Photoluminescent materials containing phosphorus additives to reduce photodegradation - Patent Application 20070229633

Abstract

The multi-layer semiconductor particles, which can be referred to as quantum dots, can include a zinc-containing core. The particles can include a zinc- and selenium-containing inner shell on the zinc-containing core. The particles can include a zinc-containing outer shell on the zinc- and selenium-containing inner shell. The particles can include a phosphorus-containing material in contact with the zinc-containing outer shell. The phosphorus-containing material can be or include triisopropyl phosphite (TIPP), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP), tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP), triethyl phosphite, tris(2-ethylhexyl phosphite), tris(trimethylsilyl)phosphite, triphenyl phosphite, triphenylphosphine, tris(4-methoxyphenyl)phosphine, tris(1-pyrrolidinyl)phosphine, tri(2-furyl)phosphine or tris(dimethylamino)phosphine.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of and priority to U.S. patent application Ser. No. 63 / 337,243, filed May 2, 2022, entitled “PHOTOLUMINESCENT MATERIALS WITH PHOSPHOROUS ADDITIVES TO REDUCE PHOTODEGRADATION,” which is incorporated by reference in its entirety.

[0002] The present technology relates to photoluminescent materials that are resistant to photodegradation and methods for making the same, and more particularly, to quantum dots made from multilayers of inorganic materials that contain antioxidants. [Background technology]

[0003] High-resolution light-emitting diode (LED) displays can contain millions of μm-sized pixels arranged to form a display 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 display screen. Other LED displays excite organic or inorganic compounds, which then emit a particular color of light, such as red, green, or blue light, depending on the pixel. These LED displays typically require fewer filters to block undesired colors of light, which can improve their brightness and power efficiency. Liquid crystal displays (LCDs) can include quantum dot-enhanced films that provide an expanded color saturation. However, there are many challenges in creating photoluminescent materials, including challenges in creating materials that are stable over the life of the display.

[0004] Thus, there is a need for high quality materials for display devices. These and other needs are addressed by the present technology. Summary of the Invention

[0005] An embodiment of the present technology includes a multi-layered semiconductor particle, sometimes referred to as a quantum dot. The structure can include a zinc-containing core. The structure can include a zinc- and selenium-containing inner shell on the zinc-containing core. The structure can include a zinc-containing outer shell on the zinc- and selenium-containing inner shell. The structure can include a phosphorus-containing material in contact with the zinc-containing outer shell. The phosphorus-containing material can be or include triisopropyl phosphite (TIPP), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP), tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP), triethyl phosphite, tris(2-ethylhexyl phosphite), tris(trimethylsilyl)phosphite, triphenyl phosphite, triphenylphosphine, tris(4-methoxyphenyl)phosphine, tris(1-pyrrolidinyl)phosphine, tri(2-furyl)phosphine, or tris(dimethylamino)phosphine.

[0006] In embodiments, the zinc-containing core may further comprise sulfur, selenium or tellurium. The zinc and selenium-containing inner shell may further comprise tellurium or sulfur. The zinc-containing outer shell may further comprise sulfur. The multi-layered semiconductor particles may each be characterized by a longest dimension of about 4 nm or less. The phosphorus-containing material may be characterized by a boiling point of about 100° C. or greater. The phosphorus-containing material may be or include bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP) or tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP).

[0007] Some embodiments of the present technology include a pixel structure. The pixel structure can include a light emitting diode structure operable to generate light characterized by a peak emission wavelength of about 350 nm or greater. The pixel structure can include a photoluminescent region containing a photoluminescent material located in the light emitting diode structure. The photoluminescent region can include a plurality of multi-layered semiconductor particles including an antioxidant.

[0008] In embodiments, the antioxidant comprises phosphorus and may be characterized by a boiling point of about 100° C. or greater. The antioxidant may comprise a phosphorus-containing material. The phosphorus-containing material may be or may comprise triisopropyl phosphite (TIPP), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP), tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP), triethyl phosphite, tris(2-ethylhexyl phosphite), tris(trimethylsilyl)phosphite, triphenyl phosphine, tris(4-methoxyphenyl)phosphine, tris(1-pyrrolidinyl)phosphine, tri(2-furyl)phosphine, or tris(dimethylamino)phosphine. The plurality of multi-layered semiconductor particles may comprise a zinc-containing core, a zinc- and selenium-containing inner shell on the zinc-containing core, and a zinc-containing outer shell on the zinc- and selenium-containing inner shell. The photoluminescent material may comprise a quantum dot material. The quantum dot material may comprise a blue quantum dot material. Each of the multi-layered semiconductor particles may be characterized by a longest dimension of about 4 nm or less.

[0009] Some embodiments of the present technology include a method of manufacturing a display. The method can include forming a light emitting diode structure on a substrate. The method can include forming a photoluminescent region on the light emitting diode structure. The method can include forming a photoluminescent material in the photoluminescent region. The photoluminescent material can include a plurality of multi-layered semiconductor particles including an antioxidant.

