Quantum dot devices and quantum dot display apparatuses

Abstract

Disclosed is a quantum dot device and a quantum dot display apparatus including the same, the quantum dot device including: an anode disposed on a substrate and including a reflective layer; a hole auxiliary layer disposed on the anode and including a hole injection layer, a hole transport layer, or a combination thereof; a quantum dot layer disposed on the hole auxiliary layer and including quantum dots; an electron auxiliary layer disposed on the quantum dot layer; and a cathode disposed on the electron auxiliary layer, the cathode being a light transmitting electrode capable of transmitting at least a portion of light emitted from the quantum dot layer, wherein the quantum dot layer is configured to emit light of a first wavelength spectrum, the first wavelength spectrum being one of a blue wavelength spectrum, a green wavelength spectrum, and a red wavelength spectrum, the hole auxiliary layer has a thickness that causes a resonance wavelength of the quantum dot device to fall within the first wavelength spectrum, a peak emission wavelength of the quantum dot layer and a peak emission wavelength of light that passes through the cathode collectively belong to the first wavelength spectrum, and a full width at half maximum of an emission spectrum of the light that passes through the cathode is narrower than a full width at half maximum of an emission spectrum of the quantum dot layer.

Description

Technical Field

[0001] Quantum dot devices and quantum dot display devices have been disclosed. Background Technology

[0002] Unlike bulk materials, the inherent physical properties of nanoparticles (e.g., band gap, melting point, etc.) can be controlled by changing their size. For example, semiconductor nanocrystal particles, also known as quantum dots, can be supplied with light or electrical energy and can emit light at wavelengths corresponding to the size of the quantum dot. Therefore, quantum dots can be used as light emitters configured to emit light at predetermined wavelengths. Summary of the Invention

[0003] Quantum dots can be used as light emitters in devices and have become a subject of recent research. However, quantum dots differ from conventional light emitters, thus requiring new methods to improve the performance of quantum dot devices.

[0004] One implementation provides a quantum dot device capable of achieving improved performance.

[0005] Another embodiment provides a quantum dot display device including the quantum dot device.

[0006] According to one embodiment, a quantum dot device includes: an anode disposed on a substrate; a hole-assisted layer disposed on the anode and including a hole injection layer, a hole transport layer, or a combination thereof; a quantum dot layer disposed on the hole-assisted layer and including quantum dots; an electron-assisted layer disposed on the quantum dot layer; and a cathode disposed on the electron-assisted layer, wherein the anode includes a reflective layer, the cathode is a light-transmitting electrode configured to transmit at least a portion of light emitted from the quantum dot layer, the quantum dot layer is configured to emit light of a first wavelength spectrum, the first wavelength spectrum being one of a blue wavelength spectrum, a green wavelength spectrum, and a red wavelength spectrum, the hole-assisted layer has a thickness such that the resonant wavelength of the quantum dot device falls within the first wavelength spectrum, the peak emission wavelength of the quantum dot layer and the peak emission wavelength of the light passing through the cathode both belong to the first wavelength spectrum, and the full width at half maximum (FWHM) of the emission spectrum of the light passing through the cathode is narrower than the FWHM of the emission spectrum of the quantum dot layer.

[0007] The hole auxiliary layer can be thicker than the electron auxiliary layer.

[0008] Quantum dots may include cadmium-free quantum dots, and the difference between the refractive index of the quantum dot layer and the refractive index of the electronically assisted layer may be from about 0.20 to about 1.0.

[0009] The first wavelength spectrum can be the blue wavelength spectrum, and the thickness of the hole auxiliary layer can be from about 100 nm to about 160 nm.

[0010] The thickness of the electronic auxiliary layer can be greater than or equal to about 5 nm and less than about 80 nm.

[0011] The first wavelength spectrum can be the blue wavelength spectrum, and the total thickness of the hole-assisted layer, quantum dot layer, and electron-assisted layer can be from about 160 nm to about 230 nm.

[0012] The first wavelength spectrum can be the red wavelength spectrum, and the thickness of the hole auxiliary layer can be from about 30 nm to about 80 nm or from about 230 nm to about 280 nm.

[0013] The thickness of the electronic auxiliary layer can be greater than or equal to about 5 nm and less than about 80 nm.

[0014] The first wavelength spectrum can be the red wavelength spectrum, and the total thickness of the hole-assisted layer, quantum dot layer, and electron-assisted layer can be about 75 nm to about 135 nm or about 270 nm to about 330 nm.

[0015] The electronic auxiliary layer may include inorganic nanoparticles containing alkaline earth metals.

[0016] The difference between the peak emission wavelength of the quantum dot layer and the peak emission wavelength of the light passing through the cathode can be approximately ±5 nm.

[0017] The FWHM of the emission spectrum of light passing through the cathode can be about 0.2 to about 0.9 of the FWHM of the emission spectrum of the quantum dot layer.

[0018] Quantum dot devices may further include an optical auxiliary layer disposed on the cathode.

[0019] According to another embodiment, a quantum dot display device including quantum dot devices is provided.

[0020] According to another embodiment, a quantum dot display device includes a quantum dot device array, in which unit devices, including a blue quantum dot device configured to display blue, a green quantum dot device configured to display green, and a red quantum dot device configured to display red, are repeatedly arranged, wherein each of the blue, green, and red quantum dot devices includes: an anode including a reflective layer; a hole auxiliary layer on the anode and including a hole injection layer, a hole transport layer, or a combination thereof; a quantum dot layer on the hole auxiliary layer and including quantum dots; an electron auxiliary layer on the quantum dot layer; and a cathode on the electron auxiliary layer and configured to transmit at least a portion of light emitted from the quantum dot layer, wherein the thickness of the hole auxiliary layer of the blue quantum dot device is about 100 nm to about 160 nm, and the thickness of the hole auxiliary layer of the red quantum dot device is different from the thickness of the hole auxiliary layer of the blue quantum dot device.

[0021] The thickness of the hole auxiliary layer in a red quantum dot device can be about 0.1 to about 0.9 times, or about 1.2 times to about 3 times, the thickness of the hole auxiliary layer in a blue quantum dot device.

[0022] The thickness of the hole-assisted layer in red quantum dot devices can be approximately 30 nm to approximately 80 nm or approximately 230 nm to approximately 280 nm.

[0023] The thickness of the electronic auxiliary layer in blue quantum dot devices can be approximately the same as that in red quantum dot devices.

[0024] The thickness of the quantum dot layer in blue quantum dot devices can be approximately the same as that in red quantum dot devices.

[0025] The total thickness of the hole-assisted layer, quantum dot layer, and electron-assisted layer of a blue quantum dot device can be from about 160 nm to about 230 nm, while the total thickness of the hole-assisted layer, quantum dot layer, and electron-assisted layer of a red quantum dot device can be from about 75 nm to about 135 nm or from about 270 nm to about 330 nm.

[0026] The quantum dots included in the quantum dot layer of the blue quantum dot device may include cadmium-free quantum dots, and the quantum dots included in the quantum dot layer of the red quantum dot device may include cadmium-free quantum dots. The difference between the refractive indices of the quantum dot layer and the electronic auxiliary layer of the blue quantum dot device and the difference between the refractive indices of the quantum dot layer and the electronic auxiliary layer of the red quantum dot device may be about 0.20 to about 1.0, respectively.

[0027] The electronic auxiliary layer of blue quantum dot devices and the electronic auxiliary layer of red quantum dot devices can each include inorganic nanoparticles containing alkaline earth metals.

[0028] The difference between the peak emission wavelength of the quantum dot layer of a blue quantum dot device and the peak emission wavelength of the emission spectrum displayed by the blue quantum dot device can be approximately ±5 nm, and the difference between the peak emission wavelength of the quantum dot layer of a red quantum dot device and the peak emission wavelength of the emission spectrum displayed by the red quantum dot device can be approximately ±5 nm.

[0029] Each of the blue quantum dot devices and the red quantum dot devices may further include an optical auxiliary layer on the cathode, and the thickness of the optical auxiliary layer included in the blue quantum dot devices and the red quantum dot devices may be substantially equal.

[0030] It can improve the performance of quantum dot devices. Attached Figure Description

[0031] Figure 1 This is a schematic cross-sectional view showing a quantum dot device according to one embodiment;

[0032] Figure 2 This is a schematic diagram illustrating an example of a quantum dot display panel of a quantum dot display device according to one embodiment;

[0033] Figure 3 yes Figure 2 A cross-sectional view of the quantum dot display panel taken along line III-III;

[0034] Figure 4 This is a graph showing the brightness variation based on the thickness of the hole-assisted layer in a blue quantum dot device;

[0035] Figure 5 This is a graph showing the brightness variation based on the thickness of the electronic auxiliary layer of a blue quantum dot device;

[0036] Figure 6 This is a graph showing the brightness variation based on the thickness of the hole-assisted layer in a red quantum dot device; and

[0037] Figure 7 This is a graph showing the brightness variation based on the thickness of the electronic auxiliary layer of the red quantum dot device. Detailed Implementation

[0038] In the following, exemplary embodiments of the present disclosure will be described in detail so that those skilled in the art will understand these exemplary embodiments. However, the present disclosure may be embodied in many different forms and is not to be construed as limited to the exemplary embodiments set forth herein.

[0039] In the accompanying drawings, the thickness of layers, films, panels, regions, etc., is exaggerated for clarity. Throughout the specification, the same reference numerals denote the same elements. It will be understood that when an element such as a layer, film, region, or substrate is referred to as "on" another element, it may be directly on said other element, or an intervening element may be present. In contrast, when an element is referred to as "directly on" another element, no intervening element is present.

[0040] In the following text, the term "combination" includes two or more mixed and stacked structures.

[0041] In the following text, the values ​​of the work function, HOMO level, or LUMO level are expressed as absolute values ​​from the vacuum level. Furthermore, a deep, high, or large work function, HOMO level, or LUMO level means a large absolute value when the vacuum level is set to "0 eV," while a shallow, low, or small work function, HOMO level, or LUMO level means a small absolute value when the vacuum level is set to "0 eV."

[0042] In the following description, a quantum dot device according to one embodiment will be described with reference to the accompanying drawings.

[0043] According to one embodiment, a quantum dot device can be a quantum dot electroluminescent device configured to emit light from a quantum dot by applying an electric field to an electrode.

[0044] Figure 1 This is a schematic cross-sectional view showing a quantum dot device according to one embodiment.

[0045] Reference Figure 1 According to one embodiment, a quantum dot device 10 includes: an anode 11; a cathode 12; a quantum dot layer 13 disposed between the anode 11 and the cathode 12; a hole auxiliary layer 14 disposed between the anode 11 and the quantum dot layer 13; an electron auxiliary layer 15 disposed between the cathode 12 and the quantum dot layer 13; and optionally, an optical auxiliary layer 16.

[0046] Substrate 110 may be disposed below anode 11. Substrate 110 may include: a semiconductor substrate, such as a silicon substrate; a glass substrate; or a polymer substrate, such as polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyethersulfone, or combinations thereof, but is not limited thereto. Substrate 110 may be omitted.

[0047] The anode 11 can be a reflective electrode that includes a reflective layer.

[0048] As an example, the anode 11 may be formed of a reflective layer comprising an optically opaque material. The reflective layer may, for example, have the following light transmittance: less than about 10%, such as less than or equal to about 8%, less than or equal to about 7%, less than or equal to about 5%, less than or equal to about 3%, or less than or equal to about 1%. The reflective layer may, for example, have the following reflectance: greater than or equal to about 10%, such as greater than or equal to about 20%, greater than or equal to about 30%, greater than or equal to about 50%, or greater than or equal to about 70%. The optically opaque material may include, but is not limited to, metals, metal nitrides, or combinations thereof, such as silver (Ag), copper (Cu), aluminum (Al), gold (Au), titanium (Ti), chromium (Cr), nickel (Ni), their alloys, their nitrides (e.g., TiN), or combinations thereof. The reflective layer may be one, two, or more layers.

[0049] For example, the anode 11 may include a reflective layer comprising an optically opaque material and a light-transmitting layer comprising an optically transparent material. The reflective layer is as described above. The light-transmitting layer may have a high transmittance of about 80%, about 85%, about 88%, or about 90%, and may include an optically transparent conductor. The light-transmitting layer may include at least one of, for example, oxide conductors, carbon conductors, and / or metal thin films. The oxide conductor may include at least one of, for example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc tin oxide (ZTO), aluminum tin oxide (ATO), and aluminum zinc oxide (AZO); the carbon conductor may be at least one of graphene and carbon nanostructures; and the metal thin film may be, for example, a metal thin film formed with a thickness of several nanometers to tens of nanometers, or a single-layer or multi-layer metal thin film doped with metal oxides with a thickness of several nanometers to tens of nanometers.

[0050] For example, the anode 11 can be formed of a reflective layer, or it can have a stacked structure of reflective layer / light transmission layer or light transmission layer / reflective layer / light transmission layer.

