CN110423616B

CN110423616B - Core-shell quantum dot preparation method and quantum dot photoelectric device

Info

Publication number: CN110423616B
Application number: CN201910543254.0A
Authority: CN
Inventors: 周健海; 蔡祥周
Original assignee: Najing Technology Corp Ltd
Current assignee: Najing Technology Corp Ltd
Priority date: 2019-06-21
Filing date: 2019-06-21
Publication date: 2023-02-10
Anticipated expiration: 2039-06-21
Also published as: CN110423616A

Abstract

The invention discloses a preparation method of a core-shell quantum dot and a quantum dot photoelectric device. The preparation method of the core-shell quantum dot comprises the following steps: providing first quantum dots, second quantum dots, a ligand and a first solution containing fatty amine, wherein the average particle size of the second quantum dots is smaller than that of the first quantum dots; and mixing the first quantum dots, the second quantum dots, the ligand and the first solution to form a reaction system, wherein the second quantum dots are gradually dissolved in the reaction system, and a dissolved product of the second quantum dots grows outside the first quantum dots to form a shell layer, so that the core-shell quantum dots are prepared. The method has the advantages of simple synthesis steps, short reaction time and good repeatability, is favorable for large-scale production of the core-shell quantum dots, and is also favorable for obtaining the core-shell quantum dots with good monodispersity.

Description

Core-shell quantum dot preparation method and quantum dot photoelectric device

Technical Field

The invention relates to the technical field of quantum dot materials, in particular to a preparation method of a core-shell quantum dot and a quantum dot photoelectric device.

Background

Among nanomaterials, solution semiconductor nanocrystals (solution quantum dots) having a size within the quantum confinement range have attracted extensive attention in the scientific and industrial fields due to their excellent optical properties, such as high fluorescence quantum yield, wide absorption bandwidth, narrow emission peak, and good optical stability. In the fields of biological marking and imaging, light emitting diodes, lasers, quantum dot photovoltaic devices and the like, quantum dot research has become one of the hot spots in each field. In the fields of display (quantum dot backlight television), illumination and the like which affect the daily life of people, quantum dots have been practically applied. Especially in the field of display, compare in organic fluorescent material and inorganic phosphor powder, quantum dot can restore the image color more really, realizes that the gamut covers, and then promotes the feel and the third dimension of picture.

As a new class of light-emitting and photoelectric materials, the synthetic chemistry of solution quantum dots is the determining factor of the development of the materials. Compared with the core quantum dot with a single component, the core-shell quantum dot has higher optical and chemical stability. When the core-shell quantum dot is prepared, two key problems need to be solved, particularly in the shell growth process, one is to avoid the self-nucleation of the shell precursor as much as possible, and the other is to ensure that the shell precursor grows uniformly on the surface of the core quantum dot.

In 2003, researchers in the field proposed alternating ionic layer adsorption growth (SILAR) to grow CdS shells of controlled thickness on CdSe quantum dots, namely: the method comprises the steps of firstly measuring the concentration of CdSe quantum dots to obtain the amount of an anion precursor and a cation precursor required for coating each CdS layer, and adding the anion precursor and the cation precursor alternately, wherein the precursors can be well adsorbed on the surfaces of the quantum dots, so that the self-nucleation phenomenon of the anion precursor and the cation precursor can be inhibited. After the SILAR method is adopted, the nuclear shell quantum dots are good in appearance and size distribution, and narrow in fluorescence half-peak width. However, the SILAR method is only suitable for coating the thin-layer core-shell quantum dots, and the amount of the precursor required by each layer is correspondingly increased along with the increase of the shell layer, so that the anion precursor and the cation precursor are easy to perform self-nucleation in the coating process. In addition, the appearance of the quantum dot can be changed by increasing the concentration of the precursor, and the appearance of the core-shell quantum dot can be changed to be non-spherical. Then, researchers in the field have further developed a thermal cycle alternating ion layer adsorption growth method (TC-SILAR) in 2007, that is, precursors are injected at a low temperature, the reactivity of the precursors is reduced, the precursors are well and uniformly adsorbed on the surfaces of quantum dots, and then the temperature is raised for reaction. By adopting the method, the core-shell structure still keeps the spherical morphology with the increase of the shell thickness. In addition, in 2013, another group of researchers developed a method for synthesizing the core-shell quantum dots, namely at 300 ℃, cadmium oleate and octyl mercaptan are used as precursors for forming a CdS shell layer, the CdSe/CdS core-shell structure with narrow emission half-peak width is synthesized, the fluorescence half-peak width is in the range of single-particle fluorescence, the narrowest width reaches 65.3meV, and the fluorescence quantum yield is close to 100%.

