JP4148374B2 - Photoelectric conversion element and photoelectrochemical cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoelectric conversion element and an electrochemical cell using the photoelectric conversion element, and more particularly to a photoelectric conversion element and an electrochemical cell using semiconductor fine particles sensitized with a dye.
[0002]
[Prior art]
Photoelectric conversion elements are used in various optical sensors, copying machines, and photovoltaic power generation devices. Various systems such as those using metals, semiconductors, organic pigments and dyes, or combinations thereof have been put to practical use as photoelectric conversion elements.
[0003]
U.S. Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440 and JP-A-7-249790 used semiconductor fine particles sensitized with a dye. A photoelectric conversion element (hereinafter abbreviated as a dye-sensitized photoelectric conversion element), or a material and a manufacturing technique for producing the photoelectric conversion element are disclosed. The first advantage of this method is that an inexpensive oxide semiconductor such as titanium dioxide can be used without being purified with high purity, so that a relatively inexpensive photoelectric conversion element can be provided. The second advantage is that the absorption of the dye used is broad, so that light in almost all wavelength regions of visible light can be converted into electricity. Since these characteristics are advantageous when applied to a photoelectric conversion element (so-called solar cell) for the purpose of converting solar energy into electricity, application in this direction is being actively studied.
[0004]
However, there are at least two points that require improvement in dye-sensitized photoelectric conversion elements. The first is to use an expensive ruthenium complex dye as the sensitizing dye, and the second is that the light that can be photoelectrically converted is limited to visible light or near-infrared light having a wavelength shorter than 800 nm. Photoelectric conversion elements having sensitivity at wavelengths longer than 800 nm can be applied to various analytical instruments and are also useful for solar cell applications. Sunlight contains a large amount of infrared light having a wavelength longer than 800 nm. If such low-energy light can be converted into electricity, the conversion efficiency of the element can be improved.
[0005]
For these reasons, it has been desired to develop a photoelectric conversion element that is sensitized by an inexpensive organic dye and can convert low-energy light having a wavelength of 800 nm or more into electricity.
[0006]
[Problems to be solved by the invention]
The first object of the present invention is to provide a dye-sensitized photoelectric conversion element using an organic dye. The second object is to provide a dye-sensitized photoelectric conversion element capable of converting low energy light having a wavelength of 800 nm or more into electricity. And the 3rd objective is to provide the photoelectrochemical cell which improved the conversion efficiency using such a photoelectric conversion element.
[0007]
[Means for Solving the Problems]
As a result of research, it has been found that the following (1) to (7) are suitable for the purpose of the present invention. (1) A photoelectric conversion element having at least a conductive support and a photosensitive layer, wherein the photosensitive layer contains semiconductor fine particles sensitized with a polymethine dye.
(2) The photoelectric conversion element according to (1), wherein the polymethine dye is represented by the following general formula (1).
[0008]
[Formula 4]
[0009]
[In general formula (1), R ₁ And R _Five Each represents a hydrogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic residue; ₂ , R _Three And R _Four Each represents a hydrogen atom or a monovalent substituent. R ₁ ~ R _Five May combine with each other to form a ring. X ₁₁ And X ₁₂ Each represents a nitrogen atom, an oxygen atom, a sulfur atom, a selenium atom or a tellurium atom. n ₁₁ And n ₁₃ Each represents an integer from 0 to 2; ₁₂ Represents an integer of 1-6. The compound represented by the general formula (1) may have a counter ion according to the charge of the whole molecule. ]
(3) The photoelectric conversion element according to (2), wherein the polymethine dye is represented by the following general formula (2), (3), or (4).
[0010]
[Chemical formula 5]
[0011]
[In general formula (2), R ₁₁ , R ₁₂ And R ₁₃ Each represents a hydrogen atom or a monovalent substituent. R ₁₁ ~ R ₁₃ May combine with each other to form a ring. R ₁₄ And R ₁₅ Each represents an alkyl group. A ₁₁ And A ₁₂ Each represents an atomic group for forming a 3- to 9-membered ring with a carbon atom and a nitrogen atom, and n ₁ Represents an integer of 0-4. The compound represented by the general formula (2) may have a counter ion according to the charge of the whole molecule.
In general formula (3), R _{twenty one} , R _{twenty two} And R _{twenty three} Each represents a hydrogen atom or a monovalent substituent. R _{twenty one} ~ R _{twenty three} May combine with each other to form a ring. R _{twenty four} And R _{twenty five} Each represents an alkyl group. A _{twenty one} And A _{twenty two} Each represents an atomic group for forming a 5- to 9-membered ring with a carbon atom and a nitrogen atom, and n ₂ Represents an integer of 0-4. The compound represented by the general formula (3) may have a counter ion according to the charge of the whole molecule.
In general formula (4), R ₃₁ , R ₃₂ And R ₃₃ Each represents a hydrogen atom or a monovalent substituent. R ₃₁ ~ R ₃₃ May combine with each other to form a ring. A ₃₁ And A ₃₂ Each represents an atomic group for forming a 3- to 9-membered ring with carbon atoms, and n _Three Represents an integer of 0-4. The compound represented by the general formula (4) may have a counter ion according to the charge of the whole molecule. ]
(4) The photoelectric conversion element according to (3), wherein the polymethine dye is represented by the following general formula (5).
