Perovskite cell preparation method, laminated cell and photovoltaic module

Abstract

The invention relates to the technical field of photovoltaic power generation, in particular to a perovskite cell preparation method, a laminated cell and a photovoltaic module. The preparation method of the perovskite cell comprises the following steps: providing a glass substrate; preparing an electron transport layer or a hole transport layer on the glass substrate to form a substrate; dissolving lead iodide and iodine methylamine in a mixed solvent to form a precursor solution; a substrate is coated with the precursor solution, and a wet film is formed on the side, away from the glass substrate, of the electron transport layer or the hole transport layer; the substrate coated with the precursor solution is placed in the atmosphere of organic solvent saturated steam, an organic solvent is dissolved in a mixed solvent, but lead iodide and methylamine iodide cannot be dissolved, and pretreatment is conducted; and carrying out annealing treatment on the pretreated substrate for at least two times. Pretreatment can slow down the volatilization speed of a solvent in a precursor solution, ordered self-assembly and uniform nucleation of solute molecules are promoted, and at least two times of annealing treatment reduce the possibility that pinholes and grain boundaries appear in a perovskite layer formed after annealing.

Description

Technical Field

[0001] This application relates to the field of photovoltaic power generation technology, and in particular to perovskite cell preparation methods, tandem cells and photovoltaic modules. Background Technology

[0002] Perovskite solar cells have become a research hotspot in next-generation photovoltaic technology due to their advantages such as high photoelectric conversion efficiency, low raw material cost, and simple solution processing technology. The light-absorbing layer in a perovskite solar cell is usually a thin film formed from metal halide perovskite materials. Currently, in the preparation of perovskite thin films, a precursor solution is first coated onto the substrate surface by spin coating. During spin coating, an antisolvent is added dropwise to the precursor solution. The antisolvent and the precursor solvent undergo liquid-phase impact, forcibly triggering a thermodynamic phase transition. This rapidly extracts solute molecules from the precursor solution, inducing a large number of nuclei to form instantaneously within the precursor solution. This process easily leads to problems such as uneven film formation, high defect density, and poor stability. Summary of the Invention

[0003] This application provides a method for preparing perovskite solar cells, tandem solar cells, and photovoltaic modules to address the problem of poor quality of perovskite thin films after deposition.

[0004] In a first aspect, this application relates to a method for preparing a perovskite solar cell, the method comprising: Provide glass substrates; An electron transport layer or a hole transport layer is fabricated on the glass substrate to form a substrate; Lead iodide and methyl iodide are dissolved in a mixed solvent to form a precursor solution; The precursor solution is coated onto the substrate to form a wet film on the side of the electron transport layer or the hole transport layer away from the glass substrate; The substrate coated with the precursor solution is placed in an atmosphere of saturated vapor of an organic solvent, which is miscible with the mixed solvent but will not dissolve the lead iodide and methyl iodide in the precursor solution for pretreatment. The pretreated substrate is subjected to at least two annealing processes.

[0005] Secondly, this application relates to a stacked battery, the stacked battery comprising a bottom battery and a top battery, the top battery being stacked on the bottom battery; the top battery being prepared by any of the perovskite battery preparation methods described above.

[0006] Thirdly, this application relates to a photovoltaic module, which includes a plurality of solar cells interconnected with each other; the solar cells are the aforementioned stacked solar cells.

[0007] The beneficial effects of this application are as follows: After the precursor solution is coated onto the substrate, it is pretreated in an atmosphere of saturated organic solvent vapor. The saturated organic solvent vapor is miscible with the solvent in the precursor solution but does not dissolve the solute in the precursor solution. It can also slow down the evaporation rate of the solvent in the precursor solution, promote the orderly self-assembly and uniform nucleation of solute molecules in the precursor solution, and lay a good foundation for subsequent grain growth. Combined with at least two annealing treatments, the possibility of pinholes and grain boundaries appearing in the perovskite layer formed after annealing is reduced, which is beneficial to improving the performance and stability of perovskite solar cells.

[0008] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit this application. Attached Figure Description

[0009] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0010] Figure 1 A flowchart of the perovskite solar cell fabrication method provided in the embodiments of this application; Figure 2 A schematic diagram of the structure of a perovskite battery prepared by the perovskite battery preparation method provided in this application; Figure 3 A schematic diagram of another embodiment of a perovskite battery prepared by the perovskite battery preparation method provided in this application; Figure 4 This is a schematic diagram of the structure of the stacked battery provided in the embodiments of this application; Figure 5 This is a schematic diagram of the structure of a photovoltaic module provided in an embodiment of this application.

