Near-ultraviolet-visible materials with a class of carbazole as donor bridge, and preparation method and application thereof

Abstract

The application discloses a kind of carbazole as donor bridge near ultraviolet-ultraviolet material and preparation method and application, it is related to the technical field of organic electroluminescent material and device, as carbazole is donor bridge, N site is introduced acceptor unit, C site is introduced second donor unit, constructs the preparation method of efficient stable near ultraviolet and ultraviolet organic electroluminescent material based on donor'-'-donor-acceptor (D'-D-A) structure and application in OLED.The structure of the material includes giving electricity and absorbing electricity structural unit, with excellent light thermal stability, simple synthesis step, high yield and the like, and with high fluorescent efficiency, high exciton utilization efficiency and excellent electron and hole transport characteristics.The prepared doped and non-doped OLED shows the advantages of lower than 420nm electroluminescence peak, low opening voltage, high color purity, high efficiency, high brightness, low efficiency roll-down and long life, etc., has important application prospect in the field of anti-counterfeiting, ultraviolet curing, excitation light source, medical diagnosis and treatment, sterilization and disinfection.

Description

Technical Field

[0001] The present invention relates to the technical field of organic semiconductor materials and light-emitting devices, and in particular to a near-ultraviolet-ultraviolet material with carbazole as a donor bridge, a preparation method and an application thereof. Background Art

[0002] With the continuous advancement of science and technology, organic light-emitting diode (OLED) technology has achieved remarkable results and is widely used in the fields of full-color display and solid-state lighting. Compared with red / green / blue primary color OLEDs, near-ultraviolet and ultraviolet OLEDs lag far behind in terms of material types, quantity and device performance due to their wider band gap (emission peak is less than 420nm). However, due to their unique spectral characteristics, near-ultraviolet and ultraviolet OLEDs have broad application space and development prospects in optoelectronics, excitation light sources, high-density information storage, biological and medical applications and other fields. Generally, the external quantum efficiency of near-ultraviolet and ultraviolet OLEDs reported in the past is generally less than 5%. Although significant progress has been made in molecular design, the number of high-efficiency near-ultraviolet and ultraviolet OLEDs is still limited. Therefore, the development of efficient and stable near-ultraviolet and ultraviolet OLEDs has become an urgent need.

[0003] In the pursuit of superior and efficient near-UV and UV OLED devices, the structural design of near-UV and UV organic electroluminescent materials plays a crucial role, requiring careful consideration of the following aspects: First, the near-UV and UV materials must be endowed with just the right molecular rigidity and sufficient molecular weight to improve the thermal stability and film morphology stability of the materials, thereby mitigating the effects of Joule heating on device degradation. Second, the molecular conjugation length and intermolecular aggregation effects must be carefully controlled to achieve a balance between near-UV / UV emission and fluorescence efficiency. Furthermore, the efficient utilization of electrogenerated singlet and triplet excitons is a key factor in improving the electroluminescent performance of near-UV and UV OLED devices. Limited by exciton statistical rules, traditional fluorescent materials and triplet-triplet annihilation (TTA) materials, while exhibiting good stability, have theoretical upper limits on exciton utilization in their devices, limited to 25% and 62.5%. Thermally activated delayed fluorescence (TADF) materials and phosphorescent materials based on heavy metal complexes can fully utilize both singlet and triplet excitons, achieving 100% exciton utilization efficiency. However, due to the long exciton lifetime and sophisticated molecular design principles, effectively achieving high-efficiency and low roll-off near-UV and UV OLEDs has been virtually impossible. This has hindered the practical application of near-UV and UV OLEDs at high brightness. In contrast, the hot exciton mechanism pioneered by Chinese scientists such as Academician Ma Yuguang cleverly converts high-energy triplet excitons into singlet excitons through the high-energy reverse intersystem crossing (HRISC) process, theoretically also achieving 100% exciton utilization efficiency. Among these, a class of molecules exhibiting hybrid localized charge transfer (HLCT) excited-state properties are typical examples of hot exciton materials. The exquisite separation of exciton conversion and radiative transition channels, as well as precise control of donor / acceptor unit strengths, endow HLCT materials with not only remarkable fluorescence efficiency but also extraordinary potential and appeal in the near-UV and UV fields.

