CN112824477A - Preparation method and application of core-shell quantum dots - Google Patents

Preparation method and application of core-shell quantum dots Download PDF

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CN112824477A
CN112824477A CN201911147617.5A CN201911147617A CN112824477A CN 112824477 A CN112824477 A CN 112824477A CN 201911147617 A CN201911147617 A CN 201911147617A CN 112824477 A CN112824477 A CN 112824477A
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胡保忠
毛雁宏
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Najing Technology Corp Ltd
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Abstract

The invention relates to a preparation method and application of a core-shell quantum dot, which comprises the following steps: (1) providing a solution containing quantum dots, wherein the solution containing the quantum dots is a raw material for preparing the core-shell quantum dots; (2) mixing raw materials for preparing the core-shell quantum dots with short-chain fatty acid zinc with the carbon chain length of less than or equal to 8 and long-chain fatty acid with the carbon chain length of more than or equal to 12, and reacting at a first temperature to obtain an intermediate solution; (3) mixing the intermediate solution with a precursor containing Se element, and reacting at a second temperature to coat a ZnSe shell layer on the surface of the quantum dot to obtain a solution containing a core-shell quantum dot intermediate; (4) and (3) taking the solution containing the core-shell quantum dot intermediate as a raw material for preparing the core-shell quantum dot in the step (1), and repeating the steps (2) and (3) at least once to coat to obtain the core-shell quantum dot. The quantum yield of the core-shell quantum dot is kept above 95% along with the increase of the thickness of the ZnSe shell layer, so that the external quantum efficiency and the service life of a photoelectric device applying the core-shell quantum dot can be improved.

Description

Preparation method and application of core-shell quantum dots
Technical Field
The invention relates to the technical field of quantum dots, in particular to a preparation method and application of core-shell quantum dots.
Background
At present, the outer layers of blue light quantum dots such as CdZnS/ZnS, CdZnSeS/ZnS, ZnCdSe/ZnS and the like are all coated with thicker ZnS shell layers, so that the HOMO of the blue light quantum dots is deeper, the effective injection of holes is not facilitated, the service life of a photoelectric device is shorter, and the lowest commercialized requirement cannot be met.
In the aspect of quantum dot synthesis, because of the more appropriate positions of a conduction band and a valence band of ZnSe and the more matched unit cell parameters, ZnSe is usually taken as a shell layer to coat quantum dots such as CdSe, CdZnSe and InP. Researches show that a ZnSe shell layer with the thickness of about 7nm is coated outside ZnCdSe, so that HOMO of a blue light quantum dot can be effectively improved, the energy level difference between the HOMO and a hole transport layer TFB material is shortened, and the photoelectric device is enabled to be 100cd/m2Reaches a level of 7000h under the lighting condition of (1). However, when the ZnSe shell is prepared by the existing heating method, one-pot method or dropwise coating method, etc., ZnO and ZnSeO will be formed when the ZnSe shell has a large thickness, for example, more than 3nm3And oxidizing the product to cause lattice dislocation of the ZnSe shell layer in the growth process, thereby generating defect sites. The defect sites can capture excitons to generate non-radiative transition, so that the quantum yield of the blue light quantum dots is reduced sharply, only about 73 percent and far lower than the level that the green light quantum dots and the red light quantum dots are close to 100 percent, and the external quantum efficiency of a photoelectric device applying the blue light quantum dots is only about 8 percent and far lower than 20 percent of the external quantum efficiency of the photoelectric device applying the green light quantum dots and the red light quantum dots.
Disclosure of Invention
In view of the above, it is necessary to provide a preparation method and application of core-shell quantum dots; the quantum yield of the core-shell quantum dot obtained by the preparation method is always kept above 95% along with the improvement of the thickness of the ZnSe shell layer, so that the external quantum efficiency of a photoelectric device applying the core-shell quantum dot can be improved, and the service life of the photoelectric device can be prolonged.
In a first aspect of the present invention, a method for preparing a core-shell quantum dot is provided, which comprises the steps of:
(1) providing a solution containing quantum dots, wherein the solution containing quantum dots is a raw material for preparing core-shell quantum dots;
(2) mixing the raw materials for preparing the core-shell quantum dots with short-chain fatty acid zinc with the carbon chain length of less than or equal to 8 and long-chain fatty acid with the carbon chain length of more than or equal to 12, and reacting at a first temperature to obtain an intermediate solution;
(3) mixing the intermediate solution with a precursor containing Se element, and reacting at a second temperature to coat a ZnSe shell layer on the surface of the quantum dot to obtain a solution containing a core-shell quantum dot intermediate;
(4) and (3) taking the solution containing the core-shell quantum dot intermediate as a raw material for preparing the core-shell quantum dot in the step (1), and repeating the steps (2) and (3) at least once to coat the solution to obtain the core-shell quantum dot.
Furthermore, the thickness of the ZnSe shell layer obtained by single coating in the step (3) is less than or equal to 1.5nm, preferably 0.5nm to 1.5 nm.
Furthermore, the total thickness of the ZnSe shell layer of the core-shell quantum dot is 1nm to 10 nm.
Furthermore, the total thickness of the ZnSe shell layers is 3nm to 10 nm.
Further, the molar ratio of the long-chain fatty acid to the short-chain fatty acid zinc is 2:1 or more, preferably 2:1 to 4: 1.
