Method for improving light stability of perovskite solar cell

Abstract

The application discloses a method for improving light stability of a perovskite solar cell, which comprises the following steps: adding 2-PO into a DMF-PbI2 solution, adding a stirring rod, stirring and dissolving the solution under the condition of 70 DEG C and 900 rpm for 0.5 h, and filtering the 2-PO / DMF-PbI2 solution by using a 0.22 mu m filter membrane, so that perovskite film preparation can be carried out; the organic molecule 2-PO is used as an additive, the nucleation and growth of perovskite grains are promoted, and the film quality is improved; the =N-OH group in the 2-PO molecule can inhibit iodization of the perovskite in the photo-thermal aging process, prevent I2 from being generated, reduce I2 to I-, and enhance the film stability; meanwhile, the 2-PO interacts with PbI2, passivates internal defects of the film, and further improves the efficiency and stability of the PSCs.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, specifically to a method for improving the light stability of perovskite solar cells. Background Technology

[0002] In the post-fossil fuel era, developing efficient, stable, and cost-effective photovoltaic technologies is crucial for achieving sustainable development. In recent years, organic-inorganic metal halide perovskites have become a focus of photovoltaic research due to their excellent photoelectric properties, such as tunable band gaps, high absorption coefficients, low exciton binding energies, and long carrier diffusion lengths. Perovskite materials typically possess an ABX3-type crystal structure, where the A-site can be formed by organic cations (such as methylamine ions, MA). + Formamidinium ion (FA) + ) or inorganic cations (such as cesium ions Cs) + The structure consists of rubidium ions (Rb+), with lead ions (Pb2+) at the B site and halide ions (such as iodide ions (I-) and bromide ions (Br+) at the X site). - (and chloride ions Cl-). These materials are not only abundant and inexpensive, but can also be processed using solution methods, combining the advantages of easy film formation of organic materials and high crystallinity of inorganic materials, providing a feasible route for large-scale fabrication. From a commercialization perspective, perovskite solar cells (PSCs) need to achieve a balance between cost, efficiency, and lifetime. Although PSCs have reached efficiency levels comparable to silicon-based cells, their long-term stability remains a major obstacle to commercialization, especially under humid, light-exposed, and high-temperature environments. Therefore, achieving long-term stability in devices remains a significant challenge in their commercialization process.

[0003] Although the stability of current perovskite solar cells (PSCs) has improved from a few minutes to thousands of hours, it still falls short of the requirements for practical applications. To address this, researchers both domestically and internationally have proposed various strategies to improve the stability of perovskite materials, including optimizing encapsulation technology, designing two-dimensional perovskite structures, introducing additives, and interface modification. Among these, improving the intrinsic properties of perovskites through additives is a particularly promising direction. For example, Jiang et al., in their paper "Molecular Dipole Engineering of Carbonyl Additives for Efficient and Stable Perovskite Solar Cells," employed functional additives with a single carbonyl group and a large π-electron conjugated system structure. The results showed that the carbonyl group and oriented molecular dipoles derived from the π-electron conjugated system were effective in passivating defects, significantly increasing device efficiency from 20.8% to 23.2% while exhibiting excellent stability. In their paper "Aniline Sulfonic Acid Induced Uniform Perovskite Film for Large-Scale Photovoltaics," Wang et al. used the dual-site molecule 4-aniline sulfonic acid (4A) as an additive to regulate perovskite crystallization and passivate specific defects through hydrogen bonding and intermolecular interactions. The results showed that introducing 4A as an additive induced uniform growth of perovskite seeds on the substrate, contributing to the formation of high-quality perovskite films with large grain size and low defect density. Consequently, the fabricated device achieved a PCE of 24.1% and also exhibited excellent stability. These studies demonstrate that the additive plays a crucial role in passivating defects, enhancing film crystallinity, and stabilizing the phase state.

