Method of manufacturing quantum dot light emitting device, quantum dot light emitting device, and electronic apparatus

Abstract

Disclosed are a method of manufacturing a quantum dot light emitting device, a quantum dot light emitting device, and an electronic apparatus, the method including forming an anode, forming a quantum dot light emitting layer on the anode, forming an electron auxiliary layer including oxide nanoparticles containing an alkaline earth metal on the quantum dot light emitting layer, and forming a cathode on the electron auxiliary layer, wherein the forming of the electron auxiliary layer comprises preparing a precursor dispersion comprising an alkaline earth metal precursor, preparing an alkaline reagent solution comprising an alkaline reagent, adding the alkaline reagent solution drop by drop to the precursor dispersion at a controlled rate to grow alkaline earth metal-containing oxide nanoparticles, dispersing the alkaline earth metal-containing oxide nanoparticles in a dispersion medium to prepare an alkaline earth metal-containing oxide nanoparticle dispersion, and coating the quantum dot light-emitting layer with the alkaline earth metal-containing oxide nanoparticle dispersion.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2024-0019203, filed in the Korean Intellectual Property Office on February 7, 2024, and all rights arising therefrom, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] Disclosed are a method for manufacturing a quantum dot light-emitting device, a quantum dot light-emitting device, and an electronic device. Background Art

[0004] Unlike bulk materials, the physical properties of nanoparticles (e.g., band gap energy, melting point, etc.) as inherent properties can be controlled by changing the particle size of the nanoparticles. For example, semiconductor nanocrystal particles, also known as quantum dots, are crystalline materials with a nanometer-sized crystal structure. Quantum dots can be supplied with light energy or electrical energy and can be configured to emit light of a wavelength corresponding to the size of the quantum dots. Therefore, quantum dots can be used as light-emitting elements that emit light of a specific wavelength. Summary of the Invention

[0005] Light emitting devices may use quantum dots as light emitting materials. Quantum dots are different from conventional light emitting materials, and therefore new solutions to improve the performance of quantum dot light emitting devices are desired and implemented herein.

[0006] Embodiments provide a quantum dot light emitting device capable of achieving improved performance.

[0007] An embodiment provides a method of manufacturing the quantum dot light-emitting device.

[0008] Embodiments provide electronic devices including the quantum dot light-emitting device.

[0009] In an embodiment, a method of manufacturing a quantum dot light-emitting device includes forming an anode, forming a quantum dot light-emitting layer on the anode, forming an electron assist layer on the quantum dot light-emitting layer, the electron assist layer including alkaline earth metal oxide nanoparticles, and forming a cathode on the electron assist layer.

[0010] The formation of the electron-assisting layer includes: preparing a precursor dispersion including an alkaline earth metal precursor, preparing an alkaline reagent solution containing an alkaline reagent, adding the alkaline reagent solution to the precursor dispersion by dropwise addition at a controlled rate to grow alkaline earth metal-containing oxide nanoparticles, dispersing the alkaline earth metal-containing oxide nanoparticles in a dispersion medium to prepare an alkaline earth metal-containing oxide nanoparticle dispersion, and coating the alkaline earth metal-containing oxide nanoparticle dispersion on the quantum dot light-emitting layer.

[0011] The alkaline agent may include an alkali metal hydroxide.

[0012] The alkali metal hydroxide may include CsOH, RbOH, KOH, NaOH, LiOH, or any combination thereof.

[0013] The alkaline agent solution may be added by dropwise addition at a rate of about 0.1 millimole / minute (mmol / min) to about 1.5 mmol / min.

[0014] The alkaline agent solution may be added by dropwise addition at a rate of about 0.2 mmol / min to about 1.2 mmol / min.

[0015] The precursor dispersion may include a zinc precursor.

[0016] The alkaline earth metal-containing oxide nanoparticles may have modified and improved shapes and sizes and may satisfy the relationship Equation 1.

[0017] Relational equation 1

[0018]

[0019] In the relation Equation 1,

[0020] Abs 峰 is the absorbance (absorption) at the peak of the ultraviolet-visible (UV-Vis) absorption spectrum, and

[0021] Abs 谷 It is the absorbance at the lowest point of the valley adjacent to the peak in the ultraviolet-visible (UV-Vis) absorption spectrum.

[0022] The alkaline earth metal-containing oxide nanoparticles may have an average particle diameter of about 1.2 nanometers (nm) to about 2.2 nm.

[0023] The average particle diameter of the aggregates of the alkaline earth metal-containing oxide nanoparticles measured by dynamic light scattering (DLS) may be about 6 nm to about 15 nm.

[0024] The alkaline earth metal-containing oxide nanoparticles may have an average circularity of about 0.70 to about 1.00.

[0025] According to an embodiment, a quantum dot light-emitting device includes: an anode and a cathode, a quantum dot light-emitting layer between the anode and the cathode, and an electron assisting layer including alkaline earth metal-containing oxide nanoparticles between the cathode and the quantum dot light-emitting layer, wherein the alkaline earth metal-containing oxide nanoparticles satisfy the relationship equation 1.

[0026] The alkaline earth metal-containing oxide nanoparticles may have an average particle diameter of about 1.2 nm to about 2.2 nm.

[0027] The average particle diameter of the aggregates of the alkaline earth metal-containing oxide nanoparticles measured by dynamic light scattering (DLS) may be about 6 nm to about 15 nm.

[0028] The alkaline earth metal-containing oxide nanoparticles may have an average circularity of about 0.70 to about 1.00.

[0029] The alkaline earth metal may be magnesium.

[0030] The alkaline earth metal-containing oxide nanoparticles may include zinc.

[0031] The alkaline earth metal included in the alkaline earth metal-containing oxide nanoparticles may include an amount of about 0.01 to about 30 atomic percent (atom %) based on the total amount of atoms of the alkaline earth metal and zinc.

[0032] The alkaline earth metal-containing oxide nanoparticles may include the elements Cs, Rb, K, Na, Li, or a combination thereof, or a salt thereof.

[0033] The quantum dot light emitting device may include a hole assist layer between the anode and the quantum dot light emitting layer and including an organic material.

[0034] According to an embodiment, provided is an electronic device including the quantum dot light emitting device.

[0035] Advantageously, as a result of embodiments of the present disclosure, the performance of quantum dot light emitting devices may be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The above and other advantages and features of the present disclosure will become more apparent by describing exemplary embodiments thereof in further detail with reference to the accompanying drawings, in which:

[0037] Figure 1 is a cross-sectional view schematically showing a quantum dot light emitting device according to an embodiment,

[0038] Figure 2 is a transmission electron microscope (TEM) photograph of the alkaline earth metal oxide nanoparticles prepared in Example 3.

[0039] Figure 3 is a TEM photograph of alkaline earth metal oxide nanoparticles prepared according to Comparative Example 1.

[0040] Figure 4is a graph of normalized absorption intensity (absorbance) (arbitrary unit (AU)) versus wavelength (nm), which shows ultraviolet-visible (UV-Vis) absorption spectra of the alkaline earth metal oxide nanoparticles according to Preparation Examples 2 and 3 and Preparation Comparative Example 1,

[0041] Figure 5 Yes Display Figure 4 The enlarged view of the valley region of the UV-Vis absorption spectrum,

[0042] Figure 6 is a graph showing ultraviolet-visible (UV-Vis) absorption spectra according to the dropping time in minutes of the alkaline reagent solution during the synthesis of the alkaline earth metal oxide nanoparticles according to Preparation Examples 2 and 3, and

[0043] Figure 7 is a graph of photoluminescence (PL) intensity (normalized) versus time (nanoseconds (ns)), which shows the photoluminescence lifetime characteristics of the sample devices according to Examples 1 and 2 and Comparative Example 1. DETAILED DESCRIPTION

[0044] Hereinafter, example embodiments of the present disclosure will be described in detail so that those skilled in the art will understand it. However, the present disclosure may be embodied in many different forms and is not to be construed as limited to the example embodiments set forth herein.

[0045] In the accompanying drawings, the thickness of layers, films, panels, regions, etc., is exaggerated for clarity. The same reference numerals represent the same elements throughout the specification. It will be understood that when an element, such as a layer, film, region, or substrate, is referred to as being "on" another element, it can be directly on the other element or intervening elements may be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0046] It will be understood that although the terms "first," "second," "third," etc., may be used herein to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings herein, the "first element," "component," "region," "layer," or "part" discussed below may be referred to as a second element, component, region, layer, or part.

[0047] The terms used herein are only used to describe the purpose of specific embodiments and are not intended to be restrictive. As used herein, "one (kind) (indefinite article) (a, an)", "said (the)" and "at least one (kind)" do not represent the limitation of quantity, and are intended to include both the singular and the plural, unless the context clearly indicates otherwise. For example, "element" has the same meaning as "at least one element" unless the context clearly indicates otherwise. "At least one (kind)" will not be interpreted as limiting "one (kind)". "Or" means "and / or". As used herein, the term "and / or" includes any and all combinations of one or more of the relevant enumerated items. It will be further understood that the term "comprising" or "including" when used in this specification indicates that there are stated features, regions, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, components, and / or their sets.

[0048] As used herein, "about" 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 the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±10% or 5% relative to the stated value.

[0049] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. It will be further 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 present disclosure and the relevant art, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0050] Exemplary embodiments are described herein with reference to cross-sectional views that are schematic representations of idealized embodiments. As such, deviations from the shapes of the figures are to be expected as a result of, for example, manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the regions as illustrated herein, but rather include deviations in shape resulting from, for example, manufacturing. For example, a region illustrated or described as flat may typically have rough and / or nonlinear features. Furthermore, illustrated sharp corners may be rounded. Therefore, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of the regions and are not intended to limit the scope of the claims.

[0051] Herein, "combination" includes a mixture or stacked structure of two or more.

[0052] As used herein, when a specific definition is not otherwise provided, energy levels refer to the highest occupied molecular orbital (HOMO) energy level and the lowest unoccupied molecular orbital (LUMO) energy level.

[0053] Herein, the value of the work function, conduction band or lowest unoccupied molecular orbital (LUMO) energy level, or valence band or highest occupied molecular orbital (HOMO) energy level is expressed as an absolute value from the vacuum energy level. In addition, a deep, high, or large work function or energy level means that the absolute value is large when the vacuum energy level is set to "0 electron volts (eV)", and a shallow, low, or small work function or energy level means that the absolute value is small when the vacuum energy level is set to "0 eV".

[0054] The HOMO energy level and work function can be measured by ultraviolet photoelectron spectroscopy (UPS), and the LUMO energy level can be calculated from the energy band gap and HOMO energy level obtained at the absorption peak.

[0055] As used herein, the term "Group" refers to a Group of the Periodic Table.

[0056] As used herein, “Group I” refers to Group IA and Group IB, and examples may include Li, Na, K, Rb, and Cs, but are not limited thereto.

[0057] As used herein, “Group II” refers to Group IIA and Group IIB, and examples of Group II metals may be Cd, Zn, Hg, and Mg, but are not limited thereto.

[0058] As used herein, “Group III” refers to Group IIIA and Group IIIB, and examples of Group III metals may be Al, In, Ga, and Tl, but are not limited thereto.

[0059] As used herein, "Group IV" refers to Group IVA and Group IVB, and examples of Group IV metals may be Si, Ge, and Sn, but are not limited thereto. As used herein, "metal" includes metals and semimetals such as Si.

[0060] As used herein, "Group V" includes Group VA and includes nitrogen, phosphorus, arsenic, antimony, and bismuth, but is not limited thereto.

[0061] As used herein, "Group VI" includes Group VIA and includes, but is not limited to, sulfur, selenium, and tellurium.

[0062] As used herein, the description "does not include cadmium (or other toxic / harmful heavy metals)" means that the concentration of cadmium (or the corresponding heavy metal) is less than or equal to about 100 parts per million (ppm) (by weight), less than or equal to about 50 ppm, less than or equal to about 10 ppm, less than or equal to about 0.01 ppm, or substantially zero. In embodiments, cadmium (or other heavy metals) is substantially absent, or, if present, is present in an amount below the detection limit of a given analytical / detection tool or at an impurity level.