Further, the first temperature is 100 to 240 ℃ and the second temperature is 280 to 310 ℃.
Furthermore, the adding molar ratio of the Se element to the Zn element is 1: 2-2: 1, and the molar concentration of the Se element in the precursor containing the Se element is 0.5 mmol/mL-4 mmol/mL.
Furthermore, the solution containing the quantum dots is a product system containing the quantum dots, which is synthesized by a solution method.
Further, the quantum dots include at least one of CdZnSeS, CdSe, CdZnSe, ZnSe, CdSeS, InP, and InZnP.
In a second aspect of the present invention, there is provided a quantum dot composition, including the core-shell quantum dot prepared by the above preparation method.
In a third aspect of the present invention, an optoelectronic device is provided, which includes the core-shell quantum dot prepared by the above preparation method.
In the preparation method, the first ZnSe shell layer and the ZnSe shell layer are obtained by coating at least twice, and the coating thickness is not more than 1.5nm each time, so that excessive accumulation of long-chain fatty acid zinc is avoided, and the generation of ZnO or ZnSeO by decomposition of the long-chain fatty acid zinc under the high-temperature reaction condition is reduced3The probability of oxidation products is equal, the internal defects of the core-shell quantum dots are reduced to the maximum extent, and the ZnSe shell of the core-shell quantum dots slowly grows and maintains higher quantum yield; secondly, because the ZnSe shell layer is obtained by coating for many times, short-chain fatty acid zinc and long-chain fatty acid are supplemented in situ each time of coating, the short-chain fatty acid zinc supplemented each time cannot be excessive, and when the long-chain fatty acid supplemented each time replaces the short-chain fatty acid radical in the short-chain fatty acid zinc, the short-chain fatty acid radical can form formic acid, acetic acid, propionic acid, butyric acid and other small molecular acids which can decompose and etch oxidation products on the surface of the core-shell quantum dot, so that the internal defects of the core-shell quantum dot are further decomposed and eliminated, and the quantum yield of the core-shell quantum dot is improved; thirdly, only short-chain fatty acid zinc and long-chain fatty acid are required to be supplemented in situ for each coating, and after the coating is carried out for one shell layer, the purification of the core-shell quantum dot raw material and the core-shell quantum dot intermediate is not required, so that Se on the surfaces of the core-shell quantum dot raw material and the core-shell quantum dot intermediate is not easily oxidized, and the internal quality of the core-shell quantum dot is ensured. Therefore, the quantum yield of the core-shell quantum dot obtained by the preparation method disclosed by the invention is always kept above 95% along with the increase of the thickness of the ZnSe shell layer, and further the external quantum efficiency and the service life of a photoelectric device applying the core-shell quantum dot can be improved.
Drawings
FIG. 1 is an electron micrograph of a core-shell quantum dot obtained in example 2;
FIG. 2 is an electron micrograph of the core-shell quantum dot obtained in example 4;
FIG. 3 is an electron micrograph of the core-shell quantum dot obtained in example 7.
Detailed Description
The preparation method and the application of the core-shell quantum dot provided by the invention are further explained below.
The preparation method is mainly used for preparing the blue light quantum dots with the core-shell structure, so that the quantum yield of the blue light quantum dots is always kept above 95% along with the improvement of the thickness of the ZnSe shell layer, the external quantum efficiency and the service life of a photoelectric device applying the blue light quantum dots are further improved, and the requirements of commercial application are further met.
In the preparation method of the blue light quantum dot with ZnSe as the shell layer, the applicant finds that ZnO and ZnSeO3The iso-oxidation products are mainly formed in two stages: firstly, after the quantum dots serving as raw materials are purified, the exposed quantum dots can be slowly oxidized by air to generate oxidation products; secondly, the reaction system usually reacts at a high temperature of about 300 ℃, and the excessive zinc fatty acid precursor is decomposed to generate an oxidation product after the reaction time is too long.
In order to avoid the generation of oxidation products in the two stages, the preparation method of the core-shell quantum dot provided by the invention comprises the following steps:
(1) providing a solution containing quantum dots, wherein the solution containing quantum dots is a raw material for preparing core-shell quantum dots;
(2) mixing the raw materials for preparing the core-shell quantum dots with short-chain fatty acid zinc with the carbon chain length of less than or equal to 8 and long-chain fatty acid with the carbon chain length of more than or equal to 12, and reacting at a first temperature to obtain an intermediate solution;
(3) mixing the intermediate solution with a precursor containing Se element, and reacting at a second temperature to coat a ZnSe shell layer on the surface of the quantum dot to obtain a solution containing a core-shell quantum dot intermediate;
(4) and (3) taking the solution containing the core-shell quantum dot intermediate as a raw material for preparing the core-shell quantum dot in the step (1), and repeating the steps (2) and (3) at least once to coat to obtain the core-shell quantum dot.
In the step (1), the solution containing quantum dots is a product system containing quantum dots synthesized by a solution method, and the specific method of the solution method is not limited and mainly comprises at least one of a CdZnSeS product system, a CdZnSe product system, a ZnSe product system and a CdSeS product system. The product system containing the quantum dots synthesized by the solution method is directly used as a raw material for preparing the core-shell quantum dots, so that the purification of the quantum dots as the core raw material can be avoided, the operation is simplified, the production efficiency is improved, the slow oxidation of the naked quantum dot core raw material by air can be avoided, and the internal defects of the core-shell quantum dots are reduced.
