A small molecule hole transporting material, a preparation method thereof, and an organic solar cell using the material

Abstract

The present invention discloses a small molecule hole transporting material, a preparation method thereof, and an organic solar cell using the material. A hole transporting material is prepared by using carbazole as the main body and modifying it with a phosphoric acid group. This material has a small steric hindrance, can strengthen the intermolecular force, expands the thermal range of the mesophase of the molecule by improving the molecular crystallinity, and such molecules have the characteristics of low exciton binding energy, high charge transport efficiency, and good film-forming property. It is suitable for the preparation of high-efficiency organic solar cells, has the advantages of large-area preparation of organic solar cells, mass production and commercialization, and obtains an energy conversion efficiency with a relatively high reproducibility and a photoelectric conversion efficiency of 17.397%, which is of great significance for promoting organic solar cells.

Description

Technical Field

[0001] The present invention belongs to the technical field of organic solar cells, and particularly relates to a small molecule hole transporting material, a preparation method thereof, and an organic solar cell using the material. Background Art

[0002] The development and utilization of green energy is an important way for mankind to cope with the global energy crisis and climate change. Converting the inexhaustible solar energy into electrical energy is one of the most promising ways of solar energy utilization. The research on solar cells has become a hot topic worldwide and is developing rapidly.

[0003] Compared with the commercially available inorganic solar cells, organic solar cells have the advantages of wide material sources, low cost, light weight, good flexibility, and can be prepared by wet methods on a large scale (inkjet printing, screen printing, blade coating, etc.), and have greater development space. However, currently, highly efficient organic solar cells generally use poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) as the hole transporting layer of the device, and its acidity and hygroscopicity significantly affect the device life. Some metal oxides or metal salts have also been reported to be used as the hole transporting layer, but the device efficiency is not very high, and the preparation process often requires high vacuum evaporation, high temperature annealing (>200 °C) treatment or the use of toxic solvents, etc., with high process costs and environmental pollution. Summary of the Invention

[0004] The purpose of this part is to outline some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this part, as well as in the abstract and title of the present application, to avoid obscuring the purpose of this part, the abstract, and the title, and such simplifications or omissions shall not be used to limit the scope of the present invention.

[0005] Aiming at the deficiencies of organic solar cells in the prior art, the purpose of the present invention is to provide a small molecule hole transporting material.

[0006] To solve the above technical problems, the present invention provides the following technical solutions: including,

[0007] The material is named 1Cl-PACz, which uses halogenated carbazole as the main body and is modified with a phosphoric acid group, and its structural formula is shown in formula (A);

[0008]

[0009] To solve the above technical problems, the present invention also provides a preparation method of a small molecule hole transporting material: including,

[0010] 3-Chlorocarbazole and tetrabutylammonium bromide are dissolved in 1,2-dibromoethane. After adding a strong base solution, the reaction is carried out at 70 °C overnight. The product is purified to obtain a white solid, denoted as 1Cl-Cz-Br;

[0011] 1Cl-Cz-2Br is dissolved in triethyl phosphite and refluxed overnight. The product is purified to obtain a white oily liquid, denoted as 1Cl-PCz-2Et;

[0012] 1Cl-PCz-2Et is dissolved in anhydrous dioxane. Trimethylsilyl bromide is added dropwise. After reacting at room temperature for 20 - 24 h, the organic solvent is evaporated under reduced pressure. Then methanol is added and stirred, and deionized water is added dropwise to precipitate a white solid. The product is filtered and dried to obtain a small molecule hole transporting material, denoted as 1Cl-PACz.

[0013] As a preferred embodiment of the preparation method of the small molecule hole transporting material of the present invention, wherein: the reaction temperature in the preparation process of 1Cl-Cz-Br is 25 - 90 °C, the reaction temperature in the preparation process of 1Cl-PCz-2Et is 25 - 90 °C, and the reaction temperature in the preparation process of 1Cl-PACz is 25 - 35 °C.

