Quantum dot device, manufacturing method thereof, and electronic device

Abstract

Disclosed are a quantum dot device, a method for manufacturing the same, and an electronic device. The quantum dot device includes a first electrode and a second electrode, a quantum dot layer disposed between the first electrode and the second electrode, an electron transport layer disposed between the quantum dot layer and the second electrode and including first inorganic nanoparticles and a first organic material, and an electron injection layer disposed between the electron transport layer and the second electrode and including second inorganic nanoparticles and a second organic material, wherein the ratio by weight of the amount of the second organic material in the electron injection layer to the total amount of the second inorganic nanoparticles and the second organic material is less than the ratio by weight of the amount of the first organic material in the electron transport layer to the total amount of the first inorganic nanoparticles and the first organic material.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2020-0017693, filed on February 13, 2020, in the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Quantum dot devices and electronic devices are disclosed. Background Art

[0004] Unlike bulk (bulk) materials, the intrinsic (inherent) physical properties of nanoparticles (e.g., band gap, melting point, etc.) can be controlled by varying the size of the nanoparticles. For example, semiconductor nanocrystal particles, also known as quantum dots, can be supplied with light or electrical energy and can emit light at a wavelength corresponding to the size of the quantum dots. Thus, quantum dots can be used as light emitters configured to emit light of a predetermined wavelength. Summary of the Invention

[0005] Quantum dots can be used as light emitters in devices and have been the subject of recent research.However, quantum dots differ from conventional light emitters and therefore new methods of improving the performance of quantum dot devices are needed.

[0006] One embodiment provides quantum dot devices capable of achieving improved performance.

[0007] Another embodiment provides an electronic device including the quantum dot device.

[0008] According to one embodiment, a quantum dot device includes: a first electrode and a second electrode, a quantum dot layer between the first electrode and the second electrode, an electron transport layer between the quantum dot layer and the second electrode and including first inorganic nanoparticles and a first organic material, and an electron injection layer between the electron transport layer and the second electrode and including second inorganic nanoparticles and second organic materials, wherein the ratio by weight of the amount of the second organic material in the electron injection layer to the total amount of the second inorganic nanoparticles and the second organic material is less than the ratio by weight of the amount of the first organic material in the electron transport layer to the total amount of the first inorganic nanoparticles and the first organic material.

[0009] The ratio of the second organic material in the electron injection layer to the total amount of the second inorganic nanoparticles and the second organic material may be about 0.01 to about 0.8 times the ratio of the first organic material in the electron transport layer to the total amount of the first inorganic nanoparticles and the first organic material.

[0010] An amount of the second organic material in the electron injection layer may be less than or equal to about 25 weight percent (wt %) based on the total amount of the second inorganic nanoparticles and the second organic material.

[0011] A LUMO energy level of the electron injection layer may be shallower than a work function of the second electrode and deeper than a LUMO energy level of the electron transport layer.

[0012] The first inorganic nanoparticles may be made of Zn 1-x Q x The metal oxide nanoparticles represented by O, wherein Q is at least one metal excluding Zn, and 0≤x<0.5.

[0013] The at least one metal Q may include Mg, Co, Ni, Ga, Al, Ca, Zr, W, Li, Ti, Ta, Sn, Hf, Si, Ba, or combinations thereof.

[0014] The second inorganic nanoparticles may be metal oxide nanoparticles dispersible in water, alcohol, or a combination thereof.

[0015] The second inorganic nanoparticles may be metal oxide nanoparticles including at least one of Ti, Ce, Sn, Mg, Zr, W, and Al.

[0016] The first inorganic nanoparticles may be made of Zn 1-x Q x The metal oxide nanoparticles represented by Q are Q, wherein Q is at least one metal excluding Zn, and 0≤x<0.5, and the second inorganic nanoparticles may be different from the first inorganic nanoparticles and may be metal oxide nanoparticles including at least one of Ti, Ce, Sn, Mg, Zr, W and Al.

[0017] The electron injection layer may be thinner than the electron transport layer.

[0018] The electron injection layer may have a thickness of less than or equal to about 10 nm.

[0019] The electron injection layer may be in contact with the second electrode.

[0020] According to another embodiment, a quantum dot device includes: a first electrode and a second electrode, a quantum dot layer between the first electrode and the second electrode, and an electron injection layer between the second electrode and the quantum dot layer and including inorganic nanoparticles and an organic material, wherein the amount of the organic material in the electron injection layer is less than or equal to about 25 weight percent based on the total amount of the inorganic nanoparticles and the organic material.

[0021] The inorganic nanoparticles in the electron injection layer may be metal oxide nanoparticles including at least one of Ti, Ce, Sn, Mg, Zr, W, and Al.

[0022] The quantum dot device may further include an electron transport layer between the quantum dot layer and the electron injection layer, and the electron transport layer may include Zn 1-x Q x The metal oxide nanoparticles represented by O, wherein Q is at least one metal excluding Zn, and 0≤x<0.5, and the inorganic nanoparticles in the electron injection layer may be metal oxide nanoparticles including at least one of Ti, Ce, Sn, Mg, Zr, W and Al.

[0023] The electron transport layer may further include an organic material, and an amount of the organic material in the electron injection layer may be smaller than an amount of the organic material in the electron transport layer.

[0024] The electron injection layer may have a thickness of less than or equal to about 10 nm.

[0025] The electron injection layer may be in contact with the second electrode.

[0026] According to another embodiment, a method for manufacturing a quantum dot device includes: forming a first electrode, forming a quantum dot layer on the first electrode, forming an electron transport layer including first inorganic nanoparticles on the quantum dot layer, forming an electron injection layer including second inorganic nanoparticles on the electron transport layer, and forming a second electrode on the electron injection layer, wherein forming the electron injection layer includes: preparing a first dispersion including the second inorganic nanoparticles and a first amount of organic material, removing at least a portion of the organic material from the first dispersion to prepare a second dispersion including a second amount of organic material less than the first amount of organic material, and coating the second dispersion on the electron transport layer.

[0027] The method may further include providing a polar dispersion medium to the second dispersion before applying the second dispersion, the polar dispersion medium being water, alcohol, or a combination thereof.

[0028] An amount of the organic material (excluding the dispersion medium) in the second dispersion may be less than or equal to about 25 wt % based on the total amount of the second inorganic nanoparticles and the organic material.

[0029] According to another embodiment, an electronic device including the quantum dot device is provided.

[0030] The characteristics of the quantum dot device can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a schematic cross-sectional view of a quantum dot device according to an embodiment,

[0032] Figure 2 is a transmission electron microscope (TEM) photograph of the electron injection layer in the EOD device according to Example A, and

[0033] Figure 3 is a graph showing current characteristics of the electronic only devices (EOD) according to Example A and Comparative Example A-1. DETAILED DESCRIPTION

[0034] 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 can be embodied in many different forms and is not to be construed as limited to the example embodiments set forth herein.

[0035] In the accompanying drawings, the thickness of layers, films, panels, regions, etc., is exaggerated for clarity. In the specification, the same reference numerals represent the same elements throughout. It will be understood that when an element, such as a layer, film, region, or substrate, is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements.

[0036] Hereinafter, the term "combination" includes a mixture or a stacked structure of two or more.

[0037] Hereinafter, the term "metal" includes metals and semimetals.

[0038] The term "substituted" refers to a compound in which a hydrogen, such as a hydrogen on a ring carbon or an amine hydrogen, is replaced by deuterium, -F, -Cl, -Br, -I, -SF5, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C1-C 60 Alkyl, substituted or unsubstituted C2-C 60 Alkenyl, substituted or unsubstituted C2-C 60 Alkynyl, substituted or unsubstituted C1-C 60 Alkoxy, substituted or unsubstituted C3-C 10 Cycloalkyl, substituted or unsubstituted C1-C 10 Heterocycloalkyl, substituted or unsubstituted C3-C 10 Cycloalkenyl, substituted or unsubstituted C1-C 10 Heterocycloalkenyl, substituted or unsubstituted C6-C 60 Aryl, substituted or unsubstituted C6-C 60 Aryloxy, substituted or unsubstituted C6-C 60Arylthio, substituted or unsubstituted C1-C 60 a heteroaryl group, a substituted or unsubstituted monovalent non-aromatic fused polycyclic group, or a substituted or unsubstituted monovalent non-aromatic fused heteropolycyclic group.

[0039] Hereinafter, the work function, HOMO energy level, or LUMO energy level is expressed as an absolute value from the vacuum energy level. In addition, when the work function, HOMO energy level, or LUMO energy level is said to be "deep," "high," or "large," the absolute value is large based on the vacuum energy level of "0 eV," and when the work function, HOMO energy level, or LUMO energy level is said to be "shallow," "low," or "small," the absolute value is small based on the vacuum energy level of "0 eV."

[0040] Hereinafter, the HOMO energy level is obtained by measuring the photoelectric work function of a thin film having a thickness of about 20 nm to about 30 nm using an AC-3 device (Riken Keiki Co. Ltd.), and calculating the emission energy due to the photoelectron effect of the radiated energy by the following relational equation in the range of about 7.0 eV to about 4 eV.

[0041] [Relational equation]

[0042] E=h·c / λ

[0043] (h: Planck's constant, c: speed of light, and λ: wavelength)

[0044] The LUMO energy level may be a value measured by ultraviolet photoelectron spectroscopy (UPS).

[0045] Hereinafter, a quantum dot device according to an embodiment is described with reference to the accompanying drawings.

[0046] Figure 1 is a schematic cross-sectional view of a quantum dot device according to an embodiment.

[0047] refer to Figure 1 According to an embodiment, a quantum dot device 10 includes: a first electrode 11 and a second electrode 12 facing each other; a quantum dot layer 13 between the first electrode 11 and the second electrode 12; a hole transport layer 14 and a hole injection layer 15 between the first electrode 11 and the quantum dot layer 13; and an electron transport layer 16 and an electron injection layer 17 between the second electrode 12 and the quantum dot layer 13.