[0010] In an embodiment, the photoluminescent material may include a blue quantum dot material. The antioxidant may include a phosphorus-containing material. The phosphorus-containing material may be or include triisopropyl phosphite (TIPP), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP), tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP), triethyl phosphite, tris(2-ethylhexyl phosphite), tris(trimethylsilyl)phosphite, triphenyl phosphine, tris(4-methoxyphenyl)phosphine, tris(1-pyrrolidinyl)phosphine, tri(2-furyl)phosphine, or tris(dimethylamino)phosphine. The photoluminescent material may be characterized by a longest dimension of about 4 nm or less. The method may include handling the photoluminescent material in the presence of oxygen or ambient white light during subsequent manufacturing operations. The plurality of multi-layered semiconductor particles can include a zinc-containing core, a zinc- and selenium-containing inner shell on the zinc-containing core, and a zinc-containing outer shell on the zinc- and selenium-containing inner shell.

[0011] Embodiments of the present technology provide improved quantum dot particles that include phosphorus-containing materials. The phosphorus-containing materials can improve quantum dot materials, such as inks used to form quantum dot particles, and the storage and handling of the formed quantum dot particles. The phosphorus-containing materials can act as sacrificial molecules and prevent oxygen from reacting with the quantum dots. Furthermore, the phosphorus-containing additives cannot inhibit the function of the quantum dot particles. These and other embodiments, along with many of their advantages and features, will be described in greater 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] FIG. 1 is a flow diagram including selected operations in a method of making multi-layer semiconductor particles in accordance with an embodiment of the present technique. [Diagram 2] 1 is a simplified cross-sectional view of a multi-layer semiconductor particle according to an embodiment of the present technique. [Diagram 3] 1 is a simplified cross-sectional schematic diagram of a display device incorporating multi-layer semiconductor particles, according to an embodiment of the present technique; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Some of the figures are included as schematic diagrams. It should be understood that the figures are for illustrative purposes and are not to scale unless specifically stated as such. Additionally, the figures are presented as schematic diagrams to aid in understanding and may not include all aspects or information compared to a realistic representation and may include exaggerated material for illustrative purposes.

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

[0016] Quantum dot particles are nanometer-sized inorganic material particles 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 characteristics of the particle, including its size, shape, and composition, among other characteristics. For quantum dot particles made from inorganic semiconductor materials, the color of light emitted by these quantum dot particles depends on the energy gap between the conduction band and valence band of the dot. When a quantum dot particle is excited, one or more electrons are excited from the lower energy valence band to the higher energy conduction band. When the excited electrons fall back to the valence band, the quantum dot particle emits light with a color that 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, while the wider the energy gap, the more the emitted light is shifted to the blue. By adjusting one or more characteristics of the quantum dot particle, such as the longest dimension of the quantum dot particle, which changes the energy gap between the conduction band and the valence band, quantum dot particles can be made to emit light of virtually any color in the visible spectrum.

[0017] The efficiency of quantum dot particles in converting high-energy white or ultraviolet light into specific colors of visible light has led to their increasingly popular use in electronic displays, such as light-emitting diode (LED) displays and liquid crystal displays (LCDs). Because quantum dot particles can emit light of one color, fewer color filters and polarizers are required in displays to prevent unwanted light colors from contaminating 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 dot particles.

[0018] The inorganic semiconductor materials used to make many types of quantum dot particles can also be more stable than other types of color-specific photoluminescent compounds, such as many organic compounds used in organic light-emitting diode (OLED) displays. After undergoing many excitation-emission cycles, inorganic quantum dot particles can lose significant conversion efficiency due to chemical changes in the semiconductor materials. In contrast, the complex organic molecules used in OLED displays are more prone to chemical degradation over time. Organic molecules are also more sensitive to water and other contaminants that quench their photoluminescence than inorganic quantum dot particles.

[0019] Unfortunately, there are still many challenges in efficiently producing quantum dot particles that feature a sharp color profile centered on a precise emission wavelength. In many cases, quantum dot particles can be highly sensitive to oxygen. Exposure to white light or air can allow oxygen to interact with quantum dot particles, resulting in photodecomposition of the particles. Such photodecomposition can reduce the lifetime of quantum dot particles, i.e., blue quantum dot particles, which are more sensitive to oxygen than red and green quantum dot particles. Blue quantum dot particles can be more sensitive to photodecomposition due to the large surface area and large band gap of the particles. Quantum dot materials that undergo photodecomposition can achieve a dramatic decrease in photoluminescence quantum yield (PLQY). PLQY can be defined as the number of photons emitted per number of photons absorbed, which allows the photoluminescence of quantum dot particles to be measured.

[0020] The present technology addresses the challenge of oxidation of quantum dot materials by incorporating materials that reduce the susceptibility of the quantum dot materials in their formation. An embodiment of the present technology can incorporate an antioxidant into the quantum dot materials. The antioxidant can be a phosphorus-containing material that can reduce the effects of photodegradation during the formation and use of the quantum dot materials. It has been discovered that the incorporation of an antioxidant, such as a phosphorus-containing additive, can prevent the oxidation of the quantum dot materials because the antioxidant acts as a sacrificial material. The antioxidant can undergo oxidation prior to the quantum dot materials, thus reducing the oxidation of the quantum dot materials.

