JP2020037523A - Benzothieno benzothiophene derivative, hole transport material composed of the same, and organic el element using the same - Google Patents

Abstract

To provide a novel benzothieno benzothiophene (BTBT) derivative that has an excellent thermal stability and an improved carrier mobility as a semiconductor material constituting an organic EL element, specifically as a hole transport material.SOLUTION: The benzothieno benzothiophene derivative is provided that is represented by the following general formula (1) (in the general formula (1), Rto Reach independently represent a hydrogen atom, an aromatic substituent, or an aliphatic substituent, and Arto Arrepresent an aromatic substituent).SELECTED DRAWING: None

Description

  The present invention relates to a novel benzothienobenzothiophene derivative excellent in hole transportability, and an organic EL device using the same.

  Organic EL (electroluminescence) elements are expected as next-generation FPDs (flat panel displays), and are being applied to mobile phone displays, lighting, TVs (television receivers), etc., and are being developed with even higher functionality Has been continued.

  When such an organic EL is applied to a display or lighting, it is important to efficiently reduce power consumption. A parameter that is a measure of power consumption is power efficiency. The power efficiency is in units of lm / W, and indicates how much light can be extracted per power. Since power is a product of voltage and current, if the voltage required for the amount of current for obtaining a certain luminance can be reduced, power efficiency will be improved. To increase the current at a constant voltage, improving carrier mobility is an effective means. Power consumption can be reduced by improving carrier mobility.

  Since an organic EL element has a mechanism in which charges injected from both electrodes recombine in a light emitting layer to emit light, it is important how to efficiently transfer holes (holes) and electrons to the light emitting layer. By increasing the hole injection from the anode and blocking the electrons injected from the cathode, the probability of recombination of holes and electrons is improved, and the exciton generated in the light emitting layer is confined. Thus, high luminous efficiency is considered to be obtained. Therefore, the role played by the hole transport material is important, and there is a need for a hole transport material having high hole injection properties, high hole mobility, high electron blocking properties, and high electron durability.

NPD (N, N′-di-1-naphthyl-N, N′-diphenylbenzidine) and various aromatic amine derivatives have been known as hole transport materials used in organic EL devices. . Although NPD has a good hole transporting ability, the glass transition point (T _g ), which is an index of heat resistance, is as low as 100 ° C., and under high temperature conditions, the device characteristics are deteriorated due to crystallization. Further, the aromatic amine derivative has a hole mobility of about 10 ⁻³ cm ² / Vs, and a material having a higher hole mobility is required for improving the performance of the organic EL device.

  Since the organic EL can be driven at a low voltage by being formed as an extremely thin film, there is a problem that occurs due to the extremely thin film, such as leakage current due to unevenness of the electrode and penetration of carriers from the light emitting layer. Also, in mass production of organic EL devices in factories, it is inevitable that a small amount of dust will be deposited on the substrate to such an extent that the effect on the ultra-thin film cannot be ignored, thereby lowering the yield. In order to solve such a problem, a high mobility material that does not change the driving voltage even when the film is made thicker is required as a semiconductor material constituting the device.

On the other hand, in the field of organic thin film transistors (TFTs), since the carrier mobility of a semiconductor material directly affects the switching speed of a TFT and the performance of a driving device thereof, it is necessary to improve the carrier mobility for practical use. Research for improving carrier mobility has already been actively conducted. For example, linear acenes (pentacene and the like), which are low-molecular semiconductor materials, are useful for improving the mobility, but the energy gap becomes narrower as the conjugation expands, and the semiconductor becomes unstable to the atmosphere. Therefore, in order to develop a stable and high-performance material even in the atmosphere, a method of introducing a heterocyclic ring containing atoms such as sulfur and selenium to cause localization of electrons, weaken aromaticity, and widen the gap Is used. Among them, thienoacenes incorporating a sulfur atom are known as a skeleton having a wide gap and a wide π-conjugated plane, and benzothienobenzothiophene (BTBT) is particularly attracting attention. BTBT has long been known as a liquid crystal material, but in 2006, Takimiya et al. Reported a high mobility of 2.0 cm ² / Vs in a DPh-BTBT vapor-deposited film having phenyl groups introduced at both ends ( Non-patent document 1). As a result, various high mobility materials have been developed (Non-Patent Documents 2 to 4).

  However, almost no application examples of BTBT to an organic EL device have been reported (Non-Patent Document 5). Therefore, in order to improve the power efficiency and extend the life of the organic EL device, a hole transporting material having excellent thermal stability and high mobility is required.

K. Takimiya, H. Ebata, K. Sakamoto, T. Izawa, T. Otsubo and Y. Kunugi, J. Am. Chem. Soc., 2006, 128, 12604. H. Ebata, T. Izawa, E. Miyazaki, K. Takimiya, M. Ikeda, H. Kuwabara and T. Yui, J. Am. Chem. Soc., 2007, 129, 15732. Y. Yuan, G. Giri, A. L. Ayzner, A. P. Zoombelt, S. C. B. Mannsfeld, J. Chen, D. Nordlund, M. F. Toney, J. Huangand Z. Bao, Nat. Commun., 2014, 5, 3005. H. Iino, T. Usui and J. Hanna, Nat.Commun., 2015, 6, 6828. T. Izawa, H. Mori, Y. Shinmura, M. Iwatani, E. Miyazaki, K. Takimiya, H.-W. Hung, M. Yahiro and C. Adachi, Chem. Lett., 2009, 38, 420.

  An object of the present invention is to provide a novel benzothienobenzothiophene (BTBT) derivative having excellent thermal stability and improved carrier mobility as a semiconductor material constituting an organic EL device.

一般式（１）中、Ｒ¹〜Ｒ¹⁴はそれぞれ独立に水素原子、芳香族置換基または脂肪族置換基を表し、Ａｒ¹〜Ａｒ³は芳香族置換基を表す。
本発明のホール輸送材料は、前記ベンゾチエノベンゾチオフェン誘導体からなる。
本発明の有機ＥＬ素子は、前記ベンゾチエノベンゾチオフェン誘導体を用いたものである。 The present invention solves the above-mentioned problems in the prior art, and includes the following items.
The benzothienobenzothiophene derivative of the present invention is represented by the following general formula (1).

In the general formula (1), R ^{1 to} R ¹⁴ each independently represent a hydrogen atom, an aromatic substituent or an aliphatic substituent, and Ar ^{1 to} Ar ³ represent an aromatic substituent.
The hole transporting material of the present invention comprises the above benzothienobenzothiophene derivative.
The organic EL device of the present invention uses the benzothienobenzothiophene derivative.

