CN114695714A - Quantum dot light-emitting diode and preparation method thereof - Google Patents

Quantum dot light-emitting diode and preparation method thereof Download PDF

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CN114695714A
CN114695714A CN202011636185.7A CN202011636185A CN114695714A CN 114695714 A CN114695714 A CN 114695714A CN 202011636185 A CN202011636185 A CN 202011636185A CN 114695714 A CN114695714 A CN 114695714A
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layer
quantum dot
dot light
hole transport
transport layer
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严怡然
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TCL Technology Group Co Ltd
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K30/00—Organic devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation
    • H10K30/80—Constructional details
    • H10K30/865—Intermediate layers comprising a mixture of materials of the adjoining active layers
    • H—ELECTRICITY
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    • 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
    • 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
    • H10K50/00—Organic light-emitting devices
    • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
    • H10K50/14—Carrier transporting layers
    • H10K50/15—Hole transporting layers
    • H—ELECTRICITY
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    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K71/00—Manufacture or treatment specially adapted for the organic devices covered by this subclass
    • H—ELECTRICITY
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    • 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

Abstract

The invention discloses a quantum dot light-emitting diode and a preparation method thereof, wherein the quantum dot light-emitting diode comprises a quantum dot light-emitting layer arranged between a cathode and an anode, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein an interface layer is arranged between the hole transport layer and the quantum dot light-emitting layer, and the interface layer is made of lithium nitride or lithium nitride doped with halogen lithide; the HOMO energy level of the interface layer is larger than that of the hole transport layer and smaller than that of the quantum dot light emitting layer. According to the invention, the interface layer can effectively reduce a hole injection barrier, improve the hole injection rate, and simultaneously effectively prevent electrons from tunneling and holes from being compounded in a non-quantum dot light-emitting area, thereby improving the light-emitting efficiency of the device.

Description

Quantum dot light-emitting diode and preparation method thereof
Technical Field
The invention relates to the field of quantum dots, in particular to a quantum dot light-emitting diode and a preparation method thereof.
Background
The quantum dot light emitting diode (QLED) has the advantages of high color purity, narrow half-height peak width, high luminous efficiency, adjustable luminous color, stable device and the like, so that the quantum dot light emitting diode has wide application prospect in the fields of flat panel display, solid state lighting and the like. With the continuous progress of research and development, the External Quantum Efficiency (EQE) of the quantum dot light emitting diode has been significantly improved, wherein the external quantum efficiency of both the red light quantum dot light emitting diode and the green light quantum dot light emitting diode is higher than 25%, which is comparable to that of an Organic Light Emitting Diode (OLED) in efficiency, but the external quantum efficiency and the lifetime of the blue light quantum dot light emitting diode are still not sufficient.
Similar to the OLED device, the QLED device structure generally includes an anode, a hole injection layer, a hole transport layer, a quantum dot light emitting layer, an electron transport layer, and a cathode, where electrons and holes are injected from two ends of the cathode and the anode, respectively, and the quantum dot light emitting layer emits light compositely. The existing electron transport layer is usually composed of nano zinc oxide particles, and has higher carrier concentration and mobility; organic polymer materials used in the hole transport layer, such as PVK, TFB, etc., are difficult to inject holes due to low carrier mobility of the hole transport layer and too deep energy level of the quantum dots, so that holes are accumulated in the hole transport layer for a long time or in the interface layer between the hole transport layer and the quantum dot light emitting layer, and excessive injection of electrons causes the holes to easily jump to the hole transport layer or the interface layer between the hole transport layer and the quantum dot light emitting layer, and finally recombination of the electrons and the holes occurs in the non-light emitting layer, which seriously affects the efficiency and the service life of the QLED device.
Therefore, the prior art is still to be improved.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, the present invention is directed to a quantum dot light emitting diode and a method for manufacturing the same, which is intended to solve the problem of low light emitting efficiency of the prior quantum dot light emitting diode.
The technical scheme of the invention is as follows:
a quantum dot light-emitting diode comprises a cathode, an anode, a quantum dot light-emitting layer arranged between the cathode and the anode, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, wherein an interface layer is arranged between the hole transport layer and the quantum dot light-emitting layer, and the interface layer is made of lithium nitride or lithium nitride doped with halogen lithiide; the HOMO energy level of the interface layer is larger than that of the hole transport layer and smaller than that of the quantum dot light emitting layer.