[0014] As a preferred embodiment of the preparation method of the small molecule hole transporting material of the present invention, wherein: the strong base solution is potassium hydroxide solution with a concentration of 50 - 60%.

[0015] As a preferred embodiment of the preparation method of the small molecule hole transporting material of the present invention, wherein: in the preparation process of 1Cl-PCz-2Et, for every 0.80 g of 1Cl-Cz-2Br, the dosage of triethyl phosphite is 6 - 10 ml.

[0016] As a preferred embodiment of the preparation method of the small molecule hole transporting material of the present invention, wherein: in the preparation process of 1Cl-PACz, the equivalent ratio of 1Cl-PCz-2Et to trimethylsilyl bromide is 1:5 - 10.

[0017] As a preferred embodiment of the preparation method of the small molecule hole transporting material of the present invention, wherein: the purification of the product is that the product is successively extracted, washed with water, dried with magnesium sulfate, the solvent is removed under reduced pressure, and the crude product is purified by column chromatography.

[0018] Another object of the present invention is to provide a small molecule hole transporting material to optimize an organic solar cell device to obtain an organic solar cell using this small molecule hole transporting material.

[0019] To solve the above technical problems, the present invention provides a technical solution of an organic solar cell using this small molecule hole transporting material: including,

[0020] The solar cell comprises an anode layer, a hole transport layer, an active layer, an interface layer and a cathode layer in sequence from bottom to top;

[0021] Among them, the material of the hole transport layer is 1Cl-PACz.

[0022] As a preferred embodiment of the organic solar cell of the present invention, wherein: the preparation method of the hole transport layer includes,

[0023] In a glove box, dissolve 1Cl-PACz in ethanol, then place the reagent bottle on a magnetic stirrer and stir overnight at room temperature to obtain a hole transport layer solution;

[0024] Place the anode layer material on a spin coater, spin coat the hole transport layer solution on its surface, and anneal it on a hot stage after film formation. After the reaction is completed, the hole transport layer is obtained;

[0025] Among them, the concentration of the hole transport layer solution is 0.3 - 0.9 mg / mL, and the annealing temperature is 80 - 120 °C.

[0026] As a preferred embodiment of the organic solar cell of the present invention, wherein: the concentration of the hole transport layer solution is 0.6 mg / mL, and the annealing temperature is 100 °C.

[0027] Advantages of the present invention:

[0028] The present invention provides a hole transport material based on carbazole as the main body and modified with a phosphate group. This material is an asymmetric molecule with a large dipole moment, which can enhance the effective extraction and transport of holes; it has a small steric hindrance, can strengthen the intermolecular force, and expands the thermal range of the mesophase of the molecule by improving the molecular crystallinity. This type of molecule has the characteristics of a low exciton binding energy, a high charge transport efficiency, and a good film-forming property, and is suitable for preparing high-efficiency organic solar cells. Description of the drawings

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to these drawings. Among them:

[0030] Figure 1 It is the synthetic route diagram of the hole transport material 1Cl-PACz in Example 1 of the present invention;

[0031] Figure 2 It is of 1Cl-Cz-Br in Example 1 of the present invention 1 HNMR characterization diagram;

[0032] Figure 3 The 13 CNMR characterization diagram of 1Cl-Cz-Br in Example 1 of the present invention;

[0033] Figure 4 The 1 HNMR characterization diagram of 1Cl-PCz-2Et in Example 1 of the present invention;

[0034] Figure 5 The 13 CNMR characterization diagram of 1Cl-PCz-2Et in Example 1 of the present invention;

[0035] Figure 6 The 1 HNMR characterization diagram of 1Cl-PACz in Example 1 of the present invention;

[0036] Figure 7 The 13 CNMR characterization diagram of 1Cl-PACz in Example 1 of the present invention;

[0037] Figure 8 The UV absorption diagrams of 1Cl-PACz and PACz in Example 1 of the present invention;

[0038] Figure 9 The efficiency test diagram of 1Cl-PACz hole transport layer batteries with different concentrations in Example 3 of the present invention;

[0039] Figure 10 The efficiency test diagram of the batteries prepared at different annealing temperatures in Example 4 of the present invention; Detailed implementation manners

[0040] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following will describe the detailed implementation manners of the present invention in conjunction with the embodiments of the specification.

