Photocrosslinkable polymer, hole transport layer material and applications

Abstract

This invention discloses a photocrosslinkable polymer, a hole transport layer material, and its applications, relating to the field of optoelectronic technology. The structural formula of the aforementioned photocrosslinkable polymer is shown below: where a and b are mole fractions, 0.8 < a < 1, 0 < b < 0.2; R is a photocrosslinkable group. The photocrosslinkable polymer of this invention exhibits excellent solvent resistance and can serve as a high-mobility hole transport material. It not only demonstrates excellent solvent resistance and high hole mobility but also promotes hole injection in the quantum dot (QD) electroluminescent layer (EML) and effectively blocks electrons from entering the hole transport layer (HTL). In particular, the high surface energy of the HTL improves the wettability of the QD layer, thereby achieving better interfacial contact. When mixed with quantum dots, it can form high-performance quantum dot light-emitting diodes (QLEDs) with high efficiency and stability. The maximum EQE of the spin-coated blue QLED reaches 15%.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic technology, specifically relating to a photocrosslinkable polymer, a hole transport layer material, its preparation method, and its application. Background Technology

[0002] Quantum dot light-emitting diodes (QLEDs) have become strong competitors in display technology due to their high brightness, high color saturation, and long lifespan. In the most advanced organic-inorganic hybrid QLEDs, the electroluminescent tube (ETL) is mainly composed of ZnO nanocrystals or modified ZnO (such as ZnMgO). The high electron mobility of ZnO nanocrystals and the CBM energy levels that match the quantum dots provide efficient electron injection for the device. However, the low hole mobility of organic hydrogen dot transistors (HTLs) or a large energy level mismatch with quantum dots hinders hole injection. Therefore, excessive electron accumulation at the organic HTL / inorganic QD interface or leakage to the HTL can trigger nonradiative recombination of the HTL and even cause irreversible structural deformation.

[0003] Therefore, an ideal HTL (hole transport layer) material should not only possess excellent hole transport / injection capabilities but also good electron blocking capabilities. Among these, polymer PF8Cz is widely used as an HTL due to its high hole mobility, shallower LUMO level, and the carbazole group introduced into PF8CZ, which reduces molecular energy disorder and effectively suppresses electron leakage at the HTL / QD interface. However, because PF8CZ contains a large number of soluble alkyl groups, the films prepared from it are susceptible to potential erosion during continuous solution processing, especially in inkjet printing.

[0004] In the prior art, it is known that FLCZ-V, a thermally crosslinked small molecule HTL material with the same functional groups, was synthesized based on the repeating unit of PF8CZ. In this material, the styrene end group is used as the thermal crosslinking group. By blending PF8CZ and FLCZ-V, a crosslinked entangled HTL with excellent electron blocking ability is constructed. After heat treatment, FLCZ-V can be crosslinked in situ to form a continuous three-dimensional network polymer, in which the linear polymer PF8Cz is entangled, thereby achieving good solvent resistance (ACS Appl. Mater Interfaces, 2024, 16(37), 49563-49573). However, in this scheme, PF8CZ can only be crosslinked with FLCZ-V by thermal crosslinking. The crosslinking temperature is high and the time is long, which puts forward higher requirements for the thermal stability of the underlying material and / or substrate material. Therefore, it also limits the selection space of materials. On the other hand, the energy consumption of the high-temperature thermal crosslinking reaction is high, which increases the preparation cost and is not conducive to energy conservation and emission reduction. The cross-linked polymer reported in Chinese invention patent CN107207778A has a randomly arranged combination of three segments: fluorene, carbazole, and cross-linked carbazole, which significantly increases the energy disorder of the material and the risk of electron leakage in the device. Furthermore, the photocrosslinking groups in the disclosed technical solution require the addition of a photocatalyst to achieve the crosslinking reaction between the photocrosslinking groups; therefore, the reaction sites and crosslinking ability are limited by the number of photocrosslinking groups introduced.

[0005] In view of the above limitations, the present invention provides a polymer hole transport layer material with high photocrosslinking efficiency. By using photocrosslinking, without the need to add a photocatalyst, the photocrosslinking groups can directly crosslink with the large alkyl chain -CH bond in the polymer under photoinitiation, which greatly improves the photocrosslinking efficiency and reduces the crosslinking energy consumption, while avoiding the influence of the introduction of photoinitiator on the photoelectric properties of the material. Summary of the Invention

[0006] The purpose of this invention is to provide a photocrosslinked polymer hole transport layer material, its preparation method, and its application, so as to overcome the shortcomings of the prior art.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution.

[0008] As a first aspect of the invention, the present invention provides a photocrosslinkable polymer, the structural formula of which is shown below:

[0009]

[0010] Where a and b are mole fractions, 0.8 <a<1,0<b<0.2;

[0011] R is a photocrosslinking group.

