JP2002373712A - Photoelectric conversion element and photocell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pigment sensitizing photoelectric conversion element using a substantially nonvolatile electrolytic composition and showing excellent stability for preservation and excellent conversion efficiency, and a photocell formed of the photoelectric conversion element. SOLUTION: The photoelectric conversion element having a charge transportation layer containing a salt represented by the general formula (I) and the photocell consisting of the element are disclosed. In the general formula (I), R1 and R2 each independently represent an alkyl group, an aryl group or an alkoxy group and may have a substituent; W1 represents C(=O), S(=O), S(=O)2 , P(=O), a triazolyl group or a tetrazolyl group, with the proviso that when W1 represents C(=O), S(=O) or S(=O)2 , n1 is 1; when W1 represents P(=O), n1 is 2; and when W1 represents a triazolyl group or a tetrazolyl group, n1 is 0 or 1; W2 represents C(=O), S(=O), P(=O), a triazolyl group or a tetrazolyl group, with the proviso that when W2 represents C(=O) or S(=O), n2 is 1; when W2 represents P(=O), n2 is 2; and when W2 represents a triazolyl group or a tetrazolyl group, n2 is 0 or 1; and Q<+> is an organic cation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoelectric conversion element and a photovoltaic cell, and more particularly, to a photoelectric conversion element having a light emitting layer composed of semiconductor fine particles sensitized with a dye and a charge transport layer containing a specific salt, and the photoelectric conversion element. The present invention relates to a photovoltaic cell including an element.

[0002]

2. Description of the Related Art Photoelectric conversion elements are used in various optical sensors, copying machines, photovoltaic devices and the like. Various types of photoelectric conversion elements have been put into practical use, such as those using metals, those using semiconductors, those using organic pigments and dyes, and those combining these. U.S. Pat.
No. 37, No. 5084365, No. 5350644, No. 5463057, No. 552
No. 5440, WO98 / 50393, JP-A-7-249790 and JP-T-10
JP-504521 discloses a photoelectric conversion element using semiconductor fine particles sensitized by a dye (hereinafter, referred to as a dye-sensitized photoelectric conversion element), and a material and a manufacturing technique for producing the same. Since an inexpensive semiconductor such as titanium oxide can be used as the semiconductor fine particles without purification to a high degree of purity, such a dye-sensitized photoelectric conversion element has an advantage that it can be manufactured at low cost. However,
In these dye-sensitized photoelectric conversion elements, since an electrolytic solution containing an organic solvent or water is used as an electrolyte, there is a problem that the elements are deteriorated by volatilization of the organic solvent or water. Journal of Electrochemical Society,
Vol. 143, No. 10, pp. 3099-3108, (1996) discloses a method for solving the above problem by using a substantially non-volatile molten salt electrolyte. However, the conversion efficiency of the photoelectric conversion element using the molten salt electrolyte is low, and improvement is desired.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a dye-sensitized photoelectric conversion device using a substantially non-volatile electrolyte composition and exhibiting excellent storage stability and conversion efficiency, and the photoelectric conversion device. An object is to provide a photovoltaic cell comprising an element.

[0004]

Means for Solving the Problems As a result of intensive studies in view of the above object, the present inventors have found that a photoelectric conversion element having a charge transport layer containing a specific salt exhibits excellent storage stability and conversion efficiency. And found the present invention.

That is, the photoelectric conversion element of the present invention has the following general formula:
It has a charge transport layer containing the salt represented by (I). Further, a photovoltaic cell of the present invention is characterized by comprising the photoelectric conversion element.

Embedded image In the general formula (I), R ₁ and R ₂ are each independently an alkyl group,
Represents an aryl group or an alkoxy group, and may have a substituent. W ₁ represents C (= O), S (= O), S (= O) ₂ , P (= O), a triazolyl group or a tetrazolyl group, and W ₁ is C (= O), S (= O)
Or S (= O) is n1 to represent a ₂ a 1, n1 when W ₁ represents a P (= O) is 2, the n1 when W ₁ represents a triazolyl group or a tetrazolyl group 0 or 1 is there. W ₂ is C (= O), S (=
O), P (= O) , represents a triazolyl group or tetrazolyl group, n2 when W ₂ represents C (= O) or S (= O) is 1, W ₂ is
N2 to represent a P (= O) is 2, the n2 when W ₂ represents a triazolyl group or tetrazolyl group is 0 or 1. Q ⁺ represents an organic cation.

In the present invention, by satisfying the following preferable conditions, a photoelectric conversion element and a photovoltaic cell exhibiting more excellent storage stability and conversion efficiency can be obtained. (1) W ₁ in the general formula (I) is preferably a _{S (= O) 2, W} 2 is
C (= O) is preferably from, W ₁ is S (= O) _2, and W ₂
Is particularly preferably C (= O). (2) R ₁ in the general formula (I) is particularly preferably a perfluoroalkyl group. (3) Q ⁺ in the general formula (I) is preferably an aromatic heterocyclic quaternary cation. (4) The salt represented by the general formula (I) preferably has a molecular weight of 1,000 or less.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [1] Photoelectric conversion element The photoelectric conversion element of the present invention usually has a conductive support, a layer of semiconductor fine particles having a dye adsorbed thereon, a charge transport layer and a counter electrode. Hereinafter, the layer of the semiconductor fine particles having the dye adsorbed thereon is referred to as a photosensitive layer.

The photoelectric conversion device of the present invention preferably has the structure shown in FIG.
As shown in FIG. 2, the conductive layer 10, the undercoat layer 60, the photosensitive layer 20, the charge transport layer 30, and the counter electrode conductive layer 40 are laminated in this order.
From the semiconductor fine particles 21 sensitized by the dye 22 and the liquid or gel charge transport material 23 that has permeated into the gaps between the semiconductor fine particles 21. Charge transport material 23 in photosensitive layer 20
Is usually the same as the material used for the charge transport layer 30.
Further, a substrate 50 may be provided as a base of the conductive layer 10 and / or the counter electrode conductive layer 40 in order to impart strength to the photoelectric conversion element. In the present invention, a layer composed of the conductive layer 10 and the optional substrate 50 is referred to as a “conductive support”, and a layer composed of the counter electrode conductive layer 40 and the optional substrate 50 is referred to as a “counter electrode”. Note that the conductive layer 10, the counter electrode conductive layer 40, and the substrate 50 in FIG. 1 may be a transparent conductive layer 10a, a transparent counter electrode conductive layer 40a, and a transparent substrate 50a, respectively. A photovoltaic cell is made for the purpose of generating electrical work by connecting this photoelectric conversion element to an external load (power generation), and an optical sensor is made for the purpose of sensing optical information. Of the photovoltaic cells, a case where the charge transport material is mainly composed of an ion transport material is particularly called a photoelectrochemical cell, and a case where the main purpose is to generate power by sunlight is called a solar cell.

In the photoelectric conversion device shown in FIG. 1, when the semiconductor fine particles are n-type, the light incident on the photosensitive layer 20 containing the semiconductor fine particles 21 sensitized by the dye 22 excites the dye 22 and the like. The high-energy electrons in the dyes 22 and the like passed to the conduction band of the semiconductor fine particles 21 and reach the conductive layer 10 by diffusion. At this time, molecules such as the dye 22 are oxidized. In the photovoltaic cell, the electrons in the conductive layer 10 return to an oxidized substance such as the dye 22 through the counter electrode conductive layer 40 and the charge transport layer 30 while working in an external circuit, and the dye 22 is regenerated. The photosensitive layer 20 functions as a negative electrode (photo anode), and the counter electrode conductive layer 40 functions as a positive electrode. Each layer boundary (for example, conductive layer 10
At the boundary between the photosensitive layer 20 and the photosensitive layer 20, the boundary between the photosensitive layer 20 and the charge transport layer 30, the boundary between the charge transport layer 30 and the counter electrode conductive layer 40, etc., even if the components of each layer are diffused and mixed with each other. Good. Hereinafter, each layer will be described in detail.

