Organic light-emitting device

Abstract

The invention provides an organic electroluminescent device which is composed of a cathode, an anode and a plurality of organic functional layers between the cathode and the anode, at least one of the organic functional layers is a luminescent layer, and the raw material of the luminescent layer comprises a pure purple light organic electroluminescent material with a boron-oxygen skeleton as a core. According to the organic light-emitting device, the pure purple light organic light-emitting material with the boron-oxygen skeleton as the core is adopted as the raw material of the light-emitting layer, emission of pure purple light with the electroluminescent peak wavelength lower than 430 nm is achieved, and the organic light-emitting device has the comprehensive advantages of being low in turn-on voltage, high in external quantum efficiency, narrow in half-peak width, low in CIEy value, low in efficiency roll-off and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of light-emitting devices, in particular to an organic electroluminescent device. BACKGROUND

[0002] As a new generation of display and lighting technology, organic electroluminescent devices have outstanding advantages such as self-emission, fast response speed, wide viewing angle, and flexible device preparation, and have become the mainstream of current flat panel display field. At present, the external quantum efficiency (EQE) of various monochromatic RGB OLED devices has broken through 20%, and the emission spectrum full width at half maximum (FWHM) is less than 30 nm, with significant performance. In contrast, although violet OLEDs have important value in the fields of information storage, anti-counterfeiting technology and biomedical, there are still few reports on violet OLEDs with high efficiency and high color purity (such as Commission Internationale de l'Eclairage CIEy value less than 0.03).

[0003] The key to realizing high color purity violet electroluminescence of the device lies in effectively controlling the FWHM and color coordinates (especially CIEy value) of the emission spectrum, so that the emission is as concentrated as possible in a narrow wavelength range. The color purity is mainly affected by factors such as structural relaxation and vibrational coupling between the excited state (S1) and the ground state (S0) of the molecule, and aggregation behavior. In order to improve the color purity, the traditional method usually starts from inhibiting molecular vibration relaxation and reducing structural changes. Common molecular design strategies include increasing molecular rigidity, regulating conjugation length, inhibiting red shift or broadening of the spectrum caused by π-π stacking. In addition, improving the fluorescence quantum yield, optimizing the device structure to suppress the disturbance of the microcavity effect on the spectrum, also helps to obtain purer violet light emission.

[0004] However, only enhancing the molecular rigidity often makes it difficult to realize violet devices with high color purity, high efficiency and low efficiency roll-off. Although traditional fluorescent materials have good light color stability, the utilization rate of excitons is limited; thermal activated delayed fluorescence (TADF) materials and phosphorescent materials can improve efficiency by utilizing triplet excitons, but their emission spectrum is often wide, and there are problems such as spectrum broadening and serious efficiency roll-off in the violet region. The hot exciton mechanism initiated by Chinese scientist Academician Ma Yugong et al. uses the high-energy level RISC (hRISC) process of high-energy triplet state (T n , n ≥ 2) to singlet state (S m , m ≥ 1) to increase the proportion of singlet excitons, which can theoretically achieve 100% exciton utilization [8] . The high-energy state T n →S m exciton conversion does not need to use the frontier orbital separation to obtain a small T1-S1 energy level difference, so it can realize the S1 state with localized excited state properties, thereby ensuring high luminescent efficiency. At the same time, T n →S mThe exciton conversion channel of the pure purple light organic electroluminescent material is completely separated from the radiation transition channel of the S1 exciton, effectively avoiding the exciton annihilation problem caused by the accumulation of long-lived T1 excitons. In addition, the donor-acceptor strength of the hot exciton material is moderate, which provides potential advantages for the design of high-performance pure purple light organic electroluminescent materials and devices. However, the current technology still has problems such as difficulty in fully utilizing the triplet exciton, poor color purity (emission spectrum FWHM greater than 40 nm) and insufficient stability. Therefore, the prior art needs to be further developed. SUMMARY

[0005] In view of the various deficiencies of the prior art, in order to solve the above problems, an organic electroluminescent device is proposed, and the following technical solutions are provided. An organic electroluminescent device, which is composed of a cathode, an anode and a plurality of organic functional layers between the two electrodes, at least one of the organic functional layers is a light-emitting layer, the raw material of the light-emitting layer includes a pure purple light organic electroluminescent material with a boron-oxygen skeleton as the core, and the structure of the pure purple light organic electroluminescent material is formula I or formula II: I II Wherein, R1 is one of the following structural units: ; R2 is a structure containing a naphthyl group.

[0006] Further, the R2 is one of the following structural units: .

[0007] Further, the light-emitting layer further includes a host material, the host material and the pure purple light organic electroluminescent material are doped to obtain a doped film, and the host material is N,N'-dicarbazolyl-4,4'-diphenyl, 1,3-dicarbazol-9-ylbenzene, 9,10-dinaphthylanthracene, 9,10-bis(2-naphthyl)-2-methylanthracene or 9-(4-(10-phenylanthracene-9-yl)phenyl)-9H-carbazole.

[0008] Further, the mass ratio of the pure purple light organic electroluminescent material to the host material is 1:99-99:1.

[0009] Further, the preparation process of the pure purple light organic electroluminescent material is as follows: S1: Under the protection of nitrogen, 2,5-dibromo-1,3-difluorobenzene and 4-tert-butylphenol are used as raw materials, and an intermediate 1 is obtained by reaction under a first catalytic system; S2: under the protection of nitrogen, taking the intermediate 1 obtained in step S1 as the raw material, and through a cyclization reaction under a second catalytic system to obtain an intermediate 2; S3: under the protection of nitrogen, taking pinacol diboron and the intermediate 2 obtained in step S2 as the raw material, and through a boron esterification reaction under a third catalytic system to obtain an intermediate 3; S4: under the protection of nitrogen, taking 2,8-dibromodibenzothiophene or dibromo R2 and R1 of boric acid or boron esterification R1 as the raw material, and through a Suzuki coupling reaction under a palladium catalytic system to obtain an intermediate 4; S5: under the protection of nitrogen, taking the intermediate 3 and the intermediate 4 as the raw material, and through a Suzuki coupling reaction under a palladium catalytic system to obtain a pure purple light organic electroluminescent material.

[0010] Further, in step S1, the molar ratio of 2,5-dibromo-1,3-difluorobenzene and 4-tert-butylphenol is 1:3-30, and the first catalytic system is potassium carbonate.

[0011] Further, the second catalytic system is n-butyl lithium and boron tribromide.

[0012] Further, in step S3, the molar ratio of the intermediate 2 and pinacol diboron is 1:2-5, and the third catalytic system is potassium acetate and [1,1'-bis(diphenylphosphino)ferrocene]dichloropalladium.

[0013] Further, in step S4, the molar ratio of 2,8-dibromodibenzothiophene or dibromo R2 and R1 of boric acid or boron esterification R1 is 1-2:1, and the palladium catalytic system is potassium carbonate and tetrakis(triphenylphosphine)palladium.

[0014] Further, in step S5, the molar ratio of the intermediate 3 and the intermediate 4 is 1-2:1, and the palladium catalytic system is potassium carbonate and tetrakis(triphenylphosphine)palladium.

[0015] Beneficial effects: 1. The organic electroluminescent device of the present application adopts a pure purple light organic electroluminescent material with a boron-oxygen skeleton as the core as the raw material of the light-emitting layer, realizes pure purple light emission with an electroluminescence peak wavelength below 430 nm, and exhibits comprehensive advantages of low turn-on voltage, high external quantum efficiency, narrow half-peak width, low CIEy value and low efficiency roll-off.

