A type of quinoline acridine-5,9-dione MR-TADF red light luminescent material and its preparation method and application

Abstract

The present invention discloses a class of quinoacridine-5,9-diketone MR-TADF red light emitting materials and their preparation methods and applications, belonging to the technical field of organic photoelectric materials. The molecules of this type of material promote the minimization of bonding / antibonding of frontier molecular orbitals through the resonance effect generated by electron-deficient nitrogen / carbonyl and electron-rich oxygen / nitrogen. In addition, the rigid conjugated skeleton suppresses the structural relaxation of the molecular excited state and the vibration coupling between the excited state and the ground state, thereby obtaining a red light emitting material with a narrow half-width (<70nm) and high luminous efficiency; the introduction of a tert-butyl group on the periphery of the molecule can reduce the reorganization energy of the molecule; grafting different substituent units can regulate the stacking and film-forming properties of the molecule. The maximum emission peak of the obtained doped red light electroluminescent device is located at 601 nm, the half-width is 68 nm, and the corresponding maximum external quantum efficiency is 9.38%, which has a wide range of applications in the fields of organic electroluminescent displays and biological imaging.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic photoelectric materials, and specifically relates to a class of quinoacridine-5,9-dione MR-TADF red light emitting materials and their application in organic electroluminescent devices (OLEDs). Background Art

[0002] Since Tang and Van Slyke first reported organic light-emitting diode (OLED) devices in 1987, OLED technology has achieved remarkable breakthroughs, particularly in the fields of display technology and solid-state lighting. OLEDs, due to their self-luminous properties, wide viewing angle, ultra-thin and lightweight design, and fast response time, have gradually replaced traditional liquid crystal display (LCD) technology. Red OLED devices, a key branch of OLED technology, have attracted considerable attention from researchers due to their potential applications in display, lighting, medical, and security. As a key component of full-color display technology, red OLED devices play a key role in flat-panel displays, televisions, and mobile devices. Compared to blue and green OLEDs, the luminous efficiency of red OLEDs was relatively low in the early stages of their development. This was primarily due to the narrow band gap of the red light-emitting material, which leads to an increase in non-radiative transitions and affects the external quantum efficiency (EQE). In recent years, the efficiency and stability of red OLEDs have been significantly improved through the introduction of new luminescent materials and optimized device structures (Adv. Mater. 2022, 34, 2201442).

[0003] In the selection of red light OLED materials, phosphorescent materials and thermally activated delayed fluorescence (TADF) materials are the current research focus. Phosphorescent materials can achieve an internal quantum efficiency close to 100% due to their ability to utilize triplet excitons, significantly improving the luminescence performance of the device. However, phosphorescent materials often need to rely on complexes containing precious metals such as iridium or platinum, which are not only expensive but also scarce in resources. Therefore, in recent years, researchers have gradually turned to exploring pure organic TADF materials. TADF materials can convert triplet excitons into singlet excitons through the reverse intersystem crossing (RISC) mechanism, thereby achieving 100% exciton utilization, with lower cost and better environmental friendliness. (ACSAppl.Mater.Interfaces 2020,12,27,30652–30658)

[0004] However, most current red-light TADF materials still face the problem of low luminescence color purity. The reorganization energy of the luminescent material is high, which easily produces a wide emission peak, resulting in limited color gamut and resolution of the device. This problem is mainly due to intramolecular vibrational relaxation and intermolecular rotational coupling, which makes the emission bandwidth of TADF materials usually wide, and the half-maximum width (FWHM) of the emission peak can reach 80 to 100 nm, which is difficult to meet the requirements of high color gamut. Therefore, how to develop high-efficiency, narrow-spectrum red-light TADF materials is one of the important topics in the current OLED research field (J.Am.Chem.Soc.2024,146,47,32826–32836). In recent years, Hatakeyama et al. (Chem. Soc. Rev., 2024, 53, 1624-1692) proposed a new molecular design strategy, namely Multiple Resonance Thermally Activated Delayed Fluorescence (MR-TADF), by designing aromatic compounds containing boron and oxygen (or nitrogen) with a planar structure. This design method significantly suppresses the vibrational relaxation phenomenon of the molecule by utilizing the multiple resonance effect between boron atoms and nitrogen atoms, and effectively reduces the reorganization energy (λ) during the excited state transition process. In addition, the planar rigid structure of the MR-TADF molecule reduces the vibration and rotation of the molecule in the excited state, thereby reducing the half-width (FWHM) of the material's luminescence and achieving a narrow spectrum emission of less than 70nm. The advantage of this narrow spectrum is of great significance for improving the color purity and display performance of OLED devices.

