Quantum dot complex, composition and light-emitting device containing same, and preparation method thereof

Abstract

The present disclosure provides a quantum dot complex and a preparation method thereof, a quantum dot composition and a quantum dot light-emitting device. The quantum dot complex comprises a plurality of quantum dots and a plurality of organic ligands coordinated with the surface of the quantum dots. The organic ligands comprise a binding group and a crystallization group. The binding group is a thiol, an amino group, a -COO ‑ The organic ligands form crystals through the intermolecular forces of the crystalline groups, with the melting point of the crystals exceeding 100°C and the molecular weight of the organic ligands being less than or equal to 2000. The density of the crystals ensures that the quantum dots maintain high barrier properties even below their melting point, allowing them to resist corrosion from water and oxygen at high temperatures and light intensities, and exhibiting high stability when used in conjunction with LEDs.

Description

Technical Field

[0001] The present disclosure relates to the field of quantum dot technology, and in particular to a quantum dot complex, a composition and a light-emitting device containing the same, and a preparation method thereof. Background Art

[0002] Quantum dots, a new generation of luminescent materials, boast outstanding characteristics such as narrow half-width (FWHM), tunable wavelength, and high quantum yield. However, quantum dot materials are highly sensitive to water and oxygen, prone to failure when exposed to water and oxygen, and have a short service life. Inorganic modification of quantum dots, including surface treatments with zinc oxide, titanium oxide, and silicon-aluminum-zirconium composite oxides, leverages the high-temperature resistance and barrier properties of inorganic materials to protect quantum dots from water and oxygen. However, the disadvantage is that inorganic coating often comes with a loss in efficiency. The coating process is essentially non-lattice-matched epitaxial growth, which can damage quantum dots during the coating process due to potential lattice stress and dislocations. Therefore, this coating method inherently requires high stability of the quantum dots and is unsuitable for less stable quantum dots. Furthermore, the coating process is difficult to control, making industrialization challenging. Furthermore, the water and oxygen barrier properties of the coating layer gradually decrease with increasing temperature, making it difficult to meet the high-temperature, high-light requirements of quantum dots on LED chips. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a quantum dot complex, a composition and a light-emitting device containing the same, and a preparation method thereof, to solve the problem of poor stability of quantum dots.

[0004] In the first aspect of the present disclosure, a quantum dot complex is provided, comprising a plurality of quantum dots and a plurality of organic ligands coordinated with the surface of the quantum dots, wherein the organic ligands comprise a binding group and a crystallization group, wherein the binding group is a thiol, an amino, a -COO - , one or more of phosphate groups and phosphite groups, the organic ligands form crystals through the intermolecular forces of the crystallization groups, the crystals are coated on the surface of the quantum dots, the melting point of the crystals is greater than 100°C, and the molecular weight of the organic ligands is less than or equal to 2000.

[0005] Optionally, the crystallization group includes at least one of a benzene ring, imidazole, thiophene, thiazole or oxazole.

[0006] Optionally, the organic ligand is one or more of 2-mercaptobenzimidazole, 5-amino-2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 5-methoxy-2-mercaptobenzimidazole, 2-aminobenzothiazole, 2-mercaptobenzoxazole, and 2-mercaptobenzotriazole.

[0007] Optionally, the quantum dot complex further comprises a functional auxiliary agent, which is located in the crystal. Preferably, the functional auxiliary agent is selected from one or more of an antioxidant and an anti-UV agent.

[0008] Optionally, the melting point of the crystal is between 150 and 250°C.

[0009] In a second aspect of the present disclosure, a quantum dot composition is provided, which includes any one of the above-mentioned quantum dot composites and also includes a thermally curable or ultraviolet light-curable glue.

[0010] According to a third aspect of the present disclosure, a light-emitting device is provided, comprising an LED chip and any one of the above-mentioned quantum dot composites.