[0016] 2、The pure purple light material constructed with boron-oxygen skeleton as electron acceptor, dibenzothiophene or naphthalene as connecting bridge, on the one hand, can realize the synergistic regulation of the excited state electron structure and energy level, inhibit the triplet state internal conversion process, promote the high site anti-inter-system crossing of triplet exciton, and then improve the utilization rate of triplet exciton; on the other hand, through the modification of the functional groups on the other side of the connecting bridge, the synergistic regulation of short-range CT state, long-range CT state and local excited state (LE) is realized, the spectral red shift is effectively inhibited, the material emission is ensured to be located in the purple light region and has high color purity, and the radiation transition rate and fluorescence quantum efficiency are improved; in addition, the boron-oxygen skeleton has high rigidity and planarity, can effectively inhibit molecular vibration relaxation and reduce non-radiative transition, thereby helping to realize narrow-band emission; at the same time, the introduced dibenzothiophene or naphthalene connecting bridge and weak electron-donating functional groups are beneficial to inhibit the generation of excessive long-range CT state components, inhibit the spectral broadening problem, and promote the realization of efficient light emission in the purple light region.

[0017] 3、The organic electroluminescent device of the present application has wide application prospects in many scientific and industrial fields such as ultraviolet light excitation source, anti-fake encryption, photocuring system, medical sterilization, chemical sensing and plant and animal growth regulation. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The nuclear magnetic resonance hydrogen spectrum of the pure purple light organic electroluminescent material NA-DBT-BO constructed with boron-oxygen as acceptor and dibenzothiophene as bridge prepared in Example 1; Figure 2 The nuclear magnetic resonance hydrogen spectrum of the pure purple light organic electroluminescent material PY-DBT-BO constructed with boron-oxygen as acceptor and dibenzothiophene as bridge prepared in Example 2; Figure 3 The nuclear magnetic resonance hydrogen spectrum of the pure purple light organic electroluminescent material Cz3-DBT-BO constructed with boron-oxygen as acceptor and dibenzothiophene as bridge prepared in Example 3; Figure 4 The nuclear magnetic resonance hydrogen spectrum of the pure purple light organic electroluminescent material Cz9-DBT-BO constructed with boron-oxygen as acceptor and dibenzothiophene as bridge prepared in Example 4; Figure 5 The nuclear magnetic resonance hydrogen spectrum of the pure purple light organic electroluminescent material BONA2O constructed with boron-oxygen as acceptor and 1,8-dibromonaphthalene as bridge prepared in Example 5; Figure 6 The nuclear magnetic resonance hydrogen spectrum of the pure purple light organic electroluminescent material BONA2S constructed with boron-oxygen as acceptor and 1,8-dibromonaphthalene as bridge prepared in Example 6; Figure 7A nuclear magnetic resonance hydrogen spectrum of a pure purple light organic electroluminescent material BONACz3 with boron oxygen as an acceptor and 1,8-dibromonaphthalene as a bridge structure prepared in Example 7; Figure 8 A nuclear magnetic resonance hydrogen spectrum of a pure purple light organic electroluminescent material BONACz9 with boron oxygen as an acceptor and 1,8-dibromonaphthalene as a bridge structure prepared in Example 8; Figure 9 A mass spectrum of a pure purple light organic electroluminescent material NA-DBT-BO with boron oxygen as an acceptor and dibenzothiophene as a bridge structure prepared in Example 1; Figure 10 A mass spectrum of a pure purple light organic electroluminescent material PY-DBT-BO with boron oxygen as an acceptor and dibenzothiophene as a bridge structure prepared in Example 2; Figure 11 A mass spectrum of a pure purple light organic electroluminescent material Cz3-DBT-BO with boron oxygen as an acceptor and dibenzothiophene as a bridge structure prepared in Example 3; Figure 12 A mass spectrum of a pure purple light organic electroluminescent material Cz9-DBT-BO with boron oxygen as an acceptor and dibenzothiophene as a bridge structure prepared in Example 4; Figure 13 A mass spectrum of a pure purple light organic electroluminescent material BONA2O with boron oxygen as an acceptor and 1,8-dibromonaphthalene as a bridge structure prepared in Example 5; Figure 14 A mass spectrum of a pure purple light organic electroluminescent material BONA2S with boron oxygen as an acceptor and 1,8-dibromonaphthalene as a bridge structure prepared in Example 6; Figure 15 A mass spectrum of a pure purple light organic electroluminescent material BONACz3 with boron oxygen as an acceptor and 1,8-dibromonaphthalene as a bridge structure prepared in Example 7; Figure 16 A mass spectrum of a pure purple light organic electroluminescent material BONACz9 with boron oxygen as an acceptor and 1,8-dibromonaphthalene as a bridge structure prepared in Example 8; Figure 17 A thermogravimetric curve of a pure purple light organic electroluminescent material NA-DBT-BO with boron oxygen as an acceptor and dibenzothiophene as a bridge structure prepared in Example 1; Figure 18 A thermogravimetric curve of a pure purple light organic electroluminescent material PY-DBT-BO with boron oxygen as an acceptor and dibenzothiophene as a bridge structure prepared in Example 2; Figure 19 A thermogravimetric curve of a pure purple light organic electroluminescent material Cz3-DBT-BO with boron oxygen as an acceptor and dibenzothiophene as a bridge structure prepared in Example 3; Figure 20Thermogravimetric curve of pure purple organic electroluminescent material Cz9-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge structure prepared in Example 4; Figure 21 Thermogravimetric curve of pure purple organic electroluminescent material BONA2O with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge structure prepared in Example 5; Figure 22 Thermogravimetric curve of pure purple organic electroluminescent material BONA2S with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge structure prepared in Example 6; Figure 23 Thermogravimetric curve of pure purple organic electroluminescent material BONACz3 with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge structure prepared in Example 7; Figure 24 Thermogravimetric curve of pure purple organic electroluminescent material BONACz9 with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge structure prepared in Example 8; Figure 25 Normalized photoluminescence spectrum of 2 wt% doped film of pure purple organic electroluminescent material NA-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge structure prepared in Example 1; Figure 26 Normalized photoluminescence spectrum of 2 wt% doped film of pure purple organic electroluminescent material PY-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge structure prepared in Example 2; Figure 27 Normalized photoluminescence spectrum of 2 wt% doped film of pure purple organic electroluminescent material Cz3-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge structure prepared in Example 3; Figure 28 Normalized photoluminescence spectrum of 2 wt% doped film of pure purple organic electroluminescent material Cz9-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge structure prepared in Example 4; Figure 29 Normalized photoluminescence spectrum of 2 wt% doped film of pure purple organic electroluminescent material BONA2O with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge structure prepared in Example 5; Figure 30 Normalized photoluminescence spectrum of 2 wt% doped film of pure purple organic electroluminescent material BONA2S with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge structure prepared in Example 6; Figure 31Normalized photoluminescence spectrum of a 2 wt% doped film of the pure violet organic electroluminescent material BONACz3 with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge construction prepared for Example 7; Figure 32 Normalized photoluminescence spectrum of a 2 wt% doped film of the pure violet organic electroluminescent material BONACz9 with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge construction prepared for Example 8; Figure 33 External quantum efficiency-luminance characteristics and electroluminescence spectra of a doped organic electroluminescent device with the pure violet organic electroluminescent material NA-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge construction prepared for Example 13 using Example 1; Figure 34 External quantum efficiency-luminance characteristics and electroluminescence spectra of a doped organic electroluminescent device with the pure violet organic electroluminescent material PY-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge construction prepared for Example 13 using Example 2; Figure 35 External quantum efficiency-luminance characteristics and electroluminescence spectra of a doped organic electroluminescent device with the pure violet organic electroluminescent material Cz3-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge construction prepared for Example 13 using Example 3; Figure 36 External quantum efficiency-luminance characteristics and electroluminescence spectra of a doped organic electroluminescent device with the pure violet organic electroluminescent material Cz9-DBT-BO with boron oxide as acceptor and dibenzothiophene as bridge construction prepared for Example 13 using Example 4; Figure 37 External quantum efficiency-luminance characteristics and electroluminescence spectra of a doped organic electroluminescent device with the pure violet organic electroluminescent material BONA20 with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge construction prepared for Example 14 using Example 5; Figure 38 External quantum efficiency-luminance characteristics and electroluminescence spectra of a doped organic electroluminescent device with the pure violet organic electroluminescent material BONA2S with boron oxide as acceptor and 1,8-dibromonaphthalene as bridge construction prepared for Example 14 using Example 6. DETAILED DESCRIPTION

