Quantum Dots, Method for Manufacturing the Same, and Quantum Dot Composite, Display Device, and Electronic Device Comprising the Same

Abstract

Disclosed are quantum dots, a method for manufacturing the same, and a quantum dot composite, a display device, and an electronic device including the same. The quantum dots do not contain cadmium. The quantum dots include zinc, tellurium, and selenium, and include: a core including a first semiconductor nanocrystal; and a semiconductor nanocrystal shell disposed on the core and including a zinc chalcogenide, wherein the quantum dots further include magnesium and the molar ratio of Te:Se in the quantum dots is greater than or equal to about 0.1:1.

Description

[0001] Cross-reference to related applications

[0002] This application claims the priority and benefits of Korean Patent Application No. 10-2020-0134706, filed with the Korean Intellectual Property Office on October 16, 2020, and all benefits arising therefrom, and incorporates its entire content herein by reference. Technical Field

[0003] Quantum dots, a method for manufacturing the same, and a quantum dot composite, a display device, and an electronic device (apparatus) including the quantum dots are disclosed. Background Art

[0004] Unlike bulk materials, the physical properties (e.g., bandgap energy and melting point) of semiconductor nanoparticles can be controlled by changing the size of the nanoparticles. For example, semiconductor nanocrystal particles (also referred to as quantum dots) are crystalline materials having a size in the range of several nanometers. Since semiconductor nanocrystal particles have a relatively small size, the nanocrystal particles have a large surface area per unit volume, and thus, the particles exhibit a quantum confinement effect and will have properties different from those of bulk materials having the same chemical composition. Quantum dots can absorb energy from an excitation source such as light or an applied current, and when relaxing, e.g., returning to the ground state, the quantum dots emit light energy corresponding to the bandgap energy of the quantum dots. Summary of the Invention

[0005] Embodiments provide environmentally friendly quantum dots capable of achieving improved optical properties (e.g., luminescence efficiency).

[0006] Embodiments provide a method for manufacturing the above-described quantum dots.

[0007] Embodiments provide a quantum dot composite including the above-described quantum dots.

[0008] Embodiments provide an electronic device such as a display device including the above-described quantum dots.

[0009] In an embodiment, a quantum dot (or quantum dots, hereinafter referred to as "quantum dot") includes zinc, tellurium, and selenium. The quantum dot (hereinafter also referred to as "core-shell quantum dot") may have a core-shell structure including: a core including a first semiconductor nanocrystal, and a semiconductor nanocrystal shell disposed on the core, the semiconductor nanocrystal shell including a zinc chalcogenide. The quantum dot further includes magnesium, and in the quantum dot, the molar ratio of tellurium to selenium is greater than or equal to about 0.1:1, and the quantum dot does not include cadmium. The first semiconductor nanocrystal may include zinc, tellurium, and selenium.

[0010] The quantum dot may be configured to emit green light.

[0011] The wavelength of the maximum emission peak of the green light or the quantum dots may be in the range of greater than or equal to about 480 nanometers (nm) and less than or equal to about 580 nm. The maximum emission wavelength may be greater than or equal to about 490 nm, greater than or equal to about 500 nm, greater than or equal to about 510 nm, or greater than or equal to about 520 nm. The maximum emission wavelength may be less than or equal to about 560 nm, less than or equal to about 550 nm, or less than or equal to about 545 nm.

[0012] The quantum dots may not include lead, mercury, or a combination thereof.

[0013] The first semiconductor nanocrystal or the core may include a first zinc chalcogenide containing zinc, tellurium, and selenium.

[0014] In the quantum dots, the molar ratio of tellurium to selenium (Te:Se) may be greater than or equal to about 0.15:1, greater than or equal to about 0.2:1, greater than or equal to about 0.25:1, greater than or equal to about 0.3:1, or greater than or equal to about 0.32.

[0015] In the quantum dots, the molar ratio of magnesium to zinc (Mg:Zn) may be greater than or equal to about 0.01:1, greater than or equal to about 0.1:1, or greater than or equal to about 0.2:1. In the quantum dots, the molar ratio of magnesium to zinc (Mg:Zn) may be less than or equal to about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, less than or equal to about 0.6:1, or less than or equal to about 0.5:1.

[0016] In the quantum dots, the molar ratio of magnesium to tellurium (Mg:Te) may be greater than or equal to about 0.001:1, greater than or equal to about 0.01:1, greater than or equal to about 0.1:1, greater than or equal to about 0.5:1, greater than or equal to about 1:1, greater than or equal to about 1.5:1, greater than or equal to about 2:1, greater than or equal to about 3:1, or greater than or equal to about 3.2:1.

[0017] In the quantum dots, the molar ratio of magnesium to tellurium (Mg:Te) may be less than or equal to about 10:1, less than or equal to about 7:1, less than or equal to about 6:1, less than or equal to about 5.7:1, less than or equal to about 5:1, less than or equal to about 4:1, less than or equal to about 3.5:1, less than or equal to about 3:1, less than or equal to about 2.5:1, or less than or equal to about 2:1.

[0018] In the quantum dots, magnesium may be present in the core, in the semiconductor nanocrystal shell, or in both the core and the semiconductor nanocrystal shell. In an embodiment, magnesium may be present at the interface between the core and the semiconductor nanocrystal shell. In the quantum dots, magnesium may be present in the semiconductor nanocrystal shell.

[0019] In an embodiment, the quantum dots or the core may not include III-V compounds. The III-V compounds may include indium phosphide, zinc indium phosphide, gallium phosphide, or a combination thereof.

[0020] In an embodiment, the quantum dots may not include indium, gallium, or a combination thereof.

[0021] The quantum dots may be insoluble in water.

[0022] The first semiconductor nanocrystal or the core may include ZnTe x Se 1-x , where x is greater than or equal to about 0.15, greater than or equal to about 0.4, or greater than or equal to about 0.5 and less than or equal to about 0.95, or less than or equal to about 0.9.

[0023] In the core or in the first semiconductor nanocrystal, the molar ratio of tellurium to selenium may be greater than or equal to about 0.15:1, greater than or equal to about 0.2:1, greater than or equal to about 0.3:1, greater than or equal to about 0.4:1, or greater than or equal to about 0.5:1. In the core or in the first semiconductor nanocrystal, the molar ratio of tellurium to selenium may be less than or equal to about 5:1, less than or equal to about 4:1, less than or equal to about 3:1, less than or equal to about 2.5:1, less than or equal to about 2:1, less than or equal to about 1.5:1, less than or equal to about 1:1, or less than or equal to about 0.7:1.

[0024] The quantum dots (or the semiconductor nanocrystal shell) may include selenium and sulfur, and in the quantum dots, the molar ratio of sulfur to selenium may be greater than 0:1, greater than or equal to about 0.01:1, greater than or equal to about 0.02:1, greater than or equal to about 0.05:1, greater than or equal to about 0.1:1, greater than or equal to about 0.13:1, greater than or equal to about 0.2:1, greater than or equal to about 0.3:1, greater than or equal to about 0.4:1, greater than or equal to about 0.5:1, greater than or equal to 1:1, greater than or equal to 1.5:1, or greater than or equal to about 2:1. In the quantum dots, the molar ratio of sulfur to selenium may be less than or equal to about 8:1, less than or equal to about 6:1, less than or equal to about 4:1, less than or equal to about 3.5:1, less than or equal to about 3:1, less than or equal to about 2.5:1, less than or equal to about 2:1, less than or equal to about 1.5:1, less than or equal to about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, less than or equal to about 0.6:1, or less than or equal to about 0.55:1.

[0025] In the quantum dots, the molar ratio of the sum of sulfur and selenium to tellurium may be less than or equal to about 15:1, less than or equal to about 14:1, less than or equal to about 13:1, less than or equal to about 12:1, less than or equal to about 11:1, or less than or equal to about 10.5:1.

[0026] In the quantum dots, the molar ratio of sulfur to zinc may be less than or equal to about 0.95:1, less than or equal to about 0.6:1, less than or equal to about 0.56:1, less than or equal to about 0.4:1, less than or equal to about 0.3:1, or less than or equal to about 0.2:1.

[0027] In the quantum dots, the molar ratio of tellurium to sulfur (Te:S) may be greater than or equal to about 0.1:1, greater than or equal to about 0.12:1, greater than or equal to about 0.13:1, greater than or equal to about 0.15:1, or greater than or equal to about 0.2:1. In the quantum dots, the molar ratio of tellurium to sulfur (Te:S) may be less than or equal to about 2:1.

[0028] The quantum dots may further include additional metals, the additional metals including alkali metals, aluminum, or a combination thereof. The alkali metal may include lithium. In the quantum dots, the molar ratio of the additional metal (i.e., the alkali metal, aluminum, or a combination thereof) to tellurium may be greater than or equal to about 0.001:1, greater than or equal to about 0.01:1, or greater than or equal to about 0.05:1. The alkali metal may include lithium. In the quantum dots, the molar ratio of the additional metal (i.e., the alkali metal, aluminum, or a combination thereof) to tellurium may be less than or equal to about 10:1, less than or equal to about 8:1, less than or equal to about 7:1, or less than or equal to about 6:1.

[0029] In an embodiment, the quantum dots may further include aluminum and the molar ratio of aluminum to tellurium (Al:Te) in the quantum dots may be greater than or equal to about 0.005:1, less than or equal to about 0.5:1, or a combination thereof.

[0030] The maximum emission peak of the quantum dots may have a full width at half maximum of less than or equal to about 45 nm, less than or equal to about 43 nm, less than or equal to about 40 nm, less than or equal to about 39 nm, less than or equal to about 38 nm, or less than or equal to about 37 nm.

[0031] The quantum efficiency (or quantum yield) of the quantum dots may be greater than or equal to about 50%, greater than or equal to about 55%, greater than or equal to about 60%, greater than or equal to about 65%, greater than or equal to about 70%, or greater than or equal to about 80%.

[0032] The quantum dots may include organic ligands, such as including organic ligands on their surfaces. The organic ligands may include RCOOH, RNH2, R2NH, R3N, RSH, RH2PO, R2HPO, R3PO, RH2P, R2HP, R3P, ROH, RCOOR', RPO(OH)2, RHPOOH, R2POOH, polymer-type organic ligands, or a combination thereof, where R and R' are the same or different and independently are substituted or unsubstituted C1-C40 aliphatic hydrocarbon groups or substituted or unsubstituted C6-C40 aromatic hydrocarbon groups, or a combination thereof.

[0033] The quantum dots may have a size (or average size) greater than or equal to about 4.5 nm, or greater than or equal to about 4.8 nm. The size or average size of the quantum dots may be less than or equal to about 7 nm, less than or equal to about 6.5 nm, less than or equal to about 6 nm, or less than or equal to about 5.5 nm.

[0034] The semiconductor nanocrystal shell may include a first shell layer disposed (e.g., directly disposed) on the core and a second shell layer disposed on (e.g., directly disposed on) the first shell layer or above the first shell layer.

[0035] The first shell layer may include a second semiconductor nanocrystal. The second shell layer may include a third semiconductor nanocrystal having a composition different from that of the second semiconductor nanocrystal. The second shell layer may be the outermost layer of the quantum dot.

[0036] The second semiconductor nanocrystal may include zinc, selenium, and optionally sulfur. The second semiconductor nanocrystal may or may not include sulfur. The third semiconductor nanocrystal may include zinc and sulfur. The third semiconductor nanocrystal may or may not include selenium. The second semiconductor nanocrystal, the third semiconductor nanocrystal, or both the second semiconductor nanocrystal and the third semiconductor nanocrystal may further include magnesium.

[0037] The semiconductor nanocrystal shell may include a first shell layer disposed on the core and a second shell layer disposed on the first shell layer. The first shell layer may include a second semiconductor nanocrystal and the second shell layer may include a third semiconductor nanocrystal having a composition different from that of the second semiconductor nanocrystal. The second semiconductor nanocrystal may include zinc, selenium, and optionally sulfur, and the third semiconductor nanocrystal may include zinc and sulfur. The second semiconductor nanocrystal may include magnesium, the third semiconductor nanocrystal may include magnesium, or both the second semiconductor nanocrystal and the third semiconductor nanocrystal may include magnesium.

[0038] The second semiconductor nanocrystal may include zinc selenide and optionally magnesium selenide. The third semiconductor nanocrystal may include zinc sulfide and optionally magnesium sulfide.

[0039] The quantum dot may not exhibit, for example, a metallic magnesium peak, a magnesium oxide (magnesium - oxygen) peak, or a combination thereof, as determined by X - ray photoelectron spectroscopy analysis.

[0040] In an embodiment, a method of manufacturing the quantum dot includes:

[0041] Preparing a core particle including the core; and

[0042] Reacting a zinc precursor and a chalcogen precursor in a first organic solvent in the presence of the core particle and a first organic ligand at a shell - forming reaction temperature to form the semiconductor nanocrystal shell on the core particle to manufacture the quantum dot;

[0043] Wherein the method further includes adding a magnesium precursor to the reaction system during the preparation of the core particle, the formation of the shell, or a combination thereof.

[0044] In an embodiment, the preparation of the core particles may include reacting a zinc precursor, a selenium precursor, and a tellurium precursor at a core formation temperature. The preparation of the core particles may include preparing a zinc precursor organic solution including the zinc precursor and a second organic ligand in a second organic solvent; and

[0045] while heating the zinc precursor organic solution at the core formation temperature, adding the selenium precursor, the tellurium precursor, a hydride compound, and a third organic ligand different from the second organic ligand thereto simultaneously or sequentially.

[0046] The magnesium precursor may include magnesium carboxylate, alkylated magnesium, or a combination thereof.

[0047] In an embodiment, a quantum dot (e.g., quantum dot-polymer) composite includes a (e.g., polymer) matrix; and a plurality of quantum dots dispersed in the (polymer) matrix,

[0048] wherein the plurality of quantum dots includes the above-mentioned quantum dots.

[0049] The matrix may include a polymer.

[0050] The matrix may include a crosslinked polymer, a monomer or polymer containing a carboxylic acid group, or a combination thereof.

[0051] The crosslinked polymer may include a polymerization product of a photopolymerizable monomer containing a carbon-carbon double bond, a polymerization product of the photopolymerizable monomer and a polythiol compound having at least two thiol groups (e.g., at the ends of the polythiol compound), or a combination thereof.

[0052] The quantum dot composite may further include metal oxide particles (e.g., dispersed in the polymer matrix).

[0053] In an embodiment, a display device includes a light-emitting element, and the light-emitting element includes a plurality of the core-shell quantum dots.

[0054] In an embodiment, a display device includes a light-emitting element (e.g., a photoluminescent element) and optionally a light source, wherein the light-emitting element includes the quantum dots or the quantum dot-polymer composite. If present, the light source may be configured to provide incident light to the light-emitting element.

[0055] The incident light may have a photoluminescence peak wavelength of about 440 nm - about 560 nm (e.g., about 445 nm - about 460 nm or about 450 nm - about 460 nm).

[0056] The light-emitting element may include a sheet of the quantum dot-polymer composite.

[0057] The light-emitting element may include a stacked structure including a substrate and a light-emitting layer (e.g., a photoluminescent layer) disposed on the substrate. The light-emitting layer may include a pattern of the quantum dot-polymer composite. The pattern may include repeating segments (portions) configured to emit light of a predetermined wavelength, such as at least one or two repeating segments configured to emit light of a predetermined wavelength.

[0058] The display device may be configured to have a color reproducibility of greater than or equal to about 80% according to the BT2020 standard.

[0059] In an embodiment, an electronic device may include: a first electrode and a second electrode having opposing surfaces; and an active layer including the quantum dots, which is disposed, for example, between the first and the second electrodes.

[0060] The electronic device may further include a charge assisting layer (e.g., a hole assisting layer) disposed between the first electrode and the active layer.

[0061] The electronic device may further include a charge assisting layer (e.g., an electron assisting layer) disposed between the second electrode and the active layer.

[0062] In an embodiment, the quantum dots may exhibit improved optical properties (e.g., a narrowed full width at half maximum and enhanced luminescence efficiency) at a desired wavelength, for example, presented in the region greater than about 470 nm or the green light region, while they may not include harmful heavy metals such as cadmium.

[0063] According to an embodiment, the quantum dots may be used in a light-emitting element (e.g., a light-emitting layer) of a display device (e.g., a photoluminescent or electroluminescent display device), contributing to realizing a display having high color reproducibility, high efficiency, and high brightness.

[0064] The quantum dots of the embodiment may also be applied to, for example, be used in: biolabels (biosensors, bioimaging) and security inks (anti-counterfeiting inks), and may increase the number of distinguishable colors in the visible light region. The quantum dots of the embodiment may be used in high-sensitivity optical sensors. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The above and other advantages and features of the present disclosure will become more apparent by describing its exemplary embodiments in further detail with reference to the accompanying drawings, in which:

[0066] Figure 1 A schematic cross-sectional view of an embodiment showing quantum dots and their energy band alignment.

[0067] Figure 2ASchematically shows an embodiment of a process of manufacturing a quantum dot composite pattern using a composition.

[0068] Figure 2B Schematically shows a process of manufacturing a quantum dot composite pattern using an ink composition.

[0069] Figure 3 Is an exploded view of an embodiment of a display device.

[0070] Figure 4A Is a schematic cross-sectional view of an embodiment of a display device.

[0071] Figure 4B Is a schematic cross-sectional view of an embodiment of a display device.

[0072] Figure 5 Is a schematic cross-sectional view of an embodiment of a display device.

[0073] Figure 6A Is a schematic cross-sectional view of an embodiment of a light-emitting device.

[0074] Figure 6B Is a schematic cross-sectional view of an embodiment of a light-emitting device.

[0075] Figure 6C Is a schematic cross-sectional view of an embodiment of a light-emitting device.

[0076] Figure 7 Is the result of transmission electron microscopy-energy dispersive X-ray spectroscopy analysis of the quantum dots prepared in Example 1. Detailed embodiments

[0077] With reference to the following example embodiments together with the accompanying figures, the advantages and characteristics of the present disclosure, as well as the methods for achieving them, will become apparent. However, the embodiments should not be construed as limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0078] Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used with the meanings commonly understood by a person having ordinary knowledge in the art. It will be further understood that terms, such as those defined in common dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and should not be interpreted idealistically or exaggeratedly unless clearly defined. The terms used herein are for the purpose of describing specific embodiments only and are not intended to be limiting.

[0079] As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms, including "at least one", unless the context clearly dictates otherwise. "At least one" is not to be construed as limited to "one" or "a single". "Or" means "and / or". As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises" or "comprising", when used in this specification, specify the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or groups thereof.

[0080] In the figures, the thickness of layers, films, panels, regions, etc. is enlarged for clarity. In the specification, the same reference numerals always refer to the same elements. It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, no intervening elements are present.

[0081] It will be understood that although the terms "first", "second", "third", etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections are not to be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another. Thus, without departing from the teachings herein, the "first element", "component", "region", "layer", or "section" discussed below could be termed a second element, component, region, layer, or section.

[0082] As used herein, "about" includes the stated value and means within an acceptable deviation range for a particular value as determined by one of ordinary skill in the art in view of the measurements discussed and the error associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations of the stated value, or within the range of ±10% or ±5%.

