A multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization and its application in organic electroluminescent devices

Abstract

A multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization and its application in organic electroluminescent devices belong to the technical field of organic electroluminescent devices. The present invention introduces donors and cyano groups with different electron donating abilities into the multi-resonance framework, and designs and synthesizes molecules with both the short-range charge transfer (SR-CT) properties of MR-TADF molecules and the long-range charge transfer (LR-CT) characteristics of traditional TADF molecules. The LR-CT property of the short-axis skeleton can enhance the spin-orbit coupling of the system and promote the multi-channel reverse intersystem crossing process from triplet state to singlet state without causing emission red shift and spectral broadening; the SR-CT property of the long-axis skeleton ensures a narrow half-width and high luminous efficiency, and ensures efficient luminescence without affecting color fidelity and reducing efficiency roll-off. The prepared organic electroluminescent device achieves high efficiency, high color purity and low efficiency roll-off.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic electroluminescent devices, and in particular relates to a multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization and its application in organic electroluminescent devices. Background Art

[0002] Organic light-emitting diodes (OLEDs) are a new display technology with advantages such as high brightness, fast response, wide viewing angle, simple processing, and flexibility. They have made significant progress in full-color display and lighting applications, becoming a hot trend in current industrialization. In recent years, third-generation luminescent materials—thermally activated delayed fluorescence (TADF) materials—have been widely developed and applied in electronic devices due to their ability to effectively utilize triplet excitons, becoming a cutting-edge research hotspot in the field of luminescent materials. However, most current TADF materials utilize donor-acceptor structures. Vibrational coupling between the ground and excited states and structural relaxation of the excited state result in a wide full-width at half maximum (FWHM) of their emission spectra (>70nm), which cannot meet the high color purity requirements of full-color display technology. Although device structures using filters or optical microcavities can meet the color purity requirements of displays, this not only complicates the device structure but also results in significant energy loss, which is not conducive to energy conservation and environmental protection.

[0003] In recent years, although new TADF materials with boron / nitrogen multiple resonance effect (MR) have been reported to achieve high color purity and high luminescence efficiency. Their unique short-range charge transfer (SRCT) electronic structure not only gives these materials a large oscillator strength (f) and the resulting high fluorescence quantum yield (PLQY), but also minimizes the bonding / antibonding characteristics, structural relaxation and vibration coupling of the excited state, thereby achieving narrow-band emission characteristics. However, compared with the donor-acceptor (DA) type TADF with long-range charge transfer (LRCT), typical MR characteristic materials exhibit a relatively slow reverse intersystem crossing (RISC) rate (k RISC is 10 3 -10 4 s-1 ), which often leads to the accumulation of triplet excitons and subsequent exciton annihilation, resulting in severe efficiency roll-off at high brightness, hindering their commercial application potential. Furthermore, these boron / nitrogen multiple resonance system compounds have a relatively rigid planar structure, with strong molecular interactions and prone to aggregation. This easily leads to aggregation-induced quenching when fabricating electroluminescent devices, further deteriorating the luminescence performance of the material and the color purity of the device.

[0004] Therefore, it is of great significance to develop new organic light-emitting materials with high efficiency, high color purity and the ability to maintain high efficiency at high brightness, which will play an important role in promoting the further popularization of OLEDs technology. Summary of the Invention

[0005] The technical problem to be solved by the present invention is that k RISC The quenching effect of triplet exciton annihilation and aggregation-induced quenching between molecules is relatively slow, resulting in a serious efficiency roll-off of the electroluminescent device at high brightness. In response to the existing problems, the present invention provides a simple and effective strategy to improve the RISC of MR-TADF materials without affecting the color purity, that is, to modulate the LR-CT and SR-CT characteristics in the excited state through the "hybridized long-short axis (HLSA)" molecular design. The present invention is inspired by the long-short axis "thermal exciton" material, in which the LR-CT component of the short axis skeleton enhances the spin-orbit coupling (SOC) of the system, promotes the RISC process, and does not cause emission red shift and spectral broadening, while the SR-CT component of the long axis skeleton ensures narrowband emission and high PLQY. The electroluminescent device prepared by the present invention is conducive to achieving high efficiency at high brightness, overcoming the shortcomings of the MR-TADF material at high brightness, such as severe device efficiency attenuation and widening of the half-peak width.

