Thermal activation delayed fluorescence emission material and organic electroluminescent device prepared from same

Abstract

The invention relates to the technical field of organic electroluminescent materials, in particular to a thermal activation delayed fluorescence emission material and an organic electroluminescent device prepared from the thermal activation delayed fluorescence emission material. According to the constructed molecular structure of the multi-donor-acceptor unit, the acceptor unit is jointly constructed by oxygen or selenium-containing five-membered heterocyclic fused pyrazine and a benzene aromatic ring, a donor Y and an acceptor are connected through an N-C bond, and the charge transfer distance is reduced, so that the emission wavelength of the material is subjected to red shift, and the triplet state lifetime is greatly shortened; the compound has high glass transition temperature and thermal stability, the organic electroluminescent device prepared from the compound as a luminescent layer dye material has relatively high luminous efficiency, and the luminous efficiency and color of the device can meet practical requirements. The invention is supported by the project on the national natural science fund: folded molecular structure thermal activation delayed fluorescence material construction and exciton kinetics and light-emitting spectrum bandwidth regulation and control research, numbering 62075178.

Description

Technical Field

[0001] The present invention relates to the technical field of organic electroluminescent materials, and particularly relates to a thermally activated delayed fluorescence emitting material and an organic electroluminescent device prepared therefrom. Background Art

[0002] OLED, the full English name is Organic light-emitting diode, and the Chinese name is organic light-emitting diode. As a new type of information display technology and lighting technology, OLED technology has the characteristic of self-luminescence and does not require a backlight. Therefore, it has higher contrast and lower power consumption. Although OLED technology has been applied in small information display fields such as mobile phone and camera displays, in the fields of large-size information display and lighting applications, due to key issues such as service life, device luminous efficiency, and product cost, it has not been fully commercialized.

[0003] Thermally activated delayed fluorescence materials, the full English name is thermally active delayed fluorescence, abbreviated as TADF, are the third-generation luminescent materials. They can utilize triplet excitons to emit light, have luminescent properties comparable to phosphorescent materials, and do not contain heavy metals. Therefore, the manufacturing cost is lower. There are various molecular structure design strategies for TADF. Among them, the donor-acceptor type structural framework is one of the basic design strategies. In this structure, the charge transfer excited state usually has lower energy than the excited state of the π-conjugated system, which helps to achieve the emission of long-wavelength light. Therefore, in the research work on the donor-acceptor type molecular structure, the design of the acceptor unit and the realization of the optimal combination with the donor unit are crucial for comprehensively improving the performance of TADF materials.

[0004] The TADF material disclosed in the patent application ZL202010007502.2 uses a core framework unit containing furan[2,3-b]quinoxaline or thiophene[2,3-b]quinoxaline as the acceptor, and can achieve orange and red thermally activated delayed fluorescence. Although this TADF material realizes delayed fluorescence emission, due to its long charge distance, the triplet state lifetime is too long, such as 500 microseconds, which is not conducive to realizing a stable OLED light-emitting device. Summary of the Invention

[0005] To address the low efficiency and long triplet lifetime issues of existing thermally activated delayed fluorescent emitting materials, the present invention provides a thermally activated delayed fluorescent emitting material and an organic electroluminescent device prepared therefrom. The thermally activated delayed fluorescent emitting material of the present invention features a donor-acceptor structure, in which the donor Y and the acceptor are directly connected via an N-C bond, reducing the charge transfer distance and allowing charge transfer to occur directly between C-N chemical bonds. This donor adjustment results in a red-shifted emission wavelength and a significant shortening of the triplet lifetime. To achieve the above objectives, the present invention provides the following technical solutions.

[0006] The first aspect of the present invention provides a thermally activated delayed fluorescent emission material, the general structural formula of which is shown in the following formula (I): Wherein, M is O or Se; Ar is any one of phenyl, pyridyl, pyrazinyl, phenanthrenyl and azaphenanthrenyl; R1 and R2 are independently selected from hydrogen, C6 to C 20 Aryl, substituted C6~C 20 Aryl, C4~C 20 Heteroaryl, substituted C4~C 20 Heteroaryl, C4~C 20 The nitrogen-containing heterocyclic substituent and the substituted C4~C 20 Any one of the nitrogen-containing heterocyclic substituents; Y is a nitrogen-containing heterocyclic substituent, and Y is connected to Ar through an NC bond; R3 is selected from hydrogen, -D, halogen, -CN, C1~C 20 Alkyl, C1-C 20 Deuterated alkyl, C1-C 20 Halogenated alkyl, C1-C 20 Alkoxy and C1-C 20 Any one of the alkylmercapto groups; a is any integer between 1 and 4.