In the step (2), short-chain fatty acid zinc and long-chain fatty acid are mixed, and in the process of reacting at the first temperature, the long-chain fatty acid can react with the short-chain fatty acid zinc, specifically, the long-chain fatty acid replaces a short-chain fatty acid radical in the short-chain fatty acid zinc to form the long-chain fatty acid zinc. Wherein, the long-chain fatty acid zinc exists in the intermediate solution as a precursor of Zn element in a ZnSe shell layer, and the displaced short-chain fatty acid radical can form short-chain fatty acids such as formic acid, acetic acid, propionic acid, butyric acid and the like, and is used for decomposing oxidation products on the surfaces of the quantum dots.
In some embodiments, the short chain fatty acid zinc includes at least one of zinc formate, zinc acetate, zinc propionate, zinc butyrate, and the like, preferably at least one of zinc formate, zinc acetate, zinc propionate. The long chain fatty acid includes at least one of oleic acid, stearic acid, isostearic acid, etc.
Considering that zinc ions are divalent ions and each short-chain fatty acid zinc contains two short-chain fatty acid radicals, in order to sufficiently replace the short-chain fatty acid zinc with the long-chain fatty acid zinc, the molar ratio of the long-chain fatty acid to the short-chain fatty acid zinc is greater than or equal to 2:1, and is preferably 2: 1-4: 1.
In addition, in order to sufficiently replace the long-chain fatty acid with the long-chain fatty acid zinc, the first temperature needs to be higher than the boiling point of the short-chain fatty acid, and therefore, in some embodiments, the first temperature is preferably 100 to 240 ℃, and is specifically adjusted according to the boiling point of the short-chain fatty acid.
In the step (3), when reacting at the second temperature, the long-chain fatty acid zinc existing in the intermediate solution reacts with the precursor containing the Se element, and a ZnSe shell layer grows and forms on the surface of the quantum dot.
It can be understood that when the ZnSe shell layer is repeatedly grown, the ZnSe shell layer is continuously grown on the surface of the core-shell quantum dot intermediate, and the quantum dot at the moment refers to the core-shell quantum dot intermediate.
In order to ensure the internal quality of the core-shell quantum dot and reduce or avoid the oxidation product remaining in the core-shell quantum dot, the thickness of the single-growth ZnSe shell layer is less than or equal to 1.5nm, and considering the processing efficiency, the thickness is more preferably 0.5nm to 1.5 nm.
In some embodiments, the Se-containing precursor includes at least one of Se-TOP (selenium-trioctylphosphine), Se-TBP (selenium-tributylphosphine), and Se-DPP (selenium-diphenylphosphine).
In order to enable the Se element in the precursor to fully react with the Zn element in the long-chain fatty acid zinc to form a ZnSe shell layer with the thickness of less than or equal to 1.5nm, the molar concentration of the Se element in the precursor containing the Se element is 0.5-4 mmol/mL, and the molar ratio of the added Se element to the added Zn element is preferably 1: 2-2: 1. In order to further avoid decomposition of the long-chain fatty acid zinc to generate an oxidation product due to an excessive amount and to improve the internal mass of the core-shell quantum dot, the molar ratio of the Se element to the Zn element is more preferably 1: 1.
It is understood that the long-chain fatty acid can completely replace the short-chain fatty acid zinc with the long-chain fatty acid zinc, and therefore, the amount of Zn element added can be controlled by the amount of the short-chain fatty acid zinc added in accordance with the molar ratio range. And in the solution of the quantum dots serving as the raw material for preparing the core-shell quantum dots, the molar quantity of the quantum dots is calculated according to the factors such as the shape and the size of the quantum dots, the specific thickness of the ZnSe shell layer to be coated and the like.
In order to fully react the long-chain fatty acid zinc and the precursor containing the Se element to generate the ZnSe shell layer, in some embodiments, the second temperature is 280-310 ℃, and the heating time is 20-60 minutes, which is specifically adjusted according to the activity of the precursor containing the Se element.
In the step (4), the obtained solution containing the core-shell quantum dot intermediate is directly used as a raw material for preparing the core-shell quantum dot in the step (1), and the steps (2) and (3) are repeated to further grow the ZnSe shell layer, so that the total thickness of the ZnSe shell layer is increased, the solution containing the core-shell quantum dot intermediate does not need to be purified, the surface of the naked core-shell quantum dot intermediate can be prevented from being slowly oxidized by air, the complicated purification step can be avoided, and the operation is simple.
Meanwhile, the ZnSe shell layer is obtained in a mode of coating for many times by repeating the step (2) and the step (3), so that the using amount of short-chain fatty acid zinc during single coating can be reduced, the short-chain fatty acid zinc is not excessive, the excessive accumulation of the long-chain fatty acid zinc can be effectively avoided, the probability of generating oxidation products by decomposing the long-chain fatty acid zinc at high temperature is reduced, the internal defects of the core-shell quantum dots are reduced to the maximum extent, and the ZnSe shell layer of the core-shell quantum dots can slowly grow and maintain higher quantum yield. And when short-chain fatty acid zinc and long-chain fatty acid are supplemented in situ each time, small molecular acid such as formic acid, acetic acid, propionic acid, butyric acid and the like is generated, and ZnO or ZnSeO can be continuously decomposed and etched3And oxidizing the product, thereby further decomposing and eliminating the internal defects of the core-shell quantum dots and improving the quantum yield of the core-shell quantum dots.
