Method for manufacturing electron transport layer thin film for quantum dot light-emitting diode using supercycle atomic layer deposition and quantum dot light-emitting diode manufactured thereby

Abstract

The present invention relates to: a method for manufacturing an electron transport layer thin film for a quantum dot light-emitting diode, the method comprising a step of repeatedly performing supercycle atomic layer deposition of depositing an n-type metal oxide and at least one alloying or dopant metal oxide by using an atomic layer deposition method; an electron transport layer thin film for a quantum dot light-emitting diode obtained by the manufacturing method; and a quantum dot light-emitting diode. The electron transport layer thin film according to the present invention can exhibit high luminance and high external quantum efficiency.

Description

Method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device using supercycle atomic layer deposition and a quantum dot light-emitting device manufactured by the method

[0001] The present invention relates to a method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device using supercycle atomic layer deposition, an electron transport layer thin film for a quantum dot light-emitting device manufactured using the method, and a quantum dot light-emitting device.

[0002] Quantum dots (QDs) are promising materials for next-generation self-luminous displays, and quantum dot light-emitting devices (QD-LEDs) are increasing the brightness, stability, and efficiency of QD-LEDs by applying a hybrid structure of organic hole transport layers (HTLs) and inorganic electron transport layers (ETLs).

[0003] Metal oxides such as ZnO, TiO2, and SnO2 are widely used as ETL materials for quantum dot light-emitting devices. These metal oxides possess appropriate electron affinity and align well with the conduction band of QDs, enabling efficient electron injection and easy control of the injection amount.

[0004] Meanwhile, atomic layer deposition (ALD) can deposit metal oxides with very high quality, and its precise control of vacuum deposition and manufacturing environment allows for a variety of process approaches. Furthermore, fine thickness control enables highly uniform thin-film deposition. However, metal oxide films deposited using ALD exhibit rapid electron mobility, which worsens charge imbalance and can actually degrade device performance when applied to quantum dot light-emitting devices (QD-LEDs). Therefore, n-type metal oxides deposited using ALD have so far only been utilized as simple intermediate insertion layers and have never been used in the electron transport layer of a QD-LED.

[0005] Meanwhile, attempts have been made to improve QD-LED performance by suppressing excessive electron injection through various alloy compositions using different types of metal oxides together with metal oxide nanoparticles. However, precise control of various metal oxides remains a difficult task due to differences in the reactivity of each metal precursor, and there is a problem that the synthesis conditions become increasingly complicated as the type of metal increases.

[0006] Accordingly, the present invention is intended to solve the above problem, and the present invention provides a method for depositing an n-type metal oxide and one or more alloying or dopant metal oxides by supercycle atomic layer deposition to deposit an electron transport layer of a quantum dot light-emitting device.

[0007] The present inventors have completed the present invention by confirming that by depositing metal oxides using a supercycle atomic layer deposition method, metal oxides of various components can be densely and repeatedly deposited, and thus an electron transport layer of a quantum dot light-emitting device with excellent performance can be manufactured.

[0008] Accordingly, the present invention provides a method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, comprising a step of repeatedly performing supercycle atomic layer deposition to deposit an n-type metal oxide and one or more alloying or dopant metal oxides using an atomic layer deposition method.

[0009] In addition, the present invention is manufactured by the above manufacturing method,

[0010] Provided is an electron transport layer thin film for a quantum dot light-emitting device comprising one or more alloying or dopant metal oxides in an n-type metal oxide.

[0011] In addition, the present invention provides a quantum dot light-emitting device including a hole transport layer; a quantum dot light-emitting layer and an electron transport layer, wherein the electron transport layer includes an electron transport layer thin film manufactured by the manufacturing method.

[0012] The present invention can produce an alloy thin film having a desired composition ratio and thickness between desired metal oxides through supercycle atomic layer deposition. Furthermore, when the metal oxide alloy thin film according to the present invention is used as an electron transport layer in a quantum dot light-emitting device, it can exhibit high luminance and high external quantum efficiency.

[0013] Figure 1 is a schematic diagram showing an example of a supercycle atomic layer deposition method according to the present invention.

[0014] Figure 2a is an XPS (X-ray Photoelectron Spectroscopy) graph according to Experimental Example 1.

[0015] Figure 2b is a grazing incidence X-ray diffraction (GIXRD) graph according to Experimental Example 1.

