Preparation method of metal oxide packaged perovskite nanocrystals

Abstract

The invention discloses a preparation method of a metal oxide packaged perovskite nanocrystal, which comprises the following steps: dissolving an inorganic metal salt in a mixed solvent of water and ethanol to form a first solution; dissolving Cs2CO3, PbBr2, oleylamine and oleic acid in octadecene to form a second solution; injecting the first solution into the second solution, and performing ultrasonic treatment with the power of 300-500W to obtain a third solution; adding epoxypropane into the third solution, continuously performing ultrasonic treatment for 1 to 2 minutes, and standing to form a metal hydroxide packaged CsPbBr3 perovskite nanocrystal; and calcining the CsPbBr3 perovskite nanocrystal packaged by the metal hydroxide under a vacuum condition, so as to obtain the CsPbBr3 perovskite nanocrystal packaged by the metal oxide. The nanocrystal prepared by the invention can keep optical activity under the conditions of humidity, heat and the like.

Description

Technical Field

[0001] The present application relates to the technical field of nanocrystalline material preparation, and in particular to a method for preparing metal oxide-encapsulated perovskite nanocrystals. Background Art

[0002] Perovskite nanocrystals are an emerging class of fluorescent materials with excellent luminescence properties and the advantages of low-temperature solution preparation. They have been widely studied in new displays, photovoltaics, flexible electronics and nano-optics. However, the "soft lattice" characteristics of perovskite nanocrystals make them extremely susceptible to decomposition, phase change or ion migration under environmental conditions such as water, heat and light, resulting in rapid degradation of luminescence performance. This stability defect seriously limits its application in polar solvent environments (such as water, ethanol, ethylene glycol, etc.). Currently, most studies prepare fluorescent inks by dispersing perovskite nanocrystals in non-polar solvents (such as toluene and n-hexane) to circumvent the problem of water and oxygen erosion, but such inks are difficult to meet the application requirements of water-based systems (such as inkjet printing and biocompatible coatings). Therefore, it is necessary to develop perovskite nanocrystals that can maintain photoactivity under conditions such as humidity and heat for the preparation of water-based nanocrystal fluorescent inks. Summary of the Invention

[0003] The embodiments of the present application solve the problems raised in the background art by providing a method for preparing metal oxide-encapsulated perovskite nanocrystals.

[0004] The present invention provides a method for preparing metal oxide-encapsulated perovskite nanocrystals, comprising:

[0005] S1: dissolving an inorganic metal salt in a mixed solvent of water and ethanol to form a first solution, wherein the inorganic metal salt is at least one of Al(NO3)3.9H2O, Ce(NO3)3.6H2O, and SnBr4;

[0006] S2: dissolving Cs2CO3, PbBr2, oleylamine and oleic acid in octadecene to form a second solution;

[0007] S3: injecting the first solution into the second solution and performing ultrasonic treatment at a power of 300-500 W to obtain a third solution;

[0008] S4: adding propylene oxide to the third solution, continuing ultrasonic treatment for 1-2 minutes, and then standing for at least 1 hour to form metal hydroxide-encapsulated CsPbBr3 perovskite nanocrystals;

[0009] S5: calcining the metal hydroxide-encapsulated CsPbBr3 perovskite nanocrystals at 150-200° C. and a pressure of ≤10 Pa under vacuum conditions for 1-2 hours to achieve dehydration treatment and obtain metal oxide-encapsulated CsPbBr3 perovskite nanocrystals.

[0010] In a possible implementation, step S2 includes:

[0011] S21: Cs2CO3, PbBr2, oleylamine and oleic acid are dissolved in octadecene, and ultrasonically treated for 10-18 minutes to obtain a second solution containing CsPbBr3 perovskite nanocrystals.

[0012] In a possible implementation, in step S3, the first solution is injected into the second solution, and ultrasonic treatment is performed at a power of 300-500 W for 10-15 minutes.

[0013] In a possible implementation, the inorganic metal salt further includes at least one of ZrO(NO3)2, Mn(NO3)2·6H2O, Co(NO3)2·6H2O, Eu(NO3)3·6H2O and Ni(NO3)2·6H2O.

[0014] In a possible implementation, in step S1, the volume ratio of water to ethanol is 1:10.

