Preparation method of perovskite nanocrystals with core-shell structure

Abstract

The present invention discloses a perovskite nanocrystal with a core-shell structure and a preparation method thereof, belonging to the technical field of semiconductor nanomaterials. High-quality formamidinium lead iodide near-infrared nanocrystals are prepared by a ligand-assisted coprecipitation method based on a non-polar solvent at room temperature, and a neodymium fluoride solution is introduced during the synthesis process. After purification, a colloidal solution of near-infrared perovskite core-shell nanocrystals with uniform dispersion is obtained; this method forms a dense micro-nano structure on the surface of the perovskite nanocrystals to encapsulate the perovskite nanocrystals, enabling the neodymium fluoride material to form an inorganic outer layer, which can reduce the adverse effects of the organic shell on charge transport; moreover, this method is simple to operate, can reduce the contact between the nanocrystals and the external environment, and successfully improves the thermal stability, solution stability, ultraviolet light irradiation stability, and fluorescence stability of individual perovskite nanocrystals.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor nanomaterials, and particularly to a preparation method of perovskite nanocrystals with a core-shell structure. Background Art

[0002] As a new type of fluorescent semiconductor nanomaterial, halide perovskite nanocrystals have excellent properties such as high defect tolerance, narrow emission peaks, easy preparation, and spectral tunability across the entire visible light range, showing broad application prospects in the fields of lighting and display in recent years. In the past few years, through continuous optimization of defect passivation strategies such as surface treatment and in-situ doping, the photoluminescence quantum yield (PLQY) of perovskite nanocrystals has been significantly improved. However, the ionic nature and large specific surface area of perovskite nanocrystals make them vulnerable to damage, resulting in reduced luminescence efficiency, thus seriously hindering their practical applications. Coating a shell layer on the perovskite surface can passivate surface defects and isolate external environmental erosion, providing an effective strategy for improving stability. Using an inorganic shell structure can avoid the adverse effects of organic shell layers on the conductivity of nanocrystals, but constructing an inorganic coating shell usually requires high-temperature conditions and complex operations, which is not conducive to low-cost practical applications. Therefore, developing a low-cost method for preparing a core-shell structure is of great significance for improving the stability of perovskite nanocrystals and promoting their applications. Summary of the Invention

[0003] Aiming at the above existing problems, the present invention aims to provide a preparation method of perovskite nanocrystals with a core-shell structure. This preparation method can be carried out at room temperature, has a simple process and low cost, and the finally obtained perovskite nanocrystals with a core-shell structure have good stability.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A preparation method of perovskite nanocrystals with a core-shell structure, characterized by comprising the following steps,

[0006] S1: Prepare an A-site precursor solution using formamidinium acetate (CH3COOCH(NH2)2, FAAc)) and oleic acid;

[0007] S2: Prepare a lead iodide (PbI2) precursor solution;

[0008] S3: Prepare a neodymium fluoride (NdF3) precursor solution;

[0009] S4: Add the A-site precursor solution to the PbI2 precursor solution, stir, and then add the NdF3 precursor solution, followed by centrifugal dispersion to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution.

[0010] Further, the specific operation process of step S1 is as follows: Dissolve FAAc in oleic acid, heat and stir. After the monovalent cations are completely dissolved in oleic acid, an A-site precursor solution is obtained, and it is cooled to room temperature for standby;

[0011] Among them, the molar volume ratio of FAAc is 1:0.3 - 0.5 mmol / mL, the heating temperature is 70 - 90 °C, and the heating time is 15 - 30 min.

[0012] Further, the specific operation of step S2 includes the following steps:

[0013] S201: Dissolve PbI2 powder in a toluene solution with oleic acid and oleylamine, heat and stir at 100 °C, and then cool to room temperature;

[0014] Among them, the amounts of oleic acid and oleylamine contained in every 10 mL of toluene solution are 0.05 - 0.15 mL and 0.1 - 0.2 mL respectively; the molar volume ratio of PbI2 powder to toluene solution is 0.5 - 1.5:100 mmol / mL;

[0015] S202: Centrifuge to remove the undissolved PbI2 powder to obtain a PbI2 precursor solution.

