JP6214938B2 - Organic semiconductor and its use, and semiconductor layer forming ink - Google Patents

Description

  The present invention uses an organic semiconductor, particularly an organic semiconductor for a transistor, a semiconductor layer using the organic semiconductor, a method for forming the organic semiconductor, a semiconductor layer forming ink used for forming the semiconductor layer, and the semiconductor layer. The present invention relates to an organic electronic device, in particular, a field effect transistor and a method for manufacturing the field effect transistor.

  Conventionally, organic semiconductors for transistors are known. For example, Patent Document 1 discloses the following formula as a semiconductor material:

(Wherein, X ¹ and X ² each independently represent a sulfur atom, a selenium atom or a tellurium atom. R and R ′ each independently represent an unsubstituted or halogeno-substituted C1-C36 aliphatic hydrocarbon group.)
Is used for a field effect transistor as a semiconductor material.

  Although the above compound is a semiconductor material having semiconductor characteristics such as excellent carrier mobility, further improvement in carrier mobility is required.

  Furthermore, Patent Document 1 describes that several types of compounds represented by the above formula may be mixed and used as a material for the semiconductor layer.

  However, Patent Document 1 does not describe mixing two or more kinds of specific compounds represented by the above formula. Further, according to the study of the present inventor, when two or more kinds are arbitrarily selected and mixed from the many compounds represented by the above formula, an appropriate combination is not selected as a combination of two or more kinds of compounds. In such a case, two or more kinds of compounds are phase-separated. In such a phase-separated mixture, the carrier mobility improvement effect cannot be obtained.

  Non-Patent Document 1 describes a thin film prepared by vacuum co-evaporation of pentacene and fluoropentacene that exhibit high carrier mobility in a field effect transistor. A thin film of pentacene and fluoropentacene mixed).

  However, in the X-ray diffraction spectrum (FIG. 3A of Non-Patent Document 1), the thin film has a peak at a position corresponding to the peak of each X-ray diffraction spectrum of pentacene and fluoropentacene. Therefore, it is considered that pentacene and fluoropentacene are in a state of phase separation. Therefore, the effect of improving the carrier mobility cannot be obtained.

  Moreover, what mixed 2 or more types of organic-semiconductor compounds is conventionally known as organic semiconductors other than the organic semiconductor for transistors.

  For example, Non-Patent Document 2 describes a thin film produced by co-evaporating α-sexithiophene and α, ω-dihexylsexithiophene as an organic semiconductor whose use is unknown.

  However, the thin film has not so high carrier mobility. In addition, since the thin film uses α-sexithiophene having low solubility in an organic solvent, it cannot be formed by a solution process such as coating or printing. Note that Non-Patent Document 2 does not disclose or suggest the use of the thin film for a transistor.

  Non-Patent Document 3 describes a mixed crystal film prepared by co-evaporation of copper phthalocyanine and fluorinated copper phthalocyanine as an organic semiconductor for a solar cell.

  However, the mixed crystal film has low carrier mobility. Further, since the mixed crystal film uses copper phthalocyanine having low solubility in an organic solvent, it cannot be formed by a solution process such as coating or printing. Non-Patent Document 3 does not disclose or suggest the use of the above mixed crystal film for a transistor.

International Publication No. 2008/047896

I. Salzmann, et al., J. Am. Chem. Soc., 2008, 130, pp 12870-12871 J. Vogel, et al., J. Phys. Chem. B, 2007, 111, pp 14097-14101 A. Opitz, et al., Organic Electronics, 10, 2009, pp 1259-1267

  The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to form an organic semiconductor for a transistor with improved carrier mobility and a semiconductor layer by a solution process such as coating or printing. Another object is to provide an organic semiconductor with improved carrier mobility. Another object of the present invention is to provide a semiconductor layer having improved carrier mobility and a method for forming the same, an ink for forming a semiconductor layer capable of forming a semiconductor layer having improved carrier mobility, an organic electronic device having improved carrier mobility, particularly an electric field. An object of the present invention is to provide a method of manufacturing a field effect transistor capable of manufacturing an effect transistor and a field effect transistor with improved carrier mobility.

  The organic semiconductor for a transistor of the present invention is a p-type organic semiconductor for a transistor and is characterized by being a solid solution composed of two or more different compounds.

  According to the said structure, since it is a solid solution comprised by two or more types of different compounds, carrier mobility improves compared with the organic semiconductor for transistors which consists of each compound single-piece | unit.

  The organic semiconductor of the present invention has the following general formula (1)

(In the above formula, R ¹ and R ² each independently represents an aliphatic hydrocarbon group optionally having a halogen atom)
It is the solid solution containing 2 or more types of different compounds represented by these.

  According to the said structure, since it is a solid solution containing 2 or more types of different compounds represented by the said General formula (1), compared with the organic semiconductor which consists of a compound simple substance represented by the said General formula (1) Carrier mobility is improved. Furthermore, according to the said structure, since the compound represented by the said General formula (1) has high solubility to an organic solvent, formation of the semiconductor layer which consists of said organic semiconductor is possible by solution processes, such as application | coating and printing. It can be manufactured with good workability and low cost.

  The semiconductor layer of the present invention is characterized by comprising the organic semiconductor of the present invention.

  According to the said structure, since it consists of the organic semiconductor of this invention with improved carrier mobility, carrier mobility improves.

  The semiconductor layer forming ink of the present invention is a semiconductor layer forming ink used for forming the semiconductor layer of the present invention, and includes two or more different compounds constituting the solid solution and a solvent. Yes.

  By using the semiconductor layer forming ink having the above structure, the semiconductor layer of the present invention with improved carrier mobility can be easily formed by a method such as coating or printing.

  The method for forming a semiconductor layer of the present invention is characterized in that the semiconductor layer forming ink of the present invention is applied to the surface on which the semiconductor layer is to be formed and dried.

  According to the above method, the semiconductor layer of the present invention with improved carrier mobility can be easily formed.

  The organic electronic device of the present invention is characterized by including a semiconductor layer made of the organic semiconductor of the present invention, which is a solid solution containing two or more different compounds represented by the general formula (1).

  According to the above configuration, since the semiconductor layer can be formed by a solution process and includes the semiconductor layer made of the organic semiconductor of the present invention with improved carrier mobility, carrier mobility is improved and good workability is achieved. Moreover, it can be manufactured at low cost.

  The field effect transistor of the present invention is characterized by including the semiconductor layer of the present invention.

  According to the above configuration, since the semiconductor layer of the present invention with improved carrier mobility is included, carrier mobility is improved.

  The field effect transistor manufacturing method of the present invention is a method of manufacturing the field effect transistor of the present invention, which includes a first step of forming the semiconductor layer, and a second step of heat-treating the semiconductor layer after the first step. These processes are included.

  According to the above method, the characteristics of the field effect transistor can be improved and stabilized by heat-treating the semiconductor layer after forming the semiconductor layer of the present invention with improved carrier mobility.

  According to the present invention, an organic semiconductor for a transistor with improved carrier mobility and a semiconductor layer with a solution process such as coating or printing can be formed, and an organic semiconductor with improved carrier mobility can be provided.

  In addition, according to the present invention, a semiconductor layer having improved carrier mobility and a method for forming the same, a semiconductor layer forming ink capable of forming a semiconductor layer having improved carrier mobility, an organic electronics device having improved carrier mobility, particularly an electric field An effect transistor and a method for manufacturing a field effect transistor capable of manufacturing a field effect transistor with improved carrier mobility can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing which shows the some example of a field effect transistor of this invention, (a) is a schematic sectional drawing which shows the example of an aspect of a bottom contact-bottom gate type field effect transistor, (b) is a top contact. -It is a schematic sectional view showing an example of an embodiment of a bottom gate type field effect transistor, (c) is a schematic sectional view showing an example of an embodiment of a bottom contact-top gate type field effect transistor, and (d) is a top & bottom contact. It is a schematic sectional drawing which shows the example of an aspect of a type | mold field effect transistor, (e) is a schematic sectional drawing which shows the example of an aspect of an electrostatic induction transistor. It is explanatory drawing for demonstrating the manufacturing method of the bottom contact-bottom gate type field effect transistor as one example of the field effect transistor of this invention, (a)-(f) shows each process of the said manufacturing method. It is a schematic sectional drawing. FIG. 5 is a graph showing an out-of-plane X-ray diffraction spectrum of an organic semiconductor thin film according to an example of the present invention, together with a single out-of-plane X-ray diffraction spectrum of each of two types of compounds constituting the organic semiconductor. is there. It is a graph which shows the out-of-plane X-ray diffraction spectrum of the thin film of the organic semiconductor which concerns on an example of this invention with the out-of-plane X-ray diffraction spectrum of each of two types of compounds which comprise the organic semiconductor. It is a graph which shows the out-of-plane X-ray diffraction spectrum of the organic-semiconductor thin film which is a mixture of the state which is not a solid solution which concerns on a comparative example with the single-piece | unit out-of-plane X-ray diffraction spectrum of each of two types of compounds which comprise the mixture.

  Hereinafter, the present invention will be described in detail.

  The organic semiconductor for a transistor of the present invention is a p-type organic semiconductor for a transistor and is a solid solution.

  Here, the “solid solution” refers to a solid solution in which two or more elements are dissolved in each other and the whole is a uniform solid phase. Therefore, the solid solution constituting the organic semiconductor of the present invention is a mixture composed of two or more different compounds functioning as an organic semiconductor, and the two or more different compounds are melted together to form a uniform solid phase as a whole. It is what.

Whether the organic semiconductor of the present invention is a solid solution can be confirmed by the following method. First, whether the organic semiconductor of the present invention is a mixture composed of two or more different compounds is generally determined by using a spectrum such as ¹ H-NMR (nuclear magnetic resonance) spectrum, ¹ C-NMR spectrum, mass spectrum (MS), etc. It can be confirmed by discriminating whether the peak corresponding to each of two or more different compounds is contained in the spectrum using a typical molecular structure analysis method. Whether or not a mixture of two or more different compounds is in a solid solution state is determined in the out-of-plane X-ray diffraction spectrum at a position corresponding to the peak of each single-piece out-of-plane X-ray diffraction spectrum constituting the mixture. Further, it can be confirmed by determining whether there is no peak and a single peak is present at an intermediate position between these positions. In other words, in the present application document, the “solid solution” means that determined as a solid solution by the above confirmation method.

