Quantum dot composite particles, preparation method thereof, and photoluminescence device containing the same

Abstract

The present disclosure provides a quantum dot composite particle, a preparation method thereof, and a quantum dot photoluminescence device containing the same. The quantum dot composite particle includes quantum dots, an antioxidant layer coordinated on the surface of the quantum dots, and an inorganic oxide layer coating the antioxidant layer. The antioxidant in the antioxidant layer has a coordination group coordinated with the surface of the quantum dots, and the thickness of the antioxidant layer is 1 to 10 nm. The inorganic oxide layer serves as the first protection means for the quantum dots to block the intrusion of water and oxygen; an antioxidant is modified on the surface of the quantum dots to form an antioxidant layer to prevent the damage of small molecules passing through the inorganic oxide coating layer to the quantum dots, further improving the stability of the quantum dots.

Description

Technical Field

[0001] The present disclosure relates to the technical field of quantum dot composites, and in particular, to a quantum dot composite particle, a preparation method thereof, and a photoluminescence device containing the same. Background Art

[0002] Quantum dots have optical properties such as fluorescence emission wavelengths that can cover the entire visible light region, large Stokes shifts, narrow PL emission peaks, and high luminous efficiencies, making them the next-generation mainstream material for fabricating LED color display devices. However, due to the characteristics that quantum dots are highly sensitive to moisture, oxygen, and heat, their luminescence stability needs to be further improved. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a quantum dot composite particle, a preparation method thereof, and a photoluminescence device containing the same, to improve the lifespan of the quantum dot composite particle and the photoluminescence device.

[0004] According to a first aspect of the present disclosure, there is provided a quantum dot composite particle, which includes quantum dots, an antioxidant layer coordinated on the surface of the quantum dots, and an inorganic oxide layer coating the antioxidant layer. The antioxidant in the antioxidant layer has a coordination group coordinated with the surface of the quantum dots, and the thickness of the antioxidant layer is 1 - 10 nm.

[0005] Optionally, the thickness of the inorganic oxide layer is 2 - 40 nm; preferably, the quantum dot composite particle is 15 nm - 100 nm.

[0006] Optionally, the antioxidant is selected from one or more of hindered phenols, hindered amines, phosphite esters, thioesters, or thioethers; preferably, the material of the inorganic oxide layer includes one or more of TiO2, ZrO2, Al2O3, ZnO, ZnMgO, or SnO2.

[0007] According to a second aspect of the present disclosure, there is provided a preparation method of any of the above-mentioned quantum dot composite particles. Quantum dots with a first ligand are dispersed in an organic solvent and added to a container. A mixed solution of a long-chain silane ligand and an antioxidant is further added to the container, and at least a part of the first ligand is replaced by the long-chain silane ligand and the antioxidant. Ethanol, an ester compound containing a silicon element, and / or a metal alkoxide are further added to the container, and an acid or a base is added as a catalyst, and a reaction is carried out for a first period of time to obtain a product. The product is separated, purified, and dried to obtain the quantum dot composite particle; wherein, the long-chain silane ligand has a coordination group, the long-chain silane ligand further includes a siloxanyl group and a hydroxyl group, and the number of main-chain C atoms of the long-chain silane ligand is 8 - 30.

[0008] Optionally, the mass of the long-chain silane ligand is 5% - 50% of the mass of the quantum dots with the first ligand.

[0009] Optionally, the mass of the antioxidant is 0.1% to 20% of the mass of the quantum dots having the first ligand.

[0010] Optionally, the mass of the organic solvent is 1 to 500 times the mass of the quantum dots having the first ligand.

[0011] Optionally, the coordinating group is selected from a mercapto group, a hydroxyl group, an amino group, a carboxyl group, a phosphoric acid group or a phosphorous acid group; preferably, the long-chain silane ligand is selected from silane-PEG-carboxylic acid, 8-mercapto-1-octanol, 11-mercapto-1-undecanol or divinyltriaminepropylmethyldimethoxysilane.

[0012] Optionally, the acid or base is an organic or inorganic acid solution or base solution; preferably, the acid is a hydrochloric acid solution or an acetic acid solution, and the base is a sodium hydroxide solution or a tetramethylammonium hydroxide solution.

