Perovskite quantum dots with fluorine-containing passivation layer and construction method of fluorine-containing passivation layer thereof

Abstract

The application provides a perovskite quantum dot with a fluorine-containing passivation layer, comprising a micro / mesoporous template with incomplete closed pores, perovskite nanocrystals and a fluorine-containing passivation layer grown in the pores of the micro / mesoporous template, and the fluorine-containing passivation layer is used to passivate surface defects of the perovskite nanocrystals; the fluorine-containing passivation layer comprises BaF2. The application can passivate the surface of the perovskite nanocrystals to improve stability without collapsing the micro / mesoporous template.

Description

Technical Field

[0001] This invention belongs to the field of perovskite quantum dot technology, and particularly relates to a perovskite quantum dot with a fluorine-containing passivation layer and a method for constructing the fluorine-containing passivation layer. Background Technology

[0002] Lead halide compounds with perovskite structures are an emerging type of semiconductor material, especially all-inorganic perovskites CsPbX3 (X = Br, Cl, I), which possess high fluorescence quantum yield, narrow full width at half maximum (FWHM), and tunable emission wavelengths, making them highly valuable for research and application in lighting and display devices. However, because lead halide perovskites are ionic compounds with soft lattice properties, their structure is easily damaged in environments with high temperature, high humidity, and strong light irradiation, leading to a decrease in their luminescent performance. This hinders the practical application of perovskite materials in luminescence. For example, the lead hydroxide coating such as PbBrOH that spontaneously forms in water in perovskite nanocrystals provides good water and oxygen barrier properties. However, at temperatures above 70 degrees Celsius, the chemical stability of PbBrOH gradually decreases, leading to the destruction of its passivation effect on the perovskite and a significant decrease in the luminescence efficiency of the nanocrystals.

[0003] Encapsulating perovskite nanocrystals within a coating material can effectively enhance their stability. For example, using materials that easily collapse at high temperatures, such as mesoporous silica or molecular sieves, as the coating structure for perovskite nanocrystals can effectively isolate the perovskite from the external environment, ensuring stable luminescence in water or high-humidity air. For instance, Chinese patents with publication numbers CN110734758A and CN115772401A both require the collapse of the micro / mesoporous template (mesoporous silica, molecular sieve).

[0004] However, these coating structures usually cannot effectively passivate the surface of perovskite nanocrystals, resulting in a large number of surface defects in the perovskite nanocrystals. These defects can lead to a decrease in the fluorescence intensity of perovskite nanocrystals in high temperature or light-exposed environments, so improvements are urgently needed. Summary of the Invention

[0005] The purpose of this invention is to provide a perovskite quantum dot with a fluorine-containing passivation layer and a method for constructing the fluorine-containing passivation layer. To achieve the above objective, the technical solution adopted by this invention is as follows:

[0006] A perovskite quantum dot with a fluorine-containing passivation layer includes a micro / mesoporous template with incompletely closed pores, wherein perovskite nanocrystals are grown in the pores of the micro / mesoporous template and a fluorine-containing passivation layer is used to passivate surface defects of the perovskite nanocrystals.

[0007] The fluorine-containing passivation layer includes BaF2.

[0008] Furthermore, the fluorine-containing passivation layer is composed of BaF2 and other metal fluorides;

[0009] The other metal fluorides are metal fluorides other than BaF2.

[0010] Furthermore, when the micro / mesoporous template is MCM-41, the fluorine-containing passivation layer is composed of BaF2 and NaK2AlF6.

[0011] Furthermore, the micro / mesoporous template is a microporous material and / or a mesoporous material;

[0012] The microporous material is a microporous molecular sieve, microporous silica, microporous titanium dioxide, microporous alumina, microporous transition metal oxide, microporous sulfide, microporous silicate, microporous aluminate, or microporous transition metal nitride.

[0013] The mesoporous material is a mesoporous molecular sieve, mesoporous silica, mesoporous titanium dioxide, mesoporous alumina, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, mesoporous silicate, mesoporous aluminate, or mesoporous transition metal nitride.

[0014] Furthermore, the perovskite nanocrystals have a perovskite structure ABX3, wherein the molar ratio of A, B and X is 1:1:3, and A is Cs, B is Pb, Sn or Cu, and X is Cl, Br or I.

[0015] Furthermore, the perovskite nanocrystals have a perovskite structure ABX. 1.5 X' 1.5 In this context, the molar ratio of A, B, X, and X' is 1:1:1.5:1.5, and A is Cs, B is Pb, Sn, or Cu, and X and X' are different, each being Cl, Br, or I independently.

