Quantum dot and optoelectronic device including same

Abstract

The invention discloses a quantum dot and a photoelectric device comprising the quantum dot, the quantum dot has a core-shell structure, the mole percentage of the cadmium element in the core of the quantum dot and the shell layer containing the cadmium element is gradually increased, and when the quantum dot is applied to the photoelectric device, the photoelectric property stability of the photoelectric device can be improved.

Description

Technical Field

[0001] This application relates to the field of optoelectronic technologies, and particularly to a quantum dot and an optoelectronic device including the quantum dot. Background Art

[0002] Quantum dots (QDs), also known as semiconductor nanocrystals, are nanocrystals with a radius less than or close to the exciton Bohr radius, and the average particle size is usually between 1 nm and 30 nm. Quantum dots have unique fluorescence nano-effects. The emission wavelength of quantum dots can be regulated by changing their own size and composition, and they have the advantages of a narrow full width at half maximum of the emission spectrum, high color purity, good optical stability, a wide excitation spectrum, and a controllable emission spectrum, and have broad application prospects in technical fields such as photovoltaic power generation, optoelectronic display, and biological probes.

[0003] With the increasingly in-depth research and development of quantum dots, the existing types of quantum dots are gradually difficult to meet the requirements of more and more application scenarios. Therefore, it is urgent to develop new types of quantum dots to expand the types of quantum dots. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, this application provides a quantum dot and an optoelectronic device including the quantum dot.

[0005] The technical solution of this application is as follows:

[0006] In a first aspect, this application provides a quantum dot having a core-shell structure. Among them, in the direction of the core of the quantum dot towards the outermost shell layer, the molar percentage of cadmium element in the core of the quantum dot and the shell layer containing cadmium element gradually increases.

[0007] In a second aspect, this application provides an optoelectronic device, including an anode and a cathode arranged oppositely, and a plurality of functional layers arranged between the anode and the cathode. The material of at least one of the plurality of functional layers includes the quantum dot as described in the first aspect.

[0008] This application provides a quantum dot and an optoelectronic device including the quantum dot, having the following technical effects:

[0009] In the quantum dot of this application, the molar percentage of cadmium element in the core of the quantum dot and the shell layer containing cadmium element gradually increases. Applying the quantum dot to an optoelectronic device can improve the stability of the optoelectronic performance of the optoelectronic device. Brief Description of the Drawings

[0010] The following, in conjunction with the drawings, through a detailed description of the specific embodiments of this application, will make the technical solutions and other beneficial effects of this application obvious.

[0011] Figure 1 Schematic diagram of the structure of the first light-emitting device provided by an embodiment of the present application.

[0012] Figure 2 Schematic diagram of the structure of the second light-emitting device provided by an embodiment of the present application.

[0013] Figure 3 Photoluminescence spectrum of the quantum dots in Example 1.

[0014] Figure 4 Photoluminescence spectrum of the quantum dots in Comparative Example 1.

[0015] Figure 5 Electroluminescence spectra of the optoelectronic device in Example 1 in the first state and the second state.

[0016] Figure 6 Electroluminescence spectra of the optoelectronic device in Example 2 in the first state and the second state.

[0017] Figure 7 Electroluminescence spectra of the optoelectronic device in Example 3 in the first state and the second state.

[0018] Figure 8 Electroluminescence spectra of the optoelectronic device in Comparative Example 2 in the first state and the second state.

[0019] The reference numerals are as follows:

[0020] 1: Light-emitting device, 10: Substrate, 11: Anode, 12: Cathode, 13: Active layer, 14: Electron functional layer, 15: Hole functional layer, 151: Hole injection layer, 152: Hole transport layer. Detailed implementation manners

[0021] Next, the technical solutions in the embodiments of the present application will be clearly and completely described in conjunction with 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 in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0022] Unless otherwise defined, all professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any methods and materials similar or equivalent to the described content can be applied to the present invention. The preferred implementation methods and materials described herein are only for illustrative purposes and cannot limit the content of the present application.

[0023] It should be noted that the order of description of the following embodiments does not limit the preferred order of the embodiments. Each embodiment of the present application may exist in a range form; it should be understood that the description in a range form 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 described range description has specifically disclosed all possible sub-ranges and single values within that range. For example, it should be considered that the range description 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 the counted range, such as 1, 2, 3, 4, 5, and 6, which applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0024] In the description of the present application, the term "comprising" means "including but not limited to".

[0025] The term "at least one" means one or more, and "a plurality" means two or more. The term "at least one", "at least one of the following (items)" or its similar expressions refer to any combination of these items, including any combination of single (item) or plural items (items). For example, "at least one of (item) a, b, or c" or "at least one of (item) a, b, and c" can both be expressed as: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0026] In the present application, the description of "layer A is formed on one side of layer B" or "layer A is formed on the side of layer B away from layer C" may mean that layer A is directly formed on one side of layer B or on the side of layer B away from layer C, that is, layer A is in direct contact with layer B; it may also mean that layer A is indirectly formed on one side of layer B or on the side of layer B away from layer C, that is, other film layers may be formed between layer A and layer B.

[0027] The selection range of the term "and / or" includes any one of two or more related listed items, and also includes any and all combinations of the related listed items. The said any and all combinations include combinations of any two related listed items, any more related listed items, or all related listed items. For example, "A and / or B" includes three parallel solutions: A, B, and A + B. Another example, for the technical solution of "A, and / or, B, and / or, C, and / or, D", it includes any one of A, B, C, D (that is, the technical solutions connected by "logical or"), and also includes any and all combinations of A, B, C, D, that is, it includes combinations of any two or any three of A, B, C, D, and also includes the four-item combination of A, B, C, D (that is, the technical solutions connected by "logical and").

[0028] The term "particle size" refers to the diameter of the nanoparticles.

[0029] When describing the structural composition of the quantum dots in this application, the respective layers are arranged in the order from the inside to the outside. Taking Zn x Cd (1-x) A / Zn t Cd (1-t) D / Zn y Cd (1-y) E / ZnD as an example, Zn x Cd (1-x) A represents the composition of the quantum dot core, Zn t Cd (1-t) D represents the composition of the first shell layer, Zn y Cd (1-y) E represents the composition of the second shell layer, and ZnD represents the composition of the third shell layer. Among them, "x" represents the molar percentage of Zn in the core of the quantum dot, "1 - x" represents the molar percentage of Cd in the core of the quantum dot, "t" represents the molar percentage of Zn in the first shell layer, "1 - t" represents the molar percentage of Cd in the first shell layer, "y" represents the molar percentage of Zn in the second shell layer, and "1 - y" represents the molar percentage of Cd in the second shell layer.

[0030] Based on this, the embodiments of this application provide a quantum dot with a core - shell structure. Among them, in the direction from the core of the quantum dot towards the outermost shell layer, the molar percentage of cadmium in the core of the quantum dot and the shell layer containing cadmium element gradually increases. Applying the quantum dot to optoelectronic devices can improve the stability of the optoelectronic performance of the optoelectronic devices.

[0031] In some embodiments of this application, the shell of the quantum dot includes a first shell layer, a second shell layer, and a third shell layer arranged in sequence. The first shell layer is closer to the core of the quantum dot than the third shell layer. The core of the quantum dot contains cadmium element, and at least one of the shell layers from the first shell layer to the third shell layer contains cadmium element; among them, in the radial direction from the core of the quantum dot towards the third shell layer, the molar percentage of cadmium in the core of the quantum dot and the shell layer containing cadmium element gradually increases, thereby reducing the migration amount of cadmium in the core and the intermediate shell layer to the outermost shell layer.

[0032] In some embodiments of this application, the material of the core of the quantum dot is Zn x Cd (1-x) A, the material of the first shell layer is ZnD or Zn t Cd (1-t) D, the material of the second shell layer is Zn y Cd (1-y) E, and the material of the third shell layer is ZnG or Zn mCd (1-m) G, wherein A, D, and G are each independently selected from Se or S, and x > t > y > m.

[0033] In some embodiments of the present application, the structure of the quantum dots is Zn x Cd (1-x) A / Zn t Cd (1-t) D / Zn y Cd (1-y) E / ZnG, x is selected from 0.8 to 0.95, and x is, for example, selected from 0.8, 0.83, 0.85, 0.88, 0.9, 0.92, 0.95, or a value between any two of the foregoing values; t is selected from 0.62 to 0.8, and t is, for example, selected from 0.62, 0.65, 0.67, 0.7, 0.72, 0.75, 0.77, 0.8, or a value between any two of the foregoing values. Preferably, t is selected from 0.65 to 0.76; y is selected from 0.4 to 0.6, and y is, for example, selected from 0.4, 0.43, 0.45, 0.5, 0.55, 0.58, 0.6, or a value between any two of the foregoing values.

