JP2005078888A - Semiconductor for photoelectric conversion material, photoelectric conversion element and solar cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor for a photoelectric conversion material, a photoelectric conversion element, and a solar battery which exhibit high photoelectric conversion efficiency and superior stability. <P>SOLUTION: The semiconductor for the photoelectric conversion material contains a heterocyclic compound expressed by a general formula (1). In the formula (1), R<SB>1</SB>, R<SB>2</SB>expresses a hydrogen atom or a substituent separately. When n is 2 or more, in a cyclic unit, R<SB>1</SB>and R<SB>2</SB>may be different from each other, and R<SB>1</SB>and R<SB>2</SB>may form a ring. When n is 2 or more in an adjoining cyclic unit, R<SB>1</SB>and R<SB>1</SB>, or R<SB>2</SB>and R<SB>2</SB>may form a ring between them. R<SB>3</SB>expresses the hydrogen atom or the substituent, and R<SB>4</SB>expresses the hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group. Z<SB>1</SB>expresses a group of atoms needed to form aromatic carbocycles or heterocycles, and n expresses 1, 2, 3 or 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor for a photoelectric conversion material, a photoelectric conversion element, and a solar cell.

  A photoelectric conversion material is a material that converts light energy into electrical energy using an electrochemical reaction between electrodes. When the photoelectric conversion material is irradiated with light, electrons are generated on one electrode side and move to the counter electrode. The electrons that have moved to the counter electrode move as ions in the electrolyte and return to one electrode.

  That is, the photoelectric conversion material is a material that can continuously extract light energy as electric energy, and is used for, for example, a solar cell. There are several types of solar cells, but most of them are silicon solar cells that have been put to practical use in power generation panels for home installation, desk calculators, watches, portable game machines, and the like.

  However, recently, dye-sensitized solar cells have attracted attention and are being studied for practical use. Dye-sensitized solar cells have been studied for a long time, and the basic structure specifically includes a metal oxide semiconductor, a dye adsorbed thereon, an electrolyte solution, and a counter electrode.

  In the conventional dye-sensitized solar cell as described above, a photoelectric conversion material in which a spectral sensitizing dye having absorption in the visible light region is adsorbed on the semiconductor surface is used. For example, a solar cell having a spectral sensitizing dye layer such as a transition metal complex on the surface of a metal oxide semiconductor is described (for example, see Patent Document 1), and a titanium oxide semiconductor doped with metal ions Examples include a solar cell having a spectral sensitizing dye layer such as a transition metal complex on the surface of the layer (for example, see Patent Document 2).

On the other hand, as an oxide semiconductor electrode having photoelectric conversion ability, a semiconductor single crystal electrode has been used in the early days. The types include titanium oxide (TiO ₂ ), zinc oxide (ZnO), tin oxide (SnO ₂ ), and the like.

  However, since the single crystal electrode has a small amount of dye adsorption, the efficiency is very low and the cost is high. Thus, a high surface area semiconductor electrode having a large number of pores formed by sintering fine particles has been devised.

  For example, it has been reported by Tsubomura et al. That a porous zinc oxide electrode adsorbing an organic dye has very high performance (for example, see Non-Patent Document 1).

  After that, the dye has also been improved, and Graetzel et al. Have adsorbed the ruthenium complex dye on the porous titanium oxide electrode, so that it now has the same performance as a silicon solar cell (for example, Non-patent document 2).

However, for practical use to replace silicon solar cells, higher energy conversion efficiency, higher short-circuit current, open-circuit voltage, and form factor are required than ever before. Technological developments using reported materials such as ZnO, TiO ₂ , zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ) and the like have been carried out.

  In addition, since dye-sensitized wet solar cells are much cheaper to manufacture than silicon solar cells, in the future, there is a possibility of replacing silicon solar cells used in the above-mentioned various products. In some cases, the characteristics of the solar cell according to each product are important. Various characteristics of solar cells are shown below.

1. Short circuit current 2. Open voltage Form factor 4. 4. Energy conversion efficiency The light absorption spectrum is important. The energy conversion efficiency of the solar cell is the biggest problem for solar cells, and its improvement has been strongly desired. As one of the technical problems affecting the efficiency, there is a demand for a sensitizing dye having the ability to efficiently transfer photoexcited electrons to a semiconductor. Of the various dyes studied so far, the ruthenium complex dyes have been found to have relatively excellent characteristics, but the dyes are expensive and ruthenium, the central metal of the complex, is a rare element. Therefore, organic dyes that can be supplied at a lower cost and more stably are more preferable. Many organic dyes (see, for example, Patent Documents 3, 4, and 5) have been studied so far, and merocyanine dyes, xanthene dyes, coumarin dyes, acridine dyes, phenylmethane dyes, and the like. Is well known. Further, other new dye mother nuclei have been developed (see, for example, Patent Document 6). However, these photoelectric conversion efficiencies are not yet sufficient, and there is a demand for organic dyes that can constitute a photoelectric conversion element with higher conversion efficiency.
Japanese Patent Laid-Open No. 1-220380 Japanese National Patent Publication No. 5-504023 JP-A-11-167937 Japanese Patent Laid-Open No. 11-214730 Japanese Patent Laid-Open No. 11-214731 JP 2001-76775 A Nature, 261 (1976) p. 402 J. et al. Am. Chem. Soc. 115 (1993) 6382

  An object of the present invention is to provide a semiconductor for a photoelectric conversion material, a photoelectric conversion element, and a solar cell that exhibit high photoelectric conversion efficiency and excellent stability.

The above object of the present invention has been achieved by the following constitution.
(Claim 1)
The semiconductor for photoelectric conversion materials characterized by including the heterocyclic compound represented by following General formula (1).