[0016] Furthermore, the melting point of the fluorine-containing passivation layer (BaF2) is higher than that of perovskite nanocrystals. Therefore, BaF2 has a higher lattice energy than perovskite nanocrystals, resulting in a more stable structure that is difficult to disrupt. If BaF2 adheres to the inner wall of the micro / mesoporous template, it acts as a reinforcing rib, thereby improving the structural strength of the template and facilitating subsequent manufacturing processes.

[0017] Furthermore, a passivation interface exists between the fluorine-containing passivation layer and the perovskite nanocrystals, thereby reducing the surface defect density of the perovskite nanocrystals.

[0018] Furthermore, the fluorinated passivation layer contains perovskite nanocrystals embedded in its lattice; or some of the perovskite nanocrystals are coated by the fluorinated passivation layer. If some of the perovskite nanocrystals are coated by the fluorinated passivation layer, it is equivalent to having more passivation interfaces between the fluorinated passivation layer and the perovskite nanocrystals, resulting in a better passivation effect on the perovskite nanocrystals.

[0019] A method for constructing a fluorine-containing passivation layer of perovskite quantum dots includes a micro / mesoporous template with incompletely closed pores, wherein barium-containing perovskite nanocrystals are grown in the pores of the micro / mesoporous template, and a lead hydroxide coating layer is formed on the surface of the perovskite nanocrystals after soaking in water.

[0020] It also includes F ions enriched in the micro / mesoporous template channels, and the lead hydroxide coating layer blocks the contact between the F ions and the barium-containing perovskite nanocrystals; to put it another way: that is, the lead hydroxide coating layer is located between the F ions and the barium-containing perovskite nanocrystals to prevent the two from contacting each other.

[0021] Under hydrothermal reaction, the lead hydroxide coating layer disappears and a BaF2 passivation layer is formed on the surface of the perovskite nanocrystals.

[0022] By adopting the above scheme: hydrothermal reaction generally refers to the process of substances reacting in a high-temperature, high-pressure aqueous environment. In this application, the high-temperature, high-pressure hydrothermal conditions favor the bonding of highly negatively charged fluoride ions and highly positively charged barium ions. The pressure of the hydrothermal reaction is between 1 and 100 MPa. The temperature of the hydrothermal reaction is >70°C, and the reaction time is at least 1 hour.

[0023] Furthermore, the lead hydroxide coating layer and the fluorine passivation layer appear selectively. Researchers found that the disappearance of the lead hydroxide coating layer and the appearance of the fluorine passivation layer occur simultaneously. Considering the time dimension, the lead hydroxide coating layer and the fluorine passivation layer appear sequentially.

[0024] Furthermore, when the fluorine-containing passivation layer is composed of BaF2 and other metal fluorides,

[0025] Other metal fluorides can be used as characterization and recognition phases for constructing fluorine-containing passivation layers of perovskite quantum dots via hydrothermal reactions; for example, the other metal fluoride can be NaK2AlF6 as a characterization and recognition phase.

[0026] When the micro / mesoporous template is MCM-41, the fluorine-containing passivation layer is composed of BaF2 and NaK2AlF6, and NaK2AlF6 is used as the characterization and recognition phase for constructing the perovskite quantum dot fluorine-containing passivation layer through hydrothermal reaction.

[0027] By employing the above approach: First, researchers doped or surface-modified perovskite nanocrystals with barium metal, ensuring that barium was present on the surface of the perovskite nanocrystals. Then, fluoride ions entered the pores of the micro / mesoporous template and reacted with barium to form BaF2. This BaF2 then sat on the surface of the perovskite nanocrystals, passivating them.

[0028] If the micro / mesoporous template is doped or modified with other metals, the fluorine-containing passivation layer formed in this application will be composed of BaF2 and other metal fluorides. For example, the fluorine-containing passivation layer is composed of BaF2 and NaK2AlF6, and the composition of the substances can be identified by XRD. MCM-41 is a material with an ordered mesoporous structure, and its chemical composition is mainly silicon dioxide (SiO2), without containing metal elements such as potassium (K), aluminum (Al), and sodium (Na). However, other elements, such as metal cations or organic molecules, can be introduced into the synthesis of MCM-41 to change its physical and chemical properties. Other elements, such as potassium, aluminum, and sodium, can be introduced into MCM-41 through co-doping or surface modification. These elements can be located in the channels or on the surface of MCM-41, thereby affecting its adsorption and other properties. At this time, it is easy to form other metal fluorides, such as NaK2AlF6, with fluoride ions under hydrothermal reaction conditions. NaK2AI F6 was used as the characterization and recognition phase for constructing a fluorine-containing passivation layer of perovskite quantum dots via hydrothermal reaction to obtain a similar Morse code.

