A temperature-responsive circularly polarized fluorescence device of perovskite quantum dots and cholesteric liquid crystal and a preparation method thereof

Abstract

The present application relates to a kind of perovskite quantum dots and cholesteric liquid crystal temperature response circularly polarized fluorescence device, the perovskite quantum dots and cholesteric liquid crystal temperature response circularly polarized fluorescence device from bottom to top includes successively: lower substrate, first parallel orientation layer, first reflective layer, second parallel orientation layer, middle substrate, third parallel orientation layer, second reflective layer, fourth parallel orientation layer, upper substrate and emitting layer.The present application successfully prepared double-layer flat orientation liquid crystal box, two different chiralities with pre-transition effect cholesteric liquid crystal is filled into two-layer box respectively, by controlling temperature, the reflection band of liquid crystal is offset, combined with emitting layer, at specific temperature, the circularly polarized luminescence of adjustable g lum Value is realized.This application has high stability, good repeatability, superior performance, widen perovskite quantum dots and cholesteric liquid crystal in information encryption and anti-counterfeiting application, with good application prospect.

Description

Technical Field

[0001] This invention relates to the field of circularly polarized light emission technology, and in particular to a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal and its preparation method. Background Technology

[0002] Circularly polarized light can be considered as the superposition of two linearly polarized lights with perpendicular electric field vectors. When viewed along the direction of light propagation, the trajectory of the endpoints of the light vectors forms a circle. Based on the direction of rotation of the endpoints, circularly polarized light can be divided into left-handed circularly polarized light (L-CPL) and right-handed circularly polarized light (R-CPL). The main parameter for evaluating the performance of circularly polarized light is the luminescence asymmetry factor glum, which is expressed as g... lum =2*(I L -I R ) / (I L +I R ), where I L and I R These represent the intensity of left-handed circularly polarized light and the intensity of right-handed circularly polarized light, respectively.

[0003] There are many methods for obtaining circularly polarized light, among which cholesteric liquid crystals (CLCs) are one approach to obtaining highly polarized circularly polarized light. Cholesteric liquid crystals are typically obtained by adding chiral dopants to nematic liquid crystals. Their liquid crystal molecules are arranged in a helical pattern, hence the name chiral nematic liquid crystals, which can completely reflect light with the same rotation within their reflection band. The height of one rotation of the cholesteric liquid crystal molecule is called the pitch (P), and the size of the pitch determines the wavelength range of light that the cholesteric liquid crystal can reflect.

[0004] In cholesteric liquid crystal materials with a smectic phase, the liquid crystal transitions from a cholesteric phase to a smectic phase as the temperature decreases, inducing a change in pitch. This phenomenon is called the pre-transition effect. As the temperature decreases, the liquid crystal pitch increases, and the reflection band red-shifts. The pre-transition effect is a reversible process; as the temperature increases, the liquid crystal transitions from the smectic phase to the cholesteric phase, and the nearly infinite pitch is compressed to a finite value, resulting in a blue shift in the reflection band. Therefore, the reflection band of cholesteric liquid crystals exhibiting the pre-transition effect can be controlled by adjusting the temperature.

[0005] Perovskite quantum dots possess excellent photoelectric properties, among which pure inorganic perovskite quantum dots (CsPbX3) are highly favored due to their simple preparation process, low cost, high fluorescence quantum yield, and tunable emission wavelength. Circularly polarized light-emitting devices combining perovskite quantum dots with cholesteric liquid crystals, using perovskite quantum dots as the emitting layer and cholesteric liquid crystals as the reflecting layer, can emit circularly polarized light with a high degree of polarization. Zheng et al. fabricated a bilayer circularly polarized light-emitting device consisting of a cholesteric liquid crystal layer and a perovskite emitting layer, with an asymmetry factor g... lumUp to 1.9. Obtain a fixed g. lum Circularly polarized light-emitting devices with g-values ​​have been widely reported, but obtaining g-values ​​through a single device is still a challenge. lum Reports on circularly polarized light with tunable values ​​and rotational properties are rare. Different rotational properties, g... lum Circularly polarized light of varying values ​​can represent different information, and g can be obtained through a single device. lum Circularly polarized light with adjustable values ​​and rotation can expand its applications in information encryption and anti-counterfeiting.

