Perovskite composite fluorescent nano-material with double-coating structure and preparation method of perovskite composite fluorescent nano-material

Abstract

The invention belongs to the technical field of fluorescent nano materials, and particularly relates to a perovskite composite fluorescent nano material with a double-coating structure and a preparation method of the perovskite composite fluorescent nano material. A traditional fluorescence conversion material is low in quantum yield and insufficient in fluorescence stability. In order to solve the problems, the invention provides the perovskite composite fluorescent nano material with the double-coating structure, and the perovskite composite fluorescent nano material is obtained by compactly coating the surface of an ABX3-A4BX6 composite perovskite crystal formed by uniformly dispersing ABX3 perovskite nano crystals in an A4BX6 perovskite crystal with a shell formed by mesoporous SiO2 particles. The outermost mesoporous silica (SiO2) shell forms a compact physical and chemical barrier, so that internal perovskite crystals can be effectively isolated from moisture and oxygen in an external environment, and luminescence quenching and structural degradation caused by deliquescence and oxidation of the perovskite material are greatly inhibited. ABX3 nanocrystals are uniformly limited in A4BX6 matrix crystal lattices with more stable chemical properties and wide band gaps, so that the unification of high luminescence property and high stability is realized.

Description

Technical Field

[0001] This invention belongs to the field of fluorescent nanomaterials technology, specifically relating to a double-coated perovskite composite fluorescent nanomaterial and its preparation method. Background Technology

[0002] With the rapid development of display technology, high resolution, high color gamut, and high stability have become core pursuits in the high-end display field. Cutting-edge technologies such as Mini / Micro LED, flexible displays, and laser displays place stringent demands on fluorescent color conversion materials: they not only need high fluorescence quantum yield and narrow emission half-width to achieve accurate color reproduction, but also need to cover a wide color gamut to meet the human eye's ultimate color perception requirements; simultaneously, the materials must maintain environmental stability, thermal stability, and mechanical reliability during long-term use to meet the challenges of complex application scenarios. However, traditional fluorescent conversion materials have significant performance shortcomings: rare-earth phosphors have limited color gamut coverage and low quantum yield due to their crystal structure limitations; while quantum dot materials have tunable luminescence properties, traditional Cd-based quantum dots contain heavy metal elements, posing an environmental pollution risk, and their surface ligands are prone to detachment, resulting in insufficient stability and making it difficult to meet the reliability requirements of high-end displays.

[0003] Metal halide perovskite materials, as a new generation of fluorescent materials, have rapidly become a research hotspot due to their unique optical properties. Their emission wavelength can be continuously tunable from ultraviolet to near-infrared by adjusting the composition of halide anions (Cl⁻, Br⁻, I⁻), with a full width at half maximum (FWHM) of less than 20 nm. Their color purity is significantly superior to traditional fluorescent materials, theoretically capable of completely covering high-end display color gamut standards such as Rec. 2020. Furthermore, perovskite materials possess nearly 100% fluorescence quantum yield and can be prepared at low cost using solution methods, demonstrating enormous application potential in displays, lighting, and photoelectric detection, and are considered core candidates for next-generation fluorescent color conversion materials.

[0004] Despite the significant advantages of perovskite materials in optical properties, their inherent defects severely limit their large-scale application. First, in the traditional ABX3 type perovskite crystal structure, the binding force between cations and halide anions is weak, making the material highly sensitive to water vapor and oxygen: water vapor easily penetrates the crystal interior, triggering hydrolysis, destroying the crystal structure, and causing rapid decay of fluorescence intensity; oxygen accelerates the oxidative degradation of the crystal surface, significantly shortening the material's lifespan. Second, perovskite nanocrystals are prone to the formation of metal cations (such as Pb) during preparation and use. 2+ The migration and diffusion of ions and halide anions lead to an imbalance in the stoichiometry of the luminescent centers, resulting in a shift in emission wavelength and a decrease in color purity. These stability issues have become the primary technical bottleneck for perovskite materials in transitioning from laboratory research to practical industrial applications, and urgently need to be addressed through material design and process optimization. Summary of the Invention

[0005] The existing technology suffers from low quantum yield and insufficient fluorescence stability in traditional fluorescence conversion materials. To address these issues, this invention provides a double-coated perovskite composite fluorescent nanomaterial with the general formula ABX3-A4BX6@SiO2, where A is Cs. + 、Rb + One or two of them, B is Pb 2+ Sn 2+ One or two of them, X is Cl - ,Br - I - One or more elements in it, ABX3 as the luminescent center is a perovskite nanocrystal, and ABX3-A4BX6@SiO2 is a perovskite composite fluorescent nanomaterial obtained by uniformly dispersing ABX3 perovskite nanocrystals in A4BX6 perovskite crystals and densely coating the surface of the ABX3-A4BX6 composite perovskite crystal with a shell formed by mesoporous SiO2 particles.

