A perovskite solar cell and its fabrication method

Abstract

This invention discloses a perovskite solar cell and its fabrication method, including the step of preparing a perovskite light-absorbing layer. The step of preparing the perovskite light-absorbing layer includes: spin-coating a dissolved lead iodide precursor solution onto a substrate with a carrier transport layer deposited on its surface, followed by heat treatment to obtain a lead iodide thin film; spin-coating an organic ammonium halide salt solution containing a hydroxybenzoic acid crosslinking agent onto the lead iodide thin film, followed by heat treatment to obtain a perovskite thin film; wherein the hydroxybenzoic acid crosslinking agent contains at least hydroxyl, carboxyl, and benzene rings. The perovskite light-absorbing layer prepared by this method exhibits significantly improved performance.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a perovskite solar cell and its fabrication method. Background Technology

[0002] Flexible perovskite solar cells have attracted widespread attention due to their advantages such as flexibility, light weight, high power-to-weight ratio, low cost, and low-temperature processing capability. In recent years, the development of flexible perovskite solar cells has been rapid, with improvements in efficiency and stability to some extent; however, there is still a gap before industrialization. Currently, some publicly available flexible perovskite solar cell designs still have relatively high Young's modulus in the perovskite thin film, making it brittle under mechanical stress. This results in the perovskite thin film being prone to breakage during bending and stretching, leading to poor mechanical stability. Furthermore, some designs fail to maintain conductivity while improving mechanical stability, resulting in decreased conductivity in the photoelectric absorption layer, affecting carrier transport and limiting the photoelectric conversion efficiency. Summary of the Invention

[0003] This invention provides a perovskite solar cell and its preparation method. By modifying the perovskite layer with a hydroxybenzoic acid-based crosslinking agent, the aforementioned shortcomings of the prior art are overcome. Therefore, the modified perovskite solar cell not only has excellent photoelectric conversion efficiency but also outstanding mechanical stability. In addition, the preparation method is simple and easy to implement for industrial application.

[0004] This invention provides a method for fabricating a perovskite solar cell, including the step of fabricating a perovskite light-absorbing layer on a substrate, wherein the perovskite light-absorbing layer is obtained by modification with a hydroxybenzoic acid crosslinking agent; the step of fabricating the perovskite light-absorbing layer includes:

[0005] The dissolved lead iodide precursor solution was spin-coated onto a substrate with a carrier transport layer deposited on its surface, and then heated to obtain a lead iodide thin film.

[0006] An organic ammonium halide salt solution containing hydroxybenzoic acid crosslinking agent was spin-coated onto the lead iodide film, and then heated to obtain a perovskite light-absorbing layer located on the charge carrier transport layer.

[0007] The hydroxybenzoic acid crosslinking agent contains at least hydroxyl, carboxyl and benzene rings.

[0008] In some embodiments, the hydroxybenzoic acid crosslinking agent is one of p-hydroxybenzoic acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxyterephthalic acid, and 2-hydroxy-1,3,5-benzenetriacic acid.

[0009] In some embodiments, a lead iodide precursor solution is spin-coated onto a substrate with a carrier transport layer deposited on its surface, and then heated to obtain a lead iodide thin film, specifically including:

[0010] Lead iodide was dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and then spin-coated and annealed to obtain the lead iodide film.

[0011] An organic ammonium halide salt solution containing a hydroxybenzoic acid crosslinking agent is spin-coated onto the lead iodide film, and then heated to obtain a perovskite light-absorbing layer located on the carrier transport layer, specifically comprising:

[0012] MA containing the aforementioned hydroxybenzoic acid crosslinking agent x FA 1-x Br y I z Cl 1-y-z An organic ammonium halide salt solution is spin-coated onto the lead iodide film and then heat-treated to obtain a perovskite light-absorbing layer in contact with the carrier transport layer; where x is a number less than 1, and y and z are numbers less than 1.

[0013] In some embodiments, the spin-coating and annealing conditions for preparing the lead iodide film include: a spin-coating rate in the range of 1700–1800 r / min and a spin-coating time in the range of 25–35 s; and an annealing temperature on a heating stage in the range of 70–100 °C and an annealing time in the range of 1–2 min.

[0014] The spin-coating and annealing conditions for preparing the perovskite light-absorbing layer include: a spin-coating rate of 1500–1700 r / min and a spin-coating time of 20–60 s; an annealing time on a heating stage of 10–60 min and an annealing temperature of 80–120 °C.

[0015] In some embodiments, the volume ratio of the mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is 19:1; MA containing the hydroxybenzoic acid crosslinking agent x FA 1-x Br y I z Cl 1-y-z The concentration of hydroxybenzoic acid crosslinking agents in organohalogen ammonium salt solutions is 1–2 mmol / mL;

[0016] The organic ammonium halide salt mixed solution is a mixture of formammonium iodide (FAI), methylammonium bromide (MABr), and methylammonium chloride (MACl), which is then dissolved in isopropanol solution to form MA. x FA 1-x Br y I zCl 1-y-z Solution.

