Surface modified perovskite nanocrystal and preparation method and application thereof

Abstract

The invention provides a surface-modified perovskite nanocrystal and a preparation method and application thereof, and the surface-modified perovskite nanocrystal comprises: a perovskite nanocrystal having a chemical composition of ABX3; wherein A is selected from at least one of Cs < + >, CH3NH3 < + > and HC (NH2) 2 < + >; b is selected from at least one of Pb < 2 + >, Sn < 2 + >, Ge < 2 + > and Mn < 2 + >; x is selected from halogen anions; the surface of the perovskite nanocrystal is coated with an organic ligand layer; the organic ligand comprises a halogenated organic ligand. In the surface modified perovskite nanocrystal, the surface of the perovskite nanocrystal is coated with the organic ligand layer, so that surface defects can be effectively passivated at the same time, and the surface integrity and the crystallization quality of the nanocrystal are remarkably improved. And due to the surface consistency, the defect state density is reduced, and the exciton and phonon coupling coefficient is reduced, so that a non-radiative composite channel is remarkably inhibited, and the optical performance of the perovskite nanocrystal is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of nanotechnology, and in particular to a surface-modified perovskite nanocrystal, its preparation method, and its application. Background Technology

[0002] Perovskite nanocrystals are a class of semiconductor materials with unique quantum confinement effects, composed of nanoscale perovskite crystals, and have shown significant application value in optoelectronics, displays, and energy. Among them, perovskite nanocrystals have gained widespread attention in the field of optoelectronic devices due to their excellent luminescence properties. Because of their strong quantum confinement effect, high exciton binding energy, and precisely tunable emission wavelength, they are widely used in high-efficiency light-emitting diodes, laser devices, and novel display technologies. Compared with traditional bulk perovskite materials, perovskite nanocrystals exhibit higher luminescence efficiency and narrower emission lines. However, the surface ligand coverage of conventional perovskite nanocrystals is often incomplete, with numerous surface defects, making them prone to Oswald ripening, which leads to luminescence performance degradation and decreased material stability, making it difficult to meet the application requirements of high-brightness, long-lifetime light-emitting devices. Current methods for processing perovskite nanocrystals often require high temperatures and inert gas protection, which are not only complex but also energy-intensive, unsuitable for large-scale industrial applications. Furthermore, although current post-processing methods can improve the thermal stability of the material, they cannot improve its luminescence performance, limiting the commercial application of perovskite nanocrystals. Summary of the Invention

[0003] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a surface-modified perovskite nanocrystal, its preparation method, and its application.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention provides surface-modified perovskite nanocrystals, comprising: Perovskite nanocrystals, with the chemical composition ABX3; Where A is selected from Cs + (cesium ion), CH3NH3 + (Methylamine ion, MA), HC(NH2) 2+ At least one of (formamidinium ion, FA); B is selected from Pb 2+ (lead ions), Sn 2+ (Tin ion), Ge 2+ (germanium ions), Mn 2+ At least one of (manganese ions); X is selected from halide anions; The surface of the perovskite nanocrystals is coated with an organic ligand layer; the organic ligands include halogenated organic ligands.

[0005] In this invention, the halide-based organic ligands coated on the surface of perovskite nanocrystals can efficiently replace small cations A (such as Cs) on the surface of perovskite nanocrystals. + This process forms a dense organic chain ligand layer covering a large area on the surface of the nanocrystals, effectively passivating surface defects and significantly improving the surface integrity and crystal quality of the nanocrystals. Surface uniformity leads to a reduction in defect state density and exciton-phonon coupling coefficient, thereby significantly suppressing non-radiative recombination channels and thus significantly improving the optical properties of perovskite nanocrystals. In addition, this organic ligand layer can effectively suppress the Oswald ripening process of nanocrystals, greatly improving the photothermal and long-term stability of the material.

[0006] In some embodiments, at least 95% of the surface area of ​​the perovskite nanocrystals is coated with an organic ligand layer; such as at least 96%, at least 97%, at least 98%, at least 99%, at least 99.9%, 100%, etc.

