Diptycene bridging-based endothermic delayed fluorescent material as well as preparation method and application thereof

Abstract

The invention provides a diptycene bridging-based endothermic delayed fluorescent material and a preparation method and application thereof, and belongs to the technical field of organic luminescent materials, the diptycene bridging-based endothermic delayed fluorescent material is obtained by introducing donor and acceptor fragments which are easy to form hydrogen bonds to two sides of a diptycene molecule, in the preparation process, the acceptor raw material is terpyridyl or triphenyltriazine at different substitution positions, and the diptycene bridging-based endothermic delayed fluorescent material can be used for preparing and the donor material is 10-phenyl phenoxazine, phenoxazine, phenothiazine or 9, 9-dimethyl acridine. According to the invention, the advantages of the exciplex are ensured, and adverse factors such as low kr in the exciplex and susceptibility to non-radiation quenching and doping concentration influence are avoided, so that various properties of the exciplex OLED are improved. Wherein the diptycene, as a steric hindrance group, not only can prevent direct intramolecular charge transfer, but also has good rigidity, so that the endothermic delayed fluorescent material has good thermal stability; due to the existence of multiple intermolecular hydrogen bonds, the endothermic delayed fluorescent material has good carrier transport capacity.

Description

Technical Field

[0001] This invention belongs to the field of organic light-emitting materials technology, specifically relating to endothermic delayed fluorescent materials based on diene bridging, their preparation methods, and applications. Background Technology

[0002] In 1987, Professor Qingyun Deng and others reported the first practical double-layer heterojunction organic light-emitting diode (OLED) in *Applied Physics Letters*, which exhibited extremely low driving voltage and considerably high energy efficiency compared to previously reported devices. The luminescent material used in this report was a fluorescent material that utilizes singlet excitons for light emission. According to spin statistics, singlet excitons account for only 25% of the total generated excitons, which significantly limits the development of OLED devices. In phosphorescent materials, the spin-orbit coupling effect of heavy atoms in precious metals such as platinum and iridium allows triplet excitons to emit phosphorescence at room temperature, breaking through the efficiency limit of fluorescent OLEDs and achieving a qualitative leap in OLED performance. Currently, phosphorescent OLED devices remain the mainstream in commercial production. However, the long-term and large-scale use of precious metals such as platinum and iridium will inevitably lead to increasing material costs and environmental pollution problems.

[0003] The fabrication of high-efficiency OLED devices based on metal-free, purely organic materials holds significant implications for the future applications of organic electroluminescence technology. Thermally activated delayed fluorescence (TADF) is one of the most successful methods, and a wealth of novel material design strategies have been accumulated. Due to the extremely small energy difference between the singlet and triplet excited states, TADF materials can utilize the inverse gap crossing channel to convert triplet excitons into singlet excitons, followed by radiative transitions to release photons, theoretically achieving 100% internal quantum efficiency. However, since the internal quantum efficiency is close to the theoretical limit, the external quantum efficiency (EQE) of TADF OLEDs is increasingly constrained by the light output efficiency.

[0004] Excitocomplexes, due to the donor and acceptor being distributed on different fragments, naturally possess TADF (Transient Amplitude Difference) properties and have great development potential. Currently, excitocomplex TADFs still have ample room for development, but relatively low emission efficiency is one of the main obstacles. Spatially separated HOMO and LUMO (Homogeneous-Large-Mean Interval) results in low transition dipoles, leading to a low kr (radiative transition rate) for excited recombination emission, and severe susceptibility to non-radiative quenching. Another problem restricting the development of excitocomplex TADFs is the severe concentration quenching. Therefore, it is necessary to design new molecular systems that, while retaining the advantages of excitocomplexes, improve upon the problems of low kr and concentration quenching present in current excitocomplexes. Summary of the Invention

[0005] To address the issues of low kr and concentration quenching in existing exciton complex systems, this invention provides an endothermic delayed fluorescence material based on diene bridging, its preparation method, and its applications. By employing steric hindrance groups of specific sizes to isolate D / A groups, exciton complex emission is achieved within a single molecule. This retains the advantages of exciton complex emission while solving the problem of low kr in exciton complex systems. Furthermore, by utilizing multiple hydrogen bond active sites in the donor-acceptor fragments, a robust hydrogen bond network is formed to enhance carrier transport. This also stabilizes the molecular conformation, inhibits molecular stacking, and thus suppresses concentration quenching, allowing the material to maintain good device performance even at high concentrations.

