Preparation method of perovskite light absorption layer film and perovskite solar cell

Abstract

The invention relates to a preparation method of a perovskite light absorption layer film and a perovskite solar cell, and belongs to the technical field of perovskite solar cell preparation. Preparing a solvent-free cesium-lead-based metal halide precursor film by using lead halide and cesium halide; and carrying out surface treatment on the cesium-lead-based metal halide precursor film by using a surface modifier, and reacting the cesium-lead-based metal halide precursor film subjected to surface treatment with halogenated formamidine to obtain the required perovskite light absorption layer film. The surface modifier can interact with the cesium-lead-based metal halide in the cesium-lead-based metal halide precursor film which is prepared in advance and does not contain the solvent, so that the property and the morphology of the cesium-lead-based metal halide precursor are changed; and the reaction raw materials in the subsequent deposition step and the precursor film can react to tend to form a perovskite light absorption layer film with high crystallinity and stable black phase.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite solar cell preparation, and particularly relates to a perovskite light-absorbing layer film preparation method and a perovskite solar cell. BACKGROUND

[0002] In recent years, perovskite solar cells have attracted much attention due to their simple preparation process and low cost. The quality of perovskite film directly affects the photoelectric performance and long-term stability of perovskite solar cells. If there are a large number of crystal defects in the perovskite light-absorbing layer, these defect sites will not only cause carrier recombination, but also easily decompose the perovskite material under the influence of adverse factors (such as light, humidity, temperature, etc.), reducing the performance of the battery and destroying the long-term stability of the battery.

[0003] The preparation methods of perovskite light-absorbing layer films mainly include solution deposition, vapor-assisted deposition, vacuum evaporation, etc. The above film deposition methods can be mainly divided into two categories: one-step deposition and sequential deposition. The one-step deposition method has a short crystallization window period and is greatly affected by environmental factors, resulting in poor repeatability of this method, which is not conducive to large-area production. At present, the two-step deposition method in the sequential deposition method is a more controllable method for perovskite film crystallization, which is expected to be applied to the industrialization of large-area films. However, the perovskite films prepared by the traditional two-step deposition method are more likely to have a large number of defects and incomplete reactions, which adversely affect the performance and stability of perovskite solar cells. Therefore, effectively controlling the growth of perovskite in the two-step deposition method is of great significance for preparing high-quality formamidinium cesium lead perovskite solar cells, especially in the industrialization process of large-area perovskite film preparation.

[0004] In the process of two-step deposition of perovskite films, the cesium lead metal halide in the precursor dry film deposited in the first step is mainly composed of lead halide and cesium halide. These two metal halides will form two independent lead halide crystals and cesium halide crystals in the process of first-step deposition and crystallization, rather than being fused with each other, and the distribution of the two crystals is not uniform, which greatly affects the uniformity of crystallization in the second-step deposition, thereby leading to the decrease of phase stability and device efficiency of perovskite.

[0005] In the process of perovskite film preparation, dry film has the advantages of not being easily affected by temperature and humidity, convenient transportation and storage, good repeatability, and environmental friendliness compared with wet film. Therefore, the present application mainly optimizes the dry film deposited in the first step. SUMMARY

[0006] The application provides a preparation method of a perovskite light-absorbing layer film and a perovskite solar cell.

[0007] The application is implemented by providing a preparation method of a perovskite light-absorbing layer film, which comprises the following steps: Step one, a solvent-free cesium-lead metal halide precursor film is prepared on the surface of a substrate with a prepared transport layer by using lead halide and cesium halide; wherein the lead halide comprises at least one of lead iodide (PbI2), lead chloride (PbCl2) and lead bromide (PbBr2), and the cesium halide comprises at least one of cesium iodide (CsI), cesium chloride (CsCl) and cesium bromide (CsBr); Step two, a surface treatment is performed on the above-mentioned cesium-lead metal halide precursor film by using a surface modifier, wherein the surface modifier is any one of a pyridine compound, a selenophene compound and a phosphate compound, and the functional group in the structure of each compound is a pyridine group, a selenophene group or a phosphate group; Step three, halogenated formamidine is attached to the surface-treated cesium-lead metal halide precursor film, so that the surface-treated cesium-lead metal halide precursor film reacts with the halogenated formamidine to obtain the required perovskite light-absorbing layer film; wherein the halogenated formamidine comprises at least one of formamidinium iodide (FAI), formamidinium chloride (FACl) and formamidinium bromide (FABr).