[0011] Figure label: 100-perovskite solar cell; 1-Substrate; 11-Glass substrate; 2-Perovskite layer; 3-Electron transport layer; 4-Hole transport layer; 5-Metal electrode; 6-Intermediate composite layer; 200-Topcon battery; 201-Silicon substrate; 202 - Tunneling oxide layer; 203-doped polycrystalline silicon layer; 204-passivation layer; 205 - Electrode layer; 206 - Emitter; 207-alumina layer; 208-silicon nitride layer; 209 - Conductive layer; 300- Photovoltaic modules; 301-cell battery; 302 - First adhesive film; 303 - Second film; 304 photovoltaic glass; 305 - Backplate. Detailed Implementation

[0012] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0013] like Figure 1 As shown, an embodiment of this application provides a method for preparing a perovskite solar cell 100, comprising: S1. Provide a glass substrate 11; S2. An electron transport layer 3 or a hole transport layer 4 is prepared on a glass substrate 11 to form a substrate 1; S3. Dissolve lead iodide and methyl iodide in a mixed solvent to form a precursor solution; S4. The precursor solution is coated onto the substrate 1 to form a wet film on the side of the electron transport layer 3 or hole transport layer 4 away from the glass substrate 11. S5. The substrate 1 coated with the precursor solution is placed in an atmosphere of saturated vapor of organic solvent, wherein the organic solvent is miscible with the mixed solvent, for pretreatment. S6. Perform at least two annealing processes on the pretreated substrate 1.

[0014] Substrate 1 includes a glass substrate 11, which provides mechanical support for the perovskite solar cell 100 and improves its rigidity. In one possible embodiment, the glass substrate 11 is a fluorine-doped tin fluoride (FTO) conductive glass, making it a transparent conductive substrate. A dense electron transport layer 3 is fabricated on the FTO to form substrate 1. The electron transport layer 3 includes a titanium dioxide layer (c-TiO2) and a mesoporous titanium dioxide layer (mp-TiO2). The c-TiO2 layer can block hole backflow and prevent carrier recombination. The mp-TiO2 layer is located on the side of the c-TiO2 away from the FTO, providing a larger specific surface area to support perovskite crystallization and promote electron extraction and transport. A perovskite layer 2 is deposited on the side of the electron transport layer 3 away from the glass substrate 11, and a hole transport layer 4 and a metal electrode 5 are fabricated on the perovskite layer 2. In another embodiment, the glass substrate 11 is indium tin oxide (ITO) conductive glass, and nickel oxide (NiO) is prepared on the glass substrate 11. x A hole transport layer 4 is formed, a perovskite layer 2 is deposited on the hole transport layer 4, and an electron transport layer 3 and a metal electrode 5 are prepared on the perovskite layer 2.

[0015] The perovskite layer 2 has a structure primarily of ABX3. Lead iodide and methyl iodide are the two core precursors in perovskite layer 2. Lead iodide provides lead ions that occupy the B sites in the perovskite ABX3 structure, while iodide ions form the X-site halogen octahedra in the perovskite ABX3 structure, creating a three-dimensional network framework. Methyl iodide provides cations at the A sites in the perovskite ABX3 structure to balance the charge, making the crystal structure of perovskite layer 2 more stable. Lead iodide and methyl iodide are dissolved in a mixed solvent to facilitate the coating of the precursor solution onto substrate 1.

[0016] When depositing the perovskite layer 2, the precursor solution is first coated onto the substrate 1 to form a wet film. Then, it is placed in an organic solvent saturated vapor atmosphere. The organic solvent saturated vapor atmosphere is miscible with the mixed solvent, but will not dissolve the lead iodide and methyl iodine in the precursor solution. This slows down the evaporation rate of the solvent in the precursor solution, promotes the orderly self-assembly and uniform nucleation of solute molecules in the precursor solution, and lays a good foundation for subsequent grain growth. Combined with at least two annealing treatments, the pinholes and grain boundaries in the perovskite layer 2 are reduced, which is beneficial to improving the performance and stability of the perovskite solar cell 100.

[0017] In one possible embodiment, when the precursor solution is coated onto the substrate 1, the substrate 1 is first placed in a spin coater and rotated at a speed of 4000 rpm to spin coat the precursor solution onto the surface of the substrate 1 for 30 seconds. Centrifugal force is used to spin-spray the precursor solution and form a wet film on the surface of the electron transport layer 3 or the hole transport layer 4.

[0018] In one possible embodiment, the molar ratio of lead iodide to methyl iodide in the precursor solution is 1.05-1.2:1.

[0019] In the precursor solution, lead iodide exceeds methyl iodide, allowing a slight excess of lead iodide to fill iodine vacancies in the perovskite structure. This reduces the defect density of the perovskite crystal, increases the open-circuit voltage and fill factor of the perovskite solar cell 100, and thus improves its photoelectric conversion efficiency. However, if lead iodide is excessive, resulting in a molar ratio of lead iodide to methyl iodide exceeding 1.3:1, the excess lead iodide will form insulating lead iodide deposits, hindering charge transport in the perovskite solar cell 100, leading to a decrease in the fill factor and reducing its photoelectric conversion efficiency. Conversely, if methyl iodide is excessive, resulting in a molar ratio of lead iodide to methyl iodide below 1:1, it will trigger perovskite decomposition. The resulting residues are unstable, affecting the performance and stability of the perovskite solar cell 100. Therefore, the molar ratio of lead iodide to methyl iodide can be 1.05:1, 1.1:1, 1.2:1, etc., so that the defect density of the perovskite layer 2 formed by annealing the precursor solution is smaller, thereby improving the photoelectric conversion efficiency of the perovskite solar cell 100.