[0013] According to a third aspect of the present disclosure, there is provided a quantum dot photoluminescence device, and the quantum dot photoluminescence device includes any one of the above-mentioned quantum dot composite particles.

[0014] By adopting the above technical solution, the antioxidant is pre-modified on the surface of the quantum dots to form an antioxidant layer, so as to prevent the damage of small molecules (such as water and oxygen) passing through the inorganic oxide layer to the quantum dots, further improving the stability of the quantum dots, thereby improving the stability of the quantum dot photoluminescence device. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The specification drawings forming a part of this application are used to provide a further understanding of the present disclosure. The schematic embodiments of the present disclosure and their descriptions are used to explain the present disclosure and do not constitute an improper limitation to the present disclosure. In the drawings:

[0016] Figure 1 It is a schematic structural diagram of a quantum dot composite particle according to an embodiment of the present disclosure.

[0017] Figure 2 It is a schematic flow diagram of preparing a quantum dot composite particle according to an embodiment of the present disclosure.

[0018] Figure 3 It is a transmission electron microscope (TEM) photograph of a quantum dot composite particle according to an embodiment of the present disclosure.

[0019] Figure 4 It is a change curve graph of the brightness attenuation and aging time of a quantum dot photoluminescence device according to some embodiments of the present disclosure.

[0020] Reference numerals: 1, quantum dots; 2, antioxidant layer; 3, inorganic oxide layer; 4, long-chain silane ligand. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0021] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present application belongs.

[0022] According to a first aspect of the present disclosure, there is provided a quantum dot composite particle, which includes quantum dots, an antioxidant layer coordinated on the surface of the quantum dots, and an inorganic oxide layer coating the antioxidant layer. The antioxidant in the antioxidant layer has a coordination group coordinated with the surface of the quantum dots, and the thickness of the antioxidant layer is 1 to 10 nm.

[0023] The inventors have found that the inorganic oxide coating layer on the surface of the quantum dots cannot completely block small molecules of water and oxygen, and the quantum dots will still be slowly etched over a long time, resulting in a decrease in photochemical stability. Moreover, due to the presence of the inorganic oxide coating layer, the antioxidant used in combination cannot directly act on the surface of the quantum dots, and the effect is minimal. In the solution of the present application, the inorganic oxide layer serves as the first protection means for the quantum dots to block the invasion of water and oxygen; the antioxidant is modified on the surface of the quantum dots to form an antioxidant layer to prevent the small molecules that penetrate through the inorganic oxide coating layer from damaging the quantum dots, further improving the stability of the quantum dots.

[0024] In some embodiments, the thickness of the inorganic oxide layer is 2 to 40 nm. In some embodiments, the quantum dot composite particles are 15 nm to 100 nm. In some embodiments, the shape of the quantum dot composite particles is spherical (including quasi-spherical).

[0025] In some embodiments, the antioxidant is selected from one or more of hindered phenols, hindered amines, phosphite esters, thioesters, or thioethers.

[0026] In some embodiments, the material of the inorganic oxide layer includes one or more of TiO2, ZrO2, Al2O3, ZnO, ZnMgO, or SnO2.

[0027] In some embodiments, the above-mentioned quantum dot composite particles can be used for the preparation of polymer microspheres.

[0028] According to a second aspect of the present disclosure, there is provided a method for preparing the quantum dot composite particles as described above. The quantum dots with a first ligand are dispersed in an organic solvent and added to a container. A mixed solution of a long-chain silane ligand and an antioxidant is further added to the container, and at least a part of the first ligand is replaced by the long-chain silane ligand and the antioxidant. An alcohol, an ester compound containing silicon, or one or two of metal alkoxides is further added to the container, and an acid or a base is added as a catalyst, and the reaction is carried out for a first period of time to obtain a product; the product is separated, purified, and dried to obtain the quantum dot composite particles; wherein, the long-chain silane ligand has a coordination group, the long-chain silane ligand further includes a siloxanyl group and a hydroxyl group, and the number of main chain C atoms of the long-chain silane ligand is 8 to 30.