[0011] A fourth aspect of the present disclosure provides a method for preparing any one of the quantum dot composites, comprising:

[0012] S1, preparing an oil phase dispersion of quantum dots having a first ligand, wherein the first ligand is a non-crystalline ligand;

[0013] S2, adding a second ligand to the dispersion to replace the first ligand, wherein the mass ratio of the second ligand to the quantum dots having the first ligand is 0.2 to 10, to obtain a product system of quantum dots having the second ligand;

[0014] S3, separating and purifying the quantum dots with the second ligand from the product system and drying the product to obtain quantum dot powder;

[0015] S4, mixing the quantum dot powder, the second ligand, and the solvent to obtain a first mixed solution, wherein the mass ratio of the quantum dot powder to the second ligand is 1:80 to 1:10; or S4 further includes preparing a functional additive, and mixing the first mixed solution and the functional additive to obtain a second mixed solution;

[0016] S5, volatilizing the first mixed liquid or the second mixed liquid to obtain a quantum dot composite after volatilization.

[0017] Optionally, the mass ratio of the functional additive to the quantum dot powder is 2:1 to 6:1.

[0018] Optionally, the mass ratio of quantum dot powder to solvent is 1:400 to 1:100.

[0019] Optionally, after adding the second ligand to the dispersion, the reaction temperature of the ligand exchange reaction system is raised to 60-80°C.

[0020] Optionally, the volatilization treatment includes heating the first mixed liquid or the second mixed liquid to a first temperature, removing the heating source, and then placing it at room temperature and pressure with air circulation for volatilization. Preferably, the first temperature is 50-60°C.

[0021] Optionally, the solvent is selected from one or more of tetrahydrofuran, dioxane, dichloromethane, and petroleum ether.

[0022] In the aforementioned quantum dot complexes, the binding groups and quantum dots possess strong binding forces, i.e., a strong coordination bond exists between the quantum dots and the crystal, without significant interfacial phase separation that would degrade the crystal's barrier properties. Leveraging the crystal's compactness, the quantum dots maintain high barrier properties even below their melting point, making them resistant to water and oxygen corrosion at elevated temperatures and light intensities, and demonstrating high stability when used in conjunction with LEDs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of the present disclosure. The exemplary embodiments of the present disclosure and their descriptions are intended to explain the present disclosure and do not constitute an improper limitation of the present disclosure. In the accompanying drawings:

[0024] Figure 1 This is a schematic diagram of the cross-sectional structure of a quantum dot complex disclosed herein.

[0025] Figure 2 Schematic diagram of the structure of the light-emitting device disclosed in the present invention.

[0026] Figure 3 This is a microscope photograph of a quantum dot complex disclosed herein.

[0027] Figure 4 This is a microscope photograph of a quantum dot complex disclosed herein under blue light excitation.

[0028] Figure 5 1 is a curve showing the relative efficiency change of the light-emitting devices of the embodiment and comparative example of the present disclosure under accelerated aging conditions.

[0029] 1. Quantum dot complex; 2. LED bracket; 3. Encapsulation glue; 4. LED chip.

[0030] Note that in the embodiments described below, the same reference numerals are sometimes used in common across different drawings to denote the same parts or parts having the same functions, and their repeated descriptions are omitted. In some cases, similar reference numerals and letters are used to denote similar items, so once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0031] For ease of understanding, the positions, sizes, and ranges of various structures shown in the drawings and the like may not represent actual positions, sizes, and ranges, etc. Therefore, the present disclosure is not limited to the positions, sizes, and ranges disclosed in the drawings and the like. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. It should be noted that unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure.

[0033] The following description of at least one exemplary embodiment is merely illustrative and is not intended to limit the present disclosure, its application, or use. In other words, the structures and methods herein are presented in an exemplary manner to illustrate various embodiments of the structures and methods of the present disclosure. However, those skilled in the art will appreciate that these are merely exemplary of the disclosure that may be implemented, and are not exhaustive. Furthermore, the drawings are not necessarily drawn to scale, and some features may be exaggerated to illustrate details of specific components.

[0034] In addition, technologies, methods and devices known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods and devices should be considered part of the authorization specification.

[0035] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0036] The words "left," "right," "front," "back," "top," "bottom," "up," "down," "high," "low," and the like, if any, in the specification and claims, are used for descriptive purposes and are not necessarily intended to describe invariant relative positions. It should be understood that the words so used are interchangeable under appropriate circumstances so that the embodiments of the present disclosure described herein, for example, can operate in other orientations than those shown or otherwise described herein. For example, when the device in the figures is turned over, features previously described as "above" other features could now be described as "below" the other features. The device can also be otherwise oriented (rotated 90 degrees or in other orientations) and relative spatial relationships will be interpreted accordingly.

