JP2008166558A - Material for photoelectric conversion element and photoelectric conversion element using the same - Google Patents

Abstract

（式中、Ｘは酸素、硫黄又はセレンであり、Ａｒ_１〜Ａｒ_４の一例としては、それぞれ独立にＣ_６〜Ｃ_４０の置換又は無置換のアリール基、Ｒ_１〜Ｒ_１０の例としては、それぞれ独立に水素、ハロゲン、Ｃ_１〜Ｃ_４０の置換又は無置換のアルキル基が挙げられる。また、Ｒ_１〜Ｒ_１０は互いに結合して環を形成しても良い。）
【選択図】なしA novel material for a photoelectric conversion element that exhibits highly efficient photoelectric conversion characteristics is provided.
A material for a photoelectric conversion element containing an amine compound represented by the following formula (1) alone or as a component of a mixture.

(In the formula, X is oxygen, sulfur or selenium, and examples of Ar _{1 to} Ar ₄ are each independently a substituted or unsubstituted aryl group of C _{6 to} C ₄₀ , and examples of R _{1 to} R ₁₀ are: And each independently includes hydrogen, halogen, and a substituted or unsubstituted alkyl group having ₁ to ₄₀ carbon atoms, and R _{1 to} R ₁₀ may be bonded to each other to form a ring.)
[Selection figure] None

Description

  The present invention relates to a photoelectric conversion element material and a photoelectric conversion element using the same. More specifically, the present invention relates to an organic solar cell that can obtain particularly efficient photoelectric conversion characteristics by using a specific amine compound as an organic solar cell material.

  A photoelectric conversion element is a device that shows an electric output with respect to an optical input, as represented by a photodiode or an imaging element that converts an optical signal into an electric signal, or a solar cell that converts optical energy into electric energy. It is a device that exhibits a response opposite to that of an electroluminescent element that exhibits optical output with respect to input. In particular, solar cells have attracted a great deal of 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.

  Conventionally, silicon solar cells represented by single crystal Si, polycrystal Si, amorphous Si, etc. have been put into practical use. However, as the cost and raw material Si shortage problems surface, The demand for next generation solar cells is increasing. Against this background, organic solar cells are attracting much attention as next-generation solar cells next to silicon-based solar cells because they are inexpensive, have low toxicity, and do not have a fear of shortage of raw materials.

Organic solar cells are basically composed of an n layer for transporting electrons and a p layer for transporting holes, and is roughly classified into two types depending on the material constituting each layer.
A n-layer in which a sensitizing dye such as ruthenium dye is adsorbed on the surface of an inorganic semiconductor such as titania and an electrolyte solution is used as a p-layer is called a dye-sensitized solar cell (so-called Gretzell cell), and has a conversion efficiency. Although it has been energetically studied since 1991 because of its height, since it uses a solution, it has drawbacks such as liquid leakage when used for a long time.

  In order to overcome such drawbacks, research has been recently conducted to find an all-solid-state dye-sensitized solar cell by solidifying an electrolyte solution. However, the technology for impregnating organic matter into the pores of porous titania is difficult, and a cell that can express high conversion efficiency with high reproducibility has not been completed.

  On the other hand, organic thin-film solar cells consisting of organic thin films in both the n-layer and p-layer are all solid, so they have no drawbacks such as liquid leakage, are easy to manufacture, and do not use ruthenium, which is a rare metal. Attracted attention and researched energetically.

Organic thin-film solar cells have been studied with a single-layer film using a merocyanine dye or the like. Thereafter, it was found that conversion efficiency was improved by forming a multilayer film of p layer / n layer, and multilayer films have become mainstream since then. The materials used at this time were copper phthalocyanine (the following formula CuPc) as the p layer and peryleneimides (the following formula PTCBI) as the n layer.

  Subsequently, it has been found that the conversion efficiency is improved by inserting an i layer (a mixed layer of p material and n material) between the p layer and the n layer to increase the number of layers. However, the materials used at this time were still phthalocyanines and peryleneimides.

Thereafter, it has been found that the conversion efficiency is further improved by a stack cell configuration in which a number of p / i / n layers are stacked. The material system was phthalocyanines and C _60.

On the other hand, in an organic thin film solar cell using a polymer, a conductive polymer is used as a p material, a C ₆₀ derivative is used as an n material, and they are mixed and heat-treated to induce micro-layer separation to form a heterointerface. Research on so-called bulk heterostructures has been mainly conducted to increase the conversion efficiency and improve the conversion efficiency. Here material system that has been used is mostly soluble polythiophene derivative called following P3HT as p material was soluble C ₆₀ derivative called following PCBM as an n material.

As described above, in the organic thin film solar cell, the conversion efficiency has been improved by optimizing the cell configuration and morphology, but the material system used in the organic thin film solar cell has not made much progress since the early days, and phthalocyanines, peryleneimides still remain. Class C ₆₀ has been used. Therefore, development of a new material system to replace them has been 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. However, since organic substances generally have low carrier mobility, the exciton diffusion process and carrier transfer process are rate-limiting, and high conversion efficiency cannot often be achieved.