[0012]
[Chemical 6]
[0013]
[In general formula (5), R ₄₁ And R ₄₂ Each represents a hydrogen atom or a monovalent substituent. R ₄₃ And R ₄₄ Each represents an alkyl group. A ₄₁ And A ₄₂ Each represents an atomic group for forming a 3- to 9-membered ring with a carbon atom and a nitrogen atom. The compound represented by the general formula (5) may have a counter ion according to the charge of the whole molecule. ]
(5) A ₄₁ Heterocycle completed with ₄₂ The photoelectric conversion element according to the above (4), wherein the heterocyclic rings completed in the step are each benzothiazoline, indolenine, naphthothiazoline, or benzoindolenine.
(6) The photoelectric conversion element according to any one of (2) to (5), wherein the polymethine dye has at least one carboxyl group.
(7) A photoelectrochemical cell comprising the photoelectric conversion element according to any one of (1) to (6) above, and further comprising at least a charge transfer layer and a counter electrode.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The photoelectric conversion element of the present invention has a photosensitive layer on a conductive support, and the photosensitive layer contains semiconductor fine particles sensitized with a polymethine dye.
[0015]
Thus, by using a polymethine dye, a dye-sensitized photoelectric conversion element excellent in conversion efficiency can be obtained. In addition, by selecting a polymethine dye, infrared light having a long wavelength of 800 nm or more contained in sunlight can be used, and low energy light can be converted into electricity. For this reason, the conversion efficiency of an element improves. Moreover, it is advantageous in terms of cost.
[0016]
The general formula (1) will be described. In the general formula (1), R ₁ And R _Five Each represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic residue, and R ₂ , R _Three And R _Four Each represents a hydrogen atom or a monovalent substituent. R ₁ ~ R _Five May combine with each other to form a ring. X ₁₁ And X ₁₂ Each represents nitrogen, oxygen, sulfur, selenium or tellurium. n ₁₁ And n ₁₃ Represents an integer of 0 to 2, n ₁₂ Represents an integer of 1-6. The compound represented by the general formula (1) may have a counter ion according to the charge of the whole molecule.
[0017]
The polymethine dye represented by the general formula (1) will be described in detail.
[0018]
In the general formula (1), R ₁ , R _Five Is a hydrogen atom, an alkyl group or an alkenyl group (eg, methyl, ethyl, propyl, butyl, isobutyl, n-dodecyl, cyclohexyl, vinyl, allyl, benzyl, etc.), an aryl group (eg, phenyl, tolyl, naphthyl, etc.), or a heterocyclic ring Represents a residue (for example, pyridyl group, imidazolyl group, furyl group, thienyl group, oxazolyl group, thiazolyl group, benzimidazolyl group, quinolyl group, etc.); These may have a substituent.
[0019]
Examples of the substituent include an alkyl group, an aryl group, and a heterocyclic residue. Specific examples are the same as those described above, and further a halogen atom (for example, fluorine, chlorine, bromine), an alkoxy group (for example, Methoxy, ethoxy, benzyloxy etc.), aryloxy group (eg phenoxy etc.), alkylthio group (eg methylthio, ethylthio etc.), arylthio group (eg phenylthio etc.), hydroxy group and oxygen anion, nitro group, cyano group, amide Groups (eg, acetylamino, benzoylamino, etc.), sulfonamido groups (eg, methanesulfonylamino, benzenesulfonylamino, etc.), ureido groups (eg, 3-phenylureido, etc.), urethane groups (eg, isobutoxycarbonylamino, carbamoyloxy, etc.) ), Ester groups (eg ace Xy, benzoyloxy, methoxycarbonyl, phenoxycarbonyl, etc.), carbamoyl groups (eg N-methylcarbamoyl, N, N-diphenylcarbamoyl etc.), sulfamoyl groups (eg N-phenylsulfamoyl etc.), acyl groups (eg acetyl, Benzoyl etc.), amino groups (amino, methylamino, anilino, diphenylamino etc.), sulfonyl groups (eg methylsulfonyl etc.), phosphonyl groups and esters thereof, phosphonyloxy groups and esters thereof, carboxyl groups, sulfo groups, etc. It is done. The above substituents may be further present on the carbon atom of the substituent.
[0020]
R ₂ ~ R _Four Represents a hydrogen atom or a monovalent substituent. As the monovalent substituent, R ₁ , R _Five The same thing as the substituent of the place is mentioned. R ₂ ~ R _Four May further have a substituent. R ₂ ~ R _Four Are preferably a hydrogen atom, a halogen atom, an oxygen anion, or a substituted or unsubstituted alkyl group.