[0007] In some embodiments, the halogenated organic ligand includes at least one of the halide salts of organic ligands, such as chloride salts, bromides, and iodides.

[0008] In some embodiments, the organic ligand includes at least one selected from oleylamine, octylamine, dodecylamine, oleic acid, octanoic acid, dodecylbenzenesulphonic acid, octylphosphonic acid, lecithin, 2-hexyldecanoic acid (DA), cetyltrimethylammonium bromide (CTAB), n-dodecylammoniumthiocyanate, and tris(diethylamino)phosphine.

[0009] In some embodiments, the halogenated organic ligand includes at least one of oleylamine bromide, oleylamine chloride, oleylamine iodide, octylamine chloride, octylamine bromide, octylamine iodide, dodecylamine chloride, dodecylamine bromide, dodecylamine iodide, hexadecyltrimethylammonium chloride (CTAC), hexadecyltrimethylammonium bromide (CTAB), hexadecyltrimethylammonium iodide (CTAI), dodecylammonium hydrobromide, dodecylammonium hydroiodide, tris(diethylamino)phosphine hydrochloride, tris(diethylamino)phosphine hydrobromide, and tris(diethylamino)phosphine hydroiodide.

[0010] In some implementations, X is selected from I. - (iodide ion), Br - (bromine ion), Cl - At least one of (chloride ions); such as X being I - and Br - At that time, optimal photoelectric performance and stability can be achieved.

[0011] In some embodiments, the average particle size of the perovskite nanocrystals is 5-50 nm; such as 10-30 nm, 10-20 nm, etc.

[0012] In this invention, the composition of halide anions can be controlled (e.g., by adjusting I...). - / Br - / Cl - The ratio) and / or the average particle size of the perovskite nanocrystals are used to achieve continuously tunable luminescence of perovskite nanocrystals in the visible to near-infrared band (400~800 nm).

[0013] In some embodiments, the organic ligand layer accounts for 25-30% of the mass of the surface-modified perovskite nanocrystals; for example, 26%, 27%, 28%, 29%, etc.

[0014] A second aspect of the present invention provides a method for preparing the aforementioned surface-modified perovskite nanocrystals, comprising the following steps: The surface-modified perovskite nanocrystals were prepared by reacting perovskite nanocrystals with a mixed solution containing metal halide salts, organic acids and organic ligands.

[0015] In this invention, metal halide salts, as Lewis acids, can effectively de-paperize organic acids, thereby generating a large number of halide organic ligands in solution. These halide organic ligands can replace small cations A (such as Cs) on the surface of perovskite quantum dots. + At the same time, the defects are passivated, thereby obtaining surface-modified perovskite nanocrystals with uniform surface coating of halogenated organic ligands and few defects.

[0016] In some embodiments, the reaction temperature is 15-35°C, such as 20-30°C, 25°C, etc.; the reaction time is 1-120 min.

[0017] In some embodiments, the reaction is carried out in an air atmosphere.

[0018] In some embodiments, the solvent used in the mixed solution includes at least one of hexane, octane, and toluene.

[0019] In some embodiments, the mass ratio of the perovskite nanocrystals to the organic ligands is 8:(2~4); such as 8:3.

[0020] In some embodiments, the concentration of the metal halide salt in the mixed solution is 5-15 mmol / L, such as 8-13 mmol / L, 9-12 mmol / L, etc.

[0021] In some embodiments, the volume ratio of organic acid to organic ligand in the mixed solution is 1:(0.8-1.2), such as 1:(0.9-1.1), 1:1, etc.

[0022] In some embodiments, the concentration of the organic ligand in the mixed solution is 30-60 mmol / L, such as 35-55 mmol / L, 40-50 mmol / L, 43-47 mmol / L, etc.

[0023] In some embodiments, the metal halide salt is selected from at least one of PbI2, PbBr2, PbCl2, SnI2, SnBr2, SnCl2, ZnI2, ZnBr2, ZnCl2, CuI, CuBr, CuCl, AgI, AgBr, AgCl, CdI2, CdBr2, CdCl2, MnI2, MnBr2, and MnCl2.