[0020] In one possible embodiment, the mixed solvent includes N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0021] Lead iodide has limited solubility in a single solvent. The mixed solution includes N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), which allows methyl iodide to form a stable adduct in dimethyl sulfoxide, thus improving the solubility of methyl iodide in the mixed solvent.

[0022] In one possible embodiment, the volume percentage of dimethyl sulfoxide in the mixed solvent is 10% to 30%.

[0023] N,N-Dimethylformamide has a low boiling point and evaporates quickly, which increases the film formation rate of the precursor solution coated on substrate 1. In the mixed solvent, dimethyl sulfoxide can coordinate with lead ions to form PbI2·DMSO or MAI–PbI2–DMSO mesophases, transforming the random precipitation process into an ordered template growth process, guiding the precursor solution to form a dense, well-covered, large-grained perovskite layer 2. If the volume percentage of dimethyl sulfoxide in the mixed solvent is less than 10%, lead iodide cannot form an effective mesophase in the mixed solvent, and the perovskite layer 2 formed after annealing has a porous and rough structure, resulting in a decrease in the performance of the perovskite solar cell 100. If the volume percentage of dimethyl sulfoxide in the mixed solvent is greater than 30%, the mesophase formed by lead iodide in the mixed solvent is too stable and difficult to transform into a dense perovskite layer 2, resulting in problems such as cracking, residual mesophase, and incomplete crystallization in the formed perovskite layer 2. Therefore, the volume percentage of dimethyl sulfoxide in the mixed solvent can be 10%, 20%, 30%, etc., so that dimethyl sulfoxide can coordinate with lead ions to form an intermediate phase, thereby guiding the precursor solution to form a dense, well-covered, large-particle perovskite layer 2.

[0024] In one possible embodiment, the precursor solution is prepared as follows: 607 mg of lead iodide and 210 mg of methyl iodide are dissolved in 1 mL of a mixed solvent, the mixed solvent is heated to 70°C, and stirred until the lead iodide and methyl iodide are completely dissolved. The volume ratio of N,N-dimethylformamide to dimethyl sulfoxide in the mixed solvent is 4:1.

[0025] In one possible embodiment, the organic solvent includes at least one of diethyl ether, chlorobenzene, and toluene.

[0026] The organic solvent is miscible with the mixed solvent in the precursor solution, but it does not dissolve lead iodide and methyl iodide in the precursor solution. This triggers uniform and explosive nucleation in the precursor solution, forming a dense, large-grained perovskite film. When the evaporation rate of the liquid organic solvent and the condensation rate of the gaseous organic solvent are the same, the organic solvent vapor is in a saturated state. When the substrate 1 coated with the precursor solution is placed in a vapor atmosphere where the organic solvent is saturated, the saturated organic solvent vapor can diffuse uniformly and rapidly into the wet film formed by the precursor solution on the surface of the substrate 1, achieving global control. It can also slow down the evaporation of the mixed solvent in the precursor solution, providing sufficient self-assembly time for the perovskite precursor molecules to form a uniform, high-quality crystalline precursor.

[0027] The organic solvent can be one or a mixture of diethyl ether, chlorobenzene, and toluene. Diethyl ether has a boiling point of 34.6℃, which can form a high-concentration saturated vapor atmosphere at room temperature and has a relatively mild effect on the precursor solution. After the precursor solution crystallizes, diethyl ether is easily volatilized and thus easily removed from the crystallized perovskite film. Chlorobenzene and toluene have higher boiling points, and the saturated vapor pressure of chlorobenzene or toluene is moderate, allowing for more precise and sustained control of the crystallization of the precursor solution, enabling the precursor solution to form a high-quality intermediate phase. Based on the effects of diethyl ether, chlorobenzene, and toluene in the pretreatment process, the types and proportions of diethyl ether, chlorobenzene, and toluene in the organic solvent can be adjusted according to the crystallization quality of perovskite layer 2 to improve the crystallization quality of perovskite layer 2 in perovskite solar cell 100.

[0028] In one possible embodiment, the precursor solution is coated onto substrate 1 and then placed in an atmosphere of organic solvent saturated vapor for 1 to 5 seconds.

