Preparation method and application of chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film

Abstract

The invention belongs to the field of optoelectronic materials and nonlinear optical application, and particularly relates to a preparation method of a chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film. The method comprises the following steps: (1) preparing a chiral perovskite precursor solution; (2) preparing a perovskite quantum dot solution; (3) purifying the perovskite quantum dots; and (4) preparing the chiral perovskite / perovskite quantum dot heterojunction double-layer thin film. According to the technical scheme, the chiral perovskite thin film and the perovskite quantum dot thin film are combined, the preparation process of the constructed chiral perovskite / perovskite quantum dot heterojunction double-layer thin film is simple and rapid, and the heterojunction double-layer thin film has very high nonlinear optical activity. In addition, the chiral perovskite / perovskite quantum dot heterojunction double-layer thin film can be integrated to a device easily, and the circularly polarized light emitting and detection dual-function device can be realized easily.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optoelectronic materials and nonlinear optics, and in particular to a preparation method and application of a chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film. BACKGROUND

[0002] Perovskite is a kind of semiconductor material with excellent optical and photochemical properties, which is widely used in solar cells, light-emitting diodes, memristors, photocatalysis and other fields. The crystal structure of conventional perovskite material can be represented by ABX3, in which A represents an organic cation, B represents a metal cation, and X represents a halide anion. By changing the different chemical components in the perovskite structure, the effective regulation of the semiconductor physical properties of perovskite materials such as photo-electric-magnetic can be realized. Based on the unique crystal structure of perovskite material, the non-chiral organic cation at the A site of perovskite is replaced by a chiral organic cation to form a chiral organic-inorganic hybrid perovskite, hereinafter referred to as chiral perovskite. Chiral perovskite material has a significant chiral optical response, i.e. natural optical activity, such as circular dichroism and circularly polarized luminescence characteristics. This makes chiral perovskite material expected to be applied in the field of circularly polarized luminescence, detection, laser and other nonlinear optics.

[0003] At present, chiral perovskite single crystals are ideal materials as circularly polarized light sources. However, due to the preparation method of the single crystal material and the defects of the material itself, the application range of the chiral perovskite single crystal is greatly limited. The defects of the existing preparation method are: (1) the preparation process of the chiral perovskite single crystal is complicated and time-consuming; (2) the yield of the synthesized single crystal is low; (3) the single crystal is low in purity due to the residual solvent; (4) the single crystal is in the form of needle or powder, which is not conducive to device integration; the defects of the material itself include: (1) the introduced chiral organic molecule has a complex structure and a large volume, which can cause high distortion of the chiral perovskite crystal structure or local stress, so that new defect states are formed in the crystal. These defect states often act as non-radiative recombination centers, which can cause the excitation to dissipate energy without emitting light, thereby significantly reducing the light-emitting efficiency. (2) Strong exciton-phonon coupling effect exists in the low-dimensional structure of the chiral perovskite single crystal (such as two-dimensional or zero-dimensional), which is easy to form self-trapped excitons. The self-trapped exciton is an excited state particle which is bound by local lattice distortion and is difficult to radiate and recombine efficiently. (3) Although the chiral perovskite single crystal can produce broadband emission in some cases, the light-emitting efficiency is usually low, which is not suitable for application in high-brightness and high-efficiency electroluminescent devices. In addition, there is another method to obtain nonlinear optical effect, which is to construct a chiral perovskite-non-chiral perovskite core-shell structure by a self-assembly chemical method, wherein the chiral perovskite is used as the shell layer and the three-dimensional non-chiral perovskite is used as the core layer. Although the nonlinear optical activity of the core-shell structure is indeed stronger than that of the single chiral perovskite single crystal, due to the complex preparation process, harsh experimental conditions, uncontrollable and unstable core-shell structure in the preparation process, long experimental time, complex characterization of the core-shell structure of the sample, and the disadvantage of device integration, the development of nonlinear optical devices is seriously restricted. SUMMARY

[0004] In order to simplify the preparation method and experimental steps of the chiral perovskite single crystal, the application provides a preparation method of a chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film. The technical scheme directly configures a chiral perovskite precursor solution by using the characteristics that the bromide chiral ligand, lead bromide and the organic polar solvent are mutually soluble, and then a chiral perovskite film is prepared by a solution spin coating method, without the need to prepare a chiral perovskite single crystal and a chiral perovskite-non-chiral perovskite core-shell structure and without the need to use a high-temperature heat source and an oil bath device.

