Preparation method and application of chiral nematic mesoporous silica for inducing circularly polarized luminescence of perovskite nanocrystals

Abstract

The application discloses a preparation method of chiral nematic mesoporous silica for inducing circularly polarized luminescence of perovskite nanocrystals, and comprises the following steps: S1: cellulose nanocrystals are taken as a chiral hard template source, and are mixed with a silicon source after stirring, and then a cellulose nanocrystal / silica composite film is formed by room temperature evaporation self-assembly; S2: the cellulose nanocrystal / silica composite film is obtained by high-temperature calcination; S3: halogenated lead and methylamine halide are taken as perovskite precursors, and N, N'-dimethylformamide is taken as a solvent to form a precursor solution; S4: the chiral nematic mesoporous silica film obtained in S2 is soaked in the precursor solution prepared in S3, and a solvent is evaporated at high temperature and in vacuum to obtain a chiral nematic composite film with circularly polarized luminescence; and S5: the composite film obtained in S4 is placed on a chip, a power supply is turned on, and a fixed current voltage is set to make the chiral nematic composite film emit light. The synthesis method is simple and fast, and the circularly polarized fluorescence emission of perovskite nanocrystals induced by the chiral environment obtained by the method is strong.

Description

Technical Field

[0001] This invention relates to the field of organic-inorganic hybrid perovskite materials, specifically a method for preparing chiral nematic mesoporous silicon-induced perovskite nanocrystals to generate circularly polarized light emission and its application in circularly polarized LEDs. Background Technology

[0002] Optically active halide perovskites with circularly polarized emission (CPL) properties have emerged as a promising class of CPL-active materials for wide applications in fields such as 3D displays, optical data storage, and spintronics due to their attractive characteristics, such as wavelength stability and high luminescence efficiency. For practical applications, it is crucial to develop simple and convenient synthetic routes for producing large circularly polarized active halide perovskite materials while simultaneously improving their rotation and luminescence.

[0003] To date, chiral halide perovskites have been widely prepared by directly incorporating chiral organic cations into the perovskite lattice, endowing low-dimensional perovskites with inherent chirality. However, due to limited chiral transfer capabilities, chiral low-dimensional perovskites suffer from poor optical activity and weak luminescence. Surface functionalization of perovskite nanocrystals with chiral ligands distorts the lattice structure of the perovskite surface, thereby granting them high circularly polarized luminescence (CPL) properties. However, because chiral ligands readily dissociate from the surface of perovskite nanocrystals, this method typically requires rigorous multi-step reactions and purification, and is also strongly influenced by the stability of the surface chiral ligands. Furthermore, none of the above strategies have achieved large circular polarization, resulting in low luminescence asymmetry factors (…). g lum The value is only 10 -4 Up to 10 -2 The order of magnitude is far below the theoretical maximum of 2.0.

[0004] Inspired by the iridescent cuticle of rainbow-colored insects, self-assembled solid-state cellulose nanocrystals (CNCs) with a left-handed chiral nematic structure can serve as one-dimensional chiral photonic crystals capable of selectively reflecting left-handed circularly polarized light. Researchers have discovered that the unique chiral nematic order and nanoscale size make chiral nematic CNC solids excellent templates for constructing mesoporous inorganic films with long-range chiral nematic order. Furthermore, these photonic mesoporous inorganic films can provide both mesoporous templates and chiral photonic crystal structures, thus serving as a chiral mesoporous host combined with chiral luminescent materials for constructing CPL-active materials. By suppressing the propagation of left-handed light, the left-handed nematic mesoporous inorganic film host can effectively convert luminescence into right-handed CPL within the selective reflection (SR) band. Simultaneously, the highly ordered mesoporous film can serve as a template to guide the confined growth of perovskite nanocrystals and control their structural and morphological characteristics. Invention patents CN107082466A, CN109200990A, and CN106167705A disclose preparation methods using chiral mesoporous silica as porous templates. However, CN109200990A and CN107082466A are not luminescent material systems, while patent CN106167705A is a traditional rare-earth system that is expensive, scarce, complex to synthesize, and has insufficient photoelectric conversion efficiency. This patent only exhibits conventional non-chiral fluorescence properties and does not confirm its chiral characteristics, chiral luminescence properties, or full-chromatographic CPL activity and stability. Furthermore, the mesoporous silica substrate can provide enhanced environmental stability and processing versatility for guest perovskite nanocrystals, which is beneficial for their long-term storage and integration into various devices. For example, invention patent CN112993067A discloses the use of mesoporous silica materials to regulate the crystallization process of inorganic perovskites, but it only uses ordinary mesoporous silica materials, not mesoporous silica materials with chiral structures. To date, there have been no reports on the confined growth synthesis of stable full-color CPL active perovskite materials based on photonic mesoporous inorganic silicon thin films. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and provide a high CPL value and a high asymmetry factor. g lum A method for preparing circularly polarized light emission induced by chiral nematic mesoporous silicon with wide-spectrum emission and excellent stability, and its application in circularly polarized LEDs.

