P-type doped cross-linked hole transport layer material and preparation method and application thereof

Abstract

The invention discloses a p-type doped cross-linked hole transport layer material and a preparation method and application thereof. The p-type doped cross-linked hole transport layer material comprises a non-conjugated polymer with high hole mobility and deep HOMO energy level and a p-type strong oxidant; the non-conjugated polymer comprises a structure shown in the following formula: # imgabs0 # N element is connected with an adjacent benzene ring at any position through a covalent bond, R1-R5 are selected from hydrogen or C1-C2 alkyl, and R6 is selected from oxygen or cyclohexane. The pi conjugate length in the carbazolyl polymer monomer with the deep HOMO energy level provided by the invention is prolonged, an intermolecular pi-pi transmission channel is greatly improved, and the improvement of hole transmission capability is facilitated. And by doping the p-type strong oxidant, the carbazole group in the polymer can be subjected to oxidative coupling, so that the excellent solvent resistance is realized, and the hole injection capability at the interface of the hole injection layer / hole transport layer is also improved.

Description

Technical Field

[0001] The present invention relates to a hole transport material, specifically to a p-type doped crosslinked hole transport layer material and its preparation method, and its application in quantum dot light-emitting devices, belonging to the technical field of quantum dot light-emitting display. Background Art

[0002] Quantum dot light-emitting diodes (QLEDs) have become a research focus in next-generation displays and lighting devices due to their advantages such as tunable spectra, high color saturation, and low energy consumption. However, one challenge faced by QLEDs is that the potential barrier difference between the deep valence band maximum (VBM) of quantum dots (QDs) and the highest occupied molecular orbital (HOMO) energy level of the hole transport layer (HTL) is very large, seriously hindering the effective injection of holes into the QD emission layer. Therefore, reducing the hole injection barrier and improving the hole transport ability are crucial for improving the performance of QLEDs. In addition, when preparing a multi-layer structure by the solution method, another common problem often needs to be considered: that is, the upper-layer solvent may potentially erode, mix with, or penetrate the lower-layer film. Therefore, the interface layer is also required to have sufficient solvent resistance to withstand the deposition of printing inks.

[0003] Among them, due to its deep HOMO energy level (-5.8 eV), when the PVK polymer is used as the hole transport layer (HTL), the hole injection barrier from the HTL to the QD can be significantly reduced. However, at the same time, this also results in a large energy level barrier between it and the hole injection layer (HIL) such as PEDOT:PSS (-5.2 eV). Under the applied forward voltage, due to the 0.6 eV energy barrier, some holes will inevitably accumulate at the interface between the HIL and the HTL. To solve this problem, an effective method is to insert a p-type dopant with a deep conduction band minimum (CBM) such as hexacarbonitrile (HAT-CN), MoO 3 etc. at the HTL and HIL interface to form an interfacial dipole layer. These materials can reduce the work function of the HIL or HTL layer by capturing electrons, thereby reducing the hole injection barrier at the interface. However, due to the too low hole mobility of PVK (about 10 -6 cm 2 V -1 s -1 ), it is difficult to meet the requirements of QLEDs.

[0004] In summary, in the prior art, PVK is still used as the HTL material with a deep HOMO energy level. However, since the repeating unit of PVK only has a single carbazole group, even if a p-type doping strategy is introduced, the improvement of the hole transport ability is extremely limited. Summary of the Invention

[0005] The main purpose of the present invention is to provide a p-type doped cross-linked hole transport layer material and a preparation method thereof, so as to overcome the deficiencies in the prior art.

[0006] Another object of the present invention is to provide an application of the p-type doped cross-linked hole transport layer material in a quantum dot electroluminescent device.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0008] The embodiment of the present invention provides a p-type doped cross-linked hole transport layer material, which includes a non-conjugated polymer with high hole mobility and a deep HOMO energy level and a p-type strong oxidant; the non-conjugated polymer with high hole mobility and a deep HOMO energy level includes a structure shown in the following formula (I) to formula (V):

[0009]

[0010] Among them, the N element is connected to the adjacent benzene ring by covalent bonds at any position, R 1 ~R 5 Selected from hydrogen or C 1 ~C 2 The alkyl group, R 6 Selected from oxygen or cyclohexane, n=5-100.

[0011] In some embodiments, the p-type strong oxidant includes any one or a combination of two or more of phosphomolybdic acid, phosphotungstic acid, phosphomolybdic tungstic acid, phosphomolybdic vanadic acid, ammonium phosphomolybdate, ammonium phosphotungstate, ammonium phosphomolybdic tungstate, and ammonium phosphomolybdic vanadate.

[0012] The embodiment of the present invention also provides a method for preparing a p-type doped cross-linked hole transport layer material, which comprises:

[0013] The non-conjugated polymer with high hole mobility and deep HOMO energy level is mixed with a p-type strong oxidant to prepare the p-type doped cross-linked hole transport layer material.

[0014] The embodiment of the present invention also provides the use of the p-type doped cross-linked hole transport layer material in a quantum dot electroluminescent device.

[0015] Correspondingly, an embodiment of the present invention further provides a hole transport layer, which includes the aforementioned p-type doped cross-linked hole transport layer material.

