Quantum dot composite, color filter and display device including the same

Abstract

A quantum dot composite, a color filter and a display device including the quantum dot composite, and a quantum dot composition are provided. The quantum dot composite includes: a matrix; and a plurality of quantum dots dispersed in the matrix, wherein the plurality of quantum dots include a semiconductor nanocrystal core containing indium and phosphorus and a semiconductor nanocrystal shell disposed on the semiconductor nanocrystal core, and the semiconductor nanocrystal shell includes zinc, selenium, and sulfur. The plurality of quantum dots have an arithmetic size of approximately 8 nm or greater, wherein the quantum dot composite is configured to emit red light, and wherein when the quantum dot composite is irradiated with light having a wavelength of approximately 450 nm to approximately 470 nm for a period of approximately 500 hours or less, the luminance of the quantum dot composite increases by less than or equal to approximately 1.2% of the initial luminance of the quantum dot composite.

Description

[0001] This application claims priority from and all benefits derived from Korean Patent Application No. 10-2020-0063926 filed in the Korean Intellectual Property Office on May 27, 2020, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] Disclosed are a quantum dot complex or composition and an electronic device comprising the quantum dot complex or composition. Background Art

[0003] Unlike bulk materials, quantum dots (e.g., nanometer-sized semiconductor nanocrystals) can have different band gaps by controlling the size and composition of the quantum dots. Quantum dots can exhibit electroluminescent properties and photoluminescent properties. In colloidal synthesis, organic materials such as dispersants can be coordinated (e.g., bound) to the surface of semiconductor nanocrystals during crystal growth, and quantum dots with controlled size and luminescent properties can be provided. From an environmental perspective, it is desirable to develop cadmium-free quantum dots with improved luminescent properties. Summary of the Invention

[0004] Embodiments provide a quantum dot complex or composition that can exhibit improved luminescent properties and enhanced stability (eg, process stability or optical stability).

[0005] An embodiment provides an electronic device including a quantum dot composite or a quantum dot composition.

[0006] In an embodiment, a quantum dot composite includes: a matrix; and a plurality of quantum dots dispersed in the matrix, wherein the plurality of quantum dots include a semiconductor nanocrystal core comprising indium (In) and phosphorus (P) and a semiconductor nanocrystal shell disposed on the semiconductor nanocrystal core, the semiconductor nanocrystal shell including zinc, selenium, and sulfur.

[0007] wherein the plurality of quantum dots have an arithmetic size greater than or equal to about 8 nm (or greater than or equal to about 8.3 nm), and

[0008] Wherein, when the quantum dot complex is irradiated with light having a wavelength of about 450 nanometers (nm) to about 470 nm (e.g., in the solid state) for a period of less than or equal to about 500 hours, the brightness of the quantum dot complex increases by less than or equal to about 1.2 percent of the initial brightness of the quantum dot complex.

[0009] The quantum dot composite can be configured to emit red light.

[0010] The plurality of quantum dots or quantum dot composite may not include cadmium.

[0011] When the quantum dot complex is irradiated with light having a wavelength of about 450 nm to about 470 nm (eg, in a solid state) for about 100 hours, the quantum dot complex may exhibit a brightness reduction interval.

[0012] The maximum peak wavelength of the red light may be greater than or equal to about 600 nm.

[0013] The maximum peak wavelength of the red light may be less than or equal to approximately 650 nm.

[0014] The plurality of quantum dots may have an arithmetic size greater than or equal to about 8.5 nm.

[0015] The plurality of quantum dots may have an arithmetic size greater than or equal to about 8.7 nm.

[0016] The arithmetic size of the plurality of quantum dots may be greater than or equal to about 9 nm.

[0017] The plurality of quantum dots may include first quantum dots (ie, a first population of quantum dots) having a first arithmetic size greater than an arithmetic size of the plurality of quantum dots, and a fraction of the first quantum dots in the plurality of quantum dots may be greater than or equal to approximately sixty percent (60%).

[0018] The first arithmetic size (eg, of the first population of quantum dots) may be at least about 1% or at least about 5% larger than the arithmetic size of the plurality of quantum dots.

[0019] The fraction of the first quantum dots in the plurality of quantum dots may be greater than or equal to about 70%.

[0020] The plurality of quantum dots may include second quantum dots (ie, a second quantum dot group) having a second arithmetic size less than or equal to 7.2 nm, and a fraction of the second quantum dots in the plurality of quantum dots may be less than or equal to approximately 18%.

[0021] The fraction of the second quantum dots in the plurality of quantum dots may be less than or equal to about 15%.

[0022] In an embodiment, the total fraction of the first quantum dot population and the second quantum dot population is greater than 85 percent of the plurality of quantum dots.

[0023] In an embodiment, the plurality of quantum dots may include a first quantum dot group having a first arithmetic size and a second quantum dot group having a second arithmetic size, and the first arithmetic size is greater than the arithmetic size of the quantum dot group, and the second arithmetic size is less than or equal to approximately 7.2 nm. Among the plurality of quantum dots, the fraction of the first quantum dot group may be greater than approximately 60%, greater than or equal to approximately 75%, or greater than or equal to approximately 80%, and the fraction of the second quantum dot group may be less than or equal to approximately 15% or less than or equal to approximately 10%.

[0024] The size of the semiconductor nanocrystal core can be greater than or equal to about 3 nm. The size of the semiconductor nanocrystal core can be greater than or equal to about 3.5 nm. The size of the semiconductor nanocrystal core can be in the range of about 3.6 nm to about 3.9 nm.

[0025] The semiconductor nanocrystal shell may include: a first layer including first semiconductor nanocrystals including zinc and selenium; and a second layer disposed on the first layer, the second layer including second semiconductor nanocrystals including zinc, sulfur, and optionally selenium, wherein the composition of the first semiconductor nanocrystals may be different from the composition of the second semiconductor nanocrystals.

[0026] The first layer or first semiconductor nanocrystals can include zinc selenide, zinc selenide sulfide, or a combination thereof.

[0027] The second layer or second semiconductor nanocrystals can include zinc sulfide (eg, can consist of ZnS).

[0028] The first layer can be adjacent to (eg, disposed directly on) the semiconductor nanocrystal core.

[0029] The second layer may be the outermost layer of the semiconductor nanocrystal shell (or quantum dot).

[0030] The first layer may have a thickness greater than or equal to about 1.5 nm, a thickness greater than or equal to about 1.7 nm, or a thickness greater than or equal to about 2 nm.

[0031] The second layer may have a thickness less than or equal to about 0.7 nm.

[0032] The second layer may have a thickness less than or equal to about 0.5 nm.

[0033] In the second quantum dot or second population of quantum dots, the first layer can have a thickness of less than or equal to about 1.7 nm or at most 5 monolayers.

[0034] The plurality of quantum dots may have a molar ratio of zinc to indium (Zn:In) greater than or equal to about 13:1 and a molar ratio of sulfur to selenium (S:Se) less than or equal to about 0.6:1. The plurality of quantum dots may have a molar ratio of zinc to indium (Zn:In) greater than or equal to about 14:1 and a molar ratio of sulfur to selenium (S:Se) less than or equal to about 0.5:1.

[0035] In the plurality of quantum dots (or the first quantum dot group or the second quantum dot group), the molar ratio of phosphorus to indium (P:In) may be greater than or equal to about 0.6: 1. In the plurality of quantum dots, the molar ratio of phosphorus to indium may be less than or equal to about 0.9:1.

[0036] In the plurality of quantum dots (or the first quantum dot group or the second quantum dot group), a molar ratio of zinc to the sum of sulfur and selenium (Zn:(S+Se)) may be less than or equal to 1.1:1.

[0037] The matrix may include a polymerizable monomer including a carbon-carbon double bond, a thiol compound having at least one thiol group (eg, at its terminal end), a polymer, a liquid carrier (eg, an organic solvent), or a combination thereof.

[0038] The matrix may include a polymer matrix. The polymer matrix may include a polymerization product of a monomer combination including a thiol compound having, for example, at least one thiol group (for example, at its terminal end) and an alkene compound having a carbon-carbon unsaturated bond (for example, a polymerizable monomer).

[0039] The polymerizable monomer may include a (meth)acrylate compound having at least one (eg, at least two, at least three, or at least four) (meth)acrylate groups.

[0040] The polymer may include a linear polymer, a cross-linked polymer, or a combination thereof.

[0041] The cross-linked polymer may include a mercapto-olefin polymer, a cross-linked poly(meth)acrylate, a cross-linked polyurethane, a cross-linked epoxy resin, a cross-linked vinyl polymer, a cross-linked silicone resin, or a combination thereof.

[0042] The linear polymer may comprise repeating units derived from monomers comprising a carbon-carbon double bond and optionally a carboxylic acid group.

[0043] The matrix may include a compound containing carboxylic acid groups.

[0044] Compounds containing carboxylic acid groups may include:

[0045] a monomer combination comprising a first monomer, a second monomer, and an optional third monomer, wherein the first monomer comprises a carboxylic acid group and a carbon-carbon double bond, the second monomer comprises a carbon-carbon double bond and a hydrophobic portion but does not comprise a carboxylic acid group, and the optional third monomer comprises a carbon-carbon double bond and a hydrophilic portion but does not comprise a carboxylic acid group;

[0046] copolymers of monomer combinations;

[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 carboxylic acid group (-COOH), the quaternary carbon atom being a constituent atom of another ring portion in the backbone; or

[0048] A combination of them.

[0049] The carboxylic acid group-containing compound may have an acid value greater than or equal to about 50 milligrams of potassium hydroxide per gram (mg KOH / g).The carboxylic acid group-containing compound may have a molecular weight greater than or equal to about 400 g / mol.

[0050] The thiol compound may include a dithiol compound, a trithiol compound, a tetrathiol compound, or a combination thereof.

[0051] The liquid carrier may include an organic solvent.

[0052] The organic solvent may include an alkylene glycol compound, an alkylene glycol ether compound, an alkylene glycol ether ester (eg, acetate) compound, an amide solvent, a ketone solvent, a substituted or unsubstituted aliphatic hydrocarbon compound, a substituted or unsubstituted aromatic hydrocarbon compound, or a combination thereof.

[0053] The quantum dot composite may further include fine metal oxide particles dispersed in the matrix. The fine metal oxide particles may be non-emissive.

[0054] The quantum dot composite can be in the form of a patterned film.

[0055] The quantum dot composite may have an absorptivity greater than or equal to about 90% with respect to blue light having a wavelength of about 450 nm to about 470 nm.

[0056] In an embodiment, the color filter includes a quantum dot composite (eg, a pattern of quantum dot composite).

[0057] In an embodiment, a display device includes a light emitting element and an optional light source, wherein the light emitting element includes the above-mentioned quantum dot composite, and the light source is configured to provide incident light to the light emitting element.

[0058] The incident light may have a light emission peak wavelength of about 440 nanometers to about 460 nanometers.

[0059] In an embodiment, the color filter comprises a quantum dot polymer composite.

[0060] In an embodiment, the light emitting element may include a stacked structure including a substrate and a light emitting layer disposed on the substrate. The light emitting layer may include a pattern including a quantum dot complex.

[0061] The pattern may include at least one repeating portion configured to emit light of a predetermined wavelength.

[0062] The pattern may include a first portion configured to emit a first light.

[0063] The pattern may further include a second portion configured to emit second light having a central wavelength different from the central wavelength of the first light.

[0064] In an embodiment, the composition includes a plurality of quantum dots, wherein the plurality of quantum dots include: a first semiconductor nanocrystal comprising indium and phosphorus (e.g., indium phosphide and / or alloys thereof); and a second semiconductor nanocrystal comprising zinc chalcogenide, wherein the zinc chalcogenide may include: zinc; and selenium, sulfur, or a combination thereof, wherein the arithmetic size of the plurality of quantum dots is greater than or equal to approximately 8 nm, the plurality of quantum dots includes second quantum dots having a second arithmetic size (i.e., a second quantum dot population), wherein the second arithmetic size is less than or equal to approximately 7.2 nm, and the fraction of the second quantum dots in the plurality of quantum dots is less than or equal to approximately 18%.

[0065] The composition may include a polymerizable monomer including a carbon-carbon double bond, a thiol compound having at least one thiol group, a polymer, a liquid carrier (eg, an organic solvent), or a combination thereof.

[0066] Among the plurality of quantum dots, a fraction of the second quantum dots may be less than or equal to about 15%.

[0067] The plurality of quantum dots may include first quantum dots (eg, a first quantum dot group) having a first arithmetic size greater than or equal to about 8 nm, and a fraction of the first quantum dots in the plurality of quantum dots may be greater than 60% or greater than or equal to about 75%.

[0068] The first quantum dot group may have a first arithmetic size greater than or equal to about 8.5 nm.

[0069] The fraction of the first quantum dots in the plurality of quantum dots may be greater than or equal to about 80%.

[0070] The quantum dot composite or quantum dot composition of the embodiments can resolve an overshoot phenomenon that would otherwise occur during operation of the device, and thus a display device including the quantum dot composite can maintain an improved level of color reproducibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0071] These and / or other aspects will become apparent and more readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0072] Figure 1 is an exploded view of a display device of an embodiment;

[0073] Figure 2A is a cross-sectional view of a display device according to an embodiment;

[0074] Figure 2B is a cross-sectional view of a display device according to an embodiment;

[0075] Figure 3 is a cross-sectional view of a display device according to an embodiment;

[0076] Figure 4A A process for manufacturing a quantum dot composite pattern using a composition according to an embodiment is shown;

[0077] Figure 4B A process for manufacturing a quantum dot composite pattern using a composition according to an embodiment is shown; and

[0078] Figure 5 is a graph showing the operational reliability of the quantum dot composite of Example 1, the quantum dot composite of Example 2, and the quantum dot composite of Comparative Example 1. DETAILED DESCRIPTION

[0079] The advantages and features of the present disclosure and their implementation methods will become apparent with reference to the following exemplary embodiments and the accompanying drawings. However, the embodiments should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art. Like reference numerals refer to like elements throughout.

[0080] If not otherwise defined, all terms (including technical and scientific terms) in the specification may be defined as commonly understood by those skilled in the art. It will also be understood that terms (such as those defined in commonly used dictionaries) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and not in an idealized or overly formal sense, unless expressly defined herein.

[0081] The terms used herein are only for the purpose of describing specific embodiments and are not intended to be limiting. As used herein, unless the context clearly indicates otherwise, the singular forms "one", "one (kind / person)" and "the (described)" are intended to include the plural forms comprising "at least one (kind / person)". "At least one (kind / person)" should not be interpreted as limiting "one" or "one (kind / person)". "Or" means "and / or". As used herein, the term "and / or" includes any combination and all combinations of one or more of the relevant listed items. In addition, unless explicitly described to the contrary, the word "include" and variations such as "comprise" or "contain" will be understood to mean including the elements (elements) stated, but do not exclude any other elements (elements). It will also be understood that when the terms "include" and / or "comprising" and variations thereof are used in this specification, the description indicates the presence of stated features, regions, entireties, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, regions, entireties, steps, operations, elements, components and / or their groups. In the drawings, the thickness of layers, films, panels, regions, etc. are exaggerated for clarity. Like reference numerals refer to like elements throughout the specification.

[0082] It will be understood that when an element such as a layer, film, region, or substrate is referred to as being "on" another element, the element 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 present.

