A thermally activated delayed fluorescence luminescent material based on a benzoxazole ring core, its preparation method and applications

Abstract

The present invention discloses a thermally activated delayed fluorescence emitting material based on a benzoxazole ring core, and its preparation method and application, belonging to the technical field of organic optoelectronic semiconductors. For the thermally activated delayed fluorescence emitting material prepared by the present invention, the structure and combination mode of the donor units in the molecule can effectively regulate the electron cloud overlap between the donor and acceptor, significantly affect the energy levels, band gaps and triplet excited state energy levels, and improve the singlet-triplet energy level difference; in addition, the dihedral angles formed between the bridging unit and the donor and acceptor units in the molecule promote and enhance the molecular packing and aggregated state luminescence behavior. The thermally activated delayed fluorescence emitting material prepared by the present invention has better thermal stability, higher photoluminescence quantum efficiency and smaller ΔE ST and high reverse intersystem crossing rate, and has broad application prospects in the fields of organic semiconductor devices, biology and sensing, etc.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic optoelectronic semiconductors, and specifically relates to a thermally activated delayed fluorescence emitting material based on a benzoxazole ring core, and a preparation method and application thereof. Background Art

[0002] Organic light-emitting diodes (OLEDs) are considered to be the most promising display and lighting technologies. A typical OLED consists of a glass substrate, ITO, an anode, an organic light-emitting layer, and a cathode, among which the light-emitting material is the most important factor determining the light-emitting efficiency of the OLED. The development of OLED light-emitting materials has gone through the stages of fluorescent materials, phosphorescent materials, and the latest thermally activated delayed fluorescence stage (Thermally Activated Delayed Fluorescence; TADF). The first type of fluorescent materials can only utilize 25% of the singlet S1 excitons, which results in a great loss of quantum efficiency during the operation of the device. The second-generation phosphorescent materials can theoretically achieve 100% internal quantum efficiency because they utilize 75% of the triplet energy. Compared with the first-generation fluorescent materials, phosphorescent materials have significant technical advantages, which are beneficial to reducing the power consumption of the device, reducing heat generation, improving the stability of the device, and extending the service life of the device. However, Ir-based phosphorescent materials are not only expensive but also pollute the environment. In the prior art, a class of pure organic molecules with a perpendicular connection between the electron donor and acceptor planes has a very small triplet and singlet energy band gap (ΔE ST ), enabling the utilization of 75% of the triplet states that cannot be utilized by small molecules for light emission. The electrons in the triplet state can efficiently return to the singlet state through reverse intersystem crossing, and transition from the singlet state back to the ground state and emit fluorescence. Since ΔE ST is very small, an external force is required for the electrons to cross from the triplet state to the singlet state, and this external force is heat, and the whole process is called thermally activated delayed fluorescence TADF.

[0003] The current mainstream design principle of TADF organic materials is to reduce the overlap of the HOMO and LUMO orbits of the molecule, thereby reducing the energy level difference ΔE ST between S1 and T1. Benzimidazole-based molecules, due to their good thermal stability and unique photophysical properties, are used as good acceptor materials in organic optoelectronic devices such as organic field effect transistors, organic photovoltaic cells, and organic sensors. Summary of the Invention

[0004] The present invention provides a thermally activated delayed fluorescence emitting material based on a benzoxazole ring core, and a preparation method and application thereof, so as to obtain an organic light-emitting device with more beneficial performance, richer structure, easier functionalization, and large-scale production.

