Cesium lead bromide liquid crystal and preparation method and application thereof

Abstract

The application discloses a kind of cesium lead bromide liquid crystal and its preparation method, application, the method comprises: lead source and cesium source are dissolved in acetic acid, obtain solution A;Surfactant solution is uniformly mixed with hydrobromic acid acetic acid solution, obtain solution B;The solution A is added to the solution B, stirring is uniformly mixed, obtain solution C;After centrifugal processing to the solution C, supernatant is removed, and solid product is obtained;The solid product is added to the chlorobenzene solution containing the surfactant solution, is uniformly dispersed, and the cesium lead bromide liquid crystal is obtained.The preparation method of cesium lead bromide liquid crystal is provided in the application, the traditional hot injection method is discarded, the high temperature and inert atmosphere required by hot injection method are avoided, and high concentration cesium and lead source precursor are obtained by selecting acetic acid system to dissolve lead oxide and cesium carbonate, the method is simple, cheap, scalable, and cesium lead bromide liquid crystal can be prepared at room temperature.

Description

Technical Field

[0001] This invention relates to the field of perovskite liquid crystal technology, and in particular to a cesium lead bromide liquid crystal, its preparation method, and its applications. Background Technology

[0002] In recent years, perovskites have shown great potential in optoelectronic devices and photovoltaic technology. Among them, cesium lead bromine nanocrystals, as an emerging material, have become a hot research focus due to their superior optical and electronic properties.

[0003] The mainstream method for synthesizing cesium lead bromine nanocrystals is the hot-injection method, which has been proven to effectively control the morphology and structure of perovskites. The advantage of this method is that it can yield the desired product in a relatively short time.

[0004] However, despite its unique advantages, the hot-injection method also has some significant drawbacks. Firstly, this method requires a high-temperature environment for synthesis. This not only means higher energy consumption but can also lead to various technical problems associated with high-temperature processes, such as the thermal stability of the materials. Furthermore, the high-temperature conditions necessitate the reaction to take place in an inert atmosphere, which further increases the complexity and cost of the method.

[0005] Therefore, it is necessary to provide a new cesium lead-bromine liquid crystal, its preparation method, and its applications to address the problems in the existing technology.

[0006] The information disclosed in this background section is intended only to enhance the understanding of the overall background of the invention and should not be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0007] The purpose of this invention is to provide a cesium lead-bromine liquid crystal, its preparation method, and its application. This method is simple, low-cost, and can prepare cesium lead-bromine liquid crystals at room temperature.

[0008] To achieve the above objectives, the technical solution provided by this invention is as follows:

[0009] In a first aspect, the present invention provides a method for preparing a cesium lead-bromine liquid crystal, comprising:

[0010] A lead source and a cesium source are dissolved in acetic acid to obtain solution A; a surfactant solution is mixed with a hydrobromic acid-acetic acid solution to obtain solution B; solution A is added to solution B and stirred to obtain solution C; solution C is centrifuged and the supernatant is removed to obtain a solid product; the solid product is added to a chlorobenzene solution containing the surfactant solution and dispersed evenly to obtain the cesium-lead-bromine liquid crystal.

[0011] In one or more embodiments of the present invention, the lead source is selected from one or more of lead oxide, lead acetate trihydrate, and lead carbonate.

[0012] In one or more embodiments of the present invention, the cesium source is selected from cesium carbonate and / or cesium acetate.

[0013] In one or more embodiments of the present invention, the concentrations of lead ions and cesium ions in solution A are both 0.4 to 0.6 mol / L.

[0014] In one or more embodiments of the present invention, the surfactant solution comprises at least one of octylamine, octanoic acid and oleic acid, and the concentration of the surfactant solution is 0.8 to 1.2 mol / L.

[0015] In one or more embodiments of the present invention, a surfactant solution is mixed with a hydrobromic acid-acetic acid solution to obtain solution B, comprising:

[0016] 160 μL of surfactant solution and 180 μL of 33 wt.% hydrobromic acid-acetic acid solution were added to 10 mL of chlorobenzene solution and stirred until well mixed to obtain solution B.

