JP7493228B2 - Organic semiconductor materials and organic thin film transistors - Google Patents

Description

The present invention relates to a condensed polycyclic aromatic compound, an organic semiconductor material and an organic semiconductor composition containing the compound, an organic thin film containing the organic semiconductor material, a method for producing the organic thin film, and an organic semiconductor device having the organic thin film.

Transistors are widely used in electronic devices these days and have become indispensable. However, manufacturing field-effect transistors using inorganic semiconductor materials such as amorphous silicon and polycrystalline silicon requires numerous vacuum processes, manufacturing costs such as doping with impurities, and running costs, which increases the manufacturing cost of field-effect transistors.

On the other hand, there is a growing demand for electronic paper and RFID tags, which need to be mass-produced at low cost, and printing processes (printed electronics), which enable low-cost, mass-production, and short-time circuit manufacturing, are attracting attention, and organic semiconductors, which can be applied as films, are attracting attention as semiconductor materials.

In addition, the demand for wearable electronic devices has increased in recent years, creating a need for technology to fabricate devices such as transistors on lightweight, flexible plastic substrates. However, because amorphous silicon and polycrystalline silicon films are formed at high temperatures, there is a drawback in that plastic materials with poor thermal durability cannot be used as substrates.

To solve the above problems, a technology that uses an organic semiconductor compound that is soluble in an organic solvent and can be applied to form a film to fabricate transistors by printing is seen as promising, and hopes are high for its practical application.

Methods for forming organic semiconductor layers include vacuum deposition and coating methods. If the coating method can be used, there is no need for the conventional manufacturing method using a vacuum process, which reduces manufacturing costs. In addition, existing printing processes such as inkjet printing and screen printing can be used, making it possible to mass-produce large-area organic transistor elements.

Furthermore, the temperature required during film formation can be reduced, and organic transistors using organic semiconductor compounds can be made using plastic materials for the substrate, making them applicable to flexible devices, and there are high hopes for their practical application.

In addition, a practical organic transistor must have high carrier mobility (also simply referred to as mobility) and thermal durability.
However, organic compounds generally construct the solid phase that becomes the semiconductor layer through interactions between adjacent molecules, and therefore the interactions are weaker than those of inorganic compounds, which can construct these layers through covalent bonds. This tends to increase the hindrance to carrier movement within the solid phase, and also reduces thermal durability. In particular, organic semiconductor compounds used in the channel layer of transistors must not undergo phase transitions such as melting over a wide temperature range, centered around room temperature. Here, phase transition refers to the change of an organic compound from a solid phase to a liquid phase, from a solid phase to a liquid crystal phase, from a solid phase to another solid phase, from a liquid crystal phase to a liquid phase, or the reverse change. The temperature at which these phase transitions occur is called the phase transition point, and the temperature at which the solid or liquid crystal phase transitions to the liquid phase is called the melting point.

As described above, organic semiconductors are required to have strong intermolecular interactions to achieve high carrier mobility and a high transition temperature to obtain thermal durability sufficient for practical use, which are essential physical properties for the practical application of organic transistors.

As organic semiconductor compounds for use in the channel layer of organic transistors, compounds with a main skeleton of a condensed polycyclic aromatic compound in which benzene rings or thiophene rings are condensed, such as pentacene, which has a structure in which five benzene rings are condensed, and benzothienobenzothiophene (BTBT) and dinaphthothienothiophene (DNTT), which are made up of benzene and thiophene rings, have been considered (Non-Patent Documents 1-3). These compounds exhibit practically high mobility due to the strong intermolecular interactions of the main skeleton, and also exhibit excellent thermal durability due to their high phase transition temperatures. However, these compounds are extremely poorly soluble in solvents, which has led to the problem that coating methods cannot be used to fabricate organic transistors.

Substituting alkyl groups into condensed polycyclic aromatic compounds has been studied for the purpose of increasing solubility in organic solvents, etc. In this case, when the number of condensed rings of benzene rings or thiophene rings is small, the compound shows sufficient solubility in solvents for application of coating methods, but the problem is that it is prone to phase transition at lower temperatures, which can be detrimental to the thermal durability of organic transistor devices.
For example, as described in Non-Patent Document 4, BTBT substituted with an alkyl group has high mobility while having solubility that allows for coating film formation, but has a transition point of 110° C., and Patent Document 1 indicates a problem regarding the thermal durability of semiconductor devices.
On the other hand, when the number of fused rings is large, the phase transition temperature shifts to the higher temperature side and the thermal durability of the organic transistor device is improved, but the solvent solubility becomes insufficient for application of a coating method.
For example, the compound described in Non-Patent Document 5, in which an alkyl group is added to dinaphthobenzodithiophene (DNBDT), which has a larger number of fused rings than the above-mentioned BTBT, exhibits high mobility and has a phase transition temperature of 200° C. or higher, and is therefore expected to be used for the production of highly heat-resistant organic transistors. However, since its solubility in solvents is extremely low at room temperature, the literature also discloses a solution preparation method and a coating film formation method under heating conditions.
Thus, there is generally a trade-off between solvent solubility and thermal durability, and there is a demand for the development of organic semiconductor materials (organic semiconductor compounds) that have both high solvent solubility and high thermal durability.

In addition, the thienobenzothienobenzothiophene (BTBTT) skeleton has been reported as an organic semiconductor material contained in organic transistors (Non-Patent Document 6 and Patent Documents 2-3). However, Non-Patent Document 6 and Patent Documents 2-3 only describe the carrier mobility of organic transistors fabricated by vapor deposition film formation, and neither document makes any mention of the solvent solubility for coating film formation or the thermal durability of organic transistor devices.

JP 2018-142704 A CN108690046A Patent No. 5352260

“Molecular beam deposited thin films of pentacene for organic field effect transistor applications”, J. Appl. Phys., 1996, 80, 2501-2508. “2,7-Diphenyl[1]benzothieno[3,2-b]benzothiophene, A New Organic Semiconductor for Air-Stable Organic Field-Effect Transistors with Mobilities up to 2.0 cm2 V-1 s-1”, J. Am. Chem. Soc., 2006, 128, 12604-12605. “Facile Synthesis of Highly π-Extended Heteroarenes, Dinaphtho[2,3-b:2‘,3‘-f]chalcogenopheno[3,2-b]chalcogenophenes, and Their Application to Field-Effect Transistors”, J. Am. Chem. Soc., 2007, 129, 2224-2225. “Highly Soluble [1]Benzothieno[3,2-b]benzothiophene (BTBT) Derivatives for High-Performance, Solution-Processed Organic Field-Effect Transistors”, J. Am. Chem. Soc. 2007, 129, 15732-15733. “High-Performance Solution-Processable N-Shaped Organic Semiconducting Materials with Stabilized Crystal Phase”, Adv. Mater., 2014, 26, 4546-4551. “Five-ring-fused asymmetric thienoacenes for high mobility organic thin-film transistors: the influence of the position of the S atom in the terminal thiophene ring” J. Mater. Chem. C, 2019, 7, 3656-3664.

Up to now, organic transistors using various organic compounds in the organic semiconductor layer have been proposed, but none of them can be said to have sufficiently satisfactory properties for practical use.
As described above, if an organic semiconductor material that has sufficient solvent solubility to be applied for film formation, high thermal durability, and high carrier mobility can be developed, organic thin-film transistors can be easily fabricated on any substrate using a coating film formation method such as printing, and flexible devices can be fabricated by integrating these. For example, if this is a thin film, it can be used as a transparent electrode for touch panels, electrodes for organic electroluminescence (EL) and organic solar cells, and can also be used as an electromagnetic wave absorbing sheet. Its industrial value is extremely high, but the current situation is that an organic semiconductor material that meets such demands has not yet been developed.

The present invention was made in consideration of the current situation, and aims to provide an organic transistor that can be fabricated by applying an organic semiconductor solution, has excellent thermal durability, and has high carrier mobility.

