Aluminum ion surface passivated cesium lead perovskite quantum dots, and preparation method and application thereof

Abstract

The present application relates to a kind of aluminum ion surface passivated cesium lead perovskite quantum dots and its preparation method and application.The method comprises the following steps: synthesis a kind of by independent chlorine source preparation cesium lead perovskite quantum dots;Synthesis a kind of aluminum-containing organic compound solution;The perovskite quantum dots are mixed with aluminum-containing organic compound, and make aluminum ion passivated perovskite quantum dots surface, and aluminum ion surface passivated cesium lead perovskite quantum dots are prepared.The cesium lead quantum dots obtained by the preparation method provided by the present application have high luminescence quantum yield and high luminescence stability.In addition, the method used is simple and easy to operate, has low preparation cost and good universality.

Description

Technical Field

[0001] The present invention belongs to the technical field of luminescent material preparation, and relates to a cesium lead chloride perovskite quantum dot with aluminum ion surface passivation, a preparation method and application thereof, and is a blue light perovskite quantum dot with high quantum yield. Background Art

[0002] Cesium lead chloride perovskite quantum dots (CPCDs) possess a variety of excellent physical and chemical properties, such as a direct band gap, high luminescence color purity, large light absorption coefficient, high carrier mobility, high defect tolerance, and ease of synthesis. Therefore, CPCDs hold great potential for application in optoelectronic devices.

[0003] Currently, hot injection is the typical method for preparing perovskite quantum dots. This method is easy to control, requires simple equipment, and produces products of high purity and good dispersibility. However, the cesium lead chloride perovskite quantum dots synthesized by this method deviate from the surface stoichiometry and exhibit a high number of defects. Furthermore, the quantum dots have weak binding to their surface organic ligands, which can easily cause ligand shedding. As a result, the blue luminescence efficiency of cesium lead chloride perovskite quantum dots is low, with fluorescence quantum efficiencies generally less than 30%. Furthermore, their poor chemical stability makes it impossible to guarantee the reliability of perovskite quantum dot optoelectronic devices. In summary, existing preparation technologies need to be improved, particularly in terms of effective methods for passivating surface defects in quantum dots. Summary of the Invention

[0004] The first purpose of the present invention is to address the above-mentioned shortcomings and propose a method for preparing cesium lead chloride perovskite quantum dots with aluminum ion surface passivation, aiming to solve the problems of low luminous efficiency and poor stability of cesium lead chloride perovskite quantum dot blue light materials.

[0005] The technical solutions of the present invention are as follows:

[0006] A method for preparing cesium lead chloride perovskite quantum dots with aluminum ion surface passivation, comprising the steps of:

[0007] Step (1): 1-octadecene, oleic acid, oleylamine, cesium acetate, and lead acetate are mixed, heated and stirred at 100° C. to 200° C. under an inert atmosphere until the solution becomes clear, then heated to 180° C. to 240° C., and then a chlorine source is injected, followed by cooling to room temperature within 20 seconds to obtain a crude solution of cesium lead chloride perovskite quantum dots; the crude solution is centrifuged and washed to obtain a cesium lead chloride perovskite quantum dot solution;

[0008] Step (2): adding an aluminum compound to oleylamine and heating to obtain a translucent solution; adding acetone to the translucent solution and centrifuging to obtain a precipitate; dissolving the precipitate in n-hexane and centrifuging again to obtain a precipitate; and finally dissolving the precipitate in n-hexane to obtain an oleylamine aluminum solution;

[0009] Step (3): adding the oleylamine aluminum solution in step (2) to the cesium lead chloride perovskite quantum dot solution in step (1), stirring and mixing, standing at room temperature for a certain period of time, centrifuging and taking the supernatant to obtain aluminum ion enhanced cesium lead chloride perovskite quantum dots.

[0010] Furthermore, in the step (1), the centrifugal washing step is to centrifuge the crude solution at 10,000 rpm for 5 minutes, take the precipitate and dissolve it with n-hexane; centrifuge the solution again at 2,000 rpm for 5 minutes to take the supernatant, add the cleaning reagent; finally, centrifuge the solution at 10,000 rpm to take the precipitate, and dissolve the precipitate with n-hexane to obtain a cesium chloride lead perovskite quantum dot solution.

[0011] Furthermore, the chlorine source in step (1) is one or more of trimethylsilyl chloride, benzoyl chloride, and dichloromethane.

[0012] Furthermore, the cleaning reagent in step (1) is one or more of ethyl acetate, methyl acetate, acetone, methanol, and acetonitrile.