On the other hand, the development of organic electroluminescence devices has been energetically performed in recent years, and several excellent hole transport materials and hole injection materials have been found out of them. Typical examples thereof include the following compounds.

Since these hole transport / injection materials have excellent hole transport properties, they have the potential to be used as p-materials for organic thin film solar cells. However, since it does not show light absorption in the visible light region, it has the disadvantage that the absorption characteristics with respect to the sunlight spectrum are insufficient and the hole mobility is not sufficient.
For example, in Non-Patent Document 1, the above-described mTPD is applied to an all-solid-state dye-sensitized solar cell. However, since the absorption characteristics with respect to the sunlight spectrum are not sufficient and the carrier mobility is low, the photoelectric conversion characteristics are It was low.

Patent Documents 1-7 disclose an organic solar battery using a similar amine compound. However, all of them have insufficient absorption characteristics with respect to the sunlight spectrum, and carrier mobility is low, so that the photoelectric conversion characteristics are low.

Further, for example, the following compounds are described in Non-Patent Documents 2-9 and Patent Document 8 as aromatic compounds having an amine unit and a thiophene unit. However, an example applied to an organic thin film solar cell has not been known. Furthermore, since the amine unit and the thiophene unit are directly bonded to each other in the following compounds, the thiophene ring is excessively electron-excessive, resulting in poor thermal stability.For example, when purifying it by sublimation purification or the like, the purity is lowered. It had the disadvantage of end up.

Further, the following compounds are disclosed in Non-Patent Documents 10 and 11, but only the light emission characteristics and the electroluminescence element characteristics are disclosed, and no examples of application to organic thin film solar cells have been known.

Japanese Patent Laid-Open No. 06-085294 Japanese Patent Laid-Open No. 06-104467 Japanese Patent Laid-Open No. 06-104469 Japanese Patent Laid-Open No. 06-120538 Japanese Patent Laid-Open No. 06-120539 JP-A-06-120541 Japanese Patent Laid-Open No. 06-120542 Japanese Patent Laid-Open No. 05-213931 Synth. Met. , 102, 1125 (1999). Org. Lett. 5, 1817 (2003). Org. Lett. 3,1673 (2001). Synthesis, 610 (2005). J. et al. Phys. Chem. B, 110, 8223 (2006). Synthesis, 2487 (2002). Chem. Commun. 1628 (2001). Chem. Commun. , 1530 (2002). Chem. Lett. , 2397 (1994) Adv. Mater. 9, 239 (1997). J. et al. Mater. Chem. 9, 2177 (1999).

  An object of this invention is to provide the novel material for photoelectric conversion elements which shows a highly efficient photoelectric conversion characteristic.

  As a result of intensive studies, the present inventors have improved the properties such as visible absorption and hole mobility by introducing a heterocycle such as thiophene into the amine compound, and when this compound is used in a photoelectric conversion element, the compound is high. It came to discover that photoelectric conversion efficiency is brought about. In addition, by separating the amine unit and the thiophene unit in this compound with phenylene or the like, it has been found that the thermal stability is improved and can be highly purified by sublimation purification or the like, and the present invention has been completed.

（式中、Ｘは酸素、硫黄又はセレンであり、Ａｒ_１〜Ａｒ_４はそれぞれ独立に、Ｃ_６〜Ｃ_４０の置換もしくは無置換のアリール基、Ｃ_３〜Ｃ_４０の置換もしくは無置換のヘテロアリール基であり、Ｒ_１〜Ｒ_１０はそれぞれ独立に、水素、ハロゲン、Ｃ_１〜Ｃ_４０の置換もしくは無置換のアルキル基、Ｃ_２〜Ｃ_４０の置換もしくは無置換のアルケニル基、Ｃ_１〜Ｃ_４０の置換もしくは無置換のアルコキシ基、Ｃ_６〜Ｃ_４０の置換もしくは無置換のアリールオキシ基、Ｃ_１〜Ｃ_４０の置換もしくは無置換のアルキルチオ基、Ｃ_６〜Ｃ_４０の置換もしくは無置換のアリール基、Ｃ_３〜Ｃ_４０の置換もしくは無置換のヘテロアリール基であり、Ｒ_１〜Ｒ_１０は互いに結合して環を形成しても良い。ｎ、ｐ、ｑはそれぞれ独立に１〜６の整数である。）
２．前記Ｘが硫黄であり、Ｒ_１〜Ｒ_１０がそれぞれ独立に、水素、ハロゲン、Ｃ_１〜Ｃ_４０の置換もしくは無置換のアルキル基、Ｃ_６〜Ｃ_４０の置換もしくは無置換のアリール基、又はＣ_３〜Ｃ_４０の置換もしくは無置換のヘテロアリール基である１に記載の光電変換素子用材料。
３．有機太陽電池材料である１又は２に記載の光電変換素子用材料。
４．上記１又は２に記載の光電変換素子用材料を含む光電変換素子。
５．有機太陽電池である４記載の光電変換素子。
６．上記４又は５に記載の光電変換素子を有する装置。 According to the present invention, the following photoelectric conversion element material is provided.
1. The material for photoelectric conversion elements which contains the amine compound represented by following formula (1) individually or as a component of a mixture.