[0048] A substrate (not shown) may be provided below the first electrode 11 or on the second electrode 12. The substrate may be made of, for example, an inorganic material such as glass; an organic material such as polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyethersulfone, or a combination thereof; or a silicon wafer. The substrate may be omitted.

[0049] One of the first electrode 11 and the second electrode 12 is an anode and the other is a cathode. For example, the first electrode 11 may be an anode and the second electrode 12 may be a cathode. For example, the first electrode 11 may be a cathode and the second electrode 12 may be an anode.

[0050] The anode may include a conductor having a high work function, such as a metal, a conductive metal oxide, or a combination thereof. The anode may include, for example, a metal such as nickel, platinum, vanadium, chromium, copper, zinc, or gold, or an alloy thereof; a conductive metal oxide such as zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide; or a combination of a metal and an oxide such as ZnO and Al, or SnO2 and Sb, but is not limited thereto.

[0051] The cathode may include a conductor having a lower work function than the anode, and may include, for example, a metal, a conductive metal oxide, and / or a conductive polymer. The cathode may include, for example, a metal such as aluminum, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, silver, tin, lead, cesium, barium, or the like, or an alloy thereof; a multilayer structure such as LiF / Al, Li2O / Al, Liq / Al, LiF / Ca, and BaF2 / Ca, but is not limited thereto.

[0052] The work function of the anode may be higher than the work function of the cathode. For example, the work function of the anode may be about 4.5 eV to about 5.0 eV, and the work function of the cathode may be about 4.0 eV to about 4.7 eV. Within this range, the work function of the anode may be, for example, about 4.6 eV to about 4.9 eV or about 4.6 eV to about 4.8 eV, and the work function of the cathode may be, for example, about 4.0 eV to about 4.6 eV or about 4.3 eV to about 4.6 eV.

[0053] At least one of the first electrode 11 and the second electrode 12 may be a light-transmitting electrode, and the light-transmitting electrode may be made of, for example, 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. When one of the first electrode 11 and the second electrode 12 is a non-light-transmitting electrode, it may be made of, for example, an opaque conductor such as aluminum (Al), silver (Ag), or gold (Au).

[0054] The quantum dot layer 13 includes quantum dots. The quantum dots may be semiconductor nanocrystals and may have various shapes, such as spherical semiconductor nanocrystals, quantum rods, or quantum sheets. Here, the quantum rods may be quantum dots having an aspect ratio (length to diameter ratio) (length to width ratio) greater than about 1, such as 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 quantum rods may have an aspect ratio of less than or equal to about 50, less than or equal to about 30, or less than or equal to about 20.

[0055] The quantum dots can have a particle diameter (average maximum particle length for non-spherical shapes), for example, from about 1 nm to about 100 nm, from about 1 nm to about 80 nm, from about 1 nm to about 50 nm, or from about 1 nm to 20 nm.

[0056] The energy band gap of quantum dots can be controlled according to their size and composition, and thus the emission wavelength can be controlled. For example, when the size of quantum dots increases, the quantum dots may have a narrow energy band gap and thus be configured to emit light in a relatively long wavelength region, while when the size of quantum dots decreases, the quantum dots may have a wide energy band gap and thus be configured to emit light in a relatively short wavelength region.

[0057] For example, the quantum dots may be configured to emit light in a predetermined wavelength region in the visible light region according to their size and / or composition. For example, the quantum dots may be configured to emit blue light, red light, or green light, and the blue light may have a peak emission wavelength (λ) of, for example, about 430 nm to about 480 nm. 最大 ), the red light may have a peak emission wavelength (λ 最大 ), and the green light may have a peak emission wavelength (λ 最大 ).

[0058] For example, the average particle size of quantum dots configured to emit blue light can be, for example, less than or equal to about 4.5 nm, and, for example, 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. Within a range, for example, the average particle size of the quantum dots can be from about 2.0 nm to about 4.5 nm, such as 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.

[0059] The quantum dots can have a quantum yield of, for example, about 10% or greater, about 20% or greater, about 30% or greater, about 50% or greater, about 60% or greater, about 70% or greater, or about 90% or greater.

[0060] The quantum dots may have a relatively narrow full width at half maximum (FWHM), which is the width corresponding to half the wavelength of the peak absorption point. When the FWHM is narrow, the quantum dots may be configured to emit light in a narrow wavelength region and achieve higher color purity. The quantum dots may have a FWHM of, for example, about 50 nm or less, about 49 nm or less, about 48 nm or less, about 47 nm or less, about 46 nm or less, about 45 nm or less, about 44 nm or less, about 43 nm or less, about 42 nm or less, about 41 nm or less, about 40 nm or less, about 39 nm or less, about 38 nm or less, about 37 nm or less, about 36 nm or less, about 35 nm or less, about 34 nm or less, about 33 nm or less, about 32 nm or less, about 31 nm or less, about 30 nm or less, about 29 nm or less, or about 28 nm or less. Within the range, it can have a FWHM of, for example, 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.

[0061] For example, the quantum dots may include a II-VI semiconductor compound, a III-V semiconductor compound, a IV-VI semiconductor compound, a IV semiconductor, a I-III-VI semiconductor compound, a I-II-IV-VI semiconductor compound, a II-III-V semiconductor compound, or a combination thereof. The II-VI semiconductor compound may be, for example, selected from: a binary compound such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, or a mixture thereof; a ternary compound such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnO, or a mixture thereof; Te, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or mixtures thereof; and quaternary compounds such as HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or mixtures thereof, but are not limited thereto. The III-V semiconductor compound may be, for example, selected from: binary compounds such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or mixtures thereof; ternary compounds such as GaNPs, GaNAs, GaNSb, GaPAs, GaPSb, AlNPs, AlNAs, AlNSb, AlPAs, AlPSb, InNPs, InNAs, InNSb, InPAs, InPSb, or mixtures thereof; and quaternary compounds such as GaAlNPs, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNPs, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNPs, InAlNAs, InAlNSb, InAlPAs, InAlPSb, or mixtures thereof, but are not limited thereto. The IV-VI semiconductor compound may be, for example, selected from: binary compounds such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or mixtures thereof; ternary compounds such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or mixtures thereof; and quaternary compounds such as SnPbSSe, SnPbSeTe, SnPbSTe, or mixtures thereof, but are not limited thereto.The Group IV semiconductor may be, for example, selected from: elemental (mono) semiconductors such as Si, Ge, or mixtures thereof; and binary semiconductor compounds such as SiC, SiGe, and mixtures thereof, but not limited thereto. The Group I-III-VI semiconductor compound may be, for example, CuInSe2, CuInS2, CuInGaSe, CuInGaS, or mixtures thereof, but not limited thereto. The Group I-II-IV-VI semiconductor compound may be, for example, CuZnSnSe, CuZnSnS, or mixtures thereof, but not limited thereto. The Group II-III-V semiconductor compound may include, for example, InZnP, but not limited thereto.

[0062] The quantum dots may include the elemental semiconductor, the binary semiconductor compound, the ternary semiconductor compound, or the quaternary semiconductor compound in a substantially uniform concentration or a locally different concentration distribution.

[0063] For example, the quantum dots may include cadmium-free (Cd) quantum dots. Cadmium-free quantum dots are quantum dots that do not include cadmium (Cd). 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 used.

[0064] As an example, the quantum dots may be a semiconductor compound including zinc (Zn), and at least one of tellurium (Te) and selenium (Se). For example, the quantum dots may be a Zn-Te semiconductor compound, a Zn-Se semiconductor compound, and / or a Zn-Te-Se semiconductor compound. For example, the amount of tellurium (Te) in the Zn-Te-Se semiconductor compound may be less than the amount of selenium (Se). The semiconductor compound may have a peak emission wavelength (λ) in a wavelength region less than or equal to about 480 nm, for example, about 430 nm to about 480 nm. 最大 ), and can be configured to emit blue light.

[0065] For example, the quantum dots may be a semiconductor compound including indium (In), and at least one of zinc (Zn) and phosphorus (P). For example, the quantum dots may be an In-P semiconductor compound and / or an In-Zn-P semiconductor compound. 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. The semiconductor compound may have a peak emission wavelength (λ) in a wavelength region less than about 700 nm, for example, about 600 nm to about 650 nm. 最大 ), and can be configured to emit red light.

[0066] The quantum dot 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 the shell may have a concentration gradient at the interface, wherein the concentration of the element of the shell decreases toward the core. For example, the material composition of the shell of the quantum dot has a higher energy band gap than the material composition of the core of the quantum dot, and thus the quantum dot may exhibit a quantum confinement effect.

[0067] The quantum dot may have a quantum dot core and a multi-layer quantum dot shell surrounding the core. Here, the multi-layer shell has at least two shells, wherein each shell may be a single composition, an alloy, and / or have a concentration gradient.

[0068] For example, a shell of a multi-layer shell farther from the core 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.

[0069] For example, a quantum dot having a core-shell structure may, for example, include: a core comprising a first semiconductor compound, the first semiconductor compound comprising zinc (Zn), and at least one of tellurium (Te) and selenium (Se); and a shell comprising a second semiconductor compound disposed on at least a portion of the core and having a composition different from the composition of the core.

[0070] For example, the first semiconductor compound may be a Zn-Te-Se based semiconductor compound including zinc (Zn), tellurium (Te) and selenium (Se), for example, a Zn-Se based semiconductor compound including a small amount of tellurium (Te), for example, a ZnTe-Se based semiconductor compound. x Se 1-x A semiconductor compound represented by wherein x is greater than approximately 0 and less than or equal to 0.05.

[0071] For example, in a first semiconductor compound based on Zn-Te-Se, the molar amount of zinc (Zn) may be higher than the molar amount of selenium (Se), and the molar amount of selenium (Se) may be higher than the molar amount 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, less than or equal to about 0.04, or less than or equal to about 0.04. 29, 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, 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 0.010.

[0072] 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 a 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.

[0073] For example, the second semiconductor compound may include zinc (Zn), selenium (Se), and / or sulfur (S). For example, the shell may include ZnSeS, ZnSe, ZnS, or a 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. The inner shell may include ZnSeS, ZnSe, or a combination thereof, 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 one moves away from the core.

