KR20210143567A - Quantum dot-light-emitting diode and method for fabricating the same - Google Patents

Abstract

Provided are a quantum dot-light emitting element including an improved electron transport layer and a manufacturing method thereof. The quantum dot-light emitting element according to the present invention includes a hole transport layer, a quantum dot light emitting layer, and an electron transport layer, wherein the electron transport layer has a multi-layered structure including: a magnesium doped zinc oxide nanoparticle layer sequentially stacked on the quantum dot light emitting layer; and a layer of 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole, which is known as LG201. The present invention can increase lifespan as compared with a QLED.

Description

Quantum dot-light-emitting diode and method for manufacturing the same

The present invention relates to a light emitting device, and more particularly, to a quantum dot light-emitting diode (QLED) in which a constituent material is changed to show higher luminance and efficiency, and a method for manufacturing the same.

Colloidal semiconductor nanocrystals called quantum dots emit light as electrons in an unstable state descend from the conduction band to the valence band. This is a unique electro-optical property that is different from conventional semiconductor materials, and quantum dots are easy to modulate the wavelength of fluorescence emission by controlling their size or introducing alloy/doping.

A method of applying quantum dots to a display includes a color-conversion method and an electroluminescence (EL) method. Currently, a color-conversion method-based display has been commercialized, but the ultimate form of a quantum dot-based display is an electroluminescence method. The electroluminescent QLED has a structure similar to that of an existing organic light-emitting diode (OLED) and uses quantum dots instead of organic materials for the light emitting layer. OLED implements a single color such as white, red, and blue depending on the type of device, but there is a limit to expressing a lot of light splendidly. On the other hand, QLED can realize a desired natural color by adjusting the size of quantum dots, and has good color reproducibility and luminance is not lagging behind OLED, so it is in the spotlight as a next-generation light source material that can compensate for the shortcomings of OLED.

QLEDs generally include a hole injection layer (HIL), a hole transport layer (HTL), and charge transport layers (CTLs) such as an electron transport layer (ETL). The performance of QLED is greatly affected by the efficient luminescent recombination of excitons, which are electron-hole pairs formed by electrons and holes injected into the quantum dot light emitting layer, and this results in a balanced charge into the quantum dot light emitting layer. This is achieved by injection. As balanced charge injection is important for device performance, the performance of QLEDs has been improved with the development of charge transport layers as well as continuous improvement of quantum dot quality.

On the other hand, in order to implement a full-color display with an electroluminescent QLED, blue light-emitting quantum dots are required in addition to the red light-emitting quantum dots and green light-emitting quantum dots used in color-conversion-based displays. Conventionally, blue light-emitting quantum dots synthesized with Cd-containing II-VI compositions such as CdZnS, CdZnSe, and CdZnSeS have been studied, but harmful Cd materials are not desirable for manufacturing sustainable next-generation products without environmental destruction. Therefore, there is a great demand for a blue light-emitting QLED that does not contain Cd and whose luminance and External Quantum Efficiency (EQE) are similar to or better than those of Cd-containing quantum dot-based QLEDs.

In order to secure higher luminance and efficiency in the blue light-emitting QLED, it is necessary to improve the structure design and charge transport layer material so that charges can be injected into the quantum dot light emitting layer in the QLED in a balanced way. In addition, life characteristics for long-term use must be guaranteed.

The problem to be solved by the present invention is to provide a quantum dot-light emitting device including an improved electron transport layer.

Another problem to be solved by the present invention is to provide a method for manufacturing a quantum dot-light emitting device including an improved electron transport layer.

In order to solve the above problems, a quantum dot-light emitting device according to the present invention includes a hole transport layer, a quantum dot light emitting layer, and an electron transport layer, and the electron transport layer is sequentially stacked on the quantum dot light emitting layer and magnesium doped zinc oxide nanoparticle layer and 2 -(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole(2-(4-(9,10- di(naphthalene-2-yl)anthracene-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole (LG201) layer is characterized in that it has a multilayer structure.

