Quantum dot, preparation method thereof and light-emitting device

Abstract

The invention provides a quantum dot, a preparation method thereof and a light-emitting device. According to the preparation method disclosed by the invention, after the M1M2N1 quantum dot core is formed, the metal element M2 second precursor is added, so that the surface of the M1M2N1 quantum dot core is rich in M2 cations, lattice defects can be effectively reduced, and the PLQY of the quantum dot is remarkably improved.

Description

Technical Field

[0001] This application belongs to the technical field of quantum dots, and particularly relates to a quantum dot, a preparation method thereof, and a light-emitting device. Background Art

[0002] Quantum dots (QDs) have become the most promising luminescent materials for next-generation flat-panel displays and solid-state lighting applications due to their high fluorescence quantum yield, good monochromaticity, continuously tunable emission spectrum with size, strong photochemical and thermal stability, and the ability to be prepared by solution methods.

[0003] However, the photoluminescence quantum yield (PLQY) of existing quantum dot materials still needs to be improved. Summary of the Invention

[0004] Embodiments of this application provide a quantum dot, a preparation method thereof, and a light-emitting device to solve the problem that the photoluminescence quantum yield of existing quantum dot materials still needs to be improved.

[0005] In a first aspect, embodiments of this application provide a preparation method of a quantum dot. The preparation method includes the following steps:

[0006] Mix a metal element M1 precursor, a first metal element M2 precursor, and a solvent to obtain a first reaction system;

[0007] Mix a first non-metal element N1 precursor with the first reaction system to obtain a second reaction system containing M1M2N1 quantum dot cores;

[0008] Mix a second metal element M2 precursor with the second reaction system to obtain a third reaction system;

[0009] Mix a second non-metal element N1 precursor with the third reaction system to coat an M1N1 shell on the surface of the M1M2N1 quantum dot cores, obtaining a fourth reaction system containing M1M2N1 / M1N1 quantum dots; wherein, the dosage of the second metal element M2 precursor is greater than that of the first metal element M2 precursor.

[0010] In some embodiments of this application, the step of mixing the second non-metal element N1 precursor with the third reaction system specifically includes:

[0011] Add an amine compound to the third reaction system, react for a first period of time, then add the second non-metal element N1 precursor, and react for a second period of time.

[0012] In some embodiments of the present application, the amine compound is a saturated or unsaturated fatty amine having 6 to 36 carbon atoms. Preferably, the amine compound is selected from at least one of oleylamine, n-octylamine, dodecylamine, tetradecylamine, and hexadecylamine;

[0013] Optionally, the volume molar ratio of the amine compound to the metal element M1 precursor is (0.5 - 1) mL : (8 - 12) mmol;

[0014] Optionally, the first time is 5 min to 10 min;

[0015] Optionally, the second time is 15 min to 35 min.

[0016] In some embodiments of the present application, the step of mixing the metal element M1 precursor, the first precursor of metal element M2, and the solvent specifically includes:

[0017] Mix the metal element M1 precursor, the first precursor of metal element M2, the coordinating solvent, and the non-coordinating solvent, and then perform vacuum treatment.

[0018] Optionally, the molar volume ratio of the metal element M1 precursor, the first precursor of metal element M2, the coordinating solvent, and the non-coordinating solvent is (8 - 12) mmol : (0.5 - 1.2) mmol : (24 - 48) mmol : (12 - 15) mL;

[0019] Optionally, the coordinating solvent is selected from one of C5 - C30 saturated or unsaturated fatty acids;

[0020] Optionally, the non-coordinating solvent is selected from at least one of C6 - C30 saturated or unsaturated aliphatic hydrocarbons, C6 - C30 aromatic hydrocarbons, nitrogen-containing heterocyclic compounds, and C12 - C22 aromatic ethers;

[0021] Optionally, the conditions for the vacuum treatment are: at a reaction temperature of 120°C - 140°C, perform vacuum treatment for 60 min - 120 min.

[0022] In some embodiments of the present application, the molar ratio of the first precursor of metal element M2 to the first precursor of non-metal element N1 is (0.5 - 0.8) : 1;

[0023] And / or, the molar ratio of the second precursor of non-metal element N1 to the first precursor of non-metal element N1 is (2 - 3) : 1.

[0024] And / or, the step of mixing the first precursor of non-metal element N1 with the first reaction system specifically includes:

[0025] At a reaction temperature of 280°C to 320°C, the first precursor of the non-metallic element N1 is added to the first reaction system, and then the reaction is carried out for 30 min to 60 min.

[0026] And / or, the step of mixing the second precursor of the metal element M2 with the second reaction system specifically includes:

[0027] The second precursor of the metal element M2 is added to the second reaction system, and the reaction is carried out for 5 min to 10 min;

[0028] And / or, the molar ratio of the second precursor of the metal element M2 to the first precursor of the metal element M2 is (0.05 to 0.1):1.

[0029] In some embodiments of the present application, after obtaining the fourth reaction system containing M1M2N1 / M1N1 quantum dots, it further includes:

[0030] The third precursor of the metal element M2 and the precursor of the non-metallic element N2 are mixed with the fourth reaction system to coat the M1N1 shell surface with an M2N2 shell, obtaining a fifth reaction system containing

[0031] M1M2N1 / M1N1 / M2N2 quantum dots;

[0032] The single-molecule precursor M3 is mixed with the fifth reaction system to coat the M2N2 shell surface with an M1N2 shell, obtaining M1M2N1 / M1N1 / M2N2 / M1N2 quantum dots.

[0033] In some embodiments of the present application, the molar ratio of the third precursor of the metal element M2 to the first precursor of the metal element M2 is (1.5 to 5):1;

[0034] And / or, the molar ratio of the third precursor of the metal element M2 to the precursor of the non-metallic element N2 is 1:1;

[0035] And / or, the addition amount of the single-molecule precursor M3 is 0.5 mmol to 1 mmol;

[0036] And / or, the metal element M2 in the third precursor of the metal element M2 includes cadmium element;

[0037] And / or, the non-metallic element N2 in the precursor of the non-metallic element N2 includes at least one of sulfur element, arsenic element, tellurium element, selenium element, oxygen element, nitrogen element, phosphorus element, and antimony element;

[0038] And / or, the single-molecule precursor M3 is selected from one of zinc alkyl dithiocarboxylic acids and S-TOP.

[0039] In some embodiments of the present application, the third precursor of the metal element M2 is selected from at least one of cadmium acetate, cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate, cadmium oxide, cadmium perchlorate, cadmium phosphate, cadmium sulfate, cadmium oleate, cadmium stearate, cadmium laurate, cadmium myristate, and cadmium palmitate;

[0040] and / or, the precursor of the non-metal element N2 is selected from at least one of S-TOP, S-TBP, S-TPP, S-ODE, S-OA, S-ODA, S-TOA, S-ODPA, S-OLA, S-OCA, S, alkyl mercaptan, and mercaptopropylsilane.

[0041] and / or, the step of mixing the third precursor of the metal element M2 and the precursor of the non-metal element N2 with the fourth reaction system specifically includes: at a reaction temperature of 270°C to 290°C, adding the third precursor of the metal element M2 and the precursor of the non-metal element N2 to the fourth reaction system and reacting for 20 min to 40 min;

[0042] and / or, the step of mixing the single-molecule precursor M3 with the fifth reaction system specifically includes: at a temperature of 200°C to 240°C, adding the single-molecule precursor M3 to the fifth reaction system and reacting.

