Flexible colloid quantum dot laser device and preparation method and application thereof

Abstract

The invention relates to the technical field of laser devices, in particular to a flexible colloidal quantum dot laser device and a preparation method thereof. The device structure sequentially comprises a first reflecting layer, a first optical isolation layer, a second reflecting layer, a second optical isolation layer, a gain dielectric layer, a third optical isolation layer, a third reflecting layer, a fourth optical isolation layer and a fourth reflecting layer from bottom to top. The four reflecting layers are respectively right, left, left and right hand reflecting layers or left, right, right and left hand reflecting layers; the left / right chiral reflecting layer is a polymer cholesteric liquid crystal film; the gain dielectric layer is made of colloidal quantum dots; materials of the first to fourth optical isolation layers are respectively selected from polymethyl methacrylate, polystyrene and the like. The method has the advantages that different chiral cholesteric liquid crystal stacks are used to construct a high-quality F-P resonant cavity; the light emitted by the gain medium achieves a total reflection effect, thereby effectively enhancing the optical feedback and reducing the ASE threshold. A full-solution treatment process is adopted, preparation is easy and convenient, and cost is low.

Description

Technical Field

[0001] The present invention relates to the technical field of laser devices, and particularly to a flexible colloidal quantum dot laser device, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, with the rapid development of electronic technology and information technology, flexible electronic devices have become a research and application hotspot due to their light weight, bendability, and good scalability. Among them, flexible lasers, as an important part of flexible optoelectronic devices, show great application potential in the fields of wearable devices, flexible displays, optical communications, sensors, and medical monitoring. Especially in emerging fields such as portable lasers, wearable light sources, and integrated optoelectronic devices, the demand is increasing day by day.

[0003] Colloidal quantum dots (CQDs), as a material with excellent optoelectronic properties, have extremely broad application prospects in flexible electronic devices. CQDs materials not only have high brightness, narrow spectral emission, and efficient optical conversion characteristics, but also can precisely control the emission wavelength by adjusting the size and material composition, so as to meet diverse application requirements. However, the current amplified spontaneous emission (ASE) threshold of CQDs lasers is relatively high, which has become a bottleneck restricting their wide application. In addition, the preparation of high-quality factor resonators usually relies on high-cost technologies such as electron beam lithography, chemical vapor deposition, and dry etching. These methods are not only complex but also not conducive to large-scale production. Therefore, developing a low-cost and large-scale preparable resonator structure has become the key to improving the practicality of CQDs lasers. Summary of the Invention

[0004] The present invention provides a flexible colloidal quantum dot laser device, a preparation method thereof, and an application thereof to solve the above problems.

[0005] The first object of the present invention is to provide a flexible colloidal quantum dot laser device. The structure of the colloidal quantum dot laser device from bottom to top is successively a first reflective layer, a first optical isolation layer, a second reflective layer, a second optical isolation layer, a gain medium layer, a third optical isolation layer, a third reflective layer, a fourth optical isolation layer, and a fourth reflective layer; Among them, the first reflective layer, the second reflective layer, the third reflective layer, and the fourth reflective layer are respectively a right-handed reflective layer, a left-handed reflective layer, a left-handed reflective layer, and a right-handed reflective layer; or the first reflective layer, the second reflective layer, the third reflective layer, and the fourth reflective layer are respectively a left-handed reflective layer, a right-handed reflective layer, a right-handed reflective layer, and a left-handed reflective layer; Both the left-handed reflective layer and the right-handed reflective layer are polymer cholesteric liquid crystal thin films; The material of the gain medium layer is colloidal quantum dots; The materials of the first optical isolation layer, the second optical isolation layer, the third optical isolation layer, and the fourth optical isolation layer are each selected from at least one of polymethyl methacrylate, polystyrene, polyvinyl alcohol, and cellulose acetate.

[0006] Preferably, the raw materials for preparing the polymer cholesteric liquid crystal thin film include, by weight percentage, 80 to 95 wt% of liquid crystal monomers, 1 to 15 wt% of chiral dopants, 1 to 2 wt% of surfactants, 0.1 to 2 wt% of photoinitiators, and 1 to 2 wt% of organic solvents.

