A bromine iodine lead cesium perovskite solar cell doped with magnesium bromide prepared in a low humidity environment and a preparation method thereof

Abstract

The application discloses a kind of bromine iodine lead cesium perovskite solar cells of doping magnesium bromide prepared in low humidity environment and preparation method thereof, belong to perovskite photovoltaic technical field, including ITO transparent conductive glass and sequentially coated on ITO transparent conductive glass dense layer TiO2, SnO2 layer, bromine iodine lead cesium perovskite light-absorbing layer of doping magnesium bromide, 2,2',7,7'-tetra [N,N-di (4-methoxyphenyl) amino] -9,9'-spirobifluorene hole transport layer of doping lithium salt, silver electrode, and its preparation method is disclosed, the application is by doping into bromine iodine lead cesium perovskite precursor doping different molar magnesium bromide to optimize the energy level matching between perovskite and electron transport layer and hole transport layer, effectively reduce the recombination probability of carrier and improve the mobility of carrier, improve the crystal quality of perovskite thin film, to realize the light absorption coefficient of optimization light-absorbing layer, finally realize the improvement of bromine iodine lead cesium inorganic perovskite solar cell photoelectric conversion efficiency.

Description

Technical Field

[0001] This invention relates to a magnesium bromide-doped bromine-iodine-lead-cesium perovskite solar cell prepared in a low-humidity environment and its preparation method, belonging to the field of perovskite photovoltaic technology. Background Technology

[0002] Perovskite materials, with their outstanding photoelectric properties such as excellent light absorption coefficient, high carrier mobility, and tunable band structure, have shown great application potential in fields such as solar cells and light-emitting diodes, and have become one of the current research hotspots in the field of optoelectronic materials. Inorganic bromine-iodine-lead-cesium perovskite, as an important member of the halide perovskite family, has attracted widespread attention from researchers due to its suitable band width and good fundamental photoelectric conversion performance, and is considered one of the ideal candidate materials for constructing efficient and stable optoelectronic devices.

[0003] Despite the numerous advantages mentioned above, inorganic bromine-iodine-lead-cesium perovskite suffers from inherent defects that severely hinder its industrialization process during actual preparation and application. Specifically, this material faces two main core problems: firstly, phase instability, due to the presence of Br in the crystal lattice... - and I - The ionic radii and chemical activities of the materials differ, making them highly susceptible to halogen phase separation under external environmental stimuli. This leads to the destruction of the material's crystal structure and consequently, the degradation of its photoelectric performance. Secondly, there is the problem of moisture-induced degradation. The crystal structure of bromoiodine lead cesium perovskite is particularly sensitive to water molecules. Water molecules can easily penetrate into the crystal and interact with lattice ions, destroying the integrity of the lattice and causing the material to decompose, thus significantly shortening the lifespan of devices made from the material.

[0004] Currently, various strategies have been developed to improve the stability of perovskite materials, such as interface passivation, encapsulation protection, and element doping. Element doping can directly affect the crystal structure, defect state distribution, and electronic band structure of the material, and is considered an effective means to improve the overall performance of perovskite materials.

[0005] Therefore, by rationally using elements to optimize doping and adjusting the concentration of doping elements, the performance parameters of perovskite can be controlled, ultimately improving the photoelectric performance of bromine-iodine-lead-cesium perovskite solar cells. However, processing methods and other technologies still need further improvement to make the prepared solar cells have better performance, stronger stability, and wider commercial applications. Summary of the Invention