A preparation method of a quantum dot light-emitting diode comprises the following steps:
providing an anode substrate, and forming a hole transport layer on the anode substrate;
preparing an interface layer on the hole transport layer, wherein the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound;
preparing a quantum dot light-emitting layer on the interface layer;
preparing a cathode at the quantum dot light-emitting layer to prepare the quantum dot light-emitting diode;
or, providing a cathode substrate on which a quantum dot light emitting layer is prepared;
preparing an interface layer on the surface of the quantum dot light-emitting layer, wherein the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound;
preparing a hole transport layer on the interface layer;
and preparing an anode on the hole transport layer to obtain the quantum dot light-emitting diode.
Has the advantages that: according to the invention, the interface layer is arranged between the hole transport layer and the quantum dot light-emitting layer, and the HOMO energy level of the interface layer is positioned between the HOMO energy levels of the hole transport layer and the quantum dot light-emitting layer, so that the injection barrier of holes can be effectively reduced, and the decline of materials and devices caused by the accumulation of the holes at the barrier interface is reduced; the interface layer can also effectively block electron tunneling, and electrons and holes are prevented from being compounded in the non-quantum dot light-emitting layer, so that the light-emitting efficiency of the quantum dot light-emitting diode is improved.
Drawings
Fig. 1 is a schematic structural diagram of a quantum dot light emitting diode with a positive structure according to a preferred embodiment of the invention.
Fig. 2 is a schematic structural diagram of a quantum dot light emitting diode with an inversion structure according to a preferred embodiment of the invention.
Fig. 3 is a flowchart of a method for manufacturing a quantum dot light emitting diode with a positive structure according to a preferred embodiment of the present invention.
Fig. 4 is a flowchart of a method for manufacturing an inversion-structure quantum dot light emitting diode according to a preferred embodiment of the present invention.
Detailed Description
The invention provides a quantum dot light-emitting diode and a preparation method thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Quantum dot emitting diode has multiform, just quantum dot emitting diode divide into formal structure and trans structure, the quantum dot emitting diode of anti-type structure can include from down up range upon range of base plate, negative pole, quantum dot luminous layer, hole transport layer and the positive pole that sets up from down. The embodiments of the present invention will be described mainly by taking a quantum dot light emitting diode of a positive type structure as shown in fig. 1 as an example. Specifically, the positive quantum dot light emitting diode includes an anode disposed on a surface of a substrate, a hole transport layer disposed on a surface of the anode, an interface layer disposed on a surface of the hole transport layer, a quantum dot light emitting layer disposed on the interface layer, and a cathode disposed on a surface of the quantum dot light emitting layer, where the interface layer is made of lithium nitride or lithium halide doped lithium nitride, and a HOMO level of the interface layer is greater than a HOMO level of the hole transport layer and less than a HOMO level of the quantum dot light emitting layer.
Specifically, since a large potential barrier exists between the highest occupied energy level (HOMO) of the commonly used hole transport layer and the work function of the quantum dot light emitting layer, it is difficult to inject holes from the hole transport layer into the quantum dot light emitting layer, resulting in an imbalance between injection of holes and electrons, which seriously affects the light emitting efficiency of the quantum dot light emitting diode. In the embodiment, the interface layer prepared by lithium nitride or lithium halide doped lithium nitride is arranged between the hole transport layer and the quantum dot light emitting layer, the HOMO energy level of the interface layer is greater than that of the hole transport layer and less than that of the quantum dot light emitting layer, and the interface layer can effectively reduce the injection barrier of holes, so that the recession of materials and devices caused by the accumulation of the holes at the barrier interface is reduced, the light emitting efficiency of the quantum dot light emitting diode is effectively improved, and the service life of the quantum dot light emitting diode is prolonged. The HOMO level in this embodiment refers to the absolute value of the HOMO level. That is to say, in this embodiment, the absolute value of the HOMO level of the interface layer is greater than the absolute value of the HOMO level of the hole transport layer and less than the absolute value of the HOMO level of the quantum dot light emitting layer.
Further, since the energy level barrier between the electron transport material and the quantum dot light emitting layer is usually small, electron injection is easy to occur, which causes that part of electrons easily tunnel to the hole transport layer or the interface between the hole transport layer and the quantum dot light emitting layer and are recombined with holes in the non-quantum dot light emitting layer region, thereby affecting the overall light emitting efficiency of the quantum dot light emitting diode. This embodiment provides an interfacial layer comprising lithium nitride or lithium halide doped lithium nitride having the property of conducting ions and holes but not conducting electrons, between the hole transport layer and the quantum dot light emitting layer, and the lithium nitride or lithium halide doped lithium nitride having the ion and hole conductivity at normal temperature>10-3S/cm, the electronic conductivity of the quantum dot light-emitting diode is more than four orders of magnitude smaller than that of the ions/holes, therefore, the lithium nitride or the lithium halide doped lithium nitride can not only effectively assist hole injection, but also effectively prevent electrons from tunneling to the hole transport layer, and prevent the device from emitting light in a non-light-emitting region, thereby improving the overall light-emitting efficiency of the quantum dot light-emitting diode.