[0029] At this point, the researchers also discovered that NaK2AI F6 was not the only characterization and recognition phase. Introducing different metal elements onto micro / mesoporous templates or perovskite nanocrystals resulted in different characterization and recognition phases.

[0030] A method for preparing perovskite quantum dots includes the following steps:

[0031] S1. Preparation of perovskite nanocrystals:

[0032] A perovskite nanocrystal precursor and a micro / mesoporous template are mixed to obtain a mixture; the mixture is calcined at a temperature lower than the collapse temperature of the micro / mesoporous template to generate perovskite nanocrystals within the pores of the micro / mesoporous template.

[0033] S2, hydrothermal post-treatment;

[0034] The perovskite nanocrystals obtained in step S1 are dispersed in a high-pressure reactor containing an inorganic fluoride solution, and the mixed solution is treated by a hydrothermal method to obtain perovskite quantum dots with a fluorine passivation layer.

[0035] Furthermore, the perovskite nanocrystal precursor includes a CsPbX3 perovskite nanocrystal precursor, which is composed of a Cs source precursor, a Pb source precursor, and a halogen source precursor.

[0036] Wherein: the Cs source precursor includes one or more of cesium halide and cesium carbonate;

[0037] The Pb source precursor includes one or more of lead halide and lead acetate.

[0038] The halogen source precursor includes one or more of cesium halide, lead halide, zinc halide, potassium halide, sodium halide, lithium halide, ammonia halide, calcium halide, strontium halide, and barium halide.

[0039] Furthermore, if the halogen precursor is selected to include both bromine and iodine sources, it will form CsPbBr. 3-y I y The perovskite structure. As those skilled in the art would know, selecting different amounts of bromine and iodine sources to modulate the emission wavelength of quantum dots is a predictable approach. Therefore, the protection of perovskite nanocrystals in this application includes CsPbBr3, CsPbI3, and CsPbBr y I 3-y Perovskite structure.

[0040] Furthermore, the inorganic fluoride solution includes aqueous solutions of NaF, KF, LiF, CsF, and combinations thereof.

[0041] Furthermore, preferably, the hydrothermal reaction temperature in step S2 is between 150°C and 250°C. Under the high temperature and pressure conditions of the hydrothermal reaction, the bonding between highly negatively charged fluoride ions and highly positively charged metal ions is favored. For example, the pressure of the hydrothermal reaction is between 1 and 100 MPa.

[0042] Furthermore, the high-pressure reaction device in step S2 is a high-pressure reaction vessel.

[0043] Furthermore, the calcination temperature of the perovskite nanocrystal precursor and the micro / mesoporous template is less than 600°C to preserve the pore structure of the micro / mesoporous template from collapsing.

[0044] In the preparation of perovskite quantum dot materials with fluorine-containing passivation layers, the highest calcination temperature used in this invention is preferably sufficient to ensure that the pores of the micro / mesoporous material do not collapse. However, the collapse temperature varies among different micro / mesoporous materials, and even among the same material with different structures, the collapse temperature differs. It is certain, however, that to achieve optimal results, the calcination temperature must not exceed the material's minimum collapse temperature. For example, in the micro / mesoporous materials exemplified above, the minimum collapse temperature is 300°C. In practice, generally speaking, 300–2000°C is sufficient to ensure the collapse of most commonly used micro / mesoporous materials. For example, mesoporous silica collapses at 600°C, mesoporous titanium dioxide begins to collapse at 800°C, and so on.

[0045] Furthermore, the "calcination at a temperature lower than the collapse temperature of the micro / mesoporous template" as defined in this invention should also include scenarios using fluxing agents. For example, Chinese patent application number ZL202211559323.5 introduces a mesoporous material collapse agent to attempt to lower the collapse temperature of the micro / mesoporous material and achieve size control of perovskite nanocrystals by avoiding agglomeration. It should be noted that even with the addition of fluxing agents or collapse agents, the calcination temperature in this application for preparing perovskite nanocrystals still needs to be "calcined at a temperature lower than the collapse temperature of the micro / mesoporous template" to preserve the pores.