[0063] As used herein, when no definition is otherwise provided, "substituted" refers to a compound, functional group or moiety where a hydrogen atom is replaced by a substituent such as a C1 to C30 alkyl, a C2 to C30 alkenyl, a C2 to C30 alkynyl, a C2 to C30 epoxy, a C2 to C30 alkyl ester group, a C3 to C30 alkenyl ester group (e.g., an acrylate group, a methacrylate group), a C6 to C30 aryl, a C7 to C30 alkylaryl, a C1 to C30 alkoxy, a C1 to C30 heteroalkyl, a C3 to C30 heteroalkylaryl, a C3 to C30 cycloalkyl, a C3 to C15 cycloalkenyl, a C6 to C30 cycloalkynyl, a C2 to C30 heterocycloalkyl, a halogen (-F, -Cl, -Br or -I), a hydroxyl (-OH), a nitro (-NO2), a cyano (-CN), an amino (-NRR', wherein R and R' are each independently hydrogen or C1 to C6 alkyl), an azido group (-N3), an amidine group (-C(=NH)NH2), a hydrazine group (-NHNH2), a hydrazone group (=N(NH2)), an aldehyde group (-C(=O)H), a carbamoyl group (-C(=O)NH2), a thiol group (-SH), an ester group (-C(=O)OR, wherein R is a C1 to C6 alkyl group or a C6 to C12 aryl group), a carboxyl group (-COOH) or a salt thereof (-C(=O)OM, wherein M is an organic or inorganic cation), a sulfonic acid group (-SO3H) or a salt thereof (-SO3M, wherein M is an organic or inorganic cation), a phosphate group (-PO3H2) or a salt thereof (-PO3MH or -PO3M2, wherein M is an organic or inorganic cation), or a combination thereof.

[0064] As used herein, when no definition is provided in addition, "hydrocarbon group" refers to a group (e.g., an alkyl, alkenyl, alkynyl or aryl group) consisting of carbon and hydrogen. A hydrocarbon group can be a group having a monovalent or higher valence formed by removing one or more hydrogen atoms from an alkane, alkene, alkyne or aromatic hydrocarbon. In a hydrocarbon group, a methylene group, for example, at least one methylene group, can be replaced by an oxygen moiety (-O-), a carbonyl moiety, an ester moiety (-C(=O)-O-), -NH- or a combination thereof. Unless otherwise indicated to the contrary, a hydrocarbon (alkyl, alkenyl, alkynyl or aryl) group can have 1 to 60, 2 to 32, 3 to 24 or 4 to 12 carbon atoms.

[0065] As used herein, "aliphatic" refers to a saturated or unsaturated straight-chain or branched hydrocarbon group. An aliphatic group may be, for example, an alkyl, alkenyl, or alkynyl group.

[0066] As used herein, when no definition is otherwise provided, "alkyl" refers to a straight-chain or branched saturated monovalent hydrocarbon group (methyl, ethylhexyl, etc.).

[0067] As used herein, when a definition is not otherwise provided, "alkenyl" refers to a straight-chain or branched monovalent hydrocarbon group having a carbon-carbon double bond.

[0068] As used herein, when a definition is not otherwise provided, "alkynyl" refers to a straight-chain or branched monovalent hydrocarbon group having a carbon-carbon triple bond.

[0069] As used herein, when a definition is not otherwise provided, "aryl" refers to a group formed by removing a hydrogen, for example, at least one hydrogen, from an aromatic hydrocarbon (eg, phenyl or naphthyl).

[0070] As used herein, when no specific definition is otherwise provided, the prefix “hetero” means including 1 to 4 heteroatoms selected from N, O, S, Se, Te, Si and P.

[0071] As used herein, when no definition is otherwise provided, "alkoxy" means an alkyl group linked through an oxygen group (ie, alkyl-O-), such as methoxy, ethoxy, or sec-butoxy.

[0072] As used herein, when no definition is otherwise provided, an "amine group" may be -NRR (wherein R is independently hydrogen, C1 to C12 alkyl, C7 to C20 alkylaryl, C7 to C20 arylalkyl, or C6 to C18 aryl).

[0073] Hereinafter, a quantum dot light emitting device according to some embodiments is described with reference to the accompanying drawings.

[0074] The quantum dot light emitting device according to the embodiment may be a quantum dot electroluminescent device that emits light from quantum dots by applying an electric field to electrodes.

[0075] Figure 1 is a cross-sectional view schematically showing a quantum dot light emitting device according to an embodiment.

[0076] Reference Figure 1 According to the embodiment, the quantum dot light-emitting device 10 includes: an anode 11 and a cathode 12 facing each other as two opposite electrodes; a quantum dot light-emitting layer 13 between the anode 11 and the cathode 12; hole auxiliary layers 14 and 15 between the anode 11 and the quantum dot light-emitting layer 13; and an electron auxiliary layer 16 between the cathode 12 and the quantum dot light-emitting layer 13.

[0077] A substrate (not shown) may be disposed below the anode 11 or on the cathode 12, or at any other desired location on the quantum dot light-emitting device 10. The substrate may include an insulating material (e.g., an insulating transparent substrate). The substrate may include, for example, an inorganic material such as glass, silicon, silicon oxide, Al2O3, etc.; an organic material such as polycarbonate, polymethyl methacrylate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyamide, polyethersulfone; or any combination thereof; or a silicon wafer, but is not limited thereto. As used herein, "transparent" refers to a transmittance of greater than or equal to about 85%, such as greater than or equal to about 88%, greater than or equal to about 90%, greater than or equal to about 95%, greater than or equal to about 97%, or greater than or equal to about 99% for light of a predetermined wavelength (e.g., light emitted from quantum dots). The thickness of the substrate may be appropriately selected in consideration of the substrate material, but is not particularly limited. The transparent substrate may be flexible. The substrate may be omitted.

[0078] Anode 11 may be made of a conductor with a relatively deep work function, such as a metal, a conductive metal oxide, or any combination thereof. Anode 11 may be made of, for example, a metal or its alloys, such as nickel, platinum, vanadium, chromium, copper, zinc, or gold; a conductive metal oxide, such as zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide; or a combination of a metal and an oxide, such as ZnO and Al, or SnO2 and Sb, but is not limited thereto. In embodiments, anode 11 may include a transparent conductive metal oxide, such as ITO.

[0079] The cathode 12 may be made of a conductor having a shallower work function than the anode 11, for example, a lower or smaller work function, and may be made of, for example, a metal, a conductive metal oxide, a conductive polymer, or a combination thereof. The cathode 12 may include, for example, a metal such as aluminum, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, silver, tin, lead, cesium, barium, or an alloy thereof; a multilayer structure material such as LiF / Al, Li2O / Al, 8-hydroxyquinoline lithium (Liq) / Al, LiF / Ca, or BaF2 / Ca; or a combination thereof, but is not limited thereto. In an embodiment, the cathode 12 may include a transparent conductive metal oxide such as ITO. The work function of the anode 11 may be deeper, for example, higher or larger, than the work function of the cathode 12. As an example, the work function of the anode 11 may be, for example, from about 4.5 eV to about 5.0 eV, including about 4.6 eV, about 4.7 eV, about 4.8 eV, and about 4.9 eV, and the work function of the cathode 12 may be, for example, from about 4.0 eV to about 4.7 eV, including about 4.1 eV, about 4.2 eV, about 4.3 eV, about 4.4 eV, about 4.5 eV, and about 4.6 eV. Within the above range, the work function of the anode 11 may be, for example, from about 4.6 eV to about 4.9 eV, and the work function of the cathode 12 may be, for example, from about 4.0 eV to about 4.5 eV. Further within the above range, the work function of the anode 11 may be, for example, from about 4.7 eV to about 4.8 eV, and the work function of the cathode 12 may be, for example, from about 4.2 eV to about 4.4 eV.

[0080] The anode 11, cathode 12, or a combination thereof may be a light-transmitting electrode, and the light-transmitting electrode may be made, for example, of a conductive oxide such as zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide, or a single or multiple metal thin layers. Either the anode 11 or cathode 12 may be an opaque electrode, and the opaque electrode may be made, for example, of an opaque conductor such as aluminum (Al), silver (Ag), or gold (Au).

[0081] The thickness of the electrode (anode 11, cathode 12, or each of the anode 11 and cathode 12) is not particularly limited and can be appropriately selected in consideration of device efficiency. For example, the thickness of the electrode may be greater than or equal to about 5 nm, for example, greater than or equal to about 50 nm, or greater than or equal to about 100 nm. For example, the thickness of the electrode may be less than or equal to about 100 micrometers (μm), for example, less than or equal to about 10 μm, less than or equal to about 1 μm, less than or equal to about 900 nm, less than or equal to about 500 nm, less than or equal to about 400 nm, less than or equal to about 300 nm, less than or equal to about 200 nm, or less than or equal to about 100 nm. The quantum dot light-emitting layer 13 includes, for example, a plurality of quantum dots as a light-emitting material configured to emit light by an electric field. Quantum dots refer to semiconductor nanocrystals in a broad sense and can exhibit a quantum confinement effect.

[0082] Herein, quantum dots may have any shape, and the shape is not particularly limited. For example, quantum dots may have a variety of shapes such as the following: spheres, polyhedrons, pyramids, multi-legged shapes, hexahedrons, cubes, cuboids, nanotubes, nanorods, nanowires, nanosheets, isotropic semiconductor nanocrystals, quantum rods, quantum plates (sheets), or combinations thereof. The multi-legged shape may have at least two (e.g., at least three or at least four) branch portions and a valley portion therebetween.

[0083] Herein, quantum rods refer to quantum dots having an aspect ratio greater than about 1, such as an aspect ratio greater than or equal to about 2, greater than or equal to about 3, or greater than or equal to about 5. For example, the aspect ratio of the quantum rod may be less than or equal to about 50, less than or equal to about 30, or less than or equal to about 20.

[0084] The quantum dots may have, for example, a particle diameter (for non-spherical shapes, an average maximum particle diameter) of about 1 nm to about 100 nm, such as about 1 nm to about 80 nm, such as about 1 nm to about 50 nm, or such as about 1 nm to about 20 nm. In embodiments, the (average) size of the quantum dots may be greater than or equal to about 1 nm, greater than or equal to about 2 nm, greater than or equal to about 3 nm, greater than or equal to about 4 nm, greater than or equal to about 5 nm, greater than or equal to about 6 nm, greater than or equal to about 7 nm, greater than or equal to about 8 nm, greater than or equal to about 9 nm, greater than or equal to about 10 nm, greater than or equal to about 11 nm, or greater than or equal to about 12 nm. In embodiments, the (average) size of the quantum dots may be less than or equal to about 50 nm, less than or equal to about 40 nm, less than or equal to about 30 nm, less than or equal to about 25 nm, less than or equal to about 20 nm, less than or equal to about 19 nm, less than or equal to about 18 nm, less than or equal to about 17 nm, less than or equal to about 16 nm, or less than or equal to about 15 nm. For example, the average size of the quantum dots (e.g., emitting blue light) may be less than or equal to about 4.5 nm, such as less than or equal to about 4.3 nm, less than or equal to about 4.2 nm, less than or equal to about 4.1 nm, or less than or equal to about 4.0 nm. In embodiments, the (average) size of the quantum dots may be from about 2.0 nm to about 4.5 nm, from about 2.0 nm to about 4.3 nm, from about 2.0 nm to about 4.2 nm, from about 2.0 nm to about 4.1 nm, or from about 2.0 nm to about 4.0 nm. "Average" may refer to the mean, mode, or median.

[0085] The energy band gap of quantum dots can be controlled depending on their size and composition, and thus the emission wavelength can be controlled. For example, as the size of quantum dots increases, the quantum dots may have a narrow energy band gap and thus emit light in a relatively long wavelength region. Conversely, as the size of quantum dots decreases, the quantum dots may have a wide energy band gap and thus emit light in a relatively short wavelength region.

