Dinuclear carbazole derivatives based on styrene hybridization as well as preparation method and application of dinuclear carbazole derivatives

Abstract

The invention belongs to the technical field of organic photoelectricity, and discloses a binuclear carbazole derivative based on styrene hybridization, a preparation method of the binuclear carbazole derivative and application of the binuclear carbazole derivative to preparation of a hole transport layer of an electroluminescent device. The binuclear carbazole derivative based on styrene hybridization can be prepared into a functional film with excellent solvent erosion resistance through a thermal cross-linking method, has excellent hole transport capacity and relatively high triplet state energy level, can be used for a hole transport layer of an organic electroluminescent device, and in addition, can also be used for preparing a hole transport layer of the organic electroluminescent device. In addition, the binuclear carbazole derivative based on styrene hybridization also has a relatively low crosslinking temperature, and can be cross-linked to form a film through a convenient thermal annealing process, so that a multi-layer light-emitting device can be conveniently prepared by a solution method process, and the prepared multi-layer light-emitting device has an excellent light-emitting characteristic and can be applied to the field of light emitting devices. Good application prospects are realized in the aspects of solar cells, flexible light-emitting devices and the like.

Description

Technical Field

[0001] The present invention belongs to the field of organic optoelectronic technologies, and relates to a class of binuclear carbazole derivatives based on styrene hybridization, a preparation method thereof, and an application of using the same to prepare a hole transport layer of an electroluminescent device. Technical Background

[0002] Light-emitting diodes (OLEDs) have attracted wide attention as emerging leading technologies in the field of display applications due to their low turn-on voltage, fast response speed, and cost-effective large-scale production capacity. In terms of preparation processes, the solution method and the vacuum evaporation method are still the main methods for preparing OLED devices. Compared with the vacuum evaporation process, which has high vacuum requirements, long process time, high material waste rate, high cost in the preparation process, and difficulty in preparing large-area thin films, the solution process can quickly prepare uniform thin films and has a relatively simple operation process, which is more conducive to large-scale industrial assembly line preparation.

[0003] Crosslinking improves the stability of the thin film morphology and reduces the crystallization of materials, which is a hot topic in device preparation. The styryl group is the most used crosslinking group in the crosslinking method and can rapidly polymerize to form polystyrene at a relatively low curing temperature. For the thermal crosslinking functional material styryl group, generally a relatively high heat treatment temperature, such as above 170 °C, is required to complete crosslinking without the need for an additional initiator to initiate. For example, see the published literature Meng-Ju Tsai, Wei-Lun Huang, Li-Ming Chen, Guo-Lun Ruan, Dian Luo, Zong-Liang Tseng and Ken-Tsung Wong. Journal of Materials Chemistry C, 2023, 1056-1066. Chen et al. designed a thermally crosslinkable hole transport material (BCzC4Sy), which requires a heat treatment condition of 170 °C to complete crosslinking, which greatly hinders the application of the thermal crosslinking method in organic semiconductor devices.

[0004] Reducing the heat treatment temperature of materials in the thermal cross-linking process is crucial for the device preparation of organic semiconductors. There are relevant studies showing that see the public literature. Zhang J., Liu H., Li X., et al. Low-temperature cross-linkable hole transporting materials through chemical doping for solution-processed green PHOLEDs. Organic Electronics. 2021, 99, 106334. Zhang et al. designed a hole transporting material TRZ-VPAN, and a cross-linked HTL film with excellent solvent resistance can be obtained by irradiating with ultraviolet light at 120 °C for 20 minutes. The green phosphorescent OLED processed with the cross-linked HTL solution achieved a maximum current efficiency (CE) of 57.1 cdA -1 and an external quantum efficiency (EQE) of 16.0%.

[0005] The patent document "A Class of Styrene Hybridized Carbazole Derivatives and Their Preparation Methods and Applications" with the publication number CN117945981A provides styrene hybridized carbazole derivatives that can be prepared into functional films with excellent solvent erosion resistance through a thermal cross-linking method. They also have excellent hole transporting ability and relatively high triplet energy levels, can be used in the hole transporting layer of organic electroluminescent devices, and have a relatively low cross-linking temperature. They can be cross-linked into films through a convenient thermal annealing process, which is convenient for preparing multi-layer light-emitting devices by the solution method. The prepared multi-layer light-emitting devices have excellent light-emitting characteristics. Summary of the Invention

[0006] Based on the above technical background, the present application provides a class of styrene hybridized binuclear carbazole derivatives (V-XACz) for making hole transporting materials, which can be cross-linked at a lower heat treatment temperature. The formed cross-linked network film has good solvent resistance and film-forming ability, and an amorphous film structure. Among them, the thermal decomposition temperature is as high as 430 °C. The styrene hybridized carbazole derivatives provided by the present invention have relatively high triplet energy levels, significantly higher than typical phosphorescent light-emitting materials, providing core material support for the solution processing preparation of full-color OLEDs. The relatively low LUMO energy level forms an electron injection barrier to inhibit the penetration of electrons into the hole transporting region. The appropriate HOMO energy level can be used in the hole transporting layer of multi-layer organic electroluminescent devices prepared by the solution method, so as to prepare highly efficient organic electroluminescent devices.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] In a first aspect, the present invention provides a class of styrene hybridized binuclear carbazole derivatives, which are any one of the following structural general formulas:

[0009]

[0010]

[0011] Wherein, n is any positive integer, and R is selected from any one of the following structures, and * represents the connection site:

[0012]

[0013] As a preferred embodiment of the styrene hybridized binuclear carbazole derivatives described in the present application, the structure is selected from any one of the following compounds:

[0014]

[0015]

[0016] In a second aspect, the present invention also provides a preparation method for the above-mentioned class of styrene hybridized binuclear carbazole derivatives. The following is the preparation method for the preferred embodiment of the styrene hybridized binuclear carbazole derivatives described in the present invention, and the corresponding synthetic route for the preparation method is as follows:

[0017]