[0012] The photocrosslinking group introduced into the structure of the polymer of the present invention eliminates the need for a photoinitiator during crosslinking. Under the initiation of ultraviolet light, the photocrosslinking group can directly crosslink with the large alkyl chain -CH bond in the polymer, which greatly improves the photocrosslinking efficiency and avoids the influence of the introduction of a photoinitiator on the photoelectric properties of the material.

[0013] In some specific embodiments, R is selected from any of the following structural formulas:

[0014]

[0015] More preferably, R is selected from any of the following structural formulas:

[0016]

[0017] In some specific embodiments, one of the following structural formulas is selected:

[0018]

[0019] Where a = 0.85 to 0.9, b = 0.1 to 0.15.

[0020] More preferably, a = 0.9, b = 0.1.

[0021] Most preferably, the polymer film prepared using the following structural formula exhibits excellent solvent resistance, and the QLED device prepared using it also shows the best performance; the structural formula is:

[0022] Where a = 0.85 to 0.9, b = 0.1 to 0.15.

[0023] As another objective of the invention, the present invention also provides the application of the aforementioned photocrosslinkable polymer in the preparation of hole transport layers for organic light-emitting diodes and quantum dot light-emitting diodes.

[0024] As a third objective of the invention, the present invention also provides a hole transport layer material, comprising the aforementioned photocrosslinkable polymer.

[0025] As a fourth objective of the invention, the present invention also provides a polymer film obtained by dissolving the photocrosslinkable polymer as described above in a solvent and then spin-coating it onto the surface of a substrate material and curing it.

[0026] Preferably, the solvent includes any one of toluene, xylene, chlorobenzene, or chloroform, but is not limited thereto.

[0027] Preferably, the curing process includes annealing followed by ultraviolet light irradiation.

[0028] Preferably, the annealing includes holding at 120–150°C for 5–20 minutes.

[0029] Preferably, the wavelength of the ultraviolet light is 365 nm.

[0030] As a fifth objective of the invention, the present invention also provides a quantum dot electroluminescent device comprising at least the photocrosslinkable polymer and quantum dots as described above.

[0031] In some specific embodiments, the fabrication method of the quantum dot electroluminescent device includes the following steps:

[0032] S1. Provide a substrate;

[0033] S2. Preparation of PEDOT:PSS layer: Spin-coating PEDOT:PSS solution onto the substrate;

[0034] S3. Preparation of HTL layer: spin-coating a solution of the photocrosslinkable polymer as described in any one of claims 1-3 onto the PEDOT:PSS layer to obtain the HIL layer;

[0035] S4. Preparation of quantum dot luminescent layer: spin-coating quantum dot dispersion onto the HTL layer, followed by annealing to obtain the quantum dot luminescent layer;

[0036] S5. Preparation of ETL layer: Spin-coat Zn0.85Mg0.15O nanocrystalline dispersion onto the quantum dot light-emitting layer and bake until dry; finally place in a vacuum evaporation chamber and vacuum evaporate aluminum electrodes to obtain the quantum dot electroluminescent device.

[0037] Preferably, the quantum dot can be a blue quantum dot, or a red or green quantum dot. More preferably, the quantum dot is any one of CdSe, CdS, CdZnSe, ZnSe, InP, perovskite, etc., but is not limited thereto.

[0038] Preferably, the maximum external quantum efficiency of the quantum dot electroluminescent device is 12-15%.

[0039] Compared with the prior art, the present invention has at least the following beneficial effects:

[0040] 1. The photocrosslinkable polymer in this invention has excellent solvent resistance and can be used as a high-mobility transparent electrode (HTL) material. It not only exhibits excellent solvent resistance, high hole mobility, and gradient HOMO and shallow LUMO energy levels, but also promotes hole injection in the quantum dot (QD) electroluminescent layer (EML) and effectively blocks electrons from entering the HTL. In particular, the high surface energy of the HTL improves the wettability of the QD layer, thereby achieving better interfacial contact. When mixed with quantum dots, it can form high-performance quantum dot light-emitting diodes (QLEDs) with high efficiency and stability. The maximum EQE of spin-coated blue QLEDs reaches 15%.

[0041] 2. The photocrosslinked polymer HTL material provided by the technical solution of this invention has superior solvent resistance. The photocrosslinking groups it contains can crosslink between -CH bonds in the polymer, thereby forming a more stable and solvent-resistant crosslinked network structure. Crosslinking does not require high temperature initiation or the addition of additional catalysts. It only requires photo-initiation for rapid crosslinking, which greatly improves the crosslinking rate and reduces crosslinking energy consumption. In particular, it also has high mobility and excellent electron blocking ability, which can confine the carrier recombination region of the device in the light-emitting layer and reduce the non-radiative convergence of excitons.

