Green ZnSe / ZnSeTe core-shell quantum dot, preparation method thereof and electroluminescent device

Abstract

The invention provides a green ZnSe / ZnSeTe core-shell quantum dot, a preparation method thereof and an electroluminescent device.The preparation method comprises the steps that S1, a ZnSe inner core is prepared, specifically, a selenium precursor and a zinc precursor are added into a reaction system, and the ZnSe inner core is generated through a reaction; s2, preparing a green-light ZnSe / ZnSeTe core body: adding an activity improving agent, a selenium precursor, a tellurium precursor and a zinc precursor into S1, and reacting to generate a ZnSeTe outer core coating the ZnSe inner core so as to form the green-light ZnSe / ZnSeTe core body; the green light ZnSe / ZnSeTe core body is passivated; s3, preparing a transition layer: adding a zinc precursor, a magnesium precursor and a selenium precursor into S2, and reacting to generate a ZnMgSe transition layer coating the green ZnSe / ZnSeTe nuclear body; and S4, preparing a shell layer: adding a zinc precursor and a sulfur precursor into S3, and reacting to generate a ZnS shell layer coating the ZnMgSe transition layer.

Description

Technical Field

[0001] This application belongs to the field of quantum dot technology, specifically relating to a green ZnSe / ZnSeTe core-shell quantum dot, its preparation method, and an electroluminescent device. Background Technology

[0002] Quantum dots, also known as semiconductor nanocrystals, are a novel type of semiconductor nanomaterial with sizes ranging from 1 to 10 nm. Due to quantum size and dielectric confinement effects, they possess unique photoluminescence (PL) and electroluminescence (EL) properties. Compared to traditional organic fluorescent dyes, quantum dots exhibit superior optical properties such as high quantum yield, high photochemical stability, resistance to photolysis, broad excitation and narrow emission range, high color purity, and the ability to adjust the emitted color by controlling the quantum dot size. These characteristics make them promising candidates for applications in the display technology field.

[0003] Currently, cadmium-based quantum dots have gradually entered commercialization due to their advantages such as high quantum efficiency, small half-width, strong blue light absorption, and good stability. However, due to the presence of the heavy metal cadmium, these quantum dots no longer meet the increasingly important environmental protection requirements, making the development of new cadmium-free quantum dots extremely urgent. Environmentally friendly quantum dots include InP-based, carbon dots, perovskites, AgS, PbS, ZnSe, and ZnSeTe. However, compared with traditional cadmium-based quantum dots, existing environmentally friendly quantum dots have their own shortcomings in many aspects, such as large half-width, poor performance, and poor stability, which limit their applications.

[0004] ZnSeTe quantum dots have enormous potential applications in ultra-high-definition displays such as light-emitting diodes. Compared to blue ZnSeTe quantum dots, green ZnSeTe quantum dots are more difficult to synthesize and have poorer optical properties, especially in electroluminescent devices, where improvements are urgently needed in terms of EQE, particularly brightness and lifespan.

[0005] In view of this, this application provides a green ZnSe / ZnSeTe core-shell quantum dot and its preparation method, as well as an electroluminescent device, which improves optical performance and significantly enhances the device's EQE, brightness, and lifetime. Summary of the Invention

[0006] The purpose of this application is to provide a green ZnSe / ZnSeTe core-shell quantum dot and its preparation method, as well as an electroluminescent device, which improves optical performance and significantly enhances the device's EQE, brightness, and lifetime.

[0007] A first aspect of this application provides a method for preparing green ZnSe / ZnSeTe core-shell quantum dots, the method comprising the steps of:

[0008] S1, Preparation of ZnSe core: Selenium precursor and zinc precursor are added to the reaction system to generate ZnSe core;

[0009] S2, Preparation of green-light ZnSe / ZnSeTe core: Add an activity enhancer, selenium precursor, tellurium precursor, and zinc precursor to S1, and react to generate a ZnSeTe outer core coating the ZnSe core, forming a green-light ZnSe / ZnSeTe core; passivate the green-light ZnSe / ZnSeTe core;

[0010] S3, Preparation of the transition layer: Add zinc precursor, magnesium precursor, and selenium precursor to S2, and react to generate a coating layer for the green light.

[0011] ZnMgSe transition layer of ZnSe / ZnSeTe core;

[0012] S4, Preparation of the outer shell layer: Add zinc precursor and sulfur precursor to S3 to react and generate a ZnS outer shell layer that coats the ZnMgSe transition layer.

[0013] In some embodiments, in step S1, the molar ratio of the added selenium precursor to the zinc precursor is (0.5-1.2):1.

[0014] Preferably, in step S1, the molar ratio of the added selenium precursor to the zinc precursor is (0.6-1):1.

[0015] Furthermore, the selenium precursor includes at least one of selenium-diphenylphosphine (Se-DPP), selenium-trioctylphosphine (Se-TOP), selenium-tributylphosphine (Se-TBP), or selenium-triphenylphosphine (Se-TPP).

[0016] Furthermore, the zinc precursor includes at least one of the following: dimethyl zinc, diethyl zinc, zinc acetate, zinc acetate, zinc carbonate, zinc acetylacetone, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc cyanide, zinc nitrate, zinc oxide, zinc oleate, zinc peroxide, zinc perchlorate, zinc palmitate, zinc laurate, zinc hexanoate, and zinc sulfate.

[0017] Furthermore, the reaction system temperature is maintained at 180-220℃, and selenium precursor and zinc precursor are added to generate ZnSe core.

[0018] In some embodiments, in step S2, the activity enhancer is used to improve the reactivity of the selenium precursor and the tellurium precursor.

[0019] Furthermore, the activity enhancer includes at least one of diphenylphosphine (DPP), triphenylphosphine, tributylphosphine (TBP), and tripentylphosphine.

[0020] In some embodiments, in step S2, the molar ratio of the activity enhancer to the selenium precursor is (0.5-2):1; and the molar ratio of the selenium precursor, tellurium precursor, and zinc precursor is (1-5):1:(7-12).

[0021] Preferably, in step S2, the molar ratio of the activity enhancer to the selenium precursor is (0.8-1.5):1, and the molar ratio of the selenium precursor, tellurium precursor, and zinc precursor is (1-4):1:(7-11).

[0022] Furthermore, the tellurium precursor includes at least one of tellurium-trioctylphosphine (Te-TOP), tellurium-diphenylphosphine (Te-DPP), tellurium-tributylphosphine (Te-TBP), or tellurium-triphenylphosphine (Te-TPP).

