Quantum dot, method for manufacturing the same, and electroluminescent device and electronic device comprising the same

Abstract

Disclosed are quantum dots, methods for manufacturing the same, and electroluminescent devices and electronic devices comprising the same, wherein the quantum dots include: a core including a first semiconductor nanocrystal, and a semiconductor nanocrystal shell disposed on the core, wherein the composition of the semiconductor nanocrystal shell is different from the composition of the first semiconductor nanocrystal. The quantum dots do not include cadmium, the semiconductor nanocrystal shell includes zinc chalcogenide, the zinc chalcogenide includes selenium, tellurium, sulfur, or a combination thereof, and the quantum dots further include alkaline alkaline earth metals.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefits of Korean Patent Application No. 10-2020-0098730 filed in the Korean Intellectual Property Office on August 6, 2020, and all rights arising therefrom, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] Disclosed are quantum dots and electronic devices (devices) comprising the quantum dots. Background Art

[0004] Unlike bulk (bulk) materials, the physical properties (e.g., band gap energy) 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 of nanometer size. Because semiconductor nanocrystal particles have relatively small sizes, the nanocrystal particles have a large surface area per monomer volume, and thus, the particles present a quantum confinement effect and will have properties different from bulk materials of the same chemical composition. Quantum dots can absorb energy from excitation sources such as light or applied current, and when relaxed to the ground state, quantum dots emit light energy corresponding to the band gap energy of quantum dots. In the wet chemical method for making quantum dots, organic compounds such as ligands / coordinating solvents can be coordinated on the surface of nanocrystals, such as being bonded to the surface of nanocrystals, to control crystal growth. Summary of the invention

[0005] Embodiments provide cadmium-free semiconductor nanocrystal particles that can emit light of a desired wavelength (eg, blue light) with improved efficiency.

[0006] Embodiments provide methods of making the cadmium-free semiconductor nanocrystal particles.

[0007] Embodiments provide electronic devices such as display devices including the aforementioned cadmium-free semiconductor nanocrystal particles.

[0008] In an embodiment, a quantum dot (or multiple quantum dots) includes: a core including a first semiconductor nanocrystal, and a semiconductor nanocrystal shell disposed on the core, the composition of the semiconductor nanocrystal shell being different from the composition of the first semiconductor nanocrystal, wherein the quantum dot does not include cadmium, wherein the semiconductor nanocrystal shell includes zinc chalcogenide, the zinc chalcogenide includes selenium, tellurium, sulfur, or a combination thereof, and the quantum dot further includes an alkaline earth metal.

[0009] The quantum dots or the first semiconductor nanocrystals may not include indium phosphide.

[0010] The quantum dots or the first semiconductor nanocrystals may not include Group III-V compounds.

[0011] The first semiconductor nanocrystals may include zinc, tellurium, and selenium.

[0012] In the quantum dots, a molar ratio of tellurium to selenium may be greater than 0:1 and less than or equal to about 0.1:1.

[0013] The alkaline earth metal may include barium, strontium, magnesium, calcium, or a combination thereof.

[0014] The alkaline earth metal may be present in the semiconductor nanocrystal shell.

[0015] The semiconductor nanocrystal shell may include the alkaline earth metal.

[0016] The core may not include the alkaline earth metal.

[0017] In the quantum dot, an amount of the alkaline earth metal may be greater than or equal to about 0.001 mol and less than or equal to 1 mol per 1 mol of zinc.

[0018] In the quantum dot, an amount of the alkaline earth metal may be greater than or equal to about 0.003 mol based on one mol of zinc.

[0019] In the quantum dot, the amount of the alkaline earth metal may be greater than or equal to about 0.01 mol based on 1 mol of zinc.

[0020] The quantum dots may include barium sulfide, calcium sulfide, magnesium sulfide, calcium selenide, barium selenide, barium zinc selenide (barium zinc selenide), calcium zinc selenide (calcium zinc selenide), magnesium zinc selenide (magnesium zinc selenide), or a combination thereof.

[0021] The semiconductor nanocrystal shell may include a first shell layer disposed on the core (e.g., directly on the core) and a second shell layer disposed on the first shell layer (e.g., directly 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 that is different from the second semiconductor nanocrystal (or has a different composition than the second semiconductor nanocrystal).

[0022] The second semiconductor nanocrystals may include zinc and selenium, and optionally sulfur, and the third semiconductor nanocrystals may include sulfur, and optionally zinc, and the second semiconductor nanocrystals, the third semiconductor nanocrystals, or a combination thereof may include the alkaline earth metal.

[0023] The second shell layer may be the outermost layer (of the semiconductor nanocrystal shell or the quantum dot), and the third semiconductor nanocrystal may include zinc sulfide, alkaline earth metal sulfide, or a combination thereof.

[0024] The second semiconductor nanocrystal may include zinc selenide. The second semiconductor nanocrystal may include alkaline earth metal zinc selenide. In an embodiment, the second semiconductor nanocrystal may not include alkaline earth metal. The second semiconductor nanocrystal may not include sulfur.

[0025] The maximum luminescence (e.g., photoluminescence) peak wavelength of the quantum dots may be less than or equal to about 480 nanometers (nm). The maximum luminescence peak wavelength of the quantum dots may be greater than or equal to about 430 nm, greater than or equal to about 440 nm, greater than or equal to about 450 nm, or greater than or equal to about 455 nm.

[0026] The average particle size of the quantum dots may be greater than or equal to about 7 nm. The average particle size of the quantum dots may be greater than or equal to about 10 nm. The average particle size of the quantum dots may be less than or equal to about 20 nm, or less than or equal to about 16 nm.

[0027] The quantum dots may have a (relative or absolute) quantum efficiency of greater than or equal to about 80%. The quantum efficiency of the quantum dots may be greater than or equal to about 85%. The quantum efficiency of the quantum dots may be greater than or equal to about 90%. The quantum efficiency of the quantum dots may be greater than or equal to about 95%.

[0028] The maximum light emission peak of the quantum dots may have a half width less than or equal to about 35 nm.

[0029] The quantum dots may include selenium and sulfur, and in the quantum dots, a molar ratio of sulfur to selenium (S:Se) may be greater than 0.05:1.

[0030] The molar ratio of sulfur to selenium (S:Se) may be greater than or equal to about 0.1:1, greater than or equal to about 0.11:1, greater than or equal to about 0.3:1, greater than or equal to about 0.5:1, greater than or equal to about 0.6:1, or greater than or equal to about 0.7:1. In the quantum dots, the molar ratio of sulfur to selenium (S:Se) may be 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 0.95:1, less than or equal to about 0.94:1, less than or equal to about 0.85:1, or less than or equal to about 0.8:1.

[0031] In an embodiment, a method of manufacturing the quantum dots comprises:

[0032] preparing a mixture (e.g., a solution or dispersion) comprising an alkaline earth metal compound (e.g., an alkaline earth metal carboxylate, an alkaline earth metal halide such as an alkaline earth metal chloride, or a combination thereof) and an organic ligand (dispersed or dissolved) in an organic solvent;

[0033] combining a particle including the core and a chalcogen precursor with the mixture; and

[0034] The mixture is heated and reacted at a reaction temperature to produce the quantum dots.

[0035] The method may further include adding a zinc precursor to the mixture, and a shell layer including a zinc alkaline earth metal chalcogenide may be formed on a particle including the core (eg, on the core) by the reaction.

[0036] The particle may further include a semiconductor nanocrystal shell layer disposed on the core, and a shell layer including zinc alkaline earth metal chalcogenide may be formed on the semiconductor nanocrystal shell layer through the reaction.

[0037] In an embodiment, an electroluminescent device includes: a first electrode and a second electrode spaced apart from each other (eg, facing each other), and a quantum dot emission layer including a plurality of quantum dots and disposed between the first electrode and the second electrode, wherein the quantum dots include the aforementioned quantum dots.

[0038] The electroluminescent device may further include a charge assist layer between the first electrode and the quantum dot emission layer, between the second electrode and the quantum dot emission layer, or between the first electrode and the quantum dot emission layer and between the second electrode and the quantum dot emission layer.

[0039] The charge assisting layer may include a charge injection layer, a charge transport layer, or a combination thereof.

[0040] The electroluminescent device may have a peak external quantum efficiency greater than or equal to about 4%.

[0041] In an embodiment, an electronic device includes the aforementioned quantum dots.

[0042] In an embodiment, an electronic device (e.g., a display device) includes a light-emitting element (e.g., a photoluminescent element) and optionally a light source, wherein the light-emitting element includes a plurality of quantum dots, the plurality of quantum dots including the aforementioned quantum dots. If present, the light source may be configured to provide incident light to the light-emitting element.

[0043] The electroluminescent device or the electronic device may include (or may be) a display device, a light emitting device, a quantum dot light emitting diode, an organic light emitting diode, a sensor, an imaging sensor, a solar cell device, or a combination thereof.

[0044] In an embodiment, the quantum dot includes: a core including ZnTeSe, and a semiconductor nanocrystal shell disposed on the core, the semiconductor nanocrystal shell including a first shell layer disposed on the core, and a second shell layer disposed on the first shell layer, wherein the semiconductor nanocrystal shell includes: ZnS and CaZnSe, BaZnSe, MgZnSe, or a combination thereof; ZnSe and BaS; or a combination thereof (for example, the first shell layer includes ZnSe and the second shell layer includes BaS, or the first shell layer includes CaZnSe, BaZnSe, MgZnSe, or a combination thereof and the second shell layer includes ZnS).

[0045] In embodiments, cadmium-free quantum dots capable of emitting light (e.g., of a desired wavelength) with improved efficiency may be provided. The quantum dots of the embodiments may be applied to, for example, various display devices, biomarkers (biosensors, bioimaging), photodetectors, solar cells, hybrid composites, etc. The quantum dots of the embodiments may exhibit improved optical properties (e.g., quantum efficiency of 90% or more) and improved stability (e.g., thermal stability). BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The above and other advantages and features of the present disclosure will become apparent by further describing exemplary embodiments thereof in detail with reference to the accompanying drawings, in which:

[0047] Figure 1A is a graph of intensity (arbitrary unit (au)) versus binding energy (electron volt (eV)), which shows the results of X-ray photoelectron spectroscopy (XPS) analysis of the quantum dots synthesized in Example 1-1.

[0048] Figure 1B The results of transmission electron microscopy-energy dispersive X-ray spectroscopy of the quantum dots prepared by Example 1-2 are shown.

[0049] Figure 2A is a schematic cross-sectional view of a quantum dot (QD) light emitting diode according to an embodiment.

[0050] Figure 2B is a schematic cross-sectional view of a quantum dot light emitting diode according to an embodiment.

[0051] Figure 2C is a schematic cross-sectional view of a quantum dot light emitting diode according to an embodiment.

[0052] Figure 3 is an exploded view of a display device according to an embodiment.

[0053] Figure 4A is a schematic cross-sectional view of a quantum dot composite pattern in a light emitting device of an embodiment.

[0054] Figure 4B is a schematic cross-sectional view of an electronic device according to an embodiment.

[0055] Figure 4C is a schematic cross-sectional view of an electronic device according to an embodiment.

[0056] Figure 5 is a schematic cross-sectional view of an electronic device (eg, a display device) according to an embodiment. DETAILED DESCRIPTION

[0057] The advantages and features of the present disclosure, and methods for achieving the same, will become apparent with reference to the following example embodiments in conjunction with the accompanying drawings attached hereto. However, the embodiments should not be construed as being 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 present invention to those skilled in the art.

[0058] Unless otherwise defined, all terms (including technical and scientific terms) used in the specification may be used with the meanings generally understood by personnel with ordinary knowledge in the art. It will be further understood that terms, such as those defined in common dictionaries, should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and may not be interpreted ideally or exaggeratedly, unless clearly defined. The terms used herein are only used for the purpose of describing specific embodiments and are not intended to be limiting.