[0006] In view of this, the present invention provides a magnesium bromide-doped bromine-iodine-lead-cesium perovskite solar cell prepared in a low-humidity environment and its preparation method, wherein the magnesium bromide doping is used to prepare the Mg-doped bromine-iodine-lead-cesium perovskite solar cell. 2+ With Br - The synergistic effect of these factors fills the gaps in the bromoiodide lead cesium perovskite crystal lattice and partially removes Pb.2+ Mg 2+ Substitution thus modulates the energy level structure and suppresses nonradiative recombination while avoiding interference from high valence states. Br - This technology effectively compensates for iodine vacancies, enhances the stability of the lead halide octahedral structure, and significantly alleviates halogen migration. The composite electron transport layer, composed of C-TiO2 and SnO2, is more closely integrated with the perovskite energy levels than a single-layer electron transport layer, facilitating electron transport and effectively improving the electron transport rate of the cell, thus optimizing the photoelectric conversion efficiency of the bromine-iodine lead-cesium perovskite solar cell. Due to this incorporation into the composite electron transport layer, the bromine-iodine lead-cesium perovskite solar cell exhibits longer lifespan and superior performance under varying environmental temperatures and humidity, creating conditions for its industrial application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for fabricating magnesium bromide-doped bromoiodide lead cesium bromide perovskite solar cells in a low-humidity environment includes the following steps: S1. Apply high-temperature resistant tape to both ends of the etched ITO transparent conductive glass, with one section of tape covering the etched lines. Then, subject the glass to ultrasonic treatment and plasma treatment to obtain pretreated ITO transparent conductive glass. S2. Spin-coating a titanium dioxide precursor solution onto a pretreated ITO transparent conductive glass, followed by high-temperature annealing to obtain a dense titanium dioxide layer. S3. A tin dioxide dispersion spin-coated onto a dense titanium dioxide layer is annealed to obtain an electron transport layer composed of a titanium dioxide layer and a tin dioxide layer. S4. A magnesium bromide-doped lead cesium bromide-doped magnesium bromide thin film was spin-coated onto the electron transport layer using a one-step spin-coating method. After annealing, a lead cesium bromide-doped perovskite light-absorbing layer was obtained. S5. A lithium-doped 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene hole transport layer is spin-coated onto the surface of the bromoiodine lead cesium perovskite light-absorbing layer. S6. A silver electrode is deposited on the hole transport layer using a thermal evaporation method to finally obtain a magnesium bromide-doped bromine-iodine-lead-cesium perovskite solar cell.

[0008] Based on the above technical solution, the present invention further limits the solution as follows: Furthermore, the ultrasonic treatment in S1 involves sequential ultrasonic cleaning with deionized water and detergent, ultrasonic cleaning with acetone, and ultrasonic cleaning with isopropanol solution. Furthermore, the washing time for deionized water with detergent, acetone, and isopropanol solutions was 15 minutes each.

[0009] Furthermore, the titanium dioxide precursor solution in S2 was prepared by 60 μL of diethanolamine, 186 μL of isopropyl titanate and 1.25 mL of anhydrous ethanol, and the concentration of the titanium dioxide precursor solution was 0.420 M. The spin coating speed was 7000 r / min. The annealing temperature was increased from room temperature to 150℃ at a rate of 10℃ per minute, held at 150℃ for 10 minutes, then increased to 350℃ at a rate of 10℃ per minute, held for 10 minutes, then increased to 400℃ at the same rate, held for 10 minutes, then increased to 500℃ at the same rate, held for 10 minutes, and finally increased to 550℃ at the same rate, held for 90 minutes, and then slowly cooled to room temperature. The total annealing time was 3 hours and 10 minutes.

[0010] Furthermore, the tin dioxide dispersion in S3 is obtained by mixing 12wt% tin dioxide dispersion with ultrapure water at a volume ratio of 1:3, followed by ultrasonic treatment for 10 minutes and then treatment with a homogenizer for 10 minutes. The spin coating speed was 3000 r / min, the annealing temperature was 150℃, and the annealing time was 30 min.

[0011] Furthermore, the S4 bromo-iodide-lead-cesium perovskite was prepared using 259.8 mg of cesium iodide powder, 230.5 mg of lead iodide powder, and 183.5 mg of lead bromide powder as raw materials. These were dissolved in a 1 mL mixture of N,N-dimethylacetamide and dimethyl sulfoxide at a volume ratio of 4:1. Magnesium bromide was then added and stirred at 3000 rpm for 1 h at 10% RH to prepare a 1 mol / L bromo-iodide-lead-cesium perovskite solution with a magnesium bromide doping concentration ≤1.5 mol%. The rotation speed for the one-step spin coating method is 500 r / min-2000 r / min. The former takes 10 seconds and the annealing temperature is 300℃, while the latter takes 30 seconds and the annealing temperature is 5 min. The thickness of the bromine-iodine-lead-cesium perovskite light-absorbing layer is 320-440 nm; Furthermore, cesium iodide powder, lead iodide powder, and lead bromide powder were all dissolved in a solvent at a humidity of 10% RH, and isopropanol solution was added dropwise in the last 10 seconds of spin coating to act as an anti-solvent.