[0043] In some embodiments of the present application, the metal element M1 in the precursor of the metal element M1 includes zinc; optionally, the precursor of the metal element M1 is selected from at least one of zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc oleate, zinc stearate, zinc laurate, zinc myristate, and zinc palmitate

[0044] and / or, the metal element M2 in both the first precursor and the second precursor of the metal element M2 includes cadmium; optionally, the first precursor and the second precursor of the metal element M2 are each independently selected from at least one of cadmium acetate, cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate, cadmium oxide, cadmium perchlorate, cadmium phosphate, cadmium sulfate, cadmium oleate, cadmium stearate, cadmium laurate, cadmium myristate, and cadmium palmitate;

[0045] and / or, the non-metal element N1 in both the first precursor and the second precursor of the non-metal element N1 independently includes at least one of sulfur, arsenic, tellurium, selenium, oxygen, nitrogen, phosphorus, and antimony;

[0046] Optionally, the first precursor of the non-metallic element N1 and the second precursor of the non-metallic element N1 are each independently selected from at least one of Se-TOP, Se-TBP, Se-TPP, Se-ODE, Se-OA, Se-ODA, Se-TOA, Se-ODPA, Se-OLA, Se-OCA, and Se-DPP.

[0047] In a second aspect, an embodiment of the present application provides a quantum dot, which is prepared by the above preparation method.

[0048] In some embodiments of the present application, the quantum dot core of the quantum dot is divided into an inner core and an outer core that coats the inner core. The component of the inner core is M1 1-x M2 x N1, and the component of the outer core is M1 y M2 1-y N1, where 0.5 < x < 1, 0.5 < y < 1, and x + y < 1.

[0049] In a third aspect, an embodiment of the present application provides a light-emitting device, which includes a first electrode, a quantum dot light-emitting layer, and a second electrode stacked. The material of the quantum dot light-emitting layer is the above quantum dot.

[0050] The preparation method of the quantum dot provided by the present application can effectively improve the PLQY of the quantum dot. Description of the Drawings

[0051] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can also be obtained based on these drawings. Among them, the same reference numerals in the following description represent the same parts.

[0052] Figure 1 It is one of the flowcharts of the preparation method of the quantum dot provided by the embodiment of the present application.

[0053] Figure 2 It is the second flowchart of the preparation method of the quantum dot provided by the embodiment of the present application.

[0054] Figure 3 It is one of the structural diagrams of the light-emitting device provided by the embodiment of the present application.

[0055] Figure 4 It is the second structural diagram of the light-emitting device provided by the embodiment of the present application.

[0056] Explanation of the Reference Numerals in the Drawings:

[0057] 100, Light-emitting device; 110, First electrode; 120, Quantum dot light-emitting layer; 130, Second electrode; 141, Electron transport layer; 142, Electron injection layer; 151, Hole transport layer; 152, Hole injection layer. Detailed implementation manners

[0058] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present application.

[0059] In the description of the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the drawings. In addition, in the description of the present application, the term "including" means "including but not limited to". The term "exemplary" is used to mean "serving as an example, illustration, or description", and any embodiment described as "exemplary" is not necessarily construed as being more preferred or having more advantages than other embodiments. The term "and / or" includes any and all combinations of one or more of the associated listed items.

[0060] The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present invention; therefore, it should be considered that the description of the range has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the description of the range from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within that range, such as 1, 2, 3, 4, 5, and 6, regardless of the range.

[0061] The embodiments of the present application provide a method for preparing quantum dots, as Figure 1 shown, the preparation method includes the following steps:

[0062] S100: Mix a metal element M1 precursor, a first precursor of a metal element M2, and a solvent to obtain a first reaction system;

[0063] S200: Mix a first precursor of a non-metal element N1 with the first reaction system to obtain a second reaction system containing M1M2N1 quantum dot nuclei;

[0064] S300: Mix a second precursor of a metal element M2 with the second reaction system to obtain a third reaction system;

[0065] S400: Mix the second precursor of non-metal element N1 with the third reaction system to coat an M1N1 shell on the surface of the M1M2N1 quantum dot core, obtaining a fourth reaction system containing M1M2N1 / M1N1 quantum dots; wherein, the dosage of the second precursor of metal element M2 is greater than that of the first precursor of metal element M2.

[0066] In the method for preparing quantum dots provided by the embodiments of the present application, after forming the M1M2N1 quantum dot core, add the second precursor of metal element M2 to make the surface of the M1M2N1 quantum dot core rich in M2 cations, and then add the second precursor of non-metal element N1 to form an M1N1 shell on the surface of the M1M2N1 quantum dot core. The dosage of the second precursor of non-metal element N1 is greater than that of the first precursor of non-metal element N1, so that a gradually changing energy level from M1M2N1 to M1N1 and a relatively thick M1N1 shell can be formed. The relatively thick M1N1 shell can passivate surface defects, and the gradually changing energy level from M1M2N1 to M1N1 can reduce lattice defects, thus effectively improving the PLQY of the quantum dots.

[0067] Optionally, in the step S100, the step of mixing the precursor of metal element M1, the first precursor of metal element M2 and the solvent specifically includes: mixing the precursor of metal element M1, the first precursor of metal element M2, the coordination solvent and the non-coordination solvent, and then performing vacuum treatment. It can be understood that by reacting the precursor of metal element M1, the first precursor of metal element M2, the coordination solvent and the non-coordination solvent at a temperature of 120°C to 140°C, the reaction can proceed more fully. React at a reaction temperature of 120°C to 140°C for 60 min to 120 min.

[0068] Specifically, the conditions during the vacuum treatment can be: at a reaction temperature of 120°C to 140°C (such as 120°C, 125°C, 130°C, 135°C or 140°C), perform vacuum treatment for 60 min to 120 min (such as 60 min, 70 min, 80 min, 90 min, 100 min, 110 min or 120 min, etc.).

[0069] In some embodiments of the present application, the molar volume ratio of the precursor of metal element M1, the first precursor of metal element M2, the coordination solvent and the non-coordination solvent is (8 - 12) mmol : (0.5 - 1.2) mmol : (24 - 48) mmol : (12 - 15) mL, which can be specifically set according to actual needs. By adjusting the ratios of the precursor of metal element M1, the first precursor of metal element M2, the coordination solvent and the non-coordination solvent, quantum dot cores with different properties can be obtained, making the quantum dots provided by the embodiments of the present application have flexible structural adjustability.

[0070] Optionally, the metal element M1 in the metal element M1 precursor includes zinc element. In some embodiments of the present application, the metal element M1 precursor may be selected from, but not limited to, at least one of zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc oleate, zinc stearate, zinc dodecanoate, zinc myristate, and zinc palmitate.

[0071] Optionally, the metal element M2 in the metal element M2 first precursor includes cadmium element. In some embodiments of the present application, the metal element M2 first precursor may be selected from, but not limited to, at least one of cadmium acetate, cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate, cadmium oxide, cadmium perchlorate, cadmium phosphate, cadmium sulfate, cadmium oleate, cadmium stearate, cadmium dodecanoate, cadmium myristate, and cadmium palmitate.