[0083] As used herein, "about" or "approximately" is inclusive of the stated value and means within an acceptable range of deviation for the particular value as determined by one of ordinary skill in the art, taking into account the measurements in question and errors associated with measurement of the particular quantity (i.e., limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±10% or ±5% of the stated value.

[0084] It will be understood that although the terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings herein, the first "element," "component," "region," "layer," or "part" discussed below may be named as a second element, component, region, layer, or part.

[0085] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic diagrams of idealized embodiments. As such, variations in the shapes of the illustrations, for example, due to manufacturing techniques and / or tolerances, are expected. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the regions shown herein, but rather are intended to include deviations in shapes, for example, due to manufacturing. For example, a region shown or described as flat may typically have rough and / or nonlinear features. Furthermore, sharp angles shown may be rounded. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the precise shape of the regions and are not intended to limit the scope of the claims presented.

[0086] As used herein, unless a definition is provided otherwise, the term "substituted" refers to a compound, group or moiety wherein at least one hydrogen atom of the compound, group or moiety is replaced with a substituent. Substituents may include C1 to C30 alkyl, C2 to C30 alkenyl, C2 to C30 alkynyl, C6 to C30 aryl, C7 to C30 alkylaryl, C1 to C30 alkoxy, C1 to C30 heteroalkyl, C3 to C40 heteroaryl, C3 to C30 heteroalkylaryl, C3 to C30 cycloalkyl, C3 to C15 cycloalkenyl, C6 to C30 cycloalkynyl, C2 to C30 heterocycloalkyl, halogen (-F, -Cl, -Br or -I), hydroxyl (-OH), nitro (-NO2), cyano (-CN), amino or amine (-NRR', wherein R and R' are the same or different and are independently hydrogen or C1 to C6 alkyl), azido (-N3), amidino (-C (=NH)NH2), hydrazine group (-NHNH2), hydrazone group (=N(NH2)), aldehyde group (-C(=O)H), carbamoyl group (-C(O)NH2), thiol group (-SH), ester group (-C(=O)OR, wherein R is C1 to C6 alkyl or C6 to C12 aryl), carboxylic acid group (-COOH) or its salt (-C(=O)OM, wherein M is an organic cation or an inorganic cation), sulfonic acid group (-SO3H) or its salt (-SO3M, wherein M is an organic cation or an inorganic cation), phosphate group (-PO3H2) or its salt (-PO3MH or -PO3M2, wherein M is an organic cation or an inorganic cation) or a combination thereof.

[0087] As used herein, unless otherwise defined, the term "hetero" refers to a compound or group that includes at least one (e.g., one to three) heteroatom, wherein the heteroatoms are each independently N, O, S, Si, P, or a combination thereof.

[0088] As used herein, unless otherwise defined, the term "alkylene" refers to a straight or branched chain saturated aliphatic hydrocarbon group having a valence of 2 or greater. An alkylene group may be optionally substituted with one or more substituents.

[0089] As used herein, unless otherwise defined, the term "arylene" refers to a functional group having a valence of 2 or greater and formed by removing at least two hydrogen atoms from one or more rings of an aromatic hydrocarbon, wherein the hydrogen atoms may be removed from the same or different rings (preferably, different rings), each of which may be aromatic or non-aromatic. The arylene group may be optionally substituted with one or more substituents.

[0090] As used herein, unless otherwise defined, the term "aliphatic hydrocarbon group" refers to a C1 to C30 straight chain or branched alkyl group, a C2 to C30 straight chain or branched alkenyl group, or a C2 to C30 straight chain or branched alkynyl group, the term "aromatic hydrocarbon group" refers to a C6 to C30 aryl group or a C2 to C30 heteroaryl group, and the term "alicyclic hydrocarbon group" refers to a C3 to C30 cycloalkyl group, a C3 to C30 cycloalkenyl group, or a C3 to C30 cycloalkynyl group.

[0091] As used herein, unless otherwise defined, the term "(meth)acrylate" refers to acrylate and / or methacrylate, or a combination thereof. The (meth)acrylate may include (C1 to C10 alkyl)acrylate, (C1 to C10 alkyl)methacrylate, or a combination thereof.

[0092] As used herein, light conversion efficiency (CE%) refers to the ratio of the amount of light emitted from a quantum dot complex to the amount of light absorbed by the complex from incident light (e.g., blue light). Light conversion efficiency refers to the percentage of luminescence (A) of the quantum dot complex relative to the amount of excitation light (e.g., blue light) (B). Light absorptivity 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 light amount (B) of the excitation light can be obtained by integrating the photoluminescence (PL) spectrum of the incident light, measuring the PL spectrum of the quantum dot-polymer composite film to obtain the dose (A) of light in the green wavelength region or the red wavelength region emitted from the quantum dot composite film and the dose (B') of the incident light passing through the quantum dot composite film, and the light conversion efficiency is obtained by the following equation:

[0093] A / B×100%=light conversion rate (%)

[0094] A / (B-B') × 100% = Photoconversion efficiency (%)

[0095] (B-B') / B×100%=blue (light) absorption rate (%).

[0096] The quantum efficiency of a quantum dot can be a quantum yield that can be easily and reproducibly measured by any suitable equipment (e.g., from Hitachi Co. Ltd or Hamamatsu Co. Ltd) and with reference to the instructions for use 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, "quantum yield (or quantum efficiency)" can be, for example, the ratio of photons emitted by a nanostructure or a population of nanostructures to photons absorbed. In an embodiment, the quantum efficiency can be determined by any suitable method. For example, there can be two methods for measuring fluorescence quantum yield or efficiency: an absolute method and a relative method. The absolute method directly obtains the quantum yield by detecting the fluorescence of all samples 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 may be used as standard dyes according to photoluminescence (PL) wavelength, but are not limited thereto.

[0097] The full width at half maximum (FWHM) and the maximum PL peak wavelength can be determined from a photoluminescence spectrum obtained by a spectrophotometer (or fluorescence spectrophotometer).

[0098] As used herein, the expression "does not include cadmium (or other hazardous heavy metals)" may refer to a situation where the concentration of cadmium (or other hazardous heavy metals) may be less than or equal to about 100 ppmw (100 parts per million by weight), less than or equal to about 50 ppmw, less than or equal to about 10 ppmw, less than or equal to about 1 ppmw, less than or equal to about 0.1 ppmw, less than or equal to about 0.01 ppmw, or about zero. In embodiments, the amount of cadmium (or other hazardous heavy metals) may be substantially absent, or, if present, the amount of cadmium (or other hazardous heavy metals) may be less than or equal to the detection limit or impurity level for a given analytical tool (e.g., inductively coupled plasma atomic emission spectrometry).

[0099] As used herein, the term "first absorption peak wavelength" refers to the wavelength of the main exciton peak that first appears from the longest wavelength region of the UV-Vis absorption spectrum of the quantum dot (ie, appears in the lowest energy region in the UV-Vis absorption spectrum).

[0100] As used herein, unless otherwise defined, the term "dispersion" refers to a system in which the dispersed phase is a solid and the continuous phase comprises a liquid. For example, the term "dispersion" may refer to a colloidal dispersion in which the dispersed phase comprises particles having a size of at least about 1 nm (e.g., at least about 2 nm, at least about 3 nm, or at least about 4 nm) and less than or equal to about a few micrometers (μm) (e.g., 2 μm or less or 1 μm or less).

[0101] Semiconductor nanocrystal particles (also known as quantum dots) are nanometer-sized crystalline materials. Due to their relatively small size, semiconductor nanocrystal particles can have a large surface area per unit volume and, therefore, can exhibit properties that differ from bulk materials of the same composition due to quantum confinement effects. Quantum dots can absorb light from a light source to create an energetically excited state and, upon relaxation to a ground state, emit energy corresponding to the quantum dot's band gap.

[0102] Due to their unique photoluminescent properties, quantum dots have potential applicability in various devices (eg, electronic devices).

[0103] Quantum dots with properties suitable for electronic devices can be cadmium-based. However, cadmium can cause serious environmental / health issues and is therefore a restricted element. Therefore, it may be desirable to use cadmium-free quantum dots, such as nanocrystalline particles based on III-V groups. In embodiments, cadmium-free quantum dots that exhibit enhanced blue light absorption per given weight, improved brightness, and / or increased thermal stability may be technologically interesting or desirable.

[0104] A core comprising a III-V compound containing indium and phosphorus can be coated with a shell (e.g., a ZnSe or ZnS shell) and then formed into a composite for use in a device. However, the inventors of the present application have determined or realized that the difference in lattice constant between the ZnS outer shell and the indium phosphide core is so great that it is difficult to form a uniform coating on the core, and therefore, there are technical limitations in increasing the thickness of the shell.

[0105] In addition, the inventors of the present application have confirmed or appreciated that when the quantum dots emit light of a desired wavelength (e.g., red light) and have a shell of finite thickness, the quantum dots included in the quantum dot composite exhibit an overshoot phenomenon. The overshoot phenomenon refers to a situation in which a device including the quantum dot composite exhibits an increase in its brightness (e.g., a gradual or continuous increase) over a given operating time, such that the brightness increase exceeds a predetermined value of the device (e.g., 1.2 percent (1.2%) of the initial brightness). For example, if the initial brightness is 100%, then at a predetermined operating time (e.g., greater than or equal to about 100 hours, greater than or equal to about 150 hours, greater than or equal to about 200 hours, greater than or equal to about 250 hours, or greater than or equal to about 300 hours), the brightness of the device exhibiting the overshoot phenomenon may be 101.2% or higher.

[0106] The overshoot phenomenon can cause an undesirable change in the color coordinates of the light-emitting device. The inventors of the present application have confirmed that quantum dot complexes emitting in the red region of the visible spectrum tend to exhibit or suffer from an overshoot phenomenon, resulting in a red shift of the desired color coordinates of the light-emitting device. The inventors of the present application have also confirmed that when the device includes a quantum dot complex that emits red light and a quantum dot complex that emits light other than red light (for example, green light and / or blue light), the quantum dot complex that emits light other than red light tends not to exhibit an overshoot phenomenon. In contrast, the quantum dot complex that emits light other than red light may tend to exhibit a decrease in brightness over time. Therefore, the difference between the brightness of the red pixel and the brightness of the pixels of other colors will continue to increase over time, and therefore, the device will not emit the desired color coordinates over time.

[0107] The overshoot phenomenon and the shortcomings caused by the overshoot phenomenon can be solved by the quantum dot composite of the embodiment. In an embodiment, the quantum dot composite includes a matrix and a plurality of quantum dots dispersed in the matrix, wherein the plurality of quantum dots include a semiconductor nanocrystal core containing indium (In) and phosphorus (P) and a semiconductor nanocrystal shell disposed on the semiconductor nanocrystal core, the semiconductor nanocrystal shell including zinc, selenium and sulfur, wherein the arithmetic size of the plurality of quantum dots is greater than or equal to about 8.0 nanometers (nm) or greater than or equal to about 8.3 nm. In an embodiment, the composition includes a plurality of quantum dots, wherein the plurality of quantum dots include a first semiconductor nanocrystal and a second semiconductor nanocrystal, the first semiconductor nanocrystal including a compound containing indium and phosphorus (e.g., indium phosphide), and the second semiconductor nanocrystal including zinc chalcogenide. The zinc chalcogenide may include: zinc; and selenium, sulfur, or a combination thereof. The arithmetic size of the plurality of quantum dots is greater than or equal to about 8.0 nm. The plurality of quantum dots may include a second quantum dot having a second arithmetic size (e.g., a second quantum dot group), and the second arithmetic size may be less than or equal to about 7.2 nm. The fraction of the second quantum dots in the plurality of quantum dots may be less than or equal to about 18%.

[0108] The matrix of the quantum dot composition can include a polymerizable monomer containing a carbon-carbon double bond, a thiol compound having at least one thiol group, a polymer, a liquid carrier (e.g., an organic solvent), or a combination thereof. The quantum dot composition can provide a quantum dot composite of the embodiment in a solid state, for example, via polymerization.

[0109] In an embodiment, if the quantum dot composite of the embodiments is irradiated with light having a wavelength of about 450 nm to about 470 nm (e.g., in the solid state) for a period of time less than or equal to about 500 hours (e.g., about 400 hours or less, about 300 hours or less, about 250 hours or less, about 210 hours or less, about 200 hours or less, about 150 hours or less, about 100 hours or less, or a combination thereof), the brightness increase of the quantum dot composite can be (or be suppressed or controlled to be) less than or equal to about 1.2% of the initial brightness.

[0110] As used herein, a brightness change (e.g., a brightness increase or brightness decrease interval) is determined by an operational reliability test for a device including the composite. In the reliability test of an embodiment, for example, a light source (e.g., having a predetermined intensity (e.g., 1500 nits (cd / m2) at a predetermined wavelength (e.g., about 450 nm to about 470 nm)) is used at a temperature of about 60° C. and in air. 2 ) backlight unit) illuminates the composite.

[0111] In an embodiment of a quantum dot composite, the plurality of quantum dots may have an arithmetic size (e.g., an arithmetic size of a quantum dot population). The arithmetic size may be greater than or equal to about 8.1 nm, greater than or equal to about 8.2 nm, greater than or equal to about 8.3 nm, greater than or equal to about 8.4 nm, greater than or equal to about 8.5 nm, greater than or equal to about 8.6 nm, greater than or equal to about 8.7 nm, greater than or equal to about 8.8 nm, greater than or equal to about 8.9 nm, greater than or equal to about 9.0 nm, greater than or equal to about 9.1 nm, greater than or equal to about 9.2 nm, greater than or equal to about 9.3 nm, greater than or equal to about 9.4 nm, greater than or equal to about 9.5 nm, or any of the foregoing ranges. The arithmetic size may be less than or equal to about 15 nm, less than or equal to about 14 nm, less than or equal to about 13 nm, less than or equal to about 12 nm, less than or equal to about 11 nm, less than or equal to about 10.5 nm, less than or equal to about 10 nm, or any of the foregoing ranges. The arithmetic size can be within any range of a combination of the above boundary values ​​(e.g., about 8.1 nm to about 15 nm, about 8.5 nm to about 12 nm, about 8.7 nm to about 11 nm, about 8.8 nm to about 10 nm, about 8.9 nm to about 10.5 nm, about 9 nm to about 9.5 nm, or about 9.1 nm to about 9.4 nm).

[0112] As used herein, the term "arithmetic size" refers to the size of a given quantum dot population and can be determined by the core size and shell thickness. The core size is measured by the core composition and optical properties of the quantum dot (e.g., UV absorption wavelength such as the first absorption peak wavelength). The shell thickness is determined by the core size and the composition of the quantum dot. The composition of the core or the composition of the quantum dot can be determined by appropriate analytical tools (such as inductively coupled plasma atomic emission spectroscopy).

[0113] In an embodiment, for a given quantum dot, the core size is determined by a method using the core composition and UV-visible absorption wavelength. The measurement method is described in Nanotechnology 24 (2013) 215201 (5 pp), which is incorporated herein by reference in its entirety.

[0114] In an embodiment, if a given quantum dot includes a core of indium phosphide or an alloy thereof, the band gap energy of the quantum dot is greater than or equal to about 2 electron volts (eV) and less than or equal to about 4.8 eV, and the core size can be determined to be within a range of greater than or equal to about 1 nm and less than or equal to about 4.5 nm. For example, a quantum dot having an indium phosphide-based core can have a UV absorption wavelength (e.g., a first absorption peak wavelength) of about 570 nm, and the core size can be determined to be about 3.6 nm. The core may not include zinc.

