KR102128299B1 - Novel organic electroluminescent compound, organic electroluminescent device including the same and electric apparatus - Google Patents

Abstract

상기 식에서 R은 명세서에서 정의한 바와 같다.
상기 유기전기발광 화합물은 인광 녹색 및 황색 호스트 물질 등의 인광재료, 정공주입층 물질, 정공수송층 물질, 전자주입층 물질 또는 전자수송층 물질로서 유기전기발광소자에 적용할 수 있으며, 유기전기발광소자에 적용할 경우 구동전압을 낮추며, 발광효율, 휘도, 열적 안정성 및 소자 수명을 향상시킨다.It provides an organic electroluminescent compound represented by the following formula (I), an organic electroluminescent device comprising the same and an electronic device.
[Formula I]

In the above formula, R is as defined in the specification.
The organic electroluminescent compound can be applied to organic electroluminescent devices as phosphorescent materials such as phosphorescent green and yellow host materials, hole injection layer materials, hole transport layer materials, electron injection layer materials or electron transport layer materials, When applied, it lowers the driving voltage and improves luminous efficiency, brightness, thermal stability and device life.

Description

Novel organic electroluminescent compounds, organic electroluminescent devices and electronic devices containing the same {NOVEL ORGANIC ELECTROLUMINESCENT COMPOUND, ORGANIC ELECTROLUMINESCENT DEVICE INCLUDING THE SAME AND ELECTRIC APPARATUS}

The present invention relates to a novel organic electroluminescent compound, an organic electroluminescent device comprising the same, and an electronic device.

Until 2000, the mainstream in the display field was CRT (CRT), but as the interest in flat panel displays increased due to the demand for light weight, low power consumption, portability, and flattening, the replacement with LCD (Liquid Crystal display) rapidly On the other hand, organic light emitting diodes (OLEDs) are drawing attention as next-generation flat panel displays. OLED is a display capable of realizing characters or images of various colors by emitting organic substances by itself when a voltage is applied to an organic (high or low molecular) thin film.It is self-emission type, ultra-thin type (1/3 of LCD) compared to LCD. Because of its fast response speed (1000 times the LCD), low power consumption (1/2 of the LCD), high clarity and flexibility, it is spotlighted as a small mobile display for mobile phones and PDAs. In addition, in the future, it is expected to develop into a display of a simple and clear scroll TV as a paper after 2010, including notebook PCs and wall-mounted TVs.

OLED emits visible light by recombination of holes and electrons, and takes a form in which a plurality of organic layers are stacked between a cathode and an anode. In general, the substrate for manufacturing the OLED device uses glass, but in some cases, a bendable plastic or film type is also applied. The anode electrode on the substrate mainly uses Indium-Tin-Oxide (ITO) formed by vacuum deposition or sputtering, and the organic layer is vacuum deposited for low molecular weight compounds, spin coating for high molecular weight compounds, or inkjet printing. And the like to form a thin film. As the cathode, magnesium or lithium having a small work function is required, but aluminum is mainly used in consideration of stability with moisture and oxygen in the atmosphere.

Looking briefly at the structure of the OLED, an organic material having semiconductor characteristics has a sandwich structure between a cathode and an anode in the form of a thin film, and when a DC electric field is applied to both electrodes, electrons and holes are formed of an organic material. It is injected into the light emitting layer to emit light in the visible region. In general, in order to improve the luminous efficiency of the OLED, several types of organic materials are formed in multiple layers between the cathode and the anode. For example, a hole injection layer (HIL) is formed on the anode, and then a hole transporting layer (HTL), an emissive layer (EML), an electron transporting layer (ETL), and electrons An injection layer (EIL) and a cathode electrode are sequentially formed. In addition, in the case of the light emitting layer, it is generally composed of a host material and a dopant material, and light emission efficiency can be greatly improved by doping a small amount of dopant of 0.5 to 20%.

In general, the organic electroluminescent device is widely used a vacuum deposition method using a fine metal mask (Fine Metal Mask) as a patterning technology. However, this vacuum deposition method was difficult to apply to large displays due to its high fair price and technical limitations. Accordingly, various patterning techniques that can replace the vacuum deposition method are being researched and developed. In particular, wet processes such as spin coating, inkjet printing, and casty methods do not require vacuum technology, which can reduce equipment costs and facilitate device fabrication without material loss, making it a popular technology in the large display industry.

However, the material for the wet process is not yet capable of realizing excellent device performance compared to the material for vacuum deposition. In addition, in the case of forming an organic thin film layer by a wet process, there may be a problem in that the material of the already formed lower film is melted by an organic solvent, and it is difficult to stack the organic thin film layer in multiple layers due to such problems, so that excellent device performance cannot be realized. to be.