[0029] The saturated vapor of the organic solvent provides a mild and uniform gaseous environment for the precursor solution coated on the surface of substrate 1, delaying the evaporation of the mixed solvent in the precursor solution and providing sufficient self-assembly time for the perovskite precursor molecules in the precursor solution. This guides the formation of a uniform and high-quality crystalline precursor on the surface of substrate 1. Within 1 to 5 seconds after the precursor solution is coated on substrate 1, the mixed solvent content in the precursor solution film layer on the surface of substrate 1 is relatively high, resulting in good fluidity. This allows the saturated vapor of the organic solvent to diffuse uniformly and rapidly throughout the entire precursor solution film layer, diluting the mixed solvent and enabling the perovskite precursor molecules in the precursor solution to form a uniform and high-quality crystalline precursor on the surface of substrate 1. After the precursor solution is coated onto substrate 1, the mixed solvent in the precursor solution gradually evaporates over time. If the substrate is placed in an atmosphere of saturated organic solvent vapor more than 5 seconds after the precursor solution is coated onto substrate 1, the mixed solvent on the surface of the precursor solution on substrate 1 will begin to evaporate, making the precursor solution on the surface of substrate 1 viscous. The saturated organic solvent vapor will diffuse unevenly in the precursor solution, reducing the crystallization induction effect of the saturated organic solvent vapor on the precursor solution, resulting in a deterioration in the quality of the perovskite layer 2 in the perovskite solar cell 100. Optionally, 1 seconds, 3 seconds, or 5 seconds after the precursor solution is coated onto the substrate, the substrate 1 coated with the precursor solution can be placed in an atmosphere of saturated organic solvent vapor to enable the formation of a uniform, high-quality crystalline precursor on the surface of substrate 1.

[0030] In one possible embodiment, the substrate 1 coated with the precursor solution is pretreated in an atmosphere of organic solvent saturated vapor for 10 to 60 seconds.

[0031] The organic solvent saturated vapor dilutes the mixed solvent in the precursor solution, enabling the perovskite precursor molecules in the precursor solution to form a uniform, high-quality crystalline precursor on the surface of substrate 1. The organic solvent saturated vapor atmosphere can also delay the evaporation of the mixed solvent in the precursor solution, providing sufficient self-assembly time for the perovskite precursor molecules in the precursor solution. If the substrate 1 coated with the precursor solution is pretreated in an atmosphere of saturated organic solvent vapor for less than 10 seconds, the time the substrate 1 is in the saturated organic solvent vapor is short, and the effect of the saturated organic solvent vapor on the precursor solution on the surface of the substrate 1 is not obvious. As a result, a uniform and high-quality crystalline precursor cannot be formed on the surface of the substrate 1. If the substrate 1 coated with the precursor solution is pretreated in an atmosphere of saturated organic solvent vapor for more than 60 seconds, the time the substrate 1 is in the saturated organic solvent vapor is long, and the mixed solvent in the precursor solution on the surface of the substrate 1 is excessively diluted. During the pretreatment process, early crystallization will occur in the precursor solution on the surface of the substrate 1. After annealing, this will lead to coarse and uneven grains or the appearance of impurity phases in the perovskite layer 2 of the perovskite solar cell 100, thereby reducing the photoelectric conversion efficiency of the perovskite solar cell 100. Therefore, the pretreatment time of the substrate 1 coated with the precursor solution in an atmosphere of organic solvent saturated vapor can be 10s, 30s, 60s, etc., and the optional treatment time can be 20s to 40s, so that the precursor solution on the surface of the substrate 1 can form a uniform and high-quality crystalline precursor during the pretreatment process.

[0032] In one possible embodiment, 3 seconds after the spin coating of the precursor solution is completed, the substrate 1 coated with the precursor solution is quickly placed in a sealed container for pretreatment for 30 seconds. The bottom of the sealed container contains diethyl ether, and the interior of the sealed container is filled with saturated diethyl ether vapor, with the substrate 1 coated with the precursor solution located within the saturated diethyl ether vapor.

[0033] Comparative example: After spin-coating the precursor solution onto the substrate for 115 seconds, chlorobenzene was added dropwise as an organic solvent, and the remaining steps were the same as those in this application.

[0034] Compared to the comparative example, the scheme of this application uses gas-phase diffusion, which is a more moderate process and can delay the evaporation of solvents, improve the nucleation quality in the precursor solution, and make the annealed perovskite layer 2 have the characteristics of large grains, few defects and good orientation.

[0035] In one possible embodiment, when the pretreated substrate 1 undergoes at least two annealing processes, the preparation method includes: S61. Heat the pretreated substrate 1 to 50°C to 70°C and anneal for 1 min to 3 min.

[0036] Heating the pretreated substrate 1 to 50°C to 70°C and annealing it for 1 min to 3 min can drive the mixed solvent in the pretreated precursor solution to evaporate slowly. By controlling the evaporation rate of the mixed solvent through heating temperature, the crystallization driving force can be regulated, so that a precursor solid film with uniform composition and morphology can be formed on the surface of the substrate 1. The precursor solid film can be a Lewis acid-base adduct (e.g., PbI2·DMSO·MAI) formed by lead iodide, dimethyl sulfoxide and a small amount of methyl iodide, and is amorphous or microcrystalline, covering the substrate 1 without compositional segregation or obvious phase separation, thereby improving the quality of the perovskite layer 2 after annealing.