[0013] Furthermore, the aluminide in step (2) is one or more of aluminum chloride, aluminum acetate, aluminum hydroxide, and hydrated aluminum nitrate.

[0014] Furthermore, the room temperature in step (3) is 20° C. to 36° C., and the standing time is 1 hour to 24 hours.

[0015] Furthermore, the molar ratio of the cesium lead chloride perovskite quantum dots to the aluminum element is 1:0.1 to 1:2.

[0016] The second object of the present invention is to provide cesium lead chloride perovskite quantum dots with aluminum ion surface passivation.

[0017] The third object of the present invention is to provide an application of cesium lead chloride perovskite quantum dots with aluminum ion surface passivation in light-emitting display or photoelectric detection.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention provides a method for preparing cesium lead chloride perovskite quantum dots with aluminum ion surface passivation, and the cesium lead chloride perovskite quantum dots prepared based on the hot injection method are passivated on their surface using aluminum ions under normal atmospheric temperature. Compared with the in-situ doping method during the hot injection process (partially replacing the lead ions in nanocrystalline quantum dots with cations), the method provided by the present invention modifies the quantum dots by ionic bonding between aluminum ions and the quantum dot surface, so that the aluminum ions are effectively enriched on the surface, thereby obtaining a better surface defect passivation effect. The quantum dot material prepared by this method has high fluorescence quantum efficiency, good stability, high purity of luminescent color, and the luminescent wavelength and half-peak width are basically the same as those of untreated cesium lead chloride perovskite quantum dots. Further, the preparation method of cesium lead chloride perovskite quantum dots provided by the present invention is simple, low cost and has good versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a comparison diagram of the absorption spectra of the aluminum ion surface-passivated cesium lead chloride perovskite quantum dots described in the present invention and ordinary cesium lead chloride perovskite quantum dots.

[0021] Figure 2 This is a comparison chart of the emission spectra of the aluminum ion surface-passivated cesium lead chloride perovskite quantum dots described in the present invention and ordinary cesium lead chloride perovskite quantum dots.

[0022] Figure 3 This is a comparison chart of the emission spectra of the aluminum-doped cesium lead chloride perovskite quantum dots described in the present invention, ordinary cesium lead chloride perovskite quantum dots, and cesium lead chloride perovskite quantum dots with aluminum ion surface passivation. DETAILED DESCRIPTION

[0023] The present invention provides a method for preparing cesium lead chloride perovskite quantum dots with aluminum ion surface passivation. To make the objectives, technical solutions, and effects of the present invention more clear and explicit, the present invention is further described below. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0024] The present invention provides a method for preparing a cesium lead chloride perovskite quantum dot material with aluminum ion surface passivation, which specifically comprises the steps of:

[0025] Step (1) 1-octadecene, oleic acid, oleylamine, cesium acetate, and lead acetate are mixed, heated and stirred at 100°C to 200°C under an inert atmosphere until the solution becomes clear, then heated to 180°C to 240°C, and a chlorine source is injected. The mixture is then cooled to room temperature within 20 seconds to obtain a crude quantum dot solution. The crude solution is centrifuged and washed to obtain a cesium lead chloride perovskite quantum dot solution.

[0026] Step (2) Weigh the aluminum compound and add it to oleylamine. Heat the mixture to obtain a translucent solution. Add acetone to the translucent solution and centrifuge to obtain a precipitate. Dissolve the precipitate in n-hexane and centrifuge again to obtain a precipitate. Dissolve the precipitate in n-hexane again to obtain an oleylamine aluminum solution.

[0027] Step (3) adding the oleylamine aluminum solution described in step (2) to the cesium lead chloride perovskite quantum dot solution described in step (1), stirring and mixing, standing at room temperature for a certain period of time, centrifuging at 2000 rpm for 5 minutes, and taking the supernatant to obtain aluminum ion enhanced cesium lead chloride perovskite quantum dots.

[0028] Furthermore, in the step (1), the molar ratio of lead acetate and cesium acetate as reactants is 1:1 to 1:2, preferably 1:1.4.

[0029] Furthermore, the chlorine source in step (1) is one or more of an excess of trimethylchlorosilane, benzoyl chloride, and dichloromethane, and the preferred chlorine source is trimethylchlorosilane.

[0030] Furthermore, the cleaning reagent used in step (1) is one or more of ethyl acetate, methyl acetate, acetone, methanol, and acetonitrile, and the preferred cleaning reagent is ethyl acetate.

[0031] Furthermore, the aluminide in step (2) is one or more of aluminum chloride, aluminum acetate, aluminum hydroxide, and hydrated aluminum nitrate, and the preferred aluminide is aluminum chloride.