[0115] Given the assumption that the quantum dots have a spherical shape, the shell thickness for the quantum dots can be determined mathematically by using the following information along with the measured molar ratio of chalcogens (e.g., sulfur and selenium) relative to indium in the quantum dots:

[0116] Core size (i.e., core diameter) and core volume calculated from the core diameter; bulk density and molar mass of the core components (e.g., bulk density of indium phosphide = 4.81 g / cm 3 , the molar mass of InP = 145.79 g / mol); the number of moles of indium included in a given core calculated from the bulk density and molar mass of the core components; the volume of a shell if a ZnS or ZnSe shell having a predetermined thickness is formed on the core; and the bulk density and molar mass of each of the shell components (e.g., ZnS and / or ZnSe) (e.g., ZnSe = 5.27 g / cm 3 and 144.35 g / mol, ZnS=4.090 g / cm 3 and 97.474 g / mol).

[0117] With the above information and under the assumption that the quantum dots are spherical in form, the molar ratio of each of the chalcogen components (e.g., sulfur or selenium) of a chalcogenide shell having a predetermined thickness relative to the indium in a core having a predetermined diameter can be calculated, and information about the shell thickness for a given core diameter can be determined from the molar ratios.

[0118] The inventors of the present application have discovered that in a quantum dot composite comprising a plurality of quantum dots having an indium phosphide core and a ZnSe / ZnS shell or a ZnSeS shell, controlling the arithmetic size of the quantum dots (e.g., a first quantum dot, a second quantum dot, or a combination thereof) as described herein can suppress and / or prevent overshoot phenomena that would otherwise occur during operation of a device comprising the quantum dot composite. Without wishing to be bound by any theory, it is believed that quantum dots or a fraction thereof (e.g., a second population of quantum dots) having a relatively small arithmetic size can contribute primarily to the overshoot phenomenon. If quantum dots are prepared using a bottom-up approach and layers can be formed on the core, the resulting population of quantum dots can tend to have non-uniformity as a whole. Again, without wishing to be bound by any theory, the non-uniformity can substantially contribute to the overshoot phenomenon when the quantum dots emit light of a predetermined color (e.g., red light), particularly at an early stage of the device's operating time. The inventors of the present application have identified or appreciated that, for a given population of a plurality of quantum dots, separately controlling the (first and / or second) arithmetic size of the (first and / or second) quantum dots as described herein can suppress (or prevent) the effects caused by non-uniformity (including the contribution to overshoot). Thus, the inventors have made it possible to minimize or, in some cases, eliminate overshoot in the device.

[0119] In an embodiment, a plurality of quantum dots may have the above arithmetic size of the group. The plurality of quantum dots may include a first quantum dot (i.e., a first quantum dot group) having or exhibiting a first arithmetic size that is greater than the arithmetic size of the plurality of quantum dots. In an embodiment, the first arithmetic size may be greater than or equal to 8.5 nm. In the plurality of quantum dots, based on the total amount (number or amount such as weight) of the plurality of quantum dots, the fraction of the first quantum dots (i.e., the amount fraction such as the number or weight percentage) may be, for example, greater than or equal to about 60%, greater than or equal to about 65%, greater than or equal to about 70%, greater than or equal to about 75%, greater than or equal to about 80%, greater than or equal to about 81%, greater than or equal to about 82%, greater than or equal to about 83%, greater than or equal to about 84%, or greater than or equal to about 85%. As used herein, with respect to the fraction of quantum dots or quantum dot groups, the term "fraction" refers to the percentage (e.g., number percentage or weight percentage) of a particular subset of quantum dots based on the total amount of the plurality of quantum dots included in the composition or composite.

[0120] The first arithmetic size of the first quantum dot (i.e., the first quantum dot group) can be at least about 1% larger than the arithmetic size of the plurality of quantum dots, for example, greater than or equal to about 2%, greater than or equal to about 3%, greater than or equal to about 4%, or greater than or equal to about 5% of the arithmetic size of the plurality of quantum dots. The first arithmetic size of the first quantum dot can be in the range of about 1% to about 5%, about 2% to about 4%, or about 3% to about 5% larger than the arithmetic size of the plurality of quantum dots. In an embodiment, the arithmetic size of the plurality of quantum dots can be greater than or equal to about 8.8 nm, and / or, in an embodiment, the first arithmetic size can be greater than or equal to about 8.9 nm, greater than or equal to about 9.0 nm, greater than or equal to about 9.1 nm, or greater than or equal to about 9.2 nm and / or less than or equal to about 10 nm, less than or equal to about 9.8 nm, less than or equal to about 9.7 nm, less than or equal to about 9.6 nm, or less than or equal to about 9.5 nm.

[0121] In embodiments, the arithmetic size of the plurality of quantum dots may be greater than or equal to about 9.1 nm, and / or, in embodiments, the first arithmetic size may be greater than or equal to about 9.2 nm, greater than or equal to about 9.3 nm, greater than or equal to about 9.4 nm, or greater than or equal to about 9.5 nm and / or less than or equal to about 11.0 nm, less than or equal to about 10.5 nm, less than or equal to about 10.0 nm, less than or equal to about 9.8 nm, less than or equal to about 9.7 nm, less than or equal to about 9.6 nm, or less than or equal to about 9.5 nm.

[0122] In the plurality of quantum dots included in the quantum dot composite of the embodiment, the amount (e.g., number or weight) of second quantum dots (e.g., a second quantum dot group or a second group of quantum dots) having an arithmetic size smaller than the plurality of quantum dots or a second arithmetic size less than or equal to about 7.2 nm can be limited. In the plurality of quantum dots, the amount fraction (number or weight percentage) of the second quantum dots (e.g., a second quantum dot group) having the second arithmetic size can be less than or equal to about 30%, less than or equal to about 25%, 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%, or less than or equal to about 10%.

[0123] The second arithmetic size may be varied or controlled according to the arithmetic size of the plurality of quantum dots (ie, the total population of quantum dots). In an embodiment, the total quantum dot population (total population of quantum dots) (i.e., multiple quantum dots) in the composite can have an arithmetic size within any of the above ranges, and the second arithmetic size can be less than or equal to about 8.7 nm, less than or equal to about 8.6 nm, less than or equal to about 8.5 nm, less than or equal to about 8.4 nm, less than or equal to about 8.3 nm, less than or equal to about 8.2 nm, less than or equal to about 8.1 nm, less than or equal to about 8.0 nm, less than or equal to about 7.9 nm, less than or equal to about 7.8 nm, less than or equal to about 7.7 nm, less than or equal to about 7.6 nm, less than or equal to about 7.5 nm, less than or equal to about 7.4 nm, less than or equal to about 7.3 nm, less than or equal to about 7.2 nm, less than or equal to about 7.1 nm, less than or equal to about 7.0 nm, less than or equal to about 6.9 nm, less than or equal to about 6.8 nm, less than or equal to about 6.7 nm, less than or equal to about 6.6 nm, or less than or equal to about 6.5 nm.

[0124] In embodiments, the arithmetic size of the plurality of quantum dots in the quantum dot composite may be within any of the above ranges (e.g., greater than or equal to about 8 nm, greater than or equal to about 8.1 nm, greater than or equal to about 8.2 nm and less than or equal to about 9.3 nm, less than or equal to about 9.2 nm, less than or equal to about 9.1 nm, less than or equal to about 9 nm, less than or equal to about 8.9 nm, less than or equal to about 8.8 nm, less than or equal to about 8.7 nm, less than or equal to about 8.6 nm, or less than or equal to about 8.5 nm), and the plurality of quantum dots may include a second quantum dot group or a third quantum dot group having an arithmetic size less than or equal to about 7.5 nm, less than or equal to about 7.4 nm, less than or equal to about 7.3 nm, less than or equal to about 7.2 nm, less than or equal to about 7.1 nm, less than or equal to about 7.0 nm, or less than or equal to about 6.5 nm. Based on the total number or total weight of the plurality of quantum dots, the fraction of the second quantum dots or the third quantum dots can be less than or equal to about 30%, less than or equal to about 25%, 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%, or less than or equal to about 9%.

[0125] In an embodiment, the arithmetic size of the plurality of quantum dots in the quantum dot composite may be within any of the above ranges (e.g., greater than or equal to about 8.2 nm, greater than or equal to about 8.5 nm, greater than or equal to about 9.0 nm, greater than or equal to about 9.1 nm, or greater than or equal to about 9.15 nm). In an embodiment, the arithmetic size of the plurality of quantum dots in the quantum dot composite may be less than or equal to about 9.3 nm, less than or equal to about 9.2 nm, or less than or equal to about 9.0 nm (e.g., about 8 nm to about 9.3 nm, about 8.2 nm to about 9.2 nm, about 8.5 nm to about 9.0 nm, about 8.6 nm to about 8.9 nm, or about 8.8 nm to about 9.2 nm), and the first arithmetic size of the first quantum dot included in the plurality of quantum dots may be greater than or equal to about 8.9 nm or greater than or equal to about 9 nm. In a plurality of quantum dots (e.g., a total population of a plurality of quantum dots), the fraction of the first quantum dot population can be greater than or equal to about 60%, greater than or equal to about 65%, greater than or equal to about 70%, greater than or equal to about 75%, greater than or equal to about 80%, greater than or equal to about 81%, or greater than or equal to about 82%.

[0126] Among the plurality of quantum dots, the first quantum dot, the second quantum dot, and / or the third quantum dot can be separated by precipitation using an appropriate precipitation solvent (e.g., a mixture of a non-solvent and a dispersing solvent). The details of the non-solvent, dispersing solvent, and separation are described or explained herein (e.g., with respect to quantum dots and / or exemplary methods).

[0127] In a plurality of quantum dots, the semiconductor nanocrystal core (e.g., the size of the semiconductor nanocrystal core) can control the emission wavelength of the quantum dot. In an embodiment, the quantum dot composite is configured to emit red light, and the average size of the core can be greater than or equal to about 3.0 nm, for example, greater than or equal to about 3.1 nm, greater than or equal to about 3.2 nm, greater than or equal to about 3.3 nm, greater than or equal to about 3.4 nm, or greater than or equal to about 3.5 nm. In a plurality of quantum dots, the size of the semiconductor nanocrystal core can be less than or equal to about 4.5 nm, less than or equal to about 4.0 nm, less than or equal to about 3.9 nm, less than or equal to about 3.8 nm, less than or equal to about 3.7 nm, or less than or equal to about 3.6 nm.

[0128] In the plurality of quantum dots included in the composite, the semiconductor nanocrystal shell may have a multilayer shell structure. The semiconductor nanocrystal shell may have: a first layer including a first semiconductor nanocrystal containing zinc, selenium, and optionally sulfur; and a second layer including a second semiconductor nanocrystal containing zinc, sulfur, and optionally selenium. The first semiconductor nanocrystal of the first layer may have a composition different from the composition of the second semiconductor nanocrystal of the second layer.

[0129] The first layer may include ZnSe, ZnSeS, or a combination thereof. The first layer may be adjacent to the semiconductor nanocrystal core (e.g., directly disposed on the semiconductor nanocrystal core). The first layer may not include sulfur. The second layer may include ZnS. The second layer may be composed of ZnS. The second layer may be the outermost layer of the semiconductor nanocrystal shell (or quantum dot).

[0130] The thickness of the first layer (or semiconductor nanocrystal shell) can be greater than or equal to about 1.5 nm, greater than or equal to about 1.7 nm, greater than or equal to about 1.9 nm, greater than or equal to about 2.0 nm, or greater than or equal to about 2.1 nm. The thickness of the first layer (or semiconductor nanocrystal shell) can be less than or equal to about 5.0 nm, less than or equal to about 4.0 nm, less than or equal to about 3.5 nm, less than or equal to about 3.0 nm, or less than or equal to about 2.5 nm.

[0131] If present, the second layer may have a thickness of less than or equal to about 0.7 nm, less than or equal to about 0.6 nm, or less than or equal to about 0.5 nm. In an embodiment, the second layer may have a thickness of greater than or equal to about 0.3 nm, greater than or equal to about 0.35 nm, or greater than or equal to about 0.4 nm.

[0132] In multiple quantum dots (or in the first quantum dot or the second quantum dot), the molar ratio of zinc to indium (Zn:In) can be greater than or equal to about 13:1, greater than or equal to about 14:1, greater than or equal to about 14.8:1, greater than or equal to about 15:1, greater than or equal to about 15.2:1, greater than or equal to about 15.5:1, greater than or equal to about 16:1, greater than or equal to about 16.2:1, greater than or equal to about 16.5:1, greater than or equal to about 17:1, greater than or equal to about 17.2:1, greater than or equal to about 17.5:1, or greater than or equal to about 18:1. In the plurality of quantum dots (or the first quantum dot and / or the second quantum dot), the molar ratio of zinc to indium may be less than or equal to about 50:1, less than or equal to about 40:1, 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 19:1, less than or equal to about 18:1, or less than or equal to about 16.5:1.

[0133] In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of sulfur to selenium (S:Se) may be less than or equal to about 2: 1, less than or equal to about 1.5: 1, less than or equal to about 1: 1, less than or equal to about 0.9: 1, less than or equal to about 0.8: 1, less than or equal to about 0.7: 1, less than or equal to about 0.6: 1, less than or equal to about 0.5: 1, or less than or equal to about 0.4: 1. In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of sulfur to selenium (S:Se) may be greater than or equal to about 0.1: 1, greater than or equal to about 0.2: 1, or greater than or equal to about 0.3: 1.

[0134] In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of phosphorus to indium (P:In) 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, greater than or equal to about 0.72:1, greater than or equal to about 0.75:1, or greater than or equal to about 0.8: 1. In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of phosphorus to indium (P:In) may be less than or equal to about 1:1, less than or equal to about 0.9:1, less than or equal to about 0.85:1, or less than or equal to about 0.8:1.

[0135] In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of selenium to indium (Se:In) may be greater than or equal to about 6:1, greater than or equal to about 6.5:1, greater than or equal to about 7:1, greater than or equal to about 7.5:1, greater than or equal to about 8:1, greater than or equal to about 8.5:1, greater than or equal to about 8.8:1, greater than or equal to about 9:1, greater than or equal to about 9.1:1, greater than or equal to about 9.5:1, greater than or equal to about 10:1, greater than or equal to about 10.5:1, or greater than or equal to about 11: 1. In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of selenium to indium may be less than or equal to about 20:1, less than or equal to about 18:1, less than or equal to about 16:1, less than or equal to about 14:1, or less than or equal to about 13:1.

[0136] In multiple quantum dots (either the first quantum dot or the second quantum dot), the molar ratio of sulfur to indium (S:In) can be greater than or equal to about 2.5:1, greater than or equal to about 2.6:1, greater than or equal to about 2.7:1, greater than or equal to about 2.8:1, greater than or equal to about 2.9:1, greater than or equal to about 3:1, greater than or equal to about 3.5:1, greater than or equal to about 3.6:1, greater than or equal to about 3.7:1, greater than or equal to about 3.8:1, greater than or equal to about 3.9:1, greater than or equal to about 4:1 or greater than or equal to about 4.4:1. In multiple quantum dots (either the first quantum dot or the second quantum dot), the molar ratio of sulfur to indium can be less than or equal to about 10:1, less than or equal to about 9:1, less than or equal to about 8:1, less than or equal to about 7:1, less than or equal to about 6.5:1, less than or equal to about 6:1, less than or equal to about 5.5:1, less than or equal to about 5:1, or less than or equal to about 4.9:1.

