Organic compound and application thereof

Abstract

The invention provides an organic compound and application thereof, the organic compound is a phosphorescent host compound containing a carbazole derivative, the triplet state energy level of a molecule is improved, and efficiency loss caused by the fact that triplet state energy of a doped material is transmitted back to a host material is effectively prevented; meanwhile, the molecular steric hindrance designed by the invention is relatively large, the glass-transition temperature and thermal stability of the material molecules are improved, the stability and service life of the organic electroluminescent device are greatly improved, and the organic electroluminescent device has a good industrialization prospect.

Description

Technical Field

[0001] The invention belongs to the field of organic electroluminescence and relates to an organic compound and application thereof. Background Art

[0002] Organic light emitting diodes (OLED) have the unique advantages of being thin, self-luminous, having a wide viewing angle, low energy consumption, high efficiency, rich colors, fast response speed, wide applicable temperature, low driving voltage, being able to produce flexible, bendable and transparent display panels, and being environmentally friendly, and have a wide range of application prospects. Generally, they are composed of two opposing electrodes and at least one layer of organic light-emitting compounds inserted between the two electrodes. Charges are injected into the organic layer formed between the anode and the cathode to form electron and hole pairs, so that the organic compounds with fluorescent or phosphorescent properties produce light emission.

[0003] Luminescent materials are divided into fluorescent materials and phosphorescent materials. The method of forming the luminescent layer is a method of doping a phosphorescent material (organic metal) into a fluorescent host material or a method of doping a fluorescent dopant (organic matter containing nitrogen) into a fluorescent host material. In order to achieve effective energy transfer, it is usually required that the energy gap of the host material is larger than the dye, and the triplet energy level is higher than the triplet energy level of the dye molecule, so that the T1 state energy can be smoothly transferred from the host material to the phosphorescent dye or the triplet excitons can be confined to the dye molecule, thereby achieving efficient phosphorescent emission.

[0004] At present, in organic light-emitting devices prepared using phosphorescent materials, electrophosphorescence requires the use of host-guest doping technology, and most of them use triphenylamine group-containing materials such as CBP as the main light-emitting material of the light-emitting layer. The glass transition temperature Tg of this type of material is generally low and the thermal stability is poor, resulting in a short life of organic light-emitting devices using phosphorescent materials, thereby reducing the use of such materials. How to design new materials with better performance for adjustment has always been a problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In view of the deficiencies in the prior art, an object of the present invention is to provide an organic compound and application thereof, wherein the organic compound can enable a device to have the characteristics of low driving voltage and long service life.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In one aspect, the present invention provides an organic compound having a structure shown in Formula I:

[0008]

[0009] Wherein, R1 and R2 are the same or different and are independently selected from any one of the following structures:

[0010]

[0011] R1 and R2 are fused together through any fused bond on the structure and the L1-L2 bond, L2-L3 bond or L3-L4 bond.

[0012] Preferably, the organic compound is any one of the following compounds:

[0013]

[0014]

[0015] In another aspect, the present invention provides a phosphorescent host material, wherein the phosphorescent host material comprises the organic compound as described above.

[0016] In another aspect, the present invention provides an organic electroluminescent layer, which comprises the organic compound as described above as a phosphorescent host material.

[0017] Preferably, the organic electroluminescent layer further comprises a phosphorescent doping material, preferably a green phosphorescent doping material.

[0018] In another aspect, the present invention provides an organic electroluminescent device, comprising an anode, a cathode, and an organic layer disposed between the anode and the cathode, wherein the organic layer comprises a light-emitting layer, and the light-emitting layer comprises the organic compound as described above.

[0019] Preferably, the organic electroluminescent compound is used as a phosphorescent host material of the light-emitting layer.

[0020] Preferably, the light-emitting layer further comprises a phosphorescent doping material, preferably a green phosphorescent doping material.

[0021] Preferably, the organic layer further comprises at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer or an electron injection layer.

[0022] Preferably, the organic electroluminescent device further comprises a substrate.

[0023] In the present invention, the transparent substrate layer can use the substrate in the conventional organic light-emitting organic electroluminescent device, such as glass or plastic; the anode layer can use transparent high-conductivity materials, such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO2), zinc oxide (ZnO), etc.; in this application embodiment, the glass substrate and ITO are used in the manufacture of the organic electroluminescent device;

[0024] The material required for the hole transport region needs to have good hole transport performance and be able to effectively transport holes from the anode to the light-emitting layer; the hole transport region can be a single-layer structure formed by a single material, a single-layer structure formed by a variety of different materials, or a multi-layer structure formed by a variety of different materials; the hole transport region can have a hole transport layer / hole injection layer structure, an electron blocking layer / hole transport layer / hole injection layer structure, but is not limited to this; in this application embodiment, NPB is selected as the hole transport material for the production of organic electroluminescent devices.

