Organic heat delayed fluorescence material based on di-tert-butyl aniline donor and preparation method

Abstract

The application provides a di-tert-butyl aniline donor-based organic heat delayed fluorescence material and a preparation method, belongs to the technical field of organic light-emitting diodes, and takes di-tert-butyl aniline donor as a core to synthesize three kinds of organic heat delayed fluorescence materials; the acceptor group R adopted in the application has strong rigidity, can effectively inhibit non-radiative transition of molecules, improve the efficiency of an organic electroluminescent device, and introduce a tert-butyl group on the di-tert-butyl aniline donor, so that the spatial steric hindrance of the molecules can be improved, concentration quenching caused by molecular stacking can be inhibited, and the emission efficiency of the device can be improved; in addition, the acceptor group R has strong electron-withdrawing capacity, and the combination of the tert-butyl group can make the luminescence wavelength of the organic electroluminescent device red-shift, realize orange-red light / red light emission, and has high external quantum efficiency, and the highest external quantum efficiency can reach 11.7%, has an optimistic application prospect, and is expected to be widely applied in the fields of illumination and display.

Description

Technical Field

[0001] This invention belongs to the field of organic light-emitting diode technology, specifically relating to organic thermally delayed fluorescent materials based on di-tert-butylaniline donors and their preparation methods. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have been a hot research topic since their invention by Tang and Van Slyke in 1987, representing an unprecedented advancement in display and lighting technology. Compared to existing liquid crystal displays (LCDs), OLEDs offer higher image quality and contrast, faster response times / refresh rates, wider viewing angles, and are thinner and lighter. Even more impressive is the ability to manufacture OLEDs on flexible substrates, allowing OLED displays to be rolled up like posters—a feat unattainable for older displays. OLEDs are more energy-efficient due to the elimination of backlighting systems and their significantly reduced size makes them lighter and more portable. Given that lighting accounts for approximately 20% of global electricity consumption, widespread adoption of OLEDs as a lighting technology could save substantial amounts of electricity. Therefore, OLEDs have broad application prospects in display and lighting fields. According to spin statistics, excitons formed through charge (hole and electron) recombination in OLED devices comprise 25% singlet states and 75% triplet states. OLEDs using first-generation traditional fluorescent materials can only emit light through singlet excitons, thus their internal quantum efficiency is theoretically limited to below 25%. Second-generation OLEDs utilize phosphorescent materials containing heavy metals such as Pt and Ir, achieving 100% internal quantum efficiency through the heavy atom effect. However, heavy metals are expensive, non-renewable, and environmentally unfriendly, limiting their application in organic electroluminescence to some extent. In recent years, OLEDs utilizing the thermally activated delayed fluorescence (TADF) mechanism have developed rapidly. Because they can achieve 100% internal quantum efficiency without the participation of heavy metals, they have been widely studied. The TADF mechanism includes, but is not limited to, intramolecular TADF (using TADF materials). After years of development, the efficiency of blue and green TADF materials and TADF excitopolymer OLEDs has reached commercial requirements. However, the non-radiative transition rate of red TADF materials and TADF excitopolymer OLEDs, essential for three-primary-color displays, is extremely high, causing their efficiency to lag far behind that of blue and green light, necessitating a solution. Summary of the Invention

[0003] To address the technical problems existing in the prior art, this invention proposes an organic thermally delayed fluorescence material based on di-tert-butylaniline donor and its preparation method. Using di-tert-butylaniline donor as the core, three organic thermally delayed fluorescence materials are synthesized.

[0004] The technical solution adopted in this invention is as follows:

[0005] The organic thermally delayed fluorescent material based on di-tert-butylaniline donor is characterized in that the organic thermally delayed fluorescent material has a molecular structure as shown in formula (1):

[0006]

[0007] Wherein, R is bispyrido[3,2-a:3',4'-c]phenazine, pyrido[3',2':5,6]pyrazino[2,3-f][1,9]phenanthroline or pyrazino[2',3':5,6]pyrazino[3,3-f][1,9]phenanthroline;

[0008] The molecular structures of the bispyrido[3,2-a:3',4'-c]phenazine, pyrido[3',2':5,6]pyrazino[2,3-f][1,9]phenanthroline, and pyrazino[2',3':5,6]pyrazino[3,3-f][1,9]phenanthroline are shown in formulas (2), (3), and (4), respectively:

[0009]

[0010] Furthermore, the molecular structure of the organic thermally delayed fluorescence material is as follows: DCPP-tBuTPA, DCPPy-tBuTPA, or DCPPm-tBuTPA.