[0015] In one possible implementation, in step S4, the molar ratio of propylene oxide to the inorganic metal salt is 17:1.

[0016] In one possible implementation, in step S2, Cs2CO3 and PbBr2 are dissolved in octadecene at a molar ratio of 1:3.

[0017] In a possible implementation, in step S3, the volume ratio of the first solution to the second solution is 1:100.

[0018] One or more technical solutions provided in the embodiments of this application have at least the following technical effects:

[0019] The embodiments of the present application provide a method for preparing metal oxide-encapsulated perovskite nanocrystals. The dual-mode encapsulation strategy (in situ / ex situ) developed in this application has a wide range of adaptability and can be flexibly adjusted according to different types of perovskite materials, showing strong application potential. This strategy is not only applicable to conventional lead-containing perovskite systems, but can also be effectively applied to most types of lead-free, organic, inorganic, and inorganic-organic hybrid perovskite systems, providing strong support for the development of environmentally friendly perovskite materials. In addition, this encapsulation strategy is also scalable and can be further extended to the encapsulation protection of other ionic crystal materials, providing new ideas and methods for related research in the field of materials science. The metal oxide encapsulation layer formed in this application has many excellent properties. It has extremely high density and can be tightly wrapped around the surface of the perovskite nanocrystal to form a solid barrier. At the same time, the encapsulation layer also has excellent chemical stability and can maintain a stable structure and performance under various environments. This excellent density and chemical stability enable the encapsulation layer to effectively block the penetration of water molecules and oxygen, thereby significantly improving the stability of the perovskite nanocrystals in harsh environments and extending their service life. During the encapsulation process, the technology in this application also simultaneously passivates surface defects in perovskite nanocrystals. This reduction in surface defects facilitates smoother carrier transport in the material, effectively reducing the probability of non-radiative recombination and significantly improving the material's optoelectronic properties. The encapsulated nanocrystals exhibit superior luminescence properties, such as enhanced luminescence intensity and improved wavelength stability.

[0020] More importantly, the technology in this application solves the fundamental problem of perovskite nanocrystal instability in polar solvents. This breakthrough opens up a new avenue for the application of perovskite nanocrystals in aqueous systems, giving them broader application prospects in fields such as bioimaging, optoelectronic devices, and sensors, and is expected to promote the rapid development of related industries. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments of the present application. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0022] Figure 1 This is a performance comparison chart of Example 1, Example 2 and Comparative Example 1 of this application;

[0023] Figure 2 AlO prepared in this embodiment x Comparison of the luminescence stability of @CsPbBr3 and its transmission electron microscopy (TEM) images in solvents of different polarities;

[0024] Figure 3 CsPbBr3 and SnO provided in the embodiment of this application x Comparison of the luminescence performance of @CsPbBr3 dispersed in water for 7 days. DETAILED DESCRIPTION

[0025] The following will be combined with the accompanying drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0026] In the description of the embodiments of the present application, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limitations on the present application. The terms "first", "second" and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0027] The present invention provides a method for preparing metal oxide-encapsulated perovskite nanocrystals, comprising:

[0028] S1: dissolving an inorganic metal salt in a mixed solvent of water and ethanol to form a first solution, wherein the inorganic metal salt is at least one of Al(NO3)3.9H2O (aluminum nitrate nonahydrate), Ce(NO3)3.6H2O (cerium nitrate hexahydrate), and SnBr4 (tin tetrabromide).

[0029] It should be noted that the first solution prepared in step S1 is a metal oxide precursor solution.

[0030] S2: Cs2CO3 (cesium carbonate), PbBr2 (lead bromide), oleylamine and oleic acid are dissolved in octadecene to form a second solution.

[0031] It should be noted that the second solution prepared in step S2 is a perovskite precursor solution.

[0032] S3: injecting the first solution into the second solution and performing ultrasonic treatment at a power of 300-500 W to obtain a third solution.

[0033] S4: adding propylene oxide to the third solution, continuing ultrasonic treatment for 1-2 minutes, and then standing for at least 1 hour to form metal hydroxide-encapsulated CsPbBr3 perovskite nanocrystals;

[0034] S5: calcining the metal hydroxide-encapsulated CsPbBr3 perovskite nanocrystals at 150-200° C. and a pressure of ≤10 Pa under vacuum conditions for 1-2 hours to achieve dehydration treatment and obtain metal oxide-encapsulated CsPbBr3 perovskite nanocrystals.