[0042] 3. The technical solution of the present invention is not limited to blue QLED, but can also be compatible with red or green QLED. Furthermore, QLED devices can be upright or inverted. Therefore, the technical solution provided by the present invention is a general strategy that is suitable for large-scale promotion and application. Attached Figure Description

[0043] Figure 1 The image shows a comparison of the UV absorption intensity of the films formed by the photocrosslinkable polymers provided in Examples 7-12 of this invention before and after solvent cleaning without UV irradiation.

[0044] Figure 2 The image shows a comparison of the UV absorption intensity of the films formed by the photocrosslinkable polymers provided in Examples 7-12 of this invention before and after solvent cleaning under UV irradiation.

[0045] Figure 3 Solvent resistance tests were conducted on the photocrosslinked polymer films prepared with different b-doping amounts of the polymers obtained in Examples 13-17. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments.

[0047] The technical solution of the present invention will be explained in more detail below with reference to several embodiments.

[0048] Example 1

[0049] This embodiment provides a method for preparing intermediate a1, the specific steps of which include:

[0050] 9-oxo-9H-thioxanthene-2-carboxylic acid (0.653 g, 2.55 mmol), 4-pyrrolylpyridine (0.0378 g, 0.255 mmol), and N,N-dicycloethylcarbodiimide (0.528 g, 2.55 mmol) were mixed and added to a 50 mL three-necked flask. Then, dichloromethane (20 mL) and diethyl ether (5 mL) were added. The mixture was placed under nitrogen atmosphere and evacuated three times to create an oxygen-free atmosphere. Under nitrogen atmosphere, a dichloromethane solution (10 mL) of (3,6-dibromo-9H-carbazol-9-yl)methanol (0.9 g, 2.55 mmol) was added dropwise to the reaction system, and the mixture was stirred overnight at room temperature. The reaction was stopped, and the filtrate was washed three times each with deionized water and dilute acetic acid solution, and then dried with anhydrous sodium sulfate. The solution was then concentrated by rotary evaporation, and finally separated by silica gel column chromatography to obtain intermediate a1 0.54 g, with a yield of 40%.

[0051] Elemental analysis (measured values): C: 59.47%; H: 2.77%; Br: 29.31%; N: 2.56%; S: 5.87%.

[0052] The reaction principle is as follows:

[0053]

[0054] Example 2

[0055] This embodiment provides a method for preparing intermediate a2, the specific steps of which include:

[0056] 4-(2-oxo-2-phenylacetyl)benzoic acid (0.648 g, 2.55 mmol), 4-pyrrolylpyridine (0.0378 g, 0.255 mmol), and N,N-dicycloethylcarbodiimide (0.528 g, 2.55 mmol) were mixed and added to a 50 mL three-necked flask. Then, dichloromethane (20 mL) and diethyl ether (5 mL) were added. The mixture was placed under nitrogen atmosphere and evacuated three times to ensure an oxygen-free atmosphere. Under nitrogen atmosphere, a dichloromethane solution (10 mL) of (3,6-dibromo-9H-carbazol-9-yl)methanol (0.9 g, 2.55 mmol) was added dropwise to the reaction system, and the mixture was stirred overnight at room temperature. The reaction was stopped, and the filtrate was washed three times each with deionized water and dilute acetic acid solution, and then dried with anhydrous sodium sulfate. The solution was then concentrated by rotary evaporation, and finally separated by silica gel column chromatography to obtain intermediate a20.68 g, with a yield of 45%.

[0057] Elemental analysis (measured values): C: 63.78%; H: 3.25%; Br: 30.30%; N: 2.65%.

[0058] The reaction principle is as follows:

[0059]

[0060] Example 3

[0061] This embodiment provides a method for preparing intermediate a3, the specific steps of which include:

[0062] 2-diazo-2-phenylacetic acid (0.413 g, 2.55 mmol), 4-pyrrolylpyridine (0.0378 g, 0.255 mmol), and N,N-dicycloethylcarbodiimide (0.528 g, 2.55 mmol) were mixed and added to a 50 mL three-necked flask. Then, dichloromethane (20 mL) and diethyl ether (5 mL) were added. The mixture was kept under nitrogen atmosphere and evacuated three times to ensure an oxygen-free atmosphere. Under nitrogen atmosphere, a dichloromethane solution (10 mL) of (3,6-dibromo-9H-carbazol-9-yl)methanol (0.9 g, 2.55 mmol) was added dropwise to the reaction system, and the mixture was stirred overnight at room temperature. The reaction was stopped, and the filtrate was washed three times each with deionized water and dilute acetic acid solution, and then dried with anhydrous sodium sulfate. The solution was then concentrated by rotary evaporation, and finally separated by silica gel column chromatography to obtain intermediate a 30.41 g, with a yield of 32%.

[0063] Elemental analysis (measured values): C: 54.00%; H: 2.81%; Br: 34.20%; N: 8.99%.