[0008] Further, in step one, the method for preparing the cesium-lead metal halide precursor thin film comprises the following steps: a certain amount of lead halide and cesium halide are dissolved in an organic solvent A to prepare a cesium-lead metal halide precursor solution, wherein the concentration of lead halide is 0.5 mol / L-1.5 mol / L, and the concentration of cesium halide is 0.05 mol / L-0.5 mol / L; the above-mentioned cesium-lead metal halide precursor solution is deposited on the surface of the prepared transport layer by a solution deposition method, and after annealing at 50-250°C for 10 s-2 h, a cesium-lead metal halide precursor thin film without organic solvent A is obtained; wherein the solution deposition method includes any one of spin coating, blade coating, spraying, and slot coating processing methods, and the organic solvent A is any one of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methyl pyrrolidone (NMP), and γ-butyrolactone (GBL).

[0009] Further, in step one, the method for preparing the cesium-lead metal halide precursor thin film comprises the following steps: lead halide and cesium halide are placed in different evaporation boats by a vapor deposition method, and the lead halide and cesium halide vapors are uniformly deposited on the surface of the prepared transport layer to obtain a cesium-lead metal halide precursor thin film; wherein the vapor deposition method includes any one of vacuum thermal evaporation, multi-source co-evaporation, chemical vapor deposition, near-space sublimation, and vapor-phase transport deposition processing methods.

[0010] Further, in step two, the surface treatment method comprises the following steps: the surface modifier is diluted with a solvent B to 0.1 mg / ml-2 mg / ml to obtain a surface modifier solution, and the solvent B is any one of methanol, ethanol, isopropanol, and 2-methoxyethanol; the above-mentioned surface modifier solution is coated on the surface of the cesium-lead metal halide precursor thin film without solvent by a coating method, the surface modifier solution is contacted with the cesium-lead metal halide thin film for a certain period of time, and then heating or vacuum pumping is performed to remove the solvent B, thereby obtaining a cesium-lead metal halide precursor thin film treated by a surface modifier; wherein the coating method includes any one of spin coating, blade coating, spraying, and slot coating processing methods.

[0011] Further, in step two, the surface treatment method comprises the following steps: the surface modifier is transported to the surface of the cesium-lead metal halide precursor thin film by direct thermal evaporation or by a carrier gas, the surface modifier is contacted with the cesium-lead metal halide thin film and reacts for a certain period of time, thereby obtaining a cesium-lead metal halide precursor thin film treated by a surface modifier.

[0012] Further, in step three, the method of reacting the surface-treated cesium lead-based metal halide precursor film with formamidine halide includes: dissolving formamidine halide in organic solvent C to obtain a formamidine halide solution with a concentration of 0.01 mol / L to 10 mol / L; coating the formamidine halide solution onto the surface of the surface-treated cesium lead-based metal halide precursor film; and annealing at 50°C to 300°C to obtain a formamidine cesium lead-based perovskite film, i.e., the desired perovskite light-absorbing layer film. The organic solvent C is any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and γ-butyrolactone.

[0013] Further, in step three, the method of reacting the surface-treated cesium lead-based metal halide precursor film with formamidine halide includes: transporting formamidine halide to the surface of the surface-treated cesium lead-based metal halide precursor film by direct thermal evaporation or carrier gas; after the formamidine halide fully reacts with the surface-treated cesium lead-based metal halide precursor film, heating and annealing are performed to obtain a formamidine cesium lead-based perovskite film, which is the desired perovskite light-absorbing layer film.