[0032] Furthermore, the molar amount of the aluminum compound in step (2) is 10% to 200% of the molar amount of the quantum dot solution.

[0033] Furthermore, the room temperature in step (3) is 20° C. to 36° C., and the standing time is 1 hour to 24 hours.

[0034] Specifically, the present invention uses the preparation of aluminum ion-surface-passivated cesium lead chloride perovskite quantum dot materials as an example. First, lead acetate and cesium acetate are added to an anhydrous 1-octadecene solvent. Then, anhydrous oleylamine and oleic acid are added as surfactants. The solution is stirred and heated to 100-200°C until the lead acetate and cesium acetate are completely dissolved, resulting in a clear solution. The preferred heating temperature in the present invention is 120°C.

[0035] After the clarified solution is further heated to 180°C to 240°C, preferably to 240°C, an excess of trimethylsilyl chloride is injected. After the solution reacts for a predetermined time, it is cooled in an ice-water bath. Then, a precipitate of cesium lead chloride perovskite quantum dots is obtained by centrifugation at 10,000 rpm, and the precipitate is dispersed in n-hexane, and then centrifuged at 2,000 rpm to obtain a supernatant. Thereafter, the solution is further washed with ethyl acetate, and then centrifuged at 5,000 rpm to obtain a precipitate. The obtained precipitate is dispersed again in n-hexane, and centrifuged again at 2,000 rpm to obtain a supernatant to obtain a perovskite blue light quantum dot material prepared by the hot injection method - a cesium lead chloride perovskite quantum dot solution.

[0036] Then, aluminum chloride (0.5 mmol) and oleylamine (5-10 ml) are added to a 25 ml round-bottom three-necked flask and heated with stirring to 100°C to 200°C, preferably 120°C, for 1-4 hours. After cooling, 10-30 ml of acetone is added to the solution, which is then centrifuged at 5,000-10,000 rpm to remove the precipitate, which is then dissolved with n-hexane. The resulting solution is centrifuged at 5,000-10,000 rpm to remove the precipitate, which is then dissolved with 3-10 ml of n-hexane to obtain an oleylamine aluminum solution.

[0037] An appropriate amount of oleylamine aluminum solution is added to the cesium lead chloride perovskite quantum dot solution, and after standing for a period of time at room temperature, the solution is centrifuged at 2000 rpm, and the supernatant is collected to obtain aluminum ion enhanced cesium lead chloride perovskite quantum dots.

[0038] Furthermore, the aluminum ion surface-passivated cesium lead chloride perovskite quantum dots can be effectively excited by a light source with a wavelength in the range of 250nm to 410nm, generating narrow-band blue light with a luminescence range of 380nm to 450nm and a half-width of 20nm to 30nm, and a quantum yield of 40% to 70%.

[0039] Specifically, lead-halide perovskite quantum dot materials have a high defect tolerance, but reducing surface defects in quantum dots can significantly improve the material's performance and stability. A common approach is to dope non-halogen substituted ions to improve performance and stability, but these doped ions tend to enter lead sites, affecting the quantum dot's luminescence peak. This study, using an organic solvent containing aluminum compounds at room temperature to passivate the quantum dot surface, enhances the short-range order of the quantum dot lattice, and produces a blue fluorescent quantum dot material with high fluorescence quantum yield and stable performance.

[0040] The preparation method of the present invention is further explained below by taking the preparation of cesium lead chloride perovskite quantum dot material with aluminum ion surface passivation as an example:

[0041] Example 1

[0042] 1. Prepare perovskite quantum dots using the hot injection method: Add lead acetate (0.28 mmol), cesium acetate (0.2 mmol), 1 ml of oleic acid, 0.5 ml of oleylamine, and 5 ml of 1-octadecene to a 50 ml round-bottom three-necked flask. Stir and heat to 120°C for 1 hour, until the liquid in the flask becomes colorless and transparent. Then, raise the temperature to 220°C, inject 0.2 ml of trimethylsilyl chloride, and after 5 seconds, cool the three-necked flask in ice water to obtain a crude quantum dot solution. A nitrogen atmosphere was used throughout the preparation of the crude quantum dot solution. The obtained crude quantum dot solution was centrifuged at 10,000 rpm, and the precipitate was taken out, which was dissolved with n-hexane; the solution was then centrifuged at 2,000 rpm, and the supernatant was taken out. Ethyl acetate was added to the supernatant to precipitate the quantum dots in the supernatant; the solution containing the precipitate was then centrifuged at 10,000 rpm, and the precipitate was taken out. The precipitate was dissolved with 8 ml of n-hexane; the solution was centrifuged again at 2,000 rpm, and the supernatant was taken out to obtain the final cesium lead chloride perovskite quantum dot solution.

