JP5438363B2 - Organic semiconductor material characterized by wide band gap - Google Patents

Description

The present invention relates to an organic semiconductor material.

Organic semiconductors are likely to be able to be fabricated by wet processes such as coating and printing, and therefore it is expected that the cost per unit area can be greatly reduced as compared with conventional semiconductor devices using silicon. Applications are expected to be applied to flexible displays typified by organic EL and electronic paper, and next-generation energy devices typified by organic thin-film solar cells. In particular, organic thin-film solar cells, unlike conventional silicon-based solar cells, are light, thin and colorful so that they do not require a frame, so solar cells that can be attached to roofs, walls, windows, etc. can be realized. There is a possibility, and it is highly expected from the industry.

Organic semiconductors used in such organic thin-film solar cells can be broadly divided into p-type organic semiconductors and n-type organic semiconductors. For p-type organic semiconductor materials, the open-circuit photovoltage (V _oc ) can be increased. Therefore, an organic semiconductor material having a wide band gap that can be expected to improve photoelectric conversion efficiency is demanded.

The relationship between the band gap and the open photovoltage has been reported, for example, by Sasa et al., Fixing an n-type organic semiconductor to fullerene, and using a typical pentacene (band gap: about 1.9 eV) as a p-type organic semiconductor. open light voltage of the solar cell using) _{(V OC),} compared to about 0.4V, rubrene as a p-type organic semiconductor (band gap: from organic solar cell using about 2.2 eV), about A vastly large V _{OC of} 0.9 V has been reported. (Non-Patent Document 1)

In addition, as an organic semiconductor excellent in organic transistor characteristics, dinaphtho [2,3-b: 2 ′, 3′-f] thieno [3,2-b] thienothiophene reported by Kamiya et al. The proponent of Document 2 refers to this organic semiconductor as DNTT. In order to distinguish it from the present invention, it is assumed here that 2,3-DNTT is used, and the carrier mobility is as good as 2.0 cm ² / Vs. Have been reported to exhibit excellent electrical properties. The band gap of 2,3-DNTT was estimated to be 3.38 eV in Non-Patent Document 2.

Tetsuya Satsuma et al. “High efficiency and durability improvement of organic solar cells” p. 125-133 [ISBN: 978-4-903413-56-3] T.A. Yamamoto, K .; Takimiya “Journalof American Chemical Society” 2007, 129, 2224-2225 Y. Y. Lin, D.D. J. et al. Gundlach, S.M. F. Nelson, T .; N. Jackson, “IEEE Electron Device Letters” 1997, 18, 606 H. Okamoto, N .; Kawasaki, Y. et al. Kaji, Y. et al. Kubozono, A.M. Fujiwara, M .; Yamaji "Journal of American Chemical Society" 2008, 130, 10470-10471

As described above, research has been conducted on compounds having various chemical structures as organic semiconductor materials. However, pentacene, which is a typical organic semiconductor, is oxidized and deteriorated in air or in solution. Therefore, a compound having oxidation resistance is required. Further, in the organic thin film solar cell, p-type semiconductor as phthalocyanine (band gap: 1.6 eV), but such is utilized, in order to obtain a high open photovoltage _{(V OC),} wider (HOMO-LUMO) Band There is a need for compounds with gaps.

Here, the present inventors paid attention to the difference between pentacene [Chemical 4] and picene [Chemical 5], which are well-known organic semiconductors as shown below. Pentacene [Chemical Formula 4] and Picene [Chemical Formula 5] are polycyclic aromatic compounds in which five benzene nuclei are combined, and there is no significant difference in the organic semiconductor properties of both compounds. ing. For example, the carrier mobility is 1.5 cm ² / Vs for pentacene (Non-Patent Document 3) and 1.1 cm ² / Vs for picene. (Non-Patent Document 4)



[Chemical 4]
[Chemical 5]

However, it is known that there is a difference between oxidation resistance and band gap. Regarding oxidation resistance, specifically, an organic transistor using pentacene deteriorates quickly in the air, but an organic transistor using picene can be driven in the air. Regarding the band gap, the band gap of pentacene is about 1.9 eV, whereas the band gap of picene is as wide as about 3.3 eV. The difference in the band gap is reflected in the color of the crystal through the absorption spectrum. The picene crystal is white, but pentacene is a black-violet crystal.