[0021]
X ₁₁ And X ₁₂ Represents nitrogen, oxygen, sulfur, selenium or tellurium. n ₁₁ And n ₁₃ Represents an integer of 0-2. n ₁₂ Represents an integer of 0-6. However, due to chemical restrictions, X ₁₁ N is oxygen, sulfur, selenium, tellurium ₁₁ Represents an integer of 0 to 1. n ₁₃ The same applies to. The length of the methine chain is related to the absorption wavelength of the dye, and n ₁₂ The larger the value of, the longer the light that is absorbed.
[0022]
R ₁ ~ R _Five Arbitrary pairs selected from the above groups may be bonded to each other to form a ring. For example R ₁ And R ₂ Or R _Four And R _Five May combine to form a 3-9 membered heterocyclic ring, or R ₂ And R _Three Or R _Three And R _Four May combine to form a 3- to 8-membered aromatic ring, heterocyclic ring, or alicyclic ring, and the rings formed thereby may be condensed with each other. Preferred rings include cyclobutene, cyclopentene, cyclohexene, benzene, dehydrodecalin, pyridine, dihydropyridine, tetrahydropyridine, furan, dihydrofuran, thiophene, dihydrothiophene, hexahydroquinoline and the like. All these rings may be further condensed with a 3- to 8-membered aromatic ring, heterocyclic ring or alicyclic ring. For example R ₁ And R ₂ Or R _Four And R _Five Rings formed by bonding (including fused rings) are A in general formulas (2) to (4) described later. ₁₁ , A ₁₂ , A _{twenty one} , A _{twenty two} , A ₃₁ , A ₃₂ The same ring as that formed by can be exemplified.
[0023]
When the compound represented by the general formula (1) has a charge as a whole molecule, it may have a counter ion for neutralizing the charge. The counter ion is not particularly limited and may be either organic or inorganic. Typical examples are halogen ion (fluorine ion, chlorine ion, bromine ion, iodine ion), hydroxide ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion, acetate ion, trifluoroacetate ion. , Anions such as methanesulfonate ion, p-toluenesulfonate ion, trifluoromethanesulfonate ion, alkali metals (lithium, sodium, potassium, etc.), alkaline earth metals (magnesium, calcium, etc.), ammonium, alkylammonium (eg, diethyl) Cations such as ammonium and tetrabutylammonium), pyridinium, alkylpyridinium (for example, methylpyridinium), guanidinium, and tetraalkylphosphonium.
[0024]
When the compound represented by the general formula (1) has an acidic group, it is particularly preferable because of its excellent adsorptivity to semiconductor fine particles. As the acidic group, those having a pKa of 10 or less in a water-tetrahydrofuran mixed solvent (volume ratio 50:50) are preferable. Particularly preferred are carboxyl group, sulfonic acid group, sulfinic acid group, phosphonic acid group, hydroxyl group, phosphoric acid monoester and diester group. Of these, carboxyl groups are most preferred. These groups may form a salt with an alkali metal or the like. In addition, an inner salt may be formed.
[0025]
Specific examples of such polymethine dyes are described in detail in M. Okawara, T. Kitao, T. Hirasima, Organic Colorants (Elsevier) by M. Matuoka, and the like.
[0026]
Represented by general formula (1) The polymethine dye is more preferably represented by the general formulas (2) to (4).
[0027]
The polymethine dye represented by the general formula (2) will be described in detail.
In the general formula (2), R ₁₁ , R ₁₂ And R ₁₃ Each represents a hydrogen atom or a monovalent substituent. Examples of monovalent substituents include alkyl groups and alkenyl groups (eg, methyl, ethyl, propyl, butyl, isobutyl, n-dodecyl, cyclohexyl, vinyl, allyl, benzyl, etc.), aryl groups (eg, phenyl, tolyl, naphthyl, etc.), Heterocyclic residues (eg, pyridyl, imidazolyl, furyl, thienyl, oxazolyl, thiazolyl, benzimidazolyl, quinolyl, etc.), halogen atoms (eg, fluorine, chlorine, bromine), alkoxy groups (eg, methoxy) , Ethoxy, benzyloxy etc.), aryloxy groups (eg phenoxy etc.), alkylthio groups (eg methylthio, ethylthio etc.), arylthio groups (eg phenylthio etc.), hydroxy groups and oxygen anions, nitro groups, cyano groups, amide groups (Eg acetylamino, Nzoylamino etc.), sulfonamide groups (eg methanesulfonylamino, benzenesulfonylamino etc.), ureido groups (eg 3-phenylureido etc.), urethane groups (eg isobutoxycarbonylamino, carbamoyloxy etc.), ester groups (eg acetoxy etc.) , Benzoyloxy, methoxycarbonyl, phenoxycarbonyl, etc.), carbamoyl groups (eg N-methylcarbamoyl, N, N-diphenylcarbamoyl etc.), sulfamoyl groups (eg N-phenylsulfamoyl etc.), acyl groups (eg acetyl, benzoyl) Etc.), amino group (amino, methylamino, anilino, diphenylamino etc.), sulfonyl group (eg methylsulfonyl etc.), phosphonyl group and its ester, phosphonyloxy group and its ester Carboxyl group, such as sulfo group. The above substituents may be further present on the carbon atom of the substituent.
