Boron-nitrogen compound and preparation method thereof, luminescent layer, organic electroluminescent device and display device

Abstract

The invention belongs to the technical field of organic electroluminescence, and particularly discloses a boron-nitrogen compound and a preparation method thereof, a luminescent layer, an organic electroluminescent device and a display device. The structure of the boron-nitrogen compound is shown as a formula I, a formula II or a formula III, the boron-nitrogen compound can be used as a guest luminescent material in a luminescent layer, and can be used in an organic electroluminescent device. According to the boron-nitrogen compound provided by the invention, the anti-gap crossing efficiency can be further improved, and the efficiency of an organic electroluminescent device under high brightness and doping concentration is improved. # imgabs0 #

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electroluminescence, and specifically relates to a boron nitrogen compound and a preparation method thereof, a light-emitting layer, an organic electroluminescent device, and a display device. Background Art

[0002] Display technology has undergone several generations of changes so far. As the first display technology, cathode ray tube display (CRT) has many disadvantages such as large size, high energy consumption, unstable display, etc., and was soon replaced by the next generation of liquid crystal display (LCD) technology. LCD technology has greater advantages than previous CRT in terms of size, energy consumption and imaging effect. Therefore, liquid crystal display screens quickly occupied the display market. However, with the development of current IT technology, VR technology and artificial intelligence technology, people's requirements for display technology are constantly increasing. LCD has problems such as long response time, light leakage, and poor anti-interference ability, so it can no longer meet people's requirements in the field of high-tech display technology. In this case, the third generation of organic light-emitting diodes (OLED) came into being.

[0003] As a new generation of display and lighting technology, organic light-emitting diodes (OLEDs) have shown good application prospects and have attracted widespread attention. Compared with previous light-emitting devices, organic light-emitting diodes have the advantages of self-luminous performance, full-color display capability, high luminous efficiency, high contrast, low driving voltage, and large-area flexible display in terms of optical performance. In 2012, researchers first reported thermally activated delayed fluorescence (TADF) materials. The singlet energy level and triplet energy level of the designed materials are very small, allowing triplet excitons to become singlet excitons through reverse intersystem crossing (RISC) and emit fluorescence. In theory, 100% exciton utilization can be achieved. This is a new generation of high-efficiency organic light-emitting materials after traditional fluorescent materials and second-generation phosphorescent materials. Due to its advantages such as metal-free, high efficiency and good stability, TADF materials have become a hot spot in the field of OLED research.

[0004] In traditional TADF molecular design, the highly twisted donor-acceptor (DA) structure often used not only reduces the transition oscillation intensity, but also leads to large vibration coupling and vibration relaxation (VR, S1*→S1). These characteristics are not conducive to the molar absorptivity and photoluminescence quantum yield (Φ PL), and leads to a broadening of the emission band and energy waste when entering the triplet state (S1*→T1). In 2016, researchers proposed the concept of multiple resonance thermally activated delayed fluorescence (MR-TADF), which effectively solved the above shortcomings. Molecules with MR-TADF properties are usually composed of a polycyclic skeleton based on boron / nitrogen (B / N), and the opposite resonance effects of B and N atoms are used to achieve the separation of frontier orbitals, resulting in a small Stokes shift and extremely narrow emission. In addition, the short-range charge transfer (SR-CT) characteristics of these compounds give them strong oscillator strength, making their absorption and luminescence efficiency very high. Nevertheless, due to the small S1-T1 spin-orbit coupling (SOC) and the non-negligible ΔE ST value (about 0.1eV), the performance of current MR-TADF materials is still limited by insufficient ISC and RISC. For electroluminescence, a small RISC rate constant leads to concentration aggregation of triplet excitons and a sharp drop in efficiency at high brightness. For photosensitive applications, inefficient ISC makes it difficult to store excitation energy as triplet excitons, resulting in triplet-triplet annihilation. In this context, designing efficient molecular structures of MR-TADF materials is still urgently needed. Summary of the invention

[0005] The purpose of the present invention is to solve the deficiencies of the prior art and provide a novel boron nitrogen compound and a preparation method, a light-emitting layer, an organic electroluminescent device, and a display device; based on this, the first aspect of the present invention provides a boron nitrogen compound, the structure of which is shown in Formula I, Formula II or Formula III:

[0006]

[0007] Wherein, R1, R2, R3, R4 and R5 are independently selected from hydrogen, methyl, tert-butyl, phenyl, alkyl composed of C3-C18, cycloalkyl, aryl, heteroaryl, carbazolyl, tert-butylcarbazolyl, phenylcarbazolyl, diphenylamino and tert-butyldiphenylamino; X is oxygen or sulfur.