[0017] In one or more embodiments of the present invention, solution A is added to solution B and stirred until homogeneous to obtain solution C, comprising:

[0018] Add 100 μL of solution A to solution B at a rate of 50 μL / min, place the mixture in a magnetic stirrer, and stir at a speed of 800–1500 rpm for 1–3 min to obtain solution C.

[0019] In one or more embodiments of the present invention, after centrifugation of the solution C, the supernatant is removed to obtain a solid product, comprising:

[0020] Solution C was centrifuged at 5000–7000 rpm to remove the supernatant, and then added to 10 mL of chlorobenzene solution containing 160 μL of surfactant solution. The mixture was dispersed evenly to obtain solution D. Solution D was then centrifuged at 5000–7000 rpm to remove the supernatant, and the solid product was obtained.

[0021] In one or more embodiments of the present invention, the solid product is added to a chlorobenzene solution containing octylamine solution and octanoic acid solution, and dispersed uniformly to obtain the cesium lead bromine liquid crystal, comprising:

[0022] The solid product was added to a 500 μL chlorobenzene solution containing 160 μL of surfactant solution and ultrasonically dispersed to obtain the cesium lead bromine liquid crystal.

[0023] Secondly, the present invention provides a cesium lead-bromine liquid crystal, which is prepared by the aforementioned method.

[0024] Thirdly, the present invention provides an application of the cesium lead bromine liquid crystal as described above in optoelectronic devices.

[0025] Compared with the prior art, the method for preparing cesium lead-bromine liquid crystal provided by the present invention abandons the traditional hot injection method, avoids the high temperature and inert atmosphere required by the hot injection method, and selects an acetic acid system to dissolve lead oxide and cesium carbonate to obtain high concentrations of cesium and lead source precursors. This method is simple, inexpensive, scalable, and can prepare cesium lead-bromine liquid crystal at room temperature. Attached Figure Description

[0026] Figure 1 This is a flowchart of a method for preparing cesium lead bromine liquid crystal according to one embodiment of the present invention;

[0027] Figure 2 The photoluminescence spectrum of the cesium lead bromine liquid crystal prepared in Example 1 of this invention is shown.

[0028] Figure 3 The UV-Vis absorption spectrum of the cesium lead bromine liquid crystal prepared in Example 1 of this invention is shown below.

[0029] Figure 4 The fluorescence quantum yield spectrum of the cesium lead bromine liquid crystal prepared in Example 1 of this invention;

[0030] Figure 5 This is a scanning electron microscope image of the cesium lead bromine liquid crystal prepared in Example 1 of the present invention;

[0031] Figure 6 This is an atomic force microscope image showing the thickness of the cesium lead bromine liquid crystal prepared in Example 1 of the present invention.

[0032] Figure 7 The X-ray scanning spectrum of the cesium lead bromine liquid crystal prepared in Example 1 of this invention;

[0033] Figure 8 This is a microscope image of the cesium lead bromine liquid crystal obtained in Example 1 of the present invention between cross polarizers;

[0034] Figure 9 The image shows a cross-sectional scanning electron microscope (SEM) image of the cesium lead bromine liquid crystal prepared in Example 1 of this invention after removing the solvent chlorobenzene and forming a thin film. Detailed Implementation

[0035] The specific embodiments of the present invention will be described in detail below with reference to the examples, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0036] It should be noted that, unless otherwise specified, "%" and "parts" in the following description refer to quantities based on weight. Unless otherwise indicated, all figures used in this specification and claims to indicate characteristic dimensions, quantities, and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless stated to the contrary, the numerical parameters listed in the foregoing specification and appended claims are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired characteristics using the teachings disclosed herein. The use of numerical ranges expressed as endpoints includes all numbers within that range and any range within that range; for example, 1 to 5 includes 1, 1.2, 1.4, 1.55, 2, 2.75, 3, 3.80, 4, and 5, etc.

[0037] It should also be noted that the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus; the term “preferred” refers to a preferred alternative, but is not limited to the chosen alternative.