[0007] Preferably, the liquid crystal monomers are selected from at least one of 1,4-bis-[4-(6-acryloyloxyhexyloxy)benzoyloxy]-2-methylbenzene, 2-methyl-1,4-diphenol (4-(((4-(acryloyloxy)butoxy)carbonyl)oxy)benzoate), 4'-pentyl-4-biphenylcarbonitrile, and 1,4-bis-[4-(3-acryloyloxypropoxy)benzoyloxy]-2-methylbenzene; The chiral dopants include left-handed chiral dopants or right-handed chiral dopants; the left-handed chiral dopants are selected from at least one of 2-octyl 4-(4'-hexyloxy)benzoyloxybenzoate and 5,6-dihydro-5-(trans-4-propylcyclohexyl)-4H-dinaphtho[2,1-f:1',2'-h][1,5]dioxacyclononatetraene; the right-handed chiral dopants are selected from at least one of R-2-octyl 4-(4'-hexyloxy)benzoyloxybenzoate, (13bR)-5,6-dihydro-5-(trans-4-propylcyclohexyl)-4H-dinaphtho[2,1-f:1',2'-h][1,5]dioxacyclononatetraene, bis(4-(4'-pentylcyclohexyl)benzoic acid)-(1R)-1-phenyl-1,2-ethanediol ester, and LC-756; The surfactant is N-ethyl perfluorooctanesulfonamidoethyl methacrylate; The photoinitiators are selected from at least one of benzoin diethyl ether, phenyl(2,4,6-trimethylphenylacyl)phosphine oxide, bis(1-(2,4-difluorophenyl)-3-pyrrolyl)titanocene, and 2-hydroxy-2-methylpropiophenone.

[0008] Preferably, the colloidal quantum dots are cadmium selenide quantum dots, indium phosphide quantum dots, cadmium sulfide quantum dots, or perovskite quantum dots.

[0009] Preferably, the thicknesses of the first reflective layer and the fourth reflective layer are different, and the thicknesses of the second reflective layer and the third reflective layer are different; the cavity length of the F-P resonant cavity of the flexible colloidal quantum dot laser device is an integer multiple of the half wavelength of the ASE emission of the gain medium layer.

[0010] Preferably, the thicknesses of the first reflective layer, the first optical isolation layer, the second reflective layer, the second optical isolation layer, the gain medium layer, the third optical isolation layer, the third reflective layer, the fourth optical isolation layer, and the fourth reflective layer are 3 - 6 μm, 120 - 150 nm, 3 - 6 μm, 100 - 120 nm, 40 - 60 nm, 100 - 120 nm, 2 - 4 μm, 120 - 150 nm, and 2 - 4 μm, respectively.

[0011] The second object of the present invention is to provide a method for preparing a flexible colloidal quantum dot laser device, which specifically includes the following steps: S1. Weigh liquid crystal monomers, chiral dopants, surfactants, photoinitiators, and organic solvents according to mass fractions to prepare a chiral liquid crystal mixture; scrape the chiral liquid crystal mixture onto a support substrate and cure it by light to obtain the first reflective layer; S2. Prepare an optical isolation layer solution, scrape it onto the first reflective layer, and anneal it at 60 - 80 °C for 0.1 - 1 hour to obtain the first optical isolation layer; S3. Weigh liquid crystal monomers, chiral dopants, surfactants, photoinitiators, and organic solvents according to mass fractions to prepare a chiral liquid crystal mixture; scrape the chiral liquid crystal mixture onto the first optical isolation layer and cure it by light to obtain the second reflective layer; S4. Prepare an optical isolation layer solution, scrape it onto the second reflective layer, and anneal it at 60 - 80 °C for 0.1 - 1 hour to obtain the second optical isolation layer; S5. Prepare a colloidal quantum dot dispersion liquid, scrape the colloidal quantum dot dispersion liquid onto the second optical isolation layer to form a gain medium layer; S6. Prepare an optical isolation layer solution according to the method of step S4, scrape it onto the gain medium layer, and anneal it at 60 - 80 °C for 0.1 - 1 hour to obtain the third optical isolation layer; S7. Prepare a chiral liquid crystal mixture according to the method of step S3; scrape the chiral liquid crystal mixture onto the third optical isolation layer and cure it by light to obtain the third reflective layer; S8. Prepare an optical isolation layer solution according to the method of step S2, scrape it onto the third reflective layer, and anneal it at 60 - 80 °C for 0.1 - 1 hour to obtain the fourth optical isolation layer; S9. Prepare a chiral liquid crystal mixture according to the method of step S1; scrape the chiral liquid crystal mixture onto the fourth optical isolation layer and cure it by light to obtain the fourth reflective layer; separate the substrate by mechanical peeling to obtain an independent flexible colloidal quantum dot laser device.

[0012] Preferably, the support substrate material in step S1 includes glass, silicon wafer, or sapphire; the light curing is ultraviolet lamp curing, and the curing time is 5 minutes.

[0013] Preferably, the annealing temperatures in steps S2, S4, S6, and S8 are 60 °C.

