阅读说明：本技术 一类有机小分子空穴传输材料及其制备方法和应用 (Organic small molecule hole transport material and preparation method and application thereof ) 是由 应磊 郭婷 石林瑞 胡黎文 曹镛 于 2020-12-25 设计创作，主要内容包括：本发明属于有机光电材料的技术领域,公开了一类有机小分子空穴传输材料及其制备方法和应用。所述小分子空穴传输材料,其结构式为式(I)。本发明还公开了小分子空穴传输材料的制备方法,其制备方法简单,可大规模生产。本发明的小分子空穴传输材料空间位阻较大,具有优异的溶解性,成膜质量佳,有利于空穴的注入和传输,降低器件的启亮电压；而且以本发明的小分子材料为空穴传输层的OLED器件的最大流明效率能达到11.0坎德拉每安培,表现出优异的电致发光性能。(The invention belongs to the technical field of organic photoelectric materials, and discloses an organic small molecule hole transport material, and a preparation method and application thereof. The structural formula of the micromolecule hole transport material is shown as a formula (I). The invention also discloses a preparation method of the micromolecule hole transport material, which is simple and can be produced in large scale. The micromolecule hole transport material has larger steric hindrance, excellent solubility and good film forming quality, is beneficial to the injection and the transmission of holes, and reduces the turn-on voltage of devices; moreover, the maximum lumen efficiency of the OLED device taking the small molecular material as the hole transport layer can reach 11.0 candela per ampere, and the OLED device shows excellent electroluminescent performance.)

1. An organic micromolecule hole transport material is characterized in that the structural formula is shown as formula I:

in the formula, R₁、R₂And R₃Which may be identical or different, R₁、R₂And R₃The aryl group is one of hydrogen, substituted or unsubstituted aryl, straight-chain, branched or cyclic alkyl, alkoxy or alkylthio with 1-20 carbon atoms, straight-chain, branched or cyclic alkenyl, alkenyloxy or alkenylthio with 2-20 carbon atoms, and straight-chain, branched or cyclic alkynyl with 2-20 carbon atoms.

2. A method for preparing the organic small molecule hole transport material of claim 1, comprising the steps of,

(1) in an inert gas atmosphere and an organic solvent, adding a compound N, N-di (4-bromophenyl) -R₁Carrying out boron esterification reaction on substituted aniline and pinacol diboron under the action of a catalytic system, and purifying to obtain a compound M1;

(2) reacting compound M1 with 3-bromo-9- (R) in an inert gas atmosphere and a solvent₂Substituted) phenyl-9H-carbazole to perform Suzuki coupling reaction in a catalytic system, and purifying to obtain a compound M2;

(3) reacting compound M2 with 1-bromo-9- (R) in an inert gas atmosphere and a solvent₃Substituted) phenyl-9H-carbazoles in catalytic systemsThen, Suzuki coupling reaction is carried out, and purification is carried out to obtain a final product M3.

3. The method for preparing the organic small molecule hole transport material according to claim 2, wherein the organic solvent in step (1) is one or a mixture of 1, 4-dioxane, N-dimethylformamide and tetrahydrofuran, the catalytic system comprises alkali and a catalyst, the reaction temperature is 60-140 ℃, and the reaction time is 12-36 h.

4. The method for preparing the organic small-molecule hole transport material according to claim 3, wherein the compound N, N-bis (4-bromophenyl) -R₁The molar ratio of the substituted aniline to the pinacol diboron, the base and the catalyst is 1 (2-5) to (3-10) to (0.02-0.5); the alkali is potassium acetate, sodium carbonate and potassium carbonate, and the catalyst is tetratriphenylphosphine palladium, palladium acetate and 1, 1' -bis (diphenylphosphino) ferrocene palladium dichloride.

5. The preparation method of the organic small molecule hole transport material according to claim 2, wherein the solvent in the step (2) is a mixed system of toluene, ethanol and water, the catalytic system comprises alkali and a catalyst, the reaction temperature is 90-140 ℃, and the reaction time is 12-36 h.