[0064] The reaction principle is as follows:

[0065]

[0066] Example 4

[0067] This embodiment provides a method for preparing intermediate a4, the specific steps of which include:

[0068] 4-azido-2,3,5,6-tetrafluorobenzoic acid (0.586 g, 2.55 mmol), 4-pyrrolylpyridine (0.0378 g, 0.255 mmol), and N,N-dicycloethylcarbodiimide (0.528 g, 2.55 mmol) were mixed and added to a 50 mL three-necked flask. Then, dichloromethane (20 mL) and diethyl ether (5 mL) were added. The mixture was placed under nitrogen atmosphere and evacuated three times to ensure an oxygen-free atmosphere. Under nitrogen atmosphere, a dichloromethane solution (10 mL) of (3,6-dibromo-9H-carbazol-9-yl)methanol (0.9 g, 2.55 mmol) was added dropwise to the reaction system, and the mixture was stirred overnight at room temperature. The reaction was stopped, and the filtrate was washed three times each with deionized water and dilute acetic acid solution, and then dried with anhydrous sodium sulfate. The solution was then concentrated by rotary evaporation, and finally separated by silica gel column chromatography to obtain intermediate a 40.62 g, with a yield of 43%.

[0069] Elemental analysis (measured values): C: 44.47%; H: 1.49%; Br: 29.58%; F: 14.06%; N: 10.36%.

[0070] The reaction principle is as follows:

[0071]

[0072] Example 5

[0073] This embodiment provides a method for preparing intermediate a5, the specific steps of which include:

[0074] 4-(3-(trifluoromethyl)-3H-diazirin-3-yl)benzoic acid (0.586 g, 2.55 mmol), 4-pyrrolidinylpyridine (0.0378 g, 0.255 mmol), and N,N-dicycloethylcarbodiimide (0.528 g, 2.55 mmol) were mixed and added to a 50 mL three-necked flask. Then, dichloromethane (20 mL) and diethyl ether (5 mL) were added. Under nitrogen protection, the mixture was evacuated three times to ensure an oxygen-free atmosphere. Under a nitrogen atmosphere, a 10 mL solution of (3,6-dibromo-9H-carbazol-9-yl)methanol (0.9 g, 2.55 mmol) in dichloromethane was added dropwise to the reaction system, and the mixture was stirred overnight at room temperature. After the reaction was stopped, the filtrate was filtered and washed three times each with deionized water and dilute acetic acid solution, and dried over anhydrous sodium sulfate. The solution was then concentrated by rotary evaporation, and the crude product was finally separated by silica gel column chromatography to obtain intermediate a 50.53 g, with a yield of 37%.

[0075] Elemental analysis (measured values): 49.37%; H: 2.25%; Br: 29.86%; F: 10.65%; N: 7.85%.

[0076] The reaction principle is as follows:

[0077]

[0078] Example 6

[0079] This embodiment provides a method for preparing intermediate a6, the specific steps of which include:

[0080] 2-diazo-3-oxobutanoic acid (0.326 g, 2.55 mmol), 4-pyrrolylpyridine (0.0378 g, 0.255 mmol), and N,N-dicycloethylcarbodiimide (0.528 g, 2.55 mmol) were mixed and added to a 50 mL three-necked flask. Then, dichloromethane (20 mL) and diethyl ether (5 mL) were added. The mixture was kept under nitrogen atmosphere and evacuated three times to ensure an oxygen-free atmosphere. Under nitrogen atmosphere, a dichloromethane solution (10 mL) of (3,6-dibromo-9H-carbazol-9-yl)methanol (0.9 g, 2.55 mmol) was added dropwise to the reaction system, and the mixture was stirred overnight at room temperature. The reaction was stopped, and the filtrate was washed three times each with deionized water and dilute acetic acid solution, and then dried with anhydrous sodium sulfate. The solution was then concentrated by rotary evaporation, and finally separated by silica gel column chromatography to obtain intermediate a 60.28 g, with a yield of 24%.

[0081] Elemental analysis (measured values): C: 48.95%; H: 2.65%; Br: 38.31%; N: 1.0%.

[0082] The reaction principle is as follows:

[0083]

[0084] Example 7

[0085] This embodiment provides a method for preparing polymer 1, the specific steps of which include:

[0086] Under nitrogen protection, monomer 1 (0.31 g, 0.48 mmol), monomer 2 (0.18 g, 0.432 mmol), intermediate a1 (0.028 g, 0.048 mmol), tetra(triphenylphosphine)palladium (0.017 g, 13.9 mmol), tetraethylammonium hydroxide (20% aq, 2.8 mL), and three drops of methyltrioctylammonium chloride were added to a 50 mL Schulenck tube and dissolved in 10 mL of toluene solution and sealed. The reaction was carried out under nitrogen atmosphere at 95 °C for 72 hours. The resulting solution was cooled to room temperature and placed in atmospheric air. The mixture was poured into methanol, and the precipitate was collected by filtration. The crude product was washed successively with methanol and n-hexane solvents for 24 hours each in a Soxhlet extractor. Finally, the residue was extracted with dichloromethane, and the residue was filtered through a 0.45 μm polytetrafluoroethylene filter. The polymer was dried in a vacuum at 80°C for 30 hours, with a yield of 88% (0.27 g).