Furthermore, because the hole transport layer of the quantum dot light emitting diode is usually made of an organic material, such as PEDOT (polythiophene), which is sensitive to water and oxygen, and the stability of hole injection and transmission is affected by the gradual permeation of water and oxygen from the encapsulation adhesive, the interface layer formed by lithium nitride or lithium halogen-doped lithium nitride is arranged between the hole transport layer and the quantum dot light emitting layer, so that the permeation of water and oxygen can be further effectively prevented, and the service life of the device can be prolonged.
In some embodiments, the lithium nitride doped with the halogen lithium compound may be LiCl, LiBr or LiI doped lithium nitride, and the chemical stability of the lithium nitride may be effectively improved by doping the halogen lithium compound.
In some embodiments, the interface layer has a thickness of 10 to 200nm, and in this range, the interface layer can increase the injection rate of holes and block the tunneling of electrons. If the thickness of the interface layer is less than 10nm, the effect of blocking electron tunneling to the hole transport layer is poor; if the thickness of the interface layer is larger than 200nm, the injection distance of the hole is increased, and the efficiency of hole transmission to the quantum dot light-emitting layer is influenced.
In some embodiments, the HOMO level of the interfacial layer is 4.9-6.0 eV. In this embodiment, since the HOMO level of the hole transport layer is usually 4.9 to 5.4eV, the HOMO level of the quantum dot light emitting layer is usually 5.9 to 6.5eV, and the HOMO level of the interface layer is located between the HOMO levels of the hole transport layer and the quantum dot light emitting layer, an injection barrier of a hole can be effectively reduced, and an injection rate of a hole is promoted, so that material and device recession caused by accumulation of a hole at a barrier interface is reduced, and the light emitting efficiency and the service life of the quantum dot light emitting diode are effectively improved. By way of example, when TFB (HOMO level 5.4eV) is used as the hole transport layer material and Cds-ZnSe quantum dots (HOMO level 5.9-6.1eV) are used as the quantum dot light emitting layer material, the HOMO level of the interface layer at this time may be 5.4-6 eV.
In some embodiments, the interface layer material is Li3And N is added. In this example, the Li3The HOMO energy level of N is positioned between the HOMO energy levels of the hole transport layer and the quantum dot light-emitting layer, so that the interface layer can effectively reduce the injection barrier of holes and promote the injection rate of the holes, thereby reducing the decline of materials and devices caused by the accumulation of the holes at the barrier interface, effectively improving the light-emitting efficiency of the quantum dot light-emitting diode and prolonging the service life of the quantum dot light-emitting diode.
In some embodiments, the hole transport layer material is selected from Poly (9, 9-dioctylfluorene-CO-N- (4-butylphenyl) diphenylamine) (TFB), Polyvinylcarbazole (PVK), Poly (N, N ' bis (4-butylphenyl) -N, N ' -bis (phenyl) benzidine) (Poly-TPD), Poly (9, 9-dioctylfluorene-CO-bis-N, N-phenyl-1, 4-Phenylenediamine) (PFB), 4', 4 ″ -tris (carbazol-9-yl) triphenylamine (TCTA), 4' -bis (9-Carbazole) Biphenyl (CBP), N ' -diphenyl-N, N ' -bis (3-methylphenyl) -1,1 ' -biphenyl-4, 4' -diamine (TPD), N ' -diphenyl-N, N ' - (1-naphthyl) -1,1 ' -biphenyl-4, 4' -diamine (NPB), but is not limited thereto.
In some embodiments, the quantum dot light emitting layer is selected from one or more of binary phase quantum dots, ternary phase quantum dots, and quaternary phase quantum dots, but is not limited thereto. By way of example, the binary phase quantum dots are at least one of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, HgS; and/or the ternary phase quantum dots are ZnXCd1-XS、CuXIn1- XS、ZnXCd1-XSe、ZnXSe1-XS、ZnXCd1-XTe、PbSeXS1-XAt least one of; and/or the quaternary phase quantum dots are ZnXCd1-XS/ZnSe、CuXIn1-XS/ZnS、ZnXCd1-XSe/ZnS、CuInSeS、ZnXCd1-XTe/ZnS、PbSeXS1-XAt least one of/ZnS, wherein 0<X<1。
In some embodiments, an electron functional layer including, but not limited to, a hole blocking layer, an electron injection layer, and an electron transport layer is disposed between the quantum dot light emitting layer and the cathode.