[0006] In summary, developing a stable device to realize g lum The ability to adjust the value and rotation of circularly polarized light is of great significance. Summary of the Invention

[0007] To address the shortcomings and deficiencies of the existing technology, one objective of this invention is to provide a temperature-responsive circularly polarized light-emitting device composed of perovskite quantum dots and cholesteric liquid crystals, enabling it to exhibit different rotational and gamma-ray polarization at different temperatures. lum This invention aims to broaden the application of perovskite quantum dots and cholesteric liquid crystals in information encryption and anti-counterfeiting. Using perovskite quantum dots as the emitting layer, this invention stacks two cholesteric liquid crystals with different chiralities and pre-transition effects, and by controlling the ratio of chiral dopants, staggers their reflection bands. Furthermore, this invention utilizes ultraviolet laser excitation, and by changing the temperature, it can obtain the rotational and gamma values. lum This invention produces circularly polarized light with adjustable polarization values. It exhibits high stability, good repeatability, and superior performance, demonstrating promising application prospects.

[0008] One object of the present invention is to provide a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal, wherein the perovskite quantum dot and cholesteric liquid crystal temperature-responsive circularly polarized fluorescent device comprises, from bottom to top: a lower substrate, a first parallel alignment layer, a first reflective layer, a second parallel alignment layer, a middle substrate, a third parallel alignment layer, a second reflective layer, a fourth parallel alignment layer, an upper substrate, and a light-emitting layer;

[0009] The lower substrate and the middle substrate constitute the first liquid crystal cell;

[0010] The first reflective layer is disposed inside the first liquid crystal cell;

[0011] The middle substrate and the upper substrate constitute a second liquid crystal cell;

[0012] The second reflective layer is disposed inside the second liquid crystal cell;

[0013] in,

[0014] The first and second reflective layers are composed of cholesteric liquid crystals;

[0015] The light-emitting layer is composed of perovskite quantum dots.

[0016] Furthermore, the cholesteric liquid crystal is formed by mixing a nematic liquid crystal with a chiral dopant;

[0017] in,

[0018] The nematic liquid crystal is E7;

[0019] The chiral dopant is selected from one or more of R811, R5011, or S811.

[0020] Furthermore, the first reflective layer and the second reflective layer have different compositions, one of which includes E7 and R811, and the other layer includes E7 and S811.

[0021] Furthermore, the perovskite quantum dots are CsPbX3;

[0022] in,

[0023] X is selected from Cl, Cl m Br 1-m Br, Br m I 1-m One of I and I, where the value of m ranges from 0 to m and from 1.

[0024] Furthermore, the perovskite quantum dots include three types of perovskite quantum dots, which emit red light at 640-680nm, green light at 520-580nm, and blue light at 460-480nm, respectively.

[0025] Another object of the present invention is to provide a method for fabricating the above-mentioned temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal, comprising the following steps:

[0026] S1. Preparation of perovskite quantum dots: Cesium carbonate, oleic acid and octadecene are blended and heated to obtain cesium oleate precursor; PbX2, oleic acid, oleylamine and octadecene are blended and heated to obtain perovskite quantum dot crude solution, heated and kept warm under inert environment, the cesium oleate precursor is added and cooled at low temperature to obtain perovskite quantum dot crude solution, purified to obtain perovskite quantum dots, and then prepared into perovskite quantum dot dispersion;

[0027] S2. Preparation of a liquid crystal cell with a first reflective layer and a second reflective layer: Prepare a substrate with a parallel alignment layer, then adhere three substrates with parallel alignment layers together, and obtain a first liquid crystal cell and a second liquid crystal cell after photocuring; Mix nematic liquid crystal with a chiral dopant, heat and stir to obtain cholesteric liquid crystal, and fill different cholesteric liquid crystals into the liquid crystal cell to obtain a liquid crystal cell with a first reflective layer and a second reflective layer.

[0028] S3. Preparation of a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal: The perovskite quantum dot dispersion is coated on the liquid crystal cell having a first reflective layer and a second reflective layer to obtain a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal.

[0029] Furthermore, the thickness of the filling region in the first and second liquid crystal cells is 10-30 μm.

[0030] Furthermore, the X in PbX2 is selected from Cl, Br, or I.

[0031] Furthermore, in step S1, the heating temperature is 120-180℃.

[0032] Furthermore, in step S2, the heating temperature is 50-70°C.

[0033] In some embodiments of the present invention, polyvinyl alcohol (PVA) is used as a parallel alignment agent in the preparation of the parallel alignment layer glass substrate. Ordinary glass is prepared and ultrasonically cleaned sequentially in acetone solution, ethanol solution, and deionized water for 30 minutes, then dried. The cleaned glass is then irradiated in an ultraviolet ozone generator for 10 minutes to further clean the glass surface and improve its hydrophilicity. A 5 wt% PVA solution is prepared in advance and spin-coated onto the glass at 2000 rpm for 30 seconds. The solution is then transferred to a hot plate at 60°C and left to evaporate the solvent for 1 hour. Finally, it is cooled to room temperature to obtain a glass substrate with a PVA layer. The side with the PVA layer is then placed on a black velvet cloth and oriented by vertical rubbing to obtain a PVA film layer with parallel grooves, thus obtaining a glass substrate with a parallel alignment layer.