[0016] Figure 2c is a cross-sectional high-angle annular dark-field (HAADF) TEM image of a thin film according to Experimental Example 1.

[0017] Figure 3a is an ultraviolet photoelectron spectroscopy (UPS) graph according to Experimental Example 2.

[0018] Figure 3b is a graph showing the carrier concentration and hole mobility of the thin film according to Experimental Example 2.

[0019] Figure 4a shows a schematic diagram and a cross-sectional TEM image of an example of a quantum dot light-emitting device according to Experimental Example 3.

[0020] Figure 4b is a graph showing the luminescence (PL) intensity according to Experimental Example 3.

[0021] Figure 4c is a graph showing the quantum efficiency (PLQY) according to Experimental Example 3.

[0022] Figure 4d is a graph showing the JVL curve of the electron transport layer thin film of the present invention according to Experimental Example 3.

[0023] Figure 4e is a graph showing the EQE current density of the electron transport layer thin film of the present invention according to Experimental Example 3.

[0024] The present invention is described in detail below.

[0025] Meanwhile, each description and embodiment disclosed herein can also be applied to each other description and embodiment. That is, all combinations of the various elements disclosed herein fall within the scope of the present invention. Furthermore, the scope of the present invention is not limited by the specific descriptions described below.

[0026] When a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may have other components, unless otherwise stated.

[0027] A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device according to the present invention,

[0028] It comprises a step of repeatedly performing supercycle atomic layer deposition to deposit an n-type metal oxide and one or more alloying or dopant metal oxides using an atomic layer deposition method.

[0029] In the present invention, by repeating supercycle atomic layer deposition, two or more metal oxides can be deposited as an alloy thin film having a desired composition ratio and a desired thickness, and the composition and thickness can be controlled more precisely than with existing known wet synthesis methods.

[0030] In the present invention, one supercycle is composed of two or more subcycles of metal oxides, which are in turn composed of multiple unit cycles, each representing a single metal oxide atomic layer deposition process. In the supercycle atomic layer deposition of the present invention, one subcycle may be composed of 1 to 100 unit cycles, and one supercycle may be composed of 1 to 10 subcycles.

[0031] In the present invention, the n-type metal oxide of the supercycle atomic layer deposition according to the present invention can serve as a host matrix of the electron transport layer thin film, and the alloying or dopant metal oxide can be deposited together with the n-type metal oxide to improve the luminance and external quantum efficiency of the electron transport layer.

[0032] In the present invention, the subcycle deposition of the alloying or dopant metal oxide may be performed simultaneously with the deposition of the n-type metal oxide, or may be performed after the deposition of the n-type metal oxide is performed to form one supercycle atomic layer deposition.

[0033] In the present invention, when manufacturing an electron transport layer thin film by atomic layer deposition of a binary metal oxide, a subcycle of one type of n-type metal oxide and one type of alloying or dopant metal oxide may be repeated.

[0034] In the present invention, when manufacturing an electron transport layer thin film by atomic layer deposition of a ternary metal oxide, the method may include repeating subcycle atomic layer deposition of one n-type metal oxide and two alloying or dopant metal oxides. For example, the method may include a step of depositing an n-type metal oxide and one alloying or dopant metal oxide using an atomic layer deposition method; and a step of depositing an n-type metal oxide and another alloying or dopant metal oxide using an atomic layer deposition method. More specifically, the step of performing subcycle deposition of an n-type metal oxide and subcycle deposition of one alloying or dopant metal oxide; and the step of performing subcycle deposition of an n-type metal oxide and another subcycle deposition of one alloying or dopant metal oxide may be repeated.

[0035] In the present invention, the number of repetitions of supercycle atomic layer deposition may be 2 to 1000 times.

[0036] In the present invention, the supercycle atomic layer deposition may include a step of performing 3 to 100 atomic layer depositions of an n-type metal oxide, followed by 1 to 20 atomic layer depositions of one or more alloying or dopant metal oxides. More preferably, the atomic layer depositions of the n-type metal oxide may be 3 to 80, 3 to 50, or 3 to 20, and the atomic layer depositions of one or more metal oxides different from the n-type metal oxide may be 1 to 10, or 1 to 3.