[0008] The present invention proposes for the first time to introduce a benzodithiophene structure and condense it with a double specific light-emitting unit containing B and N to form a new type of boron nitrogen compound, in which the atomic sulfur can improve the spin-orbit coupling of the material (i.e., the aforementioned compound), and combined with the conjugated extension of the specific structure, it can further improve the anti-gap crossing efficiency and enhance the efficiency of organic electroluminescent devices at high brightness and doping concentration.

[0009] In some preferred embodiments, the structure of the boron nitrogen compound is any one of compounds BN-1 to BN-60:

[0010]

[0011]

[0012]

[0013]

[0014] More preferably, when the structure of the boron nitrogen compound is as shown in compound BN-52 or compound BN-57, the effect is better, and the maximum electroluminescent external quantum efficiency of the organic electroluminescent device composed of the compound is 1000 cd / m 2 The electroluminescence external quantum efficiency at brightness can reach 36.2%, 24.3%, 37.6%, and 24.6% respectively.

[0015] The second aspect of the present invention provides a method for preparing the above-mentioned boron nitrogen compound. When the structure of the above-mentioned boron nitrogen compound is as shown in formula I, the preparation method thereof includes synthetic route one; when the structure of the above-mentioned boron nitrogen compound is as shown in formula II, the preparation method thereof includes synthetic route two; when the structure of the above-mentioned boron nitrogen compound is as shown in formula III, the preparation method thereof includes synthetic route three;

[0016] The above-mentioned synthetic route 1 is as follows:

[0017]

[0018] The above-mentioned synthetic route 2 is as follows:

[0019]

[0020] The above-mentioned synthetic route three is as follows:

[0021]

[0022] The third aspect of the present invention provides a light-emitting layer, comprising the above-mentioned boron nitrogen compound as a light-emitting guest material, wherein the light-emitting layer also comprises a host material, and the content of the above-mentioned light-emitting guest material is 0.1%-20% by mass, and the content of the above-mentioned host material is 80%-99.9% by mass.

[0023] The fourth aspect of the present invention provides an organic electroluminescent device, comprising the above-mentioned light-emitting layer. Specifically, the above-mentioned organic electroluminescent device comprises, in sequence: an anode, a hole transport layer, the above-mentioned light-emitting layer, an electron transport layer, and a cathode. In some other embodiments, an electron blocking layer is provided between the above-mentioned light-emitting layer and the above-mentioned hole transport layer; a hole transition layer is provided between the above-mentioned electron blocking layer and the above-mentioned hole transport layer; and an electron injection layer is provided between the above-mentioned electron transport layer and the above-mentioned cathode.

[0024] The fifth aspect of the present invention further provides a display device, comprising the above-mentioned organic electroluminescent device.

[0025] The beneficial effects of the present invention are as follows: the boron nitrogen compound proposed by the present invention can further improve the anti-gap crossing efficiency and enhance the efficiency of the organic electroluminescent device under high brightness and doping concentration. DETAILED DESCRIPTION

[0026] The following will be combined with the embodiments to clearly and completely describe the concept and technical effects of the present invention so as to fully understand the purpose, scheme and effect of the present invention. It should be noted that the embodiments and features in the embodiments of the present invention can be combined with each other without conflict.

[0027] In the following content, the product was characterized, and the test instrument used for elemental analysis was Vario Micro Cube from Agilent, USA, and the test elements were C, H, N, and S. The instrument used for mass spectrometry testing was the ThermoFisher TSQ Endura ultra-high performance liquid chromatography tandem triple quadrupole mass spectrometer from the United States.

