Light-emitting devices, methods for manufacturing light-emitting devices, and display devices including light-emitting devices.

Abstract

The present invention discloses a light-emitting device, a method for manufacturing a light-emitting device, and a display device including the light-emitting device. The light-emitting device includes: a first electrode and a second electrode, each having surfaces opposite to each other; a light-emitting layer comprising quantum dots disposed between the first electrode and the second electrode; and an electronic auxiliary layer disposed between the light-emitting layer and the second electrode, wherein the electronic auxiliary layer comprises metal oxide nanoparticles, and the metal oxide nanoparticles comprise anions of organic acids bound to the surface of the metal oxide nanoparticles.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to and all benefits arising therefrom of Korean Patent Application No. 10-2020-0081057, filed on July 1, 2020, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The invention discloses a light-emitting device, a method for manufacturing a light-emitting device, and a display device including a light-emitting device. Background Technology

[0004] Unlike bulk materials, the known physical properties of nanoparticles (e.g., band gap, melting point, etc.) can be controlled by changing their particle size. For example, when a semiconductor nanocrystal, also known as a quantum dot (QD), is illuminated or an electric current flows through it, the quantum dot emits light at a wavelength corresponding to its size. Therefore, quantum dots can be used as light emitters that emit light at specific wavelengths. Summary of the Invention

[0005] Describe a light-emitting device that addresses the technical problem of increased undesirable leakage current due to nanoparticle defects in the electron transport layer, and the resulting decrease in device efficiency.

[0006] The presence of residual organic matter on the surface of nanoparticles can lead to reduced electron mobility, decreased brightness, or charging phenomena that cause device degradation, such as reduced lifetime. Therefore, a light-emitting device is described that addresses the technical problems arising from residual organic matter at the interface between the quantum dot-based luminescent layer and the electron transport layer.

[0007] The embodiments provide a display device including the light-emitting device.

[0008] According to one embodiment, the light-emitting device includes: a first electrode and a second electrode, each having surfaces opposite to each other; a light-emitting layer comprising quantum dots disposed between the first electrode and the second electrode; and an electronic auxiliary layer disposed between the light-emitting layer and the second electrode, wherein the electronic auxiliary layer comprises metal oxide nanoparticles, and the metal oxide nanoparticles comprise anions of organic acids bound to the surface of the metal oxide nanoparticles.

[0009] The anion of the organic acid can chemically bond with the metal ions on the surface of the metal oxide nanoparticles, or provide a bonding product of the metal ions with oxygen or hydroxyl groups, or a combination thereof.

[0010] The organic acid may have a molecular weight of about 30 g / mol to about 600 g / mol.

[0011] The organic acid may have a pK value of about 1 to about 5. a .

[0012] The anions of the organic acid may include the following anions: RCOOH, RSO2H, RSO3H, ArOH, ArSH, RCH=NOH, RCH=C(OH)R', RCONHCOR', ArSO2NH2, ArSO2NHR, RCH2NO2, R2CHNO2 (wherein R and R' are the same or different and are each independently hydrogen, substituted or unsubstituted C1-C24 aliphatic hydrocarbon groups, substituted or unsubstituted C3-C40 alicyclic hydrocarbon groups, or combinations thereof, wherein at least one R in R2CHNO2 is not hydrogen, and Ar is a substituted or unsubstituted C6-C20 aromatic hydrocarbon group), or combinations thereof.

[0013] The anions of the organic acid may include citrate ions, acetate ions, oxalate ions, sulfonate ions, or combinations thereof.

[0014] The anions of the organic acid may be present on the surface of the metal oxide nanoparticles in an amount of about 0.001% by weight (wt%) to about 10% by weight, based on the total weight of the metal oxide nanoparticles in the electronic auxiliary layer.

[0015] The electronic auxiliary layer may have a molar ratio of carbon atoms to all metal atoms of the metal oxide nanoparticles of less than or equal to about 1.3:1.

[0016] The content of alkaline material in the metal oxide nanoparticles may be less than or equal to about 2% by weight, based on the total weight of the metal oxide nanoparticles in the electronic auxiliary layer.

[0017] If present, the alkaline material may include tetramethylammonium hydroxide (TMAH), potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), or combinations thereof. The aforementioned alkaline materials may not be present in the metal oxide nanoparticles.

[0018] The electronic auxiliary layer may have a size greater than approximately 6.5 × 10⁻⁶. -8 Siemens conductivity per centimeter (S / cm).

[0019] The metal oxide may include Zn, Mg, Ca, Zr, W, Li, Ti, Y, Al, or combinations thereof.

[0020] The metal oxide can be represented by chemical formula 1.

[0021] Chemical Formula 1

[0022] Zn 1-x M x O

[0023] In chemical formula 1, M is Mg, Ca, Zr, W, Li, Ti, Y, Al, or a combination thereof, and 0 ≤ x ≤ 0.5.

[0024] The metal oxide may include zinc oxide, zinc magnesium oxide, or a combination thereof.

[0025] The metal oxide nanoparticles may have an average particle size greater than or equal to about 1 nanometer (nm) and less than or equal to about 100 nm.

[0026] The light-emitting device may further include a hole-assisted layer between the first electrode and the light-emitting layer, the hole-assisted layer including a hole injection layer (HIL), a hole transport layer (HTL), an electron blocking layer (EBL), or a combination thereof.

[0027] The light-emitting device may have a maximum external quantum efficiency (EQE) greater than or equal to about 10%. 最大 And a brightness of approximately 50,000 nits or more.

[0028] According to another embodiment, a method for manufacturing a light-emitting device includes: forming an electron-assisted layer comprising metal oxide nanoparticles; and contacting the electron-assisted layer with an organic acid or a solution comprising an organic acid. The contact may include contact with a solution comprising an organic acid. Preferably, a solution of the organic acid is used.

[0029] Contacting the electronic auxiliary layer with an organic acid or a solution containing an organic acid may include coating the electronic auxiliary layer with the organic acid or the solution containing an organic acid, or immersing the electronic auxiliary layer in the organic acid or the solution containing an organic acid.

[0030] Coating processes may include spin coating, bar coating, spray coating, slot coating, inkjet printing, nozzle printing, jetting, or doctor blade coating.

[0031] According to another embodiment, a display device including the light-emitting device is provided.

[0032] In the light-emitting device according to the embodiment, the driving voltage is reduced and the device efficiency is improved due to the reduction in hole leakage current of the electron transport layer. Furthermore, the hole blocking of the electron transport layer is more effective, and the electron mobility is increased, thereby improving the device brightness. Interface charging between the light-emitting layer and the electron transport layer, including the quantum dots, is also addressed to reduce device degradation and thus improve the device lifetime. Attached Figure Description

[0033] Figure 1 This is a schematic cross-sectional view of the light-emitting device according to an embodiment.

[0034] Figure 2 This is a schematic diagram of metal oxide nanoparticles containing anions of organic acids included in the electronic auxiliary layer of a light-emitting device according to an embodiment.

[0035] Figure 3 This is a comparison graph of the current density versus voltage of the light-emitting devices in Example 1 and Comparative Example 1.

[0036] Figure 4 This is a comparison graph showing the quantum efficiency versus brightness of the light-emitting devices in Example 1 and Comparative Example 1.

[0037] Figure 5 This is a comparison graph showing the brightness of the light-emitting devices in Example 1 and Comparative Example 1 versus voltage.

[0038] Figure 6 This is a comparison chart of the brightness lifetime of the light-emitting devices in Example 1 and Comparative Example 1.

[0039] Figure 7 This is a comparison diagram of the driving voltage of the light-emitting devices in Example 1 and Comparative Example 1.

[0040] Figure 8 The emission patterns of the light-emitting devices of Example 1 and Comparative Example 1 at 650 nits are shown.

[0041] Figure 9 This is a comparison graph of the current density versus voltage of the light-emitting devices in Example 2 and Comparative Example 2.

[0042] Figure 10 This is a comparison graph showing the quantum efficiency versus brightness of the light-emitting devices in Example 2 and Comparative Example 2.

[0043] Figure 11 This is a comparison graph showing the brightness of the light-emitting devices in Example 2 and Comparative Example 2 versus voltage.

[0044] Figure 12 This is a comparison chart of the brightness lifetime of the light-emitting devices in Example 2 and Comparative Example 2.

[0045] Figure 13 This is a comparison diagram of the driving voltage of the light-emitting devices in Example 2 and Comparative Example 2.

[0046] Figure 14 This is a comparison graph of the current density versus voltage of the light-emitting devices in Examples 3-1 and 3-2 and Comparative Example 3.

[0047] Figure 15This is a comparison graph showing the quantum efficiency versus brightness of the light-emitting devices in Examples 3-1 and 3-2 and Comparative Example 3.

[0048] Figure 16 This is a comparison graph showing the brightness of the light-emitting devices in Examples 3-1 and 3-2 and Comparative Example 3 against voltage.

[0049] Figure 17 This is a comparison chart of the brightness lifetime of the light-emitting devices in Examples 3-1 and 3-2 and Comparative Example 3.

[0050] Figure 18 This is a comparison diagram of the driving voltage of the light-emitting devices in Examples 3-1 and 3-2 and Comparative Example 3.

[0051] Figure 19 This is a comparison of the selected area diffraction pattern (SADP) analysis of the electron-assisted layer in Experimental Example 4, Examples 1 and 2, and Comparative Example 1.