[0005] Technical solution: A thermally activated delayed fluorescence (TADF) emitting material based on a benzoxazole ring core, wherein the TADF emitting material is a compound represented by the general formula (I):

[0006]

[0007] Wherein, X is O, S, Se, N-R or , R is selected from a linear or branched alkyl group having 1 to 24 carbon atoms, a substituted aryl group having 6 to 30 carbon atoms, or a heteroaryl group having 5 to 30 carbon atoms; R1 and R2 are selected from a substituted aryl group having 6 to 30 carbon atoms or a heteroaryl group having 5 to 30 carbon atoms; L1 and L2 are a single bond or an arylene group; Y is CH or N; Ar1 and Ar2 are each independently an aryl group connected to L1 and L2 through an N atom, and at least one of them has a structure represented by the general formula (II);

[0008]

[0009] In the general formula (II), Ar3 and Ar4 are each independently selected from a substituted or unsubstituted benzene ring, naphthalene ring, thiophene ring, benzothiophene, benzofuran, anthracene ring, phenanthrene ring, or pyrene ring.

[0010] Preferably, Ar3 and Ar4 are each independently one of the following formulas:

[0011]

[0012] Wherein, R3 represents a substituent on Ar3 and Ar4, n is an integer selected from 0 to 4, representing 0 to 4 substituents represented by R3, and m is an integer selected from 0 to 2, representing 0 to 2 substituents represented by R3; R3 are each independently selected from deuterium, halogen, cyano, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, or a substituted or unsubstituted heteroaryl group having 3 to 30 carbon atoms. When n≥2, each R3 may be the same or different.

[0013] Preferably, in the thermally activated delayed fluorescence emitting material, and are each independently one of the following formulas:

[0014]

[0015] .

[0016] Preferably, the thermally activated delayed fluorescence emitting material includes the following compounds:

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026] 。

[0027] The thermally activated delayed fluorescence emitting material described in the present invention can be used to prepare an organic electroluminescent device, which includes an anode, a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer, an electron injection layer and a cathode sequentially stacked on a substrate; the organic light emitting layer includes a host material and a guest material, and the guest material includes one or two of the thermally activated delayed fluorescence emitting materials described above. In the perovskite solar cell composition for a perovskite solar cell device, the thermally activated delayed luminescence molecule is used as a hole transport layer.

[0028] The preparation method of the thermally activated delayed fluorescence emitting material includes the following six cases:

[0029] (1) When L1 and L2 are single bonds and Ar1 and Ar2 are the same, the preparation reaction equation is:

[0030] ;

[0031] The specific steps are as follows:

[0032] Step 1.1. Under a nitrogen atmosphere, and are added to an acetic acid solvent, stirred at 60 °C for 5 hours. After the reaction is completed, the reaction solution is cooled to room temperature, and ammonia solution is added dropwise with stirring until the pH = 7. The precipitate is filtered, washed with acetic acid, and then recrystallized with ethanol to obtain compound ;

[0033] Step 1.2. The compound obtained in Step 1.1, , the catalyst (potassium carbonate, cuprous iodide, phenanthroline, 18-crown-6) was added to the solvent N,N-dimethylformamide, and the mixture was refluxed under condensation at 180 °C for 12 h. After the reaction was completed, the reaction was cooled to room temperature, the reaction solution was poured into brine, and the crude product was obtained by filtration. Then, it was purified by silica gel column chromatography to obtain the compound .

[0034] (2) When L1 and L2 are single bonds and Ar1 and Ar2 are different, the preparation reaction equation is:

[0035] ;

[0036] The specific steps are as follows:

[0037] Step 2.1: Compounds Ar1 and Ar2 were obtained according to the method of Step 1.1;

[0038] Step 2.2: Ar1, , the catalyst (potassium carbonate, cuprous iodide, phenanthroline, 18-crown-6) were added to the solvent N,N-dimethylformamide, and the mixture was refluxed under condensation at 180 °C for 12 h. After the reaction was completed, the reaction was cooled to room temperature, the reaction solution was poured into brine, and the crude product was obtained by filtration. Then, it was purified by silica gel column chromatography to obtain the compound ;

[0039] Step 2.3: The compound obtained in Step 2.2 and Ar2 were used to obtain the compound according to the method of Step 2.2.