[0087] Elemental analysis (measured values): C: 87.41%; H: 8.49%; N: 1.91%; S: 2.17%.

[0088] GPC (tetrahydrofuran): Mw = 3.1 kDa, PDI = 3.0.

[0089]

[0090] Example 8

[0091] This embodiment provides a method for preparing polymer 2, the specific steps of which include:

[0092] Under nitrogen protection, monomer 1 (0.31 g, 0.48 mmol), monomer 2 (0.18 g, 0.432 mmol), intermediate a2 (0.028 g, 0.048 mmol), tetra(triphenylphosphine)palladium (0.017 g, 13.9 mmol), tetraethylammonium hydroxide (20% aq, 2.8 mL), and three drops of methyltrioctylammonium chloride were added to a 50 mL Schulenck tube and dissolved in 10 mL of toluene solution and sealed. The reaction was carried out under nitrogen atmosphere at 95 °C for 72 hours. The resulting solution was cooled to room temperature and placed in atmospheric air. The mixture was poured into methanol, and the precipitate was collected by filtration. The crude product was washed successively with methanol and n-hexane solvents for 24 hours each in a Soxhlet extractor. Finally, the residue was extracted with dichloromethane, and the residue was filtered through a 0.45 μm PTFE filter. The polymer was dried in a vacuum at 80°C for 30 hours, with a yield of 90% (0.3 g).

[0093] Elemental analysis (measured values): C: 89.3%; H: 8.74%; N: 1.93%.

[0094] GPC (tetrahydrofuran): Mw = 2.8 kDa, PDI = 3.5.

[0095]

[0096] Example 9

[0097] This embodiment provides a method for preparing polymer 3, the specific steps of which include:

[0098] Under nitrogen protection, monomer 1 (0.31 g, 0.48 mmol), monomer 2 (0.18 g, 0.432 mmol), intermediate a3 (0.024 g, 0.048 mmol), tetra(triphenylphosphine)palladium (0.017 g, 13.9 mmol), tetraethylammonium hydroxide (20% aq, 2.8 mL), and three drops of methyltrioctylammonium chloride were added to a 50 mL Schulenck tube and dissolved in 10 mL of toluene solution and sealed. The reaction was carried out under nitrogen atmosphere at 95 °C for 72 hours. The resulting solution was cooled to room temperature and placed under atmospheric pressure. The mixture was poured into methanol, and the precipitate was collected by filtration. The crude product was washed successively with methanol and n-hexane solvents for 24 hours each in a Soxhlet extractor. Finally, the residue was extracted with dichloromethane, and the residue was filtered through a 0.45 μm PTFE filter. The polymer was dried under vacuum at 80 °C for 30 hours. Yield 85% (0.28g).

[0099] Elemental analysis (measured values): C: 87.14; H: 8.83; N: 4.02%.

[0100] GPC (tetrahydrofuran): Mw = 3.8 kDa, PDI = 2.4.

[0101]

[0102] Example 10

[0103] This embodiment provides a method for preparing polymer 4, the specific steps of which include:

[0104] Under nitrogen protection, monomer 1 (0.31 g, 0.48 mmol), monomer 2 (0.18 g, 0.432 mmol), intermediate a4 (0.027 g, 0.048 mmol), tetra(triphenylphosphine)palladium (0.017 g, 13.9 mmol), tetraethylammonium hydroxide (20% aq, 2.8 mL), and three drops of methyltrioctylammonium chloride were added to a 50 mL Schulenck tube and dissolved in 10 mL of toluene solution and sealed. The reaction was carried out under nitrogen atmosphere at 95 °C for 72 hours. The resulting solution was cooled to room temperature and placed under atmospheric pressure. The mixture was poured into methanol, and the precipitate was collected by filtration. The crude product was washed successively with methanol and n-hexane solvents for 24 hours each in a Soxhlet extractor. Finally, the residue was extracted with dichloromethane, and the residue was filtered through a 0.45 μm PTFE filter. The polymer was dried under vacuum at 80 °C for 30 hours. Yield: 86% (0.286g).

[0105] Elemental analysis (measured values): C: 81.98%; H: 8.05%; F: 5.19%; N: 4.78%.

[0106] GPC (tetrahydrofuran): Mw = 3.8 kDa.