[0037] In the specification and claims, when an element is referred to as being "on," "attached," "connected," "coupled," or "coupled" to another element, the element may be directly on, directly attached, directly connected, directly coupled, or directly coupled to another element, or one or more intervening elements may be present. In contrast, when an element is referred to as being "directly" on, "directly attached," "directly connected," "directly coupled," or "directly coupled" to another element, there may be no intervening elements. In the specification and claims, when a feature is arranged "adjacent" to another feature, it may mean that the feature has a portion that overlaps with the adjacent feature or a portion that is located above or below the adjacent feature.

[0038] As used herein, the word "exemplary" means "serving as an example, instance, or illustration," rather than as a "model" to be precisely copied. Any implementation described as exemplary is not necessarily to be construed as preferred or advantageous over other implementations. Furthermore, this disclosure is not to be bound by any expressed or implied theory presented in the technical field, background, summary, or detailed description.

[0039] As used herein, the term "substantially" is intended to encompass any minor variations due to design or manufacturing imperfections, device or component tolerances, environmental influences, and / or other factors. The term "substantially" also allows for deviations from a perfect or ideal condition due to parasitic effects, noise, and other practical considerations that may be present in actual implementations.

[0040] Additionally, terms such as "first," "second," and the like may also be used herein for reference purposes only and are not intended to be limiting. For example, the terms "first," "second," and other numerical terms referring to structures or elements do not imply a sequence or order unless the context clearly indicates otherwise.

[0041] It should also be understood that when the term “include / comprises” is used in this document, it indicates the presence of the specified features, integers, steps, operations, units and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, units and / or components and / or their combinations.

[0042] In this disclosure, the term "providing" is used in a broad sense to encompass all ways of obtaining an object, so "providing an object" includes, but is not limited to, "purchasing," "preparing / manufacturing," "arranging / setting," "installing / assembling," and / or "ordering" an object, etc. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit this disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0043] According to the first aspect of the present disclosure, a quantum dot complex is provided, which includes a plurality of quantum dots and a plurality of organic ligands coordinated and bound to the surface of the quantum dots, the organic ligands including a binding group and a crystallization group, the binding group being one or more of a thiol group, an amino group, -COO-, a phosphate group, and a phosphite group, the organic ligands forming crystals through the intermolecular forces of the crystallization groups, the crystals coating the surface of the quantum dots, the melting point of the crystals being greater than 100°C, and the molecular weight of the organic ligands being less than or equal to 2000.

[0044] In the aforementioned quantum dot complexes, the binding groups and quantum dots possess strong binding forces, i.e., a strong coordination bond exists between the quantum dots and the crystal, without significant interfacial phase separation that would degrade the crystal's barrier properties. By leveraging the crystal's compactness, the quantum dots maintain high barrier properties even below their melting point, thus enabling them to resist corrosion from water and oxygen at elevated temperatures and light intensities.

[0045] The shape of the quantum dot complex is not limited. In some embodiments, the cross-sectional structure diagram of the quantum dot complex is shown in FIG. Figure 1 .

[0046] In some embodiments, the crystallization group includes at least one of a benzene ring, an imidazole, a thiophene, a thiazole, or an oxazole.

[0047] In some embodiments, the organic ligand is one or more of 2-mercaptobenzimidazole, 5-amino-2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 5-methoxy-2-mercaptobenzimidazole, 2-aminobenzothiazole, 2-mercaptobenzoxazole, and 2-mercaptobenzotriazole.

[0048] The shape of the above-mentioned crystals is not limited, and can be spherulites, columnar crystals, etc. The size of the above-mentioned quantum dot complex (crystal) is 200nm-10μm. The type of the above-mentioned quantum dots is not limited, and can be a core-shell structure compound formed by one or more II-VI main group compounds: CdSe, CdTe, MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe and CdS, or a core-shell structure compound formed by one or more III-V main group compounds: GaN, GaP, GaAs, InN, InP and InAs.

[0049] In some embodiments, the quantum dot complex further includes a functional auxiliary agent, which is located in the crystal. Preferably, the functional auxiliary agent is selected from one or more of an antioxidant and an anti-UV agent, thereby further improving the lifespan of the quantum dots.

