A boron-containing multiple resonance type thermally activated delayed fluorescence material and an organic electroluminescent device thereof

Abstract

The application belongs to the field of organic electroluminescent materials, and particularly discloses a boron-containing multiple resonance type thermally activated delayed fluorescence material and an organic electroluminescent device. The material adopts a single spiro carbon locking structure, restricts MR mother nucleus conformation vibration by means of a spiro carbon covalent bridge, suppresses excited state relaxation, narrows a spectrum, reduces non-radiation transition, and improves fluorescence quantum efficiency. A vertical three-dimensional spiro ring generates steric hindrance, suppresses intermolecular π-π stacking, relieves aggregation and concentration quenching, and is suitable for wide doping concentration. The spiro carbon condensed ring improves the thermal stability of the molecule, prevents film crystallization and phase separation, improves the stability of the film layer, and prolongs the service life of the device. Compared with a double spiro carbon structure, the single spiro carbon breaks the center symmetry of the mother nucleus, realizes asymmetric separation of the front orbital, reduces the single triplet energy level difference, accelerates the reverse intersystem crossing, and improves the device efficiency and service life under large current.

Description

Technical Field

[0001] This invention relates to the field of organic electroluminescent materials technology, and in particular to a boron-containing multiple resonance thermally activated delayed fluorescence material and its organic electroluminescent device. Background Technology

[0002] OLED technology, with its advantages of self-emission, high contrast, wide viewing angle, and flexibility, has become the mainstream technology for display products such as smartphones, televisions, and AR / VR devices. To achieve display devices that comply with the BT.2020 ultra-high-definition color standard set by the International Telecommunication Union (ITU-R), narrow-spectrum, high-color-purity red, green, and blue primary color emitting materials are required. Traditional fluorescent, phosphorescent, and thermally activated delayed fluorescence (TADF) materials have significant drawbacks: fluorescent materials typically have a half-width at half-maximum (FWHM) greater than 50 nm; phosphorescent materials rely on noble metals (such as Ir and Pt), resulting in high costs and significant spectral broadening; and traditional TADF materials, due to significant relaxation in the excited-state structure, have FWHMs mostly between 70 and 100 nm, all of which fail to meet the BT.2020 standard's requirements for green light.

[0003] The multiple resonance (MR) strategy proposed in 2016 constructs a rigid polycyclic aromatic hydrocarbon framework doped with boron (B) and nitrogen (N). By utilizing the resonance between the empty orbitals of B atoms and the lone pair electrons of N atoms in the para position, the excited state structural relaxation is restricted, which can achieve narrow spectral emission with a half width at half maximum (WWHM) of less than 25 nm. This provides a feasible path for BT.2020 compatible luminescent materials.

[0004] Currently reported MR-TADF materials still face several bottlenecks: the conjugated length of the classic B / N fused-ring core is limited, resulting in a relatively short emission wavelength. Furthermore, the strong planarity of the molecules makes them prone to π-π stacking, leading to severe aggregation-induced quenching (ACQ) and a narrow doping concentration window. Existing modification strategies mostly suppress stacking through steric hindrance from peripheral substituents, but they cannot restrict conformational relaxation at the framework level, making it difficult to simultaneously achieve synergistic optimization of spectral redshift, narrow full width at half maximum (FWHM), high doping stability, and long lifetime. Therefore, developing MR-TADF materials that combine high color purity, wide doping stability, high efficiency, and long lifetime is crucial for promoting the industrialization of ultra-high-definition OLED technology.

[0005] Therefore, existing technologies still need improvement and development. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the present invention provides a boron-containing multiple resonance thermally activated delayed fluorescence material and an organic electroluminescent device thereof. The compound of the present invention can be used as a doping material for the light-emitting layer of an organic electroluminescent device.