[0051] The cathode 12 can face the anode 11 and can be paired with the anode 11 to transfer current to the quantum dot layer 13.

[0052] The cathode 12 can be a light-transmitting electrode configured to transmit at least a portion of the light emitted from the quantum dot layer 13, which will be described later. The light-transmitting electrode may include, for example, a light-transmitting layer, a semi-transmitting layer, or a combination thereof. Thus, the quantum dot device 10 can have a top-emission structure in which light is emitted to the opposite side of the substrate 110 (i.e., towards the cathode 12).

[0053] The semi-transparent layer may have a light transmittance between the light-transmitting layer and the reflective layer, and may have a light transmittance of about 10% to about 70%, about 20% to about 60%, or about 30% to about 50%. The semi-transparent layer may, for example, be configured to selectively transmit light in a predetermined wavelength region and may be configured to reflect or absorb light in other wavelength regions. The semi-transparent layer may include, for example, a metal layer or alloy layer having a thickness of about 1 nm to about 50 nm, and may include, for example, silver (Ag), copper (Cu), aluminum (Al), magnesium (Mg), magnesium-silver (Mg-Ag), magnesium-aluminum (Mg-Al), or combinations thereof, but this disclosure is not limited thereto.

[0054] The quantum dot layer 13 comprises quantum dots. Quantum dots can be semiconductor nanocrystals and can have various shapes, such as spherical semiconductor nanocrystals, quantum rods, or quantum plates. Here, a quantum rod can be a quantum dot having an aspect ratio (length:width) greater than about 1, for example, greater than or equal to about 2, greater than or equal to about 3, or greater than or equal to about 5. For example, a quantum rod can have an aspect ratio less than or equal to about 50, less than or equal to about 30, or less than or equal to about 20.

[0055] Quantum dots can have particle diameters of, for example, the following (mean maximum particle diameter for non-spherical shapes): about 1 nm to about 100 nm, for example about 1 nm to about 80 nm, for example about 1 nm to about 50 nm, for example about 1 nm to about 20 nm.

[0056] Quantum dots can have their band gap controlled by their size and / or composition, and therefore their emission wavelength can also be controlled. For example, as the size of a quantum dot increases, the band gap can become narrower, thus allowing the emission of light in a relatively long wavelength region. As the size of a quantum dot decreases, the band gap can become wider, thus allowing the emission of light in a relatively short wavelength region.

[0057] For example, quantum dots can be configured to emit light in a predetermined wavelength region, such as the visible light region, depending on their size and / or composition. For instance, quantum dots can be configured to emit light in the blue wavelength spectrum (hereinafter referred to as "blue light"), light in the red wavelength spectrum (hereinafter referred to as "red light"), and light in the green wavelength spectrum (hereinafter referred to as "green light"). Blue light can have, for example, a peak emission wavelength (also referred to as the emission peak wavelength) in the range of about 430 nm to about 485 nm (λ). max Red light can have an emission peak wavelength (λ) in the range of approximately 600 nm to approximately 680 nm. max Green light can have an emission peak wavelength (λ) of approximately 510 nm to approximately 570 nm. max ).

[0058] For example, the average size of a quantum dot configured to emit blue light can be, for example, less than or equal to about 4.5 nm, such as less than or equal to about 4.3 nm, less than or equal to about 4.2 nm, less than or equal to about 4.1 nm, or less than or equal to about 4.0 nm. Within the above range, for example, the average size can be from about 2.0 nm to about 4.5 nm, such as from about 2.0 nm to about 4.3 nm, from about 2.0 nm to about 4.2 nm, from about 2.0 nm to about 4.1 nm, or from about 2.0 nm to about 4.0 nm.

[0059] Quantum dots can have relatively narrow full width at half maximum (FWHM). Here, FWHM is the wavelength width corresponding to half of the peak absorption point, and as the FWHM narrows, light can be emitted in a narrower wavelength region and higher color purity can be obtained. Quantum dots can have, for example, the following FWHMs: less than or equal to about 50 nm, less than or equal to about 49 nm, less than or equal to about 48 nm, less than or equal to about 47 nm, less than or equal to about 46 nm, less than or equal to about 45 nm, less than or equal to about 44 nm, less than or equal to about 43 nm, less than or equal to about 42 nm, less than or equal to about 41 nm, less than or equal to about 40 nm, less than or equal to about 39 nm, less than or equal to about 38 nm, less than or equal to about 37 nm, less than or equal to about 36 nm, less than or equal to about 35 nm, less than or equal to about 34 nm, less than or equal to about 33 nm, less than or equal to about 32 nm, less than or equal to about 31 nm, or less than or equal to about 30 nm. Quantum dots can have the following FWHMs, for example: about 10 nm to 50 nm, about 10 nm to about 49 nm, about 10 nm to about 48 nm, about 10 nm to about 47 nm, about 10 nm to about 46 nm, about 10 nm to about 45 nm, about 10 nm to about 44 nm, about 10 nm to about 43 nm, about 10 nm to about 42 nm, about 10 nm to about 41 nm, about 10 nm to about 40 nm, about 10 nm to about 39 nm, about 10 nm to about 38 nm, about 10 nm to about 37 nm, about 10 nm to about 36 nm, about 10 nm to about 35 nm, about 10 nm to about 34 nm, about 10 nm to about 33 nm, about 10 nm to about 32 nm, about 10 nm to about 31 nm, or about 10 nm to about 30 nm.

[0060] For example, quantum dots may include group II-VI semiconductor compounds, group III-V semiconductor compounds, group IV-VI semiconductor compounds, group IV semiconductor compounds, group I-III-VI semiconductor compounds, group I-II-IV-VI semiconductor compounds, group II-III-V semiconductor compounds, or combinations thereof.

[0061] As an example, quantum dots can include Cd-free quantum dots. Cd-free quantum dots are quantum dots that do not contain cadmium (Cd). Cadmium (Cd) can cause serious environmental / health problems and is a restricted element under the Restriction of Hazardous Substances Directive (RoHS) in many countries, therefore cadmium-free quantum dots can be used effectively. Because cadmium-free quantum dots are different from cadmium quantum dots, quantum dot devices 10 that include cadmium-free quantum dots require different constructions and designs than conventional devices that include cadmium quantum dots.

[0062] Group II-VI semiconductor compounds may include, for example: binary semiconductor compounds such as ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS or mixtures thereof; ternary semiconductor compounds such as ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS or mixtures thereof; and quaternary semiconductor compounds such as HgZnTeS, HgZnSeS, HgZnSeTe, HgZnSTe or mixtures thereof, but are not limited thereto. III-V semiconductor compounds may include, for example: binary semiconductor compounds such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb or mixtures thereof; ternary semiconductor compounds such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InNP, InNAs, InNSb, InPAs, InPSb or mixtures thereof; and quaternary semiconductor compounds such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb or mixtures thereof, but are not limited thereto. Group IV-VI semiconductor compounds may include, for example: binary semiconductor compounds such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, or mixtures thereof; ternary semiconductor compounds such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, or mixtures thereof; and quaternary semiconductor compounds such as SnPbSSe, SnPbSeTe, SnPbSTe, or mixtures thereof, but are not limited thereto. Group IV semiconductor compounds may include, for example: single-element semiconductor compounds such as Si, Ge, or mixtures thereof; and binary semiconductor compounds such as SiC, SiGe, or mixtures thereof, but are not limited thereto. Group I-III-VI semiconductor compounds may include, for example: CuInSe2, CuInS2, CuInGaSe, CuInGaS, or mixtures thereof, but are not limited thereto. Group I-II-IV-VI semiconductor compounds may include, for example: CuZnSnSe, CuZnSnS, or mixtures thereof, but are not limited thereto. Group II-III-V semiconductor compounds may include, for example, InZnP, but are not limited to, this.

[0063] Quantum dots can be binary, ternary, or quaternary semiconductor compounds with substantially uniform concentrations or with partially different concentration distributions (e.g., forming a continuous gradient or a step gradient).

[0064] As an example, a quantum dot can be a semiconductor compound comprising zinc (Zn) and at least one of tellurium (Te) and selenium (Se). For example, a quantum dot can be a Zn-Te semiconductor compound, a Zn-Se semiconductor compound, and / or a Zn-Te-Se semiconductor compound. For example, the tellurium (Te) content in a Zn-Te-Se semiconductor compound can be less than the selenium (Se) content. The semiconductor compound can have a peak emission wavelength in the following wavelength regions: less than or equal to about 485 nm, for example, about 430 nm to about 485 nm, about 430 nm to about 480 nm, about 430 nm to about 475 nm, or about 430 nm to about 470 nm, and the semiconductor compound can be configured to emit blue light.

[0065] As an example, quantum dots can be semiconductor compounds comprising indium (In), phosphorus (P), and optionally zinc (Zn). For example, quantum dots can be In-P semiconductor compounds and / or In-Zn-P semiconductor compounds. For example, in an In-Zn-P semiconductor compound, the molar ratio of zinc (Zn) to indium (In) can be greater than or equal to about 25. The semiconductor compound can have a peak emission wavelength in a wavelength region less than about 700 nm, for example, from about 600 nm to about 680 nm, and can be configured to emit red light.

[0066] Quantum dots can have a core-shell structure in which one quantum dot surrounds another. For example, the core and shell of a quantum dot can have an interface, and at the interface, at least one element in the core or shell can have a concentration gradient, wherein the concentration of (multiple) elements in the shell decreases toward the core. For example, the material composition of the shell of a quantum dot has a higher band gap than the material composition of the core of the quantum dot, thus allowing the quantum dot to exhibit a quantum confinement effect.

[0067] A quantum dot can comprise a quantum dot core and multiple layers of quantum dot shells surrounding it. In this case, the multiple shells have two or more shells, and each layer can independently have a single composition, alloy, and / or concentration gradient. For example, the shells farther from the core in a multi-shell system can have a higher band gap than the shells closer to the core, thus allowing the quantum dot to exhibit quantum confinement effects.

[0068] For example, a quantum dot having a core-shell structure may include: a core comprising a first semiconductor compound containing at least one of zinc (Zn) and tellurium (Te) and selenium (Se); and a shell disposed on at least a portion of the core and comprising a second semiconductor compound having a composition different from that of the core.

[0069] For example, the first semiconductor compound may be a Zn-Te-Se based semiconductor compound comprising zinc (Zn), tellurium (Te), and selenium (Se), such as a Zn-Se based semiconductor compound comprising a small amount of tellurium (Te), for example, a semiconductor compound composed of ZnTe x Se 1-x The semiconductor compound is represented by x, where x is greater than about 0 and less than or equal to about 0.05.

[0070] For example, in a first semiconductor compound based on Zn-Te-Se, the molar content of zinc (Zn) can be greater than the molar content of selenium (Se), and the molar content of selenium (Se) can be greater than the molar content of tellurium (Te). For example, in the first semiconductor compound, the molar ratio of tellurium (Te) to selenium (Se) can be less than or equal to about 0.05, less than or equal to about 0.049, less than or equal to about 0.048, less than or equal to about 0.047, less than or equal to about 0.045, less than or equal to about 0.044, less than or equal to about 0.043, less than or equal to about 0.042, less than or equal to about 0.041, less than or equal to about 0.04, less than or equal to about 0.039, less than or equal to about 0.035, less than or equal to about 0.03, less than or equal to about 0.02, or less than or equal to about 0.02. 9. Less than or equal to about 0.025, less than or equal to about 0.024, less than or equal to about 0.023, less than or equal to about 0.022, less than or equal to about 0.021, less than or equal to about 0.02, less than or equal to about 0.019, less than or equal to about 0.018, less than or equal to about 0.017, less than or equal to about 0.016, less than or equal to about 0.015, less than or equal to about 0.014, less than or equal to about 0.013, less than or equal to about 0.012, less than or equal to about 0.011, or less than or equal to about 0.01. For example, in the first semiconductor compound, the molar ratio of tellurium (Te) to zinc (Zn) may be less than or equal to about 0.02, less than or equal to about 0.019, less than or equal to about 0.018, less than or equal to about 0.017, less than or equal to about 0.016, less than or equal to about 0.015, less than or equal to about 0.014, less than or equal to about 0.013, less than or equal to about 0.012, less than or equal to about 0.011, or less than or equal to about 0.01.

[0071] The second semiconductor compound may include, for example, group II-VI semiconductor compounds, group III-V semiconductor compounds, group IV-VI semiconductor compounds, group IV semiconductor compounds, group I-III-VI semiconductor compounds, group I-II-IV-VI semiconductor compounds, group II-III-V semiconductor compounds, or combinations thereof. Examples of group II-VI semiconductor compounds, group III-V semiconductor compounds, group IV-VI semiconductor compounds, group I-III-VI semiconductor compounds, group I-II-IV-VI semiconductor compounds, and group II-III-V semiconductor compounds are the same as described above.

