Hole transport material and preparation method thereof and perovskite solar cell

Abstract

The present application relates to the field of solar cell technology, and more particularly to a hole transport material, a preparation method thereof, and a perovskite solar cell. The hole transport material comprises a compound of Formula I. The compound of Formula I has a strong interaction with the components of the perovskite light-absorbing layer, and can passivate grain boundary defects and interface defects without the need for additives such as P-type dopants or interface modifiers, thereby achieving high photoelectric conversion efficiency and excellent cell stability.

Description

Technical Field

[0001] The present application relates to the technical field of solar cells, and in particular to a hole transport material and a preparation method thereof, and a perovskite solar cell. Background Art

[0002] Perovskite solar cells (PSCs) use perovskite-type organometallic halide semiconductors as light-absorbing materials, converting light energy directly into electricity through the photovoltaic effect. Hole transport materials are crucial for the fabrication of perovskite solar cells, playing a crucial role in improving cell performance and achieving large-scale commercial applications.

[0003] Currently, hole transport materials in perovskite solar cells are mainly divided into three categories: inorganic hole transport materials, small molecule hole transport materials, and organic polymer hole transport materials. Among them, small molecule hole transport materials have the advantages of high purity and easy solution processing, and are widely used in perovskite solar cells. According to the spatial structure, traditional small molecule hole transport materials can be divided into three categories: linear structure, spiro structure, and star structure. According to the different groups contained in the molecular structure, traditional small molecule hole transport materials can also be divided into dithienopyrrole type, triphenylamine type, carbazole type, bifluorene type, thiophene type, etc. In order to consider battery performance, additives are generally added when preparing the hole transport layer using traditional small molecule hole transport materials. However, the addition of additives has an adverse effect on the stability of the battery, which restricts the development of perovskite solar cells. Summary of the Invention

[0004] Based on this, the first aspect of this application provides a hole transport material, a preparation method thereof, and a perovskite solar cell. The technical solution is as follows:

[0005] A hole transport material comprising a compound of formula I:

[0006]

[0007] Wherein, L is selected from C 3-5 alkylene;

[0008] R is selected from C 1-3 alkyl;

[0009] X is selected from O or S.

[0010] The second aspect of the present application provides a method for preparing a hole transport material, the technical solution of which is as follows:

[0011] A method for preparing a hole transport material comprises the following steps:

[0012] Allowing the compound of formula I-5 to undergo a substitution reaction with the compound of formula I-6 to generate a compound of formula I-7;

[0013] The compound of formula I-4 is subjected to a Suzuki coupling reaction with the compound of formula I-7 to generate a compound of formula I-8; the compound of formula I-8 is hydrolyzed to generate a compound of formula I;

[0014]

[0015]

[0016] Wherein, L is selected from C 3-5 alkylene;

[0017] R is selected from C 1-3 alkyl;

[0018] X is selected from O or S;

[0019] Y1 is independently selected from halogen.

[0020] The third aspect of the present application provides a perovskite solar cell, the technical solution of which is as follows:

[0021] A perovskite solar cell comprises a transparent conductive electrode, a first charge transport layer, a perovskite light absorbing layer, a second charge transport layer and a metal electrode stacked in sequence; the first charge transport layer or the second charge transport layer comprises the hole transport material as described above or comprises a hole transport material prepared by the preparation method as described above.

[0022] Compared with traditional solutions, this application has the following beneficial effects:

[0023] The compound of formula I of the present application has a strong interaction with the ingredients in the perovskite light-absorbing layer, and in the case where there is no need to add additives such as P-type dopants or interface modifiers, it is possible to passivate grain boundary defects and interface defects, and the battery photoelectric conversion efficiency is high while the battery stability is good. Meanwhile, the compound of formula I has a HOMO energy level that matches the perovskite and is deeper, has good hole mobility, is conducive to the extraction and transmission of holes, is conducive to the improvement of the battery photoelectric conversion efficiency, and has high repeatability. Meanwhile, the decomposition temperature of the compound of formula I is high, and has good thermal stability, and can be stably present under an annealing process. Meanwhile, in the preparation process of inverted perovskite solar cells, a perovskite precursor solution is usually printed on the hole transport layer to form a perovskite light-absorbing layer, and the tolerance of traditional small molecule hole transport materials to the perovskite precursor solution is poor, resulting in the presence of pinhole morphology defects, and the battery photoelectric conversion efficiency is affected. The compound of formula I has good tolerance to the perovskite precursor solution and has excellent film-forming properties. At the same time, after film formation, it has good wettability with the perovskite precursor solution, which is beneficial to the crystallization and film formation of the perovskite light-absorbing layer and is beneficial to improving the photoelectric conversion efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more fully understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0025] Figure 1 is the hydrogen nuclear magnetic resonance spectrum of the compound of formula II in Example 1;