The organic semiconductor for a transistor of the present invention preferably has a hole mobility of 0.01 cm ² / V · s or more, and more preferably has a hole mobility of 0.1 cm ² / V · s or more. . Thereby, a transistor having practical characteristics can be realized.

  Here, the hole mobility of the organic semiconductor for a transistor of the present invention is such that a field effect transistor having a semiconductor layer with a channel length of 200 μm is produced using the organic semiconductor for a transistor, and the drain current-gate of this field effect transistor It is assumed that the value is calculated from the voltage characteristics.

  The two or more different compounds constituting the organic semiconductor for the transistor of the present invention are not particularly limited as long as they have a molecular structure similar to the extent that a solid solution can be formed, and the following general formula (1)

(In the above formula, R ¹ and R ² each independently represents an aliphatic hydrocarbon group optionally having a halogen atom)
The compound represented by these is preferable.

  The organic semiconductor of the present invention is a solid solution containing two or more different compounds represented by the general formula (1).

  In the organic semiconductor of the present invention, two or more different compounds represented by the general formula (1) are mixed with another organic semiconductor compound in order to improve the characteristics of the field effect transistor or to impart other characteristics. In that case, the content of the compound represented by the general formula (1) in the organic semiconductor of the present invention is basically 50% by weight or more, preferably 80% by weight or more. Yes, more preferably 95% by weight or more.

  The organic semiconductor of the present invention is a linear or branched aliphatic carbonization in which the aliphatic hydrocarbon group which may have the halogen atom in the general formula (1) may have a halogen atom. When it is a hydrogen group, the chain length of the linear or branched aliphatic hydrocarbon group contained in two or more compounds represented by the general formula (1) is the longest chain length and the shortest chain length. The difference is preferably less than 4. Thereby, the mixture of two or more types of compounds represented by the general formula (1) can easily realize a solid solution state.

  When the organic semiconductor of the present invention is a solid solution containing two different compounds having linear or branched aliphatic hydrocarbon groups having different chain lengths represented by the general formula (1), the chain length is It is preferable to contain 30 to 85% by mass of a compound having a shorter linear or branched aliphatic hydrocarbon group, and it is more preferable to contain 50 to 80% by mass.

  Examples of the method for producing the organic semiconductor of the present invention include a method in which two or more different compounds constituting the organic semiconductor are dissolved in a solvent to prepare a solution, and then the solvent is removed (dried); For example, a method of co-evaporating two or more kinds of different compounds can be used.

[Compound represented by the general formula (1)]
Next, the compound represented by the general formula (1) will be described in detail below.

R ¹ and R ² in the general formula (1) each independently represent an aliphatic hydrocarbon group which may have a halogen atom.

  The aliphatic hydrocarbon group is a saturated or unsaturated linear, branched, or cyclic aliphatic hydrocarbon group. That is, the aliphatic hydrocarbon group is a linear saturated aliphatic hydrocarbon group, a branched saturated aliphatic hydrocarbon group, a cyclic saturated aliphatic hydrocarbon group, a linear unsaturated aliphatic hydrocarbon group, It is a branched unsaturated aliphatic hydrocarbon group or a cyclic unsaturated aliphatic hydrocarbon group. The aliphatic hydrocarbon group is preferably a linear or branched aliphatic hydrocarbon group, more preferably a linear aliphatic hydrocarbon group, still more preferably a linear saturated aliphatic hydrocarbon group. (Linear alkyl group).

  Carbon number of the said aliphatic hydrocarbon group is 1-36 normally, Preferably it is 2-24, More preferably, it is 4-20. When carbon number of the said aliphatic hydrocarbon group is below the upper limit of these numerical ranges, the solubility of the compound represented with the said General formula (1) with respect to an organic solvent can be made higher. Moreover, when the carbon number of the said aliphatic hydrocarbon group is 2 or more, More preferably, the solubility of the compound represented by the said General formula (1) with respect to an organic solvent can be made higher.

  Examples of the linear saturated aliphatic hydrocarbon group include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, and n-octyl group. N-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, n-tetradecyl group, n-pentadecyl group, n-hexadecyl group, n-heptadecyl group, n-octadecyl group N-nonadecyl group, n-eicosyl group, n-heneicosyl group, n-docosyl group, n-tricosyl group, n-tetracosyl group, n-pentacosyl group, n-hexacosyl group, n-heptacosyl group, n-octacosyl group , N-nonacosyl group, n-triacontyl group, n-dotriacontyl group, n-hexatriacontyl group and the like.

  Examples of the branched saturated aliphatic hydrocarbon group include iso-propyl group, iso-butyl group, t-butyl group, iso-pentyl group, t-pentyl group, sec-pentyl group, iso-hexyl group, A sec-heptyl group, a sec-nonyl group, a 5- (n-pentyl) decyl group, and the like can be given.

  Examples of the cyclic saturated aliphatic hydrocarbon group include a cyclohexyl group, a cyclopentyl group, an adamantyl group, and a norbornyl group.

  The aliphatic hydrocarbon group includes a saturated aliphatic hydrocarbon group, that is, an alkyl group and an unsaturated aliphatic hydrocarbon group. The unsaturated aliphatic hydrocarbon group includes an alkenyl group containing a carbon-carbon double bond and an alkynyl group containing a carbon-carbon triple bond. The unsaturated aliphatic hydrocarbon group includes a combination thereof, that is, a case where a carbon-carbon double bond and a carbon-carbon triple bond are simultaneously included in a part of the aliphatic hydrocarbon group. The aliphatic hydrocarbon group is preferably an alkyl group or an alkynyl group, and more preferably an alkyl group.

  Examples of the linear unsaturated aliphatic hydrocarbon group include linear alkenyl groups such as vinyl group, allyl group, eicosadienyl group (for example, 11,14-eicosadienyl group), 4-pentenyl group; 1-propynyl, Examples thereof include linear alkynyl groups such as 1-hexynyl, 1-octynyl, 1-decynyl, 1-undecynyl, 1-dodecynyl, 1-tetradecynyl, 1-hexadecynyl and 1-nonadecynyl.

  Examples of the branched unsaturated aliphatic hydrocarbon group include geranyl group (trans-3,7-dimethyl-2,6-octadien-1-yl group), farnesyl group (trans, trans-3,7, 11-trimethyl-2,6,10-dodecatrien-1-yl group) and the like.

When the aliphatic hydrocarbon group represented by R ¹ or R ² in the general formula (1) is an unsaturated aliphatic hydrocarbon group, the unsaturated carbon-carbon bond in the unsaturated aliphatic hydrocarbon group Is present at a position conjugated with the benzene ring (substituted with R ¹ or R ² ), that is, one carbon atom of the unsaturated carbon-carbon bond is preferably directly connected to the benzene ring. Also in this case, the alkynyl group is more preferable than the alkenyl group as the unsaturated aliphatic hydrocarbon group as described above.

The aliphatic hydrocarbon group represented by R ¹ or R ² in the general formula (1) is an aliphatic hydrocarbon group having no halogen atom (an unsubstituted aliphatic hydrocarbon group), particularly 1 to 1 carbon atoms. Although it is preferably 36 unsubstituted saturated aliphatic hydrocarbon groups (alkyl groups), it may be an aliphatic hydrocarbon group having a halogen atom, that is, a halogen-substituted aliphatic hydrocarbon group. The halogen-substituted aliphatic hydrocarbon group means one in which a hydrogen atom at any position of the aliphatic hydrocarbon group is substituted with any number and any kind of halogen atoms.

  The halogen atom is preferably a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom, more preferably a fluorine atom, a chlorine atom, or a bromine atom, and further preferably a fluorine atom or a bromine atom.

  Examples of the halogen-substituted aliphatic hydrocarbon group include chloromethyl group, bromomethyl group, trifluoromethyl group, pentafluoroethyl group, n-perfluoropropyl group, n-perfluorobutyl group, and n-perfluoropentyl group. N-perfluorooctyl group, n-perfluorodecyl group, n- (dodecafluoro) -6-iodohexyl group, 2,2,3,3,3-pentafluoropropyl group, 2,2,3,3 -A tetrafluoropropyl group etc. are mentioned.

[Method for producing compound represented by general formula (1)]
The compound represented by the general formula (1) is synthesized by a known method described in, for example, K. Takimiya, et al., J. Am. Chem. Soc., 2006, 128, pp 3044-3050. Can do. Moreover, the compound represented by the said General formula (1) can also be obtained according to the method as described in the international publication 2006/077788, for example.

  That is, the following general formula (2)

(In the above formula, X represents a halogen atom)
A compound represented by formula (2), for example, a compound in which X is an iodine atom in the above general formula (2) is used as a raw material, and an acetylene derivative is allowed to act on this compound to carry out a coupling reaction, whereby the following general formula (3)

(In the above formula, R ³ and R ⁴ each independently represents an aliphatic hydrocarbon group optionally having a halogen atom)
Can be obtained. The compound represented by the general formula (3) is a compound having a carbon-carbon triple bond at a position where R ¹ or R ² is conjugated with the benzene ring among the compounds represented by the general formula (1). This corresponds to the case of 3 or more alkynyl groups (which may have a halogen atom). Therefore, the compound represented by the general formula (1) in this case can be obtained by the above coupling reaction.

Furthermore, by reducing (hydrogen addition) the obtained compound represented by the general formula (3) by a conventional method, R ¹ or R ² in the general formula (1) may have a halogen atom. A compound which is a saturated aliphatic hydrocarbon group (alkyl group) having 3 or more carbon atoms which may have an alkenyl group having 3 or more atoms or a halogen atom is obtained.

  If the conditions for the reduction reaction of the compound represented by the above general formula (3), for example, the type and amount of the reaction reagent used in the reduction reaction, the reaction solvent, and a combination thereof are appropriately selected, the reduction reaction can be carried out by carbon-carbon triplet. It can be stopped in the state where the bond has progressed to a carbon-carbon double bond, or the reduction reaction can proceed until the aliphatic hydrocarbon group containing a carbon-carbon triple bond becomes a saturated aliphatic hydrocarbon group. It is.