[0046] The beneficial effects of this invention are mainly reflected in:

[0047] 1. In this invention, the micro / mesoporous template is not closed to retain nanopores. Since the ionic diameter of F ions is about 0.26 nm, which is much smaller than the nanopores of the mesoporous template agent (the pore diameter is usually greater than 2 nm), F ions can be effectively enriched inside the micro / mesoporous template.

[0048] 2. Because F ions have strong electronegativity, they can bond with unpaired metal ions (such as barium ions) on the perovskite surface, thereby achieving the effect of blocking and passivating the perovskite surface.

[0049] 3. Because perovskite quantum dots readily react with water, thus reducing their luminescence performance, the field of perovskite display luminescence research often suffers from a technical bias that "complete water isolation is required during perovskite preparation." However, this application takes the opposite approach, utilizing the characteristic that the lead hydroxide coating, such as PbBrOH, spontaneously forms in water when perovskite nanocrystals, possessing good water and oxygen barrier capabilities, but whose chemical stability gradually deteriorates above 70°C. Before the PbBrOH coating fails, time is provided for F ions to effectively accumulate within the pores of the micro / mesoporous template. After gradually heating to 70°C using a hydrothermal method, the high-temperature and high-pressure environment provided by the high-pressure reactor destroys the PbBrOH coating. At this point, the F ions already inside the micro / mesoporous template can immediately form bonds with unpaired, highly positively charged metal ions (such as Ba ions) on the perovskite surface, achieving the effect of blocking and passivating the perovskite surface. Attached Figure Description

[0050] Figure 1 The image shows an aberration-corrected transmission electron microscope (AC-TEM) image of the perovskite quantum dots prepared in Example 1.

[0051] Figure 2 The XRD patterns of the perovskite quantum dots in Example 1 were measured at various stages.

[0052] Figure 3 The images show the XRD patterns of the perovskite quantum dots in Example 2 at various stages. Detailed Implementation

[0053] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0054] Example 1:

[0055] Step S1: Grind and mix 5 mmol CsBr, 5 mmol PbBr2, 1 mmol BaBr2, and 2 g MCM-41 molecular sieve until homogeneous. Place the mixed powder in a muffle furnace and heat from room temperature to 450°C, then maintain the temperature at 450°C for 120 minutes. Allow the powder to cool naturally to room temperature before removing it.

[0056] Step S2: Take 300 mg of the calcined powder and disperse it in 30 ml of KF solution with a KF concentration of 3 mol / L. Place the mixed solution in a 50 ml high-pressure reactor and heat the reactor at 180 °C for 10 hours. Then, allow it to cool naturally to room temperature to obtain CsPbBr3 perovskite quantum dots with a fluorine passivation layer.

[0057] Experimental Analysis: The final product from the above preparation process was tested for its stability in a high-temperature environment of 100℃ and under strong blue light irradiation (350mW / cm2), as shown in Table 1. After 100 hours of high-temperature storage, the luminescence intensity of the powder remained at 84% of its original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity remained at 76% of its original intensity. In comparison (see Comparative Example 1), the powder sample obtained by high-temperature calcination alone, under the same high-temperature storage and blue light irradiation conditions for 100 hours, showed a decrease in luminescence intensity to 20% and 33% of its initial intensity, respectively. These results demonstrate that hydrothermal treatment with KF solution can improve the stability of perovskite quantum dots.

[0058] like Figure 1 As shown, perovskite nanocrystals are embedded in the lattice of the fluorine-containing passivation layer, creating a passivation interface between them. Analysis of the data in Table 1 shows that the fluorine-containing passivation layer can passivate surface defects in the perovskite nanocrystals, thus improving stability.

[0059] Figure 2 These are XRD patterns of the perovskite quantum dots from Example 1 measured at various stages.

[0060] The MCM-41 molecular sieve used in this embodiment contains sodium, potassium, and aluminum ions, which are introduced during the doping, modification, or synthesis stages to construct the characterization and recognition phase NaK2AI F6.

[0061] Example 2:

[0062] This embodiment will demonstrate that other micro / mesoporous templates are also applicable in this invention.

[0063] The difference between this embodiment and Embodiment 1 is that mesoporous silica nanoparticles are used as micro / mesoporous templates.

[0064] Experimental Analysis: The final product from the above preparation process was tested for its stability in a high-temperature environment of 100℃ and under strong blue light irradiation (350mW / cm2), as shown in Table 1. After 100 hours of high-temperature storage, the luminescence intensity of the powder remained at 76% of its original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity of the powder remained at 70% of its original intensity. As a comparison (see Comparative Example 2), the powder sample obtained by high-temperature calcination alone, under the same high-temperature storage and blue light irradiation conditions, showed a decrease in luminescence intensity to 51% and 27% of its initial intensity after 100 hours.