[0011]

[0012] The method for preparing organic thermally delayed fluorescent materials based on di-tert-butylaniline donors is characterized by the following steps in the reaction synthesis of organic thermally delayed fluorescent materials with molecular structures of DCPP-tBuTPA or DCPPy-tBuTPA:

[0013] Step 1: Add 1,10-phenanthroline-5,6-dione and the reactants to a round-bottom flask at a molar ratio of 1:1. Add acetic acid under nitrogen protection to obtain a mixed solution A with a concentration of 0.03-0.05 mol / L of 1,10-phenanthroline-5,6-dione. Heat to 110-120℃ and rotate the reaction mixture. After the 1,10-phenanthroline-5,6-dione has completely reacted, add deionized water, filter, and dry to obtain crude product A. When the molecular structure synthesized by the reaction is DCPP-tBuTPA, the reactant is 4-bromophenyl-1,2-diamine; when the molecular structure synthesized by the reaction is DCPPy-tBuTPA, the reactant is 2,3-diamino-5-bromopyridine.

[0014] Step 2: Crude product A, 4',4'-di-tert-butyl-4-borate pinacol ester triphenylamine, and tetra(triphenylphosphine)palladium were added to a round-bottom flask in a molar ratio of 1:(1.1-1.3):(0.05-0.1). Under nitrogen protection, ultra-dry 1,4-dioxane (volume ratio 4:1) and 2M potassium carbonate aqueous solution were added sequentially to obtain a mixed solution B with a crude product A concentration of 0.03-0.05 mol / L. The temperature was raised to 90-100℃ until crude product A reacted completely, and mixture B was obtained. After cooling to room temperature, 1,4-dioxane and water were removed. Then, a mixed solution of methanol and dichloromethane (volume ratio 1:20) was used as the eluent to purify mixture B by silica gel column chromatography. Finally, after recrystallization, filtration, and drying, the mixture was further purified by sublimation under a temperature gradient in a vacuum to obtain the organic thermal delayed fluorescence material.

[0015] The method for preparing organic thermally delayed fluorescent materials based on di-tert-butylaniline donors is characterized by the following steps in the reaction synthesis of organic thermally delayed fluorescent materials with the molecular structure DCPPm-tBuTPA:

[0016] Step 1: Add 5-bromo-2,3-diaminopyrazine, 4',4'-di-tert-butyl-4-boronic acid pinacol ester triphenylamine, and tetra(triphenylphosphine)palladium to a round-bottom flask in a molar ratio of 1:(1.1-1.3):(0.05-0.1). Under nitrogen protection, add ultra-dry 1,4-dioxane (4:1 volume ratio) and 2M potassium carbonate aqueous solution sequentially to obtain a mixed solution E with a concentration of 0.03-0.05 mol / L of 5-bromo-2,3-diaminopyrazine. Heat to 90-100℃ until 5-bromo-2,3-diaminopyrazine reacts completely to obtain mixture E. After cooling to room temperature, remove 1,4-dioxane and water. Then, use a mixed solution of methanol and dichloromethane (1:20 volume ratio) as eluent to purify mixture E by silica gel column chromatography. After recrystallization, filtration, and drying, obtain intermediate E.

