Crab-like structure multi-resonance thermally activated delayed fluorescence material and preparation and application thereof

Abstract

This invention discloses a crab-like structure multi-resonance thermally activated delayed fluorescence material, its preparation method, and its applications, belonging to the field of organic optoelectronic materials technology. The material uses boron-nitrogen-doped rigid heterocycles as a "hard shell" (molecular backbone), with differentiated donor units introduced on both sides or one side as "flexible chelates." By controlling the intramolecular charge transfer (ICT) intensity, it achieves synergistic optimization of narrow-band emission, efficient reverse intersystem crossing, and low-efficiency roll-off. The asymmetric molecule DB-BFCz of this invention has an emission peak of 450 nm in solution, a full width at half maximum (FWHM) of only 17 nm, and a reverse intersystem crossing rate (…). k RISC The photoluminescence quantum yield (PLQY) reaches 9.63 × 10⁵ s⁻¹, with a photoluminescence quantum yield (PLQY) ≥ 99%; the non-sensitized OLED device fabricated based on it has color coordinates (0.13, 0.12) and a maximum external quantum efficiency (EQE). max With an efficiency exceeding 40% and significant suppression of efficiency roll-off at high brightness, it breaks through the trade-off dilemma of "efficiency-roll-off-color purity" in existing blue light MR-TADF materials, and can be widely used in ultra-high-definition displays, lighting and other fields.

Description

Technical Field

[0001] This invention belongs to the field of organic optoelectronic materials technology, specifically relating to a narrowband blue light multi-resonance thermally activated delayed fluorescence material based on a crab-like structure design, its preparation method, and its application in organic electroluminescent devices. Background Technology

[0002] Organic light-emitting diodes (OLEDs) have become a core technology for next-generation displays and lighting due to their advantages such as high flexibility, low power consumption, and wide color gamut. Among the three primary color emitting materials, blue light materials are key to achieving full-color displays and white light illumination, but the development of high-performance narrowband blue light materials has long been a bottleneck in this field. In recent years, the emergence of multi-resonance thermally activated delayed fluorescence (MR-TADF) technology has provided a new approach to solving this problem. MR-TADF materials possess a rigid π-conjugated framework and alternating donor-acceptor (DA) resonance structures, exhibiting narrow emission spectra (FWHM < 40 nm) and high luminous efficiency, making them ideal candidate materials for high-performance blue OLEDs. However, the practical application of existing blue MR-TADF materials is limited by a severe efficiency roll-off problem, mainly caused by triplet-triplet annihilation (TTA) and triplet-polaron annihilation (TPA). Furthermore, the high triplet energy level (Et) of blue MR-TADF materials... T The annihilation process was further exacerbated by the presence of >2.6 eV and the tight molecular packing in the thin film.

[0003] To address the efficiency roll-off problem, researchers have proposed strategies such as optimizing device structure (e.g., introducing sensitizers) or controlling thin film morphology (e.g., using high ET host materials). However, these methods often increase device complexity and manufacturing costs. At the molecular design level, introducing donor / acceptor units to construct intramolecular charge transfer (ICT) effects is a common method for regulating reverse intersystem crossing (RISC) and suppressing efficiency roll-off. However, this strategy has a clear "regulation trade-off": weak ICT effects cannot effectively reduce the single triplet energy level difference (Δ). E ST This results in low RISC speeds (only 10³-10). 4 While strong ICT effects can promote RISC, they can also disrupt the resonance structure of MR-TADF materials, leading to emission spectrum broadening and a decrease in photoluminescence quantum yield (PLQY). Therefore, developing a blue MR-TADF molecule design strategy that can simultaneously achieve high luminous efficiency, high color purity, and low efficiency roll-off is a pressing technical problem to be solved in this field. Summary of the Invention

[0004] This invention discloses a narrowband blue multi-resonance thermally activated delayed fluorescence (MR-TADF) material based on a "rigid hard shell + flexible pincer" crab-like structure, its preparation method, and its applications. It aims to solve the technical bottlenecks of existing narrowband blue MR-TADF materials, such as the difficulty in simultaneously achieving "efficiency-roll-off-color purity" and the imbalance in charge transfer (ICT) regulation. It also addresses the problems of multiple synthesis steps, high raw material costs, complex purification processes, low yields, and difficulty in large-scale mass production of existing narrowband blue MR-TADF materials. In particular, the OLED device prepared by doping the emitting layer with this crab-like structure narrowband blue MR-TADF material achieves its maximum external quantum efficiency (EQE). max The target is over 40%. The present invention adopts the following technical solution: A crab-like structure multi-resonance thermally activated delayed fluorescence material is disclosed. This material has a boron-nitrogen-doped rigid heterocycle as its core, with electron donor units connected to both sides. The material possesses a bifunctional structure of "rigid shell + flexible chelate," with the molecular framework centered on a boron-nitrogen-doped rigid heterocycle and connected to electron donor units on both sides to achieve charge transfer regulation. The electron donor units include one or more of dibenzofuran and carbazole structures.

[0005] In this invention, the crab-structured multi-resonance thermally activated delayed fluorescence material is DB-DBF or DB-BFCz. Specifically, the material is selected from any one of the following two types of molecules: DB-DBF: The donor units on both sides of the main framework are dibenzofuran (BF), forming a symmetrical structure; DB-BFCz: The main framework has a donor unit of dibenzofuran (BF) on one side and carbazole (Cz) on the other side, forming an asymmetric differential structure. Furthermore, the present invention relates to a narrowband blue MR-TADF material based on a crab-like structure design, the chemical structural formula of which is as follows:

[0006] This invention enables wavelength modulation, from sky blue light to deep blue light. By utilizing an asymmetric structure, charge transfer can be further modulated, accelerating reverse intersystem crossing and suppressing efficiency roll-off.