[Wherein, R _1, R ₂ represents a hydrogen atom or a substituent independently when n is 2 or more, R ₁ and R ₂ in a unit which is repeated may be different from each other, also, R ₁ and R ₂ may form a ring, and when n is 2 or more, R ₁ and R ₁ or R ₂ and R ₂ may form a ring in adjacent repeating units, and R ₃ is a hydrogen atom Or a substituent, R ₄ represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, Z ₁ represents an atomic group necessary to form an aromatic carbocycle or a heterocyclic ring, and n is 1, 2, 3 or 4 is represented. ]
(Claim 2) A semiconductor for a photoelectric conversion material comprising a heterocyclic compound represented by the following general formula (2).

[Wherein, R _1, R ₂ represents a hydrogen atom or a substituent independently when n is 2 or more, R ₁ and R ₂ in a unit which is repeated may be different from each other, also, R ₁ and R ₂ may form a ring, and when n is 2 or more, R ₁ and R ₁ or R ₂ and R ₂ may form a ring in adjacent repeating units, and R ₃ is a hydrogen atom Or R ₄ represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, R ₅ , R ₆ and R ₇ each independently represents a hydrogen atom or a substituent, and R ₈ , R ₉ represents an aliphatic group, an aromatic group or a heterocyclic group, and R ₆ and R ₈ , R ₇ and R ₉ , R ₈ and R ₉ may form a ring, and n is 1, 2, 3 or 4 is represented. ]
(Claim 3)
The general formulas (1) and (2), wherein R ₁ and R ₂ form a ring, and the formed ring structure is a benzene ring, a furan ring, or a thiophene ring. Semiconductor for photoelectric conversion material.
(Claim 4)
The said semiconductor for photoelectric conversion materials is a metal oxide semiconductor or a metal sulfide semiconductor, The semiconductor for photoelectric conversion materials of any one of Claims 1-3 characterized by the above-mentioned.
(Claim 5)
The photoelectric conversion element of any one of Claims 1-4 is provided on the electroconductive support body, The photoelectric conversion element characterized by the above-mentioned.
(Claim 6)
A solar cell comprising the photoelectric conversion element according to claim 5, a charge transfer layer, and a counter electrode.

  By using the compounds represented by the general formulas (1) and (2) of the present invention, it is possible to provide a semiconductor for a photoelectric conversion material, a photoelectric conversion element, and a solar cell that exhibit high photoelectric conversion efficiency and excellent stability. done.

  Hereinafter, the present invention will be described in detail.

  As a result of intensive studies to solve the above problems, the present inventors have found specific structures as represented by the general formulas (1) and (2) described in claims 1 to 6, respectively. The semiconductor for photoelectric conversion materials which sensitized using the compound which has it succeeded in obtaining the semiconductor for photoelectric conversion materials which shows the effect as described in this invention, ie, the high photoelectric conversion efficiency, and the outstanding stability.

<< Semiconductor for photoelectric conversion material >>
As a semiconductor used for the semiconductor for a photoelectric conversion material of the present invention, a simple substance such as silicon or germanium, a group 3 to group 5 of a periodic table (also referred to as an element periodic table), or a group 13 to group 15 system. A compound having an element, a metal chalcogenide (eg, an oxide, sulfide, selenide, etc.), a metal nitride, or the like can be used.

  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 or Bismuth sulfide, cadmium or lead selenide, cadmium telluride and the like. Other compound semiconductors include phosphides such as zinc, gallium, indium and cadmium, gallium-arsenic or copper-indium selenide, copper-indium sulfide, titanium nitride, and the like.

Specific examples of the semiconductor according to the semiconductor for photoelectric conversion material of the present invention include TiO ₂ , SnO ₂ , Fe ₂ O ₃ , WO ₃ , ZnO, Nb ₂ O ₅ , CdS, ZnS, PbS, Bi ₂ S ₃ , CdSe. , CdTe, GaP, InP, GaAs, CuInS ₂ , CuInSe ₂ , Ti ₃ N _4, etc., but TiO ₂ , ZnO, SnO ₂ , Fe ₂ O ₃ , WO ₃ , Nb ₂ O are preferably used. ₅ , CdS, and PbS, and TiO ₂ or Nb ₂ O ₅ is more preferably used, and TiO ₂ is preferably used among them.

The semiconductor used for the photoelectric conversion material semiconductor of the present invention may be a combination of the above-described plurality of semiconductors. For example, several types of metal oxides or metal sulfides described above can be used in combination, or 20% by mass of titanium nitride (Ti ₃ N ₄ ) may be mixed and used in the titanium oxide semiconductor. In addition, J.H. Chem. Soc. , Chem. Commun. 15 (1999). At this time, when a component is added as a semiconductor in addition to the metal oxide or metal sulfide, the mass ratio of the additional component to the metal oxide or metal sulfide semiconductor is preferably 30% or less.

  High photoelectric conversion, which is one of the objects described in the present invention, by sensitizing the semiconductor for photoelectric conversion material with any one compound represented by the general formulas (1) and (2) The semiconductor for photoelectric conversion materials of the present invention showing efficiency and excellent stability can be obtained.

  Hereinafter, the heterocyclic compounds represented by the general formulas (1) and (2) will be described.

