KR102615534B1 - Novel organic electroluminescent compound, organic electroluminescent device including the same and electric apparatus - Google Patents

Abstract

An organic electroluminescent compound represented by the following formula (1), an organic electroluminescent device and an electronic device containing the same are provided. The following organic electroluminescent compounds can be applied to organic electroluminescent devices as phosphorescent materials such as phosphorescent red 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 lifespan.
[Formula 1]
.

Description

Novel organic electroluminescent compound, organic electroluminescent device and electronic device containing the same

The present invention relates to novel organic electroluminescent compounds, organic electroluminescent devices and electronic devices containing them.

Until 2000, the mainstream in the display field was the cathode ray tube display (CRT), but as interest in flat panel displays increased due to demands for weight reduction, low power consumption, portability, and flatness, they were rapidly replaced by liquid crystal displays (LCD). Meanwhile, organic light emitting diode (OLED) is currently attracting attention as a next-generation flat display. OLED is a display that can produce text or images in various colors by applying voltage to a thin film of organic material (polymer or low molecule), causing the organic material to emit light on its own. Compared to LCD, it is self-luminous, ultra-thin (1/3 of LCD), and Because it features fast response speed (1000 times that of LCD), low power consumption (1/2 of LCD), high definition and flexibility, it is attracting attention as a small mobile display for mobile phones and PDAs. In addition, it is expected that in the future, displays for laptop PCs, wall-mounted TVs, and after 2010 will develop into displays for roll-up TVs that are as simple as paper and clearer.

OLED emits visible light by recombination of holes and electrons and takes the form of multiple organic layers stacked between the cathode and anode. Generally, glass is used as a substrate for manufacturing OLED devices, but in some cases, bendable plastic or film types are used. The anode electrode on the substrate mainly uses Indium-Tin-Oxide (ITO) formed by vacuum deposition or sputtering, and the organic layer is vacuum deposition for low-molecular compounds, spin coating, or inkjet printing for high-molecular compounds. Form a thin film using, etc. The cathode requires magnesium or lithium, which have a small work function, but aluminum is mainly used considering its stability against moisture and oxygen in the atmosphere.

Looking briefly at the structure of OLED, it takes a sandwich structure in which an organic material with semiconductor properties exists between a cathode and an anode in the form of a thin film. When a direct current electric field is applied to the two electrodes, electrons and holes are formed from organic materials. It is injected into the light emitting layer and emits light in the visible light range. In general, in order to improve the luminous efficiency of OLED, various types of organic materials are formed in multiple layers between the cathode and anode. For example, a hole injection layer (HIL) is formed on the top of the anode, followed by a hole transport layer (HTL), an emissive layer (EML), an electron transport layer (ETL), and an electron transport layer (HTL). An injection layer (electron injection layer: EIL) and a cathode electrode are sequentially formed. In addition, the light-emitting layer is generally composed of a host material and a dopant material, and the light-emitting efficiency can be greatly improved by doping with a trace amount of dopant of 0.5 to 20%.

In general, organic electroluminescent devices widely use vacuum deposition using a fine metal mask as a patterning technology. However, this vacuum deposition method had limitations that made it difficult to apply to large displays due to the high process cost and technical limitations. As a result, various patterning technologies that can replace vacuum deposition are being researched and developed. In particular, wet processes such as spin coating, inkjet printing, and castee methods do not require vacuum technology, can reduce equipment costs, and are easy to manufacture devices without material loss, making them a technology that is attracting attention in the large-scale display industry.

However, wet process materials cannot yet achieve superior device performance compared to vacuum deposition materials. In addition, when forming an organic thin film layer through a wet process, a problem may arise where the material of the already formed lower film is dissolved by the organic solvent. Due to this problem, it is difficult to stack the organic thin film layer in multiple layers, making it impossible to realize excellent device performance. am.