[0137] In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of the sum of selenium and sulfur to indium ((Se+S):In) may be greater than or equal to about 10:1, greater than or equal to about 11:1, greater than or equal to about 12:1, greater than or equal to about 13:1, greater than or equal to about 13.5:1, greater than or equal to about 14:1, greater than or equal to about 14.5:1, or greater than or equal to about 15: 1. In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of the sum of selenium and sulfur to indium may be 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 18:1, less than or equal to about 17:1, less than or equal to about 16:1, or less than or equal to about 15.5:1.

[0138] In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of zinc to the sum of selenium and sulfur (Zn:(Se+S)) may be 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, or less than or equal to about 1.06: 1. In the plurality of quantum dots (or the first quantum dot or the second quantum dot), the molar ratio of zinc to the sum of selenium and sulfur 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, greater than or equal to about 0.8:1, greater than or equal to about 0.9:1, or greater than or equal to about 1:1.

[0139] The plurality of quantum dots may have an arithmetic size within the above range and may have an irregular shape.

[0140] Thus, in embodiments, the shapes of the plurality of quantum dots may be so irregular that no (average) solidity or average circularity of the quantum dots is achieved.

[0141] In an embodiment, a quantum dot composition or composite includes the plurality of quantum dots described above, and in a solid state, if irradiated with light having a wavelength of about 450 nm to about 470 nm (e.g., in a solid state) for a predetermined time, the quantum dot composition or composite may exhibit a luminance decrease interval. In an embodiment, the luminance decrease interval may occur within an irradiation time of less than or equal to about 100 hours, less than or equal to about 90 hours, less than or equal to about 80 hours, less than or equal to about 70 hours, less than or equal to about 60 hours, or less than or equal to about 50 hours. During the luminance decrease interval, the lowest value of the luminance may be 98% of the initial luminance, for example, greater than or equal to about 98.5% or greater than or equal to about 99% of the initial luminance.

[0142] The quantum dot composite or composition, or the plurality of quantum dots included therein, can be configured to emit red light. The maximum peak wavelength of the red light can be greater than or equal to about 600 nm, greater than or equal to about 610 nm, greater than or equal to about 620 nm, or greater than or equal to about 625 nm. The maximum peak wavelength of the red light can be less than or equal to about 650 nm, less than or equal to about 645 nm, less than or equal to about 640 nm, or less than or equal to about 635 nm.

[0143] The quantum yield or efficiency of the quantum dot complex or composition or a plurality of quantum dots can be greater than or equal to about 85%, greater than or equal to about 86%, greater than or equal to about 87%, greater than or equal to about 88%, greater than or equal to about 89%, or greater than or equal to about 90%. The quantum yield or efficiency of the quantum dot complex or composition or a plurality of quantum dots can be readily measured by absolute or relative methods using a commercially available fluorescence spectrophotometer or quantum yield spectrum analyzer.

[0144] In embodiments, a quantum dot composite or composition or a plurality of quantum dots (or a population of quantum dots) may exhibit a full width at half maximum of less than 41 nm (e.g., less than or equal to about 40 nm, less than or equal to about 39 nm, less than or equal to about 38 nm, or less than or equal to about 37 nm).

[0145] In an embodiment, in the plurality of quantum dots, the molar ratio of zinc to indium may be greater than or equal to about 13:1, and the molar ratio of sulfur to selenium may be less than or equal to about 0.5:1; and the plurality of quantum dots including the first quantum dot group and the second quantum dot group may have an arithmetic size greater than 8.0 nanometers, and the total fraction of the first quantum dot group and the second quantum dot group may be greater than 85% of the plurality of quantum dots.

[0146] Quantum dot-based display devices can exhibit improved color purity, brightness, etc. For example, a liquid crystal display (hereinafter, LCD) realizes color by passing polarized light through an absorptive color filter after the light has passed through the liquid crystal. Due to the absorptive color filter, the LCD has the disadvantages of a narrow viewing angle and low light transmittance. Quantum dots can emit light with a theoretical quantum efficiency or quantum yield (QY) of about 100% and high color purity (for example, a full width at half maximum (FWHM) of less than or equal to about 40 nm), thereby achieving increased luminous efficiency and improved color reproducibility. The absorptive color filter can be replaced with a photoluminescent color filter including a quantum dot composite to achieve a wider viewing angle and improved brightness.

[0147] Quantum dots can be dispersed in a host matrix (e.g., including a polymer, an inorganic material, or a combination thereof) to form a quantum dot composite that can be applied to a device. Multiple quantum dots can exhibit improved optical properties and process stability, and therefore, if included in a display device as a quantum dot polymer composite or a patterned quantum dot polymer composite, improved brightness, wide viewing angle, and improved color reproducibility can be achieved. Under the next-generation standard BT2020 for display devices, the multiple quantum dots of the embodiment can maintain an improved level of color reproducibility.

[0148] The quantum dot may include an organic ligand, an organic solvent, or a combination thereof, which will be described below, on the surface of the quantum dot. The organic ligand, the organic solvent, or the combination thereof may be bound to the surface of the quantum dot.

[0149] The plurality of quantum dots included in the quantum dot composite of the embodiment can be prepared by the method described herein. The method includes reacting a zinc precursor with a selenium precursor and a sulfur precursor in the presence of a semiconductor nanocrystal core including indium and phosphorus in a heated mixture of an organic solvent and an organic ligand (e.g., for a predetermined time), wherein the size and amount of the semiconductor nanocrystal core, the amount of the precursor (if necessary, the molar ratio between each component and / or the reaction time) are controlled to achieve the above characteristics (e.g., arithmetic size, first arithmetic size, second arithmetic size, molar ratio between elements included in the quantum dots, or a combination thereof).

[0150] In an embodiment, the method for manufacturing the quantum dots may include the following steps:

[0151] obtaining a first mixture, the first mixture comprising a zinc precursor, an organic ligand, and an organic solvent;

[0152] optionally heating the first mixture;

[0153] injecting semiconductor nanocrystal cores comprising indium and phosphorus and a selenium precursor into the (optionally heated) first mixture to obtain a second mixture;

[0154] heating the second mixture at a first reaction temperature and maintaining the second mixture at the first reaction temperature, for example, for at least about 40 minutes (e.g., at least about 50 minutes), to obtain a third mixture comprising particles comprising a first semiconductor nanocrystal shell comprising zinc and selenium formed on a semiconductor nanocrystal core;

[0155] A sulfur precursor (e.g., a stock solution containing a sulfur precursor) is injected into the third mixture at a second reaction temperature and reacted to form a second semiconductor nanocrystal shell on the first semiconductor nanocrystal shell. In the method of the embodiment, the amount of selenium precursor relative to the core and the amount of sulfur precursor relative to the core in the second mixture and the third mixture can be controlled, respectively, and the reaction duration in each step can be optionally controlled to provide quantum dots that meet the above-mentioned shell composition.

[0156] If desired, in order to obtain a desired arithmetic size and / or distribution (e.g., the fraction of the first quantum dot population and / or the second quantum dot population), the prepared plurality of quantum dots can be subjected to a reprecipitation process by adding a precipitation solvent (prepared by mixing a dispersing solvent and a non-solvent in a predetermined ratio) to a crude solution comprising a plurality of quantum dots dispersed in an organic solvent. The reprecipitation step can be repeated (e.g., at least twice, at least three times, at least four times, or at least five times). In the precipitation solvent, the volume ratio of the nonsolvent to the dispersing solvent may be greater than or equal to about 1:1, greater than or equal to about 1.2:1, greater than or equal to about 1.3:1, greater than or equal to about 1.4:1, greater than or equal to about 1.5:1, greater than or equal to about 1.6:1, greater than or equal to about 1.7:1, greater than or equal to about 1.8:1, greater than or equal to about 1.9:1, greater than or equal to about 2:1, greater than or equal to about 2.1:1, greater than or equal to about 2.2:1, greater than or equal to about 2.3:1, or greater than or equal to about 2.4: 1. In the precipitation solvent, the volume ratio of the nonsolvent to the dispersing solvent may be less than or equal to about 5:1, less than or equal to about 4:1, less than or equal to about 3.5:1, less than or equal to about 3:1, or less than or equal to about 2.5:1.

[0157] The details of the semiconductor nanocrystal core are the same as those described above. The semiconductor nanocrystal core can be prepared by reacting an indium precursor and a phosphorus precursor in an organic solvent and in the presence of an organic ligand at a core formation temperature for a predetermined time. In an embodiment, before the precursor is injected into the reaction system, the organic solvent and the organic ligand can be first mixed and pretreated (e.g., heated to a predetermined temperature (e.g., greater than or equal to about 100°C, e.g., greater than or equal to about 120°C or greater than or equal to about 150°C) and less than or equal to the core formation temperature) under vacuum, an inert atmosphere, or a combination thereof. If desired, a zinc precursor can be added to the formation of the core. In an embodiment, the core can be synthesized by injecting a solution comprising a metal precursor (e.g., an indium precursor), and optionally, heating the ligand at a high temperature (e.g., greater than or equal to about 200°C), and then injecting the phosphorus precursor into the heated solution. The prepared core can be separated from the reaction system by precipitation using a non-solvent, which will be described in detail below, and the separated core is then added to the reaction system for forming a shell on the core. The prepared core may be added (eg, injected) into a heated organic solvent at a temperature greater than or equal to about 100°C.

[0158] The organic solvent and the organic ligand can be pretreated for the shell formation reaction. The core can be added (e.g., injected) to the pretreated reaction system, and a shell precursor (e.g., a zinc precursor, a selenium precursor, and a sulfur precursor) can be added, and the shell formation reaction can be performed. Taking into account the desired shell composition, the amount and order of the precursors can be controlled. In an embodiment, the shell formation can include injecting a zinc precursor, followed by injecting a selenium precursor, to react at a first temperature and form a first layer; and then injecting a sulfur precursor into the reaction system, optionally with an additional amount of the zinc precursor, to react at a second temperature and form a second layer.

[0159] The organic ligand can include RCOOH, RNH2, R2NH, R3N, RSH, RH2PO, R2HPO, R3PO, RH2P, R2HP, R3P, ROH, RCOOR', RPO(OH)2, RHPOOH, R2POOH (wherein, R and R' are the same or different and are independently hydrogen, C1 to C40 (or C3 to C24) aliphatic hydrocarbon groups (e.g., alkyl, alkenyl, or alkynyl), C6 to C40 aromatic hydrocarbon groups (such as C6 to C20 aryl)), polymeric organic ligands, or combinations thereof. The organic ligand can coordinate to (e.g., bind to) the surface of the obtained nanocrystals and can help the nanocrystals to be well dispersed in the solution.

[0160] Examples of the organic ligand may include: methyl mercaptan, ethyl mercaptan, propyl mercaptan, butyl mercaptan, pentyl mercaptan, hexyl mercaptan, octyl mercaptan, dodecanethiol, hexadecanethiol, octadecanethiol, or benzyl mercaptan; methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, dodecane, hexadecane, octadecane, dimethylamine, diethylamine, or dipropylamine; formic acid, acetic acid, propionic acid, butyric acid, pentyl acid, hexanoic acid, heptanoic acid, octanoic acid, dodecane, hexadecane, octadecane, oleic acid, or benzoic acid; phosphine, 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 oxide, such as substituted or unsubstituted methyl phosphine oxide (e.g., trimethyl phosphine oxide, methyldiphenyl phosphine oxide, etc.), substituted or unsubstituted ethyl phosphine oxide (e.g., triethyl phosphine oxide, ethyldiphenyl phosphine oxide, etc.), substituted or unsubstituted propyl phosphine oxide, substituted or unsubstituted butyl phosphine oxide, or substituted or unsubstituted octyl phosphine oxide (e.g., trioctyl phosphine oxide (TOPO)); diphenyl phosphine, triphenyl phosphine, diphenyl phosphine oxide, or triphenyl phosphine oxide; alkyl phosphinic acid, for example, C5 to C20 alkyl phosphinic acid (e.g., hexyl phosphinic acid, octyl phosphinic acid, dodecyl phosphinic acid, tetradecyl phosphinic acid, hexadecyl phosphinic acid, octadecyl phosphinic acid, etc.), alkyl phosphonic acid (such as C5 to C20 alkyl phosphinic acid); and the like, but are not limited thereto. The organic ligand may be used alone or as a mixture of at least two ligand compounds.

[0161] 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; a phosphine oxide 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 in consideration of the precursor and the organic ligand. The organic solvent can be a dispersing solvent.

[0162] The zinc precursor is not particularly limited and can be appropriately selected. In an embodiment, the zinc precursor can include Zn metal powder, alkylated Zn compounds (e.g., dimethyl zinc, diethyl zinc or a combination thereof), alcohol Zn, carboxylic acid Zn (e.g., zinc acetate), zinc carbonate, Zn nitrate, Zn perchlorate, Zn sulfuric acid, Zn acetylacetonate, Zn halides (e.g., zinc chloride, zinc bromide, zinc iodide, zinc fluoride or a combination thereof), Zn cyanide, Zn hydroxide, Zn oxide, Zn peroxide or a combination thereof. The example of the zinc precursor can include but is not limited to dimethyl zinc, diethyl zinc, zinc acetate, zinc acetylacetonate, zinc iodide, zinc bromide, zinc chloride, zinc fluoride, zinc carbonate, zinc cyanide, zinc nitrate, zinc oxide, zinc peroxide, zinc perchlorate, zinc sulfate, zinc oleate etc. The zinc-containing precursor can be used alone or in combination of two or more compounds.

[0163] The selenium precursor is not particularly limited and can be selected as desired. In an embodiment, the selenium precursor includes selenium-trioctylphosphine (Se-TOP), selenium-tributylphosphine (Se-TBP), selenium-triphenylphosphine (Se-TPP) or a combination thereof, but is not limited thereto.

[0164] The first reaction temperature may be appropriately selected, for example, greater than or equal to about 280° C., greater than or equal to about 290° C., greater than or equal to about 300° C., greater than or equal to about 310° C., or greater than or equal to about 315° C. and less than or equal to about 390° C., less than or equal to about 380° C., less than or equal to about 370° C., less than or equal to about 360° C., less than or equal to about 350° C., less than or equal to about 340° C., or less than or equal to about 330° C. After heating to the first reaction temperature or during heating to the first reaction temperature, the selenium-containing precursor may be injected at least once (for example, at least twice or at least three times).

[0165] The reaction time at the first reaction temperature can be greater than or equal to about 40 minutes, e.g., greater than or equal to about 50 minutes, greater than or equal to about 60 minutes, greater than or equal to about 70 minutes, greater than or equal to about 80 minutes, greater than or equal to about 90 minutes and less than or equal to about 4 hours, e.g., less than or equal to about 3 hours or less than or equal to about 2 hours.

[0166] By reacting the above-mentioned time period at the first reaction temperature, a first semiconductor nanocrystalline shell comprising zinc and selenium and having a thickness greater than or equal to about 3 monolayers (ML), greater than or equal to about 4 ML, greater than or equal to about 5 ML, or greater than or equal to about 6 ML (and / or less than or equal to about 10 ML) can be formed to provide a third mixture. As used herein, the term "monolayer" can refer to a unit of measurement, such as for shell thickness, obtained from the bulk crystal structure of the shell material as the closest distance between relevant lattice planes. For example, the thickness of one monolayer can be determined as the distance between adjacent lattice planes for a cubic lattice structure.

