Narrow band quantum dots and methods for making same - Patents.com

Abstract

A method for making multi-layered semiconductor particles, which can also be referred to as quantum dots, is described. The method includes mixing a first zinc-containing compound and a selenium-containing compound to form a ZnSe mixture. The zinc-containing compound and the selenium-containing compound are rapidly mixed in less than or about 5 seconds. The method also includes adding a tellurium-containing compound to the ZnSe mixture to form at least one ZnSeTe particle in the ZnSeTe mixture. Still further, the method includes forming a first shell layer on the ZnSeTe particle and forming a second shell layer on the first shell layer to make the multi-layered semiconductor particle. In additional embodiments, the reactants and particle mixture can be rapidly stirred. The light emitted by the multi-layered semiconductor particle can be characterized by an improved narrowband emission profile (i.e., sharpness).

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. Provisional Application No. 63 / 285,573, filed December 3, 2021, and U.S. Nonprovisional Application No. 18 / 070,703, filed November 29, 2022, which are incorporated herein by reference in their entireties for all purposes.

[0002] FIELD OF THE DISCLOSURE The present technology relates to narrow band emission quantum dots and methods of making same, and more particularly, to quantum dots made with multiple layers of inorganic materials. [Background technology]

[0003] High-resolution light-emitting diode (LED) displays can contain millions of micrometer-sized pixels arranged to form a viewing screen. Traditional LED displays generate color images by filtering white light from an LED light source into red, green, and blue pixels that emit at various intensities across the viewing screen. Other LED displays excite organic or inorganic compounds so that they emit specific colors of light, e.g., red, green, or blue light, depending on the pixel. These LED displays typically require fewer filters to block light of undesired colors, which can improve their brightness and power efficiency. However, many challenges exist with making luminescent materials, including making materials that emit consistent, sharp colors from batch to batch, and that are stable over the life of the display. Summary of the Invention [Problem to be solved by the invention]

[0004] Thus, there is a need for high quality materials for LED display devices. These and other needs are addressed by the present technology. [Means for solving the problem]

[0005] An embodiment of the present technology includes a method for making multi-layered semiconductor particles, which can also be referred to as quantum dots. The method includes a step of mixing a first zinc-containing compound and a selenium-containing compound to form a ZnSe mixture. The zinc-containing compound and the selenium-containing compound are mixed quickly in less than or about 5 seconds. The method also includes a step of adding a tellurium-containing compound to the ZnSe mixture to form at least one ZnSeTe particle in the ZnSeTe mixture. The method also further includes a step of forming a first shell layer on the ZnSeTe particle and a step of forming a second shell layer on the first shell layer to make the multi-layered semiconductor particle.

[0006] In an additional embodiment, the tellurium-containing compound is added to the ZnSe mixture in less than or about 5 seconds. In a further embodiment, the method also includes increasing the temperature of the ZnSeTe mixture at a rate of greater than or about 10° C. / min. In a further embodiment, the method also includes stirring the ZnSeTe mixture with a stirring mechanism rotating at greater than or about 1500 RPM. In yet a further embodiment, the tellurium-containing compound is added to the ZnSe mixture in an atmosphere containing less than or about 1 mol% oxygen. In a further embodiment, the ZnSeTe mixture contains less than or about 1 wt% water. In yet a further embodiment, the first shell layer includes zinc selenide (ZnSe). In a further embodiment, the second shell layer includes zinc sulfide (ZnS).

[0007] An embodiment of the present technology includes a further method of making multi-layer semiconductor particles. The method includes a step of combining a first zinc-containing compound and a selenium-containing compound to form a ZnSe mixture. The method also includes a step of adding a tellurium-containing compound to the ZnSe mixture to form at least one ZnSeTe particle in the particle-forming mixture. The particle-forming mixture is stirred with a stirring mechanism rotating at or about 1500 RPM during the formation of the at least one ZnSeTe particle. The method further includes a step of forming a ZnSe-containing shell layer on the ZnSeTe particle, and a step of forming a ZnS-containing shell layer on the ZnSe-containing shell layer to make the multi-layer semiconductor particle.

[0008] In an additional embodiment, the particle formation mixture is stirred with a stirring mechanism rotating at or about 1500 RPM during the formation of the ZnSe-containing and ZnS-containing shell layers. In yet an additional embodiment, the zinc-containing compound and the selenium-containing compound are mixed together for less than or about 5 seconds. In a further embodiment, the tellurium-containing compound is added to the ZnSe mixture for less than or about 5 seconds. In a further embodiment, the particle formation mixture is characterized by a temperature of greater than or about 300° C. during the formation of the at least one ZnSeTe particle. In a further embodiment, the particle formation mixture includes an alkylphosphine compound.

[0009] The embodiment of the present technology further includes a multi-layer semiconductor particle. The particle includes a core including ZnSeTe and an inner shell layer including ZnSe in contact with the core. The particle also includes an outer shell layer including ZnS in contact with the inner shell layer. The multi-layer semiconductor particle has an emission spectrum characterized by a primary peak having a full width at half maximum wavelength range of less than or about 40 nm.

[0010] In additional embodiments, the primary peak of the emission spectrum of the particles is less than or about 455 nm. In further embodiments, the emission intensity of the primary peak of the emission spectrum exceeds the emission intensity of all other emission peaks in the emission spectrum by a ratio of greater than or about 10:1. In further embodiments, the multi-layered semiconductor particles are characterized by an average particle size of less than or about 10 nm. In yet further embodiments, the core is sulfur-free. In further embodiments, the multi-layered semiconductor particles are incorporated into a micro LED device.

[0011] Embodiments of the present technology provide improved quantum dot particles characterized by narrowband emission. In embodiments, the present quantum dot particles may be characterized by an emission peak having a full width at half maximum (FWHM) size of less than or about 40 nm. In some embodiments, the emission peak may be characterized by a FWHM of less than or about 10 nm. In further embodiments, the primary narrowband emission peak may have an intensity significantly stronger than any other emission peak from the quantum dot particle. In embodiments, the intensity ratio of the primary emission peak to the next strongest emission peak may be greater than or about 10:1. These properties of the present quantum dot particles enable them to emit very sharp and monochromatic light. They may find application in displays such as micro LED displays where it is desired to reproduce sharp colors without the need for one or more layers of color filters that may significantly reduce the brightness of the display. These and other embodiments, along with many of their advantages and features, will be described in more detail in conjunction with the following description and accompanying figures.