[0005] The core of MR-TADF is to optimize the excited state energy level structure of the molecule by utilizing the multiple resonance effect. In the traditional TADF molecular design, the energy difference between the triplet state and the singlet state (ΔE ST ) is a key factor affecting RISC efficiency. In order to improve the efficiency of TADF, molecular design is usually used to minimize ΔE ST value, triplet excitons can be effectively converted into singlet excitons through the RISC mechanism, thereby improving the luminescence efficiency. However, this reduction in ΔE STThe strategy often leads to changes in the molecular structure, which in turn increases the vibrational relaxation phenomenon of the molecule, making the luminescence spectrum wider and affecting the color purity of the device. The MR-TADF molecule maintains the energy difference between the excited state and the ground state of the molecule in an ideal range through the multiple resonance effect, which can significantly suppress the effect of the vibration energy level and ultimately achieve narrow spectrum luminescence. The design of the multiple resonance effect of MR-TADF depends on a specific molecular structure. Currently, most research focuses on aromatic compounds containing boron and nitrogen. This molecular design system is relatively single, resulting in limited space for the development of new materials. Especially in the red light band (Mater. Horiz., 2023, 10, 3712-3718), MR-TADF materials that can achieve efficient narrow spectrum emission are still scarce, limiting their practical application in these bands. The synthesis of MR-TADF molecules usually involves multiple complex reaction steps and requires precise molecular structure control, which not only increases the research and development cost of the material, but also increases the difficulty of synthesis, limiting the feasibility of large-scale production. In addition, the yield in the synthesis process is often low, further increasing the barriers to commercialization. It is urgent to develop new red light MR-TADF materials with simple structure and easy synthesis. Summary of the Invention

[0006] In order to overcome the shortcomings of the existing technology, the present invention designs a class of organic red light-emitting materials with MR-TADF characteristics. By utilizing the synergistic effect of MR and TADF light emission, the efficient narrow-band light emission of MR-TADF red light-emitting materials and their application in organic electroluminescent diodes are achieved.

[0007] The present invention uses quinolino[3,2,1-de]acridine-5,9-dione as the central core and fused oxygen-bridged triphenylamine to construct a class of MR-TADF red light emitting materials with a rigid large plane.

[0008] The present invention provides a type of MR-TADF red light emitting material with a narrow half-width, which has a structure shown in Formula 1:

[0009]

[0010] Wherein: the R units are independently selected from any one of the following formulae:

[0011]

[0012] The specific structures of the preferred MR-TADF red light emitting materials are shown below. These compounds are only representative compounds:

[0013]

[0014] The more preferred R unit in the MR-TADF red light emitting material is tert-butyl, and the molecular structure is named LYZ.

[0015]

[0016] The preparation steps of MR-TADF red light emitting material LYZ are as follows:

[0017] Using 4-(tert-butyl)phenol as the raw material, 4-(tert-butyl)-2-iodo-1-methoxybenzene was obtained by iodination and methoxy protection of the hydroxyl group, and 4-bromo-2,6-difluoroaniline was reacted through Ullmann reaction, methoxy deprotection and nucleophilic substitution ring closure to obtain the tert-butyl nitrogen oxide core unit (D); using methyl 2-iodobenzoate and methyl 2-aminobenzoate as the raw materials, 6,6'-azadiylbis(3-(tert-butyl)benzoic acid dimethyl ester) unit (A) was obtained through Ullmann reaction and Friedel-Crafts alkylation; the D and A units were reacted through Ullmann reaction, ester hydrolysis and Friedel-Crafts acylation ring closure to obtain the target product.

[0018] The present invention also provides the application of MR-TADF red light emitting material, which is used as a light emitting layer material in the preparation of red light OLEDs.