[0024] In some embodiments, the organic ligand includes at least one of oleylamine, octylamine, dodecylamine, oleic acid, octanoic acid, dodecylbenzenesulfonic acid, octylphosphonic acid, lecithin, 2-hexyldecanoic acid, hexadecyltrimethylammonium bromide, dodecyl thiocyanate, and tris(diethylamino)phosphine.

[0025] In some embodiments, the organic acid includes at least one of oleic acid, octanoic acid, and dodecanoic acid.

[0026] In some embodiments, the perovskite nanocrystals can be obtained commercially or prepared using methods for preparing perovskite nanocrystals disclosed in the art. In this invention, to further improve the luminescent properties and stability of the product, the method for preparing the perovskite nanocrystals includes the following steps: reacting a solution containing a salt of type A and a first organic ligand with a solution containing a halide salt of type B and a second organic ligand to obtain the perovskite nanocrystals.

[0027] In some embodiments, the reaction includes at least one of the following: hot injection method, ligand-assisted reprecipitation method, room temperature synthesis method, and microwave-assisted method.

[0028] In some embodiments, the first organic ligand and the second organic ligand are each independently selected from at least one of oleylamine, octylamine, dodecylamine, oleic acid, octanoic acid, dodecylbenzenesulfonic acid, octylphosphonic acid, lecithin, 2-hexyldecanoic acid, hexadecyltrimethylammonium bromide, dodecyl thiocyanate, and tris(diethylamino)phosphine.

[0029] In some embodiments, the method for preparing the perovskite nanocrystals includes the following steps: injecting a solution containing a salt of A and a first organic ligand into a solution containing a halide salt of B and a second organic ligand to react and obtain the perovskite nanocrystals.

[0030] In some embodiments, the salt of A includes at least one of Cs2CO3, CsAc, Cs-oleate, methylammonium iodide (MAI), methylammonium bromide (MABr), methylammonium chloride (MACl), formamidine iodide (FAI), formamidine bromide (FABr), and formamidine chloride (FACl).

[0031] In some embodiments, the halide B salt includes at least one of PbI2, PbBr2, PbCl2, SnI2, SnBr2, and SnCl2.

[0032] In some embodiments, the reaction does not require additional heating; the reaction is carried out in an air atmosphere; the reaction time is 1 s to 60 min, such as 10 s to 30 min or 1 to 10 min. In this invention, the preparation of perovskite nanocrystals does not require heating or control of an inert atmosphere, the reaction conditions are mild, the operation is convenient, and the cost is low.

[0033] In some embodiments, the solvent used in the reaction includes at least one selected from toluene, chlorobenzene, n-hexane, cyclohexane, octane, octadecene, N,N-dimethylformamide, and dimethyl sulfoxide.

[0034] In some embodiments, the method for preparing the perovskite nanocrystals further includes purifying the reaction products, wherein the purification process includes at least one of centrifugation, precipitation, and extraction. In some embodiments, the purification process specifically includes adding a purification solvent to the reaction product, centrifuging, and obtaining the perovskite nanocrystals.

[0035] In some embodiments, the purification solvent includes at least one of ethyl acetate, acetone, methanol, and ethanol.

[0036] A third aspect of the present invention provides a device comprising the aforementioned surface-modified perovskite nanocrystals.

[0037] In some embodiments, the device includes a light-emitting diode, a solar cell, or a photodetector.

[0038] The beneficial effects of this invention are: In the surface-modified perovskite nanocrystals of this invention, the surface of the perovskite nanocrystals is coated with an organic ligand layer, which can effectively passivate surface defects and significantly improve the surface integrity and crystal quality of the nanocrystals. Surface uniformity leads to a reduction in defect state density and exciton-phonon coupling coefficient, thereby significantly suppressing non-radiative recombination channels. This results in a 3-fold increase in luminescence intensity, a decrease in full width at half maximum (FWHM), a 2-fold increase in fluorescence lifetime, and a 3-fold increase in fluorescence quantum yield of the treated nanocrystals. Furthermore, this surface-coated organic ligand layer can effectively suppress the Oswald ripening process of the nanocrystals, significantly improving the photothermal and long-term stability of the material.