[0016] Furthermore, an embodiment of the present invention also provides a quantum dot electroluminescent device, which includes the aforementioned hole transport layer.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] The π conjugation length in the carbazole-based polymer monomer of the deep HOMO energy level for the quantum dot electroluminescent device provided by the present invention is extended, which greatly improves the π-π transmission channel between molecules, which is conducive to the improvement of hole transmission capacity. And by doping with a p-type strong oxidant, the carbazole groups in the polymer can be oxidatively coupled, thereby achieving excellent solvent resistance. In addition, the introduction of the p-type strong oxidant also improves the hole injection capacity at the interface of the hole injection layer / hole transport layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a JV curve diagram of a single hole device based on PVK, compounds 1, 3, and 4 in a typical embodiment of the present invention;

[0021] Figure 2 This is a graph showing the intensity of the ultraviolet absorption spectrum of a film of compound 1 before and after cleaning with chlorobenzene in a typical embodiment of the present invention;

[0022] Figure 3 This is a graph showing the intensity of the ultraviolet absorption spectrum of a film of compound 3 before and after cleaning with chlorobenzene in a typical embodiment of the present invention;

[0023] Figure 4 This is a graph showing the intensity of the ultraviolet absorption spectrum of a film of compound 4 before and after cleaning with chlorobenzene in a typical embodiment of the present invention;

[0024] Figure 5 This is a graph showing the intensity of the ultraviolet absorption spectrum of a compound 1:PMA mixed film before and after washing with chlorobenzene in a typical embodiment of the present invention;

[0025] Figure 6 This is a graph showing the intensity of the ultraviolet absorption spectrum of a compound 3:PMA mixed film before and after washing with chlorobenzene in a typical embodiment of the present invention;

[0026] Figure 7 This is a graph showing the intensity of the ultraviolet absorption spectrum of a compound 4:PMA mixed film before and after washing with chlorobenzene in a typical embodiment of the present invention;

[0027] Figure 8 Schematic diagram of the energy levels of a quantum dot electroluminescent device in a typical embodiment of the present invention. DETAILED DESCRIPTION

[0028] In view of the defects of the prior art, the inventors of this case have proposed the technical solution of the present invention after long-term research and extensive practice, which mainly provides a class of polymer hole transport materials with higher mobility and deep HOMO energy level, combined with p-type doping cross-linking, to further improve hole injection and achieve solvent resistance.

[0029] The following terms need to be explained:

[0030] QLED: quantum dot electroluminescent device; QD: quantum dot; ZnO: zinc oxide; ETL: electron transport layer; HTL: hole transport layer; HIL: hole injection layer; VBM: top of valence band; HOMO: highest occupied molecular orbital; LUMO: lowest unoccupied molecular orbital.

[0031] For ease of understanding of the present application, the present application will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0032] Specifically, as one aspect of the technical solution of the present invention, a p-type doped cross-linked hole transport layer material includes a non-conjugated polymer with high hole mobility and deep HOMO energy level and a p-type strong oxidant.

[0033] In some embodiments, the non-conjugated polymer having high hole mobility and deep HOMO energy level comprises structures shown in the following formulas (I) to (V):

[0034]

[0035]

[0036] Among them, based on the fact that the N element in the carbazole group is covalently bonded to the adjacent benzene ring at any position, R 1 ~R 5 Selected from hydrogen or C 1 ~C 2 The alkyl group, R 6 Selected from oxygen or cyclohexane, n=5-100.

[0037] In some more specific embodiments, the non-conjugated polymer having high hole mobility and deep HOMO energy level comprises structures shown in the following formulas (1) to (9):

[0038]

[0039] Among them, n=5~100.

[0040] The above carbazole-based polymer materials with deep HOMO energy level and high mobility are blended with p-type materials of strong oxidants to achieve high hole injection ability and cross-linked hole transport materials.

[0041] In some embodiments, the p-type strong oxidant can be any one or a combination of two or more of phosphomolybdic acid, phosphotungstic acid, phosphomolybdic tungstic acid, phosphomolybdic vanadic acid, ammonium phosphomolybdate, ammonium phosphotungstate, ammonium phosphomolybdic tungstate, ammonium phosphomolybdic vanadate, etc., but is not limited thereto.

[0042] In some specific embodiments, the mass ratio of the non-conjugated polymer having high hole mobility and deep HOMO energy level to the p-type strong oxidant is 7:3 to 9:1.

[0043] In summary, the π conjugation length in the carbazole-based polymer monomer for the deep HOMO energy level of the quantum dot electroluminescent device provided by the present invention is extended, which greatly improves the π-π transmission channel between molecules, which is conducive to the improvement of hole transport capacity. And by doping with a p-type strong oxidant, the carbazole groups in the polymer can be oxidatively coupled, thereby achieving excellent solvent resistance. In addition, the introduction of a p-type strong oxidant also improves the hole injection capacity at the interface of the hole injection layer / hole transport layer.

[0044] As another aspect of the technical solution of the present invention, a method for preparing a p-type doped cross-linked hole transport layer material involves: mixing a non-conjugated polymer with high hole mobility and deep HOMO energy level with a p-type strong oxidant to obtain the p-type doped cross-linked hole transport layer material.

[0045] In some embodiments, the preparation method comprises: blending any one of the above non-conjugated polymers having high hole mobility and deep HOMO energy level with a p-type strong oxidant to form a cross-linked hole transport material with high hole injection efficiency.

[0046] In some more preferred embodiments, the preparation method includes: mixing a non-conjugated polymer with high hole mobility and high HOMO energy level, a p-type strong oxidant and an organic solvent to form a mixed solution, spin coating, and then annealing to obtain the p-type doped cross-linked hole transport layer material.

[0047] Furthermore, the organic solvent comprises a combination of chlorobenzene and acetonitrile, wherein the volume ratio of chlorobenzene to acetonitrile is 7:3 to 9:1.

[0048] Furthermore, the spin coating is performed at a rotation speed of 2000 to 4000 rpm, and the spin coating time is 5 to 60 seconds, preferably 10 to 60 seconds.

[0049] Furthermore, the annealing temperature is 100-150° C., and the time is 3-15 minutes.

[0050] As another aspect of the technical solution of the present invention, it also relates to the application of the aforementioned p-type doped cross-linked hole transport layer material in a quantum dot electroluminescent device.

[0051] Correspondingly, as another aspect of the technical solution of the present invention, a hole transport layer involved includes the aforementioned p-type doped cross-linked hole transport layer material.

[0052] Furthermore, another aspect of the present invention relates to a quantum dot electroluminescent device comprising the aforementioned hole transport layer.

[0053] In some preferred embodiments, the quantum dot electroluminescent device comprises an anode, a hole injection layer (HIL), a hole transport layer (HTL), a quantum dot light-emitting layer, an electron transport layer (ETL) and a cathode arranged in sequence along a set direction.