[0059] As used herein, the singular forms "one (the indefinite article a, an)" and "the" are intended to include plural forms, including "at least one", unless the content clearly indicates otherwise. "At least one" will not be interpreted as limiting "one". "Or" means "and / or". As used herein, the term "and / or" includes any and all combinations of one or more of the relevant listed items. It will be further understood that the terms "comprising" or "including" when used in this specification indicate the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more additional features, regions, wholes, steps, operations, elements, components, and / or sets thereof.

[0060] In the accompanying drawings, the thickness of layers, films, panels, regions, etc. is exaggerated for clarity. The same reference numerals throughout the specification represent 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 may be directly on the other element or there may be intervening elements. Conversely, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0061] 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 parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings herein, the "first element", "component", "region", "layer" or "part" discussed below may be referred to as a second element, component, region, layer or part.

[0062] As used herein, "about" includes the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art taking into account the measurement in question and the errors 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, or within ±10% or ±5% relative to the stated value.

[0063] Exemplary embodiments are described herein with reference to cross-sectional views as schematic diagrams 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. Therefore, the embodiments described herein should not be construed as being limited to the specific shapes of the regions as illustrated herein, but rather include deviations in shape caused by, for example, manufacturing. For example, a region illustrated or described as flat may typically have rough and / or nonlinear features. In addition, the illustrated sharp corners may be rounded. Therefore, the regions illustrated in the figures are schematic in nature, and their shapes are not intended to illustrate the precise shapes of the regions and are not intended to limit the scope of the claims.

[0064] As used herein, when no definition is otherwise provided, "substituted" may refer to a compound or group in which a hydrogen atom is replaced by a substituent such as a C1-C30 alkyl, a C2-C30 alkenyl, a C2-C30 alkynyl, a C6-C30 aryl, a C7-C30 alkaryl, a C1-C30 alkoxyl, a C1-C30 heteroalkyl, a C3-C30 heteroalkaryl, a C3-C30 cycloalkyl, a C3-C15 cycloalkenyl, a C6-C30 cycloalkynyl, a C2-C30 heterocycloalkyl, a halogen (-F, -Cl, -Br, or -I), a hydroxyl (-OH), a nitro (-NO), or a cycloalkyl. 2 ), cyano (-CN), amino (-NRR' wherein R and R' are independently hydrogen or C1-C6 alkyl), azido (-N 3 ), amidino (-C(=NH)NH 2 ), hydrazino (-NHNH 2 ), hydrazone (=N(NH 2)), aldehyde group (-C(=O)H), carbamoyl group (-C(O)NH 2 ), thiol group (-SH), ester group (-C(=O)OR, wherein R is C1-C6 alkyl or C6-C12 aryl), carboxyl group (-COOH) or its salt (-C(=O)OM, wherein M is an organic or inorganic cation), sulfonic acid group (-SO 3 H) or its salt (-SO 3 M, where M is an organic or inorganic cation), a phosphate group (-PO 3 H 2 ) or its salt (-PO 3 MH or -PO 3 M 2 , wherein M is an organic or inorganic cation), or a combination thereof.

[0065] As used herein, when no definition is otherwise provided, a hydrocarbon or hydrocarbon group refers to a group (e.g., an alkyl, alkenyl, alkynyl, or aryl) comprising carbon and hydrogen (or consisting of carbon and hydrogen). A hydrocarbon group may be a group having a valence of 1 or greater formed by removing a hydrogen atom, e.g., at least one hydrogen atom, from an alkane, alkene, alkyne, or aromatic hydrocarbon. In a hydrocarbon group, a methylene group, e.g., at least one methylene group, may be replaced by an oxygen moiety, a carbonyl moiety, an ester moiety, -NH-, or a combination thereof.

[0066] As used herein, when no definition is otherwise provided, "aliphatic" may refer to a saturated or unsaturated straight chain or branched hydrocarbon group. The aliphatic group may be, for example, an alkyl, alkenyl, or alkynyl group.

[0067] As used herein, when no definition is otherwise provided, "alkyl" refers to a linear or branched, saturated, monovalent hydrocarbon group (methyl, ethyl, hexyl, etc.).

[0068] As used herein, when a definition is not otherwise provided, "alkenyl" refers to a straight-chain or branched monovalent hydrocarbon group having one or more carbon-carbon double bonds.

[0069] As used herein, when a definition is not otherwise provided, "alkynyl" refers to a straight-chain or branched monovalent hydrocarbon group having one or more carbon-carbon triple bonds.

[0070] As used herein, when no definition is otherwise provided, "aromatic" refers to an organic compound or group that includes an unsaturated cyclic group having delocalized π electrons, such as at least one unsaturated cyclic group having delocalized π electrons. The term encompasses both hydrocarbon aromatic compounds and heteroaromatic compounds.

[0071] As used herein, when a definition is not otherwise provided, "aryl" refers to a group formed by removing hydrogen, for example, at least one hydrogen, from an aromatic hydrocarbon (eg, phenyl or naphthyl).

[0072] As used herein, when no definition is otherwise provided, "hetero" refers to including one or more (eg, 1-3) heteroatoms of N, O, S, Si, P, or a combination thereof.

[0073] As used herein, when no definition is otherwise provided, "Group" refers to a Group of the Periodic Table.

[0074] As used herein, when no definition is otherwise provided, “Group III” may refer to Group IIIA and Group IIIB, and examples of Group III metals may be In, Ga, Tl, or a combination thereof, but are not limited thereto.

[0075] As used herein, when no definition is otherwise provided, "Group V" may include nitrogen, phosphorus, arsenic, antimony, bismuth, or a combination thereof, but is not limited thereto.

[0076] As used herein, when no definition is otherwise provided, "Group VI" may include sulfur, selenium, tellurium, or a combination thereof, but is not limited thereto.

[0077] As used herein, when no definition is otherwise provided, the expression "does not include cadmium (or other harmful heavy metals)" may refer to situations where the concentration of cadmium (or another heavy metal considered to be harmful, see below) may 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 embodiments, substantially no cadmium (or other heavy metal) may be present, or if present, the amount of cadmium (or other heavy metal) may be less than or equal to the detection limit of a given analytical tool (e.g., inductively coupled plasma atomic emission spectrometry) or as an impurity level thereof.

[0078] As used herein, when no definition is otherwise provided, the term "average" (eg, average size of quantum dots) used in the present disclosure may be a mean or a median. In an embodiment, the average may be a "mean" average.

[0079] As used herein, when no definition is provided in addition, quantum efficiency may be a relative quantum yield or an absolute quantum yield, which can be easily measured, for example, by any suitable commercially available equipment. Quantum efficiency (or quantum yield) can be measured in a solution state or a solid state (such as in a complex). In an embodiment, "quantum yield (or quantum efficiency)" may be the ratio of photons emitted by a quantum dot complex, for example, a nanostructure or a group of nanostructures to photons absorbed. In an embodiment, quantum efficiency may be measured by any suitable method. For example, quantum efficiency may be measured by an absolute method and a relative method. The absolute method directly obtains quantum yield by: detecting all sample fluorescence using an integrating sphere. In a relative method, the fluorescence intensity of a standard sample (e.g., a standard dye) may 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 may be used as standard dyes, but are not limited thereto.

[0080] The quantum yield (QY) can be easily and reproducibly determined by using commercially available equipment (eg, from Hitachi Co. Ltd or Hamamatsu Co. Ltd) and by referring to the instructions for use provided by the manufacturer.

[0081] The full width at half maximum (FWHM) and the maximum emission peak wavelength can be determined by a (photo)luminescence spectrum obtained via a spectrophotometer (or fluorescence spectrophotometer).

[0082] Semiconductor nanocrystal particles (e.g., quantum dots) can absorb light from an excitation source and can emit light corresponding to the band gap energy of the quantum dots. The band gap energy of the quantum dots can change with the size, composition, or combination thereof of the quantum dots. Semiconductor nanocrystals can be used as luminescent materials in a variety of fields such as display devices, energy devices, or bioluminescent devices.

[0083] Quantum dots with relatively enhanced photoluminescent properties may include toxic heavy metals such as cadmium (Cd), lead (Pb), mercury (Hg), or a combination thereof. Toxic heavy metals such as cadmium may cause environmental problems, health problems, or a combination thereof, and are one of the restricted elements under the Restriction of Hazardous Substances Directive (RoHS) in many countries. Therefore, the development of cadmium-free quantum dots with improved photoluminescent properties is desired.

[0084] The quantum dots of the embodiments and the method of manufacturing the quantum dots will be described in detail herein.The quantum dots of the embodiments may exhibit improved optical properties (eg, increased quantum yield) and stability (eg, thermal stability), while they may not include cadmium.

[0085] In an embodiment, a quantum dot comprises: a core comprising a first semiconductor nanocrystal, and a semiconductor nanocrystal shell disposed on the core (or at least a portion of a surface of the core) and having a composition different from that of the first semiconductor nanocrystal. The quantum dot may not include cadmium, lead, mercury, or a combination thereof. The semiconductor nanocrystal shell comprises zinc chalcogenide. The zinc chalcogenide comprises: zinc; and selenium, tellurium, sulfur, or a combination thereof.

[0086] The quantum dots or the first semiconductor nanocrystals may not include indium phosphide, gallium phosphide, or a combination thereof. The quantum dots or the first semiconductor nanocrystals may not include a III-V compound.

[0087] The quantum dot (or the core) may include tellurium in a predetermined (or defined) amount. The amount of elemental components included in the quantum dots as described herein may be measured by appropriate analytical instruments and methods (e.g., inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), etc.).

[0088] In the quantum dot of the embodiment, the core or the first semiconductor nanocrystal may include ZnTe x Se 1-x (wherein x is about 0 to about 0.2, about 0.001 to about 0.15, about 0.003 to about 0.12, about 0.004 to about 0.11, about 0.005 to about 0.1, about 0.005 to about 0.09, about 0.008 to about 0.08, about 0.009 to about 0.07, about 0.01 to about 0.06, or a combination thereof.) In the core, by increasing the amount ratio of tellurium to selenium, the maximum emission peak wavelength of the quantum dot can be increased.

[0089] In the core or the first semiconductor nanocrystal, the amount of tellurium per mole of selenium may be greater than or equal to about 0.0001 mole, greater than or equal to about 0.0005 mole, greater than or equal to about 0.001 mole, greater than or equal to about 0.002 mole, greater than or equal to about 0.003 mole, greater than or equal to about 0.004 mole, greater than or equal to about 0.005 mole, greater than or equal to about 0.006 mole, greater than or equal to about 0.007 mole, greater than or equal to about 0.008 mole, greater than or equal to about 0.009 mole, greater than or equal to about 0.01 mole, or greater than or equal to about 0.02 mole. In the core or the first semiconductor nanocrystal, the amount of tellurium per mole of selenium may be less than or equal to about 0.1 mole, less than or equal to about 0.09 mole, less than or equal to about 0.08 mole, less than or equal to about 0.07 mole, less than or equal to about 0.06 mole, less than or equal to about 0.055 mole, less than or equal to about 0.053 mole, less than or equal to about 0.05 mole, less than or equal to about 0.049 mole, less than or equal to about 0.048 mole, less than or equal to about 0.047 mole, less than or equal to about 0.046 mole, less than or equal to about 0.045 mole, less than or equal to about 0.044 mole, less than or equal to about 0.043 mole, less than or equal to about 0.042 mole, less than or equal to about 0.041 mole, or less than or equal to about 0.04 mole.

[0090] The core or the quantum dot may not include manganese, copper, or a combination thereof. The core or the first semiconductor nanocrystal may not include an alkaline earth metal.

[0091] The semiconductor nanocrystal shell includes a zinc chalcogenide. The zinc chalcogenide includes: zinc; and selenium, tellurium, sulfur, or a combination thereof. The zinc chalcogenide may include zinc selenide, zinc sulfide, zinc selenium telluride, zinc selenium sulfide, or a combination thereof.