[0052] Figure 20 This is a comparison graph of infrared spectroscopy (IR) analysis of the electronic auxiliary layer of Example 2 and Comparative Example 2 based on Experimental Example 5.

[0053] Figure 21 For comparative gas chromatography (GC) analysis of the electronic auxiliary layer of Experimental Example 5, Example 2 and Comparative Example 2. Detailed Implementation

[0054] The advantages and features of the technology, as well as the methods of implementing it, will become clear with reference to the embodiments and accompanying drawings. However, the embodiments should not be construed as limited to those described herein.

[0055] Unless otherwise defined, all terms in this specification (including technical and scientific terms) are to be defined as commonly understood by those skilled in the art. It will be further understood that terms, such as those defined in common dictionaries, should not be interpreted ideally or exaggeratedly, and should be interpreted as having a meaning consistent with their meaning in the context of the relevant field and in the present disclosure, and will not be interpreted in an idealized or overly formal sense unless clearly defined herein.

[0056] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a” (indefinite article) and “the” are intended to include the plural forms, including “at least one”, unless the context clearly indicates otherwise. “At least one” shall not be construed as limited to “a”. “Or” means “and / or”. As used herein, the term “and / or” includes any and all combinations of one or more of the associated listed items.

[0057] It will be further understood that the terms “comprising” or “including” as used in this specification indicate the presence of the stated features, areas, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more additional features, areas, integrals, steps, operations, elements, components and / or combinations thereof.

[0058] In the accompanying drawings, the thicknesses of layers, films, panels, regions, etc., are enlarged for clarity. Exemplary embodiments are described herein with reference to cross-sectional views, which are schematic diagrams of idealized embodiments. Thus, deviations from the shapes shown in the drawings will be expected as a result of, for example, manufacturing techniques and / or tolerances. Therefore, the embodiments described herein should not be construed as limited to the specific shapes of the regions illustrated herein, but rather include deviations in shape caused, for example, by manufacturing processes. Throughout the specification, the same reference numerals denote the same elements.

[0059] It will be understood that when an element, such as a layer, film, region, or substrate, is referred to as being "on" another element, it may be directly on said other element or there may be intermediate elements present. Conversely, when an element is referred to as being "directly on" another element, there are no intermediate elements present.

[0060] As used herein, “about” or “approximately” includes the stated value and means within an acceptable range of deviation from the specific value, as determined by one of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the specific quantity (i.e., limitations of the measurement system). For example, “about” may mean a deviation relative to the stated value within one or more standard deviations, or within ±10%.

[0061] As used herein, unless otherwise defined, “substituted” means that the hydrogen in a compound or the corresponding moiety is replaced by a substituent, which is a C1-C30 alkyl, C2-C30 alkenyl, C2-C30 alkynyl, C6-C30 aryl, C7-C30 alkylaryl, C1-C30 alkoxy, C1-C30 heteroalkyl, C3-C30 heteroalkylaryl, C3-C30 cycloalkyl, C3-C30 (or C15) cycloalkenyl, C6-C30 cycloalkynyl, C2-C30 heterocycloalkyl, halogen (-F, -Cl, -Br or -I), hydroxyl (-OH), nitro (-NO2), cyano (-CN), amino (-NRR', where R and R' are independently hydrogen or C1-C6). Alkyl, azide (-N3), amidine (-C(=NH)NH2)), hydrazine (-NHNH2), hydrazone (=N(NH2)), aldehyde (-C(=O)H), carbamoyl (-C(O)NH2), thiol (-SH), ester (-C(=O)OR, where R is C1-C6 alkyl or C6-C12 aryl), carboxyl (-COOH) or its salt (-C(=O)OM, where M is an organic or inorganic cation), sulfonic acid (-SO3H) or its salt (-SO3M, where M is an organic or inorganic cation), phosphate (-PO3H2) or its salt (-PO3MH or -PO3M2, where M is an organic or inorganic cation), or combinations thereof.

[0062] As used herein, “monocyclic aromatic group” refers to a carbocyclic group (e.g., C6-C12 aryl or C6-C8 aryl) that provides a conjugated structure or a heterocyclic group (e.g., C2-C12 heteroaryl or C2-C4 heteroaryl) that provides a conjugated structure.

[0063] As used herein, “fused polycyclic aromatic cyclic group” refers to a cyclic group formed by fusion of at least two monocyclic aromatic cyclic groups, such as C8-C20 aryl, C8-C15 aryl, or C4-C20 heteroaryl, such as C4-C15 heteroaryl.

[0064] As used herein, “heteroatom” refers to a compound or group that includes atoms that are not carbon or hydrogen, such as a compound or group that includes 1 to 3 heteroatoms of N, O, S, Si, P, or combinations thereof.

[0065] As used in this article, "family" refers to a family of the periodic table.

[0066] As used herein, “Group II” may include Group IIA and Group IIB, and examples of Group II metals may be, but are not limited to, Cd, Zn, Hg, and Mg.

[0067] As used herein, “Group III” may include Group IIIA and Group IIIB, and examples of Group III metals may be Al, In, Ga, and Tl, but are not limited thereto.

[0068] As used herein, “Group IV” may include Group IVA and Group IVB, and examples of Group IV metals may be, but are not limited to, Si, Ge and Sn. As used herein, “metal” may include half-metals such as Si.

[0069] As used herein, “family I” can include families IA and IB, and instances can include, but are not limited to, Li, Na, K, Rb, and Cs.

[0070] As used herein, “family V” may include, but is not limited to, families VA, and examples may include, but are not limited to, nitrogen, phosphorus, arsenic, antimony and bismuth.

[0071] As used herein, “VI group” may include VIA group, and examples may include, but are not limited to, sulfur, selenium and tellurium.

[0072] The light-emitting device according to the embodiments will be described below with reference to the accompanying drawings.

[0073] Figure 1 This is a schematic cross-sectional view of the light-emitting device according to an embodiment.

[0074] Reference Figure 1 The light-emitting device 10 according to the embodiment includes: a first electrode 11 and a second electrode 15 each having surfaces opposite to each other; a light-emitting layer 13 including quantum dots and disposed between the first electrode 11 and the second electrode 15; a hole auxiliary layer 12 between the first electrode 11 and the light-emitting layer 13; and an electron auxiliary layer 14 disposed between the second electrode 15 and the light-emitting layer 13.

[0075] A substrate (not shown) may be disposed on the side of the first electrode 11 or the second electrode 15. For example, the substrate may be disposed on the side of the first electrode. The substrate may be a substrate comprising an electrically insulating material (hereinafter also referred to as "insulating material") (e.g., an electrically insulating transparent substrate). The substrate may include glass; various polymers such as polyesters (e.g., polyethylene terephthalate (PET), polyethylene naphthalate (PEN)), polycarbonate, polyacrylate, polyimide, and polyamide-imide); polysiloxanes (e.g., polydimethylsiloxane (PDMS)); inorganic materials such as Al2O3 and ZnO; or combinations thereof, but not limited thereto. The substrate may be made of a silicon wafer. "Transparent" as used herein may refer to a transmittance of more than or equal to about 85%, for example, more than or equal to about 88%, more than or equal to about 90%, more than or equal to about 95%, more than or equal to about 97%, or more than or equal to about 99% for light of a predetermined wavelength (e.g., light emitted from the quantum dot). The thickness of the substrate can be appropriately selected considering the substrate material without particular limitation. The transparent substrate may be flexible. The substrate may be omitted.

[0076] One of the first electrode 11 and the second electrode 15 can be an anode and the other can be a cathode. For example, the first electrode 11 can be an anode and the second electrode 15 can be a cathode.

[0077] The first electrode 11 may be made of a conductive material (hereinafter also referred to as a "conductor") such as a metal, a conductive metal oxide, or a combination thereof. The first electrode 11 may be made, for example, of a metal or alloy thereof such as nickel, platinum, vanadium, chromium, copper, zinc, and gold; a conductive metal oxide such as zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide; or a combination of metal and oxide such as ZnO and Al, or SnO2 and Sb, but is not limited thereto. For example, the first electrode 11 may include a transparent conductive metal oxide such as indium tin oxide (ITO).

[0078] The second electrode 15 may be made of a conductor such as a metal, a conductive metal oxide, and / or a conductive polymer. The second electrode 15 may be made of, for example, a metal or alloy thereof such as aluminum, magnesium, calcium, sodium, potassium, titanium, indium, yttrium, lithium, gadolinium, silver, tin, lead, cesium, or barium; or a multilayer material such as LiF / Al, LiO2 / Al, Liq / Al, LiF / Ca, and BaF2 / Ca, but is not limited thereto. The conductive metal oxide is the same as described above.

[0079] At least one of the first electrode 11 or the second electrode 15 may be a light-transmitting electrode, and the light-transmitting electrode may be made, for example, of a conductive oxide such as zinc oxide, indium oxide, tin oxide, indium tin oxide (ITO), indium zinc oxide (IZO), or fluorine-doped tin oxide, or a single or multiple metal layer. If one of the first electrode 11 and the second electrode 15 is a non-light-transmitting electrode, then the electrode may be made of, for example, an opaque conductor such as aluminum (Al), silver (Ag), or gold (Au).