[0018] Both i and ii in the above synthetic route represent the synthesis conditions as: tris(tert-butylphosphine) tetrafluoroborate (P(t-Bu)3BF4), tris(dibenzylideneacetone) dipalladium (Pd2(dba)3), sodium tert-butoxide (t-BuONa), nitrogen atmosphere, toluene, reaction temperature 115 °C, reaction time 24 h; iii in the above preparation route represents the synthesis conditions as: dichloromethane (CH2Cl2), boron tribromide (BBr3), reaction temperature 0 °C, reaction time 8 h; iv in the above preparation route represents the synthesis conditions as: potassium carbonate (K2CO3), tetrabutylammonium bromide (TBABr), anhydrous acetonitrile, reaction temperature 85 °C, reaction time 26 h;

[0019] R is selected from any one of the following structures:

[0020]

[0021]

[0022] The preparation method for the styrene hybridized binuclear carbazole derivatives is as follows:

[0023] Preparation of Intermediate Compound 1: Add Br-R-Br, sodium tert-butoxide and aniline into a dry reaction flask, then evacuate with nitrogen for 3 times. Under a nitrogen atmosphere, quickly add tris(tert-butylphosphine) tetrafluoroborate and tris(dibenzylideneacetone) dipalladium into the above dry reaction flask. Subsequently, add toluene solvent that has been strictly dehydrated and deoxygenated, heat to 115 °C and reflux with stirring for 24 hours. After the stirring is completed, cool to room temperature, add dichloromethane and an appropriate amount of water for liquid-liquid extraction. Repeat the extraction operation multiple times and collect the organic phase. After drying over anhydrous magnesium sulfate, remove the solvent; the sample is separated and purified by a silica gel chromatographic column to obtain a white solid, which is Intermediate Compound 1;

[0024] Preparation of Intermediate Compound 2: Add 9,9'-(5-bromo-1,3-phenylene)bis(4-methoxy-9H-carbazole), Intermediate Compound 1 and sodium tert-butoxide into a dried reaction flask, and then evacuate with nitrogen for 3 times; under a nitrogen atmosphere, quickly add tert-butylphosphine tetrafluoroborate and tris(dibenzylideneacetone) dipalladium into the reaction flask. Subsequently, add toluene solvent that has been strictly dehydrated and deoxygenated, heat to 115 °C and reflux with stirring for 24 hours. After the stirring is completed, cool to room temperature, add dichloromethane and an appropriate amount of water for liquid-liquid extraction. Repeat the extraction operation multiple times and collect the organic phase. After drying over anhydrous magnesium sulfate, remove the solvent. The sample is separated and purified to obtain a white solid, which is Intermediate Compound 2;

[0025] Preparation of Intermediate Compound 3: Dissolve Intermediate Compound 2 in ultra-dry dichloromethane solvent in a strictly dry reaction flask, cool the reaction system to 0 °C by means of an ice-water bath, and then slowly add boron tribromide. After the addition is completed, react at 0 °C for 2 hours, and then transfer to room temperature and stir for 6 hours; slowly add the reaction solution into water for quenching, and then adjust the pH of the system to neutral with 1 mol / L sodium hydroxide solution; perform liquid-liquid extraction with dichloromethane, extract 3 times and collect the organic phase. After drying over anhydrous magnesium sulfate, remove the organic solvent to obtain a dark brown product, which is Intermediate Compound 3.

[0026] Preparation of Intermediate Compound X: Add 4-hydroxystyrene and potassium carbonate into a three-necked flask, then add acetone, stir at room temperature for 30 minutes, and finally slowly add 1,6-dibromohexane. Heat to 70 °C and react for 12 h; after the reaction is completed, cool to room temperature, add dichloromethane and water for liquid-liquid extraction, repeat the extraction operation 3 times and collect the organic phase; remove the solvent from the collected organic phase, and after separation and purification, obtain a colorless liquid, which is Crosslinked Compound X; preferably, the volume ratio of dichloromethane to water is 2:3.

[0027] Synthesis of Product V-XACz: Potassium carbonate, tetrabutylammonium bromide, intermediate compound 3 and intermediate compound X were added to the dried reaction flask, and finally acetonitrile was added; then the temperature was raised to 85 °C and stirred under reflux for 26 h; after the reaction was completed, it was cooled to room temperature, and liquid-liquid extraction was carried out with dichloromethane and water. The extraction operation was repeated many times to collect the organic phase, which was dried over anhydrous magnesium sulfate, the organic solvent was removed, and finally it was separated and purified to obtain the product.

[0028] In a third aspect, the present invention provides the use of the above-mentioned styrene hybridized binuclear carbazole derivatives in the preparation of a hole transport layer of an organic electroluminescent device. The hole transport layer is formed by mixing the styrene hybridized carbazole derivatives and a coupling agent and then coating it on the hole injection layer by a solution method, and a cross-linking reaction is carried out by thermal annealing treatment under ultraviolet light of 365 nm to prepare a thin film. The temperature of the annealing treatment is not lower than 80 °C, and the time of the annealing treatment is not less than 30 minutes; the thickness is preferably 5-20 nm.

[0029] Preferably, the coupling agent is pentaerythritol tetra(3-mercaptopropionate), i.e., PETMP; more preferably, the ratio of the carbazole derivative to the coupling agent is: adding 3 wt% of the coupling agent PETMP or adding 5 wt% of the coupling agent PETMP, where wt% refers to the mass ratio of the mercapto coupling agent to the carbazole derivative.

[0030] The styrene hybridized benzidine carbazole derivatives provided by the present invention as hole transport materials have high triplet energy levels and appropriate highest occupied molecular orbital (HOMO) energy levels, enabling them to have the ability of hole transport and blocking the spillage of excitons from the light-emitting layer, and can be used to prepare the hole transport layer of an organic electroluminescent device; moreover, the styrene hybridized binuclear carbazole derivatives provided by the present invention also have a low thermal cross-linking temperature, greatly optimizing the process conditions for preparing electroluminescent devices by the solution method; when used to prepare the hole transport layer, it can improve the device efficiency of the organic electroluminescent device.