[0086] For example, the quantum dot may be configured to emit light in a predetermined wavelength region in the visible light region according to its size, composition, or a combination thereof. For example, the quantum dot may be configured to emit blue light, red light, or green light, and the blue light may have a maximum emission wavelength (or referred to as a peak emission wavelength) (λ) of, for example, about 430 nm to about 480 nm. max,L ), the red light may have a maximum emission wavelength of, for example, about 600 nm to about 670 nm, and the green light may have a maximum emission wavelength of, for example, about 520 nm to about 560 nm (λ max,L ).

[0087] In the quantum dot light emitting device 10 of the embodiment, the maximum emission wavelength (λ max,L ) may be greater than or equal to about 300 nm, greater than or equal to about 400 nm, greater than or equal to about 430 nm, greater than or equal to about 450 nm, for example, greater than or equal to about 500 nm, greater than or equal to about 510 nm, greater than or equal to about 520 nm, greater than or equal to about 530 nm, greater than or equal to about 540 nm, greater than or equal to about 550 nm, greater than or equal to about 560 nm, greater than or equal to about 570 nm, greater than or equal to about 580 nm, greater than or equal to about 590 nm, greater than or equal to about 600 nm, or greater than or equal to about 610 nm. The maximum emission wavelength (λ) of the quantum dot light-emitting layer 13 or the quantum dots may be greater than or equal to about 500 nm, greater than or equal to about 510 nm, greater than or equal to about 520 nm, greater than or equal to about 530 nm, greater than or equal to about 540 nm, greater than or equal to about 550 nm, greater than or equal to about 560 nm, greater than or equal to about 570 nm, greater than or equal to about 580 nm, greater than or equal to about 590 nm, greater than or equal to about 600 nm, or greater than or equal to about 610 nm. max,L ) may be within the range of about 800 nm or less, about 780 nm or less, about 750 nm or less, about 700 nm or less, about 670 nm or less, about 650 nm or less, about 640 nm or less, about 630 nm or less, about 620 nm or less, about 610 nm or less, about 600 nm or less, about 590 nm or less, about 580 nm or less, about 570 nm or less, about 560 nm or less, about 550 nm or less, or about 540 nm or less. The maximum emission wavelength (λ) of the quantum dot light emitting layer 13 or the quantum dots may be within the range of about 800 nm or less, about 780 nm or less, about 750 nm or less, about 700 nm or less, about 670 nm or less, about 650 nm or less, about 640 nm or less, about 630 nm or less, about 620 nm or less, about 610 nm or less, about 600 nm or less, about 590 nm or less, about 580 nm or less, about 570 nm or less, about 560 nm or less, about 550 nm or less, or about 540 nm or less. max,L ) may be in the range of about 430 nm to about 670 nm.

[0088] In the quantum dot light emitting device 10 of the embodiment, the quantum dot light emitting layer 13 or the quantum dots may be configured to emit green light, and the maximum emission wavelength (λ max,L ) may be in a range of about 500 nm or more (e.g., about 510 nm or more or about 520 nm or more) and may be less than or equal to about 560 nm (e.g., about 550 nm or less or about 540 nm or less). In the quantum dot light emitting device 10 of the embodiment, the quantum dot light emitting layer 13 or the quantum dots may be configured to emit red light, and the maximum emission wavelength (λ max,L ) may be in a range of greater than or equal to about 600 nm (e.g., greater than or equal to about 610 nm) and less than or equal to about 670 nm (e.g., less than or equal to about 650 nm or less than or equal to about 640 nm). In the quantum dot light emitting device 10 of the embodiment, the quantum dot light emitting layer 13 or the quantum dots may be configured to emit blue light, and the maximum emission wavelength (λ max,L ) may be in a range of greater than or equal to about 430 nm (e.g., greater than or equal to about 440 nm or greater than or equal to about 450 nm) and less than or equal to about 480 nm (e.g., less than or equal to about 470 nm or less than or equal to about 465 nm).

[0089] The quantum dots can have a quantum yield, for example, greater than or equal to about 10%, within the above ranges such as greater than or equal to about 20%, greater than or equal to about 30%, greater than or equal to about 50%, greater than or equal to about 60%, greater than or equal to about 70%, or greater than or equal to about 90%.

[0090] The emission spectrum of quantum dots can have a relatively narrow full width at half maximum (FWHM). Herein, FWHM is the wavelength width corresponding to half the maximum emission intensity in the emission spectrum. By applying quantum dots having an emission spectrum with a relatively narrow FWHM and the quantum dot light-emitting layer 13 including the same to the quantum dot light-emitting device 10, high color purity (or color gamut) can be advantageously achieved.

[0091] The FWHM of the quantum dots (or quantum dot light emitting layer 13) can be, for example, less than or equal to about 60 nm, within the above ranges, for example, less than or equal to about 55 nm, less than or equal to about 52 nm, less than or equal to about 50 nm, less than or equal to about 49 nm, less than or equal to about 48 nm, less than or equal to about 47 nm, less than or equal to about 46 nm, less than or equal to about 45 nm, less than or equal to about 44 nm, less than or equal to about 43 nm, less than or equal to about 42 nm, less than or equal to about 41 nm, less than or equal to about 40 nm, less than or equal to about 39 nm, less than or equal to about 38 nm, less than or equal to about 37 nm, less than or equal to about 36 nm, less than or equal to about 35 nm, less than or equal to about 34 nm, less than or equal to about 33 nm, less than or equal to about 32 nm, less than or equal to about 31 nm, less than or equal to about 30 nm, less than or equal to about 29 nm, or less than or equal to about 28 nm, for example, from about 2 nm to about 60 nm. nm, about 2 nm to about 55 nm, about 2 nm to about 50 nm, about 2 nm to about 49 nm, about 2 nm to about 48 nm, about 2 nm to about 47 nm, about 2 nm to about 46 nm, about 2 nm to about 45 nm, about 2 nm to about 44 nm, about 2 nm to about 43 nm, about 2 nm to about 42 nm, about 2 nm to about 41 nm, about 2 nm to about 40 nm, about 2 nm to about 39 nm, about 2 nm to about 38 nm, about 2 nm to about 37 nm, about 2 nm to about 36 nm, about 2 nm to about 35 nm, about 2 nm to about 34 nm, about 2 nm to about 33 nm, about 2 nm to about 32 nm, about 2 nm to about 31 nm, about 2 nm to about 30 nm, about 2 nm to about 29 nm, or about 2 nm to about 28 nm.

[0092] For example, quantum dots may include Group II-VI semiconductor compounds, Group III-V semiconductor compounds, Group IV-VI semiconductor compounds, Group IV semiconductors, Group I-III-VI semiconductor compounds, Group I-II-IV-VI semiconductor compounds, Group II-III-V semiconductor compounds, or any combination thereof.

[0093] The II-VI semiconductor compound may be, for example, a binary compound selected from the group consisting of CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, and combinations thereof; a binary compound selected from the group consisting of CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdH CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, and combinations thereof; and ternary compounds selected from HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, and combinations thereof, but are not limited thereto. The III-V semiconductor compound may be, for example, a binary compound selected from GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, and combinations thereof; a ternary compound selected from GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, and combinations thereof; and a quaternary compound selected from GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and combinations thereof, but is not limited thereto. Group IV-VI semiconductor compounds may be, for example, binary compounds selected from SnS, SnSe, SnTe, PbS, PbSe, PbTe, and combinations thereof; ternary compounds selected from SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and combinations thereof; and quaternary compounds selected from SnPbSSe, SnPbSeTe, SnPbSTe, and combinations thereof, but are not limited thereto. Group IV semiconductors may be, for example, unary (single element) semiconductors selected from Si, Ge, and combinations thereof; and binary semiconductors selected from SiC, SiGe, and combinations thereof, but are not limited thereto.The Group I-III-VI semiconductor compound may be, for example, a ternary compound selected from AgInS, AgInS2, AgInSe2, AgGaS, AgGaS2, AgGaSe2, CuInS, CuInS2, CuInSe2, CuGaS2, CuGaSe2, CuGaO2, AgGaO2, and AgAlO2; a quaternary compound selected from AgInGaS2, AgInGaSe2, CuInGaSe, and CuInGaS; or any combination thereof, but is not limited thereto. The Group I-II-IV-VI semiconductor compound may be, for example, selected from CuZnSnSe, CuZnSnS, or any combination thereof, but is not limited thereto. The Group II-III-V semiconductor compound may include, for example, InZnP, but is not limited thereto.

[0094] The quantum dots may include the mono-semiconductor, binary semiconductor compound, ternary semiconductor compound or quaternary semiconductor compound in a substantially uniform concentration or a locally different concentration distribution. Each element included in a multi-element compound such as a binary semiconductor compound, a ternary semiconductor compound and a quaternary semiconductor compound may be present in the quantum dot particles in a uniform or non-uniform concentration. In other words, the chemical formula representing the compound represents the type of elements included in the compound, but does not limit the element ratio of each element. All elements included in each compound may have different element ratios, for example, AgInGaS2 may mean AgInGaS2. x Ga 1-x S2 (0≤x≤1).

[0095] For example, the quantum dots may include cadmium (Cd)-free quantum dots. Cadmium (Cd) can cause serious environmental / health issues and is a restricted element in many countries under the Restriction of Hazardous Substances (RoHS) directive, and therefore non-cadmium-based quantum dots can be effectively and advantageously used. In an embodiment, the quantum dot light-emitting layer 13 does not include cadmium. In an embodiment, the quantum dot light-emitting layer 13 does not include cadmium, lead, mercury, or any combination thereof.

[0096] For example, the quantum dots may include a semiconductor compound containing zinc (Zn) and at least one of tellurium (Te) and selenium (Se). For example, the quantum dots may include a Zn-Te semiconductor compound, a Zn-Se semiconductor compound, a Zn-Se-Te semiconductor compound, or a combination thereof. For example, in the Zn-Se-Te semiconductor compound, the molar fraction of tellurium (Te) may be less than the molar fraction of selenium (Se). The semiconductor compound may have a maximum emission wavelength in a wavelength region less than or equal to about 480 nm, for example, about 430 nm to about 480 nm, and may be configured to emit blue light.

[0097] For example, the quantum dots may include a semiconductor compound containing indium (In), zinc (Zn), and phosphorus (P). For example, the quantum dots may include an In-P semiconductor compound, an In-Zn-P semiconductor compound, or a combination thereof. For example, in the In-Zn-P semiconductor compound, the molar ratio of zinc (Zn) to indium (In) may be greater than or equal to about 25:1.

[0098] Quantum dots may have a core-shell structure in which one quantum dot surrounds another quantum dot. For example, the core and shell of the quantum dot may have an interface, and an element of at least one of the core or shell at the interface may have a concentration gradient, wherein the concentration of the element(s) decreases from the shell toward the core. For example, the material of the quantum dot shell has a higher energy band gap than the material of the quantum dot core, and thus the quantum dot may exhibit a quantum confinement effect.

[0099] A quantum dot may have a quantum dot core and a multilayer quantum dot shell surrounding the core. Here, the multilayer shell has at least two shells, wherein each shell may be a single composition, an alloy, a shell having a concentration gradient, or a combination thereof.

[0100] For example, a shell farther from the core of a multi-layer shell may have a higher energy band gap than a shell closer to the core, and thus the quantum dot may exhibit a quantum confinement effect.

[0101] For example, a quantum dot having a core-shell structure may, for example, include a core and a shell, wherein the core includes a first semiconductor compound containing zinc (Zn), and at least one of tellurium (Te) and selenium (Se), and the shell includes a second semiconductor compound disposed on at least a portion of the core and having a composition different from the composition of the core.

[0102] For example, the first semiconductor compound may be a Zn-Se-Te based semiconductor compound including zinc (Zn), selenium (Se), and tellurium (Te), for example, a Zn-Se based semiconductor compound including a small amount of tellurium (Te), and for example, a Zn-Se based semiconductor compound composed of ZnSe. 1-x Te x (wherein x is greater than 0 and less than or equal to approximately 0.05).

