Quantum dots, quantum dot polymer composites including the quantum dots, and display devices

Abstract

Disclosed are a quantum dot, a quantum dot polymer composite including the quantum dot, and a display device. The quantum dot includes: a template including a first semiconductor nanocrystal; a quantum well (e.g., a quantum well layer) disposed on the template; and a shell disposed on the quantum well, the shell including a second semiconductor nanocrystal, and wherein the quantum dot does not include cadmium, wherein the first semiconductor nanocrystal includes a first zinc chalcogenide, wherein the second semiconductor nanocrystal includes a second zinc chalcogenide, and the quantum well layer includes an alloy semiconductor nanocrystal containing indium (In), phosphorus (P), zinc (Zn), and a chalcogen element, and wherein the bandgap energy of the alloy semiconductor nanocrystal is smaller than the bandgap energy of the first semiconductor nanocrystal and smaller than the bandgap energy of the second semiconductor nanocrystal.

Description

[0001] This application claims the priority and benefits of, and all rights obtained therefrom, Korean Patent Application No. 10-2020-0031618, filed with the Korean Intellectual Property Office on March 13, 2020, the content of which is incorporated herein by reference in its entirety. Technical Field

[0002] A quantum dot, a composition or composite including the quantum dot, and a display device including the quantum dot are disclosed. Background Art

[0003] Unlike bulk materials, the physical properties (e.g., bandgap energy and melting point) of semiconductor nanoparticles can be controlled by changing the size of the nanoparticles. For example, semiconductor nanocrystal particles (also referred to as quantum dots) are crystalline materials having a size in the range of several nanometers. Because semiconductor nanocrystal particles have a relatively small size, the nanocrystal particles have a large surface area per unit volume. Therefore, the particles exhibit a quantum confinement effect and will have properties different from those of bulk materials having the same chemical composition. Quantum dots can absorb energy from an excitation source (e.g., light or an applied current), and when relaxing to the ground state, the quantum dots emit light energy corresponding to the bandgap energy of the quantum dots. Summary of the Invention

[0004] Embodiments provide quantum dots and a composition including the quantum dots that can exhibit improved photoluminescence properties.

[0005] Embodiments provide a quantum dot composite including quantum dots.

[0006] Embodiments provide a method for manufacturing quantum dots.

[0007] Embodiments provide an electronic device including quantum dots.

[0008] In an embodiment, the quantum dot(s) includes: a template including a first semiconductor nanocrystal; a quantum well (e.g., a quantum well layer) disposed on the template; and a shell disposed on the quantum well layer, the shell including a second semiconductor nanocrystal, and wherein the quantum dot does not include cadmium, wherein the first semiconductor nanocrystal includes a first zinc chalcogenide, wherein the second semiconductor nanocrystal includes a second zinc chalcogenide, and the quantum well layer includes an alloy semiconductor nanocrystal including indium (In), phosphorus (P), zinc (Zn), and a chalcogen element, and wherein the bandgap energy of the alloy semiconductor nanocrystal is smaller than the bandgap energy of the first semiconductor nanocrystal and smaller than the bandgap energy of the second semiconductor nanocrystal.

[0009] The first zinc chalcogenide may include ZnSe, ZnTeSe, ZnSeS, ZnS, or a combination thereof, and the second zinc chalcogenide may independently include ZnSe, ZnTeSe, ZnSeS, ZnS, or a combination thereof.

[0010] The first semiconductor nanocrystal and the second semiconductor nanocrystal may have different compositions from each other.

[0011] The first semiconductor nanocrystal and the second semiconductor nanocrystal may have the same composition as each other.

[0012] The quantum well layer may be adjacent to the template (e.g., directly) (e.g., (e.g., directly) on the template or in contact with the template (e.g., directly)).

[0013] The quantum well layer may be adjacent to the shell (e.g., directly) (e.g., (e.g., directly) on the shell or in contact with the shell (e.g., directly)).

[0014] The first semiconductor nanocrystal may include ZnSe, ZnTeSe, ZnSeS, ZnS, or a combination thereof.

[0015] The second semiconductor nanocrystal may include ZnSe, ZnSeS, ZnS, or a combination thereof.

[0016] The chalcogen element may include sulfur.

[0017] The difference between the lattice constants of the alloy semiconductor nanocrystal and the first semiconductor nanocrystal may be less than or equal to about 3%.

[0018] The difference between the lattice constants of the alloy semiconductor nanocrystal and the second semiconductor nanocrystal may be less than or equal to about 3%.

[0019] Based on the total molar amount of elements in the quantum dots (e.g., measured by ICP analysis), the quantum dots may have a total molar amount of indium and phosphorus of less than or equal to about 20%.

[0020] In the quantum dots, the molar ratio of phosphorus to indium (P:In) may be greater than or equal to about 0.5:1 and less than or equal to about 0.9:1.

[0021] In the quantum dots, the molar ratio of sulfur to indium (S:In) may be greater than or equal to about 5:1 and less than or equal to about 25:1.

[0022] In the quantum dots, the molar ratio of zinc to indium (Zn:In) may be about 15:1 to about 30:1, about 20:1 to about 55:1, or a combination thereof.

[0023] In the quantum dots, the molar ratio of the sum of sulfur and selenium to zinc ((S + Se):Zn) can be greater than or equal to about 0.5:1 and less than or equal to about 1:1.

[0024] In the quantum dots, the molar ratio of sulfur to selenium (S:Se) can be greater than or equal to about 0.3:1 and less than or equal to about 0.9:1.

[0025] The shell can include: a first layer including a third zinc chalcogenide; and a second layer including a fourth zinc chalcogenide having a composition different from that of the third zinc chalcogenide.

[0026] The first layer and the second layer can be (e.g., directly) on each other (e.g., (e.g., directly) in contact with each other).

[0027] The first layer can include ZnSe, ZnSeS, or a combination thereof.

[0028] The second layer can include ZnS.

[0029] The first layer can be (e.g., directly) adjacent to the quantum well layer (or (e.g., directly) on the quantum well layer or (e.g., directly) near the quantum well layer), and the second layer can be the outermost layer of the shell (e.g., the outermost layer of the quantum dots) (e.g., included in the outermost layer of the shell (e.g., the outermost layer of the quantum dots)).

[0030] The thickness of the quantum well layer can be greater than or equal to about 0.1 nanometer (nm) (e.g., greater than or equal to about 0.15 nm, greater than or equal to about 0.2 nm, or greater than or equal to about 0.22 nm) and less than or equal to about 1 nm (e.g., less than or equal to about 0.8 nm, less than or equal to about 0.6 nm, or less than or equal to about 0.5 nm).

[0031] The thickness of the quantum well layer can be less than or equal to about 0.4 nm or less than or equal to about 0.35 nm.

[0032] The size (average size) of the quantum dots can be less than or equal to about 6.5 nm, less than or equal to about 6 nm, less than or equal to about 5.5 nm, less than or equal to about 5 nm, less than or equal to about 4.5 nm, less than or equal to about 4 nm, or less than or equal to about 3.5 nm.

[0033] The size (average size) of the quantum dots can be greater than or equal to about 2 nm, greater than or equal to about 3 nm, greater than or equal to about 4 nm, or greater than or equal to about 5 nm.

[0034] The quantum dots can include organic ligands located on the surface of the quantum dots.

[0035] The organic ligand may include RCOOH, RCOOCOR, RNH2, R2NH, R3N, RSH, R3PO, R3P, ROH, RCOOR', RPO(OH)2, R2POOH, or a combination thereof, wherein R and R' are independently a substituted or unsubstituted C1-C30 aliphatic hydrocarbon, a substituted or unsubstituted C6-C30 aromatic hydrocarbon, or a combination thereof.

[0036] The ultraviolet-visible (UV-Vis) absorption spectral curve of the quantum dots may not have an inflection point in the wavelength range of about 400 nm to about 650 nm or about 450 nm to about 620 nm (or less than or equal to about 580 nm or less than or equal to about 540 nm).

[0037] The quantum dots may emit green light.

[0038] The quantum dots (or green light) may have (e.g., exhibit) a maximum emission peak wavelength in the range of greater than or equal to about 500 nm and / or less than or equal to about 540 nm.

[0039] The quantum efficiency (e.g., quantum yield) of the quantum dots may be greater than or equal to about 50%.

[0040] In an embodiment, the quantum dot composite (e.g., quantum dot polymer composite) includes a matrix (e.g., polymer matrix) and the above-mentioned quantum dots (e.g., a plurality of them) dispersed in the (polymer) matrix.

[0041] (Polymer) matrix may be a linear polymer, a crosslinked polymer, or a combination thereof.

[0042] The crosslinked polymer may include thiol-ene polymer, crosslinked poly(meth)acrylate, crosslinked polyurethane, crosslinked epoxy resin, crosslinked vinyl polymer, crosslinked silicone resin, or a combination thereof.

[0043] The linear polymer may include repeating units having carboxylic acid.

[0044] The linear polymer may include units derived from monomers including a carbon-carbon double bond and a carboxylic acid group, units derived from monomers having a dianhydride moiety, or a combination thereof.

[0045] The linear polymer may include:

[0046] A copolymer of a monomer combination, the monomer combination including a first monomer, a second monomer, and an optional third monomer, the first monomer including a carboxylic acid group and a carbon-carbon double bond, the second monomer including a carbon-carbon double bond and a hydrophobic moiety and not including a carboxylic acid group, the optional third monomer including a carbon-carbon double bond and a hydrophilic moiety and not including a carboxylic acid group;

[0047] A polymer containing multiple aromatic rings, having a backbone structure in which two aromatic rings are bonded to a quaternary carbon atom and including a carboxyl group (-COOH), wherein the quaternary carbon atom is a constituent atom of another ring portion in the main chain; or

[0048] A combination thereof.

[0049] The quantum dot (polymer) composite may further include metal oxide fine particles (e.g., dispersed in a matrix) or a combination thereof.

[0050] The quantum dot (polymer) composite may have the form of a patterned film.

[0051] The quantum dot (polymer) composite may have (e.g., exhibit) an absorption rate of greater than or equal to about 90% for blue light (e.g., having a wavelength in the range of about 450 nm to about 470 nm).

[0052] In an embodiment, the quantum dot (polymer) composite may have a blue light conversion efficiency (CE%) or a blue light conversion rate (QE%) of greater than or equal to about 15%, greater than or equal to about 16%, greater than or equal to about 17%, greater than or equal to about 18%, or greater than or equal to about 19%.

[0053] In an embodiment, a display device includes a photoluminescent element and an optional light source, wherein the photoluminescent element includes the above-mentioned quantum dot composite, and the light source is configured to provide incident light to the photoluminescent element.

[0054] The incident light may include light having a peak wavelength of about 440 nm to about 460 nm or about 450 nm to about 455 nm.

[0055] The photoluminescent element may include a sheet of the quantum dot polymer composite.

[0056] The photoluminescent element may be a stacked structure including a substrate and a light-emitting layer provided on the substrate, wherein the light-emitting layer includes a quantum dot composite pattern.

[0057] The pattern may include, for example, at least one repeating portion to emit light of a predetermined wavelength.

[0058] The repeating portion may include a first repeating portion that emits first light (e.g., red light).

[0059] The repeating portion may include a second repeating portion that emits second light (e.g., green light) having a wavelength different from that of the first light.

[0060] The repeating portion may include a first portion that emits red light and a second portion that emits green light.

[0061] The pattern may include a first repeating portion that emits a first light and a second repeating portion that emits a second light having an emission peak wavelength different from that of the first light.

[0062] In an embodiment, the quantum dot(s) includes: a template including a first semiconductor nanocrystal; a quantum well (e.g., a quantum well layer) disposed on the template, and wherein the quantum dot does not include cadmium, wherein the first semiconductor nanocrystal includes zinc chalcogenide, and the quantum well layer includes an alloy semiconductor nanocrystal containing indium (In), phosphorus (P), zinc (Zn), and a chalcogen element, and wherein the bandgap energy of the alloy semiconductor nanocrystal is smaller than the bandgap energy of the first semiconductor nanocrystal.

[0063] In the quantum dot, the molar ratio of sulfur to indium may be 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, or greater than or equal to about 0.8:1. In the quantum dot, the molar ratio of sulfur to indium may be less than or equal to about 1.5:1, less than or equal to about 1.3:1, or less than or equal to about 1:1.

[0064] In the quantum well layer, the molar ratio of the sum of indium and zinc to the sum of phosphorus and sulfur ((In + Zn):(P + S)) may be greater than or equal to about 0.95:1 and less than or equal to about 1.6:1.

[0065] The first semiconductor nanocrystal may include zinc selenide.

[0066] In the quantum dot, the molar ratio of phosphorus to indium may be 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, or greater than or equal to about 0.8:1 and less than or equal to about 1.5:1, less than or equal to about 1.4:1, less than or equal to about 1.3:1, less than or equal to about 1.2:1, less than or equal to about 1.1:1, or less than or equal to about 1:1.

[0067] In an embodiment, the composition may include: (e.g., multiple) the above-mentioned quantum dots; a dispersant; a (photo)polymerizable monomer including a carbon-carbon unsaturated bond (e.g., a C═C double bond); a (thermal or photo)initiator; and an (organic) solvent (or a liquid carrier).

[0068] The dispersant may include a carboxylic acid group-containing compound (e.g., the above-mentioned binder polymer or its monomer).

[0069] The composition may further include a polythiol compound, metal oxide fine particles, or a combination thereof.

[0070] Quantum dots according to embodiments may exhibit improved properties (e.g., improved luminescence efficiency and enhanced blue light absorption). The quantum dots of the embodiments can be used in various display devices and biological markers (e.g., biosensors or bioimaging), photodetectors, solar cells, hybrid composites, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] The above and other advantages and features of the present disclosure will become more apparent by describing exemplary embodiments of the present disclosure in more detail with reference to the accompanying drawings, in which:

[0072] Figure 1 is a schematic view showing a cross-section of a quantum dot according to an embodiment,

[0073] Figure 2 is a schematic view showing a cross-section of a display device according to an embodiment,

[0074] Figure 3 is a schematic view showing a cross-section of a display device according to an embodiment,

[0075] Figure 4 is a schematic view showing a cross-section of a display device according to an embodiment,

[0076] Figure 5A schematically shows a patterning process using a composition according to an embodiment,

[0077] Figure 5B schematically shows a patterning process using a composition according to an embodiment, and

[0078] Figure 6 is a graph showing absorbance (arbitrary unit (a.u.)) versus wavelength (nm) of the results of the UV-Vis spectrum of the quantum dots prepared in Example 1. DETAILED DESCRIPTION

[0079] With reference to the following exemplary embodiments and the accompanying drawings, the advantages and characteristics of the present disclosure and methods for realizing the same will become apparent. However, the embodiments should not be construed as being limited to the embodiments set forth herein. All terms (including technical and scientific terms) in the specification may be defined as commonly understood by those of ordinary skill in the art unless otherwise defined. Terms defined in a general dictionary will not be idealized or exaggerated unless clearly defined otherwise. Also, unless explicitly described to the contrary, the word "comprise" and variations such as "comprises" or "comprising" will be understood to mean including the stated elements (features) but not excluding any other elements (features).