[0035] In an embodiment of the present application, a metal oxide precursor solution is added to a perovskite precursor solution to construct a synergistic and unique in-situ reaction system. In this in-situ reaction system, during the synthesis process of perovskite nanocrystals, the encapsulation reaction of the metal hydroxide (which will be subsequently converted into a metal oxide) is carried out simultaneously. Specifically, the metal oxide precursor solution and the perovskite precursor solution interact with each other in the same reaction system, and the crystallization process of the perovskite nanocrystals and the encapsulation process of the metal hydroxide are simultaneously promoted. This one-step synthesis strategy greatly simplifies the process flow, reduces subsequent processing steps, and facilitates large-scale production and practical applications.

[0036] In the embodiment of the present application, step S2 includes:

[0037] S21: Cs2CO3, PbBr2, oleylamine and oleic acid are dissolved in octadecene, and ultrasonically treated for 10-18 minutes to obtain a second solution containing CsPbBr3 perovskite nanocrystals.

[0038] Specifically, Cs2CO3, PbBr2, oleylamine and oleic acid were dissolved in octadecene, and ultrasonicated at 300W for 8 minutes (to induce nucleation) and 500W for 8 minutes (to promote crystal growth). After the reaction, the solution was cooled to room temperature in a water bath to obtain a second solution containing CsPbBr3 (cesium lead bromide) perovskite nanocrystals.

[0039] The preparation method of the present application is carried out in a non-in situ reaction system, adopting a staged ultrasound strategy: low-power ultrasound is used in the initial stage to promote uniform dispersion of the precursor and induce crystal nucleation; then switch to high-power ultrasound to accelerate the orderly growth of the crystals, thereby precisely controlling the size uniformity and crystallinity of the nanocrystals. In this process, oleylamine and oleic acid, as bifunctional ligands, are dynamically adsorbed on the surface of the nanocrystals under the drive of the ultrasonic cavitation effect, covering the uncoordinated metal ion sites, effectively inhibiting the generation of surface defects, and improving the photoluminescence efficiency and environmental tolerance of the material. During preparation, the first solution is slowly injected into the CsPbBr3 perovskite nanocrystal solution (second solution), and with the help of ultrasonic cavitation and mechanical shear force, the uniform dispersion and hydrolysis reaction of the metal ions are promoted to generate metal hydroxide nanoparticles, and by regulating the reaction kinetics, the directional deposition of the hydroxide on the surface of the nanocrystal is achieved to form a preliminary encapsulation interface. Propylene oxide is then introduced as a gel promoter, and its active group coordinates with the metal hydroxide, accelerating the sol-gel conversion process and promoting the densification of the encapsulation layer structure. Finally, after subsequent low-temperature calcination treatment, the metal hydroxide is dehydrated and converted into a stable metal oxide shell, which forms a chemical bond with the perovskite lattice to construct a core-shell structure. Therefore, the staged ultrasonic strategy of this application regulates the crystal growth dynamics through energy gradient, effectively inhibits the Ostwald ripening phenomenon, and obtains monodisperse nanocrystals; the synergistic effect of the dual ligands achieves surface passivation and hydrophobic modification, reduces non-radiative recombination centers, and enhances the intrinsic stability of the material; the propylene oxide-mediated gelation process optimizes the density of the encapsulation layer, and the metal oxide shell provides a dual protection mechanism of physical barrier and chemical passivation, which can effectively resist polar solvent erosion and ion migration; at the same time, the low-temperature solution method avoids the damage of high-temperature thermal stress to the perovskite lattice, adapting to the needs of flexible devices and solution processing technology.

[0040] Furthermore, the metal oxide encapsulation layer formed in this application exhibits excellent compactness and chemical stability. This encapsulation layer can effectively isolate water molecules and oxygen from penetrating, thereby significantly improving the stability of perovskite nanocrystals in complex environments.

[0041] It should be noted that in the field of perovskite nanocrystal encapsulation technology, traditional encapsulation technology is strictly dependent on an inert atmosphere and usually requires operation under strictly oxygen and water-free conditions. This not only greatly increases the complexity and cost of the process, but also places extremely high demands on equipment, limiting its large-scale application. However, this application takes a different approach and successfully breaks through this traditional constraint, developing a new encapsulation process that can operate under normal pressure.