または

（上記一般式（１）および（２）中、Ｒ^１は芳香族炭化水素基または複素環基または炭素数１～２０のアルキル基であり、Ｒ^２およびＲ^３はいずれか一方が水素原子であり、もう一方はＲ^１が芳香族炭化水素基または複素環基であるときは炭素数１～２０のアルキル基であり、Ｒ^１が炭素数１～２０のアルキル基であるときは芳香族炭化水素基または複素環基である） As a result of intensive research aimed at solving the above-mentioned problems, the present inventors have found that a compound having a BTBTT skeleton represented by the following formula (1) or (2) and having different substituents at specific substitution positions exhibits sufficient solvent solubility and high phase transition temperature for forming a thin film by coating film formation, and further, an organic transistor using this compound as an organic semiconductor layer has extremely high carrier mobility and excellent heat durability, which has led to the completion of the present invention.

or

(In the above general formulas (1) and (2), R ¹ is an aromatic hydrocarbon group, a heterocyclic group, or an alkyl group having 1 to 20 carbon atoms, and one of R ² and R ³ is a hydrogen atom, and the other is an alkyl group having 1 to 20 carbon atoms when R ¹ is an aromatic hydrocarbon group or a heterocyclic group, and is an aromatic hydrocarbon group or a heterocyclic group when R ¹ is an alkyl group having 1 to 20 carbon atoms.)

（上記一般式（１）および（２）中、Ｒ^１は芳香族炭化水素基または複素環基または炭素数１～２０のアルキル基であり、Ｒ^２およびＲ^３はいずれか一方が水素原子であり、もう一方はＲ^１が芳香族炭化水素基または複素環基であるときは炭素数１～２０のアルキル基であり、Ｒ^１が炭素数１～２０のアルキル基であるときは芳香族炭化水素基または複素環基である）
〈２〉Ｒ^１は芳香族炭化水素基または複素環基であり、Ｒ^２およびＲ^３はいずれか一方が水素原子であり、もう一方は炭素数１～２０のアルキル基である、〈１〉に記載の化合物。
〈３〉Ｒ^２が水素原子である、〈１〉または〈２〉に記載の化合物。
〈４〉アルキル基が炭素数６～１２のアルキル基である、〈１〉～〈３〉のいずれかに記載の化合物。
〈５〉一般式（１）で示される、〈１〉～〈４〉のいずれかに記載の化合物。
〈６〉有機溶媒に対する２５℃における溶解度が０．０１質量％以上の、〈１〉～〈５〉のいずれかに記載の化合物。
〈７〉示差走査熱測定において１６０℃未満に相転移を示すピークが観測されない、〈１〉～〈６〉のいずれかに記載の化合物。
〈８〉〈１〉～〈７〉のいずれかに記載の化合物と有機溶媒とを含有する組成物。
〈９〉〈１〉～〈７〉のいずれかに記載の化合物を含有する有機半導体薄膜。
〈１０〉〈９〉に記載の有機半導体薄膜を含んでなる有機半導体デバイス。
〈１１〉〈９〉に記載の有機半導体薄膜を含んでなる有機トランジスタ。
〈１２〉有機半導体薄膜が単結晶である、〈１１〉に記載の有機トランジスタ。
〈１３〉〈８〉に記載の有機半導体組成物を基材上に塗布することにより有機半導体薄膜を製膜することを特徴とする、有機トランジスタの製造方法。
〈１４〉有機半導体薄膜が単結晶であることを特徴とする、〈１３〉に記載の有機トランジスタの製造方法。 Specifically, the present application provides the following inventions:
<1> A compound represented by the following general formula (1) or (2):

(In the above general formulas (1) and (2), R ¹ is an aromatic hydrocarbon group, a heterocyclic group, or an alkyl group having 1 to 20 carbon atoms, and one of R ² and R ³ is a hydrogen atom, and the other is an alkyl group having 1 to 20 carbon atoms when R ¹ is an aromatic hydrocarbon group or a heterocyclic group, and is an aromatic hydrocarbon group or a heterocyclic group when R ¹ is an alkyl group having 1 to 20 carbon atoms.)
<2> The compound according to <1>, wherein R ¹ is an aromatic hydrocarbon group or a heterocyclic group, and one of R ² and R ³ is a hydrogen atom and the other is an alkyl group having 1 to 20 carbon atoms.
<3> The compound according to <1> or <2>, wherein R ² is a hydrogen atom.
<4> The compound according to any one of <1> to <3>, wherein the alkyl group is an alkyl group having 6 to 12 carbon atoms.
<5> The compound according to any one of <1> to <4>, which is represented by general formula (1).
<6> The compound according to any one of <1> to <5>, which has a solubility of 0.01% by mass or more in an organic solvent at 25° C.
<7> The compound according to any one of <1> to <6>, which does not show a peak indicating a phase transition at less than 160° C. in differential scanning calorimetry.
<8> A composition containing the compound according to any one of <1> to <7> and an organic solvent.
<9> An organic semiconductor thin film containing the compound according to any one of <1> to <7>.
<10> An organic semiconductor device comprising the organic semiconductor thin film according to <9>.
<11> An organic transistor comprising the organic semiconductor thin film according to <9>.
<12> The organic transistor according to <11>, wherein the organic semiconductor thin film is a single crystal.
<13> A method for producing an organic transistor, comprising applying the organic semiconductor composition according to <8> onto a substrate to form an organic semiconductor thin film.
<14> The method for producing an organic transistor according to <13>, wherein the organic semiconductor thin film is a single crystal.

The condensed polycyclic aromatic compound of the present invention exhibits sufficient solvent solubility to produce a thin film by coating film formation, and organic semiconductor devices such as organic thin film transistors with high carrier mobility and excellent heat durability can be produced by coating film formation that does not require high-temperature treatment. Therefore, the condensed polycyclic aromatic compound of the present invention is particularly suitable as an organic semiconductor material in applications that use plastic as a substrate, such as wearable electronic devices.

FIG. 1 is a schematic diagram showing the structures of various main organic transistor elements, in which (a) shows an organic transistor with a bottom-contact-bottom-gate structure, (b) shows an organic transistor with a top-contact-bottom-gate structure, (c) shows an organic transistor with a top-contact-top-gate structure, (d) shows a top-and-bottom-contact bottom-gate type organic transistor, (e) shows a static induction type organic transistor, and (f) shows an organic transistor with a bottom-contact-top-gate structure. 1 is a schematic diagram of a process for manufacturing one embodiment of an organic transistor of the present invention. FIG. 2 is a diagram showing the results of differential thermal and thermogravimetric analysis of the condensed polycyclic aromatic compound No. 1 of the present invention. 1 is a diagram showing a differential scanning calorimetric curve of condensed polycyclic aromatic compound No. 1 of the present invention. FIG. 1 is a graph showing the change in drain current (transfer curve) when a transistor element using condensed polycyclic aromatic compound No. 1 of the present invention is subjected to a drain voltage of −50 V and a gate voltage sweep from 0 V to −50 V.

The present invention will be described in detail below.
The condensed polycyclic aromatic compound of the present invention has a structure represented by the above formula (1) or (2). In formulas (1) and (2), ^R1 represents an aromatic hydrocarbon group, a heterocyclic group, or an alkyl group having 1 to 20 carbon atoms, and one of ^R2 and ^R3 is a hydrogen atom, and the other represents an alkyl group having 1 to 20 carbon atoms when ^R1 is an aromatic hydrocarbon group or a heterocyclic group, or an aromatic hydrocarbon group or a heterocyclic group when ^R1 is an alkyl group having 1 to 20 carbon atoms.

The alkyl group having 1 to 20 carbon atoms represented by R ¹ to R ³ in formulas (1) and (2) is not limited to any of straight chain, branched chain, and alicyclic.
Specific examples of linear alkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl, n-nonadecyl, and n-eicosyl groups, etc. Specific examples of branched alkyl groups include isopropyl, isobutyl, t-butyl, isopentyl, t-pentyl, sec-pentyl, isohexyl, sec-heptyl, sec-nonyl, 2-ethylhexyl, and 2-hexyldecyl groups, etc. Specific examples of the alicyclic alkyl group include a cyclohexyl group, a cyclopentyl group, an adamantyl group, and a norbornyl group.
The alkyl groups represented by R ¹ to R ³ in formulas (1) and (2) are preferably linear or branched alkyl groups, more preferably linear alkyl groups. The number of carbon atoms in the alkyl groups represented by R ¹ to R ³ is preferably 4 to 14, more preferably 6 to 14, even more preferably 6 to 12, and most preferably 6 to 10, since the solubility and phase transition temperature decrease with an increase in the carbon number.

