WO2022252052A1 - 量子点发光二极管及其制备方法、显示装置 - Google Patents

量子点发光二极管及其制备方法、显示装置 Download PDF

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WO2022252052A1
WO2022252052A1 PCT/CN2021/097396 CN2021097396W WO2022252052A1 WO 2022252052 A1 WO2022252052 A1 WO 2022252052A1 CN 2021097396 W CN2021097396 W CN 2021097396W WO 2022252052 A1 WO2022252052 A1 WO 2022252052A1
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energy level
layer
level structure
structure layer
quantum dot
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PCT/CN2021/097396
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English (en)
French (fr)
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李东
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京东方科技集团股份有限公司
北京京东方技术开发有限公司
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Priority to CN202180001378.1A priority Critical patent/CN115700045A/zh
Priority to US17/772,612 priority patent/US20240172469A1/en
Priority to PCT/CN2021/097396 priority patent/WO2022252052A1/zh
Publication of WO2022252052A1 publication Critical patent/WO2022252052A1/zh

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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14—Carrier transporting layers
    • H10K50/16—Electron transporting layers
    • H10K50/166—Electron transporting layers comprising a multilayered structure
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
    • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H10K71/10—Deposition of organic active material
    • H10K71/12—Deposition of organic active material using liquid deposition, e.g. spin coating
    • H10K71/13—Deposition of organic active material using liquid deposition, e.g. spin coating using printing techniques, e.g. ink-jet printing or screen printing
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2101/00—Properties of the organic materials covered by group H10K85/00
    • H10K2101/40—Interrelation of parameters between multiple constituent active layers or sublayers, e.g. HOMO values in adjacent layers
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K2102/00—Constructional details relating to the organic devices covered by this subclass
    • H10K2102/301—Details of OLEDs
    • H10K2102/351—Thickness

Definitions

  • the disclosure belongs to the field of display technology, and in particular relates to a quantum dot light-emitting diode, a preparation method thereof, and a display device.
  • Quantum Dot Light Emitting Diodes (Quantum Dot Light Emitting Diodes, referred to as QLED) generally include a light emitting layer with a plurality of quantum dot nanocrystals. The light emitting layer is sandwiched between the electron transport layer and the hole transport layer. By applying an electric field to the quantum dot light-emitting diode, electrons and holes can be moved into the light-emitting layer. In the light-emitting layer, electrons and holes are trapped in quantum dots and recombine to emit photons.
  • An embodiment of the present disclosure provides a quantum dot light-emitting diode, including an anode layer, a cathode layer, a quantum dot light-emitting layer between the anode layer and the cathode layer, and a quantum dot light-emitting layer between the cathode layer and the quantum dot light-emitting layer.
  • the electron transport layer between them, wherein, the electron transport layer at least includes a first energy level structure layer, a second energy level structure layer and a first energy level structure layer stacked in sequence, and the first energy level structure layer is different from the first energy level structure layer A two-level structure layer, and the lowest unoccupied molecular orbital energy level of the first energy level structure layer is different from the lowest unoccupied molecular orbital energy level of the second energy level structure layer.
  • the lowest unoccupied molecular orbital energy level of the first energy level structure layer is higher than the lowest unoccupied molecular orbital energy level of the second energy level structure layer.
  • the lowest unoccupied molecular orbital energy level of the first energy level structure layer is lower than the lowest unoccupied molecular orbital energy level of the second energy level structure layer.
  • the difference between the lowest unoccupied molecular orbital energy level of the first energy level structure layer and the lowest unoccupied molecular orbital energy level of the second energy level structure layer is 0.1 eV to 0.5 eV.
  • the electron transport layer has a total thickness of 20 nm to 150 nm.
  • the material of at least one of the first energy level structure layer and the second energy level structure layer is doped zinc oxide.
  • the material of one of the first energy level structure layer and the second energy level structure layer is zinc oxide, and the material of the other is doped zinc oxide.
  • the doped zinc oxide is doped with at least one of gallium, indium, yttrium, copper, zirconium, aluminum, magnesium or any combination thereof.
  • the doping concentration in the doped zinc oxide is 0% to 50%.
  • the electron transport layer includes a plurality of first energy level structure layers and a plurality of second energy level structure layers, and the first energy level structure layers and the second energy level structure layers are stacked alternately, And the side of the electron transport layer close to the cathode and the side close to the quantum dot light-emitting layer are both the first energy level structure layer or the second energy level structure layer.
  • the root mean square value of the surface roughness of the electron transport layer ranges from 1 nm to 10 nm.
  • the quantum dot light emitting diode further includes a hole transport layer and a hole injection layer, wherein the cathode layer, the electron transport layer, the quantum dot light emitting layer, the hole transport layer , the hole injection layer and the anode layer are sequentially stacked on the substrate.
  • An embodiment of the present disclosure also provides a method for preparing a quantum dot light-emitting diode, including forming an anode layer, a cathode layer, a quantum dot light-emitting layer between the anode layer and the cathode layer, and the cathode layer and the quantum dot layer the step of pointing the electron transport layer between the light-emitting layers, wherein,
  • the steps of forming the electron transport layer include:
  • first energy level structure layer is different from the second energy level structure layer
  • first energy level structure layer is different from the first energy level structure layer
  • first energy level structure The lowest unoccupied molecular orbital energy level of the layer is different from the lowest unoccupied molecular orbital energy level of the second energy level structure layer.
  • forming the sequentially stacked first energy level structure layer, second energy level structure layer and first energy level structure layer includes:
  • the first energy level structure layer, the second energy level structure layer and the first energy level structure layer are deposited by a sputtering method, a sol-gel method, or an atomic layer deposition method.
  • the preparation method of the quantum dot light-emitting diode also includes:
  • a hole transport layer and a hole injection layer are sequentially deposited on the quantum dot light-emitting layer by evaporation.
  • the electron transport layer is formed such that the lowest unoccupied molecular orbital energy level of the first energy level structure layer and the lowest unoccupied molecular orbital energy level of the second energy level structure layer are The difference is 0.1eV to 0.5eV.
  • forming the sequentially stacked first energy level structure layer, second energy level structure layer and third energy level structure layer includes:
  • At least one of the first energy level structure layer and the second energy level structure layer is formed using a doped zinc oxide material.
  • forming the sequentially stacked first energy level structure layer, second energy level structure layer and first energy level structure layer includes:
  • the other of the first energy level structure layer and the second energy level structure layer is formed using a doped zinc oxide material.
  • the use of doped zinc oxide materials includes:
  • a doped zinc oxide material doped with at least one of gallium, indium, yttrium, copper, zirconium, aluminum, magnesium or any combination thereof is used.
  • the use of doped zinc oxide materials includes:
  • a doped zinc oxide material with a doping concentration of 0% to 50% is used.
  • forming the first energy level structure layer, the second energy level structure layer and the second energy level structure layer stacked in sequence includes:
  • first energy level structure layers and the second energy level structure layers Forming a plurality of first energy level structure layers and a plurality of second energy level structure layers, the first energy level structure layers and the second energy level structure layers are alternately stacked, and the electron transport layer is close to the cathode
  • the side of the quantum dot light-emitting layer and the side close to the quantum dot light-emitting layer are both the first energy level structure layer or the second energy level structure layer.
  • An embodiment of the present disclosure also provides a display device, including a display substrate, and the display substrate includes a plurality of quantum dot light-emitting diodes arranged in an array, wherein the plurality of quantum dot light-emitting diodes include the above-mentioned embodiments of the present disclosure. quantum dot light-emitting diodes.
  • FIG. 1 shows a schematic structural view of an inverted QLED applied to a display substrate according to an embodiment of the present disclosure
  • FIG. 2 shows a schematic diagram of energy levels of an electron transport layer in a QLED according to an embodiment of the present disclosure
  • FIG. 3 shows a schematic diagram of the relationship between the current density and the voltage of the electron transport layer having the energy level shown in FIG. 2 and the relationship between the current density and the voltage of the electron transport layer in the related art;
  • FIG. 4 shows a schematic diagram of the relationship between the current efficiency and the voltage of the electron transport layer having the energy level shown in FIG. 2 and the relationship between the current efficiency and the voltage of the electron transport layer in the related art;
  • Figure 5 shows a schematic diagram of the relationship between the thickness of the second energy level structure layer and the device efficiency in the electron transport layer having the energy level shown in Figure 2;
  • FIG. 6 shows a schematic diagram of the energy level relationship of each layer in a QLED according to an embodiment of the present disclosure.
  • FIG. 7 shows a schematic diagram of the change in bandgap of the second energy level structure layer as the doping amount increases
  • Figure 15(a) and Figure 15(b) are schematic diagrams showing the surface roughness of the electron transport layer in the QLED of the embodiment of the present disclosure.
  • FIG. 16 shows a flow chart of a method for fabricating a QLED according to an embodiment of the present disclosure.
  • the basic structure of a light emitting device includes an anode layer, a cathode layer, and a light emitting layer between the anode layer and the cathode layer. Under the action of an applied voltage, electrons and holes are injected from the cathode direction and the anode direction respectively, then migrate and meet and recombine in the light-emitting layer to generate excitons, and the energy of the excitons decays in the form of light, that is, radiates light.
  • the material of the light-emitting layer is quantum dots
  • the light-emitting layer is a quantum-dot light-emitting layer
  • the light-emitting device is a quantum-dot light-emitting diode.
  • the light emitting device may be an upright light emitting device or an inverted light emitting device.
  • a light-emitting device generally includes a base, and the anode layer of the upright light-emitting device is closer to the base than the cathode layer; the cathode layer of the inverted light-emitting device is closer to the base than the anode layer.
  • the light emitting device can be a top emission light emitting device or a bottom emission light emitting device; when the light emitting device is a positive top emission light emitting device, the anode layer is a reflective electrode, and the cathode layer is a transmissive electrode; when the light-emitting device is a bottom-emission light-emitting device, the anode layer is a transmissive electrode, and the cathode layer is a reflective electrode; when the light-emitting device is an inverted top-emission light-emitting device, the anode layer is The transmissive electrode, the cathode layer is a reflective electrode; when the light-emitting device is an inverted bottom-emitting light-emitting device, the anode layer is a reflective electrode, and the cathode layer is a transmissive electrode.