Accordingly, a polymer material is mainly used as a material for wet processing. These polymer materials are made of a conjugated form in which aromatic substituents such as an aryl group and an arylamine group are long connected by covalent bonds. In general, as the molecular length increases, the conjugate length also increases. As a result, the energy band gap of the molecule decreases. Even if the polymer material uses the same monomer, various polymer materials having different energy band gaps are synthesized according to the degree of polymerization, and polymer materials having various molecular weight distributions are synthesized in one reactor. It is very difficult to obtain a thin film layer.

Therefore, in order to provide an organic photoelectric device having excellent life and efficiency characteristics by using a wet process, which is easy to manufacture the device and has more advantages in terms of price and size, it has excellent interfacial stability between the organic thin film layers and an energy band gap. There is a need to develop a new polymer polymer that can be easily controlled.

On the other hand, phosphorescent organic light emitting diodes (PhOLED) based on heavy metal complexes are of great interest because they can theoretically achieve 100% internal quantum efficiency by using both singlet and triplet excitation. (JAG Williams, Top. Curr. Chem., 2007, 281, 205-268.; L. Flamigni, A. Barbieri, C. Sabatini, B.Ventura and F. Barigelletti, Top. Curr. Chem., 2007, 281 , 143-20). To prevent triplet-triplet termination and termination of concentration, PhOLED generally employs an active layer, where the phosphorescent material is doped inside a suitable host material. In general, PhOLED's host material should have a higher triplet energy level (ET) than phosphorescent emitters for efficient energy transfer from the host into the guest and confinement of the triplet excitation of the guest material.

Although studies on low molecular host materials based on carbazole derivatives have been well established (V. Cleave, G. Yahioglu, P. LeBarny, RH Friend and N. Tessler, Adv. Mater., 1999, 11, 285-288.; K. Brunner, A. van Dijken, H.Borner, JJAM Bastiaansen, NMM Kiggen and BMW Langeveld, J. Am. Chem. Soc., 2004, 126,6035-6042), polymer host materials are also capable of their high solution manufacturability Therefore, it is considered as an object of interest, and it may be useful for volume production of OLEDs using printing technology when applied to electrical signals, light emission, and displays. In view of this, many studies are under way in the development of conjugated polymer hosts for phosphors. In particular, red PhOLED devices with high device efficiencies similar to vacuum deposited devices have been demonstrated by several groups (H. Zhen, C. Luo, W. Yang, W. Song, B. Du, J. Jiang, C. Jiang, Y. Zhang and Y. Cao, Macromolecules, 2006, 39, 1693-1700.; F.-I. Wu, P.-I. Shih, Y.-H. Tseng, G.-Y. Chen, C .-H. Chien, C.-F. Shu, Y.-L.Tung, Y. Chi and AK-Y. Jen, J. Phys. Chem. B, 2005, 109, 14000-14005.). However, few successful polymer host materials as green emitters have been reported, although recently it has been reported that high efficiency is achieved through modification of the main chain polymer structure due to the increase in ET (T. Fei, G.Cheng, D. Hu, P. Lu and Y. Ma, J. Polym. Sci., Part A: Polym. Chem., 2009, 47, 4784-4792.; H.-C. Yeh, C.- H. Chien, P.-I. Shih, M.-C. Yuan and C.-F. Shu, Macromolecules, 2008, 41, 3801-3807.), which is the most well-conjugated polymer (Z. Wu, Y. Xiong, J. Zou, L. Wang, J. Liu, Q. Chen, W. Yang, J. Peng and Y.Cao, Adv. Mater., 2008, 20, 2359-2364. Is a typical green emitter fac-tris(2-phenylpyridine)iridium(III)(fac-Ir(ppy)3, ET = 2.41 eV) (AB Tamayo, BD Alleyne, PI Djurovich, S. Lamansky, I. Tsyba, NN Ho , R. Bau and ME Thompson, J. Am. Chem. Soc., 2003, 125, 7377-7387.). Alternatively, unbound side chain polymers such as poly(9-vinylcarbazole) (PVK) are often applied as polymer hosts due to their relatively high triplet energy (ET = 2.5 eV) (KM Vaeth and CW Tang, J. Appl. Phys., 2002, 92, 3447-3453.), there is a problem that the efficiency is reduced due to low charge transport characteristics.

The present invention is designed to solve the problems of the prior art as described above, and is applied to an organic electroluminescent device as a phosphorescent material such as a phosphorescent green host material, a hole injection layer material, a hole transport layer material, an electron injection layer material or an electron transport layer material It is an object of the present invention to provide an organic electroluminescent compound capable of lowering a driving voltage when applied to an organic electroluminescent device, and improving luminous efficiency, brightness, thermal stability, and device life.