[0023] Furthermore, at 250-270℃, an activity enhancer, selenium precursor, tellurium precursor, and zinc precursor are added to S1 to form a green ZnSe / ZnSeTe nucleus.

[0024] In some embodiments, after generating the green ZnSe / ZnSeTe core in step S2, an etchant solution is added to etch the green ZnSe / ZnSeTe core.

[0025] Furthermore, the etching solution is a fluoride-polar aprotic solvent; the fluoride includes at least one of: hydrofluoric acid, phenylcarbonyl fluoride, sodium fluoride, lead tetrafluoride, aluminum fluoride, tetrabutylammonium fluoride, or cesium fluoride; the polar aprotic solvent has a boiling point ≤85℃, and the polar aprotic solvent includes at least one of: acetone, methyl ethyl ketone, tetrahydrofuran, dichloromethane, or ethyl acetate.

[0026] Furthermore, in step S2, after the green ZnSe / ZnSeTe core is generated, an etchant solution is added for the first time, and the temperature is increased by gradient. An etchant solution is added for the second time to etch the green ZnSe / ZnSeTe core.

[0027] Furthermore, in the fluoride-polar aprotic solvent, the concentration of fluoride is 1-10%.

[0028] In some embodiments, in step S3, the molar ratio of the zinc precursor, magnesium precursor, and selenium precursor added is (2-6):1:(1-5).

[0029] Preferably, in step S3, the molar ratio of the zinc precursor, magnesium precursor, and selenium precursor added is (3-4.5):1:(2-4).

[0030] In some embodiments, the magnesium precursor comprises magnesium carboxylate. The magnesium carboxylate includes at least one of magnesium acetate, magnesium propionate, magnesium stearate, magnesium citrate, and magnesium oleate.

[0031] Furthermore, at 300-320℃, zinc and magnesium precursors are added to S2, and then selenium precursor is added dropwise at a rate of 2-6 mL / h to form a ZnMgSe transition layer.

[0032] In some embodiments, in step S4, the molar ratio of the sulfur precursor to the zinc precursor is 1:(0.5-4).

[0033] Preferably, in step S4, the molar ratio of the added sulfur precursor to the added zinc precursor is 1:(0.8-2).

[0034] In some embodiments, the sulfur precursor includes at least one of the following: hexamethylenetetramine, octanethiol, decanethiol, dodecanethiol, hexadecylthiol, mercaptopropylsilane, thio-trioctylphosphine (S-TOP), thio-tributylphosphine (S-TBP), thio-triphenylphosphine (S-TPP), thio-trioctylamine (S-TOA), bis(trimethylsilyl)sulfur, ammonium sulfide, and sodium sulfide.

[0035] Furthermore, zinc precursor is added dropwise at 300-320℃ at a rate of 8-14 mL / h, the temperature is raised to 330-350℃, and sulfur precursor is added dropwise at a rate of 2-6 mL / h to form a ZnS outer shell layer.

[0036] In some embodiments, the preparation method further includes the step of: S5, adding the amine-containing zinc precursor and sulfur precursor to S4 to increase the thickness of the ZnS outer shell layer.

[0037] Furthermore, the zinc-containing amine precursor includes at least one of zinc oleamide (Zn / OlAm), zinc n-octylamine, zinc tetradecylamine, and zinc hexadecylamine.

[0038] Furthermore, in step S5, the molar ratio of the zinc amine precursor to the sulfur precursor is (0.5-3):1.

[0039] Preferably, in step S5, the molar ratio of the zinc amine precursor to the sulfur precursor is (0.8-1.5):1.

[0040] Furthermore, in step S5, at 230-250°C, the amine-containing zinc precursor is added dropwise to S4 at a rate of 12-18 mL / h, while the sulfur precursor is added dropwise at a rate of 2-7 mL / h, to increase the thickness of the ZnS outer shell layer.

[0041] A second aspect of this application provides a green-emitting ZnSe / ZnSeTe core-shell quantum dot, wherein the green-emitting ZnSe / ZnSeTe core-shell quantum dot comprises, from the inside out: a ZnSe core, a ZnSeTe outer core enclosing the ZnSe core, and a green-emitting outer core.

[0042] The ZnMgSe transition layer of the ZnSe / ZnSeTe core, and the ZnS outer shell layer covering the ZnMgSe transition layer.

[0043] In some embodiments, the maximum emission peak wavelength of the green ZnSe / ZnSeTe core-shell quantum dots is 500-540 nm. Preferably, the maximum emission peak wavelength of the green ZnSe / ZnSeTe core-shell quantum dots is 515-535 nm. More preferably, the maximum emission peak wavelength of the green ZnSe / ZnSeTe core-shell quantum dots is 520-530 nm.

[0044] A third aspect of this application provides an electroluminescent device comprising the aforementioned green ZnSe / ZnSeTe core-shell quantum dots.

[0045] The green ZnSe / ZnSeTe core-shell quantum dots and their preparation method disclosed in this application have at least the following advantages compared with existing technologies:

[0046] (1) This application uses green ZnSe / ZnSeTe as the core and ZnSeMg as the inner shell (i.e., transition layer) to form quantum dots, which helps to alleviate the stress difference between the core and shell and the shell layer, and releases stress in both directions (to the inner ZnSe core and to the outer ZnSeMg inner shell), thereby reducing the generation of defects at the core-shell interface, improving the stability of quantum dots, and thus increasing the performance of electroluminescent devices.

[0047] (2) The green ZnSe / ZnSeTe core is etched by gradient heating and etched twice in succession, which effectively prevents the reintroduction of impurity defects, oxide defects and the like during the core-shell growth process.

[0048] (3) Based on the green light ZnSe / ZnSeTe as the core and ZnS as the outer shell, this application uses ZnMgSe as the intermediate shell (i.e., the transition layer) to alleviate the potential difference at the core-shell interface, smooth the band gradient, and passivate the surface defects of the shell by the joint action of Mg / Zn ions, thereby improving the stability and luminescence performance of quantum dots.

[0049] (4) Using the ZnSe / ZnSeTe / ZnMgSe / ZnS quantum dots of this application as the light-emitting layer of the electroluminescent device can better realize carrier recombination and improve recombination efficiency, thereby achieving higher photon output, with a maximum brightness of L@6V>80000cd / m 2The device lifetime T50@1000nit>400h solves the problems of low brightness and poor lifetime of existing green ZnSeTe quantum dots. Detailed Implementation

[0050] The following embodiments are described to aid in understanding this application. These embodiments are not, and should not be, construed in any way as limiting the scope of protection of this application.

