Quantum dot-based light-emitting device using zinc oxide for suppressing photoluminescence quenching, and manufacturing method therefor

Abstract

A quantum dot (QD)-based light-emitting device is disclosed. The light-emitting device comprises: an emission layer that includes a quantum dot structure including a core and a shell; an electron transport layer (ETL) electrically connected to one side surface of the emission layer so as to inject electrons into the emission layer; a hole transport layer (HTL) electrically connected to another side surface of the emission layer; and a hole injection layer (HIL) for injecting holes into the HTL. Here, the ETL is composed of a metal oxide including zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg).

Description

Quantum dot-based light-emitting device using zinc oxide that suppresses photoluminescence reduction and method for manufacturing the same

[0001] The embodiments relate to a quantum dot-based light-emitting device and a method for manufacturing the same. More specifically, the embodiments relate to a technology for suppressing quenching of the photoluminescence of quantum dots by configuring the electron transport layer (ETL) of the quantum dot-based light-emitting device with zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg), which is different from conventional materials.

[0002] Quantum dot (QD) light-emitting devices are devices that utilize optical properties arising from the quantized energy levels of electrons and holes by confining them to a dimension smaller than the Bohr radius of excitons. For example, Patent Publication No. 10-2021-0000074 discloses a quantum dot light-emitting diode including a quantum dot light-emitting layer, a method for manufacturing the same, and a quantum dot light-emitting display device.

[0003] In a quantum dot light-emitting device, electrons move from the cathode through the electron transport layer (ETL) to the quantum dot, and holes move from the anode through the hole transport layer (HTL) to the quantum dot. When the electrons and holes meet in the core of the quantum dot, which has a core-shell structure, light is generated. However, if the electron transport characteristics of the ETL and the hole transport characteristics of the HTL are not balanced, energy is lost as heat due to trap emission caused by excessive electron injection, which results in quenching of photoluminescence, lowering the efficiency of the light-emitting device.

[0004] In conventional light-emitting devices, zinc oxide (ZnO) was mainly used for ETL. However, zinc oxide (ZnO) has a problem in that it has too high electron injection characteristics and many surface defects, which leads to a high reduction in photoluminescence of quantum dots. To solve this problem, a method of doping magnesium (Mg) into the zinc oxide (ZnO) of the ETL was used. However, in order for the magnesium (Mg) doping to be effective, a high content of magnesium (Mg) of 10% or more is required, and even with this doping, there is still a problem in that the capture emission and photoluminescence reduction characteristics of quantum dots are high.

[0005] [Prior Art Literature]

[0006] (Patent Document 001) Patent Publication No. 10-2021-0000074

[0007] According to one aspect of the present invention for solving the problems of the above-described prior art, a quantum dot-based light-emitting device and a method for manufacturing the same can be provided in which the electron transport layer (ETL) of the quantum dot-based light-emitting device is composed of zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg), which is different from conventional materials, thereby suppressing the quenching of the quantum dot's light emission.

[0008] A quantum dot (QD)-based light-emitting device according to one aspect of the present invention comprises: a light-emitting layer including a quantum dot structure including a core and a shell; an electron transport layer (ETL) electrically connected to one side of the light-emitting layer and configured to inject electrons into the light-emitting layer; a hole transport layer (HTL) electrically connected to the other side of the light-emitting layer; and a hole injection layer (HIL) configured to inject holes into the hole transport layer. In this case, the electron transport layer is made of a metal oxide including zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg).

[0009] In one embodiment, the electron transport layer is made of zinc oxide (ZnMgSnO) containing 1 to 20 mol % tin (Sn) and 1 to 20 mol % magnesium (Mg). In another embodiment, the electron transport layer is made of zinc oxide (ZnMgSnO) containing 1 to 10 mol % tin (Sn) and 5 to 15 mol % magnesium (Mg).

[0010] In one embodiment, the metal oxide has a band gap of 3.65 eV to 4.13 eV and has ultraviolet absorption properties.

[0011] In one embodiment, the metal oxide has an average particle size of 2 to 5 nm. In another embodiment, the metal oxide has an average particle size of 2 to 3.5 nm.

[0012] A method for manufacturing a quantum dot-based light-emitting device according to one aspect of the present invention comprises the steps of: preparing an ethanol solution containing an organic or inorganic base reagent; preparing a cationic solution containing a zinc (Zn) compound, a magnesium (Mg) compound, and a tin (Sn) compound; mixing the ethanol solution with the cationic solution to synthesize zinc tin magnesium oxide (ZnSnMgO) particles; adding ethyl acetate to the synthesized zinc tin magnesium oxide (ZnSnMgO) particles to precipitate them; and dissolving the precipitate produced in the precipitating step in ethanol, thereby forming an electron transport layer made of a metal oxide containing zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg).

[0013] In one embodiment, the step of preparing the ethanol solution comprises dissolving 0.55 M tetramethylammonium hydroxide (TMAH) in 8 ml of ethanol.

[0014] In one embodiment, the step of preparing the cationic solution includes dissolving 2.4 to 2.7 mmol of zinc (Zn) acetate dihydrate, 0.15 to 0.45 mmol of magnesium (Mg) acetate tetrahydrate, and 0.15 to 0.3 mmol of tin (Sn) acetate in 30 ml of a dimethyl sulfoxide (DMSO) solution.

[0015] In one embodiment, the step of precipitating and the step of dissolving the precipitate in ethanol may be repeated multiple times (e.g., three times).

[0016] A light-generating method according to one aspect of the present invention comprises the steps of: preparing a light-emitting device including a light-emitting layer including a quantum dot structure including a core and a shell, an electron transport layer electrically connected to one side of the light-emitting layer and configured to inject electrons into the light-emitting layer, a hole transport layer electrically connected to the other side of the light-emitting layer, and a hole injection layer configured to inject holes into the hole transport layer; and a step of generating light by the quantum dot structure by applying a voltage between the electron transport layer and the hole injection layer. At this time, the electron transport layer is made of a metal oxide including zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg).

[0017] A quantum dot (QD)-based light-emitting device according to one aspect of the present invention is different from a conventional light-emitting device in that the electron transport layer (ETL) of the quantum dot-based light-emitting device is made of zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg).