[0004] Donor-acceptor (DA) emitters are a common molecular paradigm used to alleviate carrier injection and transport issues, effectively broadening the exciton recombination zone and further suppressing exciton quenching. However, strong intramolecular CT effects can also, to a certain extent, cause red-shifts in the emission spectrum, deterioration in color purity, and reduced molecular orbital overlap (resulting in lower fluorescence efficiency). Although DA-based thermoexciton materials have been applied in near-ultraviolet and ultraviolet OLEDs, and device performance has also achieved certain breakthroughs, the molecular species, quantity, and device performance of these materials still require further development and improvement. Summary of the Invention

[0005] To achieve the aforementioned objectives and address the shortcomings and limitations of the prior art, the present invention provides a method for preparing a class of "donor'-donor-acceptor" (D'-DA) near-ultraviolet and ultraviolet organic electroluminescent materials using carbazole as a donor bridge, and their application in OLEDs. This material design utilizes the weakly electron-donating group carbazole as the core donor bridge. An electron-withdrawing or electron-deficient end group is innovatively introduced at the nitrogen atom at position 9 of the carbazole to modulate the CT state component of the excited state. A second auxiliary donor, linked to the C2 or C3 positions with para, meta, or ortho bonds, modulates the localized state component, thereby constructing a unique D'-DA molecular system. This structural design promotes the HRISC process while effectively ensuring the material's high fluorescence efficiency and bipolarity. Furthermore, by leveraging steric hindrance and weak conjugation effects, the material's emission wavelength is effectively reduced and its color purity is improved. In addition, the near-ultraviolet and ultraviolet organic light-emitting materials of the present invention not only have excellent photothermal stability, simple synthesis steps, high yield and other characteristics, but also have good morphological stability. The prepared doped and non-doped OLEDs exhibit electroluminescence peaks below 420nm, low turn-on voltage, high color purity, high efficiency, high brightness, low efficiency roll-off and long life, and have important application prospects in anti-counterfeiting, high-density information storage, ultraviolet curing, excitation light sources, medical diagnosis and treatment, sterilization and disinfection, 3D printing and plant lighting. These features greatly enhance its applicability and reliability in practical application scenarios. Through this innovative design, it is expected to promote the technological progress of near-ultraviolet and ultraviolet OLEDs and other optoelectronic devices.

[0006] Another object of the present invention is to provide a method for preparing the D'-DA type near-ultraviolet and ultraviolet organic electroluminescent material using carbazole as a donor bridge.

[0007] Another object of the present invention is to provide the application of the D'-DA type near-ultraviolet and ultraviolet organic electroluminescent material with carbazole as a donor bridge, and the application of the near-ultraviolet and ultraviolet organic electroluminescent material as a luminescent material in OLEDs, especially in doped devices.

[0008] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

[0009] A class of highly efficient and stable near-ultraviolet and ultraviolet organic electroluminescent materials with a D'-DA structure constructed with carbazole as a donor bridge, characterized in that the structural formula is Formula I or Formula II:

[0010]

[0011] Preferably, the R1 is one of the following power-donating structural units:

[0012]

[0013] Preferably, R2 is one of the following electricity-absorbing structural units:

[0014]

[0015] The present invention also provides a method for preparing the above-mentioned highly efficient and stable near-ultraviolet and ultraviolet organic electroluminescent material having a D'-DA structure constructed with carbazole as a donor bridge, characterized in that the preparation method comprises method one or method two:

[0016] The method 1 comprises the following steps:

[0017] Under nitrogen protection, A1 uses 3-(or 2-)bromocarbazole and a fluorinated or iodinated compound substituted with R2 as raw materials, undergoes a nucleophilic substitution reaction or a carbon-nitrogen coupling reaction in a catalytic system, and then performs extraction and column chromatography purification to obtain an intermediate;

[0018] A2, under nitrogen protection, uses the intermediate obtained in step A1 and the boronic acid, boron ester or NH aromatic heterocycle substituted by R1 as raw materials, undergoes a Suzuki coupling reaction or a carbon-nitrogen coupling reaction under a catalytic system, and then performs extraction, column chromatography purification and sublimation treatment to obtain a luminescent material.

[0019] The second method comprises the following steps:

[0020] B1, under nitrogen protection, uses 3-(or 2-)bromocarbazole and R1-substituted boronic acid (or ester) as raw materials to carry out Suzuki coupling reaction in a catalytic system; extracts and column chromatography purification are performed to obtain an intermediate product;

[0021] B2: Under nitrogen protection, the intermediate obtained in step B1 and the fluorine, bromine or iodine substituted by R2 are used as raw materials, and after undergoing a nucleophilic substitution reaction or a carbon-nitrogen coupling reaction under a catalytic system, extraction, column chromatography purification and sublimation treatment are performed to obtain a luminescent material.

[0022] Preferably,

[0023] In step A1, the molar ratio of the reactants 3-(or 2-)bromocarbazole and the fluorinated or iodinated compound substituted by R2 is 1:1.05-1:1.5, and the catalyst system is potassium carbonate or cuprous iodide;

[0024] In step A2, the molar ratio of the boronic acid, boron ester or NH aromatic heterocycle substituted by the reactant R1 to the intermediate obtained in step A1 is 1:1-1:1.5, and the catalyst system is tetrakis(triphenylphosphine)palladium;

[0025] In step B1, the molar ratio of the boronic acid (or ester) substituted by reactant R1 to 3-(or 2-)bromocarbazole is 1:1-1:2, and the catalyst system is tetrakis(triphenylphosphine)palladium;

[0026] In step B2, the molar ratio of the intermediate obtained in step B1 to the fluorine, bromine or iodide substituted by R2 is 1:1.1-1:5, and the catalyst system is potassium carbonate, cesium carbonate, sodium hydride, cuprous iodide, ferrocene-palladium dichloride or palladium acetate.