  The benzothienobenzothiophene (BTBT) derivative of the present invention has a hole transporting performance equal to or higher than that of NPD which is a conventional material, and has an excellent electron blocking ability. Further, the glass transition point, which is an index of heat resistance, is 141 to 184 ° C., which is higher than that of NPD, and the thin film state is stable, so that it is suitable as a material for a hole transport layer of an organic EL device. The organic EL device manufactured using the BTBT derivative exhibits high luminous efficiency and power efficiency without lowering the practical driving voltage, and has improved durability.

FIG. 1 shows the ¹ H-NMR spectrum of BTBTPP (1a), BTBTPB (1b), BTBTPSF (1c), and BTBTPDF (1d). FIG. 2 shows a PYS measurement result (2a), a UV-vis absorption spectrum (2b), and a PL spectrum (2c) of BTBTPP, BTBTPB, BTBTPSF, and BTBTPDF. FIG. 3 shows an energy diagram of the hole transport layer 4 / light emitting layer 5 / electron transport layer 6 in the device of device evaluation 1. FIG. 4 shows a current density-voltage characteristic (4a), a luminance-voltage characteristic (4b), an external quantum efficiency-luminance characteristic (4c), and an EL spectrum (4d) when a current is applied to the element of element evaluation 1. . FIG. 5 shows a current density-voltage characteristic (5a), a luminance-voltage characteristic (5b), an external quantum efficiency-luminance characteristic (5c), and an EL spectrum (5d) when a current is applied to the element of element evaluation 2. . FIG. 6 is an energy diagram (6a) of the hole transport layer 4 / light emitting layer 5 / electron transport layer 6 in the device of device evaluation 3, an EL spectrum (6b) when a current is applied to the device of device evaluation 3, and a current density. -Voltage characteristic (6c), luminance-voltage characteristic (6d), external quantum efficiency-luminance characteristic (6e), and life characteristic (6f). FIG. 7 shows a typical configuration of the organic EL device of the present invention.

Hereinafter, the present invention will be described in detail.
The benzothienobenzothiophene (hereinafter also referred to as “BTBT”) derivative of the present invention is represented by the following general formula (1).

In the general formula (1), R ^{1 to} R ¹⁴ each independently represent a hydrogen atom, an aromatic substituent or an aliphatic substituent.
The aromatic substituent includes an aromatic hydrocarbon group and an aromatic heterocyclic group. For example, phenyl, 2-biphenyl, 3-biphenyl, 4-biphenyl, 1-naphthyl, 2-naphthyl, o-terphenyl, m-terphenyl, p-terphenyl, 2- Aromatic substituents such as a pyridyl group, a 3-pyridyl group, a 4-pyridyl group, hexaphenylbenzene, a 2-dibenzofuranyl group, a 2-dibenzothiophenyl group and a triphenylenyl group are exemplified. Of these, a phenyl group and a 2-biphenyl group are preferred.

  The aliphatic substituent is a substituent composed of a chain carbon compound, specifically, an alkyl group, an alkenyl group, and an alkynyl group, and at least a part of hydrogen atoms constituting the alkyl group, the alkenyl group, and the alkynyl group. Is a group substituted with a hydroxyl group, a halogen atom, an amino group, a carboxyl group, or the like. Among these substituents, an alkyl group and an alkenyl group are preferred. Examples of the alkyl group include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, t-butyl, n-pentyl, n-hexyl, n-octyl, and n. -Decyl group, n-dodecyl group, n-stearyl group, 2-ethylhexyl group and neopentyl group. Examples of the alkenyl group include an allyl group, an n-butenyl group, a 1-pentenyl group, and a 1-methyl-1-butenyl group. Of these, substituents of relatively small molecular weight, such as methyl and isopropyl, are preferred.

Ar ¹ includes a 1,3-phenylene group, a 1,4-phenylene group, a 4,4′-biphenylene group, a 2,4′-biphenylene group, a 2,2′-biphenylene group, and a 2,3′-biphenylene group , 3,3'-biphenylene group, 3,4'-biphenylene group, 2,6-naphthylene group, 1,5-naphthylene group, 1,6-naphthylene group, 1,8-naphthylene group, 1,3-naphthylene Group, 1,4-naphthylene group, 9,9-spiro-bifluorene-2,7-diyl group, terphenylene group, 9,9-diphenylfluorene-2,7-diyl group, naphthylene group, pyridine-2,5 And aromatic substituents such as a -diyl group, a pyridine-2,6-diyl group, a 3,7-dibenzothiophenyl group and a 3,7-dibenzofuranyl group. Of these, those in which two bonds are mutually symmetrical from the center of the aromatic substituent are preferable, and 1,4-phenylene group, 4,4′-biphenylene group, 9,9-spiro-bifluorene-2, Preferred are a 7-diyl group, a 9,9-diphenylfluorene-2,7-diyl group, a 3,7-dibenzothiophenyl group and a 3,7-dibenzofuranyl group.

Ar ² and Ar ³ include phenyl, 2-biphenyl, 3-biphenyl, 4-biphenyl, 1-naphthyl, 2-naphthyl, o-terphenyl, m-terphenyl, p- And aromatic substituents such as a terphenyl group, a 2-pyridyl group, a 3-pyridyl group, a 4-pyridyl group, a 2-dibenzothiophenyl group and a triphenylenyl group. Of these, Ar ² and Ar ³ include a phenyl group and a 2-biphenyl, from the viewpoint of a reduction in the reaction rate during synthesis if the substituent is excessively bulky, or distortion of the π plane due to steric hindrance. And the like.

これらのうち、下記構造式で表されるＢＴＢＴＰＰ、ＢＴＢＴＰＢ、ＢＴＢＴＰＳＦ、およびＢＴＢＴＰＤＦ（化合物３１〜３４）が特に好ましい。

The compound represented by the general formula (1) may have any of a symmetrical structure and an asymmetrical structure, but preferably has a symmetrical structure centered on an N-Ar ¹ -N skeleton. . Specifically, compounds 1 to 34 having the following structural formula are preferred.

Of these, BTBTPP, BTBTPB, BTBTPSF, and BTBTPDF (compounds 31 to 34) represented by the following structural formulas are particularly preferred.

The BTBT derivative represented by the general formula (1) can be produced by various known methods. As an example, a method of synthesizing BBTTPP will be described.

After stirring BTBT-Br and an excess amount of aniline relative to BTBT-Br with a strong base such as tert-butoxy sodium, a Pd (0) catalyst and [ ^t Bu ₃ PH] ⁺ BF ₄ ^- are added, and the mixture is heated to reflux. I do. After stopping the reaction, purification is performed to obtain 2-anilino-BTBT. Further, after stirring p-dibromobenzene and 2 equivalents of 2-anilino-BTBT together with tert-butoxy sodium, a Pd (0) catalyst and [ ^t Bu ₃ PH] ⁺ BF ₄ ^- are added, and the mixture is heated under reflux. After terminating the reaction, the reaction is purified to obtain BTBTPP in a good yield.
However, the BTBT derivative of the present invention is not limited to the above method, and can be produced by combining various known methods.

