JP2015029020A - Liquid solution for organic semiconductor layer formation, organic semiconductor layer, and organic thin film transistor - Google Patents

Abstract

A solution for forming an organic semiconductor layer having excellent coatability and an organic thin film transistor having excellent semiconductor and electrical properties are provided. (A) the following general formula (1) (wherein the substituents R1 and R2 may be the same or different and represent an alkyl group having 3 to 9 carbon atoms, T1 to T4; may be the same or different and represent an oxygen atom or a sulfur atom.), (B) a surfactant, and an organic semiconductor containing an organic solvent having a boiling point of 140° C. or higher at normal pressure. The layer-forming solution has excellent coatability, and the resulting organic semiconductor layer can exhibit high semiconductor and electrical properties. [Selection figure] None

Description

  Organic semiconductor devices typified by organic thin film transistors have attracted attention in recent years because they have features not found in inorganic semiconductor devices such as energy saving, low cost, and flexibility. This organic semiconductor device is composed of several kinds of materials such as an organic semiconductor layer, a substrate, an insulating layer, and an electrode. Among them, the organic semiconductor layer responsible for charge carrier movement has a central role of the device. And since organic-semiconductor device performance is influenced by the carrier mobility of the organic material which comprises this organic-semiconductor layer, the appearance of the organic material which gives a high carrier mobility is desired.

  As a method for producing an organic semiconductor layer, generally known are a vacuum deposition method in which an organic material is vaporized under a high temperature vacuum, and a coating method in which an organic material is dissolved in an appropriate solvent and applied. It has been. Since the coating can be carried out using printing technology without using high-temperature and high-vacuum conditions, it is considered to be an economically preferable process, and an organic semiconductor layer having high coating properties and excellent carrier mobility. It is desired.

  An organic thin film transistor manufactured by a wet process using an organic semiconductor material having a dithienobenzodithiophene skeleton as a coating type organic semiconductor layer is disclosed (Patent Document 1). Moreover, in order to provide a coating type organic semiconductor layer with high carrier transportability, an organic semiconductor composition in which a low molecular weight compound and a polymer compound having carrier transportability are combined is disclosed (Patent Document 2).

JP 2012-209329 A JP 2009-267372 A

  An object of the present invention is to provide a solution for forming an organic semiconductor layer having excellent coating properties, an organic semiconductor layer using the same, and an organic thin film transistor having high semiconductor / electrical properties.

  As a result of intensive studies to solve the above problems, the present inventors have found that an organic semiconductor layer forming solution using a specific component has excellent coating properties, and further uses the obtained organic semiconductor layer. The present inventors have found that an organic thin film transistor has excellent semiconductor / electrical properties and have completed the present invention.

  That is, the present invention provides (A) the following general formula (1)

(Wherein, the substituents R ¹ and R ² may be the same or different and each represents an alkyl group having 3 to 9 carbon atoms, and T ^{1 to} T ⁴ may be the same or different, and each represents an oxygen atom. Or a sulfur atom.)
And (B) a solution for forming an organic semiconductor layer containing a surfactant and an organic solvent, an organic semiconductor layer formed using the organic semiconductor layer, and an organic thin film transistor.

  Hereinafter, the present invention will be described in more detail.

  The organic semiconductor layer forming solution of the present invention was formed using (A) a solution for forming an organic semiconductor layer containing a heteroacene derivative represented by the general formula (1), (B) a surfactant, and an organic solvent. The present invention relates to an organic semiconductor layer having a continuous phase separation structure and an organic thin film transistor.

  The heteroacene derivative constituting the organic semiconductor layer forming solution of the present invention is characterized by having a condensed ring skeleton represented by the general formula (1).

In general formula (1), R ¹ and R ² may be the same or different and represent an alkyl group having 3 to 9 carbon atoms, and particularly preferably an alkyl group having 4 to 8 carbon atoms. When R ¹ and R ² are alkyl groups having 2 or less carbon atoms, the solubility of the heteroacene derivative in an organic solvent is poor, and it becomes difficult to prepare a stable solution for forming an organic semiconductor layer.

In addition, when R ¹ and R ² are alkyl groups having 10 or more carbon atoms, the resulting organic thin film transistor has poor semiconductor and electrical characteristics.

Specific examples of R ¹ and R ² include, for example, a linear or branched alkyl group. Specific examples include n-propyl, n-butyl group, isobutyl group, n-pentyl group, n- A hexyl group, n-heptyl group, n-octyl, 2-ethylhexyl group, n-nonyl group, etc. can be mentioned.