[0017] Step 2: Intermediate E and 1,10-phenanthroline-5,6-dione were added to a round-bottom flask at a molar ratio of 1:(1.1-1.3). Acetic acid was added under nitrogen protection to obtain a mixed solution F with a concentration of 0.03-0.05 mol / L of intermediate E. The mixture was heated to 110-120℃ and rotated for reaction. After intermediate E had completely reacted, mixture F was extracted with water and dichloromethane at a volume ratio of 2:1 to remove dichloromethane and acetic acid. Then, a mixed solution of methanol and dichloromethane at a volume ratio of 1:20 was used as the eluent to purify mixture F by silica gel column chromatography. After recrystallization, filtration and drying, the mixture was further purified by sublimation under a temperature gradient in a vacuum to obtain the organic thermal delayed fluorescence material.

[0018] Furthermore, the water oxygen content of the ultra-dry 1,4-dioxane does not exceed 50 ppm.

[0019] An organic electroluminescent device containing an organic thermally delayed fluorescent material based on a di-tert-butylaniline donor, characterized in that it comprises a light-emitting layer composed of a host material and an organic thermally delayed fluorescent material based on a di-tert-butylaniline donor; wherein the mass percentage of the organic thermally delayed fluorescent material in the light-emitting layer is 3-10%.

[0020] Furthermore, the organic electroluminescent device further includes, from bottom to top, a substrate, an anode electrode, a hole transport layer, an electron blocking layer, an electron transport layer, an electron injection layer, and a cathode electrode, wherein the light-emitting layer is located between the electron blocking layer and the electron transport layer.

[0021] Furthermore, the anode electrode is ITO; the hole transport layer is TAPC; the electron blocking layer is TcTa; the electron transport layer is TmPyPB; the electron injection layer is LiF; the cathode electrode is Al metal; and the main material in the light-emitting layer is CBP.

[0022] Furthermore, ITO conductive glass is used as the substrate and anode electrode.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This invention proposes an organic thermally delayed fluorescence (TADF) material based on di-tert-butylaniline as a donor and its preparation method. Using the electron-donating di-tert-butylaniline structural unit as the donor core, three organic TADF materials are synthesized, exhibiting small energy difference (ΔEst) and large band gap (f), demonstrating excellent TADF characteristics. The acceptor group R possesses strong rigidity, effectively suppressing non-radiative transitions and improving device efficiency. However, the strong rigidity of the acceptor group R can enhance molecular planarity, causing molecular stacking and reducing device efficiency. Therefore, introducing a tert-butyl group onto the donor can increase the steric hindrance of the molecule, suppressing concentration quenching caused by molecular stacking and improving the device's emission efficiency. Simultaneously, the acceptor group R has strong electron-withdrawing ability; combining with the tert-butyl group can redshift the emission wavelength of the device, achieving red light emission.

[0025] 2. Organic electroluminescent devices containing organic thermally delayed fluorescent materials based on di-tert-butylaniline donors can emit orange / red light, with an external quantum efficiency (EQE) of up to 11.7%, exhibiting excellent luminescence performance and broad application prospects. They are expected to be widely used in flat panel displays and solid-state lighting.

[0026] 3. The organic thermally delayed fluorescent material based on di-tert-butylaniline donor proposed in this invention has easily adjustable emission color and good thermal stability. Attached Figure Description

[0027] Figure 1 The above is the absorption-emission (AbsFL) spectrum of the organic thermally delayed fluorescent material with the molecular structure DCPP-tBuTPA obtained in Example 1 of this invention at room temperature.

[0028] Figure 2 The redox potential curves are for the organic thermally delayed fluorescent material with the molecular structure DCPP-tBuTPA obtained in Example 1 of this invention.

[0029] Figure 3 The electroluminescence spectra of organic electroluminescent devices containing different proportions of organic thermally delayed fluorescent material (DCPP-tBuTPA) obtained in Example 1 of the present invention are shown.

[0030] Figure 4 The external quantum efficiency diagrams of organic electroluminescent devices containing different proportions of organic thermally delayed fluorescent material (DCPP-tBuTPA) obtained in Example 1 of the present invention are shown.

[0031] Figure 5 The absorption and emission spectrum of the organic thermally delayed fluorescent material with the molecular structure DCPPy-tBuTPA obtained in Example 2 of this invention is shown at room temperature.

