JP5283980B2 - Organic thin film solar cell material and organic thin film solar cell using the same - Google Patents

Description

  The present invention relates to an organic thin film solar cell material and an organic thin film solar cell using the same.

  A solar cell is a device that exhibits an electrical output with respect to an optical input, similar to a photodiode or an imaging device that converts an optical signal into an electrical signal. What is an electroluminescence (EL) device that exhibits an optical output with respect to an electrical input? It is a device that shows the opposite response. This solar cell has been attracting much attention as a clean energy source in recent years against the background of fossil fuel depletion and global warming, and research and development have been actively conducted. So far, silicon solar cells using single crystal silicon, polycrystalline silicon, amorphous silicon, etc. have been put into practical use, but the problems such as the high cost of silicon solar cells and the lack of raw material silicon have surfaced. As a result, there is a growing demand for the development of next-generation solar cells. Under such circumstances, organic thin-film solar cells that are inexpensive, low in toxicity, and have no fear of shortage of raw materials are attracting much attention as next-generation solar cells after silicon-based solar cells.

Research on organic thin-film solar cells has initially been based on single-layer films using merocyanine dyes. However, by further research and development, the conversion efficiency from light input to electrical output (photoelectric conversion efficiency) can be improved by making a multilayer film with “p layer” for transporting electrons and “n layer” for transporting holes. Since it has been found to improve, multilayer films have become mainstream. The materials used at the beginning of the study of the multilayer film were copper phthalocyanine (CuPc) for the p layer and peryleneimides (PTCBI) for the n layer. After that, it was found that the photoelectric conversion efficiency is improved by inserting “i layer (mixed layer of p material and n material)” between the p layer and the n layer to increase the number of layers. The same material was used for each of the p layer and the n layer.
Thereafter, it has been found that the photoelectric conversion efficiency is further improved by the stack cell configuration in which “p layer / i layer / n layer” is repeatedly laminated. The materials used at this time were phthalocyanines for the p layer and fullerene (C ₆₀ ) for the n layer.

On the other hand, in the organic thin-film solar cells using a polymer, induce microlayer separation by using a conductive polymer as a material of the p-layer, using a C ₆₀ derivative as the material of the n-layer mixture thereof, a heat treatment Research on so-called bulk heterostructures, in which the number of heterointerfaces is increased and the photoelectric conversion efficiency is improved, has been mainly conducted. The material system used here was mainly poly-3-hexylthiophene (P3HT) as the material for the p layer and C ₆₀ derivative (PCBM) as the material for the n layer.
Thus, in the organic thin film solar cell, the material of each layer has not progressed much from the early days, and phthalocyanine derivatives, perylene imide derivatives, and C ₆₀ derivatives are still used. Therefore, in order to increase the photoelectric conversion efficiency, development of a new material replacing these conventional materials is eagerly desired.

  By the way, in general, the operation process of an organic solar cell is as follows: (1) light absorption and exciton generation, (2) exciton diffusion, (3) charge separation, (4) carrier movement, and (5) electromotive force generation. In general, organic substances do not generally have an absorption characteristic that matches the solar spectrum, and thus high photoelectric conversion efficiency cannot often be achieved. For example, in organic EL devices that have been energetically developed in recent years, excellent hole transport materials and amine compounds that are hole injection materials have been found. Even if it is used as a material for the layer, it has a drawback that the absorption characteristics with respect to the sunlight spectrum are insufficient and the photoelectric conversion efficiency cannot be sufficiently obtained.

In order to give absorption in the visible light region in an organic compound, it is known that the π-electron conjugated structure may be enlarged to increase the absorption maximum wavelength. However, if the conjugated system is expanded too much and the molecular weight becomes too large, the solubility in the solvent is lowered and purification becomes difficult, and the sublimation temperature rises and sublimation purification becomes impossible. Thus, thienoacenes have been developed as materials that efficiently lengthen the absorption wavelength while suppressing the molecular weight to some extent (see Patent Document 1 and Non-Patent Document 1).
However, the thienoacenes described in Patent Literature 1 and Non-Patent Literature 1 (i) increase the number of condensed rings in the polyacene structure portion in order to widen the visible absorption region, so that the stability to light and oxygen decreases. It is difficult to handle and high purity is difficult. (Ii) Since it has a triple bond or silyl group in the side chain, it is unstable to heat and light, and has mechanical performance and photoelectric conversion. There was a problem that it was poor in practicality because of its insufficient efficiency.

JP 2007-335760 A Journal of American Chemical Society, 129, 9144 (2007)

  The present invention has been made under such circumstances, and is a novel material that is stable to light, oxygen, and heat and can exhibit highly efficient photoelectric conversion characteristics when used in an organic thin film solar cell. The purpose is to provide.

  As a result of intensive studies to achieve the above object, the present inventors have used a compound having a specific thienoacene skeleton, and are stable to light, oxygen, and heat, and have high efficiency. It discovered that the organic thin-film solar cell which shows a characteristic could be obtained, and completed this invention.

That is, the present invention
[1] Organic thin film solar cell material comprising a compound represented by general formula (I) and / or general formula (II),