Accordingly, polymer materials are mainly used as materials for wet processes. These polymer materials are made in a conjugated form in which aromatic substituents such as aryl groups and arylamine groups are connected by long covalent bonds. Generally, as the molecule length increases, the conjugate length also increases, and in this case, the energy band gap of the molecule ultimately decreases. Even if the same monomer is used, various polymer materials with different energy band gaps are synthesized depending on the degree of polymerization, and polymer materials with various molecular weight distributions are synthesized even within one reactor. Therefore, organic materials with a specific energy band gap are synthesized using polymer materials. Obtaining a thin film layer is very difficult.

Therefore, in order to provide an organic photovoltaic device with excellent lifespan and efficiency characteristics using a wet process that is easy to manufacture and has more advantages in terms of price and size, the interfacial stability between organic thin film layers is excellent and the energy band gap is There is a need for the development of new polymers that can easily control .

Meanwhile, phosphorescent organic light-emitting diodes (PhOLEDs) based on heavy metal complexes are attracting great attention because they can theoretically achieve 100% internal quantum efficiency by using both singlet and triplet excitation. (J.A. G. 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 annihilation and concentration termination, PhOLEDs generally employ an active layer, in which the phosphorescent emitter is doped inside a suitable host material. In general, the host material of a PhOLED must have a higher triplet energy level (ET) than the phosphorescent emitter for efficient energy transfer from the host into the guest and confinement of the triplet excitation of the guest material.

Although small molecule host materials based on carbazole derivatives have been well studied (V. Cleave, G. Yahioglu, P. LeBarny, R. H. Friend and N. Tessler, Adv. Mater., 1999, 11, 285-288; K. Brunner, A. van Dijken, H.Borner, J. J. A. M. Bastiaansen, N. M. M. Kiggen and B. M. W. Langeveld, J. Am. Chem. Soc., 2004, 126,6035-6042), polymer host materials also show their high solution manufacturability. Therefore, it is considered a subject of interest, and it may be useful for volumetric manufacturing of OLEDs using printing technology for applications in electrical signals, light emission, and displays. In this respect, much research is being conducted on the development of conjugated polymer hosts for phosphorescent materials. In particular, red PhOLED devices with high device efficiency 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 A. K.-Y. Jen, J. Phys. Chem. B, 2005, 109, 14000-14005.). However, few successful polymer host materials as red and yellow bipolar emitters have been reported.

The present invention was designed to solve the problems of the prior art as described above, and is applied to an organic electroluminescent device using a phosphorescent material such as a yellow or red host material, a hole injection layer material, a hole transport layer material, an electron injection layer material, or an electron transport layer material. The purpose is to provide an organic electroluminescent compound that can be applied to an organic electroluminescent device, can lower the driving voltage, and can improve luminous efficiency, luminance, thermal stability, and device lifespan.

Additionally, the present invention aims to provide an organic electroluminescent device using the organic electroluminescent compound.

Additionally, the present invention provides an electronic device using the organic electroluminescent device.

One embodiment of the present invention provides an organic electroluminescent compound represented by the following formula (1).

[Formula 1]

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

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 red 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 lifespan.

In addition, organic electroluminescent devices manufactured using the organic electroluminescent compounds have the characteristic of excellent luminous efficiency.

Figure 1 shows the results of differential scanning calorimetry and thermogravimetric analysis.
Figure 2 shows the UV-Vis absorption spectrum and photoluminescence spectrum results.
Figure 3 shows the frontier molecular orbital distribution of DBT-INFUR.
Figure 4 shows the structure of an organic electroluminescent device according to the DBT-INFUR emitter and host material.
Figure 5 shows the current density-voltage and emission voltage results of red and yellow phosphorescent OLEDs.
Figure 6 shows the external quantum efficiency results of yellow and red 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 the claims to be described later.

In one embodiment of the present invention, an organic electroluminescent compound represented by the following formula (I) is provided.

[Formula 1]

The organic electroluminescent compound is a phosphorescent material such as a phosphorescent red host material, a phosphorescent red-yellow host material, and a phosphorescent yellow host material among materials for an organic electroluminescent device, a hole injection layer material, a hole transport layer material, an electron injection layer material, or an electron transport layer material. It can be usefully used, and can preferably be used as a phosphorescent yellow host material and a phosphorescent yellow host material.