[0039] The surface-modified perovskite nanocrystals of this invention exhibit excellent optoelectronic properties, including significantly improved photoluminescence quantum yield (up to 3 times), significantly improved photoluminescence intensity (up to 3 times), significantly improved fluorescence lifetime (up to 2 times), narrower emission peak half width at half maximum (less than 14 nm), and excellent photothermal and long-term stability, making them of great application value in optoelectronic devices such as light-emitting diodes, lasers, and display devices.

[0040] The method for preparing surface-modified perovskite nanocrystals presented in this invention is simple, can be carried out at room temperature and in an air atmosphere, without the need for high temperature and inert gas atmosphere protection, has mild reaction conditions, is convenient to operate, and is low in cost. Furthermore, it has good compatibility with existing perovskite nanocrystal preparation processes, which is beneficial for large-scale industrial application. This method is applicable to perovskite nanocrystal systems of different sizes and compositions, exhibiting wide applicability and good scalability, which is conducive to the large-scale preparation of high-performance perovskite nanocrystals. Attached Figure Description

[0041] Figure 1 The diagram shows the structure of the perovskite nanocrystals before and after surface modification in Example 1 of the present invention (a) and the preparation process of the passivation solution (b).

[0042] Figure 2The diagram shows a comparison of the atomic proportions of perovskite nanocrystals in Example 1 and Comparative Example 1 of the present invention. (a) is a schematic diagram of the atomic structure of perovskite nanocrystals before and after post-treatment; (b) is an XSP spectrum; and (c) is a quantitative diagram of elemental content.

[0043] Figure 3 These are simulation diagrams of the crystal structure of perovskite nanocrystals in Example 1 and Comparative Example 1 of the present invention; wherein, (a) is a simulation diagram of the crystal structure of perovskite nanocrystals in Comparative Example 1; and (b) is a simulation diagram of the crystal structure of perovskite nanocrystals in Example 1.

[0044] Figure 4 The images show a comparison of the surface ligands of the perovskite nanocrystals in Example 1 and Comparative Example 1 of the present invention; wherein, (a) the perovskite nanocrystals in Example 1 and Comparative Example 1 are high-resolution XPS spectra of Pb 4d; and (b) the perovskite nanocrystals in Example 1 and Comparative Example 1 are thermogravimetric analysis (TGA) images.

[0045] Figure 5 The graphs show the performance characteristics of the perovskite nanocrystals in Example 1 and Comparative Example 1 of this invention; where (a) is the ultraviolet-visible light absorption; (b) is the fluorescence intensity; (c) is the fluorescence lifetime; and (d) is the fluorescence quantum yield.

[0046] Figure 6 The diagram shows a comparison of the transient absorption lifetimes of the perovskite nanocrystals in Example 1 and Comparative Example 1 of this invention; where (a) is the transient absorption spectrum and (b) is the result of time normalization.

[0047] Figure 7 The images show the absorption and fluorescence spectra of the perovskite nanocrystals in Example 1 and Comparative Example 1 under a 100° heating condition. Specifically, (a) is the absorption spectrum of the perovskite nanocrystals in Example 1 under a 100° heating condition; (b) is the fluorescence spectrum of the perovskite nanocrystals in Example 1 under a 100° heating condition; (c) is the absorption spectrum of the perovskite nanocrystals in Comparative Example 1 under a 100° heating condition; and (d) is the fluorescence spectrum of the perovskite nanocrystals in Comparative Example 1 under a 100° heating condition.

[0048] Figure 8 The images show a comparison of the fluorescence spectra of perovskite nanocrystals in Example 1 and Comparative Example 1 under continuous laser irradiation. (a) shows the fluorescence spectrum of the perovskite nanocrystals in Comparative Example 1 under continuous laser irradiation, and (b) shows the fluorescence spectrum of the perovskite nanocrystals in Example 1 under continuous laser irradiation.

