A formal perovskite solar cell with rubidium acetate doped electron transport layer and its preparation method

Abstract

The present invention belongs to the field of photovoltaic cell technology, and specifically relates to a formal perovskite solar cell with a rubidium acetate-doped electron transport layer and a preparation method thereof. The solar cell device structure comprises, from bottom to top, an FTO substrate, an electron transport layer, a doped electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode layer. The doped electron transport layer is a thin film layer prepared by spin-coating and annealing rubidium acetate doped into a tin dioxide (SnO2) aqueous solution. The present invention introduces rubidium ions and acetate ions at the buried interface of the perovskite film to promote the crystallization process of the perovskite film, improve the crystallization quality of the perovskite film, and fill iodine vacancy defects at the buried interface, successfully reducing the carrier recombination rate, optimizing the energy level matching between the electron transport layer and the perovskite layer, and ultimately improving the power conversion efficiency of the formal perovskite solar cell, laying a solid foundation for its commercial application and further technological development.

Description

Technical Field

[0001] The present invention belongs to the technical field of photovoltaic cells, and in particular relates to a formal perovskite solar cell with a rubidium acetate-doped electron transport layer and a preparation method thereof. Background Art

[0002] Perovskite has the characteristics of easy solution preparation and excellent photovoltaic performance. As an excellent optoelectronic material, organic-inorganic hybrid perovskite has many advantages such as adjustable band gap, high light absorption coefficient, low exciton dissociation energy and relatively simple and low-cost preparation process. In the past few years, the efficiency of formal perovskite solar cells has been greatly improved. Perovskite solar cells were first introduced in 2009, when their photoelectric conversion efficiency (PCE) was only 3.8%. After more than ten years of rapid development, the PCE of single-junction perovskite solar cells has exceeded 26%, which is very close to the highest efficiency of single-crystal silicon solar cells, but it is still lower than the Shockley-Queise theoretical limit efficiency of 33.4%. Therefore, it is still necessary to further improve the power conversion efficiency of perovskite solar cells.

[0003] In the structure of perovskite solar cells, the perovskite layer is undoubtedly the key element that determines the performance of the cell. In addition to optimizing the perovskite light-absorbing layer itself to optimize its quality, the buried interface of the formal perovskite solar cell, also known as the electron transport layer, also significantly influences the morphology, defect generation, and continuity of the perovskite film, thereby affecting the power conversion efficiency of the device. In particular, heterogeneity of the perovskite composition at the buried interface can lead to defect accumulation and unintended non-radiative recombination losses. Furthermore, while interface modification at the buried interface does not alter the perovskite nucleation mechanism, it can significantly prolong the perovskite growth process near the buried interface, thereby affecting subsequent surface recrystallization. This bottom-up modulation of the crystallization dynamics results in larger grains in the resulting film while reducing crystal defects. Furthermore, energy level mismatch at the buried interface can significantly affect the extraction of electron (formal perovskite solar cells) and hole (inverted perovskite solar cells) charge carriers from the perovskite solar cell. It is reported that the height of the interface energy barrier affects carrier dynamics. When the interface barrier is greater than 0.1eV, it hinders the extraction of majority carriers, leading to charge accumulation and recombination losses. Therefore, how to obtain high-quality, highly crystalline perovskite films and optimize interface energy level matching has become a technical challenge to be solved in the preparation of high-efficiency formal perovskite solar cells. Summary of the Invention

[0004] The purpose of the present invention is to address the above-mentioned problems existing in the buried interface of formal perovskite solar cells and provide a formal perovskite solar cell with a rubidium acetate-doped electron transport layer and a preparation method thereof. By using the method of rubidium acetate-doped electron transport layer, the crystallization quality of the perovskite film is improved, the harmful defects in the perovskite light-absorbing layer are reduced, and the problem of interface energy level mismatch is alleviated, thereby improving the power conversion efficiency of the formal perovskite solar cell.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A formal perovskite solar cell with a rubidium acetate-doped electron transport layer comprises FTO conductive glass, an electron transport layer, a doped electron transport layer, a perovskite light-absorbing layer, a hole transport layer and a metal electrode layer sequentially deposited on the FTO conductive glass; the electron transport layer is a tin dioxide (SnO2) layer prepared by a water bath deposition method; the second electron transport layer is a thin film prepared by doping rubidium acetate small molecules in a tin dioxide (SnO2) aqueous solution and undergoing spin coating annealing.