[0014] A third object of the present invention is to provide an application of a flexible colloidal quantum dot laser device in flexible display, optical communication, biosensing, or wearable devices.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: (1) The flexible colloidal quantum dot laser device provided by the present invention based on all-solution processing uses two different chiral CLC thin film stacks to construct a Fabry-Perot (F-P) resonator with high quality factor; the colloidal quantum dots serve as the laser medium, and its emission peak matches the CLC photonic bandgap, enabling efficient optical feedback and significantly reducing the ASE threshold; (2) The laser device provided by the present invention is prepared by an all-solution process, avoiding high-cost preparation methods such as traditional electron beam lithography and chemical vapor deposition, and having the advantages of simple process, low cost, and large-scale production; (3) The colloidal quantum dot laser device based on all-solution processing provided by the present invention has excellent optical performance and flexible stability, and is expected to play an important application value in the fields of flexible display, optical communication, biosensing, wearable devices, etc.; In summary, the present invention provides a flexible colloidal quantum dot laser device based on all-solution processing and a preparation method thereof. This method constructs a Fabry-Perot (F-P) resonator with high quality factor by using a stack of cholesteric liquid crystals (CLC) with different chiralities. The light emitted by the gain medium is reflected by the left-handed and right-handed cholesteric liquid crystal reflection layers, achieving a total reflection effect, effectively enhancing optical feedback and reducing the ASE threshold. The prepared CQDs laser device adopts an all-solution processing technology, having the advantages of simple preparation, low cost, and large-scale production, greatly improving its feasibility and economy in practical applications. Description of the Drawings

[0016] Figure 1 is a schematic structural diagram of a flexible colloidal quantum dot laser device provided according to an embodiment of the present invention.

[0017] Figure 2 is the emission spectrum of the gain medium layer (perovskite quantum dot film) provided according to an embodiment of the present invention.

[0018] Figure 3 is the reflectivity spectrum of the first reflection layer provided according to an embodiment of the present invention.

[0019] Figure 4 is the transmission spectrum of the right-handed / left-handed CLC stack architecture provided according to an embodiment of the present invention.

[0020] Figure 5 It is the dependence spectrum of the ASE intensity of the gain medium layer on the pump light energy density provided according to an embodiment of the present invention.

[0021] Figure 6 It is the dependence spectrum of the ASE intensity of the flexible colloidal quantum dot laser device on the pump light energy density provided according to an embodiment of the present invention.

[0022] Reference numerals: 1. First reflective layer; 2. First optical isolation layer; 3. Second reflective layer; 4. Second optical isolation layer; 5. Gain medium layer; 6. Third optical isolation layer; 7. Third reflective layer; 8. Fourth optical isolation layer; 9. Fourth reflective layer. Detailed implementation manners

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are denoted by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, their detailed descriptions will not be repeated.

[0024] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention.

[0025] The present invention provides a flexible colloidal quantum dot laser device, and the structure from bottom to top is successively a first reflective layer, a first optical isolation layer, a second reflective layer, a second optical isolation layer, a gain medium layer, a third optical isolation layer, a third reflective layer, a fourth optical isolation layer and a fourth reflective layer; Among them, the first reflective layer, the second reflective layer, the third reflective layer and the fourth reflective layer are respectively a right-handed reflective layer, a left-handed reflective layer, a left-handed reflective layer and a right-handed reflective layer; or the first reflective layer, the second reflective layer, the third reflective layer and the fourth reflective layer are respectively a left-handed reflective layer, a right-handed reflective layer, a right-handed reflective layer and a left-handed reflective layer; The thicknesses of the first reflective layer and the fourth reflective layer are different, and the thicknesses of the second reflective layer and the third reflective layer are different, that is, the thicknesses of the two right-handed reflective layers are different, and the thicknesses of the two left-handed reflective layers are different. The thickness of the reflective layer is changed by controlling the distance between the doctor blade and the substrate during preparation; Both the left-handed reflective layer and the right-handed reflective layer are polymer cholesteric liquid crystal films; Specifically, the raw materials for preparing the polymer cholesteric liquid crystal film include, by weight percentage, 80 - 95 wt% of liquid crystal monomers, 1 - 15 wt% of chiral dopants, 1 - 2 wt% of surfactants, 0.1 - 2 wt% of photoinitiators, and 1 - 2 wt% of organic solvents; Furthermore, the liquid crystal monomers are selected from at least one of 1,4 - bis - [4 - (6 - acryloyloxyhexyloxy)benzoyloxy] - 2 - methylbenzene (RM82), 4 - ((((4 - (acryloyloxy)butoxy)carbonyl)oxy)benzoic acid 2 - methyl - 1,4 - diphenylester (LC - 242), 4'-pentyl-4-biphenylcarbonitrile (5CB), 1,4 - bis - [4 - (3 - acryloyloxypropoxy)benzoyloxy] - 2 - methylbenzene (RM257); Furthermore, the chiral dopants include left-handed chiral dopants or right-handed chiral dopants; the left-handed chiral dopants are selected from at least one of 4 - (4'-hexyloxy)benzoyloxybenzoic acid - 2 - octanol ester (S811), 5,6 - dihydro - 5 - (trans - 4 - propylcyclohexyl) - 4H - dinaphtho[2,1 - f:1',2'-h][1,5]dioxacyclononatetraene (S5011); the right-handed chiral dopants are selected from at least one of 4 - (4'-hexyloxy)benzoyloxybenzoic acid - R - 2 - octanol ester (R811), (13bR) - 5,6 - dihydro - 5 - (trans - 4 - propylcyclohexyl) - 4H - dinaphtho[2,1 - f:1',2'-h][1,5]dioxacyclononatetraene (R5011), bis - 4 - (4'-pentylcyclohexylbenzoic acid) - (1R) - 1 - phenyl - 1,2 - ethanediol ester (R1011), LC - 756; Furthermore, the surfactant is N - ethyl perfluorooctanesulfonamidoethyl methacrylate; Furthermore, the photoinitiators are selected from at least one of benzoin diethyl ether (Irg651), phenyl(2,4,6 - trimethylphenylacyl)phosphine oxide (Irg819), bis(1 - (2,4 - difluorophenyl) - 3 - pyrrolyl)titanocene (Irg784), 2 - hydroxy - 2 - methylphenylacetone (Irg1173); Furthermore, the organic solvent is xylene.