  • the light-emitting device not only includes an anode layer, a cathode layer and a light-emitting layer; a hole injection layer (Hole Injection Layer, referred to as HIL), a hole transport layer, etc.
  • HIL Hole Transport Layer
  • ETL Electrode Transport Layer
  • EIL Electron injection Layer
  • an electron injection layer may also be provided between the electron transport layer and the cathode layer.
  • inorganic zinc oxide is gradually being used as an electron transport layer material due to its wide bandgap, high electron mobility, transparency, and high conductivity.
  • the fast electron transport rate of ZnO 200 cm 2 V -1 s -1 to 300 cm 2 V -1 s -1
  • the electron transport rate is greater than the hole transport rate, resulting in excess electron injection
  • electrons are excessively accumulated in the quantum dot light-emitting layer, resulting in unbalanced carrier (electron and hole) injection
  • the quantum dot light-emitting layer causes quantum yield (quantum yield, QY ) is reduced, thereby affecting QLED performance (such as luminous efficiency).
  • the added electron blocking layer generally includes insulating materials, such as polymethyl methacrylate (PMMA), aluminum oxide (Al 2 O 3 ), silicon dioxide (SiO 2 ), etc., for electrons using these materials
  • PMMA polymethyl methacrylate
  • Al 2 O 3 aluminum oxide
  • SiO 2 silicon dioxide
  • the thickness of the barrier layer must be precisely controlled, generally less than 1nm, thus demanding the process. If the thickness of the electron blocking layer is slightly larger, the turn-on voltage of the QLED will be significantly increased. If the thickness of the electron blocking layer is further increased, electrons may not be injected into the quantum dots (QD), resulting in the failure of the QLED to emit light normally.
  • QD quantum dots
  • the electron transport rate can also be adjusted by doping other metal elements (such as magnesium, aluminum, etc. or a combination thereof) in the electron transport layer.
  • doping other metal elements such as magnesium, aluminum, etc. or a combination thereof
  • changing the doping element ratio of the electron transport layer changes the energy level of the electron transport layer, and also changes the energy level difference between the electron transport layer and its adjacent layers (such as the cathode layer and the quantum dot light-emitting layer). If the injection of electrons from the cathode layer to the electron transport layer becomes easy, the injection of electrons from the electron transport layer to the quantum dot light-emitting layer will become difficult.
  • an embodiment of the present disclosure provides a quantum dot light-emitting diode, which includes an anode layer, a cathode layer, a quantum dot light-emitting layer between the anode layer and the cathode layer, and the cathode layer and the quantum dot layer.
  • the electron transport layer between the light-emitting layers wherein the electron transport layer at least includes a first energy level structure layer, a second energy level structure layer and a second energy level structure layer stacked in sequence, and the first energy level structure layer different from the second energy level structure layer, and the lowest unoccupied molecular orbital (LUMO) energy level of the first energy level structure layer is different from the lowest unoccupied molecular orbital (LUMO) energy level of the second energy level structure layer .
  • LUMO lowest unoccupied molecular orbital
  • quantum dot light-emitting diodes in the embodiments of the present disclosure can be upright or inverted, and can be top-emitting or bottom-emitting, which is not specifically limited in the present disclosure.
  • FIG. 1 shows a schematic structural view of an inverted QLED according to an embodiment of the present disclosure applied to a display substrate.
  • the display substrate includes a substrate 1 and an array of inverted QLEDs disposed on the substrate 1 .
  • Each inverted QLED may include a cathode 2 , an electron transport layer 3 , a quantum dot (QD) light emitting layer, a hole transport layer 8 , a hole injection layer 9 , and an anode 10 sequentially stacked on the substrate 1 .
  • QD quantum dot
  • Each QLED is respectively disposed in each opening of the pixel defining layer 4 on the substrate 1 .
  • the substrate 1 can be a transparent substrate, such as glass, quartz, polyethylene terephthalate (PET) and other materials, but the embodiments of the present disclosure are not limited thereto, and those skilled in the art can It is necessary to select a substrate 1 made of an appropriate material.
  • a transparent substrate such as glass, quartz, polyethylene terephthalate (PET) and other materials, but the embodiments of the present disclosure are not limited thereto, and those skilled in the art can It is necessary to select a substrate 1 made of an appropriate material.
  • the cathode 2 may be a transparent electrode, such as a single-layer film made of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), or conductive polymer.
  • the cathode 2 can also be an opaque electrode, for example, a metal electrode made of opaque metal aluminum (Al), silver (Ag) and the like.
  • the cathode 2 can also be a multi-layer ITO/Ag/ITO film made of, for example, ITO and other metal materials (such as Ag).
  • the embodiments of the present disclosure are not limited thereto, and those skilled in the art can select the cathode 2 made of appropriate materials according to needs.
  • the cathode 2 may have a thickness of about 10 nm to about 100 nm.
  • the electron transport layer 3 at least includes a first energy level structure layer 31, a second energy level structure layer 32 and a first energy level structure layer 31 stacked in sequence, and the first energy level structure layer 31 is different from the second energy level structure layer 32 , and the LUMO energy level of the first level structure layer 31 is different from the LUMO energy level of the second energy level structure layer 32 .
  • both the side near the cathode 2 and the side near the quantum dot light-emitting layer of the electron transport layer 3 can include a first energy level structure layer 31, and two first energy level structure layers 31 can be sandwiched between them.
  • the LUMO energy level of the second energy level structure layer 32 may be higher or lower than the LUMO energy levels of the first energy level structure layer 31 on both sides thereof.
  • the LUMO energy level of the second energy level structure layer 32 is higher than the LUMO energy level of the first energy level structure layer 31 on both sides thereof, an energy level barrier for electron transmission will be formed in the electron transport layer 3, which hinders electron transport, Reduce the electron transport rate; if the LUMO energy level of the second energy level structure layer 32 is higher than the LUMO energy level of the first energy level structure layer 31 on both sides, the energy level traps of electron transport will be formed in the electron transport layer 3, Hinder electron transport and reduce electron transport rate.
  • the electron transport layer 3 including the first energy level structure layer 31, the second energy level structure layer 32 and the first energy level structure layer 31 stacked in sequence is used, the electron transport rate is reduced, and the electron transport rate is reduced.
  • the phenomenon of unbalanced carrier injection is alleviated, and the accumulation of electrons in the quantum dot light-emitting layer is reduced, effectively reducing or avoiding the quantum yield (quantum yield, QY ) is reduced, to a certain extent, the performance of QLED (such as luminous efficiency) is ensured, thereby ensuring the display effect of the display substrate.
  • the change of the energy level structure in the electron transport layer 3 may not affect the energy level difference between the electron transport layer 3 and the cathode 2, and the energy level difference between the electron transport layer 3 and the quantum dot light-emitting layer.
  • the level difference can more effectively balance the carrier injection in QLEDs.
  • the thickness of the electron transport layer 3 does not need to be strictly controlled in a very thin range, and the process requirements are relatively simple.
  • the thickness of the electron transport layer 3 may range from about 20 nm to about 150 nm.
  • the thickness of the electron transport layer 3 may be about 80 nm.
  • the thickness of the first energy level structure layer 31 may be about 30 nm, and the thickness of the second energy level structure layer 32 may be about 20 nm.
  • the thickness of the electron transport layer 3 may be 60 nm.
  • the thickness of the first energy level structure layer 31 may be about 20 nm
  • the thickness of the second energy level structure layer 32 may be about 20 nm.
  • the thickness of the first energy level structure layer 31 can be about 5nm to about 50nm
  • the thickness of the second energy level structure layer 32 can be about 10nm to about 50nm
  • the two sides of the second energy level structure layer 32 The thickness of the first energy level structure layer 31 may be the same or different, and the thickness of the first energy level structure layer 31 and the thickness of the second energy level structure layer 32 may be the same or different.
  • the thickness of the electron transport layer 3 applied to the QLEDs of the same display substrate may be the same or different, which is not specifically limited in the embodiment of the present disclosure, and those skilled in the art can make a selection according to needs.
  • the pixel definition layer 4 is used to define each QLED, prevent short circuit between each QLED, and prevent cross-color between QLEDs of each color, and the like.
  • the specific structure and material of the pixel defining layer 4 are not specifically limited in the embodiments of the present disclosure, and those skilled in the art can select an appropriate structure and appropriate material of the pixel defining layer 4 as required.
  • the quantum dot light emitting layer may include a red quantum dot light emitting layer 5 , a green quantum dot light emitting layer 6 , or a blue quantum dot light emitting layer 7 , thereby forming QLEDs of corresponding colors.
  • the thickness of the quantum dot light-emitting layer of each color can be about 20nm to about 50nm, and the thickness of the quantum dot light-emitting layer of each color can be the same or different, which is not specifically limited in the embodiments of the present disclosure, and those skilled in the art can according to A choice needs to be made.
  • the thickness of the hole transport layer 8 of each QLED applied to the same display substrate can be the same or different, and the thickness of the hole injection layer 9 of each QLED applied to the same display substrate can be the same or different.
  • Embodiments of the present disclosure This is not specifically limited, and those skilled in the art can make selections as needed.
  • the hole transport layer 8 and the hole injection layer 9 may be omitted in the QLED of the embodiments of the present disclosure.
  • the anode 10 of each QLED applied to the same display substrate can be shared, and the anode 10 can be a transparent or opaque conductive film, for example, the material of the anode 10 can be indium zinc oxide (IZO) , metal aluminum (Al) or silver (Ag), etc., which are not specifically limited in the embodiments of the present disclosure, and those skilled in the art can select according to needs.
  • IZO indium zinc oxide
  • Al metal aluminum
  • Ag silver
  • the thickness of the anode 10 may be about 10 nm to about 100 nm.
  • FIG. 2 shows a schematic diagram of energy levels of an electron transport layer in a QLED according to an embodiment of the present disclosure.
  • the energy levels of the first energy level structure layer 31 , the second energy level structure layer 32 and the first energy level structure layer 31 are respectively shown in order from left to right or from right to left.
  • the LUMO energy level of the second energy level structure layer 32 can be higher than the LUMO energy level of the first energy level structure layer 31.