[0021] The present technology can produce inorganic quantum dot particles that feature improved PLQY. In an embodiment, the quantum dot particles can include a multi-layer structure of a semiconductor material that includes a particle core made from a first group of semiconductor materials, an inner shell made from a second group of semiconductor materials, an outer shell made from a third group of materials, and an antioxidant material. The antioxidant material can reduce the decomposition of the quantum dot particles, allowing for less stringent processing conditions.

[0022] FIG. 1 shows a flow diagram illustrating some of the operations in an embodiment of the present method for making a multi-layer semiconductor particle. FIG. 2 shows a simplified cross-sectional view of one embodiment of such a multi-layer semiconductor particle made by the present technology. The method 100 shown in FIG. 1 may or may not include operations prior to the start of the present method, including preparation of reactants that are combined to make the core and shell of the multi-layer semiconductor particle. The method 100 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.

[0023] With specific reference to FIG. 1, the method 100 can include combining first reactants to be incorporated into the core of the multi-layer semiconductor particle (i.e., quantum dot) in operation 105. In an embodiment, these first reactants can be rapidly combined in a short period of time. The first reactants can be rapidly combined in about 10 seconds or less, about 7.5 seconds or less, about 5 seconds or less, about 2.5 seconds or less, about 1 second or less, or less. Combining the reactants quickly can reduce local concentration concentrations of one of the reactants that can result in less homogeneous formation of the quantum dot core, such as the quantum dot core 202 of the multi-layer semiconductor particle 200 shown in FIG. 2.

[0024] The first reactant combined in operation 105 can include two or more semiconductor-containing reactants. In an embodiment, the first reactant can include at least one zinc-containing compound, and, for example, at least one selenium-containing compound, at least one sulfur-containing compound, or at least one tellurium-containing compound, among other first reactants. The at least one zinc-containing compound can be an organozinc compound, among other zinc-containing compounds. The organozinc compound can be zinc acetate or zinc stearate, among other organozinc compounds. In an embodiment, the organozinc compound can be an anhydride, such as anhydrous zinc acetate. The at least one selenium compound can be selenium complexed with an organophosphorus complexing agent. The organophosphorus complexing agent can be a trialkyl-phosphine compound. The trialkyl-phosphine compound can be one or more of trihexylphosphine, triseptylphosphine, trioctylphosphine, and trinonylphosphine, among other trialkylphosphine compounds.

[0025] In an embodiment, the first reactant may include additional compounds that facilitate rapid combination of at least one zinc-containing compound and at least one selenium-containing compound. These additional compounds may include unsaturated or saturated alkyl hydrocarbons having about 10 or more carbon atoms, about 12 or more carbon atoms, about 15 or more carbon atoms, about 18 or more carbon atoms, about 20 or more carbon atoms, or more. The alkyl hydrocarbons may include one or more of 1-octadecene, 1-decene, 1-hexadecene, 1-dodecene, 1-eicosene, and tetradecene, among other alkyl hydrocarbons. These additional compounds may include organic acids having about 12 or more carbon atoms, about 15 or more carbon atoms, about 18 or more carbon atoms, about 20 or more carbon atoms, or more. For example, the organic acids include 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, hepta-6-enoic acid, among others. The carboxylic acid may be or may include one or more of 1-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.

[0026] The first reactants may be combined at a temperature of about 90° C. or higher, about 100° C. or higher, about 110° C. or higher, about 120° C. or higher, about 130° C. or higher, about 140° C. or higher, about 150° C. or higher, or higher. During reaction of the combined first reactants to form the first portion of the quantum dot core, the temperature of the combined first reactants may be increased to about 160° C. or higher, about 170° C. or higher, about 180° C. or higher, about 190° C. or higher, about 200° C. or higher, about 210° C. or higher, about 220° C. or higher, or higher. The first portion of the quantum dot core may include zinc and selenium, sulfur, tellurium, or a combination thereof.

[0027] The method 100 can include adding additional reactants to the first portion of the quantum dot core in operation 110. These additional reactants can be added quickly to the mixture containing the first portion of the quantum dot core in a short period of time. The addition time can be about 10 seconds or less, about 7.5 seconds or less, about 5 seconds or less, about 2.5 seconds or less, about 1 second or less, or less. The rapid addition of the additional reactants can reduce localized concentration concentrations of one of the reactants that can result in less homogeneous incorporation of the additional reactants into the first portion of the quantum dot core. The additional reactants can include one or more tellurium-containing reactants. The tellurium-containing reactants can include tellurium complexed with an organophosphorus complexing agent. The organophosphorus complexing agent can be a trialkyl-phosphine compound. The trialkyl-phosphine compound can be one or more of trihexylphosphine, triseptylphosphine, trioctylphosphine, and trinonylphosphine, among other trialkylphosphine compounds. Addition of additional reactants to the first portion of the quantum dot core can produce a mixture of quantum dot core reactants.