[0017] This invention provides a perovskite solar cell, comprising a substrate, a first carrier transport layer located on the substrate, and a perovskite light-absorbing layer located on and in contact with the first carrier transport layer. The perovskite light-absorbing layer is obtained by modification with a hydroxybenzoic acid crosslinking agent; the hydroxybenzoic acid crosslinking agent contains at least hydroxyl, carboxyl, and benzene rings.

[0018] In some embodiments, the Young's modulus of the perovskite light-absorbing layer ranges from 24 GPa to 26 GPa.

[0019] In some embodiments, the conductivity of the perovskite light-absorbing layer ranges from 8 × 10⁻⁶. -5 S / cm~10×10 -5 S / cm.

[0020] In some embodiments, a first electrode is also included on the substrate; the first electrode is located between the substrate and the first carrier transport layer;

[0021] It also includes a second carrier transport layer and a second electrode located sequentially on the perovskite light-absorbing layer.

[0022] In some embodiments, the first carrier transport layer is an electron transport layer, the second carrier transport layer is a hole transport layer, the first electrode is a cathode, and the second electrode is an anode; or

[0023] The first carrier transport layer is a hole transport layer, the second carrier transport layer is an electron transport layer, the first electrode is an anode, and the second electrode is a cathode.

[0024] Some embodiments of the present invention also provide a perovskite solar cell, which is fabricated using the preparation method of any of the foregoing embodiments.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The light-absorbing layer of the perovskite solar cell provided by this invention is obtained by spin-coating a mixed solution of organic ammonium halide salts doped with hydroxybenzoic acid crosslinking agents onto a lead iodide thin film formed by a lead iodide solution and then heat-treating. This method is simple, and the resulting perovskite solar cell can at least improve the conductivity of the perovskite light-absorbing layer and reduce the Young's modulus, thus enabling the perovskite solar cell to achieve excellent mechanical stability while improving photoelectric conversion efficiency. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a structural diagram of the solar cell of the present invention;

[0029] Figure 2 (a) is a scanning electron microscope image of the perovskite light-absorbing layer of the control group, with an average grain size of 584 nm for the perovskite grains.

[0030] Figure 2 Image (b) is a scanning electron microscope image of the perovskite light-absorbing layer modified with p-hydroxybenzoic acid crosslinking agent according to an embodiment of the present invention. The average grain size of the perovskite grains is 937 nm.

[0031] Figure 3 In the middle (a), the atomic force microscope image of the perovskite light-absorbing layer of the control group is shown. The average surface roughness of the perovskite film is 24.2 nm.

[0032] Figure 3 Image (b) is an atomic force microscope image of the perovskite light-absorbing layer modified with p-hydroxybenzoic acid crosslinking agent according to an embodiment of the present invention. The average surface roughness of the perovskite film is 11.5 nm.

[0033] Figure 4 In the middle (a), the conductivity of the perovskite light-absorbing layer of the control group is shown, and the calculated conductivity is 7.1 × 10⁻⁶. -5 S / cm;

[0034] Figure 4 (b) shows the conductivity of the perovskite light-absorbing layer modified with p-hydroxybenzoic acid crosslinking agent according to an embodiment of the present invention. The calculated conductivity is 9.3 × 10⁻⁶. -5 S / cm;

[0035] Figure 5 (a) shows the current density-voltage curve of the control group rigid perovskite solar cell measured under AM1.5G sunlight, and the photoelectric conversion efficiency of the cell is 22.32%.

[0036] Figure 5 (b) shows the current density-voltage curve of a rigid perovskite solar cell modified with p-hydroxybenzoic acid crosslinking agent according to an embodiment of the present invention, and the photoelectric conversion efficiency of the cell is 24.76%.

[0037] Figure 6In the middle (a), the nanoindentation test diagram of the perovskite light absorption layer of the control group is shown. The elastic modulus of the perovskite light layer is calculated to be 40.19 GPa.

[0038] Figure 6 (b) is a nanoindentation test diagram of the perovskite light absorption layer modified with p-hydroxybenzoic acid crosslinking agent according to an embodiment of the present invention. The elastic modulus of the perovskite light absorption layer was calculated to be 25.05 GPa.

[0039] Figure 7 In the middle (a), the current density-voltage curve of the control group flexible perovskite solar cell was measured under AM1.5G sunlight, and the photoelectric conversion efficiency of the cell was found to be 20.69%.

[0040] Figure 7 Figure (b) shows the current density-voltage curve of a flexible perovskite solar cell modified with p-hydroxybenzoic acid crosslinking agent according to an embodiment of the present invention, and the photoelectric conversion efficiency of the cell is 22.73%.