[0012] Furthermore, the hole transport layer in S5 uses 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene as the main raw material, dissolved in chlorobenzene, and doped with lithium bis(trifluoromethanesulfonyl)imide. 7.7 μL-10 μL of 4-tert-butylpyridine is used to improve the solubility of the solute, ensuring that the lithium salt is fully dissolved in chlorobenzene without particulate precipitation. The solution is pale green, clear, and transparent. The concentration of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene is 0.066 M-0.08 M, and the concentration of lithium bis(trifluoromethanesulfonyl)imide is 1.2 M-1.8 M. The thickness of the hole transport layer is 100nm-120nm.

[0013] Furthermore, in S6, the thermal evaporation method is carried out in an evaporation apparatus within a glove box, with an evaporation pressure of 2 × 10⁻⁶. -5 mbar-9×10 -6 The process was carried out at a speed of 2.5 nm / min to 3 nm / min, under conditions of mbar. The thickness of the vapor-deposited silver electrode is 100nm-110nm.

[0014] Another technical solution of the present invention is a magnesium bromide-doped lead cesium bromide perovskite solar cell prepared by the above method.

[0015] The beneficial effects of this invention are as follows: 1. This invention utilizes the Mg in magnesium bromide. 2+ With Br - The synergistic effect of the incorporation of magnesium bromide in different proportions fills the gaps in the lattice of bromoiodide-lead-cesium perovskite crystals and partially removes Pb. 2+ Mg 2+ By replacing high-valence state interference, adjusting the energy level structure and suppressing nonradiative recombination, bromo-iodine-lead-cesium perovskite solar cells can achieve longer lifespan and better performance under ambient temperature and humidity conditions.

[0016] 2. The composite electron transport layer C-TiO2 and SnO2 used in this invention are more closely aligned with the perovskite energy levels than a single-layer electron transport layer, which is more conducive to electron transport. This effectively improves the electron transport rate of the battery and the photoelectric conversion efficiency of the bromine-iodine-lead-cesium inorganic perovskite solar cell, creating conditions for its industrial application.

[0017] 3. The preparation and modification of this invention are all completed in a low-humidity air environment, which is easy to learn and simple, and does not need to be carried out in a glove box. Attached Figure Description

[0018] Figure 1The graphs show the relevant performance test results of bromoiodide lead cesium perovskite thin films doped with different concentrations of magnesium bromide according to the present invention. Figure 2 This is a metallographic microscope top view of the bromine-iodine-lead-cesium perovskite thin films of the present invention with different doping concentrations. Figure 3 This is a schematic diagram of the structure of a perovskite solar cell according to an embodiment of the present invention, and a schematic diagram of the changes in the bromine-iodine-lead-cesium lattice after magnesium bromide doping. Figure 4 These are the photoelectric performance test diagrams and stability demonstration diagrams of the bromine-iodine-lead-cesium perovskite solar cells doped with different concentrations of magnesium bromide according to the present invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] In the following examples, the ITO transparent conductive glass substrate used was purchased from Liaoning Youxuan New Energy Technology Co., Ltd., lead bromide and lead iodide were purchased from Shanghai Titan Technology Co., Ltd., and cesium iodide was purchased from Macklin. All of them had a purity greater than 99.9%.

[0021] The perovskite precursor solution was prepared as follows: The reagents were weighed according to a CsI:PbI2:PbBr2 ratio of 2:1:1 (259.8 mg:230.5 mg:183.5 mg), and magnesium bromide crystal particles were added in a mass ratio of 0 mol%, 0.5 mol%, 1 mol%, and 1.5 mol%. This solution was then dissolved in 1 mL of a mixed solution of N,N-dimethylacetamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of 4:1. The solution was stirred at 3000 rpm for 1 hour at 10% RH humidity to prepare a bromine-iodine-lead-cesium precursor solution with a concentration of 1 mol / L.

