Perovskite thin film with surface defects passivated and method for passivating surface defects of perovskite thin film

Abstract

This invention discloses a perovskite thin film with surface defect passivation and a method for passivating surface defects in a perovskite thin film. The method includes the following steps: Step 1, taking 0.430~0.530 g PbI2, 0.170~0.190 g FAI, 0.075~0.085 g PbBr2, 0.015~0.025 g MABr and 0.015~0.020 g CsI, and dispersing them while stirring in a mixed solvent of 800 mL N,N-dimethylformamide and 200 mL dimethyl sulfoxide to prepare a perovskite precursor solution; Step 2, adding LiF to an organic solvent to prepare a solution with a concentration of 0.05~35 mmol L. ‑1 Additive solution A; Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, and turn on the spin coater to coat it into a perovskite thin film; Step 4: In the last 10 seconds before the spin coater stops rotating, rapidly drop additive solution A onto the surface of the perovskite thin film, anneal it under an argon atmosphere, and after drying, obtain a perovskite thin film with passivated surface defects, which improves the solar energy utilization rate of the perovskite thin film, thereby improving the photoelectric conversion efficiency and stability of the perovskite solar cell.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically a perovskite thin film with surface defect passivation and a method for passivating surface defects of perovskite thin films. Background Technology

[0002] With the increasing depletion of traditional fossil fuels and the ever-growing demand for energy, finding a new renewable energy source has become a new challenge for human society. Solar energy, as an important renewable energy source, is receiving increasing attention from researchers. Currently, the most widespread way to utilize solar energy is to fabricate solar cell devices using the photovoltaic effect of semiconductor materials, thereby converting solar energy into electrical energy. Therefore, developing high-efficiency, low-cost new solar cells has become a necessary technological foundation for realizing the application of solar photovoltaic power generation.

[0003] Perovskite materials possess excellent photoelectric properties, such as long carrier diffusion distance, high photoluminescence quantum yield, and tunable bandgap, making them suitable for application in the photovoltaic field. Since Professor Miyasaka first achieved a photoelectric conversion efficiency of 3.8% in 2009, perovskite solar cells have seen their efficiency reach 25.7% in just over a decade. Due to their advantages such as low cost, simple fabrication process, and solution-processability, perovskite solar cells have developed rapidly in recent years and become a hot research topic.

[0004] However, perovskite solar cells are still difficult to commercialize, mainly because of defects in the light-absorbing thin film. During solution-based film preparation, numerous defects such as undercoordinated Pb ions, I vacancies, and Pb-I antisite defects are generated on the surface and at grain boundaries, inducing electron localization. Under photoexcitation, these defects easily form deep traps and recombination centers, thus reducing the photoelectric performance of the film. To reduce the defect density, anions and cations are typically introduced to repair positively and negatively charged defects at grain boundaries and on the surface of the perovskite film.

[0005] Current research results indicate that Li + It can prevent the formation of negatively charged defects in perovskites, and at the same time, F - LiF possesses strong electronegativity, enabling it to effectively repair positively charged defects. Therefore, it holds promise for modifying perovskite films by introducing LiF, utilizing Li... + With F - The synergistic effect passivates positive and negative charge defects on the surface of perovskite thin films, suppresses the formation of deep traps and recombination centers, thereby improving the carrier transport characteristics of the thin film and thus improving the photoelectric conversion efficiency and stability of the device. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this invention is to provide a perovskite thin film with passivated surface defects and a method for passivating surface defects in perovskite thin films, thereby improving the solar energy utilization rate of perovskite thin films and thus enhancing the photoelectric conversion efficiency and stability of perovskite solar cells.