[0042] This technology innovatively utilizes a propylene oxide-mediated sol-gel process to cleverly achieve controlled encapsulation in an air environment. This unique process significantly simplifies the encapsulation process and reduces equipment requirements, providing a more convenient and efficient solution for encapsulating perovskite nanocrystals.

[0043] More importantly, this application innovatively combines ultrasound technology with the sol-gel method. Under the action of ultrasound, a strong ultrasonic cavitation effect is generated, which can effectively promote the ring-opening reaction of propylene oxide and the subsequent hydrolysis-condensation reaction. This series of reactions enables the metal hydroxide to be evenly deposited on the surface of the nanocrystals, successfully solving the technical problem of uneven encapsulation in traditional methods and providing more stable and reliable encapsulation protection for perovskite nanocrystals.

[0044] The dual-mode encapsulation strategy (in situ / ex situ) developed in this application has wide adaptability and can be flexibly adjusted according to the type of perovskite material, showing strong application potential. This strategy is not only applicable to conventional lead-containing perovskite systems, but can also be effectively applied to most types of lead-free, organic, inorganic, and inorganic-organic hybrid perovskite systems, providing strong support for the development of environmentally friendly perovskite materials. In addition, this encapsulation strategy is also scalable and can be further extended to the encapsulation and protection of other ionic crystal materials, providing new ideas and methods for related research in the field of materials science. The metal oxide encapsulation layer formed in this application has many excellent properties. It has extremely high density and can be tightly wrapped on the surface of perovskite nanocrystals to form a solid barrier. At the same time, the encapsulation layer also has excellent chemical stability and can maintain stable structure and performance under various environments. This excellent density and chemical stability enable the encapsulation layer to effectively block the penetration of water molecules and oxygen, thereby significantly improving the stability of perovskite nanocrystals in harsh environments and extending their service life. During the encapsulation process, the technology of this application also simultaneously achieves the passivation of surface defects of perovskite nanocrystals. The reduction of surface defects allows for smoother carrier transport in the material, effectively reducing the probability of non-radiative recombination, thereby significantly improving the material's optoelectronic properties. The encapsulated nanocrystals exhibit superior luminescence properties, such as enhanced luminescence intensity and improved wavelength stability.

[0045] More importantly, the technology in this application solves the fundamental problem of perovskite nanocrystal instability in polar solvents. This breakthrough opens up a new avenue for the application of perovskite nanocrystals in aqueous systems, giving them broader application prospects in fields such as bioimaging, optoelectronic devices, and sensors, and is expected to promote the rapid development of related industries.

[0046] In the embodiment of the present application, in step S3, the first solution is injected into the second solution, and an ultrasonic treatment with a power of 300-500W is carried out for 10-15min. The embodiment of the present application is a supplement to the in-situ reaction system. After the first solution is injected into the second solution, the components in the two solutions need to be fully contacted and mixed. The ultrasonic treatment of 300-500W can produce a strong cavitation effect and mechanical stirring effect. The cavitation effect will form tiny bubbles in the solution, and the rupture of the bubbles will produce local high temperature and high pressure and microjets. These effects can effectively break the intermolecular forces in the solution, so that the ions, molecules and other components in the first solution and the second solution are rapidly diffused and mixed to form a uniform reaction system, which provides good conditions for subsequent in-situ reactions.

[0047] In the embodiment of the present application, the inorganic metal salt further includes at least one of ZrO(NO3)2 (zirconium oxynitrate), Mn(NO3)2·6H2O (manganese nitrate hexahydrate), Co(NO3)2·6H2O (cobalt nitrate hexahydrate), Eu(NO3)3·6H2O (europium nitrate hexahydrate), and Ni(NO3)2·6H2O (nickel nitrate hexahydrate). Of course, the embodiment of the present application is not limited to the above-mentioned inorganic metal salts.

[0048] In the embodiment of the present application, in step S1, the volume ratio of water to ethanol is 1:10, forming a first solution with a concentration of 0.182 mol / L.

[0049] In the embodiment of the present application, in step S4, the molar ratio of propylene oxide to inorganic metal salt is 17:1.