[0019] In order to enable persons skilled in the art to better understand the technical solutions of the present application, the technical solutions of the present application will be described clearly and completely below in combination with the embodiments of the present application. Based on the embodiments in the present application, other similar embodiments obtained by persons skilled in the art without making creative efforts should all belong to the scope of protection of the present application.

[0020] An organic electroluminescent device, which is composed of a cathode, an anode and a plurality of organic functional layers between the two electrodes, at least one of the organic functional layers being an emitting layer, the raw material of the emitting layer comprising a pure-violet organic electroluminescent material with a boron-oxygen skeleton as the core, the structure of the pure-violet organic electroluminescent material being Formula I or Formula II: Formula I Formula II wherein R1 is one of the following structural units: ; R2 is a naphthyl group.

[0021] The R2 is one of the following structural units: .

[0022] The application creatively prepares an organic electroluminescent device, realizes pure-violet emission with an electroluminescent peak wavelength below 430 nm, and exhibits comprehensive advantages such as low turn-on voltage, high external quantum efficiency, narrow FWHM, low CIEy value and low efficiency roll-off.

[0023] The mass ratio of the pure-violet organic electroluminescent material to the host material is 1:99-99:1. The addition amount of the pure-violet organic electroluminescent material in the application can be adjusted, and the organic electroluminescent device can be prepared within 1:99-99:1.

[0024] The preparation process of the pure-violet organic electroluminescent material is as follows: S1: under nitrogen protection, 2,5-dibromo-1,3-difluorobenzene and 4-tert-butylphenol are used as raw materials to obtain an intermediate 1 under a first catalytic system; S2: under nitrogen protection, the intermediate 1 obtained in step S1 is used as a raw material to obtain an intermediate 2 through cyclization reaction under a second catalytic system; S3: under nitrogen protection, pinacol diboron and the intermediate 2 obtained in step S2 are used as raw materials to obtain an intermediate 3 through boron esterification under a third catalytic system; S4: under nitrogen protection, 2,8-dibromodibenzothiophene or dibromo R2 and R1 of boric acid or R1 of boron esterification are used as raw materials to obtain an intermediate 4 through Suzuki coupling reaction under a palladium catalytic system; S5: under nitrogen protection, the intermediate 3 and the intermediate 4 are used as raw materials to obtain the pure-violet organic electroluminescent material through Suzuki coupling reaction under a palladium catalytic system.

[0025] Specifically, in step S1, the molar ratio of 2,5-dibromo-1,3-difluorobenzene and 4-tert-butylphenol is 1:3-30. In step S3, the molar ratio of intermediate 2 and pinacol diboronate is 1:2-5. In step S4, the molar ratio of 2,8-dibromodibenzothiophene or dibromo-R2 and boric acid R1 or boron-esterified R1 is 1-2:1. In step S5, the molar ratio of intermediate 3 and intermediate 4 is 1-2:1. Through the synergistic ratio of the above raw materials, a luminescent material for use in organic electroluminescent devices is finally provided, promoting its efficient emission in the violet region.

[0026] Next, in order to prepare organic electroluminescent devices, a variety of pure violet organic electroluminescent materials required for organic electroluminescent devices were first synthesized, as shown in Examples 1-12.

[0027] Example 1 Pure violet organic electroluminescent material NA-DBT-BO A pure violet organic electroluminescent material, NA-DBT-BO, namely 2,12-di-tert-butyl-7-(8-(naphth-1-yl)dibenzo[b,d]thiaindene-2-yl)-5,9-dioxy-13b-boron-naphthalene[3,2,1-de]anthracene, has the following structure: The preparation method of the pure violet organic electroluminescent material NA-DBT-BO includes the following steps: Step (1), synthesis of intermediate 4,4'-((2,5-dibromo-1,3-phenylene)bis(oxy))bis(tert-butylbenzene): Under a nitrogen atmosphere, a mixture of 2,5-dibromo-1,3-difluorobenzene (10876 mg, 40 mmol), 4-tert-butylphenol (18026 mg, 120 mmol), and potassium carbonate (16584 mg, 120 mmol) was added to a 250 mL double-necked round-bottom flask. Dimethyl sulfoxide (100 mL) was then added, and the reaction mixture was heated to 100°C and refluxed for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried over anhydrous MgSO4. After evaporation of the solvent under reduced pressure, the residue was purified by recrystallization from methanol to give a white solid (20015 mg, yield: 94%).

[0028] Step (2), synthesis of intermediate 7-bromo-2,12-di-t-butyl-5,9-dioxo-13b-boronnaphthalene[3,2,1-de]anthracene: Under a nitrogen atmosphere, 4,4'-((2,5-dibromo-1,3-phenyl)bis(oxy))bis(tert- butylbenzene) (10114 mg, 19 mmol) was added to dry m-xylene (80 mL) at 0°C. After 15 minutes, a solution of n-butyllithium in n-hexane (13.06 mL, 1.6 M, 21 mmol) was added dropwise to the reaction mixture, which was then stirred in an ice bath for 1 hour. Subsequently, n-hexane was removed by distillation under reduced pressure. Then, boron tribromide (5.49 mL, 57 mmol) was slowly added under an ice bath. After 20 minutes, N,N-diisopropylethylamine (7367 mg, 57 mmol) was added, and the reaction mixture was stirred at 150°C for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the resulting residue was purified by column chromatography on silica gel using petroleum ether as eluent. Finally, the crude product was recrystallized in methanol to give a white solid (4907 mg, yield 56%).

[0029] Step (3), synthesis of intermediate 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2- dioxaborolan-2-yl)-5,9-dioxo-13b-boronaphtho[3,2,1-de]anthracene: Under a nitrogen atmosphere, intermediate 7-bromo-2,12-di-tert-butyl-5,9-dioxo- 13b-boronaphtho[3,2,1-de]anthracene (5073 mg, 11 mmol), bis(pinacolato)diboron (5587 mg, 22 mmol), [1,1’-bis(diphenylphosphino)ferrocene]palladium dichloride (322 mg, 0.04 mmol) and potassium acetate (4318 mg, 44 mmol) were added to a 250 mL two-necked round-bottomed flask. Then, dioxane (40 mL) was added and the reaction was heated to 110°C for 12 hours under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with ethyl acetate. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the resulting residue was purified by column chromatography on silica gel using first petroleum ether / dichloromethane (20:1, v / v) as eluent to remove impurities and then petroleum ether / ethyl acetate (4:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to give a white solid (2516 mg, yield: 45%).

