Imidazolyl dibenzo [a, h] anthracene organic fluorescent small molecular material as well as preparation method and application thereof

Abstract

The invention provides an imidazolyl dibenzo [a, h] anthracene organic fluorescent small molecular material as well as a preparation method and application thereof. A molecular skeleton of the compound is composed of central imidazolyl 3, 10-di-tert-butyl dibenzo [a, h] anthracene (DBA) and imidazole ring C2 substitution units A and N1 substitution units B on the two sides, all of which are of symmetrical X-shaped line-plane conjugated structures, emit blue light or dark blue light in solution and film states, and have good solubility, luminous efficiency, thermal stability and carrier transport capacity. With TCTA as a host material and six materials as object dopants, preparing a blue light or dark blue light OLED device by adopting a solution spin-coating method; under the condition that a hole transport layer is not added, the six devices are pure in light color, high in external quantum efficiency (EQE), slow in efficiency roll-off and good in efficiency stability and have practical application value in the field of dark blue light OLEDs, and the two new materials subjected to position isomerization can provide a new direction for development of the dark blue light OLED devices based on N1 substituted imidazole derivatives.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic materials, and particularly relates to an imidazole-based dibenzo[a,h]anthracene organic fluorescent small molecule material, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, the development of the information technology industry has promoted the rapid progress of human social civilization. As a high-tech technology integrating electronics, information, materials, energy conservation and other fields, display technology has innovative, high added value, wide market application value and strong industrial driving effects, and is one of the cornerstones of China's information electronics industry. As a new generation of display and lighting technology, organic electroluminescence (OLED) has novel characteristics such as being thin, flexible, and having high contrast. The commercialization process of related products has developed rapidly and is closely related to human life. Although OLED products have been applied in the market, there are still many problems to be solved, such as how to improve the device lifetime, how to increase the light color purity, how to reduce the manufacturing cost, and how to balance high efficiency and low efficiency roll-off. These problems seriously restrict the further development of OLED technology. Among them, organic blue light materials, as the core components of full-color display and white light lighting devices, still have problems such as few types, fast efficiency roll-off, unbalanced carrier transport, and high device manufacturing costs. Solving these problems based on new material design strategies is the key to realizing high-performance blue OLED devices.

[0003] High-performance deep blue light materials can be used as energy transfer donors for white light devices, which can effectively reduce power consumption and increase the color gamut of full-color displays. Compared with red and green light devices, since saturated blue light emission requires emitters with a wide bandgap, that is, low carrier mobility and high carrier injection barriers, but this will lead to poor electrical performance. This opposite requirement of optical and electrical properties makes it difficult to develop organic deep blue light materials with well-matched device performance. In the molecular design of organic blue light materials, in order to maintain the light color purity, planar or linear molecular structures should be avoided as much as possible to eliminate the ACQ phenomenon caused by the close packing of molecules. However, planar linear molecules have a large conjugation effect, and the π-π stacking interaction between molecules can provide a charge transfer channel, improve the carrier transport ability, and is conducive to obtaining good luminous efficiency. How to balance the contradiction of this molecular design strategy is the key to realizing high-performance deep blue light materials.

[0004] As a coplanar polycyclic aromatic hydrocarbon composed of three parallel benzene rings, anthracene molecule has a large bandgap (3.9 eV), excellent stability, strong blue light emission and high fluorescence quantum yield (Ф f= 64%), relatively few active sites and good solubility, which are more easily subjected to functional modification and have great advantages in the directional synthesis of target molecules. However, due to the relatively small conjugated system, the molecular structure rigidity and carrier mobility are very low. In the pentacene ring molecule, the electrons are delocalized within the molecule, and the electron cloud density at the C6 and C13 positions is relatively large, having a high carrier mobility (40 cm 2 / V·s), being photosensitive, easily oxidized, having high reaction activity and many active sites, etc., making it difficult to achieve precise synthesis. They have a planar conjugation effect and strong intermolecular coupling effect, and the fluorescence quenching phenomenon is serious. It is a long and arduous task to solve these problems. The extension of the benzene ring conjugated system is beneficial to obtaining luminescent materials with high mobility. Introducing substituents that increase the steric hindrance of the molecule can also inhibit the ACQ effect and more easily achieve strong solid-state luminescence characteristics. In addition, the introduction of terminal alkyl chains can significantly improve the solubility of the material, enhance or weaken the intermolecular interaction force, and ultimately improve the optoelectronic properties. Taking the pentacene ring as the basic unit, simultaneously realizing strong luminescence and high carrier transport characteristics by connecting azafused polycyclic aromatic hydrocarbon molecules is of great significance for the development and application of high-efficiency OLED materials.

[0005] Dibenzo[a,h]anthracene (DBA), as an isomeric molecule of linear pentacene, has five benzene rings fused in an N-shaped bend and at a certain angle. This planar π-conjugated structure presents large rotation and translation radii, which can effectively limit the unfavorable molecular vibrations in the solid state and improve the carrier mobility and thermal stability of the material.

[0006] Imidazole, as a typical azafused polycyclic aromatic hydrocarbon molecule with a rigid structure, is simple to synthesize, easy to modify, stable and reliable, and emits deep blue light. It has a relatively high triplet energy, can reduce the recombination energy during the charge transfer process, and effectively inhibit solid-state stacking and molecular aggregation. In addition, due to the different connection modes between the C2 positions of the imidazole ring, imidazole derivatives have unique bipolar characteristics. When an electron-withdrawing group or a neutral group is connected to the C2 position of the imidazole ring, the imidazole heterocycle exhibits electron-donating characteristics; when an electron-donating unit is connected to the C2 position, the imidazole heterocycle exhibits electron-accepting characteristics. At the same time, the active imidazole derivatives containing substituents can achieve strong fluorescence, high PLQY and mechanochromism, have balanced carrier transport performance, a rigid structure and π-electron delocalization that are easy to modify, good thermal stability, hole mobility, electron-donating ability and hydrogen-bonding formation ability, and are suitable for constructing blue OLEDs with mild ICT, fluorescence, phosphorescence, nonlinear optical and mechanochromic characteristics, and have broad application prospects in the field of optoelectronic materials.

[0007] In view of this, the present invention is specifically proposed. Summary of the Invention

[0008] The object of the present invention is to provide an imidazole-based dibenzo[a,h]anthracene organic fluorescent small molecule material, its preparation method and application.

[0009] As a typical representative of polycyclic aromatic hydrocarbon molecules, dibenzo[a,h]anthracene (DBA) has the advantages of easy modification, high efficiency, blue light emission, and photothermal stability. At the same time, as an isomeric molecule of linearly parallel pentacene rings, DBA has five benzene rings connected by small angles in an N-shaped bending manner, with a large rotational and translational radius in its structure, which can effectively limit the unfavorable molecular vibrations in the solid state, has stronger rigidity and a larger π-conjugated plane, and helps to endow the material with strong deep blue light emission, good thermal stability, and higher carrier mobility.

[0010] Imidazole derivatives with bipolar characteristics have the advantages of simple synthesis, easy modification, adjustable photochromism, high triplet energy levels, aggregation-induced emission, and mechanochromic fluorescence, etc. They have good hole mobility, electron-donating ability, and the ability to form hydrogen bonds, and have the potential to construct deep blue light-emitting OLED materials.