[0080] In the drawings, for clarity, the thickness of layers, films, panels, regions, etc. is exaggerated. Throughout the specification, like reference numerals denote like elements.

[0081] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements.

[0082] Furthermore, unless otherwise noted, the singular includes the plural. As used herein, unless the context clearly dictates otherwise, the terms “a,” “an,” “the,” and “at least one” do not denote a limitation of quantity, but rather are intended to include both the singular and the plural. For example, unless the context clearly dictates otherwise, “element” has the same meaning as “at least one element.” “At least one” is not to be construed as limiting “a” or “an.” “Or” means “and / or.” As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items. It will also be understood that when the terms “comprises” and / or “comprising” or their variants are used in this specification, they specify the presence of the stated features, regions, wholes, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or groups thereof.

[0083] 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 portions, these elements, components, regions, layers, and / or portions are not to be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or portion from another. Thus, the first “element,” “component,” “region,” “layer,” or “portion” discussed below could be termed a second element, component, region, layer, or portion without departing from the teachings herein.

[0084] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another element as shown in the figures. It will be understood that the relative terms are intended to cover different orientations of the device in addition to the orientation depicted in the figures. For example, if the device in one figure is flipped over, an element described as on the "lower" side of another element will then be positioned on the "upper" side of the other element. Thus, the exemplary term "lower" can include both the "lower" and "upper" orientations depending on the specific orientation of the figure. Similarly, if the device in one figure is flipped over, an element described as "beneath" or "under" another element will then be positioned "above" the other element. Thus, the exemplary terms "beneath" or "under" can include both the above and below orientations.

[0085] Taking into account the measurements discussed and the errors associated with the measurement of a particular quantity (i.e., the limitations of the measurement system), "about" as used herein includes the stated value and represents an acceptable deviation from the particular value as determined by one of ordinary skill in the art. For example, "about" can mean within one or more standard deviations, or within ±10% or ±5% of the stated value.

[0086] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic illustrations of idealized embodiments. As such, variations in the shape of the illustrations due to, for example, manufacturing techniques and / or tolerances are to be expected. Accordingly, the embodiments described herein should not be construed as limited to the particular shapes of regions shown herein, but will include deviations in shapes due to, for example, manufacturing. For example, a region shown or described as flat will typically have rough and / or non-linear features. Additionally, sharp corners shown may be rounded. Thus, the regions shown in the figures are schematic in nature, and their shapes are not intended to show the exact shape of the region and are not intended to limit the scope of the claims presented.

[0087] As used herein, when no other definition is provided, "substituted" means that a hydrogen of a compound is replaced by a substituent such as a C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C6-C30 aryl, C7-C30 alkylaryl, C1-C30 alkoxy, C1-C30 heteroalkyl, C3-C30 heteroalkylaryl, C3-C30 cycloalkyl, C3-C15 cycloalkenyl, C6-C30 cycloalkynyl, C2-C30 heterocycloalkyl, halogen (-F, -Cl, -Br or -I), hydroxy (-OH), nitro (-NO2), cyano (-CN), amino or amine (-NRR', where R and R' are each independently hydrogen or a C1-C6 alkyl), azido (-N3), amidino (-C(=NH)NH2), hydrazino (-NHNH2), hydrazono (=N(NH2)), aldehyde (-C(=O)H), carbamoyl (-C(O)NH2), mercapto (-SH), ester (-C(=O)OR, where R is a C1-C6 alkyl or a C6-C12 aryl), carboxy (-COOH) or its salt (-C(=O)OM, where M is an organic cation or an inorganic cation), sulfo (-SO3H) or its salt (-SO3M, where M is an organic cation or an inorganic cation), phosphono (-PO3H2) or its salt (-PO3MH or -PO3M2, where M is an organic cation or an inorganic cation), or a combination thereof.

[0088] As used herein, when no other definition is provided, "hetero" means including one to three heteroatoms such as N, O, S, Si or P.

[0089] As used herein, when no other definition is provided, "aliphatic hydrocarbon group" may mean a C1-C30 straight or branched alkyl, C2-C30 straight or branched alkenyl or C2-C30 straight or branched alkynyl.

[0090] As used herein, when no other definition is provided, "aromatic hydrocarbon group" may mean a C6-C30 aryl or a C2-C30 heteroaryl.

[0091] As used herein, when no other definition is provided, "(meth)acrylate" means acrylate, methacrylate or a combination thereof. (Meth)acrylate may include (C1-C10 alkyl) acrylate, (C1-C10 alkyl) methacrylate or a combination thereof.

[0092] As used herein, "dispersion" refers to a dispersion in which the dispersed phase is solid and the continuous phase comprises a liquid (or fluid). For example, "dispersion" may refer to a colloidal dispersion in which the dispersed phase has a size greater than or equal to about 1 nm (e.g., 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) and a few micrometers (μm) or less (e.g., about 2 μm or less, or about 1 μm or less).

[0093] As used herein, the term photoconversion efficiency refers to the percentage of the light emission (A) of the quantum dot complex relative to the excitation light (e.g., blue light) (B). As used herein, light absorption refers to the percentage of the amount of light absorbed by the quantum dot complex relative to the amount of incident light (e.g., blue light). The total amount of excitation light (B) is obtained by integrating the emission spectrum of the incident light, the amount of incident light (B') passing through the quantum dot polymer complex film is obtained, and the photoconversion rate, photoconversion efficiency, and light absorption rate are obtained by the following equations:

[0094] (A / B)×100% = photoconversion rate (%)

[0095] [A / (B - B')]×100% = (blue) photoconversion efficiency (CE%)

[0096] ((B - B') / B)×100% = blue light absorption rate (%).

[0097] The term "average" as used in this specification (e.g., the average size of quantum dots) may be the average value or the median value. In an embodiment, the average may be the "average" average value.

[0098] The quantum efficiency of the quantum dots can be a quantum yield that can be easily and reproducibly measured by any commercially available device (e.g., a device from Hitachi Co., Ltd. or Hamamatsu Co., Ltd.) with reference to the instruction manual provided by the manufacturer. In an embodiment, the quantum efficiency (or quantum yield) can be measured in a solution state or a solid state (in a complex). In an embodiment, the “quantum yield (or quantum efficiency)” can be, for example, the ratio of the photons emitted by a nanostructure or a population of nanostructures to the photons absorbed. In an embodiment, the quantum efficiency can be determined by any method. For example, there can be two methods for measuring the fluorescence quantum yield or efficiency: an absolute method and a relative method. The absolute method directly obtains the quantum yield by detecting all sample fluorescence using an integrating sphere. In the relative method, the fluorescence intensity of a standard sample (e.g., a standard dye) can be compared with the fluorescence intensity of an unknown sample to calculate the quantum yield of the unknown sample. Coumarin 153, Coumarin 545, Rhodamine 101 inner salt, Anthracene, and Rhodamine 6G can be used as standard dyes according to the photoluminescence (PL) wavelength, but are not limited thereto.

[0099] The full width at half maximum (FWHM) and the maximum PL peak wavelength can be determined by the photoluminescence spectrum obtained by a spectrophotometer (or a fluorescence spectrophotometer).

[0100] As used herein, the expression “excluding cadmium (or other harmful heavy metals)” can refer to a case where the concentration of cadmium (or other harmful heavy metals) can be less than or equal to about 100 parts per million by weight (ppmw), less than or equal to about 50 ppmw, less than or equal to about 10 ppmw, less than or equal to about 1 ppmw, less than or equal to about 0.1 ppmw, less than or equal to about 0.01 ppmw, or about zero. In an embodiment, the amount of cadmium (or other harmful heavy metals) can be substantially absent, or if present, the amount of cadmium (or other harmful heavy metals) can be less than or equal to the detection limit or the impurity level of a given analytical tool (e.g., inductively coupled plasma atomic emission spectrometry).

[0101] As used herein, the “first absorption peak” or its wavelength refers to the main peak that first appears in the lowest energy region of the ultraviolet-visible absorption spectrum and its wavelength.

[0102] Quantum dots (or semiconductor nanocrystal particles) are crystalline semiconductor materials having a size of several nanometers. Quantum dots can have a large surface area per unit volume and can exhibit a quantum confinement effect. Quantum dots can be excited by absorbing light from an excitation source and can emit energy corresponding to the bandgap energy of the quantum dots.

[0103] Due to the unique photoluminescence properties of quantum dots, quantum dots have potential utility in various electronic devices, for example. Quantum dots having properties that can be applicable (e.g., for) to electronic devices and the like can be cadmium-based quantum dots. However, cadmium causes environmental / health problems and is thus a restricted element. Cadmium-free quantum dots (hereinafter, also referred to as non-cadmium quantum dots) can include, for example, III-V-based nanocrystals. Compared with cadmium-based quantum dots, non-cadmium quantum dots may have poor photoluminescence properties (e.g., blue light absorption) and stability. Blue light (e.g., having a wavelength of about 450 nm) can be used as an energy excitation source for quantum dots. Cadmium-based quantum dots can have a high absorption intensity for blue light, but in the case of non-cadmium-based quantum dots, the absorption intensity at, for example, blue light (e.g., a wavelength of about 450 nm) is not high, and a display device including non-cadmium-based quantum dots will exhibit reduced brightness.

[0104] In an LCD device, polarized light from the liquid crystal layer passes through (via) an absorption type color filter and exhibits color, so a liquid crystal display (LCD) device can have problems of a narrow viewing angle and brightness degradation due to the low light transmittance of the absorption type color filter. A photoluminescence type color filter can be an alternative that overcomes the technical limitations of an LCD device including an absorption type color filter. A quantum dot-based color filter can use blue light instead of white light as an excitation light, and the color filter can be disposed in front of the display device to convert the excitation light into desired light (e.g., green light / red light). Therefore, a quantum dot-based color filter can reduce (e.g., minimize or solve) technical problems of a liquid crystal display, such as a narrow viewing angle and light loss. Light having linearity (passing through the liquid crystal layer and traveling straight) can be scattered in all directions, which can reduce (e.g., minimize or solve) the viewing angle problem. Light loss that may occur by using an absorption type color filter can also be reduced or minimized.

[0105] However, when a quantum dot-based color filter is adopted, the excitation light propagating in the forward direction of the display device (e.g., in the red light emitting part or the green light emitting part) may become a technical problem, and it may be necessary to block the excitation light propagating in the forward direction of the display device. Non-cadmium-based quantum dots cannot provide sufficient absorption to block the excitation light from propagating in the forward direction of the display device.

[0106] The introduction of a light scatterer can improve absorption. However, a light scatterer increases the manufacturing cost. A light scatterer can have a high external light reflectance, which may lead to an increase in external light reflection, and an increase in the solid content caused by the light scatterer provides additional difficulties in the process. To block the excitation light, a blue light filter can be used, which may cause additional costs and an increase in external light reflection, and may result in light loss, contrast degradation, and reduced image clarity of the display device.

[0107] The quantum dots according to an embodiment can exhibit increased blue light absorption (or blue light absorption rate) while not including cadmium, and can reduce (e.g., minimize or solve) the above problems. In the case of the quantum dots according to an embodiment, this increased excitation light absorption can contribute to, for example, suppressing blue light leakage in the case of a reduced amount (e.g., number) of light scatterers without the need to use a blue (excitation) light filter or a combination thereof.

[0108] In an embodiment, the quantum dot (or quantum dots, hereinafter may be referred to as quantum dots) does not include cadmium.

[0109] Referring to Figure 1 , the quantum dots of the embodiment include a template and a quantum well layer. The template includes a first semiconductor nanocrystal, and the quantum well layer is disposed on the template and includes an alloy semiconductor nanocrystal. The quantum well layer can surround a part (or all) of the surface of the template. A shell including a second semiconductor nanocrystal can be disposed on the quantum well layer.

[0110] The bandgap energy of the alloy semiconductor nanocrystal is smaller (e.g., less) than the bandgap energy of the first semiconductor nanocrystal, and is smaller (e.g., less) than the bandgap energy of the second semiconductor nanocrystal (if present). Referring to Figure 1 , in the energy band alignment, the valence band edge and the conduction band edge of the alloy semiconductor nanocrystal can be within the bandgap of the first semiconductor nanocrystal. The valence band edge and the conduction band edge of the alloy semiconductor nanocrystal can be within the bandgap of the second semiconductor nanocrystal. The bandgap energy can be known for bulk materials (e.g., ZnSe, InP, ZnS, ZnSeS, etc.) or can be calculated therefrom.

[0111] The bandgap energy of the first semiconductor nanocrystal and the bandgap energy of the second semiconductor nanocrystal can be the same or different. In an embodiment, the bandgap energy of the first semiconductor nanocrystal can be smaller than the bandgap energy of the second semiconductor nanocrystal. In an embodiment, the bandgap energy of the first semiconductor nanocrystal can be greater than or equal to the bandgap energy of the second semiconductor nanocrystal.

[0112] Both the first semiconductor nanocrystal and the second semiconductor nanocrystal independently include zinc chalcogenide (e.g., a compound including zinc and a chalcogen element such as selenium, tellurium, sulfur, or a combination thereof). The first zinc chalcogenide included in the first semiconductor nanocrystal and the second zinc chalcogenide included in the second semiconductor nanocrystal can have the same composition as each other. The first zinc chalcogenide and the second zinc chalcogenide can have different compositions from each other.

[0113] The zinc chalcogenide (e.g., the first semiconductor nanocrystal or the second semiconductor nanocrystal) can include ZnSe, ZnTeSe, ZnSeS, ZnS, ZnTeS, or a combination thereof. The first semiconductor nanocrystal can include zinc and selenium. The first semiconductor nanocrystal can include ZnSe, ZnSeS, ZnTeSe, or a combination thereof. The first semiconductor nanocrystal can include ZnSe. In an embodiment, the first semiconductor nanocrystal can include zinc and sulfur.

[0114] In an embodiment, the second semiconductor nanocrystal can include zinc and sulfur. The second semiconductor nanocrystal can include ZnSeS, ZnS, or a combination thereof. The shell can be a multi-layer shell. The multi-layer shell can include a first layer containing a third zinc chalcogenide and a second layer disposed (e.g., directly disposed) on the first layer and containing a fourth zinc chalcogenide. The fourth zinc chalcogenide can include a composition different from that of the third zinc chalcogenide. The first layer and the second layer can be (e.g., directly) on each other (e.g., (e.g., directly) in contact). The first layer can be directly disposed on the quantum well layer. The first layer and the second layer can include zinc chalcogenides having different compositions. The third zinc chalcogenide can include ZnSe, ZnTeSe, ZnSeS, ZnS, or a combination thereof, and the fourth zinc chalcogenide can independently include ZnSe, ZnTeSe, ZnSeS, ZnS, or a combination thereof. The first layer can include ZnSe, ZnSeS, or a combination thereof, and the second layer can include ZnS. The shell can have a ZnSe / ZnS structure. The second shell can form the outermost layer of the shell (e.g., the second shell can be the outermost layer of the shell).

