JP4363553B2 - Electrolyte composition, photoelectric conversion element and photoelectrochemical cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electrolyte composition suitable for use in an electrochemical element such as a battery, a capacitor, a sensor, a display element, and a recording element, and a photoelectric conversion element and a photoelectric element using the electrolyte composition and a semiconductor photosensitive agent. It relates to chemical batteries.
[0002]
[Prior art]
Conventionally, liquid electrolytes have been used as electrolytes for electrochemical elements such as batteries, capacitors, sensors, display elements, and recording elements. However, the liquid electrolyte may be leaked during long-term use and storage, and lacks reliability.
[0003]
For example, Nature (Vol. 353, pages 737 to 740, 1991) and US Pat. No. 4927721 are photoelectric conversion elements using semiconductor particles sensitized with a dye (hereinafter referred to as “dye-sensitized photoelectric conversion element”) and Although the photoelectrochemical cell using this is disclosed, since the liquid electrolyte is also used in the charge transport layer in these, the electrolyte solution leaks or is exhausted by long-term use, and the photoelectric conversion efficiency is remarkably lowered. There is a concern that it will not function as an element.
[0004]
In order to overcome such drawbacks, International Patent No. 93/20565 proposes a photoelectric conversion element using a solid electrolyte, and also disclosed in JP-A-7-2881142, Solid State Ionics, 89, 263 (1986) and Kaihei 9-27352 proposes a photoelectric conversion element solidified using a crosslinked polyethylene oxide polymer solid electrolyte. However, it has been found that photoelectric conversion elements using these solid electrolytes are not only at an insufficient level of photoelectric conversion characteristics, particularly short-circuit current density, but also at an insufficient level of durability.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide an electrolyte composition excellent in light durability and charge transport ability that solves the conventional problems. Another object of the present invention is to provide a photoelectric conversion element having excellent photoelectric conversion characteristics and durability due to the use of this electrolyte composition, and a photoelectrochemical cell having such a photoelectric conversion element.
[0006]
[Means for Solving the Problems]
As a result of diligent research in view of the above object, the present inventor has obtained the following formula (II)
[Chemical formula 2]
(However, R₁Is a hydrogen atom orMethyl groupWhere L is-COO-, -OCO-, -CON (R ₂ )-Or -N (R _Three ) CO- or a linking group obtained by combining one or more of these groups with one or more divalent groups selected from an alkylene group, an arylene group and -O- (provided that R ₂ And R _Three Is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. )Z representsPyridine ring or imidazole ringE represents a group derived from a compound containing an ethylenically unsaturated group, x and y represent a weight composition ratio of repeating units, x is 5 to 100% by weight, and y is 0 to 95% by weight. It is. And a polymer compound represented byAlkyl halides or aralkyl halides having 2-4 functionalities as electrophilesIt was discovered that an electrolyte composition excellent in durability and charge transportability can be obtained by using a cross-linked polymer obtained by reacting with the present invention.
[0007]
The photoelectric conversion device of the present invention is characterized in that a conductive support, a photosensitive layer, a charge transfer layer, and a counter electrode are laminated in this order, and the charge transfer layer contains the above electrolyte composition.
[0008]
Furthermore, the photoelectrochemical cell of the present invention has the above-described photoelectric conversion element.
[0009]
Moreover, by satisfying the following conditions, an electrolyte composition, a photoelectric conversion element, and a photoelectrochemical cell having further excellent photoelectric conversion characteristics and durability can be obtained.(1) Formula (II)Is preferably obtained by reacting in a solvent in which a salt is dissolved.(2) In the photoelectric conversion element, the charge transfer layer isThe electrolyte compositionIs preferably included.(3)In the above photoelectric conversion element, the photosensitive layer is preferably composed of semiconductor fine particles sensitized with a dye and an electrolyte composition filled in a gap between the dye-sensitized semiconductor fine particles. The semiconductor fine particles are preferably titanium dioxide fine particles. The dye is preferably a metal complex dye, a phthalocyanine dye or a polymethine dye.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The photoelectric conversion element and the photoelectrochemical cell of the present invention comprise an electrolyte composition comprising a cross-linked polymer obtained by a reaction of a pendant polymer compound having a nitrogen-containing heterocycle at a side chain end and an electrophile for the nitrogen atom. It is characterized by using. Thereby, it is possible to obtain a photoelectric conversion element and a photoelectrochemical cell which are excellent in photoelectric conversion characteristics and prevent deterioration of characteristics over time.
[0011]
[1] Electrolyte composition
Electrolyte compositionIncludes a cross-linked polymer obtained by the reaction of (A) a nitrogen-containing polymer compound and (B) an electrophile. Hereinafter, these compounds and reaction conditions will be described in detail.
[0012]
(A) Nitrogen-containing polymer compound
In nitrogen-containing polymer compoundsNitrogen-containing heterocyclic groupThe nitrogen atom is alkylated or quaternized with an electrophile to form a crosslinked polymer. Nitrogen-containing polymer is a side chain terminalNitrogen-containing heterocyclic groupIs a pendant type polymer compound having the following formula (I).
[Chemical 3]
(However, R₁Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, L represents a divalent linking group, Z represents a nitrogen-containing heterocyclic group, and E represents a compound containing an ethylenically unsaturated group. X and y represent the weight composition ratio of the repeating unit, x is 5 to 100% by weight, and y is 0 to 95% by weight. )
[0013]
The nitrogen-containing heterocyclic ring in the nitrogen-containing heterocyclic group represented by Z may be an unsaturated ring or a saturated ring, and may have an atom other than a nitrogen atom. Examples of the unsaturated heterocyclic ring include a pyridine ring, an imidazole ring, a thiazole ring, an oxazole ring, and a triazole ring. Examples of saturated heterocycles include morpholine ring, piperidine ring, piperazine ring and the like. Preferred nitrogen-containing heterocycles are unsaturated heterocycles, more preferably pyridine rings or imidazole rings. These are preferably unsubstituted, but may be substituted with an alkyl group such as a methyl group.
[0014]
R₁Represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. R₁Is preferably a hydrogen atom or a methyl group.
[0015]
The linking group L may be any divalent linking group having at least one atom selected from the group consisting of C, O, N and S, but —COO—, —OCO—, —CON (R₂)-Or -N (R_ThreeCO- or a linking group obtained by combining one or more of these groups with one or more divalent groups selected from an alkylene group, an arylene group and -O- is preferred. However, R₂And R_ThreeIs a hydrogen atom or a lower alkyl group, preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. Here, an alkylene group or an arylene group is a halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom), hydroxyl group, amino group, nitro group, carboxy group, carbamoyl group, sulfonic acid group, sulfonamide group, acyl Group (for example, formyl group, acetyl group), acyloxy group, acylamino group (for example, acetamido group, benzamide group), alkyl group, alkoxy group (for example, methoxy group, ethoxy group, methoxyethoxy group), acoxycarbonyl group, alkylsulfonyl May have a substituent such as a group, an aryl group, an aryloxy group (for example, phenoxy), and an arylsulfonyl group.
[0016]
Of these, -COO-, -COO- (CH₂CH₂O)_n-(N is an integer from 1 to 30), -COO- (C_ThreeH₆O)_n-(N is an integer from 1 to 30), -COO- (CH₂)_n-(N is an integer from 1 to 10), -COO- (CH₂)_n-OCO- (n is an integer from 1 to 10), -COO- (CH₂)_m-OCO- (CH₂)_n-(M and n are integers from 1 to 10), -COO- (CH₂CH₂O)_n-CO- (n is an integer from 1 to 30), -COO- (CH₂CH₂O)_m-CO- (CH₂)_n-(M is an integer from 1 to 30, n is an integer from 1 to 10), -COO- (C_ThreeH₆O)_n-CO- (n is an integer from 1 to 30), -COO- (C_ThreeH₆O)_m-CO- (CH₂)_n-(M is an integer from 1 to 30, n is an integer from 1 to 10), -CONH-, -CON (CH_Three)-, -CONH- (CH₂)_n-(N is an integer from 1 to 10), -CONH- (CH₂)_Three-O- (CH₂CH₂O)_n-(CH₂)_Three-NHCO- (n is an integer from 1 to 30), -CONH-C_ThreeH₆-O- (CH₂CH₂O)_n-C_ThreeH₆-NHCO- (n is an integer from 1 to 30), -CONH-C_ThreeH₆-O- (C_ThreeH₆O)_n-C_ThreeH₆-NHCO- (n is an integer from 1 to 30), -COO- (CH₂)_n-O-COO- (n is an integer from 1 to 10), -COO- (CH₂)_n-NHCO- (n is an integer from 1 to 10), -OCO-, -OCO- (CH₂)_n-(N is an integer from 1 to 10), -O-COO- (CH₂)_n-(N is an integer from 1 to 10), -NHCO- (CH₂)_n-(N is an integer from 1 to 10), -NHCO- (CH₂)_n-CONH- (n is an integer from 1 to 10), -NHCO- (CH₂)_m-CONH- (CH₂)_n-(M and n are integers from 1 to 10) or -NHCO-O- (CH₂)_n-OCO- (n is an integer from 1 to 10) is particularly preferred.
