WO2005121098A1 - Squarilium compound, photoelectric conversion material using same, photoelectric converter and photoelectrochemical cell - Google Patents

Abstract

Disclosed is a squarilium compound represented by the following general formula (I) (wherein R1 and R2 may be the same or different and respectively represent a hydrogen atom, an optionally substituted alkyl group, an optionally substituted aryl group or the like; R3, R4, R5 and R6 may be the same or different and respectively represent a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxyl group or the like; X represents a nitrogen atom or an oxygen atom; and A represents an acidic group). Also disclosed is a photoelectric conversion material or the like which contains such a squarilium compound and a semiconductor.

Description

 Specification

 SQUARYLIUM COMPOUND AND PHOTOELECTRIC CONVERSION MATERIAL, PHOTOELECTRIC CONVERSION ELEMENT AND PHOTOELECTROCHEMICAL CELL

 Technical field

 The present invention relates to a squarylium compound that can be used for a photoelectric conversion element, a photoelectrochemical cell using the squarylium compound, and the like. Background art

 [0002] In solar power generation, solar cells such as single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells, etc. have been put into practical use or have been the subject of major research and development. It is necessary to overcome problems such as cost and securing raw materials. On the other hand, many solar cells using organic materials aimed at film formation and cost reduction have been proposed so far, but there is a problem that the energy conversion efficiency is low and the durability is poor. Under such circumstances, photoelectric conversion elements and photoelectrochemical cells using semiconductor thin film electrodes sensitized with a dye, and materials and manufacturing techniques for producing them are known. This battery is a wet solar battery using a ruthenium complex as a photosensitizer and a titanium dioxide porous thin film as a working electrode (see, for example, Patent Document 1 and Non-Patent Document 1). However, since the ruthenium complex of the sensitizing dye is expensive, development of a photoelectric conversion element that is sensitized by an inexpensive organic dye is desired.

 [0003] In addition, attempts to use organic dyes as sensitizing dyes have been problematic, such as low power-energy conversion efficiency, and are not satisfactory in practice (for example, Patent Document 2, Patent Document) 3).

 In addition, it is known to use a squaric acid derivative for a photoelectric conversion element (see, for example, Patent Document 4).

 Patent Document 1: U.S. Pat.No. 4,927,721

 Patent Document 2: JP-A-11 86916

 Patent Document 3: Specification of European Patent No. 911841

Patent Document 4: Japanese Patent Laid-Open No. 2001-76773 Non-Patent Document 1: “Nature”, 1991, No. 353, ρ · 737-740 Disclosure of Invention

 Problems to be solved by the invention

[0004] An object of the present invention is to provide a squarylium compound that can be used for a photoelectric conversion element that is inexpensive and has high energy conversion efficiency, a photoelectrochemical cell using the same, etc. Means for Solving the Problems

[0005] The present invention provides the following [1] to [5].

 [1] General formula (I)

[0006] [Chemical 1]

R⁵および R⁶は同一または異なって、水素原 子、置換基を有していてもよいアルキル基、置換基を有していてもよいアルコキシノレ 基、ヒドロキシノレ基、またはハロゲン原子を表し、 R¹および R³、または R²および R⁴は それぞれが隣接する N— C— Cと一緒になつて、置換基を有していてもよい複素環を 形成してもよぐ R⁷は水素原子、置換基を有していてもよいアルキル基、置換基を有 してレ、てもよレ、ァラルキル基、置換基を有してレ、てもよレ、ァリール基または置換基を 有していてもよい複素環基を表し、 Xは窒素原子または酸素原子を表し (ただし、 Xが 酸素原子である場合、 R⁷は存在しない）、 Aは酸性基を表す]で表されるスクァリリウ ム化合物。 [In the formula, R ¹ and R ² are the same or different and are each a hydrogen atom, an alkyl group optionally having a substituent, a substituent having a substituent, an atom group, an aryl group or Having a substituent, a force representing a radical aralkyl group, R ¹ and R ² together with the adjacent nitrogen atom form an optionally substituted heterocyclic ring; R ³ ,

R ⁵ and R ⁶ are the same or different and represent a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxy group, a hydroxy group, or a halogen atom, R ¹ and R ³ , or R ² and R ⁴ may be combined with adjacent N—C—C to form an optionally substituted heterocycle R ⁷ is hydrogen An atom, an alkyl group which may have a substituent, a group having a substituent, a group having a substituent, an aralkyl group, a group having a substituent, a group having a substituent, a group having a aryl group or a substituent; X represents a nitrogen atom or an oxygen atom (provided that when X is an oxygen atom, R ⁷ does not exist), and A represents an acidic group]. Compounds.