[0050] In some embodiments, the antioxidant is selected from one or more of phenolic antioxidants, thioester antioxidants, or phosphate antioxidants.

[0051] Phenolic antioxidants can be selected from 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 alcohol ester, β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate octadecyl alcohol ester, tetrakis[β-(3.5-di-tert-butyl, 4-hydroxyphenyl)propionate]pentaerythritol ester, triethylene glycol bisβ-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate; thioester antioxidants can be selected from dioctadecyl thiodipropionate, ... Di(tridecyl), 3-(dodecylthio)propionic acid-2,2-bis[[3-(dodecylthio)-propionyloxy]methyl]-1,3-propylene glycol ester, 4,4'-thiobis(6-tert-butyl-m-cresol), 4,4'-thiobis(6-tert-butyl-2-methylphenol); the phosphate antioxidant can be selected from the phosphite antioxidants: bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphite, tris(2.4-di-tert-butylphenyl) phosphite, dioctadecylpentaerythritol diphosphite, bis(2,4-dicumylphenyl)pentaerythritol-diphosphite, and diphenyl isooctyl phosphite.

[0052] In some embodiments, the anti-UV agent is selected from poly (4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate, bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacic acid, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacic acid, 1- (methyl) -10- (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacic acid, poly (4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinyl) sebacic acid, ethanol) ester, poly{[6-[(1,1,3,3-tetramethylbutyl)amino]]-1,3,5-triazine-2,4-[(2,2,6,6,-tetramethyl-piperidinyl)imino]-1,6-hexanediyl[(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].

[0053] In some embodiments, the melting point of the crystal is between 150° C. and 250° C. At temperatures below the melting point, the ligand crystal structure does not change, and the density and barrier properties do not change much, thereby protecting the quantum dots from water and oxygen corrosion.

[0054] According to a second aspect of the present disclosure, a quantum dot composition is provided, comprising any of the aforementioned quantum dot complexes and a heat-curable or UV-curable adhesive. The quantum dots utilize the density of the crystals to maintain high barrier properties below their melting point, thereby resisting corrosion from water and oxygen even at elevated temperatures and light intensities (after an LED is illuminated).

[0055] In some embodiments, the quantum dot composition further includes diffusing particles.

[0056] According to a third aspect of the present disclosure, a light emitting device is provided, comprising an LED chip and any one of the above-mentioned quantum dot composites. The use of the above-mentioned quantum dot composites can improve the life of the light emitting device. In some embodiments, the structural schematic diagram of the light emitting device is shown in FIG. Figure 2 .

[0057] According to a fourth aspect of the present disclosure, a method for preparing any of the above-mentioned quantum dot composites is provided, comprising:

[0058] S1, preparing an oil phase dispersion of quantum dots having a first ligand, wherein the first ligand is a non-crystalline ligand;

[0059] S2, adding a second ligand to the dispersion to replace the first ligand, wherein the mass ratio of the second ligand to the quantum dots having the first ligand is 0.2 to 10, to obtain a product system of quantum dots having the second ligand;

[0060] S3, separating and purifying the quantum dots with the second ligand from the product system and drying the product to obtain quantum dot powder;

[0061] S4, mixing the quantum dot powder, the second ligand, and the solvent to obtain a first mixed solution, wherein the mass ratio of the quantum dot powder to the second ligand is 1:80 to 1:10; or S4 further includes preparing a functional additive, and mixing the first mixed solution and the functional additive to obtain a second mixed solution;

[0062] S5, volatilizing the first mixed liquid or the second mixed liquid to obtain a quantum dot composite after volatilization.

[0063] By controlling the concentration of the organic ligand, the organic ligand is allowed to be in excess, thereby precipitating crystals due to supersaturation, and the functional additives can also be coated in the crystals formed by the organic ligand. The above preparation methods are all completed in the organic ligand phase. The quantum efficiency retention rate of the quantum dots can reach more than 95%, and there is a strong coordination effect between the quantum dots and the crystals. There is no obvious interface phase separation, which maximizes the barrier performance of the crystals. Through the quality control of the above-mentioned first ligand and second ligand, the molar ratio of the second ligand to the first ligand can be indirectly controlled to be greater than 1:1. By controlling the mass ratio of the quantum dot powder to the second ligand, the quantum dot surface has more second ligands, which facilitates the formation of crystals.