[0028]
R ₁₁ ~ R ₁₃ May be combined with each other to form a 3- to 8-membered monocyclic or polycyclic aromatic ring, heterocyclic ring, or alicyclic ring. Preferred rings include cyclobutene, cyclopentene, cyclohexene, benzene, dehydrodecalin, pyridine, dihydropyridine, tetrahydropyridine, furan, dihydrofuran, thiophene, dihydrothiophene, hexahydroquinoline and the like. All these rings may be further condensed with a 3- to 8-membered aromatic ring, heterocyclic ring or alicyclic ring. In the general formula (2), R ₁₄ And R ₁₅ Represents a substituted or unsubstituted alkyl group having 1 to 12 carbon atoms in total. Examples of alkyl groups, examples of substituents are R ₁₁ ~ R ₁₃ This is the case in the explanation of.
[0029]
In the general formula (2), A ₁₁ And A ₁₂ Each represents an atomic group for forming a 3- to 9-membered monocyclic or condensed ring together with a carbon atom and a nitrogen atom. The atoms constituting the ring in the atomic group are carbon, nitrogen, oxygen, sulfur, selenium and tellurium. A ₁₁ Or A ₁₂ Examples of the heterocyclic ring completed in are indolenine, benzoindolenine, benzimidazoline, benzoxazoline, benzothiazoline, quinoline, benzoselenazoline, benzotelrazoline, naphthoxazoline, naphthothiazoline and the like. These may have the aforementioned substituents. n ₁ Represents an integer of 0-4. The length of the methine chain is related to the absorption wavelength of the dye, and n ₁ The larger the value of, the longer the light that is absorbed.
[0030]
The compound represented by the general formula (2) may have a counter ion according to the charge of the whole molecule. The counter ion is not particularly limited and may be either organic or inorganic. Typical examples are halogen ion (fluorine ion, chlorine ion, bromine ion, iodine ion), hydroxide ion, perchlorate ion, tetrafluoroborate ion, hexafluorophosphate ion, acetate ion, trifluoroacetate ion. , Anions such as methanesulfonate ion, paratoluenesulfonate ion, trifluoromethanesulfonate ion, alkali metals (lithium, sodium, potassium, etc.), alkaline earth metals (magnesium, calcium, etc.), ammonium, alkylammonium (e.g. Cations such as diethylammonium, tetrabutylammonium, etc.), pyridinium, alkylpyridinium (for example, methylpyridinium), guanidinium, tetraalkylphosphonium and the like.
[0031]
When the compound represented by the general formula (2) has an acidic group, it is particularly preferable because it has excellent adsorptivity to semiconductor fine particles. As the acidic group, those having a pKa of 10 or less in a water-tetrahydrofuran mixed solvent (volume ratio 50:50) are preferable. Particularly preferred are carboxyl group, sulfonic acid group, sulfinic acid group, phosphonic acid group, hydroxyl group, phosphoric acid monoester and diester group. Of these, carboxyl groups are most preferred. These groups may form a salt with an alkali metal or the like. In addition, an inner salt may be formed.
[0032]
Next, the general formula (3) will be described. In the general formula (3), R _{twenty one} ~ R _{twenty three} Is R in the general formula (2) ₁₁ It is synonymous with. R _{twenty four} And R _{twenty five} Is R in the general formula (2) ₁₄ It is synonymous with. A _{twenty one} And A _{twenty two} Each represents an atomic group for forming a 5- or 9-membered monocyclic or condensed ring together with a carbon atom and a nitrogen atom. The atoms constituting the ring in the atomic group are carbon, nitrogen, oxygen, sulfur, selenium and tellurium. A _{twenty one} Or A _{twenty two} As the heterocyclic ring completed in step 1, dihydroquinoline and the like are preferable. These may have the aforementioned substituents. n ₂ Represents an integer of 0-4. The compound represented by the general formula (3) may have the aforementioned counter ion according to the charge of the whole molecule. The compound represented by the general formula (3) also preferably has the aforementioned acidic group, and the carboxyl group is most preferable as the acidic group.
[0033]
Next, the general formula (4) will be described. In the general formula (4), R ₃₁ ~ R ₃₃ Is R in the general formula (2) ₁₁ It is synonymous with. A ₃₁ And A ₃₂ Each represents an atomic group for forming a 3- to 9-membered monocyclic or condensed ring with a carbon atom. The atoms constituting the ring in the atomic group are carbon, nitrogen, oxygen, sulfur, selenium and tellurium. A ₃₁ Or A ₃₂ As the heterocyclic ring completed by the above, heterocyclic cyclic ketones (including thioketones) are preferred, and those having pyrimidine, pyridine, pyrazole, etc. as the heterocyclic ring are preferred. These may have the aforementioned substituents. n _Three Represents an integer of 0-4. The acidic hydroxyl group at the conjugated end may be dissociated. The compound represented by the general formula (4) may have the aforementioned counter ion according to the charge of the whole molecule. The compound represented by the general formula (4) also preferably has the aforementioned acidic group, and the carboxyl group is most preferable as the acidic group.
