WO2020191821A1

WO2020191821A1 - Quantum dot material processing method, highly stable quantum dot material and application thereof

Info

Publication number: WO2020191821A1
Application number: PCT/CN2019/082410
Authority: WO
Inventors: 卢睿; 边盾; 马昊玥; 杨磊; 刘莹
Original assignee: 天津市中环量子科技有限公司
Priority date: 2019-03-27
Filing date: 2019-04-12
Publication date: 2020-10-01
Also published as: CN109825281A

Abstract

A quantum dot material processing method, a highly stable quantum dot material and an application thereof; the surface of the quantum dot material contains the element sulfur, and the quantum dot material processing method comprises the following steps: (1) dispersing a metal salt in a solvent under an inert atmosphere to obtain a metal salt stock solution; (2) taking or preparing a dispersion liquid of a quantum dot material, and adding same to the metal salt stock solution for reaction under an inert atmosphere. For quantum dots the surfaces of which contain the element sulfur, a metal sulfide cation having strong binding force is introduced by means of a reaction between metal salt and the element sulfur on the surface of the quantum dots, thereby terminating the reaction activity by which the quantum dots may be continuously grown, and improving the chemical stability of the quantum dots. The present invention has a high quantum dot fluorescence yield, and has good application prospects in the field of lighting and display.

Description

Processing method of quantum dot material, high-stability quantum dot material and application To

Technical field

The invention relates to the technical field of material processing, in particular to a processing method of quantum dot materials, high-stability quantum dot materials and applications.

Background technique

Colloidal semiconductor quantum dots dots, QDs) is a kind of nano luminescent material with high luminous efficiency and high stability. Compared with traditional luminescent materials, it has: good color purity, high luminous efficiency, high luminous brightness, strong light stability and continuously adjustable luminous color , Is widely used in high-efficiency quantum dot light-emitting diodes (Quantum Dots Light Emitting Diode, QLEDs) new lighting and display technology, with many advantages such as high luminous efficiency, low energy consumption, high stability and long life, is the most promising lighting and display technology.

At present, there are two main technical routes for the preparation of compound colloidal quantum dots: one is to prepare in the water phase, that is, to prepare the non-metallic element and the aqueous phase precursor liquid of the metallic element separately, and mix and react to produce quantum dots in an oxygen-free environment; It is prepared in an organic system, that is, in an organic solvent environment with coordination properties, the metal organic compound is mixed and reacted with non-metal elements to grow into nanoparticles. The above-mentioned existing colloidal method for preparing fluorescent quantum dots has the characteristics of lower synthesis temperature and higher reaction activity, which is beneficial to the efficient batch preparation of fluorescent quantum dots. However, during the preparation of fluorescent quantum dots, the growth of quantum dots is usually stopped by cooling down and reducing the concentration of reactants. The surface of the quantum dots itself still has high reactivity, resulting in poor chemical stability, leading to purification, application and processing. When the device is working, it is usually absorbed by the surface of the fluorescent quantum dot due to the use of solvents or impure atmosphere, and the introduction of impurities, which causes the fluorescent quantum dots to form a non-radiative composite channel, which reduces the fluorescence yield, making it difficult to apply to efficient and stable In white light QLEDs, its application in the field of lighting and display is restricted. In addition, when fluorescent quantum dots are mixed and packaged with encapsulating glue, their monomer active sites are cross-linked under the action of a catalyst, and their active sites are easily ligand exchanged with quantum dots, which will also cause a decrease in fluorescence quantum yield.

In order to improve the stability of quantum dots, the existing technology mainly adopts the protection idea of external packaging to avoid the corrosion of quantum dots by impurities such as water and oxygen. Generally, polymer coating and outer barrier packaging are adopted, and high purity is used in applications. The inert atmosphere prevents the fluorescence degradation of the quantum dots, but the above-mentioned external packaging method is complicated to operate, the particle size of the quantum dots after packaging will increase significantly, and the external packaging material affects the fluorescence yield of the internal quantum dots.

Summary of the invention

In view of the shortcomings in the prior art, the purpose of the present invention is to provide a method for processing quantum dot materials, high-stability quantum dot materials and applications. For quantum dots containing sulfur on the surface, the metal salt and the quantum dot surface have high The reactive sulfur element reaction introduces a strong binding force of metal sulfide cations, which terminates the reactivity of the quantum dots that can continue to grow, improves the chemical stability of the quantum dots, and has a higher quantum dot fluorescence yield.

The technical scheme adopted by the present invention is:

The present invention provides a method for processing quantum dot materials, the surface of which contains sulfur, and includes the following steps:

(1) Disperse the metal salt in a solvent under an inert atmosphere to obtain a metal salt stock solution;

(2) Take or prepare a dispersion liquid of quantum dot material, and add the metal salt stock solution to react under an inert atmosphere.