[0115] The quantum well layer can be disposed between the template and the shell. The quantum well layer can be configured to absorb excitation light (e.g., blue light) and emit light whose emission can be controlled according to its bandgap energy (e.g., band-edge emission).

[0116] The quantum well layer includes an alloy semiconductor nanocrystal containing indium (In), phosphorus (P), zinc (Zn), and a chalcogen element. The chalcogen element may not include selenium. The alloy semiconductor nanocrystal can be a ternary alloy of InPZnS. The quantum well layer can include, for example, a relatively uniform alloy composition in the thickness direction of the quantum well layer.

[0117] In the quantum dots of the embodiments, a quantum well layer having a relatively narrow bandgap is disposed on a template having a relatively wide bandgap, and a passivation shell can be coated on the quantum well layer. The quantum well layer can act as an emission center. Compared with core-shell quantum dots having a similar structure, colloidal semiconductor nanocrystal particles having such a quantum well structure (hereinafter, may also be referred to as quantum well (QW) quantum dots) can exhibit improved blue light absorption. Without wishing to be bound by any theory, it is believed that, compared with an emission core of the same composition, the quantum well layer can achieve (e.g., exhibit) an increased volume, which can enhance light absorption. However, QW quantum dots tend to show (e.g., exhibit) a significant red shift in the emission wavelength of the QW quantum dots, which makes it difficult for QW quantum dots (e.g., in the green light region) to have a desired optical wavelength.

[0118] Without wishing to be bound by any theory, it is believed that QW quantum dots can have an interface between the template and the emission layer and an interface between the emission layer and the shell, and thus can have a much wider area than that of core-shell quantum dots having a similar composition. Therefore, the emission layer tends to have a larger number of defects and seriously hinders the uniform growth of the particles.

[0119] Without wishing to be bound by any theory, it is believed that, according to the energy levels, quantum dots having a quantum well structure will have an excessive number of tail states not only at the top of the conduction band but also at the bottom of the valence band, which also results in a red shift of the photoluminescence wavelength.

[0120] Surprisingly, the inventors have found that, by introducing the above alloy composition into the quantum well layer, the quantum dots of the embodiments can alleviate the red shift problem with substantially no adverse effects. Without wishing to be bound by any theory, it is believed that alloy semiconductor nanocrystals provided with a quantum well layer can significantly reduce the lattice mismatch (or "lattice misfit") at the interface between the template and the quantum well layer (and at the interface between the quantum well layer and the shell). This reduced lattice mismatch can control the number of defects in the formation of the quantum well layer and the subsequent formation of the shell, and also contribute to the uniform growth of the particles, enabling control of the emission wavelength with substantially no adverse effects such as a reduction in efficiency.

[0121] In the case of the quantum dots of the embodiments, the thickness of the quantum well layer for emitting a desired wavelength can be increased, which can also reduce structural disorder.

[0122] In the quantum dots of the embodiments, the difference between the lattice mismatch of the alloy semiconductor nanocrystals and the lattice mismatch of the first semiconductor nanocrystals can be less than or equal to about 3%. In the quantum dots of the embodiments, the difference between the lattice mismatch of the alloy semiconductor nanocrystals and the lattice mismatch of the second semiconductor nanocrystals can be less than or equal to about 3%. The quantum dots of the embodiments can emit light of a desired wavelength with a relatively high emission efficiency, and a polymer composite film including the quantum dots can exhibit (e.g., present) improved absorption and an increased level of light conversion rate or light conversion efficiency (CE%).

[0123] In an embodiment, the quantum well layer can include In 1-x P 1-y Zn x S y (where x is greater than 0, greater than or equal to about 0.01, greater than or equal to about 0.05, greater than or equal to about 0.1, greater than or equal to about 0.2, greater than or equal to about 0.3, greater than or equal to about 0.4, greater than or equal to about 0.5 and less than about 1, less than or equal to about 0.95, less than or equal to about 0.9, less than or equal to about 0.85, less than or equal to about 0.8, less than or equal to about 0.75, less than or equal to about 0.7 or less than or equal to about 0.6, and y is greater than 0, greater than or equal to about 0.01, greater than or equal to about 0.05, greater than or equal to about 0.1, greater than or equal to about 0.2, greater than or equal to about 0.3, greater than or equal to about 0.4, greater than or equal to about 0.5 and less than about 1, less than or equal to about 0.95, less than or equal to about 0.9, less than or equal to about 0.85, less than or equal to about 0.8, less than or equal to about 0.75, less than or equal to about 0.7, less than or equal to about 0.6 or less than or equal to about 0.55).

[0124] In the quantum dots of the embodiments, the template can include zinc and selenium, and the quantum well layer can include In 1-x P 1-y Zn x S y , and the shell can include zinc and sulfur. The shell can be a multi-layer shell, and the outermost layer can include ZnS. The shell can also include selenium.

[0125] In the quantum dots of the embodiments, based on the total molar amount of all elements of the quantum dots, the total molar amount of indium and phosphorus can be less than or equal to about 20%, less than or equal to about 19%, less than or equal to about 18%, less than or equal to about 17%, less than or equal to about 16%, less than or equal to about 15%, less than or equal to about 14%, less than or equal to about 13%, less than or equal to about 12%, less than or equal to about 11%, less than or equal to about 10%, less than or equal to about 9%, less than or equal to about 8%, less than or equal to about 7%, less than or equal to about 6%, less than or equal to about 5%, less than or equal to about 4%, or less than or equal to about 3% (as determined by suitable analytical tools such as XPS, ICP, etc.). Based on the total quantum dots, the total molar amount of indium and phosphorus can be greater than or equal to about 0.01%, greater than or equal to about 0.05%, greater than or equal to about 0.1%, greater than or equal to about 0.2%, greater than or equal to about 0.3%, greater than or equal to about 0.4%, greater than or equal to about 0.5%, greater than or equal to about 0.6%, greater than or equal to about 0.7%, greater than or equal to about 0.8%, greater than or equal to about 0.9%, or greater than or equal to about 1%.

[0126] As used herein, the amount of each component in the quantum dots can be measured (or determined) by using ICP, XPS, or another suitable measurement.

[0127] In the quantum dots of the embodiments, the molar ratio of zinc to indium can be greater than or equal to about 7:1, greater than or equal to about 9:1, greater than or equal to about 10:1, greater than or equal to about 13:1, greater than or equal to about 15:1, greater than or equal to about 18:1, greater than or equal to about 20:1, greater than or equal to about 22:1, greater than or equal to about 23:1, greater than or equal to about 24:1, greater than or equal to about 25:1, greater than or equal to about 26:1, greater than or equal to about 27:1, greater than or equal to about 28:1, greater than or equal to about 29:1, or greater than or equal to about 30:1. In the quantum dots of the embodiments, the molar ratio of zinc to indium can be less than or equal to about 55:1, less than or equal to about 50:1, less than or equal to about 45:1, less than or equal to about 40:1, less than or equal to about 35:1, less than or equal to about 30:1, less than or equal to about 25:1, or less than or equal to about 23:1.

[0128] In the quantum dots of the embodiments, the molar ratio of phosphorus to indium can be 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 0.51:1, greater than or equal to about 0.52:1, greater than or equal to about 0.53:1, greater than or equal to about 0.54:1, greater than or equal to about 0.55:1, greater than or equal to about 0.56:1, greater than or equal to about 0.57:1, greater than or equal to about 0.58:1, greater than or equal to about 0.59:1, greater than or equal to about 0.6:1, greater than or equal to about 0.65:1, greater than or equal to about 0.7:1 or greater than or equal to about 0.75:1. In the quantum dots of the embodiments, the molar ratio of phosphorus to indium can be less than or equal to about 1.5:1, less than or equal to about 1.4:1, less than or equal to about 1.3:1, less than or equal to about 1.2:1, less than or equal to about 1.1:1, less than or equal to about 1.09:1, less than or equal to about 1.08:1, less than or equal to about 1.07:1, less than or equal to about 1.06:1, less than or equal to about 1.05:1, less than or equal to about 1.04:1, less than or equal to about 1.03:1, less than or equal to about 1.02:1, less than or equal to about 1.01:1, less than or equal to about 1:1, less than or equal to about 0.95:1, less than or equal to about 0.9:1, less than or equal to about 0.85:1 or less than or equal to about 0.75:1.

[0129] In the quantum dots of the embodiments, the molar ratio of the sum of sulfur and selenium to zinc can be 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 or greater than or equal to about 0.8:1 and less than or equal to about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.85:1 or less than or equal to about 0.8:1.

[0130] In the quantum dots of the embodiments, the molar ratio of sulfur to selenium can be less than or equal to about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, less than or equal to about 0.6:1, less than or equal to about 0.5:1, less than or equal to about 0.4:1, less than or equal to about 0.39:1 or less than or equal to about 0.3:1 and greater than or equal to about 0.2:1, greater than or equal to about 0.3:1, greater than or equal to about 0.34:1 or greater than or equal to about 0.4:1.

[0131] In the quantum dots of the embodiments, the molar ratio of selenium to indium can be greater than or equal to about 9:1, greater than or equal to about 10:1, or greater than or equal to about 11:1. In the quantum dots of the embodiments, the molar ratio of selenium to indium can be less than or equal to about 40:1, less than or equal to about 35:1, less than or equal to about 30:1, less than or equal to about 25:1, less than or equal to about 20:1, less than or equal to about 15:1, or less than or equal to about 13:1. In the quantum dots of the embodiments, the molar ratio of selenium to indium can be greater than or equal to about 5:1, greater than or equal to about 6:1, greater than or equal to about 7:1, greater than or equal to about 8:1, greater than or equal to about 9:1, or greater than or equal to about 10:1.

[0132] In the quantum dots of the embodiments, the molar ratio of sulfur to indium can be greater than or equal to about 5:1, greater than or equal to about 6:1, greater than or equal to about 7:1, greater than or equal to about 8:1, greater than or equal to about 9:1, or greater than or equal to about 10:1. In the quantum dots of the embodiments, the molar ratio of sulfur to indium can be less than or equal to about 15:1, less than or equal to about 12:1, or less than or equal to about 10:1.

[0133] In the quantum dots of the embodiments, the molar ratio of zinc to selenium can be less than or equal to about 3:1 or less than or equal to about 2:1. In the quantum dots of the embodiments, the molar ratio of zinc to selenium can be greater than or equal to about 1.5:1.

[0134] In the quantum dots of the embodiments, the molar ratio of indium to selenium (or phosphorus to selenium) can be less than or equal to about 0.2:1, 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, or less than or equal to about 0.06:1; and / or greater than or equal to about 0.05:1.

[0135] The size of the template (e.g., diameter or equivalent diameter) or the thickness of the quantum well layer can be controlled by considering the desired wavelength and composition of the quantum dots. In the quantum dots of the embodiments, the size of the template can be greater than or equal to about 0.8 nm, greater than or equal to about 1 nm, greater than or equal to about 1.1 nm, greater than or equal to about 1.2 nm, greater than or equal to about 1.3 nm, greater than or equal to about 1.4 nm, greater than or equal to about 1.5 nm, greater than or equal to about 1.6 nm, greater than or equal to about 1.7 nm, greater than or equal to about 1.8 nm, greater than or equal to about 1.9 nm, greater than or equal to about 2 nm, greater than or equal to about 2.1 nm, greater than or equal to about 2.2 nm, greater than or equal to about 2.3 nm, greater than or equal to about 2.4 nm, greater than or equal to about 2.5 nm, greater than or equal to about 2.6 nm, greater than or equal to about 2.7 nm, greater than or equal to about 2.8 nm, greater than or equal to about 2.9 nm or greater than or equal to about 3.0 nm. The size of the template can be less than or equal to about 5 nm, less than or equal to about 4 nm, less than or equal to about 3.5 nm, less than or equal to about 3.45 nm, less than or equal to about 3.4 nm, less than or equal to about 3.3 nm, less than or equal to about 3.2 nm, less than or equal to about 3.1 nm, less than or equal to about 3 nm, less than or equal to about 2.9 nm, less than or equal to about 2.8 nm, less than or equal to about 2.7 nm, less than or equal to about 2.6 nm, less than or equal to about 2.5 nm, less than or equal to about 2.4 nm, less than or equal to about 2.3 nm, less than or equal to about 2.2 nm, less than or equal to about 2.1 nm or less than or equal to about 2 nm.

[0136] The thickness of the quantum well layer can be greater than or equal to about 0.05 nm, greater than or equal to about 0.1 nm, greater than or equal to about 0.15 nm, greater than or equal to about 0.2 nm, greater than or equal to about 0.25 nm, greater than or equal to about 0.3 nm, greater than or equal to about 0.35 nm, greater than or equal to about 0.4 nm, greater than or equal to about 0.45 nm or greater than or equal to about 0.5 nm. The thickness of the quantum well layer can be less than or equal to about 1.5 nm, less than or equal to about 1.4 nm, less than or equal to about 1.35 nm, less than or equal to about 1.33 nm, less than or equal to about 1.32 nm, less than or equal to about 1.31 nm, less than or equal to about 1.3 nm, less than or equal to about 1.2 nm, less than or equal to about 1.1 nm, less than or equal to about 1.0 nm, less than or equal to about 0.9 nm, less than or equal to about 0.8 nm, less than or equal to about 0.7 nm, less than or equal to about 0.6 nm, less than or equal to about 0.5 nm or less than or equal to about 0.35 nm.

[0137] The thickness of the shell can be greater than or equal to about 0.3 nm, greater than or equal to about 0.4 nm, greater than or equal to about 0.5 nm, greater than or equal to about 0.6 nm, greater than or equal to about 0.7 nm, greater than or equal to about 0.8 nm, greater than or equal to about 0.9 nm, greater than or equal to about 1 nm, greater than or equal to about 1.1 nm, greater than or equal to about 1.2 nm, greater than or equal to about 1.3 nm, greater than or equal to about 1.4 nm, or greater than or equal to about 1.5 nm and less than or equal to about 4 nm, less than or equal to about 3.5 nm, less than or equal to about 3.0 nm, less than or equal to about 2.9 nm, less than or equal to about 2.8 nm, less than or equal to about 2.7 nm, less than or equal to about 2.6 nm, less than or equal to about 2.4 nm, less than or equal to about 2.3 nm, less than or equal to about 2.2 nm, less than or equal to about 2.1 nm, less than or equal to about 2.0 nm, less than or equal to about 1.5 nm, less than or equal to about 1 nm, less than or equal to about 0.8 nm, or less than or equal to about 0.6 nm.