[0018] According to one aspect of the present invention, a light-emitting device can achieve higher performance than a conventional quantum dot light-emitting device by adjusting the electron transport characteristics of an electron transport layer to be similar to the hole transport characteristics through simultaneous doping of tin (Sn) and magnesium (Mg), thereby significantly reducing the trap emission phenomenon of quantum dots and suppressing the photoluminescence quenching characteristic.

[0019] FIG. 1 is a cross-sectional view of a quantum dot-based light-emitting device according to one embodiment.

[0020] FIG. 2 is a flowchart showing each step of a method for manufacturing a quantum dot-based light-emitting device according to one embodiment.

[0021] FIG. 3 is a cross-sectional view showing a state after a thin film encapsulation (TFE) process of a quantum dot-based light-emitting device according to one embodiment.

[0022] FIGS. 4A and 4B are diagrams showing the energy levels of each layer of a quantum dot-based light-emitting device according to one embodiment.

[0023] FIG. 5 is a scanning transmission electron microscope (TEM) image of zinc tin magnesium oxide (ZnSnMgO) particles according to one embodiment.

[0024] FIG. 6 is a graph comparing the ultraviolet (UV) absorption characteristics of an electron transport layer of a quantum dot-based light-emitting device according to one embodiment and a conventional electron transport layer material.

[0025] FIG. 7 is a graph comparing the photoluminescence (PL) of a quantum dot-based light-emitting device according to one embodiment and a conventional electron transport layer material in a solution state.

[0026] FIG. 8 is a graph showing the PL of a quantum dot-based light-emitting device according to one embodiment when the electron transport layer is combined with quantum dots compared to a conventional electron transport layer material.

[0027] FIG. 9 is a graph showing the current density according to voltage of a quantum dot-based light-emitting device according to one embodiment compared to a conventional light-emitting device.

[0028] Fig. 10 shows the luminance (cd / m) according to voltage of a quantum dot-based light-emitting device according to one embodiment. 2 ) is a graph comparing it with conventional light-emitting elements.

[0029] FIG. 11 is a graph showing the external quantum efficiency (EQE) according to voltage of a quantum dot-based light-emitting device according to one embodiment compared to a conventional light-emitting device.

[0030] Fig. 12 is a graph showing the lifespan characteristics of a quantum dot-based light-emitting device according to one embodiment compared to a conventional light-emitting device.

[0031] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0032] In describing the embodiments of this specification, if a detailed description of a known configuration or function is judged to obscure the gist of the embodiments of this specification, a detailed description thereof will be omitted. In addition, parts of the drawings that are not related to the description of the embodiments of this specification have been omitted, and similar parts have been designated with similar drawing reference numerals.

[0033] In the embodiments of this specification, when a component is said to be "connected," "coupled," or "connected" to another component, this may include not only a direct connection, but also an indirect connection in which another component exists in between. Furthermore, when a component is said to "include" or "have" another component, unless otherwise specifically stated, this does not exclude the other component, but rather implies that the other component may be included.

[0034] In the embodiments of this specification, the terms first, second, etc. are used only for the purpose of distinguishing one component from another component, and do not limit the order or importance between components unless specifically stated otherwise. Therefore, within the scope of the embodiments of this specification, a first component in an embodiment may be referred to as a second component in another embodiment, and similarly, a second component in an embodiment may be referred to as a first component in another embodiment.

[0035] Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0036] When a layer is referred to herein as being "on" another layer or substrate, it may be formed directly on the other layer or substrate, or a third layer may be interposed therebetween. Furthermore, directional expressions such as "upper," "upper," and "top" in this specification may be interpreted to mean "lower," "lower," and "bottom," depending on the reference. In other words, expressions of spatial direction should be understood as relative directions and should not be construed as limiting them to mean absolute directions.

[0037]

[0038] Quantum dot-based light-emitting devices

[0039] FIG. 1 is a perspective view showing a light-emitting structure using a self-luminous quantum dot (QD) according to one embodiment.

[0040] Referring to FIG. 1, a quantum dot-based light-emitting structure included in a light-emitting device according to embodiments includes a first electrode (e.g., an anode) (201), a second electrode (e.g., a cathode) (206), an electron transport layer (ETL) (205), an emissive layer (EML) (204), a hole transport layer (HTL) (203), and a hole injection layer (HIL) (202).

[0041] The light-emitting layer (204) is a place where electrons and holes transmitted by the current supplied from the first electrode (201) and the second electrode (206) combine, and may include one or more light-emitting particles. The electrons and holes meet and combine in the light-emitting layer (204) to generate excitons, and the generated excitons can generate light with a wavelength corresponding to the size of the light-emitting particles while transitioning from an excited state to a ground state.

[0042] Accordingly, the light-emitting layer (204) can emit light within a predetermined wavelength range determined by the particle size. The light within the predetermined wavelength range is a wavelength range within the visible light range, and may include, for example, any one of a first wavelength range of 380 nm to 488 nm, a second wavelength range of 490 nm to 510 nm, a third wavelength range of 510 nm to 580 nm, a fourth wavelength range of 582 nm to 600 nm, and a fifth wavelength range of 620 nm to 680 nm.

[0043] The light-emitting particles constituting the light-emitting layer (204) may include at least one quantum dot (or, also referred to as a quantum dot structure). That is, the light-emitting particles may all be composed of quantum dots, or one of the light-emitting particles may be composed of a quantum dot and the other may be composed of another type of light-emitting material distinct from the quantum dot, such as a commercially available phosphor.

[0044] Since quantum dots have a discontinuous energy band gap due to the quantum confinement effect, they can convert incident light into light having a specific wavelength and emit it. Therefore, when all of the light-emitting particles constituting the light-emitting layer (204) are made of quantum dots, the light-emitting layer can generate light having excellent color reproducibility and color purity.

[0045] When the light-emitting particles of the light-emitting layer (204) are made of quantum dots, the light-emitting layer (204) includes a plurality of quantum dot structures (10) having a diameter on the nanometer level. In one embodiment, the quantum dot structures (10) used in the light-emitting layer (204) are made of a crystalline inorganic semiconductor material, and thus have significantly improved light-emitting efficiency and durability compared to conventional lighting devices such as organic light-emitting diodes (OLEDs). In addition, since light emitted through the quantum dot structures (10) is emitted in all directions, excellent wide viewing angle characteristics can be obtained by using them in the light-emitting layer (204).