[0034] In order to further reduce the migration amount of cadmium elements in the core and cadmium elements in the intermediate shell layer to the outermost shell layer, in some embodiments of the present application, the shell of the quantum dots further includes an auxiliary shell layer, and the auxiliary shell layer is disposed between the core of the quantum dots and the first shell layer, wherein the auxiliary shell layer does not contain cadmium elements; or, the auxiliary shell layer contains cadmium elements, and the molar percentage of cadmium elements in the auxiliary shell layer is higher than the molar percentage of cadmium elements in the core of the quantum dots.

[0035] In order to improve the electron confinement ability and / or hole confinement ability of the quantum dots, in some embodiments of the present application, the material of the auxiliary shell layer is selected from ZnR or Zn z Cd (1-z) R, R is selected from Se or S, and z is selected from 0.62 to 0.8, and z is, for example, selected from 0.62, 0.65, 0.67, 0.7, 0.72, 0.75, 0.77, 0.8, or a value between any two of the foregoing values.

[0036] In some embodiments of the present application, the average thickness of the auxiliary shell layer is 0.8 nm to 1.5 nm, for example, 0.8 nm, 1.0 nm, 1.2 nm, 1.5 nm, or a value between any two of the foregoing values.

[0037] In some embodiments of the present application, the structure of the quantum dots is Zn x Cd (1-x) A / ZnR / ZnD / Zn y Cd (1-y)E / ZnG, where x is selected from 0.8 to 0.95, and x is for example selected from 0.8, 0.83, 0.85, 0.88, 0.9, 0.92, 0.95 or a value between any two of the foregoing values; y is selected from 0.4 to 0.6, and y is for example selected from 0.4, 0.43, 0.45, 0.5, 0.55, 0.58, 0.6 or a value between any two of the foregoing values.

[0038] In some other embodiments of the present application, the quantum dot has a structure of Zn x Cd (1-x) A / ZnR / Zn t Cd (1-t) D / Zn y Cd (1-y) E / ZnG, where x is selected from 0.8 to 0.95, and x is for example selected from 0.8, 0.83, 0.85, 0.88, 0.9, 0.92, 0.95 or a value between any two of the foregoing values; t is selected from 0.62 to 0.8, preferably, t is selected from 0.75 to 0.8, and t is for example selected from 0.62, 0.65, 0.7, 0.75, 0.77, 0.8 or a value between any two of the foregoing numerical values.

[0039] In some other embodiments of the present application, the quantum dot has a structure of Zn x Cd (1-x) A / Zn z Cd (1-z) R / ZnD / Zn y Cd (1-y) E / ZnG, where x is selected from 0.8 to 0.95, and x is for example selected from 0.8, 0.83, 0.85, 0.88, 0.9, 0.92, 0.95 or a value between any two of the foregoing values; z is selected from 0.62 to 0.8, preferably, z is selected from 0.62 to 0.7, and z is for example selected from 0.62, 0.65, 0.67, 0.7 or a value between any two of the foregoing values; y is selected from 0.4 to 0.6, and y is for example selected from 0.4, 0.43, 0.45, 0.5, 0.55, 0.58, 0.6 or a value between any two of the foregoing values.

[0040] In some other embodiments of the present application, the quantum dot has a structure of Zn x Cd (1-x) A / Zn z Cd (1-z) R / Zn t Cd (1-t) D / Zn y Cd (1-y)E / ZnG, where x is selected from 0.8 to 0.95, z is selected from 0.62 to 0.8, t is selected from 0.62 to 0.8, and y is selected from 0.4 to 0.6; preferably, z is selected from 0.75 to 0.8 and t is selected from 0.62 to 0.7.

[0041] In some embodiments of the present application, the average particle size of the quantum dots is 6 nm to 10 nm, such as 6 nm, 7 nm, 8 nm, 9 nm, 10 nm or a value between any two of the foregoing values; and / or, the average thickness of the first shell layer is 0.8 nm to 1.5 nm, such as 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm or a value between any two of the foregoing values; and / or, the average thickness of the second shell layer is 0.3 nm to 0.5 nm, such as 0.3 nm, 0.4 nm, 0.5 nm or a value between any two of the foregoing values; and / or, the average thickness of the third shell layer is 1.1 nm to 2 nm, such as 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, 1.7 nm, 1.8 nm, 1.9 nm, 2 nm or a value between any two of the foregoing values.

[0042] It should be noted that ligands may also be connected to the surface of the above-mentioned quantum dots. The ligands may be common ligands in the art, including but not limited to fatty carboxylic acid ligands of C1-C 30 aromatic carboxylic acid ligands of C6-C 30 fatty thiol ligands of C1-C 30 thiol aromatic ligands of C6-C 30 fatty amine ligands of C1-C 30 aromatic amine ligands of C6-C 30 fatty phosphine ligands of C1-C 30 aromatic phosphine ligands of C6-C 30 aromatic phosphate ligands of C6-C 30 and one or more of halogen ligands.

[0043] Among them, the fatty carboxylic acid ligands of C1-C 30 include but are not limited to one or more of octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tetradecanoic acid, hexadecanoic acid, octadecanoic acid, eicosanoic acid, tetracosanoic acid, hexacosanoic acid, oleic acid, linoleic acid, arachidic acid, arachidonic acid, erucic acid and docosahexaenoic acid; the aromatic carboxylic acid ligands of C6-C 30 include but are not limited to one or more of benzoic acid, dibenzoic acid and 1-naphthoic acid. The fatty carboxylic acid ligands of C1-C 30The fatty thiol ligands include, but are not limited to, one or more of hexanethiol, octanethiol, nonanethiol, decanethiol, undecanethiol, dodecanethiol, hexadecanethiol, and octadecanethiol, C6-C 30 The thiol aromatic ligands include, but are not limited to, one or more of benzenethiol, triphenylmethanethiol, and p-terphenyl-4,4”-dithiol. C1-C 30 The fatty amine ligands include, but are not limited to, one or more of hexylamine, octylamine, dioctylamine, trioctylamine, nonylamine, decylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, and oleylamine, C6-C 30 The aromatic amine ligands include, but are not limited to, one or more of aniline, indanylpropylamine, 4-octylaniline, and benzidine. C1-C 30 The fatty phosphine ligands include, but are not limited to, one or more of trimethylphosphine, triethylphosphine, tripropylphosphine, tributylphosphine, trihexylphosphine, trioctylphosphine, tridecylphosphine, tributyloxophosphine, trihexylphosphine oxide, trioctylphosphine oxide, and tridecylphosphine oxide, C6-C 30 The aromatic phosphine ligands include, but are not limited to, one or more of bis(2-diphenylphosphinoethyl)phenylphosphine and triphenylphosphine oxide, C6-C 30 The aromatic phosphate ligands include, but are not limited to, one or more of tetraethyl p-xylene diphosphate and ethyl diphenyl phosphate. The halogen ligands include, but are not limited to, one or more of -Cl, -F, -I, and -Br.

[0044] It can be understood that the above quantum dots can be synthesized by a conventional thermal injection method. As an example, the synthesis method of the quantum dots includes the following steps:

[0045] S1. Prepare a base solution and an anion precursor. Among them, the preparation method of the base solution includes the steps of: providing a container filled with a cation precursor, where the cation precursor is a solution containing a zinc source and a cadmium source, then introducing an inert gas at room temperature. After the air in the container is completely removed, heat up to 125°C - 180°C, and perform a constant temperature treatment for 30 min - 90 min in an inert gas atmosphere to remove the moisture and low-boiling impurities in the solution, obtaining the base solution;

[0046] S2. Heat the base solution to the reaction temperature, and quickly inject the anion precursor into it to instantaneously nucleate the reaction system, and perform constant temperature ripening to obtain the core;

[0047] S3. Prepare and form multiple shell layers on the surface of the core obtained in step S1 to obtain a reaction solution containing quantum dots.

[0048] Specifically, in step S1, the zinc source includes but is not limited to one or more of zinc oleate, zinc stearate, zinc dodecanoate, zinc tetradecanoate, zinc hexadecanoate, zinc palmitate, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, and zinc sulfate. The cadmium source includes but is not limited to one or more of cadmium oxide, 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.

