Preparation method of organic-inorganic double-coated rare earth doped perovskite quantum dots

Abstract

The invention provides a preparation method of an organic-inorganic double-coated rare earth doped perovskite quantum dot, which comprises the following steps: step 1, blending and grinding a perovskite quantum dot precursor, a rare earth metal oxide and a mesoporous material with a Si-OH group to obtain a sintering precursor; 2, dynamically sintering the sintering precursor obtained in the step 1 under the condition that the temperature is lower than the pore channel collapse temperature of the mesoporous material to obtain the perovskite illuminant, and 3, mixing the perovskite luminous body obtained in the step 2 with a silane coupling agent, a high-boiling-point liquid-phase medium and sodium salt containing sulfur and oxygen anions, carrying out hydrolysis and condensation reaction at 120-200 DEG C, and after the reaction is finished, sequentially washing, centrifuging and drying the obtained solid to obtain the organic-inorganic double-coated rare earth doped perovskite quantum dot. An organic protection layer is further introduced on the basis of inorganic mesoporous coating, a synergistic double-layer stable structure is constructed, and the rare earth doped perovskite quantum dots obtain the environment isolation capacity.

Description

Technical Field

[0001] This invention belongs to the field of perovskite quantum dot preparation technology, and particularly relates to a method for preparing organic-inorganic dual-coated rare earth-doped perovskite quantum dots. Background Technology

[0002] Metal halide perovskite quantum dots, as rapidly developing photofunctional nanomaterials in recent years, have shown broad application prospects in optoelectronic fields such as light-emitting diodes (LEDs), display backlights, lasers, and solar cells due to their high photoluminescence quantum efficiency, narrow emission half-width, high color purity, and tunable visible light emission. To further improve their luminescence behavior and energy level structure, the introduction of rare-earth ions has gradually attracted attention. Rare-earth doping can enhance the luminescence efficiency, stability, and multicolor emission capability of perovskite quantum dots through energy transfer, lattice modulation, or defect suppression mechanisms, thus becoming one of the effective ways to improve the performance of perovskite quantum dots.

[0003] However, perovskite quantum dots are soft-lattice ionic crystals, and their surfaces are prone to defects such as uncoordinated ions, lattice distortions, or halogen vacancies. Especially under humid, high-temperature, or strong light environments, they are more susceptible to phase decomposition, ion migration, and non-radiative recombination, leading to a rapid degradation of their optical properties. Although rare-earth doping can improve their intrinsic structural stability to some extent, it is still insufficient to resist continuous environmental degradation. Therefore, constructing a highly stable protection system suitable for rare-earth-doped perovskite quantum dots has become an urgent problem to be solved.

[0004] As described in application number CN202310599312.8, existing technologies embed perovskite materials into mesoporous carriers via high-temperature solid-state synthesis to form inorganic coating structures that suppress the intrusion of moisture, oxygen, and thermal stress, resulting in perovskite luminescent materials exhibiting excellent moisture and heat resistance. However, when the calcination temperature exceeds the structural maintenance limit of the mesoporous material channels, the carrier channels collapse or close, leaving the quantum dots in a completely coated state. Although this structure can further improve environmental stability, the closed channels hinder external molecular transport, making it difficult to subsequently re-tune the surface of rare-earth-doped perovskite quantum dots, passivate defects, or functionalize interfaces, which is detrimental to the continuous improvement of optical performance and the expansion of applications.

[0005] Therefore, existing mesoporous coating strategies present a technical dilemma when processing rare-earth-doped perovskite quantum dots, where stability and modifiability are difficult to achieve simultaneously. An innovative preparation route that can maintain the openness of the carrier channels while constructing a stable protective system is urgently needed, and thus requires improvement. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing rare earth-doped perovskite quantum dots with organic-inorganic dual coating. By introducing an organic protective layer on the basis of inorganic mesoporous coating, a synergistic bilayer stable structure is constructed, so that rare earth-doped perovskite quantum dots can obtain environmental isolation ability while retaining surface modifiability.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a method for preparing organic-inorganic dual-coated rare-earth-doped perovskite quantum dots, comprising the following steps: Step 1: Blend and grind the perovskite quantum dot precursor, rare earth metal oxide, and mesoporous material with Si–OH groups to obtain a sintering precursor; Step 2: The sintering precursor obtained in Step 1 is dynamically sintered under conditions lower than the pore collapse temperature of the mesoporous material, so that rare earth-doped perovskite quantum dots are formed in situ and loaded into the open pores of the mesoporous material to obtain a perovskite luminescent body. Step 3: The perovskite luminescent material obtained in Step 2 is mixed with a silane coupling agent, a high-boiling-point liquid medium, and a sodium salt containing sulfur-oxygen anions. The mixture is subjected to hydrolysis and condensation reactions at 120-200℃. After the reaction is completed, the resulting solid is washed with water, centrifuged, and dried to obtain organic-inorganic double-coated rare earth-doped perovskite quantum dots.