[0030] Step (4), synthesis of intermediate 2-bromo-8-(naphthalen-1-yl)dibenzo[b,d]thiophene: Under a nitrogen atmosphere, 2,8-dibromodibenzo[b,d]thiophene (3010 mg, 8.8 mmol), 1-naphthaleneboronic acid (1376 mg, 8 mmol), tetrakis(triphenylphosphine)palladium (370 mg, 0.32 mmol) and potassium carbonate (2211 mg, 16 mmol) were added to a 250 mL two-necked round-bottomed flask. Then water (8 mL), ethanol (8 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C under reflux for 12 h. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1488 mg, yield: 48%).

[0031] Step (5), synthesis of the target molecule 2,12-di-tert-butyl-7-(8-(naphthalen-1- yl)dibenzo[b,d]thiophen-2-yl)-5,9-dioxo-13b-bora-naphthacene: Under a nitrogen atmosphere, intermediate 2-bromo-8-(naphthalen-1-yl)dibenzo[b,d]thiophene (1557 mg, 4 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b-bora-naphthacene (2033 mg, 4.4 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round-bottomed flask, respectively. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C under reflux for 24 h. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1432 mg, yield: 52%).

[0032] 1H NMR (400 MHz, Chloroform- d ) δ 8.75 (d, J = 2.5 Hz, 2H), 8.53 (d, J =1.8 Hz, 1H), 8.40 (d, J= 1.6 Hz, 1H), 8.01 (dd, J = 8.3, 5.9 Hz, 2H), 7.98 –7.93 (m, 2H), 7.91 (td, J = 8.8, 8.3, 1.8 Hz, 2H), 7.77 (dd, J = 8.9, 2.4 Hz, 2H), 7.65 (dd, J = 8.2, 1.6 Hz, 1H), 7.59 – 7.57 (m, 1H), 7.57 – 7.52 (m, 4H), 7.51 – 7.47 (m, 3H), 1.49 (s, 18H). Example 2 PY-DBT-BO, a pure violet organic electroluminescent material A pure violet organic electroluminescent material, PY-DBT-BO, namely 2,12-di-tert-butyl-7-(8-(pyrene-1-yl)dibenzo[b,d]thiophene-2-yl)-5,9-dioxo-13b-boronnaphthalene[3,2,1-de]anthracene, has the following structure: The preparation method of the pure violet organic electroluminescent material PY-DBT-BO includes the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0033] Step (4), synthesis of intermediate 2-bromo-8-(pyrene-1-yl)dibenzo[b,d]thiophene: Under a nitrogen atmosphere, 2,8-dibromodibenzothiophene (3010 mg, 8.8 mmol), 1-pyreneboronic acid (1969 mg, 8 mmol), tetrakis(triphenylphosphine)palladium (370 mg, 0.32 mmol), and potassium carbonate (2211 mg, 16 mmol) were added to a 250 mL double-necked round-bottom flask. Water (8 mL), ethanol (8 mL), and toluene (60 mL) were then added, and the reaction mixture was heated to 100°C and refluxed for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried over anhydrous MgSO4. After evaporation of the solvent under reduced pressure, the residue was purified by silica gel column chromatography using petroleum ether / dichloromethane (20:1, v / v) as the eluent. Finally, the crude product was recrystallized from methanol to give a white solid (1297 mg, yield: 35%).

[0034] Step (5), synthesis of the target molecule 2,12-di-tert-butyl-7-(8-(pyren-1-yl)dibenzo[b,d]thiophene-2-yl)-5,9-dioxo-13b-boratetralin[3,2,1-de]anthracene: Under a nitrogen atmosphere, intermediate 2-bromo-8-(pyren-1-yl)dibenzo[b,d]thiophene (1854 mg, 4 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b-boratetralin[3,2,1-de]anthracene (2033 mg, 4.4 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round bottom flask, respectively. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C under reflux for 24 h. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the obtained residue was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (857 mg, yield: 28%).

[0035] 1 H NMR (400 MHz, Chloroform- d ) δ 8.75 (d, J = 2.5 Hz, 2H), 8.58 (d, J =1.8 Hz, 1H), 8.54 (d, J = 1.9 Hz, 1H), 8.27 (dd, J = 12.1, 8.5 Hz, 2H), 8.21 (dd, J = 15.3, 7.6 Hz, 2H), 8.14 (d, J = 1.8 Hz, 2H), 8.12 (d, J = 7.8 Hz, 1H), 8.07(dd, J = 7.9, 2.7 Hz, 2H), 8.04 (dd, J = 7.2, 2.3 Hz, 2H), 7.92 (dd, J = 8.4, 1.8Hz, 1H), 7.79 (dd, J= 8.2, 1.6 Hz, 1H), 7.77 (d, J = 2.4 Hz, 1H), 7.75 (d, J = 2.5Hz, 1H), 7.56 (s, 2H), 7.48 (d, J = 8.8 Hz, 2H), 1.48 (s, 18H). Example 3 Cz3-DBT-BO, a pure violet organic electroluminescent material A pure violet organic electroluminescent material, Cz3-DBT-BO, namely 3-(8-(2,12-di-tert-butyl-5,9-dioxo-13b-boronnaphthalene[3,2,1-de]anthracite-7-yl)dibenzo[b,d]thiophene-2-yl)-9-phenyl-9H-carbazole, has the following structure: The preparation method of the pure violet organic electroluminescent material Cz3-DBT-BO includes the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0036] Step (4), synthesis of intermediate 3-(8-bromodibenzo[b,d]thiophene-2-yl)-9-phenyl-9H-carbazole: Under a nitrogen atmosphere, 2,8-dibromodibenzothiophene (3010 mg, 8.8 mmol), (9-phenyl-9H-carbazole-3-yl)boronic acid (2297 mg, 8 mmol), tetrakis(triphenylphosphine)palladium (370 mg, 0.32 mmol), and potassium carbonate (2211 mg, 16 mmol) were added to a 250 mL double-necked round-bottom flask. Water (8 mL), ethanol (8 mL), and toluene (60 mL) were then added, and the reaction mixture was heated to 100°C and refluxed for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried over anhydrous MgSO4. After evaporation of the solvent under reduced pressure, the residue was purified by silica gel column chromatography using petroleum ether / dichloromethane (20:1, v / v) as the eluent. Finally, the crude product was recrystallized from methanol to give a white solid (1735 mg, yield: 43%).

[0037] Step (5), synthesis of the target molecule 3-(8-(2,12-di-tert-butyl-5,9-dioxo-13b-boronaphthalene[3,2,1-de]anthracite-7-yl)dibenzo[b,d]thiophene-2-yl)-9-phenyl-9H-carbazole: Intermediate 3-(8-bromodibenzo[b,d]thiophen-2-yl)-9-phenyl-9H-carbazole (2018 mg, 4 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b- boronaphtho[3,2,1-de]anthracene (2033 mg, 4.4 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round bottom flask under nitrogen atmosphere. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C for 24 h under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the obtained residue was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (2095 mg, yield: 65%).