[0138] In embodiments, the size (or average size) of the quantum dots can be greater than or equal to about 3 nm, greater than or equal to about 4 nm, greater than or equal to about 5 nm, or greater than or equal to about 6 nm. In embodiments, the size (or average size) of the quantum dots can be less than or equal to about 20 nm, less than or equal to about 19 nm, less than or equal to about 18 nm, less than or equal to about 17 nm, less than or equal to about 16 nm, less than or equal to about 15 nm, less than or equal to about 14 nm, less than or equal to about 13 nm, less than or equal to about 12 nm, less than or equal to about 10 nm, less than or equal to about 9 nm, less than or equal to about 8 nm, less than or equal to about 7 nm, less than or equal to about 6 nm, or less than or equal to about 5 nm.

[0139] The size of the quantum dots can be the particle diameter. The size of the quantum dots can be the diameter or equivalent diameter calculated by converting the two-dimensional area identified by transmission electron microscopy. As used herein, a dimension such as size (e.g., a quantum dot-related dimension) can refer to its average (mean or median average) value (e.g., average size).

[0140] Quantum dots can form a group of quantum dots that emit green or red light (e.g., are included in a group of quantum dots that emit green or red light). The average size of the group of quantum dots can be greater than or equal to about 3 nm, greater than or equal to about 3.5 nm, greater than or equal to about 4 nm, greater than or equal to about 4.5 nm, greater than or equal to about 5.5 nm, greater than or equal to about 5.6 nm, greater than or equal to about 5.7 nm, greater than or equal to about 5.8 nm, greater than or equal to about 5.9 nm, or greater than or equal to about 6.0 nm. In an embodiment, the size of the quantum dots (e.g., emitting green light) can be less than or equal to about 30 nm, less than or equal to about 25 nm, less than or equal to about 20 nm, less than or equal to about 15 nm, less than or equal to about 14 nm, less than or equal to about 13 nm, less than or equal to about 12 nm, less than or equal to about 11 nm, or less than or equal to about 10 nm.

[0141] In an embodiment, the group of quantum dots can have a particle size distribution with an average size less than or equal to about 20%, less than or equal to about 19%, less than or equal to about 18%, less than or equal to about 17%, less than or equal to about 16%, or less than or equal to about 15% as the standard deviation.

[0142] In an embodiment, the quantum dots can include organic ligands located on the surface of the quantum dots. The organic ligands can include RCOOH, NH2, R2NH, R3N, RSH, RH2PO, R2HPO, R3PO, RH2P, R2HP, R3P, ROH, RCOOR, RPO(OH)2, RPOOH, RHPOOH, R2POOH, or a combination thereof (wherein R is the same or different and is independently a C1 to C40 aliphatic hydrocarbon group (e.g., a C1 to C40 or C3 to C24 alkyl group, a C2 to C40 or C3 to C24 alkenyl group, a C2 to C40 or C3 to C24 alkynyl group) or a C6 to C40 aromatic hydrocarbon group (e.g., a C6 to C20 aryl group)) or a combination thereof.

[0143] The organic ligands can coordinate to (e.g., or bind to) the surface of the obtained nanocrystals and can cause the nanocrystals to be well-dispersed in the solution, affect the luminescent properties and electrical properties of the quantum dots, or a combination thereof.

[0144] Examples of the organic ligand may include: methanethiol, ethanethiol, propanethiol, butanethiol, pentanethiol, hexanethiol, octanethiol, dodecanethiol, hexadecanethiol, octadecanethiol, or benzyl mercaptan; methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, dodecylamine, hexadecylamine, octadecylamine, dimethylamine, diethylamine, or dipropylamine; formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, lauric acid, palmitic acid, stearic acid, oleic acid, or benzoic acid; phosphines such as substituted or unsubstituted methylphosphine (e.g., trimethylphosphine, methyldiphenylphosphine, etc.), substituted or unsubstituted ethylphosphine (e.g., triethylphosphine, ethyldiphenylphosphine, etc.), substituted or unsubstituted propylphosphine, substituted or unsubstituted butylphosphine, substituted or unsubstituted pentylphosphine, or substituted or unsubstituted octylphosphine (e.g., trioctylphosphine (TOP)); phosphine oxides such as substituted or unsubstituted methylphosphine oxide (e.g., trimethylphosphine oxide, methyldiphenylphosphine oxide, etc.), substituted or unsubstituted ethylphosphine oxide (e.g., triethylphosphine oxide, ethyldiphenylphosphine oxide, etc.), substituted or unsubstituted propylphosphine oxide, substituted or unsubstituted butylphosphine oxide, or substituted or unsubstituted octylphosphine oxide (e.g., trioctylphosphine oxide (TOPO)); diphenylphosphine, triphenylphosphine, or their oxides; C5 to C20 alkylphosphinic acids or C5 to C20 alkylphosphonic acids (such as phosphonic acid, hexylphosphinic acid, octylphosphinic acid, dodecylphosphinic acid, tetradecylphosphinic acid, hexadecylphosphinic acid, or octadecylphosphinic acid), etc.; but not limited thereto. Two or more different organic ligands may be used. The organic ligand may include a mixture of a carboxylic acid compound and an amine compound.

[0145] In a quantum dot according to an embodiment, the UV-Vis absorption spectral curve of the quantum dot may not have an inflection point or a valley (i.e., a point at which the slope of the tangent to the curve changes from negative to positive) within a wavelength range that is greater than or equal to about 390 nm, greater than or equal to about 400 nm, greater than or equal to about 410 nm, greater than or equal to about 415 nm, greater than or equal to about 420 nm, greater than or equal to about 425 nm, greater than or equal to about 430 nm, greater than or equal to about 435 nm, greater than or equal to about 440 nm, greater than or equal to about 445 nm, greater than or equal to about 450 nm, greater than or equal to about 455 nm, greater than or equal to about 460 nm, greater than or equal to about 465 nm, greater than or equal to about 470 nm, greater than or equal to about 475 nm, greater than or equal to about 480 nm, greater than or equal to about 485 nm, or greater than or equal to about 490 nm and less than or equal to about 620 nm, less than or equal to about 550 nm, less than or equal to about 540 nm, less than or equal to about 530 nm, less than or equal to about 520 nm, less than or equal to about 510 nm, less than or equal to about 500 nm, less than or equal to about 495 nm, less than or equal to about 490 nm, less than or equal to about 485 nm, less than or equal to about 480 nm, less than or equal to about 475 nm, less than or equal to about 470 nm, less than or equal to about 465 nm, less than or equal to about 460 nm, less than or equal to about 455 nm, less than or equal to about 450 nm, less than or equal to about 445 nm, less than or equal to about 440 nm, less than or equal to about 435 nm, less than or equal to about 430 nm, less than or equal to about 425 nm, or less than or equal to about 420 nm (or a combined range of the listed limit values). In an embodiment, the UV-Vis absorption spectral curve of the quantum dot may not have a first absorption peak. Without wishing to be bound by any theory, it is believed that by including alloy semiconductor nanocrystals in the quantum well layer, the quantum dot can have a UV-Vis absorption spectrum that does not have an inflection point within the above wavelength range.

[0146] As used herein, an inflection point is a point on a curve at which the concavity changes. In an embodiment, the inflection point can be a point on a continuously differentiable planar curve at which the curve intersects the tangent to the curve. In an embodiment, the curve can exhibit a change from concave down to concave up or vice versa.

[0147] Without wishing to be bound by any theory, it is believed that the UV-Vis absorption spectrum of the embodiment can indicate that in the case of the quantum dot of the embodiment, the emission region exists in the quantum well layer including alloy semiconductor nanocrystals (different from core-shell structured quantum dots), and thus a quantum dot showing (e.g., presenting) the disclosed UV-Vis absorption spectrum can exhibit increased blue light absorption and increased quantum efficiency.

[0148] In the quantum dots of the embodiments, the alloy semiconductor nanocrystals can be included in the quantum well layer, can mitigate the lattice mismatch at the interfaces between the template and the quantum well layer and between the quantum well layer and the shell, and can control the bandgap energy of the quantum well layer such that the thickness of the quantum well layer for a desired emission wavelength can be increased. The quantum dots of the embodiments can solve the significant red-shift problem that would otherwise occur in the final QW structure, with substantially no adverse effect on the luminescence properties (e.g., quantum efficiency).

[0149] The quantum dots of the embodiments can emit light having wavelengths in a desired range (e.g., green or red light).

[0150] The quantum dots or green light can have a maximum emission peak wavelength in the range of greater than or equal to about 490 nm, greater than or equal to about 495 nm, greater than or equal to about 500 nm, greater than or equal to about 505 nm, greater than or equal to about 510 nm, greater than or equal to about 515 nm, or greater than or equal to about 520 nm and less than or equal to about 550 nm, less than or equal to about 545 nm, less than or equal to about 540 nm, less than or equal to about 535 nm, less than or equal to about 530 nm, less than or equal to about 525 nm, or less than or equal to about 520 nm. The quantum dots or red light can have a maximum emission peak wavelength in the range of greater than or equal to about 600 nm, greater than or equal to about 605 nm, greater than or equal to about 610 nm, greater than or equal to about 615 nm, or greater than or equal to about 620 nm and less than or equal to about 650 nm, less than or equal to about 645 nm, less than or equal to about 640 nm, less than or equal to about 635 nm, or less than or equal to about 620 nm.

[0151] The quantum dots of the embodiments (or the maximum emission peak of the quantum dots of the embodiments) can exhibit (e.g., present) a full width at half maximum of less than or equal to about 100 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 35 nm.

[0152] The quantum dots of the embodiments can have a quantum efficiency of greater than or equal to about 40% or greater than or equal to about 50%.

[0153] The quantum dots according to the embodiments are prepared by colloidal synthesis and thus can include organic ligands, organic solvents, or a combination thereof as described herein on the surface of the quantum dots. The organic ligands, organic solvents, or a combination thereof can bind to the surface of the quantum dots.

[0154] Thus, in an embodiment, a method of preparing the above-described quantum dots includes the following steps: obtaining a template including a first semiconductor nanocrystal; forming a quantum well layer including an alloy semiconductor nanocrystal; and, if desired, forming a shell including a second semiconductor nanocrystal on the quantum well layer.

[0155] Details of the template, the quantum well layer, and the shell are the same as those described herein. Metal precursors and non-metal precursors can be appropriately selected according to the compositions of the template, the quantum well layer, and the shell. The metal precursors can include metal powders, alkylated metals, metal carboxylates, metal hydroxides, metal halides, metal oxides, metal inorganic salts (e.g., metal nitrates, metal sulfates, etc.), metal acetylacetonates, or combinations thereof, but are not limited thereto. The non-metal precursors can include non-nitrogen-containing compounds used in quantum dot synthesis.

[0156] Hereinafter, the preparation of quantum dots including a template, a quantum well, and a shell is described, where the template includes a first semiconductor nanocrystal including zinc selenide, the quantum well includes a second semiconductor nanocrystal including indium, phosphorus, zinc, and sulfur, and the shell includes zinc and a chalcogen element (e.g., sulfur, selenium, or a combination thereof), but the present disclosure is not limited thereto.

[0157] To form the template, a zinc precursor and a selenium precursor react in an organic solvent in the presence of an organic ligand. The method can further include separating the formed template.

[0158] Details of the organic ligand are the same as those set forth herein. The organic solvent can be: a C6 to C22 primary amine, such as hexadecylamine; a C6 to C22 secondary amine, such as dioctylamine; a C6 to C40 tertiary amine, such as trioctylamine; a nitrogen-containing heterocyclic compound, such as pyridine; a C6 to C40 aliphatic hydrocarbon (e.g., alkane, alkene, alkyne, etc.), such as hexadecane, octadecane, octadecene, or squalane; a C6 to C30 aromatic hydrocarbon, such as phenyldodecane, phenyltetradecane, or phenylhexadecane; a phosphine substituted with a C6 to C22 alkyl group, such as trioctylphosphine; an oxide phosphine substituted with a C6 to C22 alkyl group, such as trioctylphosphine oxide; a C12 to C22 aromatic ether, such as phenyl ether or benzyl ether; or a combination thereof. The type and amount of the organic solvent can be appropriately selected considering the precursors and the organic ligand.

[0159] The formed template can be separated by adding a non-solvent, but is not limited thereto. For example, adding a non-solvent to the final reaction solution prepared can cause the nanocrystals coordinated (e.g., bound to the organic ligand) with the organic ligand to separate (e.g., precipitate). The separated template can be washed with the non-solvent. The non-solvent can be a polar solvent that is miscible with the solvent used in the reaction and in which the nanocrystals are not dispersible.

[0160] The non-solvent can be selected according to the organic 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 having a solubility parameter similar to that of the above solvents, or a combination thereof. Separation can be carried out by centrifugation, precipitation, chromatography or distillation. If desired, the separated nanocrystals can be added to a washing solvent and then washed. The washing solvent is not particularly limited, and a solvent having a solubility parameter similar to that of the organic ligand can be used. Examples of the washing solvent can include hexane, heptane, octane, chloroform, toluene and benzene.

[0161] To form a quantum well, an indium precursor, a phosphorus precursor, a zinc precursor and a chalcogen-containing precursor (e.g., a sulfur precursor) can be added simultaneously or sequentially to a reaction medium including an organic solvent, a template and optionally an organic ligand, and the reaction can be carried out therein. In the formation of the quantum well, the type and amount of the metal precursor / non-metal precursor can be selected by considering the composition and thickness of the quantum well. In an embodiment, the formation of the quantum well layer can be carried out in the presence of an excess of the zinc precursor. The amount of the indium precursor added to the reaction medium per 1 mole of zinc can be greater than or equal to about 0.1 mole, greater than or equal to about 0.3 mole, greater than or equal to about 0.5 mole and less than or equal to 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 or less than or equal to about 0.4 mole.

[0162] In an embodiment, similar to the formation of the template, the particles in which the quantum well layer is formed can be separated by adding a non-solvent to the reaction system. In an embodiment, the particles including the quantum well layer can be subjected to a shell formation reaction without separation.

[0163] The zinc precursor and the chalcogen-containing precursor can react to form a shell having a desired composition on the particles having the formed quantum well layer. To form a multi-layer shell, a desired combination of shell precursors can be added simultaneously or sequentially to the reaction system to carry out the reaction for forming each layer of the shell.

[0164] The reaction temperature in each step described herein can be selected by considering the type of the precursor compound, the organic ligand and the organic solvent.

[0165] The reaction time for forming a template, forming a quantum well layer, forming a shell, or a combination thereof can be controlled by taking into account the reactivity between precursors, the reaction temperature, and the desired thickness or size of the layer or particles. The reaction temperature can 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 220 °C, greater than or equal to about 230 °C, greater than or equal to about 240 °C, greater than or equal to about 250 °C, greater than or equal to about 260 °C, greater than or equal to about 270 °C, greater than or equal to about 280 °C, greater than or equal to about 290 °C, or greater than or equal to about 300 °C and less than or equal to about 360 °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 320 °C. The reaction time in each step can be less than or equal to about 2 hours, less than or equal to about 1 hour, or less than or equal to about 50 minutes. The reaction time can be greater than or equal to about 20 minutes, for example, greater than or equal to about 30 minutes.