In addition, an object of the present invention is to provide an organic electroluminescent device using the organic electroluminescent compound.

In addition, the present invention provides an electronic device to which the organic electroluminescent device is applied.

One embodiment of the present invention provides an organic electroluminescent compound represented by the following formula (I).

[Formula I]

In Chemical Formula 1

또는

이다.R is

or

to be.

Another embodiment of the present invention is an organic electroluminescent device in which an organic thin film layer composed of one or more layers including at least a light emitting layer is sandwiched between a cathode and an anode, and at least one or more of the organic thin film layers is the organic electroluminescent compound. It provides an organic electroluminescent device containing one or a combination of two or more.

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

The organic electroluminescent compound can be applied to organic electroluminescent devices as phosphorescent materials such as phosphorescent green and yellow host materials, hole injection layer materials, hole transport layer materials, electron injection layer materials or electron transport layer materials, When applied, it lowers the driving voltage and improves luminous efficiency, brightness, thermal stability and device life.

In addition, the organic electroluminescent device manufactured by using the organic electroluminescent compound has a characteristic of excellent luminous efficiency.

Figure 1 shows the synthesis process of host materials TRZ 1 and PYR 1.
Figure 2 shows the differential scanning calorimeter curves of TRZ 1 and PYR 1.
Figure 3 shows the results of UV-VIS absorption and photoluminescence spectra of hosts TRZ 1 and PYR 1.
4 shows the results of cyclic voltage-current measurement of TRZ 1 and PYR 1.
5 shows the spatial distribution of HOMO-LUMO of TRZ 1 and PYR 1.
Figure 6 shows the device arrangement of TRZ 1, PYR 1 and CBP host materials.
7 shows the current density-voltage (JV) and luminance-voltage (LV) characteristics of the reference CBP host and TRZ 1 and PYR 1.
Figure 8 shows the HOD and EOD efficiency of TRZ 1, PYR 1 and CBP bipolar host material.
9 shows the electroluminescence spectra of TRZ 1, PYR 1 and CBP green phosphorescent OLEDs.

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 thereby, and the present invention is only defined by the scope of claims to be described later.

In one embodiment of the present invention, an organic electroluminescent compound represented by Formula I is provided.

[Formula I]

In Chemical Formula 1

또는

이다.R is

or

to be.

인 경우 4-(2-(4,6-디페닐-1,3,5-트리아진-2-일)-9H-카바졸-9-일)-N,N-디페닐아닐린(TRZ-1)로 명명된다.In the present invention, R in the compound

For 4-(2-(4,6-diphenyl-1,3,5-triazin-2-yl)-9H-carbazole-9-yl)-N,N-diphenylaniline (TRZ-1 ).

인 경우 4-(2-(4,6-디페닐피리미딘-2-일)-9H-카바졸-9-일)-N,N-디페닐아닐린(PYR-1)로 명명된다.In the present invention, R in the compound

In the case of 4-(2-(4,6-diphenylpyrimidin-2-yl)-9H-carbazol-9-yl)-N,N-diphenylaniline (PYR-1).

The organic electroluminescent compound can be usefully used as a phosphorescent material such as a phosphorescent green host material or a phosphorescent yellow host material, a hole injection layer material, a hole transport layer material, an electron injection layer material, or an electron transport layer material among the materials for an organic electroluminescent device, , Preferably phosphorescent green host material and phosphorescent yellow host material.

In one embodiment of the present invention, the organic electroluminescent compound may be used as a phosphorescent green host material or a hole transport layer material.

In another embodiment of the present invention, an organic electroluminescent device in which an organic thin film layer composed of one or more layers including at least a light emitting layer is sandwiched between a cathode and an anode, and at least one or more of the organic thin film layers is the organic electroluminescent compound It provides an organic electroluminescent device containing one or a combination of two or more.

The organic thin film layer may be formed by a soluble process using the organic electroluminescent compound.

The organic electroluminescent compound may be included in an organic electroluminescent device as a phosphorescent green host material, a phosphorescent yellow host material, a hole injection layer material, a hole transport layer material, an electron injection layer material or an electron transport layer material, in particular, a phosphorescent green host material and It can be usefully used as a phosphorescent yellow host material.

In addition, the organic electroluminescent device may have a structure in which an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode are stacked in this order.

In another embodiment of the present invention, an electronic device including the organic electroluminescent device is provided.

