A method for improving stability of quantum dots

Abstract

The application discloses a method for improving stability of quantum dots, and belongs to the technical field of photoelectric display materials. The method comprises the following steps: (1) obtaining core-shell quantum dot material; (2) dissolving the core-shell quantum dot material, vacuumizing until no air bubbles exist, heating, adding quantum dot exchange ligand, cooling to room temperature, adding precipitant, centrifuging, and obtaining polar quantum dot material; (3) heating and dissolving a mixture containing the polar quantum dot material and a polymer until a uniform and stable quantum dot polymer precursor glue liquid is formed; (4) sequentially performing atomization and instantaneous drying on the quantum dot polymer precursor glue liquid to obtain quantum dot polymer microspheres; and (5) performing atomic layer deposition of aluminum oxide on the quantum dot polymer microspheres to obtain coated quantum dot polymer microspheres. In the application, the polymer and the ALD coating layer can protect the quantum dots from the influence of oxygen and water vapor, and greatly improve the service life of the quantum dots.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optoelectronic display materials, and particularly relates to a method for improving stability of quantum dots. BACKGROUND

[0002] Quantum dots are excellent semiconductor light-emitting materials, and have unique photoelectric properties and broad application prospects. According to their physical properties, the application of quantum dots in display mainly includes electroluminescence and photoluminescence. At present, quantum dot light-emitting diodes (AM-QLED) based on electroluminescence are in the research and development stage and are close to commercialization. Applications using photoluminescence mainly include quantum dot light conversion films / quantum dot diffusion plates and quantum dot color filters. The former has been widely used in television products. By adding a layer of quantum dot light conversion film / quantum dot diffusion plate on a blue backlight, a white backlight is obtained, and then combined with the color filter film inside the liquid crystal display panel, full-color display is realized, and the color gamut, color purity and resolution are significantly enhanced.

[0003] Taking the micro display technology Micro-LED as an example, compared with LCD, OLED and other display technologies, Micro-LED has greater advantages in brightness, resolution, contrast, energy consumption, service life, response speed, thermal stability and the like. These advantages enable Micro-LED to be applied in AR / VR, wearable display and other applications with high requirements for power consumption, brightness and response speed. The difficulty of full-colorization of Micro-LED mainly lies in that to realize full-colorization of Micro-LED, the traditional method needs RGB three kinds of LEDs, and the driving voltage of each LED is different, which will increase the requirements for driving circuit design. Secondly, the materials of RGB three kinds of LEDs are different, and due to the difference in aging and attenuation curves of different materials, it is more likely to cause fluctuation of LED color accuracy in the full life cycle. Similarly, for Micro-LED full-colorization using quantum dot scheme, the life improvement of red and green quantum dots is crucial and is also the promotion of high-end display technology. SUMMARY

[0004] To solve the above technical problems, the application provides a method for improving the stability of quantum dots, which comprises the following steps: synthesizing alloyed core-shell quantum dots by high-temperature hot injection, and then performing surface ligand exchange, so that the quantum dots can be highly soluble in a polar solvent DMF; removing the solvent by high-temperature spraying, so that a polymer coats the quantum dots; further depositing a layer of Al2O3 with a uniform and controllable thickness on the outside of the polymer layer by atomic layer deposition (ALD), so as to further coat the quantum dots; and finally mixing a photosensitive resin, coating the photosensitive resin on an optically transparent substrate, and performing light curing to form a film, thereby solving the problem of unstable optical performance of quantum dot materials applied in a harsh environment with ultra-high light intensity, temperature and humidity. Moreover, the surface ligand exchange effectively ensures that the optical performance of the quantum dots is not affected, and the solubility of the quantum dots in the DMF system is increased. The polymer coating layer and the ALD coating layer can well protect the quantum dots from the influence of oxygen and water vapor, so that the quantum dots are more likely to be applied in commercial MiniLED scenes and Micro LED scenes, and a new technical route is opened up for improving the service life of the quantum dots and the scene application.