[0004] In addition, recent research in AEu 3+ -Eu 2+ The article "Ion Redox Shuttle Impparts Operational Durability to Pb-IPerovskite Solar Cells" highlights the importance of iodine-related photochemical reactions in perovskite degradation. Under light and thermal stress, iodine vacancies (V...) I The formation of iodine-related defects accelerates the generation and release of gaseous iodine (I2), leading to perovskite decomposition and device performance degradation. This decomposition process not only increases defects and pinholes but also provides channels for moisture and oxygen permeation, accelerating degradation. Therefore, suppressing iodine-related defects in perovskite films and slowing down I2 formation are crucial for achieving high-temperature photostability of PSCs.

[0005] To address the performance issues of perovskite devices (PSCs) caused by poor perovskite film quality and poor optical and thermal stability, this invention proposes introducing 2-pyridine aldehyde oxime (2-PO) as a functional additive into the perovskite precursor solution. 2-PO not only improves the crystallinity of the perovskite film but also effectively passivates defects, while simultaneously enhancing the stability of PSCs under light and high-temperature conditions. Summary of the Invention

[0006] The purpose of this invention is to utilize the strongly reducing =N-OH group in the 2-pyridine aldehyde oxime (2-PO) molecule to interact with PbI2 during the perovskite thin film preparation process, thereby passivating internal defects and preparing high-quality perovskite thin films. The =N-OH group in the 2-PO molecule not only effectively inhibits the formation of I2 inside the perovskite under long-term light exposure and high temperature conditions, but also reduces the generated I2 to I... - This improves the thermo-optical stability of thin films and enhances the overall performance of devices.

[0007] Taking the organic compound 2-pyridine aldehyde oxime (2-PO) as an example, this invention introduces 2-PO into the precursor solution of dimethylformamide (DMF)-PbI2, providing a gradient concentration range of 0.5-4 mg / mL;

[0008] 2-PO is a carefully selected perovskite additive whose unique molecular structure endows it with special functions. The =N-OH group has strong reducing properties and forms intramolecular hydrogen bonds with the nitrogen atom of the pyridine ring, further enhancing the reducing power of the entire molecule. This synergistic effect not only promotes the passivation of film defects but also effectively inhibits iodination of perovskite materials under long-term light and high-temperature conditions, preventing I2 formation and reducing it to I. - This enhances the photothermal stability of the perovskite film. Simultaneously, the interaction between 2-PO molecules and PbI2 forms chemical bonds, improving the nucleation ability of the perovskite crystals. This facilitates the growth of large grains, reduces the number of grain boundaries, and results in high-quality perovskite films, improving photoelectric conversion efficiency and extending device lifespan.

[0009] Specifically, the technical solution provided by this invention is as follows:

[0010] A method for improving the light stability of perovskite solar cells, characterized by comprising the following steps:

[0011] (1) Preparation of electron transport layer solution:

[0012] Dilute the SnO2 colloidal solution with deionized water, stir at room temperature for 30 minutes, and then filter the solution using a syringe and a water filter.

[0013] (2) Preparation of perovskite solution:

[0014] (2.1) Dissolve PbI2 powder in a mixed solution of DMF and DMSO, and stir to dissolve and form a mixed solution of PbI2;

[0015] (2.2) Add 2-PO powder to the above PbI2 mixed solution to form a 2-PO-PbI2 mixed solution;

[0016] (2.3) Dissolve FAI and MACl in IPA solution and stir to form a solution salt solution;

[0017] (3) Preparation of hole transport layer:

[0018] Spiro-OMeTAD solution, Li-TFSI solution and 1 ml of 4-tBP chlorobenzene solution were mixed to form Spiro-OMeTAD solution;

[0019] (4) Preparation of experimental devices:

[0020] (4.1) Cleaning of ITO glass:

[0021] First, wipe the ITO glass substrate with a cleaning agent, and then wash the ITO glass substrate in deionized water, acetone and isopropanol in sequence using an ultrasonic machine for 30 minutes.

[0022] (4.2) Fabrication of the electron transport layer:

[0023] Using a spin coater in an air atmosphere, the SnO2 colloidal solution diluted in step (1) is spin-coated onto the ITO glass substrate treated in step (4.1), and then the ITO glass substrate with the SnO2 colloidal solution spin-coated is annealed on a hot plate.