[0007] Furthermore, the material of the perovskite light absorbing layer is FA x MA 1-x PbI3, where 0 <x<1。

[0008] Furthermore, the hole transport layer comprises Spiro-OMeTAD, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 4-tert-butylpyridine (TBP).

[0009] A method for preparing a formal perovskite solar cell with a rubidium acetate-doped electron transport layer comprises the following steps:

[0010] Step 1: Clean the FTO conductive glass and prepare an electron transport layer on the FTO conductive glass by a water bath deposition method;

[0011] Step 2: Prepare a doped electron transport layer on the electron transport layer by spin coating, which is achieved by:

[0012] 2.1. Add deionized water to the tin dioxide aqueous dispersion, mix and dilute, and shake to uniformly mix the two to obtain tin dioxide aqueous solution A; wherein the ratio of tin dioxide aqueous dispersion to deionized water is 5:1;

[0013] 2.2. Adding rubidium acetate as a dopant to tin dioxide aqueous solution A to obtain tin dioxide aqueous solution B; the concentration of the added rubidium acetate is 0.5-3 mg / mL;

[0014] 2.3. Spin-coat the tin dioxide aqueous solution B on the electron transport layer obtained in step 2 at a spin-coating speed of 3000-5000 rpm for 30-40 seconds, and anneal at a temperature range of 120-150°C for 30-40 minutes to obtain a doped electron transport layer;

[0015] Step 3: preparing a lead iodide precursor solution and a mixed organic salt solution respectively, and sequentially spin-coating the lead iodide precursor solution and the mixed organic salt solution on the doped electron transport layer using a two-step spin coating method, and annealing to obtain a perovskite light absorbing layer;

[0016] Step 4: Spin-coat the hole transport layer on the perovskite light-absorbing layer and deposit the metal electrode to obtain a formal perovskite solar cell with a rubidium acetate-doped electron transport layer.

[0017] Furthermore, the method for preparing the electron transport layer on the FTO conductive glass by water bath deposition in step 1 is as follows:

[0018] 1.1. Prepare solution C by mixing 1.25 mL of HCl solution, 25 μL of thioglycolic acid (TGA), and 100 mL of deionized water.

[0019] 1.2. Add 1250 mg of urea and 275 mg of SnCl2·2H2O to solution C obtained in step 2.1 to prepare solution D;

[0020] 1.3. Immerse the FTO glass prepared in step 1 in solution D obtained in step 2.2 and heat in an oven at 90°C for 4 h;

[0021] 1.4. The FTO glass with water-bath deposited SnO2 obtained in step 2.3 was cleaned with deionized water in an ultrasonic oscillator for 10 minutes, dried, and then placed on a hot plate at 170°C for 60 minutes to prepare an electron transport layer.

[0022] Furthermore, the implementation method of step 3 includes the following steps:

[0023] 3.1. Add a mixed solvent to lead iodide, wherein the mixed solvent consists of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 9:1, and heat and stir at 60-80°C until dissolved to prepare a lead iodide precursor solution;

[0024] 3.2. Weigh 180-184 mg of FAI, 12.8 mg of MAI, and 9-9.5 mg of MACL and dissolve them in 1 mL of isopropanol to prepare a mixed organic salt solution.

[0025] 3.3. The prepared lead iodide precursor solution was spin-coated onto the obtained doped electron transport layer at a rotation speed of 1200-1800 rpm for 30 s, and the lead iodide film was prepared by annealing at 70°C. The prepared mixed organic salt solution was spin-coated onto the obtained lead iodide film at a rotation speed of 1800-2000 rpm for 30 s, and then transferred to an environment with a relative humidity of 30%-40%, and annealed at 150°C to obtain a perovskite light absorbing layer.

[0026] Furthermore, the method for preparing the hole layer in step 4 is:

[0027] 4.1. Weigh 500-520 mg of LiTFSI and add 1 mL of acetonitrile. Stir at room temperature until dissolved to prepare a LiTFSI solution.