[0032] Figure 6 The redox potential curve of the organic thermal delayed fluorescent material with the molecular structure DCPPy-tBuTPA obtained in Example 2 of this invention;

[0033] Figure 7 The electroluminescence spectra of organic electroluminescent devices containing different proportions of organic thermally delayed fluorescent material (DCPPy-tBuTPA) obtained in Example 2 of the present invention are shown.

[0034] Figure 8 The external quantum efficiency diagrams of organic electroluminescent devices containing different proportions of organic thermally delayed fluorescent material (DCPPy-tBuTPA) obtained in Example 2 of the present invention are shown.

[0035] Figure 9 The absorption and emission spectrum of the organic thermally delayed fluorescent material with the molecular structure DCPPm-tBuTPA obtained in Example 3 of this invention is shown at room temperature.

[0036] Figure 10 The redox potential curve of the organic thermal delayed fluorescent material with the molecular structure DCPPm-tBuTPA obtained in Example 3 of this invention;

[0037] Figure 11 The electroluminescence spectra of the organic electroluminescent devices containing different proportions of organic thermally delayed fluorescent material (DCPPm-tBuTPA) obtained in Example 3 of the present invention are shown.

[0038] Figure 12 The external quantum efficiency diagram shows the organic electroluminescent devices containing different proportions of organic thermally delayed fluorescent material (DCPPm-tBuTPA) obtained in Example 3 of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in conjunction with the following specific embodiments and with reference to the accompanying drawings.

[0040] Example 1

[0041] This embodiment proposes an organic thermally delayed fluorescence material based on di-tert-butylaniline donor, DCPP-tBuTPA, with the molecular structure shown below:

[0042]

[0043] The synthesis route is as follows:

[0044]

[0045] Specifically, the following steps are included:

[0046] Step 1: Add 1,10-phenanthroline-5,6-dione (210.19 mg, 1 mmol) and 4-bromophenyl-1,2-diamine (186.36 mg, 1 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Replace the nitrogen gas three times. Under nitrogen protection, use a 50 mL syringe to inject 30 mL of acetic acid into the round-bottom flask. Rotate the reaction in an oil bath at 120 °C. Detect the reaction using thin-layer chromatography (TCL). After the 1,10-phenanthroline-5,6-dione has completely reacted (reaction time 24 h), cool to room temperature and pour into ice-cold deionized water. Filter and dry the precipitate to obtain crude product A.

[0047] Step 2: Add crude product A (361.2 mg, 1 mmol), 4',4'-di-tert-butyl-4-borate pinacol ester triphenylamine (531.85 mg, 1.1 mmol), and tetra(triphenylphosphine)palladium (115.56 mg, 0.1 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Replace the nitrogen gas three times. Then, under nitrogen protection, sequentially inject 6 mL of 2M potassium carbonate aqueous solution and 24 mL of ultra-dry 1,4-dioxane. Rotate the reaction mixture at 100°C in an oil bath. Thin-layer chromatography (TCL) was used for detection. After crude product A had completely reacted (reaction time 24 h), mixture B was obtained. After cooling to room temperature, 1,4-dioxane and water were removed by rotary evaporation. Then, a mixed solution of methanol and dichloromethane (volume ratio 1:20) was used as the eluent to purify mixture B by silica gel column chromatography. Finally, it was recrystallized with a mixed solution of dichloromethane and n-hexane, filtered, dried, and further purified by sublimation under vacuum with a temperature gradient to obtain a pure orange-red powder (510 mg), with a yield of 80%. The ultra-dried 1,4-dioxane was 1,4-dioxane with a water and oxygen content not exceeding 50 ppm.

[0048] In 10 -5 The absorption and emission spectra of an organic thermally delayed fluorescent material with the molecular structure DCPP-tBuTPA were measured in a dilute toluene solution at room temperature, as shown in the figure. Figure 1 As shown, a distinct CT (charge transfer) absorption band can be observed from 400 to 550 nm, indicating that it has good thermo-induced delayed fluorescence characteristics; the emission peak in dilute toluene solution is 558 nm, which enables it to emit red light. Figure 2 The redox potential curve of DCPP-tBuTPA was obtained by cyclic voltammetry (CV). From the initial oxidation position and the initial reduction position, its HOMO and LUMO energy levels are 5.18 eV and 3.28 eV, respectively. Its deeper LUMO energy level can ensure the realization of organic thermoinduced delayed fluorescence red light emission.