[0029] In some embodiments, the quantum dots with the first ligand are in a powder state, and preferably the first ligand is a carboxylic acid with no more than 22 carbon atoms.

[0030] In some embodiments, more than 50% of the first ligand is replaced by the long-chain silane ligand and the antioxidant. In some embodiments, the pH of the reaction system is 4 to 12 and not equal to 7.

[0031] In some embodiments, the temperature of the above ligand exchange step is selected from 0 to 90 °C, preferably 25 °C to 35 °C. In some embodiments, the temperature of the above alcoholysis condensation reaction is selected from 0 to 50 °C, preferably 25 °C to 35 °C.

[0032] In some embodiments, after obtaining the product, a precipitant is added to the product system to precipitate the product, thereby facilitating further separation and purification.

[0033] In some embodiments, the mass of the long-chain silane ligand is 5% to 50% of the mass of the quantum dots with the first ligand, preferably 10% to 30%.

[0034] In some embodiments, the mass of the antioxidant is 0.1% to 20% of the mass of the quantum dots with the first ligand, preferably 2% to 10%.

[0035] In some embodiments, the mass of the organic solvent is 1 to 500 times the mass of the quantum dots with the first ligand, preferably 50 to 200 times.

[0036] In some embodiments, the mass of ethanol is 100% to 1000% of the mass of the organic solvent.

[0037] In some embodiments, the coordination group of the long-chain silane ligand or the antioxidant is selected from a mercapto group, a hydroxyl group, an amino group, a carboxyl group, a phosphoric acid group, or a phosphorous acid group.

[0038] In some embodiments, the long-chain silane ligand is selected from silane-PEG-carboxylic acid, 8-mercapto-1-octanol, 11-mercapto-1-undecanol, and divinyltriaminopropylmethyldimethoxysilane.

[0039] The silicon-containing ester compounds are not limited as long as they can react to form an inorganic oxide layer. In some embodiments, the silicon-containing ester compounds are selected from tetrabutyl orthosilicate, tetramethyl orthosilicate, tetraethyl orthosilicate, or tetrapropyl orthosilicate.

[0040] In some embodiments, the acid or base is an organic or inorganic acid solution or base solution. Preferably, the acid is a hydrochloric acid solution or an acetic acid solution, and the base is a sodium hydroxide solution or a tetramethylammonium hydroxide solution.

[0041] According to the third aspect of the present disclosure, a quantum dot photoluminescence device is provided. The quantum dot photoluminescence device includes any of the above-mentioned quantum dot composite particles. The quantum dot photoluminescence device has excellent use stability.

[0042] In some embodiments, the above-mentioned quantum dot photoluminescence device includes an LED chip and silica gel, and the above-mentioned quantum dot composite particles are dispersed in the silica gel. The size of the LED chip is not limited.

[0043] In some embodiments, the above-mentioned quantum dot photoluminescence device is used in a display device.

[0044] Hereinafter, the embodiments will be described in more detail with reference to specific examples. However, they are exemplary examples of the present disclosure, and the present disclosure is not limited thereto.

[0045] Example 1

[0046] Take 1.5 g of quantum dot powder (the first ligand is oleate) and dissolve it in 100 g of toluene. Add 0.2 g of divinyltriaminopropylmethyldimethoxysilane and 0.05 g of antioxidant 264 (containing a hydroxyl coordination group) at room temperature, mix and dissolve evenly, heat up to 70 °C and stir continuously for 5 h. After the liquid is cooled, pour it into 250 mL of absolute ethanol, and stir magnetically to obtain a uniform mixed solution A.

[0047] Add 30 mL of absolute ethanol, 30 mL of water, and 4 mL of a sodium hydroxide aqueous solution with a concentration of 25% - 28% to 30 mL of absolute ethanol, mix evenly to obtain a mixed solution B; pour the mixed solution B, 20 mL of tetrabutyl orthosilicate, and 6 mL of zirconium n-propoxide into the mixed solution A, and stir at room temperature for 24 h. Centrifuge the reaction product, wash it 3 times with a mixed solution of toluene and ethanol, and dry it in vacuum to obtain quantum dot composite particles 1. The TEM morphology of the quantum dot composite particles 1 is as Figure 3 shown.