[0007] Preferably, is an acceptor group; the acceptor group is selected from any one of the following structural formulas:

[0008] Preferably, R1 and R2 are independently selected from hydrogen, phenyl, pyridyl, furyl, thienyl, pyrrolyl, naphthyl, quinolyl, biphenyl, terphenyl, anthracenyl, phenylanthracenyl or any one of the groups represented by formula (III-1) to formula (III-16):

[0009]

[0010] Wherein, X is O, S or N.

[0011] Preferably, Y is any one of the groups represented by formula (IV-1) to formula (IV-10):

[0012]

[0013] Preferably, R3 is selected from any one of hydrogen, -D, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, pentyl, hexyl, octyl, heptyl, dodecyl, -CF3, methoxy, ethoxy, propoxy, butoxy, methylthio, ethylthio, propylthio, isopropylthio, butylthio, tert-butylthio, and octylthio.

[0014] Preferably, the thermally activated delayed fluorescence emitting material is selected from any one of the following compounds:

[0015]

[0016]

[0017]

[0018]

[0019]

[0020]

[0021]

[0022]

[0023] In a second aspect of the present invention, there is provided an application of the thermally activated delayed fluorescence emitting material described in the first aspect as a luminescent layer dye material for preparing an organic electroluminescent device. Preferably, the organic electroluminescent device is used for preparing a display device or a lighting device.

[0024] In a third aspect of the present invention, there is provided an application of a thermally activated delayed fluorescence emitting material for preparing a mechanical sensing element or a temperature sensing element, wherein the thermally activated delayed fluorescence emitting material is the thermally activated delayed fluorescence emitting material described in the first aspect, and Y is a group represented by formula (IV-4); the thermally activated delayed fluorescence emitting material has fluorescence / thermally activated delayed fluorescence and phosphorescence dual-wavelength emission characteristics, and has mechanochromic and thermochromic phenomena.

[0025] In a fourth aspect of the present invention, there is provided an organic electroluminescent device, which sequentially includes an ITO anode, a hole injection layer, a hole transport layer, an electron blocking layer, a luminescent layer, an electron transport layer, and a cathode, and the luminescent layer includes the thermally activated delayed fluorescence emitting material described in the first aspect.

[0026] Advantages of the present invention:

[0027] 1. The molecular structure of the multi-donor-acceptor unit constructed by the present invention is composed of a five-membered heterocyclic ring containing oxygen or selenium fused with pyrazine and a benzene-based aromatic ring with high luminous efficiency to form an acceptor unit. Among them, the donor Y and the acceptor are directly connected by an N-C bond, reducing the charge transfer distance and enabling charge transfer to occur directly between the C-N chemical bonds. Such a donor adjustment causes a red shift in the emission wavelength of the material and a significant shortening of the triplet lifetime.

[0028] 2. In the acceptor unit of the present invention, the introduction of multiple N atoms into the fused ring system can not only regulate the electron-deficient characteristics of the acceptor unit but also, through the heavy atom effect, regulate the intersystem crossing conversion rate constant between the singlet state and the triplet state, effectively reducing the triplet exciton density under high current density and suppressing the efficiency roll-off under high brightness.

[0029] 3. The present invention arranges the donor Y at different positions of the aromatic ring Ar of the acceptor skeleton. On the one hand, it can produce a steric effect to reduce the aggregation quenching of the luminescent molecules, and on the other hand, it can effectively regulate the charge transfer state intensity of the luminescent molecules.

[0030] 4. The donor of the present invention is arranged at the 3-position of the acceptor, generating a steric effect with the aromatic substitution group at the 2-position to reduce the energy difference between the singlet state and the triplet state, facilitating reverse intersystem crossing and generating delayed fluorescence.

[0031] 5. The thermally activated delayed fluorescence emitting material of the present invention can be used as a luminescent layer dye material for preparing organic electroluminescent devices. Compared with existing devices, the organic electroluminescent devices of the present invention have relatively high luminous efficiency, and the luminous efficiency and color can meet the requirements of practical applications.

[0032] 6. The thermally activated delayed fluorescence emitting material of the present invention can emit orange and red light, has a small singlet-triplet energy gap, a fast reverse intersystem conversion process, and a short triplet lifetime; when used as a luminescent layer dye material for organic electroluminescent devices, it has high luminous efficiency and slow efficiency decay, and is an organic luminescent material with good performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is the NMR spectrum diagram of compound (1).

[0034] Figure 2 It is the NMR spectrum diagram of compound (17).

[0035] Figure 3 It is the NMR spectrum diagram of compound (4).

[0036] Figure 4 It is the NMR spectrum diagram of compound (20).

[0037] Figure 5 It is the NMR spectrum diagram of compound (5).

[0038] Figure 6 It is the NMR spectrum diagram of compound (21).

[0039] Figure 7 It is the photoluminescence spectrum diagrams of compound (1), compound (4), compound (5), compound (17), compound (20) and compound (21). Among them, (a) is the photoluminescence spectrum diagrams of compound (1), compound (4) and compound (5); (b) is the photoluminescence spectrum diagrams of compound (17), compound (20) and compound (21).