[0005] The specific technical scheme of the application is as follows:

[0006] 1. A preparation method of a chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film, comprising the following steps:

[0007] (1) The chiral perovskite precursor solution is configured by mixing a chiral organic ligand, lead bromide solid powder and a polar solution, and the chiral organic ligand is R-(+)-3-bromo-1-phenylethyl amine or S-(-)-3-bromo-1-phenylethyl amine;

[0008] (2) The perovskite quantum dot solution is prepared by first preparing a lead bromide precursor solution by dissolving lead bromide, tetra-n-octylammonium bromide and toluene; then mixing cesium carbonate solution and formamidine acetate solution to obtain a cesium precursor solution; dissolving dodecyl dimethyl ammonium bromide and 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene in toluene respectively to obtain passivator A and passivator B, respectively; mixing the lead bromide precursor solution and the cesium precursor solution and stirring uniformly, then adding passivator A and stirring uniformly, and then adding passivator B and stirring uniformly, and then sealing and standing the solution to obtain a CsPbBr3 perovskite quantum dot solution;

[0009] (3) The perovskite quantum dot is purified by mixing the supernatant with methyl acetate solution after orange precipitate appears in the CsPbBr3 perovskite quantum dot solution, centrifuging the mixture to collect the precipitate, mixing the precipitate with n-hexane and methyl acetate, centrifuging, and collecting the final precipitate, and dispersing the precipitate in a non-polar solvent to obtain a purified perovskite quantum dot solution;

[0010] (4) The chiral perovskite / perovskite quantum dot heterojunction double-layer film is prepared by spin coating or blade coating the chiral perovskite precursor solution on a substrate to obtain a chiral perovskite film, and then depositing the perovskite quantum dot solution on the chiral perovskite film by spin coating or blade coating to obtain a chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film.

[0011] The solvent for the chiral perovskite is a polar solvent, and the solvent for the perovskite quantum dot is a non-polar solvent, which ensures that the chiral perovskite film and the perovskite quantum dot film do not dissolve each other, and thus can be well compatible to form a chiral perovskite / perovskite quantum dot heterojunction double-layer film.

[0012] Preferably, in step (1), the same mass fraction of chiral ligand R-(+)-3-bromo-1-phenylethyl amine and chiral ligand S-(-)-3-bromo-1-phenylethyl amine is placed in containers A and B, respectively, and the same mass fraction of lead bromide solid powder is placed in containers A and B, respectively, and the same volume of N,N-dimethylformamide solution is added to containers A and B, respectively, and the solutions in containers A and B are stirred at 50℃ until clear to obtain R- and S-configurations of chiral perovskite precursor solutions;

[0013] Preferably, the mass-volume ratio (mg / mg / ml) of the lead bromide, tetra-n-octylammonium bromide and toluene in step (2) is 367:1093.6:10.

[0014] Preferably, the preparation method of the cesium carbonate solution in step (2) is to dissolve cesium carbonate and n-octanoic acid into a solution according to a mass-volume ratio (mg / ml) of 32.5:1, and the preparation method of the formamidinium acetate solution is to dissolve formamidinium acetate and n-octanoic acid into a solution according to a mass-volume ratio (mg / ml) of 20.8:1, and the volume ratio of the cesium carbonate solution to the formamidinium acetate solution is 0.85:0.15.

[0015] Preferably, the concentration of the purified perovskite quantum dot solution in step (3) ranges from 80 to 100 mg / mL, and the solution is n-hexane.

[0016] Preferably, when the chiral perovskite precursor solution in step (4) is spin-coated, the spin-coating speed is 1000-2000 rpm, and the spin-coating time is 30 s, and the spin-coating speed of the perovskite quantum dot solution is 1000-8000 rpm, and the spin-coating time is 10-60 s.

