Chiral perovskite thin films, methods of preparation, and circularly polarized light emitting diode devices

Abstract

This invention belongs to the field of polarized light-emitting materials technology, specifically relating to chiral perovskite thin films, their preparation methods, and circularly polarized light-emitting diode devices. The invention uses phenylalanine hydrochloride as a raw material, mixing phenylalanine hydrochloride solution and tetrafluoroborate solution to undergo an ion exchange reaction, forming a chiral compound with tetrafluoroborate as the anion and phenylalanine as the cation, thus obtaining a pseudohalogenated chiral ligand. Using an antisolvent, the pseudohalogenated chiral ligand is introduced into the perovskite precursor solution, forming a chiral perovskite thin film at the perovskite interface. This allows for the effective injection of spin-polarized charge carriers through chiral-induced spin selectivity, resulting in recombination within the device and the generation of circularly polarized light emission.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polarized light-emitting materials, and particularly relates to a chiral perovskite film, a preparation method and a circularly polarized light-emitting diode device. BACKGROUND

[0002] Traditional 3D display schemes mainly rely on polarization multiplexing technology to realize stereoscopic imaging, and the principle is to separate different polarization state light rays in natural light through optical devices, and independently modulate each polarization state light field. However, this technical path has the following inherent defects: the introduction of optical devices leads to the complication of the system structure, the polarization conversion efficiency is limited by the material optical anisotropy, and the actual device efficiency is difficult to break through the theoretical limit; the viewing angle range and the depth of field are limited by the light field modulation dimension, and it is difficult to meet the demand of free viewing at large viewing angles.

[0003] To break through the traditional technical framework, circularly polarized light-emitting diode technology based on chiral light-emitting materials has become a research hotspot. This technology directly emits circularly polarized light through the intrinsic chiral optical properties of the material, which fundamentally avoids the efficiency loss of optical devices. However, the existing chiral light-emitting material system is mainly organic polymers and organic small molecule materials, which are limited by factors such as high cost, low carrier mobility, and low electric circularly polarized light polarization rate. Therefore, it is difficult to simultaneously consider the light-emitting efficiency and the light-emitting polarization rate of the devices prepared by using chiral light-emitting materials, which is not conducive to the application in the field of 3D display.

[0004] In recent years, organic-inorganic metal halide perovskite materials have attracted industry attention due to their excellent optoelectronic properties. This material system has achieved a leap from 3.8% to 33.9% in the efficiency of light-emitting diodes, showing great potential as a new generation of display material. In particular, by introducing chiral organic ligands, perovskite materials can be endowed with intrinsic circularly polarized light-emitting properties, achieving a circularly polarized light asymmetry factor of up to 0.8 at room temperature. In addition, the chiral perovskite system exhibits spin selection characteristics, and the carrier injection efficiency is highly selective to the spin direction of the chiral layer, providing a theoretical possibility for realizing high-polarization electric circularly polarized light emission.

[0005] For example, Reference 1: Ma J, Fang C, Chen C, et al. Chiral 2D perovskites with a high degree of circularly polarized photoluminescence[J]. ACS Nano, 2019, 13(3): 3659-3665.; Reference 1 used (S / R)-1-(1-naphthyl)ethylammonium iodide to partially replace the non-chiral phenylethylammonium iodide to prepare a chiral perovskite film, obtaining a circularly polarized light polarization of 2.1%; using the chiral perovskite film as the light-emitting layer of a spin LED device, the spin LED device obtained an external quantum efficiency of 3.7% and a circularly polarized electroluminescence polarization of 0.4%. Reference 2: Gao H, Chen Y, Zhang R, et al. Dual-ligand quasi-2Dperovskites with chiral-induced spin selectivity for room temperature spin-LEDs[J]. Materials Horizons, 2024, 11(12): 2906-2913.; Reference 2 uses R- / S-methylbenzylammonium and R- / S-2-phenylethylammonium as dual ligands for chiral perovskites. It utilizes the synergistic effect of the dual ligands to achieve efficient chiral transfer, obtaining a circular polarization luminescence polarization of 2.5% and an external quantum efficiency of 3.8%.