[0041] Figure 8 The middle (a) is a normalized statistical graph of the efficiency of the control group flexible perovskite solar cell after 10,000 bending cycles at a bending radius of 5 mm. It shows that the efficiency of the cell is 0 after maintaining 4,000 bending cycles.

[0042] Figure 8 Figure (b) is a normalized statistical graph of the efficiency of the flexible perovskite solar cell modified with p-hydroxybenzoic acid crosslinking agent according to an embodiment of the present invention after 10,000 bending cycles at a bending radius of 5 mm. It shows that the cell can maintain 91% of its original efficiency after 10,000 bending cycles.

[0043] Figure 9 (a) is a normalized statistical graph of the efficiency of flexible perovskite solar cells in the control group after self-healing treatment. After self-healing, the efficiency can be restored to 45% of the original efficiency.

[0044] Figure 9 (b) The normalized statistical graph of the efficiency of the flexible perovskite solar cell modified with crosslinking agent after self-healing treatment in the embodiment of the present invention shows that the efficiency can be restored to 89% of the original efficiency after self-healing. Detailed Implementation

[0045] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] Researchers have applied crosslinking agents to perovskite solar cells, hoping that the crosslinking agents will combine with the perovskite to form chain-like or network structures, creating a flexible crosslinked elastomer scaffold and improving the flexibility and toughness of the perovskite film. For example, perovskite solar cells modified with carboxylic acid ester crosslinking agents can effectively release mechanical stress at the perovskite grain boundaries. However, under complex stress environments, the perovskite film can still fracture and become irreparable, leading to a permanent degradation in device performance. Another example is crosslinked elastomer polymers such as polyurethane, which can release residual stress in flexible films through in-situ crosslinking. However, the presence of these elastomer polymers at the perovskite grain boundaries can cause electrical insulation effects, thereby reducing the conductivity of the perovskite film. Therefore, it is impossible to guarantee both mechanical stability and conductivity simultaneously.

[0047] In addition, the high nucleation sites of perovskite on flexible substrates lead to excessive nucleation, resulting in small grain size, rough surface, poor uniformity, and numerous grain boundary defects in the formed perovskite thin film.

[0048] The perovskite light-absorbing layer of the perovskite solar cell of the present invention is obtained by spin-coating a mixed solution of organic ammonium halide salts doped with hydroxybenzoic acid crosslinking agents onto a lead iodide film formed by lead iodide solution and then heating it; the hydroxybenzoic acid crosslinking agent contains at least a benzene ring, hydroxyl group and carboxyl group.

[0049] The hydroxybenzoic acid-based crosslinking agent, such as p-hydroxybenzoic acid, can achieve partial self-crosslinking under certain conditions. The partially crosslinked hydroxybenzoic acid and the uncrosslinked hydroxybenzoic acid form a network structure through dynamic hydrogen bonds, serving as a support to anchor the perovskite film. This effectively releases mechanical stress during bending and stretching, reduces the Young's modulus of the perovskite film, and enables the perovskite solar cell to achieve excellent mechanical stability. Simultaneously, the benzene rings in the hydroxybenzoic acid are used to achieve π-π stacking, forming charge extraction and transport channels, and improving the conductivity of the perovskite light-absorbing layer formed by crosslinked elastomers and other materials. Furthermore, the hydroxyl groups and some carboxyl groups in the hydroxybenzoic acid participate in esterification reactions; the remaining carboxyl groups in the hydroxybenzoic acid act as catalysts for the esterification reaction; and the hydroxybenzoic acid interacts with the perovskite through coordination bonds and hydrogen bonds, promoting the growth of perovskite crystals and passivating grain boundary defects.

[0050] The present invention discloses a perovskite solar cell, comprising a substrate and a carrier transport layer located on the substrate, and a perovskite light absorption layer located on the carrier transport layer, wherein the perovskite light absorption layer is obtained by modification with a hydroxybenzoic acid crosslinking agent; the hydroxybenzoic acid crosslinking agent contains at least hydroxyl, carboxyl and benzene rings.

[0051] This invention improves the photoelectric conversion efficiency and mechanical stability of flexible perovskite layers by modifying them with hydroxybenzoic acid crosslinking agents. The principle is briefly described as follows: Hydroxybenzoic acid crosslinking agents, containing functional groups such as hydroxyl and carboxyl groups, can interact with perovskite through coordination bonds and hydrogen bonds, promoting perovskite crystal growth, passivating grain boundary defects, and reducing non-radiative recombination losses. The benzene rings in the hydroxybenzoic acid crosslinking agent can form charge extraction and transport channels through π-π stacking, improving the carrier mobility of the perovskite film and mitigating its poor conductivity. Furthermore, the crosslinked material forms a network structure at the perovskite grain boundaries, acting as a support to anchor the perovskite film, effectively releasing mechanical stress during bending and stretching, reducing the Young's modulus of the perovskite film, and giving the perovskite solar cell excellent mechanical stability. Simultaneously, the dynamic hydrogen bonds in the crosslinking agent can form rapidly under mild conditions, endowing the perovskite film with strong self-healing capabilities.