[0166] In each of the above steps, the type, content, or combination thereof, or the ratio between them of the precursors can be determined by considering the composition of the precursors in the final quantum dots (templates, quantum wells, and shells), the reactivity of the precursors, etc.

[0167] Each of the above steps (e.g., formation of a template, formation of a quantum well layer, and formation of a shell) can include: heating (or vacuum treating) an organic solvent and a metal precursor (optionally, and a ligand compound) under vacuum at a predetermined temperature (e.g., greater than or equal to about 100 °C), and then heating them again at a predetermined temperature (e.g., greater than or equal to about 100 °C) after switching to an inert gas atmosphere.

[0168] The injection of a metal precursor, a non-metal precursor, or a combination thereof can be carried out sequentially or simultaneously, and the injection temperature can be appropriately selected. In an embodiment, during the formation of a multi-layer shell or a multi-layer quantum well, during the reaction time, a metal precursor, a non-metal precursor, or a combination thereof can be added several times in different ratios.

[0169] The precursors are not particularly limited and can be appropriately selected. In an embodiment, a zinc precursor can be appropriately selected.

[0170] In an embodiment, the type of zinc precursor can be appropriately selected. Examples of the zinc precursor can be Zn metal powder, alkylated Zn compounds (e.g., dimethylzinc, diethylzinc, etc.), Zn alcohol, Zn carboxylate (e.g., the reaction product between a zinc compound and a carboxylic acid compound having an alkyl group of C8 to C40, such as zinc oleate, zinc laurate, zinc stearate, etc.), Zn nitrate, Zn perchlorate, Zn sulfate, Zn acetylacetonate, Zn halide, Zn cyanide, Zn hydroxide, Zn oxide, Zn peroxide, or a combination thereof. Two or more different zinc precursors can be used.

[0171] The selenium precursor can include selenium-tri-n-octylphosphine (Se-TOP), selenium-tri-n-butylphosphine (Se-TBP), selenium-triphenylphosphine (Se-TPP), selenium-diphenylphosphine (Se-DPP), or a combination thereof, but is not limited thereto.

[0172] The indium precursor can be appropriately selected. Examples of the indium precursor can be trimethylindium, indium carboxylate of C1 or higher, C5 or higher, C10 or higher, or C12 or higher (such as indium acetate, indium palmitate, or indium stearate), indium hydroxide, indium chloride, indium oxide, indium nitrate, indium sulfate, or a combination thereof.

[0173] The phosphorus precursor can be appropriately selected. Examples of the phosphorus precursor can be tris(trimethylsilyl)phosphine, tris(dimethylamino)phosphine, triethylphosphine, tributylphosphine, trioctylphosphine, triphenylphosphine, tricyclohexylphosphine, or a combination thereof.

[0174] The sulfur precursor can be appropriately selected. The sulfur precursor can be a C6 to C20 alkyl (or alkenyl) thiol compound (having, for example, at least one thiol group), such as hexanethiol, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, mercaptopropylsilane, sulfur-tri-n-octylphosphine (S-TOP), sulfur-tri-n-butylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP), sulfur-tri-n-octylamine (S-TOA), bis(trimethylsilyl)sulfide, ammonium sulfide, sodium sulfide, or a combination thereof.

[0175] In an embodiment, the composition can include: (e.g., a plurality of) the above-mentioned quantum dots; a dispersant; and an (organic) solvent, a liquid carrier, or a combination thereof. The dispersant can disperse the quantum dots. The composition can further include a carboxylic acid group-containing compound (e.g., a monomer or a binder polymer). The composition can further include a (photo)polymerizable monomer containing a carbon-carbon double bond and an optional (thermal or photo)initiator. The composition can have photosensitivity.

[0176] Details of the quantum dots in the composition are described herein. The amount of the quantum dots in the composition can be appropriately adjusted considering the desired end use (e.g., color filters, etc.). In an embodiment, based on the solid content of the composition, the amount of the quantum dots can be greater than or equal to about 1 weight percent (wt%), e.g., greater than or equal to about 2 wt%, greater than or equal to about 3 wt%, greater than or equal to about 4 wt%, greater than or equal to about 5 wt%, greater than or equal to about 6 wt%, greater than or equal to about 7 wt%, greater than or equal to about 8 wt%, greater than or equal to about 9 wt%, greater than or equal to about 10 wt%, greater than or equal to about 15 wt%, greater than or equal to about 20 wt%, greater than or equal to about 25 wt%, greater than or equal to about 30 wt%, greater than or equal to about 35 wt%, or greater than or equal to about 40 wt%. Based on the solid content of the composition, the amount of the quantum dots can be less than or equal to about 70 wt%, e.g., less than or equal to about 65 wt%, less than or equal to about 60 wt%, less than or equal to about 55 wt%, or less than or equal to about 50 wt%. The weight percentages of the components in the composition relative to the total solid content can represent the contents of the components in the composite, which will be described herein.

[0177] The composition according to an embodiment can be used to provide a quantum dot polymer composite pattern. The composition according to an embodiment can be a photoresist composition including quantum dots applicable to lithography. The composition according to an embodiment can be an ink composition that can provide a pattern by printing (e.g., a droplet ejection method such as inkjet printing). The composition according to an embodiment may not include a conjugated (or conductive) polymer (except for the cardo binder to be described herein). The composition according to an embodiment can include a conjugated polymer. Herein, a conjugated polymer refers to a polymer having conjugated double bonds in the main chain of the polymer (e.g., poly(phenylene vinylene), etc.).

[0178] In the composition according to an embodiment, a dispersant can ensure the dispersion of the quantum dots. In an embodiment, the dispersant can be a binder (or binder polymer). The binder polymer can include a carboxylic acid group (e.g., in its repeating unit). The binder can be a compound (monomer or polymer) containing a carboxylic acid group. The binder can include a compound containing a carboxylic acid group. The binder can be an insulating polymer.

[0179] The dispersant or binder polymer may include: a monomer combination or their copolymer, the monomer combination including a first monomer containing a carboxyl group and a carbon-carbon double bond, a second monomer having a carbon-carbon double bond and a hydrophobic moiety and not including a carboxyl group, and an optional third monomer including a carbon-carbon double bond and a hydrophilic moiety and not including a carboxyl group; a polymer containing multiple aromatic rings, having a backbone structure in which two aromatic rings are bonded to a quaternary carbon atom and including a carboxyl group (-COOH) (hereinafter, cardo binder), the quaternary carbon atom being a constituent atom of another ring portion in the main chain; or a combination thereof. The dispersant may include the first monomer, the second monomer, and the optional third monomer.

[0180] In the composition, based on the total weight (or solid content) of the composition, the amount of the dispersant or binder polymer may be greater than or equal to about 0.5 wt%, for example, greater than or equal to about 1 wt%, greater than or equal to about 5 wt%, greater than or equal to about 10 wt%, greater than or equal to about 15 wt%, or greater than or equal to about 20 wt%, but not limited thereto. Based on the total weight (or solid content) of the composition, the amount of the binder polymer may be less than or equal to about 55 wt%, for example, less than or equal to about 50 wt%, less than or equal to about 40 wt%, less than or equal to about 35 wt%, less than or equal to about 33 wt%, or less than or equal to about 30 wt%. Based on the total weight of the solid content of the composition, the amount of the binder polymer may be about 0.5 wt% to about 55 wt%.

[0181] In the composition, polymerizable (e.g., photopolymerizable) monomers including carbon-carbon double bonds (hereinafter, may be referred to as "monomers") may include (e.g., photopolymerizable) (meth)acryloyl monomers. The monomers may be precursors for insulating polymers.

[0182] Based on the total weight of the composition, the amount of the monomer may be greater than or equal to about 0.5 wt%, for example, greater than or equal to about 1 wt% or greater than or equal to about 2 wt%. Based on the total weight of the composition, the amount of the monomer may be less than or equal to about 30 wt%, for example, less than or equal to about 28 wt%, less than or equal to about 25 wt%, less than or equal to about 23 wt%, less than or equal to about 20 wt%, less than or equal to about 18 wt%, less than or equal to about 17 wt%, less than or equal to about 16 wt%, or less than or equal to about 15 wt%.

[0183] The (photo)initiator included in the composition is a compound that initiates the (photo)polymerization of the above monomers in the composition. The initiator is a compound that promotes a radical reaction (e.g., radical polymerization of monomers) by generating radical chemicals under mild conditions (e.g., by heat or light). The initiator may be a thermal initiator or a photoinitiator. The initiator is not particularly limited and may be appropriately selected.

[0184] In the composition, the amount of the initiator can be appropriately adjusted by considering the type and amount of the polymerizable monomer. In the examples, based on the total weight of the composition (or the total weight of the solid content), the amount of the initiator can be greater than or equal to about 0.01 wt%, for example, greater than or equal to about 1 wt% and less than or equal to about 10 wt%, for example, less than or equal to about 9 wt%, less than or equal to about 8 wt%, less than or equal to about 7 wt%, less than or equal to about 6 wt% or less than or equal to about 5 wt%, but not limited thereto.

[0185] The composition (or the polymer matrix to be described later) can also include a (polyfunctional or monofunctional) thiol compound, metal oxide particles or a combination thereof, and the (polyfunctional or monofunctional) thiol compound has, for example, at least one thiol group at its end.

[0186] The metal oxide particles can include TiO2, SiO2, BaTiO3, Ba2TiO4, ZnO or a combination thereof. In the composition, based on the total weight of the composition (or its solid content), the amount of the metal oxide particles can be greater than or equal to about 1 wt%, greater than or equal to about 5 wt% or greater than or equal to about 10 wt% and less than or equal to about 50 wt%, less than or equal to about 40 wt%, less than or equal to about 30 wt%, less than or equal to about 25 wt%, less than or equal to about 20 wt%, less than or equal to about 15 wt%, less than or equal to about 10 wt% or less than or equal to about 5 wt%.

[0187] The metal oxide particles can have a diameter selected appropriately without particular limitation. The diameter of the metal oxide particles can be greater than or equal to about 100 nm, for example, greater than or equal to about 150 nm or greater than or equal to about 200 nm and less than or equal to about 1000 nm or less than or equal to about 800 nm.

[0188] The thiol compound can be a dithiol compound, a trithiol compound, a tetrathiol compound or a combination thereof. For example, the thiol compound can be ethylene glycol bis-3-mercaptopropionate, ethylene glycol dimercaptoacetate, trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetra(3-mercaptopropionate), pentaerythritol tetra(2-mercaptoacetate), 1,6-hexanedithiol, 1,3-propanedithiol, 1,2-ethanedithiol, polyethylene glycol dithiol including 1 to 10 ethylene glycol repeating units or a combination thereof.

[0189] Based on the total weight of the composition (or the total weight of the solid content), the amount of the thiol compound can be less than or equal to about 50 wt%, less than or equal to about 40 wt%, less than or equal to about 30 wt%, less than or equal to about 20 wt%, less than or equal to about 10 wt%, less than or equal to about 9 wt%, less than or equal to about 8 wt%, less than or equal to about 7 wt%, less than or equal to about 6 wt% or less than or equal to about 5 wt%. Based on the total weight of the composition (or the total weight of the solid content), the amount of the thiol compound can be greater than or equal to about 0.1 wt%, for example, greater than or equal to about 0.5 wt%, greater than or equal to about 1 wt%, greater than or equal to about 5 wt%, greater than or equal to about 10 wt% or greater than or equal to about 15 wt%.

[0190] The composition may further include an organic solvent (or a liquid carrier, hereinafter referred to as a solvent). The type of the available organic solvent is not particularly limited.

[0191] Examples of the solvent may include, but are not limited to: ethyl 3 - ethoxypropionate; ethylene glycol series such as ethylene glycol, diethylene glycol or polyethylene glycol; ethylene glycol ether series such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, diethylene glycol monomethyl ether, ethylene glycol diethyl ether or diethylene glycol dimethyl ether; ethylene glycol ether acetate series such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monoethyl ether acetate or diethylene glycol monobutyl ether acetate; propylene glycol series such as propylene glycol; propylene glycol ether series such as propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, propylene glycol dimethyl ether, dipropylene glycol dimethyl ether, propylene glycol diethyl ether or dipropylene glycol diethyl ether; propylene glycol ether acetate series such as propylene glycol monomethyl ether acetate or dipropylene glycol monoethyl ether acetate; amide series such as N - methylpyrrolidone, dimethylformamide or dimethylacetamide; ketone series such as methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK) or cyclohexanone; petroleum product series such as toluene, xylene or solvent naphtha; ester series such as ethyl acetate, propyl acetate, butyl acetate, cyclohexyl acetate or ethyl lactate; ether series such as diethyl ether, dipropyl ether or dibutyl ether; chloroform, C1 - C40 aliphatic hydrocarbons (e.g., alkanes, alkenes or alkynes), halogen (e.g., chlorine) - substituted C1 - C40 aliphatic hydrocarbons (e.g., dichloroethane, chloroform, etc.), C6 - C40 aromatic hydrocarbons (e.g., toluene, xylene, etc.), halogen (e.g., chlorine) - substituted C6 - C40 aromatic hydrocarbons; or combinations thereof.

[0192] The type and amount of the solvent can be appropriately selected by considering the above - mentioned main components (i.e., quantum dots, dispersants, photopolymerizable monomers, photoinitiators and, if used, thiol compounds) and the type and amount of the additives to be described herein. The composition may include the remaining amount of the solvent in addition to the desired amount of the solid content (non - volatile components).

[0193] A composition (e.g., an inkjet composition) may have a viscosity at 25 °C that is greater than or equal to about 4 centipoise (cPs), greater than or equal to about 5 cPs, greater than or equal to about 5.5 cPs, greater than or equal to about 6.0 cPs, or greater than or equal to about 7.0 cPs. The composition (e.g., an inkjet composition) may have a viscosity at 25 °C that is less than or equal to about 12 cPs, less than or equal to about 10 cPs, or less than or equal to about 9 cPs.

[0194] If the composition is applied in an inkjet process, the composition may be ejected onto a substrate at room temperature and may form, for example, a quantum dot polymer complex or a pattern of the quantum dot polymer complex by heating. Together with the disclosed viscosity, the ink composition may have a surface tension at 23 °C that is greater than or equal to about 21 millinewtons per meter (mN / m), greater than or equal to about 22 mN / m, greater than or equal to about 23 mN / m, greater than or equal to about 24 mN / m, greater than or equal to about 25 mN / m, greater than or equal to about 26 mN / m, greater than or equal to about 27 mN / m, greater than or equal to about 28 mN / m, greater than or equal to about 29 mN / m, greater than or equal to about 30 mN / m, or greater than or equal to about 31 mN / m and less than or equal to about 40 mN / m, less than or equal to about 39 mN / m, less than or equal to about 38 mN / m, less than or equal to about 37 mN / m, less than or equal to about 36 mN / m, less than or equal to about 35 mN / m, less than or equal to about 34 mN / m, less than or equal to about 33 mN / m, or less than or equal to about 32 mN / m. The surface tension of the ink composition may be less than or equal to about 31 mN / m, less than or equal to about 30 mN / m, less than or equal to about 29 mN / m, or less than or equal to about 28 mN / m.