[0167] In an embodiment, the amount of selenium precursor relative to indium can be controlled so that during a predetermined reaction time, a desired composition of the shell (e.g., a first layer having a predetermined thickness) can be formed. In an embodiment, the amount of selenium added per 1 mole of indium in the reaction system can be greater than or equal to about 7 moles, greater than or equal to about 8 moles, greater than or equal to about 9 moles, greater than or equal to about 10 moles, greater than or equal to about 11 moles, greater than or equal to about 12 moles, greater than or equal to about 13 moles, greater than or equal to about 14 moles, or greater than or equal to about 15 moles. In an embodiment, the amount of selenium per 1 mole of indium can be less than or equal to about 30 moles, less than or equal to about 25 moles, less than or equal to about 20 moles, less than or equal to about 18 moles, or less than or equal to about 15 moles.

[0168] In an embodiment, the method may not include lowering the temperature of the reaction mixture containing particles having a first layer of semiconductor nanocrystal shells to about 100° C. or less, e.g., about 50° C. or less (e.g., 30° C. or less or room temperature). In other words, the method may include maintaining the temperature of the reaction mixture containing particles having a first layer on a core at a temperature greater than or equal to 100° C. (e.g., greater than or equal to 50° C. or greater than or equal to 30° C.).

[0169] The type of sulfur precursor is not particularly limited and can be appropriately selected. The sulfur precursor may include hexanethiol, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, mercaptopropylsilane, sulfur-trioctylphosphine (S-TOP), sulfur-tributylphosphine (S-TBP), sulfur-triphenylphosphine (S-TPP), sulfur-trioctylamine (S-TOA), trimethylsilylsulfide, ammonium sulfide, sodium sulfide, or a combination thereof. The sulfur precursor may be injected at least once (e.g., at least twice).

[0170] The second reaction temperature may be appropriately selected and may be greater than or equal to about 280° C., greater than or equal to about 290° C., greater than or equal to about 300° C., greater than or equal to about 310° C., or greater than or equal to about 315° C. The second reaction temperature may be less than or equal to about 350° C., less than or equal to about 340° C., or less than or equal to about 330° C. After heating to the second reaction temperature or during heating to the second reaction temperature, the sulfur precursor may be injected at least once (e.g., at least twice or at least three times).

[0171] The reaction times at the second reaction temperature can be appropriately selected, and are not particularly limited. For example, the reaction times at the second reaction temperature can be greater than or equal to approximately 30 minutes, greater than or equal to approximately 40 minutes, greater than or equal to approximately 50 minutes, greater than or equal to approximately 60 minutes, greater than or equal to approximately 70 minutes, greater than or equal to approximately 80 minutes, or greater than or equal to approximately 90 minutes. In an embodiment, the reaction times at the second reaction temperature can be less than or equal to approximately 4 hours, less than or equal to approximately 3 hours, or less than or equal to approximately 2 hours.

[0172] In an embodiment, the amount of sulfur precursor relative to indium can be controlled so that the desired composition of the shell (e.g., a second layer having a predetermined thickness) can be formed during a predetermined reaction time. In an embodiment, the amount of sulfur in the reaction system relative to one mole of indium can be greater than or equal to about 3 moles, greater than or equal to about 4 moles, greater than or equal to about 5 moles, greater than or equal to about 6 moles, greater than or equal to about 7 moles, greater than or equal to about 8 moles, greater than or equal to about 9 moles, greater than or equal to about 10 moles, greater than or equal to about 11 moles, greater than or equal to about 12 moles, greater than or equal to about 13 moles, greater than or equal to about 14 moles, greater than or equal to about 15 moles, greater than or equal to about 16 moles, greater than or equal to about 17 moles, greater than or equal to about 18 moles, or greater than or equal to about 19 moles. The amount of sulfur in the third mixture relative to one mole of indium can be less than or equal to about 40 moles, less than or equal to about 35 moles, less than or equal to about 30 moles, less than or equal to about 25 moles, less than or equal to about 20 moles, or less than or equal to about 15 moles.

[0173] The amount of zinc precursor, selenium precursor, and sulfur precursor relative to the indium of the semiconductor nanocrystal core can be selected in consideration of the structure and properties of the final quantum dot.

[0174] After the reaction, a non-solvent is added to the final reaction solution obtained to promote the precipitation of the quantum dots coordinated by the organic ligand (which can then be separated). The non-solvent can be a polar solvent miscible with the solvent used in the reaction. The semiconductor nanocrystals and quantum dots can be non-dispersible in the non-solvent. The non-solvent can be selected according to the solvent used in the reaction, and can be, for example, acetone, ethanol, butanol, isopropanol, ethylene glycol, water, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), diethyl ether, formaldehyde, acetaldehyde, a solvent with a solubility parameter similar to the solubility parameter of the above-mentioned solvent, or a combination thereof. Separation can be performed by centrifugation, filtration, chromatography or distillation. If desired, the separated semiconductor nanocrystals (or the first semiconductor nanocrystal and the second semiconductor nanocrystal) can be added to a washing solvent and washed. The washing solvent is not particularly limited and can include a solvent with a solubility parameter similar to the solubility parameter of the organic solvent or the organic ligand, and for example can include alkanes, chloroform, toluene, benzene, etc. such as hexane, heptane or octane.

[0175] The quantum dots or quantum dot groups can be dispersed in a dispersing solvent. The dispersing solvent is not particularly limited and can be appropriately selected. The dispersing solvent can include the above-mentioned organic solvent (or be composed of the above-mentioned organic solvent). The dispersing solvent can include substituted or unsubstituted C1 to C40 aliphatic hydrocarbons, substituted or unsubstituted C6 to C40 aromatic hydrocarbons, or a combination thereof (or be composed of substituted or unsubstituted C1 to C40 aliphatic hydrocarbons, substituted or unsubstituted C6 to C40 aromatic hydrocarbons, or a combination thereof). As described above, the non-solvent and the dispersing solvent can be used as precipitation solvents in the process of inducing precipitation (i.e., reprecipitation). The separation of the quantum dots after the process of inducing precipitation can be carried out using a method similar to that described above or a method substantially the same as that described above.

[0176] In the quantum dot composite of the embodiment, a plurality of quantum dots may be dispersed in a matrix. In the quantum dot composite of the embodiment or the composition of the embodiment including quantum dots, the amount of quantum dots may be appropriately selected, for example, depending on the final application (eg, color filter).

[0177] In an embodiment, the amount of quantum dots can be greater than or equal to about 1 weight percent (wt%), for example, greater than or equal to about 2 wt%, greater than or equal to about 3 wt%, greater than or equal to about 4 wt%, greater than or equal to about 5 wt%, greater than or equal to about 6 wt%, greater than or equal to about 7 wt%, greater than or equal to about 8 wt%, greater than or equal to about 9 wt%, greater than or equal to about 10 wt%, greater than or equal to about 15 wt%, greater than or equal to about 20 wt%, greater than or equal to about 25 wt%, greater than or equal to about 30 wt%, greater than or equal to about 35 wt%, or greater than or equal to about 40 wt%, based on the total solid content (or total weight) of the composite or composition. The amount of quantum dots can be less than or equal to about 70 wt%, for example, 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%, based on the total solid content (or total weight) of the composite or composition.

[0178] The total solids content (TSC) of the composite or composition may be greater than or equal to about 10%, greater than or equal to about 15%, greater than or equal to about 20%, greater than or equal to about 25%, greater than or equal to about 30%, greater than or equal to about 35%, greater than or equal to about 40%, greater than or equal to about 45%, greater than or equal to about 50%, greater than or equal to about 55%, greater than or equal to about 60%, or greater than or equal to about 65%. In embodiments, the total solids content (TSC) of the composite or composition may be less than or equal to about 90%, less than or equal to about 80%, less than or equal to about 70%, less than or equal to about 60%, less than or equal to about 50%, less than or equal to about 40%, or less than or equal to about 30%.

[0179] The matrix of the quantum dot complex (or composition) may include (or may also include) a polymerizable monomer or its polymer containing a carbon-carbon double bond, a thiol compound having at least one thiol group, a polymer, a liquid carrier (e.g., an organic solvent or a volatile liquid), or a combination thereof. The monomer may be a non-volatile liquid compound. The matrix (or composition) may become solid via polymerization and optional drying or removal of a volatile compound (e.g., an organic solvent). The complex or composition may be a liquid composition. The composition that may be in liquid form may also include an initiator for polymerizing the polymerizable monomer. The complex or composition may be in the form of a solid film or a liquid film. The film may be a patterned film having a predetermined repeating portion (e.g., corresponding to a sub-pixel pattern).

[0180] In an embodiment, the composition comprising quantum dots and a matrix component for forming a pattern can be a photoresist composition or an inkjet composition that can be suitable for a photolithography process to produce a pattern via a printing method (e.g., a droplet discharge method such as inkjet printing). The details of each method will be described herein. The ink composition can include a polymerizable monomer, a liquid carrier, or a combination thereof. The liquid carrier can include an organic solvent. In an embodiment, the ink composition can include no (volatile) organic solvent. The matrix or composition can include an electrically insulating polymer. The polymerizable monomer can provide an electrically insulating polymer via polymerization.

[0181] The polymerizable monomer may include a (meth)acrylate compound having at least one (meth)acrylate group. If desired, the polymerizable monomer may include or may not include a carboxylic acid group. The monomer may include a (photopolymerizable) (meth)acrylate monomer. The monomer may be a precursor for an insulating polymer. Examples of monomers may include, but are not limited to, C1 to C10 alkyl (meth)acrylates, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, diquaternary tert-butyl ether ... Pentaerythritol di(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, bisphenol A epoxy (meth)acrylate, bisphenol A di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ethylene glycol monomethyl ether (meth)acrylate, novolac epoxy (meth)acrylate, propylene glycol di(meth)acrylate, tri(meth)acryloyloxyethyl phosphate, or a combination thereof.

[0182] The amount of the (photopolymerizable) 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 %, relative to the total weight (or total solids content) of the composite or composition. The amount of the (photopolymerizable) monomer may be less than or equal to about 50 wt %, for example, less than or equal to about 40 wt %, less than or equal to about 30 wt %, 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 %, relative to the total weight (or total solids content) of the composite or composition.

[0183] The thiol compound may include a dithiol compound, a trithiol compound, a tetrathiol compound, or a combination thereof. For example, the thiol compound may include a glycol di-3-mercaptopropionate (e.g., ethylene glycol di-3-mercaptopropionate), a glycol dimercaptoacetate (e.g., ethylene glycol dimercaptoacetate), trimethylolpropane tris(3-mercaptopropionate), pentaerythritol tetrakis(3-mercaptopropionate), pentaerythritol tetrakis(2-mercaptoacetate), 1,6-hexanedithiol, 1,3-propanedithiol, 1,2-ethanedithiol, a polyethylene glycol dithiol comprising 1 to 10 ethylene glycol repeating units, or a combination thereof.

[0184] The amount of the thiol compound may be less than or equal to about 50 wt %, less than or equal to about 40 wt %, less than or equal to about 30 wt %, less than or equal to about 20 wt %, less than or equal to about 10 wt %, less than or equal to about 9 wt %, less than or equal to about 8 wt %, less than or equal to about 7 wt %, less than or equal to about 6 wt %, or less than or equal to about 5 wt %, based on the total weight (or total solid content) of the composition. The amount of the thiol compound may 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 %, based on the total weight (or total solid content) of the composition.

[0185] Polymer can comprise linear polymer, cross-linked polymer or their combination.(Linear or cross-linked) polymer can comprise the polymerization product of polymerizable monomer.Cross-linked polymer can comprise mercapto alkene (thiolene) polymer (for example, comprise the polymerization product of above monomer and mercaptan compound), cross-linked poly (methyl) acrylate, cross-linked polyurethane, cross-linked epoxy resin, cross-linked vinyl polymer, cross-linked silicone resin or their combination.Linear polymer can comprise the repeating unit derived from the monomer that comprises carbon-carbon double bond and optional carboxylic acid group.

[0186] In the quantum dot composites or compositions of the embodiments, a polymerizable monomer or a linear polymer (eg, optionally having carboxylic acid groups) can help disperse the quantum dots in the composite or composition. The linear polymer can be an electrically insulating polymer.

[0187] The matrix may include a compound containing carboxylic acid groups.

[0188] The polymerizable monomer or linear polymer including a carboxylic acid group (hereinafter, referred to as a dispersant) may include:

[0189] a monomer combination comprising a first monomer, a second monomer, and an optional third monomer, wherein the first monomer comprises a carboxylic acid group and a carbon-carbon double bond, the second monomer comprises a carbon-carbon double bond and a hydrophobic portion but does not comprise a carboxylic acid group, and the optional third monomer comprises a carbon-carbon double bond and a hydrophilic portion but does not comprise a carboxylic acid group;

[0190] copolymers of monomer combinations;

[0191] 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 carboxylic acid group (-COOH), the quaternary carbon atom being a constituent atom of another ring portion in the backbone; or

[0192] A combination of them.

[0193] The carboxylic acid group-containing compound may have an acid value greater than or equal to about 50 milligrams of potassium hydroxide per gram (mg KOH / g).The carboxylic acid group-containing compound may have a molecular weight greater than or equal to about 400 g / mol.

[0194] In the quantum dot composition or quantum dot composite, the amount of the dispersant (e.g., linear 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 %, based on the total weight (or total solid content) of the composition or composite. In an embodiment, the amount of the dispersant (e.g., linear polymer or carboxylic acid group-containing binder) may be 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 (or total solid content) of the composition or composite. The amount of the dispersant (e.g., binder polymer) may be greater than or equal to about 0.5 wt % and less than or equal to about 55 wt %, based on the total weight (or total solid content) of the composition or composite.

[0195] The composition may further include a liquid carrier (eg, an organic solvent) (hereinafter, simply referred to as "solvent"). The type of solvent is not particularly limited. Non-limiting examples of solvents and liquid carriers can 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 to C40 aliphatic hydrocarbons (e.g., alkanes, alkenes or alkynes), halogen (e.g., chlorine) substituted C1 to C40 aliphatic hydrocarbons (e.g., dichloroethane, chloroform, etc.), C6 to C40 aromatic hydrocarbons (e.g., toluene, xylene, etc.), halogen (e.g., chlorine) substituted C6 to C40 aromatic hydrocarbons; or combinations thereof.

[0196] The type and amount of the solvent can be appropriately selected by considering the above-mentioned main components (i.e., quantum dots, dispersant, photopolymerizable monomer, photoinitiator, and thiol compound if used) and the type and amount of the additives described below. The composition may include a remaining amount of solvent in addition to the desired amount of solid content (non-volatile components).

[0197] The components (dispersant, monomer, liquid carrier, additive, thiol compound, cardo binder, etc.) included in the composition (e.g., photoresist composition) or composite of the embodiment can be appropriately selected, and for details, reference can be made to the details described in, for example, US-2017-0052444-A1, which is incorporated herein by reference.

[0198] The viscosity of the composition (e.g., inkjet composition) at 25° C. may be 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 viscosity of the composition (e.g., inkjet composition) at 25° C. may be 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.

[0199] If the composition is applied in an inkjet process, the composition can be discharged onto a substrate at room temperature, and a quantum dot polymer composite or pattern of quantum dot polymer composites can be formed, for example, by heating. Together with the disclosed viscosities, the surface tension of the ink composition at 23° C. can be 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.