[0017] Preferably, after the chiral perovskite precursor solution in step (4) is spin-coated, it can be placed on a heating stage for annealing at 100℃ for 10 minutes, and after the perovskite quantum dot solution is spin-coated, the film is transferred into a low-pressure chamber for 10-20 minutes.

[0018] Preferably, before the chiral perovskite precursor solution in step (4) is deposited on the substrate by the doctor blade method, the substrate is first placed on a heating stage preheated at 70-90℃ for 20-30 minutes.

[0019] 2. The chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film prepared by the above method.

[0020] 3. The use of the chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film in a bifunctional device integrating circularly polarized light emission and detection.

[0021] The present application has the following beneficial effects:

[0022] (1) The scheme of the present application effectively combines the excellent optical activity of chiral perovskite and the high luminescent efficiency of perovskite quantum dots to construct a chiral perovskite / perovskite quantum dot heterojunction nonlinear optical film. Based on the adjustable advantage of the chemical components of chiral perovskite and perovskite quantum dots, the energy level structure of the two is changed to enhance the recombination efficiency of electron-hole carriers at the heterojunction interface, thereby improving the nonlinear optical response of the chiral perovskite / perovskite quantum dot heterojunction.

[0023] (2) When the chiral perovskite and the perovskite quantum dot have the same halogen component, the chiral organic molecule can act as a passivation agent for the peroviskite quantum dot layer, reduce the interface defects between the double-layer thin film, and make the chiral transfer process efficient, so as to fully utilize the excellent light-emitting performance of the peroviskite quantum dot to improve the nonlinear optical activity of the whole heterojunction. In addition, compared with the chiral perovskite single crystal and the chiral perovskite-non-chiral perovskite core-shell structure system, the chiral perovskite / peroviskite quantum dot heterojunction nonlinear optical thin film has more advantages in preparation method, optical activity and application prospect. Moreover, the chiral perovskite / peroviskite quantum dot heterojunction nonlinear optical thin film is easy to be integrated into a device, and can be directly applied to a circularly polarized light-emitting and detecting dual-function device.

[0024] Other advantages, objects, and features of the application will be apparent from the following specification and appended claims, and realized by practice of the application. The application is capable of other objects and of being practiced or being carried out in various ways. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to make the objects, technical solutions and advantages of the present application clearer, the preferred embodiments of the present application will be described in detail below with reference to the drawings, in which:

[0026] Figure 1 Absorption spectra of (R-3BrMBA)2PbBr4 monolayer, (S-3BrMBA)2PbBr4 monolayer, and peroviskite quantum dot CsPbBr3 monolayer;

[0027] Figure 2 X-ray diffraction patterns of (R-3BrMBA)2PbBr4 monolayer and (S-3BrMBA)2PbBr4 monolayer thin film;

[0028] Figure 3 Absorption spectra of (R-3BrMBA)2PbBr4 / CsPbBr3 heterojunction double-layer thin film and (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction double-layer thin film;

[0029] Figure 4 Circular dichroism spectrum of (R / S-3BrMBA)2PbBr4 thin film;

[0030] Figure 5 Circular dichroism spectra of (R-3BrMBA)2PbBr4 / CsPbBr3 and (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction double-layer thin film;

[0031] Figure 6Circular polarization degree of (R-3BrMBA)2PbBr4 / CsPbBr3 and (S-3BrMBA)2PbBr4 / CsPbBr3;

[0032] Figure 7 Structure diagram of chiral perovskite (R / S-3BrMBA)2PbBr4 / CsPbBr3 for spin / circular polarization luminescence device and circular polarization light detection device. DETAILED DESCRIPTION

[0033] Other advantages and effects of the present application can be easily understood by those skilled in the art from the description of the embodiments of the present application. The present application can also be implemented or applied by other different embodiments, and various modifications or changes can be made to the details in the description based on different views and applications without departing from the spirit of the present application. It should be noted that the drawings provided in the following examples only illustrate the basic concept of the present application in a schematic manner, and the features in the following examples and embodiments can be combined with each other without conflict.