(A) Charge transport layer The charge transport layer comprises an electrolyte composition containing a salt represented by the following general formula (I). The electrolyte composition preferably further contains other iodide salts and iodine. Hereinafter, the salt represented by the general formula (I) is referred to as “salt (I)”.

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When the charge transport layer contains a salt (I), an iodide salt and iodine, an iodide ion and iodine (or a triiodide ion generated by a reaction between iodine and iodide ion) form a redox pair. The salt (I) serves as a medium for this redox couple. The electrolyte composition composed of these three components is preferably a uniform liquid at room temperature. The lower the viscosity of this electrolyte composition is, the more preferable it is.
It is 500 cp or less, particularly preferably 300 cp or less.

The electrolyte composition used for the charge transport layer is the above salt
It may contain a medium or an additive other than (I), an iodide salt and iodine. Also in this case, the electrolyte composition is preferably a uniform liquid at room temperature. Further, the electrolyte composition may contain a gel matrix. In this case, the electrolyte composition becomes a gel having no fluidity as a whole, but each component is preferably uniform.

The composition of the electrolyte composition is not particularly limited, but the mass ratio of the salt (I) is 1 to 60 with respect to the whole electrolyte composition.
%, More preferably from 10 to 30% by mass. The mass ratio of the iodide salt is preferably from 10 to 98% by mass, and more preferably from 40 to 90% by mass based on the whole electrolyte composition.
Is more preferable. Further, the concentration of iodine in the electrolyte composition is preferably 1 to 500 mmol / l, and 10 to 200 mmol / l.
More preferably, it is mmol / l. Hereinafter, the components used in the electrolyte composition, the gelation of the electrolyte composition, and the method of forming the charge transport layer will be described in detail.

(1) Salt (I) In the general formula (I), R ₁ and R ₂ are each independently an alkyl group (methyl, ethyl, isobutyl, n-dodecyl,
Cyclohexyl group), aryl group (phenyl group, tolyl group, naphthyl group, etc.) or alkoxy group (methoxy group,
Ethoxy group). R ₁ and R ₂ may have a substituent, examples of the substituent include a halogen atom, an alkyl group (cycloalkyl group, including a bicycloalkyl group), an alkenyl group (a cycloalkenyl group, a bicyclo Alkenyl group), alkynyl group, aryl group, heterocyclic group, cyano group, hydroxyl group, nitro group, carboxyl group, alkoxy group, aryloxy group, silyloxy group, acyloxy group, carbamoyloxy group, alkoxycarbonyloxy group, Aryloxycarbonyloxy group, amino group (including anilino group), acylamino group, aminocarbonylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfamoylamino group, alkylsulfonylamino group, arylsulfonylamino group, Mercap Group, alkylthio group, arylthio group, sulfamoyl group, sulfo group, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, acyl group, aryloxycarbonyl group, alkoxycarbonyl group, carbamoyl group, arylazo group, imide group Phosphino group, phosphinyl group, phosphinyloxy group, phosphinylamino group, silyl group and the like. R ₁ is preferably an alkyl group, more preferably a halogen-substituted alkyl group having 6 or less carbon atoms, and particularly preferably a perfluoroalkyl group having 6 or less carbon atoms. R ₂ is preferably an alkyl group,
Particularly preferred is an alkyl group having 6 or less carbon atoms.

In the general formula (I), W ₁ represents C (= O), S (= O), S (=
O) ₂ , P (= O), a triazolyl group or a tetrazolyl group, preferably S (= O) ₂ . N1 indicating the number of R ₁ is, W ₁ is
C (= O), a 1 to represent an S (= O) or _{S (= O) 2, W} 1 is P
When it represents (= O), it is 2, and when W ₁ represents a triazolyl group or a tetrazolyl group, it is 0 or 1. General formula (I)
In, W ₂ represents C (= O), S ( = O), P (= O), triazolyl group or tetrazolyl group, preferably a C (= O). N2 indicating the number of R ₂ is 1 when W ₂ represents C (= O) or S (= O), when W ₂ represents a P (= O) is 2, W ₂ is When it represents a triazolyl group or a tetrazolyl group, it is 0 or 1.

In the general formula (I), Q ⁺ represents an organic cation. Q
⁺ Examples of the tetraalkyl ammonium cations (tetramethylammonium cation, tetraethylammonium cation, tetrabutylammonium cation, trimethylbenzylammonium cation, etc.), trialkyl sulfonium cation (trimethylsulfonium cation, triethylsulfonium cation, etc.),
Tetraalkylphosphonium cation (such as tetraethylphosphonium cation), tetraarylphosphonium cation (such as tetraphenylphosphonium cation),
Aromatic quaternary cations (N-alkylpyridinium cations, 1,3-dialkylimidazolium cations, 1,
2-dialkylpyrazolium cation, dialkyltriazolium cation, N-alkyloxazolium cation, N-alkylthiazolium cation, 1,3-dialkylbenzimidazolium cation, pyrylium cation,
Thiopyrylium cation, etc.), non-aromatic heterocyclic quaternary cation (N, N-dialkylpyrrolidinium cation, N, N-
Dialkylpiperidinium cation, N, N-dialkylmorpholinium cation, etc.). These cations may have a substituent, and examples of the substituent include those described above as examples of the substituent on R ₁ and R ₂ . Q ⁺ is preferably an aromatic heterocyclic quaternary cation, more preferably an N-alkylpyridinium cation, a 1,3-dialkylimidazolium cation or a 1,2-dialkylpyrazolium cation, Particular preference is given to -dialkylimidazolium cations.

The salt (I) is usually solid or liquid. The salt (I) is preferably a liquid, so that the molecular weight of the salt (I) is preferably 1000 or less, more preferably 600 or less, particularly preferably 400 or less. If the molecular weight exceeds 1,000, the viscosity of the electrolyte composition increases, which is not preferable.

The salt (I) may be used alone or in combination of two or more. Further, a salt (I) prepared in advance may be added to the electrolyte composition, or an anion may be added.
The salt having (R ₁ ) _n1 -W ₁ -N ^-- W _2- (R ₂ ) _n2 and the salt having cation Q ⁺ may be mixed to generate the salt (I) in the system.
Specific examples of the salt (I) are shown below, but the present invention is not limited thereto.

[0019]

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[0020]

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[0021]

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[0022]

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[0023]

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(2) Iodide salt The iodide salt used in the present invention preferably has a melting point of 100 ° C.
And more preferably liquid at room temperature.
In the present invention, an iodide salt represented by any of the following general formulas (Ya), (Yb) and (Yc) can be preferably used.

[0025]

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In the general formula (Ya), Q _y1 represents an atomic group which forms a 5- or 6-membered aromatic cation together with a nitrogen atom. Q
_y1 is preferably constituted by an atom selected from the group consisting of a carbon atom, a hydrogen atom, a nitrogen atom, an oxygen atom and a sulfur atom. The 5-membered ring formed by Q _y1 is an oxazole ring, a thiazole ring, an imidazole ring, a pyrazole ring, an isoxazole ring, a thiadiazole ring, an oxadiazole ring,
It is preferably a triazole ring, an indole ring or a pyrrole ring, more preferably an oxazole ring, a thiazole ring or an imidazole ring, and particularly preferably an oxazole ring or an imidazole ring. The 6-membered ring formed by Q _y1 is a pyridine ring, a pyrimidine ring, a pyridazine ring,
It is preferably a pyrazine ring or a triazine ring, and particularly preferably a pyridine ring.

