Organic electroluminescent compound, preparation method thereof, organic electroluminescent device and display device

Abstract

The invention discloses an organic electroluminescent compound, a preparation method thereof, an organic electroluminescent device and a display device, and relates to the technical field of luminescent materials. The blue multi-resonance thermally activated delayed fluorescent material with high color purity, high luminous efficiency and high stability, namely the organic electroluminescent compound, is designed by utilizing the multi-resonance effect of carbonyl and nitrogen atoms through an intramolecular cyclization strategy, and meanwhile, the material is excellent in electroluminescent performance and has a wide application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of luminescent materials, and in particular to an organic electroluminescent compound and a preparation method thereof, an organic electroluminescent device and a display device. Background Art

[0002] Organic light-emitting diodes (OLEDs) are widely used in display screens, lighting and other fields due to their advantages such as flexible display, low energy consumption and high contrast. Among them, efficient and stable blue light-emitting materials are crucial to achieving full-color display and white light OLEDs. However, the research and development of blue light-emitting materials faces many challenges, especially in terms of color purity, luminous efficiency and device life. Traditional charge transfer light-emitting materials often have problems of low color purity, low luminous efficiency and poor thermal stability, which cannot meet the needs of practical applications.

[0003] The above contents are only used to assist in understanding the technical solution of the present invention and do not constitute an admission that the above contents are prior art. Summary of the invention

[0004] The main purpose of the present invention is to provide an organic electroluminescent compound and a preparation method thereof, an organic electroluminescent device and a display device, aiming to improve the color purity, luminous efficiency and thermal stability of the material.

[0005] To achieve the purpose of the present invention, the present invention provides an organic electroluminescent compound, the structure of the organic electroluminescent compound is: ; Wherein, R is selected from one of the following structural formulas: .

[0006] In one embodiment, the organic electroluminescent compound has a structural formula of at least one of the following structural formulas: .

[0007] The present invention also provides a method for preparing the organic electroluminescent compound as described above, comprising the following steps: Using 5-bromo-2-iodoisophthalic acid dimethyl ester and 9,9-dimethylacridine as raw materials, 5-bromo-2-(9,9-dimethyl-9H-acridine-10-yl)isophthalic acid dimethyl ester was synthesized; Using 5-bromo-2-(9,9-dimethyl-9H-acridin-10-yl)isophthalic acid dimethyl ester as raw material, 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione is obtained after intramolecular cyclization reaction; The organic electroluminescent compound is synthesized by taking 6-bromo-12,12-dimethyl-benzoquinoline acridiniumdione as a raw material.

[0008] In one embodiment, the steps of synthesizing the organic electroluminescent compound using 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione as a raw material include: An organic electroluminescent compound is synthesized using 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione and phenylboronic acid as raw materials. The structural formula of the organic electroluminescent compound is .

[0009] In one embodiment, the steps of synthesizing the organic electroluminescent compound using 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione as a raw material include: An organic electroluminescent compound is synthesized using 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione and 2-pyrimidine boronic acid as raw materials. The structural formula of the organic electroluminescent compound is .

[0010] The present invention also provides an organic electroluminescent device, which includes an anode, a cathode and an organic thin film layer, wherein the organic thin film layer is arranged between the anode and the cathode, and the organic thin film layer includes at least one organic light-emitting layer, and the organic light-emitting layer includes the organic electroluminescent compound as described above.

[0011] In one embodiment, the mass of the organic electroluminescent compound accounts for 1wt%-10wt% of the mass of the organic light-emitting layer; and / or the thickness of the light-emitting layer is 20nm-40nm.

[0012] In one embodiment, the organic thin film layer also includes a hole injection layer, a hole transport layer, an electron transport layer and an electron injection layer, and the anode, the hole injection layer, the hole transport layer, the organic light-emitting layer, the electron transport layer, the electron injection layer and the cathode are arranged in sequence along the height direction of the organic electroluminescent device.

[0013] In one embodiment, the organic thin film layer further includes an electron blocking layer, a hole blocking layer and an exciton blocking layer, the electron blocking layer is arranged between the hole transport layer and the organic light-emitting layer, the hole blocking layer is arranged between the organic light-emitting layer and the electron transport layer, and the exciton blocking layer is arranged between the organic light-emitting layer and the hole transport layer or between the organic light-emitting layer and the electron transport layer.