[0006] The first aspect of this invention is to provide a method for preparing chiral nematic mesoporous silicon-induced perovskite nanocrystals to generate circularly polarized luminescence, comprising the following steps:

[0007] S1: Using cellulose nanocrystals as a chiral hard template source, after mixing with a silicon source, the cellulose nanocrystal / silica composite film is formed by evaporation at room temperature.

[0008] S2: Chiral nematic mesoporous silicon thin film is obtained by high-temperature calcination of cellulose nanocrystal / silica composite film;

[0009] S3: A precursor solution is formed using lead halide and methylamine halide as perovskite precursors and N,N'-dimethylformamide as solvent;

[0010] S4: The chiral nematic mesoporous silicon film obtained in S2 is immersed in the precursor solution prepared in S3, and the solvent is evaporated at high temperature and vacuum to obtain a chiral nematic composite film with circularly polarized light emission.

[0011] S5: Place the composite film obtained in S4 onto the chip, turn on the power, and set a fixed current and voltage to make it emit light.

[0012] A further setting is that the silicon source in step S1 is tetramethoxysilane, and the photonic bandgap of the photonic crystal is adjusted by regulating the ratio of cellulose nanocrystals to tetramethoxysilane.

[0013] The further setting is that the high-temperature calcination in step S2 is carried out in a muffle furnace.

[0014] A further setting is that in step S3, the lead halide is lead chloride, lead bromide, or lead iodide.

[0015] A further setting is that the methylamine halide in step S3 is methylamine chloride, methylamine bromide, or methylamine iodine.

[0016] A further setting is that the molar ratio of the mixed methylamine halide cations and lead halide in the precursor solution in step S3 is 1:1.

[0017] A further setting is that the high-temperature solvent evaporation process in step S4 is carried out in a vacuum drying oven.

[0018] A further setting is that the chip in step S5 is a blue light chip with a wavelength of 365-385 nm.

[0019] A further setting is that the number of composite films in step S5 is no less than 3 pieces.

[0020] Secondly, the present invention also provides an application of the preparation method described above in circularly polarized LEDs.

[0021] This application constructs a method for generating circularly polarized light from achiral perovskite nanocrystals induced by a chiral environment and applies it to circularly polarized LEDs. The effects of PBG concentration in chiral nematic mesoporous silicon and the concentration of the perovskite precursor solution on the circular polarization performance were investigated. By changing the halogen atom at the X-position of the perovskite nanocrystals, perovskite nanocrystals coated with chiral nematic mesoporous silicon exhibiting full-spectrum circularly polarized emission can be obtained.