6. The method for preparing the organic small molecule hole transport material according to claim 5, wherein the solvent comprises toluene, ethanol and water in a volume ratio of 10: (1-4): (1 to 4) the compound M1, 3-bromo-9- (R)₂The molar ratio of the substituted) phenyl-9H-carbazole to the alkali to the catalyst is 1 (0.8-1.2) to (3-20) to (0.02-0.5); the alkali is potassium acetate, sodium carbonate and potassium carbonate, and the catalyst is tetratriphenylphosphine palladium, palladium acetate and 1, 1' -bis (diphenylphosphino) ferrocene palladium dichloride.

7. The preparation method of the organic small molecule hole transport material according to claim 2, wherein the solvent in the step (3) is a mixed system of toluene, ethanol and water, the catalytic system comprises alkali and a catalyst, the reaction temperature is 90-140 ℃, and the reaction time is 12-36 h.

8. The method for preparing the organic small molecule hole transport material according to claim 7, wherein the volume ratio of the solvents of toluene, ethanol and water is 10: (1-4): (1 to 4) the compound M2, 1-bromo-9- (R)₃The molar ratio of the substituted) phenyl-9H-carbazole to the alkali to the catalyst is 1 (0.8-1.2) to (3-20) to (0.02-0.5); the alkali is cesium carbonate, potassium acetate, sodium carbonate and potassium carbonate, and the catalyst is palladium tetratriphenylphosphine, palladium acetate and 1, 1' -bis (diphenylphosphino) ferrocene palladium dichloride.

9. The method for preparing an organic small molecule hole transporting material according to any one of claims 2-8, wherein the purification in steps (1) - (3) is cooling the obtained reaction solution to room temperature, extracting with deionized water and dichloromethane, dissolving the crude product with dichloromethane, separating by column chromatography, concentrating, and drying.

10. Use of the small organic molecule hole transport material of claim 1 in the preparation of an organic light emitting diode.

Technical Field

The invention belongs to the technical field of organic photoelectric materials, and particularly relates to an organic small molecule hole transport material, and a preparation method and application thereof.

Background

In recent years, organic/polymer light emitting diodes (O/PLEDs) have gradually moved into the public, and OLEDs are mainly used in two fields of display and illumination. In the display field, compared with a liquid crystal display, the OLED display has the advantages of active light emission, no need of a back plate, high contrast, wide viewing angle, high response speed, low driving voltage, large working temperature range and the like. In the field of illumination, the OLED light source does not contain ultraviolet radiation, does not cause glare, does not contain mercury and the like in a device structure, and is a green healthy light source. Many advantages in the field of display and lighting make OLEDs a focus of scientific research.

The light emitting process of the OLED device mainly comprises the following steps: the carrier injection, the carrier transmission and the carrier recombination form four parts of an exciton and exciton radiation transition luminescence. In the process, due to the problems of overlarge carrier injection potential barrier, unbalanced carrier mobility and the like, the OLED has low device performance, overhigh starting voltage and low luminous efficiency. There is therefore a need to introduce hole transport layers into OLED devices to optimize and improve device performance.

As the hole transport material, the following five conditions need to be satisfied: (1) the appropriate HOMO energy level is matched with the energy level of the adjacent organic layer, so that the hole injection barrier of the device is reduced; (2) the light-emitting diode has a shallow LUMO energy level, electrons are limited in the light-emitting layer, and annihilation of the electrons at an anode interface is reduced; (3) the overlapping degree of the absorption spectrum of the material and the emission spectrum of the luminescent layer is small, so that the energy of the luminescent layer is prevented from being transferred to the interface layer, and the luminescent efficiency loss of the luminescent layer is reduced; (4) the hole mobility is suitable, so that the hole mobility and the electron mobility in the device are balanced; (5) the thermal stability is good, the stability of the film is good, and the service life of the device is prolonged.