[0037] If the annealing temperature is less than 50℃ or the annealing time is less than 1 min, the mixed solvent in the pretreated precursor solution will not evaporate completely, and the residual mixed solvent will lead to an incomplete intermediate phase, affecting the quality of the perovskite layer 2 after annealing. If the annealing temperature is greater than 70℃ or the annealing time is greater than 3 min, the pretreated precursor solution will skip the process of forming a precursor solid film and crystallize rapidly, resulting in defects in the rapidly crystallized perovskite phase, affecting the quality of the perovskite layer 2 in the perovskite solar cell 100. Optionally, the annealing temperature can be 50℃, 60℃, 70℃, etc., and the annealing time can be 1 min, 2 min, 3 min, etc., so that the mixed solvent in the pretreated precursor solution can evaporate slowly and form a uniform precursor solid film, improving the quality of the perovskite layer 2 after annealing.

[0038] In one possible embodiment, after the substrate 1 undergoes the first stage of annealing in S61, a second stage of annealing is also required. The preparation method includes: S62. Heat substrate 1 to 90°C to 110°C and anneal for 5 min to 15 min.

[0039] In the second stage of annealing, substrate 1 is heated to allow the precursor solid film generated in the first stage of annealing to complete its phase transformation and grain growth, thus transforming the precursor solid film into perovskite. If the annealing temperature is less than 90°C or the annealing time is less than 5 minutes, the transformation of the precursor solid film will be incomplete, and non-perovskite phases will remain in the perovskite layer 2 after annealing, reducing the photoelectric conversion efficiency of the perovskite solar cell 100. If the annealing temperature is greater than 110°C or the annealing time is greater than 15 minutes, it will lead to abnormally coarse perovskite grains or even thermal decomposition.

[0040] Optionally, the annealing temperature can be 90℃, 100℃, 110℃, etc., and the annealing time can be 5min, 10min, 15min, etc., to ensure complete phase transformation of the precursor solid film and moderate grain growth through Ostwald ripening, resulting in a well-crystallized perovskite layer 2 after annealing. In X-ray diffraction (XRD) detection, the perovskite layer 2 prepared by the above method exhibits sharp, high-intensity, and small full width at half maximum (FWHM) peaks, and no impurity phase peaks in the XRD pattern, indicating good crystallinity of the perovskite layer 2. The perovskite grains in the perovskite layer 2 are relatively large and preferentially oriented, which is beneficial for charge transport in the perovskite layer 2. In the scanning electron microscope image of perovskite layer 2, it can be seen that the grain size of perovskite layer 2 is large and the boundaries are clear. This can reduce light scattering, improve the collection efficiency of charge carriers in perovskite layer 2, reduce the migration channels of water and oxygen ions, and improve the degradation resistance of perovskite layer 2.

[0041] During the annealing process, the first annealing in S61, under mild conditions of 50°C to 70°C, allows the residual mixed solvent in the wet film of the precursor solution to evaporate slowly and steadily. At the same time, it can induce the self-assembly of precursor molecules to form a uniform and dense mesophase film on the substrate surface, which is the basis for the subsequent large-scale structure of perovskite crystals. The second annealing in S62, at a temperature of 90°C to 110°C, provides sufficient energy to completely transform the mesophase formed in step S61 into perovskite crystals, and allows the grains to grow moderately through the Ostwald ripening process, forming a light-absorbing layer dominated by the perovskite phase.

[0042] If the pretreated precursor solution undergoes only one high-temperature annealing, the perovskite crystallization process will be too rapid. This will result in a large accumulation of internal stress in the annealed perovskite layer, leading to uneven grain size, high defect density, and ultimately, poor performance of the perovskite solar cell. If annealing is performed more than twice, the excessive heating will cause the perovskite material to be under heat for extended periods, potentially triggering the volatilization of organic components or thermal decomposition of the material, thus introducing new defects. Furthermore, the process is complex and time-consuming.

[0043] In one possible embodiment, after the substrate 1 undergoes the second stage of annealing in S62, a third stage of annealing can be performed, and the preparation method includes: S63. Heat substrate 1 to 100°C to 120°C and anneal for 1 min to 5 min.

