High-performance blue perovskite nanosheets and preparation method thereof

Abstract

The application discloses a high-performance blue light perovskite nanosheet and a preparation method thereof. The blue light perovskite nanosheet is a two-dimensional semiconductor nanomaterial with CsPbBr3 as a component and an average thickness of about 2 nm. Polystyrene sulfonic acid (PSS) is modified on the surface of the nanosheet at room temperature through a surface ligand post-treatment strategy. The sulfonate and the cations on the surface of the nanosheet are fully passivated through strong coordination interaction, so that the surface state of the nanosheet is improved, and the light-emitting efficiency of the nanosheet is improved. Meanwhile, the size of the modified nanosheet is basically unchanged, and the original light-emitting peak position and the narrow-band optical characteristics are still maintained. The high-performance blue light perovskite nanosheet modified by polystyrene sulfonic acid and the preparation method thereof are simple, efficient, easy to realize mass production of the high-performance blue light perovskite nanosheet, and lay a solid material preparation technical foundation for industrialization, so that the development and application of the high-quality perovskite nanosheet-based light-emitting device are promoted.

Description

Technical Field

[0001] This invention belongs to the field of low-dimensional semiconductor nanomaterials for light-emitting devices, specifically relating to a high-performance blue light perovskite nanosheet and its preparation method. Background Technology

[0002] Colloidal semiconductor nanosheets possess an electronic structure similar to quantum wells. Their anisotropic crystal growth facilitates atomically precise control over nanosheet thickness, making them a novel type of semiconductor nanomaterial. Excitons within the nanosheets can move freely in the transverse plane, experiencing strong quantum confinement only in the thickness direction. Compared to quasi-zero-dimensional quantum dots, two-dimensional nanosheets exhibit significant one-dimensional quantum confinement characteristics, such as narrow emission peaks, rapid exciton radiative recombination rates, ultra-large absorption cross-sections, and high oscillator strength. These superior optical properties make nanosheets a high-performance optoelectronic functional material with broad application prospects, applicable to display and lighting devices.

[0003] Blue light is a crucial component of display backlights, and the development of high-performance blue nanosheet light-emitting devices is key to realizing full-color nanosheet display technology. Currently, research on two-dimensional colloidal nanosheets mainly focuses on the optical properties of red and green nanosheet light-emitting materials and their light-emitting devices, while progress on the performance and applications of blue light-emitting nanosheets has been relatively slow. The inherent ultra-wide bandgap and excessive defect states induced by the ultra-thin nanostructure (<2nm) result in poor and unstable optical performance of blue nanosheets, limiting their potential applications in ultra-wide color gamut displays. Although room-temperature perovskite two-dimensional nanosheets offer advantages in low cost and rapid synthesis, the aforementioned challenges remain. Ultra-thin metal halide perovskite nanosheets for display device applications face even greater challenges. For example, perovskite nanosheets tend to grow slowly in solution environments, forming large particles; the ultra-thin physical structure generates more defect states, leading to extremely poor luminous efficiency; and post-treatment methods for nanosheet surface ligands can easily cause secondary growth, resulting in spectral peak shifts or broadening. These factors hinder the application of the optical properties of ultra-thin two-dimensional nanosheets in the field of light-emitting devices. Therefore, researchers have been committed to developing a more optimized technical solution to solve existing problems and further extend the optical performance advantages of room temperature preparation of higher quality perovskite nanosheets in practical applications. Summary of the Invention

[0004] Technical problems to be solved:

[0005] This application addresses the shortcomings of existing technologies, such as the poor optical performance of semiconductor blue light-emitting perovskite nanosheets due to their ultrathin nanometer thickness, the relatively slow progress in research on the performance and application of blue light-emitting nanosheets, the poor and unstable optical performance of blue light-emitting nanosheets, the lack of literature reports on their potential applications in ultra-wide color gamut displays, the tendency of perovskite nanosheets to grow slowly in solution environments to form large particles, the generation of more defect states in the ultrathin physical structure leading to extremely poor luminous efficiency, and the tendency of nanosheet surface ligand post-treatment schemes to cause secondary growth of nanosheets resulting in spectral peak shifting or broadening. This application provides a high-performance blue light-emitting perovskite nanosheet and its preparation method. This method can rapidly passivate the defect states on the nanosheet surface at room temperature to form high-luminous-efficiency nanosheets, while maintaining their original fluorescence peak positions and narrow-band emission optical characteristics.