[0006] The boron-containing multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization described in the present invention has the following structural formula:

[0007]

[0008] Where R is:

[0009]

[0010] Furthermore, the present invention provides a multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization, the structural formula of which is shown as one of the following:

[0011]

[0012] An organic electroluminescent device prepared using the product of the present invention comprises a cathode, an anode, and one or more organic layers between the two electrodes, at least one of which is an organic light-emitting layer. The organic light-emitting layer is composed of the multi-resonance thermally activated delayed fluorescent material based on long-short axis hybridization prepared by the present invention as a doped guest material and PhCzBCz as a doped host material, with the guest material doping ratio being 2-5% by weight. The electroluminescent device can be used to prepare an organic electroluminescent display or an organic electroluminescent lighting source.

[0013] Furthermore, the present invention provides an organic electroluminescent device, which is composed of a transparent substrate, an ITO conductive film (anode), a hole injection layer (HATCN), a hole transport layer (TAPC), an exciton blocking layer (TCTA and mCP), an organic light-emitting layer, an electron transport layer (TmPyPB), an electron injection layer (LiF) and a cathode layer (Al) from bottom to top. All functional layers can be prepared by a vacuum evaporation film-forming process.

[0014] Preferably, the organic compounds used in the device are commercially available or prepared according to known literature or patents, and the molecular structure is shown below:

[0015]

[0016] The beneficial effects of the present invention are:

[0017] The multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization of the present invention has high luminescence efficiency, high reverse intersystem crossing rate and narrow half-width. In response to the existing problems, the present invention provides a simple and effective strategy to improve the RISC of MR-TADF materials without affecting the color purity. By introducing donors and cyano groups with different electron donating abilities into the MR-TADF framework, the designed and synthesized "HLSA" molecules have both the SR-CT properties of MR-TADF molecules and the characteristics of traditional DA molecules LR-CT. The LR-CT properties of the short-axis skeleton can enhance the SOC of the system and promote the multi-channel RISC process from triplet state to singlet state without causing emission red shift and spectral broadening; the SR-CT properties of the long-axis skeleton ensure narrow half-width and high PLQY, and ensure efficient luminescence without affecting color fidelity and reducing efficiency roll-off. The organic electroluminescent device prepared in this way overcomes the shortcomings of MR-TADF materials such as severe efficiency attenuation at high brightness, and realizes the preparation of organic electroluminescent devices with high efficiency, high color purity and low efficiency roll-off, which plays an important role in promoting the further popularization of organic electroluminescent technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1: Schematic diagram of the structure of the organic electroluminescent device prepared by the present invention, in which 1 is a transparent substrate, 2 is an ITO anode, 3 is a hole injection layer, 4 is a hole transport layer, 5 is an exciton blocking layer, 6 is an organic light-emitting layer, 7 is an electron transport layer, 8 is an electron injection layer, and 9 is a cathode.

[0019] Figure 2 : UV (Abs.), fluorescence (FL.) and low-temperature phosphorescence spectra (Phos.) of compound BN-1; the maximum absorption peak is 475nm, the main emission peak is at 496nm, which is blue-green emission, with a half-peak width of 21nm; the energies of S1 and T1 calculated from the main peak positions of fluorescence and low-temperature phosphorescence are 2.50eV and 2.32eV, respectively, and the ΔE of the two molecules can be calculated. ST is 0.18eV.

[0020] Figure 3 : UV, fluorescence and low-temperature phosphorescence spectra of compound BN-2; the maximum absorption peak is 474nm, the main emission peak is at 491nm, which is blue-green emission, with a half-peak width of 23nm; the energies of S1 and T1 are calculated to be 2.52eV and 2.32eV respectively through the main peak positions of fluorescence and low-temperature phosphorescence, and the ΔE of the two molecules can be calculated ST is 0.20eV.