The coupling reaction between the compound represented by the general formula (2) and the ethylene derivative proceeds in the same manner as the coupling reaction between the compound represented by the general formula (2) and the acetylene derivative. In this case, an alkenyl compound in which the carbon-carbon triple bond in the general formula (3) is replaced with a carbon-carbon double bond is obtained. This alkenyl compound is an alkenyl group having 3 or more carbon atoms having a carbon-carbon double bond at a position where R ¹ or R ² is conjugated with a benzene ring among the compounds represented by the general formula (1) (however, This may be the case with a halogen atom. Therefore, the compound represented by the general formula (1) in this case can be obtained by the above coupling reaction.

  The purification method of the compound represented by the general formula (1) is not particularly limited, and known methods such as recrystallization, column chromatography, and vacuum sublimation purification can be adopted. You may use it combining.

  Specific examples of the compound represented by the general formula (1) are shown in Tables 1 to 3 below.

[Semiconductor layer and method for forming the same, and ink for forming semiconductor layer used therein]
The semiconductor layer of the present invention is made of the organic semiconductor of the present invention.

  Various methods can be used as a method for forming a semiconductor layer made of the organic semiconductor of the present invention. The formation method of the semiconductor layer is roughly classified into a formation method by a vacuum process and a formation method by a solution process, and any of them may be used. Examples of the method for forming a semiconductor layer by a vacuum process include sputtering, CVD, molecular beam epitaxial growth, and vacuum deposition. As a method for forming a semiconductor layer by a solution process, coating methods such as a dip coating method, a die coater method, a roll coater method, a bar coater method, and a spin coating method; an inkjet method; a screen printing method; an offset printing method; a microcontact printing method Etc. Hereinafter, a method for forming a semiconductor layer will be described in detail.

  First, a method for forming a semiconductor layer made of the organic semiconductor of the present invention by a vacuum process using an organic material containing the organic semiconductor of the present invention will be described.

In this method, the organic material is evaporated by heating under vacuum in a container such as a crucible or a metal boat, and the evaporated organic material is converted into an object (hereinafter referred to as an “adherent”) that forms a semiconductor layer. The method of adhering (vapor deposition) to the surface (hereinafter referred to as “deposition surface”) (vacuum deposition method) is preferably employed. The degree of vacuum at the time of vapor deposition is usually 1.0 × 10 ⁻¹ Pa or less, and preferably 1.0 × 10 ⁻⁴ Pa or less. In addition, the characteristics of the semiconductor layer change depending on the temperature of the deposit during vapor deposition (if the semiconductor layer is a semiconductor layer of a field effect transistor, this changes the characteristics of the field effect transistor). It is preferred to carefully select the temperature of the deposit at the time. The temperature of the adherend during vapor deposition is usually 0 to 200 ° C, preferably 10 to 150 ° C. Moreover, a vapor deposition rate is 0.001-10 nm / second normally, Preferably it is 0.01-1 nm / second. The thickness of the semiconductor layer 2 formed from an organic material is usually 0.1 nm to 10 μm, preferably 0.5 nm to 5 μm, more preferably 1 nm to 3 μm.

  Instead of heating and evaporating the organic material for forming the semiconductor layer and attaching it to the deposition surface, accelerated ions such as argon collide with the material target to knock out material atoms and attach them to the substrate. A sputtering method may be used.

  Next, a method for forming a semiconductor layer made of the organic semiconductor of the present invention by a solution process using a solution (ink) containing the organic semiconductor of the present invention will be described.

  As a method for forming a semiconductor layer of the present invention, a semiconductor layer forming ink containing two or more different compounds constituting a solid solution and a solvent is applied on the surface (attachment surface) on which the semiconductor layer is to be formed. However, a method of drying is preferable.

  Among the organic semiconductors of the present invention, an organic semiconductor which is a solid solution containing two or more different compounds represented by the general formula (1) is suitable for a solution process because it is easily dissolved in an organic solvent. When a semiconductor layer is formed by a solution process, a semiconductor layer having practical semiconductor characteristics can be obtained. The method of forming a semiconductor layer by coating is advantageous because a large-area field effect transistor can be manufactured with good workability and low cost because the manufacturing environment does not need to be in a vacuum or high temperature state. It is preferable also in the formation method of a layer.

  In the method of forming a semiconductor layer by a solution process, first, an ink for forming a semiconductor layer is prepared by dissolving two or more different compounds constituting the solid solution in a solvent. The semiconductor layer forming ink of the present invention is a semiconductor layer forming ink used for forming a semiconductor layer comprising the organic semiconductor of the present invention, and includes two or more different compounds constituting the solid solution and a solvent. It is out.

  As the solvent used for the semiconductor layer forming ink, two or more different compounds constituting the solid solution can be dissolved in the solvent, and the semiconductor layer can be formed on the adherend using the ink. If there is, it will not specifically limit. As the solvent, an organic solvent is preferable. Specific examples of the organic solvent include halogenated hydrocarbon solvents such as chloroform, methylene chloride and dichloroethane; alcohol solvents such as methanol, ethanol, isopropyl alcohol and butanol; octafluoropentanol and pentafluoropropanol. Fluorinated alcohol solvents such as ethyl acetate, butyl acetate, ethyl benzoate, diethyl carbonate, and other ester solvents; toluene, xylene, benzene, chlorobenzene, dichlorobenzene, and other aromatic hydrocarbon solvents; acetone, methyl ethyl ketone, methyl Ketone solvents such as isobutyl ketone, cyclopentanone and cyclohexanone; Amide solvents such as dimethylformamide, dimethylacetamide and N-methylpyrrolidone; Tetrahydrofuran, diisobutyl ether, etc. Ether solvents, and the like. These may be used individually by 1 type, and may mix and use 2 or more types.

  The concentration of two or more different compounds constituting the solid solution in the semiconductor layer forming ink varies depending on the type of solvent and the thickness of the semiconductor layer to be formed, but is usually 0.001 to 50% by mass. Preferably, it is 0.01-20 mass%.

  In the case where the semiconductor layer forming ink contains two or more different compounds represented by the general formula (1), for the purpose of improving the film formability of the semiconductor layer and doping described later, A semiconductor material other than the compound represented by the general formula (1) can be contained in the semiconductor layer forming ink.

  When preparing the ink for forming a semiconductor layer, two or more different compounds constituting the solid solution are dissolved in a solvent, and if necessary, heat dissolution treatment (treatment that promotes dissolution of the compound in the solvent by heating) ) To obtain a solution. Furthermore, solid content, such as an impurity, is removed by filtering the obtained solution using a filter. Thereby, the semiconductor layer forming ink is obtained. When such a semiconductor layer forming ink is used, the film formability of the semiconductor layer is improved, which is preferable in forming the semiconductor layer.

  By using the semiconductor layer forming ink, it is possible to pattern an organic semiconductor and create a circuit using an ink jet recording method.

  Next, the ink for forming a semiconductor layer is applied onto the adherend surface and dried (the solvent is removed). As the method for applying the semiconductor layer forming ink, there are coating methods such as casting, spin coating, dip coating, blade coating, wire bar coating, and spray coating; ink jet printing, screen printing, offset printing, letterpress printing, gravure printing, etc. Printing techniques; soft lithography techniques such as microcontact printing; and a combination of these techniques.

  Further, as a method of forming a semiconductor layer similar to the coating method, a monomolecular film of the semiconductor layer is produced by dropping the above-described ink for forming a semiconductor layer on the water surface, and the monomolecular film of the semiconductor layer is formed on the deposition surface. The Langmuir project method in which the organic semiconductor in the liquid crystal state or the melt state is sandwiched between two substrates; the method in which the organic semiconductor in the liquid crystal state or the melt state is introduced between the substrates by capillary action, or the like can also be employed.

  The thickness of the semiconductor layer formed by this method is preferably thin as long as the function is not impaired. When the thickness of the semiconductor layer increases, there is a concern that the leakage current increases when the semiconductor layer is a semiconductor layer of a field effect transistor. The thickness of the semiconductor layer is usually 0.1 nm to 10 μm, preferably 0.5 nm to 5 μm, more preferably 1 nm to 3 μm.

[Field Effect Transistor]
A field effect transistor (hereinafter, sometimes abbreviated as “FET”) of the present invention includes a semiconductor layer made of the organic semiconductor of the present invention. In more detail, the field effect transistor of the present invention includes at least one semiconductor layer including a semiconductor layer made of the organic semiconductor of the present invention, and two electrodes disposed so as to be in contact with and separated from the semiconductor layer, That is, a source electrode and a drain electrode, and another electrode called a gate electrode disposed so as to face a region (channel region) between a surface in contact with the source electrode and a surface in contact with the drain electrode in the semiconductor layer, The current flowing between the source electrode and the drain electrode is controlled by the voltage applied to the gate electrode.

  In general, a field effect transistor having a structure in which a gate electrode is insulated from a semiconductor layer by an insulator layer (Metal-Insulator-Semiconductor) (MIS structure) is often used as a field effect transistor. The MIS structure using a metal oxide film as an insulator layer is called a MOS (Metal-Oxide-Semiconductor) structure. Other field effect transistors include a structure in which a gate electrode is formed on a semiconductor layer through a Schottky barrier (Metal Semiconductor: MES structure), but a field effect using an organic semiconductor is used. In the case of a transistor, a MIS structure is often used.

  Hereinafter, the field effect transistor of the present invention will be described in more detail with reference to FIG. 1, but the present invention is not limited to these structures.

  FIG. 1 is a schematic diagram showing some examples of the field effect transistor of the present invention. A field effect transistor 10A to 10D of each example shown in FIGS. 1A to 1D includes a source electrode 1, at least one semiconductor layer 2 including a semiconductor layer made of the organic semiconductor of the present invention, a drain electrode 3, An insulator layer 4, a gate electrode 5, and a substrate 6 are provided. The field effect transistor 10E in the example shown in FIG. 1E includes a source electrode 1, at least one semiconductor layer 2 including a semiconductor layer made of the organic semiconductor of the present invention, a drain electrode 3, and a gate electrode 5. The arrangement of the layers 2 and 4 and the electrodes 1, 3, and 5 can be appropriately selected depending on the use of the field effect transistor.