[0019] The MR-TADF red organic electroluminescent device has a structure of: ITO / PEDOT:PSS (40nm) / PVK (5nm) / CBP:LYZ (1:1, 40nm) / TmPyPB (40nm) / LiF (1.2nm) / Al (120nm). The hole transport layer is a polyvinylcarbazole (PVK) coating; the electron transport layer is TmPyPB; the emissive layer is a blend of a guest material (LYZ) and a host material; the host material is 4,4'-bis(9-carbazole)biphenyl (CBP); and the cathode layer is composed of lithium fluoride and aluminum.

[0020] The MR-TADF red light emitting material LYZ was used to prepare the light-emitting layer of red light OLEDs. The maximum emission peak of the obtained red light emitting device was located at 601nm, the half-maximum width was 68nm, and the corresponding maximum external quantum efficiency (EQE) was 9.38%.

[0021] The present invention provides a class of quinoline acridine-5,9-dione MR-TADF red light emitting material molecules. The resonance effect generated by electron-deficient nitrogen / carbonyl and electron-rich oxygen / nitrogen minimizes the bonding / anti-bonding of frontier molecular orbitals. In addition, the rigid conjugated skeleton can suppress the structural relaxation of the molecular excited state and the vibration coupling between the excited state and the ground state, thereby obtaining a red light emitting material with a narrow half-peak width (<70nm) and high luminescence efficiency. In order to weaken the face-to-face vibration of the molecule and effectively suppress the interaction between molecules, the introduction of tert-butyl groups on the periphery of the molecule can reduce the reorganization energy of the molecule. The grafting of different substituent units can regulate the molecular stacking and film-forming properties.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The molecular structure of the MR-TADF red light emitting material of the present invention breaks through the limitation of the MR-TADF red light emitting material being limited to a boron-carbon structure.

[0024] (2) The resonance effect between electron-deficient nitrogen / carbonyl and electron-rich oxygen / nitrogen minimizes the bonding / antibonding of the frontier molecular orbitals, thereby reducing the vibrational relaxation of the fused ring structure, resulting in a narrow half-peak width and high luminescence efficiency.

[0025] (3) Compared with the reported MR-TADF red-light emitting material molecules, the MR-TADF red-light emitting material of the present invention has a larger coplanarity, which not only further suppresses the vibrational relaxation of the molecules during the transition process, but also greatly suppresses the energy loss caused by the vibration and rotation of the molecular plane, further reducing the reorganization energy of the molecules during the transition from the excited state to the ground state, thereby obtaining a narrower emission spectrum.

[0026] (4) The introduction of tert-butyl, tert-butylphenyl, triarylamine, and carbazole groups on the periphery of the molecule can not only reduce the reorganization energy of the molecule, but also regulate the stacking of the molecule and its film-forming properties; it also reduces the structural deformation of the molecule in the excited state.

[0027] (5) The MR-TADF red light organic light-emitting material of the present invention can be used as a light-emitting layer material in red light OLEDs devices to achieve efficient red light emission of OLEDs devices.

[0028] (6) This type of MR-TADF red light organic light-emitting small molecule material has high thermal stability and excellent carrier transport performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The figures are the UV-visible absorption spectrum and photoluminescence spectrum of the compound LYZ prepared in Example 1 of the present invention in toluene solution.

[0030] Figure 2 This is the CV diagram of compound LYZ prepared in Example 1 of the present invention.

[0031] Figure 3 This is the TGA chart of compound LYZ prepared in Example 1 of the present invention.

[0032] Figure 4 Schematic diagram of the device structure of compound LYZ prepared in Example 1 of the present invention.

[0033] Figure 5 This is the EL spectrum of the compound LYZ prepared in Example 1 of the present invention under 10% doping.

[0034] Figure 6 This is an EQE spectrum diagram of the compound LYZ prepared in Example 1 of the present invention under 10% doping.

[0035] Figure 7 This is the JVL diagram of the compound LYZ prepared in Example 1 of the present invention under 10% doping. DETAILED DESCRIPTION

[0036] The present invention is further illustrated below by a specific example of a red light MR-TADF material LYZ based on quinolino[3,2,1-de]acridine-5,9-dione / dithione, but these specific embodiments do not limit the scope of protection of the present invention in any way.