[0011] Therefore, in the present invention, DBA is selected as the main core, combined with the excellent optoelectronic properties of imidazole derivatives substituted with functional groups, to design and synthesize six novel symmetrically structured nitrogen-containing polycyclic aromatic hydrocarbon blue light small molecule materials, and use the solution spin-coating process to prepare OLED devices. The overall design scheme is reasonable, feasible, and novel, providing a theoretical reference for the design and synthesis of arylimidazole-functionalized (nitrogen-containing) polycyclic aromatic hydrocarbon materials, and also bringing new opportunities and challenges to the development and application of novel deep blue light-emitting OLEDs.

[0012] To achieve the above object, the present invention provides an imidazole-based dibenzo[a,h]anthracene organic fluorescent small molecule material, having a structural general formula as shown in formula (1):

[0013]

[0014] Among them, A or B in the formula (1) includes any one of the following structures of formula (1)-1 to formula (1)-4:

[0015]

[0016] Preferably, A includes at least one of p-tert-butylphenyl, tetraphenylethylenyl, triphenylamine, 3,6-di-tert-butyl-9-phenyl-9H-carbazolyl; B includes at least one of p-tert-butylphenyl, triphenylamine, 3,6-di-tert-butyl-9-phenyl-9H-carbazolyl; more preferably, the structural formulas of A and B are different.

[0017] In a preferred embodiment, the organic fluorescent small molecule material includes any one of the following structures:

[0018]

[0019] The present invention provides a preparation method for any of the above-mentioned imidazolyl dibenzo[a,h]anthracene-based organic fluorescent small molecule materials, comprising the following steps: performing a Debus-Radziszewski one-pot reaction on a diketone compound having the general structural formula shown in formula (2), an aromatic aldehyde compound C, an aromatic amine compound D, and ammonium acetate to obtain the imidazolyl dibenzo[a,h]anthracene-based organic fluorescent small molecule material; wherein,

[0020] The aromatic aldehyde compound C and / or the aromatic amine compound D each include at least one of derivatives of p-tert-butylbenzene, tetraphenylethylene, triphenylamine, and tert-butylcarbazole.

[0021] In a preferred embodiment, the aromatic aldehyde compound C includes any one of the following structures of formula (3)-1 to (3)-4:

[0022]

[0023] The aromatic amine compound D includes any one of the following structures of formula (4)-1 to (4)-3:

[0024]

[0025] In a preferred embodiment, the molar mass ratio of the diketone compound, the aromatic aldehyde compound C, the aromatic amine compound D, and ammonium acetate is 1.0:(1.8 - 2.6):(2.8 - 3.6):(25 - 35); preferably, the molar mass ratio of the diketone compound, the aromatic aldehyde compound C, the aromatic amine compound D, and ammonium acetate is 1.0:2.2:3.2:30.0.

[0026] In a preferred embodiment, the conditions for the Debus-Radziszewski one-pot reaction include: fully dissolving the diketone compound, the aromatic aldehyde compound C, the aromatic amine compound D, and ammonium acetate in glacial acetic acid, and refluxing the reaction mixture at 100 - 140 °C for 18 - 30 h; preferably, the mixture is refluxed at 120 °C for 24 h.

[0027] In a preferred embodiment, the molar volume ratio of the diketone compound to glacial acetic acid is 1.0 mol:(20 - 40) ml; preferably, the molar volume ratio of the diketone compound to glacial acetic acid is 1.0 mol:30 ml.

[0028] The present invention provides the application of any of the above-mentioned imidazolyl dibenzo[a,h]anthracene-based organic fluorescent small molecule materials in the preparation of organic electroluminescent devices.

[0029] In a preferred embodiment, the organic electroluminescent device is successively composed of a glass substrate, an ITO anode, a light-emitting layer, an electron transport layer, and a cathode;

[0030] Wherein, the light-emitting layer is composed of a host material 4,4′,4″-tris(N-carbazolyl)triphenylamine and a guest dopant; the guest dopant contains at least one organic fluorescent small molecule material based on imidazolyl dibenzo[a,h]anthracene as described in any one of claims 1-3.

[0031] In a preferred embodiment, when the guest dopant is 2tBuPCz-DBAI, the emission peak of the prepared organic electroluminescent device is 428 nm, the CIE color coordinates are located at (0.16, 0.11), showing deep blue light, L max is 1601 cd / m 2 , CE max is 8.98 cd / A, PE max is 7.84 lm / W, EQE max reaches 3.19%.

[0032] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0033] The molecular design strategy of the present invention includes: (1) introducing different functional units on the middle DBA to regulate the molecular conjugation degree, adjusting the spectral red shift through the band gap change to further regulate the light color, and obtaining pure blue light or deep blue light materials; (2) symmetrically introducing AIE characteristic groups on both sides to effectively reduce the ACQ effect of the molecule; (3) increasing the overall rigidity of the molecule by fine structural adjustment of the functional unit, thereby reducing the FWHM to make the light color purity higher and improving the light color purity; (4) selecting a suitable host material, preparing a doped OLED by solution spin coating method, and optimizing the device performance; (5) introducing a strong electron-donating unit at the C2 position of the imidazole ring to synthesize an X-shaped D-A-D structure organic blue light material, and improving the optoelectronic performance by regulating the conjugation degree; (6) introducing two strong electron-donating units at the N1 position of the imidazole ring to synthesize a D-A-D type blue light isomer, and regulating the molecular conjugation degree to improve the optoelectronic performance.

[0034] According to the above molecular design strategy, the present invention uses DBA as the main core, and synthesizes six novel aryl-functionalized and position-isomeric organic deep blue light materials through the Debus-Radziszewski one-pot reaction. And TCTA is selected as the host material, and the synthesized new material is used as the guest dopant, and a deep blue light or blue light multi-layer doped OLED device is successfully prepared by solution spin coating process. Under the condition of not adding a hole transport layer, the emission peak of the doped device based on 2tBuPCz-DBAI is 428 nm, the CIE color coordinates are located at (0.16, 0.11), showing deep blue light, L max is 1601 cd / m2 , CE max is 8.98 cd / A, and PE max is 7.84 lm / W, and EQE max reaches 3.19%, showing good electroluminescence performance, and can provide theoretical guidance for the development and application of high-efficiency deep blue OLEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] From the following detailed description of the embodiments of the present invention in conjunction with the drawings, these and / or other aspects and advantages of the present invention will become clearer and easier to understand, where:

[0036] Figure 1 is the synthesis route for preparing DBAT in Embodiment 1 of the present invention;

[0037] Figure 2 is the synthesis route for preparing six new materials in Embodiment 2 of the present invention;

[0038] Figure 3 is the UV-vis spectrum and PL spectrum of DBA and six new materials in DCM solution or film in Embodiment 3 of the present invention;

[0039] Figure 4 is the cyclic voltammogram of DBA, six new materials and ferrocene in Embodiment 3 of the present invention;

[0040] Figure 5 is the TGA and DTA curves of DBA and six new materials under nitrogen in Embodiment 3 of the present invention;