Thus, it has been found that the combination of benzene nuclei has a large effect on oxidation resistance and band gap. The present invention has been achieved by applying this concept to symmetrical three types of DNTT (chemical formulas and their formal names and abbreviations are shown in [Chemical Formula 6] to [Chemical Formula 8]. Details will be described later).

[Chemical 6] Dinaphtho [2,3-b: 2 ′, 3′-f] thieno [3,2-b] thienothiophene
Embedded image Dinaphtho [2,1-b: 2 ′, 1′-f] thieno [3,2-b] thienothiophene
Embedded image Dinaphtho [1,2-b: 1 ′, 2′-f] thieno [3,2-b] thienothiophene

That is, when the HOMO-LUMO band gap of each compound having different benzene ring combinations was estimated using molecular orbital calculation (basis function: RB3LYP / 6-31G), the results shown in Table 1 below were obtained. .
From the above results, it was estimated that the band gap of 1,2-DNTT was the maximum among the three types of DNTT. 1,2-DNTT was actually synthesized and compared with the other two types (2,3-DNTT is described in Non-Patent Document 2 and 2,1-DNTT is described in Patent Document 1). The present invention was reached because it was supported.

Japanese Patent Application No. 2008-154756

The present invention is described in detail below.

According to one aspect of the present invention, Ru is represented by the following chemical formula: [Formula 1], an organic semiconductor material characterized Ji eno thiophene skeleton.
[Chemical 1]
However, from the substituent R ¹ in the chemical formula [Chemical Formula 1] R ¹² represents a hydrogen atom and a halogen atom, aryl group, heterocyclic group, alkyl group, fluoroalkyl group, alkenyl group, fluoroalkenyl group, alkynyl group, fluoroalkynyl group, alkoxyl group, fluoroalkoxyl group, amino group, amide group , An imino group, a carboxyl group, a hydroxyl group, an ester group, a nitro group, a nitrile group, a sulfide group, a mercapto group, a sulfonyl group, and a silyl group.

The formal name of the chemical formula [Chemical Formula 1] is dinaphtho [1,2-b: 1 ′, 2′-f] thieno [3,2-b] thiophene, and is hereinafter referred to as 1,2-DNTT.

From substituent R ^{1 in} chemical formula [Chemical Formula 1] R ¹² represents a hydrogen atom and a halogen atom, aryl group, heterocyclic group, alkyl group, fluoroalkyl group, alkenyl group, fluoroalkenyl group, alkynyl group, fluoroalkynyl group, alkoxyl group, fluoroalkoxyl group, amino group, amide group , An imino group, a carboxyl group, a hydroxyl group, an ester group, a nitro group, a nitrile group, a sulfide group, a mercapto group, a sulfonyl group, and a silyl group. In addition, from the substituent R ¹ Preferred examples of R ¹² are a hydrogen atom, a fluorine atom, an aryl group, a heterocyclic group, an alkyl group, a fluoroalkyl group, an alkenyl group, an alkynyl group, an alkoxyl group, a fluoroalkoxyl group, and an amino group.

From the substituent R ¹ The halogen atom in R ¹² is fluorine, chlorine, bromine or iodine, and a preferred example is a fluorine atom.

From the substituent R ¹ The aryl group in R ¹² is not particularly limited, and examples thereof include a phenyl group, p-tolyl group, p-fluorophenyl group, pentafluorophenyl group, p- (trifluoromethyl) phenyl group, 1-naphthyl group, 2- A naphthyl group biphenyl group, a terphenyl group, a (diphenylamino) phenyl group, etc. are mentioned.

