A method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets
The two-step vapor deposition method for preparing large-size all-inorganic CsPbI3 nanosheets solves the problems of ligand residue, size limitation and insufficient stability in the preparation of CsPbI3 perovskite nanosheets in the prior art, and realizes the preparation of high-quality and stable nanosheets, which are suitable for photodetectors and light-emitting devices.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LUOYANG INST OF SCI & TECH
- Filing Date
- 2026-06-09
- Publication Date
- 2026-07-10
AI Technical Summary
In the existing technology, the preparation methods of CsPbI3 perovskite nanosheets have problems such as ligand residue, many impurity phases, size limitation, poor crystal quality and insufficient stability. In particular, there is no simple method for the controllable preparation of large-size all-inorganic CsPbI3 perovskite nanosheets.
A two-step vapor deposition method was adopted. First, high-quality PbI2 nanosheets were grown by physical vapor deposition, and then they were transformed into CsPbI3 nanosheets by chemical vapor deposition. By using a dual-temperature zone tube furnace and precise control of vapor phase thermodynamic parameters, the reaction process was ensured to be controllable, the generation of impurity phases was avoided, and large-size, single-crystal, low-defect CsPbI3 nanosheets were formed.
The controllable preparation of large-size all-inorganic CsPbI3 nanosheets has been achieved, which significantly improves the photoelectric properties and stability of the material, simplifies the preparation process, reduces the difficulty of operation, and is suitable for fields such as photodetectors and light-emitting devices.
Smart Images
Figure CN122355338A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of quantum dot technology, specifically relating to a method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets. Background Technology
[0002] The chemical structure of all-inorganic perovskite is ABX3, where the A-site is an inorganic ion (cesium ion (Cs+)); the B-site is a metal ion, such as divalent lead ion (Pb). 2+ ), Tin ions (Sn) 2+ ) and germanium ions (Ge 2+ ) etc.; the X position is a halide anion (Cl - , Br - I - CsPbI3 perovskite nanosheets, with crystal forms classified into three main categories: cubic, orthorhombic, and tetragonal, possess key characteristics including strong emissivity, high photovoltaic conversion efficiency (PCE > 19%), and a tunable bandgap covering the entire visible spectrum, making them promising candidates for micro- and nano-optoelectronic devices. In particular, two-dimensional CsPbI3 perovskite nanosheets, due to their unique quantum confinement effect and large exciton binding energy, exhibit superior optical and electrical properties compared to three-dimensional bulk materials, becoming a current research hotspot in the field of nano-optoelectronics. However, the susceptibility of CsPbI3 perovskite to oxidation during preparation leads to a sharp decline in photoelectric conversion efficiency, significantly limiting its commercial application as an optoelectronic device. Therefore, studying the stability of all-inorganic CsPbI3 perovskite nanosheets is crucial for optimizing their controllable preparation.
[0003] Currently, the main methods for preparing CsPbI3 perovskite nanosheets include solution methods and one-step vapor deposition methods. Solution methods, such as hot injection and ligand-assisted reprecipitation, can synthesize nanosheets, but they suffer from problems such as residual organic impurities, poor controllability, and difficulty in obtaining high-quality, stable CsPbI3 perovskite nanosheets. Traditional one-step vapor deposition methods have extremely stringent requirements for controlling parameters such as reaction temperature, gas flow, and pressure. Large differences in gas pressure between the two evaporation sources can easily lead to uneven product composition, numerous crystal defects, and irregular morphology. Furthermore, there are no reports in the existing technology of a simple and controllable method for preparing large-size CsPbI3 perovskite nanosheets.
