Quantum dot composite particles, methods of preparation, and uses thereof

Abstract

The application discloses a quantum dot composite particle, a preparation method and application of the quantum dot composite particle in a light conversion device. The quantum dot composite particle comprises a single quantum dot core, a first shell layer coated outside the quantum dot core, and a second shell layer coated outside the first shell layer. The first shell layer is adsorbed with a stabilizer. The volume porosity of the second shell layer is less than that of the first shell layer. The stabilizer is a compound or a combination thereof used for maintaining the stability of the fluorescence properties of the quantum dot during storage or use. The quantum dot composite particle has good stability and effectively prolongs the service life of the device.

Description

Technical Field

[0001] This application relates to the field of nano-semiconductor materials, specifically to a quantum dot composite particle, its preparation method, and its application. Background Technology

[0002] Quantum dots are inorganic semiconductor light-emitting nanocrystals with three-dimensional dimensions ranging from 1 nm to 20 nm. Due to their particle size being smaller than or close to the exciton Bohr radius, quantum dots have advantages such as a wide excitation wavelength range, controllable particle size, narrow half-peak width, large Stokes shift, and strong photostability. Therefore, they are widely used in display, biological labeling, solar cell and other fields.

[0003] Quantum dot technology has been applied to the display field. Due to its narrow half-width at half-maximum (HWHM), the color gamut of quantum dot-based displays has been greatly improved. However, quantum dot materials can experience reduced efficiency and shifted emission peaks under environmental factors such as water, oxygen, light, and heat, due to problems such as water-oxygen etching, free radical attack, and ligand shedding. Therefore, one of the technologies related to quantum dots is how to increase their stability and maintain their excellent luminescent properties.

[0004] Existing quantum dot materials are designed with a coating layer to improve the stability of the material. However, the composite material still has a certain degree of water and oxygen permeability. Under long-term light and heat exposure, as trace amounts of water and oxygen continue to seep in, the quantum dots will inevitably gradually fail, resulting in the device's effective lifespan not meeting the usage requirements. Summary of the Invention

[0005] The purpose of this application is to improve the stability of quantum dots and maintain their excellent luminescent properties.

[0006] To achieve the above objectives, the technical solution adopted in this application is as follows: a quantum dot composite particle, comprising a single quantum dot core and a first shell layer covering the quantum dot core, wherein the first shell layer adsorbs a stabilizer, and a second shell layer is coated on the first shell layer, wherein the volume porosity of the second shell layer is less than that of the first shell layer.

[0007] As a preferred embodiment, the volumetric porosity of the first shell layer is 0.3 cm³. 3 / cm 3 ~0.8cm 3 / cm 3 The volumetric porosity of the second shell is 0.05–0.4 cm³. 3 / cm 3 .

[0008] As another preferred embodiment, the thickness of the first shell layer is 4nm to 20nm, and the thickness of the second shell layer is 2nm to 60nm.

[0009] As another preferred option, the first shell and the second shell are oxides with the same composition or different compositions.

[0010] As another preferred embodiment, the first shell is Si. x Al y O 2x+3 / 2y Zn x Mg y O x+y The first shell is made of SiO2, TiO2, ZrO2, Al2O3, ZnO, or SnO2; the second shell is made of Si. x Al y O 2x+3 / 2y Zn x Mg y O x+y The materials used are SiO2, TiO2, ZrO2, Al2O3, ZnO, or SnO2; preferably, x = 1 and y is a value from 0 to 0.8.

[0011] Alternatively, both the first shell layer and the second shell layer are made of Si. x Al y O 2x+3 / 2y .

[0012] As another preferred option, the stabilizer is selected from one or more of antioxidants, UV stabilizers, water absorbers, or quantum dot ligands.

