KR20210123631A - Hole transporting material and Organic electroluminescent display device using the same - Google Patents

Abstract

Provided are a hole transport material represented by chemical formula 1, and an organic electroluminescent device and an electronic apparatus including the same. In the chemical formula 1, R is as defined in the specification. The hole transport material has excellent external quantum efficiency and excellent luminous efficiency, luminance, thermal stability, and device lifespan, thereby being able to be easily used to produce long-term stable OLED devices.

Description

Hole transporting material and organic electroluminescent device using the same

The present invention relates to a hole transport material and an organic electroluminescent device using the same.

Organic light emitting diodes (OLEDs) have become an interesting element in research and commercial markets. OLEDs show significant advantages over conventional displays: high contrast, high brightness, wide viewing angles, no backlight requirements, light weight, and thin film. Organic light-emitting diodes (OLEDs) are next-generation displays for mobile phones, TVs, and other lighting sources, helping to reduce energy consumption.

First-generation organic light-emitting diodes only accounted for 25% of their internal quantum efficiency, and 75% was lost non-radiative. Since then, fluorescent OLEDs with metal and ligand complexes have been identified as second-generation emitters in OLEDs. In this case, triplet and singlet energies were obtained using an iridium- and platinum-based heavy metal complex, showing an achievable internal quantum efficiency of 100%. Such maximum internal quantum efficiency could be reached through an intersystem crossing mechanism (ISC). This process requires doping the heavy metal-based fluorescence emitter with a suitable host material at an appropriate doping concentration. This helps to reduce quenching processes such as aggregation caused quenching (ACQ) and triplet-triplet annihilation (TTA).

Third-generation organic light-emitting diodes (OLEDs) are metal-free fluorescence emitters that use appropriate donor and acceptor molecules as building blocks. This type of emitter is known as thermally activated delayed fluorescence (TADF) emitter and is known to operate based on a reverse intersystem crossing (RISC) mechanism. Both fluorescent and TADF OLEDs require efficient host materials to increase device efficiency.

There are three types of reported host materials: a hole transport type (HT), an electron transport type (ET), and a bipolar host material.

The hole transport host material is made of electron-donating triphenylamine, carbazole and atridine derivatives. 4,4′-(N-carbazolyl)-1,1′-biphenyl, 1,3-bis(N-carbazolyl)-benzene and 4,4′-cyclohexylidenebis[N,N-bis (4-methylphenyl)benzeneamine] is a well-known hole material, but they are unstable in thermal stability. Tris(8-hydroxyquinoline)aluminum and bis[2-(diphenylphosphino)phenyl]etheroxide are electron transporting host materials used in fluorescent and TADF OLEDs. The host material is an essential energy source for the dopant material while preventing the return of energy flow from the dopant. The host material should have more triplet energy than the dopant material. At the same time, the host material must have adequate frontier molecular orbital energies (FMO) to ensure efficient carrier transport from adjacent layers. Bipolar materials have received a lot of attention from the research community because of their polarity. The bipolar host material contains electron donating and electron donating units in a single molecule. The bipolar host material can also provide proper carrier balance while supporting effective carrier recombination in the emissive layer. In most cases, a bipolar material can be used for both the fluorescent emitter and the host material.

In this study, there are two types of bipolar materials, N ¹ -(9,9-diphenyl-9H-fluoren-2-yl)-N ¹ -(4,6-diphenylpyrimidin-2-yl)- N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine (FLU-TPA/PYR) and N ¹ -(4-(4,6-diphenyl-1,3,5-triazin-2-yl) Design and synthesis of phenyl)-N ¹ -(9,9-diphenyl-9H-fluoren-2-yl)-N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine (FLU-TPA/TRZ) These include N ¹ -(9,9-diphenyl-9H-fluoren-2-yl)-N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine donor and triazine or pyrimidine acceptor got mixed up These two bipolar materials were treated with a yellow material and an undoped phosphor emitter. Iridium(III) bis(4-(4-tert-butylphenyl)thieno[3,2-c]pyridinato-N,C2`)acetylacetonate was employed as a yellow phosphorescent dopant.

It is an object of the present invention to provide a novel hole transport material having excellent quantum efficiency.

It is also an object of the present invention to provide an organic electroluminescent device including the hole transport material.

It is also an object of the present invention to provide an electronic device including the organic electroluminescent device.

One embodiment of the present invention provides a hole transport compound represented by the following formula (I).

[Formula 1]

In Formula 1 above

또는

이다.R is

or

am.

Another embodiment of the present invention is

a first electrode;

a second electrode facing the first electrode;

a light emitting material layer positioned between the first and second electrodes;

and a hole transport layer positioned between the first electrode and the light emitting material layer,

The hole transport layer,

It provides an organic electroluminescent device characterized in that it is made of any one of the hole transport material of the hole transport material.