[0051] Unless otherwise defined, all terms (including technical and scientific terms) in this specification may be defined as commonly understood by one of ordinary skill in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having meanings consistent with their meanings in the context of this disclosure and the relevant field, and will be interpreted in a non-idealized or overly formal sense unless clearly defined herein.

[0052] As used herein, the term "at least one," when modifying the entire list of elements without modifying any individual elements of the list before or after it, shall not be construed as limiting "one." "Or" means "and / or." The terms "comprising" and "including," when used in this specification, indicate the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or collections thereof. Therefore, the above wording shall be understood to mean including the stated elements, but not excluding any other elements. The term "and / or" includes any and all combinations of one or more of the associated listed items. The term "multiple" refers to two or more. The term "connected" refers to a direct or indirect connection. The terms "first," "second," "third," etc., may be used herein to describe and distinguish different elements, components, regions, layers, and / or portions, but these elements, components, regions, layers, and / or portions should not be limited by these terms.

[0053] A first aspect of this application provides a method for preparing green ZnSe / ZnSeTe core-shell quantum dots, the method comprising the steps of:

[0054] S1, Preparation of ZnSe core: Selenium precursor and zinc precursor are added to the reaction system to generate ZnSe core;

[0055] S2, Preparation of green-light ZnSe / ZnSeTe core: Add an activity enhancer, selenium precursor, tellurium precursor, and zinc precursor to S1, and react to generate a ZnSeTe outer core coating the ZnSe core, forming a green-light ZnSe / ZnSeTe core; passivate the green-light ZnSe / ZnSeTe core;

[0056] S3, Preparation of the transition layer: Add zinc precursor, magnesium precursor, and selenium precursor to S2, and react to generate a coating layer for the green light.

[0057] ZnMgSe transition layer of ZnSe / ZnSeTe core;

[0058] S4, Preparation of the outer shell layer: Add zinc precursor and sulfur precursor to S3 to react and generate a ZnS outer shell layer that coats the ZnMgSe transition layer.

[0059] In some embodiments, in step S1, the molar ratio of the selenium precursor to the zinc precursor is (0.5-1.2):1, for example, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, or 1.2:1, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0060] Preferably, in step S1, the molar ratio of the added selenium precursor to the zinc precursor is (0.6-1):1.

[0061] Furthermore, the selenium precursor includes at least one of selenium-diphenylphosphine (Se-DPP), selenium-trioctylphosphine (Se-TOP), selenium-tributylphosphine (Se-TBP), or selenium-triphenylphosphine (Se-TPP).

[0062] Furthermore, the zinc precursor includes at least one of the following: dimethyl zinc, diethyl zinc, zinc acetate, zinc acetate, zinc carbonate, zinc acetylacetone, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc cyanide, zinc nitrate, zinc oxide, zinc oleate, zinc peroxide, zinc perchlorate, zinc palmitate, zinc laurate, zinc hexanoate, and zinc sulfate. In addition to these listed zinc precursors, other common similar zinc precursors are also within the scope of protection of this application.

[0063] Furthermore, the reaction system temperature is maintained at 180-220℃, and selenium precursor and zinc precursor are added to generate ZnSe core.

[0064] The reaction system temperature is maintained at 180-220℃. Selenium precursor and zinc precursor are added sequentially in one step, and the reaction is carried out for 20-40 minutes to generate ZnSe cores. For example, 180℃, 185℃, 190℃, 195℃, 200℃, 205℃, 210℃, 215℃, or 220℃, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable. For example, 20 minutes, 25 minutes, 30 minutes, 35 minutes, or 40 minutes, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0065] Add fatty acids, oily ligands, and organic solvents, evacuate, introduce inert gas for protection, and then heat to 180-220℃ to form the reaction system.

[0066] First, add fatty acids, oily ligands, and organic solvents. Evacuate the system and heat to 100-140°C (e.g., 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, or 140°C, but not limited to the listed values; other unlisted values ​​within the above range also apply.). Maintain this vacuum for 1-4 hours (e.g., 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours, but not limited to the listed values; other unlisted values ​​within the above range also apply.). Then, introduce an inert gas for protection and heat to 180-220°C (e.g., 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, or 220°C, but not limited to the listed values; other unlisted values ​​within the above range also apply) to form the reaction system.

[0067] The fatty acids include at least one of palmitic acid (PA), oleic acid, stearic acid, lauric acid, and undecenoic acid.

[0068] The oily ligands include at least one of oleylamine (OlAm), n-octylamine, tetradecylamine, and hexadecylamine.

[0069] The organic solvent includes at least one of the following: trioctylamine (TOA), hexadecylamine, dioctylamine, hexadecane, octadecane, squalane, phenyldodecane, phenyltetradecane, and phenylhexadecane.

[0070] In some embodiments, in step S2, the activity enhancer is used to improve the reactivity of the selenium precursor and the tellurium precursor.

[0071] Furthermore, the activity enhancer includes at least one of diphenylphosphine (DPP), triphenylphosphine, tributylphosphine (TBP), and tripentylphosphine.

[0072] In some embodiments, in step S2, the molar ratio of the activity enhancer to the selenium precursor is (0.5-2):1, for example, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, or 2:1, but not limited to the listed values. Other unlisted values ​​also apply; the molar ratio of the selenium precursor, tellurium precursor, and zinc precursor is (1-5):1:(7-12), for example, 1:1:7, 1.5:1:8, 2:1:9, 2.5:1:9, 3:1:10, 3.5:1:10, 4:1:10.5, 4:1:11, 4.5:1:11.5, or 5:1:12, but is not limited to the listed values, and other unlisted values ​​within the above range also apply.

[0073] Preferably, in step S2, the molar ratio of the activity enhancer to the selenium precursor is (0.8-1.5):1, and the molar ratio of the selenium precursor, tellurium precursor, and zinc precursor is (1-4):1:(7-11).

[0074] Furthermore, the tellurium precursor includes at least one of tellurium-trioctylphosphine (Te-TOP), tellurium-diphenylphosphine (Te-DPP), tellurium-tributylphosphine (Te-TBP), or tellurium-triphenylphosphine (Te-TPP).

[0075] Furthermore, at 250-270℃, an activity enhancer, selenium precursor, tellurium precursor, and zinc precursor are added to S1 to form a green ZnSe / ZnSeTe nucleus.