[0080] The thickness of the first electrode 11 and / or the second electrode 15 is not particularly limited and can be appropriately selected with consideration of device efficiency. For example, the thickness of the electrodes may be greater than or equal to about 5 nanometers (nm), for example, greater than or equal to about 50 nm. For example, the thickness of the electrodes may be less than or equal to about 100 micrometers (μm), for example, less than or equal to about 10 μm, less than or equal to about 1 μm, less than or equal to about 900 nm, less than or equal to about 500 nm, or less than or equal to about 100 nm.

[0081] The light-emitting layer 13 comprises a plurality of quantum dots. The quantum dots (hereinafter also referred to as semiconductor nanocrystals) may include II-VI compounds, III-V compounds, IV-VI compounds, group IV elements or compounds, I-III-VI compounds, I-II-IV-VI compounds, or combinations thereof.

[0082] The group II-VI compounds may be binary compounds such as CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, or mixtures thereof; ternary compounds such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZn Te, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, or mixtures thereof; or quaternary compounds such as HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, or mixtures thereof. The group II-VI compounds may further include group III metals. The group III-V compounds may be binary compounds such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, or mixtures thereof; ternary compounds such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb, or mixtures thereof; or quaternary compounds such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, InAlAsSb, or mixtures thereof. The group III-V compounds may further include group II metals (e.g., InZnP). The group IV-VI compounds may be 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; or quaternary compounds such as SnPbSSe, SnPbSeTe, SnPbSTe, or mixtures thereof. Examples of group I-III-VI compounds may include, but are not limited to, CuInSe2, CuInS2, CuInGaSe, or CuInGaS. Examples of group I-II-IV-VI compounds may include, but are not limited to, CuZnSnSe or CuZnSnS.The group IV elements or compounds may be simple substances such as Si, Ge, or mixtures thereof; or binary compounds such as SiC, SiGe, or mixtures thereof.

[0083] For example, the quantum dots may not include cadmium. The quantum dots may include semiconductor nanocrystals based on group III-V compounds containing indium and phosphorus. The group III-V compounds may further include zinc. The quantum dots may include semiconductor nanocrystals based on group II-VI compounds containing chalcogenides (e.g., sulfur, selenium, tellurium, or combinations thereof) and zinc.

[0084] In the quantum dot, the aforementioned elemental, binary, ternary, and / or quaternary compounds exist at uniform concentrations within the semiconductor nanocrystal particles or at least partially different concentrations within the same particles. The semiconductor nanocrystal may have a core / shell structure, wherein a first semiconductor nanocrystal (core) is surrounded by a second semiconductor nanocrystal (shell) having the same or a different composition. In embodiments, the quantum dot may include: a core comprising InP, InZnP, ZnSe, ZnSeTe, or combinations thereof; and a shell (or multiple shells) having a different composition from the core and comprising InP, InZnP, ZnSe, ZnS, ZnSeTe, ZnSeS, or combinations thereof.

[0085] The core and the shell may have an interface, and at least one element of the core or the shell at the interface may have a concentration gradient in which the concentration of the elements in the shell decreases toward the core. The semiconductor nanocrystal may have a structure comprising a semiconductor nanocrystal core and a multilayer shell surrounding it. Here, the multilayer shell has at least two shells, wherein each shell may be a single composition, an alloy, and / or a shell with a concentration gradient.

[0086] In the quantum dot, the shell material and the core material can each have different band gaps. For example, the band gap of the shell material can be larger than that of the core material. Alternatively, the band gap of the shell material can be smaller than that of the core material. The quantum dot can have multiple shells. In the multi-shell structure, the band gap of the outer layer can be larger than that of the inner layer (i.e., the layer closer to the core). In the multi-shell structure, the band gap of the outer layer can be smaller than that of the inner layer.

[0087] By adjusting the composition and size of the quantum dots, the quantum dots can have controlled absorption / photoluminescence wavelengths. The maximum photoluminescence peak wavelength of the quantum dots can be in the ultraviolet (UV) to infrared (IR) wavelength range or a wavelength greater than the above range. For example, the maximum photoluminescence peak wavelength of the quantum dots can be greater than or equal to about 300 nm, such as greater than or equal to about 500 nm, greater than or equal to about 510 nm, greater than or equal to about 520 nm, greater than or equal to about 530 nm, greater than or equal to about 540 nm, greater than or equal to about 550 nm, greater than or equal to about 560 nm, greater than or equal to about 570 nm, greater than or equal to about 580 nm, greater than or equal to about 590 nm, greater than or equal to about 600 nm, or greater than or equal to about 610 nm. The maximum photoluminescence wavelength of the quantum dot can be less than or equal to about 800 nm, for example, less than or equal to about 650 nm, less than or equal to about 640 nm, less than or equal to about 630 nm, less than or equal to about 620 nm, less than or equal to about 610 nm, less than or equal to about 600 nm, less than or equal to about 590 nm, less than or equal to about 580 nm, less than or equal to about 570 nm, less than or equal to about 560 nm, less than or equal to about 550 nm, or less than or equal to about 540 nm. The maximum photoluminescence wavelength of the quantum dot can be in the range of about 500 nm to about 650 nm. The maximum photoluminescence wavelength of the quantum dot can be in the range of about 500 nm to about 540 nm. The maximum photoluminescence wavelength of the quantum dot can be in the range of about 610 nm to about 640 nm.

[0088] The quantum dot may have a quantum efficiency of about 10%, for example, about 30%, about 50%, about 60%, about 70%, about 90%, or even about 100%. The quantum dot may have a relatively narrow photoluminescence wavelength spectrum. The quantum dot may have a half-width (FWHM) of the photoluminescence wavelength spectrum, for example, less than or equal to about 50 nm, for example, less than or equal to about 45 nm, less than or equal to about 40 nm, or less than or equal to about 30 nm.

[0089] The quantum dots may have an average particle size (e.g., diameter or maximum straight length through the particle) greater than or equal to about 1 nm and less than or equal to about 100 nm. The quantum dots may have a particle size of about 1 nm to about 100 nm, for example, greater than or equal to about 2 nm, greater than or equal to about 3 nm, or greater than or equal to about 4 nm and less than or equal to about 50 nm, less than or equal to about 40 nm, less than or equal to about 30 nm, less than or equal to about 20 nm, less than or equal to about 15 nm, or less than or equal to about 10 nm. The shape of the quantum dots is not particularly limited. For example, the shape of the quantum dots may be spheres, polyhedra, pyramids, multi-legged objects, cubes, cuboids, nanotubes, nanorods, nanowires, nanosheets, or combinations thereof, but is not limited thereto.

[0090] As used herein, particle size (e.g., those of metal oxide nanoparticles and quantum dot particles) can be obtained using images (two-dimensional images) obtained by electron microscopy analysis using commercially available image analysis programs (e.g., ImageJ). The term "average" in "average particle size" can be the mean, mode, or median.

[0091] The quantum dots may be commercially available or may be suitably synthesized. When the quantum dots are synthesized in a colloidal manner, the particle size can be controlled relatively freely (e.g., randomly) or uniformly.

[0092] The quantum dots may include, for example, organic ligands having a hydrophobic portion. The organic ligand portion may be bound to the surface of the quantum dots. The organic ligands may include RCOOH, RNH2, R2NH, R3N, RSH, R3PO, R3P, ROH, RCOOR, RPO(OH)2, RHPOOH, R2POOH, or combinations thereof, wherein R is independently a C3 (or C5)-C24 substituted or unsubstituted aliphatic hydrocarbon group, such as a C3 (or C5)-C24 alkyl or alkenyl group, a C6-C20 substituted or unsubstituted aromatic hydrocarbon group, such as a C6-C20 aryl group, or combinations thereof.

[0093] Examples of the organic ligand may be thiols such as methanethiol, ethanethiol, propanethiol, butanethiol, pentylenetetrazol, hexanethiol, octylthiol, dodecylthiol, hexadecylthiol, octadecylthiol, or benzylthiol; amines such as methylamine, ethylamine, propylamine, butylamine, pentylemine, hexylamine, octylamine, nonylamine, decylamine, dodecylamine, hexadecylamine, octadecylamine, dimethylamine, diethylamine, dipropylamine, tributylamine, or trioctylamine; carboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, heptanoic acid, octanoic acid, dodecanoic acid, hexadecanoic acid, octadecanoic acid, oleic acid, or benzoic acid; and phosphine compounds such as methylphosphine. The quantum dots may include, but are not limited to, ethylphosphine, propylphosphine, butylphosphine, pentylphosphine, octylphosphine, dioctylphosphine, tributylphosphine, or trioctylphosphine oxides; phosphine oxides such as methylphosphine oxide, ethylphosphine oxide, propylphosphine oxide, butylphosphine oxide, pentylphosphine oxide, tributylphosphine oxide, octylphosphine oxide, dioctylphosphine oxide, or trioctylphosphine oxide; diphenylphosphine, triphenylphosphine compounds, or their oxides; C5-C20 alkylphosphino acids such as hexylphosphino acid, octylphosphino acid, dodecylphosphino acid, tetradecylphosphino acid, hexadecylphosphino acid, octadecylphosphino acid; C5-C20 alkylphosphino acids; and so on. The quantum dots may include a single type of hydrophobic organic ligand or a mixture of at least two types. The hydrophobic organic ligand may not include a photopolymerizable portion, such as an acrylate group, a methacrylate group, etc.

