A flexible perovskite solar cell based on in-situ cross-linkable small organic molecules

Abstract

The application discloses a flexible perovskite solar cell based on an in-situ cross-linking organic small molecule and a preparation method thereof, realizes synchronization of a cross-linking process and a perovskite growth process, thereby achieving the effect of small molecule in-situ cross-linking regulation of perovskite crystallization, and can simply prepare a high-efficiency and mechanically stable flexible perovskite solar cell. Based on the in-situ cross-linking strategy, the perovskite thin film growth greatly reduces the dependence on a flexible conductive substrate through a simple doping method, and a perovskite thin film with high crystalline quality, large grain size and low defect density is obtained on the flexible conductive substrate. Based on the perovskite thin film, not only a high-efficiency flexible perovskite solar cell can be prepared, but also the preparation of a large-area flexible device is applicable. In addition, the organic small molecule is aggregated at a perovskite grain boundary after in-situ cross-linking, effectively releases mechanical stress in the bending process, and reduces the Young's modulus of the perovskite thin film, so that the obtained flexible device has excellent mechanical stability.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic materials, specifically relating to the application of in-situ crosslinkable organic small molecules in flexible perovskite solar cells, which can obtain highly efficient and mechanically stable flexible perovskite solar cells. Background Technology

[0002] Flexible perovskite solar cells possess unique advantages such as lightweight and flexibility, showing great promise for applications in portable electronics and building-integrated photovoltaics (BIPV). However, the growth of perovskite thin films is highly sensitive to the substrate material. Flexible conductive substrates with rough and wrinkled surfaces provide numerous nucleation sites, leading to over-crystallization during perovskite film growth. This results in small, irregularly shaped perovskite grains, severely impacting device performance. Consequently, the photoelectric conversion efficiency of flexible perovskite solar cells remains significantly lower than that of rigid perovskite solar cells. Furthermore, the inherent properties of polycrystalline perovskite thin films result in poor mechanical properties in flexible devices, leading to a substantial decrease in efficiency during bending, which severely hinders the commercialization of flexible perovskite solar cells.

[0003] To improve the quality of perovskite thin films, researchers have used small organic molecule additives containing S, N, or O atoms as molecular templates to reduce perovskite nucleation sites, thereby obtaining high-quality perovskite thin films with large grain sizes on flexible conductive substrates. For example, in the fabrication of perovskite solar cells, perovskite thin films prepared by adding passivation defect additives to the perovskite precursor solution serve as perovskite light-absorbing layers. The small molecule structures of the passivation defect additives include sulfonyl, carbonyl, amino, benzene ring, and fluorine groups. Existing technology discloses an electronically typed small molecule based on a perylene diimide-fluorene structure, its preparation method, and its application, belonging to the field of perovskite solar cell cathode interface materials and their preparation technology. However, during continuous device operation, the small molecule undergoes severe diffusion within the perovskite layer, leading to molecular migration between different functional layers. In existing technologies, elastomers such as polyurethane and polyacrylamide are used as grain boundary modification materials introduced into perovskite thin films. The low Young's modulus of elastomers helps release mechanical stress, thereby effectively reducing the Young's modulus of the perovskite thin film. However, the mechanical mixing of these long polymer chains can easily entangle the perovskite colloid, hindering the growth of perovskite crystals and leading to the formation of inhomogeneous and poorly crystallized perovskite films.

[0004] Therefore, there is an urgent need to explore an effective method that, without affecting the long-term stability of perovskite, can both regulate the crystallization of perovskite and improve the mechanical properties of perovskite films, so as to achieve the growth of high-quality, low Young's modulus perovskite films on flexible conductive substrates, and thus prepare flexible perovskite solar cells with high efficiency and excellent mechanical stability. Summary of the Invention

[0005] The purpose of this invention is to provide a flexible perovskite solar cell and its preparation method. By doping a perovskite precursor solution with organic small molecules that can be cross-linked in situ, a high-quality perovskite thin film is prepared on a flexible conductive substrate, thereby obtaining a highly efficient and mechanically stable flexible perovskite solar cell.

[0006] The in-situ crosslinkable small organic molecules designed in this invention, in addition to possessing highly active crosslinking groups (cyclic ethers, azides, alkenes, alkynes), also contain functional groups such as thiophene, carbazole, and carbonyl groups. These groups have coordination bonds with lead iodide, which not only affect the micellar state of the perovskite precursor solution but also further influence the film growth of lead iodide and perovskite. Due to the synergistic effect of the crosslinking groups and functional groups, they have the functions of regulating crystallization, passivating defects, promoting transport, and reducing modulus in perovskite.

[0007] This invention discloses a method for fabricating a flexible perovskite solar cell based on in-situ crosslinkable organic small molecules, comprising the following steps: fabricating an electron transport layer on a flexible conductive substrate; then spin-coating a perovskite precursor solution doped with in-situ crosslinkable organic small molecules onto the electron transport layer, followed by heat treatment to obtain a perovskite thin film layer; then sequentially fabricating a hole transport layer and an anode on the perovskite thin film to obtain a flexible perovskite solar cell based on in-situ crosslinkable organic small molecules, which has high quality and low Young's modulus.

[0008] The present invention also discloses a method for growing perovskite thin films on a flexible conductive substrate, comprising the following steps: preparing an electron transport layer on the flexible conductive substrate; then spin-coating a perovskite precursor solution doped with in-situ crosslinkable organic small molecules onto the electron transport layer; and then heat-treating to obtain a perovskite thin film layer.

[0009] In this invention, the heat treatment is performed at 140–160°C for 10–20 minutes; the perovskite solution doped with in-situ crosslinkable organic small molecules has a doping concentration of 1.0–2.5 mmol / mL, preferably 1.5–2.0 mmol / mL.

[0010] In this invention, the perovskite precursor solution is either a solution containing all perovskite precursors, or a solution containing a portion of the perovskite precursors and another solution containing the remaining portion of the perovskite precursors; the former is prepared using a one-step spin-coating method, preferably a one-step spin-coating anti-solvent method, while the latter is prepared using a two-step spin-coating method. This is a conventional method for preparing perovskite thin films. The inventiveness of this invention lies in the doping with small organic molecules that can be crosslinked in situ, without changing the perovskite raw material itself or its film preparation method.

