CN113969161A

CN113969161A - Preparation method of quantum dot, composition containing quantum dot and luminescent device

Info

Publication number: CN113969161A
Application number: CN202010714482.2A
Authority: CN
Inventors: 乔培胜; 余文华; 袁秀玲; 谢阳腊; 汪均
Original assignee: Najing Technology Corp Ltd
Current assignee: Najing Technology Corp Ltd
Priority date: 2020-07-23
Filing date: 2020-07-23
Publication date: 2022-01-25
Anticipated expiration: 2040-07-23
Also published as: CN113969161B

Abstract

The application provides a preparation method of a quantum dot, the quantum dot, a composition and a light-emitting device. By coating the II-III-V-VI-VI shell layer outside the III-V group quantum dot core, the problems of large fluorescence emission half-peak width, low fluorescence efficiency and poor stability of the III-V group quantum dot in the prior art are solved, and the prepared core-shell quantum dot has the advantages of narrow fluorescence emission half-peak width, high fluorescence efficiency and good stability in a quantum dot film.

Description

Preparation method of quantum dot, composition containing quantum dot and luminescent device

Technical Field

The application relates to the technical field of photoelectricity, in particular to a preparation method of quantum dots, the quantum dots, a composition containing the quantum dots and a light-emitting device.

Background

The quantum dot material is an inorganic material with the size of nanometer, has excellent luminous performance, and has wide application prospect in the fields of display, illumination, biology and the like. Compared with luminescent materials such as fluorescent powder and the like, the quantum dot has the advantages of adjustable luminescent range, narrow fluorescence half-peak width, high quantum efficiency, strong stability and the like. In consideration of environmental protection, the application of the existing cadmium-containing quantum dot material is greatly limited, and cadmium-free quantum dots represented by indium phosphide are the key points of research and development in recent years. In the indium phosphide nucleation, the indium phosphide has the characteristics of covalent bond combination, high nucleation speed, more lattice defects and the like, so that the fluorescence emission half-peak width is wider and the quantum efficiency is lower. Especially, the red light quantum dots further increase the difficulty of preparation due to the large nucleation size required. In addition, the intrinsic indium phosphide has more lattice defects and very low quantum efficiency, and the luminescent performance needs to be improved by coating a shell layer outside a quantum dot core. However, the InP quantum dots of III-V group have higher lattice mismatch with commonly used ZnSe or ZnS shell of II-VI group, which results in poor cladding effect.

The InP-based quantum dots in the prior art have the main problems of low fluorescence quantum yield, large luminescence half-peak width (low color purity) and poor light, heat and water stability which are main reasons for restricting the application of the InP-based quantum dots. How to reduce the half-peak width is always a hotspot and difficulty in the research of cadmium-free quantum dots.

Disclosure of Invention

The present application is directed to a quantum dot comprising a group III-V core and a group II-III-V-VI shell disposed directly on a surface of at least a portion of the group III-V core, the group II-III-V-VI shell comprising elemental selenium and elemental sulfur.

Further, the quantum dot may further include a multi-layer shell disposed on the group II-III-V-VI-VI shell layer and including at least two layers, and preferably, the multi-layer shell may include at least one group II-VI shell layer.

Further, the multilayer shell includes ZnSe, ZnSeS, ZnS, or a combination thereof, and preferably the thickness of the multilayer shell is 4 to 15 single layers.

Further, the ratio of the amounts of the two group VI elements in the group II-III-V-VI-VI shell is (0.02 to 8): 1, the ratio of the total molar amount of the group V element in the group III-V core and the group V element in the group II-III-V-VI-VI shell to the total molar amount of the two group VI elements in the group II-III-V-VI-VI shell is (0.08 to 9): 1.

furthermore, the average size of the quantum dots is 3.5-5.0 nm.

Further, the absorption ratio of the ultraviolet visible absorption spectrum of the quantum dot to the optical density at the position of 400nm to 450nm is (1.5-4): 1.

furthermore, the wavelength of the ultraviolet-visible absorption peak of the quantum dot is 580-630 nm, the half-peak width of the ultraviolet-visible absorption peak is less than or equal to 23nm, and the quantum dot is a cadmium-free quantum dot.

Further, the group III-V core includes at least one of indium and phosphorus and arsenic of group V elements, and the group II-III-V-VI-VI shell includes at least one of indium, zinc and phosphorus and arsenic of group V elements.

Further, the group III-V core and/or the group II-III-V-VI-VI shell further comprises a doped metal element or a doped non-metal element, the doped metal element is selected from Al, Ga, Tl, Li, Na, K, Rb, Cs, Be, Mg, Sr, Ba, V, Fe, Co, Zr, W, Ti, Mn, Ni, Sn, or a combination thereof, and the doped non-metal element is selected from B, O, S, Se, Te, F, Cl, Br, I, Si, or a combination thereof.

Furthermore, the maximum fluorescence emission wavelength of the quantum dots is adjustable within 600-650 nm.

Furthermore, the fluorescence emission half-peak width of the quantum dots is less than or equal to 36nm, and the fluorescence quantum efficiency is more than or equal to 60%.

The application also provides a preparation method of the quantum dot, which comprises the following steps: s1, preparing III-V group/II-III-V-VI group quantum dots; s2, mixing and heating a first II group element precursor, a first solvent and an optional first ligand to obtain a first system, mixing and reacting the first system and the III-V group/II-III-V-VI group quantum dots to obtain a second system, mixing the second system and the first VI group element precursor, continuing to react, and obtaining a third solution containing the III-V group/II-III-V-VI group quantum dots after the reaction is ended; wherein, the VI element in the II-III-V-VI shell of the III-V group/II-III-V-VI group quantum dot is selenium element or sulfur element, the VI element of the first VI element precursor is one or two of selenium element and sulfur element, when the VI element of the first VI element precursor is only one element, the one element is different from the VI element in the II-III-V-VI group shell, and the feeding molar quantity of the first II element precursor is larger than that of the first VI element precursor.

Further, the step S1 includes: preparing a first solution containing III-V group nucleus and a second solution containing II-III-V-VI group quantum dots; and mixing the first solution and the second solution, heating for reaction, and obtaining the III-V group/II-III-V-VI group quantum dot after the reaction is finished.

Further, the ratio of the amounts of the group II element in the first group II element precursor and the group VI element in the first group VI element precursor is (200 to 5): 1; preferably, the ratio of the amount of the group II element in the first group II element precursor to the amount of the first ligand is (40 to 5): 1.

further, the preparation method further comprises the following steps: s3, adding long chain fatty acid into the third solution, reacting the long chain fatty acid with the remaining first group II element precursor and the remaining first group VI element precursor in the step S2, and obtaining a fourth solution containing the first group III-V/group II-V-group VI-group/group II-VI quantum dot or group III-V/group II-III-V-group VI/group II-VI-group quantum dot after the reaction is completed, or the preparation method further comprises: s3', adding a long chain fatty acid and a fourth group VI element precursor into the third solution, wherein the long chain fatty acid reacts with the first group II element precursor and the fourth group VI element precursor remaining in the step S2, and the reaction is terminated to obtain a fourth solution containing the first group III-V/group II-V-VI-group/group II-VI quantum dot or group III-V/group II-V-VI-group/group II-VI-group quantum dot; preferably, the ratio of the amount of the group II element in the first group II element precursor to the amount of the long-chain fatty acid is (0.25 to 2): 1.

further, the preparation method further comprises the following steps: s4, adding a first selenium precursor into the fourth solution, heating and reacting for a certain time, obtaining a fifth solution containing second III-V group/II-III-V-VI-VI group/II-VI group quantum dots or first III-V group/II-III-V-VI-VI group/II-VI group quantum dots or III-V group/II-V-VI-VI group/II-VI group/VI group quantum dots after the reaction is finished, preferably, the ratio of the amount of the II group element in the first II group element precursor to the amount of the selenium element in the first selenium precursor is (50-2): 1.

further, the preparation method further comprises the following steps: s5, adding a first sulfur precursor into the fifth solution, heating and reacting for a certain time, obtaining a sixth solution containing second III-V group/II-III-V-VI-VI group/II-VI group quantum dots or III-V group/II-III-V-VI group/II-VI group quantum dots after the reaction is finished, preferably, the mass ratio of the II group element in the first II group element precursor to the sulfur element in the first sulfur precursor is (50-2): 1.

further, the step of preparing the first solution containing group III-V nuclei includes: mixing a first III group element precursor, optional fatty acid and a second solvent, heating to a first temperature, then cooling to a second temperature, adding a first V group element precursor, heating to a third temperature, and obtaining a first solution containing III-V group nuclei after the reaction is terminated; preferably, the ratio of the amounts of the group II element in the first group II element precursor and the group V element in the first group V element precursor is (200 to 40): 1, the ratio of the amounts of the group II element in the first group II element precursor and the group III element in the first group III element precursor is (200 to 8): 1.

further, the step of preparing the second solution containing the group II-III-V-VI quantum dots comprises: mixing a second III group element precursor, a second II group element precursor, a second ligand and a third solvent, heating and reacting for a certain time at a fourth temperature, then cooling to a fifth temperature, adding a second V group element precursor, a third ligand and a third VI group element precursor for reaction, and obtaining a second solution containing II-III-V-VI group quantum dots after the reaction is terminated; preferably, the ratio of the amounts of the group II element in the first group II element precursor and the group III element in the second group III element precursor is (40 to 4): 1, the ratio of the amounts of the group II element in the first group II element precursor and the group V element in the second group V element precursor is (40 to 4): 1, the ratio of the amounts of the group II element in the first group II element precursor and the group VI element in the third group VI element precursor is (40 to 4): 1.

further, the wavelength of the ultraviolet-visible absorption peak of the III-V group core is 460 to 550nm, the half-peak width of the ultraviolet-visible absorption peak of the III-V group core is 27 to 35nm, and preferably, the starting point of the ultraviolet-visible absorption peak of the II-III-V-VI group quantum dot is 400 to 500 nm.