[0049] This embodiment also provides an organic electroluminescent device containing an organic thermally delayed fluorescent material (DCPP-tBuTPA), comprising, from bottom to top, a glass substrate, an ITO anode electrode, a 40 nm thick TAPC hole transport layer, a 10 nm thick TCTA electron blocking layer, a 20 nm thick CBP:DCPP-tBuTPA emitting layer, a 55 nm thick TmPyPB electron transport layer, a 1 nm thick LiF electron injection layer, and a 100 nm thick Al cathode electrode; wherein the CBP:DCPP-tBuTPA emitting layer is a hybrid thin film formed by mixing the host material CBP and an organic thermally delayed fluorescent material with a molecular structure of DCPP-tBuTPA.

[0050] In this embodiment, luminescent layers containing 3wt%, 5wt%, 7wt%, and 10wt% of an organic thermally delayed fluorescent material with the molecular structure DCPP-tBuTPA were prepared. The luminescent performance of organic electroluminescent devices containing this DCPP-tBuTPA organic thermally delayed fluorescent material was tested, and the results were as follows: Figure 3 The electroluminescence spectrum shown indicates that as the proportion of DCPP-tBuTPA in the material increases, the emission peaks of the device gradually increase, reaching 564 nm, 572 nm, 580 nm, and 584 nm, respectively, achieving red light emission. Figure 4 As shown in the external quantum efficiency diagram, the organic electroluminescent device fabricated using DCPP-tBuTPA material achieved a high EQE of 7.1%, as illustrated in Table 1.

[0051] Table 1. Data on organic electroluminescent devices containing organic thermally delayed fluorescence material (DCPP-tBuTPA)

[0052]

[0053] Example 2

[0054] This embodiment proposes an organic thermally delayed fluorescence material based on di-tert-butylaniline donor, DCPPy-tBuTPA, with the molecular structure shown below:

[0055]

[0056] The synthesis route is as follows:

[0057]

[0058] Specifically, the following steps are included:

[0059] Step 1: Add 1,10-phenanthroline-5,6-dione (210.19 mg, 1 mmol) and 2,3-diamino-5-bromopyridine (188.03 mg, 1 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Replace the nitrogen gas three times. Under nitrogen protection, use a 50 mL syringe to inject 30 mL of acetic acid into the round-bottom flask. Rotate the reaction in an oil bath at 120 °C. Detect the reaction using thin-layer chromatography (TCL). After the 1,10-phenanthroline-5,6-dione has completely reacted (reaction time 24 h), cool to room temperature and pour into ice-cold deionized water. Filter and dry the precipitate to obtain crude product C.

[0060] Step 2: Add crude C (362.19 mg, 1 mmol), 4',4'-di-tert-butyl-4-borate pinacol ester triphenylamine (531.85 mg, 1.1 mmol), and tetra(triphenylphosphine)palladium (115.56 mg, 0.1 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Purge the flask three times with nitrogen. Then, under nitrogen protection, sequentially inject 6 mL of 2M potassium carbonate aqueous solution and 24 mL of ultra-dry 1,4-dioxane. Rotate the flask during the reaction at 100°C in an oil bath. Utilize a thin-film magnet... TCL (Temperature Chromatography) was used for detection. After intermediate material A had completely reacted (reaction time 24 h), mixture D was obtained. After cooling to room temperature, 1,4-dioxane and water were removed by rotary evaporation. Then, mixture B was purified by silica gel column chromatography using a 1:20 (v / v) methanol and dichloromethane mixture as eluent. Finally, it was recrystallized with a dichloromethane and n-hexane mixture, filtered, dried, and further purified by sublimation under a temperature gradient in vacuum to obtain a pure, dark red powder (543 mg), with a yield of 85%. The ultra-dry 1,4-dioxane was defined as 1,4-dioxane with a water and oxygen content not exceeding 50 ppm.