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

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

In another embodiment of the present invention, an organic electroluminescent device is provided between a cathode and an anode, and an organic thin film layer consisting of one or multiple layers including at least a light emitting layer is sandwiched, and at least one layer of the organic thin film layer contains the organic electroluminescent compound. Provides an organic electroluminescent device comprising a.

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

The organic electroluminescent compound may be included in an organic electroluminescent device as a phosphorescent red 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, and in particular, a phosphorescent red host material and It can be usefully used as a phosphorescent yellow host material.

Additionally, 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.

Electronic devices including the organic electroluminescent device include organic integrated circuits (O-IC), organic field-effect transistors (O-FET), organic thin film transistors (O-TFT), and organic electroluminescent transistors (O-LET). , organic solar cells (O-SC), organic optical detectors, organic photoreceptors, organic field-quench devices (O-FQD), light-emitting electrochemical cells (LEC), organic laser diodes (O-lasers) or organic light-emitting devices ( OLED).

Below, the organic electroluminescent device will be described as an example. However, the contents illustrated 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), an emission layer (EML), and a cathode (electron injection electrode) are sequentially stacked, Preferably, an electron blocking layer (EBL) may be further included 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.

In the method of manufacturing the organic electroluminescent device, first, an anode material is coated on the surface of a substrate using a conventional method to form an anode. At this time, the substrate used is preferably a glass substrate or a transparent plastic substrate with excellent transparency, surface smoothness, ease of handling, and waterproofness. In addition, indium tin oxide (ITO), indium zinc oxide (IZO), tin oxide (SnO ₂ ), zinc oxide (ZnO), etc., which are transparent and have excellent conductivity, can be used as materials for the anode.

Next, a hole injection layer (HIL) material is formed on the anode surface by vacuum thermal evaporation or spin coating using a conventional method. The above organic electroluminescent compounds can be used as the hole injection layer material, and in addition, copper phthalocyanine (CuPc), 4,4',4"-tris(3-methylphenylamino)triphenylamine (m-MTDATA), 4 ,4',4"-tris(3-methylphenylamino)phenoxybenzene (m-MTDAPB), 4,4',4"-tri(N-carbazolyl)triphenylamine (starburst type amines) TCTA), 4,4',4"-tris(N-(2-naphthyl)-N-phenylamino)-triphenylamine (2-TNATA) or IDE406 available from Idemitsu. there is.

A hole transport layer (HTL) material is formed on the surface of the hole injection layer by vacuum thermal evaporation or spin coating using a conventional method. At this time, 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.

An emission layer (EML) material is formed on the surface of the hole transport layer by vacuum thermal evaporation or spin coating using a conventional method. At this time, the single light-emitting material or light-emitting host material among the light-emitting layer materials used may be, in the case of red, the organic electroluminescent compound may be used as a phosphorescent red host material, 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, dopants that can be used with the light-emitting host include IDE102 and IDE105, available from Idemitsu as fluorescent dopants, 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) (Reference [Chihaya Adachi et al., Appl. Phys Lett., 2001, 79, 3082-3084]), platinum (II) octaethylporphyrin (PtOEP), TBE002 (Covion), etc. can be used.

An electron transport layer (ETL) material is formed on the surface of the light emitting layer by vacuum thermal evaporation or spin coating using a conventional method. At this time, the organic electroluminescent compound can be used as the electron transport layer material, and tris(8-hydroxyquinolinolato)aluminum (Alq3) can also 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 in the light emitting layer, diffusion of triplet excitons or holes into the electron transport layer can be prevented.

The formation of the hole blocking layer can be performed by vacuum thermal evaporation and spin coating of the hole blocking layer material by conventional methods. The hole blocking layer material is not particularly limited, but is preferably (8-hydroxyquinolinola) To) Lithium (Liq), bis(8-hydroxy-2-methylquinolinolnato)-aluminum biphenoxide (BAlq), bathocuproine (BCP), and LiF can be used.

An electron injection layer (EIL) material is formed on the surface of the electron transport layer by vacuum thermal evaporation or spin coating using a conventional method. At this time, the organic electroluminescent compound can be used as the electron injection layer material, and other materials such as LiF, Liq, Li ₂ O, BaO, NaCl, or CsF can be used.