[0028] Example 1

[0029] A class of boron nitrogen compounds, whose structures are shown in compounds BN-1 to BN-60:

[0030]

[0031]

[0032]

[0033]

[0034] The preparation methods thereof are as follows: Synthesis route 1, synthesis route 2 and synthesis route 3; Synthesis route 1 is as follows:

[0035]

[0036] Synthesis route 2 is as follows:

[0037]

[0038] Synthesis route three is as follows:

[0039]

[0040] Among them, the first raw materials involved are as follows:

[0041]

[0042] The second raw materials involved are as follows:

[0043]

[0044]

[0045] The third raw material involved is The fourth raw material involved is

[0046] 1. Synthesis of compound BN-1

[0047] The specific synthesis route of compound BN-1 is as follows:

[0048]

[0049] The preparation method comprises the following steps:

[0050] (1) Synthesis of compound BN-1-A

[0051] The compound 2-chloro-1,3-dibromobenzene (10.0 g, 37.0 mmol), diphenylamine (7.5 g, 44.4 mmol) and sodium tert-butoxide (6.4 g, 66.6 mmol) were dissolved in 200 mL of toluene, and 83 mg of palladium acetate and 870 mg of tri-tert-butylphosphine tetrafluoroborate were added under nitrogen, and the temperature was raised to 60 ° C and stirred for 6 hours. After the reaction was completed, the mixture was washed with dichloromethane and water, and the organic phase was concentrated and purified by column chromatography to obtain 12.5 g of white solid with a yield of 94.2%. The target product BN-1-A was confirmed by mass spectrometry, MS: 358.96 (calculated value: 358.99).

[0052] (2) Synthesis of compound BN-1-B

[0053] Compound BN-1-A (8.0 g, 22.3 mmol), aniline (2.5 g, 26.8 mmol) and sodium tert-butoxide (3.8 g, 40.2 mmol) were dissolved in 150 mL of toluene, 50 mg of palladium acetate and 520 mg of tri-tert-butylphosphine tetrafluoroborate were added under nitrogen, the temperature was raised to 120 ° C, and stirring was maintained for 12 hours. After the reaction was completed, the mixture was washed with dichloromethane and water, and the organic phase was concentrated and purified by column chromatography to obtain 7.4 g of a white solid with a yield of 89.4%. The target product BN-1-B was confirmed by mass spectrometry, MS: 370.18 (calculated value: 370.12).

[0054] (3) Synthesis of Compound BN-1-C

[0055] Compound 3,7-dibromobenzo[1,2-b:4,5-b']bithiophene (4.0g, 11.5mmol), compound BN-1-B (9.4g, 25.3mmol) and sodium tert-butoxide (3.6g, 38.0mmol) were dissolved in 200mL toluene, 55mg of palladium acetate and 580mg of tri-tert-butylphosphine tetrafluoroborate were added under nitrogen, the temperature was raised to 120°C, and stirring was maintained for 24 hours. After the reaction was completed, the mixture was washed with dichloromethane and water, the organic phase was concentrated, and then purified by column chromatography to obtain 8.5g of white solid with a yield of 79.7%. The target product BN-1-C was confirmed by mass spectrometry, MS: 926.24 (calculated value: 926.21).

[0056] (4) Synthesis of Compound BN-1

[0057] Compound BN-1-C (7.4 g, 8.0 mmol) was dissolved in 50 mL of tert-butylbenzene, cooled to 0°C under nitrogen, tert-butyl lithium (18.5 mL, 1.3 M, 24.0 mmol) was added dropwise, the temperature was raised to 60°C, stirred for 2 hours, cooled to 0°C again, boron tribromide (8.0 g, 32.0 mmol) was added dropwise, the temperature was raised to room temperature and stirred for 1 hour, cooled to 0°C again, N, N-diisopropylethylamine (5.1 g, 40.0 mmol) was added dropwise, the temperature was raised to 120°C, and stirring was continued for 24 hours. After the reaction was completed, methanol and water were used to quench the reaction, dichloromethane and water were used to wash, the organic phase was concentrated, and column chromatography was used for purification to obtain 0.8 g of yellow solid with a yield of 11.4%. The target product BN-1 was confirmed by mass spectrometry, MS: 874.28 (calculated value: 874.26), elemental analysis: C, 79.68; H, 4.17; N, 6.40; S, 7.25, calculated value (C, 79.64; H, 4.15; B, 2.47; N, 6.41; S, 7.33).