Literature reports (organic electronics, page number 111-118 of volume 51 in 2017) report blankHole transport material N-biphenyl-4-yl-9, 9-dimethyl-N- [4- (9-phenyl-9H-carbazole-3-yl) phenyl]The performance of the (9H) -fluorene-2-amine (BCFN) is improved when the (BCFN) is introduced into a blue light polymer electroluminescent device taking polyfluorene as a light emitting layer, but the maximum luminous efficiency is only 4.31cd A^-1. The blue electroluminescence efficiency is still to be improved. The hole transport material applied by the patent has more excellent performance when being used in a blue light electroluminescent device, and has commercial application prospect.

Disclosure of Invention

In order to improve the performance of OLED devices and develop new hole transport materials, the invention aims to provide a hole transport material and a preparation method and application thereof. The hole transport material is composed of triphenylamine, carbazole and derivatives thereof, and electron-rich units are introduced, so that a hole injection barrier can be reduced, the hole mobility is improved, and the photoelectric performance of an OLED device is improved.

The invention is realized by the following technical scheme:

a kind of organic small molecule hole transport material, its structural formula is formula (I):

in the formula, R₁、R₂And R₃May be the same or different; r₁、R₂And R₃The aryl group is one of hydrogen, substituted or unsubstituted aryl, straight-chain, branched or cyclic alkyl, alkoxy or alkylthio with 1-20 carbon atoms, straight-chain, branched or cyclic alkenyl, alkenyloxy or alkenylthio with 2-20 carbon atoms, and straight-chain, branched or cyclic alkynyl with 2-20 carbon atoms.

The preparation method of the organic micromolecule hole transport material comprises the following steps:

(1) in an inert gas atmosphere and an organic solvent, adding a compound N, N-di (4-bromophenyl) -R₁Carrying out boron esterification reaction on substituted aniline and pinacol diboron under the action of a catalytic system, and purifying to obtain a compound M1;

(2) reacting compound M1 with 3-bromo-9- (R) in an inert gas atmosphere and an organic solvent₂Substituted) phenyl-9H-carbazole to perform Suzuki coupling reaction in a catalytic system, and purifying to obtain a compound M2;

(3) in an inert gas atmosphere and an organic solvent, the compound M2 is mixed with 1-bromo-9- (R)₃Substituted) phenyl-9H-carbazole is subjected to Suzuki coupling reaction in a catalytic system, and then purified to obtain a final product M3.

Preferably, the organic solvent in the step (1) is one or a mixture of two of 1, 4-dioxane, N, N-dimethylformamide, tetrahydrofuran and the like, the catalytic system comprises alkali and a catalyst, the reaction temperature is 60-140 ℃, and the reaction time is 12-36 h;

further preferably, in the step (1), the compound N, N-bis (4-bromophenyl) -R₁The molar ratio of the substituted aniline to the pinacol diboron, the base and the catalyst is 1 (2-5) to (3-10) to (0.02-0.5); the alkali is potassium acetate, sodium carbonate, and potassium carbonate, preferably potassium acetate; the catalyst is tetratriphenylphosphine palladium, palladium acetate, 1 '-bis (diphenylphosphino) ferrocene palladium dichloride and the like, and 1, 1' -bis (diphenylphosphino) ferrocene palladium dichloride is more preferable.

Preferably, the purification in step (1) means that the obtained reaction solution is cooled to room temperature, extracted by using deionized water and dichloromethane, the crude product is dissolved by dichloromethane, separated by column chromatography, concentrated and dried to obtain the target product M1.

Preferably, the organic solvent in the step (2) is a mixed system of toluene, ethanol and water, the catalytic system comprises alkali and a catalyst, the reaction temperature is 90-140 ℃, and the reaction time is 12-36 h;

more preferably, in the step (2), the volume ratio of the solvents toluene, ethanol and water is 10: (1-4): (1 to 4) the compound M1, 3-bromo-9- (R)₂The molar ratio of the substituted) phenyl-9H-carbazole to the alkali to the catalyst is 1 (0.8-1.2) to (3-20) to (0.02-0.5); the alkali is potassium acetate, sodium carbonate, and potassium carbonate, preferably potassium carbonate; the catalyst is tetratriphenylphosphine palladium, palladium acetate and 1, 1' -bis (diphenylphosphine)Yl) ferrocene palladium dichloride and the like, and tetratriphenylphosphine palladium is more preferable.