[0008] This invention employs a high-boiling-point liquid medium with a boiling point higher than the reaction temperature. This medium maintains a stable liquid environment at 120-200 °C and provides a uniform high-temperature nonpolar reaction system, allowing the silane coupling agent and the sodium salt containing sulfur oxide anions to diffuse smoothly within the mesoporous structure and participate in the reaction. Furthermore, due to the nonpolar nature of this liquid medium, it does not cause dissolution, hydrolysis, or ion migration of rare-earth-doped perovskite quantum dots at high temperatures. This effectively prevents damage to the quantum dot crystal structure and rare-earth-doped energy level structure, ensuring that the post-processing can be carried out at high temperatures without compromising the optical properties and lattice integrity of the quantum dots.

[0009] In this invention, the silane coupling agent can fully diffuse into the mesoporous material under the action of a high-boiling-point liquid medium, and undergo an interfacial reaction with the rare-earth-doped perovskite quantum dot surface formed in situ within the pores. The silanol resulting from the hydrolysis of the silane coupling agent undergoes a condensation reaction with the Si–OH groups on the surface of the mesoporous material to form stable Si–O–Si chemical bonds, achieving chemical anchoring between the quantum dots and the mesoporous support, and constructing a stable surface silane layer. Without damaging the perovskite crystal structure and rare-earth doping sites, this surface silane layer can significantly improve the quantum dots' resistance to moisture, heat, and photo-oxidation, and enhance their luminescence efficiency and carrier recombination characteristics. The quantum dot particle size increases significantly after silanization treatment, with an increase exceeding 25%, indicating the successful construction of the outer silane coating layer, achieving dual organic-inorganic protection.

[0010] Hydrolysis of silane coupling agents typically produces polar byproducts such as water and lower alcohols. Rare-earth-doped perovskite quantum dots are susceptible to erosion by water and polar solvents, leading to lattice relaxation, ion migration, and luminescence decay. This invention introduces a sodium salt containing sulfur oxide anions as a regulator of moisture and polar substances. In a non-polar high-temperature system, it can adsorb free water, causing controlled hydrolysis of the silane coupling agent. This achieves a directional hydrolysis-condensation reaction of silane at the quantum dot / mesoporous composite interface, forming a dense and stable silane coating layer. Furthermore, the sodium salt containing sulfur oxide anions can enter the mesoporous channels with the liquid medium, synergistically passivating the surface of rare-earth-doped perovskite quantum dots: Na… + Ions can selectively replace some A-site cations, modulate lattice stress, and fill surface vacancies; sulfate ions can react with uncoordinated Pb. 2+ Complexation occurs, eliminating deep-level defects. The combined effect of rare-earth doping and sulfur-containing oxygen anion passivation can significantly reduce the density of non-radiative recombination centers, thereby improving the structural stability, photoluminescence intensity, and long-term environmental reliability of quantum dots.

[0011] Furthermore, the rare earth metal oxide is a lanthanide oxide, selected from at least one of the oxides corresponding to elements numbered 57 to 71 in the periodic table; specifically, it can be at least one of all rare earth metal oxides such as zirconium oxide, yttrium oxide, europium oxide, 8Y zirconium yttrium oxide, cerium oxide, neodymium oxide, samarium oxide, gadolinium oxide, terbium oxide, and scandium oxide.

[0012] The perovskite quantum dot precursor includes an A-site cation source, a lead source, and a halogen source, wherein the A-site cation source is selected from Cs. + FA + or MA + The lead source is an inorganic or organic salt, wherein the lead source is selected from PbCl2, PbBr2, or PbI2, and the halogen source is a compound containing a halide anion, wherein the halide anion is selected from Cl... - ,Br - and I - At least one of them.