[0034] The chemical reagents required for preparing chiral perovskite / perovskite quantum dot heterojunction double-layer films in the present application are all of analytical purity grade and do not need further purification. The main materials used in the experiment are:

[0035] (a) R-(+)-3-bromo-1-phenylethylammonium bromide (R-(+)-3-Bromo-1-Phenylethylammonium Bromide), abbreviated as R-3BrMBA; S-(-)-3-bromo-1-phenylethylammonium bromide (S-(-)-3-Bromo-1-Phenylethylammonium Bromide), abbreviated as S-3BrMBA. Both of these two chiral ligands are white powders. The purity of the material is > 98.0% (used for chromatographic purification). Brand: Xi'an Yurayouguang.

[0036] (b) Lead bromide (PbBr2): This material is a white powder. The purity is > 99.999% metal-based, orthorhombic system.

[0037] Brand: Aladdin;

[0038] (c) 1 mL of N,N-dimethylformamide (DMF): colorless transparent liquid. Purity: > 99.9%, brand: Aladdin;

[0039] (d) 10 mL of toluene solution (C6H5CH3): This material is a colorless transparent solution. Purity: > 99.5% (analytical purity).

[0040] Brand: Chongqing Chuandong Chemical Industry;

[0041] (e) 2 mL methyl acetate (MeOAc): This material was a colorless transparent solution. Purity: >99% (analytical pure).

[0042] Brand: Macklin;

[0043] (f) 1093.6 mg tetra-n-octylammonium bromide (TOAB): white crystalline powder. Purity: >98%. Brand: Sigma-Aldrich;

[0044] (g) 32.5 mg cesium carbonate (CsCO3): white solid. Purity: >99.9%. Brand: Taesong (Jiangsu) Kechuang Development Co., Ltd;

[0045] (h) 20.8 mg formamidinium acetate (FA): white solid. Purity: >99%. Brand: Leyen;

[0046] (i) 1 mL n-octanoic acid (OATC): transparent liquid. Purity: >99%. Brand: Macklin;

[0047] (j) 30 mg didodecyldimethylammonium bromide (DDAB): crystalline powder. Purity: >97%. Brand: Macklin;

[0048] (k) 20 mg 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene (TBTB): crystalline powder. Purity: >95%. Brand: Leyen.

[0049] Embodiment

[0050] A preparation method of a chiral perovskite / perovskite quantum dot heterojunction nonlinear optical active film, comprising the following steps:

[0051] Step (1): Preparation of chiral perovskite precursor solution. Two magnetic stir bars of SA-10 type and two clean 5 mL glass vials were prepared, and one magnetic rotor was placed in each glass vial. Two portions of lead bromide (PbBr2) solid powder with a mass of 73.4 mg were weighed and added into the two glass vials, respectively. Then, 112.4 mg of halide chiral ligand R-(+)-3-Bromo-1-Phenylethylammonium Bromide was weighed and poured into one of the glass vials and labeled; similarly, 112.4 mg of halide chiral ligand S-(-)-3-Bromo-1-Phenylethylammonium Bromide was weighed and poured into the other glass vial and labeled. Then, 1 mL of N,N-dimethylformamide (DMF) solution was added into each of the two glass vials. The two glass vials were transferred into a glovebox system and placed on a heating stir plate, which was set to 50 °C in advance, and stirred for 12 h until the solid was completely dissolved to obtain a clear chiral perovskite precursor solution;