The purpose of using an inert atmosphere in step (1) is to protect the reactants from oxidation. In order to disperse the metal salt uniformly in the solvent more easily, the dispersion treatment can be carried out under heating conditions. Specifically, the heating temperature can be selected according to the added metal salt, for example, the heating temperature can be 20 to 500°C.

The idea of this application is to process quantum dot materials containing sulfur on the surface. The metal salt stock solution can be added directly after the preparation of the existing quantum dots to complete the processing process, so as to save the need to prepare a dispersion of quantum dot materials separately The process is beneficial to improve the efficiency of the overall material preparation. The existing prepared quantum dots can also be dispersed in a solvent to prepare a dispersion of quantum dot materials, and then react with the metal salt stock solution. Step (2) is more conducive to the reaction between the quantum dot material and the metal salt under heating conditions. The heating temperature depends on the solvent of the reaction system. Preferably, the upper limit of the heating temperature range does not exceed the boiling point range of the solvent used.

Preferably, the metal element in the metal salt is selected from at least one of group IB, group IIB element, group VIII element, alkaline earth metal, scandium, yttrium and lanthanide.

Further, the metal element is selected from at least one of silver, mercury, zinc, copper, gold, cadmium, nickel, and platinum.

In some preferred embodiments, the metal salt is selected from at least one of silver salt, mercury salt, and zinc salt. In a further embodiment, the silver salt is selected from silver oxide, silver acetate or silver chloride.

Preferably, the quantum dot material is a metal sulfide nanocrystalline colloidal quantum dot or a nanocrystalline colloidal quantum dot containing a metal sulfide on the surface. The quantum dot materials include but are not limited to cadmium sulfide quantum dots and zinc sulfide quantum dots.

Preferably, the concentration of the metal salt in the metal salt stock solution is 0.001 mmol/L-10 mol/L.

Preferably, the solvent is a coordination type solvent or a non-coordination type solvent; preferably the coordination type non-polar solvent is an acid with carbon atoms ≥ 6, preferably the non-coordination type solvent has carbon atoms ≥ 9 At least one of alkanes, alkenes, and esters.

Further, the coordination type solvent is selected from at least one of myristic acid, oleic acid, stearic acid, and lauric acid; the non-coordination type solvent is selected from liquid paraffin, octadecene, and octadecane At least one of.

The present invention also provides a highly stable quantum dot material, which is obtained by the above-mentioned processing method of quantum dot material.

Application of the above-mentioned highly stable quantum dot materials in lighting or display. The quantum dot material obtained by the above-mentioned processing method of the quantum dot material has high chemical stability, and has a good application prospect in the field of lighting or display.

Preferably, the application is an application in QLEDs lighting or backlight display.

The beneficial effects of the present invention are:

In the photoluminescence application of fluorescent quantum dots, since quantum dots continue to work in a high temperature and high energy environment, their surface is prone to photo-oxidation reactions. For quantum dots containing sulfur on the surface, such as the sulfur in zinc sulfide quantum dots Elements are easily oxidized into sulfate ions or sulfur dioxide, which can damage the structure of quantum dots and reduce the fluorescence quantum yield. The invention provides a method for processing quantum dots, which adopts the idea of performing a termination reaction on the surface of quantum dots to reduce the surface chemical activity of the quantum dots so that the processed quantum dots have higher chemical stability, and specifically aim at the surface containing sulfur elements. The quantum dots, through the reaction of metal salt with the sulfur element on the surface of the quantum dots, introduce a strong binding force of metal sulfide cations, which can terminate the reactivity of the quantum dots that can continue to grow, and enhance the ability of the quantum dots to resist photooxidation. The chemical stability of quantum dots is improved, and it has good application prospects in the field of lighting and display.

Description of the drawings

1 is a graph showing the yield test results of fluorescent quantum dots of cadmium selenide/zinc sulfide alloy structure quantum dots before and after heating treatment in effect embodiment 2;

2 is a graph showing the yield test results of fluorescent quantum dots of the quantum dot material obtained in Example 1 before and after the heating treatment in Effect Example 2;

FIG. 3 is a graph of the aging test result in effect embodiment 3.

detailed description

In the following, the concept of the present invention and the technical effects produced by it will be clearly and completely described in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work belong to The scope of protection of the present invention.

