Method for repairing defects of tin-based perovskite structure by using hydrostatic pressure

Abstract

A method for repairing tin-based perovskite structure defects by using hydrostatic pressure, the method comprising the following steps: step one: sample cavity assembly and sample loading: a diamond table and a gasket are used to form a sample chamber, and a two-dimensional tin-based iodide perovskite (BA) 2MASn2I7 sample is ground into a uniform powder and placed in the sample chamber; step two: pressurization: a compression spring sheet is compressed by rotating a pressurizing nut to extrude a piston and a cylinder, the pressure is transmitted to the diamond table, thereby generating high pressure, and the pressure is adjusted by the distance of the nut's rotation, and the structure defects are repaired. The hydrostatic pressure regulation technology does not change the intrinsic properties of the material on the basis of improving the defect properties of the material. Therefore, the pressure regulation technology can be considered as a precise, controllable and impurity-free post-preparation structure defect repair technology for tin-based perovskite materials.

Description

Technical Field

[0001] This invention relates to a technique for controlling the physical properties of materials using hydrostatic pressure, specifically to a technique and application of compressing and depressurizing tin-based iodide perovskite using a diamond anvil cell for material modification. Background Technology

[0002] As a class of perovskites that can effectively replace lead-based halide perovskites (APbX3, A=CH3NH3) + HC(NH2)2 + Cs + ;X=I - , Br - Cl - Tin-based (Sn(II)) perovskites have been studied and achieved considerable optoelectronic performance in recent years. As a metal in the same group as lead with the same outermost electron structure, Sn(II) has been successfully used to replace Pb(II) ions to form lead-free perovskite materials (ASnX3), and has been extensively studied and developed in recent years. Because the chemical bonds formed by Sn(II) and halogens have higher covalent properties than lead-halogen bonds, tin-based perovskite materials have smaller optical band gaps and higher carrier mobility than lead-based perovskites, achieving a maximum photoelectric conversion efficiency of 15.38% in single-junction photovoltaic cells. However, this efficiency is still far lower than the highest photovoltaic efficiency (26.1%) of lead-based perovskite solar cells. Furthermore, the stability of tin-based perovskite solar cells is far inferior to that of similar lead-based devices. The reason for this is that the Sn(II) cations in tin-based iodide perovskite materials are easily oxidized to Sn(IV) in the presence of oxygen, leading to structural defects, severe p-type doping, and carrier recombination centers. Simultaneously, due to the strong antibonding coupling effect between the Sn 5s and I 5p atomic orbitals, tin vacancies have a very low formation energy, further exacerbating the p-type doping and defect properties of the material at the thermodynamic level. These two factors directly result in the metallic properties of tin-based iodide perovskites, rather than their photovoltaic properties as semiconductors. Therefore, mitigating the antibonding coupling effect between Sn 5s and I 5p at the thermodynamic level and suppressing the oxidation of Sn(II) ions can significantly improve the stability and photoelectric properties of this type of lead-free perovskite material.

[0003] Previous studies have shown that modifying tin-based perovskite materials using 1) Sn(II)-rich additives and 2) organic antioxidants (such as hydroquinone, vitamin C, epicatechin, etc.) can effectively reduce the defect density of the material and enhance the antioxidant capacity of Sn(II), thus improving the stability of photovoltaic devices under humid conditions to some extent. However, the above methods can only be achieved by doping the precursor solution components of tin-based perovskite. The synthesized tin-based perovskite has optical, electrical, chemical composition and other properties different from the intrinsic material, and the defect properties of tin-based perovskite materials cannot be precisely and controllably controlled. Based on this, it has become a key focus to find a technical method that allows for controllable intrinsic properties and targeted repair of only the lattice defects of the material. Summary of the Invention

[0004] This invention addresses the problem of lattice defects in tin-based perovskite materials by providing a method to improve the defect properties of these materials. In the post-processing stage after the material has crystallized, this invention reduces divalent tin defects in the tin-based perovskite; the optimization of the tin defect properties is transformed into a permanent, irreversible physicochemical process; and the problems of material property changes and uncontrollability caused by wet chemical processes are resolved.

[0005] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0006] A method for repairing structural defects in tin-based perovskites using hydrostatic pressure, the method comprising:

[0007] Step 1: Sample chamber assembly and sample loading: Assemble the sample chamber with the diamond stage and the gasket, grind the two-dimensional tin-based iodide perovskite (BA)2MASn2I7 sample into a uniform powder, and place it into the sample chamber;

[0008] Step Two: Pressurization: Rotating the pressure nut compresses the spring plate, squeezing the piston and cylinder, transmitting pressure to the diamond anvil cell, thus generating high pressure. The pressure is adjusted by the precession distance of the nut, achieving the repair of structural defects. The device involved in Step Two is a Beijing Yijie Sb type diamond anvil cell device.

