Perovskite nanocrystal and application thereof as white light diode luminescent material

Abstract

The invention relates to a perovskite nanocrystal and application thereof as a white light diode luminescent material, and belongs to the technical field of luminescent materials. A thin film prepared from the perovskite nanocrystal disclosed by the invention has relatively high fluorescence quantum yield and good temperature-resistant and moisture-resistant stability. In the perovskite nanocrystal synthesis and film forming process, the functional carboxylic acid compound adopted in the invention can provide corresponding carboxyl functional groups and a large number of quaternary ammonium salt groups to play a ligand role and combine with Pb < 2 + >, so that the surface defects of the nanocrystal are effectively passivated; and a branched aliphatic chain, annular morpholine, branched carboxyl and branched quaternary ammonium salt in the branched carboxyl quaternary ammonium salt compound can be tightly combined on the surface of the perovskite nanocrystal through physical and chemical effects, and agglomeration of the CsPbBr3 nanocrystal is prevented through a steric effect.

Description

TECHNICAL FIELD

[0001] The present application relates to a perovskite nanocrystal and application thereof as a white light diode light emitting material, and belongs to the technical field of light emitting materials. BACKGROUND

[0002] Light emitting materials are widely used in daily life and are indispensable. With the rapid development of the optoelectronic industry, the demand for energy is also increasing, and developing new light emitting materials with excellent performance and low energy consumption is the goal pursued by researchers. Semiconductor nanomaterials (quantum dots) have been attracting more and more attention due to their excellent physical and chemical properties.

[0003] Among them, metal halide perovskite is a new type of optoelectronic material developed in recent years that has attracted much attention. Perovskite is composed of three main ions, and its structure can be represented by ABX3. Among them, A is a monovalent organic or inorganic cation (Cs + , CH3NH 3+ ), B is a divalent metal ion (usually Pb 2+ or Sn 2+ ), and X is a halide anion (Cl - , Br - and I - ) or a mixture thereof. However, Sn 2+ is easily oxidized to Sn 4+ in the environment, resulting in instability of its perovskite structure. Therefore, most researches focus on lead-based perovskite materials. Lead-based perovskite nanostructures have the advantages of few surface defects, high photoluminescence quantum efficiency, narrow emission peak, and continuous tunable emission peak, and are considered as a good alternative to traditional quantum dots, which have shown great application potential in solar cells, light emitting LEDs, lasers, and photodetectors.

[0004] However, due to the inherent characteristics of its ionic crystal, lead-based perovskite nanocrystals are easily affected by environmental factors such as humidity, resulting in unstable optical properties, which cannot meet the use requirements. SUMMARY

[0005] The purpose of the present application is to provide a perovskite nanocrystal and application thereof as a white light diode light emitting material, in order to solve the problem that the current lead-based perovskite nanocrystal is easily affected by environmental factors such as humidity, resulting in unstable optical properties.

[0006] The present application provides a perovskite nanocrystal, which is prepared by a method comprising the following steps: mixing cesium acetate, lead acetate and a functional carboxylic acid compound in a solvent and reacting, and obtaining the perovskite nanocrystal after impurity removal; the structure of the functional carboxylic acid compound is as follows: .

[0007] Preferably, the solvent consists of toluene and acetic acid.

[0008] Preferably, the mixing reaction is performed by using a microfluidic system; the method of the mixing reaction is as follows: cesium acetate and lead acetate are dissolved in acetic acid to obtain solution A; a functional carboxylic acid compound is dissolved in toluene to obtain solution B; solution A and solution B are injected into a reaction chip by using injection pumps of the microfluidic system to perform the mixing reaction.

[0009] Preferably, in solution A, the concentration of cesium acetate is 0.01-0.015 mol / L.

[0010] Preferably, in solution A, the concentration of lead acetate is 0.025-0.03 mol / L.

[0011] Preferably, in solution B, the mass fraction of the functional carboxylic acid compound is 6-7%.