[0013] As another preferred embodiment, the antioxidant comprises one or more of phenolic antioxidants, thioester antioxidants, or phosphate antioxidants; the quantum dot ligand is selected from one or more of the following: metal carboxylates, metal phosphonates, alkylamine compounds, carboxylic acid compounds, alkylphosphine compounds, alkylphosphine oxides, alkylphosphine derivatives, and mercapto compounds; preferably, the water-absorbing agent is selected from one or more of the following: polyvinyl alcohol, polyethylene glycol, polyacrylate, sulfonated polystyrene salts, glycerol, calcium chloride, and magnesium sulfate; preferably, the phenolic antioxidant is selected from the following... One or a mixture thereof: 2,6-di-tert-butyl-p-cresol, 4,6-bis(octylthiomethyl)o-cresol, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, isooctyl ester of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, octadecyl ester of β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate], triethylene glycol bisβ-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate, 3,9-bis[1,1-dimethyl] -2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane, 1,3,5-trimethyl-2,4,6,-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene; preferably, the thioester antioxidant is selected from one or more of the following mixtures: di(octadecyl)thiodipropionate, di(decadecyl)thiodipropionate, 3-(dodecylthio)propionate-2,2-bis[[3-(dodecylthio)-propionyloxy]methyl]-1,3-propanediol ester, 4,4 '-Thiobis(6-tert-butyl-m-cresol), 4,4'-Thiobis(6-tert-butyl-2-methylphenol); preferably, the phosphate ester antioxidant is selected from one or more of the following mixtures: bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, bis(octadecyl) pentaerythritol diphosphite, bis(2,4-dicumylphenyl) pentaerythritol-diphosphite, 4,4'-butylenebis-(3-methyl-6-tert-butylphenyl)-tetra(tetrazyl) diphosphite, diphenyl isooctyl phosphite;Preferably, the UV-resistant agent is selected from one or more of the following mixtures: poly(4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinol) ester, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1-(methyl)-10-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) ester, poly{[6-[(1, [1,3,3-Tetramethylbutyl)amino]]-1,3,5-triazine-2,4-[(2,2,6,6,-tetramethyl-piperidinyl)imine]-1,6-hexamethylenediamine[(2,2,6,6-tetramethyl-4-piperidinyl)imine]}, poly{[N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine]-[2,4,6-trichloro-1,3,5-triazine and N-butyl-1-butylamine]-[N-butyl-2,2,6,6-tetramethyl-4-piperidinylamine]}.

[0014] As another preferred embodiment, the quantum dot core is a quantum dot modified with a water-soluble ligand, and the size of the quantum dot core is 5nm to 30nm, FWHM < 35nm, and QY > 60%.

[0015] A method for preparing quantum dot composite particles is provided, comprising the following preparation steps:

[0016] S100, a first solution containing quantum dot cores is provided, and an oxide synthesis reaction is carried out in the first solution to coat the single quantum dot cores with a first shell layer, thereby obtaining a first nanoparticle; S200, the first nanoparticles are placed in a stabilizer environment, so that the stabilizer is adsorbed onto the first shell layer, thereby obtaining a second nanoparticle; S300, a second inorganic oxide synthesis reaction is carried out in a second solution containing the second nanoparticles, and the conditions of the synthesis reaction of the second oxide are controlled so that the volume porosity of the second shell layer is less than that of the first shell layer, thereby forming a second shell layer coating the outside of the first shell layer, thereby obtaining the quantum dot composite particle.

[0017] As another preferred option, the synthesis reaction of inorganic oxides is carried out in the first solution and the second solution using the sol-gel method, wherein the control conditions for the synthesis reaction of inorganic oxides include the raw material ratio and pH value.

[0018] As another preferred embodiment, the first shell layer is synthesized using silicate ester and organic aluminum alkoxide in step S100; the second shell layer is synthesized using silicate ester and organic aluminum alkoxide in step S300.

[0019] As another preferred embodiment, in step S100, the amount of silicate used is less than 85% of the total mass of the silicate and the aluminum alkoxide, and in step S300, the amount of silicate used is greater than 95% of the total mass of the silicate and the aluminum alkoxide, so that the volume porosity of the second shell is less than that of the first shell; the pH range in step S100 is 10-13, and the pH range in step S300 is 9-11.

[0020] As another preferred option, in step S200, the stabilizer is an antioxidant or an anti-UV agent, and the mass ratio of the stabilizer to the first nanoparticle is (1-7):20; or, the stabilizer is a quantum dot ligand, and the mass ratio of the stabilizer to the first nanoparticle is 1:(200-20).

[0021] A light conversion device is provided, comprising quantum dot composite particles of any of the above-mentioned types, or quantum dot composite particles prepared by any of the above-mentioned preparation methods.

[0022] A composition is provided comprising quantum dot composite particles of any of the above-described types, or quantum dot composite particles prepared by any of the above-described preparation methods.

[0023] Compared with the prior art, the beneficial effects of this application are as follows:

[0024] (1) The quantum dot composite nanoparticles of this application adsorb the stabilizer in the first shell layer through the first shell layer with high porosity. The stabilizer has properties such as anti-oxidation, anti-UV and hydrophobicity, which effectively improves the stability of quantum dots.

[0025] (2) The quantum dot composite nanoparticles of this application are coated with a second shell with low porosity on the outside of the first shell on which the stabilizer is adsorbed, which effectively prevents the stabilizer adsorbed on the first shell from seeping out and the external water from seeping in, so that the stabilizer can play its role better and improve the service life of the device; the two shells work together to make the fluorescence properties of the quantum dot composite nanoparticles more stable. Attached Figure Description

[0026] Figure 1 This is a schematic diagram illustrating the synthesis of quantum dot composite particles according to an embodiment of this application;

[0027] Figure 2 Stability test curves of LEDs using quantum dot composite particles from Examples 1, 1, and 2 are shown.