Another embodiment of the present invention provides an electronic device including the organic electroluminescent device.

The hole transport material has excellent external quantum efficiency and has a low roll-off, so that it can be easily used to produce an organic electroluminescent device that is stable in the long term.

In addition, the organic electroluminescent device manufactured using the hole transport material has a characteristic of excellent luminous efficiency.

1 shows the thermal characteristics analysis results of FLU-TPA/PYR and FLU-TPA/TRZ.
2 shows the measurement results of UV-Vis absorption and photoluminescence (PL) spectra of FLU-TPA/PYR and FLU-TPA/TRZ.
3 shows the analysis results of the HOMO energy level of FLU-TPA/PYR and FLU-TPA/TRZ.
4 shows the structure of the yellow phosphorescent OLED device prepared in Example 7.
5 shows the results of analysis of current density voltage, current density power, and current efficiency of FLU-TPA/PYR and FLU-TPA/TRZ devices.
6 shows the electroluminescence spectra of FLU-TPA/PYR and FLU-TPA/TRZ devices.
7 shows the structure of an undoped fluorescent device.
8 shows the current, power and external quantum efficiency of an undoped FLU-TPA/TRZ based device.
9 shows the electroluminescence emission wavelength of an undoped FLU-TPA/TRZ based device.

Hereinafter, embodiments of the present invention will be described in detail. However, this is presented as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

In one embodiment of the present invention, there is provided a hole transport material represented by the following formula (1).

[Formula 1]

In Formula 1 above

또는

이다.R is

or

am.

인 경우 상기 화합물은 N¹-(9,9-디페닐-9H-플루오렌-2-일)-N¹-(4,6-디페닐피리미딘-2-일)-N⁴,N⁴-디페닐벤젠-1,4-디아민의 합성 (FLU-TPA/PYR)로 명명된다.In the present invention, R in the compound

When the compound is N ¹ -(9,9-diphenyl-9H-fluoren-2-yl)-N ¹ -(4,6-diphenylpyrimidin-2-yl)-N ⁴ ,N ⁴ - Synthesis of diphenylbenzene-1,4-diamine (FLU-TPA/PYR).

인 경우 상기 화합물은 N¹-(4-(4,6-디페닐-1,3,5-트리아진-2-일)페닐)-N¹-(9,9-디페닐-9H-플루오렌-2-일)-N⁴,N⁴-디페닐벤젠-1,4-디아민의 합성 (FLU-TPA/TRZ)로 명명된다.In the present invention, R in the compound

When the compound is N ¹ -(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-N ¹ -(9,9-diphenyl-9H-fluorene Synthesis of -2-yl)-N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine (FLU-TPA/TRZ).

In one embodiment of the present invention,

a first electrode;

a second electrode facing the first electrode;

a light emitting material layer positioned between the first and second electrodes;

and a hole transport layer positioned between the first electrode and the light emitting material layer,

The hole transport layer,

It provides an organic electroluminescent device characterized in that it is made of any one of the hole transport material.

In one embodiment of the present invention, the hole transport layer may be formed by any one of a spin coating process, a nozzle printing process, an inkjet printing process, a slot coating process, a dip coating process, and a roll-to-roll process, but is not necessarily limited thereto Any process capable of manufacturing an appropriate organic light emitting device may be used.

In one embodiment of the present invention,

a hole injection layer positioned between the first electrode and the hole transport layer;

an electron transport layer positioned between the light emitting material layer and the second electrode;

It provides an organic electroluminescent device comprising an electron injection layer positioned between the electron transport layer and the second electrode.

The present invention provides an electronic device including the organic electroluminescent device.

In addition, the present invention provides that the electronic device is an organic integrated circuit (O-IC), an organic electric-effect transistor (O-FET), an organic thin film transistor (O-TFT), an organic electroluminescent transistor (O-LET), and an organic solar cell. (O-SC), organic optical detector, organic photoreceptor, organic electro-quenching device (O-FQD), light emitting electrochemical cell (LEC), organic laser diode (O-laser) or organic electroluminescent device (OLED) Electronic devices are provided.

Hereinafter, the organic electroluminescent device will be described as an example. However, the contents exemplified below are not limited to the organic electroluminescent device of the present invention.

The organic electroluminescent device may have a structure in which an anode (hole injection electrode), a hole injection layer (HIL) and/or a hole transport layer (HTL), a light emitting layer (EML) and a cathode (electron injection electrode) are sequentially stacked, Preferably, it may further include an electron blocking layer (EBL) between the anode and the light emitting layer, and an electron transport layer (ETL), an electron injection layer (EIL) or a hole blocking layer (HBL) between the cathode and the light emitting layer.