[0038] Semiconductor liquid crystals (SLCs) are liquid crystal materials that possess both the photoelectric properties of semiconductors and the polarization properties of liquid crystals. These materials show broad application prospects in 3D optical displays, optical data storage, and the emission and detection of polarized light. Typical SLC materials include cadmium selenide nanorods, organic SLCs, supramolecular compounds, coordination compounds, and polymers. Organic SLCs possess excellent solution processability, high hole mobility, and controllable molecular orientation, making them ideal candidates for high-performance semiconductor thin films. However, low luminous efficiency, poor conductivity, and difficulty in continuously adjusting the bandgap are inherent drawbacks of this type of SLC. Cadmium selenide nanorod liquid crystals exhibit bright photoluminescence with up to 100% polarization, but bandgap adjustment requires controlling the size and shape of the nanorods, which is difficult to control precisely. Furthermore, the preparation of cadmium selenide nanorods cannot be achieved at room temperature.

[0039] In recent years, perovskite nanocrystals with excellent photoelectric properties have attracted much attention as a new potential semiconductor material. Among them, cesium lead bromide, as a typical all-inorganic metal halide perovskite, possesses excellent photoluminescence properties, a tunable optical bandgap, and a high photoluminescence quantum yield. Therefore, this type of material has potential application value in the fields of solar cells, photodetectors, lasers, and sensors. By endowing cesium lead bromide with liquid crystal properties, it is hoped that a new semiconductor liquid crystal with high quantum yield and continuously tunable bandgap can be obtained, thereby overcoming the defects of existing semiconductor liquid crystals.

[0040] There are two main factors influencing liquid crystal formation: aspect ratio (or width / thickness ratio) and sufficient dispersibility / solubility. At a sufficiently high aspect ratio, anisotropic nanomaterials will spontaneously undergo an ordered transformation as their volume fraction increases, forming a liquid crystal phase. Typically, nanorods, nanowires, and nanosheets with sufficient aspect ratios can serve as liquid crystal building blocks. Secondly, sufficient dispersibility is crucial to ensure the material can be stably dispersed in a solvent. However, cesium lead bromide, as a three-dimensional perovskite, is more likely to form three-dimensional cubes and is less likely to form two-dimensional nanosheets or one-dimensional nanorods with sufficiently high aspect ratios.

[0041] The current mainstream method for preparing cesium lead bromine nanocrystals is the hot injection method. Although this method can effectively control the morphology and structure of perovskites, the requirements of high temperature and inert atmosphere increase production costs and complexity, limiting its application in a wider range of fields and the possibility of large-scale production.

[0042] Therefore, this invention proposes a novel method for preparing cesium lead-bromine liquid crystals. This method, through a series of chemical and physical treatment steps, enables the production of high-quality cesium lead-bromine liquid crystals at relatively low temperatures (room temperature) and under simpler environmental conditions. This not only significantly reduces production costs and environmental impact but also helps lower the production costs for large-scale industrial production.

[0043] Please refer to Figure 1 As shown, the method for preparing cesium lead-bromine liquid crystal according to one embodiment of the present invention specifically includes the following steps:

[0044] S101: Dissolve the lead source and cesium source in acetic acid to obtain solution A.

[0045] In step S101, by dissolving a lead source and a cesium source in acetic acid, a solution A containing lead ions and cesium ions can be obtained. The lead source is selected from one or more of lead oxide, lead acetate trihydrate, and lead carbonate; the cesium source is selected from cesium carbonate and / or cesium acetate; the concentration of lead ions and cesium ions in solution A is preferably 0.5 mol / L.

[0046] In step S101, acetic acid reacts with a metal oxide or metal salt in an acid-base reaction to produce a soluble metal acetate and water. For example, the chemical equation for the reaction between lead oxide and acetic acid is:

[0047] PbO+2CH3COOH→Pb(CH3COO)2+H2O

[0048] The chemical equation for the reaction between cesium carbonate and acetic acid is:

[0049] Cs2CO3+2CH3COOH→2CH3COOCs+H2O+CO2

[0050] Through the aforementioned reactions, lead oxide and cesium carbonate can be converted into Pb(CH3COO)2 and CH3COOCs, respectively. These two metal acetates have high solubility in acetic acid, thus forming a homogeneous solution. In solution A, the metal acetates ionize, releasing metal ions and acetate ions. For example, the chemical equation for the ionization of Pb(CH3COO)2 in solution is:

[0051] Pb(CH3COO)2→Pb 2+ +2CH3COO -

[0052] CH3COOC s The chemical equation for ionization in solution is:

[0053] CH3COOCs→Cs + CH3COO -

[0054] Therefore, through step S101, a solution A containing lead and cesium ions can be obtained. The purpose of this step is to provide a metallic precursor for the perovskite and ensure its ionic presence in solution, thereby facilitating subsequent reactions and crystallization processes. This step improves the accuracy and uniformity of the perovskite's stoichiometry, thus guaranteeing the crystal quality and optical properties of the perovskite.

[0055] S102: Mix the surfactant solution with the hydrobromic acid-acetic acid solution to obtain solution B.

[0056] Specifically, 160 μL of surfactant solution and 180 μL of 33 wt.% hydrobromic acid-acetic acid solution are added to 10 mL of chlorobenzene solution and stirred until homogeneous to obtain solution B. Preferably, the surfactant solution contains octylamine and at least one of octanoic acid and oleic acid, and the concentration of the surfactant solution is 0.8–1.2 mol / L.

[0057] In step S102, a reaction medium with a specific pH value and buffering capacity is formed by mixing a surfactant, acting as a surface ligand, with a hydrobromic acid-acetic acid solution. The purpose of this step is to regulate the reaction environment to suit the growth and crystallization of perovskite.

[0058] By using surfactants as surface ligands, the surface of perovskite nanocrystals can be effectively coated to prevent them from agglomerating or oxidizing, thereby improving the dispersibility and stability of perovskite. Furthermore, the morphology and structure of perovskite nanocrystals can be adjusted to achieve sufficiently high aspect ratios and dispersibility, thus realizing liquid crystal properties.

[0059] S103: Add solution A to solution B and stir to mix well to obtain solution C.

[0060] Specifically, solution A is added to solution B at a rate of 50 μL / min, and the mixture is placed in a magnetic stirrer and stirred at a speed of 800–1500 rpm for 1–3 min to obtain solution C.

[0061] In step S103, solution A containing lead ions and cesium ions is mixed and reacted with solution B containing surfactant and hydrobromic acid and acetic acid to form the core of perovskite nanocrystals, thereby achieving rapid growth and crystallization of perovskite nanocrystals.

[0062] By slowly adding solution A to solution B, the uneven size of perovskite nanocrystals or the formation of impurity phases caused by an excessively rapid reaction rate can be avoided. High-speed stirring using a magnetic stirrer promotes sufficient contact and diffusion of the reactants, thereby improving the growth rate and crystallinity of the perovskite nanocrystals.

[0063] S104: After centrifuging the solution C, the supernatant is removed to obtain a solid product.

[0064] Specifically, solution C was centrifuged at 5000–7000 rpm to remove the supernatant, and then added to 10 mL of chlorobenzene solution containing 160 μL of surfactant solution. The solution was dispersed evenly to obtain solution D. Solution D was then centrifuged at 5000–7000 rpm to remove the supernatant and obtain the solid product.

[0065] In step S104, solution C can be transferred to a centrifuge tube and centrifuged at 5000–7000 rpm to deposit perovskite nanocrystals at the bottom of the tube, while the reaction medium and impurities remain in the supernatant. Then, the supernatant is discarded, and the product from the bottom of the tube is added to a chlorobenzene solution containing a surfactant solution. The perovskite nanocrystals are then redispersed in the chlorobenzene using ultrasound or other suitable methods to obtain solution D. Finally, solution D is centrifuged again at 5000–7000 rpm to deposit perovskite nanocrystals at the bottom of the tube, while the chlorobenzene and excess surfactant remain in the supernatant. The supernatant is discarded to remove residual chlorobenzene and surfactant, finally yielding a solid product.

[0066] S105: The solid product is added to a chlorobenzene solution containing a surfactant solution and an octanoic acid solution and dispersed evenly to obtain the cesium lead bromine liquid crystal.

[0067] Specifically, the solid product is added to a 500 μL chlorobenzene solution containing 160 μL of surfactant solution and ultrasonically dispersed to obtain the cesium lead bromine liquid crystal.