It can be understood that the step (2) and the step (3) can be repeated once or for multiple times to obtain the core-shell quantum dot with the total thickness of the ZnSe shell layer being 1 nm-10 nm. The total thickness of the ZnSe shell layer is preferably 3nm to 10nm in consideration of the effect of the core-shell quantum dot when applied to a photoelectric device.
In some embodiments, when the total thickness X of the ZnSe shell layers of the core-shell quantum dot is less than or equal to 1.5nm, the thickness Y of the ZnSe shell layer coated each time in the step (3) is less than X, so that the core-shell quantum dot is obtained by at least two times of coating. When the total thickness X of the ZnSe shell layers of the core-shell quantum dots is more than 1.5nm, the thickness Y of the ZnSe shell layers coated each time in the step (3) is less than or equal to 1.5nm, preferably 0.5nm to 1.5nm, so that the core-shell quantum dots are obtained by at least two times of coating.
It can be understood that the thickness Y of the ZnSe shell obtained by coating can be the same or different in each coating.
For example, the core-shell quantum dot is obtained by two times of coating, the total thickness of the shell layers of the core-shell quantum dot is X, and when the thickness of the ZnSe shell layer obtained by the first coating and the thickness of the ZnSe shell layer obtained by the second coating are Y1When X is 2Y1(ii) a When it comes toThe thickness of the ZnSe shell layer obtained by primary coating is Y1The thickness of the ZnSe shell obtained by the second coating is Y2When X is equal to Y1+Y2。
Similarly, the core-shell quantum dot is obtained through five times of coating, the total thickness of the shell layers of the core-shell quantum dot is X, and when the thickness of the ZnSe shell layer obtained through each coating is Y1When X is 5Y1(ii) a When the thicknesses of the ZnSe shell layers obtained by the first and second coating are Y1The thickness of the ZnSe shell obtained by the third and fourth coating is Y2The thickness of the ZnSe shell obtained by the fifth coating is Y3When X is 2Y1+2Y2+Y3(ii) a When the thicknesses of the ZnSe shell layers obtained by each coating are different, the ZnSe shell layers are respectively Y1、Y2、Y3、Y4、Y5When X is equal to Y1+Y2+Y3+Y4+Y5。
Therefore, in the preparation method, the ZnSe shell is prepared by coating for multiple times, the thickness of the ZnSe shell obtained by single coating and the recycling use of the solution are controlled, the purification is not required, and ZnO or ZnSeO in two stages can be effectively avoided3And the generated oxidation products are generated, and the generated oxidation products can be effectively eliminated, so that the internal quality of the core-shell quantum dot can be effectively improved, and the quantum yield of the obtained core-shell quantum dot is always kept above 95% along with the improvement of the thickness of the ZnSe shell layer.
It will be appreciated that in other methods of preparing core-shell quantum dots (non-blue quantum dots), such as CdSe product systems, InP product systems, InZnP product systems, if ZnSe is used as the shell, the at least two-cladding method of the present invention can be used.
The invention also provides a quantum dot composition, which comprises the core-shell quantum dot prepared by the preparation method. The quantum dot composition also comprises quantum dot ink, quantum dot glue and the like.
The invention also provides a photoelectric device which adopts the core-shell quantum dot. 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.
The quantum yield of the core-shell quantum dot is always kept above 95% along with the improvement of the thickness of the ZnSe shell layer, so that the external quantum efficiency and the service life of the quantum dot composition and the photoelectric device can be effectively improved.
Hereinafter, the preparation method and the application of the core-shell quantum dot will be further described by the following specific examples.
Example 1:
0.2mmol of cadmium oleate, 2mmol of zinc oleate and 10g of ODE (octadecene) are weighed in a three-necked bottle, the temperature is raised to 280 ℃ under the protection of nitrogen atmosphere, 1mL of 0.5mmol/mL Se-ODE (selenium-octadecene) is injected, and the temperature is raised to 300 ℃ for reaction for 10 min. Then adding 0.33mL of 3mmol/mL Se-TBP (selenium-tributylphosphine) solution, reacting for 20min at 300 ℃, and cooling to room temperature to obtain 4.0nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, 1mmol of zinc acetate and 3mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 150 ℃. Then, 0.33mL of 3mmol/mL Se-TBP solution is supplemented into the solution, the temperature is raised to 300 ℃ for reaction for 30min, and CdZnSe/ZnSe quantum dot intermediate solution is obtained, wherein the thickness of a ZnSe shell layer is 0.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 1mmol of zinc acetate and 2mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 150 ℃. Then, 0.66mL of 3mmol/mL Se-TBP solution is supplemented into the solution, the temperature is raised to 300 ℃ for reaction for 30min, and the CdZnSe/ZnSe quantum dot is obtained, wherein the total thickness of a ZnSe shell layer is 1.0 nm.
Example 2:
0.2mmol of cadmium oleate, 2mmol of zinc oleate and 10g of ODE (octadecene) are weighed in a three-necked bottle, the temperature is raised to 280 ℃ under the protection of nitrogen atmosphere, 1mL of 0.5mmol/mL Se-ODE (selenium-octadecene) is injected, and the temperature is raised to 300 ℃ for reaction for 10 min. Then adding 0.33mL of 3mmol/mL Se-TBP (selenium-tributylphosphine) solution, reacting for 20min at 300 ℃, and cooling to room temperature to obtain 4.0nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, under the protection of nitrogen, 3mmol of zinc acetate and 7mmol of oleic acid are added through a funnel, and then the temperature is raised to 150 ℃ and nitrogen is introduced for 30 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 30min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer is 1.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 4mmol of zinc acetate and 8mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 150 ℃. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain the CdZnSe/ZnSe quantum dot shown in figure 1, wherein the total thickness of a ZnSe shell layer is 3 nm.