[0014] This invention is implemented as follows, and also provides a perovskite solar cell, including a perovskite light-absorbing layer, wherein the perovskite light-absorbing layer is prepared using the perovskite light-absorbing layer thin film preparation method described above.

[0015] Compared with the prior art, the preparation method of the perovskite light-absorbing layer thin film and the perovskite solar cell of the present invention include the following steps: preparing a solvent-free cesium lead-based metal halide precursor film on the surface of a substrate on which a transport layer has been prepared, using lead halide and cesium halide; performing surface treatment on the above-mentioned cesium lead-based metal halide precursor film using a surface modifier; and reacting the surface-treated cesium lead-based metal halide precursor film with formamidinium halide to obtain the desired perovskite light-absorbing layer thin film. The surface modifier is any one of pyridine compounds, selenophene compounds, and phosphate ester compounds, and correspondingly, the functional groups in the structure of each compound are pyridine groups, selenophene groups, and phosphate ester groups. The surface modifier of this invention interacts with the cesium lead-based metal halide in the pre-prepared solvent-free cesium lead-based metal halide precursor film, changing the properties and morphology of the cesium lead-based metal halide precursor, providing higher quality perovskite nuclei, which is beneficial for the reaction of the reactants and the precursor film in the subsequent deposition steps to form a high-crystallinity, black-phase-stable, high-quality perovskite light-absorbing layer film. Attached Figure Description

[0016] Figure 1 This is a schematic diagram comparing the XRD diffraction of the perovskite light-absorbing layer films prepared in Example 1 and the comparative example of the present invention. Figure 2This is a schematic diagram of the SEM image of the perovskite light-absorbing layer film prepared in Example 1 of the present invention. Detailed Implementation

[0017] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0018] A preferred embodiment of the method for preparing the perovskite light-absorbing layer thin film of the present invention includes the following steps: Step 1: On the substrate surface where the transport layer has been prepared, a solvent-free cesium lead-based metal halide precursor film is prepared using lead halide and cesium halide; wherein, lead halide includes at least one of lead iodide (PbI2), lead chloride (PbCl2), and lead bromide (PbBr2), and cesium halide includes at least one of cesium iodide (CsI), cesium chloride (CsCl), and cesium bromide (CsBr).

[0019] Step 2: The above-mentioned cesium lead-based metal halide precursor film is surface-treated using a surface modifier. The surface modifier is any one of pyridine compounds, selenophene compounds, or phosphate ester compounds. Correspondingly, the functional groups in the structure of each compound are pyridine groups, selenophene groups, or phosphate ester groups.

[0020] Step 3: Attach formamidine halide to the surface-treated cesium lead-based metal halide precursor film, so that the surface-treated cesium lead-based metal halide precursor film reacts with formamidine halide to obtain the desired perovskite light-absorbing layer film; wherein, formamidine halide includes at least one of formamidine iodide (FAI), formamidine chloride (FACl), and formamidine bromide (FABr).

[0021] In the conventional two-step deposition process of perovskite light-absorbing thin film, the cesium lead-based metal halide in the perovskite precursor dry film deposited in the first step is mainly composed of lead halide and cesium halide. These two metal halides will form two independent lead halide crystals and cesium halide crystals during the deposition and crystallization process, rather than being fused together. This results in the uneven distribution of cesium in the perovskite crystal, which affects the phase stability of the perovskite crystal and the efficiency of the perovskite solar cell.

[0022] In the preparation method of this invention, a surface modifier is used to treat the prepared cesium lead-based metal halide precursor film. The surface modifier interacts with the cesium lead-based metal halide in the cesium lead-based metal halide precursor film, helping cesium halide and lead halide to transform from two independent crystals into a single fused crystal nucleus, improving the uniformity of cesium distribution in the perovskite crystal, thereby enhancing the crystallinity of the cesium lead-based metal halide precursor film and effectively aiding the growth of the perovskite crystal after the second deposition step.