[0054] In some preferred embodiments, the quantum dots contained in the quantum dot light-emitting layer include any one of blue light quantum dots, red light quantum dots, and green light quantum dots, preferably blue light quantum dots, but not limited thereto. That is, the present invention is not limited to blue light QLEDs, but is also applicable to red and green light QLEDs.

[0055] Furthermore, the quantum dots may be any one of CdSe, CdS, CdZnSe, ZnSe, InP, perovskite and the like quantum dots, but are not limited thereto.

[0056] Furthermore, the quantum dot electroluminescent device includes but is not limited to an upright device or an inverted device.

[0057] The present invention is further described by the following examples: The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the specific material ratios, process conditions and results described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0058] Unless otherwise specified, the various raw materials, reaction equipment, testing equipment and testing methods used in the following examples are all well known in the art.

[0059] Example 1

[0060] 1. Synthesis of intermediate a1, the reaction equation is as follows:

[0061]

[0062] 4-(bis(4-iodophenyl)amino)benzaldehyde (4.25 g, 8.1 mmol), 9H-carbazole (1.35 g, 8.1 mmol), copper(I) iodide (0.23 g, 1.215 mmol), lithium chloride (0.34 g, 8.1 mmol) and cesium carbonate (3.16 g, 9.72 mmol) were mixed and added to a 50 mL three-necked flask. Then 25 mL of N,N-dimethylformamide was added, protected by nitrogen, evacuated and filled three times to ensure an anaerobic atmosphere. Heated to 170 °C under a nitrogen atmosphere, refluxed overnight. The reaction was stopped, cooled to room temperature, a large amount of water was added to the system, and extracted with dichloromethane three times. The organic phases were combined and dried over anhydrous sodium sulfate. Subsequently, it was concentrated by rotary evaporation, and finally the crude product was separated by silica gel column chromatography, and the eluent was n-hexane / ethyl acetate (3:1 volume ratio). 2.93 g of a pale yellow solid was obtained, with a yield of 60%.

[0063] The NMR data of the product are as follows: 1 H NMR (400 MHz, CDCl 3 ) δ ppm: 9.92 (s, 1H), 8.17 (d, J = 7.7 Hz, 4H), 7.88 - 7.82 (m, 2H), 7.65 - 7.58 (m, 4H), 7.54 - 7.42 (m, 12H), 7.35 - 7.28 (m, 6H).

[0064] II. Synthesis of intermediate b1, the reaction equation is as follows:

[0065]

[0066] Under nitrogen protection, a solution of intermediate a1 (2.90 g, 4.8 mmol) in tetrahydrofuran (50 mL) was added to n-butyllithium (5 mL, 8 mmol). After stirring at room temperature for 2 h, methyltriphenylphosphonium bromide (2.9 g, 8.1 mmol, dissolved in 15 mL of tetrahydrofuran) was added dropwise. The reaction mixture was stirred at room temperature overnight and then quenched with water. The organic layer was washed three times with brine, dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography, and the eluent was n-hexane / ethyl acetate (1:1 volume ratio) to obtain the target compound b1 as a white solid (2.45 g, yield 85%).

[0067] The NMR data of the product are as follows:

[0068] 1 H NMR (400 MHz, DMSO-d 6)δppm: 8.25 (d, J=7.7Hz, 4H), 7.64-7.58 (m, 4H), 7.58-7.53 (m, 2H), 7.51-7.39 (m, 12H), 7.29 (ddt, J =8.6, 6.0, 2.9Hz, 6H), 6.76 (dd, J=17.6, 10.9Hz, 1H), 5.80 (d, J=17.6Hz, 1H), 5.24 (d, J=11.0Hz, 1H).

[0069] 13 C NMR (400 MHz, CDCl 3 )δppm: 146.85, 146.53, 141.04, 136.11, 133.32, 132.39, 128.11, 127.56, 125.95, 124.95, 124.88, 123.34, 120.37, 119.91, 113.10, 109.85.

[0070] HRMS: Calcd.for C 44 H 31 N 3 , 602.2596[M+1]; Found: 602.2599.

[0071] 3. Synthesis of the compound represented by formula (1), the reaction equation is as follows:

[0072]

[0073] In a glove box with a nitrogen atmosphere, add intermediate b1 (2.4 g, 4 mmol) and N,N-azobisisobutyronitrile (32 mg, 0.2 mmol) to a 50 mL Schlenk tube, dissolve in 20 mL of anhydrous tetrahydrofuran solution and seal. The reaction was carried out in a glove box at 50 ° C for 60 hours. The resulting solution was cooled to room temperature and exposed to the atmosphere. The mixture was poured into methanol and the precipitate was collected by filtration. The crude product was washed with methanol and n-hexane solvents in a Soxhlet extractor for 24 hours each. Finally, the residue was extracted with dichloromethane and the residue was filtered using a polytetrafluoroethylene filter with a pore size of 0.45 μm. The polymer was dried at 80 ° C in a vacuum for 30 hours with a yield of 76% (1.82 g).

[0074] The NMR data of the product are as follows:

[0075] 1 H NMR (400 MHz, CDCl 3 )δppm: 8.22-7.60 (aromatic region), 7.60-6.00 (aromatic region), 1.30, 0.92 (alkyl chain).

[0076] GPC (tetrahydrofuran): Mw = 1.1 kDa, PDI = 3.0.