[0012] Preferably, the volume ratio of solution A to solution B is 0.1-0.3:10-15.

[0013] Preferably, the method of removing impurities is as follows: the system after the mixing reaction is centrifuged at a speed of 4000-4500 r / min for 5-6 min, the lower precipitate is discarded, the supernatant and ethyl acetate are mixed at a volume ratio of 1:4-5, and then centrifuged again, and the solid obtained by centrifugation is vacuum dried to obtain perovskite nanocrystals.

[0014] Preferably, the preparation method of the functional carboxylic acid compound is as follows: 2-hydroxy-1,3-propanediamine is first mixed with N-allylmorpholine, and then mixed with (1-tert-butylvinyl oxo)trimethylsilane to obtain a multifunctional alcohol compound; then the multifunctional alcohol compound is subjected to a quaternary ammonium salt reaction with bromoiso-octane to obtain a quaternary ammonium salt alcohol compound; finally, the quaternary ammonium salt alcohol compound is first mixed with dimethyl phosphoramine chloride, and then mixed with malic acid to obtain the functional carboxylic acid compound; the molar ratio of 2-hydroxy-1,3-propanediamine, N-allylmorpholine and (1-tert-butylvinyl oxo)trimethylsilane is 1:2:2, the molar ratio of the multifunctional alcohol compound and bromoiso-octane is 1:4.5-5, and the molar ratio of dimethyl phosphoramine chloride, the quaternary ammonium salt alcohol compound and malic acid is 1:1:1.

[0015] The application further provides a use of the perovskite nanocrystals as described above as a white light diode luminescent material.

[0016] Compared with the prior art, the application has the following beneficial effects: The perovskite nanocrystals of this invention produce films with high fluorescence quantum yield (greater than 70%) and good temperature and humidity stability. During the synthesis and film formation of the perovskite nanocrystals, the branched carboxyl quaternary ammonium salt compound used in this invention can provide corresponding carboxyl functional groups and a large number of quaternary ammonium salt groups, acting as a ligand and reacting with Pb. 2+ By combining these components, surface defects in the nanocrystals are effectively passivated, enhancing their resistance to external stimuli and improving their stability. Furthermore, the branched aliphatic chains, cyclic morpholine, branched carboxyl groups, and branched quaternary ammonium salts in the branched carboxyl quaternary ammonium salt compound are tightly bound to the perovskite nanocrystal surface through physicochemical interactions, exhibiting stronger adsorption energy. This prevents the aggregation of CsPbBr3 nanocrystals through steric hindrance, and the high-density branched hydrophobic structure improves the dispersion uniformity of perovskite nanocrystals in organic solvents and prevents the erosion and damage caused by unstable factors such as moisture. In addition, the white light-emitting diodes made from the perovskite nanocrystals of this invention have a luminous efficiency greater than 50 lm / W, demonstrating a high ability to convert electrical energy into light energy. Attached Figure Description

[0017] Figure 1 The above is the 1H NMR spectrum of the multifunctional alcohol compound prepared in Example 1 of this invention; Figure 2 This is the 1H NMR spectrum of the functional carboxylic acid compound prepared in Example 1 of the present invention. Detailed Implementation

[0018] The following examples are intended to further illustrate the content of the present invention, rather than to limit the scope of protection of the present invention.

[0019] I. Specific embodiments of the perovskite nanocrystals of the present invention are as follows: Example 1 The perovskite nanocrystals of this embodiment are prepared by a method including the following steps: (1) 2-hydroxy-1,3-propanediamine, N-allylmorpholine, triethylamine and tetrahydrofuran are added into a reaction kettle, stirred uniformly, heated to 75°C, stirred under reflux for 6h, then (1-tert-butylvinyl oxo) trimethylsilane is added into the reaction kettle, continues to be stirred under reflux for 10h, cooled to room temperature, distilled under reduced pressure, and the solvent is removed to obtain a concentrated solution, which is purified by column chromatography (the eluent used in column chromatography is composed of dichloromethane, ethyl acetate and methanol in a volume ratio of 5:2:1), to obtain a multifunctional alcohol compound; wherein the molar ratio of 2-hydroxy-1,3-propanediamine, N-allylmorpholine and (1-tert-butylvinyl oxo) trimethylsilane is 1:2:2, the mass of triethylamine is 3% of the sum of the masses of 2-hydroxy-1,3-propanediamine and N-allylmorpholine, and the mass of tetrahydrofuran is 110% of the sum of the masses of 2-hydroxy-1,3-propanediamine and N-allylmorpholine, and the nuclear magnetic resonance hydrogen spectrum of the multifunctional alcohol compound is shown in Figure 1 , and the chemical structure is as follows: .