Specific examples of the aromatic hydrocarbon group represented by R ¹ to R ³ in formulas (1) and (2) include a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a pyrenyl group, and a phenalenyl group, etc. Since the aromatic hydrocarbon group having fewer carbon atoms has higher solubility, a phenyl group or a naphthyl group is preferable, and a phenyl group is more preferable.
The aromatic hydrocarbon groups represented by R ¹ to R ³ in formulas (1) and (2) may have an alkyl group as a substituent, and the alkyl group is not limited to being linear, branched, or alicyclic. Specific examples thereof include the same alkyl groups as those represented by R ¹ to R ³ in formulas (1) and (2).
Specific examples of the heterocyclic group represented by R ¹ to R ³ in formulas (1) and (2) include a pyridyl group, a pyrazyl group, a pyrimidyl group, a quinolyl group, an isoquinolyl group, a pyrrolyl group, an indolenyl group, an imidazolyl group, a carbazolyl group, a thienyl group, a furyl group, a pyranyl group, a pyridonyl group, a benzoquinolyl group, an anthraquinolyl group, a benzothienyl group, a benzofuryl group, and a thienothienyl group, etc. Since the heterocyclic group having fewer carbon atoms has higher solubility, a pyridyl group, a thienyl group, a benzothienyl group, or a thienothienyl group is preferred, a pyridyl group, a thienyl group, or a benzothienyl group is more preferred, and a pyridyl group or a thienyl group is even more preferred.
The heterocyclic groups represented by R ¹ to R ³ in formulae (1) and (2) may have an alkyl group as a substituent, and the alkyl group is not limited to being linear, branched, or alicyclic. Specific examples thereof include the same alkyl groups as those represented by R ¹ to R ³ in formulae (1) and (2).

Specific examples of compounds represented by formulas (1) and (2) are shown in Tables 1-1 to 1-3 below.

The condensed polycyclic aromatic compounds represented by the general formulas (1) and (2) are required to be soluble in an organic solvent in order to prepare a semiconductor layer by coating. Therefore, the organic solvent can be used without any particular limitation as long as it can dissolve the organic compounds represented by the general formulas (1) and (2). In addition, the solubility of the condensed polycyclic aromatic compounds in the organic solvent is preferably as high as possible, so there is no particular upper limit. However, when forming an organic semiconductor thin film by a solution process, if the concentration of the compound in the solution becomes too high, it may be difficult to form a thin film with high homogeneity, so the concentration of the compound may be appropriately adjusted according to the printing process. In addition, the lower the concentration, the more difficult it is to form a semiconductor thin film, so the lower limit is preferably 0.01 wt% or more, more preferably 0.02 wt%, and even more preferably 0.05 wt%.
As the organic solvent, halogenated solvents such as chloroform, chlorobenzene, dichlorobenzene, etc. can be used, but aromatic hydrocarbons such as benzene, toluene, xylene, mesitylene, tetrahydronaphthalene, cyclohexylbenzene, etc., ethers such as tetrahydrofuran, anisole, phenetole, butoxybenzene, etc. can also be used, and these organic solvents can be used alone or in combination of a plurality of organic solvents. From a practical standpoint and in consideration of environmental issues, etc., non-halogenated solvents are preferred.

The condensed polycyclic aromatic compounds represented by the general formulas (1) and (2) are characterized by not having a phase transition point below 160°C. Phase transition points indicate the temperature at which a substance undergoes a phase transition, such as the liquid crystal transition point indicating the transition temperature from a crystalline phase to a liquid crystal phase, the melting point indicating the transition temperature at which the solid phase and liquid crystal phase become isotropic liquids, and the sublimation point indicating the temperature at which the solid phase and liquid crystal phase directly transition to a gas phase without passing through a liquid. These temperatures are usually indicated by performing differential scanning calorimetry of the compound and observing the endothermic or exothermic peaks. In particular, the melting point at which the solid phase changes into a liquid phase, as well as the transition temperature at which a phase change with a large volume change, such as a nematic phase or a smectic A phase, is preferable to be higher, since it significantly impairs the carrier conduction of the semiconductor layer. In addition, taking into consideration the manufacturing process of the organic transistor device, i.e., sealing of the semiconductor layer with a resist or the like, the front plane manufacturing process, etc., and the use environment of the transistor device, it is preferable that the phase transition temperature is not less than 160°C, more preferably that the phase transition temperature is not less than 180°C, and even more preferably that the phase transition temperature is not less than 200°C.

The condensed polycyclic aromatic compounds represented by the general formulas (1) and (2) may be used alone as compounds having a single molecular structure, but may also be used in combination with a plurality of compounds depending on the intended use.Furthermore, they may also be used in combination with organic semiconductor compounds other than the condensed polycyclic aromatic compounds represented by the general formulas (1) and (2).
The condensed polycyclic aromatic compound represented by formula (1) or (2) may contain other organic semiconductor materials or various additives as necessary. Examples of the additives include semiconducting polymer compounds exhibiting semiconductivity and insulating polymer compounds exhibiting insulating properties. Specific examples of the semiconducting polymer compounds include polyacetylene-based polymers, polydiacetylene-based polymers, polyparaphenylene-based polymers, polyaniline-based polymers, polythiophene-based polymers, polyarylamine-based polymers, polypyrrole-based polymers, polythienylenevinylene-based polymers, polycarbazole-based polymers, polyindole-based polymers, polyparaphenylenevinylene-based polymers, and derivatives thereof. Specific examples of the insulating polymer materials include acrylic-based polymers, polyethylene-based polymers, polymethacrylate-based polymers, polystyrene-based polymers, polyethylene terephthalate-based polymers, nylon-based polymers, polyamide-based polymers, polyester-based polymers, vinylon-based polymers, polyisoprene-based polymers, cellulose-based polymers, copolymer-based polymers, and derivatives thereof. In addition, other additives, such as dopants, conductive materials, viscosity modifiers, leveling agents, and rheology modifiers, may be added as long as they do not impair the properties of the semiconductor device.

An organic thin film can be prepared using an organic semiconductor composition containing the condensed polycyclic aromatic compounds represented by the general formulas (1) and (2) of the present invention. The organic thin film may be in any form of glass, amorphous, or crystalline. The thickness of the organic thin film varies depending on the application, but is usually 0.5 nm to 1 μm, and preferably 1 nm to 1 μm.

Various methods can be used as the method for forming the organic semiconductor thin film of the present invention. Generally, the method for forming the organic semiconductor thin film is roughly divided into a method for forming by a vacuum process and a method for forming by a solution process, and either method may be used, but from a more practical viewpoint, a method for forming by a solution process is preferable. Examples of the method for forming the organic semiconductor thin film by the vacuum process include resistance heating deposition, electron beam deposition, sputtering, CVD, molecular beam epitaxial growth, and vacuum deposition. Examples of the solution process include printing methods such as spin coating, drop casting, dip coating, roll coater, bar coater, slit coating, die coater, and spraying, as well as inkjet printing, nanoimprinting, flexographic printing, and letterpress printing such as resin letterpress printing, offset printing, and lithographic printing, gravure printing, and intaglio printing such as lithographic printing, and hole plate printing such as screen printing. The organic semiconductor thin film can be formed by one of the above-mentioned formation methods, or by combining a plurality of the above-mentioned formation methods. In addition, by appropriately selecting the film-forming method and film-forming conditions, the size of the crystals can be adjusted, making it possible to produce films with low crystallinity as well as single crystal films.

The condensed polycyclic aromatic compounds represented by the general formulas (1) and (2) can be used as materials to fabricate organic semiconductor devices, and are suitable for use as materials for the organic thin films of organic semiconductor devices such as organic EL elements, organic solar cell elements, organic photoelectric conversion elements, and organic transistor elements. As an example, an organic transistor will be described in detail.

An organic transistor has two electrodes (a source electrode and a drain electrode) in contact with an organic semiconductor, and the current flowing between these electrodes is controlled by the voltage applied to another electrode called the gate electrode. In general, organic transistors often have a structure in which the gate electrode is insulated by an insulating film (Metal-Insulator-Semiconductor: MIS structure).

For practical performance of an organic transistor, it is necessary to have characteristics such as high carrier mobility (also simply called mobility) and a large on/off ratio. The on/off ratio refers to the ratio of the current value in the energized (on) state to the blocked (off) state, and the larger this ratio is, the better the switch is. The on/off ratio is preferable as it is higher, so there is no particular upper limit. In practical use, 1×10 ⁴ or more is preferable, and 1×10 ⁵ or more is more preferable. In addition, carrier mobility is a value indicating the ease of carrier movement, and depends on the structure of the organic device, such as carrier density, traps near the channel, and the dielectric constant of the insulator layer, and in organic semiconductor materials, it depends greatly on the interaction between adjacent molecules in the thin film (the degree of overlap of the π-conjugated systems of adjacent molecules) and the size of the crystal domain, so it depends greatly on the type of compound. It is one of the important indicators related to the response speed of the switch, and the higher it is, the better it is, so there is no particular upper limit. In practical terms, the carrier mobility is preferably 1 cm ² /Vs or more, more preferably 2 cm ² /Vs or more, even more preferably 5 cm ² /Vs or more, and most preferably 10 cm ² /Vs or more. The condensed polycyclic aromatic compounds represented by the general formulas (1) and (2) have molecular arrangements and overlapping π-conjugated systems that are suitable for carrier migration in the solid, and therefore thin-film devices using these condensed polycyclic aromatic compounds can easily achieve high carrier mobility.