[0107]

[0108] Example 11

[0109] This embodiment provides a method for preparing polymer 5, the specific steps of which include:

[0110] Under nitrogen protection, monomer 1 (0.31 g, 0.48 mmol), monomer 2 (0.18 g, 0.432 mmol), intermediate a5 (0.027 g, 0.048 mmol), tetra(triphenylphosphine)palladium (0.017 g, 13.9 mmol), tetraethylammonium hydroxide (20% aq, 2.8 mL), and three drops of methyltrioctylammonium chloride were added to a 50 mL Schulenck tube and dissolved in 10 mL of toluene solution before sealing. The reaction was carried out under nitrogen atmosphere at 95 °C for 72 hours.

[0111] The resulting solution was cooled to room temperature and placed in atmospheric atmosphere. The mixture was poured into methanol, and the precipitate was collected by filtration. The crude product was washed successively with methanol and n-hexane in a Soxhlet extractor for 24 hours each. Finally, the residue was extracted with dichloromethane, and the residue was filtered through a 0.45 μm PTFE filter. The polymer was dried under vacuum at 80 °C for 30 hours. Yield: 81% (0.27 g).

[0112] Elemental analysis (measured values): C: 83.9%; H: 8.34%; F: 3.9%; N: 3.83%.

[0113] GPC (tetrahydrofuran): Mw = 4.2 kDa.

[0114]

[0115] Example 12

[0116] This embodiment provides a method for preparing polymer 6, the specific steps of which include:

[0117] Under nitrogen protection, monomer 1 (0.31 g, 0.48 mmol), monomer 2 (0.18 g, 0.432 mmol), intermediate a6 (0.022 g, 0.048 mmol), tetra(triphenylphosphine)palladium (0.017 g, 13.9 mmol), tetraethylammonium hydroxide (20% aq, 2.8 mL), and three drops of methyltrioctylammonium chloride were added to a 50 mL Schulenck tube and dissolved in 10 mL of toluene solution before sealing. The reaction was carried out under nitrogen atmosphere at 95 °C for 72 hours.

[0118] The resulting solution was cooled to room temperature and placed in atmospheric atmosphere. The mixture was poured into methanol, and the precipitate was collected by filtration. The crude product was washed successively with methanol and n-hexane in a Soxhlet extractor for 24 hours each. Finally, the residue was extracted with dichloromethane, and the residue was filtered through a 0.45 μm PTFE filter. The polymer was dried under vacuum at 80 °C for 30 hours. Yield: 76% (0.25 g).

[0119] Elemental analysis (measured values): C: 86.8%; H: 9.01%; N: 4.17%.

[0120] GPC (tetrahydrofuran): Mw = 5.7 kDa.

[0121]

[0122] Example 13

[0123] The difference between this embodiment and embodiment 7 is that the addition ratio of intermediate a1 is different, and polymer 7 with a b doping amount of 0.01 (addition amount of intermediate a1: 2.8 mg, 0.0048 mmol) is obtained, and then photocrosslinked polymer film is formed.

[0124] Example 14

[0125] The difference between this embodiment and embodiment 7 is that the addition ratio of intermediate a2 is different, and polymer 8 with a b doping amount of 0.03 (addition amount of intermediate a1: 8.4 mg, 0.0144 mmol) is obtained, and then photocrosslinked polymer film is formed.

[0126] Example 15

[0127] The difference between this embodiment and embodiment 7 is that the addition ratio of intermediate a3 is different, and polymer 9 with a b doping amount of 0.05 (addition amount of intermediate a1, 14mg, 0.024mmol) is obtained, and it is photocrosslinked into a polymer film.

[0128] Example 16

[0129] The difference between this embodiment and embodiment 9 is that the addition ratio of intermediate a4 is different, and polymer 10 with a b doping amount of 0.15 (addition amount of intermediate a1, 42mg, 0.072mmol) is obtained, and it is photocrosslinked into a polymer film.

[0130] Example 17

[0131] The difference between this embodiment and Example 10 is that the addition ratio of intermediate a5 is different, and polymer 11 with a b doping amount of 0.2 (addition amount of intermediate a1, 48mg, 0.096mmol) is obtained, and it is photocrosslinked into a polymer film.

[0132] Example 18

[0133] In this embodiment, polymers 1-11 provided in Examples 7-17 above are crosslinked after being irradiated with ultraviolet light to form a polymer film, and solvent resistance tests are performed. The specific implementation is as follows:

[0134] The quartz substrate was subjected to O-plasma treatment for 3 minutes. Then, the solutions of polymers 1-11 provided in Examples 7-17 (with chlorobenzene as solvent) with a concentration of 8 mg / mL were spin-coated onto the surface of the treated quartz substrate. The substrate was annealed at 130°C for 10 minutes and then irradiated with a 365 nm wavelength ultraviolet curing lamp for 300 s to form polymer films with a thickness of 20 nm.

