Perovskite light absorption layer, preparation method thereof and flexible perovskite solar cell

Abstract

This application discloses a perovskite light-absorbing layer and its preparation method, as well as a flexible perovskite solar cell, belonging to the field of perovskite solar cells. Compared with existing technologies, this application introduces a zwitterionic polymer as an additive into the perovskite light-absorbing layer. During the perovskite crystallization and film formation process, the zwitterionic polymer can form a strong ion-dipole interaction with the solvent and slow down the solvent evaporation rate, thereby controlling the perovskite crystallization process and improving crystal quality, resulting in perovskite materials with large-sized grains. Simultaneously, the zwitterionic polymer undergoes in-situ cross-linking and precipitation during perovskite crystallization, concentrating at the grain boundaries of the polycrystalline perovskite thin film layer. This promotes the complete removal of residual solvent and eliminates interface porosity defects, while constructing stress buffer regions to reduce local mechanical stress concentration during bending. Therefore, a perovskite thin film layer with both high crystal quality and excellent bending resistance is obtained, improving the photoelectric conversion efficiency and mechanical stability of the perovskite solar cell.

Description

Technical Field

[0001] This application belongs to the field of surface repair materials, specifically relating to a perovskite light-absorbing layer and its preparation method, and a flexible perovskite solar cell. Background Technology

[0002] As a next-generation photovoltaic technology, perovskite solar cells have demonstrated enormous application potential in the photovoltaic field due to their unique photoelectric properties, such as high light absorption coefficient, long carrier diffusion length, and adjustable bandgap, making them a research hotspot in recent years. In particular, flexible perovskite solar cells, with their high power density and mechanical flexibility, show broad application prospects in wearable electronics, building-integrated photovoltaics, and aerospace.

[0003] As a core component of perovskite solar cells, the perovskite light-absorbing layer directly determines the cell's efficiency in photon absorption and carrier generation and transport. Its performance plays a crucial role in the overall photoelectric conversion efficiency and stability of the cell. Currently, the fabrication of high-quality perovskite light-absorbing layers faces many challenges, among which crystal quality and bending tolerance are two key issues that require further improvement. Summary of the Invention

[0004] This application aims to at least partially address one of the technical problems in the related art. Therefore, the purpose of this application is to provide a perovskite light-absorbing layer and its preparation method, as well as a flexible perovskite solar cell.

[0005] This application provides a perovskite light-absorbing layer in a first aspect. According to an embodiment of this application, the perovskite light-absorbing layer comprises: Metal halide perovskite material, wherein the average grain size of the metal halide perovskite material is ≥1.2 micrometers; The additive includes a zwitterionic polymer, which comprises a main chain, positive ionic side groups, and negative ionic side groups. The main chain has carbon-carbon unsaturated bonds, and the positive ionic side groups include at least one of quaternary ammonium and quaternary phosphine. The negative ionic side groups include at least one of sulfonate, phosphate, and carboxylate.

[0006] Compared to the prior art, the perovskite light-absorbing layer of the above embodiments of this application introduces a zwitterionic polymer as an additive into the perovskite light-absorbing layer. During the perovskite crystallization and film formation process, the zwitterionic polymer can form a strong ion-dipole interaction with the solvent and slow down the solvent evaporation rate, thereby controlling the perovskite crystallization process and improving the crystallization quality to obtain a perovskite material with large-sized grains. Simultaneously, the zwitterionic polymer undergoes in-situ cross-linking and precipitation during perovskite crystallization and is concentrated at the grain boundaries of the polycrystalline perovskite film layer. This promotes the complete removal of residual solvent and eliminates interface porosity defects, while constructing stress buffer regions to reduce local mechanical stress concentration during bending. Therefore, a flexible perovskite film layer with both high crystallization quality and excellent bending resistance can be obtained.

[0007] In addition, the perovskite light-absorbing layer according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the zwitterionic polymer includes at least one of phosphoric acid choline polymers, sulfobetaine polymers, and carboxybetaine polymers.

[0008] In some embodiments of this application, the monomers of the phosphorocholine polymers include 2-methacryloyloxyethyl phosphorocholine, the monomers of the sulfobetaine polymers include sulfobetaine methacrylate, and the monomers of the carboxybetaine polymers include carboxybetaine methacrylate.