[0017]
E represents a repeating unit derived from a compound containing an ethylenically unsaturated group. Preferable examples of the compound having an ethylenically unsaturated group for deriving the repeating unit represented by E include esters or amides derived from acrylic acid or α-alkylacrylic acid (for example, methacrylic acid) (for example, N-iso-propylacrylamide, Nn-butylacrylamide, Nt-butylacrylamide, N, N-dimethylacrylamide, N-methylmethacrylamide, acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, acrylamidopropyltrimethylammonium chloride, methacryl Amides, diacetone acrylamide, N-methylol acrylamide, N-methylol methacrylamide, methyl acrylate, ethyl acrylate, hydroxyethyl acrylate, n-propyl acrylate, iso-propyl acrylate 2-hydroxypropyl acrylate, 2-methyl-2-nitropropyl acrylate, n-butyl acrylate, iso-butyl acrylate, t-butyl acrylate, t-pentyl acrylate, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2 -Methoxyethoxyethyl acrylate, 2,2,2-trifluoroethyl acrylate, 2,2-dimethylbutyl acrylate, 3-methoxybutyl acrylate, ethyl carbitol acrylate, phenoxyethyl acrylate, n-pentyl acrylate, 3-pentyl acrylate, Octafluoropentyl acrylate, n-hexyl acrylate, cyclohexyl acrylate, cyclopentyl acrylate, cetyl acrylate, benzyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate 4-methyl-2-propylpentyl acrylate, heptadecafluorodecyl acrylate, n-octadecyl acrylate, methyl methacrylate, 2-methoxyethoxyethyl methacrylate, ethylene glycol ethyl carbonate methacrylate, 2,2,2-trifluoroethyl methacrylate , Tetraglutoropropyl methacrylate, hexafluoropropyl methacrylate, hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, t-butyl methacrylate, t-pentyl methacrylate, 2-methoxyethyl methacrylate, 2- Ethoxyethyl methacrylate, benzyl methacrylate, heptadecafluorodecyl methacrylate, n-octadecyl methacrylate, 2-isobo Nyl methacrylate, 2-norbornylmethyl methacrylate, 5-norbornen-2-ylmethyl methacrylate, 3-methyl-2-norbornylmethyl methacrylate, dimethylaminoethyl methacrylate, etc.), vinyl esters (for example, vinyl acetate, etc.), Esters derived from maleic acid or fumaric acid (dimethyl maleate, dibutyl maleate, diethyl fumarate, etc.), maleic acid, fumaric acid, sodium salt of p-styrenesulfonic acid, acrylonitrile, methacrylonitrile, dienes ( For example, butadiene, cyclopentadiene, isoprene, etc.), aromatic vinyl compounds (eg, styrene, p-chlorostyrene, t-butylstyrene, α-methylstyrene, sodium styrenesulfonate), N-vinylformamide, N-vinyl -N-Mech Formamide, N-vinylacetamide, N-vinyl-N-methylacetamide, vinyl sulfonic acid, sodium vinyl sulfonate, sodium allyl sulfonate, sodium methallyl sulfonate, vinylidene fluoride, vinylidene chloride, vinyl alkyl ethers (for example, Methyl vinyl ether), ethylene, propylene, 1-butene, isobutene, N-phenylmaleimide and the like.
[0018]
As compounds having an ethylenically unsaturated group other than the above, those described in Research Disclosure No. 1995 (1980, July) can be used.
[0019]
x and y represent the weight composition ratio of the repeating unit derived from a compound containing a nitrogen-containing heterocyclic group Z and a compound containing an ethylenically unsaturated group, respectively, x is 5 to 100% by weight, and y is 0 -95 wt% is preferred. More preferably, x is 10 to 95% by weight and y is 5 to 90% by weight. The repeating unit containing Z and the structural unit having an ethylenically unsaturated group may be used in combination of two or more.
[0020]
The weight average molecular weight of the nitrogen-containing polymer compound is preferably 1,000,000 to 1,000,000. More preferably, it is 2000-100,000.
[0021]
Preferred specific examples of the nitrogen-containing polymer compound represented by the formula (I) are shown below, but the present invention is not limited thereto.
[0022]
[Formula 4]
[0023]
[Chemical formula 5]
[0024]
[Chemical 6]
[0025]
[Chemical 7]
[0026]
[Chemical 8]
[0027]
Nitrogen-containing polymer compounds represented by formula (I) are written by Takayuki Otsu and Masaaki Kinoshita: Experimental methods for polymer synthesis (Chemical Doujin) and Takatsu Otsu: Lecture Polymerization Reaction Theory 1 Radical Polymerization (1) (Chemical Doujin) ) Can be synthesized by radical polymerization, which is a general polymer synthesis method described in (1). The nitrogen-containing polymer compound can be radically polymerized by heating, light, electron beam, or electrochemically, but is particularly preferably radically polymerized by heating. Polymerization initiators preferably used when formed by heating are, for example, 2,2-azobisisobutyronitrile, 2,2-azobis (2,4-dimethylvaleronitrile), dimethyl 2,2-azobis (2-methylpropionate), azo initiators such as dimethyl 2,2-azobisisobutyrate, peroxide initiators such as lauryl peroxide, benzoyl peroxide, tert-butyl peroctoate, etc. is there.
[0028]
(B) Electrophile
The electrophile to be reacted with the nitrogen-containing polymer is not particularly limited as long as it is a bifunctional or higher functional compound capable of electrophilic reaction with a nitrogen atom. For example, a bifunctional or higher alkyl halide or halogenated Examples include aralkyl, sulfonic acid ester, acid anhydride, acid chloride, and isocyanate. Of these, alkyl halides, halogenated aralkyls or sulfonic acid esters are more preferred, alkyl halides or halogenated aralkyls are particularly preferred, and alkyl halides are most preferred. The most preferable embodiment is one having an ether bond in the alkylene chain of a bifunctional or higher alkyl halide and a halogenated aralkyl.
[0029]
Examples of the bifunctional or higher functional alkyl halide (aralkyl) include alkyl iodide (aralkyl), alkyl bromide (aralkyl), alkyl chloride (aralkyl) and the like. Of these, alkyl iodide (aralkyl) and alkyl bromide (aralkyl) are preferable, and alkyl iodide (aralkyl) is particularly preferable.
[0030]
Examples of the sulfonic acid ester include alkyl sulfonic acid esters such as methane sulfonic acid ester and trifluoromethane sulfonic acid ester, and aryl sulfonic acid esters such as p-toluene sulfonic acid ester.
[0031]
The number of sites capable of reacting with the nitrogen atom of these bifunctional or higher electrophiles is preferably 2 to 10, more preferably 2 to 5, and particularly preferably 2 to 4.
[0032]
Although the preferable specific example of an electrophile is shown below, this invention is not limited to these.
[0033]
[Chemical 9]
[0034]
Embedded image
[0035]
Embedded image
[0036]
(C) Cross-linking reaction
Electrolyte compositionThe crosslinked polymer used for the formula (I)Or formula (II)It is obtained by a crosslinking reaction between a nitrogen atom of the nitrogen-containing polymer compound represented by The cross-linking reaction is preferably performed in a state in which a salt is present in addition to the nitrogen-containing polymer compound and the electrophile. In the electrolyte composition of the present invention, a salt is essential as an electrolyte. A salt may be added after crosslinking, but in this case, it is difficult to uniformly disperse the salt in the crosslinked polymer, which is not preferable.
[0037]
The reaction solution includes (i) a nitrogen-containing polymer compound, an electrophile, a salt dissolved in a solvent, or (ii) monomers constituting the nitrogen-containing polymer compound, a polymerization initiator, an electrophile, and a salt. Can be used, but it is preferable to use (i).