[0028] 4.2. Weigh 70-75 mg of Spiro-OMeTAD, add 1 mL of chlorobenzene, 25-30 μL of TBP, and 15-18 μL of the LiTFSI solution obtained in step 4.1, and stir at room temperature until dissolved to prepare a Spiro-OMeTAD solution;

[0029] 4.3. Spin-coat the Spiro-OMeTAD solution obtained in step 4.2 onto the perovskite light-absorbing layer at a rotation speed of 3000-5000 rpm for 30-40 s to obtain a hole transport layer.

[0030] The present invention significantly improves battery performance by adding a doped electron transport layer between the electron transport layer and the perovskite light-absorbing layer and introducing rubidium acetate small molecules into the doped transport layer. During the critical stage of perovskite film growth, rubidium ions play a crucial role at the interface between the perovskite film and the underlying substrate. These rubidium ions serve as nucleation centers, effectively catalyzing the crystallization of the perovskite film. This process not only significantly increases the grain size of the perovskite film but also significantly improves the overall crystallinity of the film. Furthermore, this improvement significantly reduces the harmful excess PbI2 in the film, optimizing perovskite film performance and enhancing the device stability of perovskite solar cells. Second, acetate has a stronger coordination ability than halide ions, enabling it to more efficiently fill iodine vacancy defects at the perovskite buried interface, thereby suppressing carrier recombination and improving the open-circuit voltage and fill factor. This significantly reduces the most common and harmful lattice defects in the film, further improving the film's quality and stability.

[0031] Furthermore, by adding a doped electron transport layer (ETL) incorporating rubidium acetate between the ETL and the perovskite light-absorbing layer, the team successfully optimized the energy level matching between the ETL and the perovskite layer. This optimization significantly reduced the energy barrier for interfacial carriers, facilitating their rapid extraction and transport. Consequently, the efficiency of carrier transfer between the perovskite layer and the ETL was significantly improved, directly impacting the overall performance of the solar cell.

[0032] In summary, the present invention promotes the crystallization process of the perovskite film by introducing rubidium ions and acetate ions at the buried interface of the perovskite film, effectively improves the crystallization quality of the film, reduces the excess PbI2 in the perovskite film, fills the iodine vacancy defects at the buried interface, thereby reducing the recombination of carriers, and optimizes the energy level matching between the electron transport layer and the perovskite layer, thereby improving the power conversion efficiency of the formal perovskite solar cell, laying a solid foundation for its commercial application and further technological development. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 Schematic diagram of the solar cell structure of Example 1;

[0034] Figure 2 This is a schematic diagram of the solar cell structure of Comparative Example 1;

[0035] Figure 3 The morphologies of the perovskite films of Example 1 and Comparative Example 1 under a scanning electron microscope (SEM) are shown; (a) is the perovskite film obtained in Comparative Example 1, and (b) is the perovskite film obtained in Example 1;

[0036] Figure 4 X-ray diffraction (XRD) patterns of the perovskite films obtained in Example 1 and Comparative Example 1;

[0037] Figure 5 Graphs of the photoluminescence (PL) spectra of the perovskite films obtained in Example 1 and Comparative Example 1;

[0038] Figure 6 Graphs showing the JV curves of the formal perovskite solar cells obtained in Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments and drawings. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] Unless otherwise defined, the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0041] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0042] Example 1

[0043] This embodiment provides a method for preparing a formal perovskite solar cell with a rubidium acetate-doped electron transport layer:

[0044] Step 1: Clean the substrate:

[0045] In this embodiment, fluorine-doped indium tin oxide (FTO) glass was used as the substrate. First, ultrasonic cleaning was performed with acetone and anhydrous ethanol for 15 minutes each. The washed substrate was blown dry with a nitrogen gun and stored in a dry environment. Before use, it was treated with a UV-ozone cleaning device for 30 minutes.

[0046] Step 2: Preparation of electron transport layer:

[0047] In this embodiment, a tin dioxide electron transport layer is deposited on FTO conductive glass using a water bath deposition method. The preparation steps are as follows:

[0048] Step 2.1: Prepare solution C by mixing 1.25 mL of HCl solution, 25 μL of thioglycolic acid (TGA), and 100 mL of deionized water.