[0005] To achieve the above-mentioned purposes, the application provides the following technical solutions:

[0006] In one aspect, the application provides a method for improving the stability of quantum dots, comprising the following steps:

[0007] (1) obtaining core-shell quantum dot material;

[0008] (2) dissolving the core-shell quantum dot material, vacuumizing until no bubbles are generated, heating, adding quantum dot exchange ligand, cooling to room temperature, adding a precipitating agent, and centrifuging to obtain polar quantum dot material;

[0009] (3) heating and dissolving a mixture containing the polar quantum dot material and a polymer until a uniform and stable quantum dot polymer precursor glue solution is formed;

[0010] (4) sequentially performing atomization and instantaneous drying on the quantum dot polymer precursor glue solution to obtain quantum dot polymer microspheres;

[0011] (5) performing Al2O3 atomic layer deposition on the quantum dot polymer microspheres to obtain coated quantum dot polymer microspheres.

[0012] Optionally, in step (1), the core-shell quantum dot material comprises at least one of CdSe@ZnS, CdSe@CdS, ZnSe@ZnS and ZnSe@CdS.

[0013] Optionally, in step (1), the method for obtaining the core-shell quantum dot material comprises a high-temperature hot injection synthesis method.

[0014] Optionally, in step (2), the solvent used for the dissolving is a polar solvent.

[0015] Optionally, the polar solvent comprises N,N-dimethylformamide (DMF) and / or dimethyl sulfoxide (DMSO).

[0016] Optionally, in step (2), the heating is performed under a non-reactive gas atmosphere.

[0017] Optionally, in step (2), the heating is heating to 100-350°C.

[0018] Optionally, in step (2), the heating is heating to 320°C.

[0019] Optionally, in step (2), the quantum dot exchange ligand comprises at least one of 6-mercapto-1-hexanol, 2-mercapto-3-butanol, 3-mercapto-1-propanol, 2,3-dimercapto-1-propanol.

[0020] Optionally, in step (2), the ratio of the amount of the core-shell quantum dot material to the amount of the quantum dot exchange ligand is 45-55 mg: 1-3 mL.

[0021] Optionally, in step (2), the cooling is performed under a nitrogen atmosphere.

[0022] Optionally, in step (2), the precipitant comprises toluene.

[0023] Optionally, in step (2), the ratio of the amount of the core-shell quantum dot material to the amount of the precipitant is 45-55 mg: 5-13 mL.

[0024] Optionally, in step (2), the centrifugation is performed at a speed of 6000-8000 rpm.

[0025] Optionally, in step (2), the centrifugation is performed for a time of 1-5 min.

[0026] Optionally, in step (2), the centrifugation is performed at a speed independently selected from any value or a range between any two values of 6000 rpm, 6500 rpm, 7000 rpm, 7500 rpm, 8000 rpm.

[0027] Optionally, in step (2), the centrifugation is performed for a time independently selected from any value or a range between any two values of 1 min, 2 min, 3 min, 4 min, 5 min.

[0028] Optionally, in step (3), the polymer comprises at least one of polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polystyrene (PS), polycarbonate (PC), styrene-methyl methacrylate copolymer (MS), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polyacrylonitrile (PAN), acrylonitrile-styrene resin (AS).

[0029] Optionally, in step (3), the mixing mass ratio of the polar quantum dot material and the polymer is 1-3:20-35.

[0030] Optionally, in step (3), the solvent used for heating and dissolving is a polar solvent.

[0031] Optionally, the polar solvent comprises N,N-dimethylformamide (DMF) and / or dimethyl sulfoxide (DMSO).

[0032] Optionally, in step (3), the temperature for heating and dissolving is 40-60°C.

[0033] Optionally, in step (4), the temperature for atomization is 60-100°C.

[0034] The gas pressure for atomization is 70-100 MPa.

[0035] The fan frequency for atomization is 20-50 Hz.

[0036] Optionally, in step (4), the temperature for atomization is independently selected from any value or a range value between any two of 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, and 100°C.

[0037] Optionally, the gas pressure for atomization is independently selected from any value or a range value between any two of 70 MPa, 75 MPa, 80 MPa, 85 MPa, 90 MPa, 95 MPa, and 100 MPa.