[0006] Preferably, the particle size of ABX3 perovskite nanocrystals does not exceed 50 nm.

[0007] Preferably, the particle size of the ABX3-A4BX6 composite perovskite crystal is larger than that of the ABX3 perovskite nanocrystal, but does not exceed 10 μm.

[0008] Preferably, the particle size of the ABX3-A4BX6@SiO2 perovskite composite fluorescent nanomaterial is larger than that of the ABX3-A4BX6 composite perovskite crystal, but does not exceed 100 μm.

[0009] Preferably, the size range of the mesoporous SiO2 particles is 50 nm to 100 μm.

[0010] Preferably, the preparation method of the aforementioned double-coated perovskite composite fluorescent nanomaterial includes the following steps:

[0011] (1) Weigh the metal halides corresponding to A and B in ABX3-A4BX6 according to the stoichiometric coefficients, mix and grind them evenly to obtain a mixed powder;

[0012] (2) The mixed powder and mesoporous SiO2 particles are mixed evenly and sintered at high temperature. After cooling to room temperature, sintered powder is obtained.

[0013] (3) The sintered powder is washed, dried and ground in sequence to obtain a perovskite composite fluorescent nanomaterial with a double coating structure.

[0014] Preferably, the mass ratio of the mixed powder to the mesoporous SiO2 particles in step (2) is 1:4.

[0015] Preferably, the high-temperature sintering holding time is 0.1~12 h.

[0016] Preferably, the heating and cooling rates for high-temperature sintering are both 2~10℃ / min.

[0017] Preferably, the ABX3-A4BX6 is CsPbBr3 / Cs4PbBr6 or CsPbCl. 1.5 Br 1.5 / Cs4PbCl3Br3、CsPbI 1.5 Br 1.5 / Cs4PbI3Br3、Cs 0.5 Rb 0.5 At least one of PbBr3 / Cs2Rb2PbBr6.

[0018] An optical display screen may employ the aforementioned double-coated perovskite composite fluorescent nanomaterial as a fluorescent color conversion material for the display screen.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] (1) Significantly enhanced stability

[0021] The outermost mesoporous silica (SiO2) shell of the double-coated perovskite composite fluorescent nanomaterial designed in this invention forms a dense physical and chemical barrier, effectively isolating the internal perovskite crystals from contact with moisture and oxygen in the external environment, and greatly inhibiting luminescence quenching and structural degradation of the perovskite material caused by deliquescence and oxidation. Simultaneously, this shell can also buffer thermal and mechanical stress, improving the overall stability and durability of the material.

[0022] (2) A balance is achieved between luminescent properties and stability.

[0023] The double-coated perovskite composite fluorescent nanomaterial ABX3-A4BX6@SiO2 designed in this invention creates a unique dual protection mechanism through its "ABX3-A4BX6" composite structure. Specifically, the ABX3 nanocrystals, serving as the luminescent centers, are uniformly confined within the more chemically stable and wide-bandgap A4BX6 matrix lattice. This structure, on the one hand, reduces surface defects of the ABX3 nanocrystals through matrix isolation, helping to maintain or even improve their luminescence efficiency (such as photoluminescence quantum yield) and color purity; on the other hand, the matrix layer, acting as the first line of defense, further prevents direct attacks on the luminescent centers from external factors, achieving a balance between high luminescence performance and high stability.

[0024] (3) Balancing material properties and machinability

[0025] This invention optimizes luminescent properties at the microscale by controlling the dimensions of each layer of ABX3-A4BX6@SiO2 (e.g., ABX3 nanocrystals ≤50 nm, composite crystals ≤10 μm, final material ≤100 μm), while simultaneously yielding a powder material suitable for subsequent processing at the macroscale. The introduction of a mesoporous SiO2 shell also improves the material's dispersibility and compatibility with matrices such as polymers, facilitating its formulation into inks or composite materials for use in various device manufacturing processes.