[0022] The innovative mechanism of this invention is a simple yet efficient method for confining the growth of perovskite nanocrystals to produce CPL-active chiral nematic mesoporous silica (CNMS) film-templated halide perovskite nanocrystal materials. The silica matrix imparts selective reflection, stability, and solution processability, while the perovskite nanocrystals retain their shape- and composition-dependent optical properties. Through precise control of the photonic bandgap (PBG) of the chiral nematic mesoporous silica film template and the perovskite nanocrystal loading, the CPL properties can be significantly improved. g lum |Customization available. Value up to 0.17. Furthermore, by adjusting the halide anions in perovskite nanocrystals, a series of wavelength-tunable CPL-active halide perovskite materials can be obtained, achieving full-color luminescence, further verifying the universality of this method. The outer chiral nematic mesoporous silicon film significantly improves the environmental, optical, and thermal stability of the perovskite nanocrystals. The reversible chiral optical property switching can be easily achieved through external stimuli (e.g., chemical environmental reactions). This work provides a general platform for preparing highly circularly polarized photoluminescent materials, with broad application prospects in CPL-related applications.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. The synthesis method of this invention is simple and rapid, and the resulting chiral environment-induced perovskite nanocrystals exhibit strong polarized fluorescence emission. In one embodiment of this invention, its asymmetry factor and anisotropy factor are | g lum |=0.17、| g abs With a value of 0.98 and a tunable wavelength, it can achieve circularly polarized fluorescence emission from blue to red.

[0025] 2. This invention studies the stability of perovskite nanocrystals coated with chiral nematic mesoporous silicon. Due to the protective effect of silicon dioxide, the stability of perovskite nanocrystals is greatly improved, and they exhibit excellent reversibility in heating-cooling cycles.

[0026] 3. This invention studies the circular polarization response induced by a chiral environment in achiral perovskite nanocrystals, which can provide a basis for designing high CPL values ​​and asymmetry factors. g lum Chiral perovskites provide new avenues for the development of chiral optics and improve their performance. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0028] Figure 1 These are scanning electron microscope images of the chiral nematic (CNC / SiO2) composite film and the chiral nematic mesoporous silicon (CNMS) thin film in Embodiment 1 of the present invention;

[0029] Figure 2 This is the circular dichroism (CD) spectrum of the chiral nematic mesoporous silicon (CNMS) thin film in Embodiment 1 of the present invention.

[0030] Figure 3 The images shown are (a) TEM images and (b) mapping images of the chiral nematic perovskite (MAPbBr3-CNMS-510) composite film in Example 1 of this invention.

[0031] Figure 4 The images shown are (a) XRD pattern and (b) XPS pattern of the chiral nematic perovskite (MAPbBr3-CNMS-510) composite film in Example 1 of this invention.

[0032] Figure 5 The images show (a) fluorescence emission spectrum and ultraviolet absorption spectrum, and (b) circularly polarized fluorescence (CPL) spectrum of the chiral nematic perovskite (MAPbBr3-CNMS-510) composite film in Example 1 of this invention.

[0033] Figure 6 The images show (a) UV absorption spectra and (b) fluorescence emission spectra of chiral nematic perovskite (MAPbBr3-CNMS) composite films with different PBGs in Example 1 of this invention.

[0034] Figure 7 The images show (a) circularly polarized fluorescence (CPL) patterns and (b) asymmetry factors of chiral nematic perovskite (MAPbBr3-CNMS) composite films with different PBGs in Example 1 of this invention. g lum A bar chart;

[0035] Figure 8 The images show (a) UV absorption spectra and (b) fluorescence emission spectra of chiral nematic perovskite (MAPbBr3-CNMS) composite films with different loading amounts in Example 2 of this invention.

[0036] Figure 9The images show (a) circularly polarized fluorescence (CPL) patterns and (b) asymmetry factors of chiral nematic perovskite (MAPbBr3-CNMS) composite films with different PBGs in Example 2 of this invention. g lum A bar chart;

[0037] Figure 10 The images show the UV absorption and fluorescence emission spectra of the chiral nematic perovskite (MAPbX3-CNMS) composite films with different halogen compositions in Example 2 of this invention.

[0038] Figure 11 The following are (a) circularly polarized fluorescence (CPL) images and (b) asymmetry factor of the chiral nematic perovskite (MAPbX3-CNMS) composite films with different halogen compositions exhibiting full-spectrum emission in Example 2 of this invention. g lum A bar chart;

[0039] Figure 12 The graphs show (a) the photodynamic stability (PL) of the chiral nematic perovskite (MAPbBr3-CNMS-510) composite film under environmental conditions and (b) the photodynamic stability (PL) under 365 nm UV light irradiation in Example 1 of this invention.

