WO2013084835A1

WO2013084835A1 - Organic semiconductor material and organic electronic devices

Info

Publication number: WO2013084835A1
Application number: PCT/JP2012/081245
Authority: WO
Inventors: 真名軸丸
Original assignee: 新日鉄住金化学株式会社
Priority date: 2011-12-08
Filing date: 2012-12-03
Publication date: 2013-06-13
Also published as: TW201326177A; JPWO2013084835A1; TWI516490B; JP5978228B2

Abstract

Provided are: an organic semiconductor material that has a high charge mobility, solvent solubility, oxidation stability, and good film forming characteristics; and organic electronic devices, for example, organic semiconductor elements, that use said organic semiconductor material. The organic semiconductor material contains a compound having an indolocarbazole skeleton represented by general formula (1). Organic semiconductor films and organic electronic devices use the organic semiconductor material. Organic electronic devices provided with the organic semiconductor material as a thin film layer include light-emitting elements, organic thin-film transistor elements and photovoltaic elements.

Description

Organic semiconductor materials and organic electronic devices

The present invention relates to an organic semiconductor material, an organic semiconductor film, an organic electronic device, and an organic thin film transistor.

Generally, in a semiconductor device using silicon as an inorganic semiconductor material, a high temperature process and a high vacuum process are indispensable for forming a thin film. Since a high temperature process is required, silicon cannot be formed into a thin film on a plastic substrate or the like, and it has been difficult to impart flexibility and weight reduction to a product incorporating a semiconductor device. In addition, since a high vacuum process is required, it is difficult to increase the area and cost of a product incorporating a semiconductor device.

Therefore, in recent years, research on organic electronic devices (for example, organic electroluminescence (organic EL) elements, organic thin film transistor elements, or organic thin film photoelectric conversion elements) using organic semiconductor materials as organic electronic components has been conducted. Since these organic semiconductor materials can significantly reduce the manufacturing process temperature as compared with inorganic semiconductor materials, they can be formed on a plastic substrate or the like. Furthermore, by using an organic semiconductor material that is highly soluble in a solvent and has good film formability, it becomes possible to form a thin film using an application method that does not require a vacuum process, for example, an inkjet device, As a result, it is expected to realize an increase in area and cost, which has been difficult with a semiconductor element using silicon, which is an inorganic semiconductor material. As described above, organic semiconductor materials are advantageous in terms of large area, flexibility, weight reduction, cost reduction, and the like compared to inorganic semiconductor materials. Applications such as information tags, large-area sensors such as electronic artificial skin sheets and sheet-type scanners, displays such as liquid crystal displays, electronic paper, and organic EL panels are expected.

As described above, high charge mobility is required for an organic semiconductor material used in an organic electronic device expected to be widely used. For example, in organic transistor devices, since it directly affects the switching speed and the performance of the driven device, improvement of charge mobility is an essential issue for practical use. Further, as described above, solvent solubility, oxidation stability, and good film forming properties are required to enable the production of an organic semiconductor element by a coating method.

In particular, high charge mobility is a required characteristic for organic semiconductors. From this viewpoint, in recent years, organic semiconductor materials having charge transport properties comparable to amorphous silicon have been reported. For example, in organic field-effect transistor elements (OFETs) that use pentacene, a hydrocarbon-based acene-type polycyclic aromatic molecule in which five benzene rings are linearly condensed, as an organic semiconductor material, charge transfer is similar to that of amorphous silicon. Degrees have been reported (Non-Patent Document 1). In addition, a method of forming a pentacene crystal in a dilute solution of trichlorobenzene without using a vacuum deposition method has been proposed, but a manufacturing method is difficult and a stable element has not been obtained (Patent Document 1). A hydrocarbon-based acene-type polycyclic aromatic molecule such as pentacene also has a low oxidation stability.

In addition, pentathienoacene fused with a thiophene ring has improved oxidation resistance as compared with pentacene, but has low carrier mobility and requires many steps for its synthesis (Non-patent Document 2). It was not a preferable material.

In the early stages of development, organic thin-film solar cells constructed by laminating organic semiconductor materials into thin films have been studied with single-layer films using merocyanine dyes as organic semiconductor materials, but transport holes. Since it was found that a multi-layer film having a p-type organic semiconductor layer and an n-type organic semiconductor layer for transporting electrons improves the conversion efficiency from light input to electrical output (photoelectric conversion efficiency), Multilayer films are becoming mainstream. The organic semiconductor materials used when the multilayer film began to be studied were copper phthalocyanine (CuPc) as the p-type organic semiconductor material and peryleneimides (PTCBI) as the n-type organic semiconductor material. On the other hand, in an organic thin film solar cell using a polymer, a conductive polymer is used as a p-type organic semiconductor material, a fullerene (C60) derivative is used as an n-type organic semiconductor material, and they are mixed and heat-treated. Research on so-called bulk heterostructures, in which layer separation is induced to increase heterointerfaces and photoelectric conversion efficiency is improved, has been mainly conducted. The material system used here was mainly poly-3-hexylthiophene (P3HT) as the p-type organic semiconductor material and C60 derivative (PCBM) as the n-type organic semiconductor material.