[0049] In step S1, the solvent of the cation precursor includes but is not limited to one or more of octadecene, paraffin oil, diphenyl ether, dioctyl ether, oleic acid, stearic acid, palmitic acid, and olive oil. The solvent of the cation precursor is, for example, composed of oleic acid and octadecene. In some embodiments of the present application, in order to balance the improvement of the synthesis yield of quantum dots and the improvement of the mixing efficiency of the cation and anion precursors in the subsequent process, the volume ratio of oleic acid to octadecene is 1:(1 - 5).

[0050] In some embodiments of the present application, in order to obtain blue quantum dots, the molar ratio of zinc to cadmium in the cation precursor is 100:(5 - 20).

[0051] In some embodiments of the present application, in order to balance the improvement of the synthesis yield of quantum dots and the improvement of the solution processability of the cation precursor, the concentration of zinc element in the cation precursor is 0.05 mol / L - 1 mol / L.

[0052] In the process of evacuating the air in the container, the inert gas includes but is not limited to one or more of nitrogen, argon, helium, neon, krypton, and xenon. The flow rate of the inert gas is, for example, 50 mL / min - 300 mL / min, and the evacuation time is, for example, 10 min - 30 min.

[0053] In step S1, the anion precursor can be a selenium precursor and / or a sulfur precursor. Among them, the selenium precursor is 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; the sulfur precursor 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-DPP, mercaptopropylsilane, and alkyl mercaptan. Among them, taking S-TOP as an example, the preparation method of S-TOP includes the steps of: providing a container filled with sulfur powder and trioctylphosphine (TOP), introducing an inert gas at room temperature, and after the air in the container is completely removed, heating to 25°C to 80°C, and stirring at a constant temperature under the atmosphere of the inert gas until the sulfur powder is completely dispersed to obtain an S-TOP solution, where the concentration of sulfur in the S-TOP solution is 0.1 mol / L to 2 mol / L.

[0054] In step S2, the injection rate of the anion precursor is, for example, 1 mmol / min to 5 mmol / min.

[0055] In order to increase the nucleation rate of the quantum dots and improve the crystallinity of the quantum dots, thereby enhancing the optical properties of the quantum dots, in some embodiments of the present application, the reaction temperature is 250°C to 315°C, for example, 250°C, 260°C, 270°C, 280°C, 290°C, 315°C, or a value between any two of the foregoing values.

[0056] In order to further enhance the optical properties of the quantum dots, in some embodiments of the present application, the molar ratio of the anion in the anion precursor injected in step S2 to the cadmium ions in the base solution is 10:(0.5 to 8).

[0057] In order to further increase the synthesis rate and optical properties of the quantum dots, in some embodiments of the present application, the aging time is 10 min to 60 min.

[0058] In step S3, during the process of forming multiple shell layers, in order to improve the shell layer quality, the injection rate of the anion precursor is, for example, 1 mmol / min to 5 mmol / min.

[0059] In order to enhance the binding ability of the shell layer of the quantum dots to the excitons in the core and reduce the defect density of the quantum dots, thereby enhancing the quantum efficiency of the quantum dots, in some embodiments of the present application, for the quantum dots prepared in step S3, the molar ratio of the anion in the shell layer of the quantum dots to the anion in the core is 1:(0.5 to 3).

[0060] To improve the purity of quantum dots, after step S3, a conventional method can be used to separate and purify the reaction product containing quantum dots to obtain purified quantum dots. The purification method generally includes the steps of: transferring the reaction solution containing quantum dots into a centrifuge tube, adding n-hexane and ethanol thereto to obtain a first mixture, wherein the volume ratio of the reaction solution to n-hexane is 1:1, and the volume ratio of the reaction solution to ethanol is 1:0.8. Then, the first mixture is centrifuged at 10,000 r / min for 5 min, and the precipitate at the bottom of the centrifuge tube is collected to obtain a first precipitate. Next, the first precipitate is completely dispersed with n-hexane and then centrifuged at 5,000 r / min for 5 min, and the supernatant is collected. Subsequently, ethanol is added to the supernatant to obtain a second mixture, wherein the volume ratio of the supernatant to ethanol is 1:0.5. Then, the second mixture is centrifuged at 10,000 r / min for 5 min, and the precipitate at the bottom of the centrifuge tube is collected to obtain a second precipitate. Finally, the second precipitate is redispersed in n-hexane to obtain a dispersion, and the dispersion is subjected to vacuum drying at room temperature to obtain purified quantum dots.

[0061] It should be noted that quantum dot materials generally improve the binding ability of excitons through a core-shell structure. Under ideal conditions, a wide-bandgap shell material can effectively confine excitons within the core, preventing the delocalization of excitons to the surface of the quantum dots. Currently, when the shell of the quantum dots used as the light-emitting material in quantum dot light-emitting diodes has a well structure, on the one hand, excitons can be confined within the core of the quantum dots and the shell with a lower energy band of the well structure, so that during the operation of the quantum dot light-emitting diode, more carriers can be provided for the core of the quantum dots, improving the recombination luminescence efficiency of the quantum dots, and further enhancing the device efficiency of the quantum dot light-emitting diode; on the other hand, the shell with a well structure can increase the accumulation of carriers to raise the valence band, thereby reducing the energy barrier difference between the hole functional layer and the active layer, promoting hole injection, and being beneficial to improving the problem that the electron injection level in the quantum dot light-emitting diode is much greater than the hole injection level.

[0062] The applicant has found that the general formula of common quantum dots with a well-structured shell is Zn x0 Cd (1-x0) Se / ZnD / Zn y0 Cd (1-y0) E / ZnD, where x0 is 0.6 to 0.8, y0 is 0.35 to 0.95, D is S or Se. When the quantum dots with a well-structured shell are applied to quantum dot light-emitting diodes, during the lifetime aging process of the quantum dot light-emitting diodes, excitons are likely to recombine at the well shell to generate a long-wavelength light, and as the quantum dot core Zn x0 Cd (1-x0) Se or the second shell Zn y0 Cd (1-y0)When Cd ions in E migrate to other shells, problems such as the widening of the quantum dot bandgap, the disappearance of the well-like characteristics of the shell layer, and the weakening of long-wavelength luminescence will occur, resulting in a certain range of blue shift in the emission wavelength of the quantum dot light-emitting diode. Especially for blue quantum dot light-emitting diodes, the wavelength blue shift is more serious. It is detected that when the wavelength of the quantum dot light-emitting diode undergoes a certain range of blue shift, for example, the wavelength blue shifts from 470nm - 480nm to 466nm - 474nm, on the premise that the optical power remains unchanged, the brightness of the quantum dot light-emitting diode decays by about 15%, and the device lifetime is significantly reduced; in addition, when the wavelength of the quantum dot light-emitting diode undergoes an obvious blue shift, the color visible to the naked eye changes during the operation of the quantum dot light-emitting diode, which has an adverse impact on the industrialization of QLED.

[0063] Based on this, the embodiments of the present application provide an optoelectronic device, such as Figure 1 shown, the optoelectronic device 1 includes an anode 11, a cathode 12, and multiple functional layers. The material of at least one functional layer among the multiple functional layers includes the quantum dots described in any one of the foregoing, which can improve the stability of the optoelectronic performance of the optoelectronic device 1.

[0064] In some embodiments of the present application, the materials of the anode 11 and the cathode 12 are independently selected from one or more of metals, carbon materials, and third metal oxides. Among them, the metals include, but are not limited to, one or more of Al, Ag, Cu, Mo, Au, Ba, Pt, Ca, Ir, Ni, and Mg. The carbon materials include, but are not limited to, one or more of graphite, carbon nanotubes, graphene, and carbon fibers. The third metal oxides include, but are not limited to, one or more of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), antimony tin oxide (ATO), aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide (GZO), indium-doped zinc oxide (IZO), magnesium-doped zinc oxide (MZO), SnO2, ZnO, and In2O3. The anode 11 or the cathode 12 can also be a composite electrode. The composite electrode has a structure similar to a "sandwich". The materials of the upper layer and the bottom layer are respectively doped or undoped transparent metal oxides, and the material of the middle layer is a metal. For example, it can be one or more 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. The average thickness of the middle layer does not exceed 35nm. The average thickness of the anode 11 can be, for example, 20nm - 300nm, and the average thickness of the cathode 12 can be, for example, 20nm - 300nm.

