JP2010168305A - Polyacene compound, and organic semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic semiconductor material exhibiting high mobility and excellent in stability as well as in solubility to a solvent, and to provide an organic semiconductor thin film exhibiting high mobility and an organic semiconductor device excellent in electronic characteristics. <P>SOLUTION: A thin film of 2-(dimethylpentylsilyl)pentacene made to have a transistor structure is produced by applying a tetralin solution of 2-(dimethylpentylsilyl)pentacene onto a silicon substrate whereon a source drain electrode is formed, and subsequently drying the same. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polyacene compound which is an organic semiconductor material and a method for producing the same. The present invention also relates to an organic semiconductor thin film and an organic semiconductor element using the organic semiconductor material.

Devices using organic semiconductors have milder film formation conditions than conventional inorganic semiconductor devices, and it is possible to form semiconductor thin films on various substrates or to form films at room temperature. Costs and flexibility by forming a thin film on a polymer film or the like are expected.
As organic semiconductor materials, conjugated polymer compounds such as polyphenylene vinylene, polypyrrole, and polythiophene, and oligomers thereof, as well as aromatic compounds centering on polyacene compounds such as anthracene, tetracene, and pentacene have been studied. In particular, it has been reported that polyacene compounds have high crystallinity due to their strong intermolecular cohesion, thereby exhibiting high carrier mobility and thereby excellent semiconductor device characteristics.

A polyacene compound is used in a device as a deposited film or a single crystal, and its application to a transistor, a solar cell, a laser, or the like has been studied (see Non-Patent Documents 1 to 3).
In addition, as a method for forming a polyacene compound thin film by a method other than the vapor deposition method, a method of forming a pentacene thin film by applying a solution of a precursor of pentacene, which is a kind of polyacene compound, onto a substrate and heating it has been reported. (See Non-Patent Document 4). In this method, since the polyacene compound has low solubility in a solvent, a thin film is formed using a solution of a highly soluble precursor, and the precursor is converted into a polyacene compound by heat.

  On the other hand, polyacene compounds having substituents are reported by Takahashi et al. (Non-Patent Document 5), Graham et al. (Non-Patent Document 6), Anthony et al. (Non-Patent Document 7), and Miller et al. Non-patent document 9 describes a synthesis example of 2,3,9,10-tetramethylpentacene, and non-patent document 10 describes 2,3,9,10-tetrachloro. Examples of synthesis of pentacene are described in Non-Patent Document 11, and examples of synthesis of perfluoropentacene are described. Patent Document 1 discloses a condensed polycyclic aromatic compound substituted with a reactive silyl group.

International Publication No. 01/064611 Pamphlet

“Advanced Materials”, 2002, Vol. 14, p. 99 Jimitrakopouras et al., "Journal of Applied Physics", 1996, Vol. 80, p. 2501 Croke et al., “IEEE Transactions on Electron Devices”, 1999, 46, p. 1258 Brown et al., "Journal of Applied Physics", 1996, Vol. 79, p. 2136 Takahashi et al., “Journal of American Chemical Society”, 2000, Vol. 122, p. 12876 Graham et al., “Journal of Organic Chemistry”, 1995, Volume 60, p. 5770 Anthony et al., “Organic Letters”, 2000, Volume 2, p. 85 Miller et al., “Organic Letters”, 2000, Volume 2, p. 3979 “Advanced Materials”, 2003, Vol. 15, p. 1090 “Journal of American Chemical Society”, 2003, vol. 125, p. 10190 “Journal of American Chemical Society”, 2004, vol. 126, p. 8138

  However, the method of forming a polyacene compound thin film using the precursor as described above has a problem that a high temperature treatment is required to convert the precursor into a polyacene compound (for example, In the case of pentacene, about 150 ° C.). Further, since it is difficult to completely carry out the conversion reaction to the polyacene compound, the unreacted portion remains as a defect, or a modification occurs due to a high temperature, resulting in a defect.

  On the other hand, Takahashi et al.'S report and the like describe derivatives in which substituents are introduced into various polyacene compounds, but do not describe characteristics or thinning as organic semiconductor materials. Further, 2,3,9,10-tetramethylpentacene, 2,3,9,10-tetrachloropentacene and perfluoropentacene are synthesized, but the mobility of each thin film is inferior to that of pentacene. These pentacene derivatives have poor solubility in general organic solvents, and in particular, 2,3,9,10-tetrachloropentacene does not show properties as a semiconductor because modification occurs in the process of forming a thin film at a high temperature.

The condensed polycyclic aromatic compound substituted with a reactive silyl group is intended to fix the condensed polycyclic aromatic compound molecule to the substrate by the reaction between the reactive silyl group and the substrate. However, such a condensed polycyclic aromatic compound needs to be handled with care because the reactive silyl group easily reacts with water to be modified.
Then, this invention solves the problem which the above prior arts have, and it is a subject to provide the organic semiconductor material which expresses high mobility, and is excellent in stability and the solubility with respect to a solvent, and its manufacturing method. To do. Another object is to provide an organic semiconductor thin film having high mobility and an organic semiconductor element having excellent electronic characteristics. Furthermore, another object is to provide a solution and an ink excellent in the film forming property of the organic semiconductor thin film.

  In order to solve the above problems, the present invention has the following configuration. That is, the polyacene compound according to claim 1 of the present invention has a structure represented by the following chemical formula (I).

However, X in chemical formula (I) is a halogen group or a hydrogen atom, respectively, and m is an integer of 1-6. In addition, at least one of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R _{8 in} the chemical formula (I) is a silicon-containing group represented by the chemical formula (II). The balance is a hydrogen atom. Further, B ₁ , B ₂ and B ₃ in the chemical formula (II) are respectively an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group and an alkynyl group, an aromatic hydrocarbon group, an alkoxy group, an aryloxy group and an acyl group. , Ester group, alkyloxycarbonyl group, aryloxycarbonyl group, carboxyl group, formyl group, hydroxyl group, halogen group, amino group, imino group, amide group, cyano group, siloxy group, mercapto group, sulfide group, disulfide group, sulfonyl A group, or a composite functional group containing two or more of these groups. Further, A in the chemical formula (II) is a single bond, a methylene group, an alkylene group, an alkenylene group, an alkynylene group, a bifunctional aromatic hydrocarbon group, a carbonyl group, or an ether group.