[0006] Technical solution:

[0007] To achieve the above objectives, this application provides the following technical solution:

[0008] A method for preparing high-performance blue light perovskite nanosheets specifically includes the following steps:

[0009] Step 1, Preparation of precursor solutions: 64 mg of cesium bromide was ultrasonically dispersed and dissolved in 0.5 mL of deionized water to prepare solution A. 110 mg of lead bromide was ultrasonically dispersed and dissolved in 0.5 mL of N,N-dimethylformamide (DMF) to prepare solution B. Both solution A and solution B are colorless and transparent liquids.

[0010] The second step is the preparation of blue-light perovskite CsPbBr3 nanosheets: 20 mL of n-hexane was added to a sampling bottle, along with 0.5 mL of oleic acid and 0.25 mL of oleylamine. The mixture was magnetically stirred at 1000-1500 rpm for 2 minutes at room temperature to obtain a mixed solution. Solution A and solution B were added to the mixed solution in the sampling bottle, followed by 4 mL of acetone solution. The mixture was magnetically stirred at 1000-1500 rpm for 10 minutes at room temperature. Then, 20 mL of n-hexane was added and mixed thoroughly to obtain a perovskite nanosheet solution. Finally, the perovskite nanosheet solution was centrifuged at 8000-10000 rpm for 5 minutes to remove large precipitate particles, thus obtaining a transparent blue-light perovskite CsPbBr3 nanosheet solution.

[0011] The third step is the preparation of PSS-toluene solution: Weigh 1g of PSS according to the mass-volume ratio and add it to a new 4mL sampling bottle. Add 3mL of toluene and then sonicate at a frequency of 40kHz for 10min to obtain the PSS-toluene solution.

[0012] Step 4: Preparation of polystyrene sulfonic acid modified blue perovskite nanosheets: Take 1.5 mL of blue perovskite CsPbBr3 nanosheet solution by volume ratio, add 3 mL of methyl acetate solution, and purify by centrifugation at 6000 rpm for 4-5 min; after discarding the supernatant, disperse the bottom nanosheet precipitate with 3 mL of toluene solution to obtain nanosheet toluene solution; add 0.1-2 mL of PSS-toluene solution to 3 mL of nanosheet toluene solution and stir at room temperature for 1 h.

[0013] Furthermore, in the second step, the magnetic stirring speed is 1000 rpm.

[0014] Furthermore, the centrifugation rate for purification in the second step is 8000 rpm.

[0015] Furthermore, the centrifugation time in the fourth step is 5 minutes.

[0016] A high-performance blue light perovskite nanosheet prepared by any of the above preparation methods.

[0017] Beneficial effects:

[0018] This application provides a high-performance blue light perovskite nanosheet and its preparation method, which has the following advantages compared with the prior art:

[0019] 1. This application utilizes a surface ligand post-treatment method to prepare high-efficiency blue light-emitting perovskite CsPbBr3 nanosheets modified with polystyrene sulfonic acid at room temperature. The ligand engineering strategy developed in this invention is easy to realize the mass production of nano-light-emitting materials at room temperature, which helps to promote the development and application of light-emitting devices based on high-performance blue light-emitting perovskite nanosheets.

[0020] 2. This invention is based on high-performance blue light perovskite nanosheets modified with polystyrene sulfonate (PSS). The obtained perovskite nanosheet luminescent material can maintain the optical properties of narrow-band emission while improving its luminous efficiency.