[0094] For example, the light-emitting layer 13 may comprise a quantum dot monolayer. Alternatively, the light-emitting layer 13 may comprise a quantum dot monolayer, such as two or more layers, three or more layers, or four or more layers and 20 or fewer layers, such as 10 or fewer layers, nine or fewer layers, eight or fewer layers, seven or fewer layers, or six or fewer layers. The light-emitting layer 13 may have a thickness greater than or equal to about 5 nm, such as greater than or equal to about 10 nm, greater than or equal to about 20 nm, or greater than or equal to about 30 nm and less than or equal to about 200 nm, such as less than or equal to about 150 nm, less than or equal to about 100 nm, less than or equal to about 90 nm, less than or equal to about 80 nm, less than or equal to about 70 nm, less than or equal to about 60 nm, or less than or equal to about 50 nm. The light-emitting layer 13 may have a thickness, such as about 10 nm to about 150 nm, such as about 10 nm to about 100 nm, or such as about 10 nm to about 50 nm.

[0095] The emitting layer 13 may have a highest occupied molecular orbital (HOMO) energy level greater than or equal to about 5.4 eV, greater than or equal to about 5.6 eV, greater than or equal to about 5.7 eV, greater than or equal to about 5.8 eV, greater than or equal to about 5.9 eV, or greater than or equal to about 6.0 eV. The emitting layer 13 may also have HOMO energy levels less than or equal to about 7.0 eV, less than or equal to about 6.8 eV, less than or equal to about 6.7 eV, less than or equal to about 6.5 eV, less than or equal to about 6.3 eV, or less than or equal to about 6.2 eV. For example, the emitting layer 13 may have HOMO energy levels from about 5.6 eV to about 6.0 eV.

[0096] The emitting layer 13 may have a lowest unoccupied molecular orbital (LUMO) energy level, for example, less than or equal to about 3.8 eV, less than or equal to about 3.7 eV, less than or equal to about 3.6 eV, less than or equal to about 3.5 eV, less than or equal to about 3.4 eV, less than or equal to about 3.3 eV, less than or equal to about 3.2 eV, or less than or equal to about 3.0 eV. The emitting layer 13 may have a LUMO energy level greater than or equal to about 2.4 eV, for example, greater than or equal to about 2.5 eV. For example, the emitting layer 13 may have a band gap of about 2.4 eV to about 2.9 eV.

[0097] A hole-assist layer 12 is disposed between the first electrode 11 and the light-emitting layer 13. The hole-assist layer 12 may have one layer or two or more layers, and may include, for example, a hole injection layer (HIL), a hole transport layer (HTL), and / or an electron blocking layer.

[0098] The hole auxiliary layer 12 may have the following HOMO energy level: it can match the HOMO energy level of the luminescent layer 13 and can enhance the migration rate of holes from the hole auxiliary layer 12 to the luminescent layer 13.

[0099] The HOMO level of the hole auxiliary layer 12 (e.g., hole transport layer (HTL)) contacting the light-emitting layer 13 may be the same as or smaller than the HOMO level of the light-emitting layer 13 by a value in the range of less than or equal to about 1.0 eV. For example, the difference between the HOMO levels of the hole auxiliary layer 12 and the light-emitting layer 13 may be 0 eV to about 1.0 eV, such as about 0.01 eV to about 0.8 eV, about 0.01 eV to about 0.7 eV, about 0.01 eV to about 0.5 eV, about 0.01 eV to about 0.4 eV, about 0.01 eV to about 0.3 eV, about 0.01 eV to about 0.2 eV, or about 0.01 eV to about 0.1 eV.

[0100] The HOMO level of the hole-access layer 12 may be, for example, greater than or equal to about 5.0 eV, for example, greater than or equal to about 5.2 eV, greater than or equal to about 5.4 eV, greater than or equal to about 5.6 eV, or greater than or equal to about 5.8 eV. For example, the HOMO level of the hole-access layer 12 may be about 5.0 eV to about 7.0 eV, for example, about 5.2 eV to about 6.8 eV, about 5.4 eV to about 6.8 eV, about 5.4 eV to about 6.7 eV, about 5.4 eV to about 6.5 eV, about 5.4 eV to about 6.3 eV, about 5.4 eV to about 6.2 eV, about 5.4 eV to about 6.1 eV, about 5.6 eV to about 7.0 eV, about 5.6 eV to about 6.8 eV, or about 5.6 eV. eV to about 6.7 eV, about 5.6 eV to about 6.5 eV, about 5.6 eV to about 6.3 eV, about 5.6 eV to about 6.2 eV, about 5.6 eV to about 6.1 eV, about 5.8 eV to about 7.0 eV, about 5.8 eV to about 6.8 eV, about 5.8 eV to about 6.7 eV, about 5.8 eV to about 6.5 eV, about 5.8 eV to about 6.3 eV, about 5.8 eV to about 6.2 eV, or about 5.8 eV to about 6.1 eV.

[0101] For example, the hole auxiliary layer 12 may include a hole injection layer near the first electrode 11 and a hole transport layer near the light-emitting layer 13. Here, the HOMO energy level of the hole injection layer may be about 5.0 eV to about 6.0 eV, about 5.0 eV to about 5.5 eV, or about 5.0 eV to about 5.4 eV, and the HOMO energy level of the hole transport layer may be about 5.2 eV to about 7.0 eV, about 5.4 eV to about 6.8 eV, about 5.4 eV to about 6.7 eV, about 5.4 eV to about 6.5 eV, about 5.4 eV to about 6.3 eV, about 5.4 eV to about 6.2 eV, or about 5.4 eV to about 6.1 eV.

[0102] The materials included in the hole assist layer 12 are not particularly limited and may include at least one of the following: poly(9,9-dioctyl-fluorene-co-N-(4-butylphenyl)-diphenylamine) (TFB), polyarylamine (polyarylamine), poly(N-vinylcarbazole), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene)polysulfonated styrene (PEDOT:PSS), polyaniline, polypyrrole, N,N,N',N'-tetra(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[4-(N,N-bis-4-tolylamino)phenyl]cyclohexane (TAPC), p-type metal oxides (e.g., NiO, WO3, MoO3, etc.), carbon-based materials such as graphene oxide, or combinations thereof, but not limited thereto.

[0103] In the hole-assisted layer, the thickness of each layer can be appropriately selected. For example, the thickness of each layer can be greater than or equal to about 10 nm, for example greater than or equal to about 15 nm, or greater than or equal to about 20 nm and less than or equal to about 100 nm, for example less than or equal to about 90 nm, less than or equal to about 80 nm, less than or equal to about 70 nm, less than or equal to about 60 nm, or less than or equal to about 50 nm, but is not limited thereto.

[0104] An electron auxiliary layer 14 is disposed between the light-emitting layer 13 and the second electrode 15. The electron auxiliary layer 14 may include, for example, an electron injection layer, an electron transport layer, and / or a hole blocking layer, but is not limited thereto.

[0105] For example, the electron auxiliary layer 14 may be an electron transport layer. The electron auxiliary layer 14 includes metal oxide nanoparticles, which include anions of organic acids bound to the surface of the metal oxide nanoparticles.

[0106] The metal oxide may be an oxide of a metal including Zn, Mg, Ca, Zr, W, Li, Ti, Y, Al, or combinations thereof.

[0107] For example, the metal oxide may be represented by chemical formula 1.

[0108] Chemical Formula 1

[0109] Zn 1-x M x O

[0110] In Formula 1, M can be Mg, Ca, Zr, W, Li, Ti, Y, Al, or combinations thereof, such as Mg. In Formula 1, x can be greater than or equal to 0 and less than or equal to about 0.5, for example, greater than or equal to about 0.01 and less than or equal to about 0.3, or greater than or equal to about 0.01 and less than or equal to about 0.15.

[0111] For example, the metal oxide may include zinc oxide, zinc magnesium oxide, or a combination thereof.

[0112] The nanoparticles may have an average particle size greater than or equal to about 1 nm, for example, greater than or equal to about 1.5 nm, greater than or equal to about 2 nm, greater than or equal to about 2.5 nm, or greater than or equal to about 3 nm and less than or equal to about 100 nm, for example, less than or equal to about 90 nm, less than or equal to about 80 nm, less than or equal to about 70 nm, less than or equal to about 60 nm, less than or equal to about 50 nm, less than or equal to about 40 nm, less than or equal to about 30 nm, less than or equal to about 20 nm, less than or equal to about 10 nm, less than or equal to about 9 nm, less than or equal to about 8 nm, less than or equal to about 7 nm, less than or equal to about 6 nm, or less than or equal to about 5 nm. The nanoparticles may not have a rod shape or nanowire shape. In one embodiment, the nanoparticles may be spherical or substantially spherical.

[0113] The absolute value of the LUMO of the quantum dot can be smaller than the absolute value of the LUMO of the metal oxide. Conversely, the absolute value of the LUMO of the quantum dot can be greater than the absolute value of the LUMO of the metal oxide.

[0114] The metal oxide may have an absolute LUMO value greater than or equal to about 2 eV, greater than or equal to about 2.5 eV, greater than or equal to about 3 eV, greater than or equal to about 3.5 eV, or greater than or equal to about 4 eV and less than or equal to about 5 eV, less than or equal to about 4.5 eV, less than or equal to about 4 eV, less than or equal to about 3.5 eV, or less than or equal to about 3 eV.