Further, the group III-V core of the quantum dot includes at least one of indium and phosphorus and arsenic of group V elements, and the group II-III-V-VI-VI shell of the quantum dot includes at least one of indium, zinc, selenium, sulfur and phosphorus and arsenic of group V elements.

The application also provides a composition comprising the quantum dot obtained by any preparation method or any quantum dot.

The application also provides a light-emitting device comprising the quantum dots obtained by any one of the preparation methods or any one of the quantum dots.

By applying the technical scheme of the application and coating the II-III-V-VI-VI shell layer outside the III-V group quantum dot core, the problems of large half-peak width, low fluorescence efficiency and poor stability of the III-V group quantum dot in the prior art are solved, and the prepared core-shell quantum dot has the advantages of narrow half-peak width, high fluorescence efficiency and good stability in a quantum dot film.

Drawings

Fig. 1 is a diagram of the uv-vis absorption spectra of the mixed solution containing InZnPS quaternary quantum dots, the solution containing InP cores, and the purified InP/InZnPS quantum dots of example 1 of the present application;

FIG. 2 is a transmission electron microscope image of InP/InZnPS quantum dots of example 1 of the present application;

FIG. 3 is a transmission electron microscope image of InP/InZnPSSe/ZnSe/ZnS quantum dots of embodiment 3 of the present application;

FIG. 4 is a graph of the UV-VIS absorption spectrum of InP/InZnPSSe/ZnSe/ZnS quantum dots of example 3 of the present application;

FIG. 5 is a transmission electron microscope image of InP/InZnPS/ZnSe/ZnS quantum dots of the comparative example of the present application.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

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

The present application provides a quantum dot comprising a group III-V core, and a group II-III-V-VI-VI shell disposed directly on a surface of at least a portion of the group III-V core, the group II-III-V-VI-VI shell comprising elemental selenium and elemental sulfur. By coating the II-III-V-VI-VI shell layer outside the III-V group quantum dot core, the problems of large half-peak width, low fluorescence efficiency and poor stability of the III-V group quantum dot in the prior art are solved, and the prepared core-shell quantum dot has the advantages of narrow half-peak width, high fluorescence efficiency and good stability in a quantum dot film.

"group II" in this application refers to group IIA and group IIB elements, which may include Cd, Zn, Hg, and Mg, but is not limited thereto.

In some embodiments, the quantum dot further comprises a multilayer shell disposed on the group II-III-V-VI-VI shell layer and comprising at least two layers, preferably the multilayer shell comprises at least one group II-VI shell layer. For example, the quantum dot includes a ZnSe shell layer disposed outside the group III-V/II-III-V-VI-VI core-shell structure and a ZnS shell layer covering the ZnSe shell layer. Each of the at least two layers of the above-mentioned multilayer shell comprises one or more monolayers (monolayers).

In some embodiments, the group II-III-V-VI-VI shell described above is a fully alloyed shell or a partially alloyed shell. The complete alloying means that all elements are uniformly distributed, and the partial alloying means that all elements in partial regions are uniformly distributed or partial elements are uniformly distributed in all regions.

In some embodiments, the multilayer shell comprises ZnSe, ZnSeS, ZnS, or a combination thereof, preferably the multilayer shell has a thickness of 4 to 15 monolayers (monolayers).

In some embodiments, the multi-layer shell has a thickness of 4-8 monolayers. In some embodiments, the multi-layer shell has a thickness of 9-15 monolayers.

In some embodiments, the ratio of the amounts of species of the two group VI elements in the II-III-V-VI-VI shell is (0.02-8): 1, the ratio of the total molar amount of group V elements in the group III-V core and group V elements in the group II-III-V-VI-VI shell to the total molar amount of two group VI elements in the group II-III-V-VI-VI shell is (0.08-9): 1. namely, the ratio of the amount of the selenium element to the amount of the sulfur element in the II-III-V-VI-VI family shell is (0.02-8): the ratio of the amounts of the sulfur element and the selenium element in the 1, or II-III-V-VI-VI family shell is (0.02-8): 1.

in some embodiments, the ratio of the amounts of species of the two group VI elements in the II-III-V-VI-VI shell is (0.02-4): 1 or (4.1-8): 1, the ratio of the total molar amount of group V elements in the group III-V core and group V elements in the group II-III-V-VI-VI shell to the total molar amount of two group VI elements in the group II-III-V-VI-VI shell is (0.08-3): 1 or (3.1-5.9): 1 or (6-9): 1.

in some embodiments, the average size of the quantum dots is 3.5-5.0 nm. The quantum dots prepared in the same batch may have a relatively constant particle shape, and the average size is determined by transmission electron microscope images, but is not limited thereto. When the quantum dots have a spherical shape, the average size of the quantum dots may be a diameter. When the quantum dot is a particle having a non-spherical shape, the size of the quantum dot may be the diameter of a circle having an equivalent (equal) area calculated from a two-dimensional area of an electron microscope image of the quantum dot.

In some embodiments, the absorption ratio of the ultraviolet visible absorption spectrum of the quantum dot coated with the multi-shell layer to the optical density at 450nm is (1.5-4): 1, the absorption ratio is expressed as OD_450nm/OD_400nm。

In some embodiments, the wavelength of the ultraviolet-visible absorption peak of the quantum dot is 580-630 nm, the half-peak width of the ultraviolet-visible absorption peak is less than or equal to 23nm, and the quantum dot is a cadmium-free quantum dot.

In some embodiments, the group III-V core includes at least one of indium and phosphorus and arsenic of group V elements, and the group II-III-V-VI-VI shell further includes at least one of indium, zinc, and phosphorus and arsenic of group V elements.

In some embodiments, the group III-V core and/or the group II-III-V-VI-VI shell layer further comprises a doped metallic element selected from Al, Ga, Tl, Li, Na, K, Rb, Cs, Be, Mg, Sr, Ba, V, Fe, Co, Zr, W, Ti, Mn, Ni, Sn, or combinations thereof or a doped non-metallic element selected from B, O, S, Se, Te, F, Cl, Br, I, Si, or combinations thereof. The doping elements are doped in the III-V group core, the II-III-V-VI-VI group shell, or the combination thereof.

In some embodiments, the group III-V nucleus may include: GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb.

The group II-III-V-VI quantum dots can include: GaZnPS, GaZnPSe, GaZnPTe, GaZnAsS, GaZnAsSe, GaZnAsTe, GaZnNS, GaZnNSe, GaZnNTe, GaZnSbS, GaZnSbSe, GaZnSbTe, AlZnPS, AlZnPSe, AlZnPTe, AlZnAsS, AlZnAsSe, AlZnAsTe, AlZnNS, AlZnNSe, AlZnNTe, AlZnSbS, AlZnSbSe, AlZnSbTe, InZnPS, InZnPSe, InZnPTe, InZnAsS, InZnAsSe, InZnAsTe, InZnNS, InZnNSe, InZnNTe, InZnSbS, InZnSbSe, InZnSbTe.

In some embodiments, the quantum dots are InP/InZnPSSe/ZnSe/ZnS, InP/InZnPSSe/ZnS/ZnSe/ZnS, InP/InZnPSSe/ZnSeS/ZnSe/ZnS, InP/InZnAsSSe/ZnSeS/ZnSe, InAs/InZnPSSe/ZnSe/ZnS, InAs/InZnPSSe/ZnSe/ZnS, InAs/InZnPSSe/ZnSeS/ZnSe/ZnS, InAs/InZnAsSSe/ZnSe or InAs/InZnAsSSe/ZnSeS/ZnSe.

In some embodiments, the maximum fluorescence emission wavelength of the quantum dots is tunable within 600-650 nm.

In some embodiments, the 34nm quantum dot has a fluorescence emission half-peak width of 39nm and a fluorescence quantum efficiency of 60% or more.