[0046] For example, the quantum dot structures (10) can be formed by including II-VI compound semiconductor nanocrystals such as CdS, CdSe, ZnS, ZnSe, ZnTe, HgS, HgSe, HgTe and other II-VI compositions; III-V compound semiconductor nanocrystals such as GaP, GaAs, InP and InAs and PbS, PbSe, PbTe and other III-V compositions.

[0047] However, this is an example, and the quantum dot structure (10) may be any semiconductor nanocrystal that can be selected from a group II-VI compound, a group III-V compound, a group IV-VI compound, a group IV element, a group IV compound, and a combination thereof.

[0048] At this time, the II-VI group compound is a binary compound selected from the group consisting of CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS and mixtures thereof, AgInS, CuInS, CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS and mixtures thereof, and a ternary compound selected from the group consisting of HgZnTeS, CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, It may be a material selected from the group consisting of four-element compounds selected from the group consisting of CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe and mixtures thereof.

[0049] In addition, the group III-V compound may be a material selected from the group consisting of a binary compound selected from the group consisting of GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, and mixtures thereof, a ternary compound selected from the group consisting of GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, and mixtures thereof, and a quaternary compound selected from the group consisting of GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and mixtures thereof.

[0050] Furthermore, the Group IV-VI compound may be selected from the group consisting of a binary compound selected from the group consisting of SnS, SnSe, SnTe, PbS, PbSe, PbTe, and mixtures thereof, a ternary compound selected from the group consisting of SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and mixtures thereof, and a quaternary compound selected from the group consisting of SnPbSSe, SnPbSeTe, SnPbSTe, and mixtures thereof. The Group IV element may be a material selected from the group consisting of Si, Ge, and mixtures thereof. The Group IV compound may be a binary compound selected from the group consisting of SiC, SiGe, and mixtures thereof. At this time, the binary compound, ternary compound, or quaternary compound may exist in the particle at a uniform concentration, or may exist in the same particle by being divided into states in which the concentration distribution is partially different.

[0051] In one embodiment, the quantum dot structure (10) constituting the light-emitting layer (204) may have a core (11)-shell (12) structure in which one quantum dot surrounds another quantum dot. In this case, the shell (12) may function as a protective layer that maintains semiconductor properties by preventing chemical modification of the core (11), and / or may function as a charging layer that imparts electrophoretic properties to the quantum dot structure (10).

[0052] The shell (12) may be formed of, for example, a metal or non-metal oxide, a semiconductor compound, or a combination thereof. In addition, the shell (12) may be a single layer or a multilayer composed of multiple layers. In one embodiment, the interface between the core (11) and the shell (12) may have a concentration gradient in which the concentration of elements present in the shell decreases toward the center of the quantum dot structure (10).

[0053] In one embodiment, the core (11) portion of the quantum dot structure (10) may be formed of semiconductor nanocrystals, and the shell (12) portion surrounding the core (11) portion may be formed of a crystalline inorganic semiconductor material. For example, the core (11) portion may be formed of semiconductor nanocrystals such as CdSe or CdS, and the shell (12) portion may be formed of a crystalline inorganic semiconductor material such as ZnS or ZnSe, so that nanocrystals having a core (11) / shell (12) structure of CdSe / ZnS, CdS / ZnSe, InP / ZnS, etc. may correspond to the quantum dot structure (10) of the light-emitting device according to the embodiments.

[0054] The color of light emitted through the light-emitting layer (204) can be controlled by the composition, structure, and / or size of the quantum dot structures (10) and the magnitude of the voltage applied by the first and second electrodes (201, 206). In one embodiment, the quantum dot structure (10) can be configured such that the full width of half maximum (FWHM) of the emission wavelength spectrum is about 45 nm or less to achieve excellent color purity and color reproducibility. Furthermore, in one embodiment, the quantum dot structure (10) can be configured such that the FWHM is about 30 nm or less.

[0055] In one embodiment, a ligand (not shown) made of an organic or halogen-based element may be further attached to the surface of the quantum dot structure (10). This serves to prevent nanoparticles from agglomerating in the solution and maintain the particle structure when forming the quantum dot structure (10), and also controls electron and / or hole injection into the light-emitting device, thereby affecting the brightness, lifespan, and electroluminescence efficiency of the device.

[0056] In one embodiment, the ligand attached to the surface of the quantum dot structure (10) may include an alkyl group (e.g., C1-C20). In addition, the ligand may be linear, branched, or cyclic. In addition, some of the elements constituting the ligand may be substituted with other elements (e.g., halogen elements such as F, Cl, Br, and I).

[0057] The second electrode (206) corresponds to a cathode and may include Ag, Mg, Cu, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, Li, Ca, LiF / Ca, LiF / Al, Mo, Ti, Yb, or a compound containing these (e.g., AgYb, AgMg and MgAg compounds depending on the content, etc.) or a mixture (e.g., a mixture of Ag and Mg). In addition, the second electrode (206) may be configured as a semi-transparent electrode that is at least partially optically transparent, or may be configured as a reflective electrode.

[0058] In one embodiment, the second electrode (206) may have a multi-layer structure including an optically transparent conductive film formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium tin zinc oxide (ITZO), etc., in addition to a reflective film or a semi-transparent film formed of the aforementioned material.

[0059] The electron transport layer (205) is electrically connected between the second electrode (206) and the light-emitting layer (204) and serves to transport electrons to the light-emitting layer (204). In embodiments of the present invention, the light-emitting device is differentiated from a conventional light-emitting device in that the electron transport layer (205) is made of a metal oxide including zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg). The electron transport layer (205) can be manufactured by forming a thin film by spin coating or the like using a certain amount (e.g., 30 to 50 mg / ml) of a solution in which zinc magnesium tin oxide (ZnMgSnO) particles are dissolved in ethanol. The manufacturing process of the electron transport layer (205) will be described in detail below.