[0006] The technical solution adopted in this invention is as follows: The endothermic delayed fluorescence material based on diene bridging has the structural formula shown in Formula 1:

[0007] Formula 1 Where R is a common donor fragment; R1 is a terpyridine or triphenyltriazine with different substitution positions.

[0008] Furthermore, R is selected from any of the following structures:

[0009] R1 is selected from any of the following structures: .

[0010] Furthermore, the endothermic delayed fluorescence material based on diene bridging specifically comprises the following materials 1 to 16: .

[0011] Another object of the present invention is to provide a method for preparing endothermic delayed fluorescence materials based on diene bridging, comprising the following steps: Step 1: Under acidic conditions, 2,6-dibromoanthraquinone is reduced to 2,6-dibromoanthracene using hypophosphorous acid and hydroiodic acid, which is used as intermediate A1.

[0012] Step 2: Intermediate A1 reacts with dimethyl butynedioate via the Diels-Alder reaction at 140℃~180℃ to obtain intermediate A2;

[0013] Step 3: Intermediate A2 is hydrolyzed under alkaline conditions to generate a carboxylate, which is then acidified with salt to obtain intermediate A3;

[0014] Step 4: Intermediate A3 undergoes a decarboxylation reaction catalyzed by copper powder at 180℃~200℃ to obtain intermediate A4; ; Step 5: Intermediate A4 and the acceptor material are coupled via a Suzuki-Miyaura reaction to obtain intermediate A5; wherein the acceptor material is 4'-[3-(4,4,5,5-tetramethyl-1,3,2-dioxoboronyl-2-yl)phenyl]-4,2':6',4''-terpyridine, 4'-[4-(4,4,5,5-tetramethyl-1,3,2-dioxoboronyl-2-yl)phenyl]-4,2':6',4''-terpyridine, 2,4-diphenyl-6-(p-tolyl)-1,3,5-triphenyltriazine, or 2,4-diphenyl-6-(m-tolyl)-1,3,5-triphenyltriazine;

[0015] Step 6: Intermediate A5 reacts with the donor material to obtain an endothermic delayed fluorescent material based on diene bridging; wherein, when the donor material is 10-phenylphenoxazine, the reaction is Suzuki-Miyaura coupling; when the donor material is phenoxazine, phenothiazine or 9,9-dimethylacridine, the reaction is CN coupling. .

[0016] Furthermore, glacial acetic acid is used as a solvent in step 1 to create acidic conditions.

[0017] Furthermore, in step 1, the molar ratio of 2,6-dibromoanthraquinone to hypophosphite and hydroiodic acid is 1:(12~15):(15~20).

[0018] Furthermore, in step 2, the mass ratio of intermediate A1 to dimethyl butynedioate is 1:(1.2~1.8).

[0019] Furthermore, the Suzuki-Miyaura coupling reaction in steps 5 and 6 uses potassium carbonate, potassium hydroxide, or sodium hydroxide as a base, 1,4-dioxane / deionized water or toluene / anhydrous ethanol as a solvent, and tetra-triphenylphosphine palladium or 1,1-bis(diphenylphosphine)ferrocene palladium dichloride as a catalyst.

[0020] Furthermore, in step 6, the CN coupling reaction uses sodium tert-butoxide or cesium carbonate as a base, toluene or o-xylene as a solvent, and palladium acetate or tris(dibenzylacetone)dipalladium as a catalyst.

[0021] Another object of the present invention is to provide an organic electroluminescent device comprising a light-emitting layer formed by mixing a host material and the diene-bridged endothermic delayed fluorescent material; wherein the mass percentage of the diene-bridged endothermic delayed fluorescent material in the light-emitting layer is not less than 25%.

[0022] The present invention can also provide another organic electroluminescent device, including a light-emitting layer, the material of which is the aforementioned endothermic delayed fluorescence material based on diene bridging, and the molecular structure is as follows: m-PXZ-Dp-Tpy .

[0023] 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; the light-emitting layer is located between the electron blocking layer and the electron transport layer.