[0028] In the diagram: 1. Quantum dot core; 10. First nanoparticle; 2. First shell; 20. Second nanoparticle; 3. Second shell. Detailed Implementation

[0029] The present application will be further described below with reference to specific embodiments. It should be noted that, without conflict, the various embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0030] In the description of this application, it should be noted that the directional terms such as "center", "lateral", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this application.

[0031] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0032] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0033] One embodiment of this application provides a quantum dot composite particle, including a single quantum dot core 1, a first shell 2 covering the quantum dot core 1, and a second shell 3 covering the first shell 2. The volume porosity of the second shell 3 is less than that of the first shell 2, and the first shell 2 is adsorbed with a stabilizer. Figure 1 This illustrates a synthesis pathway for quantum dot composite particles.

[0034] The single quantum dot core mentioned in this application refers to an independent quantum dot particle. In other words, what is encased within the first shell layer 2 is not multiple quantum dots, but a single quantum dot. This helps to avoid the effects of aggregation and precipitation on the optical and electrical properties of the quantum dots. It should be noted that the quantum dot particle itself can have a core-shell structure. The stabilizer mentioned in this application refers to a compound or combination thereof used to maintain the stability of the fluorescence properties of quantum dots during storage or use.

[0035] Furthermore, the high volumetric porosity of the first shell layer 2 provides ample pore space, enabling better adsorption of stabilizers to coat the quantum dot core 1 and enhance its stability. Quantum dot composite particles adsorbing different stabilizers can be configured to achieve stabilization functions at various levels, such as improving antioxidant capacity, UV resistance, and hydrophobicity.

[0036] The adsorbent can be adsorbed inside and / or on the surface of the first shell 2. Together with the first shell 2, it encapsulates the quantum dot core 1 inside, which can effectively prevent the quantum dot core 1 from coming into contact with air, thereby avoiding the problem of quantum dot failure and helping to extend the service life of the device.

[0037] The adsorbent is adsorbed inside and / or on the surface of the first shell 2, which can prevent the quantum dot ligands from falling off and effectively improve the stability of the quantum dot composite particles.

[0038] The low volumetric porosity of the second shell 3 prevents the precipitation of the stabilizer adsorbed in the first shell 2, allowing the stabilizer to continue to function and continuously block the erosion of water and oxygen in the environment.

[0039] The design of the second shell 3 further increases the difficulty for water molecules and free oxygen to attack the quantum dots. Water molecules or free oxygen need to pass through the double-layer shell structure and stabilizer before they can contact the internal quantum dots, which helps to avoid quantum dot failure and further improves the lifespan of the device.

[0040] When only mesopores of 1.7 nm to 30 nm are considered, preferably, the volumetric porosity of the first shell layer 2 is 0.3 cm³. 3 / cm 3 ~0.8cm 3 / cm 3 The volumetric porosity of the second shell layer 3 is 0.05 cm³. 3 / cm 3 ~0.4cm 3 / cm 3 .

[0041] The stabilizer mentioned in this application is a compound or combination thereof used to maintain the stability of the fluorescence properties of quantum dots during storage or use. The stabilizer may be, but is not limited to, antioxidants, UV stabilizers, water absorbers, or quantum dot ligands.

[0042] Among them, antioxidants can be, but are not limited to, phenolic antioxidants, thioester antioxidants, and phosphate antioxidants.

[0043] Phenolic antioxidants may include, but are not limited to: 2,6-di-tert-butyl-p-cresol, 4,6-bis(octylthiomethyl)-o-cresol, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate isooctyl ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl ester, tetra[β-(3,5-di-tert-butyl,4-hydroxyphenyl)propionate]... [3,9-Bis[1,1-dimethyl-2-[(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]-2,4,8,10-tetraoxaspiro[5,5]undecane, 1,3,5-trimethyl-2,4,6,-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene.

[0044] Thioester antioxidants may include, but are not limited to: di(octadecyl)thiodipropionate, di(decadecyl)thiodipropionate, 2,2-bis[[3-(dodecylthio)-propionyloxy]methyl]-1,3-propanediol ester, 4,4'-thiobis(6-tert-butyl-m-cresol), and 4,4'-thiobis(6-tert-butyl-2-methylphenol).

[0045] Phosphate ester antioxidants may include, but are not limited to: bis(2,4-di-tert-butylphenyl) pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl) phosphite, bis(octadecyl) pentaerythritol diphosphite, bis(2,4-dicumylphenyl) pentaerythritol-diphosphite, 4,4'-butylenebis-(3-methyl-6-tert-butylphenyl)tetra(tetrazyl) diphosphite, and diphenylisooctyl phosphite.