[0031] In a fourth aspect, the present invention provides a class of organic electroluminescent devices, and the hole transport layer of the organic electroluminescent device is the hole transport layer provided by the third aspect of the present invention; as Figure 1As shown, the organic electroluminescent device sequentially includes, from the anode to the cathode: a metal anode, an electron injection layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and an ITO cathode; the metal anode layer is made of metal Ag, and preferably, the metal anode layer is formed into a film with a thickness of 100 nm by a vacuum evaporation process; the electron injection layer is made of Ca metal, and preferably, the electron injection layer is formed by a vacuum evaporation process with a film thickness of 10 nm; the electron transport layer is 1,3,5-tris(1-phenyl-1H-benzoimidazol-2-yl)benzene TPBi, and preferably, the electron transport layer is also formed by a vacuum evaporation process with a film thickness of 30 nm; the light-emitting layer is prepared by a solution method from 26DCzPPy and a thermally activated delayed fluorescence material in different mass ratios; the hole injection layer is a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate PEDOT:PSS thin film, and preferably, the PEDOT:PSS thin film of the hole injection layer is spin-coated on an ITO glass substrate by a solution process with a film thickness of about 30 nm; the anode substrate is ITO glass, and ITO is a conductive anode, and preferably, the required ITO glass substrate is cleaned, dried, and subjected to ozone treatment.

[0032] As an embodiment of the organic electroluminescent device of the present invention, the light-emitting layer material is 26DCzPPy:4CzIPN, and the mass concentrations of 26DCzPPy and 4CzIPN are 90% and 10% respectively. The organic electroluminescent device is a green-light-emitting device, and the thickness of the hole transport layer is 5 nm.

[0033] As an embodiment of the organic electroluminescent device of the present invention, the light-emitting layer material is 26DCzPPy:4TCzBN, and the mass concentrations of 26DCzPPy and 4TCzBN are 60% and 40% respectively. The organic electroluminescent device is a blue-light-emitting device, and the thickness of the hole transport layer is 5 nm.

[0034] As an embodiment of the organic electroluminescent device of the present invention, the light-emitting layer material is 26DCzPPy:TXO-TPA, and the mass concentrations of 26DCzPPy and TXO-TPA are 60% and 40% respectively; the organic electroluminescent device is a red-light-emitting device, and the thickness of the hole transport layer is 20 nm.

[0035] The beneficial effects of the present invention are:

[0036] First, the styrene hybridized binuclear carbazole derivatives provided by the present application are constructed by introducing the thermally crosslinkable functional group styrene onto the molecular core with a high HOMO energy level through an alkyl chain. Moreover, the constructed styrene hybridized binuclear carbazole derivatives can still maintain a relatively high HOMO energy level and also possess a relatively high triplet energy level. In addition, through characterization in the aspects of photophysics, electrochemistry, and thermodynamics, it can be verified that the styrene hybridized binuclear carbazole derivatives provided by the present application can be completely crosslinked under thermal initiation as a thermally crosslinkable hole transport material, and the formed film after crosslinking has good solvent resistance and film-forming properties.

[0037] Secondly, the electro-luminescent devices prepared with the styrene hybridized binuclear carbazole derivatives provided by the present application as the thermally crosslinkable hole transport material have good device efficiency.

[0038] Finally, the styrene hybridized binuclear carbazole derivatives provided by the present application can obtain a film with good solvent resistance and film-forming properties as the hole transport layer of the electro-luminescent device under relatively low heat treatment process conditions as the thermally crosslinkable hole transport material; thereby reducing the preparation process of the electro-luminescent device to be simple, efficient, environmentally friendly and pollution-free. Moreover, the thermally crosslinkable hole transport material disclosed in the present invention can be applied to the preparation of devices such as large area and large scale in the field of optoelectronic information, and also has good application prospects in the fields of solar cells, flexible materials, electrochromic materials, etc. Description of the Drawings

[0039] Figure 1 It is the structural diagram of the organic electro-luminescent device described in the present invention;

[0040] Figure 2a It is the ultraviolet absorption, fluorescence, and low-temperature transient spectrogram of the compound V-HBACz solution in Example 1 of the present invention;

[0041] Figure 2b It is the ultraviolet absorption, fluorescence, and low-temperature transient spectrogram of the compound V-OBACz solution in Example 3 of the present invention;

[0042] Figure 2c It is the ultraviolet absorption, fluorescence, and low-temperature transient spectrogram of the compound V-MEACz solution in Example 2 of the present invention;

[0043] Figure 3a It is the oxidation curve diagram of the compound V-HBACz in Example 1 of the present invention;

[0044] Figure 3b It is the oxidation curve diagram of the compound V-OBACz in Example 3 of the present invention;

[0045] Figure 3cThis is an oxidation curve of the compound V-MEACz in Example 2 of the present invention;

[0046] Figure 4 is a thermogravimetric analysis (TGA) curve of the cross-linked compound in the embodiment of the present invention;

[0047] Figure 5a This is the differential scanning calorimetry (DSC) curve of the cross-linked compound V-HBACz in Example 1 of the present invention; Figure 5b This is the differential scanning calorimetry (DSC) curve of the cross-linked compound V-OBACz in Example 3 of the present invention;

[0048] Figure 5c This is the differential scanning calorimetry (DSC) curve of the cross-linked compound V-MEACz in Example 2 of the present invention;

[0049] Figure 6a This is an atomic force microscopy (AFM) image of the compound V-HBACz in Example 1 of the present invention after cross-linking; Figure 6b This is an atomic force microscopy (AFM) image of the compound V-OBACz after cross-linking in Example 3 of the present invention; Figure 6c This is an atomic force microscopy (AFM) image of the compound V-MEACz after cross-linking in Example 2 of the present invention;

[0050] Figure 7a This is a comparison of the UV absorption spectra of the compound V-HBACz in Example 1 of the present invention before and after film formation and elution after thermal cross-linking treatment at 80°C;

[0051] Figure 7b This is a comparison of the UV absorption spectra of the compound V-OBACz in Example 3 of the present invention before and after film formation and elution after thermal cross-linking treatment at 80°C;

[0052] Figure 7c This is a comparison of the UV absorption spectra of the compound V-MEACz in Example 2 of the present invention before and after film formation and elution after thermal cross-linking treatment at 80°C;

[0053] Figure 8a is a current density-voltage-brightness characteristic curve of a green light device manufactured in an embodiment;