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 C60 derivatives are still used, which is the most important characteristic of the organic thin film solar cell. The photoelectric conversion efficiency was not sufficient. In order to improve the photoelectric conversion efficiency, an organic semiconductor material having high charge mobility is required. In addition, as in the case of the organic thin film transistor described above, solvent solubility, oxidation stability, and good film forming properties are required in order to enable the production of an organic semiconductor element by a coating method.

Therefore, in order to increase the photoelectric conversion efficiency, development of new materials that replace these conventional materials is eagerly desired. For example, Patent Document 2 discloses an organic thin film solar cell using a compound having a fluoranthene skeleton, but does not give satisfactory photoelectric conversion efficiency.

WO2003 / 016599 JP2009-290091A

An object of the present invention is to provide an organic semiconductor material having high charge mobility and oxidation stability and an organic electronic device using the same.

As a result of intensive studies, the present inventors have found a new organic semiconductor material having high charge mobility, oxidation stability, and solvent solubility, and by using this for an organic electronic device, a high-performance organic electronic device can be obtained. As a result, the present invention was reached.

The present invention relates to an organic semiconductor material containing a compound represented by the following general formula (1).

In formula (1), each R independently represents hydrogen or an aliphatic hydrocarbon group having 1 to 30 carbon atoms, and n represents an integer of 1 to 4.

Examples of the compound represented by the general formula (1) include a compound represented by the general formula (2). Here, R is the same as the general formula (1).

Further, another embodiment of the present invention is an organic semiconductor film characterized by containing the organic semiconductor material described above. Furthermore, another embodiment of the present invention is an organic semiconductor film formed by applying and drying an organic solvent solution of the above organic semiconductor material.

Further, another embodiment of the present invention is an organic electronic device characterized by using the organic semiconductor material described above. The organic electronic device is preferably a light emitting element, an organic thin film transistor element, or a photovoltaic element, and more preferably an organic thin film transistor element.

The schematic cross section which showed an example of the organic thin-film transistor element is shown. The schematic cross section which showed an example of the organic thin-film transistor element is shown. The schematic cross section which showed an example of the organic thin-film transistor element is shown. The schematic cross section which showed an example of the organic thin-film transistor element is shown. The schematic cross section which showed one structural example of the photovoltaic device is shown. The schematic cross section which showed one structural example of the photovoltaic device is shown.

The organic semiconductor material of the present invention essentially requires the compound represented by the general formula (1). The organic semiconductor material of the present invention may consist only of the compound represented by the general formula (1) or may contain other compounds. As the other compound, an organic compound having a charge transfer property is suitable. Since the compound represented by the general formula (1) itself has characteristics as an organic semiconductor material, this compound is also an organic semiconductor material.

In general formula (1), each R independently represents hydrogen or an aliphatic hydrocarbon group having 1 to 30 carbon atoms, preferably hydrogen or an aliphatic hydrocarbon group having 1 to 16 carbon atoms. As the aliphatic hydrocarbon group, an alkyl group is preferable, and an unsubstituted alkyl group is more preferable. These aliphatic hydrocarbon groups may be linear, branched, or alicyclic, and may be saturated or unsaturated. Moreover, the hydrogen atom of these aliphatic hydrocarbon groups may be substituted with a halogen atom such as fluorine. Moreover, these aliphatic hydrocarbon groups may have a substituent, and when it has one or more substituents, the number of carbons of these substituents is included in the calculation of the number of carbons. A plurality of R may be the same or different. In the general formula (1), there are a maximum of 16 Rs, of which 8 or more are preferably H, more preferably 14 to 16 are H.

Specific examples of preferred aliphatic hydrocarbon groups include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-octyl group, n-dodecyl group, n- Linear saturated hydrocarbon group such as tetradecyl group, n-octadecyl group, n-docosyl group, n-tetracosyl group, i-propyl group, isobutyl group, t-butyl group, neopentyl group, 2-ethylhexyl group, 2-hexyl Branched saturated hydrocarbon groups such as octyl group, 4-decyldodecyl group, ethenyl group, 1-propenyl group, 2-propenyl group, i-propenyl group, 1-butenyl group, 2-butenyl group, 3-butenyl group, ethynyl Group, 1-propynyl group, 2-propynyl group, 1-butynyl group, 2-butynyl group, 3-butynyl group and other unsaturated hydrocarbon groups, cyclopentyl group, cyclohexyl group, cyclooctyl group, 4-butynyl Cyclohexyl, 4-dodecyl saturated alicyclic hydrocarbon groups such as a cyclohexyl group, a cyclopentenyl group, cyclopentadienyl group, can be exemplified unsaturated alicyclic hydrocarbon groups such as a cyclohexenyl group. More preferably, a C1-16 alkyl group, a C2-8 alkenyl group, a C2-8 alkynyl group, a C5-8 cycloalkyl group, a C5-8 cycloalkyl group substituted by a C1-16 alkyl group, Or a C5-8 unsaturated alicyclic hydrocarbon group.