[0072] For example, the second semiconductor compound may include zinc (Zn), selenium (Se), and / or sulfur (S). For example, the shell may include ZnSeS, ZnSe, ZnS, or combinations thereof. For example, the shell may include one or more inner shells disposed near the core and an outermost shell disposed on the outermost side of the quantum dot; the inner shells may include ZnSeS, ZnSe, or combinations thereof, and the outermost shell may include ZnS. For example, the shell may have a concentration gradient with respect to a composition. For example, the shell may have a concentration gradient in which the sulfur (S) content increases with departure from the core.

[0073] For example, a quantum dot having a core-shell structure may include: a core comprising a third semiconductor compound containing indium (In), phosphorus (P) and optionally zinc (Zn); and a shell disposed on at least a portion of the core and comprising a fourth semiconductor compound having a composition different from that of the core.

[0074] In In-Zn-P based third semiconductor compounds, the molar ratio of zinc (Zn) to indium (In) can be greater than or equal to about 25. For example, the molar ratio of zinc (Zn) to indium (In) in In-Zn-P based third semiconductor compounds can be greater than or equal to about 28, greater than or equal to about 29, or greater than or equal to about 30. For example, the molar ratio of zinc (Zn) to indium (In) in In-Zn-P based third semiconductor compounds can be less than or equal to about 55, for example, less than or equal to about 50, less than or equal to about 45, less than or equal to about 40, less than or equal to about 35, less than or equal to about 34, less than or equal to about 33, or less than or equal to about 32.

[0075] The fourth semiconductor compound may include, for example, group II-VI semiconductor compounds, group III-V semiconductor compounds, group IV-VI semiconductor compounds, group IV semiconductor compounds, group I-III-VI semiconductor compounds, group I-II-IV-VI semiconductor compounds, group II-III-V semiconductor compounds, or combinations thereof. Examples of group II-VI semiconductor compounds, group III-V semiconductor compounds, group IV-VI semiconductor compounds, group IV semiconductor compounds, group I-III-VI semiconductor compounds, group I-II-IV-VI semiconductor compounds, and group II-III-V semiconductor compounds are the same as described above.

[0076] For example, the fourth semiconductor compound may include zinc (Zn) and include at least one selected from sulfur (S) and selenium (Se). For example, the shell may include ZnSeS, ZnSe, ZnS, or combinations thereof. For example, the shell may include one or more inner shells near the core and an outermost shell on the outermost side of the quantum dot, at least one of the outermost shell and the inner shell may include a fourth semiconductor compound of ZnS, ZnSe, or ZnSeS.

[0077] The quantum dot layer 13 may have relatively deep HOMO energy levels, for example, HOMO energy levels greater than or equal to about 5.4 eV, HOMO energy levels greater than or equal to about 5.6 eV, and within the aforementioned range, HOMO energy levels greater than or equal to about 5.7 eV, greater than or equal to about 5.8 eV, greater than or equal to 5.9 eV, or greater than or equal to about 6.0 eV. The quantum dot layer 13 may have HOMO energy levels, for example, from about 5.4 eV to about 7.0 eV, for example, from about 5.4 eV to about 6.8 eV, from about 5.4 eV to about 6.7 eV, from about 5.4 eV to about 6.5 eV, from about 5.4 eV to about 6.3 eV, from about 5.4 eV to about 6.2 eV, or from about 5.4 eV to about 6.1 eV, within the aforementioned range, for example, from about 5.6 eV to about 7.0 eV. HOMO energy levels ranging from approximately 5.6 eV to approximately 6.8 eV, approximately 5.6 eV to approximately 6.7 eV, approximately 5.6 eV to approximately 6.5 eV, approximately 5.6 eV to approximately 6.3 eV, approximately 5.6 eV to approximately 6.2 eV, and approximately 5.6 eV to approximately 6.1 eV, and within the aforementioned ranges, for example, approximately 5.7 eV to approximately 7.0 eV, approximately 5.7 eV to approximately 6.8 eV, and approximately 5.7 eV to approximately 6.1 eV. HOMO levels of 0.7 eV, for example, about 5.7 eV to about 6.5 eV, for example, about 5.7 eV to about 6.3 eV, for example, about 5.7 eV to about 6.2 eV, for example, about 5.7 eV to about 6.1 eV, and within the above range, for example, about 5.8 eV to about 7.0 eV, for example, about 5.8 eV to about 6.8 eV, for example, about 5.8 eV to about 6.7 eV, for example, about 5.8 eV to about 6.5 eV, for example, about 5.8 eV to... HOMO levels of about 6.3 eV, for example about 5.8 eV to about 6.2 eV, for example about 5.8 eV to about 6.1 eV, and within the above range, for example about 6.0 eV to about 7.0 eV, for example about 6.0 eV to about 6.8 eV, for example about 6.0 eV to about 6.7 eV, for example about 6.0 eV to about 6.5 eV, for example about 6.0 eV to about 6.3 eV, for example about 6.0 eV to about 6.2 eV.

[0078] The quantum dot layer 13 may have a relatively shallow LUMO level, for example less than or equal to about 3.6 eV, in the range of, for example less than or equal to about 3.5 eV, for example less than or equal to about 3.4 eV, for example less than or equal to about 3.3 eV, for example less than or equal to about 3.2 eV, or for example less than or equal to about 3.0 eV. Within this range, the quantum dot layer 13 may have LUMO energy levels, for example, about 2.5 eV to about 3.6 eV, about 2.5 eV to about 3.5 eV, for example, about 2.5 eV to about 3.4 eV, for example, about 2.5 eV to about 3.3 eV, for example, about 2.5 eV to about 3.2 eV, for example, about 2.5 eV to about 3.1 eV, for example, about 2.5 eV to about 3.0 eV, for example, about 2.8 eV to about 3.6 eV, about 2.8 eV to about 3.5 eV, for example, about 2.8 eV to about 3.4 eV, for example, about 2.8 eV to about 3.3 eV, for example, about 2.8 eV to about 3.2 eV, about 3.0 eV to about 3.6 eV, about 3.0 eV to about 3.5 eV, or for example, about 3.0 eV to about 3.4 eV.

[0079] The quantum dot layer 13 can be one, two, or more layers comprising the same or different quantum dots.

[0080] The refractive index of the quantum dot layer 13 in the visible light wavelength region can be from about 1.65 to about 2.70, for example, the refractive indices at about 460 nm, about 540 nm, and about 630 nm can respectively satisfy the above range. Within this range, the quantum dot layer 13 can have each of the following refractive indices in the visible light wavelength region (e.g., about 460 nm, about 540 nm, and about 630 nm): about 1.70 to about 2.65, about 1.75 to about 2.60, about 1.80 to about 2.55, about 1.80 to about 2.50, about 1.80 to about 2.40, about 1.80 to about 2.30, about 1.80 to about 2.20, about 1.80 to about 2.10, about 1.80 to about 2.00, or about 1.80 to about 1.95.

[0081] The quantum dot layer 13 may have a thickness of, for example, from about 5 nm to about 200 nm, within the above range, for example, from about 10 nm to about 150 nm, from about 10 nm to about 100 nm, from about 10 nm to about 80 nm, or from about 10 nm to about 50 nm.

[0082] A hole-assist layer 14 may be disposed between the anode 11 and the quantum dot layer 13, specifically on the anode 11 and below the quantum dot layer 13. The hole-assist layer 14 includes a hole injection layer 14a, a hole transport layer 14b, or a combination thereof. The hole injection layer 14a is disposed near the anode 11, and the hole transport layer 14b is disposed near the quantum dot layer 13. The hole injection layer 14a facilitates the injection of holes from the anode 11, and the hole transport layer 14b efficiently transfers the injected holes to the quantum dot layer 13. The hole injection layer 14a and the hole transport layer 14b may each have one, two, or more layers, and may include a generalized electron-blocking layer. Either the hole injection layer 14a or the hole transport layer 14b may be omitted.

[0083] Hole injection layer 14a and hole transport layer 14b may each have a HOMO level between the work function of anode 11 and the HOMO level of quantum dot layer 13. For example, the work function of anode 11, the HOMO level of hole injection layer 14a, the HOMO level of hole transport layer 14b and the HOMO level of quantum dot layer 13 may be deepened and may be, for example, stepped.

[0084] The HOMO level of the hole transport layer 14b can have a relatively deep HOMO level, thereby matching the HOMO level of the quantum dot layer 13. Therefore, the charge mobility of holes transferred from the hole transport layer 14b to the quantum dot layer 13 can be improved.

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

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

[0087] For example, the HOMO level of the hole transport layer 14b can be from about 5.0 eV to about 7.0 eV, within the above range, for example, from about 5.2 eV to about 6.8 eV, within the above range, for example, from about 5.4 eV to about 6.8 eV, for example, from about 5.4 eV to about 6.7 eV, for example, from about 5.4 eV to about 6.5 eV, for example, from about 5.4 eV to about 6.3 eV, for example, from about 5.4 eV to about 6.2 eV, for example, from about 5.4 eV to about 6.1 eV, for example, from about 5.6 eV to about 7.0 eV, for example, from about 5.6 eV to about 6.8 eV. For example, about 5.6 eV to about 6.7 eV, for example, about 5.6 eV to about 6.5 eV, for example, about 5.6 eV to about 6.3 eV, for example, about 5.6 eV to about 6.2 eV, for example, about 5.6 eV to about 6.1 eV, for example, about 5.8 eV to about 7.0 eV, for example, about 5.8 eV to about 6.8 eV, for example, about 5.8 eV to about 6.7 eV, for example, about 5.8 eV to about 6.5 eV, for example, about 5.8 eV to about 6.3 eV, for example, about 5.8 eV to about 6.2 eV, for example, about 5.8 eV to about 6.1 eV.

[0088] The refractive indices of the hole injection layer 14a and the hole transport layer 14b in the visible light wavelength region can be lower than the refractive index of the quantum dot layer 13 in the visible light wavelength region. For example, the difference between the refractive index of the quantum dot layer 13 and the refractive index of the hole injection layer 14a / hole transport layer 14b can be greater than or equal to about 0.01, within the aforementioned range, about 0.01 to about 1.00, about 0.02 to about 0.80, about 0.03 to about 0.60, about 0.03 to about 0.50, about 0.03 to about 0.40, or about 0.03 to about 0.30.

[0089] For example, the refractive index of the hole injection layer 14a and the hole transport layer 14b in the visible light wavelength region can be from about 1.20 to about 2.5, for example, the refractive indices at about 460 nm, about 540 nm, and about 630 nm can all satisfy the above range. Within the above range, the refractive index of the electron-assisted layer 15 in the visible light wavelength region (e.g., about 460 nm, about 540 nm, and about 630 nm) can be from about 1.20 to about 2.3, from about 1.25 to about 2.2, from about 1.3 to about 2.1, from about 1.4 to about 2.0, from about 1.45 to about 1.9, or from about 1.50 to about 1.9, respectively.

[0090] Hole injection layer 14a and hole transport layer 14b may comprise, for example, organic materials, inorganic materials, organic-inorganic materials, or combinations thereof, and may include, for example, at least one selected from the following: poly(9,9-dioctylfluorene-co-N-(4-butylphenyl)-diphenylamine (TFB), polyarylamine, poly(N-vinylcarbazole), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(3,4-ethylenedioxythiophene)polystyrene sulfonic acid (PEDOT:PSS), polyaniline, polypyrrole, N,N,N',N'-tetra(4- Methoxyphenyl)benzidine (TPD), 4-bis[N-(1-naphthyl)-N-phenyl-amino]biphenyl (α-NPD), m-MTDATA (4,4',4”-tris[phenyl(m-tolyl)amino]triphenylamine), 4,4',4”-tris(N-carbazolyl)triphenylamine (TCTA), 1,1-bis[(di-4-tolylamino)phenylcyclohexane (TAPC), p-type metal oxides (e.g., NiO, WO3, MoO3, etc.), carbon-based materials such as graphene oxides, and combinations thereof, but not limited thereto.

[0091] An electron auxiliary layer 15 may be disposed between the cathode 12 and the quantum dot layer 13, specifically, disposed on the quantum dot layer 13 and below the cathode 12. The electron auxiliary layer 15 may be one, two, or more layers, and may be an electron injection layer, an electron transport layer, a hole blocking layer, or a combination thereof.

[0092] The electron auxiliary layer 15 can facilitate the injection of electrons from the cathode 12 and can efficiently transfer the injected electrons to the quantum dot layer 13.

[0093] The LUMO level of the electron-assisted layer 15 can be between, for example, the LUMO level of the quantum dot layer 13 and the work function of the cathode 12. For example, the work function of the cathode 12, the LUMO level of the electron-assisted layer 15, and the LUMO level of the quantum dot layer 13 can be shallower and can be, for example, stepped.

[0094] The HOMO level of the electron-assisted layer 15 may be, for example, deeper than the HOMO level of the quantum dot layer 13. For example, the HOMO level of the electron-assisted layer 15 may be about 0.2 eV or greater, about 0.5 eV or greater, about 0.8 eV or greater, about 1.0 eV or greater, about 1.2 eV or greater, or about 1.5 eV deeper than the HOMO level of the quantum dot layer 13, for example, about 0.2 eV to about 3.0 eV, about 0.5 eV to about 3.0 eV, about 0.8 eV to about 3.0 eV, about 1.0 eV to about 3.0 eV, about 1.2 eV to about 3.0 eV, or about 1.5 eV to about 3.0 eV.