[0012] A further understanding of the nature and advantages of the disclosed embodiments may be realized by reference to the remaining portions of the specification and the drawings. [Brief description of the drawings]

[0013] [Figure 1] 1 is a flow chart of selected operations in a method of making multi-layer semiconductor particles in accordance with an embodiment of the present technique. [Diagram 2] 4 is another flowchart of selected operations in a method of making multi-layer semiconductor particles in accordance with embodiments of the present technique. [Diagram 3] 1 is a simplified cross-sectional view of a multi-layer semiconductor particle according to an embodiment of the present technique. [Figure 4] 1 is a simplified schematic cross-sectional view of a display device incorporating multi-layer semiconductor particles according to an embodiment of the present technology. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Some of the figures are included as schematic diagrams. It is understood that the figures are for illustrative purposes and are not to be considered to scale unless specifically stated to be to scale. Furthermore, as schematic diagrams, the figures are provided to aid understanding and may not include all aspects or information compared to realistic representations and may include exaggerated material for illustrative purposes.

[0015] In the figures, similar components and / or features may have the same reference numeral label. Furthermore, various components of the same type may be distinguished by following a letter reference label that distinguishes between the similar components and / or features. If only a first reference numeral label is used in this specification, the description is applicable to any one of the similar components and / or features having the same first reference numeral label regardless of the letter suffix.

[0016] Quantum dots are nanometer-sized particles of inorganic materials that can emit light of a particular color after being excited by higher energy light. The color of the emitted light can depend on one or more properties of the particle, including the size, shape, and composition of the particle, among other properties. For quantum dots made of inorganic semiconductor materials, the color of the light they emit depends on the energy gap between the conduction band and valence band of the dot. When a quantum dot is excited, one or more electrons jump from the lower energy conduction band to the higher energy valence band. When the excited electrons drop back into the conduction band, they emit light whose color depends on the size of the energy gap between the valence band and the conduction band. The narrower the energy gap, the more the emitted light is shifted to the red, and the wider the energy gap, the more the emitted light is shifted to the blue. By adjusting one or more properties of the quantum dot that change the energy gap between the conduction band and the valence band, quantum dots can be made to emit light of virtually any color within the visible spectrum.

[0017] Due to the efficiency of quantum dots in converting high-energy white or ultraviolet light into visible light of a specific color, they have become increasingly popular for use in electronic displays, such as light-emitting diode (LED) displays. The ability of quantum dots to emit light of one color reduces the number of color filters and polarizers required in a display to block undesirable colored light from spoiling the displayed image. In many cases, quantum dot-containing displays are brighter, have higher contrast, and are more energy efficient than conventional LED displays without quantum dots.

[0018] The inorganic semiconductor materials used to make many types of quantum dots are also more stable than other types of color-specific photoluminescent compounds, such as many of the organic compounds used in organic light-emitting diode (OLED) displays. Inorganic quantum dots can be subjected to many excitation-emission cycles before chemical changes in the semiconductor material significantly reduce their conversion efficiency. On the other hand, the complex organic molecules used in OLED displays are more susceptible to chemical degradation over time. Organic molecules are also more sensitive than inorganic quantum dots to water and other contaminants that quench their photoluminescence.

[0019] Unfortunately, many challenges remain with the efficient manufacture of quantum dots that feature sharp color profiles centered around precise emission wavelengths. Often, quantum dots are formed with a lot of variability in the size, shape, and composition of the dots, among other variables. Quantum dots that include multiple layers of material beginning with an inner core and one or more surrounding shells may experience additional variability in the relative size and composition of the core and shell components. This variability can result in batches of quantum dots with broad color profiles that feature broad wavelength emission peaks with full width at half maximum (FWHM) of 50 nm or more. The variability can also result in alternating quantum dot formation pathways that produce prominent secondary emission peaks in the quantum dot material. In some cases, the ratio of emission intensities between prominent secondary emission peaks and the primary emission peaks may be greater than or about 0.1:1, greater than or about 0.2:1, greater than or about 0.5:1, or higher. In some instances, the secondary peaks may appear as shoulders to the primary emission peaks, while in other instances, the secondary peaks may be distinct peaks in the emission spectrum of the quantum dot material.

[0020] A broad emission peak near the primary emission wavelength and one or more prominent secondary emission peaks can substantially reduce the sharpness of the color emitted by the quantum dot material. Emissions characterized by sharper colors have narrower FWHM spectral peak profiles than emissions with less color sharpness. This reduction in color sharpness can result in display images characterized by duller colors, reduced color contrast, and undesirable hues, among other color defects. In many instances, the reduction in color sharpness can be correlated to shorter wavelength (i.e., bluer) emission peaks. In these instances, a quantum dot material made for a 550 nm emission peak (i.e., green light) can have a sharper color profile than a similar quantum dot material made for a 450 nm emission peak (i.e., blue light).

[0021] The present technology addresses this variability issue by using one or more techniques in the manufacture of quantum dots to reduce the variability of the luminescence properties of inorganic quantum dot materials and increase the sharpness of the color of the emitted light. An embodiment of the present technology includes a method of making multi-layer semiconductor quantum dot particles, including a step of rapidly mixing at least some of the reactants to create a core of the particle. It has been discovered that the rapid combination of these reactants results in a more uniform particle core, which contributes to reduced variability in the luminescence and increased sharpness of the color of the light emitted from the quantum dot material. In further embodiments, the reactants for creating the shell layer in contact with the core may also be rapidly mixed. Additional embodiments of the present technology include rapid stirring of the mixture in one or more operations in the formation of multi-layer quantum dots. It has been discovered that rapid stirring of the mixture from which the particle core is formed results in a more uniform particle core, which may also contribute to reduced variability in the luminescence and increased sharpness of the color of the light emitted from the quantum dot material. In further embodiments, the particle mixture may be rapidly stirred during the operation to create the shell layer in contact with the core. In a further embodiment, the particle mixture can be rapidly agitated during formation of the additional layer on the first shell layer in contact with the core.

[0022] The present technology can produce inorganic quantum dots that are characterized by increased color sharpness and fewer and less intense secondary emission peaks compared to conventional manufacturing methods.In an embodiment, the quantum dots can include a multi-layer structure of semiconductor materials, including a particle core made from a first group of semiconductor materials, an inner shell made from a second group of semiconductor materials, and an outer shell made from a third group of materials.In an additional embodiment, the present technology can include quantum dots that are characterized by a peak emission wavelength of less than or about 455 nm, and a full width at half maximum wavelength range of less than or about 40 nm.These quantum dots can be said to have a sharp blue light emission profile.