[0021] Figure 4 : UV, fluorescence and low-temperature phosphorescence spectra of compound BN-3; the maximum absorption peak is 475nm, the main emission peak is at 495nm, which is blue-green emission, with a half-peak width of 26nm; the energies of S1 and T1 calculated from the main peak positions of fluorescence and low-temperature phosphorescence are 2.50eV and 2.32eV respectively, and the ΔE of the two molecules can be calculated ST is 0.18eV.

[0022] Figure 5 : The external quantum efficiency curve of the electroluminescent device prepared by compound BN-1, the maximum external quantum efficiency is 35.7%, at a brightness of 100 cd m -2 When , the external quantum efficiency is 32.1%; the inset is the electroluminescence spectrum under a driving voltage of 6V. The main peak of electroluminescence is at 504nm, which is green light emission with high color purity and a half-peak width of 31nm.

[0023] Figure 6 : The external quantum efficiency curve of the electroluminescent device prepared by compound BN-2, the maximum external quantum efficiency is 37.9%, at a brightness of 100 cd m -2 When , the external quantum efficiency is 34.8%; the inset is the electroluminescence spectrum under a driving voltage of 6V. The main peak of electroluminescence is at 504nm, which is green light emission with high color purity and a half-peak width of 31nm.

[0024] Figure 7 : The external quantum efficiency curve of the electroluminescent device prepared by compound BN-3, the maximum external quantum efficiency is 33.7%, at a brightness of 100 cd m -2 When the external quantum efficiency is 25.2%, the inset is the electroluminescence spectrum under a driving voltage of 6V. The main peak of electroluminescence is located at 504nm, which is green light emission with high color purity and a half-peak width of 35nm. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with the accompanying drawings to facilitate understanding of the present invention by those skilled in the art. Obviously, the embodiments described are only a part of the present experiment and are not complete embodiments. Non-essential modifications, equivalent substitutions and improvements made to the present invention based on the above invention by those skilled in the art should all be included in the scope of protection of the present invention. The raw materials mentioned below are all commercially available or prepared according to known literature or patents. The process steps and preparation methods not mentioned are all process steps and preparation methods well known to those skilled in the art.

[0026] Example 1: The preparation of BN-1 in this example is as follows:

[0027]

[0028] Synthesis of M1: Under nitrogen protection, a solution of 3,6-di-tert-butylcarbazole (9.8 g, 35.2 mmol) in 60 mL of anhydrous DMF (N,N-dimethylformamide) was slowly added dropwise to a mixture of cesium carbonate (13.0 g, 40.0 mmol) and 50 mL of anhydrous DMF over 20 minutes. After the reaction system was stirred at room temperature for 2 hours, a solution of 1-bromo-2,6-difluorobenzene (3.1 g, 16.0 mmol) in 20 mL of anhydrous DMF was added dropwise over 15 minutes. The mixture was heated to 140°C and stirred for 24 hours, then cooled to room temperature. The reaction system was poured into ice water (2000 g), the white solid was filtered and dried in a vacuum oven, and then further purified by column chromatography using a mixed eluent of dichloromethane / petroleum ether (volume ratio 1:3) to obtain M1 (9.1 g) as a white solid with a yield of 80%. 1 H NMR (500MHz, CDCl3) δ (ppm): 8.16 (d, J = 1.9 Hz, 4H), 7.67 (dd, J = 8.8, 6.6 Hz, 1H), 7.6 1(d,J=8.4Hz,2H),7.51(dd,J=8.6,1.9Hz,4H),7.12(d,J=8.6Hz,4H),1.47(s,36H). 13C NMR (151 MHz, CDCl3) δ (ppm): 143.03, 139.66, 139.27, 130.86, 129.30, 125.83, 123.81, 123.38, 116.47, 109.40, 34.81, 32.07; Mass spectrum MALDI-TOF (m / z) [M + ]: The measured value is 711.5 and the theoretical value is 711.8.