Among these exemplified groups, R ¹ and R ² in the heteroacene derivative represented by the general formula (1) are particularly preferably an n-butyl group, an n-hexyl group, and an n-heptyl group.

In the general formula (1), T ^{1 to} T ⁴ may be the same or different and each represents an oxygen atom or a sulfur atom. Here, when all of T ^{1 to} T ⁴ are sulfur atoms, the general formula (1) represents a dithienobenzodithiophene skeleton, and when all of them are oxygen atoms, a difuranobenzodifuran skeleton.

  Specific examples of the heteroacene derivative represented by the general formula (1) are not particularly limited, and examples thereof include the following compounds.

  Particularly preferable examples of the organic heteroacene derivative represented by the general formula (1) include 2,7-di (n-butyl) dithienobenzodithiophene, 2,7-di (n-pentyl) dithienobenzodithiophene, List 2,7-di (n-hexyl) dithienobenzodithiophene, 2,7-di (n-heptyl) dithienobenzodithiophene, 2,7-di (n-octyl) dithienobenzodithiophene Can do.

  The surfactant (B), which is one of the components constituting the organic semiconductor layer forming solution of the present invention, acts on the interface between the organic semiconductor solution and the substrate when forming the organic semiconductor layer. It is a compound that has the effect of improving the familiarity of the substrate to the substrate and has the role of improving the coating performance.

  The surfactant used in the present invention can be any compound as long as it has the above-described action, and is a siloxane-based surfactant in consideration of the influence on semiconductor / electrical properties. It is desirable.

  The siloxane-based surfactant, which is a preferred example of the (B) surfactant used in the present invention, is preferably a compound having a structure represented by the general formula (2) or (3). Here, the siloxane-based surfactant represented by the general formula (2) is a siloxane compound having a structure in which a siloxy group is linearly bonded, and the siloxane-based surfactant represented by the general formula (3) is The cyclic siloxane compound in which the siloxy group has a cyclic structure and does not have a terminal structure is shown.

In the siloxane-based surfactant represented by the general formula (2) or (3), R ^{3 to} R ⁸ may be the same or different, and are a hydrogen atom, a fluorine atom, or a methyl group, an ethyl group, a propyl group, C1-C10 hydrocarbon groups, such as isopropyl group, phenyl group, benzyl group, etc., trifluoromethyl group, trifluoroethyl group, pentafluorophenyl group, etc. . m and n represent an integer of 1 to 5, and indicate the number of chains of the siloxy group.

  As the siloxane-based surfactant used in the present invention, only the linear siloxane compound represented by the general formula (2) may be used alone, or the cyclic siloxane compound represented by the general formula (3) may be used alone. It may be used. Further, a mixture of the linear siloxane compound represented by the general formula (2) and the cyclic siloxane compound represented by the general formula (3), or the compound represented by the general formula (2) and the general formula (3) may be used in any ratio. You may use the compound mixed by.

  The siloxane-based surfactant represented by the general formula (2) used in the present invention is not particularly limited, and examples thereof include disiloxane, hexamethyldisiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, dodecamethylpentasiloxane, and the like. Examples include compounds in which a part of the substituents of these compounds are replaced with fluorine atoms, among which hexamethyldisiloxane, octamethyltrisiloxane and the like are preferable. The siloxane-based surfactant represented by the general formula (3) is not particularly limited, and examples thereof include tetramethylcyclodisiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and these compounds. And compounds in which some of the substituents are replaced with fluorine atoms. Among them, hexamethylcyclotrisiloxane and the like are preferable.

  (C) The organic solvent having a boiling point of 140 ° C. or higher at normal pressure used as a component of the organic semiconductor layer forming solution of the present invention is a heteroacene derivative represented by the general formula (1) and a polymer (D) described later. Any organic solvent that can dissolve the compound may be used. By using an organic solvent having a boiling point of 140 ° C. or higher, it becomes possible to easily control the drying rate of the solvent when applying the organic semiconductor layer forming solution, and to form a high-quality crystal film. Become.

  Further, (C) an organic solvent having a boiling point of 140 ° C. or higher at normal pressure, which is used as a constituent of the organic semiconductor layer forming solution of the present invention, (C-1) a low boiling point solvent, and (C-2) a high boiling point It is possible to use a combination of (C-1) a low boiling point solvent and (C-2) a high boiling point solvent. In the present invention, (C-1) a low boiling point solvent has a boiling point of 140 ° C. or more and less than 200 ° C. at normal pressure, and (C-2) a high boiling point solvent has a boiling point of 200 ° C. or more at normal pressure. The organic solvent is shown.