[0076] At 250-270℃ (e.g., 250℃, 255℃, 260℃, 265℃, or 270℃, but not limited to the listed values, and other unlisted values ​​within the above range are also applicable), the activity enhancer, selenium precursor, tellurium precursor, and zinc precursor are added sequentially to S1 in one step, and the reaction is carried out for 20-40 min (e.g., 20 min, 25 min, 30 min, 35 min, or 40 min, but not limited to the listed values, and other unlisted values ​​within the above range are also applicable) to form a green ZnSe / ZnSeTe nucleus.

[0077] This application uses green ZnSe / ZnSeTe as the core and ZnSeMg as the inner shell (i.e., transition layer) to form quantum dots, which helps to alleviate the stress difference between the core and shell and the shell layer, and releases stress in both directions (towards the inner ZnSe core and the outer ZnSeMg inner shell), thereby reducing the generation of core-shell interface defects, improving the stability of quantum dots, and thus increasing the performance of electroluminescent devices.

[0078] In some embodiments, after generating the green ZnSe / ZnSeTe core in step S2, an etchant solution is added to etch the green ZnSe / ZnSeTe core.

[0079] Furthermore, the etching solution is a fluoride-polar aprotic solvent; the fluoride includes at least one of: hydrofluoric acid, phenylcarbonyl fluoride, sodium fluoride, lead tetrafluoride, aluminum fluoride, tetrabutylammonium fluoride, or cesium fluoride; the polar aprotic solvent has a boiling point ≤85℃, and the polar aprotic solvent includes at least one of: acetone, methyl ethyl ketone, tetrahydrofuran, dichloromethane, or ethyl acetate.

[0080] Furthermore, in step S2, after the green ZnSe / ZnSeTe core is generated, an etchant solution is added for the first time, and the temperature is increased by gradient. An etchant solution is added for the second time to etch the green ZnSe / ZnSeTe core.

[0081] In step S2, after the green ZnSe / ZnSeTe core is generated, the temperature is maintained at 250-270℃ (e.g., 250℃, 255℃, 260℃, 265℃, or 270℃, but not limited to the listed values; other unlisted values ​​within the above range are also applicable). The etchant solution is added for the first time and reacted for 1-5 minutes. The temperature is then gradually increased to 290-310℃ (e.g., 290℃, 295℃, 300℃, 305℃, or 310℃, but not limited to the listed values; other unlisted values ​​within the above range are also applicable). The etchant solution is added for the second time and reacted for 1-5 minutes to etch the green ZnSe / ZnSeTe core.

[0082] Furthermore, in the fluoride-polar aprotic solvent, the concentration of fluoride is 1-10%, for example 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, but not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0083] This application etches a green ZnSe / ZnSeTe core using a gradient temperature method, etching twice consecutively to effectively prevent the reintroduction of impurity defects and oxide defects during core-shell growth.

[0084] In some embodiments, in step S3, the molar ratio of the zinc precursor, magnesium precursor, and selenium precursor added is (2-6):1:(1-5), for example, 2:1:1, 2.5:1:1.5, 3:1:2, 3.5:1:2.5, 4:1:3, 4.5:1:3.5, 5:1:4, 5.5:1:4.5, or 6:1:5, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0085] Preferably, in step S3, the molar ratio of the zinc precursor, magnesium precursor, and selenium precursor added is (3-4.5):1:(2-4).

[0086] In some embodiments, the magnesium precursor comprises magnesium carboxylate. The magnesium carboxylate includes at least one of magnesium acetate, magnesium propionate, magnesium stearate, magnesium citrate, and magnesium oleate.

[0087] Furthermore, at 300-320℃ (e.g., 300℃, 305℃, 310℃, 315℃, or 320℃, but not limited to the listed values, and other unlisted values ​​within the above range are also applicable), zinc precursor and magnesium precursor are added to S2, and then selenium precursor is added dropwise at a rate of 2-6 mL / h (e.g., 2 mL / h, 2.5 mL / h, 3 mL / h, 3.5 mL / h, 4 mL / h, 4.5 mL / h, 5 mL / h, 5.5 mL / h, or 6 mL / h, but not limited to the listed values, and other unlisted values ​​within the above range are also applicable) to form a ZnMgSe transition layer.

[0088] This application uses ZnSe / ZnSeTe as the core and ZnS as the outer shell, with ZnMgSe as the intermediate shell (i.e., transition layer) to reduce the surface potential difference and improve the stability and luminescence performance of the quantum dots. Since the band gap of ternary ZnSeTe alloy quantum dots is modulated by the Se / Te ratio, the band gap narrows further when achieving green light emission from ZnSeTe, increasing the interfacial potential difference between the ZnSeTe core and the traditional ZnSe intermediate shell. This leads to interfacial defects and vacancies, resulting in a decrease in shell growth quality. To address this, this application designs a green-emitting ZnSe / ZnSeTe core and ZnMgSe as the intermediate shell to alleviate the core-shell interfacial potential difference, smooth the band gradient, and allow Mg / Zn ions to passivate surface defects in the shell, thereby increasing the stability of the quantum dots.

[0089] In some embodiments, in step S4, the molar ratio of the sulfur precursor to the zinc precursor is 1:(0.5-4), such as 1:0.5, 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5, or 1:4, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0090] Preferably, in step S4, the molar ratio of the added sulfur precursor to the added zinc precursor is 1:(0.8-2).

[0091] In some embodiments, the sulfur precursor includes at least one of the following: hexamethylenetetramine, octanethiol, decanethiol, dodecathiol, hexadecylthiol, mercaptopropylsilane, thio-trioctylphosphine (S-TOP), thio-tributylphosphine (S-TBP), thio-triphenylphosphine (S-TPP), thio-trioctylamine (S-TOA), bis(trimethylsilyl)sulfur, ammonium sulfide, and sodium sulfide. In addition to these listed sulfur precursors, other common sulfur precursors for synthesizing quantum dots are also within the scope of this application.

[0092] Furthermore, at 300-320℃ (e.g., 300℃, 305℃, 310℃, 315℃, or 320℃, but not limited to the listed values; other unlisted values ​​within the above range also apply), add the zinc precursor dropwise at a rate of 8-14 mL / h (e.g., 8 mL / h, 9 mL / h, 10 mL / h, 11 mL / h, 12 mL / h, 13 mL / h, or 14 mL / h, but not limited to the listed values; other unlisted values ​​within the above range also apply). The same applies), heat to 330-350℃ (e.g., 330℃, 335℃, 340℃, 345℃, or 350℃, but not limited to the listed values, and other unlisted values ​​within the above range also apply), and then add sulfur precursor dropwise at a rate of 2-6 mL / h (e.g., 2 mL / h, 3 mL / h, 4 mL / h, 5 mL / h, or 6 mL / h, but not limited to the listed values, and other unlisted values ​​within the above range also apply) to form a ZnS outer shell layer.