[0050] In the embodiment of the present application, in step S2, Cs2CO3 and PbBr2 are dissolved in octadecene at a molar ratio of 1:3 to form a second solution with a lead ion concentration of 0.03 mol / L.

[0051] In the embodiment of the present application, in step S3, the volume ratio of the first solution to the second solution is 1:100.

[0052] Example 1:

[0053] AlO x The steps of the in-situ preparation method for encapsulating CsPbBr3 perovskite nanocrystals are as follows:

[0054] 0.2 mmol Al(NO3)3.9H2O was dissolved in a mixed solution of water and ethanol in a volume ratio of 1:10 and stirred at room temperature to form a first solution;

[0055] 0.1 mmol Cs2CO3, 0.3 mmol PbBr2, 300 μL oleylamine and 300 μL oleic acid were dissolved in 10 ml octadecene to form a perovskite precursor solution, i.e., the second solution;

[0056] 250 μL of the first solution was injected into the second solution, and ultrasonicated at 300 W for 8 minutes. The ultrasonic power was then increased to 500 W and ultrasonicated for another 8 minutes to form an orange nanocrystal suspension, i.e., the third solution.

[0057] Then, 0.57 mol of propylene oxide was added to the third solution, and after ultrasonication at 500 W for 1 minute, the reaction system was cooled to room temperature in a water bath and then allowed to stand for 12 hours to obtain aluminum hydroxide-coated CsPbBr3 perovskite nanocrystals.

[0058] The aluminum hydroxide-coated CsPbBr3 perovskite nanocrystals were calcined at 150 ° C and a pressure of ≤10 Pa under vacuum conditions for 1 h to obtain aluminum oxide-coated CsPbBr3 perovskite nanocrystals (AlO x @CsPbBr3).

[0059] Example 2:

[0060] AlO x The steps of the ex-situ preparation method for encapsulating CsPbBr3 perovskite nanocrystals are as follows:

[0061] 0.1mmolCs2CO3, 0.3mmolPbBr2, 300μL oleylamine and 300μL oleic acid were dissolved in 10mL of octadecene to form a perovskite precursor solution, which was then ultrasonicated at 300W for 8 minutes. The ultrasonic power was then increased to 500W and ultrasonicated for another 8 minutes. After the reaction was completed, the reaction system was cooled to room temperature in a water bath to obtain a second solution containing CsPbBr3 perovskite nanocrystals;

[0062] 0.2 mmol Al(NO3)3.9H2O was dissolved in a mixed solution of water and ethanol in a volume ratio of 1:10 and stirred at room temperature to form a first solution;

[0063] 250 μL of the first solution was added to the second solution containing CsPbBr3 perovskite nanocrystals, and the solution was dispersed in the CsPbBr3 perovskite nanocrystals under 100W ultrasound for 5 minutes to obtain a third solution;

[0064] Then, 0.57 mol of propylene oxide was added to the third solution and ultrasonic treatment was continued at 100 W for 1 minute. Then, the entire reaction system was allowed to stand at room temperature for 12 hours to obtain aluminum hydroxide-coated CsPbBr3 perovskite nanocrystals.

[0065] The aluminum hydroxide-coated CsPbBr3 perovskite nanocrystals were calcined at 150 ° C and a pressure of ≤10 Pa under vacuum conditions for 1 h to obtain aluminum oxide-coated CsPbBr3 perovskite nanocrystals (AlO x@CsPbBr3).

[0066] Comparative Example 1

[0067] Take a certain proportion of Cs2CO3, PbBr2, oleylamine, and oleic acid and dissolve them in octadecene, then ultrasonicate at 300 watts for 8 minutes, and then ultrasonicate at 500 watts for 8 minutes. After the reaction is completed, cool it to room temperature in a water bath, then centrifuge it at 9000 rpm for 10 minutes to remove the lower layer of precipitate, and disperse it in n-hexane and centrifuge it at 2000 rpm for 10 minutes to take the upper clear liquid, and you can get a perovskite nanocrystal colloidal solution with uniform size and good dispersion.

[0068] Performance comparison table of Example 1, Example 2 and Comparative Example 1:

[0069] like Figure 1 As shown, the alumina-coated CsPbBr3 perovskite nanocrystals (AlO x @CsPbBr3) demonstrated significant advantages in hydrothermal stability testing. After immersion in 50°C water with continuous stirring for 30 minutes, both coated samples maintained stable photoluminescence properties, while the uncoated blank CsPbBr3 nanocrystals (Comparative Example 1) exhibited significant fluorescence quenching. This demonstrates that the aluminum oxide encapsulation layer effectively blocks water molecules from corroding the perovskite's soft lattice structure, validating the protective effectiveness of both coating methods in humid environments.