[0038] Optionally, the fan frequency for atomization is independently selected from any value or a range value between any two of 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz, and 50 Hz.

[0039] Optionally, in step (4), the temperature for instantaneous drying is 100-150°C.

[0040] Optionally, in step (5), the thickness of the Al2O3 atomic layer deposition is 10-100 nm.

[0041] Optionally, in step (5), the thickness of the Al2O3 atomic layer deposition is independently selected from any value of 10 nm, 20 nm, 30 nm, 50 nm, 70 nm, 100 nm or a range between any two of the values.

[0042] Optionally, further comprising step (6): coating and photocuring the mixed glue liquid containing the coated quantum dot polymer microspheres, prepolymers, monomers and photoinitiators in sequence to obtain a quantum dot film.

[0043] Optionally, the prepolymers include at least one of aliphatic polyurethane acrylate, aliphatic polyurethane hexa-acrylate, tin-free aliphatic polyurethane di-acrylate, aromatic polyurethane acrylate, aromatic polyurethane hexa-acrylate, fluorine-modified polyurethane acrylate, silicone-modified polyurethane acrylate, 2-hydroxy-3-phenoxypropyl acrylate, epoxy acrylate, modified epoxy acrylate, epoxy methacrylate, fatty acid-modified epoxy acrylate, modified bisphenol A epoxy acrylate, phenolic epoxy acrylate, epoxy soybean oil acrylate, fatty acid-modified polyester hexa-acrylate, fatty acid-modified polyester acrylate, chlorinated polyester resin, modified polyester acrylate, amine-modified polyester acrylate, hyperbranched polyester acrylate, rosin-modified polyester acrylate, tertiary amine acrylate, hot-melt pure acrylate resin, pure acrylate resin, organic-inorganic hybrid acrylate oligomer, melamine acrylate, silicon-modified polyurethane acrylate, and polycaprolactone acrylate.

[0044] Optionally, the monomers include at least one of 4-tert-butylcyclohexyl acrylate, methacrylate ethylene urea ethoxy ester, m-phenoxyphenyl acrylate, dicyclopentenyl acrylate, dicyclopentenyl ethoxylate acrylate, ethoxylated phenoxy acrylate, 3,3,5-trimethylcyclohexyl acrylate, o-phenylphenoxyethyl acrylate, 2-(p-isopropylphenyl-phenoxy)-ethyl acrylate, ethoxy ethoxy ethyl acrylate, 3-hydroxy-2,2-dimethylpropyl-3-hydroxy-2,2-dimethylpropyl acrylate, tricyclodecane dimethanol diacrylate, dioxane diol diacrylate, polypropylene glycol (700) diacrylate, 1,6-hexanediol diacrylate, ethoxylated 1,6-hexanediol diacrylate, and dipropylene glycol diacrylate.

[0045] Optionally, the photoinitiator comprises at least one of 2-methyl-1-[4- (methylthio)phenyl]-2-morpholinopropanone, 2,4,6-trimethylbenzoyl- diphenylphosphine oxide, benzoin methyl ether, 2-hydroxy-2-methyl-1-phenyl-1- propanone, 1-hydroxycyclohexyl-phenyl ketone, benzophenone, isopropylthioxanthone (2,4 isomer mixture), 4-(N,N-dimethylamino)benzoic acid ethyl ester, 4-(N,N-dimethyl)benzoic acid isooctyl ester, 2-isopropylthioxanthone, 2-benzyl-2-(dimethylamino)-4-morpholine, 4-phenylbenzophenone, methyl o-benzoylbenzoate.

[0046] Optionally, the mass ratio of the quantum dot polymer microsphere product, the prepolymer, the monomer, the photoinitiator is 1-3:1-4:2-5:0.1-0.3.

[0047] Optionally, the coating is to coat the mixed glue liquid between the PET surfaces of the diffusion barrier film, and both the upper and lower surfaces are diffusion barrier films.

[0048] Optionally, the thickness of the coating is 20-60 μm.

[0049] Optionally, the thickness of the coating is independently selected from any value or a range value between any two values of 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm.