[0041] In the following description, many specific details are set forth to facilitate a thorough understanding of the present invention. However, the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar extensions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0042] Secondly, the so-called "one embodiment" or "embodiment" herein refers to a specific feature, structure or characteristic that can be included in at least one implementation manner of the present invention. The appearances of "in one embodiment" in different places in this specification do not all refer to the same embodiment, nor are they separate or alternative embodiments that exclude each other with other embodiments.

[0043] The materials used in the process of preparing the organic solar cells of the present invention are:

[0044] PM6: Solid powder with a molecular weight of 40,000 to 50,000;

[0045] Deionized water: Liquid

[0046] Isopropyl alcohol: Liquid with analytical purity

[0047] Conductive glass (indium tin oxide), solid, with a transmittance of about 88% and a sheet resistance of 15 Ω·cm

[0048] Silver: Solid cylindrical granular with a purity of 99.99%

[0049] Unless otherwise specified, the remaining raw materials are all commercially available.

[0050] Example 1

[0051] Refer to Figures 1 to 8 , this example provides a preparation method of a small molecule hole transporting material 1Cl-PACz, and the synthetic route is as Figure 1 shown, specifically:

[0052] 1) Synthesize 1Cl-Cz-Br:

[0053] Under a nitrogen atmosphere, 3-chlorocarbazole (1.00 g, 4.96 mmol) and tetrabutylammonium bromide (0.80 g, 2.48 mmol) were successively dissolved in 15 mL of 1,2-dibromoethane, and then 50% KOH solution (3.00 mL, 39.67 mmol) was added, and the reaction was carried out overnight at 70 °C;

[0054] After the reaction, the product was successively extracted, washed with water, dried over magnesium sulfate, and the solvent was removed under reduced pressure. The crude product was purified by column chromatography to obtain a white solid (1.03 g, yield 67%), which was 1Cl-Cz-Br. The product was characterized, and the results were as Figure 2 , Figure 3 shown.

[0055] Figure 2 is the 1 1H NMR characterization diagram of 1Cl-Cz-Br, and the relevant characterization data are: 1 1H NMR (400 MHz, CDCl3) δ 8.05 (dd, J = 5.1, 3.0 Hz, 2H), 7.55 - 7.48 (m, 1H), 7.43 (dd, J = 6.8, 2.0 Hz, 2H), 7.36 (d, J = 8.7 Hz, 1H), 7.29 (d, J = 7.5 Hz, 1H), 4.68 (t, J = 7.4 Hz, 2H), 3.67 (t, J = 7.4 Hz, 2H).

[0056] Figure 3For 1Cl-Cz-Br 13 13C NMR characterization chart, and the relevant characterization data are as follows: 13 13C NMR (100 MHz, CDCl3) δ 140.59, 138.54, 126.87, 126.17, 125.31, 124.42, 122.44, 120.95, 120.48, 120.16, 109.69, 108.90, 44.97, 28.23.

[0057] 2) Synthesis of 1Cl-PCz-2Et:

[0058] Under a nitrogen atmosphere, 1Cl-Cz-2Br (0.80 g, 2.59 mmol) was dissolved in 10 mL of triethyl phosphite and refluxed overnight.

[0059] After the reaction, the product was successively extracted, washed with water, dried over magnesium sulfate, and the solvent was removed under reduced pressure. The crude product was purified by column chromatography to obtain a white oily liquid (0.86 g, yield 91%). The product was characterized, and the results are as Figure 4 、 Figure 5 shown.