[0024] (4.3) Preparation of the perovskite active layer:

[0025] Under a nitrogen atmosphere, a spin coater was used to spin coat the 2-PO-PbI2 mixed solution prepared in step (2.2). The ITO glass substrate with the spin-coated 2-PO-PbI2 mixed solution was then annealed and cooled on a hot plate. Then, the solution salt solution prepared in step (2.3) was spin-coated, and then annealed on a hot plate in an air atmosphere.

[0026] (5) Preparation of hole transport layer: The Spro-OMeTAD solution prepared in step (3) was spin-coated onto the perovskite-coated ITO glass substrate under a nitrogen atmosphere using a spin coater.

[0027] (6) Preparation of gold electrodes: Using a thermal evaporation apparatus, at a depth of 5 x 10⁻⁶... -4 Under a vacuum of Pa, 80 nm gold was deposited as the back electrode.

[0028] The advantages of this invention compared to existing technologies are as follows: This invention uses the organic molecule 2-PO as an additive to promote the nucleation and growth of perovskite grains and improve the film quality; the =N-OH group in the 2-PO molecule can inhibit the iodination of perovskite during photothermal aging, prevent the formation of I2, and reduce it to I. - This enhances the stability of the thin film. Simultaneously, the interaction between 2-PO and PbI2 passivates internal defects in the film, further improving the efficiency and stability of PSCs. Attached Figure Description

[0029] Figure 1 This is the XPS test graph from Embodiment 1 of the present invention.

[0030] Figure 2 This is the TRPL test diagram from Embodiment 1 of the present invention.

[0031] Figure 3 This is a photothermal stability test diagram from Embodiment 1 of the present invention.

[0032] Figure 4 This is a test image of two perovskite films immersed in toluene in Example 1 of the present invention.

[0033] Figure 1 (a) Pb4f XPS spectra of the control group and the perovskite films modified with 2-PO; (b) I3d XPS spectra of the control group and the perovskite films modified with 2-PO.

[0034] Figure 2 (a) TRPL spectra of ITO / SnO2 / PVSK substrate and ITO / SnO2 / 2-PO-PVSK substrate; (b) TRPL spectra of Quartzglass / PVSK substrate and Quartzglass / 2-PO-PVSK substrate.

[0035] Figure 4 The illustration shows the state of two thin-film toluene solutions. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0037] Example 1:

[0038] (1) Preparation of electron transport layer: dilute SnO2 colloidal solution with deionized water, stir at room temperature for 30 min, and then filter the above solution using a syringe and a water filter; wherein, SnO2 colloidal solution is 15 wt% SnO2 colloidal solution, and the dilution ratio of SnO2 colloidal solution to deionized water is 1:3.

[0039] (2) Preparation of perovskite thin film PVSK:

[0040] (2.1) Mix 950 μL of DMF solution and 50 μL of DMSO solution, and dissolve 599.3 mg of PbI2 powder in the above mixture. Then stir at 70 °C for 6 h to form a PbI2 mixed solution.

[0041] (2.2) Add 2 mg of 2-PO powder to the PbI2 mixed solution in step (2.1) to form a 2-PO-PbI2 mixed solution; dissolve 90 mg of FAI and 12 mg of MACl in 1 mL of IPA solution and stir at room temperature for 30 min to form a solution salt solution;

[0042] (3) Preparation of hole transport layer: 72.3 mg of Spiro-OMeTAD, 17.5 μL of Li-TFSI solution and 29 μL of 1 ml of 4-tBP chlorobenzene solution were mixed to form Spiro-OMeTAD solution;

[0043] (4) Preparation of experimental devices:

[0044] (4.1) Cleaning of ITO glass: First, wipe the ITO glass substrate with a cleaning agent, and then wash the ITO glass substrate in deionized water, acetone and isopropanol in turn using an ultrasonic machine for 30 minutes.