[0022] The fabrication steps for perovskite solar cells are as follows: (1) The etched ITO transparent conductive glass was ultrasonically cleaned for 15 min each with deionized water and detergent, acetone and isopropanol solutions, and then baked for 20 min until all solvents and moisture were removed. Next, the treated ITO transparent conductive glass was treated with plasma for 15 min, and then a dense titanium dioxide layer was spin-coated onto the treated ITO transparent conductive glass. The preparation process of the dense titanium dioxide layer was as follows: 0.186 ml of isopropyl titanate was slowly added dropwise to 1.25 ml of anhydrous ethanol, followed by 0.06 ml of diethanolamine. The mixture was stirred for 1 h. After stirring, it was filtered using a 0.22 μm filter head. The titanium dioxide precursor... The concentration of the bulk solution was 0.420 M. 90 μl of the dense titanium dioxide precursor solution was dropped onto ITO transparent conductive glass and a dense titanium dioxide film was prepared at 7000 rpm for 30 s. The film was placed in a muffle furnace and heated from room temperature to 150 °C at a rate of 10 °C per minute. The temperature was held at 150 °C for 10 min, then increased to 350 °C at a rate of 10 °C per minute and held for 10 min. The temperature was then increased to 400 °C at the same rate and held for 10 min. The temperature was then increased to 500 °C at the same rate and held for 10 min. Finally, the temperature was increased to 550 °C at the same rate and held for 90 min. The film was then slowly cooled to room temperature. The total annealing time was 3 h 10 min.

[0023] (2) The prepared dense titanium dioxide film was cleaned in a plasma cleaner for 15 min, and then a tin dioxide dispersion was added dropwise and spin-coated to form a tin dioxide layer. The preparation process of the tin dioxide layer was as follows: 12 wt% tin dioxide dispersion was mixed with ultrapure water at a volume ratio of 1:3, and then ultrasonicated for 10 min, followed by homogenization for 10 min. 90 μl of the solution was pipetted onto the dense titanium dioxide film, and the tin dioxide layer was prepared at 3000 rpm for 30 s. The annealing temperature was 150 °C and the annealing time was 30 min, thus preparing a dense titanium dioxide and tin dioxide composite electron transport layer.

[0024] (3) The ITO substrate with the prepared dense titanium dioxide and tin dioxide composite electron transport layer was placed in a plasma cleaner for plasma treatment for 15 min, and then removed to a humidity environment of 10% RH. Subsequently, the perovskite precursor solution was spin-coated onto the substrate to form a film. The spin-coating speed was 500 r / min to 2000 r / min, with the former for 10 s and the latter for 30 s. In the last 10 s, 90 μl of isopropanol was added as an anti-solvent to accelerate the evaporation of the perovskite solvent. The substrate was immediately transferred to a heating stage for annealing at 300℃ for 5 min.

[0025] (4) A chlorobenzene solution of 4-tert-butylpyridine, a chlorobenzene solution of 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), and a lithium bis(trifluoromethanesulfonyl)imide-acetonitrile solution were mixed, and 7.7 μL-10 μL of 4-tert-butylpyridine was used to improve the solubility of the solute, so that the lithium salt was fully dissolved in the chlorobenzene without particulate precipitation. The solution was light green, clear, and transparent, yielding a hole transport layer precursor solution. The concentration of 7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene was 0.066M-0.08M, and the concentration of lithium bis(trifluoromethanesulfonyl)imide was 1.2M-1.8M. The hole transport layer solution was spin-coated onto the prepared magnesium bromide-doped lead cesium bromide perovskite light-absorbing layer at 3000 rpm for 30 s. The layer was then oxidized in a 99.99% oxygen environment and a 10% RH humidity environment for 6 h to obtain the final hole transport layer. The thickness of the hole transport layer was 100 nm-120 nm.

[0026] (5) A silver electrode was deposited on the hole transport layer by thermal evaporation. The thickness of the deposited silver electrode was 100nm-110nm, and finally magnesium bromide-doped bromine-iodine-lead-cesium perovskite solar cell was obtained.

[0027] The performance of the magnesium bromide-doped lead bromine cesium bromide perovskite solar cells prepared above was tested. The test items and results are shown in Table 1 below. Figure 1-4 As shown.