[0014] The present invention also provides a display device, which includes the organic electroluminescent device as described above.

[0015] The present invention adopts the strategy of intramolecular cyclization and utilizes the multiple resonance effects of carbonyl and nitrogen atoms to design a blue multiple resonance thermally activated delayed fluorescence material with high color purity, high luminous efficiency and high stability, that is, an organic electroluminescent compound. At the same time, the material has excellent electroluminescent performance and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 This is the electroluminescence spectrum of the organic electroluminescent compound P2 of the present invention.

[0018] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0019] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0020] To make the purpose, technical scheme and advantages of the embodiment of the present invention clearer, the technical scheme in the embodiment of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiment, it is carried out according to the normal conditions or the conditions recommended by the manufacturer. If the reagents or instruments used do not specify the manufacturer, they are all conventional products that can be purchased commercially. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes, taking "A and / or B" as an example, including scheme A, or scheme B, or schemes that A and B meet at the same time. In addition, the technical schemes between the various embodiments can be combined with each other, but must be based on the ability of ordinary technicians in the field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that the combination of such technical solutions does not exist, and is not within the scope of protection required by the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present invention.

[0021] In order to solve the problems of low color purity, low luminous efficiency and poor thermal stability existing in traditional charge transfer type luminescent materials, the present invention provides an organic electroluminescent compound.

[0022] Due to its unique molecular orbital distribution characteristics, the multi-resonance thermally activated delayed fluorescence (MR-TADF) material can achieve efficient electroluminescence and has a narrow emission bandwidth, which makes it have great potential in the development of blue luminescent materials. To this end, the organic electroluminescent compound provided by the present invention is a blue MR-TADF material.

[0023] The present invention adopts the strategy of intramolecular cyclization and utilizes the multiple resonance effects of carbonyl and nitrogen atoms to design a blue multiple resonance thermally activated delayed fluorescent material with high color purity, high luminous efficiency and high stability. At the same time, the material has excellent electroluminescent performance and has broad application prospects.

[0024] The structure of the organic electroluminescent compound provided by the present invention is: ; Wherein, R is selected from one of the following structural formulas: .

[0025] In one embodiment of the present invention, the structural formula of the organic electroluminescent compound is at least one of the following structural formulas: .

[0026] The present invention introduces nitrogen carbonyl groups by doping boron-nitrogen (or oxygen) atoms into the molecular structure to achieve a narrow half-peak width, thereby further improving the color purity and stability of the material.

[0027] The present invention also provides a method for preparing the above organic electroluminescent compound, comprising the following steps: (1) Synthesis of intermediate product M1: Using 5-bromo-2-iodoisophthalic acid dimethyl ester and 9,9-dimethylacridine as raw materials, 5-bromo-2-(9,9-dimethyl-9H-acridine-10-yl)isophthalic acid dimethyl ester, namely M1, was synthesized; Specifically, under a nitrogen atmosphere, 9,9-dimethylacridine, 5-bromo-2-iodoisophthalic acid dimethyl ester, copper powder, cuprous iodide, potassium carbonate and a mixture of 18-crown-6 are added to a double-necked flask, and o-dichlorobenzene is used as a solvent. The mixture is heated to reflux and stirred for 48h to 96h to fully react. After cooling to room temperature, the reaction mixture is poured into a large amount of water, extracted three times with dichloromethane, the organic layer is dried with magnesium sulfate, and concentrated under reduced pressure. The crude product is then purified by silica gel column chromatography (the eluent is a mixed solvent of dichloromethane and petroleum ether in a volume ratio of 1:5) to obtain the intermediate product M1. The reaction formula is as follows: .

[0028] (2) Synthesis of intermediate product M2: Using 5-bromo-2-(9,9-dimethyl-9H-acridin-10-yl)isophthalic acid dimethyl ester as raw material, an intramolecular cyclization reaction was performed to obtain 6-bromo-12,12-dimethyl-benzoquinolineacridinedione, namely M2.