In some embodiments, the quantum dots have a fluorescence emission half-peak width of 36nm or less and a fluorescence quantum efficiency of 60% or more.

In some embodiments, the quantum dots have a fluorescence emission half-peak width of less than or equal to 34nm and a fluorescence quantum efficiency of greater than or equal to 70%.

In some embodiments, the quantum dots have a fluorescence emission half-peak width of less than or equal to 34nm and a fluorescence quantum efficiency of less than 80%.

In some embodiments, 30nm < quantum dots have a fluorescence emission half-peak width of less than or equal to 34nm and a fluorescence quantum efficiency of less than 80%.

The application also provides a preparation method of the quantum dot, which comprises the following steps: s1, preparing III-V group/II-III-V-VI group quantum dots; s2, mixing and heating a first II group element precursor, a first solvent and an optional first ligand to obtain a first system, mixing and reacting the first system and the III-V group/II-III-V-VI group quantum dots for a certain time to obtain a second system, mixing the second system and the first VI group element precursor, continuing to react, and obtaining a third solution containing the III-V group/II-III-V-VI group quantum dots after the reaction is terminated; the VI element in the II-III-V-VI shell layer of the III-V group/II-III-V-VI group quantum dot is selenium element or sulfur element, the VI element of the first VI element precursor is one or two of selenium element and sulfur element, and when the VI element of the first VI element precursor is only one element, the one element is different from the VI element in the II-III-V-VI group shell layer, and the feeding molar quantity of the first II element precursor is larger than that of the first VI element precursor.

In the production method of the present invention, "molar ratio" or "ratio of amounts of substances" refers to a ratio of amounts of substances of raw materials, and is not a ratio of amounts of substances in a reaction process. In addition, the reaction of adding substance A to substance B in the present application means that substance A and substance B are allowed to contact each other to cause a physical or chemical reaction by an addition means, and the addition means may be a means of adding substance A to a container in which substance B is placed, a means of adding substance B to a container in which substance A is placed, or a means of adding substance A and substance B to the same container at the same time, unless otherwise specified, only which addition means is specified. The charged molar amounts of the first group II element precursor and the first group VI element precursor are calculated as the molar amounts of the group II element and the group VI element, respectively.

In step S2, the first group II element precursor and the first group II element precursor are grown on the basis of the group II-III-V-VI shell by mixing the first group II element precursor with the group III-V/group II-III-V-VI quantum dot to react and controlling the input amount of the first group VI element precursor to be smaller than the input amount of the first group II element precursor, thereby forming the group II-III-V-VI shell. According to the method, the II-III-V-VI-VI shell layer is coated outside the III-V group quantum dot core, so that the problems of large fluorescence emission half-peak width, low fluorescence efficiency and poor stability of the III-V group quantum dot in the prior art are solved, and the prepared core-shell quantum dot has the advantages of narrow fluorescence emission half-peak width, high fluorescence efficiency and good stability in a quantum dot film.

In some embodiments, step S1 includes: preparing a first solution containing III-V group nucleus and a second solution containing II-III-V-VI group quantum dots; and mixing the first solution and the second solution, heating for reaction, and obtaining the III-V group/II-III-V-VI group quantum dot after the reaction is ended. The group II-III-V-VI quantum dots in the raw material are fully alloyed quantum dots or partially alloyed quantum dots, and the group II-III-V-VI quantum dots as the raw material are preferably fully alloyed quantum dots in order to promote more uniform distribution of elements in the group II-III-V-VI shell layer of the obtained group III-V/group II-III-V-VI quantum dots.

In some embodiments, the first solution and the second solution are mixed and then heated to react at a reaction temperature of 250 to 320 ℃.

In some embodiments, the group III-V core of the quantum dot includes at least one of indium and phosphorous and arsenic of group V elements, and the group II-III-V-VI shell of the quantum dot includes at least one of indium, zinc, selenium, sulfur, and phosphorous and arsenic of group V elements.

In some embodiments, the wavelength of the UV-visible absorption peak of the III-V group quantum dot core is 460-550 nm, the half-peak width of the UV-visible absorption peak of the III-V group quantum dot core is 27-35 nm, and the starting point of the bottom of the UV-visible absorption peak of the II-III-V-VI group quantum dot is 400-500 nm. It should be noted that the ultraviolet-visible absorption peak in the present application refers to the first exciton peak in the ultraviolet-visible absorption spectrum, the first exciton peak in the ultraviolet-visible absorption spectrum of the III-V group quantum dot is more obvious, and the other peak peaks are not obvious.

In some embodiments, the maximum fluorescence emission wavelength of the quantum dot prepared by the method is adjustable within 600-650 nm, the fluorescence emission half-peak width of the quantum dot is less than or equal to 36nm, and the fluorescence quantum efficiency is more than or equal to 60%. In some preferred embodiments, the fluorescence emission half-peak width of the quantum dots is less than or equal to 34nm, and the fluorescence quantum efficiency is more than or equal to 70%.

In some embodiments, the group III-V/group II-III-V-VI-VI core-shell quantum dots prepared by the present application have an average size of 3.5 to 5.0 nm.

In some embodiments, the quantum dot coated with the multi-shell layer prepared by the present application has an absorption ratio of 400nm to 450nm in the ultraviolet-visible absorption spectrum of (1.5-4): 1.

in some embodiments, the reaction temperature of step S2 is 250-320 ℃.

In some embodiments, the first group II element precursor is a zinc precursor, which can be, but is not limited to, zinc acetate, zinc propionate, zinc acetylacetonate, zinc butyrate. The first group VI element precursor may be, but is not limited to, Se-TBP (selenium-tributylphosphine), Se-TOP (selenium-trioctylphosphine), Se-TPP (selenium-triphenylphosphine), Se-ODE (selenium-octadecene), Se-TOPO (selenium-octadecene)Trioctyloxyphosphine), S-TBP (thio-tributylphosphine), S-TOP (thio-trioctylphosphine), S-ODE (thio-octadecene), S-OA (thio-oleic acid), S- (TMS)₂(bis (trimethylsilyl) sulfide), S-OLA (thio-oleylamine), DDT (dodecylmercaptan), Se-S-TOP (selenium-thio-trioctylphosphine), Se-S-TBP (selenium-thio-tributylphosphine), Se-S-ODE (selenium-thio-octadecene).

In some embodiments, the group VI element of the first group VI element precursor is two of elemental selenium and elemental sulfur, i.e., a selenium-sulfur mixed precursor. When the VI element in the II-III-V-VI shell is sulfur element, the molar ratio of the selenium element to the sulfur element in the selenium-sulfur mixed precursor is (0.2-5): 1, when the VI group element in the II-III-V-VI group shell layer is selenium element, the molar ratio of the sulfur element in the selenium-sulfur mixed precursor to the selenium element is (0.2-5): 1.

in some embodiments, the first solvent is a non-coordinating solvent, and can be, but is not limited to, ODE (octadecene), squalane, octadecane, docosane, paraffin oil, eicosene, trioctylamine.

In some embodiments, the first ligand is an organophosphine ligand, which may be, but is not limited to, TOP (trioctylphosphine), TBP (tributylphosphine), TPP (triphenylphosphine), dioctylphosphine, diphenylphosphine.

To further ensure formation of the group II-III-V-VI-VI shell structure outside the group III-V core and to avoid excess first group VI element precursor leading to self-nucleation of the group II-VI particles (e.g., ZnSe self-nucleation) and thereby affecting the half-peak width of the group III-V/group II-V-VI-VI quantum dots, in some embodiments the ratio of the amount of species of group II element in the first group II element precursor to the group VI element in the first group VI element precursor is (200-5): 1. preferably, the ratio of the amount of the group II element in the first group II element precursor to the amount of the first ligand is (40 to 5): 1, the ligand in the proportion is favorable for dissolving the first II group element precursor and is used as a surface ligand of the III-V group/II-III-V-VI group quantum dot in the reaction, so that the reaction is better carried out.

In some embodiments, the ratio of the amount of species of group II elements in the first group II element precursor to group VI elements in the first group VI element precursor is (100-5): 1, or (80-5): 1, or (50-5): 1, or (20-5): 1, or (10-5): 1, or (200-150): 1, or (150-100): 1.

in some embodiments, the method of making further comprises: s3, adding long-chain fatty acid into the third solution, reacting the long-chain fatty acid with the remaining first group II element precursor and the remaining first group VI element precursor in the step S2, and obtaining a fourth solution containing the first group III-V/group II-V-VI-group/group II-VI quantum dots or the group III-V/group II-V-VI-group/group II-VI-VI quantum dots after the reaction is finished, or the preparation method further comprises the following steps: s3', adding long-chain fatty acid and a fourth group VI element precursor into the third solution, reacting the long-chain fatty acid with the first group II element precursor and the fourth group VI element precursor remained in the step S2, and obtaining a fourth solution containing the first group III-V/group II-V-VI-group/group II-VI quantum dots or group III-V/group II-V-VI-group/group II-VI-VI quantum dots after the reaction is finished.