[0072] Optionally, the coordination solvent may be selected from one of C5 - C30 saturated or unsaturated fatty acids (i.e., saturated or unsaturated fatty acids with 5 to 30 carbons), preferably C8 - C20 saturated or unsaturated fatty acids (i.e., saturated or unsaturated fatty acids with 8 to 20 carbons), such as octanoic acid, decanoic acid, dodecanoic acid, myristic acid, palmitic acid, stearic acid, or oleic acid, etc.

[0073] Optionally, the non - coordination solvent is selected from at least one of C6 - C30 saturated or unsaturated aliphatic hydrocarbons (i.e., aliphatic hydrocarbons with 6 to 30 carbons), C6 - C30 aromatic hydrocarbons (i.e., aromatic hydrocarbons with 6 to 30 carbons), nitrogen - containing heterocyclic compounds (such as pyridine), and C12 - C22 aromatic ethers (i.e., aromatic ethers with 12 to 22 carbons). Among them, the C6 - C30 aliphatic hydrocarbon can be, for example, alkane, alkene, or alkyne, more specifically, hexadecane, octadecane, octadecene, or squalane, etc.; the C6 - C30 aromatic hydrocarbon can be, for example, phenyldodecane, phenyltetradecane, or phenylhexadecane, etc.; the C12 - C22 aromatic ether can be, for example, phenyl ether or benzyl ether, etc.

[0074] In some embodiments of the present application, in the step S200, the step of mixing the non - metal element N1 first precursor with the first reaction system specifically includes: at a reaction temperature of 280°C - 320°C, adding the non - metal element N1 first precursor to the first reaction system, and then reacting for 30 min - 60 min. By setting the reaction temperature to 280°C - 320°C, it is beneficial to the occurrence of the nucleation reaction to better generate the quantum dot core; by setting the nucleation reaction time to 30 min - 60 min, it is beneficial to the state stability of the quantum core, so that the subsequent shell growth is uniform, and at the same time, it is beneficial to improve the PLQY of the quantum dots.

[0075] Exemplarily, the first precursor of non-metal element N1 can be added to the cationic precursor solution at a reaction temperature of 280 °C, 285 °C, 290 °C, 295 °C, 300 °C, 305 °C, 310 °C, 315 °C or 320 °C for a nucleation reaction for 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, etc. The specific reaction temperature and reaction time can be set according to actual requirements.

[0076] Among them, the molar ratio of the first precursor of metal element M2 to the first precursor of non-metal element N1 can be (0.5 - 0.8):1, for example, it can be 0.5:1, 0.6:1, 0.7:1 or 0.8:1, etc. Specifically, it can be set according to actual requirements.

[0077] Optionally, the metal element N1 in the first precursor of non-metal element N1 includes at least one of sulfur element, arsenic element, tellurium element, selenium element, oxygen element, nitrogen element, phosphorus element and antimony element. In some embodiments of the present application, the first precursor of non-metal element N1 can be selected from

[0078] Se-TOP (selenium-Tri-n-octylphosphine), Se-TBP (selenium-Tributylphosphine), Se-TPP (selenium-triphenylphosphine), Se-ODE (selenium-1-octadecene), Se-OA (selenium-oleic acid), Se-ODA (selenium-octadecylamine), Se-TOA

[0079] (selenium-trioctylamine), Se-ODPA (selenium-octadecylphosphonic acid), Se-OLA (selenium-oleylamine), Se-OCA (selenium-octylamine) and

[0080] at least one of Se-DPP (selenium-diphenylphosphine).

[0081] In some embodiments of the present application, in the step S300, the step of mixing the second precursor of metal element M2 with the second reaction system specifically includes: adding the second precursor of metal element M2 to the second reaction system and reacting for 5 min to 10 min. For example, the reaction can be carried out for 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, etc. The specific reaction time can be set according to actual requirements.

[0082] Optionally, the molar ratio of the second precursor of metal element M2 to the first precursor of metal element M2 is (0.05 - 0.1):1. For example, it can be 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1 or 0.1:1, etc. Specifically, it can be set according to actual requirements.

[0083] Optionally, the metal element M2 in the second precursor of metal element M2 includes cadmium element. In some embodiments of the present application, the second precursor of metal element M2 can be selected from but not limited to at least one of cadmium acetate, cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate, cadmium oxide, cadmium perchlorate, cadmium phosphate, cadmium sulfate, cadmium oleate, cadmium stearate, cadmium dodecanoate, cadmium tetradecanoate and cadmium hexadecanoate.

[0084] In some embodiments of the present application, in the step S400, the molar ratio of the second precursor of non-metal element N1 to the first precursor of non-metal element N1 is (2 - 3):1. For example, it can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.3:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1 or 3:1, etc. Specifically, it can be set according to actual requirements.

[0085] Optionally, the non-metallic element N1 in the second precursor of the non-metallic element N1 includes at least one of sulfur element, arsenic element, tellurium element, selenium element, oxygen element, nitrogen element, phosphorus element, and antimony element. In some embodiments of the present application, the second precursor of the non-metallic element N1 may be selected from but not limited to Se-TOP (selenium-Tri-n-octylphosphine), Se-TBP (selenium-Tributyl phosphine), Se-TPP (selenium-triphenylphosphine), Se-ODE (selenium-1-octadecene), Se-OA (selenium-oleic acid), Se-ODA (selenium-octadecylamine), Se-TOA (selenium-trioctylamine), Se-ODPA (selenium-octadecylphosphonic acid), Se-OLA (selenium-oleylamine), Se-OCA (selenium-octylamine), and

[0086] at least one of Se-DPP (selenium-diphenylphosphine).

[0087] In some embodiments of the present application, in the step S400, the step of mixing the second precursor of the non-metallic element N1 with the third reaction system specifically includes: adding an amine compound to the third reaction system, reacting for a first time, and then adding the second precursor of the non-metallic element N1 and reacting for a second time. By adding the amine compound, it helps to improve the activity of the metal element M1, so as to better form the M1N1 shell and the gradient energy level from the M1M2N1 quantum dot core to the M1N1 shell.

[0088] Among them, the amine compound is a saturated or unsaturated fatty amine with 6 to 36 carbon atoms. Preferably, the amine compound is selected from at least one of oleylamine, n-octylamine, dodecylamine, tetradecylamine, and hexadecylamine. Optionally, the volume molar ratio of the amine compound to the precursor of the metal element M1 is (0.5 to 1) mL:

[0089] (8 to 12) mmol, which can be specifically set according to actual needs.

[0090] Optionally, the first time may be 5 min to 10 min, for example, it may be 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min, etc., which can be specifically set according to actual needs.

[0091] Optionally, the second time can be 15 min to 35 min. For example, it can be 15 min, 16 min, 17 min, 18 min, 19 min, 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min, or 35 min, etc. Specifically, it can be set according to actual requirements.

[0092] In some embodiments of the present application, as Figure 2 shown, after obtaining the fourth reaction system containing M1M2N1 / M1N1 quantum dots, the following steps are further included:

[0093] S500: Mix the third precursor of metal element M2 and the precursor of non-metal element N2 with the fourth reaction system to coat the M2N2 shell on the surface of the M1N1 shell, obtaining a

[0094] fifth reaction system containing M1M2N1 / M1N1 / M2N2 quantum dots;

[0095] S600: Mix the single-molecule precursor M3 with the fifth reaction system to coat the M1N2 shell on the surface of the M2N2 shell, obtaining M1M2N1 / M1N1 / M2N2 / M1N2 quantum dots. By coating the M2N2 shell on the surface of the M1N1 shell and coating the M1N2 shell on the surface of the M2N2 shell, the stability of the quantum dots can be improved and the PLQY decay rate of the quantum dots can be slowed down.

