A thermally activated delayed fluorescence material and an organic electroluminescent device thereof

Abstract

The application belongs to the technical field of organic electroluminescent materials, and particularly relates to a thermally activated delayed fluorescence material and an organic electroluminescent device thereof, wherein through precise design of an outer carbazole derivative part deuterium substitution, efficient balance of cost, stability and photoelectric performance is achieved. In terms of photoelectric performance, the outer carbazole part deuterium substitution retains the hole transport characteristics of carbazole, the low vibration frequency of C-D bond inhibits non-radiative transition, and the quantum efficiency is improved. Meanwhile, the cost of the carbazole part deuterium substitution is also lower than that of full deuterium substitution, which is conducive to reducing the production cost.

Description

Technical Field

[0001] This invention belongs to the field of organic electroluminescent materials technology, and particularly relates to a thermally activated delayed fluorescence material and its organic electroluminescent device. Background Technology

[0002] Currently, the global display and lighting industry is accelerating its iterative upgrade towards high performance, low energy consumption, and flexibility, with consumer electronics, automotive displays, and high-end lighting demanding increasingly higher device performance. Under this trend, organic light-emitting diodes (OLEDs), with their unique advantages such as self-illumination, high contrast, wide viewing angle, fast response, and flexible fabrication, have surpassed traditional display technologies to become the core development direction in this field, with market penetration increasing year by year.

[0003] As the "heart" of OLED devices, luminescent materials directly determine key performance indicators such as photoelectric conversion efficiency, color performance, lifespan, and stability. Technological breakthroughs and optimizations in luminescent materials are not only crucial for enhancing the competitiveness of OLED products but also a key driving force for the high-quality upgrading of the entire OLED industry. Looking back at the evolution of OLED technology, from the early limitations of traditional fluorescent materials with a quantum efficiency below 25%, to the cost and environmental issues associated with phosphorescent materials due to heavy metals, the industry has consistently explored luminescent technology solutions that balance high efficiency, high color purity, high stability, and low cost.

[0004] Against this backdrop, TADF sensitization (also known as "superfluorescence") technology, through the synergistic design of "sensitizer-terminal emitter," has achieved nearly 100% of the theoretical internal quantum efficiency of fluorescent OLEDs while perfectly preserving the advantages of traditional fluorescent materials in color purity and stability, making it a core technological path for realizing high-end OLED devices. Deuteration modification, as a precise molecular engineering method, effectively reduces non-radiative energy loss and improves the thermal stability and excited-state lifetime of materials by replacing hydrogen atoms at key molecular sites with deuterium atoms. It is crucial for optimizing the energy transfer efficiency of TADF sensitization systems and suppressing efficiency roll-off, gradually becoming an indispensable core supporting technology in the research and development of high-end OLED materials, laying a solid foundation for breakthroughs in OLED technology towards higher performance. Summary of the Invention

[0005] To address the problems existing in the background art, the present invention provides a thermally activated delayed fluorescence material having the structure shown in Formula I: ; R1 and R2 are each independently selected from hydrogen, deuterium, and C1-C. 10 Alkyl, C3-C 10 cycloalkyl, substituted or unsubstituted C6-C 18 aryl, substituted or unsubstituted C6-C18 heteroaryl groups; The structure of A is: X is independently selected from O, S, and Se; R3-R6 are each independently selected from hydrogen, deuterium, deuterated or undeuterated C1-C. 10 Alkyl, C3-C 10 cycloalkyl, substituted or unsubstituted C6-C 18 aryl, substituted or unsubstituted C6-C 18 heteroaryl groups; * indicates a connection site. When substitution is present, the substituents are independently selected from deuterium, C6-C. 12 The aryl group, n, is independently 1 up to the largest substitution site number in the ring.

[0006] As a preferred embodiment of the present invention, R1 and R2 are selected from hydrogen, deuterium, or phenyl.

[0007] As a preferred embodiment of the present invention, each of R3-R6 is independently selected from hydrogen, deuterium, substituted or unsubstituted phenyl groups.

[0008] As a preferred embodiment of the present invention, when substitution is present, the substituent is deuterium.