[0061] In 10 -5 The absorption and emission spectra of an organic thermally delayed fluorescent material with the molecular structure DCPPy-tBuTPA were measured in a dilute toluene solution at room temperature, as shown in the figure. Figure 5 As shown, the absorption from 400 nm to 550 nm is a distinct CT absorption band, indicating that it has good thermo-induced delayed fluorescence characteristics; the emission peak in dilute toluene solution is 593 nm, indicating that it can achieve red light emission. Figure 6 The redox potential curve of DCPPy-tBuTPA was obtained by cyclic voltammetry (CV). From the initial oxidation position and the initial reduction position, its HOMO and LUMO energy levels are 5.20 eV and 3.60 eV, respectively. Its deep LUMO energy level can ensure the realization of organic thermoinduced delayed fluorescence red light emission.

[0062] This embodiment also provides an organic electroluminescent device containing an organic thermally delayed fluorescent material (DCPPy-tBuTPA), comprising, from bottom to top, a glass substrate, an ITO anode electrode, a 40 nm thick TAPC hole transport layer, a 10 nm thick TCTA electron blocking layer, a 20 nm thick CBP:DCPPy-tBuTPA emitting layer, a 55 nm thick TmPyPB electron transport layer, a 1 nm thick LiF electron injection layer, and a 100 nm thick Al cathode electrode; wherein the CBP:DCPPy-tBuTPA emitting layer is a hybrid thin film formed by mixing the host material CBP and an organic thermally delayed fluorescent material with a molecular structure of DCPPy-tBuTPA.

[0063] In this embodiment, luminescent layers containing 3wt%, 5wt%, 7wt%, and 10wt% of an organic thermally delayed fluorescent material with the molecular structure DCPPy-tBuTPA were prepared. The luminescent performance of organic electroluminescent devices containing this organic thermally delayed fluorescent material was tested, and the results were as follows: Figure 7 The electroluminescence spectrum shown indicates that as the proportion of DCPPy-tBuTPA in the material increases, the emission peaks of the device gradually increase, reaching 588nm, 600nm, 604nm, and 612nm respectively, achieving red light emission. Figure 8 The external quantum efficiency plot shown indicates that the maximum EQE of the electroluminescent device fabricated using DCPPy-tBuTPA material reaches 11.7%, as shown in Table 2.

[0064] Table 2 Data on organic electroluminescent devices containing organic thermally delayed fluorescence material (DCPPy-tBuTPA)

[0065]

[0066] Example 3

[0067] This embodiment proposes an organic thermally delayed fluorescence material based on di-tert-butylaniline donor, DCPPm-tBuTPA, with the molecular structure shown below:

[0068]

[0069] The synthesis route is as follows:

[0070]

[0071] Specifically, the following steps are included:

[0072] Step 1: Add 5-bromo-2,3-diaminopyrazine (189.02 mg, 1 mmol), 4',4'-di-tert-butyl-4-boronate triphenylamine (531.85 mg, 1.1 mmol), and tetra(triphenylphosphine)palladium (115.56 mg, 0.1 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Purge the flask three times with nitrogen. Then, under nitrogen protection, sequentially inject 6 mL of 2M potassium carbonate aqueous solution and 24 mL of ultra-dry 1,4-dioxane. Incubate the mixture in an oil bath at 100 °C. Rotational reaction; thin-layer chromatography (TCL) was used for detection. After the 5-bromo-2,3-diaminopyrazine had completely reacted (reaction time 24 h), mixture E was obtained. After cooling to room temperature, 1,4-dioxane and water were removed by rotary evaporation. Then, a mixed solution of methanol and dichloromethane with a volume ratio of 1:20 was used as the eluent to purify mixture E by silica gel column chromatography. Finally, after recrystallization, filtration and drying, a relatively pure intermediate E was obtained. The ultra-dried 1,4-dioxane was 1,4-dioxane with a water and oxygen content not exceeding 50 ppm.