[0009] In some embodiments of this application, the zwitterionic polymer accounts for 0.1wt%-8.3wt% of the mass percentage in the perovskite light-absorbing layer.

[0010] In some embodiments of this application, the metal halide perovskite material includes ABX3 type perovskite material; wherein, A includes at least one of formamidine ion, methylamine ion, cesium ion and rubidium ion, B includes at least one of lead ion and tin ion, and X includes at least one of chloride ion, bromide ion and iodide ion; And / or, the thickness of the perovskite light-absorbing layer is 500nm-900nm.

[0011] A second aspect of this application provides a method for preparing the perovskite light-absorbing layer described in the first aspect. According to embodiments of this application, the method includes the following steps: A zwitterionic polymer monomer and an initiator are added to a perovskite precursor solution to obtain a mixed solution; The mixed solution is coated and annealed to obtain the perovskite light-absorbing layer.

[0012] The method for preparing the perovskite light-absorbing layer in the above embodiments of this application is simple to operate, requires no additional specific equipment, and is suitable for industrial mass production.

[0013] In addition, the method for preparing the perovskite light-absorbing layer according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the concentration of the perovskite precursor solution is 0.5 mol / L-3 mol / L, and the solvent of the perovskite precursor solution includes a mixed solvent composed of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of (7-10):1. And / or, in the mixed solution, the concentration of the zwitterionic polymer monomer is 0.5 mg / mL-50 mg / mL, and the concentration of the initiator is 0.1 mg / mL-10 mg / mL; And / or, the coating method includes spin coating, and the working conditions parameters of the spin coating include: spin coating speed of 1500rpm-5000rpm and spin coating time of 20s-40s; the working conditions parameters of the annealing include: annealing temperature of 60℃-200℃ and annealing time of 5min-20min.

[0014] A third aspect of this application provides a flexible perovskite solar cell. According to an embodiment of this application, the flexible perovskite solar cell includes the perovskite light-absorbing layer described in the first aspect or a perovskite light-absorbing layer prepared using the method described in the second aspect. Therefore, the photoelectric conversion efficiency and mechanical stability of the flexible perovskite solar cell provided by this application are significantly improved.

[0015] In some embodiments of this application, the flexible perovskite solar cell includes a conductive layer, an electron transport layer, the perovskite light absorption layer, a hole transport layer, and a metal electrode layer stacked together.

[0016] In some embodiments of this application, the thickness of the conductive layer is 50nm-300nm, and the material of the conductive layer includes at least one of indium tin oxide, indium-doped zinc oxide, aluminum-doped zinc oxide, and silver nanowires; And / or, the thickness of the electron transport layer is 10nm-30nm, and the material of the electron transport layer includes at least one of SnO2, TiO2 and ZnO; And / or, the hole transport layer has a thickness of 100nm-200nm, and the material of the hole transport layer includes at least one of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate; And / or, the thickness of the metal electrode layer is 50nm-150nm, and the material of the metal electrode layer includes at least one of gold, silver, copper, aluminum, carbon, and transparent conductive oxide.

[0017] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0018] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the crystallization mechanism of the perovskite light-absorbing layer in Example 1 and Comparative Example 1 of this application.

[0019] Figure 2 The images show the nuclear magnetic resonance spectra of the zwitterionic monomer used in Example 1 of this application before and after its interaction with the solvent DMSO.

[0020] Figure 3 The images show the in-situ atomic force microscopy infrared spectra and the changes in solvent-DMSO content during the crystallization process of the perovskite light-absorbing layer in Examples 1 and 1 of this application.

[0021] Figure 4 These are scanning electron microscope images of the lower surface and cross-section of the perovskite after exfoliation in Examples 1, 2, and 1 of this application.

[0022] Figure 5 The images shown are atomic force microscopy images of the perovskite surface in Example 1 and Comparative Example 1 of this application, and finite element simulation results of the bending stress distribution of flexible perovskite.

[0023] Figure 6 These are X-ray diffraction spectra of perovskite in Examples 1, 2 and Comparative Example 1 of this application.

[0024] Figure 7 The graph shows the bending stability test results of the flexible perovskite solar cells prepared in Example 1 and Comparative Example 1 of this application. Detailed Implementation

[0025] The embodiments of this application are described in detail below, and the embodiments described below with reference to the accompanying drawings are merely exemplary and intended to explain this application, and should not be construed as limiting this application.