[0007] To achieve this objective, the present invention adopts the following technical solution: A boron-containing multiple resonance thermally activated delayed fluorescence material, the molecular structure of which is shown in general formula (I) and general formula (II): ; Rings A, B, C, and D are each independently selected from substituted or unsubstituted C6 to C6 rings. 24 Aromatic rings, substituted or unsubstituted C5-C 24 Mixed fragrance ring; Rings A and B, and rings C and D are not connected, or are connected by single bonds, O, S, or Se; R1 and R2 may be the same or different, and each is independently selected from substituted or unsubstituted C1 to C2. 10 Alkyl, substituted or unsubstituted C6-C 24 Aryl group, and R1 and R2 are not connected to each other, or are connected by single bonds, O, S, or Se; R3 through R8 are each independently selected from hydrogen atoms, substituted or unsubstituted C1 through C8 atoms. 10 alkyl; X1 and X2 are each independently selected from NR 11 One of O, S, and Se; R 11 Selected from substituted or unsubstituted C6-C 24 Aryl; When substitution is present, each substituent independently represents a monosubstituted group up to the maximum permissible number of substitutions, optionally selected from deuterium, tritium, halogen, cyano, trifluoromethyl, C1-C2. 12 Alkyl, C1-C 24 Alkoxy, C1-C 24 Alkylthio group, C3-C 24 Cycloalkyl, C1-C6 alkyl-substituted or unsubstituted aromatic amino groups, C1-C6 alkyl-substituted or unsubstituted C6-C6 alkyl groups 60 Aryl, C1-C6 alkyl substituted or unsubstituted C4-C6 60 Heteroaryl groups, wherein the heteroatoms in the heteroaryl group or heteroaryl ring are selected from one or more of N, O, S, Se, Te, or B.

[0008] As a preferred embodiment of the present invention, rings A, B, C, and D are each independently represented as substituted or unsubstituted C6 to C6. 18 The fragrance ring.

[0009] As a preferred embodiment of the present invention, ring A, ring B, ring C, and ring D are each independently represented as a substituted or unsubstituted phenyl, a substituted or unsubstituted biphenyl, or a substituted or unsubstituted naphthyl group.

[0010] Preferably, R1 and R2 may be the same or different, and each is independently selected from C1 to C6 alkyl, substituted or unsubstituted C6 to C6 alkyl groups. 12Aryl.

[0011] As a preferred embodiment of the present invention, X1 and X2 are each independently represented as NR. 11 One of O, S, R 11 The phenyl group can be substituted or unsubstituted.

[0012] As a preferred embodiment of the present invention, the boron-containing multiple resonance thermally activated delayed fluorescence material has a structure selected from any one of the following compounds: ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; .

[0013] The present invention also provides an organic electroluminescent device having an anode, a cathode, and an organic layer, wherein the organic layer includes a light-emitting layer, and the light-emitting side includes the aforementioned boron-containing multiple resonance thermally activated delayed fluorescence material; the material serves as a light-emitting dopant in the light-emitting layer.

[0014] The beneficial effects of this invention are as follows: The boron-containing multi-resonance thermally activated delayed fluorescence material provided by this invention is based on the "single-spiral carbon locking strategy". Compared with the prior art, (1) the covalent bridging effect of the spirocarbon atoms can constrain the conformational vibration of the MR core at the framework level, greatly suppress the excited state structural relaxation, reduce the spectral broadening caused by the vibrational energy level, and at the same time reduce the non-radiative transition probability and improve the fluorescence quantum efficiency; (2) the spiro-ring unit has a vertically intersecting three-dimensional structure, which can form a significant steric barrier around the molecule, effectively blocking the planar π-π stacking between MR molecules, significantly suppressing the aggregation-induced quenching (ACQ) and concentration quenching effects, so that the material can maintain high luminescence efficiency in a wide doping concentration range; (3) the spirocarbon fused ring structure can significantly increase the glass transition temperature (T) of the molecule. g ) and thermal decomposition temperature (T) d ), enhance the thermal stability of the material; at the same time, the three-dimensional structure can suppress thin film crystallization and phase separation, improve the morphological stability of the light-emitting film, and ultimately effectively extend the working life of OLED devices; (4) compared with dual-spiral carbon-locked compounds, the single-spiral carbon-locked unilateral modification characteristics will break the central symmetry of the B / N multiple resonance core, causing the frontier molecular orbitals to exhibit spatially asymmetrical separation distribution, thereby reducing the single-triple state energy level difference (ΔE). ST This significantly improves the rate and efficiency of reverse system crosstalk (RISC), allowing more triplet excitons to be converted into radiative singlet excitons, which can improve device efficiency under high current density and extend device lifetime. Detailed Implementation

[0015] The technical solution of the present invention will be clearly and completely described below with reference to preparation examples and device examples. Obviously, the described examples are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] Preparation Examples The present invention does not impose any particular restrictions on the source of the raw materials used in the following embodiments, which can be commercially available products or prepared by methods known to those skilled in the art.