[0044] Due to the different coefficients of thermal expansion between substrate 1 and the wet film formed by the precursor solution coated on substrate 1, as well as the precursor solid film formed during annealing, their deformation during heating or cooling processes differs, easily leading to stress between substrate 1 and perovskite layer 2 after annealing. During crystallization and grain growth, processes such as lattice mismatch, grain boundary formation, and escape of mixed solvents in the precursor solution coated on the surface of substrate 1 can cause internal changes such as volume shrinkage in the wet film formed by the precursor solution coated on the surface of substrate 1, easily generating stress within the perovskite layer 2 after annealing. During high-temperature annealing or pretreatment with saturated vapor from organic solvents, the precursor solution coated on the surface of substrate 1 undergoes rapid, non-equilibrium crystallization, resulting in numerous defects and lattice distortions within the perovskite layer 2, further leading to stress within the perovskite layer 2. If stress exists inside the perovskite layer 2, stress concentration points can easily become defect aggregation points, leading to instability of the perovskite phase in the perovskite layer 2, making it prone to decomposition. It also reduces the thermodynamic stability of the perovskite layer 2, making it susceptible to problems such as water and oxygen intrusion and ion migration, thus reducing the long-term stability of the perovskite solar cell 100. Stress can also change the band structure of the perovskite layer 2, affecting the open-circuit voltage of the solar cell, as well as light absorption and charge transport. Large stress inside the perovskite solar cell 100 can also cause the perovskite layer 2 to crack, damaging the mechanical integrity and electrical continuity of the perovskite solar cell 100.

[0045] During the second-stage annealing process, the precursor solution crystallizes to form perovskite layer 2. The third-stage annealing process is at a temperature slightly higher than the second-stage temperature, providing short-term additional kinetic energy for grain boundary fusion and atomic rearrangement in perovskite layer 2 to eliminate internal stress and optimize its quality. If the annealing temperature is less than 100℃, the third-stage annealing temperature will be lower than the second-stage annealing temperature, failing to eliminate stress in perovskite layer 2. If the annealing time is less than 1 minute, the time for grain boundary fusion and atomic rearrangement in perovskite layer 2 is too short to completely eliminate stress. If the annealing temperature is greater than 120℃ or the annealing time is greater than 5 minutes, perovskite layer 2 is at risk of thermal damage.

[0046] In one possible embodiment, the pretreated substrate 1 is removed and placed on a hot plate. It is first annealed at 60°C for 2 minutes to form a uniform precursor solid film on the surface of substrate 1, and then annealed at 100°C for 10 minutes to form a perovskite layer 2 on the surface of substrate 1. Optionally, after the perovskite layer 2 is formed on the surface of substrate 1, it is annealed at 110°C for 3 minutes to remove stress generated within the perovskite layer 2.

[0047] The third-stage annealing process S63 is optional. If the perovskite layer formed after the first-stage annealing S61 and the second-stage annealing S62 results in a high-quality film with large grain size, good grain boundary fusion, and low internal stress, then the third-stage annealing process S63 is not necessary, which can shorten the process flow and improve production efficiency. If the perovskite components in the precursor solution are sensitive to high temperatures, for example, if the precursor solution contains a large amount of formamidinium (FA), cesium (Cs), or a mixed halogen system, the temperature of the third-stage annealing process may cause thermal decomposition of the perovskite material. To reduce the possibility of damage to the perovskite material, the third-stage annealing can be omitted.

[0048] After the substrate 1 and the perovskite layer 2 are cooled, a hole transport layer 4 or an electron transport layer 3 is fabricated on the side of the perovskite layer 2 away from the substrate 1. When the electron transport layer 3 is fabricated on the glass substrate 11, the hole transport layer 4 is fabricated on the side of the perovskite layer 2 away from the substrate 1. When the hole transport layer 4 is fabricated on the glass substrate 11, the electron transport layer 3 is fabricated on the side of the perovskite layer 2 away from the substrate 1. Then, a buffer layer and a metal electrode 5 are fabricated on the side of the hole transport layer 4 or the electron transport layer 3 away from the perovskite layer 2.

[0049] Optionally, after the substrate 1 and the perovskite layer 2 are cooled, a 20 nm C60 layer is vacuum-deposited on the side of the perovskite layer 2 away from the substrate 1, an 8 nm BCP layer is vacuum-deposited on the C60 surface, and a 100 nm Ag electrode is vacuum-deposited on the BCP surface, thus completing the fabrication of the perovskite solar cell 100.

[0050] like Figure 2 and Figure 3 As shown, this application also provides a perovskite solar cell 100, which can be either a normal or an inverted structure. In the normal structure, a c-TiO2 layer and an mp-TiO2 layer are fabricated on an FTO conductive glass to form a substrate 1. A perovskite layer 2 is fabricated on the side of the substrate 1 where the mp-TiO2 layer is located. The perovskite layer 2 is fabricated using the same method as described above for the perovskite solar cell 100. A hole transport layer 4 and a metal electrode 5 are fabricated on the side of the perovskite layer 2 away from the substrate 1. In the inverted structure, a hole transport layer 4 is fabricated on an ITO conductive glass to form a substrate 1. A perovskite layer 2 is fabricated on the side of the substrate 1 where the hole transport layer 4 is located. The perovskite layer 2 is fabricated using the same method as described above for the perovskite solar cell 100. An electron transport layer 3 and a metal electrode 5 are fabricated on the side of the perovskite layer 2 away from the substrate 1.