[0029] Specifically, 5-bromo-2-(9,9-dimethyl-9H-acridin-10-yl) dimethyl isophthalate and sodium hydroxide are dissolved in a mixed solution of ethanol and water with a volume ratio of 1:1 in a round-bottom flask, and the temperature is raised and refluxed for 12 hours under stirring, wherein the final temperature of the heating operation is the boiling point of the solvent, the same below. After the hydrolysis is complete, it is cooled to room temperature, concentrated to half of the reaction system, and then concentrated hydrochloric acid is added for acidification, filtered and washed with water, and the filter residue is vacuum dried at 80°C to obtain a solid; the above solid is dissolved in ultra-dry dichloromethane in a three-necked flask, and then oxalyl chloride and a few drops of ultra-dry DMF are added. After heating and reflux for 0.5 hours, tin tetrachloride is added and reflux is maintained, and the reaction is continued for 12 hours. After the reaction is complete, cool to room temperature, add a 1 mol / L sodium hydroxide aqueous solution dropwise until neutral, extract with dichloromethane 2-3 times, combine all dichloromethane extraction layers, and dry with anhydrous magnesium sulfate; filter and perform rotary evaporation to obtain a crude product, which is purified by silica gel column chromatography using a mixed solvent of dichloromethane and petroleum ether in a volume ratio of 1:5; collect the purified product, and finally concentrate by rotary evaporation to obtain M2, the reaction formula is as follows: .

[0030] (3) Synthesis of organic electroluminescent compounds: Using 6-bromo-12,12-dimethyl-benzoquinoline acridiniumdione as raw material, an organic electroluminescent compound was synthesized through Suzuki coupling reaction.

[0031] In one embodiment, 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione and phenylboronic acid are used as raw materials to synthesize an organic electroluminescent compound, the structural formula of which is .

[0032] Specifically, under the protection of nitrogen atmosphere, 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione and phenylboronic acid are dissolved in toluene, 0.03 mol~0.05 mol of tetrakistriphenylphosphine palladium is added as a catalyst, and then 2 equivalents of 2 mol / L potassium carbonate solution and a few drops of ethanol are added, and after reacting at 90°C~110°C for 24h-26h, sufficient methanol is added to precipitate solids, and the solids obtained are filtered and washed with acetone to obtain a crude product. Further purification is performed by silica gel column chromatography; finally, the purified product is collected and concentrated by rotary evaporation to obtain an organic electroluminescent compound P1, wherein the reaction formula is as follows: .

[0033] In another embodiment, 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione and 2-pyrimidine boronic acid are used as raw materials to synthesize an organic electroluminescent compound, the structural formula of which is .

[0034] Specifically, under the protection of nitrogen atmosphere, 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione and 2-pyrimidine boronic acid are dissolved in toluene, 0.03 mol~0.05 mol of tetrakistriphenylphosphine palladium is added as a catalyst, and then 2 equivalents of 2 mol / L potassium carbonate solution and a few drops of ethanol are added, and after reacting at 90°C~110°C for 24h-26h, sufficient methanol is added to precipitate solids, and the solids obtained are filtered and washed with acetone to obtain a crude product. Further purification is performed by silica gel column chromatography; finally, the purified product is collected and concentrated by rotary evaporation to obtain an organic electroluminescent compound P2, wherein the reaction formula is as follows: .

[0035] The preparation process of the organic electroluminescent compound of the present invention is relatively simple, the conditions are relatively mild, and the yield is high. At the same time, the electroluminescent performance of the material is relatively excellent, and it has broad application prospects.

[0036] The organic electroluminescent compound and the preparation method thereof of the present invention are described in detail below through specific examples.

[0037] Example 1 This embodiment provides an organic electroluminescent compound with a molecular formula of P1, and a preparation method thereof comprises the following steps: (1) Synthesis of intermediate product M1: Under nitrogen atmosphere, 9,9-dimethylacridine (12.0 mmol, 1.1 eq), 5-bromo-2-iodoisophthalic acid dimethyl ester (10.0 mmol, 1 eq), activated copper powder (1.0 mmol), cuprous iodide (3.0 mmol, 0.3 eq) and a mixture of potassium carbonate (20.0 mmol, 2.0 eq) and 18-crown-6 (2.0 mmol, 0.2 eq) were added to a 250 mL double-necked flask, 100 mL of o-dichlorobenzene was used as solvent, and the mixture was heated under reflux and stirred for 3 days to allow it to react fully. After cooling to room temperature, the reaction mixture was poured into a large amount of water and extracted three times with dichloromethane. The organic layer was dried with magnesium sulfate and concentrated under reduced pressure. The crude product was then purified by silica gel column chromatography (the eluent was a mixed solvent of dichloromethane and petroleum ether in a volume ratio of 1:5) to obtain intermediate product M1 with a yield of 50%.