[0017] Example 1: Preparation of Compound 5 ; Synthesis of 5-3: 5-1 (0.38 g, 1.2 mmol), 5-2 (0.20 g, 1.2 mmol), Pd2(dba)3 (20.0 mg, 0.02 mmol), tri-tert-butylphosphide tetrafluoroborate (14.0 mg, 0.05 mmol), and sodium tert-butoxide (0.7 g, 7.3 mmol) were mixed in dry toluene (20 mL) and refluxed under nitrogen for 24 h. After cooling to room temperature, the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 5-3 (0.35 g, yield 82.1%). LC-MS analysis by liquid chromatography-mass spectrometry yielded the following m / z values: theoretical value 358.66, measured value 358.79. Synthesis of 5-5: Under a nitrogen atmosphere, a solution of n-butyllithium in n-hexane (3.6 mL, 2.5 M, 8.4 mmol) was slowly added dropwise to a solution of 5-3 (3.01 g, 8.4 mmol) in anhydrous tetrahydrofuran (50 mL) at -78ºC. After stirring for 2 h, a solution of 5-4 (1.82 g, 10.1 mmol) in anhydrous tetrahydrofuran was slowly added at -60ºC, also under a nitrogen atmosphere. Subsequently, the reaction mixture was slowly heated to room temperature and stirred overnight. The aqueous phase was separated and extracted three times with dichloromethane (100 mL). The organic layers were combined, dried over sodium sulfate, and filtered. After removing the solvent under reduced pressure, the crude product was dissolved in anhydrous dichloromethane (100 mL), and then methanesulfonic acid (5 mL) was slowly added at room temperature. The reaction mixture was stirred for 3 hours, then slowly quenched with 100 mL of sodium bicarbonate aqueous solution to separate the aqueous phase, which was extracted with dichloromethane (50 mL). The organic layers were combined, dried over sodium sulfate, filtered, and concentrated by rotary evaporation. The product was further purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 5-5 (1.55 g, yield 41.8%). LC-MS analysis by liquid chromatography-mass spectrometry yielded the following values: theoretical value 441.96, measured value 442.10. Synthesis of 5-8: 5-5 (0.53 g, 1.2 mmol), 5-6 (0.34 g, 1.2 mmol), 5-7 (0.31 g, 1.2 mmol), Pd2(dba)3 (20.0 mg, 0.02 mmol), tri-tert-butylphosphide tetrafluoroborate (14.0 mg, 0.05 mmol), and sodium tert-butoxide (0.7 g, 7.3 mmol) were mixed in dry toluene (20 mL) and refluxed under nitrogen for 24 h. After cooling to room temperature, the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 5-8 (0.89 g, yield 81.3%). LC-MS analysis by liquid chromatography-mass spectrometry yielded the following m / z values: theoretical value 909.15, measured value 909.29. Synthesis of Compound 5: Under a nitrogen atmosphere, boron tribromide (4.4 g, 17.7 mmol) was added to an ultra-dry o-dichlorobenzene solution containing 5-8 (0.64 g, 0.7 mmol). After sealing the tube, the mixture was heated to 180 °C in a sand bath and stirred for 24 h. After cooling to room temperature, the reaction system was quenched with methanol, and the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give compound 5 (0.27 g, yield 41.2%). LC-MS analysis showed a theoretical value of 924.72 and a measured value of 924.85.

