Polymer hole transport material and preparation method and application thereof

Abstract

This invention provides a polymer hole transport material, its preparation method, and its applications. The polymer hole transport material has a structure as shown in Formula I and / or Formula II. The hole transport layer prepared from the polymer hole transport material provided by this invention not only has excellent ultraviolet stability but also high conductivity and is insensitive to thickness changes. The polymer hole transport material provided by this invention greatly improves the stability of perovskite solar cells.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic device technology, and relates to a polymer hole transport material, its preparation method and application. Background Technology

[0002] Metal halide perovskite solar cells (PSCs) have attracted widespread research interest due to their solution processability, mechanical flexibility, and excellent photoelectric properties. Among them, inverted PSCs with a positive-intrinsic-negative (pin) structure show promising prospects for commercial applications due to their simple fabrication process and low cost. However, the commercialization of pin-type PSCs is limited by their poor long-term stability, especially in practical applications where the devices are exposed to various environmental stresses such as heat, humidity, and ultraviolet radiation, which significantly affect their performance. Although a large amount of research has been conducted on the thermal and optical stability (mainly visible light) of PSCs, research on their intrinsic ultraviolet stability remains relatively scarce. Ultraviolet light accounts for only 4% to 5% of the global solar spectrum in the AM 1.5G region, but it can induce deep-level defect states (such as Pb) at the device interface. 2+ To Pb 0 The conversion of sunlight into perovskite film (PSC) significantly impairs the operational stability of PSCs. In single-junction pin-type PSCs, sunlight enters from the transparent conductive oxide (TCO) / hole transport layer (HTL) side, making the hole transport layer more susceptible to photodegradation. Therefore, the commercialization of inverted PSCs urgently requires a hole transport layer with excellent photostability (especially UV stability). Furthermore, an ideal hole transport layer must be able to efficiently transport holes and promote the formation of uniform and well-crystallized perovskite films to meet the demands of large-scale production. However, during processing in ambient atmospheres, environmental factors such as humidity, oxygen, and temperature significantly affect the morphology and microstructure of perovskite films, making the achievement of these requirements even more challenging.

[0003] Recent advances in self-assembled monolayers (SAMs), particularly carbazole phosphonate (PACz) materials, have significantly revolutionized the hole transport performance of pin-type power storage devices (PSCs), enabling them to surpass the efficiency of nip-structured devices. SAMs, consisting of anchoring groups, spacer groups, and terminal groups, represent a breakthrough in pin-type PSC research. Through meticulous design and modification, record-breaking efficiency improvements in PSCs have been achieved multiple times.

[0004] However, unlike traditional polymer-type hole transport layers such as poly(3,4-ethylenedioxythiophene):poly(sodium styrene sulfonate) (PEDOT:PSS) and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), small-molecule PACz hole transport layers have low conductivity and rely on the formation of self-assembled monolayers for hole extraction. Their performance is extremely sensitive to layer thickness and coverage, resulting in a narrow processing window and difficulty in achieving uniformity over large areas. This makes it difficult for single SAMs-type hole transport layers to meet mass production requirements. Furthermore, since perovskite devices need to withstand light (including ultraviolet light) incident from one side of the hole transport layer, the hole transport layer must possess good mechanical and optical stability. However, research on the ultraviolet stability and degradation mechanisms of SAMs is still very scarce. Recent research by Wu et al. shows that conjugated molecular structures have more efficient electron / charge delocalization than non-conjugated MeO-2PACz, and their frontier level modulation strategy helps improve the ultraviolet stability of SAMs, making them superior to non-conjugated PACz SAMs.

[0005] Studies have found that traditional PACz hole transport layers have poor irradiation stability, mainly because the bonding between phosphonic acid groups and TCO is weak, and the material is prone to UV-induced decomposition.