[0048] Weigh 70 parts by mass of thermosetting methyl-phenyl silicone resin. After uniformly mixing 20 ppm of platinum catalyst and 30 parts by mass of quantum dot composite particles 1, place them in a vacuum stirring and degassing machine, and carry out vacuum stirring and degassing for 5 min to 10 min under the conditions of a revolution speed of 600 rpm and a rotation speed of 500 rpm to obtain a mixed glue.

[0049] Use a dispensing machine to pour the mixed glue into the encapsulation cavity of an LED bracket with the model number 4014, and place the LED bracket in an oven for baking at 150 °C for 2 h for curing.

[0050] After the curing is completed, take out the quantum dot LED package and place it in an oven at 65 °C and a relative humidity of RH95%, turn it on and age it under a current of 80 mA, and regularly take out the chip and test its optical performance with an integrating sphere.

[0051] Generally, for LED aging, we look at the brightness attenuation, which basically corresponds to the decrease in quantum dot efficiency. Taking the first test point as 100%, the brightness data measured after aging is divided by the first test point to obtain the brightness percentage.

[0052] Example 2

[0053] Take 2 g of quantum dot powder (the first ligand is oleate) and dissolve it in 120 g of n-octane. Add 0.5 g of 11-mercapto-1-undecanol and 0.05 g of antioxidant 168 (containing phosphite groups) at 30 °C, mix and dissolve evenly, heat up to 70 °C and stir continuously for 5 h. After the liquid cools, inject 350 mL of absolute ethanol and stir magnetically to obtain a uniform mixed solution A.

[0054] Add 30 mL of absolute ethanol, 30 mL of water and 6 mL of acetic acid solution to 30 mL of absolute ethanol, mix evenly to obtain a mixed solution B; inject the mixed solution B, 10 mL of aluminum isopropoxide and 12 mL of zirconium n-butoxide into the mixed solution A, and stir at room temperature for 24 h. Centrifuge the reaction product and wash it 3 times with a mixed solution of toluene and ethanol, and obtain quantum dot composite particles 2 after vacuum drying.

[0055] Weigh 70 parts by mass of thermosetting methyl-phenyl silicone resin. After uniformly mixing 20 ppm of platinum catalyst and 30 parts by mass of quantum dot composite particles 2, place them in a vacuum stirring and degassing machine, and carry out vacuum stirring and degassing for 5 min to 10 min under the conditions of a revolution speed of 600 rpm and a rotation speed of 500 rpm to obtain a mixed glue.

[0056] Use a dispensing machine to pour the mixed glue into the encapsulation cavity of an LED bracket with the model number 4014, and place the LED bracket in an oven for baking at 150 °C for 2 h for curing.

[0057] After the curing is completed, take out the quantum dot LED package and place it in an oven at 65 °C and RH95%. Light it at a current of 80 mA for aging, and regularly take out the chip and test its optical performance with an integrating sphere.

[0058] Example 3

[0059] Take 1.8 g of quantum dot powder (the first ligand is oleate) and dissolve it in 90 g of cyclohexane. At room temperature, add 0.4 g of 8-mercapto-1-octanol and 0.15 g of glutathione (an antioxidant containing a mercapto coordination group), mix and dissolve evenly. Heat up to 70 °C and stir continuously for 5 h. After the liquid cools, inject 220 mL of absolute ethanol and stir magnetically to obtain a uniform mixed solution A.

[0060] Add 30 mL of absolute ethanol, 30 mL of water and 5 mL of a 25% aqueous solution of tetramethylammonium hydroxide to 30 mL of absolute ethanol, mix evenly to obtain a mixed solution B; inject the mixed solution B, 5 mL of tetrabutyl orthosilicate and 26 mL of tetrabutyl titanate into the mixed solution A and stir at room temperature for 24 h. Centrifuge the reaction product and wash it 3 times with a mixed solution of toluene and ethanol, and then dry it under vacuum to obtain quantum dot composite particles 3.