[0018] Example 2: Preparation of compound 282 ; Synthesis of 282-3: 282-1 (0.31 g, 1.5 mmol) and 282-2 (0.25 g, 1.5 mmol) were dissolved in 100 mL of dry... N , N - Dimethylformamide. Then, cesium carbonate (7.3 g, 2.2 mmol) was added under a nitrogen atmosphere. The solution was heated at 160ºC for 20 h, and the reaction mixture was cooled to room temperature. The resulting solution was slowly poured into ice water (500 ml) and stirred with a glass rod. The powder solid was filtered off, dried under vacuum, and further purified by silica gel column chromatography (dichloromethane:hexane (1:10)) to give 282-3 (0.41 g, yield 76.8%). LC-MS analysis by liquid chromatography-mass spectrometry showed the following m / z values: theoretical value 356.65, measured value 356.77. Synthesis of 282-4: Under a nitrogen atmosphere, a solution of n-butyllithium in n-hexane (3.6 mL, 2.5 M, 8.4 mmol) was slowly added dropwise to a solution of 282-3 (3.00 g, 8.4 mmol) in anhydrous tetrahydrofuran (50 mL) at -78ºC. After stirring for 2 h, a solution of 5-4 (1.82 g, 10.1 mmol) in anhydrous tetrahydrofuran was slowly added at -60ºC, also under a nitrogen atmosphere. Subsequently, the reaction mixture was slowly heated to room temperature and stirred overnight. The aqueous phase was separated and extracted three times with dichloromethane (100 mL). The organic layers were combined, dried over sodium sulfate, and filtered. After removing the solvent under reduced pressure, the crude product was dissolved in anhydrous dichloromethane (100 mL), and then methanesulfonic acid (5 mL) was slowly added at room temperature. The reaction mixture was stirred for 3 hours, then slowly quenched with 100 mL of sodium bicarbonate aqueous solution to separate the aqueous phase, which was extracted with dichloromethane (50 mL). The organic layers were combined, dried over sodium sulfate, filtered, and concentrated by rotary evaporation. The product was further purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 282-4 (1.53 g, yield 41.5%). LC-MS analysis by liquid chromatography-mass spectrometry yielded the following values: theoretical value 439.94, measured value 440.06. Synthesis of 282-6: 282-4 (0.53 g, 1.2 mmol), 282-5 (0.33 g, 1.2 mmol), 5-7 (0.31 g, 1.2 mmol), Pd2(dba)3 (20.0 mg, 0.02 mmol), tri-tert-butylphosphide tetrafluoroborate (14.0 mg, 0.05 mmol), and sodium tert-butoxide (0.7 g, 7.3 mmol) were mixed in dry toluene (20 mL) and refluxed under nitrogen for 24 h. After cooling to room temperature, the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 282-6 (0.88 g, 80.9% yield). The LC-MS (m / z) values ​​obtained by liquid chromatography-mass spectrometry were: theoretical value 905.12, measured value 905.25. Synthesis of compound 282: Under a nitrogen atmosphere, boron tribromide (4.4 g, 17.7 mmol) was added to an ultra-dry o-dichlorobenzene solution containing 282-6 (0.63 g, 0.7 mmol). After sealing the tube, the mixture was heated to 180 °C in a sand bath and stirred for 24 h. After cooling to room temperature, the reaction system was quenched with methanol, and the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give compound 282 (0.27 g, yield 42.1%). LC-MS analysis showed a theoretical value of 920.69 and a measured value of 920.81.

[0019] Example 3: Preparation of compound 378 ; Synthesis of 378-2: 378-1 (0.23 g, 1.2 mmol) and 282-2 (0.17 g, 1.0 mmol) were mixed and dissolved in 100 mL of dry... N , N - Dimethylformamide. Then, cesium carbonate (3.9 g, 1.2 mmol) was added under a nitrogen atmosphere. The solution was heated at 100°C for 4 h, and the reaction mixture was cooled to room temperature. The reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, it was further purified by silica gel column chromatography (dichloromethane:hexane (1:10)) to give 378-2 (0.28 g, yield 81.2%). LC-MS analysis by liquid chromatography-mass spectrometry showed the following m / z values: theoretical value 340.20, measured value 340.34. Synthesis of 378-3: Under a nitrogen atmosphere, a hexane solution of n-butyllithium (3.6 mL, 2.5 M, 8.4 mmol) was slowly added dropwise to a solution of 378-2 (2.86 g, 8.4 mmol) in anhydrous tetrahydrofuran (50 mL) at -78ºC. After stirring for 2 h, a solution of 5-4 (1.82 g, 10.1 mmol) in anhydrous tetrahydrofuran was slowly added at -60ºC, also under a nitrogen atmosphere. Subsequently, the reaction mixture was slowly heated to room temperature and stirred overnight. The aqueous phase was separated and extracted three times with dichloromethane (100 mL). The organic layers were combined, dried over sodium sulfate, and filtered. After removing the solvent under reduced pressure, the crude product was dissolved in anhydrous dichloromethane (100 mL), and then methanesulfonic acid (5 mL) was slowly added at room temperature. The reaction mixture was stirred for 3 hours, then slowly quenched with 100 mL of sodium bicarbonate aqueous solution to separate the aqueous phase, which was extracted with dichloromethane (50 mL). The organic layers were combined, dried over sodium sulfate, filtered, and concentrated by rotary evaporation. The product was further purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 378-3 (1.48 g, yield 41.5%). LC-MS analysis by liquid chromatography-mass spectrometry yielded the following values: theoretical value 423.49, measured value 423.62. Synthesis of 378-6: Under a nitrogen atmosphere, 378-3 (1.69 g, 4 mmol), 378-4 (1.05 g, 4 mmol), and 378-5 (0.12 g, 1.0 mmol) were mixed and dissolved in 20 mL of dry precipitate. N , N - Dimethylformamide. Then, cesium carbonate (7.8 g, 2.4 mmol) was added under a nitrogen atmosphere. The solution was heated at 160°C for 10 h, and the reaction mixture was cooled to room temperature. The reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, it was further purified by silica gel column chromatography (dichloromethane:hexane (1:10)) to give 378-6 (0.61 g, yield 79.1%). LC-MS analysis by liquid chromatography-mass spectrometry showed the following m / z values: theoretical value 768.92, measured value 769.03. Synthesis of compound 378: Under a nitrogen atmosphere, boron tribromide (4.4 g, 17.7 mmol) was added to an ultra-dry o-dichlorobenzene solution containing 378-6 (0.54 g, 0.7 mmol). After sealing the tube, the mixture was heated to 180 °C in a sand bath and stirred for 24 h. After cooling to room temperature, the reaction system was quenched with methanol, and the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give compound 378 (0.23 g, yield 41.8%). Analysis by liquid chromatography-mass spectrometry (LC-MS) yielded a theoretical value of 784.49 and a measured value of 784.62.