[0026] This application provides a perovskite light-absorbing layer in a first aspect. According to an embodiment of this application, the perovskite light-absorbing layer comprises: Metal halide perovskite material, wherein the average grain size of the metal halide perovskite material is ≥1.2 micrometers; The additive includes a zwitterionic polymer, which comprises a main chain, positive ionic side groups, and negative ionic side groups. The main chain has carbon-carbon unsaturated bonds, and the positive ionic side groups include at least one of quaternary ammonium and quaternary phosphine. The negative ionic side groups include at least one of sulfonate, phosphate, and carboxylate.

[0027] Compared to the prior art, the perovskite light-absorbing layer of the above embodiments of this application introduces a zwitterionic polymer as an additive into the perovskite light-absorbing layer. During the perovskite crystallization and film formation process, the zwitterionic polymer can form a strong ion-dipole interaction with the solvent and slow down the solvent evaporation rate, thereby controlling the perovskite crystallization process and improving the crystallization quality to obtain a perovskite material with large-sized grains. Simultaneously, the zwitterionic polymer undergoes in-situ cross-linking and precipitation during perovskite crystallization and is concentrated at the grain boundaries of the polycrystalline perovskite film layer. This promotes the complete removal of residual solvent and eliminates interface porosity defects, while constructing stress buffer regions to reduce local mechanical stress concentration during bending. Therefore, a flexible perovskite film layer with both high crystallization quality and excellent bending resistance can be obtained.

[0028] In this application, the average grain size of the aforementioned metal halide perovskite material can be measured by means such as scanning electron microscopy, and can be, for example, 1.2 micrometers, 1.3 micrometers, 1.4 micrometers, 1.5 micrometers, 1.6 micrometers, 1.7 micrometers, 1.8 micrometers, 1.9 micrometers, 2.0 micrometers or any of the aforementioned values.

[0029] In addition, the perovskite light-absorbing layer according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the zwitterionic polymer includes at least one of phosphoric acid choline polymers, sulfobetaine polymers, and carboxybetaine polymers.

[0030] In some embodiments of this application, the monomers of the phosphorocholine polymers include 2-methacryloyloxyethyl phosphorocholine, the monomers of the sulfobetaine polymers include sulfobetaine methacrylate, and the monomers of the carboxybetaine polymers include carboxybetaine methacrylate.

[0031] In some embodiments of this application, the zwitterionic polymer accounts for 0.1 wt% to 8.3 wt% of the perovskite light-absorbing layer by mass percentage, for example, 0.1 wt%, 0.5 wt%, 1.0 wt%, 5.0 wt%, 8.0 wt%, or any of the aforementioned values. By controlling the mass percentage of the zwitterionic polymer in the perovskite light-absorbing layer to the above range, this application can synergistically regulate crystallization kinetics and effectively passivate defects, while simultaneously constructing a flexible ionic cross-linking network at the grain boundaries. If the mass percentage of the zwitterionic polymer is too small, the regulation and passivation effects are insufficient, making it difficult to form a continuous network. Conversely, if the mass percentage of the zwitterionic polymer is too large, the large amount of organic phase leads to slow crystallization and the formation of inactive regions, reducing light absorption.

[0032] In some embodiments of this application, the metal halide perovskite material includes ABX3 type perovskite material; wherein, A includes at least one of formamidine ion, methylamine ion, cesium ion and rubidium ion, B includes at least one of lead ion and tin ion, and X includes at least one of chloride ion, bromide ion and iodide ion; And / or, the thickness of the perovskite light-absorbing layer is 500nm-900nm, for example, it can be 500nm, 600nm, 700nm, 750nm, 800nm, 850nm, 900nm or any of the aforementioned values.

[0033] A second aspect of this application provides a method for preparing the perovskite light-absorbing layer described in the first aspect. According to embodiments of this application, the method includes the following steps: A zwitterionic polymer monomer and an initiator are added to a perovskite precursor solution to obtain a mixed solution; The mixed solution is coated and annealed to obtain the perovskite light-absorbing layer.

[0034] The method for preparing the perovskite light-absorbing layer in the above embodiments of this application is simple to operate, requires no additional specific equipment, and is suitable for industrial mass production.