[0021] 3. The addition of hexane to dilute the perovskite nanosheet solution reduces the ligand concentration in the original reaction solution, enabling the prepared blue perovskite nanosheets to maintain stable optical properties in a room temperature solution environment, and preventing them from slowly growing and forming large particle precipitates in a room temperature solution environment.

[0022] 4. The optimal luminescence efficiency of blue perovskite nanosheets was obtained by adding an appropriate amount of high bond energy ligand polystyrene sulfonic acid. The optimal concentration of polystyrene sulfonic acid is crucial for achieving passivation of surface defects on the nanosheets and avoiding corrosion of the perovskite crystal structure. The surface states of the nanosheets are fully passivated by the coordination interaction between sulfonate groups and cations on the nanosheet surface, thereby greatly improving the luminescence efficiency of the nanosheets. At the same time, the fluorescence peak position of the blue perovskite nanosheets before and after modification remains unchanged, and the emission peak half-width at half-maximum (FWHM) still maintains the narrow-band emission characteristics.

[0023] 5. A method is provided for obtaining high-quality blue light perovskite nanosheets based on room temperature in-situ perovskite nanosheet solution through strong coordination interaction of surface cations, which greatly improves the optical performance of the blue light perovskite nanosheets obtained at room temperature.

[0024] 6. By developing a simple and controllable method for the mass production of high-quality perovskite nanosheets, a material preparation technology foundation is laid for their commercial application in the field of light-emitting devices.

[0025] 7. This invention proposes a method for preparing high-performance blue light perovskite nanosheets by surface modification with polystyrene sulfonic acid. At room temperature, the surface defect states of the perovskite nanosheets can be passivated through the coordination interaction between sulfonate groups and cations on the nanosheet surface. This results in a fluorescence emission intensity of more than 2 times that of the unmodified sample, greatly improving the luminescence efficiency of the blue light nanosheets. The fluorescence quantum yield of the obtained nanosheets reaches more than 80%. At the same time, the fluorescence peak position of the blue light perovskite nanosheets before and after modification remains unchanged, and the emission peak half-width at half-maximum (FWHM) still maintains the narrow-band emission characteristics. The perovskite nanosheets modified with PSS exhibited a distinct S=O characteristic absorption peak, and the electron energy of lead ions in the modified nanosheets shifted, confirming the successful binding of sulfonate ions in PSS to cations on the surface of the perovskite nanosheets. Finally, the prepared blue-light perovskite nanosheets maintained uniform size and morphology overall. This preparation method has advantages such as good scalability, easy control and simplicity of experimental steps, and can meet the needs of mass production on semiconductor perovskite nanomaterial production lines, laying the material preparation technology foundation for the commercial application of light-emitting devices based on semiconductor perovskite nanomaterials. Attached Figure Description

[0026] Figure 1 The images show the fluorescence spectra and fluorescence intensity trends of high-performance blue CsPbBr3 nanosheets prepared with different amounts of PSS in the embodiments of this application; where a is the fluorescence spectrum of nanosheets with different amounts of PSS, and b is the fluorescence intensity trend of nanosheet solutions with different amounts of PSS.

[0027] Figure 2These are the fluorescence and absorption spectra of perovskite CsPbBr3 nanosheets before and after modification with 0.5 mLPSS in the embodiments of this application;

[0028] Figure 3 These are Fourier transform infrared (FTIR) and X-ray photoelectron spectra of perovskite CsPbBr3 nanosheets before and after PSS modification in this application. In the figure, a is a comparison of the infrared characteristic absorption peaks of specific functional groups in the samples before and after modification, and b is the lead ion electron spectrum of the samples before and after modification.

[0029] Figure 4 These are transmission electron microscope images of blue perovskite CsPbBr3 nanosheets before and after PSS modification in this application.