In some embodiments, the electron transport layer material is selected from ZnO, TiO, NiO, W2O3、Mo2O3、TiO2、SnO、ZrO2And Ta2O3But is not limited thereto.
In some modes, a hole injection layer is further disposed between the anode and the hole transport layer.
In some embodiments, the hole injection layer is PEDOT PSS, WO3、MoO3And V2O5But is not limited thereto.
In some embodiments, the hole injection layer has a thickness of 30 to 120 nm.
In some embodiments, the cathode may be Au, Ag, Al, Cu, Mo, or an alloy thereof, but is not limited thereto.
In some embodiments, the anode has a thickness of 5 to 120 nm.
In some embodiments, the hole transport layer has a thickness of 30-120 nm.
In some embodiments, the quantum dot light emitting layer has a thickness of 10 to 200 nm.
In some embodiments, the electron transport layer has a thickness of 5 to 100 nm; the thickness of the cathode is 5-120 nm.
In some embodiments, the anode is one or more of ITO, FTO, ATO, AZO, GZO, IZO, MZO, AMO, but is not limited thereto.
In some embodiments, the present invention further provides an inverted quantum dot light emitting diode, as shown in fig. 2, the inverted quantum dot light emitting diode includes a cathode disposed on a surface of a substrate, a quantum dot light emitting layer disposed on a surface of the cathode, an interface layer disposed on a surface of the quantum dot light emitting layer, a hole transport layer disposed on a surface of the interface layer, and an anode disposed on a surface of the hole transport layer, wherein the interface layer material is lithium nitride or lithium halide doped lithium nitride; the HOMO energy level of the interface layer is larger than that of the hole transport layer and smaller than that of the quantum dot light emitting layer.
In the embodiment, the interface layer prepared by lithium nitride or lithium halide doped lithium nitride is arranged between the hole transport layer and the quantum dot light emitting layer, the HOMO energy level of the interface layer is greater than that of the hole transport layer and less than that of the quantum dot light emitting layer, and the interface layer can effectively reduce the injection barrier of holes, so that the recession of materials and devices caused by the accumulation of the holes at the barrier interface is reduced, the light emitting efficiency of the quantum dot light emitting diode is effectively improved, and the service life of the quantum dot light emitting diode is prolonged. The interface layer material is lithium nitride or lithium nitride doped with halogen lithium compound, and the lithium nitride or lithium nitride doped with halogen lithium compound has the performance of conducting ions and holes but not conducting electrons, so that the lithium nitride or lithium nitride doped with halogen lithium compound can not only effectively assist hole injection, but also effectively prevent electrons from tunneling to a hole transport layer, and prevent a device from emitting light in a non-light-emitting region, thereby improving the overall luminous efficiency of the quantum dot light-emitting diode.
In some embodiments, there is also provided a method for preparing a quantum dot light emitting diode with a positive structure as shown in fig. 1, as shown in fig. 3, which includes the steps of:
s10, providing an anode substrate, and forming a hole transport layer on the anode substrate;
s20, preparing an interface layer on the hole transport layer, wherein the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound;
s30, preparing a quantum dot light-emitting layer on the interface layer;
and S40, preparing a cathode at the quantum dot light-emitting layer to obtain the quantum dot light-emitting diode.
In this embodiment, the above-mentioned layers may be prepared by a chemical method or a physical method, wherein the chemical method includes, but is not limited to, one or more of a chemical vapor deposition method, a continuous ion layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method, and a coprecipitation method; physical methods include, but are not limited to, physical coating methods or solution methods, wherein solution methods include, but are not limited to, spin coating, printing, knife coating, dip-coating, dipping, spraying, roll coating, casting, slot coating, bar coating; physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition.