[0011] As an example, when the perovskite precursor solution is a solution containing a portion of the perovskite precursor (such as lead iodide) and another solution containing the remaining portion of the perovskite precursor (such as formamidine FAI), a PbI2 solution doped with in-situ crosslinkable organic small molecules is spin-coated onto the electron transport layer, followed by annealing and then spin-coating with the FAI solution, and then heat treatment to obtain a perovskite thin film layer; or a PbI2 solution is spin-coated onto the electron transport layer, followed by annealing and then spin-coating with the FAI solution doped with in-situ crosslinkable organic small molecules, and then heat treatment to obtain a perovskite thin film layer. In the PbI2 solution doped with in-situ crosslinkable small organic molecules, the solvent is DMF, the concentration of PbI2 is 600–750 mg / mL, and the concentration of small molecule doping is 1.0–2.5 mmol / mL. Preferably, the concentration of PbI2 is 645–738 mg / mL, and the concentration of small molecule doping is 1.5–2.0 mmol / mL. In the FAI solution, the solvent is isopropanol, and the concentration is 90–110 mg / mL.

[0012] In this invention, the small molecule crosslinking reaction and perovskite growth occur simultaneously during the heat treatment process, achieving in-situ crosslinking to regulate perovskite crystallization, thereby obtaining a high-quality, low Young's modulus perovskite film on a flexible conductive substrate. The fabrication of the electron transport layer on the flexible conductive substrate, as well as the subsequent fabrication of the hole transport layer and the anode on the hole transport layer, are all existing technologies, resulting in a highly efficient and mechanically stable flexible perovskite solar cell.

[0013] This invention discloses a method for preparing perovskite layers that reduces the dependence of perovskite film growth on flexible conductive substrates, enabling the growth of high-quality, low Young's modulus perovskite films on flexible conductive substrates. Therefore, by increasing the area of ​​the flexible conductive substrate, high-quality, large-area perovskite films can be prepared, thereby obtaining high-efficiency, large-area flexible perovskite solar cells.

[0014] In this invention, the chemical structural formula of the in-situ crosslinkable small organic molecule is as follows:

[0015]

[0016] Wherein, A is an alkyl chain, a cycloalkane group, or a heterocyclic substituent; preferably, the alkyl chain or cycloalkane group has 1 to 20 carbon atoms; the chemical structural formula of the heterocyclic substituent is as follows:

[0017]

[0018] X is a substituent containing a lone pair of electrons, and the preferred chemical structure is as follows:

[0019]

[0020] This invention creatively introduces in-situ crosslinkable organic small molecules into the perovskite precursor solution to solve the problem of uncontrolled growth of perovskite films on flexible conductive substrates. This results in perovskite films with preferential crystal orientation, large grain size, and low defect density on flexible conductive substrates. Due to the improved film quality, this perovskite film can be used not only to fabricate high-efficiency flexible perovskite solar cells but also for large-area flexible perovskite solar cells. Furthermore, the in-situ crosslinking of the organic small molecules aggregates at the perovskite grain boundaries, effectively releasing mechanical stress and reducing the Young's modulus of the perovskite film. Therefore, the resulting flexible devices also possess excellent mechanical stability.

[0021] Beneficial effects of the present invention

[0022] 1. This invention grows a high-quality, low-Young's modulus perovskite thin film on a flexible conductive substrate by doping a perovskite precursor solution with an in-situ crosslinkable organic small molecule, and then prepares a highly efficient and mechanically stable flexible perovskite solar cell based on this film.

[0023] 2. This invention cleverly designs crosslinking groups and functional groups of organic small molecules that can be crosslinked in situ. Both groups regulate the morphology of lead iodide films and perovskite crystallization, greatly improving the uncontrollable growth of perovskite films on flexible conductive substrates. As a result, perovskite films comparable to those on glass substrates are obtained on flexible conductive substrates.

[0024] 3. The method for preparing perovskite thin films of the present invention is also applicable to the preparation of large-area flexible perovskite thin films, thereby obtaining high-efficiency large-area flexible perovskite solar cells.

[0025] 4. The preparation method of the present invention is simple, does not introduce an additional interface layer or post-processing process, and the product has excellent performance and is suitable for industrial production.

[0026] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail in the following embodiments and their accompanying drawings. Attached Figure Description

[0027] Figure 1 2,5-(3-methyloxetane)dicarboxylic acid thiophene 1 HNMR spectrum;

[0028] Figure 2 SEM images of cross-sections of flexible lead iodide films before and after doping with in-situ crosslinkable organic small molecules;

[0029] Figure 3FTIR spectra of perovskite films doped with in-situ crosslinkable organic small molecules at different annealing temperatures;

[0030] Figure 4 SEM images of the surface morphology of the flexible perovskite film before and after doping with organic small molecules that can be crosslinked in situ;

[0031] Figure 5 Current-voltage curve of perovskite solar cell (effective area 0.062 cm²) 2 );

[0032] Figure 6 The current-voltage curves of flexible perovskite solar cells based on different introduction schemes of in-situ crosslinkable organic small molecules are shown.

[0033] Figure 7 The current-voltage curves of flexible perovskite solar cells based on in-situ crosslinkable organic small molecules with different doping amounts are shown.

[0034] Figure 8 Current-voltage curves of flexible perovskite solar cells doped with different types of small organic molecules;

[0035] Figure 9 Current-voltage curves of flexible perovskite solar cells based on different perovskite systems with in-situ crosslinkable organic small molecules.

[0036] Figure 10 Steady-state fluorescence spectra of flexible perovskite films before and after doping with in-situ crosslinkable organic small molecules;

[0037] Figure 11 Current-voltage curves of flexible perovskite solar cells before and after doping with in-situ crosslinkable organic small molecules (effective area 1.004 cm²). 2 );

[0038] Figure 12 HR-TEM image of perovskite thin film after doping with organic small molecules that can be crosslinked in situ;

[0039] Figure 13 Load-unloading curves of perovskite films before and after doping with in-situ crosslinkable organic small molecules;

[0040] Figure 14 SEM image of the surface morphology of the flexible perovskite film after bending test;

[0041] Figure 15 The bending stability curves of flexible perovskite solar cells before and after doping with organic small molecules that can be crosslinked in situ;

[0042] Figure 16Environmental stability curves of flexible perovskite solar cells before and after doping with in-situ crosslinkable organic small molecules. Detailed Implementation

[0043] The detailed steps of the present invention for the preparation of a highly efficient and mechanically stable flexible perovskite solar cell based on in-situ crosslinkable organic small molecules are as follows:

[0044] (1) First, prepare a PbI2 DMF solution and a FAI isopropanol solution doped with organic small molecules that can be crosslinked in situ; or prepare a PbI2 DMF solution and a FAI isopropanol solution doped with organic small molecules that can be crosslinked in situ.