[0016] Further, in step S201, the amounts of oleic acid and oleylamine contained in every 10 mL of toluene solution are 0.1 mL and 0.15 mL respectively; the molar volume ratio of PbI2 to toluene solution is 1:100 mmol / mL.

[0017] Further, the specific operation process of step S3 is as follows: Add NdF3 to an isopropanol solution, and stir at room temperature for 2 - 4 hours to obtain an NdF3 precursor solution;

[0018] Among them, the molar volume ratio of NdF3 to isopropanol is 0.1:0.5 - 1.5 mmol / mL.

[0019] Further, the molar volume ratio of NdF3 to isopropanol in step S3 is 0.1:1 mmol / mL.

[0020] Further, the specific operation process of step S4 includes:

[0021] S401: Add the A-site precursor solution to the PbI2 precursor solution; among them, the volume ratio of the A-site precursor solution to the PbI2 precursor solution is 4 - 6:100;

[0022] S402: Stir the mixture obtained in step S401 at a rotation speed of 1000 rmp for 2.5 min;

[0023] S403: Add the NdF3 precursor solution to the mixed solution obtained by stirring evenly in step S402, where the volume ratio of the NdF3 precursor solution to the A-site precursor solution is 2:4 - 6;

[0024] S404: Centrifuge and disperse the mixed solution obtained in step S403 to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution.

[0025] Further, the specific operation of step S404 includes the following steps:

[0026] S4041: After centrifuging the mixed solution obtained in step S403 at 9000 rmp, pour off the supernatant, invert it to obtain nanocrystal sediment;

[0027] S4042: Add a dispersant to the nanocrystal sediment obtained in step S4041. After dispersing evenly, centrifuge it for the second time, take the supernatant, and add n-hexane for dilution to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution.

[0028] Further, the perovskite nanocrystals are prepared by using the above-mentioned preparation method.

[0029] Further, the molecular formula of the perovskite nanocrystals is ABX3; where A is FA + ; B is Pb 2+ ; X is I - 。

[0030] The beneficial effects of the present invention are as follows:

[0031] 1. The preparation method of the perovskite nanocrystals with a core-shell structure in the present invention can be carried out at room temperature, with less energy consumption and simple operation; the finally formed perovskite nanocrystals are coated with an inorganic core-shell layer, effectively passivating the defects on the surface of the perovskite nanocrystals, which is beneficial to the improvement of the optical properties of the perovskite nanocrystals.

[0032] 2. The near-infrared perovskite core-shell nanocrystal colloidal solution prepared by using the preparation method in the present invention, through stability tests, has been found to have significantly improved solution stability, phase stability, thermal stability, ultraviolet light irradiation stability, and fluorescence stability of individual nanocrystals. Description of the Drawings

[0033] Figure 1 It is a transmission electron microscope (TEM) photograph of the formamidinium lead iodide (FAPbI3) nanocrystals and FAPbI3@NdF3 perovskite core-shell nanocrystals prepared in Example 1 and Example 2 of the present invention.

[0034] Figure 2High-resolution TEM images of the FAPbI3@NdF3 perovskite core-shell nanocrystals prepared in Example 1 of the present invention and the corresponding lattice spacings.

[0035] Figure 3 Photoluminescence curves and absorption curves of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 of the present invention.

[0036] Figure 4 Photoluminescence stability of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 of the present invention in solution.

[0037] Figure 5 Thermal stability of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 of the present invention.

[0038] Figure 6 UV light irradiation stability of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 of the present invention.