[0052] In some embodiments, the Young's modulus of the perovskite light-absorbing layer ranges from 24 GPa to 26 GPa. In some embodiments, the conductivity of the perovskite light-absorbing layer ranges from 8 × 10⁻⁶. -5 S / cm~10×10 -5 S / cm. Compared to the previous solution, this invention has a significant effect, at least in terms of Young's modulus and electrical conductivity.

[0053] In some embodiments of the perovskite solar cell described in this invention, in addition to a substrate, a first carrier transport layer on the substrate, and a perovskite light absorption layer, a second carrier transport layer is also included. Furthermore, a first electrode and a second electrode are also included. The first electrode is deposited on the substrate below the first carrier transport layer, the second carrier transport layer is located on the perovskite light absorption layer, and the second electrode is located on the second carrier transport layer.

[0054] In some embodiments, one of the first electrode and the second electrode is an anode, and the other is a cathode. One of the first carrier transport layer and the second carrier transport layer is an electron transport layer, and the other is a hole transport layer.

[0055] One embodiment is shown below. Figure 1 As shown, the solar cell includes: a substrate 10, a transparent conductive electrode 11 on the substrate, and the substrate on which the transparent conductive electrode is deposited is called the transparent conductive substrate 10 (11). It also includes an electron transport layer 12 (first carrier transport layer), a perovskite layer 13 (perovskite light absorption layer), a hole transport layer 14 (second carrier transport layer) and a silver electrode 15 (cathode) stacked sequentially on the transparent conductive substrate 10 (11).

[0056] In some embodiments, the method for fabricating a perovskite solar cell includes the step of fabricating a perovskite light-absorbing layer, specifically including:

[0057] S1: Steps for preparing lead iodide thin film: Spin-coat the dissolved lead iodide precursor solution onto an ITO conductive substrate with an electron transport layer deposited, and then heat-treat to obtain lead iodide thin film;

[0058] In some embodiments, a cathode and an electron transport layer are first fabricated on a flexible or rigid substrate, and a lead iodide thin film formed by dissolution is spin-coated onto the electron transport layer. Spin-coating the lead iodide thin film onto the electron transport layer not only makes the lead iodide thin film more uniform and flat, but also allows for the control of perovskite crystal growth and improves battery stability.

[0059] S2: Steps for preparing a perovskite thin film, i.e., a perovskite light-absorbing layer: spin-coating an organic ammonium halide salt solution containing a hydroxybenzoic acid crosslinking agent onto the lead iodide thin film, followed by heat treatment to obtain a perovskite thin film located on a carrier transport layer (e.g., an electron transport layer); wherein the hydroxybenzoic acid crosslinking agent contains at least hydroxyl, carboxyl, and benzene rings.

[0060] The perovskite thin film is obtained through this heating process because the heat treatment not only promotes the chemical reaction between lead iodide and organoammonium halide solutions to form perovskite crystals, but also allows hydroxybenzoic acid to partially self-crosslink during this process. This self-crosslinking reaction is a type of esterification reaction, in which the hydroxyl groups and some carboxyl groups in the hydroxybenzoic acid participate in the esterification reaction, while the remaining carboxyl groups act as a catalyst for the esterification reaction. The partially crosslinked hydroxybenzoic acid and the uncrosslinked hydroxybenzoic acid form a network structure through dynamic hydrogen bonds, which acts as a scaffold to anchor the perovskite thin film and reduce the Young's modulus of the perovskite thin film. Simultaneously, the benzene rings in the hydroxybenzoic acid are used to achieve π-π stacking, forming charge extraction and transport channels, improving the conductivity of perovskite crystals formed from crosslinked elastomers and other materials. Furthermore, the hydroxybenzoic acid crosslinking agent interacts with the perovskite through coordination bonds and hydrogen bonds, promoting the growth of perovskite crystals and passivating grain boundary defects.

[0061] In step S1, in some embodiments, lead iodide can be dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), followed by spin coating and heat treatment to obtain the lead iodide film.

[0062] More specifically, in some embodiments, the volume ratio of DMF to DMSO in the mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is 19:1; 1.3–1.5 mmol of lead iodide (PbI2) is dissolved in 1 mL of the mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), followed by spin coating at a spin coating rate of 1700–1800 r / min for 25–35 s, for example, 30 s, and then heat-treated at a temperature of 70–100 °C for 1–2 min to obtain a PbI2 film.