[0037] In the present invention, when depositing a ternary metal oxide, the supercycle atomic layer deposition may include a step of performing 3 to 100 atomic layer depositions of an n-type metal oxide, 1 to 20 atomic layer depositions of an alloying or dopant metal oxide, and then a step of performing 1 to 20 atomic layer depositions of another alloying or dopant metal oxide after 3 to 100 atomic layer depositions of an n-type metal oxide.

[0038] In the present invention, the number of n-type metal oxide atomic layer deposition and alloying or dopant metal oxide atomic layer deposition can be performed at a ratio of 2 to 10:1 or 3 to 8:1.

[0039] In the present invention, the n-type metal oxide may be selected from the group consisting of ZnO, TiO2, SnO2In2O3, and WO3, and specifically may be ZnO.

[0040] In the present invention, the alloying or dopant metal oxide may be selected from the group consisting of MgO, Y2O3, NiO, Al2O3, and Ga2O3. The metal oxide may be divided into two or more types of metal oxides depending on the properties within the electron transport layer, and for example, the alloying or dopant metal oxide according to the present invention may be divided into an alloying metal oxide that is included together with an n-type metal oxide to form an alloy, and a dopant metal oxide that acts as a dopant in the n-type metal oxide.

[0041] The above alloying metal oxide may be selected from the group consisting of MgO, Y2O3, and NiO, and the dopant metal oxide may be selected from the group consisting of Al2O3 and GaO. Preferably, the alloying metal oxide may be MgO, and the dopant metal oxide may be Al2O3. The alloying metal oxide in the electron transport layer may increase the external quantum efficiency (EQE) through leakage current suppression and may increase brightness. The dopant metal oxide in the electron transport layer may increase brightness by reducing the work function.

[0042] In the thin film deposited according to the manufacturing method of the present invention, the ratio of one or more alloying or dopant metal oxides may be 1 to 50%, or 3 to 40%, or 5 to 30%, relative to the entire thin film. Here, % means the number of atoms. If the content of the alloying or dopant metal oxide exceeds the above range, the thin film may exhibit non-conductive properties or may have increased defects within the thin film.

[0043] According to the manufacturing method of the present invention, a multi-component metal oxide thin film can be ultimately manufactured in which an n-type metal oxide and one or more alloying or dopant metal oxides are deposited. Specifically, a multi-component metal oxide thin film can be manufactured in which an n-type metal oxide is alloyed with one or more metal oxides and / or doped with one or more metal oxides.

[0044] In the present invention, the metal oxide is introduced into the atomic layer deposition process in the form of a metal oxide precursor, and the precursor of each metal oxide can be used without limitation as long as it can be applied to the atomic layer deposition process of the metal oxide, and for example, it can be in the form of a halide or organic salt of each metal atom.

[0045] A single unit cycle process may include a metal oxide precursor pulsing and purging step followed by a reactant pulsing and purging step. Here, the reactant may be purified water or deionized water. In the present invention, the duration of the metal oxide pulsing and purging may vary depending on the type of metal oxide.

[0046] When the above n-type metal oxide is ZnO, a unit cycle of ALD of ZnO can be performed in the order of pulsing the ZnO precursor for 0.1 seconds, purging for 15 seconds, pulsing the reactant for 0.1 seconds, and purging for 50 seconds.

[0047] When the one or more alloying or dopant metal oxides are MgO, a unit cycle of ALD of MgO may be performed in the following order: pulse of MgO precursor for 0.2 seconds, purge for 15 seconds, pulse of reactant for 0.2 seconds, and purge for 50 seconds.

[0048] When the above one or more alloying or dopant metal oxides are Al2O3, a unit cycle of ALD of Al2O3 may be performed in the order of Al2O3 precursor pulse for 0.1 second, purge for 50 seconds, reactant pulse for 0.1 second, and purge for 50 seconds.

[0049] The atomic layer deposition method according to the present invention can be performed at a substrate temperature of 100 to 300 degrees and can be performed under a nitrogen atmosphere.

[0050] The present invention relates to a multi-component metal oxide thin film deposition method using an atomic layer deposition method, wherein a super cycle consisting of sub-cycles for depositing an n-type metal oxide and one or more alloying or dopant metal oxides is repeated two or more times. In this case, the number of unit cycles performed within a sub-cycle of each metal oxide, the number of sub-cycles performed within a super-cycle, and the number of super-cycles performed can be controlled to form a thin film having a desired composition ratio of metal oxides and a desired thickness.