[0034] In some embodiments of the present invention, in order to obtain a liquid crystal cell with a certain thickness, when the glass substrate is adhered using UV-curable adhesive, the spacers and UV adhesive are mixed in a ratio of spacer:UV adhesive = 1:99 and stirred at room temperature.

[0035] Furthermore, the spacer size is 10-30 μm.

[0036] Preferably, the spacer size is 15 μm.

[0037] Another object of the present invention is to provide the application of the above-mentioned temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal in information encryption, optical anti-counterfeiting or 3D display.

[0038] The present invention has the following beneficial effects:

[0039] This invention successfully fabricated a bilayer planar alignment liquid crystal cell. Two cholesteric phase liquid crystals with different chiralities and pre-transition effects were respectively filled into two cells. By controlling the temperature, the reflective band of the liquid crystal was shifted and combined with the emitting layer, achieving rotational and gamma-axis alignment at a specific temperature. lum Circularly polarized light emission with adjustable values. Attached Figure Description

[0040] Figure 1 A transmission electron microscope image of CsPbBr3 quantum dots in Example 1 is shown.

[0041] Figure 2 The fluorescence spectrum of CsPbBr3 quantum dots in Example 1 under 365 nm ultraviolet light excitation is shown.

[0042] Figure 3 A schematic diagram of the fabrication of the double-layer liquid crystal cell in Example 1 is shown.

[0043] Figure 4 The transmission spectra of the double-layer liquid crystal cell in Example 1 at different temperatures are shown.

[0044] Figure 5 A schematic diagram of the temperature-responsive circularly polarized light-emitting device in Embodiment 1 is shown. Reference numerals: 100: Liquid crystal cell; 110: First liquid crystal cell; 120: Second liquid crystal cell; 111: Lower substrate; 112: First parallel alignment layer; 113: First reflective layer; 114: Second parallel alignment layer; 115: Middle substrate; 121: Third parallel alignment layer; 122: Second reflective layer; 123: Fourth parallel alignment layer; 124: Upper substrate; 200: Light-emitting layer.

[0045] Figure 6 The spectrum of the temperature-responsive circularly polarized light-emitting device in Example 1 at different temperatures is shown.

[0046] Figure 7 The following diagram illustrates the g values ​​of the temperature-responsive circularly polarized light-emitting device in Example 1 at different temperatures. lum Value change.

[0047] Figure 8 The following diagram illustrates the g values ​​of the temperature-responsive circularly polarized light-emitting device in Example 2 at different temperatures. lum Value change.

[0048] Figure 9 The following diagram illustrates the g values ​​of the temperature-responsive circularly polarized light-emitting device in Example 3 at different temperatures. lum Value change. Detailed Implementation

[0049] To more clearly illustrate the technical solution of the present invention, the following embodiments are provided. Unless otherwise stated, the raw materials, reactions, and post-processing methods appearing in the embodiments are all commercially available raw materials and technical methods well known to those skilled in the art.

[0050] The terms "preferred," "more preferably," and "more suitable" used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0051] It should be understood that, except in any operational instance or otherwise indicated, the amounts or all figures representing ingredients used, for example, in the specification and claims, should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters set forth in the following specification and appended claims are approximate values ​​varying according to the desired performance to be obtained according to the invention.

[0052] All reagents and materials involved in this invention are commercially available conventional materials.

[0053] Example 1

[0054] A temperature-responsive circularly polarized fluorescent device combining perovskite quantum dots and cholesteric liquid crystals, which can emit polarized fluorescence at different temperatures. lum The adjustable green circularly polarized phosphor has the following structure from bottom to top: lower substrate (1.5 mm), first parallel alignment layer (200 nm), first reflective layer (15 μm), second parallel alignment layer (200 nm), middle substrate (1.5 mm), third parallel alignment layer (200 nm), second reflective layer (15 μm), fourth parallel alignment layer (200 nm), upper substrate (1.5 mm), and light-emitting layer (1.5 μm);

[0055] The lower substrate and the middle substrate constitute the first liquid crystal cell;

[0056] The first reflective layer is disposed inside the first liquid crystal cell;

[0057] The middle substrate and the upper substrate constitute a second liquid crystal cell;

[0058] The second reflective layer is disposed inside the second liquid crystal cell.