Preferably, the purification in the step (2) is to cool the obtained reaction solution to room temperature, extract the reaction solution by using deionized water and dichloromethane, dissolve the crude product by using dichloromethane, separate by column chromatography, concentrate and dry the product to obtain the target product M2.

Preferably, the organic solvent in the step (3) is a mixed system of toluene, ethanol and water, the catalytic system comprises alkali and a catalyst, the reaction temperature is 90-140 ℃, and the reaction time is 12-36 h;

preferably, in the step (3), the volume ratio of the solvents toluene, ethanol and water is 10: (1-4): (1 to 4) the compound M2, 1-bromo-9- (R)₃The molar ratio of the substituted) phenyl-9H-carbazole to the alkali to the catalyst is 1 (0.8-1.2) to (3-20) to (0.02-0.5); the base is cesium carbonate, potassium acetate, sodium carbonate, potassium carbonate, more preferably cesium carbonate; the catalyst is tetratriphenylphosphine palladium, palladium acetate, 1' -bis (diphenylphosphino) ferrocene palladium dichloride and the like, and tetratriphenylphosphine palladium is more preferable.

Preferably, the purification in step (3) means that the obtained reaction solution is cooled to room temperature, extracted by using deionized water and dichloromethane, the crude product is dissolved by dichloromethane, separated by column chromatography, concentrated and dried to obtain the final target product M3.

The organic micromolecule hole transport material is applied to the preparation of organic light-emitting diodes and is used as a hole transport material.

The reaction equation of the small molecule hole transport material is as follows:

boron esterification of compound M1 preparation:

suzuki coupling preparation of compound M2:

suzuki coupling preparation of compound M3:

compared with the prior art, the micromolecule hole transport material provided by the invention has the beneficial effects that:

(1) the micromolecule hole transport material has simple preparation method, easy purification and large-scale production;

(2) the micromolecule hole transport material has distorted structure, larger steric hindrance, excellent solubility, good film forming property and stable film form, is beneficial to the injection and the transmission of holes, and reduces the turn-on voltage of devices;

(3) the maximum lumen efficiency of OLED devices blending the hole transport material of the present invention with Polyvinylcarbazole (PVK) is up to 11.0 candela per ampere.

Drawings

Fig. 1 is a hole transporting material M1-3 of example 1: PVK 7:3 current density-operating voltage-brightness relation curve;

fig. 2 is a hole transporting material M1-3 of example 1: PVK 7:3 lumen efficiency-current density relation;

fig. 3 is a hole transporting material M1-3 of example 1: PVK 7:3 electroluminescence spectrum.

Detailed Description

The present invention will be described in further detail with reference to the following specific examples and drawings, but the embodiments and the scope of the present invention are not limited thereto.

Example 1

Preparation of Small molecule M1-3

(1) Synthesis of N, N-bis (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) phenyl) aniline (M1-1):

4, 4-dibromotriphenylamine (1.00g, 2.48mmol), pinacol diboride (1.89g, 7.44mmol), potassium acetate (1.46g, 14.89mmol), and 1, 1' -bis (diphenylphosphino) metallocene as a catalyst under an argon atmosphereIron Palladium dichloride (Pd (dppf) Cl₂) (0.054g, 0.074mmol) is dissolved in 1, 4-dioxane (20ml), heated to generate reflux, and reacted for 24 hours under the reflux condition; the solvent and potassium acetate were removed and purified by silica gel column chromatography with eluent petroleum ether/dichloromethane 3/1 (vol/vol) followed by recrystallization in tetrahydrofuran/ethanol to give a white powder (M1-1).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