An electronic device including the organic electroluminescent device includes an organic integrated circuit (O-IC), an organic field-effect transistor (O-FET), an organic thin film transistor (O-TFT), and an organic electroluminescent transistor (O-LET). , Organic solar cell (O-SC), organic optical detector, organic photoreceptor, organic field-quench device (O-FQD), luminescent electrochemical cell (LEC), organic laser diode (O-laser) or organic light emitting device ( OLED).

Hereinafter, the organic electroluminescent device will be described as an example. However, the contents exemplified below do not limit 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, 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) may be further included between the cathode and the light emitting layer.

As a method for manufacturing the organic electroluminescent device, first, a positive electrode is formed on a surface of a substrate by coating a material for a positive electrode. At this time, the substrate used is preferably a glass substrate or a transparent plastic substrate having excellent transparency, surface smoothness, ease of handling and waterproofness. 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 excellent in conductivity, may be used.

Next, a hole injection layer (HIL) material is vacuum-deposited or spin coated on the anode surface in a conventional manner to form a hole injection layer. The organic electroluminescent compound may be used as the hole injection layer material, in addition, 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 commercially available from Idemitsu. have.

A hole transport layer (HTL) material is vacuum-deposited or spin coated on the surface of the hole injection layer in a conventional manner to form a hole transport layer. At this time, as the hole transport layer material, the organic electroluminescent compound may be used, 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 exemplified.

A light emitting layer (EML) material is vacuum-deposited or spin coated on the surface of the hole transport layer in a conventional manner to form a light emitting layer. At this time, among the light emitting layer materials used, the single light emitting material or the light emitting host material may be used as the phosphorescent green host material in the case of green, and the organic electroluminescent compound may be used as the phosphorescent yellow host material in the case of yellow. .

In the case of a dopant that can be used together with a light emitting host among the light emitting layer materials, IDE102, IDE105, available from Idemitsu as a fluorescent dopant, and tris(2-phenylpyridine)iridium(III) (Ir(ppy) as a phosphorescent dopant ) ₃ ), iridium(III)bis[(4,6-difluorophenyl)pyridinato-N,C-2']picolinate (FIrpic) (Chihaya Adachi et al., Appl. Phys .Let., 2001, 79, 3082-3084]), platinum (II) octaethyl porphyrin (PtOEP), TBE002 (Kobeon Co.), 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 in a conventional manner to form an electron transport layer. In this case, as the electron transport layer material used, the organic electroluminescent compound may be used, and tris(8-hydroxyquinolinolato)aluminum (Alq3) may be used.

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

The hole blocking layer may be formed 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) Lithium (Liq), bis(8-hydroxy-2-methylquinolinolnato)-aluminum biphenoxide (BAlq), bathocuproine (BCP), LiF, and the like can be used.

An electron injection layer (EIL) material is vacuum-deposited or spin coated on the surface of the electron transport layer in a conventional manner to form an electron injection layer. At this time, as the electron injection layer material used, the organic electroluminescent compound may be used, and materials such as LiF, Liq, Li ₂ O, BaO, NaCl, or CsF may be used.

Finally, a negative electrode is formed on the surface of the electron injection layer by vacuum thermal vapor deposition of a material for a negative electrode in a conventional manner.

At this time, the negative electrode material used is 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 front emission organic electroluminescent device, a transparent cathode through which light can pass may be formed using indium tin oxide (ITO) or indium zinc oxide (IZO).

The organic electroluminescent device may be manufactured in the order described above, that is, in the order of the anode/hole injection layer/hole transport layer/light emitting layer/hole blocking layer/electron transport layer/electron injection layer/cathode, and vice versa. It may be manufactured in the order of /electron transport layer/hole blocking layer/light emitting layer/hole transport layer/hole injection layer/anode.

Hereinafter, a method for synthesizing the compounds will be described below as a representative example. However, the method for synthesizing the compounds is not limited to the methods exemplified below, and the compounds can be prepared by the methods exemplified below and methods known in the art.