From the substituent R ¹ The heterocyclic group in R ¹² is not particularly limited, and a 2-thienyl group, a 5- (n-1-octyl) thienyl group, a 2-benzothienyl group, a 2-furyl group, a 1-methyl-2-pyrrolyl group, 2-pyridyl group, 2-bipyridyl group, etc. are mentioned.

From the substituent R ¹ The alkyl group in R ¹² is not particularly limited, and is a linear, branched, or cyclic alkyl group such as an n-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, n -Octyl group, n-nonyl group, n-decyl group, n-undecyl group, n-dodecyl group, n-tridecyl group, isopropyl group, t-butyl group, cyclopropyl group, cyclopentyl group, adamantyl group, etc. The fluoroalkyl group is not particularly limited, and examples thereof include a trifluoromethyl group, a perfluorooctyl group, and a perfluorododecyl group.

The alkenyl group in the substituents R ¹ to R ¹² is not particularly limited, and examples thereof include an ethenyl group, a methylethenyl group, a (n-octyl) ethenyl group, a phenylethenyl group, a naphthylethenyl group, a biphenylethenyl group, and a terphenylethenyl group. Group, perfluorophenylethenyl group and the like.

The alkenyl group in the substituents R ¹ to R ¹² is not particularly limited, and examples thereof include an ethynyl group, a methylethynyl group, an (n-octyl) ethynyl group, a phenylethynyl group, a naphthylethynyl group, a biphenylethynyl group, and a terphenylethynyl group. And a perfluorophenylethynyl group.

From the substituent R ¹ The alkoxyl group in R ¹² is not particularly limited. For example, n-butoxy group, n-pentyloxy group, n-hexyloxy group, n-heptoxy group, n-octyloxy group, n-nonyloxy group, n-decyloxy group, n -Undecoxy group, n-dodecyloxy group, n-tridecyloxy group, isopropoxy group, t-butyloxy group, cyclopropoxy group, cyclopentyloxy group and the like, and fluoroalkoxy group is not particularly limited, trifluoromethoxy group, Examples include perfluorooctyloxy groups and perfluorododecyloxy groups.

The amino group in the substituents R ¹ to R ¹² is not particularly limited, and examples thereof include a diphenylamino group, a di (p-tolyl) amino group, a dinaphthylamino group, a dithienylamino group, and a dipyridylamino group.

Subsequently, the invention according to claim 2 is the organic semiconductor material according to claim 1, wherein R ⁿ and R ^{n + 6 in} the chemical formula [Chemical Formula 1] are the same substituents other than hydrogen atoms. .

The organic semiconductor material according to claim 2 can be easily synthesized by using a compound having a substituent at the n + 2, (n + 2) ′ position of the compound E described later, but the synthesis method is particularly limited. It is not a thing. The n + 2 and (n + 2) ′ positions of Compound E are position numbers as shown in [Chemical Formula 3]. Here, n is an integer of 1-6.

[Chemical formula 3]

Substituents R ⁿ and R ^{n + 6} are a halogen atom, aryl group, heterocyclic group, alkyl group, fluoroalkyl group, alkenyl group, fluoroalkenyl group, alkynyl group, fluoroalkynyl group, alkoxyl group, fluoroalkoxyl group, amino group, Amide group, imino group, carboxyl group, hydroxyl group, ester group, nitro group, nitrile group, sulfide group, mercapto group, sulfonyl group, silyl group, preferred examples are fluorine atom, aryl group, heterocyclic group, alkyl Group, fluoroalkyl group, alkenyl group, alkynyl group and amino group.

Then, the invention of claim 3, any one of organic semiconductor material according to claim 2 claim 1, or a combination of a plurality of any of the organic semiconductor material according to claim 2 claim 1, consisting of an organic It is an electronic device. An organic electronic device here is an electronic device that utilizes the electrical characteristics of the organic semiconductor material . Specifically, an organic transistor, an organic light emitting diode, an organic diode, an organic laser, an organic thin film solar cell, an organic thin film Memory etc. are mentioned.