[0054] Figure 8b is a current efficiency-brightness-external quantum efficiency characteristic curve of a green light device manufactured in an embodiment;

[0055] Figure 8c The electroluminescence spectrum of the green light device produced in the embodiment is shown;

[0056] Figure 9a is a current density-voltage-brightness characteristic curve of a blue light device manufactured in an embodiment;

[0057] Figure 9b The current efficiency-luminance-external quantum efficiency characteristic curve of the blue light device fabricated in the embodiment;

[0058] Figure 9c The electroluminescence spectrum of the blue light device fabricated in the embodiment;

[0059] Figure 10a The current density-voltage-luminance characteristic curve of the red light device fabricated in the embodiment;

[0060] Figure 10b The current efficiency-luminance-external quantum efficiency characteristic curve of the red light device fabricated in the embodiment;

[0061] Figure 10c The electroluminescence spectrum of the red light device fabricated in the embodiment. Specific embodiments

[0062] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited to the following embodiments. Unless otherwise specified in the following methods, all are carried out under conventional conditions or the conditions recommended by the manufacturer. For the instruments and reagents not indicating the manufacturer, they can all be obtained through commercial purchase. Among them, pentaerythritol tetra(3-mercaptopropionate) (PETMP) is purchased from Nanjing Wanqing Company.

[0063] Example 1: Preparation of V-HBACz

[0064] The synthetic route of the V-HBACz is shown as follows:

[0065]

[0066] Synthesis of intermediate compound 1: Add 2.6 g of 3,3'-dibromobiphenyl (8.33 mmol), 2 g of sodium tert-butoxide (t-BuONa, 20.8 mmol), and 1.7 g of aniline (18.33 mmol) to a dry reaction flask, and then evacuate and replace with nitrogen three times through a double-tube. Under a nitrogen atmosphere, quickly add 0.3 g of tris(tert-butyl)phosphine tetrafluoroborate (P(t-Bu)3BF4) and 0.03 g of tris(dibenzylideneacetone) dipalladium (Pd2(dba)3) to the reaction flask, and then add 60 mL of toluene solvent that has been strictly dehydrated and deoxygenated. Heat to 115 °C and reflux with stirring for 24 hours. After the stirring is completed, cool to room temperature, add 100 mL of dichloromethane and 150 mL of water for liquid-liquid extraction. Repeat the extraction operation multiple times to collect the organic phase, and dry it over anhydrous magnesium sulfate and then remove the solvent. The sample is separated and purified by a silica gel chromatography column (eluent: PE:DCM = 5:1, V / V) to obtain 1.2 g of a white solid, which is intermediate compound 1, and the yield is 42%. 1H NMR spectrum: 1HNMR (400 MHz, Chloroform-d) δ 7.25–7.22 (m, 1H), 7.22–7.19 (m, 3H), 7.07–7.03 (m, 3H), 6.98 (ddd, J=8.0, 2.4, 1.0 Hz, 1H), 6.88 (tt, J=7.3, 1.1 Hz, 1H), 5.72 (s, 1H).

[0067] Synthesis of Intermediate Compound 2: Add 3 g of 9,9'-(5-bromo-1,3-phenylene)bis(4-methoxy-9H-carbazole), 0.81 g of Intermediate Compound 1, and 2 g of sodium tert-butoxide (t-BuONa, 20.8 mmol) into a dried 50 mL three-necked flask, and then evacuate and refill with nitrogen three times through a double-tube. Under a nitrogen atmosphere, quickly add 0.3 g of tris(tert-butyl)phosphine tetrafluoroborate (P(t-Bu)3BF4) and 0.03 g of tris(dibenzylideneacetone)dipalladium (Pd2(dba)3) to the reaction flask, and then add 50 mL of toluene solvent that has been strictly dehydrated and deoxygenated. Heat to 115 °C and reflux with stirring for 24 hours. After the stirring is completed, cool to room temperature, add 100 mL of dichloromethane and 150 mL of water for liquid-liquid extraction. Repeat the extraction operation multiple times and collect the organic phase. After drying over anhydrous magnesium sulfate, remove the solvent. The sample is separated and purified by silica gel column chromatography (eluent: PE:DCM = 3:1, V / V) to obtain 1.5 g of white solid, which is Intermediate Compound 2 with a yield of 51%. 1H NMR: 1 HNMR (400 MHz, Chloroform-d) δ 8.38–8.30 (m, 1H), 7.61 (t, J=2.0 Hz, 1H), 7.48 (dt, J=8.3, 0.9 Hz, 1H), 7.41–7.34 (m, 3H), 7.29 (d, J=1.5 Hz, 1H), 7.25 (d, J=1.4 Hz, 1H), 7.22–7.14 (m, 1H), 7.14–7.07 (m, 3H), 6.70 (d, J=7.9 Hz, 1H), 4.08 (s, 3H); Among them, the synthesis route and preparation conditions of the raw material 9,9'-(5-bromo-1,3-phenylene)bis(4-methoxy-9H-carbazole) are from the published literature "Zhou Z, Li Y, Tang X, et al. Low-Temperature Cross-Linkable Hole Transport Material Based on Carbazole Derivatives Design and Applications in Solution-Processed OLEDs[J]. Macromolecules, 2024,

[0068] The preparation steps in "Supporting Information" in "57(9):11.DOI:10.1021 / acs.macromol.4c00227."