Examples of the aliphatic hydrocarbon group in which the aliphatic hydrocarbon group is substituted with a halogen atom include perfluorinated alkyl groups such as trifluoromethyl group, pentafluoroethyl group, perfluorobutyl group, perfluorooctyl group, and difluoroethyl group. Examples thereof include partially fluorinated alkyl groups such as a group, a difluorobutyl group, and a difluorooctyl group.

When R is an aliphatic hydrocarbon group and the aliphatic hydrocarbon group has a substituent, the substituent is not limited as long as the performance of the organic semiconductor material is not impaired, but the total number of substituents is 1 to 4 Preferably, it is 1 to 2. These preferred substituents include an alkoxy group having 1 to 20 carbon atoms, an alkylthio group having 1 to 20 carbon atoms, an alkoxycarbonyl group having 2 to 10 carbon atoms, an alkoxycarbonyloxy group having 2 to 10 carbon atoms, and 2 carbon atoms. An acyloxy group having 1 to 10 carbon atoms, an alkylsulfonyl group having 1 to 10 carbon atoms, an alkylamide group having 2 to 10 carbon atoms, a trialkylsilyl group having 3 to 20 carbon atoms, a trialkylsilylalkenyl group having 5 to 20 carbon atoms, carbon Examples thereof include a trialkylsilylalkynyl group having a number of 5 to 20. These substituents may have one kind or two or more kinds. More preferable examples include an alkoxy group having 1 to 12 carbon atoms, an alkylthio group having 1 to 12 carbon atoms, an alkoxycarbonyl group having 2 to 8 carbon atoms, and an alkoxycarbonyloxy group having 2 to 8 carbon atoms. Specific examples include Methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-hexyloxy group, methylthio group, ethylthio group, methoxycarbonyl group, ethoxycarbonyl group, methoxycarbonyloxy group, ethoxycarbonyloxy group, triisopropylsilylethynyl Group, triethylsilylethynyl group, trimethylsilylethynyl group and the like. When it has two or more substituents, they may be the same or different.

Among the compounds represented by the general formula (1), there is a compound represented by the general formula (2) as a preferable compound. In general formula (2), R has the same meaning as in general formula (1). Although there are 8 R, 4 or more of them are preferably H, more preferably 6 to 8 are H.

The compound represented by the general formula (1) can be synthesized by the following reaction formula (A) with reference to the synthesis example shown in New Journal of Chemistry, 34 (7), p1243-1246 (2010). However, it is not limited to these methods.

The above formula (A) is a synthesis example of the compound (100) in the case where all the Rs are H in the compound represented by the general formula (1). By reacting indole and 2-chlorobenzaldehyde, the intermediate A -1 is obtained through a two-stage cyclization reaction.

In the compound represented by the general formula (1), synthesis examples in the case where the benzene rings at both ends have an alkyl group as the substituent R can be synthesized by the reaction formula shown in the formula (B), but are limited to these methods. Not what you want.
As shown in the formula (B), after obtaining an intermediate B-3 by a method using n-bromoindole and 2-chloro-n-bromobenzaldehyde, a Sonogashira reaction between B-3 and an alkyne derivative is performed. Compound (3) which is a desired alkyl-substituted product can be obtained.

It is also possible to obtain a desired compound by performing a reaction using a raw material having a substituent R in the general formula (1) as in the following two reaction formulas. In the case of reaction formula (C), compound C-3 having a desired alkyl group can be obtained by reacting an alkyl-substituted indole with 2-chlorobenzaldehyde. According to reaction formula (D), compound C-3 can also be obtained by reacting indole and 2-chlorobenzaldehyde having an alkyl group.

That is, by using indole having a desired substituent and 2-chlorobenzaldehyde as raw materials, and performing a cyclization reaction and a substitution reaction as in reaction formula (B), (C) or (D), the desired general formula The compound represented by (1) can be obtained. The same can be achieved by using 2-bromobenzaldehyde or 2-iodobenzaldehyde instead of 2-chlorobenzaldehyde.

Evaluation of charge mobility, which is a basic characteristic of the organic semiconductor material of the present invention containing a compound obtained by such a method, can be performed by various methods such as TOF (Time of Flight) method or FET method. The TOF method is a method for obtaining the charge mobility by irradiating the surface of the organic semiconductor material thin film with an electric field and measuring the movement time of the generated charge in the film from the transient photocurrent waveform. . The FET method is a method of creating an organic field effect transistor element using an organic semiconductor material and evaluating its characteristics. By these methods, charge mobility can be evaluated as a basic characteristic of the organic semiconductor material of the present invention, and any method exhibits high characteristics.

Specific examples of the compound represented by the general formula (1) are shown below, but are not limited thereto.

The organic semiconductor material of the present invention contains the compound of the general formula (1), but preferably contains 50 wt% or more, more preferably 90 wt% or more of this compound. It is also preferable that the compound of the general formula (1) itself is an organic semiconductor material. The component contained in the organic semiconductor material together with the compound of the general formula (1) is not particularly limited as long as it does not impair the performance as the organic semiconductor material, but is preferably a charge transporting compound. .