[0083] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. Thus, deviations from the shapes of the figures as a result of, for example, manufacturing techniques and / or tolerances are to be expected. Accordingly, the embodiments described herein should not be construed as limited to the specific shapes of regions as illustrated herein, but include deviations in shapes resulting from, for example, manufacturing. For example, regions illustrated or described as flat may typically have rough and / or non-linear features. Also, sharp corners illustrated may be rounded. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of the regions and are not intended to limit the scope of the claims.

[0084] As used herein, when no definition is otherwise provided, "substituted" may refer to the replacement of a hydrogen of a compound or group with a substituent such as: C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C6-C30 aryl, C7-C30 alkylaryl, C1-C30 alkoxy, C1-C30 heteroalkyl, C3-C30 heteroalkylaryl, C3-C30 cycloalkyl, C3-C15 cycloalkenyl, C6-C30 cycloalkynyl, C2-C30 heterocycloalkyl, halogen (-F, -Cl, -Br, or -I), hydroxy (-OH), nitro (-NO2), cyano (-CN), amino (-NRR', where R and R' are independently hydrogen or C1-C6 alkyl), azido (-N3), amidino (-C(=NH)NH2), hydrazino (-NHNH2), hydrazono (=N(NH2)), aldehyde (-C(=O)H), carbamoyl (-C(O)NH2), mercapto (-SH), ester (-C(=O)OR, where R is C1-C6 alkyl or C6-C12 aryl), carboxy (-COOH) or its salt (-C(=O)OM, where M is an organic or inorganic cation), sulfonic acid group (-SO3H) or its salt (-SO3M, where M is an organic or inorganic cation), phosphoric acid group (-PO3H2) or its salt (-PO3MH or -PO3M2, where M is an organic or inorganic cation), or a combination thereof.

[0085] As used herein, a hydrocarbon group refers to a group that includes carbon and hydrogen (or is composed of carbon and hydrogen) (e.g., alkyl, alkenyl, alkynyl, or aryl). A hydrocarbon group may be a group having a valence of 1 (or greater) formed by removing a hydrogen atom (or, for example, a hydrogen atom, such as at least one hydrogen atom) from an alkane, alkene, alkyne, or arene. In a hydrocarbon group, a methylene group, such as at least one methylene group, may be replaced by an oxygen moiety, a carbonyl moiety, an ester moiety, -NH-, or a combination thereof.

[0086] As used herein, "aromatic" refers to an organic compound or group containing an unsaturated cyclic group having delocalized π electrons, such as at least one unsaturated cyclic group having delocalized π electrons. The term encompasses both aromatic hydrocarbon groups or compounds and heteroaromatic hydrocarbon groups or compounds.

[0087] As used herein, "aliphatic" refers to a saturated or unsaturated straight-chain or branched hydrocarbon compound or group. Aliphatic groups can be, for example, alkyl, alkenyl, or alkynyl.

[0088] As used herein, "alkyl" refers to a straight-chain or branched saturated monovalent hydrocarbon group (such as methyl, ethyl, hexyl, etc.).

[0089] As used herein, "alkenyl" refers to a straight-chain or branched monovalent hydrocarbon group having a carbon-carbon double bond.

[0090] As used herein, "alkynyl" refers to a straight-chain or branched monovalent hydrocarbon group having a carbon-carbon triple bond.

[0091] As used herein, "aryl" refers to a group formed by removing hydrogen, such as at least one hydrogen, from an aromatic hydrocarbon (e.g., phenyl or naphthyl).

[0092] As used herein, "hetero" refers to including one or more (e.g., 1 - 3) of the following heteroatoms: N, O, S, Si, P, or a combination thereof.

[0093] As used herein, "(meth)acryloyl" refers to acryloyl, methacryloyl, or a combination thereof (e.g., in acrylate or methacrylate).

[0094] As used herein, "group" refers to a group of the periodic table.

[0095] As used herein, "Group II" refers to Group IIA and Group IIB, and examples of Group II metals can be Zn, Hg, and Mg, but are not limited thereto.

[0096] As used herein, "Group III" can refer to Group IIIA and Group IIIB, and examples of Group III metals can be In, Ga, Tl, or a combination thereof, but are not limited thereto.

[0097] As used herein, "Group V" can include nitrogen, phosphorus, arsenic, antimony, bismuth, or a combination thereof, but is not limited thereto.

[0098] As used herein, "Group VI" can include sulfur, selenium, tellurium, or a combination thereof, but is not limited thereto.

[0099] As used herein, the term "average" (e.g., the average size of a quantum dot) can be a mean or a median. In an embodiment, the average can be a "mean" average.

[0100] As used herein, the quantum efficiency (also referred to as the quantum yield) can be the ratio of photons emitted from a quantum dot relative to photons absorbed by the quantum dot, e.g., a relative amount. In an embodiment, the quantum efficiency can be determined by any suitable method. For example, the quantum efficiency can be measured by an absolute method and a relative method. The quantum efficiency can be determined by a comparative method using a well-characterized standard sample with a known quantum yield or by an absolute method using an integrating sphere with a commercially available device. The quantum efficiency can be a relative quantum yield or an absolute quantum yield. The quantum efficiency (or quantum yield) can be measured in a solution state or a solid state (such as in a complex).

[0101] In the absolute method, the quantum yield can be determined by detecting all sample fluorescence using an integrating sphere. In the relative method, the fluorescence intensity of a standard sample (e.g., a standard dye) can be compared with the fluorescence intensity of an unknown sample to calculate the quantum yield of the unknown sample. Depending on the photoluminescence wavelength, coumarin 153, coumarin 545, rhodamine 101 inner salt, anthracene, and rhodamine 6G can be used as standard dyes, but are not limited thereto.

[0102] By using, for example, a device commercially available from Hitachi Co., Ltd. or Hamamatsu Co., Ltd. and referring to the instruction manual provided by the manufacturer, the quantum yield (QY) can be easily and reproducibly determined.

[0103] The full width at half maximum (FWHM) and the maximum emission peak wavelength can be determined from the (photo)luminescence spectrum obtained by a spectrophotometer (or a fluorescence spectrophotometer).

[0104] As used herein, the expression "excluding cadmium (or other harmful heavy metals)" can refer to a situation where the concentration of cadmium (or other additional heavy metals considered harmful) can be less than or equal to about 100 parts per million by weight (ppmw), less than or equal to about 50 ppmw, less than or equal to about 10 ppmw, less than or equal to about 1 ppmw, less than or equal to about 0.1 ppmw, less than or equal to about 0.01 ppmw, or about zero. In an embodiment, cadmium (or other heavy metals) can be substantially absent, or if present, the amount of cadmium (or other heavy metals) can be less than or equal to the detection limit or the impurity level of a given analytical tool (e.g., inductively coupled plasma atomic emission spectrometry).

[0105] Semiconductor nanocrystal particles (e.g., quantum dots) can absorb energy from an excitation source (e.g., a light source providing incident light or electrodes facing each other) and can emit light corresponding to the bandgap energy of the quantum dots. The bandgap energy of the quantum dots can be changed with the size, composition, or a combination thereof of the quantum dots. The semiconductor nanocrystals can be used as luminescent materials in various fields such as display devices, energy devices, or bioluminescent devices.

[0106] Quantum dots having relatively improved photoluminescence properties may include toxic heavy metals such as cadmium (Cd), lead (Pb), mercury (Hg), or a combination thereof. Toxic heavy metals such as cadmium can cause environmental problems, health problems, or a combination thereof and are one of the restricted elements according to the Restriction of Hazardous Substances Directive (RoHS) in many countries. Therefore, the development of environmentally friendly quantum dots having improved luminescence characteristics at desired wavelengths (when applied to luminescent devices such as electro- or photoluminescent devices, for example) may be desired. Quantum dots based on indium phosphide can be applied to practical devices, for example, used therein.

[0107] For application to quantum dot display devices (e.g., including a color conversion layer containing the quantum dots), for example, used therein, and for realizing a display device providing relatively high color reproducibility according to next-generation color standards such as BT2020, for example, quantum dots having a relatively narrow full width at half maximum (FWHM) may be desired. For example, in order for a device to achieve improved color reproducibility such as an improvement according to the BT2020 standard, it may be desired that the luminescent material used therein has a reduced level of FWHM, such as a narrower FWHM. However, compared with a Cd-based core (e.g., a CdSe core), quantum dots based on group III-V compounds including indium and phosphorus have a smaller bandgap and a larger Bohr radius, and the change in terms of FWHM depending on the size of the quantum dots can be significant. Therefore, InP-based quantum dots may not be able to have a reduced level of FWHM, such as a narrower FWHM, while emitting light at a desired wavelength (e.g., greater than about 470 nm, greater than or equal to about 475 nm, greater than or equal to about 480 nm and less than or equal to about 580 nm). In addition, a core including indium and phosphorus can be prone to surface oxidation and quantum dots including it may have an increased FWHM when including a shell (e.g., the shell is coated on the core of the quantum dots), and it may be difficult to achieve a desired level of quantum efficiency and a desired FWHM.

[0108] In the case of cadmium-free quantum dots based on zinc tellurium selenide (zinc tellurium selenide), compared with indium phosphide quantum dots or cadmium-based quantum dots, the wavelength difference caused by the particle distribution can be maintained at a desired low level. In other words, even if the change in the particle size distribution is relatively significant, the change in the emission wavelength may not be obvious, which can be beneficial for the obtained quantum dots to exhibit, for example, a reduced level of FWHM, such as a narrower FWHM.

[0109] However, a quantum dot structure including a ZnTeSe-based core and an inorganic shell coated thereon may not exhibit desired dispersion properties (e.g., organic solvent dispersibility) and may not show, for example, desired luminescence properties.

[0110] Without being bound by any theory, it is considered that if the band gap offset between the core and the shell in a ZnSe core including tellurium and a zinc chalcogenide shell is not sufficiently large, even a physically well-formed shell layer may not result in a sufficiently and desirably high quantum yield. The inventors have surprisingly found that providing a ZnSe-based shell on a core including a relatively large amount of tellurium can cause a significant red shift in the emission wavelength of the core, which can make it more difficult to design quantum dots to emit light of a desired wavelength.

[0111] In an embodiment, by introducing magnesium into zinc tellurium selenide-based quantum dots, the quantum dots can exhibit improved luminescence properties while emitting light of a desired wavelength. Without wishing to be bound by any theory, as will be described in more detail herein, the introduction of the quantum dots of the embodiment can enable control of the increase in the conduction band offset between the core and the shell or band gap engineering. Furthermore, the inventors have surprisingly found that adding magnesium to a zinc tellurium selenide-based core, such as ZnTe where x is from about 0.1 to about 1, or from about 0.6 to about 0.67 x Se 1-xA core providing a zinc selenide-based shell including magnesium can reduce or suppress the red-shift phenomenon of the emission wavelength of the quantum dots to a desired extent. Without wishing to be bound by any theory, the introduction of magnesium can increase the band offset between the core and the shell while minimizing the lattice strain therebetween, thereby generally enhancing the electron confinement effect in the quantum dots while reducing the chance of defects appearing on the surface of the quantum dots. Thus, the quantum dots of embodiments including zinc tellurium selenide can exhibit improvements in both their optical properties and stability. In addition, the inventors have surprisingly found that introducing magnesium into the quantum dots of embodiments can suppress the red-shift of the wavelength that would otherwise occur during shell formation, which can make it possible for the final quantum dots to emit light in the green light wavelength region (e.g., a photoluminescence (PL) peak at about 500 nm - about 550 nm or about 525 nm - about 540 nm, or at about 530 nm) even when they have a relatively thick shell having a thickness greater than or equal to about 1 monolayer (ML). In summary, the quantum dots of embodiments can emit light of a desired wavelength (e.g., green light) with enhanced optical properties without including toxic heavy metals such as cadmium, lead, mercury, or combinations thereof.

[0112] In an embodiment, a quantum dot (hereinafter referred to as "quantum dot") includes zinc, selenium, and tellurium. The quantum dot has a core-shell structure. The core-shell structure includes a core material including a first semiconductor nanocrystal; and a semiconductor nanocrystal shell disposed on the core (or its surface) and including a zinc chalcogenide. The quantum dot may further include magnesium.

[0113] The quantum dot (or its core) may include a predetermined amount of tellurium. In an embodiment, the first semiconductor nanocrystal or the core may include a first zinc chalcogenide including zinc, selenium, and tellurium. The amounts of the components included in the quantum dots as described herein can be determined by suitable analytical tools (e.g., inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray photoelectron spectroscopy (XPS), ion chromatography, transmission electron microscopy energy-dispersive X-ray spectroscopy (TEM-EDS), etc.).

[0114] The core may include crystals such as nanocrystals of a first zinc chalcogenide (e.g., a zinc compound including selenium and tellurium in alloy form or doped form). In the core or in the quantum dot, the amount of tellurium may be greater than the amount of selenium. The semiconductor nanocrystal shell may include a second zinc chalcogenide different from the core or the first zinc chalcogenide (or having a different composition from the core or the first zinc chalcogenide). The second zinc chalcogenide may include zinc; and selenium, sulfur, tellurium, or a combination thereof.

[0115] In the quantum dots of an embodiment, the first semiconductor nanocrystal included in the core may include ZnTex Se 1-x (where x is greater than 0.1, greater than or equal to about 0.2, greater than or equal to about 0.3, greater than or equal to about 0.4, greater than or equal to about 0.5, greater than or equal to about 0.51, greater than or equal to about 0.52, greater than or equal to about 0.53, greater than or equal to about 0.54, greater than or equal to about 0.55, greater than or equal to about 0.56, greater than or equal to about 0.57, greater than or equal to about 0.58, greater than or equal to about 0.59, greater than or equal to about 0.6, greater than or equal to about 0.61, greater than or equal to about 0.62, greater than or equal to about 0.63, greater than or equal to about 0.64, greater than or equal to about 0.65, greater than or equal to about 0.66, greater than or equal to about 0.67, greater than or equal to about 0.68, greater than or equal to about 0.69, greater than or equal to about 0.70, greater than or equal to about 0.71, greater than or equal to about 0.72, greater than or equal to about 0.73, greater than or equal to about 0.74, greater than or equal to about 0.75, or greater than or equal to about 0.8 and less than or equal to about 0.9, less than or equal to about 0.89, less than or equal to about 0.88, less than or equal to about 0.87, less than or equal to about 0.86, less than or equal to about 0.85, less than or equal to about 0.84, less than or equal to about 0.83, less than or equal to about 0.82, less than or equal to about 0.8, less than or equal to about 0.75, less than or equal to about 0.7, less than or equal to about 0.65, less than or equal to about 0.6, less than or equal to about 0.5, less than or equal to about 0.4, less than or equal to about 0.3, or less than or equal to about 0.2).

[0116] In the quantum dots of the embodiments, the molar ratio of tellurium to selenium (Te:Se) can be greater than or equal to about 0.1:1, greater than or equal to about 0.15:1, greater than or equal to about 0.2:1, greater than or equal to about 0.25:1, greater than or equal to about 0.3:1, greater than or equal to about 0.35:1, greater than or equal to about 0.4:1, greater than or equal to about 0.45:1, greater than or equal to about 0.5:1, greater than or equal to about 0.55:1, greater than or equal to about 0.6:1, greater than or equal to about 0.65:1, greater than or equal to about 0.7:1, greater than or equal to about 0.75:1, greater than or equal to about 0.8:1, greater than or equal to about 0.85:1, greater than or equal to about 0.9:1, greater than or equal to about 0.93:1, greater than or equal to about 0.95:1, greater than or equal to about 1:1, greater than or equal to about 1.1:1, greater than or equal to about 1.2:1, greater than or equal to about 1.3:1, greater than or equal to about 1.4:1, greater than or equal to about 1.5:1, greater than or equal to about 1.6:1, greater than or equal to about 1.7:1, greater than or equal to about 1.8:1, greater than or equal to about 1.9:1, greater than or equal to about 2:1, greater than or equal to about 2.1:1, greater than or equal to about 2.2:1, greater than or equal to about 2.3:1, greater than or equal to about 2.4:1, greater than or equal to about 2.5:1, greater than or equal to about 2.6:1, greater than or equal to about 2.7:1, greater than or equal to about 2.8:1, greater than or equal to about 2.9:1, or greater than or equal to about 3:1.

[0117] In the quantum dots of the embodiments, the molar ratio of tellurium to selenium (Te:Se) can be less than or equal to about 4:1, less than or equal to about 3.9:1, less than or equal to about 3.8:1, less than or equal to about 3.7:1, less than or equal to about 3.6:1, less than or equal to about 3.5:1, less than or equal to about 3.4:1, less than or equal to about 3.3:1, less than or equal to about 3.2:1, less than or equal to about 3.1:1, less than or equal to about 3:1, less than or equal to about 2.9:1, less than or equal to about 2.8:1, less than or equal to about 2.7:1, less than or equal to about 2.6:1, less than or equal to about 2.5:1, less than or equal to about 2.4:1, less than or equal to about 2.3:1, less than or equal to about 2.2:1, less than or equal to about 2.1:1, less than or equal to about 2.0:1, less than or equal to about 1.9:1, less than or equal to about 1.8:1, less than or equal to about 1.7:1, less than or equal to about 1.6:1, less than or equal to about 1.5:1, less than or equal to about 1.4:1, less than or equal to about 1.3:1, less than or equal to about 1.2:1, less than or equal to about 1.1:1, less than or equal to about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, or less than or equal to about 0.6:1.

[0118] In the quantum dots of the embodiments or in the core (or the first semiconductor nanocrystal), the molar ratio of selenium to tellurium (Se:Te) can be less than or equal to about 7:1, less than or equal to about 6.5:1, less than or equal to about 6:1, less than or equal to about 5.5:1, less than or equal to about 5:1, less than or equal to about 4.5:1, less than or equal to about 4:1, less than or equal to about 3.5:1, less than or equal to about 3:1, less than or equal to about 2.5:1, less than or equal to about 2:1, less than or equal to about 1.5:1, less than or equal to about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, less than or equal to about 0.6:1, less than or equal to about 0.5:1, or less than or equal to about 0.45:1.

[0119] In the quantum dots of the embodiments or in the core (or the first semiconductor nanocrystal), the molar ratio of selenium to tellurium (Se:Te) can be greater than or equal to about 0.1:1, greater than or equal to about 0.15:1, greater than or equal to about 0.2:1, greater than or equal to about 0.25:1, greater than or equal to about 0.3:1, greater than or equal to about 0.35:1, greater than or equal to about 0.4:1, greater than or equal to about 0.5:1, greater than or equal to about 0.55:1, greater than or equal to about 0.6:1, greater than or equal to about 0.65:1, greater than or equal to about 0.7:1, greater than or equal to about 0.75:1, greater than or equal to about 0.8:1, greater than or equal to about 0.85:1, greater than or equal to about 0.9:1, greater than or equal to about 0.95:1, greater than or equal to about 1:1, greater than or equal to about 1.1:1, greater than or equal to about 1.2:1, greater than or equal to about 1.3:1, greater than or equal to about 1.4:1, greater than or equal to about 1.5:1, greater than or equal to about 1.6:1, greater than or equal to about 1.7:1, greater than or equal to about 1.8:1, greater than or equal to about 1.9:1, greater than or equal to about 2:1, greater than or equal to about 2.5:1, greater than or equal to about 3:1, greater than or equal to about 3.5:1, greater than or equal to about 4:1, greater than or equal to about 4.5:1, greater than or equal to about 5:1, or greater than or equal to about 5.5:1.