[0026] Figure 2 is the hydrogen nuclear magnetic resonance spectrum of the compound of formula III in Example 2;

[0027] Figure 3 Current density-voltage curves of perovskite solar cells prepared with different hole transport materials. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below with reference to specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to provide a more thorough and comprehensive understanding of the present application's disclosure.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0030] the term

[0031] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0032] "Alkyl" refers to straight-chain and branched saturated aliphatic hydrocarbon groups. 1-3 Non-limiting examples of alkyl groups include methyl, ethyl, n-propyl, and isopropyl.

[0033] For battery performance considerations, when using traditional small molecule hole transport materials to prepare hole transport layers, additives such as P-type dopants or interface modifiers are generally added to passivate grain boundary defects and interface defects. However, the addition of additives has an adverse effect on battery stability, restricting the development of perovskite solar cells.

[0034] In view of this, the first aspect of the present application provides a hole transport material, including a compound of formula I:

[0035]

[0036] Wherein, L is selected from C 3-5 alkylene;

[0037] R is selected from C 1-3 alkyl;

[0038] X is selected from O or S.

[0039] Alternatively, L is -(CH2)4-, and R is -CH3. In this case, the hole transport material comprises a compound of formula II or a compound of formula III:

[0040]

[0041]

[0042] The present application introduces a methoxy or methylthiotriphenylamine group into acridine phosphate side chain, and the obtained compound of formula I has a strong interaction with the components in the perovskite light-absorbing layer, without the need to add additives such as P-type dopants or interface modifiers, that is, it can play a role in passivating grain boundary defects and interface defects, and the battery photoelectric conversion efficiency is high while the battery stability is good. At the same time, the compound of formula I has a HOMO energy level that matches the perovskite and is deeper, has a good hole mobility, is conducive to the extraction and transmission of holes, is conducive to the improvement of the battery photoelectric conversion efficiency, and has high repeatability. At the same time, the decomposition temperature of the compound of formula I is high, the thermal stability is good, and it can be stably present under the annealing process. At the same time, in the preparation process of inverted perovskite solar cells, a perovskite precursor solution is usually printed on the hole transport layer to form a perovskite light-absorbing layer, and the tolerance of traditional small molecule hole transport materials to the perovskite precursor solution is poor, resulting in the hole transport layer always having pinhole morphology defects, and the battery photoelectric conversion efficiency is affected. The compound of formula I has good tolerance to the perovskite precursor solution and has excellent film-forming properties. At the same time, after film formation, it has good wettability with the perovskite precursor solution, which is beneficial to the crystallization and film formation of the perovskite light-absorbing layer and is beneficial to improving the photoelectric conversion efficiency of the battery.

[0043] A second aspect of the present application provides a method for preparing a hole transport material, comprising the following steps:

[0044] S10, subjecting the compound of formula I-1 to a substitution reaction to generate a compound of formula I-2.

[0045] Optionally, the compound of formula I-1 is subjected to a substitution reaction, comprising the following steps:

[0046] The compound of formula I-1, N-bromosuccinimide and a first solvent are mixed to cause a first substitution reaction.

[0047] Optionally, the molar ratio of the compound of formula I-1 to the N-bromosuccinimide is 1:(2-3).

[0048] Optionally, the first solvent is dichloromethane.

[0049] Optionally, the temperature of the first substitution reaction is 15° C. to 40° C., and the time of the first substitution reaction is 10 h to 14 h.

[0050] S20, subjecting the compound of formula I-2 to a substitution reaction to generate a compound of formula I-3.

[0051] Alternatively, the compound of formula I-2 is subjected to a substitution reaction, comprising the following steps:

[0052] Mixing the compound of formula I-2, The first catalyst and the first alkaline agent undergo a second substitution reaction.

[0053] Optionally, the compound of formula I-2 and The molar ratio is 1:(40~60).

[0054] Optionally, It is 1,4-dibromobutane.

[0055] Optionally, the first catalyst is selected from tetrabutylammonium bromide.