[0026] (4) It has broad application prospects, especially suitable for high-end displays.

[0027] The ABX3-A4BX6@SiO2 fluorescent composite material designed in this invention comprehensively solves the key bottleneck problems of traditional perovskite nanomaterials, such as poor stability, easy agglomeration, and difficult processing. When applied as a fluorescent color conversion material to optical displays (such as Micro-LED displays), it can provide pixel units with high luminous efficiency, wide color gamut, pure color, and long-term stable operation, significantly improving the overall performance and reliability of the display, and has important industrial application value. Attached Figure Description

[0028] Figure 1 Schematic diagram of the double-coated structure of ABX3-A4BX6@SiO2 perovskite composite fluorescent nanomaterial.

[0029] Figure 2 Flowchart of the synthesis method of ABX3-A4BX6@SiO2 perovskite composite fluorescent nanomaterials.

[0030] Figure 3 XRD pattern of CsPbBr3 / Cs4PbBr6@SiO2 perovskite composite fluorescent nanomaterial.

[0031] Figure 4 Fluorescence spectrum of CsPbBr3 / Cs4PbBr6@SiO2 perovskite composite fluorescent nanomaterial.

[0032] Figure 5 Fluorescence water resistance curve of CsPbBr3 / Cs4PbBr6@SiO2 perovskite composite fluorescent nanomaterial.

[0033] Figure 6 CsPbCl 1.5 Br 1.5 Fluorescence spectrum of / Cs4PbCl3Br3@SiO2 perovskite composite fluorescent nanomaterial.

[0034] Figure 7 CsPbCl 1.5Br 1.5 Fluorescence water resistance curve of / Cs4PbCl3Br3@SiO2 perovskite composite fluorescent nanomaterial.

[0035] Figure 8 CsPbI 1.5 Br 1.5 Fluorescence spectrum of / Cs4PbI3Br3@SiO2 perovskite composite fluorescent nanomaterial.

[0036] Figure 9 CsPbI 1.5 Br 1.5 Fluorescence water resistance curve of / Cs4PbI3Br3@SiO2 perovskite composite fluorescent nanomaterial.

[0037] Figure 10 :Cs 0.5 Rb 0.5 Fluorescence spectrum of PbBr3 / Cs2Rb2PbBr6@SiO2 perovskite composite fluorescent nanomaterial.

[0038] Figure 11 :Cs 0.5 Rb 0.5 Fluorescence spectrum of PbBr3 / Cs2Rb2PbBr6@SiO2 perovskite composite fluorescent nanomaterial.

[0039] Figure 12 Fluorescence spectrum of CsPbBr3@SiO2 perovskite composite fluorescent nanomaterial.

[0040] Figure 13 Figure: PL stability test results of CsPbBr3@SiO2 perovskite composite fluorescent nanomaterial after long-term immersion in water.

[0041] Figure 14 Stability curves of fluorescent nanomaterials obtained in Examples 1-3 and Comparative Examples 1-2. Detailed Implementation

[0042] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0043] Example 1

[0044] A method for preparing ABX3-A4BX6@SiO2, the steps of which are as follows:

[0045] Step 1: Dissolve 350 mg of cetyltrimethylammonium bromide in 500 mL of water, add 5 mL of 1 M NaOH solution, and then slowly add 20 mL of tetraethyl orthosilicate dropwise at a rate of 0.2 mL / h. After the addition is complete, stir for 24 h. Filter and wash the above suspension to obtain powder, then place it in a muffle furnace and sinter at 500 °C for 2 h to obtain mesoporous silica powder.

[0046] Step 2: Mix CsBr and PbBr2 in a molar ratio of 4:1 until homogeneous and grind for 2 h to obtain a mixed powder;

[0047] Step 3: Weigh 50 mg of the above mixed powder and mix it evenly with 200 mg of mesoporous silica to obtain a premixed powder;

[0048] Step 4: Place the above premixed powder in a muffle furnace for high-temperature sintering at 650℃ for 2 hours to obtain sintered powder. The muffle furnace heating rate is 5℃ / min and the muffle furnace cooling rate is 5℃ / min.