[0038] After testing, the nuclear magnetic resonance data of the intermediate product M1 are as follows: 1 H NMR (500 MHz, CDCl3) δ = 8.12 (s, 2H), 7.34 (ddd, J = 8.7, 7.5, 1.2 Hz, 2H), 7.06 (ddd, J = 7.9, 7.5, 1.3 Hz, 2H), 7.00 (dd, J = 8.0, 7.6 Hz, 2H), 6.89 (d, J = 8.1 Hz, 2H), 3.78 (s, 6H), 1.75 (s, 6H). It can be seen from the NMR data that the composition of the intermediate M1 is 5-bromo-2-(9,9-dimethyl-9H-acridin-10-yl) dimethyl isophthalate.

[0039] (2) Synthesis of intermediate product M2: In a round-bottom flask, dimethyl 5-bromo-2-(9,9-dimethyl-9H-acridin-10-yl)isophthalate (5.0 mmol, 1.0 eq) and sodium hydroxide (25.0 mmol, 5 eq) were dissolved in 50 mL of a 1:1 ethanol-water mixture. The mixture was heated to reflux for 12 h under stirring. After the hydrolysis was complete, the mixture was cooled to room temperature and concentrated to half of the reaction system. Concentrated hydrochloric acid was added to acidify the mixture. The mixture was filtered and washed with water. The residue was dried under vacuum at 80°C to obtain a solid. In a 100 mL three-necked flask, the solid was dissolved in 40 mL of ultra-dry dichloromethane, followed by the addition of oxalyl chloride (12 mmol, 2.4 eq) and a few drops of ultra-dry DMF. The mixture was heated to reflux for 0.5 h, and then tin tetrachloride (12 mmol, 2.4 eq) was added and the mixture was kept under reflux for 12 h. After the reaction is complete, cool to room temperature, add 1M sodium hydroxide aqueous solution dropwise until neutral, extract with dichloromethane 2-3 times, combine all dichloromethane extraction layers, and dry with anhydrous magnesium sulfate; filter and rotary evaporate to obtain a crude product, which is purified by silica gel column chromatography with a mixed solvent of dichloromethane and petroleum ether in a volume ratio of 1:5; collect the purified products, and finally concentrate by rotary evaporation to obtain M2 with a yield of 75%.

[0040] After testing, the nuclear magnetic resonance data of the intermediate product M2 are as follows: 1 H NMR (500 MHz, CDCl3) δ = 8.65 (s, 2H), 8.24 (dd, J = 7.8,1.4 Hz, 2H), 7.77 (dd, J = 7.8 7.5 Hz, 2H), 7.21 (t, J = 8.0 Hz, 2H), 1.86 (s, 6H). It can be seen from the NMR data that the composition of the intermediate M2 is 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione.

[0041] (3) Synthesis of organic electroluminescent compound P1: Under nitrogen atmosphere, 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione (5.0 mmol, 1 eq) and phenylboronic acid (6 mmol, 1.2 eq) were dissolved in 20 ml toluene, 3%-5% mol tetrakistriphenylphosphine palladium was added as a catalyst, and then 2 equivalents of 2 mol / L potassium carbonate solution (10 mmol, 2.0 eq) and a few drops of ethanol were added. o After reacting at 400 °C for 24-26 hours, sufficient methanol was added to precipitate solids, and the solids were filtered and washed with acetone to obtain a crude product. The product was further purified by silica gel column chromatography; finally, the purified product was collected and concentrated by rotary evaporation to obtain an organic electroluminescent compound P1 with a yield of 80%.