device

All reagents and solvents were obtained commercially and used without further purification. 1H and ¹³ C NMR spectra were recorded using a JEON JNM-ECP FT-NMR spectrometer (JEOL, Peabody, MA, USA) at 500 MHz. The absorbance spectra was obtained using a SINCO S-4100 UV-Visable Spectrometer (SINCO, Seoul, Korea). The band gap (eG) was evaluated on-set of UV-Visible absorbance spectra. The photoluminescence (PL) spectra was measured using a JASCO FP-8500 spectrofluorimeter (JASCO, Tokyo, Japan) and THF was used as a solvent. The triplet energy (ET) level was confirmed by comparing the normal temperature PL spectra and the low temperature (~77K) PL spectra. To measure the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) levels, cyclic voltammetry (CV) was performed using BioLogic SP-50 (Biologic, Paris, France) and HOMO Levels were calculated by subtracting the change in oxidation potential between ferrocene and HTMs. The LUMO level was evaluated by adding the obtained HOMO level and band gap. The current density-voltage-luminance (JVL) characteristics of each device were measured using a luminance color meter (Konica Minolta CS-100A) and a source meter unit Keithley 2635A, and electroluminesence (EL) spectra and CIE (Commission). Internationale l'Eclairage) 1931 Curly coordinator was obtained using a Konica Minolta CS-2000 spectroradiometer. Molecular simulations were performed using density function theory (DFT) calculations using B3LYP (beck three parameter hybrid functional and Lee-Yang-Parr correlation functional) and Gaussian 09's 6-31G (d) base set. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed at SDC Q600 V20.9 Build 20 and DSC Q200 V24.9 Build 121 (TA instruments, New) at a heating rate of 10°C/min. castle, DE, USA). Mass spectrometry was performed using a Xevo TQ-S spectrometer (Waters, Milford, MA, USA).

Synthesis process

The production process of the novel host materials TRZ 1 and PYR 1 of the present invention is shown in FIG. 1 and the synthesis process is specifically described in Examples 1 to 4 below.

Example 1. Preparation of 2-chloro-4,6-diphenyl-1,3,5-triazine (2Ph-TRZ)

2,4,6-Trichloro-1,3,5-triazine CYC (5 g, 1 eq.) was kept under vacuum for 15 minutes, then provided internal conditions and 100 ml of dry THF was added. Thereafter, the mixture was stirred at 0° C. and phenyl magnesium bromide (Ph-MgBr, 3M, 20 ml) was added dropwise and injected, and the mixture was maintained at room temperature for 12 hours. After the reaction was completed, the mixture was evaporated and recrystallized using methanol as a solvent to obtain a target product 2Ph-TRZ as a pale white solid.

Yield: 89%; Pale white solid; ¹ H NMR (500 MHz, CDCl3) δ 8.61-8.63 (d, J = 7 Hz, 4H), 7.61-7.64 (t, J = 7.5 Hz, 2H), 7.53-7.56 (t, J = 7.5 Hz, 4H ); ¹³ C NMR (500 MHz, CDCl ₃ ) δ 173.4, 172.2, 134.4, 133.6, 129.4, 128.9.

Example 2. Preparation of 2-chloro-4,6-diphenylpyrimidine (2Ph-PYR)

2,4,6-trichloropyrimidine (PYR, 1.3 ml, 1 eq), phenylboronic acid (Ph-BoA), Pd (PPh ₃ P) ₄ (0.2 g, 0.03 eq), K ₂ CO ₃ (2M , 40ml), 40ml of water, 25ml of ethanol and 80ml of toluene were added and refluxed at 110°C for 8 hours. After completion of the reaction, the mixture was worked up using ethyl-acetate and water. The organic layer was dried over anhydrous magnesium sulfate, filtered and concentrated. The crude residue was separated through a silica column using an n-hexane:dichloromethane solvent system to give a 2Ph-PYR intermediate as a white solid.

Yield: 74%; White solid; ¹ H NMR (500 MHz, CDCl ₃ ) δ 8.13-8.14 (d, J = 8 Hz, 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.

Example 3. 4-(2-(4,6-Diphenyl-1,3,5-triazin-2-yl)-9H-carbazole-9-yl)-N,N-diphenyl aniline (TRZ Synthesis of -1)

2-Chloro-4,6-diphenyl-1,3,5-triazine 2Ph-TRZ (1 g, 1 equivalent), (9-(4-(diphenylamino)phenyl)-9H-carbazole-2- 1) A mixture of boronic acid 1 (2,2 g, 1.2 eq), Pd (PPh ₃ P) ₄ (0.01 g, 0.03 eq), K ₂ CO ₃ (2M, 40 ml), 40 ml of water, 30 ml of THF and 80 ml of toluene It was added and stirred at 110° C. for 12 hours. The residue was extracted with dichloromethane and water. The organic layer was collected and dried over anhydrous magnesium sulfate. Finally, the crude was separated through a silica column using a mobile phase based on n-hexane:dichloromethane gradient to obtain pure TRZ 1 target molecule.