[0045] (4.2) Preparation of electron transport layer: In an air atmosphere, the SnO2 colloidal solution diluted in step (1) was spin-coated onto the ITO glass substrate after treatment in step (4.1) using a spin coater. The volume of the SnO2 colloidal solution was 70 μL, the spin-coating speed was 3000 rpm, and the spin-coating time was 50 s. Then, the ITO glass substrate with the SnO2 colloidal solution was annealed on a hot plate at room temperature of 150°C for 25 min.

[0046] (4.3) Preparation of perovskite active layer: Under nitrogen atmosphere, spin coater was used to spin coat the 2-PO-PbI2 mixed solution prepared in step (2), wherein the volume of the 2-PO-PbI2 mixed solution was 70 μL, the rotation speed was 2000 rpm, and the spin coating time was 30 s. The ITO glass substrate with the spin-coated 2-PO-PbI2 mixed solution was annealed on a hot plate at room temperature of 70°C for 1 min, cooled for 10 min, and then the solution salt solution prepared in step (2) was spin-coated, wherein the volume of the solution salt solution was 70 μL, the rotation speed was 1800 rpm, and the spin coating time was 30 s. Then, the substrate was annealed on a hot plate at 150°C for 30 min under air atmosphere, wherein the humidity of the air atmosphere was 30%-40%.

[0047] (5) Preparation of hole transport layer: The Spro-OMeTAD solution prepared in step (3) was spin-coated on a perovskite-coated ITO glass substrate under a nitrogen atmosphere using a spin coater. The volume of the Spro-OMeTAD solution was 50 μL, the rotation speed was 3000 rpm, and the time was 30 s.

[0048] (6) Preparation of gold electrode: Using a thermal evaporation apparatus, 80 nm of gold was deposited as the back electrode under a vacuum of 5*10-4 Pa.

[0049] The performance of the perovskite thin film was tested below, and the specific details are as follows:

[0050] I. Preparation of Control Group Devices

[0051] In step (2.2) of Example 1, 2-PO powder was not added, and the remaining steps were consistent with the preparation process of the device in Example 1.

[0052] II. X-ray photoelectron spectroscopy (XPS) testing of perovskite thin films

[0053] X-ray photoelectron spectroscopy (XPS) was used to characterize the control group perovskite film and the 2-PO modified perovskite film.

[0054] like Figure 1 As shown, the Pb4f peak and I3d peak of the perovskite film modified with 2-PO (2 mg / mL) shifted to higher binding energies compared to the control group, indicating that 2-PO binds to Pb in the perovskite. 2+ and I - There are obvious interactions; in addition, such as Figure 1 As indicated by arrow a, both films exhibit peaks of metallic Pb species at 136.5 eV and 141.5 eV, which are typically considered carrier recombination centers and detrimental to device performance. However, after 2-PO modification, the intensity of this peak significantly decreases, indicating a reduction in metallic Pb content, further confirming the interaction between 2-PO and Pb. 2+The interaction between the two promotes the transformation of PbI2 to perovskite, improves film quality, reduces defects, and inhibits recombination.

[0055] III. Time-Resolved Photoluminescence (TRPL) Testing of Perovskite Thin Films

[0056] Two different perovskite films were tested: an ITO / SnO2 / PVSK substrate and an ITO / SnO2 / 2-PO-PVSK substrate.

[0057] like Figure 2 As shown in Figure a, it was found that the fluorescence lifetime of the film treated with 2-PO (2 mg / mL) could decrease from 280.7 ns to 101.1 ns. The specific lifetime parameters are shown in Table 1 below. 2-PO modification significantly promoted the extraction of charge carriers at the electron transport layer interface.

[0058] Two different perovskite films were tested: Quartzglass / PVSK substrate and Quartzglass / 2-PO-PVSK substrate.

[0059] like Figure 2 As shown in b, the fluorescence lifetime of the film treated with 2-PO (2 mg / mL) increased from 332.7 ns to 1122.7 ns. Specific lifetime parameters are shown in Table 2 below. The significantly enhanced lifetime of the perovskite film after 2-PO modification indicates that the crystallinity of the perovskite film was effectively improved, and non-radiative recombination was significantly suppressed.