[0040] Figure 8 It is the structure diagram of the OLED device.

[0041] Figure 9 It is the electroluminescence spectrum diagram and current efficiency - luminance curve diagram based on compound (1), compound (4) and compound (5) as luminescent materials. Among them, (a) is the electroluminescence spectrum diagram; (b) is the current efficiency - luminance curve diagram.

[0042] Figure 10 It is the luminance - quantum efficiency curve diagram and electroluminescence spectrum diagram based on compound (1), compound (4) and compound (5) as luminescent materials. Among them, (a) is the luminance - quantum efficiency curve diagram; (b) is the electroluminescence spectrum diagram; the inset in diagram (b) is the physical diagram of the electroluminescence of compound (1).

[0043] Figure 11 It is the electroluminescence spectrum diagram of the single - molecule white - light OLED of compound (5). Among them, the inset is the application photo of the electroluminescence of compound (5).

[0044] Figure 12 It is the relevant application pictures of pressure - temperature sensing made by using compound (5). Among them, (I) is the application picture of force - induced color change of pressure - temperature sensing made by using compound (5); (II) is the application picture of temperature - induced color change of pressure - temperature sensing made by using compound (5). Detailed implementation manners

[0045] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the following further details the present invention in combination with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0046] The present invention provides a thermally activated delayed fluorescence emitting material and an organic electroluminescent device prepared therefrom, so as to achieve red, deep red, and even near-infrared light, with high luminescence efficiency in the aggregated state and excellent thermal stability; in the present invention, the donor and acceptor are directly connected through a C-N bond, reducing the charge transfer distance. The charge transfer directly occurs between the C-N chemical bonds. Such a donor adjustment causes the emission wavelength of the material to redshift, and the triplet lifetime is significantly shortened. A red light and deep red light material with a redder emission color and a faster reverse intersystem crossing (RISC) process is obtained, achieving better device stability.

[0047] The present invention provides a thermally activated delayed fluorescence emitting material with a multi-donor-acceptor structural feature, and its structural general formula is shown as the following formula (I): Wherein, M is O or Se; Ar is any one of phenyl, pyridyl, pyrazinyl, phenanthryl, and azaphenanthryl; R1 and R2 are each independently selected from hydrogen, aryl of C6-C 20 , substituted aryl of C6-C 20 , aryl of C4-C 20 , substituted aryl of C4-C 20 , heteroaryl of C4-C 20 , substituted heteroaryl of C4-C 20 , nitrogen-containing heterocyclic substituent of C4-C 20 and substituted nitrogen-containing heterocyclic substituent of C4-C 20 ; Y is a nitrogen-containing heterocyclic substituent, and Y is connected to Ar through an N-C bond; R3 is selected from hydrogen, -D, halogen, -CN, alkyl of C1-C 20 , deuterated alkyl of C1-C 20 , haloalkyl of C1-C 20 , alkoxy of C1-C

[0048] is an acceptor group; the acceptor group is selected from any one of the following structural formulas:

[0049]

[0050]

[0051] Y is a nitrogen-containing heterocyclic with electron-donating ability, and the N atom is directly connected to the acceptor backbone; the donor Y is any one of the groups shown in formulas (IV-1) to (IV-10): * represents the connection site.

[0052]

[0053] In the present invention, the donor Y is arranged at different positions of the aromatic ring Ar of the acceptor skeleton. On the one hand, it can produce a steric effect to reduce the aggregation quenching of the luminescent molecules. On the other hand, it can effectively regulate the intensity of the charge transfer state of the luminescent molecules.

[0054] In the present invention, the donor is arranged at the 3-position of the acceptor, generating a steric effect with the aromatic substituent group at the 2-position to reduce the energy difference between the singlet state and the triplet state, facilitating reverse intersystem crossing and generating delayed fluorescence.

[0055] The thermally activated delayed fluorescence emitting material for use in organic electroluminescent devices of the present invention comprises a derivative constructed from a fused heterocyclic acceptor represented by any one of the above structural general formulas (I) and an aromatic amine.

[0056] Specific examples of the derivative constructed from a fused heterocyclic represented by any one of the general formulas (I) and an aromatic amine include, but are not limited to, any one of Compounds (1) to (282).

[0057] The present invention also provides an organic electroluminescent device, comprising an ITO anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, an electron transport layer, and a cathode, wherein the light emitting layer comprises a thermally activated delayed fluorescence emitting material.

[0058] Please refer to Figure 9 , for the structure of the implemented organic electroluminescent device. In the implemented device, the hole injection layer is 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HTA-CN), the hole transport layer is 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC), the electron blocking layer is 4,4',4''-tris(carbazol-9-yl)triphenylamine (TCTA), the light emitting layer dye material is 4,4'-bis(9-carbazolyl)biphenyl (CBP), the electron transport layer is 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]dipyridine (TmPyPB), and ITO conductive glass and metallic aluminum are used as the anode and the cathode, respectively.