[0045] (2) Spin-coat a layer of SnO2 with a thickness of 30-50 nm onto a clean PET / ITO substrate;

[0046] (3) Spin-coat the prepared PbI2 solution onto SnO2 and anneal to obtain a lead iodide film; then spin-coat the FAI solution and anneal to obtain a perovskite film with a thickness of 500-700 nm; or spin-coat the PbI2 solution onto the SnO2 layer, anneal and then spin-coat the FAI solution doped with in-situ crosslinkable organic small molecules, and then heat-treat to obtain a perovskite film layer.

[0047] (4) Spin-coating Spiro-OMeTAD as a hole transport layer with a thickness of 100–120 nm;

[0048] (5) The electrode is a gold electrode, which is deposited by vacuum evaporation machine with a thickness of 100 nm.

[0049] This invention discloses four chemically structured in-situ crosslinkable organic small molecules. As an example, this invention discloses a method for preparing a representative in-situ crosslinkable organic small molecule.

[0050] A method for preparing thiophene ester (OETC), a crosslinkable organic small molecule, includes the following steps: thiophene-2,5-dicarboxylic acid, N,N-dicyclohexylcarbodiimide (DCC), and a catalytic amount of 4-diiminopyridine (DMAP) are added to a two-necked flask. The flask is purged several times with dry nitrogen, followed by the addition of purified dichloromethane and 3-methyl-3-oxetane-methanol. The reaction is carried out at room temperature for 12 h, followed by extraction and purification to obtain a white crystalline product. The above reaction process can be represented as follows:

[0051]

[0052] A method for preparing in-situ crosslinkable organic small molecule 2,6-disulfonylpyran (DSAP) includes the following steps: dissolving pyran-2,6-disulfonyl bromide in THF; dissolving sodium azide and 18-crown-6 in DMF; adding the DMF solution to the THF solution; and refluxing under a nitrogen atmosphere for 8 h. After extraction and purification, a yellow solid product is obtained. The above reaction process can be represented as follows:

[0053]

[0054] A method for preparing in-situ crosslinkable organic small molecule 2,5-diacrylate pyrrole (DAP) includes the following steps: pyrrole-2,5-diol, triethylamine (TEA), and dichloromethane (DCM) are added to a single-necked round-bottom flask and cooled to 0 °C. A dichloromethane solution of acryloyl chloride is added dropwise with stirring. After the addition is complete, the temperature is raised to room temperature and the reaction continues for 12 h. The product is purified by extraction and washing to obtain a yellow solid product. The above reaction process can be represented as follows:

[0055]

[0056] A method for preparing the in-situ crosslinkable organic small molecule 2,7-dipropynamide carbazole (DPAC) includes the following steps: carbazole-2,7-diamine and propynic acid are dissolved in DMF and added to a two-necked flask, followed by the addition of N,N-dicyclohexylcarbodiimide (DCC) and a catalytic amount of 4-diiminopyridine (DMAP), and the reaction is carried out at room temperature for 24 h. After extraction and purification, a white solid product is obtained. The above reaction process can be represented as follows:

[0057]

[0058] The present invention will be described in detail below with reference to the embodiments. All raw materials involved are existing products, and the specific preparation methods and performance testing are conventional techniques; PET / ITO is routinely cleaned before use as a flexible conductive substrate; ITO glass is routinely cleaned before use as a rigid conductive substrate.

[0059] The device's photoelectric performance was simulated using a Newport xenon lamp at AM 1.5G under a solar irradiance of 100 mW / cm². 2 Under these conditions, light intensity was obtained using a source meter (Keithley 2400) and calibrated using a standard silicon cell with a KG-5 filter. Steady-state power conversion efficiency was calculated by measuring the stable photocurrent density at a constant bias voltage (Vmax point), with the effective area of ​​the device corrected using precisely calibrated apertures (0.062 and 1.004 cm²). 2 ).

[0060] Example 1

[0061] A method for preparing an in-situ crosslinkable organic small molecule 2,5-(3-methyloxetane)dicarboxylic acid thiophene (OETC) specifically includes the following steps:

[0062] Thiophene-2,5-dicarboxylic acid (1 g, 5.8 mmol), N,N-dicyclohexylcarbodiimide (DCC) (1.2 g, 5.8 mmol), and 4-diiminopyridine (DMAP) (0.04 g, 0.3 mmol) were added to a 50 mL round-bottom flask. The flask was evacuated and rinsed three times with dry nitrogen, then purified dichloromethane (30 mL) and 3-methyl-3-oxetane-methanol (2.5 g, 24 mmol) were added. After stirring at room temperature for 12 h, byproducts were removed by filtration, and the filtrate was extracted three times with water and dichloromethane. The organic phase was collected and purified by column chromatography using neutral alumina with methanol / dichloromethane (1 / 10, v / v) as the developing solvent. The crude product was purified by silica gel chromatography to obtain a white crystalline product.

[0063] Figure 1 2,5-(3-methyloxetane)dicarboxylic acid thiophene (OETC) 1 HNMR image. 1 H NMR (300MHz, CDCl3) δ 7.78 (s, 2H), 4.59 (m, 4H), 4.43 (m, 8H), 1.42 (s, 6H).

[0064] Example 2

[0065] A method for growing a lead iodide-doped thin film on a flexible conductive substrate includes the following steps:

[0066] (1) First, prepare a PbI2 DMF solution doped with 1.8 mmol / mL of organic small molecule OETC that can be crosslinked in situ. The concentration of PbI2 is 692 mg / mL.

[0067] (2) Spin-coat a layer of SnO2 onto a clean PET / ITO using a tin dioxide dispersion (7.5% hydrocolloid), spin-coating at 3000 rpm and annealing at 120 ℃ for 40 min;

[0068] (3) Spin-coat the prepared PbI2 solution onto SnO2 and anneal it to obtain a lead iodide film. The rotation speed is 1500 rpm and the annealing temperature is 70℃ for 1 min.