[0120] In the quantum dots of the embodiments, the molar ratio of tellurium to zinc (Te:Zn) can be greater than 0.03:1, greater than or equal to about 0.1:1, greater than or equal to about 0.15:1, greater than or equal to about 0.2:1, greater than or equal to about 0.25:1, greater than or equal to about 0.3:1, greater than or equal to about 0.35:1, greater than or equal to about 0.4:1, or greater than or equal to about 0.43:1. In the quantum dots of the embodiments, the molar ratio of tellurium to zinc (Te:Zn) (which can be measured, for example, by inductively coupled plasma-atomic emission spectrometry (ICP-AES)) can be less than about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, less than or equal to about 0.6:1, less than or equal to about 0.5:1, less than or equal to about 0.45:1, less than or equal to about 0.4:1, less than or equal to about 0.35:1, less than or equal to about 0.3:1, less than or equal to about 0.25:1, less than or equal to about 0.2:1, less than or equal to about 0.15:1, or less than or equal to about 0.1:1.

[0121] In the quantum dots of the embodiments, the molar ratio of zinc to tellurium (Zn:Te) can be greater than or equal to about 0.5:1, greater than or equal to about 1:1, greater than or equal to about 1.5:1, greater than or equal to about 2:1, greater than or equal to about 2.1:1, greater than or equal to about 2.15:1, greater than or equal to about 2.2:1, greater than or equal to about 3:1, greater than or equal to about 3.5:1, greater than or equal to about 4:1, greater than or equal to about 4.5:1, greater than or equal to about 5:1, or greater than or equal to about 5.5:1. In the quantum dots of the embodiments, the molar ratio of zinc to tellurium (Zn:Te) can be less than or equal to about 40:1, less than or equal to about 35:1, less than or equal to about 30:1, less than or equal to about 25:1, less than or equal to about 20:1, less than or equal to about 15:1, less than or equal to about 10:1, less than or equal to about 9:1, less than or equal to about 8.5:1, less than or equal to about 8:1, less than or equal to about 7.5:1, less than or equal to about 7:1, less than or equal to about 6.5:1, less than or equal to about 6:1, less than or equal to about 5.5:1, less than or equal to about 4.5:1, less than or equal to about 4:1, less than or equal to about 3.5:1, less than or equal to about 3:1, less than or equal to about 2.5:1, less than or equal to about 2.4:1, less than or equal to about 2.3:1, or less than or equal to about 2.25:1.

[0122] The quantum dots of the embodiments may further include sulfur, and if present, the molar ratio of sulfur to zinc may be greater than or equal to about 0.005:1, greater than or equal to about 0.01:1, greater than or equal to about 0.015:1, greater than or equal to about 0.02:1, greater than or equal to about 0.025:1, greater than or equal to about 0.03:1, greater than or equal to about 0.035:1, greater than or equal to about 0.04:1, greater than or equal to about 0.045:1, greater than or equal to about 0.05:1, greater than or equal to about 0.06:1, greater than or equal to about 0.07:1, greater than or equal to about 0.08:1, greater than or equal to about 0.09:1, greater than or equal to about 0.1:1, greater than or equal to about 0.15:1, greater than or equal to about 0.2:1, greater than or equal to about 0.25:1, greater than or equal to about 0.3:1, or greater than or equal to about 0.35 and less than or equal to about 0.95:1, less than or equal to about 0.9:1, less than or equal to about 0.85:1, less than or equal to about 0.8:1, less than or equal to about 0.75:1, less than or equal to about 0.7:1, less than or equal to about 0.65:1, less than or equal to about 0.6:1, less than or equal to about 0.5:1, less than or equal to about 0.4:1, or less than or equal to about 0.3:1.

[0123] In the core-shell quantum dots of the embodiments, the molar ratio of sulfur to tellurium (S:Te) may be greater than or equal to about 0.1:1, greater than or equal to about 0.2:1, greater than or equal to about 0.3:1, greater than or equal to about 0.4:1, greater than or equal to about 0.5:1, greater than or equal to about 1:1, greater than or equal to about 3:1, greater than or equal to about 5:1, greater than or equal to about 6:1, greater than or equal to about 7:1, greater than or equal to about 9:1, or greater than or equal to about 10:1 and less than or equal to about 20:1, less than or equal to about 18:1, less than or equal to about 16:1, less than or equal to about 14:1, less than or equal to about 12:1, less than or equal to about 10:1, less than or equal to about 6:1, less than or equal to about 5:1, less than or equal to about 4.5:1, less than or equal to about 4:1, less than or equal to about 3.5:1, less than or equal to about 3:1, less than or equal to about 2.5:1, less than or equal to about 2:1, less than or equal to about 1.5:1, less than or equal to about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, less than or equal to about 0.6:1, less than or equal to about 0.5:1, or less than or equal to about 0.4:1.

[0124] In the quantum dots of the embodiments, the molar ratio of the sum of sulfur and selenium to tellurium ((Se+S):Te) can be greater than or equal to about 2:1, greater than or equal to about 3:1, greater than or equal to about 4:1, greater than or equal to about 5:1, greater than or equal to about 6:1, greater than or equal to about 7:1, greater than or equal to about 8:1, greater than or equal to about 9:1, or greater than or equal to about 10:1. In the quantum dots of the embodiments, the molar ratio of the sum of sulfur and selenium to tellurium ((Se+S):Te) can be less than or equal to about 16:1, less than or equal to about 15:1, less than or equal to about 14:1, less than or equal to about 13:1, less than or equal to about 12:1, less than or equal to about 11:1, less than or equal to about 10:1, less than or equal to about 9:1, less than or equal to about 8:1, less than or equal to about 7:1, less than or equal to about 6:1, less than or equal to about 5:1, less than or equal to about 4:1, less than or equal to about 3:1, or less than or equal to about 2:1.

[0125] In an embodiment, the quantum dots may not include manganese, copper, or a combination thereof, for example, not include manganese, copper, or a combination thereof in the core or in the shell. In an embodiment, the quantum dots may not include III-V compounds. The III-V compounds may include indium phosphide, zinc indium phosphide, gallium phosphide, or a combination thereof.

[0126] In X-ray diffraction analysis, the core-shell quantum dots may not exhibit peaks attributable to the III-V compounds (e.g., indium phosphide or gallium phosphide). The quantum dots may not include indium, gallium, or a combination thereof.

[0127] In an embodiment, the quantum dots (e.g., in the core, at the interface between the core and the semiconductor nanocrystal shell, in the shell, or a combination thereof) further include magnesium. In an embodiment, magnesium may be introduced into the quantum dots during the formation of the core described herein, during the formation of the shell, or during the formation of both the core and the shell.

[0128] In the quantum dots of the embodiments, the amount of magnesium per 1 mole of tellurium can be greater than or equal to about 0.001 mole, greater than or equal to about 0.005 mole, greater than or equal to about 0.01 mole, greater than or equal to about 0.05 mole, greater than or equal to about 0.1 mole, greater than or equal to about 0.15 mole, greater than or equal to about 0.2 mole, greater than or equal to about 0.25 mole, greater than or equal to about 0.3 mole, greater than or equal to about 0.35 mole, greater than or equal to about 0.4 mole, greater than or equal to about 0.45 mole, greater than or equal to about 0.5 mole, greater than or equal to about 0.55 mole, greater than or equal to about 0.6 mole, greater than or equal to about 0.65 mole, greater than or equal to about 0.7 mole, greater than or equal to about 0.75 mole, greater than or equal to about 0.8 mole, greater than or equal to about 0.85 mole, greater than or equal to about 0.9 mole, greater than or equal to about 0.95 mole, greater than or equal to about 1 mole, greater than or equal to about 1.1 moles, greater than or equal to about 1.2 moles, greater than or equal to about 1.3 moles, greater than or equal to about 1.4 moles, greater than or equal to about 1.5 moles, greater than or equal to about 1.6 moles, greater than or equal to about 1.7 moles, greater than or equal to about 1.8 moles, greater than or equal to about 1.9 moles, greater than or equal to about 2 moles, greater than or equal to about 2.1 moles, greater than or equal to about 2.2 moles, greater than or equal to about 2.3 moles, greater than or equal to about 2.4 moles, greater than or equal to about 2.5 moles, greater than or equal to about 2.6 moles, greater than or equal to about 2.7 moles, greater than or equal to about 2.8 moles, greater than or equal to about 2.9 moles, greater than or equal to about 3.1 moles, greater than or equal to about 3.2 moles, greater than or equal to about 3.3 moles, greater than or equal to about 3.4 moles, greater than or equal to about 3.5 moles, greater than or equal to about 3.6 moles, greater than or equal to about 3.7 moles, greater than or equal to about 3.8 moles, greater than or equal to about 3.9 moles, or greater than or equal to about 4 moles.

[0129] In the quantum dots of the embodiments, the amount of magnesium per 1 mole of tellurium can be less than or equal to about 10 moles, less than or equal to about 9 moles, less than or equal to about 8 moles, less than or equal to about 7 moles, less than or equal to about 6.5 moles, less than or equal to about 6 moles, less than or equal to about 5.5 moles, less than or equal to about 5 moles, less than or equal to about 4.5 moles, less than or equal to about 4 moles, less than or equal to about 3.9 moles, less than or equal to about 3.8 moles, less than or equal to about 3.7 moles, less than or equal to about 3.6 moles, less than or equal to about 3.5 moles, less than or equal to about 3 moles, less than or equal to about 2.5 moles, or less than or equal to about 2 moles.

[0130] In the quantum dots of the embodiments, the atomic ratio of magnesium to zinc can be, for example, as determined by X-ray photoelectron spectroscopy, greater than or equal to about 0.01:1, greater than or equal to about 0.05:1, greater than or equal to about 0.1:1, greater than or equal to about 0.15:1, or greater than or equal to about 0.2:1. In the quantum dots of the embodiments, the atomic ratio of magnesium to zinc can be, for example, as determined by X-ray photoelectron spectroscopy, less than or equal to about 1:1, less than or equal to about 0.7:1, less than or equal to about 0.5:1, less than or equal to about 0.4:1, or less than or equal to about 0.3:1.

[0131] The quantum dots of the embodiments can further include an alkali metal, aluminum, or a combination thereof as an additional metal. The alkali metal can include lithium, sodium, potassium, cesium, rubidium, or a combination thereof. The alkali metal can include lithium. In the quantum dots, for every 1 mole of tellurium, the amount of the additional metal (lithium, sodium, potassium, cesium, rubidium, aluminum, or a combination thereof) can be greater than or equal to about 0.005 moles, greater than or equal to about 0.01 moles, greater than or equal to about 0.05 moles, greater than or equal to about 0.1 moles, greater than or equal to about 0.2 moles, greater than or equal to about 0.3 moles, greater than or equal to about 0.4 moles, greater than or equal to about 0.5 moles, greater than or equal to about 0.6 moles, greater than or equal to about 0.7 moles, greater than or equal to about 0.8 moles, greater than or equal to about 0.9 moles, or greater than or equal to about 1 mole. In the quantum dots, for every 1 mole of tellurium, the amount of the additional metal can be less than or equal to about 10 moles, less than or equal to about 9.5 moles, less than or equal to about 9 moles, less than or equal to about 8.5 moles, less than or equal to about 8 moles, less than or equal to about 7.5 moles, less than or equal to about 7 moles, less than or equal to about 6.5 moles, less than or equal to about 6 moles, less than or equal to about 5.5 moles, less than or equal to about 5 moles, less than or equal to about 4.5 moles, less than or equal to about 4 moles, less than or equal to about 3.5 moles, less than or equal to about 3 moles, less than or equal to about 2.5 moles, less than or equal to about 2 moles, less than or equal to about 1.5 moles, less than or equal to about 1 mole, less than or equal to about 0.9 moles, less than or equal to about 0.85 moles, less than or equal to about 0.8 moles, less than or equal to about 0.75 moles, less than or equal to about 0.7 moles, less than or equal to about 0.65 moles, less than or equal to about 0.6 moles, or less than or equal to about 0.55 moles.

[0132] The shell may be a multi-layer shell including multiple layers. Among the multiple layers of the shell, adjacent layers may have semiconductor nanocrystal materials with different compositions. The multi-layer shell may include a first shell layer disposed (e.g., directly disposed) on the core and a second shell layer disposed on (e.g., directly disposed on) the first shell layer or above the first shell layer. The first shell layer may include a second semiconductor nanocrystal. The second shell layer may include a third semiconductor nanocrystal having a composition different from that of the second semiconductor nanocrystal. The second shell layer may be the outermost layer of the quantum dot.

[0133] The semiconductor nanocrystal shell may further include magnesium. The semiconductor nanocrystal shell may include zinc magnesium selenium sulfide or Zn 1-y (Mg) y Se z S 1-z (where 0 < y < 1, 0 ≤ z ≤ 1). y or z may be 0.1 - 0.9, 0.2 - 0.8, 0.3 - 0.7, or 0.4 - 0.6.

[0134] Referring to Figure 1 , the quantum dots of the embodiments may include a shell that includes zinc selenide containing magnesium (e.g., magnesium-rich zinc selenide). In an embodiment, the magnesium-rich zinc selenide layer may be directly disposed on the ZnTe x Se 1-x core. The quantum dots may include a semiconductor nanocrystal shell (e.g., a first shell layer) containing zinc selenide and the zinc selenide may include magnesium at different concentrations. The concentration of magnesium may vary, for example, radially in the semiconductor nanocrystal shell (or in the first shell layer). Without wishing to be bound by any theory, zinc selenide containing magnesium in the semiconductor nanocrystal shell may have lattice parameters similar to those of zinc tellurium selenide (e.g., including a relatively increased amount of tellurium or capable of emitting green light), and may provide a desired band energy offset in the band energy alignment. Therefore, without wishing to be bound by any theory, in an embodiment, it is considered that a shell including zinc chalcogenide and magnesium may enable the final quantum dots to exhibit, for example, an improved level of electron confinement, which may mitigate the otherwise occurring red shift phenomenon, for example, when a relatively thick shell is provided to the ZnTeSe core. In an embodiment, the second shell layer may further include magnesium, which may further reduce the lattice parameter difference between the shell layers, thereby reducing the strain between the interface surfaces of the heteroshell materials and also reducing the chance of defect formation. Therefore, the quantum dots of the embodiments may exhibit an improved quantum yield, enhanced stability, or a combination thereof.

[0135] The first shell or the second semiconductor nanocrystal may include zinc, selenium, and optionally sulfur. In an embodiment, the first shell or the second semiconductor nanocrystal may not include sulfur. The second shell or the third semiconductor nanocrystal may include zinc and sulfur. In an embodiment, the second shell or the third semiconductor nanocrystal may not include selenium. In an embodiment, the first shell may include ZnSe, ZnSeS, ZnS, or a combination thereof. The second shell may be composed of ZnS.

[0136] At least one of the second semiconductor nanocrystal and the third semiconductor nanocrystal (e.g., the second semiconductor nanocrystal, the third semiconductor nanocrystal, or a combination thereof) may include magnesium. At least one of the second semiconductor nanocrystal and the third semiconductor nanocrystal may include ZnMgSe, ZnMgS, ZnMgSeS, or a combination thereof.

[0137] In a multi-layer shell, the thickness of each layer can be appropriately selected. The thickness of the shell (e.g., the first shell, the second shell, or a combination thereof) can be independently greater than or equal to about 1 monolayer (ML), such as greater than or equal to about 2 ML, greater than or equal to about 3 ML, greater than or equal to about 4 ML, greater than or equal to about 5 ML and less than or equal to about 10 ML, such as less than or equal to about 9 ML, less than or equal to about 8 ML, less than or equal to about 7 ML, less than or equal to about 6 ML, or less than or equal to about 5 ML. The thickness of each layer in the multi-layer shell can be selected considering the desired composition of the final quantum dot.

[0138] The thickness of the semiconductor nanocrystal shell can be greater than or equal to about 1 monolayer (ML), such as greater than or equal to about 2 ML, greater than or equal to about 3 ML, greater than or equal to about 4 ML, greater than or equal to about 5 ML and less than or equal to about 20 ML, such as less than or equal to about 19 ML, less than or equal to about 18 ML, less than or equal to about 17 ML, less than or equal to about 16 ML, less than or equal to about 15 ML, less than or equal to about 14 ML, less than or equal to about 13 ML, less than or equal to about 12 ML, less than or equal to about 11 ML, less than or equal to about 10 ML, such as less than or equal to about 9 ML, less than or equal to about 8 ML, less than or equal to about 7 ML, less than or equal to about 6 ML, less than or equal to about 5 ML, or less than or equal to about 4 ML.

[0139] In an embodiment, each of the shell or the shell layers in the multi-layer shell may comprise a gradient alloy having a composition that varies in the radial direction, e.g., from the core of the quantum dot towards the outermost surface. In an embodiment, the amount of sulfur in the semiconductor nanocrystal shell may increase towards the surface of the quantum dot. For example, in the shell, the amount of sulfur may increase in a direction away from the core, e.g., radially from the core of the quantum dot towards the outermost surface.

[0140] In the quantum dots of an embodiment, the size (or average size) of the core may be greater than or equal to about 1 nm, e.g., greater than or equal to about 2 nm, greater than or equal to about 2.5 nm, greater than or equal to about 3 nm, greater than or equal to about 3.5 nm, greater than or equal to about 4 nm, or greater than or equal to about 4.5 nm. The size (or average size) of the core may be less than or equal to about 7 nm, less than or equal to about 6 nm, less than or equal to about 5 nm, less than or equal to about 4 nm, less than or equal to about 3 nm, or less than or equal to about 2 nm.

[0141] The quantum dots (or groups thereof) can have a particle (average) size as follows: greater than or equal to about 2 nm, greater than or equal to about 3 nm, greater than or equal to about 4 nm, greater than or equal to about 5 nm, greater than or equal to about 6 nm, greater than or equal to about 7 nm, greater than or equal to about 7.5 nm, greater than or equal to about 8 nm, greater than or equal to about 8.5 nm, greater than or equal to about 9 nm, greater than or equal to about 9.5 nm, or greater than or equal to about 10 nm. The size (or average size) of the quantum dots (or groups thereof) can be less than or equal to about 50 nm, such as less than or equal to about 45 nm, less than or equal to about 40 nm, less than or equal to about 35 nm, less than or equal to about 30 nm, less than or equal to about 25 nm, less than or equal to about 24 nm, less than or equal to about 23 nm, less than or equal to about 22 nm, less than or equal to about 21 nm, less than or equal to about 20 nm, less than or equal to about 19 nm, less than or equal to about 18 nm, less than or equal to about 17 nm, less than or equal to about 16 nm, less than or equal to about 15 nm, less than or equal to about 14 nm, less than or equal to about 13 nm, less than or equal to about 12 nm, less than or equal to about 11 nm, less than or equal to about 10 nm, less than or equal to about 9 nm, less than or equal to about 8 nm, less than or equal to about 7 nm, less than or equal to about 6 nm, less than or equal to about 5.5 nm, or less than or equal to about 5 nm. In an embodiment, the size of the quantum dots can refer to the diameter or equivalent diameter (e.g., under the assumption of circularity) obtained from a two-dimensional image analyzed by electron microscopy. In an embodiment, "size" can refer to the size of a single quantum dot or the (e.g., mean or median) average of multiple quantum dots or groups of multiple quantum dots. The size of the quantum dots can be determined by the results (e.g., images) analyzed by using (transmission) electron microscopy and any suitable image analysis computer program (e.g., Image J). As used herein, average can refer to mean average or median average.