[0027] The present invention also provides a use of the above-mentioned D'-DA structured, highly efficient and stable near-ultraviolet and ultraviolet organic electroluminescent material constructed with carbazole as a donor bridge as a light-emitting layer in the preparation of doped and non-doped layer OLEDs devices.

[0028] Preferably, the light-emitting layer material is a pure film containing the near-ultraviolet and ultraviolet organic electroluminescent molecules, or a doped film containing the near-ultraviolet and ultraviolet organic electroluminescent molecules and a host material, and the mass ratio of the light-emitting molecules to the host material is 1:99-99:1.

[0029] Preferably, the main material used for the doped film is one of: N,N'-dicarbazolyl-4,4'-biphenyl (CBP), 1,3-dicarbazol-9-ylbenzene (mCP), 9,10-dinaphthylanthracene (ADN), 9,10-di(2-naphthyl)-2-methylanthracene (MADN) and 9-(4-(10-phenylanthracene-9-yl)phenyl)-9H-carbazole.

[0030] The present invention uses the weak electron-donating group carbazole as the core donor bridge, and innovatively introduces an electron-withdrawing or electron-deficient end group on the nitrogen atom at position 9 of carbazole to regulate the CT state component in the excited state, and introduces a second auxiliary donor with a para-, meta- or ortho-bonding on C2 or C3 to regulate the localized state component, thereby constructing a unique D'-DA type near-ultraviolet and ultraviolet organic electroluminescent molecular system.

[0031] The technical solution provided by the present invention brings beneficial effects:

[0032] The D'-DA structured near-ultraviolet and ultraviolet organic electroluminescent materials prepared by the present invention using carbazole as a donor bridge can achieve precise control of CT and localized states, promote the HRISC process, and at the same time, effectively ensure the near-ultraviolet and ultraviolet light emission and high color purity of the material, and also give the material high fluorescence efficiency and bipolarity.

[0033] The D'-DA structured near-ultraviolet and ultraviolet organic electroluminescent material prepared by the invention using carbazole as a donor bridge has the characteristics of excellent photothermal stability, film morphology stability, simple synthesis steps, high yield and the like.

[0034] The D'-DA structured near-ultraviolet and ultraviolet organic electroluminescent materials prepared by the present invention with carbazole as a donor bridge can be used to prepare high-performance doped and non-doped OLEDs, which have the advantages of an electroluminescent peak below 420nm, low turn-on voltage, high color purity, high efficiency, high brightness, low efficiency roll-off and long life.

[0035] The D'-DA structured near-ultraviolet and ultraviolet organic electroluminescent materials prepared by the present invention, which use carbazole as a donor bridge, can be used to prepare high-performance doped and non-doped OLEDs, and have important application prospects in the fields of anti-counterfeiting, high-density information storage, ultraviolet curing, excitation light sources, medical diagnosis and treatment, sterilization and disinfection, 3D printing, and plant lighting. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is the H NMR spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZCN with a D'-DA structure constructed with carbazole as a donor bridge prepared in Example 1;

[0037] Figure 2 This is the H NMR spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZCN with a D'-DA structure constructed with carbazole as a donor bridge, prepared in Example 2;

[0038] Figure 3 This is the H NMR spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD prepared in Example 3, which has a D'-DA structure constructed with carbazole as a donor bridge;

[0039] Figure 4 The H NMR spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD with D'-DA structure constructed with carbazole as the donor bridge prepared in embodiment 4.

[0040] Figure 5 The mass spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZCN prepared in Example 1 with a D'-DA structure constructed using carbazole as a donor bridge;

[0041] Figure 6 The mass spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZCN prepared in Example 2 with a D'-DA structure constructed using carbazole as a donor bridge;

[0042] Figure 7 The mass spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD prepared in Example 3 with a D'-DA structure constructed using carbazole as a donor bridge;

[0043] Figure 8This is the mass spectrum of the D'-DA structured near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD prepared in Example 4 using carbazole as a donor bridge.

[0044] Figure 9 The thermogravimetric curve of the D'-DA structure near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZCN prepared in Example 1 with carbazole as the donor bridge;

[0045] Figure 10 This is the thermogravimetric curve of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZCN with a D'-DA structure constructed with carbazole as a donor bridge prepared in Example 2;

[0046] Figure 11 This is the thermogravimetric curve of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD prepared in Example 3 with a D'-DA structure constructed using carbazole as a donor bridge;

[0047] Figure 12 This is the thermogravimetric curve of the D'-DA structured near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD prepared in Example 4 using carbazole as a donor bridge.