[0035] In addition, the method for preparing the perovskite light-absorbing layer according to the above embodiments of this application may also have the following additional technical features: In some embodiments of this application, the concentration of the perovskite precursor solution is 0.5 mol / L-3 mol / L, for example, it can be 0.5 mol / L, 1.5 mol / L, 1.5 mol / L, 2.5 mol / L, 3 mol / L or any range between the aforementioned values; the solvent of the perovskite precursor solution includes a mixed solvent composed of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a volume ratio of (7-10):1, for example, it can be a mixed solvent composed of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 9:1; And / or, in the mixed solution, the concentration of the zwitterionic polymer monomer is 0.5 mg / mL to 50 mg / mL, for example, it can be 0.5 mg / mL, 5 mg / mL, 10 mg / mL, 15 mg / mL, 20 mg / mL, 25 mg / mL, 30 mg / mL, 50 mg / mL, or any range between the aforementioned values; the concentration of the initiator is 0.1 mg / mL to 10 mg / mL, for example, it can be 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 3 mg / mL, 5 mg / mL, 5.5 mg / mL, 7 mg / mL, 9 mg / mL, 10 mg / mL, or any range between the aforementioned values; And / or, the coating method includes spin coating, and the working conditions parameters of the spin coating include: a spin coating speed of 1500rpm-5000rpm, for example, 1500rpm, 2000rpm, 3000rpm, 4500rpm, 5000rpm or any of the aforementioned values; a spin coating time of 20s-40s, for example, 20s, 25s, 35s, 40s or any of the aforementioned values; and the working conditions parameters of the annealing include: an annealing temperature of 60℃-200℃, for example, 60℃, 100℃, 120℃, 150℃, 180℃, 200℃ or any of the aforementioned values; and an annealing time of 5min-20min, for example, 5min, 8min, 10min, 15min, 20min or any of the aforementioned values.

[0036] A third aspect of this application provides a flexible perovskite solar cell. According to an embodiment of this application, the flexible perovskite solar cell includes the perovskite light-absorbing layer described in the first aspect or a perovskite light-absorbing layer prepared using the method described in the second aspect. Therefore, the photoelectric conversion efficiency and mechanical stability of the flexible perovskite solar cell provided by this application are significantly improved. Specifically, the photoelectric conversion efficiency of the flexible perovskite solar cell provided by this application can reach 25.86%. Simultaneously, under unencapsulated conditions with a bending radius of 5 mm, it can still maintain 91.4% of its initial efficiency after 15,000 bends, demonstrating the mechanical stability of the flexible perovskite solar cell.

[0037] In some embodiments of this application, the flexible perovskite solar cell includes a conductive layer, an electron transport layer, the perovskite light absorption layer, a hole transport layer, and a metal electrode layer stacked together.

[0038] In some embodiments of this application, the thickness of the conductive layer is 50nm-300nm, and the material of the conductive layer includes at least one of indium tin oxide, indium-doped zinc oxide, aluminum-doped zinc oxide, and silver nanowires; And / or, the thickness of the electron transport layer is 10nm-30nm, for example, it can be 10nm, 15nm, 20nm, 30nm or any range between the aforementioned values; the material of the electron transport layer includes at least one of SnO2, TiO2 and ZnO; And / or, the thickness of the hole transport layer is 100nm-200nm, for example, it can be 100nm, 150nm, 180nm, 200nm or any range between the aforementioned values; the material of the hole transport layer includes at least one of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Spiro-OMeTAD), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS); And / or, the thickness of the metal electrode layer is 50nm-150nm, for example, it can be 50nm, 80nm, 100nm, 120nm, 150nm or any of the aforementioned values; the material of the metal electrode layer includes at least one of gold, silver, copper, aluminum, carbon, and transparent conductive oxide.