[0046] UV stabilizers may be, but are not limited to: poly(4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinol) ester, bis(2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1-(methyl)-10-(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, poly(4-hydroxy-2,2,6,6-tetramethyl-1-piperidinol) ester, poly{[6-[(1,1,3,3 [-Tetramethylbutyl)amino]]-1,3,5-triazine-2,4-[(2,2,6,6-tetramethyl-piperidinyl)imino]-1,6-hexamethylenediamine[(2,2,6,6-tetramethyl-4-piperidinyl)imino]}, poly{[N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine]-[2,4,6-trichloro-1,3,5-triazine and N-butyl-1-butylamine]-[N-butyl-2,2,6,6-tetramethyl-4-piperidinylamine]}.

[0047] The absorbent agent may be, but is not limited to: polyvinyl alcohol, polyethylene glycol, polyacrylate, sulfonated polystyrene salt, glycerol, calcium chloride, and magnesium sulfate.

[0048] Quantum dot ligands are compounds that can coordinate with quantum dot nucleus 1, and can be, but are not limited to: metal carboxylates, metal phosphonates, alkylamine compounds, carboxylic acid compounds, alkylphosphine compounds, alkylphosphine oxides, alkylphosphine acids, and mercapto compounds.

[0049] Among them, metal carboxylates can be metal carboxylates with 8 to 22 carbon atoms on the carboxylate group, such as oleate, tetradecanoate, octanoate, butyrate, and oleic acid-octanoate.

[0050] Metal phosphonates can be hydrocarbon groups having 4 to 22 carbon atoms.

[0051] The metal ions in the metal salt can be any one or more of sodium, magnesium, aluminum, potassium, calcium, cesium, zirconium, manganese, zinc, and cadmium.

[0052] In some implementations, quantum dot ligands include combinations of multiple metal salts.

[0053] Alkylamine compounds may be, but are not limited to: methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, nonylamine, decylamine, dodecylamine, hexadecylamine, octadecylamine, dimethylamine, diethylamine, dipropylamine, tributylamine, or trioctylamine;

[0054] Carboxylic acid compounds include, but are not limited to: formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, octanoic acid, oleic acid, or benzoic acid;

[0055] Alkylphosphine compounds include, but are not limited to: methylphosphine, ethylphosphine, propylphosphine, butylphosphine, pentylphosphine, octylphosphine, dioctylphosphine, tributylphosphine, or trioctylphosphine;

[0056] Alkylphosphine oxide compounds include, but are not limited to: methylphosphine oxide, ethylphosphine oxide, propylphosphine oxide, butylphosphine oxide, pentylphosphine oxide, tributylphosphine oxide, octylphosphine oxide, dioctylphosphine oxide, trioctylphosphine oxide, diphenylphosphine, triphenylphosphine or oxide compounds thereof;

[0057] Alkylphosphonic acids include, but are not limited to: hexylphosphonic acid, octylphosphonic acid, dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, C5-C20 alkylphosphonic acids, etc.

[0058] Sulfur-based compounds include, but are not limited to: ethoxylated pentaerythritol tetra(3-mercaptopropionate), trimethylolpropane tri(3-mercaptopropionate), trimethylolpropane tri(2-mercaptoacetate), diol di-3-mercaptopropionate, polypropylene glycol di(3-mercaptopropionate), ethoxylated trimethylolpropane tri(3-mercaptopropionate), diol dimercaptoacetate, ethoxylated diol dimercaptoacetate, 1,4-bis(3-mercaptobutyryloxy)butane, Tris[2-(3-mercaptopropionyloxy)ethyl]isocyanurate, 1,3,5-tris(3-mercaptobutoxyethyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetra(2-mercaptoacetate), 1,6-hexanedithiol, 1,3-propanedithiol, 1,2-ethanedithiol, polyethylene glycol dithiol comprising 1-10 ethylene glycol repeating units, or combinations thereof.

[0059] In some embodiments, the thickness of the first shell layer 2 is 4nm to 20nm, and the thickness of the second shell layer 3 is 2nm to 60nm.

[0060] In some embodiments, the density of the first shell layer 2 is less than 0.8 g / cm³. 3 The density of the second shell 3 is greater than 1 g / cm³. 3 .

[0061] In some embodiments, both the first shell 2 and the second shell 3 are oxide materials, such as Si. x Al y O 2x+3 / 2y Zn x Mg y O x+y The oxides are SiO2, TiO2, ZrO2, Al2O3, ZnO, or SnO2; preferably, x = 1, and y is a value from 0 to 0.8. The oxides possess good corrosion resistance and thermal stability, which can impart better stability to quantum dots.

[0062] The first shell 2 and the second shell 3 can be made of the same oxide or different oxides. In a preferred embodiment, the first shell 2 and the second shell 3 are made of the same oxide.

[0063] Furthermore, in one embodiment, both the first shell layer 2 and the second shell layer 3 are made of Si. x Al y O 2x+3 / 2y Preferably, x = 1, and y takes values ​​from 0 to 0.8.