[0026] Specifically, the materials of the first optical isolation layer, the second optical isolation layer, the third optical isolation layer, and the fourth optical isolation layer are respectively selected from at least one of polymethyl methacrylate (PMMA), polystyrene (PS), polyvinyl alcohol (PVA), and cellulose acetate (CA).

[0027] Specifically, the material of the gain medium layer is colloidal quantum dots; Further, the colloidal quantum dots are cadmium selenide quantum dots, indium phosphide quantum dots, cadmium sulfide quantum dots or perovskite quantum dots.

[0028] A method for preparing a colloidal quantum dot laser device specifically includes the following steps: S1. Weigh liquid crystal monomers, chiral dopants, surfactants, photoinitiators and organic solvents according to mass fractions to prepare a chiral liquid crystal mixture; scrape the chiral liquid crystal mixture onto a support substrate and cure it by light to obtain a first reflective layer; S2. Prepare an optical isolation layer solution, scrape it onto the first reflective layer, and anneal it at 60 - 80 °C for 0.1 - 1 hour to obtain a first optical isolation layer; S3. Weigh liquid crystal monomers, chiral dopants, surfactants, photoinitiators and organic solvents according to mass fractions to prepare a chiral liquid crystal mixture; scrape the chiral liquid crystal mixture onto the first optical isolation layer and cure it by light to obtain a second reflective layer; S4. Prepare an optical isolation layer solution, scrape it onto the second reflective layer, and anneal it at 60 - 80 °C for 0.1 - 1 hour to obtain a second optical isolation layer; S5. Prepare a colloidal quantum dot dispersion liquid, scrape the colloidal quantum dot dispersion liquid onto the second optical isolation layer to form a gain medium layer; S6. Prepare an optical isolation layer solution according to the method of step S4, scrape it onto the gain medium layer, and anneal it at 60 - 80 °C for 0.1 - 1 hour to obtain a third optical isolation layer; S7. Prepare a chiral liquid crystal mixture according to the method of step S3; scrape the chiral liquid crystal mixture onto the third optical isolation layer and cure it by light to obtain a third reflective layer; S8. Prepare an optical isolation layer solution according to the method of step S2, scrape it onto the third reflective layer, and anneal it at 60 - 80 °C for 0.1 - 1 hour to obtain a fourth optical isolation layer; S9. Prepare a chiral liquid crystal mixture according to the method of step S1; scrape the chiral liquid crystal mixture onto the fourth optical isolation layer and cure it by light to obtain a fourth reflective layer; separate the substrate by mechanical peeling to obtain an independent flexible colloidal quantum dot laser device.

[0029] Specifically, the support substrate materials include glass, silicon wafers, sapphire, etc., all of which are suitable for the peeling process; Specifically, the light curing in step S1 is ultraviolet lamp curing, and the curing time is 5 minutes; Specifically, the optical isolation layer solution is prepared by dissolving at least one of polymethyl methacrylate (PMMA), polystyrene (PS), polyvinyl alcohol (PVA), and cellulose acetate (CA) in deionized water or an organic solvent; preferably, it is a polyvinyl alcohol solution prepared by dissolving polyvinyl alcohol in deionized water; or PMMA is dissolved in chlorobenzene to prepare a PMMA chlorobenzene solution with a concentration of 10 mg / mL. In a specific embodiment, the annealing temperature is 60 °C, and the annealing time is 30 min or 1 h. Specifically, the thickness of the left-handed reflective layer and the right-handed reflective layer is controlled by the distance between the doctor blade and the substrate and the coating speed; the reflectivity of the left-handed reflective layer and the right-handed reflective layer for different lights is controlled by changing the type and concentration of the chiral dopant; the reflectivity formula of the left-handed reflective layer and the right-handed reflective layer for different lights is:

[0030] Among them, is the birefringence index of the polymer cholesteric liquid crystal film (CLC mixture), HTP is the helical twisting power of the chiral monomer, and c is the concentration of the chiral monomer in the CLC mixture.