Finally, a cathode is formed by vacuum thermal deposition of a cathode material on the surface of the electron injection layer using a conventional method.

At this time, the cathode materials used include lithium (Li), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium (Mg), magnesium-indium (Mg-In), and magnesium-silver. (Mg-Ag) etc. may be used. Additionally, in the case of a top-emitting organic electroluminescent device, indium tin oxide (ITO) or indium zinc oxide (IZO) can be used to form a transparent cathode through which light can transmit.

The organic electroluminescent device may be manufactured in the same order as described above, that is, anode/hole injection layer/hole transport layer/light-emitting layer/hole blocking layer/electron transport layer/electron injection layer/cathode, or vice versa, cathode/electron injection layer. It may be manufactured in the following order: /electron transport layer/hole blocking layer/light emitting layer/hole transport layer/hole injection layer/anode.

Hereinafter, methods for synthesizing the above compounds will be described as representative examples. However, the method of 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 field.

ingredient

All reagents and solvents were purchased from commercial suppliers. Analytical thin-layer chromatography (TLC) was performed using aluminum-backed Merck Kieselgel 60, and column chromatography was performed using silica gel with a mesh size (200-300) from Merck (Seoul, Korea).

¹ H and ¹³ C NMR spectra were recorded using a JEON JNM-ECP FT-NMR spectrometer (Peabody, MA, USA) operating at 500 MHz. Mass spectrometry was performed by a Xevo TQ-S spectrometer (Waters, Milford, MA, USA). Elemental analysis (EA) was recorded with a ThermoFisher (Flash 2000) elemental analyzer (Loughborough, England). Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were measured using PerkinElmer DSC 4000 and TGA 8000 systems (Melville, NY, USA) under nitrogen atmosphere at a heating rate of 10 °C/min. Absorbance spectra were recorded by a JASCO V-750 UV-Vis spectrophotometer (JASCO, Tokyo, Japan). Photoluminescence (PL) spectra were obtained with a JASCO FP-8500 spectrofluorometer (JASCO, Tokyo, Japan). Absolute PLQY values were recorded with the same spectrometer equipped with an integrating sphere. To obtain HOMO energy levels, cyclic voltammetry (CV) was performed using a BioLogic SP-50 (Biologic, Paris, France). Transient PL decay was measured using a Quantaurus-Tau fluorescence lifetime measurement system C11367-03 (Hamamatsu Photonics, Iwata, Japan) under N ₂ atmosphere. The low-temperature photoluminescence spectrum of the film state was also measured using the same Quantaurus-Tau fluorescence lifetime measurement system with cryostat. The current density-voltage-luminance (JVL) performance of each device was measured with a luminance color meter (Konica Minolta CS-100A) with source meter units (Keithley 2635A, USA). Electroluminescence (EL) spectra and Commission Internationale'Eclairage (ICIE) 1931 color coordinates were recorded with a Konica Minolta CS-2000 spectroradiometer (Osaka, Japan). Molecular simulations were performed at the 6-31G(d) molecular level using density functional theory (DFT) calculations using the Beck 3-parameter hybrid function and the Lee-Yang-Parr correlation function (B3LYP), which was performed using the Gaussian 16 program (Wallingford, CT, USA) was used.

Synthesis Example 1. Synthesis of 2-bromodibenzothiophene 5,5-dioxide (DBTO-Br)

A mixture of 2-bromodibenzothiophene (DBT-Br, 4.0 g, 15 mmol) and acetic acid (AcOH, 200 ml) was refluxed at 60°C for 30 minutes while stirring in a two-necked round bottom flask equipped with a condenser. After 30 minutes, 30% hydrogen peroxide (H ₂ O ₂ , 100 ml) was added dropwise to the reaction mixture. The reaction mixture was stirred at 80°C for another 2 hours. Afterwards, the white precipitate was filtered, washed several times with deionized water, and dried to obtain 3.8 g of the target compound DBTO-Br.