Subsequently, an organic electronic device formed from the organic semiconductor material of the present invention will be described with reference to FIGS. 1 to 4, taking an organic thin film transistor element (OTFT element) as an example. The organic electronic device is preferably an organic semiconductor device using an organic semiconductor material.

1, FIG. 2, FIG. 3 and FIG. 4 are schematic cross-sectional views illustrating embodiments of the OTFT device of the present invention.
Explanation of symbols;
1 substrate, 2 gate electrode, 3 insulating film layer, 4 organic semiconductor layer, 5 source electrode, 6 drain electrode, 7 substrate, 8 positive electrode, 9 organic semiconductor layer, 9-a electron donating organic semiconductor layer, 9-b electron Receptive organic semiconductor layer, 10 negative electrode.

The OTFT device shown in FIG. 1 includes a gate electrode 2 on the surface of a substrate 1, an insulating film layer 3 is formed on the gate electrode 2, and a source electrode 5 and a drain electrode 6 are formed on the insulating film layer 3. And an organic semiconductor layer 4 is formed.

The OTFT device shown in FIG. 2 includes a gate electrode 2 on the surface of a substrate 1, an insulating film layer 3 is formed on the gate electrode 2, and an organic semiconductor layer 4 is formed thereon. On 4, a source electrode 5 and a drain electrode 6 are provided.

In the OTFT device shown in FIG. 3, a source electrode 5 and a drain electrode 6 are provided on the surface of a substrate 1, and a gate electrode 2 is formed on the outermost surface via an organic semiconductor layer 4 and an insulating film layer 3.

In the OTFT device shown in FIG. 4, an organic semiconductor layer 4, a source electrode 5 and a drain electrode 6 are provided on the surface of a substrate 1, and a gate electrode 2 is formed on the outermost surface via an insulating film layer 3.

Examples of the substrate 1 that can be used include ceramic substrates such as glass, quartz, aluminum oxide, sapphire, silicon nitride, and silicon carbide, semiconductor substrates such as silicon, germanium, gallium silicon, gallium phosphorus, and gallium nitrogen, polyethylene terephthalate, Examples thereof include polyesters such as polynaphthalene terephthalate, resin substrates such as polyethylene, polypropylene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, cyclic polyolefin, polyimide, polyamide, and polystyrene. The thickness of the substrate can be from about 10 μm to about 2 mm, but in particular about 50 to about 100 μm for flexible plastic substrates, for example about 0.1 to about 0.1 to about rigid substrates such as glass plates or silicon wafers. It can be about 2 mm.

The gate electrode 2 may be a metal thin film, a conductive polymer film, a conductive film made from a conductive ink or paste, or the substrate itself as a gate electrode, such as heavily doped silicon. can do. Examples of gate electrode materials include aluminum, copper, stainless steel, gold, chromium, n-doped or p-doped silicon, indium tin oxide, conductive polymers such as poly (3,4-polystyrene) doped with polystyrene sulfonic acid. Examples thereof include a conductive ink / paste containing ethylenedioxythiophene), carbon black / graphite, or a colloidal silver dispersed in a polymer binder.

The gate electrode 2 can be formed by using vacuum deposition, sputtering of a metal or conductive metal oxide, spin coating of a conductive polymer solution or conductive ink, inkjet, spraying, coating, casting, or the like. The thickness of the gate electrode 2 is preferably in the range of about 10 nm to 10 μm, for example.

The insulating film layer 3 can generally be an inorganic material film or an organic polymer film. Examples of inorganic materials suitable for the insulating film layer 3 include silicon oxide, silicon nitride, aluminum oxide, barium titanate, and barium zirconium titanate. Examples of organic compounds suitable for the insulating film layer 3 include polyesters, polycarbonates, poly (vinylphenol), polyimides, polystyrene, poly (methacrylates), poly (acrylates), and epoxy resins. Further, an inorganic material may be dispersed in an organic polymer and used as an insulating layer film. The thickness of the insulating film layer varies depending on the dielectric constant of the insulating material used, but is, for example, about 10 nm to 10 μm.

Examples of the means for forming the insulating film layer include dry film formation methods such as vacuum deposition, CVD, sputtering, and laser deposition, spin coating, blade coating, screen printing, ink jet printing, and stamping. Examples include a wet film forming method such as a method, which can be used depending on the material.

The source electrode 5 and the drain electrode 6 can be made of a material that gives low resistance ohmic contact to the organic semiconductor layer 4 described later. As a preferable material for the source electrode 5 and the drain electrode 6, those exemplified as a preferable material for the gate electrode 2 can be used, and examples thereof include gold, nickel, aluminum, platinum, a conductive polymer, and a conductive ink. The thicknesses of the source electrode 5 and the drain electrode 6 are typically, for example, from about 10 nm to about 10 μm, and more preferably from 10 nm to 1 μm.