[0142] The quantum dots can form a group of quantum dots. The above group of quantum dots can have a size standard deviation that is less than or equal to about 18%, less than or equal to about 17%, less than or equal to about 16%, less than or equal to about 15%, less than or equal to about 14%, less than or equal to about 13%, less than or equal to about 12%, or less than or equal to about 11% of the average size of the quantum dots. The above group of quantum dots can have a size standard deviation that is greater than or equal to about 8%, greater than or equal to about 9%, or greater than or equal to about 10% of the average size of the quantum dots.

[0143] In an embodiment, the ultraviolet-visible (UV-Vis) absorption spectrum of the (core or core-shell) quantum dots can include valleys that can be relatively clearly noted.

[0144] In the UV-vis absorption spectrum, the quantum dots of the embodiments may have a valley adjacent to the first absorption peak or within a wavelength range greater than or equal to about 450 nm (or greater than or equal to about 440 nm, greater than or equal to about 430 nm, or greater than or equal to about 420 nm, or greater than or equal to about 410 nm, or greater than or equal to about 400 nm) up to the wavelength of the first absorption peak.

[0145] The quantum dots of the embodiments may exhibit a valley depth of at least a predetermined value. In the UV-vis absorption spectrum of the quantum dots of the embodiments, the valley or the lowest point thereof may occur at a wavelength lower, e.g., shorter, than the wavelength of the first absorption peak. In the UV-vis absorption spectrum of the quantum dots, the intensity of the first absorption peak may be greater than the intensity at the lowest point of the valley adjacent thereto.

[0146] Without being bound by any theory, it is believed that in the ultraviolet-visible (UV-Vis) absorption spectrum, the presence of the valley or the valley depth may represent the size uniformity of the quantum dots (or cores) or the shell coating (layer) uniformity of the quantum dots. An obvious valley depth of the core-shell quantum dots or core quantum dots may indicate that the (core-shell) quantum dots may have an improved size distribution, improved coating (layer) quality, or a combination thereof, and may provide a narrower FWHM and higher luminescence efficiency.

[0147] In the quantum dots of the embodiments, the valley depth (VD) defined herein may be greater than or equal to about 0.01, e.g., greater than or equal to about 0.02, greater than or equal to about 0.03, greater than or equal to about 0.04, greater than or equal to about 0.05, greater than or equal to about 0.06, greater than or equal to about 0.07, greater than or equal to about 0.08, greater than or equal to about 0.09, or greater than or equal to about 0.1:

[0148] (Abs 第一 -Abs 谷 ) / Abs 第一 =VD

[0149] where Abs 第一 is the absorption intensity at the wavelength of the first absorption peak and Abs 谷 is the absorption intensity at the lowest point of the valley.

[0150] The first absorption peak of the quantum dots may be present in a wavelength range of: greater than or equal to about 410 nm, e.g., greater than or equal to about 420 nm, greater than or equal to about 430 nm, greater than or equal to about 440 nm, greater than or equal to about 450 nm, greater than or equal to about 460 nm, greater than or equal to about 465 nm, greater than or equal to about 470 nm, greater than or equal to about 475 nm, or greater than or equal to about 480 nm.

[0151] The lowest point of the valley of the quantum dots can exist within the following wavelength ranges: greater than or equal to about 410 nm, such as greater than or equal to about 420 nm, greater than or equal to about 430 nm, greater than or equal to about 440 nm, greater than or equal to about 450 nm, greater than or equal to about 460 nm, greater than or equal to about 465 nm, greater than or equal to about 470 nm, greater than or equal to about 475 nm, or greater than or equal to about 480 nm.

[0152] The first absorption peak of the quantum dots can exist within the following wavelength ranges: less than or equal to about 530 nm, less than or equal to about 525 nm, less than or equal to about 520 nm, less than or equal to about 515 nm, less than or equal to about 510 nm, less than or equal to about 505 nm, less than or equal to about 500 nm, less than or equal to about 495 nm, less than or equal to about 490 nm, less than or equal to about 485 nm, less than or equal to about 480 nm, less than or equal to about 475 nm, less than or equal to about 465 nm, less than or equal to about 460 nm, less than or equal to about 455 nm, less than or equal to about 450 nm, or less than or equal to about 445 nm.

[0153] The lowest point of the valley of the quantum dots can exist within the following wavelength ranges: less than or equal to about 530 nm, less than or equal to about 525 nm, less than or equal to about 520 nm, less than or equal to about 515 nm, less than or equal to about 510 nm, less than or equal to about 505 nm, less than or equal to about 500 nm, less than or equal to about 495 nm, less than or equal to about 490 nm, less than or equal to about 485 nm, less than or equal to about 480 nm, less than or equal to about 475 nm, less than or equal to about 465 nm, less than or equal to about 460 nm, less than or equal to about 455 nm, less than or equal to about 450 nm, or less than or equal to about 445 nm.

[0154] The quantum dots of the embodiments can emit green light. In an embodiment, the quantum dots can have the following maximum (photoluminescence) emission peak wavelengths: greater than or equal to about 480 nm, greater than or equal to about 485 nm, greater than or equal to about 490 nm, greater than or equal to about 495 nm, greater than or equal to about 500 nm, greater than or equal to about 505 nm, greater than or equal to about 510 nm, greater than or equal to about 515 nm, or greater than or equal to about 520 nm. The quantum dots of the embodiments can have the following maximum emission (e.g., photoluminescence) peak wavelengths: less than or equal to about 580 nm, less than or equal to about 570 nm, less than or equal to about 560 nm, less than or equal to about 550 nm, less than or equal to about 540 nm, or less than or equal to about 535 nm. The quantum dots or the green light can have a maximum emission peak wavelength in the above ranges (e.g., about 500 nm - about 560 nm (e.g., about 515 nm - about 535 nm)).

[0155] Compared with quantum dots based on zinc, selenium, and tellurium, the quantum dots of the embodiments can exhibit a significantly improved (photoluminescence) quantum efficiency (or quantum yield) (e.g., greater than or equal to about 60%). The quantum efficiency can be determined by a comparative method using a well-characterized standard sample with a known quantum yield value or measured absolutely using an integrating sphere. Measuring devices for quantum efficiency are commercially available from multiple manufacturers (e.g., Hitachi Co., Ltd., Hammamatsu Co., Ltd.).

[0156] In an embodiment, the quantum dots can exhibit a quantum efficiency greater than or equal to about 60%, greater than or equal to about 65%, greater than or equal to about 70%, greater than or equal to about 75%, or greater than or equal to about 80%. In an embodiment, the quantum efficiency (or quantum yield) of the quantum dots can be less than or equal to about 100%.

[0157] In an embodiment, (in photoluminescence spectrometry analysis) the quantum dots may exhibit a full width at half maximum (FWHM) as follows: less than or equal to about 45 nm, less than or equal to about 40 nm, less than or equal to about 39 nm, less than or equal to about 38 nm, less than or equal to about 37 nm, less than or equal to about 36 nm, less than or equal to about 35 nm, less than or equal to about 34 nm, less than or equal to about 33 nm, less than or equal to about 32 nm, less than or equal to about 31 nm, less than or equal to about 30 nm, less than or equal to about 29 nm, less than or equal to about 28 nm, less than or equal to about 27 nm, less than or equal to about 26 nm, or less than or equal to about 25 nm. In an embodiment, (in photoluminescence spectrometry analysis) the quantum dots may exhibit a full width at half maximum (FWHM) greater than or equal to about 1 nm. The FWHM of the quantum dots may be greater than or equal to about 1 nm, greater than or equal to about 5 nm, greater than or equal to about 10 nm, or greater than or equal to about 15 nm.

[0158] In an embodiment, the quantum dots may include, for example on their surface, organic ligands. The organic ligands may include RCOOH, RNH2, R2NH, R3N, RSH, RH2PO, R2HPO, R3PO, RH2P, R2HP, R3P, ROH, RCOOR', RPO(OH)2, RHPOOH, R2POOH, polymeric organic ligands, or combinations thereof, where R and R' are the same or different and independently are substituted or unsubstituted C1-C40 (e.g., C3-C30 or C6-C24) aliphatic hydrocarbon groups (e.g., alkyl, alkenyl, or alkynyl) or substituted or unsubstituted C6-C40 aromatic hydrocarbon groups, or combinations thereof. Two or more different organic ligands may be used.

[0159] The organic ligand can coordinate to, for example, bind to the surface of the quantum dots, helping the nanocrystals to disperse well in the solution. Examples of the organic ligand can include methanethiol, ethanethiol, propanethiol, butanethiol, pentanethiol, hexanethiol, octanethiol, dodecanethiol, hexadecanethiol, octadecanethiol, or benzyl mercaptan; methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, dimethylamine, diethylamine, dipropylamine; formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid, oleic acid, or benzoic acid; phosphines such as substituted or unsubstituted methylphosphine (e.g., trimethylphosphine, methyldiphenylphosphine, etc.), substituted or unsubstituted ethylphosphine (e.g., triethylphosphine, ethyldiphenylphosphine, etc.), substituted or unsubstituted propylphosphine, substituted or unsubstituted butylphosphine, substituted or unsubstituted pentylphosphine, or substituted or unsubstituted octylphosphine (e.g., trioctylphosphine (TOP)); phosphine oxides such as substituted or unsubstituted methylphosphine oxide (e.g., trimethylphosphine oxide, methyldiphenylphosphine oxide, etc.), substituted or unsubstituted ethylphosphine oxide (e.g., triethylphosphine oxide, ethyldiphenylphosphine oxide, etc.), substituted or unsubstituted propylphosphine oxide, substituted or unsubstituted butylphosphine oxide, or substituted or unsubstituted octylphosphine oxide (e.g., trioctylphosphine oxide (TOPO)); diphenylphosphine, diphenylphosphine oxide, triphenylphosphine, or triphenylphosphine oxide; mono- or di(C5-C20 alkyl)phosphinic acid such as mono- or dihexylphosphinic acid, mono- or dioctylphosphinic acid, mono- or di(dodecyl)phosphinic acid, mono- or di(tetradecyl)phosphinic acid, mono- or di(hexadecyl)phosphinic acid, mono- or di(octadecyl)phosphinic acid, or a combination thereof; C5-C20 alkylphosphinic acid; C5-C20 alkylphosphonic acid such as hexylphosphonic acid, octylphosphonic acid, dodecylphosphonic acid, tetradecylphosphonic acid, hexadecylphosphonic acid, octadecylphosphonic acid, or a combination thereof; or a combination thereof, etc., but not limited thereto. Two or more different organic ligand compounds can be used.

[0160] In an embodiment, the organic ligand compound can be a combination of RCOOH and an amine (e.g., RNH2, R2NH, R3N, or a combination thereof).

[0161] In an embodiment, the organic ligand may not include a multifunctional organic compound having a thiol moiety and an amino group, a carboxylic acid group, or a combination thereof. In an embodiment, the organic ligand may not include a glutathione compound. The quantum dots can be insoluble in water.

[0162] When dispersed in water, the quantum dots can exhibit an average particle size of, for example, greater than or equal to about 300 nm, greater than or equal to about 400 nm, greater than or equal to about 500 nm, or greater than or equal to about 900 nm as determined by dynamic light scattering (DLS) analysis. When dispersed in an organic solvent (such as toluene, octane, etc.), the quantum dots can be configured to form an organic solution having an average particle size of less than or equal to about 500 nm, less than or equal to about 400 nm, less than or equal to about 300 nm, less than or equal to about 200 nm, less than or equal to about 100 nm, or less than or equal to about 90 nm as determined by DLS analysis. Examples of the organic solvents are described herein.

[0163] In an embodiment, a method of manufacturing the quantum dots includes:

[0164] Preparing a particle including a core, the core including a first semiconductor nanocrystal comprising zinc, selenium, and tellurium; and

[0165] Reacting a zinc precursor and a chalcogen precursor in a first organic solvent in the presence of the particle including the core and a first organic ligand at a shell formation reaction temperature to form the semiconductor nanocrystal shell on the particle including the core;

[0166] wherein the method further includes adding a magnesium precursor to the reaction system during the preparation of the particle including the core, the formation of the shell, or a combination thereof.

[0167] In an embodiment, the preparation of the core can include preparing a zinc precursor organic solution including the zinc precursor and a second organic ligand in a second organic solvent; and

[0168] While heating the zinc precursor organic solution at a core formation temperature, adding the selenium precursor, the tellurium precursor, a hydride compound, and a third organic ligand different from the second organic ligand thereto simultaneously or sequentially.

[0169] The reaction temperature for the core formation can be greater than or equal to about 250 °C, greater than or equal to about 260 °C, greater than or equal to about 270 °C, greater than or equal to about 280 °C, greater than or equal to about 290 °C, or greater than or equal to about 300 °C. The reaction temperature for the core formation can be less than or equal to about 350 °C, for example, less than or equal to about 340 °C, less than or equal to about 330 °C, less than or equal to about 320 °C, or less than or equal to about 310 °C. The reaction time for the core formation is not particularly limited and can be appropriately selected in consideration of the precursors for the core formation, the reaction temperature, the desired size of the core, etc.

[0170] For example, before the formation of the shell, the synthesized core can be separated from the reaction system, for example, by using a non-solvent. The separation using the non-solvent will be described in detail herein.

[0171] Details of the composition of the quantum dots and the formation of the shell are the same as those described herein.

[0172] In an embodiment, the tellurium precursor used during the core synthesis can include tellurium dispersed in a third organic solvent and the concentration of tellurium in the tellurium precursor can be greater than about 0.1 mole per liter (molarity (M)), for example, greater than or equal to about 0.5 M, greater than or equal to about 1 M, greater than or equal to about 1.5 M, greater than or equal to about 2 M, or greater than or equal to about 2.5 M. The concentration of tellurium can be less than or equal to about 10 M, less than or equal to about 5 M, or less than or equal to about 4 M. In an embodiment, using the tellurium precursor at the above concentrations can contribute to enhancing the reactivity of the tellurium precursor, providing improved quality of the core.

[0173] In an embodiment, when synthesizing the core, before adding to the zinc precursor organic solution, the selenium precursor, the tellurium precursor, the metal hydride compound, and the third organic ligand can be mixed at a temperature of less than about 80 °C, for example, less than or equal to about 75 °C, less than or equal to about 70 °C, less than or equal to about 65 °C, less than or equal to about 60 °C, less than or equal to about 55 °C, less than or equal to about 50 °C, or less than or equal to about 45 °C to form a single stock solution. This temperature can be greater than or equal to about 10 °C, greater than or equal to about 20 °C, or, for example, about room temperature.

[0174] The third organic ligand can include an aliphatic organic amine or a combination thereof.

[0175] The metal hydride compound can include lithium, aluminum, or a combination thereof. The metal hydride compound can include an aluminum hydride compound, a lithium hydride compound, or a combination thereof. The metal hydride compound can include an organometallic hydride compound (e.g., having a hydrocarbon group, for example, at least one hydrocarbon group (e.g., C1-C18 alkyl, C2-C18 alkenyl, or C2-C18 alkynyl), or a C6-C40 aromatic hydrocarbon group, or a combination thereof), an inorganic metal hydride compound, or a combination thereof. The metal hydride compound can include an alkyllithium hydride (e.g., lithium dialkylborohydride, for example, where each alkyl can have 1-10 carbon atoms), a lithium aluminum hydride compound, or a combination thereof.

[0176] The amount of the metal hydride is not particularly limited and can be appropriately selected. Per 1 mole of tellurium, the amount of the metal hydride can be greater than or equal to about 0.01 mole, greater than or equal to about 0.05 mole, greater than or equal to about 0.1 mole, greater than or equal to about 0.5 mole, or greater than or equal to about 1 mole. Per 1 mole of tellurium, the amount of the metal hydride can be less than or equal to about 10 moles, less than or equal to about 5 moles, or less than or equal to about 3 moles.

[0177] During the preparation of the core, the molar ratio of tellurium to selenium (Te:Se) introduced into the reaction system can be greater than about 0.25:1, greater than or equal to about 0.3:1, greater than or equal to about 0.4:1, greater than or equal to about 0.5:1, greater than or equal to about 0.7:1, greater than or equal to about 0.9:1, greater than or equal to about 1:1, greater than or equal to about 1.1:1, greater than or equal to about 1.2:1, greater than or equal to about 1.3:1, greater than or equal to about 1.4:1, greater than or equal to about 1.5:1, greater than or equal to about 1.6:1, greater than or equal to about 1.7:1, greater than or equal to about 1.8:1, greater than or equal to about 1.9:1, greater than or equal to about 2:1, or greater than or equal to about 2.5:1.

[0178] During the preparation of the core, the molar ratio of tellurium to selenium (Te:Se) introduced into the reaction system can be less than or equal to about 10:1, less than or equal to about 9:1, less than or equal to about 8:1, less than or equal to about 7:1, less than or equal to about 6:1, less than or equal to about 5:1, less than or equal to about 4:1, less than or equal to about 3:1, less than or equal to about 2:1, or less than or equal to about 1.5:1.

[0179] During the preparation of the core, the molar ratio of zinc to tellurium can be appropriately selected in consideration of the desired composition, precursors, etc. According to an embodiment, during the preparation of the core, the amount of zinc relative to 1 mole of tellurium can be greater than or equal to about 1 mole, greater than or equal to about 2 moles, greater than or equal to about 3 moles, greater than or equal to about 4 moles, or greater than or equal to about 5 moles. According to an embodiment, during the preparation of the core, the amount of zinc relative to 1 mole of tellurium can be less than or equal to about 20 moles, less than or equal to about 15 moles, less than or equal to about 10 moles, less than or equal to about 9 moles, less than or equal to about 8 moles, less than or equal to about 7 moles, less than or equal to about 6 moles, less than or equal to about 5 moles, less than or equal to about 4 moles, less than or equal to about 3 moles, or less than or equal to about 2 moles.

[0180] In an embodiment, the formation of the shell may include heating (or vacuum treating) a first organic ligand in a first organic solvent at a predetermined temperature (e.g., at a temperature greater than or equal to about 100 °C, such as greater than or equal to about 120 °C) under vacuum, changing the atmosphere of the reaction system to an inert gas, and heating it at a predetermined reaction temperature. A Group IIB metal precursor (hereinafter, an embodiment using the zinc precursor will be described, but it is not limited thereto) and a chalcogen precursor may be added to the heated reaction system while heating the reaction system to the shell formation temperature. For the continuation of the reaction, the Group IIB metal precursor and the chalcogen precursor may be added simultaneously or in any suitable order in consideration of the desired shell composition. The addition of the shell precursor may be controlled or adjusted to achieve a shell having a desired composition (e.g., a single composition or a gradient or multi-layer composition).

[0181] The reaction temperature for the shell formation may be appropriately selected within any suitable range as follows: greater than or equal to about 200 °C, such as greater than or equal to about 210 °C, greater than or equal to about 220 °C, greater than or equal to about 230 °C, greater than or equal to about 240 °C, greater than or equal to about 250 °C, greater than or equal to about 260 °C, greater than or equal to about 270 °C, greater than or equal to about 280 °C, or greater than or equal to about 290 °C and less than or equal to about 340 °C, such as less than or equal to about 325 °C. The reaction time for the shell formation may be appropriately selected in consideration of the desired shell composition, the precursors used, the shell formation temperature, the desired shell thickness, etc.