[0069] A method for growing a lead iodide thin film on a flexible conductive substrate includes the following steps:

[0070] (1) First, prepare a PbI2 DMF solution with a PbI2 concentration of 692 mg / mL;

[0071] (2) Spin-coat a layer of SnO2 onto a clean PET / ITO using a tin dioxide dispersion (7.5% hydrocolloid), spin-coating at 3000 rpm and annealing at 120 ℃ for 40 min;

[0072] (3) Spin-coat the prepared PbI2 solution onto SnO2 and anneal it to obtain a lead iodide film. The rotation speed is 1500 rpm and the annealing temperature is 70℃ for 1 min.

[0073] like Figure 2 The image shows cross-sectional SEM images of the doped and undoped lead iodide films. The doped lead iodide film exhibits a sparse and porous morphology.

[0074] Example 3

[0075] A method for preparing a flexible perovskite thin film doped with in-situ crosslinkable organic small molecules includes the following steps:

[0076] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) doped with 1.8 mmol / mL in situ crosslinkable organic small molecule DSAP and a FAI isopropanol solution (concentration is 90 mg / mL).

[0077] (2) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto a clean silicon wafer substrate and annealed to obtain a lead iodide film at 1500 rpm and 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film.

[0078] (3) Then, the films were annealed at 25 °C, 70 °C, 110 °C and 150 °C for 15 min to obtain doped perovskite films.

[0079] A method for preparing a flexible perovskite thin film includes the following steps:

[0080] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) and a FAI isopropanol solution (concentration is 90 mg / mL).

[0081] (2) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto a clean silicon wafer substrate and annealed to obtain a lead iodide film at 1500 rpm and 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film.

[0082] (3) Then anneal at 150 °C for 15 min to obtain an undoped perovskite film.

[0083] The prepared thin film was used for FTIR testing, such as... Figure 3 The image shows the FTIR spectra of perovskite films doped with in-situ crosslinkable organic small molecules at different annealing temperatures. FTIR measurements indicate that at low-temperature annealing conditions (25 °C and 70 °C), the vibrational peaks of the crosslinking groups (1270 and 820 cm⁻¹) are significantly different. -1 The presence of these characteristic peaks indicates that no crosslinking occurs under these conditions. However, as the temperature increases to 150 °C, these characteristic peaks gradually disappear, indicating that at the specific annealing temperature of perovskite, organic small molecules undergo in-situ crosslinking along with the growth of the perovskite film.

[0084] Example 4

[0085] A method for growing high-quality perovskite thin films on a flexible conductive substrate includes the following steps:

[0086] (1) First, prepare a PbI2 DMF solution (PbI2 concentration of 692 mg / mL) and a FAI isopropanol solution (concentration of 90 mg / mL) doped with 1.8 mmol / mL of in-situ crosslinkable organic small molecules OETC or DSAP respectively.

[0087] (2) Spin-coat a layer of SnO2 onto a clean PET / ITO using a tin dioxide dispersion (7.5% hydrocolloid), spin-coating at 3000 rpm and annealing at 120 ℃ for 40 min;

[0088] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film. The rotation speed was 1500 rpm and the film was annealed at 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. The film was annealed on a hot plate at 150°C for 15 min to obtain a doped OETC perovskite film or a doped DSAP perovskite film.

[0089] A method for growing perovskite thin films on a flexible conductive substrate includes the following steps:

[0090] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) and a FAI isopropanol solution (concentration is 90 mg / mL).

[0091] (2) Spin-coat a layer of SnO2 onto a clean PET / ITO using a tin dioxide dispersion (7.5% hydrocolloid), spin-coating at 3000 rpm and annealing at 120 ℃ for 40 min;

[0092] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film. The rotation speed was 1500 rpm and the film was annealed at 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. The film was annealed on a hot plate at 150°C for 15 min to obtain an undoped perovskite film.

[0093] like Figure 4 The figure shows the SEM surface morphology of the above-mentioned flexible perovskite film. As can be seen from the figure, the perovskite grains doped with OETC and DSAP are relatively uniform and dense, and can also form relatively large grains, which is in stark contrast to the small and irregular grains of the undoped film. Therefore, the present invention solves the problem of poor growth of perovskite film on flexible conductive substrate.

[0094] Example 5

[0095] A high-efficiency flexible perovskite solar cell (effective area 0.062 cm²) 2 The preparation method of ) includes the following steps:

[0096] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) doped with 1.8 mmol / mL organic small molecule DAP that can be crosslinked in situ and a FAI isopropanol solution (concentration is 90 mg / mL).

[0097] (2) In a clean 1.5×1.5 cm 2 A layer of SnO2 was spin-coated onto a flexible conductive substrate using a tin dioxide dispersion (7.5% aqueous colloid). The spin-coating speed was 3000 rpm, and the substrate was annealed at 120 °C for 40 min.

[0098] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film at 1500 rpm and 70 °C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. Finally, the film was annealed on a hot plate at 150 °C for 15 min to obtain the perovskite film.

[0099] (4) Spiro-OMeTAD was prepared on the perovskite film as a hole transport layer. The solvent was chlorobenzene with a concentration of 72.3 mg / mL and the spin coating speed was 2000 rpm.

[0100] (5) The thin film was placed in a vacuum coating machine to deposit gold electrodes with a thickness of 100 nm, resulting in an effective area of ​​0.062 cm². 2 Doped flexible perovskite solar cells.

[0101] By replacing the flexible conductive substrate with a rigid conductive substrate, while keeping everything else the same, a doped rigid perovskite solar cell is obtained.

[0102] A flexible perovskite solar cell (effective area 0.062 cm²) 2 The preparation method of ) includes the following steps:

[0103] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) and a FAI isopropanol solution (concentration is 90 mg / mL).

[0104] (2) In a clean 1.5×1.5 cm 2 A layer of SnO2 was spin-coated onto a flexible conductive substrate using a tin dioxide dispersion (7.5% aqueous colloid). The spin-coating speed was 3000 rpm, and the substrate was annealed at 120 °C for 40 min.

[0105] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film at 1500 rpm and 70 °C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. Finally, the film was annealed on a hot plate at 150 °C for 15 min to obtain the perovskite film.