  • an energy level barrier will be formed in the electron transport layer 3, hindering electrons. Transport, reducing the electron transport rate.
  • the LUMO energy level of the second energy level structure layer 32 may be higher than the LUMO energy level of the first energy level structure layer 31 by about 0.1 eV to about 0.5eV.
  • the material of the first energy level structure layer 31 may be zinc oxide (ZnO) material, and its LUMO energy level may be about -4.8eV to about -4.6eV, and the material of the second energy level structure layer 32 It can be a zinc oxide material (hereinafter referred to as GZO) doped with gallium element (Ga), and its LUMO energy level can be about -4.6eV to about -4.3eV.
  • GZO zinc oxide material
  • Ga gallium element
  • the LUMO energy level may be higher than the LUMO energy level of the first energy level structure layer 31 .
  • FIG. 3 shows a schematic diagram of the relationship between the current density and voltage of the electron transport layer 3 having the energy levels shown in FIG. 2 and the relationship between the current density and voltage of the electron transport layer in the related art.
  • the solid line shows the relationship between the current density and the voltage of the electron transport layer in the related art
  • the dotted line shows the relationship between the current density and the voltage of the electron transport layer 3 with the energy level shown in Figure 2 Relationship.
  • the material of the electron transport layer in the related art is ZnO
  • the material of the first energy level structure layer 31 is ZnO
  • the material of the second energy level structure layer 32 The material is GZO.
  • the current density of the electron transport layer 3 having the energy levels shown in FIG. 2 is lowered, that is, its electron transport rate is lowered, compared to the electron transport layer in the related art.
  • FIG. 4 is a schematic diagram showing the relationship between the current efficiency and voltage of the electron transport layer having the energy levels shown in FIG. 2 and the relationship between the current efficiency and voltage of the electron transport layer in the related art.
  • the solid line shows the relationship between the current efficiency and the voltage of the electron transport layer in the related art
  • the dotted line shows the relationship between the current efficiency and the voltage of the electron transport layer 3 with the energy level shown in Figure 2 Relationship.
  • the material of the electron transport layer in the related art is ZnO
  • the material of the first energy level structure layer 31 is ZnO
  • the material of the second energy level structure layer 32 The material is GZO.
  • the current efficiency of the electron transport layer 3 having the energy levels shown in FIG. 2 is slightly lower at first, it is improved to a certain extent later.
  • 3 and 4 show the relationship between the current density and the voltage of the electron transport layer 3 whose LUMO energy level of the second energy level structure layer 32 is higher than the LUMO energy level of the first energy level structure layer 31 and the current efficiency and the voltage. relationship between voltages.
  • the LUMO energy level of the second energy level structure layer 32 can also be lower than the LUMO energy level of the first energy level structure layer 31. In this case, energy level traps will be formed in the electron transport layer 3, hindering electrons. Transport, reducing the electron transport rate.
  • the LUMO energy level of the second energy level structure layer 32 may be lower than the LUMO energy level of the first energy level structure layer 31 by about 0.1 eV to about 0.5eV.
  • the HOMO energy level of the second energy level structure layer 32 may be higher than the HOMO energy level of the first energy level structure layer 31, as shown in FIG.
  • the HOMO energy level of the two-level structure layer 32 may also be lower than the HOMO energy level of the first energy-level structure layer 31 , which is not specifically limited in the embodiments of the present disclosure, and those skilled in the art can make selections according to needs.
  • the electron transport layer 3 can also block holes from reaching the cathode, thereby reducing hole leakage current.
  • the HOMO energy levels of the first energy level structure layer 31 and the second energy level structure layer 32 can also be properly set, so that the electron transport layer 3. It can effectively prevent holes from reaching the cathode, thereby reducing the hole current, and then making the injection of electrons and holes in the QLED more balanced, and the QLED luminescence is more stable.
  • FIG. 5 shows a schematic diagram of the relationship between the thickness of the second energy level structure layer 32 in the electron transport layer 3 having the energy levels shown in FIG. 2 and the device efficiency.
  • FIG. 6 shows the energy level relationship of each layer in the QLED according to the embodiment of the present disclosure.
  • 7 shows a schematic diagram of the change of the bandgap of the second energy level structure layer 32 with the increase of Ga doping amount.
  • the bandgap of the second energy level structure layer 32 increases, resulting in weaker conductivity of the second energy level structure layer 32 .
  • the above only gave an example in which the material of the first energy level structure layer 31 is ZnO and the material of the second energy level structure layer 32 is GZO.
  • the LUMO energy level is different from the LUMO energy level of the second energy level structure layer 32 , and there are many choices of materials for the first energy level structure layer 31 and the second energy level structure layer 32 .
  • the material of the first energy level structure layer 31 may be GZO, and the material of the second energy level structure layer 32 may be ZnO.
  • the material of one of the first energy level structure layer 31 and the second energy level structure layer 32 may be ZnO, and the material of the other may be doped ZnO.
  • ZnO can be doped with elements whose oxide lattice constant is close to but not identical to that of ZnO, and/or doped with elements whose electronegativity and radius are different from those of Zn, for example,
  • the doped ZnO may be doped with at least one of gallium (Ga), indium (In), yttrium (Y), copper (Cu), zirconium (Zr), aluminum (Al), and magnesium (Mg) or any group thereof. If the band gap of the oxide of the doped element is larger than that of ZnO, the band gap of the doped ZnO generally increases and the conductivity becomes weak.
  • the materials of the first energy level structure layer 31 and the second energy level structure layer 32 may also be doped ZnO.
  • the doping type of the first energy level structure layer 31 and the doping type of the second energy level structure layer 32 may be the same or different.
  • the doping concentration of the first energy level structure layer 31 and the doping concentration of the second energy level structure layer 32 may be the same or different.
  • the energy of the first energy level structure layer 31 and the second energy level structure layer 32 can be adjusted by adjusting the material and thickness of the first energy level structure layer 31 and the second energy level structure layer 32. level, so that at least the LUMO energy level of the second energy level structure layer 32 is different from the LUMO energy level of the first energy level structure layer 31 .
  • the doping concentration in the doped zinc oxide may be 0% to about 50%.
  • the electron transport layer 3 corresponding to the energy level diagrams shown in FIGS. 8 to 10 includes a first energy level structure layer 31 , a second energy level structure layer 32 and a first energy level structure layer 31 stacked in sequence.
  • the LUMO energy level of the second energy level structure layer 32 is higher than the LUMO energy level of the first energy level structure layer 31, and the second energy level structure layer 31
  • the HOMO energy level of the level structure layer 32 is lower than the HOMO energy level of the first energy level structure layer 31.
  • an energy level barrier will be formed in the electron transport layer 3, which hinders electron transport and reduces the electron transport rate.
  • the LUMO energy level of the second energy level structure layer 32 is lower than the LUMO energy level of the first energy level structure layer 31, and the second energy level structure layer
  • the HOMO energy level of 32 is lower than the HOMO energy level of the first energy level structure layer 31. In this case, energy level traps will be formed in the electron transport layer 3, which hinders electron transport and reduces the electron transport rate.
  • the LUMO energy level of the second energy level structure layer 32 is lower than the LUMO energy level of the first energy level structure layer 31, and the second energy level structure layer
  • the HOMO energy level of 32 is higher than the HOMO energy level of the first energy level structure layer 31.
  • energy level traps will also be formed in the electron transport layer 3, which hinders electron transport and reduces the electron transport rate.
  • the electron transport layer 3 includes at least the first energy level structure layer 31 , the second energy level structure layer 32 and the first energy level structure layer 31 stacked in sequence.
  • the electron transport layer 3 may include stacked multiple first energy level structure layers 31 and multiple second energy level structure layers 32, each first energy level structure layer 31 and each second energy level structure layer
  • the layers 32 can be stacked alternately, and the side of the electron transport layer 3 close to the cathode 2 and the side close to the quantum dot light-emitting layer are both the first energy level structure layer 31 or the second energy level structure layer 31.
  • Level structure layer 32 is stacked alternately, and the side of the electron transport layer 3 close to the cathode 2 and the side close to the quantum dot light-emitting layer are both the first energy level structure layer 31 or the second energy level structure layer 31.
  • Level structure layer 32 .
  • the electron transport layer 3 may include a second energy level structure layer 32, a first energy level structure layer 31, a second energy level structure layer 32, ..., a first energy level structure layer 31, and a second energy level structure layer stacked in sequence.
  • the second energy level structure layer 32 may include sequentially stacked first energy level structure layer 31, second energy level structure layer 32, first energy level structure layer 31, ..., second energy level structure layer 32, and the second energy level structure layer.
  • a level structure layer 31 .
  • the side close to the cathode 2 of the electron transport layer 3 and the side close to the quantum dot luminescent layer can both be the first energy level structure layer 31, or the side close to the cathode 2 of the electron transport layer 3
  • the side and the side close to the quantum dot light-emitting layer can be both the second energy level structure layer 32, it can be ensured that when the energy level structure in the electron transport layer 3 changes, the electron transport layer 3 and the The energy level difference between the cathodes 2 and the energy level difference between the electron transport layer 3 and the quantum dot light-emitting layer remain unchanged.
  • 11 to 14 show schematic diagrams of energy levels of an electron transport layer 3 including a plurality of first energy level structure layers 31 and a plurality of second energy level structure layers 32 .
  • the electron transport layer 3 includes a second energy level structure layer 32 , a first energy level structure layer 31 , a second energy level structure layer 32 , ..., the first energy level structure layer 31, and the second energy level structure layer 32
  • the LUMO energy level of the second energy level structure layer 32 is higher than the LUMO energy level of the first energy level structure layer 31, so The HOMO energy level of the second energy level structure layer 32 is lower than the HOMO energy level of the first energy level structure layer 31 .
  • the electron transport layer 3 includes a first energy level structure layer 31 , a second energy level structure layer 32 , a first energy level structure layer 31 , ..., the second energy level structure layer 32, and the first energy level structure layer 31, the LUMO energy level of the second energy level structure layer 32 is higher than the LUMO energy level of the first energy level structure layer 31, so The HOMO energy level of the second energy level structure layer 32 is lower than the HOMO energy level of the first energy level structure layer 31 .