[0095] As an example, the electron auxiliary layer 15 may have a relatively deep HOMO level. The HOMO level of the electron auxiliary layer 15 may be, for example, about 5.6 eV to about 8.5 eV, within the above range, about 5.8 eV to about 8.2 eV, about 6.0 eV to about 8.0 eV, about 6.2 eV to about 8.0 eV, about 6.5 eV to about 8.0 eV, about 6.8 eV to about 8.0 eV, about 7.0 eV to about 8.0 eV, about 7.2 eV to about 7.9 eV, or about 7.3 eV to about 7.8 eV.

[0096] Because the electron auxiliary layer 15 has such an energy level, electrons can be effectively transferred and holes can be effectively blocked, thereby improving the stability of quantum dot devices.

[0097] The electronic auxiliary layer 15 may include materials that satisfy the aforementioned energy levels, such as inorganic nanoparticles. Inorganic nanoparticles may be, for example, oxide nanoparticles, and may be, for example, metal oxide nanoparticles. As an example, inorganic nanoparticles may be metal oxide nanoparticles comprising two or more types of metals. For example, inorganic nanoparticles may be inorganic semiconductors.

[0098] Inorganic nanoparticles can be two-dimensional or three-dimensional nanoparticles having an average particle diameter of less than or equal to about 10 nm and an average particle diameter of less than or equal to about 8 nm, less than or equal to about 7 nm, less than or equal to about 5 nm, less than or equal to about 4 nm, or less than or equal to about 3.5 nm, within the above ranges, about 1 nm to about 10 nm, about 1 nm to about 9 nm, about 1 nm to about 8 nm, about 1 nm to about 7 nm, about 1 nm to about 5 nm, about 1 nm to about 4 nm, or about 1 nm to about 3.5 nm.

[0099] As an example, inorganic nanoparticles can be metal oxide nanoparticles that include alkaline earth metals. For instance, inorganic nanoparticles can be metal oxide nanoparticles that include beryllium (Be), magnesium (Mg), calcium (Ca), barium (Ba), strontium (Sr), radium (Ra), or combinations thereof.

[0100] Inorganic nanoparticles can be metal oxide nanoparticles that include at least one of zinc (Zn), cobalt (Co), nickel (Ni), gallium (Ga), zirconium (Zr), tungsten (W), titanium (Ti), tantalum (Ta), tin (Sn), and hafnium (Hf), in addition to alkaline earth metals.

[0101] For example, the inorganic nanoparticles can be metal oxide nanoparticles including an alkaline earth metal and zinc (Zn), wherein the alkaline earth metal can be included in an amount less than that of zinc. For example, the alkaline earth metal can be included in an amount of about 0.01 at% to about 30 at% or about 0.01 at% to about 20 at% based on the total number of metal atoms (i.e., the total number of alkaline earth metal and zinc included in the inorganic nanoparticles).

[0102] For example, the inorganic nanoparticles can be composed of Zn 1-x Q x is represented by O, wherein Q is Be, Mg, Ca, Ba, Sr, Re or a combination thereof, and 0 < x < 0.5. For example, Q can include Mg, such as 0.01 ≦ x ≦ 0.3 or 0.01 ≦ x ≦ 0.2.

[0103] The electron assisting layer 15 can further include an additive. The additive can be included in the form of a mixture with the inorganic nanoparticles and can be included in a small amount to improve the electron transport characteristics and / or electron injection characteristics of the electron assisting layer 15.

[0104] The additive can be selected from, for example, alkali metals, alkali metal compounds, alkali metal salts or a combination thereof. The alkali metals can include, for example, lithium (Li), sodium (Na), potassium (K), cesium (Cs), rubidium (Rb), francium (Fr) or a combination thereof. The alkali metal compounds can be compounds including alkali metals, and the alkali metal salts can be metal cations derived from alkali metal compounds. The additive can be, for example, an alkali metal compound and / or an alkali metal salt derived therefrom, wherein the additive can further include anions such as carbonate (CO3 2- ), phosphate (PO4 3- ), vanadate (VO4 3- ), azide (N3 - ), or nitride (N 3- ).

[0105] For example, the additive can include lithium (Li), sodium (Na), potassium (K), cesium (Cs), rubidium (Rb), francium (Fr), cesium carbonate (Cs2CO3), cesium phosphate (Cs3PO4), cesium vanadate (Cs3VO4), cesium azide (CsN3), lithium carbonate (LiCO3), lithium nitride (Li3N), sodium carbonate (Na2CO3), potassium carbonate (K2CO3), rubidium carbonate (Rb2CO3) or a combination thereof, but is not limited thereto.

[0106] The additive may be included in a smaller amount than the inorganic nanoparticles. For example, the additive may be included based on the total amount of the mixture of inorganic nanoparticles and the additive in the following amounts: from about 0.1 vol% to 30 vol%, within the above range, from about 0.1 vol% to about 25 vol%, from about 0.1 vol% to about 20 vol%, from about 0.5 vol% to about 18 vol%, from about 1 vol% to about 15 vol%, or from about 3 vol% to about 15 vol%.

[0107] The refractive index of the electron-assisted layer 15 in the visible light wavelength region may be lower than that of the quantum dot layer 13 in the visible light wavelength region. For example, the difference between the refractive index of the quantum dot layer 13 and the refractive index of the electron-assisted layer 15 may be greater than or equal to about 0.20, within the range of about 0.20 to about 1.00, about 0.20 to about 0.80, about 0.20 to about 0.60, about 0.20 to about 0.50, about 0.20 to about 0.40, or about 0.20 to about 0.30.

[0108] For example, the refractive index of the electron-assisted layer 15 in the visible light wavelength region can be from about 1.40 to about 2.5, for example, the refractive indices at about 460 nm, about 540 nm, and about 630 nm can each satisfy the above range. Within the above range, the refractive indices of the electron-assisted layer 15 at about 460 nm, about 540 nm, and about 630 nm can be from about 1.40 to about 2.3, from about 1.45 to about 2.2, from about 1.5 to about 2.1, from about 1.5 to about 2.0, from about 1.5 to about 1.9, from about 1.5 to about 1.8, from about 1.5 to about 1.7, or from about 1.5 to about 1.65, respectively.

[0109] The thickness of the electronic auxiliary layer 15 may be, for example, greater than or equal to about 5 nm and less than about 80 nm, within the above range, for example, about 5 nm to about 70 nm, for example, about 5 nm to about 60 nm, or for example, about 5 nm to about 50 nm.

[0110] An optical auxiliary layer 16 may be disposed on the cathode 12 to further improve the optical properties of light emitted towards the top. The optical auxiliary layer 16 may be, for example, a light-transmitting layer or a semi-transmitting layer. The optical auxiliary layer 16 may comprise organic materials, inorganic materials, and / or inorganic-organic materials. The optical auxiliary layer 16 may be one, two, or more layers. The optical auxiliary layer 16 may be omitted.

[0111] The thickness of the optical auxiliary layer 16 can be from about 10 nm to about 200 nm, within the above range, about 20 nm to about 200 nm, about 20 nm to about 150 nm, about 20 nm to about 100 nm, about 20 nm to about 80 nm, about 25 nm to about 200 nm, about 25 nm to about 150 nm, about 25 nm to about 100 nm, about 25 nm to about 80 nm, about 30 nm to about 150 nm, about 30 nm to about 100 nm, about 30 nm to about 80 nm, about 35 nm to about 150 nm, about 35 nm to about 100 nm, about 35 nm to about 80 nm, about 40 nm to about 150 nm, about 40 nm to about 100 nm, or about 40 nm to about 80 nm.

[0112] The quantum dot device 10 includes an anode 11 containing a reflective layer, a cathode 12 containing a semitransparent layer and / or an optical auxiliary layer 16, a quantum dot layer 13, a hole auxiliary layer 14, and an electron auxiliary layer 15 between the reflective layer and the semitransparent layer, thereby allowing a microcavity structure to be formed.

[0113] Due to the isotropic light-emitting properties of quantum dots, unlike conventional light emitters such as organic light-emitting materials, the light extraction efficiency of the cathode 12 facing the quantum dot device 10 can be low. Therefore, the microcavity structure in the quantum dot device 10 can differ from the microcavity structure in conventional organic light-emitting devices.

[0114] Specifically, due to the isotropic light emission properties of quantum dots, light emitted from quantum dot layer 13 can radiate in all directions. Therefore, a portion of the light emitted from quantum dot layer 13 can move towards anode 11 and be reflected by the reflective layer of anode 11, while another portion can move towards cathode 12 and be reflected by cathode 12 and / or optical auxiliary layer 16. This reflected light can resonate repeatedly between anode 11 and cathode 12 to be amplified and modified into light of a predetermined wavelength spectrum, and the modified light can pass through cathode 12 and be emitted to the outside. That is, in quantum dot device 10, the modified light emitted through cathode 12 can be different from the light emitted from quantum dot layer 13.

[0115] By precisely controlling the microcavity structure, the optical properties of the modified light emitted through the cathode 12 (hereinafter referred to as "modified light") can be effectively tuned.

[0116] For example, the properties of the modified light can be adjusted by the following: the path of the light emitted from the light-emitting point (e.g., quantum dot), such as the distance between the quantum dot layer 13 and the reflective layer of the anode 11, the distance between the quantum dot layer 13 and the cathode 12; the refractive index of each layer; and / or the difference in refractive index between adjacent layers.

[0117] For example, the properties of the modified light can be tuned by the distance between the quantum dot layer 13 and the reflective layer of the anode 11 and / or the distance between the quantum dot layer 13 and the cathode 12.

[0118] As reflection is repeated, the number of passes between the quantum dot layer 13 and the reflective layer of the anode 11 is greater than the number of passes between the quantum dot layer 13 and the cathode 12. This allows the distance between the quantum dot layer 13 and the reflective layer 11 of the anode to be greater than the distance between the quantum dot layer 13 and the cathode 12, thus effectively modulating the microcavity. In this case, the distance between the quantum dot layer 13 and the reflective layer of the anode 11 can be adjusted, for example, by the thickness of the hole-assisted layer 14, and the distance between the quantum dot layer 13 and the cathode 12 can be adjusted, for example, by the thickness of the electron-assisted layer 15. For example, by making the hole-assisted layer 14 thicker than the electron-assisted layer 15, the properties of the modified light can be effectively modulated.

[0119] The thickness of the hole-assisted layer 14 can be determined based on the emission spectrum of the quantum dot layer 13. For example, the thickness of the hole-assisted layer 14 can be determined such that the resonant wavelength of the microcavity structure of the quantum dot device 10 belongs to the same wavelength spectrum as the emission spectrum of the quantum dot layer 13.

[0120] For example, when quantum dot layer 13 is configured to emit light of the blue wavelength spectrum, the thickness of hole-assisted layer 14 can be set to have a resonant wavelength belonging to the blue wavelength spectrum. Similarly, when quantum dot layer 13 is configured to emit light of the green wavelength spectrum, the thickness of hole-assisted layer 14 can be set to have a resonant wavelength belonging to the green wavelength spectrum. Likewise, when quantum dot layer 30 is configured to emit light of the red wavelength spectrum, the thickness of hole-assisted layer 14 can be set to have a resonant wavelength belonging to the red wavelength spectrum. These resonant wavelengths can be one, two, or more.

[0121] For example, when quantum dot layer 13 is configured to emit light with a blue wavelength spectrum (e.g., λ), max1 When the thickness is from about 430 nm to about 485 nm, the thickness of the hole auxiliary layer 14 can be from about 100 nm to about 160 nm. Within the above range, the thickness of the hole auxiliary layer 14 can be from about 110 nm to about 150 nm, from about 120 nm to about 145 nm, or from about 125 nm to about 140 nm.

[0122] For example, when quantum dot layer 13 is configured to emit light of the blue wavelength spectrum (e.g., λ) max1When the light emission point is between approximately 430 nm and approximately 485 nm, the total thickness of the hole-assisted layer 14, the quantum dot layer 13, and the electron-assisted layer 15 disposed in the path of light emitted from the light-emitting point (e.g., a quantum dot) can be between approximately 160 nm and approximately 230 nm. Within the above range, the total thickness of the hole-assisted layer 14, the quantum dot layer 13, and the electron-assisted layer 15 can be between approximately 165 nm and approximately 225 nm, between approximately 160 nm and approximately 220 nm, or between approximately 155 nm and approximately 215 nm.