[0092] In the quantum dots of the embodiments, the molar ratio of tellurium to selenium (Te:Se) may be less than or equal to about 0.1:1, less than or equal to about 0.09:1, less than or equal to about 0.08:1, less than or equal to about 0.07:1, less than or equal to about 0.06:1, less than or equal to about 0.05:1, less than or equal to about 0.04:1, less than or equal to about 0.03:1, less than or equal to about 0.02:1, less than or equal to about 0.015:1, or less than or equal to about 0.01:1, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis.

[0093] In the quantum dots of the embodiments, the molar ratio of tellurium to selenium may be greater than or equal to about 0.0001:1, e.g., greater than or equal to about 0.0005:1, greater than or equal to about 0.001:1, greater than or equal to about 0.0015:1, greater than or equal to about 0.002:1, greater than or equal to about 0.0025:1, greater than or equal to about 0.003:1, greater than or equal to about 0.0035:1, greater than or equal to about 0.004:1, greater than or equal to about 0.0045:1, greater than or equal to about 0.005:1, or greater than or equal to about 0.005:1. 0.055:1, greater than or equal to about 0.006:1, greater than or equal to about 0.0065:1, greater than or equal to about 0.007:1, greater than or equal to about 0.0075:1, greater than or equal to about 0.008:1, greater than or equal to about 0.0085:1, greater than or equal to about 0.009:1, greater than or equal to about 0.0095:1, greater than or equal to about 0.01:1, greater than or equal to about 0.015:1, or greater than or equal to about 0.02:1, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis.

[0094] In an embodiment, the molar ratio of tellurium to selenium may be from about 0.001:1 to about 0.1:1. In an embodiment, the molar ratio of tellurium to selenium may be from about 0.002:1 to about 0.09:1. In an embodiment, the molar ratio of tellurium to selenium may be from about 0.003:1 to about 0.08:1.

[0095] In the quantum dots of the embodiments, the molar ratio of tellurium to zinc can be less than or equal to about 0.02:1, less than or equal to about 0.019:1, less than or equal to about 0.018:1, less than or equal to about 0.017:1, less than or equal to about 0.016:1, less than or equal to about 0.015:1, less than or equal to about 0.014:1, less than or equal to about 0.013:1, less than or equal to about 0.012:1, less than or equal to about 0.011:1, less than or equal to about 0.01:1, less than or equal to about 0.009:1, less than or equal to about 0.008:1, less than or equal to about 0.007:1, less than or equal to about 0.006:1, or less than or equal to about 0.005:1, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis. In embodiments, the molar ratio of tellurium to zinc may be greater than or equal to about 0.0005:1, greater than or equal to about 0.001:1, greater than or equal to about 0.0015:1, greater than or equal to about 0.002:1, greater than or equal to about 0.0025:1, greater than or equal to about 0.003:1, or greater than or equal to about 0.0035:1.

[0096] In the quantum dots of the embodiment, the molar ratio of selenium (Se) to zinc (Zn) may be less than or equal to about 1:1, less than or equal to about 0.99:1, less than or equal to about 0.95:1, less than or equal to about 0.90:1, less than or equal to about 0.85:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, 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, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis. In the quantum dots of the embodiment, the molar ratio of selenium (Se) to zinc (Zn) 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, or greater than or equal to about 0.45:1, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis.

[0097] In the quantum dots of the embodiment, the molar ratio of sulfur to zinc (Zn) may be greater than or equal to about 0.05:1, 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 0.3:1, greater than or equal to about 0.4:1, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis. In the quantum dots of the embodiment, the molar ratio of sulfur to zinc (Zn) may be 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 0.65:1, less than or equal to about 0.6:1, less than or equal to about 0.55:1, less than or equal to about 0.5:1, less than or equal to about 0.45:1, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis.

[0098] In the quantum dots of the embodiments, the molar ratio of sulfur to selenium (S:Se) may be 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 0.95:1, less than or equal to about 0.94:1, less than or equal to about 0.93:1, less than or equal to about 0.92:1, less than or equal to about 0.91:1, less than or equal to about 0.9:1, less than or equal to about 0.89:1, less than or equal to about 0.88:1, less than or equal to about 0.87:1, less than or equal to about 0.86:1, less than or equal to about 0.85:1, less than or equal to about 0.84:1, less than or equal to about 0.83:1, less than or equal to about 0.82:1, less than or equal to about 0.81:1, less than or equal to about 0.80:1, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis. In the quantum dots of the embodiments, the molar ratio of sulfur to selenium (S:Se) may be greater than or equal to about 0.1:1, greater than or equal to about 0.11:1, greater than or equal to about 0.12:1, greater than or equal to about 0.13:1, greater than or equal to about 0.14:1, greater than or equal to about 0.15:1, greater than or equal to about 0.2:1, greater than or equal to about 0.3:1, greater than or equal to about 0.4:1, greater than or equal to about 0.5:1, greater than or equal to about 0.6:1, greater than or equal to about 0.7:1, greater than or equal to about 0.71:1, greater than or equal to about 0.72:1, or greater than or equal to about 0.73:1, for example, as determined by inductively coupled plasma atomic emission spectrometry analysis.

[0099] The quantum dots of an embodiment further include an alkaline earth metal.

[0100] The inventors have found that quantum dots having a zinc chalcogenide-based core and not including cadmium can emit light of a desired wavelength (e.g., in the green or blue range), for example, light of a wavelength that can be difficult to emit by quantum dots based on group III-V compounds. The inventors have also found that although the introduction of an inorganic shell (e.g., a zinc chalcogenide shell such as a ZnSe, ZnS, or ZnSeS shell) on a zinc chalcogenide core (e.g., a ZnSeTe core) can improve the luminescence efficiency of the quantum dots, the extent of such improvement may be very limited or insufficient. Although not wishing to be bound by any theory, it is believed that while a III-V compound (e.g., InP) based core may have a relatively large difference in band gap energy with a zinc chalcogenide shell, a zinc chalcogenide core may have a relatively small or insufficient difference in band gap energy with a zinc chalcogenide shell (see Table 1), and thus, in the case of zinc chalcogenide core / zinc chalcogenide shell quantum dots, it may be difficult to control / adjust the offset between the conduction bands of a given core and shell material and achieve a desired band alignment therebetween, e.g., sufficiently large as in indium phosphide quantum dots. Thus, without wishing to be bound by any theory, it is believed that the offset band alignment of the final quantum dot may not contribute sufficiently to the improvement in quantum yield or may even have an adverse effect thereon.

[0101] In an embodiment, the quantum dot includes a semiconductor nanocrystal shell further comprising an alkaline earth metal, and exhibits improved quantum efficiency. Although not wishing to be bound by any theory, since the alkaline earth metal included in the semiconductor nanocrystal shell has a valence substantially the same as zinc, chalcogenides are easily formed in the semiconductor nanocrystal shell, and the alkaline earth chalcogenide thus formed may have a lattice constant similar to that of zinc chalcogenide. In an embodiment, the difference between the lattice constant of the alkaline earth chalcogenide thus formed and the lattice constant of the zinc chalcogenide may be less than or equal to about 0.1, less than or equal to about 0.09, or less than or equal to about 0.08. In addition, without wishing to be bound by any theory, it is believed that since the alkaline earth chalcogenide may provide a wider, for example, larger band gap energy, the alkaline earth chalcogenide included in the shell may allow for relatively sufficient shell band gap adjustment, and the shell providing an adjusted band gap arrangement may further contribute to improving the quantum confinement effect of a given quantum dot.

[0102] Table 1

[0103] Material Band Gap Energy InP 1.34eV ZnSe 2.82eV ZnS 3.68eV ZnTeSe About 2.6eV MgS 6.4eV CaS 5.0eV SrS 4.5eV B S 3.9eV

[0104] The alkaline earth metal may be any one or combination of the elements beryllium, magnesium, calcium, strontium, barium, and radium occupying Group IIA(2) of the periodic table. In an embodiment, the alkaline earth metal may include barium, magnesium, strontium, calcium, or a combination thereof. In an embodiment, the alkaline earth metal may include calcium, barium, magnesium, or a combination thereof. The alkaline earth metal may be included in the semiconductor nanocrystal shell. In the quantum dots, the amount of the alkaline earth metal may be greater than or equal to about 0.0005 mol, greater than or equal to about 0.001 mol, greater than or equal to about 0.002 mol, greater than or equal to about 0.003 mol, greater than or equal to about 0.004 mol, greater than or equal to about 0.005 mol, greater than or equal to about 0.006 mol, greater than or equal to about 0.007 mol, greater than or equal to about 0.008 mol, greater than or equal to about 0.009 mol, greater than or equal to about 0.01 mol, greater than or equal to about 0.02 mol, greater than or equal to about 0.03 mol, greater than or equal to about 0.04 mol, greater than or equal to about 0.05 mol, greater than or equal to about 0.06 mol, greater than or equal to about 0.07 mol, greater than or equal to about 0.08 mol, greater than or equal to about 0.09 mol, or greater than or equal to about 0.1 mol, based on one mol of zinc.

[0105] In the quantum dot, the amount of the alkaline earth metal may be less than about 1 mole, less than or equal to about 0.9 mole, less than or equal to about 0.8 mole, less than or equal to about 0.7 mole, less than or equal to about 0.6 mole, less than or equal to about 0.5 mole, less than or equal to about 0.4 mole, less than or equal to about 0.3 mole, less than or equal to about 0.25 mole, less than or equal to about 0.2 mole, less than or equal to about 0.17 mole, less than or equal to about 0.15 mole, less than or equal to about 0.13 mole, less than or equal to about 0.12 mole, less than or equal to about 0.11 mole, less than or equal to about 0.1 mole, less than or equal to about 0.09 mole, less than or equal to about 0.08 mole, less than or equal to about 0.07 mole, or less than or equal to about 0.06 mole, based on one mole of zinc. The amount of the alkaline earth metal may be determined by XPS or ICP-AES analysis, but is not limited thereto.

[0106] The quantum dot or the semiconductor nanocrystal shell may include alkaline earth metal sulfide, alkaline earth metal selenide, or a combination thereof. The quantum dot or the semiconductor nanocrystal shell may include barium sulfide, calcium sulfide, magnesium sulfide, calcium selenide, barium zinc selenide, calcium zinc selenide, magnesium zinc selenide, or a combination thereof. In an embodiment, by including the alkaline earth metal sulfide, the quantum dot may exhibit further improved optical properties.

[0107] The semiconductor nanocrystal shell may be a multilayer shell including a plurality of layers. In the plurality of layers of the shell, adjacent layers may have semiconductor nanocrystal materials of different compositions. The semiconductor nanocrystal shell may include a first shell layer disposed on the core (e.g., directly on the core) and a second shell layer disposed on the first shell layer (e.g., directly on 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.

[0108] The second semiconductor nanocrystal may include zinc and selenium, and optionally sulfur. The second semiconductor nanocrystal may not include sulfur. The third semiconductor nanocrystal may include sulfur and optionally zinc. The second semiconductor nanocrystal, the third semiconductor nanocrystal, or a combination thereof may include the alkaline earth metal. The second shell may be the outermost shell of the shell or the quantum dot. The third semiconductor nanocrystal may include zinc sulfide, alkaline earth metal sulfide, or a combination thereof.

[0109] The second semiconductor nanocrystal may include zinc selenide. The second semiconductor nanocrystal may include alkaline earth metal zinc selenide. The first shell layer or the second semiconductor nanocrystal may not include sulfur. The second semiconductor nanocrystal may include CaZnSe, MgZnSe, BaZnSe, SrZnSe, or a combination thereof. The third semiconductor nanocrystal may include zinc sulfide or may be composed of ZnS.

[0110] In an embodiment, the second semiconductor nanocrystal may not include an alkaline earth metal. In this or other embodiments, the third semiconductor nanocrystal may include an alkaline earth metal sulfide. In an embodiment, a third shell layer may be disposed between the first shell layer and the second shell layer and may include a fourth semiconductor nanocrystal that is different from the second semiconductor nanocrystal and the third semiconductor nanocrystal. The fourth semiconductor nanocrystal may include (or may consist of): zinc sulfide, zinc selenide sulfide, or a combination thereof.