In the method of manufacturing the organic electroluminescent device, first, a material for an anode is coated on the surface of a substrate by a conventional method to form an anode. In this case, the substrate used is preferably a glass substrate or a transparent plastic substrate excellent in transparency, surface smoothness, handling and waterproofing properties. In addition, as the material for the anode, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), zinc oxide (ZnO), etc., which are transparent and have excellent conductivity, may be used.

Next, a hole injection layer (HIL) material is vacuum-deposited or spin-coated on the surface of the anode by a conventional method to form a hole injection layer. As the hole injection layer material, the organic electroluminescent compound may be used, in addition to copper phthalocyanine (CuPc), 4,4',4"-tris(3-methylphenylamino)triphenylamine (m-MTDATA), 4 ,4',4"-tris(3-methylphenylamino)phenoxybenzene (m-MTDAPB), starburst type amines 4,4',4"-tri(N-carbazolyl)triphenylamine ( TCTA), 4,4',4"-tris(N-(2-naphthyl)-N-phenylamino)-triphenylamine (2-TNATA) or IDE406 available from Idemitsu. have.

A hole transport layer (HTL) material is vacuum-deposited or spin-coated on the surface of the hole injection layer by a conventional method to form a hole transport layer. In this case, the organic electroluminescent compound may be used as the hole transport layer material, and in addition, bis(N-(1-naphthyl-n-phenyl))benzidine (α-NPD), N,N′-di(naphthalene- 1-yl)-N,N'-biphenyl-benzidine (NPB) or N,N'-biphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4' -Diamine (TPD) is an example.

The light emitting layer is formed by vacuum thermal evaporation or spin coating of the light emitting layer (EML) material on the surface of the hole transport layer in a conventional manner. In this case, the organic electroluminescent compound may be used as a phosphorescent green host material in the case of green as a single light emitting material or a light emitting host material among the light emitting layer materials used, and in the case of yellow, the organic electroluminescent compound may be used as a phosphorescent yellow host material. .

Among the light emitting layer materials, in the case of a dopant that can be used together with a light emitting host, IDE102 and IDE105 available from Idemitsu as fluorescent dopants, and tris(2-phenylpyridine)iridium(III)(Ir) as phosphorescent dopants. (ppy) ₃ ), iridium(III)bis[(4,6-difluorophenyl)pyridinato-N,C-2′]picolinic acid salt (FIrpic) (Chihaya Adachi et al., Appl Phys. Lett., 2001, 79, 3082-3084]), platinum (II) octaethyl porphyrin (PtOEP), TBE002 (Cobion), and the like can be used.

An electron transport layer (ETL) material is vacuum-deposited or spin-coated on the surface of the light emitting layer by a conventional method to form an electron transport layer. In this case, as the material for the electron transport layer used, the organic electroluminescent compound may be used, and in addition, tris(8-hydroxyquinolinolato)aluminum (Alq3), etc. may be used.

Optionally, by additionally forming a hole blocking layer (HBL) between the light emitting layer and the electron transport layer and using a phosphorescent dopant together in the light emitting layer, it is possible to prevent the diffusion of triplet excitons or holes into the electron transport layer.

The formation of the hole blocking layer can be carried out by vacuum thermal evaporation and spin coating of the hole blocking layer material in a conventional manner, and the hole blocking layer material is not particularly limited, but preferably (8-hydroxyquinolinola Earth) lithium (Liq), bis(8-hydroxy-2-methylquinolinolnato)-aluminum biphenoxide (BAlq), bathocuproine (BCP), LiF, and the like may be used.

An electron injection layer is formed by vacuum thermal evaporation or spin coating of an electron injection layer (EIL) material on the surface of the electron transport layer in a conventional manner. In this case, as the material for the electron injection layer used, the organic electroluminescent compound may be used, and other _{materials such as LiF, Liq, Li 2} O, BaO, NaCl or CsF may be used.

Finally, a cathode is formed by vacuum thermal evaporation of a material for a cathode on the surface of the electron injection layer in a conventional manner.

At this time, as the material for the anode used, lithium (Li), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium (Mg), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag) and the like can be used. In addition, in the case of a top-emitting organic electroluminescent device, a transparent cathode through which light can pass may be formed using indium tin oxide (ITO) or indium zinc oxide (IZO).