[0115] The metal oxide may have an absolute HOMO value greater than or equal to about 5 eV, greater than or equal to about 5.5 eV, greater than or equal to about 6 eV, greater than or equal to about 6.5 eV, or greater than or equal to about 7 eV and less than or equal to about 8 eV, less than or equal to about 7.5 eV, less than or equal to about 7 eV, less than or equal to about 6.5 eV, or less than or equal to about 6 eV.

[0116] The metal oxide may have a band gap greater than or equal to about 2 eV, greater than or equal to about 2.5 eV, greater than or equal to about 3 eV, greater than or equal to about 3.5 eV, or greater than or equal to about 4 eV and less than or equal to about 5 eV, less than or equal to about 4.5 eV, less than or equal to about 4 eV, less than or equal to about 3.5 eV, or less than or equal to about 3 eV.

[0117] In a quantum dot light-emitting device (QD-LED), holes and electrons are injected from a first electrode 11 and a second electrode 15, respectively. The injected electrons pass through a common layer (e.g., an electron-assisted layer such as an electron injection layer or an electron transport layer). The injected holes pass through a hole-assisted layer such as a hole injection layer or a hole transport layer. Electrons and holes can combine in the light-emitting layer 13, which includes quantum dots, to form excitons and emit light.

[0118] When a voltage is applied, holes and electrons are injected into the common layer disposed between the light-emitting layer 13 and the first electrode 11, and into the common layer disposed between the light-emitting layer 13 and the second electrode 15, respectively. In the electron-assisted layer, for example, the electron transport layer (ETL) has sufficient electron mobility to balance the hole / electron ratio in the light-emitting layer 13, and serves to efficiently transfer electrons from the second electrode 15 to the quantum dot light-emitting layer 13. Furthermore, the electron-assisted layer has a suitably deep HOMO energy level, and therefore effectively blocks holes that could escape from the quantum dot light-emitting layer 13.

[0119] For example, the electron transport layer (ETL) comprises metal oxide nanoparticles, which may have electron mobility superior to that of organic semiconductor materials widely used in electron transport layers (ETLs) for OLEDs, but in some cases, promote hole transfer through defects located on the surface of the nanoparticles. The presence of such defects can lead to relatively high leakage currents, which can ultimately degrade the efficiency of quantum dot light-emitting devices (QD-LEDs). Furthermore, when metal oxide nanoparticles are synthesized using various organic-inorganic precursors, the organic materials present or formed during synthesis can act as separators on the surface of the metal oxide nanoparticles or between the nanoparticles (i.e., between them), thus degrading electron mobility and causing charging due to charge accumulation at the interface between the quantum dot light-emitting layer 13 and the electron transport layer (ETL). The presence of this charge accumulation can lead to a deterioration in the brightness and lifetime of the quantum dot light-emitting device (QD-LED).

[0120] In the light-emitting device 10 according to an embodiment, the electron auxiliary layer 14 (e.g., an electron transport layer (ETL)) may include metal oxide nanoparticles, the metal oxide nanoparticles including anions of an organic acid bound to the surface of the metal oxide nanoparticles. The metal oxide nanoparticles are surface-modified with the organic acid. The term "surface-modified with an organic acid" refers to the surface of the metal oxide nanoparticles modified by contact with the anions of the organic acid.

[0121] As described herein, the added organic acid anion can form bonds (such as ionic bonds, covalent bonds, or coordination bonds as described below) with the metal sites of the metal oxide nanoparticles, for example in... Figure 2 As seen in the schematic diagram. Therefore, the electronic auxiliary layer 14 of the surface-modified metal oxide nanoparticles can exhibit a reduction in leakage current, or a reduction, if not all, but most of the reduction or elimination of electron or charge accumulation on the surface of the metal oxide nanoparticles.

[0122] The anion of the organic acid can form chemical bonds with metal ions on the surface of the metal oxide nanoparticles, or provide a bonding product of the metal ions with oxygen or hydroxyl groups, or a combination thereof. Without being bound by theory, it is believed that the anion of the organic acid passivates surface defects of the metal oxide nanoparticles and desorbs residual organic matter that may be present or formed on the surface of the nanoparticles during synthesis. Such passivation results in metal oxide nanoparticles with high conductivity and fewer or smaller surface defects. Therefore, the electron auxiliary layer 14 can improve the quantum and / or voltage efficiency, or lifetime, of the quantum dot light-emitting device 10.

[0123] The anion of the organic acid can be an acidic organic material having functional groups capable of binding to the surface of the metal oxide nanoparticles, such as the following anions: RCOOH, RSO2H, RSO3H, ArOH, ArSH, RCH=NOH, RCH=C(OH)R', RCONHCOR', ArSO2NH2, ArSO2NHR, RCH2NO2, R2CHNO2, or combinations thereof, wherein R and R' are the same or different, and each is independently hydrogen, substituted or... Unsubstituted C1 (or C3)-C40 (or C24) aliphatic hydrocarbon groups (e.g., C1 (or C3)-C40 (or C24) alkyl, C2 (or C3)-C40 (or C24) alkenyl, or C2 (or C3)-C40 (or C24) alkynyl), substituted or unsubstituted C3-C40 alicyclic hydrocarbon groups, or combinations thereof, provided that at least one R in R2CHNO2 is not hydrogen, and Ar is a substituted or unsubstituted C6-C20 aromatic hydrocarbon group (e.g., C6-C20 aryl).

[0124] The organic acid may have a molecular weight greater than or equal to about 30 g / mol, for example greater than or equal to about 40 g / mol, greater than or equal to about 50 g / mol, greater than or equal to about 60 g / mol, greater than or equal to about 70 g / mol, greater than or equal to about 80 g / mol, greater than or equal to about 90 g / mol, or greater than or equal to about 100 g / mol and less than or equal to about 600 g / mol, for example less than or equal to about 500 g / mol, less than or equal to about 400 g / mol, less than or equal to about 300 g / mol, or less than or equal to about 200 g / mol, for example about 30 g / mol to about 600 g / mol, for example about 50 g / mol to about 500 g / mol, about 80 g / mol to about 400 g / mol, about 100 g / mol to about 300 g / mol, or about 50 g / mol to about 200 g / mol.

[0125] The organic acid may have a pK ratio greater than or equal to about 1, for example greater than or equal to about 1.5, greater than or equal to about 2, or greater than or equal to about 2.5 and less than or equal to about 5, for example less than or equal to about 4.5, less than or equal to about 4, or less than or equal to about 3.5, about 1 to about 5, for example about 1.5 to about 4.5, about 2 to about 4, or about 2.5 to about 3.5. a .

[0126] For example, citrate ions, acetate ions, oxalate ions, sulfonate ions, or combinations thereof can be exemplified as satisfying the molecular weight and pK of the organic acid. a The range of anions of organic acids. In particular, sulfonic acids having a molecular weight of less than or equal to about 600 g / mol can be used.

[0127] Figure 2 This is a schematic diagram illustrating the metal oxide nanoparticles containing anions of organic acids included in the electronic auxiliary layer of the light-emitting device according to an embodiment. Figure 2 This indicates that the metal oxide nanoparticles are Zn. 1-x Mg x O (where 0 ≤ x ≤ 0.5) (hereinafter also referred to as ZnMgO) and the anion of the organic acid is RCOO - However, this disclosure is not limited to this situation.

[0128] Reference Figure 2 ZnMgO nanoparticles are grown via a sol-gel dehydration condensation reaction of precursors (e.g., Zn(CH3COO)2, Mg(CH3COO)2) and a base (e.g., tetramethylammonium hydroxide TMAH). On the surface of the synthesized nanoparticles, surface species such as Zn... 2+ Mg 2+O 2- The -OH groups remain unreacted and act as surface defects that, when the light-emitting device is driven, act as trapping sites for holes, resulting in leakage current.

[0129] When the metal oxide nanoparticles are surface-treated with the organic acid, the surface of the nanoparticles is modified through a chemical reaction. For example, it is believed that when acid treatment is performed using an organic acid with a carboxyl group, surface defects are reduced by RCOO. - The form is passivated, thus resulting in the removal of trapping sites. This hole-blocking effect, which suppresses leakage current through the trapping sites of the metal oxide nanoparticles, contributes to improving the luminous efficiency of the light-emitting device.

[0130] Thus, the anion of the organic acid forms a chemical bond with a trapping site, such as a metal ion, on the surface of the metal oxide nanoparticle, or provides a bonded product of the metal ion with oxygen or hydroxyl, or a combination thereof, which is different from forming a coating layer on the surface of the metal oxide nanoparticle or forming an interface layer on the surface of the electronic auxiliary layer 14 between the light-emitting layer 13 and the electronic auxiliary layer 14.

[0131] The anion of the organic acid may be present on the surface of the metal oxide nanoparticles in an amount less than or equal to about 10 wt%, for example, less than or equal to about 9 wt%, less than or equal to about 8 wt%, less than or equal to about 7 wt%, less than or equal to about 6 wt%, or less than or equal to about 5 wt% and greater than or equal to about 0.001 wt%, for example, greater than or equal to about 0.01 wt%, greater than or equal to about 0.1 wt%, greater than or equal to about 1 wt%, greater than or equal to about 2 wt%, or greater than or equal to about 3 wt%, based on the total weight of the metal oxide nanoparticles in the electron-assisted layer 14. It may be present on the surface of the metal oxide nanoparticles in an amount from about 0.001 wt% to about 10 wt%, for example, from about 0.01 wt% to about 9 wt%, from about 0.1 wt% to about 8 wt%, or from about 1 wt% to about 7 wt%, based on the total weight of the metal oxide nanoparticles in the electron-assisted layer 14.