Yield: 86%; Light yellow solid; ¹ H NMR (500 MHz, CDCl ₃ ) δ 8.73-8.78 (m, 5H), 8.28-8.30 (d, J = 10 Hz, 1H), 8.21-8.23 (d, J = 10 Hz, 1H), 7.56- 7.64 (m, 7H), 7.48-7.52 (m, 3H), 7.31-7.37 (m, 7H), 7.26-7.28 (m, 4H), 7.09-7.21 (t, J = 7.5 Hz, 2H); ¹³ C NMR (500 MHz, CDCl ₃ ) δ 172.2, 171.6, 147.6, 140.3, 136.4, 132.5, 129.6, 128.1, 127.1, 124.8, 124.2, 123.5, 121.1, 120.7, 120.2, 110.9, 110.3, 100.0; GC-MS: 641.83 for C ₄₅ H ₃₁ N ₅ [M+H ⁺ ].

Example 4. Synthesis of 4-(2-(4,6-diphenylpyrimidin-2-yl)-9H-carbazole-9-yl)-N,N-diphenyl aniline (PYR-1)

2-chloro-4,6-diphenyl-4,6-diphenylpyridine 2Ph-PYR(1g, 1 eq.), (9-(4-(diphenylamino)phenyl)-9H-carbazol-2-yl )Added a mixture of boronic acid 1 (2,2 g, 1.2 eq), Pd (PPh ₃ P) ₄ (0.01 g, 0.03 eq), K ₂ CO ₃ (2M, 40 ml), 40 ml of water, 30 ml of THF and 80 ml of toluene And stirred at 110° C. for 12 hours. The residue was extracted with dichloromethane and water. The organic layer was collected and dried over anhydrous magnesium sulfate. Finally, the crude was separated through a silica column using a mobile phase based on n-hexane:dichloromethane gradient to obtain pure TRZ 1 target molecule.

Yield: 77%; Yellow solid; ¹ H NMR (500 MHz, CDCl ₃ ) δ 8.83 (s, 1H), 8.70-8.71 (d, J = 8.5 Hz, 1H), 8.22-8.26 (m, 5H), 8.20-8.21 ((d, J = 8.5 Hz, 1H), 8.01 (s, 1H), 7.45-7.58 (m, 10H), 7.26-7.35 (m, 7H), 7.24-7.26 (m, 4H), 7.08-7.10 (t, J = 8.5 Hz , 2H); ¹³ C NMR (500 MHz, CDCl ₃ ) δ 165.1, 164.7, 147.7, 147.2, 142.2, 141.5, 137.7, 136.0, 130.8, 129.5, 129.0, 128.1, 127.3, 126.5, 125.4, 124.7, 124.4, 123.3 , 120.8, 120.5, 120.1, 120.0, 110.3, 110.1, 110.1; GC-MS: 640.76 for C ₄₆ H ₃₂ N ₄ [M+H ⁺ ].

Experimental Example 1. Analysis of thermal properties of TRZ 1 and PYR 1 host materials

The thermal stability of the host material was evaluated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) measurements, which are shown in Table 1 below and shown in FIG. 2. TRZ 1 and PYR 1 have a glass transition temperature much higher than that of CBP (4,4`-bis(N-carbazolyl-1,1`-biphenyl)), which is a material widely used as 252℃ and 239℃. It was shown. The T _g value of the CBP host material is 62°C. All of the host materials of the present invention showed a high decomposition temperature of 400° C. or more at 5% weight loss, and can demonstrate the morphology and thermal stability of the thin film in the device.

Host T _g ^a
( ^o C) T _d ^b
( ^o C) UV-Vis (nm) PL max (nm) HOMO
(eV) LUMO
(eV) E _g ^c (eV) E _T ^d (eV) E _s ^e (eV) TRZ 1 253 425 429 508 5.59 2.70 2.89 2.44 2.62 PYR 1 240 400 405 446 5.63 2.57 3.06 2.63 2.88

^a glass transition temperature, ^b decomposition temperature at 5% weight loss, ^c energy band gap, ^d triplet energy, ^e singlet energy

Experimental Example 2. Analysis of photophysical properties of TRZ 1 and PYR 1 host materials

Figure 3 shows the UV-Vis absorption and photoluminescence (PL) spectra of TRZ 1 and PYR 1 at room temperature, and the results are shown in Table 1 above. Both peaks appeared similar, with a sharply increased absorption intensity at 320 nm in both TRZ 1 and PYR 1, π- from the electron donor carbazole-triphenylamine residue to the electron withdrawing triazine and pyrimidine residues. It is due to π ^* electron transition. The band gap values were 2.89 eV and 3.06 eV for TRZ 1 and PYR 1 at absorption boundaries at 429 nm and 405 nm, respectively. The high band gap values of TRZ 1 and PYR 1 are represented by meta-coupling between the electron donor and the acceptor, which firmly reduces pi conjugation and widens the band gap by affecting the intramolecular electron transport process. The PL spectra at room temperature for TRZ 1 and PYR 1 were 508 nm and 446 nm. Triplet energy is a key element for host materials that ensure device efficiency by preventing the transfer of energy from guest to host. The triplet energies of TRZ 1 and PYR 1 were 2.44 eV and 2.63 eV, evaluated with low temperature PL spectra, which are more suitable for green phosphorescence based OLEDs. The PYR 1 triplet energy of TRZ 1 is different due to the difference in electron drag attached to a similar electron donor. The triplet energy of PYR 1 was higher than that of the reference CBP material (2.58 eV), and PYR 1 based devices were found to be able to increase efficiency compared to TRZ 1 and CBP based devices.