[0106] (4) Spiro-OMeTAD was prepared on the perovskite film as a hole transport layer. The solvent was chlorobenzene with a concentration of 72.3 mg / mL and the spin coating speed was 2000 rpm.

[0107] (5) The thin film was placed in a vacuum coating machine to deposit gold electrodes with a thickness of 100 nm, resulting in an effective area of ​​0.062 cm². 2 Undoped flexible perovskite solar cells.

[0108] By replacing the flexible conductive substrate with a rigid conductive substrate, and keeping everything else the same, an undoped rigid perovskite solar cell is obtained.

[0109] Comparing the performance of the perovskite solar cells in Example 5, we obtain Figure 5 (Current-voltage curve of perovskite solar cell (effective area 0.062 cm²)) 2 According to Table 1, the light intensity is AM1.5G 100 mW / cm². 2 .

[0110]

[0111] from Figure 5As shown in Table 1, doping the perovskite bulk with the in-situ crosslinkable organic small molecules of this invention significantly improves both the circuit voltage and fill factor in both flexible and rigid devices, thereby achieving PCEs exceeding 23% and 24% (effective area 0.062 cm²) in flexible and rigid devices, respectively. 2 Studies have shown that flexible perovskite solar cells prepared using the in-situ crosslinkable organic small molecules of this invention can improve the uncontrollable growth of perovskite films on flexible conductive substrates through a simple doping method. This results in perovskite films with similar morphologies on both flexible and rigid conductive substrates, exhibiting high crystallinity, large grain size, and low defect density, thereby promoting charge transport and reducing non-radiative recombination. Without doping with the in-situ crosslinkable organic small molecules, the PCE difference between rigid and flexible substrates is 2.36%, mainly due to a significant difference in FF (force factor). However, after doping with the in-situ crosslinkable organic small molecules, the difference between the two decreases to 0.65%, demonstrating the unique advantages of doping with these molecules.

[0112] Example 6: OETC-Modified Flexible Perovskite Solar Cell

[0113] Solution preparation: Isopropanol solution of OETC (1.8 mmol / mL) capable of in-situ crosslinking; PbI2 DMF solution doped with 1.8 mmol / mL OETC capable of in-situ crosslinking (PbI2 concentration 692 mg / mL); PbI2 DMF solution, concentration 692 mg / mL; FAI isopropanol solution, concentration 90 mg / mL; FAI isopropanol solution doped with 1.8 mmol / mL OETC capable of in-situ crosslinking (FAI concentration 90 mg / mL).

[0114] In a clean 1.5 × 1.5 cm 2 A layer of SnO2 was spin-coated onto a flexible conductive substrate using a tin dioxide dispersion (7.5% aqueous colloid). The spin-coating speed was 3000 rpm, and the substrate was annealed at 120 °C for 40 min.

[0115] The perovskite thin films were prepared using the following methods:

[0116] (1) Introduction of perovskite lower interface: OETC solution was spin-coated onto SnO2 and annealed to obtain cross-linked polymer at 3000 rpm and 150 ℃ for 5 min; then lead iodide solution was spin-coated onto the OETC film and annealed to obtain lead iodide film at 1500 rpm and 70 ℃ for 1 min; FAI solution was spin-coated onto the dry PbI2 film; then annealed on a hot plate at 150 ℃ for 15 min to obtain perovskite film;

[0117] (2) Introducing the perovskite interface: PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film at 1500 rpm and 70 °C for 1 min. Then, FAI solution was spin-coated onto the dried PbI2 film. The film was then annealed at 150 °C for 15 min on a hot plate to obtain a film. OETC solution was spin-coated onto the film and annealed to obtain a perovskite film at 3000 rpm and 150 °C for 5 min.

[0118] (3) FAI doping: PbI2 solution was spin-coated onto SnO2 and annealed to obtain lead iodide film at 1500 rpm and 70℃ for 1 min. Then, FAI solution doped with OETC was spin-coated onto the dry PbI2 film. Then, it was annealed on a hot plate at 150℃ for 15 min to obtain perovskite film.

[0119] (4) PbI2 doping: The PbI2 solution doped with OETC was spin-coated onto SnO2 and annealed to obtain a lead iodide film at 1500 rpm and 70 °C for 1 min. Then, FAI solution was spin-coated onto the dried PbI2 film. Finally, the film was annealed on a hot plate at 150 °C for 15 min to obtain a perovskite film.

[0120] Spiro-OMeTAD was then prepared as a hole transport layer on the perovskite film using chlorobenzene at a concentration of 72.3 mg / mL as the solvent, and spin-coated at 2000 rpm. A gold electrode with a thickness of 100 nm was then deposited on the film using a vacuum deposition machine, resulting in an effective area of ​​0.062 cm². 2 The flexible perovskite solar cells consist of four cells.

[0121] The performance of the above-mentioned flexible perovskite solar cells is as follows: Figure 6 (Current-voltage curves of flexible perovskite solar cells based on different introduction schemes of in-situ crosslinkable organic small molecules) and Table 2, with a light intensity of AM1.5G 100 mW / cm². 2 For undoped batteries, see Example 5.

[0122]

[0123] In-situ crosslinking with small organic molecules offers advantages in regulating perovskite crystallization and passivating defects. In particular, doping with PbI2 can control the PbI2 micelle size, resulting in a mesoporous structure in the PbI2 film doped with in-situ crosslinkable small organic molecules. This facilitates the subsequent full reaction between PbI2 and FAI. Therefore, this approach yields the best results in introducing in-situ crosslinkable small organic molecules, achieving a PCE exceeding 23% for flexible devices. In contrast, the technique of crosslinking polymer layers at the upper and lower interfaces offers minimal improvement in battery performance.

[0124] Example 7: Flexible perovskite solar cells modified with different amounts of OETC

[0125] The optimal doping level screening experiment for in-situ crosslinkable small organic molecules includes the following steps:

[0126] (1) First, PbI2 DMF solution (PbI2 concentration of 692 mg / mL) and FAI isopropanol solution (concentration of 90 mg / mL) of in-situ crosslinkable organic small molecules OETC with different doping amounts (1.5, 2.1 mmol / mL) were prepared respectively.