[0007] To achieve the above objectives, the present invention employs the following technical solution:

[0008] A method for passivating surface defects in perovskite thin films includes the following steps:

[0009] Step 1: Take 0.430~0.530 g PbI2, 0.170~0.190 g FAI, 0.075~0.085 g PbBr2, 0.015~0.025 g MABr and 0.015~0.020 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide and 200 mL dimethyl sulfoxide while stirring to prepare a perovskite precursor solution;

[0010] Step 2: Add LiF to the organic solvent to prepare a solution with a concentration of 0.05~35 mmol / L. -1 Additive solution A;

[0011] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, and then turn on the spin coater to coat it into a perovskite thin film.

[0012] Step 4: 10 seconds before the spin coater stops rotating, add additive solution A is quickly dropped onto the surface of the perovskite film, annealed under an argon atmosphere, and dried to obtain a perovskite film with passivated surface defects.

[0013] Furthermore, the stirring time in step 1 shall be no less than 6 hours.

[0014] Furthermore, the organic solvent in step 2 is one of isopropanol, ethanol, diethyl ether, anisole, acetonitrile, toluene, chlorobenzene, or trichlorotoluene.

[0015] Furthermore, after the spin coater in step 3 is turned on, it is initially set at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm. -1 It accelerates to a speed of 5500 rpm and rotates at high speed for 25 seconds.

[0016] Furthermore, the annealing process in step 4 is performed at 80~180℃ for 1~120 min.

[0017] A perovskite thin film with surface defect passivation exhibits a reduced steady-state photoluminescence peak intensity near 766 nm, along with a blue shift in the peak position.

[0018] Compared with the prior art, the present invention has the following technical effects:

[0019] This invention first uniformly drop-coats a perovskite precursor solution onto an FTO conductive glass substrate, and then uses a spin coater to prepare a perovskite light-absorbing layer film. The key aspect is that, 10 seconds before the high-speed spin coater finishes, an organic solvent containing dissolved LiF is rapidly drop-dropped onto the surface of the perovskite light-absorbing layer film. Since the perovskite film is in an intermediate state from the start of spin coater to drying, spin coater dynamically adds LiF molecules to the surface of the perovskite film. + With F - The synergistic effect of these technologies passivates positively and negatively charged defects on the surface of the perovskite thin film, suppresses the formation of deep traps and recombination centers, thereby improving the carrier transport characteristics of the thin film. This results in a decrease in the steady-state photoluminescence peak intensity near 766 nm and a blue shift in the peak position of the perovskite light absorption layer thin film after annealing and drying, leading to a reduction in surface defect density and a significant improvement in quality. Furthermore, its light absorption characteristics in the wavelength range of 450–530 nm are significantly enhanced, exhibiting excellent solar energy utilization. When applied to perovskite solar cells, it can improve the photoelectric conversion efficiency and stability of perovskite solar cells. Attached Figure Description

[0020] Figure 1 The XRD patterns of the perovskite thin films prepared in Examples 1, 6 and Comparative Example 1 of this invention are shown below.

[0021] Figure 2 SEM images of the perovskite films prepared in Examples 1, 6 and Comparative Example 1 of this invention;

[0022] Figure 3 These are cross-sectional SEM images of the perovskite films prepared in Examples 1, 6 and Comparative Example 1 of this invention.

[0023] Figure 4 The UV-vis absorption spectra of the perovskite thin films prepared in Examples 1, 6 and Comparative Example 1 of this invention;

[0024] Figure 5 The photoluminescence spectra of the perovskite thin films prepared in Examples 1, 6 and Comparative Example 1 of this invention are shown below.

[0025] Figure 6 Box plots of photoelectric conversion efficiency (PCE) for the perovskite solar cell devices prepared in Examples 1, 6, and Comparative Example 1 of this invention;

[0026] Figure 7 Box plots of the short-circuit current density Jsc of the perovskite solar cell devices prepared in Examples 1, 6 and Comparative Example 1 of this invention;

[0027] Figure 8 Box plots of the open-circuit voltage Voc of the perovskite solar cell devices prepared in Examples 1, 6 and Comparative Example 1 of this invention;

[0028] Figure 9 Box plots showing the fill factor FF of the perovskite solar cell devices prepared in Examples 1, 6 and Comparative Example 1 of this invention. Detailed Implementation

[0029] The specific content of the present invention will be further explained in detail below with reference to the embodiments.