[0020] Example 4: Preparation of compound 470 ; Synthesis of 470-2: Under a nitrogen atmosphere, a solution of n-butyllithium in n-hexane (3.6 mL, 2.5 M, 8.4 mmol) was slowly added dropwise to a solution of 282-3 (3.00 g, 8.4 mmol) in anhydrous tetrahydrofuran (50 mL) at -78ºC. After stirring for 2 h, a solution of 470-1 (1.98 g, 10.1 mmol) in anhydrous tetrahydrofuran was slowly added at -60ºC, also under a nitrogen atmosphere. Subsequently, the reaction mixture was slowly heated to room temperature and stirred overnight. The aqueous phase was separated and extracted three times with dichloromethane (100 mL). The organic layers were combined, dried over sodium sulfate, and filtered. After removing the solvent under reduced pressure, the crude product was dissolved in anhydrous dichloromethane (100 mL), and then methanesulfonic acid (5 mL) was slowly added at room temperature. The reaction mixture was stirred for 3 hours, then slowly quenched with 100 mL of sodium bicarbonate aqueous solution to separate the aqueous phase, which was extracted with dichloromethane (50 mL). The organic layers were combined, dried over sodium sulfate, filtered, and concentrated by rotary evaporation. The product was further purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 470-2 (1.62 g, yield 42.3%). LC-MS analysis by liquid chromatography-mass spectrometry yielded the following values: theoretical value 455.94, measured value 456.07. Synthesis of 470-4: 470-2 (0.55, 1.2 mmol), 470-3 (0.11 g, 1.2 mmol), Pd2(dba)3 (20.0 mg, 0.02 mmol), tri-tert-butylphosphide tetrafluoroborate (14.0 mg, 0.05 mmol), and sodium tert-butoxide (0.7 g, 7.3 mmol) were mixed in dry toluene (20 mL) and refluxed under nitrogen for 24 h. After cooling to room temperature, the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 470-4 (0.50 g, yield 81.4%). LC-MS analysis by liquid chromatography-mass spectrometry yielded the following m / z values: theoretical value 512.61, measured value 512.75. Synthesis of 470-5: 282-5 (0.33 g, 1.2 mmol), 470-3 (0.11 g, 1.2 mmol), Pd2(dba)3 (20.0 mg, 0.02 mmol), tri-tert-butylphosphide tetrafluoroborate (14.0 mg, 0.05 mmol), and sodium tert-butoxide (0.7 g, 7.3 mmol) were mixed in dry toluene (20 mL) and refluxed under nitrogen for 24 h. After cooling to room temperature, the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 470-5 (0.32 g, 80.8% yield). LC-MS analysis by liquid chromatography-mass spectrometry yielded the following m / z values: theoretical value 334.42, measured value 334.55. Synthesis of 470-7: 470-4 (0.62 g, 1.2 mmol), 470-5 (0.40 g, 1.2 mmol), 470-6 (0.28 g, 1.2 mmol), Pd2(dba)3 (20.0 mg, 0.02 mmol), tri-tert-butylphosphide tetrafluoroborate (14.0 mg, 0.05 mmol), and sodium tert-butoxide (0.7 g, 7.3 mmol) were mixed in dry toluene (20 mL) and refluxed under nitrogen for 24 h. After cooling to room temperature, the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give 470-7 (0.90 g, 81.3% yield). The theoretical value was 921.12 and the measured value was 921.25, obtained by liquid chromatography-mass spectrometry (LC-MS). Synthesis of compound 470: Under a nitrogen atmosphere, boron tribromide (4.4 g, 17.7 mmol) was added to an ultra-dry o-dichlorobenzene solution containing 470-7 (0.64 g, 0.7 mmol). After sealing the tube, the mixture was heated to 180 °C in a sand bath and stirred for 24 h. After cooling to room temperature, the reaction system was quenched with methanol, and the reaction mixture was extracted with dichloromethane and dried over anhydrous sodium sulfate. After filtration and evaporation, the crude product was purified by silica gel column chromatography (dichloromethane:hexane (1:5)) to give compound 470 (0.28 g, yield 42.8%). Analysis by liquid chromatography-mass spectrometry (LC-MS) yielded a theoretical value of 936.69 and a measured value of 936.83.

