Preparation and application method of high stability csPbX3 quantum dots based on double passivation strategy

Abstract

The application provides a preparation method of high-stability CsPbX3 quantum dots based on a double-passivation strategy and application of the CsPbX3 quantum dots in a wide color gamut backlight display field. The preparation method is as follows: 1) a cesium precursor solution is obtained by reacting a cesium source with an organic acid and a high-boiling-point solvent under an argon atmosphere; 2) a lead precursor solution is obtained by mixing a lead source, a halogen supplement, an organic acid and a non-coordination solvent and heating under the protection of argon; 3) a certain amount of the cesium precursor solution is injected into the lead precursor solution to obtain a CsPbX3 (X=Br, I) quantum dot reaction stock solution; 4) a perovskite light conversion film is obtained by compounding the CsPbX3 (X=Br, I) quantum dots with a polymer matrix; and 5) a series of blue-source color LED devices are obtained by assembling light conversion films with different light-emitting colors and commercial GaN LED chips, wide color gamut coverage is achieved, and the devices have great application potential in the backlight display field. The application greatly improves the stability of the cesium halide lead perovskite through double passivation of strong combination ligands and inorganic encapsulation layers.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of light emitting and display technology. Specifically, it relates to a preparation method of high-stability CsPbX3(X=Br, I) quantum dots based on a double passivation strategy, which is applied to light conversion films. By using the CBB (Color By Blue) technology, the blue light emitted by a commercial GaN LED chip is used to excite the luminescent material, thereby realizing the preparation of a wide color gamut backlight device with red, green and blue three primary colors. BACKGROUND

[0002] In recent years, metal halide perovskite quantum dots as a new emerging optoelectronic material are booming. Compared with traditional organic dyes or inorganic fluorescent powder, metal halide perovskite quantum dots have high luminescent quantum efficiency, narrow emission half-width, high color purity and adjustable emission spectrum. These excellent properties make metal halide perovskite quantum dots have great application potential in many cutting-edge fields. For example, they are widely used in light absorbers of photovoltaic devices, phosphors of light-emitting diodes, quantum dot infrared detectors, quantum dot lasers, anti-counterfeiting technology, and fluorescent probes for biological imaging.

[0003] As a new material with great application prospects, metal halide perovskite quantum dots have poor stability in the atmosphere. The phase transition and decomposition of the material are the current bottleneck for the commercialization of perovskite. When perovskite materials are exposed to the atmosphere, water, oxygen, light and heat can induce phase transition or decomposition of the crystal structure, so that the related devices can only work stably under the protection of inert atmosphere, which is a fatal defect for the practical application of perovskite materials. The main source of instability of metal halide perovskite quantum dots is the dynamic combination of quantum dot crystal surface ligands, which makes the surface ligands easily fall off during purification, storage or use, forming defect sites. Defects act as carrier traps to capture carriers, greatly reducing the optical performance of the material.

[0004] The quantum dots prepared by traditional hot injection method use oleic acid and oleylamine as end-capping ligands, which have weak binding ability with the crystal surface, so the ligands are easily desorbed, leading to quantum dot agglomeration. This phenomenon is particularly serious for cesium lead iodide quantum dots, because the iodide ion, as a soft base, is easily desorbed from the hard acid -NH4 +The binding force between the two is weak, so the cesium lead iodide will cause obvious light degradation after experiencing anti-solvent purification. In order to improve the stability of the cesium lead halide perovskite quantum dots, the researchers developed a ligand engineering strategy, which exchanged the original ligand with a ligand with strong binding effect. In addition, the influence of external stimulation on the perovskite crystal is also reduced by encapsulating the quantum dots with a polymer or inorganic oxide layer. These strategies enhance the stability of the perovskite to some extent, and extend the shelf life of the perovskite to about one month. In addition, most of the synthesis of perovskite needs to be carried out at high temperature (160-220 DEG C), and a large amount of anti-solvent is needed in the process of purifying quantum dots. The present application simplifies the steps and conditions of synthesis, and prepares high-stability CsPbX3 (X=Br, I) quantum dots by a double passivation strategy, which can extend the shelf life of the dispersed state to three months, and is expected to promote its practical application. SUMMARY