[0064] The functional additive can be a mixture dispersed in a medium. The first ligand is not limited, but must ensure that the quantum dots are dispersed in a non-polar solvent (oil phase). For example, it can be oleic acid, oleylamine, or a trialkylphosphine ligand. Because the second ligand has a stronger coordination ability than the first ligand, the second ligand can easily replace the first ligand.

[0065] In some embodiments, the mass ratio of the second ligand to the quantum dots having the first ligand is 0.5-2.

[0066] In some embodiments, the mass ratio of the functional additive to the quantum dot powder is 2:1 to 6:1.

[0067] In some embodiments, the mass ratio of quantum dot powder to solvent is 1:400 to 1:100.

[0068] In some embodiments, after the second ligand is added to the dispersion, the reaction temperature of the ligand exchange reaction system is raised to 60-80°C.

[0069] In some embodiments, the volatilization treatment includes heating the first mixed liquid or the second mixed liquid to a first temperature, removing the heat source, and then placing it under normal temperature and pressure with air circulation for volatilization. Preferably, the first temperature is 50-60°C.

[0070] In some embodiments, the solvent is selected from one or more of tetrahydrofuran, dioxane, dichloromethane, and petroleum ether.

[0071] Hereinafter, the embodiments are described in more detail with reference to specific examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0072] Example 1

[0073] Quantum dots (CdSeS / CdS / ZnS; peak PL wavelength = 625nm; average size 7nm; FWHM = 24nm; QY = 75%) with oleic acid ligands were dissolved in toluene (quantum dot mass fraction 0.5% wt). 2-mercaptobenzimidazole was added (controlling the 2-mercaptobenzimidazole / quantum dot mass ratio = 0.5), and the temperature was raised to 60°C and stirred for 6 hours. A mixture of methanol and ethyl acetate in equal volumes was then added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 hours. One part by mass of the quantum dot powder and 10 parts by mass of 2-mercaptobenzimidazole were then added to 100 parts by mass of a solvent (tetrahydrofuran) and stirred to dissolve, yielding a first mixed solution.

[0074] The first mixed solution was stirred at 60°C for 1 hour and then transferred to a 1-liter open container. The container was then placed in a well-ventilated room temperature environment and allowed to slowly evaporate. During this evaporation process, the supersaturated ligand crystallized first, followed by the quantum dots, which were then encapsulated within the crystals formed by the 2-mercaptobenzimidazole ligand. The quantum efficiency of the quantum dot crystal complex was measured to be 72%.

[0075] Example 2

[0076] The oleic acid ligand quantum dots (same as in Example 1) were dissolved in toluene (quantum dot mass fraction 40% wt), 2-mercaptobenzimidazole was added (controlling the 2-mercaptobenzimidazole / quantum dot mass ratio = 2), and the temperature was raised to 80°C and stirred for 6 hours. Then, a mixture of methanol and ethyl acetate in equal volumes was added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 hours. Then, 1 part by mass of the quantum dot powder and 40 parts by mass of 2-mercaptobenzimidazole were added to 200 parts by mass of a solvent (dichloromethane) and stirred to dissolve, yielding a first mixed solution.

[0077] The volatilization treatment was the same as in Example 1 to obtain a quantum dot composite. The quantum efficiency of the quantum dot crystal composite was measured to be 71%.

[0078] Example 3

[0079] The oleic acid ligand quantum dots (same as in Example 1) were dissolved in toluene (quantum dot mass fraction 10% wt), 2-mercaptobenzimidazole was added (controlling the 2-mercaptobenzimidazole / quantum dot mass ratio = 1), and the temperature was raised to 70°C and stirred for 8 hours. Then, a mixture of methanol and ethyl acetate in equal volumes was added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 minutes. Then, 1 part by mass of the quantum dot powder and 30 parts by mass of 2-mercaptobenzimidazole were added to 150 parts by mass of a solvent (petroleum ether) and stirred to dissolve, thereby obtaining a first mixed solution.

[0080] The volatilization treatment was the same as in Example 1 to obtain a quantum dot composite. The quantum efficiency of the quantum dot crystal composite was measured to be 72%.