[0039] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0040] Example 1 This embodiment provides a perovskite light-absorbing layer and a flexible perovskite solar cell containing the perovskite light-absorbing layer. The flexible perovskite solar cell, from bottom to top, consists of a transparent flexible conductive layer of PEN / ITO, an electron transport layer of SnO2, a perovskite absorber layer of FAPbI3 with added zwitterionic elastomer, a hole transport layer of Spiro-OMeTAD, and an electrode layer of gold. The specific fabrication steps are as follows: Step (1) Treatment of the flexible conductive layer: The flexible substrate is laser-etched and cut into 20mm*20mm pieces. It is then ultrasonically cleaned with deionized water, ethanol, and isopropanol for 15 minutes each, and dried in an oven. The ITO transparent conductive PEN is pasted onto the glass substrate covered with a PDMS adhesive layer and treated with ultraviolet ozone equipment for 15 minutes for later use. (Note: The conductive ITO layer is deposited on the PEN polymer to form PEN / ITO. PEN / ITO is a commercial product that can be purchased directly. Here, it is only to improve its surface wettability to facilitate subsequent coating.) Step (2) Preparation of the electron transport layer: A SnO2 precursor solution was prepared by mixing a 12 wt.% SnO2 colloidal aqueous solution with deionized water at a volume ratio of 1:3.5. 100 μL of the SnO2 precursor solution was extracted and coated onto an ITO flexible substrate at a spin-coating speed of 4000 rpm for 30 s. After spin-coating, the substrate was annealed at 120 °C for 40 minutes. A 25 nm thick SnO2 electron transport layer was deposited.

[0041] Step (3) Preparation of the perovskite layer: Weigh 691.5 mg of PbI2 and dissolve it in 1 mL of a mixed solution of DMF and DMSO (V DMF :V DMSOA PbI2 precursor solution was prepared by mixing a 9:1 volume ratio of PbI2 and adding 1 mg of 2-methacryloyloxyethyl phosphocholine (MPC) additive. 50 μL of this solution was statically spin-coated onto the electron transport layer at 1500 rpm for 30 seconds and annealed at 70°C for 60 seconds to obtain a porous PbI2 layer. 180.0 mg of FAI and 36.0 mg of MACl were dissolved in 2 ml of IPA to prepare an organic salt solution. 0.2 mg of azobisisobutyronitrile (AIBN) crosslinking initiator was added. 100 μL of this solution was statically spin-coated onto the porous PbI2 layer at 1800 rpm for 30 seconds and annealed at 150°C for 15 minutes to obtain a 700 nm thick perovskite layer. The zwitterionic polymer constituted 0.2 wt% of the perovskite light-absorbing layer by mass.

[0042] Step (4) Preparation of the hole transport layer: Weigh 72.3 mg of Spiro-OMeTAD, 30 μL of 4-tert-butylpyridine, and 35 μL of lithium salt acetonitrile solution and add them to 1 mL of chlorobenzene to prepare the Spiro-OMeTAD hole transport layer solution. Take 60 μL of this solution and spin-coat it onto the surface of the perovskite layer prepared in step (3) at a spin-coating speed of 4000 rpm for 30 s. The hole transport layer thickness obtained is 150 nm.

[0043] Step (5) Preparation of the electrode layer: The flexible device is peeled off from the glass substrate and placed in a thermal evaporation vacuum deposition apparatus to deposit an 80 nm thick gold electrode at a speed of 0.03 nm / s, thus completing the preparation of the entire perovskite solar cell. Figure 1 The structure shown is a PEN / ITO / SnO2 / FAPbI3-MPC / Spiro-OMeTAD / Au perovskite solar cell device.

[0044] Example 2 The difference between Example 2 and Example 1: In step (3) of Example 2, the organic salt solution did not contain AIBN initiator.

[0045] Example 3 The difference between Example 3 and Example 1: In step (3) of Example 3, the PbI2 precursor solution did not contain the MPC zwitterionic monomer.

[0046] Example 4 The difference between Example 4 and Example 1: In Example 4, 0.5 mg of 2-methacryloyloxyethyl phosphocholine (MPC) was weighed and dissolved in 1 mL of perovskite precursor solution to prepare a perovskite light-absorbing layer.

[0047] Example 5 The difference between Example 5 and Example 3: In Example 5, 2 mg of 2-methacryloyloxyethyl phosphocholine (MPC) was weighed and dissolved in 1 mL of perovskite precursor solution to prepare a perovskite light-absorbing layer.

[0048] Example 6 The difference between Example 6 and Example 3: In Example 6, 5 mg of 2-methacryloyloxyethyl phosphocholine (MPC) was weighed and dissolved in 1 mL of perovskite precursor solution to prepare a perovskite light-absorbing layer.