[0041] Figure 6 is the calculation of the molecular conformation, HOMO / LUMO energy levels and electron spatial distribution of DBA and six new materials in Embodiment 3 of the present invention; where, from left to right in the middle of Figure (A) are DBA, 2TBB-DBAI and 2TPE-DBAI, and from left to right in Figure (B) are 2TPA-DBAI and 2tBuPCz-DBAI, and from left to right in Figure (C) are N-2TPA-DBAI and N-2tBuPCz-DBAI;

[0042] Figure 7 is the schematic diagram of the device structure in Embodiment 4 of the present invention (upper Figure A), and the HOMO / LUMO energy levels of each layer of materials (upper Figure B); the molecular structures of PEDOT:PSS, TCTA and TPBi (lower figure);

[0043] Figure 8 is the I-V-L curve (A), CE / PE-L curve (B), EQE-L curve (C) and EL spectrum (D) of the device prepared based on 2TBB-DBAI at different doping concentrations in Embodiment 4 of the present invention;

[0044] Figure 9 These are the I-V-L curves (A), CE / PE-L curves (B), EQE-L curves (C), and EL spectra (D) of the devices prepared based on 2TPE-DBAI at different doping concentrations in Example 4 of the present invention;

[0045] Figure 10 These are the I-V-L curves (A), CE / PE-L curves (B), EQE-L curves (C), and EL spectra (D) of the devices prepared based on 2TPA-DBAI at different doping concentrations in Example 4 of the present invention;

[0046] Figure 11 These are the I-V-L curves (A), CE / PE-L curves (B), EQE-L curves (C), and EL spectra (D) of the devices prepared based on 2tBuPCz-DBAI at different doping concentrations in Example 4 of the present invention;

[0047] Figure 12 These are the I-V-L curves (A), CE / PE-L curves (B), EQE-L curves (C), and EL spectra (D) of the devices prepared based on N-2TPA-DBAI at different doping concentrations in Example 4 of the present invention;

[0048] Figure 13 These are the I-V-L curves (A), CE / PE-L curves (B), EQE-L curves (C), and EL spectra (D) of the devices prepared based on N-2tBuPCz-DBAI at different doping concentrations in Example 4 of the present invention. Detailed implementation manners

[0049] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific implementation manners. However, it should be understood that the protection scope of the present invention is not limited by the specific implementation manners.

[0050] In the embodiments of the present invention, by providing an imidazole-based dibenzo[a,h]anthracene organic fluorescent small molecule material, its preparation method and application, the general idea is as follows:

[0051] Imidazole derivatives have an imidazole ring with N1 and C2 positions that are very easy to modify. The imidazole ring is a five-membered heteroaromatic ring containing electron-deficient atoms and has good Ф PLAnd the charge transport performance can change the rigidity and π - electron delocalization through different substituents at the C2 and N1 positions, achieving better thermal stability and luminescence efficiency and balancing the carrier transport performance. When modifying the C2 position of the imidazole ring, the torsion angle between the C2 - substituted benzene ring and the imidazole ring is small, resulting in a smaller steric hindrance, which is beneficial for obtaining an organic fluorescent molecule with a large π - conjugate plane and high luminescence efficiency. When modifying the N1 position of the imidazole ring, due to the increased steric hindrance of the surrounding hydrogen atoms, the torsion angle between the N1 - substituted benzene ring and the imidazole ring is large, sometimes close to perpendicular, which is not conducive to achieving high fluorescence efficiency, but a compound with a highly twisted structure can be obtained, reducing the solid - state π - π close packing of the material and increasing solubility, thus making the excited - state properties of the material more abundant.

[0052] In terms of the molecular design strategy, 4 - tert - butylbenzene (TBB) is a functional group with a single - benzene - ring structure and good solubility. Tetraphenylethylene (TPE) is generally composed of four benzene rings connected by ethylene bonds, presenting a twisted "propeller" structure with a large steric hindrance. In the solid - aggregation state, it can effectively prevent non - radiative transition processes such as the rotation or vibration of benzene rings. In this invention, the functional groups TBB or TPE are respectively connected to the large - π - conjugate DBA derivative, combining the excimer emission of DBA, the monomer emission of TBB, and the AIE characteristics of TPE to construct a highly efficient organic blue - light small - molecule material.

[0053] Triphenylamine (TPA) is a strong electron - donating group with a propeller structure. Due to the large steric hindrance of the benzene rings connected to the central N atom, it is not conducive to the occurrence of free - radical reactions. And the increase in the hyperconjugation electron effect helps to eliminate the tension of the free - radical center, improve the structural stability, and reduce concentration quenching.

[0054] Carbazole (Cz) is a typical rigid - planar biphenyl azo - fused - ring aromatic hydrocarbon compound with good planar conjugation, strong modifiability, high hole - mobility, and high luminescence efficiency. In this invention, N - phenylcarbazole (PCz) is substituted by tert - butyl (tBu) to obtain 3,6 - di - tert - butyl - 9 - phenyl - 9H - carbazole (tBuPCz), which can not only significantly improve the solubility and three - dimensional geometric structure of the molecule but also reduce the aggregation - caused fluorescence quenching (ACQ) phenomenon. Therefore, through the above - mentioned molecular design engineering, using the imidazole ring as the electron - acceptor unit helps to design D - A - D - structure molecules to control the excited state and improve η PL and η s and design and synthesize higher - efficiency blue - light or deep - blue - light materials.

[0055] Based on the above concept, the present invention uses DBA as the main core, combines the excellent optoelectronic properties of imidazole derivatives substituted with functional groups, designs and synthesizes six novel symmetrically structured nitrogen-containing polycyclic aromatic hydrocarbon blue-light small molecule materials, and applies them in the field of preparing organic electroluminescent devices, providing theoretical guidance for the development and application of highly efficient deep blue OLEDs.

[0056] The technical solutions of the present application are described in detail below through specific examples:

[0057] Unless otherwise specified, the technical means used in the present invention are conventional means well-known to those skilled in the art. All kinds of raw materials, reagents, instruments, and equipment used in the present invention can be obtained through market purchase or can be prepared by existing methods. The reagents used in the present invention are all of analytical grade unless otherwise specified.

[0058] Example 1

[0059] According to Figure 1 the synthesis route shown, DBAT was prepared, including the following steps:

[0060] The preparation method of ((2,5-dibromo-1,4-phenylene)bis(ethyne-2,1-diyl))bis(trimethylsilane) (Intermediate I) specifically includes:

[0061] Under nitrogen protection and in an ice-water bath at 0 °C, to a solid mixture of 1,4-dibromo-2,5-diiodobenzene (1.0 eq), CuI (0.1 eq), and PdCl2(PPh3)2 (0.1 eq), anhydrous THF (120 mL) and diisopropylamine ( i Pr2NH, 14.0 eq) were successively added. After stirring and reacting for 15 min, trimethylsilylacetylene (2.2 eq) was slowly added dropwise, and the reaction continued at room temperature for 20 h. After the reaction was completed, the mixed reactants were poured into ice-water-hydrochloric acid (V ice :V HCl = 5:1, 480 mL), and then extracted with ethyl acetate (3 × 120 mL). The combined organic phases were dried over anhydrous Na2SO4 and filtered, and purified by chromatography using pure petroleum ether as the eluent to obtain a white solid (2.11 g, 80%). m.p.: 185 - 186 °C. 1 1H NMR (500 MHz, CDCl3, δ, ppm): 7.66 (s, 2H), 0.27 (s, 18H). 13 13C NMR (125 MHz, CDCl3, δ, ppm): 136.5, 126.5, 123.8, 103.2, 101.4, -0.15.