[0013] Furthermore, the mesoporous material having Si–OH groups is one of molecular sieves, mesoporous silica, or mesoporous silicate materials; The molecules are selected from one of MCM-41, ZSM-5 or SBA-15; Alternatively, the mesoporous material may be mesoporous titanium dioxide, mesoporous alumina, or mesoporous transition metal oxide that has been pre-modified with a silicon source to introduce Si–OH groups.

[0014] Furthermore, the hydrolysis and condensation reaction in step 3 includes: the silane coupling agent hydrolyzes to generate silanol, which forms Si–O–Si bonds with the surface of the mesoporous material, while its functional groups passivate the surface defects of the perovskite quantum dots.

[0015] Furthermore, the high-boiling-point liquid medium is at least one of octadecene, polyethylene glycol, oleic acid, or oleylamine; after the reaction is completed, the high-boiling-point liquid medium is removed by repeated washing with water, centrifugation, and drying, so that the product does not contain the high-boiling-point liquid medium.

[0016] The sodium salt containing sulfur oxide anions is one or a combination of sodium sulfate, sodium sulfite, and sodium thiosulfate.

[0017] Furthermore, the perovskite quantum dots are one of rare earth-doped CsPbX3, FAPbX3, and MAPbX3 structures; Wherein, X is at least one of Cl, Br or I; The rare earth element is a lanthanide element, selected from at least one element in the periodic table 57-71.

[0018] Furthermore, the silane coupling agent has at least one hydrolyzable group and at least one functional group for surface passivation; The hydrolyzable group includes at least one of triethoxy and trimethoxy; The functional group includes at least one of amino and methacrylamide.

[0019] Furthermore, the silane coupling agent includes one of KH550, KH540, and KH570.

[0020] Furthermore, the sintering temperature in step 2 is 450-550℃; The reaction time in step 3 is at least 8 hours.

[0021] Furthermore, the average particle size of the rare earth-doped perovskite quantum dots obtained after step 3 is larger than that of the perovskite quantum dots obtained in step 2, and the increase rate is greater than 25%.

[0022] The beneficial effects of this invention are mainly reflected in the following aspects: Through the synergistic effect of high-boiling-point liquid medium, sulfur-containing oxygen anion salt and silane coupling agent, this invention achieves controllable surface modification and double coating construction of rare earth-doped perovskite quantum dots while maintaining the openness of the mesoporous structure. This results in quantum dots with high stability, high luminous efficiency, controllable defects and long-term environmental adaptability, solving the problem that traditional coating systems are difficult to balance stability and controllability. Attached Figure Description

[0023] Figure 1A scanning electron microscope (SEM) image of the sample obtained for Example 1 shows its surface microstructure at a magnification of ×5,000. Figure 2 The EDS total spectrum of the sample obtained in Example 1 shows that it is mainly composed of elements such as Pb, Cs, Br, Si, and O, with the peaks of Si and O being the most prominent. Figure 3 EDS surface scans of different regions of the sample obtained in Example 1 show the distribution of elements Si, O, Br, Pb, Cs, Zr, K, Na, and Eu, respectively. After post-processing, Na is found to be present inside the sample. Figure 4 For Example 1, the PL spectrum of the sample before water washing was obtained; Figure 5 The PL spectrum of the sample after washing with water was obtained for Example 1; Figure 6 To obtain the blue light aging of the sample before and after water washing in Example 1 (using 350 mW / cm²), 2 A comparison chart of the stability after 100 hours of continuous irradiation with 450nm blue light. Detailed Implementation

[0024] 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.

[0025] Example 1: This embodiment provides a method for preparing organic-inorganic dual-coated rare-earth-doped perovskite quantum dots, including the following steps: Step 1: Cesium bromide (94.6 g), lead bromide (149.0 g), potassium bromide (21.9 g), europium oxide (14.31 g), zirconium oxide (18.35 g) and MCM-41 (183 g) are ball-milled and mixed for 2 h.

[0026] Step 2: Place the sintering precursor from Step 1 in a rotary tube furnace and heat it to 450-550℃ at a rate of 15℃ / min, maintain the temperature for 30 minutes, and allow it to cool down naturally. This allows rare earth-doped perovskite quantum dots to be formed in situ and loaded into the open channels of the mesoporous material, thus obtaining a perovskite luminescent body. Step 3: Weigh 2 g of perovskite luminescent material, add 30 mL KH550, 30 mL octadecene (ODE), and 0.2 g sodium sulfate, place in a magnetic stirring heating mantle, stir at 400 r / min for 2 h, then heat to 160 ℃ and stir for 16 h. After cooling, remove, wash with water, centrifuge three times, and dry to obtain the desired perovskite quantum dots.