[0064] In some embodiments, the size of the quantum dot core 1 is 5 nm to 30 nm, FWHM < 35 nm, and QY > 60%.

[0065] This application does not impose any particular limitation on the quantum dot core 1 (also known as a semiconductor nanocrystal), which can be prepared by any known method or is commercially available. For example, the quantum dot core 1 can be a group II-VI compound, a group III-V compound, a group IV-VI compound, a group IV element or compound, a group I-III-VI compound, a group I-II-IV-VI compound, or a combination thereof.

[0066] In some embodiments, quantum dot core 1 is a group II-VI compound:

[0067] It can be selected from binary compounds such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, and MgS;

[0068] It can also be selected from ternary compounds such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, etc.

[0069] It can also be selected from quaternary compounds such as HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, and HgZnSTe.

[0070] Quantum dot core 1 can also be a group II-VI compound doped with group III metals.

[0071] In some embodiments, quantum dot core 1 is a group III-V compound:

[0072] It can be selected from binary compounds such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, and InSb;

[0073] It can be selected from ternary compounds such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, and InZnP.

[0074] It can also be selected from quaternary compounds such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, and InAlPSb.

[0075] Group III-V compounds may further include Group II metals, such as InZnP.

[0076] In some embodiments, quantum dot core 1 is a group IV-VI compound:

[0077] It can be selected from binary compounds such as SnS, SnSe, SnTe, PbS, PbSe, and PbTe;

[0078] It can be selected from ternary compounds such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, and SnPbTe;

[0079] It can also be selected from quaternary compounds such as SnPbSSe, SnPbSeTe, and SnPbSTe.

[0080] Group I-III-VI compounds can be, but are not limited to, CuInSe2, CuInS2, CuInGaSe, and CuInGaS.

[0081] Group I-II-IV-VI compounds can be, but are not limited to, CuZnSnSe and CuZnSnS.

[0082] In some embodiments, the quantum dot core 1 is a group IV element or compound:

[0083] It can be selected from elemental substances such as Si and Ge;

[0084] It can be selected from binary compounds such as SiC and SiGe.

[0085] In some embodiments, the quantum dot core 1 may have a particle diameter of about 1 nm to about 100 nm (in the case of non-spherical particles, the longest length of a straight line across the particle). For example, the quantum dot core 1 may have a particle diameter of about 1 nm to about 20 nm, such as 2 nm (or 3 nm) to 15 nm. In some embodiments, the quantum dot core 1 has a diameter greater than or equal to about 2 nm, greater than or equal to about 3 nm, greater than or equal to about 4 nm, or greater than or equal to about 5 nm and less than or equal to about 50 nm, less than or equal to about 45 nm, less than or equal to about 40 nm, less than or equal to about 35 nm, less than or equal to about 30 nm, less than or equal to about 25 nm, less than or equal to about 20 nm, less than or equal to about 15 nm, less than or equal to about 10 nm, less than or equal to about 9 nm, less than or equal to about 8 nm, or less than or equal to about 7 nm.

[0086] The quantum dot core 1 may have shapes commonly used in the art and is not particularly limited. For example, the quantum dot core 1 may include spherical, elliptical, pyramidal, multi-armed, or cubic nanoparticles, nanotubes, nanowires, nanofibers, nanosheet particles, or combinations thereof.

[0087] The quantum dot core 1 is commercially available or can be synthesized by any method. For example, several nanometer-sized quantum dots can be synthesized by a wet chemical process. In a wet chemical process, the precursor reacts in an organic solvent to grow nanocrystal particles, and the organic solvent or ligand compound can coordinate (or bind) to the surface of the semiconductor nanocrystal, thereby controlling the growth of the nanocrystal. Examples of organic solvents and ligand compounds are known in the art. The organic solvent coordinated to the surface of the quantum dots can affect the stability of the device, and therefore, excess organic material not coordinated to the surface of the quantum dots can be removed by pouring the quantum dots into an excess of non-solvent and centrifuging the resulting mixture. Examples of non-solvents include, but are not limited to, acetone, ethanol, methanol, etc.

[0088] One embodiment of this application also provides a method for preparing quantum dot composite particles, comprising the following preparation steps:

[0089] S100, providing a first solution containing quantum dot core 1, and carrying out a synthesis reaction of a first inorganic oxide in the first solution, so that the single quantum dot core 1 is coated with a first shell 2 to obtain a first nanoparticle 10;

[0090] S200, the first nanoparticle 10 is placed in a stabilizer environment, so that the stabilizer is adsorbed on the first shell 2 to obtain the second nanoparticle 20;

[0091] S300, a second inorganic oxide is synthesized in a second solution containing the second nanoparticles 20. The conditions of the synthesis reaction of the second oxide are controlled so that the volume porosity of the second shell 3 is less than that of the first shell 2, so as to form a second shell 3 covering the outside of the first shell 2, and thus obtain the quantum dot composite particles of this application.