In some embodiments, the interface layer is formed on the hole transport layer by spin coating, which specifically includes the steps of: dispersing the lithium nitride or the lithium halide doped lithium nitride in an organic solvent to prepare a lithium nitride solution or a lithium halide doped lithium nitride solution; and spin-coating the lithium nitride solution or the lithium nitride solution doped with the halogen lithium compound on the surface of the hole transport layer, and carrying out thermal annealing at 100 ℃ for 30 minutes to obtain the interface layer. In this embodiment, the organic solvent includes ethanol, methanol, butanol, acetone, isopropyl ketone, butyronitrile, chlorobenzene, toluene, xylene, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, ethyl acetate, and the like, but is not limited thereto. In this embodiment, the concentration of the lithium nitride solution or the lithium halide doped lithium nitride solution is 1 to 2 wt%, and in this concentration range, the prepared interface layer can reduce the interface impedance and can effectively improve the light emitting performance of the quantum dot light emitting diode.
In some embodiments, there is also provided a method for preparing a quantum dot light emitting diode having an inversion structure, which includes the steps of: the invention also provides a preparation method of the inverted-structure QLED shown in FIG. 2, which comprises the following steps as shown in FIG. 4:
s100, providing a cathode substrate, and preparing a quantum dot light-emitting layer on the cathode substrate;
s200, preparing an interface layer on the surface of the quantum dot light-emitting layer, wherein the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound;
s300, preparing a hole transport layer on the interface layer;
s400, preparing an anode on the hole transport layer to obtain the quantum dot light-emitting diode.
In one embodiment of the present invention, the cathode substrate includes a substrate, a bottom electrode disposed on the substrate, the bottom electrode being a cathode; in still another embodiment of the present invention, the cathode substrate may include a substrate, a bottom electrode stacked on a surface of the substrate, and an electron injection layer stacked on the surface of the substrate; in still another embodiment of the present invention, the cathode substrate may include a substrate, a bottom electrode stacked on a surface of the substrate, an electron injection layer stacked on the surface of the substrate, and an electron transport layer stacked on a surface of the electron injection layer; in still another embodiment of the present invention, the anode substrate may include a substrate, a bottom electrode stacked on a surface of the substrate, an electron injection layer stacked on a surface of the substrate, an electron transport layer stacked on a surface of the electron injection layer, and a hole blocking layer stacked on a surface of the electron transport layer.
The preparation method of each layer can be a chemical method or a physical method, wherein the chemical method comprises one or more of but not limited to a chemical vapor deposition method, a continuous ion layer adsorption and reaction method, an anodic oxidation method, an electrolytic deposition method and a coprecipitation method; physical methods include, but are not limited to, physical coating methods or solution methods, wherein solution methods include, but are not limited to, spin coating, printing, knife coating, dip-coating, dipping, spraying, roll coating, casting, slot coating, bar coating; physical coating methods include, but are not limited to, one or more of thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition.
The following is a further explanation of a quantum dot light emitting diode and a method for manufacturing the same according to the present invention by way of specific examples:
example 1
A preparation method of a quantum dot light-emitting diode with a positive bottom emission structure comprises the following steps:
step S1: depositing a hole injection layer on a transparent anode substrate, wherein the transparent anode is ITO, and the material of the hole injection layer is WO3The thickness of the transparent anode is 20nm, and the thickness of the hole injection layer is 60 nm;
step S2: depositing a hole transport layer on the hole injection layer, wherein the hole transport layer is made of PFB (PFB), and the thickness of the hole transport layer is 60 nm;
step S3: depositing an interface layer on the hole transport layer, wherein the interface layer is made of Li3N, the thickness of the interface layer is 100 nm;
step S4: depositing a quantum dot light-emitting layer on the interface layer, wherein the quantum dot light-emitting layer is made of PbSe, and the thickness of the quantum dot light-emitting layer is 50 nm;
step S5: depositing an electron transport layer on the quantum dot light-emitting layer, wherein the electron transport layer is made of TiO and has a thickness of 60 nm;
step S6: and depositing a metal cathode on the electron transport layer, wherein the cathode is made of Ag, the thickness of the cathode is 100nm, and the reflection of the cathode to visible light is not less than 98%.
Example 2
A preparation method of a quantum dot light-emitting diode with a positive top emission structure comprises the following steps:
step S1: depositing a hole injection layer on a transparent anode substrate, wherein the transparent anode is FTO, and the material of the hole injection layer is WO3The thickness of the transparent anode is 20nm, and the thickness of the hole injection layer is 60 nm;
step S2: depositing a hole transport layer on the hole injection layer, wherein the material of the hole transport layer is TCTA, and the thickness of the hole transport layer is 60 nm;
step S3: depositing an interface layer on the hole transport layer, wherein the interface layer is made of Li3N, the thickness of the interface layer is 100 nm;
step S4: depositing a quantum dot light-emitting layer on the interface layer, wherein the quantum dot light-emitting layer is made of InP, and the thickness of the quantum dot light-emitting layer is 50 nm;
step S5: depositing an electron transport layer on the quantum dot light-emitting layer, wherein the electron transport layer is made of NiO, and the thickness of the electron transport layer is 60 nm;
step S6: and depositing a cathode on the electron transport layer, wherein the cathode is made of Ag, the thickness of the cathode is 100nm, and the transmission of the cathode to visible light is not less than 90%.