[0034]
In the present invention Used A pigment | dye is a pigment | dye represented by General formula (5). In the general formula (5), R ₄₁ , R ₄₂ Is R in the general formula (2) ₁₁ It is synonymous with. R ₄₃ , R ₄₄ Is R in the general formula (2) ₁₄ It is synonymous with. A ₄₁ , A ₄₂ Is A in the general formula (2) ₁₁ It is synonymous with. A ₄₁ Or A ₄₂ As the heterocyclic ring completed in step 1, indolenine, benzothiazoline, quinoline, benzoindolenine, naphthothiazoline and the like are preferable, and benzothiazoline, indolenine, naphthothiazoline and benzoindolenine are particularly preferable. These are A ₁₁ And may have the same substituent. The compound represented by the general formula (5) may have the aforementioned counter ion according to the charge of the whole molecule. The compound represented by the general formula (5) also preferably has the above-mentioned acidic group, and the carboxyl group is most preferable as the acidic group.
[0035]
The general formula (2) to (5) Preferred specific examples of the polymethine dye represented by the formula:
[0036]
[Chemical 7]
[0037]
[Chemical 8]
[0038]
[Chemical 9]
[0039]
[Chemical Formula 10]
[0040]
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[0041]
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[0042]
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[0043]
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[0044]
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[0045]
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[0046]
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[0047]
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[0048]
General formula (2)- (5) The polymethine dyes represented by are “Heterocyclic Compounds-Cyanine Dyes and Related Compounds” by FM Harmer, John Willie &・ John Willey & Sons, New York, London, 1994, DMSturmer "Heterocyclic Compounds-Special Topics in Heterocyclic Compounds-Special Topics In Heterocyclic Chemistry ”, Chapter 18, verses 482-515, John Willey & Sons, New York, London, 1977,“ Rods Chemistry of Carbon. Compounds (Rodd's Chemistry of Carbon Compo unds) "2nd Edition Vol.4, Part B, Chapter 15 369-422, Elisevia Science Publishing Company Inc., New York, 1977, British Patent No. 1077611, etc. It can be synthesized by the method described in 1.
[0049]
Next, the method for synthesizing the polymethine dye used in the present invention will be described with specific examples, but the present invention is not limited to these.
[0050]
Synthesis Example 1 Synthesis of Exemplary Compound (10)
Exemplified compound (10) of the present invention was synthesized by the following synthesis route.
[0051]
Embedded image
[0052]
3.9 g of compound (A-1), 0.57 g of compound (A-2), 10 ml of toluene and 30 ml of butanol were mixed and heated to reflux for 4 hours with stirring. The solvent was distilled off under reduced pressure, and 10 cc of a 1: 1 (volume ratio) mixed solvent of isopropyl alcohol and methanol was added and left at 5 ° C. overnight. The precipitated crystals were collected by filtration to obtain 0.3 g of exemplary compound (10).
[0053]
Next, the dye-sensitized photoelectric conversion element and the photoelectrochemical cell to which the polymethine dye of the present invention is applied will be described in detail.
[0054]
In the present invention, the dye-sensitized photoelectric conversion element is an electrode comprising a conductive support and a layer (photosensitive layer) of semiconductor fine particles adsorbed with a polymethine dye coated on the conductive support. The photosensitive layer is designed according to the purpose and may have a single layer structure or a multilayer structure. The dyes in one photosensitive layer may be one kind or a mixture of various kinds. Light incident on the photosensitive layer excites the dye. The excitation dye has electrons with high energy, and these electrons are transferred from the dye to the conduction band of the semiconductor fine particles, and further reach the conductive support by diffusion. At this time, the dye molecule is an oxidant, but the electrons on the electrode return to the dye oxidant while working in the external circuit, and the dye-sensitized photoelectric conversion element is the negative electrode of this battery. Work as.
[0055]
Hereinafter, the conductive support and the photosensitive layer will be described in detail.
[0056]
The conductive support is a support made of glass or plastic having a conductive agent layer on the surface, such as a metal, which is conductive in itself. In the latter case, preferred conductive agents are metals (eg, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), carbon, or conductive metal oxides (indium-tin composite oxide, tin oxide doped with fluorine. Etc.). In this case, the thickness of the conductive agent layer is preferably 0.05 to 10 μm.
[0057]
The lower the surface resistance of the conductive support, the better. The preferred surface resistance range is 50 Ω / cm ² Or less, more preferably 10 Ω / cm ² It is as follows. This lower limit is not particularly limited, but is usually 0.1Ω / cm ² Degree.
[0058]
It is preferable that the conductive support is substantially transparent. Substantially transparent means that the light transmittance is 10% or more, preferably 50% or more, particularly preferably 80% or more. As the transparent conductive support, a glass or plastic coated with a conductive metal oxide is preferable. The amount of the conductive metal oxide applied is preferably 0.1 to 100 g per m @ 2 of glass or plastic support. When a transparent conductive support is used, light is preferably incident from the support side.