[0096] Among them, the molar ratio of the third precursor of metal element M2 to the first precursor of metal element M2 is (1.5 - 5):1. For example, it can be 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, or 5:1, etc. Specifically, it can be set according to actual requirements. Optionally, the molar ratio of the third precursor of metal element M2 to the precursor of non-metal element N2 can be 1:1.

[0097] In some embodiments of the present application, in the step S500, the step of mixing the third precursor of metal element M2 and the precursor of non-metal element N2 with the fourth reaction system specifically includes: at a reaction temperature of 270 °C to 290 °C, adding the third precursor of metal element M2 and the precursor of non-metal element N2 to the fourth reaction system and reacting for 20 min to 40 min. By setting the reaction temperature to 270 °C to 290 °C, it is beneficial for CdS to slowly epitaxially grow into a high-quality shell, avoiding too fast growth due to too high temperature, resulting in uneven epitaxial growth, and too low temperature will not allow growth.

[0098] Exemplarily, the reaction temperature in step S500 can be 270 °C, 275 °C, 280 °C, 285 °C, 290 °C, etc., and the reaction time can be 20 min, 21 min, 22 min, 23 min, 24 min, 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min, 35 min, 36 min, 37 min, 38 min, 39 min, 40 min, etc. Specifically, it can be set according to actual requirements.

[0099] In some embodiments of the present application, in step S600, the step of mixing the single-molecule precursor M3 with the fifth reaction system specifically includes: adding the single-molecule precursor M3 to the fifth reaction system and reacting it under a temperature condition of 200 °C to 240 °C. By setting the reaction temperature to 200 °C to 240 °C, it is beneficial for the single-molecule precursor to decompose slowly and epitaxially grow into a high-quality shell layer.

[0100] Exemplarily, the single-molecule precursor can be added to the first core-shell solution at a reaction temperature of 200 °C, 205 °C, 210 °C, 215 °C, 220 °C, 225 °C, 230 °C, 235 °C, or 240 °C.

[0101] Among them, the addition amount of the single-molecule precursor M3 can be 0.5 mmol to 1 mmol, for example, it can be 0.5 mmol, 0.6 mmol, 0.7 mmol, 0.8 mmol, 0.9 mmol, 1 mmol, etc. Specifically, it can be set according to actual requirements. By setting the addition amount of the single-molecule precursor M3 to 0.5 mmol to 1 mmol, the thickness of the M1N2 shell layer can be made appropriate, which is beneficial for uniform growth and binding of electron holes. If the thickness of the M1N2 shell layer is too thin, it is not conducive to binding electrons and holes, and if it is too thick, the growth is uneven.

[0102] Optionally, the metal element M2 in the third precursor of the metal element M2 includes cadmium. In some embodiments of the present application, the third precursor of the metal element M2 is selected from at least one of cadmium acetate, cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate, cadmium oxide, cadmium perchlorate, cadmium phosphate, cadmium sulfate, cadmium oleate, cadmium stearate, cadmium laurate, cadmium myristate, and cadmium palmitate.

[0103] Optionally, the non-metallic element N2 of the non-metallic element N2 precursor includes at least one of sulfur element, arsenic element, tellurium element, selenium element, oxygen element, nitrogen element, phosphorus element and antimony element. In some embodiments of the present application, the non-metallic element N2 precursor may be selected from but not limited to S-TOP (Sulfur-Tri-n-octylphosphine), S-TBP (Sulfur-Tributyl phosphine), S-TPP (Sulfur-triphenylphosphine), S-ODE (Sulfur-1-octadecene), S-OA (Sulfur-oleic acid), S-ODA (Sulfur-octadecylamine), S-TOA (Sulfur-trioctylamine), S-ODPA (Sulfur-octadecylphosphonic acid), S-OLA (Sulfur-oleylamine), S-OCA (Sulfur-octylamine), S(triphenylphosphine), alkyl mercaptans (such as hexanethiol, octanethiol, decanethiol, dodecanethiol and hexadecanethiol, etc.) and mercaptopropylsilane.

[0104] In some embodiments of the present application, the M1M2N1 quantum dot core is a ZnCdSe quantum dot core, the M1N1 shell is a ZnSe shell, and the M2N2 shell is a CdS shell. According to the band gap width, by using CdS as the second shell layer, the valence band energy level of CdS is deeper than that of the ZnCdSe quantum dot core and the first layer of ZnSe shell, which can effectively improve the hole confinement effect, thereby increasing the probability of electron-hole recombination and making the luminescence stronger.

[0105] The single molecule precursor M3 is selected from one of zinc salts of alkyl dithiocarboxylic acids and S-TOP. Among them, the zinc salts of alkyl dithiocarboxylic acids include but are not limited to at least one of zinc diethyldithiocarbamate, zinc dialkyldithiophosphate and zinc dibutyldithiocarbamate.

[0106] In some embodiments of the present application, M1N2 is a ZnS shell layer. By using zinc alkyl dithiocarboxylate as a single-molecule precursor to grow the ZnS shell layer through low-temperature pyrolysis, due to the relatively long chain length, large steric hindrance, and weak binding strength of some ligands of the quantum dots, there are dangling bonds on the surface of the quantum dots that are not passivated. The S chain length in the single-molecule precursor zinc alkyl dithiocarboxylate is short, the steric hindrance is small, and the binding ability is strong. Therefore, it can passivate the uncoordinated dangling bonds on the surface of the quantum dots. At the same time, the metal salt of alkyl dithiocarboxylic acid has the characteristic of being insensitive to water and oxygen. Therefore, using zinc alkyl dithiocarboxylate as a single-molecule precursor can effectively passivate the surface defects of the quantum dots and isolate the influence of water and oxygen, improving the stability of the quantum dots.

[0107] In some embodiments of the present application, the quantum dot core of the M1M2N1 / M1N1 / M2N2 / M1N2 quantum dots is divided into an inner core and an outer core that coats the inner core. Among them, the component of the inner core is mainly M2N1, and the inner core is specifically M1 1-x M2 x N1, and the component of the outer core is mainly M1N1, and the outer core is specifically M1 y M2 1-y N1, 0.5 < x < 1, 0.5 < y < 1, x + y < 1. By utilizing the difference in the activity of the precursors, the inner core is formed first and then the outer core is formed, that is, the alloying processes of the inner core and the outer core are carried out separately. Therefore, the components of the quantum dot core are discontinuous. Such a discontinuous structure will cause a sudden change in energy levels and has better carrier confinement. Using the quantum dots provided in the present application in the light-emitting layer of a light-emitting device can improve the charge injection, light-emitting brightness, and device efficiency of the light-emitting device.

[0108] The embodiments of the present application also provide a quantum dot, which is prepared by the above-mentioned preparation method.

[0109] In some embodiments of the present application, the quantum dot core of the quantum dot is divided into an inner core and an outer core that coats the inner core. The component of the inner core is M1 1-x M2 x N1, and the component of the outer core is M1 y M2 1-y N1, where 0.5 < x < 1, 0.5 < y < 1, x + y < 1.