The polyacene compound according to claim 2 of the present invention is the polyacene compound according to claim 1, wherein R ₁ , R ₄ , R ₅ , and R ₈ are hydrogen atoms, and R ₂ , R ₃ , R ₆ , At least one of R ₇ is the silicon-containing group.
Furthermore, the polyacene compound according to claim 3 of the present invention is the polyacene compound according to claim 1, wherein R ₁ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are hydrogen atoms, R ₂ , At least one of R ₃ is the silicon-containing group.

Furthermore, the polyacene compound according to claim 4 of the present invention is the polyacene compound according to claim 1, wherein R ₁ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are hydrogen atoms, R ₂ is the silicon-containing group.
Furthermore, the polyacene compound according to claim 5 of the present invention is the polyacene compound according to any one of claims 1 to 4, wherein at least one of B ₁ , B ₂ and B ₃ is an alkyl group. Features.

Furthermore, the polyacene compound according to claim 6 of the present invention is characterized in that m is 2 or 3 in the polyacene compound according to any one of claims 1 to 5.
Furthermore, the polyacene compound according to claim 7 of the present invention is characterized in that m is 1 in the polyacene compound according to any one of claims 1 to 5.

  Furthermore, the manufacturing method of the polyacene compound of Claim 8 which concerns on this invention is a method of manufacturing the polyacene compound as described in any one of Claims 1-7, Comprising: It represents with following Chemical formula (III) The carbonyl group of the polyacenequinone derivative having such a structure is reduced and aromatized to directly convert to the polyacene compound, or a polyacenequinone derivative having a structure represented by the following chemical formula (III) Reduction is performed to obtain a hydroxypolyacene derivative having a structure represented by the following chemical formula (IV), and the hydroxypolyacene derivative is further aromatized or halogenated and aromatized.

However, X in Chemical Formula (III) and Chemical Formula (IV) is a halogen group or a hydrogen atom, k is an integer of 1 or more, and k + 1 is an integer of 1 or more and 6 or less. In addition, at least one of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R _{8 in} the chemical formula (III) and the chemical formula (IV) is represented by the chemical formula (V). It is a silicon-containing group, and the balance is a hydrogen atom. Further, B ₁ , B ₂ and B ₃ in the chemical formula (V) are respectively an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group and an alkynyl group, an aromatic hydrocarbon group, an alkoxy group, an aryloxy group and an acyl group. , Ester group, alkyloxycarbonyl group, aryloxycarbonyl group, carboxyl group, formyl group, hydroxyl group, halogen group, amino group, imino group, amide group, cyano group, siloxy group, mercapto group, sulfide group, disulfide group, sulfonyl A group, or a composite functional group containing two or more of these groups. Further, A in the chemical formula (V) is a single bond, a methylene group, an alkylene group, an alkenylene group, an alkynylene group, a bifunctional aromatic hydrocarbon group, a carbonyl group, or an ether group.

Furthermore, the solution of Claim 9 which concerns on this invention contains the polyacene compound as described in any one of Claims 1-7, It is characterized by the above-mentioned.
Furthermore, the ink of Claim 10 which concerns on this invention contains the polyacene compound as described in any one of Claims 1-7, It is characterized by the above-mentioned.
Furthermore, the organic-semiconductor thin film of Claim 11 which concerns on this invention is comprised with the polyacene compound as described in any one of Claims 1-7, and has crystallinity.

  Furthermore, the organic semiconductor thin film of claim 12 according to the present invention is a crystalline organic semiconductor thin film formed on a substrate in the organic semiconductor thin film of claim 11, wherein the major axis of the molecule of the polyacene compound is Are oriented in a direction perpendicular to the surface of the substrate. Furthermore, an organic semiconductor element according to a thirteenth aspect of the present invention is characterized in that at least a part of the organic semiconductor thin film according to the eleventh or twelfth aspect is formed.

Furthermore, the transistor of Claim 14 which concerns on this invention is a transistor provided with a gate electrode, a dielectric material layer, a source electrode, a drain electrode, and a semiconductor layer, The said semiconductor layer is the organic semiconductor of Claim 11 or Claim 12 It is characterized by comprising a thin film.
The polyacene compound of the present invention has a structure comprising the silicon-containing group (functional group having a silyl group) on one or both of the acene rings (benzene rings) at both ends in the long axis direction of the elongated polyacene skeleton. By introducing a functional group into the acene ring at the end of the long axis direction of the polyacene compound, the present inventors have improved the solubility in organic solvents, and the silyl group of the functional group is active and easily reacts with a hydrogen atom. It was thought that the stability would be improved by not providing it, and a new polyacene compound having a structure represented by the chemical formula (I) was found.

  In addition, the present inventors have found that the polyacene compound of the present invention into which the silicon-containing group is introduced is superior in solubility to pentacene which is poorly soluble in a solvent at room temperature. Further, the present inventors have found that since the polyacene compound of the present invention is excellent in solvent solubility, a thin film formed from a solution or ink in which the polyacene compound of the present invention is dissolved is excellent in uniformity.

  And the polyacene compound of this invention and its thin film showed high crystallinity, and it discovered that the molecule | numerator of the polyacene compound arranged regularly in a thin film. Furthermore, it discovered that the organic-semiconductor element using the thin film of the polyacene compound of this invention showed the outstanding switching property as a thin-film transistor while showing the outstanding electronic characteristic. It has been found that the polyacene compound of the present invention and a thin film thereof exhibit a high mobility comparable to or exceeding that of pentacene having the highest mobility among conventional organic materials.

The polyacene compound of the present invention exhibits high mobility and is excellent in solubility and stability in a solvent. The solution and ink of the present invention are excellent in film formability. Furthermore, the organic semiconductor thin film of the present invention has high mobility. Furthermore, the organic semiconductor element of the present invention has excellent electronic properties.
Furthermore, the method for producing a polyacene compound of the present invention can easily produce the polyacene compound as described above.