Hereinafter, the organic transistor will be described in more detail using some exemplary embodiments of the organic transistor shown in FIG. 1, but the present invention is not limited to these structures.
In the organic transistors 10A to 10F of each embodiment in FIG. 1, 1 represents a source electrode, 2 represents a semiconductor layer, 3 represents a drain electrode, 4 represents an insulator layer, 5 represents a gate electrode, and 6 represents a substrate. The arrangement of each layer and electrode can be appropriately selected depending on the application of the organic transistor. The organic transistor 10A is called a bottom contact-bottom gate structure, and the organic transistor 10B is called a top contact-bottom gate structure. In addition, the organic transistor 10C is called a top contact top gate structure because a source electrode 1, a drain electrode 3, and an insulator layer 4 are provided on a semiconductor layer 2, and a gate electrode 5 is further formed thereon. The organic transistor 10D has a structure called a top and bottom contact bottom gate type transistor. The organic transistor 10F has a bottom contact-top gate structure. The organic transistor 10E is a schematic diagram of a transistor having a vertical structure, that is, a static induction transistor (SIT). In this SIT, the flow of current spreads in a plane, so a large amount of carriers 8 can move at once. In addition, since the source electrode 1 and the drain electrode 3 are vertically arranged, the distance between the electrodes can be reduced, and the response is high speed. Therefore, the organic transistor 10E can be preferably used for applications in which a large current flows, high-speed switching is performed, etc. Although a substrate is not shown in the organic transistor 10E in Fig. 1, a substrate is usually provided on the outside of the source electrode 1 or the drain electrode 3 of the organic transistor 10E.

Next, each component in each embodiment will be described.
The substrate 6 must be capable of holding each of the components formed thereon without peeling off. Examples of the substrate 6 include insulating substrates such as resin plates, resin films, paper, glass plates, quartz plates, and ceramic plates; substrates in which an insulating layer is formed by coating or the like on a conductive substrate made of metal or alloy; substrates made of various combinations such as a combination of resin and inorganic materials; and conductive substrates such as semiconductor substrates (e.g., silicon wafers). Examples of resin films that can be used include polyethylene terephthalate, polyethylene naphthalate, polyimide, and polycarbonate. The use of resin films or paper can provide flexibility to the device, making it flexible and lightweight, and improving practicality. The thickness of the substrate is usually 1 μm to 10 mm, and preferably 5 μm to 5 mm. When a conductive substrate is used, the substrate may also serve as the gate electrode of a bottom-gate transistor.

The source electrode 1, drain electrode 3, and gate electrode 5 are made of conductive materials. For example, metals such as platinum, gold, silver, aluminum, chromium, nickel, cobalt, copper, iron, zinc, and indium, and alloys containing these metals; conductive oxides such as In2O3, ZnO2, and ITO; conductive polymer compounds such as polyaniline, polypyrrole, and polythiophene; semiconductors such as silicon, germanium, and gallium arsenide; carbon materials such as carbon black, fullerene, carbon nanotubes, graphite, and graphene; and the like can be used. In addition, the conductive polymer compounds and semiconductors may be doped. Examples of dopants include inorganic acids such as hydrochloric acid and sulfuric acid; organic acids having acidic functional groups such as sulfonic acid; Lewis acids such as PF5, AsF5, and FeCl3; halogen atoms such as iodine; and metal atoms such as lithium, sodium, and potassium.

The distance between the source electrode and the drain electrode (channel length) is an important factor that determines the characteristics of the device, and an appropriate channel length is necessary. If the channel length is short, the amount of current that can be extracted increases, but short channel effects such as the influence of contact resistance occur, which may degrade the semiconductor characteristics. The channel length is usually 0.01 to 300 μm, preferably 0.1 to 100 μm. The width of the source electrode and the drain electrode (channel width) is usually 10 to 5000 μm, preferably 30 to 2000 μm. This channel width can be made even longer by using a comb-shaped electrode structure, and it is necessary to set the length appropriately depending on the required amount of current and the device structure.

The structure (shape) of each of the source electrode 1 and the drain electrode 3 will be described. The structures of the source electrode 1 and the drain electrode 3 may be the same or different. In the case of a bottom contact structure, the source electrode 1 and the drain electrode 3 are generally fabricated using a lithography method, and it is preferable to form the source electrode 1 and the drain electrode 3 into a rectangular parallelepiped. Techniques such as inkjet printing, gravure printing, or screen printing can also be used. In the case of a top contact structure in which the source electrode 1 and the drain electrode 3 are on the semiconductor layer 2, the source electrode 1 and the drain electrode 3 can be fabricated by deposition using a shadow mask or the like. It is also becoming possible to directly print electrode patterns using existing printing techniques such as inkjet printing. The length of the source electrode 1 and the drain electrode 3 is the same as the channel width described above. There is no particular regulation for the width of the source electrode 1 and the drain electrode 3, but it is preferable to make them shorter in order to reduce the area of the device within a range in which the electrical characteristics can be stabilized. The width of the source electrode 1 and the drain electrode 3 is usually 0.1 to 1000 μm, preferably 0.5 to 500 μm. The thickness of the source electrode 1 and the drain electrode 3 is usually 1 to 1000 nm, preferably 5 to 500 nm.

For the insulator layer 4, an insulating material is used. Examples of insulating materials include polymers such as polyparaxylylene, polyacrylate, polymethyl methacrylate, polystyrene, polyvinylphenol, polyimide, polycarbonate, polyester, fluororesin, epoxy resin, and phenolic resin, and copolymers combining these; metal oxides such as silicon oxide, aluminum oxide, titanium oxide, and tantalum oxide; ferroelectric metal oxides such as SrTiO3 and BaTiO3; dielectrics such as nitrides such as silicon nitride and aluminum nitride, sulfides, and fluorides; or polymers in which particles of these dielectrics are dispersed; and the like. For this insulator layer 4, a material with high electrical insulation properties is preferably used to reduce leakage current. This allows the film thickness to be reduced, the insulating capacity to be increased, and more current can be extracted. In addition, in order to improve the mobility of the semiconductor, it is preferable to reduce the surface energy of the insulator layer 4 surface and to have a smooth film without unevenness. For this purpose, a self-assembled monolayer or a two-layer insulator layer may be formed. The thickness of the insulator layer 4 varies depending on the material and application, but is usually 1 nm to 1 μm, preferably 1 nm to 500 nm, and more preferably 1 nm to 300 nm.

At least one compound selected from the condensed polycyclic aromatic compounds represented by the general formulas (1) and (2) above can be used as the organic semiconductor material for the semiconductor layer 2, which is an organic semiconductor layer. The organic thin film containing the condensed polycyclic aromatic compounds represented by the general formulas (1) and (2) can be formed as the semiconductor layer 2 by using the organic thin film formation method described above.
The semiconductor layer 2 may be formed of a plurality of layers, but a single layer structure is more preferable. The thickness of the semiconductor layer 2 is preferably as thin as possible without losing the necessary functions. This is because, in lateral organic transistors such as the organic transistors 10A, 10B, and 10D, the characteristics of the organic transistor do not depend on the film thickness if the film thickness is greater than a certain value, but an increase in the film thickness leads to a decrease in the semiconductor characteristics. The film thickness of the semiconductor layer 2 to exhibit the necessary functions is usually 1 nm to 1 μm, and preferably 5 nm to 300 nm.

The semiconductor layer 2 may be a single crystal film, a polycrystalline film, or an amorphous film, but a crystalline film is preferable because the movement of charge carriers between molecules is smoother when the molecules are regularly arranged, and it is most preferable for one single crystal to occupy the space between the source electrode and the drain electrode when used as an organic transistor. When using the condensed polycyclic aromatic compounds represented by the general formulas (1) and (2), a high-quality crystalline thin film can be easily obtained simply by applying a solution to form a film, and a thin film exhibiting high carrier mobility can be easily produced, which facilitates the process of producing high-quality devices and is suitable for reducing performance variations between devices.