[0005] In order to obtain perovskite quantum dots with excellent light emitting performance and stability, the present application discloses a preparation method of high-stability CsPbX3 (X=Br, I) quantum dots based on a double passivation strategy, which solves the problems existing in the prior art and preliminarily explores the application prospect of CsPbX3 (X=Br, I) quantum dots in the field of light emission and backlight display.

[0006] The present application adopts the following technical scheme:

[0007] The preparation method of high-stability CsPbX3 quantum dots based on a double passivation strategy comprises the following steps:

[0008] 1) Preparation of cesium precursor solution: mix cesium source, organic acid and high-boiling solvent, stir at 90-200 DEG C under inert gas atmosphere for 0.5-2h, until the solution is clear and transparent without solid precipitation, to obtain the cesium precursor solution;

[0009] 2) Preparation of lead precursor solution: mix lead source, halogen supplement, organic acid and organic ligand with non-coordination solvent, stir at 70-80 DEG C under inert atmosphere for 0.5-2h, then heat to 80-110 DEG C, and obtain a light yellow lead precursor solution after the solution is clear and transparent;

[0010] 3) Preparation of CsPbX3 (X=Br, I) quantum dots: inject the cesium precursor solution into the lead precursor solution, react under inert gas atmosphere and at 80-110 DEG C for 5-300s, then ice bath cooling, to obtain CsPbX3 (X=Br, I) dispersion;

[0011] 4) Purification of CsPbX3(X = Br, I): The reaction solution of CsPbX3(X = Br, I) is centrifuged at a speed of 1500-3000 rpm for 1-5 min, and the suspension is taken. After mixing with 2-4 times the volume of anti-solvent, the solution is centrifuged at a speed of 7000-10000 rpm for 1-5 min. The precipitate is reserved and dispersed in a non-polar solvent, and then 2-4 times the volume of anti-solvent is added. The process is repeated several times. The precipitate is dispersed in a certain amount of non-polar solvent and stored in a refrigerator.

[0012] Further, the cesium source in the cesium precursor solution in step 1) is selected from one of cesium stearate, cesium oxide, cesium nitrate, cesium acetate, and cesium carbonate, preferably cesium carbonate; the organic acid is one of acetic acid, oleic acid, and dodecanedioic acid, preferably oleic acid; the high-boiling-point solvent is one or a mixture of solvents selected from octadecane, octadecene, and dodecane, preferably octadecene; the molar ratio of the cesium source to the organic acid is 1:3-1:25; and the mass fraction of the cesium source and the organic acid in the high-boiling-point solvent is 8%-200%.

[0013] Further, the lead source in step 2) is selected from one or more of lead bromide and lead iodide, and the corresponding halide lead is selected according to the required luminescent color of the quantum dots; the organic acid is one or more of acetic acid, octanoic acid, oxalic acid, oleic acid, stearic acid, lauric acid, octyl phosphonic acid, tri-n-octyl phosphine, trioctylphosphine oxide, and the like, and the optimal solution is a mixture of octyl phosphonic acid and oleic acid; the organic ligand is one or more of dihexylamine, dodecylamine, decylamine, dioctylamine, ethylenediaminetetraacetic acid, tri-n-octyl phosphine, trioctylphosphine oxide, sodium dodecylbenzenesulfonate, and silane reagents, and the optimal solution is silane reagents; the non-coordinating solvent is one or a mixture of solvents selected from octadecene, octane, xylene, and toluene, and the optimal solution is toluene; the inert gas is nitrogen or argon; the bromide ion supplement is one or more of hydrobromic acid, sodium bromide, zinc bromide, bromine, 9-octadecenyl ammonium bromide, ammonium bromide, dodecane, and pyridine bromide, and the optimal solution is hydrogen bromide; and the iodide ion supplement is one or more of octyl ammonium iodide, dodecyl ammonium iodide, iodine, hydroiodic acid, and tetradecyl iodide, and the optimal solution is hydroiodic acid.