[0051] When manufactured using the supercycle atomic layer deposition method, composition and thickness ratios can be more easily controlled than with conventional wet synthesis methods. Furthermore, multicomponent metal oxide films manufactured using the supercycle atomic layer deposition method can exhibit high luminance and external quantum efficiency when used as electron transport layers in quantum dot light-emitting devices.

[0052] The present invention also provides an electron transport layer thin film for a quantum dot light-emitting device manufactured by the above manufacturing method.

[0053] The above electron transport layer thin film is deposited by a supercycle atomic layer deposition method, so that two or more different metal oxides are uniformly deposited in the form of an alloy, and can provide an electron transport layer having high brightness and external quantum efficiency.

[0054] The thickness of the above electron transport layer thin film may be 1 nm to 1 um, more specifically 10 to 100 nm.

[0055] The present invention provides a quantum dot light-emitting device comprising a hole transport layer; a quantum dot light-emitting layer and an electron transport layer, wherein the electron transport layer comprises an electron transport layer thin film according to the present invention.

[0056] More specifically, the present invention provides a quantum dot light-emitting device comprising: an anode; a cathode; a quantum dot light-emitting layer positioned between the anode and the cathode; a hole transport layer positioned between the anode and the quantum dot light-emitting layer; and an electron transport layer positioned between the cathode and the quantum dot light-emitting layer, wherein the electron transport layer comprises an electron transport layer thin film according to the present invention.

[0057] In the present invention, the quantum dot included in the quantum dot light-emitting layer means a semiconductor nanocrystal having a quantum confinement effect, and may include a nano semiconductor compound of group II-VI, group I-III-VI, or group III-V, and in particular, the quantum dot may be any one selected from ZnSe, ZnTe, ZnSeTe, ZnSeS, ZnS, and combinations thereof. For example, the quantum dot may have a ZnSe / ZnS core / shell structure. It may also have a ZnSeTe / ZnS core / shell structure.

[0058] The electron transport layer facilitates electron injection from the cathode and serves to transport electrons to the quantum dot light-emitting layer. This electron transport layer may include an electron transport layer thin film manufactured by the manufacturing method according to the present invention, and more specifically, may include an Al-doped ZnMgO alloy deposited by a super-cycle atomic layer deposition method.

[0059] When depositing a quantum dot light-emitting device, major layers including the electron transport layer, except for the quantum dot light-emitting layer, can be formed by vacuum deposition.

[0060] The electron transport layer thin film and quantum dot light-emitting device according to the present invention can be applied to the contents of the manufacturing method of the electron transport layer thin film for the quantum dot light-emitting device.

[0061] Hereinafter, the present invention will be described in detail through the following experimental examples. However, these experimental examples are merely illustrative of the present invention and are not intended to limit the scope of the present invention. Furthermore, these experimental examples are intended solely to aid understanding of the present invention and are not intended to limit the scope of the present invention in any way.

[0062] Example

[0063] Manufacturing method

[0064] 1. Materials

[0065] Diethyl zinc (DEZ) was used as a precursor for ZnO, trimethylaluminum (TMA) was used as a precursor for Al2O3, and bis(ethylcyclopentadienyl) magnesium (Mg(EtCp)2) was used as a precursor for MgO.

[0066] Deionized water (DI water) was used as a reactant.

[0067] 2. Atomic layer deposition method

[0068] Deposition of metal oxides was performed in a nitrogen atmosphere at 130°C using an ALD chamber (Lucida D100, NCD Technologies), and one ALD cycle was performed in the following order: precursor pulsing, precursor purging, reactant pulsing, and reactant purging.

[0069] For the atomic layer deposition of Mg(EtCp)2, a 1-second auxiliary pulse was performed before the precursor pulse.

[0070] The durations of the precursor pulses were 0.1 s, 0.2 s, and 1 s for ZnO, Al2O3, and MgO, respectively, and the precursor purge times were 15 s, 15 s, and 50 s, respectively. The reactant pulses were 0.1 s, 0.2 s, and 0.1 s for ZnO, Al2O3, and MgO, respectively, and the reactant purge times were all the same at 50 s.