However, the currently developed synthesis methods of various core-shell quantum dots have the defects of long reaction time, complicated reaction process, high cost, high energy consumption and the like, and are not beneficial to the large-scale production of the core-shell quantum dots. The dosage of the precursor required for forming the nuclear layer is increased along with the increase of the thickness of the shell layer, and self-nucleation is easy to occur along with the continuous addition of the precursor in the synthesis process of the shell layer, so that the phenomena of monodispersion of the size and appearance of the quantum dots, narrowing of the half-peak width of fluorescence and the like are caused, and the synthesis of the quantum dots with complex structures or special structures is difficult to perform.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide a preparation method of the core-shell quantum dot, which solves the self-nucleation phenomenon in the growth process of a shell layer and obtains the core-shell quantum dot with good monodispersity.

According to one aspect of the invention, a preparation method of the core-shell quantum dot is provided, which comprises the following steps:

providing first quantum dots, second quantum dots, a ligand and a first solution containing fatty amine, wherein the average particle size of the second quantum dots is smaller than that of the first quantum dots;

and mixing the first quantum dots, the second quantum dots, the ligand and the first solution to form a reaction system, wherein the second quantum dots are gradually dissolved in the reaction system, and a dissolved product of the second quantum dots grows outside the first quantum dots to form a shell layer, so that the core-shell quantum dots are prepared.

In one embodiment, the first quantum dot is a core quantum dot or a core-shell quantum dot, and the second quantum dot is a core quantum dot or a core-shell quantum dot.

In one embodiment, the ligand is a trialkylphosphine, preferably the trialkylphosphine is selected from one or more of the following: tributyl phosphine, trioctyl phosphine.

In one embodiment, the volume fraction of the fatty amine in the first solution is 25% to 100%.

In one embodiment, the fatty amine is a saturated or unsaturated primary amine with a carbon chain length of 8-22.

In one embodiment, the difference between the particle size of the first quantum dot and the particle size of the second quantum dot is not less than 2nm, and preferably, the particle size of the first quantum dot is 3nm to 10nm, and the particle size of the second quantum dot is 1nm to 5nm.

In one embodiment, the initial concentration of the first quantum dots is greater than the initial concentration of the second quantum dots in the reaction system.

In one embodiment, the first quantum dots and the second quantum dots are mixed and dispersed in a solvent to form a quantum dot mixed solution before mixing with the first solution, and the quantum dot mixed solution, the ligand, and the first solution are mixed to form the reaction system, wherein the concentration of the first quantum dots is higher than the concentration of the second quantum dots in the quantum dot mixed solution.

In one embodiment, the temperature of the reaction system is kept between 200 ℃ and 310 ℃ for 5min to 30min.

According to another aspect of the invention, a quantum dot photoelectric device is provided, which comprises the core-shell quantum dot prepared by the method.

Compared with the prior art, the invention has the beneficial effects that: the core-shell quantum dot has the advantages of simple synthesis steps, short reaction time and good repeatability, and is beneficial to large-scale production of the core-shell quantum dot; the preparation method of the core-shell quantum dot solves the self-nucleation phenomenon in the growth process of the shell layer, and is beneficial to obtaining the core-shell quantum dot with good monodispersity, so that the fluorescence half-peak width of the core-shell quantum dot is narrow; the preparation method of the core-shell quantum dot can obtain the core-shell quantum dot with high yield of the fluorescent quantum dot; in addition, the preparation method of the core-shell quantum dot has good universality, can be used for synthesizing different types of core-shell quantum dots, and can also be used for synthesizing core-shell quantum dots with complex structures.