[0009] As a preferred embodiment of the present invention, the specific structure of the thermally activated delayed fluorescence material is as follows: ; ; ; ; ; ; ; ; .

[0010] 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 layer includes one of the thermally activated delayed fluorescence materials described above.

[0011] As a preferred embodiment of the present invention, the organic electroluminescent device is used to manufacture display devices, lighting sources, signal lights, and signs. The display devices include mobile phone displays, computer displays, television displays, smartwatch displays, smart car display panels, and VR or AR helmet displays.

[0012] The beneficial effects of this invention are as follows: This invention provides a thermally activated delayed fluorescence material and its organic electroluminescent device, achieving a highly efficient balance between cost, stability, and photoelectric performance through precise design of partial deuteration of the outer carbazole derivative. This design utilizes the high bond energy of the CD bond to significantly suppress CH bond breaking induced by excited states and polarons, reducing reactive degradation products such as free radicals, thereby mitigating triplet annihilation and significantly improving material stability and device lifetime. The partial deuteration of the outer carbazole enhances resistance to degradation while maintaining the rigidity of the parent core, improving device stability. In terms of photoelectric performance, the partial deuteration of the outer carbazole retains the hole transport characteristics of carbazole, and the low vibrational frequency of the CD bond suppresses nonradiative transitions, improving quantum efficiency. Simultaneously, the cost of partial deuteration of the carbazole is lower than that of full deuteration, which helps reduce production costs; the steric hindrance effect of the peripheral fully deuterated benzene ring alleviates π-π stacking, improves film uniformity, and ultimately effectively suppresses efficiency roll-off at high current densities. Attached Figure Description

[0013] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of compound 7 in this invention. Detailed Implementation

[0014] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments 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.