Example 3:
0.18mmol cadmium oleate, 2mmol zinc oleate and 10g ODE are weighed in a three-neck flask, the temperature is raised to 280 ℃ under the protection of nitrogen atmosphere, 1.2mL of 0.5mmol/mL Se-ODE is injected, and the temperature is raised to 300 ℃ for reaction for 20 min. Then adding 0.4mL of 2mmol/mL Se-TBP solution, reacting for 30min at 300 ℃, and cooling to room temperature to obtain a 3.6nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, 4mmol of zinc propionate and 10mmol of myristic acid are added through a funnel under the protection of nitrogen, and then the temperature is raised to 180 ℃ and nitrogen is introduced for 20 min. Then adding 1.0mL of 3mmol/mL Se-TOP solution into the solution, heating to 290 ℃ and reacting for 60min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer is 1.4 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 3mmol of zinc formate and 10mmol of isostearic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 100 ℃. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 310 ℃ and reacting for 20min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 2.6 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 4mmol of zinc octoate and 10mmol of hexadecanoic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 240 ℃. Then 2mL of 2mmol/mL Se-TBP solution is supplemented in the solution, the temperature is raised to 300 ℃, the reaction is carried out for 30min, and CdZnSe/ZnSe quantum dot intermediate solution is obtained, wherein the thickness of a ZnSe shell layer reaches 4 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 3mmol of zinc caproate and 10mmol of stearic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 200 ℃. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 310 ℃, and reacting for 30min to obtain the CdZnSe/ZnSe quantum dot, wherein the total thickness of the ZnSe shell layer is 5 nm.
Example 4:
weighing 0.2mmol of cadmium oleate, 2mmol of zinc oleate and 10g of ODE in a three-mouth bottle, heating to 290 ℃ under the protection of nitrogen atmosphere, then injecting 0.5mmol of Se-ODE, heating to 300 ℃ and reacting for 5 min. Then 1mL of 0.5mmol/mL Se-TBP solution is added, the reaction is carried out for 20min at 300 ℃, and the temperature is reduced to room temperature, thus obtaining the 3.0nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, 4mmol of zinc acetate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then the temperature is raised to 150 ℃ and nitrogen is introduced for 20 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 20min to obtain the CdZnSe/ZnSe quantum dot solution, wherein the thickness of a ZnSe shell layer is 1.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 3mmol of zinc acetate and 6mmol of oleic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 150 ℃. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 3 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 4mmol of zinc acetate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 4.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 3mmol of zinc acetate and 6mmol of oleic acid are added through a funnel, and then the temperature is raised to 180 ℃ and nitrogen is introduced for 30 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 60min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 5.8 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 3mmol of zinc acetate and 6mmol of oleic acid are added through a funnel, and then the temperature is raised to 180 ℃ and nitrogen is introduced for 30 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 30min to obtain the CdZnSe/ZnSe quantum dot shown in figure 2, wherein the total thickness of the ZnSe shell layer is 7 nm.
Example 5:
0.2mmol cadmium oleate, 2mmol zinc oleate and 10g ODE are weighed in a three-neck flask, the temperature is raised to 290 ℃ under the protection of nitrogen atmosphere, 1.0mL of 0.5mmol/mL Se-ODE is injected, and the temperature is raised to 300 ℃ for reaction for 5 min. Then adding 1.0mL of 0.5mmol/mL Se-TBP, reacting for 20min at 300 ℃, and cooling to room temperature to obtain a 3.0nm CdZnSe quantum dot solution.
And (3) adding 3mmol of zinc butyrate and 6mmol of hexadecanoic acid into the CdZnSe quantum dot solution through a funnel under the protection of nitrogen without purification, and then heating to 200 ℃ and introducing nitrogen for 20 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 20min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer is 1.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 3mmol of zinc octoate and 8mmol of stearic acid are added through a funnel, and then the temperature is raised to 240 ℃ and nitrogen is introduced for 30 min. Then adding 1.0mL of 3mmol/mL Se-TOP solution into the solution, heating to 310 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 3 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 4mmol of zinc propionate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 4.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 5mmol of zinc caproate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 200 ℃. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 6 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 6mmol of zinc acetate and 12mmol of oleic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.67mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 60min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 7.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 6mmol of zinc formate and 12mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 120 ℃. Then, 2.0mL of 3mmol/mL Se-TBP solution is supplemented in the solution, the temperature is raised to 300 ℃ for reaction for 60min, and the CdZnSe/ZnSe quantum dot is obtained, wherein the total thickness of the ZnSe shell layer is 9 nm.
Example 6:
0.1mmol of cadmium oleate, 0.2mmol of oleic acid and 10g of ODE are weighed in a three-neck flask, the temperature is raised to 250 ℃ under the protection of nitrogen, then 0.1mL of 0.5mmol/mL Se-ODE and 0.1mL of 0.5mmol/mL S-ODE mixed solution are injected, and the reaction is carried out for 10min at 240 ℃ to obtain the CdSeS quantum dots with the particle size of 3.2 nm.
