Method for improving the diffusion coefficient of perovskite film and intercepting its high diffusion coefficient under high pressure to normal pressure

Abstract

The present invention discloses a method for improving the diffusion coefficient of a perovskite film and capturing the high diffusion coefficient under high pressure to normal pressure. The method comprises: (FAPbI3) 0.95 (MAPbBr3) 0.05 The polycrystalline film is crushed, and a suitable sample is picked up with a needle and placed in a diamond anvil. The change in the diffusion coefficient of the polycrystalline film under different pressures is measured by a time-space resolved fluorescence imaging system, and the pressure is increased from normal pressure to 1.8 GPa, maintained for 12 hours, and then the pressure is released, and the change in the diffusion coefficient of the polycrystalline film at different times since the start of pressurization is recorded. The present invention realizes the diffusion coefficient test of polycrystalline films under different pressures. It is found that with the increase of pressure, the diffusion coefficient of the polycrystalline film first increases and then tends to be constant. By maintaining the high pressure point for a long time and then releasing the pressure, the high diffusion coefficient of the polycrystalline film under high pressure is successfully retained to normal pressure.

Description

Technical Field

[0001] The invention belongs to the field of material carrier transport, and particularly relates to a method for improving the diffusion coefficient of a perovskite film and intercepting the high diffusion coefficient under high pressure to normal pressure. Background Art

[0002] Organic-inorganic hybrid perovskites, with their advantages such as high absorption coefficient, long carrier lifetime and diffusion length, and suitable band gap, have become star materials in the photovoltaic and optoelectronic fields over the past decade. Organic-inorganic hybrid perovskites have attracted extensive and systematic research by scientists worldwide. Perovskite materials can be applied in light-emitting diodes, lasers, photodetectors, photocatalysis, and solar cells. The photoelectric conversion efficiency of perovskite solar cells has increased from 3.8% in 2009 to 26% today. Producing hybrid perovskites through cation and anion doping is considered an important approach to achieving high-efficiency perovskite solar cells. However, the photoelectric conversion efficiency of perovskite solar cells is still far from the Shockley–Queisser limit (33.7%).

[0003] In order to achieve high conversion efficiency of perovskite solar cells, people have been committed to developing various chemical methods to improve the optoelectronic properties of perovskites (such as carrier lifetime and carrier transport performance). Various chemical methods include optimizing crystal growth, chemical element doping, and preparing heterojunctions, with the aim of improving the crystallinity of perovskites and optimizing the chemical composition. In addition, different chemical treatment methods, such as solvent engineering and vacuum evaporation, have also been used to improve the performance of perovskites. Chemical regulation will change the composition of elements and is difficult to control precisely. How to use simple and efficient physical methods to improve the performance of perovskites is one of the scientific challenges facing this field.

[0004] As an independent thermodynamic parameter, pressure can effectively shorten interatomic distances and enhance coupling between adjacent electron orbitals, profoundly influencing the structure and properties of materials. It plays a crucial role in discovering new phenomena, properties, and mechanisms. Pressure modulates the crystal structure and electron wave functions of materials by altering the bond lengths and angles of the lattice, thereby modifying the material's photophysical properties. Carrier lifetime and carrier migration distance are important photophysical parameters that determine the performance of optoelectronic devices. Understanding how these parameters change with pressure is crucial for evaluating the impact of pressure-treated perovskites and their devices. Summary of the Invention

[0005] For practical applications, the application of devices in high-pressure environments is still difficult to implement. Therefore, the primary task of this invention is to increase the diffusion coefficient of carriers in the perovskite film by applying pressure, and then maintain the high diffusion coefficient of the perovskite film under high pressure at normal pressure by maintaining it for a long time at the high pressure point.

[0006] The main implementation scheme adopted by the present invention is as follows: (FAPbI3) 0.95 (MAPbBr3) 0.05 The polycrystalline film was transferred to the diamond anvil of a high-pressure press using a needle pick. A stainless steel ring gasket was placed on the diamond anvil. Silicone oil was dripped into the gasket, acting as a pressure-transmitting medium, subjecting the sample to quasi-hydrostatic pressure. The high-pressure press with the sample was placed on a fluorescence scanning imaging microscope to measure the diffusion coefficient under different pressures. The experiment found that as the pressure increased, (FAPbI3) 0.95 (MAPbBr3) 0.05 The diffusion coefficient of the polycrystalline film increases first and then tends to be constant as the pressure increases. By maintaining the high pressure point for a long time and then releasing the pressure, the high pressure phase (FAPbI3) was successfully 0.95 (MAPbBr3) 0.05 The diffusion coefficient of polycrystalline thin films is preserved down to ambient pressure.