[0060] Figure 4 For 1Cl-PCz-2Et 1 1H NMR characterization chart, and the relevant characterization data are as follows: 1 1H NMR (400 MHz, CDCl3) δ 8.04 (dd, J = 5.0, 2.9 Hz, 2H), 7.50 (ddd, J = 8.3, 7.0, 1.2 Hz, 1H), 7.43 (dd, J = 8.7, 1.8 Hz, 2H), 7.36 (d, J = 8.6 Hz, 1H), 7.28 - 7.24 (m, 1H) 4.72 - 4.50 (m, 2H), 4.07 (tt, J = 14.1, 7.2 Hz, 4H), 2.37 - 2.12 (m, 2H), 1.36 - 1.15 (m, 6H).

[0061] Figure 5 For 1Cl-PCz-2Et 13 13C NMR characterization chart, and the relevant characterization data are 13 13C NMR (100 MHz, CDCl3) δ 140.35, 138.23, 126.74, 126.03, 124.99, 124.42, 122.40, 120.85, 120.37, 119.84, 109.71, 108.97, 62.15, 62.08, 37.28, 26.11, 24.73, 16.57, 16.51.

[0062] 3) Synthesis of 1Cl-PACz

[0063] Under a nitrogen atmosphere, 1Cl-PCz-2Et (0.50 g, 1.37 mmol) was dissolved in 20 mL of anhydrous dioxane, and trimethylsilyl bromide (2.09 g, 13.67 mmol) was added dropwise. The reaction was carried out at room temperature (30 °C) for 24 h;

[0064] After the reaction, the organic solvent was evaporated under reduced pressure, and then 5 mL of methanol was added and stirred for 0.5 h. Then, 25 mL of deionized water was added dropwise, and a white solid precipitated. The solid obtained by filtration was dried under vacuum (0.36 g, yield 86%). The product was characterized, and the results are as Figure 6 、 Figure 7 shown.

[0065] The product characterization data are

[0066] Figure 6 The 1H NMR characterization diagram of 1Cl-PACz, and the relevant characterization data are as follows: 1 1H NMR (400 MHz, DMSO-d6) δ 8.32 (d, J = 2.1 Hz, 1H), 8.25 (d, J = 7.8 Hz, 1H), 7.61 (dd, J = 8.4, 5.0 Hz, 2H), 7.57 - 7.46 (m, 2H), 7.27 (t, J = 7.3 Hz, 1H), 4.76 - 4.35 (m, 2H), 2.20 - 1.86 (m, 2H).

[0067] Figure 7 For 1Cl-PCz-2Et 13 The 13C NMR characterization diagram, and the relevant characterization data are as follows: 13 13C NMR (100 MHz, DMSO-d6) δ 139.97, 137.93, 126.66, 125.56, 123.61, 123.39, 121.43, 120.98, 120.04, 119.35, 110.59, 109.31, 39.11, 27.93, 26.62.

[0068] Figure 8 The UV absorption diagrams of 1Cl-PACz and PACz in the implementation of the present invention. Compared with PACz, the UV-visible absorption spectrum of 1Cl-PACz shows a slight red shift. This is mainly due to the introduction of chlorine, which makes it have a larger intramolecular charge transfer effect. However, it should be noted that in the range of 400 - 1000 nm, 1Cl-PACz has a lower absorbance value and better light transmittance, which is beneficial to the absorption of more sunlight.

[0069] Comparative Example 1

[0070] The difference between this comparative example and Example 1 is that the reaction temperature for synthesizing 1Cl-PACz in step 3) is adjusted to 50 °C, specifically as follows:

[0071] 3) Synthesize 1Cl-PACz

[0072] Under a nitrogen atmosphere, dissolve 1Cl-PCz-2Et (0.50 g, 1.37 mmol) in 20 mL of anhydrous dioxane, and slowly add trimethylsilyl bromide (2.09 g, 13.67 mmol) dropwise, and react at 50 °C for 24 h;

[0073] After the reaction is completed, the organic solvent is evaporated, then add 5 mL of methanol and stir for 0.5 h. Then slowly add 25 mL of deionized water dropwise, and white solid precipitates. The solid after filtration is dried in vacuo, and the yield is only 36%.