(In Formulas (I) and (II), X ¹ , X ² , Y ¹ and Y ² are each independently a substituted or unsubstituted aryl group having 6 to 40 ring carbon atoms, or General Formula (III) In the formulas (I) to (III), R ^{1 to} R ⁷ are each independently a hydrogen atom, a halogen atom, or a substituted or unsubstituted alkyl group having 1 to 40 carbon atoms. A substituted or unsubstituted cycloalkyl group having 3 to 10 ring carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 40 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 40 carbon atoms, or a ring forming carbon number A substituted or unsubstituted aryl group having 6 to 40 carbon atoms, a substituted or unsubstituted heteroaryl group having 6 to 40 ring atoms, a substituted or unsubstituted alkoxy group having 1 to 40 carbon atoms, and 3 to 10 carbon atoms forming a ring Replaced or unsubstituted shik An alkoxy group, a substituted or unsubstituted aryloxy group having 6 to 40 ring carbon atoms, a substituted or unsubstituted arylamino group having 6 to 40 ring carbon atoms, or a substituted or unsubstituted alkylamino group having 1 to 40 carbon atoms Represents a group.)
[2] R ^{1 to} R ⁷ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 40 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 ring carbon atoms, carbon A substituted or unsubstituted alkoxy group having 1 to 40 carbon atoms, a substituted or unsubstituted aryloxy group having 6 to 40 ring carbon atoms, or a substituted or unsubstituted arylamino group having 6 to 40 ring carbon atoms [ 1], an organic thin film solar cell material,
[3] R ^{1 to} R ⁷ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 40 carbon atoms, or a substituted or unsubstituted aryl group having 6 to 40 ring carbon atoms. The organic thin-film solar cell material according to [1],
[4] The organic thin-film solar cell material according to [1], wherein R ^{1 to} R ⁷ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 40 carbon atoms,
[5] The organic thin-film solar cell material according to any one of [1] to [4], wherein R ⁶ and R ⁷ are hydrogen atoms.
[6] An organic thin film solar cell having at least a p layer between a pair of electrodes, the p layer containing the material for an organic thin film solar cell according to any one of [1] to [5], and [7] A device comprising the organic thin-film solar cell according to [6],
Is to provide.

  ADVANTAGE OF THE INVENTION According to this invention, the material which is stable with respect to light, oxygen, and a heat | fever, and shows a highly efficient photoelectric conversion characteristic when utilized for an organic thin film solar cell can be provided.

<Materials for organic thin film solar cells>
As described above, the organic thin film solar cell material of the present invention comprises a compound represented by the following general formula (I) and / or general formula (II).

In formulas (I) and (II), X ¹ , X ² , Y ¹ and Y ² are substituted or unsubstituted aryl groups having 6 to 40 ring carbon atoms, substituted or unsubstituted 6 to 40 ring atoms or general Represents a group represented by formula (III). In formulas (I) to (III), R ^{1 to} R ⁷ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 40 carbon atoms, or a ring forming carbon number of 3 to 3. 10 substituted or unsubstituted cycloalkyl groups, substituted or unsubstituted alkenyl groups having 2 to 40 carbon atoms, substituted or unsubstituted alkynyl groups having 2 to 40 carbon atoms, substituted or unsubstituted rings having 6 to 40 carbon atoms Substituted aryl group, substituted or unsubstituted heteroaryl group having 6 to 40 ring atoms, substituted or unsubstituted alkoxy group having 1 to 40 carbon atoms, substituted or unsubstituted cyclocarbon having 3 to 10 ring carbon atoms An alkoxy group, a substituted or unsubstituted aryloxy group having 6 to 40 ring carbon atoms, a substituted or unsubstituted arylamino group having 6 to 40 ring carbon atoms, or a substitution having 1 to 40 carbon atoms Represents a non-substituted alkyl amino group.

Examples of the substituted or unsubstituted aryl group having 6 to 40 ring carbon atoms represented by X ¹ , X ² , Y ¹ and Y ² include a phenyl group, a 2-biphenylyl group, a 3-biphenylyl group, a 4-biphenylyl group, and a terphenylyl group. Group, 3,5-diphenylphenyl group, 3,4-diphenylphenyl group, pentaphenylphenyl group, fluorenyl group, 1-naphthyl group, 2-naphthyl group, 9-anthryl group, 2-anthryl group, 9-phenanthryl group 1-pyrenyl group, chrycenyl group, tetracenyl group, coronyl group and the like. Among these, from the viewpoint of availability of raw materials, an aryl group having 6 to 18 ring carbon atoms is preferable, an aryl group having 6 to 14 ring carbon atoms is more preferable, a phenyl group, a 4-biphenylyl group, 1- A naphthyl group, a 2-naphthyl group, and a 9-phenanthryl group are more preferable. The aryl group may have a substituent, and examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom; hydroxyl group; methyl group, trifluoromethyl group, ethyl group, various types An alkyl group having preferably 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms) such as propyl group and various butyl groups; vinyl group, 2,2-diphenylvinyl group, 1,2,2-triphenylvinyl group Alkenyl groups such as methoxy groups, ethoxy groups, various propoxy groups, various butoxy groups, etc., preferably alkoxy groups having 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms); phenyl groups, tolyl groups, naphthyl groups, etc. Preferably an aryl group having 6 to 14 ring carbon atoms; and a cyano group. Specific examples of the aryl group having a substituent include 2-tolyl group, 4-tolyl group, 4-trifluoromethylphenyl group, 4-methoxyphenyl group, 4-cyanophenyl group, 4- (2,2-diphenyl). Vinyl) phenyl group, 4- (1,2,2-triphenylvinyl) phenyl group and the like.

Next, examples of the halogen atom represented by R ^{1 to} R ⁷ in the general formulas (I) to (III) include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
The alkyl group having 1 to 40 carbon atoms represented by R ^{1 to} R ⁷ may be linear or branched. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, and various pentyl groups (“various” is linear and This indicates that any branched chain is included. The same shall apply hereinafter.), Various hexyl groups, 2-ethylhexyl groups, various octyl groups, 3,7-dimethyloctyl groups, various decyl groups, various dodecyl groups, various decyl groups, various dodecyl groups. And various tetradecyl groups, various hexadecyl groups, various octadecyl groups, various icosanyl groups, various docosanyl groups, various tetracosanyl groups, and the like. Among these, from the viewpoint of availability of raw materials, an alkyl group having 1 to 20 carbon atoms is preferable, an alkyl group having 1 to 5 carbon atoms is more preferable, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, A tert-butyl group is more preferred. The alkyl group may have a substituent. Examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom; hydroxyl group; methoxy group, ethoxy group, various propoxy groups and various butoxy groups. An alkoxy group having preferably 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms) such as a group; an aryl group having 6 to 14 ring carbon atoms such as a phenyl group, a tolyl group and a naphthyl group; a cyano group and the like Is mentioned. Specific examples of the alkyl group having a substituent include a trifluoromethyl group, a trichloromethyl group, a benzyl group, an α, α-dimethylbenzyl group, a 2-phenylethyl group, and a 1-phenylethyl group.