[0028] The method 100 may also include, in optional operation 115, heating the mixture of quantum dot core reactants. In embodiments, the mixture may be heated to a temperature of about 250° C. or more, about 260° C. or more, about 270° C. or more, about 280° C. or more, about 290° C. or more, about 300° C. or more, or higher. The temperature ramp may be characterized by a constant ramp rate of about 10° C. / min. or more, about 11° C. / min. or more, about 12° C. / min. or more, about 13° C. / min. or more, about 14° C. / min. or more, about 15° C. / min. or more, or more. The elevated temperature of the mixture may result in efficient incorporation of the additional reactants into the first portion of the quantum dot core to form a complete quantum dot core, such as the quantum dot core 202. In embodiments, the quantum dot core 202 may include zinc, selenium, and tellurium in a ZnSeTe core. However, it is contemplated that the quantum dot core 202 may include sulfur in addition to zinc, selenium, and / or tellurium. The quantum dot core reactant mixture may be maintained at the heated temperature for about 30 minutes or more, about 45 minutes or more, about 60 minutes or more, about 75 minutes or more, about 90 minutes or more, about 100 minutes or more, about 120 minutes or more, or longer, during which the quantum dot cores 202 are formed.

[0029] The method 100 may include, in optional operation 120, cooling the heated mixture of quantum dot core 202 particles. The cooling operation may reduce the temperature of the heated mixture to about 290° C. or less, about 280° C. or less, about 270° C. or less, about 260° C. or less, about 250° C. or less, or less. The temperature reduction may be characterized by a constant temperature reduction rate of about 10° C. / min or less, about 7.5° C. / min or less, about 5° C. / min or less, about 2.5° C. / min or less, about 1° C. / min or less, or less. The cooling operation may reduce the temperature of the heated mixture of quantum dot core 202 particles in preparation for addition of the inner shell reactants to the quantum dot core particles. The reduction in temperature may allow the inner shell reactants to be more evenly distributed throughout the quantum dot core 202 particles before the inner shell reactants react to form the inner shell 204 around the quantum dot core 202.

[0030] The method 100 may also include, in operation 125, adding reactants of the inner shell layer to the reduced temperature mixture of the quantum dot core particles. The reactants of the inner shell may be added quickly to the mixture of the quantum dot core particles in a short period of time. The addition time may be about 10 seconds or less, about 7.5 seconds or less, about 5 seconds or less, about 2.5 seconds or less, about 1 second or less, or less. The rapid addition of the reactants of the inner shell may reduce reactant concentration concentrations that may result in wider variations in the characteristics of the inner shell, such as the inner shell 204 around the quantum dot core 202 in the multi-layer semiconductor particle 200. These inner shell characteristics may include the composition and thickness of the inner shell 204, among other characteristics. The inner shell 204 can have a thickness of about 0.5 nm or more, about 1 nm or more, about 1.5 nm or more, about 2 nm or more, about 2.5 nm or more, about 3 nm or more, about 3.5 nm or more, about 4 nm or more, about 4.5 nm or more, about 5 nm or more, about 5.5 nm or more, about 6 nm or more, or greater.

[0031] The inner shell reactants may include a zinc-containing reactant and a selenium-containing reactant, among other reactants. The zinc-containing reactant may include anhydrous zinc acetate, and the selenium-containing reactant may include selenium together with a complexing agent, such as trioctylphosphine. The inner shell reactants may include additional compounds, such as unsaturated or saturated alkyl hydrocarbons and organic acids. The unsaturated or saturated alkyl hydrocarbons may include 1-octadecene, and the organic acid may include oleic acid. The inner shell 204 formed from the inner shell reactants may include a zinc-selenium (ZnSe) material. The combined mixture of the inner shell reactants and the quantum dot core particles may be heated to facilitate the formation of the inner shell 204 on the quantum dot cores 202. The combined mixture may be heated to a temperature of about 250° C. or higher, about 260° C. or higher, about 270° C. or higher, about 280° C. or higher, about 290° C. or higher, about 300° C. or higher, or higher. The combined mixture may be heated to the heating temperature for about 1 minute or more, about 2.5 minutes or more, about 5 minutes or more, about 7.5 minutes or more, about 10 minutes or more, or longer.

[0032] The method 100 may include, in operation 130, adding reactants of the outer shell layer to the particle mixture. The outer shell mixture may be added quickly to the particle mixture in a short period of time. The addition time may be about 10 seconds or less, about 7.5 seconds or less, about 5 seconds or less, about 2.5 seconds or less, about 1 second or less, or less. The rapid addition of the reactants of the outer shell may reduce reactant concentration concentrations that may result in wider variations in the characteristics of the outer shell, such as the outer shell 206 around the inner shell 204 in the multi-layer semiconductor particle 200. These outer shell characteristics may include the composition and thickness of the outer shell 206, among other characteristics. The outer shell 206 may have a thickness of about 1 nm or more, about 2 nm or more, about 3 nm or more, about 4 nm or more, about 5 nm or more, or more.