  The polyacene compound of the present invention is a compound having a structure as shown in the chemical formula (I) described above, and one or both of the acene rings at both ends in the long axis direction of the molecule contain a silicon-containing compound represented by the chemical formula (II). It is a polyacene compound having a structure having a group (functional group having a silyl group). Since such a polyacene compound has a bulky silyl group, the solubility in an organic solvent is excellent.

Note that at least one of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , R ₈ may be the silicon-containing group, and the remainder is a hydrogen atom. At this time, it is preferable that at least one of R ₂ , R ₃ , R ₆ and R ₇ is the silicon-containing group, and the remainder and R ₁ , R ₄ , R ₅ and R ₈ are hydrogen atoms. Moreover, it is preferable that at least one of R ₂ and R ₃ is the silicon-containing group, and the remainder and R ₁ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are hydrogen atoms. Further, R ₂ is preferably the silicon-containing group, and R ₁ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are preferably hydrogen atoms. Further, when a plurality of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , and R ₈ are the silicon-containing groups, some or all of them may contain the same type of silicon. It may be a group, or may be different silicon-containing groups (that is, groups in which B ₁ , B ₂ , and B ₃ are different).

Below, the polyacene compound of this invention is demonstrated in detail.
A in chemical formula (II) is a single bond, an alkylene group (for example, a methylene group), an alkenylene group, an alkynylene group, a bifunctional aromatic hydrocarbon group (for example, a phenylene group), a carbonyl group (C = O), or An ether group (—O—).

B ₁ , B ₂ and B ₃ in the chemical formula (II) are each an aliphatic hydrocarbon group (for example, an alkyl group, an alkenyl group, an alkynyl group), an aromatic hydrocarbon group, an alkoxy group, an aryloxy group, an acyl Group, ester group, alkyloxycarbonyl group, aryloxycarbonyl group, carboxyl group, formyl group, hydroxyl group, halogen group, amino group, imino group, amide group, cyano group, siloxy group, mercapto group, sulfide group, disulfide group, A sulfonyl group or a composite functional group containing two or more of these groups.
Since the silicon-containing group does not have a silyl group having an active and reactive hydrogen atom, the polyacene compound of the present invention has excellent stability.

  Among the above functional groups, an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group, and an alkynyl group is preferable, and considering the solubility in a solvent and crystallinity, the carbon number is 1 or more and 15 or less. It is preferable. In order to have higher solubility, the number of carbon atoms is more preferably 2 or more and 15 or less, and in order to have both high solubility and high crystallinity, the number of carbon atoms is 2 or more and 6 or less. It is particularly preferable that the number is not more than 1. The aliphatic hydrocarbon group may be linear or branched, or may have a cyclic structure.

  Examples of alkyl groups include methyl, ethyl, n-propyl, n-butyl, t-butyl, n-pentyl, n-hexyl, dodecanyl, trifluoromethyl, benzyl and the like. can give. Examples of alkenyl groups include methacryl and acryl groups, and examples of alkynyl groups include ethynyl and propargyl groups. In the alkenyl group and alkynyl group, the double bond and triple bond may be located at any position in the functional group. Double bonds and triple bonds are for the purpose of strengthening the structure of functional groups, for the purpose of reacting with other molecules using unsaturated bond groups, or for the purpose of reacting (bonding) or polymerizing unsaturated bond groups. Can be used.

Further, when B ₁ , B ₂ , and B ₃ in the chemical formula (II) are functional groups other than the aliphatic hydrocarbon group, the number of carbon atoms is the same as in the case of the aliphatic hydrocarbon group described above. It is preferably 1 or more and 15 or less, more preferably 2 or more and 15 or less, and particularly preferably 2 or more and 6 or less.
Examples of the alkoxy group include a methoxy group, an ethoxy group, a 2-methoxyethoxy group, and a t-butoxy group. Examples of the aryloxy group include a phenoxy group, a naphthoxy group, a phenylphenoxy group, and a 4-methylphenoxy group.

  Further, examples of the acyl group include formyl group, acetyl group, 2-methylpropanoyl group, cyclohexylcarbonyl group, octanoyl group, 2-hexyldecanoyl group, dodecanoyl group, chloroacetyl group, trifluoroacetyl group, and benzoyl group. Can be given. Further, examples of the aryloxycarbonyl group include phenoxycarbonyl group, 4-octyloxyphenoxycarbonyl group, 2-hydroxymethylphenoxycarbonyl group, and 4-dodecyloxyphenoxycarbonyl group.

  Furthermore, examples of the amino group include an amino group, a methylamino group, a dimethylamino group, a methylphenylamino group, and a phenylamino group. Furthermore, examples of the sulfide group and disulfide group include all groups having a partial structure of “—S—” or “—S—S—”, and may have a cyclic structure, and specific examples thereof. Examples include groups containing thiolane ring, 1,3-dithiolane ring, 1,2-dithiolane ring, thiane ring, dithiane ring, thiomorpholine ring and the like. Such a cyclic structure is preferable in that it has less steric influence than a chain structure.

Furthermore, examples of the siloxy group include a trimethylsiloxy group, a dimethylphenylsiloxy group, and a diphenylmethylsiloxy group. In the polyacene compound of the present invention, since the silicon-containing group represented by the chemical formula (II) has a silyl group, when any of B ₁ , B ₂ and B ₃ is a siloxy group, This means that there is an additional siloxy group in the silyl group.

Furthermore, examples of the sulfonyl group include a methylsulfonyl group, an n-butylsulfonyl group, an n-octylsulfonyl group, and a phenylsulfonyl group. Furthermore, examples of the composite functional group include 2-hydroxy-1-propenyl group, hydroxyethoxyethyl group, hydroxyethylthioethyl group, and dimethylaminocarbonyl group.
In the pentacene compound of the present invention having the silicon-containing group in one or both of the acene rings at both ends in the long axis direction of the polyacene skeleton, the silicon-containing group may become an obstacle (steric hindrance) when stacking molecules. In some cases, the overlapping of conjugate surfaces between molecules may be inhibited. Therefore, it is preferable that the number of the silicon-containing groups is small.