[0182] In the core formation, in the shell formation, or in both the core formation and the shell formation, a magnesium precursor may be supplied to the reaction system. In an embodiment, the magnesium precursor may be added together with the zinc precursor, for example, during shell formation. The magnesium precursor may include magnesium acetate, magnesium acetylacetonate, alkylated magnesium (e.g., dialkyl magnesium, where each alkyl may be a C1-C10 or C2-C4 alkyl).

[0183] In an embodiment, the formation of the semiconductor nanocrystal shell may include reacting the zinc precursor, optionally together with the magnesium precursor, with the selenium precursor, the sulfur precursor, or a combination thereof. In an embodiment, the zinc precursor may react with the selenium precursor to form a first shell layer including zinc and selenium on the core, and then react with the sulfur precursor to form a second shell layer including zinc and sulfur on the first shell layer. In an embodiment, the semiconductor nanocrystal shell formation may include reacting the zinc precursor, optionally together with the magnesium precursor and the selenium precursor, and then reacting the zinc precursor, optionally together with the magnesium precursor and the sulfur precursor. In an embodiment, the zinc precursor, optionally together with the magnesium precursor, may react with the selenium precursor and the sulfur precursor to form a semiconductor nanocrystal shell including zinc, selenium, and sulfur (e.g., ZnSeS) optionally having magnesium.

[0184] In an embodiment, the zinc metal precursor may include a metal powder (Zn powder), a metal oxide (e.g., ZnO), an alkylated metal compound (e.g., a C2-C30 alkyl (e.g., dialkyl) zinc such as dimethyl zinc, diethyl zinc), a metal alkoxide (e.g., a metal ethanolate), a metal carboxylate (e.g., a metal acetate or a zinc aliphatic carboxylate, e.g., a long-chain aliphatic carboxylate zinc such as zinc oleate), a metal nitrate, a metal perchlorate, a metal sulfate, a metal acetylacetonate, a metal halide (e.g., a metal chloride), a metal cyanide, a metal hydroxide, a metal carbonate, a metal peroxide, or a combination thereof.

[0185] Examples of the Group IIB metal precursor including zinc may include dimethyl zinc, diethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, or a combination thereof.

[0186] The selenium precursor may include selenium-tri-n-octylphosphine (Se-TOP), selenium-tri-n-butylphosphine (Se-TBP), selenium-triphenylphosphine (Se-TPP), selenium-diphenylphosphine (Se-DPP), or a combination thereof, but is not limited thereto.

[0187] The tellurium precursor may include tellurium-tri-n-octylphosphine (Te-TOP), tellurium-tri-n-butylphosphine (Te-TBP), tellurium-triphenylphosphine (Te-TPP), tellurium-diphenylphosphine (Te-DPP), or a combination thereof, but is not limited thereto.

[0188] The sulfur precursor may include hexanethiol, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, mercaptopropylsilane, sulfur-tri-n-octylphosphine (S-TOP), sulfur-tri-n-butylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP), sulfur-tri-n-octylamine (S-TOA), sulfur-1-octadecene (S-ODE), bis(trimethylsilylmethyl)sulfide, bis(trimethylsilyl)sulfide, ammonium sulfide, sodium sulfide, or a combination thereof.

[0189] The (first, second, third, or combination thereof) organic solvents may be the same as or different from each other. The (first, second, third, or combination thereof) organic solvents (hereinafter simply referred to as organic solvents) may be C6-C22 primary amines such as cetylamine, C6-C22 secondary amines such as dioctylamine, C6-C40 tertiary amines such as trioctylamine, nitrogen-containing heterocyclic compounds such as pyridine, C6-C40 olefins such as octadecene, C6-C40 aliphatic hydrocarbons such as hexadecane, octadecane, or squalane, aromatic hydrocarbons substituted with C6-C30 alkyl groups such as phenyldodecane, phenyltetradecane, or phenylhexadecane, primary, secondary, or tertiary phosphines substituted with C6-C22 alkyl groups, such as at least one (e.g., 1, 2, or 3) C6-C22 alkyl groups (e.g., trioctylphosphine), phosphine oxides substituted with C6-C22 alkyl groups, such as at least one (e.g., 1, 2, or 3) C6-C22 alkyl groups (e.g., trioctylphosphine oxide), C12-C22 aromatic ethers such as phenyl ether or benzyl ether, or a combination thereof.

[0190] At least two of the first organic ligand, the second organic ligand, and the third organic ligand may be the same as each other. At least two of the first organic ligand, the second organic ligand, and the third organic ligand may be different from each other. Details of the first, second, and third organic ligands are the same as those set forth herein for organic ligands.

[0191] In an embodiment, the second organic ligand may include a fatty acid (e.g., including an aliphatic hydrocarbon group having 5 or more, 10 or more, or 15 or more carbon atoms) and the third organic ligand may include a fatty organic amine (e.g., a primary amine including an aliphatic or aromatic hydrocarbon group having 5 or more, 10 or more, or 15 or more carbon atoms, or a combination thereof). The fatty organic amine may be a compound represented by RNH2, where R is a C5-C40 aliphatic hydrocarbon group such as an alkyl group, an alkenyl group, or an alkynyl group or a C6-C40 aryl group. The number of carbon atoms of the aliphatic hydrocarbon group may be greater than or equal to about 5, greater than or equal to about 10, greater than or equal to about 15, greater than or equal to about 16, greater than or equal to about 17, greater than or equal to about 18, greater than or equal to about 19, or greater than or equal to about 20; less than or equal to about 50, less than or equal to about 40, or less than or equal to about 30; or a combination thereof.

[0192] The amounts of the second organic ligand and the third organic ligand can be selected in consideration of the types of the organic ligand and the precursor. With respect to 1 mole of the zinc precursor, the amount of the second organic ligand (or the amount of the second ligand or the amount of the third organic ligand) can be greater than or equal to about 0.1 mole, greater than or equal to about 0.2 mole, greater than or equal to about 0.3 mole, greater than or equal to about 0.4 mole, greater than or equal to about 0.5 mole, greater than or equal to about 0.6 mole, greater than or equal to about 0.7 mole, greater than or equal to about 0.8 mole, greater than or equal to about 0.9 mole, greater than or equal to about 1 mole, greater than or equal to about 2 moles, greater than or equal to about 3 moles, greater than or equal to about 4 moles, or greater than or equal to about 5 moles. With respect to 1 mole of the zinc precursor, the amount of the first organic ligand (or the amount of the second ligand or the amount of the third organic ligand) can be less than or equal to about 20 moles, less than or equal to about 19 moles, less than or equal to about 18 moles, less than or equal to about 17 moles, less than or equal to about 16 moles, less than or equal to about 15 moles, less than or equal to about 14 moles, less than or equal to about 13 moles, less than or equal to about 12 moles, less than or equal to about 10 moles, less than or equal to about 9 moles, less than or equal to about 8 moles, less than or equal to about 7 moles, less than or equal to about 6 moles, less than or equal to about 5 moles, less than or equal to about 4 moles, less than or equal to about 3 moles, less than or equal to about 2 moles, or less than or equal to about 1 mole.

[0193] The molar ratio between the second organic ligand and the third organic ligand (the second organic ligand: the third organic ligand) can be, for example, 1: about 0.1 or greater, 1: about 0.5 or greater, 1: about 0.9 or greater, or 1: about 1 or greater; 1: about 10 or less; 1: about 5 or less, 1: about 2.5 or less, or 1: about 1.5 or less.

[0194] The amount of the additive used in the preparation of the quantum dots (e.g., the core formation reaction, the shell formation reaction, or the core and shell formation) can be appropriately controlled in consideration of the type of the precursor, the organic solvent, etc.

[0195] In an embodiment, the selenium precursor, the tellurium precursor, and the metal hydride compound can be injected into the zinc precursor organic solution in a mixed state, optionally together with the third organic ligand. In an embodiment, the selenium precursor, the tellurium precursor, and the metal hydride compound can be sequentially injected into the zinc precursor organic solution.

[0196] In the reaction system for core formation and the reaction system for shell formation, the amounts and concentrations of the respective precursors can be selected taking into account the desired composition of the core and the shell, the reactivity between the core and shell precursors, etc. In an embodiment, the ratio between the precursors can be controlled taking into account the desired composition of the final quantum dots (e.g., the ratio such as molar ratio between elements such as Zn, S, Se, Te, or combinations thereof). The composition of the final quantum dots can be determined by appropriate analytical tools such as inductively coupled plasma atomic emission spectrometry.

[0197] After the formation of the core, the shell, or a combination thereof, a non-solvent can be added to the reaction product and the nanocrystal particles that are coordinated (e.g., bound) with the ligand compound can be separated. The non-solvent can be a polar solvent that is miscible with the solvent used in the core formation reaction, shell formation reaction, or a combination thereof and that cannot disperse the produced nanocrystals therein. The non-solvent can be selected taking into account the solvent used in the reaction and can be, for example, acetone, ethanol, butanol, isopropanol, ethylene glycol, water, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), diethyl ether, formaldehyde, acetaldehyde, solvents having solubility parameters similar to those of the above non-solvents, or combinations thereof. The separation of the nanocrystal particles can involve centrifugation, sedimentation, chromatography, or distillation. If desired, the separated nanocrystal particles can be added to a washing (or dispersing) solvent and washed (or dispersed). The type of the washing (or dispersing) solvent is not particularly limited and a solvent having solubility parameters similar to those of the organic ligand can be used and examples thereof can include hexane, heptane, octane, chloroform, toluene, benzene, etc.

[0198] In an embodiment, the organic ligand may not include a polyfunctional organic compound having a thiol moiety and an amino group, a carboxylic acid group, or a combination thereof. In an embodiment, the organic ligand may not include a glutathione compound. The quantum dots may be insoluble in water.

[0199] When dispersed in water, the quantum dots can exhibit, for example, an average particle size of greater than or equal to about 300 nm, greater than or equal to about 400 nm, greater than or equal to about 500 nm, or greater than or equal to about 900 nm as determined by dynamic light scattering (DLS) analysis. When dispersed in an organic solvent (e.g., toluene, octane, etc.), the quantum dots can be configured to form an organic solution having an average particle size of less than or equal to about 500 nm, less than or equal to about 400 nm, less than or equal to about 300 nm, less than or equal to about 200 nm, less than or equal to about 100 nm, less than or equal to about 90 nm, less than or equal to about 50 nm, less than or equal to about 30 nm, or less than or equal to about 20 nm as determined by DLS analysis. Examples of the organic solvent are described herein.

[0200] In an embodiment, the quantum dot composition includes the above-described (e.g., plural) quantum dots; an organic solvent, a liquid carrier (vehicle), or a combination thereof; and optionally a monomer, a dispersant, or a combination thereof. The dispersant can disperse the quantum dots. The dispersant can include a compound containing a carboxylic acid group (e.g., a monomer or a polymer). The composition can include a polymerizable monomer having a carbon-carbon double bond, e.g., at least one carbon-carbon double bond, a (photo- or thermo-) initiator, or a combination thereof. The composition can be a photosensitive composition.

[0201] Details of the quantum dots in the composition are described herein. The amount of the quantum dots in the composition (or the composite as described herein) can be appropriately adjusted in view of the desired end use (e.g., a photoluminescent color filter, etc.) and the components of the composition (or the composite). In an embodiment, based on the total weight or total solid content (solid content) of the composition, the amount of the quantum dots can be greater than or equal to about 1 weight percent (wt%) such as greater than or equal to about 2 wt%, greater than or equal to about 3 wt%, greater than or equal to about 4 wt%, greater than or equal to about 5 wt%, greater than or equal to about 6 wt%, greater than or equal to about 7 wt%, greater than or equal to about 8 wt%, greater than or equal to about 9 wt%, greater than or equal to about 10 wt%, greater than or equal to about 15 wt%, greater than or equal to about 20 wt%, greater than or equal to about 25 wt%, greater than or equal to about 30 wt%, greater than or equal to about 35 wt%, or greater than or equal to about 40 wt%. Based on the total weight or total solid content of the composition, the amount of the quantum dots can be less than or equal to about 70 wt% such as less than or equal to about 65 wt%, less than or equal to about 60 wt%, less than or equal to about 55 wt%, or less than or equal to about 50 wt%. The weight percentages of the components in the composition relative to the total solid content can represent the contents of the components in the composite to be described herein.

[0202] In the composition according to an embodiment, the dispersant can ensure the dispersion of the quantum dots. In an embodiment, the dispersant can be an adhesive (or an adhesive polymer). The adhesive can include an organic compound (e.g., a monomer or a polymer) that optionally (e.g., in a repeating unit) includes a carboxylic acid group. The adhesive can be an insulating polymer.

[0203] The organic compound including a carboxylic acid group can include: a copolymer of a monomer mixture including: a first monomer including a carboxylic acid group and a carbon-carbon double bond, a second monomer including a carbon-carbon double bond and a hydrophobic moiety and not including a carboxylic acid group, and optionally, a third monomer including a carbon-carbon double bond and a hydrophilic moiety and not including a carboxylic acid group;

[0204] A polymer containing multiple aromatic rings (hereinafter, a cardo binder), which has a backbone structure and contains carboxylic acid groups (-COOH), in the backbone structure, two aromatic rings are bonded to a quaternary carbon atom that is a constituent atom of another cyclic moiety in the main chain; or

[0205] A combination thereof.

[0206] The dispersant may include the first monomer, the second monomer, the third monomer, or a combination thereof.

[0207] In the composition, based on the total weight of the composition, the amount of the dispersant or the binder polymer may be greater than or equal to about 0.5 wt% such as greater than or equal to about 1 wt%, greater than or equal to about 5 wt%, greater than or equal to about 10 wt%, greater than or equal to about 15 wt%, or greater than or equal to about 20 wt%, but not limited thereto. Based on the total weight or total solids content of the composition, the amount of the dispersant or the binder polymer may be less than or equal to about 35 wt% such as less than or equal to about 33 wt%, or less than or equal to about 30 wt%. Based on the total weight or total solids content of the composition, the amount of the dispersant or the binder polymer may be about 0.5 wt% - about 55 wt%.

[0208] In the composition, the polymerizable (e.g., photopolymerizable) monomer containing a carbon-carbon double bond (hereinafter, may be referred to as "monomer") may include (e.g., photopolymerizable) methacryloyl-based monomers, i.e., monomers containing a methacryloyl group. The monomer may be a precursor of an insulating polymer.

[0209] Based on the total weight of the composition, the amount of the monomer may be greater than or equal to about 0.5 wt% such as greater than or equal to about 1 wt%, or greater than or equal to about 2 wt%. Based on the total weight of the composition, the amount of the monomer may be less than or equal to about 30 wt% such as less than or equal to about 28 wt%, less than or equal to about 25 wt%, less than or equal to about 23 wt%, less than or equal to about 20 wt%, less than or equal to about 18 wt%, less than or equal to about 17 wt%, less than or equal to about 16 wt%, or less than or equal to about 15 wt%.

[0210] The (photo)initiator included in the composition is a compound that initiates the (photo)polymerization of the above monomers in the composition. The initiator is a compound that accelerates a radical reaction (e.g., radical polymerization of a monomer) by generating radical chemicals under mild conditions (e.g., by heat or light). The initiator may be a thermal initiator or a photoinitiator. The initiator is not particularly limited and can be appropriately selected.

[0211] In the composition, the amount of the initiator can be appropriately selected in consideration of the type and amount of the polymerizable monomer. In an embodiment, based on the total weight of the composition (or the total weight of the solid content), the amount of the initiator can be greater than or equal to about 0.01% by weight, such as greater than or equal to about 1% by weight and less than or equal to about 10% by weight, such as less than or equal to about 9% by weight, less than or equal to about 8% by weight, less than or equal to about 7% by weight, less than or equal to about 6% by weight, or less than or equal to about 5% by weight, but is not limited thereto.

[0212] The composition (or the composite to be described herein) may further include a (poly- or mono-functional) thiol compound having a thiol group at the end, such as at least one thiol group, metal oxide particles, or a combination thereof.

[0213] The metal oxide particles may include TiO2, SiO2, BaTiO3, Ba2TiO4, ZnO, or a combination thereof. In the composition, based on the total weight of the composition (or the solid content), the amount of the metal oxide particles can be greater than or equal to about 1% by weight, greater than or equal to about 5% by weight, or greater than or equal to about 10% by weight and less than or equal to about 50% by weight, less than or equal to about 40% by weight, less than or equal to about 30% by weight, less than or equal to about 25% by weight, less than or equal to about 20% by weight, less than or equal to about 15% by weight, less than or equal to about 10% by weight, or less than or equal to about 5% by weight. The metal oxide particles can be non-emissive (e.g., do not emit light). The metal oxide may include oxides of metals or metalloids.

[0214] The metal oxide particles can have a diameter selected appropriately without particular limitation. The diameter of the metal oxide particles can be greater than or equal to about 100 nm, such as greater than or equal to about 150 nm, or greater than or equal to about 200 nm and less than or equal to about 1000 nm or less than or equal to about 800 nm.

[0215] The polythiol compound can be a dithiol compound, a trithiol compound, a tetrathiol compound, or a combination thereof. For example, the thiol compound can be diol di-3-mercaptopropionate (e.g., ethylene glycol di-3-mercaptopropionate), diol dimercaptoacetate (e.g., ethylene glycol dimercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetra(2-mercaptoacetate), 1,6-hexanedithiol, 1,3-propanedithiol, 1,2-ethanedithiol, polyethylene glycol dithiol including 1-10 ethylene glycol repeating units, or a combination thereof.

[0216] Based on the total weight or total solids content of the composition, the amount of the thiol compound can be less than or equal to about 50 wt%, less than or equal to about 40 wt%, less than or equal to about 30 wt%, less than or equal to about 20 wt%, less than or equal to about 10 wt%, less than or equal to about 9 wt%, less than or equal to about 8 wt%, less than or equal to about 7 wt%, less than or equal to about 6 wt%, or less than or equal to about 5 wt%. Based on the total weight or total solids content of the composition, the amount of the thiol compound can be greater than or equal to about 0.1 wt% such as greater than or equal to about 0.5 wt%, greater than or equal to about 1 wt%, greater than or equal to about 5 wt%, greater than or equal to about 10 wt%, or greater than or equal to about 15 wt%.

[0217] The composition may further include an organic solvent (or liquid carrier, hereinafter referred to as a solvent). The type of organic solvent that can be used is not particularly limited. Examples of the solvent can include, but are not limited to: ethyl 3-ethoxypropionate; ethylene glycol series such as ethylene glycol, diethylene glycol, or polyethylene glycol; glycol ether series such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, ethylene glycol diethyl ether, or diethylene glycol dimethyl ether; glycol ether acetate series such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate, or diethylene glycol monobutyl ether acetate; propylene glycol series such as propylene glycol; propylene glycol ether series such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, propylene glycol diethyl ether, or dipropylene glycol diethyl ether; propylene glycol ether acetate series such as propylene glycol monomethyl ether acetate or dipropylene glycol monoethyl ether acetate; amide series such as N-methylpyrrolidone, dimethylformamide, or dimethylacetamide; ketone series such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), or cyclohexanone; petroleum products such as toluene, xylene, or solvent naphtha; ester series such as ethyl acetate, propyl acetate, butyl acetate, cyclohexyl acetate, or ethyl lactate; ethers such as diethyl ether, dipropyl ether, or dibutyl ether; chloroform; C1-C40 aliphatic hydrocarbons (e.g., alkanes, alkenes, or alkynes); halogen (e.g., chlorine)-substituted C1-C40 aliphatic hydrocarbons (e.g., dichloroethane, chloroform, etc.); C6-C40 aromatic hydrocarbons (e.g., toluene, xylene, etc.); halogen (e.g., chlorine)-substituted C6-C40 aromatic hydrocarbons; or combinations thereof.

