Preparation method of high-quality blue-light chiral perovskite quantum dots

Abstract

The invention provides a preparation method of high-quality blue-light chiral perovskite quantum dots, and belongs to the technical field of perovskite quantum dot preparation. According to the preparation method, specific chiral ligand molecules are selected to be bonded with dangling bonds of the blue light CsPbBr3 quantum dots, and the quantum dots can be induced to generate highly asymmetric spin polaritons while surface defects of the quantum dots are passivated. The blue light chiral perovskite quantum dot prepared by the invention has the photoluminescence quantum yield of 86%, and the luminescence asymmetry factor of 0.086, and provides a solution for the preparation of a high-performance blue light circular polarization light emitting diode.

Description

Technical Field

[0001] This invention belongs to the field of perovskite quantum dot technology, specifically relating to a method for preparing high-quality blue chiral perovskite quantum dots. Background Technology

[0002] In recent years, with the increasing demand for circularly polarized light in the information display industry, research on circularly polarized light-emitting diodes (LEDs) has gradually emerged. Circularly polarized light is an electromagnetic wave whose light vector rotates around its propagation direction and whose final trajectory is a circle perpendicular to the propagation direction. Compared with linearly polarized light, circularly polarized light has higher anti-scattering ability and stronger penetrating power. Although circularly polarized light can also be generated by continuously passing natural light through a linear polarizer and a quarter-wave plate, the complex optical components limit its application in small spaces. Circularly polarized LEDs avoid complex optical components and can directly emit circularly polarized light. These characteristics give them enormous development potential and application value in the field of 3D displays.

[0003] Chirality refers to the asymmetry of a molecule or crystal. Chiral perovskites, due to their asymmetry, exhibit unique optical properties, enabling circularly polarized light emission, and are often used in the fabrication of circularly polarized light-emitting diodes (LEDs). Currently, there are two main methods for preparing chiral perovskites. The first method involves directly replacing the A-sites in the perovskite lattice with chiral organic cations, thereby producing a non-centrosymmetric chiral crystal structure. However, this method easily induces perovskite lattice distortion and has limited improvement on the luminescence asymmetry factor; a larger luminescence asymmetry factor indicates higher circularly polarized light emission intensity. The second method involves the interaction of chiral ligands with excitons in the perovskite, inducing the generation of asymmetric spin-polarized excitons, thus achieving circularly polarized light emission. However, limited by the selection of chiral ligands and the synthesis methods of blue chiral perovskite quantum dots, the luminescence asymmetry factor and photoluminescence quantum yield of currently obtained blue chiral perovskite quantum dots are both relatively low.

[0004] Therefore, developing a new method that can efficiently induce asymmetric spin-polarized excitons in perovskite quantum dots while effectively passivating their surface defects and improving their photoluminescence quantum yield is crucial for obtaining high-quality blue chiral perovskite quantum dots. Summary of the Invention

[0005] To address the problems existing in the background technology, the present invention aims to provide a method for preparing high-quality blue chiral perovskite quantum dots. This method uses specific chiral ligand molecules to bond with the dangling bonds of blue CsPbBr3 quantum dots, which can passivate surface defects of the quantum dots while inducing the generation of highly asymmetric spin-polarized excitons, thereby achieving a balance between high luminescence asymmetry factor and high photoluminescence quantum yield.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A method for preparing high-quality blue chiral perovskite quantum dots includes the following steps:

[0008] Step 1. Prepare a crude solution of CsPbBr3 quantum dots;

[0009] Step 2. Chiral ligand exchange: The crude CsPbBr3 quantum dot solution prepared in Step 1 is heated to 50-60℃, and then hydrobromic acid aqueous solution and chiral ligand molecules are added sequentially to obtain a blue light-emitting chiral CsPbBr3 quantum dot crude solution; the chiral ligand molecule is (1S,2S)-N,N'-dimethyl-N,N'-bis(3,3-dimethylbutyl)cyclohexane-1,2-diamine;

[0010] Step 3. Add methyl acetate to the crude solution of blue chiral CsPbBr3 quantum dots, then centrifuge. Disperse the precipitate obtained by centrifugation in a nonpolar solvent, add methyl acetate again, centrifuge again, and then redisperse the precipitate in a nonpolar solvent to obtain a high-quality blue chiral CsPbBr3 quantum dot dispersion.