[0060] In the embodiments, the thickness of the electron transport layer (205) made of zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg) can be determined by considering the balance of charge mobility with other layers such as the hole injection layer (202), the hole transport layer (203), and the light-emitting layer (204) constituting the light-emitting element.

[0061] The thickness of the electron transport layer (205) may be, for example, 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, 30 nm or more, etc., and may also be, for example, 200 nm or less, 150 nm or less, 120 nm or less, 100 nm or less, 90 nm or less, 80 nm or less, 70 nm or less, 60 nm or less, 50 nm or less, etc., and may be determined in various ways in the range of 5 nm to 200 nm or less.

[0062] Meanwhile, if the thickness of the electron transport layer (205) is less than 5 nm, not only will it fail to meet the charge transport properties required for a light-emitting device, but there is also a concern that it will be difficult to perform the electron transport function. Furthermore, if the thickness is less than the above, it is difficult to form the electron transport layer (205) with a uniform thickness, and the formed layer is likely to be damaged, which may increase leakage current.

[0063] In one embodiment, the thickness of the electron transport layer (205) may be about 20 nm to 200 nm. In another embodiment, the thickness of the electron transport layer (205) may be about 40 nm to 150 nm. In another embodiment, the thickness of the electron transport layer (205) may be about 40 nm to 120 nm.

[0064] The average size of the metal oxide particles constituting the electron transport layer (205), i.e., zinc magnesium tin oxide (ZnMgSnO) particles, can be determined to a value that enables the electron transport layer (205) to achieve excellent electron transport efficiency and electron transport reliability within the light-emitting device. In particular, by forming the metal oxide to have an appropriate average particle size, the metal oxide can be made to have ultraviolet (UV) absorption characteristics. For example, the metal oxide can have a band gap of about 3.65 eV to about 4.13 eV, which corresponds to an absorption wavelength band of 300 to 340 nm.

[0065] For example, in one embodiment, the average particle size (or average particle diameter) of the metal oxide constituting the electron transport layer (205) may be from 1 nm to 20 nm. In another embodiment, the average particle size of the metal oxide may be from 2 nm to 5 nm. Furthermore, in one embodiment, the average particle size of the metal oxide may be from 2 nm to 3.5 nm.

[0066] The hole transport layer (203) is electrically connected between the light-emitting layer (204) and the hole injection layer (202), and is made of an organic or inorganic material that can transport and inject holes injected from the hole injection layer (202) into the light-emitting layer (204) for recombination with electrons. In one embodiment, the electron transport layer (205) is arranged to contact one side (e.g., the upper surface) of the light-emitting layer (204), and the hole transport layer (203) is formed on the other side (e.g., directly below the light-emitting layer) of the light-emitting layer (204) and can be arranged to contact the light-emitting layer (204).

[0067] In one embodiment, the hole transport layer (203) may be formed of a p-type semiconductor material, or a material doped with a p-type dopant. For example, the hole transport layer (203) may be a PEDOT [Poly(3,4-ethylenedioxythiophene)] derivative, a PSS [poly(styrene sulfonate)] derivative, a poly-N-vinylcarbazole (PVK) derivative, a polyphenylenevinylene derivative, a poly p-phenylene vinylene (PPV) derivative, a polymethacrylate derivative, a poly(9,9-octylfluorene) derivative, a poly(spiro-fluorene) derivative, a TPD (N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine). It can be formed by including, but is not limited to, metal oxides such as NPB (N,N'-di(naphthalen-1-yl)-NN'-diphenyl-benzidine), m-MTDATA (tris(3-methylphenylphenylamino)-triphenylamine), TFB (poly(9,9'-dioctylfluorene-co-N-(4-butylphenyl)diphenylamine)), PFB (poly(9,9 -dioctylfluorene)-co-N,N -diphenyl-N,N -di-(p-butylphenyl)-1,4-diaminobenzene), poly-TPD, NiO, MoO3, or combinations thereof.

[0068] The hole injection layer (202) is electrically connected to the first electrode (201) corresponding to the anode, and serves to inject holes into the hole transport layer (203). At this time, the first electrode (201) may be made of a metal oxide such as an optically transparent conductive material, at least partially, ITO (indium tin oxide), IZO (indium zinc oxide), ZnO (zinc oxide), ITZO (indium tin zinc oxide), or AZO (aluminum zinc oxide), but is not limited thereto.

[0069] Additionally, the hole injection layer (202) may include an organic or inorganic material capable of transporting and injecting holes. For example, the hole injection layer 202 may be formed of a phthalocyanine compound such as copper phthalocyanine, DNTPD (N,N'-diphenyl-N,N'-bis-[4-(phenyl-m-tolyl-amino)-phenyl]-biphenyl-4,4'-diamine), m-MTDATA(4,4',4"-[tris(3-methylphenyl)phenylamino] triphenylamine), TDATA(4,4'4"-Tris(N,Ndiphenylamino) triphenylamine), 2-TNATA(4,4',4"-tris{N,-(2-naphthyl)-N-phenylamino}-triphenylamine), PEDOT / PSS(Poly(3,4-ethylenedioxythiophene) / Poly(4-styrenesulfonate)), PANI / DBSA(Polyaniline / Dodecylbenzenesulfonic acid), It can be composed of a substance including PANI / CSA (Polyaniline / Camphor sulfonicacid), PANI / PSS (Polyaniline / Poly(4-styrenesulfonate)), NPD (N,N'-di(naphthalene-l-yl)-N,N'-diphenylbenzidine), polyether ketone containing triphenylamine (TPAPEK), 4-Isopropyl-4'-methyldiphenyliodonium[Tetrakis(pentafluorophenyl)borate], HAT-CN(dipyrazino[2,3-f: 2',3'-h] quinoxaline-2,3,6,7,10,11-hexacarbonitrile), etc.

[0070]

[0071] Method for manufacturing a light-emitting device

[0072] The light-emitting device and the manufacturing method thereof according to the embodiments of the present invention are differentiated from the conventional light-emitting device and the manufacturing method thereof in that they form an electron transport layer in which zinc tin magnesium oxide (ZnSnMgO) particles are dispersed as metal oxide particles. Therefore, in this specification, the process of forming the electron transport layer during the manufacturing process of the light-emitting device according to the embodiments is first described in detail.