[0029]

[0030] Synthesis of M2: Under nitrogen protection and an ice-water bath, a 1.3 M solution of tert-butyllithium in n-pentane (19.4 mL, 25.2 mmol) was slowly added dropwise to a solution of M1 (9.0 g, 12.6 mmol) in tert-butylbenzene (100 mL). The mixture was then heated to 60°C and stirred for 2 hours. Boron tribromide (2.4 mL, 25.2 mmol) was then added at -30°C, and the reaction system was stirred at room temperature for 1 hour. Finally, N,N-diisopropylethylamine (3.5 mL, 25.2 mmol) was added at 0°C, and the reaction system was stirred at 130°C for 6 hours before being cooled to room temperature. 5 mL of methanol was added to the reaction system to quench any residual boron tribromide. The mixture was extracted with 200 mL of water and 200 mL of dichloromethane, the organic layers were combined, concentrated in vacuo, and then further purified by column chromatography using a mixed eluent of dichloromethane / petroleum ether (volume ratio 1:20) to give M2 (2.1 g) as a yellow solid with a yield of 26%. 1 H NMR (500MHz, CDCl3) δ (ppm): 9.12 (d, J = 1.8Hz, 2H), 8.46 (d, J = 1.7Hz, 2H), 8.38 (d, J = 8.8Hz, 2H), 8.3 3–8.24(m,4H),7.99(td,J=8.3,1.3Hz,1H),7.65(dd,J=8.7,2.1Hz,2H),1.67(s,18H),1.53(s,18H). 13 C NMR (151 MHz, CDCl3) δ (ppm): 145.24, 144.58, 144.25, 141.54, 138.36, 132.99, 129.79, 127.05, 124.32, 123.65, 123.19, 121.56, 120.62, 117.22, 114.12, 107.93, 35.18, 34.81, 32.21, 31.88; Mass Spectrometry MALDI-TOF (m / z) [M + ]: The measured value is 640.5 and the theoretical value is 640.7.

[0031]

[0032] Synthesis of M3: Under nitrogen, the catalyst methoxy(cyclooctadiene)iridium(I) dimer (43.1 mg, 0.065 mmol) and 4,4'-di-tert-butyl-2,2'-bipyridine (34.9 mg, 0.13 mmol) were added to a solution of M2 (4.20 g, 6.5 mmol) and pinacol diboron (1.68 g, 6.6 mmol) in ultra-dry tetrahydrofuran (60 mL). The mixture was then sparged with nitrogen for 5 minutes, heated to reflux, and stirred for 24 hours. After cooling to room temperature, the reaction mixture was concentrated under reduced pressure and further purified by column chromatography using a mixture of dichloromethane and petroleum ether (1:20 by volume) to afford M3 (4.50 g) as a yellow solid in 90% yield. 1 H NMR (500MHz, CDCl3) δ (ppm): 9.14 (d, J = 1.9 Hz, 2H), 8.79 (s, 2H), 8.53 (d, J = 8.8 Hz, 2H), 8.48 (d, J = 1.8 Hz,2H),8.27(d,J=2.0Hz,2H),7.74(dd,J=8.8,2.1Hz,2H),1.67(s,18H),1.54(s,18H),1.49(s,12H). 13 C NMR (151 MHz, CDCl3) δ (ppm): 145.17, 144.55, 143.68, 141.64, 138.48, 129.77, 126.93, 124.59, 123.75, 121.65, 120.75, 117.10, 114.44, 113.77, 84.34, 35.18, 34.82, 32.21, 31.87, 25.09; Mass Spectrometry MALDI-TOF (m / z) [M + ]: The measured value is 766.8 and the theoretical value is 766.7.