Since the BTBT derivative of the present invention has a higher glass transition point (T _g ) and melting point (T _m ) than conventionally known hole transporting materials such as NPD, it can form a hole transporting layer having excellent heat resistance. Further, the thin film state can be stably maintained. Further, when a 30 nm-thick deposited film is formed using the BTBT derivative and the ionization potential (I _p ) is measured, it shows a low value, and good hole injection properties are expected.
In the benzothienobenzothiophene (hereinafter also referred to as “BTBT”) derivative of the present invention, the N—Ar ¹ —N skeleton has a hole injection / transport property and is formed using a BTBT derivative having such a skeleton. The organic EL element has high hole injection / mobility, can confine excitons generated in the light emitting layer, further improves the probability of recombination of holes and electrons, and can obtain high luminous efficiency. . Further, in such an organic EL element, the driving voltage is reduced, and the durability can be improved.

  The BTBT derivative of the present invention has excellent hole transporting properties and a wide band gap as compared with conventional materials, and thus can be used as a host material of a light emitting layer. By using it as a light emitting layer together with a dopant such as a phosphor or a phosphorescent light emitter, it can be expected that the driving voltage of the organic EL element is lowered and the luminous efficiency is improved.

[Organic EL device]
FIG. 7 shows a typical layer structure of the organic EL device of the present invention. The organic EL element is typically formed by depositing, for example, ITO as an anode 2 on a substrate 1, and then forming a hole injection layer 3, a hole transport layer 4, a light emitting layer 5, an electron transport layer 6, The electron injection layer 7 and the cathode 8 are laminated in this order. The hole transport layer 4 is formed of a BTBT derivative of the present invention, which is a hole transport material. An electron blocking layer may be provided between the hole transport layer 4 and the light emitting layer 5, and a hole blocking layer may be provided between the light emitting layer 5 and the electron transport layer 6. That is, in the multilayer structure, some layers may be omitted. For example, a simple layer structure in which the electron injection layer 7, the hole injection layer 3, and the like are omitted may be employed. Each layer will be described.

  As the substrate 1, a transparent and smooth substrate having a total light transmittance of at least 70% or more is used. Specifically, a flexible transparent substrate such as a glass substrate having a thickness of several μm or a special transparent substrate is used. Plastic or the like is used.

The anode 2 is an electrode having a function of injecting holes (holes) into the hole injection layer 3, the hole transport layer 4, and the light emitting layer 5. As a material of the anode 2, a metal oxide, a metal, an alloy, a conductive material, or the like having a work function of 4.5 eV or more is generally used. From the viewpoint of transmitting emitted light, the total light transmittance is Usually, those having 80% or more are preferable. Specifically, transparent conductive ceramics such as ITO and ZnO, and transparent conductive ceramics such as conductive polymer poly (3,4-ethylenedioxythiophene) / poly (4-styrenesulfonic acid) (PEDOT / PSS) and polyaniline A conductive polymer or another transparent conductive material is used. The thickness of the anode 2 is usually 5 to 500 nm, preferably 10 to 200 nm.
The resistance value of the anode 2 is preferably low from the viewpoint of power consumption of the organic EL element, and is preferably about 300 Ω / □ to several Ω / □.
The anode 2 is formed by a vapor deposition method, an electron beam method, a sputtering method, a chemical reaction method, a coating method, or the like.

The cathode 8 is an electrode having a function of injecting electrons into the electron injection layer 7, the electron transport layer 6, and the light emitting layer 5. In general, as the material of the cathode 8, a metal or an alloy having a work function of about 4 eV or less is suitable. Examples of the metal used for the cathode include platinum, gold, silver, copper, iron, tin, zinc, aluminum, indium, chromium, lithium, sodium, potassium, calcium, and magnesium. Of these, aluminum, lithium, sodium, potassium, calcium and magnesium are preferred. As a cathode using an alloy, an electrode made of an alloy of these low work function metals and a metal such as aluminum or silver, or a structure in which these low work function metals are stacked with a metal such as aluminum or silver is used. Electrodes and the like. An inorganic salt such as lithium fluoride can be used for the cathode having a laminated structure.
The resistance value of the cathode 8 is preferably low from the viewpoint of power consumption of the organic EL element, and is preferably several hundred Ω / □ to several Ω / □.
The cathode 8 is formed by a vapor deposition method, an electron beam method, a sputtering method, a chemical reaction method, a coating method, or the like.

  The hole injection layer 3 is a layer introduced for improving luminous efficiency. Since the hole injection layer 3 allows a current to flow at a low voltage, it is preferable that the film thickness be small (about 1 to 20 nm) and constant so as not to generate a pinhole or the like. Examples of such a hole injection material include (poly (arylene ether ketone) -containing triphenylamine (KLHIP: PPBI), PTPD-1: PPBI, hexaazatriphenylenecarbonitrile (HATCN), poly (3,4-ethylene Dioxythiophene) (PEDOT: PSS), phenylamine type, starburst type amine type, phthalocyanine type, amorphous carbon, poly (ether ketone) (PEK), polyaniline and the like.

  The hole transport layer 4 is provided between the anode 2 and the light emitting layer 5 and is a layer for efficiently transporting holes from the anode 2 to the light emitting layer. The BTBT derivative of the present invention is used as a hole transport material. As the hole transport material, a material having a small ionization energy, that is, a material in which electrons are easily excited from HOMO and holes are easily generated is used. Specifically, in addition to the BTBT derivative, poly (9,9-dioctyl) is used. Fluorene-alto-N- (4-butylphenyl) diphenylamine) (TFB), 4,4′-cyclohexylidenebis [N, N-bis (4-methylphenyl) benzeneamine] (TAPC), N, N ′ -Diphenyl-N, N'-di (m-tolyl) benzidine (TPD), N, N'-di (1-naphthyl) -N, N'-diphenylbenzidine (NPD), 4,4 ', 4' ' -Tri-9-carbazolyltriphenylamine (TCTA) and 4,4 ', 4' '-tris [phenyl (m-tolyl) amino] triphenylamine) And the like. These compounds may be used alone or in combination of two or more.