[0048] Figure 13 The normalized photoluminescence spectra of the near-ultraviolet and ultraviolet organic electroluminescent materials 3,9-mPPICZCN 5wt% doped films with D'-DA structure constructed with carbazole as donor bridge prepared in Examples 1, 2, 3, and 4;

[0049] Figure 14 The normalized photoluminescence spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZCN 5wt% doped film with D'-DA structure constructed with carbazole as donor bridge prepared in Example 2;

[0050] Figure 15 The normalized photoluminescence spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD 10 wt% doped film with D'-DA structure constructed with carbazole as donor bridge prepared in Example 3;

[0051] Figure 16 The normalized photoluminescence spectrum of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD 10 wt% doped film with D'-DA structure constructed with carbazole as donor bridge prepared in Example 4;

[0052] Figure 17External quantum efficiency-brightness characteristic curves of doped OLED devices prepared from near-ultraviolet and ultraviolet organic electroluminescent materials constructed with carbazole as a donor bridge in Examples 1, 2, 3 and 4;

[0053] Figure 18 Electroluminescence spectra of doped OLED devices prepared from near-ultraviolet and ultraviolet organic electroluminescent materials with carbazole as donor bridge in Examples 1, 2, 3 and 4;

[0054] Figure 19 The external quantum efficiency-brightness characteristic curve and electroluminescence spectrum of the non-doped OLED device prepared from the near-ultraviolet and ultraviolet organic electroluminescent material with D'-DA structure constructed with carbazole as the donor bridge in Example 3.

[0055] Figure 20 The external quantum efficiency-brightness characteristic curve and electroluminescence spectrum of the non-doped OLED device prepared from the near-ultraviolet and ultraviolet organic electroluminescent material with D'-DA structure constructed with carbazole as the donor bridge in Example 4.

[0056] Figure 21 This is the current density-voltage curve of the single-carrier device prepared from the D'-DA structured near-ultraviolet and ultraviolet organic electroluminescent material constructed with carbazole as the donor bridge in Example 3. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below in conjunction with the embodiments. Of course, the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0058] Example 1

[0059] Near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZCN

[0060] A near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZCN is prepared to prepare 4-(3-(3-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-9H-carbazole-9-yl)benzonitrile, whose structure is as follows:

[0061]

[0062] The preparation method of the near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZCN comprises the following steps:

[0063] Step (1), synthesis of the intermediate 4-(3-bromo-9H-carbazole-9-yl)benzonitrile:

[0064]

[0065] Under nitrogen, 3-bromo-9H-carbazole (2009 mg, 8.17 mmol), 4-iodobenzonitrile (2058 mg, 8.99 mmol), cuprous iodide (466 mg, 2.45 mmol), anhydrous potassium carbonate (2260 mg, 16.34 mmol), and N,N-dimethylformamide (DMF) (80 mL) were added to a 250 mL two-necked round-bottom flask. The mixture was heated to 110°C in a catalytic system and refluxed for 24 hours. The reaction mixture was extracted three times with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude product was purified by silica gel column chromatography using petroleum ether / dichloromethane (4 / 1, v / v) to give a white solid (1652 mg, 58%).

[0066] Step (2), synthesis of the target molecule 4-(3-(3-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-9H-carbazole-9-yl)benzonitrile:

[0067]

[0068] 1-Phenyl-2-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole (744 mg, 1.5 mmol), 4-(3-bromo-9H-carbazol-9-yl)benzonitrile (623 mg, 1.8 mmol), and tetrakis(triphenylphosphine)palladium (125 mg, 0.075 mmol) were placed in a 250 mL two-necked round-bottom flask and the nitrogen atmosphere was replaced three times. Then, tetrahydrofuran (50 mL) and 2M potassium carbonate (4.8 mL) were added to the two-necked flask. The temperature was controlled at 80°C. The reaction mixture was refluxed with stirring for 24 hours. After cooling to room temperature, the reaction mixture was extracted three times with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude product was purified by silica gel column chromatography using dichloromethane and ethyl acetate (20 / 1, v / v) as solvent to give a white solid (485 mg, 52%).

[0069] 1H NMR (400MHz, CDCl3-d) δ8.80(d,J=8.4Hz,1H),8.73(d,J=8.3Hz,1H),8.44( d,J=1.7Hz,1H),8.23(t,J=7.7Hz,2H),7.96–7.92(m,3H),7.81–7.76(m,4H) ,7.71(d,J=7.1Hz,3H),7.63(d,J=6.8Hz,2H),7.57(d,J=8.5Hz,2H),7.50–7 .46(m,4H),7.44–7.35(m,3H),7.30(t,J=7.6Hz,2H),7.22(d,J=8.3Hz,1H).