[0007] The purpose of the present invention is achieved through the following solutions.

[0008] The method of increasing the diffusion coefficient of perovskite film and intercepting its high diffusion coefficient under high pressure to normal pressure has the following specific steps:

[0009] (1)(FAPbI3) 0.95 (MAPbBr3) 0.05 Preparation of polycrystalline thin films: Dissolve the raw materials MABr, MACl, FAI, PbBr2, and PbI2 in a mixture of DMF and DMSO and stir until dissolved. The precursor solution is then dropwise added to a thin glass sheet measuring 22 mm × 22 mm × 0.13 mm (length × width × thickness). Spin coating is then performed, with trichlorotoluene added dropwise during the spin coating process. Finally, a heat treatment process is performed.

[0010] (2)(FAPbI3) 0.95 (MAPbBr3) 0.05 Transferring the polycrystalline film to the diamond anvil: The synthesized sample (1) is selected under a microscope using an embroidery needle and transferred to the diamond anvil of the high-pressure press. Stainless steel is placed on the diamond anvil as a gasket, and silicone oil is dripped into the gasket. The silicone oil serves as a pressure transmission medium to subject the sample to quasi-hydrostatic pressure.

[0011] (3) (FAPbI3) under different pressures 0.95 (MAPbBr3) 0.05 Diffusion coefficient test of polycrystalline thin film: The sample (2) mounted on the high-pressure press is placed on a fluorescence scanning imaging microscope system built in the laboratory to perform diffusion coefficient tests under different pressures.

[0012] (4) Intercepted perovskite (FAPbI3) 0.95 (MAPbBr3) 0.05 High diffusion coefficient of polycrystalline thin films under high pressure to normal pressure:

[0013] The sample (2) mounted on the high-pressure press was placed on a fluorescence scanning imaging microscope system built in the laboratory. After maintaining the high pressure point for a long time, the pressure was released and the (FAPbI3) at different times since the start of the pressurization was recorded. 0.95 (MAPbBr3) 0.05 Diffusion coefficient variation in polycrystalline thin films.

[0014] Preferably, the synthetic raw materials in step (1) are 5-10 mg of methylammonium bromide (MABr), 25-30 mg of methylammonium chloride (MACl), 210-230 mg of formamidine hydroiodide (FAI), 20-30 mg of lead bromide (PbBr2) and 600-620 mg of lead iodide (PbI2), 700-900 μl of dimethylformamide (DMF) and 100-300 μl of dimethyl sulfoxide (DMSO), and the stirring time is 10-14 hours. After adding 40-80 μl of the precursor solution, two spin coatings are performed, the speed and time of the first spin coating are: 800-1200 rpm, 8-12 seconds, and the speed and time of the second spin coating are: 3500-4500 rpm, 25-35 seconds. 4-6 seconds before the end of the second spin coating, the amount of trichlorotoluene added is 200-300 μl. The final heat treatment process is 100-140°C for 30-50 minutes.

[0015] Preferably, the size of the film in step (2) is 100-300 μm in side length and 0.01-0.09 mm in area. 2 Polygon (more than 3 sides).

[0016] Preferably, the different pressure range in step (3) is 0 GPa-3 GPa.

[0017] Preferably, in step (4), the certain pressure is 1.5 GPa-2.0 GPa, and the long time is 10 h-24 h.