  • the electron transport layer 3 includes a second energy level structure layer 32, a first energy level structure layer 31, a second energy level structure layer 32, ..., the first energy level structure layer 31, and the second energy level structure layer 32
  • the LUMO energy level of the second energy level structure layer 32 is lower than the LUMO energy level of the first energy level structure layer 31, so
  • the HOMO energy level of the second energy level structure layer 32 is lower than the HOMO energy level of the first energy level structure layer 31 .
  • the electron transport layer 3 includes a first energy level structure layer 31, a second energy level structure layer 32, a first energy level structure layer 31, ...the second energy level structure layer 32, and the first energy level structure layer 31, the LUMO energy level of the second energy level structure layer 32 is lower than the LUMO energy level of the first energy level structure layer 31, the The HOMO energy level of the second energy level structure layer 32 is lower than the HOMO energy level of the first energy level structure layer 31 .
  • the electron transport layer 3 includes a second energy level structure layer 32 , a first energy level structure layer 31 , a second energy level structure layer 32 , ..., the first energy level structure layer 31, and the second energy level structure layer 32
  • the LUMO energy level of the second energy level structure layer 32 is higher than the LUMO energy level of the first energy level structure layer 31, so
  • the HOMO energy level of the second energy level structure layer 32 is higher than the HOMO energy level of the first energy level structure layer 31 .
  • the electron transport layer 3 includes a first energy level structure layer 31 , a second energy level structure layer 32 , a first energy level structure layer 31 , ..., the second energy level structure layer 32, and the first energy level structure layer 31, the LUMO energy level of the second energy level structure layer 32 is higher than the LUMO energy level of the first energy level structure layer 31, so The HOMO energy level of the second energy level structure layer 32 is higher than the HOMO energy level of the first energy level structure layer 31 .
  • the electron transport layer 3 includes a second energy level structure layer 32, a first energy level structure layer 31, a second energy level structure layer 32, ..., the first energy level structure layer 31, and the second energy level structure layer 32
  • the LUMO energy level of the second energy level structure layer 32 is lower than the LUMO energy level of the first energy level structure layer 31, so The HOMO energy level of the second energy level structure layer 32 is higher than the HOMO energy level of the first energy level structure layer 31 .
  • the electron transport layer 3 includes a first energy level structure layer 31, a second energy level structure layer 32, a first energy level structure layer 31, ..., the second energy level structure layer 32, and the first energy level structure layer 31, the LUMO energy level of the second energy level structure layer 32 is lower than the LUMO energy level of the first energy level structure layer 31, so The HOMO energy level of the second energy level structure layer 32 is higher than the HOMO energy level of the first energy level structure layer 31 .
  • FIG. 15( a ) and FIG. 15( b ) are schematic diagrams showing the surface roughness of the electron transport layer in a QLED according to an embodiment of the present disclosure.
  • the surface roughness of the electron transport layer in the QLED of the disclosed embodiment can be measured by an atomic force microscope (AFM), and the RMS (root mean square, root mean square) value range of the surface roughness can be controlled from about 1 nm to about 10 nm, and more Specifically, it may be about 0.2 nm to about 8 nm, as shown in FIG. 15( a ), or may be about 1.1 nm to about 8.9 nm, as shown in FIG. 15( b ).
  • AFM atomic force microscope
  • the embodiment of the present disclosure also provides a method for preparing a quantum dot light emitting diode, which can be used to prepare the quantum dot light emitting diode in the above embodiment.
  • FIG. 16 shows a flow chart of a method for manufacturing a quantum dot light-emitting diode according to an embodiment of the present disclosure.
  • the method for manufacturing a quantum dot light-emitting diode according to an embodiment of the present disclosure includes the following steps S1 to S7.
  • the substrate 1 can be, for example, glass or a flexible PET substrate
  • the cathode 2 can be an electrode made of materials such as transparent ITO, FTO or conductive polymer, or can also be an opaque Al, Ag Electrodes made of metals.
  • a conductive material layer (such as forming an ITO or FTO film) can be deposited on the substrate 1 by magnetron sputtering, sol-gel, atomic layer deposition, evaporation, etc., and then patterned by a patterning process to form the The pattern of the cathode 2, the thickness of the cathode 2 (dimension perpendicular to the plane where the substrate 1 is located) may be about 10nm to about 100nm.
  • a ZnO or doped ZnO thin film can be deposited on the cathode 2 by means of magnetron sputtering, sol-gel, atomic layer deposition, evaporation, etc., as the first part of the electron transport layer 3 .
  • the thickness of the first energy level structure layer 31 may be between about 5 nm and about 50 nm.
  • a doped ZnO or ZnO thin film can be deposited on the first energy level structure layer 31 by magnetron sputtering, sol-gel, atomic layer deposition, evaporation, etc., as the second layer of the electron transport layer 3. two parts.
  • the material of the first energy level structure layer 31 is ZnO
  • the material of the second energy level structure layer 32 may be doped ZnO
  • the material of the second energy level structure layer 32 may be ZnO or doped ZnO.
  • the thickness of the second energy level structure layer 32 may be between 10 nm and 50 nm.
  • a ZnO or doped ZnO thin film can be deposited on the second energy level structure layer 32 by magnetron sputtering, sol-gel, atomic layer deposition, evaporation, etc., as the second layer of the electron transport layer 3. three parts.
  • the first energy level structure layer 31 as the first part of the electron transport layer 3, the second energy level structure layer 32 as the second part of the electron transport layer 3, and the third energy level structure layer 3 as the electron transport layer 3 Part of the first energy level structure layer 31 forms a complete electron transport layer 3 .
  • the material and thickness of the first energy level structure layer 31 on both sides of the second energy level structure layer 32 may be the same or different, as long as the LUMO energy level of the second energy level structure layer 32 is different from that of the first energy level structure layer 32.
  • the LUMO energy level of the one-level structure layer 31 is sufficient.
  • the doping element in the above-mentioned doped ZnO can be at least one of Ga, In, Y, Cu, Zr, Al, Mg or any combination thereof, and the doping concentration can be 0% to about 50%. , those skilled in the art can select as needed.
  • the doped ZnO may be GZO doped with Ga element at a doping concentration of 20%.
  • the cathode 2 and the electron transport layer 3 are formed by means of magnetron sputtering, sol-gel, atomic layer deposition, vapor deposition, etc., so that the film layers of the formed cathode 2 and electron transport layer 3 The thickness is relatively uniform.
  • the quantum dot light-emitting layer can be formed on the electron transport layer 3 by printing (for example, inkjet printing).
  • the quantum dot luminescent layer can be red quantum dot luminescent layer 5, green quantum dot luminescent layer 6, blue quantum dot luminescent layer 7, etc., its thickness can be about 20nm to about 50nm, the quantum dot luminescent layer of each color thickness may vary.
  • Forming the quantum dot luminescent layer by printing is beneficial to the effective utilization of quantum dot materials and the large-area preparation of the quantum dot luminescent layer.
  • the pixel definition layer 4 can also be formed, and the embodiment of the present disclosure does not specifically limit the formation method and material of the pixel definition layer 4 .
  • the pixel defining layer 4 can be formed by a photolithography process.
  • the hole transport layer 8 and the hole transport layer 9 can be sequentially deposited by means of spin coating, evaporation, and the like.
  • step S6 is an optional step.
  • the hole transport layer 8 and the hole injection layer 9 may not be formed.
  • the embodiment of the present disclosure does not specifically limit the material and thickness of the hole transport layer 8 and the hole injection layer 9 .
  • the anode 10 can be formed by magnetron sputtering, sol-gel, atomic layer deposition, evaporation, etc., and the material of the anode 10 can be indium zinc oxide (IZO), metal aluminum (Al) or Silver (Ag), etc., the thickness of the anode 10 may be about 10 nm to about 100 nm.
  • IZO indium zinc oxide
  • Al metal aluminum
  • Ag Silver
  • quantum dot light emitting diode prepared by the method for preparing the quantum dot light emitting diode according to the embodiment of the present disclosure, energy level traps or energy level barriers will be formed in the electron transport layer 3, which will hinder electron transport and reduce the electron transport rate, which can Effectively balancing the injection of carriers (electrons and holes) in the QLED can ensure the performance of the QLED (such as luminous efficiency) to a certain extent.
  • An embodiment of the present disclosure also provides a display device, the display device includes a display substrate, and the display substrate includes a plurality of QLEDs arranged in an array, and some or all of the plurality of QLEDs are the above-mentioned embodiments of the present disclosure.
  • QLED in .
  • the display effect of the display device in the embodiment of the present disclosure is better.
  • the display device in the embodiments of the present disclosure may be any product or component with a display function, such as electronic paper, OLED panel, QLED panel, mobile phone, tablet computer, television, monitor, notebook computer, digital photo frame, and navigator.
  • a display function such as electronic paper, OLED panel, QLED panel, mobile phone, tablet computer, television, monitor, notebook computer, digital photo frame, and navigator.