Examples of the cycloalkyl group having 3 to 40 ring carbon atoms represented by R ^{1 to} R ⁷ include a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a 1-adamantyl group, a 2-adamantyl group, and a norbornyl group. Among these, a cycloalkyl group having 3 to 20 ring carbon atoms is preferable, a cycloalkyl group having 3 to 10 ring carbon atoms is more preferable, and a cyclohexyl group is further preferable. The cycloalkyl group may have a substituent, and examples of the substituent include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom and an iodine atom; a hydroxyl group; a methyl group, a trifluoromethyl group, an ethyl group, Preferably various alkyl groups having 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms) such as various propyl groups and various butyl groups; preferably methoxy groups, ethoxy groups, various propoxy groups, various butoxy groups and the like. An alkoxy group having 10 to 10 carbon atoms (more preferably 1 to 5 carbon atoms); an aryl group having 6 to 14 ring carbon atoms such as a phenyl group, a tolyl group and a naphthyl group; and a cyano group.

The alkenyl group having 2 to 40 carbon atoms represented by R ^{1 to} R ⁷ may be linear or branched. Examples of the alkenyl group include a vinyl group, a propenyl group, a 2-butenyl group, a 3-butenyl group, an oleyl group (9-octadecenyl group), an eicosapentaenyl group, and a docosahexaenyl group. Among these, from the viewpoint of availability of raw materials, an alkenyl group having 2 to 20 carbon atoms is preferable, an alkenyl group having 2 to 5 carbon atoms is more preferable, and a vinyl group is further preferable. Such an alkenyl group may have a substituent. Examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom; hydroxyl group; methoxy group, ethoxy group, various propoxy groups and various butoxy groups. An alkoxy group having preferably 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms) such as a group; an aryl group having 6 to 14 ring carbon atoms such as a phenyl group, a tolyl group and a naphthyl group; a cyano group and the like Is mentioned. Specific examples of the alkenyl group having a substituent include a styryl group, 2,2-diphenylvinyl group, 1,2,2-triphenylvinyl group, 2-phenyl-2-propenyl group and the like. Of these, a styryl group and a 2,2-diphenylvinyl group are preferred from the viewpoint of availability of raw materials.

The alkynyl group having 2 to 40 carbon atoms represented by R ^{1 to} R ⁷ may be linear or branched. Examples of the alkynyl group include ethynyl group and propynyl group. Among these, from the viewpoint of availability of raw materials, an alkynyl group having 2 to 20 carbon atoms is preferable, an alkynyl group having 2 to 5 carbon atoms is preferable, and an ethynyl group is more preferable. The alkynyl group may have a substituent. Examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom; hydroxyl group; methoxy group, ethoxy group, various propoxy groups and various butoxy groups. An alkoxy group having preferably 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms) such as a group; an aryl group having 6 to 14 ring carbon atoms such as a phenyl group, a tolyl group and a naphthyl group; a cyano group and the like Is mentioned. Specific examples of the alkynyl group having a substituent include 2-phenylethynyl group.

The aryl group having 6 to 40 ring carbon atoms represented by R ^{1 to} R ⁷ is the same as the aryl group having 6 to 40 ring carbon atoms represented by X and Y.
Examples of the heteroaryl group having 6 to 40 ring atoms represented by R ^{1 to} R ⁷ include furanyl group, thiophenyl group, pyrrolyl group, imidazolyl group, benzoimidazolyl group, pyrazolyl group, benzopyrazolyl group, triazolyl group, oxadiazolyl group, pyridinyl Group, pyrazinyl group, triazinyl group, quinolinyl group, benzofuranyl group, dibenzofuranyl group, benzothiophenyl group, dibenzothiophenyl group, carbazolyl group and the like. Among these, from the viewpoint of availability of raw materials, a heteroaryl group having 6 to 20 ring atoms is preferable, a heteroaryl group having 6 to 14 ring atoms is more preferable, and a furanyl group, a thiophenyl group, and a pyridinyl group. A carbazolyl group is more preferable. Such a heteroaryl group may have a substituent, and the substituent is preferably a hydroxyl group; a methyl group, a trifluoromethyl group, an ethyl group, various propyl groups, various butyl groups or the like, preferably 1 to 10 carbon atoms. An alkyl group (more preferably having 1 to 5 carbon atoms); an alkoxy group having preferably 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms) such as a methoxy group, an ethoxy group, various propoxy groups, and various butoxy groups; Preferred examples include a phenyl group, a tolyl group, a naphthyl group and the like, and an aryl group having 6 to 14 ring carbon atoms.

The alkoxy group having 1 to 40 carbon atoms represented by R ¹ to R ^7, the alkyl group moiety may include the same ones as the alkyl groups for the above-mentioned R ¹ to R ⁷ are carbon atoms represented 1-40. Among these, from the viewpoint of availability of raw materials, an alkoxy group having 1 to 20 carbon atoms is preferable, an alkoxy group having 1 to 5 carbon atoms is more preferable, and a methoxy group, an ethoxy group, and a tert-butyloxy group are further preferable. Examples of the substituent that the alkoxy group may have include the same substituents that the alkyl group having 1 to 40 carbon atoms represented by R ^{1 to} R ⁷ may have.

The cycloalkoxy group having 3 to 10 ring carbon atoms represented by R ^{1 to} R ⁷ and preferred examples thereof include a cycloalkyl group moiety and preferred examples thereof having 3 to 3 ring carbon atoms represented by R ^{1 to} R ⁷ described above. Examples include 40 cycloalkyl groups and preferred examples thereof. Examples of the substituent that the cycloalkoxy group may have include the same substituents that the cycloalkyl group having 3 to 40 carbon atoms represented by R ^{1 to} R ⁷ may have. .