[0004] The patent document "A Method for In-situ Preparation of CsPbI3 Colloidal Nanosheets with NH4I Assist" (CN118307028A) discloses a method of reacting a pre-prepared lead iodide precursor solution and ammonium iodide precursor solution with a cesium oleate precursor solution, mixing and stirring to obtain a nanosheet stock solution, purifying and separating the nanosheet stock solution to obtain CsPbI3 nanosheets. The synthesized nanosheets have a narrower half-width at half-maximum and a more uniform phase distribution, which can meet the requirements for luminescence in the red light range. However, the nanosheets are prone to agglomeration, the size controllable range is narrow (only 1–5 μm), and there are a large number of grain boundaries. They cannot be directly grown in situ on the target substrate, making device fabrication difficult and unsuitable for high-performance optoelectronic applications.
[0005] The patent document "A Large-Size Ultrathin All-Inorganic Lead Halide Perovskite Nanosheet and Its Preparation Method and Application" (CN113620339B) discloses a preparation method in which a heated solution of cesium precursor, oleic acid and octadecene is mixed with a heated solution of lead halide, oleic acid and oleylamine in a volume ratio, and heated to 150-180℃ for 40-90 min to obtain ultrathin all-inorganic lead halide perovskite nanosheets with a side length of 1-5 μm and a thickness of no more than 10 nm. The obtained nanosheets have residual organic ligands, many surface defects, insufficient thermal stability and long-term environmental stability, and the entire preparation process requires inert gas protection, with harsh process conditions that are difficult to control.
[0006] The patent document CN115261979A, entitled "A Method for Preparing Halide Perovskite Nanosheets by In-situ Chemical Vapor Deposition," discloses a method of grinding and mixing lead halide powder and cesium halide powder to obtain a solid precursor, which is then mixed with a mesoporous molecular sieve. Heating in a nitrogen atmosphere causes the solid precursor to sublimate into a gaseous state and be adsorbed into the pores of the mesoporous molecular sieve. Lowering the temperature allows gaseous lead, cesium, and halogen atoms to react in-situ within the molecular sieve pores, forming halide perovskite nanocrystals. However, due to the lack of zoned temperature control, the mismatch between sublimation temperature and volatilization rate easily leads to the formation of impurity phases. It also makes it impossible to control the gaseous diffusion path of the precursor, resulting in a product dominated by nanocrystals with poor crystal uniformity, small size, and severe agglomeration, making it difficult to form large-sized continuous nanosheets.
[0007] Therefore, developing a simple reaction procedure with high crystal quality, excellent stability, few defects, and the ability to produce large-sized all-inorganic CsPbI3 perovskite nanosheets is of significant research and application value. Furthermore, a two-step gas-phase method for the direct synthesis of high-quality all-inorganic CsPbI3 perovskite nanosheets has not yet been reported. Summary of the Invention
[0008] The purpose of this invention is to address the technical shortcomings of existing solution-based and one-step vapor deposition methods for preparing all-inorganic CsPbI3 perovskite nanosheets, such as ligand residues, numerous impurity phases, size limitations, poor crystallinity, and insufficient stability. This invention provides a two-step vapor deposition method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets. By pre-preparing a large-size PbI2 nanosheet template and then reacting it with CsI in a vapor-phase topological reaction, this invention enables the direct preparation of large-size all-inorganic perovskite nanosheets. The nanosheets exhibit controllable size, single-crystal structure, low defects, high phase purity, regular morphology, and excellent stability. The preparation process is simple and easy to operate, and can be directly applied to photodetectors, light-emitting devices, and nonlinear optical devices.
[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:
[0010] A method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets includes the following steps:
[0011] Step 1: Weigh out high-purity PbI2 powder and high-purity CsI powder with a molar ratio of 1:1 and set aside. Place the weighed PbI2 powder in an agate grinding mortar and grind it thoroughly. After grinding, place it in a quartz crucible to obtain the PbI2 evaporation source.
[0012] Step 2: Place the quartz crucible in a single-temperature zone tube furnace, and place the newly peeled mica substrate approximately 14-15 cm downstream of the crucible. Evacuate the tube furnace to a vacuum level of 5 x 10. -7 After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure and gas flow rate inside the tubular furnace are controlled within a defined range.