[0049] Figure 9The images show a comparison of the fluorescence spectra of perovskite nanocrystals in Example 1 and Comparative Example 1 under room temperature and air conditions; where (a) is the fluorescence spectrum of the perovskite nanocrystals in Comparative Example 1 under room temperature and air conditions; and (b) is the fluorescence spectrum of the perovskite nanocrystals in Example 1 under room temperature and air conditions. Detailed Implementation

[0050] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0051] Example 1 This embodiment prepared a perovskite nanocrystal with the chemical composition CsPbBr3. Its surface was completely coated with oleylamine (OAm) ligands. It was obtained by post-processing ordinary nanocrystals. (Reference) Figure 1 The structural schematic diagram is shown in (a) above. The perovskite nanocrystals in this embodiment were prepared using a room-temperature solution method and post-treated at room temperature and in an air atmosphere. The specific process is as follows: (1) Preparation of precursor solution First, 110.1 mg of PbBr2 was added to 10 mL of toluene, along with 300 μL of oleic acid (OA) and 300 μL of oleylamine (OLA). The mixture was then heated to 100°C with continuous stirring and maintained for 1 hour, yielding a clear solution of the PbBr2 precursor, denoted as Solution 1. Next, 65.2 mg of Cs2CO3 and 10 mL of OA were added to a 20 mL glass bottle. The mixture was then heated to 100°C with continuous stirring and maintained for 1 hour until a clear solution of the Cs-OA precursor was obtained, denoted as Solution 2. Solutions 1 and 2 were cooled to room temperature for later use.

[0052] (2) Synthesis of nanocrystals At room temperature and in an air atmosphere, 0.45 mL of Cs-OA precursor solution (solution 2) was added to 6 mL of PbBr2 precursor solution (solution 1), and the mixture was stirred vigorously for 1 minute. Then, 5 mL of acetone was added to the mixture, and stirring was continued for 1 minute. Finally, the solution was centrifuged at 10,000 rpm for 2 minutes, and the resulting precipitate was redispersed in 4 mL of n-octane.

[0053] (3) Post-processing of nanocrystals First, prepare the nanocrystalline passivation solution by adding 22.5 mg ZnBr2, 0.16 mL OA, 0.16 mL OLA, and 10 mL n-octane to a 20 mL glass bottle. Then, heat the mixture to 100°C with stirring and maintain this temperature for 30 minutes until a clear solution forms. Cool to room temperature before use. At room temperature and in an air atmosphere, add 4 mL of the passivation solution to the perovskite nanocrystalline precipitate obtained by centrifugation in step 2 and sonicate for 1 minute. The reaction steps in the passivation solution are as follows: Figure 1 As shown in (b), a post-treatment solution was prepared using ZnBr2, oleic acid, and oleylamine. Zinc bromide, as a Lewis acid, effectively deprotonates the oleic acid, generating a large amount of oleylamine bromide in the solution. This generated oleylamine bromide can replace small cations such as Cs ions on the surface of perovskite quantum dots and passivate defects, resulting in perovskite nanocrystals with a uniformly coated surface and few defects. Furthermore, the perovskite nanocrystals coated with a large number of organic ligands effectively resist Oswald ripening and exhibit excellent stability.

[0054] Comparative Example 1 This comparative example prepared a common perovskite nanocrystal with the chemical composition CsPbBr3. Its surface is characterized by a mixed distribution of oleylamine (OAm) and small cations Cs. A schematic diagram of the structure can be found in the provided text. Figure 1 In (a), the perovskite structure was not treated. The perovskite nanocrystals in this comparative example were prepared by room temperature solution method, and the specific process is the same as in Example 1, except that the post-treatment of the nanocrystals in step (3) was not performed.

[0055] Experimental Example 1 This experimental example characterizes the perovskite nanocrystals prepared in Example 1 and Comparative Example 1, as follows: XPS full spectra and elemental composition of the perovskite nanocrystals in Comparative Example 1 and Example 1 were tested respectively. The crystal structures of the perovskite nanocrystals in Example 1 and Comparative Example 1 were also simulated, as detailed in Table 1 below. Figure 2 and Figure 3 As shown.