When using the compound of the present invention for these organic electronic devices, purification such as removal of impurities is necessary for high purity. The compound of the present invention is not limited to liquid chromatography, sublimation, zone melting, etc. It can be purified by gel permeation chromatography method, recrystallization method and the like.

Further, when the compound of the present invention is used for an organic electronic device, it is mainly used in the form of a thin film, and either a wet process or a dry process may be used as a method for forming the thin film.

The wet process here refers to a spin coating method, a dip coating method, a bar coating method, a spray coating method, an ink jet method, a screen printing method, a lithographic printing method, an intaglio printing method, a relief printing method, and the like. Can be used.

The dry process mentioned here indicates a vacuum deposition method, a sputtering method, a CVD method, a laser deposition method, a molecular beam epitaxial growth method, a vapor phase transport growth method, and the like, and these known methods can be used.

According to invention of Claim 1, the absorption efficiency in an ultraviolet region is high, and it can utilize also as a solar cell.

According to the invention of claim 2, the synthesis process is facilitated by making R ⁿ and R ^{n + 6} in the symmetrical position of the compound of claim 1 the same substituent.

According to the invention of claim 3, it is possible to clarify the use of the compound of claims 1 to 2 and to effectively use the compound.

Spectrum of UV absorption edge of 1,2-DNTT, 2,1-DNTT, 2,3-DNTT Overwrite of UV spectrum of 1,2-DNTT, 2,1-DNTT, 2,3-DNTT Examples of organic semiconductor device usage Examples of use in organic thin-film solar cells

Examples of the present invention are shown below.

The reaction formula [Chemical Formula 2] of the synthesis process of the organic semiconductor 1,2-DNTT according to claim 1 is shown below. [Chemical formula 2]

Synthesis of Compound A Under a nitrogen atmosphere, 10.6 ml (22.7 mmol) of 1-bromo-2-naphthol, 63 ml of triethylamine and 250 ml of methylene chloride were added to a 1 L four-necked flask, and trifluoromethanesulfonic acid was added to the solution under ice water cooling. A solution of 75.9 g (269 mmol) of anhydride in methylene chloride (80 ml) was added dropwise over about 1 hour, followed by stirring at room temperature for 4 hours. After completion of the reaction, the reaction solution was washed with 5% aqueous sodium hydrogen carbonate solution and 10% brine in that order, and the organic layer was dried over magnesium sulfate and concentrated under reduced pressure. The resulting crude product was purified by column chromatography to obtain Compound A. The measurement results of ¹ H-NMR and ¹³ C-NMR of Compound A are shown below. ¹ H-NMR (400 MHz, CDCl ₃ ): δ _H 7.43 (d, 1H), 7.61 (ddd, 1H), 7.69 (ddd, 1H), 7.88 (d, 2H), 8.32 (d, 1H). ¹³ C-NMR (100 MHz, CDCl ₃ ): δ _C 116.2, 119.9, 127.7, 127.8, 128.3, 128.8, 129.0, 129.7, 132.7, 133.0, 145.1.

Synthesis of Compound B Under a nitrogen atmosphere, 20 g (56.3 mmol) of Compound A , 200 ml of triethylamine, 1.25 g (1.08 mmol) of tetrakistriphenylphosphine palladium, 218 mg of copper (I) iodide (1. 14 mmol), 9.4 ml (67.9 mmol) of trimethylsilylacetylene was added, and the mixture was stirred at 40 ° C. for 48 hours. After completion of the reaction, toluene was added to the reaction solution and washed with 10% brine, and the organic layer was dried over magnesium sulfate and concentrated under reduced pressure. The resulting crude product was purified by column chromatography to obtain Compound B. The measurement results of ¹ H-NMR and ¹³ C-NMR of Compound B are shown below. ¹ H-NMR (400 MHz, CDCl ₃ ): δ _H 0.3 (d, 9H), 7.49 (d, 1H), 7.50 (ddd, 1H), 7.58 (ddd, 1H), 7.70 (d, 1H), 7.77 (d, 1H), 8.28 (d, 1H). ¹³ C-NMR (100 MHz, CDCl ₃ ): δ _C -0.1, 100.5, 104.3, 123.3, 126.8, 127.2, 127.3, 127.8, 127.9 , 128.1, 129.2, 132.2, 133.7.