[0052] Step (2): Synthesis of perovskite CsPbBr3 quantum dots. Prepare a magnetic stirrer of model HL2050 and a beaker with a capacity of 50 mL. Weigh 367 mg of lead bromide (PbBr2) and 1093.6 mg of tetra-n-octylammonium bromide (TOAB) into the beaker at room temperature, then add 10 mL of toluene, stir on the stirring table until the solid powders are completely dissolved, and then prepare a lead bromide precursor solution. Prepare two 10 mL centrifuge tubes labeled centrifuge tube 1 and tube 2, weigh 32.5 mg of cesium carbonate (CsCO3) into centrifuge tube 1 at room temperature, and weigh 20.8 mg of formamidinium acetate (FA) into centrifuge tube 2, respectively, add 1 mL of n-octanoic acid (OATC) to each of the two centrifuge tubes, and completely dissolve them in an ultrasonic cleaner for 15 minutes. Take 0.85 mL of cesium carbonate solution and 0.15 mL of formamidinium acetate solution, mix them together to obtain a cesium precursor solution. Prepare two 10 mL centrifuge tubes labeled tube 3 and tube 4, weigh 30 mg of didodecyldimethylammonium bromide (DDAB) into tube 3 at room temperature, and weigh 20 mg of 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene (TBTB) into tube 4, add 3 mL of toluene to each of the centrifuge tubes 3 and 4, and then place the centrifuge tubes in an ultrasonic cleaner for 15 minutes until the solids are completely dissolved to complete the preparation of the passivation agent. Take 9 mL of lead bromide precursor solution, add 1 mL of cesium precursor solution, stir on the stirring table for 2 minutes, then add 3 mL of DDAB solution (centrifuge tube 3) and stir for 3 minutes, then add 3 mL of TBTB solution (centrifuge tube 4) and stir for 5 minutes, then remove the beaker from the stirring table, wrap it with tin paper, and let it stand for 2 hours;

[0053] Step (3): Purification of perovskite quantum dots. After waiting for 2 hours, orange precipitate appears in the beaker, take 1 mL of light green supernatant and add it to a 10 mL capacity centrifuge tube, then add 2 mL of methyl acetate solution to the centrifuge tube, repeat 6 times to obtain 6 centrifuge tube solutions, centrifuge at 7000 rpm for 5 minutes in a high-speed centrifuge, then discard the supernatant and collect the precipitate, add 1 mL of n-hexane and 2 mL of methyl acetate again, centrifuge at 7000 rpm for 5 minutes again, collect the final precipitate, and disperse the precipitate in 1 mL of n-hexane to obtain a purified perovskite quantum dot solution;

[0054] Step (4): Preparation of chiral perovskite / perovskite quantum dot heterojunction double-layer film. A glass substrate with a size of 1.6 cm*1.6 cm was cleaned by using a high-purity nitrogen gun to blow off the surface dust, and then was sequentially placed in ionized water, acetone, and anhydrous ethanol for ultrasonic cleaning. Then, the glass substrate was placed in an 80°C oven for 30 minutes, and finally was placed in a plasma cleaning machine for surface hydrophilic treatment. After the glass substrate was transferred into a nitrogen environment glove box, a chiral perovskite film was prepared by using a solution spin coating method. 60 uL of a chiral perovskite precursor solution was dropped on a clean glass substrate, and was spin-coated at a speed of 2000 rpm for 30 seconds. Subsequently, the glass substrate was transferred to a heating table and was annealed at 100°C for 10 minutes, so as to evaporate the solvent and quickly crystallize to form chiral perovskite films (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4. The chiral perovskite film was transferred into a low-pressure chamber for 10 minutes, and then was placed on a spin coater. 70 uL of a perovskite quantum dot solution CsPbBr3 was spin-coated on the chiral perovskite film by using the spin coating technology at a speed of 2000 rpm for 30 seconds. Subsequently, the film was transferred into a low-pressure chamber for 10 minutes to obtain a chiral perovskite / perovskite quantum dot heterojunction film.

[0055] Figure 1 The visible light absorption characteristics of the single-layer chiral perovskite (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 and the single-layer perovskite quantum dot CsPbBr3 film were demonstrated. As can be seen from the figure, the absorption curves of the chiral perovskite (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 are basically coincident, and only have one obvious absorption peak, which is about 380 nm. This indicates that the (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 films have a low-dimensional structure (n=1). In addition, the absorption characteristics of the single-layer perovskite quantum dot CsPbBr3 film were also tested, and the experimental results show that the CsPbBr3 film also has only one absorption peak, which is about 500 nm. By comparing the light absorption characteristics of the (R-3BrMBA)2PbBr4, (S-3BrMBA)2PbBr4, and CsPbBr3 films, it can be known that the absorption peaks of the (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 films come from a low-dimensional crystalline phase, and the absorption peak of the CsPbBr3 film comes from a three-dimensional crystalline phase.