When the semiconductor layer 2 is a single crystal film, as described above, it is most desirable for the area between the source electrode and the drain electrode to be covered by a single single crystal, so the diameter of one single crystal domain is desirably 1 μm or more, and more desirably 10 μm or more. Furthermore, when forming an array in which many transistors are arranged, it is preferable for the entire transistor array to be single crystal, as this minimizes variation between elements, and therefore there is no particular upper limit on the diameter.

The organic transistor may have other layers on the outer surface of the organic transistor as necessary. For example, forming a protective layer directly on the semiconductor layer 2 of the organic transistor 10A or via another layer has the advantage of stabilizing the electrical characteristics, such as increasing the on/off ratio of the organic transistor by reducing the effects of external air, such as humidity.

The material of the protective layer is not particularly limited, but examples of preferred materials include films made of various resins such as epoxy resins, acrylic resins such as polymethyl methacrylate, polyurethane, polyimide, polyvinyl alcohol, fluororesins, and polyolefins; inorganic oxide films such as silicon oxide, aluminum oxide, and silicon nitride; and films made of dielectrics such as nitride films; and in particular, resins (polymers) with low oxygen and moisture permeability and water absorption are preferred. Gas barrier protective materials developed for organic EL displays can also be used. The thickness of the protective layer can be selected according to the purpose, but is usually 100 nm to 1 mm.

The characteristics of the organic transistor may be improved by previously modifying or treating the surface of the substrate 6 or the insulator layer 4 on which the semiconductor layer 2 is laminated. For example, by adjusting the degree of hydrophilicity/hydrophobicity of the surface of the substrate 6 or the insulator layer 4, the film quality and film formability of the thin film formed thereon can be improved, resulting in improved characteristics. In particular, the characteristics can be improved by making the film quality near the interface between the substrate 6 or the insulator layer 4 and the semiconductor layer 2 more uniform.

Surface treatments for improving the above characteristics include, for example, self-assembled monolayer treatments using hexamethyldisilazane, octadecyltrichlorosilane, trichloro(phenylethyl)silane, etc., surface treatments using polymers, etc., acid treatments using hydrochloric acid, sulfuric acid, acetic acid, etc., alkali treatments using sodium hydroxide, potassium hydroxide, ammonia, etc., ozone treatment, fluorination treatment, plasma treatments using oxygen, argon, etc., other processes for forming thin films of insulators or semiconductors, mechanical treatments, electrical treatments, etc., and combinations of these treatments may also be used.

Next, a method for manufacturing an organic transistor device according to the present invention will be described below with reference to FIG. 2, using the top-contact bottom-gate organic transistor 10B shown in FIG. 1(b) as an example. This manufacturing method can also be applied to the organic transistors of the other embodiments described above.

(Substrate 6 of Organic Transistor and Substrate Processing)
The organic transistor of the present invention is fabricated by providing various necessary layers and electrodes on a substrate 6 (see FIG. 2(a)). The material and thickness of the substrate 6 are as described above, and the above-mentioned surface treatment can be performed on the substrate 6. If necessary, the substrate can also be made to function as an electrode.

(Regarding formation of gate electrode 5)
A gate electrode 5 is formed on a substrate 6 (see FIG. 2(b)). The above-described materials are used for the gate electrode 5. Various methods can be used to form the gate electrode 5, such as vacuum deposition, sputtering, coating, thermal transfer, printing, and sol-gel. It is preferable to perform patterning as necessary during or after film formation to obtain a desired shape. Various methods can be used for patterning, such as photolithography combining photoresist patterning and etching. Patterning can also be performed using deposition and sputtering using a shadow mask, printing methods such as inkjet printing, screen printing, offset printing, and relief printing, soft lithography methods such as microcontact printing, and methods combining a plurality of these methods. The thickness of the gate electrode 5 varies depending on the material, but is usually 0.1 nm to 10 μm, preferably 0.5 nm to 5 μm, and more preferably 1 nm to 3 μm. In addition, when the gate electrode 5 serves as both the substrate 6 and the substrate 6, the thickness may be larger than the above thickness.

(Regarding formation of insulator layer 4)
An insulator layer 4 is formed on the gate electrode 5 (see FIG. 2(c)). The insulator material constituting the insulator layer 4 is the material described above. Various methods can be used to form the insulator layer 4. Examples include coating methods such as spin coating, drop casting, and spraying, printing methods such as screen printing, offset printing, and inkjet, and dry process methods such as vacuum deposition, molecular beam epitaxy, sputtering, atmospheric pressure plasma, and CVD. In addition, a method of forming an oxide film on a metal by a thermal oxidation method, such as anodizing on aluminum and silicon oxide on silicon, can be used. In addition, in the portion where the insulator layer 4 and the semiconductor layer 2 contact each other, a predetermined surface treatment can be performed on the insulator layer 4 by the same method as the substrate 6.

(Regarding formation of semiconductor layer 2)
The organic semiconductor material containing the condensed polycyclic aromatic compound represented by the above general formulas (1) and (2) of the present invention is used to form the semiconductor layer 2 (see FIG. 2(d)). The above-mentioned various methods can be used to form the semiconductor layer 2, and the thickness is also as described above. The semiconductor layer 2 thus formed can be further improved in properties by post-treatment. For example, the organic semiconductor can be oxidized/reduced by using a doping method in which a trace amount of element, atomic group, molecule, or polymer is added to the semiconductor layer 2 to change its properties. This is achieved by contacting the organic semiconductor with a gas phase/solution/solid phase of an acid/base, electron donor/acceptor, etc. The effects of these doping include a change in electrical conductivity due to an increase or decrease in carrier density, a change in the polarity of the carrier (p-type, n-type), a change in the Fermi level, etc.

(Formation of source and drain electrodes)
The shapes, materials used, and formation methods of the source electrode 1 and the drain electrode 3 are as described above (see FIG. 2(e)). The source electrode 1 and the drain electrode 3 can also be formed in the same manner as the gate electrode 5. In order to reduce the contact resistance with the semiconductor layer 2, various additives can be used.

(Regarding protective layer 7)
Forming the protective layer 7 on the semiconductor layer 2 has the advantage of minimizing the influence of the outside air and stabilizing the electrical characteristics of the organic transistor (see FIG. 2(f)). The material and thickness of the protective layer 7 are as described above. Various methods can be used to form the protective layer 7. When the protective layer 7 is made of a resin, for example, a method of applying a resin solution and then drying it to form a resin film; a method of applying or depositing a resin monomer and then polymerizing it; etc. may be used. A crosslinking treatment may be performed after the film formation. When the protective layer 7 is made of an inorganic material, for example, a forming method using a vacuum process such as a sputtering method or a deposition method, or a forming method using a solution process such as a sol-gel method may also be used.

The organic thin-film transistor of the present invention can be manufactured in a relatively low-temperature process because the condensed polycyclic aromatic compounds represented by the above general formulas (1) and (2) are used as the organic semiconductor material. Therefore, flexible materials such as plastic plates and plastic films that cannot be used under conditions exposed to high temperatures can be used as the substrate 6. As a result, it becomes possible to manufacture an organic transistor that is lightweight, flexible, and durable, and can be used as a switching device for the active matrix of a display, etc.

The organic thin-film transistor of the present invention can be used as a digital or analog device such as a memory circuit device, a signal driver circuit device, or a signal processing circuit device. Furthermore, by combining these, it is possible to produce displays, IC (integrated circuit) cards, IC tags, and the like. Furthermore, the organic thin-film transistor of the present invention can change its characteristics in response to external stimuli such as chemical substances, and can therefore also be used as a sensor.

The present invention will be described in more detail below with reference to examples. However, the examples are merely illustrative of the present invention, and the present invention is not limited to the examples.

In the following operations, commercially available dehydrated solvents were used for reactions under inert gas, and commercially available first- or special-grade solvents were used for other reactions and operations. Nuclear magnetic resonance spectroscopy was performed using a Bruker AVANCE III (400 MHz, σ value, ppm, internal standard TMS). Mass spectrometry was performed using a Shimadzu gas chromatograph mass spectrometer GCMS-QP2010SE.