[0073] In one embodiment, the process for forming an electron transport layer composed of zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg) first includes the step of preparing an ethanol solution containing an organic or inorganic base reagent. For example, the ethanol solution can be formed by dissolving 0.55 M tetramethylammonium hydroxide (TMAH), an organic base reagent, in 8 ml of ethanol.

[0074] However, in other embodiments, the ethanol solution may be prepared using an inorganic base reagent, such as lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), rubidium hydroxide (RbOH), cesium hydroxide (CsOH), magnesium hydroxide (Mg(OH)2) (preferably in solution form), calcium hydroxide (Ca(OH)2), strontium hydroxide (Sr(OH)2), or barium hydroxide (Ba(OH)2).

[0075] Next, a cationic solution containing a zinc (Zn) compound, a magnesium (Mg) compound, and a tin (Sn) compound can be prepared as a cationic solution to be mixed with an ethanol solution. The cationic solution can be formed by dissolving 0.4 to 2.7 mmol of zinc (Zn) acetate dihydrate, 0.15 to 0.45 mmol of magnesium (Mg) acetate tetrahydrate, and 0.15 to 0.3 mmol of tin (Sn) acetate in 30 ml of a dimethyl sulfoxide (DMSO) solution.

[0076] Next, zinc tin magnesium oxide (ZnSnMgO) particles can be synthesized by mixing the ethanol solution with the cation solution. For example, the ethanol solution can be slowly added to the cation solution and then maintained at room temperature for a certain period of time (e.g., 1 hour) to allow the zinc tin magnesium oxide (ZnSnMgO) particles to be synthesized.

[0077] Next, an excess amount of ethyl acetate is added to the zinc tin magnesium oxide (ZnSnMgO) particles synthesized as described above to precipitate the zinc tin magnesium oxide (ZnSnMgO) particles, and the precipitate can be separated. For example, a centrifuge can be used to separate the precipitate, but the present invention is not limited thereto.

[0078] Next, the separated precipitate can be dissolved in ethanol. To increase the purity of the separated precipitate, the process of forming, separating, and dissolving the precipitate in ethanol can be repeated multiple times (e.g., three times).

[0079] In the final ethanol solution generated as described above, zinc tin magnesium oxide (ZnSnMgO) particles are dissolved, and a certain amount of the solution (e.g., 10 to 50 mg / ml) is processed into a thin film on a substrate by spin coating or the like, thereby forming an electron transport layer of a light-emitting device according to the embodiments.

[0080] By performing the electron transport layer formed as described above and the subsequent process of forming other layers of the light-emitting device, a light-emitting device according to the embodiments can be manufactured. Fig. 2 is a flowchart showing each step of a method for manufacturing a quantum dot-based light-emitting device according to one embodiment.

[0081] Referring to FIGS. 1 and 2, the entire manufacturing process of a light-emitting device will be described. First, a first electrode (201) corresponding to an anode may be formed on a substrate (not shown). The first electrode (201) may be made of a conductive material such as ITO (S1). The first electrode (201) may undergo a washing process after formation. For example, a substrate on which ITO is patterned on the surface may be washed with distilled water, acetone, and isopropanol for 15 minutes each, and then treated with ultraviolet (UV) and / or ozone for 20 minutes. In one embodiment, the thickness of the first electrode (201) may be 100 nm.

[0082] Next, a material such as PEDOT:PSS can be formed on the first electrode (201) as a hole injection layer (202) by a method such as spin coating (S2). The hole injection layer (202) can be formed by spin coating PEDOT:PSS (AI 4083) at 3000 rpm for 60 seconds on a substrate on which the first electrode (201) is patterned, followed by heat treatment. In one embodiment, the hole injection layer (202) can be formed to a thickness of 30 nm. The heat treatment can be performed outdoors at 150°C for 30 minutes or in a nitrogen (N2) atmosphere for 10 minutes, but is not limited thereto.

[0083] Next, a hole transport layer (203) can be formed using a material such as TFB (S3). For example, the hole transport layer (203) can be formed by dissolving 0.04 g of TFB (average MW=30,000 or more) in 5 ml of o-xylene, spin-coating the resulting solution at 3000 rpm for 60 seconds on top of the hole injection layer (202), and then heat-treating the solution. In one embodiment, the thickness of the hole transport layer (203) made of TFB can be 25 nm. The heat treatment can be performed in a nitrogen (N2) atmosphere at 150°C for 30 minutes, but is not limited thereto.

[0084] Quantum dots forming the light-emitting layer (204) may be formed on the hole transport layer (203). In one embodiment, the thickness of the light-emitting layer (204) may be about 20 nm. The quantum dots may be formed of CdSe / ZnSe / ZnS, etc. To form the quantum dots, a certain amount (e.g., 10 mg / ml) of a solution in which a quantum dot structure (10) is dispersed in octane is prepared, and the octane solution is spin-coated at 2000 rpm for 30 seconds on the TFB hole transport layer (203), followed by heat treatment, thereby forming the light-emitting layer (204) (S4). The heat treatment may be performed at 120°C for 30 minutes, but is not limited thereto.

[0085] Next, an electron transport layer (205) can be formed by spin-coating an ethanol solution containing zinc tin magnesium oxide (ZnSnMgO) particles on the light-emitting layer (204) and then performing a heat treatment (S5). For example, the electron transport layer (205) can be formed by spin-coating a certain amount (e.g., 30 mg / ml) of an ethanol solution at 2000 rpm for 60 seconds and then performing a heat treatment. The method of forming the ethanol solution containing zinc tin magnesium oxide (ZnSnMgO) particles is as described above. In one embodiment, the thickness of the electron transport layer (205) can be 40 nm. In addition, the heat treatment can be performed at 140°C for 30 minutes, but is not limited thereto.

[0086] Next, a second electrode (206), corresponding to an anode, may be formed on the electron transport layer (205) (S6). For example, if the second electrode (206) is made of aluminum (Al), the second electrode (206) may be manufactured by depositing the material using a thermal evaporation method. In one embodiment, the thickness of the second electrode (206) may be 100 nm.

[0087] In one embodiment, a thin film encapsulation (TFE) process may be performed during the manufacturing process of the light-emitting element to surround the light-emitting element with cover glass and UV-curable resin (S7).