[0007] This invention discloses a method for preparing the above-mentioned crab-structured multi-resonance thermally activated delayed fluorescence material, comprising the following steps: reacting intermediate 3 or intermediate 5 with a boride to obtain the crab-structured multi-resonance thermally activated delayed fluorescence material.

[0008] The chemical structural formulas of intermediates 3 and 5 are as follows:

[0009] In this invention, the boride is a haloboride; the reaction temperature is 150–250°C, and the reaction time is 30–50 h.

[0010] This invention discloses the application of the above-mentioned crab-structured multi-resonance thermally activated delayed fluorescence material in the fabrication of organic electroluminescent devices; or the application of the above-mentioned crab-structured multi-resonance thermally activated delayed fluorescence material in the fabrication of the emissive layer of organic electroluminescent devices. The crab-structured multi-resonance thermally activated delayed fluorescence material is used as a guest material and doped into the host material to prepare the emissive layer. Preferably, the doping concentration of the crab-structured multi-resonance thermally activated delayed fluorescence material is 1–5 wt%.

[0011] This invention discloses an organic electroluminescent device or an organic electroluminescent device light-emitting layer, comprising the crab-structured multi-resonance thermally activated delayed fluorescence material as described in any one of claims 1 to 3.

[0012] The present invention discloses a light-emitting device, including the above-mentioned organic electroluminescent device.

[0013] In the crab-structured multi-resonance thermally activated delayed fluorescence material of this invention, DB-DBF is a symmetrical crab-structured compound with the chemical formula: C 60 H 43 B2N3O2; its chemical structural formula is as follows:

[0014] The above-mentioned method for preparing DB-DBF can be summarized in the following steps: (1) 3,5-Dibromoaniline and arylboronic acid react to give aryl-substituted dibromoaniline derivatives (intermediate 1). (2) The intermediate 1 obtained in step (1) is coupled with diphenylamine via CN coupling reaction to obtain a triamine derivative (intermediate 2). (3) The intermediate 2 obtained in step (2) is coupled with 3-bromodibenzofuran via CN coupling reaction to obtain a tetraarylamine derivative (intermediate 3). (4) The intermediate 3 obtained in step (3) is reacted with boron tribromide to obtain narrowband blue light MR-TADF material DB-DBF. In the crab-structured multi-resonance thermally activated delayed fluorescence material of this invention, DB-BFCz is an asymmetric crab-structured compound with the chemical formula: C 68 H 48 B2N4O; its chemical structural formula is as follows:

[0015] The preparation method of the above-mentioned DB-BFCz can be summarized in the following steps: (1) 3,5-Dibromoaniline and arylboronic acid react to give aryl-substituted dibromoaniline derivatives (intermediate 1). (2) The intermediate 1 obtained in step (1) is coupled with diphenylamine via CN coupling reaction to obtain a triamine derivative (intermediate 2). (3) The intermediate 2 obtained in step (2) was coupled with 3-bromodibenzofuran via CN coupling reaction to obtain a monosubstituted tetraarylamine derivative (intermediate 4). (4) The intermediate 4 obtained in step (3) was coupled with 2-bromo-9-phenylcarbazole via CN coupling reaction to obtain a disubstituted tetraarylamine derivative (intermediate 5). (5) The intermediate 5 obtained in step (4) is boronized with boron tribromide to obtain narrowband blue light MR-TADF material DB-BFCz. Further, in step (1), the molar ratio of 3,5-dibromoaniline, arylboronic acid, cuprous iodide, 1,10-o-phenanthroline, and potassium carbonate is 1:2.2:0.05:0.08:4.5; the reaction is carried out under argon protection, with 1,4-dioxane / water = 4:1 (volume ratio) as solvent, the reaction temperature is 130℃, and the reaction time is 12 h; after the reaction is completed, water and dichloromethane are added for extraction, the combined organic phases are dried over anhydrous sodium sulfate, filtered, and the solvent is removed by vacuum distillation. The crude product is purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 10:1, volume ratio) to obtain pure white solid intermediate 1; the reaction in step (1) can be referred to as follows:

[0016] Furthermore, in step (2), the molar ratio of intermediate 1, diphenylamine, tri-tert-butylphosphine tetrafluoroborate, tris(dibenzylacetone)dipalladium, and sodium tert-butoxide is 1:2.2:0.03:0.02:3.5; the reaction is carried out under argon protection, using pretreated dry toluene by vacuum distillation as solvent, at a reaction temperature of 110 °C for 12 h; after the reaction, the mixture is cooled to room temperature, and the dry toluene is removed by vacuum distillation to obtain a brownish-yellow oily crude product; the crude product is purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 5:1, volume ratio), the target component is collected and the solvent is evaporated to obtain a white solid intermediate 2; the reaction in step (2) can be referred to as follows:

[0017] On the one hand: In the above-mentioned crab-structured multi-resonance thermally activated delayed fluorescence material, the preparation method of DB-DBF includes the following steps: using intermediate 3 and boron tribromide as raw materials and o-dichlorobenzene as solvent, a narrow-band blue MR-TADF material DB-DBF is prepared by reaction; further, the molar ratio of intermediate 3 and boron tribromide is 1:10; the reaction is carried out under nitrogen protection; the reaction temperature is 210 ℃ and the reaction time is 36 h; after the reaction is completed, methanol is added under ice bath to quench, the organic solvent is removed by vacuum distillation, and the residual solid is purified by rapid silica gel column chromatography to obtain the narrow-band blue MR-TADF material DB-DBF; preferably, the column chromatography eluent is petroleum ether / dichloromethane = 3:1 (volume ratio). In this invention, intermediate 2,3-bromodibenzofuran is used as a raw material, tris(dibenzylacetone)dipalladium is used as a catalyst, tri-tert-butylphosphine tetrafluoroborate is used as a ligand, sodium tert-butoxide is used as a base, and dried toluene is used as a solvent to prepare intermediate 3. Preferably, the molar ratio of intermediate 2,3-bromodibenzofuran is 1:2.5. The reaction is carried out under nitrogen protection at a temperature of 110°C for 12 h. The reaction can be referenced as follows:

[0018] Furthermore, the reaction is carried out in the presence of tris(dibenzylacetone)dipalladium, sodium tert-butoxide, and tri-tert-butylphosphine tetrafluoroborate; preferably, the molar ratio of sodium tert-butoxide, intermediate 2, and tris(dibenzylacetone)dipalladium is 3.5:1:0.03, and the molar ratio of tris(dibenzylacetone)dipalladium to tri-tert-butylphosphine tetrafluoroborate is 1:2; tris(dibenzylacetone)dipalladium is the catalyst, and tri-tert-butylphosphine tetrafluoroborate is the phosphine ligand.

[0019] On the other hand, the preparation method of the above-mentioned crab-structured multi-resonance thermally activated delayed fluorescence material DB-BFCz includes the following steps: using intermediate 5 and boron tribromide as raw materials and o-dichlorobenzene as solvent, the narrow-band blue MR-TADF material DB-BFCz is prepared by reaction; further, the molar ratio of intermediate 5 and boron tribromide is 1:10; the reaction is carried out under nitrogen protection; the reaction temperature is 210 ℃ and the reaction time is 36 h; after the reaction is completed, methanol is added under ice bath to quench, the organic solvent is removed by vacuum distillation, and the residual solid is purified by rapid silica gel column chromatography to obtain the narrow-band blue MR-TADF material DB-BFCz; preferably, the column chromatography eluent is petroleum ether / dichloromethane = 3:1 (volume ratio). In this invention, intermediate 4, 2-bromo-9-phenylcarbazole, is used as a starting material, tris(dibenzylacetone)dipalladium is used as a catalyst, tri-tert-butylphosphine tetrafluoroborate is used as a ligand, sodium tert-butoxide is used as a base, and dried toluene is used as a solvent to prepare intermediate 5. Preferably, the molar ratio of intermediate 4 to 2-bromo-9-phenylcarbazole is 1:1.3. The reaction is carried out under inert gas (nitrogen) protection at a temperature of 110°C for 12 h. The reaction can be referenced as follows:

[0020] The molar ratio of intermediate 4, 2-bromo-9-phenylcarbazole, tri-tert-butylphosphine tetrafluoroborate, tris(dibenzylacetone)dipalladium, and sodium tert-butoxide was 1:1.3:0.03:0.02:3.5. The reaction was carried out in dry toluene as solvent at 110°C for 12 h. After the reaction was completed, the mixture was cooled to room temperature, the solvent was removed by vacuum distillation, and the crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 3:1, volume ratio) to obtain white solid intermediate 5. Furthermore, the reaction is carried out in the presence of tris(dibenzylacetone)dipalladium, sodium tert-butoxide, and tri-tert-butylphosphine tetrafluoroborate; preferably, the molar ratio of sodium tert-butoxide, intermediate 4, and tris(dibenzylacetone)dipalladium is 3.5:1:0.03, and the molar ratio of tris(dibenzylacetone)dipalladium to tri-tert-butylphosphine tetrafluoroborate is 1:2; tris(dibenzylacetone)dipalladium is the catalyst, and tri-tert-butylphosphine tetrafluoroborate is the phosphine ligand. In this invention, the molar ratio of intermediate 2,3-bromodibenzofuran, tri-tert-butylphosphine tetrafluoroborate, tris(dibenzylacetone)dipalladium, and sodium tert-butoxide is 1:1.3:0.03:0.02:3.5; the reaction is carried out under argon protection, using dry toluene as solvent, at a reaction temperature of 110 °C for 12 h; after the reaction, the mixture is cooled to room temperature, the solvent is removed by vacuum distillation, and the crude product is purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 4:1, volume ratio) to obtain a white solid intermediate 4; the reaction can be referenced as follows:

[0021] This invention discloses the application of the aforementioned narrowband blue MR-TADF material in the fabrication of organic electroluminescent devices. The emitting layer of the organic electroluminescent device comprises the aforementioned narrowband blue MR-TADF material, which serves as a guest material and a host material for doping the emitting layer. Furthermore, the doping concentration of the narrowband blue MR-TADF material is 1–5 wt%, with an optimal doping concentration of 3 wt%. The organic electroluminescent device disclosed in this invention, based on the aforementioned narrowband blue MR-TADF material, uses indium tin oxide (ITO) as the anode and bispyrazine [2,3-f: 2',3'-h]. Quinoxaline-2,3,6,7,10,11-hexanonitrile (HAT-CN) is used as the hole injection layer (HIL), 4,4'-(cyclohexane-1,1-diyl)bis(N,N-di-p-tolylaniline) (TAPC) is used as the hole transport layer (HTL), tris(4-(9H-carbazole-9-yl)phenyl)amine (TCTA) is used as the electron blocking layer, mCBP is used as the exciton blocking layer (EBL), the narrowband blue light MR-TADF material is used as the guest material and doped with mSiTRzCz2 as the host material to jointly serve as the light-emitting layer (EML), mSiTRzCz2 is used as the hole blocking layer, 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (TmPyPB) is used as the electron transport layer (ETL), lithium fluoride (LiF) is used as the electron injection layer (EIL), and aluminum (Al) is used as the cathode; furthermore, the specifications of each layer of the organic electroluminescent device are: ITO (110 (nm) / HAT-CN (5 nm) / TAPC (30 nm) / TCTA (5 nm) / mCBP (5 nm) / mSiTRzCz2: Narrow-band blue MR-TADF (crab-structured multi-resonance thermally activated delayed fluorescence material) material (3wt%) (20 nm) / mSiTRzCz2 (5 nm) / TmPyPB (35 nm) / LiF (1 nm) / Al (100 nm). This invention provides a method for synthesizing and preparing a novel crab-structured narrowband blue MR-TADF material; and an OLED based on the aforementioned narrowband blue MR-TADF material to achieve EQE. max The goal is to achieve a yield exceeding 40%; this is intended to address the challenges of balancing efficiency, roll-off, and color purity in narrowband blue MR-TADF materials, as well as the imbalance in ICT regulation; and to solve the problems of existing narrowband blue MR-TADF materials having multiple synthesis and preparation steps, expensive raw materials, complex synthesis and purification processes, low yields, and difficulty in large-scale mass production. There are no special limitations on the preparation method of the organic electroluminescent device based on the narrowband blue MR-TADF material described in this invention, nor on other raw materials. The organic thin film formed using this invention has high surface smoothness, stable chemical and physical properties, high luminous efficiency, and narrowband emission properties, resulting in an organic electroluminescent device with excellent performance. The beneficial effects of this invention are as follows: The two narrowband blue MR-TADF materials provided by this invention, DB-DBF and DB-BFCz, possess a crab-like structure of "rigid shell + flexible pincers" and differentiated donor modulation characteristics. They exhibit advantages such as multi-resonance thermally activated delayed fluorescence (MR-TADF), narrowband blue light emission characteristics, and high fluorescence quantum yield (PLQY). DB-BFCz, in particular, shows a PLQY ≥ 99% in toluene solution, an emission half-width at half-maximum (FWHM) of only 17 nm, and a reverse intersystem crossing rate (…). k RISC ) reached 9.63×10 5 s⁻¹, single triplet energy level difference (Δ E ST =0.14 eV. OLED devices based on the narrowband blue MR-TADF material provided by this invention have the advantages of low driving voltage and good luminescence stability, and the maximum external quantum efficiency (EQE) of the fabricated devices is as high as 43.57% (DB-BFCz) and 37.66% (DB-DBF). Attached Figure Description

[0022] Figure 1 This is the 1H NMR spectrum of the product DB-DBF obtained in Example 1.

[0023] Figure 2 This is the 1H NMR spectrum of the product DB-BFCz obtained in Example 2.

[0024] Figure 3 This is the mass spectrum of DB-DBF, the product obtained in Example 1.

[0025] Figure 4 This is the mass spectrum of the product DB-BFCz obtained in Example 2.

[0026] Figure 5 The images show the UV-Vis absorption spectrum and fluorescence emission spectrum of the product DB-DBF obtained in Example 1 in toluene solution.

[0027] Figure 6 The images show the UV-Vis absorption spectrum and fluorescence emission spectrum of the product DB-BFCz obtained in Example 2 in toluene solution.

[0028] Figure 7 This is the fluorescence lifetime diagram of the product DB-DBF obtained in Example 1 after deoxygenation in toluene solution.

[0029] Figure 8 This is the fluorescence lifetime diagram of the product DB-BFCz obtained in the example after deoxygenation in toluene solution.

[0030] Figure 9The performance of an organic electroluminescent device with a doping concentration of 1 wt% DB-DBF as the light-emitting layer is shown.

[0031] Figure 10 The performance of an organic electroluminescent device with a doping concentration of 3 wt% DB-DBF as the light-emitting layer is presented.

[0032] Figure 11 The performance of an organic electroluminescent device with a doping concentration of 5 wt% DB-DBF as the light-emitting layer is described.

[0033] Figure 12 The device performance of an organic electroluminescent device with a doping concentration of 1 wt% and DB-BFCz as the light-emitting layer is described.

[0034] Figure 13 The device performance of an organic electroluminescent device with a doping concentration of 3 wt% and DB-BFCz as the light-emitting layer is described.

[0035] Figure 14 The device performance of an organic electroluminescent device with a doping concentration of 5 wt% and DB-BFCz as the light-emitting layer is described. Detailed Implementation

[0036] This invention discloses a crab-like structure multi-resonance thermally activated delayed fluorescence material with a bifunctional structure of "rigid shell + flexible pincers". The molecular framework is based on a boron-nitrogen-doped rigid heterocycle as the core, with electron donor units on both sides to achieve charge transfer regulation. The chemical structure is as follows:

[0037] DB-DBF: The donor units on both sides of the main framework are dibenzofuran (BF), forming a symmetrical structure; DB-BFCz: The donor unit on one side of the main framework is dibenzofuran (BF), and the other side is carbazole (Cz), forming an asymmetric differentiated structure. The optical properties of DB-BFCz molecules in toluene solution satisfy the following: reverse intersystem crossing rate. k RISC ≥8.0×10 5 s⁻¹, photoluminescence quantum yield PLQY≥98%, emission peak 448~452 nm, full width at half maximum (FWHM)≤18 nm, singlet triplet energy level difference Δ E ST ≤0.15 eV.

[0038] This invention involves reacting intermediate 3 or intermediate 5 with a boride to obtain a crab-structured multi-resonance thermally activated delayed fluorescence material. The boride is a halogen boride; the reaction temperature is 150–250 °C, and the reaction time is 30–50 h.