Example

Hereinafter, preferred examples and experimental examples are presented to help the understanding of the present invention. However, the following Examples and Experimental Examples are only provided for easier understanding of the present invention, and the content of the present invention is not limited by the Examples and Experimental Examples.

ingredient

2-Amino-9,9-diphenylfluorene (1), 2- (4-bromophenyl) -4,6-diphenyl-1,3,5-triazine (7), 2-chloro-4 A mixture of ,6-diphenyl-1,3,5-triazine (6) and 4-iodotripphenylamine (2) was obtained from TCI Chemical (Seoul, Korea). Pd(OAc) ₂ , Pd(PPh ₃ ) ₄ , and NaOtBu were purchased from Sigma-Aldrich (Seoul, Korea). Toluene, dichloromethane, n -hexane and ethyl acetate were obtained from SK Chemicals (Gyeonggi-do, Korea). Toluene was distilled from sodium/benzophenone prior to use. Analytical thin layer chromatography (TLC) was performed using a TLC plate coated with Merck Kiesegel (Seoul, Korea) 60 supported by aluminum with visualization at 254 and 365 nm. Column chromatography was performed using silica gel (mesh size 200-300). Reverse osmosis was used for all purposes related to this work.

device

¹ H and ¹³ C NMR analysis was obtained using a JEON JNM-ECP FT-NMR spectrometer (Peabody, MA, USA) running at 500 MHz. UV-Vis absorbance properties were analyzed using a Lambda 1050 ultraviolet visible (UV-VIS) spectrophotometer (Perkin Elmer, Waltham, MA, USA). The energy of the band spacing (Eg) was obtained at the onset wavelength of the UV-Vis absorbance spectrum. The photoluminescence spectrum was measured using an HR800 spectral fluorometer (Horiba Jobin Yvon, Paris, France). Mass spectrometry analysis was performed using a Xevo TQ-S spectrometer (Waters, Milford, MA, USA). Elemental analysis was obtained with a ThermoFisher (Flash2000) elemental analyzer (Loughborough, England). Thermogravimetric analysis and differential scanning calorimetry were recorded using a PerkinElmer DSC 4000 and TGA 8000 system (Melville, NY, USA) at a heating rate of 10 °C/min under a nitrogen atmosphere. The triplet energy level was evaluated at the onset wavelength of the emission spectrum at 77 K in toluene. The highest occupied molecular orbital (HOMO) value was determined by the AC-2 method using a photoelectron spectrometer (RIKEN, Saitama, Japan). The LUMO energy was calculated by adding the band gap energy to the obtained HOMO energy. The organic light emitting diode (OLED) device was configured as a thermal evaporation system under a pressure of ^{5 × 10 -7 torr (Sunicel plus, Seoul, Korea).} Current density-voltage-luminescence (JVL) performance was observed in an organic light emitting diode (OLED) IVL test system (Polarmix M6100, Suwon, Korea). Electroluminescence (EL) spectra were recorded using a spectroradiometer (Konica Minolta CS-2000, Tokyo, Japan).

reaction formula

The compound was synthesized as shown in Scheme 1 below to produce an intermediate compound necessary for preparing the compound of Formula 1 of the present invention, and the compound used in the Scheme and the compound produced from the Scheme were 1,2, respectively, as in Scheme 1 below. , 3, 4, 5 and 6 were expressed.

[Scheme 1]

One of the compounds of Formula 1 (FLU-TPA/PYR) was prepared as in Scheme 2 below using the intermediate compounds 3 and 6 prepared in Scheme 1, and the intermediate compound 3 prepared in Scheme 1 and the novel compound 7 One of the compounds of Formula 1 (FLU-TPA/TRZ) was prepared as shown in Scheme 3 below.

[Scheme 2]

[Scheme 3]

Hereinafter, specific synthetic procedures for Schemes 1 to 3 will be described.

Example 1. N ^One -(9,9-diphenyl-9H-fluoren-2-yl)-N ⁴ ,N ⁴ -Synthesis of diphenylbenzene-1,4-diamine

9,9-diphenyl-9H-fluoren-2-amine (1, 1.0 g, 2.99 mmol), 4-iodo-N,N-diphenylaniline (2, 1.22 g, 3.29 mmol), palladium (II) ) mixture of acetate (Pd (OAc) ₂ , 0.1 g, 0.45 mmol), sodium tert-butoxide (NaOtBu, 0.43 g, 4.49 mmol), 10% tri-tert-butylphosphine in toluene (tBu ₃ P, 0.20) ml, 0.89 mmol) and anhydrous toluene (80 ml) were added to a two-necked round bottom flask equipped with a condenser. The mixture was vacuum treated and then a nitrogen atmosphere was provided. The mixture was braided by a magnetic rod and refluxed at 110 °C for 10 h. After completion of the reaction, the crude mixture was washed 3 times with dichloromethane (250 ml) and deionized water (125 ml). The organic layer was collected and dried over anhydrous magnesium sulfate. After filtration, the crude mixture was evaporated using a rotary evaporator. The target molecule, N ¹ -(9,9-diphenyl-9H-fluoren-2-yl)-N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine (3) is n-hexane:dichloromethane ( 2:1) was confirmed by silica column chromatography using a solvent system.