[0023] Figures 1 and 2 show flow charts illustrating some of the operations in the embodiments of the present method for making multi-layer semiconductor particles. Figure 3 shows a simplified cross-sectional view of one embodiment of those multi-layer semiconductor particles made by the present technology. The method 100 shown in Figure 1 and the method 200 shown in Figure 2 may or may not include operations including preparation of reactants that are combined to make the core and shell of the multi-layer semiconductor particle before the start of the method. The methods 100 and 200 may also include some optional operations that may or may not be specifically related to some embodiments of the method according to the present technology.

[0024] With particular reference to FIG. 1, the method 100 includes, in operation 105, combining first reactants to be incorporated into the core of the multi-layer semiconductor particle (i.e., quantum dot). In an embodiment, these first reactants are rapidly combined for a short period of time. In further embodiments, the combining time may be less than or about 10 seconds, less than or about 7.5 seconds, less than or about 5 seconds, less than or about 2.5 seconds, less than or about 1 second, or less than or about. The rapid combination of reactants reduces one local concentration center of the reactants, which may result in a more non-uniform formation of the quantum dot core, e.g., the QD core 302 of the multi-layer semiconductor particle 300 shown in FIG. 3.

[0025] In embodiments, the first reactants combined in operation 105 may include two or more semiconductor-containing reactants. In further embodiments, the first reactants may include at least one zinc-containing compound and at least one selenium-containing compound, among other first reactants. In further embodiments, the at least one zinc-containing compound may be an organozinc compound, among other zinc-containing compounds. In further embodiments, the organozinc compound may be zinc acetate or zinc stearate, among other organozinc compounds. In further embodiments, the organozinc compound may be anhydrous, such as anhydrous zinc acetate. In embodiments, the at least one selenium compound may be selenium complexed with an organophosphorus complexing agent. In additional embodiments, the organophosphorus complexing agent may be a trialkyl-phosphine compound. In further embodiments, the trialkyl-phosphine compound may be one or more of trihexylphosphine, triseptylphosphine, triocetylphosphine, and trinonylphosphine, among other trialkylphosphine compounds.

[0026] In further embodiments, the first reactants may further comprise additional compounds that facilitate rapid combination of at least one zinc-containing compound and at least one selenium-containing compound. In embodiments, these additional compounds may comprise unsaturated or saturated alkyl hydrocarbons having more than or about 10 carbon atoms, more than or about 12 carbon atoms, more than or about 15 carbon atoms, more than or about 18 carbon atoms, more than or about 20 carbon atoms, or more than that. In further embodiments, the alkyl hydrocarbons may comprise one or more of 1-octadecene, 1-decene, 1-hexadecene, 1-dodecene, 1-eicosene, and tetradecene, among other alkyl hydrocarbons. In further embodiments, these additional compounds may comprise organic acids having more than or about 12 carbon atoms, more than or about 15 carbon atoms, more than or about 18 carbon atoms, more than or about 20 carbon atoms, or more than that. In further embodiments, the organic acid is selected from the group consisting of acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, heptanoic acid, caprylic acid, capric acid, undecanoic acid, lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, acrylic acid, methacrylic acid, but-2-enoic acid, but-3-enoic acid, pent-2-enoic acid, pent-4-enoic acid, hex-2-enoic acid, hex-3-enoic acid, hex-4-enoic acid, hex-5-enoic acid, hex-6-enoic acid, hex-7-enoic acid, hex-8-enoic acid, hex-9-enoic acid, hex-10-enoic acid, hex-11-enoic acid, hex-12-enoic acid, hex-13-enoic acid, hex-14-enoic acid, hex-15-enoic acid, hex-16-enoic acid, hex-17-enoic acid, hex-18-enoic acid, hex-19-enoic acid, hex-20-enoic acid, hex-21-enoic acid, hex-22-enoic acid, hex-23-enoic acid, hex-24-enoic acid, hex-25-enoic acid, hex-26-enoic acid, hex-27-enoic acid, hex-28-enoic acid, hex-29-enoic acid, hex-3 ... The fatty acids may include one or more of enoic acid, hept-6-enoic acid, oct-2-enoic acid, dec-2-enoic acid, undec-10-enoic acid, dodec-5-enoic acid, oleic acid, gadoleic acid, erucic acid, linoleic acid, alpha-linolenic acid, calendic acid, eicosadienoic acid, eicosatrienoic acid, arachidonic acid, stearidonic acid, benzoic acid, para-toluic acid, ortho-toluic acid, meta-toluic acid, hydrocinnamic acid, and oleic acid.

[0027] In additional embodiments, the first reactants may be combined at a temperature of greater than or about 90° C., greater than or about 100° C., greater than or about 110° C., greater than or about 120° C., greater than or about 130° C., greater than or about 140° C., greater than or about 150° C., or higher. In further embodiments, the temperature of the combined first reactants may be increased to greater than or about 10° C., greater than or about 170° C., greater than or about 180° C., greater than or about 190° C., greater than or about 200° C., greater than or about 210° C., greater than or about 220° C., or higher, during the reaction of the combined first reactants to form the first portion of the QD core. In further embodiments, the first portion of the QD core may include zinc and selenium. In further embodiments, the first portion of the QD core may be tellurium-free.

[0028] The method 100 may further include, in operation 110, adding additional reactants to the first portion of the QD cores. In embodiments, these additional reactants may be added quickly to the mixture containing the first portion of the QD cores in a short period of time. In further embodiments, the addition time may be less than or about 10 seconds, less than or about 7.5 seconds, less than or about 5 seconds, less than or about 2.5 seconds, less than or about 1 second, or less than or about. The rapid addition of the additional reactants reduces one local concentration center of the reactants, which may result in more non-uniform incorporation of the additional reactants into the first portion of the quantum dot cores. In additional embodiments, the additional reactants may include one or more tellurium-containing reactants. In yet additional embodiments, the tellurium-containing reactants may include tellurium complexed with an organophosphorus complexing agent. In additional embodiments, the organophosphorus complexing agent may be a trialkyl-phosphine compound. In further embodiments, the trialkyl-phosphine compound may be one or more of trihexylphosphine, triceptylphosphine, triocetylphosphine, and trinonylphosphine, among other trialkylphosphine compounds. In embodiments, the addition of additional reactants to the first portion of the QD core may form a mixture of QD core reactants.