<< Heterocyclic Compound Represented by General Formula (1) >>
In the general formula (1), R ₁ and R ₂ each represent a hydrogen atom and a substituent, and preferred substituents include an aliphatic group, an aromatic group, a heterocyclic group, an alkoxy group, an amino group, an aryloxy group, A cyano group, a nitro group, a halogen atom, a carboxyl group, and a hydroxyl group are mentioned. Preferred examples of the aliphatic group represented by R ₁ and R ₂ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a tert-butyl group, an n-octyl group, an n-decyl group, Examples include eicosyl group, 2-chloroethyl group, 2-cyanoethyl group, 2-ethylhexyl group, vinyl group, allyl group, ethynyl group, (4-dimethylamino-phenyl) -vinyl group, and among these, preferred are Methyl group, ethyl group, vinyl group, allyl group, n-octyl group, and n-decyl group. Preferred examples of the aromatic group represented by R ₁ include a phenyl group, p-tolyl group, naphthyl group, m-chlorophenyl group, 4-dimethylaminophenyl group, o-hexadecanoylaminophenyl group, and the like. Among them, the preferred position is a phenyl group. Preferred examples of the heterocyclic group represented by R ₁ include a pyridyl group, a thiazolyl group, a 2-benzothiazolyl group, an oxazolyl group, an imidazolyl group, a 2-furyl group, a 2-thienyl group, a pyrrolyl group, and a pyrazinyl group. 2-pyrimidinyl group, pyridazinyl group, selenazolyl group, sulfolanyl group, piperidinyl group, pyrazolyl group, tetrazolyl group, 2- (5-dimethylamino) thienyl group, 2- (5-dimethylamino) furyl group, 2- [5 -(4-dimethylamino) -phenyl] thienyl group, 2- [5- (4-dimethylamino) -phenyl] furyl group, 2- [5- (4-dimethylamino-phenyl) -vinyl] thienyl group, 2 -[5- (4-dimethylamino-phenyl) -vinyl] furyl group and the like are mentioned, and among these, preferred is pyri Group, 2-furyl group, 2-thienyl group, a pyrrolyl group. Preferred examples of the alkoxy group represented by R ₁ include a methoxy group, an ethoxy group, a tert-butoxy group, and a 2-chloroethoxy group. Among these, a methoxy group and an ethoxy group are preferred. It is a group. Preferred amino groups for the substituent represented by R ₁ include, for example, methylamino group, dimethylamino group, diethylamino group, ethylmethylamino group, ethylbutylamino group, diphenylamino group, pyrrolidyl group, piperidyl group, ethyloctyl group. An amino group, a dioctylamino group, a didodecylamino group, a dodecyloctylamino group, a viololidium group, etc. are mentioned. Among these, a dimethylamino group, a diethylamino group, an ethylbutylamino group, a pyrrolidyl group, an ethyloctylamino group are preferable. Group, a dioctylamino group. Preferred examples of the aryloxy group represented by R ₁ include a phenoxy group and a naphthyloxy group, and among these, a phenoxy group is preferable. Examples of the halogen atom preferable as the substituent represented by R ₁ include an iodine atom, a bromine atom, a chlorine atom, and a fluorine atom. R ₁ and R ₂ may form a ring, and examples of the ring formed include a cyclohexene ring, a cyclopentene ring, a benzene ring, a naphthalene ring, a pyrrole ring, a thiophene ring, a furan ring, a pyridine ring, and an indole ring. Is mentioned.

Further, R _1, R _2, when n is 2 or more, or different each R ₁ and R ₂ in a unit to be repeated, also, R ₁ and R ₂ may form a ring, n is In the case of 2 or more, a ring may be formed between R ₁ and R ₁ or R ₂ and R ₂ in adjacent repeating units.

In the general formula (1), R ₃ represents a substituent other than a hydrogen atom or a hydroxy group, and preferred substituents include an aliphatic group, an aromatic group, a heterocyclic group, an alkoxy group, an amino group, an aryloxy group, A cyano group, a nitro group, a halogen atom, and a carboxyl group are mentioned. Examples of the aliphatic group, aromatic group, heterocyclic group, alkoxy group, amino group, aryloxy group, and halogen atom represented by R ₃ include the examples given for R ₁ .

In the general formula (1), R ₄ is a hydrogen atom, an aliphatic group, an aromatic group, or a heterocyclic group. Examples of the aliphatic group, the aromatic group, and the heterocyclic group represented by R ₄ include R _The example mentioned in ₁ is given.

In the general formula (1), Z ₁ represents an atomic group necessary for forming an aromatic carbocycle or a heterocycle, and examples of the formed aromatic carbocycle include a phenyl group and naphthyl. Examples of the heterocyclic ring formed include a furan ring, a thiophene ring, a pyridine ring, an indole ring, a quinoline ring, a pyrrole ring, a carbazole ring, a julolidine ring, an imidazole ring, a benzofuran ring, and a benzothiophene. Ring, tetrahydroquinoline ring, and among them, a phenyl ring, a furan ring, a thiophene ring, a pyrrole ring, and a julolidine ring, which may have a substituent, are represented by Z _1. that examples of the atomic group substituent which may have needed to form an aromatic carbocyclic or heterocyclic ring, include the examples given in R _1, these Chide preferred are dimethylamino group, diethoxy amino group, an ethyl butylamino group, a pyrrolidyl group, an ethyl octyl amino group, a dioctylamino group.

  In general formula (1), n represents 1, 2, 3 or 4.

<< Heterocyclic Compound Represented by General Formula (2) >>
In the general formula (2), what is represented by R _1, R ₂ has the same meaning as R _1, R ₂ in the general formula (1).

In the general formula (2), what is represented by R ₃ are the same as R ₃ in Formula (1).

In the general formula (2), what is represented by R ₄ has the same meaning as R ₄ in the formula (1).

In the general formula (2), R ₅ , R ₆ and R ₇ each independently represents a hydrogen atom or a substituent, and preferred substituents include an aliphatic group, an aromatic group, a heterocyclic group, an alkoxy group, and an amino group. An aryloxy group, a cyano group, a nitro group, a halogen atom, a hydroxyl group, a carboxyl group, and an aliphatic group, aromatic group, heterocyclic group, alkoxy group, amino group represented by R ₅ , R ₆ , or R ₇ Examples of the group, aryloxy group and halogen atom include the examples given for R ₁ .