Yield: 91%; yellow solid; ¹ H NMR (500 MHz, CDCl ₃ ) δ 9.47-9.49 (d, J = 8.0 Hz, 1H), 8.17-8.19 (d, J = 8.0 Hz, 1H), 8.09-8.11 (m, 2H), 7.95 8.02 (m, 2H), 7.75-7.89 (m, 2H), 7.59-7.60 (d, J = 8.0 Hz, 4H), 7.43-7.44 (d, J = 7.5 Hz, 3H), 7.34-7.36 (d, J = 8.5Hz, 4H), 7.17-7.19 (d, J = 8.5Hz, 3H), 6.99-7.02 (t, J = 7.5Hz, 3H), 6.90-6.93 (t, J = 7.5Hz, 3H), 6.39 -6.41 (d, J = 8.5 Hz, 3H).

Example 2. Synthesis of 2-chloro-4,6-diphenylpyrimidine

2,4,6-trichloropyrimidine (4, 0.63 ml, 5.45 mmol), phenylboronic acid (5, 1.39 g, 11.44 mmol), tetrakis(triphenylphosphine)palladium(0) ((Pd(PPh) ₃ P) _{A mixture of 4} , 0.18 g, 0.16 mmol) 2M K ₂ CO ₃ aqueous solution, 40 ml of water, 25 ml of ethanol and 80 ml of toluene was added into a two-necked round bottom flask equipped with a condenser, at 110 °C under a nitrogen atmosphere. Reflux for 10 hours.After completion of reaction, the mixture is treated with dichloromethane (100 ml) and water (80 ml).The organic layer is dried over anhydrous magnesium sulfate and concentrated.The crude residue is purified by silica column and n Separation using hexane:dichloromethane (4:1) solvent system gave intermediate 6 as a white solid.

Yield: 80%; white solid; ¹ H NMR (500 MHz, CDCl ₃ ) δ 8.13-8.14 (m, 4H), 8.01 (s, 1H), 7.51-7.55 (m, 6H); ¹³ C NMR (500 MHz, CDCl ₃ ) δ 167.7, 162.1, 135.7, 131.7, 129.1, 127.5, 111.0.

Example 3. N ^One -(9,9-diphenyl-9H-fluoren-2-yl)-N ^One -(4,6-diphenylpyrimidin-2-yl)-N ⁴ ,N ⁴ -Synthesis of diphenylbenzene-1,4-diamine (FLU-TPA/PYR)

In the same reaction as in Scheme 2, N ¹ -(9,9-diphenyl-9H-fluoren-2-yl)-N ¹ -(4,6-diphenylpyrimidin-2-yl)-N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine was synthesized.

N ¹ -(9,9-diphenyl-9H-fluoren-2-yl)-N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine (3, 1.0 g, 1.73 mmol), 2-chloro- mixture of 4,6-diphenylpyrimidine (6, 0.50 g, 1.90 mmol), palladium(II) acetate (Pd(OAc) ₂ , 0.08 g, 0.34 mmol), 10% tri-tert-butylphosphine in toluene (tBu ₃ P, 0.12 ml, 0.52 mmol), sodium tert-butoxide (NaOtBu, 0.28 g, 2.94 mmol) and 80 ml anhydrous toluene were added into a two-necked round bottom flask equipped with a condenser, and nitrogen while stirring magnetically. The atmosphere was refluxed at 110 °C for 12 h. The crude residue was separated by silica column and n-hexane-dichloromethane (1:1) solvent system to give the desired final product FLU-TPA/PYR, which was further purified using ethylether/petroleum ether.

Yield: 83%; yellow solid; FT-IR (KBr pellets): Vmax 3056.6, 1586.7, 1562.9, 1536.6, 1505.0, 1491.8, 1452.9, 1403.2, 1353.9, 1306.0, 1272.6, 1234.2, 1184.0, 1155.7, 1108.0, 1070.4, 1029.4, 1001.6, 981.5, 922.7, 883.0 , 832.9, 822.9 cm ^-1 ; ¹ H NMR (500 MHz, CDCl ₃ ) δ 7.92-7.93 (d, J = 7.0 Hz, 4H), 7.79-7.81 (d, J = 8.0 Hz, 1H), 7.76-7.77 (d, J = 7.5 Hz, 1H), 7.60 (s, 1H), 7.52 (s, 1H), 7.36-7.45 (m, 9H), 7.25-7.28 (t, J = 8.5 Hz, 5H), 7.19-7.21 (m, 6H), 7.13 -7.15 (m, 6H), 7.08-7.11 (m, 6H), 7.00-7.03 (t, J = 7.5 Hz, 2H); ¹³ C NMR (500 MHz, CDCl ₃ ) δ 165.2, 162.7, 151.9, 151.3, 147.9, 145.9, 144.7, 144.6, 140.2, 140.0, 137.5, 137.1, 130.6, 129.2, 128.8, 128.2, 127.6, 127.3, 127.1, 126.6 , 126.3, 125.5, 124.8, 123.9. 122.6, 120.6, 120.0, 104.1; MS (APCI) m/z: 806.71 for C ₅₉ H ₄₂ N ₄ [(M+H) ⁺ ]; Anal. Calcd for C ₅₉ H ₄₂ N ₄ (%): C, 87.81; H, 5.25; N, 6.94. Found: C, 88.92; H, 5.33; N, 7.02.