[0127] (2) In a clean 1.5×1.5 cm 2 A layer of SnO2 was spin-coated onto a flexible conductive substrate using a tin dioxide dispersion (7.5% aqueous colloid). The spin-coating speed was 3000 rpm, and the substrate was annealed at 120 °C for 40 min.

[0128] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film at 1500 rpm and 70 °C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. Finally, the film was annealed on a hot plate at 150 °C for 15 min to obtain the perovskite film.

[0129] (4) Spiro-OMeTAD was prepared as a hole transport layer on a perovskite film. The solvent was chlorobenzene with a concentration of 72.3 mg / mL, and the spin coating speed was 2000 rpm.

[0130] (5) The thin film was placed in a vacuum coating machine to deposit gold electrodes with a thickness of 100 nm, resulting in an effective area of ​​0.062 cm². 2 Flexible perovskite solar cells.

[0131] The performance of flexible perovskite solar cells with different doping levels is shown in the figure. Figure 7 (Current-voltage curves of flexible perovskite solar cells based on in-situ crosslinkable organic small molecules with different doping amounts) and Table 3, with a light intensity of AM1.5G 100 mW / cm. 2 Undoped batteries are shown in Example 5, and 1.8 mmol / mL is shown in Example 6 (4).

[0132]

[0133] Doping with in-situ crosslinkable organic small molecules (OETC) significantly improves the PCE of flexible devices, mainly in the following ways: V OCThe increase in FF indicates that this invention, using a simple doping method, can improve the uncontrollable growth of perovskite films on flexible conductive substrates, thereby obtaining perovskite films with high crystallinity, large grain size, and low defect density, which in turn promotes charge transport and reduces non-radiative recombination. When the doping concentration is 1.8 mmol / mL, V OC Reaching 1.14 V ， FF reached 0.82, achieving a PCE of 23.41%.

[0134] Example 8

[0135]

[0136] (1) Prepare a PbI2 DMF solution (PbI2 concentration of 692 mg / mL) doped with 1.8 mmol / mL organic small molecule MOPT (2,5-di(4-methyl-4-oxacyclobutanepropyl)thiophene) and a FAI isopropanol solution (concentration of 90 mg / mL).

[0137] (2) In a clean 1.5×1.5 cm 2 A layer of SnO2 was spin-coated onto a flexible conductive substrate using a tin dioxide dispersion (7.5% aqueous colloid). The spin-coating speed was 3000 rpm, and the substrate was annealed at 120 °C for 40 min.

[0138] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film at 1500 rpm and 70 °C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. Finally, the film was annealed on a hot plate at 150 °C for 15 min to obtain the perovskite film.

[0139] (4) Spiro-OMeTAD was prepared as a hole transport layer on a perovskite film. The solvent was chlorobenzene with a concentration of 72.3 mg / mL, and the spin coating speed was 2000 rpm.

[0140] (5) The thin film was placed in a vacuum coating machine to deposit gold electrodes with a thickness of 100 nm, resulting in an effective area of ​​0.062 cm². 2 A doped MOPT flexible perovskite solar cell.

[0141] Based on the above method, the PbI2 DMF solution doped with 1.8 mmol / mL organic small molecule MOPT was replaced with a PbI2 DMF solution doped with 1.8 mmol / mL organic small molecule MOTC (2,5-(3-methoxypropyl)dicarboxylic acid thiophene) (PbI2 concentration of 692 mg / mL), and the rest remained the same, to obtain a MOTC-doped flexible perovskite solar cell.

[0142] The performance of flexible perovskite solar cells with different doped compounds is shown in the figure. Figure 8 (Current-voltage curves of flexible perovskite solar cells doped with different types of small organic molecules) and Table 4, with a light intensity of AM1.5G 100 mW / cm². 2 Undoped batteries are shown in Example 5, and OETC-doped batteries are shown in Example 6 (4).

[0143]

[0144] Example 9

[0145] (1) Two different perovskite precursor solutions were designed: FAPbI3 system: PbI2 (1.5 M), FAI (1.5 M), MACl (0.45 M) were dissolved in a mixed solvent DMF:DMSO = 4:1 (volume ratio); Trication system: PbI2 (1.190 M), PbBr2 (0.155 M), CsI (0.105 M), FAI (1.040 M), MABr (0.155 M) were dissolved in a mixed solvent DMF:DMSO = 4:1 (volume ratio); In situ crosslinkable organic small molecule OETC with a doping concentration of 1.8 mmol / mL was added to the two perovskite precursor solutions respectively.

[0146] (2) In a clean 1.5×1.5 cm 2 A layer of SnO2 was spin-coated onto a flexible conductive substrate using a tin dioxide dispersion (7.5% aqueous colloid). The spin-coating speed was 3000 rpm, and the substrate was annealed at 120 °C for 40 min.

[0147] (3) Preparation of perovskite layer by anti-solvent method: The two prepared perovskite precursor solutions were spin-coated onto SnO2 at a speed of 1000 rpm for 10 s, followed by spin-coating at a speed of 5000 rpm for 30 s. At the 15th second of the second step, 100 mL of chlorobenzene was dropped onto the film. The film was then annealed on a hot plate at 150 °C for 15 min.

[0148] (4) Spiro-OMeTAD was prepared as a hole transport layer on a perovskite film. The solvent was chlorobenzene with a concentration of 72.3 mg / mL, and the spin coating speed was 2000 rpm.

[0149] (5) The thin film was placed in a vacuum coating machine to deposit gold electrodes with a thickness of 100 nm, resulting in an effective area of ​​0.062 cm². 2 Flexible perovskite solar cells.

[0150] Based on the above preparation method, by omitting the OETC doping, an undoped flexible perovskite solar cell is obtained.

[0151] The performance of the above flexible perovskite solar cells is shown in [link to performance data]. Figure 9 (Current-voltage curves of flexible perovskite solar cells with in-situ crosslinkable organic small molecules introduced based on different perovskite systems) and Table 5, with a light intensity of AM1.5G 100 mW / cm. 2 .

[0152]

[0153] Even in different perovskite systems using a one-step antisolvent method, doping the perovskite precursor solution with in-situ crosslinkable organic small molecules can still improve the photovoltaic performance of flexible devices, demonstrating the good universality of this invention.

[0154] Example 10

[0155] A method for growing large-area, high-quality flexible perovskite thin films includes the following steps:

[0156] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) doped with 1.8 mmol / mL organic small molecule DAP that can be crosslinked in situ and a FAI isopropanol solution (concentration is 90 mg / mL).