Yield: 85%; white solid; ^1H NMR (500 MHz, CDCl ₃ ) δ 792 (S, 1H), 782-783 (d, J = 8 Hz, 1H), 775-776 (d, J = 8 Hz, 1H), 764-769 ( m, 3H), 754-757 (t, J = 75, 1H); ₁₃ C NMR (500 MHz, CDCl ₃ ) δ 138.1, 136.5, 134.1, 133.6, 133.3, 131.1, 1303, 128.7, 125.0, 123.5, 122.4, 121.8.

Synthesis Example 2. Synthesis of 2-(dibenzo[b,d]furan-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxabororane (DBF-BOE)

2-Bromodibenzo[b,d]furan (DBF-Br, 5 g, 20.24 mmol) was placed under vacuum in a 250 ml round bottom flask for 15 minutes. 150 ml of dry THF were added under internal conditions and the mixture was continued to stir at 78° C. for 30 minutes. Next n-BuLi (2.5 M, 12.5 ml) was added rapidly dropwise and the mixture was continued to stir at the same temperature. After 1 hour, 2-isopropoxy-4,4,5,5-tetramethyl-1,3,2-dioxabororane (BOE, 7.5 ml, 36.76 mmol) was added slowly and the reaction mixture was incubated overnight. It was stirred and allowed to reach room temperature. It was extracted three times using deionized water and dichloromethane, and the organic layers were collected, dried over anhydrous magnesium sulfate, filtered, and concentrated using a rotary evaporator. The product was purified by silica gel column chromatography using an N-hexane:dichloromethane solvent system to obtain 5 g of the target compound (DBTO-BOE).

Yield: 84%; Colorless oil; ^1H NMR (500 MHz, CDCl ₃ ) δ 8.45 (S, 1H), 7.96-7.97 (d, J = 8.5 Hz, 1H), 7.92-7.94 (dd, J = 8.5, 1.5 Hz, 1H), 7.55- 7.57 (d, J = 8.5 Hz, 2H), 7.43-7.46 (m, 1H), 7.33-7.36 (m, 1H), 1.39 (s, 12H).

Synthesis Example 3. Synthesis of 2-(2-nitrophenyl)dibenzo[b,d]furan (DBF-Ph-N)

2-(dibenzo[b,d]furan-2-yl)-4,4,5,5-tetramethyl-1,3,2-dioxabororane (DBF-BOE, 6.5 g, 22.09 mmol) , 1-bromo-2-nitrobenzene (Ph-N-Br, 4.91 g, 24.30 mmol), catalyst (Pd(PPh ₃ ) ₄ , 0.77 g, 0.66 mmol), 2 MK ₂ CO ₃ (13.82 g, 100 mmol), deionized water (50 ml), ethanol (30 ml), and toluene (100 ml) were stirred and refluxed at 110° C. for 8 hours. After completion of the reaction, extraction was performed using deionized water and dichloromethane. The organic layer was dried, concentrated, and the reaction mixture was purified by silica gel column chromatography to obtain 6 g of the target compound (DBF-Ph-N).

Yield: 94%; yellow solid; ^1H NMR (500 MHz, CDCl ₃ ) δ 793-794 (d, J = 7.5 Hz, 1H), 7.88-7.90 (m, 2H), 7.58-7.66 (m, 3H), 7.46-7.54 (m, 3H) ), 7.34-7.39 (m, 2H).

Synthesis Example 4. Synthesis of 12H-benzofuro[3,2-a]carbazole (DBF-INFUR)

2-(2-nitrophenyl)dibenzo[b,d]furan (DBF-Ph-N, 6 g, 20.76 mmol), triethylphosphite (P(OEt) ₃ , 70 ml) and o -dichlorobenzene ( 70 ml) of the mixture was refluxed at 180° C. for 24 hours under inert conditions. After completion of the reaction, the reaction mixture was concentrated, and the crude mixture was separated by silica gel column chromatography using an n-hexane and dichloromethane solvent system.