Drawings

FIG. 1 shows electron micrographs of CdS, cdSe and CdSe/CdS quantum dots in example 1 of the present application.

Detailed Description

The present invention is further described below with reference to specific embodiments, and it should be noted that, without conflict, any combination between the embodiments or technical features described below may form a new embodiment.

It is noted that the terms first, second and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention provides a preparation method of a core-shell quantum dot, which comprises the following steps:

In the technical scheme, the first quantum dots are quantum dots of the shell layer to be coated, and the second quantum dots are used for providing materials required by the growth of the shell layer. In the prior art, when a shell layer grows, a cation precursor and an anion precursor are usually added into a solution containing quantum dots, and the cation precursor and the anion precursor are easy to perform self-nucleation in the shell layer coating reaction process, which is also the reason for poor monodispersity of the core-shell quantum dots prepared by the prior art. In the invention, the material for growing the shell layer firstly forms the second quantum dots with smaller size, then the second quantum dots with smaller size and the first quantum dots with larger size are mixed in the solution, the second quantum dots are dissolved in the solution under a certain condition, the dissolved products can grow outside the first quantum dots to form the shell layer, and the prepared core-shell quantum dots have good monodispersity and narrow fluorescence half-peak width.

The principle of dissolution of the second quantum dot in solution is similar to that of dissolution of small-sized particles in the Ostwald ripening phenomenon. Ostwald ripening refers to the dissolution of smaller crystals or particles in the solute and the re-deposition onto larger crystals or particles. The invention artificially provides the second quantum dots with small size and the first quantum dots with large size in the solution, when certain conditions are met, the second quantum dots with small size in the solution are dissolved and deposited on the first quantum dots with large size, which is equivalent to coating the first quantum dots with the upper shell layer.

The fatty amine in the reaction system can effectively dissolve the small-sized second quantum dots and etch the large-sized first quantum dots, thereby being beneficial to accelerating the intra-particle curing and the inter-particle curing. In addition, the aliphatic amine can also be used as a ligand for stabilizing the quantum dots, and is beneficial to improving the fluorescence quantum yield of the core-shell quantum dots.

The ligand in the reaction system mainly plays a role in stabilizing the quantum dots, and the addition of the ligand is favorable for improving the fluorescence quantum yield of the core-shell quantum dots.

The first quantum dot is used as a quantum dot of a shell layer to be coated, and can be a core quantum dot or a core-shell quantum dot. When the first quantum dot is a core quantum dot, it may be a single-component quantum dot, or an alloy quantum dot. When the first quantum dot is a core-shell quantum dot, the shell layer may be one layer or multiple layers. The first quantum dot may be one kind of quantum dot, and may also include a plurality of kinds of quantum dots.

The second quantum dot is used as a quantum dot for providing a shell layer growth material, and can be a core quantum dot or a core-shell quantum dot. When the second quantum dot is a core quantum dot, it may be a single-component quantum dot, or an alloy quantum dot. When the second quantum dot is a core-shell quantum dot, the shell layer can be a layer or a plurality of layers, in addition, in a reaction system, the shell layer outside the second quantum dot is firstly dissolved, the dissolved shell layer material is firstly coated outside the first quantum dot, the core in the second quantum dot is finally dissolved, and the dissolved core material is finally coated outside the first quantum dot. The second quantum dot may be one kind of quantum dot, and may also include a plurality of kinds of quantum dots. It is worth mentioning that the single-component quantum dot as referred to herein refers to a quantum dot including one kind of cation and one kind of anion.

The first quantum dot and the second quantum dot may be the same or different, and when the first quantum dot and the second quantum dot are the same, the growth of a homogeneous structure is equivalent.

The preparation method of the core-shell quantum dot is suitable for synthesizing various different core-shell quantum dots. In one embodiment, the first quantum dot is CdSe and the second quantum dot is CdS, and the CdSe/CdS core-shell quantum dot can be prepared by adopting the core-shell quantum dot preparation method. In another embodiment, the first quantum dot is CdSe, the second quantum dot is ZnSe, and the CdSe/ZnSe core-shell quantum dot can be prepared by adopting the preparation method of the core-shell quantum dot. In another embodiment, the first quantum dot is InP, the second quantum dot is ZnSe, and the InP/ZnSe core-shell quantum dot can be prepared by the above preparation method of the core-shell quantum dot. In another embodiment, the first quantum dot is ZnSe, the second quantum dot is ZnS, and the ZnSe/ZnS core-shell quantum dot can be prepared by the above preparation method of the core-shell quantum dot. The above first quantum dots and the second quantum dots are not exhaustive.