[0020] (2) The multifunctional alcohol compound, bromohydrocarbon and tetrahydrofuran are added into a reaction kettle, stirred uniformly, heated to 80°C, stirred under reflux for 12h, distilled under reduced pressure, and the solvent and excess bromohydrocarbon are removed to obtain a quaternary ammonium salt alcohol compound; wherein the bromohydrocarbon is bromoiso-octane, the molar ratio of the multifunctional alcohol compound and the bromohydrocarbon is 1:4.5, and the mass of tetrahydrofuran is 60% of the sum of the masses of the multifunctional alcohol compound and the bromohydrocarbon.

[0021] (3) The quaternary ammonium salt alcohol compound, triethylamine and anhydrous tetrahydrofuran are added into a reaction kettle, then the temperature of the material in the reaction kettle is adjusted to -5°C, dimethylphosphonium chloride is added dropwise into the reaction kettle under stirring, after the dropwise addition is completed, the temperature is raised to 5°C, and the stirring is continued for 3h, then malic acid is added, the temperature is raised to 25°C, and the stirring is continued for 5h, then the solvent is removed by distillation under reduced pressure to obtain a concentrate, which is purified by column chromatography (the eluent used in column chromatography is composed of dichloromethane, ethyl acetate and methanol in a volume ratio of 5:2:2), to obtain a functional carboxylic acid compound; wherein the molar ratio of dimethylphosphonium chloride, the quaternary ammonium salt alcohol compound, malic acid and triethylamine is 1:1:1:2.3, the mass of anhydrous tetrahydrofuran is 80% of the sum of the masses of the quaternary ammonium salt alcohol compound and malic acid, and the nuclear magnetic resonance hydrogen spectrum of the functional carboxylic acid compound is shown in Figure 2 , and the chemical structure is as follows: .

[0022] (4) cesium acetate and lead acetate are dissolved in acetic acid to obtain solution A, in which the concentration of cesium acetate is 0.01 mol / L and the concentration of lead acetate is 0.025 mol / L; a functional carboxylic acid compound is dissolved in toluene to obtain solution B, in which the mass fraction of the functional carboxylic acid compound is 6%; solution A and solution B are continuously injected into a reaction chip through injection pumps of a microfluidic system according to a volume ratio of 0.1:10, and a reaction solution is obtained after mixing of the two in the reaction chip; the reaction solution is centrifuged at a speed of 4000 r / min for 5 min after being collected, and the lower precipitate is discarded; the supernatant and ethyl acetate are stirred and mixed according to a volume ratio of 1:4, and then centrifuged again; the solid obtained by centrifugation is vacuum dried to obtain perovskite nanocrystals (functional carboxylic acid compound modified CsPbBr3 nanocrystals); wherein the mixing time of solution A and solution B in the reaction chip is 8 s, and the flow rate of solution A is 1 mL / min.