[0070] Example 2

[0071] Near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZCN

[0072] A near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZCN 4-(2-(3-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-9H-carbazole-9-yl)benzonitrile, whose structure is as follows:

[0073]

[0074] The preparation method of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZCN comprises the following steps:

[0075] Step (1), synthesis of the intermediate 4-(2-bromo-9H-carbazole-9-yl)benzonitrile:

[0076]

[0077] Under nitrogen, 2-bromo-9H-carbazole (2009 mg, 8.17 mmol), 4-iodobenzonitrile (2058 mg, 8.99 mmol), cuprous iodide (466 mg, 2.45 mmol), anhydrous potassium carbonate (2260 mg, 16.34 mmol), and DMF (80 mL) were added to a 250 mL two-necked round-bottom flask. The mixture was heated to 110°C in a catalytic system and refluxed for 24 hours. The reaction mixture was extracted three times with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude product was purified by silica gel column chromatography using petroleum ether / dichloromethane (4 / 1, v / v) to obtain a white solid (1300 mg, 45%).

[0078] Step (2), synthesis of the target molecule 4-(2-(3-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)-9H-carbazol-9-yl)benzonitrile:

[0079]

[0080] 1-Phenyl-2-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole (744 mg, 1.5 mmol), 4-(2-bromo-9H-carbazol-9-yl)benzonitrile (623 mg, 1.8 mmol), and tetrakis(triphenylphosphine)palladium (125 mg, 0.075 mmol) were placed in a 250 mL two-necked round-bottom flask and the nitrogen atmosphere was replaced three times. Then, tetrahydrofuran (50 mL) and 2M potassium carbonate (4.8 mL) were added to the two-necked flask. The temperature was controlled at 80°C. The reaction mixture was refluxed with stirring for 24 hours. After cooling to room temperature, the reaction mixture was extracted three times with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude product was purified by silica gel column chromatography using dichloromethane and ethyl acetate (20 / 1, v / v) as solvent to give a white solid (520 mg, 54%).

[0081] 1 H NMR(500MHz, CDCl3-d)δ8.79(d,J=8.4Hz,1H),8.72(d,J=8.3Hz,1H),8.16(dd,J=12.9,7.9Hz,2H),7.97–7.92(m,2H),7.84–7.63(m, 9H),7.62–7.50(m,7H),7.45(dd,J=3.7,1.4Hz,2H),7.35(ddd,J=7.9,5.1,3.0Hz,1H),7.29(d,J=7.9Hz,2H),7.16(d,J=8.3Hz,1H).

[0082] Example 3

[0083] Near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD

[0084] A near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD 1-phenyl-2-(3-(9-(pyrimidin-2-yl)-9H-carbazol-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole, whose structure is as follows:

[0085]

[0086] The preparation method of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD comprises the following steps:

[0087] Step (1), synthesis of the intermediate 2-(3-(9H-carbazol-2-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole:

[0088]

[0089] 1-Phenyl-2-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole (1488 mg, 3 mmol), 2-bromo-9H-carbazole (734 mg, 3.6 mmol), and tetrakis(triphenylphosphine)palladium (173 mg, 0.15 mmol) were placed in a 250 mL two-necked round-bottom flask and nitrogen was replaced three times. Then, tetrahydrofuran (50 mL) and 2M potassium carbonate (6 mL) were added to the two-necked flask. The temperature was controlled at 85°C. The reaction mixture was refluxed with stirring for 24 hours. After cooling to room temperature, the reaction mixture was extracted three times with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude product was purified by silica gel column chromatography using dichloromethane and ethyl acetate (50 / 1, v / v) as solvent to give a white solid (1100 mg, 42%).

[0090] Step (2), synthesis of the target molecule 1-phenyl-2-(3-(9-(pyrimidin-2-yl)-9H-carbazol-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole:

[0091]

[0092] Under nitrogen, 2-(3-(9H-carbazol-2-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole (680 mg, 1.27 mmol), dibromopyrimidine (947.8 mg, 6.10 mmol), cuprous iodide (77.5 mg, 0.40 mmol), anhydrous potassium carbonate (350 mg, 2.6 mmol), and dioxane (50 mL) were added to a 250 mL two-necked round-bottom flask. The mixture was heated to 110°C in a catalytic system and refluxed for 24 hours. The reaction mixture was extracted three times with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude product was purified by silica gel column chromatography using petroleum ether / dichloromethane (80 / 1, v / v) to obtain a white solid (550 mg, 70%).