[0103] For example, in a first semiconductor compound based on Zn-Se-Te, the molar fraction of zinc (Zn) may be greater than the molar fraction of selenium (Se), and the molar fraction of selenium (Se) may be greater than the molar fraction of tellurium (Te). For example, in the first semiconductor compound, the molar ratio of tellurium (Te) to selenium (Se) may be less than or equal to about 0.05, less than or equal to about 0.049, less than or equal to about 0.048, less than or equal to about 0.047, less than or equal to about 0.045, less than or equal to about 0.044, less than or equal to about 0.043, less than or equal to about 0.042, less than or equal to about 0.041, less than or equal to about 0.04, less than or equal to about 0.039, less than or equal to about 0.035, less than or equal to about 0.03, or less than or equal to about 0.03. 0.029, less than or equal to about 0.025, less than or equal to about 0.024, less than or equal to about 0.023, less than or equal to about 0.022, less than or equal to about 0.021, less than or equal to about 0.02, less than or equal to about 0.019, less than or equal to about 0.018, less than or equal to about 0.017, less than or equal to about 0.016, less than or equal to about 0.015, less than or equal to about 0.014, less than or equal to about 0.013, less than or equal to about 0.012, less than or equal to about 0.011, or less than or equal to about 0.01. For example, in the first semiconductor compound, the molar ratio of tellurium (Te) to zinc (Zn) may be less than or equal to about 0.02:1, less than or equal to about 0.019:1, less than or equal to about 0.018:1, less than or equal to about 0.017:1, less than or equal to about 0.016:1, less than or equal to about 0.015:1, less than or equal to about 0.014:1, less than or equal to about 0.013:1, less than or equal to about 0.012:1, less than or equal to about 0.011:1, or less than or equal to about 0.01:1.

[0104] The second semiconductor compound may include, for example, a II-VI semiconductor compound, a III-V semiconductor compound, a IV-VI semiconductor compound, a Group IV semiconductor, a I-III-VI semiconductor compound, a I-II-IV-VI semiconductor compound, a II-III-V semiconductor compound, or any combination thereof. Examples of the II-VI semiconductor compound, the III-V semiconductor compound, the IV-VI semiconductor compound, the IV semiconductor, the I-III-VI semiconductor compound, the I-II-IV-VI semiconductor compound, and the II-III-V semiconductor compound are the same as described above.

[0105] For example, the second semiconductor compound may include zinc (Zn), selenium (Se), and / or sulfur (S). For example, the shell may include ZnSeS, ZnS, ZnSe, or any combination thereof, and may include at least one inner shell disposed near the core and an outermost shell disposed at the outermost side of the quantum dot, and the inner shell may include ZnSeS or ZnSe and the outermost shell may include ZnS. For example, the shell may have a concentration gradient of one component, and for example, the amount of sulfur (S) may increase as the distance from the core increases.

[0106] For example, a quantum dot having a core-shell structure may include a core and a shell, wherein the core includes a third semiconductor compound containing indium (In), and at least one of zinc (Zn) and phosphorus (P), and the shell is disposed on at least a portion of the core and includes a fourth semiconductor compound having a composition different from that of the core.

[0107] In the third semiconductor compound based on In-Zn-P, a molar ratio of zinc (Zn) to indium (In) may be greater than or equal to about 25: 1. For example, in the third semiconductor compound based on In-Zn-P, a molar ratio of zinc (Zn) to indium (In) may be greater than or equal to about 28: 1, greater than or equal to about 29: 1, or greater than or equal to about 30: 1. For example, in the third semiconductor compound based on In-Zn-P, a molar ratio of zinc (Zn) to indium (In) may be less than or equal to about 55: 1, for example, less than or equal to about 50: 1, less than or equal to about 45: 1, less than or equal to about 40: 1, less than or equal to about 35: 1, less than or equal to about 34: 1, less than or equal to about 33: 1, or less than or equal to about 32: 1.

[0108] The fourth semiconductor compound may include, for example, a II-VI semiconductor compound, a III-V semiconductor compound, a IV-VI semiconductor compound, a Group IV semiconductor, a I-III-VI semiconductor compound, a I-II-IV-VI semiconductor compound, a II-III-V semiconductor compound, or any combination thereof. Examples of the II-VI semiconductor compound, the III-V semiconductor compound, the IV-VI semiconductor compound, the IV semiconductor, the I-III-VI semiconductor compound, the I-II-IV-VI semiconductor compound, and the II-III-V semiconductor compound are the same as described above.

[0109] For example, the fourth semiconductor compound may include zinc (Zn) and sulfur (S), and optionally selenium (Se). For example, the shell may include ZnSeS, ZnS, ZnSe, or any combination thereof. For example, the shell may include at least one inner shell disposed proximate to the core and an outermost shell disposed at the outermost side of the quantum dot. At least one of the inner shell and the outermost shell may include the fourth semiconductor compound ZnS, ZnSe, or ZnSeS.

[0110] The aforementioned quantum dots are commercially available or can be appropriately synthesized.

[0111] In the quantum dot device 10 of the embodiment, the quantum dot may include a first organic ligand on its surface. The first organic ligand may have a hydrophobic portion. The first organic ligand may be bound to the surface of the quantum dot. The first organic ligand may include RCOOH, RNH2, R2NH, R3N, RSH, R3PO, R3P, ROH, RC(=O)OR, RC(=O)OC(=O)R, RPO(OH)2, RHPOOH, R2POOH, or any combination thereof, wherein each R is independently a substituted or unsubstituted C1 to C40 aliphatic hydrocarbon group, such as a C3 to C40 alkyl or alkenyl group, a C1 to C40 substituted or unsubstituted aromatic hydrocarbon group, such as a C6 to C40 aryl group, or any combination thereof.

[0112] Examples of the first organic ligand may include: thiol compounds such as methyl mercaptan, ethyl mercaptan, propyl mercaptan, butyl mercaptan, pentyl mercaptan, hexyl mercaptan, octyl mercaptan, dodecanethiol, hexadecyl mercaptan, octadecyl mercaptan, benzyl mercaptan, etc.; amines such as methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, octylamine, nonylamine, decylamine, dodecylamine, hexadecylamine, octadecylamine, dimethylamine, diethylamine, dipropylamine, tributylamine, trioctylamine, etc.; carboxylic acid compounds such as formic acid, acetic acid, propionic acid, butyric acid, pentyl acid, hexanoic acid, heptanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid, oleic acid, benzoic acid, etc.; phosphine compounds such as methylphosphine, ethylphosphine, propylphosphine, butylphosphine, pentylphosphine, octylphosphine, Phosphine, dioctylphosphine, tributylphosphine, trioctylphosphine, etc.; phosphine oxide compounds such as methylphosphine oxide, ethylphosphine oxide, propylphosphine oxide, butylphosphine oxide, pentylphosphine oxide, tributylphosphine oxide, octylphosphine oxide, dioctylphosphine oxide, trioctylphosphine oxide; diphenylphosphine, triphenylphosphine compounds, or their oxide compounds; C5 to C20 alkylphosphinic acids such as hexylphosphinic acid, octylphosphinic acid, dodecanephosphinic acid, tetradecanephosphinic acid, hexadecanephosphinic acid, octadecanephosphinic acid; C5 to C20 alkylphosphinic acids such as hexylphosphinic acid, octylphosphinic acid, dodecanephosphinic acid, tetradecanephosphinic acid, hexadecanephosphinic acid, octadecanephosphinic acid; etc., but are not limited thereto. One or more organic ligands can be used. For example, quantum dots can include hydrophobic organic ligands alone or in the form of a mixture.

[0113] The quantum dots may include a halogen together with an organic ligand (e.g., a C5 or higher or C10 or higher fatty acid compound, such as oleic acid) on the surface (hereinafter referred to as "halogen-treated quantum dots"). The content of halogen in the halogen-treated quantum dots may be, for example, greater than or equal to about 1 microgram (μg), greater than or equal to about 1.5 μg, greater than or equal to about 3 μg, greater than or equal to about 4 μg, greater than or equal to about 5 μg, greater than or equal to about 6 μg, greater than or equal to about 7 μg, greater than or equal to about 8 μg, greater than or equal to about 9 μg, greater than or equal to about 10 μg, greater than or equal to about 11 μg, greater than or equal to about 12 μg, greater than or equal to about 12.5 μg, greater than or equal to about 13 μg, greater than or equal to about 14 μg, greater than or equal to about 15 μg, greater than or equal to about 16 μg, greater than or equal to about 17 μg, greater than or equal to about 18 μg, greater than or equal to about 19 μg, greater than or equal to about 20 μg, greater than or equal to about 21 μg, greater than or equal to about 22 μg, greater than or equal to about 23 μg, greater than or equal to about 24 μg, greater than or equal to about 25 μg, greater than or equal to about 26 μg, greater than or equal to about 27 μg, greater than or equal to about 28 μg, greater than or equal to about 29 μg, greater than or equal to about 30 μg, greater than or equal to about 31 μg, greater than or equal to about 32 μg, greater than or equal to about 33 μg, greater than or equal to about 34 μg, greater than or equal to about 35 μg The halogen may be less than or equal to about 16 μg, greater than or equal to about 17 μg, greater than or equal to about 18 μg, or greater than or equal to about 19 μg, and may be less than or equal to about 30 μg, less than or equal to about 25 μg, less than or equal to about 20 μg, less than or equal to about 19.5 μg, less than or equal to about 19 μg, less than or equal to about 18 μg, less than or equal to about 17 μg, less than or equal to about 15 μg, less than or equal to about 12.5 μg, or less than or equal to about 12 μg, as determined by ion chromatography. The halogen may be chlorine.

[0114] An example of a method for preparing halogen-treated quantum dots may include: obtaining an organic dispersion comprising a plurality of quantum dots including a first organic ligand on a surface thereof and a first organic solvent; obtaining a chloride solution comprising a polar organic solvent miscible with the first organic solvent and a metal halide; and adding the chloride solution to the organic dispersion such that the content of the metal halide is greater than or equal to about 0.1 weight percent (wt%) and less than or equal to about 10 wt % based on the total weight of the quantum dots, and then stirring the resulting dispersion at a temperature greater than or equal to about 45° C., for example, greater than or equal to about 50° C., greater than or equal to about 55° C., or greater than or equal to about 60° C. and less than or equal to about 150° C., less than or equal to about 140° C., less than or equal to about 100° C., less than or equal to about 90° C., less than or equal to about 80° C., or less than or equal to about 70° C. The volume ratio of the polar organic solvent to the first organic solvent may be less than or equal to about 0.1.

[0115] The metal halide (e.g., metal chloride) may include zinc halide, indium halide, gallium halide, magnesium halide, lithium halide, or any combination thereof. The first organic solvent may include substituted or unsubstituted C5 to C40 aliphatic hydrocarbons, substituted or unsubstituted C6 to C40 aromatic hydrocarbons, substituted or unsubstituted C3 to C40 alicyclic hydrocarbons, or any combination thereof. The polar organic solvent may include C1 to C10 alcohols (e.g., methanol, ethanol, propanol, isopropanol, butanol, pentanol, hexanol, heptanol, etc.), or any combination thereof.

[0116] The quantum dot light-emitting layer 13 may have a single layer or a multilayer structure in which two or more layers are stacked. In a multilayer structure, adjacent layers (e.g., a first quantum dot light-emitting layer and a second quantum dot light-emitting layer) may have the same or different physical properties and / or compositions. At least one layer of the quantum dot light-emitting layer 13 of an embodiment may include a halogen (e.g., chlorine). The quantum dot light-emitting layer 13 of an embodiment may exhibit a halogen content that varies in the thickness direction (e.g., varies with thickness).

