A synergistic encapsulation method of high-stable perovskite quantum dots

Abstract

This invention provides a co-encapsulation method for highly stable perovskite quantum dots, comprising the following preparation steps: S1, mixing and grinding a low-crystallinity all-silica zeolite carrier, cesium bromide, and lead bromide to obtain a precursor mixture; S2, heating the precursor mixture to allow the cesium, lead, and halogen components to enter the pores of the low-crystallinity all-silica zeolite carrier, and crystallizing under the confinement of the pores to form CsPbBr3 perovskite quantum dots; S3, contacting the product obtained in step S2 with an aqueous potassium chloride solution and performing hydrothermal treatment to obtain zeolite-encapsulated CsPbBr3 perovskite quantum dots containing lead hydroxide chloride. This invention can reduce the adverse effects of chlorine sources on direct halogen exchange in the perovskite quantum dot bulk lattice and promote the participation of chlorine sources in the formation of a stable protective structure at the carrier interface, thereby improving the stability of perovskite quantum dots.

Description

Technical Field

[0001] This invention belongs to the field of perovskite quantum dot material preparation technology, and particularly relates to a co-encapsulation method for highly stable perovskite quantum dots. Background Technology

[0002] All-inorganic lead halide perovskite (such as CsPbX3, X=Cl, Br, I) quantum dots have shown broad application prospects in fields such as light-emitting diodes (LEDs), displays, lasers and photoelectric detection due to their excellent optical properties such as tunable emission wavelength, narrow half-width, and high photoluminescence quantum yield (PLQY).

[0003] However, perovskite quantum dots still face significant stability issues in practical applications, especially under the influence of external environments such as light, heat, oxygen, and moisture. These environments can easily lead to structural degradation, increased surface defects, and halide ion migration, resulting in decreased luminescence intensity, emission peak shift, and even material deactivation. Under high-energy blue light excitation, quantum dots are more prone to phase separation and an increase in non-radiative recombination centers, severely limiting their application in high-brightness displays and other scenarios. To improve the stability of perovskite quantum dots, existing technologies typically employ strategies such as ligand passivation and inorganic coating. For example, modifying the surface of quantum dots with organic ligands can reduce surface defects to some extent; coating with inorganic materials such as SiO2 and Al2O3 can prevent external environmental erosion of the quantum dots. However, organic ligands are prone to desorption during light exposure, heat treatment, or long-term use, leading to a decrease in passivation. Conventional inorganic coating methods often suffer from insufficient bonding between the coating layer and the quantum dot interface, and the formation of a loose protective layer, thus their improvement on the long-term stability of quantum dots remains relatively limited.

[0004] Furthermore, in the CsPbBr3 green quantum dot system, it is generally believed in the art that when Cl - When it enters the CsPbBr3 quantum dot lattice and occupies the X site, it readily interacts with the existing Br. - Halogen exchange occurs, causing the material to gradually convert to CsPbBr. X Cl 3-X The system transformation leads to a blue shift in the emission peak and fluctuations in luminescence performance. Due to the strong diffusion and exchange capabilities of chloride ions, they can not only alter the composition of quantum dots but also potentially induce surface coordination imbalances and structural instability. Therefore, current techniques for CsPbBr3 green quantum dot systems generally avoid introducing chloride sources during post-processing or encapsulation to prevent chloride ions from entering the perovskite lattice and causing unfavorable halogen exchange reactions. However, this approach also limits the potential role of chloride sources in stabilizing inorganic protective structures.