[0111] In an embodiment, the shell or the shell layers in the multi-layer shell may each include a gradient alloy having a composition that changes in a radial direction, such as a radial direction from the core of the quantum dot toward the outermost surface. In an embodiment, the amount of sulfur in the semiconductor nanocrystal shell may increase toward the surface of the quantum dot. For example, in the shell, the amount of sulfur may increase in a direction away from the core, such as in a direction from the core of the quantum dot toward the outermost surface.

[0112] The quantum dot may have any suitable shape. For example, the quantum dot may have a spherical shape, a polyhedral shape, a multi-pod shape, or a combination thereof. In an embodiment, the quantum dot may have a multi-pod shape. The multi-pod shape may have at least two (e.g., at least three or at least four) branch portions and a valley portion therebetween.

[0113] The size (or average size) of the core may be greater than or equal to about 2 nm, greater than or equal to about 3 nm, or greater than or equal to about 4 nm. The average size of the core may be less than or equal to about 6 nm, for example, less than or equal to about 5 nm. In an embodiment, the quantum dot may have a size (or average size) greater than or equal to about 10 nm, for example, greater than or equal to about 11 nm, or greater than or equal to about 12 nm. Herein, the size of a quantum dot may be a diameter (or if the quantum dot is not a sphere, a diameter calculated by assuming a sphere from an electron microscope two-dimensional image of the quantum dot). The size (or average size) of the semiconductor nanocrystals may be less than or equal to about 50 nm, for example, 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, or less than or equal to about 16 nm.

[0114] The thickness of the semiconductor nanocrystal shell can be appropriately selected. The semiconductor nanocrystal shell (or the first shell layer, the second shell layer, the third shell layer, or a combination thereof) can have a thickness of about 0.3 nm or more, about 0.4 nm or more, about 0.5 nm or more, about 0.6 nm or more, about 0.7 nm or more, about 0.8 nm or more, about 0.9 nm or more, about 1 nm or more, about 1.1 nm or more, about 1.2 nm or more, about 1.3 nm or more, about 1.4 nm or more, about 1.5 nm or more, about 1.6 nm or more, about 1.7 nm or more, about 1.8 nm or more, about 1.9 nm or more, or about 2 nm or more. The thickness of the semiconductor nanocrystal shell (or the first shell layer, the second shell layer, the third shell layer, or a combination thereof) may be less than or equal to about 4 nm, less than or equal to about 3 nm, less than or equal to about 2.5 nm, less than or equal to about 2 nm, less than or equal to about 1.9 nm, less than or equal to about 1.8 nm, less than or equal to about 1.7 nm, less than or equal to about 1.6 nm, or less than or equal to about 1.5 nm.

[0115] The maximum luminescence (e.g., photoluminescence) peak wavelength of the quantum dot may be less than or equal to about 580 nm. The maximum luminescence (e.g., photoluminescence) peak wavelength of the quantum dot may be less than or equal to about 480 nm. The maximum luminescence peak wavelength of the quantum dot may be greater than or equal to about 430 nm, greater than or equal to about 440 nm, greater than or equal to about 450 nm, or greater than or equal to about 455 nm. In an embodiment, the quantum dot may emit light having a maximum luminescence peak wavelength greater than or equal to about 430 nm (e.g., greater than or equal to about 440 nm, greater than or equal to about 445 nm, greater than or equal to about 447 nm, greater than or equal to about 448 nm, greater than or equal to about 449 nm, or greater than or equal to about 450 nm) and less than or equal to about 480 nm (e.g., less than or equal to about 475 nm, less than or equal to about 470 nm, less than or equal to about 465 nm, less than or equal to about 460 nm, or less than or equal to about 455 nm). The blue light may have a light emission peak wavelength in the range of about 450 nm to about 480 nm, about 460 nm to about 475 nm, about 460 nm to about 470 nm, or a combination thereof.

[0116] The quantum dots may have a (relative or absolute) quantum efficiency of greater than or equal to about 80%. The quantum efficiency of the quantum dots may be greater than or equal to about 85%. The quantum efficiency of the quantum dots may be greater than or equal to about 90%. The quantum efficiency of the quantum dots may be greater than or equal to about 95%.

[0117] The maximum luminescent peak of the quantum dot may have a half width of less than or equal to about 37 nm, less than or equal to about 36 nm, or less than or equal to about 35 nm. The half width may be 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, or less than or equal to about 28 nm.

[0118] The quantum dots may exhibit improved stability (e.g., thermal stability). If the quantum dots may be formed into a film having a predetermined thickness (e.g., a three-layer quantum dot) and then subjected to a heat treatment at about 150° C. for about 30 minutes, the quantum dots (or their film) may maintain a luminous efficiency of at least about 60%, at least about 70%, at least about 80%, or at least about 90% of its initial efficiency.

[0119] In an embodiment, a method of manufacturing the quantum dots comprises:

[0120] preparing a mixture (solution or dispersion) comprising an alkaline earth metal compound (e.g., an alkaline earth metal carboxylate, an alkaline earth metal halide such as an alkaline earth metal chloride, or a combination thereof) and an organic ligand (dispersed or dissolved) in an organic solvent;

[0121] combining a particle including the core and a chalcogen precursor with the mixture; and

[0122] The mixture is heated and reacted at a reaction temperature.

[0123] The alkaline earth metal precursor may include alkaline earth metal acetylacetonate, alkaline earth metal carboxylate, alkaline earth metal chloride, or a combination thereof.

[0124] In an embodiment, the core can be obtained by preparing a zinc precursor mixture, such as a solution, including a zinc precursor and an organic ligand; preparing a selenium precursor and a tellurium precursor; heating the zinc precursor mixture to a first reaction temperature (core formation temperature) and adding the selenium precursor and the tellurium precursor thereto, optionally together with the organic ligand, to carry out a reaction therebetween.

[0125] In an embodiment, the core comprising the first semiconductor nanocrystal can be obtained by: preparing a zinc precursor mixture, such as a solution, comprising a zinc precursor and an organic ligand; preparing a selenium precursor and a tellurium precursor; heating the zinc precursor mixture, such as a solution, to a first reaction temperature and adding the selenium precursor and the tellurium precursor thereto, optionally together with an organic ligand, to carry out a reaction therebetween.

[0126] In an embodiment, the particle including the core may further include a semiconductor nanocrystal shell disposed on the core (e.g., a first shell layer including a second semiconductor nanocrystal and a third shell layer optionally including a fourth semiconductor nanocrystal), and by reaction, a layer including an alkaline earth metal sulfide may be formed on the first shell layer or the third shell layer. The second semiconductor nanocrystal and the fourth semiconductor nanocrystal may each independently include a zinc sulfide (e.g., ZnSe, ZnSeS, ZnS, or a combination thereof). The details of the formation of the first shell layer and the third shell layer may refer to the details of the formation of the semiconductor nanocrystal shell (e.g., reaction temperature, conditions, or a combination thereof and precursors) to be described in detail herein.

[0127] The method may further include adding a zinc precursor to the mixture, and a shell layer including zinc alkaline earth metal chalcogenide may be formed on a particle including the core (or on the core) by the reaction.

[0128] The particle may further include a semiconductor nanocrystal shell layer disposed on the core, and a shell layer including zinc alkaline earth metal chalcogenide may be formed on the semiconductor nanocrystal shell by the reaction.

[0129] After the formation of the layer including the alkaline earth metal chalcogenide or the zinc alkaline earth metal chalcogenide, a zinc precursor and a chalcogen precursor may be further added, and the reaction therebetween is performed to provide an outermost layer (e.g., a ZnS layer) including zinc chalcogenide on the layer including the alkaline earth metal chalcogenide or the zinc alkaline earth metal chalcogenide. The details of the formation of the outermost layer may refer to the details of the formation of the semiconductor nanocrystal shell (e.g., reaction temperature, other conditions, or a combination thereof, and precursors) to be described in detail herein.

[0130] In an embodiment, the zinc precursor may include Zn powder, ZnO, an alkylated Zn compound (e.g., C2-C30 alkyl (e.g., dialkyl) zinc such as dimethyl zinc, diethyl zinc), Zn alkoxide (e.g., zinc ethoxide), Zn carboxylate (e.g., zinc acetate or aliphatic zinc carboxylate such as long-chain aliphatic zinc carboxylate such as zinc oleate), Zn nitrate, Zn perchlorate, Zn sulfate, Zn acetylacetonate, Zn halide (e.g., zinc chloride), Zn cyanide, Zn hydroxide, zinc carbonate, zinc peroxide, or a combination thereof. Examples of the zinc precursor 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.

[0131] The selenium precursor may include selenium-trioctylphosphine (Se-TOP), selenium-tributylphosphine (Se-TBP), selenium-triphenylphosphine (Se-TPP), selenium-diphenylphosphine (Se-DPP), or a combination thereof, but is not limited thereto.

[0132] The tellurium precursor may include tellurium-trioctylphosphine (Te-TOP), tellurium-tributylphosphine (Te-TBP), tellurium-triphenylphosphine (Te-TPP), tellurium-diphenylphosphine (Te-DPP), or a combination thereof, but is not limited thereto.

[0133] The sulfur precursor may include hexanethiol, octylthiol, decanethiol, dodecanethiol, hexadecylthiol, mercaptopropylsilane, sulfur-trioctylphosphine (S-TOP), sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP), sulfur-trioctylamine (S-TOA), sulfur-octadecene (S-ODE), bis(trimethylsilylmethyl)sulfide, ammonium sulfide, sodium sulfide, or a combination thereof.

[0134] The alkaline earth metal acetylacetonate may include barium acetylacetonate, calcium acetylacetonate, magnesium acetylacetonate, strontium acetylacetonate, or a combination thereof.

[0135] The alkaline earth metal carboxylate may include barium carboxylate such as barium oleate, barium stearate, barium laurate, etc., calcium carboxylate such as calcium oleate, calcium stearate, or calcium laurate, magnesium carboxylate such as magnesium oleate, magnesium stearate, or magnesium laurate, strontium carboxylate such as strontium oleate, strontium stearate, or strontium laurate, or a combination thereof. The alkaline earth metal chloride may include barium chloride, calcium chloride, magnesium chloride, strontium chloride, or a combination thereof.

[0136] The organic solvent may be a C6-C22 primary amine such as hexadecylamine, a C6-C22 secondary amine such as dioctylamine, a C6-C40 tertiary amine such as trioctylamine, a nitrogen-containing heterocyclic compound such as pyridine, a C6-C40 olefin such as octadecene, a C6-C40 aliphatic hydrocarbon such as hexadecane, octadecane, or squalane, an aromatic hydrocarbon substituted with a C6-C30 alkyl group such as phenyldodecane, phenyltetradecane, or phenylhexadecane, a primary, secondary, or tertiary phosphine substituted with at least one (e.g., 1, 2, or 3) C6-C22 alkyl group (e.g., trioctylphosphine), a primary, secondary, or tertiary phosphine oxide substituted with at least one (e.g., 1, 2, or 3) C6-C22 alkyl group (e.g., trioctylphosphine oxide), a C12-C22 aromatic ether such as phenyl ether or benzyl ether, or a combination thereof.

[0137] The organic ligand can coordinate, for example, bind to the surface of the nanocrystal produced, and the nanocrystal can be effectively dispersed in a liquid, for example, a solution phase. Thus, the quantum dot can include the organic ligand, for example, on its surface, for example, bound to it.

[0138] The organic ligand may include RCOOH, RNH 2 , R 2 NH, R 3 N, RSH, RH 2 PO, R 2 HPO, R 3 PO, RH 2 P.R 2 HP, R 3 P, ROH, RCOOR', RPO(OH) 2 , RHPOOH, R 2 POOH, polymeric organic ligands, or combinations thereof, wherein R and R' are the same or different and are each independently a C1-C40 (e.g., C3-C30 or C6-C24) substituted or unsubstituted aliphatic hydrocarbon group (alkyl, alkenyl, or alkynyl) or a C6-C40 substituted or unsubstituted aromatic hydrocarbon group, or a combination thereof. Two or more different organic ligands may be used.