  Among the materials constituting the hole injection layer 3 and the hole transport layer 4, from the viewpoints of being capable of forming a coating film and improving the life, (poly (arylene ether ketone) -containing triphenylamine (KLHIP: PPBI), N, N′-di (1-naphthyl) -N, N′-diphenylbenzidine (NPD) and 4,4′-cyclohexylidenebis [N, N-bis (4-methylphenyl) benzeneamine] (TAPC) Is preferred.

It is preferable to use a host compound together with a light-emitting material in the light-emitting layer 5 as in other light-emitting layers used in an organic EL device. Examples of the light emitting material include tris (2-phenylpyridinato) iridium (III) (Ir (ppy) ₃ ) and bis [2- (4,6-difluorophenyl) pyridinato-C2, which are phosphorescent light emitting materials. N] (picolinato) iridium (III) (FIrpic), tris [1-phenylisoquinoline-C2, N] iridium (III) (Ir (piq) ₃ ), and a thermally activated delayed fluorescent material (4s, 6s) -2,4,5,6-tetra (9H-carbazol-9-yl) isophthalonitrile (4CzIPN), and 10,10 ′-(4,4′-sulfonylbis (4,1-phenylene)) bis ( 9,9-dimethyl-9,10-dihydroacridine)) (DMAC-DPS). Examples of the host compound include 9,9′-diphenyl-9H, 9′H-3,3′-dicarbazole (BCzPh), bis [2- (diphenylphosphino) phenyl] ether oxide (DPEPO), 6-bis (diphenylphorforyl) -9-phenylcarbazole (PO9), 4,4′-bis (N-carbazolyl) -1,1′-biphenyl (CBP), 3,3′-bis (N-carbazolyl) ) -1,1′-biphenyl (mCBP), tris (4-carbazoyl-9-ylphenyl) amine (TCTA), 2,8-bis (diphenylphosphoryl) dibenzothiophene (PPT), adamantane anthracene (Ad-Ant) ), Rubrene, and 2,2′-bi (9,10-diphenylanthracene) (TPBA).

  The electron transport layer 6 is provided between the cathode 8 and the light emitting layer 5 and is a layer for efficiently transporting electrons from the cathode to the light emitting layer. As the electron transporting material, a material having a high electron affinity, that is, a material having a low LUMO energy and easily causing excited electrons is used. Specifically, 3,3 ″, 5,5′-tetra (3-pyridyl) -1,1 ′; 3 ′, 1 ″ -terphenyl (B3PyPB), 4,6-bis (3,5-diphenyl) (Pyridin-3-yl) phenyl) -2-methylpyrimidine (B3PyMPM), 2- (4-biphenylyl) -5- (pt-butylphenyl) -1,3,4-oxadiazole (tBu-PBD) ), 1,3-bis [5- (4-t-butylphenyl) -2- [1,3,4] oxadiazolyl] benzene (OXD-7), 3- (biphenyl-4-yl) -5- ( 4-t-butylphenyl) -4-phenyl-4H-1,2,4-triazole (TAZ), bathocuproine (BCP), 1,3,5-tris (1-phenyl-1H-benzimidazol-2-yl ) Benzene (TPBi) .

  The electron injection layer 7 is a layer in contact with the cathode and having a role of transporting electrons. Examples of the electron injecting material include lithium fluoride (LiF), 8-hydroxyquinolinolato-lithium (Liq) and lithium 2- (2 ′, 2 ″ -bipyridin-6′-yl) phenolate (Libpp). Is mentioned.

Thin films formed on the substrate 1, such as the hole injection layer 3, the hole transport layer 4, the light emitting layer 5, the electron transport layer 6, and the electron injection layer 7, are stacked by a vacuum evaporation method or a coating method. The vacuum evaporation method includes a resistance heating evaporation method, an electron beam evaporation method, a sputtering method, a molecular stacking method, and the like. In the case of using a vacuum evaporation method, the evaporation is usually performed by heating the deposited material in an atmosphere reduced to 10 ⁻³ Pa or less.

  When the coating method is used, the constituent materials of each layer are, for example, dissolved in chloroform, methylene chloride, dichloroethane, tetrahydrofuran, toluene, xylene, acetone, methyl ethyl ketone, ethyl acetate, butyl acetate, ethyl cellosolve acetate, and water, and are known. Each layer is formed by a coating method. Examples of the coating method include a bar coating method, a capillary coating method, a slit coating method, an inkjet method, a spray coating method, a nozzle coating method, and a printing method. The same coating method may be used for the formation of each layer, or an optimal coating method may be used individually according to the type of ink.

The thickness of each layer varies depending on the resistance value and charge mobility of the constituent material, but is usually 1 to 100 nm, preferably 1 to 50 nm. Note that the electron injection layer 7 and the like may be formed with a thickness of 1 nm or less.
The organic EL device of the present invention may be formed by, for example, a roll-to-roll method, instead of forming each layer by a single-wafer method.

Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to the following examples.
[Synthesis of BTBT derivative represented by general formula (1)]
The equipment and measurement conditions used for identification of the compound are as follows.
(1) ¹ H Nuclear Magnetic Resonance (NMR) Apparatus (400 MHz) JNM-EX270FT-NMR type (2) Mass Spectrometry (MS) Apparatus manufactured by JEOL Ltd. JMS-K9 [Desktop GCQMS] manufactured by JEOL Ltd. and Waters Co., Ltd. Zspray (SQ detector 2))
(3) Element analyzer Perkin Elmer 2400II CHNS / O analyzer Measurement mode: CHN mode

２００ｍＬの三口フラスコにＢＴＢＴ−Ｂｒ９．７ｇ（３０．４ｍｍｏｌ）、アニリン１３．８ｍＬ（１５２ｍｍｏｌ）、ｔｅｒｔ−ブトキシナトリウム４．３ｇ（４５ｍｍｏｌ）、およびトルエン１６０ｍＬを加え、６０分間の窒素バブリングを行った。そして、Ｐｄ₂（ｄｂａ）₃ ８２４．４ｍｇ（０．９ｍｍｏｌ）および［^tＢｕ₃ＰＨ］⁺ＢＦ₄ ^- ５１８．３ｍｇ（１．８ｍｍｏｌ）を加え、加熱を開始した。２０分後、原料の消失を確認し、反応を停止した。トルエン、塩水を用いて分液を行い、有機層を濃縮した。さらに、ヘキサンおよびメタノールで超音波洗浄を行い、トルエンで原点抜きを行った。そしてトルエンで２回再結晶を行った。目的物を５．７ｇ回収した（収率５６％）。目的物は、¹Ｈ−ＮＭＲおよびＭＳにて同定した。
¹Ｈ−ＮＭＲ（４００ＭＨｚ，ＤＭＳＯ−ｄ６）：δ＝ ８．５５（ｓ，１Ｈ），８．１０（ｄ，Ｊ＝７．７Ｈｚ，１Ｈ），７．９３（ｄ，Ｊ＝７．７Ｈｚ，１Ｈ），７．８７（ｄ，Ｊ＝８．６Ｈｚ，１Ｈ），７．７５（ｄ，Ｊ＝１．８Ｈｚ，１Ｈ），７．４９（ｔ，Ｊ＝７．５Ｈｚ，１Ｈ），７．４２（ｔ，Ｊ＝７．０Ｈｚ，１Ｈ），７．３０（ｔ，Ｊ＝７．９Ｈｚ，２Ｈ），７．２５−７.１５（ｍ，３Ｈ），６．９１（ｔ，Ｊ＝７．２Ｈｚ，１Ｈ）ｐｐｍ，
ＭＳ：ｍ/ｚ＝３３２．１［Ｍ］⁺ Example 1 Synthesis of BTBTPP (i) Synthesis of 2-anilino-BTBT