[0081] Example 4

[0082] Quantum dots with oleic acid ligands (same as in Example 1) were dissolved in toluene (quantum dot mass fraction 10% wt), and 2-mercaptobenzimidazole was added (controlling the 2-mercaptobenzimidazole / quantum dot mass ratio to be 1.5). The temperature was raised to 60°C and stirred for 6-12 hours. An equal volume mixture of methanol and ethyl acetate was then added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 hours. One part by mass of the quantum dot powder and 20 parts by mass of 2-mercaptobenzimidazole were then added to 150 parts by mass of a solvent (dioxane) and stirred to dissolve, yielding a first mixed solution.

[0083] The volatilization treatment was the same as in Example 1 to obtain a quantum dot composite. The quantum efficiency of the quantum dot crystal composite was measured to be 72%.

[0084] Example 5

[0085] The oleic acid ligand quantum dots (same as in Example 1) were dissolved in toluene (quantum dot mass fraction 10% wt), and 5-amino-2-mercaptobenzimidazole was added (controlling the 5-amino-2-mercaptobenzimidazole / quantum dot mass ratio to be 1.5). The temperature was raised to 60°C and stirred for 6-12 hours. An equal volume mixture of methanol and ethyl acetate was then added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 hours. One part by mass of the quantum dot powder and 20 parts by mass of 5-amino-2-mercaptobenzimidazole were then added to 150 parts by mass of a solvent (dioxane) and stirred to dissolve, yielding a first mixed solution.

[0086] The volatilization treatment was the same as in Example 1 to obtain a quantum dot composite. The quantum efficiency of the quantum dot crystal composite was measured to be 73%.

[0087] Example 6

[0088] The oleic acid ligand quantum dots (same as in Example 1) were dissolved in toluene (quantum dot mass fraction 10% wt), 2-aminobenzothiazole was added (controlling the 2-aminobenzothiazole / quantum dot mass ratio = 1.5), and the temperature was raised to 60°C and stirred for 6-12 hours. Then, a mixture of methanol and ethyl acetate in equal volumes was added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 hours. Then, 1 part by mass of the quantum dot powder and 20 parts by mass of 2-aminobenzothiazole were added to 150 parts by mass of a solvent (dioxane) and stirred to dissolve, obtaining a first mixed solution.

[0089] The volatilization treatment was the same as in Example 1 to obtain a quantum dot composite. The quantum efficiency of the quantum dot crystal composite was measured to be 71%.

[0090] Example 7

[0091] Quantum dots (CdSe / CdSeS / ZnS) with oleic acid ligands (peak PL wavelength = 535nm; average size 10nm; FWHM = 28nm; QY = 70%) were dissolved in toluene (quantum dot mass fraction 10% wt). 2-mercaptobenzoxazole was added (controlling the 2-mercaptobenzoxazole / quantum dot mass ratio to be 1.5). The temperature was raised to 60°C and stirred for 6-12 hours. An equal volume mixture of methanol and ethyl acetate was then added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 hours. One part by mass of the quantum dot powder and 20 parts by mass of 2-mercaptobenzoxazole were then added to 150 parts by mass of a solvent (dioxane) and stirred to dissolve, yielding a first mixed solution.

[0092] The volatilization treatment was the same as in Example 1 to obtain a quantum dot composite. The quantum efficiency of the quantum dot crystal composite was measured to be 72%.

[0093] Example 8

[0094] The oleic acid ligand quantum dots (same as in Example 7) were dissolved in toluene (quantum dot mass fraction 10% wt), 2-mercaptobenzimidazole was added (controlling the 2-mercaptobenzimidazole / quantum dot mass ratio = 1.5), and the temperature was raised to 60°C with stirring for 6-12 hours. An equal volume mixture of methanol and ethyl acetate was then added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 hours. One part by mass of the quantum dot powder and 30 parts by mass of 2-mercaptobenzimidazole were then added to 150 parts by mass of a solvent (dioxane) and stirred to dissolve, yielding a first mixed solution.

[0095] 1 part by mass of an antioxidant (2,6-di-tert-butyl-p-cresol) and 0.2 parts by mass of an anti-UV agent (poly(4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate) were added to the first mixed solution, heated to 50° C., and stirred for 2 h to form a stable translucent suspension, i.e., the second mixed solution.