In some embodiments, the ligand is a trialkylphosphine, which is useful as a ligand to improve the fluorescence quantum yield of the core-shell quantum dot. The trialkylphosphine may be selected from one or more of the following: tributyl phosphine, trioctyl phosphine.

In some embodiments, the volume fraction of the fatty amine in the first solution is between 25% and 100%. The first solution may be entirely a fatty amine, or the first solution may include a fatty amine and a non-coordinating solvent (e.g., octadecene). Preferably, the fatty amine is a saturated or unsaturated primary amine with a carbon chain length of 8 to 22.

In some embodiments, the difference between the particle size of the first quantum dot and the particle size of the second quantum dot is no less than 2nm. Among them, the particle size range of the first quantum dot is preferably 3nm to 10nm, and the particle size range of the second quantum dot is preferably 1nm to 5nm.

After the first quantum dots and the second quantum dots are synthesized and purified respectively, the first quantum dots and the second quantum dots can be mixed and dispersed in a solvent according to a certain proportion, and can also be respectively dispersed in the solvent, and materials are taken according to a certain proportion when the organic light-emitting diode is used. The fluorescence peak position and the shell thickness of the final core-shell quantum dot can be controlled by adjusting the proportion of the first quantum dot to the second quantum dot in the reaction system.

In some embodiments, the first quantum dot and the second quantum dot are respectively dispersed in a solvent before being mixed with the first solution, so as to obtain a first quantum dot solution and a second quantum dot solution, and the solvents of the first quantum dot solution and the second quantum dot solution are the same or different. In the subsequent step, the first quantum dot solution, the second quantum dot solution, the ligand and the first solution are mixed to form a reaction system, and preferably, the initial concentration of the first quantum dots in the reaction system is greater than the initial concentration of the second quantum dots.

In other embodiments, the first quantum dot and the second quantum dot are mixed and dispersed in a solvent to form a quantum dot mixed solution before mixing with the first solution, and the first quantum dot and the second quantum dot may relatively stably coexist in the quantum dot mixed solution. Preferably, the concentration of the first quantum dots in the quantum dot mixed solution is greater than

A concentration of the second quantum dots. In these embodiments, the ligand may be added to the quantum dot mixed solution to form a second solution, and then the second solution is mixed with the first solution to form the reaction system, or the ligand and the quantum dot mixed solution may be sequentially added to the first solution to form the reaction system.

The method is characterized in that a size distribution focusing phenomenon exists in the growth process of the quantum dots, the size distribution of the quantum dots is firstly reduced to a certain degree in the reaction process, ostwald ripening occurs along with the reaction time, the size distribution becomes discrete, namely, a critical size exists in the growth process of the quantum dots, when the size of the quantum dots is smaller than the critical size, the growth of small-size quantum dots is fast, the growth of large-size quantum dots is slow, the size distribution is gradually reduced, after the size of the quantum dots is larger than the critical size, the particles start to ripen, the process is related to the concentration of a reaction precursor, when the size of the quantum dots starts to ripen, the reaction precursor is added, and the size distribution focusing phenomenon can occur again. In addition, a size self-focusing phenomenon exists in the quantum dot growth process, under the condition that the concentration of the quantum dots is high, the small-size quantum dots are dissolved to generate monomers, so that the large-size quantum dots grow, when the concentration of the quantum dots is reduced to a certain degree, a classical Ostwald curing phenomenon occurs, and the size distribution of the quantum dots begins to widen.