BTBT-Br 9.7 g (30.4 mmol), aniline 13.8 mL (152 mmol), tert-butoxy sodium 4.3 g (45 mmol), and toluene 160 mL were added to a 200 mL three-necked flask, and nitrogen bubbling was performed for 60 minutes. _{Then, Pd 2 (dba) 3 824.4mg} (0.9mmol) and ^{_{[t Bu 3 PH] + BF}} 4 - 518.3mg of (1.8 mmol) was added, heating was started. After 20 minutes, the disappearance of the raw materials was confirmed, and the reaction was stopped. Liquid separation was performed using toluene and brine, and the organic layer was concentrated. Further, ultrasonic cleaning was performed with hexane and methanol, and the origin was removed with toluene. Then, recrystallization was performed twice with toluene. 5.7 g of the desired product was recovered (56% yield). The target compound was identified by ¹ H-NMR and MS.
¹ H-NMR (400 MHz, DMSO-d6): δ = 8.55 (s, 1H), 8.10 (d, J = 7.7 Hz, 1H), 7.93 (d, J = 7.7 Hz, 1H), 7.87 (d, J = 8.6 Hz, 1H), 7.75 (d, J = 1.8 Hz, 1H), 7.49 (t, J = 7.5 Hz, 1H), 7. 42 (t, J = 7.0 Hz, 1H), 7.30 (t, J = 7.9 Hz, 2H), 7.25-7.15 (m, 3H), 6.91 (t, J = 7) .2Hz, 1H) ppm,
MS: m / z = 332.1 [M] ⁺

５０ｍＬの三口フラスコに２−アニリノ−ＢＴＢＴ１．１ｇ（３．３ｍｍｏｌ）、ｐ−ジブロモベンゼン３６３．０ｍｇ（１．５ｍｍｏｌ）、ｔｅｒｔ−ブトキシナトリウム４３７．３ｍｇ（４．５ｍｍｏｌ）およびトルエン１５ｍＬを加え、６０分間の窒素バブリングを行った。そして、Ｐｄ₂（ｄｂａ）₃ ８３．５ｍｇ（０．０９ｍｍｏｌ）、および［^tＢｕ₃ＰＨ］⁺ＢＦ₄ ^- ５２．６ｍｇ（０．１８ｍｍｏｌ）を加え、加熱を開始した。９０時間後、原料の消失を確認し、反応を停止した。セライトろ過を行った後、トルエン、ＴＨＦおよび塩水を用いて分液を行い、有機層を濃縮した。これらをまとめて、酢酸エチル１００ｍＬほどで超音波洗浄を行った。続いて、ろ物をトルエン３００ｍＬに溶解させ、シリカゲルを用いて、熱ろ過を行った。濃縮後、ヘキサン２００ｍＬで超音波洗浄を行った。減圧乾燥後、目的物を９４８．６ｍｇ回収した（収率８５．８％）。目的物は¹Ｈ−ＮＭＲ（図１ａ）およびＭＳにて同定した。
¹Ｈ−ＮＭＲ（４００ＭＨｚ，ＴＨＦ−ｄ８）：δ＝ ７．９６（ｄ， Ｊ ＝７．８ Ｈｚ， ２Ｈ）， ７．８７ （ｄ， Ｊ ＝ ７．３Ｈｚ， ２Ｈ）， ７．８１ （ｄ， Ｊ ＝ ８．７Ｈｚ，２Ｈ）， ７．６９（ｄ， Ｊ ＝ ２．３Ｈｚ， ２Ｈ）， ７．４７−７．４１ （ｍ，２Ｈ）， ７．３８ （ｔｄ， Ｊ ＝ ７．５，１．２ Ｈｚ，２Ｈ）， ７．３２−７．２４ （ｍ， ６Ｈ）， ７．１７ （ｄｄ，Ｊ ＝ ８．７，０．９ Ｈｚ， ４Ｈ）， ７．１１−７．０７ （４Ｈ）， ７．０３ （ｔ，Ｊ ＝ ７．３Ｈｚ， ２Ｈ）；
ＭＳ：ｍ/ｚ＝７３７．６［Ｍ］⁺ (Ii) Synthesis of BBTTPP

1.1 g (3.3 mmol) of 2-anilino-BTBT, 363.0 mg (1.5 mmol) of p-dibromobenzene, 437.3 mg (4.5 mmol) of sodium tert-butoxy and 15 mL of toluene were added to a 50 mL three-neck flask, and 60 mL of toluene was added. A nitrogen bubbling was performed for 5 minutes. _{Then, Pd 2 (dba) 3 83.5mg} (0.09mmol), and ^{_{[t Bu 3 PH] + BF}} 4 - 52.6mg of (0.18 mmol) was added, heating was started. After 90 hours, the disappearance of the raw materials was confirmed, and the reaction was stopped. After filtration through Celite, liquid separation was performed using toluene, THF, and brine, and the organic layer was concentrated. These were combined and subjected to ultrasonic cleaning with about 100 mL of ethyl acetate. Subsequently, the residue was dissolved in 300 mL of toluene, and subjected to hot filtration using silica gel. After concentration, ultrasonic cleaning was performed with 200 mL of hexane. After drying under reduced pressure, 948.6 mg of the desired product was recovered (yield: 85.8%). The target compound was identified by ¹ H-NMR (FIG. 1 a) and MS.
¹ H-NMR (400 MHz, THF-d8): δ = 7.96 (d, J = 7.8 Hz, 2H), 7.87 (d, J = 7.3 Hz, 2H), 7.81 (d , J = 8.7 Hz, 2H), 7.69 (d, J = 2.3 Hz, 2H), 7.47-7.41 (m, 2H), 7.38 (td, J = 7.5, 1.2 Hz, 2H), 7.32-7.24 (m, 6H), 7.17 (dd, J = 8.7, 0.9 Hz, 4H), 7.11-7.07 (4H ), 7.03 (t, J = 7.3 Hz, 2H);
MS: m / z = 737.6 [M] ⁺