[0009] Furthermore, the method also includes step three: pressure calibration: Cr is added to the sample chamber. 3+Doped Al₂O₃ particles (ruby) were used for pressure calibration (the sample chamber contained silicone oil, tin-based iodide perovskite, and rubber). Under ambient temperature and pressure, and with laser excitation at 420 or 532 nm, the rubber used exhibited a fluorescence emission peak of λ₀ = 694.21 nm (λ₀ may vary slightly between different batches of rubber, or even between the same batch measured on different spectrometers; therefore, λ₀ must be determined beforehand). As pressure increased, the rubber fluorescence peak redshifted, and the wavelength shift Δλ satisfied the equation related to pressure:

[0010] P = A / B{[1 + (Δλ / λ0)]} B –1}

[0011] In the formula, P is the ambient pressure, A = 19.04 Mbar, and B = 7.665. Therefore, the pressure in the cavity can be calibrated by detecting the position of Ruby's fluorescence peak. The pressure calibration is to obtain information about the pressure environment (i.e., the current pressure magnitude), and the repair of defects is achieved through pressure treatment.

[0012] Furthermore, the sample loading in step one was all carried out in a nitrogen glove box.

[0013] Furthermore, in step one, the diamond mesa used in the XRD experiment has a diameter of 300 μm, a T301 stainless steel gasket with a hole diameter of 150 μm is selected, the pressure transmission medium is silicone oil, and Ruby is used as the pressure calibrator.

[0014] For in-situ high-pressure optical absorption and fluorescence spectroscopy, grade II-A diamond should be selected in the optical experiments to avoid interference from the fluorescence background. The diamond mesa diameter should be 300 μm. T301 stainless steel gaskets with a hole diameter of 120 μm are selected, silicone oil is used as the pressure transmission medium, and Ruby is used as the pressure calibrator.

[0015] In-situ high-pressure optical absorption spectroscopy and in-situ high-pressure fluorescence spectroscopy are two techniques used to study the optical properties of substances under high pressure. Optical experiments have specific requirements regarding the type of diamond used; it is crucial to minimize interference from the fluorescence emitted by the diamond during the experiment. Therefore, the phrase "in optical experiments" is emphasized.

[0016] The diamond table refers to the two opposing sharp points of the diamond. The smaller the table size, the higher the hydrostatic pressure threshold that can be achieved.

[0017] Using the above method, static fluorescence (PL) and transient fluorescence (TRPL) tests were performed on the material in the diamond pressure chamber at one atmosphere, 1 GPa, 2 GPa, 3 GPa and 4 GPa respectively; then, the pressure chamber was depressurized and static fluorescence and transient fluorescence tests were performed at 3 GPa, 2 GPa, 1 GPa and one atmosphere respectively.

[0018] The advantages of this invention compared to existing technologies are as follows: by pressurizing tin-based perovskite to 4 GPa and then depressurizing it to normal atmospheric pressure, the steady-state photoluminescence intensity and carrier lifetime of the material are significantly improved. Specifically, the steady-state photoluminescence peak intensity is enhanced by approximately 1.67 times; and the carrier lifetime increases from 5 ns before pressure treatment to 10 ns after pressure treatment, representing a doubling in quantity. However, the depressurized tin-based perovskite material retains the same lattice parameters and optical band gap as before pressure treatment. Therefore, unlike conventional methods such as 1) excessive tin doping and 2) reducing organic antioxidants, this hydrostatic pressure control technique improves the defect properties of the material without altering its intrinsic physical properties. Thus, this pressure control technique can be considered a precise, controllable, and impurity-free post-processing structural defect repair technique for tin-based perovskite materials. Attached Figure Description

[0019] Figure 1 This is a schematic diagram illustrating the main principles of the present invention;

[0020] Figure 2 The radar image shows the lattice parameters, emission peak position, optical band gap, defects, carrier lifetime, and emission intensity of the tin-based perovskite material of the present invention.

[0021] Figure 3 The steady-state photoluminescence spectra of two-dimensional tin-based perovskite (BA)2MASn2I7 under the conditions of the example (before and after pressure treatment) are shown (yellow curve: before pressure treatment; green curve: after pressure treatment).

[0022] Figure 4 These are transient photoluminescence spectra under the conditions of the example (before and after pressure treatment) (yellow curve: before pressure treatment; green curve: after pressure treatment). Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments, but it is not limited thereto. Any modifications or equivalent substitutions to the technical solution of the present invention that do not depart from the spirit and scope of the technical solution of the present invention should be covered within the protection scope of the present invention.

[0024] The principle of this invention in repairing lattice defects through pressure application and depressurization is the change in material structure caused by pressure.