[0074] Comparative Example 2

[0075] The difference between this comparative example and Example 1 is that the solvent for synthesizing 1Cl-PACz in step 3) is adjusted to dichloromethane, specifically as follows:

[0076] 3) Synthesize 1Cl-PACz

[0077] Under a nitrogen atmosphere, dissolve 1Cl-PCz-2Et (0.50 g, 1.37 mmol) in 20 mL of anhydrous dichloromethane, and slowly add trimethylsilyl bromide (2.09 g, 13.67 mmol) dropwise, and react at 30 °C for 24 h;

[0078] After the reaction is completed, the organic solvent is evaporated, then add 5 mL of methanol and stir for 0.5 h. Then slowly add 25 mL of deionized water dropwise, and white solid precipitates. The solid after filtration is dried in vacuo, and the yield is only 48%.

[0079] Comparative Example 3

[0080] The difference between this comparative example and Example 1 is that the solvent for synthesizing 1Cl-PACz in step 3) is adjusted to dichloromethane, specifically as follows:

[0081] 3) Synthesize 1Cl-PACz

[0082] Under a nitrogen atmosphere, dissolve 1Cl-PCz-2Et (0.50 g, 1.37 mmol) in 20 mL of anhydrous chloroform, and slowly add trimethylsilyl bromide (2.09 g, 13.67 mmol) dropwise, and react at 30 °C for 24 h;

[0083] After the reaction is completed, the organic solvent is evaporated, then add 5 mL of methanol and stir for 0.5 h. Then slowly add 25 mL of deionized water dropwise, and white solid precipitates. The solid after filtration is dried in vacuo, and the yield is only 51%.

[0084] Example 2

[0085] This example provides a method for preparing an organic solar cell, which is composed of at least the following structures in sequence: an anode layer, a hole transport layer, an active layer, an interface transport layer, and a cathode layer. The specific preparation process is as follows:

[0086] 1) Preparation and treatment of the anode layer

[0087] The ITO conductive glass sheet is first ultrasonically cleaned with a cleaning agent (the main components of which are softened water, surfactant, vitamin E ester, and lemon essence) for 20 minutes;

[0088] Then it is ultrasonically cleaned with deionized water, acetone (to be recycled), and isopropanol in sequence for 20 minutes, and then dried with a vacuum drying oven;

[0089] The dried ITO conductive glass sheet is placed under UV for cleaning for 15 minutes and used as the anode layer.

[0090] 2) Preparation and treatment of the hole transport layer

[0091] In the glove box, 0.30 mg of 1Cl-PACz is dissolved in 1 ml of ethanol, and then the reagent bottle is placed on a magnetic stirrer and stirred overnight at room temperature to obtain a hole transport layer solution with a concentration of 0.3 mg / ml;

[0092] The ITO conductive glass sheet is placed on a spin coater, and the hole transport layer solution is spin-coated on its surface. After film formation, it is annealed on a hot stage, and the annealing temperature is set at 100 °C. After the reaction ends, the hole transport layer is obtained on the anode layer.

[0093] 3) Preparation and treatment of the active layer

[0094] In the glove box, 8.00 mg of PM6 and 8.00 mg of BTP-ec9 are dissolved in 1 ml of chloroform (CH3Cl), placed on a magnetic stirrer and stirred at room temperature for 2 - 3 h to obtain an active layer solution with a mass ratio of PM6:BTP-ec9 of 1:1 (16 mg / ml);

[0095] The ITO electroglass sheet with the hole transport layer obtained in step 2) is placed on a spin coater, and 20 μL of the active layer solution is spin-coated on its surface with dynamic spin coating. After the reaction ends, the active layer is obtained on the anode layer.