[0123] As an example, when quantum dot layer 13 is configured to emit a red wavelength spectrum (e.g., λ), max1 When emitting light in the blue wavelength spectrum (approximately 600 nm to approximately 680 nm), the thickness of the hole-assist layer 14 can be thicker or thinner than the thickness of the hole-assist layer 14 when the quantum dot layer 13 is configured to emit light in the blue wavelength spectrum. For example, when the quantum dot layer 13 is configured to emit light in the red wavelength spectrum, the thickness of the hole-assist layer 14 can be approximately 0.1 to approximately 0.9 times (first resonance) or approximately 1.2 times to approximately 3 times (second resonance) the thickness of the hole-assist layer 14 when the quantum dot layer 13 is configured to emit light in the blue wavelength spectrum.

[0124] For example, when the quantum dot layer 13 is configured to emit light of the red wavelength spectrum, the thickness of the hole-assisted layer 14 can be approximately 30 nm to approximately 80 nm (first resonance) or approximately 230 nm to approximately 280 nm (second resonance). Within the above range, the thickness of the hole-assisted layer 14 can be approximately 35 nm to approximately 75 nm, approximately 40 nm to approximately 70 nm, approximately 45 nm to approximately 65 nm, approximately 235 nm to approximately 275 nm, approximately 240 nm to approximately 270 nm, or approximately 245 nm to approximately 265 nm.

[0125] For example, when quantum dot layer 13 is configured to emit a red wavelength spectrum (e.g., λ) max1 When emitting light (approximately 600 nm to approximately 680 nm), the total thickness of the hole-assisted layer 14, quantum dot layer 13, and electron-assisted layer 15 disposed in the path of the light emitted from the emitting point (e.g., quantum dot) can be approximately 75 nm to approximately 135 nm or approximately 270 nm to approximately 330 nm. Within this range, the total thickness of the hole-assisted layer 14, quantum dot layer 13, and electron-assisted layer 15 can be approximately 80 nm to approximately 130 nm, approximately 85 nm to approximately 125 nm, approximately 90 nm to approximately 120 nm, approximately 275 nm to approximately 325 nm, or approximately 280 nm to approximately 320 nm.

[0126] As an example, when quantum dot layer 13 is configured to emit a green wavelength spectrum (e.g., λ), max1When emitting light in the range of approximately 510 nm to approximately 575 nm, the thickness of the hole-assist layer 14 can be thicker or thinner than the thickness of the hole-assist layer 14 when the quantum dot layer 13 is configured to emit light in the blue wavelength spectrum, or when the quantum dot layer 13 is configured to emit light in the red wavelength spectrum. For example, when the quantum dot layer 13 is configured to emit light in the green wavelength spectrum, the thickness of the hole-assist layer 14 can be approximately 0.1 to approximately 0.9 times (first resonance) or approximately 1.2 times to approximately 3 times (second resonance) the thickness of the hole-assist layer 14 when the quantum dot layer 13 is configured to emit light in the blue wavelength spectrum, or when the quantum dot layer 13 is configured to emit light in the red wavelength spectrum.

[0127] By adjusting the thickness of the hole-assisted layer 14 as described above, the emission spectrum of the modified light can belong to the same wavelength spectrum as the emission spectrum of the light emitted from the quantum dot layer 13. For example, the emission spectrum of the light emitted from the quantum dot layer 13 and the emission spectrum of the modified light can both belong to one of the blue, green, and red wavelength spectra. For example, the emission peak wavelength of the quantum dot layer 13 and the emission peak wavelength of the modified light can both belong to one of the blue, green, and red wavelength spectra.

[0128] For example, the emission peak wavelength (λ) of quantum dot layer 13 max1 ) and the peak emission wavelength of the modified light (λ) max2 The wavelengths can fall within approximately 430 nm to approximately 485 nm, and can be configured to display blue. Here, the emission peak wavelength (λ) of quantum dot layer 13 is... max1 ) and the peak emission wavelength of the modified light (λ) max2 The difference between them can be approximately ±10nm, approximately ±8nm, approximately ±7nm, approximately ±5nm, approximately ±4nm, approximately ±3nm, or approximately ±2nm.

[0129] For example, the emission peak wavelength (λ) of quantum dot layer 13 max1 ) and the peak emission wavelength of the modified light (λ) max2 The wavelengths can fall within approximately 600 nm to approximately 680 nm, and can be configured to display red. Here, the emission peak wavelength (λ) of quantum dot layer 13 is... max1 ) and the peak emission wavelength of the modified light (λ) max2 The difference between them can be approximately ±10nm, approximately ±8nm, approximately ±7nm, approximately ±5nm, approximately ±4nm, approximately ±3nm, or approximately ±2nm.

[0130] For example, the emission peak wavelength (λ) of quantum dot layer 13 max1 ) and the peak emission wavelength of the modified light (λ) max2The emission wavelength can fall within approximately 510 nm to approximately 570 nm and can be configured to display green. Here, the emission peak wavelength (λ) of quantum dot layer 13 is... max1 ) and the peak emission wavelength of the modified light (λ) max2 The difference between them can be approximately ±10nm, approximately ±8nm, approximately ±7nm, approximately ±5nm, approximately ±4nm, approximately ±3nm, or approximately ±2nm.

[0131] On the other hand, the color purity of the modified light can be higher than that of the light emitted from the quantum dot layer 13. For example, the full width at half maximum (FWHM2) of the emission spectrum of the modified light can be narrower than the full width at half maximum (FWHM1) of the emission spectrum of the quantum dot layer 13. For example, the full width at half maximum (FWHM2) of the emission spectrum of the modified light can be about 0.1 to 0.9 of the full width at half maximum (FWHM1) of the emission spectrum of the quantum dot layer 13, specifically about 0.2 to about 0.9, about 0.2 to about 0.8, about 0.3 to about 0.8, about 0.4 to about 0.8, or about 0.5 to about 0.8. For example, the difference between the full width at half maximum (FWHM1) of the emission spectrum of the quantum dot layer 13 and the full width at half maximum (FWHM2) of the emission spectrum of the modified light can be about 2 nm to about 30 nm, about 3 nm to about 30 nm, or about 5 nm to about 30 nm. Here, the full width at half maximum (FWHM1) of the emission spectrum of quantum dot layer 13 can be confirmed from a quantum dot device without using a microcavity structure.

[0132] For example, the properties of the modified light can be more effectively tuned by the refractive index of each layer and / or the refractive index difference between adjacent layers. The refractive indices of the quantum dot layer 13, hole-assisted layer 14, and electron-assisted layer 15, which are disposed in the path of light emitted from the light-emitting point (e.g., quantum dot), are the same as described above. Each of the quantum dot layer 13, hole-assisted layer 14, and electron-assisted layer 15 has the aforementioned refractive index, so that the microcavity structure of the quantum dot device 10 can be effectively tuned, thereby further improving the quality of light emitted through the cathode 12.

[0133] Thus, the quantum dot device 10 is a conventional top-emitting light-emitting device in which the anode 11, hole-assisted layer 14, quantum dot layer 13, electron-assisted layer 15, and cathode 12 are stacked sequentially on the substrate 110. By improving the extraction efficiency of light emitted through the cathode 12 and improving color purity, the display quality of the quantum dot device 10 can be improved.

[0134] The quantum dot device 10 can be manufactured by various methods, such as forming an anode 11, a hole auxiliary layer 14, a quantum dot layer 13, an electron auxiliary layer 15, a cathode 12, and optionally an optical auxiliary layer 16 on a substrate 110.

[0135] The quantum dot layer 13, the hole auxiliary layer 14 and / or the electron auxiliary layer 15 can be formed by solution processes such as spin coating, slot coating, inkjet printing, nozzle printing, spraying and / or blade coating, but this disclosure is not limited thereto.

[0136] At least one of forming the quantum dot layer 13, forming the hole-assisted layer 14, and / or forming the electron-assisted layer 15 may be further performed after the solution process by selective drying and / or heat treatment. The heat treatment may be performed, for example, at a temperature from about 50°C to about 300°C for about 1 minute to 10 hours, but this disclosure is not limited thereto.

[0137] The aforementioned quantum dot devices can be applied to various electronic devices that require light emission, and can be applied to various electronic devices such as display devices, such as TVs, monitors, computers, mobile devices, and lighting devices (e.g., light sources).

[0138] In the following text, examples of quantum dot display devices including the aforementioned quantum dot devices will be described.

[0139] The quantum dot display device includes a quantum dot display panel and a driver. The quantum dot display panel includes a quantum dot device array in which a plurality of quantum dot devices as mentioned above are arranged.

[0140] Figure 2 This is a schematic diagram illustrating an example of a quantum dot display panel of a quantum dot display device according to one embodiment. Figure 3 yes Figure 2 A cross-sectional view of the quantum dot display panel taken along line III-III.

[0141] Reference Figure 2 The quantum dot display panel 200 includes a plurality of pixels PX, which are repeatedly arranged along rows and / or columns to form a quantum dot device array. Each pixel PX may be a unit element and includes a plurality of sub-pixels PX1, PX2, and PX3 configured to display different colors. Figure 2 In the diagram, a pixel PX is shown as an example, consisting of multiple sub-pixels PX1, PX2, and PX3 configured to display different colors. However, this is not a limitation. Each pixel PX may include two or more of at least one of the sub-pixels PX1, PX2, and PX3, or each pixel PX may further include additional sub-pixels, such as a white sub-pixel (not shown). The sub-pixels PX1, PX2, and PX3 in each pixel PX may be arranged, for example, in a Bayer matrix, a PenTile matrix, a diamond matrix, etc., but are not limited to these arrangements.

[0142] In the accompanying drawings, all pixels PX are shown as having the same size, but are not limited thereto; at least one pixel PX may be larger or smaller than the other pixels PX. In the accompanying drawings, all pixels PX are shown as having the same shape, but are not limited thereto; at least one pixel PX may have a shape different from the other pixels PX.

[0143] In the accompanying drawings, all sub-pixels PX1, PX2, and PX3 are shown as having the same size, but are not limited thereto; at least one sub-pixel PX1, PX2, or PX3 may be larger or smaller than sub-pixels PX1, PX2, or PX3. In the accompanying drawings, all sub-pixels PX1, PX2, and PX3 are shown as having the same shape, but are not limited thereto; at least one sub-pixel PX1, PX2, or PX3 may have a shape different from the shapes of the other sub-pixels PX1, PX2, or PX3.

[0144] Reference Figure 3 The quantum dot display panel 200 includes a blue quantum dot device 10B configured to display blue, a green quantum dot device 10G configured to display green, and a red quantum dot device 10R configured to display red, all on a substrate 110.

[0145] Each of the blue quantum dot device 10B, the green quantum dot device 10G, and the red quantum dot device 10R can be the aforementioned quantum dot device 10.

[0146] Specifically, the blue quantum dot device 10B includes: an anode 11B, including a reflective layer; a cathode 12B; a quantum dot layer 13B, between the anode 11B and the cathode 12B; a hole auxiliary layer 14B, between the anode 11B and the quantum dot layer 13B and including a hole injection layer 14Ba and a hole transport layer 14Bb; an electron auxiliary layer 15B, between the cathode 12B and the quantum dot layer 13B; and optionally, an optical auxiliary layer 16B.

[0147] Quantum dot layer 13B may include cadmium-free quantum dots configured to emit light of a blue wavelength spectrum, and may have an emission peak wavelength (λ) belonging to about 430 nm to about 485 nm. max1 The emission spectrum of the quantum dot layer 13B. For example, the quantum dot layer 13B may include a core-shell quantum dot, which may include, for example, a semiconductor compound containing at least one of zinc (Zn) and tellurium (Te) and selenium (Se), such as: a core comprising a Zn-Te-Se based semiconductor compound containing zinc (Zn), tellurium (Te) and selenium (Se); and at least one shell comprising ZnSeS, ZnSe and / or ZnS.

[0148] The refractive index of the quantum dot layer 13B in the blue wavelength region (e.g., about 460 nm) can be about 1.65 to about 2.70, about 1.70 to about 2.65, about 1.75 to about 2.60, about 1.80 to about 2.55, about 1.80 to about 2.50, about 1.80 to about 2.40, about 1.80 to about 2.30, about 1.80 to about 2.20, about 1.80 to about 2.10, about 1.80 to about 2.00, or about 1.80 to about 1.95.

[0149] The hole-assist layer 14B can be used to adjust the distance between the quantum dot layer 13B and the reflective layer of the anode 11B in the blue quantum dot device 10B. As described above, the thickness of the hole-assist layer 14B can be determined such that the resonant wavelength of the microcavity structure of the blue quantum dot device 10B belongs to the same wavelength spectrum as the emission spectrum of the quantum dot layer 13B, that is, the blue wavelength spectrum. Therefore, the thickness of the hole-assist layer 14B can be from about 100 nm to about 160 nm, and within the above range, the thickness of the hole-assist layer 14B can be from about 110 nm to about 150 nm, from about 120 nm to about 145 nm, or from about 125 nm to about 140 nm.

[0150] For example, the total thickness of the hole auxiliary layer 14B, the quantum dot layer 13B, and the electron auxiliary layer 15B disposed in the path of light emitted from the light source (e.g., quantum dot) can be about 160 nm to about 230 nm, within the above range, about 165 nm to about 225 nm, about 160 nm to about 220 nm, or about 160 nm to about 215 nm.