[0029] Method 100 may also include, in operation 115, heating the mixture of QD core reactants. In embodiments, the mixture may be heated to a temperature of greater than or about 250° C., greater than or about 260° C., greater than or about 270° C., greater than or about 280° C., greater than or about 290° C., greater than or about 300° C., or higher. In further embodiments, the increase in temperature may be characterized by a temperature increase rate of greater than or about 10° C. / min, greater than or about 11° C. / min, greater than or about 12° C. / min, greater than or about 13° C. / min, greater than or about 14° C. / min, greater than or about 15° C. / min, or higher. The increase in temperature of the mixture provides efficient incorporation of additional reactants into the first portion of the QD core to form an intact QD core, e.g., QD core 302. In embodiments, QD core 302 may include zinc, selenium, and tellurium in a ZnSeTe core. In further embodiments, the QD core reactant mixture may remain at the heated temperature for more than 30 minutes or more, more than 45 minutes or more, more than 60 minutes or more, more than 75 minutes or more, more than 90 minutes or more, more than 100 minutes or more, more than 120 minutes or more, or longer, during which the QD cores 302 are formed.

[0030] The method 100 may also further include cooling the heated mixture of QD core 302 particles in operation 120. The cooling operation may reduce the temperature of the heated mixture to less than or about 290° C., less than or about 280° C., less than or about 270° C., less than or about 260° C., less than or about 250° C., or less. In additional embodiments, the temperature reduction may be characterized by a temperature reduction rate of less than or about 10° C. / min, less than or about 7.5° C. / min, less than or about 5° C. / min, less than or about 2.5° C. / min, less than or about 1° C. / min, or less than or about 1° C. / min. In embodiments, the cooling operation reduces the temperature of the heated mixture of QD core 302 particles in preparation for the addition of inner shell reactants to the QD core particles. The reduction in temperature allows the inner shell reactants to be more uniformly distributed across the QD core 302 particles before reacting to form the inner shell layer 304 around the QD core 302.

[0031] The method 100 may also further include adding an inner shell layer reactant to the mixture of QD core particles with reduced temperature in operation 125. In an embodiment, the inner shell reactant may be added quickly to the mixture of QD core particles in a short period of time. In further embodiments, the addition time may be less than or about 10 seconds, less than or about 7.5 seconds, less than or about 5 seconds, less than or about 2.5 seconds, less than or about 1 second, or less than or about. The rapid addition of the inner shell reactant reduces the concentration center of the reactant, which may result in a wider variation in the properties of the inner shell, such as the inner shell 304 around the QD core 302 in the multi-layer semiconductor particle 300. These inner shell properties may include the composition and thickness of the inner shell 304, among other properties. In embodiments, the inner shell 304 may have a thickness of greater than or about 0.5 nm, greater than or about 1 nm, greater than or about 1.5 nm, greater than or about 2 nm, greater than or about 2.5 nm, greater than or about 3 nm, greater than or about 3.5 nm, greater than or about 4 nm, greater than or about 4.5 nm, greater than or about 5 nm, greater than or about 5.5 nm, greater than or about 6 nm, or more.

[0032] In embodiments, the inner shell reactants may include a zinc-containing reactant and a selenium-containing reactant, among other reactants. In additional embodiments, the zinc-containing reactant may include anhydrous zinc acetate, and the selenium-containing reactant may include selenium mixed with a complexing agent, such as triocetylphosphine. In further embodiments, the inner shell reactants may include additional compounds, such as unsaturated or saturated alkyl hydrocarbons and organic acids. In further embodiments, the unsaturated or saturated alkyl hydrocarbons may include 1-octadecene, and the organic acid may include oleic acid. In further embodiments, the inner shell 304 formed from the inner shell reactants may include a zinc-selenium (ZnSe) material. In additional embodiments, the combined mixture of the inner shell reactants and the QD core particles may be heated to promote the formation of the inner shell 304 on the QD cores 302. In further embodiments, the combined mixture may be heated to a temperature of greater than or about 250° C., greater than or about 260° C., greater than or about 270° C., greater than or about 280° C., greater than or about 290° C., greater than or about 300° C., or higher. In further embodiments, the combined mixture may be heated to the heating temperature for greater than or about 1 minute, greater than or about 2.5 minutes, greater than or about 5 minutes, greater than or about 7.5 minutes, greater than or about 10 minutes, or longer.

[0033] The method 100 may also further include adding an outer shell layer reactant to the particle mixture in operation 130. In an embodiment, the outer shell mixture may be added quickly to the particle mixture in a short period of time. In further embodiments, the addition time may be less than or about 10 seconds, less than or about 7.5 seconds, less than or about 5 seconds, less than or about 2.5 seconds, less than or about 1 second, or less than or about. The rapid addition of the outer shell reactant reduces the concentration center of the reactant that may result in a wider variation in the properties of the outer shell, such as the outer shell 306 around the inner shell 304 in the multi-layer semiconductor particle 300. These outer shell properties may include the composition and thickness of the outer shell 306, among other properties. In an embodiment, the outer shell 306 may have a thickness of more than or about 1 nm, more than or about 2 nm, more than or about 3 nm, more than or about 4 nm, more than or about 5 nm, or more.

[0034] In additional embodiments, the combined mixture of outer shell reactants and particles may be maintained at the same heating temperature as the combined mixture of inner shell reactants and QD cores 302. The temperature of the combined mixture of outer shell reactants and particles may be greater than or about 250° C., greater than or about 260° C., greater than or about 270° C., greater than or about 280° C., greater than or about 290° C., greater than or about 300° C., or higher. In further embodiments, the combined mixture may be held at the heating temperature for greater than or about 1 minute, greater than or about 2.5 minutes, greater than or about 5 minutes, greater than or about 7.5 minutes, greater than or about 10 minutes, or longer to promote the formation of the outer shell 306 on the inner shell 304 of the multi-layered semiconductor particle 300.

[0035] In further embodiments, the outer shell reactants may include, among other reactants, a zinc-containing reactant and a sulfur-containing reactant. In additional embodiments, the zinc-containing reactant may include anhydrous zinc acetate and the sulfur-containing reactant may include sulfur mixed with a complexing agent such as triocetylphosphine. In yet additional embodiments, the sulfur-containing reactant may include one or more of 1-octanethiol, 1-dodecanethiol, 1-octadecanethiol, tributylphosphine sulfide, cyclohexyl isothiocyanate, α-toluenethiol, ethylene trithiocarbonate, allyl mercaptan, bis(trimethylsilyl) sulfide, trioctylphosphine sulfide, 1-undecanethiol, 1-hexadecanethiol, 1-tetradecanethiol, 1-decanethiol, 2-phenylethanethiol, 4-methylbenzenethiol, 4-methoxybenzyl mercaptan, tert-dodecyl mercaptan, 2-,3-,10-mercaptopinane, cyclohexanethiol, and di-tert-butyl disulfide, among other sulfur-containing reactants. In further embodiments, the sulfur-containing reactant may be poly(ethylene glycol) methyl ether thiol having a molecular weight of 600-3000, poly(ethylene glycol) dithiol having a molecular weight of 600-3000, poly(ethylene glycol) dithiol having the formula HSCH, among other sulfur-containing reactants. 2 (CH 2 ) n CH 2 It may contain one or more of alkanedithiols of SH (n=2 to 30), trimethylolpropane tris(3-mercaptopropionate), and 2,2'-(ethylenedioxy)diethanethiol.