[0018] The present invention realizes (FAPbI3) under different pressures 0.95 (MAPbBr3) 0.05 Diffusion coefficient test of polycrystalline thin film. It is found that with the increase of pressure, (FAPbI3) 0.95 (MAPbBr3) 0.05The diffusion coefficient of the polycrystalline film increases first and then tends to be constant as the pressure increases. By maintaining the high pressure point for a long time and then releasing the pressure, the high pressure phase (FAPbI3) was successfully 0.95 (MAPbBr3) 0.05 The diffusion coefficient of the polycrystalline film is retained at normal pressure. This patent proposes a method to increase the diffusion coefficient of the perovskite film and to capture its high diffusion coefficient under high pressure to normal pressure.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The perovskite (FAPbI3) synthesized by the method of improving the diffusion coefficient of the perovskite film and intercepting the high diffusion coefficient under high pressure to normal pressure of the present invention 0.95 (MAPbBr3) 0.05 Polycrystalline thin films have fewer surface defects.

[0021] (2) The method of the present invention for increasing the diffusion coefficient of the perovskite film and capturing the high diffusion coefficient under high pressure to normal pressure, thereby obtaining the perovskite (FAPbI3) at different pressures 0.95 (MAPbBr3) 0.05 Diffusion coefficient variation in polycrystalline thin films.

[0022] (3) The method of the present invention for increasing the diffusion coefficient of the perovskite film and capturing its high diffusion coefficient under high pressure to normal pressure, by maintaining the high pressure point for a long time and then releasing the pressure, successfully converts the high pressure phase (FAPbI3) 0.95 (MAPbBr3) 0.05 The diffusion coefficient of polycrystalline thin films is preserved down to ambient pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 (FAPbI3) prepared in Example 1 0.95 (MAPbBr3) 0.05 Polycrystalline thin film diagram.

[0024] Figure 2 (FAPbI3) prepared in Example 1 0.95 (MAPbBr3) 0.05 Carrier density curves of the fluorescence of polycrystalline films at different pressures after normalization along the x-axis, and the calculation of the diffusion coefficient.

[0025] Figure 3 (FAPbI3) prepared in Example 1 0.95 (MAPbBr3) 0.05 Diffusion coefficient D of polycrystalline thin films at different pressures.

[0026] Figure 4(FAPbI3) prepared in Example 1 0.95 (MAPbBr3) 0.05 The carrier density curve after normalization along the x-axis of the fluorescence at different times of the polycrystalline film under high pressure, as well as the calculation of the diffusion coefficient.

[0027] Figure 5 (FAPbI3) prepared in Example 1 0.95 (MAPbBr3) 0.05 The diffusion coefficient of polycrystalline thin films maintained at different times under high pressure. DETAILED DESCRIPTION

[0028] The present invention will be described in further detail below with reference to the examples and accompanying drawings, but the embodiments of the present invention are not limited thereto. The reagents used in the examples can all be purchased from conventional commercial sources.

[0029] The measurement of perovskite film fluorescence imaging and the calculation of diffusion coefficient: The sample was selected by needle picking with a side length of 100-300 μm and an area of ​​0.01-0.09 mm. 2 Polygon (FAPbI3) 0.95 (MAPbBr3) 0.05 Polycrystalline thin films (the subscripts 0.95 and 0.05 represent the stoichiometric ratios of the corresponding substances in the brackets) were placed on the diamond anvil of the high-pressure press. A stainless steel ring gasket (the inner diameter of the ring gasket was 500 μm) was placed on the diamond anvil (diameter 1000 μm). A drop of silicone oil was dripped into the gasket. The silicone oil served as a pressure-transmitting medium, subjecting the sample to quasi-hydrostatic pressure. A Ruby ball was used for standard pressure; the high-pressure press with the sample was placed on a fluorescence scanning imaging microscope system to test the carrier diffusion coefficient under different pressures. The fluorescence scanning imaging microscope system used 406 nm pulsed light as the excitation light. The excitation light passed through the entrance of the fluorescence scanning imaging system, passed through a 425 nm long-pass dichroic mirror (Dichroic Mirrors Long Pass), and then passed through the diamond anvil of the high-pressure press and acted on (FAPbI3). 0.95 (MAPbBr3) 0.05 Polycrystalline thin film sample, excitation light excitation (FAPbI3) 0.95 (MAPbBr3) 0.05The polycrystalline thin film sample generates fluorescence, which passes through a 425nm longpass dichroic filter and a 460nm longpass filter before entering the detector for fluorescence collection. The detector (single-photon detector) uses single-photon counting and synchronizes with the pulsed laser to achieve time-resolved fluorescence imaging. The diffusion coefficient is calculated as follows (J. Phys. Chem. Lett. 11, 6956-6963 (2020); Nat. Commun. 6, 7471 (2015):