Example 3
A preparation method of a quantum dot light-emitting diode with an inverted bottom emission structure comprises the following steps:
step S1: depositing an Ag layer on the substrate in an evaporation mode, wherein the thickness of the Ag layer is 5 nm;
step S2: depositing an electron transport layer on the Ag layer, wherein the electron transport layer is made of SnO, and the thickness of the electron transport layer is 50 nm;
step S3: depositing a quantum dot light-emitting layer on the electron transport layer, wherein the quantum dot light-emitting layer is made of CdSe, and the thickness of the quantum dot light-emitting layer is 50 nm;
step S4: depositing an interface layer on the quantum dot light-emitting layer, wherein the interface layer is made of Li3N, the thickness of the interface layer is 80 nm;
step S5: depositing a hole transport layer on the interface layer, wherein the hole transport layer is made of PVK (polyvinyl pyrrolidone), and the thickness of the hole transport layer is 80 nm;
step S6: a hole injection layer is deposited on the hole transport layer, the material of the hole injection layer is PEDOT, PSS, and the thickness of the hole injection layer is 60 nm;
step S7: depositing an anode on the hole injection layer, wherein the anode is made of ITO (indium tin oxide) and the thickness of the anode is 120 nm; the anode has a visible light reflection of no less than 98%.
Example 4
A preparation method of a quantum dot light-emitting diode with an inverted top emission structure comprises the following steps:
step S1: depositing an Ag layer on the substrate in an evaporation mode, wherein the thickness of the Ag layer is 5 nm;
step S2: depositing an electron transport layer on the Ag layer, wherein the electron transport layer is made of TiO, and the thickness of the electron transport layer is 60 nm;
step S3: depositing a quantum dot luminescent layer on the electron transport layer, wherein the material of the quantum dot luminescent layer is CdTe, and the thickness of the quantum dot luminescent layer is 50 nm;
step S4: depositing an interface layer on the quantum dot light-emitting layer, wherein the interface layer is made of Li3N, the thickness of the interface layer is 80 nm;
step S5, depositing a hole transport layer on the interface layer, wherein the hole transport layer is made of PFB, and the thickness of the hole transport layer is 80 nm;
step S6: depositing a hole injection layer on the hole transport layer, wherein the hole injection layer is made of MoO3The thickness of the hole injection layer is 60 nm;
step S7: depositing an anode on the hole injection layer, wherein the anode is made of ITO (indium tin oxide) and the thickness of the anode is 120 nm; the anode has a visible light transmission of no less than 90%.
Comparative example 1
A preparation method of a quantum dot light-emitting diode with a positive bottom emission structure comprises the following steps:
step S1: depositing a hole injection layer on a transparent anode substrate, wherein the transparent anode is ITO, and the material of the hole injection layer is WO3The thickness of the transparent anode is 20nm, and the thickness of the hole injection layer is 60 nm;
step S2: depositing a hole transport layer on the hole injection layer, wherein the hole transport layer is made of PFB (PFB), and the thickness of the hole transport layer is 60 nm;
step S3: depositing a quantum dot light-emitting layer on the hole transport layer, wherein the quantum dot light-emitting layer is made of PbSe, and the thickness of the quantum dot light-emitting layer is 50 nm;
step S4: depositing an electron transport layer on the quantum dot light-emitting layer, wherein the electron transport layer is made of TiO and has a thickness of 60 nm;
step S5: and depositing a metal cathode on the electron transport layer, wherein the cathode is made of Ag, the thickness of the cathode is 100nm, and the reflection of the cathode to visible light is not less than 98%.