[0050] Optionally, the light curing is performed using an ultraviolet lamp.

[0051] Optionally, the wavelength of the ultraviolet lamp is 365 nm.

[0052] Optionally, the energy of the light curing is 500-2500 mj / cm 2 .

[0053] Optionally, the energy of the light curing is independently selected from any value or a range value between any two values of 500 mj / cm 2 , 750 mj / cm 2 , 1000 mj / cm 2 , 1250 mj / cm 2 , 1500 mj / cm 2 , 1750 mj / cm 2 , 2000 mj / cm 2 , 2250 mj / cm 2 , 2500 mj / cm 2 .

[0054] Compared with the prior art, the present application has the following beneficial effects:

[0055] (1) The method of the present application first synthesizes core-shell quantum dots by high-temperature thermal injection. The quantum dots have covalent bond properties, and the physical and chemical properties are more stable. Moreover, the formation of the shell plays a good protective role for the internal light-emitting structure and defect passivation.

[0056] (2) The present application performs surface ligand exchange on the quantum dots synthesized by high-temperature thermal injection and dissolved in toluene nonpolar solvent, modifies them into alcohol-soluble quantum dots, and can be highly dissolved in DMF polar solvent and mixed with polymers for spray coating.

[0057] (3) The present application uses the method of atomic layer deposition (ALD) coating to deposit oxides on the surface of quantum dot polymer microspheres. The thickness of the surface deposition layer is controllable, and the effect of single-particle coating can be well achieved. It can be applied to various scenarios, avoiding the use of expensive water and oxygen barrier films, and the thickness of the product design can also be thinned.

[0058] (4) The present application changes the solubility by surface ligand exchange and performs subsequent polymer coating and ALD coating, which can well protect the quantum dots from external light, heat, humidity, oxygen, and water vapor stimulation, and ensure the long-term processing and service life of the quantum dots. It makes it more possible for quantum dots to be applied in commercial Mini-LED scenarios and Micro-LED scenarios, especially the high light intensity required by micro displays, which puts forward more stringent requirements for the light stability of quantum dots. The method of coating dispersion and ALD deposition can greatly improve the dispersibility of nanometer quantum dots, which is conducive to the structural design of high-concentration quantum dots. Quantum dots will not easily agglomerate, avoiding the deterioration of optical performance. BRIEF DESCRIPTION OF DRAWINGS

[0059] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some embodiments of the present application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor on the basis of these drawings.

[0060] Figure 1 The method for improving the stability of quantum dots of the present application is shown in the schematic diagram. DETAILED DESCRIPTION

[0061] The application will be further described in conjunction with specific examples. The following description is only a few embodiments of the application, and does not limit the application in any form. Although the preferred embodiments are disclosed as follows, the application is not limited thereto, and any skilled person in the art can make some changes or modifications to the disclosed technical contents without departing from the scope of the application, and the equivalent embodiments are also included in the scope of the application.

[0062] Unless otherwise specified, the raw materials in the comparative examples and the examples of the application are purchased through commercial channels and directly used without any special treatment.

[0063] Unless otherwise specified, the analysis methods in the comparative examples and the examples are all based on the conventional settings of instruments or equipment and conventional analysis methods.

[0064] The schematic diagram of the method for improving the stability of quantum dots is shown in Figure 1 , wherein A1 represents high-temperature hot injection synthesis of quantum dots, A2 represents exchange of quantum dot surface ligands, A3 represents modification of quantum dots dispersed in a DMF+polymer solution, A4 represents high-temperature spraying to form a polymer microsphere shell, A5 represents ALD coating of quantum dot polymer microspheres, and A6 represents preparation of a film for aging test.