[0033]

[0034] Synthesis of M4: Under nitrogen, carbazole (1.67 g, 10.0 mmol), 3,5-dibromobenzonitrile (3.13 g, 12.0 mmol), tris(dibenzylideneacetone)dipalladium (277 mg, 0.30 mmol), tri-tert-butylphosphine tetrafluoroborate (147 mg, 0.50 mmol), and sodium tert-butoxide (1.92 g, 20 mmol) were dissolved in 100 mL of toluene and refluxed at 110°C for 24 hours under nitrogen. The resulting mixture was extracted with dichloromethane and concentrated to obtain a crude product, which was then purified by column chromatography using petroleum ether:dichloromethane (10:1 by volume) as the developing solvent to obtain M4 (2.45 g, 71% yield) as a white solid. 1H NMR (500 MHz, DMSO) δ (ppm): 8.36–8.32 (m, 1H), 8.30–8.25 (m, 4H), 7.48 (d, J = 3.6 Hz, 4H), 7.38–7.32 (m, 2H); Mass spectrum MALDI-TOF (m / z) [M + ]: The measured value is 347.1 and the theoretical value is 347.2.

[0035]

[0036] Synthesis of BN-1: Under nitrogen protection, M4 (347 mg, 1 mmol), M3 (766 mg, 1 mmol), K2CO3 (2.76 g, 20 mmol), Pd(PPh3)4 (23 mg, 0.02 mmol) were mixed and added to a 100 mL flask. 20 mL of toluene and 10 mL of water were added, heated to 90 ° C and stirred for 12 hours. After cooling to room temperature, the reaction mixture was poured into water (100 mL), extracted with dichloromethane and water, and the combined organic layers were condensed in vacuo and purified by column chromatography with a mixed eluent of dichloromethane / petroleum ether (volume ratio 1:1) to obtain BN-1 (550 mg) as a light yellow solid with a yield of 61%. 1 H NMR (500MHz, CDCl3) δ (ppm): 9.13 (s, 2H), 8.51 (d, J = 13.6Hz, 4H), 8.43 (s, 1H), 8.39 (d, J = 8.8Hz, 2H), 8.30 (d, J = 1.7Hz, 2H), 8.27–8.21(m,3H),8.08(s,1H),7.74–7.66(m,4H),7.58(t,J=7.3Hz,2H),7.44(t,J=7.4Hz,2H),1.69(s,18H),1.56(s,18H). 13 C NMR (126 MHz, CDCl3) δ (ppm): 145.61, 144.80, 141.87, 141.60, 140.12, 139.46, 138.05, 130.12, 129.68, 129.17, 128.89, 127.20, 126.56, 124.78, 124.05, 123.70, 121.56, 121.02, 120.79, 118.19, 117.45, 114.86, 114.14, 109.41, 106.25, 35.17, 34.84, 32.14, 31.81; Mass Spectrometry MALDI-TOF (m / z) [M + ]: The measured value is 907.1 and the theoretical value is 907.0.

[0037] Example 2: The preparation of BN-2 in this example is as follows:

[0038]

[0039] Synthesis of M5: Under nitrogen, diphenylamine (1.69 g, 10.0 mmol), 3,5-dibromobenzonitrile (3.13 g, 12.0 mmol), tris(dibenzylideneacetone)dipalladium (277 mg, 0.30 mmol), tri-tert-butylphosphine tetrafluoroborate (147 mg, 0.50 mmol), and sodium tert-butoxide (1.92 g, 20 mmol) were dissolved in 100 mL of toluene and refluxed at 110°C for 24 hours under nitrogen. The resulting mixture was extracted with dichloromethane and concentrated to obtain a crude product, which was then purified by column chromatography using petroleum ether:dichloromethane (10:1 by volume) as the developing solvent to obtain M5 (2.85 g, 82% yield) as a white solid. 1 H NMR (500 MHz, DMSO) δ (ppm): 7.60 (s, 1H), 7.42 (t, J = 7.7 Hz, 4H), 7.19 (dd, J = 31.4, 13.9 Hz, 8H); Mass spectrum MALDI-TOF (m / z) [M + ]: The measured value is 349.4, and the theoretical value is 349.2.