[0042] After testing, the nuclear magnetic resonance data of the organic electroluminescent compound P1 are as follows: 1H NMR (500 MHz, CDCl3) δ (ppm) = 8.72 (s, 2H), 8.30 (dd, J = 7.8, 1.4 Hz, 2H), 7.81-7.77 (m, 4H), 7.58 (dd, J = 7.4, 7.6 Hz, 2H), 7.34 (t, J = 7.4 Hz, 1H), 7.21 (t, J = 8.0 Hz, 2H), 1.86 (s, 6H). It can be seen from the nuclear magnetic resonance data that the molecular structure of the organic electroluminescent compound P1 is as follows: .

[0043] Example 2 This embodiment provides an organic electroluminescent compound with a molecular structure of P2. In the preparation method thereof, steps (1) to (2) are the same as those in Embodiment 1. The specific operation of synthesizing the organic electroluminescent compound P2 in step (3) is as follows: Under nitrogen atmosphere, 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione (5.0 mmol, 1 eq) and 2-pyrimidine boronic acid (6 mmol, 1.2 eq) were dissolved in 20 mL toluene, 3%-5% mol tetrakistriphenylphosphine palladium was added as a catalyst, and then 2 equivalents of 2M potassium carbonate solution (10 mmol, 2.0 eq) and a few drops of ethanol were added. After reacting at 90℃-110℃ for 24-26h, sufficient methanol was added to precipitate solids, and the solids were filtered and washed with acetone to obtain a crude product. The product was further purified by silica gel column chromatography; finally, the purified product was collected and concentrated by rotary evaporation to obtain the organic electroluminescent compound P2 with a yield of 70%.

[0044] After testing, the nuclear magnetic resonance data of the organic electroluminescent compound P2 are as follows: 1H NMR (500 MHz, DMSO) δ (ppm) = 9.17 (s, 2H), 9.00 (d, J = 4.9 Hz, 2H), 8.30 (d, J = 8.0 Hz, 2H), 7.77 (d, J = 8.0 Hz, 2H), 7.32 -7.21 (m, 3H), 1.86 (s, 6H). From the nuclear magnetic resonance data, it can be seen that the molecular structure of the organic electroluminescent compound P2 is as follows: .

[0045] The present invention also provides an organic electroluminescent device, which includes an anode, a cathode and an organic thin film layer, wherein the organic thin film layer is arranged between the anode and the cathode, and the organic thin film layer includes at least one organic light-emitting layer, and the organic light-emitting layer includes the organic electroluminescent compound as described above.

[0046] The organic light-emitting layer in the organic electroluminescent device provided by the present invention adopts a blue MR-TADF material with high color purity, high luminous efficiency and high stability, which is conducive to realizing full-color display and white light OLED.

[0047] The anode can be composed of a conductive metal, a metal oxide or a conductive polymer, and can effectively inject holes into the hole transport layer or the organic light-emitting layer. The materials of the anode include, but are not limited to: aluminum (Al), copper (Cu), gold (Au), magnesium (Mg), iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), palladium (Pd), platinum (Pt), indium tin oxide (ITO), aluminum-doped zinc oxide, and alloys of these metals. The anode can be deposited by a variety of techniques, such as physical vapor deposition (PVD) including radio frequency magnetron sputtering, vacuum thermal evaporation and electron beam evaporation. In some applications, the anode may require patterning, and patterned ITO conductive substrates can be obtained on the market for the preparation of the organic electroluminescent device of the present invention.

[0048] The cathode is composed of a conductive metal or metal oxide, and can effectively inject electrons into the electron injection layer, the electron transport layer or the organic light-emitting layer. The materials of the cathode include, but are not limited to: aluminum (Al), gold (Au), silver (Ag), calcium (Ca), barium (Ba), magnesium (Mg), lithium fluoride / aluminum (LiF / Al), magnesium silver alloy (MgAg), barium fluoride / aluminum (BaF2 / Al), copper (Cu), iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn), palladium (Pd), platinum (Pt), indium tin oxide (ITO), etc.; the cathode can be deposited by a suitable physical vapor deposition method, wherein the physical vapor deposition method includes, but is not limited to, radio frequency magnetron sputtering, vacuum thermal evaporation and electron beam evaporation.

[0049] The organic light-emitting layer is the core part of the organic electroluminescent device, and includes a host material and the above-mentioned organic electroluminescent compound, wherein the host material includes but is not limited to 1,3-diphenylimidazo[2,1-b]quinoxaline.