[0139] Examples of the organic ligand may include: methyl mercaptan, ethyl mercaptan, propyl mercaptan, butyl mercaptan, pentyl mercaptan, hexyl mercaptan, octyl mercaptan, dodecanethiol, hexadecyl mercaptan, octadecyl mercaptan, or benzyl mercaptan; methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, dimethylamine, diethylamine, dipropylamine; formic acid, acetic acid, propionic acid, butyric acid, pentanoic acid, hexanoic acid, heptanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, Octadecanoic acid, oleic acid, benzoic acid, palmitic acid, or stearic acid; phosphine such as substituted or unsubstituted methyl phosphine (e.g., trimethyl phosphine, methyl diphenyl phosphine, etc.), substituted or unsubstituted ethyl phosphine (e.g., triethyl phosphine, ethyl diphenyl phosphine, etc.), substituted or unsubstituted propyl phosphine, substituted or unsubstituted butyl phosphine, substituted or unsubstituted pentyl phosphine, or substituted or unsubstituted octyl phosphine (e.g., trioctyl phosphine (TOP)); phosphine oxide such as substituted or unsubstituted methyl phosphine 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 di-hexylphosphinic acid, mono- or di-octylphosphinic acid, mono- or di-dodecylphosphinic acid, mono- or di-tetradecylphosphinic acid, mono- or di-hexadecylphosphinic acid, mono- or di-octadecylphosphinic 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; and the like, but are not limited thereto. Two or more different organic ligand compounds may be used. In an embodiment, the organic ligand compound may be RCOOH and an amine (e.g., RNH 2 , R 2 NH, R 3 N, or a combination thereof).

[0140] In the core including the first semiconductor nanocrystal, the molar ratio of tellurium to selenium can be within the range described herein. To form a core having a desired tellurium to selenium ratio, the amount of selenium precursor used to form the core can be greater than or equal to about 20 moles, such as greater than or equal to about 25 moles, greater than or equal to about 26 moles, greater than or equal to about 27 moles, greater than or equal to about 28 moles, greater than or equal to about 29 moles, greater than or equal to about 30 moles, greater than or equal to about 31 moles, greater than or equal to about 32 moles, greater than or equal to about 33 moles, greater than or equal to about 34 moles, greater than or equal to about 35 moles, greater than or equal to about 36 moles, greater than or equal to about 37 moles, greater than or equal to about 38 moles, greater than or equal to about 39 moles, or greater than or equal to about 40 moles, based on one mole of tellurium precursor. The amount of the selenium precursor may be less than or equal to about 60 mol, less than or equal to about 59 mol, less than or equal to about 58 mol, less than or equal to about 57 mol, less than or equal to about 56 mol, or less than or equal to about 55 mol, based on one mol of the tellurium precursor. Within the aforementioned amount range, a core having the aforementioned composition may be formed.

[0141] The first reaction temperature may be greater than or equal to about 200°C, for example, greater than or equal to about 210°C, greater than or equal to about 230°C, greater than or equal to about 240°C, greater than or equal to about 280°C, or greater than or equal to about 290°C; less than or equal to about 400°C, less than or equal to about 380°C, less than or equal to about 350°C, or less than or equal to about 340°C; or a combination thereof.

[0142] The reaction time for forming the core is not particularly limited and can be appropriately selected. For example, the reaction time may be greater than or equal to about 5 minutes, greater than or equal to about 10 minutes, greater than or equal to about 15 minutes, greater than or equal to about 20 minutes, greater than or equal to about 25 minutes, greater than or equal to about 30 minutes, greater than or equal to about 35 minutes, greater than or equal to about 40 minutes, greater than or equal to about 45 minutes, or greater than or equal to about 50 minutes, but is not limited thereto. For example, the reaction time may be less than or equal to about 2 hours, but is not limited thereto. By controlling the reaction time, the size of the core can be controlled.

[0143] In an embodiment, the particles included in the mixture may further include a semiconductor nanocrystal shell (e.g., a first shell layer, etc.) on the core, and in this case, the method further includes conducting a reaction between the zinc precursor and the chalcogen precursor (e.g., a selenium precursor, a sulfur precursor, or a combination thereof) in the presence of the core to prepare the particles.

[0144] The reaction conditions (e.g., reaction time and temperature) for forming the (semiconductor nanocrystal) shell layer may be appropriately selected in consideration of the desired composition of the shell (e.g., multilayer shell). In an embodiment, the solvent and optionally the organic ligand may be heated and treated, for example, under vacuum at a predetermined temperature (e.g., at a temperature of about 100° C. or more), and the atmosphere inside the reaction vessel may be changed to an inert gas, and then heated at a predetermined temperature (e.g., at a temperature of about 100° C. or more, about 200° C. or more, or about 300° C. or more). The core may then be added, and the shell precursor may be added sequentially or simultaneously to the reaction vessel, and the resulting mixture may be heated to a predetermined reaction temperature to carry out the reaction.

[0145] Mixtures of shell precursors with different ratios may be added sequentially for a given period of time, such as reaction time, to achieve a desired composition of the quantum dot or to form a gradient or multilayer shell on the core. In an embodiment, a first shell layer comprising a second semiconductor nanocrystal (e.g., comprising zinc selenide) may be formed by reacting a zinc precursor and a selenium precursor, and then, if desired, a third shell layer comprising a fourth semiconductor nanocrystal (e.g., comprising zinc sulfide) may be formed on the first shell layer by reacting a zinc precursor and a sulfur precursor (optionally together with a selenium precursor).

[0146] The reaction temperature for forming the shell may be 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, greater than or equal to about 290°C, or greater than or equal to about 300°C and less than or equal to about 380°C, less than or equal to about 350°C, less than or equal to about 340°C, less than or equal to about 330°C, or less than or equal to about 325°C.

[0147] In the reaction system, the amount and concentration of the precursor can be selected in consideration of the composition of the core and the shell and the reactivity between the precursors. The particles having the core and optionally the shell layer can be separated in substantially the same manner as described herein. The ratio between the precursors for shell formation can be selected in consideration of the desired shell thickness and the desired composition of the quantum dots and is not particularly limited.

[0148] A particle comprising the core of the first semiconductor nanocrystal or comprising the core and the first shell layer (and optionally the third shell layer) can be combined with an alkaline earth metal precursor (optionally together with a zinc precursor) and a chalcogen precursor, and then reacted to obtain a semiconductor nanocrystal shell comprising an alkaline earth metal (e.g., a semiconductor nanocrystal shell comprising an alkaline earth zinc chalcogenide, an alkaline earth metal chalcogenide, or a combination thereof).

[0149] The reaction may produce an alkaline earth metal chalcogenide. The alkaline earth metal chalcogenide thus formed may exhibit a crystalline peak in an X-ray diffraction analysis of the quantum dot. The chalcogen precursor may be a sulfur precursor, a selenium precursor, or a combination thereof. The alkaline earth metal chalcogenide thus formed may include an alkaline earth metal sulfide, an alkaline earth metal selenide, or a combination thereof. The alkaline earth metal chalcogenide thus formed may include an alloy of a zinc chalcogenide (e.g., zinc selenide or zinc sulfide) and an alkaline earth metal.

[0150] The amount of the alkaline earth metal used may be selected taking into account the type of precursor and the reaction conditions (e.g., reaction temperature). In an embodiment, the amount of the alkaline earth metal used may be greater than or equal to about 0.005 mole, greater than or equal to about 0.01 mole, or greater than or equal to about 0.015 mole, based on one mole of zinc. The amount of the alkaline earth metal used may be less than or equal to about 0.5 mole, less than or equal to about 0.3 mole, or less than or equal to about 0.1 mole, based on one mole of zinc.

[0151] After the reaction is completed, a non-solvent can be added to the reacted mixture to promote the separation of the nanocrystal particles coordinated to, for example, the organic ligand. The non-solvent can be a polar solvent that is miscible and can not disperse the nanocrystal produced with the solvent used in the core formation reaction or quantum dot formation reaction. The non-solvent can be selected in consideration of 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, a solvent with a solubility parameter similar to the aforementioned non-solvent, or a combination thereof. The separation of the nano-crystal particles can involve centrifugation, sedimentation, column chromatography, or filtration. If desired, the nano-crystal particles separated can be added to a washing (or dispersion) solvent and washing (or dispersion).

[0152] The type of the washing (or dispersing) solvent is not particularly limited, and a solvent having a solubility parameter similar to that of the ligand may be used, and examples thereof may include hexane, heptane, octane, chloroform, toluene, benzene, and the like.

[0153] In an embodiment, the quantum dots may be water-insoluble or non-dispersible in water, the aforementioned non-solvents, or a combination thereof.

[0154] In an embodiment, the quantum dots may be dispersed in the aforementioned organic solvent (e.g., to form a mixture such as a dispersion or a solution). In an embodiment, the quantum dots may be dispersed in a C3-C40 (C6-C24) substituted or unsubstituted aliphatic hydrocarbon, a C6-C40 substituted or unsubstituted aromatic hydrocarbon, or a combination thereof.

[0155] In an embodiment, an electronic device includes the quantum dots. The device may include (or may be) a display device, a light emitting diode (LED), an organic light emitting diode (OLED), a quantum dot LED, a sensor, a solar cell, an image sensor, or a liquid crystal display (LCD), but is not limited thereto.

[0156] In an embodiment, the electronic device may be (or may include) a photoluminescent element (e.g., a lighting device such as a quantum dot sheet or quantum dot track or a liquid crystal display (LCD)) or an electroluminescent device (e.g., a QD LED).

[0157] In embodiments, the electronic device may include a quantum dot sheet, and the quantum dots may be included in the quantum dot sheet (eg, in the form of a semiconductor nanocrystal-polymer composite).

[0158] In an embodiment, the electronic device may be an electroluminescent device or a display device including the same. The electroluminescent device or the display device may include an anode 1 and a cathode 5 facing each other, and a quantum dot emission layer 3 disposed between the anode and the cathode and including a plurality of quantum dots, and the plurality of quantum dots may include semiconductor nanocrystal particles emitting blue light (see Figure 2A ).

[0159] The cathode may include an electron injection conductor (e.g., having a relatively low work function). The anode may include a hole injection conductor (e.g., having a relatively high work function). The electron / hole injection conductor may include: a metal (e.g., aluminum, magnesium, tungsten, nickel, cobalt, platinum, palladium, or calcium), a metal compound (e.g., LiF), an alloy, or a combination thereof; a metal oxide such as indium gallium oxide or indium tin oxide; or a conductive polymer such as polyethylenedioxythiophene (e.g., having a relatively high work function), but is not limited thereto.

[0160] At least one of the cathode and the anode may be a light-transmitting electrode or a transparent electrode. In an embodiment, both the anode and the cathode may be light-transmitting electrodes. The electrodes may be patterned.

[0161] The light-transmitting electrode may be made of, for example, a transparent conductor such as indium tin oxide (ITO) or indium zinc oxide (IZO), gallium indium tin oxide, zinc indium tin oxide, titanium nitride, polyaniline, or LiF / Mg:Ag, or a thin single-layer or multi-layer metal film, but is not limited thereto. When one of the cathode and the anode is a non-light-transmitting electrode, the cathode or the anode may be made of, for example, an opaque conductor such as aluminum (Al), lithium aluminum (Li:Al) alloy, magnesium-silver alloy (Mg:Ag), or lithium fluoride-aluminum (LiF:Al).

[0162] The light-transmitting electrode may be disposed on a transparent substrate (eg, an insulating transparent substrate). The substrate may be rigid or flexible. The substrate may be plastic, glass, or metal.

[0163] The substrate may be a substrate including an insulating material. The substrate may include: glass; various polymers such as polyester (e.g., polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethacrylate, or polyacrylate); polycarbonate; polysiloxane (e.g., polydimethylsiloxane (PDMS)); inorganic materials such as Al 2 O 3 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 is not particularly limited. 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 light emitted from the quantum dots.