[0088] Fig. 3 is a cross-sectional view showing the state after a thin film encapsulation process of a quantum dot-based light-emitting device according to one embodiment.

[0089] Referring to FIG. 3, a quantum dot-based light-emitting device according to one embodiment may include one or more protective layers (401) that serve as passivation to protect each layer constituting the light-emitting structure from the environment. For example, a first protective layer (401) may be formed on a reflective layer (300) of a light-emitting device according to a second embodiment, each layer (201 to 206) of a light-emitting structure for forming a light-emitting device may be laminated on the first protective layer (401), and a second protective layer (402) for protecting the device may be laminated on each of the laminated layers (201 to 206).

[0090] That is, in the present embodiment, the first protective layer (401) and the second protective layer (402) may serve to encapsulate and protect the light-emitting element. Each protective layer (401, 402) may be formed of glass, a resin such as UV-curable epoxy, or any other material. In addition, at least one of the protective layers (401, 402) may include a desiccant or other hygroscopic material to protect the element from moisture. This can be easily understood by those skilled in the art from the TFE technology used in conventional thin film display devices, so a detailed description thereof will be omitted.

[0091]

[0092] FIG. 4A is a schematic diagram showing the electrical connection of each layer of a quantum dot-based light-emitting device according to one embodiment, and FIG. 4B is a diagram showing the energy level of each layer in the electrical connection illustrated in FIG. 4A. In the examples illustrated in FIGS. 4A and 4B, the light-emitting structure includes a first electrode (201) made of ITO formed on a glass substrate (100), a hole injection layer (202) made of PEDOT:PSS, a hole transport layer (203) made of TFB, a light-emitting layer (204) including InP-based quantum dots, an electron transport layer (205) including zinc tin magnesium oxide (ZnSnMgO) particles, and a second electrode (206) made of aluminum (Al). In addition, in FIG. 4B, the light-emitting layer (204) is illustrated in the form of an energy level according to the color emitted by the quantum dot structure.

[0093] As shown, due to the energy levels of the materials constituting each layer, holes move from the first electrode (201) toward the light-emitting layer (204), and electrons move from the second electrode (206) toward the light-emitting layer (204), so that a color according to the characteristics of the quantum dot structure can be expressed through the combination of electrons and holes that meet in the light-emitting layer (204).

[0094]

[0095] Examples and Comparative Examples

[0096] FIG. 5 is a scanning transmission electron microscope (TEM) image of zinc tin magnesium oxide (ZnSnMgO) particles according to one embodiment.

[0097] The present inventors, in the process of manufacturing zinc tin magnesium oxide (ZnSnMgO) particles, changed the concentrations of a zinc (Zn) compound (e.g., zinc (Zn) acetate dihydrate), a magnesium (Mg) compound (e.g., magnesium (Mg) acetate tetrahydrate), and a tin (Sn) compound (e.g., tin (Sn) acetate) mixed in 30 ml of a dimethyl sulfoxide (DMSO) solution, thereby manufacturing electron transport layers in various examples having different ratios of magnesium (Mg) and tin (Sn) to zinc oxide (ZnO).

[0098] The compound ratios used in the manufacture of the electron transport layer according to each embodiment are as shown in Table 1 below.

[0099] Zinc (Zn) Acetate DihydrateMagnesium (Mg) Acetate TetrahydrateSn (Sn) AcetateDopant ICP (Mol% Content)Magnesium (Mg)SnExample 1 (ZnSnMgO)2.7 mmol0.15 mmol0.15 mmol5%3%Example 2 (ZnSnMgO)2.55 mmol0.3 mmol0.15 mmol10%3%Example 3 (ZnSnMgO)2.4 mmol0.3 mmol0.3 mmol9%6%

[0100] However, the scope of the present invention is not limited to the above-described embodiments, and the electron transport layer of the light-emitting device according to one embodiment may be formed of zinc oxide (ZnMgSnO) containing 1 to 20 mol% of tin (Sn) and 1 to 20 mol% of magnesium (Mg), respectively. In another embodiment, the electron transport layer may contain 1 to 10 mol% of tin (Sn) and 5 to 15 mol% of magnesium (Mg).

[0101] For comparison with the examples, zinc magnesium oxide (ZnMgO) (Comparative Example 1), zinc oxide (ZnO) (Comparative Example 2), and zinc tin oxide (ZnSnO) (Comparative Example 3) were used as electron transport layer materials of light-emitting devices according to the prior art, and the electron transport layer materials of Comparative Examples 1 to 3 were manufactured as follows.

[0102] 1) Comparative Example 1 - Zinc magnesium oxide (ZnMgO)

[0103] 8 ml of a 0.55 M tetramethylammonium hydroxide (TMAH) ethanol solution was slowly added to 30 ml of a dimethyl sulfoxide (DMSO) solution containing 2.55 mmol of zinc (Zn) acetate dihydrate and 0.45 mmol of magnesium (Mg) acetate tetrahydrate, and then maintained at room temperature.

[0104] The zinc magnesium oxide (ZnMgO) particles formed as described above were precipitated by adding an excess amount of ethyl acetate, and the precipitate was separated using a centrifuge. Then, the process of dissolving the precipitate in ethanol was repeated to obtain a zinc magnesium oxide (ZnMgO) thin film having a magnesium (Mg) content of 13 mol%.

[0105] 2) Comparative Example 2 - Zinc Oxide (ZnO)

[0106] Using the same process as Comparative Example 1, only 3 mmol of zinc (Zn) acetate dihydrate was added to 30 ml of dimethyl sulfoxide (DMSO) solution as a cationic solution, and through the same precipitation and dissolution process, a zinc oxide (ZnO) thin film containing 100% zinc (Zn) was obtained.

[0107] 2) Comparative Example 3 - Zinc tin oxide (ZnSnO)

[0108] Using the same process as Comparative Example 1, 2.85 mmol of zinc (Zn) acetate dihydrate and 0.15 mmol of tin (Sn) acetate were added to 30 ml of dimethyl sulfoxide (DMSO) solution as a cationic solution, and through the same precipitation and dissolution process, a zinc oxide (ZnO) thin film having a tin (Sn) content of 5 mol% was obtained.