[0110] Exemplarily, the quantum dot is a CdZnSe / ZnSe / CdS / ZnS quantum dot, and the component of the inner core of the quantum dot core CdZnSe is Zn 1-x Cd x Se, and the component of the outer core is Zn y Cd 1-y Se, where 0.5 < x < 1, 0.5 < y < 1, x + y < 1.

[0111] The embodiment of the present application also provides a light-emitting device 100, as Figure 3 shown. The light-emitting device 100 includes a first electrode 110, a quantum dot light-emitting layer 120, and a second electrode 130 that are stacked. The material of the quantum dot light-emitting layer 120 is the quantum dot described in the above embodiments. Since the light-emitting device 100 adopts all the technical solutions of the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be elaborated here one by one.

[0112] Among them, one of the first electrode 110 and the second electrode 130 is an anode, and the other is a cathode. The first electrode 110 and the second electrode 130 can be independently selected from a composite electrode formed by one or more of a metal electrode, a carbon electrode, and a doped or undoped metal oxide electrode; among them, the material of the metal electrode is selected from at least one of Al, Ag, Cu, Mo, Au, Ba, Ca, and Mg; the material of the carbon electrode is selected from at least one of graphite, carbon nanotubes, graphene, and carbon fiber; the material of the doped or undoped metal oxide electrode is selected from at least one of ITO, FTO, ATO, AZO, GZO, IZO, MZO, and AMO; the material of the composite electrode is selected from at least one of AZO / Ag / AZO, AZO / Al / AZO, ITO / Ag / ITO, ITO / Al / ITO, ZnO / Ag / ZnO, ZnO / Al / ZnO, TiO2 / Ag / TiO2, TiO2 / Al / TiO2, ZnS / Ag / ZnS, ZnS / Al / ZnS, TiO2 / Ag / TiO2, and TiO2 / Al / TiO2.

[0113] In some embodiments of the present application, the light-emitting device 100 further includes an electron transport layer 141 and an electron injection layer 142. The electron injection layer 142 is disposed between the first electrode 110 and the quantum dot light-emitting layer 120 or between the second electrode 130 and the quantum dot light-emitting layer 120, and the electron transport layer 141 is disposed between the quantum dot light-emitting layer 120 and the electron injection layer 142. Specifically, as Figure 4 shown, when the first electrode 110 is an anode and the second electrode 130 is a cathode, the electron injection layer 142 is disposed between the second electrode 130 and the quantum dot light-emitting layer 120, and the electron transport layer 141 is disposed between the electron injection layer 142 and the quantum dot light-emitting layer 120; when the first electrode 110 is a cathode and the second electrode 130 is an anode, the electron injection layer 142 is disposed between the first electrode 110 and the light-emitting layer, and the electron transport layer 141 is disposed between the electron injection layer 142 and the quantum dot light-emitting layer 120.

[0114] Among them, the material of the electron transport layer 141 can be selected from, but not limited to, one or more of inorganic electron transport materials and organic electron transport materials. The inorganic electron transport materials are selected from, but not limited to, one or more of metal oxides, doped metal oxides, IIB-VIA group semiconductor materials, IIIA-VA group semiconductor materials, and IB-IIIA-VIA group semiconductor materials. Specifically, the metal oxides are selected from one or more of ZnO, TiO2, SnO2, Al2O3, Ga2O3, V2O5, V3O8, CrO3, WO3, Fe2O3, Fe3O4, CuO, MoO2, Nb2O5, BaO, MoO3, CdO, BaO, Ta2O5, BaTiO3, and PbCrO4; the metal oxides in the doped metal oxides include one or more of ZnO, TiO2, SnO2, Al2O3, Ga2O3, V2O5, V3O8, CrO3, WO3, Fe2O3, Fe3O4, CuO, MoO2, Nb2O5, BaO, MoO3, CdO, BaO, Ta2O5, BaTiO3, and PbCrO4, and the doping elements include one or more of Al, Mg, Li, Mn, Y, La, Cu, Ni, Zr, Ce, In, Ga, and Sn; the IIB-VIA group semiconductor materials include one or more of ZnS, ZnSe, and CdS; the IIIA-VA group semiconductor materials include one or more of InP and GaP; the IB-IIIB-VIA group semiconductor materials include one or more of CuInS and CuGaS. The organic electron transport materials include, but are not limited to, one or more of quinoxaline compounds, imidazole compounds, triazine compounds, fluorene-containing compounds, and hydroxyquinoline compounds.

[0115] Optionally, the material of the electron injection layer 142 can be selected from one or more of LiF, MgP, MgF2, Al2O3, Ga2O3, ZnO, Cs2CO3, RbBr, Rb2CO3, and LiF / Yb.

[0116] In some embodiments of the present application, the light-emitting device 100 further includes a hole transport layer 151 and a hole injection layer 152. The hole injection layer 152 is disposed between the first electrode 110 and the quantum dot light-emitting layer 120 or between the second electrode 130 and the quantum dot light-emitting layer 120, and the hole transport layer 151 is disposed between the quantum dot light-emitting layer 120 and the hole injection layer 152. Specifically, as Figure 4As shown, when the first electrode 110 is the anode and the second electrode 130 is the cathode, the hole injection layer 152 is disposed between the second electrode 130 and the quantum dot light emitting layer 120, and the hole transport layer 151 is disposed between the hole injection layer 152 and the quantum dot light emitting layer 120; when the first electrode 110 is the cathode and the second electrode 130 is the anode, the hole injection layer 152 is disposed between the first electrode 110 and the light emitting layer, and the hole transport layer 151 is disposed between the hole injection layer 152 and the quantum dot light emitting layer 120.

[0117] Among them, the material of the hole transport layer 151 can be selected from, but not limited to, 4,4'-N,N'-dicarbazolyl-biphenyl (CBP), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4”-diamine (α-NPD), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine (TPD), poly(N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine) (Poly-TPD), N,N'-bis(3-methylphenyl)-N,N'-bis(phenyl)-spiro(spiro-TPD), N,N'-bis(4-(N,N'-diphenyl-amino)phenyl)-N,N'-diphenylbenzidine (DNTPD), 4,4',4'-tris(N-carbazolyl)-triphenylamine (TCTA), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (m-MTDATA), poly[(9,9'-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine))] (TFB), poly(N-vinylcarbazole) (PVK) and its derivatives, N,N'-bis(1-naphthyl)-N,N'-diphenyl-1,1'-biphenyl-4-4'-diamine (NPB), spiro-NPB, poly(phenylene vinylene) (PPV), poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV), poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-1,4-phenylene vinylene] (MOMO-PPV), 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (spiro-omeTAD), 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (TAPC), 1,3-bis(carbazol-9-yl)benzene (MCP), polyaniline, polypyrrole, poly(p-phenylene vinylene), aromatic tertiary amines, polynuclear aromatic tertiary amines, 4,4'-bis(p-carbazolyl)-1,1'-biphenyl compounds, N,N,N',N'-tetraarylbenzidine, PEDOT:PSS and its derivatives, polymethacrylate and its derivatives, poly(9,9-octylfluorene) and its derivatives, poly(spirofluorene) and its derivatives, doped graphene, undoped graphene, C60, doped or undoped NiO, doped or undoped MoO3, doped or undoped WO3, doped or undoped V2O5, doped or undoped p-type gallium nitride, doped or undoped CrO3, doped or undoped CuO, one or more of them.