[0065] In some embodiments of the present application, with continued reference to Figure 1 , the multiple functional layers include an active layer 13, and the material of the active layer 13 includes quantum dots as described in any one of the foregoing. Optionally, the active layer 13 is a light-emitting layer or a light-absorbing layer.

[0066] The active layer 13 may include multiple quantum dot layers, and the materials of each quantum dot layer are independently selected from any one of the foregoing quantum dots, and the quantum dots in each quantum dot layer may be arranged in a single layer. In order to balance the improvement of the comprehensive performance of the optoelectronic device and the reduction of the manufacturing cost of the optoelectronic device, in some embodiments of the present application, the average thickness of the active layer 13 is 10 nm to 100 nm, for example, it may be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm or a value between any two of the foregoing values.

[0067] In order to further improve the comprehensive performance of the optoelectronic device 1, in some embodiments of the present application, with continued reference to Figure 1 , the light-emitting device further includes an electron functional layer 14, and the electron functional layer 14 is disposed between the cathode 12 and the active layer 13; the average thickness of the electron functional layer 14 is, for example, 10 nm to 200 nm. The electron functional layer 14 may be a single-layer structure or a multi-layer structure, and the electron functional layer includes, for example, one or more of an electron injection layer, an electron transport layer, and a hole blocking layer. For the electron functional layer 14 including an electron injection layer, an electron transport layer, and a hole blocking layer, the electron injection layer, the electron transport layer, and the hole blocking layer may be arranged in sequence, and the electron injection layer is closer to the cathode 12 than the hole blocking layer.

[0068] Among them, the materials of the electronic functional layer 14 include, but are not limited to, one or more of undoped first inorganic compounds and doped second inorganic compounds; the undoped first inorganic compounds include one or more of undoped first metal oxides, IIB-VIA group semiconductor materials, IIIA-VA group semiconductor materials, and IB-IIIA-VIA group semiconductor materials, the undoped first metal oxides include one or more of ZnO, TiO2, SnO2, BaO, Ta2O3, Al2O3, and ZrO2, and / or the IIB-VIA group semiconductor materials include one or more of ZnS, ZnSe, and CdS, and / or the IIIA-VA group semiconductor materials include one or more of InP and GaP, and / or the IB-IIIA-VIA group semiconductor materials include one or more of CuInS and CuGaS; and / or the doped second inorganic compounds include doped second metal oxides, the host metal oxides of the doped second metal oxides are selected from ZnO, TiO2, SnO2, BaO, Ta2O3, Al2O3, or ZrO2, and the doping elements of the doped second metal oxides are selected from one or more of Mg, Ca, Zr, W, Ga, Li, Al, Ti, Y, In, and Sn.

[0069] The doped second metal oxides are, for example, one or more of magnesium zinc oxide, calcium zinc oxide, zirconium zinc oxide, gallium zinc oxide, aluminum zinc oxide, lithium zinc oxide, titanium zinc oxide, yttrium zinc oxide, indium tin oxide, and lithium titanium oxide, exemplified as Zn (1-x) Mg x O, Zn (1-x) Ca x O, Zn (1-x) Zr x O, Zn (1-x) Ga x O, Zn (1-x) Al x O, Zn (1-x) Li x O, Al (1-x) Zn x O, Zn (1-x) Ti x O, Zn (1-x) Y x O, In (1-x) Sn x O and Ti (1-x) Li x O, and among them, x represents the molar amount, 0 < x ≤ 0.5.

[0070] It should be noted that when the electronic functional layer 14 includes multiple materials and the electronic functional layer 14 is a multi-layer structure, the multiple materials may all be in the same layer, or in different layers respectively, or part of them may be in the same layer.

[0071] In order to further improve the optoelectronic performance and device life of the optoelectronic device 1, in some embodiments of the present application, continue to refer to Figure 1 , the optoelectronic device 1 further includes a hole functional layer 15 disposed between the anode 11 and the active layer 13. The hole functional layer 15 may be a single-layer structure or a multi-layer structure. The hole functional layer 15 includes, for example, one or more of a hole injection layer, a hole transport layer, and an electron blocking layer. For the hole functional layer 15 including a hole injection layer, a hole transport layer, and an electron blocking layer, the hole injection layer, the hole transport layer, and the electron blocking layer may be arranged in sequence, and the hole injection layer is closer to the anode 11 than the electron blocking layer. The average thickness of the hole functional layer 15 is, for example, 10 nm to 200 nm.

[0072] Among them, the materials of the hole functional layer 15 include, but are not limited to, one or more of undoped third inorganic compounds, doped fourth inorganic compounds, and organic compounds. Among them, the organic compounds include, but are not limited to, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (abbreviation: PEDOT:PSS, CAS number 155090-83-8), copper phthalocyanine (CAS number 147-14-8), titanium oxyphthalocyanine (CAS number 26201-32-1), 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanoquinodimethane (CAS number 29261-33-4), 2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (CAS number 105598-27-4), polyaniline (CAS number 25233-30-1), polypyrrole (CAS number 30604-81-0), 3-hexyl-substituted polythiophene (CAS number 104934-50-1), poly(9-vinylcarbazole) (abbreviation: PVK, CAS number 25067-59-8), 4,4'-bis(9-carbazolyl)biphenyl (abbreviation: CBP, CAS number 58328-31-7), poly[bis(4-phenyl)(4-butylphenyl)amine], 4,4'-cyclohexylbis[N,N-bis(4-methylphenyl)aniline] (abbreviation: TAPC, CAS number 58473-78-2), poly[(9,9-dioctylfluorene-2,7-diyl)-co-(4,4'-(N-(4-sec-butylphenyl)diphenylamine)] (abbreviation: TFB, CAS number 220797-16-0), poly[(N,N'-(4-n-butylphenyl)-N,N'-diphenyl-1,4-phenylenediamine)-ALT-(9,9-din-octylfluorene-2,7-diyl)] (CAS number 223569-31-1), 4,4',4'-tris(N-3-methylphenyl-N-phenylamino)triphenylamine (CAS number 124729-98-2), 4,4',4”-tris(carbazol-9-yl)triphenylamine (abbreviation: TCTA, CAS number 139092-78-7), 4,4',4'-tris(2-naphthylphenylamino)triphenylamine (CAS number 185690-41-9), N,N'-diphenyl-N,N'-(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (abbreviation: NPB, CAS number 123847-85-8), N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (abbreviation: TPD, CAS number 65181-78-4), N,N'-bis[4-(diphenylamino)phenyl]-N,N'-diphenylbenzidine (CAS number 209980-53-0), N,N'-bis(3-methylphenyl)-N,N'-diphenyl-9,9-spirobifluorene-2,7-diamine (abbreviation: Spiro-TPD,One or more of those having a CAS number of 1033035-83-4), N2,N7-di-1-naphthyl-N2,N7-diphenyl-9,9'-spirobi[9H-fluorene]-2,7-diamine (CAS number: 932739-76-9), poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (abbreviation: PTTA, CAS number: 1333317-99-9), and 2,2',7,7'-tetrakis[N,N-bis(4-methoxyphenyl)amino]-9,9'-spirobifluorene (abbreviation: Spiro-omeTAD, CAS number: 207739-72-8); and / or, the non-doped type third inorganic compound includes but is not limited to one or more of graphene, C60, nickel oxide (e.g., NiO), molybdenum oxide (e.g., MoO3), tungsten oxide (e.g., WO3), vanadium oxide (e.g., V2O5), p-type gallium nitride, chromium oxide (e.g., Cr2O3), copper oxide (e.g., CuO or Cu2O), copper sulfide (e.g., CuS), molybdenum sulfide (e.g., MoS2), and tungsten sulfide (e.g., WS2); and / or, the host inorganic compound of the doped type fourth inorganic compound includes but is not limited to one or more of graphene, C60, nickel oxide (e.g., NiO), molybdenum oxide (e.g., MoO3), tungsten oxide (e.g., WO3), vanadium oxide (e.g., V2O5), p-type gallium nitride, chromium oxide (e.g., Cr2O3), copper oxide (e.g., CuO or Cu2O), copper sulfide (e.g., CuS), molybdenum sulfide (e.g., MoS2), and tungsten sulfide (e.g., WS2), and / or the doping element of the doped type second inorganic compound is selected from one or more of nickel, molybdenum, tungsten, vanadium, chromium, copper, and platinum group metal elements, and the molar percentage of the doping element is, for example, not more than 50%.