[0051] This application provides a tandem solar cell, comprising a bottom cell and a top cell. The top cell has a wide bandgap light-absorbing layer to absorb short-wavelength light, while the bottom cell has a narrow bandgap light-absorbing layer to absorb long-wavelength light. The top and bottom cells in the tandem solar cell can capture different bands of the solar spectrum, resulting in higher photoelectric conversion efficiency. An intermediate recombination layer 6 is disposed between the bottom and top cells to connect them, enabling electron-hole recombination and ensuring continuous current flow between the top and bottom cells. The top cell can be the perovskite solar cell 100 described above. The bottom cell can be a crystalline silicon bottom cell, a perovskite solar cell, etc.

[0052] When the bottom cell is a crystalline silicon cell, the crystalline silicon cell may include, but is not limited to, a passivated emitter rear cell (PERC), a tunnel oxide passivated contact cell (TOPCon), an intrinsic thin-film heterojunction cell (HJT), and an interdigitated back contact cell (IBC).

[0053] For PERC cells, along their thickness direction, they include a front-surface silver electrode, a front-surface silicon nitride passivation layer, a phosphorus emitter layer, a P-type silicon substrate, a localized aluminum back field, an aluminum back electrode, and a back passivation layer (Al2O3 / SiNx). PERC cells use a passivation film to passivate the back surface, replacing the all-aluminum back field, enhancing light reflection within the silicon substrate, reducing the recombination rate on the back surface, and improving cell efficiency.

[0054] For a TOPCon cell, along its thickness direction, it includes a silver electrode, a front surface silicon nitride layer 208, an aluminum oxide layer 207, an emitter 206, a silicon substrate 201, a tunneling oxide layer 202, a doped polycrystalline silicon layer 203, a passivation layer 204, and the silver electrode. The back of the cell consists of a tunneling oxide layer 202 (1nm~2nm) and a phosphorus-doped microcrystalline amorphous mixed Si film, which together form a passivation contact structure. This structure can block minority carrier hole recombination, improving the cell's open-circuit voltage and short-circuit current. The tunneling oxide layer 202 allows majority carrier electrons to tunnel into the polycrystalline silicon layer while blocking minority carrier hole recombination. The excellent passivation effect of the tunneling oxide layer 202 and the doped polycrystalline silicon layer 203 causes band bending on the silicon wafer surface, resulting in a field passivation effect. This significantly increases the probability of electron tunneling, reduces contact resistance, and improves the cell's open-circuit voltage and short-circuit current, thereby improving the cell's conversion efficiency.

[0055] For HJT cells, along their thickness direction, HJT cells include a front low-temperature silver electrode, a front conductive film, an N-type amorphous silicon film, an intrinsic amorphous silicon film, an N-type substrate silicon layer, an intrinsic amorphous silicon film, a P-type amorphous silicon film, a back conductive film, and a back low-temperature silver electrode.

[0056] For an IBC cell, along its thickness direction, it includes a silicon nitride inversion layer, an N+ front surface field, an N-type substrate silicon layer, a P+ emitter, an N+ back field, an aluminum oxide passivation layer, a silicon nitride antireflection layer, and a silver electrode. IBC cells utilize ion implantation technology to obtain P- and N-regions with good uniformity and precisely controllable junction depth. The absence of grid lines on the front side eliminates light-blocking current loss from the metal electrode, maximizing the utilization of incident photons. Due to the back-contact structure, grid line shading is not a concern, allowing for a wider grid line ratio, thus reducing series resistance and achieving a high fill factor. Optimized design of surface passivation and light-trapping structures can be achieved, resulting in lower front-surface recombination rates and surface reflection.

[0057] like Figure 4 As shown, taking a perovskite cell 100 as the top cell and a Topcon cell 200 as the bottom cell as an example, the intermediate composite layer 6 is located on one side of the glass substrate in the perovskite cell 100, and the side of the intermediate composite layer 6 away from the perovskite cell 100 is the Topcon cell 200. In the Topcon cell 200, the silicon substrate 201 is located on the side of the intermediate composite layer 6 away from the perovskite cell 100. On the side of the silicon substrate 201 away from the intermediate composite layer 6, there is a tunneling oxide layer 202 and a doped polycrystalline silicon layer 203. The doped polycrystalline silicon layer 203 is located on the side of the tunneling oxide layer 202 away from the tunneling oxide layer 202. A passivation layer 204 is deposited on the side of the doped polycrystalline silicon layer 203 away from the tunneling oxide layer 202. An electrode layer 205 is disposed on the silicon substrate 201, which is in contact with the doped polycrystalline silicon layer 203, so that the electrode layer 205 can conduct the charge carriers in the doped polycrystalline silicon layer 203. An emitter 206 is disposed on the side of the silicon substrate 201 near the intermediate composite layer 6. An aluminum oxide layer 207 and a silicon nitride layer 208 are disposed on the emitter 206. A conductive layer 209 is disposed on the silicon nitride layer 208. The intermediate composite layer 6 is located on the side of the conductive layer 209 away from the silicon nitride layer 208.