[0218] The type and amount of the solvent can be appropriately selected by taking into account the above-described main components (i.e., the quantum dots, the dispersant, the photopolymerizable monomer, the photoinitiator, and the thiol compound if used), as well as the type and amount of additives to be described herein. The composition may include the solvent in an amount remaining after the desired amount of the solids content (non-volatile components).

[0219] The composition (e.g., an inkjet composition) may have a viscosity at 25 °C that is greater than or equal to about 4 centipoise (cPs), greater than or equal to about 5 cPs, greater than or equal to about 5.5 cPs, greater than or equal to about 6.0 cPs, or greater than or equal to about 7.0 cPs. The composition (e.g., an inkjet composition) may have a viscosity at 25 °C that is less than or equal to about 12 cPs, less than or equal to about 10 cPs, or less than or equal to about 9 cPs.

[0220] If the composition is applied in an inkjet process, the composition may be discharged onto a substrate at room temperature and may form a quantum dot-polymer composite or a pattern of quantum dot-polymer composites, e.g., by heating. With the disclosed viscosities, the ink composition may have a surface tension at 23 °C that is greater than or equal to about 21 millinewtons per meter (mN / m), greater than or equal to about 22 mN / m, greater than or equal to about 23 mN / m, greater than or equal to about 24 mN / m, greater than or equal to about 25 mN / m, greater than or equal to about 26 mN / m, greater than or equal to about 27 mN / m, greater than or equal to about 28 mN / m, greater than or equal to about 29 mN / m, greater than or equal to about 30 mN / m, or greater than or equal to about 31 mN / m and less than or equal to about 40 mN / m, less than or equal to about 39 mN / m, less than or equal to about 38 mN / m, less than or equal to about 37 mN / m, less than or equal to about 36 mN / m, less than or equal to about 35 mN / m, less than or equal to about 34 mN / m, less than or equal to about 33 mN / m, or less than or equal to about 32 mN / m. The surface tension of the ink composition may be less than or equal to about 31 mN / m, less than or equal to about 30 mN / m, less than or equal to about 29 mN / m, or less than or equal to about 28 mN / m.

[0221] If desired, in addition to the above components, the composition may further include various additives such as a light diffusing agent, a leveling agent, or a coupling agent.

[0222] The components (binder, monomer, solvent, additive, thiol compound, cardo binder, etc.) included in the composition of the embodiment (e.g., a photoresist composition) can be appropriately selected as described, for example, in US-2017-0052444-A1.

[0223] The composition according to an embodiment can be prepared by a method including: preparing a quantum dot dispersion including the above-described quantum dots, a dispersant, and a solvent; and mixing the quantum dot dispersion with the initiator, the polymerizable monomer (e.g., acryloyl-based, i.e., monomers containing acryloyl), optionally the thiol compound, optionally the metal oxide particles, and optionally the above additives. Each of the above components can be mixed sequentially or simultaneously, but the mixing order is not particularly limited.

[0224] The composition according to an embodiment can be used to provide a quantum dot composite pattern (e.g., a patterned quantum dot-polymer composite). The composition can provide a quantum dot-polymer composite by polymerization (e.g., radical polymerization). The composition according to an embodiment can be a photoresist composition including quantum dots that can be applied to a lithography method. The composition according to an embodiment can be an ink composition that can provide a pattern by printing (e.g., a droplet discharge method such as inkjet printing).

[0225] In an embodiment, the quantum dot (polymer) composite includes a matrix (e.g., a polymer matrix); and the above-described quantum dots dispersed in the matrix. The quantum dot matrix can further include metal oxide particles dispersed in the matrix. The (polymer) matrix can include a linear polymer, a crosslinked polymer, or a combination thereof. The crosslinked polymer can include a thiol-ene resin, a crosslinked poly(meth)acrylate, a crosslinked polyurethane, a crosslinked epoxy resin, a crosslinked vinyl polymer, a crosslinked silicone resin, or a combination thereof. The linear polymer can include repeating units derived from carbon-carbon unsaturated bonds (e.g., carbon-carbon double bonds). The repeating unit can include a carboxylic acid group. The linear polymer can include ethylene repeating units.

[0226] The matrix can include a dispersant (e.g., an adhesive monomer or polymer including a carboxylic acid group), a polymerization product of a polymerizable monomer having a carbon-carbon double bond (e.g., at least one, e.g., at least two, at least three, at least four, or at least five) (e.g., an insulating polymer), optionally a polymerization product of the polymerizable monomer and a thiol compound (e.g., a polythiol compound having at least two thiol groups, e.g., at least two thiol groups at its ends), or a combination thereof.

[0227] The crosslinked polymer can include a thiol-ene resin, a crosslinked poly(meth)acrylate, or a combination thereof. In an embodiment, the crosslinked polymer can be a polymerization product of the polymerizable monomer and optionally a polythiol compound having at least two thiol groups (e.g., at its ends). The quantum dots, dispersant or binder polymer, polymerizable monomer, and polythiol compound can be the same as those described herein.

[0228] The film of the quantum dot-polymer composite (or its pattern as described herein) can have a thickness such as, for example, less than or equal to about 30 micrometers (μm), such as less than or equal to about 25 μm, less than or equal to about 20 μm, less than or equal to about 15 μm, less than or equal to about 10 μm, less than or equal to about 8 μm, or less than or equal to about 7 μm and greater than or equal to about 2 μm, such as greater than or equal to about 3 μm, greater than or equal to about 3.5 μm, greater than or equal to about 4 μm, greater than or equal to about 5 μm, or greater than or equal to about 6 μm.

[0229] In an embodiment, the patterned film of the quantum dot composite can include repeating segments configured to emit a predetermined light, such as at least one repeating segment configured to emit a predetermined light. In an embodiment, the repeating segment can include a first segment configured to emit a first light. The repeating segment can further include a second segment that emits a second light having a wavelength different from that of the first light. The first segment, the second segment, or a combination thereof can include the above-described quantum dot (polymer) composite. The first light or the second light can be red light having a maximum photoluminescence peak wavelength between about 600 nm and about 650 nm (e.g., about 620 nm - about 650 nm), or green light having a maximum photoluminescence peak wavelength between about 500 nm and about 550 nm (e.g., about 510 nm - about 540 nm). The patterned film can further include a third segment that can transmit or emit a third light (e.g., blue light) different from the first light and the second light. The third light can include excitation light. The third light (or the excitation light) can include blue light and optionally green light having a maximum peak wavelength in the range of about 380 nm - about 480 nm.

[0230] In an embodiment, the patterned quantum dot composite film can be manufactured by a method using the photoresist composition. The method can include:

[0231] Forming a film of the composition on a substrate (S1);

[0232] Optionally pre-baking the film (S2);

[0233] Exposing selected regions of the film to light (e.g., a wavelength less than or equal to about 400 nm) (S3); and

[0234] Developing the exposed film with an alkaline developer solution to obtain a pattern including the quantum dot-polymer composite (S4).

[0235] Refer to Figure 2A Illustrate a non-limiting method of forming the pattern.

[0236] The composition can be coated on a substrate to a predetermined thickness by a suitable method such as spin coating or slit coating (S1). The formed film can be optionally pre-baked (PRB) (S2). The pre-baking can be carried out by selecting appropriate conditions such as temperature, time, atmosphere, etc.

[0237] The formed (or optionally pre-baked) film is exposed to light having a predetermined wavelength under a mask having a predetermined pattern (e.g., a photomask) (S3). The wavelength and intensity of the light can be selected by taking into account the initiator (e.g., a photoinitiator), the amount of the initiator (e.g., a photoinitiator), quantum dots, the amount of quantum dots, etc. In Figure 2A BM represents a black matrix.

[0238] The exposed film is treated with an alkaline developer solution (e.g., dipping or spraying) to dissolve the unexposed areas and obtain a desired pattern (S4). The obtained pattern can be optionally post-baked (POB) to improve the crack resistance and solvent resistance of the pattern, e.g., at about 150 °C - about 230 °C for a predetermined time (e.g., greater than or equal to about 10 minutes or greater than or equal to about 20 minutes) (S5).

[0239] In an embodiment where the quantum dot-polymer composite pattern has a plurality of (types of) repeating segments, a quantum dot-polymer composite having a desired pattern can be obtained by: preparing a plurality of compositions including quantum dots (e.g., quantum dots emitting red light, quantum dots emitting green light, or optionally quantum dots emitting blue light) having desired photoluminescence properties (such as photoluminescence peak wavelength, etc.) for forming each repeating segment, and repeating the pattern formation an appropriate number of times (e.g., two or more times, or three or more times) for each composition (S6). For example, the quantum dot-polymer composite can have a pattern including at least two (types of) repeating color segments (e.g., RGB segments), e.g., provided in a pattern including at least two (types of) repeating color segments (e.g., RGB segments). The quantum dot-polymer composite pattern can be used as a photoluminescent color filter in a display device.

[0240] The quantum dot composite pattern can be formed by using an ink composition configured to form a pattern via an inkjet method. Referring to Figure 2B , the method includes: preparing an ink composition; obtaining a substrate including a pattern, e.g., an electrode formed by a bank and optionally a pattern of a pixel region; depositing the ink composition on the substrate (or the pixel region) to form a first quantum dot layer (or a first repeating segment); and depositing the ink composition on the substrate (or the pixel region) to form a second quantum dot layer (or a second repeating segment). The formation of the first quantum dot layer and the second quantum dot layer can be carried out simultaneously or sequentially.

[0241] The deposition of the ink composition can be carried out using a suitable droplet ejection system such as an inkjet printer or a nozzle printing system (e.g., having an ink reservoir and a printing head, e.g., at least one printing head). The deposited ink composition can be heated to remove the solvent and optionally to effect polymerization, and thereby provide a (first or second) quantum dot layer. The method can provide a highly precise quantum dot-polymer composite film or pattern in a relatively simple manner within a relatively short period of time.

[0242] The aforementioned quantum dots or quantum dot composites (patterns) can be included in an electronic device. Such an electronic device can include a display device, a light-emitting diode (LED), an organic light-emitting diode (OLED), a quantum dot LED, a sensor, a solar cell, an imaging sensor, a photodetector, or a liquid crystal display device, but is not limited thereto. The aforementioned quantum dots can be included in an electronic apparatus. Such an electronic apparatus can include a portable (handheld) terminal device, a monitor, a notebook personal computer (PC), a television, an electronic display, a camera, an automobile, etc., but is not limited thereto. The electronic apparatus can be a portable terminal device, a monitor, a notebook PC, or a television including a display device (or a light-emitting device) containing quantum dots. The electronic apparatus can be a camera or a portable terminal device including an image sensor containing quantum dots. The electronic apparatus can be a camera or a vehicle including a photodetector containing quantum dots.

[0243] The device (display device or light-emitting device) can further include a light-emitting element such as a light-emitting component, and optionally a light source. The light-emitting element can include a light-emitting layer. The light-emitting element can further include a substrate, and the light-emitting layer can be disposed on one surface of the substrate. The light-emitting layer can include a film or a patterned film of the quantum dot composite. The light source can be configured to provide incident light to the light-emitting element. The incident light can have a photoluminescence peak wavelength in a range of greater than or equal to about 440 nm, e.g., greater than or equal to about 450 nm and less than or equal to about 500 nm, e.g., less than or equal to about 480 nm, less than or equal to about 470 nm, or less than or equal to about 460 nm.

[0244] In an embodiment, the light-emitting element or the light-emitting layer can include a sheet of the quantum dot composite. Refer to Figure 3, The photoluminescence type device 400 includes a backlight unit and a liquid crystal panel, and the backlight unit may include a quantum dot-polymer composite sheet (QD sheet). For example, the backlight unit may include a reflector, a light guide plate (LGP), a light source (such as a blue LED), a quantum dot-polymer composite sheet (QD sheet), and an optical film (such as a prism, a double brightness enhancement film (DBEF), etc.), and so on. The liquid crystal panel may be disposed on the backlight unit and may have a structure including a thin film transistor (TFT), liquid crystal (LC), and a color filter between two polarizers (Pol). The quantum dot-polymer composite sheet (QD sheet) may include quantum dots that emit red light by absorbing light from the light source and quantum dots that emit green light. The blue light from the light source may pass through the quantum dot-polymer composite sheet, be combined with the red light and green light from the quantum dots, and be converted into white light. The white light may be separated into blue light, green light, and red light by the color filter in the liquid crystal panel and may be emitted to the outside in each pixel.

[0245] In an embodiment, the light emitting layer may be disposed on the front surface (e.g., the light extraction surface) of the device (light emitting device or display device) in the form of a film patterned with quantum dots (or their composites). The patterned film may include repeating segments configured to emit desired light. The repeating segment may include a first segment. The first segment may be a segment that emits red light. The repeating segment may include a second segment. The second segment may include a segment that emits green light. The repeating segment may include a third segment. The third segment may be a segment that emits or transmits blue light. Details of the first, second, and third segments are as described herein.

[0246] The light source may be an element that can provide incident light, emit excitation light, or a combination thereof to the light emitting layer. The incident or excitation light may include blue light and optionally green light. The light source may include an LED. The light source may include an organic LED (OLED). On the front surface (light emitting surface) of the first segment and the second segment, an optical element (such as a blue light (and optionally green light) blocking layer or a first filter) for blocking (e.g., reflecting or absorbing) blue light (and optionally green light) as described herein may be disposed. When the light source includes an organic light emitting diode for emitting blue light and an organic light emitting diode for emitting green light, a green light removal filter may be further disposed on the third segment through which blue light passes.

[0247] The light source may include a plurality of light-emitting units corresponding to the first section and the second section, respectively, and the light-emitting unit may include a first electrode and a second electrode facing each other and an (organic) electroluminescent layer between the first electrode and the second electrode. The electroluminescent layer may include an organic light-emitting material. For example, each light-emitting unit of the light source may include an electroluminescent device (e.g., an organic light-emitting diode (OLED)) configured to emit light of a predetermined wavelength (e.g., blue light, green light, or a combination thereof). The structure and material of the electroluminescent device and the organic light-emitting diode (OLED) are not particularly limited.

[0248] Figure 4A is a schematic cross-sectional view of a display device according to an embodiment, and Figure 4B is a schematic cross-sectional view of a display device according to an embodiment. Referring to Figure 4A and 4B , the light source includes an organic light-emitting diode (OLED) that emits blue (B) light (and optionally green light). The organic light-emitting diode (OLED) may include at least two pixel electrodes 90a, 90b, 90c formed on a substrate 100, pixel defining layers 150a, 150b formed between adjacent pixel electrodes 90a, 90b, 90c, organic light-emitting layers 140a, 140b, 140c formed on each pixel electrode 90a, 90b, 90c, and a common electrode layer 130 formed on the organic light-emitting layers 140a, 140b, 140c. A thin-film transistor and a substrate may be disposed under the organic light-emitting diode (OLED). A stacked structure including a quantum dot composite pattern 170 (e.g., a first section 11 or R including quantum dots that emit red light, a second section 21 or G including quantum dots that emit green light, and a third section 31 or B including or not including quantum dots such as quantum dots that emit blue light) and a substrate 240 may be disposed on the light source. The blue light emitted from the light source enters the first section and the second section and may emit red light and green light, respectively. The blue light emitted from the light source may pass through the third section. If desired, an element (a first filter 160 or an excitation light blocking layer) configured to block the excitation light may be disposed between the quantum dot composite layers R and G and the substrate. When the excitation light includes blue light and green light, a green light blocking filter may be added to the third section. The first filter or the excitation light blocking layer will be described in more detail herein.

[0249] Such a (display) device may be manufactured by separately manufacturing the above-described stacked structure and an LED or an OLED (e.g., emitting blue light) and then combining the stacked structure and the LED or the OLED. The (display) device may be manufactured by directly forming the quantum dot composite pattern on the LED or the OLED.

[0250] The substrate may be a substrate including an insulating material. The substrate may include: glass; various polymers such as polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc., polycarbonate, and polyacrylate; polysiloxane (e.g., polydimethylsiloxane (PDMS)); inorganic materials such as Al2O3 or ZnO; or a combination thereof, but not limited thereto. The thickness of the substrate may be appropriately selected in consideration of the substrate material, but there is no particular limitation. The substrate may be flexible. The substrate may have a transmittance of greater than or equal to about 50%, greater than or equal to about 60%, greater than or equal to about 70%, greater than or equal to about 80%, or greater than or equal to about 90% for the light emitted from the quantum dots.

[0251] A circuit layer including thin film transistors and the like is formed on the substrate. The circuit layer may further include a gate line, a sustain voltage line, a gate insulating layer, a data line, a source electrode, a drain electrode, a semiconductor, a protective layer, etc. The detailed structure of the circuit layer may vary depending on the implementation. The gate line and the sustain voltage line are electrically isolated from each other, and the data line is insulated and crosses the gate line and the sustain voltage line. The gate electrode, the source electrode, and the drain electrode form the control terminal, the input terminal, and the output terminal of the thin film transistor, respectively. The drain electrode is electrically connected to a pixel electrode to be described herein.

[0252] The pixel electrode may be used as an electrode (e.g., an anode) of the display device. The pixel electrode may be formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The pixel electrode may be formed of a material having a light-blocking property such as gold (Au), platinum (Pt), nickel (Ni), tungsten (W), chromium (Cr), molybdenum (Mo), iron (Fe), cobalt (Co), copper (Cu), palladium (Pd), or titanium (Ti). The pixel electrode may have a bilayer structure in which the transparent conductive material and the material having a light-blocking property are sequentially laminated.

[0253] Between two adjacent pixel electrodes, a pixel defining layer (PDL) overlaps with the ends of the pixel electrodes to divide the pixel electrodes into pixel units. The pixel defining layer is an insulating layer that can resistively block at least two pixel electrodes.

[0254] The pixel defining layer covers a part of the upper surface of the pixel electrode, and the remaining area of the pixel electrode not covered by the pixel defining layer may provide an opening. The organic light emitting layer to be described herein may be formed in the area defined by the opening.

[0255] The organic light-emitting layer defines each pixel region through the aforementioned pixel electrode and the pixel defining layer. In other words, a pixel region can be defined as a region formed by an organic light-emitting unit layer in contact with a pixel electrode divided by the pixel defining layer. In the display device according to the embodiment, the organic light-emitting layer can be defined as a first pixel region, a second pixel region, and a third pixel region, and each pixel region is spaced apart from each other by the pixel defining layer, leaving a predetermined interval.

[0256] In an embodiment, the organic light-emitting layer can emit a third type of light belonging to the visible light region or the ultraviolet (UV) region. The first to third pixel regions of the organic light-emitting layer can each emit the third type of light. In an embodiment, the third type of light can be the light with the highest energy in the visible light region. For example, it can be blue light (and optionally green light). When all pixel regions of the organic light-emitting layer are designed to emit the same light, each pixel region of the organic light-emitting layer can be formed entirely of the same or similar materials, or can exhibit the same or similar properties. Therefore, the process of forming the organic light-emitting layer can be simplified, and the display device can be easily applied to large-scale / large-area processes, such as being manufactured by large-scale / large-area processes. However, the organic light-emitting layer according to the embodiment is not limited thereto, but the organic light-emitting layer can be designed to emit at least two different lights, for example, at least two different colored lights.