[0069] Synthesis of Intermediate Compound 3: In a strictly dried reaction flask, 1.1 g of Intermediate Compound 2 (0.92 mmol) was dissolved in 50 mL of ultradry dichloromethane solvent (CH2Cl2), and a nitrogen balloon was inserted to detect the exothermic situation of the reaction system. The reaction system was cooled to 0 °C by an ice-water bath, and then 10.0 g of boron tribromide (BBr3, 40.1 mmol) was slowly added while paying attention to the volume change of the balloon during the dropping process. After the dropping was completed, the reaction was carried out at 0 °C for 2 hours, and then transferred to room temperature and stirred for 6 hours. After the stirring was completed, a drop of the reaction solution was taken and water was used to detect whether BBr3 had completely reacted. After the reaction was completed, the reaction solution was slowly added to 250 mL of water for quenching, and then the pH of the system was adjusted to neutral with 1 mol / L sodium hydroxide solution. Liquid-liquid extraction was carried out with dichloromethane, and the organic phase was collected after extraction 3 times. After drying over anhydrous magnesium sulfate, the organic solvent was removed to obtain a dark brown product, which was Intermediate Compound 3, with a mass of 0.9 g and a yield of 92%. 1H NMR spectrum: 1 H NMR(400MHz,Chloroform-d)δ8.38–8.30(m,1H),7.61(t,J=2.0Hz,1H),7.48(dt,J=8.3,0.9Hz,1H),7.41–7.34(m,3H),7.29(d,J=1.5Hz,1H),7.25(d,J=1.4Hz,1H),7.22–7.14(m,1H),7.14–7.07(m,3H),6.70(d,J=7.9Hz,1H),5.30(s,1H).

[0070] Synthesis of Intermediate Compound X6: 5.0 g of 4-hydroxystyrene (41.7 mmol) and 16.6 g of potassium carbonate (K2CO3, 120.3 mmol) were added to a 250 mL three-necked flask, and then 60 mL of acetone was added. The mixture was stirred at room temperature for 30 minutes, and finally 30.5 g of 1,6-dibromohexane (125.1 mmol) was slowly added. The temperature was raised to 70 °C and the reaction was carried out for 12 h. After the reaction was completed, it was cooled to room temperature, 100 mL of dichloromethane and an appropriate amount of water were added for liquid-liquid extraction, and the extraction operation was repeated 3 times to collect the organic phase; the solvent of the collected organic phase was removed, and purification was carried out by silica gel column chromatography (eluent: PE:DCM = 10:1, V / V) to obtain a colorless liquid, which was Crosslinked Compound X, with a mass of 1.2 g and a yield of 10.2%. 1H NMR spectrum: 1HNMR(400MHz, Chloroform-d) δ 7.25 (d, J = 8.6 Hz, 2H), 6.76 (d, J = 8.6 Hz, 2H), 6.57 (dd, J = 17.6, 10.9 Hz, 1H), 5.52 (d, J = 17.5 Hz, 1H), 5.03 (d, J = 10.8 Hz, 1H), 3.87 (t, J = 6.4 Hz, 2H), 3.34–3.31 (m, 2H), 1.82–1.78 (m, 2H), 1.79–1.63 (m, 2H), 1.42 (d, J = 3.8 Hz, 2H), 1.20 (d, J = 11.1 Hz, 2H).

[0071] Synthesis of Product V-HBACz: Add 6 g of potassium carbonate (K2CO3, 43.48 mmol), 1 g of tetrabutylammonium bromide (TBABr), 1.0 g of intermediate compound 3 (0.81 mmol), and 1.5 g of intermediate compound X6 (4.7 mmol) to a dried 50 mL three-necked flask, and finally add 50 mL of acetonitrile; then heat to 85 °C and stir under reflux for 26 h. After the reaction is completed, cool to room temperature, perform liquid-liquid extraction with 150 mL of dichloromethane and 100 mL of water, repeat the extraction operation multiple times to collect the organic phase, dry over anhydrous magnesium sulfate, remove the organic solvent, and finally separate and purify by silica gel column chromatography (eluent: PE:EA = 2:1, V / V) to obtain 0.48 g of a light yellow solid, which is the product V-HBACz, with a yield of 29%. 1H NMR spectrum: 1 H NMR(400MHz, Chloroform-d) δ 8.38–8.30 (m, 1H), 7.61 (t, J = 2.0 Hz, 1H), 7.48 (dt, J = 8.3, 0.9 Hz, 1H), 7.41–7.34 (m, 3H), 7.29 (d, J = 1.5 Hz, 1H), 7.25 (d, J = 1.4 Hz, 3H), 7.22–7.14 (m, 1H), 7.14–7.07 (m, 3H), 6.76 (d, J = 8.6 Hz, 2H), 6.70 (d, J = 7.9 Hz, 1H), 6.57 (dd, J = 17.6, 10.9 Hz, 1H), 5.52 (d, J = 17.5 Hz, 1H), 5.30 (s, 1H). 5.03 (d, J = 10.8 Hz, 1H), 3.87 (t, J = 6.4 Hz, 2H), 3.34–3.31 (m, 2H), 1.82–1.78 (m, 2H), 1.79–1.63 (m, 2H), 1.42 (d, J = 3.8 Hz, 2H), 1.20 (d, J = 11.1 Hz, 2H).

[0072] Example 2: Preparation of V-MEACz[[ID=⑨]]

[0073]

[0074] Synthesis of product V-MEACz:

[0075] In the synthesis method of intermediate compound 1 in Example 1, 3,3'-dibromobiphenyl was replaced with bis(4-bromophenyl) ether, and other conditions remained unchanged. Subsequently, other intermediate compounds were synthesized according to the method of Example 1 to obtain a series of intermediate compounds of V-MEACz. Similar to the synthesis of product V-HBACz, with conditions unchanged, intermediate compound X6 was replaced with p-chloromethylstyrene, and finally product V-MEACz was obtained. Proton nuclear magnetic resonance spectrum: 1 HNMR(400MHz,Chloroform-d)δ8.27(d,J=7.8Hz,2H),7.46–7.41(m,6H),7.39(d,J=7.8Hz,4H),7.31–7.26(m,4H),7.26–7.22(m,6H),7.21(d,J=1.7Hz,2H),7.14(d,J=7.4Hz,4H),7.07(d,J=8.2Hz,2H),7.02–6.97(m,2H),6.92(d,J=8.7Hz,2H),6.69(d,J=11.1Hz,2H),6.67–6.62(m,2H),5.70(d,J=17.6Hz,2H),5.24(s,4H),5.19(d,J=10.9Hz,2H).