In step S3, when the remaining first group VI element precursor is one of a sulfur precursor and a selenium precursor, a fourth solution containing the first group III-V/II-III-V-VI/II-VI quantum dots is obtained after the reaction is terminated; and when the rest first VI group element precursor is a selenium-sulfur mixed precursor, obtaining a fourth solution containing III-V group/II-III-V-VI-VI group/II-VI-VI group quantum dots after the reaction is ended.

In some embodiments, the fourth group VI element precursor of step S3' is a selenium precursor, a sulfur precursor, or a selenium-sulfur mixed precursor, and examples of the fourth group VI element precursor may include Se-TBP (selenium-tributylphosphine), Se-TOP (selenium-trioctylphosphine), Se-TPP (selenium-triphenylphosphine), Se-ODE (selenium-octadecene), Se-TOPO (selenium-trioctylphosphine oxide), S-TBP (sulfur-tributylphosphine), S-TOP (sulfur-trioctylphosphine), S-ODE (sulfur-octadecene), S-OA (sulfur-oleic acid), S- (TMS)₂(bis (trimethylsilyl) sulfide), S-OLA (thio-oleylamine), DDT (dodecylmercaptan), Se-S-TOP (selenium-thio-trioctylphosphine), Se-S-TBP (selenium-thio-tributylphosphine), Se-S-ODE (selenium-thio-octadecene), but are not limited thereto. Preferably, the fourth group VI element precursor is the same as the element species contained in the first group VI element precursor, but the precursor species may be different. When the precursor of the fourth VI group element is one of selenium precursor or sulfur precursor, the first VI group element containing precursor is obtained after the reaction is finishedA fourth solution of group III-V/group II-V-VI-VI/group II-VI quantum dots. And when the fourth VI element precursor is a selenium-sulfur mixed precursor, obtaining a fourth solution containing III-V group/II-III-V-VI-VI group/II-VI-VI group quantum dots after the reaction is ended.

In order to completely react the long chain fatty acid and the first group II element precursor remaining in the step S2, in some embodiments, the temperature of the third solution is controlled to be 150 to 250 ℃ when the long chain fatty acid is added in the step S3. The long-chain fatty acid reacts with the first II group element precursor to form long-chain fatty acid salt, then the long-chain fatty acid salt is heated to 250-340 ℃, preferably 280-320 ℃, and the long-chain fatty acid salt directly participates in the formation of II-VI group shells.

The carbon chain length of the long-chain fatty acid is 8 to 30, and examples thereof may include one or more of OA (oleic acid), myristic acid, stearic acid, caprylic acid, capric acid, behenic acid, and triacontanoic acid.

In some embodiments, the ratio of the amount of species of group II elements in the first group II element precursor to the group VI elements in the fourth group VI element precursor is (200-50): 1.

in some embodiments, the molar ratio of the group II element in the first group II element precursor to the long chain fatty acid added in step S3 is (0.25-2): 1, thereby promoting the long-chain fatty acid to completely react with the first II group element precursor remaining in the step S2, directly participating the subsequent coating of the II-VI group shell in the generated long-chain fatty acid salt, and absorbing the long-chain fatty acid salt on the surface of the III-V group/II-III-V-VI group quantum dot as a ligand, improving the solubility of the quantum dot in a non-coordination solvent system, passivating the surface of the quantum dot, reducing the surface defect of the quantum dot, and being beneficial to the subsequent shell coating.

In embodying the method of preparing the quantum dot, the manner of selecting whether to adopt step S3 or step S3' depends mainly on the charging ratio of the first group II element precursor and the first group VI element precursor in step S2. When the feeding ratio of the first group II element precursor to the first group VI element precursor is high, that is, the first group VI element precursor is substantially completely consumed in step S2, a small amount of group VI element precursor can be supplemented in the manner of step S3' to form a group II-VI (or group II-VI-VI) thin shell; when the feeding ratio of the first group II element precursor to the first group VI element precursor is low, i.e. the first group VI element precursor still remains in step S2, the method of step S3 is selected to directly form the group II-VI (or group II-VI-VI) thin shell layer.

In some embodiments, the method of making further comprises: s4, adding the first selenium precursor into the fourth solution, heating and reacting for a certain time, and obtaining a fifth solution containing second III-V group/II-V-VI-VI group/II-VI group quantum dots or first III-V group/II-V-VI-VI group/II-VI group quantum dots or III-V group/II-V-VI-VI group/II-VI group quantum dots after the reaction is finished.

A II-VI group (or II-VI-VI group) thin shell layer is firstly coated outside the III-V group/II-III-V-VI group core-shell structure, and then a II-VI group thick shell layer is coated on the basis of the thin layer, so that the narrowing of the half peak width of the quantum dot and the improvement of the quantum efficiency are facilitated. The group II-VI (or group II-VI-VI) thin shell layer has a thickness of not more than 3 monolayers, preferably 1 to 2 monolayers, and the group II-VI thick shell layer has a thickness of 3 to 10 monolayers, preferably 3 to 6 monolayers.

In some embodiments, the temperature of the heating reaction of step S4 is 250 to 340 ℃, preferably 280 to 320 ℃. The first selenium precursor may be, but is not limited to, Se-TBP (selenium-tributylphosphine), Se-TOP (selenium-trioctylphosphine), Se-TPP (selenium-triphenylphosphine), Se-ODE (selenium-octadecene), Se-TOPO (selenium-trioctylphosphine oxide).

To avoid excess first selenium precursor in the system, resulting in insufficient residual amount of first group II element precursor to support further coating, in some embodiments, the molar ratio of group II element in the first group II element precursor to selenium element in the first selenium precursor is (50-2): 1.in some embodiments, the molar ratio of the group II element in the first group II element precursor to the selenium element in the first selenium precursor is (30-10): 1, or (20-11): 1, or (9.9-2.1): 1.

in some embodiments, the method of making further comprises: s5, adding a first sulfur precursor into the fifth solution, heating and reacting for a certain time, and obtaining a sixth solution containing second III-V group/II-V-VI-VI group/II-VI group quantum dots or III-V group/II-III-V-VI group/II-VI group after the reaction is finished.

In some embodiments, the temperature of the heating reaction in step S5 is 250 to 340 ℃, preferably 280 to 320 ℃, the thickness of the II-VI shell formed at different temperatures is different from the luminous efficiency of the III-V/II-III-V-VI/II-VI quantum dots, and the shell grows more uniformly at high temperature. The first sulfur precursor can be, but is not limited to, S-TBP (sulfur-tributylphosphine), S-TOP (sulfur-trioctylphosphine), S-ODE (sulfur-octadecene), S-OA (sulfur-oleic acid), S- (TMS)₂Bis (trimethylsilyl) sulfide), S-OLA (thio-oleylamine), DDT (dodecylmercaptan).

In some embodiments, the molar ratio of the group II element in the first group II element precursor to the sulfur element in the first sulfur precursor is (50-2): 1.in some embodiments, the molar ratio of the group II element in the first group II element precursor to the sulfur element in the first sulfur precursor is (49-40): 1, or (39-30): 1, or (29-20): 1, or (19-9): 1, or (8-2.1): 1.

in some embodiments, the step of preparing the first solution comprising group III-V nuclei comprises: mixing a first III group element precursor, optional fatty acid and a second solvent, heating to a first temperature, then cooling to a second temperature, adding a first V group element precursor, heating to a third temperature, and obtaining a first solution containing III-V group quantum dot cores after the reaction is terminated. Preferably, the first group III element precursor is an indium precursor or a gallium precursor, the first group V element precursor is a phosphorus precursor or an arsenic precursor, and the optional fatty acid has a carbon chain length of 6 to 20, and the first temperature is 150 to 250 ℃, the second temperature is 30 to 200 ℃, the third temperature is 250 to 320 ℃, and the second temperature is preferably 30 to 100 ℃.

In some embodiments, the properties of the group III-V core are adjusted in the step of preparing the first solution comprising group III-V cores described above by adding a dopant comprising a doped metallic element selected from Al, Ga, Tl, Li, Na, K, Rb, Cs, Be, Mg, Sr, Ba, V, Fe, Co, Zr, W, Ti, Mn, Ni, Sn, or combinations thereof or a doped non-metallic element selected from B, O, S, Se, Te, F, Cl, Br, I, Si, or combinations thereof.