[0135] Ultraviolet-visible absorption spectroscopy was used to study the changes in the cross-linked film before and after solvent washing, which can clearly determine whether it has been eroded by the solvent. The ultraviolet-visible absorption spectra were measured using a Perkin-Elemer Lambda 750 ultraviolet spectrophotometer. Specifically, the ultraviolet absorption intensity of different samples was tested; all samples were washed with toluene solvent, and after the solvent dried, the ultraviolet absorption intensity of different samples was tested again. The ratio of the absorption intensity before and after was defined as the solvent resistance of the film.

[0136] See results Figure 1 As can be seen, for the photocrosslinked polymer films of polymers 1-6, the absorption intensity of the films decreased significantly after being cleaned with toluene without UV irradiation, indicating that the films were not crosslinked and were damaged by the toluene solvent. Figure 2 As shown, when the photocrosslinked polymer film of polymers 1-6 is irradiated with UV light and then cleaned with toluene, the absorption spectrum of the film is almost identical to that before cleaning, indicating that the crosslinked film has excellent solvent resistance properties with a solvent resistance rate of ≥98%.

[0137] Furthermore, in this embodiment, polymers 7-11 with different b-doping amounts (0.01, 0.03, 0.05, 0.15, 0.2) were prepared from intermediate a1. Specific preparation steps are detailed in Examples 13-17 and will not be repeated here. The obtained polymers were then used to prepare photocrosslinked polymer films, and their solvent resistance was tested. See the relevant documentation for details. Figure 3The results showed that after UV irradiation and toluene cleaning, the absorption spectrum of the film almost overlapped with that before cleaning, indicating that the cross-linked films all have excellent solvent resistance. Furthermore, even when the beta doping concentration was as low as 1%, high solvent resistance was still maintained. However, for the reference PF8CZ polymer film (see ACS Appl. Mater. Interfaces, 2024, 16(37), 49563-49573), cleaning with toluene led to a significant decrease in the film's absorption intensity, indicating that the film was corroded and damaged by toluene solvent, with a solvent resistance rate of only 23%.

[0138] Example 19

[0139] This embodiment uses blue QLED as an example, and fabricates a blue quantum dot electroluminescent device based on polymers 1-11 provided in Examples 7-17:

[0140] (1) Cleaning: Clean the surface of the ITO glass substrate with detergent, sonicate with ethanol and acetone to remove organic contaminants, rinse three times with ultrapure water, dry with nitrogen, and then treat with oxygen plasma (O-plasma) for 3 minutes to obtain a cleaned ITO glass substrate.

[0141] (2) Preparation of PEDOT:PSS layer: On the ITO glass substrate cleaned in step (1), PEDOT:PSS solution (1.4wt%) was spin-coated onto the treated ITO glass substrate (4000 rpm, 30s), and annealed at 130°C for 15 min in an atmospheric atmosphere, and then transferred to a nitrogen glove box (O2<1ppm, H2O<1ppm).

[0142] (3) Preparation of HTL layer: Spin-coat the HIL layer obtained in step (2) with a chlorobenzene solution (8 mg / mL) of HTL material at 3000 rpm for 30 seconds, anneal at 130°C for 10 min, and then irradiate with a 365 nm wavelength ultraviolet curing lamp for 300 s. The HTL material is any one of polymers 1-11.

[0143] (4) Preparation of quantum dot emitting layer: Spin-coat the HTL obtained in step (3) with a toluene-dispersed blue quantum dot solution, and then anneal at 100°C for 2 minutes. CdSe blue quantum dots were selected as the quantum dots.

[0144] (5) Preparation of ETL layer: Spin-coating Zn onto the QD obtained in step (5). 0.85 Mg 0.15 O nanocrystals (dispersed in ethanol, 25 mg / mL) -1 Spin coat at 3000 rpm for 30 seconds, then bake at 90°C for 15 minutes.

[0145] (6) The wafer is placed in a vacuum evaporation chamber and a 100nm aluminum electrode (Al) is vacuum evaporated to obtain a quantum dot electroluminescent device.

[0146] This embodiment uses polymer 1-11 as an example of the above-mentioned HTL material for illustrative purposes, and the quantum dots selected are CdSe blue quantum dots.

[0147] The structure of the fabricated QLED device is: ITO (~110nm) / PEDOT: PSS (~28nm) / HTL (25nm) / QDs (~20nm) / Zn 0.85 Mg 0.15 O (~50nm) / Al (~100nm).

[0148] The test data of the QLED device with CdSe blue quantum dots as the light-emitting layer are shown in Table 1.