[0076] Example 3: Preparation of V-OBACz

[0077]

[0078] Synthesis of product V-OBACz: The intermediate products were the same as those in the intermediate synthesis method of V-HBACz in Example 1. When synthesizing V-OBACz, intermediate compound X6 was replaced with X8, and the temperature, solvent, and time remained unchanged. Among them, the difference in the preparation of intermediate compound X8 from intermediate compound X6 was only that 1,6-dibromohexane was replaced with 1,8-dibromooctane to obtain it;

[0079] Proton nuclear magnetic resonance spectrum of product V-OBACz: 11H NMR (400 MHz, Chloroform-d) δ 8.38–8.30 (m, 1H), 7.61 (t, J = 2.0 Hz, 1H), 7.48 (dt, J = 8.3, 0.9 Hz, 1H), 7.41–7.34 (m, 3H), 7.29 (d, J = 1.5 Hz, 1H), 7.25 (d, J = 1.4 Hz, 3H), 7.22–7.14 (m, 1H), 7.14–7.07 (m, 3H), 6.76 (d, J = 8.6 Hz, 2H), 6.70 (d, J = 7.9 Hz, 1H), 6.57 (dd, J = 17.6, 10.9 Hz, 1H), 5.52 (d, J = 17.5 Hz, 1H), 5.30 (s, 1H), 5.03 (d, J = 10.8 Hz, 1H), 3.87 (t, J = 6.4 Hz, 2H), 3.34–3.31 (m, 2H), 2.28 (t, J = 7.5 Hz, 2H), 1.82–1.78 (m, 2H), 1.79–1.63 (m, 2H), 1.59–1.50 (m, 2H), 1.42 (d, J = 3.8 Hz, 2H), 1.20 (d, J = 11.1 Hz, 2H).

[0080] Prepare other types of styryl-based binuclear carbazole hole transport materials;

[0081] For example, V-HPACz with the following structural formula: (insert structural formula), the difference in its preparation process from Example 1 is only that: in the synthesis of intermediate compound 1 in Example 1, 3,3'-dibromobiphenyl is only correspondingly replaced with 4,4'-dibromobenzophenone;

[0082]

[0083] For example, V-HSACz with the following structural formula: (insert structural formula), the difference in its preparation process from Example 1 is only that: in the synthesis of intermediate compound 1 in Example 1, 3,3'-dibromobiphenyl is only correspondingly replaced with 4,4'-dibromodiphenyl sulfone;

[0084]

[0085] For example, V-MFACz with the following structural formula, the difference in its preparation process from Example 1 is only that: in the synthesis of intermediate compound 1 in Example 1, 3,3'-dibromobiphenyl is only correspondingly replaced with 2,7-dibromo-9,9-dimethylfluorene;

[0086]

[0087] For the preparation of styrene cross-linked materials with different chain lengths, reference can also be made to the preparation process of X in Example 1, which will not be elaborated here. For example, for the preparation of intermediates X10 and X12, only replace the raw material 1,6-dibromohexane with 1,10-dibromodecane and 1,12-dibromododecane respectively;

[0088] The chemical structural formula of intermediate X10 is as follows:

[0089]

[0090] Intermediate The chemical structural formula of X12 is as follows:

[0091]

[0092] Example 4: Photophysical Properties of Materials

[0093] Figure 2a 、 Figure 2b and Figure 2c respectively give the ultraviolet absorption spectra, fluorescence spectra and steady-state spectra at low temperature (77K) in solution of compounds V-HBACz, V-OBACz and V-MEACz. The compounds were dissolved in dichloromethane to prepare a solution with a concentration of 10 -5 mol / L. 0.7 mL of the solution was taken with a pipette and placed in a cuvette, and then the absorption spectrum and emission spectrum were measured in a UV-visible spectrophotometer and a fluorescence spectrophotometer. Similarly, dichloromethane was used as the solvent to prepare a solution with a concentration of 10 -5 mol / L. 2 mL of the solvent was taken and placed in a sample tube. After being cooled to 77K by liquid nitrogen, the low-temperature steady-state spectrum was measured with a phosphorescence photometer. In solution, the absorption peaks of compounds V-HBACz, V-OBACz and V-MEACz are almost the same, located at 337 nm; the emission peaks of V-HBACz, V-OBACz and V-MEACz are 391 nm, 388 nm and 381 nm respectively. Through the low-temperature steady-state spectrum, the triplet energy levels of V-HBACz, V-OBACz and V-MEACz can be calculated to be 2.76 eV, 2.75 eV and 2.76 eV respectively. The compounds prepared in this example have relatively high triplet energy levels and are used to make the hole transport layer, which can well confine the excitons in the light-emitting layer, thereby improving the efficiency of organic semiconductor devices.

[0094] Example 5: Electrochemical Performance Test of Materials

[0095] Figure 3a 、 Figure 3b 、 Figure 3cThe oxidation curves of compounds V-HBACz, V-OBACz, and V-MEACz are given respectively. To determine the energy levels of the compounds, cyclic voltammetry was used. Dichloromethane was used for the oxidation process, and the Ag / AgNO3 solution was used as the reference electrode. The ferrocene solution can be regarded as the standard solution and does not need to be mentioned. According to the oxidation potentials of compounds V-HBACz, V-OBACz, and V-MEACz, the corresponding HOMO energy levels can be calculated to be -5.12 eV, -5.15 eV, and -5.30 eV, which shows almost no change compared with the theoretically calculated HOMO energy levels. The LUMO energy levels are -1.44 eV, -1.47 eV, and -1.64 eV respectively. The HOMO energy level of the V-HBACz material is relatively high and can be used for the preparation of the hole transport layer.

[0096] Example 6: Thermal stability performance test of the material

[0097] Figure 4 The differential scanning calorimetry (DSC) diagrams of compounds V-HBACz, V-OBACz, and V-MEACz are given. It can be seen that the glass transition temperatures of compounds V-HBACz, V-OBACz, and V-MEACz are 157 °C, 140 °C, and 140 °C respectively, indicating that the two materials can be crosslinked without the need for high heat treatment conditions; Figure 5a 、 Figure 5b 、 Figure 5c The thermogravimetric diagrams (TGA) of compounds V-HBACz, V-OBACz, and V-MEACz are given respectively. From the thermogravimetric diagrams, it can be found that the thermal decomposition temperatures of the materials are 420 °C, 430 °C, and 426 °C respectively, showing good thermal stability. The good thermal stability is attributed to the three-dimensional network structure formed after the crosslinking of the styrene groups.