[0096] 4) Preparation and treatment of the interface transport layer

[0097] In the glove box, 1 mg of PDIN is dissolved in 1 ml of 3-fluoroethanol solvent and stirred at room temperature for 30 minutes to obtain an interface transport layer solution of 1 mg / mL;

[0098] Place the ITO electro-glass sheet containing the active layer obtained in step 3) on a spin coater. Then, use a pipette to measure 50 μL of the uniformly mixed PDIN solution and spin-coat it statically on the glass sheet. After the spin coating is completed, an interfacial transport layer is obtained.

[0099] 5) Preparation and treatment of the cathode layer

[0100] Transfer the ITO conductive glass sheet with the spin-coated interfacial transport layer in step 4) to the vacuum evaporation chamber. Fix the substrate on the turntable at the top of the evaporation chamber, with the side with the interfacial transport layer facing down. Place the evaporated silver metal material in the tungsten boat inside the evaporation container; adjust the quartz thickness measurement probe and the quartz monitoring probe on the furnace wall so that the quartz thickness measurement probe is aligned with the substrate on the turntable and the quartz monitoring probe is aligned with the placed silver grains. Close the hatch of the vacuum evaporation chamber and seal it.

[0101] Turn on the mechanical vacuum pump and the molecular vacuum pump to make the vacuum degree in the evaporation chamber ≤ 0.5 Pa and keep it constant. Set the evaporation rate of the instrument to 20 Å / s, which is 2 nm / s, and set the time to 50 s. Set the corresponding current until there is a stable current rate.

[0102] Turn on the power supply of the tungsten boat to evaporate the silver electrode, so that the silver sublimates from the solid state to the gaseous state. The gaseous molecules grow on the interface layer to form a planar film layer. Adjust the control knob of the tungsten boat power supply to increase the power so that the film growth rate is maintained at 2 nm / s and the film thickness is about 100 nm. During the preparation process, the quartz thickness measurement probe measures the evaporation thickness and displays its thickness value. Pay attention to observing the evaporation status during the process. After the cathode layer evaporation is completed, let it cool statically for 10 minutes, and then the organic solar cell is prepared.

[0103] The open-circuit voltage, short-circuit current, transfer efficiency, and energy conversion efficiency of the solar cell prepared in this example are 0.907 V, 25.567 mA / cm -2 ², 74.939%, and 17.397% respectively, indicating that using 1Cl-PACz prepared by the present invention as the hole transport layer material to prepare an organic solar cell can effectively improve the charge transport efficiency.

[0104] Example 3

[0105] This example is used to explore the influence of different hole transport materials on the battery performance when preparing the hole transport layer. Referring to the preparation method of Example 2, adjust the concentration of 1Cl-PACz in the hole transport layer solution in step 2) to 0.3, 0.6, and 0.9 mg / ml respectively, and the rest of the preparation processes are the same as those in Example 2. Perform performance tests on the prepared solar cells, and the results are as Figure 9 well as shown in Table 1.

[0106] Table 1 Efficiency test data of batteries with hole transport layers of different concentrations of 1Cl-PACz

[0107]

[0108] From Figure 9 As can be seen from Table 1, when the concentration of the hole transport layer material 1Cl-PACz is 0.6 mg / mL, the power conversion efficiency of this battery is the highest, exceeding 17%. This may be because too high a concentration leads to a relatively large film roughness, which is not conducive to charge collection. When the concentration is too low, holes are likely to appear in the film.

[0109] Example 4

[0110] This example is used to explore the influence of different annealing temperatures on the battery performance when preparing the hole transport layer. Referring to the preparation method of Example 2, the annealing temperatures of the hole transport layer in step 2) are adjusted to 80, 100, and 120 °C respectively, and the remaining preparation processes are the same as those in Example 2. The prepared solar cells are subjected to performance tests, and the results are as Figure 10 shown in Table 2.