(Wherein X is oxygen, sulfur or selenium, Ar _{1 to} Ar ₄ are each independently a C _{6 to} C ₄₀ substituted or unsubstituted aryl group, C _{3 to} C ₄₀ substituted or unsubstituted hetero Each of R _{1 to} R ₁₀ independently represents hydrogen, halogen, a C _{1 to} C ₄₀ substituted or unsubstituted alkyl group, a C _{2 to} C ₄₀ substituted or unsubstituted alkenyl group, or C ₁ to R ₁₀ . C ₄₀ substituted or unsubstituted alkoxy group, C _{6 to} C ₄₀ substituted or unsubstituted aryloxy group, C _{1 to} C ₄₀ substituted or unsubstituted alkylthio group, C _{6 to} C ₄₀ substituted or unsubstituted aryl _group, a substituted or unsubstituted heteroaryl group _{C 3 ~C 40, R 1 ~R} 10 mAY bonded to each other to form a ring .n, p, q are each independently 1 to 6 of an integer.)
2. X is sulfur, and R _{1 to} R ₁₀ are each independently hydrogen, halogen, a C _{1 to} C ₄₀ substituted or unsubstituted alkyl group, a C _{6 to} C ₄₀ substituted or unsubstituted aryl group, or 2. The material for a photoelectric conversion element according to 1, which is a C _{3 to} C ₄₀ substituted or unsubstituted heteroaryl group.
3. The material for photoelectric conversion elements according to 1 or 2, which is an organic solar cell material.
4). A photoelectric conversion element comprising the photoelectric conversion element material according to 1 or 2 above.
5. 5. The photoelectric conversion element according to 4, which is an organic solar cell.
6). 6. An apparatus having the photoelectric conversion element as described in 4 or 5 above.

  By using the photoelectric conversion element material of the present invention, a photoelectric conversion element exhibiting highly efficient conversion characteristics can be obtained.

The material for a photoelectric conversion element of the present invention contains an amine compound represented by the following formula (1) alone or as a component of a mixture.

Here, X is oxygen (O), sulfur (S), or selenium (Se), and Ar _{1 to} Ar ₄ are C _{6 to} C ₄₀ substituted or unsubstituted aryl groups, C _{3 to} C ₄₀ substituted or An unsubstituted heteroaryl group, wherein R _{1 to} R ₁₀ are each independently hydrogen, halogen, a C _{1 to} C ₄₀ substituted or unsubstituted alkyl group, or a C _{2 to} C ₄₀ substituted or unsubstituted alkenyl group. C ₁ -C ₄₀ substituted or unsubstituted alkoxy group, C ₆ -C ₄₀ substituted or unsubstituted aryloxy group, C ₁ -C ₄₀ substituted or unsubstituted alkylthio group, C ₆ -C ₄₀ A substituted or unsubstituted aryl group or a C ₃ -C ₄₀ substituted or unsubstituted heteroaryl group, R _{1 to} R ₁₀ may be bonded to each other to form a ring; n, p, and q are each independently an integer of 1 to 6.

  In the above structure, X is oxygen, sulfur or selenium, preferably sulfur or selenium, more preferably sulfur.

The substituted or unsubstituted aryl group of C _{6 to} C ₄₀ represented by Ar _{1 to} Ar ₄ may be linear, branched or cyclic, and specific examples thereof include phenyl, 2-tolyl, 4-tolyl, 4-trifluoromethylphenyl, 4-methoxyphenyl, 4-cyanophenyl, 2-biphenylyl, 3-biphenylyl, 4-biphenylyl, terphenylyl, 3,5-diphenylphenyl, 3,4-diphenylphenyl, penta Phenylphenyl, 4- (2,2-diphenylvinyl) phenyl, 4- (1,2,2-triphenylvinyl) phenyl, fluorenyl, 1-naphthyl, 2-naphthyl, 9-anthryl, 2-anthryl, 9- Examples include phenanthryl, 1-pyrenyl, chrycenyl, naphthacenyl, coronyl and the like. Preferred are phenyl, 4-biphenylyl, 1-naphthyl, 2-naphthyl, 9-phenanthryl and the like.

The substituted or unsubstituted heteroaryl group of C _{3 to} C ₄₀ represented by Ar _{1 to} Ar ₄ may be linear, branched or cyclic, and specific examples thereof include furan, thiophene, and pyrrole. Imidazole, benzimidazole, pyrazole, benzpyrazole, triazole, oxadiazole, pyridine, pyrazine, triazine, quinoline, benzofuran, dibenzofuran, benzothiophene, dibenzothiophene, carbazole and the like. Preferred are furan, thiophene, pyridine and the like.