[0023] Example 2 The perovskite nanocrystals of this example are prepared by a method comprising the following steps: (1) 2-hydroxy-1,3-propanediamine, N-allylmorpholine, triethylamine and tetrahydrofuran are added into a reaction kettle, stirred uniformly, heated to 80℃, and stirred to react under reflux conditions for 7 h; then (1-tert-butylvinyl oxo)trimethylsilane is added into the reaction kettle, and stirring to react under reflux conditions is continued for 11 h; after cooling to room temperature, the solvent is removed by reduced pressure distillation to obtain a concentrated solution, which is purified by column chromatography (the eluent used in column chromatography purification is composed of dichloromethane, ethyl acetate and methanol in a volume ratio of 5:2:1); and a multifunctional alcohol compound is obtained; wherein the molar ratio of 2-hydroxy-1,3-propanediamine, N-allylmorpholine and (1-tert-butylvinyl oxo)trimethylsilane is 1:2:2, the mass of triethylamine is 4% of the sum of the masses of 2-hydroxy-1,3-propanediamine and N-allylmorpholine, and the mass of tetrahydrofuran is 120% of the sum of the masses of 2-hydroxy-1,3-propanediamine and N-allylmorpholine.

[0024] (2) the multifunctional alcohol compound, a brominated hydrocarbon and tetrahydrofuran are added into a reaction kettle, stirred uniformly, heated to 82℃, and stirred to react under reflux conditions for 14 h; and the solvent and excess brominated hydrocarbon are removed by reduced pressure distillation to obtain a quaternary ammonium salt alcohol compound; wherein the brominated hydrocarbon is brominated isooctane, the molar ratio of the multifunctional alcohol compound and the brominated hydrocarbon is 1:4.8, and the mass of tetrahydrofuran is 70% of the sum of the masses of the multifunctional alcohol compound and the brominated hydrocarbon.

[0025] (3) quaternary ammonium salt alcohol compound, triethylamine and anhydrous tetrahydrofuran are added into a reaction kettle, then the temperature of the materials in the reaction kettle is adjusted to -2℃, dimethyl phosphorus amine chloride is added dropwise into the reaction kettle under stirring, after the dropwise addition is completed, the temperature is increased to 7℃, and the stirring reaction is continued for 4h, then malic acid is added, the temperature is increased to 28℃, and the stirring reaction is continued for 6h, and the solvent is removed by distillation under reduced pressure to obtain a concentrate, and the concentrate is purified by column chromatography (the eluent used in column chromatography purification is composed of dichloromethane, ethyl acetate and methanol in a volume ratio of 5:2:2), to obtain a functional carboxylic acid compound; wherein the molar ratio of dimethyl phosphorus amine chloride, quaternary ammonium salt alcohol compound, malic acid and triethylamine is 1:1:1:2.4, the mass of anhydrous tetrahydrofuran is 90% of the sum of the mass of quaternary ammonium salt alcohol compound and malic acid, and the chemical structure of the functional carboxylic acid compound is as follows: .

[0026] (4) cesium acetate and lead acetate are dissolved in acetic acid to obtain solution A, in solution A, the concentration of cesium acetate is 0.01 mol / L, and the concentration of lead acetate is 0.025 mol / L; the functional carboxylic acid compound is dissolved in toluene to obtain solution B, the mass fraction of the functional carboxylic acid compound in solution B is 6%; solution A and solution B are continuously injected into the reaction chip through the injection pumps of the microfluidic system according to a volume ratio of 0.2:12, and the reaction liquid is obtained after mixing in the reaction chip, the reaction liquid is centrifuged at a speed of 4000r / min for 5min, and the lower precipitate is discarded, the supernatant and ethyl acetate are stirred and mixed according to a volume ratio of 1:4, and then centrifuged, and the solid obtained by centrifugation is vacuum dried to obtain perovskite nanocrystals (functional carboxylic acid compound modified CsPbBr3 nanocrystals); wherein the mixing time of solution A and solution B in the reaction chip is 10s, and the flow rate of solution A is 1.2mL / min.