[0132] As an example, the anion content of the organic acid can be obtained by thermogravimetric analysis (TGA) using a TGA Q5000 at a heating rate of 10.00°C / min to 600°C. Alternatively, when the electron auxiliary layer 14 further includes an electron injection layer or a hole blocking layer in addition to the electron transport layer, the anion content of the organic acid can be measured based on the electron transport layer alone.

[0133] In addition, improved conductivity of ZnMgO nanoparticles can be achieved because organic substances or materials on the surface of ZnMgO nanoparticles are desorbed by treatment with organic acids. The desorbed organic substances can be removed by washing with an organic solvent used for acid treatment.

[0134] Therefore, the electronic auxiliary layer 14 has a molar ratio of carbon atoms to all metal atoms of the metal oxide nanoparticles that is less than or equal to about 1.3:1, for example, less than or equal to about 1.2:1, less than or equal to about 1.1:1, less than or equal to about 1.0:1, less than or equal to about 0.9:1, less than or equal to about 0.8:1, less than or equal to about 0.7:1, less than or equal to about 0.6:1, less than or equal to about 0.5:1, less than or equal to about 0.4:1, less than or equal to about 0.3:1, less than or equal to about 0.2:1, less than or equal to about 0.1:1, or even 0.

[0135] The molar ratio of carbon atoms to all metal atoms in electron auxiliary layer 14 can be determined using PhysicalElectronics, Inc.'s Quantum 2000 device at an accelerating voltage of approximately 0.5 keV to approximately 15 keV, approximately 300 W, and 200 × 200 μm. 2 The measurements are performed using X-ray photoelectron spectroscopy (XPS) under conditions of minimal analytical area. Furthermore, when the electron-assisted layer 14 further includes an electron injection layer or a hole-blocking layer in addition to the electron transport layer, the molar ratio of carbon atoms to all metal atoms can be measured based solely on the electron transport layer.

[0136] As an example, the organic material may be an alkaline substance used when growing the metal oxide nanoparticles via a sol-gel dehydration condensation reaction, such as tetramethylammonium hydroxide (TMAH), potassium hydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH), or combinations thereof.

[0137] The content of alkaline material in the metal oxide nanoparticles may be less than or equal to about 2% by weight, for example, less than or equal to about 1.9% by weight, less than or equal to about 1.8% by weight, less than or equal to about 1.7% by weight, less than or equal to about 1.6% by weight, less than or equal to about 1.5% by weight, less than or equal to about 1.4% by weight, less than or equal to about 1.3% by weight, less than or equal to about 1.2% by weight, less than or equal to about 1.1% by weight, less than or equal to about 1.0% by weight, less than or equal to about 0.9% by weight, less than or equal to about 0.8% by weight, less than or equal to about 0.7% by weight, less than or equal to about 0.6% by weight, less than or equal to about 0.5% by weight, less than or equal to about 0.4% by weight, less than or equal to about 0.3% by weight, less than or equal to about 0.2% by weight, less than or equal to about 0.1% by weight, or even less, based on the total weight of the metal oxide nanoparticles in the electronic auxiliary layer. In one embodiment, there is 0% by weight of alkaline material, based on the total weight of the metal oxide nanoparticles in the electronic auxiliary layer.

[0138] As an example, the content of the alkaline material can be determined by thermogravimetric analysis (TGA) using a TGA Q5000 at a heating rate of 10.00°C / min to 600°C. Alternatively, when the electron auxiliary layer 14 further includes an electron injection layer or a hole blocking layer in addition to the electron transport layer, the content of the alkaline material can be measured based on the electron transport layer alone. In one embodiment, 0% by weight of the alkaline material is present, based on the total weight of the metal oxide nanoparticles in the electron auxiliary layer, as determined by TGA under the aforementioned conditions.

[0139] Thus, and without being bound by theory, as the content of organic matter, such as the alkaline material, which acts as an insulator on the surface of the metal oxide nanoparticles decreases, the interfacial charging between the light-emitting layer 13 and the electronic auxiliary layer 14, including the quantum dots, can be removed to reduce degradation and improve lifetime.

[0140] Therefore, the conductivity of the electronic auxiliary layer 14 can be greater than approximately 6.5 × 10⁻⁶. -8 Siemens / cm (S / cm), for example, greater than approximately 7.0 × 10 -8 S / cm, greater than approximately 8.0 × 10 -8 S / cm, greater than approximately 8.5 × 10 -8 S / cm, greater than approximately 9.0 × 10 -8 S / cm, greater than approximately 9.5 × 10 -8 S / cm, or greater than approximately 10.0 × 10 -8 S / cm and less than about 1.0 S / cm, for example less than about 0.1 S / cm, less than about 1.0 × 10 -2S / cm, or less than approximately 1.0 × 10 -3 S / cm. It can be greater than approximately 6.5 × 10⁻⁶. -8 S / cm and less than approximately 1.0 × 10 -3 S / cm, for example, greater than approximately 7.0 × 10 -8 S / cm and less than approximately 1.0 × 10 -3 S / cm, greater than approximately 7.5 × 10 -8 S / cm and less than approximately 1.0 × 10 -3 S / cm, greater than approximately 8.0 × 10 -8 S / cm and less than approximately 1.0 × 10 -3 S / cm, greater than approximately 8.5 × 10 -8 S / cm and less than approximately 1.0 × 10 -3 S / cm, greater than approximately 9.0 × 10 -8 S / cm and less than approximately 1.0 × 10 -3 S / cm, greater than approximately 9.5 × 10 -8 S / cm and less than approximately 1.0 × 10 -3 S / cm, or greater than approximately 10.0 × 10 -8 S / cm and less than approximately 1.0 × 10 -3 S / cm. Additionally, when the electron auxiliary layer 14 further includes an electron injection layer or a hole blocking layer in addition to the electron transport layer, the conductivity can be the conductivity of the electron transport layer.

[0141] Meanwhile, when the surface of the metal oxide nanoparticles is modified with the organic acid, crystal growth of the metal oxide nanoparticles is promoted at or near the surface defect portion, thereby increasing the crystallinity of the metal oxide nanoparticles.

[0142] The thickness of the electron auxiliary layer 14 can be appropriately selected taking into account the emission wavelength of the quantum dots, the thickness of the light-emitting layer 13, the type and thickness of the hole auxiliary layer 12, etc. For example, the quantum dots in the light-emitting layer 13 can emit light with a center wavelength of about 600 nm to about 640 nm, and the electron auxiliary layer 14 can have a thickness greater than or equal to about 20 nm, for example greater than or equal to about 25 nm, greater than or equal to about 30 nm, greater than or equal to about 35 nm, greater than or equal to about 40 nm, or greater than or equal to about 45 nm and less than or equal to about 80 nm, for example less than or equal to about 75 nm, less than or equal to about 70 nm, less than or equal to about 65 nm, less than or equal to about 60 nm, or less than or equal to about 55 nm. For example, the quantum dots in the light-emitting layer 13 can emit light with a center wavelength of less than or equal to about 500 nm, and the electron-assisted layer 14 can have a thickness of more than or equal to about 60 nm, for example, more than or equal to about 65 nm, more than or equal to about 70 nm, or more than or equal to about 75 nm and less than or equal to about 120 nm, for example, less than or equal to about 115 nm, less than or equal to about 110 nm, less than or equal to about 105 nm, less than or equal to about 100 nm, less than or equal to about 95 nm, or less than or equal to about 90 nm.

[0143] The light-emitting device 10 may have a maximum external quantum efficiency (EQE) of about 10%, for example, about 11%, about 12%, about 13%, about 14%, about 15%, about 16%, or about 17%. 最大 Additionally, the light-emitting device may have a brightness of about 50,000 nits or more, for example, about 54,000 nits or more, about 61,000 nits or more, about 64,000 nits or more, or about 71,000 nits or more.

[0144] Another embodiment relates to a method for manufacturing the aforementioned light-emitting device.

[0145] The manufacturing method includes: forming an electronic auxiliary layer comprising metal oxide nanoparticles; and contacting the electronic auxiliary layer with an organic acid or a solution comprising an organic acid.

[0146] The method of manufacturing the light-emitting device may further include forming a first electrode and a second electrode, a light-emitting layer including quantum dots, or an optional hole-assisted layer.

[0147] The method for forming the electronic auxiliary layer comprising metal oxide nanoparticles can be appropriately selected and is not particularly limited. The electronic auxiliary layer comprising metal oxide nanoparticles can be formed by solution processes such as spin coating, rod coating, spraying, slot coating, inkjet printing, nozzle printing, jetting, or blade coating, but is not limited thereto.

[0148] Contacting the electronic auxiliary layer with an organic acid or a solution containing an organic acid may include coating the electronic auxiliary layer with the organic acid or a solution containing an organic acid, or immersing the electronic auxiliary layer in the organic acid or a solution containing an organic acid. Contacting the electronic auxiliary layer with an organic acid or a solution containing an organic acid can be performed using a simple solution process, which is also a method that can be used to form the electronic auxiliary layer.