A substituted or unsubstituted alkyl group of _C 1 _{-C 40} where R ₁ to R ₁₀ represents may be either linear, branched or cyclic, as their specific examples, methyl, ethyl, 1- Propyl, 2-propyl, 1-butyl, 2-butyl, sec-butyl, tert-butyl, pentyl, hexyl, octyl, decyl, dodecyl, 2-ethylhexyl, 3,7-dimethyloctyl, cyclopropyl, cyclopentyl, cyclohexyl, 1-adamantyl, 2-adamantyl, norbornyl, trifluoromethyl, trichloromethyl, benzyl, α, α-dimethylbenzyl, 2-phenylethyl, 1-phenylethyl and the like can be mentioned. Preferred are methyl, ethyl, propyl, isopropyl, tert-butyl, cyclohexyl and the like.

The C _{2 to} C ₄₀ substituted or unsubstituted alkenyl group represented by R _{1 to} R ₁₀ may be linear, branched or cyclic, and specific examples thereof include vinyl, propenyl, butenyl, Examples include oleyl, eicosapentaenyl, docosahexaenyl, 2,2-diphenylvinyl, 1,2,2-triphenylvinyl, 2-phenyl-2-propenyl and the like. Preferred are vinyl, 2,2-diphenylvinyl and the like.

The substituted or unsubstituted alkoxy group of C _{1 to} C ₄₀ represented by R _{1 to} R ₁₀ may be linear, branched or cyclic, and specific examples thereof include methoxy, ethoxy, 1- Propyloxy, 2-propyloxy, 1-butyloxy, 2-butyloxy, sec-butyloxy, tert-butyloxy, pentyloxy, hexyloxy, octyloxy, decyloxy, dodecyloxy, 2-ethylhexyloxy, 3,7-dimethyloctyloxy , Cyclopropyloxy, cyclopentyloxy, cyclohexyloxy, 1-adamantyloxy, 2-adamantyloxy, norbornyloxy, trifluoromethoxy, benzyloxy, α, α-dimethylbenzyloxy, 2-phenylethoxy, 1-phenylethoxy, etc. Raised It is done. Preferred are methoxy, ethoxy, ter-butyloxy and the like.

The substituted or unsubstituted aryloxy group of C _{6 to} C ₄₀ represented by R _{1 to} R ₁₀ may be linear, branched or cyclic, and as specific examples thereof, the aryl group is oxygen The substituent couple | bonded through this is mentioned. Preferred are phenoxy, naphthoxy, phenanthryloxy and the like.

A substituted or unsubstituted alkylthio group _C 1 _{-C 40} where R ₁ to R ₁₀ represents may be either linear, branched or cyclic, as their specific examples, methylthio, ethylthio, 1- Propylthio, 2-propylthio, 1-butylthio, 2-butylthio, sec-butylthio, tert-butylthio, pentylthio, hexylthio, octylthio, decylthio, dodecylthio, 2-ethylhexylthio, 3,7-dimethyloctylthio, cyclopropylthio, cyclopentyl Examples include thio, cyclohexylthio, 1-adamantylthio, 2-adamantylthio, norbornylthio, trifluoromethylthio, benzylthio, α, α-dimethylbenzylthio, 2-phenylethylthio, 1-phenylylthio and the like. Preferred are methylthio, ethylthio, ter-butylthio and the like.

The C ₆ -C ₄₀ substituted or unsubstituted aryl group of R _{1 to} R ₁₀ may be linear, branched or cyclic, and specific examples thereof include phenyl, 2-tolyl, 4 -Tolyl, 4-trifluoromethylphenyl, 4-methoxyphenyl, 4-cyanophenyl, 2-biphenylyl, 3-biphenylyl, 4-biphenylyl, terphenylyl, 3,5-diphenylphenyl, 3,4-diphenylphenyl, pentaphenyl Phenyl, 4- (2,2-diphenylvinyl) phenyl, 4- (1,2,2-triphenylvinyl) phenyl, fluorenyl, 1-naphthyl, 2-naphthyl, 9-anthryl, 2-anthryl, 9-phenanthryl , 1-pyrenyl, chrycenyl, naphthacenyl, coronyl and the like. Preferred are phenyl, 4-biphenylyl, 1-naphthyl, 2-naphthyl, 9-phenanthryl and the like.

The C _{3 to} C ₄₀ substituted or unsubstituted heteroaryl group represented by R _{1 to} R ₁₀ may be linear, branched or cyclic, and specific examples thereof include furan, thiophene, and pyrrole. Imidazole, benzimidazole, pyrazole, benzpyrazole, triazole, oxadiazole, pyridine, pyrazine, triazine, quinoline, benzofuran, dibenzofuran, benzothiophene, dibenzothiophene, carbazole and the like. Preferred are furan, thiophene, pyridine and the like.