In the general formula (2), R ₈ and R ₉ represent an aliphatic group, an aromatic group or a heterocyclic group, and examples of preferred aliphatic group, aromatic group and heterocyclic group are the examples given for R _1. Can be mentioned.

R ₆ and R ₈ , R ₇ and R ₉ , R ₈ and R ₉ may form a ring, and examples of the ring formed include a pipedidine ring, a pyrrolidine ring, a pyridine ring, and a tetrahydropyridine ring. It is done.

  In the general formula (2), n represents 1, 2, 3 or 4.

  Specific examples of the heterocyclic compounds represented by the general formulas (1) and (2) according to the present invention are shown below, but the present invention is not limited thereto.

<Synthesis example>
<< Synthesis of Exemplified Compound I-1 >>
Exemplified compound I-1 was synthesized according to the synthesis route described below.

  To a 100 ml three-headed flask were added 1.77 g of intermediate 1; 1.71 g of intermediate 2; 7 ml of pyridine; 10 ml of ethanol; and 10 drops of piperidine, and the mixture was stirred at 100 ° C. for 2 hours. Then, after cooling and diluting with water, crystals precipitated. The crystals were collected by filtration, and 1.5 g of the desired product, exemplified compound I-1, was obtained using a silica gel column (developing solvent: ethyl acetate).

<< Sensitivity treatment of semiconductor for photoelectric conversion material >>
The semiconductor for photoelectric conversion materials of the present invention is sensitized by containing any one compound represented by the general formulas (1) and (2), and can achieve the effects described in the present invention. Become. Here, including the compound includes various modes such as adsorption to the semiconductor surface, and when the semiconductor has a porous structure such as a porous structure, the compound enters the porous structure of the semiconductor.

The total content of each compound represented by the general formulas (1) and (2) per 1 m ² of the semiconductor layer (which may be a semiconductor) is preferably in the range of 0.01 to 100 mmol, and more preferably Is from 0.1 to 50 mmol, particularly preferably from 0.5 to 20 mmol.

  When performing sensitization using any one of the compounds represented by the general formulas (1) and (2) according to the present invention, the compounds may be used alone or in combination. Any one of the compounds represented by the general formulas (1) and (2) according to the present invention and other compounds (for example, US Pat. No. 4,684,537, US Pat. No. 4,927, No. 721, No. 5,084,365, No. 5,350,644, No. 5,463,057, No. 5,525,440, etc. The compounds described in each specification, JP-A-7-249790, JP-A-2000-150007, and the like can also be used as a mixture.

  In particular, when the application of the semiconductor for photoelectric conversion material of the present invention is a solar cell described later, two types of absorption wavelengths are different so that the wavelength range of photoelectric conversion can be made as wide as possible to effectively use sunlight. It is preferable to use a mixture of the above dyes.

  In order to include in the semiconductor any one of the compounds represented by the general formulas (1) and (2), the compound was dissolved in an appropriate solvent (such as ethanol) and dried well in the solution. A method of immersing a semiconductor for a long time is common.

  When producing a semiconductor for a photoelectric conversion material using a combination of any one of the compounds represented by the general formulas (1) and (2) or a combination with other sensitizing dye compounds, A mixed solution of these compounds may be prepared and used. Alternatively, a solution may be prepared for each compound and immersed in each solution in order. When preparing a separate solution for each compound and immersing in each solution in order, the effects described in the present invention can be obtained regardless of the order in which the semiconductor, the sensitizing dye, and the like are included in the semiconductor. be able to. Moreover, you may produce by mixing the semiconductor fine particle which adsorb | sucked the said compound independently.

  The adsorption treatment may be performed when the semiconductor is in the form of particles, or may be performed after forming a film on the support. The solution in which the compound used for the adsorption treatment is dissolved may be used at room temperature, or may be used by heating in a temperature range in which the compound does not decompose and the solution does not boil. Moreover, you may implement adsorption | suction of the said compound after application | coating of a semiconductor fine particle (after formation of a photosensitive layer) like manufacture of the photoelectric conversion element mentioned later. Moreover, you may implement adsorption | suction of the said compound by apply | coating a semiconductor fine particle and the said compound of this invention simultaneously. Unadsorbed compounds can be removed by washing.

  Moreover, about the sensitization process of the semiconductor for photoelectric conversion materials of this invention, a sensitization process is performed by including any 1 type of compounds represented by the said General formula (1), (2) about a semiconductor. However, the details of the sensitization process will be specifically described in the photoelectric conversion element described later.

  Further, in the case of a semiconductor for a photoelectric conversion material having a semiconductor thin film with a high porosity, the above compound or sensitization is performed before water is adsorbed on the semiconductor thin film and in the voids inside the semiconductor thin film by moisture, water vapor, etc. It is preferable to complete the adsorption treatment (sensitization treatment of a semiconductor for a photoelectric conversion material) such as a dye compound.

  You may surface-treat the semiconductor for photoelectric conversion materials of this invention using an organic base. Examples of the organic base include diarylamine, triarylamine, pyridine, 4-t-butylpyridine, polyvinylpyridine, quinoline, piperidine, amidine, and the like. Among them, pyridine, 4-t-butylpyridine, and polyvinylpyridine are preferable. preferable.

  When the organic base is a liquid, it can be surface treated by preparing a solution dissolved in an organic solvent as it is, and immersing the semiconductor for a photoelectric conversion material of the present invention in a liquid amine or an amine solution. .