[0039] Specifically, the preparation method of crab-structured multi-resonance thermally activated delayed fluorescence material includes the following steps: (1) Dissolve 3,5-dibromoaniline in the reaction solvent, add catalyst, ligand and base reagent, stir and mix evenly at room temperature; after purging air by inert gas, react by heating and stirring to obtain intermediate 1; (2) Dissolve intermediate 1 in dry toluene, add diphenylamine, tri-tert-butylphosphine tetrafluoroborate, tris(dibenzylideneacetone)dipalladium and sodium tert-butoxide; after purging air with an inert gas, heat and stir the reaction; after the reaction is completed, cool to room temperature and remove the solvent under reduced pressure; the crude product is purified by silica gel column chromatography to obtain intermediate 2; (3) Preparation of DB-DBF intermediate: Intermediate 2, 3-bromodibenzofuran, tris(dibenzylacetone)dipalladium, tritert-butylphosphine tetrafluoroborate and sodium tert-butoxide were added to a round-bottom flask; the flask was evacuated and backfilled with dry nitrogen three times, and dry toluene was injected; the reaction was refluxed and stirred under a nitrogen atmosphere to obtain intermediate 3; Preparation of DB-BFCz intermediate: Intermediate 2 was reacted with 3-bromodibenzofuran in the same manner as above to obtain intermediate 4, and then intermediate 4 was reacted with 2-bromo-9-phenylcarbazole under the same conditions to obtain intermediate 5; (4) Dissolve intermediate 3 (or intermediate 5) in o-dichlorobenzene, add boron tribromide and seal the reaction tube; heat and stir the reaction under nitrogen atmosphere, and obtain bright yellow solid DB-DBF (or DB-BFCz) after quenching and purification. The raw material molar ratios for the above steps satisfy the following: Step (1): The molar ratio of 3,5-dibromoaniline, copper catalyst, ligand, and base reagent is 1:0.03~0.06:0.05~0.1:3~6; Step (2): The molar ratio of intermediate 1, diphenylamine, tri-tert-butylphosphine tetrafluoroborate, tris(dibenzylideneacetone)dipalladium, and sodium tert-butoxide is 1:2~2.5:0.02~0.05:0.01~0.03:3~4; Step (3): The molar ratio of intermediate 2, aromatic ring bromide, tris(dibenzylacetone)palladium, tritert-butylphosphine tetrafluoroborate, and sodium tert-butoxide is 1:2.2~2.8:0.02~0.04:0.04~0.08:3~4; Step (4): The molar ratio of intermediate 3 (or intermediate 5) to boron tribromide is 1:8~12. Preferably, the reaction conditions for the above steps are as follows: Step S1: The heating temperature is 120~150 ℃, and the reaction time is 10~14 h; Step S2: The heating temperature is 100~120 ℃, and the reaction time is 10~14 h; Step S3: The reflux reaction temperature is 100~120 ℃, and the reaction time is 10~14 h; Step S4: The heating temperature is 200~220 ℃, and the reaction time is 30~40 h. The above-mentioned crab-structured multi-resonance thermally activated delayed fluorescence material of this invention is composited with the host material mSiTRzCz2 to form the emitting layer. The narrowband blue MR-TADF material has a doping concentration of 1–5 wt%, with an optimal doping concentration of 3 wt%, at which point the device achieves its maximum external quantum efficiency (EQE). max ≥40%.

[0040] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0041] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0042] Preparation of intermediate 1 in the synthesis example: 3,5-Dibromoaniline (5.00 g, 20.00 mmol), aryl halide (8.80 g, 44.00 mmol), cuprous iodide (0.19 g, 1.00 mmol), 1,10-o-phenanthroline (0.29 g, 1.60 mmol), and potassium carbonate (12.43 g, 90.00 mmol) were added to a 100 mL reaction flask at room temperature, along with 60 mL of a 1,4-dioxane / water mixed solvent (volume ratio 4:1). After purging with argon gas for 15 minutes, the mixture was heated to 130 °C and stirred for 12 hours, followed by cooling to room temperature. Add 50 mL of water and 50 mL of dichloromethane to the system to extract the product. Repeat the extraction 3 times. Combine the organic phases and dry them with anhydrous sodium sulfate. After filtration, remove the solvent by vacuum distillation. The crude product is purified by silica gel column chromatography (eluent: petroleum ether / ethyl acetate = 10:1, volume ratio) to give pure white solid intermediate 1 with a yield of 82%.

[0043]

[0044] Preparation of intermediate 2: Intermediate 1 (6.50 g, 16.00 mmol), trimethylaniline (6.92 g, 35.20 mmol), tri-tert-butylphosphine tetrafluoroborate (0.15 g, 0.48 mmol), tris(dibenzylacetone)dipalladium (0.19 g, 0.32 mmol), and sodium tert-butoxide (5.38 g, 56.00 mmol) were added to a 100 mL reaction flask, followed by 50 mL of dried toluene pretreated by vacuum distillation. After purging with argon for 15 minutes, the reaction system was heated to 110 °C and stirred for 12 hours, then cooled to room temperature. Toluene was removed by rotary evaporation, and the crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 5:1, v / v). The target fraction was collected and the solvent was evaporated to obtain a white solid intermediate 2 in 78% yield.

[0045] Preparation of Intermediate 3: Intermediate 2 (0.95 g, 1.80 mmol), 3-bromodibenzofuran (1.12 g, 4.50 mmol), tris(dibenzylacetone)palladium (Pd2(dba)3, 0.05 g, 0.054 mmol), tri-tert-butylphosphine tetrafluoroborate (t-Bu3P・HBF4, 0.05 g, 0.108 mmol), and sodium tert-butoxide (t-BuONa, 0.51 g, 5.40 mmol) were added to a 50 mL round-bottom flask equipped with a reflux condenser. The flask was evacuated and backfilled with dry nitrogen, repeated three times; then 25 mL of dry toluene was injected, and the reaction mixture was refluxed and stirred for 12 hours under a nitrogen atmosphere. After cooling to room temperature, the mixture was poured into 50 mL of water and extracted with dichloromethane (3 × 30 mL). The organic extracts were combined, dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 6:1, volume ratio) to give a white solid intermediate 3 with a yield of 80%.