[0073] It can be understood that when the hole functional layer 15 contains multiple materials and the hole functional layer 15 is a multilayer structure, the multiple materials can all be in the same layer, or in different layers respectively, or part of them in the same layer. For example, as Figures 2 to 4 shown, when the hole functional layer 15 is composed of a hole injection layer and a hole transport layer arranged in a stacked manner, the materials of the hole functional layer 15 include PEDOT:PSS and TFB, PEDOT:PSS and TFB are in different layers respectively, the material of the hole injection layer is PEDOT:PSS, and the material of the hole transport layer is TFB.

[0074] It should be noted that the preparation methods of the various functional film layers in the light-emitting device include, but are not limited to, chemical methods and / or physical methods. Among them, the chemical methods include, but are not limited to, one or more of chemical vapor deposition, sequential ionic layer adsorption and reaction, anodic oxidation, electrodeposition, and coprecipitation. The physical methods include, but are not limited to, physical coating methods and solution methods. The physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, and pulsed laser deposition. The solution methods include, but are not limited to, one or more of spin coating, printing, inkjet printing, blade coating, printing, dip coating, immersion, spraying, roll coating, casting, slot die coating, and bar coating. When preparing the functional film layer by the solution method, a drying treatment process needs to be added to remove the solvent to form a cured film. The drying treatment process includes, but is not limited to, heat treatment, vacuum drying treatment, natural air drying treatment, etc. Among them, for the functional film layer (the material is an inorganic compound, especially inorganic nanoparticles) located above the active layer, after forming the cured film by using low-temperature (the temperature is not higher than 80 °C) drying treatment processes such as vacuum drying treatment and natural air drying treatment, in order to further improve the film-forming quality, a process that can control the annealing depth, such as laser annealing, electron beam annealing, atomic annealing, and infrared irradiation annealing, can be used to further anneal the cured film.

[0075] After preparing the various functional film layers of the light-emitting device, a packaging treatment process is also required. The packaging treatment can be carried out by using common machine packaging or manual packaging. In the environment of the packaging treatment, the oxygen content and the water content are both lower than 0.1 ppm to ensure the stability of the light-emitting device.

[0076] The embodiment of the present application also provides an electronic device, and the electronic device includes any one of the light-emitting devices described in the embodiment of the present application. The electronic device can be, for example, any electronic product with a display function, including, but not limited to, a smart phone, a tablet computer, a notebook computer, a digital camera, a digital video camera, a smart wearable device, a smart weighing electronic scale, a vehicle-mounted display, a television, or an e-book reader. Among them, the smart wearable device can be, for example, a smart bracelet, a smart watch, a virtual reality (VR) helmet, etc.

[0077] The technical solutions and technical effects of the present application will be described in detail below through specific examples, comparative examples, and experimental examples. The following examples are only partial examples of the present application and do not specifically limit the present application.

[0078] Among them, the preparation method of the base solution includes the steps of: adding 10 mmol of zinc acetate, 0.3 mmol of cadmium oxide (CdO), 20 mL of oleic acid, and 80 mL of octadecene into a 250 mL three-necked flask in sequence. Argon gas is introduced at room temperature with a flow rate of 100 mL / min. After exhausting for 15 min, the temperature is raised to 150 °C, and it is kept at a constant temperature for 60 min under an argon atmosphere to obtain the base solution.

[0079] The preparation method of the S-TOP solution includes the steps of: adding 5 mmol of sulfur powder and 10 mL of TOP into a 50 mL three-necked flask in sequence. Argon gas is introduced at room temperature with a flow rate of 50 mL / min. After exhausting for 15 min, the temperature is raised to 100 °C, and it is stirred at a constant temperature under an argon atmosphere until the sulfur powder is completely dispersed to obtain the S-TOP precursor solution.

[0080] The preparation method of the Se-TOP solution includes the steps of: adding 5 mmol of selenium powder and 10 mL of TOP into a 50 mL three-necked flask in sequence. Argon gas is introduced at room temperature with a flow rate of 50 mL / min. After exhausting for 15 min, the temperature is raised to 100 °C, and it is stirred at a constant temperature under an argon atmosphere until the selenium powder is completely dispersed to obtain the Se-TOP precursor solution.

[0081] The purification method of the quantum dots includes the steps of: transferring the reaction solution containing the quantum dots into a centrifuge tube, adding n-hexane and ethanol thereto to obtain a first mixture, wherein the volume ratio of the reaction solution to n-hexane is 1:1, and the volume ratio of the reaction solution to ethanol is 1:0.8. Then, the first mixture is centrifuged at 10000 r / min for 5 min, and the precipitate at the bottom of the centrifuge tube is collected to obtain a first precipitate; then, the first precipitate is completely dispersed with n-hexane and then centrifuged at 5000 r / min for 5 min, and the supernatant is collected; subsequently, ethanol is added to the supernatant to obtain a second mixture, wherein the volume ratio of the supernatant to ethanol is 1:0.5. Then, the second mixture is centrifuged at 10000 r / min for 5 min, and the precipitate at the bottom of the centrifuge tube is collected to obtain a second precipitate; finally, the second precipitate is redispersed in n-hexane to obtain a dispersion, and the dispersion is subjected to vacuum drying at room temperature to obtain the purified quantum dots.

[0082] The preparation method of the cadmium oleate solution includes the steps of: adding 5 mmol of cadmium oxide, 5 mL of oleic acid, and 20 mL of octadecene into a 100 mL three-necked flask in sequence. Argon gas is introduced at room temperature with a flow rate of 100 mL / min. After exhausting for 15 min, the temperature is raised to 150 °C, and it is kept at a constant temperature for 60 min under an argon atmosphere, and then the temperature is raised to 240 °C and kept at a constant temperature for 30 min under an argon atmosphere to obtain a cadmium oleate solution with a concentration of 0.2 mmol / ml.

[0083] Example 1

[0084] This example provides an optoelectronic device and a preparation method thereof. The optoelectronic device is a quantum dot light-emitting diode with an upright structure. As shown, in the direction from bottom to top, the optoelectronic device 1 includes a substrate 10, an anode 11, a hole functional layer 15, an active layer 13, an electron functional layer 14, and a cathode 12 stacked in sequence. Among them, the hole functional layer 15 is composed of a hole injection layer 151 and a hole transport layer 152 stacked. The hole injection layer 151 is closer to the anode 11 than the hole transport layer 152; the electron functional layer 14 is a single-layer structure. Figure 2 As shown, in the direction from bottom to top, the optoelectronic device 1 includes a substrate 10, an anode 11, a hole functional layer 15, an active layer 13, an electron functional layer 14, and a cathode 12 stacked in sequence. Among them, the hole functional layer 15 is composed of a hole injection layer 151 and a hole transport layer 152 stacked. The hole injection layer 151 is closer to the anode 11 than the hole transport layer 152; the electron functional layer 14 is a single-layer structure.

[0085] The materials and average thicknesses of each layer in the optoelectronic device 1 are as follows:

[0086] The material of the substrate 10 is glass, and the average thickness of the substrate 10 is 2 mm;

[0087] The material of the anode 11 is ITO, and the average thickness of the anode 11 is 110 nm;

[0088] The material of the cathode 12 is Ag, and the average thickness of the cathode 12 is 100 nm;

[0089] The material of the active layer 13 is Zn 0.9 Cd 0.1 Se / ZnSe / Zn 0.78 Cd 0.22 S / Zn 0.5 Cd 0.5 S / ZnS quantum dots, the particle size of the core Zn 0.9 Cd 0.1 Se is 4 nm, the average thickness of the auxiliary shell layer (material is ZnSe) is 0.9 nm, the average thickness of the first shell layer is 0.9 nm, the average thickness of the second shell layer is 0.4 nm, the average thickness of the third shell layer is 1.5 nm, and the average thickness of the active layer 13 is 20 nm;

[0090] The material of the electron functional layer 14 is nano-ZnO (average particle size is 4 nm), and the average thickness is 40 nm;

[0091] The material of the hole injection layer 151 is PEDOT:PSS, and the average thickness of the hole injection layer 151 is 60 nm;

[0092] The material of the hole transport layer 152 is TFB, and the average thickness of the hole transport layer 152 is 70 nm.