[0024] Furthermore, the anode electrode is indium tin oxide (ITO); the hole transport layer is 4,4'-cyclohexylbis[N,N-di(4-methylphenyl)aniline (TAPC); the electron blocking layer is tris(4-carbazole-9-ylphenyl)amine (TCTA); the electron transport layer is 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]dipyridine (TmPyPB); the electron injection layer is LiF; the cathode electrode is metallic Al; and the host material in the light-emitting layer is 4,4-bis(9-carbazole)biphenyl (CBP).

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention designs an endothermic delayed fluorescence material based on diene bridging by introducing donor-acceptor fragments that easily form hydrogen bonds on both sides of the diene molecule. On the one hand, it maintains the advantages of excitocomplexes, with a small ΔEst and retains TADF characteristics. On the other hand, it avoids the disadvantages of excitocomplexes, such as low kr and susceptibility to nonradiative quenching and doping concentration. This improves the various performance characteristics of the corresponding excitocomplex OLED. 2. In this invention, dieptene, as a sterically hindered group, has a specific spatial size that can break molecular conjugation and prevent direct intramolecular charge transfer, thus achieving the design goal of a monomolecular excitocomplex. Furthermore, due to the good rigidity of dieptene itself, its introduction does not destroy the rigidity of the molecule, resulting in endothermic delayed fluorescence materials with good thermal stability, suitable for device fabrication by vacuum evaporation. Compared to tripterene molecules, dieptene has a more suitable size and rigidity, effectively increasing the distance between donors and acceptors, suppressing π-π stacking and exciton quenching caused by excessive proximity, without causing the distance between donors and acceptors to be too far, making it a better choice for preparing monomolecular excitocomplexes. 3. In this invention, the CH atoms on the terpyridine and triphenyltriazine rings can form hydrogen bonds with the N atoms on another terpyridine or triphenyltriazine ring, or form weaker hydrogen bonds with the N / O atoms on the donor fragment, thereby forming multiple intermolecular hydrogen bonds. However, due to the different positions of the N atoms, the directions of hydrogen bond formation are also different. Due to the presence of multiple intermolecular hydrogen bonds, the molecules are arranged in an orderly manner, which makes the endothermic delayed fluorescent material have good carrier transport capabilities. 4. The endothermic delayed fluorescence material based on diene bridging obtained in this invention can be applied to green and yellow-green delayed fluorescence OLEDs. Thanks to its strong rigidity and ordered arrangement between molecules, it achieves a high-efficiency light-emitting device. Due to the presence of the sterically hindered diene group and the formation of multiple hydrogen bond networks, the close packing between molecules is effectively suppressed, making the device exhibit excellent concentration insensitivity, which meets the requirements for commercial large-scale preparation. Therefore, the organic thermotropic delayed fluorescence material based on diene bridging has broad application prospects and is expected to be widely used in flat panel displays and solid-state lighting. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 The absorption-emission (Abs-FL) spectrum of the diene-bridged endothermic delayed fluorescent material with molecular structure m-PXZ-Dp-TPy obtained in Example 1 of this invention was tested in toluene at room temperature. Figure 2 The electroluminescence spectra of organic electroluminescent devices containing different proportions of m-PXZ-Dp-TPy obtained in Example 1 of the present invention are shown. Figure 3 The external quantum efficiency (EQE) of organic electroluminescent devices containing different proportions of m-PXZ-Dp-TPy obtained in Example 1 of the present invention is shown. Figure 4 The absorption-emission spectrum of the diene-bridged endothermic delayed fluorescent material with molecular structure p-PXZ-Dp-TPy obtained in Example 2 of this invention was tested in toluene at room temperature. Figure 5 The electroluminescence spectra of organic electroluminescent devices containing different proportions of p-PXZ-Dp-TPy obtained in Example 2 of the present invention are shown. Figure 6The external quantum efficiency diagrams are shown for the organic electroluminescent devices containing different proportions of p-PXZ-Dp-TPy obtained in Example 2 of this invention. Figure 7 The absorption-emission spectrum of the diene-bridged endothermic delayed fluorescent material with molecular structure p-PXZ-Dp-Trz obtained in Example 3 of this invention is measured in toluene at room temperature. Figure 8 The electroluminescence spectra of organic electroluminescent devices containing different proportions of p-PXZ-Dp-Trz obtained in Example 3 of the present invention are shown. Figure 9 The external quantum efficiency diagrams are shown for the organic electroluminescent devices containing different proportions of p-PXZ-Dp-Trz obtained in Example 3 of the present invention. Detailed Implementation

[0028] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims.