[0149] Table 1 Summary of performance of blue QLED devices with different HTL materials

[0150] Devices Start-up voltage (V) Maximum external quantum efficiency (%) CIE(x, y) PF8CZ 2.4 6.4 0.12，0.10 Polymer 1 2.4 13.5 0.12,0.10 Polymer 2 2.4 14.2 0.12.0.10 Polymer 3 2.4 12.7 0.12，0.10 Polymer 4 2.4 13.1 0.12，0.10 Polymer 5 2.4 11.6 0.12，0.10 Polymer 6 2.4 11.9 0.12，0.10 Polymer 7 2.4 9.8 0.12，0.10 Polymer 8 2.4 10.6 0.12，0.10 Polymer 9 2.4 11.7 0.12，0.10 Polymer 10 2.4 12.9 0.12，0.10 Polymer 11 2.4 9.9 0.12，0.10

[0151] Start-up voltage: at 1 cd·m -2 At that brightness.

[0152] According to the performance comparison of blue QLED devices in Table 1, when the b doping amount is 0.1, the maximum external quantum efficiency (%) of devices prepared using intermediates a1 to a6 is ≥12, especially polymer 2, which is the best, followed by polymer 1 and polymer 4. Taking intermediate a1 as an example, polymers 7-11 were obtained with different b doping amounts (0.01, 0.03, 0.05, 0.15, 0.2) and blue QLED devices were prepared. The maximum external quantum efficiency (%) of polymer 7-11 was lower than that of polymer 1 with b=0.1, followed by polymer 1 with a doping amount of 0.05. When the doping amounts were 0.01 and 0.2, the maximum external quantum efficiency (%) was already lower than 10.

[0153] Based on the above analysis, the preferred doping amount of b in this application is 0.15 to 0.1, and the most preferred amount is b = 0.1.

[0154] Furthermore, in the technical solution of the present invention, the HIL material is not limited to the structural formula of the polymer already shown, and its photocrosslinking group can also be selected from other structures that can crosslink between -CH bonds in the polymer to achieve the purpose of the present invention.

[0155] On the other hand, the quantum dots in this invention are not limited to the blue quantum dots mentioned above, but can also be other types such as red quantum dots, indium quantum dots, perovskites, etc., or any one of CdSe, CdS, CdZnSe, ZnSe, etc.

[0156] It should be noted that the above description is only a preferred embodiment of the present invention and the foregoing embodiments have been used to describe the present invention in detail. The embodiments are not intended to limit the present application. Although those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included within the protection scope of the present invention.

Claims

1. A photocrosslinkable polymer, characterized in that, Its structural formula is shown below: Where a and b are mole fractions, 0.8 <a<1,0<b<0.2; R is a photocrosslinkable group.

2. The photocrosslinkable polymer according to claim 1, characterized in that, R is selected from any of the following structural formulas:

3. The photocrosslinkable polymer according to claim 1, characterized in that, Choose one of the following structural formulas: Where a = 0.85 to 0.9, b = 0.1 to 0.

15.

4. The application of a photocrosslinkable polymer as described in any one of claims 1-3 in the preparation of hole transport layers for organic light-emitting diodes and quantum dot light-emitting diodes.

5. A hole transport layer material comprising the photocrosslinkable polymer as described in any one of claims 1-3.

6. A polymer film, obtained by dissolving the photocrosslinkable polymer as described in any one of claims 1-3 in a solvent, and then spin-coating it onto the surface of a substrate material and curing it.

7. The polymer film according to claim 6, characterized in that, The solvent includes any one of toluene, xylene, chlorobenzene, or chloroform; And / or, the curing includes annealing followed by ultraviolet light irradiation; And / or, the annealing includes holding at 120–150°C for 5–20 minutes; And / or, the wavelength of ultraviolet light is 365nm.

8. A quantum dot electroluminescent device, comprising at least the photocrosslinkable polymer and quantum dots as described in any one of claims 1-3.

9. The quantum dot electroluminescent device according to claim 8, characterized in that, Its preparation method includes the following steps: S1. Provide a substrate; S2. Preparation of PEDOT:PSS layer: Spin-coating PEDOT:PSS solution onto the substrate; S3. Preparation of HTL layer: spin-coating the solution of the photocrosslinking polymer as described in any one of claims 1-3 onto the PEDOT:PSS layer to obtain HIL layer; S4. Preparation of quantum dot luminescent layer: spin-coating quantum dot dispersion onto the HTL layer, followed by annealing to obtain the quantum dot luminescent layer; S5. Fabrication of ETL layer: Spin-coating ZnO onto the quantum dot light-emitting layer n0.85 Mg 0.15 The O-nanocrystalline dispersion was baked until dry; finally, it was placed in a vacuum evaporation chamber and a metallic aluminum electrode was vacuum-deposited to obtain the quantum dot electroluminescent device.

10. The quantum dot electroluminescent device according to claim 9, characterized in that, The quantum dot is any one of CdSe, CdS, CdZnSe, ZnSe, InP, or perovskite; The maximum external quantum efficiency of the quantum dot electroluminescent device is 12-15%.

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