[0109] The inventors recorded the ultraviolet absorption spectra and emission spectra of the electron transport layer materials according to the examples and comparative examples using UV-Vis absorption spectroscopy (Shimadzu, UV-2450) and a 500 W xenon lamp-equipped spectrophotometer (PSI Inc., Darsa Pro-5200), respectively.

[0110] In addition, the band gap of the electron transport layer material was calculated using the absorption results for visible light, and specifically, the conduction band edge (LUMO), Fermi level, and valence band edge (HOMO) were derived from the measurement results using a UPS device.

[0111] In addition, in order to evaluate the brightness and efficiency according to the voltage of the quantum dot light-emitting diode to which the examples and comparative examples were applied, a preset reference brightness (30,000 cd / m 2 ) was evaluated for the luminance reduction characteristics when continuously driven.

[0112] Table 2 below summarizes the ultraviolet absorption characteristics and doping element contents of electron transport layer materials manufactured according to examples and comparative examples.

[0113] Particle average size Ultraviolet (UV) First absorption wavelength ICP (metal-based mol% content) Zinc (Zn) Magnesium (Mg) Tin (Sn) Example 1 (ZnSnMgO) 3.3 nm 3 25 nm 92% 5% 3% Example 2 (ZnSnMgO) 3.1 nm 3 10 nm 87% 10% 3% Example 3 (ZnSnMgO) 3.2 nm 3 13 nm 85% 9% 6% Comparative Example 1 (ZnO) 3.7 nm 3 35 nm 100% 0% 0% Comparative Example 2 (ZnMgO) 2.3 nm 3 02 nm 87% 13% 0% Comparative Example 3 (ZnSnO) 3.5 nm 3 30 nm 97% 0% 5%

[0114] In addition, Table 3 below summarizes the HOMO (highest occupied molecular orbital) and LUMO (lowest unoccupied molecular orbital) energy levels of the electron transport layer materials manufactured according to the examples and comparative examples.

[0115] Valence band, HOMO (eV) Conduction band, LUMO (eV) Band gap Example 1 (ZnSnMgO) - 7.5 - 3.7 3.8 eV Example 2 (ZnSnMgO) - 7.4 - 3.4 4.0 eV Example 3 (ZnSnMgO) - 7.3 - 3.3 4.0 eV Comparative Example 1 (ZnO) - 7.7 - 4.0 3.7 eV Comparative Example 2 (ZnMgO) - 7.4 - 3.3 4.1 eV Comparative Example 3 (ZnSnO) - 7.4 - 3.6 3.8 eV

[0116] As shown in Table 3, the electron transport layers manufactured according to the embodiments exhibit changes in energy levels due to doping of magnesium (Mg) and tin (Sn) into the conventional zinc oxide (ZnO) material, and in particular, it can be confirmed that the current injection rate is suppressed as the conduction band energy level increases. Through this, it is possible to prevent the efficiency of the light-emitting device from being lowered due to trap emission and photoluminescence (PL) quenching caused by excessive electron injection.

[0117] FIG. 6 is a graph comparing the ultraviolet (UV) absorption characteristics of an electron transport layer of a quantum dot-based light-emitting device according to one embodiment and a conventional electron transport layer material.

[0118] Referring to FIG. 6, pure zinc oxide (ZnO) has long wavelength absorption, but magnesium (Mg) doping causes a blue shift in the absorption wavelength toward short wavelengths. On the other hand, tin (Sn) doping does not significantly shift the absorption wavelength. The zinc tin magnesium oxide (ZnSnMgO) of the hole transport layer according to embodiments may have an ultraviolet (UV) absorption wavelength of about 300 to 340 nm as illustrated. More specifically, the hole transport layer according to one embodiment may have an absorption wavelength of 305 to 330 nm.

[0119] FIG. 7 is a graph comparing the PL in a solution state of an electron transport layer of a quantum dot-based light-emitting device according to one embodiment and a conventional electron transport layer material.

[0120] Referring to Fig. 7, when ultraviolet rays are applied to zinc oxide (ZnO) and zinc magnesium oxide (ZnMgO), significant luminescence occurs due to surface defects on the particle surface, which causes a decrease in photoluminescence (PL quenching) of quantum dot-based light-emitting devices and shortens their lifespan. On the other hand, in the case of zinc tin magnesium oxide (ZnSnMgO) of the electron transport layer according to the embodiments, it can be confirmed that the decrease in photoluminescence is much lower than that of conventional materials.

[0121] FIG. 8 is a graph showing the PL of a quantum dot-based light-emitting device according to one embodiment when the electron transport layer is combined with quantum dots compared to a conventional electron transport layer material.

[0122] Referring to Fig. 8, it can be confirmed that the photoluminescence is reduced by less than 50% when the electron transport layer composed of zinc oxide (ZnO) and zinc magnesium oxide (ZnMgO) is in contact with the quantum dots, compared to when a pure quantum dot (QD only) thin film is irradiated with UV light. This indicates a direct result of the decrease in photoluminescence (PL quenching). On the other hand, in the case of the zinc tin magnesium oxide (ZnSnMgO) electron transport layer according to the examples, the decrease in photoluminescence is only about 30%, confirming that the decrease in photoluminescence is greatly suppressed compared to the conventional electron transport layer material.

[0123] FIG. 9 is a graph showing the current density according to voltage of a quantum dot-based light-emitting device according to one embodiment compared to a conventional light-emitting device, and FIG. 10 is a graph showing the luminance (cd / m) according to voltage of a quantum dot-based light-emitting device according to one embodiment. 2 ) is a graph showing the external quantum efficiency (EQE) according to voltage of a quantum dot-based light-emitting device according to an embodiment, compared to a conventional light-emitting device. Referring to FIGS. 9 to 11, it can be confirmed that the maximum brightness and light efficiency are improved compared to a conventional light-emitting device by forming an electron transport layer with zinc tin magnesium oxide (ZnSnMgO) according to embodiments.

[0124] Fig. 12 is a graph showing the lifespan characteristics of a quantum dot-based light-emitting device according to one embodiment compared to a conventional light-emitting device.