[0049] Step 5: The powder was washed and dried (50℃, 8h) sequentially with water and ethanol, and then sintered to obtain the purified fluorescent composite material CsPbBr3 / Cs4PbBr6@SiO2. The fluorescence emission wavelength of CsPbBr3 / Cs4PbBr6@SiO2 was 510 nm, with an external quantum yield (EQE) of 29.02% and an emission half-width (FWHM) of 18 nm. After completely immersing CsPbBr3 / Cs4PbBr6@SiO2 in room temperature water for 186 days, the remaining fluorescence intensity was 101.1% of the initial value. When the above CsPbBr3 / Cs4PbBr6@SiO2 was encapsulated in an LED lamp and operated continuously for 486 h, the remaining fluorescence intensity was 99.2% of the initial value.

[0050] Example 2

[0051] A method for preparing ABX3-A4BX6@SiO2, the steps of which are as follows:

[0052] Step 1: Mix CsBr, CsCl, PbCl2 and PbBr2 in a molar ratio of 4:4:1:1 until homogeneous and grind for 2 hours to obtain a mixed powder;

[0053] Step 2: Weigh 50 mg of the above mixed powder and mix it evenly with 200 mg of the mesoporous silica prepared in Example 1 to obtain a premixed powder;

[0054] Step 3: Place the above premixed powder in a muffle furnace and sinter at a high temperature of 650℃ for 2 hours to obtain sintered powder. The muffle furnace heating rate is 5℃ / min and the muffle furnace cooling rate is 5℃ / min.

[0055] Step 4: Wash and dry sequentially with water and ethanol (90℃, 6h) to obtain purified fluorescent composite material CsPbCl 1.5 Br 1.5 / Cs4PbCl3Br3@SiO2. CsPbCl 1.5 Br 1.5 The fluorescence emission wavelength of / Cs4PbCl3Br3@SiO2 is 455 nm, the EQE is 34.6%, and the FWHM is 16 nm. (The last part, "CsPbCl3Br3@SiO2", appears to be an unrelated fragment and is omitted from the translation.) 1.5 Br 1.5 After Cs4PbCl3Br3@SiO2 was completely immersed in room temperature water for 186 days, the remaining fluorescence intensity was 98.3% of the initial value. (The text abruptly ends here, likely due to an incomplete translation or missing information.) 1.5 Br 1.5 When Cs4PbCl3Br3@SiO2 is encapsulated in an LED lamp, the remaining fluorescence intensity is 109.7% of the initial value after 486 hours of continuous operation.

[0056] Example 3

[0057] A method for preparing ABX3-A4BX6@SiO2, the steps of which are as follows:

[0058] Step 1: Mix CsBr, CsI, PbI2 and PbBr2 in a molar ratio of 4:4:1:1 until homogeneous and grind for 2 hours to obtain a mixed powder;

[0059] Step 2: Weigh 50 mg of the above mixed powder and mix it evenly with 200 mg of the mesoporous silica prepared in Example 1 to obtain a premixed powder;

[0060] Step 3: Place the above premixed powder in a muffle furnace and sinter at a high temperature of 650℃ for 2 hours to obtain sintered powder. The muffle furnace heating rate is 5℃ / min and the muffle furnace cooling rate is 5℃ / min.

[0061] Step 4: Wash and dry sequentially with water and ethanol (90℃, 6h) to obtain purified fluorescent composite material CsPbI 1.5 Br 1.5 / Cs4PbI3Br3@SiO2. CsPbI 1.5 Br 1.5 The fluorescence emission wavelength of / Cs4PbI3Br3@SiO2 is 620 nm, with an EQE of 38.7% and an FWHM of 23 nm. (The last part, "CsPbI," appears to be a typo and can be omitted.) 1.5 Br 1.5 After Cs4PbI3Br3@SiO2 was completely immersed in room temperature water for 186 days, the remaining fluorescence intensity was 94.6% of the initial value. (The text abruptly ends here, likely due to an incomplete translation or missing information.)1.5 Br 1.5 When Cs4PbI3Br3@SiO2 is packaged in an LED lamp, the remaining fluorescence intensity is 96.8% of the initial value after 486 hours of continuous operation.