[0014] Further, in step 3), the volume ratio of the cesium precursor solution to the lead precursor solution is 1:8-1:12, and the optimal volume ratio is 1:10.

[0015] Further, in step 4), the anti-solvent is one or more of ethyl acetate, ethyl formate, methyl acetate, acetone, and isopropyl alcohol, and the optimal solution is methyl acetate; the volume ratio of the anti-solvent to the quantum dot dispersion is 2:1-4:1; and the non-polar solvent is one or more of toluene, xylene, n-hexane, petroleum ether, and octane, and the optimal solution is toluene.

[0016] The application of high-stability CsPbX3 quantum dots prepared by the method as described above, characterized in that: the CsPbX3 (X = Br, I) quantum dot dispersion liquid is used for preparing a wide color gamut backlight device, and the preparation steps are as follows:

[0017] 1) Preparation of light conversion film: a small amount of CsPbX3 (X = Br, I) quantum dot dispersion liquid is mixed with a polymer solution with a concentration of 0.2 g / mL, the mixed solution is coated on a glass substrate, and then placed in a vacuum drying box until the solvent is completely volatilized, and then the quantum dot composite film is taken off to obtain a light conversion film;

[0018] 2) Preparation of wide color gamut backlight device: green and red light conversion films are assembled on the surface of a commercial GaN LED chip respectively to obtain a series of LED blue source color forming devices with different light emitting colors; the green and red light conversion films are assembled on the surface of a commercial GaN LED chip to obtain a white light LED wide color gamut backlight.

[0019] Further, the polymer in step 1) is one or more of polymethyl methacrylate, polyvinyl alcohol, polyvinyl butyral, polystyrene, epoxy resin, etc.

[0020] Further, the maximum emission wavelength of the commercial blue light GaN LED chip in step 2) is 450 nm.

[0021] Compared with the prior art, the present application has the following beneficial effects:

[0022] 1) The present application uses toluene as a non-coordinating solvent, which reduces the synthesis temperature and required time of lead precursor solution and CsPbX3 (X = Br, I) quantum dots compared with traditional synthesis temperature (160-200°C), thereby reducing the energy consumption of the preparation process; the reaction solvent can be concentrated by rotary evaporation, which greatly reduces the use of anti-solvent and improves the purification yield of quantum dots;

[0023] 2) During the synthesis process, the halogen supplement provides a halogen-rich environment for crystal growth, which promotes the growth of complete [PbX6] octahedral structure on the crystal surface, reduces the density of halogen vacancy defects, and is beneficial to the improvement of optical properties; 4-

[0024] 3) The double passivation strategy greatly improves the stability of CsPbX3 (X = Br, I) quantum dots (with cesium lead iodide quantum dots as the best): under the double passivation of strong binding ligand and inorganic encapsulating layer, high-stability CsPbX3 (X = Br, I) quantum dots are prepared, which effectively avoids the decrease of optical properties and stability caused by ligand shedding during subsequent purification or storage process; the introduction of ligands containing strong electron-withdrawing groups during the preparation process avoids subsequent ligand exchange process and simplifies the experimental process;​