[0200] If desired, the composition or composite may include various additives such as a light diffuser, a leveling agent, or a coupling agent in addition to the above-mentioned components.

[0201] The composition can form a composite of a matrix in the solid state via polymerization. The composition can also include a (photo)initiator for the (photo)polymerization of the above-mentioned monomers. An initiator is a compound that accelerates a free radical reaction (e.g., free radical polymerization of a monomer) by generating free radical chemicals under mild conditions (e.g., by heat or light). The initiator can be a thermal initiator or a photoinitiator. The initiator is not particularly limited and can be appropriately selected.

[0202] In the composition, the type and amount of the polymerizable monomer can be considered to appropriately adjust the amount of the initiator. In an embodiment, based on the gross weight (or gross weight of the solid content) of the composition, the amount of the initiator can be greater than or equal to about 0.01wt%, for example, greater than or equal to about 1wt% and less than or equal to about 10wt%, for example, less than or equal to about 9wt%, less than or equal to about 8wt%, less than or equal to about 7wt%, less than or equal to about 6wt% or less than or equal to about 5wt%. But it is not limited thereto.

[0203] The composition or composite may also include fine metal oxide particles (e.g., dispersed in a matrix). The fine metal oxide particles may include TiO2, SiO2, BaTiO3, Ba2TiO4, ZnO, or a combination thereof. In the composition, based on the gross weight (or its solid content) of the composition, the amount of the fine metal oxide particles may be greater than or equal to about 1wt%, greater than or equal to about 5wt%, or greater than or equal to about 10wt% and less than or equal to about 50wt%, less than or equal to about 40wt%, less than or equal to about 30wt%, less than or equal to about 25wt%, less than or equal to about 20wt%, less than or equal to about 15wt%, less than or equal to about 10wt%, or less than or equal to about 5wt%. The fine metal oxide particles may be non-radiative. The fine metal oxide particles may have a suitably selected diameter without particular limitation. The diameter of the metal oxide fine particles may 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.

[0204] The composition according to the embodiment can be prepared by a method comprising the following steps: preparing a quantum dot dispersion comprising the above-mentioned quantum dots, a dispersant and a solvent; and mixing the quantum dot dispersion with an initiator, a polymerizable monomer (e.g., an acryl-based monomer), an optional thiol compound, optional metal oxide particles, and the optional above-mentioned additives. Each of the above-mentioned components can be mixed sequentially or simultaneously, but the mixing order is not particularly limited. The (ink or photoresist) composition can provide a quantum dot composite or quantum dot pattern via (free radical) polymerization and / or removal of the solvent.

[0205] The thickness of the film of the quantum dot-polymer composite or quantum dot-polymer composite pattern described below can be, for example, less than or equal to about 30 micrometers (μm), for example, 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 about 2 μm, for example, 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.

[0206] In an embodiment, a patterned film includes a repeating portion, the repeating portion including a first portion that emits a first light, wherein the first portion includes a quantum dot composite. The repeating patterned film may include a second portion that emits a second light having a maximum peak wavelength different from the maximum peak wavelength of the first light. The second portion may include a quantum dot polymer composite. The quantum dot polymer composite of the second portion may include second quantum dots configured to emit the second light. The second quantum dots may include the above-mentioned quantum dots. The first light or the second light may be red light having a maximum photoluminescence peak wavelength in the range of about 600 nm to about 650 nm (e.g., about 620 nm to about 650 nm) or green light having a maximum photoluminescence peak wavelength in the range of about 500 nm to about 550 nm (e.g., about 510 nm to about 540 nm). The patterned film may further include a third portion that emits or passes 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.

[0207] In an embodiment, the display device includes a light-emitting element (e.g., a photoluminescent element) and an optional light source. The light-emitting element includes a light-emitting layer, and the light-emitting layer includes a film or a patterned film of a quantum dot composite. The light-emitting layer can be provided on a (e.g., transparent) substrate. The light source is configured to provide incident light to the light-emitting element. The peak emission wavelength of the incident light can be greater than or equal to about 440 nm, for example, greater than or equal to about 450 nm and less than or equal to about 500 nm, for example, 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.

[0208] In an embodiment, the light emitting element or light emitting layer may include a sheet of a quantum dot polymer composite. Figure 1, a photoluminescent display device 400 may include a backlight unit (for example, including a blue light source) and a liquid crystal panel (LC), and the backlight unit may include a sheet of quantum dot polymer composite (QD sheet). The backlight unit may have a structure in which a blue light source, a quantum dot-polymer composite sheet (QD sheet) and various optical films (such as prisms, dual brightness enhancement films (DBEF)), etc.) are stacked, and the liquid crystal panel is arranged on the backlight unit. The backlight unit may also include a reflector, a light guide panel (LGP), or a combination thereof. Thin film transistors (TFT), liquid crystal panel LC, and color filters may be arranged between two polarizers (Pol). The quantum dot polymer composite (QD sheet) may include red quantum dots and green quantum dots that absorb light from the light source and emit red light and green light, respectively. The blue light provided from the light source can pass through the quantum dot polymer composite sheet, and if combined with the red light and green light emitted from the quantum dots, the blue light is converted into white light. The white light can be separated into blue light, green light, and red light by the color filters in the liquid crystal panel and extracted to the outside according to the pixels.

[0209] In the light-emitting layer of a display device according to an embodiment (e.g., a patterned film of a quantum dot polymer composite), 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 or optionally green light. In an embodiment, a first optical element that cuts (e.g., absorbs or reflects) blue light and optionally green light may be provided on the front side (i.e., the light-emitting surface) of the first and second portions. In an embodiment, the light source may include an OLED that emits blue light and an OLED that emits green light, and a green light-cutting element may be provided on the third portion that allows the blue light to pass through.

[0210] In the above-mentioned display device, the light source may include a plurality of light-emitting units corresponding to the first part and the second part, respectively, and the light-emitting units may include a first electrode and a second electrode each having surfaces opposite to each other and an electroluminescent layer arranged between the first electrode and the second electrode. The electroluminescent layer may include an organic light-emitting material. For example, each light-emitting unit of the light source may include an electroluminescent device (e.g., an organic light-emitting diode (OLED)) configured to emit light of a predetermined wavelength (e.g., blue light, green light, or a combination thereof). The structure and material of the electroluminescent device and the organic light-emitting diode (OLED) are not particularly limited. The light source includes an organic light-emitting diode (OLED) that emits blue light (and optionally green light).

[0211] Figure 2A is a schematic cross-sectional view of a display device according to an embodiment, Figure 2B is a schematic cross-sectional view of a display device according to an embodiment. Figure 2A and Figure 2BThe light source includes an organic light-emitting diode (OLED) that emits blue light. The organic light-emitting diode (OLED) may include: (at least two, for example, three or more) pixel electrodes 90a, 90b, 90c formed on a substrate 100; pixel defining layers 150a, 150b formed between adjacent pixel electrodes 90a, 90b, 90c; organic light-emitting layers 140a, 140b, 140c formed on the pixel electrodes 90a, 90b, 90c; and a common electrode (layer) 130 formed on the organic light-emitting layers 140a, 140b, 140c. The thin film transistor and the substrate may be disposed below the organic light-emitting diode (OLED).

[0212] A stacked structure including a quantum dot composite pattern 170 (e.g., a portion 31 including or not including, for example, blue-emitting quantum dots, a portion 11 including red-emitting quantum dots, and a portion 21 including green-emitting quantum dots), an optical filter layer 160, and a transparent substrate (or referred to as an upper substrate) 240 may be disposed on a light source. Light emitted from the light source (e.g., blue light) may enter the first portion 11 and the second portion 21 of the pattern 170 to emit (e.g., converted) red light R and green light G, respectively. Blue light B emitted from the light source passes through or is transmitted from the third portion 31.

[0213] Between the quantum dot composite layer (R, G) and the substrate, a filter layer (optical element) 160 (a first filter or excitation light cutting layer) may be provided to cut light from the light source. In an embodiment, the light from the light source may include blue light or green light, and a green light cutting filter may be provided above the third portion. Details of the first filter or excitation light cutting filter are further described herein.

[0214] The display device can be obtained by separately manufacturing a stacked structure and a (eg, blue-emitting) LED or OLED and then assembling them. Alternatively, the display device can be obtained by directly forming a quantum dot polymer composite pattern on the LED or OLED.

[0215] The substrate may be a substrate comprising an insulating material. The substrate may include: glass; various polymers such as polyester (e.g., polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polymethacrylate, or polyacrylate); polycarbonate; polysiloxane (e.g., polydimethylsiloxane (PDMS)); inorganic materials such as Al2O3 or ZnO; or a combination thereof, but not limited thereto. The thickness of the substrate may be appropriately selected in consideration of the substrate material, but is not particularly limited. The substrate may be flexible. The transmittance of the substrate may be greater than or equal to about 50%, greater than or equal to about 60%, greater than or equal to about 70%, greater than or equal to about 80%, or greater than or equal to about 90% for light emitted from the quantum dots.

[0216] A wiring layer including thin film transistors, etc. is formed on a substrate. The wiring layer may also include a gate line, a sustaining voltage line, a gate insulating layer, a data line, a source electrode, a drain electrode, a semiconductor, a protective layer, etc. Depending on the embodiment, the detailed structure of the wiring layer can be determined. The gate line and the sustaining voltage line are electrically separated from each other, and the data line is insulated from and intersects the gate line and the sustaining voltage line. The gate electrode, the source electrode, and the drain electrode respectively form the control terminal, the input terminal, and the output terminal of the thin film transistor. The drain electrode is electrically connected to the pixel electrode to be described below.

[0217] The pixel electrode can be used as an anode of the display device. The pixel electrode can be formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The pixel electrode can be formed of a material with 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 can have a double-layer structure in which a transparent conductive material and a material with light-blocking properties are sequentially stacked.

[0218] Between two adjacent pixel electrodes, a pixel defining layer (PDL) overlaps the ends of the pixel electrodes to divide the pixel electrodes into pixel units. The pixel defining layer is an insulating layer that can electrically block at least two pixel electrodes.

[0219] The pixel defining layer covers a portion 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. An organic emission layer to be described below may be formed in the area defined by the opening.

[0220] The organic emission layer defines each pixel region through the pixel electrode and the pixel defining layer. In other words, one pixel region can be defined as a region where one organic emission unit layer is formed, and the organic emission unit layer contacts one pixel electrode divided by the pixel defining layer.

[0221] For example, in the display device according to the embodiment, the organic emission layer may be defined into first, second, and third pixel regions, each pixel region being separated from each other by a pixel defining layer with a predetermined interval.

[0222] In an embodiment, the organic emission layer may emit a third light in the visible light region or the UV region. That is, each of the first to third pixel regions of the organic emission layer may emit a third light. In an embodiment, the third light may be light with the highest energy in the visible light region, for example, it may be blue light. The third light may also include green light. When all pixel regions of the organic emission layer are designed to emit the same light, each pixel region of the organic emission layer may all be formed of the same or similar materials, or may exhibit the same or similar properties. Therefore, the difficulty of the manufacturing process for forming the organic emission layer may be significantly reduced. Therefore, the display device can be easily applied to large-scale / large-area processing. However, the organic emission layer according to the embodiment is not necessarily limited to this, but the organic emission layer may be designed to emit at least two different lights.

[0223] The organic emission layer includes an organic emission unit layer in each pixel area. In addition to the emission layer, each organic emission unit layer may also include auxiliary layers (e.g., hole injection layer (HIL), hole transport layer (HTL), electron transport layer (ETL), etc.).

[0224] The common electrode may serve as a cathode of the display device. The common electrode may be formed of a transparent conductive material such as indium tin oxide (ITO) or indium zinc oxide (IZO). The common electrode may be formed on the organic emission layer and may be integrated with the organic emission layer.

[0225] A planarization layer or a passivation layer may be formed on the common electrode. The planarization layer may include an insulating material (eg, transparent) for ensuring electrical insulation from the common electrode.

[0226] In an embodiment, the display device may further include a lower substrate, a polarizer disposed below the lower substrate, and a liquid crystal layer disposed between the stacked structure and the lower substrate. In the stacked structure, the light-emitting layer may be disposed facing the liquid crystal layer. The display device may further include a polarizer located between the liquid crystal layer and the light-emitting layer. The light source may further include an LED and, if desired, a light guide panel.

[0227] Non-limiting examples of a display device (eg, a liquid crystal display device) according to an embodiment are described with reference to the accompanying drawings. Figure 3 1 is a schematic cross-sectional view showing a liquid crystal display device according to an embodiment of the present invention. The display device of the embodiment includes a liquid crystal panel 200, a polarizer 300 disposed below the liquid crystal panel 200, and a backlight unit (110, 120) disposed below the polarizer 300.

[0228] 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 and a photoluminescent layer 230 including a pattern containing a quantum dot polymer composite.

[0229] The lower substrate 210, also referred to as the array substrate, may be a transparent insulating material substrate. The substrate is the same as described above. A wiring board 211 is disposed on the upper surface of the lower substrate 210. The wiring board 211 may include, but is not limited to, a plurality of gate wirings and a plurality of data wirings defining pixel regions, thin-film transistors disposed adjacent to the intersections of the gate wirings and the data wirings, and a pixel electrode for each pixel region. The details of such a wiring board are well known and are not particularly limited.

[0230] The liquid crystal layer 220 may be provided on the wiring board 211. The liquid crystal panel 200 may include an alignment layer 221 on or below the liquid crystal layer 220 to initially align the liquid crystal material included therein. Details of the liquid crystal layer and the alignment layer (e.g., liquid crystal material, alignment layer material, method of forming the liquid crystal layer, thickness of the liquid crystal layer, etc.) are known and are not particularly limited.

[0231] The lower polarizer 300 is disposed under the lower substrate 210. The material and structure of the polarizer 300 are known and are not particularly limited. A backlight unit (eg, emitting blue light) may be disposed under the polarizer 300.

[0232] The upper optical element or 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 300 may be disposed between the liquid crystal layer 220 and the photoluminescent (e.g., light-emitting) layer 230. The polarizer may be any polarizer used in a liquid crystal display device. The polarizer may be TAC (triacetyl cellulose) having a thickness of less than or equal to about 200 μm, but is not limited thereto. In an embodiment, the upper optical element may be a coating that controls the refractive index without a polarization function.

[0233] 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.

[0234] The backlight unit may further include a light guide panel 120. In an embodiment, the backlight unit may be edge-type lighting. For example, the backlight unit may include a reflector, a light guide panel disposed on the reflector and providing a planar light source to the liquid crystal panel 200, at least one optical sheet (e.g., a diffuser, a prism sheet, etc.) located on the light guide panel, or a combination thereof, but is not limited thereto. Alternatively, the backlight unit may not include a light guide panel. In an embodiment, the backlight unit may be direct-type lighting. For example, the backlight unit may have a reflector and may have a plurality of fluorescent lamps disposed on the reflector at regular intervals, or may have an LED operating substrate on which a plurality of light-emitting diodes may be disposed, a diffuser located on the LED operating substrate, and optionally at least one optical sheet. The details of such a backlight unit (e.g., each component of the light-emitting diodes, fluorescent lamps, light guide panels, various optical sheets, and reflectors) are known and are not particularly limited.