[0059] The thermally activated delayed fluorescence emitting material of the present invention has a donor-acceptor skeleton. The constructed acceptor unit is jointly constructed from a five-membered heterocyclic fused pyrazine containing oxygen or selenium with high luminescence efficiency and a benzene-based aromatic ring. The donor unit Y and the acceptor are directly connected by an N-C bond, reducing the charge transfer distance and enabling the charge transfer to occur directly between the C-N chemical bonds. Such a donor adjustment causes a red shift in the emission wavelength of the material and a significant shortening of the triplet state lifetime; when it is used in an organic electroluminescent device, it can effectively reduce the triplet exciton density under a high current density and suppress the efficiency roll-off at high brightness.

[0060] The technical solution of the present invention will be further described below through specific embodiments. In the following embodiments, unless otherwise specified, the methods are all conventional methods; the reagents and materials, unless otherwise specified, can all be purchased in the market.

[0061] Example 1, Synthesis of Compound (1) and Compound (17):

[0062] Step 1, Chemical Synthesis of Intermediate 1 and Intermediate 2:

[0063]

[0064] 5.3 mmol of 4-bromo-o-phenylenediamine, 5.3 mmol of 5-phenylfuran-2,3-dione and 80 mL of glacial acetic acid were added to a dry three-necked flask. The mixture was replaced with a nitrogen environment and heated to 110 °C for reaction for 6 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, and a large amount of solid precipitate was formed. The solid was collected by filtration and washed with methanol. The crude product was not further purified and was directly used for the next reaction. The crude product was added to a dry three-necked flask, and then 30 g of polyphosphoric acid PPA was added. After heating to 140 °C under a nitrogen atmosphere, it was stirred thoroughly for 8 hours. After the reaction was completed, the reaction mixture was cooled to room temperature, diluted with 350 mL of water, and then the mixture was neutralized with NaOH to pH = 7. Then it was filtered to obtain a dark gray solid crude product, which was recrystallized to obtain 0.9 g of a light gray solid product, which was a mixture of Intermediate 1 and Intermediate 2.

[0065] Step 2, The synthesis scheme of Compound (1) and Compound (17) is as follows:

[0066]

[0067] 12.0 mmol of the mixture of Intermediate 1 and Intermediate 2, 10.0 mmol of 4,4'-dimethoxydiphenylamine and 200 mL of anhydrous toluene were added to a dry three-necked flask. The mixture was replaced with a nitrogen atmosphere, and 0.2 mmol of catalyst Pd(OAc)2, 0.4 mmol of ligand bis[(2-diphenylphosphino)phenyl] ether and 20 mmol of cesium carbonate were added to the mixed solution. Under a nitrogen atmosphere, the reaction mixture was continuously stirred at 110 °C for 6 hours. Subsequently, it was cooled to room temperature, filtered through diatomaceous earth, and the solid was washed with dichloromethane 3×50 mL. The filtrates were combined and concentrated under reduced pressure. Using a volume ratio of dichloromethane to petroleum ether of 1:2, the residue was purified by column chromatography to finally obtain 2.88 g of target product Compound 1 and 2.61 g of Compound 17.

[0068] The NMR data diagram of Compound (1) is as Figure 1 shown, 11H NMR (400 MHz, DMSO-d6) δ 8.13 - 8.10 (m, 2H), 7.85 (d, 1H), 7.74 (s, 1H), 7.65 - 7.57 (m, 3H), 7.33 - 7.30 (m, 1H), 7.21 (s, 2H), 7.18 (d, 2H), 7.12 (d, 1H), 7.01 (s, 2H), 6.99 (d, 2H), 3.79 (s, 6H). The NMR data of compound (17) is as shown in Figure 2 shown below, 1 1H NMR (400 MHz, DMSO-d6) δ 8.07 (d, 2H), 7.92 (d, 1H), 7.78 (s, 1H), 7.61 - 7.53 (m, 3H), 7.31 - 7.21 (m, 1H), 7.22 (d, 4H), 7.05 - 6.98 (m, 5H), 3.80 (s, 6H).

[0069] Example 2, Synthesis of Compound (4) and Compound (20):

[0070] The method of Example 2 is basically the same as that of Example 1, except that in Example 2, 4,4'-dimethoxydiphenylamine needs to be replaced with 10.0 mmol of phenoxazine in an equimolar amount.

[0071]

[0072] The NMR data of compound (4) is as shown in Figure 3 shown below, 1 1H NMR (400 MHz, DMSO-d6) δ 8.44 (d, 1H), 8.25 - 8.10 (m, 3H), 7.99 (s, 1H), 7.85 - 7.82 (m, 1H), 7.75 - 7.59 (m, 3H), 6.81 (d, 2H), 6.75 - 6.65 (m, 4H), 6.01 - 5.99 (m, 2H).