[0098] Example 7: Atomic force microscopy images of the material after thermal crosslinking into a film

[0099] Figure 6a 、 Figure 6b 、 Figure 6c The film formation conditions of compounds V-HBACz, V-OBACz, and V-MEACz under heat treatment at 80 °C are given respectively. It can be seen that the compounds have been completely crosslinked at 80 °C and no pinholes appear; the root mean square roughness of the compounds is less than 1 nm, indicating that all three materials V-HBACz, V-OBACz, and V-MEACz have excellent film-forming morphologies.

[0100] Example 8: Solvent resistance performance test of the material

[0101] Figure 7a 、 Figure 7b 、 Figure 7cThe ultraviolet absorption spectra of compounds V-HBACz, V-OBACz, and V-MEACz after crosslinking at 80 °C and after elution with chlorobenzene are given respectively. To test the solvent resistance of the crosslinked thin films of the compounds. In this example, the compounds were deposited on PEDOT:PSS. For these three molecules, they were completely crosslinked after only 30 minutes of heat treatment at 80 °C. Then, the crosslinked thin films were eluted three times with chlorobenzene, and the ultraviolet absorption spectra of the thin films before and after elution were measured. It was found that the absorbance of the thin films after elution with the solvent hardly changed after crosslinking, indicating that the material was completely crosslinked at this temperature and exhibited excellent solvent resistance.

[0102] Using the three materials V-HBACz, V-OBACz, and V-MEACz prepared in Example 1 above as hole-transporting materials, organic electroluminescent devices with different emission colors were fabricated respectively according to the preparation methods in Examples 9 to 11. It should be noted that the following prepared organic electroluminescent devices are all preferred embodiments provided by the present invention, and cannot limit the application scope of the derivatives of the present invention in organic electroluminescent devices.

[0103] Taking the organic electroluminescent device with the structure as Figure 1 shown as an example, the structure and preparation method of the organic electroluminescent device described in this example are elaborated. The structure of the used organic electroluminescent device from top to bottom is: anode ITO glass (indium tin oxide), hole injection layer PEDOT:PSS, hole transport layer, light-emitting layer, electron transport layer TPBi, electron injection layer Ca metal cathode Ag.

[0104] Example 9: Green light device based on 4CzIPN guest doping

[0105] The device structure of this example can be simply expressed as:

[0106] Device 1 (green light): ITO / PEDOT:PSS (30 nm) / X-HTL:PETMP (5 nm) / 26DCzPPy:4CzIPN (25 nm) / TPBi (30 nm) / Ca:Ag; The specific manufacturing steps of the device in this example are as follows: It is studied to fabricate OLED devices by solution method, and all devices are based on commercial indium tin oxide (ITO) glass substrates (sheet resistance 10 Ω / sq).

[0107] The preparation process is as follows:

[0108] Step S1, substrate pretreatment: The substrate was ultrasonically cleaned (20 minutes each) with an aqueous detergent solution, deionized water, acetone, and absolute ethanol in sequence, and then subjected to 15 minutes of ultraviolet ozone treatment to improve surface hydrophilicity.

[0109] Step S2, Preparation of hole injection layer: Deposit a PEDOT:PSS thin film on the surface of the substrate by spin coating method, and anneal it at 120 °C for 20 minutes to remove the solvent and enhance the film densification. Subsequently, transfer the substrate to a nitrogen atmosphere glove box for subsequent processes;

[0110] Step S3, Preparation of crosslinked hole transport layer: Dissolve V-HBACz, V-OBACz, and V-MEACz materials in chloroform (4 mg / mL) respectively, and dope pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) in proportion. Among them, 3 wt% PETMP is added to V-HBACz and V-MEACz, and 5 wt% PETMP is added to V-OBACz. Spin coat the mixed solution on the surface of the PEDOT:PSS layer at 3000 rpm for 30 seconds, and then synchronously irradiate and cure it with 365 nm ultraviolet light at 80 °C for 30 minutes to complete the crosslinking reaction;

[0111] Step S4, Preparation of light-emitting layer: Adopt a host-guest doping system, co-dissolve the guest luminescent materials TXO-TPA, 4CzIPN, or 4TCzBN with the host material 26DCzPPy in chloroform (4 mg / mL) in a specific proportion, spin coat it on the surface of the HTL layer, and then anneal it at 120 °C for 20 minutes to remove the residual solvent.

[0112] Step S5, Preparation of electron transport layer (ETL) and electrode: Deposit 40 nm thick TPBi as the electron transport layer, 3 nm calcium (Ca) as the electron injection layer, and 100 nm silver (Ag) as the cathode in sequence by thermal evaporation process under a vacuum of 5×10 -4 Pa, and finally complete the device encapsulation.

[0113] As Figure 8a shown is the current density-voltage-luminance characteristic curve graph of the green light device. It can be found that with the addition of the crosslinked hole transport layer, although the turn-on voltage of the device increases slightly and its maximum luminance decreases, they can all meet the requirements; as Figure 8b shown is the current efficiency-luminance-external quantum efficiency characteristic curve graph of the green light device. Compared with the device without the hole transport layer, the maximum current efficiency of the device containing the crosslinked hole transport layer increases from 19.6 cdA -1 to 78.2 cdA -1 , and the external quantum efficiency increases from 6.1% to 24.5; and it shows excellent device efficiency and stability; as Figure 8c shown is the electroluminescence spectrum graph of the green light device. It can be found that after the addition of the hole layer transport layer, there is almost no influence on the light emission of the device. Generally speaking, the thermally crosslinked hole transport layer greatly improves the performance of the green light device, and at the same time its preparation process temperature is lower.

[0114] Example 10: Blue-light device based on 4TCzBN guest doping

[0115] This Example 10 is the same as Example 9 in terms of structural components and preparation steps except for the different luminescent layer materials. Therefore, the preparation process will not be elaborated here. The device structure of this example can be simply expressed as:

[0116] Device 2 (blue light): ITO / PEDOT:PSS(30nm) / X-HTL:PETMP(5nm) / 26DCzPPy:4TCzBN(25nm) / TPBi(10nm) / Ca:Ag.