As the aryloxy group having 6 to 40 ring carbon atoms represented by R ^{1 to} R ⁷ and preferred examples thereof, the aryl group part and preferred examples thereof are those having 6 to 40 ring carbon atoms represented by R ^{1 to} R ⁷ described above. And the same aryl groups and preferred examples thereof. Among these, from the viewpoint of availability of raw materials, an aryloxy group having 6 to 20 ring carbon atoms is preferable, an aryloxy group having 6 to 14 ring carbon atoms is more preferable, and a phenoxy group, a naphthoxy group, and phenane. A tolyloxy group is more preferred. Examples of the substituent that the aryloxy group may have include the same substituents that the aryl group having 6 to 40 carbon atoms represented by R ^{1 to} R ⁷ may have.

In the arylamino group having 6 to 40 ring carbon atoms represented by R ^{1 to} R ^7, at least one of the substituents bonded to the amino group may be an aryl group. Such arylamino groups include monoarylamino groups such as phenylamino groups; alkylarylamino groups such as methylphenylamino groups and phenyl t-butylamino groups; diphenylamino groups, phenyl-1-naphthylamino groups, and phenyl-2 -Diarylamino groups such as a naphthylamino group. Of these, a diphenylamino group, a ditolylamino group, and a bis (4-methoxyphenyl) amino group are preferable from the viewpoint of availability of raw materials. The arylamino group may have a substituent, and examples of the substituent include halogen atoms such as fluorine atom, chlorine atom, bromine atom and iodine atom; hydroxyl group; methyl group, trifluoromethyl group, ethyl group, Preferred alkyl groups having 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms) such as various propyl groups and various butyl groups; vinyl groups, 2,2-diphenylvinyl groups, 1,2,2-triphenylvinyl Alkenyl groups such as methoxy groups; methoxy groups, ethoxy groups, various propoxy groups, various butoxy groups, etc., preferably alkoxy groups having 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms); phenyl groups, tolyl groups, naphthyl groups And preferably an aryl group having 6 to 14 ring carbon atoms; a cyano group and the like. Specific examples of the arylamino group having a substituent include di-p-tolylamino group, dim-tolylamino group, phenyl m-tolylamino group, phenyl (sec-butylphenyl) amino group, and bis (4-methoxyphenyl) amino group. Etc.

In the dialkylamino group, the alkylamino group having 1 to 40 carbon atoms represented by R ^{1 to} R ⁷ may be the same or different, and the alkyl group bonded to the amino group may be bonded to each other to form a ring (part of the ring). May be substituted with a nitrogen atom or an oxygen atom. Examples of the alkylamino group include a monoalkylamino group such as a methylamino group; a dialkylamino group such as a dimethylamino group, a methylethylamino group, and a diethylamino group; The nitrogen-containing heterocyclic group of several 5-20 (preferably 5-10) is mentioned. Of these, from the viewpoint of availability of raw materials, a dialkylamino group and a nitrogen-containing heterocyclic group are preferable, and a dimethylamino group, a diethylamino group, and a piperidino group are more preferable. In the monoalkylamino group and dialkylamino group, the alkyl group moiety preferably has 1 to 20, more preferably 1 to 10, and even more preferably 1 to 5 carbon atoms.
The alkylamino group may have a substituent, and the substituent is preferably a hydroxyl group; a methyl group, a trifluoromethyl group, an ethyl group, various propyl groups, various butyl groups, etc., preferably 1 to 10 carbon atoms ( More preferably, an alkyl group having 1 to 5 carbon atoms; an alkoxy group having 1 to 10 carbon atoms (more preferably 1 to 5 carbon atoms) such as a methoxy group, an ethoxy group, various propoxy groups, and various butoxy groups. Can be mentioned. Specific examples of the alkylamino group having a substituent include a bis (2-hydroxyethyl) amino group, a bis (2-methoxyethyl) amino group, and a pipecolino group.

R ^{1 to} R ⁷ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 40 carbon atoms, a substituted or unsubstituted aryl group having 6 to 40 ring carbon atoms, or 1 to 40 carbon atoms. A substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group having 6 to 40 ring carbon atoms, or a substituted or unsubstituted arylamino group having 6 to 40 ring carbon atoms, preferably a hydrogen atom More preferably a substituted or unsubstituted alkyl group having 1 to 40 carbon atoms or a substituted or unsubstituted aryl group having 6 to 40 ring carbon atoms, a hydrogen atom, a substituted or unsubstituted group having 1 to 40 carbon atoms More preferably, it is an alkyl group. R ⁶ and R ⁷ are particularly preferably hydrogen atoms.

  Specific preferred examples of the compounds represented by the general formulas (I) and (II) are listed below, but are not particularly limited thereto.

  Among the materials described above, the following compounds are preferable as the organic thin film solar cell material.

<Method for producing organic thin-film solar cell material>
The method for producing the organic thin film solar cell material of the present invention is not particularly limited. For example, the synthesis route using an anthraquinone derivative as a starting material is easy to obtain the raw material, the reaction conditions are mild, and the yield is high. It is preferable because the desired product can be obtained. An example of a production method by a synthetic route using an anthraquinone derivative as a starting material is shown below.

(Wherein, R ^1a to R ^5a and R ^1b to R ^5b are the same as each said R ¹ ~R ^5, R ⁶ and R ⁷ are as defined above.)

(Process 1)
Step 1 is a step of synthesizing a diol by reacting an anthraquinone derivative with an organometallic reagent. Examples of the organometallic reagent used for this reaction include a Grignard reagent typified by arylmagnesium bromide and a lithium reagent typified by aryllithium. Of these, lithium reagents are preferred because they give good yields.

(Process 2)
Step 2 is a step of reducing and aromatizing the diol obtained in Step 1, and as the reducing agent that can be used at that time, potassium iodide, iodides typified by sodium iodide, chloride, etc. Examples thereof include a tin reagent typified by stannous (SnCl ₂ ). Of these, iodide is preferred because no harmful waste is generated and the reaction conditions are mild.