[0058] 2. Synthesis of compound BN-5

[0059] The specific synthesis route of compound BN-5 is as follows:

[0060]

[0061] The preparation method comprises the following steps:

[0062] (1) Synthesis of compound BN-5-A

[0063] The compound 3-bromo-2-chlorofluorobenzene (8.0 g, 38.2 mmol), carbazole (6.4 g, 38.2 mmol) and cesium carbonate (14.9 g, 45.8 mmol) were dissolved in 150 mL N, N-dimethylformamide, heated to 140 ° C under nitrogen, and stirred for 12 hours. After the reaction was completed and cooled to room temperature, it was washed with saturated ammonium chloride solution and dichloromethane. After the organic phase was concentrated, it was purified by column chromatography to obtain 12.8 g of white solid with a yield of 94.0%. The target product BN-5-A was confirmed by mass spectrometry, MS: 357.03 (calculated value: 356.97).

[0064] (2) Synthesis of compound BN-5-B

[0065] The synthesis of compound BN-5-B is similar to that of compound BN-1-B, except that compound BN-5-A (8.0 g, 22.3 mmol) is used instead of compound BN-1-A, and the amounts of other compounds and the synthesis methods are the same. After purification by column chromatography, 7.3 g of a white solid was obtained with a yield of 89.3%. The target product BN-5-B was confirmed by mass spectrometry, MS: 368.09 (calculated value: 368.11).

[0066] (3) Synthesis of compound BN-5-C

[0067] The synthesis of compound BN-5-C is similar to that of compound BN-1-C, except that compound BN-5-B (9.3 g, 25.3 mmol) is used instead of compound BN-1-B, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 9.6 g of white solid was obtained with a yield of 90.7%. The target product BN-5-C was confirmed by mass spectrometry, MS: 922.09 (calculated value: 922.18).

[0068] (4) Synthesis of Compound BN-5

[0069] The synthesis of compound BN-5 is similar to that of compound BN-1, except that compound BN-5-C (7.4 g, 8.0 mmol) is used instead of compound BN-1-C, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 0.9 g of yellow solid is obtained with a yield of 12.7%. The target product BN-5 is confirmed by mass spectrometry, MS: 870.25 (calculated value: 870.23), elemental analysis: C, 79.99; H, 3.75; N, 6.41; S, 7.33, calculated value (C, 80.01; H, 3.70; B, 2.48; N, 6.44; S, 7.36).

[0070] 3. Synthesis of compound BN-30

[0071] The specific synthesis route of compound BN-30 is as follows:

[0072]

[0073] The preparation method comprises the following steps:

[0074] (1) Synthesis of compound BN-30-A

[0075] The synthesis of compound BN-30-A is similar to that of compound BN-1-A, except that 3-methyl-5-bromo-6-chlorophenol (8.2 g, 37.0 mmol) is used instead of 2-chloro-1,3-dibromobenzene. The amounts of other compounds and the synthesis methods are the same. After purification by column chromatography, 8.4 g of white solid was obtained with a yield of 73.2%. The target product BN-30-A was confirmed by mass spectrometry, MS: 309.12 (calculated value: 309.09).

[0076] (2) Synthesis of compound BN-30-B

[0077] Compound 3,7-dibromobenzo[1,2-b:4,5-b']bithiophene (4.0 g, 11.5 mmol), compound BN-30-A (7.1 g, 23.0 mmol) and potassium carbonate (6.3 g, 46.0 mmol) were dissolved in 100 mL 1,3-dimethyl-2-imidazolidinone, and 1.0 g 2-pyridinecarboxylic acid and 1.5 g CuI were added under nitrogen. The reaction system was heated to 140 ° C and stirred for 48 hours. After the reaction was completed, it was washed with dichloromethane and water, and the organic phase was concentrated and purified by column chromatography to obtain 6.5 g of white solid with a yield of 73.2%. The target product BN-30-B was confirmed by mass spectrometry, MS: 804.18 (calculated value: 804.14).

[0078] (3) Synthesis of compound BN-30

[0079] The synthesis of compound BN-30 is similar to that of compound BN-1, with compound BN-30-B (6.4 g, 8.0 mmol) used instead of compound BN-1-C, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 0.5 g of a light yellow solid was obtained with a yield of 8.9%. The target product BN-30 was confirmed by mass spectrometry, MS: 752.20 (calculated value: 752.19), elemental analysis: C, 76.63; H, 4.05; N, 3.71; S, 8.49, calculated value (C, 76.61; H, 4.02; B, 2.87; N, 3.72; O, 4.25; S, 8.52).