Based on the above analysis, in the reaction system, at the beginning of the reaction, the second quantum dots are not completely dissolved, the size difference between the two kinds of quantum dots in the solution gradually increases as the reaction proceeds, the size distribution of the quantum dots is large, most of the second quantum dots are dissolved as the reaction continues, at this time, the size distribution of the quantum dots in the solution is small, and if the reaction continues, the core-shell quantum dots in the solution are easily cured, the size distribution of the quantum dots becomes wide again, and further the fluorescence quantum yield of the core-shell quantum dots is reduced, and the half-peak width becomes large, so that the reaction time needs to be controlled within a reasonable range. Preferably, the temperature of the reaction system is kept between 200 ℃ and 310 ℃, and the reaction is carried out for 5min to 30min, so as to prepare the core-shell quantum dot.

In some embodiments, the method for preparing the core-shell quantum dot of the present invention further comprises the following steps:

mixing fatty amine with a solvent, and keeping the temperature at 200-310 ℃ to obtain a first solution;

respectively synthesizing a first quantum dot and a second quantum dot, mixing and dispersing the first quantum dot and the second quantum dot in a solvent to form a quantum dot mixed solution, then adding a ligand into the quantum dot mixed solution, and keeping the temperature at 200-310 ℃ to obtain a second solution;

and mixing the first solution and the second solution to form a reaction system, keeping the temperature at 200-310 ℃, reacting for 5-30 min, and obtaining the core-shell quantum dots in the solution after the reaction.

In another aspect of the present application, there is provided a quantum dot optoelectronic device including the core-shell quantum dot prepared by the foregoing method. The photoelectric device can be a quantum dot light conversion film, a quantum dot color film and a device used by combining the quantum dot color film with an LED, a quantum dot light-emitting diode and the like. According to the invention, the material for growing the shell layer firstly forms the second quantum dot with smaller size, then the second quantum dot with smaller size and the first quantum dot with larger size are mixed in the solution, under a certain condition, the second quantum dot is dissolved in the solution, the dissolved product can grow outside the first quantum dot to form the shell layer, and the prepared core-shell quantum dot has good monodispersity and narrow fluorescence half-peak width. Therefore, the photoelectric device of the core-shell quantum dot prepared by the preparation method has higher luminous efficiency.

Preparing a reaction precursor:

preparation of 0.1mmol/mL selenium powder suspension: selenium powder (0.0237g, 0.3mmol) was dispersed in 3mL ODE and sonicated for 5min to make a suspension of 0.1 mmol/mL. The preparation of the selenium powder suspension with other concentrations is similar to that of the suspension, and the amount of the selenium powder is only required to be changed. Shaking before application.

Preparation of 0.1mmol/mL S-ODE solution: sulfur powder (0.032g, 1mmol) was dispersed in 10mL of ODE and dissolved by ultrasonic agitation. The preparation of S-ODE solutions with other concentrations is similar to that of the S-ODE solution, and only the amount of the sulfur powder needs to be changed.

[ example 1 ]

Synthesizing a first quantum dot (CdSe quantum dot with an average particle size of 6 nm): placing CdO (0.1280g and 1mmol), myristic acid (0.5g and 2.2mmol) and ODE (4 mL) into a 25mL three-necked bottle, stirring and ventilating for 10 minutes, heating to 280 ℃ to obtain a clear solution, and controlling the temperature to be 250 ℃; 1mL of selenium powder suspension with the concentration of 0.05mmol/mL is quickly injected into a three-necked bottle, the reaction temperature is controlled at 250 ℃, after the reaction is carried out for 10 minutes, 0.1mL of selenium powder suspension with the concentration of 0.1mmol/mL is added at the speed of 0.9mL/h, after the dripping of the selenium powder suspension is finished, the reaction is continued for 5 minutes, then 1.5mmol of oleic acid is added at the speed of 12mL/h, after the reaction is carried out for 5 minutes, 0.1mL of selenium powder suspension with the concentration of 0.1mmol/mL is added at the speed of 0.9mL/h, then the reaction is carried out for 10 minutes, 0.1mL of the selenium powder suspension is added again, the steps are sequentially circulated until quantum dots with the target size are obtained, and the quantum dots are dissolved in a small amount of purified ODE to form a first quantum dot solution.