  The field effect transistors 10 </ b> A to 10 </ b> D are called lateral FETs because current flows in a direction parallel to the substrate 6, the source electrode 1, and the drain electrode 3. The field effect transistor 10A and the field effect transistor 10C have a structure in which the source electrode 1 and the drain electrode 3 are disposed on the lower surface (surface on the substrate 6 side) of the semiconductor layer 2, and this structure is called a bottom contact structure. . The field effect transistor 10B has a structure in which the source electrode 1 and the drain electrode 3 are disposed on the upper surface (surface far from the substrate 6) of the semiconductor layer 2, and this structure is called a top contact structure. The field effect transistor 10D has a structure in which one of the source electrode 1 and the drain electrode 3 is disposed on the upper surface of the semiconductor layer 2, and the other is disposed on the lower surface of the semiconductor layer 2. This is called a bottom contact structure.

  The field effect transistor 10A, the field effect transistor 10B, and the field effect transistor 10D have a structure in which the gate electrode 5 is disposed on the lower side (substrate 6 side) of the semiconductor layer 2, and this structure is called a bottom gate structure. . In the bottom gate structure, a single conductive substrate (for example, a silicon wafer) may serve as the gate electrode 5 and the substrate 6. The field effect transistor 10C has a structure in which the gate electrode 5 is disposed on the upper side (the side far from the substrate 6) of the semiconductor layer 2, and this structure is called a top gate structure.

  The field effect transistor 10A is called a bottom contact-bottom gate field effect transistor. The field effect transistor 10A includes a substrate 6, a gate electrode 5 disposed on the upper surface of the substrate 6, an insulator layer 4 disposed on the upper surface of the gate electrode 5, and one end of the upper surface of the insulator layer 4. A source electrode 1 disposed on the portion, a drain electrode 3 disposed on the other end portion of the upper surface of the insulator layer 4, a central portion (portion excluding both end portions) of the upper surface of the insulator layer 4, The semiconductor layer 2 is provided on a part of the upper surface of the source electrode 1 and a part of the upper surface of the drain electrode 3.

  The field effect transistor 10B is called a top contact-bottom gate type field effect transistor. The field effect transistor 10B includes a substrate 6, a gate electrode 5 disposed on the upper surface of the substrate 6, an insulator layer 4 disposed on the upper surface of the gate electrode 5, and an upper surface of the insulator layer 4. The semiconductor layer 2 is provided, and the source electrode 1 and the drain electrode 3 are provided on a part of the upper surface of the semiconductor layer 2 so as to be separated from each other.

  The field effect transistor 10C is called a bottom contact-top gate field effect transistor. The field effect transistor 10C has a structure often used for a field effect transistor using an organic single crystal semiconductor. The field effect transistor 10 </ b> C includes a substrate 6, a semiconductor layer 2 disposed on the upper surface of the substrate 6, and a source electrode 1 and a drain disposed on a part of the upper surface of the semiconductor layer 2 so as to be separated from each other. Insulation disposed on the upper surface of the electrode 3 and the insulator layer 4 (except for the portion where the source electrode 1 and the drain electrode 3 are disposed), the upper surface of the source electrode 1 and the upper surface of the drain electrode 3 A body layer 4 and a gate electrode 5 disposed on the insulator layer 4 are provided.

  The field effect transistor 10D is called a top & bottom contact type field effect transistor. The field effect transistor 10D includes a substrate 6, a gate electrode 5 disposed on the upper surface of the substrate 6, an insulator layer 4 disposed on the upper surface of the gate electrode 5, and one end of the upper surface of the insulator layer 4. A source electrode 1 disposed on the portion, an upper surface of the insulator layer 4 (except for a portion where the source electrode 1 is disposed) and a semiconductor layer 2 disposed on the upper surface of the source electrode 1 And a drain electrode 3 disposed on an end of the upper surface of the semiconductor layer 2 on the side far from the source electrode 1.

  The field effect transistor 10E is a type of field effect transistor having a vertical structure in which current flows in a direction perpendicular to the source electrode 1 and the drain electrode 3, and is a static induction transistor (SIT). The field effect transistor 10E includes a source electrode 1 and a drain electrode 3 disposed so as to be parallel and spaced apart from each other, and a semiconductor layer 2 disposed so as to be sandwiched between the source electrode 1 and the drain electrode 3. And a plurality of gate electrodes 5 embedded in the semiconductor layer 2 in a mesh shape parallel to the source electrode 1 and the drain electrode 3. In this electrostatic induction transistor (field effect transistor 10E), the flow of current in the semiconductor layer 2 spreads in a plane, so that a large number of carriers 8 are generated at a time at the source electrode 1 as shown by arrows in FIG. It can move from the side to the drain electrode 3 side. Further, since the electrostatic induction transistor (field effect transistor 10E) is arranged such that the source electrode 1 and the drain electrode 3 are arranged in the vertical direction (direction perpendicular to the semiconductor layer 2), the source electrode 1 and the drain electrode Since the distance to 3 can be shortened, the response is fast. Therefore, this electrostatic induction transistor (field effect transistor 10E) can be preferably applied to applications such as passing a large current or performing high-speed switching. Although FIG. 1E does not show a substrate, in the normal case, a substrate similar to the substrate 6 is provided outside the source electrode 1 and the drain electrode 3 in the field effect transistor 10E.

  Next, each component in the field effect transistors 10A to 10D of each embodiment will be described below.

  The board | substrate 6 needs to be able to hold | maintain without peeling each component formed on it. Examples of the material of the substrate 6 include an insulating substrate such as a resin plate, a resin film, paper, a glass plate, a quartz plate, and a ceramic plate; an insulating layer formed by coating or the like on a conductive substrate made of a metal or an alloy. The formed substrate; a substrate composed of various combinations such as a combination of a resin and an inorganic material; and a conductive substrate such as a semiconductor substrate (for example, a silicon wafer) can be used. Examples of the resin constituting the resin plate and the resin film include polyethylene terephthalate, polyethylene naphthalate, polyethersulfone, polyamide, polyimide, polycarbonate, cellulose triacetate, and polyetherimide. When a resin film or paper is used as the substrate 6, the field effect transistors 10A to 10D can be made flexible. The field effect transistors 10A to 10D are flexible and light, and the field effect transistors 10A to 10D are practical. improves. The thickness of the substrate 6 is usually 1 μm to 10 mm, preferably 5 μm to 5 mm.

A conductive material is used for the source electrode 1, the drain electrode 3, and the gate electrode 5. Examples of the conductive material include platinum, gold, silver, aluminum, chromium, tungsten, tantalum, nickel, cobalt, copper, iron, lead, tin, titanium, indium, palladium, molybdenum, magnesium, calcium, and barium. Metals such as lithium, potassium and sodium and alloys containing them; conductive oxides such as InO ₂ , ZnO ₂ , SnO ₂ and ITO (indium tin oxide); polyaniline, polypyrrole, polythiophene, polyacetylene, polyparaphenylene vinylene, Conductive polymer compounds such as polydiacetylene; semiconductors such as silicon, germanium, and gallium arsenide; carbon materials such as carbon black, fullerene, carbon nanotube, and graphite can be used. Further, the conductive polymer compound or the semiconductor may be doped. Examples of the dopant used for the doping include acids such as hydrochloric acid, sulfuric acid and sulfonic acid; Lewis acids such as PF ₅ , AsF ₅ and FeCl ₃ ; halogens such as iodine; metals such as lithium, sodium and potassium. . In addition, conductive composite materials in which particles such as carbon black and metal particles (gold particles, platinum particles, silver particles, copper particles, etc.) are dispersed in these materials (however, materials different from those described later) are also used. .

  Although not shown in FIG. 1, wiring is connected to the source electrode 1, the drain electrode 3, and the gate electrode 5. The wiring is made of a material having substantially the same conductivity as that used for the source electrode 1, the drain electrode 3, and the gate electrode 5.

As the insulator layer 4, an insulating material (insulator material) is used. Examples of the insulating material include polyparaxylylene, polyacrylate, polymethyl methacrylate, polystyrene, polyvinylphenol, polyamide, polyimide, polycarbonate, polyester, polyvinyl alcohol, polyvinyl acetate, polyurethane, polysulfone, epoxy resin, Polymers such as phenol resins and copolymers in which two or more of these polymer structural units are combined; oxides (non-ferroelectric) such as silicon dioxide, aluminum oxide, titanium oxide, tantalum oxide; SrTiO ₃ , BaTiO _3, etc. Ferroelectric oxides; nitrides such as silicon nitride and aluminum nitride; sulfides; dielectrics such as fluorides can be used. In addition, as the material having the insulating property, a material in which particles of the dielectric (however, a material different from the polymer) are dispersed in a polymer can be used. The thickness of the insulator layer 4 varies depending on the material constituting the insulator layer 4, but is usually 0.1 nm to 100 μm, preferably 0.5 nm to 50 μm, more preferably 5 nm to 10 μm.

  The semiconductor layer 2 may be at least one semiconductor layer made of the organic semiconductor of the present invention, and is laminated with at least one semiconductor layer made of the organic semiconductor of the present invention and at least one semiconductor layer made of another organic semiconductor. It may be what you did.

  The thickness of the semiconductor layer 2 is preferably as thin as possible without losing necessary functions. In lateral field effect transistors such as the field effect transistors 10A, 10B, and 10D, the characteristics of the field effect transistor do not depend on the thickness of the semiconductor layer 2 as long as the semiconductor layer 2 has a predetermined thickness or more. Since the leakage current often increases as the thickness of the semiconductor layer 2 increases, the thickness of the semiconductor layer 2 is preferably in an appropriate range. The thickness of the semiconductor layer 2 is usually 0.1 nm to 10 μm, preferably 0.5 nm to 5 μm, more preferably 1 nm to 1 nm in order for the semiconductor layer 2 to perform the function required for the semiconductor layer 2. 3 μm.

  In the field effect transistor of the present invention, other layers may be provided between the above-described components or on the exposed surfaces of the above-described components as necessary. For example, the protective layer may be formed directly or via another layer on the semiconductor layer in the field effect transistor of the present invention. As a result, the influence of outside air such as humidity on the electrical characteristics of the field effect transistor can be reduced to stabilize the electrical characteristics of the field effect transistor, and the electrical characteristics such as the ON / OFF ratio of the field effect transistor can be improved. Can be made.