[0117] Examples of the quantum dot light-emitting layer 13 may include a layer comprising quantum dots and having a surface treated with a halogen (e.g., chlorine) (hereinafter referred to as a surface-treated first quantum dot light-emitting layer or the first layer). A second layer comprising halogen-treated quantum dots, a third layer comprising quantum dots having organic ligands, or a combination thereof may be disposed on the first layer. The second layer may be disposed between the first and third layers. The organic material (e.g., carbon) content (e.g., concentration) of the first layer may be lower than the organic material content of the second layer. The halogen (e.g., chlorine) content (e.g., concentration) of the first layer may be higher than the halogen content of the second layer. The organic material content of the first layer may be higher than the organic material content of the second layer. The halogen content of the first layer may be lower than the organic material content of the second layer. The organic material content of the quantum dot light-emitting layer 13 may be controlled by appropriate means (post-treatment of the formed layer).

[0118] The quantum dot light-emitting layer 13 may have a relatively deep HOMO energy level, for example, a HOMO energy level greater than or equal to about 5.4 eV, for example, greater than or equal to about 5.6 eV, for example, greater than or equal to about 5.7 eV, for example, greater than or equal to about 5.8 eV, for example, greater than or equal to about 5.9 eV, for example, greater than or equal to about 6.0 eV. The HOMO energy level of the quantum dot light-emitting layer 13 may be, for example, from about 5.4 eV to about 7.0 eV, for example, from about 5.4 eV to about 6.8 eV, for example, from about 5.4 eV to about 6.7 eV, for example, from about 5.4 eV to about 6.5 eV, for example, from about 5.4 eV to about 6.3 eV, for example, from about 5.4 eV to about 6.2 eV, for example, from about 5.4 eV to about 6.1 eV, within the above range, for example, from about 5.6 eV to about about 7.0 eV, for example, about 5.6 eV to about 6.8 eV, for example, about 5.6 eV to about 6.7 eV, for example, about 5.6 eV to about 6.5 eV, for example, about 5.6 eV to about 6.3 eV, for example, about 5.6 eV to about 6.2 eV, for example, about 5.6 eV to about 6.1 eV, within the above range, for example, about 5.7 eV to about 7.0 eV, for example, about 5.7 eV to about 6.8 eV, for example, about 5.7 eV to about 6.7eV, for example, about 5.7eV to about 6.5eV, for example, about 5.7eV to about 6.3eV, for example, about 5.7eV to about 6.2eV, for example, about 5.7eV to about 6.1eV, within the above range, for example, about 5.8eV to about 7.0eV, for example, about 5.8eV to about 6.8eV, for example, about 5.8eV to about 6.7eV, for example, about 5.8eV to about 6.5eV, for example, about 5.8eV to about 6.3eV, for example, about 5.8eV to about 6.2eV, for example, about 5.8eV to about 6.1eV, within the above range, for example, about 6.0eV to about 7.0eV, for example, about 6.0eV to about 6.8eV, for example, about 6.0eV to about 6.7eV, for example, about 6.0eV to about 6.5eV, for example, about 6.0eV to about 6.3eV, for example, about 6.0eV to about 6.2eV.

[0119] The quantum dot light-emitting layer 13 may have a relatively shallow LUMO energy level, for example, less than or equal to about 3.6 eV, for example, less than or equal to about 3.5 eV, for example, less than or equal to about 3.4 eV, for example, less than or equal to about 3.3 eV, for example, less than or equal to about 3.2 eV, or for example, less than or equal to about 3.0 eV. The LUMO energy level of the quantum dot light-emitting layer 13 may be from about 2.5 eV to about 3.6 eV, from about 2.5 eV to about 3.5 eV, for example, from about 2.5 eV to about 3.4 eV, for example, from about 2.5 eV to about 3.3 eV, for example, from about 2.5 eV to about 3.2 eV, for example, from about 2.5 eV to about 3.1 eV, for example, from about 2.5 eV to about 3.0 eV, for example, from about 2.8 eV to about 3.6 eV, from about 2.8 eV to about 3.5 eV, for example, from about 2.8 eV to about 3.4 eV, for example, from about 2.8 eV to about 3.3 eV, for example, from about 2.8 eV to about 3.2 eV, from about 3.0 eV to about 3.6 eV, from about 3.0 eV to about 3.5 eV, or for example, from about 3.0 eV to about 3.4 eV.

[0120] The quantum dot light emitting layer 13 may have an energy bandgap of about 2.4 eV to 3.9 eV, within the above range, for example, about 2.5 eV to about 3.8 eV, and within the above range, for example, about 2.6 eV to about 3.7 eV.

[0121] The thickness of the quantum dot light-emitting layer 13 may be less than or equal to about 200 nm, for example, about 5 nm to about 200 nm, about 10 nm to about 200 nm, about 20 nm to about 150 nm, about 20 nm to about 100 nm, about 30 nm to about 100 nm, about 20 nm to about 80 nm, or about 30 nm to about 80 nm.

[0122] The hole auxiliary layers 14 and 15 may include a first hole auxiliary layer 14 and a second hole auxiliary layer 15. The first hole auxiliary layer 14 and the second hole auxiliary layer 15 may be located between the anode 11 and the quantum dot light-emitting layer 13 to improve the electrical (electrical) performance between the anode 11 and the quantum dot light-emitting layer 13. The first hole auxiliary layer 14 may be located closer to the anode 11 between the anode 11 and the quantum dot light-emitting layer 13, and the second hole auxiliary layer 15 may be located closer to the quantum dot light-emitting layer 13 between the anode 11 and the quantum dot light-emitting layer 13. The first hole auxiliary layer 14 and the second hole auxiliary layer 15 may enhance (increase) the injection and transport of holes from the anode 11 to the quantum dot light-emitting layer 13. For example, the first hole auxiliary layer 14 may be a hole injection layer that enhances hole injection from the anode 11, and the second hole auxiliary layer 15 may be a hole transport layer that enhances hole transport to the quantum dot light-emitting layer 13. At least one of the first hole auxiliary layer 14 and the second hole auxiliary layer 15 may have electron blocking properties.

[0123] The first and second hole auxiliary layers 14 and 15 may have relatively high HOMO levels to match the HOMO level of the quantum dot light emitting layer 13. Therefore, the mobility of holes passing through the first and second hole auxiliary layers 14 and 15 and transferred to the quantum dot light emitting layer 13 may increase.

[0124] The HOMO energy levels of the first hole assisting layer 14 and the second hole assisting layer 15 may be equal to the HOMO energy level of the quantum dot light emitting layer 13 or less than or equal to about 1.0 eV of the HOMO energy level of the quantum dot light emitting layer 13. For example, the difference in HOMO energy level between the second hole assisting layer 15 and the quantum dot light emitting layer 13 may be about 0 eV to about 1.0 eV, within the above range, for example, about 0.01 eV to about 0.8 eV, for example, about 0.01 eV to about 0.7 eV, about 0.01 eV to about 0.5 eV, for example, about 0.01 eV to about 0.4 eV, for example, about 0.01 eV to about 0.3 eV, for example, about 0.01 eV to about 0.2 eV, for example, about 0.01 eV to about 0.1 eV.

[0125] The HOMO energy levels of the first and second hole assisting layers 14 and 15 may be, for example, greater than or equal to about 5.0 eV, for example, greater than or equal to about 5.2 eV, for example, greater than or equal to about 5.4 eV, for example, greater than or equal to about 5.6 eV, for example, greater than or equal to about 5.8 eV.

[0126] For example, the HOMO energy levels of the first hole assisting layer 14 and the second hole assisting layer 15 may be about 5.0 eV to about 7.0 eV, within the above ranges, for example, about 5.2 eV to about 6.8 eV, about 5.4 eV to 6.8 eV, for example, about 5.4 eV to 6.7 eV, for example, about 5.4 eV to about 6.5 eV, for example, about 5.4 eV to about 6.3 eV, for example, about 5.4 eV to about 6.2 eV, for example, about 5.4 eV to about 6.1 eV, for example, about 5.6 eV to about 7.0 eV, for example, about 5.6 eV to about 6.8 eV, For example, from about 5.6eV to about 6.7eV, for example, from about 5.6eV to about 6.5eV, for example, from about 5.6eV to about 6.3eV, for example, from about 5.6eV to about 6.2eV, for example, from about 5.6eV to about 6.1eV, for example, from about 5.8eV to about 7.0eV, for example, from about 5.8eV to about 6.8eV, for example, from about 5.8eV to about 6.7eV, for example, from about 5.8eV to about 6.5eV, for example, from about 5.8eV to about 6.3eV, for example, from about 5.8eV to about 6.2eV, for example, from about 5.8eV to about 6.1eV.

[0127] The first hole auxiliary layer 14 and the second hole auxiliary layer 15 may include one or more hole transport materials, and the hole transport materials may include, for example, an organic material, an inorganic material, an organic / inorganic material, or any combination thereof, for example, N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (TPD), N,N'-bis(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine (NPD), 4,4',4''-tris[phenyl(m-tolyl)amino]triphenylamine (m-MTDATA), 4,4',4''-tris(N-carbazolyl)-triphenylamine (TCTA), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), N2,N7-di(naphthalen-1-yl)-9,9-dioctyl-N2,N7-diphenyl-9H -fluorene-2,7-diamine (NPB), 2,7-bis(carbazol-9-yl)-9,9-spirobifluorene (Spiro-2CBP), 2,2',7,7'-tetrakis(N,N-di-p-tolyl)amino-9,9-spirobifluorene (Spiro-TTB), 2,2',7,7'-tetrakis(N,N-diphenylamino)-9,9-spirobifluorene (Spiro-TAD), 1,1-bis[ [4-tolylamino]phenyl]cyclohexane (TAPC), 4,4'-bis(N-carbazolyl)-1,1'-biphenyl (CBP), 4,4',4''-tris[2-naphthyl(phenyl)amino]triphenylamine (2-TNATA), 1,3,5-tris(4-diphenylaminophenyl)benzene (TDAPB), poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), polyarylamine (PAA), poly(N-vinylcarbazole), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), polyaniline, polypyrrole, Spiro-PMATD, triphenylbismuth dichloride (TPBC), poly(triarylamine) (PTAA), poly(3-hexylthiophene-2,5-diyl) (P3HT), poly[3-(5-carboxypentyl)thiophene-2,5-diyl] (P3CPenT), poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b']dithiophene)-alt-4,7(2,1,3-benzothiadiazole)] (PCPDT-t), poly(2,3-dihydrothieno[3,4-b][1,4]dioxane-5,7-diyl) (PEDOT-S), polyferric sulfate (PFS), CuI, Cu2O, CuO, CuS, nickel oxide, CuGaO2, CuPc, CuSCN, molybdenum oxide, MoS2, vanadium oxide, cobalt oxide, graphene oxide, or any combination thereof, but not limited thereto.

[0128] The electron assist layer 16 can improve the electrical properties between the cathode 12 and the quantum dot light-emitting layer 13. For example, it can enhance the transport of electrons from the cathode 12 to the quantum dot light-emitting layer 13 and effectively block the reverse injection of holes from the quantum dot light-emitting layer 13 to the cathode 12. The electron assist layer 16 can have one layer or two or more layers. The electron assist layer 16 can include one or more electron assist materials, and the electron assist materials can be electron transport materials, electron injection materials, or a combination thereof.

[0129] The LUMO energy level of the electron assist material may be deeper than the LUMO energy level of the quantum dot light-emitting layer 13 (the quantum dots included in the quantum dot light-emitting layer). The difference between the LUMO energy level of the electron assist material and the LUMO energy level of the quantum dot light-emitting layer 13 (the quantum dots included in the quantum dot light-emitting layer) may be less than or equal to about 2.5 eV, less than or equal to about 2.3 eV, less than or equal to about 2.0 eV, or less than or equal to about 1.8 eV. The LUMO energy level of the electron assist material may be, for example, about 2.5 eV to about 4.8 eV, and within the above range, for example, about 2.6 eV to about 4.6 eV or about 2.7 eV to about 4.5 eV.