[0027] Example 3 The perovskite nanocrystals of this example are prepared by a method comprising the following steps: (1) 2-hydroxy-1,3-propanediamine, N-allylmorpholine, triethylamine and tetrahydrofuran are added into a reaction kettle, stirred uniformly, heated to 85°C, stirred under reflux for 9h, then (1-tert-butylvinyl oxo) trimethylsilane is added into the reaction kettle, continues to be stirred under reflux for 12h, cooled to room temperature, removed solvent by distillation under reduced pressure, to obtain a concentrated solution, the concentrated solution is purified by column chromatography (the eluent used in column chromatography consists of dichloromethane, ethyl acetate and methanol in a volume ratio of 5:2:1), to obtain a multifunctional alcohol compound; wherein the molar ratio of 2-hydroxy-1,3-propanediamine, N-allylmorpholine and (1-tert-butylvinyl oxo) trimethylsilane is 1:2:2, the mass of triethylamine is 5% of the sum of the masses of 2-hydroxy-1,3-propanediamine and N-allylmorpholine, and the mass of tetrahydrofuran is 130% of the sum of the masses of 2-hydroxy-1,3-propanediamine and N-allylmorpholine.

[0028] (2) The multifunctional alcohol compound, bromohydrocarbon and tetrahydrofuran are added into a reaction kettle, stirred uniformly, heated to 85°C, stirred under reflux for 15h, removed solvent and excess bromohydrocarbon by distillation under reduced pressure, to obtain a quaternary ammonium salt alcohol compound; wherein the bromohydrocarbon is bromoiso-octane, the molar ratio of the multifunctional alcohol compound and the bromohydrocarbon is 1:5, and the mass of tetrahydrofuran is 80% of the sum of the masses of the multifunctional alcohol compound and the bromohydrocarbon.

[0029] (3) The quaternary ammonium salt alcohol compound, triethylamine and anhydrous tetrahydrofuran are added into a reaction kettle, then the temperature of the materials in the reaction kettle is adjusted to 0°C, dimethylphosphoramide chloride is added dropwise into the reaction kettle under stirring, after the dropwise addition is completed, the temperature is increased to 10°C, and the reaction is continued to be stirred for 5h, then malic acid is added, the temperature is increased to 30°C, and the reaction is continued to be stirred for 8h, the solvent is removed by distillation under reduced pressure, to obtain a concentrate, the concentrate is purified by column chromatography (the eluent used in column chromatography consists of dichloromethane, ethyl acetate and methanol in a volume ratio of 5:2:2), to obtain a functional carboxylic acid compound; wherein the molar ratio of dimethylphosphoramide chloride, the quaternary ammonium salt alcohol compound, malic acid and triethylamine is 1:1:1:2.5, the mass of anhydrous tetrahydrofuran is 110% of the sum of the masses of the quaternary ammonium salt alcohol compound and malic acid, and the chemical structure of the functional carboxylic acid compound is as follows: .

[0030] (4) cesium acetate and lead acetate are dissolved in acetic acid to obtain solution A, in which the concentration of cesium acetate is 0.01 mol / L and the concentration of lead acetate is 0.025 mol / L; the functional carboxylic acid compound is dissolved in toluene to obtain solution B, in which the mass fraction of the functional carboxylic acid compound is 7%; solution A and solution B are continuously injected into the reaction chip through the injection pumps of the microfluidic system according to a volume ratio of 0.3:15, and the two are mixed in the reaction chip to obtain a reaction solution, which is collected and centrifuged at a speed of 4000 r / min for 5 min, and the lower precipitate is discarded; the supernatant and ethyl acetate are stirred and mixed according to a volume ratio of 1:4, and then centrifuged again, and the obtained solid is vacuum dried to obtain perovskite nanocrystals (functional carboxylic acid compound modified CsPbBr3 nanocrystals); wherein, the mixing time of solution A and solution B in the reaction chip is 12 s, and the flow rate of solution A is 1.5 mL / min.

[0031] Comparative Example 1 The perovskite nanocrystals of the present comparative example differ from the perovskite nanocrystals of Example 1 only in that, in step (1) of the preparation, the N-allylmorpholine is replaced by 1-allylpiperidine.

[0032] Comparative Example 2 The perovskite nanocrystals of the present comparative example differ from the perovskite nanocrystals of Example 1 only in that, in step (1) of the preparation, the (1-tert-butylvinyl oxo)trimethylsilane is replaced by vinyltrimethylsilane.