[0059] The fabrication method of the above-mentioned temperature-responsive circularly polarized fluorescent device composed of perovskite quantum dots and cholesteric liquid crystals includes the following steps:

[0060] S1. Preparation of perovskite quantum dots.

[0061] S1-1: Weigh 0.814 g of cesium carbonate powder, 40 ml of octadecene, and 2.5 ml of oleic acid into a three-necked flask and seal the flask. Vacuum the flask and simultaneously heat to 120°C and stir for 1 hour. Increase the temperature to 150°C until the solution becomes clear and transparent. Allow it to cool naturally to room temperature and store to obtain the cesium oleate precursor.

[0062] S1-2. Weigh 0.138g of lead bromide powder and 10ml of octadecene into another three-necked flask, and seal the flask. Evacuate the flask, heat to 120℃ and stir for 1 hour. Then, purge with nitrogen and inject 1ml of oleic acid and 1ml of oleylamine into the three-necked flask. Increase the temperature to 160℃ and stir for 30 minutes. Take 1ml of the cesium oleate precursor, preheated to 90℃, and inject it into the three-necked flask. React for 5 seconds, then quickly cool with ice water to obtain a crude CsPbBr3 quantum dot solution.

[0063] S1-3. Add 13 ml of ethyl acetate to the crude CsPbBr3 quantum dot solution, dispense into centrifuge tubes, and centrifuge at 13000 r / min for 6 min. Discard the supernatant obtained after centrifugation, disperse the precipitate with 13 ml of toluene and 13 ml of ethyl acetate, and centrifuge again at 13000 r / min for 6 min. Discard the supernatant obtained after centrifugation to obtain CsPbBr3 quantum dots, disperse them with 2 ml of toluene to obtain a CsPbBr3 quantum dot dispersion.

[0064] Figure 1 A transmission electron microscope image of CsPbBr3 quantum dots in Example 1 is shown.

[0065] Figure 2 The fluorescence spectrum of CsPbBr3 quantum dots in Example 1 under 365 nm ultraviolet light excitation is shown.

[0066] S2. Prepare a liquid crystal cell having a first reflective layer and a second reflective layer.

[0067] S2-1: Weigh 0.31g of chiral dopant R811 and 0.69g of liquid crystal E7 into a brown sample bottle, add a magnetic stir bar, and stir at 60℃ for 2h to obtain CLC-1. Weigh 0.275g of chiral dopant S811 and 0.725g of liquid crystal E7 into a brown sample bottle, add a magnetic stir bar, and stir at 60℃ for 2h to obtain CLC-2.

[0068] S2-2. A suitable amount of 5wt% PVA aqueous solution is dropped onto clean ordinary glass irradiated by an ultraviolet ozone generator. The solution is spin-coated at 2000 r / min for 30 s, then placed on a 60℃ hot table for 1 hour to dry all moisture. After the glass cools naturally to room temperature, the PVA-coated side of the glass is oriented by rubbing on velvet to form a glass substrate with a parallel alignment layer. Then, a suitable amount of a mixture of 15μm spacers and UV-curable adhesive is adhered to the four corners of the rubbed-aligned PVA surface. Another rubbed-aligned glass is placed on top of this glass along the same alignment direction, and then transferred to an ultraviolet curing machine for UV curing to obtain a first liquid crystal cell with a lower substrate, a first parallel alignment layer, a second parallel alignment layer, and a middle substrate.

[0069] S2-3. After irradiating the first liquid crystal cell and clean ordinary glass with a UV ozone generator for 10 minutes, a 5wt% PVA aqueous solution is added dropwise and spin-coated at 2000 r / min for 30 seconds. Then, it is placed on a 60°C hot table for 1 hour to dry all moisture. After the first liquid crystal cell and ordinary glass have cooled to room temperature, the PVA-containing side of the first liquid crystal cell is oriented by rubbing on velvet. Then, a suitable amount of a mixture of 15μm spacers and UV-curable adhesive is attached to the four corners of the PVA side. Subsequently, the PVA-containing side of the ordinary glass is oriented by rubbing on velvet and placed on the first liquid crystal cell along the same orientation direction. It is then transferred to a UV curing machine for UV curing to form a second liquid crystal cell, resulting in a double-layer empty liquid crystal cell with a lower substrate, a first parallel alignment layer, a second parallel alignment layer, a middle substrate, a third parallel alignment layer, a fourth parallel alignment layer, and an upper substrate.