  In particular, when the silicon-containing group is present only in one of the acene rings at both ends of the long axis direction, the molecules can be arranged so that the acene rings having the silicon-containing group are alternately opposite when stacking each other. This is preferable. In addition, in the case where the silicon-containing group is present in only one of the acene rings at both ends of the long axis direction, polarity is generated in the long axis direction of the molecule, so that the solubility in a solvent is improved.

A plurality of X bonded to the acene ring other than both ends in the long axis direction of the polyacene skeleton are halogen groups or hydrogen atoms. A part of the plurality of Xs may be a halogen group and all the others may be hydrogen atoms. Further, all of the plurality of Xs may be halogen groups, or all may be hydrogen atoms.
The polyacene compound in which an even number of a plurality of X is a halogen group, and two of these halogen groups are bonded to the same acene ring is a polyacene quinone having two carbonyl groups in the same acene ring. It is preferable from the viewpoint that synthesis of (which becomes a precursor in the case of synthesizing a polyacene compound) is easy and that there is little steric hindrance between halogen groups when molecules are stacked.

Furthermore, the halogen group bonded to the acene ring other than both ends in the long axis direction contributes to the improvement of the oxidation resistance of the polyacene compound, but among the halogen groups, a fluorine atom having the smallest van der Waals radius is more preferable.
In addition, regarding the number of condensed rings of the polyacene skeleton, m in the above-described chemical formula (I) is preferably 2 or 3. In general, as the number of condensed rings increases, the solubility in organic solvents decreases and the reactivity to oxygen increases (that is, the oxidation resistance decreases). On the other hand, as the number of condensed rings increases, the HOMO-LUMO gap decreases, so that high mobility is expected. Considering these solubility, stability and semiconductor characteristics, pentacene where m is 2 (that is, the number of condensed rings is 5) and hexacene where m is 3 (that is, where the number of condensed rings is 6) are preferable. Further, tetracene where m is 1 (that is, the number of condensed rings is 4) is preferable from the viewpoint of solubility in an organic solvent and high stability to oxygen.

Next, a method for synthesizing the polyacene compound of the present invention will be described. The synthesis method of the polyacene compound in the present invention can be roughly classified into two.
(1) Method of converting hydroxyl group of hydroxy polyacene derivative to halogen group (2) Method of reducing carbonyl group of polyacene quinone derivative and converting directly to polyacene compound Halogen substitution obtained by the method of (1) The polyacene compound can be synthesized in two steps using a polyacene quinone compound having a chemical structure corresponding to the polyacene compound as a raw material. In addition, since the polyacene quinone compound has a chemical structure corresponding to the polyacene compound, the number of six-membered rings, the types of functional groups provided, the number, and the substitution position are the same as those of the polyacene compound. Since the compound has a carbonyl group, the ring structure is not a polyacene structure.

  First, the carbonyl group of the polyacenequinone compound is reduced to a hydroxyl group with a metal hydride salt (reducing agent) such as lithium aluminum hydride. When the obtained reduced product (hydroxypolyacene derivative) is reacted with a halogenating agent such as N-chlorosuccinimide in the presence of dimethyl sulfide, a halogen substitution reaction and aromatization proceed continuously to obtain a halogen substituted polyacene derivative. Can do.

  That is, a halogen group is introduced into the carbonyl carbon of the polyacene quinone compound to become a halogen-substituted polyacene derivative. One or a plurality of quinone moieties may be used, and a polyhalogen-substituted polyacene derivative can be obtained from a polyacenequinone compound having a plurality of quinone moieties. The hydroxy polyacene derivative has a chemical structure corresponding to that of the polyacene compound, and the number of six-membered rings and the type, number, and substitution position of the functional group provided are the same as those of the polyacene compound. Has a carbon atom bonded to a hydroxyl group and a hydrogen atom, the ring structure is not a polyacene structure.

  For example, a 6,13-dihalogenated pentacene derivative can be synthesized in two steps from a 6,13-pentacenequinone derivative. The 6,13-pentacenequinone derivative having the silicon-containing group on the acene ring at both ends in the long axis direction can be easily obtained by a cyclocondensation reaction between a phthalaldehyde derivative and cyclohexane-1,4-dione. On the other hand, the 6,13-pentacenequinone derivative having the silicon-containing group only in the acene ring at one end of the long axis direction can be easily obtained by a cyclization condensation reaction between a phthalaldehyde derivative and 1,4-dihydroxyanthracene. Regarding phthalaldehyde derivatives, for example, 4,5- (methylenedioxy) -1,2-benzdialdehyde and 3,4- (methylenedioxy) -1,2-benzdialdehyde are known methods or similar methods. Can be easily synthesized.

  The 6,13-pentacenequinone derivative in which the acene ring at both ends of the long axis direction or the acene ring at one end of the long axis direction is substituted with the silicon-containing group is obtained at both ends or one end by the above reduction reaction and halogenation-aromatization reaction. Can be converted to a 6,13-dihalogenated pentacene derivative having the silicon-containing group in the acene ring. The polyacene compound of the present invention can be synthesized by a method similar to the synthesis method described above, and a desired polyhalogenated polyacene compound can be obtained efficiently.

Moreover, when the reduction reaction using an aluminum trialkoxide etc. is performed with respect to the quinone part of a polyacene quinone compound like the method of above-mentioned (2), it can also convert into a polyacene derivative directly.
After the polyacene compound of the present invention is synthesized by the above-described method, it can be purified by a conventional purification method such as sublimation, recrystallization, column purification, and the like to be highly purified.