[0046] Preparation of DB-DBF compound: Under a nitrogen atmosphere, intermediate 3 (0.82 g, 1.0 mmol) and 15 mL of o-dichlorobenzene (o-DCB) were added to a 100 mL sealed reaction tube. Boron tribromide (2.50 g, 10.0 mmol) was slowly added, the reaction tube was sealed, and the reaction mixture was heated to 210 °C and stirred for 36 hours. After cooling to room temperature, the reaction was quenched by slowly adding 8.0 mL of methanol under ice bath conditions (controlling the dropping rate to avoid bumping); the organic solvent was removed by vacuum distillation, and the residual solid was purified by rapid silica gel column chromatography (eluent: petroleum ether / dichloromethane = 3:1, v / v) to give a bright yellow solid DB-DBF (0.36 g, 42% yield).

[0047] Example 2 DB-BFCz compound Intermediate 2 (0.95 g, 1.80 mmol), 3-bromodibenzofuran (0.57 g, 2.34 mmol), tris(dibenzylacetone)palladium (Pd2(dba)3, 0.05 g, 0.054 mmol), tri-tert-butylphosphine tetrafluoroborate (t-Bu3P·HBF4, 0.05 g, 0.108 mmol), and sodium tert-butoxide (t-BuONa, 0.51 g, 5.40 mmol) were added to a 50 mL round-bottom flask equipped with a reflux condenser. The flask was evacuated and backfilled with dry nitrogen, repeated three times; then 25 mL of dry toluene was injected, and the reaction mixture was refluxed and stirred for 12 hours under a nitrogen atmosphere. After cooling to room temperature, the mixture was poured into 50 mL of water and extracted with dichloromethane (3 × 30 mL). The organic extracts were combined, dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = 4:1, volume ratio) to give white solid intermediate 4, with a yield of 76%.

[0048]

[0049] Intermediate 4 (0.78 g, 1.0 mmol), 2-bromo-9-phenylcarbazole (0.42 g, 1.3 mmol), tris(dibenzylacetone)palladium (Pd2(dba)3, 0.03 g, 0.03 mmol), tri-tert-butylphosphine tetrafluoroborate (t-Bu3P・HBF4, 0.03 g, 0.06 mmol), and sodium tert-butoxide (t-BuONa, 0.29 g, 3.0 mmol) were added to a 50 mL round-bottom flask equipped with a reflux condenser. The flask was evacuated and backfilled with dry nitrogen, repeated three times; then 20 mL of dry toluene was injected, and the reaction mixture was refluxed and stirred for 12 hours under a nitrogen atmosphere. After cooling to room temperature, the mixture was poured into 50 mL of water and extracted with dichloromethane (3 × 30 mL). The organic extracts were combined, dried over anhydrous magnesium sulfate, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (eluent: petroleum ether / dichloromethane = : 1, volume ratio) to give a white solid intermediate 5 with a yield of 75%.

[0050]

[0051] Preparation of DB-BFCz compound: Under a nitrogen atmosphere, intermediate 5 (1.05 g, 1.0 mmol) and 15 mL of o-dichlorobenzene (o-DCB) were added to a 100 mL sealed reaction tube. Boron tribromide (2.50 g, 10.0 mmol) was slowly added, the reaction tube was sealed, and the reaction mixture was heated to 210 °C and stirred for 36 hours. After cooling to room temperature, the reaction was quenched by adding 8.0 mL of methanol under ice bath conditions (the dropping rate was controlled to avoid bumping). The organic solvent was removed by vacuum distillation, and the residual solid was purified by rapid silica gel column chromatography (eluent: petroleum ether / dichloromethane = 3:1, v / v) to give a bright yellow solid DB-BFCz (0.44 g, yield 38%).

[0052] Hydrogen nuclear magnetic resonance (HMR) spectra: The products obtained in Examples 1 and 2 were subjected to NMR scanning using a Bruker 400 MHz superconducting NMR spectrometer to obtain... Figures 1-2 ¹H NMR spectrum. from Figure 1 It can be seen that, 1¹H NMR (400 MHz, C6D6) δ 9.21 (s, 2H), 8.84 – 8.76 (m, 2H), 8.15 – 8.06 (m, 2H), 7.49 (s, 2H), 7.22 (d, J = 8.2 Hz, 2H), 7.12 – 7.03 (m, 6H), 6.74 – 6.55 (m, 8H), 5.24 (s, 1H), 2.12 (s, 6H), 1.54 (d, J = 21.5 Hz, 12H). The molecular ¹H NMR peak energies correspond one-to-one with the target product DB-DBF in Example 1. The chemical shifts and peak shapes conform to the characteristics of hydrogen atoms in different environments within the molecular structure, and the peak area ratio is reasonable, proving that the DB-DBF structure is correct. from Figure 2 It can be seen that, 1 H NMR (400 MHz, CDCl3) δ 9.60 (d, J = 4.2 Hz, 1H), 9.22 (dd, J = 7.8, 1.7 Hz, 1H), 8.96 (td, J = 6.8, 2.0 Hz, 1H), 8.42 – 8.25 (m,3H), 7.89 (dd, J = 12.5, 8.1 Hz, 2H), 7.71 (d, J = 8.1 Hz, 1H), 7.52 (dd, J =7.0, 2.9 Hz, 3H), 7.41 – 7.25 (m, 11H), 6.90 – 6.67 (m, 6H), 5.26 (s, 1H),2.32 (d, J = 18.4 Hz, The peak energies of the proton NMR spectrum correspond one-to-one with the target product DB-BFCz in Example 2. The chemical shifts and peak shapes are consistent with the characteristics of hydrogen atoms in different environments within the molecular structure, and the peak area ratio is reasonable, proving that the structure of DB-BFCz is correct. Mass spectrometry: 5 mg of the products obtained in Examples 1 and 2 were dissolved in dichloromethane, and acetonitrile was added dropwise to 5 mL. The solutions were then filtered through a 0.22 μm filter membrane to remove particles larger than 0.22 μm, minimizing detection interference. The samples were then placed in a liquid chromatography-mass spectrometry (LC-MS) system for routine analysis. Figures 3-4 The mass spectrum is used to determine its mass. from Figure 3 It can be seen that the relative molecular mass of the product obtained in Example 1 is 860.3592, which is similar to that of the synthesized DB-DBF (chemical formula C). 60 H 43The theoretical relative molecular mass of B2N3O2 is consistent with that of B2N3O2 (860.3575); from Figure 4 It can be seen that the relative molecular mass of the product obtained in Example 2 is 935.4108, which is similar to that of the synthesized DB-BFCz (chemical formula C). 68 H 48 The theoretical relative molecular mass of B2N4O (935.4147) is consistent with that of B2N4O, further proving that the target product was successfully synthesized. Ultraviolet-visible absorption spectrum and fluorescence spectrum.