[0021] In addition, it should be noted that other compounds in this application can be obtained by referring to the preparation methods of the examples listed above, so they will not be listed one by one here.

[0022] Device Examples Based on the same inventive concept, embodiments of the present invention also provide an organic light-emitting device comprising the compounds of the above embodiments. The following example uses an OLED as an organic light-emitting device for illustration; however, it should be understood that the following detailed description is not a limitation of the present invention, and those skilled in the art can extend the application of the following detailed description to other organic light-emitting devices.

[0023] In one embodiment, the OLED includes a first electrode and a second electrode, and a plurality of organic material layers located between the electrodes. The organic material layers can be further divided into multiple regions. For example, the organic material layer may include a hole transport region, a light-emitting layer, and an electron transport region. In specific embodiments, a substrate can be used below the first electrode or above the second electrode. The substrate is typically made of glass or polymer material with excellent mechanical strength, thermal stability, water resistance, and transparency. Furthermore, the substrate used for a display can also incorporate thin-film transistors (TFTs). The first electrode can be formed by sputtering or depositing a material used as the first electrode on a substrate. When the first electrode is used as the anode, it can be a transparent conductive oxide material such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO2), zinc oxide (ZnO), or any combination thereof. When the first electrode is used as the cathode, it can be a metal or alloy such as magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), magnesium-silver (Mg-Ag), or any combination thereof. Organic material layers can be formed on electrodes using methods such as vacuum thermal evaporation, spin coating, and printing. Compounds used as organic material layers can be small organic molecules, large organic molecules, polymers, and combinations thereof. The hole transport region is located between the anode and the light-emitting layer. The hole transport region can be a single-layer hole transport layer (HTL), including single-layer hole transport layers containing only one compound and single-layer hole transport layers containing multiple compounds. The hole transport region can also be a multilayer structure including at least one of a hole injection layer (HIL), a hole transport layer (HTL), and an electron blocking layer (EBL). The material for the hole transport region may be selected from, but is not limited to, phthalocyanine derivatives such as CuPc, conductive polymers or polymers containing conductive dopants such as polyphenylenevinyl chloride, polyaniline / dodecylbenzenesulfonic acid (Pani / DBSA), poly(3,4-ethylenedioxythiophene) / poly(4-styrenesulfonate) (PEDOT / PSS), polyaniline / camphorsulfonic acid (Pani / CSA), polyaniline / poly(4-styrenesulfonate) (Pani / PSS), aromatic amine derivatives as shown in HTL-1 to HTL-20 below; or any combination thereof: ; The hole injection layer is located between the anode and the hole transport layer. The hole injection layer can be a single compound material or a combination of multiple compounds. For example, the hole injection layer can use one or more compounds from HTL-1 to HTL-20 described above, or one or more compounds from HI-1 to HI-3 described below; alternatively, one or more compounds from HTL-1 to HTL-20 can be used to dope one or more compounds from HI-1 to HI-3 described below. ; The luminescent layer comprises one or more compounds as shown in Formula I or Formula II above as luminescent dopant materials, and may also simultaneously include a host material and / or a sensitizer material. In one aspect of the invention, the host material of the luminescent layer may be selected from, but not limited to, one or more combinations of H-1 to H-8 listed below: ; In one aspect of the invention, the sensitizer material of the luminescent layer can be a TADF material or a phosphorescent material, and can be selected from, but not limited to, one or more combinations of the following S-1 to S-13: ; The OLED organic material layer may also include an electron transport region between the light-emitting layer and the cathode. The electron transport region can be a single-layer electron transport layer (ETL), including single-layer electron transport layers containing only one compound and single-layer electron transport layers containing multiple compounds. The electron transport region can also be a multilayer structure including at least one of an electron injection layer (EIL), an electron transport layer (ETL), and a hole blocking layer (HBL). In a specific example, the electron transport layer material may be selected from, but is not limited to, one or more combinations of ETL-1 to ETL-22 listed below: ; In one example, the device may also include an electron injection layer located between the electron transport layer and the cathode, the electron injection layer material including but not limited to one or more combinations of the following: LiQ, LiF, CsF, Li2O, Cs2CO3, BaO, Na, Li and / or Ca.