[0006] Therefore, it is desirable in this field to develop a hole transport material from which the hole transport layer has excellent UV stability and is insensitive to changes in thickness. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a polymeric hole transport material, its preparation method, and its applications. To overcome the aforementioned defects of PACz hole transport layers, this invention develops a polymeric hole transport material by polymerizing small phosphate molecules. Compared with traditional small-molecule SAMs, this polymeric SAM not only possesses excellent UV stability but also high conductivity and is insensitive to thickness variations, laying the foundation for the fabrication of efficient and stable large-area devices. Hole transport layers based on this polymeric hole transport material, when prepared using an ambient atmosphere coating method, achieve an efficiency of 23.0%. After 1000 hours of maximum power point (MPP) testing under AM 1.5G 1 full-spectrum solar irradiation, the device efficiency still maintains over 98% of its initial value. This design strategy for polymeric hole transport layers not only provides crucial support for the commercialization of PSCs but also opens new pathways for developing more efficient and stable PSC hole transport layers.

[0008] To achieve this objective, the present invention employs the following technical solution: In a first aspect, the present invention provides a polymer hole transport material having the structure shown in Formula I and / or Formula II: In Equations I and II, m is an independent integer from 2 to 4, for example, 2, 3 or 4; In Equations I and II, n is independently 10 to 20, for example, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20.

[0009] The hole transport layer made from the polymer hole transport material provided by this invention not only has excellent ultraviolet stability but also high conductivity and is insensitive to thickness changes. The polymer hole transport material provided by this invention greatly improves the stability of perovskite solar cells.

[0010] Preferably, the molecular weight of the polymer hole transport material is 4000~10000, such as 4000, 4318, 4946, 5564, 6184, 6800, 7418, 8036, 8654 or 10000.

[0011] Preferably, the polymer hole transport material is any one of the following polymers: .

[0012] In a second aspect, the present invention provides a method for preparing a polymer hole transport material as described in the first aspect, the method comprising the following steps: (1) Mix bis(1,5-cyclooctadiene)nickel (Ni(COD)2), 2,2'-bipyridine (bipy), 1,5-cyclooctadiene (1,5-COD) and organic solvent, then add raw material A, react, then add pH adjuster to adjust the pH value of the system, and post-process to obtain intermediate A; (2) Mix intermediate A with solvent, then add BrSi(Me)3, react, then add organic solvent, stir, and post-process to obtain the polymer hole transport material.

[0013] Preferably, the molar ratio of bis(1,5-cyclooctadiene)nickel (Ni(COD)2), 2,2'-bipyridine (bipy), and 1,5-cyclooctadiene in step (1) is 1:(0.8~1.2):(0.8~1.2), for example, 1:0.8:0.8, 1:0.8:1, 1:0.8:1.2, 1:1:0.8, 1:1:1, 1:1:1.2, 1:1.2:0.8, 1:1.2:1, or 1:1.2:1.2, etc.

[0014] Preferably, the organic solvent in step (1) includes N,N-dimethylformamide (DMF).

[0015] Preferably, the mixing temperature in step (1) is 70~90℃, such as 70℃, 75℃, 80℃, 85℃ or 90℃, and the mixing time is 0.5~1 hour, such as 0.5 hours, 0.8 hours or 1 hour.

[0016] Preferably, the raw material A in step (1) includes and / or , where m is an integer from 2 to 4, such as 2, 3 or 4.

[0017] Preferably, the molar ratio of bis(1,5-cyclooctadiene)nickel (Ni(COD)2) to raw material A in step (1) is 1:(0.6~1), for example 1:0.6, 1:0.7, 1:0.8, 1:0.9 or 1:1, etc.

[0018] Preferably, the reaction temperature in step (1) is 70~90℃, for example 70℃, 75℃, 80℃, 85℃ or 90℃, and the reaction time is 8~24 hours, for example 8 hours, 10 hours, 12 hours, 14 hours, 15 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours.

[0019] Preferably, the pH adjuster in step (1) includes hydrochloric acid with a concentration of 0.8~1.2 mol / L (e.g., 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L or 1.2 mol / L).

[0020] Preferably, the pH value of the system in step (1) is adjusted to 1~2, such as 1, 1.2, 1.4, 1.5, 1.6, 1.8 or 2.

[0021] Preferably, the post-processing in step (1) includes filtration, sedimentation, washing, and drying.

[0022] Preferably, the solvent in step (2) includes dichloromethane.