[0235] The black matrix 241 is disposed below the transparent substrate 240 and has an opening, 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 can have a grid shape. The photoluminescent layer 230 is disposed in the opening of the black matrix 241 and has a quantum dot-polymer composite pattern, which includes a first portion (R) configured to emit a first light (e.g., red light), a second portion (G) configured to emit a second light (e.g., green light), and a third portion (B) configured to emit / transmit, for example, blue light. If desired, the photoluminescent layer 230 may further include at least one fourth portion. The fourth portion may include quantum dots that emit light of a color different from the color of the light emitted from the first portion to the third portion (e.g., cyan light, magenta light, and yellow light).

[0236] In the photoluminescent layer 230, a patterned portion may be repeated corresponding to a pixel region formed on the lower substrate 210. A transparent common electrode 231 may be disposed on the photoluminescent layer 230 (eg, a photoluminescent color filter layer).

[0237] The third portion (B), configured to emit / transmit blue light, can be a transparent color filter that does not alter the light spectrum of the light source. In this case, blue light emitted from the backlight unit can enter in a polarized state and be emitted intact through the polarizer and liquid crystal layer. If desired, the third portion can include quantum dots that emit blue light.

[0238] If desired, the display device may further include an excitation (e.g., blue) light blocking layer (blue light cutting filter) or a first filter layer. The blue light blocking layer or the first filter layer may be disposed between the bottom surface of the first portion (R) and the second portion (G) 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 area (e.g., the third portion) configured to emit blue light, and the blue light blocking layer or the first filter layer may be formed on a portion corresponding to the first portion and the second portion. The first filter layer (310) may be integrally formed as an integral structure with respect to the red portion and the green portion, or may be integrally formed as an integral structure at a portion other than the portion overlapping the third portion, but is not limited thereto. At least two first filter layers may be separated and disposed on each of the portions overlapping the first portion and the second portion. If the light source includes a green light emitting element, the green light cutting filter may be disposed on the third portion.

[0239] In an embodiment, the first optical filter layer may block light having a portion of a wavelength range in the visible light region and transmit light having other wavelength ranges. For example, the first optical filter layer may block blue light and transmit light other than blue light. For example, the first optical filter layer may transmit green light, red light, and / or yellow light that is a mixture of green light and red light.

[0240] 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 other visible light wavelength regions greater than or equal to about 500 nm and less than or equal to about 700 nm.

[0241] In an embodiment, the first filter layer may have a transmittance of greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or close to about 100% with respect to visible light greater than about 500nm and less than or equal to about 700nm.

[0242] The first filter layer may include a polymer film including a dye, a pigment, or a combination thereof to absorb light of the wavelength to be blocked. The first filter layer may block at least 80%, at least 90%, or even at least 95% of blue light having a wavelength of about 480 nm or less, and may have a transmittance of about 70% or more, about 80% or more, about 90% or more, or nearly 100% with respect to other visible light having a wavelength of about 500 nm or more and about 700 nm or less.

[0243] The first filter layer can block (e.g., by absorbing light of selected wavelengths), including blocking blue light having a wavelength of less than or equal to about 500 nm, and can selectively transmit green light or red light, for example. In certain cases, at least two first filter layers can be separated and disposed on and overlap the first portion and the second portion, respectively. For example, a first filter layer that selectively transmits red light can be disposed on a portion that overlaps with a portion that emits red light, and a first filter layer that selectively transmits green light can be disposed on a portion that overlaps with a portion that emits green light. For example, the first filter layer can include at least one of a first region and a second region, wherein the first region blocks (e.g., absorbs) blue light and red light and transmits a wavelength having a predetermined range (e.g., greater than or equal to about 500 nm, greater than or equal to about 510 nm, or greater than or equal to about 515 nm and less than or equal to about 550 nm, less than or equal to about 545 nm, less than or equal to about 540 nm, less than or equal to about 535 nm, less than or equal to about 530 nm, less than or equal to about 525 nm, or less than or equal to about 530 nm). The first region may be provided at a position overlapping with the portion emitting green light, and the second region may be provided at a position overlapping with the portion emitting red light. The first and second regions may be optically isolated. The first filter (layer) may help improve the color purity of the display device.

[0244] The first filter layer can be a reflective filter comprising a plurality of layers (e.g., inorganic material layers) having different refractive indices. For example, two layers having different refractive indices can be stacked alternately with each other, or, for example, a layer having a high refractive index and a layer having a low refractive index can be stacked alternately with each other. As the refractive index difference between the layer having a high refractive index and the layer having a low refractive index increases, a first filter layer having higher wavelength selectivity can be provided. The thickness and number of stacked layers of the layer having a high refractive index and the layer having a low refractive index can be determined based on the refractive index and the reflection wavelength of each layer. For example, each layer having a high refractive index can have a thickness of about 3 nm to about 300 nm, and each layer having a low refractive index can have a thickness of about 3 nm to about 300 nm.

[0245] The total thickness of the first filter layer can be, for example, from about 3 nm (or about 6 nm) to about 10,000 nm, from about 300 nm to about 10,000 nm, or from about 1,000 nm to about 10,000 nm. The high refractive index layers can have the same thickness, be made of the same material, or a combination thereof. Alternatively, the high refractive index layers can have different thicknesses, be made of different materials, or a combination thereof. The low refractive index layers can have the same thickness, be made of the same material, or a combination thereof. Alternatively, the low refractive index layers can have different thicknesses, be made of different materials, or a combination thereof.

[0246] The display device may further include a second filter layer 311 (e.g., a red / green or yellow light recycling layer) disposed between the photoluminescent layer and the liquid crystal layer (e.g., between the photoluminescent layer and the upper polarizer) and transmitting at least a portion of the third light and reflecting at least a portion of the first and second lights. The second filter layer may reflect light in a wavelength range greater than approximately 500 nm. The first light may be red light, the second light may be green light, and the third light may be blue light.

[0247] In the display device according to the embodiment, the second filter layer may be formed as an integrated single layer having a substantially flat surface.

[0248] 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 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.

[0249] The second filter layer having a low refractive index may include, for example, porous silicon oxide, a porous organic material, a porous organic / inorganic composite, or a combination thereof.

[0250] 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 the second filter layer may be formed by alternately stacking a material having a high refractive index and a material having a relatively low refractive index.

[0251] The layer with a high refractive index in the second filter layer may include, for example, at least one of hafnium oxide, tantalum oxide, titanium oxide, zirconium oxide, magnesium oxide, cesium oxide, lanthanum oxide, indium oxide, niobium oxide, aluminum oxide and silicon nitride, but according to an embodiment, it may include various materials having a higher refractive index than the layer with a low refractive index.

[0252] The layer having the low refractive index in the second filter layer may include, for example, silicon oxide, but according to embodiments, it may include various materials having a lower refractive index than the layer having the high refractive index.

[0253] As the refractive index difference between the layer having a high refractive index and the layer having a low refractive index increases, the second filter layer can have higher wavelength selectivity.

[0254] In the second filter layer, the thickness of each layer with a high refractive index and the layer with a low refractive index, or the number of layers stacked together, can be determined based on the refractive index and reflection wavelength of each layer. For example, each layer with a high refractive index in the second filter layer can have a thickness of approximately 3 nm to approximately 300 nm, and each layer with a low refractive index in the second filter layer can have a thickness of approximately 3 nm to approximately 300 nm. The total thickness of the second filter layer can be, for example, from approximately 3 nm (or approximately 6 nm) to approximately 10,000 nm, from approximately 300 nm to approximately 10,000 nm, or from approximately 1,000 nm to approximately 10,000 nm. Each of the layers with a high refractive index and the layers with a low refractive index in the second filter layer can have the same thickness and material, or different thicknesses and materials.

[0255] The second filter layer may reflect at least a portion of the first light (R) or the second light (G), and transmit at least a portion (or all) of the third light (B). For example, the second filter layer may transmit only the third light (B) in the blue light wavelength region of approximately 500 nm or less, and may not transmit light in the wavelength region of approximately 500 nm or more (i.e., green light (G), yellow light, red light (R), etc.). Therefore, the reflected green and red light may pass through the second portion and the first portion to be emitted to the outside of the display device 10.

[0256] The second filter layer may reflect the wavelength region greater than about 500 nm at greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, or even about 100%.

[0257] At the same time, 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 even about 100% for a wavelength region less than or equal to about 500 nm.

[0258] In an embodiment, the stacked structure can be manufactured by a method using a photoresist composition. The method may include the following steps:

[0259] forming a film of the composition on a substrate;

[0260] exposing selected areas of the film to light (e.g., a wavelength less than or equal to about 400 nm); and

[0261] The exposed film is developed with an alkaline developing solution to obtain a pattern including quantum dot-polymer composites.

[0262] The substrate and composition are the same as described herein. Figure 4A , showing a non-limiting method of forming a pattern.

[0263] The composition is coated on a substrate to a predetermined thickness by a suitable method such as spin coating or slit coating (step 1). Optionally, the formed film may be pre-baked (PRB) (step 2). Pre-baking may be performed by appropriately selecting conditions such as temperature, time, and atmosphere.

[0264] Under a mask having a predetermined pattern, the formed (or optionally pre-baked) film is exposed to light having a predetermined wavelength (step 3). The wavelength and intensity of the light can be selected by considering the type of initiator (e.g., photoinitiator), the amount of initiator (e.g., photoinitiator), the type of quantum dots, the amount of quantum dots, etc.

[0265] The exposed film is treated with an alkaline developing solution (e.g., dipping or spraying) to dissolve the unexposed areas and obtain a desired pattern (step 4). Optionally, the obtained pattern may be post-baked (POB) at, for example, about 150° C. to about 230° C. for a predetermined time (e.g., about 10 minutes or more or about 20 minutes or more) (step 5) to improve the crack resistance and solvent resistance of the pattern.

[0266] In embodiments 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 multiple compositions comprising multiple quantum dots as described herein and having desired photoluminescent properties (photoluminescent peak wavelength, etc.) to form each repeating portion (e.g., red-emitting quantum dots, green-emitting quantum dots, or optionally blue-emitting quantum dots). The portion (e.g., sub-pixel) can be repeated any appropriate number of times (e.g., two or more times or three or more times) to provide a pattern for each composition (step 6). For example, the quantum dot-polymer composite can have (e.g., be configured to) have a pattern comprising at least two repeating color portions (e.g., RGB portions). The quantum dot composite pattern can be used as a photoluminescent color filter in a display device.

[0267] The quantum dot composite pattern can be formed by using an ink composition configured to form a pattern via an inkjet method. Figure 4BThe method includes the following steps: preparing an ink composition; obtaining a substrate, the substrate including, for example, an electrode and an optional pattern of pixel regions formed by banks; depositing the ink composition on the substrate (or pixel region) to form a first quantum dot layer (or a first repeating portion); and depositing the ink composition on the substrate (or 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 performed simultaneously or sequentially. The deposition of the ink composition can be performed using a suitable droplet discharge system such as an inkjet printer or a nozzle printing system (e.g., having an ink reservoir and, for example, at least one print head).

[0268] The deposited ink composition can be heated to remove the solvent and optionally polymerize to provide a (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.

[0269] The embodiment provides an electronic device including quantum dots. The electronic device may 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.

[0270] The quantum dots of the embodiments may be included in electronic devices. The electronic devices may include, but are not limited to, handheld terminals, monitors, notebook computers, televisions, electronic display panels, cameras, and autonomous vehicles. The electronic devices may be handheld terminals, monitors, notebook computers, or televisions each including a display device (or light-emitting device) containing quantum dots. The electronic devices may be cameras or handheld terminals each including an image sensor containing quantum dots. The electronic devices may be cameras or autonomous vehicles each including a photodetector containing core-shell quantum dots.

[0271] Hereinafter, the embodiments are 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.

[0272] Example

[0273] Analytical methods

[0274] 1. Ultraviolet (UV)-visible (Vis) absorption spectrum

[0275] UV-visible absorption spectra and analyses were obtained and performed using an Agilent Cary 5000 spectrophotometer.

[0276] 2. Photoluminescence analysis

[0277] Photoluminescence spectroscopy and analysis were performed using a Hitachi F-7000 spectrophotometer.

[0278] 3. Quantum yield measurement

[0279] For the quantum dot dispersion or quantum dot polymer complex, the quantum yield was measured by using QE-2100 (from Otsuka Electronics Co., Ltd.) The measured quantum yield is a value obtained by dividing the number of photons emitted by light emission from the quantum dot dispersion or quantum dot polymer complex by the number of photons absorbed by the dispersion or complex, respectively.

[0280] 4. Operation reliability test

[0281] The operational reliability was evaluated at a temperature of 60° C. in air using a 1500 nit backlight unit as a light source (wavelength: 450 nm).

[0282] 5. ICP analysis

[0283] Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis was performed using a Shimadzu ICPS-8100.

[0284] 6. Arithmetic size and density functional theory

[0285] The nuclear diameter was determined using the experimental method described in Jang et al., Nanotechnology 2013, 24, 215201 (page 5) (eg, Figure 2.(b) and related description).

[0286] 7. Centrifugation

[0287] Centrifugation was performed by using an Eppendorf Centrifuge 5810R.

[0288] Preparation Example 1 (Sample B)

[0289] [1] Preparation of semiconductor nanocrystal cores

[0290] In a 200 milliliter (mL) reaction flask, indium acetate and palmitic acid are dissolved in 1-octadecene, and the solution is subjected to a vacuum state at 120°C for 1 hour. A molar ratio of indium to palmitic acid of 1:3 is used. The atmosphere in the flask is replaced with N2, and the flask is heated to 280°C. A mixed solution of tri(trimethylsilyl)phosphine (TMS3P) and trioctylphosphine (TOP) is quickly injected, and the reaction is carried out for a predetermined time (e.g., about 20 minutes). The reaction mixture is quickly cooled to room temperature and acetone is added to promote the precipitation of nanocrystals, which are then separated by centrifugation and dispersed in toluene to obtain a toluene dispersion of InP core nanocrystals. The amount of TMS3P added to the reaction flask is about 0.5 moles per mole of indium. The amount of trioctylphosphine added to the reaction flask is about 0.1 moles to about 10 moles (e.g., about 0.5 moles) per mole of indium. The average particle size of the InP core is about 3.6 nanometers (nm) to 3.8nm.

[0291] [2] Shell coating

[0292] Selenium and sulfur were dispersed in trioctylphosphine (TOP) to obtain Se / TOP stock solution and S / TOP stock solution, respectively.

[0293] In a 200mL reaction flask, zinc acetate and oleic acid were dissolved in trioctylamine, and the solution was subjected to vacuum at 120°C for 10 minutes. The atmosphere in the reaction flask was then replaced with N2. The solution was heated to approximately 320°C, and a toluene dispersion of the InP semiconductor nanocrystal core prepared above was injected into the reaction flask, followed by a Se / TOP stock solution and optional zinc acetate. The reaction was performed to obtain a reaction solution comprising particles having a ZnSe shell disposed on the core. The total reaction time was 100 minutes.

[0294] The S / TOP stock solution and zinc acetate were injected into the reaction mixture at about 320° C. The reaction was carried out to obtain a resulting solution comprising particles having a ZnS shell disposed on a ZnSe shell. The total reaction time was 40 minutes.

[0295] Excess ethanol was added to the final reaction mixture comprising the resulting InP / ZnSe / ZnS semiconductor nanocrystals, and the mixture was centrifuged. After centrifugation, the supernatant was discarded, and the precipitate was dried and dispersed in chloroform to obtain a quantum dot solution (hereinafter referred to as a QD solution).