[0062] Preparation method of ((4,4″-di-tert-butyl-[1,1:4′,1″-terphenyl]-2′,5′-diyl)bis(ethyne-2,1-diyl))bis(trimethylsilane) (Intermediate II), specifically including:

[0063] Under nitrogen protection, anhydrous toluene (120 mL) and aqueous Na2CO3 solution (10.0 eq) were added to a solid mixture of Intermediate I (1.0 eq), 4-tert-butylphenylboronic acid (3.0 eq), Pd(PPh3)4 (0.1 eq) and TBAB (0.1 eq). The mixture was heated to 110 °C and refluxed for 14 h. After the reaction was completed, toluene was removed by evaporation, and the mixture was extracted with dichloromethane (3 × 150 mL). The organic phase was dried over anhydrous Na2SO4 and the solvent was removed. The white solid (1.6 g, 63%) was purified by chromatography using pure petroleum ether as the eluent. m.p.: 212 - 214 °C. 1 H NMR (500 MHz, CDCl3, δ, ppm): 7.59 (s, 2H), 7.58 (d, J = 8.5 Hz, 4H), 7.42 (d, J = 8.5 Hz, 4H), 1.36 (s, 18H), 0.13 (s, 18H). 13 C NMR (125 MHz, CDCl3, δ, ppm): 151.0, 143.0, 136.8, 134.3, 129.4, 125.2, 122.2, 105.8, 99.6, 35.1, 31.7, -0.11. HRMS: Calcd. for C 36 H 46 Si2,535.3210 [M + H] + ; Found: 535.3211. Error = 0.19 ppm.

[0064] Preparation method of 4,4”-di-tert-butyl-2',5'-diethynyl-1,1':4',1”-terphenyl (Intermediate IV), specifically including:

[0065] Intermediate II (5.00 g, 9.35 mmol) was completely dissolved in THF (50 mL), then n-hexane (100 mL), anhydrous methanol (MeOH, 200 mL) and saturated aqueous K2CO3 solution (20 mL) were added. The mixed reaction solution was stirred at room temperature for 6 h. After the reaction was completed, the solvent was removed under vacuum, and the organic phase was separated by extraction with water and DCM (3 × 150 mL) and dried over anhydrous Na2SO4. After evaporation of the solvent, the white solid (3.2 g, 88%) was purified by chromatography using pure petroleum ether as the eluent. m.p.: 252 - 254 °C. 11H NMR (500 MHz, CDCl3, δ, ppm): 7.64 (s, 2H), 7.59 (d, J = 8.4 Hz, 4H), 7.46 (d, J = 8.4 Hz, 4H), 3.15 (s, 2H), 1.38 (s, 18H). 13 13C NMR (125 MHz, CDCl3, δ, ppm): 151.0, 142.5, 146.1, 135.2, 128.9, 125.2, 125.1, 83.0, 81.8, 34.8, 31.5.

[0066] Preparation method of 3,10 - di - tert - butyldibenzo[a,h]anthracene (DBA), specifically including:

[0067] After drying PtCl2 (0.25 eq) under vacuum for 2 h, intermediate III (1.0 eq) and a solution of ultradry toluene (100 mL) were added under nitrogen protection and at room temperature. The mixture was stirred and reacted at 110 °C for 8 h. After the reaction was completed, the mixed product was filtered through a diatomaceous earth pad using DCM as the eluent. The solvent was removed, and the brown solid was washed with petroleum ether until no color was observed in the washing liquid. Then, a light brown solid was separated and recrystallized from DCM to obtain a white solid (1.95 g, 65%). m.p.: >280 °C. 1 1H NMR (500 MHz, CDCl3, δ, ppm): 9.10 (s, 2H), 8.79 (d, J = 8.6 Hz, 2H), 7.95 (d, J = 8.9 Hz, 2H), 7.87 (d, J = 2.1 Hz, 2H), 7.78 (dd, J = 8.6, 2.1 Hz, 2H), 7.74 (d, J = 8.9 Hz, 2H), 1.49 (s, 18H). 13 13C NMR (125 MHz, CDCl3, δ, ppm): 150.0, 131.9, 130.8, 129.0, 128.2, 127.6, 127.5, 125.1, 124.7, 122.8, 122.0, 35.0, 31.6. HRMS: Calcd for C 30 H 30 , 390.2342 [M + H] + ; Found: 390.2341. Error = 0.15 ppm.

[0068] Preparation method of 3,10 - di - tert - butyldibenzo[a,h]anthracene - 5,6,12,13 - tetrone (DBAT), specifically including:

[0069] Dissolve DBA (1.0 eq) and RuCl3·H2O (0.25 eq) thoroughly in a mixed solution of CHCl3:CH3CN:H2O (1:1:1.2, 64 mL), and add NaIO4 (8.8 eq) in batches. React the mixture at 60 °C for 24 h and filter by suction. Suspend the slightly red solid cake in AcOH (15 mL), add K2Cr2O7 (0.22 eq) and react at 120 °C for 1 h. After the reaction is completed, extract with water and DCM (3 × 150 mL) to obtain the organic phase, and dry it over anhydrous Na2SO4. After removing the solvent, purify by column chromatography using DCM and petroleum ether (V DCM :V PE = 3:1) as the eluent to obtain the target product as a white solid (1.20 g, 58%). m.p.: >280 °C. 1 1H NMR (500 MHz, CDCl3, δ, ppm): 8.76 (s, 2H), 8.25 (d, J = 2.2 Hz, 2H), 8.11 (d, J = 8.4 Hz, 2H), 7.84 (dd, J = 8.4, 2.2 Hz, 2H), 1.40 (s, 18H). 13 13C NMR (125 MHz, CDCl3, δ, ppm): 180.4, 179.5, 154.6, 136.1, 134.8, 134.1, 131.9, 131.0, 127.8, 126.1, 124.9, 35.3, 31.1. HRMS: Calcd for C 30 H 26 O4, 450.1904 [M+H] + ; Found: 450.1903. Error = 0.22 ppm.