  By using a combination of (C-1) a low-boiling solvent and (C-2) a high-boiling solvent, it is possible to adjust the coating performance on the substrate and the production control of the crystal film.

  The organic solvent having a boiling point of 140 ° C. or higher that can be used in the present invention is not particularly limited. For example, xylene, ethylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, isopropylbenzene Anisole, cyclohexanone, mesitylene, 1,2,4-trimethylbenzene, 3-methoxybutyl acetate, 1,3-dichlorobenzene, cyclohexanol acetate, 1,4-dichlorobenzene, decane, dipropylene glycol dimethyl ether, 1,2 -(C-1) low boiling point solubility of dichlorobenzene, 2,6-dimethylanisole, decalin, dipropylene glycol diacetate, phenyl acetate, 2,3-dimethylanisole, etc. 3,4-dimethylanisole, dipropylene glycol methyl-n-propyl ether, pentylbenzene, tetralin, dipropylene glycol methyl ether acetate, dodecane, diethylene glycol monoethyl ether acetate, 1,4-butanediol diacetate, (C-2) high boiling point solvents such as 1,3-butylene glycol diacetate, cyclohexylbenzene, diethylene glycol monobutyl ether acetate, 1,6-hexanediol diacetate, 1,3 butylene glycol diacetate, decahydronaphthol . Among them, (C-1) as the low-boiling solvent is preferably xylene, isopropylbenzene, anisole, cyclohexanone, mesitylene, 1,2-dichlorobenzene, etc. (C-2) as the high-boiling solvent, 3,4-dimethylanisole, Pentylbenzene, tetralin, cyclohexylbenzene, decahydronaphthol and the like are preferable.

  As the organic solvent used in the present invention, one kind of organic solvent can be used alone, or two or more kinds of organic solvents having different properties such as boiling point, polarity and solubility parameter can be used.

  In order to efficiently obtain high semiconductor / electrical characteristics using the organic semiconductor layer forming solution of the present invention, it is preferable that the organic semiconductor layer forming solution contains (D) a polymer compound. By containing (D) the polymer compound in the organic semiconductor layer forming solution, a continuous phase separation structure is formed, and the crystal grain of the organic semiconductor crystal film to be formed becomes large, so that the semiconductor is high. It becomes possible to have electrical characteristics.

  (D) The polymer compound is not particularly limited as long as it is a compound capable of forming an organic semiconductor layer, and the organic semiconductor layer forming solution can exhibit excellent coating properties. The molecular weight (Mw) is preferably in the range of 50,000 to 2,000,000, and more preferably in the range of 100,000 to 2,000,000.

  Further, as the polymer compound (D) used in the present invention, it is preferable to use a polymer compound having a characteristic that the contact angle of water measured according to the method described in JIS R3257 is 70 ° or more.

  Here, the polymer compound having a water contact angle of 70 ° or more refers to a polymer compound having a water contact angle of 70 ° or more of the polymer compound formed into a sheet or film. The contact angle of water indicates the angle formed by droplets formed by dropping water on the surface of a polymer compound sheet or film. The measurement of the contact angle of water is generally performed by measuring the contact angle of a known solid surface. The contact angle of water of the polymer compound used in the present invention with the heteroacene derivative represented by the general formula (1) and the polymer when the organic semiconductor layer forming solution is prepared It is preferable that the value obtained by JIS R3257 is 70 ° or more because the organic thin film transistor from which a continuous phase separation structure of the compound can be formed is excellent.

    Specific examples of the polymer compound that can be used in the present invention include, for example, polystyrene, poly (α-methylstyrene), poly (4-methylstyrene), poly (1-vinylnaphthalene), and poly (2-vinyl). Naphthalene), poly (styrene-block-butadiene-block-styrene), poly (styrene-block-isoprene-block-styrene), poly (vinyltoluene), poly (styrene-co-2,4-dimethylstyrene), poly (Chlorostyrene), poly (styrene-co-α-methylstyrene), poly (styrene-co-butadiene), poly (ethylene-co-norbornene), polycarbazole, polytriarylamine, poly (9,9-dioctyl) Fluorene-co-dimethyltriarylamine) or poly (N-vinyl) Lucarbazole) and the like, preferably polystyrene and poly (α-methylstyrene).

  As the polymer compound used in the present invention, one kind of polymer compound can be used alone, or a mixture of two or more kinds of polymer compounds can be used. Furthermore, it is also possible to use a mixture of polymer compounds having different molecular weights.