[0038] 1 H NMR (400 MHz, Chloroform- d ) δ 8.70 (d, J = 2.5 Hz, 2H), 8.58 (d, J =1.8 Hz, 1H), 8.51 (d, J = 1.8 Hz, 1H), 8.44 (d, J = 1.8 Hz, 1H), 8.24 – 8.20 (m,1H), 7.91 (t, J = 8.5 Hz, 2H), 7.83 – 7.79 (m, 2H), 7.75 – 7.70 (m, 3H), 7.57(s, 2H), 7.55 (d, J = 6.9 Hz, 5H), 7.46 (d, J = 8.8 Hz, 3H), 7.38 (d, J = 3.7 Hz,2H), 7.28 – 7.24 (m, 1H), 1.43 (s, 18H). Example 4 Pure violet organic electroluminescent material Cz9-DBT-BO A pure violet organic electroluminescent material, Cz9-DBT-BO, namely 9-(4-(8-(2,12-di-tert-butyl-5,9-dioxo-13b-boronaphtho[3,2,1-de]fluorene-7-yl)dibenzo[b,d]thiophen-2-yl)phenyl)-9H-carbazole, has the following structure: A method for preparing the pure violet organic electroluminescent material, Cz9-DBT-BO, includes the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0039] Step (4), synthesis of intermediate 9-(4-(8-bromodibenzo[b,d]thiophen-2-yl)phenyl)-9H-carbazole: Under a nitrogen atmosphere, 2,8-dibromodibenzo-thiophene (3010 mg, 8.8 mmol), (4-(9H-carbazol-9-yl)phenyl)boronic acid (2297 mg, 8 mmol), tetrakis(triphenylphosphine)palladium (370 mg, 0.32 mmol) and potassium carbonate (2211 mg, 16 mmol) were added to a 250 mL two-necked round-bottomed flask. Water (8 mL), ethanol (8 mL) and toluene (60 mL) were then added and the reaction was heated to 100°C under reflux for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (2139 mg, yield: 53%).

[0040] Step (5), synthesis of the target molecule 9-(4-(8-(2,12-di-tert-butyl-5,9-dioxo-13b-boronaphtho[3,2,1-de]fluorene-7-yl)dibenzo[b,d]thiophen-2-yl)phenyl)-9H-carbazole: Intermediate 9-(4-(8-bromodibenzo[b,d]thiophen-2-yl)phenyl)-9H-carbazole (2018 mg, 4 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b- boronaphtho[3,2,1-de]anthracene (2033 mg, 4.4 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added separately to a 250 mL two-necked round bottom flask under nitrogen atmosphere. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C for 24 h under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the obtained residue was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (2031 mg, yield: 63%).

[0041] 1H NMR (400 MHz, Chloroform- d ) δ 8.78 (d, J = 2.5 Hz, 2H), 8.64 (d, J =1.7 Hz, 1H), 8.57 (d, J = 1.7 Hz, 1H), 8.18 (dt, J = 7.7, 1.0 Hz, 2H), 8.02 (d, J =1.7 Hz, 1H), 8.01 – 7.99 (m, 2H), 7.98 (d, J = 1.8 Hz, 1H), 7.92 (dd, J = 8.3,1.8 Hz, 1H), 7.84 (dd, J = 8.3, 1.8 Hz, 1H), 7.79 (dd, J = 8.8, 2.5 Hz, 2H), 7.74– 7.71 (m, 2H), 7.61 (s, 2H), 7.54 – 7.51 (m, 4H), 7.47 – 7.43 (m, 2H), 7.34– 7.30 (m, 2H), 1.50 (s, 18H). Example 5 Pure violet organic electroluminescent material BONA2O A pure purple light organic electroluminescent material BONA2O, namely 2,12-di-tert-butyl-7-(8-(dibenzo[b,d]furan-2-yl)naphthalen-1-yl)-5,9-dioxo-13b-bora-naphthacene[3,2,1-de]anthracene, has the following structure: A preparation method of the pure purple light organic electroluminescent material BONA2O, comprising the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0042] Synthesis of intermediate 2-(8-bromonaphthalen-1-yl)dibenzo[b,d]furan in step (4): Under a nitrogen atmosphere, 1,8-dibromonaphthalene (1716 mg, 6 mmol), dibenzo[b,d]furan-2-ylboronic acid (1493 mg, 4 mmol), tetrakis(triphenylphosphine)palladium (277 mg, 0.24 mmol) and potassium carbonate (1104 mg, 8 mmol) were added to a 250 mL two-necked round-bottomed flask. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100°C under reflux for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgSO4. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (881 mg, yield: 59%).

[0043] Synthesis of target molecule 2,12-di-tert-butyl-7-(8-(dibenzo[b,d]furan-2-yl)naphthalen-1-yl)-5,9-dioxo-13b-bora-naphthacene[3,2,1-de]anthracene in step (5): Intermediate 2-(8-bromonaphthalen-1-yl)dibenzo[b,d]furan (1493 mg, 4 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b- boronaphtho[3,2,1-de]anthracene (2236 mg, 4.4 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round bottom flask under nitrogen atmosphere. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C for 24 h under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the obtained residue was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1376 mg, yield: 51 %).

[0044] 1 H NMR (400 MHz, Chloroform- d ) δ 8.48 (d, J = 2.5 Hz, 1H), 8.27 (d, J =2.5 Hz, 1H), 7.96 (ddd, J = 14.7, 7.7, 2.0 Hz, 2H), 7.72 – 7.68 (m, 1H), 7.66(dd, J = 8.7, 2.5 Hz, 1H), 7.60 (d, J = 1.7 Hz, 1H), 7.57 – 7.51 (m, 4H), 7.38(dd, J = 8.8, 2.4 Hz, 1H), 7.29 (d, J = 8.7 Hz, 1H), 7.08 (d, J = 2.0 Hz, 1H), 6.99(dd, J = 8.3, 1.7 Hz, 1H), 6.88 (d, J = 1.2 Hz, 1H), 6.83 (d, J = 8.7 Hz, 1H), 6.77– 6.72 (m, 2H), 6.69 (d, J = 8.4 Hz, 1H), 6.52 (d, J= 1.2 Hz, 1H), 1.40 (d, J =22.3 Hz, 18H). Example 6 Pure violet organic electroluminescent material BONA2S A pure violet organic electroluminescent material BONA2S, namely 2,12-di-tert-butyl-7-(8-(dibenzo[b,d]thiophen-2-yl)naphthalen-1-yl)-5,9-dioxo-13b-boratanaphthacene[3,2,1-de]anthracene, whose structure is as follows: The method for preparing the pure violet organic electroluminescent material BONA2S comprises the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0045] Synthesis of intermediate 2-(8-bromonaphthalen-1-yl)dibenzo[b,d]thiophene in step (4): Under a nitrogen atmosphere, 1,8-dibromonaphthalene (1716 mg, 6 mmol), dibenzo[d,b]thiophen-2-ylboronic acid (913 mg, 4 mmol), tetrakis(triphenylphosphine)palladium (277 mg, 0.24 mmol) and potassium carbonate (1104 mg, 8 mmol) were added to a 250 mL two-necked round-bottomed flask. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100°C under reflux for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (860 mg, yield: 54%).

[0046] Synthesis of target molecule 2,12-di-tert-butyl-7-(8-(dibenzo[b,d]thiophen-2-yl)naphthalen-1-yl)-5,9-dioxo-13b-boratanaphthacene[3,2,1-de]anthracene in step (5): Intermediate 2-(8-bromonaphthalen-1-yl)dibenzo[b,d]thiophene (1557 mg, 4 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b- boronaphtho[3,2,1-de]anthracene (2236 mg, 4.4 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round bottom flask under nitrogen atmosphere. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C for 24 h under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the obtained residue was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1437 mg, yield: 52 %).