[0071]

[0072] Manufacturing Example 1. Deposition of Al-doped ZnO thin film (Al:ZnO)

[0073] ZnO deposition and Al2O3 deposition were performed alternately using DEZ, TMA, and deionized water according to the above-described atomic layer deposition method. Specifically, one cycle of ZnO ALD deposition was performed using DEZ pulsing for 0.1 sec, 15 sec purge, deionized water pulsing for 0.1 sec, and 50 sec purge, and one cycle of Al2O3 ALD deposition was performed using TMA pulsing for 0.2 sec, 15 sec purge, deionized water pulsing for 0.2 sec, and 50 sec purge.

[0074] This was performed by performing 4 cycles of ZnO ALD deposition followed by 1 cycle of Al2O3 ALD deposition, and the degree of Al doping can be controlled by changing the number of cycles during ZnO deposition. For example, when the doping ratio of Al is 3%, n=32, when it is 6%, n=17, and when it is 9%, n=11 (where n is the number of ZnO ALD depositions per 1 cycle of Al2O3 ALD deposition). In this Manufacturing Example 1, the mixing ratio of Al is 6 atomic %.

[0075]

[0076] Manufacturing Example 2. Deposition of ZnMgO thin film

[0077] ZnO deposition and MgO deposition were alternately performed using DEZ and Mg(EtCp)2 according to the above atomic layer deposition method.

[0078] Mg(EtCp)21 sec pulsing, 50 sec purge, deionized water 0.1 sec pulsing, 50 sec purge were performed once for MgO ALD deposition.

[0079] The process was performed by performing 8 cycles of ZnO ALD deposition followed by 1 cycle of MgO ALD deposition. The degree of Mg alloying can be controlled by changing the number of cycles during ZnO deposition. In this manufacturing example 2, the Mg mixing ratio is 10 atomic %.

[0080]

[0081] Manufacturing Example 3. Deposition of Al-doped ZnMgO thin film (Al:ZnMgO)

[0082] DEZ, TMA, and Mg(EtCp)2 and deionized water were used, and a total of 19 unit cycles consisting of ALD deposition of Al-doped Al:ZnO and ALD deposition of ZnMgO according to the atomic layer deposition method formed one supercycle, and the deposition order was 8 cycles of ZnO, 1 cycle of MgO, 4 cycles of ZnO, 1 cycle of Al2O3, 4 cycles of ZnO, and 1 cycle of MgO.

[0083] After completing 7 supercycles, 7 additional unit cycles of ZnO ALD deposition were performed. In this manufacturing example 3, the mixing ratio of Al was 6 atomic %, and the mixing ratio of Mg was 11 atomic %.

[0084]

[0085] Manufacturing Example 4. QD-LED Manufacturing

[0086] A glass substrate patterned with ITO (150 nm) was ultrasonically cleaned in acetone for 20 minutes and in IPA (Isopropyl Alcohol) for 20 minutes. Afterwards, it was dried in a vacuum oven at 60°C. An ALD thin film was deposited on the substrate at a thickness of 20 nm using the methods of Manufacturing Examples 1 to 3 in an ALD chamber. To deposit QDs on the substrate on which the ALD thin film was deposited, it was moved to a glove box with a nitrogen atmosphere (O2, H2O ≤ 1 ppm). A single layer of QDs was spin-coated at 4000 rpm for 30 seconds and dried on a hot plate at 90°C for 30 minutes. Afterwards, it was transferred to a thermal evaporator to deposit a hole transport layer (HTL) and a hole injection layer (HIL). The hole transport layer was TCTA (tris(4-carbazoyl-9-ylphenyl)amine) (60 nm), the hole injection layer was HATCN (1,4,5,8,9,11-Hexaazatriphenylenehexacarbonitrile) (7 nm), and the anode was an Al electrode (100 nm) with a density of 4.0 x 10 -6Under vacuum pressures less than 10 torr, TCTA, HATCN, and Al were deposited at deposition rates of 0.6, 0.2, and 1 Å / s, respectively. Finally, encapsulation was performed using encapsulating glass and UV resin (XNR 5570) after UV irradiation on the substrate.

[0087]

[0088] Experimental Example 1. Confirmation of compositional changes and structural characteristics

[0089] To confirm that Al and Mg were well deposited together with ZnO by the super cycle atomic layer deposition method, XPS (X-ray photoelectron spectroscopy) measurements were performed, and the results are shown in Fig. 2a.