[0028] Table 1. Mg doping concentrations at different levels 2+ Performance statistics of solar cells Control 0.5 mol% 1mol% 1.5 mol% PCE 14.3% 15.42% 14.09% 13.22% Jsc <![CDATA[14.92mA / cm 2 ]]> <![CDATA[15.22mA / cm 2 ]]> <![CDATA[15.14mA / cm 2 ]]> <![CDATA[14.01mA / cm 2 ]]> FF 77.43% 79.96% 74.55% 71.43% Table 1 lists the different concentrations of Mg doped with different amounts of Mg. 2+ The performance of solar cells fabricated from bromine-iodine-lead-cesium perovskite precursors was statistically analyzed, showing that 0.5 mol% Mg doping... 2+ The PCE of perovskite solar cells is the best by comparison, which may be due to the appropriate Mg 2+ With the doping of Pb, the damage caused by Pb is compensated. 2+ The vacancy and replacement of some Pb 2+ This results in a denser perovskite film with fewer defects, improving carrier transport efficiency and consequently increasing the open-circuit voltage Voc (1.26V) and fill factor FF (79.96%). Excess Mg... 2+ Doping with Mg causes impurity phase precipitation, leading to disruption of the grain structure and an increase in defect density instead of a decrease. This ultimately affects carrier transport, resulting in a decrease in short-circuit current and open-circuit voltage. The table shows that doping with 1.5 mol% Mg... 2+The PCE of the perovskite solar cell dropped to 13.22%, and the fill factor FF was only 71.43%.

[0029] Figure 1 (a) is Mg doped at concentrations of 0.0 mol%, 0.5 mol%, 1.0 mol%, and 1.5 mol%. 2+ Photoluminescence testing of thin films shows that as Mg... 2+ With increasing doping concentration, the PL spectrum of the perovskite layer becomes stronger, reaching a peak at a doping concentration of 0.5 mol%. Subsequently, further increases in doping concentration lead to an increase in the perovskite's Mg content. 2+ The incorporation of impurity phases leads to the collapse of the perovskite lattice and the precipitation of impurity phases, ultimately resulting in a decrease in the intensity of the PL spectrum. Figure 1 (b) is the original CsPbBrI2 perovskite layer and doped with 0.5 mol% Mg. 2+ The photoluminescence (PL) spectrum and absorption spectrum of CsPbBrI2 perovskite were obtained. The PL spectrum did not shift significantly, but the absorption peak red-shifted from 638 nm to 643 nm after doping. This indicates that the doping amount did not significantly change the PL peak value of the absorbing layer, but only slightly changed the band gap of the perovskite. Figure 1 (c) represents Mg concentrations of 0.0 mol%, 0.5 mol%, 1.0 mol%, and 1.5 mol%. 2+ The absorption spectrum of the doped CsPbBrI2 perovskite layer is accompanied by its corresponding band gap. The figure shows that as the doping concentration increases, the absorption peak first red-shifts and then blue-shifts. The band gap of the perovskite layer was successfully reduced from 1.88 eV to 1.869 eV by calculation of the absorption band gap.

[0030] Figure 2 This is a top view under a metallographic microscope of the perovskite film prepared using step (3), where (a) is the original CsPbBrI2 perovskite film, showing a large number of irregularly distributed stripe-like structures on the film surface. (b) is the film doped with 0.5 mol% Mg. 2+ The CsPbBrI2 thin film shows striations on the surface due to the low concentration of Mg. 2+ The doping is filled; By observing Figures (c) and (d), it can be seen that when the doping concentration exceeds 0.5 mol%, the film quality actually decreases. First, shallow grooves and stripes appear on the film with a doping concentration of 1 mol%. Then, when the concentration increases to 1.5 mol%, the film surface becomes uneven, showing an unevenly distributed pore phenomenon.

[0031] Figure 3(a) Shows a perovskite solar cell with C-TiO2 and SnO2 as a composite electron transport layer, CsPbBrI2 as a light-absorbing layer, Spiro-OMeTAD as a hole transport layer, and Ag electrode at the end. The purpose of the experiment is to dope the light-absorbing layer with Mg. 2+ The MgBr2 ion introduces divalent magnesium ions (Mg²⁺) into the CsPbBrI2 lattice in the form of MgBr2. The ionic radius of Mg²⁺ (0.72 Å) is significantly smaller than that of Pb²⁺ (1.19 Å), and its +2 valence state matches that of Pb²⁺. It is expected to fill interstitial spaces or partially replace Pb²⁺ more effectively without introducing high valence state perturbations. At the same time, the Br⁻ ions introduced along with it can directly compensate for iodine vacancies. Figure 3 (b) is a 3d diagram illustrating the doping of MgBr2 into the CsPbBrI2 lattice, showing that some Mg can be incorporated. 2+ Doping atoms can replace atoms in the original crystal lattice, filling gaps, while Br - This regulates the halogen ratio within the crystal lattice.