Yield: 75%; Cloudy white solid; ^1H NMR (500 MHz, CDCl ₃ ) δ 8.55 (S, 1H), 8.14-8.16 (d, J = 8.5 Hz, 1H), 8.11-8.13 (d, J = 8 Hz, 1H), 8.06-8.08 ( d, J = 8 Hz, 1H), 7.66-7.67 (d, J = 8 Hz, 1H), 7.58-7.60 (d, J = 8 Hz, 1H) 7.42-7.51 (m, 5H), 7.30-7.33 ( t, J = 7.5 Hz, 1H).

Example 1. 2- (12H-benzofuro [3,2-a] Carbazole -12-day) Dibenzo[b,d]thiophene 5,5- d Oxide ( DBT - INFUR ) synthesis of

2-Bromodibenzothiophene 5,5-dioxide (DBTO-Br, 1.0 g, 3.38 mmol), 12H-benzofuro[3,2-a]carbazole (DBF-INFUR, 1.0 g, 3.88 mmol), A mixture of Pd(OAc) ₂ (0.05 g, 0.20 mmol), 10% t -Bu ₃ P in toluene (0.98 ml, 4.06 mmol), NaO tBu (1.0 g, 10.40 mmol) and 80 ml of anhydrous toluene was added to the condenser. It was added to the equipped two-necked flask. The mixture was refluxed at 110° C. in an inert atmosphere for 18 hours. The crude residue was separated by silica gel column promatography using an n-hexane and dichloromethane solvent system to obtain 0.96 g of the target compound DBT-INFUR.

Yield: 60%; Pale yellow solid; ^1H NMR (500 MHz, CDCl ₃ ) δ 8.25-8.27 (d, J = 8.5 Hz, 1H), 8.18-8.19 (d, J = 7.5 Hz, 1H), 8.11-8.13 (d, J = 8 Hz, 1H), 7.96 (s, 1H), 7.91-7.93 (m, 1H), 7.75-7.77 (d, J = 7.5 Hz, 1H), 7.55-7.64 (m, 4H), 7.37-7.44 (m, 3H) , 7.25-7.31 (m, 1H), 6.92-6.95 (t, J = 7.5 Hz, 1H), 6.03-6.04 (d, J = 8 Hz, 1H)); ¹³ C NMR (500 MHz, CDCl ₃ ) δ 156.7, 155.8, 144.8, 141.4, 138.4, 137.3, 135.4, 134.2, 134.0, 131.3, 130.6, 130.5, 126.3, 125.6, 124.5 , 124.0, 122.8, 122.7, 122.5, 122.1 , 121.8, 121.6, 120.0, 119.8, 119.6, 11.4, 109.9, 109.0, 105.8. MS (APCI) m/z of C ₃₀ H ₁₇ NO ₃ S [(M+H) ⁺ ]: 472.28; MS (TOF) of C ₃₀ H ₁₇ NO ₃ S (471.0929) m/z: 471.0929; Calculated values for C ₃₀ H ₁₇ NO ₃ S (%): C, 76.42; H, 3.63; N, 2.97; O, 10.18; S, 6.80. Measurements: C, 75.32; H, 3.62; N, 3.05; O, 9.97; S, 6.51.

Example 2. Device fabrication

A glass substrate coated with 50 nm of indium tin oxide (ITO) was cleaned using an excess of isopropyl alcohol and acetone for 10 minutes in an ultrasonic bath. The residue was then washed with deionized water and the substrate was dried under N ₂ gas. The cleaned substrate was treated in a UV-ozone chamber for 10 minutes. All organic layers were deposited at various deposition rates of 0.1 to 0.5 Å s ^-1 on the ITO substrate in a high vacuum evaporator under a pressure of 1 × 10 ^-7 torr or less. LiF and aluminum were deposited at a ratio of 0.15 and 4) Å-s ^-1 , respectively. After deposition, all devices were encapsulated with a glass cover with UV-curable resin under a N ₂ atmosphere glove box. The active area of each device was 4 mm ² .

Test example One. thermogravity Analysis and differential scanning calorimetry analysis

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were performed to understand the thermal stability of the DBT-INFUR emitter of Example 1, and the results are shown in Table 1 and Figure 1. It was.

As shown in Figure 1 and Table 1, thermal decomposition showed a 10% weight loss at 371 °C and the melting point was confirmed at 236 °C. These thermal characteristics can promote the morphological stability of the device.