[0006] However, the introduction of chiral organic ligands into perovskite materials can lead to lattice distortion at the perovskite interface due to the large steric hindrance effect of the cations in the chiral organic ligands, which disrupts the structural symmetry. Although chirality can be generated, a large number of deep-level defects will be formed at the interface, resulting in severe exciton quenching and affecting the stability of the material and the efficiency of the device. Summary of the Invention

[0007] To address the technical problem that the large steric hindrance effect of cations in existing chiral organic ligands induces lattice distortion at the perovskite interface, disrupts structural symmetry, and forms numerous defects at the interface, this invention provides a chiral perovskite thin film, a preparation method, and a circularly polarized light-emitting diode device.

[0008] This invention uses phenylalanine hydrochloride as a raw material. A solution of phenylalanine hydrochloride and a solution of tetrafluoroborate are mixed to undergo an ion exchange reaction, forming a chiral compound with tetrafluoroborate as the anion and phenylalanine as the cation, yielding a pseudohalogenated chiral ligand. This invention utilizes an antisolvent to introduce the pseudohalogenated chiral ligand into a perovskite film, forming a chiral perovskite layer at the perovskite interface. The phenylalanine cation in the chiral ligand interacts with the coordinatingly unsaturated Pb at the perovskite interface through the lone pair electrons on the carbonyl C=O group. 2+ Ion coordination can effectively passivate deep-level defects, thereby improving device efficiency. At the same time, the introduction of a chiral perovskite layer can effectively inject spin-polarized charge carriers through chirality-induced spin selectivity, which recombine inside the device to generate circularly polarized light emission. This solves the technical problem that the large steric hindrance effect of cations in existing chiral organic ligands induces lattice distortion at the perovskite interface, destroys structural symmetry, and forms a large number of defects at the interface, which seriously affects the stability of materials and device efficiency.

[0009] The first objective of this invention is to provide a method for preparing a chiral perovskite thin film, comprising the following steps:

[0010] A phenylalanine hydrochloride solution and a tetrafluoroborate solution were mixed to undergo an ion exchange reaction, forming a chiral compound with tetrafluoroborate as the anion and phenylalanine as the cation. After the reaction, the mixture was filtered, and the filtrate was distilled under reduced pressure to obtain a pseudohalogenated chiral ligand. The pseudohalogenated chiral ligand was mixed with an antisolvent to obtain an antisolvent containing the chiral ligand. The perovskite precursor solution was coated onto a substrate material, and the antisolvent containing the chiral ligand was added dropwise before the spin coating was completed. After spin coating, the mixture was annealed to obtain a chiral perovskite film formed on the substrate material.

[0011] Preferably, the molar ratio of phenylalanine hydrochloride in the phenylalanine hydrochloride solution to tetrafluoroborate in the tetrafluoroborate solution is 1:1.

[0012] Preferably, the phenylalanine hydrochloride solution is obtained by dissolving phenylalanine hydrochloride in a solvent.

[0013] Preferably, the tetrafluoroborate solution is obtained by dissolving tetrafluoroborate in water.

[0014] Preferably, the phenylalanine hydrochloride is D-phenylalanine hydrochloride or L-phenylalanine hydrochloride; the tetrafluoroborate is silver tetrafluoroborate.

[0015] It should be noted that phenylalanine hydrochloride ionizes in the solvent, forming phenylalanine cations and chloride ions; silver tetrafluoroborate ionizes in water to produce silver ions and tetrafluoroborate ions. When silver tetrafluoroborate and phenylalanine hydrochloride solutions are mixed, the silver ions combine with the chloride ions to form a sparingly soluble silver chloride precipitate, promoting the reaction towards the formation of phenylalanine tetrafluoroborate. This yields a chiral compound with tetrafluoroborate as the anion and phenylalanine as the cation, resulting in a pseudohalogenated chiral ligand. The phenylalanine cation in the pseudohalogenated chiral ligand interacts with the coordinatingly unsaturated Pb at the perovskite interface via the lone pair electrons on the carbonyl C=O group. 2+ Ion coordination passivates deep-level defects; simultaneously, BF4 in pseudohalogen-substituted chiral ligands is utilized. - Anions passivate the movement of halide ions, creating shallow energy level defects with vacancies. The chirality in chiral perovskites is achieved through the interaction of chiral ammonia with the inorganic metal octahedron [PbBr6]. -4 The ionic interactions enable the transformation from chiral ligands to [PbBr6]. -4 Chiral transfer.

[0016] To control the reaction rate between silver tetrafluoroborate solution and phenylalanine hydrochloride solution, the silver tetrafluoroborate solution was slowly added dropwise to the phenylalanine hydrochloride solution. This avoided excessively vigorous local reactions, facilitated sufficient ion exchange, and improved the reaction yield and product purity.