In some embodiments, the ratio of the amount of species of group II elements in the first group II precursor to group V elements in the first group V precursor is (200-40): 1, the ratio of the amounts of the group II element in the first group II element precursor and the group III element in the first group III element precursor is (200 to 8): 1.

in some embodiments, the ratio of the amount of species of group II elements in the first group II precursor to group V elements in the first group V precursor is (199-185): 1, or (184-165): 1, or (164-155): 1, or (154-135): 1, or (134-115): 1, or (114-95): 1, or (94-85): 1, or (84-55): 1, or (54-40): 1. the ratio of the amounts of the group II element in the first group II element precursor to the group III element in the first group III element precursor is (199-185): 1, or (184-165): 1, or (164-155): 1, or (154-135): 1, or (134-115): 1, or (114-95): 1, or (94-85): 1, or (84-55): 1, or (54-35): 1, or (34-25): 1, or (24-15): 1, or (14-8): 1.

examples of the first group III element precursor may include indium acetate, indium chloride, indium oxide, indium hydroxide, indium bromide, or indium iodide, but are not limited thereto; examples of the first group V element precursor may include TMS-P (tris (trimethylsilyl) phosphine), TES-P (tris (triethylsilyl) phosphine), TPS-P (tris (triphenylsilyl) phosphine), TMS-As (tris (trimethylsilyl) arsenic), or TES-As (tris (triethylsilyl) arsenic), but are not limited thereto; examples of the fatty acid may include one or more of caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, but are not limited thereto; examples of the second solvent may include one or more of ODE (octadecene), squalane, octadecane, docosane, paraffin oil, eicosene, trioctylamine, but are not limited thereto.

In some embodiments, the step of preparing the second solution comprising group II-III-V-VI quantum dots comprises: mixing a second III group element precursor, a second II group element precursor, a second ligand and a third solvent, heating and reacting for a certain time at a fourth temperature, then cooling to a fifth temperature, adding a second V group element precursor, a third ligand and a third VI group element precursor for reaction, and obtaining a second solution containing the II-III-V-VI group quantum dots after the reaction is terminated. Preferably, the second group III element precursor is an indium precursor or a gallium precursor, the first group II element precursor is a zinc precursor, the second group V element precursor is a phosphorus precursor or an arsenic precursor, and the third group VI element precursor is a selenium precursor or a sulfur precursor; the second ligand is fatty acid with a carbon chain length of 6-20, and the second ligand can be one or more of oleic acid, caproic acid, caprylic acid, capric acid, myristic acid, stearic acid and arachidic acid; the third ligand is alkyl phosphine or alkylamine, and the third ligand can be one or more of TOP (trioctyl phosphine), TBP (tributyl phosphine), TPP (triphenyl phosphine), dioctyl phosphine and diphenyl phosphine; the third solvent may be, but is not limited to, one or more of ODE (octadecene), squalane, octadecane, docosane, paraffin oil, eicosene, trioctylamine. More preferably, the fourth temperature is 150 to 250 ℃ and the fifth temperature is 25 to 150 ℃. Preferably, the fourth temperature is 150-180 ℃ and the fifth temperature is 25-80 ℃.

In some embodiments, the properties of the group III-V core are adjusted in the step of preparing the second solution containing group II-III-V-VI quantum dots by adding a dopant comprising a doped metallic element selected from Al, Ga, Tl, Li, Na, K, Rb, Cs, Be, Mg, Sr, Ba, V, Fe, Co, Zr, W, Ti, Mn, Ni, Sn, or a combination thereof or a doped non-metallic element selected from B, O, S, Se, Te, F, Cl, Br, I, Si, or a combination thereof.

In some embodiments, in the step of preparing the second solution containing the group II-III-V-VI quantum dots, the temperature is decreased to the fifth temperature, and the second group V element precursor, the third ligand, and the third group VI element precursor are added, preferably, a mixture of the second group V element precursor and the third ligand is added, and then the third group VI element precursor is added.

In some embodiments, the ratio of the amount of species of group II elements in the first group II element precursor to group III elements in the second group III element precursor is (40-4): 1, the ratio of the amounts of the group II element in the first group II element precursor and the group V element in the second group V element precursor is (40-4): 1, the ratio of the amounts of the group II element in the first group II element precursor and the group VI element in the third group VI element precursor is (40-4): 1.in some embodiments, the ratio of the amount of species of group II elements in the first group II element precursor to group III elements in the second group III element precursor is (40-20): 1 or (19-4): 1.in some embodiments, the ratio of the amount of species of group II elements in the first group II element precursor to the group V elements in the second group V element precursor is (40-20): 1 or (19-4): 1.in some embodiments, the ratio of the amount of species of group II elements in the first group II element precursor to group VI elements in the third group VI element precursor is (40-20): 1 or (19-4): 1.

in some embodiments, the wavelength of the ultraviolet visible absorption peak of the III-V group/II-III-V-VI-VI group core-shell quantum dot is 580-630 nm, and the half-peak width of the ultraviolet visible absorption peak is less than or equal to 23 nm. The half-width half maximum of the ultraviolet-visible absorption peak is the peak width of the right half-width half maximum of the ultraviolet-visible absorption peak of the quantum dot, and is known by the english name half width at half-maximum (hwhm). The ultraviolet-visible absorption spectrum of the III-V group equivalent quantum dots is asymmetric left and right, and the fluorescence spectrum is very weak, so the uniformity of the quantum dots is generally explained by the half-peak width of the right side of the ultraviolet-visible absorption spectrum.

In some embodiments, the III-V group core has a UV-visible absorption peak wavelength of 460-550 nm, a half-peak width of the UV-visible absorption peak of 27-35 nm, and the starting point of the UV-visible absorption peak of the II-III-V-VI group quantum dot is 400-500 nm.

The application also provides a light-emitting device comprising the quantum dots obtained by any one of the preparation methods or any one of the quantum dots. The quantum dot has narrow fluorescence emission half-peak width, high fluorescence efficiency and good stability, so that a light-emitting device comprising the quantum dot has good luminous efficiency and service life.

The light emitting device may be an electroluminescent device or a photoluminescent device. The photoluminescence device can comprise a quantum dot film, a quantum dot diffusion plate, a quantum dot light guide plate, a quantum dot color film or a quantum dot LED, and can also be a backlight module containing quantum dots. The light emitting device may be a lighting or display device.

The application also provides a composition, and the quantum dot obtained by any one of the preparation methods or the composition comprises any one of the quantum dots. The quantum dot has narrow half-peak width, high fluorescence efficiency and good stability, so that a light-emitting device comprising the quantum dot has good luminous efficiency and service life. The composition may be an optical material, a color conversion material, an ink, a coating, a labeling agent, a luminescent material, or the like.

In some embodiments, the composition includes a glue, a polymeric colloid, or a solvent.

In certain embodiments, the host material may be present in the composition in an amount of about 80 to about 99.5 weight percent. Examples of particularly useful host materials include, but are not limited to, polymers, oligomers, monomers, resins, adhesives, glasses, metal oxides, and other non-polymeric materials. Preferred host materials include polymeric and non-polymeric materials that are at least partially transparent, and preferably completely transparent, to the preselected wavelength of light.

The advantageous effects of the present application will be further described below with reference to examples and comparative examples. As used herein, "about" includes the stated value and is meant to be within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art in view of the measurement method or measurement error (i.e., limitations of the measurement system) for the particular parameter. For example, "about" may mean within one or more standard deviations, or within ± 10%, or 5%, of the stated value.

[ example 1 ]

Synthesis of InP/InZnPS Quantum dot (UV-visible absorption peak position: 585nm, half-peak width of UV-visible absorption peak: 23nm)

(1) Accurately weigh 1mmol of In (Ac)₃(indium acetate), 1mmol Zn (Ac)₂(Zinc acetate), 5mmol tetradecanoic acid, 20mL ODE in 100mL three-necked flask, nitrogen for 10 min. Heating to 180 deg.C, exhausting gas for 30min, cooling to 100 deg.C, injecting mixed solution of 0.5mmol TMS-P (30 wt%, ODE solution), 5mmol TOP and 1mmol DDT, stirring for 60min to form mixed solution containing InZnPS quaternary quantum dots, and measuring the absorption peak of ultraviolet and visible lightThe starting point of the bottom of the peak is 400nm (figure 1) for standby. Due to quantum confinement effect, the size of the nanocrystal is reflected by the position of the starting point of the bottom of the ultraviolet-visible absorption peak, and the wavelength of the position of the starting point of the bottom of the ultraviolet-visible absorption peak is shorter because the size of the InZnPS quaternary quantum dot in the mixed solution containing the InZnPS quaternary quantum dot is smaller.

(2) Accurately weigh 0.5mmol of In (Ac)₃1.5mmol octadecanoic acid and 20mL ODE were placed in a 100mL three-necked flask and purged with nitrogen for 10 min. And then raising the temperature to 180 ℃ and continuing exhausting for 30min, then reducing the temperature of the system to 100 ℃, injecting 0.2mmol of TMS-P (30 wt%, ODE solution), then raising the temperature to 300 ℃, keeping the temperature at 300 ℃ for 10min and then reducing the temperature to room temperature to form a solution containing initial InP nuclei, wherein the wavelength of the ultraviolet visible absorption peak is 510nm and the half-peak width of the ultraviolet visible absorption peak is 28nm (shown in figure 1). Here, due to the peak shape characteristic of the ultraviolet-visible absorption peak, the accurate half-peak width thereof cannot be obtained, and the size uniformity of the nanocrystal can be represented by the half-peak width on the right side thereof, i.e., the half-peak width.