[0033] The combined mixture of the outer shell reactants and particles may be maintained at the same heating temperature as the combined mixture of the inner shell reactants and quantum dot cores 202. The temperature of the combined mixture of the outer shell reactants and particles may be about 250° C. or higher, about 260° C. or higher, about 270° C. or higher, about 280° C. or higher, about 290° C. or higher, about 300° C. or higher, or higher. The combined mixture may be held at the heating temperature for about 1 minute or higher, about 2.5 minutes or higher, about 5 minutes or higher, about 7.5 minutes or higher, about 10 minutes or higher, or longer to facilitate the formation of the outer shell 206 on the inner shell 204 of the multi-layered semiconductor particle 200.

[0034] The reactants of the outer shell may include, among other reactants, a zinc-containing reactant and a sulfur-containing reactant. The zinc-containing reactant may include anhydrous zinc acetate, and the sulfur-containing reactant may include sulfur together with a complexing agent such as trioctylphosphine. The sulfur-containing reactant may be or 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. The sulfur-containing reactant may be, among other sulfur-containing reactants, poly(ethylene glycol) methyl ether thiols having a molecular weight of 600 to 3000, poly(ethylene glycol) dithiols having a molecular weight of 600 to 3000, and sulfur-containing reactants of the formula HSCH 2 (CH 2 ) n CH 2 The alkylthiol group may be one or more of alkanedithiol SH (n=2 to 30), trimethylolpropane, tris(3-mercaptopropionate), and 2,2'-(ethylenedioxy)diethanethiol, or may contain these.

[0035] The outer shell reactants may include additional compounds such as unsaturated or saturated alkyl hydrocarbons and organic acids. The unsaturated or saturated alkyl hydrocarbons may be or include 1-octadecene, and the organic acid may be or include oleic acid. The outer shell 206 formed from the outer shell reactants may include zinc sulfide (ZnS) material. The outer shell 206 provides improved bonding and dispersion properties to the multi-layer semiconductor particle 200 when added to a polymer binder. In an embodiment of the multi-layer semiconductor particle 200 including an outer shell 206 containing a ZnS material, the disulfide bonds of the sulfur component can provide cross-linking between the particle and the surrounding polymer binder. The cross-linking can facilitate a more uniform dispersion of the particle in the polymer binder, reducing the number of luminescent hot spots and dark spots within the layer of quantum dot material.

[0036] The method 100 may include, in optional operation 135, cooling the mixture of fully formed multi-layer semiconductor particles 200. In an embodiment, operation 135 may include more than one cooling stage characterized by different constant cooling 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 206 and the size of the multi-layer semiconductor particles 200. The heated mixture of fully formed particles may be cooled in a first cooling stage characterized by a first constant cooling rate and then a second cooling stage characterized by a second constant cooling rate. The first constant cooling rate may be about 5° C. / min or more, about 6° C. / min or more, about 7° C. / min or more, about 8° C. / min or more, about 9° C. / min or more, about 10° C. / min or more, or more. The second constant cooling rate may be about 4° C. / min or less, about 3° C. / min or less, about 2° C. / min or less, about 1° C. / min or less, or less. The transition temperature from the first to the second cooling stage may occur when the fully formed multi-layer semiconductor particle 200 mixture 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. Operation 135 may reach completion when the fully formed multi-layer semiconductor particle 200 is characterized by a temperature of about 30° C. or less.

[0037] The method 100 may include, in optional operation 140, separating the multi-layer semiconductor particles 200 from the remaining components of the mixture in which they were formed. In an embodiment, the mixture of fully formed multi-layer semiconductor particles 200 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. These liquid organic compounds may be separated from the multi-layer semiconductor particles 200 by decanting the supernatant liquid from the concentrated mixture of particles. The concentrated mixture of particles may be mixed with one or more volatile organic solvents, such as hexane and acetone, among other organic solvents. The solvent mixture may be centrifuged to separate the mixture from the particle-formed mixture into a precipitate containing the multi-layer semiconductor particles 200, and another supernatant containing the added organic solvent, and further portions of the residual liquid organic compounds. The supernatant may be separated from the precipitate containing the multi-layer semiconductor particles 200. The separated precipitate may be contacted with additional volatile organic solvent, centrifuged, and separated during one or more additional washing cycles to produce an isolated batch of multi-layer semiconductor particles 200. An isolated batch of multi-layered semiconductor particles 200 may be stored in contact with a binder polymer composition until use. The binder polymer composition may include an acrylate compound. The acrylate compound may be or may include 1,6-hexanediol diacrylate.

[0038] In the method 100, the various reactant and particle mixtures may be characterized by low moisture. The mixtures may be characterized by moisture levels of about 1% or less, about 0.75% or less, about 0.5% or less, about 0.25% or less, about 0.1% or less, about 0.05% or less, or less by weight. The mixtures may be characterized as free of hydrated compounds in which one or more water molecules are incorporated into the compound. Low moisture levels in the reactants and mixtures may reduce the number of by-products that are produced instead of the multi-layered semiconductor particles 200. Low moisture levels may result in mixtures with fewer amounts of semiconductor hydroxide compounds, such as zinc hydroxide, selenium hydroxide, and tellurium hydroxide, among others, that may precipitate from the mixture to prevent the semiconductor material from being incorporated into the multi-layered semiconductor particles 200.