[0070] Example 2

[0071] According to Figure 2 the synthetic route shown, symmetrically connect functional groups TBB, TPE, TPA, and tBuPCz at the C2 position or N1 of the imidazole ring of DBAT to synthesize six novel imidazole-functionalized dibenzo[a,h]anthracene materials, including the following steps:

[0072] Preparation method of 5,13-di-tert-butyl-1,2,9,10-tetrakis(4-(tert-butyl)phenyl)-1,9-dihydrobenzo[8,9]tetrabenzo[5,6-d:10,11-d']diimidazole (2TBB-DBAI), specifically including:

[0073] Under nitrogen protection, DBAT (1.0 eq), ammonium acetate (30.0 eq), p-tert-butylbenzaldehyde (2.2 eq) and p-tert-butylaniline (3.2 eq) were fully dissolved in glacial acetic acid (AcOH, 150 mL). The mixture was refluxed at 120 °C for 24 h. After the reaction was completed, the mixed reaction solution was cooled to room temperature and poured into ice water to precipitate the solid crude product. The green solid was collected by vacuum filtration and purified by column chromatography using DCM and petroleum ether (V DCM :V PE = 1:2) as the eluent to obtain the target product as a white solid (1.24 g, 55%). m.p.: >280 °C. 1 1H NMR (500 MHz, CDCl3, δ, ppm): 10.12 (s, 1H), 9.14 - 9.07 (dd, J = 10.0 Hz, 2H), 8.87 (s, 1H), 8.57 (s, 1H), 7.77 - 7.76 (d, J = 5.0 Hz, 3H), 7.64 - 7.63 (d, J = 5.0 Hz, 11H), 7.55 - 7.47 (dd, J = 10.0 Hz, 4H), 7.18 (s, 1H), 1.46 - 1.44 (d, J = 10.0 Hz, 15H), 1.32 (s, 21H), 1.26 (s, 3H), 1.14 (s, 7H), 1.06 (s, 8H). 13 13C NMR (125 MHz, CDCl3, δ, ppm): 151.6, 150.8, 149.9, 147.9, 146.0, 145.9, 142.1, 141.7, 136.4, 129.0, 128.9, 128.9, 128.7, 127.3, 127.1, 126.3, 125.3, 125.2, 117.6, 115.2, 35.2, 34.7, 34.5, 31.2. HRMS: Calcd for C 72 H 78 N4, 999.6299 [M + H] + ; Found: 999.6299. Error = 0.01 ppm.

[0074] A preparation method of 5,13 - di - tert - butyl - 1,9 - bis(4 - (tert - butyl)phenyl) - 2,10 - bis(4 - (1,2,2 - triphenylethynyl)phenyl) - 1,9 - dihydrobenzo[8,9]tetrabenzo[5,6 - d:10,11 - d']diimidazole (2TPE - DBAI) specifically includes:

[0075] In the raw materials, 4-(1,2,2-triphenylethynyl)benzaldehyde (1.78 g, 4.95 mmol, 2.2 eq) was used to replace p-tert-butylbenzaldehyde, and the rest was similar to the synthesis steps of 2TBB-DBAI above. Column chromatography purification was carried out using DCM and petroleum ether (VDCM:VPE = 1:1) as the eluent, and the final target product was a yellow solid (1.60 g, 51%). m.p.: >280 °C. 1H NMR (500 MHz, CDCl3, δ, ppm): 10.06 (s, 1H), 9.11 - 9.05 (dd, J = 10.0 Hz, 2H), 8.82 (s, 1H), 8.56 (s, 1H), 7.76 - 7.71 (dd, J = 5.0 Hz, 4H), 7.60 - 7.53 (d, J = 10.0 Hz, 7H), 7.41 (s, 7H), 7.10 - 7.02 (d, J = 40.0 Hz, 31H), 1.46 - 1.44 (d, J = 10.0 Hz, 12H), 1.26 (s, 13H), 1.13 (s, 4H), 1.05 (s, 7H). 13C NMR (125 MHz, CDCl3, δ, ppm): 168.6, 150.9, 150.5, 135.7, 131.5, 131.4, 128.6, 127.7, 127.0, 126.6, 108.0, 106.3, 103.0, 95.5, 93.1, 80.4, 77.3, 31.6, 31.1, 29.7, 23.8. HRMS: Calcd for C104H90N4, 1395.7238 [M+H]+; Found: 1395.7250. Error = 0.86 ppm.

[0076] Preparation method of 4,4'-(5,13-di-tert-butyl-1,9-bis(4-(tert-butyl)phenyl)-1,9-dihydrobenzo[8,9]tetrabenzo[5,6-d:10,11-d']diimidazole-2,10-diyl)bis(N,N-diphenylaniline) (2TPA-DBAI), specifically including:

[0077] Under N2 protection, DBAT (1.0 eq), ammonium acetate (30.0 eq), 4-diphenylaminobenzaldehyde (2.2 eq) and p-tert-butylaniline (3.2 eq) were fully dissolved in glacial acetic acid (AcOH, 150 mL), and the mixture was refluxed at 120 °C for 24 h. The mixed reactants were cooled to room temperature and poured into an ice-water mixture to precipitate a solid crude product. The solid product obtained by vacuum filtration was purified by column chromatography using DCM and petroleum ether (V DCM :V PE = 1:2) as the eluent, and the final target product was a white solid (1.32 g, 48%). m.p.: >280 °C.1 1H NMR (500 MHz, CDCl3, δ, ppm): 10.10 (s, 1H), 9.13 - 9.06 (dd, J = 10.0 Hz, 2H), 8.85 (s, 1H), 8.58 (s, 1H), 7.76 - 7.74 (d, J = 10.0 Hz, 3H), 7.65 - 7.62 (dd, J = 15.0 Hz, 5.0 Hz, 7H), 7.55 - 7.54 (d, J = 5.0 Hz, 8H), 7.49 - 7.47 (d, J = 10.0 Hz, 2H), 7.11 - 7.05 (d, J = 10.0 Hz, 5.0 Hz, 19H), 1.45 - 1.42 (d, J = 15.0 Hz, 18H), 1.13 (s, 10H), 1.06 (s, 8H). 13 13C NMR (125 MHz, CDCl3, δ, ppm): 153.3, 147.4, 130.9, 130.2, 129.3, 128.9, 127.1, 124.9, 124.2, 123.3, 122.4, 112.9, 106.0, 31.7, 31.4, 31.1, 29.7, 22.1, 14.1. HRMS: Calcd for C 88 H 80 N6, 1222.6590 [M + H] + ; Found: 1222.6590. Error = 0.03 ppm.

[0078] Preparation method of 5,13 - di - tert - butyl - 1,9 - bis(4 - (tert - butyl)phenyl) - 2,10 - bis(4 - (3,6 - di - tert - butyl - 9H - carbazol - 9 - yl)phenyl) - 1,9 - dihydrobenzo[8,9]tetrabenzo[5,6 - d:10,11 - d']diimidazole (2tBuPCz - DBAI) specifically includes:

[0079] In the raw materials, 4 - (3,6 - di - tert - butyl - 9H - carbazol - 9 - yl)benzaldehyde (2.2 eq) is used to replace 4 - diphenylaminobenzaldehyde, and the rest is similar to the synthesis steps of the above - mentioned 2TPA - DBAI. Dichloromethane and petroleum ether (V DCM :V PE = 1:1) is used as the eluent for purification by column chromatography, and the final target product is a pale yellow solid (1.62 g, 50%). m.p.: >280 °C. 11H NMR (500 MHz, CDCl3, δ, ppm): 10.18 (s, 1H), 9.19 - 9.13 (dd, J = 10.0 Hz, 5.0 Hz 2H), 8.92 (s, 1H), 8.68 (s, 1H), 8.14 (s, 5H), 7.95 - 7.90 (dd, J = 10.0 Hz, 5H), 7.84 - 7.82 (d, J = 10.0 Hz, 3H), 7.72 - 7.68 (t, J = 10.0 Hz, 6H), 7.57 - 7.55 (d, J = 10.0 Hz, 7H), 7.48 - 7.47 (d, J = 5.0 Hz, 5H), 1.47 - 1.45 (d, J = 10.0 Hz, 56H), 1.26 (s, 3H), 1.16 (s, 5H), 1.09 (s, 8H). 13 13C NMR (125 MHz, CDCl3, δ, ppm): 162.9, 156.8, 143.2, 138.9, 135.4, 130.7, 128.9, 127.3, 126.2, 123.7, 117.3, 116.3, 109.3, 63.6, 52.7, 35.3, 34.8, 32.0, 31.6, 31.4, 31.1. HRMS: Calcd for C 104 H 108 N6, 1442.8763 [M + H] + ; Found: 1442.8781. Error = 1.24 ppm.