In the general formula (Yb), A _y1 represents a nitrogen atom or a phosphorus atom.

R _{y1 to} R in the general formulas (Ya), (Yb) and (Yc)
_y11 is each independently a substituted or unsubstituted alkyl group (preferably having 1 to 24 carbon atoms, and may be linear, branched, or cyclic; for example, a methyl group , Ethyl group, propyl group, isopropyl group, pentyl group, hexyl group, octyl group, 2-ethylhexyl group,
t-octyl group, decyl group, dodecyl group, tetradecyl group, 2-hexyldecyl group, octadecyl group, cyclohexyl group, cyclopentyl group, etc., or a substituted or unsubstituted alkenyl group (preferably having 2 to 24 carbon atoms) ,
It may be linear or branched and represents, for example, a vinyl group, an allyl group, etc.). R _{y1 to} R _y11 are each independently preferably an alkyl group having 2 to 18 carbon atoms or an alkenyl group having 2 to 18 carbon atoms, and particularly preferably an alkyl group having 2 to 6 carbon atoms.

Two or more of R _{y2 to} R _{y5 in} the general formula (Yb) may be linked to each other to form a non-aromatic ring containing A _y1, and R _y6 to R _y6 in the general formula (Yc) Two or more of R _y11 may be linked to each other to form a ring.

The above Q _y1 and R _{y1 to} R _y11 may have a substituent. Preferred examples of the substituent include a halogen atom (such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom), a cyano group, an alkoxy group (such as a methoxy group, an ethoxy group, a methoxyethoxy group and a methoxyethoxyethoxy group), and an aryloxy group. Group (phenoxy group, etc.), alkylthio group (methylthio group, ethylthio group, etc.), alkoxycarbonyl group (ethoxycarbonyl group, etc.), carbonate group (ethoxycarbonyloxy group, etc.), acyl group (acetyl group, propionyl group, benzoyl group) ), Sulfonyl group (methanesulfonyl group, benzenesulfonyl group, etc.), acyloxy group (acetoxy group, benzoyloxy group, etc.), sulfonyloxy group (methanesulfonyloxy group, toluenesulfonyloxy group, etc.), phosphonyl group (diethylphosphonyl) Group, etc.), Group (an acetylamino group, benzoylamino group, etc.), a carbamoyl group (N, N-
Dimethylcarbamoyl group), alkyl group (methyl group,
Ethyl group, propyl group, isopropyl group, cyclopropyl group, butyl group, 2-carboxyethyl group, benzyl group, etc., aryl group (phenyl group, toluyl group, etc.), heterocyclic group (pyridyl group, imidazolyl group, furanyl group) etc),
Examples include an alkenyl group (vinyl group, 1-propenyl group, etc.), a silyl group, a silyloxy group, and the like.

The iodide salt represented by any of the general formulas (Ya), (Yb) and (Yc) may form a multimer via Q _y1 and any of R _{y1 to} R _y11. .

The iodide salts may be used alone or as a mixture of two or more. Specific examples of the iodide salt preferably used in the present invention are shown below, but the present invention is not limited thereto.

[0033]

[Formula 10]

[0034]

[Formula 11]

[0035]

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[0036]

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[0037]

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[0038]

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(3) Additives For the purpose of lowering the viscosity of the electrolyte composition, a molten salt may be added. The molten salt is a salt that is liquid at room temperature, and examples of preferred molten salts that can be used in the present invention include salts in which the iodide ion is replaced with another anion as exemplified above as the preferred iodide salt. The anion replacing the iodide ion is preferably SCN ⁻ , BF ₄ ⁻ , PF ₆ ⁻ ,
_{^{ClO 4 -, (CF 3 SO}} 2) 2 N -, (CF 3 CF 2 SO 2) 2 N -, CH 3 SO 3 -, CF 3 SO
_{^{3 -, CF 3 COO -,}} Ph 4 B -, (CF 3 SO 2) 3 C - is like, more preferably _{^{SCN -, CF 3 SO 3 -}} , CF 3 COO -, (CF 3 SO 2) 2 N ^- or BF ₄ ^-
It is. This molten salt functions as a medium for a redox couple similarly to the salt (I). The addition amount of the molten salt is appropriately adjusted so that the mass ratio of the iodide salt does not become 10% by mass or less based on the whole electrolyte composition. The mass ratio of the molten salt is preferably 1 to 50% by mass, more preferably 5 to 50% by mass based on the whole electrolyte composition.
~ 30% by mass.

For the purpose of improving the photoelectric conversion characteristics of the photoelectric conversion element, a salt composed of an alkali metal cation or an alkaline earth metal cation and iodide ions (lithium iodide, sodium iodide, magnesium iodide, etc.) Alkali metal salts (CF ₃ COOLi, CF ₃ COONa, LiSCN, NaSCN
Etc.) may be added to the electrolyte composition. The mass ratio of these salts is preferably 0.02 to 2% by mass, more preferably 0.1 to 1% by mass, based on the whole electrolyte composition.

In order to increase the open voltage of the photoelectric conversion element,
Pyridine may be added to the electrolyte composition. The mass ratio of pyridines is preferably from 1 to 30% by mass based on the whole electrolyte composition.

(4) Solvent The electrolyte composition forming the charge transport layer preferably does not contain a solvent, but may contain a solvent. The solvent used in the electrolyte composition desirably exhibits excellent ionic conductivity by lowering the viscosity and improving the ion mobility or increasing the dielectric constant and improving the effective carrier concentration. As such a solvent, carbonate compounds such as ethylene carbonate and propylene carbonate,
Heterocyclic compounds such as 3-methyl-2-oxazolidinone, dioxane, ether compounds such as diethyl ether, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, chain ethers such as polypropylene glycol dialkyl ether, methanol, ethanol,
Alcohols such as ethylene glycol monoalkyl ether, propylene glycol monoalkyl ether, polyethylene glycol monoalkyl ether, and polypropylene glycol monoalkyl ether; polyhydric alcohols such as ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, and glycerin; acetonitrile; Examples thereof include nitrile compounds such as glutarodinitrile, methoxyacetonitrile, propionitrile, and benzonitrile; aprotic polar substances such as dimethyl sulfoxide and sulfolane; and water. These may be used as a mixture of two or more.

(5) Gelation In order to prevent volatilization and leakage of the electrolyte composition, to facilitate handling, etc., the electrolyte composition is added with a polymer, an oil gelling agent is added, polymerization containing polyfunctional monomers, polymer crosslinking. Gelation may be performed by a technique such as a reaction.

In the case of gelation by adding a polymer,
“Polymer Electrolyte Reviews-1 and 2” (JR Mac
Co-editing Callum and CA Vincent, ELSEVIER APPLIED SCIE
Compounds described in (NCE) can be used, and in particular, polyacrylonitrile and polyvinylidene fluoride can be preferably used.

When gelation is carried out by adding an oil gelling agent, an industrial science magazine (J. Chem. Soc. Japan, Ind. Che.
m. Sec.), 46, 779 (1943), J. Am. Chem. Soc., 111,
5542 (1989), J. Chem. Soc., Chem. Commun., 1993, 3
90, Angew. Chem. Int. Ed. Engl., 35, 1949 (1996), C
hem. Lett., 1996, 885, and J. Chem. Soc., Chem. Com.
mun., 1997, 545, and preferred compounds are compounds having an amide structure in the molecular structure. The gelling agent is usually used in an amount of 0.1 to 20% by mass relative to the whole charge transporting material,
Used by mass%. Further, the gelation method described in JP-A-2000-58140 is also applicable to the present invention.