[0056] Optionally, the molar ratio of the compound of formula I-2 to the first catalyst is 1:(0.05-0.2).

[0057] Optionally, the first alkaline agent is selected from potassium hydroxide.

[0058] Optionally, the molar ratio of the compound of formula I-2 to the first alkaline agent is 1:(7-10).

[0059] Optionally, the temperature of the second substitution reaction is 60° C. to 70° C., and the time of the second substitution reaction is 10 h to 14 h.

[0060] S30, allowing the compound of formula I-3 to undergo an esterification reaction with triethyl phosphite to generate the compound of formula I-4.

[0061] Optionally, the molar ratio of the compound of formula I-3 to the triethyl phosphite is 1:(140-160).

[0062] Optionally, the esterification reaction temperature is 150° C. to 170° C., and the reaction time is 10 h to 14 h.

[0063] S40, allowing the compound of formula I-5 to undergo a substitution reaction with the compound of formula I-6 to generate a compound of formula I-7.

[0064] Alternatively, the compound of formula I-5 and the compound of formula I-6 are subjected to a substitution reaction, comprising the following steps:

[0065] The compound of formula I-5, the compound of formula I-6, a second catalyst, and a second solvent are mixed to cause a third substitution reaction.

[0066] Optionally, the molar ratio of the compound of formula I-5 to the compound of formula I-6 is 1:(1-2).

[0067] Optionally, the second catalyst is selected from n-butyllithium.

[0068] Optionally, the molar ratio of the compound of formula I-5 to the second catalyst is 1:(0.8-1.2).

[0069] Optionally, the second solvent is selected from tetrahydrofuran.

[0070] Optionally, the reaction conditions of the third substitution reaction include: reacting at -70°C to -90°C for 0.5h to 2h, and then reacting at 15°C to 40°C for 10h to 14h.

[0071] S50, allowing the compound of formula I-4 to undergo Suzuki coupling reaction with the compound of formula I-7 to generate a compound of formula I-8.

[0072] Alternatively, the compound of formula I-4 and the compound of formula I-7 are subjected to a Suzuki coupling reaction, comprising the following steps:

[0073] The compound of formula I-4, the compound of formula I-7, a third catalyst, a second alkaline agent and a third solvent are mixed to cause a Suzuki coupling reaction.

[0074] Optionally, the molar ratio of the compound of formula I-4 to the compound of formula I-7 is 1:(2 to 2.4).

[0075] Optionally, the third catalyst is selected from tetrakis(triphenylphosphine)palladium.

[0076] Optionally, the molar ratio of the compound of formula I-4 to the third catalyst is 1: (0.04 to 0.06)

[0077] Optionally, the second alkaline agent is selected from potassium carbonate.

[0078] Optionally, the molar ratio of the compound of formula I-4 to the second alkaline agent is 1:(4-7).

[0079] Optionally, the third solvent is selected from at least one of toluene, ethanol and water.

[0080] Optionally, the reaction temperature of the Suzuki coupling reaction is 80° C. to 90° C., and the reaction time is 4 h to 8 h. S60: hydrolyzing the compound of formula I-8 to generate the compound of formula I.

[0081] Alternatively, hydrolyzing the compound of formula I-8 comprises the following steps:

[0082] The compound of formula I-8 is hydrolyzed using a fourth solvent and a fourth catalyst.

[0083] Optionally, the fourth catalyst is selected from trimethylsilyl bromide.

[0084] Optionally, the molar ratio of the compound of formula I-8 to the fourth catalyst is 1:(8-12). Optionally, the fourth solvent includes 1,4-dioxane, methanol and water.

[0085] Optionally, the hydrolysis time is 10 h to 14 h.

[0086]

[0087]

[0088] Among them, L, R, and X are as described above and will not be repeated here.

[0089] Y1 and Y3 are each independently selected from halogen, such as Br.

[0090] Y2 is selected from halogen, such as Br.

[0091] The preparation method is simple, low-cost, and suitable for industrial production. The resulting hole transport material exhibits excellent thermal stability and film-forming properties, and its energy level matches that of perovskite. Application of this undoped hole transport material in inverted perovskite solar cells yields high photoelectric conversion efficiency and reproducibility.

[0092] The third aspect of the present application provides a perovskite solar cell, comprising a transparent conductive electrode, a first charge transport layer, a perovskite light absorbing layer, a second charge transport layer and a metal electrode stacked in sequence; the first charge transport layer or the second charge transport layer comprises the hole transport material as described above or comprises a hole transport material prepared by the preparation method as described above.