[0040] (3) When L1 and L2 are the same arylene group, Ar5 represents an arylene group, and Ar1 and Ar2 are the same, the preparation reaction equation is:

[0041]

[0042] The specific steps are as follows:

[0043] Step 3.1: , , and the compound was obtained according to the method of Step 2.2;

[0044] Step 3.2: The compound obtained in Step 3.1, bis(pinacolato)diboron, and the catalyst (potassium acetate, [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium) were added to the solvent 1,4-dioxane, and the mixture was refluxed under condensation at 95 °C for 12 h. Dichloromethane and water were used for extraction, and the organic phase was dried by evaporation to obtain the compound ;

[0045] Step 3.3: The compound obtained in Step 3.2, , The catalyst (potassium carbonate, dichloromethane complex of [1,1'-bis(diphenylphosphino)ferrocene] palladium dichloride) was dissolved in the solvent (tetrahydrofuran and water) and stirred at 70 °C for 3 h. After the reaction was completed, the reaction solution was cooled to room temperature, extracted with water and dichloromethane, and the organic phase was concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography to obtain the compound .

[0046] (4) When L1 and L2 are the same arylene group and Ar1 and Ar2 are different; or when L1 and L2 are different arylene groups, Ar5 and Ar6 represent arylene groups, and Ar1 and Ar2 are the same or different, the preparation reaction equation is:

[0047] ;

[0048] The specific steps are as follows:

[0049] Step 4.1, Compounds and were obtained according to the methods of steps 3.1 and 3.2;

[0050] Step 4.2, , , the catalyst (potassium carbonate, dichloromethane complex of [1,1'-bis(diphenylphosphino)ferrocene] palladium dichloride) were dissolved in the solvent (tetrahydrofuran and water) and stirred at 70 °C for 3 h. After the reaction was completed, the reaction solution was cooled to room temperature, extracted with water and dichloromethane, and the organic phase was concentrated under reduced pressure to obtain the crude product. The crude product was purified by silica gel column chromatography to obtain the compound ;

[0051] Step 4.3, The compound obtained in step 4.2, , was used to obtain the compound according to the method of step 4.2;

[0052] (5) When L1 is a single bond, L2 is an arylene group, Ar5 represents an arylene group, and Ar1 and Ar2 are the same or different, the preparation reaction equation is:

[0053] ;

[0054] The specific steps are as follows:

[0055] Step 5.1, The compound was obtained according to the method of step 2.2;

[0056] Step 5.2, Compounds were obtained according to the methods of steps 3.1 and 3.2;

[0057] Step 5.3, , , the compound is obtained according to the method in Step 4.2 .

[0058] (6) When L1 is an arylene group, L2 is a single bond, Ar5 represents an arylene group, and Ar1 and Ar2 are the same or different, the preparation reaction equation is:

[0059]

[0060] The specific steps are as follows:

[0061] Step 6.1, the compound is obtained according to the method in Step 4.2 ;

[0062] Step 6.2, , Ar2, are used to obtain according to the method in Step 2.2.

[0063] Beneficial effects: The compound of the present invention has a multiple D-A structure with strong donor characteristics and strong acceptor characteristics, has a high triplet energy level, a small ΔE ST , a high PLQY, near-infrared luminescence, high stability, and a high glass transition temperature. Benzimidazole molecules have good thermal stability and unique photophysical properties. The arrangement of the donor units in the molecule, on the one hand, can effectively regulate the overlap of the electron clouds between the donor and acceptor, significantly affect the energy levels, band gaps, and triplet excited state energy levels, and improve the singlet and triplet energy level differences (ΔE ST ); on the other hand, the close-packing connection mode between the donor and acceptor is affected by the dihedral angle of the bridging structure, and a better photoluminescence efficiency (PLQY) can be obtained. At the same time, the three-dimensional molecular structure of the donor part and the rigid planar large-conjugated structure of the acceptor unit affect the molecular crystallinity, and the packing mode of the molecules in the aggregated state can be effectively regulated, so that the molecules represented above have better morphological stability and excellent film stability in the electroluminescent device, which is beneficial to the corresponding device life and is conducive to improving the performance and luminescence efficiency of the OLED device. Multiple electron-rich donor units are beneficial to obtaining a high HOMO energy level and balanced electron and hole transport characteristics, which is beneficial to their application in perovskite solar cell devices. Description of the Drawings