[0077] Example 2

[0078] 1. Synthesis of intermediate a3, the reaction equation is as follows:

[0079]

[0080] 3,5-diiodobenzaldehyde (2.9g, 8.1mmol), 9H-carbazole (1.35g, 8.1mmol), cuprous iodide (0.23g, 1.215mmol), lithium chloride (0.34g, 8.1mmol) and cesium carbonate (3.16g, 9.72mmol) were mixed and added to a 50mL three-necked flask, and then 25ml of N,N-dimethylformamide was added, nitrogen protection, vacuum pumping 3 times to ensure an oxygen-free atmosphere. Heat to 170°C under a nitrogen atmosphere, reflux, overnight. Stop the reaction, cool to room temperature, add a large amount of water to the system, extract with dichloromethane 3 times, combine the organic phases, and dry with anhydrous sodium sulfate. Subsequently, it was concentrated by rotary evaporation, and finally the crude product was separated by silica gel column chromatography, and the eluent was n-hexane / ethyl acetate (3:1 volume ratio). 1.94g of light yellow solid was isolated, with a yield of 55%.

[0081] The NMR data of the product are as follows: 1 H NMR (400 MHz, CDCl 3 )δppm: 10.21 (s, 1H), 8.22 (d, J = 1.9Hz, 2H), 8.16 (d, J = 7.8Hz, 4H), 8.13- 8.10 (m, 1H), 7.54 (d, J=8.2Hz, 4H), 7.49-7.43 (m, 4H), 7.37-7.31 (m, 4H).

[0082] 2. Synthesis of intermediate b3, the reaction equation is as follows:

[0083]

[0084] Under nitrogen protection, a solution of intermediate a3 (1.90 g, 4.3 mmol) in tetrahydrofuran (50 mL) was added with n-butyl lithium (5 mL, 8 mmol). After stirring at room temperature for 2 h, methyl triphenylphosphine bromide (2.9 g, 8.1 mmol, dissolved in 15 mL tetrahydrofuran) was added dropwise. The reaction mixture was stirred at room temperature overnight and then quenched with water. The organic layer was washed three times with brine, dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography with n-hexane / ethyl acetate (1:1 volume ratio) as the eluent to obtain the target compound b3 as a white solid (1.49 g, yield 80%).

[0085] The NMR data of the product are as follows:

[0086] 1 H NMR (400 MHz, DMSO-d 6 )δppm: 8.27 (d, J=7.9Hz, 4H), 7.95 (d, J=2.4Hz, 2H), 7.73 (t, 1H), 7.57 (d, J=8.2Hz, 4H), 7.52-7.4 5 (m, 4H), 7.36-7.28 (m, 4H), 7.02 (dd, J=17.9, 11.1Hz, 1H), 6.18-6.11 (m, 1H), 5.52-5.45 (m, 1H).

[0087] 13 C NMR (400 MHz, CDCl 3 )δppm: 141.17, 140.58, 139.57, 135.36, 126.19, 124.44, 123.59, 123.55, 120.48, 120.35, 116.65, 109.71.

[0088] HRMS: Calcd.for C 32 H 22 N 2 , 435.1861[M+1]; Found: 435.1862.

[0089] 3. Synthesis of the compound represented by formula (3), the reaction equation is as follows:

[0090]

[0091] In a glove box with a nitrogen atmosphere, b3 (1.4 g, 3.2 mmol) and N,N-azobisisobutyronitrile (32 mg, 0.2 mmol) were added to a 50 mL Schlenk tube, dissolved in 20 mL of anhydrous tetrahydrofuran solution and sealed. The reaction was carried out in a glove box at 50 ° C for 60 hours. The resulting solution was cooled to room temperature and exposed to the atmosphere. The mixture was poured into methanol and the precipitate was collected by filtration. The crude product was washed with methanol and n-hexane solvents in a Soxhlet extractor for 24 hours each. Finally, the residue was extracted with dichloromethane and the residue was filtered using a polytetrafluoroethylene filter with a pore size of 0.45 μm. The polymer was dried at 80 ° C in a vacuum for 30 hours with a yield of 65% (0.91 g).

[0092] The NMR data of the product are as follows:

[0093] 1 H NMR (400 MHz, CDCl 3 )δppm: 8.60-4.00 (aromatic region), 1.30, 0.92 (alkyl chain).

[0094] GPC (tetrahydrofuran): Mw = 0.4 kDa, PDI = 2.7.

[0095] Example 3

[0096] 1. Synthesis of intermediate a4, the reaction equation is as follows:

[0097]

[0098] CBP (5 g, 10.3 mmol) was dissolved in a mixed solution of 50 mL chloroform and 15 mL N, N-dimethylformamide, and phosphorus oxychloride (1.58 g, 10.3 mmol, dissolved in 10 mL dichloromethane) was added dropwise at 0 ° C. The reaction mixture was then stirred at 80 ° C for 12 h and poured into an ice-water mixture to terminate the reaction. After neutralization with sodium bicarbonate, it was extracted with dichloromethane. The organic phases were combined and dried over anhydrous sodium sulfate. Subsequently, it was concentrated by rotary evaporation, and the crude product was finally separated by silica gel column chromatography, with the eluent being dichloromethane / ethyl acetate (100:1 volume ratio). 3.48 g of white solid was isolated with a yield of 66%.

[0099] The NMR data of the product are as follows: 1 H NMR (400 MHz, CDCl 3)δppm: 10.15 (s, 1H), 8.71 (d, J=1.6Hz, 1H), 8.24 (dd, J=7.8, 1.0Hz, 1H), 8.18 (dt, J=7.9 , 1.1Hz, 2H), 8.02-7.90(m, 5H), 7.75-7.69(m, 4H), 7.57-7.42(m, 8H), 7.35-7.31(m, 2H).

[0100] 2. Synthesis of intermediate b4, the reaction equation is as follows:

[0101]

[0102] Under nitrogen protection, a solution of intermediate a4 (2.46 g, 4.8 mmol) in tetrahydrofuran (50 mL) was added with n-butyl lithium (5 mL, 8 mmol). After stirring at room temperature for 2 h, methyl triphenylphosphine bromide (2.9 g, 8.1 mmol, dissolved in 15 mL tetrahydrofuran) was added dropwise. The reaction mixture was stirred at room temperature overnight and then quenched with water. The organic layer was washed three times with brine, dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography with n-hexane / ethyl acetate (1:1 volume ratio) as the eluent to obtain the target compound b4 as a white solid (2 g, yield 82%).