[0033] Comparative Example 3 The perovskite nanocrystals of the present comparative example differ from the perovskite nanocrystals of Example 1 only in that, in step (1) of the preparation, the (1-tert-butylvinyl oxo)trimethylsilane is replaced by tert-butyl vinyl ether.

[0034] Comparative Example 4 The perovskite nanocrystals of the present comparative example differ from the perovskite nanocrystals of Example 1 only in that, in step (2) of the preparation, the brominated hydrocarbon is 1-bromo-n-octane.

[0035] Comparative Example 5 The perovskite nanocrystals of the present comparative example differ from the perovskite nanocrystals of Example 1 only in that, in step (2) of the preparation, the brominated hydrocarbon is brominated isobutane.

[0036] Comparative Example 6 The perovskite nanocrystals of the present comparative example differ from the perovskite nanocrystals of Example 1 only in that, in step (2) of the preparation, the brominated hydrocarbon is 2-butyl-1-bromo octane.

[0037] Comparative Example 7 The only difference between the perovskite nanocrystals of this comparative example and those of Example 1 is that in step (3) of the preparation of the perovskite nanocrystals of this comparative example, dimethylphosphonoammonium chloride is replaced with ethylphosphonodichloride.

[0038] Comparative Example 8 The only difference between the perovskite nanocrystals of this comparative example and the perovskite nanocrystals of Example 1 is that malic acid is replaced with γ-hydroxybutyric acid in step (3) of the preparation of the perovskite nanocrystals of this comparative example.

[0039] Comparative Example 9 The only difference between the perovskite nanocrystals of this comparative example and the perovskite nanocrystals of Example 1 is that malic acid is replaced with citric acid in step (3) of the preparation of the perovskite nanocrystals of this comparative example.

[0040] Comparative Example 10 The only difference between the perovskite nanocrystals of this comparative example and the perovskite nanocrystals of Example 1 is that, in step (4) of the preparation of the perovskite nanocrystals of this comparative example, the functional carboxylic acid compound is replaced with dimethyl dioctylammonium bromide and oleic acid in a molar ratio of 2:1.

[0041] II. Specific embodiments of the application of the perovskite nanocrystals of the present invention as light-emitting materials for white LEDs are as follows: Using any of the perovskite nanocrystals from Examples 1-3 as a green phosphor, K2SiF6:Mn 4+ As a red phosphor, green phosphor, red phosphor and epoxy resin are mixed evenly and coated onto a blue InGaN chip, and then vacuum dried to obtain a white light-emitting diode device.

[0042] Experimental Example In order to investigate the basic properties of the perovskite nanocrystals of each embodiment and the comparative example and the application prospect in the white light-emitting diode device, the fluorescence quantum yield (PLQY), the stability of the perovskite nanocrystals of each embodiment and the comparative example and the luminous efficiency of the white light-emitting diode prepared are tested respectively, and the results are shown in Table 1. Among them, the test method of the fluorescence quantum yield (PLQY) is as follows: the perovskite nanocrystals of each embodiment and the comparative example are dispersed in toluene to obtain a dispersion liquid with a fixed concentration, then the dispersion liquid is spin-coated on glass and dried to prepare perovskite nanocrystal thin films with the same thickness, and then the fluorescence quantum yield of the perovskite nanocrystal thin films under an excitation wavelength of 365 nm is measured by using a fluorescence spectrophotometer; the test method of the stability is as follows: the perovskite nanocrystal thin films are prepared according to the method in the test method of the fluorescence quantum yield (PLQY), then the perovskite nanocrystal thin films are placed in an environment with a temperature of 85 ℃ and a humidity of 85%, and the data of the change of the fluorescence emission spectrum intensity of the sample with time under the same conditions is tested, and the stability is represented by the standing time corresponding to the 50% reduction of the fluorescence intensity, and the fluorescence intensity refers to the fluorescence intensity corresponding to the maximum emission wavelength in the obtained fluorescence emission spectrum; the luminous efficiency of the white light-emitting diode is compared when the current density is 15 mA. The experiment is repeated for 3 times, and the average value of the results of 3 experiments is taken as the final experimental result.