[0011] Furthermore, the volume ratio of the chiral ligand molecule to the aqueous hydrobromic acid solution is 0.9 to 1.1.

[0012] Furthermore, the volume of the hydrobromic acid aqueous solution is 30-50 μL, and the mass fraction is 48%.

[0013] Furthermore, the specific process for preparing the crude blue CsPbBr3 quantum dot solution in step 1 is as follows:

[0014] Step 1.1. Cesium carbonate and oleic acid are added to octadecene sequentially, stirred, and subjected to gradient heating under vacuum conditions, followed by nitrogen purging to obtain the first precursor solution;

[0015] Step 1.2. After mixing lead bromide, zinc bromide and octadecene, the mixture is heated under vacuum with a gradient, then replaced with nitrogen, and then oleic acid and oleylamine are added and stirred to obtain the second precursor solution.

[0016] Step 1.3. Set the temperature of the second precursor solution to 115~125 ℃. Under nitrogen atmosphere, add the first precursor solution to the second precursor solution. After keeping it warm for a period of time, take it out and put it in an ice water bath to stir and cool to room temperature to obtain a crude solution of blue CsPbBr3 quantum dots.

[0017] Further, in step 1.1, the mass ratio of cesium carbonate to octadecene is 8-12 mg / mL, and the volume ratio of oleic acid to octadecene is 0.06-0.08; in step 1.2, the mass ratio of lead bromide to octadecene is 13-15 mg / mL, the mass ratio of zinc bromide to octadecene is 67-69 mg / mL, the volume ratio of oleic acid to octadecene is 0.45-0.55, and the volume ratio of oleylamine to octadecene is 0.45-0.55.

[0018] Further, in step 1.1, the gradient heating conditions are 40 ℃, 60 ℃, and 100 ℃ in sequence, with each temperature stage held for 10 minutes; in step 1.2, the gradient heating conditions are 40 ℃, 60 ℃, 100 ℃, and 120 ℃ in sequence, with each temperature stage held for 10 minutes.

[0019] Furthermore, in step 1.3, the volume ratio of the second precursor to the first precursor is 11 to 14.

[0020] Furthermore, in step 2, the volume of methyl acetate added for the first time is 70-90 mL, the volume of non-polar solvent added for the first time is 1 mL, the volume of methyl acetate added for the second time is 2-3 mL, and the volume of non-polar solvent added for the second time is 0.4-0.6 mL.

[0021] Furthermore, the nonpolar solvent is one or more of n-octane, n-hexane, and toluene.

[0022] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0023] This invention discloses a method for preparing high-quality blue chiral perovskite quantum dots. This method innovatively employs (1S,2S)-N,N'-dimethyl-N,N'-bis(3,3-dimethylbutyl)cyclohexane-1,2-diamine as a chiral ligand, which can bond with the dangling bonds of the quantum dots, stabilizing the quantum dot surface. This passively passivates surface defects in blue CsPbBr3 quantum dots while inducing highly asymmetric spin-polarized excitons. The blue chiral perovskite quantum dots prepared by this invention exhibit a photoluminescence quantum yield as high as 86% and a high luminescence asymmetry factor of 0.086, providing a solution for the fabrication of high-performance blue circularly polarized light-emitting diodes. Attached Figure Description

[0024] Figure 1 This is the chemical structural formula of the chiral ligand used in this invention.

[0025] Figure 2The photoluminescence and UV-Vis absorption spectra of the blue chiral CsPbBr3 quantum dot solutions synthesized in Example 1 and the comparative example of this invention are shown. Among them, (a) is the photoluminescence spectrum and ultraviolet-visible absorption spectrum of the blue light CsPbBr3 quantum dot solution synthesized in the comparative example, and (b) is the photoluminescence spectrum and ultraviolet-visible absorption spectrum of the blue light chiral CsPbBr3 quantum dot solution synthesized in Example 1.

[0026] Figure 3 The circularly polarized emission spectrum and emission asymmetry factor of the blue chiral CsPbBr3 quantum dots prepared in Example 1 of this invention; In the figure, (a) is the circularly polarized emission spectrum, and (b) is the emission asymmetry factor.

[0027] Figure 4 These are transmission electron microscope images of Embodiment 1 and the comparative example of the present invention; Figure (a) is a transmission electron microscope image of the blue light-emitting chiral CsPbBr3 quantum dots synthesized in the comparative example, and Figure (b) is a transmission electron microscope image of the blue light-emitting chiral CsPbBr3 quantum dots synthesized in Example 1.