[0065] Comparative Example 1

[0066] Preparation of CdSe@ZnS (without polymer coating, without ALD coating):

[0067] Firstly, 40 mL of TOP precursor was taken and stirred with 0.53 g of selenium powder and 2.135 g of sulfur powder until it was clear, and then it was placed aside for use. The main reaction system A was 250 mL of a three-necked flask containing 12 mmol of zinc acetate, 1.2 mmol of cadmium oxide, 18 mL of oleic acid and 60 mL of octadecene, which was vacuumed and aerated for three times at 120°C until there was no bubble, and then it was heated to 320°C under the protection of nitrogen. At this time, the solution was a light yellow transparent solution, and the TOP precursor solution was injected rapidly. At this time, the solution changed from light yellow to red brown. The coating material system B was 250 mL of a three-necked flask containing 4.130 g of zinc acetate, 45 mL of DDT and 45 mL of ODE, which was vacuumed and aerated for three times at 100°C until there was no bubble, and then it was heated to 120°C for standby. After the main system A reacted for a period of time, the material in the main system A was coated with the system B. The peristaltic pump was adjusted to the slowest speed, and 2 mL of Zn(DDT) was injected. The total reaction time was 7 min after the injection, and then the next injection coating was carried out. According to the above method, the core-shell structure quantum dots were dispersed in an organic solvent. A three-necked flask containing the quantum dot solution was placed on a magnetic stirrer, and a precipitating agent was added in proportion. The volume ratio of methanol to acetone was 2:1. With the addition of the precipitating agent, the quantum dot solution gradually changed from clear to turbid solution. The quantum dots were precipitated in a high-speed centrifuge at a speed of 7000 rpm per minute for 3 min. The precipitate was taken out and a small amount of toluene solvent was added to dissolve the quantum dots. The above steps were repeated, and the precipitating agent was added under stirring. After the centrifugation, the precipitate was dissolved in toluene, and the precipitating agent was added under stirring. The volume ratio of acetone to acetic acid was 2:1. Similarly, the quantum dots were precipitated in a high-speed centrifuge at a speed of 7000 rpm per minute for 3 min. The precipitate was repeatedly washed twice. The obtained precipitate was placed in a vacuum drying oven for drying, and then it was ground in a mortar for standby. Thus, the stable CdSe@ZnS quantum dot material was obtained, which was recorded as sample 1.

[0068] Comparative Example 2

[0069] Preparation of CdSe@ZnS (PMMA polymer coating, no ALD coating):

[0070] The surface ligand exchange and high temperature spray were carried out on the basis of sample 1 to obtain sample 2. The specific steps are as follows: 50 mg of CdSe@ZnS quantum dots powder obtained from comparative example 1 was dispersed in 5 mL of DMF solvent, and a stirrer was used to disperse it uniformly. The reaction system was heated to 130°C under nitrogen protection, and 2 mL of 6-mercapto-1-hexanol was quickly injected. The solution changed from turbidity to clear and transparent solution after a short reaction. The solution was naturally cooled to room temperature under nitrogen protection, and a precipitant toluene was added to the original reaction system solution. As the toluene increased, the clear solution gradually became turbid, indicating that the dispersibility of the quantum dots in the solution decreased, and gradually precipitated. The quantum dots were precipitated by centrifugation at a speed of 7000 rpm per minute for 3 minutes in a high-speed centrifuge. The precipitate was taken out and dried in a fume hood. After complete drying, it was ground in a mortar and sealed for preservation. The same proportion was followed to prepare and modify a large amount of quantum dots. Then 5 g of surface modified quantum dots and 20 g of PMMA polymer were put into 100 g of polar solvent DMF, and heated at 50°C for a long time to form a uniform and stable liquid precursor solution. The prepared quantum dot polymer precursor solution was transported to the nozzle of the spray equipment through a peristaltic pump and rubber tube. High pressure nitrogen was used to disperse and atomize the solution into droplets, and the polar solvent was mostly removed instantaneously by high temperature heat field (100°C). The whole process experienced the process of droplet atomization, high temperature heat field instantaneous drying. The equipment pressure was controlled at 75 MPa, and the fan frequency was 30 Hz. Quantum dot microsphere polymer powder was formed and collected by the cyclone collector of the spray equipment. The obtained quantum dot polymer powder was recorded as sample 2.