[0030] Figure 5 These are the size distribution statistics of blue perovskite CsPbBr3 nanosheets before and after PSS modification, and the transmission electron microscope image of the modified sample under a larger field of view. In the image, a is the size distribution statistics of the nanosheets before modification, b is the size distribution statistics of the nanosheets after modification, and c is the transmission electron microscope image of the modified nanosheet sample under a larger field of view, which shows excellent size uniformity. Detailed Implementation

[0031] The following detailed embodiments further illustrate the present invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading this disclosure, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0032] Example 1:

[0033] A method for preparing high-performance blue light perovskite nanosheets specifically includes the following steps:

[0034] Step 1, Preparation of precursor solutions: 64 mg of cesium bromide was ultrasonically dispersed and dissolved in 0.5 mL of deionized water to prepare solution A. 110 mg of lead bromide was ultrasonically dispersed and dissolved in 0.5 mL of N,N-dimethylformamide (DMF) to prepare solution B. Both solution A and solution B are colorless and transparent liquids.

[0035] The second step is the preparation of blue light perovskite CsPbBr3 nanosheets: 20 mL of n-hexane was added to the sampling bottle by volume, along with 0.5 mL of oleic acid and 0.25 mL of oleylamine. The mixture was magnetically stirred at 1000 rpm for 2 min at room temperature to obtain a mixed solution. Solution A and solution B were added to the mixed solution in the sampling bottle, and then 4 mL of acetone solution was added. The mixture was magnetically stirred at 1000-1500 rpm for 10 min at room temperature.

[0036] Then, add 20 mL of n-hexane and mix well to obtain a perovskite nanosheet solution; finally, centrifuge the perovskite nanosheet solution at 8000 rpm for 5 min to remove large particle precipitates, thus obtaining a transparent blue light perovskite CsPbBr3 nanosheet solution.

[0037] The third step is the preparation of PSS-toluene solution: Weigh 1g of PSS according to the mass-volume ratio and add it to a new 4mL sampling bottle. Add 3mL of toluene and then sonicate at a frequency of 40kHz for 10min to obtain the PSS-toluene solution.

[0038] The fourth step is to prepare polystyrene sulfonic acid modified blue perovskite nanosheets: 1.5 mL of blue perovskite CsPbBr3 nanosheet solution was taken by volume and 3 mL of methyl acetate solution was added. The mixture was centrifuged at 6000 rpm for 5 min to purify the solution. After discarding the supernatant, the bottom nanosheet precipitate was dispersed with 3 mL of toluene solution to obtain a nanosheet toluene solution. 0.5 mL of PSS-toluene solution was added to the 3 mL nanosheet toluene solution and stirred at room temperature for 1 h.

[0039] This invention proposes a method for preparing high-performance blue-light perovskite nanosheets using polystyrene sulfonic acid surface modification. At room temperature, the method achieves surface defect passivation of the perovskite nanosheets through coordination interactions between sulfonate groups and cations on the nanosheet surface, resulting in a fluorescence emission intensity increase of more than two times compared to unmodified samples (e.g., ...). Figure 1 As shown in the figure, as the amount of PSS added gradually increases to 0.5 mL, the fluorescence emission intensity of CsPbBr3 nanosheets gradually increases, and then gradually decreases with further increases in the amount of PSS added, showing a shift in the spectral peak position. Figure 1 (a) Observations showed that the blue nanosheets exhibited the highest luminescence efficiency when the amount of PSS added was 0.5 mL. Figure 1 (b) significantly improved the luminescence efficiency of blue perovskite nanosheets, resulting in a fluorescence quantum yield of over 80%; simultaneously, the fluorescence peak positions of the blue perovskite nanosheets remained unchanged before and after modification (e.g., ...). Figure 2 As shown in the figure, the peak positions and full width at half maximum (FWHM) of the fluorescence and absorption spectra of perovskite CsPbBr3 nanosheets remained almost unchanged before and after modification with 0.5 mL of PSS, and the emission peak FWHM still maintained narrow-band emission characteristics. The perovskite nanosheets modified with PSS exhibited obvious S=O characteristic absorption peaks (e.g., ...). Figure 3 As shown in Figure a), and the electron energy of lead ions in the modified nanosheets shifts (e.g., as shown in Figure a). Figure 3 As shown in Figure b), the successful binding of sulfonate ions in PSS to cations on the surface of perovskite nanosheets was confirmed. Finally, the prepared blue-light perovskite nanosheets maintained a uniform size and morphology overall (as shown in Figure b). Figure 4 and Figure 5 (As shown). Figure 4In the process, the morphology and thickness of the perovskite nanosheets remained basically unchanged before and after PSS modification; Figure 5 As shown in Figures a and b, the perovskite nanosheets before and after PSS modification are basically the same size, and observation shows that the modified sample has better overall uniformity (e.g., ...). Figure 5 (As shown in c). This preparation method has advantages such as good scalability, easy control and simplicity of experimental steps, which can meet the needs of mass production on semiconductor perovskite nanomaterial production lines, and lay the material preparation technology foundation for the commercial application of light-emitting devices based on semiconductor perovskite nanomaterials.