[0028] Figure 5 The photoluminescence quantum yield of blue CsPbBr3 quantum dots synthesized in Example 1 and the comparative example of the present invention is shown. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0030] Example 1

[0031] A method for preparing high-quality blue chiral perovskite quantum dots includes the following steps:

[0032] Step 1. Prepare a crude solution of blue CsPbBr3 quantum dots. The specific process is as follows:

[0033] Step 1.1. Add 10 mL of octadecene, 0.7 mL of oleic acid, and 100 mg of cesium carbonate to a three-necked flask, transfer to a heating mantle, and then stir at 300 rpm. Perform gradient heating in a vacuum environment with step temperatures of 40 °C, 60 °C, and 100 °C, with a time interval of 10 minutes. Subsequently, replace the gas environment in the three-necked flask with nitrogen using a Schiller line to obtain the first precursor solution.

[0034] Step 1.2. Add 10 mL of octadecene, 140 mg of lead bromide, and 680 mg of zinc bromide to another three-necked flask, transfer it to a heating mantle, and then stir at 400 rpm. Perform gradient heating in a vacuum environment with step temperatures of 40 ℃, 60 ℃, 100 ℃, and 120 ℃, with each step lasting 10 minutes. Then, replace the gas environment in the three-necked flask with nitrogen using a Schiller line, and then sequentially inject 5 mL of oleic acid and 5 mL of oleylamine. Increase the stirring speed to 700 rpm. Once the solution in the three-necked flask becomes clear and transparent, the second precursor solution is obtained.

[0035] Step 1.3. Take 1.6 mL of the first precursor solution and quickly inject it into the second precursor solution at a temperature of 120 °C. After holding the solution at this temperature for 5 seconds, remove the three-necked flask and place it in an ice-water bath to stir and cool it to room temperature to obtain a crude solution of blue CsPbBr3 quantum dots.

[0036] Step 2. Heat the crude blue-light CsPbBr3 quantum dot solution obtained in Step 1 to 55 °C, and then add 40 μL of hydrobromic acid aqueous solution and 40 μL of chiral ligand (1S,2S)-N,N'-dimethyl-N,N'-bis(3,3-dimethylbutyl)cyclohexane-1,2-diamine to obtain a crude blue-light chiral CsPbBr3 quantum dot solution.

[0037] Step 3. In a centrifuge tube, add 80 mL of methyl acetate as an antisolvent to the obtained crude blue-light CsPbBr3 quantum dot solution, centrifuge at 10,000 rpm for 1 minute, discard the supernatant, add 1 mL of n-octane to the precipitate, shake, and then add 2.5 mL of methyl acetate as an antisolvent. Centrifuge at 12,000 rpm for 1 minute, discard the supernatant, and disperse the precipitate with 0.5 mL of n-octane. This is suitable for preparing a high-quality blue-light chiral CsPbBr3 quantum dot dispersion for circularly polarized light-emitting diodes.

[0038] Example 2

[0039] High-quality blue-light chiral perovskite quantum dots were prepared according to the steps of Example 1, except that the mass ratio of cesium carbonate to octadecene in step 1.1 was adjusted to 8 mg / mL, the volume ratio of oleic acid to octadecene was adjusted to 0.06, the mass ratio of lead bromide to octadecene in step 1.2 was adjusted to 13 mg / mL, the mass ratio of zinc bromide to octadecene was adjusted to 67 mg / mL, the volume ratio of oleic acid to octadecene was adjusted to 0.45, and the volume ratio of oleylamine to octadecene was adjusted to 0.45; and the temperature of the second precursor solution in step 1.3 was adjusted to 115°C.

[0040] In step 2, the temperature of the blue CsPbBr3 quantum dot crude solution was adjusted to 50 ℃, the volume of the hydrobromic acid aqueous solution was adjusted to 30 μL, and the volume ratio of the chiral ligand molecule to the hydrobromic acid aqueous solution was adjusted to 0.9.

[0041] In step 3, the volume of methyl acetate added for the first time is adjusted to 70 mL, and the non-polar solvent added for the first time is adjusted to n-hexane, with the volume remaining at 1 mL. The volume of methyl acetate added for the second time is adjusted to 2 mL, and the non-polar solvent added for the second time is adjusted to n-hexane, with the volume adjusted to 0.4 mL. The other steps remain unchanged.