[0056] In order to verify that the prepared chiral perovskite single-layer (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 films have good crystalline characteristics, the X-ray diffraction patterns of the two kinds of films were further measured. As shown in FIG. 4, the X-ray diffraction patterns of the (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 films are basically coincident, and only have one obvious diffraction peak, which is about 20°. This indicates that the (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 films have a low-dimensional structure (n=1). Figure 2As shown in the figure, (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 films exhibit obvious crystalline diffraction peaks in the diffraction angle range of 0-40°, and their crystalline peak positions are the same, indicating that the two-dimensional chiral perovskite prepared by solution spin coating has good film-forming and crystallization properties, which lays a good foundation for the preparation of (R / S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction double-layer films with two-dimensional / three-dimensional structures.

[0057] By using the solution spin coating method, (R / S-3BrMBA)2PbBr4 and CsPbBr3 were effectively combined to prepare (R-3BrMBA)2PbBr4 / CsPbBr3 and (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction double-layer films. Figure 3 As shown in the figure, the absorption spectra of the two heterojunction bilayer films were tested. The experimental results show that both (R-3BrMBA)2PbBr4 / CsPbBr3 and (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction bilayer films have two obvious absorption peaks, located at 380nm and 500nm respectively. Figure 1 Comparison of the test results shows that the two absorption peaks actually come from the absorption peaks of the chiral perovskite (R / S-3BrMBA)2PbBr4 and the perovskite quantum dot CsPbBr3, respectively. This indicates that a chiral perovskite / perovskite quantum dot heterojunction bilayer film has been successfully prepared. Moreover, this heterojunction bilayer film combines the optical properties of the two-dimensional chiral perovskite (R / S-3BrMBA)2PbBr4 and the three-dimensional perovskite quantum dot CsPbBr3, and its structure is a two-dimensional / three-dimensional heterojunction structure.

[0058] In order to characterize the chiral properties of the prepared chiral perovskite film, the circular dichroism spectra of the two films (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 were further tested, such as Figure 4The circular dichroism signals of (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 thin films are shown in the figure. As can be seen from the figure, the circular dichroism signals of (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 thin films have obvious symmetry, and they both have three relatively strong circular dichroism signals, which are located at 330 nm, 375 nm and 394 nm, respectively, and the circular dichroism signal at 394 nm is the strongest, and the circular dichroism signal of (R-3BrMBA)2PbBr4 thin film is as high as 12 mdeg, which is stronger than the circular dichroism signal of conventional chiral perovskite single crystal. This shows that the chiral perovskite thin films (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 prepared by solution spin coating method not only have strong chiral characteristics, but also this experimental technology verifies that the chiral ligand of halide can efficiently transfer its chirality to the inorganic perovskite structure, and the whole chiral perovskite thin film produces nonlinear optical activity through the electronic orbital hybridization and interaction between the chiral component and the inorganic component.

[0059] Figure 5 The circular dichroism signals of (R-3BrMBA)2PbBr4 / CsPbBr3 and (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction bilayer thin films are shown. As can be seen from the figure, (R-3BrMBA)2PbBr4 / CsPbBr3 and (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction bilayer thin films also exhibit obvious symmetrical circular dichroism signals, and a total of 5 circular dichroism signal peaks appear in the range of 300-600 nm, which are located at 340 nm, 375 nm, 425 nm, 475 nm and 500 nm, respectively, and the circular dichroism signal at 500 nm is the strongest, which is greater than 45 mdeg. The experimental results show that the (R-3BrMBA)2PbBr4 / CsPbBr3 and (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction bilayer thin films formed by combining the chiral perovskite monolayer (R-3BrMBA)2PbBr4 and (S-3BrMBA)2PbBr4 thin film with the perovskite quantum dot monolayer CsPbBr3 thin film have nonlinear optical effect. By comparing the circular dichroism signals of the chiral perovskite monolayer thin film and the chiral perovskite / perovskite quantum dot heterojunction bilayer thin film, it can be known that the nonlinear optical activity of the heterojunction bilayer thin film is much stronger than that of the chiral perovskite monolayer thin film, and its circular dichroism signal is increased by nearly 4 times. The experimental results show that the constructed chiral perovskite / perovskite quantum dot heterojunction bilayer thin film can indeed significantly improve the nonlinear optical activity, and at the same time, it also shows that the chirality of the chiral perovskite single crystal can be efficiently transferred to the perovskite quantum dot layer, so that the perovskite quantum dot layer exhibits excellent nonlinear optical activity.