[0074] For example, a quantum dot having a core-shell structure may include: a core, the core including a third semiconductor compound, the third semiconductor compound including indium (In), and at least one of zinc (Zn) and phosphorus (P); and a shell disposed on at least a portion of the core and including a fourth semiconductor compound having a composition different from that of the core.

[0075] In the third In-Zn-P based semiconductor compound, a molar ratio of zinc (Zn) to indium (In) may be greater than or equal to about 25. For example, in the third In-Zn-P based semiconductor compound, the molar ratio of zinc (Zn) to indium (In) may be greater than or equal to about 28, greater than or equal to about 29, or greater than or equal to about 30. For example, in the third In-Zn-P based semiconductor compound, the molar ratio of zinc (Zn) to indium (In) may be less than or equal to about 55, for example, less than or equal to about 50, less than or equal to about 45, less than or equal to about 40, less than or equal to about 35, less than or equal to about 34, less than or equal to about 33, or less than or equal to about 32.

[0076] 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 a 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.

[0077] For example, the fourth semiconductor compound may include zinc (Zn) and sulfur (S), and optionally selenium (Se). For example, the shell may include ZnSeS, ZnSe, ZnS, or a 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.

[0078] Quantum dot layer 13 can have a thickness of, for example, about 5 nm to about 200 nm, within the range, for example, about 10 nm to about 150 nm, for example, about 10 nm to about 100 nm, for example, about 10 nm to about 50 nm.

[0079] The quantum dot layer 13 may have a relatively deep HOMO energy level, for example, a HOMO energy level of greater than or equal to about 5.4 eV, within the range, for example, greater than or equal to about 5.5 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. Within the range, the HOMO energy level of the quantum dot layer 13 can be, for example, about 5.4 eV to about 7.0 eV, for example, about 5.4 eV to about 6.8 eV, for example, about 5.4 eV to about 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, and within the range, for example, about 5.5 eV to about 7.0 eV, for example, about 5.5 eV to about 6.8 eV, for example, about 5.5eV to about 6.7eV, for example, about 5.5eV to about 6.5eV, for example, about 5.5eV to about 6.3eV, for example, about 5.5eV to about 6.2eV, for example, about 5.5eV to about 6.1eV, for example, about 5.5eV to about 7.0eV, for example, about 5.6eV to about 6.8eV, for example, about 5.6eV to about 6.7eV, for example, about 5.6eV to about 6.5eV, for example, about 5.6eV to about 6.3eV, for example, about 5.6eV to about 6.2eV, for example, about 5 .6eV to about 6.1eV, within the range, for example, about 5.7eV to about 7.0eV, for example, about 5.7eV to about 6.8eV, for example, about 5.7eV 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 range, for example, about 5.8eV to about 7.0eV, for example, about 5.8eV to about 6.8eV, for example, about 5.8 eV 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 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.

[0080] The quantum dot layer 13 may have a relatively shallow LUMO energy level, for example, less than or equal to about 3.7 eV, within the range, 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, for example, less than or equal to about 3.0 eV. Within the range, the LUMO energy level of the quantum dot layer 13 may be about 2.5 eV to about 3.7 eV, about 2.5 eV to about 3.6 eV, about 2.5 eV to about 3.5 eV, about 2.5 eV to about 3.4 eV, about 2.5 eV to about 3.3 eV, about 2.5 eV to about 3.2 eV, about 2.5 eV to about 3.1 eV, about 2.5 eV to about 3.0 eV, about 2.5 eV to about 3.7 eV, about 2.5 eV to about 3.6 eV, about 2.5 eV to about 3.5 eV, about 2.5 eV to about 3.4 eV, about 2.5 eV to about 3.3 eV, about 2.5 eV to about 3.2 eV, about 2.5 eV to about 3.1 eV, about 2.5 eV to about 3.0 eV, about 2.5 eV to about 3. 8eV to about 3.7eV, about 2.8eV to about 3.6eV, about 2.8eV to about 3.5eV, about 2.8eV to about 3.4eV, about 2.8eV to about 3.3eV, about 2.8eV to about 3.2eV, about 3.0eV to about 3.7eV, about 3.0eV to about 3.6eV, about 3.0eV to about 3.5eV, or about 3.0eV to about 3.4eV.

[0081] The quantum dot layer 13 may have an energy band gap of about 1.7 eV to about 2.3 eV or about 2.4 eV to about 2.9 eV. Within this range, for example, the quantum dot layer 13 may have an energy band gap of about 1.8 eV to about 2.2 eV or about 2.4 eV to about 2.8 eV, and within this range, for example, about 1.9 eV to about 2.1 eV, such as about 2.4 eV to about 2.7 eV.

[0082] The hole transport layer 14 and the hole injection layer 15 are disposed between the first electrode 11 and the quantum dot layer 13. The hole transport layer 14 is disposed between the first electrode 11 and the quantum dot layer 13 and close to the quantum dot layer 13, and the hole injection layer 15 is disposed between the first electrode 11 and the quantum dot layer 13 and close to the first electrode 11. The hole injection layer 15 can facilitate the injection of holes from the first electrode 11, and the hole injection layer 15 can efficiently transfer the injected holes to the quantum dot layer 13. The hole transport layer 14 and the hole injection layer 15 can each have one or two or more layers, and in a broad sense, can include an electron blocking layer.

[0083] The hole transport layer 14 and the hole injection layer 15 may each have a HOMO energy level between the work function of the first electrode 11 and the HOMO energy level of the quantum dot layer 13. For example, the work function of the first electrode 11, the HOMO energy level of the hole injection layer 15, the HOMO energy level of the hole transport layer 14, and the HOMO energy level of the quantum dot layer 13 may gradually deepen and may be, for example, stepped.

[0084] The hole transport layer 14 may have a relatively deep HOMO energy level to match the HOMO energy level of the quantum dot layer 13. Therefore, the mobility of holes transferred from the hole transport layer 14 to the quantum dot layer 13 may be improved.

[0085] The HOMO energy level of the hole transport layer 14 may be equal to the HOMO energy level of the quantum dot layer 13 or less than the HOMO energy level of the quantum dot layer 13 within a range of about 1.0 eV or less. For example, the difference between the HOMO energy levels of the hole transport layer 14 and the quantum dot layer 13 may be from about 0 eV to about 1.0 eV, within the range, for example, from about 0.01 eV to about 0.8 eV, within the range, for example, from about 0.01 eV to about 0.7 eV, within the range, for example, from about 0.01 eV to about 0.5 eV, within the range, for example, from about 0.01 eV to about 0.4 eV, for example, from about 0.01 eV to about 0.3 eV, for example, from about 0.01 eV to about 0.2 eV, for example, from about 0.01 eV to about 0.1 eV.

[0086] The HOMO energy level of the hole transport layer 14 may be, for example, greater than or equal to about 5.0 eV, within the range, for example, greater than or equal to about 5.2 eV, within the range, for example, greater than or equal to about 5.4 eV, within the range, for example, greater than or equal to about 5.6 eV, within the range, for example, greater than or equal to about 5.8 eV.

[0087] For example, the HOMO energy level of the hole transport layer 14 can be from about 5.0 eV to about 7.0 eV, within the above range, for example, from about 5.2 eV to about 6.8 eV, within the above range, 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, for example, from about 5.6 eV to about 7.0 eV, for example, from 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.

[0088] The hole transport layer 14 and the hole injection layer 15 may include materials satisfying the energy level without particular limitation, and may include, for example, at least one selected from the group consisting of poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine (poly TPD), polyarylamine (polyarylamine), poly(N-vinylcarbazole), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), polyaniline, polypyrrole, N,N,N',N'-tetrakis(4-methoxyphenyl)-benzidine (TPD), 4,4'-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), m-MTDATA (4,4',4"-tris[phenyl(m-tolyl)amino]triphenylamine), 4,4',4"-tris(N-carbazolyl)-triphenylamine (TCTA), 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), p-type metal oxides (e.g., NiO, WO3, MoO3, etc.), carbon-based materials such as graphene oxide, and combinations thereof, but not limited thereto.

[0089] One or both of the hole transport layer 14 and the hole injection layer 15 may be omitted.

[0090] The electron transport layer 16 and the electron injection layer 17 are disposed between the second electrode 12 and the quantum dot layer 13. The electron transport layer 16 is disposed between the second electrode 12 and the quantum dot layer 13 near the quantum dot layer 13, and the electron injection layer 17 is disposed between the second electrode 12 and the quantum dot layer 13 near the second electrode 12. The electron injection layer 17 can facilitate the injection of electrons from the second electrode 12, and the electron transport layer 16 can efficiently transfer the injected electrons to the quantum dot layer 13. The electron transport layer 16 and the electron injection layer 17 can each have one or two or more layers, and can broadly include a hole blocking layer.

[0091] For example, the electron injection layer 17 may be in contact with the second electrode 12 .

[0092] For example, the electron transport layer 16 may be in contact with the quantum dot layer 13 .

[0093] For example, the electron transport layer 16 and the electron injection layer 17 may be in contact with each other.

[0094] For example, the LUMO energy levels of the second electrode 12, the electron injection layer 17, the electron transport layer 16, and the quantum dot layer 13 may gradually become shallower. For example, the LUMO energy level of the electron injection layer 17 may be shallower than the work function of the second electrode 12, the LUMO energy level of the electron transport layer 16 may be shallower than the LUMO energy level of the electron injection layer 17, and the LUMO energy level of the quantum dot layer 13 may be shallower than the LUMO energy level of the electron transport layer 16. That is, the work function of the second electrode 12, the LUMO energy level of the electron injection layer 17, the LUMO energy level of the electron transport layer 16, and the LUMO energy level of the quantum dot layer 13 may have step-wise (cascade) energy levels that gradually decrease in one direction.

[0095] The electron transport layer 16 may include first inorganic nanoparticles. The first inorganic nanoparticles may be, for example, oxide nanoparticles, and may be, for example, metal oxide nanoparticles.