[0149] The method of coating the electronic auxiliary layer with organic acid or a solution containing organic acid can be performed by spin coating, bar coating, spray coating, slot coating, inkjet printing, nozzle printing, jetting, or doctor blade coating, but is not limited thereto.

[0150] The solution comprising organic acids may include solvents capable of dissolving the organic acids, including water, acetone, alcohols (ethanol), ethers, ethyl acetate, dimethyl sulfoxide (DMSO), or combinations thereof.

[0151] Another embodiment provides a display device including the aforementioned light-emitting device.

[0152] However, the light-emitting device is not limited to the display device (e.g., as a QD-LED), but can be applied to biomarkers (biosensors, bioimaging), photodetectors, or solar cells (e.g., QD optoelectronic devices).

[0153] The following describes specific implementations of this disclosure. However, the embodiments described below are for illustrative purposes only, and the scope of this disclosure is not limited thereto.

[0154] Analytical methods

[0155] [1] Electroluminescence spectroscopy

[0156] Electroluminescence properties were evaluated using a Keithley 2200 source measurement system and a Minolta CS2000 spectroradiometer (current-voltage-luminance measurement system).

[0157] [2] Infrared spectroscopy (IR)

[0158] Using Agilent's Varian 670-IR (Harrick Seagull variable angle accessory) in inward reflection (hemispherical ATR) mode at 4000-650cm. -1IR analysis was performed under the following conditions: range, more than 128 scans, Ge crystal, and an incident angle of 64°.

[0159] [3] Gas chromatography (GC) analysis

[0160] GC analysis was performed using an Agilent GC-MS (pyrolysis unit), 7890B, 5977A, with the following settings: pyrolysis unit: 450°C; column: 30m × 0.25mm × 0.25mm (UA5); flow rate: He (1 mL / min); inlet temperature: 300°C; furnace temperature: 50°C (2 min), 20°C / min, 320°C (10 min); analyzer: quadrupole (range: 10 m / z to 550 m / z).

[0161] [4] Selected Area Diffraction Pattern (SADP) Analysis

[0162] SADP analysis was performed using JEOL's ARM 200F.

[0163] Manufacturing of light-emitting devices

[0164] Preparation Example 1

[0165] (1) Manufacturing of ZnTeSe core

[0166] Selenium and tellurium were dispersed in trioctylphosphine (TOP) to obtain 2M Se / TOP stock solutions and 2M Te / TOP stock solutions. A trioctylamine solution comprising 0.125 mmol zinc acetate and 0.25 mmol palmitic acid was prepared in a 400 mL reaction flask. The solution was heated at 120 °C for 1 hour under vacuum, then nitrogen was added to the reaction flask, and the flask was heated to 300 °C. The prepared Se / TOP and Te / TOP stock solutions were rapidly added to the reaction flask, and the resulting mixture was reacted at 300 °C for 1 hour. When the reaction was complete, the reaction solution was cooled to room temperature, acetone was added to the flask, and the resulting precipitate was centrifuged and dispersed in toluene.

[0167] (2) Preparation of ZnTeSe / ZnSeS core / shell semiconductor nanocrystals emitting blue light

[0168] 0.9 mmol zinc acetate, 1.8 mmol oleic acid, and 10 mL trioctylamine were added to a reaction flask and heated under vacuum at 120 °C for 10 min. Nitrogen gas was added to the reaction flask and the flask was heated to 280 °C. Subsequently, a toluene dispersion (OD, optical density of first exciton absorption, OD = 0.45) of the prepared ZnTeSe core was added to the reaction flask over 10 seconds, followed by the addition of 0.6 mmol Se / TOP and 2.0 mmol S / TOP (a dispersion of sulfur in trioctylphosphine), and the mixture was allowed to react at 280 °C for 120 min to prepare a (crude) reaction solution. When the reaction was complete, the reaction solution was rapidly cooled to room temperature (24 °C), ethanol was added, and the resulting precipitate was centrifuged and redispersed in cyclohexane to prepare ZnTeSe / ZnSeS semiconductor nanocrystals.

[0169] Preparation Example 2

[0170] 3.06 mmol zinc acetate dihydrate, 0.54 mmol magnesium acetate tetrahydrate, and 30 mL dimethyl sulfoxide were placed in a reactor and dissolved therein. Subsequently, 5.5 mmol tetramethylammonium hydroxide (TMAH) pentahydrate was dissolved in 10 mL ethanol, and this solution was placed in the reactor. The mixture was stirred for 1 hour to prepare Zn. 0.85 Mg 0.15 O nanoparticles (average particle diameter: approximately 3 nanometers (nm)). Zn 0.85 Mg 0.15 O nanoparticles were mixed with ethyl acetate at a volume ratio of 1:4, and the resulting mixture was centrifuged and dispersed in ethanol to obtain a ZnMgO solution for use in the electron transport layer. Examples 1 to 3

[0171] PEDOT:PSS solution (HCStarks GmbH) was spin-coated onto a glass substrate with ITO deposited (as anode) and surface-treated with UV-ozone for 15 minutes, and then heat-treated at 150°C for 30 minutes to form a 30 nm thick hole injection layer (HIL). A solution comprising poly[(9,9-dioctylfluorene-2,7-diyl-co-(4,4'-(N-4-butylphenyl)-diphenylamine](TFB) (Sumitomo Corp.) was then spin-coated onto the hole injection layer (HIL), and the coated substrate was heat-treated at 150°C for 30 minutes to form a 25 nm thick hole transport layer (HTL). A quantum dot light-emitting layer emitting light at a wavelength of 465 nm was formed on the HTL as follows: a dispersion of ZnTeSe / ZnSeS semiconductor nanocrystals prepared in Preparation Example 1 in cyclohexane was coated onto the HTL, and it was heat-treated at 80°C for 30 minutes under a nitrogen atmosphere. A ZnMgO solution for the electron transport layer (ETL) prepared in Preparation Example 2 was spin-coated onto the quantum dot light-emitting layer and heat-treated at 80°C for 30 minutes.

[0172] Organic acids (Example 1: citric acid, Example 2: acetic acid, Example 3: oxalic acid) were dissolved in ethanol, and the solution was spin-coated onto the electron transport layer (ETL), then dried at room temperature for 1 hour under a nitrogen atmosphere. Aluminum electrodes patterned into electrode shapes were vacuum deposited as the upper cathode to fabricate a quantum dot light-emitting device.

[0173] Comparative Example 1

[0174] The quantum dot light-emitting device was manufactured according to the method of Example 1, except that: after forming the quantum dot light-emitting layer, a spin-coating process including a solution of organic acid was not performed.

[0175] Comparative Example 2

[0176] The quantum dot light-emitting device was manufactured according to the method of Example 2, except that: after forming the quantum dot light-emitting layer, a spin-coating process including an organic acid solution was not performed.

[0177] Comparative Example 3

[0178] The quantum dot light-emitting device was manufactured according to the method of Example 3, except that after forming the quantum dot light-emitting layer, a spin-coating process including an organic acid solution was not performed.

[0179] Experimental Example 1: Evaluation of the characteristics of the light-emitting devices fabricated in Example 1 and Comparative Example 1

[0180] For the quantum dot light-emitting devices fabricated in Example 1 and Comparative Example 1, the electroluminescence properties were evaluated using a Keithley 2200 source measurement apparatus and a Minolta CS2000 spectroradiometer (current-voltage-luminance measurement apparatus).

[0181] A voltage is applied to the light-emitting device, and the luminance and electroluminescence (EL) are measured using the current-voltage-luminance measurement device. The external quantum efficiency is then calculated. The results are shown in... Figures 3 to 8 middle.

[0182] Figures 3 to 8 A comparison graph showing the measurement results of current density based on voltage, external quantum efficiency based on luminance, luminance based on voltage, luminance lifetime, lifetime drive voltage, and electroluminescence (EL) spectrum of the light-emitting devices of Example 1 and Comparative Example 1 is provided. Additionally, the luminescence lifetime characteristics of the quantum dot light-emitting devices were measured. The results are listed in Table 1.

[0183] Table 1

[0184]

[0185]

[0186] 1) EQE 最大 (%): Maximum external quantum efficiency

[0187] 2) Lum. 最大 (Cd / m 2 Maximum brightness

[0188] 3) T50 (hours): The time (in hours) taken for the brightness to decrease to 50% of the initial brightness based on 100%.

[0189] 4)λ 最大 (nm): Maximum emission wavelength in the emission spectrum

[0190] 5) FWHM (nm): Half-width of emission spectrum (FWHM)

[0191] Reference Figures 3 to 8 As shown in Table 1, compared with the light-emitting device of Comparative Example 1, the light-emitting device of Example 1 exhibits an improved efficiency of 6.9% to 10.5%, an improved brightness of about 34,000 nits to about 61,000 nits, and an increased lifetime (T50) of about 53 hours to about 105 hours.

[0192] Experimental Example 2: Evaluation of the characteristics of the light-emitting devices fabricated in Example 2 and Comparative Example 2

[0193] The electroluminescence properties of the quantum dot light-emitting devices according to Example 2 and Comparative Example 2 were evaluated using the same method as in Experimental Example 1.