Examples of means for forming the source electrode 5 and the drain electrode 6 include a vacuum deposition method, a sputtering method, a coating method, a thermal transfer method, a printing method, and a sol-gel method. It is preferable to perform patterning as needed during film formation or after film formation. As a patterning method, for example, a photolithography method in which patterning and etching of a photoresist are combined can be used. Patterning can also be performed by using a technique combining a plurality of these techniques such as inkjet printing, screen printing, offset printing, soft lithography such as microcontact printing.

As a means for forming the organic semiconductor layer 4, for example, a dry film forming method such as a vacuum deposition method, a CVD method, a sputtering method, or a laser deposition method, or after applying a solution or dispersion on a substrate, a solvent or dispersion medium There is a wet film formation method in which a thin film is formed by removing the film, but it is preferable to use a wet film formation method. Examples of the wet film formation method include spin coating, blade coating, screen printing, ink jet printing, and stamping. For example, when the spin coating method is used, the organic semiconductor material of the present invention is dissolved in an appropriate solvent to prepare a solution having a concentration of 0.01 wt% to 10 wt%, and then the insulating film layer 3 formed on the substrate 1. The organic semiconductor material solution is dropped onto the solution, and then rotated at 500 to 6000 rpm for 5 to 120 seconds. The solvent is selected depending on the solubility of the organic semiconductor material and the film quality obtained by film formation. For example, water, alcohols typified by methanol, aromatic hydrocarbons typified by toluene, hexane and cyclohexane Aliphatic hydrocarbons such as nitromethane and nitrobenzene, cyclic ether compounds such as tetrahydrofuran and dioxane, nitrile compounds such as acetonitrile and benzonitrile, ketones such as acetone and methyl ethyl ketone, ethyl acetate, etc. And a solvent selected from aprotic polar solvents such as dimethyl sulfoxide, dimethylacetamide, sulfolane, N-methylpyrrolidone and dimethylimidazolidinone. These solvents may be used in combination of two or more.

The organic thin film transistor element using the organic semiconductor material of the present invention can be prepared by the above-described method. In the obtained organic thin film transistor element, the organic semiconductor layer forms a channel region, and an on / off operation is performed by controlling a current flowing between the source electrode and the drain electrode with a voltage applied to the gate electrode.

As another preferred embodiment of the organic electronic device obtained from the organic semiconductor material of the present invention, a photovoltaic element can be mentioned. Specifically, it is a photovoltaic device having a positive electrode, an organic semiconductor layer, and a negative electrode on a substrate, and the organic semiconductor device includes the organic semiconductor material of the present invention described above.

構造 The structure of the photovoltaic element of the present invention will be described with reference to the drawings, but the structure of the photovoltaic element of the present invention is not limited to that shown in the drawings.

FIG. 5 is a cross-sectional view showing an example of the structure of a general photovoltaic device used in the present invention, wherein 7 represents a substrate, 8 represents a positive electrode, 9 represents an organic semiconductor layer, and 10 represents a negative electrode. FIG. 6 is a cross-sectional view showing an example of a structure in which organic semiconductor layers are stacked, where 9-a is a p-type organic semiconductor layer and 9-b is an n-type organic semiconductor layer.

The saddle substrate is not particularly limited, and may be a conventionally known configuration, for example. It is preferable to use a glass substrate or a transparent resin film having mechanical and thermal strength and transparency. 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.

As the electrode material, it is preferable to use a conductive material having a high work function for one electrode and a conductive material having a low work function for the other electrode. An electrode using a conductive material having a large work function is a positive electrode. Conductive materials with a large work function include metals such as gold, platinum, chromium and nickel, transparent metal oxides such as indium and tin, composite metal oxides (indium tin oxide (ITO), indium Zinc oxide (IZO) or the like is preferably used. Here, the conductive material used for the positive electrode is preferably an ohmic junction with the organic semiconductor layer. Furthermore, when a hole transport layer described later is used, it is preferable that the conductive material used for the positive electrode is an ohmic contact with the hole transport layer.

An electrode using a conductive material having a small work function serves as a negative electrode. As the conductive material having a small work function, alkali metal or alkaline earth metal, specifically, lithium, magnesium, or calcium is used. Tin, silver, and aluminum are also preferably used. Furthermore, an electrode made of an alloy made of the above metal or a laminate of the above metal is also preferably used. In addition, it is possible to improve the extraction current by introducing a metal fluoride such as lithium fluoride or cesium fluoride at the interface between the negative electrode and the electron transport layer. Here, the conductive material used for the negative electrode is preferably one that is in ohmic contact with the organic semiconductor layer. Furthermore, when an electron transport layer described later is used, it is preferable that the conductive material used for the negative electrode is in ohmic contact with the electron transport layer.

-Organic semiconductor layer-
The organic semiconductor layer is formed using an organic semiconductor material containing a compound represented by the formula (1). The compound represented by the formula (1) functions as a p-type organic semiconductor material (hereinafter referred to as a p-type organic material) or an n-type organic semiconductor material (hereinafter referred to as an n-type organic material). The compound represented by formula (1) is included in at least one of the p-type organic material and the n-type organic material. Two or more compounds represented by formula (1) may be used, one or more of which may be a p-type organic material component and the other one or more may be an n-type organic material component. A compound represented by formula (1) may be used as the organic material component), and a compound other than the compound represented by formula (1) may be used as the n-type organic material component (or p-type organic material component). .