[0118] Optionally, the material of the hole injection layer 152 may be selected from, but not limited to, one or more of 2,3,6,7,10,11 - hexacyano - 1,4,5,8,9,12 - hexaazatriphenylene (HAT - CN), PEDOT, PEDOT:PSS, derivatives of PEDOT:PSS doped with s - MoO3 (PEDOT:PSS:s - MoO3), 4,4',4' - tris(N - 3 - methylphenyl - N - phenylamino) triphenylamine (m - MTDATA), tetracyanoquinodimethane (F4 - TCQN), copper phthalocyanine, nickel oxide, molybdenum oxide, tungsten oxide, vanadium oxide, molybdenum sulfide, tungsten sulfide, and copper oxide.

[0119] The technical solutions and technical effects of the present application will be described in detail below through specific examples and comparative examples. The following examples are only partial examples of the present application and do not specifically limit the present application.

[0120] Example 1

[0121] A quantum dot, the preparation method thereof comprising the following steps:

[0122] (1) Place 0.7 mmol cadmium oleate, 10 mmol zinc oleate, 15 mL oleic acid, and 15 mL ODE (octadecene) in a three - necked flask, evacuate at room temperature for 20 min, evacuate at 80 °C for 30 min, and evacuate at 130 °C for 60 min;

[0123] (2) Heat to 315 °C under an argon atmosphere, quickly inject 1 mmol Se - TOP into the three - necked flask, react for 30 min, and measure PL = 628 nm, FWHM = 23 nm, PLQY = 30%;

[0124] (3) Drop 0.05 mmol cadmium oleate into the three - necked flask, react for 5 min, and measure PL = 638 nm, FWHM = 22 nm, PLQY = 65%;

[0125] (4) At a reaction temperature of 315 °C, add 2 mmol Se - TOP to the three - necked flask, react for 20 min, and measure PL = 632 nm, FWHM = 21 nm, PLQY = 82%;

[0126] (5) At a reaction temperature of 280 °C, add 1.2 mmol cadmium oleate and 1.2 mmol S - TOP to the three - necked flask, react for 30 min, and measure PL = 632 nm, FWHM = 21 nm, PLQY = 85%;

[0127] (6) At a reaction temperature of 220 °C, 1 mmol of Zn(DDTC)2 was added to a three-necked flask, and the reaction was carried out for 15 min. After separation and purification, the quantum dots CdZnSe / ZnSe / CdS / ZnS were obtained. The measured PL was 632 nm, the FWHM was 21 nm, and the PLQY was 86%.

[0128] Example 2

[0129] A quantum dot, the preparation method of which comprises the following steps:

[0130] (1) 0.7 mmol of cadmium oleate, 10 mmol of zinc oleate, 15 mL of oleic acid and 15 mL of ODE (octadecene) were placed in a three-necked flask. Vacuum was pumped at room temperature for 20 min, at 80 °C for 30 min, and at 130 °C for 60 min.

[0131] (2) Under an argon atmosphere, the temperature was raised to 315 °C, and 1 mmol of Se-TOP was quickly injected into the three-necked flask. Then the reaction was carried out for 30 min. The measured PL was 628 nm, the FWHM was 23 nm, and the PLQY was 30%.

[0132] (3) 0.05 mmol of cadmium oleate was dropped into the three-necked flask, and the reaction was carried out for 5 min. The measured PL was 638 nm, the FWHM was 22 nm, and the PLQY was 65%.

[0133] (4) At a reaction temperature of 315 °C, 2.5 mmol of Se-TOP was added to the three-necked flask, and the reaction was carried out for 20 min. The measured PL was 628 nm, the FWHM was 21 nm, and the PLQY was 90%.

[0134] (5) At a reaction temperature of 280 °C, 1.2 mmol of cadmium oleate and 1.2 mmol of S-TOP were added to the three-necked flask, and the reaction was carried out for 30 min. The measured PL was 627 nm, the FWHM was 21 nm, and the PLQY was 95%.

[0135] (6) At a reaction temperature of 220 °C, 1 mmol of Zn(DDTC)2 was added to the three-necked flask, and the reaction was carried out for 15 min. After separation and purification, the quantum dots CdZnSe / ZnSe / CdS / ZnS were obtained. The measured PL was 627 nm, the FWHM was 21 nm, and the PLQY was 98%.

[0136] Example 3

[0137] A quantum dot, the preparation method of which comprises the following steps:

[0138] (1) Place 0.7 mmol cadmium oleate, 10 mmol zinc oleate, 15 mL oleic acid, and 15 mL ODE (octadecene) in a three-necked flask. Evacuate at room temperature for 20 min, evacuate at 80 °C for 30 min, and evacuate at 130 °C for 60 min;

[0139] (2) Under an argon atmosphere, heat up to 315 °C, quickly inject 1 mmol Se-TOP into the three-necked flask, and then react for 30 min. Measure PL = 628 nm, FWHM = 23 nm, and PLQY = 30%;

[0140] (3) Drop 0.05 mmol cadmium oleate into the three-necked flask and react for 5 min. Measure PL = 638 nm, FWHM = 22 nm, and PLQY = 65%;

[0141] (4) At a reaction temperature of 315 °C, add 3 mmol Se-TOP to the three-necked flask and react for 20 min. Measure PL = 625 nm, FWHM = 21 nm, and PLQY = 80%;

[0142] (5) At a reaction temperature of 280 °C, add 1.2 mmol cadmium oleate and 1.2 mmol S-TOP to the three-necked flask and react for 30 min. Measure PL = 625 nm, FWHM = 21 nm, and PLQY = 82%;

[0143] (6) At a reaction temperature of 220 °C, add 1 mmol Zn(DDTC)2 to the three-necked flask and react for 15 min. Separate and purify to obtain the quantum dots CdZnSe / ZnSe / CdS / ZnS. Measure PL = 625 nm, FWHM = 21 nm, and PLQY = 83%.

[0144] Example 4

[0145] A quantum dot, and its preparation method includes the following steps:

[0146] (1) Place 0.7 mmol cadmium oleate, 10 mmol zinc oleate, 15 mL oleic acid, and 15 mL ODE (octadecene) in a three-necked flask. Evacuate at room temperature for 20 min, evacuate at 80 °C for 30 min, and evacuate at 130 °C for 60 min;

[0147] (2) Under an argon atmosphere, heat up to 315 °C, quickly inject 1 mmol Se-TOP into the three-necked flask, and then react for 30 min. Measure PL = 628 nm, FWHM = 23 nm, and PLQY = 30%;

[0148] (3) 0.05 mmol of cadmium oleate was added dropwise to the three-necked flask and reacted for 5 min. The measured PL = 638 nm, FWHM = 22 nm, and PLQY = 65%;

[0149] (4) 0.5 mL of oleylamine was added dropwise to the three-necked flask and reacted for 5 min;

[0150] (5) At a reaction temperature of 315 °C, 2 mmol of Se-TOP was added to the three-necked flask and reacted for 20 min. The measured PL = 632 nm, FWHM = 21 nm, and PLQY = 86%;

[0151] (6) At a reaction temperature of 280 °C, 1.2 mmol of cadmium oleate and 1.2 mmol of S-TOP were added to the three-necked flask and reacted for 30 min. The measured PL = 632 nm, FWHM = 21 nm, and PLQY = 87%;

[0152] (7) At a reaction temperature of 220 °C, 1 mmol of Zn(DDTC)2 was added to the three-necked flask and reacted for 15 min. After separation and purification, the quantum dots CdZnSe / ZnSe / CdS / ZnS were obtained. The measured PL = 632 nm, FWHM = 21 nm, and PLQY = 88%.