[0040] Example 2:

[0041] A method for preparing high-performance blue light perovskite nanosheets specifically includes the following steps:

[0042] Step 1, Preparation of precursor solutions: 64 mg of cesium bromide was ultrasonically dispersed and dissolved in 0.5 mL of deionized water to prepare solution A. 110 mg of lead bromide was ultrasonically dispersed and dissolved in 0.5 mL of N,N-dimethylformamide (DMF) to prepare solution B. Both solution A and solution B are colorless and transparent liquids.

[0043] The second step is the preparation of blue light perovskite CsPbBr3 nanosheets: 20 mL of n-hexane was added to the sampling bottle by volume, along with 0.5 mL of oleic acid and 0.25 mL of oleylamine. The mixture was magnetically stirred at 1000 rpm for 2 min at room temperature to obtain a mixed solution. Solution A and solution B were added to the mixed solution in the sampling bottle, and then 4 mL of acetone solution was added. The mixture was magnetically stirred at 1000-1500 rpm for 10 min at room temperature.

[0044] Then, add 20 mL of n-hexane and mix well to obtain a perovskite reaction solution; finally, centrifuge the perovskite nanosheet solution at 8000 rpm for 5 min to remove large particle precipitates, thus obtaining a transparent blue light perovskite CsPbBr3 nanosheet solution.

[0045] The third step is the preparation of PSS-toluene solution: Weigh 1g of PSS according to the mass-volume ratio and add it to a new 4mL sampling bottle. Add 3mL of toluene and then sonicate at a frequency of 40kHz for 10min to obtain the PSS-toluene solution.

[0046] The fourth step is to prepare polystyrene sulfonic acid modified blue perovskite nanosheets: 1.5 mL of blue perovskite CsPbBr3 nanosheet solution was taken by volume and 3 mL of methyl acetate solution was added. The mixture was centrifuged at 6000 rpm for 5 min to purify the solution. After discarding the supernatant, the bottom nanosheet precipitate was dispersed with 3 mL of toluene solution to obtain a nanosheet toluene solution. 0.1 mL of PSS-toluene solution was added to the 3 mL nanosheet toluene solution and stirred at room temperature for 1 h.

[0047] Example 3:

[0048] A method for preparing high-performance blue light perovskite nanosheets specifically includes the following steps:

[0049] Step 1, Preparation of precursor solutions: 64 mg of cesium bromide was ultrasonically dispersed and dissolved in 0.5 mL of deionized water to prepare solution A. 110 mg of lead bromide was ultrasonically dispersed and dissolved in 0.5 mL of N,N-dimethylformamide (DMF) to prepare solution B. Both solution A and solution B are colorless and transparent liquids.

[0050] The second step is the preparation of blue-light perovskite CsPbBr3 nanosheets: 20 mL of n-hexane was added to a sampling bottle, along with 0.5 mL of oleic acid and 0.25 mL of oleylamine. The mixture was magnetically stirred at 1000 rpm for 2 minutes at room temperature to obtain a mixed solution. Solutions A and B were added to the mixed solution in the sampling bottle, followed by 4 mL of acetone solution. The mixture was magnetically stirred at 1000-1500 rpm for 10 minutes at room temperature. Then, 20 mL of n-hexane was added and mixed thoroughly to obtain a perovskite nanosheet solution. Finally, the perovskite nanosheet solution was centrifuged at 8000 rpm for 5 minutes to remove large precipitate particles, thus obtaining a transparent blue-light perovskite CsPbBr3 nanosheet solution.