[0064] Figure 1 is a schematic structural diagram of an organic electroluminescent device according to an embodiment of the present application. Among them, 1. Anode (ITO); 2. Hole injection layer (HIL); 3. Hole transport layer (HTL); 4. Organic light-emitting layer (EML); 5. Electron transport layer (ETL); 6. Electron injection layer (EIL); 7. Cathode (Al);

[0065] Figure 2 is the 1H NMR spectrum of Compound A-1 of the present invention;

[0066] Figure 3 It is the 1H NMR spectrum of compound B-4 of the present invention. Detailed implementation manners

[0067] The technical solution of the present invention will be described in detail below through examples, but the protection scope of the present invention is not limited to the described examples.

[0068] In this specification, when no other definition is provided, "substituted" means that at least one hydrogen of a substituent or a compound is replaced by deuterium, halogen, cyano, substituted or unsubstituted C1-C24 alkyl, C3-C24 cycloalkyl, C6-C24 aryl, C2-C24 heteroaryl or a combination thereof. In this specification, when no other definition is provided, "alkyl" means an aliphatic hydrocarbon group. The alkyl can be C1-C24 alkyl. More specifically, the alkyl can be C1-C20 alkyl or C1-C10 alkyl. For example, C1-C4 alkyl can have 1 to 4 carbon atoms in the alkyl chain and can be selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl and tert-butyl. Specific examples of the alkyl can be methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc. In this specification, "aryl" means a group including at least one hydrocarbon aromatic moiety, and all elements of the hydrocarbon aromatic moiety have conjugated p-orbitals, such as phenyl, naphthyl, etc., two or more hydrocarbon aromatic moieties can be connected by a σ bond and can be, for example, biphenyl, terphenyl, quaterphenyl, etc., or two or more hydrocarbon aromatic moieties are directly or indirectly fused to provide a non-aromatic fused ring. For example, it can be fluorenyl. The aryl can include monocyclic, polycyclic or fused polycyclic (i.e., rings sharing adjacent carbon atom pairs) functional groups. Compounds for which the synthesis method is not mentioned in this example can be raw material products obtained through commercial channels.

[0069] Example 1: Preparation of a thermally activated delayed fluorescence emitting material based on a benzoxazole ring core of the present invention

[0070] (1) Preparation of Compounds 1 to 13

[0071] Synthesis route of Compound 1:

[0072]

[0073] Under a nitrogen atmosphere, 2,3-diketo-indole (10 g, 68 mmol), 1,2-phenylenediamine (7.3 g, 68 mmol) and acetic acid (200 mL) were successively added to a 500 mL three-necked flask, and the mixture was stirred at 60 °C for 5 hours. After the reaction was completed, the reaction solution was cooled to room temperature, and ammonia solution was added dropwise with stirring until the pH = 7. The precipitate was filtered, washed with acetic acid, and then recrystallized with ethanol to obtain 13.3 g of pure compound 1 (yield 89%). HR-MS (ACPI-M+, m / z): 219.080.

[0074] The compounds listed in Table 1 were synthesized in the same manner as compound 1, except that starting material 1 was used instead of 2,3-diketo-indole, and starting material 2 was used instead of 1,2-phenylenediamine. The main starting materials, synthetic intermediates and their yields are shown in Table 1:

[0075] Table 1

[0076]

[0077] (2) Synthesis of compounds A-1, A-3, B-7, C-12, D-13, D-28, E-5

[0078] The synthetic route of compound A-1 is as follows:

[0079]