[0093] 1H NMR (400MHz, CDCl3-d) δ9.07 (s, 1H), 8.97 (s, 1H), 8.86 (dd, J = 11.5, 6.6Hz, 3H), 8.78 (d ,J=8.4Hz,1H),8.72(d,J=8.3Hz,1H),8.08(dd,J=8.0,3.4Hz,2H),7.98(s,1H),7.74(dd ,J=13.7,7.6Hz,2H),7.61(dp,J=9.9,3.9,3.3Hz,7H),7.51(ddd,J=8.5,5.4,1.8Hz,2H) ,7.43–7.36(m,3H),7.29(d,J=7.9Hz,1H),7.21(d,J=8.2Hz,1H),7.14(t,J=4.7Hz,1H).

[0094] Example 4

[0095] Near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD

[0096] A near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD is prepared from 1-phenyl-2-(3-(9-(pyrimidin-2-yl)-9H-carbazol-3-yl)phenyl)-1H-phenanthro[9,10-d]imidazole, the structure of which is as follows:

[0097]

[0098] The preparation method of the near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD comprises the following steps:

[0099] Step (1), synthesis of the intermediate 2-(3-(9H-carbazol-3-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole:

[0100]

[0101] 1-Phenyl-2-(3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)-1H-phenanthro[9,10-d]imidazole (1488 mg, 3 mmol), 3-bromo-9H-carbazole (734 mg, 3.6 mmol), and tetrakis(triphenylphosphine)palladium (173 mg, 0.15 mmol) were placed in a 250 mL two-necked round-bottom flask and nitrogen was replaced three times. Then, tetrahydrofuran (50 mL) and 2M potassium carbonate (6 mL) were added to the two-necked flask. The temperature was controlled at 85°C. The reaction mixture was refluxed for 24 hours with stirring. After cooling to room temperature, the reaction mixture was extracted three times with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude product was purified by silica gel column chromatography using dichloromethane and ethyl acetate (50 / 1, v / v) as solvent to obtain a white solid (1248 mg, 48%).

[0102] Step (2), synthesis of the target molecule 1-phenyl-2-(3-(9-(pyrimidin-2-yl)-9H-carbazol-3-yl)phenyl)-1H-phenanthro[9,10-d]imidazole:

[0103]

[0104] Under nitrogen, 2-(3-(9H-carbazol-3-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole (728 mg, 1.32 mmol), dibromopyrimidine (628 mg, 4 mmol), cuprous iodide (77.5 mg, 0.40 mmol), anhydrous potassium carbonate (377 mg, 2.72 mmol), and dioxane (50 mL) were added to a 250 mL two-necked round-bottom flask. The mixture was heated to 110°C in a catalytic system and refluxed for 24 hours. The reaction mixture was extracted three times with dichloromethane and water. The organic layer was dried over anhydrous magnesium sulfate, filtered, and evaporated under reduced pressure. The crude product was purified by silica gel column chromatography using petroleum ether / dichloromethane (50 / 1, v / v) to give a white solid (520 mg, 64%).

[0105] 1H NMR (400MHz, CDCl3-d) δ8.88(dd,J=8.2,5.9Hz,4H),8.80(d,J=8.4Hz,1H),8.73(d,J=8.3Hz,1H),8.17–8.08(m,2H),7.93(s,1H),7.74(dt,J=23.5, 8.6Hz,7H),7.65–7.62(m,2H),7.59–7.52(m,3H),7.45(dd,J=13.2,7.3Hz ,2H),7.30(t,J=7.6Hz,2H),7.23(d,J=8.3Hz,1H),7.15(t,J=4.8Hz,1H).

[0106] The structural and spectral tests were performed on 3,9-mPPICZCN, 2,9-mPPICZCN, 2,9-mPPICZmD and 3,9-mPPICZmD of the near-ultraviolet and ultraviolet organic electroluminescent materials of Example 1, Example 2, Example 3 and Example 4, which have a D'-DA structure constructed with carbazole as a donor bridge:

[0107] (1) H NMR spectrum; (2) Mass spectrometry; (3) Thermodynamic properties; (4) Photophysical properties

[0108] from Figures 1-16 As can be seen, the D'-DA-structured near-UV and UV organic electroluminescent materials 3,9-mPPICZCN, 2,9-mPPICZCN, 2,9-mPPICZmD, and 3,9-mPPICZmD, constructed with carbazole as the donor bridge, were successfully synthesized through a simple two-step reaction. Their molecular structures were confirmed by H-NMR spectroscopy and mass spectrometry. Thermogravimetric analysis (TGA) revealed that these materials exhibited excellent stability, with thermal decomposition temperatures (5 wt% weight loss) exceeding 475°C. Furthermore, the materials exhibited efficient UV emission in doped thin films, with fluorescence quantum efficiencies exceeding 70%, and peaks at 390, 373, 390, and 390 nm, respectively.