[0025] 4) The application explores the application of CsPbX3(X = Br, I) quantum dots in the field of blue source color backlight display. The CsPbX3(X = Br, I) quantum dots are compounded with a polymer matrix to prepare a perovskite light conversion film, and the performance of the light conversion film is improved. A commercial GaN LED chip is used as background blue light, and red and green primary colors are obtained through the light conversion film, and together with the background blue light, a wide color gamut white light LED backlight device is formed. It provides new technical guidance for realizing flat panel colorization technology. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 (A) is a transmission electron microscope morphology diagram and particle size distribution histogram (inset) of the initial CsPbI3 perovskite quantum dots prepared in Example 1; Figure 1 (B) is a transmission electron microscope morphology diagram and particle size distribution histogram of the initial CsPbI3 perovskite quantum dots prepared in Example 2; Figure 1 (C) is a transmission electron microscope morphology diagram and particle size distribution histogram of the initial CsPbI3 perovskite quantum dots prepared in Comparative Example 1; Figure 1 It is illustrated that the average particle sizes of the CsPbI3 perovskite quantum dots prepared by the three synthesis methods are 10.7 ± 2.1 nm, 9.5 ± 3.5 nm and 11.8 ± 0.9 nm, respectively.

[0027] Figure 2 The fluorescence emission spectrum and excitation spectrum (excitation wavelength is 450 nm) of the initial CsPbI3 perovskite quantum dots prepared in Example 1. Figure 2 It is illustrated that the strongest emission peak of the prepared initial CsPbI3 perovskite quantum dots is located at 652 nm, which is red fluorescence.

[0028] Figure 3 (A) is a fluorescence intensity-time change diagram of the CsPbI3 perovskite quantum dot dispersion liquid prepared in Example 1 when placed at room temperature, Figure 3 (B) is a fluorescence intensity-time change diagram of the CsPbI3 perovskite quantum dot dispersion liquid prepared in Example 2 when placed at room temperature, Figure 3 (C) is a fluorescence intensity-time change diagram of the CsPbI3 perovskite quantum dot dispersion liquid prepared in Comparative Example 1 when placed at room temperature; Figure 3 (A) illustrates that the CsPbI3 perovskite quantum dot dispersion liquid prepared in Example 1 still maintains a luminous intensity of 85.3% of the original after being placed at room temperature for 3 months, which proves its excellent storage stability; Figure 3 (B) illustrates that the CsPbI3 perovskite quantum dot dispersion liquid prepared in Example 2 is quenched after being placed at room temperature for 1 month; Figure 3(C) shows that the CsPbI3perovskite quantum dots dispersion prepared in Comparative Example 1 is quenched after 7 days at room temperature; in summary, the double passivation strategy greatly improves the stability of CsPbI3perovskite quantum dots in solution.

[0029] Figure 4 (A) is the X-ray diffraction pattern of the CsPbI3perovskite quantum dot powder prepared in Example 1 at different time periods when stored at room temperature, Figure 4 (B) is the X-ray diffraction pattern of the CsPbI3perovskite quantum dot powder prepared in Example 2 at different time periods when stored at room temperature, Figure 4 (C) is the X-ray diffraction pattern of the CsPbI3perovskite quantum dot powder prepared in Comparative Example 1 at different time periods when stored at room temperature; compared with Figure 4 (B, C), Figure 4 (A) shows that the CsPbI3perovskite quantum dot powder prepared in Example 1 still maintains the original cubic phase structure after being exposed to the atmosphere for 3 months, and its crystal structure stability is significantly improved compared with Comparative Example 1.

[0030] Figure 5 (A) is the fluorescence spectrum of the CsPbI3perovskite quantum dots prepared in Example 4 under 450 nm blue light irradiation as a function of irradiation time; Figure 5 (B) is the fluorescence spectrum of the CsPbI3perovskite quantum dots prepared in Example 1 under 450 nm blue light irradiation as a function of irradiation time; Figure 5 (B) shows that the CsPbI3perovskite quantum dots prepared using the double passivation strategy have higher blue light stability under continuous 6 h blue light irradiation.