[0039] Additionally, in method 100, the various reactants and particle mixtures in a heated state (e.g., at about 80° C. or higher) can be kept in an oxygen-free atmosphere to reduce or prevent oxidation of compounds in the mixture. The reactants and particle mixtures can 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 may also reduce the risk of fire hazards 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, these reactants and mixtures may be susceptible to ignition at such temperatures. The reactants and particle mixtures in a heated state can be maintained in an oxygen-free atmosphere, among other inert gases, such as dry nitrogen (N 2 ) and / or argon (Ar). These oxygen-free atmospheres may contain about 1% by weight or less, about 0.75% by weight or less, about 0.5% by weight or less, about 0.25% by weight or less, about 0.1% by weight or less, about 0.05% by weight or less, or less than about 1% by weight of molecular oxygen (O 2 ) level.

[0040] The method 100 may include adding an antioxidant reactant to the particle mixture in operation 145. However, it is contemplated that the antioxidant reactant may be added to the particle mixture at any stage during particle formation. The antioxidant may be characterized by a boiling point of about 100° C. or higher. At boiling points below 100° C., the antioxidant may tend to undergo diffusion and / or evaporation. Thus, antioxidants with higher molecular weights may perform better than antioxidants with lower molecular weights. The antioxidant reactant may include a phosphorus-containing material, among other materials. In embodiments, the phosphorus-containing material may be an organic ligand, including a phosphite or phosphine group, capable of binding with the particle mixture, such as a zinc-containing outer shell.

[0041] In embodiments, the phosphorus-containing material may include any material that includes phosphorus, such as, but not limited to, triisopropyl phosphite (TIPP), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP), tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP), triethyl phosphite, tris(2-ethylhexyl phosphite), tris(trimethylsilyl)phosphite, triphenyl phosphite, triphenylphosphine, tris(4-methoxyphenyl)phosphine, tris(1-pyrrolidinyl)phosphine, tri(2-furyl)phosphine, or tris(dimethylamino)phosphine. It is also contemplated that antioxidants such as phosphorus-containing materials may include reactive functional groups. The reactive functional groups may be polymerized, cured, or crosslinked with other components in the quantum dot material, such as the ink used to form the quantum dot particles. For example, the phosphorus-containing material may include triallyl phosphite, triallyl phosphine, divinylphenylphosphine, diallyl-N,N-diisopropyl phosphoramidite, or tris-(4-vinylbenzyl)phosphine, however, other phosphorus-containing materials are contemplated, and in embodiments, the antioxidant may not be limited to phosphorus-containing materials.

[0042] In embodiments, an antioxidant, such as a phosphorus-containing material, may be bound to the zinc-containing outer shell. For example, an antioxidant, such as a phosphorus-containing material, may be covalently bound to the zinc-containing outer shell.

[0043] The antioxidant can improve the stability of the quantum dot material by consuming oxygen that would otherwise react with the quantum dot material. In the absence of the antioxidant, the quantum dot material may be subject to oxidation, and the quantum dot material may be subject to photodecomposition. The phosphite in the phosphorus-containing material may be subject to oxidation to form phosphate. The phosphite in the antioxidant may be subject to oxidation to prevent oxygen from reacting with the quantum dot material, thereby improving the stability and shelf life of the quantum dot material. Thus, when an antioxidant is present in the quantum dot material, the various reactants and particle mixtures in a heated state (e.g., above about 80° C.) may not need to be kept in an oxygen-free atmosphere. The presence of oxygen may not affect the quantum dot material, but may instead react with the antioxidant. Additionally, the various reactants and particle mixtures of the quantum dot material may also be exposed to white light during manufacture, which may oxidize conventional quantum dot materials.

[0044] Each multi-layer semiconductor particle 200 may be characterized by a longest dimension (e.g., diagonal) of about 4 nm or less, about 3.5 nm or less, about 3 nm or less, about 2.5 nm or less, about 2 nm or less, or less. The method 100 may form multi-layer semiconductor particles 200 that may be characterized by increased sharpness and fewer secondary emission peaks than quantum dot particles made by conventional methods. In embodiments, the light emitted by the multi-layer semiconductor particles 200 may be characterized by a peak wavelength emission of about 500 nm or less, about 490 nm or less, about 480 nm or less, about 470 nm or less, about 460 nm or less, about 450 nm or less, about 440 nm or less, about 430 nm or less, about 420 nm or less, about 410 nm or less, about 400 nm or less, about 390 nm or less, about 380 nm or less, or less. The light emitted by the multi-layer semiconductor particles 200 may be characterized by a peak wavelength emission of about 455 nm or less. The light emitted by the multi-layer semiconductor particles 200 can have a narrowband (i.e., sharp) color profile characterized by a full width at half maximum (FWHM) primary wavelength emission peak that is about 40 nm or less, about 35 nm or less, about 30 nm or less, about 25 nm or less, about 20 nm or less, about 15 nm or less, about 10 nm or less, about 5 nm or less, about 2.5 nm or less, about 1 nm or less, or less.