[0029] There are no particular restrictions on the source of any raw materials used in this invention; they can be purchased from the market or prepared using conventional methods known to those skilled in the art.

[0030] The purity of all raw materials used in this invention is not particularly limited, but analytical grade or the purity requirements conventional in the field of atomic layer deposition are preferred.

[0031] All raw materials and processes of this invention are designated by or abbreviated as conventional designations or abbreviations in the field. Each designation or abbreviation is clearly defined in its relevant application area. Those skilled in the art can purchase them from commercially available sources or prepare them by conventional methods, or implement them using appropriate equipment, based on the designation, abbreviation, and corresponding application.

[0032] To further illustrate the present invention, the following describes in detail the method for constructing nanomaterials based on a multi-component nitrite eutectic salt system provided by the present invention with reference to embodiments. However, it should be understood that these embodiments are implemented under the premise of the technical solution of the present invention, and detailed implementation methods and specific operation processes are given only to further illustrate the features and advantages of the present invention, and are not intended to limit the scope of the claims of the present invention. The scope of protection of the present invention is not limited to the following embodiments.

[0033] Example 1

[0034] This embodiment prepares a diene-bridged endothermic delayed fluorescence material with the molecular structure m-PXZ-Dp-Tpy as shown below:

[0035] Its synthetic route is as follows:

[0036] Step 1: 2,6-Dibromoanthraquinone (1.83 g, 5 mmol) was added to a 250 mL two-necked round-bottom flask equipped with a magnetic stirrer. Nitrogen gas was applied five times. 40 mL of glacial acetic acid was added as a solvent, followed by hypophosphorous acid (12.2 g, 60 mmol) and hydroiodic acid (16.84 g, 75 mmol). The mixture was stirred at 140 °C for two days. After the reaction was complete, the mixture was cooled to room temperature, deionized water was added, and the mixture was filtered to obtain a filter cake. The filter cake was dissolved in dichloromethane, and the reaction was extracted with deionized water and dichloromethane. The organic phase was dried over anhydrous sodium sulfate. The pale yellow intermediate A1 (1.13 g, 67% yield) was purified by silica gel column chromatography using pure petroleum ether as the eluent. Step 2: Add intermediate A1 (3.75 g, 11.23 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Replace the gas in the reaction system with nitrogen using the Schlenk operation. Then, under nitrogen protection, inject dimethyl butynedioate (2.28 mL, 18.61 mmol), add 4 mL of o-dichlorobenzene as solvent, and maintain the reaction at 140 °C for 6 h in an oil bath. Cool to room temperature and continue stirring for 16 h to obtain intermediate A2, i.e., diester. Step 3: Dissolve intermediate A2 in 75 mL of methanol, add 60 mL of 4.0 M sodium hydroxide methanol solution, heat to 60 °C and stir for 3 h, then cool to 0 °C, slowly add 80 mL of 4.0 M HCl solution, stir for 3 h, and a grayish-white precipitate is formed. Collect the precipitate, wash with a large amount of deionized water, and dry in a vacuum oven at 65 °C for 6 h to obtain a mixture containing intermediate A3. Step 4: Add freshly activated copper powder (1.06 g, 11.1 mmol) to the mixture containing intermediate A3 (5 g, 11.1 mmol), grind for 2 min, then transfer to a 50 mL round-bottom flask, add 17 mL of quinoline, heat to 180 ℃ and stir for 20 h; after the reaction is complete, cool to room temperature, add 100 mL of CH2Cl2, filter the resulting mixture, and wash the filtrate successively with 100 mL of 2 M NaOH, 100 mL of deionized water, 100 mL of 2 M HCl solution and 100 mL of brine to obtain the product solution; then dry the product solution with MgSO4, and purify by silica gel column chromatography to obtain a pale yellow oily product, namely intermediate A4 (1.66 g, yield 44.2%).