[0030] Example 1

[0031] Step 1: Take 0.507 g PbI2, 0.172 g formamidinium (FAI), 0.081 g PbBr2, 0.023 g methylamine bromide (MABr) and 0.020 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 6 h to prepare a perovskite precursor solution.

[0032] Step 2: Add LiF to chlorobenzene to prepare a solution with a concentration of 2 mmol / L. -1 Additive solution A;

[0033] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0034] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 100°C for 60 min under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0035] Example 2

[0036] Step 1: Take 0.430 g PbI2, 0.170 g formamidin FAI, 0.075 g PbBr2, 0.015 g methylamine bromide MABr and 0.015 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide DMF and 200 mL dimethyl sulfoxide DMSO while stirring. Continue stirring for 7 h to prepare a perovskite precursor solution.

[0037] Step 2: Add LiF to chlorobenzene to prepare a solution with a concentration of 4 mmol / L. -1 Additive solution A;

[0038] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0039] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 80°C for 120 min under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0040] Example 3

[0041] Step 1: Take 0.480 g PbI2, 0.180 g formamidin FAI, 0.080 g PbBr2, 0.020 g methylamine bromide MABr and 0.017 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide DMF and 200 mL dimethyl sulfoxide DMSO while stirring. Continue stirring for 8 h to prepare a perovskite precursor solution.

[0042] Step 2: Add LiF to toluene to prepare a solution with a concentration of 6 mmol / L. -1 Additive solution A;

[0043] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0044] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 80°C for 100 min under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0045] Example 4

[0046] Step 1: Take 0.450 g PbI2, 0.175 g formamidinium (FAI), 0.078 g PbBr2, 0.018 g methylamine bromide (MABr) and 0.018 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 8 h to prepare a perovskite precursor solution.

[0047] Step 2: Add LiF to chlorobenzene to prepare a solution with a concentration of 8 mmol / L. -1 Additive solution A;

[0048] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0049] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 140°C for 80 min under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0050] Example 5

[0051] Step 1: Take 0.500 g PbI2, 0.174 g formamidinium (FAI), 0.082 g PbBr2, 0.022 g methylamine bromide (MABr) and 0.016 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 9 h to prepare a perovskite precursor solution.

[0052] Step 2: Add LiF to chlorobenzene to prepare a solution with a concentration of 10 mmol / L. -1 Additive solution A;

[0053] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0054] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 160°C for 70 min under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0055] Example 6

[0056] Step 1: Take 0.507 g PbI2, 0.172 g formamidinium iodide (FAI), 0.081 g PbBr2, 0.023 g methylamine bromide (MABr) and 0.020 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 6 h to prepare a perovskite precursor solution.

[0057] Step 2: Add LiF to chlorobenzene to prepare a solution with a concentration of 0.05 mmol / L. -1 Additive solution A;

[0058] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0059] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 100°C for 60 min under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0060] Example 7

[0061] Step 1: Take 0.530 g PbI2, 0.190 g formamidin FAI, 0.085 g PbBr2, 0.025 g methylamine bromide MABr and 0.020 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide DMF and 200 mL dimethyl sulfoxide DMSO while stirring. Continue stirring for 9 h to prepare a perovskite precursor solution.

[0062] Step 2: Add LiF to isopropanol to prepare a solution with a concentration of 17.5 mmol / L. -1 Additive solution A;

[0063] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0064] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 180°C for 1 minute under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0065] Example 8

[0066] Step 1: Take 0.520 g PbI2, 0.185 g formamidinium (FAI), 0.084 g PbBr2, 0.017 g methylamine bromide (MABr) and 0.019 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 12 h to prepare a perovskite precursor solution.