[2] The squarylium compound according to [1], wherein X is a nitrogen atom. [3] A photoelectric conversion material comprising the squarylium compound according to [1] or [2] and a semiconductor.

 [4] A photoelectric conversion element using the photoelectric conversion material according to [3].

 [5] A photoelectrochemical cell comprising the photoelectric conversion element according to [4].

Hereinafter, the squarylium compound represented by the general formula (I) may be expressed as squarylium compound (I). The same applies to the compounds of other formula numbers.

 The invention's effect

 [0009] According to the present invention, a squarylium compound that can be used in a photoelectric conversion element having low cost and high energy conversion efficiency, a photoelectrochemical cell using the squarylium compound, and the like are provided.

 BEST MODE FOR CARRYING OUT THE INVENTION

 [0010] In the definition of each group in the above general formula, examples of the alkyl moiety in the alkyl group and the alkoxyl group include a linear or branched alkyl group having 1 to 6 carbon atoms or a cyclic group having 3 to 8 carbon atoms. Specific examples thereof include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, isopentyl group, 1-methylbutyl group. 2-methylbutyl group, tert-pentyl group, hexyl group, cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group and the like.

 Examples of the aralkyl group include aralkyl groups having 7 to 15 carbon atoms, and specific examples thereof include a benzyl group, a phenethyl group, a phenylpropyl group, and a naphthylmethyl group.

 Examples of the aryl group include aryl groups having 6 to 14 carbon atoms, and specific examples thereof include a phenyl group, a naphthyl group, an anthryl group, and an azulenyl group.

[0012] Examples of the halogen atom include a chlorine atom, a bromine atom, a fluorine atom, and an iodine atom.

Examples of the heterocyclic ring in the heterocyclic group include, for example, a 5-membered or 6-membered monocyclic aromatic or aliphatic heterocyclic ring containing at least one atom selected from a nitrogen atom, an oxygen atom, and a sulfur atom, and 3 to 8 members. Examples thereof include condensed bicyclic or tricyclic condensed rings containing at least one atom selected from a nitrogen atom, an oxygen atom and a sulfur atom, and specific examples thereof. , Pyridine ring, pyrazine ring, pyrimidine ring, pyridazi Ring, quinoline ring, isoquinoline ring, phthalazine ring, quinazoline ring, quinoxaline ring, naphthyridine ring, cinnoline ring, pyrrole ring, pyrazole ring, imidazole ring, triazole ring, tetrazole ring, thiophene ring, furan ring, thiazole ring, oxazole Ring, indole ring, isoindole ring, indazole ring, benzimidazole ring, benzotriazole ring, benzothiazole ring, benzoxazole ring, purine ring, force rubazole ring, pyrrolidine ring, piperidine ring, piperazine ring , Monoreforin ring, thiomorpholine ring, homopiperidine ring, homopiperazine ring, tetrahydropyridine ring, tetrahydroquinoline ring, tetrahydroisoquinoline ring, tetrahydrofuran ring, tetrahydropyran ring, dihydrobenzofuran ring, tetrahydride And locarbazole ring.

[0013] The heterocycle formed by combining R ¹ and R ² with the adjacent nitrogen atom includes, for example, a 5-membered or 6-membered monocyclic heterocycle containing at least one nitrogen atom A monocyclic heterocycle may contain other nitrogen, oxygen or sulfur atoms), a bicyclic or tricyclic condensed 3- to 8-membered ring and containing at least one nitrogen atom. Cyclic heterocyclic rings (the condensed heterocyclic rings may contain other nitrogen, oxygen or sulfur atoms), and specific examples thereof include pyrrolidine ring, piperidine ring, piperidine ring, and the like. Perazine ring, morpholine ring, thiomorpholine ring, homopiperidine ring, homopiperazine ring, tetrahydropyridine ring, tetrahydroquinoline ring, tetrahydroisoquinoline ring, pyrrole ring, imidazole ring, pyrazole ring, indole ring, indoline ring, B Indole ring, and the like.