[0195] If desired, in addition to the above components, the composition may further include various additives such as a light diffusing agent, a leveling agent, or a coupling agent.

[0196] The components (binder, monomer, solvent, additive, thiol compound, cardo binder, etc.) included in the composition of the examples (e.g., a photoresist composition) may be appropriately selected, and for details, reference may be made to, for example, that described in US-2017-0052444-A1.

[0197] The composition according to the examples may be prepared by a method including the following steps: preparing a quantum dot dispersion including the above-described quantum dots, a dispersant, and a solvent; and mixing the quantum dot dispersion with an initiator, a polymerizable monomer (e.g., an acryloyl monomer), an optional thiol compound, optional metal oxide fine particles, and an optional above additive. Each of the above components may be mixed sequentially or simultaneously, but the mixing order is not particularly limited.

[0198] The composition can provide quantum dot-polymer composites by (e.g., free radical) polymerization.

[0199] In embodiments, the quantum dot (polymer) composite includes: a polymer matrix; and the above-described quantum dots, dispersed in the polymer matrix. The (polymer) matrix can include a linear polymer, a crosslinked polymer, or a combination thereof. The crosslinked polymer can include a thiolene resin, a crosslinked poly(meth)acrylate, a crosslinked polyurethane, a crosslinked epoxy resin, a crosslinked vinyl polymer, a crosslinked silicone resin, or a combination thereof. The linear polymer can include repeating units derived from carbon-carbon unsaturated bonds (e.g., carbon-carbon double bonds). The repeating units can include carboxyl groups. The linear polymer can include ethylene repeating units.

[0200] The polymer matrix can include a dispersant (e.g., a binder polymer including carboxyl groups), a polymerization product of a polymerizable monomer having (at least one, e.g., at least two, at least three, at least four, or at least five) carbon-carbon double bonds (e.g., an insulating polymer), an optional polymerization product of a polymerizable monomer and a thiol compound (e.g., a polythiol compound having at least two thiol groups at its ends), or a combination thereof. The quantum dot-polymer composite can also include the above-described metal oxide particles.

[0201] In embodiments, the polymer matrix can include a crosslinked polymer and a dispersant (e.g., a (carboxyl group-containing) binder polymer). The polymer matrix can not include a conjugated polymer (except for cardo resins). The crosslinked polymer can include a thiolene resin, a crosslinked poly(meth)acrylate, or a combination thereof. In embodiments, the crosslinked polymer can be a polymerization product of a polymerizable monomer and an optional polythiol compound having at least two thiols (e.g., at its ends).

[0202] The quantum dots, the dispersant or binder polymer, the polymerizable monomer, and the polythiol compound can be the same as those described herein.

[0203] The film (or its pattern as described herein) of the quantum dot-polymer composite can have a thickness, for example, less than or equal to about 30 μm, e.g., less than or equal to about 25 μm, less than or equal to about 20 μm, less than or equal to about 15 μm, less than or equal to about 10 μm, less than or equal to about 8 μm, or less than or equal to about 7 μm and greater than or equal to about 2 μm, e.g., greater than or equal to about 3 μm, greater than or equal to about 3.5 μm, greater than or equal to about 4 μm, greater than or equal to about 5 μm, or greater than or equal to about 6 μm.

[0204] In an embodiment, the patterned film includes a repeating portion, the repeating portion including a first portion configured to emit a first light, wherein the first portion includes the above-mentioned quantum dot (polymer) complex. The repeating portion may include a second portion that emits a second light having a wavelength different from that of the first light, wherein the second portion may include a quantum dot polymer complex. The quantum dot polymer complex of the second portion may include a second quantum dot configured to emit the second light. The second quantum dot may include the above-mentioned quantum dot. The first light or the second light may be red light having a maximum photoluminescence peak wavelength between about 600 nm and about 650 nm (e.g., between about 620 nm and about 650 nm) or green light having a maximum photoluminescence peak wavelength between about 500 nm and about 550 nm (e.g., between about 510 nm and about 540 nm). The patterned film may further include a third portion that emits a third light (e.g., blue light) different from the first light and the second light. The third light may have a maximum peak wavelength in the range of about 380 nm to about 480 nm. As disclosed herein, the third portion may allow blue excitation light to pass through the patterned film of the quantum dot polymer complex.

[0205] In an embodiment, a display device includes a light source and a photoluminescent element, the photoluminescent element including a light-emitting layer, the light-emitting layer including a film or a patterned film of a quantum dot polymer complex. The light-emitting layer may be disposed on a (e.g., transparent) substrate. The light source is configured to provide incident light to the photoluminescent element. The incident light may have a luminescence peak wavelength greater than or equal to about 440 nm, e.g., greater than or equal to about 450 nm and less than or equal to about 500 nm, e.g., less than or equal to about 480 nm, less than or equal to about 470 nm, or less than or equal to about 460 nm.

[0206] In the light-emitting layer (e.g., the patterned film of the quantum dot polymer complex) of the display device according to an embodiment, the first portion may be a portion that emits red light, the second portion may be a portion that emits green light, and the light source may be an element that emits blue light and optionally green light.

[0207] In an embodiment, a first optical element that cuts (e.g., absorbs or reflects) blue light and optionally green light may be disposed on the front side (i.e., the light-emitting surface) of the first portion and the second portion.

[0208] In the above display device, the light source includes a plurality of light-emitting units corresponding to the first part and the second part, and the light-emitting unit may include a first electrode and a second electrode each having surfaces 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 materials of the electroluminescent device and the organic light-emitting diode (OLED) are not particularly limited. The light source includes an organic light-emitting diode (OLED) that emits blue light (and optionally green light).

[0209] Figure 2 is a schematic cross-sectional view of a display device according to an embodiment, Figure 3 is a schematic cross-sectional view of a display device according to an embodiment. Referring to Figure 2 and Figure 3 , the light source includes an organic light-emitting diode (OLED) that emits blue light. The organic light-emitting diode OLED may include: (at least two, e.g., 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 the substrate may be disposed under the organic light-emitting diode (OLED).

[0210] A stacked structure including a quantum dot polymer composite pattern 170 (e.g., a portion 31 including or not including quantum dots (e.g., emitting blue light), a portion 21 including red-emitting quantum dots, and a portion 11 including green-emitting quantum dots), a filter layer 160, and a transparent substrate (or referred to as an upper substrate) 240 may be disposed on the light source. The excitation light (e.g., blue light) emitted from the light source and incident on the patterned portion is converted into red light and green light, respectively. The blue light emitted from the light source may pass through the third portion of the patterned quantum dot polymer composite.

[0211] The display device may be obtained by separately preparing the above stacked structure and an (e.g., blue light-emitting) LED or OLED and then assembling them. The display device may be obtained by directly forming a quantum dot polymer composite pattern on the LED or OLED.

[0212] 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) or polyethylene naphthalate (PEN)); polycarbonate or polyacrylate; polysiloxane (e.g., polydimethylsiloxane (PDMS)); inorganic materials such as Al2O3 or ZnO; or combinations thereof, but not limited thereto. Considering the substrate material, the thickness of the substrate can be appropriately selected, but there is no particular limitation. The substrate may be flexible. For the light emitted from the quantum dots, 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%.

[0213] A wiring layer including thin film transistors and the like is formed on the substrate. The wiring layer may further include a gate line, a sustain voltage line, a gate insulating layer, a data line, a source electrode, a drain electrode, a semiconductor, a protective layer, and the like. According to embodiments, the detailed structure of the wiring layer can be determined. The gate line and the sustain voltage line are electrically separated from each other, and the data line is insulated from and crosses the gate line and the sustain voltage line. The gate electrode, the source electrode, and the drain electrode form the control terminal, the input terminal, and the output terminal of the thin film transistor, respectively. The drain electrode is electrically connected to the pixel electrode to be described herein.

[0214] The pixel electrode may be used as the 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 light-blocking properties 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 two-layer structure in which a transparent conductive material and a material having light-blocking properties are sequentially stacked.

[0215] Between two adjacent pixel electrodes, a pixel defining layer (PDL) may be stacked with the ends of the pixel electrodes to divide the pixel electrodes into pixel units. The pixel defining layer may be an insulating layer that can resistively block at least two pixel electrodes.

[0216] The pixel defining layer may cover a part of the upper surface of the pixel electrode, and the remaining area of the pixel electrode not covered by the pixel defining layer may provide an opening. The organic emission layer to be described herein may be formed in the area defined by the opening.

[0217] 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 an area in which one organic emission unit layer is formed, and the organic emission unit layer is in contact with one pixel electrode divided by the pixel defining layer.

[0218] In a display device according to an embodiment, an organic emission layer may be defined as a first pixel region, a second pixel region, and a third pixel region, and each pixel region may be separated from each other by a pixel defining layer with a predetermined interval therebetween.

[0219] In an embodiment, the organic emission layer may emit a third light belonging to the visible light region or the ultraviolet (UV) region. In other words, each of the first pixel region to the third pixel region of the organic emission layer may emit the third light. In an embodiment, the third light may be the light with the highest energy in the visible light region, for example, it may be blue light. When all pixel regions of the organic emission layer are configured to emit the same kind of light, each pixel region of the organic emission layer may be formed of the same or similar materials, or may exhibit (e.g., present) the same or similar properties. Accordingly, the process difficulty of forming the organic emission layer may be reduced (e.g., alleviated), and the display device may be applied to (e.g., used for) large-scale / large-area processing. However, the organic emission layer according to an embodiment is not limited thereto, but the organic emission layer may be configured to emit at least two different lights.

[0220] The organic emission layer includes an organic emission unit layer in each pixel region, and in addition to the emission layer, each organic emission unit layer may further include auxiliary layers (e.g., a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), etc.).

[0221] The common electrode may serve as the 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 with the organic emission layer.

[0222] A planarization layer or a passivation layer (not shown) may be formed on the common electrode. The planarization layer may include an insulating material (e.g., transparent) for ensuring electrical insulation from the common electrode.

[0223] In an embodiment, the display device may further include a lower substrate, a polarizer disposed under the lower substrate, and a liquid crystal layer disposed between the stacked structure and the lower substrate, in which a light-emitting layer may be disposed to face the liquid crystal layer. The display device may further include a polarizer located between the liquid crystal layer and the emission layer. The light source may further include an LED, and if desired, may further include a light guide panel.

[0224] A non-limiting example of a display device (e.g., a liquid crystal display device) according to an embodiment is shown with reference to the accompanying drawings. Figure 4 is a schematic cross-sectional view showing a liquid crystal display device according to an embodiment. Refer to Figure 4, the display device of the embodiment includes a liquid crystal panel 200, a polarizer 300 disposed under the liquid crystal panel 200, and a backlight unit disposed under the polarizer 300.

[0225] The liquid crystal panel 200 includes a lower substrate 210, a stacked structure, and a liquid crystal layer 220 disposed between the stacked structure and the lower substrate 210. The stacked structure includes a transparent substrate 240, a first filter layer 310, a photoluminescent layer 230 including a pattern of a quantum dot polymer composite, and a second filter layer 311.

[0226] The lower substrate 210, also referred to as an array substrate, may be a transparent insulating material substrate. The substrate is the same as that described herein. A wiring board 211 is disposed on the upper surface of the lower substrate 210. The wiring board 211 may include a plurality of gate lines (not shown) and a plurality of data lines (not shown) that define a pixel region, thin film transistors disposed adjacent to the crossing regions of the gate lines and the data lines, and pixel electrodes for each pixel region, but is not limited thereto. The details of such a wiring board are not particularly limited.

[0227] The liquid crystal layer 220 may be disposed on the wiring board 211. The liquid crystal panel 200 may include alignment layers 221 on and under the liquid crystal layer 220 to initially align the liquid crystal material included therein. The details of the liquid crystal layer and the alignment layer (such as the liquid crystal material, the alignment layer material, the method of forming the liquid crystal layer, the thickness of the liquid crystal layer, etc.) are not particularly limited.

[0228] The lower polarizer 300 is disposed under the lower substrate 210. The material and structure of the polarizer 300 are not particularly limited. A backlight unit (e.g., emitting blue light) may be disposed under the polarizer 300.

[0229] An upper optical element or an upper polarizer 300 may be disposed between the liquid crystal layer 220 and the transparent substrate 240, but is not limited thereto. For example, the upper polarizer may be disposed 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 upper polarizer may be a TAC (triacetyl cellulose) having a thickness less than or equal to about 200 μm, but is not limited thereto. In an embodiment, the upper optical element may be a coating that controls the refractive index without a polarizing function.

[0230] The backlight unit includes a light source 110. The light source 110 may emit blue light or white light. The light source 110 may include a blue LED, a white LED, a white OLED, or a combination thereof, but is not limited thereto.

[0231] The backlight unit may further include a light guide panel 120. In an embodiment, the backlight unit may be edge lighting. For example, the backlight unit may include a reflector (not shown), a light guide panel (not shown) disposed on the reflector and providing a planar light source to the liquid crystal panel 200, an optical sheet (not shown) (e.g., a diffusion plate, a prism sheet, etc.) located on the light guide panel, or a combination thereof, but not limited thereto. In an embodiment, the backlight unit does not include a light guide panel. In an embodiment, the backlight unit may be direct-lit illumination. For example, the backlight unit may have a reflector (not shown), and may have a plurality of fluorescent lamps disposed on the reflector at regular intervals, or may have an LED operation substrate on which a plurality of light-emitting diodes may be disposed, a diffusion plate located on the LED operation substrate, and an optional optical sheet. Details of such a backlight unit (e.g., each component of the light-emitting diode, fluorescent lamp, light guide panel, various optical sheets, and reflector) are not particularly limited.

[0232] The black matrix (BM) 241 is disposed on or under the bottom surface of the transparent substrate 240 and has openings, and hides the gate lines, data lines, and thin film transistors of the wiring board located on the lower substrate. For example, the black matrix 241 may have a grid shape. The photoluminescent layer 230 is disposed in the openings of the black matrix 241 and has a quantum dot polymer composite pattern, and the quantum dot polymer composite pattern includes a first part (R) configured to emit a first light (e.g., red light), a second part (G) configured to emit a second light (e.g., green light), and a third part (B) configured to emit / transmit, for example, blue light. If desired, the photoluminescent layer 230 may further include a fourth part. The fourth part may include quantum dots that emit light of a color different from the colors of the light emitted from the first part to the third part (e.g., cyan light, magenta light, and yellow light).

[0233] In the light-emitting (photoluminescent) layer 230, the patterned parts may be repeated corresponding to the pixel regions formed on the lower substrate 210. The transparent common electrode 231 may be disposed on the photoluminescent layer (e.g., the photoluminescent color filter layer).

[0234] The third part (B) configured to emit / transmit blue light may be a transparent color filter that does not change the photoluminescent spectrum of the light source. In this case, the blue light emitted from the backlight unit may enter in a polarized state and may pass through the lower polarizer and the liquid crystal layer and be emitted as it is. If desired, the third part may include quantum dots that emit blue light.