[0151] The green quantum dot device 10G includes: an anode 11G, including a reflective layer; a cathode 12G; a quantum dot layer 13G, between the anode 11G and the cathode 12G; a hole auxiliary layer 14G, between the anode 11G and the quantum dot layer 13G and including a hole injection layer 14Ga and a hole transport layer 14Gb; an electron auxiliary layer 15G, between the cathode 12G and the quantum dot layer 13G; and optionally, an optical auxiliary layer 16G.

[0152] The quantum dot layer 13G may include cadmium-free quantum dots configured to emit light in the green wavelength spectrum, and may have an emission peak wavelength (λ) belonging to about 510 nm to about 570 nm. max1 The emission spectrum of ).

[0153] The hole auxiliary layer 14G can be used to adjust the distance between the quantum dot layer 13G and the reflective layer of the anode 11G in the green quantum dot device 10G. As described above, the thickness of the hole auxiliary layer 14G can be determined such that the resonant wavelength of the microcavity structure of the green quantum dot device 10G belongs to the same wavelength spectrum as the emission spectrum of the quantum dot layer 13G, that is, the green wavelength spectrum. The thickness of the hole auxiliary layer 14G can be different from the thickness of the hole auxiliary layer 14B. For example, the total thickness of the hole auxiliary layer 14G, the quantum dot layer 13G, and the electron auxiliary layer 15G in the path of light emitted from the light-emitting point (e.g., quantum dot) in the green quantum dot device 10G can be different from the total thickness of the hole auxiliary layer 14B, the quantum dot layer 13B, and the electron auxiliary layer 15B in the blue quantum dot device 10B.

[0154] The red quantum dot device 10R includes: an anode 11R, including a reflective layer; a cathode 12R; a quantum dot layer 13R between the anode 11R and the cathode 12R; a hole auxiliary layer 14R between the anode 11R and the quantum dot layer 13R and including a hole injection layer 14Ra and a hole transport layer 14Rb; an electron auxiliary layer 15R between the cathode 12R and the quantum dot layer 13R; and optionally, an optical auxiliary layer 16R.

[0155] The quantum dot layer 13R may include cadmium-free quantum dots configured to emit light in the red wavelength spectrum, and may have an emission peak wavelength (λ) belonging to about 600 nm to about 680 nm. max1 The emission spectrum of the quantum dot layer 13R. For example, the quantum dot layer 13R may include a core-shell quantum dot, and the core-shell quantum dot may include, for example: a core, including a semiconductor compound comprising indium (In), phosphorus (P) and optionally zinc (Zn); and at least one shell, including ZnSeS, ZnSe and / or ZnS.

[0156] The refractive index of the quantum dot layer 13R in the red wavelength region (e.g., about 630 nm) can be about 1.65 to about 2.70, about 1.70 to about 2.65, about 1.75 to about 2.60, about 1.80 to about 2.55, about 1.80 to about 2.50, about 1.80 to about 2.40, about 1.80 to about 2.30, about 1.80 to about 2.20, about 1.80 to about 2.10, about 1.80 to about 2.00, or about 1.80 to about 1.95.

[0157] The hole-assisted layer 14R can be used to adjust the distance between the quantum dot layer 13R and the reflective layer of the anode 11R in the red quantum dot device 10R. As described above, the thickness of the hole-assisted layer 14R can be determined such that the resonant wavelength of the microcavity structure of the red quantum dot device 10R belongs to the same wavelength spectrum as the emission spectrum of the quantum dot layer 13R, that is, the red wavelength spectrum. Therefore, the thickness of the hole-assisted layer 14R of the red quantum dot device 10R can be thinner or thicker than the thickness of the hole-assisted layer 14B of the blue quantum dot device 10B, and the thickness of the hole-assisted layer 14R of the red quantum dot device 10R can be about 0.1 to about 0.9 times (first resonance) or about 1.2 times to about 3 times (second resonance) of the hole-assisted layer 14B of the blue quantum dot device 10B. For example, the thickness of the hole-assisted layer 14R of the red quantum dot device 10R can be about 30 nm to about 80 nm (first resonance) or about 230 nm to about 280 nm (second resonance). Within the above range, the thickness of the hole-assisted layer 14R of the red quantum dot device 10R can be about 35 nm to about 75 nm, about 40 nm to about 70 nm, or about 45 nm to about 65 nm (first resonance), or about 235 nm to about 275 nm, about 240 nm to about 270 nm, or about 245 nm to about 265 nm (second resonance).

[0158] For example, the total thickness of the hole-assisted layer 14R, the quantum dot layer 13R, and the electron-assisted layer 15R disposed in the path of light emitted from the light-emitting point (e.g., quantum dot) can be from about 75 nm to about 135 nm (first resonance), within the above range, from about 80 nm to about 130 nm, from about 85 nm to about 125 nm, from about 90 nm to about 120 nm (first resonance), or from about 275 nm to about 325 nm or from about 280 nm to about 320 nm (second resonance).

[0159] The thickness of the electronic auxiliary layer 15B of the blue quantum dot device 10B, the thickness of the electronic auxiliary layer 15G of the green quantum dot device 10G, and the thickness of the electronic auxiliary layer 15R of the red quantum dot device 10R can be the same or different; for example, they can be the same.

[0160] The thickness of the quantum dot layer 13B of the blue quantum dot device 10B, the thickness of the quantum dot layer 13G of the green quantum dot device 10G, and the thickness of the quantum dot layer 13R of the red quantum dot device 10R can be the same or different; for example, they can be the same.

[0161] The thickness of the optical auxiliary layer 16B of the blue quantum dot device 10B, the thickness of the optical auxiliary layer 16G of the green quantum dot device 10G, and the thickness of the optical auxiliary layer 16R of the red quantum dot device 10R can be the same or different; for example, they can be the same.

[0162] The blue quantum dot device 10B can be configured to emit light of a blue wavelength spectrum through the cathode 12B and can be configured to display blue. Here, the color displayed by the blue quantum dot device 10B can be the color of modified light in the blue wavelength spectrum emitted from the quantum dot layer 13B, and can be a blue with high purity and a full width at half maximum (FWHM) narrower than that of the blue wavelength spectrum emitted from the quantum dot layer 13B. For example, the full width at half maximum (FWHM2) of the blue emission spectrum displayed by the blue quantum dot device 10B can be about 0.1 to about 0.9 of the full width at half maximum (FWHM1) of the emission spectrum of the quantum dot layer 13B, within the above range, about 0.2 to about 0.9, about 0.2 to about 0.8, about 0.3 to about 0.8, about 0.4 to about 0.8, or about 0.5 to about 0.8. For example, the full width at half maximum (FWHM2) of the blue emission spectrum displayed by the blue quantum dot device 10B can be about 2 nm to about 30 nm, about 3 nm to about 30 nm, or about 5 nm to about 30 nm.

[0163] The green quantum dot device 10G can be configured to emit light of a green wavelength spectrum through the cathode 12G and can be configured to display green. Here, the color displayed by the green quantum dot device 10G can be the color of modified light in the green wavelength spectrum emitted from the quantum dot layer 13G, and can be a green with high purity and a full width at half maximum (FWHM) narrower than that of the green wavelength spectrum emitted from the quantum dot layer 13G. For example, the full width at half maximum (FWHM2) of the green emission spectrum of the green quantum dot device 10G can be about 0.1 to about 0.9 of the full width at half maximum (FWHM1) of the quantum dot layer 13G, within the above range, about 0.2 to about 0.9, about 0.2 to about 0.8, about 0.3 to about 0.8, about 0.4 to about 0.8, or about 0.5 to about 0.8. For example, the full width at half maximum (FWHM2) of the green emission spectrum displayed by the green quantum dot device 10G can be about 2 nm to about 30 nm, about 3 nm to about 30 nm, or about 5 nm to about 30 nm.

[0164] The red quantum dot device 10R can be configured to emit light of a red wavelength spectrum through the cathode 12R and can be configured to display red. Here, the color displayed by the red quantum dot device 10R can be the color of modified light from the red wavelength spectrum emitted from the quantum dot layer 13R, and can be a red with high purity and a full width at half maximum (FWHM) narrower than that of the red wavelength spectrum emitted from the quantum dot layer 13R. For example, the full width at half maximum (FWHM2) of the red emission spectrum displayed by the red quantum dot device 10R can be about 0.1 to about 0.9 of the full width at half maximum (FWHM1) of the emission spectrum of the quantum dot layer 13R, within the above range, about 0.2 to about 0.9, about 0.2 to about 0.8, about 0.3 to about 0.8, about 0.4 to about 0.8, or about 0.5 to about 0.8. For example, the full width at half maximum (FWHM2) of the red emission spectrum displayed by the red quantum dot device 10R can be about 2 nm to about 35 nm, about 3 nm to about 35 nm, or about 5 nm to about 35 nm.

[0165] The quantum dot display panel 200 can be configured to display full color by combining a blue quantum dot device 10B, a green quantum dot device 10G, and a red quantum dot device 10R.

[0166] The implementation methods will be described in more detail below with reference to examples. However, these examples are exemplary and the scope is not limited thereto.

[0167] Calculation of light extraction efficiency

[0168] exist Figure 1 In the quantum dot devices shown (blue or red quantum dot devices), the thickness of each layer is evaluated, which can optimize light extraction efficiency.

[0169] The Fresnel constant at the interface of each layer is calculated using the refractive index (n) of each layer that makes up the device. Then, the thickness of each layer that satisfies thin-film interference and wide-angle interference is calculated using the Fresnel constant.

[0170] The refractive index is measured by the change in polarization characteristics (Δ, Ψ) using an elliptically polarized apparatus (JAWoollam Co., Inc.).

[0171] Table 1

[0172] n (at 460nm) n (at 630nm) First layer (cavitation injection layer) 1.56 1.54 Second layer (hole transport layer) 1.89 1.73 The third layer (light-emitting point, quantum dot layer) 1.94 1.89 Fourth layer (electronic auxiliary layer) 1.62 1.60

[0173] -Fresnel constant = [(n2-n1) / (n2+n1)] 2

[0174] (n1 is the refractive index of the first layer material, and n2 is the refractive index of the second layer material)

[0175] -Thin-film interference:

[0176] (a) Optical density = 2nd = mλ

[0177] (n: refractive index, d: distance between anode and cathode, m: resonance order, λ: target wavelength)

[0178] -Wide-angle interference:

[0179] (b) Optical density = 2nx = {(m-1) + 1 / 2} * λ

[0180] (n: refractive index, x: distance between the emitting point and the reflective layer, m: resonance order, λ: target wavelength)

[0181] Figure 4 This is a graph showing the changes in emissivity and brightness based on the thickness of the hole-assisted layer in a blue quantum dot device. Figure 5 This is a graph showing the changes in emissivity and brightness based on the thickness of the electron-assisted layer in a blue quantum dot device. Figure 6 This is a graph showing the changes in emissivity and brightness based on the thickness of the hole-assisted layer in a red quantum dot device. Figure 7 This is a graph showing the changes in emissivity and brightness based on the thickness of the electron-assisted layer of a red quantum dot device.

[0182] exist Figure 4 In blue quantum dot devices with microcavity structures, when the thicknesses of the electronic auxiliary layer and the optical auxiliary layer are fixed (e.g., 20 nm and 50 nm, respectively), the light extraction efficiency, which depends on the thickness of the hole auxiliary layer, can be examined.

[0183] exist Figure 5 In blue quantum dot devices with microcavity structures, when the thicknesses of the hole-assisted layer and the optical-assisted layer are fixed (e.g., 140 nm and 50 nm, respectively), the light extraction efficiency, which depends on the thickness of the electronic-assisted layer, can be examined.

[0184] Reference Figure 4 and Figure 5 In blue quantum dot devices with microcavity structures, the light-emitting characteristics change depending on the thickness of the hole-assisted layer and the electron-assisted layer. Therefore, the thickness of the hole-assisted layer and the electron-assisted layer can be designed to optimize the light extraction efficiency.

[0185] exist Figure 6 In red quantum dot devices with microcavity structures, when the thicknesses of the electronic auxiliary layer and the optical auxiliary layer are fixed (e.g., 30 nm and 80 nm, respectively), the light extraction efficiency, which depends on the thickness of the hole auxiliary layer, can be examined.

[0186] exist Figure 7In red quantum dot devices with microcavity structures, when the thicknesses of the hole-assisted layer and the optical-assisted layer are fixed (e.g., 55 nm and 80 nm, respectively), the light extraction efficiency, which depends on the thickness of the electronic-assisted layer, can be examined.

[0187] Reference Figure 6 and Figure 7 In red quantum dot devices with microcavity structures, the light-emitting characteristics vary depending on the thickness of the hole-assisted layer and the electron-assisted layer. Therefore, the thickness of the hole-assisted layer and the electron-assisted layer can be designed to optimize the light extraction efficiency.