[0038]
As salt, (a) I₂And iodide (LiI, NaI, KI, CsI, CaI₂(B) Br in combination with a metal iodide such as tetraalkylammonium iodide, pyridinium iodide, quaternary ammonium compounds such as imidazolium iodide, etc.₂And bromide (LiBr, NaBr, KBr, CsBr, CaBr₂(C) Metal complexes such as ferrocyanate-ferricyanate and ferrocene-ferricinium ions, etc., in combination with metal bromides such as tetraalkylammonium bromide, pyridinium bromide, etc. (D) Sulfur compounds such as sodium polysulfide and alkylthiol-alkyldisulfides, (e) viologen dyes, hydroquinone-quinones and the like can be used. Above all, I₂An electrolyte in which LiI, a pyridinium iodide, an iodine salt of a quaternary ammonium compound such as imidazolium iodide is combined is preferable. You may mix and use the said salt. Further, a salt in a molten state at room temperature described in EP718288, WO95 / 18456, J. Electrochem. Soc., Vol. 143, No. 10, 3099 (1996), Inorg. Chem., 35, 1168-1178 (1996) (Molten salt) can also be used. When using a molten salt as an electrolyte, the solvent may not be used.
[0039]
As the solvent, it is desirable to use a compound that can exhibit excellent ionic conductivity because it has low viscosity and high ion mobility, or has a high dielectric constant and increases effective carrier concentration, or both. Examples of such solvents include the following.
[0040]
(a) Carbonates
For example, ethylene carbonate, propylene carbonate, vinylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, dipropyl carbonate and the like are preferable.
[0041]
(b) Lactones
For example, γ-butyrolactone, γ-valerolactone, γ-caprolactone, crotolactone, γ-caprolactone, δ-valerolactone and the like are preferable.
[0042]
(c) Ethers
For example, ethyl ether, 1,2-dimethoxyethane, diethoxyethane, trimethoxymethane, ethylene glycol dimethyl ether, polyethylene glycol dimethyl ether, 1,3-dioxolane, 1,4-dioxane and the like are preferable.
[0043]
(d) Alcohols
For example, methanol, ethanol, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, polyethylene glycol monoalkyl ether, polypropylene glycol monoalkyl ether and the like are preferable.
[0044]
(e) Glycols
For example, ethylene glycol, propylene glycol, polyethylene glycol, polypropylene glycol, glycerin and the like are preferable.
[0045]
(f) Glycol ethers
For example, ethylene glycol dialkyl ether, propylene glycol dialkyl ether, polyethylene glycol dialkyl ether, polypropylene glycol dialkyl ether and the like are preferable.
[0046]
(g) Tetrahydrofurans
For example, tetrahydrofuran, 2-methyltetrahydrofuran and the like are preferable.
[0047]
(h) Nitriles
For example, acetonitrile, glutarodinitrile, propionitrile, methoxyacetonitrile, benzonitrile and the like are preferable.
[0048]
(i) Carboxylic acid esters
For example, methyl formate, methyl acetate, ethyl acetate, methyl propionate and the like are preferable.
[0049]
(j) Phosphoric acid triesters
For example, trimethyl phosphate and triethyl phosphate are preferable.
[0050]
(k) Heterocyclic compounds
For example, N-methylpyrrolidone, 4-methyl-1,3-dioxane, 2-methyl-1,3-dioxolane, 3-methyl-2-oxazolidinone, 1,3-propane sultone, sulfolane, etc.
preferable.
[0051]
(l) Other
Preferred are aprotic organic solvents such as dimethyl sulfoxide, formamide, N, N-dimethylformamide, nitromethane, and water.
[0052]
Of these, carbonate-based solvents, nitrile-based solvents, and heterocyclic compound-based solvents are preferable. These solvents may be used as a mixture of two or more if necessary.
[0053]
The concentration of the nitrogen-containing polymer compound in the reaction solution is preferably 1 to 80% by weight, more preferably 3 to 70% by weight, with [solvent + nitrogen-containing polymer compound + salt] being 100% by weight. If the nitrogen-containing polymer compound is less than 1% by weight, the strength is insufficient, and if it exceeds 80% by weight, the mobility of the carrier decreases, which is not preferable. The nitrogen-containing polymer compound may be used alone or in combination of two or more.
[0054]
The concentration of the electrophile in the reaction solution is preferably set so that the molar ratio of the electrophilic site to the number of moles of the reactive nitrogen atom in the nitrogen-containing polymer compound is 0.02 to 2, more preferably 0.05. ~ 1.5. In addition, an electrophile may be used independently or may use 2 or more types together.
[0055]
The salt concentration in the reaction solution is preferably 0.05 to 2 mol / L, more preferably 0.1 to 1.5 mol / L. AlsoElectrolyte compositionIt is also possible to add iodine (bromine in the case of a bromine salt) to form a redox couple in advance, but in this case, the preferred concentration of iodine or bromine is 0.01 to 0.3 mol / L.
[0056]
Electrolyte compositionThe proportion of the cross-linked polymer is preferably 2 to 80% by weight.
[0057]
Electrolyte compositionThe electrolyte layer can be produced by forming a reaction solution layer on the electrode by a casting method, a coating method, a dipping method, an impregnation method, an infiltration method, etc., and then crosslinking by a heating reaction.
[0058]
When an electrolyte layer is formed by a coating method, spin a homogeneous solution prepared by adding additives such as a leveling agent to a coating solution consisting of a nitrogen-containing polymer, electrophile, and a salt-dissolved solvent. Coating method, dip coating method, air knife coating method, curtain coating method, roller coating method, wire bar coating method, gravure coating method, or extrusion coating method using a hopper described in US Pat. No. 2681294, or a US patent It is applied by a method such as the multilayer simultaneous application method described in Nos. 2761418, 3508947, and 2771191, and then heated to be crosslinked. The heating temperature is appropriately selected depending on the heat-resistant temperature of the dye, etc., but is preferably 10 ° C. or higher and 200 ° C. or lower, more preferably 30 ° C. or higher and 150 ° C. or lower. Further, the heating time is about 5 minutes to 72 hours although it depends on the heating temperature and the like.
[0059]
When iodine or the like is introduced into the electrolyte composition to form a redox couple, in addition to the electrolyte solution described above, after formation of the electrolyte layer, this is placed in a sealed container together with iodine and the like in the electrolyte composition. It can be introduced by a diffusion method or the like. In addition, iodine or the like can be introduced into the electrolyte layer when a photoelectric conversion element used as a photoelectrochemical cell is assembled by a method of applying or vapor-depositing to a counter electrode described later.
[0060]
[2] photoelectric conversion elements
Photoelectric conversion elementIs formed by laminating a conductive support, a photosensitive layer, a charge transfer layer containing the above-described electrolyte composition, and a counter electrode in this order. Preferably, as shown in FIG. 1, a conductive support 10, a photosensitive layer 20, a charge transfer layer 30 and a counter electrode 40 are laminated in this order, and the conductive support layer 10 is composed of a substrate 11 and a conductive layer 12. The photosensitive layer 20 is composed of semiconductor fine particles 21 sensitized by the dye 22 and the electrolyte composition 30 filled in the gaps between the semiconductor fine particles 21. As shown in FIG. 2, a substrate 41 on which a conductive layer 42 is formed may be used as the counter electrode 40. At the boundary of each layer (for example, the boundary between the conductive layer 12 and the photosensitive layer 20 of the conductive support, the boundary between the photosensitive layer 20 and the charge transfer layer 30, the boundary between the charge transfer layer 30 and the counter electrode 40, etc.) These components may be diffusively mixed with each other. The composition and structure of each layer will be described in detail below.
[0061]
(I) Charge transfer layer
The charge transfer layer is a layer having a function of replenishing electrons to the oxidant of the dye in the photosensitive layer. In charge transfer layerAboveAlthough an electrolyte composition is used, a solid electrolyte or a hole transport material can be used in combination.
[0062]
In order to form the charge transfer layer, as described above, an electrolyte solution may be applied on the photosensitive layer by a casting method, a coating method, a dipping method, an impregnation method or the like, and then crosslinked by a heating reaction. According to a preferred embodiment, as shown in FIG. 1, a solution containing more electrolyte than the amount that completely fills the voids in the photosensitive layer 20 is applied, so that the resulting electrolyte layer is substantially conductive on the conductive support. It can be said that it exists between the boundary with the layer 12 and the boundary with the counter electrode 40. Here, when the electrolyte layer existing between the boundary with the photosensitive layer 20 containing the dye-sensitized semiconductor and the boundary with the counter electrode 40 is the charge transfer layer 30, its thickness is preferably 0.001 to 200 μm, and 0.1 to 100 μm. More preferred. If the charge transfer layer 30 is thinner than 0.001 μm, the semiconductor fine particles 21 in the photosensitive layer may come into contact with the counter electrode 40. If the charge transfer layer 30 is thicker than 200 μm, the charge transfer distance becomes too long and the resistance of the device increases. The thickness of the photosensitive layer 20 + charge transfer layer 30 (substantially equal to the thickness of the electrolyte composition) is preferably 0.1 to 300 μm, more preferably 1 to 130 μm.