[0036] In further embodiments, the outer shell reactants may include additional compounds such as unsaturated or saturated alkyl hydrocarbons and organic acids. In further embodiments, the unsaturated or saturated alkyl hydrocarbons may include 1-octadecene and the organic acid may include oleic acid. In further embodiments, the outer shell 306 formed from the outer shell reactants may include zinc sulfide (ZnS) material. The outer shell 306 provides improved bonding and dispersion properties to the multilayer semiconductor particle 300 when added to a polymer binder. In embodiments of the multilayer semiconductor particle 300 including an outer shell 306 containing a ZnS material, the disulfide bonds of the sulfur component may provide crosslinks between the particle and the surrounding polymer binder. This may promote a more uniform dispersion of the particle in the polymer binder and reduce the number of luminescent hot spots and dark spots within the layer of quantum dot material.

[0037] The method 100 may also further include cooling the mixture of fully formed multi-layer semiconductor particles 300 in operation 135. In an embodiment, the cooling operation 135 may include two or more cooling stages characterized by different cooling ramp rates. The different cooling stages may include a more rapid initial cooling of the particles to more precisely define the growth endpoint of the outer shell 306 and the size of the multi-layer semiconductor particles 300. In a further embodiment, the heated mixture of fully formed particles may be cooled in a first cooling stage characterized by a first temperature ramp rate followed by a second cooling stage characterized by a second cooling ramp rate. In an embodiment, the first temperature ramp rate may be greater than or about 5° C. / min, greater than or about 6° C. / min, greater than or about 7° C. / min, greater than or about 8° C. / min, greater than or about 9° C. / min, greater than or about 10° C. / min, or higher. In further embodiments, the second temperature ramp-down rate may be less than or about 4° C. / min, less than or about 3° C. / min, less than or about 2° C. / min, less than or about 1° C. / min, or lower. In further embodiments, the transition temperature from the first cooling stage to the second cooling stage may occur when the mixture of fully formed multi-layered semiconductor particles 300 is characterized by a temperature of about 120° C., about 110° C., about 100° C., about 90° C., or about 80° C., among other transition temperatures. In further embodiments, the cooling operation 135 may reach completion when the mixture of fully formed multi-layered semiconductor particles 300 is characterized by a temperature of less than or about 30° C.

[0038] The method 100 may also further include, in operation 140, separating the multi-layer semiconductor particles 300 from the remaining components of the mixture in which they were formed. In an embodiment, the mixture of fully formed multi-layer semiconductor particles 300 may include liquid organic compounds, including hydrocarbons, organic acids, organophosphine compounds, and organosulfur compounds, as well as the remaining reactants of the core, inner shell, and outer shell of the particles. In a further embodiment, these liquid organic compounds may be separated from the multi-layer semiconductor particles 300 by decanting the supernatant liquid from the concentrated mixture of particles. In an additional embodiment, the concentrated mixture of particles may be mixed with one or more volatile organic solvents, such as hexane and acetone, among other organic solvents. In a further embodiment, the solvent mixture may be centrifuged to separate the mixture into a sediment containing the multi-layer semiconductor particles 300 and another supernatant containing the added organic solvent and an additional portion of the remaining liquid organic compounds from the particle formation mixture. The supernatant may be separated from the sediment containing the multi-layer semiconductor particles 300. In additional embodiments, the separated precipitate can be contacted with a more volatile organic solvent, centrifuged and separated in one or more additional wash cycles to produce an isolated batch of multi-layered semiconductor particles 300. In embodiments, the isolated batch of multi-layered semiconductor particles 300 can be contacted with a binder polymer composition and stored until use. In further embodiments, the binder polymer composition can include an acrylate compound. In further embodiments, the acrylate compound can include 1,6-hexanediol diacrylate.

[0039] Referring now to FIG. 2, method 200 includes operations in additional methods of making multi-layer semiconductor particles (i.e., quantum dots) according to embodiments of the present technology. These embodiments include rapid stirring of core reactants during the formation of QD cores 302, as well as rapid stirring of inner and outer shell reactants in the particle-containing mixture of the forming multi-layer semiconductor particles 300. It has been discovered that rapid stirring of the compounds promotes their more uniform distribution throughout a mixture characterized by high viscosity and low mass transport rates. More uniform distribution of reactants promotes more uniform formation of multi-layer semiconductor particles 300, which promotes particles with desired luminescence properties.

[0040] Method 200 includes, in operation 205, combining reactants for forming quantum dot (QD) cores. In some embodiments, the QD core reactants may be combined gradually over a period of minutes or longer. In additional embodiments, the QD core reactants may be combined rapidly over a period of seconds, as described in method 100 above. In additional embodiments, the QD core reactants combined in operation 205 may include two or more semiconductor-containing reactants. In further embodiments, the QD core reactants may include at least one zinc-containing compound and at least one selenium-containing compound, among other QD core reactants. In further embodiments, the at least one zinc-containing compound may be anhydrous zinc acetate. In further embodiments, the at least one selenium compound may be selenium complexed with triocetylphosphine. In embodiments, a first portion of the QD core reactants may react to form initial QD core particles, and operation 205 may include the addition of additional QD core reactants to the mixture of initial QD core particles. In further embodiments, the additional reactants may include one or more tellurium-containing reactants, such as tellurium complexed with additional triocetylphosphine. In further embodiments, the tellurium may react with the initial ZnSe core particle to form a ZnSeTe core particle, such as a QD core particle 302. In further embodiments, the ZnSeTe core particle may be characterized by a zinc to tellurium molar ratio (Zn:Te) of less than or about 10:1, less than or about 5:1, less than or about 2.5:1, less than or about 1:1, less than or about 0.5:1, less than or about 0.25:1, or lower.

[0041] Method 200 may additionally include rapidly stirring the reactant mixture in operation 210. In an embodiment, stirring may begin with the combination of a first portion of the QD core reactants and continue throughout the formation of the initial QD core particles. In a further embodiment, stirring may occur during combination of additional reactants with the mixture of initial QD core particles and may continue throughout the formation of fully formed QD core particles, such as QD core particles 302.