[0050] In some embodiments, the mass of the organic electroluminescent compound accounts for 1 wt %-10 wt % (eg, 1 wt %, 4 wt %, 7 wt %, 10 wt % and any interval between the two end points) of the mass of the organic light-emitting layer.

[0051] In some embodiments, the thickness of the light emitting layer is 20 nm-40 nm (eg, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, and any interval between the two end points).

[0052] Furthermore, in some embodiments of the present invention, the organic thin film layer also includes a hole injection layer, a hole transport layer, an electron transport layer and an electron injection layer, and the anode, hole injection layer, hole transport layer, organic light-emitting layer, electron transport layer, electron injection layer and cathode are arranged in sequence along the height direction of the organic electroluminescent device.

[0053] The hole injection layer is located between the anode and the hole transport layer. Its function is to reduce the potential barrier between the anode and the hole transport layer, promote more effective hole injection from the anode, and improve hole injection efficiency. The materials of the hole injection layer include but are not limited to conductive polymers such as polyaniline (PANI), polythiophene (PTh) and its derivatives, as well as some metal oxides such as molybdenum oxide and tungsten oxide.

[0054] The hole transport layer is located between the anode and the light-emitting layer and is responsible for efficiently transporting holes injected from the anode. The materials of the hole transport layer include but are not limited to: 4,4'-cyclohexane-1,1-diylbis(N,N-dimethylaniline) (TAPC), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS), tri(4-(9H-carbazole-9-yl)phenyl)amine (TCTA), and N,N'-di(1-naphthyl)-N,N'-diphenylbenzidine (NPB).

[0055] The material of the electron transport layer can be a small molecule or a polymer, which is used to efficiently transfer electrons to the light-emitting layer and prevent electrons from flowing to the cathode. The materials of the electron transport layer include but are not limited to: TPBi, Alq3, dibenzo[b,d]furan-2,8-diylbis(diphenylphosphine oxide) (PPF for short), 4,7-diphenyl-1,10-phenanthroline (Bphen for short). The electron transport layer can be prepared by vacuum evaporation, solution processing, organic vapor deposition and other methods.

[0056] The electron injection layer is located between the cathode and the electron transport layer, and is intended to promote the injection of electrons from the cathode into the electron transport layer and reduce the electron injection impedance. The materials of the electron injection layer include but are not limited to lithium fluoride (LiF) and the like.

[0057] Furthermore, in some embodiments of the present invention, the organic thin film layer also includes an electron blocking layer, a hole blocking layer and an exciton blocking layer. The electron blocking layer is arranged between the hole transport layer and the organic light-emitting layer, the hole blocking layer is arranged between the organic light-emitting layer and the electron transport layer, and the exciton blocking layer is arranged between the organic light-emitting layer and the hole transport layer or between the organic light-emitting layer and the electron transport layer.

[0058] The electron blocking layer is located between the hole transport layer and the organic light-emitting layer. Its function is to block the leakage of electrons from the electron transport layer to the hole transport layer, thereby improving the luminous efficiency. The materials of the electron blocking layer include but are not limited to metal materials (such as molybdenum oxide, tungsten oxide), organic materials (such as triarylamine compounds, carbazole compounds), polymer materials (such as polyaniline (PANI) and its derivatives, polythiophene (PTh) and its derivatives) and composite materials of the above materials. The electron blocking layer can be prepared by vacuum evaporation, solution spin coating, inkjet printing or other reasonable methods.

[0059] The hole blocking layer is located between the organic light-emitting layer and the electron transport layer, and is used to prevent holes from entering the electron transport layer while allowing electrons to pass through. The materials of the hole blocking layer include but are not limited to: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi), aluminum(III)bis(8-hydroxyquinoline-2-yl)bis(benzo[d]imidazole) (BAlq), tri(8-hydroxyquinoline)aluminum (Alq3). The hole blocking layer can be prepared by vacuum evaporation, solution spin coating, inkjet printing or other reasonable methods.