[0031] The cavity length of the F-P resonator of the flexible colloidal quantum dot laser device is an integer multiple of the half-wavelength of the ASE emission of the gain medium layer. In summary, the flexible colloidal quantum dot laser device based on all-solution processing of the present invention can achieve the selection of laser modes by adjusting the cavity length and the thickness of the gain medium, etc.

[0032] The liquid crystal monomer used in the embodiment of the present invention is RM257, and its chemical structure is as follows: ; The left-handed dopant used in the embodiment of the present invention is S811, and its chemical structure is as follows: ; The right-handed dopant used in the embodiment of the present invention is LC-756, and its chemical structure is as follows: ; The photoinitiator used in the embodiment of the present invention is Irg651, and its chemical structure is as follows: ; The surfactant used in the embodiment of the present invention is N-ethyl perfluorooctanesulfonamidoethyl methacrylate, and its chemical structure is as follows: .

[0033] Example 1 As Figure 1As shown in the figure, this embodiment provides a flexible colloidal quantum dot laser device, whose structure from bottom to top is successively a first reflective layer 1, a first optical isolation layer 2, a second reflective layer 3, a second optical isolation layer 4, a gain medium layer 5, a third optical isolation layer 6, a third reflective layer 7, a fourth optical isolation layer 8, and a fourth reflective layer 9; the thicknesses are successively about: 5 μm, 140 nm, 5 μm, 115 nm, 50 nm, 115 nm, 3 μm, 140 nm, 3 μm; Among them, the first reflective layer 1, the second reflective layer 3, the third reflective layer 7, and the fourth reflective layer 9 are a right-handed reflective layer, a left-handed reflective layer, a left-handed reflective layer, and a right-handed reflective layer respectively; The preparation method specifically includes the following steps: S1. Weigh liquid crystal monomers, chiral dopants, surfactants, photoinitiators, and organic solvents according to mass fractions to prepare a chiral liquid crystal mixture; scrape the chiral liquid crystal mixture onto a support substrate and cure it by light to obtain the first reflective layer; specifically including: S101. Clean the glass substrate: Clean the glass substrate with water, acetone, ethanol, and water for 15 minutes respectively; treat the clean glass substrate with plasma for 15 minutes; S102. Prepare the first reflective layer: Coat the right-handed liquid crystal mixture on the glass substrate by scraping. Control parameters such as the height of the blade from the substrate and the coating rate; after uniform coating, polymerize with an ultraviolet lamp (7.5 mW / cm 2 ) for 5 minutes to prepare a right-handed CLC layer with a thickness of 5 μm, that is, the first reflective layer.

[0034] S2. Prepare the first optical isolation layer: Dissolve PVA in deionized water to obtain a PVA solution with a concentration of 10 mg / ml, that is, the optical isolation layer solution, and scrape it on the surface of the first reflective layer (CLC film), and anneal at 60 °C for 30 minutes.

[0035] S3. Prepare the second reflective layer: Weigh liquid crystal monomers, chiral dopants, surfactants, photoinitiators, and organic solvents according to mass fractions to prepare a left-handed liquid crystal mixture; scrape the chiral liquid crystal mixture onto the first optical isolation layer and polymerize it with an ultraviolet lamp (7.5 mW / cm 2 ) for 5 minutes and cure it by light to obtain the second reflective layer with a thickness of 5 μm.

[0036] S4. Prepare the second optical isolation layer: Dissolve PMMA in chlorobenzene to prepare a PMMA solution with a concentration of 10 mg / mL, scrape the solution on the surface of the second reflective layer, and place the sample in an environment of 60 °C for annealing for 1 hour to improve the compactness and stability of the film.