[0042] In further embodiments, rapid stirring of the reactant and / or particle mixture may be characterized by a stirring speed of the stirring mechanism in contact with the mixture of greater than or about 1000 revolutions per minute (RPM), greater than or about 1100 RPM, greater than or about 1200 RPM, greater than or about 1300 RPM, greater than or about 1400 RPM, greater than or about 1500 RPM, greater than or about 1600 RPM, greater than or about 1700 RPM, greater than or about 1800 RPM, greater than or about 1900 RPM, greater than or about 2000 RPM, or more. In further embodiments, rapid stirring of the mixture may reduce the high viscosity of the mixture in an unstirred state. In embodiments, rapid stirring of the mixture may reduce its viscosity by greater than or about 10%, greater than or about 25%, greater than or about 50%, greater than or about 75%, or more. The turbulence and reduction in viscosity of the mixture due to rapid stirring increases the mass transport rate of the reactants throughout the mixture, which may result in the formation of more uniformly sized initial QD core particles, as well as more uniform size and composition of the final formed QD core particles that contain additional semiconductor material such as tellurium.

[0043] Method 200 may also include heating the stirred reactant and / or particle mixture in operation 215. In embodiments, the stirred mixture may be heated to a temperature greater than or about 250° C., greater than or about 260° C., greater than or about 270° C., greater than or about 280° C., greater than or about 290° C., greater than or about 300° C., or higher during formation of the initial and fully formed QD cores.

[0044] The method 200 may also further include cooling the heated and stirred mixture containing the fully formed QD core particles 302 in operation 220. In some embodiments, the cooling mixture may continue to be rapidly stirred during the cooling operation. In additional embodiments, the stirring speed may be reduced during the cooling operation to facilitate cooling of the mixture. In embodiments, the stirring speed may be reduced by more than or about 5%, more than or about 10%, more than or about 15%, more than or about 20%, more than or about 25%, more than or about 30%, more than or about 40%, more than or about 50%, or more during the cooling operation. In further embodiments, the cooling operation may reduce the temperature of the heated mixture to less than or about 290° C., less than or about 280° C., less than or about 270° C., less than or about 260° C., less than or about 250° C., or less. In additional embodiments, the temperature reduction may be characterized by a temperature reduction rate of less than or about 10° C. / min, less than or about 7.5° C. / min, less than or about 5° C. / min, less than or about 2.5° C. / min, less than or about 1° C. / min, or less than or about 1° C. / min. In embodiments, the cooling operation reduces the temperature of the heated mixture of QD core 302 particles in preparation for the addition of the inner shell reactants to the QD core particles. The reduction in temperature, in conjunction with the stirring, allows the inner shell reactants to be more uniformly distributed across the QD core 302 particles before reacting to form the inner shell layer 304 around the QD core 302.

[0045] The method 200 further includes stirring the particle mixture while introducing the inner shell reactants in operation 225. In embodiments, the stirring of the mixture of inner shell reactants and QD core particles may be characterized by a stirring speed of a stirring mechanism in contact with the mixture of greater than or about 1000 revolutions per minute (RPM), greater than or about 1100 RPM, greater than or about 1200 RPM, greater than or about 1300 RPM, greater than or about 1400 RPM, greater than or about 1500 RPM, greater than or about 1600 RPM, greater than or about 1700 RPM, greater than or about 1800 RPM, greater than or about 1900 RPM, greater than or about 2000 RPM, or more. In further embodiments, the stirred mixture may be heated to temperatures greater than or about 250° C., greater than or about 260° C., greater than or about 270° C., greater than or about 280° C., greater than or about 290° C., greater than or about 300° C., or higher, during formation of the inner shell 304 on the QD cores 302.

[0046] In embodiments, the inner shell reactants may include a zinc-containing reactant and a selenium-containing reactant, among other reactants. In additional embodiments, the zinc-containing reactant may include anhydrous zinc acetate, and the selenium-containing reactant may include selenium mixed with a complexing agent, such as triocetylphosphine. In further embodiments, the inner shell reactants may include additional compounds, such as unsaturated or saturated alkyl hydrocarbons and organic acids. In further embodiments, the unsaturated or saturated alkyl hydrocarbons may include 1-octadecene, and the organic acid may include oleic acid. In further embodiments, the inner shell 304 formed from the inner shell reactants may include a zinc-selenium (ZnSe) material. In further embodiments, the inner shell 304 may be characterized by a zinc to selenium molar ratio of less than or about 4:1, less than or about 2:1, less than or about 1:1, less than or about 0.5:1, less than or about 0.25:1, or lower.

[0047] Method 200 may also further include stirring the particle mixture while introducing the outer shell reactants in operation 230. In embodiments, the stirring of the mixture of outer shell reactants and further forming QD particles may be characterized by a stirring speed of a stirring mechanism in contact with the mixture of greater than or about 1000 revolutions per minute (RPM), greater than or about 1100 RPM, greater than or about 1200 RPM, greater than or about 1300 RPM, greater than or about 1400 RPM, greater than or about 1500 RPM, greater than or about 1600 RPM, greater than or about 1700 RPM, greater than or about 1800 RPM, greater than or about 1900 RPM, greater than or about 2000 RPM, or more. In further embodiments, the stirred mixture may be heated to a temperature greater than or about 250° C., greater than or about 260° C., greater than or about 270° C., greater than or about 280° C., greater than or about 290° C., greater than or about 300° C., or higher, during formation of the outer shell 306 on the inner shell 304 of the multi-layer semiconductor particle 300.

[0048] In further embodiments, the outer shell reactants may include a zinc-containing reactant and a sulfur-containing reactant, among other reactants. In additional embodiments, the zinc-containing reactant may include anhydrous zinc acetate, and the sulfur-containing reactant may include sulfur mixed with a complexing agent, such as triocetylphosphine. In further embodiments, the outer shell reactants may include additional compounds, such as unsaturated or saturated alkyl hydrocarbons and organic acids. In further embodiments, the unsaturated or saturated alkyl hydrocarbons may include 1-octadecene, and the organic acid may include oleic acid. In further embodiments, the outer shell 306 formed from the outer shell reactants may include a zinc sulfide (ZnS) material. In further embodiments, the outer shell 306 may be characterized by a zinc to sulfur molar ratio of less than or about 5:1, less than or about 2.5:1, less than or about 1:1, less than or about 0.5:1, less than or about 0.4:1, less than or about 0.3:1, less than or about 0.2:1, or lower.

[0049] Method 200 may also further include cooling the mixture of fully formed multi-layer semiconductor particles 300 in operation 235. In embodiments, cooling operation 235 may include a single cooling stage or two or more cooling stages. In additional embodiments, the mixture may be stirred while the cooling operation is taking place. In embodiments having two or more cooling stages, the cooling stages may be characterized by different cooling ramp rates, as described above in method 100.