[0096] The first inorganic nanoparticles may be two-dimensional or three-dimensional nanoparticles having an average particle diameter of less than or equal to about 10 nm, within the range of less than or equal to about 8 nm, less than or equal to about 7 nm, less than or equal to about 5 nm, less than or equal to about 4 nm, or less than or equal to about 3.5 nm, or within the range of about 1 nm to about 10 nm, about 1 nm to about 9 nm, about 1 nm to about 8 nm, about 1 nm to about 7 nm, about 1 nm to about 5 nm, about 1 nm to about 4 nm, or about 1 nm to about 3.5 nm.

[0097] For example, the first inorganic nanoparticles may be metal oxide nanoparticles, and the metal oxide nanoparticles include at least one of the following: zinc (Zn), magnesium (Mg), cobalt (Co), nickel (Ni), gallium (Ga), aluminum (Al), calcium (Ca), zirconium (Zr), tungsten (W), lithium (Li), titanium (Ti), tantalum (Ta), tin (Sn), hafnium (Hf), and barium (Ba).

[0098] As an example, the first inorganic nanoparticles may include metal oxide nanoparticles including zinc (Zn), and may include a Zn 1-x Q x Metal oxide nanoparticles represented by Q (0≤x<0.5). Here, Q is at least one metal other than Zn, such as magnesium (Mg), cobalt (Co), nickel (Ni), gallium (Ga), aluminum (Al), calcium (Ca), zirconium (Zr), tungsten (W), lithium (Li), titanium (Ti), tantalum (Ta), tin (Sn), hafnium (Hf), silicon (Si), barium (Ba), or a combination thereof.

[0099] For example, Q may include magnesium (Mg).

[0100] For example, x may be within the range of 0.01≤x≤0.3, eg, 0.01≤x≤0.2.

[0101] For example, the electron transport layer 16 may include first inorganic nanoparticles and / or aggregates thereof.

[0102] The electron transport layer 16 may further include an organic material. The organic material may be a material included in the synthesis step of the first inorganic nanoparticles, or may be a material additionally supplied to the dispersion including the first inorganic nanoparticles. For example, the material included in the synthesis step of the first inorganic nanoparticles may be an organic counter anion (counter anion) of a salt included as a precursor of the first inorganic nanoparticles. For example, the organic material additionally supplied to the dispersion including the first inorganic nanoparticles may be, for example, a dispersant for preventing aggregation of the first inorganic nanoparticles, or an auxiliary agent for controlling the electrical properties of the electron transport layer 16.

[0103] The organic material may be derived from, for example, acetate; carbonyl; carboxylate; acetylacetonate; organic amine; or a combination thereof, but is not limited thereto. The organic amine may include, for example, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or a combination thereof, and may include, for example, trimethylamine, triethylamine, tripropylamine, tributylamine, or a combination thereof, but is not limited thereto.

[0104] The organic material in the electron transport layer 16 may be disposed on the surface of the first inorganic nanoparticles and / or between adjacent first inorganic nanoparticles to prevent or reduce aggregation of the first inorganic nanoparticles. Therefore, by effectively preventing aggregation of the first inorganic nanoparticles in the dispersion for the electron transport layer including the first inorganic nanoparticles, the dispersibility of the first inorganic nanoparticles can be improved.

[0105] The organic material in the electron transport layer 16 may be in an amount of greater than or equal to about 20 wt %, for example, greater than or equal to about 23 wt %, greater than or equal to about 25 wt %, greater than or equal to about 26 wt %, greater than or equal to about 27 wt %, greater than or equal to about 28 wt %, greater than or equal to about 30 wt %, greater than or equal to about 32 wt %, greater than or equal to about 35 wt %, greater than or equal to about 38 wt %, greater than or equal to about 40 wt %, greater than or equal to about 42 wt %, or greater than or equal to about 45 wt %, based on the total amount of the first inorganic nanoparticles and the organic material (excluding the dispersion medium) in the electron transport layer 16. Within the range, the organic material in the electron transport layer 16 can be in an amount of about 20 wt % to about 70 wt %, about 23 wt % to about 70 wt %, about 25 wt % to about 70 wt %, about 26 wt % to about 70 wt %, about 27 wt % to about 70 wt %, about 28 wt % to about 70 wt %, about 30 wt % to about 70 wt %, about 32 wt % to about 70 wt %, about 35 wt % to about 70 wt %, about 38 wt % to about 70 wt %, about 40 wt % to about 70 wt %, about 42 wt % to about 70 wt %, about 45 wt % to about 70 wt %, about 20 wt % to about 60 wt %, about 23 wt % to about 60 wt %, about 25 wt % to about 60 wt %, about 26 wt % to about 60 wt %, about 27 wt % to about %, about 25 wt % to about 50 wt %, about 26 wt % to about 50 wt %, about 27 wt % to about 50 wt %, about 28 wt % to about 60 wt %, about 30 wt % to about 60 wt %, about 32 wt % to about 60 wt %, about 35 wt % to about 60 wt %, about 38 wt % to about 60 wt %, about 40 wt % to about 60 wt %, about 42 wt % to about 60 wt %, or about 45 wt % to about 60 wt %, about 20 wt % to about 50 wt %, about 23 wt % to about 50 wt %, about 25 wt % to about 50 wt %, about 26 wt % to about 50 wt %, about 27 wt % to about 50 wt %, about 28 wt % to about 50 wt %, about 30 wt % to about 50 wt %, about 32 wt % to about 50 wt %, about 35 wt % to about 50 wt %, about 38 wt % to about 50 wt %, or about 40 wt % to about 50 wt %.

[0106] By including an organic material within the above range in the electron transport layer 16, aggregation of the first inorganic nanoparticles in the first inorganic nanoparticle dispersion including the first inorganic nanoparticles can be effectively prevented, thereby effectively improving the dispersibility of the first inorganic nanoparticles and ultimately improving the coating performance, morphology and electrical properties of the electron transport layer 16.

[0107] The LUMO energy level of the electron transport layer 16 may be a value between the LUMO energy level of the quantum dot layer 13 and the LUMO energy level of the electron injection layer 17 to be described later, and may be about 3.2 eV to about 4.8 eV, about 3.2 eV to about 4.6 eV, about 3.2 eV to about 4.5 eV, about 3.2 eV to about 4.3 eV, about 3.2 eV to about 4.1 eV, about 3.4 eV to 4.1 eV, about 3.5 eV to about 4.6 eV, about 3.6 eV to about 4.6 eV, about 3.6 eV to about 4.3 eV, about 3.6 eV to about 4.1 eV, about 3.6 eV to about 3.9 eV, about 3.7 eV to about 4.6 eV, about 3.7 eV to about 4.3 eV, about 3.7 eV to about 4.1 eV, or about 3.7 eV to about 3.9 eV.

[0108] The thickness of electron transport layer 16 can be greater than about 10 nm and less than or equal to about 80 nm, and within the range, greater than about 10 nm and less than or equal to about 70 nm, greater than about 10 nm and less than or equal to about 60 nm, greater than about 10 nm and less than or equal to about 50 nm, greater than about 10 nm and less than or equal to about 40 nm, or greater than about 10 nm and less than or equal to about 30 nm.

[0109] The electron injection layer 17 may include second inorganic nanoparticles different from the first inorganic nanoparticles. The second inorganic nanoparticles may be, for example, oxide nanoparticles, and may be, for example, metal oxide nanoparticles. The second inorganic nanoparticles may be selected taking into account the relationship between the LUMO energy levels of the electron transport layer 16 and the electron injection layer 17. The second inorganic nanoparticles may be selected so that the LUMO energy level of the electron injection layer 17 including the second inorganic nanoparticles is deeper than the LUMO energy level of the electron transport layer 16 including the first inorganic nanoparticles.

[0110] The second inorganic nanoparticles may be two-dimensional or three-dimensional nanoparticles having an average particle diameter of less than or equal to about 10 nm, within the range of less than or equal to about 9 nm, less than or equal to about 8 nm, less than or equal to about 7 nm, less than or equal to about 5 nm, less than or equal to about 4 nm, or less than or equal to about 3.5 nm, or within the range of about 1 nm to about 10 nm, about 1 nm to about 9 nm, about 1 nm to about 8 nm, about 1 nm to about 7 nm, about 1 nm to about 5 nm, about 1 nm to about 4 nm, or about 1 nm to about 3.5 nm.

[0111] For example, the second inorganic nanoparticles may be hydrophilic metal oxide nanoparticles dispersible in a polar dispersion medium, wherein the polar dispersion medium may be, for example, water; an alcohol such as methanol, ethanol, propanol, and butanol; or a combination thereof. The second inorganic nanoparticles may have a higher dispersibility in the dispersion medium than the first inorganic nanoparticles, and such higher dispersibility may be due to interactions between the second inorganic nanoparticles, such as binding energy, van der Waals energy, and repulsion, but the present disclosure is not limited thereto.

[0112] The second inorganic nanoparticles may be selected from materials having a higher dispersibility in the dispersion medium than the first inorganic nanoparticles, and may be, for example, metal oxide nanoparticles of at least one metal selected from titanium (Ti), cerium (Ce), tin (Sn), magnesium (Mg), zirconium (Zr), tungsten (W), and aluminum (Al). The second inorganic nanoparticles may be, for example, TiO2, CeO2, SnO2, MgO, ZrO2, WO3, Al2O3, or a combination thereof, but are not limited thereto.

[0113] The electron injection layer 17 may further include an organic material. The organic material in the electron injection layer 17 may be the same as or different from the organic material in the electron transport layer 16. The organic material may be, for example, a material included in the synthesis step of the second inorganic nanoparticles, and may be derived from an organic counter anion of a salt included as a precursor of the second inorganic nanoparticles, such as acetate (acetate), carbonyl, carboxylate (carboxylate), acetylacetonate (acetylacetonate), organic amine (organic amine salt), or a combination thereof, but not limited thereto. Here, the organic amine may include, for example, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C6-C20 aryl group, or a combination thereof, and may include, for example, trimethylamine, triethylamine, tripropylamine, tributylamine, or a combination thereof, but not limited thereto.