(2) synthesis of N-phenyl-4- (9-phenyl-9H-carbazol-3-yl) -N- (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) phenyl) aniline (M1-2):

placing N, N-bis (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) phenyl) aniline (M1-1, 1.00g, 2.01mmol), 3-bromo-9-phenyl-9H-carbazole (0.71g, 2.21mmol), potassium carbonate (5.56g, 40.22mmol), palladium tetratriphenylphosphine (0.19g, 0.16mmol), 10ml toluene, 3ml ethanol, 3ml deionized water in a container under an argon atmosphere, heating to generate reflux, and reacting under reflux conditions for 24H; after the reaction was stopped, the inorganic salts and water were removed and the crude product was purified by column chromatography with a eluent of petroleum ether/dichloromethane (4/1 vol) to give a white solid (M1-2).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

(3) n-phenyl-4- (9-phenyl-9H-carbazol-1-yl) -N- (4- (9-phenyl-9H-carbazol-3-yl)

Synthesis of phenyl) aniline (M1-3):

under argon atmosphere, N-phenyl-4- (9-phenyl-9H-carbazol-3-yl) -N- (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) phenyl) aniline (M1-21.00g, 1.63mmol), 1-bromo-9-phenyl-9H-carbazole (1.05g, 3.26mmol), cesium carbonate (10.62g, 32.60mmol), palladium tetrakistriphenylphosphine (0.151g, 0.131mmol), 10ml toluene, 3ml ethanol, 3ml deionized water are placed in a container, heated to generate reflux, and reacted for 24 hours under reflux conditions; after the reaction was stopped, the inorganic salts and water were removed and the crude product was purified by column chromatography with a eluent of petroleum ether/dichloromethane (4/1 vol) to give a white solid (M1-3).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

example 2

Preparation of Polymer M2-3

(1) Synthesis of 4-methyl-N, N-bis (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) phenyl) aniline (M2-1):

4-bromo-N- (4-bromophenyl) -N- (p-tolyl) aniline (1.00g, 2.40mmol), pinacol diboron (1.83g, 7.19mmol), potassium acetate (1.41g, 14.38mmol), catalyst 1, 1' -bis (diphenylphosphino) ferrocene dichloropalladium (Pd) (dppf) Cl₂) (0.052g, 0.072mmol) is dissolved in 1, 4-dioxane (20ml), heated to generate reflux, and reacted for 24h under reflux; the solvent and potassium acetate were removed and purified by silica gel column chromatography with eluent petroleum ether/dichloromethane 3/1 (vol/vol) followed by recrystallization in tetrahydrofuran/ethanol to give a white powder (M2-1).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

(2) synthesis of 4-methyl-N- (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) phenyl) -N- (4- (9- (p-tolyl) -9H-carbazol-3-yl) phenyl) aniline (M2-2):

placing 4-methyl-N, N-bis (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) phenyl) aniline (M2-1, 1.00g, 1.96mmol), 3-bromo-9- (p-tolyl) -9H-carbazole (0.72g, 2.15mmol), potassium carbonate (5.41g, 39.12mmol), palladium tetratriphenylphosphine (0.18g, 0.16mmol), 10ml toluene, 3ml ethanol, 3ml deionized water in a container under an argon atmosphere, heating to generate reflux, and reacting for 24H under reflux conditions; after the reaction was stopped, the inorganic salts and water were removed and the crude product was purified by column chromatography with a eluent of petroleum ether/dichloromethane (4/1 vol) to give a white solid (M2-2).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

(3) synthesis of 4-methyl-N- (4- (9- (p-tolyl) -9H-carbazol-1-yl) phenyl) -N- (4- (9- (p-tolyl) -9H-carbazol-3-yl) benzene) aniline (M2-3):

placing 4-methyl-N- (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) phenyl) -N- (4- (9- (p-tolyl) -9H-carbazole-3-yl) phenyl) aniline (M2-2, 1.00g, 1.56mmol), 1-bromo-9- (p-tolyl) -9H-carbazole (1.05g, 3.12mmol), cesium carbonate (10.17g, 31.2mmol), tetratriphenylphosphine palladium (0.144g, 0.125mmol), and 10ml of toluene, 3ml of ethanol and 3ml of deionized water in a container under an argon atmosphere, heating to generate reflux, and reacting under reflux conditions for 24H; after the reaction was stopped, the inorganic salts and water were removed and the crude product was purified by column chromatography with a eluent of petroleum ether/dichloromethane (4/1 vol) to give a white solid (M2-3).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

example 3

Preparation of Small molecule M3-3

(1) Synthesis of 4-methoxy-N, N-bis (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) phenyl) aniline (M3-1):