[0030] (FAPbI3) 0.95 (MAPbBr3) 0.05 The carrier distribution at the initial moment of the polycrystalline film conforms to the Gaussian distribution, so the lateral carrier distribution at any time t can be expressed by the two-dimensional Gaussian distribution equation:

[0031]

[0032] Fluorescence intensity distribution I PL (x,y,t) is:

[0033] I PL (x, y, t) ∝ n(x, y, t)

[0034] where x0 and y0 are the locations of the excitation points, σ 2 t,x and σ 2 t,y is the Gaussian broadening that changes with time along the x and y directions. Their changes at different delay times represent the carrier transport process. For diffusion along the x axis:

[0035]

[0036] Where l = 2(Dt) 1 / 2 , represents the mean square displacement of the carrier from its initial position (along the +x and -x directions) at time t. Therefore, (FAPbI3) 0.95 (MAPbBr3) 0.05 The diffusion coefficient D of the polycrystalline film can be obtained by the following formula:

[0037]

[0038] (FAPbI3) 0.95 (MAPbBr3) 0.05 The diffusion coefficient of the polycrystalline film increases first and then tends to be constant as the pressure increases. By maintaining the high pressure point for a long time and then releasing the pressure, the high pressure phase (FAPbI3) was successfully 0.95 (MAPbBr3) 0.05The diffusion coefficient of polycrystalline thin films is preserved down to ambient pressure.

[0039] Example 1

[0040] The method for improving the diffusion coefficient of perovskite film and capturing its high diffusion coefficient under high pressure to normal pressure specifically comprises the following steps: (1) Preparation of perovskite film: accurately weighing methylammonium bromide (MABr) (7.84 mg), methylammonium chloride (MACl) (26.94 mg), formamidine hydroiodide (FAI) (228.72 mg), lead bromide (PbBr2) (25.69 mg) and lead iodide (PbI2) (613.14 mg) and dissolving them in dimethylformamide (DMF) (800 μl) and dimethyl sulfoxide (DMSO) (200 μl) and stirring for 12 hours. 60 μl of the precursor solution is dropped onto a thin glass of 22 mm × 22 mm × 0.13 mm (length × width × thickness), and then spin-coated twice, with the first spin-coating speed and time being 1000 rpm for 10 s and the second spin-coating speed and time being 4000 rpm for 30 s. At 25 seconds after the second spin coating, 250 μl of benzotrichloride was added dropwise. The final heat treatment process was 120° C. for 40 minutes.

[0041] According to the above process (measurement of perovskite film fluorescence imaging and calculation of diffusion coefficient), the perovskite film fluorescence imaging and diffusion coefficient calculation were performed: a sample with a side length of 100-300 μm and an area of ​​0.01-0.09 mm was selected by needle picking. 2 Polygon (FAPbI3) 0.95 (MAPbBr3) 0.05 polycrystalline film

[0042] (2) Measured at 0.0 GPa (normal pressure), 0.5, 1.3, 1.6, and 2.3 GPa (FAPbI3) 0.95 (MAPbBr3) 0.05 Fluorescence imaging of polycrystalline thin films.

[0043] (3) Calculate the FAPbI3 at 0.0 GPa (normal pressure), 0.5, 1.3, 1.6, and 2.3 GPa respectively 0.95 (MAPbBr3) 0.05 Diffusion coefficient D of polycrystalline thin film.

[0044] (4) Measure (FAPbI3) at 0.0 GPa (normal pressure), pressurized to 1.8 GPa, maintained at 1.8 GPa for 5 h, maintained at 1.8 GPa for 8 h, maintained at 1.8 GPa for 12 h, and then released to normal pressure at 1.8 GPa for 12 h, 2 h after unloading, 7 h after unloading, 12 h after unloading, 19 h after unloading, 24 h after unloading, and 26 h after unloading.0.95 (MAPbBr3) 0.05 Fluorescence imaging of polycrystalline thin films.