[0080] 4. Synthesis of compound BN-47

[0081] The specific synthesis route of compound BN-47 is as follows:

[0082]

[0083] The preparation method comprises the following steps:

[0084] (1) Synthesis of compound BN-47-A

[0085] The synthesis of compound BN-47-A is similar to that of compound BN-5-A, except that 5-tert-butyl-2-chloro-3-fluorobenzenethiol (8.3 g, 38.2 mmol) is used instead of 3-bromo-2-chlorofluorobenzene, and 3,6-di-tert-butylcarbazole (10.6 g, 38.2 mmol) is used instead of carbazole. The amounts of other compounds and the synthesis methods are the same. After purification by column chromatography, 15.6 g of white solid was obtained with a yield of 85.6%. The target product BN-47-A was confirmed by mass spectrometry, MS: 477.28 (calculated value: 477.23).

[0086] (2) Synthesis of compound BN-47-B

[0087] The synthesis of compound BN-47-B is similar to that of compound BN-30-B, except that BN-47-A (11.0 g, 38.2 mmol) is used instead of compound BN-30-A. The amounts of other compounds and the synthesis methods are the same. After purification by column chromatography, 9.2 g of white solid was obtained with a yield of 70.5%. The target product BN-47-B was confirmed by mass spectrometry, MS: 1140.51 (calculated value: 1140.41).

[0088] (3) Synthesis of compound BN-47

[0089] The synthesis of compound BN-47 is similar to that of compound BN-1, with compound BN-47-B (9.1 g, 8.0 mmol) used instead of compound BN-1-C, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 0.8 g of a light yellow solid was obtained with a yield of 9.3%. The target product BN-47 was confirmed by mass spectrometry, MS: 1088.50 (calculated value: 1088.46), elemental analysis: C, 77.26; H, 6.53; N, 2.58; S, 11.83, calculated value (C, 77.19; H, 6.48; B, 1.98; N, 2.57; S, 11.77).

[0090] 5. Synthesis of compound BN-52

[0091] The specific synthesis route of compound BN-52 is as follows:

[0092]

[0093] The preparation method comprises the following steps:

[0094] (1) Synthesis of compound BN-52-A

[0095] The compound 3-bromo-4-chloro-5-fluoro-1,1'-biphenyl (8.0 g, 28.0 mmol), phenol (3.2 g, 33.6 mmol) and potassium carbonate (7.0 g, 50.4 mmol) were dissolved in 200 mL DMF, heated to 140 ° C under nitrogen, and stirred for 10 hours. After the reaction was completed, it was washed with saturated ammonium chloride solution and dichloromethane, and the organic phase was concentrated and purified by column chromatography to obtain 8.6 g of white solid with a yield of 85.4%. The target product BN-52-A was confirmed by mass spectrometry, MS: 359.88 (calculated value: 359.97).

[0096] (2) Synthesis of compound BN-52-B

[0097] The synthesis of compound BN-52-B is similar to that of compound BN-1-B, except that compound BN-52-A (8.0 g, 22.3 mmol) is used instead of compound BN-1-A, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 6.9 g of white solid was obtained with a yield of 83.5%. The target product BN-57-B was confirmed by mass spectrometry, MS: 371.15 (calculated value: 371.11).

[0098] (3) Synthesis of compound BN-52-C

[0099] The synthesis of compound BN-52-C is similar to that of compound BN-1-C, except that compound BN-52-B (9.4 g, 25.3 mmol) is used instead of compound BN-1-B, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 8.6 g of white solid is obtained with a yield of 80.2%. The target product BN-52-C is confirmed by mass spectrometry, MS: 928.16 (calculated value: 928.18).