(3) Slowly dripping the mixed solution containing the InZnPS quaternary quantum dots in the step (1) into the solution containing the initial InP nucleus in the step (2), continuously growing to a required peak position, and cooling and purifying to obtain the InP/InZnPS quantum dots. The determination of the position of the ultraviolet-visible absorption peak: 585nm, half-peak width of the uv-visible absorption peak: 23nm (FIG. 1). The mixed liquid containing the InZnPS quaternary quantum dots is dripped, so that InP nuclei continuously grow, and the red shift of an ultraviolet visible absorption peak is caused; in addition, the InP/InZnPS structure formed gradually continuously improves the size distribution uniformity of the quantum dots, so that the half-peak width of the ultraviolet visible absorption peak is continuously narrowed.

Synthesis of InP/InZnPSSe Quantum dot (UV-visible absorption peak position: 592nm, half-peak width of UV-visible absorption peak: 23nm)

(1) Accurately weighing 20mmol Zn (Ac)₂30mL of ODE was placed in a 100mL three-necked flask, and after introducing nitrogen gas for 30min, 2mmol of TBP was injected at room temperature. And then stopping exhausting, starting nitrogen protection gas, heating to 300 ℃, injecting InP/InZnPS quantum dots, and reacting for 30 min.

(2) Injecting 0.2mmol Se-TBP (solution with the concentration of 1 mmol/mL) and reacting for 10min to obtain the solution containing InP/InZnPSSe quantum dots. FIG. 2 is a transmission electron microscope picture of the quantum dots, the average size of the quantum dots is 4.0nm, and the distribution of the quantum dots is uniform.

[ example 2 ]

40mmol of OA is injected into the InP/InZnPSSe quantum dot-containing solution in the example 1, the solution is exhausted at 200 ℃ for 20min, the temperature is increased to 300 ℃, after reaction for 30min, 1mmol of Se-TBP (solution with the concentration of 1 mmol/mL) is injected, and the reaction for 30min is carried out, so as to obtain the InP/InZnPSSe/ZnSe quantum dot-containing solution.

[ example 3 ]

2mmol of S-TBP (solution with the concentration of 1 mmol/mL) is injected into the solution containing the InP/InZnPSSe/ZnSe quantum dots obtained in the example 2, and the solution containing the InP/InZnPSSe/ZnSe quantum dots is obtained after reaction for 30min at 300 ℃. And purifying to obtain InP/InZnPSSe/ZnSe/ZnS quantum dots. FIG. 3 is a transmission electron microscope picture of the quantum dots, the average size of the quantum dots is 9.0nm, the size distribution of the quantum dots is uniform, the coating of the shell layer is uniform, and the total number of the ZnSe/ZnS shell layer is about 8 monolayers. FIG. 4 is a graph showing the UV-visible absorption spectrum, in which the absorption ratio of optical density at 400nm to 450nm is 3.2: 1.

[ example 4 ]

This example differs from example 1 in that: the synthesis step (1) of InP/InZnPS quantum dots is added with 0.5mmol of In (Ac)₃3.5mmol tetradecanoic acid, 5mmol DDT, to which (2) 0.1mmol In (Ac) was added₃0.3mmol of hexadecanoic acid and 0.1mmol of TMS-P, wherein 0.5mmol of TBP is added in the synthesis step (1) of the InP/InZnPSSe quantum dot, 0.1mmol of Se-TBP is added in the synthesis step (2), and the average size of the InP/InZnPSSe quantum dot is 3.5 nm.

[ example 5 ]

This example differs from example 1 in that: InP/InZnPS quantum dot synthesis step (1) is added with 5mmol of In (Ac)₃17mmol octadecanoic acid, 5mmol TMS-P (30 wt%, ODE solution), 0.5mmol DDT and 2.5mmol In (Ac) added to (2)₃7.5mmol dodecanoic acid, 0.5mmol TMS-P (30 wt%, ODE solution), 4mmol TBP was added in the synthesis step (1) of InP/InZnPSSe quantum dots, 4mmol Se-TBP was added in the synthesis step (2), and the average size of the InP/InZnPSSe quantum dots was 5.0 nm.

[ example 6 ]

Synthesis of InP/InZnPSe Quantum dot (UV-visible absorption peak position: 595nm, half-peak width of UV-visible absorption peak: 27nm)

(1) Accurately weigh 1mmol of In (Ac)₃(indium acetate), 1mmol Zn (Ac)₂(Zinc acetate), 5mmol tetradecanoic acid, 20mL ODE in 100mL three-necked flask, nitrogen for 10 min. And then raising the temperature to 180 ℃ and continuing exhausting for 30min, then lowering the temperature to 100 ℃, injecting a mixed solution of 0.5mmol of TMS-P (30 wt%, ODE solution), 5mmol of TOP and 1mmol of Se-TBP (solution with the concentration of 1 mmol/mL), and stirring for 60min to form a mixed solution containing InZnPSe quaternary quantum dots, wherein the starting point of the peak bottom of the ultraviolet visible absorption peak is 500nm through determination for later use.

(2) Accurately weigh 0.5mmol of In (Ac)₃1.5mmol octadecanoic acid and 20mL ODE were placed in a 100mL three-necked flask and purged with nitrogen for 10 min. And then raising the temperature to 180 ℃ and continuing exhausting for 30min, cooling the system to 100 ℃, injecting 0.25mmol of TMS-P (30 wt%, ODE solution), then raising the temperature to 300 ℃, keeping the temperature at 300 ℃ for 10min and then cooling to room temperature to form a solution containing InP nuclei, wherein the wavelength of the ultraviolet-visible absorption peak is 500nm and the half-peak width of the ultraviolet-visible absorption peak is 28 nm.

(3) Slowly dripping the mixed solution containing the InZnPSe quaternary quantum dots in the step (1) into the solution containing the InP nucleus in the step (2), and continuously growing to a required peak position (the position of an ultraviolet-visible absorption peak: 595nm) to obtain the solution containing the InP/InZnPSe quantum dots.

Synthesis of InP/InZnPSeS Quantum dots (UV-visible absorption peak position: 600nm, half-peak width of UV-visible absorption peak: 26nm)

(3) Accurately weighing 20mmol Zn (AC)₂30mL of ODE was placed in a 100mL three-necked flask, and after introducing nitrogen gas for 30min, 2mmol of TBP was injected at room temperature. And then stopping exhausting, starting nitrogen protection gas, heating to 300 ℃, injecting InP/InZnPSe quantum dots, and reacting for 30 min.

(4) And (3) injecting 0.2mmol S-TBP (solution with the concentration of 1 mmol/mL) and reacting for 10min to obtain a solution containing InP/InZnPSeS quantum dots. The average size of the InP/InZnPSeS quantum dots is 4.5 nm.

[ example 7 ]

Synthesis of InAs/InZnAsS Quantum dot (UV-visible absorption peak position: 585nm, half-peak width of UV-visible absorption peak: 28nm)

(1) Accurately weigh 1mmol of In (Ac)₃(indium acetate), 1mmol Zn (Ac)₂(Zinc acetate), 5mmol tetradecanoic acid, 20mL ODE in 100mL three-necked flask, nitrogen for 10 min. And then raising the temperature to 180 ℃ and continuing exhausting for 30min, then lowering the temperature to 100 ℃, injecting a mixed solution of 0.5mmol of TMS-As (30 wt%, ODE solution), 5mmol of TOP and 1mmol of DDT, stirring for 60min to form a mixed solution containing InZnAsS quaternary quantum dots, and determining that the starting point of the bottom of the ultraviolet-visible absorption peak is 450nm for later use.

(2) Accurately weigh 0.5mmol of In (Ac)₃1.5mmol octadecanoic acid and 20mL ODE were placed in a 100mL three-necked flask and purged with nitrogen for 10 min. And then raising the temperature to 180 ℃, continuing to exhaust for 30min, cooling the system to 100 ℃, injecting 0.2mmol of TMS-As (30 wt%, ODE solution), then raising the temperature to 300 ℃, preserving the temperature for 10min at 300 ℃, then cooling to room temperature to form a solution containing InAs nuclei, and determining that the wavelength of the ultraviolet-visible absorption peak is 530nm and the half-peak width of the ultraviolet-visible absorption peak is 30 nm.

(3) Slowly dripping the mixed solution containing the InZnAsS quaternary quantum dots in the step (1) into the solution containing the InAs core in the step (2), and continuously growing to a required peak position (ultraviolet visible absorption peak position: 610nm) to obtain the solution containing the InAs/InZnAsS quantum dots.

