A novel triarylamine compound and an organic electroluminescent device containing the same

Abstract

The invention discloses a novel triarylamine compound and an organic electroluminescent device containing the compound. The arylamine and the 1-position of a naphthalene unit are connected to ensure the electron cloud distribution of HOMO and LUMO, and a steric hindering group is introduced at the 2-position of the naphthalene unit to further regulate the mobility of the material to match the hole transport material, thereby improving the device efficiency and greatly improving the device life while maintaining the driving voltage of the OLED.

Description

Technical Field

[0001] The invention relates to the technical field of organic electroluminescence, and in particular to a novel organic compound and application thereof, and an organic electroluminescence device containing the compound. Background Art

[0002] OLED light-emitting devices include cathodes, anodes and an organic layer in between. The organic layer includes a hole injection layer, a hole transport layer, an electron blocking layer, a light-emitting layer, a hole blocking layer, an electron transport layer, and an electron injection layer. For the organic layer, the appropriate mobility and energy level are key factors for achieving effective and rapid transmission of electrons and holes between different layers of materials, compounding to form excitons, and then emitting light. At present, OLED display technology has been applied in smart phones, tablet computers, televisions and other fields. However, compared with the actual product application requirements, the low voltage, high efficiency and long life of OLED devices are still the goals pursued by product performance. In order to continuously improve the performance of OLED devices, it is necessary to continuously innovate the structure and manufacturing process of OLED devices, and more importantly, it is necessary to continuously research and innovate the OLED materials themselves to prepare higher performance OLED materials.

[0003] OLED optoelectronic materials can be divided into two categories based on their uses, namely charge transport layer materials and light-emitting layer materials. Furthermore, charge transport layer materials can be divided into electron injection, transport layer materials, electron blocking layer materials, hole injection, transport layer materials and hole blocking layer materials. At the same time, light-emitting layer materials can be divided into main materials and doped light-emitting materials. In order to make high-performance OLED light-emitting devices, various organic functional materials are required to have good optoelectronic properties. For example, as charge transport layer materials, they are required to have good carrier mobility, appropriate HOMO / LUMO energy levels, high glass transition temperature, etc.; as the main material of the light-emitting layer, the material is required to be stable to light and electricity, and have appropriate HOMO / LUMO energy levels, etc.

[0004] Common OLED device structures include multiple film layers such as hole injection layer, hole transport layer, electron blocking layer, light-emitting layer, hole blocking layer, electron transport layer, electron injection layer, etc., that is, the organic OLED materials used in OLED devices at least include hole injection materials, hole transport materials, light-emitting materials, electron transport materials, etc. Therefore, the material types and matching forms are rich and diverse. In addition, for the matching of OLED devices with different structures, the OLED materials used have strong selectivity, and the performance of the same material in devices with different structures may be completely different. Therefore, in view of the current industrial application requirements of OLED devices, as well as the different functional film layers of OLED devices and the photoelectric characteristics of the devices, it is necessary to select more suitable materials or material combinations with high performance to achieve the comprehensive characteristics of the device such as low voltage, high efficiency and long life. In terms of the actual needs of the current OLED display lighting industry, the current development of OLED materials is far from enough and lags behind the requirements of panel manufacturers. It is particularly important to develop higher performance organic materials. Summary of the invention

[0005] The present invention aims to solve the above technical problems. It is found that in the electron blocking layer (EBL), the naphthalene unit can effectively regulate the distribution of HOMO and LUMO electron clouds, thereby reducing the exciton-polaron quenching formed by holes and excitons, thereby improving the device efficiency and lifespan, but the planar characteristics of the naphthalene unit make the mobility of the material change greatly. After in-depth research, the inventors connect the 1-position of the aromatic amine and the naphthalene unit to ensure the distribution of the electron cloud of HOMO and LUMO, and introduce steric hindering groups such as phenyl, biphenyl, and dibenzofuran at the 2-position of the naphthalene unit, thereby regulating the mobility of the material to match the hole transport material, thereby maintaining the driving voltage of the OLED while improving the device efficiency and greatly improving the device lifespan.