[0067] Step 2: Add LiF to ethanol to prepare a solution with a concentration of 20 mmol / L. -1 Additive solution A;

[0068] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0069] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 130°C for 110 min under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0070] Example 9

[0071] Step 1: Take 0.510 g PbI2, 0.188 g formamidinium (FAI), 0.083 g PbBr2, 0.019 g methylamine bromide (MABr) and 0.015 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 11 h to prepare a perovskite precursor solution.

[0072] Step 2: Add LiF to diethyl ether to prepare a solution with a concentration of 30 mmol / L. -1 Additive solution A;

[0073] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0074] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 170°C for 95 minutes under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0075] Example 10

[0076] Step 1: Take 0.490 g PbI2, 0.178 g formamidinium (FAI), 0.076 g PbBr2, 0.021 g methylamine bromide (MABr) and 0.017 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 10 h to prepare a perovskite precursor solution.

[0077] Step 2: Add LiF to anethole to prepare a solution with a concentration of 32 mmol / L. -1 Additive solution A;

[0078] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0079] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 150°C for 30 minutes under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0080] Example 11

[0081] Step 1: Take 0.440 g PbI2, 0.182 g formamidinium (FAI), 0.077 g PbBr2, 0.024 g methylamine bromide (MABr) and 0.018 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 8 h to prepare a perovskite precursor solution.

[0082] Step 2: Add LiF to trichlorotoluene to prepare a solution with a concentration of 35 mmol / L. -1 Additive solution A;

[0083] Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1 The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0084] Step 4: 10 seconds before the spin coater stops rotating at high speed, add additive solution A to the surface of the perovskite film. Anneal at 130°C for 15 minutes under an argon atmosphere. After drying, a perovskite film with passivated surface defects is obtained.

[0085] Comparative Example 1

[0086] Step 1: Take 0.507 g PbI2, 0.172 g formamidinium (FAI), 0.081 g PbBr2, 0.023 g methylamine bromide (MABr) and 0.020 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide (DMF) and 200 mL dimethyl sulfoxide (DMSO) while stirring. Continue stirring for 6 h to prepare a perovskite precursor solution.

[0087] Step 2: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, start the spin coater, initially at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm for 1 second. -1The acceleration was increased to a speed of 5500 rpm and rotated at high speed for 25 seconds to spin-coat a perovskite thin film.

[0088] Step 3: 10 seconds before the spin coater stops rotating at high speed, chlorobenzene is dropped onto the surface of the perovskite film. The film is then annealed at 100°C for 60 minutes under an argon atmosphere and dried to obtain a perovskite film with passivated surface defects.

[0089] Figure 1 The XRD patterns of the perovskite films prepared in Examples 1, 6, and Comparative Example 1 of this invention are shown. The XRD results indicate that obvious diffraction peaks can be observed at 2θ values ​​of 14.64°, 20.36°, 26.95°, 32.24°, 38.17°, 40.89°, and 51.91° for the perovskite films dissolved in the three different solvents. This indicates that perovskite with good crystallinity was prepared. The peak positions of the three components of perovskite are basically the same, indicating that the crystal orientation of the perovskite film does not change due to the change of the additive solvent. At 2θ of 14.64°, the peak value of Example 1 is the strongest, which is more obvious than the characteristic peaks of Example 6 and Comparative Example 1. This indicates that chlorobenzene solvent can better dissolve LiF, thus resulting in the best crystallinity of perovskite. The diffraction peak of the sample in Example 6 is lower, indicating that acetonitrile is not effective in dissolving LiF as a solution, which may affect the crystallization of the perovskite substrate.