[0043] 2. Add aluminum chloride (0.5 mmol) and 5 ml of oleylamine to a 25 ml round-bottom three-necked flask, stir, and heat to 120°C for 2 hours. Use nitrogen throughout the process. After cooling, add 20 ml of acetone to the solution, centrifuge at 10,000 rpm, remove the precipitate, and dissolve it in n-hexane. Centrifuge the resulting solution at 10,000 rpm, remove the precipitate, and dissolve it in 5 ml of n-hexane to obtain an aluminum oleylamine solution.

[0044] 3. Take 50ul of oleylamine aluminum solution and add it to 1ml of cesium lead chloride perovskite quantum dot solution. Let it stand for 5 hours, then centrifuge it at 2000 rpm and take the supernatant to obtain cesium lead chloride perovskite blue light quantum dot material with aluminum ion surface passivation.

[0045] The absorption spectra of aluminum ion enhanced cesium lead chloride quantum dots and ordinary cesium lead chloride quantum dots were measured by UV-visible absorption spectrometer (such as Figure 1 The emission spectrum of quantum dots was measured by fluorescence spectrometer (as shown in Figure 2 As shown in Figure 2, the luminescence intensity of aluminum-enhanced cesium lead chloride quantum dots was significantly enhanced compared to conventional cesium lead chloride quantum dots, with a quantum yield of 72.4%. The present invention conducted stability tests on the prepared quantum dots. After one week, the luminescence intensity of the aluminum-enhanced cesium lead chloride quantum dots still maintained 54% of its initial intensity, while the intensity of conventional cesium lead chloride quantum dots dropped to 0% after one day. Therefore, aluminum-enhanced cesium lead chloride quantum dots exhibited better stability.

[0046] Example 2

[0047] 1. Preparation of perovskite quantum dots by hot injection: Lead acetate (0.28 mmol), cesium acetate (0.2 mmol), 1 ml of oleic acid, 0.5 ml of oleylamine, and 5 ml of 1-octadecene were added to a 50 ml round-bottom three-necked flask, heated to 120 ° C, and maintained for 1 hour until the liquid in the flask was colorless and transparent. The temperature was then raised to 240 ° C, with nitrogen protection throughout the process, and 0.2 ml of trimethylsilyl chloride was hot injected. After 5 seconds, an ice-water bath was placed to obtain a crude quantum dot solution. The crude solution was centrifuged at 10,000 rpm to obtain a precipitate, which was dissolved with n-hexane. The supernatant was centrifuged at 2,000 rpm to obtain a precipitate. The quantum dots in the supernatant were precipitated with ethyl acetate. The precipitate was centrifuged at 10,000 rpm to obtain a precipitate, which was dissolved with 10 ml of n-hexane. The supernatant was centrifuged again at 2,000 rpm to obtain a final cesium lead chloride perovskite quantum dot solution.

[0048] 2. Add aluminum chloride (0.5 mmol) and 8 ml of oleylamine to a 25 ml round-bottom three-necked flask, heat to 150 ° C, and maintain for 3 hours. The liquid in the flask is a colorless and transparent liquid. Nitrogen protection is used throughout the process. After cooling, add 30 ml of acetone, centrifuge at 10,000 rpm to obtain a precipitate, dissolve the precipitate with n-hexane, centrifuge at 10,000 rpm to obtain a precipitate, and finally dissolve the precipitate with 10 ml of n-hexane to obtain an oleylamine aluminum solution.

[0049] 3. Take 200ul of oleylamine aluminum solution and add it to 1ml of cesium lead chloride perovskite quantum dot solution. Let it stand for 10 hours and centrifuge at 2000 rpm to obtain the supernatant to obtain cesium lead chloride perovskite blue light quantum dot material with aluminum ion surface passivation.

[0050] Its absorption spectrum is similar to that in Example 1. Its emission spectrum is also similar to that in Example 1. Compared with ordinary cesium lead chloride quantum dots, aluminum ion surface-enhanced cesium lead chloride quantum dots have higher luminescence intensity and significantly improved stability.