The polyacene compound of the present invention has crystallinity, and this crystal structure is a herringbone type and shows a structure in which molecules are arranged. This herringbone crystal structure has a lattice structure in which elongated molecules are stacked in an arrowhead shape. These crystal structures can be determined by X-ray diffraction using crystals purified and purified as described above.
In addition, the polyacene compound of the present invention exhibits an orthorhombic structure or a cubic structure similarly to the unsubstituted polyacene compound. Here, the lattice constants a, b, and c of the crystal can be determined. The c-axis lattice constant corresponds to the lattice unit length in which the molecular lengths of the elongated molecules are arranged, and the a-axis and b-axis lattice constants are the conjugate planes of the molecules. Corresponds to the size of the lattice unit in the surface of the stacked molecular column.

  Furthermore, the polyacene compound of the present invention has a structure in which the intermolecular distance (corresponding to the a-axis and b-axis lattice constants) where the conjugated surfaces of the molecules are stacked is equivalent or reduced as compared with the unsubstituted polyacene compound. Show. This is because the overlap of π electrons between the molecules is large, and the carriers can easily move between the molecules, which is considered to be a cause of high mobility. Also. The c-axis lattice constant changes corresponding to the molecular length in the major axis direction of the polyacene compound, and is almost equal to or slightly smaller than the molecular length.

  Furthermore, among the polyacene compounds of the present invention, those having a halogen element in the molecular structure are superior in oxidation resistance compared to those having no halogen element. This is because the introduction of a halogen element increases the ionization potential of the molecule and decreases the reactivity with oxidizing agents such as oxygen. In addition, introduction of a halogen element also suppresses charge transfer with the electron-accepting molecule, which leads to stability of fluctuation in carrier concentration of the semiconductor.

  Furthermore, when a field effect transistor is manufactured using the polyacene compound of the present invention, the drain current changes greatly with respect to the gate voltage, and a high on / off current ratio can be obtained stably. And since the change of this drain current is abrupt, the outstanding device performance is shown.

Next, the organic semiconductor thin film of the present invention will be described.
As a method for forming the organic semiconductor thin film of the present invention, a known method can be adopted, and it can also be formed by a wet process. Conventionally known unsubstituted polyacene compounds are hardly soluble in ordinary solvents at room temperature, and it has been difficult to form a thin film by applying a solution and applying a solution. However, the polyacene compound of the present invention can be added to a solvent by introducing a functional group. Since the solubility is equal to or higher than that of the unsubstituted polyacene compound, it is possible to form a solution and form a thin film by applying the solution.

  Also. As a method for forming the organic semiconductor thin film of the present invention, a method of applying or spraying a dispersion in which crystal particles of a polyacene compound are dispersed in a solvent can be employed. The polyacene compound of the present invention has high crystallinity, and it is easy to form crystal grains by vapor phase growth or liquid phase growth. The polyacene compound of the present invention forms columnar crystals in which elongated molecules are stacked as described above, and the form of crystal particles tends to be a plate-like structure. A dispersion in which these plate-like crystals are dispersed can be applied or sprayed, and the solvent can be removed by evaporation, extraction, or the like, to form a thin film in which crystal particles are laminated in a single layer or multiple layers.

  The organic semiconductor thin film of the present invention can be obtained by coating the solution or dispersion of the polyacene compound of the present invention on a base such as a substrate and then evaporating or extracting the solvent by a method such as heating. Examples of a method of coating the base with the solution or dispersion include a method of bringing the base into contact with the solution or dispersion in addition to coating and spraying. Specific examples include known methods such as spin coating, dip coating, screen printing, ink jet printing, blade coating, printing (lithographic printing, intaglio printing, letterpress printing, etc.).

In these printing methods, the polyacene compound solution or dispersion of the present invention includes additives for adjusting viscosity, surface energy, and the like, and reactive impurity removers for removing reactive impurities such as water and oxygen. Ink added with the above stabilizer can be used.
Such an operation can be performed in a normal atmosphere or an inert gas atmosphere such as nitrogen or argon. However, since some polyacene compound solutions may be easily oxidized, preparation and storage of the solution and preparation of the organic semiconductor thin film are preferably performed in an inert gas atmosphere.

  When the solvent is vaporized, crystal growth can be controlled by adjusting the solvent vaporization rate at the gas-liquid interface according to the temperature near the base and the solvent vapor pressure of the atmosphere. Furthermore, it is also possible to form an organic semiconductor thin film on the surface of the base in a supersaturated state by bringing the base into contact with a solution of a polyacene compound. Furthermore, if desired, crystal growth can be controlled by applying at least one of a temperature gradient, an electric field, and a magnetic field to the interface between the polyacene compound solution and the base. By these methods, a highly crystalline organic semiconductor thin film can be produced, and the obtained organic semiconductor thin film has high crystallinity and thus has excellent semiconductor characteristics.

  Furthermore, the amount of the solvent remaining in the organic semiconductor thin film is preferably low from the viewpoint of the stability and semiconductor characteristics of the organic semiconductor thin film. Therefore, it is usually preferable to remove the solvent remaining in the organic semiconductor thin film almost completely by performing a heat treatment and / or a reduced pressure treatment again after forming the organic semiconductor thin film. However, since the polyacene compound of the present invention has higher crystallinity than ordinary organic compounds and the amount of the solvent remaining in the thin film is small, this drying step can be simplified.

On the other hand, the organic semiconductor thin film of the present invention can also be formed by a thin film forming method of a dry process. For example, vacuum deposition, MBE (Molecular Beam Epitaxy), sputtering, laser deposition, vapor transport growth, and the like can be mentioned. And by such a method, a thin film can be formed on the substrate surface.
Since the polyacene compound used in the present invention exhibits sublimation properties, it is possible to form a thin film by the method described above. In the MBE method, the vacuum deposition method, and the vapor transport growth method, a vapor obtained by heating a polyacene compound and sublimating it is transported to the substrate surface at high vacuum, vacuum, low vacuum, or normal pressure to form a thin film. .

  The sputtering method is a method of forming a thin film by ionizing a polyacene compound in plasma and depositing molecules of the polyacene compound on a substrate. Further, the laser vapor deposition method is a method of forming a thin film by heating a polyacene compound by laser irradiation to generate vapor and depositing molecules of the polyacene compound on a substrate. Among the above-mentioned production methods, the MBE method, the vacuum evaporation method, and the vapor transport growth method are preferable because they are excellent in flatness and crystallinity of a thin film to be formed.