[0073] The NMR data of compound (20) is as shown in Figure 4 shown below, 1 1H NMR (400 MHz, DMSO-d6) δ 8.38 (d, 1H), 8.27 (d, 1H), 8.21 (d, 2H), 7.99 (s, 1H), 7.85 - 7.82 (m, 1H), 7.67 (d, 3H), 6.82 - 6.80 (m, 2H), 6.75 - 6.65 (m, 4H), 6.04 - 5.96 (m, 2H).

[0074] Example 3, Synthesis of Compound (5) and Compound (21):

[0075] Example 3 is basically the same as the method of Example 1, except that: in Example 3, 4,4'-dimethoxydiphenylamine needs to be replaced with 10.0 mmol of phenothiazine in an equimolar amount.

[0076]

[0077] The NMR data graph of compound (5) is as Figure 5 shown 1 H NMR(400MHz,DMSO-d6)δ8.27(d,1H),8.19(d,2H),8.04(d,1H),7.93(s,1H),7.78-7.75(m,1H),7.68-7.63(m,3H),7.30-7.22(m,2H),7.12-7.01(m,4H),6.62(d,2H).

[0078] The NMR data graph of compound (21) is as Figure 6 shown 1 H NMR(400MHz,DMSO-d6)δ8.29(d,1H),8.19-8.12(m,2H),7.95-7.84(m,2H),7.74-7.71(m,1H),7.67-7.59(m,3H),7.34-7.32(m,2H),7.18-7.14(m,2H),7.10-7.06(m,2H),6.79(d,2H).

[0079] Synthesis of compound (9) in Example 4:

[0080]

[0081] Synthesis of Intermediate 3: In a dry three-necked flask, add 3.76 mmol of 4-bromo-o-phenylenediamine, 4.14 mmol of oxalic acid, 3 g of silica gel powder with a mesh size of 200-300, and 20 mL of toluene. Replace the air with nitrogen and react at 110 °C for 5 hours. After detecting the completion of the reaction by thin-layer chromatography plate (TLC), without treating the reaction, slowly add POCl3 (8.4 mL) and dimethylformamide (DMF, 5 mL) to the system and continue to react at 110 °C for 1 hour. After detecting the end of the reaction by TLC, add 100 mL of ice water to quench, then add 100 mL of ethyl acetate for extraction. After several extractions, combine the organic layers, dry with anhydrous sodium sulfate, and evaporate the solvent to obtain 1.2 g of Intermediate 3 (white solid), with a yield of 89%.

[0082] Synthesis of Intermediate 4: In a dry three-necked flask, add Intermediate 3 (1.68 mmol), Pd(PPh3)2Cl2 (0.084 mmol), CuI (0.084 mmol), phenylacetylene (1.75 mmol), triethylamine (4.20 mmol), and acetonitrile (20 mL). Heat the mixture to 60 °C and react for 5 hours under a N2 atmosphere. Then add 2 mL of DMF and NaHSe (2.0 eq). After the reaction is detected to be complete by TLC, add 100 mL of water to the system and directly filter to obtain the crude product. Perform column chromatography separation using an eluent of dichloromethane:petroleum ether = 1:1 (volume ratio) to obtain 0.5 g of Intermediate 4 respectively.

[0083]

[0084] Synthesis of Compound (9): Add Intermediate 4 (12.0 mmol), 4,4'-dimethoxydiphenylamine (10.0 mmol), and anhydrous toluene (200 mL) to a dry three-necked flask. Replace the mixture with a nitrogen atmosphere, and add catalyst Pd(OAc)2 (0.2 mmol), ligand bis[(2-diphenylphosphino)phenyl] ether (0.4 mmol), and cesium carbonate (20 mmol) to the mixed solution. Under a nitrogen atmosphere, stir the reaction mixture at 110 °C for 6 hours. Then cool to room temperature, filter through diatomaceous earth, and wash the solid with dichloromethane (3 × 50 mL). Combine the filtrates and concentrate under reduced pressure. Select a volume ratio of dichloromethane to petroleum ether of 1:2, and purify the residue by column chromatography to finally obtain the target product Compound 9 (5.21 g).

[0085] 1H NMR data of Compound (9): 1 H NMR (400 MHz, Chloroform-d) δ 7.74 (d, J = 1.8 Hz, 1H), 7.65 - 7.59 (m, 3H), 7.53 - 7.4 (m, 2H), 7.44 - 7.35 (m, 3H), 7.15 - 7.09 (m, 3H), 6.95 - 6.89 (m, 5H), 3.79 (s, 6H).