[0040]

[0041] Synthesis of BN-2: Under nitrogen protection, M5 (349 mg, 1 mmol), M3 (766 mg, 1 mmol), K2CO3 (2.76 g, 20 mmol), Pd(PPh3)4 (23 mg, 0.02 mmol) were mixed and added to a 100 mL flask, and 20 mL of toluene and 10 mL of water were added. The mixture was heated to 90 ° C and stirred for 12 hours. After cooling to room temperature, the reaction mixture was poured into water (100 mL), extracted with dichloromethane and water, and the combined organic layers were condensed in vacuo and purified by column chromatography with a mixed eluent of dichloromethane / petroleum ether (volume ratio 1: 1) to obtain a light yellow solid BN-2 (580 mg) with a yield of 64%. 1 H NMR (500MHz, CD2Cl2) δ (ppm): 9.05 (s, 2H), 8.52 (s, 2H), 8.30 (d, J = 1.6Hz, 2H), 8.13 (s, 2H), 8.02 (d, J = 8.7Hz, 2H), 7. 72(s,1H),7.63(dd,J=8.7,1.6Hz,2H),7.45(dd,J=18.9,11.0Hz,5H),7.34–7.20(m,7H),1.71(s,18H),1.61(s,18H). 13C NMR (126 MHz, CDCl3) δ (ppm): 149.14, 146.58, 145.27, 144.62, 142.89, 142.59, 141.59, 138.06, 129.76, 127.12, 125.39, 124.62, 123.77, 123.09, 122.57, 121.57, 120.87, 119.08, 117.32, 113.91, 105.97, 35.20, 34.85, 32.21, 31.89; Mass Spectrometry MALDI-TOF (m / z) [M + ]: The measured value is 909.2, and the theoretical value is 909.0.

[0042] Example 3: The preparation of BN-3 in this example is as follows:

[0043]

[0044] Synthesis of M6: Under nitrogen, diphenylamine (1.99 g, 10.0 mmol), 3,5-dibromobenzonitrile (3.13 g, 12.0 mmol), tris(dibenzylideneacetone)dipalladium (277 mg, 0.30 mmol), tri-tert-butylphosphine tetrafluoroborate (147 mg, 0.50 mmol), and sodium tert-butoxide (1.92 g, 20 mmol) were dissolved in 100 mL of toluene and refluxed at 110°C for 24 hours under nitrogen. The resulting mixture was extracted with dichloromethane and concentrated to obtain a crude product, which was then purified by column chromatography using petroleum ether:dichloromethane (10:1 by volume) as the developing solvent to obtain M6 (2.65 g, 70% yield) as a white solid. 1 H NMR (500MHz, DMSO) δ (ppm): 8.03 (s, 1H), 7.69 (d, J = 10.0Hz, 2H), 7.37 (d, J = 7.6Hz, 2H), 7 .24(t,J=7.6Hz,2H),7.14(t,J=7.5Hz,2H),6.88(d,J=8.1Hz,2H); Mass spectrum MALDI-TOF(m / z)[M + ]: The measured value is 379.4, and the theoretical value is 379.3.

[0045]

[0046] Synthesis of BN-3: Under nitrogen protection, M6 (379 mg, 1 mmol), M3 (766 mg, 1 mmol), K2CO3 (2.76 g, 20 mmol), Pd(PPh3)4 (23 mg, 0.02 mmol) were mixed and added to a 100 mL flask, and 20 mL of toluene and 10 mL of water were added. The mixture was heated to 90 ° C and stirred for 12 hours. After cooling to room temperature, the reaction mixture was poured into water (100 mL), extracted with dichloromethane and water, and the combined organic layers were condensed in vacuo and purified by column chromatography with a mixed eluent of dichloromethane / petroleum ether (volume ratio 1:1) to obtain a light yellow solid BN-3 (530 mg) with a yield of 56%. 1 H NMR(500MHz, CD2Cl2)δ(ppm):9.03(s,1H),8.54(t,J=5.8Hz,1H),8.40–8.17(m,7H),7.93(d,J=9.3Hz,1H),7.81(s,1H),7.76–7.5 8(m,4H),7.55(s,1H),7.53–7.46(m,2H),7.39(dd,J=12.0,5.9Hz,2H),7.25(dt,J=21.5,6.2Hz,3H),1.68(s,18H),1.58(s,18H). 13 C NMR (126 MHz, CDCl3) δ (ppm): 145.91, 145.48, 144.79, 142.01, 141.60, 138.08, 130.20, 129.70, 129.03, 128.58, 127.50, 127.19, 125.61, 124.63, 124.13, 123.60 (s), 123.10, 121.56, 120.96, 118.79, 117.41, 114.48, 114.04, 109.52, 106.22, 35.16, 34.85, 32.00, 22.55; Mass Spectrometry MALDI-TOF (m / z) [M + ]: The measured value is 939.4 and the theoretical value is 939.1.