[0040] Figure 13 The graphs show the following: (a) PL thermal stability at 65 °C, (b) PL thermal stability during heating-cooling cycles at 25-95 °C, and (c) circular dichroism performance of the chiral nematic perovskite (MAPbBr3-CNMS-510) composite film in Example 1 of this invention.

[0041] Figure 14 The images show (a) LED diagram and (b) L-CPL and R-CPL diagrams of the chiral nematic perovskite (MAPbBr3-CNMS-510) composite film in Example 1 of this invention. Detailed Implementation

[0042] 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 accompanying drawings.

[0043] In the following examples, cellulose nanocrystals, tetramethoxysilane, cellulose nanocrystal / silica composite membranes, chiral nematic mesoporous silicon films, methylamine halides, and lead halides are referred to by abbreviations:

[0044] Cellulose nanocrystals (CNC), tetramethoxysilane (TMOS), cellulose nanocrystal / silica composite film (CNC / SiO2), chiral nematic mesoporous silica film (CNMS), methylamine halides (MACl, MABr, MAI), lead halides (PbCl2, PbBr2, PbI2).

[0045] Example 1:

[0046] The preparation of a chiral nematic mesoporous silica-coated perovskite nanocrystal with different optical band gaps (PBG) is as follows: The raw materials for the preparation of this composite film include: a certain amount of CNC and TMOS, MABr (0.2 mmol), PbBr2 (0.2 mmol), and N,N-dimethylformamide (1 mL).

[0047] The specific steps are as follows: CNC and TMOS are mixed at room temperature according to a certain ratio (see Table 1 for details), and then self-assembled by evaporation at room temperature to form a CNC / SiO2 composite film; the CNC / SiO2 composite film is calcined at high temperature to obtain a CNMS film. The high-temperature calcination program is to heat from 20 ℃ to 100 ℃ at a rate of 2 ℃ / min, hold for 2 h, then heat to 540 ℃ at a rate of 2 ℃ / min, hold for 6 h, and slowly cool to room temperature. This film is vacuum dried at 150 ℃ for 6 h before complexing with perovskite nanocrystals; MABr (0.2 mmol) and PbBr2 (0.2 mmol) are dissolved in N,N'-dimethylformamide (1 mL) to prepare a perovskite precursor solution; the CNMS film is immersed in the perovskite precursor solution, and the solvent is evaporated at high temperature under vacuum (120 ℃ for 40 min) to obtain MAPbBr3-CNMS composite films with circularly polarized luminescence of different PBGs.

[0048] The specific proportions are shown in Table 1 below:

[0049] CNC TMOS CNMS-400 2 mL 100 µL CNMS-450 2 mL 120 µL CNMS-510 2 mL 140 µL CNMS-580 2 mL 160 µL CNMS-700 2 mL 200 µL

[0050] Example 2:

[0051] The preparation of chiral nematic mesoporous silica-coated perovskite nanocrystals with different perovskite loadings is as follows: The raw materials for the preparation of the composite film include: CNC (2 mL), TMOS (140 µL), MABr and PbBr2 in certain amounts, and N,N-dimethylformamide (1 mL).

[0052] The specific steps are as follows: CNC (2 mL) and TMOS (140 µL) were mixed at room temperature and then evaporated at room temperature to form a CNC / SiO2 composite film. The CNC / SiO2 composite film of this ratio was calcined at high temperature to obtain a CNMS-510 film. The high-temperature calcination program was to heat the film from 20 °C to 100 °C at a rate of 2 °C / min and hold it for 2 h, then heat it to 540 °C at a rate of 2 °C / min and hold it for 6 h, and then slowly cool it to room temperature. The film was vacuum dried at 150 °C for 6 h before complexing with perovskite nanocrystals. A certain amount of MABr and PbBr2 (see Table 2 for details) were dissolved in N,N'-dimethylformamide (1 mL) to prepare a perovskite precursor solution. The CNMS-510 film was immersed in perovskite precursor solutions of different ratios, and the solvent was evaporated at high temperature under vacuum (120 °C for 40 min) to obtain MAPbBr3-CNMS composite films with different loadings of circularly polarized light emission.