In the present invention, the electron transport layer may have a thickness of 1 nm to 120 nm.

In the present invention, the quantum dots do not contain Cd, that is, non-cadmium-based (Cd-free) quantum dots may be.

In the present invention, the quantum dots may be any one selected from ZnSe, ZnTe, ZnSeTe, ZnSeS, ZnS, and combinations thereof.

In the present invention, the hole transport layer may be an organic material.

In the present invention, the quantum dot-light emitting device further includes an anode, a hole injection layer and a cathode, wherein the hole transport layer and the hole injection layer are poly(ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS), poly[(9, 9-) dioctyl-fluorenyl-2, 7-diyl)-co-(4, 4'-(N-(p-butylphenyl))diphenylamine)](TFB), poly(9-vinlycarbazole)(PVK), N, N, N , N', N'-tetrakis(4-methoxyphenyl)-benzidine(TPD), poly-TPD, 4, 4', 4''-tris(N-carbazolyl)-triphenylamine(TCTA), N, N'-bis (naphthalen-1-yl)-N, N'bis(phenyl)-9, 9-spiro-bifluorene(spiro-NPB), dipyrazino[2, 3-f:2', 3'-h]quinoxaline-2, 3, 6, 7, 10, 11-hexacarbonitrile (HATCN), 1, 1-bis[(di-4-tolylamino)phenylcyclohexane (TAPC), VNPB(N4,N4'-Di(naphthalen-1-yl)-N4 ,N4'-bis(4-vinylphenyl)biphenyl-4,4'-diamine), may be any one selected from p-type metal oxides and combinations thereof.

In order to solve the other problems, quantum dots according to the present invention-a light emitting device manufacturing method is as follows. A method comprising: forming a hole transport layer, a quantum dot emission layer, and an electron transport layer, wherein the forming of the electron transport layer includes: forming a magnesium-doped zinc oxide nanoparticle layer on the quantum dot emission layer; and 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole on the magnesium-doped zinc oxide nanoparticle layer. (2-(4-(9,10-di(naphthalene-2-yl)anthracene-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole; LG201) do.

In the present invention, the hole transport layer, the quantum dot emission layer, and the magnesium-doped zinc oxide nanoparticle layer are formed by a solution process, and the 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl) )Phenyl)-1-phenyl-1H-benzo-[D]imidazole layer may be formed by vapor deposition.

The quantum dot-light emitting device according to the present invention has an increased lifetime. For example, compared to the conventional QLED having only a magnesium-doped zinc oxide nanoparticle layer as an electron transport layer, the lifetime can be increased by 10 times or more.

The quantum dot-light emitting device according to the present invention has a high color gamut. Increase lifetime by including 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole layer in electron transport layer -[4-(9,10-di-2-naphthalenyl-2-anthracenyl)phenyl]-1-phenyl-1H because it further includes a magnesium-doped zinc oxide nanoparticle layer between the quantum dot light emitting layer and the quantum dot light emitting layer -Benzimidazole layer self-emission or quantum dot emission layer and 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imi There is no problem of a decrease in color gamut that may be caused by interfacial light emission occurring at the interface between the dazole layers.

Magnesium-doped zinc oxide nanoparticle layer and 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole layer The electron transport layer of a multilayer structure including: improves the charge imbalance phenomenon when manufacturing a quantum dot-light emitting device including blue light emitting quantum dots having an emission wavelength of 435 nm to 460 nm can do it

1 is a schematic cross-sectional view showing a QLED according to the present invention.
FIG. 2 is a diagram schematically illustrating bandgap energies of HOMO energy levels and LUMO energy levels of an electrode constituting a QLED according to an embodiment of the present invention and layered materials positioned between the electrodes.
3 is a normalized EL spectrum of a QLED according to experimental examples.
4 is a CIE color coordinates of a QLED according to experimental examples.
5 is a graph of normalized EQE over time of QLEDs according to experimental examples.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, only this embodiment allows the disclosure of the present invention to be complete, and the scope of the invention to those of ordinary skill in the art completely It is provided to inform you.