[0073] Step 2: Add intermediate E (465.65 mg, 1 mmol) and 1,10-phenanthroline-5,6-dione (231.21 mg, 1.1 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Purge the flask three times with nitrogen. Under nitrogen protection, inject 30 mL of acetic acid into the flask using a 50 mL syringe. Rotate the flask during the reaction at 120 °C in an oil bath. Detect the reaction using thin-layer chromatography (TCL). Wait until intermediate E has completely reacted (reaction 2) before proceeding. After 4 hours, mixture F was obtained. After cooling to room temperature, mixture F was extracted with water and dichloromethane. Then, dichloromethane and acetic acid were removed by rotary evaporation. Then, mixture F was purified by silica gel column chromatography using a mixed solution of methanol and dichloromethane at a volume ratio of 1:20 as the eluent. Finally, it was recrystallized with a mixed solution of dichloromethane and n-hexane. After filtration and drying, it was further purified by sublimation under vacuum through a temperature gradient to obtain a pure purple-red powder (480 mg) with a yield of 75%.

[0074] In 10 -5 The absorption and emission spectra of an organic thermally delayed fluorescent material with the molecular structure DCPPm-tBuTPA were measured in a dilute toluene solution at room temperature, as shown in the figure. Figure 9 As shown, the absorption from 425 nm to 625 nm is a distinct CT absorption band, indicating that it has good thermo-induced delayed fluorescence characteristics; the emission peak in dilute toluene solution is 642 nm, indicating that it can achieve red light emission. Figure 10The redox potential curve of DCPP-tBuTPA was obtained by cyclic voltammetry (CV). From the initial oxidation position and the initial reduction position, its HOMO and LUMO energy levels are 5.19 eV and 3.68 eV, respectively. Its deep LUMO energy level can ensure the realization of organic thermoinduced delayed fluorescence red light emission.

[0075] This embodiment also provides an organic electroluminescent device containing an organic thermally delayed fluorescent material (DCPPm-tBuTPA), comprising, from bottom to top, a glass substrate, an ITO anode electrode, a 40 nm thick TAPC hole transport layer, a 10 nm thick TCTA electron blocking layer, a 20 nm thick CBP:DCPP-tBuTPA emitting layer, a 55 nm thick TmPyPB electron transport layer, a 1 nm thick LiF electron injection layer, and a 100 nm thick Al cathode electrode; wherein the CBP:DCPPm-tBuTPA emitting layer is a hybrid thin film formed by mixing the host material CBP and an organic thermally delayed fluorescent material with a molecular structure of DCPPm-tBuTPA.

[0076] In this embodiment, luminescent layers containing 3wt%, 5wt%, 7wt%, and 10wt% of an organic thermally delayed fluorescent material with the molecular structure DCPPm-tBuTPA were prepared. The luminescent performance of organic electroluminescent devices containing this organic thermally delayed fluorescent material was tested, and the results were as follows: Figure 11 The electroluminescence spectrum shown indicates that as the proportion of DCPPm-tBuTPA in the material increases, the emission peaks of the device gradually increase, reaching 648 nm, 656 nm, 668 nm, and 672 nm, respectively, achieving red light emission. Figure 12 As shown in the external quantum efficiency diagram, the electroluminescent device fabricated using DCPPm-tBuTPA material achieves an EQQ of nearly 8%, as shown in Table 3.

[0077] Table 3. Data on organic electroluminescent devices containing organic thermally delayed fluorescence material (DCPPm-tBuTPA)

[0078]