[0164] The thickness of the anode and the cathode is not particularly limited and may be selected in consideration of equipment efficiency. For example, the thickness of the anode (or the cathode) may be greater than or equal to about 5 nm, such as greater than or equal to about 50 nm, but is not limited thereto. For example, the thickness of the anode (or the cathode) may be less than or equal to about 100 micrometers (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, but is not limited thereto.

[0165] The quantum dot emission layer may include a plurality of quantum dots. The plurality of quantum dots may include the quantum dots of an embodiment. The quantum dot emission layer may include a single layer film of the quantum dots.

[0166] The emission layer may be formed by preparing a dispersion comprising the quantum dots dispersed in a solvent, applying the dispersion via spin coating, inkjet coating, or spray coating, and drying the dispersion. The emission layer may have a thickness of greater than or equal to about 5 nm, such as greater than or equal to about 10 nm, greater than or equal to about 15 nm, greater than or equal to about 20 nm, or greater than or equal to about 25 nm and less than or equal to about 100 nm, such as 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, or less than or equal to about 30 nm.

[0167] The electronic device may include a charge (hole or electron) auxiliary layer between the anode and the cathode. For example, the electronic device may include a hole auxiliary layer 2 between the anode and the quantum dot emission layer, an electron auxiliary layer 4 between the cathode and the quantum dot emission layer, or a combination thereof. (See Figure 2A )

[0168] In the drawing, the electron / hole assisting layer is formed as a single layer, but the electron / hole assisting layer is not limited thereto and may include a plurality of layers including at least two stacked layers.

[0169] The hole auxiliary layer may include, for example, a hole injection layer (HIL) for promoting hole injection, a hole transport layer (HTL) for promoting hole transport, an electron blocking layer (EBL) for inhibiting electron transport, or a combination thereof. For example, the hole injection layer may be disposed between the hole transport layer and the anode. For example, the electron blocking layer may be disposed between the emission layer and the hole transport (injection) layer, but is not limited thereto. The thickness of each layer may be appropriately selected. For example, the thickness of each layer 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, greater than or equal to about 15 nm, greater than or equal to about 20 nm, or greater than or equal to about 25 nm and 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 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, but is not limited thereto. The hole injection layer may be an organic layer such as poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) formed by a solution process (e.g., spin coating, etc.). The hole transport layer may be an organic layer formed by a solution process (e.g., spin coating, etc.).

[0170] The electron auxiliary layer may include, for example, an electron injection layer (EIL) for facilitating electron injection, an electron transport layer (ETL) for facilitating electron transport, a hole blocking layer (HBL) for inhibiting hole transport, or a combination thereof. For example, the electron injection layer may be disposed between the electron transport layer and the cathode. For example, the hole blocking layer may be disposed between the emission layer and the electron transport (injection) layer, but is not limited thereto. The thickness of each layer may be appropriately selected. For example, the thickness of each layer may 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 may be an organic layer formed by deposition. The electron transport layer may include inorganic oxides or (nano or fine) inorganic oxide particles or may include an organic layer formed by deposition.

[0171] The quantum dot emission layer may be disposed in the hole injection (or transport) layer or the electron injection (or transport) layer. The quantum dot emission layer may be disposed as a separate layer between the hole auxiliary layer and the electron auxiliary layer.

[0172] The charge auxiliary layer, the electron blocking layer, and the hole blocking layer may include, for example, an organic material, an inorganic material, or an organic / inorganic material. The organic material may be a compound having hole or electron related properties. The inorganic material may be, for example, a metal oxide such as molybdenum oxide, tungsten oxide, zinc oxide, or nickel oxide, but is not limited thereto.

[0173] The hole transport layer (HTL), the hole injection layer, or a combination thereof may include, for example, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), polyarylamine (polyarylamine), poly(N-vinylcarbazole) (PVK), 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"-tri[phenyl(m-tolyl)amino]triphenylamine), 4,4',4"-tri(N-carbazolyl)-triphenylamine (TCTA), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), p-type metal oxides (e.g., NiO, WO 3 、MoO 3 etc.), carbonaceous materials such as graphene oxide, or a combination thereof, but not limited thereto.

[0174] The electron blocking layer (EBL) may include, for example, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), polyarylamine (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 is not limited thereto.

[0175] The electron transport layer (ETL), the electron injection layer, or a combination thereof may include, for example, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), bathocuproine (BCP), tris[3-(3-pyridyl)- yl]borane (3TPYMB), LiF, Alq3 , Gaq 3 、Inq 3 、Znq 2 、Zn(BTZ) 2 、BeBq 2 , 8-(4-(4,6-di(naphthalene-2-yl)-1,3,5-triazine-2-yl)phenyl)quinolone (ET204), 8-hydroxyquinoline lithium (Liq), n-type metal oxides (e.g., zinc oxide, HfO 2 etc.), 8-(4-(4,6-di(naphthalene-2-yl)-1,3,5-triazine-2-yl)phenyl)quinolone:8-hydroxyquinoline lithium (ET204:Liq), 2,2',2"-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimidazole) (TPBi), or a combination thereof, but not limited thereto. In the foregoing, "q" is 8-hydroxyquinoline, "BTZ" is 2-(2-hydroxyphenyl)benzothiazole, and "Bq" is 10-hydroxybenzo[h]quinoline.

[0176] The hole blocking layer (HBL) may include, for example, 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA), bathocuproin (BCP), tris[3-(3-pyridyl)- yl]borane (3TPYMB), LiF, Alq 3 , Gaq 3 、Inq 3 、Znq 2 、Zn(BTZ) 2 、BeBq 2 , or a combination thereof, but not limited thereto.

[0177] In the device according to the embodiment, the anode 10 disposed on the transparent substrate 100 may include a metal oxide transparent electrode (e.g., an ITO electrode), and the cathode 50 facing the anode may include a metal (Mg, Al, etc.) with a predetermined (e.g., relatively low) work function. TFB, PVK, or a combination thereof (e.g., as a hole transport layer 20) and PEDOT:PSS, a p-type metal oxide, or a combination thereof (e.g., as a hole injection layer 20) may be disposed between the transparent electrode 10 and the emission layer 30. The electron auxiliary layer (e.g., an electron transport layer) 40 may be disposed between the quantum dot emission layer 30 and the cathode 50. (See Figure 2B )

[0178] The device according to the embodiment has an inverted structure. Here, the cathode 50 provided on the transparent substrate 100 may include a metal oxide transparent electrode (e.g., ITO), and the anode 10 facing the cathode may include a metal with a predetermined (e.g., relatively high) work function (e.g., Au, Ag, etc.). For example, an n-type metal oxide (ZnO) may be provided on the transparent electrode 50 and the emission layer 30 as an electron auxiliary layer (e.g., electron transport layer) 40. The hole auxiliary layer 20 (e.g., a hole transport layer including TFB, PVK, or a combination thereof; a hole transport layer including MoO 3 or another hole injection layer of a p-type metal oxide; or a combination thereof) may be disposed between the metal anode 10 and the quantum dot emission layer 30. (See Figure 2C )

[0179] In an embodiment, a photoluminescent device or a display device including the same may include a light-emitting element (e.g., a photoluminescent element) and optionally a light source, and the light-emitting element includes a light-emitting layer, which may optionally be disposed on a (transparent) substrate, and the light-emitting layer includes a film or a patterned film of the quantum dot complex.

[0180] If present, the light source is configured to provide incident light to the light emitting element. The incident light may have a peak wavelength greater than or equal to about 440 nm, such as greater than or equal to about 450 nm, greater than or equal to about 455 nm, or greater than or equal to about 460 nm and less than or equal to about 560 nm, less than or equal to about 500 nm, 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.

[0181] In an embodiment, the light emitting element or the light emitting layer may include a sheet of the quantum dot composite. Figure 3 , which shows an exploded view of an embodiment of a display device 400, the photoluminescent device of the embodiment may have a structure in which a reflector, a light guide plate (LGP), a blue LED light source (blue LED), a quantum dot-polymer composite sheet (QD sheet), and various optical films such as prisms, double brightness enhancement films (DBEF), etc. are stacked and a liquid crystal panel is disposed thereon. The liquid crystal panel may have a structure including a thin film transistor (TFT), a liquid crystal (LC), and a color filter between two polarizers (Pol).

[0182] In an embodiment, the light emitting layer may include a quantum dot-polymer composite pattern. The pattern may include at least one repeating segment for emitting light of a predetermined wavelength. (See Figure 4A) In the light emitting device / display device of the embodiment, a layered structure including a quantum dot composite pattern and a substrate may be disposed above a light emitting source. The quantum dot composite pattern may include: a first repeating segment 10 including quantum dots emitting a first light (G), a second repeating segment 20 including quantum dots emitting a second light (R), and a third repeating segment 30 which may include quantum dots emitting a third light (B), configured to transmit the third light, or a combination thereof. The layered structure includes a black matrix 241 between each of the segments. The repeating segments are disposed on a substrate 100.

[0183] In the photoluminescent device or the display device including the same, the light source may include an element emitting light of a predetermined wavelength (eg, excitation light). The light source may include an LED. The light source may include an organic LED (eg, an OLED).

[0184] The light source may include a plurality of light emitting units corresponding to the first segment and the second segment, respectively, and each of the light emitting units may include a first electrode and a second electrode facing each other and an electroluminescent layer disposed 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, such as an organic light emitting diode (OLED), are not particularly limited.

[0185] Figure 4B is a schematic cross-sectional view of a display device according to an embodiment, and Figure 4C is a schematic cross-sectional view of a display device according to an embodiment. Figure 4B and 4C , the light source includes an organic light emitting diode (OLED) that emits short wavelength light (e.g., blue light, green light, or blue light and green light). The organic light emitting diode OLED may include: (at least two, for example, three or more) 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 the pixel electrodes 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 below the organic light emitting diode (OLED). The pixel regions of the OLED may be disposed corresponding to the first, second, and third sections described herein, respectively.

[0186] A quantum dot complex pattern (e.g., comprising: a first repeating segment comprising quantum dots that emit a first light, a second repeating segment comprising quantum dots that emit a second light, or a combination thereof) can be arranged, for example, as a stacked structure that further includes a substrate, for example, on the light source (e.g., directly on the light source) or above the light source, if the light source exists.

[0187] Light emitted from the light source (e.g., blue light, green light, or a combination thereof) may enter the second segment 21 and the first segment 11 of the pattern 170 (e.g., QD color filter (C / F)) to emit (e.g., converted) second light (e.g., red light R) and first light (e.g., green light G), respectively. Blue light B emitted from the light source passes through the third segment 31 or is transmitted from the third segment 31.

[0188] An excitation light cutoff layer or optical element 160 (e.g., a blue light filter) may be disposed above the second segment 21 emitting red light, the first segment 11 emitting green light, or a combination thereof. The optical element may be an excitation light cutoff layer or a first filter that cuts off (e.g., reflects or absorbs) excitation light (e.g., blue light, green light, or a combination thereof). The excitation light cutoff layer or optical element 160 may be disposed on the upper substrate 240, or as shown, the excitation light cutoff layer 160 may be disposed below the upper substrate 240 (e.g., on the bottom surface of the upper substrate 240). The excitation light cutoff layer 160 may be disposed between the upper substrate 240 and the quantum dot-polymer composite pattern and above the first segment 11 and the second segment 21, and if desired, the third segment 31. The details of the excitation light cutoff layer are the same as those described herein for the first filter.

[0189] The display device can be obtained by separately manufacturing the stacked structure and an LED or OLED (eg, emitting blue light) and then assembling them. Alternatively, the display device can be obtained by directly forming a quantum dot-polymer composite pattern on the LED or OLED.

[0190] The details of the substrate are the same as those described herein. A circuit layer including a thin film transistor and the like is formed on the substrate. The circuit layer may further include a gate line, a sustaining voltage line, a gate insulating layer, a data line, a source electrode, a drain electrode, a semiconductor, a protective layer, and the like. The detailed structure of the circuit layer can be verified according to the implementation. The gate line and the sustaining voltage line are electrically isolated from each other, and the data line is insulated and crosses the gate line and the sustaining voltage line. The gate electrode, the source electrode, and the drain electrode form a control terminal, an input terminal, and an output terminal of the thin film transistor, respectively. The drain electrode is electrically connected to a pixel electrode to be described herein.