[0045] 3, a simplified cross-section of a display device 300 is shown, including a pixel structure 301. The pixel structure 301 may include a photoluminescent region 302, which may include a photoluminescent material 304. The photoluminescent material 304 may include one or more multi-layered semiconductor particles (i.e., quantum dot particles) with an antioxidant, such as a phosphorus-containing material, according to an embodiment of the present technology. In an embodiment, the quantum dot particles (i.e., quantum dot material) of the photoluminescent material 304 may be blue quantum dot particles (i.e., blue quantum dot material). The pixel structure 301 of the display device 300 may include a light source 306. The photoluminescent region and / or the photoluminescent material may be located above the light source 306. The light source 306 may excite three regions of quantum dot particles 308a-c, which are operable to emit different colors of light upon excitation by the light source 306. The first quantum dot region 308a may be operable to emit blue light, the second quantum dot region 308b may be operable to emit green light, and the third quantum dot region 308c may be operable to emit red light. Multi-layered semiconductor particles according to embodiments of the present technology may be incorporated into the first quantum dot region 308a and may be operable to emit a sharp blue color having a peak narrowband emission wavelength of about 455 nm or less.

[0046] The display device 300 may be operable to excite the regions of quantum dot particles 308a-c with varying intensities by the light source 306. The light source 306 may include one or more light emitting diode structures operable to emit light at shorter, more energetic wavelengths than the light emitted by the regions of quantum dot particles 308a-c. The light source 306 may be operable to emit ultraviolet excitation light, characterized by a peak emission wavelength of about 350 nm or less. In an embodiment, the light source 306 may be operable to emit white light, characterized by a broad emission across the visible spectrum (e.g., 380 nm-750 nm).

[0047] The display device 300 may be operable to display an image by driving the light source 306 to excite the regions of quantum dot particles 308a-c, which emit colored light across a translucent front panel 310 onto which the image is projected. A controller 312 may be coupled via electronic circuitry (not shown) to the light source 306 and the regions of quantum dot particles 308a-c. The controller 312 may be operable to receive input signals to display an image and to send output signals to drive and de-drive portions of the light source 306 and the regions of quantum dot particles 308a-c.

[0048] Forming the display device 300 may include forming a light source 306, such as a light emitting diode structure, on a substrate (not shown), forming a photoluminescent region 302 on the light emitting diode structure, and forming a photoluminescent material 304 in the photoluminescent region 302. As previously discussed, the photoluminescent material 304 may include a plurality of multi-layered semiconductor particles including an antioxidant, such as multi-layered semiconductor particles according to the present disclosure. In an embodiment, the photoluminescent material may include a blue quantum dot material. During formation of the display device 300, the photoluminescent material may be handled in the presence of oxygen or ambient white light.

[0049] Embodiments of the present technology allow for the fabrication of multi-layer semiconductor particles (i.e., quantum dot particles) that feature improved PLQY. Embodiments include the addition of an antioxidant, such as a phosphorus-containing material, that can act as a sacrificial compound that undergoes oxidation. By including an oxidizing agent, materials within the multi-layer semiconductor particles that are critical to the performance of the photoluminescent material may be less prone to photodegradation through oxidation. The incorporation of an antioxidant may allow the quantum dot particles to be fabricated in an oxygen-containing environment, such as air. This may reduce the complexity of fabrication and improve the lifetime of the quantum dot particles compared to the prior art.

[0050] For purposes of explanation, numerous details have been described above 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 can be practiced without some of these details or with additional details. For example, other substrates that can benefit from the wet techniques described can also be used with the present technology.

[0051] Although several embodiments have been disclosed, it will be recognized by those skilled in the art that various modifications, alternative configurations and equivalents may be used without departing from the spirit of the present embodiments. Moreover, some well-known processes and elements have not been described to avoid unnecessarily obscuring the technology. Thus, the above should not be taken as a limitation on the scope of the technology.

[0052] Where a range of values ​​is presented, unless the context clearly dictates otherwise, each intervening value between the upper and lower limit of that range (to the smallest fraction of the unit of the lower limit) is also understood to be specifically disclosed. Any stated value or unstated intervening value in a stated range and any other stated or intervening value in that stated range are included in any smaller range. The upper and lower limits of those smaller ranges may be independently included or excluded in the range, and each range in which one limit is included, neither limit is included, or both limits are included in the smaller range is also included within the scope of the technology, subject to any specifically excluded limit in the stated range. Where a stated range includes one or both limits, ranges excluding one or both of those included limits are also included. Where multiple values ​​are presented in a list, any range including or based on any of those values ​​is specifically disclosed as well.

[0053] As used herein and in the appended claims, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to a "light emitting diode structure" includes a plurality of such structures, reference to a "photoluminescent region" includes reference to one or more photoluminescent regions and equivalents thereof known to those skilled in the art, and so forth.

[0054] Similarly, the words "comprise(s)", "comprising", "contain(s)", "containing", "include(s)" and "including" as used in this specification and the claims that follow are intended to specify the presence of stated features, integers, components or operations, but such words do not exclude the presence or addition of one or more other features, integers, components, operations, acts or groups.