[0023] Preferably, in step (2), the mass ratio of intermediate A to BrSi(Me)3 is 1:(1~2), for example 1:1, 1:1.2, 1:1.4, 1:1.5, 1:1.6, 1:1.8 or 1:2, etc.

[0024] Preferably, the reaction temperature in step (2) is room temperature, and the reaction time is 10 to 16 hours, such as 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or 16 hours.

[0025] Preferably, the reaction in step (2) is carried out under stirring conditions.

[0026] Preferably, the organic solvent in step (2) includes methanol (MeOH).

[0027] Preferably, the stirring time in step (2) is 10 to 16 hours, for example, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours or 16 hours.

[0028] Preferably, the post-processing in step (2) includes concentration and precipitation.

[0029] Thirdly, the present invention provides a perovskite solar cell, the perovskite solar cell comprising a hole transport layer, the hole transport layer comprising the polymer hole transport material described in the first aspect.

[0030] Preferably, the perovskite solar cell is a pin-type perovskite solar cell.

[0031] Preferably, the perovskite solar cell comprises an anode, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, a hole blocking layer, and a cathode arranged sequentially.

[0032] Preferably, the hole transport layer is obtained by coating a solution of the polymer hole transport material as described in the first aspect onto the anode surface and then performing thermal annealing.

[0033] Preferably, the solvent in the solution of the polymer hole transport material includes any one or a combination of at least two of methanol, chloroform, dimethyl sulfoxide (DMSO), and N,N-dimethylformamide.

[0034] Preferably, the concentration of the polymer hole transport material solution is 0.2~1 mg / mL, for example 0.2 mg / mL, 0.3 mg / mL, 0.4 mg / mL, 0.5 mg / mL, 0.6 mg / mL, 0.7 mg / mL, 0.8 mg / mL, 0.9 mg / mL or 1 mg / mL, etc.

[0035] Preferably, the temperature of the heat annealing is 90~110℃, such as 90℃, 95℃, 100℃, 105℃ or 110℃, and the heat annealing time is 5~15 minutes, such as 5 minutes, 10 minutes or 15 minutes.

[0036] Compared with the prior art, the present invention has the following beneficial effects: The hole transport layer made from the polymer hole transport material provided by this invention not only has excellent ultraviolet stability but also high conductivity and is insensitive to thickness changes. The polymer hole transport material provided by this invention greatly improves the stability of perovskite solar cells (photoelectric conversion efficiency after 1000h: 16.5%~22.5%, preferably 18.0%~22.5%). Attached Figure Description

[0037] Figure 1 The efficiency variation of the perovskite solar cell provided in Embodiment 1 of the present invention under AM 1.5G 1 full-spectrum solar irradiation.

[0038] Figure 2 The efficiency variation of the perovskite solar cell provided in Embodiment 2 of the present invention under AM 1.5G 1 full-spectrum solar irradiation. Detailed Implementation

[0039] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0040] Example 1 This embodiment provides a polymer hole transport material A3, the synthesis route of which is shown below: The preparation method includes the following steps: (1) Ni(COD)2 (0.36 g, 1.30 mmol), 2,2'-bipyridine (0.20 g, 1.30 mmol), and 1,5-cyclooctadiene (0.16 g, 1.30 mmol) were stirred in 10 mL of DMF at 80 °C for 0.5 h. Then, raw material A-1 (0.878 g, 1.08 mmol) was added to the reaction mixture. Subsequently, the reaction mixture was stirred at 80 °C overnight. After cooling to room temperature, 1 M hydrochloric acid was added to adjust the pH to 1-2. The precipitate was separated by filtration. The polymer was added to dichloromethane and then reprecipitated in diethyl ether. The mixture was washed successively with 200 mL of hot 0.01 M EDTA solution (pH = 3-4), 200 mL of hot 0.01 M EDTA solution (pH = 8-9), and 200 mL of water. The sample was then dried under vacuum to obtain 0.21 g of pale yellow powder (i.e., intermediate-1), with a yield of 59%.