[0070] To further explore the universality of the packaging system, Figure 2 As shown, the AlO prepared in Example 2 x After being immersed in polar solvents such as water, isopropanol, ethanol and acetone for 7 days, @CsPbBr3 still maintained its luminescence activity. Further characterization by transmission electron microscopy (TEM) confirmed that the CsPbBr3 perovskite nanocrystals were effectively confined and encapsulated in the AlO x layer, and no lattice distortion was observed. This result shows that AlO x The encapsulation layer can successfully block the erosion of polar molecules in polar solvents on the surface of perovskite nanocrystals with a soft lattice structure, significantly improving the stability of the nanocrystals in polar solvent environments.

[0071] Furthermore, this packaging strategy exhibits excellent process adaptability. Figure 3 As shown, SnO prepared by the same sol-gel process x The @CsPbBr3 composite system still maintains >90% of its initial fluorescence intensity after being dispersed in water for 7 days. x x / SnO x) combined with perovskite systems can achieve effective surface passivation, demonstrating the universal applicability of this encapsulation method. This metal oxide encapsulation technology provides a reliable technical path for expanding the practical application of perovskite nanocrystals in humid environments, organic solvent systems, and solution processing.

[0072] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0073] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A method for preparing metal oxide encapsulated perovskite nanocrystals, characterized in that: include: S1: dissolving an inorganic metal salt in a mixed solvent of water and ethanol to form a first solution, wherein the inorganic metal salt is at least one of Al(NO3)3.9H2O, Ce(NO3)3.6H2O, and SnBr4; S2: dissolving Cs2CO3, PbBr2, oleylamine and oleic acid in octadecene to form a second solution; S3: injecting the first solution into the second solution and performing ultrasonic treatment at a power of 300-500 W to obtain a third solution; S4: adding propylene oxide to the third solution, continuing ultrasonic treatment for 1-2 minutes, and then standing for at least 1 hour to form metal hydroxide-encapsulated CsPbBr3 perovskite nanocrystals; S5: calcining the metal hydroxide-encapsulated CsPbBr3 perovskite nanocrystals at 150-200° C. and a pressure of ≤10 Pa under vacuum conditions for 1-2 hours to achieve dehydration treatment and obtain metal oxide-encapsulated CsPbBr3 perovskite nanocrystals.

2. The method for preparing metal oxide-encapsulated perovskite nanocrystals according to claim 1, characterized in that: Step S2 includes: S21: Cs2CO3, PbBr2, oleylamine and oleic acid are dissolved in octadecene, and ultrasonically treated for 10-18 minutes to obtain a second solution containing CsPbBr3 perovskite nanocrystals.

3. The method for preparing metal oxide encapsulated perovskite nanocrystals according to claim 1, characterized in that: In step S3, the first solution is injected into the second solution, and ultrasonic treatment is performed at a power of 300-500 W for 10-15 minutes.

4. The method for preparing metal oxide-encapsulated perovskite nanocrystals according to claim 1, wherein: The inorganic metal salt further includes at least one of ZrO(NO3)2, Mn(NO3)2·6H2O, Co(NO3)2·6H2O, Eu(NO3)3·6H2O and Ni(NO3)2·6H2O.

5. The method for preparing metal oxide encapsulated perovskite nanocrystals according to claim 1, characterized in that: In step S1, the volume ratio of water to ethanol is 1:

10.

6. The method for preparing metal oxide-encapsulated perovskite nanocrystals according to claim 1, characterized in that: In step S4, the molar ratio of propylene oxide to the inorganic metal salt is 17:

1.

7. The method for preparing metal oxide-encapsulated perovskite nanocrystals according to claim 1 or 2, characterized in that: In step S2, Cs2CO3 and PbBr2 are dissolved in octadecene at a molar ratio of 1:

3.

8. The method for preparing metal oxide-encapsulated perovskite nanocrystals according to claim 1, wherein: In step S3, the volume ratio of the first solution to the second solution is 1:100.

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