[0006] Specifically, the present invention provides: 1) a triarylamine compound for an organic electroluminescent device, characterized in that the compound is represented by formula (1):

[0007]

[0008] Wherein, R1 to R6 are the same or different from each other and are independently hydrogen or deutrium;

[0009] L is selected from a single bond, a substituted or unsubstituted phenylene group, and a substituted or unsubstituted naphthylene group;

[0010] Ar1 is selected from substituted or unsubstituted aryl, heteroaryl;

[0011] Ar2 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazolyl;

[0012] Provided that the compound is not:

[0013]

[0014] 2) The triarylamine compound for an organic electroluminescent device according to 1), characterized in that the compound is represented by formula (2):

[0015]

[0016] Wherein, Ar1 is selected from substituted or unsubstituted aryl, heteroaryl;

[0017] Ar2 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazolyl;

[0018] Here, the term "substituted" means that the substituent is selected from a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, and a linear or branched alkyl group having 1 to 6 carbon atoms.

[0019] 3) The triarylamine compound for an organic electroluminescent device according to 1) or 2), characterized in that Ar1 is selected from a substituted or unsubstituted aromatic group having 6 to 50 ring carbon atoms and a heteroaryl group having 5 to 50 ring atoms, and the heteroaryl group contains one or more of O, N and S as a heteroatom.

[0020] 4) The triarylamine compound for an organic electroluminescent device according to 1) or 2), characterized in that Ar1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazolyl;

[0021] Here, the term "substituted" means that the substituent is selected from a deuterium atom, a fluorine atom, a chlorine atom, a cyano group, a nitro group, and a linear or branched alkyl group having 1 to 6 carbon atoms.

[0022] 5) The triarylamine compound for an organic electroluminescent device according to 1) or 2), characterized in that Ar2 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazolyl;

[0023] Herein, the "substituted" means that the substituent is selected from deuterium atoms.

[0024] 6) The triarylamine compound for an organic electroluminescent device according to 1), characterized in that the triarylamine compound is selected from the following structures:

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

[0041]

[0042]

[0043]

[0044]

[0045]

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[0047]

[0048]

[0049]

[0050]

[0051]

[0052]

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059] 7) An organic electroluminescent device, characterized in that the organic electroluminescent device comprises an anode, a cathode and at least one organic thin film located between the anode and the cathode, and the organic thin film contains the compound described in any one of 1) to 6).

[0060] 8) The organic electroluminescent device according to 7), characterized in that the compound is used as an electron blocking material and / or a hole transport material in the organic electroluminescent device.

[0061] Compared with the prior art, the invention has the following beneficial effects: while maintaining the driving voltage of the OLED, the device efficiency is improved and the device life is greatly improved. The introduction of a steric hindering group at the 2-position of the naphthalene unit can not only ensure that the device obtains high performance, but also inhibit molecular aggregation, obtain a higher glass transition temperature (Tg), and a smaller intermolecular force. The smaller intermolecular force makes it easier for the molecules to be evaporated, so that there is a larger safety window (temperature difference) between the evaporation temperature and the decomposition temperature of the material, thereby improving the mass production stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0063] Figure 1This is a schematic diagram of the structure of an organic electroluminescent device to which the compound of the present invention is applied, wherein the meanings of the various layers of the device structure are as follows:

[0064] 1. Transparent substrate layer, 2. ITO anode layer, 3. Hole injection layer, 4. Hole transport layer A, 5. Hole transport layer B (or electron blocking layer), 6. Light-emitting layer, 7. Electron transport layer B (or hole blocking layer), 8. Electron transport layer A, 9. Electron injection layer, 10. Cathode reflective electrode layer. DETAILED DESCRIPTION

[0065] The principles and features of the present invention will be further illustrated below by taking a number of synthesis examples and device examples as examples. The examples cited are only used to explain the present invention, but are not used to limit the scope of the present invention. In addition, the isotopic types of hydrogen atoms present in the molecules of the compounds used in the present invention are not particularly limited. For example, all hydrogen atoms in the molecules can be 1 H, or part or all of it 2 H (deuterium D).

[0066] Synthesis Example 1:

[0067]

[0068] Synthesis of intermediate M1:

[0069] b1 Synthesis: Add 1-bromo-2-naphthol a1 (10 g, 45.0 mmol) and 200 mL of anhydrous dichloromethane to a 500 mL round-bottom flask and stir to dissolve. Then add anhydrous pyridine (12.7 mL, 158.0 mmol) to the reaction flask and cool to 0°C. Then slowly add trifluoromethanesulfonic anhydride a2 (15.2 ml, 90 mmol) to the reaction solution, react at 0°C for 0.5 h, and then react at room temperature for 12 h. Add 200 ml of deionized water and extract three times with dichloromethane. Dry over anhydrous sodium sulfate, concentrate the filtrate, pulp with ethanol, filter, vacuum dry the filter cake, and use the crude product directly in the next step. The molecular weight measured by liquid chromatography-mass spectrometry is m / z=354;