As a thin film production condition in the MBE method or the vacuum vapor deposition method, for example, the substrate temperature is preferably set to room temperature to 100 ° C. When the substrate temperature is low, an amorphous thin film is likely to be formed, and when the substrate temperature exceeds 100 ° C., the surface smoothness of the thin film decreases. In the case of the vapor transport growth method, the substrate temperature is preferably room temperature or higher and 200 ° C. or lower.
In addition, the polyacene compound of the present invention can easily form a thin film with good crystallinity even when the thin film growth rate is high, and high-speed film formation is possible. The growth rate is preferably in the range of 0.1 nm / min to 1 μm / sec. If it is less than 0.1 nm / min, the crystallinity tends to decrease, and if it exceeds 1 μm / sec, the surface smoothness of the thin film decreases.

Thus, an organic semiconductor thin film made of a polyacene compound can be formed by a dry process or a wet process.
As described above, the polyacene compound of the present invention can form a thin film having excellent crystallinity and semiconductor characteristics. In the organic semiconductor thin film of the present invention, the polyacene compound has the long axis of the molecule oriented in the direction perpendicular to the base surface. This is considered to be because the molecular cohesion of the molecules of the polyacene compound is strong, and it is easy to form a molecular column stacked on the molecular surfaces. Therefore, the X-ray diffraction pattern of the organic semiconductor thin film tends to appear with a strong (00n) plane strength of the crystal. This inter-plane distance corresponds to the c-axis lattice constant of the crystal.

  Further, in the polyacene compound of the present invention, the intermolecular distance in the a-axis direction and / or the b-axis direction of the crystal axis of the crystal may be reduced, and carrier movement is likely to occur due to the reduction in the intermolecular distance. Show high mobility. An organic semiconductor element composed of such an organic semiconductor thin film is considered to have a property that carriers can easily flow along a molecular column formed in layers. The a-axis and b-axis lattice constants can be observed by oblique incident X-ray diffraction, transmission electron diffraction, a method in which X-rays are incident on the edge of a thin film, and diffraction is measured.

Furthermore, although the normal inorganic semiconductor thin film is affected by the crystallinity and plane orientation of the base material, the organic semiconductor thin film of the present invention is highly crystalline regardless of the crystallinity and plane orientation of the base material. A thin film. Therefore, various materials can be used for the base material regardless of crystallinity or amorphousness.
Examples thereof include ceramics such as glass, quartz, aluminum oxide, sapphire, silicon nitride, and silicon carbide, and semiconductors such as silicon, germanium, gallium arsenide, gallium phosphide, and gallium nitrogen. Polyester (polyethylene terephthalate, polyethylene naphthalate, etc.), polyethylene, polypropylene, polyvinyl alcohol, ethylene vinyl alcohol copolymer, cyclic polyolefin, polyimide, polyamide, polystyrene, polycarbonate, polyether sulfone, polysulfone, polymethyl methacrylate, etc. Examples include resin, paper, and non-woven fabric.

  When a thin film is formed on a substrate made of these materials, an ultrathin layer of a solution or dispersion is formed on the surface of the substrate, and both are reacted to adjust the surface energy of the substrate. The crystallinity of the thin film can also be adjusted. When the organic semiconductor thin film of the present invention is used for a transistor, it is usually preferable to make the surface of the substrate hydrophobic in order to increase the crystal grains to grow and to reduce carrier traps.

  In addition, a locally hydrophobized / hydrophilized pattern or physical partition structure is formed on the surface of the substrate, and the organic semiconductor thin film is formed by a dry process or a wet process. It is also possible to have a distribution locally in the. In particular, when a solution or dispersion is applied to a substrate in a wet process, the wettability varies depending on the surface energy of the substrate, and the flow and movement of the solution or dispersion are controlled by physical partition walls. Thus, a pattern of the organic semiconductor thin film can be obtained by a wet / dewet pattern.

Further, the shape of the base is not particularly limited, but a sheet-like base or a plate-like base (substrate) is usually used.
The organic semiconductor thin film of the present invention is characterized by high carrier mobility, and is preferably 1 × 10 ⁻⁴ cm ² / V · s or more. More preferably, it is 1 × 10 ⁻³ cm ² / V · s or more, and most preferably 1 × 10 ⁻² cm ² / V · s or more.

By using such an organic semiconductor thin film, a semiconductor element useful in fields such as electronics, photonics, and bioelectronics can be manufactured. Examples of such semiconductor elements include diodes, transistors, thin film transistors, memories, photodiodes, light emitting diodes, light emitting transistors, sensors, and the like.
Transistors and thin film transistors can be used in various display elements such as liquid crystal displays, distributed liquid crystal displays, electrophoretic displays, particle rotating display elements, electrochromic displays, organic light-emitting displays, and electronic paper. Various display devices can be manufactured using the. Transistors and thin film transistors are used in these display elements as switching transistors, signal driver circuit elements, memory circuit elements, signal processing circuit elements, and the like of display pixels.

  When the semiconductor element is a transistor, the element structure includes, for example, a structure of substrate / gate electrode / insulator layer (dielectric layer) / source electrode / drain electrode / semiconductor layer, substrate / semiconductor layer / source electrode. -Structure of drain electrode / insulator layer (dielectric layer) / gate electrode, substrate / source electrode (or drain electrode) / semiconductor layer + insulator layer (dielectric layer) + gate electrode / drain electrode (or source electrode) The structure etc. are mention | raise | lifted. At this time, a plurality of source electrodes, drain electrodes, and gate electrodes may be provided. Further, a plurality of semiconductor layers may be provided in the same plane or may be provided in a stacked manner.

  As the structure of the transistor, either a MOS (metal-oxide (insulator layer) -semiconductor) type or a bipolar type can be employed. Since the polyacene compound is usually a p-type semiconductor, the device can be configured by combining with a polyacene compound that is an n-type semiconductor by donor doping or by combining with an n-type semiconductor other than the polyacene compound.