[0071] Example 1

[0072] Preparation of CdSe@ZnS (PMMA polymer coated, ALD coated):

[0073] The surface ligand exchange and high-temperature spraying and ALD coating are carried out on the basis of sample 1 to obtain sample 3. The specific steps are as follows: 50 mg of CdSe@ZnS quantum dot powder obtained in Comparative Example 1 is dispersed in 5 mL of DMF solvent, and a stirrer is used to disperse it uniformly, vacuum air exchange is carried out 3 times until there is no bubble, the reaction system is heated to 130 DEG C under nitrogen protection, 2 mL of 6-mercapto-1-hexanol is quickly injected, and the solution changes from turbidity to clear and transparent solution after a short reaction. Under nitrogen protection, it is naturally cooled to room temperature, and the precipitant toluene is added to the original reaction system solution. With the increase of toluene, the clear solution gradually becomes turbid, indicating that the dispersibility of the quantum dots in the solution is weakened, and gradually precipitates. In a high-speed centrifuge, a speed of 7000 rpm per minute is used to centrifuge for 3 min, and the quantum dots are precipitated. The precipitate is taken out and dried in a fume hood. After complete drying, it is ground in a mortar and sealed. Repeat the preparation and modification of the quantum dots in large quantities in the same proportion. Then 5 g of the surface-modified quantum dots and 20 g of PMMA polymer are put into 100 g of polar solvent DMF, and heated at 50 DEG C for a long time to form a uniform and stable liquid precursor glue solution. The prepared quantum dot polymer precursor solution is delivered to the nozzle of the spraying equipment through a peristaltic pump and rubber tube, and is dispersed and atomized into droplets by high-pressure nitrogen gas. The polar solvent is mostly removed instantaneously by high-temperature heat field (100 DEG C). The whole process goes through the process of droplet atomization, high-temperature heat field instantaneous drying, equipment pressure control is 75 MPa, and fan frequency is 30 Hz. Quantum dot microsphere polymer powder is formed and collected by the cyclone collector of the spraying equipment. By setting the ALD coating equipment parameters, the thickness of the Al2O3 deposition layer is controlled to be 20 nm, and the quantum dot polymer powder is subjected to ALD coating. The obtained ALD coated quantum dot polymer powder is recorded as sample 3.

[0074] Example 2

[0075] Preparation of CdSe@ZnS (PVDF polymer coating, ALD coating):

[0076] The surface ligand exchange and high-temperature spraying and ALD coating are carried out on the basis of sample 1 to obtain sample 4. The specific process is as follows: 50 mg of CdSe@ZnS quantum dot powder obtained from comparative example 1 is dispersed in 5 mL of DMF solvent, and a stirrer is used to disperse it uniformly, and the reaction system is heated to 130 DEG C under nitrogen protection, and 2 mL of 6-mercapto-1-hexanol is quickly injected, and the solution changes from turbidity to clear and transparent solution after a short time. Under nitrogen protection, the solution is naturally cooled to room temperature, and the precipitant toluene is added to the original reaction system solution, and as the toluene increases, the clear solution gradually becomes turbid, indicating that the dispersibility of the quantum dots in the solution is weakened, and gradually precipitates, and the quantum dots are precipitated in a high-speed centrifuge at a speed of 7000 rpm per minute for 3 minutes, and the precipitate is taken out and dried in a fume hood, and after complete drying, it is ground in a mortar and sealed. Repeat the preparation and modification of a large amount of quantum dots in the same proportion. Then 5 g of the surface-modified quantum dots and 20 g of PVDF polymer are put into 100 g of polar solvent DMF, and heated at 50 DEG C for a long time to form a uniform and stable liquid precursor solution. The prepared quantum dot polymer precursor solution is delivered to the nozzle of the spraying equipment through a peristaltic pump and rubber tube, and is dispersed and atomized into droplets by high-pressure nitrogen gas, and is subjected to a high-temperature heat field (100 DEG C) to instantaneously remove most of the polar solvent. The whole process undergoes the processes of droplet atomization, high-temperature heat field instant drying, equipment pressure control of 75 MPa, and fan frequency of 30 Hz, and quantum dot microsphere polymer powder is formed and collected by the cyclone collector of the spraying equipment. By setting the ALD coating equipment parameters, the thickness of the Al2O3 deposition layer is controlled to be 20 nm, and the quantum dot polymer powder is subjected to ALD coating, and the obtained ALD coated quantum dot polymer powder is recorded as sample 4.