[0024] To evaluate the luminescence performance of the compounds described in this invention in organic electroluminescent devices, a series of OLED devices based on multilayer organic thin film structures were designed and constructed, and the specific fabrication process is shown below:

[0025] Preparation of Example 1: The glass plate coated with the ITO transparent conductive layer was ultrasonically treated in a cleaning agent, rinsed in deionized water, ultrasonically degreased in a mixed solvent of acetone and ethanol, baked in a clean environment until all moisture was removed, cleaned with ultraviolet light and ozone, and bombarded with a low-energy cation beam. The treated ITO transparent conductive layer was placed in a vacuum evaporation chamber. After the system reached a high vacuum, a hole injection layer with a thickness of 10 nm was deposited first. This layer used a co-evaporation combination of HTL-2 and HIL-3 (mass ratio 97:3, w / w), with the two materials placed in different evaporation sources. Precise ratio control was achieved by adjusting the evaporation rate. This doping system aims to improve the energy level matching between the anode and the organic layer and reduce the hole injection barrier. A 15 nm thick HTL-2 layer is deposited on top of the hole injection layer as a hole transport layer. The main function of this layer is to efficiently transport holes and suppress electron back injection, maintaining a good charge balance in the device. Subsequently, a 20 nm thick HTL-3 layer is deposited as an electron blocking layer to restrict electron penetration to the hole transport layer, thereby effectively improving the exciton binding ability and recombination efficiency in the light-emitting region. A 30nm thick light-emitting layer was deposited on the electron blocking layer using a multi-source co-evaporation process. The main material was H-2, the sensitizing material was S4, and the dopant was compound 5. The materials were placed in independent evaporation sources, and a composite light-emitting film was formed by controlling the evaporation rate ratio of 79:20:1 (w / w / w). A 30 nm thick electron transport layer was deposited on the hole blocking layer using an ETL-10 and LiQ doping system (mass ratio 50:50, w / w). This combination helps to improve the electron transport rate and interface injection efficiency. Depositing a 1 nm LiQ layer on the electron transport layer as an electron injection layer, its extremely low work function helps to form an interfacial dipole and improves the injection efficiency of electrons from the Al cathode to the electron transport layer. An Al electrode layer with a thickness of 13 nm is deposited on top of the electron injection layer; this layer serves as the cathode layer. The entire organic layer and cathode evaporation process is completed in a continuous vacuum to avoid interface oxidation or contamination, with the deposition rate set to 0.1 nm / s.

[0026] In the glove box, the vapor-deposited device is coated with UV adhesive using a coating equipment. The coated cover plate is then moved to the lamination section, where the vapor-deposited substrate is placed on top of the cover plate. Finally, the substrate and cover plate are laminated using a bonding equipment and cured with UV adhesive.

[0027] Preparation of Examples 2-25: When forming the light-emitting layer, the corresponding compound in Table 1 was used to replace compound 5 in Example 1, and the organic electroluminescent device was prepared using the same method as in Example 1.

[0028] Preparation of Comparative Examples 1-2: Except that, when forming the light-emitting layer, the corresponding compound in Table 1 was used to replace compound 5 in Example 1, and the organic electroluminescent device was prepared using the same method as in Example 1.

[0029] The structures of Ref-1 to Ref-2 in Table 1 are as follows: .

[0030] The organic electroluminescent devices prepared by the above process were subjected to the following performance measurements: At 10mA / cm 2 The current efficiency of the device examples and comparative examples was determined at a current density of 10 mA / cm². The current efficiency was measured using an IVL (current-voltage-luminance) testing system (Suzhou Fushida Scientific Instruments Co., Ltd.). 2 The time required for the brightness to decrease to 95% of the initial brightness at a given current density (LT95) was measured. The lifetime testing system was the OLED lifetime testing system from Suzhou Fosstar Scientific Instruments Co., Ltd.; at 10 mA / cm 2 The maximum emission peak position, full width at half maximum (FWHM), and current efficiency were obtained at this time; the efficiency roll-off was equal to the maximum current efficiency plus 10 mA / cm². 2 The difference in current efficiency divided by the maximum current efficiency is shown in Table 1 below: ; As shown in Table 1, compared with the comparative example, the embodiment with the same framework structure exhibits lower efficiency roll-off and longer device lifetime. This is because the compound involved in this invention breaks the centrosymmetry of the B / N multiple resonance core by introducing a single spirocarbon group to lock one side of the donor, resulting in a spatially asymmetric separation of the frontier molecular orbitals, thereby reducing the singlet-triplet energy level difference (ΔE). ST This significantly improves the rate and efficiency of reverse system crosstalk (RISC), allowing more triplet excitons to be converted into radiative singlet excitons, effectively reducing efficiency roll-off and extending device lifetime.