[0070] S2-4. Place the double-layer empty liquid crystal cell, CLC-1, and CLC-2 on a 60°C hot stage. Take 20 μl of CLC-1 and drop it onto the edge of the second liquid crystal cell. Relying on capillary force, CLC-1 will automatically fill into the cell to form the second reflective layer. Then take 20 μl of CLC-2 and drop it onto the edge of the first liquid crystal cell. Relying on capillary force, CLC-2 will automatically fill into the cell to form the first reflective layer. Slowly cool to room temperature to obtain a liquid crystal cell with a first reflective layer and a second reflective layer.

[0071] Figure 3 A schematic diagram of the fabrication of the double-layer liquid crystal cell in Example 1 is shown.

[0072] Figure 4 The transmission spectra of the double-layer liquid crystal cell in Example 1 at different temperatures are shown.

[0073] S3. Preparation of a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal. 200 μl of the CsPbBr3 quantum dot dispersion was drop-coated onto the glass near CLC-1 of the liquid crystal cell having a first reflective layer and a second reflective layer, forming a light-emitting layer, thus obtaining the temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal.

[0074] Figure 5 A schematic diagram of the temperature-responsive circularly polarized light-emitting device in Example 1 is shown.

[0075] Figure 6 The spectrum of the temperature-responsive circularly polarized light-emitting device in Example 1 at different temperatures is shown.

[0076] Depend on Figure 6 It can be seen that the reflection bands of CLC-1 and CLC-2 change accordingly with temperature. When the temperature reaches 33-36℃, the reflection band of CLC-1 coincides with the emission peak of CsPbBr3 quantum dots. CLC-1 reflects the right-hand circularly polarized light portion of the fluorescence emitted by CsPbBr3 quantum dots, while the left-hand circularly polarized light passes through, resulting in the device emitting left-hand circularly polarized light. When the temperature reaches 38℃, the reflection band of CLC-2 coincides with the emission peak of CsPbBr3 quantum dots. CLC-2 reflects the left-hand circularly polarized light portion of the fluorescence emitted by CsPbBr3 quantum dots, while the right-hand circularly polarized light passes through, resulting in the device emitting right-hand circularly polarized light. When the temperature is outside these two ranges, the device emits unpolarized light.

[0077] Figure 7 The following diagram illustrates the g values ​​of the temperature-responsive circularly polarized light-emitting device in Example 1 at different temperatures. lum Value change.

[0078] Example 2

[0079] A temperature-responsive circularly polarized fluorescent device combining perovskite quantum dots and cholesteric liquid crystals, which can emit polarized fluorescence at different temperatures. lum The red circularly polarized phosphor with adjustable values ​​has the following structure from bottom to top: lower substrate (1.5 mm), first parallel alignment layer (200 nm), first reflective layer (15 μm), second parallel alignment layer (200 nm), middle substrate (1.5 mm), third parallel alignment layer (200 nm), second reflective layer (15 μm), fourth parallel alignment layer (200 nm), upper substrate (1.5 mm), and light-emitting layer (1.5 μm);

[0080] The lower substrate and the middle substrate constitute the first liquid crystal cell;

[0081] The first reflective layer is disposed inside the first liquid crystal cell;

[0082] The middle substrate and the upper substrate constitute a second liquid crystal cell;

[0083] The second reflective layer is disposed inside the second liquid crystal cell.

[0084] The fabrication method of the above-mentioned temperature-responsive circularly polarized fluorescent device composed of perovskite quantum dots and cholesteric liquid crystals includes the following steps:

[0085] S1. Preparation of perovskite quantum dots.

[0086] S1-1. Weigh 0.814 g of cesium carbonate powder, 40 ml of octadecene, and 2.5 ml of oleic acid into a three-necked flask and seal the flask. Vacuum the mixture and simultaneously heat it to 120°C and stir for 1 hour. Increase the temperature to 150°C until the solution becomes clear and transparent. Allow it to cool naturally to room temperature and store it to obtain the cesium oleate precursor.

[0087] S1-2. Weigh 0.046g of lead bromide powder, 0.118g of lead iodide powder, and 10ml of octadecene into another three-necked flask, and seal the flask. Evacuate the flask, heat to 120℃, and stir for 1 hour. Then, purge with nitrogen and inject 1ml of oleic acid and 1ml of oleylamine into the flask. Increase the temperature to 170℃, stir for 30 minutes, and then inject 1ml of the cesium oleate precursor, preheated to 90℃, into the flask. React for 7 seconds, then rapidly cool with ice water to obtain a crude CsPbBrI2 quantum dot solution.