５０ｍＬの三口フラスコに、実施例１で合成した２−アニリノ−ＢＴＢＴ ２．０ｇ（６．０ｍｍｏｌ）、４，４’−ジブロモビフェニル９４１．９ｍｇ（３．０ｍｍｏｌ）、ｔｅｒｔ−ブトキシナトリウム ８６７．０ｍｇ（９．０ｍｍｏｌ）およびトルエン３０ｍＬを加え、６０分間の窒素バブリングを行った。そして、Ｐｄ₂（ｄｂａ）₃ ２７７．２ｍｇ（０．３ｍｍｏｌ）および［^tＢｕ₃ＰＨ］⁺ＢＦ₄ ^- １７４．６ｍｇ（０．６ｍｍｏｌ）を加え、加熱を開始した。４０分後、原料の消失を確認し、反応を停止した。吸引ろ過を行い、ろ物は水、メタノールで洗浄し、ろ液はトルエンおよび塩水を用いて分液を行い、有機層を濃縮した。これらをまとめて、トルエン５００ｍＬに溶解させ、シリカゲルを用いて、熱ろ過を行った。濃縮後、メタノール６００ｍＬおよびヘキサン５００ｍＬで超音波洗浄を行った。そして、キシレン２１０ｍＬを用いて再結晶を行い、８０６．６ｍｇの目的物を回収した（収率３３．４％）。目的物は、¹Ｈ−ＮＭＲ（図１ｂ）およびＭＳにて同定した。
¹Ｈ−ＮＭＲ（４００ＭＨｚ，ＴＨＦ−ｄ８）：δ＝７．９７（ｄ，Ｊ＝８．２Ｈｚ，２Ｈ），７．８８（ｄ，Ｊ＝７．２Ｈｚ，２Ｈ），７．８３（ｄ，Ｊ＝８．６Ｈｚ，２Ｈ），７．６９（ｓ，２Ｈ），７．５７（ｄ，Ｊ＝８．６Ｈｚ，４Ｈ），７．４１（ｄ，Ｊ＝２４．５Ｈｚ，４Ｈ），７．２９（ｄ，Ｊ＝７．７Ｈｚ，６Ｈ），７．１７（ｔ，Ｊ＝４．３Ｈｚ，８Ｈ），７．０６（ｓ，２Ｈ））ｐｐｍ；
ＭＳ：ｍ/ｚ＝８１３．１［Ｍ］⁺ Example 2 Synthesis of BTBTPB

In a 50 mL three-necked flask, 2.0 g (6.0 mmol) of 2-anilino-BTBT synthesized in Example 1, 941.9 mg (3.0 mmol) of 4,4′-dibromobiphenyl, and 867.0 mg of sodium tert-butoxy ( 9.0 mmol) and 30 mL of toluene were added, and nitrogen bubbling was performed for 60 minutes. _{Then, Pd 2 (dba) 3 277.2mg} (0.3mmol) and ^{_{[t Bu 3 PH] + BF}} 4 - 174.6mg of (0.6 mmol) was added, heating was started. After 40 minutes, the disappearance of the raw materials was confirmed, and the reaction was stopped. Suction filtration was performed, the filtrate was washed with water and methanol, and the filtrate was separated using toluene and brine, and the organic layer was concentrated. These were combined, dissolved in 500 mL of toluene, and subjected to hot filtration using silica gel. After concentration, ultrasonic cleaning was performed with 600 mL of methanol and 500 mL of hexane. Then, recrystallization was performed using 210 mL of xylene, and 806.6 mg of the desired product was recovered (yield: 33.4%). The target compound was identified by ¹ H-NMR (FIG. ¹ b) and MS.
¹ H-NMR (400 MHz, THF-d8): δ = 7.97 (d, J = 8.2 Hz, 2H), 7.88 (d, J = 7.2 Hz, 2H), 7.83 (d, J = 8.6 Hz, 2H), 7.69 (s, 2H), 7.57 (d, J = 8.6 Hz, 4H), 7.41 (d, J = 24.5 Hz, 4H), 7. 29 (d, J = 7.7 Hz, 6H), 7.17 (t, J = 4.3 Hz, 8H), 7.06 (s, 2H)) ppm;
MS: m / z = 813.1 [M] ⁺

５０ｍＬの三口フラスコに、実施例１で合成した２−アニリノ−ＢＴＢＴ ９９５．０ｍｇ（３．０ｍｍｏｌ）、２，７−ジブロモ−９，９’−スピロビ［９Ｈ−フルオレン］７１１．９ｍｇ（６．０ｍｍｏｌ）、ｔｅｒｔ−ブトキシナトリウム４３５．８ｍｇ（４．５ｍｍｏｌ）、およびトルエン１５ｍＬを加え、６０分間の窒素バブリングを行った。そして、Ｐｄ₂（ｄｂａ）₃ ８２．４ｍｇ（０．０９ｍｍｏｌ）および［^tＢｕ₃ＰＨ］⁺ＢＦ₄ ^- ５９．０ｍｇ（０．２０ｍｍｏｌ）を加え、加熱を開始した。１５分後、原料の消失を確認し、反応を停止した。吸引ろ過を行った後、トルエン、塩水を用いて分液を行い、有機層を濃縮した。これらをまとめて、トルエン３００ｍＬに溶解させ、シリカゲルを用いて、熱ろ過を行った。濃縮後、メタノール４００ｍＬで超音波洗浄を行った。続けて、メタノール３００ｍＬで超音波洗浄を行った。さらに、酢酸エチル３００ｍＬで超音波洗浄を行った。減圧乾燥後、目的物を７５８．６ｍｇ回収した（収率５１．９％）。目的物は¹Ｈ−ＮＭＲ（図１ｃ）およびＭＳにて同定した。
¹Ｈ−ＮＭＲ（４００ＭＨｚ，ＴＨＦ−ｄ８）：δ＝７．９１（ｄ，Ｊ＝８．２Ｈｚ，２Ｈ），７．８１（ｄ，Ｊ＝８．２Ｈｚ，２Ｈ），７．７４（ｄ，Ｊ＝８．２Ｈｚ，２Ｈ），７．６２（ｄ，Ｊ＝８．６Ｈｚ，４Ｈ），７．４５（ｓ，２Ｈ），７．３６（ｑ，Ｊ＝８．３Ｈｚ，４Ｈ），７．２１（ｄ，Ｊ＝８．２Ｈｚ，２Ｈ），７．１８−７．０７（ｍ，６Ｈ），７．０２（ｔ，Ｊ＝８．４Ｈｚ，４Ｈ），６．９５（ｄ，Ｊ＝８．２Ｈｚ，４Ｈ），６．８８（ｑ，Ｊ＝７．２Ｈｚ，４Ｈ），６．５０（ｓ，２Ｈ）ｐｐｍ；
ＭＳ：ｍ/ｚ＝９７５．７［Ｍ］⁺ Example 3 Synthesis of BTBTPSF