[0053] The specific proportions are shown in Table 2 below:

[0054] MABr <![CDATA[PbBr2]]> 0.05 M 0.05 mmol 0.05 mmol 0.1 M 0.1 mmol 0.1 mmol 0.2 M 0.2 mmol 0.2 mmol 0.3 M 0.3 mmol 0.3 mmol 0.4 M 0.4 mmol 0.4 mmol 0.5 M 0.5 mmol 0.5 mmol

[0055] Example 3:

[0056] The preparation of a perovskite nanocrystal coated with different halogens by a full-spectrum circularly polarized fluorescent emission chiral nematic mesoporous silica is as follows: The raw materials for the preparation of this composite film include: CNC, TMOS, MABr and PbBr2 in certain amounts (see Table 3 for details), and N,N-dimethylformamide (1 mL).

[0057] The specific steps are as follows: CNC and TMOS are mixed at a certain room temperature and then evaporated at room temperature to form a CNC / SiO2 composite film. The CNC / SiO2 composite film of this ratio is calcined at high temperature to obtain a CNMS film. The high-temperature calcination program is to heat from 20 ℃ to 100 ℃ at a rate of 2 ℃ / min, hold for 2 h, then heat to 540 ℃ at a rate of 2 ℃ / min, hold for 6 h, and slowly cool to room temperature. This film is vacuum dried at 150 ℃ for 6 h before complexing perovskite nanocrystals. A certain amount of MABr (MACl, MAI) and PbBr2 (PbCl2, PbI2) are dissolved in N,N'-dimethylformamide (1 mL) to prepare a perovskite precursor solution. CNMS films with different PBGs are immersed in different perovskite precursor solutions, and the solvent is evaporated at high temperature (120 ℃ for 40 min) to obtain a MAPbX3-CNMS composite film with full-spectrum circularly polarized fluorescence emission.

[0058] The specific proportions are shown in Table 3 below:

[0059] CNC TMOS MAX <![CDATA[PbX2]]> <![CDATA[MAPbCl2Br]]> 2 mL 120 µL 0.2 mmol MABr <![CDATA[0.2 mmol PbCl2]]> <![CDATA[MAPbClBr2]]> 2 mL 140 µL 0.2 mmol MACl <![CDATA[0.2 mmol PbBr2]]> <![CDATA[MAPbBr3]]> 2 mL 140 µL 0.2 mmol MABr <![CDATA[0.2 mmol PbBr2]]> <![CDATA[MAPbBr2I]]> 2 mL 160 µL 0.2 mmol MAI <![CDATA[0.2 mmol PbBr2]]> <![CDATA[MAPbBrI2]]> 2 mL 160 µL 0.2 mmol MABr <![CDATA[0.2 mmol PbI2]]> <![CDATA[MAPbI3]]> 2 mL 200 µL 0.2 mmol MAI <![CDATA[0.2 mmol PbI2]]>

[0060] Performance testing:

[0061] (a) Template-based representation

[0062] 1. SEM testing of CNC / SiO2 composite film and CNMS thin film

[0063] SEM Sample Preparation: The thin film was adhered to the sample stage using carbon adhesive, aligning the cross-section with the vertical sample stage. Gold was then sprayed onto the film for 40 seconds before testing. Test results are as follows: Figure 1 As shown in the figure, both the prepared CNC / SiO2 composite film and CNMS film exhibit a periodic arrangement and a left-handed helical structure.

[0064] 2. CNMS thin film CD test

[0065] CNMS films with different CNC and TMOS ratios (0.5 cm × 0.5 cm) were mounted on petri dishes for testing. The test results are as follows: Figure 2 As shown, the CD signal peak redshifts as the TMOS content increases.

[0066] (II) Basic Characterization of MAPbBr3-CNMS Thin Films

[0067] 1. MAPbBr3-CNMS thin film TEM test

[0068] First, the composite film was ground into fragments, and then the sample was fixed onto the carbon film for testing. The test results are as follows: Figure 3 As shown, perovskite has been successfully confined within CNMS thin films.

[0069] 2. MAPbBr3-CNMS thin film XRD and XPS tests

[0070] XRD testing: The thin film is placed on the sample stage and tested using a copper target, such as... Figure 4 As shown in figure a, the diffraction peaks of perovskite conform to the cubic crystal system.