[0037] Example 1

[0038] The synthesis scheme of the red-light MR-TADF material LYZ based on quinolin-[3,2,1-de]acridine-5,9-dione is as follows:

[0039]

[0040] Synthesis route of target compound LYZ

[0041] Synthesis of compound M1

[0042] To a 500 mL single-necked flask, add 4-(tert-butyl)phenol (A, 100 g, 665.7 mmol, 1 eq), N-iodosuccinimide (NIS, 149.8 g, 665.8 mmol, 1 eq), p-toluenesulfonic acid (TsOH, 114.5 g, 664.9 mmol, 1 eq), and acetonitrile solution (CH3CN, 300.0 mL). Stir and react at room temperature for 6 hours in the dark. Stop the reaction, pour the reaction solution into 300 mL of ice water, add 300 mL of saturated sodium sulfite solution, and stir vigorously for 10 minutes. Separate the organic phase, remove the acetonitrile solution under reduced pressure, and dry in vacuo at 60°C to obtain 173.9 g of a dark red viscous liquid with a yield of 94.61%. 1H NMR (400MHz, CDCl3) δ7.63 (s, 1H), 7.26 (d, J = 8.4Hz, 1H), 6.91 (d, J = 8.5Hz, 1H), 5.30 (s, 1H), 1.27 (s, 9H).

[0043] Synthesis of compound M2

[0044] To a 500 mL single-necked flask, add 4-(tert-butyl)-2-iodophenol (150 g, 543.2 mmol, 1.0 eq), iodomethane (CH3I, 92.37 g, 650.76 mmol, 1.2 eq), potassium carbonate (K2CO3, 112.6 g, 814.8 mmol, 1.5 eq), and N,N-dimethylformamide solution (DMF, 300.0 mL). Stir and react at room temperature for 12 hours. Stop the reaction, pour the reaction solution into 800 mL of water, and extract with DCM three times (100 mL x 3). The organic phases are combined and washed with water five times (500 mL x 5). The organic phases are separated, dried over magnesium sulfate, filtered to remove the magnesium sulfate, and the DCM is removed under reduced pressure. The product is purified by flash column chromatography using DCM as the developing solvent and dried under vacuum at 60°C to obtain 128.7 g of a colorless, viscous liquid in an 82.54% yield. 1 H NMR (400MHz, CDCl3) δ7.77 (s, 1H), 7.32 (d, J = 8.6 Hz, 1H), 6.76 (d, J = 8.6 Hz, 1H), 3.86 (s, 3H), 1.28 (s, 9H).

[0045] Synthesis of compound M3

[0046] Under a nitrogen atmosphere, a 1000 mL single-necked flask was charged with 4-(tert-butyl)-2-iodo-1-methoxybenzene (M2, 100 g, 344.67 mmol, 2.5 eq), 4-bromo-2,6-difluoroaniline (28.68 g, 137.87 mmol, 1 eq), activated copper powder (Cu, 35.05 g, 551.48 mmol, 4 eq), potassium carbonate (K2CO3, 95.26 g, 689.35 mmol, 5 eq), 18-crown-6 (18-Crown-6, 9.11 g, 34.47 mmol, 0.1 eq), and o-dichlorobenzene (o-DCB, 500.0 mL). The mixture was heated to 180°C and stirred for 72 hours. The reaction was stopped, cooled to room temperature, filtered, and the filter cake was washed with 300 mL of DCM. The filtrate was collected and the organic solvent was removed by distillation under reduced pressure. The residue was poured into 300 mL of water and extracted three times with DCM (50 mL x 3). The organic phases were combined and washed five times with water (100 mL x 5). The organic phase was separated and dried over magnesium sulfate, filtered to remove the magnesium sulfate, and the DCM was removed under reduced pressure. The product was purified by column chromatography using PE:DCM = 2:1 as the developing solvent and dried under vacuum at 60°C to obtain 61.27 g of a white solid with a yield of 83.45%. 1 H NMR (400MHz, CDCl3) δ7.06 (dd, J = 8.5, 2.3Hz, 2H), 6.99 (d, J = 8.0Hz, 2H), 6.92 (d, J = 2.2Hz, 2H), 6.81 (d, J = 8.5Hz, 2H), 3.56 (s, 6H), 1.20 (s, 18H).