[0042] Example 3

[0043] High-quality blue-light chiral perovskite quantum dots were prepared according to the steps of Example 1, except that the mass ratio of cesium carbonate to octadecene in step 1.1 was adjusted to 12 mg / mL, the volume ratio of oleic acid to octadecene was adjusted to 0.08, the mass ratio of lead bromide to octadecene in step 1.2 was adjusted to 15 mg / mL, the mass ratio of zinc bromide to octadecene was adjusted to 69 mg / mL, the volume ratio of oleic acid to octadecene was adjusted to 0.55, and the volume ratio of oleylamine to octadecene was adjusted to 0.55; and the temperature of the second precursor solution in step 1.3 was adjusted to 125°C.

[0044] In step 2, the temperature of the crude blue CsPbBr3 quantum dot solution was adjusted to 60 °C, the volume of the hydrobromic acid aqueous solution was adjusted to 50 μL, and the volume ratio of the chiral ligand molecule to the hydrobromic acid aqueous solution was adjusted to 1.1.

[0045] In step 3, the volume of methyl acetate added for the first time is adjusted to 90 mL, and the volume of the non-polar solvent added for the first time is adjusted to toluene, which remains 1 mL. The volume of methyl acetate added for the second time is adjusted to 3 mL, and the volume of the non-polar solvent added for the second time is adjusted to toluene, which remains 0.6 mL. The other steps remain unchanged.

[0046] Comparative Example

[0047] Blue CsPbBr3 quantum dots were prepared according to the steps in Example 1, except that step 2 was omitted.

[0048] Figure 1 This is the chemical structural formula of the chiral ligand used in this invention; the chirality of this ligand molecule comes from two carbon-nitrogen bonds connected to cyclohexane.

[0049] Figure 2The figures show the photoluminescence and UV-Vis absorption spectra of the blue chiral CsPbBr3 quantum dot solutions synthesized in Example 1 and the comparative example of this invention. Figure (a) shows the blue chiral CsPbBr3 quantum dot solution synthesized in the comparative example, and Figure (b) shows the blue chiral CsPbBr3 quantum dot solution synthesized in Example 1. As can be seen from the figures, the photoluminescence peak of the non-chiral quantum dots prepared in the comparative example is 477 nm, while the photoluminescence peak of the chiral quantum dots prepared in Example 1 is 475 nm. Although there is a certain blue shift, it is still within the blue light band and still exhibits a significant exciton absorption peak, indicating that the chiral quantum dots prepared in this invention still possess a strong quantum confinement effect.

[0050] Figure 3 The circularly polarized emission spectrum and emission asymmetry factor of the blue chiral CsPbBr3 quantum dots prepared in Example 1 of this invention are shown in Figure (a). Figure (b) shows the circularly polarized emission spectrum and the emission asymmetry factor. As can be seen from Figure (a), the blue chiral CsPbBr3 quantum dots exhibit a positively circularly polarized emission peak, indicating that the quantum dots can generate highly asymmetric spin-polarized excitons under the induction of chiral ligand molecules. These spin-polarized excitons emit right-handed circularly polarized light through radiative recombination. As can be seen from Figure (b), the emission asymmetry factor reaches 0.086. A larger emission asymmetry factor indicates a higher intensity of circularly polarized emission.

[0051] Figure 4 These are transmission electron microscope images of Example 1 and the comparative example of the present invention. Figure (a) shows the blue light-emitting achiral CsPbBr3 quantum dots synthesized in the comparative example, and Figure (b) shows the blue light-emitting chiral CsPbBr3 quantum dots synthesized in Example 1. Comparing the two images, it can be seen that after introducing chiral ligand molecules, the perovskite quantum dots have a more stable surface and are more resistant to high-energy electron irradiation. Specifically, the amount of metallic lead nanocrystals that are reduced and grown by high-energy electrons due to the presence of lead dangling bonds on the quantum dot surface (the areas with higher brightness on the quantum dot surface in the figures) is significantly reduced.

[0052] Figure 5 The photoluminescence quantum yields of the blue CsPbBr3 quantum dots synthesized in Example 1 and the comparative example of this invention are shown. The introduction of chiral ligand molecules in this invention increased the photoluminescence quantum yield of the quantum dots from 69% to 86%, indicating that the chiral molecules of this invention can effectively passivate the defect states on the surface of the quantum dots while inducing the generation of high luminescence asymmetry factors, thereby improving their radiative recombination rate.