[0068] Step S105 achieves a concentration effect, reducing the total volume of the solution. This allows for a higher density of grafting between the surfactant and the cesium lead bromine liquid crystal building blocks, improving the dispersibility and stability of the liquid crystal building blocks. Simultaneously, it allows the concentration of the cesium lead bromine colloidal solution to reach the threshold for liquid crystal formation.

[0069] In one embodiment of the present invention, a cesium lead-bromine liquid crystal is also provided, which is prepared by the aforementioned method for preparing cesium lead-bromine liquid crystal.

[0070] One embodiment of the present invention also provides an application of the cesium lead bromide liquid crystal as described above in optoelectronic devices.

[0071] The present invention will be further described below with reference to specific embodiments.

[0072] Example 1

[0073] 223.20 mg of lead oxide and 162.91 mg of cesium carbonate were dissolved in an appropriate amount of acetic acid until the total volume reached 2.0 mL, so that the concentrations of lead ions and cesium ions were both 0.5 mol / L, thus obtaining solution A.

[0074] Prepare 1 mol / L octylamine and octanoic acid solutions in the nonpolar solvent chlorobenzene; add 80 μL of octylamine solution, 80 μL of octanoic acid solution and 180 μL of 33 wt.% hydrobromic acid-acetic acid solution to 10 mL of chlorobenzene solution, and stir on a magnetic stirrer at 600 rpm for 5 min to obtain solution B.

[0075] Add 100 μL of solution A to solution B at a rate of 50 μL / min, place the solution in a magnetic stirrer, and stir at 1200 rpm for 2 min to obtain solution C.

[0076] Solution C was centrifuged at 6000 rpm to remove the supernatant, and then added to 10 mL of chlorobenzene solution containing 80 μL of octylamine solution (concentration 1 mol / L) and 80 μL of octanoic acid solution (concentration 1 mol / L). The solution was ultrasonically dispersed for 5 min to obtain solution D. Solution D was then centrifuged at 6000 rpm to remove the supernatant and obtain the solid product.

[0077] The solid product was added to a 500 μL chlorobenzene solution containing 80 μL octylamine solution (1 mol / L) and 80 μL octanoic acid solution (1 mol / L), and ultrasonically dispersed to obtain cesium lead bromine liquid crystal.

[0078] Example 2

[0079] 223.20 mg of lead oxide and 162.91 mg of cesium carbonate were dissolved in an appropriate amount of acetic acid until the total volume reached 2.0 mL, so that the concentrations of lead ions and cesium ions were both 0.5 mol / L, thus obtaining solution A.

[0080] Prepare a 1 mol / L octylamine solution and an oleic acid solution in the nonpolar solvent chlorobenzene; add 80 μL of octylamine solution, 80 μL of oleic acid solution and 180 μL of 33 wt.% hydrobromic acid-acetic acid solution to 10 mL of chlorobenzene solution, and stir on a magnetic stirrer at 600 rpm for 5 min to obtain solution B.

[0081] Add 100 μL of solution A to solution B at a rate of 50 μL / min, place the solution in a magnetic stirrer, and stir at 1200 rpm for 2 min to obtain solution C.

[0082] Solution C was centrifuged at 6000 rpm to remove the supernatant. It was then added to 10 mL of chlorobenzene solution containing 80 μL of octylamine solution (1 mol / L) and 80 μL of oleic acid solution (1 mol / L). The solution was ultrasonically dispersed for 5 min to obtain solution D. Solution D was then centrifuged at 6000 rpm to remove the supernatant, yielding the solid product.

[0083] The solid product was added to a 500 μL chlorobenzene solution containing 80 μL octylamine solution (1 mol / L) and 80 μL oleic acid solution (1 mol / L), and ultrasonically dispersed to obtain cesium lead bromine liquid crystal.

[0084] Example 3

[0085] 379 mg of lead acetate trihydrate and 192 mg of cesium acetate were dissolved in an appropriate amount of acetic acid until the total volume reached 2.0 mL, so that the concentrations of lead ions and cesium ions were both 0.5 mol / L, thus obtaining solution A.