[0088] S1-3. Add 13 ml of ethyl acetate to the crude CsPbBrI2 quantum dot solution, dispense into centrifuge tubes, and centrifuge at 13000 r / min for 6 min. Discard the supernatant obtained after centrifugation, disperse the precipitate with 13 ml of toluene and 13 ml of ethyl acetate, and centrifuge again at 13000 r / min for 6 min. Discard the supernatant obtained after centrifugation to obtain CsPbBrI2 quantum dots, disperse them with 2 ml of toluene to obtain a CsPbBrI2 quantum dot dispersion.

[0089] S2. Prepare a liquid crystal cell having a first reflective layer and a second reflective layer.

[0090] S2-1: Weigh 0.275g of chiral dopant R811 and 0.725g of liquid crystal E7 into a brown sample bottle, add a magnetic stir bar, and stir at 60℃ for 2 hours to obtain CLC-3. Weigh 0.225g of chiral dopant S811 and 0.775g of liquid crystal E7 into a brown sample bottle, add a magnetic stir bar, and stir at 60℃ for 2 hours to obtain CLC-4.

[0091] S2-2. A suitable amount of 5wt% PVA aqueous solution is dropped onto clean ordinary glass irradiated by an ultraviolet ozone generator. The solution is spin-coated at 2000 r / min for 30 s, then placed on a 60℃ hot table for 1 hour to dry all moisture. After the glass cools naturally to room temperature, the PVA-coated side of the glass is oriented by rubbing on velvet to form a glass substrate with a parallel alignment layer. Then, a suitable amount of a mixture of 15μm spacers and UV-curable adhesive is adhered to the four corners of the rubbed-aligned PVA surface. Another rubbed-aligned glass is placed on top of this glass along the same alignment direction, and then transferred to an ultraviolet curing machine for UV curing to obtain a first liquid crystal cell with a lower substrate, a first parallel alignment layer, a second parallel alignment layer, and a middle substrate.

[0092] S2-3. After irradiating the first liquid crystal cell and clean ordinary glass with a UV ozone generator for 10 minutes, a 5wt% PVA aqueous solution is added dropwise and spin-coated at 2000 r / min for 30 seconds. Then, it is placed on a 60°C hot table for 1 hour to dry all moisture. After the first liquid crystal cell and ordinary glass have cooled to room temperature, the PVA-containing side of the first liquid crystal cell is oriented by rubbing on velvet. Then, a suitable amount of a mixture of 15μm spacers and UV-curable adhesive is attached to the four corners of the PVA side. Subsequently, the PVA-containing side of the ordinary glass is oriented by rubbing on velvet and placed on the first liquid crystal cell along the same orientation direction. It is then transferred to a UV curing machine for UV curing to form a second liquid crystal cell, resulting in a double-layer empty liquid crystal cell with a lower substrate, a first parallel alignment layer, a second parallel alignment layer, a middle substrate, a third parallel alignment layer, a fourth parallel alignment layer, and an upper substrate.

[0093] S2-4. Place the double-layer empty liquid crystal cell, CLC-3, and CLC-4 on a 60°C hot stage. Take 20 μl of CLC-3 and drop it onto the edge of the second liquid crystal cell. Relying on capillary force, CLC-3 will automatically fill into the cell to form the second reflective layer. Then take 20 μl of CLC-4 and drop it onto the edge of the first liquid crystal cell. Relying on capillary force, CLC-4 will automatically fill into the cell to form the first reflective layer. Slowly cool to room temperature to obtain a liquid crystal cell with a first reflective layer and a second reflective layer.

[0094] S3. Preparation of a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal. 200 μl of the CsPbBrI2 quantum dot dispersion was drop-coated onto the glass near CLC-3 of the liquid crystal cell having a first reflective layer and a second reflective layer, forming a light-emitting layer, thus obtaining the temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal.

[0095] Figure 8The variation of glum value of the temperature-responsive circularly polarized light-emitting device in Example 2 at different temperatures is shown.

[0096] Example 3

[0097] A temperature-responsive circularly polarized fluorescent device combining perovskite quantum dots and cholesteric liquid crystals, which can emit polarized fluorescence at different temperatures. lum The structure of the blue circularly polarized phosphor with adjustable values, from bottom to top, is as follows: lower substrate (1.5 mm), first parallel alignment layer (200 nm), first reflective layer (15 μm), second parallel alignment layer (200 nm), middle substrate (1.5 mm), third parallel alignment layer (200 nm), second reflective layer (15 μm), fourth parallel alignment layer (200 nm), upper substrate (1.5 mm), and light-emitting layer (1.5 μm);

[0098] The lower substrate and the middle substrate constitute the first liquid crystal cell;

[0099] The first reflective layer is disposed inside the first liquid crystal cell;

[0100] The middle substrate and the upper substrate constitute a second liquid crystal cell;

[0101] The second reflective layer is disposed inside the second liquid crystal cell.