[0013] Step 3: Heat the tube furnace at a rate of 18℃ / min to the sublimation temperature of the PbI2 evaporation source, maintain the temperature for a certain deposition time, and allow PbI2 to be physically vapor-deposited on the mica substrate. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain a mica substrate containing large-sized PbI2 nanosheets for later use.
[0014] Step 4: Place the weighed CsI powder in an agate grinding mortar and grind it thoroughly. After grinding, place it in a quartz crucible to obtain a CsI evaporation source.
[0015] Step 5: Place the CsI evaporation source and the mica substrate with deposited PbI2 nanosheets into a dual-temperature zone tube furnace. The mica substrate with PbI2 nanosheets should be positioned approximately 14-15 cm away from the heating zone of the CsI evaporation source. Evacuate the tube furnace to a vacuum level of 5 x 10. - 7 After the torsion is applied, high-purity argon gas is introduced as the carrier gas, and the pressure and gas flow rate inside the tubular furnace are controlled within a defined range.
[0016] Step 6: Heat the tube furnace at a rate of 18℃ / min to bring the quartz tube to the sublimation temperature of the CsI evaporation source. Maintain a certain deposition time to allow CsI to be chemically vapor-deposited on the substrate. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain high-quality CsPbI3 nanosheets with large size.
[0017] In step one, the purity of high-purity PbI2 and CsI is analytical grade.
[0018] In step two, the pressure inside the tubular furnace is within 5 to 50 Torr, and the gas flow rate is within 20 to 100 sccm.
[0019] In step three, the sublimation temperature is controlled at 300~450℃ and the physical vapor deposition time is 10~50min.
[0020] In step five, the pressure inside the tubular furnace is within 5 to 50 Torr, and the gas flow rate is within 10 to 50 sccm.
[0021] In step six, the sublimation temperature is controlled at 500~600℃, and the chemical vapor deposition time is 30~90min;
[0022] In steps one through six, the resulting large-size, high-quality CsPbI3 nanosheets have a single-crystal structure, regular morphology, and low crystal defect density.
[0023] In step two, maintaining the pressure inside the tube furnace can effectively reduce the sublimation temperature of PbI2 and increase the synthesis rate of PbI2 nanosheets.
[0024] In step three, the PbI2 nanosheets obtained by physical vapor deposition can provide a high-quality precursor for the synthesis of CsPbI3 nanosheets.
[0025] In step five, argon gas is introduced at a certain flow rate while maintaining the pressure inside the tubular furnace. This can reduce the reaction temperature inside the tubular furnace, suppress gas flow turbulence, and improve deposition efficiency and material uniformity.
[0026] This invention innovatively employs a two-step vapor deposition method. In the first step, using mica sheets as van der Waals epitaxial substrates, the pressure and flow rate of argon gas within a tube furnace are controlled to effectively reduce the sublimation temperature of PbI₂ and increase its diffusion rate, thereby enhancing the synthesis rate of PbI₂ nanosheets. Simultaneously, the quality of PbI₂ vapor deposition on the mica substrate is controlled, ensuring its directional growth into large-sized, regularly morphologically regular two-dimensional PbI₂ nanosheets. These nanosheets serve as high-quality precursors for the successful synthesis of CsPbI₃ nanosheets, providing a good substrate for constructing large-size crystal templates. The second step utilizes a dual-temperature zone tube furnace for zoned temperature control. Argon gas is introduced at a specific flow rate under negative pressure, which regulates the CsI sublimation temperature, suppresses turbulent airflow within the furnace, and ensures uniform diffusion of CsI vapor onto the PbI₂ nanosheet surface. This also improves the deposition efficiency of CsI vapor on the substrate, reduces the reaction temperature within the tube furnace, and results in more uniform formation of CsPbI₃ nanosheets. PbI2 and CsI undergo an in-situ solid-state topological reaction on a PbI2 nanosheet substrate. The sublimation temperature and rate are matched, making it difficult to generate impurity phases. The product is mainly composed of nanocrystals, which fully inherit the two-dimensional morphology and large-size structure of PbI2 nanosheets, forming larger CsPbI3 nanosheets with uniform crystal form and ordered structure.