When the electrolyte composition is gelled by a crosslinking reaction of the polymer, it is desirable to use a polymer having a crosslinkable reactive group and a crosslinking agent together. In this case, the crosslinkable reactive group is preferably an amino group or a nitrogen-containing heterocyclic group (pyridine ring, imidazole ring, thiazole ring, oxazole ring, triazole ring, morpholine ring,
A group containing a piperidine ring, a piperazine ring or the like), and the crosslinking agent is preferably a bifunctional or higher functional reagent capable of electrophilic reaction with respect to a nitrogen atom (an alkyl halide, an aralkyl halide, a sulfonic acid ester, an acid anhydride, Acid chloride,
Isocyanate compounds, α, β-unsaturated sulfonyl compounds, α, β-unsaturated carbonyl compounds, α, β-unsaturated nitrile compounds, etc.). JP 2000-17076 and JP 2000
The crosslinking technique described in -86724 is also applicable to the present invention.

(6) Formation of charge transport layer Regarding the method of forming the charge transport layer, two methods can be considered. One is a method in which a counter electrode is first stuck on the photosensitive layer, and a liquid electrolyte composition is sandwiched in the gap. The other is a method in which a charge transport layer is provided directly on the photosensitive layer, and a counter electrode is subsequently provided.

In the case of the former method, as a method of sandwiching the electrolyte composition, a normal pressure process utilizing a capillary phenomenon by immersion or the like, or a vacuum process of replacing the gas phase in the gap with a liquid phase at a pressure lower than normal pressure is used. Available.

In the case of the latter method, when using a liquid electrolyte composition, a counter electrode is provided in an undried state to take measures to prevent liquid leakage at the edge portion. When a gel electrolyte composition is used, there is a method of applying the composition in a wet manner and solidifying it by a method such as polymerization. In this case, a counter electrode can be provided after drying and fixing.

(B) Conductive Support The conductive support comprises (1) a single layer of a conductive layer, or (2) two layers of a conductive layer and a substrate. In the case of (1), a material that maintains sufficient strength and sealing properties as a conductive layer, for example, a metal material (platinum, gold, silver, copper, zinc, titanium, aluminum,
Alloys containing these, etc.) can be used. In the case of (2), a substrate having a conductive layer containing a conductive agent on the photosensitive layer side can be used. Preferred conductive agents include metals (platinum, gold, silver, copper, zinc, titanium, aluminum, rhodium, indium, alloys containing them, etc.), carbon, and conductive metal oxides (indium-tin composite oxide, tin oxide Which is doped with fluorine or antimony). The thickness of the conductive layer is preferably about 0.02 to 10 μm.

The lower the surface resistance of the conductive support, the better. A preferred range of the surface resistance is 100 Ω / □ or less, more preferably 40 Ω / □ or less. Although the lower limit of the surface resistance is not limited, it is usually about 0.1Ω / □.

When light is irradiated from the conductive support side, the conductive support is preferably substantially transparent.
Substantially transparent means that the light transmittance is 10% or more, preferably 50% or more, and more preferably 70% or more.

As the transparent conductive support, it is preferable that a transparent conductive layer made of a conductive metal oxide is formed on the surface of a transparent substrate such as glass or plastic by coating or vapor deposition. In particular, a conductive glass in which a conductive layer made of fluorine-doped tin dioxide is deposited on a transparent substrate made of low-cost soda-lime float glass is preferable.
To obtain a flexible photoelectric conversion element at low cost, it is preferable to use a transparent polymer film provided with a conductive layer. Transparent polymer film materials include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndiotactic polystyrene (SPS), polyphenylene sulfide (PPS), and polycarbonate (P
C), polyarylate (PAr), polysulfone (PS)
F), polyester sulfone (PES), polyimide (P
I), polyetherimide (PEI), cyclic polyolefin, brominated phenoxy resin and the like can be used. In order to ensure sufficient transparency, the amount of the conductive metal oxide to be applied is 0.01 to 10 per m ² of a glass or plastic support.
It is preferably 0 g.

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

(C) Photosensitive Layer In the photosensitive layer, the semiconductor acts as a photoreceptor, absorbs light to separate charges, and generates electrons and holes. In a dye-sensitized semiconductor, light absorption and the resulting generation of electrons and holes mainly occur in the dye, and semiconductor fine particles have a role of receiving and transmitting the electrons (or holes). The semiconductor used in the present invention is preferably an n-type semiconductor in which a conductor electron becomes a carrier under photoexcitation and gives an anode current.

(1) Semiconductors Semiconductors include simple semiconductors such as silicon and germanium, III-V group compound semiconductors, metal chalcogenides (oxides, sulfides, selenides, composites thereof, etc.), and perovskite structures. (Such as strontium titanate, calcium titanate, sodium titanate, barium titanate, and potassium niobate) can be used.

Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium,
Hafnium, strontium, indium, cerium,
Examples include oxides of yttrium, lanthanum, vanadium, niobium or tantalum, sulfides of cadmium, zinc, lead, silver, antimony or bismuth, selenides of cadmium or lead, tellurides of cadmium, and the like. Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, selenides of gallium-arsenic or copper-indium, and sulfides of copper-indium. Further, M _x O _y S _z or M _1x M _2y O _z (M, M ₁ and M ₂ are metal elements, O is oxygen, x, y and z are the number of combinations whose valence is neutral) Compounds such as are also preferably used.

Preferred examples of the semiconductor used in the present invention include Si, TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, Z
nS, PbS, Bi ₂ S ₃ , CdSe, CdTe, SrTiO ₃ , GaP, InP, GaA
s, CuInS ₂ , CuInSe _{2 and the} like, more preferably TiO ₂ , Zn
_{O, SnO 2, Fe 2 O} 3, WO 3, Nb 2 O 5, CdS, PbS, CdSe, SrTi
O ₃ , InP, GaAs, CuInS ₂ or CuInSe ₂ , particularly preferably TiO ₂ or Nb ₂ O ₅ , most preferably TiO ₂ . TiO ₂ containing 70% or more of anatase crystal among TiO ₂
Is preferred, and TiO ₂ of 100% anatase type crystal is particularly preferred. It is also effective to dope a metal for the purpose of increasing electron conductivity in these semiconductors. The metal to be doped is preferably a divalent or trivalent metal. It is also effective to dope the semiconductor with a monovalent metal for the purpose of preventing a reverse current from flowing from the semiconductor to the charge transport layer.

The semiconductor used in the present invention may be a single crystal or a polycrystal, but is preferably a polycrystal from the viewpoints of production cost, securing of raw materials, energy payback time and the like, and the layer of semiconductor fine particles is particularly preferably a porous film. preferable. Also,
A part may include an amorphous portion.

The particle size of the semiconductor fine particles is generally on the order of nm to μm, but the average particle size of the primary particles obtained from the diameter when the projected area is converted into a circle is preferably from 5 to 200 nm, and from 8 to 200 nm. 100 nm is more preferred. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 30 μm. Two or more types of fine particles having different particle size distributions may be mixed. In this case, the average size of the small particles is preferably 25 nm or less, more preferably 10 nm or less.
For the purpose of improving the light capture rate by scattering incident light, it is also preferable to mix semiconductor particles having a large particle diameter, for example, about 100 to 300 nm.