[0153] Comparative Example 1

[0154] A kind of quantum dots, and its preparation method includes the following steps:

[0155] (1) 0.7 mmol of cadmium oleate, 10 mmol of zinc oleate, 15 mL of oleic acid, and 15 mL of ODE (octadecene) were placed in a three-necked flask. Vacuum was pumped at room temperature for 20 min, at 80 °C for 30 min, and at 130 °C for 60 min;

[0156] (2) Under an argon atmosphere, the temperature was raised to 315 °C, and 1 mmol of Se-TOP was quickly injected into the three-necked flask and reacted for 30 min. The measured PL = 628 nm, FWHM = 23 nm, and PLQY = 30%;

[0157] (3) 0.05 mmol of cadmium oleate was added dropwise to the three-necked flask and reacted for 5 min. The measured PL = 638 nm, FWHM = 22 nm, and PLQY = 65%;

[0158] (4) At a reaction temperature of 315 °C, 1 mmol of Se-TOP was added to the three-necked flask and reacted for 20 min. The measured PL = 629 nm, FWHM = 22 nm, and PLQY = 65%;

[0159] (5) At a reaction temperature of 280 °C, 1.2 mmol of cadmium oleate and 1.2 mmol of S-TOP were added to a three-necked flask and reacted for 30 min. The measured PL = 629 nm, FWHM = 22 nm, and PLQY = 67%;

[0160] (6) At a reaction temperature of 220 °C, 1 mmol of Zn(DDTC)2 was added to a three-necked flask and reacted for 15 min. After separation and purification, the quantum dots CdZnSe / ZnSe / CdS / ZnS were obtained. The measured PL = 629 nm, FWHM = 22 nm, and PLQY = 68%.

[0161] Comparative Example 2

[0162] A kind of quantum dots, and its preparation method includes the following steps:

[0163] (1) 0.7 mmol of cadmium oleate, 10 mmol of zinc oleate, 15 mL of oleic acid, and 15 mL of ODE (octadecene) were placed in a three-necked flask, evacuated at room temperature for 20 min, evacuated at 80 °C for 30 min, and evacuated at 130 °C for 60 min;

[0164] (2) Under an argon atmosphere, the temperature was raised to 315 °C, and 1 mmol of Se-TOP was quickly injected into the three-necked flask and reacted for 30 min. The measured PL = 628 nm, FWHM = 23 nm, and PLQY = 30%;

[0165] (3) At a reaction temperature of 315 °C, 2 mmol of Se-TOP was added to the three-necked flask and reacted for 20 min. The measured PL = 618 nm, FWHM = 24 nm, and PLQY = 45%;

[0166] (4) At a reaction temperature of 280 °C, 1.2 mmol of cadmium oleate and 1.2 mmol of S-TOP were added to the three-necked flask and reacted for 30 min. The measured PL = 620 nm, FWHM = 23 nm, and PLQY = 50%;

[0167] (5) At a reaction temperature of 220 °C, 1 mmol of Zn(DDTC)2 was added to the three-necked flask and reacted for 15 min. After separation and purification, the quantum dots CdZnSe / ZnSe / CdS / ZnS were obtained. The measured PL = 621 nm, FWHM = 24 nm, and PLQY = 52%.

[0168] The test characterization methods in the above examples are specifically as follows:

[0169] The cleaned quantum dot solution was measured for PLQY (photoluminescence quantum yield), PL (band), and FWHM (full width at half maximum) on a steady-state fluorescence spectrometer (model FS5) from Edinburgh Instruments, combined with a photoluminescence quantum yield attachment (model SC-30). When measuring PL (band) and FWHM (full width at half maximum), the fluorescence excitation wavelength was 350 nm, the scanning range was 370 nm to 680 nm, and the scanning speed was 2400 nm / min.

[0170] It can be seen by comparison that the PLQY of the quantum dots prepared in Examples 1 to 3 is significantly higher than that of the quantum dots prepared in Comparative Example 1 and Comparative Example 2. The reason may be that in the process of preparing quantum dots in Examples 1 to 3, after forming the CdZnSe quantum dot core, the metal element M2 second precursor cadmium oleate was first added, and then the non-metal element N1 second precursor Se-TOP was added to form a ZnSe shell layer on the surface of the CdZnSe quantum dot core, and the amount of the non-metal element N1 second precursor Se-TOP is greater than that of the non-metal element N1 second precursor Se-TOP, so that a graded energy level from CdZnSe to ZnSe and a thicker ZnSe shell layer can be formed. The thicker ZnSe shell layer can passivate surface defects, and the graded energy level from CdZnSe to ZnSe can reduce lattice defects, thus effectively improving the PLQY of the quantum dots. In Comparative Example 1, although the metal element M2 second precursor cadmium oleate was also added after forming the quantum dot core, the amount of the non-metal element N1 second precursor Se-TOP in Comparative Example 1 is the same as that of the non-metal element N1 second precursor Se-TOP, and a thicker ZnSe shell layer cannot be formed; although the amount of the non-metal element N1 second precursor Se-TOP in Comparative Example 2 is greater than that of the non-metal element N1 second precursor Se-TOP, in Comparative Example 2, the metal element M2 second precursor cadmium oleate was not added after forming the quantum dot core, and a graded energy level from CdZnSe to ZnSe cannot be formed, resulting in the PLQY of the quantum dots prepared in Comparative Example 1 and Comparative Example 2 being lower than that of the quantum dots prepared in Examples 1 to 3.

[0171] It can be seen by comparing Example 1 and Example 4 that the PLQY of the quantum dots prepared in Example 4 is higher than that of the quantum dots prepared in Example 1. The reason may be that oleylamine was added before adding the non-metal element N1 second precursor Se-TOP in Example 4. Oleylamine can increase the Zn activity, so it helps to better form the ZnSe shell layer and the graded energy level from the CdZnSe quantum dot core to the ZnSe shell layer subsequently, effectively improving the PLQY of the quantum dots.

[0172] In the above examples, the descriptions of each example have their own focuses. For parts not detailed in a certain example, reference can be made to the relevant descriptions of other examples.

[0173] The preparation method of quantum dots, quantum dots and light-emitting devices provided by the embodiments of the present application have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A method for preparing quantum dots, characterized in that, It includes the following steps: Mix a metal element M1 precursor, a first metal element M2 precursor, and a solvent to obtain a first reaction system; Mix a first non-metal element N1 precursor with the first reaction system to obtain a second reaction system containing M1M2N1 quantum dot cores; Mix a second metal element M2 precursor with the second reaction system to obtain a third reaction system; Mix a second non-metal element N1 precursor with the third reaction system to coat an M1N1 shell on the surface of the M1M2N1 quantum dot cores, obtaining a fourth reaction system containing M1M2N1 / M1N1 quantum dots; Wherein, the dosage of the second metal element M2 precursor is greater than that of the first metal element M2 precursor.