[0100] (4) Synthesis of compound BN-52

[0101] The synthesis of compound BN-52 is similar to that of compound BN-1, except that compound BN-52-C (7.4 g, 8.0 mmol) is used instead of compound BN-1-C, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 0.7 g of a light yellow solid is obtained with a yield of 10.2%. The target product BN-52 is confirmed by mass spectrometry, MS: 876.25 (calculated value: 876.22), elemental analysis: C, 79.45; H, 3.93; N, 3.18; S, 7.35, calculated value (C, 79.46; H, 3.91; B, 2.47; N, 3.20; O, 3.65; S, 7.31).

[0102] 6. Synthesis of compound BN-57

[0103] The specific synthesis route of compound BN-57 is as follows:

[0104]

[0105] The preparation method comprises the following steps:

[0106] (1) Synthesis of compound BN-57-A

[0107] The synthesis of compound BN-57-A is similar to that of compound BN-52-A, except that 3-bromo-2-chloro-fluorobenzene (5.9 g, 28.0 mmol) is used instead of 3-bromo-4-chloro-5-fluoro-1,1'-biphenyl, and 4-tert-butylthiophenol (5.6 g, 33.6 mmol) is used instead of phenol. The amounts of other compounds and the synthesis methods are the same. After purification by column chromatography, 7.2 g of white solid was obtained with a yield of 71.9%. The target product BN-57-A was confirmed by mass spectrometry, MS: 360.02 (calculated value: 355.98).

[0108] (2) Synthesis of compound BN-57-B

[0109] The synthesis of compound BN-57-B is similar to that of compound BN-1-B, except that compound BN-57-A (7.9 g, 22.3 mmol) is used instead of compound BN-1-A, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 6.2 g of white solid was obtained with a yield of 76.4%. The target product BN-57-B was confirmed by mass spectrometry, MS: 367.15 (calculated value: 367.12).

[0110] (3) Synthesis of compound BN-57-C

[0111] The synthesis of compound BN-57-C is similar to that of compound BN-1-C, using compound BN-57-B (9.3 g, 25.3 mmol) instead of compound BN-1-B, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 8.2 g of white solid was obtained with a yield of 77.6%. The target product BN-57-C was confirmed by mass spectrometry, MS: 920.23 (calculated value: 920.19).

[0112] (4) Synthesis of compound BN-57

[0113] The synthesis of compound BN-57 is similar to that of compound BN-1, except that compound BN-57-C (7.4 g, 8.0 mmol) is used instead of compound BN-1-C, and the amounts and synthesis methods of other compounds are the same. After purification by column chromatography, 0.7 g of a light yellow solid is obtained with a yield of 10.2%. The target product BN-57 is confirmed by mass spectrometry, MS: 868.28 (calculated value: 868.24), elemental analysis: C, 74.68; H, 4.88; N, 3.28; S, 14.80, calculated value (C, 74.65; H, 4.87; B, 2.49; N, 3.22; S, 14.76).

[0114] According to the similar synthetic routes and preparation methods of the above representative compounds, other compounds among compounds BN-1 to BN-60 were synthesized. The specific conditions and elemental analysis (characterization) are shown in Table 1.

[0115] Table 1

[0116]

[0117]

[0118] Example 2

[0119] An organic electroluminescent device, the structure of which comprises in sequence: an anode, a hole transport layer, a hole transition layer, an electron blocking layer, a light-emitting layer, an electron transport layer, an electron injection layer and a cathode; and a preparation method thereof comprises the following steps:

[0120] (1) Substrate treatment: Transparent ITO glass was used as the substrate material for the device preparation. It was first ultrasonically treated with 5% ITO washing solution for 30 min, and then ultrasonically washed with distilled water (2 times), acetone (2 times), and isopropanol (2 times) in sequence. Before use, the surface of the ITO glass was carefully wiped with acetone cotton balls and isopropanol cotton balls, rinsed with isopropanol and dried, and then treated with plasma for 5 min for use.