When the semiconductor element is a diode, the element structure includes, for example, a structure of electrode / n-type semiconductor layer / p-type semiconductor layer / electrode. And the organic-semiconductor thin film of this invention is used for a p-type semiconductor layer, and the above-mentioned n-type semiconductor is used for an n-type semiconductor layer.
At least a part of the interface between the organic semiconductor thin film in the semiconductor element or the surface of the organic semiconductor thin film and the electrode can be a Schottky junction and / or a tunnel junction. A semiconductor element having such a junction structure is preferable because a diode or a transistor can be manufactured with a simple structure. Furthermore, a plurality of organic semiconductor elements having such a junction structure can be joined to form elements such as an inverter, an oscillator, a memory, and a sensor.

  Further, when the semiconductor element of the present invention is used as a display element, it can be used as a transistor element (display TFT) that is arranged in each pixel of the display element and switches display of each pixel. Since such an active drive display element does not require patterning of an opposing conductive substrate, depending on the circuit configuration, pixel wiring can be simplified compared to a passive drive display element that does not have a transistor for switching pixels. Usually, one to several switching transistors are arranged per pixel. Such a display element has a structure in which a data line and a gate line which are two-dimensionally formed on a substrate surface cross each other, and the data line and the gate line are respectively joined to the gate electrode, the source electrode and the drain electrode of the transistor. ing. It is possible to divide the data line and the gate line, and to add a current supply line and a signal line.

In addition to the pixel wiring and the transistor, a capacitor can be provided in addition to the pixel of the display element to provide a signal recording function. Furthermore, a data line and gate line driver, a pixel signal memory, a pulse generator, a signal divider, a controller, and the like can be mounted on the substrate on which the display element is formed.
The organic semiconductor element of the present invention can also be used as an arithmetic element and a storage element in an IC card, a smart card, and an electronic tag. In that case, even if these are a contact type or a non-contact type, they can be applied without any problem. The IC card, smart card, and electronic tag are composed of a memory, a pulse generator, a signal divider, a controller, a capacitor, and the like, and may further include an antenna and a battery.

  Furthermore, if the organic semiconductor element of the present invention is configured as a diode, an element having a Schottky junction structure, or an element having a tunnel junction structure, the element can be used as a light receiving element such as a photoelectric conversion element, a solar cell, an infrared sensor, or a photodiode. It can be used as a light emitting element. In addition, when a transistor is constituted by the organic semiconductor element of the present invention, the transistor can be used as a light emitting transistor. A known organic material or inorganic material can be used for the light emitting layer of these light emitting elements.

  Furthermore, the organic semiconductor element of the present invention can be used as a sensor and applied to various sensors such as a gas sensor, biosensor, blood sensor, immune sensor, artificial retina, taste sensor, pressure sensor, scanner, and position sensor. Can do. Usually, the measurement object can be analyzed by a change in the resistance value of the organic semiconductor thin film that occurs when the measurement object is brought into contact with or adjacent to the organic semiconductor thin film constituting the organic semiconductor element. However, the present invention is not limited to this, and the sensor using the polyacene compound of the present invention can be used as a signal amplification unit or a signal transfer unit other than the detection unit, or as a single element, a composite element, or an array.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Example 1: 2- (dimethylpentylsilyl) pentacene]
[Synthesis of polyacene compounds]
A compound synthesized by Diels-Alder reaction of 2- (dimethylpentylsilyl) -1,3-butadiene and dimethyl acetylenedicarboxylate is oxidized with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) Thus, dimethyl 4- (dimethylpentylsilyl) phthalate was obtained. This was reduced and then subjected to Swern oxidation to obtain 4- (dimethylpentylsilyl) phthalaldehyde. Next, this phthalaldehyde derivative and 1,4-dihydroxyanthracene were condensed and cyclized using an equimolar amount to synthesize 2- (dimethylpentylsilyl) pentacene-6,13-quinone.

  Next, a mixture of 300 mg of 2- (dimethylpentylsilyl) pentacene-6,13-quinone and 1.2 g of aluminum triisopropoxide was heated to 180-220 ° C. under reduced pressure and kept in that state for 1.5 hours. Reacted. By this reaction, reduction and aromatization of 2- (dimethylpentylsilyl) pentacene-6,13-quinone proceed to produce 2- (dimethylpentylsilyl) pentacene.

  The mixture was cooled and then treated with dilute hydrochloric acid, and the product insoluble in the aqueous solution was collected by filtration. This crude product was repeatedly washed and filtered with a mixed solvent of hexane and chloroform and then acetonitrile, and the by-product was completely removed from the crude product to obtain a purified product. This blue-blue purified product was vacuum-dried to obtain 40 mg of high-purity 2- (dimethylpentylsilyl) pentacene (see the following chemical formula (VI)). The yield in this reaction was 14.5%.

The obtained 2- (dimethylpentylsilyl) pentacene was dissolved in deuterated 1,1,2,2-tetrachloroethane, and nuclear magnetic resonance (NMR) spectrum measurement was performed at 80 ° C. The results are shown below.
¹ H-NMR (ppm): δ 0.41 (s, 6H), 0.91 (m, 6H), 1.34 to 1.40 (m, 5H), 7.34 (s, 2H), 7. 43 (d, 1H), 7.90 (d, 1H), 7.95 (s, 2H), 8.11 (s, 1H), 8.63 (s, 4H), 8.67 (s, 3H) ), 8.97 (s, 2H)
In addition, mass spectrometry was performed on 2- (dimethylpentylsilyl) pentacene. The results are as follows.

FAB-MS (NBA): m / z = 406
Calculated value: m / z = 406
[Production of organic semiconductor thin film]
10 mg of tetralin was mixed with 10 mg of 2- (dimethylpentylsilyl) pentacene synthesized as described above to prepare a solution at room temperature. A silicon substrate on which a surface was thermally oxidized to form a SiO ₂ film having a thickness of 200 nm was prepared by spin-coating hexamethyldisilazane, and the tetralin solution was dropped onto the surface of the silicon substrate. And the solvent was vaporized and the thin film with an average film thickness of 150 nm was formed on the silicon substrate.