Claims

1. a zinc-containing core; a zinc and selenium containing inner shell on a zinc containing core; a zinc-containing outer shell over a zinc and selenium-containing inner shell; a phosphorus-containing material in contact with the zinc-containing outer shell, the phosphorus-containing material comprising triisopropyl phosphite (TIPP), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP), tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP), triethyl phosphite, tris(2-ethylhexyl phosphite), tris(trimethylsilyl)phosphite, triphenyl phosphine, tris(4-methoxyphenyl)phosphine, tris(1-pyrrolidinyl)phosphine, tri(2-furyl)phosphine, tris(dimethylamino)phosphine, triallyl phosphite, triallyl phosphine, divinylphenylphosphine, diallyl-N,N-diisopropyl phosphoramidite, or tris-(4-vinylbenzyl)phosphine; A multi-layer semiconductor particle comprising:

2. 10. The multi-layered semiconductor particle of claim 1, wherein the zinc-containing core further comprises sulfur, selenium or tellurium.

3. 10. The multi-layered semiconductor particle of claim 1, wherein the zinc and selenium-containing inner shell further comprises tellurium or sulfur.

4. The multi-layered semiconductor particle of claim 1 , wherein the zinc-containing outer shell further comprises sulfur.

5. The multi-layered semiconductor particles of claim 1 , wherein each multi-layered semiconductor particle is characterized by a longest dimension of about 4 nm or less.

6. The multi-layered semiconductor particle of claim 1 , wherein the phosphorus-containing material is characterized by a boiling point of about 100° C. or greater.

7. 2. The multi-layered semiconductor particle of claim 1, wherein the phosphorus-containing material comprises bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP) or tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP).

8. a light emitting diode structure operable to generate light characterized by a peak emission wavelength of about 350 nm or greater; a photoluminescent region containing a photoluminescent material located over the light emitting diode structure, the photoluminescent region comprising a plurality of multi-layered semiconductor particles including an antioxidant; The pixel structure, including

9. 9. The pixel structure of claim 8, wherein the antioxidant comprises phosphorus and is characterized by a boiling point of about 100 degrees Celsius or greater.

10. the antioxidant comprises a phosphorus-containing material; the phosphorus-containing material comprises triisopropyl phosphite (TIPP), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP), tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP), triethyl phosphite, tris(2-ethylhexyl phosphite), tris(trimethylsilyl)phosphite, triphenyl phosphine, tris(4-methoxyphenyl)phosphine, tris(1-pyrrolidinyl)phosphine, tri(2-furyl)phosphine, tris(dimethylamino)phosphine, triallyl phosphite, triallyl phosphine, divinylphenylphosphine, diallyl-N,N-diisopropyl phosphoramidite or tris-(4-vinylbenzyl)phosphine; The pixel structure of claim 8.

11. A plurality of multi-layer semiconductor particles a zinc-containing core; a zinc and selenium containing inner shell on a zinc containing core; A zinc-containing outer shell over a zinc- and selenium-containing inner shell. The pixel structure of claim 8 , comprising:

12. The pixel structure of claim 8 , wherein the photoluminescent material comprises a quantum dot material.

13. 13. The pixel structure of claim 12, wherein the quantum dot material comprises a blue quantum dot material.

14. 9. The pixel structure of claim 8, wherein each of the multi-layered semiconductor particles is characterized by a longest dimension of about 4 nm or less.

15. 1. A method of manufacturing a display, comprising the steps of: forming a light emitting diode structure on a substrate; forming a photoluminescent region over the light emitting diode structure; forming a photoluminescent material in a photoluminescent region, the photoluminescent material comprising a plurality of multi-layered semiconductor particles including an antioxidant; A method for manufacturing a display comprising:

16. 16. The method of manufacturing a display of claim 15, wherein the photoluminescent material comprises a blue quantum dot material.

17. the antioxidant comprises a phosphorus-containing material; the phosphorus-containing material comprises triisopropyl phosphite (TIPP), bis(2,4-di-tert-butylphenyl)pentaerythritol diphosphate (B PEDP), tris(2,4-di-tert-butylphenyl)phosphite (TDTBPP), triethyl phosphite, tris(2-ethylhexyl phosphite), tris(trimethylsilyl)phosphite, triphenyl phosphine, tris(4-methoxyphenyl)phosphine, tris(1-pyrrolidinyl)phosphine, tri(2-furyl)phosphine, tris(dimethylamino)phosphine, triallyl phosphite, triallyl phosphine, divinylphenylphosphine, diallyl-N,N-diisopropyl phosphoramidite or tris-(4-vinylbenzyl)phosphine; A method for manufacturing a display according to claim 15.

18. 16. The method of manufacturing a display of claim 15, wherein the photoluminescent material is characterized by a longest dimension of about 4 nm or less.

19. handling the photoluminescent material in the presence of oxygen or ambient white light during subsequent manufacturing operations.

16. A method of manufacturing the display of claim 15 further comprising:

20. A plurality of multi-layer semiconductor particles A zinc-containing core; a zinc and selenium containing inner shell on a zinc containing core; A zinc-containing outer shell over a zinc- and selenium-containing inner shell.

16. A method of manufacturing the display of claim 15, comprising:

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