[0092] In some embodiments, in steps S200 and S300, the inorganic oxide is synthesized using a sol-gel method in a first solution and a second solution to prepare a first shell 2 and a second shell 3.

[0093] In some embodiments, a first inorganic oxide and a second inorganic oxide are synthesized using silicate esters and organosilanes to obtain a first shell 2 and a second shell 3.

[0094] In some embodiments, by controlling the synthesis reaction conditions of the first oxide and the second oxide, the volumetric porosity of the second shell 3 is made smaller than that of the first shell 2, wherein the synthesis reaction conditions include the proportion of inorganic oxide synthesis raw materials and pH value.

[0095] Furthermore, in step S100, the amount of silicate ester used is less than 85% of the total mass of silicate ester and organic aluminum alkoxide, and in step S300, the amount of silicate ester used is greater than 95% of the total mass of silicate ester and organic aluminum alkoxide, so that the volume porosity of the second shell layer 3 is less than that of the first shell layer 2.

[0096] In some embodiments, the pH range in step S100 is 10 to 13, and the pH range in step S300 is 9 to 11, so that the volumetric porosity of the second shell 3 is less than that of the first shell 2.

[0097] The silicate ester can be, but is not limited to, tetraethyl orthosilicate.

[0098] Aluminum alkoxides can be, but are not limited to, aluminum isopropoxide, aluminum isobutoxide, or aluminum sec-butoxide.

[0099] In some embodiments, in step S200, the stabilizer is an antioxidant or an anti-UV agent, and the mass ratio of the stabilizer to the first nanoparticle 10 is (1-7):20.

[0100] In some embodiments, in step S200, the stabilizer is a quantum dot ligand, and the mass ratio of the stabilizer to the first nanoparticle 10 is 1:(200-20).

[0101] In some embodiments, in step S200, the first nanoparticles 10 are placed in a stabilizer environment, including but not limited to adsorbing the stabilizer into the first shell layer 2 by means of solvent replacement, adsorption, rotary evaporation, etc.

[0102] In some embodiments, the quantum dot core 1 is a quantum dot core modified with water-soluble ligands.

[0103] Furthermore, the specific method for preparing the quantum dot composite particles in this application is as follows:

[0104] S100: The quantum dot core 1 modified with water-soluble ligands is dissolved in a first solution. Silicate and organic aluminum alkoxide are added to the first solution. The amount of silicate added is less than 85% of the total mass of silicate and organic aluminum alkoxide. The pH of the solution is adjusted to 10-13. The reaction is carried out by stirring at room temperature for 6-48 hours to form the first shell 2 covering the quantum dot core 1. After washing, purification and drying, the first nanoparticle 10 is obtained.

[0105] S200: Provide a dispersion containing first nanoparticles 10, add a stabilizer to it, stir until the stabilizer is completely dissolved, and then remove the solvent by rotary evaporation to obtain second nanoparticles 20;

[0106] S300: Dissolve the second nanoparticle 20 in the second solution, and add silicate ester and organic aluminum alkoxide, wherein the amount of silicate ester added is greater than 95% of the total mass of silicate ester and organic aluminum alkoxide. Adjust the pH of the solution to 9-11, and stir at room temperature for 6-48 hours to form a second shell 3 covering the second nanoparticle 20. After washing, purification and drying, the quantum dot composite particles of this application are obtained.

[0107] In some embodiments, both the first solution and the second solution are aqueous solutions of ethanol, wherein the mass fraction of water is 3 wt% to 40 wt%.

[0108] In some embodiments, the concentration of quantum dot core 1 in the first solution is 0.2 wt% to 10 wt‰, and the concentration of second nanoparticle 20 in the second solution is 0.2 wt‰ to 10 wt‰.

[0109] In some embodiments, the water-soluble ligands include, but are not limited to: mercaptopropionic acid, 5'-adenosine, glutaric acid, polyethyleneimine, and carboxylated polyethylene oxide.

[0110] In some embodiments, the first nanoparticles 10 are dispersed in a non-alcoholic, low-polarity solvent and ultrasonically dispersed to form a suspension, thereby obtaining a dispersion of the first nanoparticles 10. The non-alcoholic, low-polarity solvent may be, but is not limited to, toluene, ethyl acetate, cyclohexane, and n-octane.

[0111] In some embodiments, the pH adjuster is alkaline, including but not limited to ammonia, tetramethylammonium hydroxide, and alkali metal hydroxides.

[0112] A light conversion device is provided, comprising quantum dot composite particles according to any of the above-described methods, or quantum dot composite particles prepared by any of the above-described methods. The light conversion device can be a quantum dot LED, a quantum dot film, a quantum dot diffuser plate, or a quantum dot color filter.

[0113] This application also provides a composition comprising any of the quantum dot composite particles described above, or quantum dot composite particles prepared by any of the preparation methods described above.