As a result of analyzing the crystal structure of the thin film by wide-angle X-ray diffraction pattern measurement, a diffraction peak with an interplane distance of 2.66 nm was observed. From this result, it was found that the long axis of the 2- (dimethylpentylsilyl) pentacene molecule was aligned along the direction perpendicular to the substrate.
[Production of thin film transistor]
A gold / titanium thin film (with a thickness of 22 nm for gold and 3 nm for titanium) is patterned by photolithography on the surface of a silicon substrate having a thermal oxide film having a thickness of 200 nm as described above. A drain electrode was formed. The source / drain electrodes have a channel length of 20 μm and a channel width of 500 μm.

Next, a 2- (dimethylpentylsilyl) pentacene thin film having an average film thickness of 150 nm was formed as a semiconductor layer on the silicon substrate on which such an electrode pattern was formed in the same manner as described above to obtain a transistor structure.
Using the silicon substrate of the transistor as the gate electrode, the drain current / gate voltage curve between the source and drain electrodes was measured. At that time, the gate electrode was scanned with a voltage of 40 V to −60 V, the drain voltage was set to −20 V, and the change in the drain current was observed. The obtained transfer characteristics showed p-type semiconductor operation, the carrier mobility determined in the saturation region was 0.16 cm ² / Vs, and the threshold voltage was −1.3 V.

  The present invention is suitable for electronics, photonics, bioelectronics and the like.

Claims (14)

A polyacene compound having a structure represented by the following chemical formula (I):

However, X in chemical formula (I) is a halogen group or a hydrogen atom, respectively, and m is an integer of 1-6. In addition, at least one of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R _{8 in} the chemical formula (I) is a silicon-containing group represented by the chemical formula (II). The balance is a hydrogen atom. Further, B ₁ , B ₂ and B ₃ in the chemical formula (II) are respectively an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group and an alkynyl group, an aromatic hydrocarbon group, an alkoxy group, an aryloxy group and an acyl group. , Ester group, alkyloxycarbonyl group, aryloxycarbonyl group, carboxyl group, formyl group, hydroxyl group, halogen group, amino group, imino group, amide group, cyano group, siloxy group, mercapto group, sulfide group, disulfide group, sulfonyl A group, or a composite functional group containing two or more of these groups. Further, A in the chemical formula (II) is a single bond, a methylene group, an alkylene group, an alkenylene group, an alkynylene group, a bifunctional aromatic hydrocarbon group, a carbonyl group, or an ether group. The polyacene according to claim 1, wherein R ₁ , R ₄ , R ₅ and R ₈ are hydrogen atoms, and at least one of R ₂ , R ₃ , R ₆ and R ₇ is the silicon-containing group. Compound. The polyacene according to claim 1, wherein R ₁ , R ₄ , R ₅ , R ₆ , R ₇ and R ₈ are hydrogen atoms, and at least one of R ₂ and R ₃ is the silicon-containing group. Compound. _2. The polyacene compound according to claim 1, wherein R ₁ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ , and R ₈ are hydrogen atoms, and R ₂ is the silicon-containing group. The polyacene compound according to any one of claims 1 to 4, wherein at least one of B ₁ , B ₂ , and B ₃ is an alkyl group.   m is 2 or 3, The polyacene compound as described in any one of Claims 1-5 characterized by the above-mentioned.   m is 1, The polyacene compound as described in any one of Claims 1-5 characterized by the above-mentioned. A method for producing the polyacene compound according to any one of claims 1 to 7, wherein the carbonyl group of the polyacenequinone derivative having a structure represented by the following chemical formula (III) is reduced and aromatized. Directly converted into the polyacene compound, or a polyacene quinone derivative having a structure represented by the following chemical formula (III) is reduced to form a structure represented by the following chemical formula (IV): A method for producing a polyacene compound, characterized in that a hydroxypolyacene derivative having a hydrofluoric acid derivative and further aromatizing, halogenating or aromatizing the hydroxypolyacene derivative.

However, X in Chemical Formula (III) and Chemical Formula (IV) is a halogen group or a hydrogen atom, k is an integer of 1 or more, and k + 1 is an integer of 1 or more and 6 or less. In addition, at least one of R ₁ , R ₂ , R ₃ , R ₄ , R ₅ , R ₆ , R ₇ and R _{8 in} the chemical formula (III) and the chemical formula (IV) is represented by the chemical formula (V). It is a silicon-containing group, and the balance is a hydrogen atom. Further, B ₁ , B ₂ and B ₃ in the chemical formula (V) are respectively an aliphatic hydrocarbon group such as an alkyl group, an alkenyl group and an alkynyl group, an aromatic hydrocarbon group, an alkoxy group, an aryloxy group and an acyl group. , Ester group, alkyloxycarbonyl group, aryloxycarbonyl group, carboxyl group, formyl group, hydroxyl group, halogen group, amino group, imino group, amide group, cyano group, siloxy group, mercapto group, sulfide group, disulfide group, sulfonyl A group, or a composite functional group containing two or more of these groups. Further, A in the chemical formula (V) is a single bond, a methylene group, an alkylene group, an alkenylene group, an alkynylene group, a bifunctional aromatic hydrocarbon group, a carbonyl group, or an ether group.   A solution comprising the polyacene compound according to claim 1.   An ink comprising the polyacene compound according to any one of claims 1 to 7.   An organic semiconductor thin film comprising the polyacene compound according to claim 1 and having crystallinity.   The crystalline organic semiconductor thin film formed on the substrate, wherein the major axis of the molecule of the polyacene compound is oriented in a direction perpendicular to the surface of the substrate. Organic semiconductor thin film.   An organic semiconductor device comprising at least a part of the organic semiconductor thin film according to claim 11.   13. A transistor comprising a gate electrode, a dielectric layer, a source electrode, a drain electrode, and a semiconductor layer, wherein the semiconductor layer comprises the organic semiconductor thin film according to claim 11 or 12.