[0031] Figure 6 (A-C) are the emission spectra of the red LED, green LED and commercial GaN LED chip prepared in Example 1 (the inset is the picture of the LED device); Figure 6 (D) is the color gamut and color coordinates of the white light emitting LED backlight device prepared by integrating the red conversion film, green conversion film and commercial GaN LED chip; Figure 6 (A-C) shows that the emission centers of the red LED, green LED backlight device and commercial GaN LED chip prepared in Example 1 are located at 652 nm, 520 nm and 450 nm, respectively; Figure 6 (D) shows that the color coordinates of the prepared series of blue source color backlight devices are located at (0.33, 0.31) and can achieve a NTSC color gamut coverage of 120.01%. DETAILED DESCRIPTION

[0032] The following examples are provided to illustrate specific embodiments of the application and are not intended to limit the scope of the application. Each example is provided as a separate embodiment and particular features described as part of one example can be used in other examples to produce yet further embodiments. Modifications and alterations can occur to one of ordinary skill in the art without departing from the scope or spirit of the application. For example, the subject matter described with respect to one embodiment can be used in another embodiment to produce a further embodiment.

[0033] The application is further explained with respect to the following specific examples.

[0034] Example 1

[0035] 1) 2.5 mmol of Cs2CO3 was added to a three-necked flask with 30 mL of a mixed solution of oleic acid and octadecene, argon was bubbled, and after stirring at 120°C for 30 min, the temperature was raised to 150°C until the solution was clear and transparent without precipitated particles, obtaining a cesium precursor solution;

[0036] 2) 1 mmol of lead iodide and 1 mmol of hydroiodic acid were added to 25 mL of toluene, vacuum degassing was performed for 0.5 h, argon was pumped in, and an appropriate amount of octyl phosphonic acid, oleic acid, and a small amount of amino silane coupling agent were added; the temperature was raised to 100°C, and stirring was performed until the system was clear without precipitation, obtaining a lead-iodine precursor solution;

[0037] 3) 3 mL of the cesium precursor solution was injected into the lead-iodine precursor solution, and the reaction was performed for 15 s, obtaining initial CsPbI3 quantum dots with uniform size and an average particle size of 10.7 ± 2.1 nm (as shown in FIG. 1(a)); the CsPbI3 quantum dot stock solution was centrifuged at a speed of 1500 rpm for 1 min to take the upper suspension, the stock solution was concentrated by rotary evaporation, 3 times the volume of methyl acetate was added, and centrifugation was performed at a speed of 9000 rpm for 3 min; the precipitate was dispersed in toluene, and the purification process was repeated 2-3 times, and the final centrifugation obtained precipitate was dispersed in toluene and stored in a refrigerator; Figure 1

[0038] 4) 1 mmol of lead bromide and 1 mmol of hydrobromic acid were added to 25 mL of toluene, vacuum degassing was performed for 0.5 h at room temperature, argon was pumped in, and an appropriate amount of octyl phosphonic acid and oleic acid and a small amount of amino silane coupling agent were added; the temperature was raised to 110°C, and stirring was performed until the system was clear without precipitation, obtaining a lead-bromine precursor solution;

[0039] ​5) Inject 3 mL of the cesium precursor solution into the lead-bromide precursor solution, and react for 10 s to obtain the initial CsPbBr3 quantum dots; centrifuge the CsPbBr3 quantum dot stock solution at a speed of 1500 rpm for 1 min to take the upper suspension, and then add 3 times the volume of methyl acetate to the concentrated stock solution after rotary evaporation, and centrifuge at a speed of 9000 rpm for 3 min; disperse the precipitate in toluene, repeat the purification process 2-3 times, and store the precipitate obtained after the final centrifugation in toluene in a refrigerator;

[0040] 6) Mix an appropriate amount of the CsPbBr3 quantum dot dispersion with 2 mL of the polymer / toluene solution (0.2 g / mL); take a small amount of the mixed solution and coat it on a clean substrate, and place it in a vacuum drying box until the solvent is completely volatilized. Remove the polymer layer from the substrate to obtain a green light conversion film;

[0041] 7) Mix an appropriate amount of the CsPbI3 quantum dot dispersion with 2 mL of the polymer / toluene solution (0.2 g / mL); take a small amount of the mixed solution and coat it on a clean substrate, and place it in a vacuum drying box until the solvent is completely volatilized. Remove the polymer layer from the substrate to obtain a red light conversion film;

[0042] 8) Assemble the green light conversion film on a commercial GaN LED chip to obtain a green light LED; assemble the red light conversion film on a commercial GaN LED chip to obtain a red light LED; assemble the red light conversion film and the green light conversion film on a commercial GaN LED chip to obtain a white light LED.