[0041] The characterization results of intermediate-1 are as follows: 1H NMR (400 MHz, CDCl3, ppm) δ 7.98-7.88 (m, 2H), 7.82-7.58 (m, 8H), 4.47-4.07 (m, 6H), 1.88-1.61 (m, 10H), 1.57-1.44 (m, 2H), 1.23 (dt, J = 10.6, 8.0 Hz, 6H). GPC analysis (THF for polystyrene): Mn = 5052 g / mol, Mw = 6289 g / mol, PDI = 1.3.

[0042] (2) Intermediate-1 (0.05 g) was dissolved in 10 mL of dichloromethane, and then BrSi(Me)3 (0.07 g) was added to the solution. The reaction mixture was stirred at room temperature for 12 hours, followed by the addition of 5 mL of methanol and stirring for another 12 hours. The solution was concentrated and then precipitated dropwise into ether to obtain 25 mg of brown solid, which was the polymer hole transport material A3, with a yield of 55%.

[0043] Example 2 This embodiment provides a polymer hole transport material B3, and the synthesis route is shown below: The preparation method includes the following steps: (1) Ni(COD)₂ (0.36 g, 1.30 mmol), 2,2'-bipyridine (0.20 g, 1.30 mmol), and cyclooctadiene (0.16 g, 1.30 mmol) were stirred in 10 mL of DMF at 80 °C for 0.5 h. Then, starting material A-2 (0.963 g, 1.08 mmol) was added to the reaction mixture. Subsequently, the reaction mixture was stirred at 80 °C overnight. After cooling to room temperature, 1 M hydrochloric acid was added to adjust the pH to 1-2. The precipitate was separated by filtration. The polymer was added to dichloromethane and then reprecipitated in diethyl ether. The mixture was washed successively with 200 mL of hot 0.01 M EDTA solution (pH = 3-4), 200 mL of hot 0.01 M EDTA solution (pH = 8-9), and 200 mL of water. The mixture was then dried under vacuum to give 0.25 g of pale yellow powder (i.e., intermediate-2), with a yield of 64%.

[0044] The characterization results of intermediate-2 are as follows: 1H NMR (400 MHz, CDCl3, ppm): 7.89-8.59 (m, 6H), 4.35-4.77 (m, 2H), 3.90-4.28 (m, 4H), 2.15-2.43 (m, 2H), 1.12-1.38 (m, 6H).

[0045] GPC analysis (THF for polystyrene): Mn = 6152 g / mol, Mw = 7354 g / mol, PDI = 1.2.

[0046] (2) Intermediate-2 (0.05 g) was dissolved in 10 mL of dichloromethane, and then BrSi(Me)3 (0.07 g) was added to the solution. The reaction mixture was stirred at room temperature for 12 hours, followed by the addition of 5 mL of methanol and stirring for another 12 hours. The solution was concentrated and then precipitated dropwise into ether to obtain 28 mg of brown solid, which was the polymer hole transport material B3, with a yield of 61%.

[0047] In addition, it should be noted that other polymer hole transport materials of the present invention can be obtained by referring to the preparation methods of Examples 1 and 2 listed above, and will not be described in detail here.

[0048] Device Example 1 This device embodiment provides a perovskite solar cell (which is an inverted perovskite solar cell), and the fabrication method includes the following steps: The ITO glass substrate (1.5 cm × 1.5 cm) was first ultrasonically cleaned using soap, deionized water, and isopropanol, and then subjected to UV ozone treatment for 15 minutes before use. The perovskite solar cells (PSCs) were selectively coated at room temperature in a fume hood with 30% to 40% relative humidity. A hole transport layer (HTL) solution (A3 dissolved in methanol:chloroform = 1:1, 0.5 mg / mL) was coated onto the ITO glass substrate at 2000 rpm, followed by thermal annealing in air at 100°C for 10 minutes. 1.35 M Cs were prepared by dissolving the corresponding organohalides and lead iodide in NMP:DMF = 1:9 in a nitrogen-filled glove box. 0.1 FA 0.9A PbI3 precursor solution was then coated onto an ITO glass substrate covered with HTL at 1500 rpm. The perovskite film was then annealed in air at 120°C for 10 minutes to remove residual solvent. C60 (30 nm, 0.3 Å / s), BCP (6 nm, 0.1 Å / s), and copper (100 nm, 1 Å / s) were evaporated by thermal evaporation to complete the fabrication of the perovskite solar cell. The PSCs were then encapsulated in a cover glass using an acrylate encapsulant. The effective area of ​​the solar cell was 1.0 cm². 2 .