[0086] Prepare 1 mol / L octylamine and octanoic acid solutions in the nonpolar solvent chlorobenzene; add 80 μL of octylamine solution, 80 μL of octanoic acid solution and 180 μL of 33 wt.% hydrobromic acid-acetic acid solution to 10 mL of chlorobenzene solution, and stir on a magnetic stirrer at 600 rpm for 5 min to obtain solution B.

[0087] Add 100 μL of solution A to solution B at a rate of 50 μL / min, place the solution in a magnetic stirrer, and stir at 1200 rpm for 2 min to obtain solution C.

[0088] Solution C was centrifuged at 6000 rpm to remove the supernatant, and then added to 10 mL of chlorobenzene solution containing 80 μL of octylamine solution (concentration 1 mol / L) and 80 μL of octanoic acid solution (concentration 1 mol / L). The solution was ultrasonically dispersed for 5 min to obtain solution D. Solution D was then centrifuged at 6000 rpm to remove the supernatant and obtain the solid product.

[0089] The solid product was added to a 500 μL chlorobenzene solution containing 80 μL octylamine solution (1 mol / L) and 80 μL octanoic acid solution (1 mol / L), and ultrasonically dispersed to obtain cesium lead bromine liquid crystal.

[0090] Figure 2 This is the photoluminescence spectrum of the cesium lead bromine liquid crystal prepared in Example 1 of the present invention. Figure 3 The image shows the ultraviolet-visible absorption spectrum of the cesium lead-bromine liquid crystal prepared in Example 1 of this invention. The photoluminescence spectrum (excitation wavelength 365 nm) shows that the cesium lead-bromine liquid crystal has a single peak centered at 519 nm, and the ultraviolet absorption peak measured by the ultraviolet-visible absorption spectrum is located at 519 nm.

[0091] Figure 4 The image shows the fluorescence quantum yield spectrum of the cesium lead-bromine liquid crystal prepared in Example 1 of this invention. The photoluminescence quantum yield of the liquid crystal was measured to be approximately 7.83% by fluorescence quantum yield testing.

[0092] Figure 5 This is a scanning electron microscope (SEM) image of the cesium lead-bromine liquid crystal prepared in Example 1 of the present invention. Figure 5 It can be seen that the liquid crystal unit of cesium lead bromine liquid crystal is a hexagonal nanosheet with a diameter range of 3 to 10 μm.

[0093] Figure 6 This is an atomic force microscope image showing the thickness of the cesium lead-bromine liquid crystal prepared in Example 1 of this invention. Figure 6 It can be seen that the thickness of the cesium lead bromine nanosheets is about 200 nm, and the corresponding width / thickness ratio is greater than 10, which meets the basic conditions for liquid crystal formation.

[0094] Figure 7 This is an X-ray scanning image of the cesium lead-bromine liquid crystal prepared in Example 1 of the present invention. Figure 7 It can be seen that the diffraction peaks at 2θ = 15.211°, 21.498°, 30.698°, 34.195°, 37.603° and 43.692° correspond to the (100), (110), (200), (210), (211) and (202) planes, respectively, confirming the formation of cesium lead bromine liquid crystal.

[0095] Figure 8This is a microscope image of the cesium lead-bromine liquid crystal prepared in Example 1 of the present invention between cross polarizers. Figure 8 As can be seen, the microscopic image of the cesium lead-bromine liquid crystal between the cross polarizers observed by polarizing optical microscopy has strong birefringent fringes in the form of brushes, showing the typical texture of the nematic phase and indicating the anisotropy of the cesium lead-bromine liquid crystal.

[0096] Figure 9 This is a cross-sectional scanning electron microscope (SEM) image of the cesium lead-bromine liquid crystal prepared in Example 1 of this invention, after removing the solvent chlorobenzene and forming a thin film. Figure 9 As can be seen, after removing the solvent chlorobenzene, the cesium lead bromine liquid crystal was made into a thin film. By observing the cross-section of the cesium lead bromine liquid crystal film with a scanning electron microscope, the local orientation of the cesium lead bromine liquid crystal can be clearly observed. The cross-section shows the ordered stacking and arrangement of cesium lead bromine nanosheets, which proves that the cesium lead bromine liquid crystal has self-assembly behavior and can spontaneously form nematic liquid crystal in chlorobenzene solvent.