[0188] Quantum dot synthesis

[0189] Synthesis Example 1: Synthesis of Blue Quantum Dots

[0190] (1) Synthesis of ZnTeSe nuclear quantum dot dispersion

[0191] Selenium (Se) and tellurium (Te) were dispersed separately in trioctylphosphine (TOP) to obtain Se / TOP stock solutions and Te / TOP stock solutions. In a reactor containing trioctylamine, 0.125 mmol of zinc acetate was added together with oleic acid, and then the reactor was heated at 120 °C under vacuum. After 1 hour, the atmosphere in the reactor was changed to nitrogen. After heating the reactor to 300 °C, the prepared Se / TOP and Te / TOP stock solutions were rapidly injected at a Te / Se ratio of 1 / 25. When the reaction was complete, the reaction solution was rapidly cooled to room temperature, and acetone was added. The mixture was then centrifuged to obtain a precipitate, which was dispersed in toluene to obtain a ZnTeSe quantum dot dispersion.

[0192] (2) Synthesis of ZnTeSe core / ZnSeS shell quantum dot dispersions

[0193] 1.8 mmol (0.336 g) of zinc acetate was placed in a flask containing trioctylamine along with oleic acid, and then the mixture was vacuum-treated at 120 °C for 10 min. The inside of the flask was purged with nitrogen (N2) and then heated to 180 °C. Subsequently, the obtained ZnTeSe quantum dot dispersion was added, along with Se / TOP and S / TOP. The reaction temperature was set at approximately 280 °C. When the reaction was complete, the reactor was cooled, and the obtained nanocrystals were centrifuged with ethanol and then dispersed in toluene to obtain a ZnTeSe core / ZnSeS shell quantum dot dispersion.

[0194] Synthesis Example 2: Synthesis of Blue Quantum Dots

[0195] Zinc chloride was dissolved in ethanol to obtain a 10 wt% zinc chloride solution. 0.01 mL of the zinc chloride solution was added to the ZnTeSe core / ZnSeS shell quantum dot dispersion according to Synthesis Example 1, and the mixture was stirred at 60 °C for 30 min to carry out a surface exchange reaction. After the reaction, ethanol was added to induce precipitation, followed by centrifugation. This process was repeated several times to obtain a precipitate, which was then dispersed in cyclohexane to obtain a halogenated ZnTeSe core / ZnSeS shell quantum dot dispersion.

[0196] Synthesis Example 3: Synthesis of Red Emitting Quantum Dots

[0197] (1) Synthesis of InP nuclear quantum dot dispersion

[0198] In a 300 mL reaction flask, 0.2 mmol of indium acetate was dissolved in 1-octadecene along with palmitic acid, and then heated under vacuum at 120 °C. After 1 hour, the atmosphere in the reactor was switched to nitrogen. Subsequently, after heating the reactor to 280 °C, a solution of tris(trimethylsilyl)phosphine (TMS3P) in trioctylphosphine was rapidly injected, and the reaction was allowed to proceed for 30 minutes. The reaction solution was rapidly cooled to room temperature, acetone was added, and the mixture was centrifuged to obtain a precipitate. The precipitate was then dispersed in toluene to obtain an InP quantum dot dispersion.

[0199] (2) Synthesis of InP core / ZnSeS shell quantum dot dispersion

[0200] Se and S powders were dissolved in TOP to prepare Se / TOP and S / TOP stock solutions, respectively. Zinc acetate and oleic acid were dissolved in trioctylamine in a 300 mL reaction flask, and then the mixture was vacuum-treated at 120 °C for 10 min. The flask was then purged with nitrogen (N2) and heated to 180 °C. The obtained InP quantum dot dispersion was added, along with predetermined amounts of Se / TOP and S / TOP stock solutions, and the mixture was heated at 280 °C and reacted for 60 min. Excess ethanol was added to the reactants, followed by centrifugation. After centrifugation, the supernatant was discarded, and the precipitate was dried and dispersed in chloroform or toluene to obtain an InP core / ZnSeS shell quantum dot dispersion.

[0201] Synthesis of Inorganic Nanoparticles

[0202] Synthesis Example 4

[0203] 0.93 mmol magnesium acetate tetrahydrate, 8.07 mmol zinc acetate dihydrate, and 90 mL dimethyl sulfoxide were placed in a reactor and heated in air at 60 °C. Subsequently, 15 mmol tetramethylammonium hydroxide pentahydrate was dissolved in 30 mL ethanol, and the solution was added dropwise to the reactor at a rate of 3 mL per minute. After stirring for 1 hour, the obtained Zn was added in a 1:9 volume ratio. 0.85 Mg 0.15 O nanoparticles were centrifuged with ethyl acetate and then dispersed in ethanol to obtain Zn. 0.85 Mg 0.15 O nanoparticle dispersion.

[0204] Synthesis Example 5

[0205] 0.06 mg of Cs₂CO₃ was added to 6 mL of ethanol and then stirred overnight (6 hours or longer) with a magnetic rod to prepare a Cs₂CO₃ solution. Subsequently, Zn was added according to synthesis example 4. 0.85 Mg 0.15 O nanoparticle dispersion and Cs2CO3 solution were mixed at a volume ratio of 5:1 to prepare Cs-Zn 0.85 Mg 0.15 O nanoparticle dispersion.

[0206] Fabrication of quantum dot devices

[0207] Example 1

[0208] ITO 10 nm, silver (Ag) 1000 nm, and ITO 10 nm were sequentially deposited on a glass substrate to form an anode with an ITO / Ag / ITO electrode structure. The anode was then surface-treated using UV-ozone. Subsequently, a PEDOT:PSS solution was spin-coated onto the anode and heat-treated at 150 °C for 30 min under a nitrogen atmosphere to form a 30 nm thick hole injection layer (refractive index (n) = 1.56 at 460 nm). Then, a polymer solution comprising polymer A was spin-coated onto the hole injection layer, followed by heat treatment at 150 °C for 30 min to form a 95 nm thick hole transport layer (n = 1.68 at 460 nm). Here, polymer A comprises alkyl-substituted fluorene structural units and phenyl-substituted carbazole-substituted triphenylamine structural units. Subsequently, a halogenated ZnTeSe core / ZnSeS shell quantum dot dispersion obtained from Synthesis Example 2 was coated onto the hole transport layer, and then cured at 80°C for 30 minutes under a nitrogen atmosphere to form a 20 nm thick lower quantum dot layer (refractive index (n) = 2.18, at 460 nm, λ). max=453nm), on the lower quantum dot layer, a halogen-treated ZnTeSe core / ZnSeS shell quantum dot dispersion obtained from Synthesis Example 2 is coated, and then cured under the same conditions as above to form a 20nm thick upper quantum dot layer (refractive index (n) = 2.18, at 460nm, λ = 453nm), and then cured to form a 20nm thick upper quantum dot layer (refractive index (n) = 2.18, at 460nm, λ = 453nm). max =453nm). On the upper quantum dot layer, Zn obtained from synthesis example 4 was spin-coated. 0.85 Mg 0.15 O nanoparticle dispersions were then heat-treated at 140 °C for 30 min to form a 20 nm thick electron transport layer (n = 1.62, at 460 nm). Magnesium silver (MgAg) (90:10 w / w) was deposited on the electron transport layer to form a 12 nm thick cathode. An arylamine compound was then deposited on the cathode to form a 50 nm thick optical auxiliary layer, thereby fabricating a blue light-emitting quantum dot device with a top-emission structure.

[0209] Example 2

[0210] In addition to forming the lower quantum dot layer and the upper quantum dot layer (λ) max =462nm) rather than the lower quantum dot layer and the upper quantum dot layer (λ max =453nm) and except for forming a 105nm thick hole transport layer instead of a 95nm thick hole transport layer, a blue light-emitting quantum dot device with a top-emission structure is fabricated according to the same method as in Example 1.

[0211] Example 3

[0212] In addition to forming a 105 nm thick hole transport layer instead of a 95 nm thick hole transport layer and using Cs-Zn obtained from synthesis example 5 0.85 Mg 0.15 O nanoparticle dispersion instead of Zn obtained from synthesis example 4 0.85 Mg 0.15 In addition to the O nanoparticle dispersion, blue light-emitting quantum dot devices with a top-emission structure are fabricated using the same method as in Example 1.

[0213] Example 4

[0214] Except for spin-coating a solution of poly[(9,9-dioctylfluorenyl-2,7-diyl-co-(4,4'-(N-4-butylphenyl)diphenylamine)](TFB) instead of polymer A and heat-treating at 150°C for 30 minutes to form a 100 nm thick hole transport layer (n = 1.89 at 460 nm), a blue light-emitting quantum dot device with a top-emission structure was fabricated according to the same method as in Example 1.

[0215] Example 5

[0216] ITO 10 nm, silver (Ag) 1000 nm, and ITO 10 nm were sequentially deposited on a glass substrate to form an anode with an ITO / Ag / ITO electrode structure. The anode was then surface-treated using UV-ozone. Subsequently, a PEDOT:PSS solution was spin-coated onto the anode, and the anode was heat-treated at 150°C for 30 minutes under a nitrogen atmosphere to form a 30 nm thick hole injection layer (n = 1.56, at 460 nm). A solution of poly[(9,9-dioctylfluorenyl-2,7-diyl-co-(4,4'-(N-4-butylphenyl)diphenylamine)](TFB) was spin-coated onto the hole injection layer, followed by heat treatment at 150 °C for 30 min to form a 110 nm thick hole transport layer (n = 1.89, at 460 nm). A blue quantum dot dispersion obtained from Synthesis Example 1 was spin-coated onto the hole transport layer, followed by curing at 80 °C for 30 min under a nitrogen atmosphere to form a 28 nm thick quantum dot layer (refractive index (n) = 2.18, at 460 nm, λ). max =453nm). Subsequently, Zn obtained from Synthesis Example 4 was spin-coated onto the quantum dot layer. 0.85 Mg 0.15 O nanoparticle dispersions were then heat-treated at 140 °C for 30 minutes to form a 20 nm thick electron transport layer (n = 1.62, at 460 nm, λ). max =453nm). On the electron transport layer, magnesium silver (MgAg) (90:10 w / w) is deposited to form a 13nm thick cathode. Then, an aromatic amine compound is deposited on the cathode to form a 50nm thick optical auxiliary layer, thereby fabricating a blue light-emitting quantum dot device with a top-emission structure.

[0217] Example 6

[0218] In addition to forming quantum dot layers (λ) max =462nm) rather than quantum dot layer (λ) max =453nm) and except for forming a 30nm thick electron transport layer instead of a 20nm thick electron transport layer, a blue light-emitting quantum dot device with a top-emission structure is fabricated according to the same method as in Example 5.

[0219] Comparative Example 1

[0220] In addition to forming a 25 nm thick hole transport layer, a blue light-emitting quantum dot device with a top-emission structure was fabricated using the same method as in Example 5.

[0221] Comparative Example 2

[0222] In addition to forming the lower quantum dot layer and the upper quantum dot layer (λ) max =462nm) rather than the lower quantum dot layer and the upper quantum dot layer (λ max=453nm) and, apart from forming a 20nm thick hole injection layer and a 20nm thick hole transport layer, a blue light-emitting quantum dot device with a top-emission structure is fabricated according to the same method as in Example 3.

[0223] Comparative Example 3

[0224] Except for using ITO instead of ITO / Ag / ITO to form a 150 nm thick ITO anode (transparent anode), using aluminum instead of magnesium silver to form a 120 nm thick cathode (reflective cathode), and forming a 25 nm thick hole transport layer, a blue light-emitting quantum dot device with a bottom-emission structure is fabricated according to the same method as in Example 5.

[0225] Assessment I

[0226] The characteristics of the blue luminescent quantum dot devices according to Examples 1 to 6 and Comparative Examples 1 to 3 were evaluated.

[0227] The characteristics of quantum dot devices were measured using current-voltage-brightness measurement equipment (Keithley 2200, Minolta CS200).

[0228] The results are shown in Table 2.

[0229] Table 2

[0230] <![CDATA[EQE max (%)]]> <![CDATA[λ max (nm)]]> FWHM(nm) <![CDATA[CIE x ]]> <![CDATA[CIE y ]]> Example 1 28.2 450 14 0.1530 0.0230 Example 2 19.4 461 19 0.1361 0.0499 Example 3 34.9 457 17 0.1420 0.0400 Example 4 23.6 452 14 0.1520 0.0240 Example 5 17.8 450 16 0.1530 0.0230 Example 6 19.6 462 20 0.1420 0.038 Comparative Example 1 1.7 455 32 0.1830 0.1770 Comparative Example 2 10.1 466 41 0.1280 0.1543 Comparative Example 3 6.2 453 24 0.1508 0.0856

[0231] *EQE max Maximum external quantum efficiency

[0232] *λ max Maximum emission wavelength

[0233] *FWHM: Full Width at Half Peak

[0234] Referring to Table 2, compared with the blue quantum dot devices according to Comparative Examples 1 to 3, the blue quantum dot devices according to Examples 1 to 6 exhibit high efficiency and narrow full width at half maximum (FWHM).