[0063] In step S2, in some embodiments, MA containing hydroxybenzoic acid is used. 0.3 FA 0.7 Br 0.1 I 0.7 Cl 0.2 An organoammonium halide solution was spin-coated onto a PbI2 film and then heat-treated to obtain a perovskite film. Specifically, in some embodiments, the spin-coating rate was 1500–1700 r / min, the spin-coating time was 20–60 s, and the film was annealed on a heating stage for 10–60 min at an annealing temperature of 80–120 °C. The organoammonium halide solution was a mixture of formamidinium iodide (FAI), methylammonium bromide (MABr), and methylammonium chloride (MACl) in a mass ratio of 10:1:1, which was then dissolved in 2 mL of isopropanol solution to form MA with a concentration of 72 mg / mL. 0.3 FA 0.7 Br 0.1 I 0.7 Cl 0.2 Solution; the MA containing hydroxybenzoic acid 0.3 FA 0.7 Br 0.1 I 0.7 Cl 0.2 The organic halide ammonium salt solution is prepared by adding 1 mL of isopropanol solution of hydroxybenzoic acid with a concentration of 1–2 mmol / mL to the above organic halide ammonium salt solution.

[0064] In some embodiments, the thickness of the prepared perovskite light-absorbing layer is 450–550 nm, for example, 500 nm.

[0065] The substrate is a supporting substrate, such as a rigid glass substrate, or a flexible substrate such as polyethylene terephthalate (PET), or a flexible substrate such as polyethylene naphthalate (PEN), or a flexible substrate such as polyimide (PI).

[0066] For example, the electron transport layer may be, but is not limited to, a SnO2 thin film.

[0067] The following section specifically compares the preparation methods and performance test data of the improved invention with those of the original solution to illustrate the technical problems solved and the technical effects achieved by this application.

[0068] Example 1: Perovskite solar cells modified with p-hydroxybenzoic acid crosslinking agent according to the present invention

[0069] A specific process for preparing a p-hydroxybenzoic acid perovskite solar cell includes:

[0070] S1. Clean the glass substrate or flexible substrate on which the cathode (e.g., ITO) is deposited. The substrate on which the cathode is deposited is called the conductive substrate.

[0071] Specifically, the process includes: ultrasonically cleaning the conductive substrate with deionized water, acetone, and alcohol for 10–15 minutes each, then drying the substrate with pure nitrogen; and finally treating the conductive substrate with ozone for 10–15 minutes after cooling to room temperature.

[0072] S2. Spin-coat an electron transport layer SnO2 onto the conductive substrate.

[0073] Specifically, the process involves spin-coating a SnO2 precursor solution onto a pretreated ITO conductive glass substrate (conductive substrate), followed by heat treatment at 150°C for 30 minutes to form an electron transport layer (SnO2 film) on the conductive glass substrate.

[0074] S3, Preparation of MA 0.3 FA 0.7 PbBr 0.1 I 2.7 Cl 0.2 Perovskite thin films specifically include the following steps:

[0075] S31. For example, 1.3 mmol of lead iodide (PbI2) is dissolved in 1 mL of a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), wherein the volume ratio of DMF to DMSO in the mixed solvent is 19:1, to prepare a PbI2 solution.

[0076] S32. Subsequently, the PbI2 solution was spin-coated at a spin rate of 1800 r / min for 30 s, followed by heat treatment at 70 °C for 1 min to obtain a PbI2 thin film.

[0077] S33. Next, dissolve 2 mmol of p-hydroxybenzoic acid in 1 mL of isopropanol; mix formamidinium iodide (FAI), methylammonium bromide (MABr), and methylammonium chloride (MACl) in a mass ratio of 10:1:1, and then dissolve them in 2 mL of isopropanol solution to form MA with a concentration of 72 mg / mL. 0.3 FA0.7 Br 0.1 I 0.7 Cl 0.2 Prepare a mixed solution of organic ammonium halides; then mix the two solutions together.

[0078] S34, subsequently MA containing p-hydroxybenzoic acid 0.3 FA 0.7 Br 0.1 I 0.7 Cl 0.2 An organic ammonium halide mixed solution was spin-coated onto a PbI2 film at a spin-coating rate of 1700 r / min for 30 s, and then heat-treated at 100 °C for 25 min to obtain a perovskite light-absorbing layer.

[0079] S4. Spin-coat the hole transport layer Spiro-OMeTAD onto the conductive substrate.

[0080] Specifically, the process involves dissolving 540 mg of lithium bis(trifluoromethanesulfonate)imide in 1 mL of acetonitrile solution and shaking thoroughly to obtain a Li-TFSI acetonitrile solution; then dissolving 720 mg of 2,2,7,7′-tetratetra[N,N′-di(4-methoxyphenyl)amino]-9,9′-spirocyclic difluorene solution (Spiro-OMeTAD) in 1 mL of chlorobenzene, adding 18 μL of Li-TFSI acetonitrile solution, and finally adding 29 μL of... 4-tert-butylpyridine was thoroughly shaken to obtain a 2,2,7,7′-tetrakis[N,N′-di(4-methoxyphenyl)amino]-9,9′-spirocyclic difluorenechlorobenzene solution containing Li-TFSI and 4-tert-butylpyridine dopants. Finally, the above mixed solution was spin-coated onto the perovskite light-absorbing layer using a solution spin-coating method at a spin-coating rate of 4000 rpm and a spin-coating time between 25 and 35 s, for example, 30 s, to obtain the hole transport layer Spiro-OMeTAD.