[0093] In some embodiments, the preparation method further includes the step of: S5, adding the amine-containing zinc precursor and sulfur precursor to S4 to increase the thickness of the ZnS outer shell layer.

[0094] Furthermore, the zinc-containing amine precursor includes at least one of zinc oleamide (Zn / OlAm), zinc n-octylamine, zinc tetradecylamine, and zinc hexadecylamine.

[0095] Furthermore, in step S5, the molar ratio of the added amine-containing zinc precursor to the sulfur precursor is (0.5-3):1, for example, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, or 3:1, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0096] Preferably, in step S5, the molar ratio of the zinc amine precursor to the sulfur precursor is (0.8-1.5):1.

[0097] Furthermore, in step S5, at 230-250°C (e.g., 230°C, 235°C, 240°C, 245°C, or 250°C, but not limited to the listed values, and other unlisted values ​​within the above range also apply), the amine-containing zinc precursor is added dropwise to S4 at a rate of 12-18 mL / h (e.g., 12 mL / h, 13 mL / h, 14 mL / h, 15 mL / h, 16 mL / h, 17 mL / h, or 18 mL / h, but not limited to the listed values, and other unlisted values ​​within the above range also apply), while the sulfur precursor is added dropwise at a rate of 2-7 mL / h (e.g., 2 mL / h, 3 mL / h, 4 mL / h, 5 mL / h, 6 mL / h, or 7 mL / h, but not limited to the listed values, and other unlisted values ​​within the above range also apply), to increase the thickness of the ZnS outer shell layer.

[0098] Using the ZnSe / ZnSeTe / ZnMgSe / ZnS quantum dots of this application as the emitting layer of an electroluminescent device can better achieve carrier recombination and improve recombination efficiency, thereby achieving higher photon output, with a maximum brightness of L@6V > 80000 cd / m². 2 The device lifetime T50@1000nit>400h solves the problems of low brightness and poor lifetime of existing green ZnSeTe quantum dots.

[0099] A second aspect of this application provides a green-emitting ZnSe / ZnSeTe core-shell quantum dot, wherein the green-emitting ZnSe / ZnSeTe core-shell quantum dot comprises, from the inside out: a ZnSe core, a ZnSeTe outer core enclosing the ZnSe core, and a green-emitting outer core.

[0100] The ZnMgSe transition layer of the ZnSe / ZnSeTe core, and the ZnS outer shell layer covering the ZnMgSe transition layer.

[0101] In some embodiments, the maximum emission peak wavelength of the green ZnSe / ZnSeTe core-shell quantum dots is 500-540 nm. Preferably, the maximum emission peak wavelength of the green ZnSe / ZnSeTe core-shell quantum dots is 515-535 nm. More preferably, the maximum emission peak wavelength of the green ZnSe / ZnSeTe core-shell quantum dots is 520-530 nm.

[0102] A third aspect of this application provides an electroluminescent device comprising the aforementioned green ZnSe / ZnSeTe core-shell quantum dots.

[0103] In addition to having the core-shell quantum dot film described above, the display device may also include structures known to those skilled in the art, i.e., the present invention includes a display device capable of using the core-shell quantum dot film of the present invention.

[0104] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific use. The conditions not specified are conventional conditions in the industry.

[0105] Example 1:

[0106] Preparation of ZnSe kernels:

[0107] In a 100 mL three-necked flask, 0.5 g palmitic acid (PA, 2 mmol), 3 mL oleylamine (OlAm), and 8 mL trioctylamine (TOA) were rapidly added in one go. The flask was then evacuated and heated to 120 °C, maintaining this vacuum for 2 hours. Ar was then introduced, and the reaction temperature was set to 200 °C. Once the temperature reached 200 °C, 0.4 mL selenium-trioctylphosphine (Se-TOP, 2 mol / L) and 1 mL diethylzinc (DEZ, 1 mol / L) were rapidly added sequentially, and the reaction was allowed to proceed for 30 minutes.

[0108] Preparation of green-light ZnSe / ZnSeTe cores:

[0109] The temperature was raised to 260℃, and 0.5 mL of diphenylphosphine (DPP), 0.24 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L), 1.6 mL of tellurium-trioctylphosphine (Te-TOP, 0.1 mol / L), and 1.4 mL of diethylzinc (DEZ, 1 mol / L) were rapidly injected into a three-necked flask in sequence. The reaction was allowed to proceed for 30 min.

[0110] Maintain the temperature at 260°C, add 0.5 mL of hydrofluoric acid-acetone (2% HF, 98% acetone) to the three-necked flask, and react for 2 min; raise the temperature to 300°C, add another 0.5 mL of hydrofluoric acid-acetone (2% HF, 98% acetone), and react for 2 min.

[0111] Preparation of ZnMgSe transition layer:

[0112] The temperature was raised to 310℃, and 10 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) and 4 mL of magnesium oleate (Mg(OA)2, 0.5 mol / L) were added to the three-necked flask. The temperature was raised to 310℃ again, and 3 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L) was added dropwise at a rate of 3 mL / h using a syringe pump.

[0113] Preparation of ZnS outer shell:

[0114] Add 10 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) to a three-necked flask, heat to 340 °C, and use a syringe pump to add 3 mL of thio-trioctylphosphine (S-TOP, 2 mol / L) dropwise at a rate of 3 mL / h.

[0115] Cool to 240℃, and add 15 mL of zinc oleamide (Zn / OlAm, 0.4 mol / L) dropwise to a three-necked flask at a rate of 15 mL / h using a syringe pump. Simultaneously, add 4 mL of thio-trioctylphosphine (S-TOP, 2 mol / L) dropwise at a rate of 4 mL / h using a syringe pump. After the reaction is complete, stop heating and allow to cool to room temperature. Then, extract and purify the green-glossy ZnSe / ZnSeTe / ZnMgSe / ZnS quantum dots for later use.

[0116] Example 2:

[0117] Preparation of ZnSe kernels:

[0118] In a 100 mL three-necked flask, 0.51 g palmitic acid (PA, 2 mmol), 3 mL oleylamine (OlAm), and 8 mL trioctylamine (TOA) were rapidly added in one go. The flask was then evacuated and heated to 120 °C, maintaining this vacuum for 2 hours. Ar was then introduced, and the reaction temperature was set to 200 °C. Once the temperature reached 200 °C, 0.4 mL selenium-diphenylphosphine (Se-DPP, 2 mol / L) and 1 mL diethylzinc (DEZ, 1 mol / L) were rapidly added sequentially, and the reaction was allowed to proceed for 30 minutes.