[0017] Preferably, the solvent is ethanol, which can disperse phenylalanine hydrochloride, ensuring its complete dissolution and providing conditions for subsequent ion exchange reactions. Simultaneously, ethanol allows for uniform mixing of phenylalanine hydrochloride, guaranteeing the full progress of the reaction.

[0018] Preferably, the chemical formula of the perovskite precursor solution is PEA2FA2Pb3Br. 10 .

[0019] Preferably, the antisolvent is chlorobenzene.

[0020] Preferably, the annealing temperature is 90℃~100℃ and the time is 10min~15min.

[0021] Preferably, the antisolvent containing the chiral ligand is added 30 to 40 seconds before the spin coating is finished.

[0022] A second objective of this invention is to provide a chiral perovskite thin film, which is prepared by the above-described method for preparing chiral perovskite thin films.

[0023] A third objective of this invention is to provide a circularly polarized light-emitting diode (LED) device, which includes an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode layer stacked sequentially.

[0024] Preferably, the light-emitting layer is a chiral perovskite thin film.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] This invention uses phenylalanine hydrochloride as a raw material. A solution of phenylalanine hydrochloride and a solution of tetrafluoroborate are mixed to undergo an ion exchange reaction, forming a chiral compound with tetrafluoroborate as the anion and phenylalanine as the cation, yielding a pseudohalogenated chiral ligand. This invention utilizes an antisolvent to introduce the pseudohalogenated chiral ligand into a perovskite film, forming a chiral perovskite layer at the perovskite interface. The phenylalanine cation in the chiral ligand interacts with the coordinatingly unsaturated Pb at the perovskite interface through the lone pair electrons on the carbonyl C=O group. 2+ Ion coordination can effectively passivate deep-level defects, thereby improving device efficiency. At the same time, the introduction of a chiral perovskite layer can effectively inject spin-polarized charge carriers through chirality-induced spin selectivity, which recombine inside the device to generate circularly polarized light emission. This solves the technical problem that the large steric hindrance effect of cations in existing chiral organic ligands induces lattice distortion at the perovskite interface, destroys structural symmetry, and forms a large number of defects at the interface, which seriously affects the stability of materials and device efficiency.

[0027] The process of this invention is simple and does not require the separate fabrication of a chiral perovskite layer to induce spin carrier injection. The circularly polarized light-emitting diode (LED) device of this invention exhibits high external quantum efficiency. The defect passivation capability of chiral ions improves the film quality, suppresses nonradiative recombination, and enhances device efficiency. The circularly polarized LED device of this invention also exhibits high circular polarization susceptibility. By forming a high-quality chiral perovskite interface in situ, the lifetime of spin excitons is improved, thereby increasing the diffusion length of spin excitons and enhancing the circular polarization luminescence efficiency. Attached Figure Description

[0028] Figure 1 The images show the 1H NMR spectrum of L-phenylalanine hydrochloride and the 1H NMR spectrum of its chiral ligand L-CHP. (a) is the 1H NMR spectrum of L-phenylalanine hydrochloride; (b) is the 1H NMR spectrum of its chiral ligand L-CHP.

[0029] Figure 2 The images show the 1H NMR spectrum of D-phenylalanine hydrochloride and the 1H NMR spectrum of its chiral ligand D-CHP. (a) is the 1H NMR spectrum of D-phenylalanine hydrochloride; (b) is the 1H NMR spectrum of its chiral ligand D-CHP.

[0030] Figure 3 Field emission scanning electron microscope (FESEM) images of chiral perovskite thin films prepared in Examples 1 and 2. (a) is Example 1; (b) is Example 2.

[0031] Figure 4 Field emission scanning electron microscopy (FEM) image of the cross-section of the circularly polarized light-emitting diode (LED) device prepared in Example 1. In this image, ITO (indium tin oxide) is used as the anode layer; PEDOT:PSS is the hole transport layer; Q-2D perovskite is a chiral perovskite film used as the light-emitting layer; TPBi is the electron transport layer; LiF is the electron injection layer; and Al is the cathode layer.