[0023] In step one, the method for preparing the cesium lead-based metal halide precursor film includes the following steps: a certain amount of lead halide and cesium halide are weighed and dissolved in organic solvent A and uniformly mixed to prepare a cesium lead-based metal halide precursor solution for later use, wherein the concentration of lead halide is 0.5 mol / L~1.5 mol / L and the concentration of cesium halide is 0.05 mol / L~0.5 mol / L. The above cesium lead-based metal halide precursor solution is deposited on the substrate surface of the prepared transport layer by solution deposition, and annealed at 50℃~250℃ for 10s~2h to obtain a cesium lead-based metal halide precursor film with organic solvent A removed. The solution deposition method includes any one of spin coating, blade coating, spray coating, and slot coating, and organic solvent A is any one of dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), and γ-butyrolactone (GBL).

[0024] In step one, the method for preparing the cesium lead-based metal halide precursor film includes the following steps: Lead halide and cesium halide are placed in separate evaporation boats via vapor deposition, and lead halide and cesium halide vapors are uniformly deposited on the substrate surface where the transport layer has been prepared, thereby obtaining the cesium lead-based metal halide precursor film. The vapor deposition method includes any one of vacuum thermal evaporation, multi-source co-evaporation, chemical vapor deposition, near-space sublimation, and vapor transport deposition.

[0025] In step two, the surface treatment method includes the following steps: diluting the surface modifier with solvent B to 0.1 mg / ml~2 mg / ml to obtain a surface modifier solution for later use. Solvent B is a poor solvent for the aforementioned cesium lead-based metal halide and can be any one of methanol, ethanol, isopropanol, 2-methoxyethanol, or other alcohol solvents. The surface modifier solution is coated onto the surface of the solvent-free cesium lead-based metal halide precursor film using a coating method. After the surface modifier solution contacts the cesium lead-based metal halide film for a certain period, solvent B is removed by heating or vacuuming, thereby obtaining a cesium lead-based metal halide precursor film treated with the surface modifier. The coating method includes any one of spin coating, blade coating, spray coating, or slot coating.

[0026] In step two, the surface treatment method includes the following steps: the surface modifier is directly thermally evaporated or transported to the surface of the cesium lead-based metal halide precursor film by a carrier gas, so that the surface modifier comes into contact with the cesium lead-based metal halide film and reacts for a certain period of time, thereby obtaining the cesium lead-based metal halide precursor film treated with the surface modifier.

[0027] In step three, the method for reacting the surface-treated cesium lead-based metal halide precursor film with formamidine halide includes: dissolving formamidine halide in organic solvent C to obtain a formamidine halide solution with a concentration of 0.01 mol / L to 10 mol / L; coating the formamidine halide solution onto the surface of the surface-treated cesium lead-based metal halide precursor film; and annealing at 50°C to 300°C to obtain a formamidine cesium lead-based perovskite film, i.e., the desired perovskite light-absorbing layer film. The organic solvent C is any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and γ-butyrolactone.

[0028] In step three, the method of reacting the surface-treated cesium lead-based metal halide precursor film with formamidine halide includes: transporting formamidine halide to the surface of the surface-treated cesium lead-based metal halide precursor film by direct thermal evaporation or carrier gas; after the formamidine halide fully reacts with the surface-treated cesium lead-based metal halide precursor film, heating and annealing are performed to obtain a formamidine cesium lead-based perovskite film, which is the desired perovskite light-absorbing layer film.

[0029] The present invention also discloses a perovskite solar cell, comprising a perovskite light-absorbing layer, wherein the perovskite light-absorbing layer is prepared by the perovskite light-absorbing layer thin film preparation method described above.

[0030] The following specific embodiments further illustrate the preparation method of the perovskite light-absorbing layer thin film and the perovskite solar cell of the present invention. Example 1

[0031] The first embodiment of the perovskite solar cell fabrication method of the present invention includes the following steps: (11) Clean the FTO transparent conductive glass in sequence with cleaning agent, deionized water, acetone and ethanol, and then irradiate it with UV light for 20 minutes before use.