[0014] The heterocyclic ring formed by combining R ¹ and R ³ , or R ² and R ⁴ together with adjacent N—C—C includes, for example, a 5-membered structure containing at least one nitrogen atom Or a 6-membered monocyclic heterocycle (this monocyclic heterocycle may contain other nitrogen, oxygen or sulfur atoms), a bicyclic or tricyclic condensed 3- to 8-membered ring Specific examples of the condensed heterocyclic ring containing at least one nitrogen atom (the condensed heterocyclic ring may contain other nitrogen atom, oxygen atom or sulfur atom). As a pyrroline ring, 1, 2, 3, 4-tetrahydropyridine ring, 1, 2, 3, 4-tetrahydrovirazine ring, 2, 3-dihydronozole. Examples include raoxazine ring, 2,3-dihydro-1,4_thiazine ring, tetrahydroazepine ring, tetrahydrazepine ring, tetrahydroquinoline ring, tetrahydroisoquinoline ring, pyrrole ring, imidazole ring, pyrazole ring, indole ring and the like. [0015] an aralkyl group, an aryl group, a heterocyclic group, a heterocyclic ring formed by combining R ¹ and R ² with an adjacent nitrogen atom, and R ¹ and, or R ² and R ⁴ are adjacent to each other Examples of the substituent of the heterocyclic ring formed together with N—C—C include the same or different 1 to 5 substituents, specifically, hydroxyl group, carboxyl group, phosphono A group, a snorejo group, a halogen atom, an anolenoquinole group, an alkoxyl group, a nitro group, an alkyl-substituted or unsubstituted amino group, and the like. A halogen atom, an alkyl group, and an alkoxy group are as defined above, and an alkyl portion of the alkyl-substituted amino group is as defined above.

 [0016] Examples of the substituent of the alkyl group and alkoxyl group are the same or different:! To 3 substituents, specifically, a hydroxyl group, a carboxyl group, a phosphono group, a sulfo group, a halogen atom, an alkoxyl Group and the like. The halogen atom and the alkoxyl group have the same meanings as described above.

 An acidic group refers to a group having a hydrogen atom that can be dissociated, and examples thereof include a carboxyleno group, a hydroxyl group, a phosphono group, and a sulfo group. These groups may form salts with alkali metal ions, ammonium ions, organic ammonium ions, etc. Moreover, it may form an intramolecular complex salt. Examples of alkali metals in alkali metal ions include lithium, sodium, and potassium. Organic ammonium In organic ions, tetraptylammonium and the like can be mentioned.

 [0017] The squarylium compound (I) is produced by a known method (WO01 / 44233 or the like) or a method equivalent thereto. Hereinafter, although the example of the manufacturing method of squarylium compound (I) is demonstrated, this invention is not limited to this.

 Opposite, ', formula (a)

 [0018] [Chemical 2]

(II) (IV) [0019] Reaction formula (b)

[0020] [Chemical 3]

Compound (I V)

[0021] Reaction formula (c)

[0022] [Chemical 4]

Compound (V) Compound (I

Aおよび Xは、それぞれ前記と同義であり、 W は塩素、臭素等のハロゲン原子、または OR⁸ (式中、 R⁸は前記と同義のアルキル基を 表す)を表す] [0023] [wherein R, R ² , R ³ ,

A and X are each as defined above, W is a halogen atom such as chlorine or bromine, or OR ⁸ (wherein R ⁸ represents an alkyl group as defined above)]

 Reaction formula a)

 Compound (IV) is obtained by reacting Compound (II) with 1 to 2 moles of Compound (III) in the presence of 1 to 2 moles of a base in a solvent at 0 to 40 ° C for 1 to 20 hours. Can be obtained.

 [0024] Examples of the solvent include halogenated hydrocarbons such as chloroform, dichloromethane, 1,2-dichloroethane, ethers such as jetyl ether and tert-butyl methyl ether, and aromatics such as toluene and benzene. Examples include hydrocarbons, methanol, alcohols such as ethanol and propanol, tetrahydrofuran, ethyl acetate, dimethylformamide, and dimethylsulfoxide (DMSO).

[0025] As the base, for example, an organic base such as quinoline, triethylamine, pyridine or the like, or an inorganic base such as potassium carbonate, potassium hydrogen carbonate, sodium carbonate, sodium hydrogen carbonate, potassium hydroxide, sodium hydroxide or the like is used. Compound (III) can be obtained, for example, as a commercial product. Compound (V) is compound (IV) in 50-90% by volume aqueous acetic acid solution, 90-: 120 ° C. for 0.7: -7 hours, or 50-99% by weight trifluoroacetic acid aqueous solution, It can be obtained by treating at 45 to 50 ° C for 0.:! To 3 hours.