[0005] Therefore, how to introduce a chlorine source into the CsPbBr3 green quantum dot system while suppressing the direct halogen exchange effect of the chlorine source on the perovskite quantum dot host lattice, so that it preferentially participates in the construction of a stable inorganic protective structure, thereby achieving the directional utilization of the chlorine source and further improving the luminescence performance and environmental stability of the perovskite quantum dots, remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a synergistic encapsulation method for highly stable perovskite quantum dots. By introducing a chlorine source into the CsPbBr3 green quantum dot system and combining it with a low-crystallinity all-silica zeolite carrier and excess cesium bromide for regulation, the chlorine source is more inclined to participate in the formation of the carrier interface protection structure, thereby synergistically improving the luminescence efficiency and light stability of the quantum dots.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a co-encapsulation method for highly stable perovskite quantum dots, comprising the following preparation method: S1. Provide a low-crystallinity all-silica zeolite carrier obtained by demolding treatment, mix and grind the low-crystallinity all-silica zeolite carrier, cesium bromide, and lead bromide to obtain a precursor mixture; wherein the amount of cesium bromide added is greater than the stoichiometric ratio required to form CsPbBr3; S2. The precursor mixture is heated to allow cesium, lead and halogen components to enter the pores of the low crystallinity all-silica zeolite carrier, and CsPbBr3 perovskite quantum dots are formed under the confinement of the pores. S3. The product obtained in step S2 is contacted with an aqueous solution of potassium chloride and subjected to hydrothermal treatment, so that chloride ions diffuse into the pores and / or surface regions of the low crystallinity all-silica zeolite carrier and promote the conversion of lead-containing species in the surface and / or pore regions to form lead hydroxide chloride, thereby obtaining zeolite-encapsulated CsPbBr3 perovskite quantum dots containing lead hydroxide chloride.

[0008] In the above, the "lead-containing species" mentioned in this invention refers to lead-related components distributed on the surface of quantum dots and / or the interface region of the carrier, which are not completely integrated into the CsPbBr3 host lattice and can further participate in the reaction during subsequent processing. These can be precursor residues that are not completely incorporated into the host lattice, lead-rich components at the interface, or other lead-related intermediates that can be further transformed.

[0009] In this invention, the directional utilization of the chlorine source refers to enabling the chlorine source to participate more in the formation of the protective structure, rather than primarily causing adverse effects on the main crystal lattice.

[0010] Furthermore, the preparation method of the low-crystallinity all-silica zeolite carrier includes the following steps: tetraethyl orthosilicate and tetrapropylammonium hydroxide solution are added dropwise to a container containing deionized water, and the mixture is continuously stirred until a clear and transparent solution is obtained. The solution is then transferred to a high-pressure reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 180°C for 15 hours. The resulting product is washed with ethanol, dried in air, and then calcined at 550°C for 5 hours to obtain a demolded low-crystallinity all-silica zeolite carrier.

[0011] Furthermore, in step S1, the molar ratio of cesium bromide to lead bromide is (1.4-1.6):1.

[0012] Furthermore, in step S3, the potassium chloride aqueous solution is a saturated potassium chloride solution, the hydrothermal treatment is carried out in a high-pressure reactor lined with polytetrafluoroethylene, the hydrothermal treatment temperature is 130°C, and the hydrothermal treatment time is 10 h.

[0013] Furthermore, the low-crystallinity all-silica zeolite support exhibits reduced diffraction peak intensity and / or broadened diffraction peaks in X-ray diffraction patterns compared to commercial MFI-type all-silica zeolite.

[0014] Furthermore, in step S3, the generated lead hydroxide chloride is distributed on the quantum dot surface and / or the interface region of the low-crystallinity all-silica zeolite carrier to form a protective structure.

[0015] Furthermore, the excess cesium bromide helps to reduce the impact of halogen exchange on the CsPbBr3 host lattice during chlorine source treatment.

[0016] Furthermore, the low-crystallinity all-silica zeolite support has a porous and / or surface structure that facilitates the confined growth of quantum dots and the formation of interface protection structures.

[0017] The beneficial effects of this invention are mainly reflected in the following aspects: Although commercially available all-silica zeolite has high crystallinity, its framework structure is more regular, with relatively few defect sites and interfacial active sites, which is not conducive to lead residue on the surface and in the pore region. In contrast, low-crystallinity all-silica zeolite support can provide a confined growth environment for CsPbBr3 perovskite quantum dots and provide a more favorable interfacial structure; on this basis, by introducing excess cesium bromide and combining it with potassium chloride hydrothermal treatment, it is beneficial to reduce the adverse effects of chlorine source treatment on the host lattice and promote the formation of inorganic protective structures on the quantum dot surface and / or the support interface.