Among R _{1 to} R ₁₀ described above, hydrogen, halogen, C _{1 to} C ₄₀ substituted or unsubstituted alkyl group, C _{6 to} C ₄₀ substituted or unsubstituted aryl group, or C _{3 to} C ₄₀ substitution Or an unsubstituted heteroaryl group is preferable.

n, p, and q are each independently an integer of 1 to 6, and increasing the number of arylene units improves the solar cell characteristics such as visible absorption and carrier mobility, but conversely, the solubility in a solvent or the like decreases, and purification Since 1 handling becomes difficult, 1-4 are preferable.
When n, p, and q are 2 or more, the plurality of R _{1 to} R ₁₀ may be the same as or different from each other.

（式中、Ｍｅはメチル基を示す。） A preferred example of the above formula (1) is shown below.

(In the formula, Me represents a methyl group.)

In the material for a photoelectric conversion element of the present invention, characteristics such as visible absorption and hole mobility are improved by introducing a heterocycle such as thiophene into an amine compound. Therefore, when used for a photoelectric conversion element, high photoelectric conversion efficiency is obtained.
Moreover, by separating the amine unit and the thiophene unit with phenylene or the like, the thermal stability is improved, and it can be highly purified by sublimation purification or the like.

Next, a typical synthesis method of the amine compound of the formula (1) will be described.
The first method uses cross-coupling using transition metals such as nickel and palladium, and there are two possible synthetic routes depending on the position where the C—C bond is formed. Can do. In the following reaction formula, M is a magnesium compound typified by MgBr or the like, a Kumada-Tamao coupling, a zinc compound typified by ZnCl or the like is a Negishi coupling, SnBu ₃ or the like tin Those that are compounds are Kosugi-Umeda-Still coupling, those that are silicon compounds typified by Si (OH) ₃ etc. are those that are boron compounds typified by Hiyama coupling, B (OH) ₂ etc. -Although called Miyaura coupling, any reaction can be used. Here, Hal represents a halogen represented by chlorine, bromine and iodine, or a pseudohalogen group represented by trifluoromethanesulfonyloxy group. Among the above reactions, the Suzuki-Miyaura reaction is preferable because the raw material typical metal compound has low toxicity, the generation of impurities due to scrambling during the reaction is small, and the unreacted typical metal compound can be easily removed. . Further, the transition metal used as the catalyst is preferably coordinated with phosphines such as Pd (PPh ₃ ) ₄ and NiCl ₂ (dppp). Note that dppp is 1,3-bis (diphenylphosphino) propane.

The second method uses a transition metal such as nickel, palladium, or copper to perform a CN bond formation reaction. A reaction using nickel or palladium is called a Buchwald-Hartwig reaction, and a reaction using copper is called a Ullmann reaction. Any reaction can be used. Among the above reactions, the Buchwald-Hartwig reaction is preferred because the reaction conditions are mild and the various functional group selectivity is excellent. In addition, when Ar _{1 to} Ar ₄ are different substituents, the amino group may be introduced stepwise by adjusting the stoichiometric ratio of amine to halide.

  The material for a photoelectric conversion element of the present invention is used as a material for forming a photoelectric conversion element such as a photodiode, an imaging element, a solar cell, etc. alone or in a mixture containing the compound of the above formula (1). it can. Hereinafter, an organic solar cell will be described as an example of the photoelectric conversion element.

The cell structure of the organic solar battery in the present invention is not particularly limited as long as it is a structure containing the photoelectric conversion element 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 / organic compound layer / upper electrode (2) Lower electrode / p layer / n layer / upper electrode (3) Lower electrode / p layer / i layer (or a mixed layer of p and n materials) / n Layer / upper electrode (4) Lower electrode / mixed layer of p material and n material / upper electrode A structure in which the p layer and the n layer in the structures (2) and (3) are replaced may be used.

Moreover, you may provide a buffer layer between an electrode and an organic layer as needed. As a specific example, when the buffer layer is provided in the above configuration (2), it has the following structure.
(5) Lower electrode / buffer layer / p layer / n layer / upper electrode (6) Lower electrode / p layer / n layer / buffer layer / upper electrode (7) Lower electrode / buffer layer / p layer / n layer / buffer Layer / Top electrode

The photoelectric conversion element material of the present invention can be used for, for example, an organic compound layer, a p layer, an n layer, an i layer, a mixed layer of p material and n material, and a buffer layer.
In the organic solar battery of the present invention, any member constituting the battery may contain the photoelectric conversion element material of the present invention. About the member or mixed material not including the photoelectric conversion element material of the present invention Well-known members used in solar cells can be used. Hereinafter, each component will be briefly described.

1. Lower electrode, upper electrode There is no particular limitation, and a known conductive material can be used. For example, a metal such as tin-doped indium oxide (ITO), gold (Au), osmium (Os), palladium (Pd) can be used as the electrode connected to the p layer, and silver as the electrode connected to the n layer. Metals such as (Ag), aluminum (Al), indium (In), calcium (Ca), platinum (Pt) lithium (Li) and the like, and binary metal systems such as Mg: Ag, Mg: In and Al: Li, Can use the electrode exemplified material connected to the P layer.
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. The transparent electrode is set using a known conductive material so that predetermined translucency is ensured by a method such as vapor deposition or sputtering. The light transmittance of the electrode on the light receiving surface is preferably 10% or more. A preferable configuration of the pair of electrode configurations is that one of the electrode portions includes a metal having a high work function and the other includes a metal having a low work function.