[0032] (12) A TiO2 electron transport layer with a thickness of 20 nm was prepared on FTO transparent conductive glass by spraying.

[0033] (13) Weigh 0.461g of PbI2 and 0.26g of CsI and dissolve them in a mixed solvent of DMF:DMSO=9:1. Stir for 6h to obtain a cesium lead-based metal halide precursor solution for later use.

[0034] (14) The above-mentioned cesium lead-based metal halide precursor liquid was deposited on the surface of TiO2 electron transport layer by a blade coating method, and annealed at 150°C for 10 min to obtain a cesium lead-based metal halide precursor film.

[0035] (15) After heating and evaporating the trimethyl phosphate surface modifier, it was transported to the surface of the cesium lead-based metal halide precursor film through N2 and contacted for 2 min to obtain the cesium lead-based metal halide precursor film after being treated with trimethyl phosphate surface modification.

[0036] (16) Dissolve 90 mg of FAI (formamidinium hydroiodide) in 1 mL of IPA, stir until dissolved, and then coat it onto a cesium lead-based metal halide precursor film that has been modified by trimethyl phosphate by spin coating. Spin coat at 3000 rpm for 30 s, and after sufficient reaction, heat and anneal at 180 °C for 30 min to obtain a high-quality perovskite light-absorbing layer film.

[0037] (17) A hole transport layer Spiro-OMeTAD was prepared on the perovskite light-absorbing layer by using the slit coating method, and a Spiro-OMeTAD hole transport layer with a thickness of 100 nm was obtained.

[0038] (18) An electrode layer Al was prepared on the hole transport layer by vapor deposition to obtain a metal electrode layer with a thickness of 100 nm, and a perovskite solar cell was prepared. Example 2

[0039] A second embodiment of the method for fabricating perovskite solar cells of the present invention includes the following steps: (21) Clean the ITO transparent conductive glass with cleaning agent, deionized water, acetone and ethanol in sequence, and then irradiate it with UV light for 20 minutes before use.

[0040] (22) A PEDOT:PSS hole transport layer with a thickness of 20 nm was prepared on ITO conductive glass by spin coating.

[0041] (23) PbCl2 and CsI are spread evenly in the evaporation boat, and PbCl2 and CsI are uniformly deposited on the surface of the hole transport layer by heating co-evaporation to obtain a metal halide film.

[0042] (24) Take 100 μL of selenophene surface modifier and disperse it in 1 mL of isopropanol. Apply the selenophene isopropanol solution to the surface of the above metal halide film by spraying. Anneal at 100°C for 5 min to obtain a metal halide precursor film after selenophene surface modification treatment.

[0043] (25) The modified metal halide precursor film is placed in the film forming chamber, and the gas pressure is controlled at 10 using a vacuum pump.-5 Pa~10 5 Pa, the heating temperature of formamidinium hydroiodide (FAI) was controlled at 100℃~200℃, and the substrate heating temperature was controlled at 30℃~180℃. The FAI was fully reacted with the modified metal halide precursor film by vapor deposition for 30 min, and then annealed at 150℃ for 60 min to obtain a high-quality perovskite light-absorbing layer film with a thickness of 450 nm.

[0044] (26) Deposit an electron transport layer PCBM on the substrate with a thickness of 20nm~50nm.

[0045] (27) A perovskite solar cell is prepared by evaporating an Ag metal electrode on the electron transport layer. Example 3

[0046] A third embodiment of the method for fabricating perovskite solar cells of the present invention includes the following steps: (31) Clean the BZO transparent conductive glass with cleaning agent, deionized water, acetone and ethanol in sequence, and then UV-treated for 20 minutes before use.

[0047] (32) A TiO2 electron transport layer with a thickness of 120 nm was prepared on BZO transparent conductive glass by spraying.

[0048] (33) Weigh 0.461g of PbI2 and 0.26g of CsI and dissolve them in DMF. Stir for 6h to obtain a cesium lead-based metal halide precursor solution for later use.