[0093] Alternatively, the first charge transport layer is a hole transport layer, and the second charge layer is an electron transport layer, and the first charge transport layer includes the hole transport material or includes a hole transport material prepared by the preparation method. At this time, the perovskite solar cell is an inverted perovskite solar cell, and the above-mentioned hole transport layer material is particularly suitable for inverted perovskite solar cells. In the preparation process of inverted perovskite solar cells, perovskite precursor solutions are usually printed on the hole transport layer to form a perovskite light absorbing layer, and traditional small molecule hole transport materials have poor tolerance to perovskite precursor solutions, resulting in the presence of pinhole morphology defects, and the battery photoelectric conversion efficiency is affected. The compound of formula I has good tolerance to perovskite precursor solutions, and itself has good film forming properties. At the same time, after film formation, it also has good wettability with the perovskite precursor solution, which is beneficial to the crystallization and film formation of the perovskite light absorbing layer, and is beneficial to improving the battery photoelectric conversion efficiency.

[0094] In one embodiment, see Figure 1 The structure of the perovskite solar cell 100 includes a transparent conductive electrode 11, a hole transport layer 12, a perovskite absorption layer 13, an electron transport layer 14, and a metal electrode 15 stacked in sequence.

[0095] The transparent conductive electrode 11 is made of ITO glass.

[0096] The hole transport layer 12 includes the hole transport material described above or includes a hole transport material prepared by the preparation method described above. The hole transport layer 12 can be prepared by dissolving the hole transport material in a solvent to obtain a solution, applying the solution, and then annealing. Optionally, each 1 mL of the solution contains 3 mg to 15 mg of the hole transport material. Optionally, the solvent can be chlorobenzene, toluene, dichloromethane, etc. The above-mentioned hole transport materials have good solubility in solvents such as toluene, chlorobenzene, and dichloromethane. Optionally, the annealing temperature is 90 to 110°C.

[0097] The perovskite absorbing layer 13 is a quasi-two-dimensional perovskite. The perovskite absorbing layer 13 can be prepared by dissolving a perovskite material in a solvent to obtain a solution, coating the solution, and then annealing. Optionally, the perovskite material is selected from at least one of 3-bromobenzylammonium iodide, 3-chlorobenzylammonium iodide, methylammonium chloride, and lead iodide. Optionally, the solvent can be at least one of DMF and DMSO.

[0098] The electron transport layer 14 includes PC61BM.

[0099] The metal electrode is at least one of chromium (Cr) and gold (Au).

[0100] The following is further described in conjunction with specific examples and comparative examples. Unless otherwise specified, the raw materials involved in the following specific examples and comparative examples can be sourced from commercial sources. The instruments used can be sourced from commercial sources unless otherwise specified. The processes involved can be selected conventionally by those skilled in the art unless otherwise specified.

[0101] Example 1

[0102] S10, subjecting the compound of formula (1) to a substitution reaction to generate a compound of formula (2)

[0103]

[0104] In a 100 mL round-bottom flask, compound (1) (0.89 g, 4.24 mmol) and dichloromethane (10 mL) were added, followed by N-bromosuccinimide (1.51 g, 8.48 mmol). The mixture was heated to room temperature and stirred overnight. The reaction was quenched with water, extracted with dichloromethane, and the organic layers were combined and dried over anhydrous magnesium sulfate. The organic solvent was then removed on a rotary evaporator to obtain a crude product. Further purification was performed by flash column chromatography using petroleum ether / dichloromethane 10 / 1 as the eluent. Compound (2) was obtained as a white solid (1.40 g, 90% yield).

[0105] S20, causing the compound of formula (2) to undergo a substitution reaction to generate a compound of formula (3)

[0106]

[0107] In a 100 mL double-necked flask, the compound of formula (2) (1.00 g, 2.72 mmol) was added, tetrabutylammonium bromide (0.32 g, 0.27 mmol) was dissolved in 1,4-dibromobutane (15 mL, 125 mmol), and then a 50 wt% aqueous potassium hydroxide solution (5 mL) was added dropwise. The mixture was heated to 65°C and then stirred overnight. The reaction was quenched with water, extracted with dichloromethane, and the organic layer was combined with anhydrous magnesium sulfate and dried, and then the organic solvent was removed by rotary evaporation to obtain a crude product. Further purification was performed by silica gel column chromatography with an eluent of petroleum ether / dichloromethane = 10 / 1 to obtain the compound of formula (3) as a colorless oil (1.20 g, yield 89%).