[0018] Therefore, this invention achieves targeted utilization of the chlorine source, avoiding its preferential entry into the CsPbBr3 host lattice and causing unfavorable halogen exchange, while simultaneously utilizing it to construct a protective encapsulation structure. Through the synergistic effect of the low-crystallinity all-silica zeolite carrier, excess cesium bromide, and lead hydroxide chlorine, this invention can significantly improve the photostability and environmental stability of perovskite quantum dots while maintaining their high luminescence performance. Attached Figure Description

[0019] Figure 1 The X-ray diffraction (XRD) pattern of the product prepared in Example 1 of this invention; Figure 2 The X-ray diffraction (XRD) pattern of the product prepared in Comparative Example 2 of this invention; Figure 3 This is a comparison of X-ray diffraction (XRD) images of the self-made low-crystallinity all-silica zeolite in Example 1 of the present invention and the commercial all-silica zeolite in Comparative Example 3. Figure 4 The product prepared in Example 1 of this invention has a strength of 350 mW / cm². 2 Comparison of fluorescence emission spectra before and after 168 hours of continuous irradiation with 450nm blue light; Figure 5 The product prepared for Comparative Example 1 of this invention was at 350 mW / cm 2 Comparison of fluorescence emission spectra before and after 168 hours of continuous irradiation with 450nm blue light. Detailed Implementation

[0020] 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.

[0021] Example 1: Step 1: 40 mL of (TEOS) tetraethyl orthosilicate and 48 mL of (TPAOH) tetrapropylammonium hydroxide solution were sequentially added dropwise to a container containing 32 mL of deionized water while continuously and vigorously stirring. After the mixture was stirred for 4 hours to form a clear solution, it was transferred to a 50 mL high-pressure reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 180 °C for 15 hours. The resulting product was washed with ethanol, dried in air, and then calcined at 550 °C for 5 hours to finally obtain the demolded zeolite sample.

[0022] Step 2: Grind and mix 318 mg of cesium bromide, 367 mg of lead bromide, and 289 mg of demolded zeolite for 1 hour at a ball mill speed of 240 r / min to obtain the corresponding CsPbBr3 solid precursor. Heat the mixed powder in a muffle furnace to 600 degrees Celsius and maintain the temperature for 60 minutes. Then cool it down and open the lid to allow it to rapidly crystallize in the pores to form halide perovskite, which is CsPbBr3.

[0023] Step 3: Transfer the CsPbBr3 obtained in Step 2 to a high-pressure reactor lined with polytetrafluoroethylene, add 1 mL of saturated potassium chloride solution, and perform a hydrothermal reaction at 130℃ for 10 h. After this treatment, a lead hydroxide-chloride-related protective phase is formed on the sample surface and / or at the support interface, resulting in a post-treated composite material.

[0024] Experimental Analysis: The powder after the above treatment was analyzed for specific surface area and pore size using a BSD-660M A3M specific surface area analyzer. The results show that the specific surface area and pore size of the zeolite and perovskite after calcination and hydrothermal treatment in this embodiment are shown in Table 1. Table 1. Comparison of specific surface area and pore size test results of samples from different embodiments (comparative examples)

[0025] The fluorescence quantum yield (PLQY) of the powder after the above treatment was tested, as shown in Table 2. The PLQY of this sample was 99%. In comparison, the PLQY of the perovskite quantum dots without excess CsBr provided in Comparative Example 1 was 88%, and the PLQY of the perovskite quantum dots with excess CsBr but without hydrothermal treatment in potassium chloride solution provided in Comparative Example 2 was 75%.

[0026] As shown in Tables 1 and 2, neither using excess cesium bromide alone nor using potassium chloride hydrothermal treatment alone can simultaneously achieve high photoluminescence quantum efficiency and high photostability. However, when low-crystallinity all-silica zeolite, excess cesium bromide, and potassium chloride hydrothermal treatment are used together, the resulting sample exhibits better luminescence performance and photostability, indicating that the scheme of the present invention has a significant synergistic effect.

[0027] The stability of the powder after the above treatment was tested in a strong blue light irradiation environment, as shown in Table 2, using 350mW / cm 2After 168 hours of continuous irradiation with blue light (450nm), the luminescence intensity of the quantum dot remained at 91% of its original intensity. In contrast, the perovskite quantum dots in Comparative Example 1, without excess CsBr, showed a decrease in luminescence intensity to 34% of their initial intensity after 168 hours under the same blue light testing conditions, exhibiting significant phase separation. In Comparative Example 2, the perovskite quantum dots with excess CsBr but without potassium chloride hydrothermal treatment showed a decrease in luminescence intensity to 42% of their initial intensity after 168 hours under the same blue light testing conditions. In Comparative Example 3, commercial zeolite (Qingdao Yuanke Catalyst Co., Ltd.: S-1 all-silica molecular sieve) was used. Due to its higher crystallinity, fewer sites could be anchored to Pb compared to the self-made zeolite. Under the same blue light testing conditions, its luminescence intensity decreased to 29% of its initial intensity after 168 hours. The blue light stability test demonstrated that the synergistic constraint of lead hydroxide chloride and zeolite significantly improved the photostability of the CsPbBr3 quantum dots.