[0063]
(II) Photosensitive layer
The photosensitive layer is a layer having a semiconductor, and the semiconductor absorbs light and performs charge separation to generate electrons and holes. As shown in FIG. 1, the photosensitive layer is preferably a layer 20 having a structure in which the voids in the layer of the semiconductor fine particles 21 sensitized by the dye 22 (adsorbed and supported by the dye 22) are filled with the electrolyte composition. . In the case of FIG. 1, the incident light excites the dye 22 and the like, and high-energy electrons in the excited dye 22 and the like are passed to the conduction band of the semiconductor fine particles 21 and further reach the conductive support 10 by diffusion. . At this time, the molecule such as the dye 22 is an oxidant. In the photoelectrochemical cell, electrons in the conductive support 10 return to an oxidant such as the dye 22 through the counter electrode 40 and the charge transfer layer while working in an external circuit, and the dye 22 is regenerated. The semiconductor fine particles and dyes that can be preferably used in the photosensitive layer are described in detail below.
[0064]
(A) Semiconductor fine particles
The semiconductor fine particles act as the negative electrode of the photoelectrochemical cell. The dye-sensitized semiconductor fine particle is a so-called photoconductor, which absorbs light and separates charges to generate electrons and holes. In the dye-sensitized semiconductor fine particles, light absorption and generation of electrons and holes thereby occur mainly in the dye, and the semiconductor fine particles play a role of receiving and transmitting the electrons.
[0065]
Semiconductor fine particles include simple semiconductors such as silicon and germanium, III-V compound semiconductors, metal chalcogenides (eg oxides, sulfides, selenides, etc.), or compounds having a perovskite structure (eg strontium titanate, titanium). Calcium oxide, sodium titanate, barium titanate, potassium niobate, etc.) can be used.
[0066]
Preferred metal chalcogenides include titanium, tin, zinc, iron, tungsten, zirconium, hafnium, strontium, indium, cerium, yttrium, lanthanum, vanadium, niobium or tantalum oxides, cadmium, zinc, lead, silver, antimony, Bismuth sulfide, cadmium, lead selenide, cadmium telluride and the like. Other compound semiconductors include phosphides such as zinc, gallium, indium, cadmium, gallium arsenide, copper-indium-selenide, copper-indium-sulfide, and the like.
[0067]
Preferred specific examples of the semiconductor used in the present invention include Si and TiO.₂, SnO₂, Fe₂O_Three, WO_Three, ZnO, Nb₂O_Five, CdS, ZnS, PbS, Bi₂S_Three, CdSe, CdTe, GaP, InP, GaAs, CuInS₂, CuInSe₂More preferably, TiO₂, ZnO, SnO₂, Fe₂O_Three, WO_Three, Nb₂O_Five, CdS, PbS, CdSe, InP, GaAs, CuInS₂, CuInSe₂And particularly preferably TiO₂Or Nb₂O_FiveAnd most preferably TiO₂It is.
[0068]
The semiconductor used in the present invention may be single crystal or polycrystalline. Single crystals are preferable from the viewpoint of conversion efficiency, but polycrystals are preferable from the viewpoints of manufacturing cost, securing raw materials, energy payback time, and the like.
[0069]
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 5 to 200 nm, more preferably 8 to 100 nm. preferable. The average particle size of the semiconductor fine particles (secondary particles) in the dispersion is preferably 0.01 to 100 μm.
[0070]
Two or more kinds of fine particles having different particle size distributions may be mixed. In this case, the average size of the small particles is preferably 5 nm or less. For the purpose of improving the light capture rate by scattering incident light, semiconductor particles having a large particle diameter, for example, about 300 nm may be mixed.
[0071]
Semiconductor fine particles are prepared by Sakuo Sakuo's "Sol-gel Method Science" Agne Jofusha (1998), Technical Information Association "Sol-gel Method Thin Film Coating Technology" (1995), etc. The described sol-gel method, Tadao Sugimoto, “Synthesis and size control of monodisperse particles by the new synthetic gel-sol method”, “Materia”, Vol. 35, No. 9, pp. 1012-1018 (1996) The gel-sol method described in the "year" is preferred. Also preferred is a method developed by Degussa to produce an oxide by high-temperature hydrolysis of chloride in an oxyhydrogen salt.
[0072]
When the semiconductor fine particles are titanium oxide, the sol-gel method, gel-sol method, and high-temperature hydrolysis method in oxyhydrogen salt of chloride are all preferred, but Kiyoshi Manabu's “Titanium oxide properties and applied technology” The sulfuric acid method and the chlorine method described in Gihodo Publishing (1997) can also be used. Furthermore, as a sol-gel method, the method described in “Journal of American Ceramic Society” such as Barb, Vol. 80, No. 12, pp. 3157-3171 (1997), and “Chemicals such as Burnside” The method described in “Materials”, Vol. 10, No. 9, pages 2419-2425 is also preferable.
[0073]
In order to apply the semiconductor fine particles on the conductive support, in addition to the method of applying a dispersion or colloidal solution of semiconductor fine particles on the conductive support, the above-described sol-gel method or the like can also be used. In consideration of mass production of photoelectric conversion elements, physical properties of semiconductor fine particle liquid, flexibility of conductive support, etc., a wet film forming method is relatively advantageous. As a wet film forming method, a coating method and a printing method are typical.
[0074]
In addition to the sol-gel method described above, a method for preparing a dispersion of semiconductor fine particles includes a method of grinding with a mortar, a method of dispersing while grinding using a mill, or a fine particle in a solvent when synthesizing a semiconductor. The method of depositing and using as it is is mentioned.
[0075]
Examples of the dispersion medium include water or various organic solvents (for example, methanol, ethanol, isopropyl alcohol, dichloromethane, acetone, acetonitrile, ethyl acetate, and the like). During dispersion, a polymer, surfactant, acid, chelating agent, or the like may be used as a dispersion aid as necessary.
[0076]
The application method is disclosed in Japanese Patent Publication No. 58-4589 as a roller method, a dip method as an application system, an air knife method, a blade method, etc. as a metering system, and the application and metering can be performed in the same part. The wire bar method, the slide hopper method, the extrusion method, the curtain method and the like described in U.S. Pat. Nos. 2,681,294, 2,714,419 and 2,767,911, are preferred. Moreover, a spin method and a spray method are also preferable as a general purpose machine. Further, as the wet printing method, intaglio, rubber plate, screen printing and the like are preferred, including the three major printing methods of letterpress, offset and gravure. From these, a preferred film forming method is selected according to the liquid viscosity and the wet thickness.
[0077]
The viscosity of the dispersion of semiconductor fine particles greatly depends on the type and dispersibility of the semiconductor fine particles, the type of solvent used, and additives such as surfactants and binders. For a high viscosity liquid (for example, 0.01 to 500 Poise), an extrusion method, a casting method, a screen printing method, or the like is preferable. For low-viscosity liquids (for example, 0.1 Poise or less), the slide hopper method, wire bar method, or spin method is preferable, and a uniform film can be obtained. If there is a certain amount of coating, coating by the extrusion method is possible even in the case of a low viscosity liquid. Thus, a wet film forming method may be selected as appropriate according to the viscosity of the coating solution, the coating amount, the support, the coating speed, and the like.
[0078]
The semiconductor fine particle layer is not limited to a single layer, but a multi-layer coating of a dispersion of semiconductor fine particles having different particle diameters, or a multi-layer coating of a coating layer containing different types of semiconductor fine particles (or different binders and additives) You can also Multi-layer coating is also effective when the film thickness is insufficient with a single coating. For multilayer coating, an extrusion method or a slide hopper method is suitable. In the case of applying multiple layers, the multiple layers may be applied at the same time, or may be successively applied several times to several dozen times. Further, screen printing can be preferably used as long as it is sequentially overcoated.
[0079]
In general, as the thickness of the semiconductor fine particle layer (same as the thickness of the photosensitive layer) increases, the amount of supported dye increases per unit projected area, so that the light capture rate increases. Resistance increases. Therefore, the preferable thickness of the semiconductor fine particle layer is 0.1 to 100 μm. When used in a photoelectrochemical cell, the thickness of the semiconductor fine particle layer is preferably 1 to 30 μm, and more preferably 2 to 25 μm. Semiconductor fine particle support 1m²The coating amount per unit is preferably 0.5 to 400 g, more preferably 5 to 100 g.