Example 4. N ^One -(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-N ^One -(9,9-diphenyl-9H-fluoren-2-yl)-N ⁴ ,N ⁴ -Synthesis of diphenylbenzene-1,4-diamine (FLU-TPA/TRZ)

In the same reaction as in Scheme 3, N ¹ -(4-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl)-N ¹ -(9,9-diphenyl-9H- Fluoren-2-yl)-N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine was synthesized.

N ¹ -(9,9-diphenyl-9H-fluoren-2-yl)-N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine (3, 1.0 g, 1.73 mmol), 2-(4 -Bromophenyl)-4,6-diphenyl-1,3,5-triazine (7, 0.74 g, 1.90 mmol), palladium (II) acetate (Pd(OAc) ₂ , 0.08 g, 0.34 mmol), 10% tri-tert-butylphosphine toluene (tBu ₃ P, 0.12 ml, 0.52 mmol), sodium tert-butoxide (NaOtBu, 0.28 g, 2.94 mmol) and 80 ml anhydrous toluene were mixed in a two-necked round bottom flask equipped with a condenser. was added and refluxed at 110° C. for 12 hours in a nitrogen atmosphere with magnetic stirring. The crude residue was separated by silica column and n-hexane-dichloromethane (1:1) solvent system to give the target end product FLU-TPA/TRZ as a yellow solid.

Yield: 81%; yellow solid; FT-IR (KBr pellets): Vmax 3034.2, 1587.9, 1523.6, 1505.5, 1489.7, 1444.0, 1427.0, 1410.4, 1366.1, 1308.8, 1281.0, 1266.4, 1183.0, 1147.7, 1109.7, 1077.8, 1026.9, 964.4, 934.6, 892.3, 828.0 cm ^-1 ; ¹ H NMR (500 MHz, CDCl ₃ ) δ 8.65-8.67 (d, J= 7.5 Hz, 4H), 8.50-8.51 (d, J= 8.5 Hz, 2H), 7.90-7.91 (d, J= 8.0 Hz, 1H), 7.85-7.87 (d, J= 7.5 Hz, 1H), 7.59-7.66 (m, 6H), 7.36-7.41 (m, 2H), 7.26-7.30 (m, 5H), 7.20-7.22 (m, 7H), 7.11 (s, 1H), 6.99-7.07 (m, 4H), 6.93-6.95 (d, J=9.0 Hz, 2H); ¹³ C NMR (500 MHz, CDCl ₃ ) δ 147.6, 145.7, 136.1, 133.9, 133.4, 130.1, 129.4, 129.0, 128.9, 128.1, 127.2, 124.2, 123.5; MS (APCI) m/z: 883.63 for C ₆₄ H ₄₅ N ₅ [(M+H) ⁺ ]; Anal. Calcd for C ₆₄ H ₄₅ N ₅ (%): C, 86.95; H, 5.13; N, 7.92. Found: C, 87.62; H, 5.18; N, 8.01.

Example 5. OLED device fabrication

To construct the OLED device, the indium-tin-oxide (ITO) coated glass substrate was washed with isopropyl alcohol and deionized water in an ultrasonic bath for 20 minutes. The cleaned substrates were UV-ozonated for about 6 minutes. All organic layers and metal cathodes were prepared on pre-cleaned ITO coated glass substrates. A deposition rate of ~ 5 × 10 ^-7 Torr pressure was applied using a Sunic organic evaporator (Suwon, Korea). All deposition processes were performed in a glove box under inert conditions. Each device size area was fabricated to be ^{2 mm 2 .}

Example 6. Thermal Characterization of FLU-TPA/PYR and FLU-TPA/TRZ

Thermal properties of FLU-TPA/PYR and FLU-TPA/TRZ were measured by thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) under nitrogen atmosphere. The glass transition temperatures of FLU-TPA/PYR and FLU-TPA/TRZ were 153 and 147 °C, respectively. The thermal decomposition of FLU-TPA/PYR and FLU-TPA/TRZ was measured at about 426 and 478 °C at 5% weight loss. Both materials showed good thermal stability and could improve shape stability during device operation. The thermal characteristic measurement results are shown in FIG. 1 , and specific data are shown in Table 1 below.

