CN111446382A - Electroluminescent device, preparation method thereof and display device - Google Patents

Electroluminescent device, preparation method thereof and display device Download PDF

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CN111446382A
CN111446382A CN202010257280.XA CN202010257280A CN111446382A CN 111446382 A CN111446382 A CN 111446382A CN 202010257280 A CN202010257280 A CN 202010257280A CN 111446382 A CN111446382 A CN 111446382A
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coating
metal nanowire
electroluminescent device
nanowires
metal
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CN111446382B (en
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孙佳
王红琴
史横舟
王允军
许金平
马金锁
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Suzhou Xingshuo Nanotech 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
    • H10K50/00—Organic light-emitting devices
    • H10K50/80—Constructional details
    • H10K50/805—Electrodes
    • H10K50/81—Anodes
    • H10K50/814—Anodes combined with auxiliary electrodes, e.g. ITO layer combined with metal lines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • 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
    • 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
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract

The invention discloses a preparation method of an electroluminescent device, which comprises the following steps: providing a substrate; sequentially forming a bottom electrode, a first functional layer, an electroluminescent layer and a second functional layer on the substrate; coating the metal nanowire solution on the second functional layer in a mode of coating for a plurality of times to form a top electrode; each coating comprises the following steps: coating the metal nanowire solution on the substrate; drying the metal nanowire solution to form a metal nanowire film; and irradiating the metal nanowire film with ultraviolet light. Therefore, the top electrode of the electroluminescent device is completely composed of the metal nanowires, the surface resistance of the whole top electrode is very small, the prepared electroluminescent device is simple and convenient to manufacture, and the production and manufacturing cost of the display device containing the electroluminescent device is reduced.