[0102] The fabrication method of the above-mentioned temperature-responsive circularly polarized fluorescent device composed of perovskite quantum dots and cholesteric liquid crystals includes the following steps:

[0103] S1. Preparation of perovskite quantum dots.

[0104] S1-1. Weigh 0.814 g of cesium carbonate powder, 40 ml of octadecene, and 2.5 ml of oleic acid into a three-necked flask and seal the flask. Vacuum the mixture and simultaneously heat it to 120°C and stir for 1 hour. Increase the temperature to 150°C until the solution becomes clear and transparent. Allow it to cool naturally to room temperature and store it to obtain the cesium oleate precursor.

[0105] S1-2. Weigh 0.069g of lead bromide powder, 0.052g of lead chloride powder, and 10ml of octadecene into another three-necked flask, and seal the flask. Evacuate the flask, heat to 120℃, and stir for 1 hour. Then, purge with nitrogen and inject 1ml of oleic acid and 1ml of oleylamine into the three-necked flask. Increase the temperature to 150℃ and stir for 30 minutes. Take 1ml of the cesium oleate precursor, preheated to 90℃, and inject it into the three-necked flask. React for 5 seconds, then rapidly cool with ice water to obtain CsPbBr. 1.5 Cl 1.5 Quantum dot crude solution;

[0106] S1-3, Add 13 ml of ethyl acetate to the CsPbBr 1.5 Cl 1.5 The crude quantum dot solution was aliquoted into centrifuge tubes and centrifuged at 13000 rpm for 6 min. The supernatant was discarded, and the precipitate was dispersed with 13 ml of toluene and 13 ml of ethyl acetate, then centrifuged again at 13000 rpm for 6 min. The supernatant was discarded to obtain CsPbBr. 1.5 Cl 1.5 Quantum dots were dispersed in 2 ml of toluene to obtain CsPbBr 1.5 Cl 1.5 Quantum dot dispersion.

[0107] S2. Prepare a liquid crystal cell having a first reflective layer and a second reflective layer.

[0108] S2-1: Weigh 0.22g of chiral dopant R811, 0.014g of chiral dopant R5011, and 0.766g of liquid crystal E7 into a brown sample bottle, add a magnetic stir bar, and stir at 60℃ for 2 hours to obtain CLC-5. Weigh 0.31g of chiral dopant S811 and 0.69g of liquid crystal E7 into a brown sample bottle, add a magnetic stir bar, and stir at 60℃ for 2 hours to obtain CLC-6.

[0109] S2-2. A suitable amount of 5wt% PVA aqueous solution is dropped onto clean ordinary glass irradiated by an ultraviolet ozone generator. The solution is spin-coated at 2000 r / min for 30 s, then placed on a 60℃ hot table for 1 hour to dry all moisture. After the glass cools naturally to room temperature, the PVA-coated side of the glass is oriented by rubbing on velvet to form a glass substrate with a parallel alignment layer. Then, a suitable amount of a mixture of 15μm spacers and UV-curable adhesive is adhered to the four corners of the rubbed-aligned PVA surface. Another rubbed-aligned glass is placed on top of this glass along the same alignment direction, and then transferred to an ultraviolet curing machine for UV curing to obtain a first liquid crystal cell with a lower substrate, a first parallel alignment layer, a second parallel alignment layer, and a middle substrate.

[0110] S2-3. After irradiating the first liquid crystal cell and clean ordinary glass with a UV ozone generator for 10 minutes, a 5wt% PVA aqueous solution is added dropwise and spin-coated at 2000 r / min for 30 seconds. Then, it is placed on a 60°C hot table for 1 hour to dry all moisture. After the first liquid crystal cell and ordinary glass have cooled to room temperature, the PVA-containing side of the first liquid crystal cell is oriented by rubbing on velvet. Then, a suitable amount of a mixture of 15μm spacers and UV-curable adhesive is attached to the four corners of the PVA side. Subsequently, the PVA-containing side of the ordinary glass is oriented by rubbing on velvet and placed on the first liquid crystal cell along the same orientation direction. It is then transferred to a UV curing machine for UV curing to form a second liquid crystal cell, resulting in a double-layer empty liquid crystal cell with a lower substrate, a first parallel alignment layer, a second parallel alignment layer, a middle substrate, a third parallel alignment layer, a fourth parallel alignment layer, and an upper substrate.