[0235] If desired, the display device may further include a blue light blocking layer (e.g., a blue light cut-off color filter) or a first filter layer. The blue light blocking layer or the first filter layer may be disposed between the first portion (R) and the second portion (G) (bottom surface thereof) and the upper substrate 240 or on the top surface of the upper substrate 240. The blue light blocking layer or the first filter layer may include a sheet having an opening corresponding to a pixel region that displays blue (e.g., the third portion), and may be formed on a portion corresponding to the first portion and the second portion. As Figure 4 shown, the first filter layer 310 may be integrally formed as an integral structure at the remaining positions except for the position where it overlaps with the third portion, but is not limited thereto. At least two first filter layers may be separated and disposed on each of the positions where they overlap with the first portion and the second portion.

[0236] In an embodiment, the first filter layer may block light having a part of the wavelength region in the visible light region and transmit light having other wavelength regions. In an embodiment, the first filter layer may block blue light and transmit light other than blue light. In an embodiment, the first filter layer may transmit green light, red light, and / or yellow light that is a mixed light of green light and red light.

[0237] In an embodiment, the first filter layer may substantially block blue light having a wavelength less than or equal to about 500 nm, and may transmit light in the visible light having a wavelength in the range greater than about 500 nm and less than or equal to about 700 nm.

[0238] In an embodiment, with respect to visible light greater than about 500 nm and less than or equal to about 700 nm, the first filter layer may have a light transmittance greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or about 100%.

[0239] The first filter layer may include a polymer film that includes a dye, a pigment, or a combination thereof that absorbs light having a wavelength to be blocked. The first filter layer may block (e.g., absorb) blue light having a wavelength less than or equal to about 480 nm by greater than or equal to about 80%, greater than or equal to about 90%, or greater than or equal to about 95%, and may have a light transmittance greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or about 100% with respect to other visible light greater than about 500 nm and less than or equal to about 700 nm.

[0240] The first filter layer may block (e.g., absorb) or substantially block blue light having a wavelength less than or equal to about 500 nm, and may selectively transmit, for example, green light or red light. In this case, at least two first filter layers may be separated and respectively disposed on each of the portions that overlap with the first portion and the second portion. For example, respectively, the first filter layer that selectively transmits red light may be disposed on the portion that overlaps with the portion emitting red light, and the first filter layer that selectively transmits green light may be disposed on the portion that overlaps with the portion emitting green light. For example, the first filter layer may include a first region, a second region, or a combination thereof, where the first region blocks (e.g., absorbs) blue light and red light and transmits light having a predetermined range of wavelengths (e.g., greater than or equal to about 500 nm, greater than or equal to about 510 nm, or greater than or equal to about 515 nm and less than or equal to about 550 nm, less than or equal to about 545 nm, less than or equal to about 540 nm, less than or equal to about 535 nm, less than or equal to about 530 nm, less than or equal to about 525 nm, or less than or equal to about 520 nm), and the second region blocks (e.g., absorbs) blue light and green light and transmits light having a predetermined range of wavelengths (e.g., greater than or equal to about 600 nm, greater than or equal to about 610 nm, or greater than or equal to about 615 nm and less than or equal to about 650 nm, less than or equal to about 645 nm, less than or equal to about 640 nm, less than or equal to 635 nm, less than or equal to about 630 nm, less than or equal to about 625 nm, or less than or equal to about 620 nm). The first region may be disposed at a position that overlaps with the portion emitting green light, and the second region may be disposed at a position that overlaps with the portion emitting red light. The first region and the second region may be optically isolated. The first filter (layer) may contribute to improving the color purity of the display device.

[0241] The first filter layer may be a reflective filter including a plurality of layers (e.g., inorganic material layers) having different refractive indices. For example, two layers having different refractive indices may be stacked alternately with each other, or for example, a layer having a high refractive index and a layer having a low refractive index may be stacked alternately with each other.

[0242] When the difference in refractive index between the layer having a high refractive index and the layer having a low refractive index increases, the first filter layer thus formed may have higher (e.g., greater) wavelength selectivity. The thicknesses and stacking numbers of the layer having a high refractive index and the layer having a low refractive index may be determined based on the refractive index and reflection wavelength of each layer. For example, each layer having a high refractive index may have a thickness of about 3 nm to about 300 nm, and each layer having a low refractive index may have a thickness of about 3 nm to about 300 nm.

[0243] The total thickness of the first filter layer can be, for example, about 3 nm to about 10,000 nm, about 300 nm to about 10,000 nm, or about 1,000 nm to about 10,000 nm. All the layers with a high refractive index can have the same thickness and the same material as each other or can have different thicknesses and different materials from each other, and all the layers with a low refractive index can have the same thickness and the same material as each other or can have different thicknesses and different materials from each other.

[0244] The display device may further include a second filter layer (e.g., a red / green or yellow recycling layer), the second filter layer (e.g., a red / green or yellow recycling layer) being disposed between the light-emitting layer and the liquid crystal layer (e.g., between the light-emitting layer and the upper polarizer) and transmitting at least a part of the third light and reflecting at least a part of the first light and the second light. The second filter layer may reflect light in a wavelength region greater than about 500 nm. The first light may be red light, the second light may be green light, and the third light may be blue light.

[0245] In the display device according to an embodiment, the second filter layer may be formed as an integrated single layer having a relatively flat surface.

[0246] In an embodiment, the second filter layer may include a single layer having a low refractive index. For example, the second filter layer may be a transparent thin film having a refractive index less than or equal to about 1.4, less than or equal to about 1.3, or less than or equal to about 1.2.

[0247] The second filter layer having a low refractive index may be, for example, porous silica, porous organic material, porous organic / inorganic composite, or a combination thereof.

[0248] In an embodiment, the second filter layer may include a plurality of layers having different refractive indices. For example, the second filter layer may be formed by alternately stacking two layers having different refractive indices, or for example, the second filter layer may be formed by alternately stacking a material having a high refractive index and a material having a low refractive index.

[0249] The layer having a high refractive index in the second filter layer may include, for example, hafnium oxide, tantalum oxide, titanium oxide, zirconium oxide, magnesium oxide, cesium oxide, lanthanum oxide, indium oxide, niobium oxide, aluminum oxide, silicon nitride, or a combination thereof. According to an embodiment, the layer having a high refractive index in the second filter layer may include various materials having a refractive index higher than that of the layer having a low refractive index.

[0250] The layer having a low refractive index in the second filter layer may include, for example, silicon oxide. According to an embodiment, the layer having a low refractive index in the second filter layer may include various materials having a refractive index lower than that of the layer having a high refractive index.

[0251] When the refractive index difference between the layer with a high refractive index and the layer with a low refractive index increases, the second filter layer can have higher (e.g., greater) wavelength selectivity.

[0252] In the second filter layer, the respective thicknesses and the number of stacks of the layer with a high refractive index and the layer with a low refractive index can be determined based on the refractive index and the reflection wavelength of each layer. For example, each layer with a high refractive index in the second filter layer can have a thickness of about 3 nm to about 300 nm, and each layer with a low refractive index in the second filter layer can have a thickness of about 3 nm to about 300 nm. The total thickness of the second filter layer can be, for example, about 3 nm to about 10,000 nm, about 300 nm to about 10,000 nm, or about 1,000 nm to about 10,000 nm. Each of the layer with a high refractive index and the layer with a low refractive index in the second filter layer can have the same thickness and material as each other or different thicknesses and materials from each other.

[0253] The second filter layer can reflect at least a part of the first light (R) and the second light (G), and transmit at least a part (e.g., all) of the third light (B). For example, the second filter layer can transmit only the third light (B) in the blue light wavelength region of less than or equal to about 500 nm, and the light in the wavelength region greater than about 500 nm (i.e., green light (G), yellow light, red light (R), etc.) can neither pass through the second filter layer 311 nor be reflected. Therefore, the reflected green light and red light can pass through the first part and the second part to be emitted to the outside of the display device.

[0254] The second filter layer can reflect greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or about 100% of the light in the wavelength region greater than about 500 nm.

[0255] Meanwhile, the second filter layer can have a transmittance of, for example, greater than or equal to about 90%, greater than or equal to about 92%, greater than or equal to about 94%, greater than or equal to about 96%, greater than or equal to about 98%, greater than or equal to about 99%, or about 100% for the light in the wavelength region less than or equal to about 500 nm.

[0256] In an embodiment, the stacked structure can be prepared by a method using a photoresist composition. The method can include the following steps:

[0257] Forming a film of the composition on a substrate;

[0258] Exposing selected regions of the film to light (e.g., a wavelength of less than or equal to about 400 nm); and

[0259] Develop the exposed film with an alkaline developer solution to obtain a pattern including the quantum dot polymer composite.

[0260] The substrate and the composition are the same as those described herein. Refer to Figure 5A for a non-limiting method of forming a pattern.

[0261] Coat the composition on the substrate by a suitable method such as spin coating or slot coating to have a predetermined thickness (S1). Optionally, the formed film can be pre-baked (PRB) (S2). The pre-baking can be performed by selecting appropriate conditions such as temperature, time, atmosphere, etc.

[0262] Under a mask having a predetermined pattern, expose the formed (or optionally pre-baked) film to light having a predetermined wavelength (S3). The wavelength and intensity of the light can be selected by considering the initiator (e.g., photoinitiator), the amount of the initiator (e.g., photoinitiator), the quantum dots, the amount of the quantum dots, etc.

[0263] Treat the exposed film with an alkaline developer solution (e.g., dipping or spraying) to dissolve the unexposed areas and obtain the desired pattern (S4). Optionally, the obtained pattern can be post-baked (POB) at, for example, about 150 °C to about 230 °C for a predetermined time (e.g., greater than or equal to about 10 minutes or greater than or equal to about 20 minutes) (S5) to improve the crack resistance and solvent resistance of the pattern.

[0264] In an embodiment where the quantum dot polymer composite pattern has multiple repeating portions, a quantum dot polymer composite having a desired pattern can be obtained by: preparing a plurality of compositions including quantum dots having desired photoluminescence properties (such as photoluminescence peak wavelength, etc.) to form each repeating portion (e.g., red-emitting quantum dots, green-emitting quantum dots, or optionally blue-emitting quantum dots); and repeating the formation of the pattern an appropriate number of times (e.g., two or more times or three or more times) for each composition (S6). For example, the quantum dot polymer composite can have a pattern including at least two repeating color portions (e.g., RGB portions), and can be set to have a pattern including at least two repeating color portions (e.g., RGB portions). The quantum dot polymer composite pattern can be used as a photoluminescent color filter in a display device.

[0265] The quantum dot composite pattern can be formed by using an ink composition configured to form a pattern via an inkjet method. Refer to Figure 5B, the method includes the following steps: preparing an ink composition; obtaining a substrate including a pattern such as an electrode and an optional pixel region formed by a bank; depositing the ink composition on the substrate (or the pixel region) to form a first quantum dot layer (or a first repeating portion); and depositing the ink composition on the substrate (or the pixel region) to form a second quantum dot layer (or a second repeating portion). The formation of the first quantum dot layer and the second quantum dot layer can be carried out simultaneously or sequentially.

[0266] The deposition of the ink composition can be carried out using a suitable droplet ejection system such as an inkjet printer or a nozzle printing system (e.g., having an ink reservoir and at least one print head, for example).

[0267] The deposited ink composition can be heated to remove the solvent and optionally polymerized to provide the (first or second) quantum dot layer. The method can provide a highly precise quantum dot polymer composite film or pattern in a simple manner and in a short time.

[0268] Embodiments provide an electronic device including quantum dots. The electronic device can include a light emitting diode (LED), an organic light emitting diode (OLED), a sensor, a solar cell, an imaging sensor, or a liquid crystal display (LCD), but is not limited thereto.

[0269] Hereinafter, the embodiments will be described in more detail with reference to examples. However, they are exemplary embodiments of the present invention, and the present invention is not limited thereto.

[0270] Examples

[0271] Analysis methods

[0272] 1. Ultraviolet-visible (UV-Vis) absorption spectroscopy

[0273] UV-Vis absorption spectroscopy was carried out, and the UV-visible absorption spectrum was obtained by using an Agilent Cary5000 spectrophotometer.

[0274] 2. Photoluminescence analysis

[0275] The photoluminescence (PL) spectrum of the produced quantum dots at an excitation wavelength of 450 nanometers (nm) was obtained using a Hitachi F-7000 spectrophotometer.

[0276] 3. Inductively coupled plasma atomic emission spectroscopy (ICP-AES)

[0277] Inductively coupled plasma atomic emission spectroscopy (ICP-AES) was carried out using a Shimadzu ICPS-8100.

[0278] 4. Blue light absorption rate and conversion efficiency (CE) of the composite

[0279] Measure the amount of blue excitation light (B) using an integrating sphere. Then, place the quantum dot polymer composite in the integrating sphere and irradiate it with blue excitation light to measure the amount of green light (A) and the amount of blue light (B') emitted from the composite.

[0280] Calculate the blue light absorption and the light conversion efficiency according to the following equations.

[0281] Blue light absorption rate (%) = ((B - B') / B) × 100 (%)

[0282] Light conversion efficiency (%) = (A / (B - B')) × 100 (%)

[0283] Light conversion rate (%, QE) = (A / B) × 100 (%)

[0284] Example 1:

[0285] 1. Synthesis of quantum well (QW) quantum dots

[0286] Template synthesis:

[0287] Disperse selenium in trioctylphosphine (TOP) to obtain a Se / TOP stock solution. In a 300 milliliter (mL) reaction flask containing trioctylamine, add an organic ligand including oleic acid, and then heat it under vacuum at 120 °C. After about 1 hour, the atmosphere in the reactor is changed to an inert gas. When the temperature of the reactor rises to 300 °C, inject diethylzinc, diphenylphosphine oxide, and the Se / TOP stock solution into it. After the injection is completed, carry out the reaction for 40 minutes.

[0288] When the reaction is completed, add acetone to the reaction solution that is quickly cooled to room temperature, and disperse the precipitate obtained by centrifuging the mixture in toluene to obtain a ZnSe template. The ZnSe template has an average size of about 2.5 nm.

[0289] The amounts of the Zn precursor and the Se precursor used here are 0.9 millimole (mmol) and 0.45 mmol, respectively.

[0290] Formation of the quantum well layer:

[0291] An organic ligand including oleic acid was placed in a 300 mL reaction flask containing octadecene (ODE) and vacuum-treated at 120 °C. The atmosphere in the flask was changed to nitrogen (N₂). When the temperature of the reactor was raised to 300 °C, a toluene dispersion of ZnSe templates was quickly placed in the reaction flask, and then a TOP dispersion of indium laurate, dodecanethiol, zinc oleate, and tris(trimethylsilyl)phosphine (hereinafter also referred to as "TMSP") was injected into it. Then, the reaction was carried out for 30 minutes to form a quantum well layer on the template.