[0108] S30, esterifying the compound of formula (3) with triethyl phosphite to generate the compound of formula (4)

[0109]

[0110] In a 100 mL double-necked flask, compound (3) (1.20 g, 2.39 mmol) and triethyl phosphite (10 mL) were added, and the mixture was heated to 160° C. and stirred overnight under a nitrogen atmosphere. The organic solvent was then removed using a rotary evaporator to obtain a crude product of compound (4) (1.30 g, 2.27 mmol).

[0111] S40, causing the compound of formula (5) to undergo a substitution reaction with the compound of formula (6) to generate a compound of formula (7)

[0112]

[0113] The compound of formula (5) (3.84 g, 10 mmol) was weighed and added to a 500 mL three-necked flask. 30 mL of dry THF was then added. The mixture was cooled to -78°C under N2 and stirred for 10 min. Then, n-butyl lithium (3.75 mL, 1.00 equiv, 1.6 Min n-hexane) was slowly added dropwise. The reaction was continued at -78°C for 1 hour. The compound of formula (6) (2.75 mL, 15 mmol) was then added. The reaction was continued at -78°C for 1 hour. Finally, the mixture was moved to room temperature and reacted for 12 hours. The reaction was quenched with 50 mL of deionized water, extracted with saturated NaCl solution and DCM, and the organic phase was dried over anhydrous Mg2SO4, filtered, and finally purified by column chromatography (PE:DCM = 15:1) to obtain 3.4 g of a white solid compound of formula (7) with a yield of 79%.

[0114] S50, causing the compound of formula (4) and the compound of formula (7) to undergo Suzuki coupling reaction to generate a compound of formula (8)

[0115]

[0116] To a 100 mL double-necked flask, the compound of formula (4) (0.58 g, 1 mmol), the compound of formula (7) (0.9 g, 2.2 mmol), tetrakis(triphenylphosphine)palladium (57 mg, 0.05 mmol), and potassium carbonate (0.83 g, 6 mmol) were added. The solvent was toluene, ethanol, and water (in a ratio of 2:1:1). The reaction was carried out at 85° C. for 6 hours. After cooling to room temperature, the mixture was extracted with DCM. The organic phase was dried over anhydrous MgSO, filtered, and distilled under reduced pressure. Finally, it was purified by column chromatography (PE:DCM=4:1) to obtain the compound of formula (8) (0.75 g, 0.74 mmol) with a yield of 75%.

[0117] S60, hydrolyzing the compound of formula (8) to generate a compound of formula II

[0118]

[0119] In a 100mL double-necked flask, compound (8) (2.04g, 2mmol) was added to anhydrous 1,4-dioxane (10mL) at room temperature, and trimethylsilane bromide (3.06g, 20mmol) was added dropwise, and then stirred overnight. 1,4-dioxane was removed by rotary evaporator to obtain a solid powder. The solid powder was dissolved in methanol (10mL) at room temperature, and then deionized water was added dropwise until the mixture became opaque, and then stirred for 12 hours. The crude product was collected by filtration and washed with deionized water. The crude product was dissolved in THF (5mL), reprecipitated in acetone (20mL), and filtered to obtain the final product, which was a compound of formula II (1.2g, yield 75%). The hydrogen nuclear magnetic resonance spectrum of the compound of formula II is shown as follows Figure 1 shown.

[0120] Example 2

[0121] S10 to S30 refer to Example 1.

[0122] S40, causing the compound of formula (9) to undergo a substitution reaction with the compound of formula (6) to generate a compound of formula (10)

[0123]

[0124] The compound of formula (5) (4.17 g, 10 mmol) was weighed and added to a 500 mL three-necked flask. 30 mL of dry THF was then added. The mixture was cooled to -78°C under N2 and stirred for 10 min. Then, n-butyl lithium (3.75 mL, 1.00 equiv, 1.6 Min n-hexane) was slowly added dropwise. The reaction was continued at -78°C for 1 hour. The compound of formula (6) (2.75 mL, 15 mmol) was then added. The reaction was continued at -78°C for 1 hour. Finally, the mixture was moved to room temperature and reacted for 12 hours. The reaction was quenched with 50 mL of deionized water, extracted with saturated NaCl solution and DCM, and the organic phase was dried over anhydrous Mg2SO4, filtered, and finally purified by column chromatography (PE:DCM = 15:1) to obtain 3.3 g of a white solid compound of formula (7) with a yield of 78%.