[0049] (34) Preparation of metal halide precursor thin film: Using spin coating, 100 μL of the above cesium lead-based metal halide precursor liquid was dropped onto the surface of TiO2 electron transport layer, spin coated at 6000 rpm for 30 s, and annealed at 150 °C for 10 min to obtain cesium lead-based metal halide precursor thin film.

[0050] (35) The 4-tert-butylpyridine surface modifier was coated onto the surface of the cesium lead-based metal halide precursor film by slit coating and contacted for 2 min to obtain the cesium lead-based metal halide precursor film after 4-tert-butylpyridine surface modification.

[0051] (36) Dissolve 1 mmol of FAI in 1 mL of ethanol, stir until dissolved, and then coat it onto the cesium lead-based metal halide precursor film that has been surface modified with 4-tert-butylpyridine. After the reaction is complete, heat and anneal at 100 °C for 30 min to obtain a high-quality perovskite light-absorbing layer film.

[0052] (37) A hole transport layer Spiro-OMeTAD was prepared on a two-dimensional perovskite light-absorbing layer by spin coating, resulting in a Spiro-OMeTAD hole transport layer with a thickness of 100 nm.

[0053] (38) Electrode layers Au and Ag were prepared on the hole transport layer by vapor deposition to obtain Au metal electrodes with a thickness of 20 nm and Ag metal electrodes with a thickness of 150 nm, thus obtaining a perovskite solar cell.

[0054] Comparative Example The steps for preparing the perovskite solar cell in this comparative example are similar to those in Example 1, except that step (15) is not performed, the cesium lead-based metal halide precursor film is not treated with trimethyl phosphate surface modifier, and the FAI IPA solution is directly coated onto the cesium lead-based metal halide precursor film. The other steps are the same as in Example 1.

[0055] The perovskite light-absorbing thin films of the perovskite solar cells prepared in Example 1 and the comparative example were subjected to X-ray diffraction analysis, and the results were as follows: Figure 1 The diagram shows a comparison of XRD diffraction patterns. From... Figure 1 It can be seen that the crystallinity of the cesium lead-based metal halide precursor film after surface modification with trimethyl phosphate is significantly improved.

[0056] The perovskite light-absorbing layer film of the perovskite solar cell prepared in Example 1 was examined by electron microscopy, and the results were as follows: Figure 2 The diagram shown is a schematic of a SEM electrophoresis image. Figure 2 -a is a cesium lead-based metal halide precursor film without surface treatment modification, and it can be seen that there are multiple crystal morphologies in the film; Figure 2 -b represents the cesium lead-based metal halide precursor film after surface modification. It can be seen that the two types of crystals in the cesium lead-based metal halide precursor film after trimethyl phosphate surface modification are fused into a single crystal nucleus, and the size and morphology of the crystal nucleus tend to be consistent, which is beneficial to subsequent reactions and the growth and formation of high-quality crystals.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a perovskite light-absorbing thin film, characterized in that, Includes the following steps: Step 1: On the substrate surface where the transport layer has been prepared, a solvent-free cesium lead-based metal halide precursor film is prepared using lead halide and cesium halide; wherein, lead halide includes at least one of lead iodide, lead chloride, and lead bromide, and cesium halide includes at least one of cesium iodide, cesium chloride, and cesium bromide; Step 2: The above-mentioned cesium lead-based metal halide precursor film is surface-treated using a surface modifier, wherein the surface modifier is any one of pyridine compounds, selenophene compounds, or phosphate ester compounds, and the corresponding functional groups in the structure of each compound are pyridine groups, selenophene groups, or phosphate ester groups. Step 3: Attach formamidine halide to the surface-treated cesium lead-based metal halide precursor film, so that the surface-treated cesium lead-based metal halide precursor film reacts with formamidine halide to obtain the desired perovskite light-absorbing layer film; wherein, formamidine halide includes at least one of formamidine iodide, formamidine chloride, and formamidine bromide.