[0059]
Semiconductor fine particles used in the photosensitive layer are metal chalcogenides (for example, oxide, sulfide, selenide, etc.) or perovskite fine particles. Preferred examples of the metal chalcogenide include titanium, tin, zinc, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium, tantalum oxide, cadmium sulfide, and cadmium selenide. Preferred perovskites include strontium titanate and calcium titanate. Of these, titanium oxide, zinc oxide, tin oxide, and tungsten oxide are particularly preferable.
[0060]
The particle diameters of these semiconductor fine particles are 0.001 to 1 μm as primary particles and 0.01 to 100 μm as the average particle diameter of the dispersion in terms of the average particle diameter when the projected area is converted into a circle. It is preferable.
[0061]
As a method of coating the semiconductor fine particles on the conductive support, a method of coating a dispersion or colloidal solution of the semiconductor fine particles on the conductive support, a method of coating the precursor of the semiconductor fine particles on the conductive support, and air. Examples thereof include a method of obtaining a semiconductor fine particle film by hydrolysis with moisture therein. Examples of the method for preparing a dispersion of semiconductor fine particles include a method of pulverizing in a mortar, a method of dispersing while pulverizing using a mill, or a method of depositing fine particles in a solvent and using them as they are when a semiconductor is synthesized. . Examples of the dispersion medium include water or various organic solvents (for example, methanol, ethanol, dichloromethane, acetone, acetonitrile, ethyl acetate, etc.). During dispersion, a polymer, surfactant, acid, chelating agent, or the like may be used as a dispersion aid as necessary.
[0062]
The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. For example, in a state where the semiconductor fine particles are coated on the support, the surface area is preferably 10 times or more, more preferably 100 times or more the projected area. Although there is no restriction | limiting in particular in this upper limit, Usually, it is about 5000 times.
[0063]
In general, as the thickness of the semiconductor fine particle layer increases, the amount of dye that can be carried per unit area increases, so that the light absorption efficiency increases. The preferred thickness of the semiconductor fine particle layer (that is, the photosensitive layer) varies depending on the use of the device, but is typically 0.1 to 100 μm. When used as a photoelectrochemical cell, the thickness is preferably 1 to 50 μm, more preferably 3 to 30 μm. The semiconductor fine particles may be fired at a temperature of 100 to 800 ° C. for 10 minutes to 10 hours in order to adhere the particles to each other after being applied to the support.
[0064]
Semiconductor fine particle support 1m ² The coating amount per unit is preferably 0.5 to 500 g, more preferably 5 to 100 g.
[0065]
In the present invention, the semiconductor fine particles are sensitized by the adsorption of the polymethine dye. In order to adsorb the dye to the semiconductor fine particles, a method of immersing well-dried semiconductor fine particles in a dye solution for a long time is general. The dye solution may be heated to 50 ° C. to 100 ° C. as necessary. The adsorption of the dye may be performed before or after application of the semiconductor fine particles. Further, the semiconductor fine particles and the pigment may be applied and adsorbed simultaneously. Unadsorbed dye is removed by washing. When baking a coating film, it is preferable to adsorb | suck a pigment | dye after baking. It is particularly preferable that the dye is quickly adsorbed after the baking and before water adsorbs on the surface of the coating film. One type of dye may be adsorbed or a mixture of several types may be used. In the case of mixing, the polymethine dyes of the present invention may be mixed together, US Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440, and You may mix the complex pigment | dye described in 7-249790, and the pigment | dye of this invention. When the application is a photoelectrochemical cell, a dye to be mixed is selected so as to make the wavelength range of photoelectric conversion as wide as possible.
[0066]
The total amount of dye used is 1m on the support. ² The amount is preferably from 0.01 to 100 mmol, more preferably from 0.1 to 50 mmol, particularly preferably from 0.5 to 10 mmol. In this case, the amount of the polymethine dye of the present invention is preferably 5 mol% or more.
[0067]
The amount of the dye adsorbed on the semiconductor fine particles is preferably 0.001 to 1 mmol, more preferably 0.1 to 0.5 mmol, per 1 g of the semiconductor fine particles.
[0068]
By using such a dye amount, a sensitizing effect in a semiconductor can be sufficiently obtained. On the other hand, when the amount of the dye is small, the sensitizing effect becomes insufficient, and when the amount of the dye is too large, the dye not attached to the semiconductor floats and causes the sensitizing effect to be reduced.
[0069]
Further, 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).
[0070]
After adsorbing the dye, the surface of the semiconductor fine particles may be treated with amines. Preferable amines include pyridine, 4-tert-butylpyridine, polyvinylpyridine and the like. These may be used as they are in the case of a liquid, or may be used by dissolving in an organic solvent.
[0071]
In the present invention, the conductive agent and the semiconductor fine particles may be diffused and mixed with each other in the vicinity of the interface between the conductive support and the photosensitive layer.
[0072]
The dye-sensitized photoelectric conversion element thus prepared can be applied to various sensors and photoregenerative photoelectrochemical cells. When applied to a photoelectrochemical cell, a charge transfer layer and a counter electrode are required as shown in FIG.