[0047] Synthesis of compound M4

[0048] Under a nitrogen atmosphere, a 500 mL two-necked flask was charged with 4-bromo-N,N-bis(5-(tert-butyl)-2-methoxyphenyl)-2,6-difluoroaniline (M3, 5 g, 93.90 mmol, 1 eq) and a dry dichloromethane solution (DCM, 300.0 mL). The mixture was cooled to 0°C and slowly added with boron tribromide (BBr3, 51.75 g, 206.58 mmol, 2.2 eq). The mixture was returned to room temperature and stirred for 12 h. The reaction solution was poured into 500 mL of ice water to quench the reaction. The mixture was extracted with DCM three times (50 mL x 3). The organic phases were combined and washed with water three times (200 mL x 3). The organic phase was separated, dried over magnesium sulfate, filtered to remove the magnesium sulfate, and the DCM was removed under reduced pressure to obtain an off-white solid residue, which was used directly in the next step without further treatment. Under a nitrogen atmosphere, a 500 mL two-necked flask was charged with the off-white solid residue, potassium carbonate (K2CO3, 38.93 g, 281.7 mmol, 3 eq), and N,N-dimethylformamide solution (DMF, 300.0 mL). The temperature was raised to 120°C and stirred for 12 h. The reaction was stopped, cooled to room temperature, and poured into 800 mL of water. A large amount of white solid precipitated. The mixture was vigorously stirred for 30 min, filtered, and the filter cake was washed with distilled water (1500 mL). No further purification was required. The filter cake was vacuum-dried at 60°C to obtain 42.41 g of a white solid in a yield of 97.25%. 1 H NMR (400MHz, CDCl3) δ7.36 (s, 2H), 6.92 (dd, J = 8.5, 1.7Hz, 2H), 6.85-6.80 (m, 2H), 6.64 (s, 2H), 1.28 (s, 18H). MALDI-TOF MS(mass m / z):464.12[M]+.Calcd for C 26 H 26 BrNO2:464.40.

[0049] Synthesis of compound M5

[0050] Under a nitrogen atmosphere, a 500 mL single-necked flask was charged with methyl 2-iodobenzoate (28.83 g, 110 mmol, 1.1 eq), methyl 2-aminobenzoate (15.1 g, 100 mmol, 1 eq), activated copper powder (Cu, 12.7 g, 200 mmol, 2 eq), cuprous iodide (CuI, 3.8 g, 20 mmol, 0.2 eq), potassium carbonate (K2CO3, 27.6 g, 200 mmol, 2 eq), 18-crown-6 (18-Crown-6, 5.28 g, 20 mmol, 0.2 eq), and dry o-dichlorobenzene (o-DCB, 200.0 mL). The mixture was heated to 180°C and stirred for 48 h. The reaction was stopped, cooled to room temperature, filtered, and the filter cake was washed with 300 mL of DCM. The filtrate was collected and the organic solvent o-DCB was removed by distillation under reduced pressure. The residue was dissolved in a small amount of DCM and poured into 150 mL of petroleum ether (PE) to precipitate a white solid. The filter cake was filtered and washed with petroleum ether and dried in vacuo at 60° C. to obtain 27.92 g of a white solid with a yield of 97.96%. 1 HNMR (400MHz, CDCl3) δ11.07(s,1H),7.99(dd,J=8.0,1.6Hz,2H),7.55(d,J=8.0Hz,2H),7.37(t,J=7.8Hz,2H),6.90(t,J=7.6Hz,2H),3.95(s,6H).

[0051] Synthesis of compound M6

[0052] To a 250 mL single-necked flask, add dimethyl 2,2'-azadiyldibenzoate (M5, 10 g, 35 mmol, 1 eq) and tert-butyl chloride (C(CH3)3Cl, 60 mL). Slowly add aluminum chloride (AlCl3, 11.67 g, 87.5 mmol, 2.5 eq) in portions under an ice bath. Heat to 70°C, pass condensed water through, connect a drying tube, and stir for 12 h. Stop the reaction, cool to room temperature, pour into 300 mL of ice water, and extract three times with DCM (50 mL x 3). Combine the organic phases and wash three times with water (50 mL x 3). Separate the organic phase, dry over magnesium sulfate, filter to remove the magnesium sulfate, and remove the DCM and excess tert-butyl chloride under reduced pressure. The residue was dissolved in a small amount of DCM and poured into 150 mL of petroleum ether (PE) to precipitate a white solid. The solid was filtered and the filter cake was washed with petroleum ether and dried in vacuo at 60° C. to obtain 11.56 g of a white solid with a yield of 83.17%. 1H NMR (400MHz, CDCl3) δ 10.85 (s, 1H), 7.96 (s, 2H), 7.48 (d, J = 8.8Hz, 2H), 7.40 (dd, J = 8.8, 2.4Hz, 2H), 3.94 (s, 6H), 1.32 (s, 18H).