1 is a schematic cross-sectional view showing a QLED according to the present invention.

1, the QLED 100 of the present invention includes a hole transport layer 40, HTL, a quantum dot light emitting layer 50, EML, and an electron transport layer 80, ETL. The quantum dot light emitting layer 50 is a layer that emits light by combining holes and electrons coming from the hole transport layer 40 and the electron transport layer 80 , respectively. Such a multilayer structure may be formed on the substrate 10 serving as a mechanical support, an anode 20 for hole injection, a cathode 90 for electron injection, and an anode 20 and a hole transport layer The hole injection layer 30 (HIL) may be further included between the 40 .

The substrate 10 may be a transparent and flat glass substrate or a transparent plastic substrate. The substrate 10 may be used after ultrasonic cleaning with a solvent such as isopropyl alcohol (IPA), acetone, or methanol to remove contaminants and UV-ozone (O _{3 ) treatment.}

The anode 20 and the cathode 90 are made of a metal oxide suitable for each transparent/opaque condition, including metal, or other non-oxide inorganic materials. For lower emission, the anode 20 may be made of a transparent conductive metal such as ITO, IZO, ITZO, or AZO, and the cathode 90 is a metal having a small work function to facilitate electron injection, that is, I, Ca, Ba, Ca/Al, LiF/Ca, LiF/Al, BaF ₂ /Al, BaF ₂ /Ca/Al, Al, Mg, Ag:Mg alloy and the like can be used. The cathode 90 may be formed using a conductive polymer or graphene. For example, the cathode 90 may be formed of Al having a thickness of 80 nm or more.

In this embodiment, although the structure in which the anode 20 is located at the bottom and the cathode 90 is located at the top is taken as an example, the reverse is also possible. In this embodiment, the structure of the lower light emitting device in which the transparent electrode is located at the bottom is taken as an example, but the reverse is also possible.

The hole injection layer 30 and the hole transport layer 40 facilitate hole injection from the anode 20 and serve to transfer holes to the quantum dot emission layer 50 . It is possible to apply organic or inorganic materials to form them. The hole injection layer 30 and the hole transport layer 40 are poly(ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS), poly[(9, 9-dioctyl-fluorenyl-2, 7-diyl)-co-(4, 4) '-(N-(p-butylphenyl))diphenylamine)](TFB), poly(9-vinlycarbazole)(PVK), N, N, N, N', N'-tetrakis(4-methoxyphenyl)-benzidine(TPD) ), poly-TPD, 4, 4', 4''-tris(N-carbazolyl)-triphenylamine(TCTA), N, N'-bis(naphthalen-1-yl)-N, N'bis(phenyl)- 9, 9-spiro-bifluorene (spiro-NPB), dipyrazino[2, 3-f:2', 3'-h]quinoxaline-2, 3, 6, 7, 10, 11-hexacarbonitrile (HATCN), 1, 1-bis[(di-4-tolylamino)phenylcyclohexane(TAPC), VNPB(N4,N4'-Di(naphthalen-1-yl)-N4,N4'-bis(4-vinylphenyl)biphenyl-4,4'- diamine), a p-type metal oxide, and a combination thereof. Here, the p-type metal oxide may be, for example, NiO, MoO ₃ , V ₂ O ₅ , WO ₃ .

According to a preferred embodiment, the hole transport layer 40 is an organic material. In one specific example, the hole injection layer 30 is PEDOT:PSS, and the hole transport layer 40 is PVK or TFB. For example, the molecular weight (Mn) of PVK may be 25,000 to 50,000.

If the hole injection layer 30 is PEDOT:PSS, it may be formed by spin coating. If the hole injection layer 30 is MoO _{3 ,} it may be formed by a deposition method. If the hole transport layer 40 is PVK, it may be formed by spin coating. The thickness of the hole injection layer 30 may be 5 nm to 100 nm. The hole transport layer 40 may have a thickness of 10 nm to 100 nm.