[0257] The organic light-emitting layer includes an organic light-emitting unit layer in each pixel region, and in addition to the light-emitting layer, each organic light-emitting unit layer can further include auxiliary layers (such as a hole injection layer, a hole transport layer, an electron transport layer, etc.).

[0258] The common electrode can be used as the cathode of the display device. The common electrode can be formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The common electrode can be formed on the organic light-emitting layer and integrated therewith.

[0259] A planarization layer or a passivation layer (not shown) can be formed on the common electrode. The planarization layer can include an (e.g., transparent) insulating material for ensuring electrical insulation from the common electrode.

[0260] In an embodiment, the display device can further include a lower substrate, a polarizer disposed under the lower substrate, and a liquid crystal layer disposed between the stacked structure and the lower substrate. In the stacked structure, the photoluminescent layer (i.e., the light-emitting layer) can be disposed to face the liquid crystal layer. The display device can further include a polarizer between the liquid crystal layer and the light-emitting layer. The light source can further include an LED, and if desired, a light guide plate.

[0261] A non - limiting example of a display device (e.g., a liquid crystal display device) according to an embodiment is described with reference to the accompanying drawings. Figure 5 FIG. is a schematic cross - sectional view of a liquid crystal display according to an embodiment. Refer to Figure 5 , the display device according to the embodiment includes a liquid crystal panel 200, a polarizer 300 provided under the liquid crystal panel 200, and a backlight unit provided under the polarizer 300.

[0262] The liquid crystal panel 200 includes a lower substrate 210, a stacked structure, and a liquid crystal layer 220 provided between the stacked structure and the lower substrate. The stacked structure includes a transparent substrate 240, a first filter layer 310, a photoluminescent layer 230 including a pattern of a quantum dot - polymer composite, and a second filter layer 311.

[0263] The lower substrate 210, called an array substrate, may be a transparent insulating material substrate. The substrate is the same as that described herein. A circuit board 211 is provided on the upper surface of the lower substrate 210. The circuit board 211 may include a plurality of gate lines (not shown) and data lines (not shown) defining pixel regions, thin - film transistors provided adjacent to the intersection regions of the gate lines and the data lines, and pixel electrodes for each pixel region, but is not limited thereto. Details of such a circuit board are not particularly limited.

[0264] The liquid crystal panel 200 may include alignment layers 221 above and below the liquid crystal layer 220 to initially align the liquid crystal material included therein. Details of the liquid crystal layer and the alignment layer (e.g., liquid crystal material, alignment layer material, method of forming the liquid crystal layer, thickness of the liquid crystal layer, etc.) are not particularly limited.

[0265] The lower polarizer 300 is provided under the lower substrate 210. The material and structure of the polarizer 300 are not particularly limited. A backlight unit (e.g., emitting blue light) may be provided under the polarizer 300. An upper optical element or polarizer 300 may be provided between the liquid crystal layer 220 and the transparent substrate 240, but is not limited thereto. For example, an upper polarizer may be provided between the liquid crystal layer 220 and the photoluminescent layer 230. The polarizer may be any suitable polarizer used in a liquid crystal display device. The polarizer may be a TAC (triacetyl cellulose) having a thickness less than or equal to about 200 μm, but is not limited thereto. In an embodiment, the upper optical element may be a coating that controls the refractive index without a polarizing function.

[0266] The backlight unit includes a light source 110. The light source 110 may emit blue light or white light. The light source 110 may include a blue LED, a white LED, a white OLED, or a combination thereof, but is not limited thereto.

[0267] The backlight unit may further include a light guide plate 120. In an embodiment, the backlight unit may be an edge-type lighting device. For example, the backlight unit may include a reflector (not shown), a light guide plate (not shown) provided on the reflector and providing a planar light source to the liquid crystal panel 200, (e.g., at least one) optical sheet (not shown) such as a diffusion plate, a prism sheet, etc. on the light guide plate, or a combination thereof, but not limited thereto. The backlight unit may not include a light guide plate. In an embodiment, the backlight unit may be a direct lighting device. For example, the backlight unit may have a reflector (not shown), and may have a plurality of fluorescent lamps provided on the reflector at regular intervals, or may have an LED driving substrate on which a plurality of light emitting diodes may be provided, a diffusion plate thereon, and optionally an optical sheet such as at least one optical sheet. Details of such a backlight unit (e.g., components of the light emitting diodes, fluorescent lamps, light guide plate, various optical sheets, and reflector) are not particularly limited.

[0268] The black matrix 241 is provided under the transparent substrate 240 and has openings and hides the gate lines, data lines, and thin film transistors of the circuit board on the lower substrate. For example, the black matrix 241 may have a lattice shape. The photoluminescent layer 230 is provided in the openings of the black matrix 241 and has a quantum dot composite pattern including a first segment (R) configured to emit a first light (e.g., red light), a second segment (G) configured to emit a second light (e.g., green light), and a third segment (B) configured to emit / transmit e.g., blue light. If desired, the photoluminescent layer 230 may further include a fourth segment, e.g., at least one fourth segment. The fourth segment may include quantum dots that emit light of a color different from the light emitted from the first to third segments (e.g., cyan, magenta, and yellow light).

[0269] In the photoluminescent layer 230, segments in which the pattern is repeatedly formed may correspond to pixel regions formed on the lower substrate 210. The transparent common electrode 231 may be provided on the photoluminescent color filter layer.

[0270] The third segment (B) configured to emit / transmit blue light may be a transparent color filter that does not change the emission spectrum of the light source. The blue light emitted from the backlight unit may enter in a polarized state and may be emitted as it is through the polarizer and the liquid crystal layer. If desired, the third segment may include quantum dots that emit blue light.

[0271] As described herein, if desired, the display device or the light-emitting device of the embodiment may further include an excitation light blocking layer or a first filter layer (hereinafter referred to as the first filter layer). The first filter layer may be disposed between the bottom surfaces of the first segment (R) and the second segment (G) and the substrate (e.g., the upper substrate 240), or on the upper surface of the substrate. The first filter layer 310 may be a sheet having an opening in a region corresponding to the pixel region (third segment) that displays blue and thus formed in a region corresponding to the first and second segments. The first filter layer may be disposed at a position other than the position overlapping with the third segment and integrally therewith, as shown in Figure 4A , 4B and Figure 5 , but is not limited thereto. For example, at least two first filter layers may be spaced apart and disposed at each position overlapping with the first and second segments. When the light source includes an element that emits green light, a green light blocking layer may be disposed on the third segment.

[0272] The first filter layer may block (e.g., absorb) or substantially block light having, for example, a predetermined wavelength region in the visible light region, and may transmit light in other wavelength regions. For example, the first filter layer may block blue light (or green light) and may transmit light other than the blue light (or green light). The first filter layer may transmit, for example, green light, red light, and / or yellow light as a mixed color thereof.

[0273] The first filter layer may substantially block excitation light and transmit light in a desired wavelength range. The transmittance of the first filter layer for light in the desired wavelength range may be greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or even about 100%.

[0274] A first filter layer configured to selectively transmit red light may be disposed at a position overlapping with the red light emitting segment, and a first filter layer configured to selectively transmit green light may be disposed at a position overlapping with the green light emitting segment. The first filter layer may include a first region that blocks (e.g., absorbs) blue light and red light and selectively transmits light in a predetermined range (e.g., greater than or equal to about 500 nm, greater than or equal to about 510 nm, or greater than or equal to about 515 nm and less than or equal to about 550 nm, less than or equal to about 545 nm, less than or equal to about 540 nm, less than or equal to about 535 nm, less than or equal to about 530 nm, less than or equal to about 525 nm, or less than or equal to about 520 nm); a second region that blocks (e.g., absorbs) blue light and green light and selectively transmits light in a predetermined range (e.g., greater than or equal to about 600 nm, greater than or equal to about 610 nm, or greater than or equal to about 615 nm and less than or equal to about 650 nm, less than or equal to about 645 nm, less than or equal to about 640 nm, less than or equal to about 635 nm, less than or equal to about 630 nm, less than or equal to about 625 nm, or less than or equal to about 620 nm); or a combination thereof. When the light source emits blue and green mixed light, the first filter may further include a third region that selectively transmits blue light and blocks green light.

[0275] The first region may be disposed at a position overlapping with the segment emitting green light. The second region may be disposed at a position overlapping with the segment emitting red light. The third region may be disposed at a position overlapping with the segment emitting blue light.

[0276] The first region, the second region, and optionally the third region may be optically isolated. Such a first filter layer may contribute to the improvement of the color purity of the display device.

[0277] The display device may further include a second filter layer (e.g., a red / green or yellow light recycling layer) 311 disposed between the photoluminescent layer and the liquid crystal layer (e.g., between the photoluminescent layer and the upper polarizer such as a polarizer), which transmits at least a part of the third light (excitation light), and reflects a part (e.g., at least a part) of the first light, a part (e.g., at least a part) of the second light, or parts (e.g., at least a part) of the first light and the second light respectively. The first light may be red light, the second light may be green light, and the third light may be blue light. For example, the second filter layer may transmit only the third light (B) in the blue light wavelength region having a wavelength region less than or equal to about 500 nm, and the light in the wavelength region greater than about 500 nm such as green light (G), yellow light, red light (R), etc. may not pass through the second filter layer and is reflected. The reflected green light and red light may pass through the first and second segments and be emitted to the outside of the display device.

[0278] The second filter layer or the first filter layer may be formed as an integrated layer having a relatively flat surface.

[0279] The first filter layer may include a polymer film including a dye that absorbs light of a wavelength to be blocked, a pigment that absorbs light of a wavelength to be blocked, or a combination thereof. The second filter layer and the first filter layer may include a single layer having a low refractive index and may be, for example, a transparent film having a refractive index less than or equal to about 1.4, less than or equal to about 1.3, or less than or equal to about 1.2. The second filter layer or the first filter layer having a low refractive index may be, for example, porous silica, porous organic material, porous organic / inorganic composite, or a combination thereof.

[0280] The first filter layer or the second filter layer may include a plurality of layers having different refractive indices. The first filter layer or the second filter layer may be formed by laminating two layers having different refractive indices. For example, the first / second filter layer may be formed by alternately laminating a material having a high refractive index and a material having a low refractive index.

[0281] Reference Figure 6A , the electronic device 10 includes: a first electrode 11 and a second electrode 15 facing each other, and an active layer 13 disposed between the first electrode 11 and the second electrode 15 and including the above-described quantum dots.

[0282] In an embodiment, the electronic device including the quantum dots may be an electroluminescent device. The quantum dots in the active layer 13 may be a light-emitting layer in which electrons and holes injected from the first electrode 11 and the second electrode 15 recombine to form excitons, and light of a constant wavelength may be emitted by the energy of the formed excitons. In addition, the electronic device including the quantum dots may be a photodetector or a solar cell. For example, the active layer 13 may be a light-absorbing layer in which the quantum dots absorb external photons and separate the external photons into electrons and holes to supply the electrons and holes to the first electrode 11 and the second electrode 15.

[0283] A hole auxiliary layer 12 may be disposed between the first electrode 11 and the active layer 13, and an electron auxiliary layer 14 may be disposed between the second electrode 15 and the active layer 13.

[0284] The electronic device 10 may further include a substrate (not shown). The substrate may be disposed on the side of the first electrode 11 or the second electrode 15. The substrate may be a substrate including an insulating material (e.g., an insulating transparent substrate). In addition, the substrate may include: glass, various polymers such as polyester (e.g., polyethylene terephthalate (PET), polyethylene naphthalate (PEN)), polycarbonate, polyacrylate, polyimide, polyamideimide, etc., inorganic materials such as polysiloxane (e.g., PDMS), Al2O3, ZnO, etc., or a combination thereof, or may be made of a silicon wafer. Here, "transparent" may mean that the transmittance through which light of a certain wavelength (e.g., light emitted from the quantum dots) passes through is greater than or equal to about 85%, greater than or equal to about 88%, greater than or equal to about 90%, greater than or equal to about 95%, greater than or equal to about 97%, or greater than or equal to about 99%. The thickness of the substrate may be appropriately selected in consideration of the substrate material, etc., but there is no particular limitation. The transparent substrate may be flexible.

[0285] One of the first electrode 11 and the second electrode 15 may be an anode and the other may be a cathode. For example, the first electrode 11 may be an anode and the second electrode 15 may be a cathode.

[0286] The first electrode 11 can be made of a conductor such as a metal, a conductive metal oxide, or a combination thereof. The first electrode 11 can be made, for example, of: a metal such as nickel, platinum, vanadium, chromium, copper, zinc, and gold, or an alloy thereof; a conductive metal oxide such as zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide; or a combination of a metal and an oxide such as ZnO and Al, or SnO2 and Sb, but is not limited thereto. The second electrode 15 can be made of a conductor such as a metal, a conductive metal oxide, a conductive polymer, or a combination thereof. The second electrode 15 can be made, for example, of: a metal such as aluminum, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, silver, gold, platinum, tin, lead, cesium, and barium, or an alloy thereof; a multilayer structure material such as LiF / Al, lithium oxide (Li2O) / Al, lithium 8-hydroxyquinoline (Liq) / Al, LiF / Ca, and BaF2 / Ca, but is not limited thereto. The conductive metal oxide is the same as that described herein.

[0287] There is no particular limitation on the work functions of the first electrode 11 and the second electrode 15, and they can be appropriately selected. The work function of the first electrode 11 can be higher or lower than the work function of the second electrode 15.

[0288] The first electrode 11, the second electrode 15, or a combination thereof can be a light-transmissive electrode, and the light-transmissive electrode can be made, for example, of: a conductive oxide such as zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide, or a single-layer or multi-layer thin metal layer. When one of the first electrode 11 and the second electrode 15 is a non-light-transmissive electrode, the non-light-transmissive electrode can be made of, for example, an opaque conductor such as aluminum (Al), silver (Ag), or gold (Au).

[0289] There is no particular limitation on the thickness of the first electrode, the second electrode, or each of the first and second electrodes, and it can be appropriately selected in consideration of device efficiency. For example, the thickness of the electrode can be greater than or equal to about 5 nm, such as greater than or equal to about 50 nm and less than or equal to about 100 μm, such as less than or equal to about 10 μm, less than or equal to about 1 μm, less than or equal to about 900 nm, less than or equal to about 500 nm, or less than or equal to about 100 nm.

[0290] The active layer 13 includes quantum dots described herein. The active layer 13 may include a single layer or multiple single layers of quantum dot layers. The multiple single layers may be two or more, three or more, or four or more and 20 or less, 10 or less, 9 or less, 8 or less, 7 or less, or 6 or less. The active layer 13 may have a thickness greater than or equal to about 5 nm, such as greater than or equal to about 10 nm, greater than or equal to about 20 nm, or greater than or equal to about 30 nm and less than or equal to about 200 nm, such as less than or equal to about 150 nm, less than or equal to about 100 nm, less than or equal to about 90 nm, less than or equal to about 80 nm, less than or equal to about 70 nm, less than or equal to about 60 nm, or less than or equal to about 50 nm. The active layer 13 may have a thickness of about 10 nm - about 150 nm, about 10 nm - about 100 nm, or about 10 nm - about 50 nm.

[0291] The electronic device 10 may further include a hole auxiliary layer 12. The hole auxiliary layer 12 is disposed between the first electrode 11 and the active layer 13. The hole auxiliary layer 12 may include a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), or a combination thereof. The hole auxiliary layer 12 may be a single-layer structure or a multi-layer structure in which adjacent layers include different components.

[0292] The highest occupied molecular orbital (HOMO) energy level of the hole auxiliary layer 12 may match the HOMO energy level of the active layer 13 to enhance the mobility of holes transferred from the hole auxiliary layer 12 to the active layer 13. For example, the hole auxiliary layer 12 may include a hole injection layer close to the first electrode 11 and a hole transport layer close to the active layer 13.

[0293] The material included in the hole auxiliary layer 12 (for example, a hole transport layer or a hole injection layer) is not particularly limited, and may include, for example, poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), polyarylamine (polyarylamine), poly(N-vinylcarbazole), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), polyaniline, polypyrrole, N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (TPD), 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), 4,4',4''-tris[phenyl(m-tolyl)amino]triphenylamine (m-MTDATA), 4,4',4''-tris(N-carbazolyl)-triphenylamine (TCTA), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), p-type metal oxides (for example, NiO, WO3, MoO3, etc.), carbon-based materials such as graphene oxide, or a combination thereof, but not limited thereto.

[0294] When an electron blocking layer (EBL) is used, the electron blocking layer (EBL) may include, for example, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), polyarylamine, poly(N-vinylcarbazole), polyaniline, polypyrrole, N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (TPD), 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), m-MTDATA, 4,4',4''-tris(N-carbazolyl)-triphenylamine (TCTA), or a combination thereof, but not limited thereto.

[0295] In the hole auxiliary layer, the thickness of each layer can be appropriately selected. For example, the thickness of each layer can be greater than or equal to about 5 nm, greater than or equal to about 10 nm, greater than or equal to about 15 nm, or greater than or equal to about 20 nm and less than or equal to about 50 nm, such as less than or equal to about 40 nm, less than or equal to about 35 nm, or less than or equal to about 30 nm, but not limited thereto.

[0296] The electron assisting layer 14 can be disposed between the active layer 13 and the second electrode 15. The electron assisting layer 14 can include, for example, an electron injection layer (EIL) that promotes electron injection, an electron transport layer (ETL) that promotes electron transport, a hole blocking layer (HBL) that blocks hole movement, or a combination thereof. For example, the electron injection layer can be disposed between the electron transport layer and the cathode. For example, the hole blocking layer (HBL) can be disposed between the active layer and the electron transport (injection) layer, but is not limited thereto. For example, the thickness of each layer can be greater than or equal to about 1 nm and less than or equal to about 500 nm, but is not limited thereto. The electron injection layer can be an organic layer formed by vapor deposition, and the electron transport layer can include inorganic oxide nanoparticles.

[0297] The electron transport layer (ETL) can include, for example, 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA), bathocuproine (BCP), tris[3-(3-pyridyl)- yl]borane (3TPYMB), LiF, tris(8-hydroxyquinoline)aluminum (Alq3), tris(8-hydroxyquinoline)gallium (Gaq3), tris(8-hydroxyquinoline)indium (Inq3), bis(8-hydroxyquinoline)zinc (Znq2), bis(2-(2-hydroxyphenyl)benzothiazole)zinc (Zn(BTZ)2), bis(10-hydroxybenzo[h]quinoline)beryllium (BeBq2), 8-(4-(4,6-bis(naphthalen-2-yl)-1,3,5-triazin-2-yl)phenyl)quinolone (ET204), lithium 8-hydroxyquinolate (Liq), n-type metal oxides (e.g., ZnO, HfO2, etc.), or a combination thereof, but is not limited thereto.

[0298] In addition, the electron transport layer (ETL) can include a plurality of nanoparticles. The nanoparticles can include a zinc-containing metal oxide such as zinc oxide, zinc magnesium oxide, or a combination thereof. The metal oxide can include Zn 1-x M xO (wherein, M is Mg, Ca, Zr, W, Li, Ti, Y, Al, or a combination thereof, and 0 ≤ x ≤ 0.5). In the chemical formula, x can be greater than or equal to about 0.01 and less than or equal to about 0.3, such as less than or equal to about 0.25, less than or equal to about 0.2, or less than or equal to about 0.15. The absolute value of the lowest unoccupied molecular orbital (LUMO) of the quantum dots included in the active layer can be less than the absolute value of the LUMO of the metal oxide. The average size of the nanoparticles can be greater than or equal to about 1 nm, such as greater than or equal to about 1.5 nm, greater than or equal to about 2 nm, greater than or equal to about 2.5 nm, or greater than or equal to about 3 nm and less than or equal to about 10 nm, less than or equal to about 9 nm, less than or equal to about 8 nm, less than or equal to about 7 nm, less than or equal to about 6 nm, or less than or equal to about 5 nm.)