[0194] Figures 9 to 13 A comparison graph showing the measurement results of current density based on voltage, external quantum efficiency based on luminance, luminance based on voltage, luminance lifetime, and lifetime driving voltage for the light-emitting devices of Example 2 and Comparative Example 2 is provided. Additionally, the luminescence lifetime characteristics of the quantum dot light-emitting devices were measured. The results are listed in Table 2.

[0195] Table 2

[0196]

[0197]

[0198] Reference Figures 9 to 13 As shown in Table 2, compared with the light-emitting device according to Comparative Example 2, the light-emitting device according to Example 2 exhibits an improved efficiency of 9.8% to 13.1%, an improved brightness of about 45,000 nits to about 71,000 nits, and an increased lifetime (T50) of 46 hours to 136 hours.

[0199] Experimental Example 3: Evaluation of the characteristics of the light-emitting devices fabricated in Example 3 and Comparative Example 3

[0200] The electroluminescence properties of the quantum dot light-emitting devices according to Example 3 and Comparative Example 3 were evaluated using the same method as in Experimental Example 1. Here, the content of oxalic acid in the organic acid solution was increased by 10 times for additional experiments, which were labeled as Example 3-1 (oxalic acid content × 1) and Example 3-2 (oxalic acid content × 10), respectively.

[0201] Figures 14 to 18 A comparative graph showing the measurement results of current density based on voltage, external quantum efficiency based on luminance, luminance based on voltage, luminance lifetime, and lifetime driving voltage for the light-emitting devices of Examples 3-1, 3-2, and Comparative Example 3 is provided. Additionally, the luminescence lifetime characteristics of the quantum dot light-emitting devices were measured. The results are listed in Table 3.

[0202] Table 3

[0203]

[0204] Reference Figures 14 to 18 As shown in Table 3, compared with the light-emitting device according to Comparative Example 3, the light-emitting device according to Examples 3-2 exhibits an improved efficiency of 13.1% to 16.5%, an improved brightness of about 40,500 nits to about 55,000 nits, and an increased lifetime (T50) of 16 hours to 71 hours.

[0205] Experimental Example 4: Evaluation of SADP Analysis of the Electronic Assist Layer

[0206] SADP analysis was performed on the metal oxide nanoparticles included in the electronic auxiliary layer of the light-emitting devices according to Examples 1 and 2 and Comparative Example 1, and the results are shown in Figure 19 In. Figure 19 In the pattern, the stronger the intensity, the greater the crystallinity of the metal oxide particles.

[0207] Experimental Example 5: Evaluation of IR and GC Analysis of the Electronic Assist Layer

[0208] IR analysis was performed on the electronic auxiliary layer of the light-emitting device according to Example 2 and Comparative Example 2, and the results are shown in Figure 20 middle.

[0209] In addition, GC analysis was performed on the electronic auxiliary layer of the light-emitting device according to Example 2 and Comparative Example 2, and the results are shown in... Figure 21 In. Figure 21 The bottom figure shows the results of the light-emitting device according to Example 2, and the top figure shows the results of the light-emitting device according to Comparative Example 2.

[0210] Reference Figure 20 Compared to Comparative Example 2, Example 2 exhibited a growth rate of 1486 cm⁻¹ due to organic acid treatment. -1 Approximately 945cm -1 The content of TMAH(N-CH3) in the vicinity is reduced.

[0211] Additionally, refer to Figure 21 Compared with Comparative Example 2, Example 2 exhibited the presence of acetic acid or methyl ester in the range of about 2 minutes to about 2.1 minutes and around 2.4 minutes, respectively, due to organic acid treatment.

[0212] Experimental Example 6: Evaluation of the content of organic matter in the electron auxiliary layer

[0213] By using the Quantum2000 manufactured by Physical Electronics, Inc., with an accelerating voltage of 0.5 keV to 15 keV, 300 W, and 200 × 200 square micrometers (μm), 2 X-ray photoelectron spectroscopy (XPS) was performed on the electron auxiliary layer of the light-emitting devices according to Example 1 and Comparative Example 1 under the condition of minimum analytical area to determine the molar ratio of carbon atoms to metal atoms, and the results are shown in Table 4.

[0214] Table 4

[0215] C O Mg Zn C:(Mg+Zn) Comparative Example 1 31.32 45.43 5.72 17.53 1.347 Example 1 25.97 44.24 3.64 25.00 0.907

[0216] Referring to Table 4, because the electronic auxiliary layer is treated with a solution including organic acids to desorb organic substances including alkaline materials such as TMAH on the surface of the metal oxide nanoparticles, and then the layer is washed with an organic solvent used in the acid treatment to remove the desorbed substances, Example 1 exhibits a molar ratio of carbon atoms to metal atoms (i.e., Zn and Mg) of less than or equal to 1.3:1.

[0217] In addition, XPS analysis of the surface-modified metal oxide particles of Example 1 showed a higher Zn:Mg molar ratio than that of Comparative Example 1.

[0218] Although this disclosure has been described with respect to exemplary embodiments which are now considered practical, it will be understood that this disclosure is not limited to the disclosed embodiments. Rather, it is intended to cover various variations and equivalent arrangements included within the spirit and scope of the appended claims.

[0219] Symbol Explanation

[0220] 10: Light-emitting devices

[0221] 11: First electrode

[0222] 12: Hole auxiliary layer

[0223] 13: Emissive layer

[0224] 14: Electronic auxiliary layer

[0225] 15: Second electrode

Claims

1. Light-emitting devices, including: First and second electrodes, each with surfaces opposite to each other, A light-emitting layer disposed between the first electrode and the second electrode, wherein the light-emitting layer comprises quantum dots, and An electronic auxiliary layer disposed between the light-emitting layer and the second electrode. The electronic auxiliary layer comprises metal oxide nanoparticles, wherein the metal oxide nanoparticles include anions of organic acids bound to the surface of the metal oxide nanoparticles, and The anions of the organic acids mentioned above include citrate ions, oxalate ions, sulfonate ions, or combinations thereof.

2. The light-emitting device of claim 1, wherein the anion of the organic acid is chemically bonded to a metal ion at the surface of the metal oxide nanoparticle, or provides a bonding product of the metal ion with oxygen or hydroxyl, or a combination thereof.

3. The light-emitting device of claim 1, wherein the organic acid has a molecular weight of 30 g / mol to 600 g / mol and a pK value of 1 to 5. a .

4. The light-emitting device of claim 1, wherein the anion of the organic acid is present on the surface of the metal oxide nanoparticles in an amount of 0.001 to 10% by weight, based on the total weight of the metal oxide nanoparticles in the electronic auxiliary layer.

5. The light-emitting device of claim 1, wherein the electronic auxiliary layer has a molar ratio of carbon atoms to all metal atoms of the metal oxide nanoparticles of less than or equal to 1.3:

1.

6. The light-emitting device of claim 1, wherein the content of alkaline material in the metal oxide nanoparticles is less than or equal to 2% by weight, based on the total weight of the metal oxide nanoparticles in the electronic auxiliary layer.

7. The light-emitting device of claim 6, wherein the alkaline material is present and comprises tetramethylammonium hydroxide, potassium hydroxide, sodium hydroxide, lithium hydroxide, or a combination thereof.

8. The light-emitting device of claim 1, wherein the electronic auxiliary layer has a size greater than 6.5 × 10⁻⁶. -8 Siemens conductivity per centimeter.

9. The light-emitting device of claim 1, wherein the metal oxide comprises Zn, Mg, Ca, Zr, W, Li, Ti, Y, Al, or combinations thereof.

10. The light-emitting device of claim 1, wherein the metal oxide is represented by chemical formula 1: Chemical Formula 1 Zn 1-x M x O in, In chemical formula 1, M is Mg, Ca, Zr, W, Li, Ti, Y, Al, or a combination thereof, and 0≤x≤0.5。 11. The light-emitting device of claim 1, wherein the metal oxide comprises zinc oxide, zinc magnesium oxide, or a combination thereof.

12. The light-emitting device of claim 1, wherein the metal oxide nanoparticles have an average particle size greater than or equal to 1 nanometer and less than or equal to 100 nanometers.

13. The light-emitting device of claim 1, wherein the light-emitting device further comprises a hole-assisting layer disposed between the first electrode and the light-emitting layer, the hole-assisting layer comprising a hole injection layer, a hole transport layer, an electron blocking layer, or a combination thereof.

14. The light-emitting device of claim 1, wherein the light-emitting device has a maximum external quantum efficiency of 10% or greater and a brightness of 50,000 nits or greater.

15. A method for manufacturing a light-emitting device as described in any one of claims 1-14, comprising: Forming an electronically assisted layer comprising metal oxide nanoparticles; and The electronic auxiliary layer is brought into contact with an organic acid or a solution containing an organic acid.

16. The method of claim 15, wherein contacting the electronic auxiliary layer with an organic acid or a solution comprising an organic acid comprises coating the electronic auxiliary layer with the organic acid or the solution comprising an organic acid, or immersing the electronic auxiliary layer in the organic acid or the solution comprising an organic acid.

17. The method of claim 16, wherein the coating comprises spin coating, bar coating, spray coating, slot coating, inkjet printing, nozzle printing, jetting, or blade coating.

18. A display device, comprising a light-emitting device as claimed in any one of claims 1-14.

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