[0061] Weigh 70 parts by mass of a thermosetting methyl-phenyl silicone resin, uniformly mix 20 ppm of a platinum catalyst with 30 parts by mass of quantum dot composite particles 3, and place them in a vacuum stirring degassing machine. Under the conditions of a revolution speed of 600 rpm and a rotation speed of 500 rpm, carry out vacuum stirring degassing for 5 min to 10 min to obtain a mixed glue.

[0062] Use a dispensing machine to pour the mixed glue into the encapsulation cavity of an LED bracket with the model number 4014, and place the LED bracket in an oven at 150 °C for baking for 2 h for curing.

[0063] After the curing is completed, take out the quantum dot LED package and place it in an oven at 65 °C and RH95%. Light it at a current of 80 mA for aging, and regularly take out the chip and test its optical performance with an integrating sphere.

[0064] Example 4

[0065] Take 2.5 g of quantum dot powder (the first ligand is oleate) and dissolve it in 150 g of toluene. At room temperature, add 0.7 g of silane-PEG-carboxylic acid and 0.12 g of antioxidant 2246 (containing a hydroxyl coordination group), mix and dissolve evenly. Heat up to 60 °C and stir continuously for 6 h. After the liquid cools, inject 270 mL of absolute ethanol and stir magnetically to obtain a uniform mixed solution A.

[0066] Add 35 mL of absolute ethanol, 40 mL of water and 3 mL of a 0.1 mol·L -1A hydrochloric acid solution was taken, and after mixing evenly, a mixed solution B was obtained; the mixed solution B and 31 mL of aluminum isopropoxide were injected into the mixed solution A, and stirred at room temperature for 24 h. The reaction product was centrifuged and washed 3 times with a mixed solution of toluene and ethanol, and quantum dot composite particles 4 were obtained after vacuum drying.

[0067] 70 parts by mass of a thermosetting methyl-phenyl silicone resin, 20 ppm of a platinum catalyst and 30 parts by mass of quantum dot composite particles 4 were evenly mixed and placed in a vacuum stirring and degassing machine, and vacuum stirred and degassed for 5 min to 10 min under the conditions of a revolution speed of 600 rpm and a rotation speed of 500 rpm to obtain a mixed glue.

[0068] The mixed glue was filled into the encapsulation cavity of an LED bracket of model 4014 by a dispensing machine, and the LED bracket was placed in an oven and baked at 150 °C for 2 h for curing.

[0069] After curing, the quantum dot LED package was taken out and placed in an oven at 65 °C and RH95%, and lit at a current of 80 mA for aging. The chip was taken out regularly and its optical properties were tested with an integrating sphere.

[0070] Comparative Example 1

[0071] 1.5 g of quantum dot powder was dissolved in 100 g of toluene, 0.2 g of diethylenetriaminepropylmethyldimethoxysilane was added at room temperature, and the mixture was dissolved evenly. The temperature was raised to 70 °C and stirred continuously for 5 h. After the liquid was cooled, 250 mL of absolute ethanol was injected, and magnetic stirring was carried out to obtain a uniform mixed solution A.

[0072] 30 mL of water and 4 mL of sodium hydroxide ammonia water with a concentration of 25% to 28% were added to 30 mL of absolute ethanol, and after mixing evenly, a mixed solution B was obtained; the mixed solution B, 20 mL of tetrabutyl orthosilicate and 6 mL of zirconium n-propoxide were injected into the mixed solution A, and stirred at room temperature for 24 h. The reaction product was centrifuged and washed 3 times with a mixed solution of toluene and ethanol, and quantum dot composite particles were obtained after vacuum drying.

[0073] 70 parts by mass of a thermosetting methyl-phenyl silicone resin, 20 ppm of a platinum catalyst and 30 parts by mass of composite particles 5 were evenly mixed and placed in a vacuum stirring and degassing machine, and vacuum stirred and degassed for 5 min to 10 min under the conditions of a revolution speed of 600 rpm and a rotation speed of 500 rpm to obtain a mixed glue.

[0074] The mixed glue was filled into the encapsulation cavity of an LED bracket of model 4014 by a dispensing machine, and the LED bracket was placed in an oven and baked at 150 °C for 2 h for curing.

[0075] After the curing is completed, take out the quantum dot LED package and place it in an oven at 65 °C and RH95%. Light it at a current of 80 mA for aging. Take out the chip regularly and test its optical performance with an integrating sphere.