[0032] Figure 5 The performance characterization results of the circularly polarized light-emitting diode devices prepared in Application Example 1 and Application Example 2 are shown below. (a) shows the voltage-luminance curve; (b) shows the external quantum efficiency and current efficiency; (c) shows the electroluminescence spectra of left- and right-circularly polarized light from the circularly polarized light of the device prepared in Application Example 1; (d) shows the electroluminescence spectra of left- and right-circularly polarized light from the device prepared in Application Example 2; (e) shows the electro-circularly polarized emission spectrum; and (f) shows the electro-circularly polarized light polarization susceptibility in the wavelength range of 510 nm to 550 nm. Detailed Implementation

[0033] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0034] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0035] The preparation method of the chiral ligand L-CHP includes the following steps:

[0036] 1.652 g of L-phenylalanine hydrochloride was dissolved in 20 mL of ethanol and stirred at room temperature until completely dissolved to obtain an L-phenylalanine hydrochloride solution.

[0037] Silver tetrafluoroborate was dissolved in 20 mL of deionized water and stirred at room temperature until completely dissolved to obtain a silver tetrafluoroborate solution.

[0038] Silver tetrafluoroborate solution was slowly added dropwise to L-phenylalanine hydrochloride solution, at which point a large amount of white solid precipitated. After stirring for 2 hours, the mixture was filtered, and the filtrate was distilled under reduced pressure to obtain a white solid chiral organic ligand, namely L-phenylalanine tetrafluoroborate, denoted as L-CHP. The synthetic route is shown below:

[0039] .

[0040] The preparation method of the chiral ligand D-CHP includes the following steps:

[0041] Dissolve 1.652 g of D-phenylalanine hydrochloride in 20 mL of ethanol and stir at room temperature until completely dissolved to obtain a D-phenylalanine hydrochloride solution.

[0042] Silver tetrafluoroborate was dissolved in 20 mL of deionized water and stirred at room temperature until completely dissolved to obtain a silver tetrafluoroborate solution.

[0043] Silver tetrafluoroborate solution was slowly added dropwise to D-phenylalanine hydrochloride solution, at which point a large amount of white solid precipitated. After stirring for 2 hours, the mixture was filtered, and the filtrate was distilled under reduced pressure to obtain a white solid chiral organic ligand, namely D-phenylalanine tetrafluoroborate, denoted as D-CHP. Its synthetic route is shown in the following formula:

[0044] .

[0045] Example 1

[0046] A method for preparing a chiral perovskite thin film includes the following steps:

[0047] Step 1: Prepare perovskite precursor solution:

[0048] In a glove box under a nitrogen atmosphere, 4.04 mg of methylammonium chloride, 23.8 mg of potassium bromide, 220.2 mg of lead bromide, 50 mg of formamidinium hydrobromide, and 80.8 mg of phenylethylammonium bromide were added to a glass bottle, along with 1 mL of dimethyl sulfoxide. The mixture was heated and stirred at 60 °C for 3 hours until all the solids were dissolved. The solution was then filtered through a 0.22 μm filter to obtain the filtrate, which is the perovskite precursor solution. The perovskite precursor solution was kept heated at 60 °C for later use.

[0049] Step 2: Prepare an antisolvent containing a chiral ligand:

[0050] The chiral ligand L-CHP was dissolved in chlorobenzene to obtain an antisolvent containing the chiral ligand at a concentration of 1 mg / mL, which was then left to stand in a glove box for later use.

[0051] Step 3: Preparation of chiral perovskite thin films:

[0052] After cleaning the glass, it is treated with plasma irradiation for 15 minutes to obtain pretreated glass.

[0053] In a glove box under nitrogen atmosphere, the pretreated glass was placed on a spin coater and fixed under vacuum. The spin coating conditions were set as follows: spin at 1000 rpm for 7 seconds, and then at 5000 rpm for 60 seconds. 60 L of perovskite precursor solution was measured with a pipette and added dropwise to the pretreated glass. When the glass was rotated at 5000 rpm for 20 seconds, an antisolvent containing chiral ligands was added dropwise. After spin coating, the glass was annealed on a 90°C heating plate for 10 minutes to obtain a chiral perovskite film.

[0054] Example 2

[0055] A method for preparing a chiral perovskite thin film includes the following steps:

[0056] The difference between Example 2 and Example 1 is as follows:

[0057] Chiral ligand D-CHP was used to prepare antisolvents containing chiral ligands.

[0058] Application Example 1

[0059] A method for fabricating a circularly polarized light-emitting diode (LED) device includes the following steps:

[0060] Step 1: Prepare the hole transport layer:

[0061] After cleaning the ITO glass, it was treated with plasma irradiation for 15 minutes to obtain pretreated ITO glass. A layer of poly(2,3-dihydrothiophene-1,4-dioxin)-poly(styrene sulfonate) was spin-coated on the pretreated ITO glass to obtain a hole transport layer, denoted as PEDOT:PSS.