Synthesizing a second quantum dot (CdS quantum dot with the average particle size of 3 nm): placing CdO (0.0256g, 0.2mmol), oleic acid (0.282g, 1mmol) and ODE (4 mL) into a 25mL three-necked bottle, stirring and ventilating for 10 minutes, heating to 280 ℃ to obtain a clear solution, controlling the temperature at 250 ℃, quickly injecting 1mL of S-ODE solution with the concentration of 0.1mmol/mL into the three-necked bottle, controlling the reaction temperature at 250 ℃, reacting for 15 minutes, stopping the reaction, purifying, and dissolving in a small amount of ODE to form a second quantum dot solution.

Synthesizing CdSe/CdS core-shell quantum dots:

(1) Mixing the first quantum dot solution with one fourth of the second quantum dot solution to obtain a quantum dot mixed solution;

(2) 3mL of ODE and 2mL of oleylamine were mixed in a 25mL three-necked flask, and after stirring and aeration for 10 minutes, the temperature was raised to 250 ℃ and 0.1mL of Tributylphosphine (TBP) was injected, and then the quantum dot mixed solution of step (1) was rapidly injected, reacted for 20min, and the reaction was stopped.

[ example 2 ] A method for producing a polycarbonate

Synthesis of InP quantum dots as first quantum dots: 0.15mmol (0.043 g) of indium acetate, 0.45mmol (0.1036 g) of tetradecanoic acid and 10mL of ODE were weighed into a 50mL three-necked flask, heated to 180 ℃ and evacuated for 30 minutes, then cooled to room temperature, and 0.1mmol (TMS) was injected ₃ A mixed solution of P and 1mL of TOP was then raised to 260 ℃ for 5 minutes, purified and dissolved in 1mL of ODE.

Synthesizing small-size ZnSe quantum dots: weighing 0.1mmol zinc stearate, 5mLODE and a 25mL three-neck flask, raising the temperature to 280 ℃, injecting 1mL0.05mmol/mLSe-ODE suspension, reacting for 5min, stopping the reaction, purifying, and dissolving in 1mL ODE.

And (3) synthesis of InP/ZnSe core-shell quantum dots:

[ example 3 ]

A first quantum dot: cdSe/CdSnS core-shell quantum dots with red light emission wavelength of 620nm, which are produced by Nyquist science and technology Limited.

Synthesizing small-size ZnS quantum dots: weighing 0.1mmol of zinc stearate, 5mL of ODE and a 25mL three-neck flask, raising the temperature to 280 ℃, injecting 1mL of 0.05mmol/mL S-ODE solution, reacting for 5min, stopping the reaction, purifying, and dissolving in 1mL of ODE.

Synthesizing CdSe/CdSnS/ZnS core-shell quantum dots:

[ example 4 ] A method for producing a polycarbonate

The differences from example 1 are: step (2) 5mL of oleylamine was placed in a 25mL three-necked flask without mixing with ODE.

[ example 5 ]

The differences from example 1 are: in step (2), 3mL of ODE and 2mL of octamine were mixed in a 25mL three-necked flask.

[ example 6 ] A method for producing a polycarbonate

The differences from example 1 are: and (3) quickly injecting the quantum dot mixed solution in the step (1) in the step (2), reacting for 5min, and stopping the reaction.

[ example 7 ]

The differences from example 1 are: and (3) quickly injecting the quantum dot mixed solution obtained in the step (1) in the step (2), reacting for 30min, and stopping the reaction.

Comparative example 1

CdSe quantum dots with average particle size of 3 nm: placing CdO (0.0256g, 0.1mmol), stearic acid (0.142g, 0.5mmol) and ODE (4 mL) into a 25mL three-necked bottle, stirring and ventilating for 10 minutes, heating to 280 ℃ to obtain a clear solution, and controlling the temperature at 250 ℃; and (2) quickly injecting 1mL of selenium powder suspension with the concentration of 0.1mmol/mL into a three-necked bottle, controlling the reaction temperature at 250 ℃, after reacting for 10 minutes, injecting 0.1mL of selenium powder suspension with the concentration of 0.1mmol/mL every 5 minutes until quantum dots with the target size are obtained, purifying and dissolving in a small amount of ODE.