[0130] The HOMO energy level of the electron assist material may be deeper than the HOMO energy level of the quantum dot light-emitting layer 13 (the quantum dots included in the quantum dot light-emitting layer). For example, the HOMO energy level of the electron assist material may be deeper than the HOMO energy level of the quantum dot light-emitting layer 13 (the quantum dots included in the quantum dot light-emitting layer) by greater than or equal to about 0.2 eV, greater than or equal to about 0.5 eV, greater than or equal to about 0.8 eV, greater than or equal to about 1.0 eV, greater than or equal to about 1.2 eV, or greater than or equal to about 1.5 eV, such as about 0.2 eV to about 3.0 eV, about 0.5 eV to about 3.0 eV, about 0.8 eV to about 3.0 eV, about 1.0 eV to about 3.0 eV, about 1.2 eV to about 3.0 eV, or about 1.5 eV to about 3.0 eV.

[0131] For example, the HOMO energy level of the electron assist material can be, for example, from about 5.6 eV to about 8.5 eV, from about 5.8 eV to about 8.2 eV within the above range, from about 6.0 eV to about 8.0 eV, from about 6.2 eV to about 8.0 eV, from about 6.5 eV to about 8.0 eV, from about 6.8 eV to about 8.0 eV, from about 7.0 eV to about 8.0 eV, from about 7.2 eV to about 7.9 eV, or from about 7.3 eV to about 7.8 eV.

[0132] For example, the electron assist material may have a band gap of greater than or equal to about 2.0 eV and less than about 4.0 eV, and within the above ranges of about 2.1 eV to about 3.9 eV, about 2.3 eV to about 3.8 eV, or about 2.5 eV to about 3.8 eV.

[0133] For example, the electronic auxiliary material may include inorganic nanoparticles. The inorganic nanoparticles may be, for example, oxide nanoparticles, such as metal oxide nanoparticles, such as metal oxide nanoparticles including two or more types of metals. The inorganic nanoparticles may be three-dimensional nanoparticles having an average particle diameter of several nanometers, and may be, for example, inorganic semiconductors, such as n-type inorganic semiconductors.

[0134] As an example, the inorganic nanoparticles may be alkaline earth metal-containing oxide nanoparticles. The alkaline earth metal may be selected from, for example, beryllium (Be), magnesium (Mg), calcium (Ca), barium (Ba), strontium (Sr), radium (Ra), or any combination thereof. The alkaline earth metal may include, for example, magnesium (Mg). The alkaline earth metal-containing oxide nanoparticles may further include one or more metals different from the alkaline earth metal, and may include, for example, at least one selected from zinc (Zn), cobalt (Co), nickel (Ni), gallium (Ga), zirconium (Zr), tungsten (W), titanium (Ti), tantalum (Ta), tin (Sn), and hafnium (Hf).

[0135] As an example, the alkaline earth metal-containing oxide nanoparticles may include an alkaline earth metal and zinc (Zn). In the alkaline earth metal-containing oxide nanoparticles, the alkaline earth metal may have a content smaller than that of zinc (Zn). For example, based on the total number of metal atoms included in the alkaline earth metal-containing oxide nanoparticles, that is, the total number of atoms of the alkaline earth metal and zinc, the alkaline earth metal may be included in an amount of about 0.01 atomic % to about 30 atomic %, about 0.01 atomic % to about 20 atomic %, about 1 atomic % to about 19 atomic %, about 5 atomic % to about 18 atomic %, about 10 atomic % to about 17 atomic %, or about 11 atomic % to about 16 atomic %.

[0136] For example, the alkaline earth metal-containing oxide nanoparticles may be represented as Zn 1-x Q x O (where Q is Be, Mg, Ca, Ba, Sr, Re, or any combination thereof, and 0 < x < 0.5). For example, Q may include Mg. Alternatively or additionally, 0.01 ≤ x ≤ 0.3, 0.01 ≤ x ≤ 0.2, 0.01 ≤ x ≤ 0.19, 0.05 ≤ x ≤ 0.18, 0.10 ≤ x ≤ 0.17, or 0.11 ≤ x ≤ 0.16.

[0137] The alkaline earth metal-containing oxide nanoparticles may be synthesized, for example, by a sol-gel method or a solution precipitation method, in which during the synthesis process, the conversion process from the metal precursor to the metal hydroxide and the growth rate of the metal precursor into the oxide nanoparticles can be effectively controlled to reduce the defects inside the oxide nanoparticles, thereby allowing them to have adjusted and improved shapes and sizes.

[0138] For example, the alkaline earth metal-containing oxide nanoparticles may uniformly grow to have a smaller and more spherical shape, for example, satisfying the valley depth (VD) expressed by the relationship Equation 1.

[0139] Relational equation 1

[0140]

[0141] In the relation Equation 1,

[0142] Abs 峰 is the absorbance at the peak of the UV-Vis absorption spectrum, and

[0143] Abs 谷 It is the absorbance at the lowest point of the valley adjacent to the peak in the UV-Vis absorption spectrum.

[0144] In the relational equation 1, the valley may be a region indicating a valley-shaped absorbance variation near a peak in the UV-Vis absorption spectrum, and Abs 谷 It may be the absorbance at the lowest point (inflection point). For example, in a normalized UV-Vis absorption spectrum in which the absorbance at the peak of the UV-Vis absorption spectrum is normalized to 1, Abs 谷 It can be defined as the difference between the absorbance at the peak (maximum absorbance) and the absorbance at the lowest point of the valley (minimum absorbance). For example, in the UV-Vis absorption spectrum, the peak wavelength may be about 250 nm to about 340 nm, and within the range of about 270 nm to about 330 nm or about 280 nm to about 330 nm.

[0145] The valley depth (VD) represented by the relationship Equation 1 can be used to evaluate the uniformity of the nanoparticles, wherein a higher valley depth (VD) can be predicted to result in higher uniformity of the nanoparticles.

[0146] For example, the valley depth (VD) may satisfy the relationship Equation 1a.

[0147] Relational Equation 1a

[0148]

[0149] For example, the valley depth (VD) may satisfy the relationship Equation 1b.

[0150] Relational equation 1b

[0151]

[0152] For example, the valley depth (VD) may satisfy the relationship Equation 1c.

[0153] Relational equation 1c

[0154]

[0155] For example, the valley depth (VD) may satisfy the relationship Equation 1d.

[0156] Relational equation 1d

[0157]

[0158] The average circularity (C) of the alkaline earth metal-containing oxide nanoparticles is an average value obtained by dividing the area of the oxide nanoparticles by the square of the perimeter and multiplying the result by 4π, and can be a criterion for indicating whether the shape of the oxide nanoparticles is close to a perfect sphere. As the average circularity (C) is closer to 1, the oxide nanoparticles may be closer to a perfect spherical shape.

[0159] For example, the alkaline earth metal-containing oxide nanoparticles can have an average particle diameter of less than or equal to about 2.2 nm, and within the ranges of about 1.2 nm to about 2.2 nm, about 1.2 nm to about 2.1 nm, about 1.2 nm to about 2.0 nm, about 1.4 nm to about 2.2 nm, about 1.4 nm to about 2.1 nm, about 1.4 nm to about 2.0 nm, about 1.5 nm to about 2.2 nm, about 1.5 nm to about 2.1 nm, or about 1.5 nm to about 2.0 nm. The standard deviation of the average particle diameter can be less than or equal to about 0.70, for example, about 0.10 to about 0.70 or about 0.20 to about 0.65.

[0160] For example, the average circularity of the alkaline earth metal-containing oxide nanoparticles can be greater than or equal to about 0.70, and within the ranges of about 0.70 to about 1.00, about 0.70 to about 0.95, about 0.70 to about 0.90, about 0.71 to about 0.89, about 0.72 to about 0.88, or about 0.73 to about 0.87. The standard deviation of the average circularity can be less than or equal to about 0.10, for example, about 0.001 to about 0.10.

[0161] For example, the alkaline earth metal-containing oxide nanoparticles can form relatively large aggregates. For example, the average particle diameter of the aggregates of the alkaline earth metal-containing oxide nanoparticles measured by dynamic light scattering (DLS) can be from about 6 nm to about 15 nm, and within the range of from about 8 nm to about 15 nm, from about 8 nm to about 14 nm, or from about 10 nm to about 13 nm.

[0162] Therefore, compared to relatively large and non-uniform alkaline earth metal-containing oxide nanoparticles, the alkaline earth metal-containing oxide nanoparticles with adjusted and improved shape and size obtained by controlling the growth rate of the oxide nanoparticles during synthesis can have firmly and uniformly bound surface ligands, thereby improving the electrical properties of the electron assist layer 16 including the alkaline earth metal-containing oxide nanoparticles.

[0163] The thickness of the electron assist layer 16 can be, for example, about 5 nm to about 100 nm, and within the ranges about 10 nm to about 80 nm, about 15 nm to about 80 nm, about 15 nm to about 60 nm, or about 20 nm to about 50 nm.

[0164] Hereinafter, a method of manufacturing the aforementioned quantum dot light emitting device 10 is described.

[0165] An example of a method for manufacturing the aforementioned quantum dot light-emitting device 10 according to some embodiments includes: forming an anode 11 on a substrate (not shown), sequentially forming hole auxiliary layers 14 and 15 on the anode 11, forming a quantum dot light-emitting layer 13 on the hole auxiliary layer 15, forming an electron auxiliary layer 16 on the quantum dot light-emitting layer 13, and forming a cathode 12 on the electron auxiliary layer 16.

[0166] The formation of the hole assisting layers 14 and 15, the formation of the quantum dot light emitting layer 13, and the formation of the electron assisting layer 16 may each include a solution process such as spin coating, slit coating, inkjet printing, nozzle printing, spray coating, doctor blade coating, or a combination thereof, but is not limited thereto.

[0167] At least a portion of each process of forming the hole auxiliary layers 14 and 15, forming the quantum dot light-emitting layer 13, and forming the electron auxiliary layer 16 may further include optional drying, heat treatment after the solution process, or a combination thereof, and the heat treatment may be performed, for example, at about 50°C to about 300°C for about 1 minute to about 10 hours, but the present disclosure is not limited thereto.

[0168] As an example, the formation of the electron assist layer 16 may include synthesizing the above-mentioned alkaline earth metal-containing oxide nanoparticles, dispersing the synthesized alkaline earth metal-containing oxide nanoparticles in a dispersion medium to prepare an alkaline earth metal-containing oxide nanoparticle dispersion, and coating the alkaline earth metal-containing oxide nanoparticle dispersion on the quantum dot light-emitting layer 13.

[0169] The synthesis of alkaline earth metal-containing oxide nanoparticles can be performed, for example, by a sol-gel method or a solution precipitation method, wherein the dispersion medium can be, for example, water; an alcohol such as methanol, ethanol, propanol, or butanol; or any combination thereof, but is not limited thereto.

[0170] For example, the synthesis of alkaline earth metal-containing oxide nanoparticles may include preparing a precursor dispersion including an alkaline earth metal precursor, preparing an alkaline reagent solution including an alkaline reagent, and adding the alkaline reagent solution dropwise into the precursor dispersion at a controlled rate to grow alkaline earth metal-containing oxide nanoparticles having adjusted and improved shape and size.

[0171] In addition to the alkaline earth metal precursor, the precursor dispersion may further include a metal precursor containing other metals other than the alkaline earth metal, for example, at least one selected from a zinc precursor, a cobalt precursor, a nickel precursor, a gallium precursor, a zirconium precursor, a tungsten precursor, a titanium precursor, a tantalum precursor, a tin precursor, and a hafnium precursor, for example, further including a zinc precursor. For example, the ratio of the alkaline earth metal precursor and the zinc precursor can be adjusted by taking into account the atomic ratio of the alkaline earth metal and zinc in the alkaline earth metal-containing oxide nanoparticles. For example, more zinc precursor can be included than the alkaline earth metal precursor. For example, based on the total molar number of the alkaline earth metal precursor and the zinc precursor, the amount of the alkaline earth metal precursor can be about 0.01 to about 30 mol%, about 0.01 to about 20 mol%, about 1 to about 19 mol%, about 5 to about 18 mol%, about 10 to about 17 mol%, or about 11 to about 16 mol%.