[0086] Example 5, Synthesis of Compounds (49), (52), (53), and (283):

[0087]

[0088]

[0089] Step 1, Synthesis of 3-bromo-9,10-phenanthrenedioxime: Replace the air in a dry three-necked flask with N2, and successively add 14.4 mmol of 3-bromo-benzoquinone, 72 mmol of hydroxylamine hydrochloride, and 9 mL of pyridine to 150 mL of ethanol. Stir the mixture at 90 °C for 3 h. After 3 h, remove the solvent using a rotary evaporator and pour it into a mixed solution of methanol and water with a volume ratio of methanol to water of 1:10. The resulting precipitate is filtered and dried to obtain 3.7 g of a yellow product with a yield of 80%.

[0090] Step 2, Synthesis of 3-bromo-9,10-phenanthrenediamine: Replace the air in a dry three-necked flask with N2, add 50 mL of ethanol, stir under a nitrogen atmosphere, add 4.2 mmol of 3-bromo-9,10-phenanthrenedioxime to the flask, heat to 90 °C, and stir for 3 minutes. After the 3-bromo-9,10-phenanthrenedioxime is completely dissolved, add 0.5 g of palladium on activated carbon (Pd / C). After reacting for 10 minutes, slowly add a mixed solution of 10 mL of hydrazine hydrate and 10 mL of ethanol to the reaction system. React at 90 °C for 24 h, and after the reaction is completed, terminate the reaction and filter Pd / C. Rotate and evaporate to remove the solvent, and pour it into 300 mL of cold water to quench. Filter the precipitated product and wash it with water. Dry it in a vacuum oven to obtain 0.84 g of product with a yield of 70%.

[0091] Step 3, Synthesis of target intermediate 1 (abbreviated as 3-Br-diBFQ): Add 30 mmol of 3-bromo-9,10-phenanthrenediamine, 33 mmol of 5-phenylfuran-2,3-dione, and 300 mL of glacial acetic acid to a 500 mL single-necked flask. Replace the air in the dry three-necked flask with N2, and heat to reflux and react overnight. After the reaction is completed, wait for it to cool to room temperature, filter and collect the solid, and directly use the crude product in the next step without purification. Then, add the crude product to a 500 mL single-necked flask, add 50 g of polyphosphoric acid (PPA), and heat to 140 °C under a N2 atmosphere and react for 12 h. After the reaction is completed, wait for it to cool to room temperature, add a large amount of water to quench the reaction and dissolve the excess polyphosphoric acid and inorganic salts, neutralize with NaOH and filter. The crude product is separated and purified by column chromatography, and the eluent is a mixed solution of dichloromethane and polyethylene (PE) with a volume ratio of 1:3; obtain 6.83 g of target intermediate 1 (3-Br-diBFQ) with a yield of 66%.

[0092] Step 4, Synthesis of Compound (49) (3-Bis(4-methoxyphenyl)-11-phenyldibenzof[f,h]furo[2,3-b]quinoxaline): Replace the air in a dry three-necked flask with N2. Sequentially add 2 mmol of the target intermediate 1, 2.4 mmol of 4',4'-dimethoxydiphenylamine, and 6 mmol of cesium carbonate to the three-necked flask. Continue to evacuate and replace with N2 to ensure the reaction atmosphere. Subsequently, continue to add 0.19 g of the ligand bis[(2-diphenylphosphino)phenyl] ether and 0.04 g of palladium acetate. Add 120 mL of ultra-dry toluene as the solvent, heat to 110 °C, and reflux with stirring. After the reaction is completed, cool to room temperature, add ultrapure water to quench the reaction, extract with dichloromethane and collect the organic phase. Collect the target product by column chromatography, and the eluent is a mixture of dichloromethane and polyethylene PE in a volume ratio of 1:3; Compound (49) is obtained with a yield of 50.42%.

[0093] 1H NMR data of Compound (49): 1 H NMR (400 MHz, Chloroform-d) δ (ppm): 9.41 (d, J = 2.5 Hz, 1H), 8.54 (d, J = 2.5 Hz, 1H), 8.11 - 8.02 (m, 2H), 7.67 - 7.51 (m, 5H), 7.40 (s, 1H), 7.19 - 7.03 (m, 6H), 6.94 - 6.85 (m, 4H), 3.83 (s, 6H).

[0094] Step 5, Synthesis of Compound (283) (3-((4-Dimethylaminophenyl)-N,N-dimethyl)-11-phenyldibenzof[f,h]furo[2,3-b]quinoxaline): Replace the air in a dry three-necked flask with N2. Sequentially add 2 mmol of the target intermediate 1, 2.4 mmol of 4',4'-dimethylaminodiphenylamine, and 6 mmol of cesium carbonate to the three-necked flask. Continue to evacuate and replace with N2 to ensure the reaction atmosphere. Subsequently, continue to add 0.19 g of the ligand bis[(2-diphenylphosphino)phenyl] ether and 0.04 g of palladium acetate. Add 120 mL of ultra-dry toluene as the solvent, heat to 110 °C, and reflux with stirring. After the reaction is completed, cool to room temperature, add ultrapure water to quench the reaction, extract with dichloromethane and collect the organic phase. Collect the target product by column chromatography, and the eluent is a mixture of dichloromethane and polyethylene PE in a volume ratio of 1:3; Compound (283) is obtained with a yield of 50.42%.