[0080] Under a nitrogen atmosphere, 4,7-dibromobenzofuran (5 g, 17.9 mmol), compound 1 (9.8 g, 44.8 mmol), potassium carbonate (9.9 g, 71.6 mmol), copper(I) iodide (3.8 mg, 0.2 mmol), 1,10-phenanthroline (3.6 mg, 0.2 mmol), 18-crown-6 (5.3 mmol, 0.2 mmol) and dry N,N-dimethylformamide (200 mL) were successively added to a 500 mL three-necked flask. The mixture was refluxed under condensation at 180 °C for 12 h. After the reaction was completed, the reaction was cooled to room temperature, and the reaction solution was poured into 500 mL of 0.01 M saline. The crude product was obtained by filtration. The crude product was purified by silica gel column chromatography using a dichloromethane / hexanol (volume ratio 1:2.5) system to obtain 5.9 g of pure compound A-1 (yield 60%). HR-MS (ACPI-M+, m / z): 554.160. The 1H NMR spectrum of compound A-1 is as Figure 2 shown.

[0081] The compounds listed in Table 2 were synthesized in the same manner as compound A-1, except that starting material 3 was used instead of compound 1, and starting material 4 was used instead of 4,7-dibromobenzofuran. The main starting materials, synthetic intermediates and their yields are shown in Table 2:

[0082] Table 2

[0083]

[0084] (3) Preparation of Compounds 15 to 23

[0085] The synthetic route of Compound 15 is as follows:

[0086]

[0087] Under a nitrogen atmosphere, Compound 14 (CAS: 1380238-96-9, 5 g, 17.9 mmol), Compound 4 (5.8 g, 21.5 mmol), potassium carbonate (9.9 g, 71.6 mmol), copper(I) iodide (3.8 mg, 0.2 mmol), 1,10-phenanthroline (3.6 mg, 0.2 mmol), 18-crown-6 (5.3 mmol, 0.2 mmol), and dry N,N-dimethylformamide (200 ml) were successively added to a 500-ml three-necked flask. The mixture was refluxed under condensation at 180 °C for 12 h. After the reaction was completed, the reaction was cooled to room temperature, and the reaction solution was poured into 500 ml of 0.01 M saline. The crude product was obtained by filtration. The crude product was purified by silica gel column chromatography using a dichloromethane / hexanol (volume ratio 1:2.5) system to obtain 5.0 g of pure Compound 15 (yield 58%). HR-MS (ACPI-M+, m / z): 481.995.

[0088] The compounds listed in Table 3 were synthesized in the same manner as Compound 15, except that starting material 5 was used instead of Compound 4, starting material 6 was used instead of Compound 14, and the main starting materials, synthetic intermediates, and their yields are shown in Table 3:

[0089] Table 3

[0090]

[0091] (4)Synthesis of Compounds B-4, A-4, A-14, C-11, C-29, E-28

[0092] The synthetic route of Compound B-4 is as follows:

[0093]

[0094] Under a nitrogen atmosphere, 15 (5 g, 10.4 mmol), 10 (3.4 g, 12.5 mmol), potassium carbonate (5.7 g, 41.6 mmol), copper(I) iodide (1.9 mg, 0.1 mmol), 1,10-phenanthroline (1.8 mg, 0.1 mmol), 18-crown-6 (2.7 mg, 0.1 mmol) and dry N,N-dimethylformamide (200 ml) were successively added to a 500 ml three-necked flask. The mixture was refluxed under condensation at 180 °C for 12 h. After the reaction was completed, the reaction was cooled to room temperature, and the reaction solution was poured into 500 ml of brine. The crude product was obtained by filtration. The crude product was purified by silica gel column chromatography using a dichloromethane / hexanol (volume ratio 1:2.5) system to obtain 4.1 g of pure compound B-4 (yield 59%). HR-MS (ACPI-M+, m / z): 671.164. The 1H NMR spectrum of compound B-4 is as shown in Figure 3 shown.