[0114] Example 1

[0115] The quantum dot composite particles of this application were prepared according to the following steps:

[0116] S100: The mercaptopropionic acid-modified quantum dot core 1 is dissolved in an aqueous ethanol solution, wherein the mass fraction of water is 40 wt% and the concentration of quantum dot core 1 is 10 wt%; tetraethyl orthosilicate and aluminum isopropoxide are added, wherein the amount of tetraethyl orthosilicate added is less than 85 wt% of the total mass of tetraethyl orthosilicate and aluminum isopropoxide; the pH of the solution is adjusted to 13; the reaction is carried out by stirring at room temperature for 48 h to form the first shell 2 coating the quantum dot core 1; the first nanoparticle 10 is obtained by washing three times alternately with deionized water and ethanol solution, purification and drying;

[0117] S200: The first nanoparticle 10 was stirred in ethyl acetate and ultrasonically dispersed for 20 min to obtain a dispersion of the first nanoparticle 10. 2,6-Di-tert-butyl-p-cresol was added, with a mass ratio of 2,6-di-tert-butyl-p-cresol to the first nanoparticle 10 of 7:20. The mixture was stirred at room temperature until the 2,6-di-tert-butyl-p-cresol was completely dissolved. The ethyl acetate was removed by rotary evaporation to obtain the second nanoparticle 20.

[0118] S300: Dissolve the second nanoparticle 20 in an aqueous ethanol solution, wherein the mass fraction of water is 40 wt% and the concentration of the second nanoparticle 20 is 10 wt%; add tetraethyl orthosilicate and aluminum isopropoxide, wherein the amount of tetraethyl orthosilicate added is greater than 95 wt% of the total mass of tetraethyl orthosilicate and aluminum isopropoxide; adjust the pH of the solution to 11; stir at room temperature for 48 h to react and form a second shell coating the second nanoparticle 20; wash three times alternately with deionized water and ethanol solution; purify and dry to obtain the quantum dot composite particle A of this application.

[0119] Comparative Example 1

[0120] A quantum dot composite particle B was prepared using a double-layer coating, in which no stabilizer was adsorbed within the shell:

[0121] The first nanoparticles were prepared according to step S100 in Example 1;

[0122] The first nanoparticle was dissolved in an aqueous ethanol solution with a water mass fraction of 40 wt% and a first nanoparticle concentration of 10 wt%. Tetraethyl orthosilicate and aluminum isopropoxide were added, with the amount of tetraethyl orthosilicate added being greater than 95 wt% of the total amount of tetraethyl orthosilicate and aluminum isopropoxide. The pH of the solution was adjusted to 11, and the mixture was stirred at room temperature for 48 h to form a second shell coating the first nanoparticle. The mixture was washed three times alternately with deionized water and ethanol solution, purified, and dried to obtain a quantum dot composite particle B.

[0123] Comparative Example 2

[0124] A quantum dot composite particle C was prepared according to steps S100 and S200 in Implementation 1.

[0125] Performance testing

[0126] The quantum dot composite particles prepared in the examples and comparative examples were mixed with encapsulating adhesive, and additives such as phosphors and diffusion particles were optionally added. The mixed adhesive was then applied to LED chips, cured, and its optical stability was tested.

[0127] The specific steps are as follows:

[0128] Mixed adhesive: Weigh 55 parts by weight of thermosetting methyl-phenyl silicone resin, 30 parts by weight of red fluorescent powder, and 15 parts by weight of green quantum dot composite particles of this application, mix them evenly, and place them in a vacuum stirrer to degas, so as to obtain a mixed adhesive sealant;

[0129] Dispensing: The mixed adhesive is poured into the encapsulation cavity of the LED bracket using a dispensing machine;

[0130] Centrifugation: Place the sealed LED bracket in an automatic centrifugal sedimentation machine and centrifuge at 300 rpm to 1000 rpm for 2 to 5 minutes;

[0131] Curing: Place the centrifuged LED holder in an oven at 130℃~150℃ and bake for 1h~3h.

[0132] Stability testing method: The LED is continuously lit with a current of 20mA in an environment of 60℃ and 90% relative humidity, and the relationship between its luminous efficiency and time is tested.

[0133] Performance Analysis

[0134] like Figure 2As shown, the quantum dot composite particles B prepared in Comparative Example 1 experienced a 50% loss in luminous efficiency after approximately 120 hours of LED illumination, and the luminous efficiency dropped to below 20% after 1008 hours. This indicates that even with a double-shell design, the quantum dot composite particles, despite possessing some water and oxygen permeability, will still be susceptible to attack by free radicals such as water and oxygen in prolonged exposure to water, oxygen, light, and heat, leading to their failure and shortening the lifespan of electronic devices.