[0090] Figure 2 (a) is a SEM image of the perovskite thin film prepared in Comparative Example 1 of this invention. Figure 2 (b) is a SEM image of the perovskite thin film surface prepared in Example 1 of this invention. Figure 2 (c) is a SEM image of the perovskite film surface prepared in Example 6 of this invention. The comparison shows that: 1) the perovskite film without LiF has dense spherical particles distributed on its surface, and the film has many pores; 2) the perovskite film with added LiF dissolved in chlorobenzene has a smooth surface, uniform particle distribution, and relatively few pores; 3) compared to the perovskite film without LiF in Comparative Example 1, the perovskite film with added LiF dissolved in acetonitrile in Example 6 has a relatively smooth surface; however, compared to the perovskite film with added LiF dissolved in chlorobenzene in Example 1, the perovskite film with added LiF dissolved in acetonitrile in Example 6 has a rough surface, relatively many pores, and a large number of cracks. Therefore, from the three images, it can be seen that the perovskite film of Example 1 exhibits the best morphology and has the fewest pores. The reduction in pores proves that LiF can improve the surface defects of the film, which is beneficial to improving the performance of perovskite solar cells.

[0091] Figure 3 (a) is a cross-sectional SEM image of the perovskite film in Comparative Example 1. Figure 3(b) is a cross-sectional SEM image of the perovskite thin film of Example 1. Figure 3 (c) is a cross-sectional SEM image of the perovskite film of Example 6. Comparing the three images, it can be seen that the perovskite film of Example 1 with added LiF dissolved in chlorobenzene grows well, with uniform longitudinal particle size distribution, no obvious pores, and smooth and flat grain growth on the surface. This is consistent with... Figure 2 (a) The surface SEM characterization results are consistent.

[0092] Figure 4 The figures show the UV-vis absorption spectra of the perovskite films of Comparative Example 1, Example 1, and Example 6 of this invention at wavelengths of 450–900 nm. It is clear from the figures that the light absorption performance of the films after adding LiF was significantly improved compared to the original films. Moreover, after adding LiF dissolved in chlorobenzene, the absorption spectrum of the perovskite film was significantly enhanced in the 450–530 nm light absorption band, indicating that its light absorption performance was optimal. Furthermore, the perovskite film of Example 6 after adding LiF dissolved in acetonitrile showed significantly higher light absorption in the 800–900 nm light absorption band than the films of Comparative Example 1 and Example 1. This may be because the surface of this film is rough and has many pores and cracks, leading to increased light absorption intensity in the near-infrared region, which is detrimental to the performance of perovskite solar cells.

[0093] Figure 5 The figures show the photoluminescence spectra of the perovskite films of Examples 1, 1, and 6 of this invention. As can be seen from the figures, the PL peak of the perovskite film without LiF in Comparative Example 1 is much higher than that of Examples 1 and 6. The perovskite film in Example 1 with added LiF dissolved in chlorobenzene shows the lowest steady-state photoluminescence peak PL peak, and the intensity of the steady-state photoluminescence peak near 766 nm is reduced, and the peak position is blue-shifted. This indicates that the number of charge carriers participating in photoluminescence in the film is reduced after passivation with LiF dissolved in chlorobenzene, thereby ensuring that more charge carriers participate in the charge transport process and improving the charge carrier transport process. This means that holes can be extracted from the perovskite film layer and transferred to the hole transport layer more quickly, thereby effectively suppressing the electron-hole recombination phenomenon at the perovskite / hole transport layer interface, which has a certain promoting effect on improving the efficiency of perovskite solar cells.

[0094] Perovskite solar cells were assembled using surface-defect-passivated perovskite films prepared in Examples 1, 6, and Comparative Example 1: First, a TiO2 electron transport layer was spin-coated onto a cleaned FTO / G1ass substrate, and annealed in a muffle furnace at 450°C for 30 min. Then, the substrate was transferred to a glove box, and a surface-defect-passivated perovskite film prepared in Examples 1, 6, or Comparative Example 1 was spin-coated as a light absorption layer under an argon atmosphere. Next, 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD) was spin-coated as a hole transport layer under an argon atmosphere. Finally, the substrate was removed from the glove box, oxidized for 12-20 h, and then carbon electrodes were coated using a blade coating method to assemble a perovskite solar cell.