[0037] S5. Prepare a perovskite quantum dot dispersion. Spin-coat 75 μL of the perovskite quantum dot dispersion on the second optical isolation layer and anneal it at 80 °C for 30 minutes to form a gain medium layer with a thickness of 50 nm, and the photoluminescence peak is 540 nm ( Figure 2 ); The preparation method of the perovskite quantum dot dispersion is as follows: S501. Add Cs2CO3 (0.386 g, 1.18 mmol), OA (1.27 mL), and ODE (18.73 mL) into a 50 mL three-necked flask, stir under an argon atmosphere, heat up to 120 °C and keep for 1 hour, then heat up the mixture to 150 °C under an argon atmosphere. After the mixture is completely dissolved, a Cs-OA precursor is prepared. S502. Add PbBr2 (0.0734 g, 0.2 mmol) and ODE (12 mL) into a 50 mL three-necked flask, stir under an argon atmosphere, and heat up to 120 °C and keep for 1 hour; Mix OA (0.5 ml) and OAm (1.5 ml), quickly inject the mixture into the reaction flask with a syringe, and continue stirring until completely dissolved; After the solution becomes clear, heat up to 180 °C, turn on the cooling water, quickly inject 1 ml of the Cs-OA precursor solution, react for 1 minute, and then cool with an ice-water bath to terminate the reaction. S503. Mix the CsPbBr3 perovskite quantum dots obtained in step S502 with about 15 mL of ethyl acetate, centrifuge at a speed of 8000 revolutions per minute for 10 minutes; Pour off the supernatant, evaporate the remaining liquid, and disperse the quantum dots at the bottom of the centrifuge tube in n-hexane to obtain a perovskite quantum dot dispersion.

[0038] In this embodiment, the perovskite quantum dots, as the core material of the gain medium layer, not only provide the mechanism of optical gain and stimulated emission, but also achieve tunable laser output through the synergistic effect with the CLC mirror. At the same time, the excellent optical properties and stability of the perovskite quantum dots also ensure the high performance and durability of the laser.

[0039] S6. Prepare the third optical isolation layer: According to the method in step S4, dissolve PMMA in chlorobenzene to prepare a PMMA chlorobenzene solution with a concentration of 10 mg / mL. Spin-coat the solution on the surface of the gain medium layer, and anneal the sample in an environment of 60 °C for 1 hour to obtain the third optical isolation layer.

[0040] S7. Prepare the chiral liquid crystal mixture according to the method in step S3; Spin-coat the chiral liquid crystal mixture on the third optical isolation layer and polymerize it with a UV lamp (7.5 mW / cm 2 ) for 5 minutes to obtain the third reflective layer by photocuring; S8. Prepare the optical isolation layer solution according to the method of step S2, scrape and coat it on the third reflective layer, and anneal it at 60 °C for 30 hours to obtain the fourth optical isolation layer; S9. Prepare the chiral liquid crystal mixture according to the method of step S1; scrape and coat the chiral liquid crystal mixture on the fourth optical isolation layer, and polymerize it with a UV lamp (7.5 mW / cm 2 ) for 5 minutes, and obtain the fourth reflective layer by photocuring; separate the substrate by mechanical peeling to obtain an independent flexible colloidal quantum dot laser device.

[0041] Figure 3 The reflection spectrum of the first reflective layer is shown. Figure 4 The transmission spectra of the right-handed / left-handed CLC stack architectures of each reflective layer are shown. Figure 5 The ASE intensity vs. pump light energy density dependence spectrum of the gain medium layer (i.e., the perovskite quantum dot film) is shown; it can be seen from the figure that the perovskite quantum dot film has a relatively high ASE threshold and a relatively low ASE intensity. Figure 6 The ASE intensity vs. pump light energy density dependence spectrum of the flexible colloidal quantum dot laser device is shown; it can be seen from the figure that the CLC stack architecture significantly reduces the ASE threshold of the perovskite quantum dot film and greatly enhances its ASE intensity.

[0042] In this embodiment, the preparation method of the right-handed chiral liquid crystal mixture: dissolve the liquid crystal monomer RM-257 (93 wt%), the chiral dopant LC-765 (5%), the photoinitiator Irg651 (1 wt%) and the surfactant N-ethyl perfluorooctanesulfonamidoethyl methacrylate (1 wt%) in 1.5 wt% xylene, and stir at 50 °C for one hour.

[0043] In this embodiment, the preparation method of the left-handed chiral liquid crystal mixture: dissolve the liquid crystal 5CB (82.53 wt%), the chiral dopant S811 (14.47%), the photoinitiator Irg651 (2 wt%) and the surfactant N-ethyl perfluorooctanesulfonamidoethyl methacrylate (1 wt%) in 1.5 wt% xylene, and stir at 50 °C for one hour.