[0039] Figure 7 Fluorescence stability of individual nanocrystals of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 of the present invention. Detailed implementation manners

[0040] In order to enable those of ordinary skill in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0041] Example 1:

[0042] A method for preparing perovskite nanocrystals with a core-shell structure, comprising the following steps,

[0043] S1: Prepare an A-site precursor solution using FAAc and oleic acid;

[0044] Specifically, dissolve 0.25 mmol of FAAc in 1 mL of oleic acid, heat and stir at 80 °C for 20 min. After the monovalent cations are completely dissolved in oleic acid, an A-site precursor solution is obtained and cooled to room temperature for standby;

[0045] S2: Prepare a PbI2 precursor solution;

[0046] Specifically, 0.1 mmol of PbI2 powder was dissolved in 10 mL of toluene solution containing oleic acid and oleylamine, and after heating and stirring at 100 °C for 1 h, it was cooled to room temperature; among them, the amounts of oleic acid and oleylamine in the 10 mL of toluene solution were 100 μL and 150 μL respectively;

[0047] Centrifuge at a speed of 3000 revolutions for 3 minutes to remove the undissolved PbI2 powder, obtaining a PbI2 precursor solution, which was left standing for later use.

[0048] S3: Prepare an NdF3 precursor solution;

[0049] Specifically, 0.1 mmol of NdF3 was added to 1.0 mL of isopropanol solution and stirred at room temperature for 3 hours to obtain an NdF3 precursor solution;

[0050] S4: Add the A-site precursor solution to the PbI2 precursor solution, stir, and then add the NdF3 precursor solution, followed by centrifugal dispersion to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution;

[0051] Specifically, S401: Take 50 μL of the A-site precursor solution and add it to 1 mL of the PbI2 precursor solution;

[0052] S402: Stir the mixture obtained in step S401 at a rotation speed of 1000 rmp for 2.5 min;

[0053] S403: Add 20 μL of the NdF3 precursor solution to the mixture after being stirred evenly in step S402,

[0054] S404: Centrifugally disperse the mixture obtained in step S403 to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution; more specifically,

[0055] First, centrifuge the mixture obtained in step S403 at 9000 rmp for 3 min, then pour off the supernatant, invert it for 10 min to obtain a nanocrystal sediment, and disperse it in a n-hexane solvent; after uniform dispersion, centrifuge it again (centrifuge at 3000 rmp for 3 min), take the supernatant, and add 1 mL of n-hexane for dilution to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution, denoted as FAPbI3@NdF3 perovskite core-shell nanocrystals.

[0056] Example 2:

[0057] In Example 2, a perovskite nanocrystal was prepared without using the NdF3 precursor solution for encapsulation, and a comparison was made with Example 1. Specifically,

[0058] The preparation method of the perovskite nanocrystal includes the following steps,

[0059] S1: Prepare the A-site precursor solution using FAAc and oleic acid;

[0060] Specifically, dissolve 0.25 mmol of FAAc in 1 mL of oleic acid, heat and stir at 80 °C for 20 min. After the monovalent cations are completely dissolved in oleic acid, obtain the A-site precursor solution, and cool it to room temperature for standby;

[0061] S2: Prepare the PbI2 precursor solution;

[0062] Specifically, dissolve 0.1 mmol of PbI2 powder in 10 mL of toluene solution with oleic acid and oleylamine, heat and stir at 100 °C for 1 h and then cool to room temperature; among them, the amounts of oleic acid and oleylamine contained in the 10 mL toluene solution are 100 μL and 150 μL respectively;

[0063] Centrifuge at a speed of 3000 revolutions for 3 minutes to remove the undissolved PbI2 powder, obtain the PbI2 precursor solution, and let it stand for standby.

[0064] S3: Add the A-site precursor solution to the PbI2 precursor solution, stir, and centrifuge and disperse to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution;

[0065] Specifically, S401: Take 50 μL of the A-site precursor solution and add it to 1 mL of the PbI2 precursor solution;

[0066] S402: Stir the mixture obtained in step S401 at a rotation speed of 1000 rmp for 2.5 min;

[0067] S403: Centrifuge and disperse the mixture obtained in step S402 to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution; more specifically,

[0068] First, centrifuge the mixture obtained in step S402 at 9000 rmp for 3 min, pour off the supernatant, invert it for 10 min to obtain nanocrystal sediment, and disperse it in n-hexane solvent; after uniform dispersion, centrifuge it twice (centrifuge at 3000 rmp for 3 min), take the supernatant, and add 1 mL of n-hexane for dilution to obtain a near-infrared perovskite nanocrystal colloidal solution, denoted as FAPbI3 nanocrystals.