2. Organic compound layer A p-layer, a mixed layer of p-material and n-material, or an n-layer, and has a single-layer structure made of an organic substance. Specifically, lower electrode / single layer / upper electrode of compound of formula (1) above, lower electrode / compound of formula (1) and mixed layer / upper electrode of n layer material or p layer material described later / upper electrode, etc. The structure is mentioned.

3. p layer, n layer, i layer When the material of the present invention is used for the p layer, the n layer is not particularly limited, but a compound having a function as an electron acceptor is preferable. For example, if the organic _compound, fullerene derivatives such as _{C 60,} carbon nanotube, perylene derivatives, polycyclic quinone, quinacridone, the polymeric CN- poly (phenylene - vinylene), MEH-CN-PPV, -CN group or Mention may be made of materials of CF ₃ group-containing polymers, their -CF ₃ substituted polymers, poly (fluorene) derivatives. Among these, a material having high electron mobility is preferable. Furthermore, it is preferable that the electron affinity is smaller. Thus, a sufficient open-circuit voltage can be realized by combining materials having a small electron affinity as the n layer.

Moreover, if it is an inorganic compound, the inorganic semiconductor compound of an n-type characteristic can be mentioned. Specifically, doped semiconductors and compound semiconductors such as n-Si, GaAs, CdS, PbS, CdSe, InP, Nb ₂ O ₅ , WO ₃ , Fe ₂ O ₃ , titanium dioxide (TiO ₂ ), monoxide Examples include titanium oxide such as titanium (TiO) and dititanium trioxide (Ti ₂ O ₃ ), and conductive oxides such as zinc oxide (ZnO) and tin oxide (SnO ₂ ). You may use combining more than a seed. It is preferable to use titanium oxide, particularly titanium dioxide.

  When the material of the present invention is used for the n layer, the p layer is not particularly limited, but a compound having a function as a hole acceptor is preferable. For example, in the case of an organic compound, N, N′-bis (3-tolyl) -N, N′-diphenylbenzidine (mTPD), N, N′-dinaphthyl-N, N′-diphenylbenzidine (NPD), 4, Amine compounds represented by 4 ′, 4 ″ -tris (phenyl-3-tolylamino) triphenylamine (MTDATA), etc., phthalocyanine (Pc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), titanyl phthalocyanine (TiOPc) ), Phthalocyanines such as octaethylporphyrin (OEP), platinum octaethylporphyrin (PtOEP), zinc tetraphenylporphyrin (ZnTPP) and the like, and polymer compounds such as polyhexylthiophene (P3HT), Methoxyethylhexyloxyphe Vinylene (MEHPPV) main chain type conjugated polymers such as side chain type polymers such as represented by polyvinyl carbazole, and the like.

  When the material of the present invention is used as an i layer, the i layer may be formed by mixing with the p layer compound or the n layer compound, but the compound of the present invention can also be used alone as an i layer. In this case, any of the above exemplary compounds can be used for the p layer or the n layer.

4). Buffer layer In general, the total thickness of organic solar cells is often small, so 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 compound, the aromatic cyclic acid anhydride represented by NTCDA shown below etc. will be mentioned, and if it is a high molecular compound, poly (3,4-ethylenedioxy) thiophene: polystyrene sulfonate (PEDOT: PSS), polyaniline: camphorsulfonic acid (PANI: CSA), and other known conductive polymers.

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. The exciton blocking layer can be inserted on either the anode side or the cathode side, or both can be inserted simultaneously.
As a preferable material for the exciton blocking layer, for example, a well-known material for a hole barrier layer or a material for an electron barrier layer for use in an organic EL device can be used. A preferable material for the hole blocking layer is a compound having a sufficiently large ionization potential, and a preferable material for the electron blocking layer is a compound having a sufficiently small electron affinity. Specifically, bathocuproin (BCP), bathophenanthroline (BPhen), etc. are mentioned as a cathode side hole barrier layer material, Ir (ppz) ₃ etc. are mentioned as an anode side electron barrier layer material.

Furthermore, you may use the inorganic semiconductor compound illustrated as said n layer material for a buffer layer. As the p-type inorganic semiconductor compound, CdTe, p-Si, SiC, GaAs, WO ₃ or the like can be used.

5. Substrate The substrate preferably has mechanical and thermal strength and transparency. For example, there are a glass substrate and a transparent resin film. 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, Polyvinylidene fluoride, polyester, polycarbonate, polyurethane, polyimide, polyetherimide, polyimide, polypropylene, etc. It is.

The formation of each layer of the organic solar cell of the present invention is performed by a dry film formation method such as vacuum deposition, sputtering, plasma, ion plating, or a wet film formation method such as spin coating, dip coating, casting, roll coating, flow coating, and ink jet. Any of these methods can be applied.
The film thickness is not particularly limited, but must be set to an appropriate film thickness. 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. The normal film thickness is suitably in the range of 1 nm to 10 μm, but more preferably in the range of 5 nm to 0.2 μm.