[0028] Combined fluorescence quantum yield and blue light stability test data demonstrate that the synergistic confinement of perovskite by lead hydroxide chlorine and zeolite improves both PLQY and photostability.

[0029] Comparative Example 1: The difference from Example 1 is that no excess cesium bromide is added.

[0030] Step 1: Grind and mix 233 mg of cesium bromide, 367 mg of lead bromide, and 289 mg of demolded zeolite for 1 hour at a ball mill speed of 240 r / min to obtain the corresponding CsPbBr3 solid precursor. Heat the mixed powder in a muffle furnace to 600 degrees Celsius and maintain the temperature for 60 minutes. Then cool down and open the lid to allow it to rapidly crystallize in the pores to form halide perovskite, which is CsPbBr3.

[0031] Step 2: Transfer the CsPbBr3 obtained in Step 1 to a high-pressure reactor lined with polytetrafluoroethylene, add 1 mL of saturated potassium chloride solution, and perform a hydrothermal reaction at 130℃ for 10 h to obtain a control sample post-treated with chlorine source.

[0032] Experimental analysis: The product obtained in Comparative Example 1 showed a fluorescence quantum yield of 88% and a blue light stability of 34%, and exhibited significant blue shift and phase separation with increasing aging time (e.g., Figure 5 As shown, the emission peak shifts towards the blue light band.

[0033] Comparative Example 2: The difference from Example 1 is that no hydrothermal post-treatment is performed.

[0034] Step 1: Grind and mix 318 mg of cesium bromide, 367 mg of lead bromide, and 289 mg of demolded zeolite for 1 hour at a ball mill speed of 240 r / min to obtain the corresponding CsPbBr3 solid precursor. Heat the mixed powder in a muffle furnace to 600 degrees Celsius and maintain the temperature for 60 minutes. Then cool it down and open the lid to allow it to rapidly crystallize in the pores to form halide perovskite, which is CsPbBr3.

[0035] Experimental analysis: Comparative Example 2 yielded products such as... Figure 2 As shown, no Pb(OH)Cl phase was observed in the XRD pattern. The fluorescence quantum yield and blue light stability were measured to be 75% and 42%, respectively.

[0036] Comparative Example 3: The difference from Example 1 is that the template agent was replaced with commercial zeolite (Qingdao Yuanke Catalyst Co., Ltd.: S-1 all-silica molecular sieve).

[0037] Step 1: Grind and mix 318 mg of cesium bromide, 367 mg of lead bromide, and 289 mg of commercial zeolite for 1 hour at a ball mill speed of 240 r / min to obtain the corresponding CsPbBr3 solid precursor. Heat the mixed powder in a muffle furnace at 600 degrees Celsius for 60 minutes, then cool and open the lid. This halide perovskite is CsPbBr3.

[0038] Step 2: Transfer the CsPbBr3 obtained in Step 1 to a high-pressure reactor lined with polytetrafluoroethylene, add 1 mL of saturated potassium chloride solution, and perform a hydrothermal reaction at 130°C for 10 h. The resulting halide perovskite is CsPbBr3@commercial zeolite.

[0039] Experimental analysis: such as Figure 3 The XRD patterns of commercial and self-made zeolites are shown. Their diffraction peaks correspond to the standard card (Silicon-1) of MFI topology. It can be seen that the diffraction peak intensity of the self-made zeolite is lower than that of the commercial zeolite. Due to the weak diffraction peak signal of the self-made zeolite, the background noise is relatively obvious, and the spectrum looks more "rough". Secondly, the presence of some amorphous components in the low crystallinity sample will broaden the diffraction peaks. The fluorescence quantum yield and blue light stability were tested to be 73% and 29%, respectively.

[0040] While commercially available all-silica zeolites have higher crystallinity, their more regular framework and relatively fewer defect sites and interfacial active sites are not conducive to the formation of the co-encapsulation system of this invention. Although the all-silica zeolite obtained in Example 1 of this invention has low crystallinity, it can provide more defect sites and reaction areas for lead residues.