[0051] The third step is the preparation of PSS-toluene solution: Weigh 1g of PSS according to the mass-volume ratio and add it to a new 4mL sampling bottle. Add 3mL of toluene and then sonicate at a frequency of 40kHz for 10min to obtain the PSS-toluene solution.

[0052] The fourth step is to prepare polystyrene sulfonic acid modified blue perovskite nanosheets: 1.5 mL of blue perovskite CsPbBr3 nanosheet solution was taken by volume and 3 mL of methyl acetate solution was added. The solution was purified by centrifugation at 6000 rpm for 5 min. After discarding the supernatant, the bottom nanosheet precipitate was dispersed with 3 mL of toluene solution to obtain a nanosheet toluene solution. 2 mL of PSS-toluene solution was added to the 3 mL nanosheet toluene solution and stirred at room temperature for 1 h.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, improved experimental schemes, provided that the principles of the present invention are followed, should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-performance blue light perovskite nanosheets, characterized in that, Specifically, the steps include the following: Step 1, Preparation of precursor solutions: 64 mg of cesium bromide was ultrasonically dispersed and dissolved in 0.5 mL of deionized water to prepare solution A. 110 mg of lead bromide was ultrasonically dispersed and dissolved in 0.5 mL of N,N-dimethylformamide (DMF) to prepare solution B. Both solutions A and B are colorless and transparent liquids. The second step is the preparation of blue-light perovskite CsPbBr3 nanosheets: 20 mL of n-hexane was added to a sampling bottle, followed by 0.5 mL of oleic acid and 0.25 mL of oleylamine. The mixture was magnetically stirred at 1000-1500 rpm for 2 minutes at room temperature to obtain a mixed solution. Solution A and solution B were added to the mixed solution in the sampling bottle, and then 4 mL of acetone solution was added. The mixture was magnetically stirred at 1000-1500 rpm for 10 minutes at room temperature. Then, 20 mL of n-hexane was added and mixed evenly to obtain a perovskite nanosheet solution. Finally, the perovskite nanosheet solution was centrifuged at 8000-10000 rpm for 5 minutes to remove large precipitate particles, thus obtaining a transparent blue-light perovskite CsPbBr3 nanosheet solution. The third step is the preparation of PSS-toluene solution: Weigh 1 g of PSS according to the mass-volume ratio and add it to a new 4 mL sampling bottle. Add 3 mL of toluene and then sonicate at a frequency of 40 kHz for 10 min to obtain PSS-toluene solution. The fourth step is to prepare polystyrene sulfonic acid modified blue perovskite nanosheets: 1.5 mL of blue perovskite CsPbBr3 nanosheet solution was taken by volume and 3 mL of methyl acetate solution was added. The mixture was centrifuged at 6000 rpm for 4-5 min to purify the solution. After discarding the supernatant, the bottom nanosheet precipitate was dispersed with 3 mL of toluene solution to obtain a nanosheet toluene solution. 0.5 mL of PSS-toluene solution was added to the 3 mL nanosheet toluene solution and stirred at room temperature for 1 h.

2. The method for preparing high-performance blue light perovskite nanosheets according to claim 1, characterized in that: In the second step, the first magnetic stirring speed is 1000 rpm.

3. The method for preparing high-performance blue light perovskite nanosheets according to claim 1, characterized in that: The centrifugation rate for purification in the second step is 8000 rpm.

4. The method for preparing high-performance blue light perovskite nanosheets according to claim 1, characterized in that: The centrifugation time in the fourth step is 5 minutes.

5. A high-performance blue light perovskite nanosheet prepared by any one of the preparation methods described in claims 1-4.

Images