[0015] Preparation Examples Example 1: Preparation of Compound 3 ; Synthesis of 3-2: Under a nitrogen atmosphere, 3-1 (3.8 g, 10 mmol), 50 mL of heavy water, and 20 mL of toluene were added to a 250 mL three-necked flask and stirred at 120 °C for 24 h. After cooling the reaction system to room temperature, it was extracted three times with dichloromethane and water. After separation, the organic phase was used to remove the solvent using a rotary evaporator to obtain the crude product. The crude product was purified by column chromatography to obtain 3-2 (3.6 g, 91%), with a molecular weight determined by mass spectrometry of 397.71 (theoretical value: 391.57). Synthesis of 3-5: Under a nitrogen atmosphere, 3-3 (2.8 g, 10 mmol), 3-4 (2.7 g, 22 mmol), Pd(pph3)4 (149 mg, 0.2 mmol), and K2CO3 (8.3 g, 60 mmol) were added to a 250 mL three-necked flask, along with a mixed solution of 51 mL tetrahydrofuran and 17 mL water. The mixture was refluxed for 4 hours. After the reaction was complete, the mixture was allowed to return to room temperature and filtered to obtain the organic phase. The organic phase was dried over anhydrous magnesium sulfate and then distilled under reduced pressure. The resulting solid was recrystallized from toluene to give 3-5 (2.1 g, 75%). The molecular weight determined by mass spectrometry was 285.24 (theoretical value: 285.37). Synthesis of 3-6: Under a nitrogen atmosphere, 3-5 (1.4 g, 5 mmol), triphenylphosphine (6.6 g, 25 mmol), and 30 ml of o-dichlorobenzene were added to a 100 ml three-necked flask, stirred and mixed, heated to 180 °C, and reacted for 12 hours. A TLC sample was taken, showing no residue, indicating complete reaction. The mixture was allowed to cool naturally to room temperature, filtered, and the filtrate was rotary evaporated under reduced pressure until no fraction remained. The filtrate was then passed through a neutral silica gel column to obtain 3-6 (0.84 g, 72%). Mass spectrometry analysis determined the molecular weight to be 252.21 (theoretical value: 252.36). Synthesis of 3-8: Under a nitrogen atmosphere, 3-7 (16.3 g, 60 mmol), cuprous cyanide (CuCN) (12 g, 134 mmol), and N-methyl-2-pyrrolidone (NMP) (80 mL) were added to a 2 L three-necked flask, and the mixture was stirred at 150 °C for 5 hours. 100 mL of dichloromethane was added to the reaction mixture, the mixture was filtered through diatomaceous earth, and the filtrate was concentrated using an evaporator. After purification and concentration by silica gel chromatography, 3-8 (6.1 g, 62%) was obtained. The molecular weight determined by mass spectrometry was 164.26 (theoretical value: 164.11). Synthesis of 3-10: Under a nitrogen atmosphere, 3-18 (2.0 g, 12 mmol), potassium carbonate (3.3 g, 24 mmol), palladium acetate (0.1 g, 0.6 mmol), tricyclohexylphosphine (P(Cy)3) (0.5 g, 1.8 mmol), 3-9 (4.9 mL, 30 mmol), 2-ethylhexanoic acid (7.8 mL, 5 mmol), and xylene (50 mL) were added to a 500 mL three-necked flask and stirred at 100 °C for 5 hours. 100 mL of dichloromethane was added to the reaction solution and passed through diatomaceous earth. The dichloromethane in the resulting solution was removed, and the precipitated solid was filtered. The solid was purified by silica gel column chromatography to obtain 3-10 (1.4 g, 37%), with a molecular weight determined by mass spectrometry of 326.48 (theoretical value: 326.37). Synthesis of 3-11: Under a nitrogen atmosphere, 3-10 (3.3 g, 10 mmol), 3-2 (3.9 g, 10 mmol), cesium carbonate (8.2 g, 25 mmol), and N,N-dimethylformamide (50 mL) were added to a 250 mL two-necked flask. The reaction was carried out overnight at 120 °C under nitrogen protection. Heating was stopped, and after cooling to room temperature, 150 mL of water was added and stirred for 10 min. A large amount of white solid precipitated. The solid was filtered, and the filter cake was washed with ethanol for 2 h. After cooling, the solid was filtered again to obtain 3-11 (4.9 g, 70%). The molecular weight determined by mass spectrometry was 698.06 (theoretical value: 697.93). Synthesis of Compound 3: Under a nitrogen atmosphere, 3-11 (7.0 g, 10 mmol), 3-6 (2.5 g, 10 mmol), cesium carbonate (8.2 g, 25 mmol), and N,N-dimethylformamide (50 mL) were added to a 250 mL two-necked flask. The reaction was carried out overnight at 120 °C under nitrogen protection. Heating was stopped, and after cooling to room temperature, 150 mL of water was added and stirred for 10 min. A large amount of white solid precipitated. The solid was filtered, and the filter cake was washed with ethanol for 2 h. After cooling, the solid was filtered again to obtain Compound 3 (7.0 g, 75%). The molecular weight determined by mass spectrometry was 930.15 (theoretical value: 930.29).