[0062] Example 4

[0063] A method for preparing ABX3-A4BX6@SiO2, the steps of which are as follows:

[0064] Step 1: Mix RbBr, CsBr, RbBr2 and PbBr2 in a molar ratio of 4:4:1:1 until homogeneous and grind for 2 hours to obtain a mixed powder;

[0065] Step 2: Weigh 50 mg of the above mixed powder and mix it evenly with 200 mg of the mesoporous silica prepared in Example 1 to obtain a premixed powder;

[0066] Step 3: Place the above premixed powder in a muffle furnace and sinter at a high temperature of 650℃ for 2 hours to obtain sintered powder. The muffle furnace heating rate is 5℃ / min and the muffle furnace cooling rate is 5℃ / min.

[0067] Step 4: Wash and dry sequentially with water and ethanol (90℃, 6h) to obtain purified fluorescent composite material Cs. 0.5 Rb 0.5 PbBr3 / Cs2Rb2PbBr6@SiO2. Cs 0.5 Rb 0.5 The fluorescence emission wavelength of PbBr3 / Cs2Rb2PbBr6@SiO2 is 507 nm, with an EQE of 11.5% and an FWHM of 57 nm. (The last part, "Cs," appears to be an unrelated fragment and is omitted from the translation.) 0.5 Rb 0.5 After PbBr3 / Cs2Rb2PbBr6@SiO2 was completely immersed in room temperature water for 22 days, the remaining fluorescence intensity was 99.2% of the initial value.

[0068] Comparative Example 1 is the perovskite fluorescent nanomaterial CsPbBr3. The preparation method of CsPbBr3 is as follows:

[0069] Step 1: Mix CsBr and PbBr2 in a molar ratio of 1:1 until homogeneous, and dissolve 300 mg of the mixture in 10 mL of dimethyl sulfoxide to obtain a mixed solution;

[0070] Step 2: Take the above mixed solution, mix it with an equal volume of toluene, and stir for 1 hour to obtain the reaction solution;

[0071] Step 3: Separate the solid from the above reaction solution using a speed of 6000 rpm, and wash and purify it with toluene to obtain CsPbBr3 perovskite fluorescent nanomaterials.

[0072] Step 4: The purified CsPbBr3 perovskite fluorescent nanomaterial was air-dried naturally. Its emission wavelength was 512 nm, EQE was 0.16%, and FWHM was 38 nm. After completely immersing CsPbBr3 in room temperature water for 5 min, the remaining fluorescence intensity was 0. After encapsulating CsPbBr3 in an LED lamp and operating it continuously for 16 h, the remaining fluorescence intensity was 18.2% of the initial value.

[0073] Comparative Example 2 is a single-layer coated perovskite composite fluorescent nanomaterial CsPbBr3@SiO2, prepared by the following method:

[0074] Step 1: Mix CsBr and PbBr2 in a molar ratio of 1:1 until homogeneous and grind for 2 hours to obtain a mixture;

[0075] Step 2: Weigh 50 mg of the above mixture and mix it evenly with 200 mg of the mesoporous silica prepared in Example 1 to obtain a mixed powder;

[0076] Step 3: Place the above mixed powder in a muffle furnace for high-temperature sintering for 2 hours at a temperature of 650°C and hold for 2 hours to obtain sintered powder. The muffle furnace heating rate is 5°C / min and the muffle furnace cooling rate is 5°C / min.

[0077] Step 4: The purified fluorescent composite material CsPbBr3@SiO2 was obtained by washing and drying sequentially with water and ethanol (90℃, 6h). The fluorescence emission wavelength of CsPbBr3@SiO2 was 515 nm, with an EQE of 44.1% and an emission half-width of 26 nm. After completely immersing CsPbBr3@SiO2 in room temperature water for 186 days, the remaining fluorescence intensity was 88.3% of the initial value. After encapsulating CsPbBr3@SiO2 in an LED lamp and operating continuously for 294 h, the remaining fluorescence intensity was 62.7% of the initial value.

[0078] Performance testing experiment

[0079] 1. X-ray powder diffraction (XRD) was performed on the CsPbBr3 / Cs4PbBr6@SiO2 perovskite composite fluorescent nanomaterial prepared in Example 1 of the present invention. The test results are as shown in the appendix to the specification. Figure 3 As shown, the test spectrum matches the simulated peak height of the Cs4PbBr6 standard card, indicating that the internal perovskite crystal Cs4PbBr6 is mainly a coating layer, and the proportion of CsPbBr3, which is the luminescence center, is small. The XRD signal is extremely weak and cannot be identified in the spectrum.