(Method for synthesizing anthraquinone derivatives)
As an anthraquinone derivative as a starting material, a method using an aldol condensation reaction between a thiophene derivative and an anthraquinone as shown below is simple and preferable. Anthraquinone derivatives obtained by utilizing this aldol condensation reaction are a mixture of an anti isomer and a syn isomer, and it is generally difficult to separate these isomers. In such a case, the anthraquinone derivative can be used as a starting material in the above-described method for producing a material for an organic thin film solar cell of the present invention without being separated as a mixture of an anti isomer and a syn isomer.

(Wherein R ⁶ and R ⁷ are the same as described above.)

The aldol condensation reaction is usually performed in the presence of an acid or a base. Examples of the acid include organic acids such as acetic acid and propionic acid. Examples of the base include organic amines such as triethylamine and lithium diisopropylamide; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as magnesium hydroxide and the like. When using an acid, it is preferable that the usage-amount is 0.01-1 times mole normally with respect to anthraquinone. On the other hand, when using a base, it is preferable that the usage-amount is 0.01-1 times mole normally with respect to anthraquinone.
The aldol condensation reaction may be performed in the presence of a solvent. Examples of the solvent include methanol and ethanol. The reaction temperature is usually preferably room temperature to 100 ° C., and the reaction time is not particularly limited, but is usually 1 to 24 hours.

  Purity can be increased by appropriately purifying the organic thin-film solar cell material obtained in this way by a conventional means for purifying organic compounds such as column chromatography, recrystallization and sublimation purification.

<Organic thin film solar cell>
In the organic thin film solar cell including the organic thin film solar cell material of the present invention, layers other than the electrode may be formed of the material of the present invention alone or a mixture of the material of the present invention and other components. May be.
The organic thin film solar cell using the material of the present invention exhibits highly efficient photoelectric conversion characteristics.

The cell structure of the organic thin film solar cell of the present invention is not particularly limited as long as it is a structure containing the organic thin film solar cell material of the present invention between a pair of electrodes. Specifically, a structure having the following configuration on a stable insulating substrate can be given.
(1) Lower electrode / single layer of organic thin film solar cell material of the present invention / upper electrode (2) lower electrode / p layer / n layer / upper electrode (3) lower electrode / p layer / i layer (p layer Mixed layer of material and n layer material) / n layer / upper electrode (4) lower electrode / mixed layer of material of p layer and n layer material / upper electrode (5) lower electrode / [p layer / (i layer) /) Repeating layer of n layers] / A structure in which the upper electrode and the p layer and the n layer having the configurations of (2) and (3) above are replaced.

Moreover, you may provide a buffer layer between an electrode and an organic layer as needed. For example, as a specific example, when a buffer layer is provided in the configuration (1), a structure having the following configuration can be given.
(6) Lower electrode / buffer layer / p layer / (i layer /) n layer / upper electrode (7) lower electrode / p layer / (i layer /) n layer / buffer layer / upper electrode (8) lower electrode / Buffer layer / p layer / (i layer /) n layer / buffer layer / upper electrode (9) lower electrode / buffer layer / [p layer / (i layer /) repetitive layer of n layer] / upper electrode (10) lower part Electrode / [p layer / (i layer /) n layer repeat layer] / buffer layer / upper electrode (11) lower electrode / buffer layer / [p layer / (i layer /) n layer repeat layer] / buffer layer / Upper electrode

The organic thin film solar cell material of the present invention can be used as a single layer between both electrodes, but can also be used for the p layer, n layer, i layer, and buffer layer, for example.
As the material of the layer not including the organic thin film solar cell material of the present invention and the material of the layer mixed with the organic thin film solar cell material of the present invention, a known material used in the organic thin film solar cell should be used. Can do.
Next, the material of each layer that can be used in the above configuration will be described.

(Lower electrode, upper electrode)
There is no restriction | limiting in particular in the material of a lower electrode and an upper electrode, A well-known electroconductive material can be used.
For example, a metal such as tin-doped indium oxide (ITO), gold (Au), osmium (Os), or palladium (Pd) can be used as the electrode connected to the p layer. In addition, as an electrode connected to the n layer, one component metal such as silver (Ag), aluminum (Al), indium (In), calcium (Ca), platinum (Pt), lithium (Li), magnesium (Mg) ) -Ag, Mg-In, Al-Li, and other binary metals, and further, the metals exemplified as the electrodes connected to the p layer can be used.
Note that a preferable configuration of the pair of electrode configurations is a configuration in which one of the electrode portions includes a metal having a high work function and the other includes a metal having a low work function. Examples of the electrode material having a high work function include ITO, Os, and Pd. Examples of the electrode material having a low work function include Al, In, Mg—Ag alloys, Ca, Li, and Mg.

In order to obtain highly efficient photoelectric conversion characteristics, it is desirable that at least one surface of the solar cell be sufficiently transparent in the sunlight spectrum. For this purpose, a known conductive material is used, and an electrode may be formed by a method such as vapor deposition or sputtering so as to ensure a predetermined translucency. The light transmittance of the electrode on the light receiving surface is preferably 10% or more, more preferably 60% or more, and still more preferably 90% or more.
The film thickness can be appropriately selected depending on the material, but is preferably 1 nm to 10 μm, and more preferably 5 nm to 1 μm.

(P layer)
As a material that can be used for the p layer, a known material having a function as a hole acceptor can be used.
As the material of the p layer, N, N′-bis (3-tolyl) -N, N′-diphenylbenzidine (mTPD), N, N′-dinaphthyl-N, N′-diphenylbenzidine (NPD), 4, Amine compounds such as 4 ′, 4 ″ -tris (phenyl-3-tolylamino) triphenylamine (MTDATA); phthalocyanine (Pc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), titanyl phthalocyanine (TiOPc), etc. Phthalocyanines; porphyrins such as octaethylporphyrin (OEP), platinum octaethylporphyrin (PtOEP), and zinc tetraphenylporphyrin (ZnTPP); main chains such as polyhexylthiophene (P3HT) and methoxyethylhexyloxyphenylene vinylene (MEHPPV) Type conjugated polymer And polymer compounds such as side chain polymers such as polyvinylcarbazole.
The film thickness of the p layer is preferably 5 nm to 5 μm, more preferably 10 nm to 1 μm.