The quantum dot light emitting layer 50 is a layer made of quantum dots having a diameter of several nm to tens of nm filled with quantum dots, and may be, for example, 5 nm to 80 nm thick. Here, the quantum dot emission layer 50 may be formed by, for example, coating on the hole transport layer 40 by a solution process of coating a dispersion containing quantum dots in a solvent, and then volatilizing the solvent. The coating method is, for example, drop casting, spin coating, dip coating, spray coating, flow coating, screen printing, or inkjet printing alone. Or they can be used in combination.

Quantum dots included in the quantum dot light emitting layer 50 means semiconductor nanocrystals having a quantum limiting effect, and may include a group II-VI, group I-III-VI or group III-V nano-semiconductor compound, preferably It is a non-cadmium-based (Cd-free) quantum dot. The quantum dots may have a single structure or a core/shell structure. Preferably, the quantum dot has a core component emitting light in the center, and has a core/shell structure surrounded by a shell for protection on its surface. In addition, only a single shell may be formed or a plurality of shells having different compositions may be applied. The shell surface is surrounded by a ligand component for dispersion in a solvent. In some cases, the ligand is a component that can be removed when the quantum dot emission layer 50 is formed. The ligand may be advantageous in improving the stability of the quantum dot and protecting the quantum dot from harmful external conditions including high temperature, high strength, external gas or moisture. For example, the ligand is a ligand that is conjugated, cooperating, associated with or attached to the surface of the quantum dot. A ligand capable of exhibiting suitable properties on the surface of the quantum dot and a method for forming the same are known, and such a method may be applied without limitation in the present application.

In particular, the quantum dots are preferably any one selected from ZnSe, ZnTe, ZnSeTe, ZnSeS, ZnS, and combinations thereof. For example, the quantum dots may have a ZnSe/ZnS core/shell structure. It may be a ZnSeTe/ZnS core/shell structure. The quantum dot may be a quantum dot having an emission wavelength of 435 nm to 460 nm for blue light emission. To have such an emission wavelength, ZnSe, ZnTe, ZnSeTe, ZnSeS, and ZnS may be used in various combinations of cores and shells to form the quantum dots.

The quantum dots may be mainly synthesized by a wet process in which a precursor material is added in an organic solvent and particles are grown. It is possible to obtain light in various wavelength bands according to the control of the energy bandgap according to the growth degree of the particles.

The electron transport layer 80 facilitates electron injection from the cathode 90 , and serves to transport electrons to the quantum dot emission layer 50 . According to the present invention, the electron transport layer 80 is a magnesium doped zinc oxide nanoparticle layer 60 and 2-(4-(9,10-di(naphthalen-2-yl)) sequentially stacked on the quantum dot emission layer 50 according to the present invention. Anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole is characterized in that it has a multilayer structure including a layer (70).

The magnesium-doped zinc oxide may be represented by Formula 1 below.

[Formula 1]

Zn _(1-x) Mg _x O

In Formula 1, x may be a number within the range of 0.10 to 0.35. In general, considering the limit value of magnesium that can be doped into zinc oxide, x in Formula 1 may be in the range of about 0.3, specifically 0.25 to 0.32.

2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole is LG201 (trade name, manufacturer: LGC) Also known as, it is a compound represented by the following formula (2).

[Formula 2]

The electron transport layer 80 may have a thickness of 1 nm to 120 nm. If it is too thin (less than 1 nm), pinhole defects and leakage currents are highly likely to occur. If the thickness exceeds 120 nm, the resistance of the electron transport layer 80 becomes too large.

To form the electron transport layer 80 , the magnesium-doped zinc oxide nanoparticle layer 60 is first formed on the quantum dot emission layer 50 . Then, a 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole layer 70 is formed thereon do.

The magnesium-doped zinc oxide nanoparticle layer 60 may be formed by coating on the quantum dot light emitting layer 50 by a solution process of coating a dispersion containing magnesium-doped zinc oxide nanoparticles in a solvent, and then volatilizing the solvent. . The size of the magnesium-doped zinc oxide nanoparticles may be 1 nm to 30 nm.