  The organic semiconductor layer forming solution of the present invention comprises (A) a heteroacene derivative represented by the general formula (1), (B) a surfactant, and (C) an organic solvent having a boiling point of 140 ° C. or higher at normal pressure, (A) a heteroacene derivative represented by general formula (1), (B) a surfactant, (C) an organic solvent having a boiling point of 140 ° C. or higher at normal pressure, and (D) a polymer compound that can be preferably used Prepare by mixing and dissolving.

  The method for preparing the organic semiconductor layer forming solution is not particularly limited, and any method may be used as long as it can dissolve the components of the organic semiconductor layer forming solution in an organic solvent.

  As an order for preparing the organic semiconductor layer forming solution, for example, a method of dissolving the component (A) in a mixed solution of the component (B) and the component (C), the component (A) as the component (B), and the component (C) (D) Method of dissolving in component mixture, (A) Method of dissolving mixture of component and (B) component in mixture of component (C) and (D), component (A) and component (B) Of (C) component solution, (A) component, (B) component and (D) mixture solution in (C) component solution, (A) component and (D) component A method of dissolving the mixture in the mixture of component (B) and component (C), a method of dissolving the mixture of component (B) and component (D) in the mixture of component (A) and component (C), (B ) Component is dissolved in the mixture of component (A), component (C) and component (D), component (B) is composed of component (A), component (B) and component (C). The method of dissolving in the liquid, the method of dissolving the component (B) in the solution of the component (A), the component (B) and the component (D), the component (B) in the solution of the component (A) and the component (C) And a method of dissolving the component (B) in the solution of the component (A), the component (C) and the component (D).

  The temperature for preparing the organic semiconductor layer forming solution is preferably 0 to 100 ° C., more preferably 10 to 80 ° C. The time for preparing the organic semiconductor layer forming solution is preferably 1 minute to 2 days.

  Since the surfactant (B) used in the present invention has the effect of a surfactant, (C) the organic solvent having a boiling point at normal pressure of 140 ° C. or higher is at a concentration of 0.1% by weight or higher. It is preferable to use it. In order to efficiently dissolve the organic semiconductor in the organic solvent, the surfactant (B) is preferably used at a concentration of 50% by weight or less.

  (A) The mixed composition ratio of the heteroacene derivative represented by the general formula (1) and the polymer compound (D) preferably used is 100 parts by mass in total of the heteroacene derivative represented by the general formula (1) and the polymer compound. In addition, the content ratio of the heteroacene derivative represented by the general formula (1) is preferably in the range of 5 to 95 parts by mass, and more preferably in the range of 30 to 70 parts by mass.

  When the concentration of the heteroacene derivative represented by the general formula (1) in the solution for forming an organic semiconductor layer of the present invention is in the range of 0.01 to 20.0% by weight, the organic semiconductor layer is easily handled. Excellent efficiency in forming. Moreover, suitable coating property is expressed as the viscosity of the solution for organic-semiconductor layer formation is the range of 0.3-100 mPa * s.

  The method for forming the organic semiconductor layer using the organic semiconductor layer forming solution of the present invention is not particularly limited as long as the organic semiconductor layer can be formed as long as the organic semiconductor layer can be formed. The organic semiconductor layer can be formed by methods such as drop casting, spin coating, cast coating, ink jetting, and slit coating.

  In particular, an organic semiconductor layer having high carrier mobility can be easily formed by drop casting or spin coating. The organic semiconductor layer can also be formed by using a printing technique such as screen printing, inkjet printing, flexographic printing, or gravure printing.

  After applying the organic semiconductor layer forming solution of the present invention, an organic semiconductor layer can be formed by drying and removing an organic solvent having a boiling point of 140 ° C. or higher at normal pressure.

  When an organic solvent having a boiling point of 140 ° C. or higher at atmospheric pressure is dried and removed from the applied organic semiconductor layer, there are no restrictions on the drying conditions. For example, the boiling point at atmospheric pressure or normal pressure is 140 ° C. or higher. It is possible to remove the organic solvent by drying.

  There is no limit to the temperature at which the organic solvent having a boiling point of 140 ° C. or higher at atmospheric pressure is dried and removed from the coated organic semiconductor layer. The solvent can be removed by drying, and an organic semiconductor layer can be formed.

  When the organic solvent having a boiling point of 140 ° C. or higher at normal pressure is dried and removed from the applied organic semiconductor layer, the vaporization rate of the organic solvent having a boiling point of 140 ° C. or higher at normal pressure to be removed is adjusted by the general formula ( It is possible to control the crystal growth of the heteroacene derivative represented by 1).