[0114] The amount of the organic material in the electron injection layer 17 may be controlled to a predetermined amount or less. Although the organic material in the electron injection layer 17 may exhibit an effect of preventing or reducing aggregation of the second inorganic nanoparticles on the surface of the second inorganic nanoparticles and / or between adjacent second inorganic nanoparticles, an excessive (excessive) amount of the organic material in the electron injection layer 17 may interfere with the injection of electrons from the second electrode 12, thereby increasing the driving voltage of the quantum dot device 10 and reducing the life of the quantum dot device 10.

[0115] For example, in the step of preparing the dispersion of the second inorganic nanoparticles including the second inorganic nanoparticles, the amount of the organic material may be reduced by removing at least a portion of the organic material. Removal of the organic material may include, for example, centrifugation, precipitation using a solvent and / or dispersion medium, redistribution, and / or washing, but is not limited thereto.

[0116] In this way, by including the organic material in a controlled amount, the electron injection layer 17 can include less organic material than the electron transport layer 16. For example, the ratio by weight of the amount of the organic material in the electron injection layer 17 to the total amount of the second inorganic nanoparticles and the organic material can be less than the ratio by weight of the amount of the organic material in the electron transport layer 16 to the total amount of the first inorganic nanoparticles and the organic material. For example, the ratio by weight of the amount of the organic material in the electron injection layer 17 to the total amount of the second inorganic nanoparticles and the second organic material can be about 0.01 times to about 0.9 times, about 0.01 times to about 0.8 times, about 0.01 times to about 0.7 times, or about 0.01 times to about 0.5 times the ratio by weight of the amount of the organic material in the electron transport layer 16 to the total amount of the first inorganic nanoparticles and the first organic material, but is not limited thereto.

[0117] As described above, the second inorganic nanoparticles in the electron injection layer 17 can have a higher dispersibility in the dispersion medium than the first inorganic nanoparticles in the electron transport layer 16, and thus, even when the amount of the organic material in the electron injection layer 17 is controlled, excessive aggregation of the second inorganic nanoparticles can be prevented. In addition, as will be described later, since the electron injection layer 17 has a thin thickness of less than or equal to about 10 nm, even if the electron injection layer 17 has a controlled amount of the organic material, the influence on the coating performance, morphology, and electrical characteristics of the electron injection layer 17 can be negligible.

[0118] The amount of the organic material in the electron injection layer 17 can be controlled to a range that can prevent or reduce aggregation of the second inorganic nanoparticles while effectively improving electron injection from the second electrode 12. For example, the amount of the organic material in the electron injection layer 17 can be controlled to be less than or equal to about 25 wt % based on the total amount of the second inorganic nanoparticles and the organic material. Within this range, the amount of the organic material in the electron injection layer 17 can be controlled to be less than or equal to about 23 wt %, less than or equal to about 22 wt %, less than or equal to about 20 wt %, less than or equal to about 18 wt %, less than or equal to about 15 wt %, less than or equal to about 12 wt %, less than or equal to about 10 wt %, less than or equal to about 9 wt %, less than or equal to about 8 wt %, less than or equal to about 7 wt %, less than or equal to about 6 wt %, less than or equal to about 5 wt %, less than or equal to about 4 wt %, less than or equal to about 3 wt %, or less than or equal to about 2 wt % based on the total amount of the second inorganic nanoparticles and the organic material. Within the range, it can be controlled to about 1 weight % to about 25 weight %, about 1 weight % to about 23 weight %, about 1 weight % to about 22 weight %, about 1 weight % to about 20 weight %, about 1 weight % to about 18 weight %, about 1 weight % to about 15 weight %, about 1 weight % to about 12 weight %, about 1 weight % to about 10 weight %, about 1 weight % to about 9 weight %, about 1 weight % to about 8 weight %, about 1 weight % to about 7 weight %, about 1 weight % to about 6 weight %, about 1 weight % to about 5 weight %, about 1 weight % to about 4 weight %, about 1 weight % to about 3 weight %, or about 1 weight % to about 2 weight %.

[0119] The LUMO energy level of the electron injection layer 17 may be between the work function of the second electrode 12 and the LUMO energy level of the electron transport layer 16. For example, the difference between the work function of the second electrode 12 and the LUMO energy level of the electron injection layer 17 may be less than about 0.5 eV, about 0.001 eV to about 0.5 eV, about 0.001 eV to about 0.4 eV, or about 0.001 eV to about 0.3 eV. As an example, the difference between the LUMO energy level of the electron injection layer 17 and the LUMO energy level of the electron transport layer 16 may be less than about 0.5 eV, about 0.001 eV to about 0.5 eV, about 0.001 eV to about 0.4 eV, or about 0.001 eV to about 0.3 eV. Therefore, electrons can be easily injected from the second electrode 12 into the electron injection layer 17 to reduce the driving voltage of the quantum dot device 10, and electrons can be efficiently transferred from the electron injection layer 17 to the electron transport layer 16 to improve efficiency. Within the range satisfying the aforementioned energy levels, the LUMO energy level of the electron injection layer 17 may be about 3.4 eV to about 4.8 eV, about 3.4 eV to about 4.6 eV, about 3.4 eV to about 4.5 eV, about 3.6 eV to about 4.8 eV, about 3.6 eV to about 4.6 eV, about 3.6 eV to about 4.5 eV, about 3.6 eV to about 4.3 eV, about 3.9 eV to about 4.8 eV, about 3.9 eV to about 4.6 eV, about 3.9 eV to about 4.5 eV, or about 3.9 eV to about 4.3 eV.

[0120] The electron injection layer 17 may be thinner than the electron transport layer 16. For example, the thickness of the electron injection layer 17 may be about 0.01 times to about 0.8 times, about 0.01 times to about 0.7 times, about 0.01 times to about 0.5 times, about 0.1 times to about 0.8 times, about 0.1 times to about 0.7 times, or about 0.1 times to about 0.5 times the thickness of the electron transport layer 16. The thickness of the electron injection layer 17 may be, for example, less than or equal to about 10 nm, less than or equal to about 7 nm, or less than or equal to about 5 nm. Within the range, the thickness of the electron injection layer 17 may be about 1 nm to about 10 nm, about 1 nm to about 8 nm, about 1 nm to about 7 nm, or about 1 nm to about 5 nm.

[0121] The quantum dot device 10 includes an electron injection layer 17 including a controlled amount of organic material between the second electrode 12 and the electron transport layer 16, and thus electron injection can be effectively promoted, and the injected electrons can be effectively transferred to the quantum dot layer 13 through the electron transport layer 16. Therefore, the driving voltage of the quantum dot device 10 can be effectively reduced, thereby improving brightness and lifespan.

[0122] For example, the driving voltage (at 5 mA) of the quantum dot device 10 can be less than or equal to about 3.0 V, and within the range, less than or equal to about 2.9 V, less than or equal to about 2.8 eV, less than or equal to about 2.7 eV, less than or equal to about 2.6 eV, or less than or equal to about 2.5 eV. As an example, the driving voltage (at 5 mA) of the quantum dot device 10 can be about 0.1 eV to about 1.0 eV lower than the driving voltage (at 5 mA) of a quantum dot device that does not include the aforementioned electron injection layer 17, and within the above range, about 0.2 eV to about 0.9 eV, or about 0.3 eV to about 0.8 eV.

[0123] As an example, the brightness characteristics of the quantum dot device 10 can be improved by about 1.05 times to about 3 times, and within the range, about 1.1 times to about 3 times, or about 1.1 times to about 2.5 times, compared to a quantum dot device that does not include the aforementioned electron injection layer 17.

[0124] As an example, the lifetime characteristics (T95 or T80) of the quantum dot device 10 can be improved by about 1.5 times to about 20 times, and within the range, about 2 times to about 18 times, or about 3 times to about 15 times, compared to a quantum dot device that does not include the aforementioned electron injection layer 17.

[0125] For example, the method 10 for manufacturing a quantum dot device may include forming a first electrode 11 on a substrate (not shown), forming a hole injection layer 15, forming a hole transport layer 14, forming a quantum dot layer 13, forming an electron transport layer 16, forming an electron injection layer 17, and forming a second electrode 12. One or both of forming the hole injection layer 15 and forming the hole transport layer 14 may be omitted.

[0126] The quantum dot layer 13, the hole transport layer 14, the hole injection layer 15, the electron transport layer 16, and / or the electron injection layer 17 can be formed by solution processes such as spin coating, slit coating, inkjet printing, nozzle printing, spraying, and / or doctor blade coating, but is not limited thereto.

[0127] In at least some of the forming of the quantum dot layer 13, the forming of the hole transport layer 14, the forming of the hole injection layer 15, the forming of the electron transport layer 16, and / or the forming of the electron injection layer 17, drying and / or heat treatment may be further performed optionally after the solution process, 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 is not limited thereto.

[0128] For example, forming electron transport layer 16 may include applying a first inorganic nanoparticle dispersion comprising first inorganic nanoparticles, and optionally drying and / or heat treating the dispersion. The first inorganic nanoparticles may be obtained using a sol-gel synthesis method using metal salts, but is not limited thereto. The dispersion medium may be water; an alcohol such as methanol, ethanol, propanol, or butanol; or a combination thereof, but is not limited thereto. Forming electron transport layer 16 may also include centrifugation and / or washing.

[0129] For example, forming the electron injection layer 17 may include applying a second inorganic nanoparticle dispersion including second inorganic nanoparticles, and optionally drying and / or heat treating the dispersion. The second inorganic nanoparticles may be obtained using a sol-gel synthesis method using metal salts, but is not limited thereto. The dispersion medium may be water; an alcohol such as methanol, ethanol, propanol, or butanol; or a combination thereof, but is not limited thereto.