2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole layer 70 can be formed by vapor deposition have.

In terms of reducing the cost of the entire manufacturing process and increasing the size of the device, it is advantageous to apply a solution process to form each layer. In the present invention, the quantum dot emission layer 50 and the magnesium-doped zinc oxide nanoparticle layer 60 may be formed by a solution process.

Additionally, an electron blocking layer (EBL) may be further included between the anode 20 and the quantum dot emission layer 50 . Similarly, an electron injection layer (EIL) or a hole blocking layer (HBL) may be further included between the cathode 90 and the quantum dot emission layer 50 .

Meanwhile, when the thickness of any layer exemplified above is not constant, the thickness of the layer may mean the maximum thickness, the minimum thickness, or the average thickness of the layer. In addition, the method of controlling the thickness of each layer is not particularly limited, and the thickness may be adjusted according to the type of material constituting the layer, a coating method, or curing conditions, and the like. In addition, such a layer thickness may be appropriately adjusted from the viewpoint of improving luminous efficiency or luminance, for example, and the present application is not limited by this layer thickness.

Hereinafter, the present invention will be described in more detail by describing the experimental examples of the present invention in detail. Hereinafter, magnesium-doped zinc oxide is referred to as ZnMgO. 2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole is denoted as LG201.

Invention Example 1

A QLED was prepared using blue light-emitting quantum dots, ZnMgO nanoparticles (nano particles, NP), and LG201. The stacking order was glass/ITO anode/PEDOT:PSS HIL/PVK HTL/quantum dot EML/ZnMgO NP and LG201 ETL/Al cathode.

The glass substrate on which the patterned ITO anode was deposited was washed and then treated with UV-ozone. PEDOT:PSS (AI 4083) was spin-coated and then baked to form a hole injection layer. PVK was spin-coated thereon and then baked under the same conditions as the hole injection layer to form a hole transport layer. After spin coating the quantum dot dispersion on the hole transport layer, it was dried. Thereafter, a solution of ZnMgO nanoparticles dispersed in ethanol (5 mg/mL) was spin-coated on the quantum dot emission layer at 2000 rpm, and then dried to form a ZnMgO NP layer with a thickness of 8 nm. A 35nm-thick LG201 layer was formed thereon at a deposition rate of 1 Å/s at a vacuum degree of 1x10 ^{-8 torr.} Finally, an Al cathode was formed through a linear metal mask and a thermal evaporator to complete the fabrication of the QLED.

Comparative Example 1

A QLED using only the ZnMgO NP layer as ETL was fabricated. Other configurations and conditions are the same as in Example 1.

Comparative Example 2

A QLED using only the LG201 layer as ETL was manufactured. Other configurations and conditions are the same as in Example 1.

evaluation:

The EL spectra, Commission Internationale de l'Eclairage (CIE) color coordinates and luminance-current density-voltage characteristics of QLEDs were measured using a Konica-Minolta CS-2000 spectroradiometer coupled with a Keithley 2400 voltage and current source. A 10 mA/cm ² driving current was applied to the QLED to measure the light emission luminance.

FIG. 2 is a diagram schematically illustrating bandgap energies of HOMO energy levels and LUMO energy levels of an electrode constituting a QLED according to an embodiment of the present invention and layered materials positioned between the electrodes.

The difference between the HOMO energy level of the quantum dot used in the quantum dot emission layer and the HOMO energy level of the ZnMgO NP used as the electron transport layer material is not small. Therefore, in the case of having the same stacking order as in the embodiment of the present invention, there is no concern that some of the holes injected into the quantum dot light emitting layer may leak into the electron transport layer. The LUMO energy level of ZnMgO NPs is relatively shallow from the vacuum level. Accordingly, electron injection into the quantum dot light emitting layer is facilitated through the reduction of the electron injection barrier. In addition, since it is an inorganic ETL, it has high electron mobility, enabling efficient electron injection.

Due to the characteristics of organic materials, the LUMO energy level of LG201 is shallower than that of ZnMgO NPs, so it is energetically more favorable in terms of electron injection, which can bring about improvement in lifespan.