[0096] The volatilization process was the same as in Example 1 except that the first mixed liquid was replaced by the second mixed liquid to obtain a quantum dot composite. The quantum efficiency of the quantum dot crystal composite was measured to be 73%.

[0097] Example 9

[0098] Oleic acid ligand quantum dots (same as in Example 1) were dissolved in toluene (quantum dot mass fraction 10% wt) and 2-mercaptobenzimidazole (controlling the 2-mercaptobenzimidazole / quantum dot mass ratio to 0.5). The temperature was raised to 60°C and stirred for 6 hours. An equal volume mixture of methanol and ethyl acetate was then added to precipitate the quantum dots. The precipitate was removed and dried in a vacuum oven at 50°C for 0.5 hours. One part by mass of the quantum dot powder and 10 parts by mass of 2-mercaptobenzimidazole were then added to 100 parts by mass of a solvent (tetrahydrofuran) and stirred to dissolve, yielding a first mixed solution.

[0099] 1 part by mass of an antioxidant (2,6-di-tert-butyl-p-cresol) and 0.2 parts by mass of an anti-UV agent (poly(4-hydroxyethyl-2,2,6,6-tetramethyl-1-piperidinylethanol) succinate) were added to the first mixed solution, heated to 50° C., and stirred for 2 h to form a stable translucent suspension, i.e., the second mixed solution.

[0100] The volatilization process was the same as in Example 1 except that the first mixed liquid was replaced by the second mixed liquid to obtain a quantum dot composite. The quantum efficiency of the quantum dot crystal composite was measured to be 71%.

[0101] The quantum dot complex of Example 1 was taken and observed under an optical microscope. Figure 3 is a microscope photo of the corresponding quantum dot crystal. Figure 4 for Figure 3 Microscope photos taken under 450nm blue light show that red quantum dots are located in the crystal.

[0102] The luminous efficiency test method of the quantum dot complex of the above embodiment is as follows: the quantum dot complex is dispersed in toluene solution, and the luminous efficiency of the solution is measured using an Ocean Optics test system.

[0103] Example 10

[0104] Weigh 60 parts by mass of thermosetting methyl-phenyl silicone resin, 20 parts by mass of the quantum dot complex obtained in Example 1, 30 parts by mass of the quantum dot complex obtained in Example 7, and 2 parts by mass of titanium dioxide scattering particles, mix them, and perform vacuum stirring and degassing treatment to obtain a mixed glue. Use a glue dispenser to seal the above-mentioned mixed glue into a packaging cavity with a gallium nitride LED (450nm) bracket; centrifuge the LED bracket, and then place the LED bracket in an oven and bake it at 100°C for 2 hours. The thickness of the cured glue layer is 0.2 mm.

[0105] Example 11

[0106] The difference from Example 10 is that 20 parts by mass of the quantum dot complex obtained in Example 9 and 30 parts by mass of the quantum dot complex obtained in Example 8 were used.

[0107] Comparative Example 1

[0108] Weigh 60 parts by mass of thermosetting methyl-phenyl silicone resin, 30 parts by mass of quantum dots (the same quantum dots with oleic acid ligands used in Example 1 and the green quantum dots used in Example 7), and 2 parts by mass of titanium dioxide scattering particles, mix them, and perform vacuum stirring and degassing treatment to obtain a mixed glue. Use a glue dispenser to seal the above-mentioned mixed glue into a packaging cavity with a gallium nitride LED (450nm) bracket; centrifuge the LED bracket, and then place the LED bracket in an oven and bake it at 100°C for 2 hours. The thickness of the cured glue layer is 0.2 mm.

[0109] Light-emitting device stability test method: In an environment with a temperature of 60°C and a relative humidity of 90%, the quantum dot LEDs of Example 10, Example 11, and Comparative Example 1 were continuously illuminated using a current of 20 mA. Quantum efficiency (integrating sphere method) was tested at multiple time points, and the initial efficiency at 0 h was defined as 100%. The ratio of the quantum efficiency after a specific time to the initial efficiency was changed according to this ratio to obtain the relative efficiency. After 1008 hours of monitoring, the curve of the relative efficiency change can be found in the figure. Figure 5 It can be seen that the quantum dot complex of crystal-coated quantum dots has improved stability, and the addition of antioxidants and other additives can further improve the stability of the light-emitting device.