[0060] Figure 6Circular polarization degree of (R-3BrMBA)2PbBr4 / CsPbBr3 and (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction bilayer films are shown. Based on the test results, the circular polarization degree of (R-3BrMBA)2PbBr4 / CsPbBr3 heterojunction bilayer film is as high as 10%, and the circular polarization of (S-3BrMBA)2PbBr4 / CsPbBr3 heterojunction bilayer film is as high as 15%. The circular polarization degree of the two kinds of heterojunction bilayer films is also the highest at present, which shows that the chiral perovskite / perovskite quantum dot heterojunction bilayer film constructed by using solution spin coating method has advantages and exhibits very strong nonlinear optical activity.

[0061] As shown in Figure 7 The prepared chiral perovskite / perovskite quantum dot heterojunction bilayer film can be well and conveniently used for integrating circular polarization light-emitting diode and circular polarization light detector, so that the device has the dual functions of circular polarization light emission and detecting circular polarization light. The structure of the dual-function electronic device is: conductive glass substrate / hole injection layer / hole transport layer / chiral perovskite / perovskite quantum dot / electron transport layer / aluminum electrode. The principle of the circular polarization light-emitting device is that holes and electrons are injected from the conductive substrate and the aluminum electrode of the device, respectively, the holes pass through the hole injection layer and the hole transport layer in turn, and then enter the chiral perovskite, at this time the holes are spin-polarized, so that they have the characteristics of spin-up or spin-down, and then are transmitted to the perovskite quantum dot layer. The electrons from the aluminum electrode enter the perovskite quantum dot layer through the electron transport layer, so the electrons and the spin-polarized holes recombine in the perovskite quantum dot layer to emit left-handed or right-handed circularly polarized light.

[0062] The working principle of the circular polarization detection device is just the opposite of the working principle of the circular polarization light-emitting device. When the device is irradiated by external left-handed or right-handed circularly polarized light, the perovskite quantum dot layer can generate photo-generated electron and hole carriers, and these holes pass through the chiral perovskite layer and the hole transport layer to reach the glass conductive substrate, and the electrons pass through the electron transport layer to reach the aluminum electrode, and finally the electron and spin-polarized hole carriers are detected by the source table, so that the device can realize the detection of left-handed or right-handed circularly polarized light.

[0063] In summary, the technical scheme proposes to combine chiral perovskite film and perovskite quantum dot film, and the chiral perovskite / perovskite quantum dot heterojunction bilayer film constructed thereby not only has a simple and fast preparation process, but also has very strong nonlinear optical activity. In addition, the chiral perovskite / perovskite quantum dot heterojunction bilayer film is also conducive to integration into a device, and is expected to realize a circular polarization light-emitting and detecting dual-function device.

[0064] Finally, it is to be explained that the above embodiments are only used to illustrate the technical solutions of the present application but not to limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced without departing from the purpose and scope of the present application, and all should be covered in the scope of the claims of the present application.