[0130] Forming the electron injection layer 17 may further include removing at least some of the excess organic material from the dispersion to control the amount of the organic material as described above. For example, forming the electron injection layer 17 may include preparing a first dispersion including second inorganic nanoparticles and a first amount of organic material (excess organic material), removing at least a portion of the organic material from the first dispersion to prepare a second dispersion including a second amount of organic material less than the first amount, and coating the second dispersion on the electron transport layer 16.

[0131] Removing at least a portion of the organic material from the first dispersion may include: further centrifuging one or more times (e.g., 1 to 10 times, 2 to 10 times, or 3 to 8 times), or further precipitating, redispersing, and / or washing one or more times (e.g., 1 to 10 times, 2 to 10 times, or 3 to 8 times) using at least one selected from a polar dispersion medium and / or a non-polar dispersion medium, the polar dispersion medium being, for example, water; an alcohol being, for example, methanol, ethanol, propanol, and butanol; or a combination thereof, the non-polar dispersion medium being, for example, hexane, cyclohexane, benzene, toluene, chloroform, diethyl ether, acetone, etc., or a combination thereof, but not limited thereto.

[0132] The amount of the organic material in the second dispersion (the second amount) can be less than or equal to about 80 weight percent, less than or equal to about 70 weight percent, less than or equal to about 50 weight percent, less than or equal to about 40 weight percent, less than or equal to about 30 weight percent, or less than or equal to about 20 weight percent, within the range of about 3 weight percent to about 80 weight percent, about 3 weight percent to about 70 weight percent, about 3 weight percent to about 50 weight percent, about 3 weight percent to about 40 weight percent, about 3 weight percent to about 30 weight percent, or about 3 weight percent to about 20 weight percent of the amount of the organic material in the first dispersion (the first amount).

[0133] For example, as described above, the amount of the organic material (the second amount) in the second dispersion can be controlled to be less than or equal to about 25 wt %, based on the total amount of the second inorganic nanoparticles and the organic material (excluding the dispersion medium). Within the range, the amount of the organic material (the second amount) can be controlled to be less than or equal to about 23 wt %, less than or equal to about 22 wt %, less than or equal to about 20 wt %, less than or equal to about 18 wt %, less than or equal to about 15 wt %, less than or equal to about 12 wt %, less than or equal to about 10 wt %, less than or equal to about 9 wt %, less than or equal to about 8 wt %, less than or equal to about 7 wt %, less than or equal to about 6 wt %, less than or equal to about 5 wt %, less than or equal to about 4 wt %, less than or equal to about 3 wt %, or less than or equal to about 2 wt %. %, and within the ranges from about 1 weight % to about 23 weight %, about 1 weight % to about 22 weight %, about 1 weight % to about 20 weight %, about 1 weight % to about 18 weight %, about 1 weight % to about 15 weight %, about 1 weight % to about 12 weight %, about 1 weight % to about 10 weight %, about 1 weight % to about 9 weight %, about 1 weight % to about 8 weight %, about 1 weight % to about 7 weight %, about 1 weight % to about 6 weight %, about 1 weight % to about 5 weight %, about 1 weight % to about 4 weight %, about 1 weight % to about 3 weight %, or about 1 weight % to about 2 weight %.

[0134] For example, the method may further include diluting the second dispersion before applying the second dispersion. Diluting the second dispersion may include, for example, further supplying a polar dispersion medium such as water, alcohol, or a combination thereof to the second dispersion, and for example, the polar dispersion medium may be additionally supplied at about 2 to about 10 times, about 2 to about 7 times, or about 2 to about 5 times the total volume of the second dispersion.

[0135] The aforementioned quantum dot device can be applied to various electronic devices requiring light emission, and can be applied to various electronic devices, for example, display devices such as TVs, monitors, computers, and mobile devices, or lighting devices such as light sources.

[0136] Hereinafter, the embodiments are described in more detail with reference to Examples. However, the following Examples are for illustrative purposes and do not limit the scope of rights.

[0137] Synthesis Example I: Synthesis of Quantum Dot Dispersion

[0138] Synthesis Example 1

[0139] (1) Synthesis of ZnTeSe core quantum dot dispersion

[0140] Selenium (Se) and tellurium (Te) were dispersed in trioctylphosphine (TOP) to obtain 2M Se / TOP stock solution and 0.1M Te / TOP stock solution, respectively.

[0141] 0.125 mmol of zinc acetate was placed in a reactor together with 0.25 mmol of oleic acid, 0.25 mmol of hexadecylamine and 10 mL of trioctylamine, and then heated under vacuum at 120° C. After 1 hour, the atmosphere in the reactor was changed to nitrogen.

[0142] After heating the reactor at 240°C, the Se / TOP stock solution and the Te / TOP stock solution having a Te / Se molar ratio of 1 / 25 were rapidly injected therein. The reaction solution was heated to 300°C and maintained for 30 minutes, then rapidly cooled to room temperature, acetone was added thereto, and the precipitate obtained therefrom by centrifugation was dispersed in toluene to obtain a ZnTeSe core quantum dot dispersion.

[0143] (2) Synthesis of ZnTeSe core / ZnSeS shell quantum dot dispersions

[0144] Trioctylamine was placed in a 10 mL flask. Subsequently, 0.6 mmol of zinc acetate and 1.2 mmol of oleic acid were added thereto, and then vacuum treated at 120 ° C for 10 minutes. The flask was then internally replaced with nitrogen (N2), and the ZnTeSe core quantum dot dispersion was quickly injected therein, and 2M Se / TOP and 1M S / TOP with a Se:S molar ratio of 1.2:2.8 were injected therein, and then heated to 340 ° C for reaction. When the reaction was complete, the reactor was cooled, the nanocrystals were centrifuged with ethanol, and then dispersed in toluene to obtain a ZnTeSe core / ZnSeS shell quantum dot dispersion.

[0145] Synthesis Example 2

[0146] (1) Synthesis of InP core quantum dot dispersion

[0147] In a 200mL reaction flask, indium acetate and palmitic acid are dissolved in 1-octadecene and then heated at 120°C under vacuum. Here, indium and palmitic acid have a molar ratio of 1:3. After 1 hour, the atmosphere in the reactor is converted to nitrogen. Subsequently, after the reactor is heated at 280°C, a mixed solution of tris(trimethylsilyl)phosphine (TMS3P) and trioctylphosphine is quickly injected thereinto, and the reaction is continued for 20 minutes. Here, TMS3P is used in an amount of 0.5 moles per 1 mole of indium. Subsequently, acetone is added to the reaction solution cooled to room temperature, and then the precipitate centrifuged therefrom is dispersed in toluene again to prepare an InP core quantum dot dispersion. The InP core quantum dot has a particle diameter of about 3nm.

[0148] (2) Synthesis of InP core / ZnSe shell / ZnS shell quantum dot dispersions

[0149] Selenium (Se) was dispersed in trioctylphosphine (TOP) to prepare a Se / TOP stock solution, and sulfur (S) was dispersed in trioctylphosphine (TOP) to prepare an S / TOP stock solution.

[0150] In a 200 mL reaction flask, zinc acetate and oleic acid were dissolved in trioctylamine and then vacuum treated for 10 minutes at 120° C. Subsequently, the reaction flask was internally replaced with N 2 and heated to 180° C., and then the InP core quantum dot dispersion was added thereto.

[0151] The obtained mixture is heated to 280°C, Se / TOP is injected thereinto, and then reacted. The obtained mixture is heated again to 320°C, and the remaining portion of Se / TOP is injected thereinto, and then reacted for a predetermined time to form a ZnSe shell on the InP core. Subsequently, the S / TOP stock solution is placed in the reaction mixture and reacted with it for a predetermined time to form a ZnS shell on the ZnSe shell to obtain InP core / ZnSe shell / ZnS shell quantum dots. The ZnSe shell is formed with a total reaction time of 60 minutes, and the total amount of Se is about 20 moles based on 1 mole of indium; and the ZnS shell is also formed with a total reaction time of 60 minutes, and the total amount of S is about 10 moles based on 1 mole of indium.

[0152] The obtained InP core / ZnSe shell / ZnS shell quantum dots were added to an excess of ethanol and then centrifuged. After centrifugation, the supernatant was poured out, and the precipitate therefrom was dried and dispersed in chloroform or toluene to obtain an InP core / ZnSe shell / ZnS shell quantum dot dispersion.

[0153] Synthesis Example II: Synthesis of the First Inorganic Nanoparticles

[0154] Synthesis Example 3

[0155] 8.07 mmol of zinc acetate dihydrate, 0.93 mmol of magnesium acetate tetrahydrate, and 90 mL of dimethyl sulfoxide were placed in a reactor and then heated at 60° C. in air. Subsequently, 15 mmol of tetramethylammonium hydroxide pentahydrate was dissolved in 30 mL of ethanol and then added dropwise 3 mL at a time to the reactor. After the mixture was stirred for 1 hour, the obtained Zn 200 was added to the reactor at a volume ratio of 1:9. 0.85 Mg 0.15 O nanoparticles and ethyl acetate were centrifuged and then dispersed in ethanol to obtain Zn 0.85 Mg 0.15 O nanoparticle dispersion.

[0156] The Zn 0.85 Mg 0.15 The ZnO nanoparticles have an average particle diameter of about 3.0 nm.0.85 Mg 0.15 The average particle diameter of the O nanoparticles was measured by using a UT F30 Tecnai electron microscope.

[0157] If the Zn 0.85 Mg 0.15 The O nanoparticle dispersion is additionally washed and redispersed to reduce the amount of organic material, then the Zn 0.85 Mg 0.15 O nanoparticles were severely aggregated, extremely deteriorating dispersibility and coating properties, and therefore, additional washing and redispersion were not performed.

[0158] Synthesis Example III: Synthesis of Second Inorganic Nanoparticles

[0159] Synthesis Example 4

[0160] Titanium oxide (TiO 2 ) nanoparticles (anatase, PlasmaChem) were dispersed in water at a concentration of 20 wt % to prepare a titanium oxide nanoparticle dispersion (first dispersion).