[0103] The NMR data of the product are as follows:

[0104] 1 H NMR (400 MHz, Benzene-d 6 )δppm: 8.21 (d, J=1.6Hz, 1H), 8.10 (dd, J=9.5, 8.1Hz, 3H), 7.54 (dd, J=8.5, 1.7Hz, 1H), 7.52-7.46 (m, 4H), 7.41 (t, J=8.6Hz, 3H), 7.35 (ddt, J=9.3, 5.5, 3.2Hz, 4H), 7.32-7.24 (m, 7H), 7.00-6.90 (m, 1H), 5.81 (d, J=17.5Hz, 1H), 5.22 (d, J=10.9Hz, 1H).

[0105] 13 C NMR (400 MHz, CDCl 3)δppm: 141.21, 140.81, 140.59, 139.33, 139.27, 139.23, 137.34, 137.27, 137.24, 137.12, 132.80, 130.15, 128.54, 128.52, 127.49, 127.38, 126.19, 126.04, 124.38, 123.72, 123.55, 123.50, 120.41, 120.27, 120.10, 118.40, 111.63, 109.98, 109.84.

[0106] HRMS: Calcd.for C 38 H 26 N 2 , 511.2174[M+1]; Found: 511.2177.

[0107] 3. Synthesis of the compound represented by formula (4), the reaction equation is as follows:

[0108]

[0109] In a glove box with a nitrogen atmosphere, b4 (2 g, 4 mmol) and N,N-azobisisobutyronitrile (32 mg, 0.2 mmol) were added to a 50 mL Schlenk tube, dissolved in 20 mL of anhydrous tetrahydrofuran solution and sealed. The reaction was carried out in a glove box at 50 ° C for 60 hours. The resulting solution was cooled to room temperature and exposed to the atmosphere. The mixture was poured into methanol and the precipitate was collected by filtration. The crude product was washed with methanol and n-hexane solvents in a Soxhlet extractor for 24 hours each. Finally, the residue was extracted with dichloromethane and the residue was filtered using a polytetrafluoroethylene filter with a pore size of 0.45 μm. The polymer was dried at 80 ° C in a vacuum for 30 hours with a yield of 82% (1.64 g).

[0110] The NMR data of the product are as follows:

[0111] 1 H NMR (400 MHz, CDCl 3 )δppm: 8.30-7.85 (aromatic region), 7.85-6.00 (aromatic region), 1.30, 0.92 (alkyl chain).

[0112] GPC (tetrahydrofuran): Mw = 2.8 kDa, PDI = 2.5.

[0113] Example 4

[0114] 1. Synthesis of intermediate a5, the reaction equation is as follows:

[0115]

[0116] BCBP (5 g, 10.3 mmol) was dissolved in a mixed solution of 50 mL chloroform and 15 mL N, N-dimethylformamide, and phosphorus oxychloride (1.58 g, 10.3 mmol, dissolved in 10 mL dichloromethane) was added dropwise at 0 ° C. The reaction mixture was then stirred at 80 ° C for 12 h and poured into an ice-water mixture to terminate the reaction. After neutralization with sodium bicarbonate, it was extracted with dichloromethane. The organic phases were combined and dried over anhydrous sodium sulfate. Subsequently, it was concentrated by rotary evaporation, and the crude product was finally separated by silica gel column chromatography, with the eluent being dichloromethane / ethyl acetate (100:1 volume ratio). 3.12 g of white solid was isolated, with a yield of 59.2%.

[0117] Elemental analysis: C, 89.49%; H, 4.87%; N, 5.63% (found); C, 86.69; H, 4.72; N, 5.46; O, 3.12 (C 37 H 24 N 2 (O theoretical value).

[0118] 2. Synthesis of intermediate b5, the reaction equation is as follows:

[0119]

[0120] Under nitrogen protection, a solution of intermediate a5 (2.46 g, 4.8 mmol) in tetrahydrofuran (50 mL) was added with n-butyl lithium (5 mL, 8 mmol). After stirring at room temperature for 2 h, methyl triphenylphosphine bromide (2.9 g, 8.1 mmol, dissolved in 15 mL tetrahydrofuran) was added dropwise. The reaction mixture was stirred at room temperature overnight and then quenched with water. The organic layer was washed three times with brine, dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography with n-hexane / ethyl acetate (1:1 volume ratio) as the eluent to obtain the target compound b5 as a white solid (1.9 g, yield 77%).

[0121] Elemental analysis: C, 89.28%; H, 5.20%; N, 5.51% (found value); C, 89.38; H, 5.13; N, 5.49 (C 38 H 26 N 2 theoretical value).

[0122] 3. Synthesis of the compound represented by formula (5), the reaction equation is as follows:

[0123]

[0124] In a glove box with a nitrogen atmosphere, b5 (2 g, 4 mmol) and N,N-azobisisobutyronitrile (32 mg, 0.2 mmol) were added to a 50 mL Schlenk tube, dissolved in 20 mL of anhydrous tetrahydrofuran solution and sealed. The reaction was carried out in a glove box at 50 ° C for 60 hours. The resulting solution was cooled to room temperature and exposed to the atmosphere. The mixture was poured into methanol and the precipitate was collected by filtration. The crude product was washed with methanol and n-hexane solvents in a Soxhlet extractor for 24 hours each. Finally, the residue was extracted with dichloromethane and the residue was filtered using a polytetrafluoroethylene filter with a pore size of 0.45 μm. The polymer was dried at 80 ° C in a vacuum for 30 hours with a yield of 86% (1.72 g).