[0050] The method 200 may also further include, in operation 240, separating the multi-layer semiconductor particles 300 from the remaining components of the mixture in which they were formed. In an embodiment, the mixture of fully formed multi-layer semiconductor particles 300 may include liquid organic compounds, including hydrocarbons, organic acids, organophosphine compounds, and organosulfur compounds, as well as the remaining reactants of the core, inner shell, and outer shell of the particles. In a further embodiment, these liquid organic compounds may be separated from the multi-layer semiconductor particles 300 by decanting the supernatant liquid from the concentrated mixture of particles. In an additional embodiment, the concentrated mixture of particles may be mixed with one or more volatile organic solvents, such as hexane and acetone, among other organic solvents. In a further embodiment, the solvent mixture may be centrifuged to separate the mixture into a sediment containing the multi-layer semiconductor particles 300 and another supernatant containing the added organic solvent and an additional portion of the remaining liquid organic compounds from the particle formation mixture. The supernatant may be separated from the sediment containing the multi-layer semiconductor particles 300. In additional embodiments, the separated precipitate can be contacted with a more volatile organic solvent, centrifuged and separated in one or more additional wash cycles to produce an isolated batch of multi-layered semiconductor particles 300. In embodiments, the isolated batch of multi-layered semiconductor particles 300 can be contacted with a binder polymer composition and stored until use. In further embodiments, the binder polymer composition can include an acrylate compound. In further embodiments, the acrylate compound can include 1,6-hexanediol diacrylate.

[0051] In both methods 100 and 200, various reactant and particle mixtures may be characterized by low moisture. In embodiments, the mixtures may be characterized by moisture levels of less than or about 1% by weight, less than or about 0.75% by weight, less than or about 0.5% by weight, less than or about 0.25% by weight, less than or about 0.1% by weight, less than or about 0.05% by weight, or lower. In further embodiments, the mixtures may be characterized by not including hydrated compounds in which one or more water molecules are incorporated into the compound. Low moisture levels in the reactants and mixtures reduce the number of by-products produced instead of the multi-layered semiconductor particles 300. In embodiments, low moisture levels provide mixtures with lower amounts of semiconductor hydroxide compounds such as zinc hydroxide, selenium hydroxide, and tellurium hydroxide, among other semiconductor hydroxides, that may precipitate from the mixture and prevent the semiconductor material from being incorporated into the multi-layered semiconductor particles 300.

[0052] Also, in methods 100 and 200, the various reactants and particle mixtures in a heated state (e.g., above or at about 80° C.) are kept in an oxygen-free atmosphere to reduce or prevent oxidation of compounds in the mixture. In embodiments, the reactants and particle mixtures may be heated in an oxygen-free atmosphere to reduce or prevent oxidation of zinc-containing compounds, selenium-containing compounds, tellurium-containing compounds, and trialkyl-phosphine compounds, among other compounds in the mixture. The oxygen-free atmosphere also reduces the risk of fire during the formation of quantum dot particles. The reactants and mixtures contain many pyrophoric compounds that can be heated to temperatures of 300° C. or higher. In an oxygen-containing environment, such as ambient air, there is a high likelihood that these reactants and mixtures will ignite at such temperatures. In embodiments, the reactants and particle mixtures in a heated state are kept in an oxygen-free atmosphere, among other inert gases, such as dry nitrogen (N 2In embodiments, the oxygen-free atmosphere contains less than or about 1% by weight, less than or about 0.75% by weight, less than or about 0.5% by weight, less than or about 0.25% by weight, less than or about 0.1% by weight, less than or about 0.05% by weight, or less than or about 0.5% by weight. 2 ) levels.

[0053] Methods 100 and 200 may produce multi-layer semiconductor particles 300 characterized by increased sharpness and fewer secondary emission peaks than quantum dot particles produced by conventional methods. In embodiments, the light emitted by multi-layer semiconductor particles 300 may be characterized by a peak wavelength emission of less than or about 500 nm, less than or about 490 nm, less than or about 480 nm, less than or about 470 nm, less than or about 460 nm, less than or about 450 nm, less than or about 440 nm, less than or about 430 nm, less than or about 420 nm, less than or about 410 nm, less than or about 400 nm, less than or about 390 nm, less than or about 380 nm, or shorter. In additional embodiments, the light emitted by multi-layer semiconductor particles 300 may be characterized by a peak wavelength emission of less than or about 455 nm. In further embodiments, the light emitted by the multi-layer semiconductor particle 300 may have a narrowband (i.e., sharp) color profile characterized by a full width at half maximum (FWHM) primary wavelength emission peak that is less than or about 40 nm, less than or about 35 nm, less than or about 30 nm, less than or about 25 nm, less than or about 20 nm, less than or about 15 nm, less than or about 10 nm, less than or about 5 nm, less than or about 2.5 nm, less than or about 1 nm, or less than or about.

[0054] In embodiments, the sharpness of the primary wavelength emission peak is due, at least in part, to the fewer and weaker secondary wavelength emission peaks from the excited multilayer semiconductor particles 300. In additional embodiments, the ratio of emission intensity between the primary wavelength emission peak and the next strongest secondary wavelength emission peak may be greater than or about 5:1, greater than or about 10:1, greater than or about 15:1, greater than or about 20:1, greater than or about 30:1, greater than or about 40:1, greater than or about 50:1, or higher. The reduced intensity of the secondary wavelength emission peak is due, at least in part, to the increased uniformity of composition, size, and morphology of the multilayer semiconductor particles 300 fabricated according to embodiments of the present technology.

[0055] 4, a simplified cross-section of a display device 400 including multi-layered semiconductor particles (i.e., quantum dots) according to embodiments of the present technology is shown. The display device 400 includes a light source 402 that excites three regions 404a-c of quantum dots, which are operable to emit different colors of light when excited by the light source 402. In an embodiment, the first quantum dot region 404a may be operable to emit blue light, the second quantum dot region 404b may be operable to emit green light, and the third quantum dot region 404c may be operable to emit red light. In a further embodiment, multi-layered semiconductor particles according to embodiments of the present technology may be incorporated into the first quantum dot region 404a and may be operable to emit a sharp blue color having a peak narrowband emission wavelength less than or about 455 nm.

[0056] In an embodiment, the display device 400 may be operable to excite the quantum dot regions 404a-c with a variety of intensities with the source light 402. In a further embodiment, the source light 402 may include one or more light emitting diodes operable to emit light at shorter and more energetic wavelengths than the light emitted by the quantum dot regions 404a-c. In an additional embodiment, the source light may be operable to emit ultraviolet excitation light characterized by a peak emission wavelength less than or about 350 nm. In a further embodiment, the source light may be operable to emit white light characterized by a broad emission of light across the visible spectrum (e.g., 380 nm-750 nm).