[0125] S50, causing the compound of formula (4) to undergo Suzuki coupling reaction with the compound of formula (10) to generate a compound of formula (11)

[0126]

[0127] To a 100 mL double-necked flask were added the compound of formula (4) (0.58 g, 1 mmol), the compound of formula (10) (1.02 g, 2.2 mmol), tetrakis(triphenylphosphine)palladium (57 mg, 0.05 mmol), and potassium carbonate (0.83 g, 6 mmol). The solvent was toluene, ethanol, and water (in a ratio of 2:1:1), and the reaction was carried out at 85° C. for 6 hours. After cooling to room temperature, the mixture was extracted with DCM, and the organic phase was dried over anhydrous MgSO, filtered, and distilled under reduced pressure. Finally, it was purified by column chromatography (PE:DCM=4:1) to obtain the compound of formula (11) (0.78 g, 0.72 mmol) with a yield of 72%.

[0128] S60, hydrolyzing the compound of formula (10) to generate a compound of formula III

[0129]

[0130] In a 100mL double-necked flask, compound (11) (2.17g, 2mmol) was added to anhydrous 1,4-dioxane (10mL) at room temperature, and trimethylsilane bromide (3.06g, 20mmol) was added dropwise, and then stirred overnight. 1,4-dioxane was removed by rotary evaporator to obtain a solid powder. The solid powder was dissolved in methanol (10mL) at room temperature, and then deionized water was added dropwise until the mixture became opaque, and then stirred for 12 hours. The crude product was collected by filtration and washed with deionized water. The crude product was dissolved in THF (5mL), reprecipitated in acetone (20mL), and filtered to obtain the final product, which was a compound of formula III (1.3g, yield 75%). The nuclear magnetic resonance hydrogen spectrum of the compound of formula II is shown as follows Figure 2 shown.

[0131] Example 3

[0132] The compound of formula II prepared in Example 1 and the compound of formula III prepared in Example 2 were used as hole transport materials to prepare perovskite solar cells in the following steps:

[0133] (1) Cleaning: The ITO glass sheet was ultrasonically cleaned with deionized water, acetone, and ethanol for 15 minutes in sequence. The residual solvent on the surface of the ITO glass sheet was then blown dry with an N2 air gun. The sheet was then treated with oxygen plasma for 15 minutes and then transferred to a nitrogen glove box.

[0134] (2) Preparation of hole transport layer: 10 mg of the compound of formula II or III was completely dissolved in 1 mL of chlorobenzene solution. An appropriate amount of the solution was evenly added dropwise onto the ITO glass substrate, spin-coated at 5000 rpm for 20 seconds, and then annealed at 100°C for 10 minutes.

[0135] (3) Preparation of perovskite absorption layer: The ITO / hole transport layer substrate obtained above was cooled to room temperature, preheated at 130°C for 5 minutes, 50 μL of perovskite solution was spread over the ITO / hole transport layer substrate, spin-coated at 5000 rpm for 20 seconds, and then annealed at 100°C for 10 minutes to prepare a perovskite absorption layer. The perovskite solution was a DMSO solution of 3-bromobenzylammonium iodide.

[0136] (4) Preparation of electron transport layer: The ITO / hole transport layer / perovskite substrate obtained above was cooled to room temperature, PC61BM was prepared into a 15 mg / mL solution, and then 40 μL of PC61BM solution was taken to cover the ITO / hole transport layer / perovskite substrate and spin-coated at 1000 rpm for 30 to 50 seconds;

[0137] (5) Preparation of electrodes: Place the above substrate in a vacuum evaporation chamber, and evaporate Cr (6 nm) and Au (80 nm) on the PC61BM layer respectively to obtain the desired inverted perovskite solar cell.

[0138] Comparative Example

[0139] An inverted perovskite solar cell was prepared using PTAA as a hole transport material according to the method of Example 3.