  Although it does not specifically limit as a material which comprises the said protective layer, For example, various resins, such as acrylic resins, such as an epoxy resin and polymethylmethacrylate, a polyurethane, a polyimide, polyvinyl alcohol, a fluororesin, polyolefin; silicon oxide, aluminum oxide, An inorganic oxide film such as silicon nitride; a dielectric such as a nitride film is preferable, and a resin (polymer) having a low oxygen transmission rate, a water transmission rate, and a low water absorption rate is more preferable. As a material constituting the protective layer, a protective material that has been developed for an organic EL display in recent years can also be used. Although the arbitrary thickness can be employ | adopted for the thickness of the said protective layer according to the objective, Usually, they are 100 nm-1 mm.

  In addition, by performing surface treatment on the surface on which the semiconductor layer is formed (substrate surface, insulator layer surface, or the like) before forming the semiconductor layer, the characteristics of the field effect transistor can be improved. For example, the quality of the semiconductor layer formed on the surface can be improved by adjusting the degree of hydrophilicity / hydrophobicity of the surface on which the semiconductor layer is formed. In particular, the characteristics of a semiconductor layer made of an organic semiconductor may vary greatly depending on the state of the layer, such as molecular orientation. Therefore, the surface treatment on the surface where the semiconductor layer is formed controls the molecular orientation at the interface between the surface where the semiconductor layer is formed and the semiconductor layer formed on the surface, and the semiconductor layer is formed. It is considered that trap sites in the base material (substrate, insulator layer, etc.) to be formed are reduced, and these improve characteristics such as carrier mobility of the field effect transistor. The trap site refers to a functional group such as a hydroxyl group present in an untreated substrate. When such a functional group is present in the base material on which the semiconductor layer is formed, electrons are attracted to the functional group, and as a result, the carrier mobility of the field effect transistor decreases. Therefore, reducing trap sites in the base material on which the semiconductor layer is formed is often effective in improving characteristics such as carrier mobility of the field effect transistor. Examples of the surface treatment of the substrate on which such a semiconductor layer is formed include, for example, a hydrophobic treatment with hexamethyldisilazane, cyclohexene, octadecyltrichlorosilane, etc .; an acid treatment with acids such as hydrochloric acid, sulfuric acid, acetic acid; sodium hydroxide Alkali treatment with alkali such as potassium hydroxide, calcium hydroxide, ammonia, etc .; ozone treatment; fluorination treatment; plasma treatment with plasma such as oxygen plasma or argon plasma; formation treatment of Langmuir / Blodgett film; Examples include a process for forming a semiconductor thin film; a mechanical process; an electrical process such as corona discharge; and a rubbing process using fibers.

  As a method for forming each layer and each electrode of the field effect transistor of the present invention, for example, a vacuum deposition method, a sputtering method, a coating method, a printing method (inkjet printing or the like), a sol-gel method, or the like can be appropriately employed. As a method for forming each layer and each electrode, a coating method or a printing method such as inkjet printing is preferable in consideration of cost and labor.

[Method of Manufacturing Field Effect Transistor]
Next, a method for manufacturing a field effect transistor according to the present invention will be described below with reference to FIG. 2, taking as an example a bottom contact-bottom contact field effect transistor (FET) 10A of the embodiment shown in FIG. .

  This manufacturing method can be similarly applied to field effect transistors of other modes such as the above-described field effect transistors 10B to 10E.

(Preparation of substrate 6 and surface treatment of substrate 6)
In the method of manufacturing the field effect transistor 10A, first, the substrate 6 is prepared (see FIG. 2A), and the field effect transistor 10A is manufactured by providing various layers and electrodes necessary on the substrate 6. As the substrate 6, those described above can be used. It is also possible to perform the above-described surface treatment on the substrate 6. The thickness of the substrate 6 is preferably thin as long as necessary functions are not hindered. Although the thickness of the board | substrate 6 changes also with the material which comprises the board | substrate 6, it is 1 micrometer-10 mm normally, Preferably it is 5 micrometers-5 mm. If necessary, the substrate 6 may have an electrode function.

(Formation of the gate electrode 5)
Next, the gate electrode 5 is formed on the substrate 6 (see FIG. 2B). As a method for forming the gate electrode 5, various methods can be used. For example, a vacuum deposition method, a sputtering method, a coating method, a thermal transfer method, a printing method, a sol-gel method, or the like can be employed. When forming a layer of a material (electrode material) constituting the gate electrode 5, or after forming the layer, the layer is preferably patterned so as to have a desired shape as necessary. Various methods can be used as the layer patterning method, and examples thereof include a photolithography method in which patterning and etching of a photoresist are combined. It is also possible to pattern layers using printing methods such as inkjet printing, screen printing, offset printing, letterpress printing, etc .; soft lithography techniques such as microcontact printing; or a combination of these techniques. is there. The thickness of the gate electrode 5 varies depending on the material constituting the gate electrode 5, but is usually 0.1 nm to 10 μm, preferably 0.5 nm to 5 μm, more preferably 1 nm to 3 μm. When a single conductive substrate serves as the gate electrode 5 and the substrate 6, the thickness of the single conductive substrate may be larger than the range of the thickness of the gate electrode 5 described above.

(Formation of insulator layer 4)
Next, the insulator layer 4 is formed on the gate electrode 5 (see FIG. 2C). Various methods can be used to form the insulator layer 4. Examples of methods that can be used for forming the insulator layer 4 include spin coating, spray coating, dip coating, casting, bar coating, blade coating, and other coating methods; screen printing, offset printing, inkjet printing, and the like; Various methods such as a vacuum process, a molecular beam epitaxial growth method, an ion cluster beam method, an ion plating method, a sputtering method, an atmospheric pressure plasma method, a dry process method such as a CVD (chemical vapor deposition) method and the like can be mentioned. As a method for forming the insulator layer 4, other methods such as a sol-gel method or a method of forming an oxide film by oxidizing a metal surface layer, such as a method of forming alumite on aluminum, can be employed.

  In the portion where the insulator layer 4 and the semiconductor layer 2 are in contact with each other, a molecule of a compound constituting the semiconductor layer 2 at the interface between the insulator layer 4 and the semiconductor layer 2, for example, represented by the general formula (1) above. In order to satisfactorily align the compound molecules, the insulator layer 4 may be subjected to a predetermined surface treatment. As the surface treatment method of the insulator layer 4, the same method as the surface treatment method of the substrate 6 can be used. The thickness of the insulator layer 4 is preferably as thin as possible without impairing its function. The thickness of the insulator layer 4 is usually 0.1 nm to 100 μm, preferably 0.5 nm to 50 μm, more preferably 5 nm to 10 μm.

(Formation of source electrode 1 and drain electrode 3)
Next, the source electrode 1 and the drain electrode 3 are formed on the insulator layer 4 (see FIG. 2D). The method for forming the source electrode 1 and the drain electrode 3 can be based on the method for forming the gate electrode 5.

(Formation of semiconductor layer 2)
Next, the semiconductor layer 2 is formed on the exposed portion of the upper surface of the insulator layer 4, a part of the upper surface of the source electrode 1, and a part of the upper surface of the drain electrode 3 (FIG. 2E). reference). In forming the semiconductor layer 2, the above-described method for forming a semiconductor layer can be used. In this step, an object (adherent) on which the semiconductor layer 2 is formed is composed of the source electrode 1, the drain electrode 3, the insulator layer 4, the gate electrode 5, and the substrate 6 shown in FIG. The surface (deposition surface) on which the semiconductor layer 2 is formed is an exposed portion on the upper surface of the insulator layer 4, a portion of the upper surface of the source electrode 1, and a portion of the upper surface of the drain electrode 3. It is.

(Post-processing of semiconductor layer 2)
The semiconductor layer 2 formed in this way can be further improved in characteristics by post-processing. For example, by performing heat treatment as a post-treatment of the semiconductor layer 2, the semiconductor characteristics of the semiconductor layer 2 can be improved and stabilized. This is because the strain in the semiconductor layer 2 generated during the formation of the semiconductor layer 2 is relaxed, pinholes in the semiconductor layer 2 are reduced, and the arrangement and orientation of molecules in the semiconductor layer 2 are controlled. It depends on what is considered possible.

  Therefore, when the field effect transistor of the present invention is manufactured, the above heat treatment is effective for improving the characteristics of the field effect transistor. That is, in order to improve the characteristics of the field effect transistor, the field effect transistor manufacturing method includes a first step of forming the semiconductor layer 2 and a second step of heat-treating the semiconductor layer 2 after the first step. Are preferably included.

  The heat treatment is performed by heating the stacked body including the semiconductor layer 2 (here, the field effect transistor 10A shown in FIG. 2E) after the semiconductor layer 2 is formed. The temperature of the heat treatment is not particularly limited, but is usually from room temperature to 150 ° C., preferably 40 to 120 ° C., more preferably 45 to 100 ° C. The heat treatment time is not particularly limited, but is usually 1 minute to 24 hours, preferably 2 minutes to 3 hours. Regarding the atmosphere of the heat treatment, the heat treatment may be performed in the air, or the heat treatment may be performed in an inert atmosphere such as nitrogen or argon.

  The heat treatment may be performed at any stage as long as the semiconductor layer 2 is formed. For example, when this manufacturing method is applied to the top contact type field effect transistors 10B, 10C, etc., the source electrode 1 and the drain electrode 3 may be formed in addition to the semiconductor layer 2 and then heat treatment may be performed. After the formation of 2, heat treatment may be performed before the formation of the source electrode 1 and the drain electrode 3.

The compound of the general formula (1) preferably used for the semiconductor layer 2 has a melting point that varies depending on the length of the aliphatic hydrocarbon group which may have a halogen atom represented by R ¹ and R ^2. In some cases, it has two thermal phase transition points. About melting | fusing point, what is necessary is just to measure by visual observation by a normal method using a hotplate type melting | fusing point measuring device (made by Yanaco apparatus development laboratory). The thermal phase transition point can be measured by performing differential thermal analysis using a device such as a differential scanning calorimeter (trade name “EXSTAR DSC6200” manufactured by Hitachi High-Tech Science Co., Ltd.).