[0080]
After the semiconductor fine particles are applied on the conductive support, the semiconductor fine particles are preferably brought into contact with each other electronically, and heat treatment is preferably performed in order to improve the coating strength and the adhesion to the support. A preferable heating temperature range is 40 ° C. or higher and lower than 700 ° C., and more preferably 100 ° C. or higher and 600 ° C. or lower. The heating time is about 10 minutes to 10 hours. When using a support having a low melting point or softening point such as a polymer film, high temperature treatment is not preferable because it causes deterioration of the support. Moreover, it is preferable that it is as low as possible also from a viewpoint of cost. The temperature can be lowered by using a combination of small semiconductor fine particles of 5 nm or less or heat treatment in the presence of a mineral acid as described above.
[0081]
In order to increase the surface area of the semiconductor fine particles after heat treatment, increase the purity near the semiconductor fine particles, and increase the efficiency of electron injection from the dye to the semiconductor particles, for example, chemical plating using a titanium tetrachloride aqueous solution or a titanium trichloride aqueous solution is used. The electrochemical plating process used may be performed.
[0082]
The semiconductor fine particles preferably have a large surface area so that many dyes can be adsorbed. For this reason, the surface area of the semiconductor fine particle layer coated on the support is preferably 10 times or more, more preferably 100 times or more the projected area. The upper limit is not particularly limited, but is usually about 1000 times.
[0083]
(B) Dye
The dye used in the photosensitive layer is preferably a metal complex dye, a phthalocyanine dye or a methine dye. In order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency, two or more kinds of dyes can be mixed. Further, the dye to be mixed and its ratio can be selected so as to match the wavelength range and intensity distribution of the target light source. Such a dye preferably has a suitable interlocking group for the surface of the semiconductor fine particles. Preferred linking groups include COOH groups and SO_ThreeH group, cyano group, -P (O) (OH)₂Group, -OP (O) (OH)₂Groups or chelating groups with π-conductivity such as oximes, dioximes, hydroxyquinolines, salicylates and α-ketoenolates. Among them, COOH group, -P (O) (OH)₂Group, -OP (O) (OH)₂The group is particularly preferred. These groups may form a salt with an alkali metal or the like, or may form an internal salt. In the case of a polymethine dye, if the methine chain contains an acidic group as in the case where the methine chain forms a squarylium ring or a croconium ring, this part may be used as a linking group.
[0084]
Dyes that are preferably used in the photosensitive layer will be specifically described below. When the dye is a metal complex dye, a ruthenium complex dye is preferable, and further the following formula (III):
(A₁)_pRuB_aB_bB_c(III)
Is preferred. However, p is 0-2, Preferably it is 2. Ru represents ruthenium. A₁Is Cl, SCN, H₂It is at least one ligand selected from the group consisting of O, Br, I, CN, NCO and SeCN. Also B_a, B_b, B_cAre each independently at least one organic ligand selected from the group consisting of B-1 to B-8, which may be the same or different.
[0085]
Embedded image
[0086]
Where R_aIs a hydrogen atom, 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, or a substituted or unsubstituted aryl group having 6 to 12 carbon atoms. To express. The alkyl part of the alkyl group and aralkyl group may be linear or branched, and the aryl part and the aryl part of the aralkyl group may be monocyclic or polycyclic (fused ring, ring assembly).
[0087]
Examples of the ruthenium complex dye include complex dyes described in U.S. Pat.
[0088]
Although the preferable specific example of a metal complex dye is shown below, this invention is not limited to these.
[0089]
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[0090]
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[0091]
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[0092]
When the dye is a methine dye, a dye represented by the following formula (IV), formula (V), formula (VI) or formula (VII) is preferred.
[0093]
(1) Dye represented by formula (IV)
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However, R_bAnd R_fEach represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group, and R_c~ R_eEach represents a hydrogen atom or a substituent. R_b~ R_fMay combine with each other to form a ring. X₁₁And X₁₂Represents nitrogen, oxygen, sulfur, selenium and tellurium, respectively. n₁₁And n₁₃Each represents an integer from 0 to 2;₁₂Represents an integer of 1-6. The compound represented by the formula (IV) may have a counter ion according to the charge of the whole molecule.
[0094]
The alkyl group, aryl group and heterocyclic group may have a substituent. The alkyl group may be linear or branched, and the aryl group and heterocyclic group may be monocyclic or polycyclic (fused ring, ring assembly). Also R_b~ R_fThe ring formed by may have a substituent and may be a single ring or a condensed ring.
[0095]
(2) Dye represented by formula (V)
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However, Z_aRepresents a nonmetallic atom group necessary for forming a nitrogen-containing heterocycle. R_gIs an alkyl group or an aryl group. Q_aRepresents a methine group or polymethine group necessary for the compound represented by the formula (V) to form a methine dye. X₁₃Represents a charge balanced counter ion and n₁₄Is the charge-balanced counter ion X necessary to neutralize the charge of the molecule₁₃Represents an equivalent weight of 0 to 10.
[0096]
Z above_aThe nitrogen-containing heterocyclic ring formed by may have a substituent and may be a monocyclic ring or a condensed ring. The alkyl group and aryl group may have a substituent, the alkyl group may be linear or branched, and the aryl group may be monocyclic or polycyclic (fused ring, ring assembly).
[0097]
Of the dyes represented by the formula (V), dyes represented by the following formulas (Va) to (Vd) are preferable.
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However, R₁₁~ R₁₅, R_{twenty one}~ R_{twenty four}, R₃₁~ R₃₃, And R₄₁~ R₄₃Each independently represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group;₁₁, Y₁₂, Y_{twenty one}, Y_{twenty two}, Y₃₁~ Y₃₅And Y₄₁~ Y₄₆Are independently oxygen, sulfur, selenium, tellurium, -CR₁₆R₁₇-Or -NR₁₈-Represents. R₁₆~ R₁₈Each independently represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group. Y_{twenty three}Is O-, S-, Se-, Te- or -NR₁₈-Represents.
[0098]
V₁₁, V₁₂, V_{twenty one}, V_{twenty two}, V₃₁And V₄₁Each independently represents a substituent, and n₁₅, N₃₁And n₄₁Each independently represents an integer of 1-6. The compounds represented by the formulas (Va) to (Vd) may have a counter ion depending on the charge of the whole molecule.
[0099]
The alkyl group, aryl group and heterocyclic group may have a substituent, the alkyl group may be linear or branched, and the aryl group and heterocyclic group may be monocyclic or polycyclic (fused ring, Ring assembly).
[0100]
Specific examples of the polymethine dye as described above are described in detail in Organic Colorants (Elsevier) by M. Okawara, T. Kitao, T. Hirasima, and M. Matuoka.
[0101]
(3) Dye represented by formula (VI)
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However, Q_bRepresents an atomic group necessary to complete a 5- or 6-membered nitrogen-containing heterocycle, and Q_bMay be condensed and may have a substituent.
[0102]
Q_bPreferred examples of the nitrogen-containing heterocycle completed in benzothiazole nucleus, benzoxazole nucleus, benzoselenazole nucleus, benzotelrazole nucleus, 2-quinoline nucleus, 4-quinoline nucleus, benzimidazole nucleus, thiazoline nucleus, India Examples include a renin nucleus, an oxadiazole nucleus, a thiazole nucleus, and an imidazole nucleus, more preferably a benzothiazole nucleus, a benzoxazole nucleus, a benzimidazole nucleus, a benzoselenazole nucleus, a 2-quinoline nucleus, a 4-quinoline nucleus, and an indolenine nucleus. Particularly preferred are a benzothiazole nucleus, a benzoxazole nucleus, a 2-quinoline nucleus, a 4-quinoline nucleus, and an indolenine nucleus. Examples of the substituent on the nitrogen-containing heterocycle include a carboxylic acid group, a phosphonic acid group, a sulfonic acid group, a halogen atom (F, Cl, Br, I), a cyano group, an alkoxy group (methoxy, ethoxy, methoxyethoxy, etc.), Aryloxy groups (phenoxy, etc.), alkyl groups (methyl, ethyl, cyclopropyl, cyclohexyl, trifluoromethyl, methoxyethyl, allyl, benzyl, etc.), alkylthio groups (methylthio, ethylthio, etc.), alkenyl groups (vinyl, 1- Propenyl etc.), aryl groups or heterocyclic groups (phenyl, thienyl, toluyl, chlorophenyl etc.) and the like.
[0103]
Z_bIs an atomic group necessary for completing a 3- to 9-membered ring, and is composed of atoms selected from a carbon atom, an oxygen atom, a nitrogen atom, a sulfur atom and a hydrogen atom. Z_bThe ring completed by is preferably a ring having a skeleton formed of 4 to 6 carbons, more preferably those represented by the following (a) to (e), most preferably (a) It is.