[0060] Table 1. TRPL lifetime parameters for ITO / SnO2 / PVSK substrates and ITO / SnO2 / 2-PO-PVSK substrates

[0061] Films A1(％) τ1(ns) A2(％) τ2(ns) τav(ns) ITO / SnO2 / PVSK 0.63 42 0.47 321.3 280.7 ITO / SnO2 / 2-POPVSK 0.66 24.3 0.45 123.2 101.1

[0062] Table 2. TRPL lifetime parameters for Quartzglass / PVSK substrate and Quartzglass / 2-PO-PVSK substrate

[0063] Films A1(％) τ1(ns) A2(％) τ2(ns) τav(ns) ITO / SnO2 / PVSK 0.66 106.67 0.37 432.2 332.7 ITO / SnO2 / 2-POPVSK 0.93 455.1 0.21 1850.1 1122.7

[0064] IV. Photovoltaic performance testing of perovskite devices:

[0065] Two types of devices were tested using a solar simulator: a control group and an experimental group. After comparing a series of 2-PO concentrations, it was found that the optimal 2-PO treatment concentration was 2 mg / mL. The device treated with 2-PO can effectively improve its photovoltaic performance, and the energy conversion efficiency can be increased from 22.48% to 25.23%. The specific photovoltaic parameters are shown in the table below.

[0066] Table 3. List of Photovoltaic Performance Test Results of Devices

[0067]

[0068]

[0069] V. Photothermal stability test:

[0070] To evaluate the thermal stability of the prepared PSCs, they were placed on a heating plate at 85±5℃ and monitored for a long time under ambient air conditions with a relative humidity of 25%, and the change trend of photoelectric conversion efficiency (PCE) over time was recorded.

[0071] like Figure 3 As shown, both the PSCs devices containing the 2-PO additive and the control devices without the additive exhibit a decreasing trend in PCE. However, after 600 hours, the PSCs devices based on the 2-PO additive retained 85% of the initial PCE, while the control devices dropped to below 60%. This indicates that the introduction of the 2-PO additive significantly improves the photothermal stability of PSCs. This improvement is mainly attributed to the protective effect of the 2-PO additive on the perovskite active layer under high-temperature conditions, which inhibits degradation mechanisms such as thermally induced lattice distortion and ion migration.

[0072] To directly compare the photostability of perovskite films, two types of perovskite films were immersed in toluene and tested under sunlight. Toluene effectively extracted the degradation products of perovskite.

[0073] like Figure 4 As shown in the inset, the control sample exhibited faster degradation after 10 hours, resulting in the generated I₂ turning the solution brown. UV-Vis absorption measurements of both solutions indicated that the perovskite containing 2-PO₄ showed lower absorbance, suggesting a slower degradation rate. These results suggest that the reduction of the =N-OH group is related to the nitrogen atom pair of the pyridine ring with the V₂ group. I The synergistic effect of inhibition can effectively enhance the photostability of perovskite films.

[0074] VI. Experimental Results:

[0075] The test results above show that by introducing 2-PO as a multifunctional additive, this invention not only optimizes the crystallization process and quality of perovskite films, but also effectively inhibits the iodination process under photothermal conditions, significantly improving the efficiency and long-term stability of PSCs, and providing a new strategy for achieving high-performance, long-life PSCs.