[0299] The hole blocking layer (HBL) can include, for example, 1,4,5,8-naphthalene-tetracarboxylic dianhydride (NTCDA), bathocuproine (BCP), tris[3-(3-pyridyl)- yl]borane (3TPYMB), LiF, Alq3, Gaq3, Inq3, Znq2, Zn(BTZ)2, BeBq2, or a combination thereof, but is not limited thereto.

[0300] Each thickness of the electron assisting layer 14 (such as an electron injection layer, an electron transport layer, or a hole blocking layer) can be greater than or equal to about 5 nm, greater than or equal to about 6 nm, greater than or equal to about 7 nm, greater than or equal to about 8 nm, greater than or equal to about 9 nm, greater than or equal to about 10 nm, greater than or equal to about 11 nm, greater than or equal to about 12 nm, greater than or equal to about 13 nm, greater than or equal to about 14 nm, greater than or equal to about 15 nm, greater than or equal to about 16 nm, greater than or equal to about 17 nm, greater than or equal to about 18 nm, greater than or equal to about 19 nm, or greater than or equal to about 20 nm and less than or equal to about 120 nm, less than or equal to about 110 nm, less than or equal to about 100 nm, less than or equal to about 90 nm, less than or equal to about 80 nm, less than or equal to about 70 nm, less than or equal to about 60 nm, less than or equal to about 50 nm, less than or equal to about 40 nm, less than or equal to about 30 nm, or less than or equal to about 25 nm, but is not limited thereto.

[0301] Reference Figure 6B, the device according to an embodiment may have a normal structure. The electroluminescent device 200 may include an anode 10 disposed on a transparent substrate 100 and a cathode 50 facing the anode 10. The anode 10 may include a transparent electrode based on a metal oxide, and the cathode 50 facing the anode 10 may include a conductive metal having a low work function. For example, the anode may include an indium tin oxide (ITO, work function of about 4.6 electron volts (eV) - about 5.1 eV) electrode, and the cathode 50 may include an electrode containing magnesium (Mg, work function of about 3.66 eV), aluminum (Al, work function of about 4.28 eV), or a combination thereof. In addition, a hole assisting layer 20 may be disposed between the anode 10 and the quantum dot active layer 30. The hole assisting layer 20 may include a hole injection layer, a hole transport layer, or a combination thereof. The hole injection layer may be disposed near the anode 10 and the hole transport layer may be disposed near the quantum dot active layer. In addition, an electron assisting layer 40 may be disposed between the quantum dot active layer 30 and the cathode 50. The electron assisting layer 40 may include an electron injection layer, an electron transport layer, or a combination thereof. The electron injection layer may be disposed near the cathode 50 and the electron transport layer may be disposed near the quantum dot active layer 30.

[0302] Reference Figure 6C , the device according to an embodiment may have an inverted structure. The inverted electroluminescent device 300 may include a cathode 50 disposed on a transparent substrate 100 and an anode 10 facing the cathode 50. The cathode 50 may include a transparent electrode based on a metal oxide, and the anode 10 facing the cathode 50 may include a conductive metal having a high work function. For example, the cathode 50 may be an indium tin oxide (ITO, work function of about 4.6 eV - 5.1 eV) electrode, and the anode 10 may be an electrode including gold (Au, work function of about 5.1 eV), silver (Ag, work function of about 4.26), aluminum (Al, work function of 4.28 eV), or a combination thereof. In addition, an electron assisting layer 40 may be disposed between the quantum dot active layer 30 and the cathode 50. The electron assisting layer 40 may include an electron injection layer, an electron transport layer, or a combination thereof. The electron injection layer may be disposed near the cathode 50 and the electron transport layer may be disposed near the quantum dot active layer 30. The electron assisting layer 40 may include, for example, a metal oxide in the electron transport layer, such as crystalline Zn oxide or an n-type doped metal oxide. In addition, a hole assisting layer 20 may be disposed between the anode 10 and the quantum dot active layer 30. The hole assisting layer 20 may include a hole injection layer, a hole transport layer, or a combination thereof. The hole injection layer may be disposed near the anode 10, and the hole transport layer may be disposed near the quantum dot active layer 30. The hole transport layer may include TFB, PVK, or a combination thereof, and the hole injection layer may include MoO3 or other p-type metal oxides.

[0303] In the electroluminescent device, light of a certain wavelength generated in the active layer 30 is emitted to the outside through the light-transmitting electrode and the transparent substrate. For example, referring to Figure 6B or Figure 6C , when a metal-oxide-based transparent electrode (e.g., indium tin oxide (ITO)) serving as a light-transmitting electrode is applied to the anode 10, the light formed in the active layer is emitted to the outside through the anode 10 and the transparent substrate 100. Referring to Figure 6B or Figure 6C , when a metal-oxide-based transparent electrode (e.g., indium tin oxide (ITO)) serving as a light-transmitting electrode is applied to the cathode 50, the light formed in the active layer is emitted to the outside through the cathode 50 and the transparent substrate 100.

[0304] The above-described electronic device can be manufactured by a suitable method. For example, the electroluminescent device can be manufactured as follows: a hole-assist layer (or an electron-assist layer) is formed on a substrate on which an electrode is formed, an active layer including quantum dots (e.g., a pattern of the above-described quantum dots) is formed, and an electron-assist layer (or a hole-assist layer) and an electrode are formed. The electrode, the hole-assist layer, and the electron-assist layer can each be independently formed by a suitable method, and can be formed, for example, by vapor deposition or coating, but there is no particular limitation.

[0305] Hereinafter, the embodiments will be described in more detail with reference to examples. However, they are exemplary examples of the present disclosure, and the present disclosure is not limited thereto.

[0306] Examples

[0307] Analysis methods

[0308] 1. Photoluminescence analysis

[0309] The photoluminescence (PL) spectrum of the manufactured nanocrystals was obtained using a Hitachi F-7000 spectrometer.

[0310] 2. Ultraviolet (UV) spectrometry analysis

[0311] UV spectrometry analysis was performed using an Agilent Cary 5000 spectrometer.

[0312] 3. Inductively coupled plasma-atomic emission spectrometry (ICP-AES) analysis

[0313] Inductively coupled plasma-atomic emission spectrometry (ICP-AES) analysis was performed using a Shimadzu ICPS-8100.

[0314] 4. X-ray photoelectron spectroscopy (XPS) analysis

[0315] X-ray photoelectron spectroscopy analysis was performed using a Quantum 2000 manufactured by Physical Electronics.

[0316] 5. Transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) analysis

[0317] TEM-EDX analysis was performed using a TGA Q5000 V3.17 Build 265.

[0318] Unless otherwise specifically stated, the synthesis was carried out under an inert gas atmosphere (or nitrogen flow conditions).

[0319] Example 1:

[0320] 1. Selenium and tellurium were separately dispersed in trioctylphosphine (TOP) to obtain a 0.4 molar concentration (M) Se / TOP stock solution and a 0.5 M Te / TOP stock solution. Then, a mixed solution was prepared including the Te / TOP stock solution, an organic ligand including oleylamine, and lithium aluminum hydride.

[0321] In a 300 milliliter (mL) reaction flask, 0.9 mmol of zinc acetate was dissolved in octadecene and oleic acid was added. The reaction mixture (flask) was heated under vacuum at 120 °C. After 1 hour at 120 °C, the atmosphere in the flask was replaced with an inert gas (nitrogen), and the reaction flask was heated to 300 °C.

[0322] The Se / TOP stock solution and the mixed solution were injected into the heated reaction flask to carry out a core formation reaction. The reaction time for core formation was about 2 minutes.

[0323] The reaction mixture was cooled to room temperature, then acetone was added to promote the formation of a precipitate, and the precipitate was separated by centrifugation to provide ZnTe x Se 1-x core (x = about 0.6, average diameter: about 3.2 nanometers (nm), hereinafter simply referred to as ZnTeSe core). Then the ZnTeSe core was dispersed in toluene.

[0324] Zinc acetate was heated in trioctylamine (TOA) in the presence of oleic acid to prepare a zinc precursor.

[0325] Tri-n-octylamine was placed in a 300 mL reaction flask and the zinc precursor and dibutylmagnesium were added thereto. Then, the obtained mixture was heated under vacuum at 120 °C for 1 hour. The atmosphere in the flask was replaced with an inert atmosphere (nitrogen), and during the period when the flask was heated to a temperature greater than about 250 °C, the prepared ZnTeSe core, the Se / TOP stock solution, and optionally the zinc precursor were added and the reaction proceeded to form a ZnSe shell (Zn(Mg)Se) containing magnesium on the core to synthesize ZnTeSe / Zn(Mg)Se quantum dots.

[0326] After the reaction was completed, the flask was cooled to room temperature and acetone was added to promote the formation of a precipitate, and the ZnTeSe / Zn(Mg)Se / ZnS quantum dots were separated by centrifugation. The separated ZnTeSe / Zn(Mg)Se / ZnS quantum dots were dispersed in toluene.

[0327] The (average) size of the quantum dots was about 5.5 nm.

[0328] 2. Analysis

[0329] For the prepared ZnTeSe / Zn(Mg)Se / ZnS quantum dots, XPS analysis was performed and the results are shown in Table 1. For the prepared quantum dots, TEM-EDX analysis was performed and the results are shown in Figure 7 in.

[0330] Table 1

[0331]

[0332] The results of the XPS analysis confirmed that peaks of Mg (e.g., Mg 2p or Mg 1s) were detected, and in the atomic composition, the ratio of Mg:Zn was about 0.24:1. Peaks of Mg metal and MgO were not detected.

[0333] Example 2

[0334] A ZnTeSe core dispersion was prepared in the same manner as in Example 1.

[0335] Sulfur was dispersed in trioctylphosphine (TOP) to obtain a 1 molar concentration (M) S / TOP stock solution.

[0336] Place trioctylamine in a 250 mL reaction flask, and add the zinc precursor and dibutylmagnesium thereto. Then, heat the obtained mixture under vacuum at 120 °C for about 15 minutes to about 1 hour. Then, replace the atmosphere in the flask with an inert atmosphere (nitrogen), and then, during the period of heating the flask to the shell formation temperature (e.g., greater than about 250 °C), add the prepared ZnTeSe core, the Se / TOP stock solution, and optionally the zinc precursor and allow the reaction to proceed to form a ZnSe shell layer containing magnesium on the core. Then, at the same temperature, add the S / TOP stock solution and allow the reaction to proceed to form a ZnS shell layer. The reaction time is about 60 minutes.

[0337] After the reaction is completed, cool the flask to room temperature and add acetone to promote the formation of a precipitate. Centrifuge the precipitate to obtain ZnTeSe / Zn(Mg)Se / ZnS quantum dots. Disperse the separated quantum dots in toluene. The (average) size of the quantum dots is about 5.34 nm.

[0338] During shell formation, adjust the usage amount of the precursor relative to the core to obtain quantum dots having the composition shown in Table 2.

[0339] For the as-prepared quantum dots, perform photoluminescence spectroscopy analysis and summarize the results in Table 2. For the quantum dots, perform ICP-AES analysis and show the results in Table 2.

[0340] Comparative Example 1

[0341] Prepare ZnTeSe / ZnSe / ZnS quantum dots in the same manner as described in Example 2, except that: do not use the magnesium precursor.

[0342] For the as-prepared quantum dots, perform photoluminescence spectroscopy analysis and summarize the results in Table 2. For the quantum dots, perform ICP-AES analysis and show the results in Table 2.

[0343] Example 3

[0344] Prepare a ZnTeSe core dispersion in the same manner as in Example 1.

[0345] Prepare ZnTeSe / Zn(Mg)Se / Zn(Mg)S quantum dots in the same manner as described in Example 2, except that: add the magnesium precursor during ZnS shell formation, and change the amount of the precursor to obtain the composition described in Table 2. The (average) size of the quantum dots is about 5.72 nm.

[0346] For the as-prepared quantum dots, photoluminescence spectrometry analysis was performed and the results are summarized in Table 2. For the quantum dots, ICP-AES analysis was performed and the results are shown in Table 2.

[0347] Table 2

[0348]

[0349] The results in Table 2 confirm that, in the case of the quantum dots of the examples, the red-shift phenomenon is significantly suppressed.

[0350] Example 4

[0351] A ZnTeSe core dispersion was prepared in the same manner as in Example 1.

[0352] ZnTeSe / Zn(Mg)Se / ZnS quantum dots were prepared in the same manner as described in Example 2, except that: the amounts of the precursors were changed to obtain the compositions described in Table 3. The (average) size of the quantum dots was about 4.43 nm.

[0353] For the as-prepared quantum dots, photoluminescence spectrometry analysis was performed and the results are summarized in Table 3. For the quantum dots, ICP-AES analysis was performed and the results are shown in Table 3.

[0354] Comparative Example 2

[0355] ZnTeSe / ZnSe / ZnS quantum dots were prepared in the same manner as described in Example 4, except that: the magnesium precursor was not used.

[0356] For the as-prepared quantum dots, photoluminescence spectrometry analysis was performed and the results are summarized in Table 3. For the quantum dots, ICP-AES analysis was performed and the results are shown in Table 3.

[0357] Table 3

[0358]

[0359] Wavelength shift: Shift value relative to the core PL wavelength

[0360] QY: Quantum yield

[0361] FWHM: Full width at half maximum

[0362] VD: Valley depth

[0363] The results in Table 3 confirm that, compared with the quantum dots of Comparative Example 2, the quantum dots of Example 4 exhibit significantly improved optical properties.

[0364] While the present disclosure has been described in connection with what is presently considered to be practical example embodiments, it will be understood that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A quantum dot, comprising: a core including a first semiconductor nanocrystal, and a semiconductor nanocrystal shell disposed on the core, wherein the first semiconductor nanocrystal includes a first zinc chalcogenide comprising zinc, tellurium, and selenium, the semiconductor nanocrystal shell includes a first shell layer disposed on the core and a second shell layer disposed on the first shell layer, the first shell layer includes a second semiconductor nanocrystal and the second shell layer includes a third semiconductor nanocrystal having a composition different from that of the second semiconductor nanocrystal, the second semiconductor nanocrystal includes zinc, selenium, and optionally sulfur, and the third semiconductor nanocrystal includes zinc and sulfur, the second semiconductor nanocrystal includes magnesium, or the third semiconductor nanocrystal includes magnesium, or both the second semiconductor nanocrystal and the third semiconductor nanocrystal include magnesium, in the quantum dot, the molar ratio of tellurium to selenium is greater than or equal to 0.1:1, the quantum dot does not include cadmium, the quantum dot is configured to emit green light, the green light has a maximum emission peak wavelength in the range of 480 nanometers to 560 nanometers, and the maximum emission peak of the quantum dot has a full width at half maximum less than or equal to 45 nanometers.

2. The quantum dot according to claim 1, wherein in the quantum dot, the molar ratio of magnesium to tellurium is greater than or equal to 1:1 and less than or equal to 10:

1.

3. The quantum dot according to claim 1, wherein in the quantum dot, the molar ratio of tellurium to selenium is greater than or equal to 0.15:

1.

4. The quantum dot according to claim 1, wherein in the quantum dot, the molar ratio of magnesium to tellurium is greater than or equal to 0.001:1 and less than or equal to 10:

1.

5. The quantum dot according to claim 1, wherein in the quantum dot, the molar ratio of magnesium to tellurium is greater than 1:

1.

6. The quantum dot according to claim 1, wherein the quantum dot further includes an additional metal, and the additional metal includes an alkali metal, aluminum, or a combination thereof, and the alkali metal is lithium, sodium, potassium, cesium, rubidium, or a combination thereof.

7. The quantum dot according to claim 6, wherein in the quantum dot, the molar ratio of the alkali metal to tellurium is greater than or equal to 0.01:

1.

8. The quantum dot according to claim 1, wherein the quantum dot does not include indium phosphide, gallium phosphide, or a combination thereof.

9. The quantum dot according to claim 1, wherein in the quantum dot, the molar ratio of magnesium to tellurium is greater than or equal to 2:1 and less than or equal to 10:

1.

10. The quantum dot according to claim 1, wherein in the quantum dot, the molar ratio of magnesium to tellurium is greater than or equal to 3:1 and less than or equal to 7:

1.

11. The quantum dot according to claim 1, wherein the quantum dot exhibits a quantum efficiency greater than or equal to 60%.

12. The quantum dot according to claim 1, wherein the quantum dot has a size greater than or equal to 4.5 nanometers and less than or equal to 7 nanometers.

13. The quantum dot according to claim 1, wherein in the quantum dot, the molar ratio of sulfur to selenium is greater than or equal to 0.1:1; or The molar ratio of the sum of sulfur and selenium to tellurium is less than or equal to 15:1; or The molar ratio of tellurium to selenium is less than or equal to 4:1; or The molar ratio of sulfur to zinc is less than or equal to 0.95:1; or The molar ratio of tellurium to sulfur is greater than 0.12:

1.

14. The quantum dot according to claim 1, wherein the quantum dot comprises an organic ligand and the organic ligand comprises RCOOH, RNH2, R2NH, R3N, RSH, RH2PO, R2HPO, R3PO, RH2P, R2HP, R3P, ROH, RCOOR', RHPO(OH), RPO(OH)2, R2POOH, a polymer-type organic ligand, or a combination thereof, wherein R and R' are the same or different and each independently is a substituted or unsubstituted C1-C40 aliphatic hydrocarbon group, a substituted or unsubstituted C6-C40 aromatic hydrocarbon group, or a combination thereof.

15. A method for manufacturing the quantum dot according to any one of claims 1-14, comprising: Preparing particles comprising the core; and Reacting a zinc precursor and a chalcogen precursor in a first organic solvent in the presence of the particles comprising the core and a first organic ligand at a shell-forming reaction temperature to form the semiconductor nanocrystal shell on the particles comprising the core to manufacture the quantum dot; wherein the method further comprises adding a magnesium precursor to the reaction system during the formation of the shell.

16. The method according to claim 15, wherein the magnesium precursor comprises magnesium carboxylate, alkylated magnesium, or a combination thereof.

17. A quantum dot composite, comprising a matrix, and a plurality of quantum dots dispersed in the matrix, wherein the plurality of quantum dots comprises the quantum dot according to any one of claims 1-14.

18. A display device, comprising a light-emitting element, wherein the light-emitting element comprises a plurality of core-shell quantum dots, and the plurality of core-shell quantum dots comprises the quantum dot according to any one of claims 1-14.

19. An electronic device, comprising: a first electrode and a second electrode having opposite surfaces to each other, and an active layer disposed between the first electrode and the second electrode, the active layer comprising a plurality of quantum dots, and the plurality of quantum dots comprises the quantum dot according to any one of claims 1-14.

20. A quantum dot composition, comprising: the quantum dot according to any one of claims 1-14; an organic solvent, a liquid carrier, or a combination thereof; and optionally a monomer, a dispersant, or a combination thereof.

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