Comparative example 2
A preparation method of a quantum dot light-emitting diode with a positive top emission structure comprises the following steps:
step S1: depositing a hole injection layer on a transparent anode substrate, wherein the transparent anode is FTO, and the material of the hole injection layer is WO3The thickness of the transparent anode is 20nm, and the thickness of the hole injection layer is 60 nm;
step S2: depositing a hole transport layer on the hole injection layer, wherein the material of the hole transport layer is TCTA, and the thickness of the hole transport layer is 60 nm;
step S3: depositing a quantum dot light-emitting layer on the hole transport layer, wherein the quantum dot light-emitting layer is made of InP, and the thickness of the quantum dot light-emitting layer is 50 nm;
step S4: depositing an electron transport layer on the quantum dot light-emitting layer, wherein the electron transport layer is made of NiO, and the thickness of the electron transport layer is 60 nm;
step S5: and depositing a cathode on the electron transport layer, wherein the cathode is made of Ag, the thickness of the cathode is 100nm, and the transmission of the cathode to visible light is not less than 90%.
Comparative example 3
A preparation method of a quantum dot light-emitting diode with an inverted bottom emission structure comprises the following steps:
step S1: depositing an Ag layer on the substrate in an evaporation mode, wherein the thickness of the Ag layer is 5 nm;
step S2: depositing an electron transport layer on the Ag layer, wherein the electron transport layer is made of SnO, and the thickness of the electron transport layer is 50 nm;
step S3: depositing a quantum dot light-emitting layer on the electron transport layer, wherein the quantum dot light-emitting layer is made of CdSe, and the thickness of the quantum dot light-emitting layer is 50 nm;
step S4: depositing a hole transport layer on the quantum dot light-emitting layer, wherein the hole transport layer is made of PVK (polyvinyl pyrrolidone), and the thickness of the hole transport layer is 80 nm;
step S5: a hole injection layer is deposited on the hole transport layer, the material of the hole injection layer is PEDOT, PSS, and the thickness of the hole injection layer is 60 nm;
step S6: depositing an anode on the hole injection layer, wherein the anode is made of ITO (indium tin oxide) and the thickness of the anode is 120 nm; the anode has a visible light reflection of no less than 98%.
Comparative example 4
A preparation method of a quantum dot light-emitting diode with an inverted top emission structure comprises the following steps:
step S1: depositing an Ag layer on the substrate in an evaporation mode, wherein the thickness of the Ag layer is 5 nm;
step S2: depositing an electron transport layer on the Ag layer, wherein the electron transport layer is made of TiO, and the thickness of the electron transport layer is 60 nm;
step S3: depositing a quantum dot luminescent layer on the electron transport layer, wherein the quantum dot luminescent layer is made of CdTe, and the thickness of the quantum dot luminescent layer is 50 nm;
step S4: depositing a hole transport layer on the quantum dot light-emitting layer, wherein the hole transport layer is made of PFB (PFB), and the thickness of the hole transport layer is 80 nm;
step S5: depositing a hole injection layer on the hole transport layer, wherein the hole injection layer is made of MoO3The thickness of the hole injection layer is 60 nm;
step S6: depositing an anode on the hole injection layer, wherein the anode is made of ITO (indium tin oxide), and the thickness of the anode is 120 nm; the anode has a visible light transmission of no less than 90%.
The quantum dot light emitting diodes prepared in examples 1 to 4 and comparative examples 1 to 4 were tested for their performance, and the results are shown in table 1:
TABLE 1 Performance test results for Quantum dot light emitting diodes
External quantum efficiency-EQE (%) LT95(h)
Example 1 8.3 5.8
Example 2 15.2 4.4
Example 3 9.1 6.0
Example 4 16.4 4.9
Comparative example 1 7.9 5.4
Comparative example 2 14.6 3.9
Comparative example 3 8.3 5.9
Comparative example 4 15.8 4.1
Comparing the data in table 1, it can be seen that example 1 is different from comparative example 1 only in that Li is added between the hole transport layer and the quantum dot light emitting layer3The external quantum efficiency of the interface layer formed by the N material is improved from 7.9% to 8.3%, and the service life of the interface layer is prolonged from 5.4h to 5.8 h; example 2 is different from comparative example 2 only in that Li is added between the hole transport layer and the quantum dot light emitting layer3The external quantum efficiency of the interface layer formed by the N material is improved from 14.6% to 15.2%, and the service life of the interface layer is prolonged from 3.9h to 4.4 h; example 3 is different from comparative example 3 only in that Li is added between the hole transport layer and the quantum dot light emitting layer3The external quantum efficiency of an interface layer formed by the N material is improved from 8.3% to 9.1%, and the service life of the interface layer is improved from 5.9h to 6.0 h; example 4 differs from comparative example 4 only in the hole transport layer and the quantum dotsLi is added between the luminescent layers3The external quantum efficiency of the interfacial layer formed by the N material is improved from 15.8% to 16.4%, and the service life of the interfacial layer is improved from 4.1h to 4.9 h. Through the data, the external quantum efficiency and the service life of the quantum dot light-emitting diode can be effectively improved by arranging the interface layer between the hole transport layer and the quantum dot light-emitting layer.