4-bromo-N- (4-bromophenyl) -N- (4-methoxyphenyl) aniline (1.00g, 2.31mmol), pinacol diboron (1.76g, 6.93mmol), potassium acetate (1.36g, 13.86mmol), catalyst 1, 1' -bis (diphenylphosphino) ferrocene dichloropalladium (Pd (dppf) Cl₂) Dissolving (0.051g, 0.069mmol) in 1, 4-dioxane (20ml), heating to generate reflux, and reacting for 24h under the reflux condition; the solvent and potassium acetate were removed and purified by silica gel column chromatography with eluent petroleum ether/dichloromethane 3/1 (vol/vol) followed by recrystallization in tetrahydrofuran/ethanol to give a white powder (M3-1).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

(2) synthesis of 4-methoxy-N- (4- (9- (4-methoxyphenyl) -9H-carbazol-3-yl) phenyl) -N- (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) phenyl) aniline (M3-2):

placing 4-methoxy-N, N-bis (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) phenyl) aniline (M3-1, 1.00g, 1.90mmol), 3-bromo-9- (4-methoxyphenyl) -9H-carbazole (0.73g, 2.09mmol), potassium carbonate (5.25g, 38.0mmol), palladium tetratriphenylphosphine (0.176g, 0.152mmol), and 10ml of toluene, 3ml of ethanol and 3ml of deionized water in a container under an argon atmosphere, heating to generate reflux, and reacting for 24 hours under reflux conditions; after the reaction was stopped, the inorganic salts and water were removed and the crude product was purified by column chromatography with a eluent of petroleum ether/dichloromethane (4/1 vol) to give a white solid (M3-2).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

(3) synthesis of 4-methoxy-N- (4- (9- (4-methoxyphenyl) -9H-carbazol-1-yl) phenyl) -N- (4- (9- (4-methoxyphenyl) -9H-carbazol-3-yl) benzene) aniline (M3-3):

placing 4-methoxy-N- (4- (9- (4-methoxyphenyl) -9H-carbazol-3-yl) phenyl) -N- (4- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) phenyl) aniline (M3-2, 1.00g, 1.49mmol), 1-bromo-9- (4-methoxyphenyl) -9H-carbazole (1.05g, 2.97mmol), cesium carbonate (9.71g, 29.8mmol), tetratriphenylphosphine palladium (0.138g, 0.119mmol), and 10ml of toluene, 3ml of ethanol, 3ml of deionized water in a container under an argon atmosphere, heating to generate reflux, and reacting under reflux conditions for 24H; after the reaction was stopped, the inorganic salts and water were removed and the crude product was purified by column chromatography with a eluent of petroleum ether/dichloromethane (4/1 vol) to give a white solid (M3-3).¹HNMR、¹³The results of CNMR, MS and element analysis show that the obtained compound is a target product, and the chemical reaction equation of the preparation process is as follows:

example 4

Preparation of electroluminescent devices

(1) Cleaning a conductive glass ITO substrate: sequentially placing the ITO glass substrate in acetone, isopropanol, cleaning liquid, deionized water and isopropanol for ultrasonic cleaning, removing possible residual stains (such as photoresist and the like) on the surface of the ITO glass substrate and improving interface contact, and after cleaning, placing the ITO glass substrate in a vacuum oven for drying;

(2) placing the ITO in an oxygen plasma etcher using an oxygen plasma (O)₂Plasma) bombarding for twenty minutes to thoroughly remove possible residual organic matters on the surface of the ITO glass substrate;

(3) PSS (Baytron P4083), a 40nm thick hole injection layer, was spin coated on ITO and then dried in a vacuum oven at 80 ℃ for 12 hours;