[0121] (2) Using the evaporation process to prepare electroluminescent devices; using the evaporation process to prepare the hole transport layer, electron blocking layer, luminescent layer, hole blocking layer, electron transport layer, electron injection layer and metal electrode; when the vacuum degree of the vacuum evaporation system reaches 5×10 -4 When the thickness is below 100 Pa, the deposition rate is controlled by a film thickness meter. The electron transport layer, LiF electron injection layer and metal Al electrode are deposited on the light-emitting layer in sequence by vacuum deposition process. The deposition rate of organic materials is The deposition rate of LiF is The deposition rate of Al is

[0122] Among them, ITO is used as anode, TAPC is used as hole transport layer; TCTA is used as hole transition layer; mCP is used as electron blocking layer; in the light-emitting layer, PhCzBCz is used as host material, and some compounds BN-1 to BN-60 and Ref-1 to Ref-3 are used as doped guest light-emitting materials (the doping concentration is 2wt%; i.e., light-emitting compound); TmPyPb is used as electron transport layer; LiF is used as electron injection layer; Al is used as metal cathode. The specific structure of the organic electroluminescent device is: [ITO / TAPC (30nm) / TCTA (5nm) / mCP (5nm) / PhCzBCz: 2wt% Emitters (30nm) / TmPyPb (30nm) / LiF (0.5nm) / Al (150nm)].

[0123] The molecular structures of the materials involved are as follows:

[0124]

[0125]

[0126] The above-mentioned organic electroluminescent device was tested, wherein the current, voltage, brightness, luminescence spectrum and other characteristics of the device were tested synchronously using a Photo Research PR 655 spectral scanning luminance meter and a Keithley K 2400 digital source meter system. The performance test of the device was carried out at room temperature and in an ambient atmosphere. The external quantum efficiency (EQE) of the device was calculated from the current density, brightness and electroluminescence spectrum combined with the visual function under the condition of Lambertian distribution of luminescence. The evaporation device was recorded as Dn (n = 1-20), and the test results are shown in Table 2.

[0127] Table 2

[0128]

[0129]

[0130] As can be seen from Table 2, the novel boron nitrogen compound of the present invention can effectively improve the device efficiency, especially the external quantum efficiency under high brightness, and its luminous efficiency is much higher than the device performance of the comparative compounds Ref-1 to Ref-3.

[0131] The above is only a preferred embodiment of the present invention. The present invention is not limited to the above implementation. As long as the technical effect of the present invention is achieved by the same means, it should belong to the protection scope of the present invention. Within the protection scope of the present invention, its technical scheme and / or implementation method can have various modifications and changes.

Claims

1. A boron-nitrogen compound, characterized in that: Its structure is shown in Formula I, Formula II or Formula III: Wherein, R1, R2, R3, R4 and R5 are independently selected from hydrogen, methyl, tert-butyl, phenyl, alkyl composed of C3-C18, cycloalkyl, aryl, heteroaryl, carbazolyl, tert-butylcarbazolyl, phenylcarbazolyl, diphenylamino and tert-butyldiphenylamino; X is oxygen or sulfur.

2. The boron nitrogen compound according to claim 1, characterized in that Its structure is any one of compounds BN-1 to BN-60:

3. The boron nitrogen compound according to claim 2, characterized in that Its structure is shown in compound BN-52 or compound BN-57.

4. A method for preparing a boron nitrogen compound as claimed in claim 1, characterized in that: When the structure of the boron nitrogen compound is as shown in Formula I, its preparation method includes synthetic route one; when the structure of the boron nitrogen compound is as shown in Formula II, its preparation method includes synthetic route two; when the structure of the boron nitrogen compound is as shown in Formula III, its preparation method includes synthetic route three; Described synthetic route 1 is as follows: Described synthetic route 2 is as follows: Described synthetic route three is as follows:

5. A light-emitting layer, characterized in that: It comprises a luminescent guest material, wherein the luminescent guest material is the boron nitrogen compound according to any one of claims 1 to 3.

6. The light-emitting layer according to claim 5, characterized in that It also includes a host material. In terms of mass percentage, the content of the luminescent guest material is 0.1%-20%, and the content of the host material is 80%-99.9%.

7. An organic electroluminescent device, characterized in that: Comprising the light-emitting layer according to claim 5 or 6.

8. The organic electroluminescent device according to claim 7, characterized in that: Including in order: Anode, hole transport layer, the light emitting layer, electron transport layer, cathode.

9. The organic electroluminescent device according to claim 8, characterized in that: An electron blocking layer is provided between the light-emitting layer and the hole transport layer; a hole transition layer is provided between the electron blocking layer and the hole transport layer; and an electron injection layer is provided between the electron transport layer and the cathode.

10. A display device, characterized in that: An organic electroluminescent device comprising any one of claims 7 to 9.

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