[0027] When the molar ratio of PbI2 to CsI is 1:1, precise adjustment of process parameters such as pressure, gas flow rate, reaction temperature, and deposition time within the tube furnace ensures a matched ion diffusion rate, uniform gas-phase reaction interface, and the most thorough reaction between PbI2 and CsI with minimal byproducts. This leads to preferential crystal growth along the two-dimensional direction, effectively suppressing the formation of impurities and particles, preserving the layered structure of the two-dimensional nanosheets, and significantly improving the crystal quality of the product. The application of the dual-temperature zone tube furnace and stepwise deposition avoids the problem of mismatched sublimation temperatures between CsI and PbI2. The mica substrate is free of interfacial stress, which facilitates preferential lateral growth of PbI2 crystals. The lateral growth rate is much greater than the longitudinal growth rate, which is conducive to the formation of large-size PbI2 nanosheet precursors, ultimately yielding single-crystal, low-defect, pure-phase large-size CsPbI3 nanosheets.
[0028] This invention achieves stable and controllable preparation of impurity-free, high-quality, large-size CsPbI3 nanosheets by precisely controlling gas-phase thermodynamics and reaction kinetics. It overcomes the technical shortcomings of existing liquid-phase and one-step deposition methods, and provides a good foundation for the widespread application of large-size all-inorganic CsPbI3 nanosheet optoelectronic materials.
[0029] The beneficial effects of this invention are as follows:
[0030] (1) This invention creatively employs a two-step vapor phase conversion method. First, high-quality PbI2 nanosheets are grown by physical vapor deposition, and then they are converted into CsPbI3 nanosheets by chemical vapor deposition. The reaction process is precise and controllable. Compared with the traditional solution method, the vapor phase method avoids the introduction of solvent molecules, fundamentally eliminating microscopic defects such as point defects, lattice distortions and pinholes caused by solvent residues or excessively rapid crystallization. The resulting CsPbI3 nanosheets have regular morphology and good crystallinity, which significantly improves the photoelectric properties of the material.
[0031] (2) The preparation method provided by this invention can precisely control the size and morphology of CsPbI3 nanosheets. By precisely controlling the transport rate of CsI vapor and reaction kinetics, the size of CsPbI3 nanosheets can be effectively controlled. This method is simple to operate, has good process repeatability, and can meet the differentiated requirements of perovskite material size for different micro-nano optoelectronic devices;
[0032] (3) The preparation method provided by this invention has simple reaction steps and good process compatibility. Compared with the traditional vapor deposition method, which requires simultaneous control of the temperature and vapor pressure of multiple sources, this invention decomposes the synthesis of CsPbI3 into two independent steps, with a wider process window for each step, significantly reducing the difficulty of operation. This method has good compatibility with existing semiconductor micro-nano fabrication processes and is easy to scale up.
[0033] (4) The dense, low-defect crystal structure obtained by the present invention through the gas phase method reduces the number of grain boundaries and surface dangling bonds, thereby reducing the active sites for chemical reactions between the material and environmental media (such as H2O, O2), effectively inhibiting the oxidation of CsPbI3 at room temperature, and improving the long-term stability of the material.
[0034] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be perceived and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.
[0035] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description
[0036] Figure 1 This is a schematic diagram of the reaction apparatus used in this invention;
[0037] Figure 2 A scanning electron microscope (SEM) image of the large-sized PbI2 nanosheets prepared in Example 1 of this invention.
[0038] Figure 3The large-size PbI2 nanoparticle energy dispersive X-ray spectrometer (EDS) prepared in Example 1 of this invention is shown in the surface scanning energy spectrum.
[0039] Figure 4 This is a scanning electron microscope (SEM) image of the all-inorganic CsPbI3 nanosheets prepared in Example 1 of this invention.
[0040] Figure 5 X-ray diffraction (XRD) pattern of the all-inorganic CsPbI3 nanosheets prepared in Example 1 of this invention;
[0041] Figure 6 This is a scanning electron microscope (SEM) image of the all-inorganic CsPbI3 nanosheets prepared in Example 2 of this invention.