[0047] 1 H NMR (400 MHz, Chloroform- d ) δ 8.57 (d, J = 2.5 Hz, 1H), 8.44 (d, J =2.5 Hz, 1H), 8.05 (td, J = 7.8, 1.8 Hz, 2H), 7.77 (d, J = 8.1 Hz, 1H), 7.76 –7.72 (m, 1H), 7.66 – 7.60 (m, 3H), 7.57 (dt, J = 7.0, 1.3 Hz, 2H), 7.45 (dd, J =8.8, 2.5 Hz, 1H), 7.40 (d, J = 8.8 Hz, 1H), 7.26 (s, 1H), 7.24 (s, 1H), 7.19(dd, J = 8.1, 1.7 Hz, 1H), 7.09 (ddd, J = 8.0, 7.0, 1.1 Hz, 1H), 7.04 (d, J = 8.0Hz, 1H), 6.90 (d, J = 1.2 Hz, 1H), 6.86 – 6.81 (m, 2H), 6.49 (d, J= 1.2 Hz, 1H),1.52 (s, 9H), 1.50 (s, 9H). Example 7 Pure-violet organic electroluminescent material BONACz3 A pure-violet organic electroluminescent material BONACz3, namely 3-(8-(2,12-di-tert-butyl-5,9-dioxo-13b-boronaphtho[3,2,1-de]anthracen-7-yl)naphthalen-1-yl)-9- phenyl-9H-carbazole, has the following structure: A method for preparing the pure-violet organic electroluminescent material BONACz3, comprising the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0048] Synthesis of intermediate 3-(8-bromonaphthalen-1-yl)-9-phenyl-9H-azaxanthene in step (4): Under a nitrogen atmosphere, 1,8-dibromonaphthalene (1716 mg, 6 mmol), (9-phenyl-9H-carbazol-3-yl)boronic acid (1149 mg, 4 mmol), tetrakis(triphenylphosphine)palladium (277 mg, 0.24 mmol) and potassium carbonate (1104 mg, 8 mmol) were added to a 250 mL two-necked round-bottomed flask. Then water (6 mL), ethanol (6 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C under reflux for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (628 mg, yield: 35%).

[0049] Synthesis of target molecule 2,12-di-tert-butyl-7-(8-(dibenzo[b,d]furan-2-yl)naphthalen-1-yl)-5,9-dioxo-13b-boronaphtho[3,2,1-de]anthracene in step (5): Intermediate 3-(8-bromonaphthalen-1-yl)-9-phenyl-9H-xanthene (1793 mg, 4 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b- boronaphtho[3,2,1-de]anthracene (2236 mg, 4.4 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round bottom flask under nitrogen atmosphere. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C for 24 h under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1649 mg, yield: 55 %).

[0050] 1 H NMR (400 MHz, Chloroform- d ) δ 8.55 (d, J = 2.5 Hz, 1H), 8.40 (d, J =2.5 Hz, 1H), 8.04 (ddd, J = 9.4, 8.0, 1.6 Hz, 2H), 7.76 (dd, J = 8.8, 2.5 Hz,1H), 7.64 – 7.58 (m, 3H), 7.56 (dd, J = 6.2, 1.6 Hz, 1H), 7.53 (dd, J = 3.8, 1.6Hz, 1H), 7.49 – 7.46 (m, 1H), 7.45 (d, J = 1.8 Hz, 1H), 7.43 (d, J = 8.7 Hz, 1H),7.12 (dd, J = 8.4, 1.8 Hz, 1H), 6.92 (d, J = 8.4 Hz, 2H), 6.86 (t, J = 1.2 Hz, 1H),6.85 – 6.83 (m, 1H), 6.81 (dd, J = 7.3, 1.4 Hz, 1H), 6.77 (dd,J = 8.1, 1.3 Hz, 1H), 6.59 (d, J = 1.2 Hz, 1H), 1.50 (d, J = 11.8 Hz, 18H). Example 8 BONACz9, a pure violet organic electroluminescent material A pure violet organic electroluminescent material, BONACz9, namely 9-(4-(8-(2,12-di-tert-butyl-5,9-dioxo-13b-boronaphthalene[3,2,1-de]anthracene-7-yl)naphth-1-yl)phenyl)-9H-carbazole, has the following structure: The preparation method of the pure violet organic electroluminescent material BONACz9 includes the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0051] Step (4) Synthesis of intermediate 9-(4-(8-bromonaphth-1-yl)phenyl)-9H-azaanthracene: Under a nitrogen atmosphere, 1,8-dibromonaphthalene (1716 mg, 6 mmol), (9-phenyl-9H-carbazole-3-yl)boronic acid (1149 mg, 4 mmol), tetrakis(triphenylphosphine)palladium (277 mg, 0.24 mmol), and potassium carbonate (1104 mg, 8 mmol) were added to a 250 mL double-necked round-bottom flask. Water (6 mL), ethanol (6 mL), and toluene (60 mL) were then added, and the reaction mixture was heated to 100°C and refluxed for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried over anhydrous MgSO4. After evaporation of the solvent under reduced pressure, the residue was purified by silica gel column chromatography using petroleum ether / dichloromethane (20:1, v / v) as the eluent. Finally, the crude product was recrystallized from methanol to give a white solid (771 mg, yield: 43%).

[0052] Step (5), synthesis of the target molecule 9-(4-(8-(2,12-di-tert-butyl-5,9-dioxo-13b-boronnaphthalene[3,2,1-de]anthracene-7-yl)naphthalene-1-yl)phenyl)-9H-carbazole: Intermediate 9-(4-(8-bromonaphthalen-1-yl)phenyl)-9H-aza xanthene (1793 mg, 4 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b- boronaphtho[3,2,1-de]anthracene (2236 mg, 4.4 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round bottom flask under nitrogen atmosphere. Then water (4 mL), ethanol (4 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C for 24 h under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the obtained residue was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1589 mg, yield: 53 %).

[0053] 1 H NMR (400 MHz, Chloroform- d ) δ 8.62 (d, J = 2.5 Hz, 2H), 8.07 – 8.02(m, 2H), 7.88 (d, J = 7.8 Hz, 2H), 7.74 (dd, J = 8.8, 2.5 Hz, 2H), 7.69 – 7.64(m, 2H), 7.64 (s, 2H), 7.58 (dd, J = 7.1, 1.4 Hz, 1H), 7.45 (d, J = 8.7 Hz, 2H),7.40 – 7.37 (m, 2H), 7.07 (d, J = 2.0 Hz, 1H), 7.05 (s, 3H), 6.98 (t, J = 7.4 Hz,2H), 6.64 (d, J = 58.9 Hz, 3H), 1.46 (s, 18H). Example 9 Pure violet organic electroluminescent material BNS14 A pure purple light organic electroluminescent material BNS14, namely 2,12-di-tert-butyl-7-(4-(dibenzo[b,d]thiophen-4-yl)naphthalen-1-yl)-5,9-dioxo-13b- boronaphtho[3,2,1-de]anthracene, has the following structure: A preparation method of the pure purple light organic electroluminescent material BNS14, comprising the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0054] Synthesis of intermediate 4-(4-bromonaphthalen-1-yl)dibenzo[b,d]thiophene in step (4): Under a nitrogen atmosphere, 1,4-dibromonaphthalene (1716 mg, 6 mmol), dibenzo[b,d]thiophen-4-ylboronic acid (912 mg, 4 mmol), tetrakis(triphenylphosphine)palladium (277 mg, 0.24 mmol) and potassium carbonate (1104 mg, 8 mmol) were added to a 250 mL two-necked round-bottomed flask. Then water (6 mL), ethanol (6 mL) and toluene (60 mL) were added and the reaction was heated to 100°C under reflux for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgSO4. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (872 mg, yield: 56%).