[0045] (5) Calculate the (FAPbI3) at 0.0 GPa (normal pressure), pressurized to 1.8 GPa, maintained at 1.8 GPa for 5 h, maintained at 1.8 GPa for 8 h, maintained at 1.8 GPa for 12 h, and then released to normal pressure after 12 h at 1.8 GPa, 2 h after unloading, 7 h after unloading, 12 h after unloading, 19 h after unloading, 24 h after unloading, and 26 h after unloading. 0.95 (MAPbBr3) 0.05 Diffusion coefficient of polycrystalline thin films.

[0046] (FAPbI3) prepared in this example 0.95 (MAPbBr3) 0.05 Polycrystalline thin films such as Figure 1 As shown. Prepared (FAPbI3) 0.95 (MAPbBr3) 0.05 The polycrystalline film has regular morphology and few surface defects.

[0047] (FAPbI3) prepared in this example 0.95 (MAPbBr3) 0.05 The carrier density curve of the fluorescence of the polycrystalline film at different pressures after normalization along the x-axis, and the calculation of the diffusion coefficient are as follows: Figure 2 It can be clearly seen that the broadening of the carrier density curve under high pressure is more obvious than that under normal pressure, which means that under high pressure (FAPbI3) 0.95 (MAPbBr3) 0.05 The diffusion coefficient of polycrystalline thin films is larger than that at normal pressure.

[0048] (FAPbI3) prepared in Example 1 0.95 (MAPbBr3) 0.05 Diffusion coefficient test of polycrystalline thin film under different pressures Figure 3 As shown. It is found that with the increase of pressure, (FAPbI3) 0.95 (MAPbBr3) 0.05 The diffusion coefficient of polycrystalline thin films first increases and then tends to be constant with the increase of pressure.

[0049] (FAPbI3) prepared in Example 1 0.95 (MAPbBr3) 0.05 The carrier density curve after normalization along the x-axis of the fluorescence at different times of the polycrystalline film under high pressure, as well as the calculation of the diffusion coefficient are as follows: Figure 4As shown in the figure. After the high pressure is maintained for a long time and then the pressure is released, the carrier density curve of the film is larger than that of the film under normal pressure, which is comparable to the broadening of the carrier density curve under high pressure. By maintaining the high pressure point for a long time and then releasing the pressure, the high pressure phase (FAPbI3) is successfully 0.95 (MAPbBr3) 0.05 The diffusion coefficient of polycrystalline thin films is preserved down to ambient pressure.

[0050] (FAPbI3) prepared in Example 1 0.95 (MAPbBr3) 0.05 The diffusion coefficient of polycrystalline thin film maintained at different times under high pressure is as follows Figure 5 As shown. It is found that the diffusion coefficient under high pressure is greater than that under normal pressure, and the diffusion coefficient after long-term maintenance under high pressure is the same as the diffusion coefficient under high pressure. Therefore, by maintaining the high pressure point for a long time and then releasing the pressure, the high pressure phase (FAPbI3) is successfully 0.95 (MAPbBr3) 0.05 The diffusion coefficient of polycrystalline thin films is preserved down to ambient pressure.

[0051] The above examples are preferred implementation schemes of the present invention, but the implementation schemes of the present invention are not specifically limited by the examples described above. Any other changes, modifications, simplifications, combinations, substitutions, etc. made without departing from the spirit and principles of the present invention are within the scope of protection of the present invention.

Claims

1. A method for capturing the high diffusion coefficient of a perovskite film under high pressure to normal pressure, characterized by: The perovskite film is pressurized to 1.0 GPa-2.3 GPa for 5 h-36 h, and then depressurized to normal pressure. The perovskite film is (FAPbI3) 0.95 (MAPbBr3) 0.05 Polycrystalline film.

2. The method according to claim 1, wherein: The perovskite film is pressurized to 1.5 GPa-2.0 GPa for 10 h-24 h; then the pressure is released to atmospheric pressure.

3. The method according to claim 1 or 2, characterized in that: The specific process is: smash the perovskite film attached to the glass substrate, and then select the area of ​​0.01-0.09 mm 2 The polygonal perovskite film is placed on the diamond anvil of a high-pressure press. Silicone oil is used as the pressure transmission medium and an annular gasket with an inner diameter of 400-800μm is used to pressurize the perovskite film to a certain pressure. The high pressure point is maintained for a long time and then the pressure is released to normal pressure.

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