  In addition, as a dye that can be used in combination with any one of the compounds represented by the general formulas (1) and (2) according to the present invention, those that can spectrally sensitize the semiconductor according to the present invention. Any dye can be used. In order to make the wavelength range of photoelectric conversion as wide as possible and increase the conversion efficiency, it is preferable to mix two or more kinds of dyes. Moreover, the pigment | dye to mix and its ratio can be selected so that it may match with the wavelength range and intensity distribution of the target light source.

  As a dye that can be used in combination with the compound according to the present invention, a metal complex dye, a phthalocyanine dye, a porphyrin dye, from a comprehensive viewpoint such as photoelectron transfer reaction activity, light durability, and photochemical stability, Polymethine dyes are preferably used.

  Among the metal complex dyes, JP-A Nos. 2001-223037, 2001-226607, US Pat. Nos. 4,927,721, 4,684,537, 5,084,365, 5,350,644, 5,463,057, 5,525,440, JP-A-7-249750, JP 10-504512, World Patent 989/50393, etc. Ruthenium complex dyes are preferably used.

  Examples of the porphyrin dye and the phthalocyanine dye include dyes described in JP-A No. 2001-223037 as preferable dyes.

  Examples of the polymethine dye include conventionally known methine dyes, JP-A Nos. 11-35836, 11-158395, 11-163378, 11-214730, and 11-214731. 10-093118, 11-273754, JP-A-2000-106224, 2000-357809, 2001-052766, EP 892,411, 911,841, etc. Those described are mentioned.

<< Method for Manufacturing Semiconductor for Photoelectric Conversion Material >>
A method for manufacturing a semiconductor for a photoelectric conversion material of the present invention will be described.

  As one embodiment of the semiconductor for a photoelectric conversion material of the present invention, a method such as forming the above semiconductor for a photoelectric conversion material on a conductive support by firing is exemplified.

  When the semiconductor for a photoelectric conversion material of the present invention is produced by firing, the semiconductor is sensitized (adsorption, penetration into a porous layer, etc.) with the above-described compound or sensitizing dye after firing. It is preferable to do. It is particularly preferable to perform the compound adsorption treatment quickly after the firing and before the water is adsorbed to the semiconductor.

  When the semiconductor for photoelectric conversion materials of the present invention is in the form of particles, the semiconductor electrode is preferably prepared by applying or spraying the semiconductor for photoelectric conversion materials onto a conductive support. Moreover, when the semiconductor for photoelectric conversion materials of this invention is a film | membrane form, Comprising: It is not hold | maintained on an electroconductive support body, the semiconductor electrode for photoelectric conversion materials is bonded on an electroconductive support body, and a semiconductor electrode is attached. It is preferable to produce it.

  Hereinafter, a process for producing a semiconductor for a photoelectric conversion material of the present invention will be specifically described.

<< Preparation of coating liquid containing semiconductor fine powder >>
First, a coating solution containing fine semiconductor powder is prepared. The semiconductor fine powder preferably has a finer primary particle diameter, and the primary particle diameter is preferably 1 nm to 5000 nm, and more preferably 2 nm to 50 nm. The coating liquid containing the semiconductor fine powder can be prepared by dispersing the semiconductor fine powder in a solvent. The semiconductor fine powder dispersed in the solvent is dispersed in the form of primary particles. The solvent is not particularly limited as long as it can disperse the semiconductor fine powder.

  Examples of the solvent include water, an organic solvent, and a mixed solution of water and an organic solvent. As the organic solvent, alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone, acetone and acetyl acetone, hydrocarbons such as hexane and cyclohexane, and the like are used. A surfactant and a viscosity modifier (polyhydric alcohol such as polyethylene glycol) can be added to the coating solution as necessary. The range of the semiconductor fine powder concentration in the solvent is preferably 0.1% by mass to 70% by mass, and more preferably 0.1% by mass to 30% by mass.

<< Application of Semiconductor Fine Powder-Containing Coating Liquid and Firing Process of Formed Semiconductor Layer >>
The semiconductor fine powder-containing coating solution obtained as described above is applied or sprayed onto a conductive support, dried, etc., and then baked in air or in an inert gas, on the conductive support. A semiconductor layer (semiconductor film) is formed.

  The film obtained by applying and drying the coating liquid on the conductive support is composed of an aggregate of semiconductor fine particles, and the particle size of the fine particles corresponds to the primary particle size of the semiconductor fine powder used. is there.

  The semiconductor fine particle aggregate film formed on the substrate such as the conductive support in this way has a low bonding strength with the conductive support and a bonding strength between the fine particles and a low mechanical strength. From the above, the semiconductor fine particle aggregate film is preferably fired to increase the mechanical strength and to obtain a fired product film firmly fixed to the substrate.

  In the present invention, the fired product film may have any structure, but is preferably a porous structure film (also referred to as a porous layer having voids).

  Here, the porosity of the semiconductor thin film according to the present invention is preferably 10% by volume or less, more preferably 8% by volume or less, and particularly preferably 0.01% by volume to 5% by volume. The porosity of the semiconductor thin film means a porosity that is penetrable in the thickness direction of the dielectric, and can be measured using a commercially available apparatus such as a mercury porosimeter (Shimadzu Polarizer 9220 type).

  The film thickness of the semiconductor layer that is a fired product film having a porous structure is preferably at least 10 nm or more, more preferably 100 nm to 10,000 nm.

  From the viewpoint of appropriately adjusting the actual surface area of the fired product film during the firing treatment and obtaining a fired product film having the above porosity, the firing temperature is preferably lower than 1000 ° C, more preferably 200 ° C to 800 ° C. It is the range of 300 degreeC, Most preferably, it is the range of 300 to 800 degreeC.

  Further, the ratio of the actual surface area to the apparent surface area can be controlled by the particle diameter and specific surface area of the semiconductor fine particles, the firing temperature, and the like. In addition, after heat treatment, for example, chemical plating or aqueous trichloride using a titanium tetrachloride aqueous solution is used to increase the surface area of the semiconductor particles, increase the purity in the vicinity of the semiconductor particles, and increase the efficiency of electron injection from the dye into the semiconductor particles. Electrochemical plating using a titanium aqueous solution may be performed.