[0047] The technical effects and advantages of the present invention are demonstrated and verified by applying the compound of the present invention to an organic electroluminescent device to test its actual performance.

[0048] Effect Example 1: Preparation of organic electroluminescent device BN-1

[0049] The following demonstrates and verifies the technical effects and advantages of the present invention by applying the compounds of the present invention to organic electroluminescent devices and testing their actual performance. The specific device preparation process and device performance testing experimental procedures are as follows: The device preparation process is as follows: Preparation of an indium tin oxide (ITO) conductive glass substrate: The substrate is cleaned in an ultrasonic bath with deionized water, isopropyl alcohol, acetone, toluene, acetone, and isopropyl alcohol for 20 minutes each, and then dried in an oven; After treating the surface of the ITO conductive glass substrate in a UV ozone cleaner for 40 minutes, it is transferred to a vacuum evaporation device (the pressure in the chamber is less than 2×10 -4 Pa); on the anode ITO conductive glass, the hole injection layer HATCN is vacuum-deposited with a thickness of 6 nm; on the HATCN, the hole transport layer TAPC is vacuum-deposited with a thickness of 30 nm; on the TAPC, the exciton blocking layer TCTA is evaporated with a thickness of 5 nm; on the TCTA, the exciton blocking layer mCP is evaporated with a thickness of 5 nm; on the mCP, the organic light-emitting layer EML is evaporated with a thickness of 20 nm; on the organic light-emitting layer, the electron transport layer TmPyPB is evaporated with a thickness of 40 nm; on the TmPyPB, the electron injection layer LiF is evaporated with a thickness of 1 nm; on the LiF, the cathode Al is evaporated with a thickness of 100 nm.

[0050] The structure of the organic electroluminescent device BN-1 is as follows: ITO / HATCN (6nm) / TAPC (30nm) / TCTA (5nm) / mCP (5nm) / EML (20nm) / TmPyPB (40nm) / LiF (1nm) / Al (100nm), where EML represents the light-emitting layer, and the light-emitting layer is composed of a host material PhCzBCz with a mass percentage of 97% and a guest light-emitting material BN-1 with a mass percentage of 3%.

[0051] A DC voltage was applied to the organic electroluminescent device BN-1 prepared in this example, and the luminescence performance was evaluated using a Spectrascan PR655 luminance meter. The current-voltage characteristics were measured using a computer-controlled Keithley 2400 digital source meter. As luminescence characteristics, the electroluminescent spectrum, half-peak width, CIE color coordinates, external quantum efficiency (%), power efficiency (lm / W), and maximum brightness (cd / m2) were measured as a function of the applied DC voltage. 2 The detailed electroluminescent performance data of the device are listed in Table 1. The measured values ​​of the device are as follows: the spectral peak is 504nm, the half-maximum width is 31nm, the CIE color coordinates are (0.13, 0.62), the maximum power efficiency is 91.1lm / W and the maximum brightness is 37258cd / m 2 , the maximum external quantum efficiency is 35.7%. When the brightness reaches 100cd / m 2 and 1000cd / m2 When , the external quantum efficiency can still be maintained at 32.1% and 18.5%.

[0052] Effect Example 2: Preparation of organic electroluminescent device BN-2

[0053] The preparation method is the same as that of Example 1, except that the guest luminescent material BN-1 used in the luminescent layer is replaced by BN-2. The specific device structure is as follows: ITO / HATCN (6nm) / TAPC (30nm) / TCTA (5nm) / mCP (5nm) / EML (20nm) / TmPyPB (40nm) / LiF (1nm) / Al (100nm), where EML represents the luminescent layer, and the luminescent layer is composed of 97% by mass of the main material PhCzBCz and 3% by mass of the guest luminescent material BN-2.