Test example 2.UV- vis absorption and photoluminescence using emission photophysical analyze

Photophysical studies were conducted using UV-vis absorption and photoluminescence (PL) emission in toluene solvent and are shown in Table 1 and Figure 2.

As shown in Table 1 and Figure 2, UV-vis absorption peaks were observed at 297, 327, and 342 nm, respectively. The short-wavelength absorption around 297 nm corresponds to the π-π* transition of the benzofurocarbazole moiety, and the weak long-wavelength absorption around 327 nm is due to the π-π* transition. A band gap energy of 3.26 eV was observed, which is almost similar to that of the indolocarbazole-based DBTO-IN/CAR molecule. The charge transfer absorption from benzofurocarbazole to dibenzothiophene oxide was identified at 342 nm. The maximum photoluminescence emission was found at 431 and 460 nm in toluene and THF solvents, respectively. Low-temperature (77 K) photoluminescence emission was recorded at 457 nm, and the triplet energy was calculated to be 2.71 eV. The triplet energy of toluene was calculated to be 2.53 eV. Triplet energy is one of the important parameters that prevents energy backflow in dopant materials. Therefore, DBT-INFUR according to the present invention can support significant efficiency improvement in yellow and red phosphorescent OLED devices.

host T _m ^a (℃) T _d ^b (℃) UV-Vis ^c (nm) PL max ^d (nm) HOMO ^e (eV) LUMO ^f (eV) E _g ^g (eV) E _T ^h (eV) Example 1 236 371 297, 327 341 460 ⁱ
457 ^j -5.87 -2.61 3.26 2.71

^a melting point, ^b thermal decomposition temperature, ^c UV absorption wavelength of toluene, ^d photoluminescence maximum emission of THF, ^e highest occupied molecular orbital energy, ^f lowest unoccupied molecular orbital energy, ^g energy band gap, ^h triplet energy, ⁱ room temperature, ^j low temperature

Test example 3. Analysis of structural properties through molecular structure simulation

To confirm the electronic properties of DBT-INFUR, density functional theory (DFT) simulations for optimization of the ground state and time-dependent DFT (TD-DFT) for the excited state were calculated using Gaussian 09, as shown in Table 1. , the frontier molecular orbital distribution is shown in Figure 3.

Confirmed using the AC2 photoelectron spectrometer, the highest occupied molecular orbital (HOMO) energy level was obtained as 5.87 eV, and the lowest unoccupied molecular orbital (LUMO) energy was calculated by adding the band gap value to the HOMO energy level and found to be 2.61 eV. Confirmed. The LUMO distribution was found in the electron-withdrawing dibenzothiophene oxide moiety, whereas the HOMO distribution was found in the electron-donating benzofurocarbazole unit. The dihedral angle between the electron donor and electron acceptor was calculated to be 64°.

Meanwhile, a small overlapping was observed on the aromatic ring in the dibenzothiophene oxide moiety, which increased the energy difference (0.15 eV) between the excited singlet and triplet states. The calculated data is shown in Table 2.

optical properties Electrochemical properties T ₁ (eV) S ₁ (eV) ΔE _st (eV) HOMO (eV) LUMO (eV) Band gap (eV) 2.929 3.086 0.157 5.97 2.93 3.03

Test example 4. Multi-layer OLED Device fabrication and physical properties

To evaluate the electroluminescence properties of DBT-INFUR, a bipolar host material, various phosphorescent OLED devices were fabricated with red and yellow phosphorescent dopants.