[0032] Figure 4 The figures show the photoelectric performance and stability of CsPbBrI2 perovskite solar cells doped with different concentrations of magnesium bromide. The original CsPbBrI2 perovskite solar cell, measured under reverse scanning, exhibits a photoelectric conversion efficiency (PCE) of 14.3% and a short-circuit current (Jsc) of 14.92 mA / cm². 2 The open-circuit voltage (Voc) is 1.24V, and the fill factor (FF) is 77.43%. It is doped with 0.5 mol% Mg. 2+ The device's PCE measured under reverse scanning was 15.42%, and Jsc was 15.12 mA / cm². 2 The Voc is 1.26V and the fill factor (FF) is 79.96%. Figure (a) shows the device performance at various doping concentrations, due to excessive Mg. 2+ Doping leads to perovskite lattice distortion and the precipitation of some insulating impurity phases, which hinders carrier transport and ultimately affects the photoelectric performance of the device. The performance of the device actually decreases with increasing doping concentration. (b) Under continuous simulated sunlight (AM1.5G) irradiation, the photoelectric conversion efficiency of CsPbBrI2 perovskite solar cells doped with different concentrations of magnesium bromide remained at the initial 58% after 1000 hours, while the efficiency of cells doped with 1 mol% Mg... 2+ The CsPbBrI2 perovskite solar cell maintained an initial efficiency of 69% after 1000 hours, but its PCE decreased at the fastest rate among all solar cells during subsequent testing periods, while the 0.5 mol% Mg... 2+Although the PCE of the CsPbBrI2 perovskite solar cell prepared by doping remained at 61% of its original value after 1000h, the efficiency decline rate from 1000h to 3000h was basically the same as that of the control cell, or even slower. (c) is a schematic diagram of the morphological evolution of CsPbBrI2 perovskite films doped with different concentrations of MgBr2 observed directly through optical images. Under normal environmental conditions (humidity less than 20%), the initially prepared CsPbBrI2 perovskite film was reddish-brown with black inclusions. This may be due to the diffuse reflection of the large grains of CsPbBrI2. Under the same conditions, films with different doping concentrations degraded after 40 days, showing a yellow phase. This may be due to water molecules entering the interstitial spaces of the crystal lattice, destroying the grain structure of the perovskite and reacting with Pb. 2+ A certain degree of bonding occurs, transforming the δ phase. Furthermore, halogen atoms in the film are detached from the lattice due to the influence of water molecules, leading to the decomposition of CsPbBrI2. However, after 80 days, a significant amount of Mg can be observed in the figure. 2+ Insertion alleviates the degradation process of the film, but excessive doping will obviously have the opposite effect. After 120 days of aging, the perovskite film is basically degraded.

Claims

1. A method for preparing magnesium bromide-doped bromine-iodide-lead-cesium perovskite solar cells in a low-humidity environment, characterized in that, Includes the following steps: S1. Apply high-temperature resistant tape to both ends of the etched ITO transparent conductive glass, with one section of tape covering the etched lines. Then, subject the glass to ultrasonic treatment and plasma treatment to obtain pretreated ITO transparent conductive glass. S2. Spin-coating a titanium dioxide precursor solution onto a pretreated ITO transparent conductive glass, followed by high-temperature annealing to obtain a dense titanium dioxide layer. S3. A tin dioxide dispersion spin-coated onto a dense titanium dioxide layer is annealed to obtain an electron transport layer composed of a titanium dioxide layer and a tin dioxide layer. S4. A magnesium bromide-doped lead cesium bromide-doped magnesium bromide thin film was spin-coated onto the electron transport layer using a one-step spin-coating method. After annealing, a lead cesium bromide-doped perovskite light-absorbing layer was obtained. S5. A lithium-doped 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene hole transport layer is spin-coated onto the surface of the bromoiodine lead cesium perovskite light-absorbing layer. S6. A silver electrode is deposited on the hole transport layer using a thermal evaporation method to finally obtain a magnesium bromide-doped bromine-iodine-lead-cesium perovskite solar cell.