[0125] Example 5

[0126] 1. Synthesis of intermediate a7, the reaction equation is as follows:

[0127]

[0128] CDBP (5.28 g, 10.3 mmol) was dissolved in a mixed solution of 50 mL chloroform and 15 mL N, N-dimethylformamide, and phosphorus oxychloride (1.58 g, 10.3 mmol, dissolved in 10 mL dichloromethane) was added dropwise at 0 ° C. The reaction mixture was then stirred at 80 ° C for 12 h and poured into an ice-water mixture to terminate the reaction. After neutralization with sodium bicarbonate, it was extracted with dichloromethane. The organic phases were combined and dried over anhydrous sodium sulfate. Subsequently, it was concentrated by rotary evaporation, and the crude product was finally separated by silica gel column chromatography, with the eluent being dichloromethane / ethyl acetate (100:1 volume ratio). 3.95 g of white solid was isolated with a yield of 71%.

[0129] Elemental analysis: C, 89.29%; H, 5.38%; N, 5.33% (found); C, 86.64; H, 5.22; N, 5.18; O, 2.96 (C 39 H 28 N 2 (O theoretical value).

[0130] 2. Synthesis of intermediate b7, the reaction equation is as follows:

[0131]

[0132] Under nitrogen protection, a solution of intermediate a7 (2.6 g, 4.8 mmol) in tetrahydrofuran (50 mL) was added with n-butyl lithium (5 mL, 8 mmol). After stirring at room temperature for 2 h, methyl triphenylphosphine bromide (2.9 g, 8.1 mmol, dissolved in 15 mL tetrahydrofuran) was added dropwise. The reaction mixture was stirred at room temperature overnight and then quenched with water. The organic layer was washed three times with brine, dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography with n-hexane / ethyl acetate (1:1 volume ratio) as the eluent to obtain the target compound b7 as a white solid (2.07 g, yield 80%).

[0133] Elemental analysis: C, 89.16%; H, 5.65%; N, 5.18% (found); C, 89.19; H, 5.61; N, 5.20 (C 40 H 30 N 2 theoretical value).

[0134] 3. Synthesis of the compound represented by formula (7), the reaction equation is as follows:

[0135]

[0136] In a glove box with a nitrogen atmosphere, b7 (2.15 g, 4 mmol) and N,N-azobisisobutyronitrile (32 mg, 0.2 mmol) were added to a 50 mL Schlenk tube, dissolved in 20 mL of anhydrous tetrahydrofuran solution and sealed. The reaction was carried out in a glove box at 50 ° C for 60 hours. The resulting solution was cooled to room temperature and exposed to the atmosphere. The mixture was poured into methanol and the precipitate was collected by filtration. The crude product was washed with methanol and n-hexane solvents in a Soxhlet extractor for 24 hours each. Finally, the residue was extracted with dichloromethane and the residue was filtered using a polytetrafluoroethylene filter with a pore size of 0.45 μm. The polymer was dried at 80 ° C in a vacuum for 30 hours with a yield of 80% (1.72 g).

[0137] Example 6

[0138] 1. Synthesis of intermediate a8, the reaction equation is as follows:

[0139]

[0140] O-CBP (5.15 g, 10.3 mmol) was dissolved in a mixed solution of 50 mL chloroform and 15 mL N, N-dimethylformamide, and phosphorus oxychloride (1.58 g, 10.3 mmol, dissolved in 10 mL dichloromethane) was added dropwise at 0 ° C. The reaction mixture was then stirred at 80 ° C for 12 h and poured into an ice-water mixture to terminate the reaction. After neutralization with sodium bicarbonate, it was extracted with dichloromethane. The organic phases were combined and dried over anhydrous sodium sulfate. Subsequently, it was concentrated by rotary evaporation, and the crude product was finally separated by silica gel column chromatography, with the eluent being dichloromethane / ethyl acetate (100:1 volume ratio). 3.76 g of white solid was isolated with a yield of 69%.

[0141] Elemental analysis: C, 89.48%; H, 4.87%; N, 5.64% (found value); C, 84.07; H, 4.58; N, 5.30; O, 6.05 (C 37 H 24 N 2 O 2 theoretical value).

[0142] 2. Synthesis of intermediate b8, the reaction equation is as follows:

[0143]

[0144] Under nitrogen protection, a solution of intermediate a8 (2.54 g, 4.8 mmol) in tetrahydrofuran (50 mL) was added with n-butyl lithium (5 mL, 8 mmol). After stirring at room temperature for 2 h, methyl triphenylphosphine bromide (2.9 g, 8.1 mmol, dissolved in 15 mL tetrahydrofuran) was added dropwise. The reaction mixture was stirred at room temperature overnight and then quenched with water. The organic layer was washed three times with brine, dried over anhydrous sodium sulfate, filtered, and concentrated by rotary evaporation. The crude product was purified by silica gel column chromatography with n-hexane / ethyl acetate (1:1 volume ratio) as the eluent to obtain the target compound b8 as a white solid (2.15 g, yield 85%).

[0145] Elemental analysis: C, 89.38%; H, 5.14%; N, 5.48% (found); C, 86.67; H, 4.98; N, 5.32; O, 3.04 (C 38 H 26 N 2 (O theoretical value).

[0146] 3. Synthesis of the compound represented by formula (8), the reaction equation is as follows:

[0147]

[0148] In a glove box with a nitrogen atmosphere, b8 (2.1 g, 4 mmol) and N,N-azobisisobutyronitrile (32 mg, 0.2 mmol) were added to a 50 mL Schlenk tube, dissolved in 20 mL of anhydrous tetrahydrofuran solution and sealed. The reaction was carried out in a glove box at 50 ° C for 60 hours. The resulting solution was cooled to room temperature and exposed to the atmosphere. The mixture was poured into methanol and the precipitate was collected by filtration. The crude product was washed with methanol and n-hexane solvents in a Soxhlet extractor for 24 hours each. Finally, the residue was extracted with dichloromethane and the residue was filtered using a polytetrafluoroethylene filter with a pore size of 0.45 μm. The polymer was dried at 80 ° C in a vacuum for 30 hours with a yield of 84% (1.76 g).

[0149] Test Example 1 Study on the Hole Transport Performance of HTL

[0150] In this example, single hole devices of PVK, compound 1, compound 3, and compound 4 were prepared to study the hole transport properties of different hole transport layers.