窒素雰囲気下、１００ｍＬフラスコに上記Ｐｒｅｃｕｒｓｏｒ３０２ｍｇ（０．５００ｍｍｏｌ）、２，６－ジメチル安息香酸１１３ｍｇ（０．７５０ｍｍｏｌ）、酢酸パラジウム（ＩＩ）５６ｍｇ（０．２５ｍｍｏｌ）およびｏ－キシレン５ｍＬを加え、１５０℃で２４時間加熱した。反応混合物をシリカゲルカラムに担持し、熱トルエンを展開溶媒として分取した。トルエンを一部濃縮し、加熱・再結晶することで上記Ｎｏ．１で表される本発明の縮合多環芳香族化合物５１ｍｇ（０．０９９ｍｍｏｌ、収率２０％）を白色固体として得た。
実施例１で得られたＮｏ．１で表される縮合多環芳香族化合物の核磁気共鳴分光および質量分析の測定結果は以下のとおりであった。
^１Ｈ－ＮＭＲ（４００ＭＨｚ，ＣＤＣｌ_３）：σ８．３４０（ｓ，１Ｈ），８．２５（ｓ，１Ｈ），７．８３（ｄ，Ｊ＝８．４ Ｈｚ，１Ｈ），７．７８－７．７５（ｍ，２Ｈ），７．６９－７．６６（ｍ，２Ｈ），７．４９－７．４４（ｍ，２Ｈ），７．３８（ｔ，Ｊ＝７．６ Ｈｚ，１Ｈ），７．２７－７．２４（ｍ，１Ｈ），２．７８（ｔ，Ｊ＝７．６Ｈｚ，２Ｈ），１．７７－１．６７（ｍ，２Ｈ），１．４２－１．２４（ｍ，１４Ｈ），０．８８（ｔ，Ｊ＝６．８ Ｈｚ，３Ｈ）．ＭＳ（ＥＩ）：ｍ／ｚ５１２． Example 1 Synthesis of the condensed polycyclic aromatic compound of the present invention (Compound No. 1)
The condensed polycyclic aromatic compound of the present invention represented by compound No. 1 in which R ¹ is a phenyl group, R ² is hydrogen, and R ³ is an n-decyl group in general formula (1) was synthesized according to the following synthesis flow.

In a nitrogen atmosphere, 302 mg (0.500 mmol) of the above precursor, 113 mg (0.750 mmol) of 2,6-dimethylbenzoic acid, 56 mg (0.25 mmol) of palladium (II) acetate, and 5 mL of o-xylene were added to a 100 mL flask, and the mixture was heated at 150° C. for 24 hours. The reaction mixture was loaded onto a silica gel column, and hot toluene was used as a developing solvent to separate the product. The toluene was partially concentrated, and the mixture was heated and recrystallized to obtain 51 mg (0.099 mmol, 20% yield) of the condensed polycyclic aromatic compound of the present invention represented by No. 1 above as a white solid.
The results of measurement of the nuclear magnetic resonance spectrometry and mass spectrometry of the fused polycyclic aromatic compound represented by No. 1 obtained in Example 1 were as follows.
^1H -NMR (400MHz, _CDCl3 ): σ 8.340 (s, 1H), 8.25 (s, 1H), 7.83 (d, J = 8.4 Hz, 1H), 7.78-7.75 (m, 2H), 7.69-7.66 (m, 2H), 7.49-7.44 (m, 2H), 7.38 (t, J = 7.6 Hz, 1H), 7.27-7.24 (m, 1H), 2.78 (t, J = 7.6 Hz, 2H), 1.77-1.67 (m, 2H), 1.42-1.24 (m, 14H), 0.88 (t, J = 6.8 Hz, 3H). MS(EI): m/z 512.

Example 2 (Synthesis of condensed polycyclic aromatic compound of the present invention (Compound No. 2))
A condensed polycyclic aromatic compound of the present invention represented by compound No. 2 in which R ¹ is a phenyl group, R ² is hydrogen, and R ³ is an n-hexyl group in general formula (1) was synthesized in the same manner as in Example 1, except that a precursor in which the n-decyl group was replaced with an n-hexyl group was used.
The results of measurement of the nuclear magnetic resonance spectrometry and mass spectrometry of the condensed polycyclic aromatic compound represented by No. 2 obtained in Example 2 were as follows.
^1H -NMR (400MHz, _CDCl3 ): σ 8.34 (s, 1H), 8.25 (s, 1H), 7.83 (d, J = 8.4 Hz, 1H), 7.78-7.74 (m, 2H), 7.69-7.66 (m, 2H), 7.49-7.44 (m, 2H), 7.40-7.35 (m, 1H), 7.27-7.24 (m, 1H), 2.78 (t, J = 7.6 Hz, 2H), 1.76-1.68 (m, 2H), 1.43-1.30 (m, 6H), 0.90 (t, J = 6.8 Hz, 3H). MS(EI): m/z 456.

大気下、５０ｍＬフラスコに上記Ｐｒｅｃｕｒｓｏｒ１００ｍｇ（０．１７ｍｍｏｌ）およびトリフルオロメタンスルホン酸３ｍＬを加え、室温で１時間撹拌した。反応混合物を氷水に注ぎ、析出した淡黄色固体をろ過で回収し、水で洗浄した。得られた固体とピリジン１０ｍＬを５０ｍＬフラスコに入れ、大気下、１１０℃で３時間加熱した。反応混合物をメタノールで希釈し、析出した淡黄色固体をろ過で回収し、メタノールで洗浄した後、トルエンで再結晶することで、上記Ｎｏ．２１で表される本発明の縮合多環芳香族化合物１６ｍｇ（０．０３ｍｍｏｌ、収率１８％）を白色固体として得た。
実施例３で得られたＮｏ．２１で表される縮合多環芳香族化合物の核磁気共鳴分光および質量分析の測定結果は以下のとおりであった。
^１Ｈ－ＮＭＲ（３００ＭＨｚ，１，１，２，２－ｔｅｔｒａｃｈｌｏｒｏｅｔｈａｎｅ－ｄ２）：σ８．３８（ｓ，１Ｈ），８．２７（ｓ，１Ｈ），７．８４－７．７７（ｍ，４Ｈ），７．６９（ｓ，１Ｈ），７．５４－７．４７（ｍ，２Ｈ），７．４２（ｔ，Ｊ＝７．２ Ｈｚ，１Ｈ），７．３６（ｄ，Ｊ＝８．１Ｈｚ，１Ｈ），２．８４（ｔ，Ｊ＝７．５Ｈｚ，２Ｈ），１．８３－１．７３（ｍ，２Ｈ），１．４５－１．３２（ｍ，１４Ｈ），０．９５（ｔ，Ｊ＝６．９ Ｈｚ，３Ｈ）．ＭＳ（ＥＩ）：ｍ／ｚ５１２． Example 3 Synthesis of the condensed polycyclic aromatic compound of the present invention (Compound No. 21)
A condensed polycyclic aromatic compound of the present invention represented by compound No. 21 in which R ¹ is a phenyl group, R ² is an n-decyl group, and R ³ is hydrogen in general formula (1) was synthesized according to the following synthesis flow.

In the atmosphere, 100 mg (0.17 mmol) of the precursor and 3 mL of trifluoromethanesulfonic acid were added to a 50 mL flask, and the mixture was stirred at room temperature for 1 hour. The reaction mixture was poured into ice water, and the precipitated pale yellow solid was collected by filtration and washed with water. The obtained solid and 10 mL of pyridine were placed in a 50 mL flask, and the mixture was heated at 110° C. for 3 hours in the atmosphere. The reaction mixture was diluted with methanol, and the precipitated pale yellow solid was collected by filtration, washed with methanol, and then recrystallized with toluene to obtain 16 mg (0.03 mmol, 18% yield) of the condensed polycyclic aromatic compound of the present invention represented by No. 21 as a white solid.
The results of measurement of the fused polycyclic aromatic compound represented by No. 21 obtained in Example 3 by nuclear magnetic resonance spectroscopy and mass spectrometry are as follows.
^1H -NMR (300MHz, 1,1,2,2-tetrachloroethane-d2): σ8.38 (s, 1H), 8.27 (s, 1H), 7.84-7.77 (m, 4H), 7.69 (s, 1H), 7.54-7.47 (m, 2H), 7.42 (t, J = 7.2 Hz, 1H), 7.36 (d, J = 8.1 Hz, 1H), 2.84 (t, J = 7.5 Hz, 2H), 1.83-1.73 (m, 2H), 1.45-1.32 (m, 14H), 0.95 (t, J = 6.9 Hz, 3H). MS(EI): m/z 512.