Synthesis of Compound C 30 g (98.9 mmol) of Compound B , methanol 15 in a 500 ml eggplant flask under a nitrogen atmosphere
0 ml and 1.37 g (9.91 mmol) of potassium carbonate were added and stirred at room temperature for 2 hours. After completion of the reaction, toluene was added to the reaction solution and washed with 10% brine, and the organic layer was dried over magnesium sulfate and concentrated under reduced pressure. The resulting crude product was purified by column chromatography to obtain Compound C. The measurement results of ¹ H-NMR and ¹³ C-NMR of Compound C are shown below. ¹ H-NMR (400 MHz, CDCl ₃ ): δ _H 3.50 (s, 1H), 7.53 (d, 1H), 7.51-7.55 (m, 1H), 7.61 (ddd , 1H), 7.74 (d, 1H), 7.80 (d, 1H), 8.29 (d, 1H). ^{13 C-NMR (100 MHz,} CDCl 3): δ C 82.5, 83.2, 122.3, 126.8, 127.4,127.5, 127.9, 128.0,128.2, 129.3, 132.1, 133.9.

Synthesis of Compound D Under a nitrogen atmosphere, 29 g (81.7 mmol) of Compound A , 180 ml of DMF, 70 ml of triethylamine, 1.41 g (1.22 mmol) of tetrakistriphenylphosphine palladium, 232 mg of copper (I) iodide (1 mg) 1.22 mmol) was added, and the mixture was heated to 50 ° C., and a solution of 17.9 g (77.4 mmol) of Compound C in 180 ml of DMF was added dropwise over about 4 hours, followed by stirring for 10 hours. After completion of the reaction, toluene was added to the reaction solution and washed with 10% brine, and the organic layer was dried over magnesium sulfate and concentrated under reduced pressure. The resulting crude product was purified by column chromatography and hot washing to obtain Compound D. The measurement results of ¹ H-NMR and ¹³ C-NMR of Compound D are shown below. ¹ H-NMR (400 MHz, CDCl ₃ ): δ _H 7.55 (ddd, 2H), 7.62 (ddd, 2H), 7.69 (d, 2H), 7.80 (d, 2H), 7.83 (d, 2H), 8.34 (d, 2H). ¹³ C-NMR (100 MHz, CDCl ₃ ): δ _C 94.5, 123.3, 126.7, 127.4, 127.5, 127.9, 128.0, 128.2, 129.2 132.3, 133.9.

Synthesis of Compound E In a nitrogen atmosphere, 7.0 g (16.1 mmol) of Compound D and 500 ml of THF were added to a 1 L four-necked flask, cooled to −70 ° C., and then a 2.69 M butyllithium hexane solution (13.1 ml). Added and stirred for 1 hour. After stirring, 1.03 g (32.1 mmol) of sulfur powder was added, and the temperature was gradually raised to -20 ° C. At −20 ° C., 2.5 ml (40.1 mmol) of iodomethane was added, and the temperature was raised to room temperature. After completion of the reaction, 7% dilute hydrochloric acid (200 ml) and toluene were added to the reaction solution, and the mixture was washed with 5% aqueous sodium hydrogen carbonate solution and 10% brine in that order. The organic layer was dried over magnesium sulfate and concentrated under reduced pressure. The resulting crude product was purified by column chromatography and recrystallization to obtain Compound E. ¹ H-NMR (400 MHz, CDCl ₃ ): δ _H 2.63 (s, 6H), 7.52 (ddd, 2H), 7.61 (ddd, 2H), 7.73 (d, 2H), 7.80 (d, 2H), 7.83 (d, 2H), 8.74 (d, 2H). ¹³ C-NMR (100 MHz, CDCl ₃ ): δ _C 95.0, 126.7, 126.8, 127.2, 127.3, 128.4, 128.6, 129.5, 133.5, 134.7, 137.2.