[0056] Phase diagrams, XPS full spectra, and elemental ratios of perovskite nanocrystals in Example 1 and Comparative Example 1 are shown below. Figure 2 As shown, by Figure 2 As shown in Table 1, the Cs atomic ratio on the surface of the perovskite nanocrystals in Example 1 is 0.61, while the Cs atomic ratio on the surface of the perovskite nanocrystals in Comparative Example 1 is 1.10, which is consistent with the simulated structure ( Figure 3The obtained atomic ratios match very well, indicating that almost 100% of the Cs atoms on the surface of the perovskite nanocrystals were removed after post-treatment, leaving only the internal Cs atoms. Meanwhile, the Br atom ratio on the surface of the perovskite nanocrystals in Example 1 was 4.56, while the Br atom ratio on the surface of the perovskite nanocrystals in Comparative Example 1 was 4.21, indicating that the Br atom vacancies on the surface of the perovskite nanocrystals were filled after post-treatment, and the defect states were significantly reduced.

[0057] Table 1. Atomic proportions of perovskite nanocrystals in Example 1 and Comparative Example 1, and in their simulated structures.

[0058] Note: For ease of comparison, the lead atomic ratio in all samples has been normalized to 1.00.

[0059] High-resolution XPS spectra and thermogravimetric analyses of Pb 4d in perovskite nanocrystals of Example 1 and Comparative Example 1 are as follows: Figure 4 As shown. By Figure 4 As shown in (a), the ratio of N atoms to Pb atoms in the perovskite nanocrystals of Example 1 is 2.1, while the ratio of N atoms to Pb atoms in the perovskite nanocrystals of Comparative Example 1 is 1.2. This indicates that the amount of oleamide on the surface of the perovskite nanocrystals increased by nearly 75% after post-treatment, while the oleamide content on the surface of the untreated sample was about 60%. Calculated as follows, the oleamide content on the surface of the treated sample is approximately 60% * (1 + 75%) = 105%, thus indicating that the surface of the perovskite nanocrystals is 100% coated with oleamide. Figure 4 As shown in (b), the mass ratio of oleylamine in the perovskite nanocrystals in Example 1 is 27.3%, while the mass ratio of oleylamine in the perovskite nanocrystals in Comparative Example 1 is about 12.4%. This further illustrates that the Cs ions on the surface of the post-treated perovskite nanocrystals have been almost 100% replaced by oleylamine, indicating that the surface of the post-treated perovskite nanocrystals is completely coated with oleylamine.