[0037] Step 5: Add intermediate A4 (1.00 g, 2.2 mmol), 4'-[3-(4,4,5,5-tetramethyl-1,3,2-dioxoboronyl-2-yl)phenyl]-4,2':6',4''-terpyridine (957 mg, 2.2 mmol), tetraphenylphosphine palladium (127 mg, 0.11 mmol), and potassium carbonate (1.21 g, 8.8 mmol) to a 50 mL two-necked round-bottom flask equipped with a magnetic stirrer. Then add 1,4-dioxane and deionized water (volume ratio 4:1) as solvents. React for 12 h. Monitor the reaction by thin-layer chromatography (TCL). After the reaction is complete, cool to room temperature, then extract the reaction solution with deionized water and dichloromethane. Dry the organic phase with anhydrous sodium sulfate and purify by silica gel column chromatography to obtain white intermediate A5. Step 6: Add intermediate A5 (0.8 g, 1.9 mmol) and phenoxazine (0.36 g, 1.9 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Under nitrogen protection, add tetrakis(triphenylphosphine)palladium (109 mg, 0.095 mmol) and sodium tert-butoxide (730 mg, 7.6 mmol), and then add toluene as a solvent. React for 12 h. After the reaction is complete as monitored by TCL, cool to room temperature, then extract the reaction solution with deionized water and dichloromethane, and dry the organic phase with anhydrous sodium sulfate. Purify the product m-PXZ-Dp-TPy (0.88 g, yield 82%) by silica gel column chromatography.

[0038] The m-PXZ-Dp-TPy obtained in this embodiment is used at 1*10 -5 A concentration of mmol / mL was dissolved in toluene solvent, and its absorption-emission spectrum at room temperature was measured, as follows: Figure 1 As shown, the visible absorption spectrum shows a sharp peak near 280 nm and a weak shoulder peak at 314 nm, corresponding to local excitation absorption, without obvious charge transfer excitation; correspondingly, the emission peak shows obvious charge transfer properties, with a peak value at 517 nm, proving the formation of a monomolecular excitosome complex.

[0039] This embodiment also provides an organic electroluminescent device containing m-PXZ-Dp-TPy, comprising, from bottom to top, a glass substrate, an ITO anode electrode, a 35 nm thick TAPC hole transport layer, a 10 nm thick TCTA electron blocking layer, a 20 nm thick CBP: m-PXZ-Dp-TPy 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: m-PXZ-Dp-TPy emitting layer is a thin film formed by mixing the host material CBP and a diene-bridged endothermic delayed fluorescence material with a molecular structure of m-PXZ-Dp-TPy obtained in this embodiment.

[0040] In this embodiment, light-emitting layers with m-PXZ-Dp-TPy doping ratios of 25%, 50%, 75%, and 100% (i.e., undoped devices without the host material) were prepared. The luminescent performance of the organic electroluminescent devices containing m-PXZ-Dp-TPy was tested, and the results were as follows: Figure 2 The electroluminescence spectra shown reveal that all four devices exhibit green light emission. With increasing m-PXZ-Dp-TPy ratio, the emission peaks gradually redshift to 536 nm, 540 nm, 548 nm, and 552 nm, respectively. Further, based on... Figure 3 The efficiency curves shown demonstrate that all four devices exhibit excellent performance, especially the devices at 75% and 100% concentrations, which possess maximum external quantum efficiencies of 7.27% and 6.43%, respectively. Performance data for the four devices are presented in Table 1. The optimal luminescence performance of this device is at a high level in the field of monomolecular excimer complexes. Furthermore, the presence of the sterically hindered diene group and various intermolecular hydrogen bonds suppresses excessive molecular stacking, allowing the device to maintain good performance even at high concentrations (75% and 100%), indicating excellent doping concentration insensitivity of the designed molecules.

[0041] Table 1 Doping ratio Emission peak (nm) Qi Liang (V) <![CDATA[Maximum brightness (cd / m 2 ).]]> CEmax(cd / A) PEmax (lm / W) EQEmax(%) 25% 536 3.7 2600 16.2 12.7 5.09 50% 540 3.65 7180 18.9 11.5 5.80 75% 548 3.50 9240 23.4 16.3 7.27 100% 552 3.50 8820 20.6 14.4 6.43 Example 2

[0042] This embodiment prepares a diene-bridged endothermic delayed fluorescence material with the molecular structure shown below: p-PXZ-Dp-Tpy

[0043] Its synthetic route is as follows:

[0044] Steps 1-4 are the same as steps 1-4 in Example 1; Step 5: Add intermediate A4 (1.00 g, 2.2 mmol), 4'-[4-(4,4,5,5-tetramethyl-1,3,2-dioxoboronylpentane-2-yl)phenyl]-4,2':6',4''-terpyridine (957 mg, 2.2 mmol), tetraphenylphosphine palladium (127 mg, 0.11 mmol), and potassium carbonate (1.21 g, 8.8 mmol) to a 50 mL two-necked round-bottom flask equipped with a magnetic stirrer. Then add 1,4-dioxane and deionized water (volume ratio 4:1) as solvents. React for 12 h. After the reaction is complete as monitored by thin-layer chromatography, cool to room temperature. Then extract the reaction solution with deionized water and dichloromethane, dry the organic phase with anhydrous sodium sulfate, and purify by silica gel column chromatography to obtain white intermediate A6. Step 6: Add intermediate A6 (0.8 g, 1.9 mmol) and phenoxazine (0.36 g, 1.9 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Under nitrogen protection, add tetrakis(triphenylphosphine)palladium (109 mg, 0.095 mmol) and sodium tert-butoxide (730 mg, 7.6 mmol), and then add toluene as a solvent. React for 12 h. After the reaction is complete as monitored by TCL, cool to room temperature, extract the reaction solution with deionized water and dichloromethane, and dry the organic phase with anhydrous sodium sulfate. Purify the product p-PXZ-Dp-TPy (0.61 g, 65% yield) by silica gel column chromatography.

[0045] The p-PXZ-Dp-TPy obtained in this embodiment is used at 1*10 -5 A concentration of mmol / mL was dissolved in toluene solvent, and its absorption-emission spectrum at room temperature was measured, as follows: Figure 4 As shown, the visible absorption spectrum shows a sharp peak near 280 nm corresponding to local excitation absorption, and a shoulder peak at 310 nm, without obvious charge transfer excitation; correspondingly, the emission peak shows obvious charge transfer properties, with a peak value at 513 nm, proving the formation of a monomolecular excitosome complex.

[0046] This embodiment also provides an organic electroluminescent device containing p-PXZ-Dp-TPy, comprising, from bottom to top, a glass substrate, an ITO anode electrode, a 35 nm thick TAPC hole transport layer, a 10 nm thick TCTA electron blocking layer, a 20 nm thick CBP: p-PXZ-Dp-TPy 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: p-PXZ-Dp-TPy emitting layer is a thin film formed by mixing the host material CBP and a diene-bridged endothermic delayed fluorescence material with a molecular structure of p-PXZ-Dp-TPy obtained in this embodiment.

[0047] In this embodiment, light-emitting layers with p-PXZ-Dp-TPy doping ratios of 25%, 50%, 75%, and 100% (i.e., undoped devices without the host material) were prepared. The luminescent performance of the organic electroluminescent devices containing p-PXZ-Dp-TPy was tested, and the results were as follows: Figure 5 The electroluminescence spectra shown reveal that all four devices exhibit yellow-green light emission. With increasing p-PXZ-Dp-TPy proportions, the emission peaks gradually redshift to 552 nm, 560 nm, 560 nm, and 564 nm, respectively. Further, based on... Figure 6 The efficiency curves shown demonstrate that all four groups of devices exhibit excellent performance, especially the devices with 25% and 50% doping ratios, which have maximum external quantum efficiencies of 7.82% and 7.67%, respectively. Even at 100% doping ratio, the maximum external quantum efficiency remains at 6.61%. Performance data for the four groups of devices are shown in Table 2. Due to the presence of the sterically hindered diene group and various intermolecular hydrogen bonds, excessive molecular packing is suppressed, resulting in excellent doping concentration insensitivity. This indicates that the addition of diene effectively suppresses concentration quenching.

[0048] Table 2 Doping ratio Emission peak (nm) Qi Liang (V) <![CDATA[Maximum brightness (cd / m 2 ).]]> CEmax(cd / A) PEmax (lm / W) EQEmax(%) 25wt% 552 3.8 9640 26.1 21..6 8.36 50wt% 560 3.9 14200 24.4 17.4 7.82 75wt% 560 3.7 14700 22.8 19.4 7.67 100% 564 3.7 13400 19.6 14.7 6.61 Example 3

[0049] This embodiment prepares a diene-bridged endothermic delayed fluorescence material with the molecular structure shown below: p-PXZ-Dp-Trz

[0050] Its synthetic route is as follows:

[0051] Steps 1-4 are the same as steps 1-4 in Example 1; Step 5: Add intermediate A4 (1.00 g, 2.2 mmol), 2,4-diphenyl-6-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborhexacyclopentan-2-yl)phenyl)-1,3,5-triazine (957 mg, 2.2 mmol), tetratriphenylphosphine palladium (127 mg, 0.11 mmol), and potassium carbonate (1.21 g, 8.8 mmol) to a 50 mL two-necked round-bottom flask equipped with a magnetic stirrer. Then add 1,4-dioxane and deionized water (volume ratio 4:1) as solvents. React for 12 h. After the reaction is complete as monitored by thin-layer chromatography, cool to room temperature. Then extract the reaction solution with deionized water and dichloromethane, dry the organic phase with anhydrous sodium sulfate, and purify by silica gel column chromatography to obtain white intermediate A7. Step 6: Add intermediate A6 (0.8 g, 1.9 mmol) and phenoxazine (0.36 g, 1.9 mmol) to a 100 mL two-necked round-bottom flask equipped with a magnetic stirrer. Under nitrogen protection, add tetrakis(triphenylphosphine)palladium (109 mg, 0.095 mmol) and sodium tert-butoxide (730 mg, 7.6 mmol), and then add toluene as a solvent. React for 12 h. After the reaction is complete as monitored by TCL, cool to room temperature, extract the reaction solution with deionized water and dichloromethane, and dry the organic phase with anhydrous sodium sulfate. Purify the product p-PXZ-Dp-Trz (0.68 g, 72% yield) by silica gel column chromatography.

[0052] The p-PXZ-Dp-Trz obtained in this embodiment is used at 1*10 -5 A concentration of mmol / mL was dissolved in toluene solvent, and its absorption-emission spectrum at room temperature was measured, as follows: Figure 7 As shown, the absorption peak at 320 nm in the visible absorption spectrum is attributed to the π–π* transition within the molecule; the emission peak exhibits obvious charge transfer properties, with a peak value at 491 nm, proving the formation of a monomolecular excimer complex.

[0053] This embodiment also provides an organic electroluminescent device containing p-PXZ-Dp-Trz, comprising, from bottom to top, a glass substrate, an ITO anode electrode, a 35 nm thick TAPC hole transport layer, a 10 nm thick TCTA electron blocking layer, a 20 nm thick CBP: p-PXZ-Dp-Trz 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: p-PXZ-Dp-Trz emitting layer is a thin film formed by mixing the host material CBP and a diene-bridged endothermic delayed fluorescence material with a molecular structure of p-PXZ-Dp-Trz obtained in this embodiment.

[0054] In this embodiment, light-emitting layers with p-PXZ-Dp-Trz doping ratios of 25%, 50%, 75%, and 100% (i.e., undoped devices without the host material) were prepared. The luminescent performance of the organic electroluminescent devices containing p-PXZ-Dp-Trz was tested, and the results were as follows: Figure 8 The electroluminescence spectra shown indicate that all four devices exhibit green light emission. With the increase of the p-PXZ-Dp-Trz ratio, the emission peaks gradually redshift to 540 nm, 544 nm, 552 nm, and 552 nm, respectively. Further, based on... Figure 9 The efficiency curves shown demonstrate that all four device groups exhibit excellent performance, especially the 75% dopant group, which achieves a maximum external quantum efficiency of 6.20%; even at 100% dopant, it maintains a maximum external quantum efficiency of 5.35%. Performance data for the four device groups are shown in Table 3. Due to the presence of the sterically hindered dierene group and various intramolecular and intermolecular hydrogen bonds, excessive molecular packing is suppressed, resulting in excellent doping concentration insensitivity. This indicates that the addition of dierene effectively suppresses concentration quenching. This also demonstrates that the dierene group has a certain degree of universality in suppressing concentration quenching.

[0055] Table 3 Doping ratio Emission peak (nm) Qi Liang (V) <![CDATA[Maximum brightness (cd / m 2 )]]> CEmax(cd / A) PEmax (lm / W) EQEmax(%) 25wt% 540 3.2 4050 8.16 8.91 3.12 50wt% 544 3.2 8820 16.5 14.0 5.03 75wt% 552 3 8420 19.9 15.6 6.20 100% 552 3 8620 17.4 13.7 5.35 .