[0080] Preparation method of 4,4'-(5,13 - di - tert - butyl - 2,10 - bis(4-(tert - butyl)phenyl)-dihydrobenzo[8,9]tetrabenzo[5,6 - d:10,11 - d']diimidazole - 1,9 - diyl)bis(N,N - diphenylaniline) (N - 2TPA - DBAI) specifically includes:

[0081] Under N2 protection, dissolve DBAT (1.0 eq), ammonium acetate (30.0 eq), p - tert - butylbenzaldehyde (2.2 eq) and 4 - aminotriphenylamine (3.2 eq) fully in glacial acetic acid (AcOH, 150 mL). The mixed reactants are refluxed at 120 °C for 24 h. Cool the mixed reaction solution to room temperature, pour it into the ice - water mixture to precipitate the solid crude product, then filter it by vacuum suction. Take the solid product and purify it through a chromatographic column using DCM and petroleum ether (V DCM :V PE = 1:2) as the eluent to obtain the final target product as a pale yellow solid (1.15 g, 42%). m.p.: >280 °C. 11H NMR (500 MHz, CDCl3, δ, ppm): 10.13 - 10.11 (dd, J = 10.0 Hz, 1H), 9.17 - 9.08 (dd, J = 10.0 Hz, 5 Hz, 2H), 8.93 (s, 1H), 8.86 (s, 1H), 8.16 - 8.14 (d, J = 10.0 Hz, 1H), 7.78 - 7.76 (d, J = 10.0 Hz, 1H), 7.74 - 7.72 (d, J = 10.0 Hz, 2H), 7.69 - 7.65 (dd, J = 10.0 Hz, 5.0 Hz, 6H), 7.59 - 7.57 (d, J = 10.0 Hz, 1H), 7.51 - 7.49 (d, J = 10.0 Hz, 2H), 7.43 - 7.41 (t, J = 5.0 Hz, 6H), 7.35 - 7.32 (dd, J = 10.0 Hz, 5.0 Hz, 9H), 7.20 - 7.19 (d, J = 5.0 Hz, 6H), 7.13 - 7.10 (t, J = 5.0 Hz, 5H), 1.38 - 1.37 (d, J = 5.0 Hz, 18H), 1.33 (s, 9H), 1.29 (s, 9H). 13 13C NMR (125 MHz, CDCl3, δ, ppm): 158.5, 157.9, 149.0, 147.2, 146.0, 145.7, 132.3, 129.7, 129.6, 129.2, 125.2, 124.2, 123.6, 120.5, 117.8, 115.5, 112.6, 110.5, 102.8, 94.0, 45.4, 44.9, 41.7, 34.9, 34.7, 31.7, 31.3. HRMS: Calcd for C 88 H 80 N6, 1222.6524 [M + H] + ; Found: 1222.6517. Error = 0.57 ppm.

[0082] Preparation method of 5,13 - di - tert - butyl - 2,10 - bis(4 - (tert - butyl)phenyl) - 1,9 - bis(4 - (3,6 - di - tert - butyl - 9H - carbazol - 9 - yl)phenyl) - 1,9 - dihydrobenzo[8,9]tetrabenzo[5,6 - d:10,11 - d']diimidazole (N - 2tBuPCz - DBAI) specifically includes:

[0083] In the raw materials, 3,6 - di - tert - butyl - 9 - (4 - aminophenyl)carbazole (3.2 eq) is used to replace 4 - aminotriphenylamine, and the rest is similar to the synthesis steps of the above N - 2TPA - DBAI. Using dichloromethane and petroleum ether (V DCM :V PEPurified by column chromatography using a 1:1 mixture of dichloromethane and methanol as the eluent to obtain the final target product as a pale yellow solid (1.30 g, 40%). m.p.: >280 °C. 1 H NMR (500 MHz, CDCl₃, δ, ppm): 10.20 - 10.18 (d, J = 5.0 Hz, 1H), 9.21 - 9.12 (dd, J = 15.0 Hz, 10.0 Hz 2H), 8.92 - 8.87 (d, J = 25.0 Hz, 2H), 8.25 (s, 2H), 8.20 - 8.18 (t, J = 10.0 Hz, 4H), 8.05 - 8.03 (d, J = 10.0 Hz, 2H), 7.96 - 7.94 (d, J = 10.0 Hz, 3H), 7.86 - 7.82 (t, J = 10.0 Hz, 5H), 7.78 - 7.76 (d, J = 10.0 Hz, 3H), 7.67 - 7.64 (t, J = 10.0 Hz, 5.0 Hz, 4H), 7.45 - 7.42 (t, J = 10.0 Hz, 5.0 Hz, 7H), 7.10 - 7.08 (d, J = 10.0 Hz, 1H), 1.50 (s, 33H), 1.36 (s, 23H), 1.28 (s, 8H), 1.05 (s, 8H). 13 C NMR (125 MHz, CDCl₃, δ, ppm): 159.6, 159.0, 143.8, 143.7, 140.1, 138.7, 135.1, 129.2, 127.8, 125.4, 123.8, 116.8, 116.6, 111.9, 109.2, 90.8, 38.8, 34.9, 32.0, 31.2, 29.7, 26.6, 17.8, 13.8. HRMS: Calcd for C 104 H 108 N₆, 1442.8728 [M + H] + ; Found: 1442.8781. Error = 3.64 ppm.

[0084] Example 3

[0085] For DBA and the six newly prepared materials, material property tests were carried out. The specific test methods and results are as follows:

[0086] (1) Molecular structure characterization: The molecular structures of all synthesized intermediates I - IV, DBA, DBAT, and the six new materials were mainly characterized by Nuclear Magnetic Resonance (NMR) and High Resolution Mass Spectrometry (HR - MS). Proton Nuclear Magnetic Resonance 11H NMR) and carbon nuclear magnetic resonance ( 13 13C NMR) were measured by a BRUKER 500MHz AVANCE NEO superconducting nuclear magnetic resonance spectrometer from Bruker Corporation, Germany; the HR-MS spectra were measured by a Bruker Esquire 6000 high-resolution mass spectrometer.