[0043] Example 2

[0044] 1) Add 2.5 mmol of Cs2CO3 and 30 mL of a mixed solution of oleic acid and octadecene to a three-necked flask, introduce argon, and stir at 120°C for 30 min, and then increase the temperature to 150°C until the solution is clear and transparent without precipitated particles to obtain a cesium precursor solution;

[0045] 2) Add 1 mmol of lead iodide and 1 mmol of hydroiodic acid to 25 mL of toluene, vacuum degas for 0.5 h, pump in argon, and add an appropriate amount of octyl phosphonic acid and oleylamine; increase the temperature to 100°C and stir until the system is clear without precipitates to obtain a lead-iodine precursor solution;

[0046] 3) Inject 3 mL of the cesium precursor solution into the lead-iodine precursor solution, and react for 15 s to obtain the initial CsPbI3 quantum dots (as shown in FIG. 1A); Figure 1(b) as shown); centrifuging the CsPbI3 quantum dot stock solution at a rotation speed of 1500 rpm for 1 min to take the upper suspension, adding 3 times the volume of methyl acetate to the concentrated stock solution by rotary evaporation, and centrifuging at a rotation speed of 9000 rpm for 3 min; dispersing the precipitate in toluene, repeating the purification process 2-3 times, and storing the precipitate obtained by the final centrifugation in toluene in a refrigerator;

[0047] 4) Adding 1 mmol of lead bromide and 1 mmol of hydrobromic acid to 25 mL of toluene, vacuum degassing for 0.5 h at room temperature, pumping in argon, adding an appropriate amount of octyl phosphonic acid and oleylamine, increasing the temperature to 110°C, and stirring until the system is clear and free of precipitate to obtain a lead-bromine precursor solution;

[0048] 5) Adding 3 mL of the cesium precursor solution to the lead-bromine precursor solution, and reacting for 10 s to obtain initial CsPbBr3 quantum dots; centrifuging the CsPbBr3 quantum dot stock solution at a rotation speed of 1500 rpm for 1 min to take the upper suspension, adding 3 times the volume of methyl acetate to the concentrated stock solution by rotary evaporation, and centrifuging at a rotation speed of 9000 rpm for 3 min; dispersing the precipitate in toluene, repeating the purification process 2-3 times, and storing the precipitate obtained by the final centrifugation in toluene in a refrigerator;

[0049] 6) Mixing an appropriate amount of the CsPbBr3 quantum dot dispersion with 2 mL of a polymer / toluene solution (0.2 g / mL); coating a small amount of the mixed solution on a clean substrate, and placing it in a vacuum drying oven until the solvent is completely volatilized. Removing the polymer layer from the substrate to obtain a green light conversion film;

[0050] 7) Mixing an appropriate amount of the CsPbI3 quantum dot dispersion with 2 mL of a polymer / toluene solution (0.2 g / mL); coating a small amount of the mixed solution on a clean substrate, and placing it in a vacuum drying oven until the solvent is completely volatilized. Removing the polymer layer from the substrate to obtain a red light conversion film;

[0051] 8) Assembling the green light conversion film on a commercial GaN LED chip to obtain a green light LED; assembling the red light conversion film on a commercial GaN LED chip to obtain a red light LED; and assembling the red light conversion film and the green light conversion film together on a commercial GaN LED chip to obtain a white light LED.