[0093] The preparation method of the optoelectronic device in this example includes the following steps:

[0094] S1.1. Provide a substrate, sputter ITO on one side of the substrate to obtain an ITO layer, wipe the surface of the ITO layer with a cotton swab dipped in a small amount of soapy water to remove impurities visible to the naked eye on the surface, and then ultrasonically clean the substrate including the ITO with deionized water for 15 minutes, acetone for 15 minutes, ethanol for 15 minutes, and isopropanol for 15 minutes, and then dry and perform ultraviolet-ozone surface treatment for 20 minutes to obtain a substrate including an anode;

[0095] S1.2, in an air environment at room temperature and pressure, spin-coat a 10 mg / mL PEDOT:PSS aqueous solution on the side of the anode away from the substrate, and then heat-treat at 115°C to solidify the film to obtain a hole injection layer;

[0096] S1.3, in a nitrogen environment at room temperature and pressure, spin-coat a TFB-chlorobenzene solution with a concentration of 8 mg / mL on the side of the hole injection layer away from the anode, and then heat-treat at 125°C to solidify the film to obtain a hole transport layer;

[0097] S1.4. In a nitrogen environment at room temperature and pressure, a quantum dot-n-octane solution with a concentration of 30 mg / mL is spin-coated on the side of the hole transport layer away from the hole injection layer, and then subjected to a constant temperature heat treatment at 110° C. to solidify the film to obtain an active layer;

[0098] S1.5. In a nitrogen environment at room temperature and pressure, a nano ZnO-ethanol solution with a concentration of 30 mg / mL is spin-coated on the side of the active layer away from the hole transport layer, and then subjected to a constant temperature heat treatment at 100° C. to solidify the film to obtain an electronic functional layer;

[0099] S1.6. Transfer the prefabricated device that has completed step S1.5 to a vapor deposition machine, and use an electron beam with a current of 35A to bombard the silver element to evaporate the silver element into atomic vapor, so that a cathode is formed on the side of the electronic functional layer away from the active layer, and then encapsulate to obtain a photoelectric device.

[0100] Among them, Zn 0.9 Cd 0.1 Se / ZnSe / Zn 0.78 Cd 0.22 S / Zn 0.5 Cd 0.5 The preparation method of S / ZnS quantum dots comprises the following steps:

[0101] S10.1, heating the base solution to 300°C, rapidly injecting 6 mL of Se-TOP solution thereinto, and aging at a constant temperature for 20 min to obtain a first solution containing the core;

[0102] S10.2. At 300 °C, inject 4 mL of Se-TOP solution into the first solution at a rate of 8 mL / h, and mix and react for 5 min to obtain a second solution containing a core and an auxiliary shell, where the auxiliary shell coats the core;

[0103] S10.3. At 300 °C, inject 4 mL of S-TOP solution into the second solution at a rate of 8 mL / h. At the same time, inject 2.2 mL of cadmium oleate solution into the second solution at a rate of 4.4 mL / h, and react and ripen at 300 °C for 40 min to obtain a third solution containing a core, an auxiliary shell, and a first shell, where the first shell coats the auxiliary shell;

[0104] S10.4. At 300 °C, inject 2 mL of S-TOP solution into the third solution at a rate of 8 mL / h. At the same time, inject 2.5 mL of cadmium oleate solution into the third solution at a rate of 10 mL / h, and mix and react to obtain a fourth solution containing a core, an auxiliary shell, a first shell, and a second shell, where the second shell coats the first shell;

[0105] S10.5. At 300 °C, inject 8 mL of S-TOP solution into the fourth solution at a rate of 8 mL / h, and mix and react to obtain a reaction solution containing quantum dots. Cool to room temperature, and then purify the reaction solution containing quantum dots to obtain purified quantum dots.

[0106] Example 2

[0107] This example provides an optoelectronic device and a preparation method thereof. Compared with the optoelectronic device in Example 1, the difference of the optoelectronic device in this example is that the average thickness of the auxiliary shell is replaced with "1.2 nm".

[0108] The preparation method of the optoelectronic device in this example is carried out with reference to Example 1.

[0109] Compared with the preparation method of the quantum dots in Example 1, the difference of the preparation method of the quantum dots in this example is that step S10.2 is replaced with "At 300 °C, inject 6 mL of Se-TOP solution into the first solution at a rate of 8 mL / h, and mix and react for 5 min to obtain a second solution containing a core and an auxiliary shell, where the auxiliary shell coats the core".

[0110] Example 3

[0111] This example provides an optoelectronic device and a preparation method thereof. Compared with the optoelectronic device in Example 1, the difference of the optoelectronic device in this example is that the material of the active layer is replaced with "Zn 0.9 Cd 0.1 Se / ZnSe / ZnS / Zn 0.5 Cd0.5 "S / ZnS quantum dots", where the core is Zn 0.9 Cd 0.1 The particle size of CdSe is 4 nm, the average thickness of the auxiliary shell is 1.2 nm, the average thickness of the first shell is 0.9 nm, the average thickness of the second shell is 0.4 nm, and the average thickness of the third shell is 1.5 nm.

[0112] The preparation method of the optoelectronic device in this example is carried out with reference to Example 1.

[0113] The preparation method of the quantum dots in this example includes the following steps:

[0114] S11.1: Consistent with step S10.1;

[0115] S11.2: At 300 °C, at a rate of 8 mL / h, inject 6 mL of Se-TOP solution into the first solution, and mix and react for 5 min to obtain a second solution containing the core and the auxiliary shell, where the auxiliary shell coats the core;

[0116] S11.3: At 300 °C, at a rate of 8 mL / h, inject 4 mL of S-TOP solution into the second solution, and react and ripen at 300 °C for 40 min to obtain a third solution containing the core, the auxiliary shell and the first shell, where the first shell coats the auxiliary shell;

[0117] S11.4: Consistent with step S10.4;

[0118] S11.5: Consistent with step S10.5.

[0119] Example 4

[0120] This example provides an optoelectronic device and its preparation method. Compared with the optoelectronic device in Example 2, the difference of the optoelectronic device in this example is that: the average thickness of the auxiliary shell is replaced by "0.9 nm".

[0121] Compared with the preparation method of the quantum dots in Example 1, the difference of the preparation method of the quantum dots in this example is that: step S11.2 is replaced by "At 300 °C, at a rate of 8 mL / h, inject 4 mL of Se-TOP solution into the first solution, and mix and react for 5 min to obtain a second solution containing the core and the auxiliary shell, where the auxiliary shell coats the core".

[0122] Example 5

[0123] This example provides an optoelectronic device and its preparation method. Compared with the optoelectronic device in Example 1, the difference of the optoelectronic device in this example is that: the material of the active layer is replaced by "Zn 0.9 Cd0.1 Se / Zn 0.68 Cd 0.32 Se / ZnS / Zn 0.5 Cd 0.5 S / ZnS quantum dots, where the core is Zn 0.9 Cd 0.1 The particle size of Se is 4 nm, the average thickness of the auxiliary shell is 0.9 nm, the average thickness of the first shell is 0.9 nm, the average thickness of the second shell is 0.4 nm, and the average thickness of the third shell is 1.5 nm.

[0124] The preparation method of the optoelectronic device in this example is carried out with reference to Example 1.

[0125] The preparation method of the quantum dots in this example includes the following steps:

[0126] S12.1: Consistent with step S10.1;

[0127] S12.2: At 300 °C, inject 4 mL of Se-TOP solution into the first solution at a rate of 8 mL / h. At the same time, inject 3.2 mL of cadmium oleate solution into the second solution at a rate of 6.4 mL / h, and mix and react for 5 min to obtain a second solution containing the core and the auxiliary shell, where the auxiliary shell coats the core;

[0128] S12.3: At 300 °C, inject 4 mL of S-TOP solution into the second solution at a rate of 8 mL / h, and react and ripen at 300 °C for 40 min to obtain a third solution containing the core, the auxiliary shell and the first shell, where the first shell coats the auxiliary shell;

[0129] S12.4: At 300 °C, inject 2 mL of S-TOP solution into the third solution at a rate of 8 mL / h. At the same time, inject 2.5 mL of cadmium oleate solution into the third solution at a rate of 10 mL / h, and mix and react to obtain a fourth solution containing the core, the auxiliary shell, the first shell and the second shell, where the second shell coats the first shell;

[0130] S12.5: Consistent with step S10.5.

[0131] Example 6

[0132] This example provides an optoelectronic device and its preparation method. Compared with the optoelectronic device in Example 1, the difference of the optoelectronic device in this example is that: the material of the active layer is replaced with "Zn 0.9 Cd 0.1 Se / Zn 0.68 Cd 0.32 Se / Zn 0.65 Cd0.35 S / Zn 0.5 Cd 0.5 S / ZnS quantum dots, where the core Zn 0.9 Cd 0.1 Se has a particle size of 4 nm, the average thickness of the auxiliary shell is 0.9 nm, the average thickness of the first shell is 0.9 nm, the average thickness of the second shell is 0.4 nm, and the average thickness of the third shell is 1.5 nm.