[0080] 2. The CsPbBr3 / Cs4PbBr6@SiO2 perovskite composite fluorescent nanomaterial prepared in Example 1 of the present invention was subjected to fluorescence spectroscopy (PL) testing. The excitation wavelength was set to 365 nm, and the testing wavelength range was 400–700 nm. The test results are as shown in the appendix to the specification. Figure 4 As shown, the maximum emission wavelength of CsPbBr3 / Cs4PbBr6@SiO2 prepared in Example 1 is 510 nm, the EQE is 29.02%, and the FWHM is 18 nm.

[0081] 3. The CsPbBr3 / Cs4PbBr6@SiO2 perovskite composite fluorescent nanomaterial prepared in Example 1 of the present invention was subjected to a long-term water immersion PL stability test. The material was completely immersed in room temperature water, and the fluorescence spectrum was measured every few days. The excitation wavelength was set to 365 nm, and the test wavelength range was 400~700 nm. The measured fluorescence intensity was compared with the initial intensity to obtain the fluorescence intensity shown in the appendix to the specification. Figure 5 The fluorescence water resistance curve is shown. The fluorescence intensity of CsPbBr3 / Cs4PbBr6@SiO2 prepared in Example 1 was 101.1% of the initial value after soaking in water for 186 days.

[0082] 4. The CsPbCl prepared in Example 2 of the present invention 1.5 Br 1.5 Photoluminescence (PL) tests were performed on the / Cs4PbCl3Br3@SiO2 perovskite composite fluorescent nanomaterial. The excitation wavelength was set to 365 nm, and the test wavelength range was 400–700 nm. The test results are shown in the attached instruction manual. Figure 6 As shown, the CsPbCl prepared in Example 2 1.5 Br 1.5 The maximum emission wavelength of / Cs4PbCl3Br3@SiO2 is 455nm, and the FWHM is 16nm.

[0083] 5. The CsPbCl prepared in Example 2 of the present invention 1.5 Br 1.5 The long-term immersion stability test of the Cs4PbCl3Br3@SiO2 perovskite composite fluorescent nanomaterial was carried out. 1.5 Br 1.5 / Cs4PbCl3Br3@SiO2 was immersed in room temperature water, and its fluorescence spectrum was measured every few days. The excitation wavelength was set to 365 nm, and the test wavelength range was 400~700 nm. The measured fluorescence intensity was compared with the initial intensity to obtain the result shown in the instruction manual. Figure 7 The fluorescence water resistance curve is shown. Example 2: CsPbCl prepared... 1.5 Br1.5 The fluorescence intensity of / Cs4PbCl3Br3@SiO2 after immersion in water at room temperature for 186 days was 98.3% of the initial value.

[0084] 6. The CsPbI prepared in Example 3 of the present invention 1.5 Br 1.5 PL testing was performed on the / Cs4PbI3Br3@SiO2 perovskite composite fluorescent nanomaterial. The excitation wavelength was set to 365 nm, and the testing wavelength range was 400–700 nm. The test results are shown in the attached instruction manual. Figure 8 As shown, CsPbI prepared in Example 3 1.5 Br 1.5 The maximum emission wavelength of / Cs4PbI3Br3@SiO2 is 620nm, the EQE is 34.6%, and the FWHM is 23nm.

[0085] 7. The CsPbI prepared in Example 3 of the present invention 1.5 Br 1.5 The fluorescence stability of the / Cs4PbI3Br3@SiO2 perovskite composite fluorescent nanomaterial underwent a long-term water immersion test. The material was completely immersed in water, and the fluorescence spectrum was measured every few days. The excitation wavelength was set to 365 nm, and the test wavelength range was 400–700 nm. The measured fluorescence intensity was compared with the initial intensity to obtain the results shown in the attached instruction manual. Figure 9 The fluorescence water resistance curve is shown. CsPbI prepared in Example 3. 1.5 Br 1.5 The fluorescence intensity of / Cs4PbI3Br3@SiO2 after immersion in water at room temperature for 186 days was 94.6% of the initial value.

[0086] 8. The CsPbI prepared in Example 4 of the present invention 1.5 Br 1.5 PL testing was performed on the / Cs4PbI3Br3@SiO2 perovskite composite fluorescent nanomaterial. The excitation wavelength was set to 365 nm, and the testing wavelength range was 400–700 nm. The test results are shown in the attached instruction manual. Figure 10 As shown, the CsPbI prepared in Example 4 1.5 Br 1.5 The maximum emission wavelength of / Cs4PbI3Br3@SiO2 is 620nm, the EQE is 38.7%, and the FWHM is 57nm.