[0053] The above description is merely a specific embodiment of the present invention. Any feature disclosed in this specification may be replaced by other equivalent or similar features unless otherwise specified. All disclosed features, or steps in all methods or processes, may be combined in any way except for mutually exclusive features and / or steps.

Claims

1. A method for preparing high-quality blue chiral perovskite quantum dots, characterized in that, Includes the following steps: Step 1. Prepare a crude solution of CsPbBr3 quantum dots; Step 2. Chiral ligand exchange: The crude CsPbBr3 quantum dot solution prepared in Step 1 is heated to 50-60 °C, and then hydrobromic acid aqueous solution and chiral ligand molecules are added sequentially to obtain a blue-light-emitting chiral CsPbBr3 quantum dot crude solution; the chiral ligand molecule is (1S,2S)-N,N'-dimethyl-N,N'-bis(3,3-dimethylbutyl)cyclohexane-1,2-diamine; Step 3. Add methyl acetate to the crude solution of blue chiral CsPbBr3 quantum dots, then centrifuge. Disperse the precipitate obtained by centrifugation in a nonpolar solvent, add methyl acetate again, centrifuge again, and then redisperse the precipitate in a nonpolar solvent to obtain a high-quality blue chiral CsPbBr3 quantum dot dispersion.

2. The method for preparing high-quality blue chiral perovskite quantum dots as described in claim 1, characterized in that, The volume ratio of the chiral ligand molecule to the aqueous hydrobromic acid solution is 0.9 to 1.

1.

3. The method for preparing high-quality blue chiral perovskite quantum dots as described in claim 2, characterized in that, The volume of the hydrobromic acid aqueous solution is 30~50 μL, and the mass fraction is 48%.

4. The method for preparing high-quality blue chiral perovskite quantum dots as described in claim 1, characterized in that, The specific process for preparing the crude solution of blue CsPbBr3 quantum dots in step 1 is as follows: Step 1.

1. Cesium carbonate and oleic acid are added to octadecene sequentially, stirred, and subjected to gradient heating under vacuum conditions, followed by nitrogen purging to obtain the first precursor solution; Step 1.

2. After mixing lead bromide, zinc bromide and octadecene, the mixture is heated under vacuum with a gradient, then replaced with nitrogen, and then oleic acid and oleylamine are added and stirred to obtain the second precursor solution. Step 1.

3. Set the temperature of the second precursor solution to 115~125 ℃. Under nitrogen atmosphere, add the first precursor solution to the second precursor solution. After keeping it warm for a period of time, take it out and put it in an ice water bath to stir and cool to room temperature to obtain a crude solution of blue CsPbBr3 quantum dots.

5. The method for preparing high-quality blue chiral perovskite quantum dots as described in claim 4, characterized in that, In step 1.1, the mass ratio of cesium carbonate to octadecene is 8-12 mg / mL, and the volume ratio of oleic acid to octadecene is 0.06-0.08; in step 1.2, the mass ratio of lead bromide to octadecene is 13-15 mg / mL, the mass ratio of zinc bromide to octadecene is 67-69 mg / mL, the volume ratio of oleic acid to octadecene is 0.45-0.55, and the volume ratio of oleylamine to octadecene is 0.45-0.

55.

6. The method for preparing high-quality blue chiral perovskite quantum dots as described in claim 4, characterized in that, In step 1.1, the gradient heating conditions are 40 ℃, 60 ℃, and 100 ℃ in sequence, with each temperature stage held for 10 minutes; in step 1.2, the gradient heating conditions are 40 ℃, 60 ℃, 100 ℃, and 120 ℃ in sequence, with each temperature stage held for 10 minutes.

7. The method for preparing high-quality blue chiral perovskite quantum dots as described in claim 4, characterized in that, In step 1.3, the volume ratio of the second precursor to the first precursor is 11 to 14.

8. The method for preparing high-quality blue chiral perovskite quantum dots as described in claim 1, characterized in that, In step 2, the volume of methyl acetate added for the first time is 70-90 mL, the volume of non-polar solvent added for the first time is 1 mL, the volume of methyl acetate added for the second time is 2-3 mL, and the volume of non-polar solvent added for the second time is 0.4-0.6 mL.

9. The method for preparing high-quality blue chiral perovskite quantum dots as described in claim 8, characterized in that, The nonpolar solvent is one or more of n-octane, n-hexane, and toluene.

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