[0095] The compounds listed in Table 4 were synthesized in the same manner as compound B-4, except that starting material 7 was used instead of compound 15, starting material 8 was used instead of compound 10, and the main starting materials, synthetic intermediates and their yields are shown in Table 4:

[0096] Table 4

[0097]

[0098] (5) Preparation of Compounds 24 to 26

[0099] The synthetic route of compound 24 is as follows:

[0100]

[0101] Under a nitrogen atmosphere, 21 (10 g, 24.5 mmol), bis(pinacolato)diboron (8.7 g, 34.3 mmol), potassium acetate (7.2 g, 73.5 mmol), [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium(II) (1.5 mg, 0.2 mmol) were successively added to a 500 ml three-necked flask and dissolved in 1,4-dioxane (200 ml). The mixture was refluxed under condensation at 95 °C for 12 h. After the reaction was completed, it was extracted with dichloromethane and water. The organic phase was concentrated under reduced pressure to remove the solvent to obtain 9.14 g of compound 24 (yield 82%). HR-MS (ACPI-M+, m / z): 455.383.

[0102] The compounds listed in Table 5 were synthesized in the same manner as compound 24, except that starting material 9 was used instead of compound 21. The main starting materials, synthetic intermediates and their yields are shown in Table 5:

[0103] Table 5

[0104]

[0105] (6) Preparation of Compound A-18

[0106] The synthetic route of Compound A-18 is as follows:

[0107]

[0108] Under a nitrogen atmosphere, 10 g (22 mmol) of Compound 24, 13.4 g (48.4 mmol) of Compound 27, 12.1 g (88 mmol) of potassium carbonate, and 0.2 g (0.2 mmol) of [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium dichloromethane complex were successively added to a 500 mL two-necked flask. The solvents were 100 mL of tetrahydrofuran and 20 mL of water, and the mixture was stirred at 70 °C for 3 h. After the reaction was completed, the reaction solution was cooled to room temperature, extracted with water and dichloromethane, and the organic phase was concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography using a dichloromethane / petroleum ether (volume ratio 1:5) system to obtain 12.8 g of pure Compound A-18 (yield 75%), HR-MS (ACPI-M+, m / z): 775.909.

[0109] (7)Preparation of Compound 29

[0110] The synthetic route of Compound 29 is as follows:

[0111]

[0112] Under a nitrogen atmosphere, 10 g (17 mmol) of Compound 25, 8.2 g (18.7 mmol) of Compound 28, 9.4 g (68 mmol) of potassium carbonate, and 0.2 g (0.2 mmol) of [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium dichloromethane complex were successively added to a 500 mL two-necked flask. The solvents were 100 mL of tetrahydrofuran and 20 mL of water, and the mixture was stirred at 70 °C for 3 h. After the reaction was completed, the reaction solution was cooled to room temperature, extracted with water and dichloromethane, and the organic phase was concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography using a dichloromethane / petroleum ether (volume ratio 1:5) system to obtain 9.6 g of pure Compound 29 (yield 70%), HR-MS (ACPI-M+, m / z): 807.755.

[0113] (8)Preparation of Compound E-16

[0114] The synthetic route of Compound E-16 is as follows:

[0115]

[0116] Under a nitrogen atmosphere, 10 g (12.4 mmol) of Compound 29, 5.7 g (13.6 mmol) of Compound 26, 6.8 g (49.6 mmol) of potassium carbonate, and 0.1 g (0.1 mmol) of [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium dichloromethane complex were successively added to a 500 mL two-necked flask. The solvents were 100 mL of tetrahydrofuran and 20 mL of water, and the mixture was stirred at 70 °C for 3 h. After the reaction was completed, the reaction solution was cooled to room temperature, extracted with water and dichloromethane, and the organic phase was concentrated under reduced pressure to obtain a crude product. The crude product was purified by silica gel column chromatography using a dichloromethane / petroleum ether (volume ratio 1:5) system to obtain 9.3 g of pure Compound E-16 (yield: 73%). HR-MS (ACPI-M+, m / z): 1022.188.