bipolar material FLU-TPA/PYR FLU-TPA/TRZ T _g ( ^o C) 153 147 T _d ( ^o C) 426 478 UV-Vis (nm) 410 412 PL (nm) 548 606 band gap (eV) 2.41 2.49 triplet energy (eV) 2.57 2.77 HOMO (eV) 5.27 5.35 LUMO (eV) 2.86 2.86

Example 7. UV-vis absorption and photoluminescence spectral analysis of FLU-TPA/PYR and FLU-TPA/TRZ

UV-Vis absorption and photoluminescence (PL) spectra of FLU-TPA/PYR and FLU-TPA/TRZ were measured and shown in FIG. 2 . FLU-TPA/PYR and FLU-TPA/TRZ showed similar absorption at 410 and 412 nm, respectively. The band gap energy values of FLU-TPA/PYR and FLU-TPA/TRZ were recorded at 2.41 and 2.49 eV, which are associated with onset absorption wavelengths of 515 and 498 nm, respectively. FLU-TPA/PYR showed extended absorption when compared to FLU-TPA/TRZ. Photoluminescence spectral maxima in toluene solvent for FLU-TPA/PYR and FLU-TPA/TRZ were found at 548 and 606 nm. The triazine receptor-based FLU-TPA/TRZ showed a longer emission peak at room temperature. The triplet energies of FLU-TPA/PYR and FLU-TPA/TRZ were obtained as 2.57 and 2.77 eV, respectively, which is more important for the host material to prevent energy backflow from the dopant material. Due to this, the material of the present invention exhibited excellent efficiency improvement with yellow phosphorescent OLED. Table 1 shows the UV-vis absorption and photoluminescence spectral analysis data.

Example 8. Analysis of HOMO Energy Levels of FLU-TPA/PYR and FLU-TPA/TRZ

The HOMO energy levels of FLU-TPA/PYR and FLU-TPA/TRZ were calculated, which were -5.27 and 5.35 eV for FLU-TPA/PYR and FLU-TPA/TRZ, respectively. The lowest unoccupied molecular orbital (LUMO) energy value obtained by adding the HOMO energy to the band gap energy was -2.86 eV for both FLU-TPA/PYR and FLU-TPA/TRZ. The frontier molecular energy should promote effective charge transport from both electrodes. To understand the molecular orbital distribution, we performed basic density functional theory calculations with the basic set 6-31G using Gaussian 09. The frontier molecular orbital distribution according to the above calculation is shown in FIG. 3 . The LUMO distribution appears on the electron donor triazine and pyrimidine residues. The HOMO distribution was shown on the electron donating triphenylamine units, but the HOMO distribution showed significant overlap. The HOMO energy level analysis data is shown in Table 1.

Example 9. Fabrication of FLU-TPA/PYR and FLU-TPA/TRZ OLED devices

To establish the electroluminescent properties of the bipolar host materials FLU-TPA/PYR and FLU-TPA/TRZ, iridium(III) bis(4-(4-tert-butylphenyl)thieno[3,2-c]pyridinato -N, C2`) A yellow phosphorescent OLED device was fabricated with a yellow dopant of acetylacetonate. The structure of the yellow phosphorescent OLED device is shown in FIG. 4 . The structure of the yellow phosphorescent device is as follows: indium tin oxide (ITO) (150 nm) / 1,4,5,8,9,11-hexaazatriphenylenehexacapitrile (HATCN) (7 nm) / 4 ,4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzamine] (TAPC) (43 nm) / FLU-TPA/PYR or FLU-TPA/TRZ: 10 wt % iridium(III) Bis(4-(4-tert-butylphenyl)thieno[3,2-c]pyridinato-N,C2')acetylacetonate (20nm)/1,3,5-tri(m-pyridine-3 -ylphenyl)benzene (TmPyPB) (35nm) / 8-quinolinolatolithium (Liq) (1.5nm) / aluminum (Al) (100nm). ITO and Al used for the anode and cathode, HATCN for the hole injection layer, Liq for the electron injection layer, TAPC as the hole transport layer and TmPyPB used as the electron transport layer (ETL).