[0104]
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[0105]
L₁, L₂, L_Three, L_FourAnd L_FiveEach independently represents a methine group optionally having a substituent. As the substituent, a substituted or unsubstituted alkyl group (preferably having 1 to 12 carbon atoms, more preferably 1 to 7 carbon atoms such as methyl, ethyl, propyl, isopropyl, cyclopropyl, butyl, 2-carboxyethyl) Benzyl, etc.), substituted or unsubstituted aryl groups (preferably having 6 to 10 carbon atoms, more preferably 6 to 8 carbon atoms such as phenyl, toluyl, chlorophenyl, o-carboxyphenyl, etc.), heterocyclic groups ( For example, pyridyl, thienyl, furanyl, pyridyl, barbituric acid, etc.), halogen atom (eg, chlorine, bromine), alkoxy group (eg, methoxy, ethoxy, etc.), amino group (preferably having 1 to 12 carbon atoms, more preferably 6 to 6). For example, diphenylamino, methylphenylamino, 4-acetylpiperazine-1-yl Etc.), oxo group, and the like. These substituents on the methine group may be linked to each other to form a ring such as a cyclopentene ring, a cyclohexene ring, or a squarylium ring, or may form a ring with an auxiliary color group. Note that n represents the number of -L2 = L3-₅₁Is an integer of 0-4, preferably 0-3. N representing the number of -L4 = L5-₅₂Is 0 or 1.
[0106]
R_FiveRepresents a substituent. A preferred substituent is an aromatic group (which may have a substituent) or an aliphatic group (which may have a substituent), and the aromatic group preferably has 1 to 16 carbon atoms, and more preferably Is 5-6. The number of carbon atoms of the aliphatic group is preferably 1-10, more preferably 1-6. Examples of the unsubstituted aliphatic group and aromatic group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, a phenyl group, and a naphthyl group.
[0107]
W₁Represents a counter ion when a counter ion is required to neutralize the charge. Whether a dye is a cation or an anion or has a net ionic charge depends on its auxiliary color groups and substituents. When the substituent has a dissociable group, it may be dissociated and have a negative charge. In this case, the charge of the entire molecule is W₁Neutralized by Typical cations are inorganic or organic ammonium ions (eg, tetraalkylammonium ions, pyridinium ions, etc.) and alkali metal ions, while anions can be either inorganic or organic anions, for example Halogen anion (eg fluoride ion, chloride ion, bromide ion, iodide ion etc.), substituted aryl sulfonate ion (eg p-toluene sulfonate ion, p-chlorobenzene sulfonate ion etc.), aryl disulfonate ion ( For example, 1,3-benzenedisulfonate ion, 1,5-naphthalenedisulfonate ion, 2,6-naphthalenedisulfonate ion, alkyl sulfate ion (for example, methyl sulfate ion), sulfate ion, thiocyanate ion, perchlorine Acid ion, tetrafluoroborate ion, Examples thereof include acrylate ion, acetate ion, trifluoromethanesulfonate ion and the like.
[0108]
Furthermore, an ionic polymer or another dye having a charge opposite to that of the dye may be used as the charge balance counter ion, or a metal complex ion such as bisbenzene-1,2-dithiolatonickel (III) is used. May be.
[0109]
(4) Dye represented by formula (VII)
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[0110]
However, D represents an aromatic group having at least four functional groups, and X₁, X₂Are sulfur atom, selenium atom or CR respectively₆₃R₆₄(However, R₆₃And R₆₄Are each a hydrogen atom or an alkyl group. And may be the same or different, preferably a sulfur atom or CR₆₃R₆₄And more preferably CR₆₃R₆₄It is. Also R₆₁And R₆₂Each represents an alkyl group or an aromatic group, and P₁And P₂Each independently represents a group of nonmetallic atoms necessary to form a polymethine dye. W₂Represents a counter ion when a counter ion is required to neutralize the charge.
[0111]
Examples of at least tetrafunctional or higher aromatic groups D include those derived from aromatic hydrocarbons such as benzene, naphthalene, anthracene, phenanthrene, anthraquinone, carbazole, pyridine, quinoline, thiophene, furan, xanthene, thianthrene, etc. These may be derived from an aromatic heterocycle, and these may have a substituent in addition to the linking moiety. The aromatic group represented by D is preferably an aromatic hydrocarbon derivative group, more preferably a benzene or naphthalene derivative group.
[0112]
P₁And P₂Each independently represents a group of nonmetallic atoms necessary to form a polymethine dye. P₁And P₂It is possible to form any methine dye, preferably cyanine dye, merocyanine dye, rhodacyanine dye, trinuclear merocyanine dye, allopolar dye, hemicyanine dye, styryl dye and the like. Cyanine dyes include those in which a substituent on the methine chain forming the dye forms a squalium ring or a croconium ring. For more information on these dyes, see FMHarmer, “Heterocyclic Compounds-Cyanine Dyes and Related Compounds,” John Willie, "Heterocyclic Compounds-Special Topics in Heterocyclic Chemistry" by John Wiley & Sons, New York, London, 1964, DMSturmer Compounds-Special Topics in Heterocyclic Chemistry), Chapter 18, Section 14, pages 482-515. The cyanine dyes, merocyanine dyes and rhodacyanine dyes are preferably those shown in (XI), (XII) and (XIII) of US Pat. No. 5,340,694, pages 21-22. P₁And P₂Those having a squarylium ring in at least one methine chain portion of the polymethine dye formed by the above are preferred, and those having both are more preferred.
[0113]
R₆₁And R₆₂Is an aromatic group or an aliphatic group, and these may have a substituent. The number of carbon atoms in the aromatic group is preferably 5 to 16, more preferably 5 to 6. The number of carbon atoms of the aliphatic group is preferably 1 to 10, more preferably 1 to 6. Examples of the unsubstituted aliphatic group and aromatic group include a methyl group, an ethyl group, an n-propyl group, an n-butyl group, a phenyl group, and a naphthyl group.
[0114]
R₆₁, R₆₂, P₁And P₂At least one of them preferably has an acidic group. Here, the acidic group is a substituent having a dissociable proton, and examples thereof include a carboxylic acid group, a phosphonic acid group, a sulfonic acid group, and a boric acid group, and a carboxylic acid group is preferable. Further, such an acidic group may take a form of releasing a proton and dissociating. W₂Is W in formula (VI)₁It is synonymous with.
[0115]
Although the preferable specific example of the polymethine pigment | dye represented by Formula (IV)-(VII) is shown below, this invention is not limited to these.
[0116]
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[0117]
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[0118]
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[0119]
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[0120]
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[0121]
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[0122]
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[0123]
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[0124]
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[0125]
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[0126]
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[0127]
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[0128]
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[0129]
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[0130]
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[0131]
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[0132]
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[0133]
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[0134]
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[0135]
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[0136]
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[0137]
The compounds represented by formula (IV) and formula (V) are described in “Heterocyclic Compounds-Cyanine Dyes and Related” by FM Harmer. Compounds), John Wiley & Sons (New York, London, 1964), DMSturmer's "Heterocyclic Compounds-Special Topics in Heterocyclic Compounds-Special Topics in Heterocyclic Chemistry, Chapter 18, Section 14, pp. 482-515, John Wiley & Sons-New York, London, 1977, “Rodd's Chemistry of Carbon Compounds”, 2nd.Ed. vol.IV, partB, 197 7th, Chapter 15, pp. 369-422, synthesized based on the method described in Elsevier Science Publishing Company Inc., New York, British Patent No. 1,077,611, etc. be able to.
[0138]
The compound represented by the formula (VI) can be synthesized with reference to the description of Dyes and Pigments, Vol. 21, pp. 227-234. The compound represented by the formula (VII) is cited in Ukrainskii Khimicheskii Zhurnal, Vol. 40, No. 3, pp. 253-258, Dyes and Pigments, Vol. 21, pp. 227-234 and these references. It can be synthesized with reference to the description in the published literature.
[0139]
(C) Dye adsorption on semiconductor fine particles
In order to adsorb the dye to the semiconductor fine particles, a method of immersing a conductive support having a well-dried semiconductor fine particle layer in the dye solution or applying a dye solution to the semiconductor fine particle layer can be used. In the former case, an immersion method, a dip method, a roller method, an air knife method or the like can be used. In the case of the immersion method, the complex dye may be adsorbed at room temperature or may be heated to reflux as described in JP-A-7-249790. Examples of the latter application method include a wire bar method, a slide hopper method, an extrusion method, a curtain method, a spin method, and a spray method. Examples of the printing method include letterpress, offset, gravure, and screen printing. The solvent can be appropriately selected according to the solubility of the dye. For example, alcohols (methanol, ethanol, t-butanol, benzyl alcohol, etc.), 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, ben Zen, toluene, etc.) and mixed solvents thereof.