Two or more different types of semiconductor fine particles may be mixed and used. When two or more kinds of semiconductor fine particles are used in combination, one of them is preferably TiO ₂ , ZnO, Nb ₂ O ₅ or SrTiO ₃ . The other is preferably SnO ₂ , Fe ₂ O ₃ or WO ₃ . More preferred combinations include combinations of ZnO and SnO ₂ , ZnO and WO ₃ , ZnO and SnO ₂ and WO _{3, and the} like. When two or more kinds of semiconductor fine particles are used as a mixture, the respective particle diameters may be different. In particular, a combination in which the above TiO ₂ , ZnO, Nb ₂ O ₅ or SrTiO ₃ has a large particle diameter and SnO ₂ , Fe ₂ O ₃ or WO ₃ is small is preferable. Preferably, particles having a large particle diameter are 100 nm or more, and particles having a small particle diameter are 15 nm or less.

As for the method of producing semiconductor fine particles, there are “Sol-gel method science” by Agaku Sakuhana, Agne Shofusha (1998), and “Thin film coating technology by sol-gel method” by the Technical Information Association (1995). ) And Tadao Sugimoto's "Synthesis of Monodisperse Particles and Control of Size and Morphology by New Synthetic Gel-Sol Method", Materia, Vol. 35, No. 9, 1012-1018.
The gel-sol method described on page (1996) is preferred. Also
A method developed by Degussa to produce an oxide by high-temperature hydrolysis of a chloride in an oxyhydrogen salt can also be preferably used.

When the semiconductor fine particles are titanium oxide, any of the above-mentioned sol-gel method, gel-sol method, and high-temperature hydrolysis method in chloride oxyhydrogen salt are preferable. Applied Technology "Gihodo Publishing (1997)
The sulfuric acid method or chlorine method described in (1) can also be used. Further, as a sol-gel method, Barbe et al.
American Ceramic Society, Vol. 80, No. 12
No., pages 3157-3171 (1997) and Burnside
La no Chemistry of Materials, Vol. 10, No. 9
Pp. 2419-2425 are also preferred.

(2) Semiconductor fine particle layer In order to coat semiconductor fine particles on a conductive support, in addition to the method of applying a dispersion or colloidal solution of semiconductor fine particles on a conductive support, the above-mentioned sol-gel A method can also be used. In consideration of mass production of photoelectric conversion elements, physical properties of semiconductor fine particle liquid, flexibility of a conductive support, and the like, a wet film forming method is relatively advantageous. Typical examples of the wet film forming method include a coating method, a printing method, an electrolytic deposition method, and an electrodeposition method. In addition, a method of oxidizing a metal, a method of depositing a metal solution in a liquid phase by ligand exchange (LPD method), a method of depositing by sputtering, a CVD method, or a metal that thermally decomposes on a heated substrate An SPD method in which an oxide precursor is sprayed to form a metal oxide can also be used.

As a method of preparing a dispersion of semiconductor fine particles, in addition to the above-mentioned sol-gel method, a method of crushing in a mortar, a method of dispersing while pulverizing using a mill, and a method of preparing a semiconductor in a solvent when synthesizing. And then use as it is as fine particles.

As the dispersion medium, water and various organic solvents (eg, methanol, ethanol, isopropyl alcohol, citronellol, terpineol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.) can be used. At the time of dispersion, a polymer such as polyethylene glycol, hydroxyethylcellulose, carboxymethylcellulose, a surfactant, an acid, a chelating agent and the like may be used as a dispersion aid, if necessary. By changing the molecular weight of polyethylene glycol, the viscosity of the dispersion can be adjusted, and a semiconductor layer that is hard to peel off can be formed,
It is preferable to add polyethylene glycol because the porosity of the semiconductor layer can be controlled.

The application method includes a roller method and a dipping method as an application system, an air knife method, a blade method, and the like as a metering system.
No. 589, the wire bar method disclosed in U.S. Pat.
The slide hopper method, extrusion method, curtain method and the like described in JP-A Nos. 94, 2761419, 2761791 and the like are preferable. As a general-purpose machine, a spin method or a spray method is also preferable. As the wet printing method, intaglio printing, rubber printing, screen printing and the like are preferable, including three major printing methods of letterpress, offset and gravure. From these, a film forming method may be selected according to the liquid viscosity and the wet thickness.

The semiconductor fine particle layer is not limited to a single layer, but a multi-layered dispersion of semiconductor fine particles having different particle diameters may be applied, or semiconductor fine particles of different types (or different binders and additives) may be used.
Can be applied in multiple layers.
Multilayer coating is effective even when the film thickness is insufficient by one coating.

In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer) is increased, the amount of dye carried per unit projected area is increased, so that the light capture rate is increased, but the diffusion distance of generated electrons is increased. Therefore, the loss due to charge recombination also increases. Therefore, the preferred thickness of the semiconductor fine particle layer is
It is 0.1-100 μm. When used for a photovoltaic cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, more preferably 2 to 25 μm. The coating amount per support 1 m ² of the semiconductor fine particles 0.
5 to 100 g is preferable, and 3 to 50 g is more preferable.

After applying the semiconductor fine particles on the conductive support, the semiconductor fine particles are brought into electronic contact with each other.
Heat treatment is preferably performed to improve the strength of the coating film and the adhesion to the support. A preferred heating temperature range is from 40 ° C to 700 ° C, more preferably from 100 ° C to 600 ° C. The heating 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 it causes deterioration of the support. From the viewpoint of cost, the temperature is preferably as low as possible (for example, 50 ° C. to 350 ° C.). Low temperature can be achieved by heat treatment in the presence of small semiconductor particles of 5 nm or less, mineral acids, and metal oxide precursors.
Further, the irradiation can be performed by irradiation of ultraviolet rays, infrared rays, microwaves, or the like, or by applying an electric field or ultrasonic waves. At the same time, for the purpose of removing unnecessary organic substances and the like, it is preferable to use a combination of heating, decompression, oxygen plasma treatment, pure water cleaning, solvent cleaning, gas cleaning and the like in addition to the above irradiation and application, as appropriate.

After the heat treatment, for example, chemical plating using an aqueous solution of titanium tetrachloride may be performed to increase the surface area of the semiconductor fine particles, increase the purity near the semiconductor fine particles, and increase the efficiency of electron injection from the dye into the semiconductor fine particles. Electrochemical plating using an aqueous solution of titanium trichloride may be performed. In order to prevent a reverse current from flowing from the semiconductor fine particles to the charge transport layer, it is also effective to adsorb an organic substance having low electron conductivity other than the dye on the particle surface. The organic substance to be adsorbed preferably has a hydrophobic group.

The semiconductor fine particle layer preferably has a large surface area so that many dyes can be adsorbed. The surface area in a state where the layer of the semiconductor fine particles is applied on the support is preferably 10 times or more, and more preferably 100 times or more with respect to the projected area. The upper limit is not particularly limited, but is usually about 1000 times.

(3) Dye The sensitizing dye used in the photosensitive layer may be any compound that has absorption in the visible or near-infrared region and can sensitize a semiconductor. Examples thereof include metal complex dyes and methine dyes. And a porphyrin dye or a phthalocyanine dye. Further, in order to widen the wavelength range of photoelectric conversion as much as possible and increase the conversion efficiency, two or more dyes can be used in combination or in combination. In this case, the pigments to be used or mixed and the ratio thereof can be selected so as to match the wavelength range and the intensity distribution of the target light source.