[0062] Step 2: Prepare the light-emitting layer:

[0063] In a glove box under a nitrogen atmosphere, 4.04 mg of methylammonium chloride, 23.8 mg of potassium bromide, 220.2 mg of lead bromide, 50 mg of formamidinium hydrobromide, and 80.8 mg of phenylethylammonium bromide were added to a glass bottle, along with 1 mL of dimethyl sulfoxide. The mixture was heated and stirred at 60 °C for 3 hours until all the solids were dissolved. The solution was then filtered through a 0.22 μm filter to obtain the filtrate, which is the perovskite precursor solution. The perovskite precursor solution was kept heated at 60 °C for later use.

[0064] The chiral ligand L-CHP was dissolved in chlorobenzene to obtain an antisolvent containing the chiral ligand at a concentration of 1 mg / mL, which was then left to stand in a glove box for later use.

[0065] In a glove box under a nitrogen atmosphere, the ITO glass coated with PEDOT:PSS was placed on a spin coater and fixed under vacuum. The spin coating conditions were set as follows: spin at 1000 rpm for 7 seconds, and then at 5000 rpm for 60 seconds. 60 L of perovskite precursor solution was pipetted onto the PEDOT:PSS. When the spin coating was at 5000 rpm for 20 seconds, an antisolvent containing chiral ligands was added. After spin coating, the film was annealed on a 90°C heating plate for 10 minutes to obtain a chiral perovskite film, i.e., the luminescent layer.

[0066] Step 3: Fabrication of the electron transport layer:

[0067] The chiral perovskite film was transferred to a vacuum evaporation chamber, and the vacuum level was reduced to 6 × 10⁻⁶. -5 Below Pa, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, abbreviated as TPBi, is deposited on the substrate, and the initial TPBi deposition rate is set to 0.2 Å / s. When the TPBi deposition thickness exceeds 10 nm, the TPBi deposition rate is increased to 0.5 Å / s to obtain an electron transport layer with a thickness of 50 nm.

[0068] Step 4: Fabrication of circularly polarized light-emitting diode device:

[0069] After TPBi deposition, LiF was deposited at a rate of 0.1 Å / s to obtain an electron injection layer with a thickness of 1 nm. Following LiF deposition, an aluminum electrode was deposited at a rate of 0.9 Å / s to obtain a circularly polarized light-emitting diode device, denoted as a spin-LED. The effective area of ​​the spin-LED depends on the overlapping portion of the ITO and aluminum electrodes, and is 4 mm². 2 .

[0070] Application Example 2

[0071] A method for fabricating a circularly polarized light-emitting diode (LED) device includes the following steps:

[0072] The difference between Application Example 2 and Application Example 1 is as follows:

[0073] Chiral ligand D-CHP was used to prepare antisolvents containing chiral ligands.

[0074] I. Nuclear magnetic resonance hydrogen spectrum test.

[0075] This invention performed NMR verification on L-phenylalanine hydrochloride raw materials, D-phenylalanine hydrochloride raw materials, and chiral ligands L-CHP and D-CHP, and the test results are as follows. Figures 1-2 As shown.

[0076] II. Surface morphology test.

[0077] like Figure 3 As shown, the chiral perovskite films prepared in Examples 1 and 2 have small and very dense grain sizes. The small grain radius can provide more recombination centers for bimolecular radiative recombination of charge carriers, and the dense film can effectively avoid the generation of leakage current, thereby improving the efficiency of the device.

[0078] like Figure 4 As shown, in the field emission scanning electron microscope imaging of the cross-section of the circularly polarized light-emitting diode device prepared in Application Example 1, ITO is used as the anode layer; PEDOT:PSS is the hole transport layer; Q-2D perovskite is a chiral perovskite film, which is the light-emitting layer of the circularly polarized light-emitting diode device; TPBi is the electron transport layer; LiF is the electron injection layer; and Al is the cathode layer. The working mechanism of the circularly polarized light-emitting diode device is as follows: When an external bias voltage is applied to the circularly polarized light-emitting diode device, electrons injected through the cathode and holes injected through the anode are transported to the perovskite layer through the electron transport layer and hole transport layer, respectively. Due to the presence of the chiral two-dimensional perovskite layer near the electron transport layer, electrons injected through the electron transport layer pass through the chiral perovskite layer at the interface. Due to the chiral-induced spin selectivity effect, only electrons with specific spin directions are allowed to pass through, generating polarized electrons, which recombine on the three-dimensional perovskite to produce circularly polarized light emission.