Synthesizing CdSe/CdS core-shell quantum dots: cdO (0.064g, 0.5 mmol), oleic acid (1.5 mmol) and ODE (4 mL) were placed in a 25mL three-necked flask, and after stirring and aeration for 10 minutes, the temperature was raised to 280 ℃ to obtain a clear solution, and the temperature was controlled at 250 ℃. Then, one quarter of CdSe core was injected, and 0.1mL S-ODE solution with concentration of 0.1mmol/mL was added at a rate of 0.9mL/h every 10 minutes until quantum dots of the target size (PL at 620 nm) were obtained, and the reaction was stopped.

Fluorescence emission spectra were used to test the fluorescence emission peak, half-peak width and quantum efficiency of the core-shell quantum dots of the above examples and comparative examples. The quantum efficiency of the core-shell quantum dots of the embodiments and the comparative examples is tested, and the detection method of the quantum efficiency is as follows: the method comprises the steps of using a 450nm blue LED lamp as a light source, using an integrating sphere to respectively test a spectrum of the blue light source and a spectrum after the blue light source penetrates through a quantum dot solution, and using an integral area of a spectrogram to calculate the luminous efficiency of the quantum dot, wherein the quantum efficiency is = (the emission peak area of the quantum dot)/(the peak area of the blue light source-the area of the blue peak which is not absorbed after the blue light source penetrates through the quantum dot solution) × 100%. The test results are shown in Table 1.

TABLE 1

	Fluorescence emission peak/nm	Half width/nm	Quantum efficiency/%)
				Example 1	650	21	95
Example 2	545	42	57
				Example 3	625	23	95
Example 4	651	22	96
				Example 5	651	23	92
Example 6	645	21	95
				Example 7	653	23	93
Comparative example 1	620	28	91

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.

Claims

1. A preparation method of the core-shell quantum dot is characterized by comprising the following steps:

providing a first solution comprising an aliphatic amine, first quantum dots, second quantum dots, and a ligand, wherein the average particle size of the second quantum dots is smaller than the average particle size of the first quantum dots; the concentration of the first quantum dots is greater than that of the second quantum dots;

2. The method for preparing the core-shell quantum dot according to claim 1, wherein the first quantum dot is a core quantum dot or a core-shell quantum dot, and the second quantum dot is a core quantum dot or a core-shell quantum dot.

3. The preparation method of the core-shell quantum dot according to claim 1, wherein the ligand is trialkylphosphine.

4. The preparation method of the core-shell quantum dot according to claim 3, wherein the trialkylphosphine is selected from one or more of the following: tributyl phosphine, trioctyl phosphine.

5. The preparation method of the core-shell quantum dot according to claim 1, wherein the volume fraction of the fatty amine in the first solution is 25% to 100%.

6. The preparation method of the core-shell quantum dot according to claim 1, wherein the aliphatic amine is a saturated or unsaturated primary amine with a carbon chain length of 8 to 22.

7. The method for preparing the core-shell quantum dot according to claim 1, wherein the difference between the particle size of the first quantum dot and the particle size of the second quantum dot is not less than 2nm.

8. The preparation method of the core-shell quantum dot according to claim 7, wherein the particle size of the first quantum dot is from 3nm to 10nm, and the particle size of the second quantum dot is from 1nm to 5nm.

9. The preparation method of the core-shell quantum dot according to claim 1, wherein in the reaction system, the initial concentration of the first quantum dot is greater than the initial concentration of the second quantum dot.

10. The method for preparing core-shell quantum dots according to claim 1, wherein the first quantum dots and the second quantum dots are mixed and dispersed in a solvent to form a quantum dot mixed solution before mixing with the first solution, wherein the concentration of the first quantum dots in the quantum dot mixed solution is greater than that of the second quantum dots, and the quantum dot mixed solution, the ligand and the first solution are mixed to form the reaction system.

11. The preparation method of the core-shell quantum dot according to any one of claims 1 to 8, wherein the temperature of the reaction system is kept at 200 ℃ to 310 ℃ and the reaction is carried out for 5min to 30min.

12. A quantum dot optoelectronic device comprising a quantum dot prepared by the core-shell quantum dot preparation method according to any one of claims 1 to 11.