[0087] 9. The CsPbBr3 perovskite fluorescent material prepared in Comparative Example 1 of the present invention was subjected to photoluminescence (PL) testing. The excitation wavelength was set to 365 nm, and the testing wavelength range was 400–700 nm. The test results are shown in the appendix to the specification. Figure 11As shown, the maximum emission wavelength of CsPbBr3 prepared in Comparative Example 1 was 512 nm, and the FWHM was 38 nm.

[0088] 10. The CsPbBr3@SiO2 perovskite composite fluorescent nanomaterial prepared in Comparative Example 2 of the present invention was subjected to photoluminescence (PL) testing. The excitation wavelength was set to 365 nm, and the testing wavelength range was 400–700 nm. The test results are shown in the appendix to the specification. Figure 12 As shown, the maximum emission wavelength of CsPbBr3@SiO2 prepared in Comparative Example 2 is 515 nm, and the FWHM is 26 nm.

[0089] 11. The CsPbBr3@SiO2 perovskite composite fluorescent nanomaterial prepared in Comparative Example 2 of the present invention was subjected to a long-term water immersion PL stability test. The material was completely immersed in room temperature water, and the fluorescence spectrum was measured every few days. The excitation wavelength was set to 365 nm, and the test wavelength range was 400~700 nm. The measured fluorescence intensity was compared with the initial intensity to obtain the fluorescence intensity shown in the appendix to the specification. Figure 13 The fluorescence water resistance curve is shown. In Comparative Example 2, the fluorescence intensity of CsPbBr3@SiO2 prepared was 88.3% of its initial value after immersion in room temperature water for 186 days.

[0090] 12. The working stability of the CsPbBr3 / Cs4PbBr6@SiO2 perovskite composite fluorescent nanomaterial prepared in Example 1 of the present invention was tested. The CsPbBr3 / Cs4PbBr6@SiO2 was encapsulated in an LED lamp. Under continuous operation, its fluorescence emission intensity was tested every few hours, and the remaining fluorescence intensity was calculated. (See attached specification). Figure 14 As shown in the figure, the working stability test shows that after CsPbBr3 / Cs4PbBr6@SiO2 packaged in the LED lamp worked continuously for 486 hours, the remaining fluorescence intensity was 99.2% of the initial value, and the fluorescence intensity was stable.

[0091] 13. The CsPbCl prepared in Example 2 of the present invention 1.5 Br 1.5 Stability testing of the Cs4PbCl3Br3@SiO2 perovskite composite fluorescent nanomaterial under working conditions was conducted. 1.5 Br 1.5 The / Cs4PbCl3Br3@SiO2 package is encapsulated in an LED lamp. During continuous operation, its fluorescence emission intensity is tested every few hours, and the remaining fluorescence intensity is calculated. (See attached instruction manual.) Figure 14 As shown, the stability test under working conditions indicates that CsPbCl 1.5 Br 1.5After continuous operation for 486 hours, the residual fluorescence intensity of the / Cs4PbCl3Br3@SiO2 encapsulated LED lamp was 109.7% of the initial value, indicating stable fluorescence intensity.

[0092] 14. The CsPbI prepared in Example 3 of the present invention 1.5 Br 1.5 Stability testing of the Cs4PbI3Br3@SiO2 perovskite composite fluorescent nanomaterial under working conditions was conducted. 1.5 Br 1.5 / Cs4PbI3Br3@SiO2 is encapsulated in an LED lamp. During continuous operation, its fluorescence emission intensity is tested every few hours, and the remaining fluorescence intensity is calculated. (See attached instruction manual.) Figure 14 As shown in the figure, the stability test under working conditions shows that CsPbI 1.5 Br 1.5 After continuous operation for 486 hours, the residual fluorescence intensity of the / Cs4PbI3Br3@SiO2 packaged in the LED lamp was 96.8% of the initial value, and the fluorescence intensity was stable.