[0025] The light-emitting layer needs to have good light-emitting properties and can adjust the range of visible light as needed; the structure of the organic electroluminescent device can be a single light-emitting layer or a multi-light-emitting layer; a single light-emitting layer structure is adopted in this application embodiment; the light-emitting layer of the organic electroluminescent device in this application embodiment comprises a main material and a doping material; the main material is composed of the compound described in the present invention; the doping material is Ir(ppy)2acac, and the mass doping concentration of the doping material is 3% to 30% (for example, 3%, 5%, 8%, 10%, 15%, 18%, 20%, 25%, 28% or 30%), preferably 5% to 15%.

[0026] The electron transport material is required to have good electron transport performance, can effectively transport electrons from the cathode to the light-emitting layer, and has a large electron mobility; the electron transport region includes one or more of a hole blocking layer and an electron transport layer, for example: the electron transport region can have the structure of an electron transport layer, a hole blocking layer / electron transport layer structure, but is not limited thereto. The electron injection layer of the organic electroluminescent device in this application embodiment can effectively inject electrons from the cathode into the organic layer, and is mainly selected from alkali metals or alkali metal compounds, or from alkaline earth metals or alkaline earth metal compounds or alkali metal complexes.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] The invention provides a phosphorescent host compound containing carbazole, the triplet energy level of the molecule is relatively high, and the exciton recombination region is effectively widened, so that the excitons are evenly distributed, and the triplet-triplet quenching of the excitons at high concentration is reduced; the compound of the invention has a relatively large conjugated structure, which is conducive to the solid-state accumulation between molecules during the film formation process of material molecules by evaporation, and effectively improves the transfer and transmission capacity of charges between molecules, and has a very high carrier mobility, so as to obtain an excellent phosphorescent host material with a relatively high triplet state and a relatively wide energy gap; at the same time, the relatively large spatial structure greatly improves the glass transition temperature Tg of the compound, and such an organic electroluminescent material has relatively high thermal and chemical stability; and furthermore, the compound of the invention has a good application effect in an OLED device, and has a good industrialization prospect. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0030] Synthetic formula

[0031]

[0032] Synthesis of Intermediate B1 Add raw material A1 and p-dibromobenzene to a three-necked flask and dissolve them with toluene; add Pd2(dba)3, tri-tert-butylphosphine and sodium tert-butoxide in sequence; bubble N2 for 10 minutes and in an inert atmosphere, react the mixed solution of the above reactants at a reaction temperature of 95-110°C for 10-24 hours, and extract the mixture three times with ethyl acetate after cooling. The extract is dried over MgSO4, filtered, concentrated and subjected to column chromatography (silica gel, gradient elution from pure PE to 10:1 PE / CH2Cl2) to obtain the target product.

[0033] Synthesis of products

[0034]

[0035] In a 50mL single-necked flask, add intermediate B1, raw material C, potassium carbonate, tetrakistriphenylphosphine palladium, 16mL of methanol and 10mL of toluene solvent in sequence, and reflux for 5h under nitrogen protection; after cooling, remove the solvent by rotary evaporation, wash with 60mL of distilled water and extract with dichloromethane 3 times; the crude product is purified by column chromatography to obtain the desired product.

[0036] Synthesis of compound 5

[0037]

[0038] Add raw material A5 and p-dibromobenzene to a three-necked flask and dissolve them with toluene; add Pd2(dba)3, tri-tert-butylphosphine and sodium tert-butoxide in sequence; bubble N2 for 10 minutes and in an inert atmosphere, react the mixed solution of the above reactants at a reaction temperature of 95-110°C for 10-24 hours, and extract the mixture three times with ethyl acetate after cooling. The extract is dried over MgSO4, filtered, concentrated and subjected to column chromatography (silica gel, gradient elution from pure PE to 10:1 PE / CH2Cl2) to obtain the target product, intermediate B5.

[0039]

[0040] In a 50mL single-necked flask, intermediate B5, raw material C, potassium carbonate, tetrakistriphenylphosphine palladium, 40mL of methanol and 30mL of toluene solvent were added in sequence, and refluxed for 5h under nitrogen protection; after cooling, the solvent was removed by rotary evaporation, washed with 20mL of distilled water and extracted with dichloromethane three times; the crude product was purified by column chromatography to obtain compound 5.