[0025] Comparative example:

[0026] The two-dimensional tin-based perovskite material in this comparative example was prepared by an aqueous solution method.

[0027] The aqueous solution method is a chemical synthesis of tin-based perovskites carried out in an aqueous medium. It typically involves mixing a tin source with an organic amine source in an aqueous solution and controlling the reaction conditions to achieve perovskite synthesis. Due to its simplicity, non-toxic solvents, high product purity, and high performance in optoelectronic applications, the aqueous solution method is an ideal method for perovskite synthesis. (Angew. Chem. Int. Ed. Engl. 2018, 57, 9650-9654)

[0028] The steps for preparing two-dimensional perovskite materials using the aqueous solution method in this embodiment are as follows: First, 1128 mg (5 mmol) of SnCl2·2H2O powder was dissolved in 20 mL of a 57% (w / w) aqueous solution of hydrogen iodide. The solution was heated to boiling for about 5 minutes with continuous magnetic stirring using a 50 mL glass graduated cylinder. Then, 225 mg (3.33 mmol) of dry MACl solid was added to the resulting solution, and it dissolved rapidly with stirring. Next, 800 μL (8 mmol) of BA was added to 4 mL of a 50% aqueous solution of H3PO2, and the resulting solution was slowly added to the reaction system. After stirring was stopped, the solution was placed on a hot plate to cool. The hot plate was initially set to 180 degrees Celsius, and then the heating was turned off, allowing the solution to cool naturally to room temperature. After approximately 18 hours, precipitation was considered complete. The crystals were separated by filtration, then vacuum annealed at 130 degrees Celsius for 18 hours. Finally, the crystals were placed in 9 mm Pyrex test tubes and annealed at 100°C for 10 hours. -4 Flame sealing under bar pressure.

[0029] The sample was compacted on a glass slide and subjected to photoluminescence spectroscopy under normal pressure and room temperature conditions. The highest intensity of the emission spectrum was approximately 3000 photons, and the center of the emission peak was located at 740 nm.

[0030] The sample was compacted on a glass slide and subjected to transient photoluminescence spectroscopy under ambient pressure and room temperature conditions. The measured carrier lifetime was 5 nanoseconds.

[0031] Example:

[0032] This embodiment uses the same perovskite material sample as the comparative example. The compacted sample from the comparative example was placed in a sealed sample chamber with a diamond anvil cell and subjected to high pressure treatment at room temperature. Silicone oil was used as the pressure transmission medium, and the pressure was calibrated using the fluorescence peak of ruby.

[0033] The steps of the room temperature high pressure treatment are as follows: The pressure inside the sample chamber of the diamond anvil device is gradually increased from atmospheric pressure to 4 GPa, maintained for 5 minutes, and then the pressure is reduced to atmospheric pressure to complete the room temperature high pressure treatment.

[0034] Photoluminescence spectroscopy of the material, such as Figure 3 As shown, the highest intensity of the emission spectrum was approximately 5000 photons (a significant increase compared to the comparative example), and the emission peak was located at 740 nm, unchanged from the comparative example.

[0035] Transient photoluminescence spectroscopy of the material, such as Figure 4 As shown, the measured carrier lifetime is 10 nanoseconds, which is a significant improvement compared to the control group.

[0036] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the scope of the technology disclosed in the present invention, and within the spirit and principles of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for repairing structural defects in tin-based perovskites using hydrostatic pressure, characterized in that: The method is as follows: Step 1: Sample chamber assembly and loading: Assemble the sample chamber with the diamond stage and gasket, grind the two-dimensional tin-based iodide perovskite (BA)2MASn2I7 sample into a uniform powder and place it into the sample chamber; all sample loading in Step 1 is carried out in a nitrogen glove box. Step 2: Pressurization: Rotate the pressure nut to compress the spring plate, which squeezes the piston and cylinder, transmitting the pressure to the diamond platform, thereby generating high pressure. The pressure is adjusted by the distance the nut is screwed in, thus repairing the structural defects.

2. The method for repairing structural defects in tin-based perovskites using hydrostatic pressure according to claim 1, characterized in that: The method also includes step three: pressure calibration: adding Cr to the sample chamber. 3+ Doped Al₂O₃ particles were used for pressure calibration; under ambient temperature and pressure, and with laser excitation at 420 or 532 nm, Cr was used. 3+ The doped Al2O3 particles were measured to have The fluorescence emission peak is at 694.21 nm; as the pressure increases, this fluorescence peak redshifts, with a wavelength shift of [missing value]. The pressure satisfies the following equation: In the formula, Given the ambient pressure, A = 19.04 Mbar, B = 7.665, therefore, by detecting Cr... 3+ The position of the fluorescence peak of the doped Al2O3 particles can be used to determine the pressure in the cavity.

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