 Anti, ', expression)

 Compound (I) is compound (V):! ~~ 2 times mole of compound (VI), optionally in the presence of 1 ~ 2 times mole of base, in solvent, 80 ~: 120 ° C 1 to: obtained by reacting for 15 hours.

 [0026] Examples of the solvent include only alcohol solvents having 2 to 8 carbon atoms such as ethanol, propanol, isopropyl alcohol, butanol, and octanol, or a mixed solvent (alcohol 40) of the alcohol solvent and benzene or toluene. Volume% or more) is used.

 Examples of the base include organic bases such as quinoline, triethylamine, and pyridine, and inorganic bases such as potassium carbonate, potassium bicarbonate, and sodium bicarbonate.

[0027] Compound (VI) can be produced by a known method (WO01 / 4437 or the like) or according thereto.

 After the reaction, for example, the compound (I) is further purified by a method usually used in organic synthetic chemistry (column chromatography, recrystallization, washing with a solvent, etc.), if necessary, by evaporating or filtering the solvent. Thus, it can be isolated and purified.

[0028] The ability to illustrate specific examples of the squarylium compound (I) of the present invention in Table 1. The squarylium compound (I) of the present invention is not limited to these. In Table 1, Me represents a methyl group, Et represents an ethynole group, and Bu represents a butyl group.

[0029] [Table 1] table 1

次に、本発明の光電変換材料、光電変換素子および光電気化学電池について詳述 する。

Next, the photoelectric conversion material, photoelectric conversion element and photoelectrochemical cell of the present invention will be described in detail.

The photoelectric conversion element of the present invention is composed of a conductive support, a semiconductor thin film electrode made of a semiconductor sensitized by the squaric compound (I) placed on the conductive support, a charge transfer layer, a counter electrode, and the like. The The photoelectrochemical cell according to the present invention is one in which this photoelectric conversion element can be used for a battery used for work in an external circuit. That is, the photoelectrochemical cell of the present invention is such that an external circuit connected to the conductive support and the counter electrode of the photoelectric conversion element of the present invention via a lead works. The photoelectrochemical cell is preferably sealed on the side with a polymer, an adhesive or the like in order to prevent deterioration of the constituents and volatilization of the electrolyte used for the charge transfer layer.

The semiconductor used for the photoelectric conversion material is a so-called photoconductor, which absorbs light and separates charges to generate electrons and holes. In semiconductors sensitized by squarylium compound (I), light absorption and the generation of electrons and holes due to this are mainly due to squarylium compound (I The semiconductor is responsible for receiving and transmitting these electrons.

 [0031] The semiconductor is not particularly limited, but for example, a simple substance such as titanium oxide, indium oxide, tin oxide, bismuth oxide, zirconium oxide, tantalum oxide, niobium oxide, tandasten oxide, iron oxide, gallium oxide, nickel oxide or the like. Monometallic oxides, composite oxides such as strontium titanate, barium titanate, potassium niobate and sodium tantalate, metal halides such as silver iodide, silver bromide, copper iodide and copper bromide, zinc sulfide , Titanium sulfide, indium sulfide, bismuth sulfide, cadmium sulfide, zirconium sulfide, tantalum sulfide, silver sulfide, tin sulfide, tungsten sulfide, molybdenum sulfide, selenium cadmium, zinc selenide, zinc selenide, titanium selenide, Indium selenide, tungsten selenide, molybdenum selenide, Ren bismuth, cadmium telluride, tellurium, tungsten, tellurium, molybdenum, zinc telluride, chalcogenide compounds such as bismuth telluride and the like.

 [0032] The semiconductors described above are used alone or in combination of two or more.

 Semiconductor thin films can be manufactured using the semiconductors listed above, which are preferably compound semiconductors having nanoporous structures composed of nanoparticles [Journal of American 'Ceramic' Society (Journal of American Ceramic Society) ", 1997, No. 80, No. 12, p. 3157].

 [0033] The semiconductor thin film electrode used in the photoelectric conversion element of the present invention is prepared, for example, by preparing a transparent electrode as a conductive support, laminating a semiconductor thin film thereon, and forming the squarylium compound ( It can be produced by adsorbing I).