[0058] like Figure 5As shown, this application embodiment provides a photovoltaic module 300, which includes multiple solar cells 301 interconnected. Two interconnected solar cells are electrically connected via a conductive material. When the solar cells are generating electricity, there is an electrical connection between the two interconnected cells, and the current generated by the multiple solar cells can be collected and output to the photovoltaic module through the conductive material. The solar cells in the photovoltaic module can be the aforementioned tandem solar cells. The photovoltaic module also includes a first encapsulating film 302 and a second encapsulating film 303, with the multiple solar cells located between the first encapsulating film 302 and the second encapsulating film 303. A photovoltaic glass 304 is disposed on the side of the first encapsulating film 302 away from the solar cells 301, and a backsheet 305 is disposed on the side of the second encapsulating film 303 away from the solar cells 301. The backsheet 305 can be photovoltaic glass, allowing sunlight to pass through the backsheet 305 and onto the solar cells 301, thereby improving the light absorption efficiency of the photovoltaic module 300. The first adhesive film 302 and the second adhesive film 303 can be at least one of ethylene vinyl acetate copolymer (EVA), polyolefin elastomer (POE), and polyvinyl butyral (PVB), enabling the first adhesive film 302 and the second adhesive film 303 to protect the solar cell 301 and reduce the possibility of external environmental influence on the performance of the solar cell 301. The photovoltaic glass 304 is bonded and fixed by the first adhesive film 302, and the light transmittance of the photovoltaic glass 304 is greater than or equal to 92% to facilitate sunlight intake into the photovoltaic module 300. The backplate 305, located on the side of the second adhesive film 303 away from the solar cell 301, is bonded and fixed by the second adhesive film 303 to improve the protection of the solar cell 301 and extend the service life of the photovoltaic module 300.

[0059] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0060] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0061] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

Claims

1. A method for preparing a perovskite solar cell, characterized in that, The preparation method includes: Provide glass substrates; An electron transport layer or a hole transport layer is fabricated on the glass substrate to form a substrate; Lead iodide and methyl iodide are dissolved in a mixed solvent to form a precursor solution; The precursor solution is coated onto the substrate to form a wet film on the side of the electron transport layer or the hole transport layer away from the glass substrate; The substrate coated with the precursor solution is placed in an atmosphere of saturated organic solvent vapor, wherein the organic solvent is miscible with the mixed solvent, for pretreatment. The pretreated substrate is subjected to at least two annealing processes.

2. The method for preparing a perovskite solar cell according to claim 1, characterized in that, After the precursor solution is coated onto the substrate, it is placed in an atmosphere of saturated organic solvent vapor for 1 to 5 seconds.

3. The method for preparing a perovskite solar cell according to claim 1, characterized in that, The organic solvent includes at least one of diethyl ether, chlorobenzene, and toluene.

4. The method for preparing a perovskite solar cell according to any one of claims 1 to 3, characterized in that, The preprocessing time is 10s to 60s.

5. The method for preparing a perovskite solar cell according to any one of claims 1 to 3, characterized in that, The preparation method includes performing at least two annealing processes on the pretreated substrate: The pretreated substrate is heated to 50°C to 70°C and annealed for 1 min to 3 min.

6. The method for preparing a perovskite solar cell according to claim 5, characterized in that, The pretreated substrate is heated to 50°C to 70°C and annealed for 1 to 3 minutes. The preparation method includes: The substrate is heated to 90°C to 110°C and annealed for 5 to 15 minutes.

7. The method for preparing a perovskite solar cell according to claim 6, characterized in that, The pretreated substrate is heated to 90°C to 110°C and annealed for 5 to 15 minutes. The preparation method includes: The substrate is heated to 100°C to 120°C and annealed for 1 min to 5 min.

8. The method for preparing a perovskite solar cell according to claim 1, characterized in that, The molar ratio of lead iodide to methyl iodide is 1.05 to 1.2:

1.

9. The method for preparing a perovskite solar cell according to claim 1, characterized in that, The mixed solvent includes N,N-dimethylformamide and dimethyl sulfoxide.

10. The method for preparing a perovskite solar cell according to claim 9, characterized in that, The volume percentage of the dimethyl sulfoxide is 10% to 30%.

11. A stacked battery, characterized in that, The stacked solar cell includes a bottom cell and a top cell, with the top cell stacked on top of the bottom cell; the top cell is prepared by the perovskite solar cell preparation method according to any one of claims 1 to 10.

12. A photovoltaic module, characterized in that, The photovoltaic module includes multiple solar cells, which are interconnected; the solar cells are the tandem solar cells as described in claim 11.

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