[0016] Example 2: Preparation of compound 22 ; Synthesis of 22-2: Under a nitrogen atmosphere, 22-1 (3.1 g, 10 mmol) and 30 mL of acetic acid were added to a 100 mL three-necked flask, stirred to dissolve, and cooled to 0 °C using an ice-salt bath. Br2 (2 g, 12.5 mmol) was dissolved in 12.5 mL of acetic acid, and the bromine-acetic acid solution was slowly added dropwise to the three-necked flask. After the addition was complete, the mixture was brought to room temperature and stirred for 12 hours. After the reaction was complete, the reaction solution was neutralized with NaOH aqueous solution, extracted with dichloromethane, separated into layers, and the organic phase was filtered. The filtrate was rotary evaporated under reduced pressure until no fraction remained, and passed through a neutral silica gel column to obtain 22-2 (2.6 g, 66%). The molecular weight determined by mass spectrometry was 389.42 (theoretical value: 389.28). Synthesis of 22-4: Under a nitrogen atmosphere, 22-2 (3.9 g, 10 mmol), 22-3 (4.3 g, 12 mmol), and 50 mL of toluene were added to a 250 mL three-necked flask and stirred. Then, a 1:1 mixture of Pd(PPh3)4 (0.23 g, 0.2 mmol), potassium carbonate (5.9 g, 30 mmol), 10 mL of water, and ethanol was added. The mixture was stirred and heated to 120 °C and refluxed for 24 hours. After the reaction was complete, it was cooled to room temperature. The mixture was filtered, and the filtrate was separated into layers. The organic phase was rotary evaporated under reduced pressure until no fraction remained. The solution was then passed through a neutral silica gel column to obtain 22-4 (4.3 g, 69%). The molecular weight determined by mass spectrometry was 620.79 (theoretical value: 620.66). The synthesis methods for 22-5 and 3-6 are the same, except that 22-4 is used instead of 3-5. The molecular mass determined by mass spectrometry is 588.82 (theoretical value: 588.66). The synthesis methods for 22-7 and 3-10 are the same, except that 3-9 is replaced by 22-6. The molecular mass determined by mass spectrometry is 316.49 (theoretical value: 316.31). The synthesis methods of 22-8 and 3-11 are the same, the difference being that 3-10 is replaced by 22-7 and 3-2 is replaced by 22-5. The molecular mass determined by mass spectrometry analysis is 885.12 (theoretical value: 884.97). Compound 22 was synthesized using the same method as compound 3, except that 3-11 was replaced with 22-8. The molecular mass determined by mass spectrometry was 1117.17 (theoretical value: 1117.32).