It is preferable that the p-type organic material and the n-type organic material are mixed, and it is preferable that the p-type organic material and the n-type organic material are compatible at the molecular level or phase-separated. The domain size of this phase separation structure is not particularly limited, but is usually 1 nm or more and 50 nm or less. In the case where a p-type organic material and an n-type organic material are stacked, a layer having a p-type organic material exhibiting p-type semiconductor characteristics is on the positive electrode side, and a layer having an n-type organic material exhibiting n-type semiconductor characteristics is provided. The negative electrode side is preferred. The organic semiconductor layer preferably has a thickness of 5 nm to 500 nm, more preferably 30 nm to 300 nm. When stacked, the layer having the p-type organic material of the present invention preferably has a thickness of 1 nm to 400 nm, more preferably 15 nm to 150 nm, out of the above thicknesses.

As the p-type organic material, a compound exhibiting p-type semiconductor characteristics among the compounds represented by the formula (1) may be used alone, or other p-type organic materials may be included. Examples of other p-type organic materials include polythiophene polymers, benzothiadiazole-thiophene derivatives, benzothiadiazole-thiophene copolymers, poly-p-phenylene vinylene polymers, poly-p-phenylene polymers, Conjugated polymers such as polyfluorene polymers, polypyrrole polymers, polyaniline polymers, polyacetylene polymers, polythienylene vinylene polymers, H2 phthalocyanine (H2Pc), copper phthalocyanine (CuPc), zinc phthalocyanine Phthalocyanine derivatives such as (ZnPc), porphyrin derivatives, N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine (TPD), N, N′-dinaphthyl-N, N′-diphenyl-4,4′-diphenyl-1,1 Triarylamine derivatives such as' -diamine (NPD), carbazole derivatives such as 4,4'-di (carbazol-9-yl) biphenyl (CBP), oligothiophene derivatives (terthiophene, quarterthiophene, sexithiophene, octi Low molecular organic compounds such as thiophene).

As the n-type organic material, a compound exhibiting n-type semiconductor characteristics among the compounds represented by the formula (1) may be used alone, or another n-type organic material may be used. Other n-type organic materials include, for example, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), 3,4, 9,10-perylenetetracarboxylic bisbenzimidazole (PTCBI), N, N′-dioctyl-3,4,9,10-naphthyltetracarboxydiimide (PTCDI-C8H), 2- (4-biphenylyl) -5 Oxazole derivatives such as (4-t-butylphenyl) -1,3,4-oxadiazole (PBD), 2,5-di (1-naphthyl) -1,3,4-oxadiazole (BND), 3- (4-Biphenylyl) -4-phenyl-5- (4-tert-butylphenyl) -1,2,4-triazole (T AZ) and other triazole derivatives, phenanthroline derivatives, phosphine oxide derivatives, fullerene compounds (unsubstituted ones such as C60, C70, C76, C78, C82, C84, C90, C94, and [6,6] -phenyl C61 Butyric acid methyl ester ([6,6] -PCBM), [5,6] -phenyl C61 butyric acid methyl ester ([5,6] -PCBM), [6,6] -phenyl C61 butyric acid hexyl Ester ([6,6] -PCBH), [6,6] -phenyl C61 butyric acid dodecyl ester ([6,6] -PCBD), phenyl C71 butyric acid methyl ester (PC70BM), phenyl C85 butyric acid Methyl ester (PC8 BM), etc.), carbon nanotubes (CNT), poly -p- phenylene vinylene-based polymer derivatives obtained by introducing cyano group into (CN-PPV) and the like.

In the photovoltaic device of the present invention, a hole transport layer may be provided between the positive electrode and the organic semiconductor layer. As the material for forming the hole transport layer, conductive polymers such as polythiophene polymers, poly-p-phenylene vinylene polymers, polyfluorene polymers, phthalocyanine derivatives (H2Pc, CuPc, ZnPc, etc.), Low molecular organic compounds exhibiting p-type semiconductor properties such as porphyrin derivatives are preferably used. In particular, polyethylenedioxythiophene (PEDOT), which is a polythiophene polymer, or PEDOT to which polystyrene sulfonate (PSS) is added is preferably used. The thickness of the hole transport layer is preferably 5 nm to 600 nm, more preferably 30 nm to 200 nm.

In the photovoltaic device of the present invention, an electron transport layer may be provided between the organic semiconductor layer and the negative electrode. The material for forming the electron transport layer is not particularly limited, but the above-described n-type organic materials (NTCDA, PTCDA, PTCDI-C8H, oxazole derivatives, triazole derivatives, phenanthroline derivatives, phosphine oxide derivatives, fullerene compounds, CNTs) An organic material exhibiting n-type semiconductor characteristics such as CN-PPV) is preferably used. The thickness of the electron transport layer is preferably 5 nm to 600 nm, more preferably 30 nm to 200 nm.