[0151] The specific implementation is as follows: spin-coat PEDOT:PSS on the ITO electrode, dry and anneal; spin-coat different hole transport layer materials, dry at 130°C for 10 minutes; and finally, -4 MoO was formed by vacuum evaporation under vacuum conditions of Pa. 3 Electron blocking layer and aluminum electrode. The structure of the single hole device is ITO (160nm) / PEDOT (35nm) / HTL (30nm) / QDs (20nm) / MoO 3 (5nm) / Al(100nm).

[0152] The hole mobility of PVK, compound 1, compound 3, and compound 4 was calculated by the space charge limited current (SCLC) method. The JV curve of the single hole device is shown in Figure 1 As shown. The calculated hole mobility of PVK is the lowest, which is 3.32×10 - 6 cm 2 V -1 s -1 In contrast, compound 1, compound 3, and compound 4 all have higher hole mobility, with values ​​of 1.03×10 -4 cm 2 V -1 s -1 , 3.27×10 -5 cm 2 V -1 s -1 , 6.70×10 -5 cm 2 V-1 s -1 The higher hole mobility of compounds 1, 3, and 4 is mainly attributed to the increase in the π-conjugated chain length of the hole transport unit within the molecule, which increases the intermolecular π-π stacking and charge transfer channels, thereby improving the hole carrier mobility.

[0153] Test Example 2 Study on Solvent Resistance of Cross-linked HTL

[0154] Taking phosphomolybdic acid (PMA) doping as an example, the solvent resistance of polymer films without and with PMA doping was characterized, and the specific implementation is as follows:

[0155] The quartz substrate was treated with O-p1asma for 3 minutes, and then different hole transport layer materials were spin-coated. The hole transport layer materials used were compound 1, compound 3 and compound 4, respectively. Pure hole transport material 4 was mixed with PMA, wherein the mass ratio of PMA was 20wt%, and the solvent was a mixed solution of chlorobenzene: acetonitrile (volume ratio 9:1), and then spin-coated on the treated quartz wafer and annealed at 130°C for 10 minutes.

[0156] UV-visible absorption spectroscopy was used to study the changes in the cross-linked film before and after solvent rinsing, which can clearly determine whether it is eroded by the solvent. The UV-visible absorption spectrum was measured by a Perkin-Elemer Lambda 750 UV spectrophotometer. Specifically, the UV absorption intensity of different samples was tested; all samples were rinsed with chlorobenzene solvent, and the UV absorption intensity of different samples was tested again after the solvent dried. The results are as follows: Figure 2 to Figure 7 As shown. Figure 2-Figure 4 It can be seen that for the pure films of compound 1, compound 3, and compound 4 without PMA doping, the absorption intensity of the films will decrease to varying degrees when washed with chlorobenzene, indicating that the films have been corroded and damaged by the chlorobenzene solvent. Figure 5-Figure 7 It can be seen that after the polymer film formed by doping PMA is washed with chlorobenzene, the absorption spectrum of the film is almost the same as that before washing, indicating that the cross-linked film has excellent solvent resistance.

[0157] Application Example 1 (Blue Light Quantum Dot Electroluminescent Device)

[0158] Figure 8 An energy level diagram of a blue light quantum dot electroluminescent device according to an application example of the present invention is shown.

[0159] The blue light quantum dot electroluminescent device was prepared as follows:

[0160] (1) Cleaning: The surface of the ITO glass substrate was cleaned with a detergent, and organic pollutants were removed by ultrasonic treatment with ethanol and acetone. The substrate was then rinsed three times with ultrapure water, dried with nitrogen, and treated with oxygen plasma (O-plasma) for 3 minutes to obtain a clean ITO glass substrate.

[0161] (2) Preparation of PEDOT:PSS HIL layer: On the ITO glass substrate cleaned in step (1), the PEDOT:PSS solution was spin-coated on the treated ITO glass substrate (4000 rpm, 30 s), annealed at 130 °C for 15 min in an atmospheric atmosphere, and then transferred to a nitrogen glove box (O 2 <1ppm, H 2 O<1ppm).

[0162] (3) Preparation of HTL layer: pure polymer was prepared into 4 mg mL-1 chlorobenzene solution, polymer: PMA (20 wt%) was prepared into 4 mg mL-1 1 Chlorobenzene: acetonitrile (volume ratio 9:1) solution was prepared and spin coated at 3000 rpm for 30 seconds and annealed at 130°C for 15 minutes. For the acetonitrile-washed polymer: PMA (20 wt%), after the above annealing was completed and cooled, the film surface was washed with 100 μL of acetonitrile and then annealed at 130°C for 5 minutes.

[0163] (4) Preparation of quantum dot light-emitting layer: Spin-coat the HTL-2 obtained in step (4) with an octane-dispersed blue light quantum dot solution, and then anneal at 100° C. for 2 minutes. The quantum dots can be any one of CdSe, CdS, CdZnSe, ZnSe, etc.

[0164] (5) Preparation of ETL layer: Spin-coat Zn onto the QDs obtained in step (5) 0.85 Mg 0.15 O nanocrystals (ethanol dispersion, 25 mg mL -1 ), spin-coated at 3000 rpm for 30 seconds, and baked at 90°C for 15 minutes.

[0165] (6) The wafer is placed in a vacuum deposition chamber, and a 100 nm thick metal aluminum electrode (A1) is vacuum deposited to produce a quantum dot electroluminescent device.

[0166] Taking compounds 1, 3-4, compound 1: PMA, compound 3: PMA, and compound 4: PMA according to the above embodiments of the present invention as HTL, the structure of the QLED device is: ITO (about 110nm) / PEDOT: PSS (about 28nm) / HTL (20nm) / QDs (about 20nm) / Zn 0.85 Mg 0.15O (about 50nm) / A1 (about 100nm). The test data of QLED devices with CdSe blue light quantum dots as the light-emitting layer are shown in Table 1:

[0167] Table 1 Summary of performance of blue light QLED devices with different HTL materials

[0168]

[0169] Turn-on voltage: at 1cd·m -2 under the brightness.