[0076] Comparative Example 2

[0077] Weigh 70 parts by mass of thermosetting methyl-phenyl silicone resin. After uniformly mixing 20 ppm of platinum catalyst and 30 parts by mass of quantum dot powder, place them in a vacuum stirring and degassing machine. Under the conditions of a revolution speed of 600 rpm and a rotation speed of 500 rpm, vacuum stir and degas for 5 min to 10 min to obtain a mixed glue.

[0078] Use a dispenser to pour the mixed glue into the encapsulation cavity of an LED bracket of model 4014. Place the LED bracket in an oven and bake it at 150 °C for 2 h for curing.

[0079] After the curing is completed, take out the quantum dot LED package and place it in an oven at 65 °C and RH95%. Light it at a current of 80 mA for aging. Take out the chip regularly and test its optical performance with an integrating sphere.

[0080] From Figure 4 the analysis of the test results, it can be seen that the LED lamps prepared by the method of Example 1 have good stability. After aging at 80 mA for 1000 h, the brightness attenuation is maintained within 4%. After aging for 1000 h, the brightness attenuation of the LED lamps prepared by the methods of Examples 2, 3, and 4 are all maintained within 7%. For Comparative Example 1 (without antioxidant), after 1008 h of aging, the brightness attenuation is 17%.

[0081] The above are only the preferred embodiments of the present disclosure and are not used to limit the present disclosure. For those skilled in the art, the present disclosure can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method for preparing quantum dot composite particles, characterized in that: Dispersing quantum dots with a first ligand in an organic solvent and adding the solution to a container, adding a mixed solution of a long-chain silane ligand and an antioxidant to the container, and replacing at least a portion of the first ligand with the long-chain silane ligand and the antioxidant; adding one or two of ethanol, a silicon-containing ester compound and a metal alkoxide to the container, adding an acid or a base as a catalyst, reacting for a first time, and obtaining a product; The product is separated, purified and dried to obtain the quantum dot composite particles; wherein the long-chain silane ligand has a coordination group, the long-chain silane ligand also includes a siloxane group and a hydroxyl group, and the number of C atoms in the main chain of the long-chain silane ligand is 8 to 30; the quantum dot composite particles include quantum dots, an antioxidant layer coordinated on the surface of the quantum dots and an inorganic oxide layer coating the antioxidant layer, the antioxidant in the antioxidant layer has a coordination group coordinated with the surface of the quantum dots, and the thickness of the antioxidant layer is 1 to 10 nm.

2. The preparation method according to claim 1, characterized in that: The thickness of the inorganic oxide layer is 2-40 nm.

3. The preparation method according to claim 1, characterized in that: The quantum dot composite particles are 15nm to 100nm.

4. The preparation method according to claim 1, characterized in that: The antioxidant is selected from one or more of hindered phenols, hindered amines, phosphites, thioesters or thioethers.

5. The preparation method according to claim 1, characterized in that: The material of the inorganic oxide layer includes one or more of TiO2, ZrO2, Al2O3, ZnO, ZnMgO or SnO2.

6. The preparation method according to claim 1, characterized in that: The mass of the long-chain silane ligand is 5% to 50% of the mass of the quantum dots having the first ligand.

7. The preparation method according to claim 1, characterized in that: The mass of the antioxidant is 0.1% to 20% of the mass of the quantum dots having the first ligand.

8. The preparation method according to claim 1, characterized in that: The mass of the organic solvent is 1 to 500 times the mass of the quantum dots having the first ligand.

9. The preparation method according to claim 1, characterized in that: The coordination group is selected from thiol, hydroxyl, amino, carboxyl, phosphate or phosphite; the long-chain silane ligand is selected from silane-PEG-carboxylic acid or diethylenetriaminepropylmethyldimethoxysilane.

10. The preparation method according to claim 1, characterized in that: The acid or base is an organic or inorganic acid solution or base solution.

11. The preparation method according to claim 10, characterized in that: The acid is hydrochloric acid solution or acetic acid solution, and the alkali is sodium hydroxide solution or tetramethylammonium hydroxide solution.

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