In addition, in the photovoltaic device of the present invention, two or more organic semiconductor layers may be stacked (tandemized) via one or more intermediate electrodes to form a series junction. For example, a laminated structure of substrate / positive electrode / first organic semiconductor layer / intermediate electrode / second organic semiconductor layer / negative electrode can be given. By laminating in this way, the open circuit voltage can be improved. Note that the hole transport layer described above may be provided between the positive electrode and the first organic semiconductor layer and between the intermediate electrode and the second organic semiconductor layer, and between the first organic semiconductor layer and the intermediate electrode. The hole transport layer described above may be provided between the second organic semiconductor layer and the negative electrode.

In the case of such a laminated structure, at least one of the organic semiconductor layers includes the organic semiconductor material of the present invention as a p-type organic material, and the other layers include the p-type organic material so as not to reduce a short-circuit current. Preferably contains p-type organic materials having different band gaps. Examples of such p-type organic materials include the polythiophene polymers, poly-p-phenylene vinylene polymers, poly-p-phenylene polymers, polyfluorene polymers, polypyrrole polymers, polyaniline polymers described above. Conjugated polymers such as polymers, polyacetylene polymers, polythienylene vinylene polymers, phthalocyanine derivatives such as H2 phthalocyanine (H2Pc), copper phthalocyanine (CuPc), zinc phthalocyanine (ZnPc), porphyrin derivatives, N, N′-diphenyl-N, N′-di (3-methylphenyl) -4,4′-diphenyl-1,1′-diamine (TPD), N, N′-dinaphthyl-N, N′-diphenyl-4 Triarylamine derivatives such as 4,4′-diphenyl-1,1′-diamine (NPD), 4,4′-di (carbazo Carbazole derivatives such as Le-9-yl) biphenyl (CBP), oligothiophene derivatives (terthiophene, quarter thiophene, sexithiophene, etc. oct thiophene) include low molecular weight organic compounds, such as.

In addition, the material for the intermediate electrode used here is preferably a material having high conductivity, for example, the above-mentioned metals such as gold, platinum, chromium, nickel, lithium, magnesium, calcium, tin, silver, aluminum, and transparent Metal oxides such as indium and tin, composite metal oxides (indium tin oxide (ITO), indium zinc oxide (IZO), etc.), alloys composed of the above metals and laminates of the above metals, polyethylene Examples include dioxythiophene (PEDOT) and those obtained by adding polystyrene sulfonate (PSS) to PEDOT. The intermediate electrode preferably has a light transmission property, but even a material such as a metal having a low light transmission property can often ensure a sufficient light transmission property by reducing the film thickness.

For organic semiconductor layer formation, spin coating, blade coating, slit die coating, screen printing coating, bar coater coating, mold coating, printing transfer method, dip pulling method, ink jet method, spray method, vacuum deposition method, etc. This method may be used, and the formation method may be selected according to the characteristics of the organic semiconductor layer to be obtained, such as film thickness control and orientation control.

The organic semiconductor material of the present invention has high charge mobility, solvent solubility, oxidation stability, and good film forming properties, and an organic electronic device using the material exhibits high characteristics. As specific organic electronic devices that can make use of the characteristics of the organic semiconductor material of the present invention, for example, organic field effect transistors and organic thin-film solar cells can be shown. Furthermore, by incorporating these organic electronic devices, information can be obtained. It can be applied to displays such as tags, large-area sensors such as electronic artificial skin sheets and sheet-type scanners, liquid crystal displays, electronic paper, and organic EL panels.

Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is of course not limited to these examples, and can be implemented in various forms as long as the gist thereof is not exceeded. is there. The compound number corresponds to the number given to the above chemical formula.

Synthesis example 1
Compound (100) was synthesized according to the above formula (A).

Indole (100 g, 848 mmol), 2-chlorobenzaldehyde (60 g, 424 mmol), and 1.2 L of methanol were added to a 2000 mL three-necked flask equipped with a reflux tube and a mechanical stirrer, and the mixture was stirred at 80 ° C. for 22 hours. After cooling to room temperature, the solvent was distilled off. The obtained residue was purified by silica gel column chromatography to obtain 85 g (A-1, 237 mmol, yield 56) of white solid 3-[(2-chlorophenyl) (1H-indolyl) methyl] -1H-indole. %).
¹ H-NMR (DMSO-d ₆ ): δ 7.65 (s, 2H), 6.80-7.30 (m, 12H), 6.42 (s, 2H), 6.17 (s, 1H)

Intermediate (A-1) 80 g (223 mmol), iodine 2.23 g (8.92 mmol) and acetonitrile 360 mL were added to a 500 mL three-necked flask equipped with a reflux tube, and the mixture was heated to reflux for 7 hours. After cooling to room temperature, filtration was performed, and white solid 6,12-bis (2-chlorophenyl) -5,11-dihydroindolo [3,2-b] carbazole 17 g (A-2, 36 mmol, Yield 16%) was obtained. ¹ H-NMR (DMSO-d ₆ ): δ 10.81 (s, 2H), 6.77-7.28 (m, 16H)