Experimental Example 3. Analysis of the electrochemical properties of TRZ 1 and PYR 1 host materials\ HOMO energy levels obtained from Cyclic Voltammetry (CV) measurements are shown in FIG. 4. The HOMO levels of TRZ 1 and PYR 1 were 5.59 eV and 5.63 eV, which were almost similar to each other. The LUMO energy level was calculated by adding the HOMO energy to the band gap energy and is shown in Table 1 above. The LUMO energy levels of TRZ 1 and PYR 1 were 2.70 eV and 2.57 eV, PYR 1 had a higher LUMO energy level compared to TRZ 1, and both the host materials had low HOMO levels and at the same time Ir(ppy) ₃ dopants ( 2.90 eV). This energy level contributes to excellent efficiency by inducing efficient recombination of charges in the emitting layer.

Experimental Example 4. Molecular design and simulation analysis of TRZ 1 and PYR 1 host materials

To study electronic structure and molecular levels, density function theory (DFT) calculations were performed at the B3LYP/6-31G* level. The distribution of frontier molecular trajectories is shown in FIG. 5. The HOMO of the two host materials is delocalized to the triphenylamine residue. The LUMO of PYR 1 is clearly localized on the pyridine moiety at the pyridine moiety, and TRZ1 is localized to the triazine and carbazole derivatives. The TRZ 1 host material exhibited an almost unexpanded distribution compared to the PYR 1 host material. This type of distribution indicated that HOMO-LUMO separation is beneficial for hole and electron transport properties in one molecule. The only difference between TRZ 1 and PYR 1 is electron drag, which makes the LUMO distribution of TRZ 1 larger. PYR 1 showed a clear separation, which provides an appropriate charge balance for the emissive layer, increasing the efficiency of the device.

Experimental Example 5. Performance analysis of green OLED-based phosphorescent devices using TRZ 1 and PYR 1 host materials

To study the properties of the synthesized bipolar host material, a green OLED-based phosphorescent device was fabricated using Ir(ppy) ₃ as a green dopant. The arrangement of the device structure is ITO/ HATCN (7 nm)/ TAPC (43 nm)/ Host: 5 wt% Ir(ppy) ₃ (20 nm)/ TmPyPB (350 nm)/ LiF (1.5 nm)/ Al (100 nm) to be. The device arrangement is shown in FIG. 6. In this arrangement, ITO and Al were used as positive and negative electrodes, respectively. TAPC was used as a hole transport layer (HTL) and TmPyPB is for an electron transport layer (ETL) in the above-configured device. At the same time, the triplet energies of HTL and ETL are 2.9 eV and 2.8 eV, high enough to block the triplet exciton quenching from the green emission layer (EML).

The current density-voltage (J-V) and luminance-voltage (L-V) characteristics are shown in FIG. 7 and Table 2. The PYR 1 based device exhibited a low turn on voltage of 2.4V compared to the CBP based reference device (2.6V). The above results indicate that PYR1 has excellent bipolar properties to achieve proper charge balance in the emission layer. The lower operation voltage (3.0V) of the PYR 1 based device further improved the device efficiency, and the TRZ 1 based device exhibited a higher driving voltage at 3.6V. PYR 1 based devices showed higher maximum current efficiency of TRZ 1 (45.3 cd/A), which is higher than TRZ 1 (45.3 cd/A) and CBP (45.8 cd/A) based devices.

characteristic CBP TRZ-1 PYR-1 Starting voltage 2.6 V 2.6 V 2.4 V Driving voltage ^a 3.3 V 3.6 V 3.0 V Maximum luminance 31,370 cd/m ² 54,170 cd/m ² 95,870 cd/m ² Current efficiency ^a 47.1 / 45.8 cd/A 45.6 / 45.3 cd/A 48.7 / 48.7 cd/A EQE ^a 15.8/15.7% 15.4 / 15.3% 16.4 / 16.4% CIE color ^b (0.28, 0.62) (0.28, 0.63) (0.28, 0.63) λ _max ^b 513 nm 512 nm 512 nm

^at 1000 cd/m ²

^{b at} 10 mA/cm ²

As a result, in the present invention, it was confirmed that the maximum luminescence of TRZ 1 and PYR 1 was 54170 cm/m ² and 95870 cd/m ² , respectively. The PYR 1 based device had a maximum emission of 3 times that of the well-known CBP based device (31370 cd/m ² ). Therefore, the PYR 1 bipolar host material of the present invention is highly applicable to green PhOLEDs.