[0054] A DC voltage was applied to the organic electroluminescent device BN-2 prepared in this example, and the luminescence performance was evaluated using a Spectrascan PR655 luminance meter. The current-voltage characteristics were measured using a computer-controlled Keithley 2400 digital source meter. As luminescence characteristics, the electroluminescent spectrum, half-peak width, CIE color coordinates, external quantum efficiency (%), power efficiency (lm / W), and maximum brightness (cd / m2) were measured as a function of the applied DC voltage. 2 The detailed electroluminescent performance data of the device are listed in Table 1. The measured values ​​of the device are as follows: the spectral peak is 504nm, the half-peak width is 31nm, the CIE color coordinates are (0.18, 0.62), the maximum power efficiency is 94.7lm / W and the maximum brightness is 32132cd / m 2 , the maximum external quantum efficiency is 37.9%. When the brightness reaches 100cd / m 2 and 1000cd / m 2 When , the external quantum efficiency can still be maintained at 34.8% and 21.8%.

[0055] Effect Example 3: Preparation of organic electroluminescent device BN-3

[0056] The preparation method is the same as that of Example 1, except that the guest luminescent material BN-1 used in the luminescent layer is replaced by BN-3. The specific device structure is as follows: ITO / HATCN (6nm) / TAPC (30nm) / TCTA (5nm) / mCP (5nm) / EML (20nm) / TmPyPB (40nm) / LiF (1nm) / Al (100nm), where EML represents the luminescent layer, and the luminescent layer is composed of 97% by mass of the main material PhCzBCz and 3% by mass of the guest luminescent material BN-3.

[0057] A DC voltage was applied to the organic electroluminescent device BN-3 prepared in this example, and the luminescence performance was evaluated using a Spectrascan PR655 luminance meter. The current-voltage characteristics were measured using a computer-controlled Keithley 2400 digital source meter. As luminescence characteristics, the electroluminescent spectrum, half-peak width, CIE color coordinates, external quantum efficiency (%), power efficiency (lm / W), maximum brightness (cd / m 2 The detailed electroluminescent performance data of the device are listed in Table 1. The measured values ​​of the device are as follows: the spectral peak is 504nm, the half-maximum width is 35nm, the CIE color coordinates are (0.13, 0.61), the maximum power efficiency is 99.4lm / W and the maximum brightness is 17515cd / m 2 , the maximum external quantum efficiency is 33.7%. When the brightness reaches 100cd / m 2 and 1000cd / m 2 When , the external quantum efficiency can still be maintained at 25.2% and 12.7%.

[0058] Table 1: Data parameters of electroluminescent devices provided by the effect embodiment

[0059]

[0060] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization, the structural formula of which is shown as one of the following: 。 2. Use of the multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization according to claim 1 in the preparation of an organic electroluminescent device.

3. Use of a multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization in the preparation of an organic electroluminescent device as claimed in claim 2, characterized in that: The organic electroluminescent device is composed of a cathode, an anode, and one or more organic layers between the two electrodes, at least one of the organic layers is an organic light-emitting layer, and the organic light-emitting layer is composed of the long-short axis hybridization-based multiple resonance thermally activated delayed fluorescence material according to claim 1 as a doped guest material and PhCzBCz as a doped host material, and the mass doping ratio of the guest material is 2-5%.

4. Use of a multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization in the preparation of an organic electroluminescent device as claimed in claim 3, characterized in that: The organic electroluminescent device consists of a transparent substrate, an ITO conductive film anode, a hole injection layer, a hole transport layer, an exciton blocking layer, an organic light-emitting layer, an electron transport layer, an electron injection layer and a cathode layer from bottom to top.

5. Use of a multi-resonance thermally activated delayed fluorescence material based on long-short axis hybridization in the preparation of an organic electroluminescent device as claimed in claim 3 or 4, characterized in that: The electroluminescent device is used for preparing an organic electroluminescent display or an organic electroluminescent lighting source.

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