<Semiconductor sensitization processing>
As described above, the semiconductor sensitization treatment is performed by dissolving the dye in an appropriate solvent and immersing the substrate obtained by firing the semiconductor in the solution. In that case, a substrate on which a semiconductor layer (also referred to as a semiconductor film) is formed by baking is subjected to pressure reduction treatment or heat treatment in advance to remove bubbles in the film, and the general formulas (1) and (2) It is preferable that any one of the above compounds can enter deep inside the semiconductor layer (semiconductor film), and it is particularly preferable when the semiconductor layer (semiconductor film) is a porous structure film.

"solvent"
The solvent used to dissolve the compound of any one of the general formulas (1) and (2) can dissolve the compound and can dissolve the semiconductor or react with the semiconductor. There is no particular limitation if it is not present, but in order to prevent moisture and gas dissolved in the solvent from entering the semiconductor film and hindering the sensitization treatment such as adsorption of the compound, degassing and distillation in advance. It is preferable to purify it.

  Solvents preferably used in dissolving the above compounds are alcohol solvents such as methanol, ethanol and n-propanol, ketone solvents such as acetone and methyl ethyl ketone, ether solvents such as diethyl ether, diisopropyl ether, tetrahydrofuran and 1,4-dioxane. Solvents and halogenated hydrocarbon solvents such as methylene chloride and 1,1,2-trichloroethane, particularly preferably methanol, ethanol, acetone, methyl ethyl ketone, tetrahydrofuran and methylene chloride.

《Tensing temperature and time》
The time for immersing the substrate on which the semiconductor is baked in the solution containing any one of the compounds of the general formulas (1) and (2) is such that the compound deeply enters the semiconductor layer (semiconductor film) and adsorbs it. From the viewpoint of sufficiently proceeding, sufficiently sensitizing the semiconductor, and suppressing degradation of the compound, which is generated by decomposition of the compound in a solution and hinders adsorption of the compound, at 25 ° C., It is preferably 3 hours to 48 hours, more preferably 4 hours to 24 hours. This effect is particularly remarkable when the semiconductor film is a porous structure film. However, the immersion time is a value under the condition of 25 ° C., and is not limited to the above when the temperature condition is changed.

  When immersed, the solution containing any one compound of the general formulas (1) and (2) may be used by heating to a temperature that does not boil as long as the compound does not decompose. A preferable temperature range is 10 ° C to 100 ° C, and more preferably 25 ° C to 80 ° C. However, as described above, this is not the case when the solvent boils in the temperature range.

<< Photoelectric conversion element >>
The photoelectric conversion element of this invention is demonstrated using FIG.

  FIG. 1 is a partial cross-sectional view showing an example of the structure of the photoelectric conversion element of the present invention.

  Reference numeral 1 denotes a conductive support, 2 denotes a photosensitive layer, 3 denotes a charge transfer layer, and 4 denotes a counter electrode. The conductive support 1 and the photosensitive layer 2 are also collectively referred to as a semiconductor electrode.

  Here, the photosensitive layer 2 is a layer having the semiconductor for a photoelectric conversion material of the present invention, and the charge transfer layer 3 usually contains a redox electrolyte and is in contact with the conductive support 1, the photosensitive layer 2, and the counter electrode 4. Used in form.

<< Method for Manufacturing Photoelectric Conversion Element >>
The manufacturing method of a photoelectric conversion element is demonstrated using FIG.

  The photoelectric conversion element of the present invention is represented by the general formulas (1) and (2) according to the present invention after forming a semiconductor thin film as described above on a conductive support 1 as shown in FIG. It is manufactured through a process of adsorbing any one kind of compound.

  Further, the surface area of the semiconductor thin film is increased or impurities on the surface of the semiconductor thin film are removed to increase the purity of the semiconductor, and the semiconductor is formed from any one compound represented by the general formulas (1) and (2). For example, chemical plating using a titanium tetrachloride aqueous solution or electrochemical plating using a titanium trichloride aqueous solution may be performed for the purpose of increasing the efficiency of electron injection into the substrate.

  The semiconductor film formed on the conductive support 1 adsorbs any one of the compounds represented by the above general formulas (1) and (2) to sensitize the semiconductor film, thereby photosensitive layer 2. Form. As described above, the sensitizing treatment method is performed by dissolving the compound in an appropriate solvent and immersing the semiconductor film formed on the conductive support 1 in the solution. In that case, the semiconductor film is subjected to pressure reduction treatment or heat treatment in advance to remove bubbles in the film, and any one compound represented by the general formulas (1) and (2) is converted into the semiconductor film. It is preferable to be able to enter deep inside.

  When any one compound represented by the general formulas (1) and (2) is adsorbed to the semiconductor according to the present invention, it may be used alone or in combination. Furthermore, conventionally known sensitizing dye compounds (for example, U.S. Pat. Nos. 4,684,537, 4,927,721, 5,084,365, 5,350,644, No. 5,463,057, 5,525,440, JP-A-7-249790, JP-A-2000-150007, etc.) may be mixed and adsorbed.

  In particular, when the application of the semiconductor is a solar cell, it is preferable to use a mixture of two or more types of dyes so that the wavelength range of photoelectric conversion can be widened and sunlight can be used as effectively as possible.

  The semiconductor for photoelectric conversion materials sensitized by using a plurality of compounds of any one of the general formulas (1) and (2) described above in combination is a solution prepared by mixing the compounds to be used together It may be prepared by immersing in a solution, or a solution may be prepared for each compound, and it may be prepared by immersing in each solution in turn.