[0095] Step 6, Synthesis of compound (53) (3-(10H-phenothiazin-10-yl)-11-phenyldibenzof [h]furo[2,3-b]quinoxaline, abbreviated as SN-diBFQ): Replace the air in a dry three-necked flask with N2. Sequentially add 2 mmol of the target intermediate 1, 2.4 mmol of phenothiazine, and 6 mmol of cesium carbonate into the three-necked flask. Continuously evacuate and replace with N2 to ensure the reaction atmosphere. Subsequently, continue to add 0.19 g of the ligand bis[(2-diphenylphosphino)phenyl] ether and 0.04 g of palladium acetate. Add 120 mL of ultra-dry toluene as the solvent, heat to 110 °C, and reflux with stirring. After the reaction is completed, cool to room temperature, add ultrapure water to quench the reaction, extract with dichloromethane and collect the organic phase. Collect the target product by column chromatography, and the eluent is a mixture of dichloromethane and polyethylene PE with a volume ratio of 1:3; obtain compound (53) with a yield of 50.42%.

[0096] 1H NMR data of compound (53): 1 H NMR δ (ppm): (400 MHz, Chloroform-d) δ 9.21 (dd, J = 18.7, 8.0 Hz, 2H), 8.24 (d, J = 8.0 Hz, 2H), 8.12 - 7.99 (m, 4H), 7.82 - 7.58 (m, 5H), 7.57 - 7.43 (m, 6H), 7.38 (d, J = 4.8 Hz, 2H).

[0097] Step 7, Synthesis of compound (52) (3-(10H-phenoxazin-10-yl)-11-phenyldibenzof [h]furo[2,3-b]quinoxaline, abbreviated as ON-diBFQ): Replace the air in a dry three-necked flask with N2. Sequentially add 2 mmol of the target intermediate 1, 2.4 mmol of phenoxazine, and 6 mmol of cesium carbonate into the three-necked flask. Continuously evacuate and replace with N2 to ensure the reaction atmosphere. Subsequently, continue to add 0.19 g of the ligand bis[(2-diphenylphosphino)phenyl] ether and 0.04 g of palladium acetate. Add 120 mL of ultra-dry toluene as the solvent, heat to 110 °C, and reflux with stirring. After the reaction is completed, cool to room temperature, add ultrapure water to quench the reaction, extract with dichloromethane and collect the organic phase. Collect the target product by column chromatography, and the eluent is a mixture of dichloromethane and polyethylene PE with a volume ratio of 1:3; obtain compound (52) with a yield of 50.42%.

[0098] 1H NMR data of compound (52): 11H NMR δ (ppm): (400 MHz, Chloroform-d) δ 9.49 - 9.26 (m, 2H), 8.60 (s, 2H), 8.12 (d, J = 7.4 Hz, 4H), 7.82 (d, J = 7.7 Hz, 4H), 7.63 - 7.52 (m, 8H), 7.02 (d, J = 20.3 Hz, 1H).

[0099] Application Example: The optoelectronic properties of the thermally activated delayed fluorescence emitting materials are analyzed as follows:

[0100] Please refer to Figures 7 to 12 , Compound (1), Compound (4) and Compound (5) emit highly efficient orange - red light in toluene solution, with emission wavelengths of 612 nm, 687 nm and 654 nm respectively. The delayed fluorescence lifetimes in 10% doped CBP thin films are 63.5 μs, 92.7 μs and 113.2 μs respectively. The emission wavelengths of Compound (17), Compound (20) and Compound (21) in toluene solution are 601 nm, 655 nm and 708 nm respectively. For the organic light - emitting devices based on Compound (1), Compound (4) and Compound (5) with a doping concentration of 10 wt%, the peak wavelengths of their electroluminescence spectra are 612 nm, 656 nm and 628 nm respectively. The organic light - emitting devices based on Compound (1), Compound (4) and Compound (5) exhibit excellent electroluminescence performance, and their maximum external quantum efficiencies EQE reach 13.1%, 13.9% and 16.7% respectively. It can be seen that the compounds of the embodiments of the present invention exhibit very excellent luminescence performance, especially showing the phenomenon of suppressing fluorescence quenching in the aggregated state, and further expanding the molecular system of thermally activated delayed fluorescence.