(N layers)
As a material that can be used for the n-layer, a known material having a function as an electron acceptor can be used.
As the material of the n-layer, if it is an organic compound, fullerene derivatives such as C ₆₀ , C ₇₀ , C ₇₆ , C ₇₈ , C ₈₄ , carbon nanotubes, perylene derivatives, polycyclic quinones, quinacridones, etc., vinyl group hydrogen CN-poly (phenylene-vinylene) [CN-PPV] or MEH-CN-PPV in which an atom is substituted with a cyano group, a cyano group or trifluoromethyl group-containing polymer, a poly (fluorene) derivative, and the like can be given. Among these, a material having a high electron mobility and a material having a low electron affinity are preferable. Thus, a sufficient open-circuit voltage can be realized by combining materials having a low electron affinity as the n layer.
In addition, as an n-layer material, if it is an inorganic compound, a doping semiconductor such as n-type silicon (n-Si), GaAs, CdS, PbS, CdSe, InP, Nb ₂ O ₅ , WO ₃ , Fe ₂ O ₃ And compound semiconductors, titanium oxides such as titanium dioxide (TiO ₂ ), titanium monoxide (TiO), and dititanium trioxide (Ti ₂ O ₃ ), and conductive materials such as zinc oxide (ZnO) and tin oxide (SnO ₂ ). An oxide is mentioned. Among these, titanium oxide is preferable and titanium dioxide is more preferable. When an inorganic compound is used as the material for the n layer, the inorganic compound may be used alone or in combination of two or more.
In addition, the organic thin film solar cell obtained by using the said well-known material for n layer and using the organic thin film solar cell material of this invention for p layer is preferable from a viewpoint of photoelectric conversion efficiency. In this case, the known material for the n layer is preferably a fullerene derivative, and more preferably fullerene (C ₆₀ ).
The film thickness of the n layer is preferably 5 nm to 5 μm, more preferably 10 nm to 1 μm.

(I layer)
When the i layer is provided between the n layer and the p layer, a mixture of the material used for the n layer and the material used for the p layer is usually used as the material of the i layer. That is, when the organic thin film solar cell material of the present invention is used for the n layer, it is a mixture of the organic thin film solar cell material of the present invention and the known material of the p layer, and the organic thin film solar cell material of the present invention. Is used for the p layer, it is a mixture of the organic thin film solar cell material of the present invention and the known material of the n layer. In addition, the organic thin film solar cell material of the present invention can be used alone as the i layer, and the above-mentioned known materials can be used as the material for the p layer and the n layer.
The mixing ratio of the material of the n layer and the material of the p layer is preferably 1: 5 to 5: 1 by volume, more preferably 1: 2 to 2: 1, and 0.9: 1.1 to 1.1. : 0.9 is more preferable.
When providing i layer, the film thickness becomes like this. Preferably it is 1 nm-2 micrometers, More preferably, it is 5 nm-1 micrometer.

(Buffer layer)
In general, an organic thin film solar cell has a thin total film thickness, so that the upper electrode and the lower electrode are short-circuited, and the yield of cell fabrication often decreases. In such a case, it is preferable to prevent this by laminating a buffer layer.
As a preferable compound for the buffer layer, a compound having sufficiently high carrier mobility is preferable so that the short-circuit current does not decrease even when the film thickness is increased. For example, if it is a low molecular weight compound, aromatic cyclic acid anhydrides represented by the following NTCDA can be mentioned. If it is a high molecular weight compound, poly (3,4-ethylenedioxy) thiophene; the following polystyrene sulfonate (PEDOT) : PSS), polyaniline; known conductive polymers represented by camphorsulfonic acid (PANI: CSA) and the like.

  In addition, the buffer layer may have a role of preventing excitons from diffusing to the electrodes and deactivating. Inserting a buffer layer as an exciton blocking layer in this way is effective for increasing efficiency. As a preferable material when the buffer layer has a role as an exciton blocking layer, for example, a well-known material for a hole barrier layer or a material for an electron barrier layer for organic electroluminescence (organic EL) applications may be used. A material preferably used as the hole blocking layer is a compound having a sufficiently high ionization potential, and a material preferably used as the electron blocking layer is a compound having a sufficiently low electron affinity. Specific examples of the cathode-side hole barrier layer material include the following bathocuproin (BCP) and the following bathophenanthroline (BPhen).

Furthermore, you may use the inorganic compound illustrated as a material of n layer for a buffer layer. Further, CdTe, p-type silicon (p-Si), SiC, GaAs, WO ₃ or the like, which are known inorganic compounds having p-type characteristics, may be used.
The film thickness of the buffer layer is preferably 1 nm to 3 μm, more preferably 5 nm to 1 μm.

  In addition, when the cell structure of the organic thin film solar cell is “lower electrode / single layer / upper electrode of the organic thin film solar cell material of the present invention”, the film pressure of the single layer is preferably 1 nm to 10 μm. More preferably, the thickness is 5 nm to 1 μm.

(substrate)
The substrate may be a substrate usually used for an organic thin film solar cell, and among them, a glass substrate or a transparent resin film having mechanical and thermal strength and having transparency is preferably used.
Transparent resin films include polyethylene, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polypropylene, polystyrene, polymethyl methacrylate, polyvinyl chloride, polyvinyl alcohol, polyvinyl butyral, nylon, polyether ether ketone. , Polysulfone, polyethersulfone, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, polyvinyl fluoride, tetrafluoroethylene-ethylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, polychlorotrifluoroethylene, Examples include polyvinylidene fluoride, polyester, polycarbonate, polyurethane, polyimide, polyetherimide, polyimide, and polypropylene. It is.