2. The method for preparing the perovskite light-absorbing layer thin film as described in claim 1, characterized in that, In step one, the method for preparing the cesium lead-based metal halide precursor film includes the following steps: weighing a certain amount of lead halide and cesium halide, dissolving them in organic solvent A, and mixing them uniformly to prepare a cesium lead-based metal halide precursor solution for later use, wherein the concentration of lead halide is 0.5 mol / L~1.5 mol / L, and the concentration of cesium halide is 0.05 mol / L~0.5 mol / L; depositing the above cesium lead-based metal halide precursor solution onto the substrate surface of the prepared transport layer by solution deposition, and annealing at 50℃~250℃ for 10s~2h to obtain a cesium lead-based metal halide precursor film with organic solvent A removed; wherein the solution deposition method includes any one of spin coating, blade coating, spray coating, and slot coating, and organic solvent A is any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and γ-butyrolactone.

3. The method for preparing the perovskite light-absorbing layer thin film as described in claim 1, characterized in that, In step one, the method for preparing the cesium lead-based metal halide precursor film includes the following steps: lead halide and cesium halide are placed in different evaporation boats by vapor deposition, and lead halide and cesium halide vapors are uniformly deposited on the substrate surface of the prepared transport layer to obtain the cesium lead-based metal halide precursor film; wherein, the vapor deposition method includes any one of vacuum thermal evaporation, multi-source co-evaporation, chemical vapor deposition, near-space sublimation, and vapor transport deposition.

4. The method for preparing the perovskite light-absorbing layer thin film as described in claim 1, characterized in that, In step two, the surface treatment method includes the following steps: diluting the surface modifier with solvent B to 0.1 mg / ml~2 mg / ml to obtain a surface modifier solution for later use; solvent B is any one of methanol, ethanol, isopropanol, and 2-methoxyethanol; coating the surface modifier solution onto the surface of the solvent-free cesium lead-based metal halide precursor film by coating method; after the surface modifier solution is in contact with the cesium lead-based metal halide film for a certain period of time, removing solvent B by heating or vacuuming, thereby obtaining a cesium lead-based metal halide precursor film treated with surface modifier; wherein, the coating method includes any one of spin coating, blade coating, spray coating, and slot coating.

5. The method for preparing the perovskite light-absorbing layer thin film as described in claim 1, characterized in that, In step two, the surface treatment method includes the following steps: the surface modifier is directly thermally evaporated or transported to the surface of the cesium lead-based metal halide precursor film by a carrier gas, so that the surface modifier comes into contact with the cesium lead-based metal halide film and reacts for a certain period of time, thereby obtaining the cesium lead-based metal halide precursor film treated with the surface modifier.

6. The method for preparing the perovskite light-absorbing layer thin film as described in claim 1, characterized in that, In step three, the method of reacting the surface-treated cesium lead-based metal halide precursor film with formamidine halide includes: dissolving formamidine halide in organic solvent C to obtain a formamidine halide solution with a concentration of 0.01 mol / L to 10 mol / L; coating the formamidine halide solution onto the surface-treated cesium lead-based metal halide precursor film; and annealing at 50°C to 300°C to obtain a formamidine cesium lead-based perovskite film, i.e., the desired perovskite light-absorbing layer film. The organic solvent C is any one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and γ-butyrolactone.

7. The method for preparing the perovskite light-absorbing layer thin film as described in claim 1, characterized in that, In step three, the method of reacting the surface-treated cesium lead-based metal halide precursor film with formamidine halide includes: transporting formamidine halide to the surface of the surface-treated cesium lead-based metal halide precursor film by direct thermal evaporation or carrier gas; after the formamidine halide fully reacts with the surface-treated cesium lead-based metal halide precursor film, heating and annealing are performed to obtain a formamidine cesium lead-based perovskite film, which is the desired perovskite light-absorbing layer film.

8. A perovskite solar cell, comprising a perovskite light-absorbing layer, characterized in that, The perovskite light-absorbing layer is prepared using the method for preparing a perovskite light-absorbing layer thin film as described in any one of claims 1 to 7.

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