Synthesis of InAs/InZnAsSSe Quantum dot (UV-visible absorption peak position: 620nm, half-peak width of UV-visible absorption peak: 28nm)

(5) Accurately weighing 20mmol Zn (Ac)₂30mL of ODE was placed in a 100mL three-necked flask, and after introducing nitrogen gas for 30min, 2mmol of TBP was injected at room temperature. And then stopping exhausting, starting nitrogen protection gas, raising the temperature to 300 ℃, injecting InAs/InZnAsS quantum dots, and reacting for 30 min.

(6) Injecting 0.2mmol Se-TBP (solution with the concentration of 1 mmol/mL) and reacting for 10min to obtain a solution containing InAs/InZnAsSSe quantum dots. The average size of InAs/InZnAsSSe quantum dots is 5.0 nm.

[ example 8 ]

80mmol OA and 0.1mmol S-TBP (solution with the concentration of 1 mmol/mL) are injected into the InP/InZnPSSe quantum dot-containing solution in the example 1, the gas is exhausted at 200 ℃ for 20min, the temperature is raised to 300 ℃, after the reaction is carried out for 30min, 1mmol Se-TBP (solution with the concentration of 1 mmol/mL) is injected, and the reaction is carried out for 30min, so as to obtain the InP/InZnPSSe/ZnSeS/ZnSe quantum dot-containing solution.

[ example 9 ]

80mmol OA and 0.4mmol S-TBP (solution with the concentration of 1 mmol/mL) are injected into the InP/InZnPSSe quantum dot-containing solution in the example 1, the gas is exhausted at 200 ℃ for 20min, the temperature is raised to 300 ℃, after the reaction is carried out for 30min, 1mmol Se-TBP (solution with the concentration of 1 mmol/mL) is injected, and the reaction is carried out for 30min, so as to obtain the InP/InZnPSSe/ZnSeS/ZnSe quantum dot-containing solution.

[ example 10 ]

This example differs from example 2 in that: the amount of OA added was 10mmol and the amount of Se-TBP added was 10 mmol.

[ example 11 ]

This example differs from example 3 in that: the amount of S-TBP added was 0.4 mmol. The shell layer ZnSe/ZnS is about 4 single layers, and the absorption ratio of the optical density at 400nm and 450nm of the ultraviolet visible absorption spectrum is 1.5: 1.

[ example 12 ]

This example differs from example 3 in that: the amount of S-TBP added was 10 mmol. The shell layer ZnSe/ZnS is about 15 single layers, and the absorption ratio of the optical density at 400nm and 450nm of the ultraviolet visible absorption spectrum is 4: 1.

[ example 13 ]

This example differs from example 1 in that: InP/InZnPS quantum dot synthesis step (1) is added with 5mmol of In (Ac)₃17mmol octadecanoic acid, 5mmol TMS-P (30 wt%, ODE solution), 0.5mmol DDT and 2.5mmol In (Ac) added to (2)₃7.5mmol dodecanoic acid, 0.4mmol TMS-P (30 wt%, ODE solution), 4mmol TBP added in the synthesis step (1) of InP/InZnPSSe quantum dots, and 0.1mmol Se-TBP added in the synthesis step (2).

[ example 14 ]

This example differs from example 1 in that: InP/InZnPS quantum dot synthesis step (1) is added with 5mmol of In (Ac)₃17mmol octadecanoic acid, 0.5mmol TMS-P (30 wt%, ODE solution), 5mmolDDT, (2) adding 2.5mmol In (Ac)₃7.5mmol dodecanoic acid, 0.14mmol TMS-P (30 wt%, ODE solution), 4mmol TBP added in the synthesis step (1) of InP/InZnPSSe quantum dots, and 3mmol Se-TBP added in the synthesis step (2).

[ COMPARATIVE EXAMPLES ]

(1) Accurately weigh 1mmol of In (Ac)₃(indium acetate), 1mmol Zn (Ac)₂(Zinc acetate), 5mmol tetradecanoic acid, 20mL ODE in 100mL three-necked flask, nitrogen for 10 min. And then raising the temperature to 180 ℃ and continuing to exhaust for 30min, then lowering the temperature to 100 ℃, injecting a mixed solution of 0.5mmol of TMS-P (30 wt%, ODE solution), 5mmol of TOP and 1mmol of DDT, and stirring for 60min to form a mixed solution containing the InZnPS quaternary quantum dots for later use.

(2) Accurately weigh 0.5mmol of In (Ac)₃1.5mmol octadecanoic acid and 20mL ODE were placed in a 100mL three-necked flask and purged with nitrogen for 10 min. And then raising the temperature to 180 ℃, continuing to exhaust for 30min, reducing the temperature of the system to 100 ℃, injecting 0.2mmol of TMS-P (30 wt%, ODE solution), raising the temperature to 300 ℃, preserving the temperature for 10min at 300 ℃, and then reducing the temperature to room temperature to form the InP core-containing solution.

(3) Slowly dripping the mixed solution containing the InZnPS quaternary quantum dots in the step (1) into the solution containing the InP nucleus in the step (2), and continuously growing to a required peak position (ultraviolet-visible absorption peak position: 585nm) to obtain the solution containing the InP/InZnPS quantum dots.

Synthesis of InP/InZnPS/ZnSe/ZnS quantum dots

(1) Accurately weighing 20mmol Zn (Ac)₂30mL of ODE and 40mmol of OA are placed in a 50mL three-neck flask, nitrogen is introduced for 10min, the mixture is heated to 180 ℃ and exhausted for 30min, 2mmol of TOP and a solution containing InP/InZnPS quantum dots are injected, 0.2mmol of Se-TBP (a solution with the concentration of 1 mmol/mL) is injected, and the temperature is raised to generate 300 ℃ for reaction for 30 min.

(2) While maintaining the system temperature at 300 ℃, 1mmol of Se-TBP (1 mmol/mL solution) was injected and reacted for 30 min.

(3) Maintaining the temperature of the system at 300 ℃, injecting 1mL S-TBP (solution with the concentration of 1 mmol/mL), and reacting for 30min to obtain a solution containing InP/InZnPS/ZnSe/ZnS quantum dots. And purifying to obtain InP/InZnPS/ZnSe/ZnS quantum dots. FIG. 5 is a transmission electron micrograph of InP/InZnPS/ZnSe/ZnS quantum dots, which has an average size of 8.0nm, a poor uniformity of the quantum dot size distribution, and a non-uniform angular cladding layer.

[ example 15 ]

The preparation method of the quantum dot film comprises the following steps:

preparing a commercial barrier film with a water vapor transmission rate of less than or equal to 0.3g/m²24h, oxygen transmission rate less than or equal to 0.3cm³/m²24 h.0.1 MPa. And (3) setting quantum dot glue on the barrier film, then setting the prepared barrier film on the quantum dot glue, and then curing the quantum dot glue to obtain the quantum dot film. The quantum dot glue is UV glue based on acrylic polymer, wherein the mass parts of the quantum dots are 2%, the mass parts of the acrylic monomer are 20%, the mass parts of the acrylic polymer are 70%, and the mass parts of other additives are 8%.

According to the preparation method of the quantum dot film, quantum dot films were prepared by using the quantum dots of examples 1 to 14 and comparative examples, respectively, and then fluorescence spectra were measured by using an integrating sphere tester, and the measurement results are recorded in table 1.

The quantum dot purification method comprises the following steps:

10mL of the stock solution was placed in a 50mL centrifuge tube, approximately 50mL of acetone was added, and the mixture was then spun down at 4000 rpm for 3 minutes. Taking out and pouring out the supernatant. The precipitate was dissolved in a certain amount of toluene.

The test method comprises the following steps:

during the reaction, a certain amount of toluene solution of quantum dots (adjusted to optical density OD of 4) was poured into a cuvette containing quartz, and the uv-vis absorption spectrum was measured. The quantum dots of each example and comparative example were subjected to measurement of fluorescence spectrum, and quantum efficiency was measured by an integrating sphere-fluorescence spectrometer, and the measurement results are respectively recorded in table 1.

The detection method of quantum efficiency comprises the following steps:

the 450nm blue LED is used as a backlight light source, the spectrum of the blue backlight and the spectrum of the transmission quantum dot luminescent material are respectively tested by an integrating sphere-fluorescence spectrometer, and the quantum efficiency of the quantum dot is calculated by the integral area of the spectrogram.

Quantum efficiency ═ quantum dot emission peak area/(peak area of blue backlight-peak area of blue light not absorbed through quantum dot light emitting material) × 100%.

TABLE 1

The detection method of the luminescence stability of the quantum dot film comprises the following steps:

respectively irradiating the quantum dot film with high-temperature blue light (70 ℃, 0.5W/cm)²) The change in quantum efficiency was measured with an integrating sphere tester under aging conditions such as high temperature and high humidity (65 ℃/95% relative humidity) and high temperature storage (85 ℃, 65 ℃), and the data were tabulated in table 2.

TABLE 2

Note: the above efficiency is relative efficiency, the efficiency of the comparative example is defined as 100%, and the other efficiencies correspond to the same ratio.