[0041] Table 1 Characterization results of compounds 1-20 (mass spectrometry and elemental analysis)

[0042]

[0043]

[0044] Table 2 Energy level determination results of compounds 1-20 (T1 energy level, thermal properties and HOMO energy level)

[0045]

[0046]

[0047] The triplet energy level T1 was tested by Hitachi’s F4600 fluorescence spectrometer, and the material testing conditions were 2×10 - 5 mol / L toluene solution; the glass transition temperature Tg is measured by differential scanning calorimetry (DSC, DSC204F1 differential scanning calorimeter from NETZSCH, Germany), and the heating rate is 10°C / min; the thermal weight loss temperature Td is the temperature at which the weight loss is 1% in a nitrogen atmosphere, and is measured on a TGA-50H thermogravimetric analyzer from Shimadzu, Japan, with a nitrogen flow rate of 20mL / min; the highest occupied molecular orbital HOMO energy level is tested by an ionization energy test system (IPS3), and the test is in an atmospheric environment.

[0048] It can be seen from Table 2 that the compounds of the present invention have a higher triplet energy level and higher thermal stability, and an appropriate HOMO energy level, and are suitable as light-emitting layer materials.

[0049] Application Examples 1-17

[0050] The present application embodiment provides an organic electroluminescent device, including: a transparent substrate layer, an anode layer, a hole injection layer, a hole transport layer, a light-emitting layer, an electron transport layer / hole blocking layer, an electron injection layer, and a cathode electrode layer.

[0051] This application example further provides a method for preparing an organic electroluminescent device:

[0052] S1, cleaning the ITO anode layer on the transparent glass substrate layer, using deionized water, acetone, and ethanol for ultrasonic cleaning for 15 minutes each, and then treating it in a plasma cleaner for 2 minutes;

[0053] S2, evaporating HAT-CN with a thickness of 10 nm on the substrate, which serves as a hole injection layer;

[0054] S3, evaporating NBP with a thickness of 50 nm, which serves as a hole transport layer;

[0055] S4, evaporating TCTA with a thickness of 5 nm, which serves as an electron blocking layer;

[0056] S5, evaporating a light-emitting layer with a thickness of 40 nm; wherein the compound 1-16 or CBP described in the embodiment is used as the host material, and Ir(ppy)2acac is used as the phosphorescent doping guest, and the doping mass concentration is 6%;

[0057] S6. On the light-emitting layer, TPBi with a thickness of 35 nm is deposited by vacuum evaporation, and this layer serves as an electron transport layer;

[0058] S7, on the electron transport layer, vacuum evaporating LiF with a thickness of 1 nm, which serves as an electron injection layer;

[0059] S8. On the electron injection layer, Al is vacuum-evaporated to a thickness of 80 nm, and this layer serves as a cathode electrode layer.

[0060]

[0061] Table 3 Test results of application examples 1-17

[0062]

[0063]

[0064] Among them, the current efficiency is 10mA / cm 2 The life test system is Chroma's MODEL58131 OLED device life tester, and the test results are all LT95 life decay at a brightness of 5000 nit. As can be seen from Table 3, the compounds of the present invention are used in organic electroluminescent devices, and both efficiency and life are greatly improved compared with CBP, especially the driving life of the device is greatly improved. It is a phosphorescent host material with excellent performance. The luminous efficiency of the device of the present invention is as high as 53 cd / A or more, and the LT90 life is more than 29 hours.

[0065] The applicant declares that the present invention illustrates the organic compounds and applications of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. An organic compound, characterized in that The organic compound has a structure shown in Formula I: Wherein, R1 and R2 are the same or different and are independently selected from any one of the following structures: R1 and R2 are fused together through any fused bond on the structure and the L1-L2 bond, L2-L3 bond or L3-L4 bond.

2. The organic compound according to claim 1, characterized in that The organic compound is any one of the following compounds:

3. A phosphorescent host material, characterized in that: The phosphorescent host material comprises the organic compound as claimed in claim 1 or 2.

4. An organic electroluminescent layer, characterized in that: The organic electroluminescent layer comprises the organic compound as claimed in claim 1 or 2 as a phosphorescent host material.

5. The organic electroluminescent layer according to claim 4, characterized in that: The organic electroluminescent layer further comprises a phosphorescent doping material, preferably a green phosphorescent doping material.

6. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises an anode, a cathode and an organic layer disposed between the anode and the cathode, wherein the organic layer comprises a light-emitting layer, and the light-emitting layer comprises the organic compound according to claim 1 or 2.

7. The organic electroluminescent device according to claim 6, characterized in that: The organic compound is used as a phosphorescent host material of the light-emitting layer.

8. The organic electroluminescent device according to claim 6, characterized in that: The light-emitting layer further comprises a phosphorescent doping material, preferably a green phosphorescent doping material.

9. The organic electroluminescent device according to claim 6, characterized in that: The organic layer further includes at least one of a hole injection layer, a hole transport layer, an electron blocking layer, a hole blocking layer, an electron transport layer or an electron injection layer.

10. The organic electroluminescent device according to claim 6, characterized in that: The organic electroluminescent device further comprises a substrate.

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