[0111] Table 2 Efficiency test data of batteries with hole transport layers treated at different annealing temperatures

[0112]

[0113] From Figure 10 As can be seen from Table 2, when the annealing temperature of the hole transport layer is 100 °C, the power conversion efficiency of this battery is the highest. This may be because when the temperature is too high, the molecules are prone to excessive focusing, resulting in a relatively rough film; when the temperature is too low, the crystallinity of the molecules is poor, which is not conducive to charge transport.

[0114] In summary, the present invention mainly introduces a synthesis method of a novel chloro-carbazole-based hole transport material and an organic solar cell using this material. The organic solar cell with PM6:ETP-ec9 as the active layer and PDIN as the interfacial transport layer can achieve a power conversion efficiency of 17.397%. This result effectively overcomes the defects such as hygroscopicity, acid intolerance, poor batch repeatability, and air instability, and has the advantages of large-area preparation of organic solar cells, mass production, and commercialization. Moreover, an energy conversion efficiency with high reproducibility and a power conversion efficiency of 17.397% is obtained, which is of great significance for promoting organic solar cells.

[0115] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a hole transport layer of an organic solar cell, characterized in that: In a glove box, dissolve 1Cl-PACz in ethanol, place the reagent bottle on a magnetic stirrer, and stir overnight at room temperature to obtain a hole transport layer solution with a concentration of 0.6 mg / mL; Place the anode layer material on a spin coater, spin-coat the hole transport layer solution on its surface, and anneal it on a hot stage at 100 °C after film formation. After the reaction is completed, the hole transport layer is obtained; Among them, the 1Cl-PACz is an asymmetric small molecule carbazole material, which uses halogenated carbazole as the main body and is modified with a phosphoric acid group, and its structural formula is shown in formula (A); Formula (A); The preparation method of the 1Cl-PACz is as follows: Dissolve 3-chlorocarbazole and tetrabutylammonium bromide in 1,2-dibromoethane, add a strong base solution, and react at 70 °C overnight. The product is purified to obtain a white solid, denoted as 1Cl-Cz-Br; Dissolve 1Cl-Cz-2Br in triethyl phosphite and reflux overnight. The product is purified to obtain a white oily liquid, denoted as 1Cl-PCz-2Et; Dissolve 1Cl-PCz-2Et in anhydrous dioxane, dropwise add trimethyl bromosilane, react at room temperature for 20-24 h, then spin-dry the organic solvent, add methanol and stir, dropwise add deionized water, precipitate a white solid, and filter and dry the product to obtain a small molecule hole transport material, denoted as 1Cl-PACz.

2. The preparation method of the hole transport layer of the organic solar cell according to claim 1, wherein: The reaction temperature in the preparation process of the 1Cl-Cz-Br is 25-90 °C, the reaction temperature in the preparation process of the 1Cl-PCz-2Et is 25-90 °C, and the reaction temperature in the preparation process of the 1Cl-PACz is 25-35 °C.

3. The preparation method of the hole transport layer of the organic solar cell according to claim 1, characterized in that: The strong base solution is a potassium hydroxide solution with a concentration of 50-60%.

4. The preparation method of the hole transport layer of the organic solar cell according to claim 1, characterized in that: In the preparation process of the 1Cl-PCz-2Et, the dosage of triethyl phosphite corresponding to every 0.80 g of 1Cl-Cz-2Br is 6-10 ml.

5. The preparation method of the hole transport layer of the organic solar cell according to claim 1, characterized in that: In the preparation process of the 1Cl-PACz, the equivalent ratio of 1Cl-PCz-2Et to trimethylsilane is 1:5-10.

6. The preparation method of the hole transport layer of the organic solar cell according to claim 1, characterized in that: The purification of the product is that the product is successively extracted, washed with water, dried with magnesium sulfate, the solvent is removed under reduced pressure, and the crude product is purified by column chromatography.

7. An organic solar cell using the hole transport layer of the organic solar cell as claimed in claim 1, characterized in that: The solar cell comprises an anode layer, a hole transport layer, an active layer, an interface layer and a cathode layer from bottom to top in sequence; Among them, the hole transport layer material is 1Cl-PACz.

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