[0049] Step 2.2: Add 1250 mg of urea and 275 mg of SnCl2·2H2O to solution C obtained in step 2.1 to prepare solution D;

[0050] Step 2.3: Immerse the FTO glass prepared in step 1 in solution D obtained in step 2.2 and heat in an oven at 90°C for 4 h;

[0051] Step 2.4: The FTO glass with water-bath deposited SnO2 obtained in step 2.3 was cleaned in an ultrasonic oscillator with deionized water for 10 minutes, dried, and then placed on a hot plate at 170°C for 60 minutes to prepare an electron transport layer.

[0052] Step 3: Preparation of doped tin dioxide electron transport layer:

[0053] Step 3.1: Add deionized water to the tin dioxide aqueous dispersion, mix and dilute, wherein the tin dioxide aqueous dispersion: deionized water = 5:1, and shake to prepare a diluted tin dioxide aqueous solution A;

[0054] Step 3.2: Adding rubidium acetate as a dopant to the obtained tin dioxide aqueous solution A, wherein the rubidium acetate concentration is 0.5 to 3 mg / mL, to obtain tin dioxide aqueous solution B;

[0055] Step 3.3: Then, spin-coat the tin dioxide aqueous solution B on the electron transport layer obtained in step 2 at a spin-coating speed of 3000-5000 rpm for 30-40 seconds, and anneal at a temperature range of 120-150° C. for 30-40 minutes to obtain a doped electron transport layer;

[0056] Step 4: Preparation of perovskite light absorbing layer:

[0057] Step 4.1: Weigh 691.5 mg of lead iodide and dissolve it in 1 mL of a mixed solvent (N,N-dimethylformamide and dimethyl sulfoxide) at a volume ratio of 9:1 at 70°C and stir for 6 h to prepare a lead iodide precursor solution.

[0058] Step 4.2: Weigh 180-184 mg of FAI, 12.8 mg of MAI, and 9-9.5 mg of MACL and dissolve them in 1 mL of isopropanol. Stir at room temperature until dissolved to prepare a mixed organic salt solution.

[0059] Step 4.3: Spin-coat the prepared lead iodide precursor solution onto the doped electron transport layer at a rotation speed of 1200-1800 rpm for 30 seconds, and anneal at 70°C to obtain a lead iodide thin film; spin-coat the prepared mixed organic salt solution onto the obtained lead iodide thin film at a rotation speed of 1800-2000 rpm for 30 seconds, then transfer the solution to an environment with a relative humidity of 30%-40%, and anneal at 150°C to obtain a perovskite light absorbing layer.

[0060] Step 5: Preparation of hole transport layer:

[0061] Step 5.1: Add 1 mL of acetonitrile to 520 mg of LiTFSI and stir at room temperature until dissolved to prepare a LiTFSI solution.

[0062] Step 5.2: Weigh 72.3 mg of Spiro-OMeTAD, add 1 mL of chlorobenzene, 30 μL of TBP, and 18 μL of the LiTFSI solution obtained in step 5.1, and stir at room temperature until dissolved to prepare a Spiro-OMeTAD solution;

[0063] Step 5.3: Spin-coat the Spiro-OMeTAD solution prepared in step 5.2 onto the perovskite light-absorbing layer at a rotation speed of 3000-5000 rpm for 30-40 s to obtain a hole transport layer.

[0064] Step 6: Preparation of metal electrodes:

[0065] In this embodiment, gold is selected as the metal electrode, and the preparation method is: 120nm of gold is deposited on the surface of the electron transport layer by vacuum thermal evaporation through a mask. Figure 1 The complete formal perovskite solar cell shown.

[0066] Comparative Example 1

[0067] This comparative example provides a method for preparing a formal perovskite solar cell. The process is different from that of Example 1 except that the process of adding the dopant rubidium acetate in step 3.2 is not included, and the tin dioxide aqueous solution obtained in step 3.1 is directly spin-coated on the substrate. The other steps are exactly the same. The structure is as follows: Figure 2 shown.