Example 1

This embodiment provides a highly stable quantum dot material, which is processed according to the following steps:

(1) Preparation of quantum dot dispersion: Take 0.6 g of cadmium selenide/zinc sulfide alloy structure quantum dots and disperse in 15 mL of oleic acid under an inert atmosphere and store;

(2) Preparation of silver oxide stock solution: take 0.05 g of silver oxide, add 10 mL of oleic acid, place it in the reaction device and under the protection of an inert atmosphere, heat to 90°C, and disperse to obtain a silver oxide stock solution;

(3) Place the quantum dot dispersion in step (1) in a reaction device and under an inert protective atmosphere, heat up to 320°C, add the silver oxide stock solution prepared in step (2), stir and disperse uniformly, and react 10 min to obtain fluorescent quantum dots.

The silver salt specifically used in this embodiment is silver oxide, and the silver salt that can be actually used includes, but is not limited to, silver oxide, silver acetate, silver chloride, silver carbonate, and the like.

Example 2

(1) Preparation of quantum dot dispersion: take 0.3 g of cadmium selenide/zinc sulfide alloy quantum dots and disperse in 10 mL of oleic acid under an inert atmosphere, and store;

(2) Preparation of mercury oxide stock solution: take 0.01 g of mercury oxide, add 15 mL of lauric acid, place it in the reaction device and heat to 90°C under the protection of an inert atmosphere to prepare a mercury oxide stock solution;

(3) Place the quantum dot dispersion in step (1) in a reaction device and under an inert protective atmosphere, heat up to 300°C, add the mercury oxide stock solution prepared in step (2), stir and disperse uniformly, and react 10 min to obtain fluorescent quantum dots.

Example 3

(1) Preparation of quantum dot dispersion: according to the steps of Example 1 in patent document CN107686731A, a dispersion containing CdSe@ZnCdS/ZnS alloy quantum dots was prepared;

(2) After the preparation of the quantum dots in step (1) is completed, before the temperature is lowered, the silver oxide stock solution prepared in Example 1 is added and reacted for 10 minutes to obtain fluorescent quantum dots.

Effect Example 1

Take the untreated cadmium selenide/zinc sulfide alloy quantum dots and the quantum dot material processed in Example 1 and clean them separately. The specific cleaning process is: add an equal volume of n-hexane to the initial quantum dot solution and disperse it. After homogenization, add 3 times the volume of absolute ethanol, continue to disperse and shake, at 10,000 After centrifugation at rpm for 2 min, a precipitate was obtained, and n-hexane was added to repeat the above cleaning process.

Perform fluorescence quantum dot yield test on the above-mentioned initial quantum dots and the quantum dots that have undergone the cleaning process. The specific process is: disperse the sub-dots to be measured in n-hexane and adjust the concentration to 300 The absorbance at the wavelength of nm is about 0.7, and the test is performed at an excitation wavelength of 450 nm using the Hamamatsu Quantaurus-QY C11347-12. The test results are shown in Table 1.

Table 1 Fluorescence quantum yield of cadmium selenide/zinc sulfide alloy structure quantum dots and the processed quantum dots in Example 1

	Cadmium selenide/zinc sulfide alloy structure quantum dot fluorescence quantum yield% (PLQY)	The fluorescence quantum yield of the quantum dot material of Example 1% (PLQY)
Initial quantum dot	57%	83%
After washing 5 times	42%	82%
After cleaning 10 times	twenty one%	83%

It can be seen from Table 1 that the fluorescence quantum yield of the cadmium selenide/zinc sulfide alloy structure quantum dots that have not been treated with metal salt drops rapidly after multiple cleanings, while the fluorescence quantum yield of the quantum dot material processed in Example 1 The rate has been significantly improved, and after multiple cleanings, the fluorescence quantum yield is almost unaffected. The reason is that the metal salt can combine with the sulfur element on the surface of the quantum dot to form a metal sulfide salt with strong binding force, which prevents the environment from affecting the quantum The influence of dot fluorescence quantum yield improves the chemical stability of quantum dots, and solves the problem of the decrease of quantum dot fluorescence quantum yield caused by oxidation and ion exchange of uncoordinated sulfur element and the sulfur of the original metal sulfide in quantum dots The experimental results prove that for quantum dots containing sulfur on the surface, the use of metal salt treatment can improve the chemical stability of such quantum dots.