[0049] Example 7 The difference between Example 7 and Example 1: In step (3) of Example 7, 1 mg of sulfobetaine methacrylate was weighed and dissolved in 1 mL of perovskite precursor solution to prepare the perovskite light absorption layer.

[0050] Example 8 The difference between Example 8 and Example 1: In step (3) of Example 8, 1 mg of carboxybetaine methacrylate was weighed and dissolved in 1 mL of perovskite precursor solution to prepare a perovskite light-absorbing layer.

[0051] Example 9 The difference between Example 8 and Example 1: In step (3) of Example 9, V DMF :V DMSO =3:1.

[0052] Example 10 The difference between Example 8 and Example 1: In step (3) of Example 10, V DMF :V DMSO =15:1.

[0053] Comparative Example 1 Difference between Comparative Example 1 and Example 1: In step (3) of Comparative Example 1, the PbI2 precursor solution did not contain MPC zwitterionic monomer, and the organic salt solution did not contain AIBN initiator.

[0054] Test case This example demonstrates the performance testing and characterization of the above embodiments and comparative examples, as shown below: Figure 1This is a schematic diagram of the microscopic mechanism of the perovskite crystallization process in Comparative Example 1 and Example 1. During the heating annealing process, the solvent preferentially escapes from the top of the film, causing the precursor concentration to rise rapidly and reach a supersaturated state, driving the perovskite to crystallize from top to bottom. In Comparative Example 1, the rapid volatilization of DMSO leads to a high perovskite nucleation rate but insufficient crystal growth, resulting in poor film crystallization quality. At the same time, the perovskite layer preferentially formed at the top and the closed grain boundaries hinder the continuous volatilization of the lower DMSO, easily forming residual solvent pores at the buried interface. In Example 1, the zwitterionic molecules MPC slow down the volatilization of DMSO through strong interactions, coordinate the perovskite nucleation and growth process, improve the film crystallization quality, and form an elastic network through in-situ crosslinking during heating, filling the grain boundaries and keeping the solvent diffusion channels open, promoting the complete escape of the lower DMSO, thereby eliminating pores at the buried interface and forming a dense and stable lower interface.

[0055] Figure 2 The NMR spectra of the zwitterionic monomer MPC used in Example 1 before and after interaction with DMSO are shown. The H atoms at positions 1 and 2 are associated with the quaternary ammonium cation group in MPC, exhibiting a significant chemical shift (0.02 ppm); the H atoms at positions 3 and 4 are associated with the phosphate anion group, showing a certain degree of chemical shift (0.01 ppm); while the H atoms at positions 5 and 6, corresponding to the C=C double bond, show virtually no significant chemical shift. These results indicate that the positive and negative ion groups of MPC bind to the negative and positive ends of the DMSO molecule through ion-dipole interactions, respectively, confirming a strong intermolecular interaction between the two.

[0056] Figure 3 The atomic force microscopy infrared spectra of the perovskite thin films of Comparative Example 1 and Example 1 are shown at 1050 cm⁻¹. -1 The S=O characteristic signal at the point represents the volatilization behavior of DMSO. In Comparative Example 1, DMSO rapidly volatilizes through the interior of the grains and unclosed grain boundaries within the first minute of annealing, but this signal essentially disappears after 2 minutes, indicating that it is difficult for DMSO to continue escaping along the grain boundaries. In contrast, the volatilization rate of DMSO in Example 1 slows down significantly in the first minute, and it can still volatilize through the grain boundaries after 2 minutes, until it is basically volatilized after 5 minutes. Quantitative analysis shows that the DMSO volatilization process can be divided into three stages, with Example 1 having a longer duration in stage two (slow volatilization along grain boundaries), thus significantly reducing the residual DMSO content from 15.3% to 4.8%.