[0161] Subsequently, the titanium oxide nanoparticle dispersion (first dispersion) was centrifuged, and then, washed repeatedly with butanol, acetone, and hexane at least twice (2 to 3 times), and redispersed to remove excess organic material and obtain a final precipitate, and the final precipitate was dispersed in ethanol to obtain a titanium oxide nanoparticle dispersion (second dispersion) at a concentration of 2 weight %.

[0162] In the titanium oxide nanoparticle dispersion (second dispersion), the particle diameters of the titanium oxide nanoparticles are distributed within a range of about 8 nm or less. The particle diameters of the titanium oxide nanoparticles are measured by using a UT F30 Tecnai electron microscope.

[0163] Subsequently, ethanol as much as three times the total volume of the titanium oxide nanoparticle dispersion (second dispersion) was further added thereto to obtain a final titanium oxide nanoparticle dispersion at a concentration of 0.5 wt %.

[0164] Comparative Synthesis Example 1

[0165] A titanium oxide nanoparticle dispersion was obtained according to the same method as in Synthesis Example 4, except that an excessive amount of organic material was not removed from the titanium oxide nanoparticle dispersion (first dispersion).

[0166] Synthesis Example 5

[0167] Tin oxide SnO 2 nanoparticles (PlasmaChem) were dispersed in water at a concentration of 20 wt % to prepare a tin oxide nanoparticle dispersion (first dispersion).

[0168] The tin oxide nanoparticles were centrifuged and then washed at least twice (2 to 3 times) with butanol, acetone, and hexane and then dispersed again to remove excess organic material and obtain a final precipitate. The final precipitate was dispersed in ethanol to obtain a tin oxide nanoparticle dispersion (second dispersion) at a concentration of 2% by weight. The particle diameter of the tin oxide nanoparticles was distributed in an approximately 8 nm or smaller range. The particle diameter distribution of the tin oxide nanoparticles was measured using a UT F30 Tecnai electron microscope. Three times as much ethanol as the tin oxide nanoparticle dispersion (second dispersion) was then added to the tin oxide nanoparticle dispersion to obtain a tin oxide nanoparticle dispersion at a concentration of 0.5% by weight.

[0169] Comparative Synthesis Example 2

[0170] A tin oxide nanoparticle dispersion was obtained according to the same method as in Synthesis Example 5, except that an excessive amount of organic material was not removed from the tin oxide nanoparticle dispersion (first dispersion).

[0171] Example I: Fabrication of Electronic Devices Only

[0172] In order to evaluate thin film characteristics and simple electrical characteristics, an electron-only device (EOD) was manufactured.

[0173] Example A

[0174] The Zn 0.85 Mg 0.15 A dispersion of titanium dioxide (TiO) nanoparticles was spin-coated on a glass substrate deposited with indium tin oxide (ITO) (anode) and then heat-treated at 80°C for 30 minutes to form a 15 nm thick electron transport layer. Subsequently, a titanium oxide (TiO2) nanoparticle dispersion, prepared by purifying an organic material according to Synthesis Example 4, was spin-coated on the electron transport layer and then heat-treated at 80°C for 30 minutes to form a 5 nm thick electron injection layer. Aluminum (Al, cathode) was then vacuum-deposited on the electron injection layer to a thickness of 90 nm to fabricate an electronic device.

[0175] Comparative Example A-1

[0176] An electron-only device was manufactured according to the same method as Example A, except that the electron injection layer was not formed on the electron transport layer.

[0177] Comparative Example A-2

[0178] An electron-only device was manufactured according to the same method as in Example A, except that the titanium oxide nanoparticle dispersion of Comparative Synthesis Example 1 was used instead of the titanium oxide nanoparticle dispersion of Synthesis Example 4 to form the electron injection layer.

[0179] Example B

[0180] An electronic device was manufactured according to the same method as in Example A, except that the tin oxide SnO 2 nanoparticle dispersion of Synthesis Example 5 was used instead of the titanium oxide TiO 2 nanoparticle dispersion of Synthesis Example 4.

[0181] Comparative Example B-1

[0182] An electron-only device was manufactured according to the same method as Example B, except that the electron injection layer was not formed on the electron transport layer.

[0183] Comparative Example B-2

[0184] An electron-only device was manufactured according to the same method as in Example B, except that the SnO 2 nanoparticle dispersion of Comparative Synthesis Example 2 was used instead of the SnO 2 dispersion of Synthesis Example 5 to form the electron injection layer.

[0185] Evaluation I

[0186] In the electron-only device according to the embodiment, the surface morphology of the electron injection layer is detected.

[0187] The surface morphology was evaluated by using a transmission electron microscope (TEM).

[0188] Figure 2 FIG4 is a transmission electron microscope (TEM) photograph of only the electron injection layer in the electronic device according to Example A. ...

[0189] refer to Figure 2 , the electron injection layer from the titanium oxide (TiO 2 ) nanoparticle dispersion obtained by purifying an organic material according to Synthesis Example 4 appears as a uniform film with little, if any, aggregation of the titanium oxide nanoparticles.

[0190] Evaluation II

[0191] In the electron-only devices according to Examples and Comparative Examples, the amounts of organic materials in the electron transport layer and the electron injection layer were detected.

[0192] The amount of the organic material was evaluated by measuring the weight loss after heating the corresponding device to 600° C. at a rate of 10° C. / min using a thermogravimetric analyzer (Q5000, TA Instruments) by a thermogravimetric analysis (TGA) method.

[0193] The results are shown in Table 1.

[0194] Table 1

[0195]

[0196] Evaluation III

[0197] In the electron-only devices according to Examples and Comparative Examples, the amount of carbon in the electron transport layer and the electron injection layer in each of the corresponding devices was evaluated by X-ray diffraction (XRD) analysis.

[0198] The results are shown in Table 2.

[0199] Table 2

[0200] C / Zn Example A 0.98 Comparative Example A-1 1.50

[0201] Referring to Table 2, the electron-only device according to Example A exhibited reduced amounts of organic materials in the electron transport layer and the electron injection layer compared to the amount of organic materials in the electron transport layer in the electron-only device according to Comparative Example A-1.

[0202] Evaluation IV

[0203] The current characteristics of only the electronic devices according to the examples and comparative examples were evaluated.

[0204] The current characteristics of the electronic device were evaluated by using a Keithley SMU2635B current source.

[0205] The results are shown in Figure 3 middle.

[0206] Figure 3 is a graph showing current characteristics of only the electronic devices according to Example A and Comparative Example A-1.

[0207] refer to Figure 3 , the electron-only device according to Example A exhibited greatly improved current characteristics compared to the current characteristics of the electron-only device according to Comparative Example A-1 that did not include an electron injection layer.

[0208] Example II: Fabrication of Quantum Dot Devices

[0209] Example 1-1

[0210] A glass substrate deposited with ITO (work function: 4.8 eV) was surface treated with UV-ozone for 15 minutes. A PEDOT:PSS solution (HC Starks) was spin-coated on the ITO, heat-treated at 150°C for 10 minutes in air, and then again at 150°C for 30 minutes in a N2 atmosphere to form a 25 nm thick lower hole transport layer (HOMO: 5.35 eV, LUMO: 3.0 eV). Subsequently, a poly[(9,9-dioctylfluorene-2,7-diyl-co-(4,4′-(N-4-butylphenyl)diphenylamine] solution (TFB, Sumitomo Corp.) was spin-coated on the lower hole transport layer and then heat-treated at 150° C. for 30 minutes to form a 25 nm thick upper hole transport layer (HOMO: 5.6 eV, LUMO: 2.69 eV). The ZnTeSe / ZnSeS core-shell quantum dot dispersion (peak emission wavelength: 452 nm to 453 nm) according to Synthesis Example 1 was spin-coated on the upper hole transport layer and then heat-treated at 80° C. for 30 minutes to form a 25 nm thick quantum dot layer (HOMO: 5.8 eV, LUMO: 3.1 eV). The ZnTeSe / ZnSeS core-shell quantum dot dispersion (peak emission wavelength: 452 nm to 453 nm) according to Synthesis Example 3 was spin-coated on the upper hole transport layer and then heat-treated at 80° C. for 30 minutes to form a 25 nm thick quantum dot layer (HOMO: 5.8 eV, LUMO: 3.1 eV). 0.85 Mg 0.15 A titanium oxide nanoparticle dispersion was spin-coated on the quantum dot layer and then heat-treated at 80°C for 30 minutes to form a 20 nm thick electron transport layer (HOMO: 7.6 eV, LUMO: 3.9 eV). A titanium oxide nanoparticle dispersion according to Synthesis Example 4 was spin-coated on the electron transport layer and then heat-treated at 80°C for 30 minutes to form a 5 nm thick electron injection layer (HOMO: 7.6 eV, LUMO: 4.1 eV). Subsequently, aluminum (Al) was vacuum-deposited on the electron injection layer to form a 100 nm thick second electrode (work function: 4.3 eV) to manufacture a quantum dot device.

[0211] Example 1-2

[0212] A quantum dot device was manufactured according to the same method as Example 1-1, except that a 3 nm thick electron injection layer was formed.

[0213] Examples 1-3

[0214] A quantum dot device was manufactured according to the same method as Example 1-1, except that a 6 nm thick electron injection layer was formed.

[0215] Comparative Example 1-1

[0216] A quantum dot device was manufactured according to the same method as Example 1-1, except that the electron injection layer was not formed on the electron transport layer.

[0217] Comparative Example 1-2

[0218] A quantum dot device was manufactured according to the same method as Example 1-1, except that the titanium oxide nanoparticle dispersion according to Comparative Synthesis Example 1 was used instead of the titanium oxide nanoparticle dispersion according to Synthesis Example 4 to form the electron injection layer.

[0219] Comparative Examples 1-3

[0220] A quantum dot device was manufactured according to the same method as in Example 1-1, except that the titanium oxide nanoparticle dispersion according to Synthesis Example 4 was used instead of the ZnO nanoparticle dispersion according to Synthesis Example 3. 0.85 Mg 0.15 O nanoparticle dispersion to form the electron transport layer, and the Zn 0.85 Mg 0.15 O nanoparticle dispersion was used instead of the titanium oxide nanoparticle dispersion according to Synthesis Example 4 to form the electron injection layer.