[0125] Fig. 12 shows the decrease in luminance over time when the light-emitting element was initially operated at a luminance of 30,000 nits. When the time required for the luminance to decrease by half from the initial value of 30,000 nits is defined as the lifespan, the lifespans of the light-emitting elements according to comparative examples in which the electron transport layer was formed of zinc oxide (ZnO) and zinc magnesium oxide (ZnMgO) were 3.4 hours and 8.8 hours, respectively, whereas by forming the electron transport layer of zinc tin magnesium oxide (ZnSnMgO) according to the embodiments, it can be confirmed that the lifespan is increased to about 19 to 24 hours.

[0126] Table 4 below summarizes the results described above with reference to FIGS. 6 to 12.

[0127] Operating voltage V on (V) Peak luminance (cd / m 2 )L max (Maximum 8V) EQE life (Half life time) 30,000 nit operation Example 1 (ZnSnMgO) 2.495, 800 9.82 4.5h Example 2 (ZnSnMgO) 2.410 7, 100 10.025.4h Example 3 (ZnSnMgO) 2.410 6, 800 9.719.4h Comparative Example 1 (ZnO) 2.055, 200 5.13.4h Comparative Example 2 (ZnMgO) 2.299, 600 8.28.8h Comparative Example 3 (ZnSnO) 2.247, 800 4.63.3h

[0128] The light-emitting devices according to the embodiments of the present invention described above have an advantage in that the reduction in photoluminescence (PL quenching) occurring at the interface between the electron transport layer and the quantum dot can be significantly suppressed (for example, by 50% or less compared to a conventional light-emitting device) by forming an electron transport layer with zinc oxide (ZnSnMgO) doped with magnesium (Mg) and tin (Sn). For example, the reduction in photoluminescence depending on the material of the electron transport layer is about 70% for zinc oxide (ZnO) and about 60% for zinc magnesium oxide (ZnMgO), whereas the reduction in photoluminescence can be suppressed to about 25% according to the embodiments.

[0129] In addition, the metal oxide of the electron transport layer according to the embodiments has the advantage of being able to suppress luminescence due to surface defects in self-luminescence that occurs when irradiated with ultraviolet (UV) light by more than 50% compared to conventional zinc oxide (ZnO). For example, while self-luminescence according to the material of the electron transport layer is about 67% in the case of zinc oxide (ZnO), self-luminescence according to the embodiments can be suppressed to about 25%.

[0130] The light-emitting elements according to the embodiments discussed above can be utilized not only in vehicle lighting devices such as rear combination lamps (RCLs), but also have the advantage of being widely utilized in lighting devices for other purposes, or display devices such as flexible displays or transparent displays.

[0131] While the present invention has been described above with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will appreciate that various modifications and variations of the embodiments are possible. However, such modifications should be considered within the technical protection scope of the present invention. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Claims

1. A light-emitting layer comprising a quantum dot structure including a core and a shell; An electron transport layer electrically connected to one side of the light-emitting layer and configured to inject electrons into the light-emitting layer; a hole transport layer electrically connected to the other side of the light-emitting layer; and A hole injection layer configured to inject holes into the hole transport layer, A quantum dot-based light-emitting device in which the electron transport layer is made of a metal oxide including zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg).

2. In paragraph 1, A quantum dot-based light-emitting device in which the electron transport layer is made of zinc oxide (ZnMgSnO) containing 1 to 20 mol% of tin (Sn) and 1 to 20 mol% of magnesium (Mg).

3. In paragraph 2, A quantum dot-based light-emitting device in which the electron transport layer is made of zinc oxide (ZnMgSnO) containing 1 to 10 mol% of tin (Sn) and 5 to 15 mol% of magnesium (Mg).

4. In paragraph 1, A light-emitting device based on a quantum dot having ultraviolet absorption properties, wherein the metal oxide has a band gap of 3.65 eV to 4.13 eV.

5. In paragraph 4, The above metal oxide is a quantum dot-based light-emitting device having an average particle size of 2 to 5 nm.

6. In paragraph 5, The above metal oxide is a quantum dot-based light-emitting device having an average particle size of 2 to 3.5 nm.

7. A step of preparing an ethanol solution containing an organic or inorganic base reagent; A step of preparing a cationic solution containing a zinc (Zn) compound, a magnesium (Mg) compound, and a tin (Sn) compound; A step of synthesizing zinc tin magnesium oxide (ZnSnMgO) particles by mixing the above ethanol solution with the above cation solution; A step of adding ethyl acetate to the synthesized zinc tin magnesium oxide (ZnSnMgO) particles to precipitate them; and A method for manufacturing a quantum dot-based light-emitting device, comprising a step of dissolving the precipitate produced in the above precipitating step in ethanol, and a step of forming an electron transport layer made of a metal oxide including zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg).

8. In paragraph 7, The step of preparing the above ethanol solution is: A method for manufacturing a quantum dot-based light-emitting device, comprising the step of dissolving 0.55 M tetramethylammonium hydroxide (TMAH) in 8 ml of ethanol.

9. In paragraph 7, The step of preparing the above cationic solution is: A method for manufacturing a quantum dot-based light-emitting device, comprising the step of dissolving 2.4 to 2.7 mmol of zinc (Zn) acetate dihydrate, 0.15 to 0.45 mmol of magnesium (Mg) acetate tetrahydrate, and 0.15 to 0.3 mmol of tin (Sn) acetate in 30 ml of a dimethyl sulfoxide (DMSO) solution.

10. In paragraph 7, A method for manufacturing a quantum dot-based light-emitting device, wherein the above-mentioned precipitating step and the step of dissolving the precipitate in ethanol are repeated multiple times.

11. A step of preparing a light-emitting device including a light-emitting layer including a quantum dot structure including a core and a shell, an electron transport layer electrically connected to one side of the light-emitting layer and configured to inject electrons into the light-emitting layer, a hole transport layer electrically connected to the other side of the light-emitting layer, and a hole injection layer configured to inject holes into the hole transport layer; and A step of generating light by the quantum dot structure by applying a voltage between the electron transport layer and the hole injection layer, A quantum dot-based light-generating method in which the electron transport layer is made of a metal oxide including zinc oxide (ZnMgSnO) doped with tin (Sn) and magnesium (Mg).

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