Such a dye is formed by a suitable interlocking group having an adsorption ability to the surface of the semiconductor fine particles.
It is preferable to have Preferred linking groups include
-COOH group, -OH group, -SO ₂ H group, -P (O) (OH) ₂ group and -OP (O) (O
H) acidic group such as a ₂ groups, as well as oxime, dioxime,
Π-conducting chelating groups such as hydroxyquinoline, salicylates and α-keto enolates. Among them, a —COOH group, a —P (O) (OH) ₂ group and a —OP (O) (OH) ₂ group are particularly preferable. These groups may form a salt with an alkali metal or the like, or may form an inner 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. Hereinafter, preferred sensitizing dyes used in the photosensitive layer will be specifically described.

(A) Metal Complex Dye When the dye is a metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye or a ruthenium complex dye is preferred, and a ruthenium complex dye is particularly preferred. Ruthenium complex dyes include, for example, U.S. Pat.
4537, 5084365, 5350644, 5463057, 5
525440, JP-A-7-249790, JP-T10-504512, WO9
8/50393 and JP-A-2000-26487.

The ruthenium complex dye used in the present invention is preferably represented by the following general formula (II): (A ₁ ) _p Ru (Ba) (Bb) (Bc) (II) In the general formula (II), A ₁ represents a mono- or bidentate ligand, preferably Cl, SCN, H ₂ O, Br,
It is a ligand selected from the group consisting of I, CN, NCO, SeCN, β-diketone derivative, oxalic acid derivative and dithiocarbamic acid derivative. p is an integer of 0 to 3. Ba, Bb and Bc each independently represent an organic ligand represented by any of the following formulas B-1 to B-10.

[0077]

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In the formulas B-1 to B-10, R ₃ represents a hydrogen atom or a substituent, and examples of the substituent include a halogen atom,
A substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, a substituted or unsubstituted aralkyl group having 7 to 12 carbon atoms, a substituted or unsubstituted aryl group having 6 to 12 carbon atoms, the above-mentioned acidic group ( These acidic groups may form a salt) and chelating groups. Here, the alkyl portion of the alkyl group and the aralkyl group may be linear or branched,
The aryl group and the aryl moiety of the aralkyl group may be monocyclic or polycyclic (condensed ring, ring assembly). Ba, Bb and B-
c may be the same or different, and any one or two
One.

Specific examples of preferable metal complex dyes are shown below, but the present invention is not limited thereto.

[0080]

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[0081]

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(B) Methine Dye Preferred methine dyes usable in the present invention are polymethine dyes such as cyanine dyes, merocyanine dyes, and squarylium dyes. Examples of preferred polymethine dyes, JP-A-11-35836, JP-A-11-67285, JP-A-11-8
No. 6916, JP-A-11-97725, JP-A-11-158395, JP-A-11-163378, JP-A-11-214730, JP-A-11-214731
No., JP-A-11-238905, JP-A-2000-26487, European Patent 8
The dyes described in Nos. 92411, 911841, and 991092 can be mentioned. Specific examples of preferred methine dyes are shown below.

[0083]

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[0084]

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(4) Adsorption of Dye on Semiconductor Fine Particles The dye is adsorbed on the semiconductor fine particles by immersing a conductive support having a well-dried semiconductor fine particle layer in a dye solution or by dissolving the dye solution in the semiconductor fine particles. A method of applying to a layer can be used. In the former case, a dipping method, a dipping method, a roller method, an air knife method, or the like can be used. In the case of the immersion method, the dye may be adsorbed at room temperature or disclosed in JP-A-7-24.
It may be carried out by heating and refluxing as described in 9790. Examples of the latter coating method include a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method. Alternatively, a dye may be applied in the form of an image by an inkjet method or the like, and the image itself may be used as a photoelectric conversion element.

Solvents used for the dye solution (adsorption solution) are preferably alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.) and nitriles (acetonitrile, propionitrile, 3-methoxypropionitrile, etc.) , Nitromethane, halogenated hydrocarbons (dichloromethane, dichloroethane, chloroform, chlorobenzene, etc.), ethers (diethyl ether, tetrahydrofuran, etc.), dimethyl sulfoxide, amides (N,
N-dimethylformamide, N, N-dimethylacetamide, etc.), N-methylpyrrolidone, 1,3-dimethylimidazolidinone, 3-methyloxazolidinone, esters (ethyl acetate, butyl acetate, etc.), carbonates ( Diethyl carbonate, ethylene carbonate, propylene carbonate, etc.), ketones (acetone, 2-butanone, cyclohexanone, etc.), hydrocarbons (hexane, petroleum ether, benzene, toluene, etc.) or a mixed solvent thereof.

The total amount of the dye adsorbed is preferably 0.01 to 100 mmol per unit area (1 m ² ) of the semiconductor fine particle layer. The amount of the dye adsorbed on the semiconductor fine particles is preferably in the range of 0.01 to 1 mmol per 1 g of the semiconductor fine particles. With such an amount of dye adsorbed, a sufficient sensitizing effect in the semiconductor can be obtained. On the other hand, if the amount of the dye is too 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. In order to increase the amount of the dye adsorbed, it is preferable to perform a heat treatment before the adsorption. After the heat treatment, the temperature of the semiconductor fine particle layer is not returned to room temperature to avoid water adsorption on the surface of the semiconductor fine particles, and the temperature of the semiconductor fine particle layer is 60 to 150 ° C.
It is preferable to carry out the dye adsorption operation quickly between the steps.

In order to reduce the interaction such as aggregation between the dyes, a colorless compound having surface active properties may be added to the dye adsorbing solution and co-adsorbed to the semiconductor fine particles. Examples of such colorless compounds include steroid compounds having a carboxyl group or a sulfonic acid group (such as chenodeoxycholic acid and taurodeoxycholic acid), and the following sulfonates.

[0089]

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It is preferable to remove unadsorbed dye by washing immediately after the adsorption. The washing is preferably performed using a wet washing tank with a polar solvent such as acetonitrile, an organic solvent such as an alcohol solvent, or the like.

After the dye is adsorbed, the surface of the semiconductor fine particles may be treated with amines or quaternary ammonium salts. Preferred amines include pyridine, 4-t-butylpyridine, polyvinylpyridine and the like. Preferred quaternary ammonium salts include tetrabutylammonium iodide, tetrahexylammonium iodide and the like. These may be used by dissolving in an organic solvent,
In the case of a liquid, it may be used as it is.

(D) Counter electrode Like the above-mentioned conductive support, the counter electrode may have a single-layer structure of a counter electrode conductive layer made of a conductive material, or may be composed of a counter electrode conductive layer and a support substrate. Examples of the conductive material used for the counter electrode conductive layer include metals (platinum, gold, silver, copper, aluminum, magnesium, indium, etc.), carbon, and conductive metal oxides (indium-tin composite oxide, fluorine-doped tin oxide, etc.). Is mentioned. Among them, platinum, gold,
Silver, copper, aluminum and magnesium can be preferably used. The support substrate used for the counter electrode is preferably a glass substrate or a plastic substrate, and the above conductive material is applied or vapor-deposited on the substrate. The thickness of the counter electrode conductive layer is not particularly limited, but is preferably 3 nm to 10 μm. The lower the surface resistance of the counter electrode conductive layer, the better. The preferred range of the surface resistance is 50 Ω / □ or less, more preferably 20 Ω / □.
/ □ or less.

Since light may be irradiated from one or both of the conductive support and the counter electrode, at least one of the conductive support and the counter electrode is substantially transparent in order for the light to reach the photosensitive layer. I just need. From the viewpoint of improving the power generation efficiency, it is preferable that the conductive support is transparent and light is incident from the conductive support side. In this case, the counter electrode preferably has a property of reflecting light. As such a counter electrode, glass or plastic on which a metal or a conductive oxide is deposited,
Alternatively, a metal thin film can be used.