[0221] Example 2

[0222] A quantum dot device was manufactured according to the same method as Example 1-1, except that the InP core / ZnSe shell / ZnS shell quantum dot dispersion according to Synthesis Example 2 (peak emission wavelength: 629 nm to 630 nm) was used instead of the ZnTeSe / ZnSeS core-shell quantum dot dispersion according to Synthesis Example 1 to form a quantum dot layer (HOMO: 5.55 eV, LUMO: 3.6 eV).

[0223] Comparative Example 2-1

[0224] A quantum dot device was manufactured according to the same method as in Example 2, except that the electron injection layer was not formed on the electron transport layer.

[0225] Comparative Example 2-2

[0226] A quantum dot device was manufactured according to the same method as Example 2, except that the titanium oxide nanoparticle dispersion according to Comparative Synthesis Example 1 was used instead of the titanium oxide nanoparticle dispersion of Synthesis Example 4 to form the electron injection layer.

[0227] Comparative Examples 2-3

[0228] The quantum dot device was manufactured according to the same method as in Example 2, except that the titanium oxide nanoparticle dispersion of Synthesis Example 4 was used instead of the ZnO2 nanoparticle dispersion of Synthesis Example 3. 0.85 Mg 0.15 O nanoparticle dispersion to form the electron transport layer, and the Zn according to Synthesis Example 3 was used. 0.85 Mg 0.15The electron injection layer was formed by replacing the titanium oxide nanoparticle dispersion of Synthesis Example 4 with the titanium oxide nanoparticle dispersion.

[0229] Example 3

[0230] A quantum dot device was manufactured according to the same method as in Example 2, except that poly(N,N'-bis-4-butylphenyl-N,N'-bisphenyl)benzidine was used instead of TFB to form the upper hole transport layer, and the tin oxide nanoparticle dispersion according to Synthesis Example 5 was used instead of the titanium oxide nanoparticle dispersion according to Synthesis Example 4 to form the electron injection layer (HOMO: 7.6 eV, LUMO: 4.1 eV).

[0231] Comparative Example 3-1

[0232] A quantum dot device was manufactured according to the same method as in Example 3, except that the electron injection layer was not formed.

[0233] Comparative Example 3-2

[0234] A quantum dot device was manufactured according to the same method as Example 3, except that the tin oxide nanoparticle dispersion according to Comparative Synthesis Example 2 was used instead of the tin oxide nanoparticle dispersion according to Synthesis Example 5 to form the electron injection layer.

[0235] Comparative Example 3-3

[0236] A quantum dot device was manufactured according to the same method as in Example 3, except that the tin oxide nanoparticle dispersion according to Synthesis Example 5 was used instead of the ZnO nanoparticle dispersion according to Synthesis Example 3. 0.85 Mg 0.15 O nanoparticle dispersion to form the electron transport layer, and the Zn according to Synthesis Example 3 was used. 0.85 Mg 0.15 The electron injection layer was formed using a tin oxide nanoparticle dispersion instead of the tin oxide nanoparticle dispersion according to Synthesis Example 5.

[0237] Rating V

[0238] The current-voltage-luminescence characteristics of the quantum dot devices according to the examples and comparative examples were evaluated.

[0239] The current-voltage-luminescence characteristics were evaluated by using a Keithley SMU2635B current source and a Minolta CS-2000A spectroradiometer.

[0240] The driving voltage thereof was evaluated by using the voltage (on voltage) for 5 mA current driving.

[0241] The lifetime characteristics are evaluated by injecting a current condition that satisfies the quantum dot device to display a brightness of 650 nits (blue quantum dot device) and 4500 nits (red quantum dot device), using the amount of brightness reduction from the initial brightness, and T 95 The time it takes for the brightness to drop to 95% of the initial brightness.

[0242] The results are shown in Tables 3 to 5.

[0243] Table 3

[0244] <![CDATA[λ 最大 (nm)]]> <![CDATA[Lum 最大 (Cd / m 2 )]]> V@5mA <![CDATA[T 95 (h)]]> Example 1-1 452 33350 2.7 12.39 Example 1-2 452 35530 3.0 11.51 Examples 1-3 452 35780 2.9 12.20 Comparative Example 1-1 452 33170 3.5 0.19 Comparative Example 1-2 452 19230 3.0 0.43 Comparative Examples 1-3 452 19620 3.0 0.19

[0245] Table 4

[0246] <![CDATA[λ 最大 (nm)]]> <![CDATA[Lum 最大 (Cd / m 2 )]]> V@5mA <![CDATA[T 95 (h)]]> Example 2 630 114740 2.3 73.91 Comparative Example 2-1 629 90490 2.8 9.81 Comparative Example 2-2 629 52800 2.7 3.52 Comparative Examples 2-3 629 52640 2.6 2.92

[0247] Table 5

[0248]

[0249]

[0250] *λ 最大 : Peak emission wavelength

[0251] *Lum 最大 : Maximum brightness

[0252] *V@5mA: Voltage for driving at 5mA current (turn-on voltage)

[0253] *T 95 (h): Time when 95% brightness appears relative to the initial brightness

[0254] Referring to Tables 3 to 5, the quantum dot device according to the embodiment simultaneously exhibits low driving voltage, improved light emitting characteristics, and high lifespan characteristics, compared to the quantum dot device according to the comparative example.

[0255] 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. Quantum dot devices, including a first electrode and a second electrode, a quantum dot layer between the first electrode and the second electrode, an electron transport layer between the quantum dot layer and the second electrode, the electron transport layer comprising first inorganic nanoparticles and a first organic material, and an electron injection layer between the electron transport layer and the second electrode, the electron injection layer comprising second inorganic nanoparticles and a second organic material, wherein the ratio by weight of the amount of the second organic material in the electron injection layer to the total amount of the second inorganic nanoparticles and the second organic material is smaller than the ratio by weight of the amount of the first organic material in the electron transport layer to the total amount of the first inorganic nanoparticles and the first organic material, The first inorganic nanoparticles are composed of Zn 1-x Q x The metal oxide nanoparticles represented by O, wherein Q is at least one metal excluding Zn, and 0≤x<0.

5.

2. A quantum dot device as described in claim 1, wherein the ratio by weight of the amount of the second organic material in the electron injection layer to the total amount of the second inorganic nanoparticles and the second organic material is 0.01 to 0.8 times the ratio by weight of the amount of the first organic material in the electron transport layer to the total amount of the first inorganic nanoparticles and the first organic material. 3 . The quantum dot device of claim 1 , wherein an amount of the second organic material in the electron injection layer is less than or equal to 25 wt %, based on the total amount of the second inorganic nanoparticles and the second organic material. The quantum dot device of claim 1 , wherein a LUMO energy level of the electron injection layer is shallower than a work function of the second electrode and deeper than a LUMO energy level of the electron transport layer.

5. The quantum dot device of claim 1, wherein Q comprises Mg, Co, Ni, Ga, Al, Ca, Zr, W, Li, Ti, Ta, Sn, Hf, Si, Ba, or a combination thereof. The quantum dot device of claim 1 , wherein the second inorganic nanoparticles are metal oxide nanoparticles dispersible in water, alcohol, or a combination thereof.

7. The quantum dot device of claim 1, wherein the second inorganic nanoparticles are metal oxide nanoparticles comprising at least one of Ti, Ce, Sn, Mg, Zr, W, and Al. The quantum dot device of claim 1 , wherein the electron injection layer is thinner than the electron transport layer.

9. Quantum dot devices, including a first electrode and a second electrode, a quantum dot layer between the first electrode and the second electrode, an electron injection layer between the second electrode and the quantum dot layer, the electron injection layer comprising inorganic nanoparticles and organic materials, wherein the amount of the organic material in the electron injection layer is less than or equal to 25 wt % based on the total amount of the inorganic nanoparticles and the organic material, The quantum dot device further comprises an electron transport layer between the quantum dot layer and the electron injection layer, The electron transport layer comprises Zn 1-x Q x The metal oxide nanoparticles represented by O, wherein Q is at least one metal excluding Zn, and 0≤x<0.

5.

10. The quantum dot device of claim 9, wherein the inorganic nanoparticles in the electron injection layer are metal oxide nanoparticles comprising at least one of Ti, Ce, Sn, Mg, Zr, W, and Al.

11. The quantum dot device according to claim 9, wherein The electron transport layer further comprises an organic material, and An amount of the organic material in the electron injection layer is smaller than an amount of the organic material in the electron transport layer.

12. The quantum dot device of claim 1 or 9, wherein the thickness of the electron injection layer is less than or equal to 10 nm.

13. The quantum dot device of claim 1 or 9, wherein the electron injection layer is in contact with the second electrode.

14. A method for manufacturing a quantum dot device according to any one of claims 1 to 11, comprising: forming a first electrode, forming a quantum dot layer on the first electrode, forming an electron transport layer on the quantum dot layer, wherein the electron transport layer comprises first inorganic nanoparticles, forming an electron injection layer on the electron transport layer, the electron injection layer comprising second inorganic nanoparticles, and forming a second electrode on the electron injection layer, The electron injection layer is formed by preparing a first dispersion comprising the second inorganic nanoparticles and a first amount of an organic material, removing at least a portion of the organic material from the first dispersion to produce a second dispersion comprising a second amount of organic material that is less than the first amount of organic material, and The second dispersion is coated on the electron transport layer. 15 . The method of claim 14 , further comprising providing a polar dispersion medium to the second dispersion before applying the second dispersion, the polar dispersion medium being water, alcohol, or a combination thereof. 16 . The method of claim 14 , wherein the amount of the organic material in the second dispersion excluding a dispersion medium is less than or equal to 25% by weight based on the total amount of the second inorganic nanoparticles and the organic material.

17. An electronic device comprising the quantum dot device according to any one of claims 1 to 13.

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