[0042] Figure 7 The X-ray diffraction (XRD) pattern of the all-inorganic CsPbI3 nanosheets prepared in Example 2 of this invention. Detailed Implementation
[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments and corresponding drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Unless otherwise specified, the experimental methods in the following embodiments are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified.
[0044] As analyzed in the background section of this invention, existing preparation methods mostly employ solution methods and one-step vapor deposition to synthesize perovskite nanosheets. While solution methods can synthesize nanosheets, they suffer from issues such as residual organic impurities, poor controllability, and difficulty in obtaining high-quality, stable perovskite nanosheets. Traditional one-step vapor deposition methods easily lead to problems such as uneven product composition, numerous crystal defects, and irregular morphology. Therefore, this invention employs a two-step vapor deposition method for the synthesis of perovskite nanosheets. The chemical formula of the all-inorganic perovskite nanosheets in this invention is CsPbI3.
[0045] To further understand the present invention, the following embodiments use the following methods: Figure 1 The schematic diagram of the reaction apparatus shown is illustrated below. The preparation method of large-size all-inorganic CsPbI3 perovskite nanosheets provided by the present invention will be described in conjunction with the embodiments. The scope of protection of the present invention is not limited by the following embodiments.
[0046] Example 1:
[0047] A method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets includes the following steps:
[0048] Step 1: Weigh 0.4610g of high-purity PbI2 powder and 0.2598g of high-purity CsI powder for later use. Place the weighed PbI2 powder in an agate grinding mortar and grind it thoroughly. After grinding, add it to a quartz crucible to obtain the PbI2 evaporation source.
[0049] Step 2: Place the quartz crucible in a single-zone tube furnace, and place the newly peeled mica substrate approximately 14 cm downstream of the crucible. Evacuate the tube furnace to a vacuum level of 5 x 10. -7 After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure inside the tube is controlled at 10 Torr and the gas flow rate is 50 sccm.
[0050] Step 3: Heat the tube furnace at a rate of 18℃ / min to the sublimation temperature of the PbI2 evaporation source, 320℃, and maintain the deposition time for 40min to allow PbI2 to be physically vapor-deposited on the mica substrate. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain a mica substrate containing large-sized PbI2 nanosheets for later use.
[0051] Step 4: Place the weighed CsI powder in an agate grinding mortar and grind it thoroughly. After grinding, place it in a quartz crucible to obtain a CsI evaporation source.
[0052] Step 5: Place the CsI evaporation source and the mica substrate with deposited PbI2 nanosheets into a dual-temperature zone tube furnace, positioning the mica substrate with PbI2 nanosheets approximately 14 cm away from the heating zone of the CsI evaporation source. Evacuate the tube furnace to a vacuum level of 5 x 10. - 7 After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure inside the tube furnace is controlled at 10 Torr and the gas flow rate is 30 sccm.
[0053] Step 6: Heat the tube furnace at a rate of 18℃ / min until the quartz tube reaches the sublimation temperature of the CsI evaporation source at 500℃. Maintain the deposition time for 60 minutes to allow CsI to be deposited on the substrate by chemical vapor deposition. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain high-quality CsPbI3 nanosheets with large size.
[0054] The scanning electron microscope image of the large-sized PbI2 nanosheets prepared in this embodiment is shown below. Figure 2 The nanosheets exhibit a regular rectangular shape and uniform size, with measurements of approximately 3-5 µm, demonstrating a highly controlled synthesis process for the large-sized PbI₂ nanosheets. The energy-dispersive X-ray spectra of the large-sized PbI₂ nanosheets prepared in this example are shown in [reference needed]. Figure 3 , Figure 3Surface scanning analysis further confirmed the elemental composition of the nanosheets, showing that the ratio of lead to iodine was close to 1:2, thus confirming that we synthesized PbI2 nanosheets.