 The transparent electrode is not particularly limited as long as it has conductivity. For example, on a transparent or translucent glass substrate or plastic plate, for example, fluorine or antimony-doped oxide oxide, tin-doped indium oxide, zinc oxide, etc. Those coated with a conductive transparent oxide semiconductor thin film, preferably those coated with a fluorine-doped tin oxide thin film are used.

[0034] Examples of the method of placing the compound semiconductor on the conductive support include a method of applying a dispersion or colloidal solution of the compound semiconductor on the conductive support. Examples of the application method include a roller method, a dip method, an air knife method, a blade method, a spin method, and a spray method.

 Compound semiconductors are used to electronically contact semiconductor fine particles after being applied to a conductive support, and to improve coating film strength and adhesion to the support.

Les, preferable to heat treatment. A preferable heat treatment temperature range is 100 to 600 ° C. The heat treatment time is 10 minutes to 10 hours. When using a conductive support with a low melting point and softening point, such as a polymer film, the high temperature treatment causes deterioration of the support. Therefore, heat treatment in the presence of mineral acid is used in combination with small semiconductor particles of 5 nm or less. A method in which a dispersion of a compound semiconductor or a mixture of a colloidal solution and a titanium salt (eg, titanium tetrachloride) is applied to a conductive support, followed by hydrothermal treatment, and the compound semiconductor in a polar organic solvent (eg, tert -Method of performing electrophoretic deposition by electrophoresis in a butanol etc., applying a compound semiconductor dispersion or colloidal solution to a conductive support and then pressing and pressing at a pressure of about 98070 kPa, compound semiconductor For example, a method of irradiating a microwave of about 28 GHz after applying a dispersion or colloidal solution on a conductive support is used. The film thickness of the semiconductor thin film is preferably 0.1 to 100 / im, more preferably 2 to 25 / im.

 [0035] The adsorption of the squarylium compound (I) onto the semiconductor thin film is performed by immersing the semiconductor thin film coated on the support in the squarylium compound (I) solution, and at room temperature for 1 minute to 2 days, or under heating conditions. It can be performed by leaving it for 1 minute to 24 hours. The solvent used when the squarylium compound (I) is adsorbed on the semiconductor thin film is not particularly limited as long as it is a solvent that dissolves the squarylium compound (I). For example, alcohol solvents such as methanol and ethanol, benzene and the like Hydrocarbon solvents, organic solvents such as tetrahydrofuran and acetonitrile, and the like, and mixed solvents thereof are preferable. Acetonitrile and the like are preferable. When the squarylium compound (I) is adsorbed on the semiconductor thin film, the concentration of the squarylium compound (I) solution is preferably not less than 0.1 Olmmol / 1, and 0.1 to 1.0 mmolZl. More preferred.

[0036] In order to make the wavelength range of photoelectric conversion as wide as possible and increase the energy conversion efficiency, the squarylium compound (I) and known dyes such as ruthenium complex dyes, other organic dyes ( For example, a polymethine dye) may be used in combination.

 In addition, for the purpose of reducing the interaction between dyes such as association, a steroid compound having a carboxynole group (for example, chenodeoxycholic acid) or the like may be co-adsorbed on a semiconductor thin film. Furthermore, you may use a ultraviolet absorber together.

 [0037] The charge transfer layer is a layer having a function of replenishing electrons to the oxidant of the squarylium compound (I). [Squarium compound (I) that absorbs light emits electrons by sensitization, Converted to oxidant].

 Examples of the charge transfer layer used in the photoelectric conversion element of the present invention include a liquid (electrolytic solution) obtained by dissolving a redoxion pair in an organic solvent, a gel electrolyte obtained by impregnating a polymer in a liquid obtained by dissolving a redox ion pair in an organic solvent, Examples thereof include a molten salt containing a redox ion pair, a solid electrolyte, an inorganic compound semiconductor, and an organic hole transport material.

 [0038] The redox ion pair includes, for example, iodine redox, bromine redox, iron redox, tin redox, chromium redox, vanadium redox, sulfide ion redox, anthraquinone redox, and the like. . More specifically, iodine redox includes imidazolium iodide derivatives, lithium iodide, potassium iodide, tetraalkylammonium iodide and iodine mixtures, and bromine redox includes imidazolium bromide derivatives. And a mixture of bromine with lithium bromide, potassium bromide, tetraalkylammonium bromide and the like. Of these, a mixture of iodine with lithium iodide, an imidazolium iodide derivative, or the like is preferred. The organic solvent that dissolves the redox ion pair is not limited as long as it is a stable solvent that dissolves the redox ion pair.For example, acetonitrile, methoxyacetonitrile, propionitol, methoxypropionitol, ethylene Examples thereof include organic solvents such as carbonate, propylene carbonate, dimethyl sulfoxide, dimethylformamide, tetrahydrofuran, and nitromethane. It is preferable to use a mixed solvent thereof. Etc. The concentration of the redox ion pair in the electrolytic solution is preferably 0.01 to 5. Omol / 1, more preferably 0.05 to 1. Omol / 1.