[0065] Figure 3 The image shows the XRD patterns of the perovskite quantum dots from Example 2 before and after hydrothermal treatment.

[0066] Example 3:

[0067] Step S1: Grind and mix 5 mmol CsBr, 2.5 mmol PbBr2, 2.5 mmol PbI2, 1 mmol BaBr2, and 2 g MCM-41 molecular sieve until homogeneous. Place the mixed powder in a muffle furnace and heat from room temperature to 450°C, maintaining the temperature at 450°C for 120 minutes. Then allow it to cool naturally to room temperature and remove the sample powder.

[0068] Step S2: Disperse 300 mg of the calcined powder in 30 mL of KF solution (KF concentration 3 mol / L). Place the mixed solution in a 50 mL high-pressure reactor and heat the reactor at 180 °C for 10 hours. Then allow it to cool naturally to room temperature to obtain CsPbBr with a fluorine passivation layer. 1.5 I 1.5 Perovskite quantum dots.

[0069] Example 4:

[0070] This embodiment will demonstrate that other inorganic fluoride solutions, such as NaF, CsF, and LiF, can also improve the stability of perovskite luminescent materials during the hydrothermal treatment stage.

[0071] The difference between this embodiment and Embodiment 1 is that NaF, CsF, and LiF are used in the hydrothermal treatment stage, and the concentration and amount of these fluoride solutions are the same as in Embodiment 1.

[0072] Experimental Analysis: The final products from the above preparation process were tested for stability in a high-temperature environment of 100℃ and under strong blue light irradiation (350mW / cm2). For the NaF hydrothermal-treated sample, after 100 hours of high-temperature storage, the luminescence intensity of the powder remained at 85% of its original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity remained at 70% of its original intensity. For the CsF hydrothermal-treated sample, after 100 hours of high-temperature storage, the luminescence intensity of the powder remained at 83% of its original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity remained at 77% of its original intensity. For the LiF hydrothermal-treated sample, after 100 hours of high-temperature storage, the luminescence intensity of the powder remained at 89% of its original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity remained at 71% of its original intensity. These results demonstrate that hydrothermal treatment with solutions such as NaF, CsF, and LiF can improve the stability of perovskite luminescent materials.

[0073] Comparative Example 1:

[0074] Grind and mix 5 mmol CsBr, 5 mmol PbBr2, and 2 g MCM-41 molecular sieve until homogeneous.

[0075] The above mixed powder was placed in a muffle furnace and heated from room temperature to 450°C, and then heated at 450°C for 120 minutes. The sample powder was then removed after naturally cooling to room temperature.

[0076] Experimental Analysis: The final product from the above preparation process was tested for its stability in a high-temperature environment of 100℃ and under strong blue light irradiation (350mW / cm2), as shown in Table 1. After 100 hours of high-temperature storage, the luminescence intensity of the powder remained at 20% of its original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity of the powder remained at 33% of its original intensity.

[0077] Comparative Example 2:

[0078] 5 mmol CsBr, 5 mmol PbBr2, and 2 g of mesoporous silica nanoparticles were ground and mixed evenly.

[0079] The above mixed powder was placed in a muffle furnace and heated from room temperature to 450°C, and then heated at 450°C for 120 minutes. The sample powder was then removed after naturally cooling to room temperature.

[0080] Experimental Analysis: The final product from the above preparation process was tested for its stability in a high-temperature environment of 100℃ and under strong blue light irradiation (350mW / cm2), as shown in Table 1. After 100 hours of high-temperature storage, the luminescence intensity of the powder remained at 51% of its original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity of the powder remained at 27% of its original intensity.

[0081] Comparative Example 3:

[0082] 5 mmol CsBr, 5 mmol PbBr2, 1 mmol BaBr2, and 2 g MCM-41 molecular sieve were ground and mixed evenly. The mixture was placed in a muffle furnace and heated from room temperature to 450°C, and then heated at 450°C for 120 minutes. The mixture was then allowed to cool naturally to room temperature before the sample powder was removed.

[0083] Take 300 mg of the calcined powder and disperse it in 30 ml of KF solution with a KF concentration of 3 mol / L. Soak the solution in water for 10 hours, and then take out the sample powder.

[0084] Experimental Analysis: The final product from the above preparation process was tested for its stability in a high-temperature environment of 100℃ and under strong blue light irradiation (350mW / cm2), as shown in Table 1. After 100 hours of high-temperature storage, the luminescence intensity of the powder remained at 45% of its original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity of the powder remained at 39% of its original intensity.