[0140]
As for the viscosity of the dye solution, as in the formation of the semiconductor fine particle layer, various printing methods other than the extrusion method are suitable for the high-viscosity liquid (for example, 0.01 to 500 poise), and the low-viscosity liquid (for example, 0.1 poise) In the following, a slide hopper method, a wire bar method, or a spin method is suitable, and any of them can form a uniform film.
[0141]
Thus, the dye adsorption method may be appropriately selected according to the viscosity of the dye coating solution, the coating amount, the conductive support, the coating speed, and the like. The time required for the dye adsorption after coating is preferably as short as possible when mass production is considered.
[0142]
Since the presence of unadsorbed dye causes disturbance in device performance, it is preferable to remove it by washing immediately after adsorption. It is preferable to use a wet cleaning tank and perform cleaning with a polar solvent such as acetonitrile or an organic solvent such as an alcohol solvent. In order to increase the adsorption amount of the dye, it is preferable to perform a heat treatment before the adsorption. In order to avoid water adsorbing on the surface of the semiconductor fine particles after the heat treatment, it is preferable to quickly adsorb the dye between 40 to 80 ° C. without returning to normal temperature.
[0143]
The total amount of dye used is the unit surface area of the conductive support (1 m²) Is preferably from 0.01 to 100 mmol. Moreover, it is preferable that the adsorption amount with respect to the semiconductor fine particle of a pigment | dye is 0.01-1 mmol per 1g of semiconductor fine particle. By setting such an amount of dye adsorption, a sensitizing effect in a semiconductor can be sufficiently 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 attached to the semiconductor floats, which causes a reduction in the sensitizing effect.
[0144]
For the purpose of reducing the interaction between dyes such as association, a colorless compound may be co-adsorbed on the semiconductor fine particles. Examples of the hydrophobic compound to be co-adsorbed include steroid compounds having a carboxyl group (for example, chenodeoxycholic acid). An ultraviolet absorber can also be used in combination.
[0145]
For the purpose of promoting the removal of excess dye, the surface of the semiconductor fine particles may be treated with amines after adsorbing the dye. Preferable amines include pyridine, 4-tert-butylpyridine, polyvinylpyridine and the like. When these are liquids, they may be used as they are, or may be used after being dissolved in an organic solvent.
[0146]
(III) Conductive support
As the conductive support, use is made of a glass or plastic substrate 11 having a conductive layer 12 containing a conductive agent on the photosensitive layer side as shown in FIG. can do. 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.). The thickness of the conductive layer is preferably about 0.02 to 10 μm.
[0147]
The lower the surface resistance of the conductive support, the better. The range of the surface resistance is preferably 100Ω / □ or less, more preferably 40Ω / □ or less. The lower limit of the surface resistance is not particularly limited, but is usually about 0.1Ω / □.
[0148]
When light is irradiated from the conductive support side, the conductive support is preferably photoelectrochemically substantially transparent. “Substantially transparent” means that the light transmittance is 10% or more, preferably 50% or more, and particularly preferably 70% or more. The transparent conductive support is preferably formed by applying or vapor-depositing a transparent conductive layer made of a conductive metal oxide on the surface of a transparent substrate such as glass or plastic. In particular, conductive glass in which a conductive layer made of tin dioxide doped with fluorine is deposited on a transparent substrate made of low-cost soda-lime float glass is preferable. In order to obtain a flexible photoelectric conversion element or solar cell at low cost, it is preferable to use a transparent polymer film provided with a conductive layer. Transparent polymer films include tetraacetyl cellulose (TAC), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), syndioctaic polyester (SPS), polyphenylene sulfide (PPS), polycarbonate (PC), polyarylate (PAr). ), Polysulfone (PSF), polyester sulfone (PES), polyetherimide (PEI), cyclic polyolefin, brominated phenoxy and the like. In order to ensure sufficient transparency, the amount of conductive metal oxide applied is 1 m of glass or plastic support.²The amount is preferably 0.01 to 100 g.
[0149]
It is preferable to use a metal lead for the purpose of reducing the resistance of the transparent conductive support. The material of the metal lead is preferably a metal such as aluminum, copper, silver, gold, platinum, nickel, and particularly preferably aluminum and silver. The metal lead is preferably installed on a transparent substrate by vapor deposition, sputtering or the like, and a transparent conductive layer made of tin oxide doped with fluorine or an ITO film is preferably provided thereon. Moreover, it is also preferable to install 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 metal lead installation is within 10%, more preferably 1 to 5%.
[0150]
(IV) Counter electrode
The counter electrode acts as a positive electrode of the photoelectrochemical cell when the photoelectric conversion element is a photoelectrochemical cell. As the counter electrode, a substrate having a conductive layer can be used in the same manner as the conductive support, but a substrate is not necessarily required if a metal plate that can maintain sufficient strength and sealability is used. As the conductive material used for the counter electrode, metal (for example, platinum, gold, silver, copper, aluminum, rhodium, indium, etc.), carbon, or conductive metal oxide (indium-tin composite oxide, tin oxide doped with fluorine) Etc.). An example of a preferred counter electrode is a thin film of metal or conductive metal oxide applied or deposited on glass or plastic. The thickness of the counter electrode is not particularly limited, but is preferably 3 nm to 10 μm. When the conductive layer is made of metal, the thickness is preferably 5 μm or less, and more preferably in the range of 5 nm to 3 μm.
[0151]
Since light may be irradiated from either or both of the conductive support and the counter electrode, in order for light to reach the photosensitive layer, it is sufficient that at least one of the conductive support and the counter electrode is substantially transparent. . From the viewpoint of improving the power generation efficiency, it is preferable to make the conductive support transparent so that 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, or a metal thin film can be used.
[0152]
As a procedure for providing the counter electrode, (a) when the charge transfer layer is formed and then provided thereon, and (b) after the counter electrode is disposed on the dye-sensitized semiconductor fine particle layer via a spacer, the gap There are two ways in which the electrolyte solution is filled in and crosslinked. In the case of (a), a conductive material is directly applied, plated or vapor deposited (PVD, CVD) on the charge transfer layer, or the conductive layer side of the substrate having the conductive layer is attached. In the case of (b), the counter electrode is assembled and fixed on the dye-sensitized semiconductor fine particle layer via a spacer, and the open end of the obtained assembly is immersed in an electrolyte solution, and capillary action or reduced pressure is used. The electrolyte solution is infiltrated into the gap between the dye-sensitized semiconductor fine particle layer and the counter electrode, and then crosslinked by heating.
[0153]
(V) Other layers
A functional layer such as a protective layer or an antireflection film may be provided on one or both of the conductive support and the counter electrode acting as an electrode. When such a functional layer is formed in multiple layers, a simultaneous multilayer coating method or a sequential coating method can be used, but the simultaneous multilayer coating method is preferable from the viewpoint of productivity. In the simultaneous multilayer coating method, the slide hopper method and the extrusion method are suitable in view of productivity and coating film uniformity. For forming these functional layers, an evaporation method, a bonding method, or the like can be used depending on the material.
[0154]
[3] photoelectrochemical cells
Photoelectrochemical cellIs to cause the photoelectric conversion element to work in an external circuit. In order to prevent deterioration of components and volatilization of the contents of the photoelectrochemical cell, it is preferable to seal the side surface with a polymer or an adhesive. The external circuit itself connected to the conductive support and the counter electrode via a lead may be a known one.
[0155]
【Example】
The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to the examples.
[0156]
1. Preparation of titanium dioxide dispersion
Inside a Teflon-coated stainless steel container with an inner volume of 200 ml, titanium dioxide fine particles (Nippon Aerosil Co., Ltd., Degussa P-25) 15 g, water 45 g, dispersant (Aldrich Triron X-100) 1 g, diameter 0.5 30 g of zirconia beads having a size of mm (manufactured by Nikkato Co., Ltd.) were added, and dispersion treatment was performed at 1500 rpm for 2 hours using a sand grinder mill (manufactured by Imex). Zirconia beads were filtered off from the resulting dispersion. The average particle diameter of the titanium dioxide fine particles in the obtained dispersion was 2.5 μm. The particle size was measured with a master sizer manufactured by MALVERN.