[0073]
A photoelectrochemical cell 1 shown in FIG. 1 has a photosensitive layer 3 on a conductive support 2, and a charge transfer layer 4 and a counter electrode 5 are provided on the photosensitive layer 3.
[0074]
Hereinafter, the charge transfer layer and the counter electrode will be described in detail.
[0075]
The charge transfer layer is a layer having a function of replenishing electrons to the oxidant of the dye. Typical examples include a liquid in which a redox couple is dissolved in an organic solvent, a so-called gel electrolyte in which a polymer matrix is impregnated with a liquid in which a redox pair is dissolved in an organic solvent, and a molten salt containing the redox couple.
[0076]
Examples of the redox pair include a combination of iodine and iodide (eg, lithium iodide, tetrabutylammonium iodide, tetrapropylammonium iodide, etc.), alkyl viologen (eg, methyl viologen chloride, hexyl viologen bromide, benzyl viologen tetrafluoroborate). ) And a reduced form thereof, a combination of polyhydroxybenzenes (eg, hydroquinone, naphthohydroquinone, etc.) and an oxidized form thereof, a combination of a divalent and trivalent iron complex (eg, red blood salt and yellow blood salt), and the like. It is done. Of these, a combination of iodine and iodide is preferred. As the organic solvent for dissolving them, an aprotic polar solvent (for example, acetonitrile, propylene carbonate, ethylene carbonate, dimethylformamide, dimethyl sulfoxide, sulfolane, 1,3-dimethylimidazolinone, 3-methyloxazolidinone, etc.) is preferable. Examples of the polymer used for the matrix of the gel electrolyte include polyacrylonitrile and polyvinylidene fluoride. Examples of the molten salt include lithium iodide and at least one other lithium salt (for example, lithium acetate, lithium perchlorate, etc.). By mixing these with a polymer such as polyethylene oxide, the fluidity at room temperature. May be increased. In this case, the amount of the polymer added is 1 to 50 wt%.
[0077]
Since the redox couple becomes an electron carrier, a certain concentration is required. The preferred concentration in the solution when used as a liquid or gel electrolyte is 0.01 mol / l or more in total, more preferably 0.1 mol / l or more, and particularly preferably 0.3 mol / l or more. It is. The upper limit in this case is not particularly limited, but is usually about 5 mol / l.
[0078]
The counter electrode serves as the positive electrode of the photoelectrochemical cell. The counter electrode is usually synonymous with the conductive support described above, but the support is not necessarily required in a configuration in which the strength is sufficiently maintained. However, having a support is advantageous in terms of hermeticity.
[0079]
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, the conductive support is preferably transparent, and sunlight is preferably incident from the support side. In this case, the counter electrode more preferably has a property of reflecting light. The counter electrode of the photoelectrochemical cell is preferably glass or plastic deposited with a metal or conductive oxide, and glass deposited with platinum is particularly preferred.
[0080]
In the photoelectrochemical battery, it is preferable to seal the side surface of the battery with a polymer, an adhesive, or the like in order to prevent evaporation of components.
[0081]
The characteristics of the photoelectrochemical cell thus obtained are 100 mW / cm at AM 1.5G. ² Open circuit voltage 0.01-3V, short circuit current density 0.001-20mA / cm ² The shape factor is 0.1 to 0.99, and the conversion efficiency is 0.001 to 25%.
[0082]
【Example】
The method for producing the dye-sensitized photoelectric conversion element and the photoelectrochemical cell of the present invention will be specifically described below with reference to examples, but the present invention is not limited thereto.
[0083]
Example 1
Preparation of titanium dioxide dispersion
Teflon-coated stainless steel vessel with inner volume of 200 ml, titanium dioxide (Nippon Aerosil Degussa P-25) 15 g, water 45 g, dispersant (Aldrich Triton X-100) 1 g, 0.5 mm diameter zirconia beads (Nikkato) 30 g), and dispersed for 2 hours at 1500 rpm using a sand grinder mill (manufactured by Imex). The zirconia beads were filtered off from the dispersion. In this case, the average particle diameter of titanium dioxide was 2.5 μm. The particle size at this time is measured with a master sizer manufactured by MALVERN.
[0084]
Creation of photoelectric conversion element
The above dispersion was applied to the conductive surface side of conductive glass coated with tin oxide doped with fluorine (TCO glass manufactured by Asahi Glass cut into a size of 20 mm × 20 mm) using a glass rod. The surface resistance of conductive glass is about 30Ω / cm. ² Met.