[0087] (2) Photophysical property tests: Tests were carried out using solution or thin film samples. The solution samples used dichloromethane (DCM, 1×10 -5 mol·L -1 ) as the solvent, and the pure solid thin film samples were obtained by uniformly coating on a quartz substrate using a solution spin-coating instrument. The ultraviolet-visible (UV-Vis) absorption spectra were measured by a UV-3600Plus type or Shimadzu UV-2550 type ultraviolet-visible spectrophotometer from Shimadzu Corporation, Japan; the absolute photoluminescence quantum yield (Φ f ) was measured by an FLS-1000 type steady-state / transient fluorescence spectrometer from Edinburgh Instruments, UK; the fluorescence emission spectra (PL) were measured by a Hitachi F-7100 type fluorescence spectrophotometer from Hitachi, Japan (at room temperature), and the results are as Figure 3 shown.

[0088] (3) Electrochemical property tests: Cyclic voltammetry (CV) curves were measured using a CHI 600D type electrochemical workstation from Ningbo Opu Instruments Co., Ltd. or an AUT87571 type electrochemical workstation from Metrohm, Switzerland. Test conditions: Room temperature, solution samples: 1×10 -5 mol·L -1 , using ferrocene (Fc / Fc + ) as the internal standard, a platinum wire as the counter electrode, a glassy carbon as the working electrode, and Ag / Ag + as the reference electrode, and a super-dry dichloromethane (DCM) solution of tetrabutylammonium hexafluorophosphate (C 16 H 36 F6NP, 0.1 mol / L) as the electrolyte (Note: The sample needs to be deoxygenated with high-purity nitrogen for more than 10 minutes before testing). According to the relative value of the potential between the sample to be measured and ferrocene, the HOMO and LUMO energy levels were calculated by formulas 2.1 - 2.3:

[0089]

[0090] where, E OX is the first oxidation potential; is the optical band gap, obtained by calculating from the UV-Vis spectrum, and the results are as Figure 4 shown.

[0091] (4) Thermal stability test: Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were measured using a TGA4000 thermogravimetric analyzer from PerkinElmer, USA. Test conditions: from room temperature to 600 °C under N2 protection, heating rate 10 °C / min. Test conditions: from room temperature to the thermal decomposition temperature T d , heating rate 10 °C / min, three cycles, and the results are as Figure 5 shown.

[0092] (5) DFT theoretical calculation: The theoretical calculation part was completed using Gaussian 16W software through density functional theory (DFT). The molecular structure and optimization model were calculated using GaussView 6.0 software, and the electron distribution diagrams of the HOMO and LUMO energy level orbits were drawn. The S0 configuration was calculated by DFT (B3LYP / 6-31G(d) basis set); the S1 energy level and T1 energy level were calculated according to the S0 optimized structure based on time-dependent density functional theory (TD-DFT) (B3LYP / 6-31G(d) basis set); the structures and natural transition orbitals (NTO) of S1 and T1 were calculated after optimization by Gaussian 16W and GaussView 6.0 based on TD-DFT (B3LYP / 6-31G(d) basis set), and the results are as Figure 6 shown.

[0093] The photophysical, electrochemical, and thermal stability test data of DBA and six new materials are shown in Table 1

[0094] Table 1

[0095]

[0096] Note: a - Measured in dichloromethane solution; b - Measured in pure thin film; c - Measured in N2 atmosphere at a heating rate of 10 °C / min; d - Measured in chloroform solution. e - Calculated according to the following equation: E opt = 1240 / λ onset ; f - Calculated from the following equation: E HOMO = -(E OX – E Fc / Fc + + 4.8) (eV) and E LUMO = (E HOMO + E opt ) (eV).

[0097] Example 4

[0098] Using the six new materials prepared as guest dopants, multilayer OLED devices were fabricated, and the EL performance of the corresponding devices was studied, specifically including:

[0099] S1 uses the solution spin-coating method to prepare multi-layer doped OLED devices and test films. The device preparation process includes the pretreatment of ITO glass substrates, the spin-coating and evaporation of each functional layer material to form a film, and the spin-coating of the host-guest doped light-emitting layer.

[0100] The OLED device structure is: ITO / PEDOT:PSS(45nm) / TCTA:dopant(xwt%)(30nm) / TPBi(20nm) / Liq(2nm) / Al(150nm). Among them, the ITO substrate is used as the anode material, poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is used as the hole injection layer (HIL), 2,2′,2″(1,3,5-benzenetribenzyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) is used as the electron transport-hole blocking layer (ETL), lithium 8-hydroxyquinoline (Liq) is used as the electron injection layer (EIL), metal Al is used as the cathode material, tris(4-carbazol-9-ylphenyl)amine (TCTA) is used as the host material, and the synthesized target material is used as the guest dopant. The structure diagram of the prepared OLED device and the energy levels and molecular structures of each layer material are as Figure 7 shown. Since the solvent used in the light-emitting layer during the preparation of OLED devices by the solution spin-coating method is likely to erode the lower layer, a hole transport layer is not added.

[0101] The specific preparation process of the multi-layer OLED device includes: on the pretreated ITO substrate, PEDOT:PSS is spin-coated at 3000 r / min for 45 s, 0.2 mL each time; annealed at 120 °C for 15 min and then cooled for 5 min. A mixed solution of a certain proportion of TCTA:dopant is spin-coated on the PEDOT:PSS layer in a glove box at a rotation speed of 2000 r / min, and then vacuum dried at 120 °C for 20 min. TPBi, Liq, and metal Al are sequentially vacuum thermally deposited on the light-emitting layer, where the thermal deposition rate of TPBi is The thermal deposition rates of Liq and metal Al are respectively and

[0102] S2 conducted performance tests on OLED devices. The EL spectrum was measured using the SpectraScan PR655 from Photo Research, USA. The brightness, turn-on voltage, current density and other performance indicators were measured using the Keithley 4200 semiconductor characteristic analysis system from Keithley Instruments, USA, in combination with the ST-86LA screen brightness meter from the Beijing Normal University Optoelectronics Instrument Factory. CE and PE were calculated using Keithley's own software. EQE was calculated using the spectral data obtained from CE and PR705. IVL curves, CE-PE-L curves, EQE-L curves and EL spectra of devices prepared from 6 new materials at different doping concentrations are shown in the figure. Figures 8 - 13 The EL performance is summarized in Table 2.

[0103] Table 2

[0104]

[0105]

[0106] Results and Discussion:

[0107] The present invention uses dibenzo[a,h]anthracene (DBA) core as the intermediate structural unit and functionalized substituted aryl imidazole as the side branching groups to design and synthesize six nitrogen-containing condensed ring aromatic blue light small molecule materials based on DAD-type rigid twisted structure, AIE functionalization, and positional isomerism, and studies the photophysical properties, electrochemical properties, and thermal stability of these materials in detail, and systematically studies the electroluminescent properties of the corresponding devices. The research results of Examples 1-4 are summarized as follows:

[0108] (1) By modifying intermediate II, a bipolar DBAT main core is obtained through dehydrogenation, condensation, and oxidation reactions. AIE functional groups TBB and TPE are respectively connected to the C2 position of the imidazole ring to successfully synthesize two symmetric X-shaped fluorescent molecules 2TBB-DBAI and 2TPE-DBAI. The main emission peaks of 2TBB-DBAI and 2TPE-DBAI in solution / thin film are 430 / 434 nm and 510 / 491 nm respectively. Due to a certain degree of molecular twisted structure and effective expansion of π-conjugation, the HOMO / LUMO of the two materials are effectively separated. The PL spectra show ICT characteristics and certain AIE characteristics. TCTA is selected as the host material, and the two target materials are used as guest dopants. OLED devices are prepared by solution spin coating method and the EL performance is tested. The emission peak in the EL spectrum of the device based on 2TBB-DBAI is 428 nm, and the CIE color coordinates are located at (0.16, 0.05), which is very close to deep blue light; while the emission peak in the EL spectrum of the device based on 2TPE-DBAI is located at 476 nm and the CIE color coordinates are located at (0.19, 0.27), presenting sky blue light. The EQE max of the two devices reaches 2.02% and 2.77% respectively, and the efficiency roll-off is slow (at a brightness of 1000 cd / m 2 , the EQE of the devices are 1.33% and 2.72% respectively, and the efficiency drops are 34% and 1.8% respectively).