[0119] Preparation of green-light ZnSe / ZnSeTe cores:

[0120] The temperature was raised to 260℃, and 0.5 mL of diphenylphosphine (DPP), 0.25 mL of selenium-diphenylphosphine (Se-DPP, 2 mol / L), 1.5 mL of tellurium-diphenylphosphine (Te-DPP, 0.1 mol / L), and 1.4 mL of diethylzinc (DEZ, 1 mol / L) were rapidly injected into a three-necked flask in sequence. The reaction was allowed to proceed for 30 min.

[0121] Maintain the temperature at 260°C, add 0.5 mL of hydrofluoric acid-acetone (2% HF, 98% acetone) to the three-necked flask, and react for 2 min; raise the temperature to 300°C, add another 0.5 mL of hydrofluoric acid-acetone (2% HF, 98% acetone), and react for 2 min.

[0122] Preparation of ZnMgSe transition layer:

[0123] The temperature was raised to 310℃, and 10 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) and 4 mL of magnesium oleate (Mg(OA)2, 0.5 mol / L) were added to the three-necked flask. The temperature was raised to 310℃ again, and 3.1 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L) was added dropwise at a rate of 4 mL / h using a syringe pump.

[0124] Preparation of ZnS outer shell:

[0125] Add 12 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) to a three-necked flask, heat to 340 °C, and add 4 mL of thio-trioctylphosphine (S-TOP, 2 mol / L) dropwise at a rate of 4 mL / h using a syringe pump.

[0126] Cool to 240℃, and add 15 mL of zinc oleamide (Zn / OlAm, 0.4 mol / L) dropwise to a three-necked flask at a rate of 12 mL / h using a syringe pump. Simultaneously, add 4 mL of thio-trioctylphosphine (S-TOP, 2 mol / L) dropwise at a rate of 3 mL / h using a syringe pump. After the reaction is complete, stop heating and allow to cool to room temperature. Then, extract and purify the green-glossy ZnSe / ZnSeTe / ZnMgSe / ZnS quantum dots for later use. Comparative Example 1:

[0127] Preparation of ZnSeTe core:

[0128] In a 250 mL three-necked flask, rapidly add 1.02 g palmitic acid (PA, 4 mmol), 5 mL oleylamine (OlAm), and 20 mL trioctylamine (TOA), evacuate the flask, and heat to 120 °C, maintaining this vacuum for 2 hours. Then, introduce Ar and set the reaction temperature to 240 °C, beginning the heating process. Once the temperature reaches 240 °C, rapidly add 0.5 mL selenium-trioctylphosphine (Se-TOP, 2 mol / L), 3.5 mL tellurium-trioctylphosphine (Te-TOP, 0.1 mol / L), and 2.5 mL diethylzinc (DEZ, 1 mol / L) sequentially, reacting for 25 minutes. Then, rapidly add 0.1 mL hydrofluoric acid-acetone (10% HF, 90% acetone) to the three-necked flask, reacting for 1 minute.

[0129] Preparation of ZnMgSe / ZnSe transition layer:

[0130] The temperature was raised to 310℃, and 20 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) and 9 mL of magnesium oleate (Mg(OA)2, 0.5 mol / L) were added to the three-necked flask. The temperature was raised to 310℃ again, and 7 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L) was added dropwise at a rate of 3 mL / h using a syringe pump.

[0131] Maintain the temperature at 310°C and quickly add 300 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) to the three-necked flask; once the temperature reaches 310°C again, use a syringe pump to add 5 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L) dropwise at a rate of 5 mL / h.

[0132] Preparation of ZnS outer shell:

[0133] Cool to 250℃, and add 28 mL of zinc oleamide (Zn / OlAm, 0.4 mol / L) dropwise to the reaction system at a rate of 28 mL / h using a syringe pump. At the same time, add 7 mL of thio-trioctylphosphine (S-TOP, 2 mol / L) dropwise to the reaction system at a rate of 7 mL / h using a syringe pump.

[0134] Maintaining the temperature at 250℃, add 8 mL of zinc oleate (Zn / OlAm, 0.4 mol / L) dropwise to the reaction system at a rate of 24 mL / h using a syringe pump, while simultaneously adding 1 mL of dodecanethiol (DDT) dropwise to the reaction system at a rate of 3 mL / h using a syringe pump. After the reaction is complete, stop heating and allow the mixture to cool to room temperature. Then, extract and purify the green-glossy ZnSeTe / ZnMgSe / ZnSe / ZnS quantum dots for later use.

[0135] Comparative Example 2:

[0136] Preparation of ZnSeTe core:

[0137] In a 250 mL three-necked flask, rapidly add 1.02 g palmitic acid (PA, 4 mmol), 5 mL oleylamine (OlAm), and 20 mL trioctylamine (TOA), evacuate the flask, and heat to 120 °C, maintaining this vacuum for 2 hours. Then, introduce Ar and set the reaction temperature to 240 °C, beginning the heating process. Once the temperature reaches 240 °C, rapidly add 0.5 mL selenium-trioctylphosphine (Se-TOP, 2 mol / L), 3.5 mL tellurium-trioctylphosphine (Te-TOP, 0.1 mol / L), and 2.5 mL diethylzinc (DEZ, 1 mol / L) sequentially, reacting for 25 minutes. Then, rapidly add 0.1 mL hydrofluoric acid-acetone (10% HF, 90% acetone) to the three-necked flask, reacting for 1 minute.

[0138] Preparation of ZnSe / ZnMgSe transition layer:

[0139] Heat to 310℃ and quickly add 300 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) to a three-necked flask; when the temperature reaches 310℃ again, use a syringe pump to add 5 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L) dropwise at a rate of 5 mL / h.

[0140] Maintain the temperature at 310°C, add 20 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) and 9 mL of magnesium oleate (Mg(OA)2, 0.5 mol / L) to the three-necked flask, and bring the temperature back to 310°C. Then, use a syringe pump to add 7 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L) dropwise at a rate of 3 mL / h.

[0141] Preparation of ZnS outer shell:

[0142] Cool to 250℃, and add 28 mL of zinc oleamide (Zn / OlAm, 0.4 mol / L) dropwise to the reaction system at a rate of 28 mL / h using a syringe pump. At the same time, add 7 mL of thio-trioctylphosphine (S-TOP, 2 mol / L) dropwise to the reaction system at a rate of 7 mL / h using a syringe pump.