[0049] Device Example 2 The only difference from device embodiment 1 is that the polymer hole transport material A3 is replaced with an equal weight of polymer hole transport material B3.

[0050] Device Example 3 The only difference from device embodiment 1 is that the polymer hole transport material A3 is replaced with an equal weight of polymer hole transport material A1.

[0051] Device Example 4 The only difference from device embodiment 1 is that the polymer hole transport material A3 is replaced with an equal weight of polymer hole transport material A2.

[0052] Device Example 5 The only difference from device embodiment 1 is that the polymer hole transport material A3 is replaced with an equal weight of polymer hole transport material B1.

[0053] Device Example 6 The only difference from Device Example 1 is that the polymer hole transport material A3 is replaced with an equal weight of polymer hole transport material B2.

[0054] Device Example 7 The only difference from Device Example 1 is that the concentration of the hole transport layer solution is 0.2 mg / mL.

[0055] Device Example 8 The only difference from Device Example 1 is that the concentration of the hole transport layer solution is 1 mg / mL.

[0056] Device Example 9 The only difference from Device Example 1 is that the polymer hole transport material A3 is replaced with an equal weight of polymer hole transport material A4, and its structure is shown below: The preparation method is the same as in Example 1. The molecular weight of the intermediate obtained during the preparation process is: Mn=2289g / mol, Mw=3204g / mol, PDI=1.4; the molecular weight of the final product polymer hole transport material A4 is less than 4000.

[0057] Device Example 10 The only difference from Device Example 1 is that the polymer hole transport material A3 is replaced with an equal weight of polymer hole transport material A5, and its structure is shown below: The preparation method is the same as in Example 1. The molecular weight of the intermediate obtained during the preparation process is: Mn=12289g / mol, Mw=15204g / mol, PDI=1.3; the molecular weight of the final product polymer hole transport material A5 is greater than 10000.

[0058] Device Comparison Example 1 The only difference from Device Example 1 is that the polymer hole transport material A3 is replaced with an equal weight of D-1, and its structure is shown below: .

[0059] Device Comparison Example 2 The only difference from Device Example 1 is that the polymer hole transport material A3 is replaced with an equal weight of D-2, and its structure is shown below: Its molecular weight is approximately 1400.

[0060] The photoelectric performance parameters were obtained by testing the JV curves of the inverted perovskite solar cells provided in the above-mentioned device embodiments and device comparison examples. The testing method is as follows: The fabricated inverted perovskite solar cells were tested under standard sunlight, 1.5 AM, using a Newport Oriel Sol3A solar simulation system. The incident monochromatic photon-electron conversion efficiency (EQE) was used to evaluate the ability of the perovskite solar cells to convert photons into electrons under monochromatic light irradiation at different wavelengths. This test was performed by measuring the photocurrent response of the device at a specific wavelength and calculating the ratio to the incident photon flux at that wavelength, reflecting the photoelectric response capability and spectral matching of the device. The long-term stability test was conducted by aging in sunlight at 85°C for a certain period of time using an open circuit, and the efficiency was tested using an IV curve. The test results are shown in Table 1 below.

[0061] Table 1 Where Voc is the open-circuit voltage, Jsc is the short-circuit current, FF is the fill factor, and Eff is the photoelectric conversion efficiency of the solar cell under standard sunlight.

[0062] As can be seen from Table 1, the perovskite solar cells made using the polymer hole transport material provided by the present invention all have high photoelectric conversion efficiency (17.5%~23.1%, preferably 19.3%~23.1%) and better stability (photoelectric conversion efficiency after 1000h: 16.5%~22.5%, preferably 18.0%~22.5%).

[0063] Compared with Device Example 1, the stability of the perovskite solar cells provided by Device Comparative Example 1 and Device Comparative Example 2 both decreased.