In a 50 mL three-necked flask, 995.0 mg (3.0 mmol) of 2-anilino-BTBT synthesized in Example 1 and 711.9 mg (6.0 mmol) of 2,7-dibromo-9,9′-spirobi [9H-fluorene] were synthesized. ), 435.8 mg (4.5 mmol) of tert-butoxy sodium and 15 mL of toluene were added, and nitrogen bubbling was performed for 60 minutes. _{Then, Pd 2 (dba) 3 82.4mg} (0.09mmol) and ^{_{[t Bu 3 PH] + BF}} 4 - 59.0mg of (0.20 mmol) was added, heating was started. After 15 minutes, the disappearance of the raw materials was confirmed, and the reaction was stopped. After performing suction filtration, liquid separation was performed using toluene and brine, and the organic layer was concentrated. These were combined, dissolved in 300 mL of toluene, and subjected to hot filtration using silica gel. After concentration, ultrasonic cleaning was performed with 400 mL of methanol. Subsequently, ultrasonic cleaning was performed with 300 mL of methanol. Further, ultrasonic cleaning was performed with 300 mL of ethyl acetate. After drying under reduced pressure, 758.6 mg of the desired product was recovered (yield 51.9%). The target compound was identified by ¹ H-NMR (FIG. 1c) and MS.
¹ H-NMR (400 MHz, THF-d8): δ = 7.91 (d, J = 8.2 Hz, 2H), 7.81 (d, J = 8.2 Hz, 2H), 7.74 (d, J = 8.2 Hz, 2H), 7.62 (d, J = 8.6 Hz, 4H), 7.45 (s, 2H), 7.36 (q, J = 8.3 Hz, 4H), 7. 21 (d, J = 8.2 Hz, 2H), 7.18-7.07 (m, 6H), 7.02 (t, J = 8.4 Hz, 4H), 6.95 (d, J = 8) .2 Hz, 4H), 6.88 (q, J = 7.2 Hz, 4H), 6.50 (s, 2H) ppm;
MS: m / z = 975.7 [M] ⁺

５０ｍＬの三口フラスコに、実施例１で合成した２−アニリノ−ＢＴＢＴ ９９７．５ｍｇ（３．０ｍｍｏｌ）、２，７−ジブロモ−９，９−ジフェニルフルオレン ７１５．０ｍｇ（６．０ｍｍｏｌ）、ｔｅｒｔ−ブトキシナトリウム４３１．２ｍｇ（４．５ｍｍｏｌ）、およびトルエン１５ｍＬを加え、６０分間の窒素バブリングを行った。そして、Ｐｄ₂（ｄｂａ）₃ ８２．４ｍｇ（０．０９ｍｍｏｌ）および［^tＢｕ₃ＰＨ］⁺ＢＦ₄ ^- ５３．１３ｍｇ（０．１８ｍｍｏｌ）を加え、加熱を開始した。３０分後、原料の消失を確認し、反応を停止した。吸引ろ過を行い、ろ物は水およびメタノールで洗浄し、ろ物はトルエンおよび塩水を用いて分液を行い、有機層を濃縮した。これらをまとめて、トルエン５００ｍＬに溶解させ、シリカゲルを用いて、熱ろ過を行った。濃縮後、酢酸エチル１５０ｍＬで超音波洗浄を行った。続けて、メタノール３００ｍＬで超音波洗浄を行った。減圧乾燥後、目的物を１．１５６ｇ回収した（収率７８．９％）。目的物は¹Ｈ−ＮＭＲ（図１ｄ）およびＭＳにて同定した。
¹Ｈ−ＮＭＲ（４００ＭＨｚ，ＴＨＦ−ｄ８）：δ＝７．９６（ｄ，Ｊ＝８．２Ｈｚ，２Ｈ），７．８７（ｄ，Ｊ＝７．７Ｈｚ，２Ｈ），７．７５（ｄ，Ｊ＝８．６Ｈｚ，２Ｈ），７．７０−７．６１（ｍ，４Ｈ），７．４４（ｔ，Ｊ＝７．５Ｈｚ，２Ｈ），７．３７（ｔ，Ｊ＝７．５Ｈｚ，２Ｈ），７．１８（ｄ，Ｊ＝６３．９Ｈｚ，２２Ｈ），７．０６（ｄｄ，Ｊ＝８．４，２．０Ｈｚ，２Ｈ），７．０１（ｔ，Ｊ＝７．５Ｈｚ，２Ｈ）；
ＭＳ：ｍ/ｚ＝９７７．５［Ｍ］⁺ Example 4 Synthesis of BTBTPDF

In a 50 mL three-necked flask, 997.5 mg (3.0 mmol) of 2-anilino-BTBT synthesized in Example 1, 715.0 mg (6.0 mmol) of 2,7-dibromo-9,9-diphenylfluorene, tert-butoxy 431.2 mg (4.5 mmol) of sodium and 15 mL of toluene were added, and nitrogen bubbling was performed for 60 minutes. _{Then, Pd 2 (dba) 3 82.4mg} (0.09mmol) and ^{_{[t Bu 3 PH] + BF}} 4 - 53.13mg of (0.18 mmol) was added, heating was started. After 30 minutes, the disappearance of the raw materials was confirmed, and the reaction was stopped. Suction filtration was performed, and the filtrate was washed with water and methanol. The filtrate was separated using toluene and brine, and the organic layer was concentrated. These were combined, dissolved in 500 mL of toluene, and subjected to hot filtration using silica gel. After concentration, ultrasonic cleaning was performed with 150 mL of ethyl acetate. Subsequently, ultrasonic cleaning was performed with 300 mL of methanol. After drying under reduced pressure, 1.156 g of the desired product was recovered (yield 78.9%). The target compound was identified by ¹ H-NMR (FIG. 1d) and MS.
¹ H-NMR (400 MHz, THF-d8): δ = 7.96 (d, J = 8.2 Hz, 2H), 7.87 (d, J = 7.7 Hz, 2H), 7.75 (d, J = 8.6 Hz, 2H), 7.70-7.61 (m, 4H), 7.44 (t, J = 7.5 Hz, 2H), 7.37 (t, J = 7.5 Hz, 2H) ), 7.18 (d, J = 63.9 Hz, 22H), 7.06 (dd, J = 8.4, 2.0 Hz, 2H), 7.01 (t, J = 7.5 Hz, 2H). ;
MS: m / z = 977.5 [M] ⁺

[Quantum chemical calculation]
Table 1 shows the results of the quantum chemistry calculation by the time-dependent density functional theory (TD-DFT) using the molecular orbital method calculation program Gaussian09 of BBTTPP, BTBTPB, BTBTPSF and BTBTPDF synthesized in Examples 1 to 4. For the energy calculation, the basis function 6-31 + G (d) and 6-311 + G (d, p) were used using the hybrid density functional B3LYP.