  There is no restriction | limiting in the film thickness of the organic-semiconductor layer formed with the solution for organic-semiconductor-layer formation of this invention, It is preferable that it is the range of 1 nm-1 micrometer, and it is still more preferable that it is the range of 10-300 nm.

  Further, the obtained organic semiconductor layer may be annealed at 40 to 150 ° C. after the organic semiconductor layer is formed.

  The organic semiconductor layer formed from the organic semiconductor layer forming solution of the present invention can be used as an organic semiconductor layer of an organic semiconductor device, particularly an organic thin film transistor.

  The organic thin film transistor can be obtained by laminating an organic semiconductor layer provided with a source electrode and a drain electrode on a substrate and a gate electrode through an insulating layer, and the organic semiconductor layer is formed on the organic semiconductor layer according to the present invention. An organic thin film transistor can be formed by using an organic semiconductor layer formed from a solution.

  FIG. 1 shows a structure of a general organic thin film transistor by a sectional shape. Here, (A) is a bottom gate-top contact type, (B) is a bottom gate-bottom contact type, (C) is a top gate-top contact type, and (D) is a top gate-bottom contact type. 1 is an organic semiconductor layer, 2 is a substrate, 3 is a gate electrode, 4 is a gate insulating layer, 5 is a source electrode, 6 is a drain electrode, and is formed from the organic semiconductor layer forming solution of the present invention. The organic semiconductor layer to be applied can be applied to any organic thin film transistor.

  Specific examples of the substrate include, for example, polyethylene terephthalate, polyethylene naphthalate, polymethyl methacrylate, polymethyl acrylate, polyethylene, polypropylene, polystyrene, cyclic polyolefin, fluorinated cyclic polyolefin, polyimide, polycarbonate, polyvinyl phenol, polyvinyl alcohol, poly ( Plastic substrates such as diisopropyl fumarate), poly (diethyl fumarate), poly (diisopropyl maleate), polyethersulfone, polyphenylene sulfide, cellulose triacetate; glass, quartz, aluminum oxide, silicon, highly doped silicon, silicon oxide, silicon dioxide Inorganic material substrates such as tantalum, tantalum pentoxide, indium tin oxide; gold, copper, chromium, titanium, aluminum Metal substrate, such as a beam, or the like can be mentioned. When highly doped silicon is used for the substrate, the substrate can also serve as the gate electrode.

  Specific examples of the gate electrode include, for example, aluminum, gold, silver, copper, highly doped silicon, tin oxide, indium oxide, indium tin oxide, molybdenum oxide, chromium, titanium, tantalum, chromium, graphene, carbon nanotube, etc. And inorganic materials such as doped conductive polymers (eg, PEDOT-PSS).

  Specific examples of the gate insulating layer include, for example, silicon oxide, silicon nitride, aluminum oxide, aluminum nitride, titanium oxide, tantalum dioxide, tantalum pentoxide, indium tin oxide, tin oxide, vanadium oxide, barium titanate, titanate. Inorganic material substrates such as bismuth; polymethyl methacrylate, polymethyl acrylate, polyimide, polycarbonate, polyvinyl phenol, polyvinyl alcohol, poly (diisopropyl fumarate), poly (diethyl fumarate), polyethylene terephthalate, polyethylene naphthalate, polyether sulfone, Examples thereof include plastic materials such as cyclic polyolefin and fluorinated cyclic polyolefin. The surfaces of these gate insulating layers are, for example, octadecyltrichlorosilane, decyltrichlorosilane, decyltrimethoxysilane, octyltrichlorosilane, octadecyltrimethoxysilane, β-phenethyltrichlorosilane, β-phenethyltrimethoxysilane, phenyltrichlorosilane. Silanes such as phenyltrimethoxysilane and phenyltriethoxysilane; and those modified with silylamines such as hexamethyldisilazane can also be used.

  Generally, the surface treatment of the gate insulating layer increases the crystal grain size and molecular orientation of the material constituting the organic semiconductor layer, so that the carrier mobility and current on / off ratio are improved, and the threshold value is increased. A favorable result is obtained that the voltage is reduced.

  As a material of the source electrode and the drain electrode, the same material as that of the gate electrode can be used, and the material may be the same as or different from the material of the gate electrode, or different materials may be stacked. In order to increase the carrier injection efficiency, surface treatment can be performed on these electrode materials. Examples thereof include benzene thiol and pentafluorobenzene thiol.