[0133] The preparation method of the optoelectronic device in this embodiment is carried out with reference to Example 1.

[0134] The preparation method of the quantum dots in this embodiment includes the following steps:

[0135] S13.1: Consistent with step S10.1;

[0136] S13.2: At 300 °C, inject 4 mL of Se-TOP solution into the first solution at a rate of 8 mL / h. At the same time, inject 3.2 mL of cadmium oleate solution into the second solution at a rate of 6.4 mL / h, and mix and react for 5 min to obtain a second solution containing the core and the auxiliary shell, where the auxiliary shell coats the core;

[0137] S13.3: At 300 °C, inject 4 mL of S-TOP solution into the first solution at a rate of 8 mL / h. At the same time, inject 3.5 mL of cadmium oleate solution into the second solution at a rate of 7 mL / h, and react and ripen at 300 °C for 40 min to obtain a third solution containing the core, the auxiliary shell and the first shell, where the first shell coats the auxiliary shell;

[0138] S13.4: Consistent with step S10.4;

[0139] S13.5: Consistent with step S10.5.

[0140] Example 7

[0141] This embodiment provides an optoelectronic device and its preparation method. Compared with the optoelectronic device in Example 1, the difference of the optoelectronic device in this embodiment is that: the material of the active layer is replaced with "Zn 0.9 Cd 0.1 Se / Zn 0.65 Cd 0.35 S / Zn 0.5 Cd 0.5 S / ZnS quantum dots", where the core Zn 0.9 Cd 0.1 Se has a particle size of 4 nm, the average thickness of the first shell is 1.2 nm, the average thickness of the second shell is 0.4 nm, and the average thickness of the third shell is 1.5 nm.

[0142] In this embodiment, the preparation method of the optoelectronic device is carried out with reference to Embodiment 1.

[0143] The preparation method of the quantum dots in this embodiment includes the following steps:

[0144] S14.1: Consistent with step S10.1;

[0145] S14.2: At 300 °C, inject 6 mL of S-TOP solution into the second solution at a rate of 8 mL / h. At the same time, inject 5.25 mL of cadmium oleate solution into the second solution at a rate of 7 mL / h, and mix and react for 5 min to obtain a second solution containing a core and a first shell layer, where the first shell layer coats the core;

[0146] S14.3: At 300 °C, inject 2 mL of S-TOP solution into the second solution at a rate of 8 mL / h. At the same time, inject 2.5 mL of cadmium oleate solution into the second solution at a rate of 10 mL / h, and mix and react to obtain a third solution containing a core, a first shell layer, and a second shell layer, where the second shell layer coats the first shell layer;

[0147] S14.4: At 300 °C, inject 8 mL of S-TOP solution into the third solution at a rate of 8 mL / h, mix and react to obtain a reaction solution containing quantum dots, cool to room temperature, and then purify the reaction solution containing quantum dots to obtain purified quantum dots.

[0148] Embodiment 8

[0149] This embodiment provides an optoelectronic device and its preparation method. Compared with the optoelectronic device in Embodiment 1, the differences of the optoelectronic device in this embodiment are: replacing the average thickness of the auxiliary shell layer with "1.2 nm", and replacing the average thickness of the first shell layer with "1.2 nm".

[0150] In this embodiment, the preparation method of the optoelectronic device is carried out with reference to Embodiment 1.

[0151] Compared with the preparation method of quantum dots in Example 1, the difference in the preparation method of quantum dots in this example is as follows: Step S10.2 is replaced with "At 300 °C, at a rate of 8 mL / h, inject 6 mL of Se-TOP solution into the first solution, and mix and react for 5 min to obtain a second solution containing a core and an auxiliary shell layer, where the auxiliary shell layer coats the core", and step S10.3 is replaced with "At 300 °C, at a rate of 8 mL / h, inject 6 mL of S-TOP solution into the second solution. At the same time, at a rate of 4.4 mL / h, inject 2.2 mL of cadmium oleate solution into the second solution, and react and ripen at 300 °C for 40 min to obtain a third solution containing a core, an auxiliary shell layer and a first shell layer, where the first shell layer coats the auxiliary shell layer".

[0152] Comparative Example 1

[0153] This comparative example provides an optoelectronic device and its preparation method. Compared with the optoelectronic device in Example 1, the difference in the optoelectronic device in this comparative example is that: the material of the active layer is replaced with "Zn 0.9 Cd 0.1 Se / ZnSe / Zn 0.5 Cd 0.5 S / ZnS quantum dots", where the average particle size of the core Zn 0.9 Cd 0.1 Se is 4 nm, the average thickness of the first shell layer is 0.9 nm, the average thickness of the second shell layer is 0.4 nm, and the average thickness of the third shell layer is 1.5 nm.

[0154] The preparation method of the optoelectronic device in this comparative example is carried out with reference to Example 1.

[0155] The preparation method of quantum dots in this comparative example includes the following steps:

[0156] S15.1. It is the same as step S10.1;

[0157] S15.2. At 300 °C, at a rate of 8 mL / h, inject 4 mL of Se-TOP solution into the first solution, and mix and react for 5 min to obtain a second solution containing a core and a first shell layer, where the first shell layer coats the core;

[0158] S15.3. At 300 °C, at a rate of 8 mL / h, inject 2 mL of S-TOP solution into the second solution. At the same time, at a rate of 10 mL / h, inject 2.5 mL of cadmium oleate solution into the second solution, and mix and react to obtain a third solution containing a core, a first shell layer and a second shell layer, where the second shell layer coats the first shell layer;

[0159] S15.4. At 300 °C, inject 8 mL of S-TOP solution into the third solution at a rate of 8 mL / h, mix and react to obtain a reaction solution containing quantum dots, cool to room temperature, and then purify the reaction solution containing quantum dots to obtain purified quantum dots.

[0160] Comparative Example 2

[0161] This comparative example provides an optoelectronic device and a preparation method thereof. Compared with the optoelectronic device in Example 1, the difference in the optoelectronic device in this comparative example is that: the material of the active layer is replaced with "Zn 0.9 Cd 0.1 Se / ZnS / Zn 0.5 Cd 0.5 S / ZnS quantum dots", where the core Zn 0.9 Cd 0.1 Se has a particle size of 4 nm, the average thickness of the first shell layer is 0.9 nm, the average thickness of the second shell layer is 0.4 nm, and the average thickness of the third shell layer is 1.5 nm.

[0162] The preparation method of the optoelectronic device in this comparative example refers to Example 1.

[0163] The preparation method of the quantum dots in this comparative example includes the following steps:

[0164] S16.1. Consistent with step S10.1;

[0165] S16.2. At 300 °C, inject 4 mL of S-TOP solution into the first solution at a rate of 8 mL / h, mix and react for 5 min to obtain a second solution containing the core and the first shell layer, where the first shell layer coats the core;

[0166] S16.3. At 300 °C, inject 2 mL of S-TOP solution into the second solution at a rate of 8 mL / h. At the same time, inject 2.5 mL of cadmium oleate solution into the second solution at a rate of 10 mL / h, mix and react to obtain a third solution containing the core, the first shell layer and the second shell layer, where the second shell layer coats the first shell layer;

[0167] S16.4. At 300 °C, inject 8 mL of S-TOP solution into the third solution at a rate of 8 mL / h, mix and react to obtain a reaction solution containing quantum dots, cool to room temperature, and then purify the reaction solution containing quantum dots to obtain purified quantum dots.

[0168] Experimental Example 1

[0169] The photoluminescence wavelength, full width at half maximum and photoluminescence efficiency of the quantum dots in the active layer of the optoelectronic devices in Examples 1 to 8, Comparative Example 1 and Comparative Example 2 are shown in Table 1 below:

[0170]

[0171] Among them, the photoluminescence wavelength, full width at half maximum, and photoluminescence efficiency of the quantum dots were all detected using a quantum dot - n - hexane solution with a concentration of 0.5 mg / mL. Figure 3 and Figure 4 respectively show the photoluminescence spectra of the quantum dots in Example 1, Comparative Example 1, and Comparative Example 2. From Figure 3 and Figure 4 it can be seen that compared with the quantum dots in Comparative Example 1 and Comparative Example 2, the quantum dots in Example 1 show a certain degree of blue - shift of the PL peak position.