In conclusion, the quantum dot light-emitting diode device is optimized, the interface layer is added into the hole transport layer and the quantum dot light-emitting layer, so that the hole injection barrier is reduced, the hole injection is improved, the accumulation of holes at the interface is avoided, the recombination of electrons tunneled to the hole transport layer in the non-quantum dot light-emitting area is effectively reduced, the efficiency and the service life of the device are improved, the influence of water and oxygen on the organic hole injection and transport layer can be effectively prevented by the interface layer, and the stability of the device is improved.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.

Claims (10)

1. A quantum dot light-emitting diode comprises a cathode, an anode, a quantum dot light-emitting layer arranged between the cathode and the anode, and a hole transport layer arranged between the anode and the quantum dot light-emitting layer, and is characterized in that an interface layer is arranged between the hole transport layer and the quantum dot light-emitting layer, and the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound; the HOMO energy level of the interface layer is larger than that of the hole transport layer and smaller than that of the quantum dot light emitting layer.
2. The quantum dot light-emitting diode of claim 1, wherein the halogen lithium compound is LiCl, LiBr or LiI.
3. The quantum dot light-emitting diode of claim 1, wherein the interface layer has a thickness of 10-200 nm.
4. A quantum dot light emitting diode according to claim 1, wherein the HOMO level of the interface layer is 4.9-6.0eV, preferably the HOMO level of the interface layer is 5.4-6 eV.
5. A quantum dot light-emitting diode according to any of claims 1 to 4, wherein the hole transport layer material is selected from one or more of TFB, PVK, Poly-TPD, PFB, TCTA, CBP, TPD and NPB, preferably the hole transport layer material is TFB.
6. The quantum dot light-emitting diode of any one of claims 1 to 4, wherein the quantum dot light-emitting layer material is selected from one or more of binary phase quantum dots, ternary phase quantum dots, and quaternary phase quantum dots.
7. The quantum dot light-emitting diode of claim 6, wherein the binary phase quantum dots are at least one of CdS, CdSe, CdTe, InP, AgS, PbS, PbSe, HgS; and/or the ternary phase quantum dots are ZnXCd1-XS、CuXIn1-XS、ZnXCd1-XSe、ZnXSe1-XS、ZnXCd1-XTe、PbSeXS1-XAt least one of; and/or the quaternary phase quantum dots are ZnXCd1-XS/ZnSe、CuXIn1-XS/ZnS、ZnXCd1-XSe/ZnS、CuInSeS、ZnXCd1-XTe/ZnS、PbSeXS1-XAt least one of/ZnS, wherein 0<X<1。
8. The quantum dot light-emitting diode of claim 1, wherein an electronic functional layer is disposed between the quantum dot light-emitting layer and the cathode.
9. A preparation method of a quantum dot light-emitting diode is characterized by comprising the following steps:
providing an anode substrate, and forming a hole transport layer on the anode substrate;
preparing an interface layer on the hole transport layer, wherein the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound;
preparing a quantum dot light-emitting layer on the interface layer;
preparing a cathode at the quantum dot light-emitting layer to prepare the quantum dot light-emitting diode;
or, providing a cathode substrate on which a quantum dot light emitting layer is prepared;
preparing an interface layer on the surface of the quantum dot light-emitting layer, wherein the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound;
preparing a hole transport layer on the interface layer;
and preparing an anode on the hole transport layer to obtain the quantum dot light-emitting diode.
10. The method of claim 9, wherein the step of forming an interfacial layer on the hole transport layer comprises:
dispersing the lithium nitride or the lithium halide doped lithium nitride in an organic solvent to prepare a lithium nitride solution or a lithium halide doped lithium nitride solution;
preparing an interface layer on the surface of the hole transport layer, wherein the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound;
or, the step of preparing the interface layer on the surface of the quantum dot light-emitting layer comprises the following steps:
dispersing the lithium nitride or the lithium halide doped lithium nitride in an organic solvent to prepare a lithium nitride solution or a lithium halide doped lithium nitride solution;
preparing an interface layer on the surface of the quantum dot light-emitting layer, wherein the interface layer is made of lithium nitride or lithium nitride doped with halogen lithium compound.
CN202011636185.7A 2020-12-31 2020-12-31 Quantum dot light-emitting diode and preparation method thereof Pending CN114695714A (en)

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