Effect Example 2

Take the untreated cadmium selenide/zinc sulfide alloy quantum dots and the quantum dot material obtained in Example 1 and heat them separately, as follows: add the quantum dot material to oleic acid, and heat it in a three-necked flask with a heating jacket , The heating interval is respectively, 50℃ 5min, 100℃ 5min, 150℃ 5min, 200℃ 10min, 300℃ 10min, 320℃ 10min. After completing the heating process, cool to room temperature. The fluorescence quantum dot yield test was performed on the above-mentioned cadmium selenide/zinc sulfide alloy quantum dots before and after the high-temperature heating treatment and the quantum dot material in Example 1. The specific process is: dispersing the dots to be measured in n-hexane, Adjust the concentration at 300 The absorbance at nm wavelength is around 0.7, using equipment Hamamatsu Quantaurus-QY C11347-12 is tested at an excitation wavelength of 450nm. The test results of the quantum dots with the cadmium selenide/zinc sulfide alloy structure before and after the heat treatment are shown in FIG. 1, and the test results of the quantum dot materials obtained in Example 1 before and after the heat treatment are shown in FIG. 2.

It can be seen from Figure 1 that the untreated cadmium selenide/zinc sulfide alloy structure quantum dot has a significant red shift in the fluorescence spectrum after heat treatment. It can be seen from Figure 2 that the quantum dot material processed by this application After the heat treatment, there is no obvious visible spectral shift in the test fluorescence spectrum. The reason is that the metal salt can react with the highly reactive sulfur element of the quantum dot to form a metal sulfide salt with strong binding force, thereby avoiding the sulfur element being oxidized to form vacancies on the surface of the quantum dot under high temperature heating, resulting in further agglomeration of quantum dot The phenomenon that causes the fluorescence spectrum of quantum dots to shift. Experimental results show that for quantum dots containing sulfur, the use of metal salt treatment can improve the chemical stability and dispersion stability of such quantum dots.

Effect Example 3

Take the untreated cadmium selenide/zinc sulfide alloy quantum dots (before treatment) and the quantum dot materials obtained by the treatment in Example 1 (after treatment) respectively for LED dispensing packaging and aging test, specifically: Dot is mixed with UV glue, and after vacuum rotation deaeration, the glue will be dispensed into 2835 blue chip LED. After the glue is cured by ultraviolet light for 30 seconds, it is put into a high temperature and high humidity accelerated aging box for aging test, and the lighting current is 20 mA. After lighting up continuously every few hours, take out the remote ATA-500 integrating sphere to test, calculate the decay of the quantum dot fluorescence spectrum, and the result is shown in Figure 3.

It can be seen from Figure 3 that the untreated cadmium selenide/zinc sulfide alloy structure quantum dots decay very fast after being lit and aged for a long time at high temperature and humidity. In contrast, the quantum dot material processed in Example 1 decays smoothly under the same conditions. The reason is that the metal salt and the unstable sulfur element of the quantum dots form a strong binding force of metal sulfide salt, which prevents the surface of the quantum dot from being oxidized by water and oxygen under high temperature and high humidity, resulting in the formation of vacancies and decomposition of the quantum dot problem. Experimental results prove that for quantum dots containing sulfur, the use of metal salt treatment can improve the oxidation stability of such quantum dots.

Claims

A processing method of quantum dot material, characterized in that the surface of the quantum dot material contains sulfur, and includes the following steps:

(1) Disperse the metal salt in a solvent under an inert atmosphere to obtain a metal salt stock solution;

(2) Take or prepare a dispersion liquid of quantum dot material, and add the metal salt stock solution to react under an inert atmosphere.
The method for processing quantum dot materials according to claim 1, wherein the metal elements in the metal salt are selected from group IB, group IIB elements, group VIII elements, alkaline earth metals, scandium, yttrium and lanthanides At least one of. To
The method for processing quantum dot materials according to claim 2, wherein the metal element is selected from at least one of silver, mercury, zinc, copper, gold, cadmium, nickel, and platinum. To
The processing method of quantum dot material according to claim 1, wherein the quantum dot material is a metal sulfide nanocrystalline colloidal quantum dot or a nanocrystalline colloidal quantum dot containing a metal sulfide on its surface. To
The method for processing quantum dot materials according to claims 1-4, wherein the concentration of the metal salt in the metal salt stock solution is 0.001 mmol/L~10 mol/L.
The method for processing quantum dot materials according to claims 1-4, wherein the solvent is a coordination type solvent or a non-coordination type solvent; preferably the coordination type non-polar solvent has a carbon number ≥ For the acid of 6, it is preferable that the non-coordinating solvent is at least one of alkane, alkene, and ester with carbon number ≥9. To
The method for processing quantum dot materials according to claim 6, wherein the coordination type solvent is selected from at least one of myristic acid, oleic acid, stearic acid, and lauric acid; the non-coordinating The type solvent is selected from at least one of liquid paraffin, octadecene, and octadecane. To
A highly stable quantum dot material, characterized in that it is obtained by the method for processing a quantum dot material according to any one of claims 1-7.
The application of the highly stable quantum dot material of claim 8 in lighting or display.
The application according to claim 9, wherein the application is an application in QLEDs lighting or backlight display.