[0085] Comparative Example 4:

[0086] 5 mmol CsBr, 5 mmol PbBr2, 1 mmol BaBr2, and 2 g MCM-41 molecular sieve were ground and mixed evenly. The mixture was placed in a muffle furnace and heated from room temperature to 450°C, and then heated at 450°C for 120 minutes. The mixture was then allowed to cool naturally to room temperature before the sample powder was removed.

[0087] Experimental Analysis: The final product from the above preparation process was tested for its stability in a high-temperature environment of 100℃ and in an environment with strong blue light irradiation (350mW / cm2), as shown in Table 1. After 100 hours of high-temperature storage, the luminescence intensity of the powder could maintain 26% of the original intensity; after 100 hours of continuous blue light irradiation, the luminescence intensity of the powder could maintain 35% of the original intensity.

[0088] Table 1: Comparison of stability test results for samples from different examples (comparative examples)

[0089]

[0090]

[0091] The above-described embodiments provide a detailed explanation of the preparation method of the present invention. It should be understood that these embodiments are only for illustrating the present invention and are not intended to limit the present invention. Any modifications, additions, or similar substitutions made within the scope of the principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A perovskite quantum dot with a fluorine-containing passivation layer, characterized in that, The invention includes a micro / mesoporous template with incompletely closed pores, wherein perovskite nanocrystals and a fluorine-containing passivation layer are grown within the pores of the micro / mesoporous template, and the fluorine-containing passivation layer is composed of BaF2 and NaK2AIF6. The perovskite nanocrystals have a perovskite structure CsPbX3 or CsPbX. 1.5 X' 1.5 ; Where X and X' are each independently Cl, Br, or I, and in CsPbX 1.5 X' 1.5 In the text, X and X' are different; The perovskite quantum dots are prepared by a method comprising the following steps: Barium-containing perovskite nanocrystals are grown within the pores of the micro / mesoporous template. After being soaked in water, a lead hydroxide coating layer is formed on the surface of the barium-containing perovskite nanocrystals. Subsequently, F ions are enriched within the pores of the micro / mesoporous template, and the lead hydroxide coating layer blocks the F ions and the barium-containing perovskite nanocrystals. Under hydrothermal reaction, the lead hydroxide coating layer disappears, and a fluorine-containing passivation layer is formed on the surface of the perovskite nanocrystals.

2. The perovskite quantum dot with a fluorine-containing passivation layer according to claim 1, characterized in that, The micro / mesoporous template is a microporous material and / or a mesoporous material; The microporous material is a microporous molecular sieve, microporous silica, microporous titanium dioxide, microporous alumina, microporous transition metal oxide, microporous sulfide, microporous silicate, microporous aluminate, or microporous transition metal nitride. The mesoporous material is a mesoporous molecular sieve, mesoporous silica, mesoporous titanium dioxide, mesoporous alumina, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, mesoporous silicate, mesoporous aluminate, or mesoporous transition metal nitride.

3. The perovskite quantum dot with a fluorine-containing passivation layer according to claim 1, characterized in that, The melting point of the fluorine-containing passivation layer is higher than that of the perovskite nanocrystals.

4. The perovskite quantum dot with a fluorine-containing passivation layer according to claim 1, characterized in that, There is a passivation interface between the fluorine-containing passivation layer and the perovskite nanocrystals.

5. A perovskite quantum dot with a fluorine-containing passivation layer according to claim 4, characterized in that, The fluorine-containing passivation layer contains perovskite nanocrystals embedded in its lattice; or, some of the perovskite nanocrystals are coated by the fluorine-containing passivation layer.

6. A method for constructing a fluorine-containing passivation layer for perovskite quantum dots according to any one of claims 1-5, characterized in that, The invention includes a micro / mesoporous template with incompletely closed pores, wherein barium-containing perovskite nanocrystals are grown in the pores of the micro / mesoporous template, and a lead hydroxide coating layer is formed on the surface of the perovskite nanocrystals after soaking in water. It also includes F ions enriched in the micro / mesoporous template channels, the lead hydroxide coating layer blocking F ions and barium-containing perovskite nanocrystals; Under hydrothermal reaction, the lead hydroxide coating layer disappears and a fluorine-containing passivation layer is formed on the surface of the perovskite nanocrystals. The fluorine-containing passivation layer is composed of BaF2 and NaK2AIF6.

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