[0191] The pixel electrode may be used as 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 double-layer structure in which the transparent conductive material and the material having a light blocking property are sequentially stacked.

[0192] Between two adjacent pixel electrodes, a pixel defining layer (PDL) may overlap ends of the pixel electrodes to divide the pixel electrodes into pixel units. The pixel defining layer is an insulating layer that may electrically block at least two pixel electrodes.

[0193] The pixel defining layer covers a portion of an upper surface of the pixel electrode, and a remaining area of ​​the pixel electrode not covered by the pixel defining layer may provide an opening. An organic emission layer to be described herein may be formed on an area defined by the opening.

[0194] The organic emission layer defines each pixel region through the pixel electrode and the pixel defining layer. In other words, one pixel region may be defined as a region formed by one organic emission unit layer in contact with one pixel electrode divided by the pixel defining layer. For example, in a display device according to an embodiment, the organic emission layer may 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.

[0195] In an embodiment, the organic emission layer may emit a third light belonging to the visible light region or to the ultraviolet (UV) region. That is, the first to third pixel regions of the organic emission layer may each emit a third light. In an embodiment, the third light may be light with higher energy in the visible light region, for example, blue light, and optionally green light. When all pixel regions of the organic emission layer are designed to emit the same light, the pixel regions of the organic emission layer may all be formed of the same or similar materials, or may exhibit the same or similar properties. The process difficulties in forming the organic emission layer may be reduced, and the display device may be applied to large-scale / large-area processes, for example, by forming or using it therein. However, the organic emission layer according to the embodiment is not necessarily limited thereto, but the organic emission layer may be designed to emit at least two different lights.

[0196] The organic emission layer includes an organic emission unit layer in each pixel area, and each organic emission unit layer may further include an auxiliary layer (e.g., a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), etc.) in addition to the emission layer.

[0197] The common electrode may be used as a cathode of the display device. The common electrode may be formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The common electrode may be formed on the organic emission layer and may be integrated therewith.

[0198] A planarization layer or a passivation layer may be formed on the common electrode. The planarization layer may include an (eg, transparent) insulating material for ensuring electrical insulation from the common electrode.

[0199] In the embodiments, a display device (eg, a liquid crystal display device) will be described with reference to the accompanying drawings. Figure 5 , the display device may include a lower substrate 210, an optical element (e.g., a polarizer) 300 disposed below the lower substrate 210, and a liquid crystal layer 220 between the stacked structure and the lower substrate 210. The stacked structure may be arranged in a manner that the light-emitting layer (i.e., the quantum dot-polymer composite pattern) faces the liquid crystal layer. The display device may further include an optical element (e.g., a polarizer) 300 between the liquid crystal layer 220 and the light-emitting layer. The material and structure of the polarizer 300 are not particularly limited. The light source 110 may further include an LED and optionally a light guide plate 120. As shown, a backlight unit (e.g., emitting blue light) may be disposed below the polarizer 300.

[0200] The stack structure includes a transparent substrate (or upper substrate) 240 and a light emitting layer (hereinafter, also referred to as a photoluminescent layer) 230 including a pattern including a quantum dot-polymer composite.

[0201] The lower substrate 210 (also referred to as an array substrate) may be a transparent insulating material substrate. The substrate is the same as 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 and data lines defining pixel areas, thin film transistors disposed adjacent to the intersection of the gate lines and the data lines, and pixel electrodes for each pixel area, but is not limited thereto. The details of such a circuit board are not particularly limited.

[0202] The liquid crystal layer 220 may be disposed on the circuit board 211. The liquid crystal layer 220 may include an alignment layer 221 on and below the liquid crystal layer 220 to initially align the liquid crystal material included therein. Details of the liquid crystal material 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.

[0203] An upper optical element or upper polarizer 300 may be provided between the liquid crystal layer 220 and the light emitting layer 230. The polarizer may be any suitable polarizer used in a liquid crystal display device. The polarizer may be TAC (triacetyl cellulose) having a thickness of 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 polarization function.

[0204] The backlight unit includes a light source 110. The light source may emit blue light (shown) or white light. The light source may include a blue (or green) LED, a (white) LED, a (white) OLED, or a combination thereof, but is not limited thereto.

[0205] 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, a light guide plate provided on the reflector and providing a surface light source to the liquid crystal panel 200, at least one optical sheet on the light guide plate such as a diffuser, a prism sheet, etc., 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, and may have a plurality of fluorescent lamps arranged on the reflector at regular intervals, or may have an LED working substrate on which a plurality of light-emitting diodes may be arranged, a diffuser plate thereon, and optionally at least one optical sheet. The details of such a backlight unit (for example, the following components: light-emitting diodes, fluorescent lamps, light guide plates, a variety of optical sheets, and reflectors) are not particularly limited.

[0206] The black matrix 241 is provided below the transparent substrate 240 and has an opening and hides the gate lines, data lines, and thin film transistors of the wiring board on the lower substrate. For example, the black matrix 241 may have a lattice shape. The photoluminescent layer 230 is provided in the opening of the black matrix 241 and has a quantum dot-polymer composite pattern, which includes: 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, for example, blue light. If desired, the photoluminescent layer may further include at least one fourth segment. The fourth segment may include quantum dots that emit light of a different color (e.g., cyan, magenta, and yellow light) than the light emitted from the first to third segments.

[0207] In the light emitting layer 230, segments forming a pattern may be repeated corresponding to a pixel region formed on the lower substrate. A transparent common electrode 231 may be provided on the photoluminescent layer 230 (eg, a photoluminescent color filter layer).

[0208] The third segment (B) configured to emit / transmit blue light may be a transparent color filter that does not change the light emission spectrum of the light source. In this case, the blue light emitted from the backlight unit may enter in a polarized state and may be emitted through the polarizer and the liquid crystal layer. If desired, the third segment may include quantum dots that emit blue light.

[0209] As described herein, if desired, the display device or the light emitting device may further include an excitation light blocking layer or a first filter layer (herein, referred to as a first filter layer). The first filter layer may be disposed between the bottom surface of the first segment (R) and the second segment (G) and the substrate (e.g., the upper substrate 240) or on the top surface of the substrate (e.g., the upper substrate 240). The first filter layer may include a sheet having an opening corresponding to a pixel area (e.g., the third segment) displaying a blue color. In other words, the first filter layer may be integrally formed as an integral structure at a portion other than a portion overlapping the third segment, but is not limited thereto. At least two (e.g., three) first filter layers may be spaced apart and disposed at each of the positions overlapping the first and second segments and optionally the third segment. When the light source includes a green light emitting element, a green light cutoff filter layer may be disposed on the third segment.

[0210] In an embodiment, the first filter layer 310 may block light having a portion of a wavelength region in the visible light region. The first filter layer may transmit light having other (visible light) wavelength regions. For example, the first filter layer may block blue light (or green light) and transmit light other than blue (or green) light. For example, the first filter layer may transmit green light, red light, or yellow light as a mixture thereof. The first filter layer may transmit blue light and block green light, and may be disposed on a pixel emitting blue light.

[0211] In an embodiment, the first filter layer may substantially block the excitation light and may transmit light of a desired wavelength. In an embodiment, the first filter layer may have a light transmittance of greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or about 100% for light of a desired wavelength range.

[0212] In an embodiment, a first filter layer that selectively transmits red light may be disposed on a portion overlapping with a segment emitting red light, and a first filter layer that selectively transmits green light may be disposed on a portion overlapping with a segment emitting green light, respectively. In an embodiment, the first filter layer may include a first region, a second region, or a combination thereof, wherein the first region blocks (e.g., absorbs) blue light and red light and transmits a wavelength having 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 530 nm). In an embodiment, the excitation light may include blue light and green light, and the first filter layer may further include a third region that blocks green light and selectively transmits blue light.

[0213] The first region may be disposed at a position overlapping with a segment emitting green light. The second region may be disposed at a position overlapping with a segment emitting red light. The third region may be disposed at a position overlapping with a segment emitting or transmitting blue light.

[0214] The first region, the second region, and optionally the third region may be optically isolated.The first filter layer may contribute to improving the color purity of the display device.

[0215] The display device may further include a second filter layer 311 (e.g., a red / green light or yellow light recycling layer) disposed between the light emitting layer 230 and the liquid crystal layer 220, and between the light emitting layer 230 (e.g., the quantum dot polymer composite layer) and the upper polarizer 300. The second filter layer 311 may transmit at least a portion of the third light (i.e., the excitation light) and reflect at least a portion of the first light, the second light, or the first light and the second light. The first light may be red light. The second light may be green light. The third light may include blue light. The second filter layer may transmit a third light (B) having a wavelength range of blue light less than or equal to 500 nm. Light having a wavelength range greater than about 500 nm (e.g., red light R, green light G, or yellow light) may not be allowed to pass through the second filter and may be reflected thereby. The reflected green light and red light are then transmitted through the first and second segments and emitted outside the display device.

[0216] In the display device according to the embodiment, the first filter layer, the second filter layer, or the first filter layer and the second filter layer may be formed as an integrated single layer having a substantially planar surface.

[0217] In an embodiment, the first filter layer may include a dye capable of absorbing light of a predetermined wavelength to be blocked, a pigment capable of absorbing light of a predetermined wavelength to be blocked, or a combination thereof. For example, the first filter layer, the second filter layer, or the first filter layer and the second filter layer may include a single layer having a low refractive index, and it may be a transparent thin film having a refractive index of 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 first or second filter layer having a low refractive index may be, for example, porous silicon oxide, a porous organic material, a porous organic / inorganic composite, or a combination thereof.

[0218] In an embodiment, the first or second filter layer may each independently include a plurality of layers having different refractive indices, for example, the first or second filter layer may be formed by alternately stacking two layers having different refractive indices, or for example, the second or first filter layer may be formed by alternately stacking a material having a high refractive index and a material having a low refractive index.

[0219] Hereinafter, the embodiments will be described in more detail with reference to Examples. However, they are illustrative examples of the present disclosure, and the present disclosure is not limited thereto.

[0220] Example

[0221] Analytical methods

[0222] 1. Photoluminescence Analysis

[0223] Photoluminescence (PL) spectra of the fabricated nanocrystals were obtained using a Hitachi F-7000 spectrophotometer at a radiation wavelength of 372 nanometers (nm).

[0224] 2. Inductively coupled plasma (ICP) analysis

[0225] Inductively coupled plasma-atomic emission spectrometry (ICP-AES) analysis was performed using Shimadzu ICPS-8100.

[0226] 3. X-ray Photoelectron Spectroscopy (XPS) Analysis

[0227] X-ray photoelectron spectroscopy analysis was performed by Quantum 2000 manufactured by Physical Electronics.

[0228] 4. Transmission electron microscopy-energy dispersive X-ray (TEM-EDX) analysis

[0229] TEM-EDX analysis was performed using a Tecnai G2 F20 S-TWIN (200 kV field emission gun (FEG) high resolution TEM / scanning transmission electron microscopy (STEM)).

[0230] The synthesis was carried out under an inert gas atmosphere (or nitrogen flowing conditions) unless otherwise specifically stated.

[0231] Embodiment 1-1:

[0232] 1. Selenium, sulfur, and tellurium were dispersed in trioctylphosphine (TOP) to obtain 2 molar (M) Se / TOP stock solution, 2M S / TOP stock solution, and 0.5M Te / TOP stock solution.

[0233] In a 300 milliliter (mL) reaction flask, zinc acetate and palmitic acid were dissolved in trioctylamine and heated under vacuum at 120° C. After one hour, the atmosphere in the flask was replaced with an inert gas (nitrogen) and then the reaction flask was heated to 300° C.

[0234] The Se / TOP stock solution and the Te / TOP stock solution were quickly injected into the heated reaction flask and the reaction was carried out for 60 minutes, after which the reactor was cooled to room temperature and acetone was added to promote the formation of a precipitate, which was separated via centrifugation to provide a ZnSeTe core. The obtained core was then dispersed in toluene.