Synthesis of Compound F Under a nitrogen atmosphere, 200 mg (0.56 mmol) of Compound E , 1.5 ml of chloroform and 28.8 g (11.3 mmol) of iodine were added to a 30 ml three-necked flask and refluxed for 24 hours. The reaction solution was washed with 5% aqueous sodium thiosulfate solution and 10% brine in that order, and the organic layer was dried over magnesium sulfate and concentrated under reduced pressure. The resulting crude product was purified by column chromatography to obtain Compound F. ¹ H-NMR (400 MHz, CDCl ₂ CDCl ₂ ): δ _H 7.54 (t, 2H), 7.62 (t, 2H), 7.86 (d, 2H), 7.96 (d, 2H) ), 7.97 (d, 2H), 8.16 (d, 2H). IR (KBr): 3022, 1890, 1612, 1589, 1514, 1431, 1379, 1321, 1255, 1137, 1056, 983, 806, 744, 665, 538 cm ⁻¹ . Mass (m / z,%) 340 (100) (M ⁺ ), 170 (40).

The spectrum of the UV absorption edge of 1,2-DNTT, 2,1-DNTT, 2,3-DNTT and its overwriting are shown in FIGS. From these figures, it can be seen that 1,2-DNTT of the present invention has high absorption in the ultraviolet region.

Examples of use of organic semiconductor devices using 1,2-DNTT according to the present invention are shown in FIGS. FIG. 3 shows an example of use in a field effect transistor (hereinafter referred to as FET). FETs are used as switching elements and amplifying elements because of their characteristics. In addition to a low gate current, the structure is planar, so that fabrication and integration by a wet process are easy and a large area can be achieved. Here, 1,2-DNTT is mainly used as a p-type semiconductor, but may function as an n-type semiconductor depending on a substituent and a solvent. FIG. 4 shows an example of use in an organic thin film solar cell. The co-evaporation layer shown in FIG. 4 is a layer in which p-type and n-type are vapor-deposited together, and this layer is intended to facilitate separation by holes and electrons by sunlight.

The 1,2-DNTT of the present invention is expected to be effectively used as a solar cell because of its high light absorption efficiency in the ultraviolet region. In addition, by introducing various substituents into 1,2-DNTT, further improvement in solubility and mobility can be expected, and it is expected to be widely used in semiconductor devices and the like in the future.

DESCRIPTION OF SYMBOLS 1 FET using organic semiconductor 2 Organic semiconductor 3 Insulating film 4 Gate 41 Gate insulating film 5 Drain 6 Source 7 Emitter 8 Collector 9 Base 10 Substrate (plastic) 11 Electrode 12 N-type semiconductor 13 P-type semiconductor 14 Co-deposition layer 15 ITO (Indium Tin Oxide)

Claims (3)

Following chemical formula Ru represented by [Chemical Formula 1, the organic semiconductor material characterized Ji eno thiophene skeleton.
[Chemical 1]
However, from the substituent R ¹ in the chemical formula [Chemical Formula 1] R ¹² represents a hydrogen atom and a halogen atom, aryl group, heterocyclic group, alkyl group, fluoroalkyl group, alkenyl group, fluoroalkenyl group, alkynyl group, fluoroalkynyl group, alkoxyl group, fluoroalkoxyl group, amino group, amide group , An imino group, a carboxyl group, a hydroxyl group, an ester group, a nitro group, a nitrile group, a sulfide group, a mercapto group, a sulfonyl group, and a silyl group. 2. The organic semiconductor material according to claim 1, wherein R ⁿ and R ^{n + 6 in the} chemical formula [Chemical Formula 1] are the same substituents other than a hydrogen atom. Any organic semiconductor material according to claim 2 claim 1 or organic electronic device by combining a plurality of one of the organic semiconductor material according to claim 2 claim 1, consisting of,.