[0085]
At this time, adhesive tape was applied to a part of the conductive surface side (3 mm from the end) to form a spacer, and glass was arranged so that the adhesive tape came to both ends, and 8 sheets were applied at a time. After application, the film was air-dried at room temperature for 1 day, and the adhesive tape was peeled off (the part to which the adhesive tape was attached was used for making electrical contact with the measuring instrument during photoelectric conversion measurement). Next, this glass was put into an electric furnace (a muffle furnace FP-32 manufactured by Yamato Scientific Co., Ltd.) and baked at 450 ° C. for 30 minutes. After the glass is taken out and cooled, it is shown in Table 1. Exemplary compounds Solution of dye in ethanol (3 × 10 ^-Four Mol / l) for 3 hours. The dyed glass was immersed in a 10 wt% ethanol solution of 4-tert-butylpyridine for 30 minutes, then washed with ethanol and naturally dried. The thickness of the photosensitive layer thus obtained is 10 μm, and the coating amount of semiconductor fine particles is 20 g / m. ² It was. The coating amount of the dye is appropriately 0.1 to 10 mmol / m depending on the kind of the dye. ² Selected from a range of
[0086]
Reflection spectrum measurement
The reflection spectrum was measured using a spectrophotometer (Hitachi, Ltd. U-3500 type) equipped with an integrating sphere. Table 1 shows the wavelength and absorbance values at the absorption peak on the longest wavelength side.
[0087]
Creation of photoelectrochemical cell
As an embodiment of the photoelectrochemical cell of FIG. 1, a photoelectrochemical cell as shown in FIG. 2 was prepared. The photoelectrochemical cell 10 in FIG. 2 uses the above-described photoelectric conversion element having a configuration in which the photosensitive layer 13 is provided on the conductive support having the conductive agent layer 12 on the glass support 11. 13 has an electrolyte layer 14 which is a charge transfer layer, and further has a platinum-deposited glass 15 disposed as a counter electrode. In this preparation, the above-described photoelectric conversion element was overlapped with a platinum-deposited glass having the same size (FIG. 2, the uncoated portion of the photoelectric conversion element was shifted so as not to contact the platinum-deposited glass). Next, using a capillary phenomenon in the gap between the two glasses, an electrolytic solution (0.05 mol / l iodine in a mixture of acetonitrile and N-methyl-2-oxazolidinone in a volume ratio of 90 to 10), lithium iodide 0 .5 mol / l solution).
[0088]
Measurement of photoelectric conversion efficiency
Simulated sunlight containing no ultraviolet rays was generated by passing light from a 500 W xenon lamp (made by Ushio) through an AM1.5G filter (made by Oriel) and a sharp cut filter (KenkoL-42). The intensity of this light is 50mW / cm ² Met.
[0089]
The photoelectric conversion element of the present invention was irradiated with this light, and the generated electricity was measured with a current-voltage measuring device (Keutley 238 type). Table 1 summarizes the open circuit voltage, short circuit current, form factor, and conversion efficiency of the photochemical battery thus determined.
[0090]
[Table 1]
[0091]
As is clear from Table 1, photoelectric conversion characteristics are recognized with any dye. In addition, the exemplary compound 12 has an absorption maximum exceeding 800 nm, and photoelectric conversion characteristics are recognized. In more detail, the dyes having the carboxyl group (Exemplary Compounds 6 to 10, 12, and 13) are superior in dyeing and coloring as compared with the dyes having no carboxyl group (Exemplary Compounds 4 and 5). It can be seen that the photoelectric conversion efficiency is high. In addition, Exemplary Compound 10 belonging to General Formula (5) 10 The photoelectric conversion element of the present invention using Shows a particularly high photoelectric conversion characteristic.
[0092]
【The invention's effect】
It became clear that the present invention provides a dye-sensitized photoelectric conversion element using an organic dye. In addition, it was confirmed that even a dye that absorbs longer waves than 800 nm performs photoelectric conversion. Therefore, a photoelectrochemical cell could be constructed using such a photoelectric conversion element.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing one structural example of the photoelectrochemical cell of the present invention.
FIG. 2 is a cross-sectional view showing a structural example of a photoelectrochemical cell used in Examples.
[Explanation of symbols]
1, 10 Photoelectrochemical cell
2 Conductive support
3,13 Photosensitive layer
4 Charge transfer layer
5 Counter electrode
11 Glass support
12 Conductive agent layer
14 Electrolyte layer
15 Platinum-deposited glass

Claims (4)

A photoelectric conversion element having at least a conductive support and a photosensitive layer, wherein the photosensitive layer contains semiconductor fine particles sensitized by a polymethine dye represented by the following general formula (5): Conversion element.
[In General Formula (5), R ₄₁ and R ₄₂ each represent a hydrogen atom or a monovalent substituent. R ₄₃ and R ₄₄ each represents an alkyl group. A ₄₁ and A ₄₂ each represent an atomic group for forming a 3- to 9-membered ring with a carbon atom and a nitrogen atom. The compound represented by the general formula (5) may have a counter ion according to the charge of the whole molecule. ] Heterocyclic rings completed by heterocyclic and A ₄₂ completed by A ₄₁ are each benzothiazoline, indolenine, photoelectric conversion element according to claim 1 which is naphthothiazoline or benzoindolenine. The photoelectric conversion element according to claim 1, wherein the polymethine dye has at least one carboxyl group. A photoelectrochemical cell comprising the photoelectric conversion element according to claim 1 , and further comprising at least a charge transfer layer and a counter electrode.