In a 500 mL three-necked flask equipped with a reflux tube under a nitrogen atmosphere, intermediate (A-2) 15 g (31 mmol), dehydrated DMF 310 mL, 38% tetrabutylammonium hydroxide methanol solution (0.15 g, 0.23 mmol), Copper iodide was added and stirred at 120 ° C. After cooling to room temperature, the solvent was distilled off. The obtained residue was purified by silica gel column chromatography to obtain dibenzo [2, 3: 5,6] pyrrolidino [1,7-bc] indolo [1,2,3-lm] carbazole 1.1 as a pale green solid. g (2.72 mmol, yield 8.8%) was obtained. This is compound (100). ¹ H-NMR (DMSO-d ₆ ): δ 7.80 (d, 4H), 7.33 (d, 4H), 6.93 (t, 4H), 6.78 (t, 4H)

Example 1
A compound (100) synthesized in Synthesis Example 1 is deposited on a 150 nm thick ITO substrate by vacuum deposition to form an organic semiconductor film having a thickness of about 2.5 mm, and then silver is deposited by vacuum deposition. A 170 nm deposited film was formed. The charge mobility of the obtained device was evaluated by the TOF method. As a result, the hole mobility was 2.6 × 10 ⁻² cm ² / Vs at an electric field strength of 53.6 MV / cm.

Example 2
The characteristics of the organic semiconductor material of the present invention were evaluated by preparing an organic field effect transistor having the configuration shown in FIG. First, a silicon wafer (n-doped) having a thermally grown silicon oxide layer having a thickness of about 300 nm was washed with a sulfuric acid-hydrogen peroxide aqueous solution, boiled with isopropyl alcohol, and then dried. The obtained silicon wafer was spin-coated with a photoresist, and then exposed with an exposure machine through a photomask. Subsequently, after developing with a developing solution, it wash | cleaned with ion-exchange water and air-dried. On the silicon wafer coated with the patterned photoresist, chromium having a thickness of 3 nm and further gold having a thickness of 50 nm were deposited by vacuum deposition. The silicon wafer was immersed in a remover solution to produce a source electrode and a drain electrode on the silicon wafer. The silicon wafer on which the source electrode and the drain electrode were formed was washed with acetone, then boiled with isopropyl alcohol and dried to produce an organic field effect transistor substrate. The channel length was L = 25 μm and the channel width was W = 15.6 cm.
Next, the compound (100) obtained in Example 1 was deposited by vacuum deposition to form an organic semiconductor film having a thickness of 50 nm on the substrate. In this way, an organic field effect transistor having the structure shown in FIG. 1 was obtained. When the characteristic of the obtained organic field effect transistor was evaluated, it was mobility; 2.0 * 10 < ^-1 > cm < ² > / Vs.

Comparative Example 1
In Example 2, instead of the compound (100), pentacene was used and the same operation was performed to produce an organic field effect transistor element. When the obtained device was evaluated in the same manner as in Example 2, the mobility was 1.0 × 10 ⁻¹ cm ² / Vs.

As described above, comparing Example 2 and Comparative Example 1 revealed that the structure represented by Formula (1) has high characteristics as an organic semiconductor.

Industrial applicability

Since the compound represented by the general formula (1) has a conjugated structure extending over the entire molecular structure, the electron orbital also extends over the entire molecular structure. Moreover, since the three-dimensional structure has a characteristic of having high planarity, packing between molecules becomes dense, and as a result, the organic semiconductor material of the present invention containing the compound represented by the general formula (1) It has high charge transfer characteristics. Organic semiconductor devices using this organic semiconductor material include, for example, organic field effect transistors, organic thin film solar cells, information tags, large-area sensors such as electronic artificial skin sheets and sheet-type scanners, liquid crystal displays, electronic paper, and organic EL A display such as a panel can be considered, and its technical value is great.

Claims

An organic semiconductor material comprising a compound represented by the following general formula (1):

In formula (1), each R independently represents hydrogen or an aliphatic hydrocarbon group having 1 to 30 carbon atoms, and n represents an integer of 1 to 4.
The organic semiconductor material according to claim 1, wherein the compound represented by the general formula (1) is a compound represented by the following general formula (2).

In formula (2), each R independently represents hydrogen or an aliphatic hydrocarbon group having 1 to 30 carbon atoms.
An organic semiconductor film formed from the organic semiconductor material according to claim 1 or 2.
An organic semiconductor film formed by applying and drying an organic solvent solution of the organic semiconductor material according to claim 1 or 2.
An organic electronic device using the organic semiconductor material according to claim 1 or 2.
The organic electronic device according to claim 5, wherein the organic electronic device is a light emitting element, an organic thin film transistor element, or a photovoltaic element.
The organic electronic device according to claim 5, wherein the organic electronic device is either an organic thin film transistor element or a photovoltaic element.
The organic electronic device according to claim 5, wherein the organic electronic device is an organic thin film transistor element.