[0090] As can be seen in Fig. 2a, the Al 2p peak was observed at 73.6 eV and the Mg 1s peak at 1302.9 eV. In the case of Al:ZnMgO, both peaks were present, and the shift of each peak of Al:ZnMgO occurred due to the difference in electronegativity between Al (1.61) and Mg (1.31). Al, which has a higher electronegativity, attracted electrons and decreased the binding energy, and Mg moved in the direction of decreasing binding energy. This means that the multicomponent film deposited by the supercycle atomic layer deposition method contains both Al and Mg components.

[0091] To determine whether these elements actually form an alloy or simply exist in the form of metal oxides (Al2O3 and MgO), grazing incidence X-ray diffraction (GIXRD) measurements were performed, the results of which are shown in Fig. 2b.

[0092] In Al:ZnMgO, the wurtzite structure of ZnO was maintained even with Al and Mg doping. In the case of Al-free ZnO, crystallization occurred in a rod-like structure growing parallel to the c-plane of the substrate, but the (002) peak disappeared when Al was introduced. The addition of Al ions hindered growth along the c-plane due to the breakdown of charge neutrality, while promoting growth along the

[0100] direction.

[0093] Cross-sectional TEM measurements were performed for detailed analysis of the thin films, and the cross-sectional high-angle annular dark-field (HAADF) TEM images of each thin film are shown in Fig. 2c.

[0094] The Al:ZnO thin film exhibited a layer-by-layer deposition pattern with alternating bright and dark stripes, with bright regions representing ZnO and dark regions representing Al. This confirms that seven Al layers were deposited using a supercycle atomic layer deposition method.

[0095] Similarly, in the ZnMgO thin film, Mg is represented by dark stripes, and the stripes are more numerous after eight Mg atomic layers have been deposited than in the Al:ZnO thin film. Moreover, this did not significantly affect the crystal growth of the ZnO thin film, so the grain morphology is clearly visible and the appearance is more robust than that of the Al.

[0096] In the case of Al:ZnMgO, the line corresponding to Mg is not clearly visible, and seven dark stripes are observed. This indicates that Mg and Al have similar atomic masses, making it difficult to clearly distinguish between Mg and Al, and that approximately 5Å of ZnO exists between each cycle. This implies that a uniform alloy thin film can be obtained through the supercycle atomic layer deposition process when fabricating ETL.

[0097]

[0098] Experimental Example 2. Energy Band Tuning and Electrical Characteristics

[0099] This experiment was conducted to adjust the energy bands of the thin film for each element and to find an appropriate composition. Absorption spectra were measured and ultraviolet photoelectron spectroscopy (UPS) was performed, and the results are shown in Figure 3a.

[0100] The optical band gap increased with the inclusion of Al and Mg (ZnO = 3.2 eV, Al:ZnO = 3.31 eV, ZnMgO = 3.43 eV, Al:ZnMgO = 3.51 eV). This is because the conduction band increased as Al and Mg were included, and the work function decreased due to the addition of Al, indicating that the alloy was successfully formed.

[0101] In order to investigate the electrical characteristics of the ALD ETL, an ALD thin film having a thickness of 30 nm was deposited on a glass substrate using the manufacturing methods of Manufacturing Examples 1 to 3, and a Hall measurement was performed on the ALD thin film. Figure 3b shows the carrier concentration and Hall mobility of the ALD film.

[0102] ZnO thin film has 1.56 × 10 19 / cm 3 The carrier concentration of Al:ZnO film with added Al cycles was 6.23×10 19 / cm 3 It showed a significantly high carrier concentration. This is about a four-fold increase compared to the original ZnO, suggesting that Al can effectively dope the ZnO film.

[0103] However, in the case of ZnMgO with added Mg cycles, the carrier concentration is 3.21×10 compared to ZnO. 18 / cm 3 was reduced. Mg can effectively passivate Ov by penetrating the empty Zn lattice. Consequently, it shows the opposite trend compared to Al, which leads to a decrease in carrier concentration.

[0104] The hole mobility tended to decrease regardless of the presence of Al or Mg, because the crystallinity of ZnO decreased as Mg and Al cycles were added, and foreign substances were introduced into the ZnO host matrix, causing a scattering effect.

[0105]

[0106] Experimental Example 3. Characterization of EL elements in QD-LEDs using ALD-ETL

[0107] In this experimental example, the thin film manufactured in the manufacturing example was used as an ETL layer to evaluate the performance of a QD-LED device.