[0060] Experimental Example 2 This experimental example tests the performance of the perovskite nanocrystals prepared in Example 1 and Comparative Example 1. The specific process is as follows: The UV-Vis absorption spectrum, photofluorescence spectrum, fluorescence lifetime spectrum, and fluorescence quantum yield of the perovskite nanocrystals in Example 1 and Comparative Example 1 were tested. Specific test results are as follows: Figure 5 As shown, by Figure 5 As shown in (a), the absorption peak of the perovskite nanocrystals in Example 1 is at 427.0 nm, while the absorption peak of the perovskite nanocrystals in Comparative Example 1 is at 425.5 nm, indicating that the composition of the nanocrystals after post-treatment did not change significantly. The steady-state fluorescence spectra of the perovskite nanocrystals in Example 1 and Comparative Example 1 were tested, and the specific test results are as follows: Figure 5 As shown in (b) above, by Figure 5 As shown in (b), the luminescence intensity of the perovskite nanocrystals in Example 1 is three times that of the perovskite nanocrystals in Comparative Example 1, indicating that the surface defects of the perovskite nanocrystals were significantly passivated after post-treatment. Meanwhile, the fluorescence half-width at half-maximum (FWHM) of the perovskite nanocrystals in Example 1 is 13.6 nm, while that in Comparative Example 1 is 14.0 nm. This indicates that the higher surface uniformity of the perovskite nanocrystals after post-treatment leads to a decrease in the exciton-phonon coupling coefficient, thereby reducing the FWHM. The fluorescence lifetimes of the perovskite nanocrystals in Example 1 and Comparative Example 1 were tested, and the specific test results are as follows: Figure 5 As shown in (c) in the figure, by Figure 5 As shown in (c), the luminescence lifetime of the perovskite nanocrystals in Example 1 was 14.2 ns, while that in Comparative Example 1 was 7.5 ns. Compared to the luminescence lifetime of the perovskite nanocrystals in Comparative Example 1, the fluorescence lifetime of the perovskite nanocrystals in Example 1 was increased by approximately 90.0%, further demonstrating that the surface defects of the perovskite nanocrystals were significantly passivated after post-treatment, the exciton-phonon coupling coefficient was reduced, the non-radiative recombination channel was significantly suppressed, and the fluorescence lifetime was significantly improved. The fluorescence quantum yield of the perovskite nanocrystals in Example 1 and Comparative Example 1 was tested, and the specific test results are as follows: Figure 5 As shown in (d) in the figure, by Figure 5 As shown in (d), the fluorescence quantum yield of the perovskite nanocrystals in Example 1 was 60.0%, while that of the perovskite nanocrystals in Comparative Example 1 was 16.8%. Compared to the fluorescence quantum yield of the perovskite nanocrystals in Comparative Example 1, the fluorescence lifetime of the perovskite nanocrystals in Example 1 was increased by about 3 times, further demonstrating that the surface defects of the perovskite nanocrystals were significantly passivated after post-treatment, the exciton-phonon coupling coefficient was reduced, the non-radiative recombination channel was significantly suppressed, and the fluorescence quantum yield was significantly improved.

[0061] The transient absorption spectra of the perovskite nanocrystals in Example 1 and Comparative Example 1 were tested, and the specific test results are as follows: Figure 6 As shown, by Figure 6 It can be seen that the transient absorption lifetime of the perovskite nanocrystals in Example 1 is 5429.7 ps, while that of the perovskite nanocrystals in Comparative Example 1 is 2929.0 ps. Compared with the transient absorption lifetime of the perovskite nanocrystals in Comparative Example 1, the transient absorption lifetime of the perovskite nanocrystals in Example 1 is improved by about 85.0%, further demonstrating that the surface defects of the perovskite nanocrystals are significantly passivated after post-treatment, the exciton-phonon coupling coefficient is reduced, the non-radiative recombination channel is significantly suppressed, and the transient absorption lifetime is significantly improved.

[0062] The UV-Vis absorption and fluorescence spectra of the perovskite nanocrystals in Example 1 and Comparative Example 1 after heating at 100°C for 30 min were measured. Specific test results are as follows: Figure 7 As shown, by Figure 7 It can be seen that the perovskite nanocrystals in Example 1, after being heated at 100°C for 30 min, did not show a significant red shift in their absorption peak and no new peaks appeared. Simultaneously, the fluorescence emission peak position remained unchanged, indicating that the thermal stability of the post-treated perovskite nanocrystals was significantly enhanced. In contrast, the perovskite nanocrystals in Comparative Example 1, after being heated at 100°C for 30 min, showed a significant red shift in their absorption peak and the appearance of obvious new peaks. At the same time, the original fluorescence emission peak decreased significantly, and new fluorescence emission peaks appeared, indicating that the untreated perovskite nanocrystals had poor thermal stability at 100°C.

[0063] The perovskite nanocrystals in Example 1 and Comparative Example 1 were tested under femtosecond laser (2.5 µJ / cm²) light. 2 The fluorescence spectrum after continuous irradiation for 60 minutes is shown in the following figures. Figure 8 As shown, by Figure 8 It can be seen that the perovskite nanocrystals in Example 1, under femtosecond laser (2.5 µJ / cm²) conditions... 2 The fluorescence emission peak remained unchanged after 60 min of continuous irradiation, indicating that the photostability of the post-treated perovskite nanocrystals was significantly enhanced. The perovskite nanocrystals in Comparative Example 1, under femtosecond laser (2.5 µJ / cm²) irradiation, showed improved photostability. 2 After continuous irradiation for 60 min, the original fluorescence emission peak decreased significantly and a new fluorescence emission peak appeared, indicating that the photostability of untreated perovskite nanocrystals is poor.