2. The method for preparing a solar cell according to claim 1, characterized in that, The ultrasonic treatment operation described in S1 is to sequentially use deionized water and detergent for ultrasonic cleaning, acetone for ultrasonic cleaning, and isopropanol solution for ultrasonic cleaning.

3. The method for preparing a solar cell according to claim 2, characterized in that, The cleaning time for deionized water with detergent, acetone and isopropanol solution was 15 minutes each.

4. The method for preparing a solar cell according to claim 1, characterized in that, The titanium dioxide precursor solution described in S2 is prepared by 60 μL of diethanolamine, 186 μL of isopropyl titanate and 1.25 mL of anhydrous ethanol, and the concentration of the titanium dioxide precursor solution is 0.420 M. The spin coating speed was 7000 r / min. The annealing temperature was increased from room temperature to 150℃ at a rate of 10℃ per minute, held at 150℃ for 10 minutes, then increased to 350℃ at a rate of 10℃ per minute, held for 10 minutes, then increased to 400℃ at the same rate, held for 10 minutes, then increased to 500℃ at the same rate, held for 10 minutes, and finally increased to 550℃ at the same rate, held for 90 minutes, and then slowly cooled to room temperature. The total annealing time was 3 hours and 10 minutes.

5. The method for preparing a solar cell according to claim 1, characterized in that, The tin dioxide dispersion described in S3 is obtained by mixing 12wt% tin dioxide dispersion with ultrapure water at a volume ratio of 1:3, followed by ultrasonic treatment for 10 minutes and then treatment with a homogenizer for 10 minutes. The spin coating speed was 3000 r / min, the annealing temperature was 150℃, and the annealing time was 30 min.

6. The method for preparing a solar cell according to claim 1, characterized in that, The bromine-iodide-lead-cesium perovskite described in S4 is prepared using 259.8 mg of cesium iodide powder, 230.5 mg of lead iodide powder, and 183.5 mg of lead bromide powder as raw materials. These materials are dissolved in a 1 mL mixture of N,N-dimethylacetamide and dimethyl sulfoxide at a volume ratio of 4:

1. Magnesium bromide is then added and stirred at 3000 rpm for 1 h at 10% RH to prepare a 1 mol / L bromine-iodide-lead-cesium perovskite solution with a magnesium bromide doping concentration ≤1.5 mol%. The rotation speed for the one-step spin coating method is 500 r / min-2000 r / min. The former lasts for 10 seconds and the annealing temperature is 300℃, while the latter lasts for 30 seconds and the annealing temperature is 5 min. The thickness of the bromine-iodine-lead-cesium perovskite light-absorbing layer is 320-440 nm.

7. The method for preparing a solar cell according to claim 6, characterized in that, The cesium iodide powder, lead iodide powder, and lead bromide powder were all dissolved in a solvent at a humidity of 10%RH, and an isopropanol solution was added dropwise in the last 10 seconds of spin coating to act as an anti-solvent.

8. The method for preparing a solar cell according to claim 1, characterized in that, The hole transport layer described in S5 uses 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene as the main raw material, dissolved in chlorobenzene, and doped with lithium bis(trifluoromethanesulfonyl)imide. 7.7 μL-10 μL of 4-tert-butylpyridine is used to improve the solubility of the solute, ensuring that the lithium salt is fully dissolved in chlorobenzene without particulate precipitation. The solution is pale green, clear, and transparent. The concentration of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene is 0.066 M-0.08 M, and the concentration of lithium bis(trifluoromethanesulfonyl)imide is 1.2 M-1.8 M. The thickness of the hole transport layer is 100nm-120nm.

9. The method for preparing a solar cell according to claim 1, characterized in that, The thermal evaporation method described in S6 is carried out in an evaporation apparatus within a glove box, with an evaporation pressure of 2 × 10⁻⁶. -5 mbar-9×10 -6 The process was carried out at a speed of 2.5 nm / min to 3 nm / min, under conditions of mbar. The thickness of the vapor-deposited silver electrode is 100nm-110nm.

10. A magnesium bromide-doped lead bromine perovskite solar cell prepared by the method according to any one of claims 1 to 9.

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