[0055] The scanning electron microscope image of the all-inorganic CsPbI3 nanosheets prepared in this embodiment is shown below. Figure 4 The X-ray diffraction pattern of the nanosheets, measuring approximately 5-10 µm, was observed, demonstrating the highly controlled synthesis process of the all-inorganic CsPbI3 nanosheets. The X-ray diffraction pattern of the all-inorganic CsPbI3 nanosheets prepared in this embodiment is shown in [reference needed]. Figure 5 This further confirmed that the elemental diffraction peaks in the nanosheets matched the characteristic peaks of CsPbI3, thus confirming that we synthesized CsPbI3 nanosheets.
[0056] Example 2:
[0057] A method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets includes the following steps:
[0058] Step 1: Weigh 0.4610g of high-purity PbI2 powder and 0.2598g of high-purity CsI powder for later use. Place the weighed PbI2 powder in an agate grinding mortar and grind it thoroughly. After grinding, add it to a quartz crucible to obtain the PbI2 evaporation source.
[0059] Step 2: Place the quartz crucible in a single-zone tube furnace, and place the newly peeled mica substrate approximately 14 cm downstream of the crucible. Evacuate the tube furnace to a vacuum level of 5 x 10. -7 After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure inside the tube furnace is controlled at 5 Torr and the gas flow rate is 20 sccm.
[0060] Step 3: Heat the tube furnace at a rate of 18℃ / min to the sublimation temperature of the PbI2 evaporation source, 450℃, and maintain the deposition time for 10min to allow PbI2 to be physically vapor-deposited on the mica substrate. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain a mica substrate containing large-sized PbI2 nanosheets for later use.
[0061] Step 4: Place the weighed CsI powder in an agate grinding mortar and grind it thoroughly. After grinding, place it in a quartz crucible to obtain a CsI evaporation source.
[0062] Step 5: Place the CsI evaporation source and the mica substrate with deposited PbI2 nanosheets into a dual-temperature zone tube furnace, positioning the mica substrate with PbI2 nanosheets approximately 14 cm away from the heating zone of the CsI evaporation source. Evacuate the tube furnace to a vacuum level of 5 x 10. - 7After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure inside the tube furnace is controlled at 5 Torr and the gas flow rate is 10 sccm.
[0063] Step 6: Heat the tube furnace at a rate of 18℃ / min until the quartz tube reaches the CsI evaporation source at a sublimation temperature of 600℃. Maintain the deposition time for 30 minutes to allow CsI to be deposited on the substrate by chemical vapor deposition. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain high-quality CsPbI3 nanosheets with large size.
[0064] The scanning electron microscope image of the all-inorganic CsPbI3 nanosheets prepared in this embodiment is shown below. Figure 6 The X-ray diffraction pattern of the nanosheets, measuring approximately 10-15 µm, demonstrates the regular shape and size consistency of the nanosheets, indicating a high degree of controllability in the synthesis of large-sized all-inorganic CsPbI3 nanosheets. The X-ray diffraction pattern of the all-inorganic CsPbI3 nanosheets prepared in this embodiment is shown in [reference needed]. Figure 7 The X-ray diffraction pattern further confirmed that the elemental diffraction peaks in the nanosheets matched the characteristic peaks of CsPbI3, thus further confirming the high purity and compositional consistency of the synthesized nanosheets.
[0065] Example 3:
[0066] A method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets includes the following steps:
[0067] Step 1: Weigh 0.4610g of high-purity PbI2 powder and 0.2598g of high-purity CsI powder for later use. Place the weighed PbI2 powder in an agate grinding mortar and grind it thoroughly. After grinding, add it to a quartz crucible to obtain the PbI2 evaporation source.
[0068] Step 2: Place the quartz crucible in a single-zone tube furnace, and place the newly peeled mica substrate approximately 15 cm downstream of the crucible. Evacuate the tube furnace to a vacuum level of 5 x 10. -7 After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure inside the tube furnace is controlled at 50 Torr and the gas flow rate is 100 sccm.