As a result of the quantum chemical calculation, the energy gap ΔE _HL between HOMO and LUMO showed a relatively wide energy gap of 3.29 to 3.38 eV. Further, triplet energy E _T showed relatively high energy level and 2.33～2.38EV. This suggests that the benzothienobenzothiophene (BTBT) derivative of the present invention is a hole transporting material deserving of application to an organic EL device.

[Thermal property evaluation]
BTBTPP, BTBTPB, BTBTPSF, and BTBTPDF synthesized in Examples 1 to 4 were purified by sublimation, and subjected to thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) to determine a glass transition point (T _g ) and a melting point (T _m ). The 5% weight decay temperature (T _d ) was measured.
[Optical property evaluation]
UV-vis absorption spectrum (FIG. 2b), PL spectrum (FIG. 2c), and PYS measurement (FIG. 2a) of BTBTPP, BTBTPB, BTBTPSF, and BTBTPDF were performed.
The equipment and measurement conditions used for the evaluation of the optical characteristics are as follows.
(1) Ultraviolet / visible (UV-vis) spectrophotometer UV-3150 manufactured by Shimadzu Corporation
Measurement conditions: scan speed medium speed, measurement range 200 to 800 nm, sampling pitch 0.5 nm, slit width 0.5 nm

(2) Photoluminescence (PL) measuring device Fluoro MAX-2 manufactured by Horiba, Ltd.
At room temperature and low temperature, a PL spectrum and a time-resolved PL spectrum (transient PL spectrum) using a streak camera (C4334 manufactured by Hamamatsu Photonics KK) were measured.

(3) Photoelectron yield spectroscopy (PYS) device Ionization potential measurement device manufactured by Sumitomo Heavy Industries, Ltd. The ionization potential (I _p ) was measured in vacuum using an ionization potential measurement device.
The electron affinity (E _a ) was calculated by estimating the energy gap (E _g ) from the absorption edge of the UV-vis absorption spectrum.

Table 2 and FIG. 2 show the results of the thermophysical property evaluation and the optical property evaluation.

  BBTTPP, BTBTPB, BTBTPSF, and BTBTPDF have glass transition points (Tg) of 141 to 184 ° C., which are superior to NPD in heat resistance. From the PL spectrum, the emission peak of BBTTPP was shifted to the longer wavelength side compared to BTBTPB, BTBTPSF and BTBTPDF (FIG. 2c). The reason may be that the electron orbit is stabilized by a strong intermolecular force.

[Production and evaluation of organic EL element]
The equipment used for evaluating the organic EL element is as follows.
EL spectrum device; PHOTONIC MULTI-CHANNEL ANALYZER PMA-1 manufactured by Hamamatsu Photonics Co., Ltd.

<Element evaluation 1>
An organic EL device was manufactured using BTBTPP, BTBTPB, BTBTPSF, and BTBTPDF as the hole transport material (HTM), and using Alq ₃ as the electron transport layer and the light emitting layer.
The element structure is shown below. The values in parentheses indicate the film thickness (nm). FIG. 3 shows an energy diagram of the device.
[ITO (130 nm) / KLHIP01: PPBI (20 nm) / HTM (20 nm) / Alq ₃ (60 nm) / LiF (0.5 nm) / Al (100 nm)]
The results of the evaluation of the initial characteristics are shown in Table 3 and FIGS.

<Element evaluation 2>
In the device of the device evaluation 1, an organic EL device in which the hole transport layer was thickened was manufactured.
The element structure is shown below. The values in parentheses indicate the film thickness (nm).
[ITO (130 nm) / KLHIP01: PPBI (20 nm) / HTM (100 nm) / Alq ₃ (60 nm) / LiF (0.5 nm) / Al (100 nm)]
The evaluation results of the initial characteristics of the device are shown in FIGS.
Even when the thickness of the hole transport layer is increased from 20 nm to 100 nm, the element of element evaluation 2 has a higher current density-voltage characteristic, luminance-voltage characteristic, external quantum efficiency-luminance characteristic, and EL than the element of element evaluation 1. Each of the spectra showed almost the same results, and it was found that the drive voltage did not change even when the film was made thicker. However, with respect to BTBTPB, the external quantum efficiency calculated from the luminance decreased when the thickness of the hole transport layer was increased. The reason for this is considered to be a carrier balance collapse due to an excessive number of electrons (FIGS. 4C and 5C).

本発明のＢＴＢＴ誘導体を用いた緑色リン光素子では、従来材料ＮＰＤと同等以上の性能を示すことが分かった。 <Element evaluation 3>
A green phosphorescent device using BTBTPB, BTBTPDF, and NPD as the hole transport material (HTM) and using Ir (ppy) ₃ as the light emitting layer was manufactured.
The element structure is shown below. The values in parentheses indicate the film thickness (nm). FIG. 6A shows an energy diagram of the device.
[ITO (130 nm) / PTPD-1: PPBI (20 nm) / HTM (25 nm) / BCzPh (5 nm) / BCzPh: 8 wt% Ir (ppy) ₃ (10 nm) / TPBi (50 nm) / Liq (1 nm) / Al ( 100 nm)]
The results of the evaluation of the initial characteristics are shown in Table 4 and FIGS.

It was found that the green phosphorescent device using the BTBT derivative of the present invention exhibited performance equal to or higher than that of the conventional material NPD.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Anode 3 Hole injection layer 4 Hole transport layer 5 Light emitting layer 6 Electron transport layer 7 Electron injection layer 8 Cathode

Claims (3)

A benzothienobenzothiophene derivative represented by the following general formula (1).

(In the general formula (1), R ^{1 to} R ¹⁴ each independently represent a hydrogen atom, an aromatic substituent or an aliphatic substituent, and Ar ^{1 to} Ar ³ represent an aromatic substituent.)   A hole transport material comprising the benzothienobenzothiophene derivative according to claim 1.   An organic EL device using the benzothienobenzothiophene derivative according to claim 1.

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