[0235] Fabrication of Quantum Dot Devices II

[0236] Example 7

[0237] On a glass substrate, ITO 10 nm, silver (Ag) 1000 nm, and ITO 10 nm were sequentially deposited to form an anode with an ITO / Ag / ITO electrode structure. The anode was surface-treated using UV-ozone. Subsequently, a PEDOT:PSS solution was spin-coated onto the anode, followed by heat treatment at 150 °C for 30 minutes under a nitrogen atmosphere to form a 30 nm thick hole injection layer (n = 1.54, at 630 nm). A solution of poly[(9,9-dioctylfluorenyl-2,7-diyl-co-(4,4'-(N-4-butylphenyl)diphenylamine)](TFB) (n = 1.73, at 630 nm) was spin-coated onto the hole injection layer, followed by heat treatment at 150 °C for 30 min to form a 25 nm thick hole transport layer. Subsequently, a red luminescent quantum dot dispersion obtained from Synthesis Example 3 was spin-coated onto the hole transport layer, followed by curing at 120 °C for 30 min under a nitrogen atmosphere to form a 20 nm thick quantum dot layer (n = 1.89, at 630 nm). Zn obtained from Synthesis Example 4 was spin-coated onto the quantum dot layer. 0.85 Mg 0.15 O nanoparticle dispersions were formed and heat-treated at 140 °C for 30 min to form a 30 nm thick electron transport layer (n = 1.60, at 630 nm). Subsequently, magnesium silver (MgAg) (90:10 w / w) was deposited on the electron transport layer to form a 13 nm thick cathode. On the cathode, an arylamine compound was deposited to form an 80 nm thick optical auxiliary layer, thereby fabricating a red light-emitting quantum dot device with a top-emission structure.

[0238] Comparative Example 6

[0239] In addition to forming a 60 nm thick hole transport layer, a red light-emitting quantum dot device with a top-emission structure was fabricated using the same method as in Example 7.

[0240] Comparative Example 7

[0241] Except for using ITO instead of ITO / Ag / ITO to form a 150 nm thick ITO anode (transparent anode) and using aluminum instead of magnesium silver to form a 120 nm thick cathode (reflective cathode), a red light-emitting quantum dot device with a bottom-emission structure is fabricated according to the same method as in Example 7.

[0242] Assessment II

[0243] The luminescence properties of the red luminescent quantum dot devices according to Example 7 and Comparative Examples 6 and 7 were evaluated.

[0244] The results are shown in Table 3.

[0245] Table 3

[0246]

[0247]

[0248] *EQE, at 5000 nits: External quantum efficiency at 5000 nits

[0249] *EQE, at 420mA / cm 2 At 420mA / cm 2 external quantum efficiency

[0250] *Cd / A max Maximum current efficiency

[0251] Referring to Table 3, compared with the red light-emitting quantum dot devices according to Comparative Examples 6 and 7, the red light-emitting quantum dot device according to Example 7 exhibits higher luminous efficiency, improved current characteristics, and narrower full width at half maximum (FWHM).

[0252] Assessment III

[0253] The lifetime characteristics of the red-emitting quantum dot devices according to Example 7 and Comparative Examples 6 and 7 were evaluated.

[0254] Lifetime characteristics are evaluated by injecting a current suitable for a reduction in brightness relative to the initial brightness of the quantum dot device, where the brightness is 4500 nits and T90 is the time when the brightness is reduced by 90% relative to the initial brightness.

[0255] The results are shown in Table 4.

[0256] Table 4

[0257] <![CDATA[T 90 (h)]]> Example 7 60 Comparative Example 6 <5 Comparative Example 7 <30

[0258] Referring to Table 4, the red light-emitting quantum dot device according to Example 7 exhibits improved lifetime characteristics compared to the red light-emitting quantum dot devices of Comparative Examples 6 and 7.

[0259] While this disclosure has been described in conjunction with what are currently considered practical exemplary embodiments, it will be understood that the invention is not limited to the disclosed embodiments, but rather is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

[0260] This application claims priority and benefit to Korean Patent Application No. 10-2020-0066616, filed on June 2, 2020, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

Claims

1. A quantum dot device, comprising: an anode disposed on a substrate, the anode comprising a reflective layer; a hole-assisting layer disposed on the anode, the hole-assisting layer comprising a hole-injecting layer, a hole-transporting layer, or a combination thereof; a quantum dot layer disposed on the hole-assisting layer, the quantum dot layer comprising quantum dots; an electron-assisting layer disposed on the quantum dot layer; and a cathode disposed on the electron-assisting layer, the cathode being a light- transmitting electrode configured to transmit at least a portion of light emitted from the quantum dot layer, wherein the quantum dot layer is configured to emit light of a first wavelength spectrum, the first wavelength spectrum being one of a blue wavelength spectrum, a green wavelength spectrum, and a red wavelength spectrum, the hole-assisting layer has a thickness that causes a resonant wavelength of the quantum dot device to fall within the first wavelength spectrum, a peak emission wavelength of the quantum dot layer and a peak emission wavelength of light transmitted through the cathode collectively belong to the first wavelength spectrum, a full width at half maximum (FWHM) of an emission spectrum of light transmitted through the cathode is narrower than a full width at half maximum of an emission spectrum of the quantum dot layer, the first wavelength spectrum is a blue wavelength spectrum, the thickness of the hole-assisting layer is from 100 nm to 160 nm, a thickness of the electron-assisting layer is greater than or equal to 5 nm and less than 80 nm, a total thickness of the hole-assisting layer, the quantum dot layer, and the electron- assisting layer is from 160 nm to 230 nm, a difference between a refractive index of the quantum dot layer and a refractive index of the electron-assisting layer is from 0.20 to 1.0, and a difference between the refractive index of the quantum dot layer and a refractive index of the hole-assisting layer is from 0.01 to 1.

0. the hole-assisting layer is thicker than the electron-assisting layer.

2. The quantum dot device of claim 1, wherein, 3. The quantum dot device of claim 1, wherein the quantum dots comprise cadmium-free quantum dots.

4. A quantum dot device, comprising: an anode disposed on a substrate, the anode comprising a reflective layer; a hole-assisting layer disposed on the anode, the hole-assisting layer comprising a hole-injecting layer, a hole-transporting layer, or a combination thereof; a quantum dot layer disposed on the hole-assisting layer, the quantum dot layer comprising quantum dots; an electron-assisting layer disposed on the quantum dot layer; and a cathode disposed on the electron-assisting layer, the cathode being a light- transmitting electrode configured to transmit at least a portion of light emitted from the quantum dot layer, wherein the quantum dot layer is configured to emit light of a first wavelength spectrum, the first wavelength spectrum being one of a blue wavelength spectrum, a green wavelength spectrum, and a red wavelength spectrum, the hole-assisting layer has a thickness that causes a resonant wavelength of the quantum dot device to fall within the first wavelength spectrum, a peak emission wavelength of the quantum dot layer and a peak emission wavelength of light transmitted through the cathode collectively belong to the first wavelength spectrum, a full width at half maximum (FWHM) of an emission spectrum of light transmitted through the cathode is narrower than a full width at half maximum of an emission spectrum of the quantum dot layer, the first wavelength spectrum is a red wavelength spectrum, and the thickness of the hole-assisting layer is from 30 nm to 80 nm or from 230 nm to 280 nm, a thickness of the electron-assisting layer is greater than or equal to 5 nm and less than 80 nm, ​ ​ a total thickness of the hole auxiliary layer, the quantum dot layer, and the electron auxiliary layer is 75 nm to 135 nm or 270 nm to 330 nm, a difference between a refractive index of the quantum dot layer and a refractive index of the electron auxiliary layer is 0.20 to 1.0, and a difference between a refractive index of the quantum dot layer and a refractive index of the hole auxiliary layer is 0.01 to 1.

0.

5. The quantum dot device of claim 4, wherein, the hole auxiliary layer is thicker than the electron auxiliary layer.

6. The quantum dot device of claim 4, wherein, the quantum dot includes a cadmium-free quantum dot.

7. The quantum dot device of claim 1 or 4, wherein, the electron auxiliary layer includes an inorganic nanoparticle including an alkaline earth metal.

8. The quantum dot device of claim 1 or 4, wherein, a difference between a peak emission wavelength of the quantum dot layer and a peak emission wavelength of light passing through the cathode is ±5 nm.

9. The quantum dot device of claim 1 or 4, wherein, a full width at half maximum (FWHM) of an emission spectrum of light passing through the cathode is 0.2 to 0.9 of a full width at half maximum of an emission spectrum of the quantum dot layer.

10. The quantum dot device of claim 1 or 4, further comprising an optical auxiliary layer disposed on the cathode.

11. A quantum dot display apparatus comprising the quantum dot device of any one of claims 1 to 10.

12. A quantum dot display apparatus comprising: an array of quantum dot devices, including a unit device of a blue quantum dot device configured to display blue, a unit device of a green quantum dot device configured to display green, and a unit device of a red quantum dot device configured to display red, arranged repeatedly therein, wherein each of the blue quantum dot device, the green quantum dot device, and the red quantum dot device includes: an anode including a reflective layer; a hole auxiliary layer disposed on the anode, the hole auxiliary layer including a hole injection layer, a hole transport layer, or a combination thereof; a quantum dot layer disposed on the hole auxiliary layer, the quantum dot layer including a quantum dot; an electron auxiliary layer disposed on the quantum dot layer; and a cathode on the electron auxiliary layer, the cathode configured to transmit at least a portion of light emitted from the quantum dot layer, wherein the hole auxiliary layer of the blue quantum dot device has a thickness that causes a resonance wavelength of the blue quantum dot device to fall within a blue wavelength spectrum, and the thickness of the hole auxiliary layer of the blue quantum dot device is 100 nm to 160 nm, the thickness of the electron auxiliary layer is greater than or equal to 5 nm and less than 80 nm, and a total thickness of the hole auxiliary layer, the quantum dot layer, and the electron auxiliary layer of the blue quantum dot device is 160 nm to 230 nm, the hole auxiliary layer of the red quantum dot device has a thickness that causes a resonance wavelength of the red quantum dot device to fall within a red wavelength spectrum, and the thickness of the hole auxiliary layer of the red quantum dot device is 30 nm to 80 nm or 230 nm to 280 nm, the thickness of the electron auxiliary layer is greater than or equal to 5 nm and less than 80 nm, and a total thickness of the hole auxiliary layer, the quantum dot layer, and the electron auxiliary layer of the red quantum dot device is 75 nm to 135 nm or 270 nm to 330 nm, and the thickness of the hole auxiliary layer of the red quantum dot device is different from the thickness of the hole auxiliary layer of the blue quantum dot device, The difference between the refractive index of the quantum dot layer of the blue quantum dot device and the refractive index of the electron auxiliary layer is 0.20 to 1.0, and the difference between the refractive index of the quantum dot layer of the blue quantum dot device and the refractive index of the hole auxiliary layer is 0.01 to 1.

0.

13. The quantum dot display apparatus of claim 12, wherein the thickness of the hole auxiliary layer of the red quantum dot device is 0.1 to 0.9 or 1.2 times to 3 times the thickness of the hole auxiliary layer of the blue quantum dot device.

14. The quantum dot display device of claim 12, wherein, The thickness of the electron auxiliary layer of the blue quantum dot device and the thickness of the electron auxiliary layer of the red quantum dot device are substantially equal.

15. The quantum dot display device of claim 12, wherein, The thickness of the quantum dot layer of the blue quantum dot device and the thickness of the quantum dot layer of the red quantum dot device are substantially equal.

16. The quantum dot display apparatus of claim 12, wherein The quantum dots included in the quantum dot layer of the blue quantum dot device contain cadmium-free quantum dots, The quantum dots included in the quantum dot layer of the red quantum dot device contain cadmium-free quantum dots, and The difference between the refractive index of the quantum dot layer and the electron auxiliary layer of the red quantum dot device is 0.20 to 1.0, respectively.

17. The quantum dot display device of claim 12, wherein, The electron auxiliary layer of the blue quantum dot device and the electron auxiliary layer of the red quantum dot device each include inorganic nanoparticles containing an alkaline earth metal.

18. The quantum dot display apparatus of claim 12, wherein The difference between the peak emission wavelength of the quantum dot layer of the blue quantum dot device and the peak emission wavelength of the emission spectrum displayed by the blue quantum dot device is ±5 nm, and The difference between the peak emission wavelength of the quantum dot layer of the red quantum dot device and the peak emission wavelength of the emission spectrum displayed by the red quantum dot device is ±5 nm.

19. The quantum dot display apparatus of claim 12, wherein Each of the blue quantum dot device and the red quantum dot device further includes an optical auxiliary layer on the cathode, and The thickness of the optical auxiliary layer included in the blue quantum dot device and the red quantum dot device is substantially equal.

Images