[0027] Experimental analysis: The fluorescence quantum yield (PLQY) and particle size of the prepared perovskite quantum dots were tested. The specific values ​​are shown in Table 1. The PLQY of this sample was 97%, and the particle size D90 was 20 μm before and after water washing.

[0028] The perovskite quantum dots obtained above were uniformly mixed with polystyrene (PS) material and extruded to form a quantum dot film. The stability of the quantum dot film under strong blue light irradiation was tested, as detailed in Table 1, using 350 mW / cm² light. 2 After being continuously irradiated with blue light (450 nm) for 100 hours, the brightness of the perovskite quantum dot diffusion film can maintain 95% of the initial intensity.

[0029] In Example 1, KH550, as an aminosilane coupling agent, forms covalent bonds with the MCM-41 shell through hydrolysis and condensation, and passivates perovskite quantum dot surface defects through amino coordination / electrostatic interaction, achieving organic coating and interface stability. Octadecylene, as a high-boiling-point non-coordinating organic solvent, provides a uniform high-temperature liquid phase environment for post-processing and maintains good dispersion of quantum dots. A small amount of sodium sulfate adsorbs trace amounts of moisture, increases ionic strength, and captures free lead ions, inhibiting perovskite structure decomposition and adverse side reactions, thereby producing a synergistic effect with KH550 and octadecylene, promoting surface ligand reconstruction and improving quantum dot stability.

[0030] Example 2: The difference from Example 1 is that the silane coupling agent is different, with KH550 replaced by KH540.

[0031] Example 3: The difference from Example 1 is that the silane coupling agent is different, with KH550 replaced by KH570.

[0032] Example 4: The difference from Example 1 is that the sodium salt containing sulfur oxide anions is different, and sodium sulfate is replaced with the same molar amount of sodium sulfite.

[0033] Example 5: The difference from Example 1 is that the sodium salt containing sulfur oxide anions is different, and sodium sulfate is replaced with the same molar amount of sodium thiosulfate.

[0034] Comparative Example 1: The difference from Example 1 is that KH550 is not incorporated.

[0035] Experimental analysis: The prepared dry powder showed a PLQY of 50% and a particle size D90 of 9 μm. The prepared perovskite quantum dot diffusion film achieved 75% of its initial intensity after 100 h of blue light irradiation.

[0036] Compared to Comparative Example 1, the amino group in KH550 in Example 1 of this invention can combine with halogen vacancies on the surface of quantum dots to fill surface defect states, reduce non-radiative recombination centers, and thus improve photoluminescence quantum efficiency (PLQY). Its ethoxy group undergoes hydrolysis at high temperature and in the presence of trace amounts of water to generate silanol groups, which further condense with the surface of quantum dots or adjacent silane molecules to form a dense protective layer and enhance stability.

[0037] Comparative Example 2: The difference from Example 1 is that ODE is not incorporated.

[0038] Experimental analysis: The prepared dry powder showed a PLQY of 85% and a particle size D90 of 30 μm. The prepared perovskite quantum dot diffusion film achieved 80% of its initial intensity after 100 h of blue light irradiation.

[0039] Comparative Example 3: The difference from Example 1 is that sodium sulfate is not added.

[0040] Experimental analysis: The prepared dry powder showed a PLQY of 90% and a particle size D90 of 23 μm. The prepared perovskite quantum dot diffusion film achieved 80% of its initial intensity after 100 h of blue light irradiation.

[0041] Comparative Example 4: The difference from Example 1 is that no post-processing is performed; that is, the perovskite luminescent material is used directly for sample testing.

[0042] Experimental analysis: The prepared dry powder showed a PLQY of 80% and a particle size D90 of 8 μm. The prepared perovskite quantum dot diffusion film had a brightness of 75% of its initial intensity after 100 h of blue light irradiation.

[0043] Comparative Example 5: The difference from Example 1 is that no rare earth doping was present, i.e., europium oxide (14.31 g) and zirconium oxide (18.35 g) were added. The perovskite quantum dots produced were tested and found to have a PLQY of 60% and a particle size D90 of 21 μm. The prepared perovskite quantum dot diffusion film exhibited 92% of its initial intensity after 100 hours of blue light irradiation.

[0044] Table 1 shows the performance test results of the samples obtained in Example 1 and Comparative Examples 1-4 of this invention.