[0043] Table 1: Photoluminescence quantum yield (PLQY), stability of perovskite nanocrystals of each embodiment and the comparative example and the luminous efficiency of the white light-emitting diode prepared

[0044] From the test results in Table 1, it can be seen that the thin films prepared from the perovskite nanocrystals of embodiments 1-3 of the present application have high fluorescence quantum yield (more than 70%) and good temperature and humidity resistance stability. In the synthesis and film forming process of the perovskite nanocrystals, the branched carboxyl quaternary ammonium salt compound used in the present application can provide corresponding carboxyl functional groups and a large number of quaternary ammonium salt groups, play a ligand role, combine with Pb 2+ , effectively passivate the surface defects of the nanocrystals, enhance the ability of the nanocrystals to resist external stimuli, improve the stability of the perovskite nanocrystals, and the branched fatty chain, cyclic morpholine, branched carboxyl and branched quaternary ammonium salt in the branched carboxyl quaternary ammonium salt compound can be tightly combined on the surface of the perovskite nanocrystals through physical and chemical action, have stronger adsorption energy, prevent the agglomeration of CsPbBr3 nanocrystals through steric hindrance effect, and the high-density branched hydrophobic structure can improve the dispersion uniformity of the perovskite nanocrystals in the organic solvent and prevent the invasion and damage of unstable factors such as moisture to the perovskite nanocrystals. In addition, the luminous efficiency of the white light-emitting diode prepared from the perovskite nanocrystals of the present application is greater than 50 lm / W, and has good light conversion ability. ​

[0045] From Example 1 and Comparative Example 1, it can be seen that the morpholine ring is more advantageous than the piperidine ring in improving the fluorescence performance and stability of the perovskite nanocrystals, because the ether bond in the piperidine ring can form hydrogen bonds with the hydroxyl groups on the surface of the nanocrystals and complex bonds with the metals such as lead in the nanocrystals, thereby improving the adhesion strength of the branched carboxyl quaternary ammonium salt compound on the surface of the nanocrystals and effectively protecting the perovskite nanocrystals.

[0046] From Example 1 and Comparative Examples 2-3, it can be seen that the (1-tert-butyl vinyl oxo) trimethylsilane contains hydrophobic silicon atoms and bulky tert-butyl groups, which can effectively improve the dispersion uniformity of the perovskite nanocrystals in organic solvents and prevent the erosion and damage of unstable factors such as moisture to the perovskite nanocrystals, thereby improving the stability of the perovskite nanocrystals.

[0047] From Example 1 and Comparative Examples 4-6, it can be seen that compared with the straight-chain n-octyl group, the branched octyl group can more effectively improve the distribution density of the hydrophobic fatty chain on the surface of the perovskite nanocrystals and improve the protection ability of the perovskite nanocrystals; compared with the branched butyl group and the branched dodecyl group, the molecular chain length of the branched octyl group is more matched with the quaternary ammonium salt carboxylic compound, forming effective protection of the internal included carboxyl group, improving the stability of the carboxyl group combined with Pb 2+ , and thereby improving the overall performance of the perovskite nanocrystals.

[0048] From Example 1 and Comparative Example 7, it can be seen that compared with ethyl dichlorophosphine, dimethyl phosphine chloride can introduce phosphorus atoms and phosphine structures into the quaternary ammonium salt carboxylic compound at the same time, which can be combined with cesium, lead, bromine, and carboxyl groups on the surface of the perovskite nanocrystals, further improving the binding strength of the quaternary ammonium salt carboxylic compound on the surface of the perovskite nanocrystals, and improving the fluorescence performance and stability of the perovskite nanocrystals.