[0044] Example 2 This embodiment provides a flexible colloidal quantum dot laser device, whose structure is the same as that of Example 1; the difference is that the ratio of the liquid crystal chiral dopant and the type of colloidal quantum dots are changed to match the reflection band of the cholesteric liquid crystal with the ASE emission wavelength of the colloidal quantum dots, so as to realize laser emission in different bands. During the preparation process: In the right-handed liquid crystal mixture, the ratio of the liquid crystal monomer to the chiral dopant is different. The mass ratios of the liquid crystal monomer RM-257, the chiral dopant LC-765, the photoinitiator Irg651, and the surfactant N-ethyl perfluorooctanesulfonamidoethyl methacrylate are 94.32%, 3.68%, 1%, and 1% respectively; In the left-handed liquid crystal mixture, the ratio of the liquid crystal monomer to the chiral dopant is different. The mass ratios of the liquid crystal monomer 5CB, the chiral dopant S811, the photoinitiator Irg651, and the surfactant N-ethyl perfluorooctanesulfonamidoethyl methacrylate are 84.38%, 12.62%, 2%, and 1% respectively; The types of colloidal quantum dots are different; in this embodiment, the colloidal quantum dots are cadmium selenide quantum dots, and the preparation method is as follows: S501. Place 1 ml of CdSe, 1 ml of n-trioctylphosphine (TOP), and 4 ml of 1-octene into a three-necked flask and react at a temperature of 310 °C; S502. Mix 2 ml of 0.5 M zinc oleate (Zn(OA)2), 3 ml of 2 M TOPSe, 3 ml of 0.5 M cadmium oleate, and 6 ml of 1-octene solution, and add it to the three-necked flask at a constant rate of 5 ml / h. Add 2 μl of Zn(OA)2 to the reactor every 40 min and continue the reaction for 120 min to finally obtain CdSe / Cd x Zn 1−x Se QDs; S503. Add 8 ml of 0.5 M Zn(OA)2, 1 ml of 2 M TOPS, and 1 ml of 2 M TOPSe to the three-necked flask. Inject 8 ml of Zn(OA)2 into the three-necked flask at one time at an injection rate of 4 ml / h to grow the ZnSe 0.5 S 0.5 shell; S504. Add 2 ml of 0.5 M Zn(OA)2 and 0.5 ml of 2 M TOPS to the three-necked flask at an injection rate of 4 ml / h to prepare a ZnS protective layer; S505. Purify the cadmium selenide quantum dots using toluene and acetonitrile, and disperse the purified QDs in octane to obtain a cadmium selenide quantum dot dispersion. The emission peak of the prepared cadmium selenide quantum dot film is near 623 nm.

[0045] Example 3 This embodiment provides a flexible colloidal quantum dot laser device, which is different from that of Embodiment 1 in that the first reflective layer, the second reflective layer, the third reflective layer, and the fourth reflective layer are a left-handed reflective layer, a right-handed reflective layer, a right-handed reflective layer, and a left-handed reflective layer respectively, and the thickness is the same as that of Embodiment 1; by changing the positions of the left / right-handed reflective layers, the right-handed polarized light is reflected first, and then the left-handed polarized light is reflected; During the preparation process, the left-handed reflective layer is prepared in steps S1 and S9; the right-handed reflective layer is prepared in steps S3 and S7; the remaining steps are the same as those in Embodiment 1.

[0046] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added, or deleted. For example, the steps described in the disclosure of the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solutions disclosed in the present invention can be achieved, and no limitations are imposed herein.

[0047] The above specific embodiments do not constitute a limitation on the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A flexible colloidal quantum dot laser device, characterized in that: The colloidal quantum dot laser device has a structure that is, from bottom to top, a first reflection layer, a first optical isolation layer, a second reflection layer, a second optical isolation layer, a gain medium layer, a third optical isolation layer, a third reflection layer, a fourth optical isolation layer and a fourth reflection layer; Wherein, the first reflection layer, the second reflection layer, the third reflection layer and the fourth reflection layer are respectively a right-handed reflection layer, a left-handed reflection layer, a left-handed reflection layer and a right-handed reflection layer; or the first reflection layer, the second reflection layer, the third reflection layer and the fourth reflection layer are respectively a left-handed reflection layer, a right-handed reflection layer, a right-handed reflection layer and a left-handed reflection layer; The left-handed reflective layer and the right-handed reflective layer are both polymer cholesteric liquid crystal films; The material of the gain medium layer is colloidal quantum dots; The materials of the first optical isolation layer, the second optical isolation layer, the third optical isolation layer and the fourth optical isolation layer are respectively selected from at least one of polymethyl methacrylate, polystyrene, polyvinyl alcohol and cellulose acetate.

2. A flexible colloidal quantum dot laser device according to claim 1, characterized in that: The raw materials for preparing the polymer cholesteric liquid crystal film include, by weight percentage, 80-95wt% of liquid crystal monomers, 1-15wt% of chiral dopants, 1-2wt% of surfactants, 0.1-2wt% of photoinitiators and 1-2wt% of organic solvents.