The HOMO energy level of LG201 is higher than the HOMO energy level of the quantum dots used in the quantum dot emission layer. Therefore, unlike Example 1 of the present invention, if the stacking order is changed and the quantum dot light emitting layer and the LG201 layer are in contact (for example, Comparative Example 2), the electrons shallowly trapped in the defect center of LG201 can undergo radiative recombination with the trapped holes. In addition to the blue by quantum dot emission, the visible light emission of LG201 occurs, and there is room for a decrease in color gamut.

In the present invention, a new hole transport layer/electron transport layer combination was attempted in consideration of the energy level between the quantum dot and the surrounding charge transport layer.

3 is a normalized EL spectrum of a QLED according to experimental examples.

Referring to FIG. 3 , it can be seen that the sizes of the EL peaks in Examples and Comparative Examples are similar, but in Comparative Example 2, the peak shape is very broad and inappropriate for use as an actual QLED. Table 1 shows their full width at half maximum (FWHM). In the case of Comparative Example 2, since the half width is larger than 30 nm, the color purity is low. On the other hand, it can be seen that Example 1 has a full width at half maximum of 19.2 nm, so that blue having high color purity can be realized.

In the order of Comparative Example 1, Example 1, and Comparative Example 2, the peak wavelengths (Wp) were measured to be 439 nm, 441 nm, and 443 nm, respectively. Since blue light-emitting quantum dots were used, the peak wavelengths of the experimental examples indicate light emission in the blue band. However, in Comparative Example 2, the wavelength is longer than the blue wavelength, and the EL peak is broad. This is because, in Comparative Example 2, since the quantum dot light emitting layer and the LG201 layer are in contact, long wavelength light emission by the LG201 layer is added. Since the quantum dots do not emit blue light as they are, in Comparative Example 2, the color reproducibility is poor.

4 is a CIE color coordinates of a QLED according to experimental examples. BT. 2020 represents the 4K/UHD broadcasting standard recommended by the ITU.

Referring to FIG. 4 , Comparative Example 2 shows a blue color mixed with a little more green, rather than a high-purity blue color compared to Example 1 or Comparative Example 1. That is, CIEy is greater than the others. CIEx and CIEy obtained in FIG. 4 are summarized in Table 1. Example 1 has a CIEy <0.14, so color purity is high. As a result of calculating the relative color gamut (%) using the red coordinates (0.701, 0.292) and the green coordinates (0.170, 0.797), a high color gamut of 90.6% was recorded in Example 1. This is the result of exceeding the 90% limit of color gamut in the currently commercialized OLED.

5 is a graph of normalized EQE over time of QLEDs according to experimental examples.

As a result of the luminance measurement, relative luminance (Cd/m ² ) was the highest in Comparative Example 2. Relative EQE (relative EQE) indicates the relative level of other QLEDs when the EQE of Comparative Example 1 is normalized to 1.00. The relative EQE of Example 1 was 2.36, which was larger than that of other QLEDs, and as shown in FIG. 5 , the decrease in EQE with time was the least, indicating a long lifespan. Table 1 summarizes the relative lifetime, expressed as T50 (the time the EQE reaches 50%).

[Table 1]

Example 1 has a high luminance, good color reproducibility, and a large EQE compared to Comparative Example 1 and has a long lifespan. Lifespan is 10 times longer. Example 1 has better color reproducibility and longer life than Comparative Example 2.

As such, in the present invention, by using ZnMgO nanoparticles and LG201 together and using the quantum dot light emitting layer in a predetermined order, higher luminance, color gamut, EQE and lifespan compared to when ZnMgO nanoparticles are used alone, and LG201 alone It shows higher color reproducibility and lifespan compared to when used as Only when the ZnMgO nanoparticle layer is first formed on the quantum dot light emitting layer and the LG201 layer is formed thereon, long wavelength light emission by LG201 can be prevented and color gamut can be increased. In particular, this effect is unique in QLED using quantum dots that emit blue light.