[0235] The molar ratio between the zinc precursor and the selenium precursor was 2:1 (Zn:Se), and the molar ratio between the tellurium precursor and the selenium precursor was 0.07:1 (Te:Se).

[0236] 2. To a 300 mL reaction flask, trioctylamine (TOA), zinc acetate and oleic acid were added, and the mixture was vacuum treated at 120° C. for one hour. The atmosphere in the flask was replaced with an inert atmosphere (nitrogen). When the flask was heated to a temperature of about 300° C., the ZnTeSe core was quickly added, followed by the Se / TOP stock solution, and the reaction was carried out for 120 minutes to form a ZnSe layer on the core. The molar ratio between the zinc precursor and the selenium precursor used in the formation of the shell layer was about 2:85:1.5.

[0237] The flask was cooled to room temperature, acetone was added to promote the formation of precipitate, and the ZnTeSe / ZnSe particles were separated via centrifugation. The separated particles were dispersed in toluene.

[0238] 3. Trioctylamine (TOA) was placed in a 300 mL reaction flask, and barium acetate and oleic acid were added thereto, and the mixture was vacuum treated at 120° C. The atmosphere in the flask was replaced with nitrogen. While heating the flask, a toluene dispersion of ZnTeSe / ZnSe particles and the S / TOP stock solution were added one by one and at a temperature of about 340° C., and the reaction was carried out for 20 minutes to form a BaS layer on the particles. The amount of barium precursor used during quantum dot formation was about 0.3 moles per mole of zinc.

[0239] The flask was cooled to room temperature, acetone was added to promote the formation of precipitate, and ZnTeSe / ZnSe particles were separated via centrifugation. The separated particles were dispersed in toluene.

[0240] ICP-AES analysis was performed on the quantum dots and the results are shown in Table 2.

[0241] For the as-prepared quantum dots, photoluminescence spectroscopy analysis was performed and the results are summarized in Table 3.

[0242] The quantum dots were subjected to XPS analysis and the results are shown in Figure 1A middle. Figure 1A The results confirmed the formation of barium sulfide in the quantum dots.

[0243] Comparative Example 1:

[0244] A ZnSe layer was formed on the ZnSeTe core in the same manner as in Example 1. Then, instead of the barium precursor, the S / TOP stock solution was added to the reaction medium together with zinc acetate, and the reaction was continued for about 120 minutes to form a ZnS layer on the ZnSe layer. In the shell formation, the molar ratio between the Zn precursor, the S precursor, and the Se precursor used was 4.05:1.2:1.2.

[0245] ICP-AES analysis was performed on the quantum dots and the results are shown in Table 2.

[0246] For the as-prepared quantum dots, photoluminescence spectroscopy analysis was performed and the results are summarized in Table 3.

[0247] Embodiment 1-2:

[0248] A ZnSe layer was formed on the ZnSeTe core in the same manner as in Example 1. Then, the S / TOP stock solution was added to the reaction medium together with zinc acetate, and the reaction was continued for about 120 minutes to form a ZnS layer on the ZnSe layer. In the shell formation, the molar ratio between the Zn precursor, the S precursor, and the Se precursor used was 4.05:1.2:1.2.

[0249] Trioctylamine (TOA) was placed in a 300 mL reaction flask, and barium acetate and oleic acid were added thereto, and the mixture was vacuum treated at 120° C. The atmosphere in the flask was replaced with nitrogen. While heating the flask, a toluene dispersion of ZnTeSe / ZnSe / ZnS particles and a S / TOP stock solution were added one by one and at a temperature of about 280° C., and the reaction was carried out for 60 minutes to form a BaS layer on the particles. The amount of barium precursor used during quantum dot formation was about 0.12 moles per mole of zinc.

[0250] ICP-AES analysis was performed on the quantum dots and the results are shown in Table 2.

[0251] The quantum dots were subjected to TEM-EDX analysis and the results are shown in Figure 1B middle.

[0252] For the as-prepared quantum dots, photoluminescence spectroscopy analysis was performed and the results are summarized in Table 3.

[0253] Table 2

[0254]

[0255] Table 3

[0256]

[0257]

[0258] PL QY: Photoluminescence quantum yield

[0259] Experimental Example 1:

[0260] Using each of the quantum dot dispersion of Example 1 and the quantum dot dispersion of Comparative Example 1, a quantum dot thin film having a thickness of about 30 nm was formed, and the resulting film was subjected to heat treatment at 150° C. for 30 minutes. Before and after the heat treatment, the quantum efficiency of each thin film was measured and the quantum efficiency retention rate was evaluated.

[0261] The results showed that the quantum efficiency retention rate of the thin film including the quantum dots of Example 1 was about 87%, while the quantum efficiency retention rate of the thin film including the quantum dots of Comparative Example 1 was about 62%.

[0262] Embodiment 2:

[0263] 1. A ZnSeTe core was prepared in the same manner as in Example 1-1.

[0264] 2. Trioctylamine (TOA) was placed in a 300 mL reaction flask, and zinc acetate, oleic acid, and calcium chloride were added thereto, and the mixture was vacuum treated at 120° C. The atmosphere in the flask was replaced with nitrogen. When the flask was heated to 300° C., a toluene dispersion of ZnTeSe particles was quickly added, followed by the Se / TOP stock solution, and the reaction was carried out for 120 minutes to form a CaZnSe layer on the core.

[0265] Then, zinc acetate and S / TOP were added to the reaction medium and reacted for 120 minutes to form a ZnS layer on the CaZnSe layer.

[0266] The molar ratio between the Zn precursor, the S precursor, and the Se precursor was 4.05:2.8:1.5.

[0267] Per mole of zinc, the CaCl used during quantum dot formation 2 The amount is about 0.04 moles.

[0268] ICP-AES analysis was performed on the quantum dots and the results are shown in Table 4.

[0269] For the as-prepared quantum dots, photoluminescence spectroscopy analysis was performed and the results are summarized in Table 5.

[0270] Embodiment 3:

[0271] Quantum dots were prepared in the same manner as in Example 2, except that barium oleate was used instead of calcium chloride.

[0272] The amount of barium oleate used during quantum dot formation was about 0.02 moles per one mole of zinc.

[0273] ICP-AES analysis was performed on the quantum dots and the results are shown in Table 4.

[0274] For the as-prepared quantum dots, photoluminescence spectroscopy analysis was performed and the results are summarized in Table 5.

[0275] Embodiment 4:

[0276] Quantum dots were prepared in the same manner as in Example 2, except that magnesium chloride was used instead of calcium chloride.

[0277] Per mole of zinc, the MgCl used during quantum dot formation 2 The amount is about 0.04 moles.

[0278] ICP-AES analysis was performed on the quantum dots and the results are shown in Table 4.

[0279] For the as-prepared quantum dots, photoluminescence spectroscopy analysis was performed and the results are summarized in Table 5.

[0280] Table 4

[0281]

[0282] Table 5

[0283]

[0284] The results of Tables 4 and 5 demonstrate that the quantum dots of Examples 2-4 exhibit significantly improved quantum efficiencies compared to the quantum dots of Comparative Example 1.

[0285] While the present disclosure has been described with reference to what are presently considered to be practical example embodiments, it is to 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. Quantum dots, including comprising a core of a first semiconductor nanocrystal, and a semiconductor nanocrystal shell disposed on the core, the semiconductor nanocrystal shell having a composition different from that of the first semiconductor nanocrystal, wherein the quantum dots do not include cadmium, wherein the semiconductor nanocrystal shell comprises zinc chalcogenide, wherein the zinc chalcogenide comprises selenium, tellurium, sulfur, or a combination thereof, wherein the quantum dots further comprise alkaline earth metals, wherein in the quantum dot, the amount of the alkaline earth metal is greater than or equal to 0.001 mole and less than or equal to 0.5 mole per mole of zinc, and wherein the alkaline earth metal comprises barium, strontium, calcium, magnesium, or a combination thereof, wherein the first semiconductor nanocrystals include zinc, tellurium, and selenium, wherein the quantum dots do not include III-V compounds, wherein the alkaline earth metal is present in the semiconductor nanocrystal shell.

2. The quantum dot of claim 1, wherein the semiconductor nanocrystal shell further comprises an alkaline earth metal zinc chalcogenide. 3 . The quantum dot of claim 1 , wherein in the quantum dot, a molar ratio of tellurium to selenium is greater than 0:1 and less than or equal to 0.1:

1.

4. The quantum dot of claim 1, wherein the alkaline earth metal comprises barium, calcium, magnesium, or a combination thereof. 5 . The quantum dot of claim 1 , wherein in the quantum dot, the amount of the alkaline earth metal is greater than or equal to 0.001 mol and less than or equal to 0.1 mol per 1 mol of zinc.

6. The quantum dot of claim 1, wherein the quantum dot comprises barium sulfide, calcium sulfide, magnesium sulfide, calcium selenide, barium selenide, barium zinc selenide, calcium zinc selenide, magnesium zinc selenide, or a combination thereof.

7. The quantum dot of claim 1, wherein the semiconductor nanocrystal shell comprises a first shell disposed on the core, and A second shell layer is 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 different from the second semiconductor nanocrystal.

8. The quantum dot according to claim 7, wherein The second semiconductor nanocrystals include zinc and selenium, and optionally sulfur, and The third semiconductor nanocrystal includes sulfur, and The second semiconductor nanocrystal, the third semiconductor nanocrystal, or a combination thereof includes the alkaline earth metal.

9. The quantum dot of claim 7, wherein The second shell is the outermost layer, and The third semiconductor nanocrystals include zinc sulfide, alkaline earth metal sulfide, or a combination thereof.

10. The quantum dot of claim 7, wherein the second semiconductor nanocrystal comprises zinc selenide. The quantum dot according to claim 1 , wherein the peak wavelength of photoluminescence of the quantum dot is less than or equal to 580 nanometers.

12. The quantum dot of claim 1, wherein the photoluminescence peak wavelength of the quantum dot is less than or equal to 480 nanometers.

13. The quantum dot of claim 1, wherein the quantum dot has a size greater than or equal to 7 nanometers and less than or equal to 50 nanometers.

14. The quantum dot of claim 1, wherein the quantum dot has a quantum efficiency greater than or equal to 80%.

15. The quantum dot of claim 1, wherein the quantum dot has a quantum efficiency greater than or equal to 95%.

16. The quantum dot of claim 1, wherein the half width of the photoluminescence peak of the quantum dot is less than or equal to 35 nanometers.

17. The quantum dot of claim 1, wherein The quantum dots include selenium and sulfur, and In the quantum dots, a molar ratio of sulfur to selenium is greater than or equal to 0.05:1 and less than or equal to 2:

1.

18. A method for manufacturing a quantum dot according to any one of claims 1 to 17, the method comprising: preparing a mixture comprising an alkaline earth metal compound and an organic ligand in an organic solvent; combining a particle including the core and a chalcogen precursor with the mixture to obtain a composition; and The composition is heated to react at a reaction temperature and produce the quantum dots.

19. The method of claim 18, wherein the method further comprises adding a zinc precursor to the mixture, and wherein a shell layer comprising an alkaline earth metal zinc chalcogenide is formed on particles comprising the core by the reaction.

20. The method of claim 18, wherein the particle further comprises a semiconductor nanocrystal shell layer disposed on the core, and a shell layer comprising an alkaline earth metal zinc chalcogenide is formed on the semiconductor nanocrystal shell layer by the reaction.

21. Electroluminescent device, comprising: a first electrode and a second electrode each having a surface opposite to the other, and A quantum dot emission layer is provided between the first electrode and the second electrode, wherein the quantum dot emission layer comprises a plurality of quantum dots, wherein the plurality of quantum dots comprises the quantum dots according to any one of claims 1 to 17.

22. Electronic equipment, including light emitting element, and Optional light source The light-emitting element comprises a plurality of quantum dots, wherein the plurality of quantum dots comprise the quantum dots as described in any one of claims 1-17.

Images