[0079] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for producing an organic thermally delayed fluorescent material based on a di-tert-butylphenylamine donor, characterized by, The molecular structure of the organic thermally delayed fluorescence material based on di-tert-butyl aniline donor is as follows: DCPPy-tBuTPA: The specific synthesis process includes the following steps: Step 1: 1,10-phenanthroline-5,6-dione and 2,3-diamino-5-bromopyridine are added to a round-bottom flask in a molar ratio of 1:1, acetic acid is added under nitrogen protection, a mixed solution A of 1,10-phenanthroline-5,6-dione with a concentration of 0.03-0.05 mol / L is obtained, and the reaction is rotated at a temperature of 110-120°C; after the complete reaction of 1,10-phenanthroline-5,6-dione, deionized water is added for filtration, and the crude product A is obtained after drying; Step 2: crude product A, 4'.4'-di-tert-butyl-4-boronic pinacol triphenylamine, and tetrakis(triphenylphosphine)palladium are added to a round-bottom flask in a molar ratio of 1:(1.1-1.3):(0.05-0.1), and then super-dry 1,4-dioxane and a 2M potassium carbonate aqueous solution with a volume ratio of 4:1 are added under nitrogen protection to obtain a mixed solution B of crude product A with a concentration of 0.03-0.05 mol / L, and the reaction is carried out at a temperature of 90-100°C; after the complete reaction of crude product A, a mixture B is obtained, and after cooling to room temperature, 1,4-dioxane and water are removed, then a mixed solution of methanol and dichloromethane with a volume ratio of 1:20 is used as an eluent, and the mixture B is purified by silica gel column chromatography, and finally, after recrystallization, suction filtration, and drying, the organic thermally delayed fluorescence material is further purified by temperature gradient sublimation in a vacuum to obtain the organic thermally delayed fluorescence material.

2. The method for preparing the organic heat-resistance delayed fluorescence material based on di-tert-butylphenylamine donor according to claim 1, characterized in that, The water oxygen content of the super-dry 1,4-dioxane is not more than 50 ppm.

3. A method for producing an organic thermally delayed fluorescent material based on a di-tert-butylphenylamine donor, characterized by, The organic thermally delayed fluorescence material with a molecular structure of DCPPm-tBuTPA The specific synthesis process includes the following steps: Step 1: 5-bromo-2,3-diaminopyrazine, 4'.4'-di-tert-butyl-4-boronic pinacol triphenylamine, and tetrakis(triphenylphosphine)palladium are added to a round-bottom flask in a molar ratio of 1:(1.1-1.3):(0.05-0.1), and then super-dry 1,4-dioxane and a 2M potassium carbonate aqueous solution with a volume ratio of 4:1 are added under nitrogen protection to obtain a mixed solution E of 5-bromo-2,3-diaminopyrazine with a concentration of 0.03-0.05 mol / L, and the reaction is carried out at a temperature of 90-100°C; after the complete reaction of 5-bromo-2,3-diaminopyrazine, a mixture E is obtained, and after cooling to room temperature, 1,4-dioxane and water are removed, then a mixed solution of methanol and dichloromethane with a volume ratio of 1:20 is used as an eluent, and the mixture E is purified by silica gel column chromatography, and finally, after recrystallization, suction filtration, and drying, the intermediate E is obtained; Step 2: Intermediate E and 1,10-phenanthroline-5,6-dione are added to a round-bottom flask in a molar ratio of 1:(1.1-1.3), acetic acid is added under nitrogen protection to obtain a mixed solution F with a concentration of 0.03-0.05 mol / L of intermediate E, and the reaction is rotated at a temperature of 110-120°C; after the complete reaction of intermediate E, the mixture F is extracted with water and dichloromethane in a volume ratio of 2:1, dichloromethane and acetic acid are removed, and then a mixed solution of methanol and dichloromethane in a volume ratio of 1:20 is used as an eluent to purify the mixture F by silica gel column chromatography, and after recrystallization, suction filtration and drying, the organic thermally delayed fluorescent material is further purified by temperature gradient sublimation in a vacuum.

4. An organic electroluminescent device comprising an organic thermally delayed fluorescent material based on a di-tert-butylaniline donor, characterized in that The light-emitting layer comprises a host material and an organic thermally delayed fluorescent material based on a di-tert-butylphenylamine donor; wherein the organic thermally delayed fluorescent material based on the di-tert-butylphenylamine donor is obtained by the preparation method of claim 1 or claim 3; and the mass fraction of the organic thermally delayed fluorescent material in the light-emitting layer is 3-10%.

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