[0070] b2 Synthesis: Add the crude product from the previous step, p-chlorophenylboronic acid a3 (7g, 45mmol), 50mL toluene, 10mL ethanol and 50mL 2M potassium carbonate aqueous solution into a 250mL round-bottom flask and stir to dissolve. Evacuate the reaction system three times, and add tetrakis(triphenylphosphine)palladium (2g, 1.8mmol) under nitrogen protection. Heat and stir under nitrogen protection, and reflux at 110°C for 12h. Stop the reaction, cool to room temperature, add 100ml deionized water, and take three times with ethyl acetate. Dry over anhydrous sodium sulfate and concentrate the filtrate. Recrystallize from methanol and toluene to obtain 13g of white solid, with a two-step yield of 75%; liquid chromatography-mass spectrometry measured the molecular weight to be m / z=386;

[0071] M1 Synthesis:

[0072] Add b2 (12 g, 31 mmol) from the previous step, phenylboronic acid a4 (4 g, 32.6 mmol), 50 mL of toluene, 10 mL of ethanol, and 70 mL of 2M potassium carbonate aqueous solution into a 250 mL round-bottom flask and stir to dissolve. The reaction system was ventilated three times, and 1,1'-bis(diphenylphosphino)ferrocenepalladium dichloride (0.45 g, 0.62 mmol) was added under nitrogen protection. Under nitrogen protection, heat and stir, and reflux at 110°C for 12 h. Stop the reaction, cool to room temperature, add 100 ml of deionized water, and take three times with ethyl acetate. Dry over anhydrous sodium sulfate and concentrate the filtrate. Recrystallize from methanol and toluene to obtain 8 g of white solid, with a two-step yield of 82%; the molecular weight measured by liquid chromatography-mass spectrometry was m / z=314;

[0073] Synthesis of EB002:

[0074] The intermediate M1 (3.14g, 10mmol), N1 (4.86g, 10mmol), tri(dibenzylideneacetone)dipalladium (0.19g, 0.2mmol), sodium tert-butoxide (1.92g, 20mmol) were used. The reaction system was ventilated three times and protected by nitrogen. Then, a syringe was used to add (0.8mL, 0.8mmol) of a toluene solution of tri-tert-butylphosphine (1mol / L) and 20ml of toluene. Under nitrogen protection, the mixture was heated and stirred, and refluxed at 120°C for 12h. The reaction was stopped, cooled to room temperature, 100ml of deionized water was added, and the mixture was extracted three times with ethyl acetate. The filtrate was concentrated after drying over anhydrous sodium sulfate. The filtrate was separated by a silica gel column, washed with dichloromethane / petroleum ether (1:5), and the solvent was dried by spin drying. Recrystallization from methanol and toluene gave 5.8g of a white solid with a yield of 76%; the molecular weight was measured by liquid chromatography-mass spectrometry to be m / z=764. Other synthesis methods are similar to those in Example 1, as shown in Table 1 below

[0075] Table 1

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[0080]

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[0086] Device Example: Fabrication of Organic Electroluminescent Devices Using Electron Blocking Layer Materials

[0087] A 30 mm × 30 mm × 1.1 mm thick glass substrate with an indium tin oxide (ITO) transparent electrode (anode) was ultrasonically cleaned in isopropyl alcohol for 5 minutes, and then ultraviolet (UV)-ozone cleaned for 30 minutes. The cleaned glass substrate was mounted on the substrate rack of a vacuum evaporation device and evacuated to 1×10 -5 ~1×10 -6 Pa, HATCN hole injection layer (HIL) is evaporated on the ITO transparent electrode with a thickness of 15nm. HT is evaporated on the hole injection layer as a hole transport layer (HTL) with a thickness of 60nm. Then, EB 002 is evaporated on the hole transport layer as an electron blocking layer (EBL) with a thickness of 10nm. Then, a light-emitting layer (EML) is co-evaporated on the electron blocking layer with a thickness of 20nm; the main material and light-emitting material (BH and BD) of the light-emitting layer (EML) are evaporated by multi-source co-evaporation, wherein the doping concentration of the light-emitting material is 2%wt. Then HB is evaporated on the light-emitting layer as a hole blocking layer (HBL) with a thickness of 5nm. Then, on the hole blocking layer, an electron transport material (ET) and 8-hydroxyquinoline lithium (Liq) are co-evaporated 1:1 as an electron transport layer (ETL) with a thickness of 30nm. In addition, Liq is evaporated on the ETL as an electron injection layer (EIL) with a thickness of 1nm. Then, a metal cathode aluminum (Al) is evaporated on the EIL to a thickness of 100 nm. The structure of the organic electroluminescent device of Example 1 is as follows: Figure 1 As shown, Figure 1 The stacking order and role of each functional layer are also shown.