The CdSeS quantum dot solution is not purified, 4mmol of zinc acetate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 20min after the temperature is raised to 200 ℃. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, and quickly heating to 310 ℃ to react for 60min to obtain CdSeS/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer is 1.5 nm.
The CdSeS/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 3mmol of zinc acetate and 10mmol of oleic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdSeS/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 2.5 nm.
The CdSeS/ZnSe quantum dot intermediate solution is not purified, 4mmol of zinc propionate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdSeS/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 4 nm.
The CdSeS/ZnSe quantum dot intermediate solution is not purified, 5mmol of zinc propionate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 60min to obtain CdSeS/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 5.5 nm.
The CdSeS/ZnSe quantum dot intermediate solution is not purified, 5mmol of zinc propionate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.66mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 20min to obtain the CdSeS/ZnSe quantum dot, wherein the thickness of a ZnSe shell layer is 7 nm.
Example 7:
0.2mmol cadmium oleate, 2mmol zinc oleate and 10g ODE are weighed in a three-neck flask, the temperature is raised to 290 ℃ under the protection of nitrogen atmosphere, 1.0mL of 0.5mmol/mL Se-ODE is injected, and the temperature is raised to 300 ℃ for reaction for 5 min. Then adding 1.0mL of 0.5mmol/mL Se-TBP, reacting for 20min at 300 ℃, and cooling to room temperature to obtain a 3.0nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, under the protection of nitrogen, 3mmol of zinc acetate and 6mmol of oleic acid are added through a funnel, and then the temperature is raised to 150 ℃ and nitrogen is introduced for 20 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 20min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer is 1.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 3mmol of zinc acetate and 8mmol of oleic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 150 ℃. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 3 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 4mmol of zinc propionate and 10mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 4.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 5mmol of zinc acetate and 10mmol of oleic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 150 ℃. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 6 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 6mmol of zinc acetate and 12mmol of oleic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 180 ℃. Then adding 1.67mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 60min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 7.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, 6mmol of zinc formate and 12mmol of oleic acid are added through a funnel under the protection of nitrogen, and then nitrogen is introduced for 30min after the temperature is raised to 120 ℃. Then, 2.0mL of 3mmol/mL Se-TBP solution is supplemented in the solution, the temperature is raised to 300 ℃ for reaction for 60min, and the CdZnSe/ZnSe quantum dot is obtained, wherein the total thickness of the ZnSe shell layer is 9 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 6mmol of zinc acetate and 12mmol of oleic acid are added through a funnel, and then nitrogen is introduced for 30min after the temperature is raised to 150 ℃. Then 2.0mL of 3mmol/mL Se-TBP solution is added into the solution, the temperature is raised to 300 ℃ for reaction for 60min, and the CdZnSe/ZnSe quantum dot shown in figure 3 is obtained, wherein the total thickness of the ZnSe shell layer is 10 nm.
Comparative example 1:
0.2mmol of cadmium oleate, 2mmol of zinc oleate and 10g of ODE are weighed in a three-neck flask, the temperature is raised to 280 ℃ under the protection of nitrogen atmosphere, then 1.0mL of 0.5mmol/mL Se-ODE is injected, and the temperature is raised to 300 ℃ for reaction for 10 min. Then adding 0.33mL of 3mmol/mL Se-TBP, reacting for 20min at 300 ℃, and cooling to room temperature to obtain 4.0nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, under the protection of nitrogen, 8mmol of zinc acetate and 20mmol of oleic acid are added through a funnel, and then the temperature is raised to 150 ℃ and nitrogen is introduced for 30 min. Then, 2.0mL of 3mmol/mL Se-TBP solution is supplemented in the solution, the temperature is raised to 300 ℃ for reaction for 60min, and the CdZnSe/ZnSe quantum dot is obtained, wherein the thickness of a ZnSe shell layer is 3 nm.
Comparative example 2:
0.18mmol cadmium oleate, 2mmol zinc oleate and 10g ODE are weighed in a three-neck flask, the temperature is raised to 280 ℃ under the protection of nitrogen atmosphere, 1.2mL of 0.5mmol/mL Se-ODE is injected, and the temperature is raised to 300 ℃ for reaction for 20 min. Then adding 0.4mL of 2mmol/mL Se-TBP solution, reacting for 30min at 300 ℃, and cooling to room temperature to obtain a 3.6nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, 15mmol of zinc acetate and 30mmol of oleic acid are added through a funnel under the protection of nitrogen, and then the temperature is raised to 180 ℃ and nitrogen is introduced for 20 min. Then adding 4.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 60min to obtain the CdZnSe/ZnSe quantum dot, wherein the thickness of a ZnSe shell layer is 5 nm.