[0108] The QD-LED device is composed of ITO (150 nm) / ALD-ETL (ZnO, Al:ZnO, ZnMgO or Al:ZnMgO according to the above manufacturing example, 20 nm) / QD (CdSe / CdxZn1-xSe / ZnSeyS1-y, 30 nm) / TCTA (tris(4-carbazoyl-9-ylphenyl)amine, 60 nm) / HAT-CN (1,4,5,8,9,11-hexaazatriphenylenehexacarbonitrile, 7 nm) / Al (100 nm), and an example of its structure is shown in Fig. 4a.

[0109] As observed in the cross-sectional TEM image shown in Fig. 4a, HAT-CN was used as a hole transport layer (HTL) and TCTA was used as a hole injection layer (HIL). Here, Al was used in a composition of 6% and Mg was used in a composition of 11%.

[0110] To understand the interaction between the ALD-ETL layer and the QD layer, the fluorescence properties of the QDs were analyzed, and the luminescence (PL) intensity and quantum efficiency (PLQY) (ITO / ALD ETLs / cg-QD) were measured, and the results are shown in Figs. 4b to 4c.

[0111] The PL intensity increased with the inclusion of both Al and Mg. In addition, while ZnO showed only 56% PLQY compared to 92% PLQY of the QD layer, Al:ZnO containing Al showed a PLQY of 68%, ZnMgO containing Mg showed a PLQY of 75%, and ternary Al:ZnMgO containing both Al and Mg showed an increase in PLQY up to 83%.

[0112] The JVL curve and EQE-current density of the manufactured ALD ETL are shown in Figures 4d and 4e, respectively.

[0113] Examining the current density at the threshold voltage shown in Fig. 4d, it was observed that adding Mg reduced mobility, thereby suppressing excessive electron injection. Furthermore, as the conduction band increased, non-radiative Auger recombination at the interface decreased, resulting in a decrease in leakage current.

[0114] Al also reduced the mobility and increased the conduction band, thereby reducing Auger recombination. However, the reduction in leakage current due to Al was significantly smaller than that due to Mg, which may be due to trap states induced by the greater number of defects in Al:ZnO.

[0115] As shown in Fig. 4e, the charge imbalance caused by the decrease in electron mobility and the increase in conduction band due to the addition of Al and Mg is resolved, and the luminance is 167,000 cd / m in the case of the Al:ZnMgO thin film. 2 In addition, the luminance of the ZnO thin film was 118,000 cd / m 2 In contrast, Al:ZnO thin films also have a light emitting diode (LED) of 140,000 cd / m 2 The value was shown, and the ZnMgO thin film also showed 133,000 cd / m 2 EQE also showed an increased value from 9.4% (ZnO) to 11.4% (Al:ZnO), 12.9% (ZnMgO), and 15.7% (Al:ZnMgO).

[0116] Also, the standard brightness is 5,000 cd / m2 It showed a lifespan of about 130 hours until the luminance was reduced by half at 100 cd / m2 with an acceleration coefficient of 1.73. 2 The lifetime was estimated to be approximately 110,400 hours. Consequently, the quantum dot light-emitting device utilizing the thin films manufactured by the present manufacturing examples 1 to 3 as electron transport layers exhibited high performance, which proves that the multicomponent metal oxide deposited by ETL through the supercycle ALD deposition process has high value.

[0117]

[0118] Experimental Example 4. Preparation and Evaluation of ZnMgO Using Wet Synthesis Method

[0119] This experiment was conducted to evaluate whether it is easy to control the composition and thickness in the same way as the atomic layer deposition method when manufacturing using the existing wet synthesis method.

[0120] Zn acetate and Mg acetate were used as precursors of ZnO and MgO, and ZnO and ZnMgO alloys were manufactured with the compositions shown in Table 1 below using a wet synthesis method, specifically, an ultrasonic wet synthesis method or a hydrothermal synthesis method, rather than an ALD deposition method, and the XPS thereof was measured and shown in Table 2 below. In Tables 1 and 2 below, X in ZnMgO X represents the percentage of added Mg precursor, s-ZnMgO represents ZnMgO nanoparticles manufactured by an ultrasonic wet synthesis method, and h-ZnMgO represents ZnMgO nanoparticles manufactured by a hydrothermal synthesis method.