[0053] UV-Vis absorption spectroscopy: The products obtained in Examples 1 and 2 were dissolved in toluene solution to prepare a 1×10⁻³mol / L stock solution. When testing with a Shimadzu UV-2700 UV-Vis spectrophotometer, the solutions were diluted to 1×10⁻³mol / L. 5 The UV-Vis absorption spectra of DB-DBF and DB-BFCz in toluene solution were obtained by measuring mol / L. Parameter settings: scan range 250–700 nm, scan speed 200 nm / min, slit width 2 nm. Fluorescence spectroscopy: The products obtained in Examples 1 and 2 were tested using an Edinburgh FL980 transient and steady-state fluorescence phosphorescence spectrometer to obtain fluorescence emission spectra of DB-DBF and DB-BFCz. Parameter settings: excitation wavelength 365 nm, slit width 5 nm, so that the ordinate value is close to one million, scan range 400-600 nm, and spectra were obtained by spectral testing. Figure 5 The images show the UV-Vis absorption and fluorescence emission spectra of the product DB-DBF obtained in Example 1 in toluene solution. As can be seen from the figures, the maximum UV absorption peak of DB-DBF is located at 438 nm, which mainly originates from the π-π transitions of the rigid framework of the "crab-like" molecular structure. The fluorescence emission peak is located at 450 nm, which is due to intramolecular charge transfer (ICT) transitions, with a full width at half maximum (FWHM) of 22 nm and a Stokes shift of 13 nm, demonstrating good narrow-band emission characteristics. Figure 6 The images show the UV-Vis absorption and fluorescence emission spectra of the product DB-BFCz obtained in Example 2 in toluene solution. The maximum UV absorption peak of DB-BFCz is located at 441 nm, a 3 nm redshift compared to DB-DBF, attributed to the moderate expansion of the molecular conjugation system after the introduction of the carbazole donor unit. The fluorescence emission peak is located at 450 nm, with a FWHM of only 17 nm, the narrowest of the two compounds, and a Stokes shift of 9 nm, exhibiting superior narrow-band emission characteristics. This is due to the differentiated donor regulation formed by the carbazole unit and the dibenzofuran unit, further enhancing the intramolecular multiple resonance (MR) effect and concentrating electronic transitions. The fluorescence lifetime of the thin films was tested using an Edinburgh FL980 transient and steady-state fluorescence phosphorescence spectrometer on the products obtained in Examples 1 and 2. The experiment used an excimer laser to generate ultraviolet light to excite the samples. The fluorescence emitted by the samples was transmitted through a telescope system to a photomultiplier tube. The signal extracted from the photomultiplier tube was then fed into a signal integrator, and finally into a computer for data acquisition and processing. The measurement conditions were: excitation pulse repetition frequency of 1000 Hz, pulse width of 10 ns, center wavelength of 375 nm, and the test environment was a deoxygenated toluene solution (purged with argon gas for 30 minutes for deoxygenation). Figure 7 The figures show the fluorescence lifetimes of DB-DBF (Product 1) and DB-BFCz (Product 2) after deoxygenation in toluene solution. As can be seen from the figures, both products exhibit both instantaneous and delayed fluorescence lifetimes, consistent with the typical characteristics of MR-TADF materials: DB-DBF has an instantaneous fluorescence lifetime (τ1) of 2.05 ns and a delayed fluorescence lifetime (τ2) of 7.90 μs; DB-BFCz has an instantaneous fluorescence lifetime (τ1) of 2.17 ns and a delayed fluorescence lifetime (τ2) of 4.19 μs. The presence of delayed fluorescence demonstrates that both materials can efficiently utilize triplet excitons through a reverse system-reinforcement crossover (RISC) process, providing a structural basis for the high external quantum efficiency of OLED devices.