2. The preparation method according to claim 1, wherein The step of mixing the second non-metal element N1 precursor with the third reaction system specifically includes: Add an amine compound to the third reaction system, after reacting for a first period of time, then add the second non-metal element N1 precursor and react for a second period of time; Optionally, the amine compound is a saturated or unsaturated fatty amine with 6 to 36 carbon atoms. Preferably, the amine compound is selected from at least one of oleylamine, n-octylamine, di-n-octylamine, tri-n-octylamine, dodecylamine, tetradecylamine, and hexadecylamine; Optionally, the volume molar ratio of the amine compound to the metal element M1 precursor is (0.5 - 1) mL : (8 - 12) mmol; Optionally, the first period of time is 5 min to 10 min; Optionally, the second period of time is 15 min to 35 min.

3. The preparation method according to claim 1, characterized in that, The step of mixing the metal element M1 precursor, the first metal element M2 precursor, and the solvent specifically includes: Mix the metal element M1 precursor, the first metal element M2 precursor, a coordinating solvent, and a non-coordinating solvent, and then perform vacuum treatment; Optionally, the molar volume ratio of the metal element M1 precursor, the first metal element M2 precursor, the coordinating solvent, and the non-coordinating solvent is (8 - 12) mmol : (0.5 - 1.2) mmol : (24 - 48) mmol : (12 - 15) mL; Optionally, the coordinating solvent is selected from one of C5 - C30 saturated or unsaturated fatty acids; Optionally, the non-coordinating solvent is selected from at least one of C6 - C30 saturated or unsaturated aliphatic hydrocarbons, C6 - C30 aromatic hydrocarbons, nitrogen-containing heterocyclic compounds, and C12 - C22 aromatic ethers; Optionally, the conditions for the vacuum treatment are: at a temperature of 120°C to 140°C, perform vacuum treatment for 60 min to 120 min.

4. The preparation method according to claim 1, wherein The molar ratio of the first metal element M2 precursor to the first non-metal element N1 precursor is (0.5 - 0.8) : 1; And / or, the molar ratio of the second non-metal element N1 precursor to the first non-metal element N1 precursor is (2 - 3) : 1; And / or, the step of mixing the first non-metal element N1 precursor with the first reaction system specifically includes: At a reaction temperature of 280 °C to 320 °C, add the first precursor of the non-metal element N1 to the first reaction system, and then react for 30 min to 60 min; And / or, the step of mixing the second precursor of the metal element M2 with the second reaction system specifically includes: Add the second precursor of the metal element M2 to the second reaction system and react for 5 min to 10 min; And / or, the molar ratio of the second precursor of the metal element M2 to the first precursor of the metal element M2 is (0.05 - 0.1):

1.

5. The preparation method according to claim 1, characterized in that, After obtaining the fourth reaction system containing M1M2N1 / M1N1 quantum dots, it further includes: Mix the third precursor of the metal element M2 and the precursor of the non-metal element N2 with the fourth reaction system to coat the M1N1 shell surface with an M2N2 shell, obtaining a fifth reaction system containing M1M2N1 / M1N1 / M2N2 quantum dots; Mix the single-molecule precursor M3 with the fifth reaction system to coat the M2N2 shell surface with an M1N2 shell, obtaining M1M2N1 / M1N1 / M2N2 / M1N2 quantum dots.

6. The preparation method according to claim 5, characterized in that, The molar ratio of the third precursor of the metal element M2 to the first precursor of the metal element M2 is (1.5 - 5):1; And / or, the molar ratio of the third precursor of the metal element M2 to the precursor of the non-metal element N2 is 1:1; And / or, the addition amount of the single-molecule precursor M3 is 0.5 mmol to 1 mmol; And / or, the metal element M2 in the third precursor of the metal element M2 includes cadmium; And / or, the non-metal element N2 in the precursor of the non-metal element N2 includes at least one of sulfur, arsenic, tellurium, selenium, oxygen, nitrogen, phosphorus, and antimony; And / or, the single-molecule precursor M3 is selected from one of zinc alkyl dithiocarboxylic acid salts and S-TOP.

7. The preparation method according to claim 6, characterized in that, The third precursor of the metal element M2 is selected from at least one of cadmium acetate, cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate, cadmium oxide, cadmium perchlorate, cadmium phosphate, cadmium sulfate, cadmium oleate, cadmium stearate, cadmium laurate, cadmium myristate, and cadmium palmitate; And / or, the precursor of the non-metal element N2 is selected from at least one of S-TOP, S-TBP, S-TPP, S-ODE, S-OA, S-ODA, S-TOA, S-ODPA, S-OLA, S-OCA, S, alkyl thiol, and mercaptopropyl silane; And / or, the step of mixing the third precursor of the metal element M2 and the precursor of the non-metal element N2 with the fourth reaction system specifically includes: at a reaction temperature of 270 °C to 290 °C, add the third precursor of the metal element M2 and the precursor of the non-metal element N2 to the fourth reaction system and react for 20 min to 40 min; And / or, the step of mixing the single-molecule precursor M3 with the fifth reaction system specifically includes: adding the single-molecule precursor M3 to the fifth reaction system and reacting at a temperature of 200°C to 240°C.

8. The preparation method according to any one of claims 1 to 7, characterized in that, The metal element M1 in the metal element M1 precursor includes zinc. Optionally, the metal element M1 precursor is selected from at least one of zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc oleate, zinc stearate, zinc dodecanoate, zinc tetradecanoate, and zinc hexadecanoate. And / or, the metal element M2 in both the metal element M2 first precursor and the metal element M2 second precursor includes cadmium. Optionally, the metal element M2 first precursor and the metal element M2 second precursor are each independently selected from at least one of cadmium acetate, cadmium acetylacetonate, cadmium iodide, cadmium bromide, cadmium chloride, cadmium fluoride, cadmium carbonate, cadmium nitrate, cadmium oxide, cadmium perchlorate, cadmium phosphate, cadmium sulfate, cadmium oleate, cadmium stearate, cadmium dodecanoate, cadmium tetradecanoate, and cadmium hexadecanoate. And / or, the non-metal element N1 in both the non-metal element N1 first precursor and the non-metal element N1 second precursor independently includes at least one of sulfur, arsenic, tellurium, selenium, oxygen, nitrogen, phosphorus, and antimony. Optionally, the non-metal element N1 first precursor and the non-metal element N1 second precursor are each independently selected from at least one of Se-TOP, Se-TBP, Se-TPP, Se-ODE, Se-OA, Se-ODA, Se-TOA, Se-ODPA, Se-OLA, Se-OCA, and Se-DPP.

9. A quantum dot, characterized in that, The quantum dots are prepared by the preparation method according to any one of claims 1 to 8. Optionally, the quantum dot core of the quantum dots is divided into an inner core and an outer core coating the inner core, and the component of the inner core is M1 1-x M2 x N1, and the component of the outer core is M1 y M2 1-y N1, where 0.5 < x < 1, 0.5 < y < 1, and x + y < 1.

10. A light-emitting device, characterized in that, The light-emitting device includes a first electrode, a quantum dot light-emitting layer, and a second electrode which are stacked, and the material of the quantum dot light-emitting layer is the quantum dot according to claim 9.

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