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Abstract

本公开实施例提供一种量子点发光二极管、一种制备量子点发光二极管的方法和一种显示装置。所述量子点发光二极管包括阳极层、阴极层、所述阳极层与所述阴极层之间的量子点发光层、以及所述阴极层与所述量子点发光层之间的电子传输层，所述电子传输层至少包括依次层叠的第一能级结构层、第二能级结构层和第一能级结构层，所述第一能级结构层不同于第二能级结构层，且所述第一能级结构层的最低未占分子轨道能级不同于所述第二能级结构层的最低未占分子轨道能级。

Description

量子点发光二极管及其制备方法、显示装置 技术领域
本公开属于显示技术领域，具体涉及量子点发光二极管及其制备方法、显示装置。
背景技术
量子点发光二极管(Quantum Dot Light Emitting Diodes，简称QLED)通常包括具有多个量子点纳米晶体的发光层。发光层夹在电子传输层和空穴传输层之间。通过将电场施加到量子点发光二极管，可以使电子和空穴移动到发光层中。在发光层中，电子和空穴被捕获在量子点中并被重新组合，从而发射光子。
发明内容
本公开的实施例提供一种量子点发光二极管，包括阳极层、阴极层、所述阳极层与所述阴极层之间的量子点发光层、以及所述阴极层与所述量子点发光层之间的电子传输层，其中，所述电子传输层至少包括依次层叠的第一能级结构层、第二能级结构层和第一能级结构层，所述第一能级结构层不同于第二能级结构层，且所述第一能级结构层的最低未占分子轨道能级不同于所述第二能级结构层的最低未占分子轨道能级。
在一些实施方式中，所述第一能级结构层的最低未占分子轨道能级高于所述第二能级结构层的最低未占分子轨道能级。
在一些实施方式中，所述第一能级结构层的最低未占分子轨道能级低于所述第二能级结构层的最低未占分子轨道能级。
在一些实施方式中，所述第一能级结构层的最低未占分子轨道能级与所述第二能级结构层的最低未占分子轨道能级之间的差为0.1eV至0.5eV。
在一些实施方式中，所述电子传输层的总厚度为20nm至150nm。
在一些实施方式中，所述第一能级结构层和所述第二能级结构层中的至少一者的材料为掺杂的氧化锌。
在一些实施方式中，所述第一能级结构层和所述第二能级结构层中的一者的材料为氧化锌，另一者的材料为掺杂的氧化锌。
在一些实施方式中，所述掺杂的氧化锌中掺杂有镓、铟、钇、铜、锆、铝、镁中的至少一种或其任意组合。
在一些实施方式中，所述掺杂的氧化锌中的掺杂浓度为0％至50％。
在一些实施方式中，所述电子传输层包括多个第一能级结构层和多个第二能级结构层，所述第一能级结构层和所述第二能级结构层交替层叠，且所述电子传输层的靠近所述阴极的一侧和靠近所述量子点发光层的一侧均为所述第一能级结构层或者所述第二能级结构层。
在一些实施方式中，所述电子传输层的表面粗糙度的均方根数值范围为1nm至10nm。
在一些实施方式中，所述量子点发光二极管还包括空穴传输层和空穴注入层，其中，所述阴极层、所述电子传输层、所述量子点发光层、所述空穴传输层、所述空穴注入层及所述阳极层依次层叠设置在衬底上。
本公开实施例还提供一种量子点发光二极管的制备方法，包括形成阳极层、阴极层、所述阳极层与所述阴极层之间的量子点发光层、以及所述阴极层与所述量子点发光层之间的电子传输层的步骤，其中，
形成所述电子传输层的步骤包括：
形成依次层叠的第一能级结构层、第二能级结构层和第二能级结构层，所述第一能级结构层不同于第二能级结构层，且所述第一能级结构层的最低未占分子轨道能级不同于所述第二能级结构层的最低未占分子轨道能级。
在一些实施方式中，形成依次层叠的第一能级结构层、第二能级结构层和第一能级结构层包括：
通过溅射法、溶胶凝胶法、原子层沉积法沉积所述第一能级结构层、所述第二能级结构层和所述第一能级结构层。
在一些实施方式中，所述量子点发光二极管的制备方法还包括：
通过打印方式在所述电子传输层上沉积所述量子点发光层；以及
通过蒸镀方式在所述量子点发光层上依次沉积空穴传输层和空穴注入层。
在一些实施方式中，所述电子传输层形成为使得所述第一能级结构层的最低未占分子轨道能级与所述第二能级结构层的最低未占分子轨道能级之间的差为0.1eV至0.5eV。
在一些实施方式中，形成依次层叠的第一能级结构层、第二能级结构层和第三能级结构层包括：
采用掺杂的氧化锌材料形成所述第一能级结构层和所述第二能级结构层中的至少一者。
在一些实施方式中，形成依次层叠的第一能级结构层、第二能级结构层和第一能级结构层包括：
采用氧化锌材料形成所述第一能级结构层和所述第二能级结构层中的一者；以及
采用掺杂的氧化锌材料形成所述第一能级结构层和所述第二能级结构层中的另一者。
在一些实施方式中，采用掺杂的氧化锌材料包括：
采用掺杂有镓、铟、钇、铜、锆、铝、镁中的至少一种或其任意组合的掺杂的氧化锌材料。
在一些实施方式中，采用掺杂的氧化锌材料包括：
采用掺杂浓度为0％至50％的掺杂的氧化锌材料。
在一些实施方式中，形成依次层叠的第一能级结构层、第二能级结构层和第二能级结构层包括：
形成多个第一能级结构层和多个第二能级结构层，所述第一能级结构层和所述第二能级结构层交替层叠，且所述电子传输层的靠近所述阴极的一侧和靠近所述量子点发光层的一侧均为所述第一能级结构层或者所述第二能级结构层。
本公开实施例还提供一种显示装置，包括显示基板，所述显示 基板包括以阵列形式排布的多个量子点发光二极管，其中，所述多个量子点发光二极管包括上述的本公开实施例的量子点发光二极管。
附图说明
图1示出了本公开实施例的倒置型QLED应用于显示基板中的结构示意图；
图2示出了本公开实施例的QLED中电子传输层的能级示意图；
图3示出了具有图2所示能级的电子传输层的电流密度与电压之间的关系及相关技术中电子传输层的电流密度与电压之间的关系的示意图；
图4示出了具有图2所示能级的电子传输层的电流效率与电压之间的关系及相关技术中电子传输层的电流效率与电压之间的关系的示意图；
图5示出了具有图2所示能级的电子传输层中的第二能级结构层的厚度与器件效率之间的关系的示意图；
图6示出了本公开实施例的QLED中各层的能级关系的示意图。
图7示出了随着掺杂量的提高第二能级结构层的带隙变化的示意图；
图8至图14示出了本公开实施例的QLED中电子传输层的能级示意图；
图15(a)和图15(b)示出了本公开实施例的QLED中电子传输层的表面粗糙度的示意图；以及
图16示出了本公开实施例的QLED的制备方法的流程图。
具体实施方式
为使本领域技术人员更好地理解本公开的技术方案，下面结合附图和具体实施方式对本公开的技术方案作进一步详细描述。
除非另外定义，本公开使用的技术术语或者科学术语应当为本公开所属领域内具有一般技能的人士所理解的通常意义。本公开中使用的“一个”、“一”或者“该”等类似词语不表示数量限制，而是 表示存在至少一个；“包括”或者“包含”等类似的词语意指出现该词前面的元件或者物件涵盖出现在该词后面列举的元件或者物件及其等同，而不排除其他元件或者物件；位置关系术语(例如“上”等)仅用于表示相对位置关系，当被描述对象的绝对位置改变后，则该相对位置关系也可能相应地改变。
发光器件的基本结构包括阳极层、阴极层、以及在阳极层和阴极层之间的发光层。在外加电压作用下，电子和空穴分别从阴极方向和阳极方向注入，然后迁移并在发光层中相遇复合产生激子，激子的能量以光的形式衰减，即辐射出光。当发光层的材料为量子点时，发光层为量子点发光层，相应地，发光器件为量子点发光二极管。
发光器件可以是正置型发光器件，也可以是倒置型发光器件。发光器件通常包括基底，正置型发光器件的阳极层较阴极层而言更靠近基底；倒置型发光器件的阴极层较阳极层而言更靠近基底。无论发光器件为正置型发光器件，还是为倒置型发光器件，该发光器件可以是顶发射型发光器件，也可以是底发射型发光器件；当发光器件为正置顶发射型发光器件时，阳极层为反射电极，阴极层为透射电极；当发光器件为正置底发射型发光器件时，阳极层为透射电极，阴极层为反射电极；当发光器件为倒置顶发射型发光器件时，阳极层为透射电极，阴极层为反射电极；当发光器件为倒置底发射型发光器件时，阳极层为反射电极，阴极层为透射电极。
随着发光器件的性能的不断优化，发光器件不仅包含阳极层、阴极层和发光层；还可以在阳极层和发光层之间设置空穴注入层(Hole Injection Layer，简称HIL)、空穴传输层(Hole Transport Layer，简称HTL)，在发光层和阴极层之间设置电子传输层(Electron Transport Layer，简称ETL)。当然，在电子传输层和阴极层之间还可以设置电子注入层(Electron Injection Layer，简称EIL)。
当前，在量子点发光二极管(QLED)领域中，无机氧化锌凭借其宽带隙、高电子迁移速率、透明性和高导电性，逐渐被用作一种电子传输层材料。但是，由于氧化锌具有较快的电子传输速率(200cm 2V -1s -1至300cm 2V -1s -1)，在QLED器件中，电子传输速率大于 空穴传输速率，导致电子注入过剩，电子在量子点发光层过度累积，从而产生载流子(电子和空穴)注入不平衡的现象，量子点发光层由于非辐射复合(例如Auger复合)而导致量子产率(quantum yield，QY)降低，进而影响QLED性能(例如发光效率)。
相关技术中，通过在电子传输层和量子点发光层之间增加电子阻挡层，可以部分缓减电子在发光层过度累积的问题。然而，增加的电子阻挡层一般包括绝缘材料，如聚甲基丙烯酸甲酯(polymethyl methacrylate，PMMA)、氧化铝(Al 2O 3)、二氧化硅(SiO 2)等，对于使用这些材料的电子阻挡层，必须精确控制其厚度，一般要使其小于1nm，从而对工艺要求苛刻。如果电子阻挡层的厚度稍大，则会明显增加QLED的启亮电压，如果电子阻挡层的厚度进一步增大，则可能会导致电子无法注入量子点(QD)中，导致QLED无法正常发光。