大気下、５０ｍＬフラスコに上記Ｐｒｅｃｕｒｓｏｒ９８ｍｇ（０．２０ｍｍｏｌ）、五酸化二リン２８ｍｇ（０．２０ｍｍｏｌ）およびトリフルオロメタンスルホン酸５ｍＬを加え、室温で４時間撹拌した。反応混合物を氷水に注ぎ、析出した黄緑色固体をろ過で回収し、水で洗浄した。得られた固体とピリジン１５ｍＬを１００ｍＬフラスコに入れ、大気下、１２０℃で２時間加熱した。反応混合物をメタノールで希釈し、析出した淡黄色固体を回収し、メタノールで洗浄した後、シリカゲルカラムに担持し、熱トルエンを展開溶媒として分取した。トルエンを濃縮した後、クロロホルム／メタノール混合溶液から再沈殿することで、上記Ｎｏ．３１で表される本発明の縮合多環芳香族化合物４９ｍｇ（０．１１ｍｍｏｌ、収率５４％）を白色固体として得た。
実施例４で得られたＮｏ．３１で表される縮合多環芳香族化合物の核磁気共鳴分光および質量分析の測定結果は以下のとおりであった。
^１Ｈ－ＮＭＲ（４００ＭＨｚ，ＣＤＣｌ_３）：σ８．３１（ｓ，１Ｈ），８．２９（ｓ，１Ｈ），７．８２（ｄ，Ｊ＝７．６ Ｈｚ，１Ｈ），７．７６（ｄ，Ｊ＝７．２Ｈｚ，２Ｈ），７．６８（ｓ，１Ｈ），７．６２（ｓ，１Ｈ），７．４８－７．４３（ｍ，２Ｈ），７．３９－７．３４（ｍ，１Ｈ），７．２６－７．２３（ｍ，１Ｈ），２．７８（ｔ，Ｊ＝７．６Ｈｚ，２Ｈ），１．７６－１．６８（ｍ，２Ｈ），１．４２－１．３１（ｍ，６Ｈ），０．９０（ｔ，Ｊ＝６．８ Ｈｚ，３Ｈ）．ＭＳ（ＥＩ）：ｍ／ｚ４５６． Example 4 (Synthesis of condensed polycyclic aromatic compound of the present invention (Compound No. 31))
A condensed polycyclic aromatic compound of the present invention represented by compound No. 31 in which R ¹ is a phenyl group, R ² is hydrogen, and R ³ is an n-hexyl group in general formula (2) was synthesized according to the following synthesis flow.

In a 50 mL flask, 98 mg (0.20 mmol) of the precursor, 28 mg (0.20 mmol) of diphosphorus pentoxide, and 5 mL of trifluoromethanesulfonic acid were added under air, and the mixture was stirred at room temperature for 4 hours. The reaction mixture was poured into ice water, and the precipitated yellow-green solid was collected by filtration and washed with water. The obtained solid and 15 mL of pyridine were placed in a 100 mL flask, and the mixture was heated at 120° C. for 2 hours under air. The reaction mixture was diluted with methanol, and the precipitated light yellow solid was collected and washed with methanol, and then loaded onto a silica gel column, and separated using hot toluene as a developing solvent. After concentrating the toluene, the mixture was reprecipitated from a chloroform/methanol mixed solution, and 49 mg (0.11 mmol, 54% yield) of the condensed polycyclic aromatic compound of the present invention represented by No. 31 was obtained as a white solid.
The results of measurement of the nuclear magnetic resonance spectrometry and mass spectrometry of the fused polycyclic aromatic compound represented by No. 31 obtained in Example 4 were as follows.
^1H -NMR (400MHz, _CDCl3 ): σ 8.31 (s, 1H), 8.29 (s, 1H), 7.82 (d, J = 7.6 Hz, 1H), 7.76 (d, J = 7.2 Hz, 2H), 7.68 (s, 1H), 7.62 (s, 1H), 7.48-7.43 (m, 2H), 7.39-7.34 (m, 1H), 7.26-7.23 (m, 1H), 2.78 (t, J = 7.6 Hz, 2H), 1.76-1.68 (m, 2H), 1.42-1.31 (m, 6H), 0.90 (t, J = 6.8 Hz, 3H). MS(EI): m/z 456.

[Example 5] (Solubility measurement of compound No. 1)
About 1 mg of the powder of the condensed polycyclic aromatic compound represented by compound No. 1 obtained in Example 1 was weighed into a vial and the mass was accurately measured. Chlorobenzene, xylene, chloroform or toluene was added thereto at each temperature, and the mass of the solution was accurately measured when the condensed polycyclic aromatic compound was completely dissolved. The solubility (mass of the condensed polycyclic aromatic compound/mass of each solution x 100) was calculated from the mass of the condensed polycyclic aromatic compound represented by No. 1 and the mass of the chlorobenzene solution, xylene solution, chloroform solution or toluene solution. The time when the compound was completely dissolved was determined by visual confirmation. The obtained solubilities are shown in Table 2.

[Example 6] (Solubility measurement of compound No. 2)
The solubility of the condensed polycyclic aromatic compound represented by Compound No. 2 obtained in Example 2 was calculated in the same manner as in Example 5. The solubilities obtained are shown in Table 2.

[Example 7] (Solubility measurement of compound No. 21)
The solubility of the condensed polycyclic aromatic compound represented by Compound No. 21 obtained in Example 3 was calculated in the same manner as in Example 5. The solubilities obtained are shown in Table 2.

[Example 8] (Solubility measurement of compound No. 31)
The solubility of the condensed polycyclic aromatic compound represented by Compound No. 31 obtained in Example 4 was calculated in the same manner as in Example 5. The solubilities obtained are shown in Table 2.

Ｎｏ．１０１ Chem. Mater. 2018, 30,5050-5060. [Comparative Example 1]
As a comparative example, the known solubility (literature value) of the following condensed polycyclic aromatic compound No. 101, which has the same degree of condensation as compounds No. 1, No. 2, No. 21, and No. 31 and has similar substituents, is shown in Table 2.

No. 101 Chem. Mater. 2018, 30,5050-5060.

Ｎｏ．１０２ Adv. Mater. 2011, 23, 1222-1225. [Comparative Example 2]
As a comparative example, the known solubility (literature value) of the following condensed polycyclic aromatic compound No. 102, which has the same degree of condensation as compounds No. 1, No. 2, No. 21, and No. 31 and has similar substituents, is shown in Table 2.

No. 102 Adv. Mater. 2011, 23, 1222-1225.

[Example 9] (Differential thermal and thermogravimetric analysis of compound No. 1)
The condensed polycyclic aromatic compound represented by No. 1 obtained in Example 1 was subjected to differential thermal and thermogravimetric analysis using a differential thermal and thermogravimetric analyzer (TG/DTA) to obtain differential thermal and thermogravimetric change curves. The results are shown in Figure 3. It was found that the synthesized condensed polycyclic aromatic compound showed no weight loss up to around 369°C and exhibited high thermal durability.

[Example 10] (Differential scanning calorimetry of compound No. 1)
The condensed polycyclic aromatic compound represented by No. 1 obtained in Example 1 was subjected to differential scanning calorimetry using a differential scanning calorimeter (DSC) to obtain a differential scanning calorimetric curve (DSC curve). The temperature at which the crystal first undergoes phase transition and the melting point obtained from the differential scanning calorimetric curve are shown in FIG. 4 and Table 3.

[Example 11] (Differential scanning calorimetry of compound No. 2)
The condensed polycyclic aromatic compound represented by No. 2 obtained in Example 2 was subjected to differential scanning calorimetry in the same manner as in Example 10. The initial phase transition temperature and melting point of the crystal obtained from the differential scanning calorimetry curve are shown in Table 3.

[Example 12] (Differential scanning calorimetry of compound No. 21)
The condensed polycyclic aromatic compound represented by No. 21 obtained in Example 3 was subjected to differential scanning calorimetry in the same manner as in Example 10. The initial phase transition temperature and melting point of the crystal obtained from the differential scanning calorimetry curve are shown in Table 3.

[Example 13] (Differential scanning calorimetry of compound No. 31)
The condensed polycyclic aromatic compound represented by No. 31 obtained in Example 4 was subjected to differential scanning calorimetry in the same manner as in Example 10. The initial phase transition temperature and melting point of the crystal obtained from the differential scanning calorimetry curve are shown in Table 3.