[0109] Example 5

[0110] Performance of near-ultraviolet and ultraviolet organic electroluminescent materials 3,9-mPPICZCN, 2,9-mPPICZCN, 2,9-mPPICZmD, and 3,9-mPPICZmD doped with carbazole as a donor bridge in OLED devices

[0111] Below, the near-ultraviolet and ultraviolet organic electroluminescent materials 3,9-mPPICZCN, 2,9-mPPICZCN, 2,9-mPPICZmD and 3,9-mPPICZmD with D'-DA structure constructed with carbazole as the donor bridge prepared in Examples 1, 2, 3 and 4 were used as the light-emitting layer materials. The main body used the commercial material CBP, and the doped OLED devices (D1, D2, D3 and D4) were prepared by vacuum evaporation, and their device performance was tested.

[0112] The specific device structures of D1 and D2 are: ITO / HATCN (20nm) / TAPC (45nm) / TCTA (10nm) / CBP: 3,9-mPPICZCN (5wt%, 20nm) and CBP: 2,9-mPPICZCN (5wt%, 20nm) / TPBi (30nm) / LiF (1nm) / Al (100nm); the specific device structures of D3 and D4 are: ITO / HATCN (20nm) / TAPC (45nm) / TCTA (10nm) / CBP: 2,9-mPPICZmD (10wt%, 20nm) and CBP: 3,9-mPPICZmD (10wt%, 20nm) / TPBi (30nm) / LiF (1nm) / Al (100nm).

[0113] The specific molecular structures of the materials in each functional layer are as follows:

[0114]

[0115] Figure 17 The external quantum efficiency-luminance characteristic curves of the near-ultraviolet and ultraviolet organic electroluminescent materials 3,9-mPPICZCN, 2,9-mPPICZCN, 2,9-mPPICZmD, and 3,9-mPPICZmD doped with D'-DA structures constructed with carbazole as the donor bridge in Examples 1, 2, 3, and 4 are shown. As can be seen from the figure and Table 1, their turn-on voltages are as low as 3.2V. The maximum external quantum efficiencies are 9.67%, 8.76%, 10.65%, and 8.83%, respectively. At 1000 cd m -2 Under different brightness levels, the external quantum efficiencies are 9.25%, 7.05%, 10.39% and 8.25% respectively, with very small efficiency roll-off.

[0116] Figure 18The electroluminescence spectra of the near-ultraviolet and ultraviolet organic electroluminescent materials 3,9-mPPICZCN, 2,9-mPPICZCN, 2,9-mPPICZmD, and 3,9-mPPICZmD-doped devices constructed with carbazole as the donor bridge, shown in Examples 1, 2, 3, and 4, are shown. As shown in the figure and Table 1, their emission peaks are located in the ultraviolet region, at 390, 391, 377, and 392 nm, respectively. They also exhibit excellent color purity, with half-value widths of 40, 40, 37, and 40 nm, respectively. The corresponding color coordinates are (0.166, 0.026), (0.167, 0.030), (0.166, 0.024), and (0.166, 0.023).

[0117] Table 1. Specific doped device performance test data. (D1, D2, D3, and D4 represent doped devices with 3,9-mPPICZCN, 2,9-mPPICZCN, 2,9-mPPICZmD, and 3,9-mPPICZmD as the light-emitting layer.)

[0118]

[0119] Example 6

[0120] Performance of non-doped OLED devices based on the D'-DA structure of near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD constructed with carbazole as donor bridge

[0121] Next, the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD with D'-DA structure constructed with carbazole as donor bridge prepared in Example 3 was used as the light-emitting layer material to prepare a non-doped OLED device (D5) by vacuum evaporation method, and its device performance was tested.

[0122] The specific device structure of D5 is: ITO / HATCN (20nm) / TAPC (45nm) / TCTA (10nm) / 2,9-mPPICZmD (20nm) / TPBi (30nm) / LiF (1nm) / Al (100nm).

[0123] Figure 19 The external quantum efficiency-brightness characteristic curve and electroluminescence spectrum of the non-doped device of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD constructed with carbazole as the donor bridge in Example 3 are shown. The figure shows that its external quantum efficiency is 6.70%. At 1000 cd m -2 At full brightness, the external quantum efficiency is 5.96%, with minimal efficiency roll-off. The emission peak is located in the ultraviolet region, at 394nm and with a half-width of 47nm. The corresponding color coordinates are (0.162, 0.035).

[0124] Example 7

[0125] Performance of non-doped OLED devices based on the D'-DA structure of near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD constructed with carbazole as donor bridge

[0126] Next, the near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD with D'-DA structure constructed with carbazole as donor bridge prepared in Example 4 was used as the light-emitting layer material, and a non-doped OLED device (D6) was prepared by vacuum evaporation method, and its device performance was tested.

[0127] The specific device structure of D6 is: ITO / HATCN (20nm) / TAPC (45nm) / TCTA (10nm) / 3,9-mPPICZmD (20nm) / TPBi (30nm) / LiF (1nm) / Al (100nm).