[0056] The foregoing provides a detailed description of the endothermic delayed fluorescence material based on diene bridging, its preparation method, and its applications. Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of these embodiments are merely illustrative of the methods and core ideas of this invention, including the best mode, and are intended to enable any person skilled in the art to practice this invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the wording of the claims, or if they include equivalent structural elements that are not substantially different from the wording of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A diene-bridged endothermic delayed fluorescence material, characterized in that, Its structural formula is shown in Equation 1: ； Formula 1 Where R is the donor fragment; R1 is a terpyridine or triphenyltriazine with different substitution positions.

2. The endothermic delayed fluorescence material based on diene bridging according to claim 1, characterized in that, R is selected from any of the following structures: ； R1 is selected from any of the following structures: 。 3. A method for preparing endothermic delayed fluorescent materials based on diene bridging, characterized in that, Includes the following steps: Step 1: Under acidic conditions, 2,6-dibromoanthraquinone is reduced to 2,6-dibromoanthracene using hypophosphorous acid and hydroiodic acid, which is used as intermediate A1. Step 2: Intermediate A1 reacts with dimethyl butynedioate via the Diels-Alder reaction at 140℃~180℃ to obtain intermediate A2; Step 3: Intermediate A2 is hydrolyzed under alkaline conditions to generate a carboxylate, which is then acidified with salt to obtain intermediate A3; Step 4: Intermediate A3 undergoes a decarboxylation reaction catalyzed by copper powder at 180℃~200℃ to obtain intermediate A4; Step 5: Intermediate A4 and the acceptor material are coupled via a Suzuki-Miyaura reaction to obtain intermediate A5; wherein the acceptor material is 4'-[3-(4,4,5,5-tetramethyl-1,3,2-dioxoboronyl-2-yl)phenyl]-4,2':6',4''-terpyridine, 4'-[4-(4,4,5,5-tetramethyl-1,3,2-dioxoboronyl-2-yl)phenyl]-4,2':6',4''-terpyridine, 2,4-diphenyl-6-(p-tolyl)-1,3,5-triphenyltriazine, or 2,4-diphenyl-6-(m-tolyl)-1,3,5-triphenyltriazine; Step 6: Intermediate A5 reacts with the donor material to obtain the endothermic delayed fluorescent material based on diene bridging as described in claim 2; wherein, when the donor material is 10-phenylphenoxazine, the reaction is Suzuki-Miyaura coupling; when the donor material is phenoxazine, phenothiazine, or 9,9-dimethylacridine, the reaction is CN coupling.

4. The method for preparing the endothermic delayed fluorescent material based on diene bridging according to claim 3, characterized in that, In step 1, glacial acetic acid is used as the solvent.

5. The method for preparing the endothermic delayed fluorescent material based on diene bridging according to claim 3, characterized in that, In step 1, the molar ratio of 2,6-dibromoanthraquinone to hypophosphite and hydroiodic acid is 1:(12~15):(15~20).

6. The method for preparing the endothermic delayed fluorescent material based on diene bridging according to claim 3, characterized in that, In step 2, the mass ratio of intermediate A1 to dimethyl butynedioate is 1:(1.2~1.8).

7. The method for preparing the endothermic delayed fluorescent material based on diene bridging according to claim 3, characterized in that, In steps 5 and 6, the Suzuki-Miyaura coupling reaction uses potassium carbonate, potassium hydroxide, or sodium hydroxide as a base, 1,4-dioxane / deionized water or toluene / anhydrous ethanol as a solvent, and tetratetraphenylphosphine palladium or 1,1-bis(diphenylphosphine)ferrocene palladium dichloride as a catalyst; in step 6, the CN coupling reaction uses sodium tert-butoxide or cesium carbonate as a base, toluene or o-xylene as a solvent, and palladium acetate or tris(dibenzylideneacetone)dipalladium as a catalyst.

8. An organic electroluminescent device, characterized in that, It includes a light-emitting layer composed of a main material and a diene-bridged endothermic delayed fluorescent material as described in claim 2; wherein the mass percentage of the diene-bridged endothermic delayed fluorescent material in the light-emitting layer is not less than 25%.

9. The organic electroluminescent device according to claim 8, characterized in that, It also 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; the light-emitting layer is located between the electron blocking layer and the electron transport layer.

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