Ｎｏ．１０３ J. Am. Chem. Soc. 2007, 129, 15732-15733. [Comparative Example 3]
The known temperature at which the crystal first undergoes phase transition and the melting point (literature values) of the following condensed polycyclic aromatic compound No. 103, which has the same degree of condensation and similar substituents as Compounds No. 1, No. 2, No. 21, and No. 31, are shown in Table 3.

No. 103 J. Am. Chem. Soc. 2007, 129, 15732-15733.

Ｎｏ．１０４ Chem. Mater. 2015, 27, 3809-3812. [Comparative Example 4]
The known temperature at which the crystal first undergoes phase transition and the melting point (literature values) of the following condensed polycyclic aromatic compound No. 104, which has the same degree of condensation and similar substituents as Compounds No. 1, No. 2, No. 21, and No. 31, are shown in Table 3.

No. 104 Chem. Mater. 2015, 27, 3809-3812.

Ｎｏ．１０５ Chem. Mater. 2018, 30, 5050-5060. [Comparative Example 5]
The known temperature at which the crystal first undergoes phase transition and the melting point (literature values) of the following condensed polycyclic aromatic compound No. 105, which has the same degree of condensation and similar substituents as Compounds No. 1, No. 2, No. 21, and No. 31, are shown in Table 3.

No. 105 Chem. Mater. 2018, 30, 5050-5060.

実施例１、２、３および４で得られたＮｏ．１、Ｎｏ．２、Ｎｏ．２１およびＮｏ．３１で表される縮合多環芳香族化合物は、加熱過程の示差走査熱量曲線において、結晶－液晶相転移を示すピークが観測されたものの、結晶相が最初に相転移する温度や融点が１８０℃以上であり、比較例３～５の化合物に比べ高い転移温度を示した。従って、実施例１、２、３および４の化合物は、比較例３～５の化合物と比較して顕著に熱耐久性が高いことが分る。

The condensed polycyclic aromatic compounds represented by No. 1, No. 2, No. 21 and No. 31 obtained in Examples 1, 2, 3 and 4 showed peaks indicating a crystal-liquid crystal phase transition in the differential scanning calorimeter curves during the heating process, but the temperature at which the crystal phase first transitioned and the melting point were 180° C. or higher, which were higher than the transition temperatures of the compounds of Comparative Examples 3 to 5. It is therefore clear that the compounds of Examples 1, 2, 3 and 4 have significantly higher heat durability than the compounds of Comparative Examples 3 to 5.

[Example 14] (Preparation of crystalline thin film of compound No. 1)
A chlorobenzene solution of the organic compound represented by No. 1 obtained in Example 1 was applied to a p-doped silicon wafer with a thermally oxidized _SiO2 film by blade sweeping to form a film, thereby obtaining a high-quality crystalline film with a diameter of about 1000 microns. When the obtained thin film was observed under a polarizing microscope under crossed Nicols, it was confirmed that it was a single domain and a single-crystalline organic thin film.

[Example 15] (Evaluation of Semiconductor Properties of Compound No. 1)
Example 14 An organic transistor device was fabricated using the obtained single crystalline organic thin film, and the transistor characteristics were evaluated.
A source/drain electrode was prepared by vacuum deposition of Au on the single crystalline organic thin film obtained in Example 14 using a shadow mask. The organic transistor device prepared this time has a channel length of 50 μm and a channel width of 200 μm. The organic transistor device thus prepared is a top contact type, and FIG. 1b) shows its structure. In the organic transistor device in this example, the thermal oxide film in the p-doped silicon wafer with the thermal oxide film functions as the insulator layer 4, and the p-doped silicon wafer functions as both the substrate 6 and the gate electrode 5.
The performance of an organic transistor device depends on the amount of current that flows when a potential is applied between the source and drain with a potential applied to the gate. By measuring this current value, the mobility, which is a characteristic of a transistor, can be determined. The mobility can be calculated from formula (a), which expresses the electrical characteristics of the carrier species generated in the organic semiconductor layer as a result of applying a gate electric field to _SiO2 as an insulator.

Formula (a)
Id=WμCi(Vg−Vt) ² /2L (a)

Here, Id is the saturated source-drain current value, W is the channel width, Ci is the capacitance of the insulator, Vg is the gate potential, Vt is the threshold potential, L is the channel length, and μ is the mobility to be determined (cm ² /Vs). Ci is the dielectric constant of the SiO ₂ insulating film used, W and L are determined by the device structure of the organic transistor device, Id and Vg are determined when the current value of the organic transistor device is measured, and Vt can be calculated from Id and Vg. By substituting each value into formula (a), the mobility at each gate potential can be calculated.
A transfer curve showing the change in drain current when the transistor element prepared as described above was subjected to a drain voltage of -50 V and a gate voltage sweep from 0 V to -50 V is shown in Figure 5. The carrier mobility calculated from formula (a) was 10.6 cm ² /Vs, the threshold voltage was -32 V, and the ratio of on current to off current (on-off ratio) was 1 x 10 ^9. These results are shown in Table 4.

Ｎｏ．１０６ [Comparative Example 6]
The following condensed polycyclic aromatic compound No. 106, which has the same degree of condensation as compound No. 1 and is known as a soluble organic transistor compound, was used to form an organic thin film by the same film formation method as compound No. 1. Experimental values obtained for a transistor device using this organic thin film as an organic semiconductor film are shown in Table 4.

No. 106

本発明により得られた化合物Ｎｏ．１を用いて作成した有機トランジスタは、可溶性有機トランジスタ材料として従来より知られている化合物Ｎｏ．１０６よりも２桁高い移動度を示し、オンオフ比は３桁向上する結果となった。

The organic transistor prepared using the compound No. 1 obtained by the present invention exhibited a mobility two orders of magnitude higher than that of the compound No. 106 conventionally known as a soluble organic transistor material, and the on/off ratio was improved by three orders of magnitude.

The condensed polycyclic aromatic compound of the present invention has good solvent solubility and is suitable for use in producing organic semiconductor devices by printing processes, which not only enables applications in existing fields such as organic transistor devices, diodes, capacitors, thin-film photoelectric conversion devices, dye-sensitized solar cells, and organic EL devices, but also makes a material that can be used for the backplanes and RF-ID tags of high-end devices that require high carrier mobility, such as 8K displays, due to its extremely high semiconductor mobility. In addition, its high thermal durability enables the use of not only low-temperature flexible substrates such as PET and PEN films, but also heat-resistant flexible substrates, which is expected to lead to a wider range of industrial applications.

The same numbers are used for the same names in FIG. 1 and FIG.
1 Source electrode 2 Semiconductor layer 3 Drain electrode 4 Insulator layer 5 Gate electrode 6 Substrate 7 Protective layers 10A to 10F Organic transistor

Claims (14)

A compound represented by the following general formula (1) or (2):

(In the above general formulas (1) and (2), R ¹ is an aromatic hydrocarbon group, a heterocyclic group, or an alkyl group having 1 to 20 carbon atoms, and one of R ² and R ³ is a hydrogen atom, and the other is an alkyl group having 1 to 20 carbon atoms when R ¹ is an aromatic hydrocarbon group or a heterocyclic group, and is an aromatic hydrocarbon group or a heterocyclic group when R ¹ is an alkyl group having 1 to 20 carbon atoms.) 2. The compound according to claim 1, wherein R ¹ is an aromatic hydrocarbon group or a heterocyclic group, and one of R ² and R ³ is a hydrogen atom, and the other is an alkyl group having 1 to 20 carbon atoms. The compound according to claim 1 or 2, wherein ^R2 is a hydrogen atom. The compound according to any one of claims 1 to 3, wherein the alkyl group is an alkyl group having 6 to 12 carbon atoms. The compound according to any one of claims 1 to 4, represented by general formula (1). The compound according to any one of claims 1 to 5, having a solubility in an organic solvent of 0.01% by mass or more at 25°C. The compound according to any one of claims 1 to 6, in which no peak indicating a phase transition is observed below 160°C in differential scanning calorimetry. A composition containing the compound according to any one of claims 1 to 7 and an organic solvent. An organic semiconductor thin film containing the compound according to any one of claims 1 to 7. An organic semiconductor device comprising the organic semiconductor thin film according to claim 9. An organic transistor comprising the organic semiconductor thin film according to claim 9. The organic transistor according to claim 11, wherein the organic semiconductor thin film is single crystal. A method for producing an organic transistor, comprising applying the organic semiconductor composition according to claim 8 onto a substrate to form an organic semiconductor thin film. The method for manufacturing an organic transistor according to claim 13, characterized in that the organic semiconductor thin film is single crystal.

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