  When the semiconductor layer 2 is composed of the compound of the general formula (1) that does not have a thermal phase transition point, the temperature of the heat treatment is preferably equal to or lower than the melting start temperature of the compound of the general formula (1). Is room temperature or higher, preferably 45 ° C. or higher, more preferably 80 ° C. or higher, and further preferably 100 ° C. or higher.

  When the semiconductor layer 2 is composed of the compound of the above general formula (1) having two thermal phase transition points (thermal phase transition temperatures), the temperature range of the heat treatment is a range between the two thermal phase transition points, That is, it is preferable that the temperature range is not less than the thermal phase transition point on the low temperature side and not more than the thermal phase transition point on the high temperature side. Since this temperature range varies depending on the type of the compound of the general formula (1), it is difficult to say generally, but the approximate range is usually 80 ° C. or higher and 150 ° C. or lower, preferably 80 ° C. It is 100 degreeC or more and 130 degrees C or less, More preferably, they are 100 degreeC or more and 130 degrees C or less.

  The temperature at which the heat treatment is performed is more important than the stage at which the heat treatment is performed. As described above, when the heat treatment is performed at an appropriate temperature, the characteristics of the semiconductor layer 2 tend to be superior to those when the heat treatment is similarly performed at an inappropriate temperature, and the carrier mobility of the semiconductor layer 2 is several times to 10 times or more. May also improve.

  Further, as another post-treatment method for the semiconductor layer 2, oxidation or reduction is performed by treating the semiconductor layer 2 with an oxidizing gas such as oxygen, a reducing gas such as hydrogen, an oxidizing liquid, a reducing liquid, or the like. A change in the characteristics of the semiconductor layer 2 can also be induced. This can be used for the purpose of increasing or decreasing the carrier density in the semiconductor layer 2, for example.

In addition, in a technique called doping, characteristics of the semiconductor layer 2 can be changed by adding (doping) a small amount of dopant (element, atomic group, molecule, or polymer) to the semiconductor layer 2. For example, oxidizing gases such as oxygen; reducing gases such as hydrogen; acids such as hydrochloric acid, sulfuric acid and sulfonic acid; Lewis acids such as PF ₅ , AsF ₅ and FeCl ₃ ; halogen atoms such as iodine; sodium and potassium The semiconductor layer 2 can be doped with a dopant such as a metal atom. This is a method in which a dopant in a gas state is brought into contact with the semiconductor layer 2 (when the dopant is a gas), and a method in which the semiconductor layer 2 is immersed in a dopant in a solution state when the dopant is a solution (the dopant is in a solution state). In the case of electrochemical doping). These dopants do not necessarily have to be added after the formation of the semiconductor layer 2. When the semiconductor layer 2 is formed by using the semiconductor layer forming ink, or when adding the semiconductor layer 2 material, It may be added to the semiconductor layer forming ink. Further, a dopant is added to the material for forming the semiconductor layer 2 and co-evaporated, or the dopant is mixed in an ambient atmosphere when the semiconductor layer 2 is formed (the semiconductor layer 2 is formed in an environment in which the dopant is present). It is also possible to perform doping by accelerating dopant ions in vacuum and colliding with the semiconductor layer 2.

  These doping effects include changes in electrical conductivity due to increase or decrease in carrier density, changes in carrier polarity (p-type and n-type), changes in Fermi level, and the like. Such doping is often used particularly in a semiconductor element using an inorganic semiconductor material such as silicon.

(Formation of protective layer 7)
The field effect transistor 10A is completed by the process of forming the semiconductor layer 2 described above (see FIG. 2E). If necessary, a protective layer 7 is formed on the semiconductor layer 2 after the formation of the semiconductor layer 2. Also good. Forming the protective layer 7 on the semiconductor layer 2 has the advantages that the influence of outside air can be minimized and the electrical characteristics of the organic field effect transistor 10A can be stabilized.

  Although the thickness of the protective layer 7 can employ | adopt arbitrary thickness according to the objective, Usually, they are 100 nm-1 mm.

  Various methods can be adopted as a method for forming the protective layer 7, but when the protective layer 7 is made of a resin, for example, a method of applying a resin-containing solution and then drying to form a resin layer, The method of polymerizing after apply | coating or vapor-depositing the monomer of resin etc. is mentioned. You may perform a crosslinking process after formation of a resin layer. When the protective layer 7 is made of an inorganic material, as a method for forming the protective layer 7, for example, a forming method by a vacuum process such as a sputtering method or a vapor deposition method; a forming method by a solution process such as a sol-gel method can be used.

  In the field effect transistor of the present invention, a protective layer can be provided as necessary between the constituent elements in addition to the semiconductor layer. Such a protective layer may help to stabilize the electrical properties of the organic field effect transistor.

  Since the field effect transistor of the present invention uses an organic material as a semiconductor material constituting the semiconductor layer, it can be manufactured in a relatively low temperature process. Therefore, in the field effect transistor of the present invention, a flexible material such as a plastic plate or a plastic film that could not be used under conditions exposed to a high temperature can be used as the substrate. As a result, in the field effect transistor of the present invention, by using a flexible material as a substrate, a light-weight and flexible field-effect transistor that is hard to break can be realized, and is suitably used as a switching element in an active matrix display. it can. Examples of the display include a liquid crystal display, a polymer dispersed liquid crystal display, an electrophoretic display, an EL (electroluminescence) display, an electrochromic display, and a particle rotation display.

  Furthermore, in the field effect transistor of the present invention, when the semiconductor layer is composed of two or more different compounds represented by the general formula (1), the semiconductor layer can be formed by a solution process such as coating. Therefore, the field effect transistor in that case can be manufactured at a very low cost compared to the case of using an organic semiconductor that cannot form a semiconductor layer without using a vacuum process such as vapor deposition, and is also suitable for manufacturing a large area display. ing.

  The field effect transistor of the present invention can also be used as a digital element or an analog element such as a memory circuit element, a signal driver circuit element, and a signal processing circuit element. Furthermore, an IC (integrated circuit) card or an IC tag can be produced by combining these. Furthermore, since the field effect transistor of the present invention can change its characteristics by an external stimulus such as a chemical substance, it can be used as an FET sensor.

  The operational characteristics of a field effect transistor are: carrier mobility of semiconductor layer, conductivity, capacitance of insulator layer, element configuration (distance between source electrode and drain electrode, width of source electrode and drain electrode, insulator It depends on the thickness of the layer). The organic semiconductor used for the field effect transistor is preferably as high as possible in carrier mobility.

  The organic semiconductor of the present invention, which is a solid solution containing two or more different compounds represented by the general formula (1), has good film formability when used for forming a semiconductor layer, and is applicable to a large area. There is. Moreover, the compound represented by the said General formula (1) can be manufactured at low cost. Furthermore, pentacene derivatives and the like are unstable and difficult to handle, such as decomposition in the atmosphere due to moisture contained in the atmosphere. On the other hand, when the compound represented by the general formula (1) of the present invention is used as a material for the semiconductor layer, a solid solution containing two or more different compounds represented by the general formula (1). The organic semiconductor of the present invention has the advantage of high stability and long life even after the formation of the semiconductor layer.

[Organic electronics devices other than field-effect transistors]
The organic semiconductor which is a solid solution containing two or more kinds of different compounds represented by the general formula (1) according to the present invention can be used for organic electronic devices other than field effect transistors. The organic electronic device of the present invention includes a semiconductor layer made of an organic semiconductor that is a solid solution containing two or more different compounds represented by the general formula (1) according to the present invention. Examples of the organic electronics device other than the field effect transistor include a photoelectric conversion element, an organic solar cell, an organic EL element, an organic light emitting transistor element, and an organic semiconductor laser element.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated still in detail, this invention is not limited to these examples.

[Example 1]
(Preparation of semiconductor layer forming ink)
0.75 parts by mass of 2,7-dihexyl [1] benzothieno [3,2-b] [1] benzothiophene (compound No. 12 in Table 1; hereinafter referred to as “C6-BTBT”); -Dioctyl [1] benzothieno [3, 2-b] [1] benzothiophene (compound No. 16 in Table 1; hereinafter referred to as "C8-BTBT") 0.25 parts by mass dissolved in 99 parts by mass of toluene As a result, a toluene solution containing a mixture (organic semiconductor) composed of 75% by mass of C6-BTBT and 25% by mass of C8-BTBT at a concentration of 1% by mass was prepared as a semiconductor layer forming ink.

(Production of bottom contact-bottom gate type field effect transistor)
In this example, a field effect transistor according to an example of the bottom contact-bottom gate type field effect transistor 10A shown in FIG.

In this example, an n-doped silicon wafer (surface resistance of 0.03 Ω · cm or less) having a 300 nm thick SiO ₂ thermal oxide film (SiO ₂ film formed by thermal oxidation of silicon) attached on one side is used as an insulator. Used as layer 4, gate electrode 5, and substrate 6. In the field effect transistor of this embodiment, the SiO ₂ thermal oxide film has the function of the insulator layer 4, and the n-doped silicon wafer has the functions of the substrate 6 and the gate electrode 5.

On the surface of SiO ₂ thermal oxide film in the n-doped silicon wafer with SiO ₂ thermal oxide film is attached, that the resist material is applied, exposed patterned, wherein the chromium is 1nm deposition, further 40nm depositing gold Thus, a source electrode 1 and a drain electrode 3 (bottom contact type electrode having a channel length of 200 μm and a channel width of 2.5 mm) made of a chromium layer having a thickness of 1 nm and a gold layer having a thickness of 40 nm were formed. Next, the resist was peeled off.

The semiconductor layer forming ink is spun on the exposed portion of the upper surface of the SiO ₂ thermal oxide film, a part of the upper surface of the source electrode 1 and a part of the upper surface of the drain electrode 3 at a rotation speed of 500 rpm for 5 seconds. Then, the semiconductor layer forming ink was spin-coated at 2000 rpm for 20 seconds to form an organic semiconductor thin film having a thickness of about 50 nm as the semiconductor layer 2. As will be described later, the organic semiconductor thin film was confirmed to be a solid solution from the measurement result of the out-of-plane X-ray diffraction spectrum.