[0041] The final products were prepared using the above embodiments. The PLQY and photostability of each product under 450nm blue laser light are shown in Table 2.

[0042] Table 2: Comparison of PLQY and stability test results for samples from different examples (comparative examples)

[0043] Comparing Example 1 with Comparative Examples 1 to 3, it is evident that adjusting the excess cesium bromide condition alone or using potassium chloride hydrothermal treatment alone is insufficient to simultaneously achieve high PLQY and high photostability; furthermore, the carrier structure also significantly influences the final performance. These results indicate that low-crystallinity all-silica zeolite, excess cesium bromide, and potassium chloride hydrothermal treatment together constitute the synergistic system of this invention.

[0044] The present invention has been illustrated with the above embodiments to explain the detailed preparation method of the present invention. However, the present invention is not limited to the above detailed preparation method, that is, it does not mean that the present invention must rely on the above product and detailed preparation method to be implemented. Those skilled in the art should understand that any improvement to the present invention, or the combination or equivalent substitution of the raw materials of the present invention, falls within the protection scope and disclosure scope of the present invention.

Claims

1. A method for co-encapsulating highly stable perovskite quantum dots, characterized in that, The preparation methods include the following: S1. Provide a low-crystallinity all-silica zeolite carrier obtained by demolding treatment, mix and grind the low-crystallinity all-silica zeolite carrier, cesium bromide, and lead bromide to obtain a precursor mixture; wherein the amount of cesium bromide added is greater than the stoichiometric ratio required to form CsPbBr3; S2. The precursor mixture is heated to allow cesium, lead and halogen components to enter the pores of the low crystallinity all-silica zeolite carrier, and CsPbBr3 perovskite quantum dots are formed under the confinement of the pores. S3. The product obtained in step S2 is contacted with an aqueous solution of potassium chloride and subjected to hydrothermal treatment, so that chloride ions diffuse into the pores and / or surface regions of the low crystallinity all-silica zeolite carrier and promote the conversion of lead-containing species in the surface and / or pore regions to form lead hydroxide chloride, thereby obtaining zeolite-encapsulated CsPbBr3 perovskite quantum dots containing lead hydroxide chloride.

2. The method for co-encapsulating highly stable perovskite quantum dots according to claim 1, characterized in that, The preparation method of the low-crystallinity all-silica zeolite carrier includes the following steps: tetraethyl orthosilicate and tetrapropylammonium hydroxide solution are added dropwise to a container containing deionized water, and the mixture is continuously stirred until a clear and transparent solution is obtained. The solution is then transferred to a high-pressure reactor lined with polytetrafluoroethylene and subjected to hydrothermal reaction at 180°C for 15 hours. The resulting product is washed with ethanol, dried in air, and then calcined at 550°C for 5 hours to obtain a demolded low-crystallinity all-silica zeolite carrier.

3. The method for co-encapsulating highly stable perovskite quantum dots according to claim 1, characterized in that, In step S1, the molar ratio of cesium bromide to lead bromide is (1.4-1.6):

1.

4. The method for co-encapsulating highly stable perovskite quantum dots according to claim 1, characterized in that, In step S3, the potassium chloride aqueous solution is a saturated potassium chloride solution, the hydrothermal treatment is carried out in a high-pressure reactor lined with polytetrafluoroethylene, the hydrothermal treatment temperature is 130°C, and the hydrothermal treatment time is 10 h.

5. The method for co-encapsulating highly stable perovskite quantum dots according to claim 2, characterized in that, The low-crystallinity all-silica zeolite support exhibits reduced diffraction peak intensity and / or broadened diffraction peaks in X-ray diffraction patterns compared to commercial MFI-type all-silica zeolite.

6. The method for co-encapsulating highly stable perovskite quantum dots according to claim 5, characterized in that, In step S3, the generated lead hydroxide chloride is distributed on the quantum dot surface and / or the interface region of the low crystallinity all-silica zeolite carrier to form a protective structure.

7. The method for co-encapsulating highly stable perovskite quantum dots according to claim 6, characterized in that, The excess cesium bromide helps to reduce the impact of halogen exchange on the CsPbBr3 host lattice during chlorine source treatment.

8. The method for co-encapsulating highly stable perovskite quantum dots according to claim 7, characterized in that, The low-crystallinity all-silica zeolite support has a porous and / or surface structure that is conducive to the confined growth of quantum dots and the formation of interface protection structures.

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