[0071] XPS: Tested using Al-Kα rays, such as Figure 4 As shown in b, the sample contains MAPbBr3 and SiO2.

[0072] 3. Fluorescence, UV absorption, and circular polarization fluorescence spectra of MAPbBr3-CNMS thin films.

[0073] from Figure 5As can be seen, the MAPbBr3-CNMS film has the optical properties of MAPbBr3, with band-edge absorption at 510 nm and emission peak at 518 nm. Furthermore, the chiral nematic mesoporous silicon provides a chiral helical structure, which enables the film to exhibit circularly polarized fluorescence emission, with the emission peak position roughly coinciding with the emission peak position of MAPbBr3.

[0074] (III) Optical property testing of MAPbBr3-CNMS composite films with different PBGs

[0075] 1. Ultraviolet absorption spectroscopy and fluorescence spectroscopy testing

[0076] from Figure 6 It can be seen that the band-edge absorption and PL emission peak positions of MAPbBr3-CNMS composite films of different PBGs are roughly the same, without significant changes, and all have the optical properties of MAPbBr3.

[0077] 2. Circular polarization fluorescence spectroscopy test

[0078] The sample was attached to the sample cell and tested using 365 nm light excitation. Figure 7 It can be seen that MAPbBr3-CNMS-510 has the strongest CPL strength. g lum The maximum (0.17) CPL of samples with PBG far from the emission peak of MAPbBr3 decreased, indicating that PBG has a significant impact on the CPL intensity. The closer PBG is to the emission peak, the stronger the CPL.

[0079] (iv) Optical property testing of MAPbBr3-CNMS composite films with different perovskite loadings

[0080] 1. Ultraviolet absorption spectroscopy and fluorescence spectroscopy testing

[0081] from Figure 8 It can be seen that the band-edge absorption and PL emission peak positions of MAPbBr3-CNMS composite films with different perovskite loadings are roughly the same, without significant changes.

[0082] 2. Circular polarization fluorescence spectroscopy test

[0083] The sample was attached to the sample cell and tested using 365 nm light excitation. Figure 9 It can be seen that 0.2 MMAPbBr3-CNMS has the strongest CPL strength. g lum |Maximum (0.17), CPL increases with increasing concentration. When the concentration is greater than 0.2M, fluorescence quenching occurs due to excessive concentration, which in turn reduces CPL.

[0084] (v) Optical property testing of full-spectrum emission MAPbX3-CNMS composite films with different halogen compositions

[0085] 1. Ultraviolet absorption spectroscopy and fluorescence spectroscopy testing

[0086] from Figure 10 It can be seen that as the halogen composition changes from Cl-I, the band edge absorption and PL emission peak positions of the MAPbX3-CNMS composite film also show a significant red shift, exhibiting the same trend as MAPbX3 without CNMS film coating.

[0087] 2. Circular polarization fluorescence spectroscopy test

[0088] The sample is attached to the sample cell and tested using corresponding light excitation. From Figure 11 It can be seen that as the halogen composition changes from Cl-I, the CPL emission peak position of the MAPbX3-CNMS composite film also shows a significant red shift, with MAPbBr3-CNMS exhibiting the strongest CPL intensity. g lum The maximum value (0.17) indicates that the stronger the light emission, the stronger the CPL intensity.

[0089] (vi) Stability test of MAPbBr3-CNMS composite membrane

[0090] 1. Environmental stability test

[0091] Place the sample RH In an environment of 65±5%, fluorescence spectroscopy was performed at fixed time intervals. The specific steps are as follows: the sample was placed in a solid sample cell and excited with 365 nm light for testing. Figure 12 It can be seen that the fluorescence emission of the sample did not decrease significantly after one week.

[0092] 2. Light stability test

[0093] The sample was continuously irradiated under a 365 nm ultraviolet lamp, and fluorescence spectroscopy was measured at fixed time intervals. The specific steps are as follows: the sample was placed in a solid sample holder and excited with 365 nm light for testing. Figure 12 It can be seen that the photostability of the MAPbBr3-CNMS composite film is much stronger than that of the MAPbBr3 thin film.