(Method for forming each layer of organic thin film solar cell)
There are no particular restrictions on the method of forming each layer of the organic thin film solar cell of the present invention, dry deposition methods such as vacuum deposition, sputtering, plasma, ion plating, spin coating, dip coating, casting, roll coating, flow coating, A wet film forming method such as an ink jet can be employed. By this method, it is preferable to adjust each layer to the thickness of each layer described above. Since it is generally known that the exciton diffusion length of an organic thin film is short, if the film thickness is too thick, the exciton is deactivated before reaching the heterointerface, resulting in low photoelectric conversion efficiency. If the film thickness is too thin, pinholes and the like are generated, so that sufficient diode characteristics cannot be obtained, resulting in a decrease in conversion efficiency.

When the dry film forming method is employed, the material is preferably heated and evaporated using a resistance heating method. Moreover, when forming a mixed layer, the film-forming method by simultaneous vapor deposition from a several evaporation source is preferable, for example. During film formation, it is preferable to control the substrate temperature to be constant.
When the wet film forming method is applied, a thin film is formed after preparing a light-emitting organic solution by dissolving or dispersing the material in an appropriate solvent. As such a solvent, any solvent can be used, for example, halogenated hydrocarbon solvents such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, tetrachloroethane, trichloroethane, chlorobenzene, dichlorobenzene, chlorotoluene; dibutyl ether, tetrahydrofuran, dioxane. , Ether solvents such as anisole; alcohol solvents such as methanol, ethanol, propanol, butanol, pentanol, hexanol, cyclohexanol, methyl cellosolve, ethyl cellosolve, ethylene glycol; benzene, toluene, xylene, ethylbenzene, hexane, octane, Examples thereof include hydrocarbon solvents such as decane and tetralin; ester solvents such as ethyl acetate, butyl acetate and amyl acetate. Of these, hydrocarbon solvents or ether solvents are preferable. These solvents may be used alone or in combination. The solvent is not particularly limited to these.

In the present invention, in any organic thin film layer of the organic thin film solar cell, an appropriate resin or additive may be contained in order to improve film formability and prevent pinholes in the film. Usable resins include polystyrene, polycarbonate, polyarylate, polyester, polyamide, polyurethane, polysulfone, polymethyl methacrylate, polymethyl acrylate, cellulose and other insulating resins and copolymers thereof; poly-N-vinylcarbazole And photoconductive resins such as polysilane; and conductive resins such as polythiophene and polypyrrole.
Examples of the additive include an antioxidant, an ultraviolet absorber, and a plasticizer.

  When the organic thin film solar cell material of the present invention thus obtained is used for the p layer in the cell structure of “lower electrode / p layer / n layer / upper electrode”, a photoelectric conversion efficiency of 0.98% or more, Depending on the material, a photoelectric conversion efficiency of 1.48% or more can be obtained.

  The organic thin film solar cell using the organic thin film solar cell material obtained in the present invention is effectively used for devices such as a solar cell module, a photovoltaic power generation panel, a watch, a portable information terminal, and a personal computer.

EXAMPLES Next, although an Example demonstrates this invention still in detail, this invention is not limited at all by these examples.
In each example, using a solar simulator (device name “SS-50XIL”, manufactured by Eihiro Seiki Co., Ltd.), the IV characteristics were measured under AM1.5 conditions (light intensity 100 mW / cm ² ). The open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and conversion efficiency (η) were determined. For the same Pin (light intensity), compounds with larger Voc, Jsc, and FF all exhibit better conversion efficiency. The photoelectric conversion efficiency was derived from the following formula.

(Production Example 1)
The following organic thin film solar cell material A was produced by the following synthesis route.

<< Production of Intermediate A1 >>
Thiophene-2,3-dicarboxaldehyde (5.0 g, 34 mmol) and 1,4-cyclohexanedione (2.4 g, 21 mmol) were dissolved in ethanol (500 ml), and 15% aqueous potassium hydroxide solution (20 ml) was dissolved therein. And stirred at room temperature for 1 hour. The reaction mixture was filtered off and washed with water and ethanol to obtain a yellow solid intermediate A1 (5.7 g, yield: 59%).
The ¹ H-NMR measurement result of the obtained intermediate A1 is shown below.

¹ H-NMR (400 MHz, CDCl ₃ , TMS) δ: 7.62 (2H, s), 7.79 (2H, s), 8.84 (2H, s), 8.93 (2H, s)

<< Production of Intermediate A2 >>
Under an argon atmosphere, Intermediate A1 (5.7 g, 18 mmol) was suspended in anhydrous THF (140 ml) and cooled to −78 ° C. in a dry ice / methanol bath. To this was added phenyllithium / ether solution (1.9 mol / l, 24 ml, 46 mmol), the cooling bath was removed, and the mixture was stirred at room temperature for 1 hour.The reaction mixture was quenched with water (100 ml), and the organic layer was separated. After drying over anhydrous sodium sulfate and evaporation of the solvent, a red solid was obtained, which was purified by column chromatography (“silica gel / hexane + 50% dichloromethane”, then “dichloromethane” and finally “dichloromethane + 3% methanol”). As a result, a light brown solid intermediate A2 (4.5 g, yield: 53%) was obtained.
The ¹ H-NMR measurement result of the obtained intermediate A2 is shown below.

¹ H-NMR (400 MHz, CDCl ₃ , TMS) δ: 3.06 (3H, s), 6.94-7.01 (10H, m), 7.38 (2H, s), 7.50 (2H , S), 8.24 (2H, s), 8.32 (2H, s)

<< Manufacture of Material A for Organic Thin Film Solar Cells >>
Intermediate A2 (4.5 g, 9.4 mmol), potassium iodide (6.2 g, 38 mmol, 4 eq.), Sodium phosphinate monohydrate (8.0 g, 75 mmol) were dissolved in acetic acid (50 ml). Reflux for hours. The resulting reaction mixture was filtered off and washed with water and methanol to give an orange solid (4.3 g). This was purified by column chromatography (“silica gel / hexane + 33% dichloromethane”, then “hexane + 50% dichloromethane” and finally “hexane + 66% dichloromethane”) to give an orange solid (3.7 g, yield 85%). . This was recrystallized from hexane and toluene to obtain Compound A (2.2 g) as orange needle crystals.
The physical properties of the obtained compound A are shown below.