From the above description, it can be seen that the problems of large half-peak width, low fluorescence efficiency and poor stability of the III-V group quantum dots in the prior art are solved by coating the II-III-V-VI-group shell layer outside the III-V group core and optionally further coating at least one II-VI group shell layer outside the II-III-V-VI-group shell layer, and the prepared core-shell quantum dots have narrow half-peak width of fluorescence emission, high fluorescence efficiency and good stability in a quantum dot film.

The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A quantum dot comprising a group III-V core, and a group II-III-V-VI shell disposed directly on a surface of at least a portion of the group III-V core, the group II-III-V-VI shell comprising elemental selenium and elemental sulfur.

2. The quantum dot of claim 1, further comprising a multi-layer shell disposed on the group II-III-V-VI shell layer and comprising at least two layers, preferably the multi-layer shell comprises at least one group II-VI shell layer.

3. The quantum dot of claim 2, wherein the multi-layer shell comprises ZnSe, ZnSeS, ZnS, or a combination thereof, preferably wherein the multi-layer shell has a thickness of 4 to 15 monolayers.

4. The quantum dot of claim 1, wherein the ratio of the amounts of species of the two group VI elements in the group II-III-V-VI shell layer is (0.02-8): 1, the ratio of the total molar amount of group V elements in the group III-V core and group V elements in the group II-III-V-VI-VI shell to the total molar amount of two group VI elements in the group II-III-V-VI-VI shell is (0.08-9): 1.

5. the quantum dot of claim 1, wherein the average size of the quantum dot is 3.5-5.0 nm.

6. The quantum dot of claim 2, wherein the absorption ratio of the ultraviolet visible absorption spectrum of the quantum dot at 400nm to the optical density at 450nm is (1.5-4): 1.

7. the quantum dot of claim 1, wherein the wavelength of the ultraviolet-visible absorption peak of the quantum dot is 580-630 nm, the half-peak width of the ultraviolet-visible absorption peak is less than or equal to 23nm, and the quantum dot is a cadmium-free quantum dot.

8. The quantum dot of claim 1, wherein the group III-V core comprises at least one of indium and phosphorus and arsenic of group V elements, and wherein the group II-III-V-VI shell further comprises at least one of indium, zinc, and phosphorus and arsenic of group V elements.

9. The quantum dot of any one of claims 1 to 8, wherein the group III-V core and/or the group II-III-V-VI-VI shell layer further comprises a doped metal element selected from Al, Ga, Tl, Li, Na, K, Rb, Cs, Be, Mg, Sr, Ba, V, Fe, Co, Zr, W, Ti, Mn, Ni, Sn, or combinations thereof, or a doped non-metal element selected from B, O, S, Se, Te, F, Cl, Br, I, Si, or combinations thereof.

10. The quantum dot according to any one of claims 1 to 8, wherein the maximum fluorescence emission wavelength of the quantum dot is tunable within 600 to 650 nm.

11. The quantum dot according to any one of claims 1 to 8, wherein the fluorescence emission half-peak width of the quantum dot is less than or equal to 36nm, and the fluorescence quantum efficiency is greater than or equal to 60%.

12. The preparation method of the quantum dot is characterized by comprising the following steps:

s1, preparing III-V group/II-III-V-VI group quantum dots;

s2, mixing and heating a first II group element precursor, a first solvent and an optional first ligand to obtain a first system, mixing and reacting the first system and the III-V group/II-III-V-VI group quantum dots to obtain a second system, mixing and continuing to react the second system and the first VI group element precursor, and obtaining a third solution containing the III-V group/II-III-V-VI group quantum dots after the reaction is terminated;

wherein the group VI element in the group II-III-V-VI shell of the III-V/II-III-V-VI quantum dot is selenium element or sulfur element, the group VI element of the first group VI element precursor is one or two of selenium element and sulfur element, and when the group VI element of the first group VI element precursor is only one element, the one element is different from the group VI element in the group II-III-V-VI shell, the feeding molar amount of the first group II element precursor is larger than that of the first group VI element precursor.

13. The method for preparing a quantum dot according to claim 12, wherein the step S1 comprises:

preparing a first solution containing III-V group nucleus and a second solution containing II-III-V-VI group quantum dots;

and mixing the first solution and the second solution, heating for reaction, and obtaining the III-V group/II-III-V-VI group quantum dot after the reaction is ended.

14. The method for preparing a quantum dot according to claim 12, wherein the mass ratio of the group II element in the first group II element precursor to the group VI element in the first group VI element precursor is (200 to 5): 1; preferably, the ratio of the amount of group II element in the first group II element precursor to the amount of substance of the first ligand is (40-5): 1.

15. the method of claim 12, further comprising: s3, adding long chain fatty acid into the third solution, wherein the long chain fatty acid reacts with the first group II element precursor and the first group VI element precursor remaining in the step S2, and after the reaction is terminated, a fourth solution containing the first group III-V/group II-V-group VI-group II/group II-VI quantum dots or group III-V/group II-III-V-group VI/group II-VI quantum dots is obtained, or the preparation method further comprises: s3', adding long chain fatty acid and fourth group VI element precursor into the third solution, wherein the long chain fatty acid reacts with the first group II element precursor and the fourth group VI element precursor remaining in the step S2, and after the reaction is terminated, a fourth solution containing the first group III-V/group II-III-V-VI-group/group II-VI quantum dot or group III-V/group II-V-VI-group II/group II-VI quantum dot is obtained; preferably, the ratio of the amount of the group II element in the first group II element precursor to the amount of the long-chain fatty acid substance is (0.25 to 2): 1.

16. the method of claim 15, further comprising: s4, adding a first selenium precursor into the fourth solution, heating and reacting for a certain time, and obtaining a fifth solution containing second III-V group/II-III-V-VI-VI group/II-VI group quantum dots or first III-V group/II-III-V-VI-VI group/II-VI group quantum dots or III-V group/II-V-VI-VI group/II-VI group quantum dots after the reaction is finished, wherein the preferable ratio of the amounts of the II group elements in the first II group element precursor and the selenium element in the first selenium precursor is (50-2): 1.

17. the method of claim 16, further comprising: s5, adding a first sulfur precursor into the fifth solution, heating and reacting for a certain time, obtaining a sixth solution containing second III-V group/II-III-V-VI-group/II-VI group quantum dots or III-V group/II-III-V-VI group/II-VI group quantum dots after the reaction is finished, preferably, the mass ratio of the II group element in the first II group element precursor to the sulfur element in the first sulfur precursor is (50-2): 1.

18. the method of claim 13, wherein the step of preparing the first solution containing the group III-V nuclei comprises: mixing a first III group element precursor, optional fatty acid and a second solvent, heating to a first temperature, then cooling to a second temperature, adding a first V group element precursor, heating to a third temperature, and obtaining a first solution containing III-V group nuclei after the reaction is terminated; preferably, the ratio of the amounts of the group II element in the first group II element precursor to the substance of the group V element in the first group V element precursor is (200 to 40): 1, the ratio of the amounts of the group II elements in the first group II element precursor to the group III elements in the first group III element precursor is (200 to 8): 1.

19. the method of claim 13, wherein the step of preparing a second solution containing group II-III-V-VI quantum dots comprises: mixing a second III group element precursor, a second II group element precursor, a second ligand and a third solvent, heating and reacting for a certain time at a fourth temperature, then cooling to a fifth temperature, adding a second V group element precursor, a third ligand and a third VI group element precursor for reaction, and obtaining a second solution containing II-III-V-VI group quantum dots after the reaction is terminated; preferably, the ratio of the amounts of the group II elements in the first group II element precursor to the group III elements in the second group III element precursor is (40-4): 1, the ratio of the amounts of the group II elements in the first group II element precursor to the group V elements in the second group V element precursor is (40-4): 1, the ratio of the amounts of the group II elements in the first group II element precursor to the group VI elements in the third group VI element precursor is (40-4): 1.

20. the preparation method of the quantum dot according to claim 13, wherein the wavelength of the ultraviolet-visible absorption peak of the III-V core is 460 to 550nm, the half-width of the ultraviolet-visible absorption peak of the III-V core is 27 to 35nm, and preferably the starting point of the ultraviolet-visible absorption peak of the II-III-V-VI quantum dot is 400 to 500 nm.

21. The method of claim 12, wherein the group III-V core of the quantum dot comprises at least one of indium and phosphorus and arsenic of group V elements, and the group II-III-V-VI shell of the quantum dot comprises at least one of indium, zinc, selenium, sulfur, and phosphorus and arsenic of group V elements.

22. A composition comprising the quantum dot obtained by the method according to any one of claims 12 to 21 or comprising the quantum dot according to any one of claims 1 to 11.

23. A light-emitting device comprising the quantum dot obtained by the production method according to any one of claims 12 to 21 or comprising the quantum dot according to any one of claims 1 to 11.