[0045] Among them, blue light stability refers to the stability of the quantum dot diffusion film, and the test conditions are: using 350 mW / cm 2After 100 hours of continuous irradiation with blue light (450 nm), the brightness of the perovskite quantum dot diffusion film maintained the initial intensity ratio. The PLQY and other data methods used for the sample products are existing technologies and will not be elaborated upon here.

[0046] Table 1: Performance test results of samples from different examples (comparative examples) 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 preparing organic-inorganic double-coated rare earth-doped perovskite quantum dots, characterized in that, The method comprises the following steps: Step 1: blending and grinding perovskite quantum dot precursors, rare earth metal oxides and mesoporous materials with Si-OH groups to obtain sintering precursors; Step 2: dynamically sintering the sintering precursors obtained in step 1 under conditions lower than the pore collapse temperature of the mesoporous material, so that the rare earth doped perovskite quantum dots are formed in situ and loaded in the open pores of the mesoporous material, to obtain perovskite luminophores; Step 3: mixing the perovskite luminophores obtained in step 2 with a silane coupling agent, a high-boiling liquid medium and a sodium salt containing a sulfur-oxygen anion, and performing hydrolysis and condensation reactions under the condition of 120-200 DEG C, and then sequentially performing water washing, centrifugation and drying on the obtained solid, to obtain organic-inorganic double-coated rare earth doped perovskite quantum dots.

2. The method for preparing organic-inorganic double-coated rare earth-doped perovskite quantum dots according to claim 1, characterized in that, The rare earth metal oxide is a lanthanide oxide, and is at least one selected from the oxides of elements 57-71 in the periodic table; The perovskite quantum dot precursor comprises an A-site cation source, a lead source, and a halogen source, wherein the A-site cation source is selected from inorganic or organic salts of Cs + , FA + , or MA + , the lead source is selected from PbCl2, PbBr2, or PbI2, and the halogen source is a compound containing halide anions selected from at least one of Cl - , Br - , and I - .

3. The method for preparing organic-inorganic double-coated rare earth-doped perovskite quantum dots according to claim 1, characterized in that, The mesoporous material with Si-OH groups is one of a molecular sieve, mesoporous silica and a mesoporous silicate material; The molecular sieve is selected from one of MCM-41, ZSM-5 or SBA-15; Or the mesoporous material is mesoporous titanium dioxide, mesoporous aluminum oxide or mesoporous transition metal oxide which is pre-modified by a silicon source to introduce Si-OH groups.

4. The preparation method of the organic-inorganic double-coated rare earth-doped perovskite quantum dots according to claim 3, characterized in that, The hydrolysis and condensation reactions in step 3 include: hydrolysis of the silane coupling agent to generate silanol, and formation of Si-O-Si bonds on the surface of the mesoporous material, while the functional groups thereof have passivation effect on the surface defects of the perovskite quantum dots.

5. The method according to claim 1, wherein the method is characterized by, The high-boiling liquid medium is at least one of octadecene, polyethylene glycol, oleic acid or oleylamine; The sodium salt containing a sulfur-oxygen anion is one or a combination of sodium sulfate, sodium sulfite and sodium thiosulfate.

6. The method for preparing organic-inorganic double-coated rare earth-doped perovskite quantum dots according to claim 1, characterized in that, The perovskite quantum dots are one of CsPbX3 structure, FAPbX3 structure and MAPbX3 structure doped with rare earth elements; X is at least one of Cl, Br or I; The rare earth element is a lanthanide element, and is at least one selected from elements 57-71 in the periodic table.

7. The method according to claim 4, wherein the method is characterized by, The silane coupling agent has at least one hydrolyzable group and at least one functional group for surface passivation; The hydrolyzable group includes at least one of triethoxyl and trimethoxyl; The functional group includes at least one of amino and methacryl.

8. The method for preparing organic-inorganic double-coated rare earth-doped perovskite quantum dots according to claim 1, characterized in that, The sintering temperature in step 2 is 450-550 DEG C; The reaction time in step 3 is at least 8 hours.

9. The method according to claim 7, wherein the method is characterized by, The silane coupling agent includes one of KH550, KH540 and KH570.

10. The method for preparing organic-inorganic double-coated rare earth-doped perovskite quantum dots according to claim 1, characterized in that, The average particle size of the rare earth doped perovskite quantum dots obtained after step 3 is larger than that of the perovskite quantum dots obtained in step 2, and the increase ratio is greater than 25%.

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