[0064] The fluorescence spectra of the perovskite nanocrystals in Example 1 and Comparative Example 1 were tested after being stored at room temperature (25°C) and in air for 5 days, respectively. The specific test results are as follows: Figure 9 As shown, by Figure 9 It can be seen that the perovskite nanocrystals in Example 1 maintained their fluorescence emission peak position without the appearance of new peaks after being stored at room temperature (25°C) and in air for 5 days, indicating that the room temperature and air stability of the post-treated perovskite nanocrystals was significantly enhanced. In contrast, the perovskite nanocrystals in Comparative Example 1, after being stored at room temperature (25°C) and in air for 5 days, showed a significant decrease in their original fluorescence emission peak and the appearance of new fluorescence emission peaks, indicating that the untreated perovskite nanocrystals had poor room temperature and air stability.

[0065] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A surface-modified perovskite nanocrystal, characterized in that: include: Perovskite nanocrystals, with the chemical composition ABX3; Where A is selected from Cs + CH3NH3 + HC(NH2) 2+ At least one of them; B is selected from Pb 2+ Sn 2+ 、Ge 2+ Mn 2+ At least one of them; X is selected from halide anions; The surface of the perovskite nanocrystals is coated with an organic ligand layer; the organic ligands include halogenated organic ligands.

2. The surface-modified perovskite nanocrystals according to claim 1, characterized in that: At least 95% of the surface area of ​​the perovskite nanocrystals is covered by an organic ligand layer.

3. The surface-modified perovskite nanocrystals according to claim 1, characterized in that: The halogenated organic ligands include halide salts of organic ligands; the organic ligands include at least one of oleylamine, octylamine, dodecylamine, oleic acid, octanoic acid, dodecylbenzenesulfonic acid, octylphosphonic acid, lecithin, 2-hexyldecanoic acid, hexadecyltrimethylammonium bromide, dodecyl thiocyanate, and tris(diethylamino)phosphine.

4. The surface-modified perovskite nanocrystals according to claim 1, characterized in that: X is selected from I - ,Br - Cl - At least one of them.

5. The surface-modified perovskite nanocrystals according to any one of claims 1 to 4, characterized in that: In the surface-modified perovskite nanocrystals, the organic ligand layer accounts for 25-30% of the mass.

6. A method for preparing surface-modified perovskite nanocrystals according to any one of claims 1 to 5, characterized in that: Includes the following steps: The surface-modified perovskite nanocrystals were prepared by reacting perovskite nanocrystals with a mixed solution containing metal halide salts, organic acids and organic ligands.

7. The method for preparing surface-modified perovskite nanocrystals according to claim 6, characterized in that: The concentration of the metal halide salt in the mixed solution is 5-15 mmol / L; and / or, the concentration of the organic ligand in the mixed solution is 30-60 mmol / L.

8. The method for preparing surface-modified perovskite nanocrystals according to claim 6, characterized in that: The metal halide salt is selected from at least one of PbI2, PbBr2, PbCl2, SnI2, SnBr2, SnCl2, ZnI2, ZnBr2, ZnCl2, CuI, CuBr, CuCl, AgI, AgBr, AgCl, CdI2, CdBr2, CdCl2, MnI2, MnBr2, and MnCl2; and / or, the organic acid includes at least one of oleic acid, octanoic acid, and dodecanoic acid.

9. The method for preparing surface-modified perovskite nanocrystals according to claim 6, characterized in that: The method for preparing the perovskite nanocrystals includes the following steps: reacting a solution containing a salt of A and a first organic ligand with a solution containing a halide salt of B and a second organic ligand to obtain the perovskite nanocrystals.

10. A device comprising the surface-modified perovskite nanocrystals as described in any one of claims 1 to 5.

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