Comparative example 3:
0.18mmol cadmium oleate, 2mmol zinc oleate and 10g ODE are weighed in a three-neck flask, the temperature is raised to 280 ℃ under the protection of nitrogen atmosphere, 1.2mL of 0.5mmol/mL Se-ODE is injected, and the temperature is raised to 300 ℃ for reaction for 20 min. Then adding 0.4mL of 2mmol/mL Se-TBP solution, reacting for 30min at 300 ℃, and cooling to room temperature to obtain a 3.6nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, under the protection of nitrogen, 8mmol of zinc acetate and 20mmol of oleic acid are added through a funnel, and then the temperature is raised to 180 ℃ and nitrogen is introduced for 20 min. Then adding 1.67mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃, and reacting for 60min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer is 2.4 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, under the protection of nitrogen, 8mmol of zinc acetate and 16mmol of oleic acid are added through a funnel, and then the temperature is raised to 180 ℃ and nitrogen is introduced for 20 min. Then, 2.33mL of 3mmol/mL Se-TBP solution is supplemented into the solution, the temperature is raised to 300 ℃, and the reaction is carried out for 60min, so as to obtain the CdZnSe/ZnSe quantum dot, wherein the total thickness of the ZnSe shell layer is 5 nm.
Comparative example 4:
0.2mmol cadmium tetradecanoate, 2mmol zinc stearate and 10g ODE are weighed in a three-neck flask, heated to 290 ℃ under the protection of nitrogen atmosphere, then injected with 1.0mL of 0.5mmol/mL Se-ODE, heated to 300 ℃ and reacted for 5 min. Then adding 1.0mL of 0.5mmol/mL Se-TBP, reacting for 20min at 300 ℃, and cooling to room temperature to obtain a 3.0nm CdZnSe quantum dot solution.
Purifying the CdZnSe quantum dot solution, then dispersing in 12g ODE again, adding 4mmol of zinc acetate and 10mmol of oleic acid through a funnel under the protection of nitrogen, and then heating to 200 ℃ and introducing nitrogen for 20 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 20min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer is 1.5 nm.
Purifying the CdZnSe/ZnSe quantum dot intermediate solution, then re-dispersing in 12g of ODE, adding 3mmol of zinc acetate and 10mmol of oleic acid through a funnel under the protection of nitrogen, and then heating to 180 ℃ and introducing nitrogen for 30 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 3 nm.
Purifying the CdZnSe/ZnSe quantum dot intermediate solution, then dispersing in 15g ODE again, adding 4mmol of zinc propionate and 10mmol of oleic acid through a funnel under the protection of nitrogen, and then heating to 180 ℃ and introducing nitrogen for 30 min. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 4.5 nm.
Purifying the CdZnSe/ZnSe quantum dot intermediate solution, then dispersing in 15g ODE again, adding 5mmol of zinc propionate and 10mmol of oleic acid through a funnel under the protection of nitrogen, and then heating to 180 ℃ and introducing nitrogen for 30 min. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 60min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 6 nm.
Purifying the CdZnSe/ZnSe quantum dot intermediate solution, then dispersing in 20g of ODE again, adding 3mmol of zinc propionate and 6mmol of oleic acid through a funnel under the protection of nitrogen, and then heating to 180 ℃ and introducing nitrogen for 30 min. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 20min to obtain the CdZnSe/ZnSe quantum dot, wherein the total thickness of the ZnSe shell layer is 7 nm.
Comparative example 5:
weighing 0.2mmol of cadmium oleate, 2mmol of zinc oleate and 10g of ODE in a three-mouth bottle, heating to 290 ℃ under the protection of nitrogen atmosphere, then injecting 0.5mmol of Se-ODE, heating to 300 ℃ and reacting for 5 min. Then 1mL of 0.5mmol/mL Se-TBP solution is added, the reaction is carried out for 20min at 300 ℃, and the temperature is reduced to room temperature, thus obtaining the 3.0nm CdZnSe quantum dot solution.
The CdZnSe quantum dot solution is not purified, and 4mmol of zinc oleate and 2mmol of oleic acid are added through a funnel under the protection of nitrogen. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 20min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer is 1.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, and 3mmol of zinc oleate is added through a funnel under the protection of nitrogen. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 3 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, and 4mmol of zinc oleate and 2mmol of oleic acid are added through a funnel under the protection of nitrogen. Then adding 1.33mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 40min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 4.5 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, and 3mmol of zinc oleate is added through a funnel under the protection of nitrogen. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 60min to obtain CdZnSe/ZnSe quantum dot intermediate solution, wherein the thickness of a ZnSe shell layer reaches 5.8 nm.
The CdZnSe/ZnSe quantum dot intermediate solution is not purified, and 3mmol of zinc oleate is added through a funnel under the protection of nitrogen. Then adding 1.0mL of 3mmol/mL Se-TBP solution into the solution, heating to 300 ℃ and reacting for 30min to obtain the CdZnSe/ZnSe quantum dot, wherein the total thickness of the ZnSe shell layer is 7 nm.
The core-shell Quantum dots of the embodiments 1 to 7 and the comparative examples 1 to 5 are made into photoelectric devices, the structure is ITO/PEDOTS, PSS/TFB/Quantum dots/ZnMgO/Al, and the specific preparation method is as follows:
cleaning of ITO glass
And (3) placing the ITO glass sheet with the number marked on the back into a glass dish filled with ethanol solution, and wiping the ITO surface clean by using a cotton swab. Sequentially carrying out ultrasonic treatment on the mixture by acetone, deionized water and ethanol for 10 minutes respectively, and then blowing the mixture by a nitrogen gun. Finally, the cleaned ITO glass sheet is placed in oxygen plasma for continuous cleaning for 10 minutes.
2. Hole injection layer
And respectively spin-coating PEDOTS (Polytetrafluoroethylene) (PSS) on the cleaned ITO glass sheet in the air at the rotating speed of 3000r/min for 45 seconds. And after the spin coating is finished, the glass is placed in the air for annealing at the annealing temperature of 150 ℃ for 30 minutes. After annealing the wafers were quickly transferred to a nitrogen atmosphere glove box.