[0077] Example 3

[0078] Preparation of CdSe@ZnS (EVOH polymer coating, ALD coating):

[0079] The surface ligand exchange and high-temperature spraying and ALD coating were carried out on the basis of sample 1 to obtain sample 5. The specific process is as follows: 50 mg of CdSe@ZnS quantum dot powder obtained from comparative example 1 was dispersed in 5 mL of DMF solvent, and a stirrer was used to disperse it uniformly, vacuum air exchange was carried out 3 times until there was no bubble, the reaction system was heated to 130 DEG C under nitrogen protection, 2 mL of 6-mercapto-1-hexanol was quickly injected, and the solution changed from turbidity to clear and transparent solution after a short reaction. Under nitrogen protection, it was naturally cooled to room temperature, and the precipitant toluene was added to the original reaction system solution. With the increase of toluene, the clear solution gradually became turbid, indicating that the dispersibility of the quantum dots in the solution was weakened, and gradually precipitated out. In a high-speed centrifuge, a speed of 7000 rpm per minute was used to centrifuge for 3 min, and the quantum dots were precipitated out. The precipitate was taken out and dried in a fume hood, and after complete drying, it was ground in a mortar and sealed for preservation. The same proportion was followed to repeat the preparation and modification of a large amount of quantum dots. Then 5 g of the surface modified quantum dots and 20 g of EVOH polymer were put into 100 g of polar solvent DMF, and heated at 50 DEG C for a long time to form a uniform and stable liquid precursor glue solution. The prepared quantum dot polymer precursor solution was transported to the nozzle of the spraying equipment through a peristaltic pump and rubber tube, and was dispersed and atomized into droplets by high-pressure nitrogen gas, and experienced a high-temperature heat field (100 DEG C) to instantaneously remove most of the polar solvent. The whole process experienced the process of droplet atomization, high-temperature heat field instant drying, and the equipment pressure was controlled at 75 MPa, and the fan frequency was 30 Hz. Quantum dot microsphere polymer powder was formed and collected by the cyclone collector of the spraying equipment. By setting the ALD coating equipment parameters, the thickness of the Al2O3 deposition layer was controlled to be 20 nm, and the quantum dot polymer powder was subjected to ALD coating. The obtained ALD coated quantum dot polymer powder is recorded as sample 5.

[0080] Experimental example 1

[0081] The above obtained samples 1-5 (CdSe@ZnS (without polymer coating, without ALD coating), CdSe@ZnS (PMMA polymer coating, without ALD coating), CdSe@ZnS (PMMA polymer coating, ALD coating), CdSe@ZnS (PVDF polymer coating, ALD coating), CdSe@ZnS (EVOH polymer coating, ALD coating) respectively) were mixed and stirred with a prepolymer (2-hydroxy-3-phenoxypropyl acrylate), a monomer (dicyclopentenyl acrylate), and a photoinitiator (2-hydroxy-2-methyl-1-phenyl-1-propanone) in a mass ratio of 2g:3g:5g:0.1g to obtain five glue solutions, and then the five glue solutions were coated on the PET (polyethylene terephthalate) surface of the barrier diffusion film using a coating machine with a thickness of 50 μm, with barrier diffusion film on both the top and bottom surfaces, and cured for 3 s under a 365 nm ultraviolet lamp to obtain five optical perovskite quantum dot films that can be used for optical performance testing and aging performance testing. The obtained five quantum dot films were subjected to corresponding optical performance testing and corresponding aging data recording, wherein the optical performance testing equipment model was Hera 01-VIS, and the aging test equipment was an aging test chamber. The test results are shown in Table 1.

[0082] Table 1 Comparison of corresponding optical performance testing and aging data of different samples

[0083]

[0084] Note: a Test conditions: temperature 65℃, humidity 95%, 1000h;

[0085] b Test conditions: temperature 45℃, humidity 95%, light intensity 38W / m 2 (450nm), 1000h.