[0081] Spin-coating a hole transport layer onto the conductive substrate is an optional embodiment; in some products or embodiments, a hole transport layer may not be fabricated.

[0082] S5. A metal Ag electrode (anode) is deposited on the hole transport layer to obtain a perovskite solar cell modified with hydroxybenzoic acid crosslinking agent.

[0083] Compare with Example 1:

[0084] The difference from Example 1 is in steps S33-S34.

[0085] In step S33 of the comparative example, formamidinium iodide (FAI), methylammonium bromide (MABr), and methylammonium chloride (MACl) are mixed in a mass ratio of 10:1:1, and then dissolved in 2 mL of isopropanol solution to form MA with a concentration of 72 mg / mL.0.3 FA 0.7 Br 0.1 I 0.7 Cl 0.2 Organic ammonium halide mixed solution.

[0086] Referring to step S34 in the example, MA is then... 0.3 FA 0.7 Br 0.1 I 0.7 Cl 0.2 An organic ammonium halide mixed solution was spin-coated onto a PbI2 film at a spin-coating rate of 1700 r / min for 30 s, and then heat-treated at 100 °C for 25 min to obtain a perovskite light-absorbing layer modified with a hydroxybenzoic acid-free crosslinking agent.

[0087] The test results are as follows:

[0088] Appendix Figure 1 This is a structural diagram of a perovskite solar cell fabricated according to an embodiment of the present invention. From bottom to top, the layers are a transparent conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a silver electrode.

[0089] Appendix Figure 2 This is a scanning electron microscope image of the perovskite light-absorbing layer obtained in an embodiment of the present invention. Figure 2 (a) shows the surface morphology of the control group perovskite light-absorbing layer based on scanning electron microscopy. Figure 2 Image (b) shows the surface morphology of the perovskite light absorption layer modified with hydroxybenzoic acid crosslinking agent according to the scanning electron microscope test of an embodiment of the present invention. The test results show that the average size of the perovskite grains modified with crosslinking agent increased from 584 nm to 937 nm in the control film. The grains at the grain boundaries are relatively smooth and dense. This is because the hydroxybenzoic acid crosslinking agent promotes crystal growth and reduces grain boundary defects. Therefore, the perovskite light absorption layer formed is uniform, dense, and has high crystallinity.

[0090] Appendix Figure 3 This is an atomic force microscope image of the perovskite light-absorbing layer obtained in this embodiment. Figure 3 (a) shows the morphology of the control group perovskite light-absorbing layer based on atomic force microscopy. Figure 3 Image (b) shows the morphology of the perovskite light-absorbing layer modified with hydroxybenzoic acid crosslinking agent according to an embodiment of the present invention, as measured by atomic force microscopy. The test results show that the surface roughness of the perovskite film with crosslinking agent is improved from 24.2 nm in the control film to within 12 nm. Figure 3 As shown in (b), the roughness is improved to 11.5 nm. This smoother surface is beneficial for enhancing contact with the carrier transport layer and improving carrier extraction.

[0091] Appendix Figure 4 This is a conductivity diagram of the perovskite light-absorbing layer obtained in this embodiment. Figure 4 (a) shows the conductivity of the perovskite light-absorbing layer in the control group. Figure 4 (b) shows the conductivity spectrum of the perovskite light-absorbing layer modified with hydroxybenzoic acid crosslinking agent; tests showed that the conductivity of the perovskite light-absorbing layer with crosslinking agent in the embodiments of the present invention is in the range of 8 × 10⁻⁶. -5 S / cm~10×10 -5 Between S / cm, preferably 9×10 -5 S / cm~9.6×10 -5 S / cm, for example, 9.3×10 -5 S / cm.

[0092] The above embodiments show that the control membrane has a thickness of 7.1 × 10⁻⁶. -5 S / cm should be increased to at least 9.3 × 10⁻⁶. -5 S / cm.

[0093] Appendix Figure 5 The current density-voltage curve of the rigid perovskite solar cell prepared in this embodiment is shown. Figure 5 (a) shows the current density-voltage curves of the control group rigid perovskite solar cells measured under AM1.5G sunlight; Figure 5 (b) shows the current density-voltage curve of the rigid perovskite solar cell based on crosslinking agent modification; compared with the control group perovskite solar cell, the short-circuit current density of the perovskite solar cell based on crosslinking agent modification in this embodiment of the invention is 24.30 mA / cm². 2 Increased to 25.77 mA / cm 2 The open-circuit voltage increased from 1.169V to 1.194V, and the photoelectric conversion efficiency increased from 22.32% to 24.76%.