[0053] Synthesis of compound M7

[0054] Under nitrogen atmosphere, a 250 mL single-necked flask was charged with 7-bromo-2,12-di-tert-butylbenzo[5,6][1,4]oxazino[2,3,4-kl]phenoxazine (M4, 2.1 g, 4.53 mmol, 1.2 eq), dimethyl 6,6'-azadiylbis(3-(tert-butyl)benzoate) (M6, 1.5 g, 3.77 mmol, 1 eq), activated copper powder (Cu, 4.76 g, 75 mmol, 20 eq), cuprous iodide (CuI, 1.43 g, 7.5 mmol, 1 eq), potassium carbonate (K2CO3, 12.44 g, 90 mmol, 24 eq), 18-crown-6-ol (1. 98g, 7.5mmol, 1eq), dried o-dichlorobenzene (o-DCB, 60.0mL), heated to 180°C and stirred for 48h. Stop the reaction, cool to room temperature, filter, and wash the filter cake with 100mL of DCM. Collect the filtrate and remove the organic solvent o-DCB by distillation under reduced pressure. Pour the residue into 200mL of water and extract three times with DCM (50mL*3). The organic phases are combined and washed three times with water (50mL*3). The organic phase is separated, dried over magnesium sulfate, filtered to remove the magnesium sulfate, and the DCM is removed under reduced pressure. The product is separated and purified by column chromatography using PE:DCM = 1:2 as the developing solvent and dried in vacuo at 60°C to obtain 1.99g of a yellow solid with a yield of 67.85%. 1 HNMR (400MHz, CDCl3) δ7.67-7.51(m,2H),7.49-7.20(m,4H),7.08-6.96(m,2H),6.92-6.53( m, 4H), 5.91 (d, J = 33.6Hz, 2H), 3.46 (d, J = 15.6Hz, 6H), 1.25 (d, J = 4.0Hz, 18H), 1.21 (s, 18H).

[0055] Synthesis of compound LYZ

[0056] A 500 mL single-necked flask was charged with 6,6'-((2,12-di-tert-butylbenzo[5,6][1,4]oxazino[2,3,4-kl]phenoxazin-7-yl)azadimethyl)bis(3-(tert-butyl)benzoate) (M7, 1.17 g, 1.5 mmol, 1 eq), sodium hydroxide (NaOH, 12 g, 300 mmol, 200 eq), tetrahydrofuran (THF, 80.0 mL), ethanol (EtOH, 80.0 mL), and distilled water (THF, 80.0 mL). The mixture was heated to 100°C and stirred under reflux for 4 h. The reaction was stopped, the THF and EtOH were removed, and the mixture was cooled to room temperature. The mixture was acidified with hydrochloric acid and the pH was adjusted to 2-3. A yellow solid precipitated, which was filtered, washed with distilled water, and dried under vacuum at 60°C to obtain 0.783 g of a yellow solid in a yield of 69.42%. The product was used directly in the next step without purification. Under a nitrogen atmosphere, the yellow solid (0.783 g, 1.04 mmol, 1 eq) from the previous step, oxalyl chloride (C2Cl2O2, 1.32 g, 10.4 mmol, 10 eq), and dry dichloromethane (DCM, 15 mL) were added to a 50 mL single-necked flask, and the mixture was heated to 50 ° C and refluxed with stirring for 3 h. The reaction was stopped, and C2Cl2O2 and DCM were removed by distillation under reduced pressure to obtain a gray solid, which was used directly in the next step without purification. Under a nitrogen atmosphere, the gray solid (0.780 g, 1 mmol, 1 eq) from the previous step, aluminum chloride (AlCl3, 1.65 g, 10 mmol, 10 eq), and dry dichloromethane (DCM, 15 mL) were added to a 100 mL single-necked flask, and the mixture was heated to 55 ° C and refluxed with stirring for 12 h. The reaction was stopped and the mixture was evaporated to remove the precipitate and DCM. The residue was poured into 300 mL of water and extracted three times with DCM (20 mL x 3). The organic phases were combined and washed three times with water (30 mL x 3). The organic phase was separated and dried over magnesium sulfate, filtered to remove the magnesium sulfate, and the DCM was removed under reduced pressure. The product was purified by column chromatography using PE:DCM = 4:1 as the developing solvent and dried under vacuum at 60°C to obtain LYZ, a red solid product (0.263 g, yield: 24.35%). 1 H NMR (400MHz, CDCl3) δ8.37(s,2H),7.87(d,J=8.9Hz,2H),7.64(d,J=8.9Hz,2H),7.3 5(s,2H),7.12(d,J=8.5Hz,2H),7.00(d,J=8.5Hz,2H),1.42(s,18H),1.30(s,18H).