The obtained field effect transistor was installed in a prober, and the semiconductor characteristics of the field effect transistor were measured using “Semiconductor Parameter Analyzer 4200-SCS” (manufactured by Keithley Instruments). Regarding the semiconductor characteristics of the field effect transistor, the drain voltage was −100 V, the gate voltage was scanned from 20 V to −100 V, and the drain current-gate voltage characteristics (transfer characteristics) were measured. From the obtained drain current-gate voltage curve, in the field effect transistor of this example, the organic semiconductor thin film functions as a p-type organic semiconductor, and the carrier mobility (hole mobility) is 1.0 cm ² / V · s. The threshold voltage was −35 V, and the on / off ratio (the ratio Ion / Ioff between the on-state current Ion and the off-state current Ioff) was 10 ⁸ .

[Example 2]
(Preparation of semiconductor layer forming ink)
0.58 parts by mass of C8-BTBT and 2,7-didecyl [1] benzothieno [3,2-b] [1] benzothiophene (compound No. 18 in Table 1; hereinafter referred to as “C10-BTBT”) 0 A semiconductor layer is formed by dissolving 50 parts by mass in 99 parts by mass of toluene to form a toluene solution containing a mixture (organic semiconductor) composed of 50% by mass of C8-BTBT and 50% by mass of C10-BTBT at a concentration of 1% by mass. It was produced as an ink.

(Production of bottom contact-bottom gate type field effect transistor)
A bottom contact-bottom gate type field effect transistor was produced in the same manner as in Example 1 except that the obtained ink for forming a semiconductor layer was used. The organic semiconductor thin film of this field effect transistor was confirmed to be a solid solution from an out-of-plane X-ray diffraction spectrum as described later.

The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, in the field effect transistor of this example, the organic semiconductor thin film functions as a p-type organic semiconductor, and carrier mobility (hole mobility). Was 0.50 cm ² / V · s, the threshold voltage was −9 V, and the on / off ratio was 10 ⁷ .

[Comparative Example 1]
(Preparation of semiconductor layer forming ink)
By dissolving 1.0 part by mass of C6-BTBT in 99 parts by mass of toluene, a toluene solution containing C6-BTBT at a concentration of 1% by mass was prepared as a semiconductor layer forming ink.

(Production of bottom contact-bottom gate type field effect transistor)
A bottom contact-bottom gate type field effect transistor was produced in the same manner as in Example 1 except that the obtained ink for forming a semiconductor layer was used. The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, the field effect transistor of this example has a carrier mobility (hole mobility) of 0.11 cm ² / V · s, and a threshold value. The voltage was −14V and the on / off ratio was 10 ⁷ .

[Comparative Example 2]
Except for using C8-BTBT instead of C6-BTBT, a semiconductor layer forming ink was prepared and a bottom contact-bottom gate type field effect transistor was prepared in the same manner as in Comparative Example 1. The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, the field effect transistor of this example has a carrier mobility (hole mobility) of 0.20 cm ² / V · s, and a threshold value. The voltage was −9 V and the on / off ratio was 10 ⁵ .

[Comparative Example 3]
Except for using C10-BTBT instead of C6-BTBT, a semiconductor layer forming ink was prepared and a bottom contact-bottom gate type field effect transistor was prepared in the same manner as in Comparative Example 1. When the characteristics of the obtained field effect transistor were measured in the same manner as in Example 1, the field effect transistor of this example had a carrier mobility (hole mobility) of 0.21 cm ² / V · s, and a threshold value. The voltage was −9 V and the on / off ratio was 10 ⁷ .

Example 3
(Preparation of semiconductor layer forming ink)
In the same manner as in Example 1, a semiconductor layer forming ink was prepared.

(Production of top contact-bottom gate type field effect transistor)
In this example, a field effect transistor according to an example of the top contact-bottom gate type field effect transistor 10B shown in FIG.

In this example, an n-doped silicon wafer (surface resistance of 0.03 Ω · cm or less) having a SiO ₂ thermal oxide film having a thickness of 300 nm (a SiO ₂ film formed by thermal oxidation of silicon) attached on one side is cleaned, This was used as the insulator layer 4, the gate electrode 5, and the substrate 6. In the field effect transistor of this embodiment, the SiO ₂ thermal oxide film has the function of the insulator layer 4, and the n-doped silicon wafer has the functions of the substrate 6 and the gate electrode 5.

On the surface of SiO ₂ thermal oxide film SiO ₂ thermal oxide film with n-doped silicon wafer is attached, the semiconductor layer forming ink was 5 seconds at a spin speed 500 rpm, followed by the semiconductor layer forming ink Was spin-coated at 2000 rpm for 20 seconds, and an organic semiconductor thin film having a thickness of about 50 nm was formed as the semiconductor layer 2. As will be described later, the organic semiconductor thin film was confirmed to be a solid solution from the measurement result of the out-of-plane X-ray diffraction spectrum.

Next, a shadow mask for electrode preparation is attached to the n-doped silicon wafer to which the SiO ₂ thermal oxide film and the organic semiconductor thin film are attached, and the shadow mask is set in a vacuum deposition apparatus. It exhausted until it became less than * 10 <^-4> Pa. Then, a field effect transistor according to an example of the present invention, which is a top contact-bottom gate type, is formed by depositing a gold electrode as a source electrode 1 and a drain electrode 3 with a thickness of 50 nm on the organic semiconductor thin film by resistance heating evaporation. (Channel length 200 μm, channel width 2.5 mm) was obtained.

The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, in the field effect transistor of this example, the organic semiconductor thin film functions as a p-type organic semiconductor (the field effect transistor is driven p-type). The carrier mobility (hole mobility) was 1.1 cm ² / V · s, the threshold voltage was −31 V, and the on / off ratio was 10 ⁵ .

Example 4
(Preparation of semiconductor layer forming ink)
A semiconductor layer forming ink containing an organic semiconductor composed of 75% by mass of C8-BTBT and 25% by mass of C10-BTBT was produced in the same manner as in Example 2 except that the amount of C8-BTBT and C10-BTBT was changed. .

(Production of top contact-bottom gate type field effect transistor)
A top contact-bottom gate type field effect transistor was produced in the same manner as in Example 3 except that the obtained ink for forming a semiconductor layer was used. The organic semiconductor thin film of this field effect transistor was confirmed to be a solid solution from an out-of-plane X-ray diffraction spectrum as described later.

The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, in the field effect transistor of this example, the organic semiconductor thin film functions as a p-type organic semiconductor, and carrier mobility (hole mobility). Was 0.93 cm ² / V · s, the threshold voltage was −34 V, and the on / off ratio was 10 ⁶ .

[Comparative Example 4]
(Preparation of semiconductor layer forming ink)
In the same manner as in Comparative Example 1, a semiconductor layer forming ink was prepared.

(Production of top contact-bottom gate type field effect transistor)
A top contact-bottom gate type field effect transistor was produced in the same manner as in Example 3 except that the obtained ink for forming a semiconductor layer was used. The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, the field effect transistor of this example has a carrier mobility (hole mobility) of 1.1 cm ² / V · s, and has a threshold value. The voltage was −34V and the on / off ratio was 10 ⁶ .

[Comparative Example 5]
A top contact-bottom gate type field effect transistor was produced in the same manner as in Comparative Example 4 except that C8-BTBT was used instead of C6-BTBT, in the same manner as in Comparative Example 4. The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, the field effect transistor of this example has a carrier mobility (hole mobility) of 0.28 cm ² / V · s, and a threshold value. The voltage was -28V and the on / off ratio was 10 ⁴ .

[Comparative Example 6]
A top contact-bottom gate type field effect transistor was prepared in the same manner as in Comparative Example 4 except that C10-BTBT was used instead of C6-BTBT in the same manner as in Comparative Example 4. The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, the field effect transistor of this example has a carrier mobility (hole mobility) of 0.30 cm ² / V · s, and a threshold value. The voltage was −20 V and the on / off ratio was 10 ⁴ .

  The composition of the organic semiconductor and the characteristics of the field effect transistors in Examples 1 and 2 and Comparative Examples 1 to 3 are shown in Table 4, and the composition of the organic semiconductor and the characteristics of the field effect transistors in Examples 3 and 4 and Comparative Examples 4 to 6 are shown in Table 4. Table 5 summarizes the results.

  From the comparison between Example 1 and Comparative Examples 1 and 2 in Table 4 and the comparison between Example 3 and Comparative Examples 4 and 5 in Table 5, a solid solution composed of C6-BTBT and C8-BTBT was used for the semiconductor layer. Compared with the field effect transistor in which the C6-BTBT single substance is used for the semiconductor layer and the field effect transistor in which the C8-BTBT single substance is used for the semiconductor layer, the field effect transistor generally improved significantly in carrier mobility. (However, the carrier mobility of the top contact-bottom gate type field effect transistor is about the same as that of a field effect transistor using a C6-BTBT alone as a semiconductor layer).

  Further, from the comparison between Example 2 and Comparative Examples 2 and 3 in Table 4 and the comparison between Example 4 and Comparative Examples 5 and 6 in Table 5, a solid solution composed of C8-BTBT and C10-BTBT was obtained as a semiconductor layer. The field effect transistor used in the present invention has a significantly improved carrier mobility compared to a field effect transistor using C8-BTBT alone as a semiconductor layer and a field effect transistor using C10-BTBT alone as a semiconductor layer. I understand.

Example 5
(Preparation of semiconductor layer forming ink)
A semiconductor layer forming ink containing an organic semiconductor composed of 50 mass% of C6-BTBT and 50 mass% of C8-BTBT was produced in the same manner as in Example 1 except that the amount of C6-BTBT and C8-BTBT was changed. .

(Production of bottom contact-bottom gate type field effect transistor)
A bottom contact-bottom gate type field effect transistor was produced in the same manner as in Example 1 except that the obtained ink for forming a semiconductor layer was used. The organic semiconductor thin film of this field effect transistor was confirmed to be a solid solution from an out-of-plane X-ray diffraction spectrum as described later.

The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, in the field effect transistor of this example, the organic semiconductor thin film functions as a p-type organic semiconductor, and carrier mobility (hole mobility). Was 0.67 cm ² / V · s, the threshold voltage was −52 V, and the on / off ratio was 10 ⁸ .