此外，通过在电子传输层中掺杂其他金属元素(例如镁、铝等或其组合)也可以调控其电子传输速率。但是，改变电子传输层的掺杂元素比例在改变电子传输层的能级的同时，也会改变电子传输层与其相邻层(例如阴极层和量子点发光层)之间的能级差。若电子从阴极层到电子传输层的注入变容易，则电子从电子传输层到量子点发光层的注入就会变困难，反之，若电子从电子传输层到量子点发光层的注入变容易，则电子从阴极层到电子传输层的注入就会变困难。因此，通过在氧化锌的电子传输层中掺杂其他金属元素来调整其电子传输速率时，QLED的性能不仅仅受该单一变量的影响，多重变量可能会导致能级调控困难且难以确保QLED具有期望的性能。
鉴于此，本公开实施例提供一种量子点发光二极管，其包括阳极层、阴极层、所述阳极层与所述阴极层之间的量子点发光层、以及所述阴极层与所述量子点发光层之间的电子传输层，其中，所述电子传输层至少包括依次层叠的第一能级结构层、第二能级结构层和第二能级结构层，所述第一能级结构层不同于第二能级结构层，且所述第一能级结构层的最低未占分子轨道(LUMO)能级不同于所述第二能级结构层的最低未占分子轨道(LUMO)能级。
应当理解，本公开实施例的量子点发光二极管可以为正置型或 倒置型，可以为顶发射型或底发射型，本公开不对其进行具体限定。
为了便于描述，以下以本公开实施例的量子点发光二极管为倒置型为例进行说明。
图1示出了本公开实施例的倒置型QLED应用于显示基板中的结构示意图。如图1所示，所述显示基板包括衬底1、及设置在衬底1上的倒置型QLED的阵列。每个倒置型QLED可包括依次层叠在所述衬底1上的阴极2、电子传输层3、量子点(QD)发光层、空穴传输层8、空穴注入层9、及阳极10。各QLED分别设置在衬底1上的像素限定层4的各开口中。
所述衬底1可以为透明衬底，例如可以选用玻璃、石英、聚对苯二甲酸乙二醇酯(PET)等材料制备，但是，本公开实施例不限于此，本领域技术人员可以根据需要选择适当材料制备的衬底1。
所述阴极2可以为透明电极，例如可以为由氧化铟锡(ITO)、掺氟氧化锡(FTO)、或导电聚合物等材料制备的单层膜层。所述阴极2也可以为不透明电极，例如可以为由不透明的金属铝(Al)、银(Ag)等制备的金属电极。此外，所述阴极2还可以为由例如ITO及其他金属材料(例如Ag)制备的多层膜层ITO/Ag/ITO。但是，本公开实施例不限于此，本领域技术人员可以根据需要选择适当材料制备的阴极2。
所述阴极2的厚度可以为约10nm至约100nm。
所述电子传输层3至少包括依次层叠的第一能级结构层31、第二能级结构层32和第一能级结构层31，所述第一能级结构层31不同于所述第二能级结构层32，且所述第一等级结构层31的LUMO能级不同于所述第二能级结构层32的LUMO能级。
也就是说，所述电子传输层3的靠近阴极2的一侧及靠近量子点发光层的一侧均可包括第一能级结构层31，两个第一能级结构层31之间可夹设第二能级结构层32，第二能级结构层32的LUMO能级可高于或低于其两侧的第一能级结构层31的LUMO能级。
如果第二能级结构层32的LUMO能级高于其两侧的第一能级结构层31的LUMO能级，则电子传输层3中会形成电子传输的能级势垒， 阻碍电子传输，降低电子传输速率；如果第二能级结构层32的LUMO能级高于其两侧的第一能级结构层31的LUMO能级，则电子传输层3中会形成电子传输的能级陷阱，阻碍电子传输，降低电子传输速率。
本公开实施例的QLED中，由于利用了包括依次层叠的第一能级结构层31、第二能级结构层32和第一能级结构层31的电子传输层3，电子传输速率降低，载流子注入不平衡现象得到缓减，电子在量子点发光层的累积减少，有效减少或避免了量子点发光层中的非辐射复合(例如Auger复合)而导致的量子产率(quantum yield，QY)降低，一定程度上确保了QLED的性能(例如发光效率)，从而保证了显示基板的显示效果。
此外，本公开实施例的QLED中，电子传输层3内的能级结构的变化可不影响电子传输层3与阴极2之间的能级差、以及电子传输层3与量子点发光层之间的能级差，可更有效地平衡QLED中的载流子注入。而且，本公开实施例的QLED中，电子传输层3的厚度不需要严格控制在非常薄的范围，对工艺要求较简单。
作为示例，本公开实施例的QLED中，电子传输层3的厚度范围可以为约20nm至约150nm。例如，电子传输层3的厚度可以为约80nm，该情况下，第一能级结构层31的厚度可以为约30nm，第二能级结构层32的厚度可以为约20nm。又例如，电子传输层3的厚度可以为60nm，该情况下，第一能级结构层31的厚度可以为约20nm，第二能级结构层32的厚度可以为约20nm。
事实上，第一能级结构层31的厚度可以为约5nm至约50nm，第二能级结构层32的厚度可以为约10nm至约50nm，而且，第二能级结构层32的两侧的第一能级结构层31的厚度可以相同或不同，第一能级结构层31的厚度与第二能级结构层32的厚度可以相同或不同。而且，应用于同一显示基板的各QLED的电子传输层3的厚度可以相同或不同，本公开实施例对此不进行具体限定，本领域技术人员可根据需要进行选择。
所述像素限定层4用于限定各QLED，防止各QLED之间短路、以及防止各颜色的QLED之间的串色等。本公开实施例中对所述像素限 定层4的具体结构及材料不进行具体限定，本领域技术人员可根据需要选择所述像素限定层4的适当结构及其适当材料。
作为示例，如图1所示，所述量子点发光层可以包括红色量子点发光层5、绿色量子点发光层6、或蓝色量子点发光层7，从而形成相应颜色的QLED。
各颜色的量子点发光层的厚度可分别为约20nm至约50nm，且各颜色的量子点发光层的厚度可相同或不同，本公开实施例对此不进行具体限定，本领域技术人员可根据需要进行选择。
根据需要，应用于同一显示基板的各QLED的空穴传输层8的厚度可以相同或不同，以及应用于同一显示基板的各QLED的空穴注入层9的厚度可以相同或不同，本公开实施例对此不进行具体限定，本领域技术人员可以根据需要进行选择。
应当理解，在一些实施方式中，本公开实施例的QLED中，可省略空穴传输层8和空穴注入层9。
如图1所示，应用于同一显示基板的各QLED的阳极10可以共用，且所述阳极10可以为透明或者不透明的导电薄膜，例如，所述阳极10的材料可以为氧化铟锌(IZO)、金属铝(Al)或银(Ag)等，本公开实施例对此不进行具体限定，本领域技术人员可以根据需要进行选择。
所述阳极10的厚度可以为约10nm至约100nm。
图2示出了本公开实施例的QLED中电子传输层的能级示意图。图2中，按照从左至右或从右至左的顺序，分别示出了第一能级结构层31、第二能级结构层32和第一能级结构层31的能级。如图2所示，第二能级结构层32的LUMO能级可高于第一能级结构层31的LUMO能级，该情况下，电子传输层3中会形成能级势垒，阻碍电子传输，降低电子传输速率。
为了使QLED中载流子(电子和空穴)注入平衡，所述第二能级结构层32的LUMO能级可高于所述第一能级结构层31的LUMO能级约0.1eV至约0.5eV。
作为示例，所述第一能级结构层31的材料可以为氧化锌(ZnO) 材料，其LUMO能级可以为约-4.8eV至约-4.6eV，所述第二能级结构层32的材料可以为掺杂镓元素(Ga)的氧化锌材料(下文以GZO表示)，其LUMO能级可以为约-4.6eV至约-4.3eV，该情况下，所述第二能级结构层32的LUMO能级可高于所述第一能级结构层31的LUMO能级。
图3示出了具有图2所示能级的电子传输层3的电流密度与电压之间的关系及相关技术中电子传输层的电流密度与电压之间的关系的示意图。
如图3所示，实线示出了相关技术中电子传输层的电流密度与电压之间的关系，虚线示出了具有图2所示能级的电子传输层3的电流密度与电压之间的关系。该示例中，相关技术中的电子传输层的材料为ZnO，具有图2所示能级的电子传输层3中，第一能级结构层31的材料为ZnO，第二能级结构层32的材料为GZO。如图3所示，相比于相关技术中的电子传输层，具有图2所示能级的电子传输层3的电流密度降低，即其电子传输速率降低。
图4示出了具有图2所示能级的电子传输层的电流效率与电压之间的关系及相关技术中电子传输层的电流效率与电压之间的关系的示意图。
如图4所示，实线示出了相关技术中电子传输层的电流效率与电压之间的关系，虚线示出了具有图2所示能级的电子传输层3的电流效率与电压之间的关系。该示例中，相关技术中的电子传输层的材料为ZnO，具有图2所示能级的电子传输层3中，第一能级结构层31的材料为ZnO，第二能级结构层32的材料为GZO。如图4所示，相比于相关技术中的电子传输层，具有图2所示能级的电子传输层3的电流效率虽然起初轻微降低，但后期有一定程度的提升。
图3和图4示出了第二能级结构层32的LUMO能级高于第一能级结构层31的LUMO能级的电子传输层3的电流密度与电压之间的关系以及电流效率与电压之间的关系。但是，如上所述，第二能级结构层32的LUMO能级也可低于第一能级结构层31的LUMO能级，该情况下，电子传输层3中会形成能级陷阱，阻碍电子传输，降低电子传输 速率。
为了使QLED中载流子(电子和空穴)注入平衡，所述第二能级结构层32的LUMO能级可低于所述第一能级结构层31的LUMO能级约0.1eV至约0.5eV。
而且，本公开实施例的QLED的电子传输层3中，第二能级结构层32的HOMO能级可高于第一能级结构层31的HOMO能级，如图2所示，但是，第二能级结构层32的HOMO能级也可低于第一能级结构层31的HOMO能级，本公开实施例对此不进行具体限定，本领域技术人员可根据需要进行选择。例如，电子传输层3还可以阻挡空穴到达阴极，从而减小空穴漏电流，因此，在适当设置所述第一能级结构层31和所述第二能级结构层32的LUMO能级以降低所述电子传输层3的电子传输速率的同时，还可以适当设置所述第一能级结构层31和所述第二能级结构层32的HOMO能级，以使得所述电子传输层3能够有效阻挡空穴到达阴极，从而减小空穴电流，进而使得QLED中的电子和空穴的注入更加平衡，QLED发光更加稳定。