The maximum external quantum efficiency (EQE) of the PYR 1 based device (16.7%) was higher than that of the reference CBP (15.7%) and TRZ 1 (15.3%) based devices. The bipolar properties of PYR 1 are superior to TRZ 1, which can increase the efficiency of the device. Through the above investigation, it was found that the CBP-based device exhibits a faster roll-off of efficiency when compared to TRZ 1 and PYR 1-based bipolar host materials. Therefore, the host material of the present invention can be used for long-term driving and can be used to improve the efficiency of a device, which is one of the key elements.

In order to understand the transport capability of electrons and holes, a hole-only device (HOD) and an electron-only device (EOD) were manufactured. The arrangement of HOD is ITO (50nm) / TAPC (20nm) / HOST (50nm) / TAPC (20nm) / Al (100nm) and the structure of EOD is ITO (50nm) / TmPyPB) / HOST (50nm) / TmPyPB (20nm) It is shown in Figure 8 / LiF (1.5nm) / Al (100nm).

From the HOD results, it was found that the TRZ 1 hole transport property was superior to the PYR 1 based device and exhibited a higher HOMO energy level. The higher LUMO energy value of PYR 1 showed a significant electron transport capacity than TRZ 1. The bipolar properties of the synthesized host material enhance the device properties and reduce the roll-off of efficiency. The electroluminescence spectra is shown in FIG. 9. The maximum EL peaks of CBP, TRZ 1 and PYR 1 were observed at 513 nm, 512 nm and 512 nm, respectively. All peaks were identical to each other and there was no chromic shift. Therefore, it was possible to confirm the perfect emission from the green dopant.

In the present invention, two new host materials (TRZ 1 and PYR 1) that provide bipolar properties were designed and synthesized using carbazole-triphenylamine electron donor and thiazine, pyrimidine-based electron attracting. The synthesized host material showed higher thermal stability due to its large volume. The triplet energy of the bipolar host material was suitable for green phosphorescent OLED and ensured efficient energy flow. PYR 1 based green OLED devices have low start (2.4V) and drive (3.0V) voltages. The maximum luminescence (95,870 cd/m ² ) of PYR 1 was 3 times higher than that of similar devices based on CBP. The PYR 1 based device has excellent maximum current efficiency of 48.7 cd/A, and at the same time, the maximum external quantum efficiency is 16.7% while the roll-off efficiency is low. Therefore, the novel bipolar host material of the present invention can be used in a thermally stable and high-luminance OLED device to increase efficiency.

Claims (7)

An organic electroluminescent compound represented by the following formula (I):
[Formula I]

In Chemical Formula 1
R is

or

to be.
According to claim 1,
The organic electroluminescent compound is one or more selected from the group consisting of a phosphorescent green host material, a phosphorescent yellow host material, a hole injection layer material, a hole transport layer material, an electron injection layer material, and an electron transport layer material among the materials for the organic electroluminescent device. Organic electroluminescent compounds that are used. An organic electroluminescent device in which an organic thin film layer composed of at least one layer or a plurality of layers including a light emitting layer is sandwiched between a cathode and an anode, and at least one or more of the organic thin film layers is one of the organic electroluminescent compounds according to claim 1 alone. Or an organic electroluminescent device. According to claim 3,
The organic electroluminescent compound is any one or more selected from the group consisting of a phosphorescent green host material, a phosphorescent yellow host material, a hole injection layer material, a hole transport layer material, an electron injection layer material and an electron transport layer material among the materials for the organic electroluminescent device. It contains an organic electroluminescent device. According to claim 3,
The organic electroluminescent device is an organic electroluminescent device characterized in that it has a structure in which an anode, a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer and a cathode are stacked in this order. An electronic device comprising the organic electroluminescent device according to claim 3. The method of claim 6,
The electronic device includes an organic integrated circuit (O-IC), an organic field-effect transistor (O-FET), an organic thin film transistor (O-TFT), an organic electroluminescent transistor (O-LET), an organic solar cell (O-SC) ), an organic optical detector, an organic photoreceptor, an organic electric field-quench device (O-FQD), a light emitting electrochemical cell (LEC), an organic laser diode (O-laser) or an organic electroluminescent device (OLED).

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