[0069] Step 3: Heat the tube furnace at a rate of 18℃ / min to the sublimation temperature of the PbI2 evaporation source of 300℃, and maintain the deposition time for 50min to allow PbI2 to be physically vapor-deposited on the mica substrate. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain a mica substrate containing large-sized PbI2 nanosheets for later use.
[0070] Step 4: Place the weighed CsI powder in an agate grinding mortar and grind it thoroughly. After grinding, place it in a quartz crucible to obtain a CsI evaporation source.
[0071] Step 5: Place the CsI evaporation source and the mica substrate with deposited PbI2 nanosheets into a dual-temperature zone tube furnace, positioning the mica substrate with PbI2 nanosheets approximately 15 cm away from the heating zone of the CsI evaporation source. Evacuate the tube furnace to a vacuum level of 5 x 10. - 7 After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure inside the tube furnace is controlled at 50 Torr and the gas flow rate is 50 sccm.
[0072] Step 6: Heat the tube furnace at a rate of 18℃ / min until the quartz tube reaches the sublimation temperature of the CsI evaporation source of 500℃. Maintain the deposition time for 90min to allow CsI to be chemically vapor-deposited on the substrate. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain high-quality CsPbI3 nanosheets with large size.
[0073] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.
Claims
1. A method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets, characterized in that: Step 1: Weigh out high-purity PbI2 powder and high-purity CsI powder with a molar ratio of 1:1 and set aside. Place the weighed PbI2 powder in an agate grinding mortar and grind it thoroughly. After grinding, place it in a quartz crucible to obtain the PbI2 evaporation source. Step 2: Place the quartz crucible in a single-zone tube furnace, and place the newly peeled mica substrate approximately 14-15 cm downstream of the crucible. Evacuate the tube furnace to a vacuum level of 5 x 10. -7 After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure and gas flow rate inside the tubular furnace are controlled within a defined range. Step 3: Heat the tube furnace at a rate of 18℃ / min to the sublimation temperature of the PbI2 evaporation source, maintain the temperature for a certain deposition time, and allow PbI2 to be physically vapor-deposited on the mica substrate. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain a mica substrate containing large-sized PbI2 nanosheets for later use. Step 4: Place the weighed CsI powder in an agate grinding mortar and grind it thoroughly. After grinding, place it in a quartz crucible to obtain a CsI evaporation source. Step 5: Place the CsI evaporation source and the mica substrate with deposited PbI2 nanosheets into a dual-temperature zone tube furnace. The mica substrate with PbI2 nanosheets should be positioned approximately 14-15 cm away from the heating zone of the CsI evaporation source. Evacuate the tube furnace to a vacuum level of 5 x 10. -7 After Torr, high-purity argon gas is introduced as the carrier gas, and the pressure and gas flow rate inside the tubular furnace are controlled within a defined range. Step 6: Heat the tube furnace at a rate of 18℃ / min to bring the quartz tube to the sublimation temperature of the CsI evaporation source. Maintain a certain deposition time to allow CsI to be chemically vapor-deposited on the substrate. After deposition, allow the tube furnace to be rapidly cooled to room temperature to obtain high-quality CsPbI3 nanosheets with large size.
2. The method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets according to claim 1, characterized in that: In step two, the pressure inside the tubular furnace is controlled within 5 to 50 Torr, and the airflow rate is controlled within 20 to 100 sccm.
3. The method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets according to claim 1, characterized in that: In step three, the sublimation temperature is controlled at 300~450℃, and the physical vapor deposition time is 10~50min.
4. The method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets according to claim 1, characterized in that: In step five, the pressure inside the tubular furnace is controlled within 5 to 50 Torr, and the airflow rate is controlled within 10 to 50 sccm.
5. The method for preparing large-size all-inorganic CsPbI3 perovskite nanosheets according to claim 1, characterized in that: In step six, the sublimation temperature is controlled at 500~600℃, and the chemical vapor deposition time is 30~90min.