[0068] The above embodiment 1 and comparative example 1 are analyzed and tested below:

[0069] The perovskite films obtained in Example 1 and Comparative Example 1 were analyzed by SEM, and the results are as follows: Figure 3 As shown, Figure 3 (a) The perovskite film obtained in Example 1, Figure 3 (b) The perovskite film obtained in Example 1. Compared to Comparative Example 1, the addition of rubidium acetate to the spin-coated tin dioxide electron transport layer in Example 1 significantly increases the perovskite grain size. Furthermore, compared to Comparative Example 1, the amount of white byproduct PbI2 on the surface of the film in Example 1 is significantly reduced. This indicates that the acetate and rubidium ions at the buried interface promote crystallization of the perovskite film, regulating the reaction of PbI2 into perovskite, which improves the crystallization quality.

[0070] XRD analysis was performed on the perovskite films obtained in Example 1 and Comparative Example 1, respectively. Figure 4 It can be seen from the XRD spectrum that the characteristic peak at 12.7° representing PbI2 is significantly reduced after the rubidium acetate-doped electron transport layer is added, indicating that the content of PbI2 in the perovskite film is reduced, indicating that the acetate ions and rubidium ions at the buried interface can effectively regulate the content of lead iodide PbI2 in the perovskite film. At the same time, the characteristic peak position at 14.2° representing the perovskite (100) crystal plane is the same as that of Example 1 and Comparative Example 1, and no shift occurs, indicating that the addition of acetate ions and rubidium ions at the buried interface does not affect the composition and structure of the perovskite film grown thereon.

[0071] PL spectrum analysis was performed on the perovskite films obtained in Example 1 and Comparative Example 1, respectively. Figure 5It can be seen that the characteristic peak intensity of the perovskite film obtained in Example 1 at 750-850 nm is much lower than that in Comparative Example 1, indicating that the acetate ions and rubidium ions at the buried interface can reduce the non-radiative recombination in the perovskite film. It also shows that the rubidium acetate-doped electron transport layer has a stronger ability to extract electrons, and the energy level of the rubidium acetate-doped electron transport layer is more matched with the perovskite light absorption layer.

[0072] Photovoltaic tests were performed on the formal perovskite solar cells obtained in Example 1 and Comparative Example 1, and the effective active area was 0.0491 cm 2 The test conditions are standard simulated sunlight AM1.5 and temperature 25℃. The obtained JV curve is shown in the figure below. Figure 6 As shown in Table 1, the photovoltaic parameters show that the open circuit voltage of the formal perovskite solar cell obtained in Example 1 is 1.07 V and the short circuit current is 25.37 mA / cm 2 , the fill factor is 79.78%, and the energy conversion efficiency is 21.66%. Compared with Comparative Example 1, the open circuit voltage and fill factor of Example 1 are greatly improved, and the photoelectric conversion efficiency is thus improved by nearly 12.6% compared with Comparative Example 1, which shows that the rubidium acetate-doped electron transport layer significantly optimizes the photovoltaic performance of the formal solar cell device.

[0073] Table 1 Comparison of perovskite solar cell performance between Example 1 and Comparative Example 1

[0074]

[0075]

[0076] The above embodiments are intended to provide a better understanding of the present invention, and are not intended to limit the optimal implementation scheme described herein, nor to limit the content and scope of protection of the present invention. Any product identical or similar to the present invention that is derived by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

Claims

1. A perovskite solar cell with a rubidium acetate-doped electron transport layer, characterized in that: It includes FTO conductive glass, on which an electron transport layer, a doped electron transport layer, a perovskite light absorption layer, a hole transport layer and a metal electrode layer are sequentially deposited; the material of the perovskite light absorption layer is FA x MA 1-x PbI3, where 0 < x < 1; the composition of the hole transport layer includes Spiro-OMeTAD, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and 4-tert-butylpyridine (TBP); the electron transport layer is a tin dioxide (SnO2) layer prepared by a water bath deposition method; the electron transport layer is a thin film prepared by doping rubidium acetate small molecules in an aqueous solution of tin dioxide (SnO2) and then spin-coating and annealing.