[0017] Example 3: Preparation of compound 45 ; Synthesis of 45-2: Under a nitrogen atmosphere, 45-1 (5.0 g, 16.4 mmol), N-bromosuccinimide (NBS) (3.2 g, 18.1 mmol), potassium acetate (KOAc) (3.2 g, 3.3 mmol), and acetonitrile (50 mL) were added to a 100 mL three-necked flask and stirred at 50 °C for 6 hours. After stirring, 40 mL of purified water was added to the reaction mixture, and the precipitated solid was purified by silica gel column chromatography to obtain 45-2 (4.4 g, 80%). The molecular weight determined by mass spectrometry was 339.14 (theoretical value: 339.25). Synthesis of 45-3: Under a nitrogen atmosphere, 2,2,6,6-tetramethylpiperidine (2.6 mL, 15.3 mmol) and THF (23.6 mL) were added to a 100 mL three-necked flask and cooled to 0°C in an ice bath. After cooling, n-butyllithium (1.6 M hexane solution) (9.6 mL, 15.3 mmol) was added dropwise to the reaction solution. After the addition was complete, the mixture was stirred at 0°C for 30 minutes. The mixture was then cooled to -78°C using a dry ice / methanol bath. After cooling, triisopropyl borate (3.3 g, 17.7 mmol) and 45-2 (4.0 g, 11.8 mmol) were added sequentially, and the mixture was slowly heated from -78°C to room temperature while stirring. After the reaction was complete, 10 ml of 10% hydrochloric acid was added dropwise. After the addition was complete, the organic layer was recovered, and the obtained solid was washed with toluene to obtain 45-3 (3.9 g, 86%). The molecular weight determined by mass spectrometry was 383.17 (theoretical value: 383.07). Synthesis of 45-4: Under a nitrogen atmosphere, 45-3 (4.0 g, 10.4 mmol), N-chlorosuccinimide (NCS) (14.0 g, 10.4 mmol), cuprous chloride (I) (1.0 g, 10.4 mmol), and acetonitrile (35 mL) were added to a 100 mL three-necked flask and stirred at 60 °C for 6 hours. 30 mL of dichloromethane was added to the reaction mixture, and then the mixture was passed through diatomaceous earth. The resulting solution was concentrated, and the solid was purified by silica gel column chromatography to give 45-4 (2.9 g, 75%). The molecular weight determined by mass spectrometry was 373.75 (theoretical value: 373.69). Synthesis of 45-6: Under a nitrogen atmosphere, 45-5 (28.8 g, 0.1 mol), aminosulfonic acid (22.6 g, 0.2 mol), acetonitrile (500 mL), and sodium hydroxide (1 M) (667 mL, 0.67 mol) were added to a 1000 mL three-necked flask and stirred at room temperature for 24 hours. After the reaction was complete, the mixture was extracted with toluene, the organic phase was collected by separation, dried over anhydrous sodium sulfate, and the organic reagents were removed under reduced pressure using a rotary evaporator. The crude product was purified by silica gel column chromatography to obtain 45-6 (13.2 g, 51%), with a molecular weight determined by mass spectrometry of 259.42 (theoretical value: 259.31). Synthesis of 45-7: Under a nitrogen atmosphere, 45-6 (10.4 g, 40 mmol), 45-4 (14.9 g, 40 mmol), tris(dibenzylacetone)dipalladium (Pd2(dba)3) (0.7 g, 0.8 mmol), 2-biscyclohexylphosphine-2',4',6'-triisopropylbiphenyl (X-phos) (0.36 g, 0.8 mmol), sodium tert-butoxide (5.8 g, 60 mmol), and 400 mL of toluene were added to a 1 L three-necked flask. The reaction mixture was heated to 110 °C and stirred for 8 hours. After the reaction was complete, the reaction mixture was cooled to room temperature. Add 300 mL of deionized water to the reaction system, collect the organic phase by separation, dry with anhydrous sodium sulfate, remove organic reagents under reduced pressure using a rotary evaporator, and purify the crude product by silica gel column chromatography to obtain 45-7 (18.8 g, 85%). The molecular weight determined by mass spectrometry is 552.23 (theoretical value: 552.09). Synthesis of 45-8: Under a nitrogen atmosphere, 45-7 (16.6 g, 30 mmol), 1,3-bis(2,6-diisopropylphenyl)imidazolium chloride (IPrHCl) (0.53 g, 1.2 mmol), palladium(II) acetate (0.136 g, 0.6 mmol), potassium carbonate (8.3 g, 42 mmol), and 90 mL of N,N-dimethylacetamide (DMAc) were added to a 200 mL three-necked flask. The reaction mixture was heated to 160 °C and stirred for 10 hours. After the reaction was complete, the reaction mixture was cooled to room temperature. The precipitated solid was collected by filtration and washed with acetone to obtain 45-8 (12.8 g, 83%). The molecular weight determined by mass spectrometry was 515.75 (theoretical value: 515.63). Synthesis of 45-9: Under a nitrogen atmosphere, 45-8 (5.2 g, 10 mmol), 50 mL of heavy water, and 20 mL of toluene were added to a 250 mL three-necked flask and stirred at 120 °C for 24 h. After cooling the reaction system to room temperature, it was extracted three times with dichloromethane and water. After separation, the organic phase was used to remove the solvent using a rotary evaporator to obtain the crude product. The crude product was purified by column chromatography to obtain 45-9 (7.9 g, 91%), with a molecular weight determined by mass spectrometry of 535.62 (theoretical value: 535.75). The synthesis methods of 45-10 and 3-11 are the same, the difference being that 22-7 is used to replace 3-10 and 45-9 is used to replace 3-2. The molecular mass determined by mass spectrometry is 832.20 (theoretical value: 832.06). Compound 45 was synthesized using the same method as compound 3, except that 3-11 was replaced with 45-10. The molecular mass determined by mass spectrometry was 1064.52 (theoretical value: 1064.41).

[0018] Unless otherwise specified, all reagents and instruments used in the examples are commercially available products. Some reaction compounds were purchased from a supplier (Zhengzhou Alpha Chemical Co., Ltd.), while others were prepared from commercially available raw materials through simple reactions. Percentages refer to mass percentages, and temperatures are in degrees Celsius (°C). The principles, procedures, routine post-treatments, silica gel column chromatography, and recrystallization purification methods of this type are well-known to those skilled in the art and can be fully implemented to obtain the target product. The reactions in each preparation example are generally carried out under positive pressure of nitrogen or argon.

[0019] 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.

[0020] Device Examples Based on the same inventive concept, embodiments of the present invention also provide an organic light-emitting device. The following example uses an OLED organic light-emitting device as an illustration; however, it should be understood that the following detailed description is not intended to limit the invention, and those skilled in the art can extend the application of the following detailed description to other organic light-emitting devices.