  When the organic semiconductor layer is formed of the organic semiconductor layer forming solution of the present invention as the organic semiconductor layer, for example, a drop casting method such as spin coating, cast coating, ink jet, slit coating, blade coating, dip coating, It is possible to use methods such as screen printing, gravure printing, flexographic printing, etc. Among them, since it becomes possible to easily and efficiently form an organic semiconductor layer, drop casting methods such as spin coating, cast coating, ink jet, etc. It is preferable that it is, and it is especially preferable that it is an inkjet. Moreover, there is no restriction | limiting in the film thickness of the organic-semiconductor layer in that case, Preferably it is 1 nm-1 micrometer, Most preferably, it is 10-300 nm.

  The organic semiconductor layer forming solution of the present invention and the organic semiconductor layer comprising the same are used for organic semiconductor layers of transistors such as electronic paper, organic EL display, liquid crystal display, IC tag (RFID tag), and sensor; organic EL display material An organic semiconductor laser material; an organic thin film solar cell material; and an electronic material such as a photonic crystal material.

  According to the present invention, a solution for forming an organic semiconductor layer with improved coatability can be obtained, and an organic thin film transistor exhibiting excellent semiconductor / electrical characteristics represented by carrier mobility and current on / off can be efficiently produced. It becomes possible to do.

  The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples.

  In the examples, the water contact angle of the polymer compound was measured according to the method described in JIS R3257 using the corresponding polymer compound sheet. The semiconductor / electrical properties were measured using a semiconductor parameter analyzer (4200SCS manufactured by Keithley) at the drain voltage (Vd) and gate voltage (Vg) described in the examples.

Example 1
(Preparation of organic semiconductor layer forming solution)
Under air, add 3.0 g of hexamethyldisiloxane tetralin solution (10 wt%) (boiling point 207 ° C.) and 61 mg of 2,7-di (n-hexyl) dithienobenzodithiophene to a 10 ml sample tube and heat to 50 ° C. Thus, an organic semiconductor layer forming solution was prepared.
(Production of organic semiconductor layer)
Organic prepared by the above-described method on a silicon substrate n-type highly doped with arsenic having a diameter of 2 inches under air (semi-tech, resistance value: 0.001 to 0.004Ω, with a 200 nm silicon oxide film on the surface) 0.5 ml of the semiconductor layer forming solution was dropped and spin coating (300 rpm × 3 seconds, 2000 rpm × 100 seconds) was performed to produce an organic semiconductor layer having a thickness of 40 nm.
(Production of organic thin film transistor)
A shadow mask having a channel length of 20 μm and a channel width of 1000 μm is placed on the organic semiconductor layer manufactured by the above-described method, and an electrode is formed by vacuum deposition of gold to form a bottom gate top contact type organic thin film transistor (1: in FIG. 1). Organic semiconductor layer, 2: silicon substrate, 3: gold gate electrode, 4: silicon oxide gate insulating layer, 5: gold source electrode, 6: equivalent to gold drain electrode).
(Measurement of semiconductor and electrical properties)
The electrical properties of the produced organic thin film were scanned with a drain voltage (Vd = -50V) and a gate voltage (Vg) from +10 to -60V in increments of 1V to evaluate the transfer characteristics. The hole mobility was 1.54 cm ² / V · s, and the current on / off ratio was 2.3 × 10 ⁷ .

Example 2
(Preparation of organic semiconductor layer forming solution)
Under air, add 3.0 g of octamethyltrisiloxane mesitylene solution (20 wt%) (boiling point 165 ° C.) and 61 mg of 2,7-di (n-octyl) dithienobenzodithiophene to a 10 ml sample tube and heat to 50 ° C. Thus, an organic semiconductor layer forming solution was prepared.
(Production of organic semiconductor layer)
An organic semiconductor layer was produced in the same manner as in Example 1.
(Production of organic thin film transistor)
An organic thin film transistor was produced by the same method as in Example 1.
(Measurement of semiconductor and electrical properties)
When the electrical properties of the obtained organic thin film transistor were evaluated in the same manner as in Example 1, the hole mobility was 1.76 cm ² / V · s and the current on / off ratio was 2.8 from the transfer characteristics. × 10 ⁷

Example 3
(Preparation of organic semiconductor layer forming solution)
Under air, add 3.0 g of hexamethylcyclotrisiloxane tetralin solution (30 wt%) (boiling point 207 ° C.) and 61 mg of 2,7-di (n-hexyl) dithienobenzodithiophene to a 10 ml sample tube at 50 ° C. The solution for forming an organic semiconductor layer was prepared by dissolving by heating.
(Production of organic semiconductor layer)
An organic semiconductor layer was produced by the same method as in Example 1.
(Measurement of semiconductor and electrical properties)
When the electrical properties were evaluated in the same manner as in Example 1, the hole mobility was 1.62 cm ² / V · s and the current on / off ratio was 2.1 × 10 ⁷ from the transfer characteristics.