[0094] 3. Thermal stability test

[0095] from Figure 13 It can be seen that the MAPbBr3-CNMS composite film exhibits superior stability at 65 ℃ compared to the MAPbBr3 film, and PL demonstrates excellent heat-cooling recovery, with a low anisotropy factor. gabs The absence of significant changes after 10 heating-cooling cycles indicates good thermal stability and strong reversibility.

[0096] Example 4:

[0097] Device fabrication: A 0.5 cm × 0.5 cm MAPbBr3-CNMS composite film was attached to a 375 nm UV lamp bead to obtain a photoluminescent LED device. A quarter-wave plate and a polarizer were placed between the sample and the spectrometer. The right-handed and left-handed circularly polarized light transmitted through the sample were detected by rotating the quarter-wave plate.

[0098] like Figure 14 As shown, the device exhibits excellent green light emission performance and good selectivity in distinguishing between left- and right-circularly polarized light.

[0099] This invention utilizes template-confined growth of perovskite nanocrystals. A multifunctional strategy was developed to create a combination of circularly polarized fluorescent metal halide perovskites and CNMS films, exhibiting excellent compositional control. The CNMS film simultaneously enhances the control over the size of the perovskite nanocrystals, the selective reflectivity of the L-CPL, and effectively protects the perovskite nanocrystals from aggregation and degradation. By rationally adjusting the photonic bandgap of the CNMS film and the loading of the perovskite nanocrystals, the luminescence asymmetry factor value was successfully obtained. g lum |in 10 -1 It exhibits orders-of-magnitude full-color emission and circularly polarized luminescence. Furthermore, the porous silica-based host provides enhanced lightfastness and high-temperature stability for the guest perovskite nanocrystals, facilitating their integration into CP-LED devices. Due to its pronounced circularly polarized fluorescence emission, it can be widely applied in photodetectors, polarization optics, and other fields.

[0100] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing chiral nematic mesoporous silicon-induced perovskite nanocrystals to generate circularly polarized luminescence, characterized in that... Its preparation method includes the following steps: S1: Using cellulose nanocrystals as the source of chiral hard templates, the cellulose nanocrystals and silicon source are mixed and then evaporated at room temperature to self-assemble into a cellulose nanocrystal / silica composite film. S2: Chiral nematic mesoporous silicon thin film is obtained by high-temperature calcination of cellulose nanocrystal / silica composite film; S3: Using lead halide and methylamine halide as perovskite precursors and N,N'-dimethylformamide as solvent, a precursor solution is formed; S4: The chiral nematic mesoporous silicon film obtained in S2 is immersed in the precursor solution prepared in S3, and the solvent is evaporated at high temperature and vacuum to obtain a chiral nematic perovskite composite film with circularly polarized light emission. The specific steps are as follows: 2 mL of cellulose nanocrystals and 140 μL of tetramethoxysilane were stirred and mixed at room temperature, and then evaporated at room temperature to form a cellulose nanocrystal / silica composite film. The cellulose nanocrystal / silica composite film was calcined at high temperature to obtain a chiral nematic mesoporous silica film. The high-temperature calcination program was as follows: the temperature was increased from 20 °C to 100 °C at a rate of 2 °C / min, held for 2 h, then increased to 540 °C at a rate of 2 °C / min, held for 6 h, and slowly cooled to room temperature. This film was vacuum dried at 150 °C for 6 h before complexing with perovskite nanocrystals. 0.2 mmol of methylamine bromide and 0.2 mmol of lead iodide were dissolved in 1 mL of N,N'-dimethylformamide to prepare a perovskite precursor solution. The chiral nematic mesoporous silica film was immersed in the perovskite precursor solution, and the solvent was vacuum evaporated at 120 °C for 40 min to obtain a chiral nematic perovskite composite film with a photonic bandgap of 510 nm and circularly polarized light emission. S5: Place the composite film obtained in S4 onto the chip, turn on the power, and set a fixed current and voltage to make it emit light.

2. The application of the preparation method as described in claim 1 in circularly polarized LEDs.

Images