[0094] Example 2: Flexible perovskite solar cell modified with p-hydroxybenzoic acid crosslinking agent.

[0095] In Example 1, a rigid substrate was used as an example. In this example, a flexible substrate is used instead, and a conductive flexible substrate with deposited ITO (cathode) is fixed on white glass using UV adhesive.

[0096] In step S2 above, the temperature for heat treatment of the spin-coated SnO2 thin film (electron transport layer) is changed to 100°C;

[0097] In step S3 above, the spin-coating rate of the PbI2 solution was changed to 1700 r / min; MA containing p-hydroxybenzoic acid... 0.3 FA 0.7 Br 0.1 I 0.7 Cl0.2 The spin coating rate of the organic ammonium halide mixed solution was changed to 1500 r / min, and the heat treatment temperature was changed to 100℃.

[0098] Compare with Example 2:

[0099] The difference from Example 2 is that steps S33-S34 are changed to:

[0100] S33. Mix formamidine iodide (FAI), methylammonium bromide (MABr), and methylammonium chloride (MACl) in a mass ratio of 10:1:1, then dissolve in 2 mL of isopropanol solution to form MA with a concentration of 72 mg / mL. 0.3 FA 0.7 Br 0.1 I 0.7 Cl 0.2 Organic ammonium halide mixed solution.

[0101] S34, then MA 0.3 FA 0.7 Br 0.1 I 0.7 Cl 0.2 An organic ammonium halide mixed solution was spin-coated onto a PbI2 film at a spin-coating rate of 1700 r / min for 30 s, and then heat-treated at 100 °C for 25 min to obtain an unmodified perovskite light-absorbing layer.

[0102] The test results are as follows:

[0103] Appendix Figure 6 This is a nanoindentation test pattern of the perovskite light-absorbing layer prepared in this embodiment. Figure 3 (a) shows the nanoindentation test pattern of the perovskite light-absorbing layer in the control group; Figure 3 (b) shows the nanoindentation test pattern of the perovskite light-absorbing layer modified with hydroxybenzene crosslinking agent; it can be found that the Young's modulus of the perovskite light-absorbing layer modified with hydroxybenzene crosslinking agent decreased from 40.19 GPa to 25.05 GPa. The decrease in Young's modulus is beneficial to improving the flexibility of the perovskite film.

[0104] Appendix Figure 7 The current density and voltage curves of the flexible perovskite solar cell prepared in this embodiment are shown. Figure 7 (a) shows the current density and voltage curves of a flexible perovskite solar cell measured under AM1.5G sunlight; Figure 7 (b) shows the current density and voltage curves of the flexible perovskite solar cell based on crosslinking agent modification; compared with the control perovskite solar cell, the short-circuit current density of the perovskite solar cell based on crosslinking agent modification increased from 22.49 mA / cm². 2 Increased to 23.63 mA / cm2 The open-circuit voltage increased from 1.166V to 1.199V, and the photoelectric conversion efficiency increased from 20.69% to 22.73%.

[0105] Appendix Figure 8 This is a normalized statistical graph showing the efficiency of the flexible perovskite solar cell fabricated in this embodiment after 10,000 bending cycles at a bending radius of 5 mm. Figure 8 The middle (a) graph shows the normalized efficiency of the control group flexible perovskite solar cells after 10,000 bends at a bending radius of 5 mm. Figure 8 Figure (b) shows the normalized statistical graph of the efficiency of the flexible perovskite solar cell modified with p-hydroxybenzoic acid crosslinking agent according to the embodiment of the present invention after 10,000 bending cycles at a bending radius of 5 mm. The flexible device with crosslinking agent can maintain 91% of its original efficiency after 10,000 bending cycles, while the efficiency of the control group flexible perovskite solar cell is 0 after 4,000 bending cycles.

[0106] Appendix Figure 9 This is a normalized statistical graph showing the efficiency of the flexible perovskite solar cell prepared in this embodiment after self-healing treatment. Figure 9 (a) is a normalized statistical graph of the efficiency of flexible perovskite solar cells in the control group after self-healing treatment; Figure 9 (b) Normalized statistics of the efficiency of flexible perovskite solar cells modified with crosslinking agent after self-healing treatment; the flexible device with crosslinking agent after self-healing treatment can recover to 89% of the original efficiency, while the flexible perovskite solar cell of the control group can only recover to 45% of the original efficiency.

[0107] The light-absorbing layer of the perovskite solar cell provided by this invention is obtained by spin-coating a mixed solution of organic ammonium halide salts doped with hydroxybenzoic acid crosslinking agents onto a lead iodide thin film formed from a lead iodide solution and then heat-treating it. This method can at least reduce the Young's modulus of the perovskite thin film, while maintaining high conductivity and preventing the device from becoming insulating and losing its photoelectric properties.