[0143] Maintaining the temperature at 250℃, add 8 mL of zinc oleate (Zn / OlAm, 0.4 mol / L) dropwise to the reaction system at a rate of 24 mL / h using a syringe pump, while simultaneously adding 1 mL of dodecanethiol (DDT) dropwise to the reaction system at a rate of 3 mL / h using a syringe pump. After the reaction is complete, stop heating and allow the mixture to cool to room temperature. Then, extract and purify the green-glossy ZnSeTe / ZnSe / ZnMgSe / ZnS quantum dots for later use.

[0144] Comparative Example 3:

[0145] Preparation of ZnSe kernels:

[0146] In a 100 mL three-necked flask, 0.5 g palmitic acid (PA, 2 mmol), 3 mL oleylamine (OlAm), and 8 mL trioctylamine (TOA) were rapidly added in one batch. The flask was then evacuated and heated to 120 °C, maintaining this vacuum for 2 hours. Ar was then introduced, and the reaction temperature was set to 200 °C. Once the temperature reached 200 °C, 0.4 mL selenium-trioctylphosphine (Se-TOP, 2 mol / L) and 0.9 mL diethylzinc (DEZ, 1 mol / L) were rapidly added sequentially, and the reaction was allowed to proceed for 30 minutes.

[0147] Preparation of green-light ZnSe / ZnSeTe cores:

[0148] The temperature was raised to 260℃, and 0.25 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L), 1.6 mL of tellurium-trioctylphosphine (Te-TOP, 0.1 mol / L), and 1.5 mL of diethylzinc (DEZ, 1 mol / L) were rapidly added sequentially to a three-necked flask in one continuous reaction. The reaction was allowed to proceed for 30 min. Then, 0.1 mL of hydrofluoric acid-acetone (10% HF, 90% acetone) was rapidly added to the three-necked flask, and the reaction was allowed to proceed for 1 min.

[0149] Preparation of ZnSe transition layer:

[0150] Heat to 310℃ and quickly add 300 mL of zinc oleate (Zn(OA)2, 0.71 mol / L) to a three-necked flask; when the temperature reaches 310℃ again, use a syringe pump to add 5 mL of selenium-trioctylphosphine (Se-TOP, 2 mol / L) dropwise at a rate of 5 mL / h.

[0151] Preparation of ZnS outer shell:

[0152] Cool to 250℃, and add 28 mL of zinc oleamide (Zn / OlAm, 0.4 mol / L) dropwise to the reaction system at a rate of 28 mL / h using a syringe pump. At the same time, add 7 mL of thio-trioctylphosphine (S-TOP, 2 mol / L) dropwise to the reaction system at a rate of 7 mL / h using a syringe pump.

[0153] Maintaining the temperature at 250℃, add 8 mL of zinc oleate (Zn / OlAm, 0.4 mol / L) dropwise to the reaction system at a rate of 24 mL / h using a syringe pump, while simultaneously adding 1 mL of dodecanethiol (DDT) dropwise to the reaction system at a rate of 3 mL / h using a syringe pump. After the reaction is complete, stop heating and allow the mixture to cool to room temperature. Then, extract and purify the green-emitting ZnSe / ZnSeTe / ZnSe / ZnS quantum dots for later use.

[0154] Photoluminescence (PL) properties:

[0155] The quantum dots of Examples 1-2 and Comparative Examples 1-3 were measured using a Hatichi F4500 fluorescence spectrophotometer to determine their maximum photoemission wavelength and full width at half maximum (FWHM), and their quantum efficiency (QY) was measured using a fluorescence quantum efficiency meter. The results are shown in Table 1.

[0156] Table 1: Results of photoluminescence performance testing for examples and comparative examples.

[0157]

[0158]

[0159] As shown in Table 1, the green quantum dots of Examples 1-3 have lower FWHM values ​​than those of Comparative Examples 1-3, indicating an improvement in FWHM; and their quantum efficiency QY is significantly better than that of Comparative Examples 1-3.

[0160] Electroluminescence (EL) properties:

[0161] The green quantum dots used in Examples 1-2 and Comparative Examples 1-3 were used to fabricate electroluminescent devices, and the steps are as follows:

[0162] The green quantum dots were mixed with photoresist and spin-coated to form a green quantum dot luminescent layer.

[0163] Provide a flexible substrate with an ITO conductive layer already formed on it;

[0164] A PEDOT:PSS layer, a PF8 layer, and a green quantum dot luminescent layer are sequentially spin-coated onto an ITO conductive layer.

[0165] A ZnO electron transport layer was spin-coated onto a green quantum dot luminescent layer;

[0166] An Al layer is deposited on the ZnO electron transport layer;

[0167] Electroluminescent devices are obtained by encapsulating with encapsulating adhesive.

[0168] The electroluminescent devices prepared in Examples 1-2 and Comparative Examples 1-3 were tested using a Spectra Scan PR-655 instrument. The maximum emission peak wavelength, full width at half maximum (FWHM), maximum external quantum efficiency at 2000 nits (EQE@2000 nits), luminance at 6V (L@6V), and time required for the luminance to decay to 50% of its initial luminance of 1000 nits (T50@1000 nits) were measured. The results are shown in Table 2.

[0169] Table 2: Electroluminescence performance test results of the examples and comparative examples.

[0170]

[0171] As shown in Table 2, the full width at half maximum (FWHM) of the green quantum dots in Examples 1-2 is lower than that in Comparative Examples 1-3, and the maximum external quantum efficiency (EQE) is higher than that in Comparative Examples 1-3. More importantly, the brightness and lifetime of the devices are significantly improved, which is significantly better than that in Comparative Examples 1-3.

[0172] Although this application discloses several aspects and embodiments, other aspects and embodiments will be obvious to those skilled in the art. Various modifications and improvements can be made without departing from the concept of this application, and these all fall within the scope of protection of this application. The various aspects and embodiments disclosed in this application are for illustrative purposes only and are not intended to limit this application. The actual scope of protection of this application is determined by the claims.