[0052] Example 3

[0053] 1) Adding 1.8 mmol of CsAc and 3.6 mmol of oleic acid to 15 mL of octadecene, vacuum heating for 30 min, pumping in argon, increasing the temperature to 150°C, and stirring until the solution is clear and transparent to obtain a cesium oleate solution;

[0054] 2) 0.75 mmol of lead bromide was added to 20 mL of ODE, and after vacuum degassing for 0.5 h, argon was pumped in, and the temperature was raised to 110°C, and then 2.0 mL of oleic acid and 2.0 mL of oleylamine were added, respectively, and the solution was stirred until it was clear and transparent, to obtain a lead-bromine precursor solution;

[0055] 3) 2 mL of cesium oleate was injected into the lead-bromine precursor solution, and the reaction was carried out at 110°C for 5 s to obtain initial CsPbBr3 quantum dots; the CsPbBr3 quantum dot stock solution was centrifuged at a speed of 2000 rpm for 2 min to take the upper suspension, and then three times the volume of methyl acetate was added and mixed well, and then centrifuged at a speed of 9500 rpm for 5 min, and the precipitate was dispersed in n-hexane, and an appropriate amount of methyl acetate was added, and the purification process was repeated 2-3 times; finally, the precipitate was dispersed in n-hexane and stored in a refrigerator;

[0056] Example 4

[0057] 1) 1.8 mmol of CsAc and 3.6 mmol of oleic acid were added to 15 mL of octadecene, and after vacuum heating for 30 min, argon was introduced, and the temperature was raised to 150°C, and the solution was stirred until it was clear and transparent, to obtain a cesium oleate solution;

[0058] 2) 0.75 mmol of lead iodide and 0.30 mmol of iodine were added to 20 mL of dodecane, and a mixed solution of oleic acid and sodium dodecylbenzenesulfonate and 2 mL of oleylamine were added, and after vacuum degassing for 0.5 h, nitrogen was pumped in, and the temperature was raised to 110°C, and the solution was stirred until it was clear and free of precipitate, to obtain a lead-iodine precursor solution;

[0059] 3) 2 mL of cesium oleate was injected into the lead-iodine precursor solution, and the reaction was carried out at 110°C for 10 s to obtain initial CsPbI3 quantum dots; the CsPbI3 quantum dot stock solution was centrifuged at a speed of 2000 rpm for 2 min to take the upper suspension, and then three times the volume of methyl acetate was added and mixed well, and then centrifuged at a speed of 9500 rpm for 5 min, and the precipitate was dispersed in n-hexane, and an appropriate amount of methyl acetate was added, and the purification process was repeated 2-3 times; finally, the precipitate was dispersed in n-hexane and stored in a refrigerator.

[0060] Comparative Example 1

[0061] 1) 2.5 mmol of Cs2CO3 and 50 mL of oleic acid were added to a three-necked flask, argon was introduced, and after stirring at 120°C for 30 min, the temperature was raised to 150°C until the solution was clear and transparent and free of precipitate particles, to obtain a cesium precursor solution;

[0062] 2) 1 mmol of lead iodide and 0.5 mmol of elemental iodine were added to 25 mL of toluene, vacuum degassed for 0.5 h, then pumped with argon, and then an appropriate amount of oleic acid and oleylamine was added; the temperature was raised to 100°C and stirred until the system was clear and no precipitate was formed, obtaining a lead-iodine precursor solution;

[0063] 3) 3 mL of cesium precursor solution was injected into the lead-iodine precursor solution, and the reaction was carried out for 15 s, obtaining the initial CsPbI3 quantum dots (as shown in FIG. 1C); Figure 1 (c); the CsPbI3 quantum dot stock solution was centrifuged at a speed of 1500 rpm for 1 min to take the upper suspension, and then 3 times the volume of methyl acetate was added to the concentrated stock solution by rotary evaporation, and centrifuged at a speed of 9000 rpm for 3 min; the precipitate was dispersed in toluene, and the purification process was repeated 2-3 times, and the final precipitate obtained by centrifugation was dispersed in toluene and stored in a refrigerator.