[0064] The efficiency variation of the perovskite solar cell provided in Embodiment 1 of the present invention under AM 1.5G 1 full-spectrum solar irradiation is shown in the figure below. Figure 1 As shown.

[0065] The efficiency variation of the perovskite solar cell provided in Embodiment 2 of the present invention under AM 1.5G 1 full-spectrum solar irradiation is shown in the figure below. Figure 2 As shown.

[0066] Depend on Figure 1 and Figure 2 It can also be seen that the perovskite solar cell made using the polymer hole transport material provided by the present invention has good ultraviolet stability. After 1000 hours of maximum power point (MPP) testing under AM 1.5G 1 full solar spectrum irradiation, the device efficiency still remains above 97% of the initial value.

[0067] The applicant declares that the present invention is illustrated by the above embodiments to demonstrate the polymer hole transport material, its preparation method, and its application. However, the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A polymer hole transport material, characterized in that, The polymer hole transport material has the structure shown in Formula I and / or Formula II as follows: In Equations I and II, m is an independent integer from 2 to 4; In Equations I and II, n is independently 10 to 20.

2. The polymer hole transport material according to claim 1, characterized in that, The molecular weight of the polymer hole transport material is 4000~10000.

3. The polymer hole transport material according to claim 1, characterized in that, The polymer hole transport material is any one of the following polymers: 。 4. A method for preparing a polymer hole transport material as described in any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) Mix bis(1,5-cyclooctadiene)nickel, 2,2'-bipyridine, 1,5-cyclooctadiene and organic solvent, then add raw material A, react, then add pH adjuster to adjust the pH value of the system, and then perform post-treatment to obtain intermediate A; (2) Mix intermediate A with solvent, then add BrSi(Me)3, react, then add organic solvent, stir, and post-process to obtain the polymer hole transport material.

5. The preparation method according to claim 4, characterized in that, The molar ratio of bis(1,5-cyclooctadiene)nickel, 2,2'-bipyridine, and 1,5-cyclooctadiene in step (1) is 1:(0.8~1.2):(0.8~1.2). The organic solvent in step (1) includes N,N-dimethylformamide; The mixing temperature in step (1) is 70~90℃, and the mixing time is 0.5~1 hour; The raw material A in step (1) includes and / or , where m is an integer from 2 to 4; In step (1), the molar ratio of bis(1,5-cyclooctadiene)nickel to raw material A is 1:(0.6~1); The reaction temperature in step (1) is 70~90℃, and the reaction time is 8~24 hours; The pH adjuster in step (1) includes hydrochloric acid with a concentration of 0.8~1.2 mol / L; The pH adjustment in step (1) is to adjust the pH of the system to 1-2; The post-processing in step (1) includes filtration, sedimentation, washing, and drying.

6. The preparation method according to claim 4, characterized in that, The solvent in step (2) includes dichloromethane; In step (2), the mass ratio of intermediate A to BrSi(Me)3 is 1:(1~2); The reaction in step (2) is carried out at room temperature for 10 to 16 hours. The reaction described in step (2) is carried out under stirring conditions; The organic solvent in step (2) includes methanol; The stirring time in step (2) is 10-16 hours; The post-processing in step (2) includes concentration and precipitation.

7. A perovskite solar cell, characterized in that, The perovskite solar cell includes a hole transport layer, which comprises the polymer hole transport material according to any one of claims 13.

8. The perovskite solar cell according to claim 7, characterized in that, The perovskite solar cell is a pin-type perovskite solar cell.

9. The perovskite solar cell according to claim 7, characterized in that, The perovskite solar cell comprises, in sequence, an anode, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, a hole blocking layer, and a cathode.

10. The perovskite solar cell according to claim 9, characterized in that, The hole transport layer is obtained by coating a solution of the polymer hole transport material as described in any one of claims 13 onto the anode surface and then performing thermal annealing. The solvent in the solution of the polymer hole transport material includes any one or a combination of at least two of methanol, chloroform, dimethyl sulfoxide, and N,N-dimethylformamide; The concentration of the polymer hole transport material solution is 0.2~1 mg / mL; The heat annealing temperature is 90~110℃, and the heat annealing time is 5~15 minutes.

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