[0157] (2) In a clean 2×2 cm 2 A layer of SnO2 was spin-coated onto PET / ITO using a tin dioxide dispersion (7.5% hydrocolloid) at a spin speed of 3000 rpm, followed by annealing at 120 ℃ for 40 min.

[0158] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film. The rotation speed was 1500 rpm and the film was annealed at 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. The film was annealed on a hot stage at 150°C for 15 min to obtain a doped perovskite film.

[0159] A method for growing large-area flexible perovskite thin films includes the following steps:

[0160] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) and a FAI isopropanol solution (concentration is 90 mg / mL).

[0161] (2) In a clean 2×2 cm 2 A layer of SnO2 was spin-coated onto PET / ITO using a tin dioxide dispersion (7.5% hydrocolloid) at a spin speed of 3000 rpm, followed by annealing at 120 ℃ for 40 min.

[0162] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film. The rotation speed was 1500 rpm and the film was annealed at 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. The film was annealed on a hot plate at 150°C for 15 min to obtain an undoped perovskite film.

[0163] See Figure 10 The figure shows the steady-state fluorescence spectrum of the flexible perovskite film. As can be seen from the figure, even on a large-area flexible conductive substrate, the doped perovskite film has a more uniform surface and exhibits stronger fluorescence intensity.

[0164] Example 11

[0165] A method for fabricating a high-efficiency, large-area flexible perovskite solar cell includes the following steps:

[0166] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) doped with 1.8 mmol / mL organic small molecule DAP that can be crosslinked in situ and a FAI isopropanol solution (concentration is 90 mg / mL).

[0167] (2) In a clean 2×2 cm 2 A layer of SnO2 was spin-coated onto a flexible conductive substrate using a tin dioxide dispersion (7.5% aqueous colloid). The spin-coating speed was 3000 rpm, and the substrate was annealed at 120 °C for 40 min.

[0168] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film at 1500 rpm and 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. The film was annealed on a hot plate at 150°C for 15 min to obtain the perovskite film.

[0169] (4) Spiro-OMeTAD was prepared as a hole transport layer on a perovskite film. The solvent was chlorobenzene with a concentration of 72.3 mg / mL, and the spin coating speed was 2000 rpm.

[0170] (5) The thin film was placed in a vacuum coating machine to deposit gold electrodes, and finally an effective area of ​​1.004 cm² was obtained. 2 Doped flexible perovskite solar cells.

[0171] A method for fabricating a large-area flexible perovskite solar cell includes the following steps:

[0172] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) and a FAI isopropanol solution (concentration is 90 mg / mL).

[0173] (2) In a clean 2×2 cm 2 A layer of SnO2 was spin-coated onto a flexible conductive substrate using a tin dioxide dispersion (7.5% aqueous colloid). The spin-coating speed was 3000 rpm, and the substrate was annealed at 120 °C for 40 min.

[0174] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film at 1500 rpm and 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. The film was annealed on a hot plate at 150°C for 15 min to obtain the perovskite film.

[0175] (4) Spiro-OMeTAD was prepared as a hole transport layer on a perovskite film. The solvent was chlorobenzene with a concentration of 72.3 mg / mL, and the spin coating speed was 2000 rpm.

[0176] (5) Place the thin film in a vacuum coating machine to deposit gold electrodes, and finally obtain an undoped flexible perovskite solar cell.

[0177] The performance of the above flexible perovskite solar cells was tested using standard methods, and the results were obtained. Figure 11 The image shows the current-voltage curve of a flexible perovskite solar cell (effective area 1.004 cm²). 2 (See Table 6) and the light intensity is AM1.5G 100 mW / cm². 2 .

[0178]

[0179] from Figure 11As shown in Table 6, during the fabrication of large-area flexible perovskite solar cells, doping the in-situ crosslinkable organic small molecules described in this invention into the perovskite matrix significantly improves all parameters of the device, thereby obtaining a large-area flexible perovskite solar cell with a photoelectric conversion efficiency exceeding 21% (effective area 1.004 cm²). 2 Studies have shown that flexible perovskite solar cells prepared using the in-situ crosslinkable organic small molecules described in this invention, through a simple doping method, can not only improve the uncontrollable growth of perovskite films on flexible conductive substrates, but also reduce the dependence of perovskite growth on substrate area. This results in flat, uniform perovskite films with low defect density on larger flexible conductive substrates, thereby promoting charge transport, reducing non-radiative recombination, and ultimately obtaining high-efficiency large-area flexible perovskite solar cells.

[0180] Mechanical properties of perovskite thin films. A method for preparing DPAC-doped perovskite thin films, comprising the following steps:

[0181] (1) First, prepare a PbI2 DMF solution (PbI2 concentration is 692 mg / mL) doped with 1.8 mmol / mL in situ crosslinkable organic small molecule DPAC and a FAI isopropanol solution (concentration is 90 mg / mL).

[0182] (2) Spin-coat a layer of SnO2 onto a clean PET / ITO using a tin dioxide dispersion (7.5% hydrocolloid), spin-coating at 3000 rpm and annealing at 120 ℃ for 40 min;

[0183] (3) A two-step method was used to prepare the perovskite layer. The prepared PbI2 solution was spin-coated onto SnO2 and annealed to obtain a lead iodide film. The rotation speed was 1500 rpm and the film was annealed at 70°C for 1 min. Then, FAI isopropanol solution was spin-coated onto the dried PbI2 film. The film was annealed on a hot stage at 150°C for 15 min to obtain a doped DPAC perovskite film.

[0184] See Example 4 for both doped and undoped OETC perovskite films.

[0185] 1. HR-TEM was performed on a perovskite film doped with DPAC, a small organic molecule that can be crosslinked in situ, to obtain... Figure 12 As shown in the figure, the lattice plane spacing of the crystalline region (region 1) is 3.1 Å, which matches the (100) plane of the α phase FAPbI3 very well, indicating that the cross-linked polymer did not enter the perovskite lattice. In addition, the amorphous region at the grain boundary (region 2) indicates that the cross-linked polymer aggregated along the grain boundary, filling the gaps between adjacent grains.