Claims

1. A method for preparing high-stability CsPbX3 quantum dots based on a double-passivation strategy, characterized in that, The method comprises the following steps: 1) Preparation of cesium precursor solution: mix cesium source with organic acid and high-boiling-point solvent, stir at 90-200℃ under inert gas atmosphere for 0.5-2h until the solution is clear and transparent without solid precipitate, to obtain the cesium precursor solution; the organic acid is one of acetic acid, oleic acid and dodecanedioic acid; the high-boiling-point solvent is one or more mixed solvents selected from octadecane, octadecene and dodecane; the molar ratio of cesium source to organic acid is 1:3-1:25; the mass fraction of cesium source and organic acid in the high-boiling-point solvent is 8%-200%; 2) Preparation of lead precursor solution: mix lead source, halogen supplement, octyl phosphonic acid and amino silane coupling agent with toluene, stir at 70-80℃ under inert atmosphere, then heat to 80-110℃, and obtain light yellow lead precursor solution after the solution is clear and transparent; the halogen supplement, wherein the bromide supplement is one or more selected from hydrobromic acid, sodium bromide, zinc bromide, bromine, 9-octadecenyl ammonium bromide, ammonium bromide, dodecane and pyridine; the iodide supplement is one or more selected from octyl ammonium iodide, dodecyl ammonium iodide, iodine, hydroiodic acid and tetradecyl iodide; 3) Preparation of CsPbX3(X=Br, I) quantum dots: inject the cesium precursor solution into the lead precursor solution, react under inert gas atmosphere and at 80-110℃ for 5-300s, then cool in ice bath, to obtain CsPbX3(X=Br, I) dispersion; the volume ratio of cesium precursor solution to lead halide precursor solution is 1:8-1:12; 4) Purification of CsPbX3(X=Br, I): centrifuge the CsPbX3(X=Br, I) dispersion at 1500-3000rpm for 1-5min, take the suspension, mix with 2-4 times volume of antisolvent, then centrifuge at 7000-10000rpm for 1-5min, reserve the precipitate and disperse in nonpolar solvent, then add 2-4 times volume of antisolvent and repeat the centrifugation process for several times, disperse the precipitate in a certain amount of nonpolar solvent, and store in refrigerator; In step 2), the molar ratio of lead source to halogen supplement is 2:1; the mass concentration of lead source in the mixed solution of octyl phosphonic acid and amino silane coupling agent is 0.5%-6.0%; the mass fraction of octyl phosphonic acid and amino silane coupling agent in toluene is 5%-10%; the mass of octyl phosphonic acid and amino silane coupling agent is 0.02-0.

05.

2. The method for preparing high stability CsPbX3 quantum dots based on a dual passivation strategy according to claim 1, characterized in that: In step 1), the cesium source in the cesium precursor solution is selected from one of cesium stearate, cesium oxide, cesium nitrate, cesium acetate and cesium carbonate.

3. The method for preparing high stability CsPbX3 quantum dots based on dual passivation strategy according to claim 1, characterized in that: In step 2), the lead source is selected from one or more of lead chloride, lead bromide and lead iodide.

4. The method for preparing high stability CsPbX3 quantum dots based on dual passivation strategy according to claim 1, characterized in that: The anti-solvent in step 4) is one or more of ethyl acetate, ethyl formate, methyl acetate, acetone, isopropyl alcohol; the non-polar solvent is one or more of toluene, xylene, n-hexane, petroleum ether, octane; the concentration of the dispersion liquid obtained by dispersing the precipitate in a certain amount of non-polar solvent is 5-50 mg / mL, the particle size of the quantum dots contained is 7-30 nm, and the fluorescence peak is in the range of 500-750 nm.

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