  When preparing a separate solution for each compound and immersing in each solution in order, the effect of the present invention regardless of the order in which the compound or a conventionally known sensitizing dye is adsorbed to the semiconductor Can be obtained.

  For the adsorption treatment, a solution in which the compound is dissolved may be used at room temperature, or the solution may be heated to a temperature that does not affect the compound. Furthermore, it is preferable to remove the dye that has not been adsorbed during the adsorption treatment by washing treatment with a solvent or the like.

  After the dye is adsorbed to the semiconductor film formed on the conductive support 1 to form the photosensitive layer 2, the counter electrode 4 is disposed so as to face the photosensitive layer 2. Further, a redox electrolyte as a charge transfer layer is injected between the semiconductor electrode and the counter electrode 4 to obtain a photoelectric conversion element.

《Solar cell》
The solar cell of the present invention will be described.

  As shown in FIG. 1, the solar cell of the present invention is optimally designed for sunlight and circuit design as one aspect of the photoelectric conversion element of the present invention, and is optimal when sunlight is used as a light source. It has a structure in which photoelectric conversion is performed. That is, the semiconductor for photoelectric conversion material has a structure that can be irradiated with sunlight. When constituting the solar cell of the present invention, it is preferable that the semiconductor electrode, the charge transfer layer and the counter electrode are housed in a case and sealed, or the whole is sealed with resin.

  When the solar cell of the present invention is irradiated with sunlight or an electromagnetic wave equivalent to sunlight, the compound of the present invention adsorbed on the semiconductor for photoelectric conversion material absorbs the irradiated light or electromagnetic wave and excites it. Electrons generated by excitation move to the semiconductor, and then move to the counter electrode 4 via the conductive support 1 to reduce the redox electrolyte of the charge transfer layer 3. On the other hand, the compound of the present invention in which electrons are transferred to a semiconductor is an oxidant, but is reduced by the supply of electrons from the counter electrode 4 via the redox electrolyte of the charge transfer layer 3 and is reduced to the original. At the same time, the redox electrolyte of the charge transfer layer 3 is oxidized and returned to a state where it can be reduced again by the electrons supplied from the counter electrode 4. In this way, electrons flow, and a solar cell using the photoelectric conversion element of the present invention can be configured.

<Conductive support>
The conductive support used in the photoelectric conversion element of the present invention and the solar battery of the present invention is provided with a conductive material such as a conductive material such as a metal plate or a non-conductive material such as a glass plate or a plastic film. A structure having a different structure can be used. Examples of materials used for the conductive support include metal (for example, platinum, gold, silver, copper, aluminum, rhodium, indium) or conductive metal oxide (for example, indium-tin composite oxide, tin oxide doped with fluorine) And carbon). The thickness of the conductive support is not particularly limited, but is preferably 0.3 mm to 5 mm.

  The conductive support is preferably substantially transparent, and substantially transparent means that the light transmittance is 10% or more, more preferably 50% or more, and 80 % Or more is most preferable. In order to obtain a transparent conductive support, it is preferable to provide a conductive layer made of a conductive metal oxide on the surface of a glass plate or a plastic film. When the transparent conductive support 1 is used, light is preferably incident from the support side.

The conductive support preferably has a surface resistance of 50 Ω / cm ² or less, and more preferably 10 Ω / cm ² or less.

《Charge transfer layer》
The charge transfer layer used in the present invention will be described.

A redox electrolyte is preferably used for the charge transfer layer. Here, examples of the redox electrolyte include I ⁻ / I ₃ ⁻ system, Br ⁻ / Br ₃ ⁻ system, and quinone / hydroquinone system. Such a redox electrolyte can be obtained by a conventionally known method. For example, an I ⁻ / I ₃ ⁻ based electrolyte can be obtained by mixing iodine ammonium salt and iodine. The charge transfer layer is composed of dispersions of these redox electrolytes. These dispersions are liquid electrolytes when they are in solution, and are dispersed in solid polymer electrolytes and gel substances when dispersed in polymers that are solid at room temperature. When called, it is called a gel electrolyte. When a liquid electrolyte is used as the charge transfer layer, an electrochemically inert solvent is used as the solvent, for example, acetonitrile, propylene carbonate, ethylene carbonate, or the like is used. Examples of the solid polymer electrolyte include the electrolyte described in JP-A No. 2001-160427, and examples of the gel electrolyte include the electrolyte described in “Surface Science” Vol. 21, No. 5, pages 288 to 293.

《Counter electrode》
The counter electrode used in the present invention will be described.

Counter electrode, as long as it has conductivity, but any conductive material is used, I ₃ ^- catalytic ability to perform fast enough the reduction reaction of oxidation and other redox ions such as ions It is preferable to use what you have. Examples of such a material include a platinum electrode, a surface of a conductive material subjected to platinum plating or platinum deposition, rhodium metal, ruthenium metal, ruthenium oxide, and carbon.

  EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these.

Example 1
<< Production of Photoelectric Conversion Element 1 >>
A photoelectric conversion device as shown in FIG. 1 was produced as described below.

  62.5 ml of titanium tetraisopropoxide (first grade, manufactured by Wako Pure Chemical Industries, Ltd.) was dropped into 375 ml of pure water at room temperature with vigorous stirring for 10 minutes (a white precipitate was formed), and then 70% aqueous nitric acid was added. After 2.65 ml was added and the reaction system was heated to 80 ° C., stirring was continued for 8 hours. Furthermore, after concentrating under reduced pressure until the volume of the reaction mixture becomes about 200 ml, 125 ml of pure water and 140 g of titanium oxide powder (Super Titania F-6 manufactured by Showa Titanium Co., Ltd.) are added to a titanium oxide suspension (about 800 ml ) Was prepared. The titanium oxide suspension is applied onto a transparent conductive glass plate coated with fluorine-doped tin oxide, dried naturally and then fired at 300 ° C. for 60 minutes to form a film-like titanium oxide on the support. did.