[0057] Example 2

[0058] UV absorption test of red light MR-TADF material LYZ in toluene solution based on quinolin[3,2,1-de]acridine-5,9-dione: dissolve compound LYZ in toluene solution to prepare 10 -5 mol / solubility solution, test its toluene solution UV-visible absorption spectrum. Figure 1 It can be seen that the UV-visible absorption spectrum of compound LYZ in toluene has two absorption peaks: the absorption band around 300-400 nm is attributed to π-π* transition, and the absorption band around 450-550 nm is attributed to intramolecular charge transfer.

[0059] Example 3

[0060] Fluorescence spectrum test of toluene solution of quinolin-[3,2,1-de]acridine-5,9-dione red light MR-TADF material LYZ: Photoluminescence performance test of compound LYZ in Example 1. Dissolve compound LYZ in toluene to prepare 10 -5 M solution, and tested its photoluminescence spectrum, such as Figure 1 As shown, under light excitation, all compounds emit light in the orange-red to red region. Compound LYZ has a maximum emission peak of 602 nm, achieving red light emission, and a half-width at half maximum of 69 nm, demonstrating narrow half-width emission characteristics.

[0061] Example 4

[0062] CV test of red light MR-TADF material LYZ based on quinolin[3,2,1-de]acridine-5,9-dione: CV test of compound LYZ in Example 1. Figure 2 As shown, cyclic voltammetry (CV) was performed in anhydrous acetonitrile solution under nitrogen atmosphere using a CHI620 voltammetric analyzer at a scan rate of 50 mV / s. A platinum working electrode, a platinum wire counter electrode, and an Ag / AgCl electrode were used as the working electrode, counter electrode, and reference electrode, respectively. An acetonitrile solution of tetrabutylammonium hexafluorophosphate (Bu4NPF6, 0.1M) was used as the reference for all measurements at a scan rate of 50 mV / s. Ferrocene / ferrocene cation (Fc / Fc + ) redox couple as a reference. The oxidation potentials of LYZ were 0.73 eV, ferrocene / ferrocene cation (Fc / Fc + ) is 0.43 eV. The HOMO energy level of LYZ is calculated to be -5.10 eV, and the LUMO energy level can be calculated from the optical band gap.

[0063] Example 5

[0064] Thermal stability (TGA) test of red light MR-TADF material LYZ based on quinolino[3,2,1-de]acridine-5,9-dione

[0065] TGA test of compound LYZ in Example 1. The test was carried out from room temperature to 600°C at a heating rate of 20°C / min under a nitrogen atmosphere. The sample mass was controlled within 1g. The crucible was made of alumina (Al2O3) to ensure the stability and accuracy of the high temperature test and to avoid sample oxidation, providing reliable data for subsequent analysis. Figure 3 As shown, the decomposition temperature (95% by mass) of compound LYZ is 382° C., which has excellent thermal stability and meets the device processing performance requirements.