[0109] It can be seen that although AIE active groups TPE are introduced on both sides in material 2TPE-DBAI, their AIE characteristics are not obvious. The molecular structure needs to be further optimized to explore AIE active fluorescent molecules with higher performance. Even though the steric hindrance increases significantly, the luminescence efficiency of the position-isomerized imidazole-based DBA molecules does not decrease significantly as expected. Through reasonable molecular design strategies, in-depth research on new materials helps to obtain deep blue OLED devices with more abundant optoelectronic properties.

[0110] (2) Two D-A-D type organic blue light materials, 2TPA-DBAI and 2tBuPCz-DBAI, were designed and synthesized by connecting the strong electron-donating units TPA and tBuPCz to the C2 position of the imidazole ring on DBAI. The twisted structure between the donor and acceptor in the molecule helps to achieve effective separation of HOMO / LUMO. The strong donor groups TPA and tBuPCz can obtain stronger ICT state emission, and the rigid planar structure of DBAI is beneficial to suppressing the non-radiative transition process. The main emission peaks of 2tBuPCz-DBAI in solution and thin film are 438 nm and 442 nm, respectively. The π-π interaction within the molecule causes a certain degree of red shift in the PL spectrum. Under the condition of not configuring a hole transport layer, TCTA was selected as the host material, and the two target materials were used as guest dopants. OLED devices were prepared by solution spin coating method and their EL properties were tested. When the doping concentration is 14 wt%, the emission peak of the doped OLED device based on 2tBuPCz-DBAI is located at 428 nm, and the CIE color coordinates are (0.16, 0.10), showing deep blue light, EQE max up to 3.19%, indicating that the EL performance of the device is excellent and can provide important reference for the design, development and application of efficient deep blue light materials.

[0111] (3) Based on the design strategy of position isomers, two D-A-D type blue light materials, N-2TPA-DBAI and N-2tBuPCz-DBAI, were synthesized by connecting the strong donor units TPA and tBuPCz to the N1 position of the imidazole ring. In order to facilitate the distinction and comparison of the luminescence properties of materials with different structures and explore new design ideas for efficient blue light small molecules, the molecules connected to the C2 position of the imidazole ring are called C2-substituted imidazole derivatives, and the molecules connected to the N1 position are called N1-substituted imidazole derivatives. The results show that due to the influence of the increased steric hindrance on the conjugated structure, the PLQY of C2-substituted imidazole derivatives is significantly larger. The donor-acceptor structure participating in the excitation process arranged in a straight line X shape is more conducive to the occurrence of the radiative transition process. Finally, the performance of multilayer doped OLED devices of N-2TPA-DBAI and N-2tBuPCz-DBAI was tested. Due to the smaller ΔE ST and higher Ф f value of N-2TPA-DBAI, good luminescence performance was achieved. Its emission peak is located at 428 nm, the CIE color coordinates are (0.16, 0.06) and it emits deep blue light, CE max is 1.36 cd / A, PE max is 0.90 lm / W, EQE max reaches 2.47%, at a brightness of 1000 cd / m 2Even at low current densities, it can still maintain an EQE of 1.91%, showing a low efficiency roll-off (23%), and proposing an effective design strategy based on isomer engineering for blue-light heteroaromatic condensed-ring small molecule materials.

[0112] The foregoing description of specific exemplary embodiments of the invention has been presented for purposes of illustration and example. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that, in light of the above teachings, many modifications and variations are possible. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical application so that those skilled in the art can implement and utilize the various different exemplary embodiments of the invention as well as various different selections and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. An imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material, characterized in that: The organic fluorescent small molecule material has a general structural formula as shown in Formula (1): Wherein, A or B in the formula (1) includes any one of the following structures of formula (1)-1 to formula (1)-4:

2. The imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material according to claim 1, characterized in that: The structural formulas of A and B are different.

3. The imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material according to claim 1, characterized in that: The organic fluorescent small molecule material includes any of the following structures:

4. The method for preparing the imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material according to any one of claims 1 to 3, characterized in that: The method comprises the following steps: a diketone compound having a general structural formula shown in formula (2) is subjected to a Debus-Radziszewski one-pot reaction with an aromatic aldehyde compound C, an aromatic amine compound D and ammonium acetate to obtain an imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material; wherein: The aromatic aldehyde compound C and / or the aromatic amine compound D respectively include at least one of the derivatives of p-tert-butylbenzene, tetraphenylethylene, triphenylamine and tert-butylcarbazole.

5. The method for preparing the imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material according to claim 4, characterized in that: The aromatic aldehyde compound C includes any one of the following structures (3)-1 to (3)-4: The aromatic amine compound D includes any one of the following structures of formula (4)-1 to (4)-3:

6. The method for preparing the imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material according to claim 4, characterized in that: The molar mass ratio of the diketone compound, the aromatic aldehyde compound C, the aromatic amine compound D and ammonium acetate is 1.0:(1.8-2.6):(2.8-3.6):(25-35).

7. The imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material according to claim 1, characterized in that: The Debus-Radziszewski one-pot reaction conditions include: fully dissolving the diketone compound, the aromatic aldehyde compound C, the aromatic amine compound D and ammonium acetate in glacial acetic acid, and reflux reacting the reaction mixture at 100-140° C. for 18-30 hours.

8. Use of the imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material according to any one of claims 1 to 3 in the preparation of an organic electroluminescent device.

9. The use of the imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material in the preparation of an organic electroluminescent device as claimed in claim 8, characterized in that: The organic electroluminescent device is composed of a glass substrate, an ITO anode, a light-emitting layer, an electron transport layer and a cathode in sequence; The light-emitting layer is composed of a main material 4,4′,4″-tri(N-carbazolyl)triphenylamine and a guest dopant; the guest dopant contains at least one imidazolyl dibenzo[a,h]anthracene-based organic fluorescent small molecule material as described in any one of claims 1 to 3.

10. The use of the imidazolyl dibenzo[a,h]anthracene organic fluorescent small molecule material in the preparation of an organic electroluminescent device as claimed in claim 9, characterized in that: When the guest dopant is 2tBuPCz-DBAI, the emission peak of the prepared organic electroluminescent device is 428nm, the CIE color coordinates are located at (0.16, 0.11), and it displays deep blue light. max 1601cd / m 2 , C.E. max 8.98cd / A, PE max 7.84lm / W, EQE max Reached 3.19%.

Images