  Next, a solution in which 5 g of Exemplified Compound I-1 was dissolved in 200 ml of methanol solution was prepared, the above-mentioned film-like titanium oxide (semiconductor layer for photoelectric conversion material) was immersed together with 1 g of trifluoroacetic acid, and 2 Ultrasonic irradiation for hours. After the reaction, the film-like titanium oxide (semiconductor layer for photoelectric conversion material) was washed with chloroform and vacuum dried to prepare a photosensitive layer 2 (semiconductor for photoelectric conversion material).

  As the counter electrode 4, a transparent conductive glass plate coated with fluorine-doped tin oxide and further carrying platinum thereon is used, and the volume ratio is 1 between the conductive support 1 and the counter electrode 4. : A redox electrolyte in which tetrapropylammonium iodide and iodine were dissolved in a mixed solvent of acetonitrile / ethylene carbonate of 4 to a concentration of 0.46 mol / liter and 0.06 mol / liter, respectively. The charge transfer layer 3 was produced, and the photoelectric conversion element 1 was produced.

<< Preparation of Photoelectric Conversion Elements 2 to 18 >>: Present Invention In the preparation of photoelectric conversion element 1, except that Exemplified Compound I-1 was changed to the compounds shown in Table 1, photoelectric conversion elements 2 to 18 were obtained. It was.

<< Preparation of Photoelectric Conversion Elements RA and RB >>: Comparative Example Photoelectric conversion elements RA and RB were obtained in the same manner as in the preparation of the photoelectric conversion element 1 except that the comparison compounds RA and RB shown in Table 1 were used.

<< Preparation of Solar Cells SC-01 to SC-18 >>: After the side surface of the photoelectric conversion element 1 of the present invention is encapsulated with a resin, lead wires are attached to each of the solar cells SC-01 to SC-18 of the present invention. Lots were made one by one.

<< Preparation of Solar Cells SC-RA and SC-RB >>: Comparative Example In the preparation of the above-described solar cell SC-01, solar cells SC-RA were similarly performed except that the comparative photoelectric conversion elements RA and RB were used. , 3 lots of SC-RB were prepared.

<< Evaluation of photoelectric conversion characteristics of solar cells >>
Each of solar cells SC-01 to SC-18 obtained above and solar cells SC-RA and SC-RB is 100 mW by a solar simulator (manufactured by JASCO (JASCO), low energy spectral sensitivity measuring device CEP-25). Table 1 shows the short-circuit current density Jsc (mA / cm ² ) and the open-circuit voltage value Voc (V) when irradiated with light having an intensity of / m ² . The indicated value was the average value of the measurement results for three solar cells having the same configuration and production method.

From Table 1, compared with the comparison, the solar cell of the present invention exhibits high photoelectric conversion characteristics, and it is effective to use any one compound represented by the general formulas (1) and (2). I understand. Moreover, the solar cells SC-01 to SC-18 of the present invention are excellent in stability because no decrease in photoelectric conversion efficiency is observed even after 100 hours of light irradiation of 100 mW / m ² by a solar simulator. Became clear.

It is a fragmentary sectional view which shows an example of the structure of the photoelectric conversion element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive support body 2 Photosensitive layer 3 Charge transfer layer 4 Counter electrode

Claims (6)

The semiconductor for photoelectric conversion materials characterized by including the heterocyclic compound represented by following General formula (1).

[Wherein, R _1, R ₂ represents a hydrogen atom or a substituent independently when n is 2 or more, R ₁ and R ₂ in a unit which is repeated may be different from each other, also, R ₁ and R ₂ may form a ring, and when n is 2 or more, R ₁ and R ₁ or R ₂ and R ₂ may form a ring in adjacent repeating units, and R ₃ is a hydrogen atom Or a substituent, R ₄ represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, Z ₁ represents an atomic group necessary to form an aromatic carbocycle or a heterocyclic ring, and n is 1, 2, 3 or 4 is represented. ] The semiconductor for photoelectric conversion materials characterized by including the heterocyclic compound represented by following General formula (2).

[Wherein, R _1, R ₂ represents a hydrogen atom or a substituent independently when n is 2 or more, R ₁ and R ₂ in a unit which is repeated may be different from each other, also, R ₁ and R ₂ may form a ring, and when n is 2 or more, R ₁ and R ₁ or R ₂ and R ₂ may form a ring in adjacent repeating units, and R ₃ is a hydrogen atom Or R ₄ represents a hydrogen atom, an aliphatic group, an aromatic group or a heterocyclic group, R ₅ , R ₆ and R ₇ each independently represents a hydrogen atom or a substituent, and R ₈ , R ₉ represents an aliphatic group, an aromatic group or a heterocyclic group, and R ₆ and R ₈ , R ₇ and R ₉ , R ₈ and R ₉ may form a ring, and n is 1, 2, 3 or 4 is represented. ] The general formulas (1) and (2), wherein R ₁ and R ₂ form a ring, and the formed ring structure is a benzene ring, a furan ring, or a thiophene ring. Semiconductor for photoelectric conversion material. The said semiconductor for photoelectric conversion materials is a metal oxide semiconductor or a metal sulfide semiconductor, The semiconductor for photoelectric conversion materials of any one of Claims 1-3 characterized by the above-mentioned. The photoelectric conversion element of any one of Claims 1-4 is provided on the electroconductive support body, The photoelectric conversion element characterized by the above-mentioned. A solar cell comprising the photoelectric conversion element according to claim 5, a charge transfer layer, and a counter electrode.

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