[0057] Figure 4The images show scanning electron microscope (SEM) images of the lower surface and cross-section of the perovskite films after peeling in Comparative Example 1, Example 1, and Example 2. In Comparative Example 1, numerous pores exist in the grain boundary region near the lower interface, primarily due to insufficient evaporation of residual DMSO. In Example 2, the introduction of MPC molecules can reduce the number of pores to some extent, but because they are dispersed in the perovskite film as isolated molecules, they are difficult to maintain grain boundary diffusion channels, and a significant amount of residual DMSO remains. In Example 1, MPC forms a cross-linked elastomer network under the action of an initiator, effectively supporting the grain boundaries and maintaining unobstructed solvent evaporation channels, thus completely eliminating residual DMSO and pore defects at the buried interface. Furthermore, this application can obtain micron-sized large grains (such as...) by delaying solvent evaporation. Figure 4 The exfoliated buried surface of Example 1 has an average grain size of 1.7 micrometers, while the grain size obtained by conventional methods is in the submicrometer range (e.g., Figure 4 The average particle size of the exfoliated buried surface in Comparative Example 1 is 0.8 micrometers.

[0058] Figure 5 The images show atomic force microscopy (AFM) images of the perovskite surfaces in Comparative Example 1 and Example 1, as well as finite element simulations of the bending stress distribution in the flexible perovskite. In Comparative Example 1, the average elastic modulus at the grain boundaries of the perovskite film is 47.6 GPa, higher than the average elastic modulus of 22.9 GPa within the grains. This is because the grain boundaries of the perovskite film contain numerous defects, which easily lead to the absence of organic cations and the enrichment of lead iodide. In Example 1, the grain boundaries of the perovskite are filled with a three-dimensional cross-linked elastomer, resulting in an average elastic modulus of 10.3 GPa, lower than the average elastic modulus of 23.5 GPa within the grains. The finite element simulation results show that, at a bending diameter of 1 mm, the average in-plane bending stress within the grains of Example 1 is 1.2 × 10⁻⁶. 8 Pa, lower than 1.5 × 10 Pa in Comparative Example 1. 8 Pa, which is mainly attributed to the fact that low-modulus elastomers can form stress buffers, reduce stress concentration and reduce bending stress on perovskites, thereby improving the bending stability of flexible cells.

[0059] Figure 6 For Comparative Example 1, the X-ray diffraction spectra of perovskite in Examples 1 and 2 show that the present application can improve the crystallinity of perovskite films, optimize crystal orientation, and reduce the content of unreacted PbI2 impurities. Figure 6 As shown, the peak intensity of perovskite (001) in Example 1 was significantly increased compared to Comparative Example 1 and Example 2, indicating a significant improvement in crystallinity; and the peak intensity signal of perovskite (111) crystal plane was weakened, indicating that the preferred orientation of (001) crystal plane was enhanced; at the same time, the signal of lead iodide PbI2 (001) was weakened, indicating that the residual PbI2 impurities were reduced, and the two-step reaction crystallization process was more complete.

[0060] The flexible perovskite solar cells of Examples 1-10 and Comparative Example 1 were tested for current-voltage characteristics under AM1.5 solar spectrum. The results are shown in Table 1. The flexible perovskite solar cell of Example 1, modified with 2-methacryloyloxyethylphosphocholine (MPC) elastomer, achieved an efficiency of 25.89%, which is 2.85% higher than the 23.04% efficiency of the unmodified flexible perovskite solar cell of Comparative Example 1. The efficiency improvement is mainly due to the improved crystal quality of the perovskite layer and the passivation of grain boundary defects. In Examples 4 and 5, when the MPC concentration decreased or increased, the performance of the perovskite solar cells slightly decreased because the grain boundaries were not fully filled or the ineffective area occupied by the grain boundaries increased. In Examples 9 and 10, excessive DMSO caused difficulty in solvent evaporation, resulting in a loose and porous film, while insufficient DMSO caused the perovskite to crystallize too quickly, forming fine grains with high defect density. Therefore, it is shown that the flexible perovskite solar cell of the present invention has excellent photoelectric conversion efficiency.

[0061] Table 1. Main performance parameters of flexible perovskite solar cells in Comparative Example 1 and Examples 1-10

[0062] Table 2 and Figure 7 The bending stability tests were conducted on the embodiments and Comparative Example 1. After the flexible cell was bent 10,000 times at a bending radius of 5 mm, the efficiency of Comparative Example 1 decreased to 70.6%, while the efficiency of Embodiment 1 remained at 92.3% after 10,000 bends, recovering to 96.9% after self-healing. After 15,000 bends, the efficiency retention rate was still 91.4%. The improvement in bending stability mainly comes from the elimination of pores at the buried interface and the improvement of interface bonding. At the same time, the zwitterionic elastomer filled at the grain boundaries can buffer mechanical stress, inhibit crack formation, and has a certain self-healing ability. Thus, it is shown that the flexible perovskite solar cell of the present invention has excellent bending stability.