[0170] As can be seen from Table 1, after PVK, Compound 1, Compound 3, and Compound 4 are doped with PMA, the turn-on voltage of the device is significantly reduced compared with the pure polymer reference device, and the performance is also greatly improved. This is mainly attributed to the fact that after PMA is doped, due to its strong electron-withdrawing ability, an interfacial dipole layer will be formed at the HIL / HTL. The electrons at the HOMO energy level (-5.2eV) in PEDOT:PSS can be spontaneously transferred to the deep LUMO energy level (-5.6eV) of PMA (such as Figure 8 As shown in the figure), the hole injection barrier from PEDOT:PSS to PVK is reduced, the hole injection capability is greatly improved, and the hole density injected into the HTL is increased.

[0171] Among them, the performance of the blue light spin-coated device based on compound 4 was the most improved, due to its deep HOMO energy level (-6.0 eV) and high hole mobility, combined with the advantages of doping with PMA. The maximum EQE of the device based on compound 4:PMA was as high as 16.6%, which was a significant improvement of 2.6 times compared with the reference PVK device (6.4% EQE).

[0172] Application Example 2

[0173] Compared with Application Example 1, the difference is that in step (3), when preparing the HTL layer, the volume ratio of chlorobenzene:acetonitrile is 7:3, and the mass ratio of polymer:PMA is 7:3. Spin coating is performed at a speed of 2000 rpm for 60 seconds and annealing is performed at 100°C for 12 minutes.

[0174] Application Example 3

[0175] Compared with Application Example 1, the difference is that in step (3), when preparing the HTL layer, the mass ratio of polymer to PMA is 9: 1. Spin coating is performed at a rotation speed of 4000 rpm for 5 seconds and annealing is performed at 150° C. for 3 minutes.

[0176] Application Example 4

[0177] Compared with Application Example 1, the difference is that in step (3): PMA is replaced by phosphotungstic acid, phosphomolybdic tungstic acid, phosphomolybdic vanadic acid, ammonium phosphomolybdate, ammonium phosphotungstate, ammonium phosphomolybdic tungstate, ammonium phosphomolybdic vanadate, etc. The test results obtained are similar to those in Application Example 1, indicating that the introduction of the p-type strong oxidant improves the hole injection ability at the interface of the hole injection layer / hole transport layer.

[0178] In addition, the inventors of this case also referred to the aforementioned embodiments and conducted experiments with other raw materials, process operations, and process conditions described in this specification, and obtained relatively ideal results.

[0179] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A p-type doped cross-linked hole transport layer material, characterized in that: The p-type doped cross-linked hole transport layer material includes a non-conjugated polymer with high hole mobility and deep HOMO energy level and a p-type strong oxidant; the non-conjugated polymer with high hole mobility and deep HOMO energy level includes the structures shown in the following formulas (I) to (V): The N element is connected to the adjacent benzene ring by a covalent bond at any position, R1 to R5 are selected from hydrogen or an alkyl group containing C1 to C2, R6 is selected from oxygen or cyclohexane, and n=5 to 100.

2. The p-type doped cross-linked hole transport layer material according to claim 1, characterized in that: The non-conjugated polymer with high hole mobility and deep HOMO energy level includes structures shown in the following formulas (1) to (9): Among them, n=5~100.

3. The p-type doped cross-linked hole transport layer material according to claim 1, characterized in that: The p-type strong oxidant includes any one of phosphomolybdic acid, phosphotungstic acid, phosphomolybdic tungstic acid, phosphomolybdic vanadic acid, ammonium phosphomolybdate, ammonium phosphotungstate, ammonium phosphomolybdic tungstate, and ammonium phosphomolybdic vanadate, or a combination of two or more thereof.

4. The p-type doped cross-linked hole transport layer material according to claim 1, characterized in that: The mass ratio of the non-conjugated polymer with high hole mobility and deep HOMO energy level to the p-type strong oxidant is 7:3-9:

1.

5. The method for preparing a p-type doped cross-linked hole transport layer material according to any one of claims 1 to 4, characterized in that: include: The p-type doped cross-linked hole transport layer material is prepared by mixing a non-conjugated polymer with high hole mobility and deep HOMO energy level with a p-type strong oxidant.

6. The preparation method according to claim 5, characterized in that: include: A non-conjugated polymer with high hole mobility and high HOMO energy level, a p-type strong oxidant and an organic solvent are mixed to form a mixed solution, which is spin-coated and then annealed to prepare the p-type doped cross-linked hole transport layer material.

7. The preparation method according to claim 6, characterized in that: The organic solvent comprises a combination of chlorobenzene and acetonitrile, preferably, the volume ratio of chlorobenzene to acetonitrile is 7:3 to 9:1; And / or, the spin coating is performed at a rotation speed of 2000 to 4000 rpm and a spin coating time of 5 to 60 seconds; And / or, the annealing temperature is 100-150° C. and the annealing time is 3-15 min.

8. Use of the p-type doped cross-linked hole transport layer material according to any one of claims 1 to 4 in a quantum dot electroluminescent device.

9. A hole transport layer, characterized in that: The p-type doped cross-linked hole transport layer material comprises the p-type doped cross-linked hole transport layer material according to any one of claims 1 to 4; preferably, the thickness of the hole transport layer is 20 to 40 nm.

10. A quantum dot electroluminescent device, characterized in that: comprising the hole transport layer according to claim 9; Preferably, the quantum dot electroluminescent device comprises an anode, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer and a cathode which are sequentially arranged along a set direction; Preferably, the quantum dots contained in the quantum dot light-emitting layer include any one of blue light quantum dots, red light quantum dots, and green light quantum dots, preferably blue light quantum dots; Preferably, the quantum dots include any one of CdSe, CdS, CdZnSe, ZnSe, InP, and perovskite quantum dots; Preferably, the quantum dot electroluminescent device includes an upright device or an inverted device.

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