(4) in a glove box under nitrogen atmosphere, a small molecule hole transport material M1-3 (example 1) was mixed with Polyvinylcarbazole (PVK) at a ratio of 7:3, mixing the materials in a mass ratio, dissolving the mixture in chlorobenzene, preparing a solution with the concentration of 20mg/mL, spin-coating a hole transport layer with the thickness of 40nm on a PEDOT (power generation optical) PSS (patterned sapphire substrate) layer, and then heating and annealing the hole transport layer for 20 minutes at 80 ℃ on a heating table to remove residual solvents and improve the appearance of the hole transport layer;

(5) in a glove box in a nitrogen atmosphere, a polymer material poly [9, 9-dioctyl fluorene-co-S, S-dioxo-dibenzothiophene ] (PFSO10) is dissolved in p-xylene to prepare a solution with the concentration of 20mg/mL, a luminescent layer film with the thickness of 40nm is spin-coated on a hole transport layer, and then heating annealing is carried out for 20 minutes at 80 ℃ on a heating table to remove residual solvent and improve the appearance of the luminescent layer film;

(6) lower than 3 x 10 in vacuum evaporation chamber^-4Under the vacuum degree of Pa, a layer of electron transport material 1,3, 5-tri (1-phenyl-1H-benzimidazole-2-yl) benzene (TPBI) with the thickness of 40nm is evaporated on an active layer film, a layer of cesium fluoride (CsF) with the thickness of 1.0nm is evaporated, and a layer of ultra-pure aluminum cathode (Al) with the thickness of 90nm is evaporated finally, wherein lithium fluoride and aluminum layers are subjected to vacuum deposition through a mask plate.

The effective area of the device is 0.09cm². The thickness of the organic layer was measured with a quartz crystal monitoring thickness gauge. After the device is prepared, epoxy resin and thin-layer glass are used for polar curing in ultraviolet light and packaging. The Electroluminescence (EL) spectrum was measured by means of a Photo Research PR705 type optical analyzer. The current density and the luminance versus driving voltage characteristics were measured by a Keithley 2400 source measurement unit and a Konica Minolta chromameter CS-200, respectively. The external quantum efficiency is calculated from the luminance, current density and EL spectra assuming a Lambertian distribution. The prepared device has the structure of ITO/PEDOT: PSS/M1-3: PVK: 7:3/PFSO 10/TPBI/CsF/Al.

Wherein the structural formula of the hole transport material polyvinyl carbazole (PVK) is as follows:

the structural formula of the luminescent layer poly [9, 9-dioctyl fluorene-co-S, S-dioxo-dibenzothiophene ] (PFSO10) is as follows:

the structural formula of the electron transport material 1,3, 5-tri (1-phenyl-1H-benzimidazole-2-yl) benzene (TPBI) is as follows:

the prepared electroluminescent devices were subjected to the photoelectric property test, and the test results are shown in table 1.

TABLE 1 electro-optical properties of electroluminescent devices

FIG. 1 shows a hole transporting material M1-3: PVK 7:3 current density-operating voltage-brightness relation curve; FIG. 2 shows a hole transporting material M1-3: PVK 7:3 lumen efficiency-current density relation; FIG. 3 shows a hole transporting material M1-3: PVK 7:3 electroluminescence spectrum.

As can be seen from the performance graphs of fig. 1 and 2 and the data in table 1, the electroluminescent device using hole transport material M1-3 as the main component, a certain content of PVK, and PFSO10 as the light-emitting layer has excellent photoelectric properties. The turn-on voltage of the device (the voltage to which the device corresponds at a luminance of 1 candela per square meter) is only 4.0 volts, with a maximum lumen efficiency of 11.0 candelas per amp.

To study the luminescence of the above devices, the electroluminescence spectra of the above devices were collected, as shown in fig. 3. FIG. 3 shows a hole transporting material M1-3: PVK 7:3 electroluminescence spectrum. As can be seen from the figure, the spectrum of the device is in the blue region, and the spectrum of the exciplex does not appear. It is explained that in the above device, electrons and holes can be efficiently recombined in the light emitting layer and blue fluorescence is emitted.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and they are included in the scope of the present invention.