[0079] III. Photoelectric performance testing.

[0080] like Figure 5 As shown in (a) of the diagram, introducing the chiral ligand L-CHP into the perovskite interface during perovskite crystal growth can effectively reduce the device's injection barrier, thereby increasing the turn-on voltage; similarly, introducing the chiral ligand D-CHP into the perovskite interface during perovskite crystal growth can effectively reduce the device's injection barrier, thereby increasing the turn-on voltage. Figure 5 As shown in (b), the spin-LED device fabricated using the chiral ligand D-CHP achieved an external quantum efficiency exceeding 13% and a current efficiency of 50 cd / A. Figure 5 As shown in (c), σ + For left-circularly polarized light, σ - The light emitted is right-circularly polarized; spin-LED devices prepared using the chiral ligand L-CHP exhibit significant left-circularly polarized light emission, with a corresponding circularly polarized emission polarization exceeding 11%; such as Figure 5 As shown in (d), σ + For left-circularly polarized light, σ - Right-circularly polarized light; spin-LED devices prepared using the chiral ligand D-CHP exhibit distinct right-circularly polarized light emission; such as Figure 5As shown in (e), the electroluminescence spectra of the spin-LED devices prepared in Application Example 1 and Application Example 2 have obvious circularly polarized emission signals.

[0081] In summary, this invention introduces chiral ligands into the perovskite interface, utilizing the pseudohalogen BF4 within the chiral ligands. - Ions can fill halide vacancies, thereby passivating vacancy defects in the perovskite interface. The lone pair electrons of oxygen on the C=O and -OH groups of the chiral ligands can effectively coordinate with the unsaturated Pb. 2+ Ions interact by forming ionic bonds, thereby effectively passivating Pb. 2+ Ion defects. Due to the defect passivation capability of chiral interfaces, the current efficiency, external quantum efficiency, and circularly polarized emission efficiency of the device are effectively improved, showing great promise for applications in the field of glasses-free 3D displays.

[0082] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0083] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If these modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a chiral perovskite thin film, characterized in that, Includes the following steps: A phenylalanine hydrochloride solution and a tetrafluoroborate solution were mixed to undergo an ion exchange reaction, forming a chiral compound with tetrafluoroborate as the anion and phenylalanine as the cation. After the reaction was completed, the mixture was filtered, and the filtrate was distilled under reduced pressure to obtain a pseudohalogenated chiral ligand. A halogen-substituted chiral ligand is mixed with an antisolvent to obtain an antisolvent containing the chiral ligand; a perovskite precursor solution is coated onto a substrate material, and the antisolvent containing the chiral ligand is dropped in before the spin coating is finished. After the spin coating is finished, an annealing treatment is performed to obtain a chiral perovskite film formed on the substrate material. The molar ratio of phenylalanine hydrochloride in the phenylalanine hydrochloride solution to tetrafluoroborate in the tetrafluoroborate solution is 1:1; Phenylalanine hydrochloride is D-phenylalanine hydrochloride or L-phenylalanine hydrochloride; tetrafluoroborate is silver tetrafluoroborate. The chemical formula of the perovskite precursor solution is PEA2FA2Pb3Br. 10 .

2. The method for preparing a chiral perovskite thin film according to claim 1, characterized in that, Phenylalanine hydrochloride solution is obtained by dissolving phenylalanine hydrochloride in a solvent; tetrafluoroborate solution is obtained by dissolving tetrafluoroborate in water.

3. The method for preparing chiral perovskite thin films according to claim 2, characterized in that, The solvent is ethanol.

4. The method for preparing a chiral perovskite thin film according to claim 1, characterized in that, The antisolvent is chlorobenzene.

5. The method for preparing a chiral perovskite thin film according to claim 1, characterized in that, The annealing temperature is 90℃~100℃.

6. A chiral perovskite thin film, characterized in that, The chiral perovskite thin film is prepared by the method for preparing chiral perovskite thin films according to any one of claims 1 to 5.

7. A circularly polarized light-emitting diode device, characterized in that, The circularly polarized light-emitting diode device comprises an anode layer, a hole transport layer, a light-emitting layer, an electron transport layer, and a cathode layer stacked sequentially; the light-emitting layer is the chiral perovskite thin film as described in claim 6.

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