¹ H-NMR (400 MHz, CDCl ₃ , TMS) d: 7.21 (2H, d, J = 7 Hz), 7.37 (2H, d, J = 8 Hz), 7.63-7.83 (10H, m), 7.16 (4H, d, J = 8 Hz)
FDMS: Calculated value C ₃₀ H ₁₈ S ₂ = 442, measured value m / z = 442 (M ⁺ , 100)
HPLC purity: 95.2% (UV254, area%)

Further, the obtained solid (2.2 g) was purified by sublimation at 280 ° C./5.3×10 ⁻¹ Pa to obtain a red amorphous solid organic thin film solar cell material A (1.7 g, purity: 94.9). %). The mixing ratio of the solid anti isomer and syn isomer was 1: 1.

Example 1
The glass substrate with ITO transparent electrode of “25 mm × 75 mm × thickness 0.7 mm” was subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes and then UV ozone cleaning for 30 minutes. A glass substrate with a transparent electrode line after cleaning is mounted on a substrate holder of a vacuum deposition apparatus. First, the transparent electrode line is formed on the surface where the transparent electrode line, which is the lower electrode, is formed. A thin film solar cell material A was formed by resistance heating vapor deposition at 1 Å / s (p layer: film thickness 30 nm). Next, fullerene (C ₆₀ ) is formed on the film of the organic thin film solar cell material A at 1 蒸 着 / s by resistance heating vapor deposition (n layer: film thickness 60 nm), and the following bathocuproin (BCP) is formed thereon. A film was formed at 1 Å / s by resistance heating vapor deposition (buffer layer: film thickness: 10 nm). Finally, metal Al was continuously deposited as a counter electrode with a film thickness of 80 nm to form an organic thin film solar cell. The area was 0.5 cm ² .
The performance of the obtained organic thin film solar cell is shown in Table 1.

(Example 2)
In Example 1, after providing the p layer and before providing the n layer, the organic thin film solar cell material A was 0.2 を / s and the fullerene (C ₆₀ ) was 0.2 Å / s by resistance heating vapor deposition. An organic thin film solar cell was produced in the same manner as in Example 1 except that the film was formed by vapor deposition (i layer: film thickness 15 nm, mixing ratio p: n = 1: 1).
The performance of the obtained organic thin film solar cell is shown in Table 1.

(Example 3)
In Example 2, the same as Example 2, except that the mixing ratio of the i layer was p: n = 2: 1 (the film formation rates were 0.2 Å / s and 0.1 に し / s, respectively). Thus, an organic thin film solar cell was produced.
The performance of the obtained organic thin film solar cell is shown in Table 1.

Example 4
Example 2 is the same as Example 2 except that the mixing ratio of the i layer is p: n = 1: 2 (the film formation rates are 0.1 Å / s and 0.2 Å / s, respectively). Thus, an organic thin film solar cell was produced.
The performance of the obtained organic thin film solar cell is shown in Table 1.

(Comparative Example 1)
In Example 1, the organic solar cell was produced like Example 1 except having changed the organic thin film solar cell material A into the following mTPD.

(Comparative Example 2)
The following compound (TES-ADT) disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2007-335760) was synthesized by the method described in Non-Patent Document (Organic Letters, Vol. 6, page 3325 (2004)).
The HPLC purity immediately after the synthesis was 98.0% (UV254, area%), but when the tetrahydrofuran solution was left for 40 minutes and remeasured, the HPLC purity was remarkably 58.0% (UV254, area%). It was falling. Moreover, although the sublimation refinement | purification of this material was tried like the manufacture example, it did not sublimate and the residue discolored black. When the HPLC purity of the residue was measured, the peak of the target product (the following compound) disappeared, and only peaks caused by a large number of impurities were detected. From these results, it was confirmed that the compound (TES-ADT) disclosed in Patent Document 1 has low stability and cannot be a material for an organic thin film solar cell that can withstand practical use.

  From Table 1, when the organic thin-film solar cell material of the present invention is used, the conversion efficiency of 1.42 to 2.35 compared to the conversion efficiency of 0.17% of Comparative Example 1 using a known compound (mTPD). %, The organic thin film solar cell material of the present invention shows excellent solar cell characteristics.

  The organic thin film solar cell material of the present invention can be used as a constituent material of an organic thin film solar cell.

Claims (5)

An organic thin film solar cell material comprising a compound represented by the following general formula (I) and / or general formula (II).

(Formula (I) and (II) ^{in, X 1, X 2, Y} 1 and Y ² each independently represent a ring formed unsubstituted aryl group having 6 to 40 carbon atoms. Further, the formula (I) And (II) , R ⁶ and R ⁷ are each independently a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group having 1 to 40 carbon atoms, or a substituted or unsubstituted ring having 3 to 10 carbon atoms. Cycloalkyl group, substituted or unsubstituted alkenyl group having 2 to 40 carbon atoms, substituted or unsubstituted alkynyl group having 2 to 40 carbon atoms, substituted or unsubstituted aryl group having 6 to 40 carbon atoms, ring A substituted or unsubstituted heteroaryl group having 6 to 40 atoms, a substituted or unsubstituted alkoxy group having 1 to 40 carbon atoms, a substituted or unsubstituted cycloalkoxy group having 3 to 10 ring carbon atoms, and a ring-forming carbon As for substitution of number 6-40 Ku denotes an unsubstituted aryloxy group, ring formation substituted or unsubstituted arylamino group or a substituted or unsubstituted alkylamino group having 1 to 40 carbon atoms having 6 to 40 carbon atoms.) X ¹ , X ² , Y ¹ And Y ² The organic thin-film solar cell material according to claim 1, wherein each independently represents a phenyl group. Wherein R ⁶ and R ⁷ are organic thin film solar cell material according to claim 1 or 2 is a hydrogen atom. The organic thin-film solar cell which has at least p layer between a pair of electrodes, and this p layer contains the organic thin-film solar cell material in any one of Claims 1-3 . The apparatus which comprises the organic thin-film solar cell of Claim 4 .