[0069] Perform TEM tests on the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2. The results are as shown in the appendix Figure 1 shown, from the appendix Figure 1It can be seen from the TEM photos that the morphology of the FAPbI3 nanocrystals prepared in Example 2 is three-dimensional nanograins; the structure of the FAPbI3@NdF3 perovskite core-shell nanocrystals prepared in Example 1 is three-dimensional nanoparticles, and the grain boundaries of the nanocrystals are more obvious and the crystallinity is enhanced. Attached Figure 2 shows the high-resolution TEM of the FAPbI3@NdF3 nanocrystals. It can be clearly seen from the attached Figure 2 that there are two different lattice constants corresponding to the interior and the boundary of the lattice respectively, to prove the formation of the core-shell structure.

[0070] The photoluminescence curves and absorption curves of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 are as shown in the attached Figure 3 ; it can be seen from the attached Figure 3 that both the FAPbI3 nanocrystals and the FAPbI3@NdF3 core-shell nanocrystals show obvious absorption edges, without obvious differences, and both achieve 100% PLQY; in contrast, the fluorescence spectrum of the FAPbI3@NdF3 core-shell nanocrystals shows a red shift and the full width at half maximum becomes narrower.

[0071] The solution stability curves of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 are as shown in the attached Figure 4 ; it can be seen from the attached Figure 4 that after being placed in the air environment for 9 days, the fluorescence intensity of the FAPbI3 perovskite colloidal solution decreases significantly, but the FAPbI3@NdF3 nanocrystals provide an effective protective layer to inhibit this process. Specifically, the PLQY of the FAPbI3 nanocrystals drops to 0 after 12 days and the fluorescence disappears, while the FAPbI3@NdF3 nanocrystals still show 92% PLQY after 20 days.

[0072] The thermal stability curves of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 are as shown in the attached Figure 5 ; it can be seen from the attached Figure 5 that after heating at 70 °C for 1 hour, the fluorescence intensity of the FAPbI3@NdF3 colloidal nanocrystal solution only shows a very small decrease, and the PLQY drops from 100% to 94%, while the PLQY of the FAPbI3 nanocrystal colloidal solution drops to 76%. This shows that the FAPbI3@NdF3 core-shell nanocrystals show good thermal stability.

[0073] The ultraviolet light irradiation stability curves of the FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 are as shown in the attached Figure 6 ; it can be seen from the attachedFigure 6 It can be seen that after the perovskite nanocrystal colloidal solution was placed under ultraviolet light irradiation for 18 hours, different degrees of degradation trends were observed, that is, the PLQY before and after NdF3 coating decreased by 40% and 21.8% respectively, indicating that the ultraviolet light irradiation stability of the FAPbI3@NdF3 core-shell nanocrystals was improved.

[0074] The fluorescence change curves of single FAPbI3@NdF3 perovskite core-shell nanocrystals and FAPbI3 nanocrystals prepared in Example 1 and Example 2 are as follows Figure 7 shown; from the following Figure 7 it can be seen that compared with FAPbI3 nanocrystals, the fluorescence quenching and fluorescence bleaching phenomena of single FAPbI3@NdF3 core-shell nanocrystals were inhibited, and the fluorescence stability of single nanocrystals was improved.

[0075] In summary, the spectral stability, solution stability, thermal stability, ultraviolet light irradiation stability and fluorescence stability of single nanocrystals of FAPbI3@NdF3 perovskite core-shell nanocrystals prepared by the preparation method in the present invention were all improved.

