platinum-evaporated glass of the same size (see FIG. 1). Next, by utilizing the capillary phenomenon in the gap between the two glasses, the solvent compound of the present invention shown in Table 1 was added to an electrolyte salt of 0.65 mol / liter and iodine 0.1 g.
Soak with the addition of 05 mol / l, TiO
_It was introduced into _two electrodes to obtain a photoelectrochemical cell.

The above steps were carried out in the same manner except that the combination of the dye, the solvent of the electrolyte and the salt was changed as shown in Table 1.

According to the present embodiment, as shown in FIG. 1, conductive glass 1 (having a conductive agent layer 2 provided on glass), TiO ₂ electrode 3, dye layer 4, electrolyte 5, platinum layer 6
Thus, a photoelectrochemical cell in which the glass and the glass 7 were sequentially laminated was produced.

4. Preparation of Photoelectrochemical Cell for Comparison In place of the compound of the present invention, a combination of a dye and an electrolyte composition using a conventional compound shown in Table 1 as a solvent was used. A photoelectrochemical cell for comparison was obtained in the same manner as in the method described in (1).

5. Measurement of Photoelectric Conversion Efficiency Simulated sunlight containing no ultraviolet light was generated by passing light of a 500 W xenon lamp (manufactured by Ushio) through a spectral filter (AM1.5 manufactured by Oriel) and a sharp cut filter (Kenko L-42). . The light intensity was 84 mW / cm ² . An alligator clip was connected to each of the conductive glass and the platinum-deposited glass of the above-mentioned photoelectrochemical cell, simulated sunlight was irradiated, and the generated electricity was measured by a current / voltage measuring device (Keisley SMU238 type).
The open-circuit voltage of the photoelectrochemical cell (Vo
c), short-circuit current density (Jsc), form factor (FF), and photoelectric conversion efficiency (η) and the rate of decrease in photoelectric conversion efficiency (η) after continuous irradiation for 240 hours are collectively shown in Table 2.

[0079]

[Table 2]

It can be seen that the use of the electrolyte of the present invention makes it possible to obtain a photoelectrochemical cell with less deterioration in photoelectric conversion characteristics as compared with the comparative example.

[0081]

By using the electrolyte of the present invention, a photoelectric conversion element and a photoelectrochemical cell having excellent photoelectric conversion characteristics and little deterioration of characteristics over time can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a photoelectrochemical cell prepared in an example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Conductive glass 2 Conductive agent layer 3 TiO ₂ electrode 4 Dye layer 5 Electrolyte 6 Platinum layer 7 Glass

Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H01M 14/00 C07C 255/13 5H032 // C07C 255/13 H01L 31/04 DF term (reference) 4H006 AA03 AB91 4J002 AA001 AB031 BB171 BC031 BG041 CF061 CF081 CG001 CH081 CM041 CN011 CN031 ET006 EU027 EU037 EU056 EU137 EU217 EV307 EV337 EZ007 FD097 GQ02 4J005 AA04 BD03 BD05 5F051 AA14 5G301 CA08 CA30 CD01 5H032 AA06 AS14CC

Claims (6)

[Claims] 1. An electrolyte containing a compound having at least one ether bond and at least two cyanoethyl groups. 2. The electrolyte of claim 1, wherein said compound is a compound of formula (I). Embedded image 3. The electrolyte according to claim 1, wherein said compound is represented by the formula (II). Embedded image [In the formula, L represents an n-valent alcohol residue. n represents an integer of 2 or more. ] 4. A photoelectric conversion element comprising an electrolyte-containing layer using the electrolyte according to claim 1, a conductive support, a semiconductor-containing layer coated on the conductive support, and a counter electrode. . 5. The photoelectric conversion device according to claim 4, wherein said semiconductor is a fine particle semiconductor sensitized by a dye. 6. A photoelectrochemical cell using the photoelectric conversion element according to claim 4.