[0031] The above embodiments only list the effect data of devices made from a portion of the structures. This is a representative sampling test. Based on the experimental data, the overall data is not significantly different and can represent the effects of other unlisted structures.

[0032] Those skilled in the art will readily recognize that many modifications and variations can be made to this invention without departing from its spirit and scope. Therefore, it is anticipated that this invention covers the modifications and variations provided within the scope of the appended claims and their equivalents. This invention has been illustrated by the above embodiments with respect to the organic electroluminescent materials and organic electroluminescent devices of this invention, but the invention is not limited to the above embodiments, i.e., it does not mean that the invention must rely on the above embodiments to be implemented.

Claims

1. A boron-containing multiple resonance thermally activated delayed fluorescence material, characterized in that, Its molecular structure is shown in general formula (I) and general formula (II): ； Rings A, B, C, and D are each independently selected from substituted or unsubstituted C6 to C6 rings. 24 Aromatic rings, substituted or unsubstituted C5-C 24 Mixed fragrance ring; Rings A and B, and rings C and D are not connected, or are connected by single bonds, O, S, or Se; R1 and R2 may be the same or different, and each is independently selected from substituted or unsubstituted C1 to C2. 10 Alkyl, substituted or unsubstituted C6-C 24 Aryl group, and R1 and R2 are not connected to each other, or are connected by single bonds, O, S, or Se; R3 to R8 are each independently selected from hydrogen atoms, substituted or unsubstituted C1 to C8 atoms. 10 alkyl; X1 and X2 are each independently selected from NR 11 One of O, S, and Se; R 11 Selected from substituted or unsubstituted C6~C 24 Aryl; When substitution is present, each substituent independently represents a monosubstituted group up to the maximum permissible number of substitutions, optionally selected from deuterium, tritium, halogen, cyano, trifluoromethyl, C1-C1, C2-C3, C4-C5, C6-C ... 12 Alkyl, C1-C 24 Alkoxy, C1-C 24 Alkylthio, C3~C 24 Cycloalkyl, C1-C6 alkyl-substituted or unsubstituted aromatic amino groups, C1-C6 alkyl-substituted or unsubstituted C6-C6 alkyl groups 60 Aryl, C1-C6 alkyl substituted or unsubstituted C4-C6 60 The heteroaryl group, wherein the heteroatom in the heteroaryl group or heteroaryl ring is selected from one or more of N, O, S, Se, Te or B.

2. The boron-containing multiple resonance thermally activated delayed fluorescence material according to claim 1, characterized in that, The rings A, B, C, and D are independently represented as substituted or unsubstituted C6 to C6 rings, respectively. 18 The fragrance ring.

3. The boron-containing multiple resonance thermally activated delayed fluorescence material according to claim 2, characterized in that, The rings A, B, C, and D are independently represented as substituted or unsubstituted phenyl, substituted or unsubstituted biphenyl, or substituted or unsubstituted naphthyl, respectively.

4. The boron-containing multiple resonance thermally activated delayed fluorescence material according to claim 1, characterized in that, R1 and R2 may be the same or different, and each is independently selected from C1 to C6 alkyl, substituted or unsubstituted C6 to C6 alkyl groups. 12 Aryl.

5. The boron-containing multiple resonance thermally activated delayed fluorescence material according to claim 1, characterized in that, X1 and X2 are each independently represented as NR 11 One of O, S, R 11 The phenyl group can be substituted or unsubstituted.

6. The boron-containing multiple resonance thermally activated delayed fluorescence material according to claim 1, characterized in that, Its structure is selected from any one of the following compounds: ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； ； 。 7. An organic electroluminescent device, comprising an anode, a cathode, and an organic layer, wherein the organic layer includes a light-emitting layer, characterized in that, The luminescent layer comprises any one of the boron-containing multiple resonance thermally activated delayed fluorescence materials described in claims 1 to 6 above.

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