3. Hole transport layer
And continuously spin-coating the ITO/PEDOTS/PSS sheet with a hole transport layer of 8-10mg/mL TFB at the rotating speed of 2000r/min for 45 seconds. And annealing in a glove box after the spin coating is finished, wherein the annealing temperature is 150 ℃, and the annealing time is 30 minutes.
4. Quantum dot light emitting layer
The optical concentration of the core-shell quantum dot at 350nm is 30-40, and the core-shell quantum dot is dissolved in an octaalkane solvent. And (3) continuing spin-coating the quantum dot solution after annealing the ITO/PEDOTS, PSS/TFB wafer, wherein the spin-coating speed is 2000r/min, and the spin-coating time is 45 seconds. The next layer can be spin coated without annealing after the spin coating is completed.
5. Electron transport layer
Spin coating of MgZnO nanocrystals (30mg/mL, ethanol solution): and spin-coating the sheet of ITO/PEDOTS, PSS/TFB/Quantum dots with MgZnO nanocrystalline solution at the rotating speed of 2000r/min for 45 seconds.
Al electrode
And putting the prepared sample wafer into a vacuum cavity, and evaporating a top electrode. The evaporation rate at the first 10nm is controlled to
Figure BDA0002282646860000201
In the range, the evaporation rate is improved to after 10nm
Figure BDA0002282646860000202
Left and right. The thickness of the aluminum electrode was 100 nm.
Performance tests were performed on photoelectric devices made from the core-shell quantum dots of examples 1 to 7 and comparative examples 1 to 5, and the results are shown in Table 1.
TABLE 1
Figure BDA0002282646860000211
As can be seen from table 1, since the core-shell structured blue light quantum dot is obtained by coating the ZnSe shell layer for multiple times, on one hand, the HOMO of the core-shell structured blue light quantum dot is improved, the energy level difference between the core-shell structured blue light quantum dot and the TFB hole transport layer is reduced, which is more beneficial to the injection of carriers, on the other hand, the size of the blue light quantum dot is increased, the nonradiative auger recombination between the blue light quantum dots is reduced, and the light efficiency of the light emitting layer is increased. Therefore, the photoluminescence efficiency of the blue light quantum dots with the core-shell structure is higher, Qys is close to 100%, the electroluminescent effect is remarkably improved, and especially when the ZnSe thickness is larger than 5nm, the service life of a blue light device is close to 10000 hours and is far higher than the experimental data of a comparative example.
The technical features of the embodiments described above may be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the embodiments described above are not described, but should be considered as being within the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (11)

1. A preparation method of the core-shell quantum dot is characterized by comprising the following steps:
(1) providing a solution containing quantum dots, wherein the solution containing quantum dots is a raw material for preparing core-shell quantum dots;
(2) mixing the raw materials for preparing the core-shell quantum dots with short-chain fatty acid zinc with the carbon chain length of less than or equal to 8 and long-chain fatty acid with the carbon chain length of more than or equal to 12, and reacting at a first temperature to obtain an intermediate solution;
(3) mixing the intermediate solution with a precursor containing Se element, and reacting at a second temperature to coat a ZnSe shell layer on the surface of the quantum dot to obtain a solution containing a core-shell quantum dot intermediate;
(4) and (3) taking the solution containing the core-shell quantum dot intermediate as a raw material for preparing the core-shell quantum dot in the step (1), and repeating the steps (2) and (3) at least once to coat to obtain the core-shell quantum dot.
2. The preparation method of the core-shell quantum dot according to claim 1, wherein the thickness of the ZnSe shell layer obtained by single coating in the step (3) is less than or equal to 1.5nm, preferably 0.5nm to 1.5 nm.
3. The preparation method of the core-shell quantum dot according to claim 1, wherein the total thickness of the ZnSe shell layer of the core-shell quantum dot is 1nm to 10 nm.
4. The preparation method of the core-shell quantum dot according to claim 3, wherein the total thickness of the ZnSe shell layer is 3nm to 10 nm.
5. The preparation method of the core-shell quantum dot according to claim 1, wherein the molar ratio of the long-chain fatty acid to the short-chain fatty acid zinc is greater than or equal to 2:1, preferably 2:1 to 4: 1.
6. The preparation method of the core-shell quantum dot according to claim 1, wherein the first temperature is 100 ℃ to 240 ℃ and the second temperature is 280 ℃ to 310 ℃.
7. The preparation method of the core-shell quantum dot according to claim 1, wherein the molar ratio of the addition amount of the Se element to the addition amount of the Zn element is 1:2 to 2:1, and the molar concentration of the Se element in the Se element-containing precursor is 0.5mmol/mL to 4 mmol/mL.
8. The preparation method of the core-shell quantum dot according to claim 1, wherein the quantum dot-containing solution is a quantum dot-containing product system synthesized by a solution method.
9. The method of claim 1, wherein the quantum dot comprises at least one of CdZnSeS, CdSe, CdZnSe, ZnSe, CdSeS, InP, and InZnP.
10. A quantum dot composition, comprising the core-shell quantum dot prepared by the preparation method of any one of claims 1 to 9.
11. An optoelectronic device, comprising the core-shell quantum dot prepared by the preparation method of any one of claims 1 to 9.
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