[0057] In an additional embodiment, the display device 400 may be operable to display an image by driving the source light 402 to excite the quantum dot regions 404a-c to emit colored light through a translucent front panel 406 that projects the image. In a further embodiment, a controller 408 is coupled to the light source 402 and the quantum dot regions 404a-c via electronic circuitry (not shown). The controller 408 may be operable to receive input signals for displaying an image and to transmit output signals to drive and deactivate portions of the light source 402 and the quantum dot regions 404a-c.

[0058] The embodiments of the present technology allow for the creation of multi-layered semiconductor particles (i.e., quantum dots) characterized by improved sharpness of the color emitted by the quantum dots. The embodiments include improvements in the manufacturing method, such as rapid combination of core and shell layer reactants, and rapid stirring of the reactants and the forming quantum dot particles. The embodiments also include the production of quantum dots in a low moisture mixture maintained in an oxygen-free atmosphere, which may include a mixture of dry nitrogen, argon, or both. The improved method may produce quantum dots with narrowband emission characteristics, such as a primary emission wavelength peak characterized by a FWHM of less than or about 40 nm.

[0059] In the above description, for purposes of explanation, numerous details are set forth to provide an understanding of various embodiments of the present technology. However, it will be apparent to one of ordinary skill in the art that certain embodiments may be practiced without some of these details or with additional details. For example, other substrates that may benefit from the wetting techniques described may be used with the present technology.

[0060] Although several embodiments have been disclosed, those skilled in the art will understand that various modifications, alternative structures and equivalents may be used without departing from the spirit of the embodiments. Moreover, some well-known processes and elements have not been described to avoid unnecessarily obscuring the technology. Thus, the above description should not be construed as limiting the scope of the technology.

[0061] Where a range of values ​​is provided, it is understood that each intervening value between the upper and lower limits of that range is also specifically disclosed, to the smallest fraction of the unit of the lower limit, unless the context clearly indicates otherwise. Any narrower range between any stated or unstated intervening value in a stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of those smaller ranges may be independently included or excluded within the range, and each range in which either, neither, or both of the limits are included within the smaller range is also encompassed by the present technology, subject to any specifically excluded limit in the stated range. Where a stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included. Where multiple values ​​are provided in a list, any range including or based on any of those values ​​is likewise specifically disclosed.

[0062] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to "a compound" includes a plurality of such compounds, and a reference to "the period of time" includes a reference to one or more periods and equivalents thereof known to those skilled in the art.

[0063] Additionally, the terms "comprise(s)", "comprising", "contain(s)", "containing", "include(s)", and "including", when used in this specification and the claims that follow, are intended to specify the presence of stated features, integers, components, or operations, but do not exclude the presence or addition of one or more other features, integers, components, operations, acts, or groups.

Claims

1. 1. A method of making a multi-layer semiconductor particle, comprising the steps of: combining a first zinc-containing compound and a selenium-containing compound to form a ZnSe mixture, the zinc-containing compound and the selenium-containing compound being combined for less than or about 5 seconds; adding a tellurium-containing compound to the ZnSe mixture to form at least one ZnSeTe particle in the ZnSeTe mixture; forming a first shell layer on the ZnSeTe particles; forming a second shell layer on the first shell layer formed on the ZnSeTe particle to create a multi-layer semiconductor particle; The method includes:

2. 10. The method of claim 1, wherein the tellurium-containing compound is added to the ZnSe mixture in less than or about 5 seconds.

3. 10. The method of claim 1, further comprising increasing the temperature of the ZnSeTe mixture at a rate of greater than or about 10°C / min.

4. 10. The method of claim 1 further comprising stirring the ZnSeTe mixture with a stirring mechanism rotating at or about greater than 1500 RPM.

5. 10. The method of claim 1, wherein the tellurium-containing compound is added to the ZnSe mixture in an atmosphere containing less than or about 1 mol% oxygen.

6. 10. The method of claim 1 , wherein the ZnSeTe mixture contains less than or about 1% water by weight.

7. The method of claim 1 , wherein the first shell layer comprises zinc selenide.

8. The method of claim 1 , wherein the second shell layer comprises zinc sulfide.

9. 1. A method of making a multi-layer semiconductor particle, comprising the steps of: combining a first zinc-containing compound and a selenium-containing compound to form a ZnSe mixture; adding a tellurium-containing compound to the ZnSe mixture to form at least one ZnSeTe particle in a particle formation mixture, the particle formation mixture being stirred with a stirring mechanism rotating at or about 1500 RPM during formation of the at least one ZnSeTe particle; forming a ZnSe-containing shell layer on the ZnSeTe particles; forming a ZnS-containing shell layer on the ZnSe-containing shell layer formed on the ZnSeTe particle to produce a multi-layer semiconductor particle; The method includes:

10. 10. The method of claim 9, wherein the particle-forming mixture is stirred with a stirring mechanism rotating at greater than or about 1500 RPM during formation of the ZnSe-containing and ZnS-containing shell layers.

11. 10. The method of claim 9, wherein the zinc-containing compound and the selenium-containing compound are combined for less than or about 5 seconds.

12. 10. The method of claim 9, wherein the tellurium-containing compound is added to the ZnSe mixture in less than or about 5 seconds.

13. 10. The method of claim 9, wherein the particle-forming mixture is characterized by a temperature of greater than or about 300°C during formation of the at least one ZnSeTe particle.

14. The method of claim 9 , wherein the particle-forming mixture comprises an alkylphosphine compound.

15. a core comprising ZnSeTe; an inner shell layer in contact with the core, the inner shell layer comprising ZnSe; 1. A multi-layered semiconductor particle comprising: an outer shell layer in contact with an inner shell layer, the outer shell layer comprising ZnS; Multi-layered semiconductor particles having an emission spectrum characterized by a primary peak having a full width at half maximum wavelength range of less than or about 40 nm.

16. 16. The multi-layered semiconductor particle of claim 15, wherein the first peak of the emission spectrum is less than or about 455 nm.

17. 16. The multi-layered semiconductor particle of claim 15, wherein the emission intensity of a primary peak in the emission spectrum exceeds the emission intensity of all other emission peaks in the emission spectrum by a ratio of greater than or about 10:

1.

18. 16. The multi-layered semiconductor particle of claim 15, characterized by an average particle size of less than or about 10 nm.

19. 16. The multi-layered semiconductor particle of claim 15, wherein the core is sulfur-free.

20. 16. The multi-layered semiconductor particle of claim 15 incorporated into a micro LED device.

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