[0060] The function of the exciton blocking layer is to prevent the excitons from diffusing from the light-emitting layer to the adjacent functional layer, thereby improving the recombination efficiency of the excitons in the light-emitting layer. The materials of the exciton blocking layer include but are not limited to metal materials (such as molybdenum oxide, tungsten oxide), organic materials (such as triarylamine compounds, carbazole compounds), polymer materials (such as polyaniline (PANI), polythiophene (PTh)). The exciton blocking layer can be prepared by vacuum evaporation, solution spin coating, inkjet printing or other reasonable methods.

[0061] The preparation method of the organic electroluminescent device of the present invention is described in detail below through a specific embodiment.

[0062] The glass plate coated with the ITO transparent conductive layer (i.e., the ITO conductive glass plate) was placed in a cleaning agent for ultrasonic treatment, rinsed with deionized water, cleaned three times in acetone and ethanol respectively, baked in a clean environment until the moisture was completely removed, cleaned with ultraviolet light and ozone, and bombarded with a low-energy cation beam on the surface; then, the ITO conductive glass plate was placed in a vacuum chamber and evacuated to a vacuum degree of less than 5×10 -5 Pa, using ITO conductive glass plate as anode, and evaporating each layer of material on the anode surface in sequence, the specific steps are as follows: 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (HATCN) is used as a hole injection material. A 5 nm thick HATCN layer is deposited on the anode surface by vacuum thermal evaporation, which is the hole injection layer. The molecular structure of HATCN is as follows: .

[0063] 4,4'-(cyclohexane-1,1-diyl)bis(N,N-p-toluidine) (TAPC for short) is used as the hole transport material. A TAPC layer with a thickness of 45 nm is deposited on the hole injection layer by vacuum thermal evaporation, which is the hole transport layer. The molecular structure of TAPC is as follows: .

[0064] Tri(4-(9H-carbazole-9-yl)phenyl)amine (TCTA for short) is used as a hole blocking material, and a 5 nm thick TCTA layer is deposited on the surface of the hole transport layer by vacuum evaporation, which is the electron blocking layer. The molecular structure of TCTA is as follows: .

[0065] Subsequently, a 5 nm thick mCP layer was deposited on the surface of the TCTA layer using 1,3-diphenylimidazo[2,1-b]quinoxaline (mCP) material by vacuum evaporation as an exciton blocking layer. The molecular structure of mCP is as follows: .

[0066] Then, mCP and an organic electroluminescent compound are used to deposit an organic light-emitting layer with a thickness of 20 nm on the surface of the main material layer by vacuum co-evaporation. Among them, the mass proportion of the organic light-emitting compound is 3wt%, and the molecular structure of the organic light-emitting compound is as follows: .

[0067] Subsequently, on the surface of the organic light-emitting layer, dibenzo[b,d]furan-2,8-diylbis(diphenylphosphine oxide) (PPF for short) is used as an electron transport material, and a 5nm thick PPF layer is deposited by vacuum evaporation, which is a hole blocking layer. The molecular structure of PPF is as follows: .

[0068] Then, on the surface of the PPF layer, a 35nm thick TPBi layer was deposited using 1,3,5-tri(1-phenyl-1H-benzo[d]imidazol-2-yl)benzene (TPBi for short) material by vacuum evaporation, which is the electron transport layer.

[0069] Afterwards, a 1 nm thick electron injection layer was deposited on the surface of the electron transport layer using a lithiated fluoride material by vacuum evaporation, and a 100 nm thick cathode was deposited on the surface of the electron injection layer using a metal aluminum material by vacuum evaporation.

[0070] During the above operation, the evaporation rates of the materials were maintained as follows: the deposition rates of the hole injection layer material and the electron injection layer material were maintained in the range of 0.4 Å / s to 0.7 Å / s; the deposition rates of the hole transport layer, electron blocking layer, light emitting layer and electron transport layer materials were maintained in the range of 2 Å / s to 4 Å / s; the deposition rate of the metal aluminum material was maintained in the range of 6 Å / s to 9 Å / s; during the entire deposition process, the vacuum degree was maintained at 1×10 -6 Torr to 5×10 -6 Torr range.