[0117] Application Example 1: Preparation of an Organic Electroluminescent Device

[0118] This application example provides an organic electroluminescent device, which includes an anode, a hole injection layer, a hole transport layer, an organic light-emitting layer, an electron transport layer, an electron injection layer, and a cathode that are sequentially stacked on a substrate. The device structure is: ITO / hole injection layer / hole transport layer / organic light-emitting layer / electron transport layer / electron injection layer / cathode, and its structural schematic diagram is as Figure 1 shown.

[0119] Among them, the anode is made of ITO material; the hole injection layer material is selected from the following structural materials: ;

[0120] The hole transport layer material is a compound with the following structure: ; The organic light-emitting layer is formed by co-doping a host material and a guest material. Among them, the host material is Compound host, and the guest material is Compound A-1. The mass ratio of the host material to the guest material is 80:20; the chemical structure of Compound Host is as follows: ; The electron transport layer material is a compound with the following structure: ; The electron injection layer material is composed of LiF. The cathode material is metal Al.

[0121] The preparation of the above organic electroluminescent device includes the following steps:

[0122] 1) Substrate cleaning: The glass substrate coated with the ITO transparent electrode is ultrasonically treated in a commercial cleaning agent, then rinsed in deionized water, ultrasonically degreased in a mixed solvent of acetone and ethanol (volume ratio of acetone to ethanol is 1:1), baked in a clean environment until all moisture is removed, and then cleaned with ultraviolet light and ozone.

[0123] 2) Preparation of the organic layer: Transfer the ITO transparent substrate to an evaporation apparatus, and sequentially evaporate a 5-nm HIL layer, a 60-nm HTL layer, a 40-nm EML layer, a 40-nm ETL layer, a 0.5-nm EIL layer, and 100 nm of aluminum as the cathode.

[0124] Application Example 2: Preparation of an organic electroluminescent device

[0125] An organic electroluminescent device was fabricated using the same method as in Application Example 1, except that the guest material in the organic light-emitting layer was replaced with Compound A-4 prepared in Example 1 instead of Compound A-1.

[0126] Application Example 3: Preparation of an organic electroluminescent device

[0127] An organic electroluminescent device was fabricated using the same method as in Application Example 1, except that the guest material in the organic light-emitting layer was replaced with Compound A-18 instead of Compound A-1.

[0128] Application Example 4: Preparation of an organic electroluminescent device

[0129] An organic electroluminescent device was fabricated using the same method as in Application Example 1, except that the guest material in the organic light-emitting layer was replaced with Compound B-4 instead of Compound A-1.

[0130] Application Example 5: Preparation of an organic electroluminescent device

[0131] An organic electroluminescent device was fabricated using the same method as in Application Example 1, except that the guest material in the organic light-emitting layer was replaced with Compound C-29 instead of Compound A-1.

[0132] Comparative Example 1: Preparation of an organic electroluminescent device

[0133] An organic electroluminescent device was fabricated using the same method as in Application Example 1. The guest material in the organic light-emitting layer was selected as R1, and the structural formula of Compound R1 is shown as follows:

[0134]

[0135] The fabricated organic electroluminescent device was tested. Among them, the voltage V J10 was measured under the condition of a current density of 10 mA / cm 2 , the external quantum efficiency EQE J60 was measured under the condition of a current density of 60 mA / cm 2 , the current efficiency CE max is the maximum current efficiency of the device, and the external quantum efficiency EQE max is the maximum external quantum efficiency of the device. The test results are shown in Table 6:

[0136] Table 6

[0137]

[0138] As can be seen from the performance of the above device embodiments, compared with Comparative Example 1, the doped materials designed by the present invention can exhibit higher efficiency in the device application examples. More importantly, the device results show that the doped materials A-1, A-4, A-18, B-4 and C-29 designed by the present invention show lower efficiency roll-off. The best test result is the organic electroluminescent device prepared in Application Example 1. The EQE of Application Example 1 measured at a current density of 60 mA / cm 2 The value of EQE measured J60 is still about 85% compared with EQE max . In comparison, the ratio of the EQE measured in Comparative Example 1 J60 to EQE max is only 0.33, which means a very large efficiency roll-off, indicating that the compounds prepared by the present invention have the characteristic of improving the luminescence efficiency. Therefore, the doped materials designed by the present invention all show a lower triplet energy level difference ΔE ST and a higher photoluminescence quantum yield, which are superior to Comparative Example 1.