[0051] Comparative Example 1: Preparation of aluminum-doped cesium lead chloride perovskite

[0052] Lead acetate (0.2mmol), cesium acetate (0.2mmol), aluminum acetate (0.08mmol), 1ml of oleic acid, 0.5ml of oleylamine, and 5ml of 1-octadecene were added to a 50ml round-bottom three-necked flask and heated to 120°C for 1h until the liquid in the flask was colorless and transparent. The temperature was then raised to 240°C, with nitrogen protection throughout, and 0.2ml of trimethylsilyl chloride was hot injected. After 5s, an ice-water bath was placed to obtain a crude quantum dot solution. The crude solution was centrifuged at 10,000 rpm to obtain a precipitate, which was dissolved in n-hexane. The supernatant was centrifuged at 2,000 rpm to obtain a supernatant. The quantum dots in the supernatant were precipitated with ethyl acetate. The precipitate was centrifuged at 10,000 rpm to obtain a precipitate, which was dissolved in 10ml of n-hexane. The supernatant was centrifuged again at 2,000 rpm to obtain the final aluminum-doped cesium lead chloride perovskite quantum dot solution.

[0053] Its absorption spectrum is similar to that in Example 1. Its emission spectrum is as follows Figure 3 As shown, the luminescence intensity of aluminum-doped cesium lead chloride quantum dots did not significantly increase compared to undoped cesium lead chloride quantum dots. Compared to cesium lead chloride quantum dots with aluminum ion surface passivation, their luminescence intensity was significantly reduced. Furthermore, their chemical stability was poor, with the luminescence intensity decaying to zero within 48 hours.

[0054] This shows that in the preparation method provided by the present invention, aluminum ions play a major role on the surface of cesium lead chloride quantum dots, effectively passivating their surface defects, thereby making the cesium lead chloride quantum dot material have luminescence characteristics with high quantum yield and strong stability. In addition, the preparation method is simple, easy to implement, low in cost, and has versatility.

[0055] The above embodiments are not limitations of the present invention, and the present invention is not limited to the above embodiments. As long as the requirements of the present invention are met, they belong to the protection scope of the present invention.

Claims

1. A method for preparing aluminum ion surface passivated cesium lead chloride perovskite quantum dots, characterized in that The following steps are involved: Step (1): 1-octadecene, oleic acid, oleylamine, cesium acetate, and lead acetate are mixed, heated and stirred at 100°C to 200°C under an inert atmosphere until the solution becomes clear, then heated to 180°C to 240°C and a chlorine source is injected, followed by cooling to room temperature within 20 seconds to obtain a crude solution of cesium lead chloride perovskite quantum dots; the crude solution is centrifuged and washed to obtain a cesium lead chloride perovskite quantum dot solution; Step (2): adding aluminum compound to oleylamine and heating to obtain a translucent solution; adding acetone to the translucent solution and centrifuging to obtain a precipitate; dissolving the precipitate in n-hexane and centrifuging again to obtain a precipitate; finally, dissolving the precipitate in n-hexane to obtain an oleylamine aluminum solution; Step (3): adding the oleylamine aluminum solution in step (2) to the cesium lead chloride perovskite quantum dot solution in step (1), stirring and mixing, standing at room temperature for a certain period of time, centrifuging and collecting the supernatant to obtain aluminum ion enhanced cesium lead chloride perovskite quantum dots.

2. The preparation method according to claim 1, wherein: In step (1), the centrifugal washing step is to centrifuge the crude solution at 10,000 rpm for 5 minutes, take the precipitate and dissolve it with n-hexane; centrifuge the solution again at 2,000 rpm for 5 minutes to take the supernatant, add the washing reagent; finally centrifuge the solution at 10,000 rpm to take the precipitate, and dissolve the precipitate with n-hexane to obtain a cesium chloride lead perovskite quantum dot solution.

3. The preparation method according to claim 1, wherein: The chlorine source in step (1) is one or more of trimethylsilyl chloride, benzoyl chloride, and dichloromethane.

4. The preparation method according to claim 1, wherein: The cleaning reagent used in step (1) is one or more of ethyl acetate, methyl acetate, acetone, methanol, and acetonitrile.

5. The preparation method according to claim 1, wherein: The aluminide in step (2) is one or more of aluminum chloride, aluminum acetate, aluminum hydroxide, and hydrated aluminum nitrate.

6. The preparation method according to claim 1, wherein: The room temperature in step (3) is 20°C~36°C.

7. The preparation method according to claim 1, wherein: The standing time in step (3) is 1 hour to 24 hours.

8. The preparation method according to claim 1, wherein: The molar ratio of cesium lead chloride perovskite quantum dots to aluminum element is 1:0.1~1:

2.

9. Aluminum ion enhanced cesium lead chloride perovskite quantum dots, prepared by the method according to any one of claims 1 to 8.

10. Application of the aluminum ion enhanced cesium lead chloride perovskite quantum dots as claimed in claim 9 in the field of light emitting display or photoelectric detection.

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