[0086] As can be seen from Table 1, the CdSe@ZnS (EVOH polymer coating, ALD coating) sample has the highest light conversion efficiency and the best humidity and heat stability and light stability. It is sufficient to prove that the method of the present application is crucial for improving the high stability of quantum dots, and can be expanded to various polymer systems and quantum dot synthesis systems.

[0087] The above is only a few embodiments of the present application, and does not limit the present application in any form. Although the preferred embodiments are disclosed as above, they are not intended to limit the present application. Any skilled person in the art can make some changes or modifications to the above disclosed technical content without departing from the scope of the technical solution of the present application, and the equivalent embodiments are equivalent to the equivalent embodiments, which are within the scope of the technical solution.

Claims

1. A method of improving stability of quantum dots, characterized by, It comprises the following steps: (1) obtaining core-shell quantum dot material; (2) dissolving the core-shell quantum dot material, vacuumizing until no bubble, heating, adding quantum dot exchange ligand, cooling to room temperature, adding precipitant, centrifuging, obtaining polar quantum dot material; (3) heating and dissolving the mixture containing the polar quantum dot material and polymer until forming uniform and stable quantum dot polymer precursor glue liquid; (4) atomizing and instantaneously drying the quantum dot polymer precursor glue liquid in sequence to obtain quantum dot polymer microspheres; (5) performing Al2O3 atomic layer deposition on the quantum dot polymer microspheres to obtain coated quantum dot polymer microspheres; In step (1), the core-shell quantum dot material is selected from at least one of CdSe@ZnS, CdSe@CdS, ZnSe@ZnS and ZnSe@CdS; In step (2), the quantum dot exchange ligand is selected from at least one of 6-mercapto-1-hexanol, 2-mercapto-3-butanol, 3-mercapto-1-propanol and 2,3-dimercapto-1-propanol; In step (3), the polymer is EVOH.

2. The method of claim 1, wherein the quantum dots are stabilized by the addition of a stabilizing agent. In step (2), the heating is performed in a non-active gas atmosphere; The heating is heating to 100-350℃.

3. The method of claim 1, wherein the quantum dots are stabilized by the addition of a stabilizing agent. In step (2), the mass ratio of the core-shell quantum dot material to the quantum dot exchange ligand is 45-55 mg:1-3 mL.

4. The method of claim 1, wherein the quantum dots are stabilized by the addition of a stabilizing agent. In step (2), the cooling is performed in a nitrogen atmosphere.

5. The method of claim 1, wherein the quantum dots are stabilized by the addition of a stabilizing agent. In step (2), the precipitant is selected from toluene; The mass ratio of the core-shell quantum dot material to the precipitant is 45-55 mg:5-13 mL; The centrifuging speed is 6000-8000 rpm, and the centrifuging time is 1-5 min.

6. The method of claim 1, wherein the quantum dots are stabilized by the addition of a stabilizing agent. In step (3), the mass ratio of the polar quantum dot material to the polymer is 1-3:20-35; The heating and dissolving temperature is 40-60℃.

7. The method of claim 1, wherein the quantum dots are stabilized by the addition of a stabilizing agent. In step (4), the atomizing temperature is 60-100℃; The atomizing gas pressure is 70-100 MPa; The atomizing fan frequency is 20-50 Hz; The instantaneously drying temperature is 100-150℃.

8. The method of claim 1, wherein the quantum dots are stabilized by the addition of a stabilizing agent. In step (5), the thickness of the Al2O3 atomic layer deposition is 10-100 nm.

9. The method of claim 1, wherein the quantum dots are stabilized by the addition of a stabilizing agent. It further comprises step (6): coating and photocuring the mixed glue liquid containing the coated quantum dot polymer microspheres, prepolymer, monomer and photoinitiator in sequence to obtain quantum dot film.

10. The method of claim 9, wherein the quantum dots are stabilized by the addition of a stabilizing agent. The mixed mass ratio of the quantum dot polymer microsphere product, prepolymer, monomer and photoinitiator is 1-3:1-4:2-5:0.1-0.3; The coating thickness is 20-60 μm; The light-cured energy is 500-2500 mj / cm 2 .

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