[0055] Synthesis of target molecule 2,12-di-tert-butyl-7-(4-(dibenzo[b,d]thiophen-4-yl)naphthalen-1-yl)-5,9-dioxo-13b-boronaphtho[3,2,1-de]anthracene in step (5): Intermediate 4-(4-bromonaphthalen-1-yl)dibenzo[b,d]thiophene (1947 mg, 5 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b- boronaphtho[3,2,1-de]anthracene (2795 mg, 5.5 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round bottom flask under nitrogen atmosphere. Then water (5 mL), ethanol (5 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C for 24 h under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1243 mg, yield: 45 %).

[0056] Example 10 Pure violet organic electroluminescent material BNS15 A pure violet organic electroluminescent material BNS15, namely 2,12-di-tert-butyl-7-(5- (dibenzo[b,d]thiophen-4-yl)naphthalen-1-yl)-5,9-dioxo-13b-boronaphtho[3,2,1-de]anthracene, whose structure is as follows: The method for preparing the pure violet organic electroluminescent material BNS15 comprises the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0057] Synthesis of intermediate 4-(5-bromonaphthalen-1-yl)dibenzo[b,d]thiophene in step (4): Under a nitrogen atmosphere, 1,5-dibromonaphthalene (1716 mg, 6 mmol), dibenzo[b,d]thiophene-4-ylboronic acid (912 mg, 4 mmol), tetrakis(triphenylphosphine)palladium (277 mg, 0.24 mmol) and potassium carbonate (1104 mg, 8 mmol) were added to a 250 mL two-necked round-bottomed flask. Then water (6 mL), ethanol (6 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C under reflux for 12 h. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (763 mg, yield: 49%).

[0058] Step (5), synthesis of the target molecule 2,12-di-tert-butyl-7-(5-(dibenzo[b,d]thiophen-4-yl)naphthalen-1-yl)-5,9-dioxa-13b-boronaphtho[3,2,1-de]anthracene: Under a nitrogen atmosphere, intermediate 4-(5-bromonaphthalen-1-yl)dibenzo[b,d]thiophene (1947 mg, 5 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxa-13b-boronaphtho[3,2,1-de]anthracene (2795 mg, 5.5 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round-bottomed flask, respectively. Then water (5 mL), ethanol (5 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C under reflux for 24 h. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1727 mg, yield: 50%).

[0059] Example 11 Pure violet organic electroluminescent material BNS26 A pure violet organic electroluminescent material BNS26, namely 2,12-di-tert-butyl-7-(4-(dibenzo[b,d]thiophen-4-yl)naphthalen-1-yl)-5,9-dioxa-13b-boronaphtho[3,2,1-de]anthracene, has the following structure: The preparation method of the pure violet organic electroluminescent material BNS26 comprises the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0060] Synthesis of intermediate 4-(6-bromonaphthalen-2-yl)dibenzo[b,d]thiophene in step (4): Under a nitrogen atmosphere, 2,6-dibromonaphthalene (1716 mg, 6 mmol), dibenzo[b,d]thiophene-4-ylboronic acid (912 mg, 4 mmol), tetrakis(triphenylphosphine)palladium (277 mg, 0.24 mmol) and potassium carbonate (1104 mg, 8 mmol) were added to a 250 mL two-necked round-bottomed flask. Then water (6 mL), ethanol (6 mL) and toluene (60 mL) were added and the reaction was heated to 100°C under reflux for 12 hours. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (701 mg, yield: 45%).

[0061] Synthesis of target molecule 2,12-di-tert-butyl-7-(4-(dibenzo[b,d]thiophen-4-yl)naphthalen-1-yl)-5,9-dioxo-13b-boronaphtho[3,2,1-de]anthracene in step (5): Intermediate 4-(6-bromonaphthalen-2-yl)dibenzo[b,d]thiophene (1947 mg, 5 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-l,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b- boranaphtho[3,2,l-de]anthracene (2795 mg, 5.5 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added to a 250 mL two-necked round bottom flask under nitrogen atmosphere. Then water (5 mL), ethanol (5 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C for 24 h under reflux. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50: 1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1437 mg, yield: 52 %).

[0062] Example 12 Pure violet organic electroluminescent material BNS27 A pure violet organic electroluminescent material BNS27, namely 2,12-di-tert-butyl-7-(7-(dibenzo[b,d]thiophen-4-yl)naphthalen-2-yl)-5,9-dioxo-13b-boranaphtho[3,2,l- de]anthracene, whose structure is as follows: A process for the preparation of the pure violet organic electroluminescent material BNS27, comprising the following steps: Steps (1), (2) and (3) are the same as in Example 1.

[0063] Synthesis of intermediate 4-(7-bromonaphthalen-2-yl)dibenzo[b,d]thiophene in step (4): Into a 250 mL two-necked round-bottom flask, under nitrogen atmosphere, 1,4-dibromonaphthalene (1716 mg, 6 mmol), dibenzo[b,d]thiophene-4-ylboronic acid (912 mg, 4 mmol), tetrakis(triphenylphosphine)palladium (277 mg, 0.24 mmol) and potassium carbonate (1104 mg, 8 mmol) were added. Then water (6 mL), ethanol (6 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C under reflux for 12 h. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (20:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (825 mg, yield: 53%).

[0064] Step (5), synthesis of the target molecule 2,12-di-tert-butyl-7-(4-(dibenzo[b,d]thiophen-4-yl)naphthalen-1-yl)-5,9-dioxo-13b-boronaphtho[3,2,1-de]anthracene: Into a 250 mL two-necked round-bottom flask, under nitrogen atmosphere, intermediate 4-(7-bromonaphthalen-2-yl)dibenzo[b,d]thiophene (1947 mg, 5 mmol), 2,12-di-tert-butyl-7-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-5,9-dioxo-13b-boronaphtho[3,2,1-de]anthracene (2795 mg, 5.5 mmol) and tetrakis(triphenylphosphine)palladium (185 mg, 0.16 mmol) were added. Then water (5 mL), ethanol (5 mL) and toluene (60 mL) were added and the reaction was heated to 100 °C under reflux for 24 h. After cooling to room temperature, the reaction mixture was poured into brine and extracted three times with dichloromethane. The organic phase was dried using anhydrous MgS04. After evaporation of the solvent under reduced pressure, the residue obtained was purified by column chromatography on silica gel using petroleum ether / dichloromethane (50:1, v / v) as eluent to receive the product. Finally, the crude product was recrystallized in methanol to obtain a white solid (1105 mg, yield: 40 %).

[0065] Structural and spectral tests of the pure purple light organic electroluminescent materials constructed with boron oxygen as the core of examples 1-8: (1) nuclear magnetic resonance hydrogen spectrum; (2) mass spectrum; (3) thermodynamic property; (4) optical physical property Figures 1-32 The nuclear magnetic resonance hydrogen spectrum, mass spectrum, thermogravimetric curve and photoluminescence spectrum of the pure purple light organic electroluminescent materials of examples 1-8, respectively. FromFigures 1-32 It can be seen that pure purple light organic electroluminescent materials NA-DBT-BO, PY-DBT-BO, Cz3-DBT-BO, Cz9-DBT-BO, BONA2O, BONA2S, BONACz3 and BONACz9 constructed with boron oxygen as the core are successfully synthesized, and their molecular structures are confirmed by nuclear magnetic hydrogen spectrum and mass spectrum. The thermal gravimetric analysis (TGA) test found that these materials all have excellent stability, and the thermal decomposition temperature (5 wt% weight loss) is above 368 ℃. At the same time, the materials show high efficient pure purple light emission in doped thin films.