Example 6
(Preparation of semiconductor layer forming ink)
A semiconductor layer forming ink containing an organic semiconductor composed of C8-BTBT 50 mass% and C10-BTBT 50 mass% was produced in the same manner as in Example 4 except that the amount of C8-BTBT and C10-BTBT was changed. .

(Production of top contact-bottom gate type field effect transistor)
A top contact-bottom gate type field effect transistor was produced in the same manner as in Example 4 except that the obtained semiconductor layer forming ink was used. The organic semiconductor thin film of this field effect transistor was confirmed to be a solid solution from an out-of-plane X-ray diffraction spectrum as described later.

The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, in the field effect transistor of this example, the organic semiconductor thin film functions as a p-type organic semiconductor, and carrier mobility (hole mobility). Was 0.60 cm ² / V · s, the threshold voltage was −35 V, and the on / off ratio was 10 ⁵ .

Example 7
(Preparation of semiconductor layer forming ink)
A semiconductor layer forming ink containing an organic semiconductor composed of 25% by mass of C8-BTBT and 75% by mass of C10-BTBT was produced in the same manner as in Example 4 except that the amount of C8-BTBT and C10-BTBT was changed. .

(Production of top contact-bottom gate type field effect transistor)
A top contact-bottom gate type field effect transistor was produced in the same manner as in Example 4 except that the obtained semiconductor layer forming ink was used. The organic semiconductor thin film of this field effect transistor was confirmed to be a solid solution from an out-of-plane X-ray diffraction spectrum as described later.

The characteristics of the obtained field effect transistor were measured in the same manner as in Example 1. As a result, in the field effect transistor of this example, the organic semiconductor thin film functions as a p-type organic semiconductor, and carrier mobility (hole mobility). Was 0.41 cm ² / V · s, the threshold voltage was −37 V, and the on / off ratio was 10 ⁶ .

  The composition of the organic semiconductor and the characteristics of the field effect transistor in Example 5 are shown together in Table 6 together with the composition of the organic semiconductor and the characteristics of the field effect transistor in Example 1 and Comparative Examples 1 and 2. The composition of the organic semiconductor and the characteristics of the field effect transistor in Examples 6 and 7 are shown together in Table 7 together with the composition of the organic semiconductor and the characteristics of the field effect transistor in Example 4 and Comparative Examples 5 and 6.

  Table 6 and Table 7 show that the organic semiconductor of the present invention contains a compound having a linear or branched aliphatic hydrocarbon group with a shorter chain length (C6-BTBT in Table 6, C8-BTBT in Table 7). When the rate is 30 to 85 mass% (particularly 50 to 80 mass%), it is considered that the carrier mobility of the field effect transistor is remarkably improved.

[Comparative Example 7]
(Preparation of semiconductor layer forming ink)
By dissolving 0.50 parts by mass of C6-BTBT and 0.50 parts by mass of C10-BTBT in 99 parts by mass of toluene, 1 mixture (organic semiconductor) composed of 50% by mass of C6-BTBT and 50% by mass of C10-BTBT is dissolved. A toluene solution containing a concentration of mass% was prepared as a semiconductor layer forming ink.

(Production of bottom contact-bottom gate type field effect transistor)
A bottom contact-bottom gate type field effect transistor was produced in the same manner as in Example 1 except that the obtained ink for forming a semiconductor layer was used. The organic semiconductor thin film of this field effect transistor was confirmed not to be a solid solution but phase-separated from an out-of-plane X-ray diffraction spectrum as described later.

  From the comparison between Examples 1 to 7 and Comparative Example 7, in order to form a solid solution, a linear or branched aliphatic hydrocarbon contained in two or more kinds of compounds represented by the above general formula (1) Regarding the chain length of the group, it is considered preferable that the difference between the longest chain length and the shortest chain length is less than 4.

[Out-of-plane X-ray diffraction spectrum of organic semiconductor thin film]
Out-of-plane X-ray diffraction spectra were measured for the organic semiconductor thin films according to all the examples and the organic semiconductor thin film according to Comparative Example 7.

  The out-of-plane X-ray diffraction spectrum of the organic semiconductor thin film (a mixture of C6-BTBT and C8-BTBT; expressed as “C6 + C8” in the drawing) according to Example 5 is compared with the organic semiconductor thin film (C6- BTBT simple substance; expressed as “C6” in the figure) and an out-of-plane X-ray diffraction spectrum of the organic semiconductor thin film (C8-BTBT simple substance; indicated as “C8” in the figure) according to Comparative Example 2 are shown in FIG. . As shown in FIG. 3, in the out-of-plane X-ray diffraction spectrum of the mixture of C6-BTBT and C8-BTBT, the position corresponding to the peak of the out-of-plane X-ray diffraction spectrum of C6-BTBT alone, and the C8-BTBT alone There is no peak at any position corresponding to the peak of the out-of-plane X-ray diffraction spectrum, and a single peak exists at an intermediate position between these two positions. As a result, it was confirmed that the organic semiconductor thin film according to Example 5 had a uniform solid phase as a whole, that is, a solid solution.

  In addition, the out-of-plane X-ray diffraction spectrum of the organic semiconductor thin film according to Example 2 (mixture of C8-BTBT and C10-BTBT; expressed as “C8 + C10” in the figure) is compared with the organic semiconductor thin film according to Comparative Example 2 ( 4 together with the out-of-plane X-ray diffraction spectrum of the organic semiconductor thin film (C10-BTBT alone; shown as “C10” in the figure) according to Comparative Example 3 and C8-BTBT alone; indicated as “C8” in the figure. Shown in As shown in FIG. 4, in the out-of-plane X-ray diffraction spectrum of the mixture of C8-BTBT and C10-BTBT, the position corresponding to the peak of the out-of-plane X-ray diffraction spectrum of C8-BTBT alone, and the C10-BTBT alone There is no peak at any position corresponding to the peak of the out-of-plane X-ray diffraction spectrum, and a single peak exists at an intermediate position between these two positions. As a result, it was confirmed that the organic semiconductor thin film according to Example 2 had a uniform solid phase as a whole, that is, a solid solution. In the same manner, it was confirmed that the organic semiconductor thin films according to the other examples were uniformly solid, that is, a solid solution. Moreover, it was confirmed that the single peak shifts as the mixing ratio of the two types of compounds changes.

  Further, the out-of-plane X-ray diffraction spectrum of the organic semiconductor thin film according to Comparative Example 7 (mixture of C6-BTBT and C10-BTBT; expressed as “C6 + C10” in the drawing) FIG. 5 together with the out-of-plane X-ray diffraction spectrum of the organic semiconductor thin film (C10-BTBT simple substance; indicated as “C10” in the figure) according to Comparative Example 3 and C6-BTBT simple substance; indicated as “C6” in the figure. Shown in As shown in FIG. 5, in the out-of-plane X-ray diffraction spectrum of the mixture of C6-BTBT and C10-BTBT, the position corresponding to the peak of the out-of-plane X-ray diffraction spectrum of C6-BTBT alone, and the C10-BTBT alone Two peaks exist at positions corresponding to the peaks of the out-of-plane X-ray diffraction spectrum. In addition, in the out-of-plane X-ray diffraction spectrum of the mixture of C6-BTBT and C10-BTBT, the peak at the position corresponding to the peak of the out-of-plane X-ray diffraction spectrum of C6-BTBT alone is not a large peak. This indicates that the crystallinity is worsening. From these, it was confirmed that the organic semiconductor thin film according to Comparative Example 7 was not a uniform solid phase as a whole but was phase-separated into two phases.

  The present invention relates to the manufacture and use of organic semiconductors, products including semiconductor layers, particularly organic electronic devices (for example, field effect transistors, photoelectric conversion elements, organic solar cell elements, organic EL elements, organic light emitting transistor elements, organic semiconductor laser elements) Etc.) can be used for manufacturing and use.

DESCRIPTION OF SYMBOLS 1 Source electrode 2 Semiconductor layer 3 Drain electrode 4 Insulator layer 5 Gate electrode 6 Substrate 7 Protective layer 10A-10E Field effect transistor

Claims (12)

The following general formula (1)

(In the above formula, R ¹ and R ² each independently represents an aliphatic hydrocarbon group optionally having a halogen atom)
An organic semiconductor comprising a solid solution containing two or more different compounds represented by the formula: The organic semiconductor according to claim 1 ,
An organic semiconductor, wherein R ¹ and R ² in the general formula (1) are each independently an alkyl group having 1 to 36 carbon atoms. The organic semiconductor according to claim 1 or 2 ,
The aliphatic hydrocarbon group which may have a halogen atom is a linear or branched aliphatic hydrocarbon group which may have a halogen atom,
The chain length of the linear or branched aliphatic hydrocarbon group contained in the two or more kinds of compounds represented by the general formula (1) is such that the difference between the longest chain length and the shortest chain length is less than 4. An organic semiconductor characterized by being. The organic semiconductor according to any one of claims 1 to 3 ,
A solid solution containing two different compounds having a linear or branched aliphatic hydrocarbon group having a different chain length represented by the general formula (1),
An organic semiconductor comprising 30 to 85% by mass of a compound having a linear or branched aliphatic hydrocarbon group having a shorter chain length. The organic semiconductor according to any one of claims 1 to 4,
Organic semiconductor it is a p-type organic semiconductors in transistors. A organic semiconductor according to claim 5,
Organic semiconductor hole mobility you characterized in that at 0.01cm ² / V · s or more.   A semiconductor layer comprising the organic semiconductor according to claim 1. A semiconductor layer forming ink used for forming a semiconductor layer according to claim 7,
Two or more different compounds constituting the solid solution,
A semiconductor layer forming ink comprising a solvent.   A method for forming a semiconductor layer, comprising applying the ink for forming a semiconductor layer according to claim 8 on a surface on which the semiconductor layer is to be formed, and drying the applied ink. An organic electronic device comprising a semiconductor layer made of the organic semiconductor according to claim 1 .   A field effect transistor comprising the semiconductor layer according to claim 7. A method of manufacturing a field effect transistor according to claim 11,
A first step of forming the semiconductor layer;
And a second step of heat-treating the semiconductor layer after the first step.

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