[0172] Experimental Example 2

[0173] The performance of the optoelectronic devices in Examples 1 to 8, Comparative Example 1, and Comparative Example 2 was detected. The turn - on voltage, current, maximum brightness, emission spectrum, etc. of each optoelectronic device were obtained by using a FushiDa FPD optical property measurement device, and the device lifetime of each optoelectronic device was tested using a lifetime test device. The detection environmental conditions were: environmental temperature 25 °C, environmental humidity 50%.

[0174] Among them, the test method for the external quantum efficiency was: the external quantum efficiency of each optoelectronic device was detected using an EQE optical test instrument, and the maximum external quantum efficiency (EQE max , %) was calculated.

[0175] The detection method for the device lifetime included the steps of: under the drive of a constant current (2 mA), the electroluminescence lifetime analysis of each optoelectronic device was carried out using a lifetime test device, the time required for each optoelectronic device to decay from the maximum brightness to 95% was recorded, and the time required for each single - hole device to decay from 100% to 95% of the brightness at a brightness of 1000 nit (T95@1000nit,h) was calculated through the decay fitting formula.

[0176] The EQE max , turn - on voltage, and T95@1000nit of each optoelectronic device were detected in the first state and the second state respectively, where the first state was just after encapsulation, and the second state was 48 h after continuous power - on after encapsulation.

[0177] In addition, the electroluminescence peaks of each optoelectronic device were detected in the first state and the third state respectively, where the first state was just after encapsulation, and the third state was 24 h after continuous power - on after encapsulation.

[0178] The performance detection data of each optoelectronic device are shown in Table 2 and Table 3 below:

[0179] Table 2 List of Performance Detection Data of Optoelectronic Devices in the First State in Examples 1 to 8, Comparative Example 1 and Comparative Example 2

[0180]

[0181] Table 3 List of Performance Detection Data of Optoelectronic Devices in the Second State in Examples 1 to 8, Comparative Example 1 and Comparative Example 2

[0182]

[0183]

[0184] As can be seen from Table 1 and Table 2, compared with the optoelectronic devices of Comparative Example 1 and Comparative Example 2, the optoelectronic devices in Examples 1 to 8 have more advantages in performance stability. Taking the optoelectronic device in Example 2 as an example, the EQE max in the second state is only 3.6% lower than the EQE max in the first state. The turn-on voltage in the second state is only 2.04V higher than that in the first state, and the T95@1000nit in the second state is 50% lower than the T95@1000nit in the first state. For the optoelectronic device in Comparative Example 2, the EQE max in the second state is 8.3% lower than the EQE max in the first state. The turn-on voltage in the second state is only 2.64V higher than that in the first state, and the T95@1000nit in the second state is 72% lower than the T95@1000nit in the first state. In addition, whether in the first state or the second state, the optoelectronic devices in Examples 1 to 8 have better optoelectronic performance and device life.

[0185] As Figures 5 to 8 can be seen, during the operation of the optoelectronic device, as the power-on time prolongs, there is an obvious "blue shift" phenomenon in the electroluminescence peak of the optoelectronic device in Comparative Example 2. Therefore, the performance stability of the optoelectronic device in Comparative Example 2 is poor. The reason may be that: Cd ions in the quantum dot core and / or the second shell migrate to other shells, resulting in problems such as the widening of the quantum dot bandgap, the weakening of the well-like characteristics of the shell, and the weakening of long-wavelength luminescence. Compared with the optoelectronic device in Comparative Example 2, the "blue shift" phenomenon of the optoelectronic devices in Examples 1 to 3 is significantly weakened. Especially for the optoelectronic device in Example 2, there is almost no "blue shift" phenomenon within 24h of continuous power-on after encapsulation. Therefore, using the quantum dots of the embodiments of the present application as the material of the active layer in the optoelectronic device can effectively improve the "blue shift" problem, thereby improving the performance stability of the optoelectronic device.

[0186] The above has introduced in detail a quantum dot and an optoelectronic device including the quantum dot provided by the embodiments of the present application. 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 technical solution and its core idea of the present application; those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A quantum dot, characterized in that, The quantum dots have a core-shell structure, wherein, in the direction from the core of the quantum dots towards the outermost shell layer, the molar percentage of cadmium in the core of the quantum dots and the shell layer containing cadmium element gradually increases.

2. The quantum dot according to claim 1, wherein The shell of the quantum dots includes a first shell layer, a second shell layer and a third shell layer arranged in sequence. The first shell layer is closer to the core of the quantum dots than the third shell layer. The core of the quantum dots contains cadmium element, and at least one of the first shell layer to the third shell layer contains cadmium element; Optionally, the material of the core of the quantum dot is Zn x Cd (1-x) A, the material of the first shell is ZnD or Zn t Cd (1-t) D, the material of the second shell is Zn y Cd (1-y) E, the material of the third shell is ZnG or Zn m Cd (1-m) G, where A, D, and G are independently selected from Se or S, and x > t > y > m.

3. The quantum dot according to claim 2, wherein The structural composition of the quantum dots is Zn x Cd (1-x) A / Zn t Cd (1-t) D / Zn y Cd (1-y) E / ZnG, where x ranges from 0.8 to 0.95, t ranges from 0.62 to 0.8, and y ranges from 0.4 to 0.6; Preferably, t is selected from 0.65 to 0.

76.

4. The quantum dot according to claim 2, wherein The shell of the quantum dots further includes an auxiliary shell layer, and the auxiliary shell layer is arranged between the core of the quantum dots and the first shell layer; The auxiliary shell layer does not contain cadmium element; or, the auxiliary shell layer contains cadmium element, and the molar percentage of cadmium in the auxiliary shell layer is higher than that in the core of the quantum dots.

5. The quantum dot according to claim 4, wherein The material of the auxiliary shell layer is selected from ZnR or Zn z Cd (1-z) R, where R is selected from Se or S,; and / or The average thickness of the auxiliary shell layer is 0.8 nm to 1.5 nm.

6. The quantum dot according to claim 5, wherein The structural composition of the quantum dots is Zn x Cd (1-x) A / ZnR / ZnD / Zn y Cd (1-y) E / ZnG, where x is selected from 0.8 to 0.95 and y is selected from 0.4 to 0.6; Alternatively, the quantum dots have a structure composition of Zn x Cd (1-x) A / ZnR / Zn t Cd (1-t) D / Zn y Cd (1-y) E / ZnG, where x is selected from 0.8 to 0.95, t is selected from 0.62 to 0.8, and y is selected from 0.4 to 0.6; preferably, t is selected from 0.75 to 0.8; Alternatively, the quantum dots have a structural composition of Zn x Cd (1-x) A / Zn z Cd (1-z) R / ZnD / Zn y Cd (1-y) E / ZnG, where x is selected from 0.8 to 0.95, z is selected from 0.62 to 0.8, and y is selected from 0.4 to 0.6; preferably, z is selected from 0.62 to 0.7; Alternatively, the quantum dots have a structure composition of Zn x Cd (1-x) A / Zn z Cd (1-z) R / Zn t Cd (1-t) D / Zn y Cd (1-y) E / ZnG, where x is selected from 0.8 to 0.95, z is selected from 0.62 to 0.8, t is selected from 0.62 to 0.8, and y is selected from 0.4 to 0.6; preferably, z is selected from 0.75 to 0.8 and t is selected from 0.62 to 0.

7.

7. The quantum dot according to any one of claims 1 to 6, characterized in that, The average particle size of the quantum dots is 6 nm to 10 nm; and / or, the average particle size of the core of the quantum dots is 3 nm to 4.5 nm; and / or, the average thickness of the first shell layer is 0.8 nm to 1.5 nm; and / or, the average thickness of the second shell layer is 0.3 nm to 0.5 nm; and / or, the average thickness of the third shell layer is 1.1 nm to 2 nm.

8. An optoelectronic device, comprising an anode and a cathode disposed opposite to each other, and a plurality of functional layers disposed between the anode and the cathode, characterized in that, The material of at least one of the multiple functional layers includes the quantum dots as described in any one of claims 1 to 7.

9. The optoelectronic device according to claim 8, characterized in that, The multiple functional layers include an active layer, and the material of the active layer includes the quantum dots as described in any one of claims 1 to 7; Optionally, the active layer is a light-emitting layer or a light-absorbing layer.

10. The optoelectronic device according to claim 9, characterized in that, The multiple functional layers further include an electron functional layer, and the electron functional layer is arranged between the active layer and the cathode; and / or, the multiple functional layers further include a hole functional layer, and the hole functional layer is arranged between the active layer and the anode.

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