[0049] From Example 1 and Comparative Examples 8-9, it can be seen that compared with γ-hydroxybutyric acid and citric acid, malic acid has two carboxyl groups, which are located between the branched octyl groups on the two quaternary ammonium salt groups and can be fully protected by the branched alkyl groups, while one carboxyl group in γ-hydroxybutyric acid is not conducive to improving the complex binding strength, and three carboxyl groups in citric acid cannot be fully protected by the branched alkyl groups, resulting in weak complex binding strength and easy influence from the external environment.

[0050] From Example 1 and Comparative Example 10, it can be seen that compared with the combination of conventional quaternary ammonium salt compounds and oleic acid, the quaternary ammonium salt carboxylic compound in the present application has multiple functional groups, which can more effectively improve the binding strength with the perovskite nanocrystals, effectively protect the perovskite nanocrystals, and improve the stability and fluorescence performance thereof.

Claims

1. A perovskite nanocrystal, characterized in that, The perovskite nanocrystals are prepared by a method comprising the following steps: mixing and reacting cesium acetate, lead acetate and a functional carboxylic compound in a solvent to obtain the perovskite nanocrystals after impurity removal; and the functional carboxylic compound has the following structure: 。 2. The perovskite nanocrystal of claim 1, wherein, The solvent is composed of toluene and acetic acid.

3. The perovskite nanocrystal of claim 1, wherein, The mixing and reacting is performed by using a microfluidic system; and the method of the mixing and reacting is as follows: dissolving the cesium acetate and the lead acetate in the acetic acid to obtain solution A; dissolving the functional carboxylic compound in toluene to obtain solution B; and injecting solution A and solution B into a reaction chip through injection pumps of the microfluidic system for mixing and reacting.

4. The perovskite nanocrystal of claim 3, wherein the perovskite nanocrystal has a composition of CH3NH3PbI3. In solution A, the concentration of the cesium acetate is 0.01-0.015 mol / L.

5. The perovskite nanocrystal of claim 3, wherein, In solution A, the concentration of the lead acetate is 0.025-0.03 mol / L.

6. The perovskite nanocrystal of claim 3, wherein, In solution B, the mass fraction of the functional carboxylic compound is 6-7%.

7. The perovskite nanocrystal of claim 3, wherein the perovskite nanocrystal has a composition of CH3NH3PbI3. The volume ratio of solution A to solution B is 0.1-0.3:10-15.

8. The perovskite nanocrystal of any one of claims 1-7, wherein, The method of the impurity removal is as follows: centrifuging the system after the mixing and reacting at a speed of 4000-4500 r / min for 5-6 min, discarding the lower sediment, mixing the supernatant and ethyl acetate according to a volume ratio of 1:4-5, centrifuging again, vacuum drying the solid obtained by centrifuging to obtain the perovskite nanocrystals.

9. The perovskite nanocrystal of any one of claims 1-7, wherein, The preparation method of the functional carboxylic compound is as follows: mixing and reacting 2-hydroxy-1,3-propanediamine and N-allylmorpholine first, and then mixing and reacting the product with (1-tert-butylvinyl oxo)trimethylsilane to obtain a multifunctional alcohol compound; then performing quaternary ammonium reaction on the multifunctional alcohol compound and bromoiso-octane to obtain a quaternary ammonium salt alcohol compound; and finally mixing and reacting the quaternary ammonium salt alcohol compound with dimethyl phosphoramine chloride first, and then mixing and reacting the product with malic acid to obtain the functional carboxylic compound; the molar ratio of 2-hydroxy-1,3-propanediamine, N-allylmorpholine and (1-tert-butylvinyl oxo)trimethylsilane is 1:2:2, the molar ratio of the multifunctional alcohol compound and bromoiso-octane is 1:4.5-5, and the molar ratio of dimethyl phosphoramine chloride, the quaternary ammonium salt alcohol compound and malic acid is 1:1:

1.

10. Use of the perovskite nanocrystals as claimed in any one of claims 1-9 as a white light diode light emitting material.

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