[0066] Example 13 The doped device performance test of pure purple light organic electroluminescent materials NA-DBT-BO, PY-DBT-BO, Cz3-DBT-BO and Cz9-DBT-BO constructed with boron oxygen as the core.

[0067] The following is to prepare the pure purple light organic electroluminescent materials NA-DBT-BO, PY-DBT-BO, Cz3-DBT-BO and Cz9-DBT-BO constructed with boron oxygen as the core, respectively as the light emitting layer material, the host uses commercial material CBP, using vacuum evaporation method to prepare doped organic electroluminescent devices (named D1, D2, D3 and D4, respectively), and test its device performance.

[0068] The specific device structure of D1-D4 is: ITO / HAT-CN (20 nm) / TAPC (30 nm) / TCTA (15nm) / mCP (10 nm) / CBP: emitter (2 wt%, 20 nm) / TPBi (35 nm) / LiF (1 nm) / Al(100 nm).

[0069] The specific molecular structure of each functional layer material is as follows: The organic electroluminescent devices D1, D2, D3 and D4 are tested for photoelectric performance by Keithley 2450 series digital source meter and LS160 luminance meter, and the test results are shown in Table 1.

[0070] Table 1 Test data of organic electroluminescent devices D1, D2, D3 and D4 Figures 33-36The external quantum efficiency-luminance characteristic curves and electroluminescence spectra of the doped devices using the pure purple light organic electroluminescent materials NA-DBT-BO, PY-DBT-BO, Cz3-DBT-BO and Cz9-DBT-BO constructed with boron oxygen as the core according to Examples 1-4 were obtained. As can be seen from the figures and Table 1, the emission peaks thereof are located in the pure purple light region, and the peak positions are 405, 405, 406 and 403 nm, respectively. At the same time, they exhibit excellent color purity, and the half-peak widths are 25, 26, 25 and 37 nm, respectively. The corresponding color coordinates are (0.166, 0.015), (0.166, 0.019), (0.166, 0.018) and (0.168, 0.020), respectively. The maximum external quantum efficiencies are 6.46%, 5.32%, 5.38% and 7.44%, respectively.

[0071] Example 14 The performance of the doped organic electroluminescent devices of BONA2O and BONA2S, the pure purple light organic electroluminescent materials constructed with boron oxygen as the core.

[0072] The doped organic electroluminescent devices (named D5 and D6, respectively) were prepared by vacuum evaporation using BONA2O and BONA2S, the pure purple light organic electroluminescent materials constructed with boron oxygen as the core prepared in Example 5 and Example 6, respectively, as the light-emitting layer material, and CBP as the host, and the device performance was tested.

[0073] The specific device structure of D5-D6 was: ITO / HAT-CN (20 nm) / TAPC (45 nm) / TCTA (10 nm) / CBP: emitter (2 wt%, 20 nm) / TPBi (35 nm) / LiF (1 nm) / Al (100 nm).

[0074] The photoelectric performance of the organic electroluminescent devices D5 and D6 was tested by Keithley 2450 series digital source meter and LS160 luminance meter, and the test results are shown in Table 2.

[0075] Table 2 Test data of organic electroluminescent devices D5 and D6 Figure 37 and 38The external quantum efficiency-luminance characteristic curves and electroluminescence spectra of the devices doped with the pure purple light organic electroluminescent materials BONA2O and BONA2S constructed by using the boron-oxygen as the core according to Examples 4 and 5 were obtained. As can be seen from the figures and Table 2, the emission peaks thereof are located in the pure purple light region, and the peak positions are 406 and 412 nm, respectively. At the same time, they exhibit excellent color purity, and the half-peak widths are 26 and 31 nm, respectively. The corresponding color coordinates are (0.167, 0.018) and (0.166, 0.016), respectively. The maximum external quantum efficiencies are 7.02% and 5.47%, respectively.

[0076] In addition, it should be understood that, although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the present specification is described in this way only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. An organic electroluminescent device, characterized by comprising: The organic electroluminescent device is composed of a cathode, an anode and a plurality of organic functional layers between the two electrodes, at least one of the organic functional layers is a light-emitting layer, the raw material of the light-emitting layer comprises a pure purple light organic electroluminescent material with a boron-oxygen skeleton as a core, and the structure of the pure purple light organic electroluminescent material is formula I or formula II: I Ⅱ In the formula, R1 is one of the following structural units: ； R2 is a structure containing a naphthyl group.

2. The organic electroluminescent device according to claim 1, wherein The R2 is one of the following structural units: 。 3. The organic electroluminescent device according to claim 1, wherein The light-emitting layer further comprises a host material, the host material is doped with the pure purple light organic electroluminescent material to obtain a doped film, and the host material is N,N'-dicarbazolyl-4,4'-biphenyl, 1,3-biscarbazol-9-ylbenzene, 9,10-dinaphthylanthracene, 9,10-bis(2-naphthyl)-2-methylanthracene or 9-(4-(10-phenylanthracene-9-yl)phenyl)-9H-carbazole.

4. The organic electroluminescent device according to claim 3, characterized in that The mass ratio of the pure purple light organic electroluminescent material to the host material is 1:99-99:

1.

5. The organic electroluminescent device according to claim 1, wherein The preparation process of the pure purple light organic electroluminescent material is as follows: S1: under nitrogen protection, 2,5-dibromo-1,3-difluorobenzene and 4-tert-butylphenol are used as raw materials to obtain an intermediate 1 under a first catalytic system; S2: under nitrogen protection, the intermediate 1 obtained in step S1 is used as a raw material to obtain an intermediate 2 through a cyclization reaction under a second catalytic system; S3: under nitrogen protection, pinacol diboron and the intermediate 2 obtained in step S2 are used as raw materials to obtain an intermediate 3 through a boron esterification reaction under a third catalytic system; S4: under nitrogen protection, 2,8-dibromodibenzothiophene or dibromo R2 and R1 of boric acid or boron esterification R1 are used as raw materials to obtain an intermediate 4 through a Suzuki coupling reaction under a palladium catalytic system; S5: under nitrogen protection, the intermediate 3 and the intermediate 4 are used as raw materials to obtain the pure purple light organic electroluminescent material through a Suzuki coupling reaction under a palladium catalytic system.

6. The organic electroluminescent device according to claim 5, characterized in that In step S1, the molar ratio of 2,5-dibromo-1,3-difluorobenzene to 4-tert-butylphenol is 1:3-30, and the first catalytic system is potassium carbonate.

7. The organic electroluminescent device according to claim 5, wherein The second catalytic system is n-butyl lithium and boron tribromide.

8. The organic electroluminescent device according to claim 5, wherein In step S3, the molar ratio of the intermediate 2 to pinacol diboron is 1:2-5, and the third catalytic system is potassium acetate and [1,1'-bis(diphenylphosphino)ferrocene]palladium dichloride.

9. The organic electroluminescent device according to claim 5, wherein In step S4, the molar ratio of 2,8-dibromodibenzothiophene or dibromo R2 to R1 of boric acid or boron esterification R1 is 1-2:1, and the palladium catalytic system is potassium carbonate and tetrakis(triphenylphosphine)palladium.

10. The organic electroluminescent device according to claim 5, wherein In step S5, the molar ratio of the intermediate 3 to the intermediate 4 is 1-2:1, and the palladium catalytic system is potassium carbonate and tetrakis(triphenylphosphine)palladium.

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