[0135] The quantum dot composite particles C prepared in Comparative Example 2 showed a 50% loss in LED luminous efficiency after approximately 252 hours of illumination, and a further reduction to around 30% after 1008 hours. This indicates that the monolayer quantum dot composite particles C with adsorbed stabilizers can slightly extend the device's lifespan. However, with the loss of stabilizers, the water and oxygen barrier function of the quantum dot composite particles C gradually fails, and the quantum dots are gradually eroded and degraded.

[0136] The quantum dot composite particles A prepared in Example 1 have a relatively stable structure. The double-layer coating structure avoids the loss of stabilizer and further blocks the attack of water and oxygen, and can achieve a luminescence efficiency loss rate of less than 40% after 1008h.

[0137] The basic principles, main features, and advantages of this application have been described above. Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely the principles of this application. Various changes and modifications can be made to this application without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection claimed by this application is defined by the appended claims and their equivalents.

Claims

1. A quantum dot composite particle, characterized in that, It includes a single quantum dot core and a first shell layer covering the quantum dot core. The first shell layer is adsorbed with a stabilizer. The first shell layer is covered with a second shell layer. The volume porosity of the second shell layer is less than that of the first shell layer. The stabilizer is a phenolic antioxidant; the volumetric porosity of the first shell layer is 0.3~0.8 cm³. 3 / cm 3 The volumetric porosity of the second shell is 0.05~0.4 cm³. 3 / cm 3 The first shell and the second shell are oxides with the same composition or different compositions.

2. The quantum dot composite particle as described in claim 1, characterized in that, The thickness of the first shell is 4 nm to 20 nm, and the thickness of the second shell is 2 nm to 60 nm.

3. The quantum dot composite particle as described in claim 1, characterized in that, The first shell is Si x Al y O 2x+3 / 2y Zn x Mg y O x+y The first shell is made of SiO2, TiO2, ZrO2, Al2O3, ZnO, or SnO2; the second shell is made of Si. x Al y O 2x+3 / 2y Zn x Mg y O x+y SiO2, TiO2, ZrO2, Al2O3, ZnO, or SnO2; x=1, y takes values ​​from 0 to 0.

8.

4. The quantum dot composite particle as described in claim 3, characterized in that, Both the first and second shells are made of Si. x Al y O 2x+3 / 2y .

5. The quantum dot composite particle as described in claim 1, characterized in that, The quantum dot core is a quantum dot modified with water-soluble ligands, and the size of the quantum dot core is 5 nm to 30 nm, FWHM < 35 nm, QY > 60%.

6. A method for preparing quantum dot composite particles, characterized in that, The preparation steps include the following: S100, providing a first solution containing quantum dot cores, and carrying out a synthesis reaction of a first inorganic oxide in the first solution, so that the quantum dot cores of individual particles are coated with a first shell to obtain first nanoparticles; S200, the first nanoparticle is placed in a stabilizer environment, so that the stabilizer is adsorbed onto the first shell layer to obtain the second nanoparticle; S300, a second inorganic oxide is synthesized in a second solution containing the second nanoparticles. The conditions of the synthesis reaction of the second oxide are controlled so that the volume porosity of the second shell is less than that of the first shell, so as to form a second shell coating the outside of the first shell, and the quantum dot composite particles are obtained. The stabilizer is a phenolic antioxidant; the volumetric porosity of the first shell layer is 0.3~0.8 cm³. 3 / cm 3 The volumetric porosity of the second shell is 0.05~0.4 cm³. 3 / cm 3 The first shell and the second shell are oxides with the same composition or different compositions; In step S100, the amount of silicate used is less than 85% of the total mass of silicate and aluminum alkoxide, and in step S300, the amount of silicate used is greater than 95% of the total mass of silicate and aluminum alkoxide, so that the volume porosity of the second shell is less than that of the first shell.

7. The preparation method according to claim 6, characterized in that, The synthesis reaction of inorganic oxides is carried out in the first solution and the second solution using the sol-gel method. The control conditions for the synthesis reaction of inorganic oxides include the raw material ratio and pH value.

8. The preparation method according to claim 7, characterized in that, In step S100, the first shell layer is synthesized using silicate ester and organic aluminum alkoxide; in step S300, the second shell layer is synthesized using silicate ester and organic aluminum alkoxide.

9. The preparation method according to claim 8, characterized in that, The pH range in step S100 is 10-13, and the pH range in step S300 is 9-11.

10. The preparation method according to claim 6, characterized in that, The mass ratio of the stabilizer to the first nanoparticle is (1~7):

20.

11. A light conversion device, characterized in that, It includes the quantum dot composite particles according to any one of claims 1 to 5, or the quantum dot composite particles prepared by any one of claims 6 to 10.

12. A composition, characterized in that, It includes the quantum dot composite particles according to any one of claims 1 to 5, or the quantum dot composite particles prepared by any one of claims 6 to 10.

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