[0110] Although some specific embodiments of the present disclosure have been described in detail by way of examples, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. The various embodiments disclosed herein may be combined in any manner without departing from the spirit and scope of the present disclosure. It should also be understood by those skilled in the art that various modifications may be made to the embodiments without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A quantum dot composite, characterized in that The invention comprises a plurality of quantum dots and a plurality of organic ligands coordinated and bound to the surfaces of the quantum dots, wherein the organic ligands comprise a binding group and a crystallization group, wherein the binding group is one or more of a mercapto group and an amino group, and the crystallization group comprises at least one of a benzene ring, an imidazole, a thiophene, a thiazole or an oxazole group. The organic ligands form crystals through the intermolecular forces of the crystallization groups, and the crystals are coated on the surfaces of the quantum dots. The melting point of the crystals is greater than 100° C. The molecular weight of the organic ligands is less than or equal to 2000, and the organic ligands are one or more of 2-mercaptobenzimidazole, 5-amino-2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 5-methoxy-2-mercaptobenzimidazole, 2-aminobenzothiazole, and 2-mercaptobenzoxazole.

2. The quantum dot composite according to claim 1, characterized in that The quantum dot complex further includes a functional auxiliary agent, which is located in the crystal and is selected from one or more of an antioxidant and an anti-UV agent.

3. The quantum dot composite according to claim 1, characterized in that The melting point of the crystal is between 150 and 250°C.

4. A quantum dot composition, characterized in that The quantum dot composition comprises the quantum dot composite according to any one of claims 1 to 3, and further comprises a thermally curable or ultraviolet light curable glue.

5. A light emitting device, characterized in that: The invention comprises an LED chip and the quantum dot composite according to any one of claims 1 to 3.

6. The method for preparing a quantum dot composite according to any one of claims 1 to 3, wherein: include: S1, preparing an oil phase dispersion of quantum dots having a first ligand, wherein the first ligand is oleic acid, oleylamine or a trialkylphosphine ligand; S2, adding a second ligand to the dispersion, wherein the second ligand is 2-mercaptobenzimidazole, 5-amino-2-mercaptobenzimidazole, 2-mercaptobenzothiazole, 5-methoxy-2-mercaptobenzimidazole, 2-aminobenzothiazole, 2-mercaptobenzoxazole, One or more of 2-mercaptophenyltriazole; replacing the first ligand, wherein the mass ratio of the second ligand to the quantum dot having the first ligand is 0.2 to 10, to obtain a product system of quantum dots having the second ligand; S3, separating and purifying the quantum dots having the second ligand from the product system and drying the product to obtain quantum dot powder; S4, mixing the quantum dot powder, the second ligand, and a solvent to obtain a first mixed liquid, wherein the mass ratio of the quantum dot powder to the second ligand is 1:80 to 1:10; or S4 further includes preparing a functional additive, wherein the functional additive is selected from one or more of an antioxidant and an anti-UV agent, and mixing the first mixed liquid and the functional additive to obtain a second mixed liquid; S5, volatilizing the first mixed liquid or the second mixed liquid to obtain the quantum dot composite after volatilization.

7. The method for preparing the quantum dot complex according to claim 6, wherein: The mass ratio of the functional additive to the quantum dot powder is 2:1 to 6:

1.

8. The method for preparing the quantum dot complex according to claim 6, wherein: The mass ratio of the quantum dot powder to the solvent is 1:400 to 1:

100.

9. The method for preparing the quantum dot complex according to claim 6, characterized in that: After adding the second ligand into the dispersion, the reaction temperature of the ligand exchange reaction system is raised to 60-80°C.

10. The method for preparing the quantum dot complex according to claim 6, characterized in that: The volatilization treatment includes heating the first mixed liquid or the second mixed liquid to a first temperature, removing the heating source, and then placing the mixed liquid under normal temperature and pressure with air circulation for volatilization.

11. The method for preparing a quantum dot composite according to claim 10, wherein: The first temperature is 50-60°C.

12. The method for preparing a quantum dot complex according to claim 6, wherein: The solvent is selected from one or more of tetrahydrofuran, dioxane, dichloromethane and petroleum ether.

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