[0021] In one embodiment, the OLED includes a first electrode and a second electrode, and a plurality of organic material layers located between the electrodes. In a specific embodiment, a substrate can be used below the first electrode or above the second electrode. The substrate is made of glass or polymer material with excellent mechanical strength, thermal stability, water resistance, and transparency. Furthermore, the substrate used for the display may also have thin-film transistors (TFTs).

[0022] The first electrode can be formed by sputtering or depositing the material to be used as the first electrode on a substrate. When the first electrode is used as the anode, transparent conductive oxide materials such as indium tin oxide (ITO), indium zinc oxide (IZO), tin dioxide (SnO2), and zinc oxide (ZnO) and any combination thereof can be used. When the first electrode is used as the cathode, metals or alloys such as magnesium (Mg), silver (Ag), aluminum (Al), aluminum-lithium (Al-Li), calcium (Ca), magnesium-indium (Mg-In), and magnesium-silver (Mg-Ag) and any combination thereof can be used.

[0023] Organic material layers can be formed on electrodes using methods such as vacuum thermal evaporation, spin coating, and printing. The compounds used as organic material layers can be small organic molecules, large organic molecules, polymers, and combinations thereof.

[0024] 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 a single-layer hole transport layer containing only one compound and a single-layer hole transport layer 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).

[0025] The material for the hole transport region can 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, etc., where the aromatic amine derivatives are compounds shown below HTL-1 to HTL-20 or any combination thereof: .

[0026] 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 HIL-1 to HIL-3 described below; alternatively, one or more compounds from HTL-1 to HTL-20 can be used to dope one or more compounds from HIL-1 to HIL-3 described below. .

[0027] The light-emitting layer includes a light-emitting dye (i.e., a dopant) capable of emitting light, and may also include a host material. In one aspect of the invention, the dopant of the light-emitting layer may be selected from, but is not limited to, compounds represented by the following general formula 1: ; R can be independently composed of hydrogen, deuterium, or C1-C. 16 Alkyl, C1-C 16 Alkoxy, C3-C 18 cycloalkyl, C6-C 24 heteroaryl, unsubstituted or C6-C substituted with one or more Ra groups 18 Aryl; Ra is independently deuterium, C1-C each time it appears. 12 Alkyl, C1-C 12 Alkoxy, C3-C 12 cycloalkyl, C6-C 18 Aryl group; R1 and R2 are each independently hydrogen, deuterium, or C1-C.12 Alkyl, C1-C 12 Alkoxy, C3-C 12 Cycloalkyl, unsubstituted or C6-C substituted with one or more Rb 18 Aryl; Rb is independently deuterium, C1-C each time it appears. 12 Alkyl, C1-C 12 Alkoxy, C3-C 12 cycloalkyl, C6-C 18 Aryl groups, n1, are each independently substituents up to the largest number of substituents in the ring.

[0028] Specific examples of dopants used in this embodiment include the following compounds. However, the present invention is not limited to these specific examples of compounds: .

[0029] In one aspect of the invention, the main material of the light-emitting layer may be selected from, but not limited to, one or more combinations of the following H-1 to H-8: .

[0030] 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. Alternatively, the electron transport region can 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).

[0031] 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-32 listed below: ; .

[0032] 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.

[0033] 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:

[0034] 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-3 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-3 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-12 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 compound 3, and the doping material was D10. They were placed in independent evaporation sources, and a composite light-emitting film was formed by controlling their evaporation rate ratio to 79:20:1 (w / w / w). A 30 nm thick electron transport layer was deposited on the light-emitting layer using an ETL-21 and LiQ doping system (mass ratio 50:50, w / w). This combination helps to improve the electron transport rate and interface injection efficiency. Depositing 1 nm of Yb on the electron transport layer as an electron injection layer, its excellent insulation and extremely low work function help to form an interfacial dipole, thereby improving the injection efficiency of electrons from the Al cathode to the electron transport layer. A Mg:Ag electrode layer with a thickness of 13 nm is deposited on top of the electron injection layer, wherein the mass ratio of Mg to Ag is 1:9. 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.

[0035] 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.