[0128] Figure 20 The external quantum efficiency-brightness characteristic curve and electroluminescence spectrum of the non-doped device of the near-ultraviolet and ultraviolet organic electroluminescent material 3,9-mPPICZmD constructed with D'-DA structure using carbazole as the donor bridge in Example 4 are shown in the figure. The external quantum efficiency is 5.54%. At 1000 cd m -2 At full brightness, the external quantum efficiency is 4.74%. The emission peak is located in the ultraviolet region, at 395nm and with a half-width of 46nm. The corresponding color coordinates are (0.161, 0.034).

[0129] Example 8

[0130] Single-carrier device performance of near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD constructed with carbazole as donor bridge

[0131] Next, the D'-DA structured near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD prepared in Example 3 with carbazole as the donor bridge was used as the active layer material. Single-electron and single-hole devices were prepared by vacuum evaporation, and their current density-voltage curves were tested.

[0132] The single-hole device structure is: ITO / HATCN (10nm) / 2,9-mPPICZmD (80nm) / HATCN (10nm) / Al (100nm). The single-electron structure is: ITO / TPBi (10nm) / 2,9-mPPICZmD (80nm) / TPBi (10nm) / LiF (1nm) / Al (100nm).

[0133] Figure 21 The current density-voltage curves for the single-carrier device of the near-ultraviolet and ultraviolet organic electroluminescent material 2,9-mPPICZmD, constructed with a D'-DA structure and carbazole as a donor bridge, as shown in Example 3. The figure shows that the current density of both the single-electron and single-hole devices increases significantly with increasing voltage, demonstrating excellent bipolar transport properties.

[0134] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A class of highly efficient and stable near-ultraviolet and ultraviolet organic electroluminescent materials with a D'-DA structure constructed with carbazole as a donor bridge, characterized in that: Its structural formula is: The specific structural formula selected is: and .

2. A method for preparing a highly efficient and stable near-ultraviolet and ultraviolet organic electroluminescent material having a D'-DA structure constructed with carbazole as a donor bridge as claimed in claim 1, characterized in that , the preparation method includes method one or method two: The method 1 comprises the following steps: Under nitrogen protection, A1 uses 2-bromocarbazole and a fluorinated or iodinated compound substituted with R2 as raw materials, undergoes a nucleophilic substitution reaction or a carbon-nitrogen coupling reaction in a catalytic system, and then performs extraction and column chromatography purification to obtain an intermediate; A2, under nitrogen protection, uses the intermediate obtained in step A1 and boronic acid, boron ester or NH aromatic heterocycle substituted by R1 as raw materials, undergoes Suzuki coupling reaction or carbon-nitrogen coupling reaction under a catalytic system, and then performs extraction, column chromatography purification and sublimation treatment to obtain a luminescent material. The second method comprises the following steps: B1, under nitrogen protection, uses 2-bromocarbazole and R1-substituted boronic acid or boronic ester as raw materials, and performs Suzuki coupling reaction or carbon-nitrogen coupling reaction in a catalytic system; extracts and column chromatography purification are performed to obtain an intermediate product; B2: Under nitrogen protection, the intermediate obtained in step B1 and the fluorine, bromine or iodine substituted by R2 are used as raw materials, and after undergoing a nucleophilic substitution reaction or a carbon-nitrogen coupling reaction under a catalytic system, extraction, column chromatography purification and sublimation treatment are performed to obtain a luminescent material.

3. The preparation method according to claim 2, wherein: In step A1, the molar ratio of the reactants 2-bromocarbazole and the fluorinated or iodinated compound substituted by R2 is 1:1.05-1:1.5, and the catalyst system is potassium carbonate; In step A2, the molar ratio of the boronic acid, boron ester or NH aromatic heterocycle substituted by the reactant R1 to the intermediate obtained in step A1 is 1:1-1:1.5, and the catalyst system is tetrakis(triphenylphosphine)palladium; In step B1, the molar ratio of the boronic acid or boronic ester substituted by reactant R1 to 2-bromocarbazole is 1:1-1:2, and the catalyst system is tetrakis(triphenylphosphine)palladium; In step B2, the molar ratio of the intermediate obtained in step B1 to the fluorine, bromine or iodide substituted by R2 is 1:1.1-1:5, and the catalyst system is potassium carbonate and cuprous iodide.

4. Use of the highly efficient and stable near-ultraviolet and ultraviolet organic electroluminescent material of D'-DA structure constructed with carbazole as a donor bridge as claimed in claim 1 as a light-emitting layer in the preparation of doped and non-doped layer OLEDs devices.

5. The use according to claim 4, characterized in that The light-emitting layer material is a doped film containing the near-ultraviolet and ultraviolet organic electroluminescent molecules and a host material, and the mass ratio of the light-emitting molecules to the host material is 1:99-99:

1.

6. The use according to claim 5, characterized in that The main material used for the doping film is: N,N'-dicarbazolyl-4,4'-biphenyl.

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