As the counter electrode, a conductive agent is applied directly on the charge transport layer,
Plating or vapor deposition (PVD, CVD) may be performed, or a conductive layer side of a substrate having a conductive layer may be attached. Further, as in the case of the conductive support, it is preferable to use a metal lead for the purpose of reducing the resistance of the counter electrode, particularly when the counter electrode is transparent. In addition, the preferable material and the installation method of the metal lead, the decrease of the incident light amount by the installation of the metal lead, and the like are the same as those of the conductive support.

(E) Other layers In order to prevent a short circuit between the counter electrode and the conductive support, a dense semiconductor thin film layer is previously coated between the conductive support and the photosensitive layer as an undercoat layer. Is preferred. The method of preventing a short circuit by using the undercoat layer is particularly effective when an electron transporting material or a hole transporting material is used for the charge transporting layer. Undercoat layer is preferably _{TiO 2, SnO 2, Fe 2} O 3, WO 3, ZnO or Nb ₂
Consist O _5, more preferably consists of TiO _2. The undercoat layer can be applied by, for example, a spray pyrolysis method described in Electrochim. Acta, 40, 643-652 (1995), a sputtering method, or the like. The preferred thickness of the undercoat layer is 5 to 1000 nm, more preferably 10 to 500 nm.

A functional layer such as a protective layer or an antireflection layer may be provided on the outer surface of one or both of the conductive support serving as an electrode and the counter electrode, between the conductive layer and the substrate or in the middle of the substrate. Good. For forming these functional layers, a coating method, a vapor deposition method, a sticking method, or the like can be used depending on the material.

(F) Specific Example of Internal Structure of Photoelectric Conversion Element As described above, the internal structure of the photoelectric conversion element can take various forms according to the purpose. When roughly divided into two, a structure that allows light to enter from both sides and a structure that allows light to enter from only one side are possible. 2 to 9 exemplify an internal structure of a photoelectric conversion element which can be preferably applied to the present invention.

The structure shown in FIG. 2 has a structure in which the photosensitive layer 20 and the charge transport layer 30 are interposed between the transparent conductive layer 10a and the transparent counter electrode conductive layer 40a. Has become. In the structure shown in FIG. 3, a metal lead 11 is partially provided on a transparent substrate 50a, a transparent conductive layer 10a is provided thereon, and an undercoat layer 60, a photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 are sequentially formed. Is provided, and further, a support substrate 50 is arranged,
Light is incident from the conductive layer side. The structure shown in FIG. 4 has the conductive layer 10 on the support substrate 50 and the undercoat layer 60.
A transparent substrate 50a provided with a charge transport layer 30 and a transparent counter electrode conductive layer 40a further provided with a metal lead 11 in a part thereof is disposed with the metal lead 11 side inside. , And light is incident from the counter electrode side. The structure shown in FIG. 5 has a structure in which a metal lead 11 is partially provided on a transparent substrate 50a, and a transparent conductive layer 10a (or 40a) is further provided. And a structure in which light is incident from both sides. The structure shown in FIG. 6 includes a transparent conductive layer 10a, an undercoat layer 60,
A photosensitive layer 20, a charge transport layer 30, and a counter electrode conductive layer 40 are provided, and a support substrate 50 is disposed thereon. In this structure, light enters from the conductive layer side. The structure shown in FIG.
Having the conductive layer 10 thereon, providing the photosensitive layer 20 via the undercoat layer 60, further providing the charge transport layer 30 and the transparent counter electrode conductive layer 40a,
A transparent substrate 50a is disposed thereon, and has a structure in which light is incident from the counter electrode side. The structure shown in FIG. 8 includes a transparent conductive layer 10a on a transparent substrate 50a, a photosensitive layer 20 provided with an undercoat layer 60 interposed therebetween, and further includes a charge transport layer 30 and a transparent counter electrode conductive layer 40.
a, on which a transparent substrate 50a is arranged,
Light is incident from both sides. In the structure shown in FIG. 9, the conductive layer 10 is provided on the support substrate 50, the photosensitive layer 20 is provided through the undercoat layer 60, and the solid charge transport layer 30 is further provided.
A part thereof has a counter electrode conductive layer 40 or a metal lead 11, and has a structure in which light is incident from the counter electrode side.

[2] Photocell A photocell of the present invention is one in which the photoelectric conversion element of the present invention is made to work with an external load. Among photovoltaic cells, the case where the charge transport material is mainly composed of an ion transport material as in the present invention is particularly called a photoelectrochemical cell,
The case where the main purpose is power generation by sunlight is called a solar cell.

The side surface of the photovoltaic cell is preferably sealed with a polymer, an adhesive or the like in order to prevent deterioration of components and volatilization of the contents. The external circuit itself connected to the conductive support and the counter electrode via the lead may be a known one.

When the photoelectric conversion device of the present invention is applied to a solar cell, the structure inside the cell is basically the same as that of the above-mentioned photoelectric conversion device. Further, the dye-sensitized solar cell using the photoelectric conversion element of the present invention can have a module structure basically similar to a conventional solar cell module. The solar cell module generally has a structure in which cells are formed on a supporting substrate such as a metal and a ceramic, and the cells are covered with a filling resin or a protective glass or the like, and light is taken in from the opposite side of the supporting substrate. It is also possible to adopt a structure in which a transparent material such as tempered glass is used for the support substrate, a cell is formed thereon, and light is taken in from the transparent support substrate side. Specifically, module structures called super straight type, substrate type, potting type,
A substrate-integrated module structure and the like used in an amorphous silicon solar cell and the like are known, and the module structure of the dye-sensitized solar cell of the present invention can be appropriately selected depending on the purpose of use, the place of use, and the environment. More specifically,
It is preferable to use the structure and embodiment described in 68892.

[0102]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples, but the present invention is not limited thereto.

1. Preparation of Titanium Oxide Dispersion 62 g of tetraisopropyl orthotitanate (manufactured by Wako Pure Chemical Industries, Ltd.) was added at once to a mixed solution of 360 g of water and 12 g of acetic acid, and the mixture was stirred for 1 hour. . 6 ml at 80 ° C
Of concentrated nitric acid was added, and the mixture was further stirred for 4 hours. 50 ml of the obtained titanium oxide sol was transferred to a stainless steel autoclave, stirred at 240 ° C. for 16 hours, and then centrifuged at 15,000 rpm for 30 minutes. Next, the supernatant was removed by decantation, 0.3 g of polyethylene glycol (molecular weight: 20,000, manufactured by Wako Pure Chemical Industries) and 11 g of water were added, and the mixture was stirred well. Further, 1 g of ethanol and 0.4 ml of concentrated nitric acid were added, and titanium oxide was dispersed. A liquid was obtained. The titanium oxide content of this titanium oxide dispersion is
It was 15% by mass. The average particle size of the titanium oxide particles in the obtained titanium oxide dispersion was determined by X-ray diffraction, and was found to be 16 nm.