Although preferred embodiments of the present invention have been illustrated and described above, the present invention is not limited to the specific preferred embodiments described above, and in the technical field to which the present invention belongs, without departing from the gist of the present invention as claimed in the claims Any person skilled in the art can make various modifications, of course, and such modifications are within the scope of the claims.

10: substrate
20: positive electrode
30: hole injection layer
40: hole transport layer
50: quantum dot light emitting layer
60: magnesium-doped zinc oxide nanoparticle layer
70: LG201 floor
80: electron transport layer
90: cathode
100: quantum dot-light emitting device

Claims (8)

It includes a hole transport layer, a quantum dot light emitting layer, and an electron transport layer, wherein the electron transport layer is sequentially stacked on the quantum dot light emitting layer and a magnesium doped zinc oxide nanoparticle layer and 2-(4-(9,10-di(naphthalen-2-yl)) Anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole(2-(4-(9,10-di(naphthalene-2-yl)anthracene-2-yl)phenyl)- 1-phenyl-1H-benzo-[D]imidazole; Quantum dot-light emitting device, characterized in that it has a multilayer structure including a layer (LG201). The quantum dot-light emitting device according to claim 1, wherein the electron transport layer has a thickness of 1 nm to 120 nm. The quantum dot-emitting device according to claim 1, wherein the quantum dots are non-cadmium-based (Cd-free) quantum dots and are blue light emitting quantum dots having an emission wavelength of 435 nm to 460 nm. The quantum dot-light emitting device of claim 1, wherein the quantum dot is any one selected from ZnSe, ZnTe, ZnSeTe, ZnSeS, ZnS, and combinations thereof. The quantum dot-light emitting device according to claim 1, wherein the hole transport layer is made of an organic material. The method of claim 1, further comprising an anode, a hole injection layer and a cathode, wherein the hole transport layer and the hole injection layer are poly(ethylenedioxythiophene):polystyrene sulphonate (PEDOT:PSS), poly[(9, 9-dioctyl-fluorenyl-) 2, 7-diyl)-co-(4, 4'-(N-(p-butylphenyl))diphenylamine)](TFB), poly(9-vinlycarbazole)(PVK), N, N, N, N', N'-tetrakis(4-methoxyphenyl)-benzidine(TPD), poly-TPD, 4, 4', 4''-tris(N-carbazolyl)-triphenylamine(TCTA), N, N'-bis(naphthalen-1 -yl)-N, N'bis(phenyl)-9, 9-spiro-bifluorene(spiro-NPB), dipyrazino[2, 3-f:2', 3'-h]quinoxaline-2, 3, 6, 7, 10, 11-hexacarbonitrile (HATCN), 1, 1-bis[(di-4-tolylamino) phenylcyclohexane (TAPC), VNPB (N4,N4'-Di(naphthalen-1-yl)-N4,N4'- bis(4-vinylphenyl)biphenyl-4,4'-diamine), a quantum dot-emitting device, characterized in that any one selected from p-type metal oxides and combinations thereof. Comprising the step of forming a hole transport layer, a quantum dot light emitting layer, and an electron transport layer, the step of forming the electron transport layer,
forming a magnesium-doped zinc oxide nanoparticle layer on the quantum dot emission layer; and
2-(4-(9,10-di(naphthalen-2-yl)anthracen-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole ( 2-(4-(9,10-di(naphthalene-2-yl)anthracene-2-yl)phenyl)-1-phenyl-1H-benzo-[D]imidazole; LG201) comprising the step of forming a layer Quantum dots, characterized in that the light-emitting device manufacturing method. The method according to claim 7, wherein the hole transport layer, the quantum dot emission layer, and the magnesium-doped zinc oxide nanoparticle layer are formed by a solution process, and the 2-(4-(9,10-di(naphthalen-2-yl)anthracene-2- 1) phenyl)-1-phenyl-1H-benzo-[D]imidazole layer is a quantum dot-light emitting device manufacturing method, characterized in that formed by a vapor deposition method.

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