[0157]
2. TiO with adsorbed dye₂Preparation of fine particle layer (electrode A)
Prepare a 20mm x 20mm conductive glass plate coated with fluorine-doped tin oxide (Asahi Glass Co., Ltd., TCO glass-U, surface resistance: about 30Ω / □). Then, a spacer pressure-sensitive adhesive tape was stretched over a portion having a width of 3 mm to 3 mm, and then the dispersion was applied onto the conductive layer using a glass rod. After application of the dispersion, the adhesive tape was peeled off and air-dried at room temperature for 1 day. Next, this semiconductor-coated glass plate was placed in an electric furnace (muffle furnace FP-32 manufactured by Yamato Scientific Co., Ltd.) and baked at 450 ° C. for 30 minutes. After the semiconductor-coated glass plate was taken out and cooled, an ethanol solution of the dyes shown in Table 1 (concentration: 3 × 10^-Fourmol / L) for 3 hours. The semiconductor-coated glass plate on which the dye was adsorbed was immersed in 4-tert-butylpyridine for 15 minutes, washed with ethanol, and air dried. The dye-sensitized TiO obtained in this way₂The thickness of the fine particle layer is 10μm and TiO₂Fine particle application amount is 20g / m²Met. The amount of dye adsorbed is 0.1 to 10 mmol / m depending on the type.²It was in the range.
[0158]
3. Production of photoelectrochemical cell
Using the solvent shown in Table 1, a solution containing 0.5 mol / L electrolyte salt and 0.05 mol / L iodine was prepared. Nitrogen-containing polymer compound (1-1) was added to this solution at the weight composition ratio shown in Table 1 (solvent + nitrogen-containing polymer compound + weight composition ratio when the salt was 100 wt%). The electrophile (2-6) was mixed at the described molar ratio (molar ratio of the electrophilic site to the reactive nitrogen atom of the nitrogen-containing polymer compound) to obtain a uniform reaction solution.
[0159]
On the other hand, dye-sensitized TiO formed on conductive glass plate₂The platinum thin film side of the counter electrode made of a glass plate on which platinum was vapor-deposited via a spacer was placed on the fine particle layer, and the conductive glass plate and the platinum vapor-deposited glass plate were fixed. The open end of the resulting assembly is immersed in the electrolyte solution and dye-sensitized TiO by capillary action₂The reaction solution was infiltrated into the fine particle layer. Subsequently, it was heated at 80 ° C. for 30 minutes to carry out a crosslinking reaction. Thus, as shown in FIG. 2, the dye-sensitized TiO 2 is formed on the conductive layer 12 of the conductive glass plate 10.₂A photoelectrochemical cell (sample No. 1) of the present invention in which the fine particle layer 20, the electrolyte layer 30, and the counter electrode 40 composed of the platinum thin film 42 and the glass plate 41 were sequentially laminated was obtained.
[0160]
In addition, the photoelectrochemical cell of the present invention having a different photosensitive layer 20 and / or charge transfer layer 30 (sample No.) was obtained by repeating the above steps except that the combination of the composition of the dye and the electrolyte composition was changed as shown in Table 1. .2-15) were obtained.
[0161]
[Table 1]
Note: (1) The symbol of the pigment is the same as that described in the column of pigment in [2] (II) (B) above.
(2) The symbol of the nitrogen-containing polymer is the same as that described in the column of nitrogen-containing polymer compound in [1] (A) above.
(3) Electrolyte salt
MHIm: 1-methyl-3-hexylimidazolium iodine salt
MBIm: 1-butyl-3-methylimidazolium iodine salt
(4) Solvent
AN: acetonitrile.
PC: Propylene carbonate.
NMO: 3-methyl-2-oxazolidinone.
(5) Symbols for electrophiles are the same as those described in the column of electrophiles in the above [1] (B).
[0162]
4). Preparation of comparative photoelectrochemical cells A and B
(1) Comparative photoelectrochemical cell A
TiO dye-sensitized with dye R-1 as described above₂Electrode A (20 mm × 20 mm) composed of a fine particle layer was superimposed on a platinum-deposited glass plate of the same size via a spacer. Next, using a capillary phenomenon in the gap between the two glass plates, electrolyte solution (0.05 mol / L of iodine and 0.5 mol of lithium iodide using a 90/10 volume ratio mixture of acetonitrile and 3-methyl-2-oxazolidinone as a solvent) / L solution) was infiltrated to produce a comparative photoelectrochemical cell A.
[0163]
(2) Comparative photoelectrochemical cell B (electrolyte described in JP-A-9-27352)
TiO dye-sensitized with dye R-1 as described above₂On the electrode A (20 mm × 20 mm) composed of a fine particle layer, an electrolytic solution was applied and impregnated. The electrolyte was 1 g of hexaethylene glycol methacrylate (Nippon Yushi Chemical Co., Ltd., Bremer PE-350), 1 g of ethylene glycol, and 2-hydroxy-2-methyl-1-phenyl-propane as a polymerization initiator. It was obtained by dissolving 500 mg of lithium iodide in a mixed solution containing 20 mg of -1-one (manufactured by Ciba Geigy Japan, Darocur 1173) and vacuum degassing for 10 minutes. Next, porous TiO impregnated with the mixed solution₂Porous TiO by placing the layer under reduced pressure₂After removing bubbles in the layer and promoting the penetration of the monomer, polymerize by ultraviolet light irradiation to form a uniform gel of the polymer compound with porous TiO₂Filled into the fine pores of the layer. The product thus obtained was exposed to an iodine atmosphere for 30 minutes to diffuse iodine in the polymer compound, and then a platinum-deposited glass plate was overlaid to obtain a comparative photoelectrochemical cell B.
[0164]
5). Measurement of photoelectric conversion efficiency
The light from a 500 W xenon lamp (USHIO INC.) Was passed through an AM1.5 filter (Oriel) and a sharp cut filter (Kenko L-42) to obtain simulated sunlight that did not contain UV light. Light intensity is 89mW / cm²Adjusted.
[0165]
Alligator clips were connected to the conductive glass plate 10 and platinum-deposited glass plate 40 of the photoelectrochemical cell described above, and each alligator clip was connected to a current-voltage measuring device (Keutley SMU238 type). This was irradiated with simulated sunlight from the conductive glass plate 10 side, and the generated electricity was measured with a current-voltage measuring device. The open-circuit voltage (Voc), short-circuit current density (Jsc), form factor (FF), conversion efficiency (η), and short-circuit current density and short-circuit current density for 360 hours continuous irradiation were calculated. The reduction rates are summarized in Table 2.
[0166]
[Table 2]
[0167]
Compared with the comparative photoelectrochemical cell A, it can be seen that the photoelectrochemical cell of the present invention is less deteriorated in photoelectric conversion characteristics. Moreover, it is clear that the photoelectrochemical cell of the present invention has a large short-circuit current density and is superior in photoelectric conversion characteristics as compared with the comparative photoelectrochemical cell B.
[0168]
【The invention's effect】
According to the present invention, an electrolyte composition excellent in durability and charge transport ability can be provided. Moreover, it is possible to provide a photoelectric conversion element and a photoelectrochemical cell that are excellent in photoelectric conversion characteristics using the electrolyte composition and have little characteristic deterioration with time.
[Brief description of the drawings]
FIG. 1 is a partial cross-sectional view showing the structure of a photoelectric conversion device according to a preferred embodiment of the present invention.
FIG. 2 is a partial cross-sectional view showing the structure of a photoelectrochemical cell according to another preferred embodiment of the present invention.
[Explanation of symbols]
10 ... Conductive support
11 ... Board
12 ... conductive layer
20 ... Photosensitive layer
21 ... Semiconductor fine particles
22 ... Dye
30 ... Electrolyte layer
40 ... Counter electrode
41 ... Board
42 ... conductive layer

Claims (5)

Following formula (II)
(Wherein R ₁ represents a hydrogen atom or a methyl group , L represents —COO—, —OCO—, —CON (R ₂ ) — or —N (R ₃ ) CO—, or one or more of these groups and alkylene) A linking group obtained by combining one or more divalent groups selected from a group, an arylene group and —O— (wherein R ₂ and R ₃ are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms) .) represents, Z is represents a pyridine ring or an imidazole ring, E is a radical derived from a compound containing an ethylenically unsaturated group, x and y represent weight compositional ratio of the repeating units, x is 5 To 100% by weight, y is 0 to 95% by weight.) The crosslinkable weight obtained by reacting the alkyl compound having 2 to 4 functionality or halogenated aralkyl as an electrophile with the polymer compound represented by An electrolyte composition comprising a coalescence. The photoelectric conversion element laminated | stacked in order of the electroconductive support body, the photosensitive layer, the charge transfer layer, and the counter electrode WHEREIN: The said charge transfer layer contains the electrolyte composition of Claim 1, The photoelectric conversion element characterized by the above-mentioned. 3. The photoelectric conversion element according to claim 2, wherein the photosensitive layer is made of a fine particle semiconductor sensitized with a dye. 4. The photoelectric conversion element according to claim 2, wherein the photosensitive layer is composed of semiconductor fine particles and the electrolyte composition filled in a space between the semiconductor fine particles. 5. A photoelectrochemical cell using the photoelectric conversion element according to claim 2.