2. The perovskite solar cell according to claim 1, wherein The method for preparing a formal perovskite solar cell comprises the following steps: Step 1: providing FTO conductive glass, and preparing an electron transport layer on the FTO conductive glass by a water bath deposition method; Step 2: Prepare a doped electron transport layer on the electron transport layer by spin coating, which is achieved by: 2.

1. Add deionized water to the tin dioxide aqueous dispersion, mix and dilute, and shake to evenly mix the two to obtain tin dioxide aqueous solution A; wherein the ratio of tin dioxide aqueous dispersion to deionized water is 5:1; 2.

2. Add rubidium acetate as a dopant to tin dioxide aqueous solution A to obtain tin dioxide aqueous solution B; the concentration of the added rubidium acetate is 0.5-3 mg / mL; 2.

3. Spin-coat the tin dioxide aqueous solution B on the electron transport layer obtained in step 2 at a spin-coating speed of 3000-5000 rpm for 30-40 s, and anneal at a temperature range of 120-150 °C for 30-40 min to obtain a doped electron transport layer; Step 3: preparing a lead iodide precursor solution and a mixed organic salt solution respectively, and sequentially spin-coating the lead iodide precursor solution and the mixed organic salt solution on the doped electron transport layer using a two-step spin coating method, and annealing to obtain a perovskite light absorbing layer; Step 4: Spin-coat the hole transport layer on the perovskite light-absorbing layer and deposit the metal electrode to obtain a formal perovskite solar cell with a rubidium acetate-doped electron transport layer.

3. The perovskite solar cell according to claim 2, characterized in that The method for preparing the electron transport layer on the FTO conductive glass by water bath deposition in step 1 is as follows: 1.

1. Prepare solution C by mixing 1.25 mL of HCl solution, 25 μL of thioglycolic acid (TGA), and 100 mL of deionized water. 1.

2. Add 1250 mg of urea and 275 mg of SnCl2·2H2O to solution C obtained in step 2.1 to prepare solution D. 1.

3. Immerse the FTO glass prepared in step 1 in solution D obtained in step 2.2 and heat in an oven at 90 °C for 4 h; 1.

4. The FTO glass with water-bath deposited SnO2 obtained in step 2.3 was cleaned with deionized water in an ultrasonic oscillator for 10 minutes, dried, and then placed on a hot plate at 170°C for 60 minutes to prepare an electron transport layer.

4. The perovskite solar cell according to claim 3, characterized in that The implementation method of step 3 includes the following steps: 3.

1. Add a mixed solvent to lead iodide, wherein the mixed solvent consists of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 9:1, and heat and stir at 60-80°C until dissolved to prepare a lead iodide precursor solution; 3.

2. Weigh 180-184 mg of FAI, 12.8 mg of MAI, and 9-9.5 mg of MACL and dissolve them in 1 mL of isopropanol to prepare a mixed organic salt solution. 3.

3. The prepared lead iodide precursor solution was spin-coated onto the obtained doped electron transport layer at a rotation speed of 1200-1800 rpm for 30 s, and the lead iodide thin film was prepared by annealing at 70°C. The prepared mixed organic salt solution was spin-coated onto the obtained lead iodide thin film at a rotation speed of 1800-2000 rpm for 30 s, and then transferred to an environment with a relative humidity of 30%-40% and annealed at 150°C to prepare the perovskite light absorbing layer.

5. The perovskite solar cell according to claim 4, characterized in that The method for preparing the hole layer in step 4 is as follows: 4.

1. Weigh 500-520 mg of LiTFSI and add 1 mL of acetonitrile. Stir at room temperature until dissolved to prepare a LiTFSI solution. 4.

2. Weigh 70-75 mg of Spiro-OMeTAD, add 1 mL of chlorobenzene, 25-30 μL of TBP, and 15-18 μL of the LiTFSI solution obtained in step 4.1, and stir at room temperature until dissolved to prepare a Spiro-OMeTAD solution; 4.

3. Spin-coat the Spiro-OMeTAD solution prepared in step 4.2 onto the perovskite light-absorbing layer at a rotation speed of 3000-5000 rpm for 30-40 s to obtain a hole transport layer.

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