[0292] When the reaction was completed, the reaction solution was quickly cooled to room temperature and ethanol was added to it. The precipitate was separated by centrifugation, and the precipitate was dispersed in toluene.

[0293] The molar ratio between the Zn precursor, indium precursor, dodecanethiol, and phosphorus precursor used herein was 1:3:1:1.

[0294] For the particles prepared thus, ICP analysis was carried out. The thickness of the prepared alloy quantum well layer was about 0.29 nm. In the quantum well layer, the value of In + Zn:(P + S) was about 1.17:1. Such results indicated the formation of alloy semiconductor nanocrystals. For the particles prepared thus, photoluminescence analysis was carried out to measure the full width at half maximum of the photoluminescence peak.

[0295] Formation of the shell layer:

[0296] Zinc acetate and oleic acid were placed in a 300 mL reaction flask containing TOA and then vacuum-treated at 120 °C. The inside of the flask was replaced with nitrogen (N₂). When the reaction temperature of the reactor was raised to 320 °C, a toluene dispersion of the particles with a quantum well layer was injected into the reaction flask, and then a Se / TOP stock solution was injected into it. Subsequently, an S / TOP stock solution and zinc acetate were also injected into it. The reaction was carried out for a predetermined time, and a ZnSe / ZnS shell layer was formed on the quantum well layer.

[0297] The amount (e.g., molar) ratio between the Zn precursor and the Se precursor was about 1:2, and the amount (e.g., molar) ratio of the Zn precursor for synthesizing the template to the Zn precursor for forming the shell was about 1:3.

[0298] When the reaction was completed, ethanol was added to the reaction solution quickly cooled to room temperature, and the precipitate obtained by centrifuging the mixture was dispersed in toluene to obtain a toluene dispersion of QW quantum dots. The obtained QW quantum dots had an average size of about 6.5 nm.

[0299] UV-Vis absorption spectroscopic analysis was carried out on the prepared QW quantum dots, and the results are shown in Figure 6 in. Figure 6The results show that the UV-Vis absorption spectral curve has neither an inflection point nor a first absorption peak.

[0300] 2. Preparation of Quantum Dot Polymer Composites and Their Patterns

[0301] (1) Preparation of Quantum Dot - Binder Dispersions

[0302] The prepared chloroform solution of quantum dots is mixed with a solution of the binder polymer to form a quantum dot - binder dispersion. The binder polymer is a quaternary copolymer of methacrylic acid, benzyl methacrylate, 2 - hydroxyethyl methacrylate, and styrene (acid value: 130 milligrams (mg) of KOH per gram (mg KOH / g), molecular weight: 8,000 grams per mole (g / mol), methacrylic acid:benzyl methacrylate:2 - hydroxyethyl methacrylate:styrene (molar ratio) = 61.5:12:16.3:10.2) (solvent: polypropylene glycol monomethyl ether acetate PGMEA at a concentration of 30 weight percent (wt%)).

[0303] (2) Preparation of Photosensitive Compositions

[0304] To the prepared quantum dot - binder dispersion, a hexaacrylate (as a photopolymerizable monomer) having the following structure, ethylene glycol bis - 3 - mercaptopropionate (hereinafter, 2T, as a polythiol compound), an oxime ester compound (as an initiator), TiO2 as fine metal oxide particles, and PGMEA (as a solvent) are added to obtain a composition.

[0305]

[0306] (Ethylene glycol bis - 3 - mercaptopropionate)

[0307]

[0308] (Hexaacrylate)

[0309] Among them,

[0310] Based on the total solid content, the prepared composition includes 40 wt% of quantum dots, 12.5 wt% of the binder polymer, 25 wt% of 2T, 12 wt% of the photopolymerizable monomer, 0.5 wt% of the photoinitiator, and 10 wt% of the fine metal oxide particles. The total solid content is approximately 25 wt%.

[0311] (3) Formation of Quantum Dot Polymer Composite Patterns and Their Heat Treatment

[0312] The obtained composition was spin-coated on a glass substrate at 150 revolutions per minute (rpm) for 5 seconds to set a film. The obtained film was pre-baked (PRB) at 100 °C. The pre-baked film was exposed to light (wavelength: 365 nanometers (nm), intensity: 100 millijoules (mJ)) for 1 second (EXP) under a mask having a predetermined pattern (e.g., a square dot or stripe pattern), and developed with an aqueous potassium hydroxide solution (concentration: 0.043 wt%) for 50 seconds to obtain a pattern of the quantum dot polymer composite.

[0313] The obtained pattern was heat-treated at a temperature of 180 °C for 30 minutes in a nitrogen atmosphere (POB).

[0314] For the obtained pattern film, the blue light absorption rate and the light conversion efficiency were measured, and the results are shown in Table 1.

[0315] Comparative Example 1:

[0316] 1. Synthesis of QW quantum dots

[0317] A template was prepared in the same manner as in Example 1. A quantum well layer was formed in the same manner as in Example 1 except that a zinc precursor and a sulfur precursor were not used.

[0318] For the prepared particles, photoluminescence spectroscopy analysis was performed, and the results are shown in Table 1. For the particles prepared in this way, ICP analysis was performed, and the thickness of the prepared alloy quantum well layer was about 0.22 nm. For the particles prepared in this way, photoluminescence analysis was performed to measure the full width at half maximum of the photoluminescence peak, and the results confirmed that the FWHM of the QW quantum dots in Comparative Example 1 was twice as wide as that of the QW quantum dots in Example 1.

[0319] Except for using the obtained particles having a QW layer, a shell layer was formed in the same manner as described in Example 1. When the reaction was completed, ethanol was added to the reaction solution that was rapidly cooled to room temperature, and the precipitate obtained by centrifuging the mixture was dispersed in toluene to obtain a toluene dispersion of QW quantum dots. The obtained QW quantum dots had an average size of about 6.5 nm.

[0320] UV-Vis absorption spectroscopy analysis was performed on the prepared QW quantum dots, and the results confirmed that the UV-Vis absorption spectral curve of the QW quantum dots in the comparative example had an inflection point and a first absorption peak.

[0321] 2. Except for using the prepared QW quantum dots, a quantum dot polymer composite pattern was prepared in the same manner as in Example 1. For the obtained pattern film, the blue light absorption and the light conversion efficiency were measured, and the results are shown in Table 1.

[0322] Table 1

[0323]

[0324] The QW quantum dots of Example 1 have a FWHM narrower than that of the QW quantum dots of Comparative Example 1, and the results in Table 1 show that the QW quantum dots of Example 1 have improved absorption and enhanced luminescence efficiency.

[0325] Example 2:

[0326] 1. Synthesis of QW quantum dots

[0327] A template was prepared in the same manner as in Example 1. A quantum well layer was formed in the same manner as in Example 1, except that the amounts of zinc precursor and sulfur precursor were adjusted such that the molar ratio of In:Zn:P:S was about 1:1:1:1.

[0328] For the particles thus prepared, ICP analysis was performed. The thickness of the prepared alloy quantum well layer was about 0.29 nm, and in the well layer, the value of In + Zn:(P + S) was about 1.4:1. Such results indicate that alloy semiconductor nanocrystals were formed.

[0329] A shell layer was formed on the prepared QW layer in the same manner as described in Example 1. When the reaction was completed, ethanol was added to the reaction solution that was rapidly cooled to room temperature, and the precipitate obtained by centrifuging the mixture was dispersed in toluene to obtain a toluene dispersion of QW quantum dots. The obtained QW quantum dots had an average size of about 6.5 nm.

[0330] 2. Except for using the prepared QW quantum dots, a quantum dot polymer composite pattern was prepared in the same manner as in Example 1. For the obtained pattern film, the blue light absorption and photoconversion efficiency were measured, and the results are shown in Table 2.

[0331] Comparative Example 2:

[0332] 1. Synthesis of QW quantum dots

[0333] A template was prepared in the same manner as in Example 1. A quantum well layer was formed in the same manner as in Example 1, except that no sulfur precursor was used and the molar ratio of In:Zn:P:S was about 1:1:1.

[0334] For the particles thus prepared, ICP analysis was performed. The thickness of the prepared alloy quantum well layer was about 0.22 nm.

[0335] A shell layer was formed on the prepared QW layer in the same manner as described in Example 1. When the reaction was completed, ethanol was added to the reaction solution that was rapidly cooled to room temperature, and the precipitate obtained by centrifuging the mixture was dispersed in toluene to obtain a toluene dispersion of QW quantum dots. The obtained QW quantum dots had an average size of about 6.5 nm.

[0336] 2. Except for using the prepared QW quantum dots, a quantum dot polymer composite pattern was prepared in the same manner as in Example 1. For the obtained pattern film, the blue light absorption and the light conversion efficiency were measured, and the results are shown in Table 2.

[0337] Table 2

[0338]

[0339] The results in Table 2 show that the QW quantum dots of Example 2 had improved absorption and enhanced luminescence efficiency compared to the QW quantum dots of Comparative Example 2.

[0340] Although the present disclosure has been described in connection with what is 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. A quantum dot, the quantum dot comprising: A template, comprising a first semiconductor nanocrystal; A quantum well layer, disposed on the template and surrounding at least a part of the surface of the template; And A shell, disposed on the quantum well layer, the shell comprising a second semiconductor nanocrystal, wherein the quantum dot does not include cadmium, wherein the first semiconductor nanocrystal comprises ZnSe, ZnTeSe, ZnSeS, ZnS or a combination thereof, wherein the second semiconductor nanocrystal comprises ZnSe, ZnTeSe, ZnSeS, ZnS or a combination thereof, wherein the quantum well layer comprises an alloy semiconductor nanocrystal comprising indium, phosphorus, zinc and a chalcogen element, wherein the chalcogen element comprises sulfur, and wherein the band gap energy of the alloy semiconductor nanocrystal is smaller than the band gap energy of the first semiconductor nanocrystal and smaller than the band gap energy of the second semiconductor nanocrystal.

2. The quantum dot according to claim 1, wherein, The first semiconductor nanocrystal and the second semiconductor nanocrystal have different compositions from each other.

3. The quantum dot according to claim 1, wherein, The second semiconductor nanocrystal comprises ZnSe, ZnSeS, ZnS or a combination thereof.

4. The quantum dot according to claim 1, wherein, The difference between the lattice constant of the alloy semiconductor nanocrystal and the lattice constant of the first semiconductor nanocrystal is less than or equal to 3%, and wherein the difference between the lattice constant of the alloy semiconductor nanocrystal and the lattice constant of the second semiconductor nanocrystal is less than or equal to 3%.

5. The quantum dot according to claim 1, wherein, Based on the total molar amount of the elements in the quantum dot, the quantum dot has a total molar amount of indium and phosphorus of less than or equal to 20%.

6. The quantum dot according to claim 1, wherein, In the quantum dot, the molar ratio of phosphorus to indium is greater than or equal to 0.5:1 and less than or equal to 0.9:

1.

7. The quantum dot according to claim 1, wherein, In the quantum dot, the molar ratio of zinc to indium is greater than or equal to 15:1 and less than or equal to 55:

1.

8. The quantum dot according to claim 1, wherein, In the quantum dot, the total molar ratio of sulfur and selenium to zinc is greater than or equal to 0.5:1 and less than or equal to 1:

1.

9. The quantum dot according to claim 1, wherein, In the quantum dot, the molar ratio of sulfur to selenium is greater than or equal to 0.3:1 and less than or equal to 0.9:

1.

10. The quantum dot according to claim 1, wherein, The shell comprises: a first layer, comprising a third zinc chalcogenide; and a second layer, comprising a fourth zinc chalcogenide having a composition different from that of the third zinc chalcogenide.

11. The quantum dot according to claim 10, wherein, The first layer comprises ZnSe, ZnSeS or a combination thereof, and the second layer comprises ZnS.

12. The quantum dot according to claim 10, wherein, The first layer is directly on the quantum well layer, and the second layer is the outermost layer of the shell.

13. The quantum dot according to claim 1, wherein, The thickness of the quantum well layer is greater than or equal to 0.1 nanometer and less than or equal to 0.35 nanometer.

14. The quantum dot according to claim 1, wherein, The size of the quantum dot is greater than or equal to 3 nanometers and less than or equal to 7 nanometers.

15. The quantum dot according to claim 1, wherein, The quantum dot comprises an organic ligand on the surface of the quantum dot, and the organic ligand comprises RCOOH, RCOOCOR, RNH2, R2NH, R3N, RSH, R3PO, R3P, ROH, RCOOR', RPO(OH)2, R2POOH or a combination thereof, wherein R and R' are independently a substituted or unsubstituted C1 to C30 aliphatic hydrocarbon, a substituted or unsubstituted C6 to C30 aromatic hydrocarbon or a combination thereof.

16. The quantum dot according to claim 1, wherein, The quantum dot emits green light, and The ultraviolet-visible absorption spectral curve of the quantum dots does not have an inflection point within the wavelength range of 450 nm to 620 nm.

17. The quantum dots according to claim 1, wherein, The quantum dots exhibit a maximum emission peak wavelength within the range of 500 nm to 540 nm.

18. The quantum dots according to claim 1, wherein, The quantum efficiency of the quantum dots is greater than or equal to 40%.

19. A quantum dot polymer composite, the quantum dot polymer composite comprising: A polymer matrix; and A plurality of quantum dots according to claim 1 dispersed in the polymer matrix.

20. The quantum dot polymer composite according to claim 19, wherein, The polymer matrix includes a linear polymer, a crosslinked polymer, or a combination thereof.

21. The quantum dot polymer composite according to claim 19, wherein, The polymer matrix further includes: a polymerization product of a monomer combination including a thiol compound and an olefin compound having a carbon-carbon unsaturated bond; metal oxide particles; or a combination thereof.

22. The quantum dot polymer composite according to claim 19, wherein, The quantum dot polymer composite is in the form of a patterned film.

23. The quantum dot polymer composite according to claim 19, wherein, After heat-treating the quantum dot polymer composite at a temperature of 180 °C for 30 minutes, the quantum dot polymer composite exhibits an absorption of greater than or equal to 90% or a blue light conversion efficiency of greater than or equal to 15% for blue light.

24. A display device, the display device comprising a light-emitting element, wherein, The light-emitting element includes the quantum dot polymer composite according to claim 19.

25. The display device according to claim 24, the display device further comprising a light source, wherein, The light source is configured to provide incident light to the light-emitting element, and wherein the incident light includes light having a peak wavelength of 440 nm to 460 nm.

26. The display device according to claim 24, wherein, The light-emitting element includes a sheet of the quantum dot polymer composite.

27. The display device according to claim 24, wherein, The light-emitting element includes a stacked structure, the stacked structure including: a substrate; and a light-emitting layer disposed on the substrate, wherein the light-emitting layer includes a pattern including the quantum dot polymer composite, and wherein the pattern includes repeating portions that emit light of a predetermined wavelength.

28. The display device according to claim 27, wherein, The pattern includes a first repeating portion that emits a first light and a second repeating portion that emits a second light having an emission peak wavelength different from the emission peak wavelength of the first light.

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