[0117] As Figure 9a shown, the current density-voltage-luminance characteristic curve of the blue-light device is presented. It can be found from the figure that compared with the device without hole transport layer, the turn-on voltage and maximum luminance of the device with hole transport layer hardly change; As Figure 9b shown, the current efficiency-luminance-external quantum efficiency characteristic curve of the green-light device is presented. Compared with the device without hole transport layer, when V-OBACz is used as the hole transport layer, its current efficiency and external quantum efficiency increase to 31.6 cd / A -1 and 11.6% respectively; As Figure 9c shown, the electroluminescence spectrum of the blue-light device is presented. It can be found from the figure that after the addition of the hole transport layer, the electroluminescence spectra of the two almost overlap, indicating that the addition of the hole transport layer hardly affects the luminescence of the blue-light material. Generally speaking, V-HBACz, V-OBACz, and V-MEACz as crosslinked hole transport layers also have a certain improvement on the performance of the blue-light device.

[0118] Example 11: Red-light device based on TXO-TPA guest doping

[0119] This example is the same as Example 9 in terms of structural components and production steps except for the different luminescent layer materials. Therefore, the preparation process will not be elaborated here. The device structure of this example can be simply expressed as:

[0120] Device 3 (red light): ITO / PEDOT:PSS(30nm) / X-HTL:PETMP(20nm) / 26DCzPPy:TXO-TPA(25nm) / TPBi(30nm) / Ca:Ag.

[0121] As Figure 10a shown, the current density-voltage-luminance characteristic curve of the red-light device is presented. With the addition of the crosslinked hole transport layer, although the turn-on voltage of the device increases slightly and its maximum luminance decreases, they can both meet the requirements; As Figure 10bshows the current efficiency-luminance-external quantum efficiency characteristic curve of the red light device. Compared with the device without the hole transport layer, the device containing the crosslinked hole transport layer V-OBACz has a current efficiency increased from 5.5 cdA -1 to 18.0 cdA -1 . At the same time, the external quantum efficiency increases from 2.6% to 9.1%; as Figure 10c shows the electroluminescence spectrum of the red light device. It can be found from the figure that after the addition of the hole transport layer, the electroluminescence spectra of the two almost coincide, indicating that the addition of the hole transport layer has little effect on the luminescence of the red light material. Generally speaking, the hole transport material has a certain generality in improving the performance of various color devices as a crosslinked hole transport layer.

[0122] The above is only a relatively ideal embodiment of the present invention, but it does not limit the patent scope of the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing specific embodiments, or perform equivalent replacements on some of the technical features. Any equivalent structure directly or indirectly using the content of the specification and drawings of the present invention in other related technical fields is equally within the scope of the patent protection of the present invention.

Claims

1. A class of binuclear carbazole derivatives based on styrene hybridization, characterized in that, The binuclear carbazole derivatives based on styrene hybridization are any one of the following structural general formulas: Among them, n is any positive integer, and R is selected from any one of the following structures, and * represents the connection site:

2. The preparation method of a class of styrene hybrid-based binuclear carbazole derivatives as described in claim 1, characterized in that, The structure of the binuclear carbazole derivatives based on styrene hybridization is selected from any one of the following compounds:

3. Application of the binuclear carbazole derivatives based on styrene hybridization described in Claim 1 in fabricating the hole transport layer of an organic electroluminescent device. The hole transport layer is formed by mixing the carbazole derivatives based on styrene hybridization and a coupling agent, and then coating it on the hole injection layer by a solution method. A cross-linking reaction is carried out through thermal annealing treatment under ultraviolet light irradiation at 365 nm to prepare a film. The temperature of the annealing treatment is not lower than 80 °C, and the time of the annealing treatment is not less than 30 minutes; the film thickness is 5 - 20 nm.

4. The application according to claim 3, characterized in that The coupling agent is pentaerythritol tetra(3-mercaptopropionate), namely PETMP.

5. The application according to claim 4, wherein The addition amount of the coupling agent PETMP is 3wt% - 5wt%.

6. A class of organic electroluminescent devices, characterized in that, The hole transport layer of the organic electroluminescent device is the hole transport layer described in Claim 3; the organic electroluminescent device sequentially includes from the anode to the cathode: a metal anode, an electron injection layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and an ITO cathode.

7. The organic electroluminescent device according to claim 6, characterized in that, The metal anode layer is metal Ag, and the film thickness is 100 nm formed by a vacuum evaporation process; the electron injection layer is Ca metal, formed by a vacuum evaporation process, and the film thickness is 10 nm; the electron transport layer is 1,3,5-tris(1-phenyl-1H-benzoimidazol-2-yl)benzene (TPBi), also formed by a vacuum evaporation process, and the film thickness is 30 nm; the light-emitting layer is prepared by a solution method from 26DCzPPy and a thermally activated delayed fluorescence material; the hole injection layer is a film formed by spin-coating PEDOT:PSS on an ITO glass substrate by a solution method, and the film thickness is 30 nm; the anode substrate is ITO glass, ITO is a conductive anode, and the required ITO glass substrate is cleaned, dried, and subjected to ozone treatment.

8. The organic electroluminescent device according to claim 6, wherein The light-emitting layer material is 26DCzPPy:4CzIPN, and the mass concentrations of 26DCzPPy and 4CzIPN are 90% and 10% respectively. The organic electroluminescent device is a green-light-emitting device, and the thickness of the hole transport layer is 5 nm.

9. The organic electroluminescent device according to claim 6, characterized in that, The light-emitting layer material is 26DCzPPy:4TCzBN, and the mass concentrations of 26DCzPPy and 4TCzBN are 60% and 40% respectively. The organic electroluminescent device is a blue-light-emitting device, and the thickness of the hole transport layer is 5 nm.

10. An organic electroluminescent device according to claim 6, wherein The light-emitting layer material is 26DCzPPy:TXO-TPA, and the mass concentrations of 26DCzPPy and TXO-TPA are 60% and 40% respectively; the organic electroluminescent device is a red-light-emitting device, and the thickness of the hole transport layer is 20 nm.

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