Example 4
(Preparation of organic semiconductor layer forming solution)
Under air, in a 10 ml sample tube, 3.0 g of tetramethyl solution of octamethyltrisiloxane (1 wt%) (boiling point 207 ° C.), 2,7-di (n-hexyl) dithienobenzodithiophene 61 mg, and poly (α-methyl) A solution for forming an organic semiconductor layer was prepared by adding 61 mg of styrene) (Mw 850,000, water contact angle 88 °) and heating to 50 ° C. to dissolve.
(Production of organic semiconductor layer)
An organic semiconductor layer was produced in the same manner as in Example 1.
(Measurement of semiconductor and electrical properties)
When the electrical properties were evaluated in the same manner as in Example 1, the hole mobility was 2.02 cm ² / V · s and the current on / off ratio was 3.1 × 10 ⁷ from the transfer characteristics.

Example 5
(Preparation of organic semiconductor layer forming solution)
Under air, a 10 ml sample tube was charged with hexamethylcyclotrisiloxane tetralin solution (1 wt%) (bp 207 ° C.) 3.0 g, 2,7-di (n-octyl) dithienobenzodithiophene 61 mg, and poly (α- A solution for forming an organic semiconductor layer was prepared by adding 61 mg of methylstyrene (Mw 850,000, water contact angle 88 °) and heating to 50 ° C. to dissolve.
(Production of organic semiconductor layer)
An organic semiconductor layer was produced in the same manner as in Example 1.
(Measurement of semiconductor and electrical properties)
When the electrical properties of the organic semiconductor layer were evaluated in the same manner as in Example 1, the hole mobility was 2.51 cm ² / V · s and the current on / off ratio was 2.5 × 10 ⁷ from the transfer characteristics. Met.

Example 6
(Preparation of organic semiconductor layer forming solution)
In a 10 ml sample tube under air, 3.0 g of an 8: 2 mixed solution (1 wt%) of mesitylene (boiling point 165 °) and dimethylanisole (boiling point 200 ° C.) of octamethylcyclotetrasiloxane, 2,7-di (n-butyl) ) 61 mg of dithienobenzodithiophene and 61 mg of polystyrene (Mw 900,000, water contact angle 84 °) were added and heated to 50 ° C. to prepare a solution for forming an organic semiconductor layer.
(Production of organic semiconductor layer)
An organic semiconductor layer was produced in the same manner as in Example 1.
(Measurement of semiconductor and electrical properties)
When the electrical properties of the organic semiconductor layer were evaluated in the same manner as in Example 1, the hole mobility was 2.03 cm ² / V · s and the current on / off ratio was 2.8 × 10 ⁷ from the transfer characteristics. Met.

Example 7
(Preparation of organic semiconductor layer forming solution)
In a 10 ml sample tube under air, 3.0 g of a 9: 1 mixed solution (1 wt%) of mesitylene (165) and decahydronaphthol (boiling point 230 ° C.) of octamethyltrisiloxane, 2,7-di (n-hexyl) di Add 61 mg of thienobenzodithiophene and 61 mg of poly (α-methylstyrene) (Mw 850,000, water contact angle 88 °), and heat to 50 ° C. to dissolve it. went.
(Production of organic semiconductor layer)
An organic semiconductor layer was produced in the same manner as in Example 1.
(Measurement of semiconductor and electrical properties)
When the electrical properties of the organic semiconductor layer were evaluated in the same manner as in Example 1, the hole mobility was 2.51 cm ² / V · s and the current on / off ratio was 4.1 × 10 ⁷ from the transfer characteristics. Met.

Example 8
(Preparation of organic semiconductor layer forming solution)
Under air, a tetralin solution of octamethyltrisiloxane (1 wt%) (boiling point 207 ° C.) 3.0 g, 2,7-di (n-octyl) dithienobenzodithiophene 61 mg, and poly (2-vinyl) in a 10 ml sample tube A solution for forming an organic semiconductor layer was prepared by adding 61 mg of naphthalene (Mw 100,000, contact angle of water 93 °) and heating to 50 ° C. to dissolve.
(Production of organic semiconductor layer)
An organic semiconductor layer was produced in the same manner as in Example 1.
(Measurement of semiconductor and electrical properties)
When the electrical properties were evaluated in the same manner as in Example 1, the hole mobility was 2.13 cm ² / V · s and the current on / off ratio was 3.0 × 10 ⁷ from the transfer characteristics.