[0095] Figures 6-9 Box plots show the performance of perovskite solar cells assembled using surface-defect-passivated perovskite thin films prepared in Examples 1, 6, and Comparative Example 1 of this invention. Figure 6 , Figure 7 , Figure 8 , Figure 9 The following are statistical graphs of the photoelectric conversion efficiency (PCE), short-circuit current density (Jsc), open-circuit voltage (Voc), and fill factor (FF) of perovskite solar cells. Through parameter comparison, it was found that: 1) When LiF was added to the surface of the light-absorbing layer film, the PCE, Jsc, Voc, and FF of the device were all significantly improved; 2) The perovskite solar cell assembled with a LiF perovskite film dissolved in chlorobenzene in Example 1 exhibited the best photoelectric performance parameters, with an open-circuit voltage of 0.60 V and a short-circuit current density of 12.51 mA cm⁻¹. 2 The fill factor was 0.30, and the photoelectric conversion efficiency was 2.31%. This demonstrates that the quality of the perovskite film in the light-absorbing layer significantly impacts the performance of perovskite solar cells. A uniform, flat light-absorbing layer with few pores can achieve good contact with the hole transport layer, thereby reducing the number of interface defects, lowering the electron-hole recombination rate, and improving the photoelectric conversion efficiency. Furthermore, the introduction of LiF effectively passivates surface defects in the perovskite film, improving the performance of perovskite solar cell devices.

Claims

1. A method for passivating surface defects in perovskite thin films, characterized in that, Includes the following steps: Step 1: Take 0.430~0.530 g PbI2, 0.170~0.190 g FAI, 0.075~0.085 g PbBr2, 0.015~0.025 g MABr and 0.015~0.020 g CsI, and disperse them in a mixed solvent of 800 mL N,N-dimethylformamide and 200 mL dimethyl sulfoxide while stirring to prepare a perovskite precursor solution; Step 2: Add LiF to the organic solvent to prepare a solution with a concentration of 0.05~35 mmol / L. -1 Additive solution A; Step 3: Uniformly drop-coat the perovskite precursor solution onto the FTO conductive glass substrate, and then turn on the spin coater to coat it into a perovskite thin film. Step 4: 10 seconds before the spin coater stops rotating, add additive solution A is rapidly dropped onto the surface of the perovskite film. After annealing in an argon atmosphere and drying, a perovskite film with passivated surface defects is obtained. Holes can be extracted from the perovskite film layer and transferred to the hole transport layer more quickly, thereby effectively suppressing the electron-hole recombination phenomenon at the perovskite / hole transport layer interface.

2. The method for passivating surface defects of perovskite thin films according to claim 1, characterized in that, The stirring time in step 1 shall not be less than 6 hours.

3. The method for passivating surface defects of perovskite thin films according to claim 1, characterized in that, The organic solvent in step 2 is one of isopropanol, ethanol, diethyl ether, anisole, acetonitrile, toluene, chlorobenzene, or trichlorotoluene.

4. The method for passivating surface defects of perovskite thin films according to claim 1, characterized in that, After the spin coater in step 3 is turned on, it should initially operate at 1000 rpm. -1 The acceleration is increased to 1000 rpm and then rotated at a low speed for 10 seconds, followed by a speed of 2000 rpm. -1 The acceleration increases the speed to 5500 rpm and it rotates at high speed for 25 seconds.

5. The method for passivating surface defects of perovskite thin films according to claim 1, characterized in that, The annealing process in step 4 is performed at 80~180℃ for 1~120 min.

6. A perovskite thin film with surface defect passivation prepared by the method according to any one of claims 1-5, characterized in that, The steady-state photoluminescence peak intensity decreases near 766 nm, and the peak position is blue-shifted.

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