[0101] Compound (5) and Compound (21) in 10 -5 M low - concentration solution or in thin films with a low doping concentration of 1 wt% - 3 wt% have fluorescence / thermally activated delayed fluorescence dual - emission characteristics. Among them, the two emission peaks of Compound (5) in toluene solution are 493 nm (fluorescence) and 687 nm (delayed fluorescence) respectively; the two emission peaks of Compound (21) in toluene solution are 509 nm (fluorescence) and 708 nm (delayed fluorescence) respectively; using this dual - wavelength emission characteristic, it can be used for single - molecule white - light OLED applications. Figure 11 The electroluminescence spectrum and application photo of the single - molecule white - light OLED of Compound (5) are shown. The CIE coordinates are (0.45, 0.41). The solid - state crystal of Compound (5) also has the phenomena of mechanochromism and thermochromism, and can be used for mechanical and temperature sensing applications. Figure 12 The related applications of pressure - temperature sensing made of Compound (5) are shown.

[0102] Table 1 OLED device performance of the use examples

[0103]

[0104] In summary, a thermally activated delayed fluorescence emitting material and an organic electroluminescent device prepared according to an embodiment of the present invention establish a new thermally activated delayed fluorescence material system, which can emit red and deep red light colors, effectively suppress the efficiency roll-off at high brightness, and has a high glass transition temperature and thermal stability; the material synthesis process is simple, suitable for large-scale industrial production, and can be used as one of the best choices for the organic light-emitting layer material of an organic electroluminescent device. The luminous efficiency of the OLEDs device prepared from the material of the present invention reaches the best reported results at present, and the luminous efficiency and color of the device can meet the requirements of practical applications.

[0105] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A thermally activated delayed fluorescence emitting material, characterized in that, Its structural general formula is shown as the following formula (I): Wherein, M is O or Se; Ar is any one of phenyl, pyridyl, pyrazinyl, phenanthryl and azaphenanthryl; R1 and R2 are each independently selected from hydrogen, an aryl group having 6 to C 20 aryl group, a substituted aryl group having 6 to C 20 aryl group, a heteroaryl group having 4 to C 20 heteroaryl group, a substituted heteroaryl group having 4 to C 20 heteroaryl group, a nitrogen-containing heterocyclic substituent having 4 to C 20 and a substituted nitrogen-containing heterocyclic substituent having 4 to C 20 and any one of them; Y is a nitrogen-containing heterocyclic substituent, and Y is connected to Ar through an N-C bond; R3 is selected from any one of hydrogen, -D, halogen, -CN, C1-C 20 alkyl, C1-C 20 deuterated alkyl, C1-C 20 haloalkyl, C1-C 20 alkoxy and C1-C 20 alkylthio; a is any integer between 1 and 4.

2. The thermally activated delayed fluorescence emitting material according to claim 1, wherein is a receptor group; the receptor group is selected from any one of the following structural formulas:

3. The thermally activated delayed fluorescence emitting material according to claim 1, characterized in that, R1 and R2 are each independently selected from hydrogen, phenyl, pyridyl, furyl, thienyl, pyrrolyl, naphthyl, quinolinyl, biphenylyl, terphenylyl, anthryl, phenylanthryl or any one of the groups shown in formula (III-1) to formula (III-16): Wherein, X is O, S or N.

4. The thermally activated delayed fluorescence emitting material according to claim 1, wherein Y is any one of the groups shown in formula (IV-1) to formula (IV-10):

5. The thermally activated delayed fluorescence emitting material according to claim 1, wherein R3 is selected from hydrogen, -D, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, pentyl, hexyl, octyl, heptyl, dodecyl, -CF3, methoxy, ethoxy, propoxy, butoxy, methylthio, ethylthio, propylthio, isopropylthio, butylthio, tert-butylthio and octylthio.

6. The thermally activated delayed fluorescence emitting material according to claim 1, wherein The thermally activated delayed fluorescence emitting material is selected from any one of the following compounds:

7. Use of the thermally activated delayed fluorescence emitting material according to any one of claims 1 to 6 as a luminescent layer dye material for preparing an organic electroluminescent device.

8. Use of a thermally activated delayed fluorescence emitting material for preparing a mechanical sensing element or a temperature sensing element, characterized in that, The thermally activated delayed fluorescence emitting material is the thermally activated delayed fluorescence emitting material of claim 4, and Y is the group shown in formula (IV-4); The thermally activated delayed fluorescence emitting material has fluorescence / thermally activated delayed fluorescence and phosphorescence dual-wavelength emission characteristics, and has mechanochromic and thermochromic phenomena.

9. An organic electroluminescent device sequentially includes an ITO anode, a hole injection layer, a hole transport layer, an electron blocking layer, a light emitting layer, an electron transport layer, and a cathode, characterized in that, The luminescent layer comprises the thermally activated delayed fluorescence emitting material according to any one of claims 1 to 6.

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