[0071] The electroluminescence spectrum of the organic light-emitting device was collected by using a photon multichannel analyzer PMA-12 (Hamamatsu C10027-01), covering the wavelength range of 200nm-950nm; the external quantum efficiency of the organic electroluminescent device was obtained by measuring the forward light intensity using an integrating sphere (Hamamatsu A10094). All measurements were performed at room temperature in an atmospheric environment. Among them, the electroluminescence spectrum of the organic electroluminescent compound P2 is shown in Figure 1 As shown, from Figure 1 The narrow-band deep-blue light emission capability of the electroluminescent device using the organic electroluminescent compound P2 as the luminescent material is demonstrated.

[0072] It should be noted that the method for forming each structural layer in the organic electroluminescent device provided by the present invention is not limited, including but not limited to vacuum evaporation method, spin coating method, etc.; at the same time, the materials used for each structural layer are also not limited, all of which are within the protection scope of the present invention.

[0073] The present invention further proposes a display device, which includes an organic electroluminescent device. The specific structure of the organic electroluminescent device refers to the above embodiment. Since the display device adopts all the technical solutions of all the above embodiments, it at least has all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.

[0074] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or system. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or system including the element.

[0075] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. Any equivalent articles or equivalent process changes made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. An organic electroluminescent compound, characterized in that: The structure of the organic electroluminescent compound is: ； Wherein, R is selected from one of the following structural formulas: 。 2. The organic electroluminescent compound according to claim 1, characterized in that The structural formula of the organic electroluminescent compound is at least one of the following structural formulas: 。 3. A method for preparing an organic electroluminescent compound as claimed in claim 1 or 2, characterized in that: The following steps are involved: Using 5-bromo-2-iodoisophthalic acid dimethyl ester and 9,9-dimethylacridine as raw materials, 5-bromo-2-(9,9-dimethyl-9H-acridine-10-yl)isophthalic acid dimethyl ester was synthesized; Using 5-bromo-2-(9,9-dimethyl-9H-acridin-10-yl)isophthalic acid dimethyl ester as raw material, 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione is obtained after intramolecular cyclization reaction; The organic electroluminescent compound is synthesized by taking 6-bromo-12,12-dimethyl-benzoquinoline acridiniumdione as a raw material.

4. The method for preparing an organic electroluminescent compound according to claim 3, characterized in that: The steps of synthesizing the organic electroluminescent compound using 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione as a raw material include: An organic electroluminescent compound is synthesized using phenylboronic acid and 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione as raw materials. The structural formula of the organic electroluminescent compound is 。 5. The method for preparing an organic electroluminescent compound according to claim 3, characterized in that: The steps of synthesizing the organic electroluminescent compound using 6-bromo-12,12-dimethyl-benzoquinoline acridinium dione as a raw material include: An organic electroluminescent compound is synthesized using 2-pyrimidineboronic acid and 6-bromo-12,12-dimethyl-benzoquinolineacridinedione as raw materials. The structural formula of the organic electroluminescent compound is 。 6. An organic electroluminescent device, characterized in that: The organic electroluminescent device comprises an anode, a cathode and an organic thin film layer, wherein the organic thin film layer is arranged between the anode and the cathode, and the organic thin film layer comprises at least one organic light-emitting layer, and the organic light-emitting layer comprises the organic electroluminescent compound as claimed in claim 1 or 2.

7. The organic electroluminescent device according to claim 6, characterized in that: The mass of the organic electroluminescent compound accounts for 1wt%-10wt% of the mass of the organic light-emitting layer; and / or, The thickness of the light-emitting layer is 20nm-40nm.

8. The organic electroluminescent device according to claim 6 or 7, characterized in that: The organic thin film layer also includes a hole injection layer, a hole transport layer, an electron transport layer and an electron injection layer. The anode, the hole injection layer, the hole transport layer, the organic light-emitting layer, the electron transport layer, the electron injection layer and the cathode are arranged in sequence along the height direction of the organic electroluminescent device.

9. The organic electroluminescent device according to claim 8, characterized in that: The organic thin film layer also includes an electron blocking layer, a hole blocking layer and an exciton blocking layer. The electron blocking layer is arranged between the hole transport layer and the organic light-emitting layer, the hole blocking layer is arranged between the organic light-emitting layer and the electron transport layer, and the exciton blocking layer is arranged between the organic light-emitting layer and the hole transport layer or between the organic light-emitting layer and the electron transport layer.

10. A display device, characterized in that: The display device comprises the organic electroluminescent device according to any one of claims 6 to 9.

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