[0172] The alkaline agent may include an alkali metal hydroxide, such as CsOH, RbOH, KOH, NaOH, LiOH, or any combination thereof. The alkaline agent may be prepared as an alkaline agent solution, for example, by dissolving the alkaline agent in water; an alcohol such as methanol, ethanol, propanol, or butanol; or any combination thereof.

[0173] The alkaline agent solution can be added dropwise to the precursor dispersion at a controlled rate. Herein, adding at a controlled rate can refer to providing it dropwise to the precursor dispersion at a constant rate, for example, slowly adding dropwise at a rate of less than or equal to about 1.5 mmol / min, and within the range of about 0.1 mmol / min to about 1.5 mmol / min, about 0.2 mmol / min to about 1.2 mmol / min, about 0.3 mmol / min to about 1.2 mmol / min, about 0.4 mmol / min to about 1.2 mmol / min, about 0.1 mmol / min to about 1.0 mmol / min, about 0.2 mmol / min to about 1.0 mmol / min, about 0.3 mmol / min to about 1.0 mmol / min, about 0.4 mmol / min to about 1.0 mmol / min, about 0.1 mmol / min to about 0.8 mmol / min, about 0.2 mmol / min to about 0.8 mmol / min, about 0.3 mmol / min to about 0.8 mmol / min, or about 0.4 mmol / min to about 0.8 mmol / min.

[0174] In this manner, adding the alkaline agent dropwise to the precursor dispersion at a controlled rate can effectively control the conversion process from the alkaline earth metal precursor to the alkaline earth metal hydroxide and the growth rate of the alkaline earth metal precursor to the alkaline earth metal-containing oxide nanoparticles, thereby effectively reducing defects within the oxide nanoparticles, thereby obtaining alkaline earth metal oxide nanoparticles with adjusted and improved shape and size. For example, the obtained alkaline earth metal oxide nanoparticles can have a smaller size and higher uniformity and can satisfy the relationship equation 1.

[0175] The aforementioned quantum dot light-emitting device 10 can be applied to a variety of electronic devices, such as display devices or lighting devices. For example, the aforementioned quantum dot light-emitting device 10 can be applied to a variety of electronic devices that require light emission, for example, it can be applied to a variety of electronic devices such as display devices such as televisions (TVs), monitors, computers, laptop computers, mobile devices, etc., or lighting devices such as light sources.

[0176] Hereinafter, the embodiments are described in more detail with reference to Examples. However, these Examples are exemplary, and the scope of the claims is not limited thereto.

[0177] Preparation of quantum dots

[0178] Preparation Example 1

[0179] 1. Synthesis of Core Quantum Dots

[0180] Selenium (Se) and tellurium (Te) were dispersed in trioctylphosphine (TOP) to prepare a 2 molar (M) Se / TOP stock solution and a 0.1 M Te / TOP stock solution, respectively. In a reactor containing trioctylamine, 0.125 mmol of zinc acetate and oleic acid were combined and then heated at 120°C under vacuum. After 1 hour, the atmosphere in the reactor was replaced with nitrogen.

[0181] After heating the reactor to 300°C, a Se / TOP stock solution and a Te / TOP stock solution with a Te / Se molar ratio of 1 / 20 were rapidly injected into it. When the reaction was complete, the reaction solution was quickly cooled to room temperature, acetone was added thereto, and then centrifuged to obtain a precipitate. The precipitate was dispersed in toluene to obtain a ZnSeTe quantum dot dispersion.

[0182] 2. Synthesis of Core-Shell Quantum Dots

[0183] In a flask containing trioctylamine, 1.8 mmol of zinc acetate was combined with oleic acid and then vacuum treated at 120°C for 10 minutes. The interior of the flask was replaced with nitrogen (N2) and heated to 180°C. Subsequently, the ZnSeTe quantum dot dispersion obtained above was quickly injected thereinto, and 1.2 mol of Se / TOP and 1.8 mol of Zn oleate were injected thereinto, and the temperature was raised to 340°C to form a ZnSe quantum dot shell on the surface of the ZnSeTe quantum dots. Subsequently, 2.8 mol of S / TOP and 3.6 mol of Zn oleate were additionally injected thereinto to react and form a ZnS quantum dot shell on the ZnSe quantum dot shell. Subsequently, the nanocrystals obtained after the reaction were dispersed in toluene to obtain a ZnSeTe / ZnSe / ZnS core-shell quantum dot dispersion.

[0184] 3. Surface exchange reaction

[0185] Zinc chloride was dissolved in ethanol to obtain a zinc chloride solution having a concentration of 10 wt %. 0.01 milliliter (mL) of the zinc chloride solution was added to the obtained ZnSeTe / ZnSe / ZnS core-shell quantum dot dispersion, followed by stirring at 60° C. for 30 minutes to perform a surface exchange reaction. After the reaction, ethanol was added thereto to cause precipitation, and the precipitate therefrom was centrifuged, and the precipitation and centrifugation were repeated several times to obtain halogenated (halogen-treated) ZnSeTe / ZnSe / ZnS core-shell quantum dots.

[0186] 4. Preparation of Quantum Dot Dispersion

[0187] The obtained ZnSeTe / ZnSe / ZnS core-shell quantum dots were precipitated with ethanol, collected by centrifugation, and dispersed in octane to prepare a quantum dot dispersion.

[0188] Preparation of oxide nanoparticles

[0189] Preparation Example 2

[0190] 0.9 mmol magnesium acetate tetrahydrate, 5.1 mmol zinc acetate dihydrate and 75mL dimethyl sulfoxide are added to the reactor, then stirred under N2 environment to prepare the precursor dispersion. Separately, CsOH is dissolved in ethanol with a concentration of 0.4 M to prepare an alkaline reagent solution. Subsequently, the alkaline reagent solution is dropwise added to the precursor dispersion at a rate of 0.4 mmol / min, while stirring. This process takes 60 minutes. An alkaline environment with a pH of about 8 to 12 is manufactured by the dropwise addition of the alkaline reagent solution. Subsequently, the resulting mixture is stirred at room temperature for another 60 minutes to obtain grown Zn 0.85 Mg 0.15 O nanoparticles.

[0191] The volume ratio of the grown Zn 0.85 Mg 0.15 The O nanoparticles and ethyl acetate were centrifuged and then dispersed in ethanol at a concentration of 1 wt % to obtain an alkaline earth metal oxide nanoparticle dispersion.

[0192] Preparation Example 3

[0193] An alkaline earth metal oxide nanoparticle dispersion was obtained in the same manner as in Preparation Example 2, except that Zn was obtained by adding an alkaline reagent solution dropwise to the precursor dispersion at a rate of 0.8 mmol / min. 0.85 Mg 0.15 O nanoparticles.

[0194] Preparation Comparative Example 1

[0195] 0.9 mmol magnesium acetate tetrahydrate, 5.1 mmol zinc acetate dihydrate and 75mL dimethyl sulfoxide are added to the reactor, then stirred under N2 environment to prepare the precursor dispersion. Separately, CsOH is dissolved in ethanol with a concentration of 0.4 M to prepare an alkaline reagent solution. Subsequently, the alkaline reagent solution is sprayed (spray) onto the precursor dispersion. An alkaline environment with a pH of about 8 to 12 is manufactured by the spraying of the alkaline reagent solution. Subsequently, the resulting mixture is stirred in addition for 60 minutes to obtain the Zn grown while keeping room temperature. 0.85 Mg 0.15 O nanoparticles.

[0196] The volume ratio of the grown Zn 0.85 Mg 0.15 The O nanoparticles and ethyl acetate were centrifuged and then dispersed in ethanol at a concentration of 1 wt % to obtain an alkaline earth metal oxide nanoparticle dispersion.

[0197] Preparation Comparative Example 2

[0198] 9.00 mmol zinc acetate dihydrate and 90 mL dimethyl sulfoxide are added to the reactor and then stirred under N2 environment to prepare a precursor dispersion. Separately, CsOH is dissolved in ethanol at a concentration of 0.4 M to prepare an alkaline reagent solution. Subsequently, the alkaline reagent solution is dropwise added to the precursor dispersion at a rate of 0.5 mmol / min. An alkaline environment with a pH of approximately 8 to 12 is manufactured by dropwise addition of the alkaline reagent solution. Subsequently, the resulting mixture is stirred for 60 minutes to obtain grown ZnO nanoparticles while maintaining room temperature.

[0199] The grown ZnO nanoparticles and ethyl acetate were centrifuged at a volume ratio of 1:9 and then dispersed in ethanol at a concentration of 1 wt % to obtain a ZnO nanoparticle dispersion.

[0200] Evaluation I

[0201] The average particle size and morphology of the alkaline earth metal oxide nanoparticles according to Preparation Examples 2 and 3 and Comparative Preparation Example 1 were evaluated.

[0202] The average particle size of the alkaline earth metal oxide nanoparticles was evaluated using a UT F30 Tecnai electron microscope.

[0203] The average circularity of the alkaline earth metal oxide nanoparticles is calculated based on the value obtained from the TEM image, and specifically, is an average value obtained by dividing the area of each alkaline earth metal oxide nanoparticle by the square of its perimeter and multiplying by 4π.

[0204] The average particle diameter of the aggregates of the alkaline earth metal oxide nanoparticles was evaluated by dynamic light scattering (DLS).

[0205] The results are shown in Tables 1 and 2 and Figure 2 and 3 middle.

[0206] Figure 2 is a TEM photograph of the alkaline earth metal oxide nanoparticles prepared in Example 3, and Figure 3 is a TEM photograph of the alkaline earth metal oxide nanoparticles prepared in Comparative Example 1.

[0207] Table 1

[0208]

[0209] Table 2

[0210]

[0211] Reference Figure 2 and 3 As well as Tables 1 and 2, the alkaline earth metal oxide nanoparticles included in the alkaline earth metal oxide nanoparticle dispersions according to Preparation Examples 2 and 3 grew more uniformly than the alkaline earth metal oxide nanoparticles included in the alkaline earth metal oxide nanoparticle dispersion according to Comparative Preparation Example 1.

[0212] Evaluation II

[0213] The alkaline earth metal oxide nanoparticle dispersions (solutions) according to Preparation Examples 2 and 3 and Comparative Preparation Example 1 were respectively subjected to UV-Vis spectroscopy analysis.

[0214] The results are shown in Figure 4 and 5 And Table 3.

[0215] Figure 4 is a graph showing normalized UV-Vis absorption spectra of the alkaline earth metal oxide nanoparticles according to Preparation Examples 2 and 3 and Comparative Preparation Example 1; and Figure 5 yes Figure 4 A magnified view of the valley region of the UV-Vis absorption spectrum. Figure 5 middle, Figure 4 The peak wavelength is displayed as 0 nm wavelength.

[0216] Table 3

[0217]

[0218] *Valley Depth (VD): 1 - (Abs 谷 / Abs 峰 )

[0219] *Abs 峰 is the absorbance at the peak of the UV-Vis absorption spectrum

[0220] *Abs 谷 is the absorbance at the lowest point of the valley adjacent to the peak in the UV-Vis absorption spectrum

[0221] Reference Figure 4 and 5 As shown in Table 3, the alkaline earth metal oxide nanoparticles according to Preparation Examples 2 and 3 have a high valley depth in the valley region of the UV-Vis spectrum compared with the alkaline earth metal oxide nanoparticles according to Preparation Comparative Example 1, which confirms that the alkaline earth metal oxide nanoparticles of Preparation Examples 2 and 3 grow more uniformly than the alkaline earth metal oxide nanoparticles of Preparation Comparative Example 1.

[0222] Evaluation III

[0223] The growth rate of the alkaline earth metal oxide nanoparticles according to the dropwise addition of the alkaline reagent solution was evaluated.

[0224] Figure 6 is a graph showing UV-Vis spectra according to the dropping time in minutes of the alkaline reagent solution during the synthesis of the alkaline earth metal oxide nanoparticles according to Preparation Examples 2 and 3.