图5示出了具有图2所示能级的电子传输层3中的第二能级结构层32的厚度与器件效率之间的关系的示意图。
以所述第一能级结构层31的材料为ZnO、所述第二能级结构层32的材料为GZO、且所述电子传输层3的总厚度为约60nm为例，如图5所示，所述第二能级结构层32的厚度为约20nm时，相应的QLED的器件效率较佳。
仍以所述第一能级结构层31的材料为ZnO、所述第二能级结构层32的材料为GZO为例，图6示出了本公开实施例的QLED中各层的能级关系的示意图，图7示出了随着Ga掺杂量的提高第二能级结构层32的带隙变化的示意图。
如图7所示，随着Ga掺杂量的提高，第二能级结构层32的带隙增大，导致第二能级结构层32的导电性变弱。
以上仅给出了所述第一能级结构层31的材料为ZnO、所述第二能级结构层32的材料为GZO的示例，事实上，只要满足所述第一能级结构层31的LUMO能级不同于所述第二能级结构层32的LUMO能级， 所述第一能级结构层31和所述第二能级结构层32的材料有多种选择。
例如，所述第一能级结构层31的材料可以为GZO、所述第二能级结构层32的材料可以为ZnO。
也就是说，所述第一能级结构层31和所述第二能级结构层32中的一者的材料可以为ZnO，另一者的材料可以为掺杂的ZnO。
作为选择，可以在ZnO中掺杂其氧化物的晶格常数与ZnO的晶格常数接近但又不完全相同的元素，和/或掺杂其电负性和半径与Zn不同的元素，例如，所述掺杂的ZnO中可掺杂有镓(Ga)、铟(In)、钇(Y)、铜(Cu)、锆(Zr)、铝(Al)、镁(Mg)中的至少一种或其任意组。如果所掺杂元素的氧化物的带隙大于ZnO的带隙，则掺杂的ZnO的带隙通常会增加，导电性变弱。
当然，所述第一能级结构层31和所述第二能级结构层32的材料也可均为掺杂的ZnO。所述第一能级结构层31的掺杂种类和所述第二能级结构层32的掺杂种类可相同或不同。所述第一能级结构层31的掺杂浓度和所述第二能级结构层32的掺杂浓度可相同或不同。
可通过调整所述第一能级结构层31和所述第二能级结构层32的材料、厚度等来调整所述第一能级结构层31和所述第二能级结构层32的能级，以至少使得所述第二能级结构层32的LUMO能级不同于所述第一能级结构层31的LUMO能级。
作为示例，所述掺杂的氧化锌中的掺杂浓度可以为0％至约50％。
图8至图10示出了本公开实施例的QLED中电子传输层的示例能级示意图。图8至图10所示的能级示意图所对应的电子传输层3均包括依次层叠的第一能级结构层31、第二能级结构层32和第一能级结构层31。
具体地，在一些实施方式中，如图8所示，所述第二能级结构层32的LUMO能级高于所述第一能级结构层31的LUMO能级，且所述第二能级结构层32的HOMO能级低于所述第一能级结构层31的HOMO能级，该情况下，电子传输层3中会形成能级势垒，阻碍电子传输，降低电子传输速率。
在一些实施方式中，如图9所示，所述第二能级结构层32的LUMO 能级低于所述第一能级结构层31的LUMO能级，且所述第二能级结构层32的HOMO能级低于所述第一能级结构层31的HOMO能级，该情况下，电子传输层3中会形成能级陷阱，阻碍电子传输，降低电子传输速率。
在一些实施方式中，如图10所示，所述第二能级结构层32的LUMO能级低于所述第一能级结构层31的LUMO能级，且所述第二能级结构层32的HOMO能级高于所述第一能级结构层31的HOMO能级，该情况下，电子传输层3中也会形成能级陷阱，阻碍电子传输，降低电子传输速率。
此外，如上所述，所述电子传输层3至少包括依次层叠的第一能级结构层31、第二能级结构层32和第一能级结构层31。在一些实施方式中，所述电子传输层3可包括层叠的多个第一能级结构层31和多个第二能级结构层32，各第能级结构层31和各第二能级结构层32可交替层叠，且所述电子传输层3的靠近所述阴极2的一侧和靠近所述量子点发光层的一侧均为所述第一能级结构层31或者所述第二能级结构层32。
例如，所述电子传输层3可包括依次层叠的第二能级结构层32、第一能级结构层31、第二能级结构层32、……、第一能级结构层31、以及第二能级结构层32，或者可包括依次层叠的第一能级结构层31、第二能级结构层32、第一能级结构层31、……、第二能级结构层32、以及第一能级结构层31。
所述电子传输层3的靠近所述阴极2一侧和靠近所述量子点发光层的一侧可以均为第一能级结构层31、或者所述电子传输层3的靠近所述阴极2一侧和靠近所述量子点发光层的一侧可以均为第二能级结构层32的情况下，可以确保在所述电子传输层3中的能级结构改变时，所述电子传输层3与所述阴极2之间的能级差以及所述电子传输层3与所述量子点发光层之间的能级差保持不变。
图11至图14示出了包括多个第一能级结构层31和多个第二能级结构层32的电子传输层3的示例能级示意图。
在一些实施方式中，如图11的左侧部分所示，所述电子传输层 3包括依次层叠的第二能级结构层32、第一能级结构层31、第二能级结构层32、……、第一能级结构层31、以及第二能级结构层32，所述第二能级结构层32的LUMO能级高于所述第一能级结构层31的LUMO能级，所述第二能级结构层32的HOMO能级低于所述第一能级结构层31的HOMO能级。
在一些实施方式中，如图11的右侧部分所示，所述电子传输层3包括依次层叠的第一能级结构层31、第二能级结构层32、第一能级结构层31、……、第二能级结构层32、以及第一能级结构层31，所述第二能级结构层32的LUMO能级高于所述第一能级结构层31的LUMO能级，所述第二能级结构层32的HOMO能级低于所述第一能级结构层31的HOMO能级。
在一些实施方式中，如图12的左侧部分所示，所述电子传输层3包括依次层叠的第二能级结构层32、第一能级结构层31、第二能级结构层32、……、第一能级结构层31、以及第二能级结构层32，所述第二能级结构层32的LUMO能级低于所述第一能级结构层31的LUMO能级，所述第二能级结构层32的HOMO能级低于所述第一能级结构层31的HOMO能级。
在一些实施方式中，如图12的右侧部分所示，所述电子传输层3包括依次层叠的第一能级结构层31、第二能级结构层32、第一能级结构层31、……第二能级结构层32、以及第一能级结构层31，所述第二能级结构层32的LUMO能级低于所述第一能级结构层31的LUMO能级，所述第二能级结构层32的HOMO能级低于所述第一能级结构层31的HOMO能级。
在一些实施方式中，如图13的左侧部分所示，所述电子传输层3包括依次层叠的第二能级结构层32、第一能级结构层31、第二能级结构层32、……、第一能级结构层31、以及第二能级结构层32，所述第二能级结构层32的LUMO能级高于所述第一能级结构层31的LUMO能级，所述第二能级结构层32的HOMO能级高于所述第一能级结构层31的HOMO能级。
在一些实施方式中，如图13的右侧部分所示，所述电子传输层 3包括依次层叠的第一能级结构层31、第二能级结构层32、第一能级结构层31、……、第二能级结构层32、以及第一能级结构层31，所述第二能级结构层32的LUMO能级高于所述第一能级结构层31的LUMO能级，所述第二能级结构层32的HOMO能级高于所述第一能级结构层31的HOMO能级。
在一些实施方式中，如图14的左侧部分所示，所述电子传输层3包括依次层叠的第二能级结构层32、第一能级结构层31、第二能级结构层32、……、第一能级结构层31、以及第二能级结构层32，所述第二能级结构层32的LUMO能级低于所述第一能级结构层31的LUMO能级，所述第二能级结构层32的HOMO能级高于所述第一能级结构层31的HOMO能级。
在一些实施方式中，如图14的右侧部分所示，所述电子传输层3包括依次层叠的第一能级结构层31、第二能级结构层32、第一能级结构层31、……、第二能级结构层32、以及第一能级结构层31，所述第二能级结构层32的LUMO能级低于所述第一能级结构层31的LUMO能级，所述第二能级结构层32的HOMO能级高于所述第一能级结构层31的HOMO能级。
图15(a)和图15(b)示出了本公开实施例的QLED中电子传输层的表面粗糙度的示意图。
本公开实施例的QLED中电子传输层的表面粗糙度可通过原子力显微镜(AFM)测得，表面粗糙度的RMS(root mean square，均方根)数值范围可控制为约1nm至约10nm，更具体地，可以为约0.2nm至约8nm，如图15(a)所示，或者可以为约1.1nm至约8.9nm，如图15(b)所示。
本公开实施例还提供一种量子点发光二极管的制备方法，该方法可用于制备上述实施例中的量子点发光二极管。
图16示出了本公开实施例的量子点发光二极管的制备方法的流程图。结合图1和图16，本公开实施例的量子点发光二极管的制备方法包括如下步骤S1至S7。
S1，在衬底1上形成阴极2的图案。
具体地，所述衬底1可以是例如玻璃、或者是柔性PET衬底，所述阴极2可以是透明的ITO、FTO或者导电聚合物等材料制备的电极，或者也可以是不透明的Al、Ag等金属制备的电极。
例如，可通过磁控溅射、溶胶-凝胶、原子层沉积、蒸镀等方式在衬底1上沉积导电材料层(例如形成ITO或者FTO薄膜)，然后通过构图工艺进行图案化以形成所述阴极2的图案，所述阴极2的厚度(垂直于所述衬底1所在平面的尺寸)可以为约10nm至约100nm。
S2，在所述阴极2上形成作为电子传输层3的第一部分的第一能级结构层31。
具体地，可通过磁控溅射、溶胶-凝胶、原子层沉积、蒸镀等方式在所述阴极2上沉积ZnO或掺杂的ZnO薄膜，作为电子传输层3的第一部分。
所述第一能级结构层31的厚度可以为约5nm至约50nm之间。
S3，在所述第一能级结构层31上形成作为电子传输层3的第二部分的第二能级结构层32。
具体地，可通过磁控溅射、溶胶-凝胶、原子层沉积、蒸镀等方式在所述第一能级结构层31上沉积掺杂的ZnO或ZnO薄膜，作为电子传输层3的第二部分。