[0036] Preparation of Examples 2-10: When forming the light-emitting layer, the corresponding compound in Table 1 was used to replace compound 3 in Example 1, and the organic electroluminescent device was prepared using the same method as in Example 1.

[0037] Preparation of Comparative Examples 1-5: Except that, when forming the light-emitting layer, the corresponding compound in Table 1 was used to replace compound 3 in Example 1, and the organic electroluminescent device was prepared using the same method as in Example 1.

[0038] The structures of ref-1 to ref-5 in Table 1 are as follows: .

[0039] Device evaluation: At 10mA / cm 2 The current efficiency of the device examples and comparative examples was determined at a current density of 35 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 100 cd / m 2 The maximum emission peak position, half-peak width, and corresponding CIE color coordinates were obtained, and the results are shown in Table 1 below: ; As shown in Table 1, among Examples 1 to 10, Examples 1, 3, 4, and 10 have the highest deuteration generation and the longest lifetime. Examples 22, 100, and 125 have fewer deuteration generation and their lifetimes are slightly lower compared to Examples 1, 3, 4, and 10. Examples 7, 8, and 9 have the fewest deuteration generation and the shortest lifetime. This is consistent with the general view that the higher the degree of deuteration, the better the stability. Furthermore, compared with Comparative Examples 1 to 4, Example 7 differs only in the number of deuteration generations. The device performance of Example 7 is superior to that of Comparative Examples 1 to 3 and comparable to that of Comparative Example 4. This indicates that increasing the number of deuteration generations can improve device performance. However, when the number of deuteration generations reaches a certain level, it will compress the space for improving device performance. For example, the partial deuteration performance of Example 7 is comparable to the full deuteration performance of Comparative Example 4, which shows that the structure designed in this application is advanced. Compared with the full deuteration structure, the partial deuteration structure of this application can achieve the goal of reducing costs. The difference between compound 125 in Example 6 and compound ref-5 in Comparative Example 5 is that ref-5 has two fully deuterated benzene-substituted structures. Although the large steric hindrance of the double benzene ring can effectively suppress intermolecular stacking and extend lifetime, it often disrupts charge transport balance and leads to a decrease in efficiency. Compared with Comparative Example 5, the series of compounds in this application have achieved optimization of the overall device performance.

[0040] 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.

[0041] 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 thermally activated delayed fluorescence material, characterized in that, It has the structure shown in Equation I: ； R1 and R2 are each independently selected from hydrogen, deuterium, and C1-C. 10 Alkyl, C3-C 10 cycloalkyl, substituted or unsubstituted C6-C 18 aryl, substituted or unsubstituted C6-C 18 heteroaryl groups; The structure of A is: X is independently selected from O, S, and Se; R3-R6 are each independently selected from hydrogen, deuterium, deuterated or undeuterated C1-C. 10 Alkyl, C3-C 10 cycloalkyl, substituted or unsubstituted C6-C 18 C6-C, substituted or unsubstituted 18 heteroaryl groups; * indicates a connection site. When substitution is present, the substituents are independently selected from deuterium, C6-C. 12 The aryl group, n, is independently 1 up to the largest substitution site number in the ring.

2. The thermally activated delayed fluorescence material according to claim 1, characterized in that, R1 and R2 are selected from hydrogen, deuterium, or phenyl.

3. The thermally activated delayed fluorescence material according to claim 1, characterized in that, Each of R3-R6 is independently selected from hydrogen, deuterium, substituted or unsubstituted phenyl groups.

4. The thermally activated delayed fluorescence material according to claim 4, characterized in that, When substitution is present, the substituent is deuterium.

5. The thermally activated delayed fluorescence material according to claim 1, characterized in that, The specific structure of this compound is as follows: ； ； ； ； ； ； ； ； 。 6. 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 the thermally activated delayed fluorescence material as described in claims 1 to 5.

7. The organic electroluminescent device according to claim 6, characterized in that, This organic electroluminescent device is used to manufacture display devices, lighting sources, signal lights, and signs. The display devices include mobile phone displays, computer displays, television displays, smartwatch displays, smart car display panels, and VR or AR helmet displays.

Images