The yellow and red device structures were constructed 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) (43 nm) / DBT-INFUR: 10% by weight Iridium(III) bis4-(4- tert-butylphenyl)thieno[3,2-c]pyridina to-N,C2') acetylacetonate (PO-O1) or bis[2-(3,5-dimethylphenyl)-4-methyl-quinoline ](acetylacetonate)iridium (III) (Ir(mphmq) ₂ (acac)) (20 nm)//1,3,5-tri(m-pyridin-3-ylphenyl)benzene (TmPyPB) (35 nm) ) / 8-quinolinolato lithium (Liq) (1.5 nm) / aluminum (Al) (100 nm). ITO was used for the anode, Al was used for the cathode, HATCN was used for the hole injection layer (HIL), Liq was used for the electron injection layer (EIL), and hole transporting layer (HTL) was used. TmPyPB was used for TAPC and electron transport layer (ETL). PO-O1 and Ir(mphmq)2(acac) were used as yellow and red phosphorescent dopants, respectively. The yellow and red phosphorescent OLED properties were compared with a reference 4,4'-bis(N-carbazolyl)-1,10-biphenyl (CBP) material of similar structure, and the device structure and energy diagram are shown in Figure 4.

The current density-voltage-emission performance of yellow and red phosphorescent OLEDs was measured and shown in Table 3 and Figures 5 and 6.

division Based on CBP
(yellow element) DBT-INFUR
(yellow element) Based on CBP
(red element) DBT-INFUR
(red element) Threshold voltage (V) 5.5 6.0 6.0 5.5 Current efficiency (cd/A) 27.66 41.07 8.73 15.49 Voltage efficiency (lm/W) 15.80 21.50 4.57 8.85 EQE (%) 10.15 16.50 7.64 12.44 CIE color coordinates (x,y) 0.48, 0.50 0.49, 0.48 0.63, 0.35 0.64, 0.35

Compared to the reference device (5.5 V), the bipolar host DBT-INFUR based device showed a higher threshold voltage (turn on voltage) of 6 eV. However, the driving voltage of both devices was the same at 7 V. The current efficiencies of DBT-INFUR and CBP-based yellow phosphorescent devices were 41.07 and 27.66 cd/A, respectively. In addition, the power efficiency of the DBT-INFUR and CBP-based yellow devices was 21.50 and 15.80 lm/W, respectively, and the DBT-INFUR of Example 1 according to the present invention showed higher efficiency, which is due to its bipolar characteristics.

The quantum efficiency of the reference device was 10.15%, but the DBT-INFUR-based yellow OLED device according to the present invention showed a higher external quantum efficiency (EQE) of 16.50%, through which the DBT-INFUR according to the present invention It was confirmed that the base yellow OLED device was superior.

Meanwhile, the current efficiency of the red phosphorescent OLED device to which DBT-INFUR was applied was 15.49 cd/A, and the external quantum efficiency was 12.44%, showing excellent device efficiency. On the other hand, the reference device containing the CBP host material had a power efficiency of 8.73 cd/A and an external quantum efficiency of 7.64%, showing significantly lower device efficiency than the present invention. Through this, it was confirmed that the DBT-INFUR-based red OLED device also had excellent performance.

As seen above, DBT-INFUR according to Example 1 of the present invention, which is a bipolar host material, showed excellent device efficiency in both yellow and red phosphorescent OLEDs. The bipolar nature of DBT-INFUR improved device efficiency while maintaining appropriate charge balance in the light-emitting layer. The CIE color coordinates (x, y) of DBT-INFUR according to the present invention were (0.49, 0.48) and (0.64, 0.35) for yellow and red phosphor devices, respectively.

Claims (7)

Red or yellow phosphorescent host material comprising a compound represented by Formula 1:
[Formula 1]
. delete An organic electroluminescent device in which an organic thin film layer consisting of one or multiple layers including at least a light emitting layer is sandwiched between a cathode and an anode, and at least one of the organic thin film layers contains the red or yellow phosphorescent host material according to claim 1. Organic electroluminescent device. delete According to paragraph 3,
The organic electroluminescent device is characterized in that the organic electroluminescent device 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 including an organic electroluminescent device according to claim 3. According to clause 6,
The electronic devices include organic integrated circuits (O-IC), organic field-effect transistors (O-FET), organic thin-film transistors (O-TFT), organic electroluminescence transistors (O-LET), and organic solar cells (O-SC). ), organic optical detectors, organic photoreceptors, organic field-quenched devices (O-FQDs), light-emitting electrochemical cells (LECs), organic laser diodes (O-lasers) or organic electroluminescent devices (OLEDs).