Claims

1. A method for preparing green ZnSe / ZnSeTe core-shell quantum dots, characterized in that, The preparation method includes the following steps: S1, Preparation of ZnSe core: Selenium precursor and zinc precursor are added to the reaction system to generate ZnSe core; S2, Preparation of green-light ZnSe / ZnSeTe core: Add an activity enhancer, selenium precursor, tellurium precursor, and zinc precursor to S1, and react to generate a ZnSeTe outer core coating the ZnSe core, forming a green-light ZnSe / ZnSeTe core; passivate the green-light ZnSe / ZnSeTe core; S3, Preparation of transition layer: Add zinc precursor, magnesium precursor and selenium precursor to S2, and react to generate ZnMgSe transition layer covering the green ZnSe / ZnSeTe core; S4, Preparation of the outer shell layer: Add zinc precursor and sulfur precursor to S3 to react and generate a ZnS outer shell layer that coats the ZnMgSe transition layer.

2. The method for preparing green ZnSe / ZnSeTe core-shell quantum dots as described in claim 1, characterized in that, In step S1, one or more features selected from the group consisting of: (1) The molar ratio of the added selenium precursor to zinc precursor is (0.5-1.2):1; (2) The selenium precursor includes at least one of selenium-diphenylphosphine, selenium-trioctylphosphine, selenium-tributylphosphine, or selenium-triphenylphosphine; (3) The zinc precursor includes at least one of the following: dimethyl zinc, diethyl zinc, zinc acetate, zinc acetate, zinc carbonate, zinc acetylacetone, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc cyanide, zinc nitrate, zinc oxide, zinc oleate, zinc peroxide, zinc perchlorate, zinc palmitate, zinc laurate, zinc hexanoate, and zinc sulfate; (4) The reaction system temperature is maintained at 180-220℃. Selenium precursor and zinc precursor are added to generate ZnSe core.

3. The method for preparing green ZnSe / ZnSeTe core-shell quantum dots as described in claim 1, characterized in that, In step S2, one or more features selected from the group consisting of: (1) The activity enhancer is used to improve the reactivity of the selenium precursor and the tellurium precursor; the activity enhancer includes at least one of diphenylphosphine, triphenylphosphine, tributylphosphine, and tripentylphosphine; (2) The molar ratio of the activity enhancer to the selenium precursor is (0.5-2):1; the molar ratio of the selenium precursor, tellurium precursor, and zinc precursor is (1-5):1:(7-12); (3) The tellurium precursor includes at least one of tellurium-trioctylphosphine, tellurium-diphenylphosphine, tellurium-tributylphosphine, or tellurium-triphenylphosphine; (4) At 250-270℃, an activity enhancer, selenium precursor, tellurium precursor and zinc precursor are added to S1 to form a green ZnSe / ZnSeTe nucleus.

4. The method for preparing green ZnSe / ZnSeTe core-shell quantum dots as described in claim 1, characterized in that, In step S2, after the green ZnSe / ZnSeTe core is generated, an etchant solution is added to etch the green ZnSe / ZnSeTe core; the etchant solution is a fluoride-polar aprotic solvent.

5. The method for preparing green ZnSe / ZnSeTe core-shell quantum dots as described in claim 4, characterized in that, Includes one or more features selected from the following group: (1) The fluoride includes at least one of hydrofluoric acid, phenylcarbonyl fluoride, sodium fluoride, lead tetrafluoride, aluminum fluoride, tetrabutylammonium fluoride, or cesium fluoride; the polar aprotic solvent has a boiling point ≤85℃, and the polar aprotic solvent includes at least one of acetone, methyl ethyl ketone, tetrahydrofuran, dichloromethane, or ethyl acetate; (2) After generating the green ZnSe / ZnSeTe core, an etchant solution is added for the first time, and the temperature is increased in a gradient. An etchant solution is added for the second time to etch the green ZnSe / ZnSeTe core. (3) In the fluoride-polar aprotic solvent, the concentration of fluoride is 1-10%.

6. The method for preparing green ZnSe / ZnSeTe core-shell quantum dots as described in claim 1, characterized in that, In step S3, one or more features selected from the group consisting of: (1) The molar ratio of the zinc precursor, magnesium precursor and selenium precursor added is (2-6):1:(1-5); (2) The magnesium precursor includes: magnesium carboxylate; (3) At 300-320℃, zinc precursor and magnesium precursor are added to S2, and then selenium precursor is added dropwise at a rate of 2-6 mL / h to form a ZnMgSe transition layer.

7. The method for preparing green ZnSe / ZnSeTe core-shell quantum dots as described in claim 1, characterized in that, In step S4, one or more features selected from the following group are included: (1) The molar ratio of the sulfur precursor to the zinc precursor is 1:(0.5-4); (2) The sulfur precursor includes at least one of the following: hexamethylenetetramine, octanethiol, decanethiol, dodecanethiol, hexadecethiol, mercaptopropylsilane, thio-trioctylphosphine, thio-tributylphosphine, thio-triphenylphosphine, thio-trioctylamine, bis(trimethylsilyl)sulfur, ammonium sulfide, and sodium sulfide; (3) Add zinc precursor at 300-320℃ at a rate of 8-14 mL / h, raise the temperature to 330-350℃, and then add sulfur precursor at a rate of 2-6 mL / h to form a ZnS outer shell layer.

8. The method for preparing green ZnSe / ZnSeTe core-shell quantum dots as described in claim 1, characterized in that, The preparation method further includes the step: S5, adding the amine-containing zinc precursor and sulfur precursor to S4 to increase the thickness of the ZnS outer shell layer; Preferably, the zinc-containing amine precursor includes at least one of zinc oleamide, zinc n-octylamine, zinc tetradecylamine, and zinc hexadecylamine. Preferably, the molar ratio of the added amine-containing zinc precursor to the sulfur precursor is (0.5-3):1; Preferably, at 230-250°C, the amine-containing zinc precursor is added dropwise to S4 at a rate of 12-18 mL / h, while the sulfur precursor is added dropwise at a rate of 2-7 mL / h, to increase the thickness of the ZnS outer shell layer.

9. A green-light-emitting ZnSe / ZnSeTe core-shell quantum dot, characterized in that, The green ZnSe / ZnSeTe core-shell quantum dot comprises, from the inside out: a ZnSe core, a ZnSeTe outer core covering the ZnSe core, a ZnMgSe transition layer covering the green ZnSe / ZnSeTe core, and a ZnS outer shell layer covering the ZnMgSe transition layer; Preferably, the maximum emission peak wavelength of the green ZnSe / ZnSeTe core-shell quantum dot is 515-535 nm.

10. An electroluminescent device, characterized in that, It comprises green ZnSe / ZnSeTe core-shell quantum dots obtained by any of the preparation methods described in claims 1-8, or comprises green ZnSe / ZnSeTe core-shell quantum dots as described in claim 9.

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