[0139] For the thermally activated delayed fluorescence luminescent materials prepared by the present invention, the structure and combination mode of the donor units in the molecule can effectively regulate the electron cloud overlap between the donor and acceptor, significantly affect the energy level, band gap and triplet excited state energy level, and improve the singlet and triplet energy level differences; in addition, the dihedral angles formed between the bridging unit and the donor and acceptor units in the molecule promote and enhance the molecular packing and aggregate state luminescence behavior. The thermally activated delayed fluorescence luminescent materials prepared by the present invention have better thermal stability, higher photoluminescence quantum efficiency and smaller ΔE ST and high reverse intersystem crossing rate, and have broad application prospects in the fields of organic semiconductor devices, biology and sensing, etc.

[0140] As described above, although the present invention has been shown and described with reference to specific preferred application examples, it should not be construed as a limitation of the present invention itself. Various changes can be made to it in form and detail without departing from the spirit and scope of the present invention.

Claims

1. A luminescent material based on a benzoxazole ring core, characterized in that: The luminescent material is a compound represented by the general formula (I): ； Wherein, X is one of O, S, and Se; L1 and L2 are single bonds, , One of; Y is CH or N; Ar1 and Ar2 are each independently selected from the structure represented by general formula (II): ； In the general formula (II), Ar3 and Ar4 are independently selected from a substituted or unsubstituted benzene ring, a substituted or unsubstituted naphthalene ring, a substituted or unsubstituted thiophene ring, a substituted or unsubstituted benzothiophene, a substituted or unsubstituted anthracene ring, a substituted or unsubstituted phenanthrene ring, and a substituted or unsubstituted pyrene ring, and the substituent is selected from a C1-C10 alkyl group.

2. The luminescent material according to claim 1, characterized in that Ar3 and Ar4 are each independently one of the following formulae: ； Wherein, R3 represents a substituent on Ar3 and Ar4, n is selected from an integer of 0-4, representing 0-4 substituents represented by R3; R3 is independently selected from C1-C10 alkyl groups.

3. The luminescent material according to claim 1, characterized in that The luminescent material is one of the following compounds: ； ； 。 4. Use of the luminescent material according to claim 3 in the preparation of an organic electroluminescent device.

5. The use according to claim 4, characterized in that: The organic electroluminescent device comprises an anode, a hole injection layer, a hole transport layer, an organic light-emitting layer, an electron transport layer, an electron injection layer and a cathode which are sequentially stacked on a substrate; the organic light-emitting layer comprises a host material and a guest material, and the guest material comprises one or two of the light-emitting materials described in claim 3.

6. The method for preparing the luminescent material according to claim 1, characterized in that: Step 1: Prepare Ar1-H and Ar2-H compounds, the reaction equations are: ； Step 2: using the prepared Ar1-H and Ar2-H compounds to synthesize the luminescent material according to claim 1; (1) When L1 and L2 are single bonds, and Ar1 and Ar2 are the same, the reaction equation for preparing the luminescent material is: ； (2) When L1 and L2 are single bonds, and Ar1 and Ar2 are different, the reaction equation for preparing the luminescent material is: ； (3) When L1 and L2 are the same or , Ar5 represents or , when Ar1 and Ar2 are the same, the preparation reaction equation of the luminescent material is: ； (4) When L1 and L2 are the same or , Ar5 and Ar6 both represent or , when Ar1 and Ar2 are different, the preparation reaction equation of the luminescent material is: ； (5) When L1 is a single bond and L2 is or , Ar5 represents or , when Ar1 and Ar2 are the same or different, the preparation reaction equation of the luminescent material is: ； (6) When L1 is or , L2 is a single bond, Ar5 represents or , when Ar1 and Ar2 are the same or different, the preparation reaction equation is: 。

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