[0225] Reference Figure 6 , the alkaline earth metal oxide nanoparticles according to Preparation Examples 2 and 3 gradually grew according to the dropwise addition of the alkaline reagent solution during the synthesis, and thus it was confirmed that the growth rate of the particles can be controlled according to the dropwise rate of the alkaline reagent solution.

[0226] Fabrication of sample devices

[0227] Example 1

[0228] The quantum dot dispersion according to Preparation Example 1 was spin-coated on a glass substrate having an ITO electrode and then heat-treated at 80°C for 30 minutes to form a 28 nm thick quantum dot light-emitting layer. Subsequently, the alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 2 was spin-coated at 80°C for 30 minutes on the quantum dot light-emitting layer to form a 20 nm thick electron-assisting layer, thereby manufacturing a sample device.

[0229] Example 2

[0230] A sample device was manufactured in the same manner as in Example 1, except that the alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 3 was used instead of the alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 2.

[0231] Comparative Example 1

[0232] A sample device was manufactured in the same manner as in Example 1, except that the alkaline earth metal oxide nanoparticle dispersion according to Comparative Preparation Example 1 was used instead of the alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 2.

[0233] Evaluation IV

[0234] Photoluminescence lifetime characteristics of the sample devices according to Examples 1 and 2 and Comparative Example 1 were evaluated by irradiating light having a wavelength of 395 nm.

[0235] The results are shown in Figure 7 middle.

[0236] Figure 7 is a graph showing the photoluminescence lifetime characteristics of the sample devices according to Examples 1 and 2 and Comparative Example 1.

[0237] Reference Figure 7, compared with the sample device according to Comparative Example 1, the sample devices according to Examples 1 and 2 exhibit sufficient photoluminescence lifetime characteristics due to less quenching.

[0238] Fabrication of Quantum Dot Light-Emitting Devices I

[0239] Example 3

[0240] The glass substrate on which the ITO anode was deposited was surface treated with UV-ozone for 15 minutes, and a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) solution was spin-coated, heat-treated at 150°C for 10 minutes in an air atmosphere, and then heat-treated again at 150°C for 30 minutes in an N2 atmosphere to form a 30 nm thick lower hole-assisting layer. Then, a poly[(9,9-dioctylfluorene-2,7-diyl-co-(4,4'-(N-4-butylphenyl)diphenylamine)] solution (TFB, Sumitomo) was spin-coated on the lower hole-assisting layer and heat-treated at 180°C for 30 minutes to form a 25 nm thick upper hole-assisting layer. On the upper hole-assisting layer, the quantum dot dispersion of Example 1 was spin-coated and heat-treated at 80°C for 30 minutes to form a 20 nm thick lower quantum dot light-emitting layer. Subsequently, a lower quantum dot light-emitting layer was formed on the lower hole-assisting layer. On the light-emitting layer, the quantum dot dispersion according to Preparation Example 1 was spin-coated and heat-treated at 80°C for 30 minutes to form a 30nm thick upper quantum dot light-emitting layer. Then, the alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 2 was spin-coated on the upper quantum dot light-emitting layer and heat-treated at 80°C for 30 minutes to form a 20nm thick electron-assisting layer. Al was then vacuum-deposited to a thickness of 100nm on the electron-assisting layer to form a cathode (WF: 4.2eV), thereby manufacturing a quantum dot light-emitting device.

[0241] Comparative Example 2

[0242] A quantum dot light-emitting device was manufactured in the same manner as in Example 3, except that the alkaline earth metal oxide nanoparticle dispersion according to Comparative Preparation Example 1 was used instead of the alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 2.

[0243] Comparative Example 3

[0244] A quantum dot light-emitting device was manufactured in the same manner as in Example 3, except that the ZnO nanoparticle dispersion according to Comparative Preparation Example 2 was used instead of the alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 2.

[0245] Rating V

[0246] The electrical characteristics, luminescent characteristics, and lifespan characteristics of the quantum dot light-emitting devices according to Example 3 and Comparative Examples 2 and 3 were evaluated.

[0247] The electrical characteristics and luminescence characteristics of the quantum dot light-emitting device were measured by using a current-voltage-luminance measurement device (Keithley 2200, Minolta CS200).

[0248] The lifetime characteristics of the quantum dot light emitting device are evaluated by measuring the decrease in brightness from the initial brightness as follows: the injection of the quantum dot light emitting device is sufficient to show a brightness of 650 candela / m2 (cd / m 2 ) or nit brightness condition current, where T 90 、T 70 and T 50 The time taken to display 90%, 70%, and 50% of the initial luminance was evaluated.

[0249] The results are shown in Table 4.

[0250] Table 4

[0251]

[0252] *EQE max : Maximum external quantum efficiency

[0253] *EQE 650nt : External quantum efficiency at 650 nits

[0254] *Lum max : Maximum luminous brightness

[0255] *The initial voltage is also called the driving voltage.

[0256] Referring to Table 4, the quantum dot light-emitting device according to Example 3 exhibited improved electrical characteristics, luminescent characteristics, and lifetime characteristics compared to the quantum dot light-emitting device according to Comparative Example 2. In addition, the quantum dot light-emitting device of Comparative Example 3, which included ZnO nanoparticles as an electron-assisting material, exhibited deteriorated electrical characteristics, luminescent characteristics, and lifetime characteristics compared to the quantum dot light-emitting device according to Example 3.

[0257] Fabrication of Quantum Dot Light-Emitting Devices II

[0258] Example 4

[0259] After the glass substrate with the ITO anode deposited thereon was surface treated with UV-ozone for 15 minutes, an ink containing PEDOT:PSS was spin-coated thereon, heat-treated at 150°C for 10 minutes in an air atmosphere, and then heat-treated again at 150°C for 30 minutes in an N2 atmosphere to form a 140 nm thick lower hole-assisting layer. Subsequently, on the lower hole auxiliary layer, an ink including poly[(9,9-dioctylfluorenyl-2,7-diyl-co-(4,4'-(N-4-butylphenyl)diphenylamine)] (TFB) was spin-coated and heat-treated at 180°C for 30 minutes to form a 35 nm thick upper hole auxiliary layer. Subsequently, on the upper hole auxiliary layer, a quantum dot dispersion according to Preparation Example 1 was spin-coated and heat-treated at 140°C for 30 minutes to form a 30 nm thick quantum dot light-emitting layer. On the quantum dot light-emitting layer, an alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 2 was spin-coated and heat-treated at 140°C for 30 minutes to form a 50 nm thick electron auxiliary layer. On the electron auxiliary layer, Al was vacuum-deposited to form a 100 nm thick cathode (WF: 4.2 eV), thereby manufacturing a quantum dot light-emitting device.

[0260] Comparative Example 4

[0261] A quantum dot light-emitting device was manufactured in the same manner as in Example 4, except that the alkaline earth metal oxide nanoparticle dispersion according to Comparative Preparation Example 1 was used instead of the alkaline earth metal oxide nanoparticle dispersion according to Preparation Example 2.

[0262] Evaluation VI

[0263] The electrical characteristics, luminescent characteristics, and lifespan characteristics of the quantum dot light-emitting devices according to Example 4 and Comparative Example 4 were evaluated.

[0264] The results are shown in Table 5.

[0265] Table 5

[0266]

[0267] *EQE@20000nt: External quantum efficiency at 20,000 nits

[0268] Referring to Table 5, the quantum dot light emitting device according to Example 4 exhibited improved electrical characteristics, luminescent characteristics, and lifespan characteristics compared to the quantum dot light emitting device according to Comparative Example 4.

[0269] While the present disclosure has been described with respect to what are presently considered to be practical example embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

1. A method for manufacturing a quantum dot light-emitting device, comprising: Forming an anode, forming a quantum dot light-emitting layer on the anode, forming an electron auxiliary layer on the quantum dot light-emitting layer, wherein the electron auxiliary layer comprises oxide nanoparticles containing alkaline earth metals, and forming a cathode on the electron assisting layer, The forming of the electron auxiliary layer comprises: preparing a precursor dispersion comprising an alkaline earth metal precursor, preparing an alkaline reagent solution containing an alkaline reagent, adding the alkaline reagent solution to the precursor dispersion by dropwise addition at a controlled rate to grow alkaline earth metal-containing oxide nanoparticles, dispersing the alkaline earth metal-containing oxide nanoparticles in a dispersion medium to prepare an alkaline earth metal-containing oxide nanoparticle dispersion, and The alkaline earth metal-containing oxide nanoparticle dispersion is coated on the quantum dot light-emitting layer.

2. The method of claim 1, wherein the alkaline agent comprises an alkali metal hydroxide.

3. The method of claim 2, wherein the alkali metal hydroxide comprises CsOH, RbOH, KOH, NaOH, LiOH, or any combination thereof. 4 . The method according to claim 1 , wherein the alkaline reagent solution is added by dropwise addition at a rate of 0.1 mmol / min to 1.5 mmol / min. The method according to claim 4 , wherein the alkaline reagent solution is added by dropwise addition at a rate of 0.2 mmol / min to 1.2 mmol / min. The method of claim 1 , wherein the precursor dispersion comprises a zinc precursor.

7. The method according to claim 1, wherein the alkaline earth metal-containing oxide nanoparticles satisfy the relationship Equation 1: Relational equation 1 in, In the relation Equation 1, Abs 峰 is the absorbance at the peak of the UV-visible absorption spectrum, and Abs 谷 It is the absorbance at the lowest point of the valley adjacent to the peak in the UV-visible absorption spectrum. 8 . The method according to claim 1 , wherein the alkaline earth metal-containing oxide nanoparticles have an average particle diameter of 1.2 nm to 2.2 nm. 9 . The method of claim 1 , wherein an average particle diameter of the aggregates of the alkaline earth metal-containing oxide nanoparticles measured by dynamic light scattering is 6 to 15 nanometers. 10 . The method of claim 1 , wherein the alkaline earth metal-containing oxide nanoparticles have an average circularity of 0.70 to 1.

00.

11. Quantum dot light-emitting device, comprising: anode and cathode, a quantum dot light-emitting layer between the anode and the cathode, and An electron-assisting layer between the cathode and the quantum dot light-emitting layer, wherein the electron-assisting layer comprises oxide nanoparticles containing alkaline earth metals, The alkaline earth metal oxide nanoparticles satisfy the relationship equation 1: Relational equation 1 Where, in the relation equation 1, Abs 峰 is the absorbance at the peak of the UV-visible absorption spectrum, and Abs 谷 It is the absorbance at the lowest point of the valley adjacent to the peak in the UV-visible absorption spectrum. 12 . The quantum dot light-emitting device according to claim 11 , wherein the average particle diameter of the alkaline earth metal-containing oxide nanoparticles is 1.2 nm to 2.2 nm. 13 . The quantum dot light-emitting device according to claim 11 , wherein an average particle diameter of the aggregates of the alkaline earth metal-containing oxide nanoparticles measured by dynamic light scattering is 6 to 15 nanometers. The quantum dot light-emitting device according to claim 11 , wherein the average circularity of the alkaline earth metal-containing oxide nanoparticles is 0.70 to 1.

00. The quantum dot light-emitting device according to claim 11 , wherein the alkaline earth metal is magnesium. The quantum dot light-emitting device of claim 11 , wherein the alkaline earth metal-containing oxide nanoparticles comprise zinc. The quantum dot light-emitting device according to claim 16 , wherein the amount of the alkaline earth metal included in the alkaline earth metal-containing oxide nanoparticles is 0.01 to 30 atomic % based on the total amount of atoms of the alkaline earth metal and zinc.

18. The quantum dot light-emitting device according to claim 11, wherein the alkaline earth metal-containing oxide nanoparticles comprise elements Cs, Rb, K, Na, Li, or a combination thereof, or a salt thereof. The quantum dot light-emitting device according to claim 11 , comprising a hole assisting layer between the anode and the quantum dot light-emitting layer, wherein the hole assisting layer comprises an organic material.

20. An electronic device comprising the quantum dot light-emitting device according to any one of claims 11 to 19.

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