2. Preparation of dye-adsorbed titanium oxide electrode Transparent conductive glass coated with fluorine-doped tin oxide (Nippon Sheet Glass, surface resistance: about 10Ω / cm ² )
The above titanium oxide dispersion was applied to the conductive surface side of the substrate using a doctor blade, dried at 25 ° C. for 30 minutes, and then heated at 450 ° C. using an electric furnace (“Muffle Furnace FP-32” manufactured by Yamato Scientific Co., Ltd.).
Firing was performed for 30 minutes to obtain a titanium oxide electrode. The amount of titanium oxide applied per unit area was determined from the change in mass before and after firing, and the amount applied was 16.2 g / m ² . The obtained titanium oxide electrode was placed on a dye adsorption solution containing the following dye RA at 25 ° C for 16 hours.
It was immersed for a time and washed sequentially with ethanol and acetonitrile to prepare a dye-adsorbed titanium oxide electrode. The dye adsorbing solution is composed of the dye RA and a mixed solvent of ethanol, t-butanol and acetonitrile (ethanol: t-butanol: acetonitrile = 1: 1: 2 (volume ratio)), and the concentration of the dye RA in the dye adsorbing solution. Was set to 0.3 mmol / l.

[0105]

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3. Preparation of photoelectric conversion element Dye-adsorbed titanium oxide electrode (2 cm × 2 c) obtained as described above
m) was overlaid with platinum-evaporated glass of the same size. Next, an electrolyte composition (1,3-dimethylimidazolium iodide (0.65 mol
l / l), iodine (0.05 mol / l) and t-butylpyridine (0.
(1 mol / l) acetonitrile solution) was impregnated and introduced into a titanium oxide electrode to obtain a photoelectric conversion element C-1 for comparison.

The above dye-adsorbed titanium oxide electrode (2 cm × 2 c
m) was coated with an electrolyte composition having the composition shown in Table 1 below,
In a dry room, allowed to stand at 60 ° C. under reduced pressure for 16 hours to allow the electrolyte composition to sufficiently permeate the electrodes, and then overlaid platinum-deposited glass of the same size on this, and a photoelectric conversion element for comparison
D-1 to D-4, and the photoelectric conversion element D of the present invention using the salt (I)
-5 to D-14 were prepared. These photoelectric conversion elements include a conductive glass 1 (a conductive layer 3 provided on a glass 2), a dye-adsorbed titanium dioxide layer 4, a charge transport layer 5, a platinum layer 6, and a conductive glass 1, as shown in FIG. It has a structure in which the glass 7 is laminated in order. Iodide salt (A) described in Table 1 and
The structures of (C) and the molten salts (B), (D) and (E) are shown below.

[0108]

[Table 1]

[0109]

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4. Measurement of Photoelectric Conversion Efficiency Simulated sunlight was generated by passing light of a 500 W xenon lamp (made by Ushio) through a spectral filter ("AM1.5" made by Oriel). The intensity of this simulated sunlight is
It was 88 mW / cm ² . A silver paste was applied to the end of the conductive glass of each photoelectric conversion element C-1 and D-1 to D-14 to form a negative electrode,
The negative electrode and platinum-deposited glass (positive electrode) were connected to a current / voltage measuring device (Keithley SMU238 type). The current-voltage characteristics were measured while simulating sunlight was vertically irradiated on each photoelectric conversion element, and the photoelectric conversion efficiency was determined. Photoelectric conversion elements C-1 and D for comparison
Table 2 shows initial characteristics (short-circuit current density, open-circuit voltage, and photoelectric conversion efficiency) of -1 to D-4 and photoelectric conversion elements D-5 to D-14 of the present invention. Further, in order to evaluate the storage stability of each photoelectric conversion element, after leaving each photoelectric conversion element at 25 ° C. for 7 days,
Similarly, the photoelectric conversion efficiency was measured. The photoelectric conversion efficiency after standing for 7 days and the maintenance ratio of the photoelectric conversion efficiency (photoelectric conversion efficiency after standing for 7 days / initial photoelectric conversion efficiency) are also shown in Table 2.

[0111]

[Table 2]

From Table 2, it can be seen that the comparative photoelectric conversion element C-1 using the electrolyte composition comprising a volatile acetonitrile solution.
Indicates poor storage stability. Also, journals
Of the Electrochemical Society, Volume 143,
No. 10, a photoelectric conversion element D-1 for comparison using the electrolyte composition described on pages 3099 to 3108, and a photoelectric conversion element D for comparison
-2 to D-4 showed excellent storage stability, but the photoelectric conversion efficiency was significantly reduced. In comparison, the photoelectric conversion elements D-5 to D-14 of the present invention exhibited excellent storage stability and photoelectric conversion efficiency. Further, among the photoelectric conversion elements D-5 to D-14 of the present invention, photoelectric conversion elements D-5 and D-8 using a salt (I) in which R ₁ in the general formula (I) is a perfluoroalkyl group. ~ D-10 and D
-12 to D-14 showed high photoelectric conversion efficiency. Moreover Among these, the general formula (I) photoelectric conversion using salt (I) is a Q ⁺ 1,3-dialkyl imidazolium cation in the element D-
5, D-9 and D-10 exhibited particularly high photoelectric conversion efficiencies.

[0113]

As described in detail above, the dye-sensitized photoelectric conversion element of the present invention exhibits excellent storage stability and photoelectric conversion efficiency.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 2 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 3 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 4 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 5 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 6 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 7 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 8 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 9 is a partial sectional view showing the structure of a preferred photoelectric conversion element of the present invention.

FIG. 10 is a partial cross-sectional view illustrating a structure of a photoelectric conversion element manufactured in an example.

[Explanation of symbols]

 10 ... Conductive layer 10a ... Transparent conductive layer 11 ... Metal lead 20 ... Photosensitive layer 21 ... Semiconductor fine particles 22 ... Dye 23 ... Charge transport material 30 ... Charge transport layer 40 ... counter electrode conductive layer 40a ... transparent counter electrode conductive layer 50 ... substrate 50a ... transparent substrate 60 ... undercoat layer 1 ... conductive glass 2 ... glass 3 ... conductive layer 4 ... Dye-adsorbed titanium dioxide layer 5 ... Charge transport layer 6 ... Platinum layer 7 ... Glass

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F051 AA14 CB13 CB30 FA04 FA06 5H032 AA06 AS16 CC16 EE04 EE20 HH00

Claims (6)

[Claims] 1. A photoelectric conversion device comprising a charge transport layer containing a salt represented by the following general formula (I). Embedded image In the general formula (I), R ₁ and R ₂ are each independently an alkyl group,
Represents an aryl group or an alkoxy group, and may have a substituent. W ₁ represents C (= O), S (= O), S (= O) ₂ , P (= O), a triazolyl group or a tetrazolyl group, and W ₁ is C (= O), S (= O)
Or S (= O) is n1 to represent a ₂ a 1, n1 when W ₁ represents a P (= O) is 2, the n1 when W ₁ represents a triazolyl group or a tetrazolyl group 0 or 1 is there. W ₂ is C (= O), S (=
O), P (= O) , represents a triazolyl group or tetrazolyl group, n2 when W ₂ represents C (= O) or S (= O) is 1, W ₂ is
N2 to represent a P (= O) is 2, the n2 when W ₂ represents a triazolyl group or tetrazolyl group is 0 or 1. Q ⁺ represents an organic cation. 2. The photoelectric conversion element according to claim 1, wherein said W ₁ is S (= O) ₂ , and said W ₂ is C (= O). 3. A photoelectric conversion device according to claim 1 or 2, a photoelectric conversion element, wherein the R ₁ is a perfluoroalkyl group. 4. The photoelectric conversion device according to claim 1, wherein said Q ⁺ is an aromatic heterocyclic quaternary cation. 5. The photoelectric conversion device according to claim 1, wherein the salt represented by the general formula (I) has a molecular weight of 1,000 or less. 6. A photovoltaic cell comprising the photoelectric conversion element according to claim 1.