[0039] The electrolytic solution may contain a basic compound such as tert-butylpyridine, 2_picoline, 2,6-lutidine. The concentration of the basic compound is preferably 0.01 to 5. Omol / 1 More preferably, 0 · 1 to: ί · Omol / 1.

 Examples of the polymer used for the gel electrolyte include polyacrylonitrile and polyvinylidene fluoride.

 [0040] Examples of the molten salt include 1_butyl_3_methylpyridinum-mouldide, 1_butyl_3-methylimidazolium mouldide, lithium iodide, lithium acetate, and lithium perchlorate. Examples thereof include thium salts, and the fluidity at room temperature may be improved by mixing a polymer such as polyethylene oxide with these.

 Examples of the solid electrolyte include polymers such as polyethylene oxide derivatives.

 [0041] Examples of the inorganic compound semiconductor include copper iodide, copper bromide, and copper thiocyanide.

 The inorganic compound semiconductor may contain a molten salt such as triethyl ammonium thiocyanate.

 Examples of the organic hole transport material include polythiophene derivatives and polypyrrole derivatives.

 When using an inorganic compound semiconductor or an organic hole transport material, a titanium dioxide thin film may be applied as an undercoat layer (short-circuit prevention layer) using a technique such as spray pyrolysis to prevent a short circuit.

 [0042] There are two methods for forming the charge transfer layer, and one is that a counter electrode is first bonded to a semiconductor thin film electrode on which a dye is adsorbed, and a liquid charge transfer layer is injected into the gap. It is a method to do. The other is a method in which a charge transfer layer is directly applied to a semiconductor thin film electrode, and a counter electrode is subsequently applied.

As the injection method of the charge transfer layer in the former case, a normal pressure process utilizing capillary action and a vacuum process in which the gas phase is replaced with a liquid phase at a pressure lower than normal pressure can be used. In the latter case, in the wet charge transfer layer, a counter electrode is provided without being dried, and measures for preventing liquid leakage at the edge are also taken. In the case of a gel electrolyte, there is a method of applying it wet and immobilizing it by a method such as polymerization. In that case, the electrode can be applied after drying and immobilization. The method for applying the electrolyte, wet organic hole transport material or gel electrolyte is the same as that for applying the semiconductor thin film electrode and the dye, dipping method, roller method, dipping method, air knife method, blade method, spin method. Law, spray method, etc. it can. In the case of a solid electrolyte, an inorganic compound semiconductor, or a solid organic hole transport material, a solution obtained by dissolving them in a solvent or the like is dropped onto a heated semiconductor thin film electrode and dried by vaporizing the solvent on the semiconductor thin film electrode. A counter electrode can be applied after the charge transfer layer is formed by forming a solidified charge transfer layer, or by forming a charge transfer layer by a dry film forming process such as a vacuum deposition method or a CVD method (chemical vapor deposition method).

[0043] Examples of the counter electrode used in the photoelectric conversion element of the present invention include platinum, rhodium, ruthenium, carbon, oxide semiconductor electrode and the like coated in a thin film on a conductive substrate. Platinum, carbon electrodes and the like coated in a thin film on a conductive substrate are preferred.

 In the photoelectric conversion element of the present invention, there is no limitation as long as it prevents contact between the semiconductor thin film electrode and the counter electrode, which may use a spacer, but for example, a polymer film such as polyethylene is used. .

 [0044] Further, the squarylium compound (I) used in the present invention is inexpensive.

 Hereinafter, the present invention will be described more specifically with reference to examples.