[0140] Test items

[0141] Adjust the solar simulator power to 100 mw / cm 2 To simulate the AM1.5G radiation standard, the device's current and voltage values ​​were read by connecting a computer to a Keithley 2450 power meter. Before measuring the current density-voltage curve, the light intensity was calibrated using a Newport standard silicon cell 91150. The device was scanned in forward and reverse mode at a scan rate of 0.05V / s. The current density-voltage curve after the test is shown in Figure 2. Figure 1 , open circuit voltage V oc , short-circuit current J sc , fill factor FF and photoelectric conversion efficiency PCE are shown in Table 1.

[0142] Table 1

[0143]

[0144] It can be seen that the open circuit voltage of the inverted perovskite solar cell device corresponding to PTAA, which is currently commonly used in inverted devices, is 1.19 V and the short circuit current is 20.72 mA / cm 2 , the filling factor is 75.01%, and the photoelectric conversion efficiency is 18.51%.

[0145] The inverted perovskite solar cell device corresponding to the compound of formula II has an open circuit voltage of 1.15 V and a short circuit current of 20.46 mA / cm 2 , the filling factor is 79.88%, and the photoelectric conversion efficiency is 18.89%.

[0146] The inverted perovskite solar cell device corresponding to the compound of formula III has an open circuit voltage of 1.16 V and a short circuit current of 20.47 mA / cm 2 , the filling factor is 80.74%, and the photoelectric conversion efficiency is 19.23%.

[0147] It can be seen that the perovskite solar cell based on the doped hole transport material of the compound of formula II or the compound of formula III can obtain good device performance.

[0148] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0149] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A hole transport material, characterized in that Includes compounds of formula I: Wherein, L is selected from C 3-5 alkylene; R is selected from C 1-3 alkyl; X is selected from O or S.

2. The hole transport material according to claim 1, characterized in that L is -(CH2)4- and R is -CH3.

3. A method for preparing a hole transport material, characterized in that: The following steps are involved: Allowing the compound of formula I-5 to undergo a substitution reaction with the compound of formula I-6 to generate a compound of formula I-7; The compound of formula I-4 is subjected to a Suzuki coupling reaction with the compound of formula I-7 to generate a compound of formula I-8; the compound of formula I-8 is hydrolyzed to generate a compound of formula I; Wherein, L is selected from C 3-5 alkylene; R is selected from C 1-3 alkyl; X is selected from O or S; Y1 and Y3 are each independently selected from halogen.

4. The method for preparing a hole transport material according to claim 3, wherein: The compound of formula I-5 and the compound of formula I-6 undergo a substitution reaction, comprising the following steps: The compound of formula I-5, the compound of formula I-6, a second catalyst, and a second solvent are mixed to cause a third substitution reaction.

5. The method for preparing a hole transport material according to claim 3, wherein: The compound of formula I-4 and the compound of formula I-7 undergo a Suzuki coupling reaction, comprising the following steps: The compound of formula I-4, the compound of formula I-7, a third catalyst, a second alkaline agent and a third solvent are mixed to cause a Suzuki coupling reaction.

6. The method for preparing a hole transport material according to claim 3, wherein: The hydrolysis of the compound of formula I-8 comprises the following steps: The compound of formula I-8 is hydrolyzed using a fourth solvent and a fourth catalyst.

7. The method for preparing a hole transport material according to any one of claims 3 to 6, characterized in that: The preparation method of the compound of formula I-4 comprises the following steps: Allowing the compound of formula I-1 to undergo a substitution reaction to generate a compound of formula I-2; Allowing the compound of formula I-2 to undergo a substitution reaction to generate a compound of formula I-3; allowing the compound of formula I-3 to undergo an esterification reaction with triethyl phosphite to generate the compound of formula I-4; wherein Y2 is selected from halogen.

8. The method for preparing a hole transport material according to claim 7, wherein: The compound of formula I-1 is subjected to a substitution reaction, comprising the following steps: The compound of formula I-1, N-bromosuccinimide and a first solvent are mixed to cause a first substitution reaction.

9. The method for preparing a hole transport material according to claim 7, wherein: The compound of formula I-2 is subjected to a substitution reaction, comprising the following steps: Mixing the compound of formula I-2, The first catalyst and the first alkaline agent undergo a second substitution reaction.

10. A perovskite solar cell, characterized in that: It comprises a transparent conductive electrode, a first charge transport layer, a perovskite light absorbing layer, a second charge transport layer and a metal electrode stacked in sequence; the first charge transport layer or the second charge transport layer comprises the hole transport material according to any one of claims 1 to 2 or comprises a hole transport material prepared by the preparation method according to any one of claims 3 to 9.

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