[0076] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A preparation method of perovskite nanocrystals with a core-shell structure, characterized in that, Comprising the following steps, S1: Prepare an A-site precursor solution using formamidinium acetate and oleic acid; S2: Prepare a lead iodide precursor solution; S3: Prepare a neodymium fluoride precursor solution; S4: Add the A-site precursor solution to the lead iodide precursor solution, stir, and then add the neodymium fluoride precursor solution, followed by centrifugal dispersion to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution.

2. The preparation method of a perovskite nanocrystal with a core-shell structure according to claim 1, characterized in that, The specific operation process of step S1 is as follows: Dissolve formamidinium acetate in oleic acid, heat and stir. After the monovalent cations are completely dissolved in oleic acid, obtain the A-site precursor solution, and cool it to room temperature for standby; Among them, the molar volume ratio of formamidinium acetate to oleic acid is 1:0.3 - 0.5 mmol / mL, the heating temperature is 70 - 90 °C, and the heating time is 15 - 30 min.

3. The preparation method of a perovskite nanocrystal with a core-shell structure according to claim 2, wherein, The specific operation of step S2 includes the following steps: S201: Dissolve lead iodide powder in a toluene solution with oleic acid and oleylamine, heat and stir at 100 °C, and then cool to room temperature; Among them, the amounts of oleic acid and oleylamine contained in every 10 mL of the toluene solution are 0.05 - 0.15 mL and 0.1 - 0.2 mL respectively; the molar volume ratio of lead iodide powder to the toluene solution is 0.5 - 1.5:100 mmol / mL; S202: Centrifuge to remove the undissolved lead iodide powder to obtain the lead iodide precursor solution.

4. The preparation method of a perovskite nanocrystal with a core-shell structure according to claim 3, characterized in that, In step S201, the amounts of oleic acid and oleylamine contained in every 10 mL of the toluene solution are 0.1 mL and 0.15 mL respectively; the molar volume ratio of lead iodide to the toluene solution is 1:100 mmol / mL.

5. The preparation method of a perovskite nanocrystal with a core-shell structure according to claim 3, characterized in that, The specific operation process of step S3 is as follows: Add neodymium fluoride to an isopropanol solution, stir at room temperature for 2 - 4 hours to obtain a neodymium fluoride precursor solution; Among them, the molar volume ratio of neodymium fluoride to isopropanol is 0.1:0.5 - 1.5 mmol / mL.

6. The preparation method of a perovskite nanocrystal with a core-shell structure according to claim 5, characterized in that, In step S3, the molar volume ratio of neodymium fluoride to isopropanol is 0.1:1 mmol / mL.

7. The preparation method of a perovskite nanocrystal with a core-shell structure according to claim 5, characterized in that, The specific operation process of step S4 includes: S401: Add the A-site precursor solution to the lead iodide precursor solution; among them, the volume ratio of the A-site precursor solution to the lead iodide precursor solution is 4 - 6:100; S402: Stir the mixture obtained in step S401; S403: Add the neodymium fluoride precursor solution to the mixture stirred evenly in step S402, where the volume ratio of the neodymium fluoride precursor solution to the A-site precursor solution is 2:4 - 6; S404: Centrifugally disperse the mixture obtained in step S403 to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution.

8. The preparation method of a perovskite nanocrystal with a core-shell structure according to claim 7, characterized in that, The specific operation of step S404 includes the following steps, S4041: Centrifuge the mixture obtained in step S403 at 9000 rmp, pour off the supernatant, invert to obtain a nanocrystal sediment; S4042: Add a dispersant to the nanocrystal sediment obtained in step S4041. After uniform dispersion, centrifuge again, take the supernatant, and add n-hexane for dilution to obtain a near-infrared perovskite core-shell nanocrystal colloidal solution.

9. Perovskite nanocrystals obtained by the preparation method according to any one of claims 1 - 8.

10. The perovskite nanocrystal according to claim 9, characterized in that: The molecular formula of the perovskite nanocrystals is ABX3; where A is FA + ; B is Pb 2+ ; X is I - .

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