[0111] S2-4. Place the double-layer empty liquid crystal cell, CLC-5, and CLC-6 on a 60°C hot stage. Take 20 μl of CLC-5 and drop it onto the edge of the second liquid crystal cell. Relying on capillary force, CLC-5 automatically fills into the cell to form the second reflective layer. Then take 20 μl of CLC-6 and drop it onto the edge of the first liquid crystal cell. Relying on capillary force, CLC-6 automatically fills into the cell to form the first reflective layer. Slowly cool to room temperature to obtain a liquid crystal cell with a first reflective layer and a second reflective layer.

[0112] S3. Fabrication of a temperature-responsive circularly polarized fluorescent device using perovskite quantum dots and cholesteric liquid crystals. Take 200 μl of CsPbBr... 1.5 Cl 1.5 A quantum dot dispersion is drop-coated onto the glass near CLC-5 of the liquid crystal cell having a first reflective layer and a second reflective layer to form a light-emitting layer, thereby obtaining a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal.

[0113] Figure 9 The following diagram illustrates the g values ​​of the temperature-responsive circularly polarized light-emitting device in Example 3 at different temperatures. lum Value change.

[0114] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0115] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A temperature-responsive circularly polarized fluorescent device combining perovskite quantum dots and cholesteric liquid crystal, characterized in that, The temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystals comprises, from bottom to top: a lower substrate, a first parallel alignment layer, a first reflective layer, a second parallel alignment layer, a middle substrate, a third parallel alignment layer, a second reflective layer, a fourth parallel alignment layer, an upper substrate, and a light-emitting layer. The lower substrate and the middle substrate constitute the first liquid crystal cell; The first reflective layer is disposed inside the first liquid crystal cell; The middle substrate and the upper substrate constitute a second liquid crystal cell; The second reflective layer is disposed inside the second liquid crystal cell; in, The first and second reflective layers are composed of cholesteric liquid crystals; The light-emitting layer is composed of perovskite quantum dots.

2. The temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal according to claim 1, characterized in that, The cholesteric liquid crystal is formed by mixing a nematic liquid crystal with a chiral dopant; in, The nematic liquid crystal is E7; The chiral dopant is selected from one or more of R811, R5011, or S811.

3. The temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal according to claim 2, characterized in that, The first and second reflective layers have different compositions, with one layer consisting of E7 and R811 and the other consisting of E7 and S811.

4. The temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal according to claim 1, characterized in that, The perovskite quantum dots are CsPbX3; in, X is selected from Cl, Cl m Br 1-m Br, Br m I 1-m One of I and I, where the value of m ranges from 0 to m and from 1.

5. A method for fabricating a temperature-responsive circularly polarized fluorescent device based on perovskite quantum dots and cholesteric liquid crystals according to any one of claims 1-4, characterized in that, Includes the following steps: S1. Preparation of perovskite quantum dots: Cesium carbonate, oleic acid and octadecene are blended and heated to obtain cesium oleate precursor; PbX2, oleic acid, oleylamine and octadecene are blended and heated to obtain perovskite quantum dot crude solution, heated and kept warm under inert environment, the cesium oleate precursor is added and cooled at low temperature to obtain perovskite quantum dot crude solution, purified to obtain perovskite quantum dots, and then prepared into perovskite quantum dot dispersion; S2. Preparation of a liquid crystal cell with a first reflective layer and a second reflective layer: Prepare a substrate with a parallel alignment layer, then adhere three substrates with parallel alignment layers together, and obtain a first liquid crystal cell and a second liquid crystal cell after photocuring; Mix nematic liquid crystal with a chiral dopant, heat and stir to obtain cholesteric liquid crystal, and fill different cholesteric liquid crystals into the liquid crystal cell to obtain a liquid crystal cell with a first reflective layer and a second reflective layer. S3. Preparation of a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal: The perovskite quantum dot dispersion is coated on the liquid crystal cell having a first reflective layer and a second reflective layer to obtain a temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystal.

6. The method for fabricating a temperature-responsive circularly polarized fluorescent device based on perovskite quantum dots and cholesteric liquid crystal according to claim 5, characterized in that, The thickness of the filling area in the first and second liquid crystal cells is 10-30 μm.

7. The method for fabricating a temperature-responsive circularly polarized fluorescent device based on perovskite quantum dots and cholesteric liquid crystal according to claim 5, characterized in that, In step S1, the heating temperature is 120-180℃.

8. The method for fabricating a temperature-responsive circularly polarized fluorescent device based on perovskite quantum dots and cholesteric liquid crystal according to claim 5, characterized in that, In step S2, the heating temperature is 50-70℃.

9. The application of the temperature-responsive circularly polarized fluorescent device of perovskite quantum dots and cholesteric liquid crystals according to any one of claims 1-4 in information encryption, optical anti-counterfeiting or 3D display.

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