[0186] 2. Nanoindentation tests were performed on perovskite films before and after doping with in-situ crosslinkable organic small molecules DPAC or OETC to obtain... Figure 13 The loading-unloading curves shown are used to calculate the Young's modulus of the perovskite films. The results show that the Young's modulus of the perovskite films is significantly reduced after doping with in-situ crosslinkable organic small molecules. The Young's modulus of the undoped perovskite film is 41.2 GPa, that of the DPAC-doped film is 32.5 GPa, and that of the OETC-doped film is 30.3 GPa.

[0187] 3. The prepared film was cyclically bent 2000 times under a bending radius of 5 mm; the bent film was then used for SEM testing, such as... Figure 14 As shown in the figure, the SEM surface morphology of the flexible perovskite film after bending test is shown. It can be seen from the figure that the undoped perovskite film has obvious cracks on the surface after 2000 cycles of bending, while the perovskite film doped with DPAC or OETC is almost undamaged. This indicates that the doping of organic small molecules that can be crosslinked in situ effectively improves the bending resistance of the perovskite film.

[0188] Mechanical properties of perovskite solar cells. A MOTC-doped flexible perovskite solar cell is shown in Example 8. An undoped flexible perovskite cell is shown in Example 5; a MOTC-doped flexible perovskite solar cell is shown in Example 6, scheme (4).

[0189] 1. The mechanical stability of the prepared flexible perovskite solar cell was tested under a bending radius of 5 mm. Figure 15 The figure shows the bending stability curves of flexible perovskite solar cells. As shown, the undoped flexible perovskite solar cell retains only 41% of its initial efficiency after 2000 bending cycles; the MOTC-doped version retains 65% of its initial efficiency, showing limited performance improvement; while the non-self-crosslinked OETC-doped flexible perovskite solar cell retains 93% of its initial efficiency even after 5000 bending cycles. This indicates that the in-situ crosslinking of small organic molecules aggregates at the perovskite grain boundaries, effectively releasing the mechanical stress during bending and reducing the Young's modulus of the perovskite film, thus resulting in flexible devices with excellent mechanical stability.

[0190] 2. The prepared flexible perovskite solar cells were placed in an environment with a temperature of 25 ℃ and a humidity of about 30% to test their environmental stability. Figure 16The figure shows the environmental stability curves of flexible perovskite solar cells doped with organic small molecules and those without. As shown, the undoped flexible perovskite solar cell retains only 29% of its initial efficiency after 1000 hours of storage; the MOTC-doped cell retains 72% of its initial efficiency, showing limited performance improvement. This indicates that although small molecule doping provides some defect passivation, it can also lead to ion migration during long-term storage, thus affecting device stability. In contrast, the OETC-doped flexible perovskite solar cell retains 91% of its initial efficiency after 1000 hours. This demonstrates that doping with in-situ crosslinkable organic small molecules improves the hydrophobicity of the perovskite film, resulting in flexible devices with excellent environmental stability.

[0191] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A flexible perovskite solar cell based on in-situ crosslinkable organic small molecules, comprising a perovskite layer, characterized in that, The raw materials for preparing the perovskite layer include in-situ crosslinkable organic small molecules; the chemical structural formula of the in-situ crosslinkable organic small molecules is selected from: ； The chemical structural formula of A is selected from: ； The chemical structural formula of X is selected from: 。 2. The flexible perovskite solar cell based on in-situ crosslinkable small organic molecules according to claim 1, characterized in that, The raw materials for preparing the perovskite layer include a perovskite precursor solution doped with small organic molecules that can be crosslinked in situ.

3. The method for preparing flexible perovskite solar cells based on in-situ crosslinkable organic small molecules as described in claim 1, characterized in that, The process includes the following steps: preparing an electron transport layer on a flexible conductive substrate; then spin-coating a perovskite precursor solution doped with in-situ crosslinkable organic small molecules onto the electron transport layer, followed by heat treatment to obtain a perovskite thin film layer; and then sequentially preparing a hole transport layer and an anode on the perovskite thin film to obtain a flexible perovskite solar cell based on in-situ crosslinkable organic small molecules.

4. The method for preparing a flexible perovskite solar cell based on in-situ crosslinkable organic small molecules according to claim 3, characterized in that, The heat treatment is carried out at 140-160℃ for 10-20 minutes.

5. The method for preparing a flexible perovskite solar cell based on in-situ crosslinkable organic small molecules according to claim 3, characterized in that, In perovskite solutions doped with in-situ crosslinkable small organic molecules, the doping concentration is 1.0–2.5 mmol / mL.

6. A method for preparing perovskite thin films modified by in-situ crosslinkable organic small molecules, characterized in that, The process includes the following steps: preparing an electron transport layer on a flexible conductive substrate; spin-coating a perovskite precursor solution doped with in-situ crosslinkable organic small molecules onto the electron transport layer; and then heat-treating to obtain a perovskite thin film layer; wherein the chemical structural formula of the in-situ crosslinkable organic small molecules is selected from: ； The chemical structural formula of A is selected from: ； The chemical structural formula of X is selected from: 。 7. The application of in-situ crosslinkable organic small molecules in the preparation of flexible perovskite solar cells, characterized in that, The chemical structural formula of the in-situ crosslinkable organic small molecule is selected from: ； The chemical structural formula of A is selected from: ； The chemical structural formula of X is selected from: 。 8. The application of in-situ crosslinkable organic small molecules in the fabrication of large-area flexible perovskite solar cells, characterized in that, The chemical structural formula of the in-situ crosslinkable organic small molecule is selected from: ； The chemical structural formula of A is selected from: ； The chemical structural formula of X is selected from: 。 9. The application of in-situ crosslinkable organic small molecules in improving the efficiency and / or mechanical properties of flexible perovskite solar cells, characterized in that, The chemical structural formula of the in-situ crosslinkable organic small molecule is selected from: ； The chemical structural formula of A is selected from: ； The chemical structural formula of X is selected from: 。 10. The application of the flexible perovskite solar cell based on in-situ crosslinkable organic small molecules as described in claim 1 in the fabrication of large-area flexible devices.

11. The application of in-situ crosslinkable organic small molecules in the preparation of flexible perovskite thin films, characterized in that, The chemical structural formula of the in-situ crosslinkable organic small molecule is selected from: ； The chemical structural formula of A is selected from: ； The chemical structural formula of X is selected from: 。

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