  In the case of a dry film forming method, a known resistance heating method is preferable, and a film forming method by simultaneous vapor deposition from a plurality of evaporation sources is given as a preferable example for forming a mixed layer. More preferably, the substrate temperature is controlled during film formation.

  In the case of a wet film forming method, a material for forming each layer is dissolved or dispersed in an appropriate solvent to prepare a luminescent organic solution to form a thin film, and any solvent may be used. For example, halogenated hydrocarbon solvents such as dichloromethane, dichloroethane, chloroform, carbon tetrachloride, tetrachloroethane, trichloroethane, chlorobenzene, dichlorobenzene, chlorotoluene, ether solvents such as dibutyl ether, tetrahydrofuran, dioxane, anisole, methanol, Alcohol solvents such as ethanol, propanol, butanol, pentanol, hexanol, cyclohexanol, methyl cellosolve, ethyl cellosolve, ethylene glycol, hydrocarbon solvents such as benzene, toluene, xylene, ethylbenzene, hexane, octane, decane, tetralin, Examples include 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. In addition, the solvent which can be used is not limited to these.

In the present invention, in any organic thin film layer of the organic solar battery, an appropriate resin or additive may be used for improving the film formability and preventing 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-vinyl. Examples thereof include photoconductive resins such as carbazole and polysilane, and conductive resins such as polythiophene and polypyrrole.
Examples of the additive include an antioxidant, an ultraviolet absorber, and a plasticizer.

  Furthermore, in order to improve the stability of the organic solar cell with respect to temperature, humidity, atmosphere, etc., it is possible to provide a protective layer on the surface of the cell, or to protect the entire cell with silicon oil, resin or the like.

[Materials for photoelectric conversion elements]
Example 1
Compound (A) was synthesized by the reaction shown below.

Under Ar atmosphere, 5,5′-dibromo-2,2′-bithiophene (2.6 g, 8.0 mmol), 4-diphenylaminophenylboronic acid (5.1 g, 18 mmol, 2.2 eq.) And tetrakis (tri Phenylphosphine) palladium (0) (0.2 g, 0.2 mmol, 1% Pd) was dissolved in 1,2-dimethoxyethane (50 ml) and 2M aqueous sodium carbonate solution (5.9 g, 53 mmol, 3 eq / 27 ml) And refluxed for 8 hours.
The reaction mixture was filtered off and washed with methanol to give a yellow solid (2.6 g). The solid obtained by concentrating the filtrate was purified by column chromatography (silica gel / hexane + 25% dichloromethane, followed by dichloromethane only) to obtain an orange solid (3.5 g).

The obtained solids were combined and recrystallized from a mixed solvent of toluene (200 ml) and hexane (50 ml) to give brown needle-like crystals as compound (A) “5,5′-bis (4-diphenylaminophenyl)- 2,2′-bithiophene ”(4.2 g, 80%) was obtained.
The solid (2 g) thus obtained was purified by sublimation at 260 ° C. and 1.7 × 10 ⁻³ Pa for 8 hours to obtain a yellow solid (1.77 g).
The results of nuclear magnetic resonance measurement ( ¹ HNMR), electrolytic detachment mass spectrometry (FDMS), and liquid chromatography (HPLC) of this yellow solid are shown below.

¹ H-NMR (400 MHz, CDCl ₃ , TMS): 7.03-7.08 (8H, m), 7.12-7.13 (12H, m), 7.21-7.29 (8H, m), 7.46 (4H, d, J = 8 Hz)
FDMS: calculated value C ₄₄ H ₃₂ N ₂ S ₂ = 652
Actual value m / z = 652 (M ⁺ , 100)
HPLC: purity 99.6% (detection wavelength 254 nm: area%)

The physical properties are as follows.
Glass transition point (Tg): 83 ° C
Maximum absorption wavelength (λmax): 418 nm
Maximum fluorescence wavelength (PLmax): 495 nm (λex = 418 nm)
Ionization potential (Ip): 5.25 eV (500 nW, powder)
5.42 eV (10 nW, thin film)

Example 2
Compound (B) was synthesized by the reaction shown below.

Synthesis was performed in the same manner as in Example 1 except that 2,5-dibromothiophene was used instead of 5,5′-dibromo-2,2′-bithiophene, and compound (B) “2,5” was obtained as a yellow solid. -Bis (4-diphenylaminophenyl) thiophene "(3.2 g, 68%) was obtained. The analysis results are shown below.
FDMS: calculated value C ₄₀ H ₃₀ N ₂ S = 570
Actual measurement value m / z = 570 (M ⁺ , 100)
HPLC: purity 98.0% (detection wavelength 254 nm: area%)

[Production of organic solar cells]
Example 3
A glass substrate with an ITO transparent electrode having a thickness of 25 mm × 75 mm × 0.7 mm was subjected to ultrasonic cleaning in isopropyl alcohol for 5 minutes, and then UV ozone cleaning was performed for 30 minutes.
The glass substrate with the transparent electrode line after the cleaning is mounted on the substrate holder of the vacuum evaporation apparatus, and first, the transparent electrode is covered as a p layer on the surface where the transparent electrode line as the lower electrode is formed. The compound (A) having a film thickness of 30 nm was formed at 1 Å / s by resistance heating vapor deposition.
Subsequently, the following compound (N1: fullerene C ₆₀ ) having a film thickness of 60 nm was formed as an n layer on this compound (A) film by resistance heating vapor deposition at 1 Å / s. Furthermore, metal Ag was continuously deposited as an upper electrode to a film thickness of 100 nm to produce an organic solar cell. The area was 0.5 cm ² .