 Example 1

 [0045] 3,4-Dichloro-1-3-cyclobutene-1,2-dione 1 · Olg and N, N-di-n-butyraniline 2. 76 g was dissolved in 46 ml of dichloromethane and stirred at 25 ° C for 2 hours. did. After the reaction, the reaction solution was concentrated under reduced pressure, 4 ml of acetic acid and 2 ml of water were added to the resulting residue, and the mixture was reacted at 110 ° C for 1 hour. After completion of the reaction, the reaction mixture was cooled to 10 ° C, and the precipitated insoluble matter was collected by filtration. To the resulting solid, 20 ml of n-butanol, 20 ml of tolenene, and 1.00 g of 5_oxo_1_phenyl_2-pyrazolin_3_carboxylic acid were added and reacted at 110 ° C. for 3 hours. Thereafter, 30 ml of methanol was added and stirred at 50 ° C. for 1 hour, and the precipitate was collected by filtration to obtain 1.50 g of Compound (1).

^J H NMR (DMSO-d) δ (ppm): 0.93 (6H, t, J = 7.3 Hz), 1.35 (4H, m), 1.56 (4

 6

 H, m), 3.49 (4H, m), 6.93-7.95 (9H, m).

 Maximum absorption wavelength (DMSO): max 570nm (extinction coefficient ε 57700)

 Example 2

[0046] Titanium dioxide paste (manufactured by Solaronix, SA) on the conductive surface side of transparent conductive glass (manufactured by Nippon Sheet Glass, surface resistance is about 15 Ω / cm ² ) coated with tin oxide doped with fluorine. Ti-Nanoxide T) was applied using a glass rod, dried at room temperature for 30 minutes, and then baked in an electric furnace at 450 ° C for 30 minutes. The thickness of titanium dioxide was 10 μΐη. After removing the glass and cooling, it was added to the acetonitrile solution (compound (1) 0.1 mmol / l, chenodeoxycholic acid 10 mmol / l) mixed with compound (1) and chenodeoxycholic acid at 75 ° C. Soaked for 30 minutes. The glass adsorbed with the dye was washed with acetonitrile and allowed to air dry.

[0047] The titanium dioxide electrode substrate (lcm X 3cm) prepared as described above was superposed on a platinum-deposited glass of the same size. Next, an electrolyte solution (iodine 0.05 mol / l, lithium iodide 0.1 mol / 1, dimethylpropylimidazolyl iodine 0.62 molZl and tert-butyl pyridine 0.5 mol / l acetonitrile solution) was placed between the two glasses. A photoelectrochemical cell was obtained by impregnating with a titanium dioxide electrode and introducing it between the titanium dioxide electrode and the counter electrode. This photoelectrochemical cell was irradiated with 100 mW / cm ² of artificial sunlight using a 500 W xenon short arc lamp (manufactured by Usio Electric), and its characteristics were evaluated with an IV curve tracer (manufactured by Eihiro Seiki). As a result, the characteristics of the obtained photoelectrochemical cell were as follows: short-circuit current density 6.7 mA / cm ² , open-circuit voltage 0.66 V, form factor (fill factor) 0.59, and energy conversion efficiency 2.5%. .

 Industrial applicability

[0048] According to the present invention, a squarylium compound that can be used in a photoelectric conversion element having low cost and high energy conversion efficiency, a photoelectrochemical cell using the squarylium compound, and the like are provided.

Claims

The scope of the claims  [1] General formula (I)  [Chemical 5]

[Wherein, R ¹ and R ² are the same or different and each represents a hydrogen atom, an alkyl group which may have a substituent, a substituent or a substituent, an aryl group or a substituent. And R, which represents a aralkyl group, R ¹ and R ² together with the adjacent nitrogen atom form an optionally substituted heterocyclic ring, R ³ ,

R ⁵ and R ⁶ are the same or different and each represents a hydrogen atom, an optionally substituted alkyl group, an optionally substituted alkoxyl group, a hydroxyl group, or a halogen atom; ¹ and R ³ , or R ² and R ⁴ may be combined with adjacent N—C—C to form an optionally substituted heterocycle R ⁷ is a hydrogen atom An alkyl group which may have a substituent, a group having a substituent, a group having a substituent, an aralkyl group, a group having a substituent, a group having a substituent, a group having a aryl group or a substituent. X represents a nitrogen atom or an oxygen atom (provided that when X is an oxygen atom, R ⁷ does not exist), and A represents an acidic group]. Compound.  [2] The squarylium compound according to [1], wherein X is a nitrogen atom. [3] A photoelectric conversion material comprising the squarylium compound according to claim 1 or 2 and a semiconductor. [4] A photoelectric conversion element using the photoelectric conversion material according to claim 3. [5] A photoelectrochemical cell comprising the photoelectric conversion element according to claim 4.