[0076] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for improving the light stability of perovskite solar cells, characterized in that, Includes the following steps: (1) Preparation of electron transport layer solution: Dilute the SnO2 colloidal solution with deionized water, stir at room temperature for 30 minutes, and then filter the solution using a syringe and a water filter. (2) Preparation of perovskite solution: (2.1) Dissolve PbI2 powder in a mixed solution of DMF and DMSO, and stir to dissolve and form a mixed solution of PbI2; (2.2) Add 2-PO powder to the above PbI2 mixed solution to form a 2-PO-PbI2 mixed solution; (2.3) Dissolve FAI and MACl in IPA solution and stir to form a solution salt solution; (3) Preparation of hole transport layer: Spiro-OMeTAD solution, Li-TFSI solution and 1 ml of 4-tBP chlorobenzene solution were mixed to form Spiro-OMeTAD solution; (4) Preparation of experimental devices: (4.1) Cleaning of ITO glass: First, wipe the ITO glass substrate with a cleaning agent, and then wash the ITO glass substrate in deionized water, acetone and isopropanol in sequence using an ultrasonic machine for 30 minutes. (4.2) Fabrication of the electron transport layer: Using a spin coater in an air atmosphere, the SnO2 colloidal solution diluted in step (1) is spin-coated onto the ITO glass substrate treated in step (4.1), and then the ITO glass substrate with the SnO2 colloidal solution spin-coated is annealed on a hot plate. (4.3) Preparation of the perovskite active layer: Under a nitrogen atmosphere, a spin coater was used to spin coat the 2-PO-PbI2 mixed solution prepared in step (2.2). The ITO glass substrate with the spin-coated 2-PO-PbI2 mixed solution was then annealed and cooled on a hot plate. Then, the solution salt solution prepared in step (2.3) was spin-coated, and then annealed on a hot plate in an air atmosphere. (5) Preparation of hole transport layer: The Spro-OMeTAD solution prepared in step (3) was spin-coated onto a perovskite-coated ITO glass substrate under a nitrogen atmosphere using a spin coater. (6) Preparation of gold electrodes: Using a thermal evaporation apparatus, at a depth of 5 x 10⁻⁶... -4 Under a vacuum of Pa, 80 nm gold was deposited as the back electrode.

2. The method for improving the light stability of perovskite solar cells according to claim 1, characterized in that, In step (1), the SnO2 colloidal solution is a 15wt% SnO2 colloidal solution.

3. The method for improving the light stability of perovskite solar cells according to claim 1, characterized in that, In step (2.1), the volume of DMF is 950 μL, the volume of DMSO is 50 μL, the mass of PbI2 powder is 599.3 mg, and the stirring conditions are: temperature 70℃, stirring for 6 h.

4. The method for improving the light stability of perovskite solar cells according to claim 1, characterized in that, In step (2.2), the mass of the 2-PO powder is 2 mg.

5. The method for improving the light stability of perovskite solar cells according to claim 1, characterized in that, In step (2.3), the mass of FAI is 90 mg, the mass of MACl is 12 mg, the volume of IPA solution is 1 mL, and the stirring conditions are: stirring at room temperature for 30 min.

6. The method for improving the light stability of perovskite solar cells according to claim 1, characterized in that, In step (3), the mass of Spiro-OMeTAD is 72.3 mg, the volume of the Li-TFSI solution is 17.5 μL, and the volume of the 4-tBP is 29 μL.

7. The method for improving the light stability of perovskite solar cells according to claim 1, characterized in that, In step (4.2), the volume of the SnO2 colloidal solution is 70 μL, the spin coating speed is 3000 rpm, the spin coating time is 50 s, and the annealing conditions are: annealing at room temperature of 150℃ for 25 min.

8. The method for improving the light stability of perovskite solar cells according to claim 1, characterized in that, In step (4.3), the volume of the 2-PO-PbI2 mixed solution is 70 μL, the rotation speed is 2000 rpm, the spin coating time is 30 s, and the annealing conditions are: annealing at room temperature of 70℃ for 1 min and cooling for 10 min. The volume of the salt solution is 70 μL, the rotation speed is 1800 rpm, the spin coating time is 30 s, and the annealing conditions are: annealing at 150℃ for 30 min, and the humidity of the air atmosphere is 30%-40%.

9. The method for improving the light stability of perovskite solar cells according to claim 1, characterized in that, In step (5), the volume of the Spro-OMeTAD solution is 50 μL, the spin coating speed is 3000 rpm, and the time is 30 s.

Images