Claims

1. A method for preparing a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film, characterized in that: The steps include: (1) preparing a chiral perovskite precursor solution, mixing a chiral organic ligand, lead bromide solid powder and a polar solution to obtain a chiral perovskite precursor solution, wherein the chiral organic ligand is R-(+)-3-bromo-1-phenethylammonium bromide or S-(-)-3-bromo-1-phenethylammonium bromide; (2) preparing a perovskite quantum dot solution, firstly dissolving lead bromide, tetra-n-octylammonium bromide and toluene to prepare a lead bromide precursor solution; then mixing a cesium carbonate solution and a formamidine acetate solution to prepare a cesium precursor solution; mixing dioctyldimethylammonium bromide and 1,3,5-tris(bromomethyl)-2,4,6-triethylbenzene with toluene and completely dissolving them, respectively marking them as passivator A and passivator B, mixing the lead bromide precursor solution and the cesium precursor solution, then adding passivator A and stirring evenly, then adding passivator B and stirring evenly, sealing the solution and letting it stand, thereby obtaining a CsPbBr3 perovskite quantum dot solution; (3) Purification of perovskite quantum dots: After an orange precipitate appears in the CsPbBr3 perovskite quantum dot solution, the supernatant is mixed with a methyl acetate solution, the mixture is centrifuged to collect the precipitate, the precipitate is then mixed with n-hexane and methyl acetate, and the final precipitate is collected and dispersed in a non-polar solvent to obtain a purified CsPbBr3 perovskite quantum dot solution; (4) Preparation of chiral perovskite / perovskite quantum dot heterojunction bilayer film: spin coating or scraping a chiral perovskite precursor solution on a substrate to obtain a chiral perovskite film, and then depositing the perovskite quantum dot solution on the chiral perovskite film by spin coating or scraping to obtain a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film.

2. The method for preparing a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film according to claim 1, characterized in that: Step (1) preparing a chiral perovskite precursor solution, taking equal parts by weight of a chiral ligand R-(+)-3-bromo-1-phenethylammonium bromide and a chiral ligand S-(-)-3-bromo-1-phenethylammonium bromide and placing them in containers A and B, respectively, then taking equal parts by weight of lead bromide solid powder and placing them in containers A and B, respectively, and then adding equal volumes of N,N-dimethylformamide solution to containers A and B, respectively, and fully stirring the solutions in containers A and B at 50° C. until they become clear, thereby obtaining two chiral perovskite precursor solutions of R configuration and S configuration; 3. The method for preparing a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film according to claim 1, characterized in that: The mass volume ratio (mg / mg / ml) of lead bromide, tetra-n-octylammonium bromide and toluene in step (2) is 367:1093.6:

10.

4. The method for preparing a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film according to claim 1, characterized in that: The cesium carbonate solution in step (2) is prepared by dissolving cesium carbonate and n-octanoic acid in a mass volume ratio (mg / ml) of 32.5:1 into a solution. The formamidine acetate solution is prepared by dissolving formamidine acetate and n-octanoic acid in a mass volume ratio (mg / ml) of 20.8:1 into a solution. The volume ratio of the cesium carbonate solution to the formamidine acetate solution is 0.85:0.

15.

5. The method for preparing a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film according to claim 1, characterized in that: The concentration range of the purified perovskite quantum dot solution in step (3) is 80-100 mg / mL, and the solution is n-hexane.

6. The method for preparing a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film according to claim 1, characterized in that: In step (4), the chiral perovskite precursor solution is spin-coated at a speed of 1000-2000 rpm and a spin-coating time of 30 s. The perovskite quantum dot solution is spin-coated at a speed of 1000-8000 rpm and a spin-coating time of 10-60 s.

7. The method for preparing a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film according to claim 6, characterized in that: After spin coating the chiral perovskite precursor solution in step (4), the film can be placed on a heating table at 100° C. for annealing for 10 minutes. After spin coating the perovskite quantum dot solution, the film is transferred into a low-pressure chamber and placed for 10-20 minutes.

8. The method for preparing a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film according to claim 1, characterized in that: Before the chiral perovskite precursor solution is deposited on the substrate by doctor blade coating in step (4), the substrate is preheated on a hot plate at 70-90° C. for 20-30 minutes.

9. A chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film prepared by the method of any one of claims 1 to 8.

10. Application of a chiral perovskite / perovskite quantum dot heterojunction nonlinear optically active film in a dual-functional device integrating circularly polarized luminescence and detection.

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