[0066] Example 6

[0067] Device fabrication scheme and luminescence performance testing of the red-light MR-TADF material LYZ based on quinolin-[3,2,1-de]acridine-5,9-dione

[0068] The structure of the red organic electroluminescent device is: ITO / PEDOT:PSS (40nm) / PVK (5nm) / CBP:LYZ (1:1, 40nm) / TmPyPB (40nm) / LiF (1.2nm) / Al (120nm). Figure 4 As shown in the figure, the hole transport layer is a polyvinylcarbazole (PVK) coating; the electron transport layer is 1,3,5-tris(p-pyridin-3-ylphenyl)benzene (TmPyPB); the light-emitting layer is a blend of a guest material (LYZ) and a host material; the host material is 4,4'-bis(9-carbazole)biphenyl (CBP); and the cathode layer is composed of lithium fluoride and aluminum.

[0069] The device fabrication process involves spin-coating a 40nm thick poly(ethylenedioxythiophene) / poly(p-styrenesulfonic acid) (PEDOT-PSS) (Bayer Batron P4083) hole injection layer, a 5nm thick PVK hole transport layer, a 40nm thick luminescent layer, and a 40nm thick electron transport layer (TmPyPB) on treated ITO glass. Subsequently, 1.2nm thick lithium fluoride and 120nm thick aluminum (Al) layers were evaporated sequentially. The device has a light-emitting area of ​​0.15cm. 2 .

[0070] The thicknesses of the hole injection layer, hole transport layer, and light-emitting layer were measured using a surface profiler (Tencor, ALFA-Step500). The thickness and deposition rate of the electron transport layer, hole injection layer, and Al were measured using a thickness / velocity meter (Sycon STM-100 thickness / velocity meter). The deposition rates for the electron transport layer, hole injection layer, and Al were 0.05-0.1 nm / s and 1-2 nm / s, respectively. All operations were performed in a nitrogen glove box.

[0071] The electroluminescence spectrum (EL) was measured using an Instaspec4 CCD grating spectrometer from Oriel; the luminous efficiency was measured using a standard silicon photodiode; the electroluminescence efficiency was measured using an S80 integrator (US Labshere) in conjunction with a UDT3 digital photometer; the laser light source was a He-Cd laser with 325 and 442 nm spectral lines (USDmni Chrone); the current-voltage (IV) curve, the luminous intensity-voltage (LV) curve, and the external quantum efficiency were measured using a Keithley source meter.

[0072] The electroluminescence spectrum and EQE curve of the light-emitting device based on LYZ material are shown in Figure 2. Figure 5-6 As shown. The LYZ-based doping device shows a red light emission spectrum, showing strong luminescence in the range of 550nm to 750nm. When the material LYZ is used to prepare red light organic light-emitting diode devices, the LYZ-based (10% doping) device has a luminous wavelength of 601nm (EQE of 9.38%) and a half-peak width of 68nm, achieving narrow-band red light emission. Figure 7 As shown in FIG. 1 , the current density, voltage-luminance (JVL) characteristic curve of the device has a medium relative current density and a turn-on voltage of (8.1V).

[0073] Although the present invention has been described in conjunction with the preferred embodiments, the present invention is not limited to the above embodiments, and it should be understood that the appended claims summarize the scope of the present invention. Under the guidance of the inventive concept, those skilled in the art should appreciate that certain changes made to the various embodiments of the present invention will be covered by the spirit and scope of the claims of the present invention.

Claims

1. A type of quinoline acridine-5,9-dione MR-TADF red light emitting material, characterized in that: The molecular structure of the luminescent material is shown in Formula 1: ， Formula 1 Wherein: the R unit is H or tert-butyl.

2. The quinoline-acridine-5,9-dione MR-TADF red light emitting material according to claim 1, characterized in that: The R unit is tert-butyl.

3. Use of the quinoacridine-5,9-dione MR-TADF red light emitting material according to claim 1 as a light emitting material in the preparation of a red light organic electroluminescent device.

4. The use according to claim 3, characterized in that The quinoline acridine-5,9-dione MR-TADF red light emitting material is used as a guest light emitting material.

5. The use according to claim 3, characterized in that The structure of the red organic electroluminescent device is: ITO / PEDOT:PSS / PVK / CBP:LYZ / TmPyPB / LiF / Al; wherein the LYZ is the quinoline acridine-5,9-dione MR-TADF red light emitting material according to claim 2.

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