[0088] The OLED has in principle the following layer structure: ITO substrate / hole injection layer (HIL) / hole transport layer (HTL) / electron blocking layer (EBL) / luminescent layer (EML) / hole blocking layer (HBL) / electron transport layer (ETL) / electron injection layer (EIL) and finally cathode. The cathode is formed by an aluminum layer with a thickness of 100 nm. The exact structure of the OLED is shown in Table 2.

[0089] Table 2 Materials used for OLED

[0090]

[0091]

[0092] Device Example 1:

[0093] ITO(130) / HATCN 15) / HT(60) / EB 002(10) / BH:BD(20,2%wt) / HB(5) / ET:Liq(30,50%wt) / Liq(1) / Al(100)

[0094] The only difference between device example 2-36 and device example 1 is that the EB002 of the present invention used in the electron blocking layer is replaced with other compounds of the present invention. The obtained device performance test data is shown in Table 2.

[0095] Comparative Examples 1 to 4:

[0096] Compared with device embodiment 1, this comparative example is different in that EB 002 in the organic electroluminescent device is changed to EB-1, EB-2, EB-3, and EB-4 which are well known in the industry and have been commercially applied. The obtained device performance test data are shown in Table 2.

[0097] The OLEDs were characterized by standard methods. For this purpose, the electroluminescence spectrum, the current efficiency (measured in cd / A), the power efficiency (measured in lm / W) and the external quantum efficiency (EQE, measured in %) were determined, which were calculated as a function of the luminous density from a current / voltage / luminous density characteristic line (IUL characteristic line) exhibiting Lambertian emission characteristics. 2 The required voltage V1000 is determined at the brightness of 1000cd / m 2 Finally, EQE1000 means the current efficiency achieved at 1000cd / m 2 External quantum efficiency at working brightness, T95 means the device is 1000cd / m 2 The operating time from the initial brightness of the device to 95% of the brightness.

[0098] The device performances of Examples 1 to 35 of the present invention and Comparative Examples 1 to 4 are summarized in Table 3:

[0099] Table 3 Device performance list

[0100]

[0101]

[0102]

[0103] As can be seen from Table 3, compared with the prior art, the use of material embodiments 1-26 of the present invention can slightly improve the device efficiency and greatly improve the device life while maintaining the driving voltage of the OLED. For example, the efficiency of CE1000 of device embodiment 1 where EB 002 is located is improved by 4% compared with comparative example 3, and the life is improved by 13.7%. The efficiency of CE1000 of device embodiment 17 where EB246 is located is improved by 10.5% compared with comparative example 3, and the life is greatly improved by nearly 30%. Secondly, by comparing EB 002, EB 613, EB 640 and EB 674, it can be seen that if the hydrogen (H) atoms in the material of the present invention are partially or completely replaced with deuterium (D) atoms, the life will be significantly improved, and the improvement ratio will increase with the increase of the deuterium substitution rate; the reason is that the CD bond is shorter than the CH bond, which makes the CD bond more stable than the CH bond, thereby improving the life of the device.

Claims

1. A triarylamine compound for an organic electroluminescent device, characterized in that: The compound is represented by formula (2): Wherein, R1 to R6 are the same or different from each other and are independently hydrogen or deutrium; Ar1 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted dibenzofuranyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted carbazolyl; Ar2 is selected from substituted or unsubstituted phenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted biphenyl, substituted or unsubstituted dibenzofuranyl; Wherein, the "substituted" means that the substituent is selected from deuterium atoms.

2. A triarylamine compound for an organic electroluminescent device, characterized in that: The triarylamine compound is selected from the following structures:

3. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises an anode, a cathode and at least one organic thin film between the anode and the cathode, wherein the organic thin film contains the compound according to any one of claims 1 to 2, and the compound is used as an electron blocking material and / or a hole transport material in the organic electroluminescent device.

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