Example 10. FLU-TPA/PYR and FLU-TPA/TRZ Electroluminescence Characterization

Electroluminescence characteristics of the device were analyzed using the device manufactured in Example 5, and current density voltage, current density power, and current efficiency are shown in FIG. 5 and data are shown in Table 2 below. The turn-on voltage of the FLU-TPA/PYR and FLU-TPA/TRZ based devices was 5V. The FLU-TPA/PYR and FLU-TPA/TRZ based devices were 21.70 and 18.72 cd/A, respectively. Consequently, the power efficiency is measured at 13.64 and 11.76 lm/W for FLU-TPA/PYR and FLU-TPA/TRZ, respectively. The external quantum efficiency (7.75%) of the FLU-TPA/PYR-based device was higher than that of the triazine-based FLU-TPA/TRZ device (6.44%). Although both devices showed similar turn-on voltages, the device efficiency of the pyrimidine-based FLU-TPA/PYR was significantly higher than that of the FLU-TPA/TRZ. Both devices exhibited low-efficiency roll-off, which is one of the important factors for longer drive devices. The electroluminescence spectra of the two devices are shown in FIG. 6 . The maximum emission of all yellow devices was similar to 562 nm, demonstrating yellow emission from the yellow dopant.

Device Characteristics FLU-TPA/PYR
(yellow element) FLU-TPA/TRZ
(yellow element) FLU-TPA/PYR
(undoped) FLU-TPA/TRZ
(undoped) Driving voltage (V) 5.0 5.0 6.5 5.0 current efficiency
(cd/A) 21.70 18.72 1.27 10.30 power efficiency
(lm/W) 13.64 11.76 0.61 6.47 EQE (%) 7.75 6.44 0.53 3.57 CIE(x,y) 0.49,0.50 0.49,0.50 0.41,0.51 0.41,0.55

Example 11. Fabrication of FLU-TPA/PYR and FLU-TPA/TRZ undoped fluorescent devices

In order to understand the molecular performance as an emitter, an undoped fluorescent device was fabricated (FIG. 7). The undoped device structure is as follows: indium tin oxide (ITO) (150 nm) / 1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile (HATCN) (7 nm) / 4, 4'-cyclohexylidenebis[N,N-bis(4-methylphenyl)benzamine] (TAPC) (43nm) / FLU-TPA/PYR or FLU-TPA/TRZ (20nm) / 1,3,5- Tri(m-pyridin-3-yl phenyl)benzene (TmPyPB) (35 nm) / 8-quinolinolatolithium (Liq) (1.5 nm) / Aluminum (Al) (100 nm).

The undoped device performance of triazine-based FLU-TPA/TRZ was superior to that of pyridine-based FLU-TPA/PYR. The current, power and external quantum efficiencies of the FLU-TPA/TRZ-based device were 10.30 cd/A, 6.47 lm/W, and 3.57%, respectively (Fig. 8 and Table 2). The maximum electroluminescent emission with green emission was 549 nm and the CIE color coordinates (x, y) were 0.41 and 0.55 (Fig. 9).

In the present invention, the two bipolar materials are N ¹ -(9,9-diphenyl-9H-fluoren-2-yl) -N ⁴ ,N ⁴ -diphenylbenzene-1,4-diamine donor and triazine or pyri It was synthesized as a midine acceptor. The bipolar materials FLU-TPA/PYR and FLU-TPA/TRZ were applied to yellow phosphorescent and undoped fluorescent OLEDs. The yellow device with FLU-TPA/PYR shows superior device characteristics when compared to the triazine-based FLU-TPA/TRZ. The current and power efficiency of the FLU-TPA/PYR-based yellow device were 21.70 cd/A and 13.64 lm/W, respectively. All devices exhibited low-efficiency roll-off.

Claims (6)

A hole transport material represented by Formula 1 below:
[Formula 1]

In Formula 1 above
R is

or

am. a first electrode;
a second electrode facing the first electrode;
a light emitting material layer positioned between the first and second electrodes;
and a hole transport layer positioned between the first electrode and the light emitting material layer,
The hole transport layer,
An organic electroluminescent device, characterized in that it is made of any one of the hole transport material of claim 1. 3. The method of claim 2,
The hole transport layer is an organic electroluminescent device characterized in that it is formed by any one selected from the group consisting of a spin coating process, a nozzle printing process, an inkjet printing process, a slot coating process, a dip coating process and a roll-to-roll process. 3. The method of claim 2,
a hole injection layer positioned between the first electrode and the hole transport layer;
an electron transport layer positioned between the light emitting material layer and the second electrode;
and an electron injection layer positioned between the electron transport layer and the second electrode. An electronic device comprising the organic electroluminescent device according to claim 2 . 6. The method of claim 5,
The electronic device is an organic integrated circuit (O-IC), an organic electric-effect transistor (O-FET), an organic thin film transistor (O-TFT), an organic electroluminescent transistor (O-LET), an organic solar cell (O-SC) ), organic optical detectors, organic photoreceptors, organic electro-quenching devices (O-FQDs), light emitting electrochemical cells (LECs), organic laser diodes (O-lasers) or organic electroluminescent devices (OLEDs).

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