[0054] Application Examples Fabrication and performance evaluation of organic electroluminescent devices with doping concentrations of 1 wt%, 3 wt%, and 5 wt% DB-DBF or DB-BFCz as the emitting layer. The fabrication steps of the organic electroluminescent devices are as follows: (1) Pretreatment of glass anode: Select a glass substrate (3×3 mm) with an indium tin oxide (ITO) film pattern as a transparent electrode; clean the glass substrate with ethanol and then treat it with UV-ozone to obtain a pretreated glass substrate. (2) Vacuum evaporation: Vacuum evaporation is performed on the pretreated glass substrate using the vacuum evaporation method. The treated glass substrate is placed in the vacuum evaporation chamber with a vacuum degree ≤2×10 -4 The device structure is as follows: ITO / HAT-CN (5nm) / TAPC (30 nm) / TCTA (5 nm) / mCBP (5 nm) / SiTrzCz2:x wt% guest material (20 nm) / SiTrzCz2 (5 nm) / TmPyPB (30 nm) / LiF (1 nm) / Al (100 nm), where the guest material is DB-DBF or DB-BFCz, x = 1, 3, 5; the specific evaporation of each layer is a conventional technique. (3) Device packaging: The prepared organic electroluminescent device is sealed in a glove box with a nitrogen atmosphere of less than 1 ppm water and oxygen concentration. Then, a glassy sealing cap with epoxy-type ultraviolet curing resin is used to cover the above film-forming substrate and UV curing is performed for sealing. The specific packaging is a conventional technique.

[0055] A direct current was applied to the fabricated organic electroluminescent device, and its luminescence performance was evaluated using a Hamamatsu C9920-12 absolute EQE measurement system (equipped with a Hamamatsu PMA-12 Photonic multichannel analyzer C10028) in conjunction with an integrating sphere. Current-voltage characteristics were measured using a computer-controlled Keithley 2400 digital source meter. Simultaneously, the system and the Keithley 2400 source meter were used to synchronously measure current density, voltage, luminance, external quantum efficiency (EQE), and electroluminescence spectrum. The luminescence properties of the organic electroluminescent device were measured under varying applied DC voltage.

[0056] The performance of organic electroluminescent devices with DB-DBF as the light-emitting layer at doping concentrations of 1 wt%, 3 wt%, and 5 wt% are shown in Table 1 and 2. Figures 9-11 .

[0057] The device performance of organic electroluminescent devices with DB-BFCz as the emitting layer at doping concentrations of 1 wt%, 3 wt%, and 5 wt% is shown in Table 1 and 2. Figures 12-14 .

[0058] Table 1 Device Performance

[0059] a) Start-up voltage; b) Maximum brightness; c) Maximum and 100 cd / m 2 External quantum efficiency at brightness; d） Efficiency roll-off rate; e) Maximum launch peak; f) Full half-peak width; g) Color coordinates.

[0060] This invention discloses a narrowband blue multi-resonance thermally activated delayed fluorescence (MR-TADF) material based on a "rigid hard shell + flexible chelate" crab-like structure, its preparation method, and its applications, belonging to the field of organic optoelectronic materials technology. The material uses boron-nitrogen-doped rigid heterocycles as the "hard shell" (molecular backbone), with differentiated donor units introduced on both sides or one side as "flexible chelates." By controlling the intramolecular charge transfer (ICT) intensity, it achieves synergistic optimization of narrowband emission, efficient reverse intersystem crossing, and low-efficiency roll-off. The asymmetric molecule DB-BFCz of this invention has an emission peak of 450 nm in solution, a full width at half maximum (FWHM) of only 17 nm, and a reverse intersystem crossing rate (…). k RISC ) reached 9.63×10 5 s⁻¹, photoluminescence quantum yield (PLQY) ≥ 99%; the color coordinates of the non-sensitized OLED device fabricated based on it are (0.13, 0.12), and the maximum external quantum efficiency (EQE) is... max With an efficiency exceeding 40% and significant suppression of efficiency roll-off at high brightness, it breaks through the trade-off dilemma of "efficiency-roll-off-color purity" in existing blue light MR-TADF materials, and can be widely used in ultra-high-definition displays, lighting and other fields.

Claims

1. A crab-structured multi-resonance thermally activated delayed fluorescence material, characterized in that, The crab-structured multi-resonance thermally activated delayed fluorescence material has a boron-nitrogen-doped rigid heterocycle as its core, with electron donor units connected to both sides.

2. The crab-structured multi-resonance thermally activated delayed fluorescence material according to claim 1, characterized in that, The electron donor unit includes one or more of the dibenzofuran structure and the carbazole structure.

3. The crab-structured multi-resonance thermally activated delayed fluorescence material according to claim 2, characterized in that, The crab-structured multi-resonance thermally activated delayed fluorescence material is DB-DBF or DB-BFCz, with the following chemical structure: 。 4. A method for preparing the crab-structured multi-resonance thermally activated delayed fluorescence material according to any one of claims 1-3, characterized in that, The process includes the following steps: reacting intermediate 3 or intermediate 5 with a boride to obtain a crab-structured multi-resonance thermally activated delayed fluorescence material.

5. The method for preparing the crab-structured multi-resonance thermally activated delayed fluorescence material according to claim 4, characterized in that, The borides are halogen borides; the reaction temperature is 150–250℃, and the reaction time is 30–50 h.

6. The application of the crab-structured multi-resonance thermally activated delayed fluorescent material according to any one of claims 1 to 3 in the preparation of organic electroluminescent devices; or the application of the crab-structured multi-resonance thermally activated delayed fluorescent material according to any one of claims 1 to 3 in the preparation of the light-emitting layer of organic electroluminescent devices.

7. The application according to claim 6, characterized in that, The crab-structured multi-resonance thermally activated delayed fluorescence material is used as a guest material and doped into the host material to prepare the luminescent layer.

8. The application according to claim 7, characterized in that, The doping concentration of the crab-structured multi-resonance thermally activated delayed fluorescent material is 1–5 wt%.

9. An organic electroluminescent device or an organic electroluminescent device light-emitting layer, characterized in that, Includes the crab-structured multi-resonance thermally activated delayed fluorescence material according to any one of claims 1 to 3.

10. A light-emitting device, characterized in that, Includes the organic electroluminescent device of claim 9.

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