3. A flexible colloidal quantum dot laser device according to claim 2, characterized in that: The liquid crystal monomer is selected from at least one of 1,4-bis-[4-(6-acryloxyhexyloxy)benzoyloxy]-2-methylbenzene, (4-(((4-(acryloxy)butoxy)carbonyl)oxy)benzoic acid 2-methyl-1,4-diphenolate, 4'-pentyl-4-biphenylcarbonitrile, and 1,4-bis-[4-(3-acryloxypropoxy)benzoyloxy]-2-methylbenzene; The chiral dopant includes a left-handed dopant or a right-handed dopant; the left-handed dopant is selected from at least one of 4-(4'-hexyloxy)benzoyloxybenzoic acid-2-octanol ester and 5,6-dihydro-5-(trans-4-propylcyclohexyl)-4H-dinaphtho[2,1-f:1',2'-h][1,5]dioxacyclononatetraene; the right-handed dopant is selected from at least one of 4-(4'-hexyloxy)benzoyloxybenzoic acid-R-2-octanol ester, (13bR)-5,6-dihydro-5-(trans-4-propylcyclohexyl)-4H-dinaphtho[2,1-f:1',2'-h][1,5]dioxacyclononatetraene, di-4-(4'-pentylcyclohexylbenzoic acid)-(1R)-1-phenyl-1,2-glycol ester and LC-756; The surfactant is N-ethyl perfluorooctanesulfonamidoethyl methacrylate; The photoinitiator is selected from at least one of benzoin diethyl ether, phenyl (2,4,6-trimethylphenyl acyl) phosphine oxide, bis (1- (2,4-difluorophenyl) -3-pyrrolyl) titanocene, and 2-hydroxy-2-methylphenyl acetone.

4. The flexible colloidal quantum dot laser device according to claim 1, characterized in that: The colloidal quantum dots are cadmium selenide quantum dots, indium phosphide quantum dots, cadmium sulfide quantum dots or perovskite quantum dots.

5. The flexible colloidal quantum dot laser device according to claim 1, characterized in that: The thickness of the first reflection layer is different from that of the fourth reflection layer, and the thickness of the second reflection layer is different from that of the third reflection layer; the length of the FP resonant cavity of the flexible colloidal quantum dot laser device is an integer multiple of half the wavelength of ASE emission of the gain medium layer.

6. A flexible colloidal quantum dot laser device according to any one of claims 1 to 5, characterized in that: The thicknesses of the first reflection layer, the first optical isolation layer, the second reflection layer, the second optical isolation layer, the gain medium layer, the third optical isolation layer, the third reflection layer, the fourth optical isolation layer and the fourth reflection layer are 3~6μm, 120~150nm, 3~6μm, 100~120nm, 40~60nm, 100~120nm, 2~4μm, 120~150nm and 2~4μm, respectively.

7. A method for preparing a flexible colloidal quantum dot laser device according to any one of claims 1 to 6, characterized in that: The specific steps include: S1. Weighing liquid crystal monomers, chiral dopants, surfactants, photoinitiators and organic solvents according to mass fractions to prepare a chiral liquid crystal mixture; applying the chiral liquid crystal mixture onto a supporting substrate, and photocuring to obtain a first reflective layer; S2. Prepare an optical isolation layer solution, apply it onto the first reflective layer, and anneal it at 60 to 80°C for 0.1 to 1 hour to obtain a first optical isolation layer; S3. Weighing liquid crystal monomers, chiral dopants, surfactants, photoinitiators and organic solvents according to mass fractions to prepare a chiral liquid crystal mixture; applying the chiral liquid crystal mixture onto the first optical isolation layer, and photocuring to obtain a second reflective layer; S4. Prepare an optical isolation layer solution, apply it onto the second reflective layer, and anneal it at 60 to 80°C for 0.1 to 1 hour to obtain a second optical isolation layer; S5. Preparing a colloidal quantum dot dispersion, and coating the colloidal quantum dot dispersion on the second optical isolation layer to form a gain medium layer; S6. Prepare an optical isolation layer solution according to the method of step S4, apply it onto the gain medium layer, and anneal it at 60-80°C for 0.1-1 hour to obtain a third optical isolation layer; S7. Prepare a chiral liquid crystal mixture according to the method of step S3; apply the chiral liquid crystal mixture onto the third optical isolation layer, and photocuring to obtain a third reflective layer; S8. Prepare an optical isolation layer solution according to the method of step S2, apply it onto the third reflective layer, and anneal it at 60-80° C. for 0.1-1 hour to obtain a fourth optical isolation layer; S9. Prepare a chiral liquid crystal mixture according to the method of step S1; scrape the chiral liquid crystal mixture onto the fourth optical isolation layer, and photocuring to obtain a fourth reflective layer; separate the substrate by mechanical peeling to obtain an independent flexible colloidal quantum dot laser device.

8. The method for preparing a flexible colloidal quantum dot laser device according to claim 7, characterized in that: The support substrate material in step S1 includes glass, silicon wafer or sapphire; the light curing is ultraviolet lamp curing, and the curing time is 5 minutes.

9. The method for preparing a flexible colloidal quantum dot laser device according to claim 7, characterized in that: The annealing temperature in steps S2, S4, S6 and S8 is 60°C.

10. Application of a flexible colloidal quantum dot laser device as described in any one of claims 1 to 6 in flexible display, optical communication, biosensing or wearable devices.

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