[0121] ZnOZnMgO 5ZnMgO 10ZnMgO 15ZnMgO 20Zn acetate(mol)0.878 g(4mmol)0.834 g(3.8mmol)0.790 g(3.6mmol)0.768 g(3.5mmol)0.746 g(3.4mmol)Mg acetate(mol)-0.0043 g(0.2mmol)0.086 g(0.4mmol)0.129 g(0.6mmol)0.172 g(0.6mmol)KOH(mol)0.293 g(5.2mmol)

[0122] s-ZnOs-ZnMgO 5s-ZnMgO 10s-ZnMgO 15s-ZnMgO 20h-ZnOh-ZnMgO 10h-ZnMgO 15O1s49.0750.6850.7150.3951.1148.3749.1849.61Zn2p50.9348.194 7.3946.4944.7051.6349.0347.68Mg1s-1.131.903.124.76-1.792.71Mg (mol %)02.563.856.2910.6503.525.38

[0123] As shown in Table 2 above, in both the ultrasonic wet synthesis method and the hydrothermal synthesis method, it can be confirmed that the proportion of Mg in the alloy confirmed through XPS is significantly lower than the precursor actually added. Accordingly, it can be seen that it is not easy to deposit the desired composition and thickness when manufacturing ZnMgO alloy using the conventional wet synthesis method, and it can be seen that the atomic layer deposition method is superior to the wet synthesis method.

Claims

1. A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, comprising the step of repeatedly performing supercycle atomic layer deposition to deposit an n-type metal oxide and one or more alloying or dopant metal oxides using an atomic layer deposition method.

2. In paragraph 1, The above supercycle atomic layer deposition method comprises a step of depositing an n-type metal oxide and one alloying or dopant metal oxide using an atomic layer deposition method; and a step of depositing an n-type metal oxide and another alloying or dopant metal oxide using an atomic layer deposition method. A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device.

3. In paragraph 1, A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, wherein the supercycle atomic layer deposition comprises a step of performing 3 to 100 atomic layer depositions of an n-type metal oxide, followed by 1 to 20 atomic layer depositions of one or more alloying or dopant metal oxides.

4. In paragraph 1, A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, comprising: performing 1 to 20 atomic layer depositions of an alloying or dopant metal oxide after 3 to 100 atomic layer depositions of an n-type metal oxide; and performing 1 to 20 atomic layer depositions of another alloying or dopant metal oxide after 3 to 100 atomic layer depositions of an n-type metal oxide.

5. In paragraph 1, A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, wherein the above n-type metal oxide is selected from the group consisting of ZnO, TiO2, SnO2In2O3, and WO3.

6. In paragraph 1, A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, wherein the above alloying or dopant metal oxide is selected from the group consisting of MgO, Y2O3, NiO, Al2O3, and Ga2O3.

7. In paragraph 1, A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, wherein the number of repetitions of the above supercycle atomic layer deposition is 2 to 1000 times.

8. In paragraph 1, A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, wherein the ratio of the above one or more alloying or dopant metal oxides is 1 to 50% with respect to the entire thin film.

9. In paragraph 1, A method for manufacturing an electron transport layer thin film for a quantum dot light-emitting device, wherein the unit cycle of the atomic layer deposition comprises a metal oxide precursor pulsing and purging step followed by a reactant pulsing and purging step, wherein the reactant is purified water or deionized water.

10. Manufactured by the manufacturing method according to Article 1, An electron transport layer thin film for a quantum dot light-emitting device comprising one or more alloying or dopant metal oxides in an n-type metal oxide.

11. In paragraph 10, An electron transport layer thin film for a quantum dot light-emitting device, wherein the ratio of the above one or more alloying or dopant metal oxides is 1 to 50% with respect to the entire thin film.

12. In paragraph 10, The above n-type metal oxide is selected from the group consisting of ZnO, TiO2, SnO2In2O3, and WO3, An electron transport layer thin film for a quantum dot light-emitting device, wherein the above alloying or dopant metal oxide is selected from the group consisting of MgO, Y2O3, NiO, Al2O3, and Ga2O3.

13. A quantum dot light-emitting device comprising a hole transport layer, a quantum dot light-emitting layer, and an electron transport layer, wherein the electron transport layer comprises an electron transport layer thin film manufactured by the manufacturing method according to claim 1.

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