[0296] The total amount of Se, S, and Zn per mole of indium was controlled so that the population of quantum dots isolated from the crude solution showed the molar ratios of the components (zinc, selenium, sulfur, and indium) as shown in Table 2. From the core size and the measured composition, the population of quantum dots obtained had an arithmetic size of 8.85 nm, and the thickness of ZnSe and the thickness of ZnS were 2.05 nm and 0.48 nm, respectively.

[0297] Photoluminescence analysis and ICP-AES analysis of the prepared quantum dots were performed, and the results are listed in Table 1A.

[0298] [3] Reprecipitation of quantum dots

[0299] The obtained quantum dot population was subjected to a reprecipitation process using reprecipitation solvent 1 (a mixture of toluene and ethanol at a ratio of 1:1.4) (i.e., reprecipitation solvent 1 was added to the QD solution at a volume ratio of QD solution: toluene: ethanol = 1:1:1.4 and the resulting mixture was centrifuged), and the first quantum dot population was separated from the mixture with solvent 1. Photoluminescence analysis and ICP-AES analysis of the first quantum dot population were performed, and the results are listed in Table 1A and Table 2.

[0300] After separating the first quantum dot population from the mixture with solvent 1, the remaining solution was subjected to additional reprecipitation using precipitation solvent 2 (a mixture of toluene and ethanol in a ratio of 1:1.6), precipitation solvent 3 (a mixture of toluene and ethanol in a ratio of 1:1.8), precipitation solvent 4 (a mixture of toluene and ethanol in a ratio of 1:2.0), and precipitation solvent 5 (a mixture of toluene and ethanol in a ratio of 1:2.2) to obtain quantum dot populations #2 to #5, respectively, and the fraction (wt %) of each population was measured.

[0301] For each of the obtained quantum dot populations #1 to #5, photoluminescence analysis and ICP-AES analysis were performed, and the results are listed in Table 1A.

[0302] Preparation Example 2 (Sample C)

[0303] A quantum dot group was prepared in the same manner as in Preparation Example 1, except that the total amount of Se, S, and Zn per mole of indium was controlled so that the quantum dot group separated from the crude solution had the molar ratio of the components (zinc, selenium, sulfur, and indium) listed in Table 2. By the core size and quantum dot composition, the obtained quantum dot group had an arithmetic size of 9.19 nm, and the thickness of ZnSe and the thickness of ZnS were 2.38 nm and 0.32 nm, respectively.

[0304] Photoluminescence analysis and ICP-AES analysis were performed on the quantum dot group obtained in Preparation Example 2. The results are listed in Table 1B and Table 2.

[0305] The prepared and separated coarse quantum dot groups are then subjected to a process of multiple reprecipitation sequences using the same precipitation solvent as in Preparation Example 1 in the same manner as in Preparation Example 1 to obtain quantum dot groups #1 to #5 of Preparation Example 2, and the fraction (wt %) of each group is measured.

[0306] For each of the obtained quantum dot groups #1 to #5, photoluminescence analysis and ICP-AES analysis were performed, and the results are listed in Table 1B.

[0307] Comparative Preparation Example 1 (Sample A)

[0308] A quantum dot group was prepared in the same manner as in Preparation Example 1, except that the total amount of Se, S, and Zn per mole of indium was controlled so that the quantum dot group isolated from the crude solution had the molar ratio of the components (zinc, selenium, sulfur, and indium) listed in Table 2. By the core size and quantum dot composition, the obtained quantum dot group had an arithmetic size of about 7.89 nm, and the thickness of ZnSe and the thickness of ZnS were 1.56 nm and 0.49 nm, respectively.

[0309] Photoluminescence analysis and ICP-AES analysis were performed on the quantum dot group obtained in Comparative Example 1. The results are listed in Table 1A and Table 2.

[0310] The quantum dot group of comparative example 1 prepared and separated was subjected to multiple reprecipitation sequences using the same precipitation solvent as in preparation example 1 in the same manner as preparation example 1 to obtain the first quantum dot group, the second quantum dot group, the third quantum dot group, the fourth quantum dot group and the fifth quantum dot group of comparative example 1, and the fraction (wt %) of each group was measured.

[0311] Photoluminescence analysis and ICP-AES analysis were performed on each of the obtained first quantum dot group, second quantum dot group, third quantum dot group, fourth quantum dot group, and fifth quantum dot group, and the results are listed in Table 1A.

[0312] Table 1A

[0313]

[0314]

[0315] Table 1B

[0316]

[0317] According to the results of Table 1A, the quantum dots of Preparation Example 1 have an arithmetic size of less than 8 nm. Among the quantum dot groups, the fraction of the first quantum dot group having a size greater than the arithmetic size is relatively low, and the fraction having an arithmetic size less than 8 nm is relatively high (40% or higher). According to the results of Table 1A and Table 1B, the quantum dots of Preparation Example 1 and the quantum dots of Preparation Example 2 have an arithmetic size greater than 8 nm, and the fractions of the first quantum dot group having a size greater than the arithmetic size are 83% and 82%, respectively.

[0318] In the quantum dots of Preparation Example 2, the first fraction (i.e., the first quantum dot group) has a ZnSe thickness of about 2.5 nm and a ZnS thickness of about 0.37 nm. In the quantum dots of Preparation Example 1, the first fraction (i.e., the first quantum dot group) has a ZnSe thickness of about 2.2 nm and a ZnS thickness of about 0.49 nm.

[0319] Table 2

[0320] Zn:(Se+S) S:Se S:In (S+Se):In Se:In Comparative Preparation Example 1 1.11 0.7 3.87 9.52 5.65 Preparation Example 1 1.07 0.5 4.82 13.79 8.97 Preparation Example 2 1.06 0.3 3.63 15.33 11.70

[0321] Fabrication and characterization of quantum dot composite patterns

[0322] Example 1

[0323] A chloroform dispersion of multiple quantum dots including the preparation of Example 1 was prepared and mixed with a solution of a binder polymer to form a quantum dot-binder dispersion, wherein the binder polymer was a tetrapolymer of methacrylic acid, benzyl methacrylate, hydroxyethyl methacrylate, and styrene (acid value: 130 milligrams (mg) of KOH per gram (mg KOH / g), molecular weight: 8,000 g / mol) (solvent: propylene glycol monomethyl ether acetate PGMEA, concentration of 30 weight percent (wt%)).

[0324] To the quantum dot-adhesive dispersion prepared above, hexaacrylate having the following structure (as a photopolymerizable monomer), ethylene glycol di-3-mercaptopropionate (hereinafter referred to as 2T, as a polythiol compound), an oxime ester compound (as an initiator), TiO2 as fine metal oxide particles (light diffuser) and PGMEA (as a solvent) are added to obtain a composition.

[0325] (Ethylene glycol di-3-mercaptopropionate)

[0326] (Hexaacrylate)

[0327] in,

[0328] The prepared composition includes 42 weight percent (wt%) of quantum dots, 14.5 wt% of a binder polymer, 25 wt% of 2T, 14 wt% of a photopolymerizable monomer, 0.5 wt% of a photoinitiator, and 4 wt% of a light diffuser, based on the total solids content. The total solids content is about 25%.

[0329] The composition obtained above was spin-coated on a glass substrate at 150 revolutions per minute (rpm) for 5 seconds (s) to provide a film. The obtained film was pre-baked at 100° C. (PRB). The pre-baked film was exposed to light (wavelength: 365 nanometers (nm), intensity: 100 millijoules (mJ)) for 1 second (s) (EXP) under a mask having a predetermined pattern (e.g., a square dot or stripe pattern), and developed with a potassium hydroxide aqueous solution (concentration: 0.043 wt%) for 50 seconds to obtain a pattern of a quantum dot polymer composite (thickness: 6 micrometers (μm)). The obtained pattern was heat-treated at a temperature of 180° C. for 30 minutes under a nitrogen atmosphere (POB).

[0330] For the quantum dot composite pattern thus obtained, the photoconversion efficiency (CE) after POB was measured, and the results are listed in Table 3.

[0331] For the quantum dot composite pattern thus obtained, the operational reliability was measured and the results are shown in Figure 5 middle.

[0332] Example 2

[0333] A quantum dot composite pattern was prepared in the same manner as in Example 1, except that the chloroform dispersion including the plurality of quantum dots of Preparation Example 2 was used. For the quantum dot composite pattern thus obtained, the light conversion efficiency (CE) after POB was measured, and the results are shown in Table 3. For the quantum dot composite pattern thus obtained, the operational reliability was measured, and the results are shown in Table 4. Figure 5 middle.

[0334] Comparative Example 1

[0335] A quantum dot composite pattern was prepared in the same manner as in Example 1 except that a chloroform dispersion including a plurality of quantum dots of Comparative Preparation Example 1 was used. For the quantum dot composite pattern thus obtained, the light conversion efficiency (CE) after POB was measured, and the results are shown in Table 3. For the quantum dot composite pattern thus obtained, the operational reliability was measured, and the results are shown in Table 4. Figure 5 middle.

[0336] Table 3

[0337] POB CE (%) Example 1 38.9 Example 2 38.1 Comparative Example 1 36.6

[0338] Table 3 and Figure 5The results confirmed that the quantum dot composite patterns of Examples 1 and 2 exhibited increased light conversion efficiency and improved operational reliability compared to the quantum dot composite pattern of Comparative Example 1.

[0339] according to Figure 5 As a result, it was confirmed that the luminance of the quantum dot composite patterns of Examples 1 and 2 showed a decrease within 100 hours or less, and thus the composites had a luminance decrease interval (period).

[0340] While the disclosure has been described in connection with what are presently considered to be practical exemplary 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 composite, comprising: a matrix; and a plurality of quantum dots dispersed in the matrix, The plurality of quantum dots include a semiconductor nanocrystal core containing indium and phosphorus and a semiconductor nanocrystal shell disposed on the semiconductor nanocrystal core, wherein the semiconductor nanocrystal shell includes zinc, selenium and sulfur. The arithmetic size of the plurality of quantum dots is greater than or equal to 8 nm and less than or equal to 15 nm. wherein the quantum dot complex is configured to emit red light, wherein the arithmetic size of the plurality of quantum dots is the size of a given quantum dot population and is determined by the core size and shell thickness, wherein the core size is determined by the composition and optical properties of the semiconductor nanocrystal core, and the shell thickness is determined by the core size and the composition of the quantum dots, Wherein, the multiple quantum dots include a first quantum dot group having a first arithmetic size, the first arithmetic size is larger than the arithmetic size of the multiple quantum dots, the first arithmetic size is greater than or equal to 8.5 nanometers, and the fraction of the first quantum dot group in the multiple quantum dots is greater than or equal to 65 percent.

2. The quantum dot composite according to claim 1, wherein When the quantum dot complex is irradiated with light having a wavelength of 450 nm to 470 nm and an intensity of 1500 nits for a period of less than or equal to 500 hours, the brightness of the quantum dot complex increases by less than or equal to 1.2% of the initial brightness of the quantum dot complex.

3. The quantum dot composite according to claim 1, wherein When the quantum dot complex is irradiated with light having a wavelength of 450 nm to 470 nm for 100 hours, the quantum dot complex exhibits a brightness reduction interval.

4. The quantum dot composite according to claim 1, wherein The quantum dot complex emits red light having a maximum peak wavelength within a range of greater than or equal to 600 nanometers to less than or equal to 650 nanometers.

5. The quantum dot composite according to claim 1, wherein The arithmetic size of the plurality of quantum dots is greater than 8.5 nanometers.

6. The quantum dot composite according to claim 1, wherein A fraction of the first quantum dot group in the plurality of quantum dots is greater than or equal to 80 percent.

7. The quantum dot composite according to claim 1, wherein The first arithmetic size is greater than or equal to 9 nanometers.

8. The quantum dot composite according to claim 1, wherein A fraction of the first quantum dot group in the plurality of quantum dots is greater than or equal to 70 percent.

9. The quantum dot composite according to claim 1, wherein The plurality of quantum dots also includes a second quantum dot population having a second arithmetic size, and the second arithmetic size is less than or equal to 7.2 nanometers, and a fraction of the second quantum dot population in the plurality of quantum dots is less than or equal to 18 percent.

10. The quantum dot composite according to claim 1, wherein The size of the semiconductor nanocrystal core is greater than 3 nanometers.

11. The quantum dot composite according to claim 1, wherein The semiconductor nanocrystal shell comprises: a first layer comprising first semiconductor nanocrystals comprising zinc and selenium; and a second layer disposed on the first layer, the second layer comprising second semiconductor nanocrystals comprising zinc, sulfur, and optionally selenium, wherein the composition of the first semiconductor nanocrystals is different from the composition of the second semiconductor nanocrystals.

12. The quantum dot composite according to claim 11, wherein The first layer has a thickness greater than or equal to 1.5 nanometers; The second layer has a thickness less than or equal to 0.7 nanometers; or The first layer has a thickness greater than or equal to 1.5 nanometers, and the second layer has a thickness less than or equal to 0.7 nanometers.

13. The quantum dot composite according to claim 1, wherein In the plurality of quantum dots, a molar ratio of zinc to indium is greater than or equal to 13:1, and a molar ratio of sulfur to selenium is less than or equal to 0.6:

1.

14. The quantum dot composite according to claim 1, wherein In the plurality of quantum dots, a molar ratio of zinc to a sum of sulfur and selenium is less than or equal to 1.1:1, and a molar ratio of sulfur to selenium is less than or equal to 0.5:

1.

15. The quantum dot composite according to claim 1, wherein The plurality of quantum dots further includes a second quantum dot population having a second arithmetic size less than or equal to 7.2 nm, and a fraction of the second quantum dot population in the plurality of quantum dots is less than or equal to 10%. 16 . A color filter comprising the quantum dot composite according to claim 1 .

17. A display device comprising a light emitting element and an optional light source, wherein: The light emitting element includes the quantum dot composite according to claim 1 , and the light source is configured to provide incident light to the light emitting element.

18. A composition comprising a plurality of quantum dots, in, The plurality of quantum dots include a first semiconductor nanocrystal containing indium and phosphorus as a core and a second semiconductor nanocrystal containing zinc chalcogenide as a shell on the core, wherein the zinc chalcogenide includes zinc and selenium, sulfur, or a combination thereof, wherein the plurality of quantum dots have an arithmetic size greater than or equal to 8 nanometers and less than or equal to 15 nm, and the plurality of quantum dots include a second quantum dot population having a second arithmetic size, wherein the second arithmetic size is less than or equal to 7.2 nanometers, and a fraction of the second quantum dots in the plurality of quantum dots is less than or equal to 18 percent, The arithmetic size of the plurality of quantum dots is the size of a given quantum dot group and is determined by the core size and shell thickness, wherein the core size is determined by the composition and optical properties of the core, and the shell thickness is determined by the core size and the composition of the quantum dots.

19. The composition according to claim 18, wherein The fraction of the second quantum dot group is less than or equal to 15 percent.

20. The composition according to claim 18, wherein The plurality of quantum dots includes a first quantum dot population having a first arithmetic size greater than or equal to 8 nanometers, and a fraction of the first quantum dots in the plurality of quantum dots is greater than or equal to 60%.

21. The composition according to claim 18, wherein The plurality of quantum dots includes a first population of quantum dots having a first arithmetic size greater than or equal to 8.5 nanometers, and a fraction of the first quantum dots in the plurality of quantum dots is greater than 80 percent.

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