例如，在所述第一能级结构层31的材料为ZnO的情况下，所述第二能级结构层32的材料可以为掺杂的ZnO；以及在所述第一能级结构层31的材料为掺杂的ZnO的情况下，所述第二能级结构层32的材料可以为ZnO或者掺杂的ZnO。
所述第二能级结构层32的厚度可以为10nm至50nm之间。
S4，在所述第二能级结构层32上形成作为电子传输层3的第三部分的第一能级结构层31。
具体地，可通过磁控溅射、溶胶-凝胶、原子层沉积、蒸镀等方式在所述第二能级结构层32上沉积ZnO或掺杂的ZnO薄膜，作为电子传输层3的第三部分。
作为所述电子传输层3的第一部分的第一能级结构层31、作为所述电子传输层3的第二部分的第二能级结构层32、以及作为所述 电子传输层3的第三部分的第一能级结构层31构成完整的电子传输层3。
所述第二能级结构层32的两侧的第一能级结构层31的材料、厚度可相同或不同，只要能够使得所述第二能级结构层32的LUMO能级不同于所述第一能级结构层31的LUMO能级即可。
作为示例，上述掺杂的ZnO中的掺杂元素可以为Ga、In、Y、Cu、Zr、Al、Mg元素中的至少一种或其任意组合，掺杂浓度可以为0％至约50％，本领域技术人员可根据需要进行选择。
例如，所述掺杂的ZnO可以为掺杂Ga元素的掺杂浓度为20％的GZO。
本公开实施例中，通过磁控溅射、溶胶-凝胶、原子层沉积、蒸镀等方式形成阴极2及电子传输层3，可以使得所形成的阴极2及电子传输层3的膜层的厚度相对均匀。
S5，在所述电子传输层3上形成量子点发光层。
具体地，可通过打印(例如喷墨打印)方式在所述电子传输层3上形成量子点发光层。例如，所述量子点发光层可以为红色量子点发光层5、绿色量子点发光层6、蓝色量子点发光层7等，其厚度可以为约20nm至约50nm，各颜色的量子点发光层的厚度可能不同。
通过打印方式形成所述量子点发光层，有利于量子点材料的有效利用、及大面积制备所述量子点发光层。
当然，在形成各颜色的量子点发光层之前，还可以形成像素限定层4，本公开实施例对像素限定层4的形成方法及材料不进行具体限定。例如，可通过光刻工艺形成所述像素限定层4。
S6，在所述量子点发光层上依次形成空穴传输层8和空穴注入层9。
具体地，可通过旋涂、蒸镀等方式，依次沉积所述空穴传输层8和所述空穴传输层9。
应当理解，步骤S6为可选步骤。在一些实施方式中，可不形成所述空穴传输层8和所述空穴注入层9。
此外，本公开实施例对所述空穴传输层8和所述空穴注入层9 的材料和厚度不进行具体限定。
S7，在所述空穴注入层9上形成阳极10。
具体地，可以通过磁控溅射、溶胶-凝胶、原子层沉积、蒸镀等方式形成所述阳极10，所述阳极10的材料可以为氧化铟锌(IZO)、金属铝(Al)或银(Ag)等，所述阳极10的厚度可以为约10nm至约100nm。
利用本公开实施例的量子点发光二极管的制备方法所制备的量子点发光二极管中，所述电子传输层3中会形成能级陷阱或能级势垒，阻碍电子传输，降低电子传输速率，可有效地平衡QLED中的载流子(电子和空穴)的注入，能够一定程度上确保QLED的性能(例如发光效率)。
本公开实施例还提供一种显示装置，所述显示装置包括显示基板，所述显示基板包括以阵列形式排布的多个QLED，所述多个QLED中的部分或全部为上述本公开实施例中的QLED。
由于采用了本公开实施例中的QLED，本公开实施例的显示装置的显示效果较好。
本公开实施例的显示装置可以为电子纸、OLED面板、QLED面板、手机、平板电脑、电视机、显示器、笔记本电脑、数码相框、导航仪等具有显示功能的任何产品或部件。
可以理解的是，以上实施方式仅仅是为了说明本公开的原理而采用的示例性实施方式，然而本公开并不局限于此。对于本领域内的普通技术人员而言，在不脱离本公开的精神和实质的情况下，可以做出各种变型和改进，这些变型和改进也视为落入本公开的保护范围。

Claims (22)

  1. 一种量子点发光二极管，包括阳极层、阴极层、所述阳极层与所述阴极层之间的量子点发光层、以及所述阴极层与所述量子点发光层之间的电子传输层，其中，
    所述电子传输层至少包括依次层叠的第一能级结构层、第二能级结构层和第一能级结构层，所述第一能级结构层不同于第二能级结构层，且所述第一能级结构层的最低未占分子轨道能级不同于所述第二能级结构层的最低未占分子轨道能级。
  2. 根据权利要求1所述的量子点发光二极管，其中，所述第一能级结构层的最低未占分子轨道能级高于所述第二能级结构层的最低未占分子轨道能级。
  3. 根据权利要求1所述的量子点发光二极管，其中，所述第一能级结构层的最低未占分子轨道能级低于所述第二能级结构层的最低未占分子轨道能级。
  4. 根据权利要求2或3所述的量子点发光二极管，其中，所述第一能级结构层与所述第二能级结构层的最低未占分子轨道能级之间相差0.1eV至0.5eV。
  5. 根据权利要求1所述的量子点发光二极管，其中，所述电子传输层的厚度为20nm至150nm。
  6. 根据权利要求1所述的量子点发光二极管，其中，所述第一能级结构层和所述第二能级结构层中的至少一者的材料为掺杂的氧化锌。
  7. 根据权利要求1所述的量子点发光二极管，其中，所述第一 能级结构层和所述第二能级结构层中的一者的材料为氧化锌，另一者的材料为掺杂的氧化锌。
  8. 根据权利要求6或7所述的量子点发光二极管，其中，所述掺杂的氧化锌中掺杂的元素包括镓、铟、钇、铜、锆、铝、镁中的至少一种或其任意组合。
  9. 根据权利要求6或7所述的量子点发光二极管，其中，所述掺杂的氧化锌中的掺杂浓度为0％至50％。
  10. 根据权利要求1所述的量子点发光二极管，其中，所述电子传输层包括多个第一能级结构层和多个第二能级结构层，所述第一能级结构层和所述第二能级结构层交替层叠，且所述电子传输层的靠近所述阴极的一侧和靠近所述量子点发光层的一侧均为所述第一能级结构层或者所述第二能级结构层。
  11. 根据权利要求1所述的量子点发光二极管，其中，所述电子传输层的表面粗糙度的均方根数值范围为1nm至10nm。
  12. 根据权利要求1所述的量子点发光二极管，还包括空穴传输层和空穴注入层，其中，
    所述阴极层、所述电子传输层、所述量子点发光层、所述空穴传输层、所述空穴注入层及所述阳极层依次层叠设置在衬底上。
  13. 一种制备量子点发光二极管的方法，包括形成阳极层、阴极层、所述阳极层与所述阴极层之间的量子点发光层、以及所述阴极层与所述量子点发光层之间的电子传输层的步骤，其中，
    形成所述电子传输层的步骤包括：
    形成依次层叠的第一能级结构层、第二能级结构层和第二能级结构层，所述第一能级结构层不同于第二能级结构层，且所述第一能 级结构层的最低未占分子轨道能级不同于所述第二能级结构层的最低未占分子轨道能级。
  14. 根据权利要求13所述的方法，其中，形成依次层叠的第一能级结构层、第二能级结构层和第一能级结构层包括：
    通过溅射法、溶胶凝胶法、或原子层沉积法形成所述第一能级结构层、所述第二能级结构层和所述第一能级结构层。
  15. 根据权利要求13所述的方法，还包括：
    通过打印方式在所述电子传输层上形成所述量子点发光层；以及
    通过蒸镀方式在所述量子点发光层上依次沉形成空穴传输层和空穴注入层。
  16. 根据权利要求13所述的方法，其中，所述电子传输层形成为使得所述第一能级结构层的最低未占分子轨道能级与所述第二能级结构层的最低未占分子轨道能级之间的差为0.1eV至0.5eV。
  17. 根据权利要求13所述的方法，其中，形成依次层叠的第一能级结构层、第二能级结构层和第一能级结构层包括：
    采用掺杂的氧化锌材料形成所述第一能级结构层和所述第二能级结构层中的至少一者。
  18. 根据权利要求13所述的方法，其中，形成依次层叠的第一能级结构层、第二能级结构层和第一能级结构层包括：
    采用氧化锌材料形成所述第一能级结构层和所述第二能级结构层中的一者；以及
    采用掺杂的氧化锌材料形成所述第一能级结构层和所述第二能级结构层中的另一者。
  19. 根据权利要求17或18所述的方法，其中，采用掺杂的氧化锌材料包括：
    采用掺杂有镓、铟、钇、铜、锆、铝、镁中的至少一种或其任意组合的掺杂的氧化锌材料。
  20. 根据权利要求17或18所述的方法，其中，采用掺杂的氧化锌材料包括：
    采用掺杂浓度为0％至50％的掺杂的氧化锌材料。
  21. 根据权利要求13所述的方法，其中，形成依次层叠的第一能级结构层、第二能级结构层和第二能级结构层包括：
    形成多个第一能级结构层和多个第二能级结构层，所述第一能级结构层和所述第二能级结构层交替层叠，且所述电子传输层的靠近所述阴极的一侧和靠近所述量子点发光层的一侧均为所述第一能级结构层或者所述第二能级结构层。
  22. 一种显示装置，包括显示基板，所述显示基板包括以阵列形式排布的多个量子点发光二极管，其中，所述多个量子点发光二极管包括根据权利要求1至12中任一项所述的量子点发光二极管。
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CN105679958A (zh) * 2016-04-20 2016-06-15 京东方科技集团股份有限公司 电致发光器件及其制作方法、显示装置
CN109148704A (zh) * 2018-08-20 2019-01-04 纳晶科技股份有限公司 量子点电致发光器件及其制备方法
CN111435710A (zh) * 2019-01-15 2020-07-21 三星电子株式会社 量子点器件和电子设备
WO2020256431A1 (ko) * 2019-06-21 2020-12-24 두산솔루스 주식회사 유기 전계 발광 소자

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