Comparative Example 1
(Preparation of organic semiconductor layer forming solution)
Preparation of a solution for forming an organic semiconductor layer by adding 3.0 g of tetralin and 61 mg of 2,7-di (n-octyl) dithienobenzodithiophene to a 10 ml sample tube in air and heating to 50 ° C. to dissolve. Went.
(Production of organic semiconductor layer)
The organic semiconductor layer was produced by the same method as in Example 1, but since the surfactant was not used, the organic semiconductor layer forming solution repelled on the substrate, and the film could not be formed. .

Comparative Example 2
(Preparation of organic semiconductor layer forming solution)
A solution for forming an organic semiconductor layer was prepared in the same manner as in Example 2 except that toluene (boiling point 111 ° C.) was used instead of mesitylene.
(Production of organic semiconductor layer)
An organic semiconductor layer was produced by the same method as in Example 1, but since an organic solvent having a boiling point of 140 ° C. or higher at normal pressure was not used, acicular crystals were deposited on the surface of the obtained organic semiconductor layer. As a result, a uniform crystal film could not be produced.
(Measurement of semiconductor and electrical properties)
When the physical properties of the crystalline semiconductor portion of the organic semiconductor layer were evaluated in the same manner as in Example 1, the hole mobility was 0.34 cm ² / V · s and the current on / off ratio was It was 2.7 × 10 ⁶ and was inferior in semiconductor / electrical characteristics.

Comparative Example 3
(Preparation of organic semiconductor layer forming solution)
Under air, 3.0 g of tetralin, 61 mg of 2,7-di (n-hexyl) dithienobenzodithiophene, and 61 mg of poly (α-methylstyrene) (Mw 850,000, water contact angle 88 °) in a 10 ml sample tube And heated to 50 ° C. for dissolution to prepare an organic semiconductor layer forming solution.
(Production of organic semiconductor layer)
Although the organic semiconductor layer was produced by the same method as in Example 1, since a surfactant was not used, acicular crystals were precipitated on the surface of the obtained organic semiconductor layer, and a uniform crystal film was obtained. Could not be generated.
(Measurement of semiconductor and electrical properties)
When the electrical properties were evaluated in the same manner as in Example 1, the hole mobility was 0.53 cm ² / V · s and the current on / off ratio was 2.8 × 10 ⁶ from the transfer characteristics.・ Inferior electrical characteristics.

; It is a figure which shows the structure by the cross-sectional shape of an organic thin-film transistor.

(A): Bottom gate-top contact type organic thin film transistor (B): Bottom gate-bottom contact type organic thin film transistor (C): Top gate-top contact type organic thin film transistor (D): Top gate-bottom contact type organic thin film transistor 1: Organic semiconductor layer 2: Substrate 3: Gate electrode 4: Gate insulating layer 5: Source electrode 6: Drain electrode

Claims (6)

(A) The following general formula (1)

(Here, R ¹ and R ² may be the same or different and each represents an alkyl group having 3 to 9 carbon atoms, and T ^{1 to} T ⁴ may be the same or different, and each represents an oxygen atom or sulfur. Indicates an atom.)
(B) a surfactant, and (C) an organic solvent having a boiling point of 140 ° C. or higher at normal pressure.   (B) Surfactant is a siloxane type surfactant, The solution for organic-semiconductor layer formation of Claim 1 characterized by the above-mentioned. (B) The surfactant is represented by the following general formula (2) or (3)

(Here, R ^{3 to} R ⁸ may be the same or different and each represents a hydrogen atom, a fluorine atom, a hydrocarbon group having 1 to 10 carbon atoms, or a hydrocarbon group containing a fluorine atom having 1 to 10 carbon atoms. M and n are each an integer of 1 to 5.)
The solution for forming an organic semiconductor layer according to claim 1, wherein the solution is a siloxane compound represented by the formula:   The solution for forming an organic semiconductor layer according to any one of claims 1 to 3, further comprising (D) a polymer compound.   It forms with the solution for organic-semiconductor-layer formation in any one of Claims 1-4, The organic-semiconductor layer characterized by the above-mentioned.   An organic thin film transistor comprising the organic semiconductor layer according to claim 5.

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