[0093] 15. The CsPbBr3 and CsPbBr3@SiO2 materials prepared in Comparative Examples 1 and 2 of the present invention were subjected to working stability tests. The fluorescent materials were encapsulated in LED lamps, and under continuous operating conditions, their fluorescence emission intensity was tested every few hours, and the remaining fluorescence intensity was calculated. (See attached specification.) Figure 14 As shown, after working in an LED lamp for 16 hours, the remaining fluorescence intensity of the material in Comparative Example 1 was 18.2% of the initial value; after CsPbBr3 and CsPbBr3@SiO2 encapsulated in an LED lamp worked continuously for 292 hours, the remaining fluorescence intensity was 62.7% of the initial value. Both of them showed faster fluorescence decay compared to the materials in Examples 1 to 3.

[0094] In summary, the ABX3-A4BX6@SiO2 perovskite composite fluorescent nanomaterial obtained by this invention has the following core performance advantages: (1) complete crystal structure and high phase purity; (2) adjustable fluorescence emission wavelength, narrow half-peak width, and excellent color purity; (3) outstanding working stability, thermal stability and cycle stability, and can effectively resist water vapor and oxygen erosion; (4) simple preparation process, convenient operation of solid phase sintering method, low cost, environmentally friendly, no need for complicated equipment, and easy to scale up industrial production.

[0095] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A perovskite composite fluorescent nanomaterial with a double-coated structure, characterized in that, The general structural formula is ABX3-A4BX6@SiO2, where A is Cs. + 、Rb + One or two of them, B is Pb 2+ Sn 2+ One or two of them, X is Cl - ,Br - I - One or more elements in it, ABX3 as the luminescent center is a perovskite nanocrystal, and ABX3-A4BX6@SiO2 is a perovskite composite fluorescent nanomaterial obtained by uniformly dispersing ABX3 perovskite nanocrystals in A4BX6 perovskite crystals and densely coating the surface of the ABX3-A4BX6 composite perovskite crystal with a shell formed by mesoporous SiO2 particles.

2. The perovskite composite fluorescent nanomaterial with a double-coated structure according to claim 1, characterized in that, The particle size of ABX3 perovskite nanocrystals does not exceed 50 nm.

3. The perovskite composite fluorescent nanomaterial with a double-coated structure according to claim 1, characterized in that, The particle size of the ABX3-A4BX6 composite perovskite crystal is larger than that of the ABX3 perovskite nanocrystal, but does not exceed 10 μm.

4. The perovskite composite fluorescent nanomaterial with a double-coated structure according to claim 1, characterized in that, The particle size of the ABX3-A4BX6@SiO2 perovskite composite fluorescent nanomaterial is larger than that of the ABX3-A4BX6 composite perovskite crystal, but does not exceed 100 μm.

5. The perovskite composite fluorescent nanomaterial with a double-coated structure according to claim 1, characterized in that, The size range of mesoporous SiO2 particles is 50 nm to 100 μm.

6. A perovskite composite fluorescent nanomaterial with a double-coated structure according to any one of claims 1-5, characterized in that, The preparation method includes the following steps: (1) Weigh the metal halides corresponding to A and B in ABX3-A4BX6 according to the stoichiometric coefficients, mix and grind them evenly to obtain a mixed powder; (2) The mixed powder and mesoporous SiO2 particles are mixed evenly and sintered at high temperature. After cooling to room temperature, sintered powder is obtained. (3) The sintered powder is washed, dried and ground in sequence to obtain a perovskite composite fluorescent nanomaterial with a double coating structure.

7. The perovskite composite fluorescent nanomaterial with a double-coated structure according to claim 6, characterized in that, In step (2), the mass ratio of the mixed powder to the mesoporous SiO2 particles is 1:

4.

8. The perovskite composite fluorescent nanomaterial with a double-coated structure according to claim 6, characterized in that, The high-temperature sintering holding time is 0.1~12 h.

9. The perovskite composite fluorescent nanomaterial with a double-coated structure according to claim 6, characterized in that, The ABX3-A4BX6 is CsPbBr3 / Cs4PbBr6, CsPbCl 1.5 Br 1.5 / Cs4PbCl3Br3、CsPbI 1.5 Br 1.5 / Cs4PbI3Br3、Cs 0.5 Rb 0.5 At least one of PbBr3 / Cs2Rb2PbBr6.

10. An optical display screen, characterized in that, The perovskite composite fluorescent nanomaterial with a double-coated structure as described in any one of claims 1-5 is used as a fluorescent color conversion material for display screens.

Images