[0108] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a perovskite solar cell, comprising the step of fabricating a perovskite light-absorbing layer on a substrate, characterized in that, The perovskite light-absorbing layer is prepared by modification with a hydroxybenzoic acid crosslinking agent; The steps for preparing the perovskite light-absorbing layer include: The dissolved lead iodide precursor solution was spin-coated onto a substrate with a carrier transport layer deposited on its surface, and then heated to obtain a lead iodide thin film. An organic ammonium halide salt solution containing hydroxybenzoic acid crosslinking agent was spin-coated onto the lead iodide film, and then heated to obtain a perovskite light-absorbing layer located on the charge carrier transport layer. The hydroxybenzoic acid crosslinking agent contains at least hydroxyl, carboxyl, and benzene rings. During the heat treatment process, the hydroxybenzoic acid achieves partial self-crosslinking. The partially crosslinked hydroxybenzoic acid and the uncrosslinked hydroxybenzoic acid form a network structure through dynamic hydrogen bonds, which serves as a scaffold to anchor the perovskite film.

2. The preparation method according to claim 1, characterized in that, The hydroxybenzoic acid crosslinking agent is one of p-hydroxybenzoic acid, o-hydroxybenzoic acid, m-hydroxybenzoic acid, 2-hydroxyterephthalic acid, and 2-hydroxy-1,3,5-benzenetriacic acid.

3. The preparation method according to claim 1 or 2, characterized in that, The dissolved lead iodide precursor solution was spin-coated onto a substrate with a carrier transport layer deposited on its surface, and then heated to obtain a lead iodide thin film, specifically including: Lead iodide was dissolved in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), and then spin-coated and annealed to obtain the lead iodide film. An organic ammonium halide salt solution containing a hydroxybenzoic acid crosslinking agent is spin-coated onto the lead iodide film, and then heated to obtain a perovskite light-absorbing layer located on the carrier transport layer, specifically comprising: MA containing the aforementioned hydroxybenzoic acid crosslinking agent x FA 1-x Br y I z Cl 1-y-z An organic ammonium halide salt solution is spin-coated onto the lead iodide film and then heat-treated to obtain a perovskite light-absorbing layer in contact with the carrier transport layer; where x is a number less than 1, and y and z are numbers less than 1.

4. The preparation method according to claim 3, characterized in that, The spin-coating and annealing conditions for preparing the lead iodide film include: a spin-coating rate of 1700–1800 r / min and a spin-coating time of 25–35 s; and an annealing temperature of 70–100 °C and an annealing time of 1–2 min on a heating stage. The spin-coating and annealing conditions for preparing the perovskite light-absorbing layer include: a spin-coating rate of 1500–1700 r / min and a spin-coating time of 20–60 s; an annealing time on a heating stage of 10–60 min and an annealing temperature of 80–120 ℃.

5. The preparation method according to claim 4, characterized in that, The volume ratio of the mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is 19:1; MA containing the hydroxybenzoic acid crosslinking agent x FA 1-x Br y I z Cl 1-y-z The concentration of hydroxybenzoic acid crosslinking agents in organohalogen ammonium salt solutions is 1–2 mmol / mL; The organic ammonium halide solution is a mixture of formammonium iodide (FAI), methylammonium bromide (MABr), and methylammonium chloride (MACl), which is then dissolved in isopropanol solution to form MA. x FA 1-x Br y I z Cl 1-y-z Solution.

6. A perovskite solar cell, characterized in that, The perovskite solar cell, fabricated by the preparation method according to any one of claims 1-5, includes a substrate, a first carrier transport layer located on the substrate, and a perovskite light-absorbing layer located on and in contact with the first carrier transport layer. The perovskite light-absorbing layer is obtained by modification with a hydroxybenzoic acid crosslinking agent. The hydroxybenzoic acid crosslinking agent contains at least hydroxyl, carboxyl, and benzene rings.

7. The perovskite solar cell according to claim 6, characterized in that, The Young's modulus of the perovskite light-absorbing layer is in the range of 24 GPa-26 GPa.

8. The perovskite solar cell according to claim 7, characterized in that, The electrical conductivity of the perovskite light-absorbing layer is in the range of 8 × 10⁻⁶. -5 S / cm ~ 10×10 -5 S / cm.

9. The perovskite solar cell according to claim 6, characterized in that, It also includes a first electrode located on the substrate; the first electrode is located between the substrate and the first carrier transport layer; It also includes a second carrier transport layer and a second electrode located sequentially on the perovskite light-absorbing layer.

10. The perovskite solar cell according to claim 9, characterized in that, The first carrier transport layer is an electron transport layer, the second carrier transport layer is a hole transport layer, the first electrode is a cathode, and the second electrode is an anode; or The first carrier transport layer is a hole transport layer, the second carrier transport layer is an electron transport layer, the first electrode is an anode, and the second electrode is a cathode.

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