[0097] In summary, the method for preparing cesium lead-bromine liquid crystals provided by this invention abandons the traditional hot injection method, avoids the high temperature and inert atmosphere required by the hot injection method, and selects an acetic acid system to dissolve lead oxide and cesium carbonate to obtain high concentrations of cesium and lead source precursors. This method is simple, inexpensive, scalable, and can prepare cesium lead-bromine liquid crystals at room temperature.

[0098] The all-inorganic perovskite cesium lead bromine liquid crystal prepared by this invention has higher luminous efficiency compared with existing organic-inorganic perovskite liquid crystals. By imparting liquid crystal properties to cesium lead bromine, compared with existing cesium lead bromine quantum dot composite materials, cesium lead bromine can be directly made into a continuous phase, making it easier to realize device fabrication.

[0099] The cesium lead bromine liquid crystal prepared by this invention has excellent photoluminescence properties, strong optical anisotropy, tunable optical band gap and high photoluminescence quantum yield, overcoming the shortcomings of low luminescence efficiency and poor conductivity of traditional organic semiconductor liquid crystals; compared with cadmium selenide nanorod semiconductor liquid crystals, the optical band gap can be continuously controlled by doping.

[0100] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a cesium lead bromide liquid crystal, characterized by, The method comprises the following steps: dissolving a lead source and a cesium source in acetic acid to obtain a solution A, the concentration of lead ions and cesium ions in the solution A being 0.4-0.6 mol / L; mixing a surfactant solution and an acetic acid hydrobromide solution uniformly to obtain a solution B, the surfactant solution comprising at least one of octylamine, octanoic acid and oleic acid, the concentration of the surfactant solution being 0.8-1.2 mol / L; adding the solution A into the solution B and stirring to mix uniformly to obtain a solution C; removing supernatant after centrifugal treatment of the solution C to obtain a solid product; adding the solid product into a chlorobenzene solution containing the surfactant solution and dispersing uniformly to obtain the cesium lead bromide liquid crystal.

2. The method for preparing cesium lead-bromine liquid crystal as described in claim 1, characterized in that, the lead source is selected from one or more of lead oxide, lead acetate trihydrate and lead carbonate; and / or the cesium source is selected from cesium carbonate and / or cesium acetate.

3. The method for preparing cesium lead-bromine liquid crystal as described in claim 1, characterized in that, The method of mixing a surfactant solution and an acetic acid hydrobromide solution uniformly to obtain a solution B comprises: adding 160 μL of the surfactant solution and 180 μL of an acetic acid hydrobromide solution with a concentration of 33 wt.% into 10 mL of a chlorobenzene solution, stirring to mix uniformly and obtaining the solution B.

4. The method for preparing cesium lead-bromine liquid crystal as described in claim 1, characterized in that, The method of adding the solution A into the solution B and stirring to mix uniformly to obtain a solution C comprises: adding 100 μL of the solution A into the solution B at a speed of 50 μL / min, stirring in a magnetic stirrer at a speed of 800-1500 rpm for 1-3 min and obtaining the solution C.

5. The method for preparing cesium lead-bromine liquid crystal as described in claim 1, characterized in that, The method of removing supernatant after centrifugal treatment of the solution C to obtain a solid product comprises: centrifugally treating the solution C at a centrifugal speed of 5000-7000 rpm, adding into 10 mL of a chlorobenzene solution containing 160 μL of the surfactant solution after removing supernatant and dispersing uniformly to obtain a solution D; centrifugally treating the solution D at a centrifugal speed of 5000-7000 rpm after removing supernatant and obtaining the solid product.

6. The method for preparing cesium lead bromine liquid crystal as described in claim 1, characterized in that, The method of adding the solid product into a chlorobenzene solution containing the surfactant solution and dispersing uniformly to obtain the cesium lead bromide liquid crystal comprises: adding the solid product into 500 μL of a chlorobenzene solution containing 160 μL of the surfactant solution, ultrasonic dispersing uniformly and obtaining the cesium lead bromide liquid crystal.

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