The IV characteristics of this organic solar cell were measured under the conditions of AM1.5 and Pin = 100 mW / cm ² . Table 1 shows open circuit voltage (Voc), short circuit current density (Jsc), fill factor (FF), and conversion efficiency (η), which are measurement results.

Example 4
An organic solar cell was prepared and evaluated in the same manner except that the compound (N1) of Example 3 was changed to the following compound (N2). The results are shown in Table 1.

Comparative Example 1
Instead of the compound (A), N, N′-bis (3-methylphenyl) -N. An organic thin-film solar cell was produced in the same manner as in Example 3 except that N′-diphenylbenzidine (the following mTPD) was used. This organic solar cell was measured for IV characteristics under the conditions of AM1.5 and Pin = 100 mW / cm ² . The results are shown in Table 1.

Comparative Example 2
An organic solar cell was prepared and evaluated in the same manner except that the compound (N1) of Comparative Example 1 was changed to the compound (N2). The results are shown in Table 1.

Example 5
In the production of the organic solar cell of Example 3, an organic thin film solar cell was similarly produced and evaluated except that the compound (A) was changed to the compound (B) synthesized in Example 2. The results are shown in Table 1.

Generally, the photoelectric conversion efficiency (η) of a solar cell is represented by the following formula.

In the equation, Voc is an open circuit voltage, Jsc is a short-circuit current density, FF is a fill factor, and Pin is incident light energy. Therefore, for the same Pin, a compound having a larger Voc, Jsc and FF shows better conversion efficiency.
As can be seen from Table 1, the material of the present invention has improved short-circuit current density and fill factor without lowering the open-circuit voltage as compared with the comparative example, resulting in improved conversion efficiency and excellent solar cell. It became clear to show the characteristics.

Evaluation Example The organic solar battery produced in Example 3 and Comparative Example 1 was irradiated with light having a wavelength of 334 nm. As a result, the photocurrent was observed. Moreover, the organic solar cell of Example 3 produced a photocurrent twice that of Comparative Example 1. From this result, it can be confirmed that the photoelectric conversion element of the present invention also functions against ultraviolet rays.

The material for a photoelectric conversion element of the present invention can be used as a material for forming a photoelectric conversion element such as a photodiode, an image sensor, or a solar cell. In particular, it can be suitably used for organic solar cells.
The photoelectric conversion element of the present invention can be used in various devices such as an optical sensor system, an imaging device (for example, an imaging unit such as a digital camera or a digital video), and a solar power generation device.

Claims (6)

The material for photoelectric conversion elements which contains the amine compound represented by following formula (1) individually or as a component of a mixture.

(Wherein X is oxygen, sulfur or selenium, Ar _{1 to} Ar ₄ are each independently a C _{6 to} C ₄₀ substituted or unsubstituted aryl group, C _{3 to} C ₄₀ substituted or unsubstituted hetero Each of R _{1 to} R ₁₀ independently represents hydrogen, halogen, a C _{1 to} C ₄₀ substituted or unsubstituted alkyl group, a C _{2 to} C ₄₀ substituted or unsubstituted alkenyl group, or C ₁ to R ₁₀ . C ₄₀ substituted or unsubstituted alkoxy group, C _{6 to} C ₄₀ substituted or unsubstituted aryloxy group, C _{1 to} C ₄₀ substituted or unsubstituted alkylthio group, C _{6 to} C ₄₀ substituted or unsubstituted aryl _group, a substituted or unsubstituted heteroaryl group _{C 3 ~C 40, R 1 ~R} 10 mAY bonded to each other to form a ring .n, p, q are each independently 1 to 6 of an integer.) X is sulfur, and R _{1 to} R ₁₀ are each independently hydrogen, halogen, a C _{1 to} C ₄₀ substituted or unsubstituted alkyl group, a C _{6 to} C ₄₀ substituted or unsubstituted aryl group, or The material for a photoelectric conversion element according to claim 1, which is a C _{3 to} C ₄₀ substituted or unsubstituted heteroaryl group.   The material for a photoelectric conversion element according to claim 1, which is an organic solar cell material.   A photoelectric conversion element comprising the photoelectric conversion element material according to claim 1.   The photoelectric conversion element according to claim 4, which is an organic solar battery.   The apparatus which has a photoelectric conversion element of Claim 4 or 5.