[0063] Table 2 shows the bending stability of flexible perovskite solar cells in Comparative Example 1 and Examples 1-10.

[0064] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0065] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A perovskite light-absorbing layer, characterized in that, include: Metal halide perovskite material, wherein the average grain size of the metal halide perovskite material is ≥1.2 micrometers; The additive includes a zwitterionic polymer, which comprises a main chain, positive ionic side groups, and negative ionic side groups. The main chain has carbon-carbon unsaturated bonds, and the positive ionic side groups include at least one of quaternary ammonium and quaternary phosphine. The negative ionic side groups include at least one of sulfonate, phosphate, and carboxylate.

2. The perovskite light-absorbing layer according to claim 1, characterized in that, The zwitterionic polymers include at least one of phosphoric acid choline polymers, sulfobetaine polymers, and carboxybetaine polymers.

3. The perovskite light-absorbing layer according to claim 2, characterized in that, The monomers of the phosphorocholine polymers include 2-methacryloyloxyethyl phosphorocholine, the monomers of the sulfobetaine polymers include sulfobetaine methacrylate, and the monomers of the carboxybetaine polymers include carboxybetaine methacrylate.

4. The perovskite light-absorbing layer according to claim 1, characterized in that, The zwitterionic polymer accounts for 0.1wt%-8.3wt% of the mass percentage in the perovskite light-absorbing layer.

5. The perovskite light-absorbing layer according to claim 1, characterized in that, The metal halide perovskite material includes ABX3 type perovskite material; wherein, A includes at least one of formamidine ion, methylamine ion, cesium ion and rubidium ion, B includes at least one of lead ion and tin ion, and X includes at least one of chloride ion, bromide ion and iodide ion; And / or, the thickness of the perovskite light-absorbing layer is 500nm-900nm.

6. A method for preparing a perovskite light-absorbing layer according to any one of claims 1-5, characterized in that, Includes the following steps: A zwitterionic polymer monomer and an initiator are added to a perovskite precursor solution to obtain a mixed solution; The mixed solution is coated and annealed to obtain the perovskite light-absorbing layer.

7. The method for preparing the perovskite light-absorbing layer according to claim 6, characterized in that, The concentration of the perovskite precursor solution is 0.5 mol / L-3 mol / L, and the solvent of the perovskite precursor solution includes a mixed solvent composed of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of (7-10):

1. And / or, in the mixed solution, the concentration of the zwitterionic polymer monomer is 0.5 mg / mL-50 mg / mL, and the concentration of the initiator is 0.1 mg / mL-10 mg / mL; And / or, the coating method includes spin coating, and the working conditions parameters of the spin coating include: spin coating speed of 1500rpm-5000rpm and spin coating time of 20s-40s; the working conditions parameters of the annealing include: annealing temperature of 60℃-200℃ and annealing time of 5min-20min.

8. A flexible perovskite solar cell, characterized in that, Includes the perovskite light-absorbing layer according to any one of claims 1-5 or the perovskite light-absorbing layer prepared by the method of any one of claims 6-7.

9. The flexible perovskite solar cell according to claim 8, characterized in that, It includes a conductive layer, an electron transport layer, a perovskite light absorption layer, a hole transport layer, and a metal electrode layer stacked together.

10. The flexible perovskite solar cell according to claim 9, characterized in that, The thickness of the conductive layer is 50nm-300nm, and the material of the conductive layer includes at least one of indium tin oxide, indium-doped zinc oxide, aluminum-doped zinc oxide, and silver nanowires. And / or, the thickness of the electron transport layer is 10nm-30nm, and the material of the electron transport layer includes at least one of SnO2, TiO2 and ZnO; And / or, the hole transport layer has a thickness of 100nm-200nm, and the material of the hole transport layer includes at least one of 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene, poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate; And / or, the thickness of the metal electrode layer is 50nm-150nm, and the material of the metal electrode layer includes at least one of gold, silver, copper, aluminum, carbon, and transparent conductive oxide.

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