Description

Electroluminescent device, preparation method thereof and display device
Technical Field
The application belongs to the technical field of display, and particularly relates to an electroluminescent device, a preparation method of the electroluminescent device and a display device.
Background
Electroluminescent devices such as organic electroluminescent diodes (O L ED) have the advantages of self-luminescence, fast response, wide viewing angle, high brightness, lightness and thinness, etc., and quantum dot light emitting diodes (Q L ED) have the advantages of high color purity, high luminous quantum efficiency, easy adjustment of luminous color, long service life, etc., and are two main directions of current display device research.
An electroluminescent device is applied to the display field, and generally has a stacked structure including at least a substrate, a cathode, a light emitting layer, and an anode, and further including a carrier transport layer for transporting holes and electrons, and the like.
In order to enable the light emission of the electroluminescent device, it is generally necessary that at least one of the electrodes (bottom electrode or/and top electrode) is a transparent conductive electrode. The transparent conductive electrode allows light to pass through while providing a conductive path. When the bottom electrode is a transparent conductive electrode, the electroluminescent device generally emits bottom light; when the top electrode is a transparent conductive electrode, the electroluminescent device generally emits light on top; when the bottom electrode and the top electrode are both transparent conductive electrodes, the electroluminescent device generally emits light from both sides.
At first, the transparent conductive electrode generally adopts Ag or MgAg (magnesium silver) alloy as an electrode, but the Ag or MgAg (magnesium silver) alloy electrode is generally semitransparent and cannot meet the requirements of high light transmittance and low sheet resistance.
The transparent conductive electrode commonly used at present is a transparent conductive oxide, generally a doped indium oxide, such as ITO, which is disposed on a glass substrate and has a good visible light transmittance within a certain thickness range.
However, ITO coatings also have a number of disadvantages in application. Specifically, ITO coatings are typically formed on glass substrates using magnetron sputtering, and when an ITO coating is provided on a functional layer of an electroluminescent device, the functional layer is easily severely damaged by energy-dense high-speed particles. This results in ITO being used only as a transparent bottom electrode on a glass substrate, and not being used as a top electrode formed on a functional layer. In addition, ITO coatings are brittle or subject to cracking, are also sensitive to acids and bases, and do not meet future requirements for flexibility characteristics.
Now, in order to overcome the problems of ITO, a network of metal nanowires (e.g., silver nanowires) is embedded into the transparent conductive oxide electrode to form a thin film, which can further reduce the sheet resistance of the transparent electrode while maintaining the visible light transmittance.
For example, "High-Performance transmissive quantity Dot L light-Emitting Diode with switchable transmissive Electrodes" published by Sunho Kim et al discloses a technique for embedding silver nanowires (AgNWs) in PMMA.
However, the above-mentioned fabrication processes are very complicated, which greatly increases the cost, and the conductivity of the nanowires (e.g., silver nanowires) is not fully utilized, so it is urgently needed to provide an electroluminescent device with a nanowire electrode that is more transparent and has a smaller sheet resistance.
Disclosure of Invention
In view of the above technical problems, the present application provides a method for manufacturing an electroluminescent device, comprising the steps of:
providing a substrate;
sequentially forming a bottom electrode, a first functional layer, an electroluminescent layer and a second functional layer on the substrate;
coating the metal nanowire solution on the second functional layer in a mode of coating for a plurality of times to form a top electrode; each coating comprises the following steps:
coating the metal nanowire solution on the second functional layer;
drying the metal nanowire solution to form a metal nanowire film;
and irradiating the metal nanowire film with ultraviolet light.
Further, the manner of drying the metal nanowire solution includes vacuum drying or thermal drying.
Further, the coating mode is wet coating;
preferably, the coating method includes at least one of spray coating, blade coating, wire bar coating, brush coating, roller bar coating, screen printing, gravure printing, relief printing, spin coating printing, and inkjet printing.
Further, the metal nanowire solution comprises metal nanowires and an organic solvent;
preferably, the concentration of the metal nanowire solution is not more than 10mg/m L.
Further, the organic solvent includes at least one of methyl ethyl ketone, acetone, methyl isobutyl ketone, acetylacetone, ethyl acetate, methyl acetate, isopropyl acetate, butyl acetate, methanol, ethanol, isopropanol, butanol, isobutanol, diacetone alcohol, toluene, and xylene.
The application also provides an electroluminescent device prepared by the manufacturing method of the electroluminescent device.
Further, the light transmittance of the top electrode is 50% -99.9%.
Further, the sheet resistance of the top electrode is less than 50 Ω/□.
Further, the metal nanowire comprises at least one of a gold nanowire, a silver nanowire, a copper nanowire, an iron nanowire, a cobalt nanowire and a nickel nanowire;
preferably, when the metal nanowire solution is coated on the second functional layer by multiple coating, the metal nanowires of at least one group of adjacent metal nanowire films are different in kind.
The application also provides a display device comprising the electroluminescent device.
Has the advantages that:
1. the top electrode of the electroluminescent device is formed by coating the metal nanowire solution for a plurality of times and irradiating the metal nanowire solution with ultraviolet light after each coating, so that the contact between the metal nanowires and the lower-layer material can be improved, and the effective lap joint between the metal nanowires can be realized;
2. the top electrode of the electroluminescent device prepared by the metal nanowire coating mode greatly reduces the lighting voltage of the device, improves the light emitting uniformity, and has better device performance than the conventional metal electrode;
3. in the prior art, metal nanowires are embedded into an organic substrate to form a composite electrode, and then the composite electrode is coated on a functional layer; in the application, the metal nanowires are directly arranged on the functional layer to form the top electrode with the metal nanowire network structure, the top electrode is formed by mutually overlapping the metal nanowires, such as silver nanowires (AgNWs), the surface resistance of the whole top electrode is very small, and the conductivity is enhanced;
4. no organic base material is mixed in the top electrode, so that the transmittance of the top electrode is greatly improved;
5. compared with the ITO in the prior art in a magnetron sputtering mode, the top electrode can be directly formed on the second functional layer of the electroluminescent device, and the second functional layer cannot be damaged;
6. the top electrode of the metal nanowire network structure in the electroluminescent device has no excessive requirement on the film smoothness of the functional layer;
7. the display device is simple and convenient to manufacture, good in repeatability, capable of reducing the production and manufacturing cost of the electroluminescent device and suitable for large-scale mass production.
Drawings
FIG. 1 is a flow chart of a method for fabricating an electroluminescent device according to an embodiment of the present disclosure;
FIG. 2 is a flow chart of a method for fabricating a top electrode according to another embodiment of the present application;
FIG. 3 is a schematic view of a metal nanowire film irradiated with ultraviolet light according to another embodiment of the present application;
fig. 4 is a schematic structural diagram of an electroluminescent device according to an embodiment of the present application.
Detailed Description
The technical solutions in the examples of the present application will be described in detail below with reference to the embodiments of the present application. It should be noted that the described embodiments are only some embodiments of the present application, and not all embodiments.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. Unless otherwise defined, all terms (including technical and scientific terms) in the specification may be defined as commonly understood by one of ordinary skill in the art. Terms defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and the present disclosure, and may not be interpreted in an idealized or overly formal sense unless expressly so defined. Furthermore, unless expressly stated to the contrary, the terms "comprises" and "comprising," when used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. Thus, the above wording will be understood to mean that the stated elements are included, but not to exclude any other elements.
It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another element, component, region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the present embodiments.
Definition of
The following definitions apply to aspects described in relation to some embodiments of the invention, and these definitions may be extended herein as well.
As used herein, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Unless the context clearly dictates otherwise, reference to an object may include multiple objects.
As used herein, the term "adjacent" refers to being proximate or contiguous. The adjacent objects may be spaced apart from each other, or may be in actual or direct contact with each other. In some cases, adjacent objects may be connected to each other, or may be integrally formed with each other.
As used herein, the term "connected" refers to an operative coupling or link. The linked objects may be directly coupled to each other or may be indirectly coupled to each other via another set of objects.
As used herein, relative terms, such as "inside," "interior," "exterior," "top," "bottom," "front," "back," "upper," "lower," "vertical," "lateral," "above … …," and "below … …," refer to the orientation of a group of objects relative to one another as a matter of manufacture or use, for example, according to the drawings, but do not require the particular orientation of the objects during manufacture or use.
As used herein, the term "nano-range" or "nm range" refers to a size range of about 1nm to about 1 μm.
As used herein, the term "nanoscale" object refers to an object having at least one dimension in the nanometer range. The nanoscale objects can have any of a wide variety of shapes, and can be formed from a wide variety of materials. Examples of nanoscale objects include metal nanowires, nanotubes, nanoplatelets, nanoparticles, and other nanostructures.
As used herein, the term "metal nanowire" refers to an elongated nanoscale object that is substantially solid. Typically, metal nanowires have lateral dimensions in the nanometer range (e.g., cross-sectional dimensions in terms of diameter, width, or width or diameter representing an average across orthogonal directions).
As shown in fig. 1, a method for manufacturing an electroluminescent device according to an embodiment of the present disclosure includes the following steps:
step S1: a substrate is provided.
In this embodiment, the substrate may be a rigid substrate or a flexible substrate. Wherein the rigid substrate includes, but is not limited to, one or more of glass, metal foil or ceramic material.
The flexible substrate comprises a polymer film comprising one or more of polyethylene terephthalate (PET), polyethylene terephthalate (PEN), Polyetheretherketone (PEEK), Polystyrene (PS), Polyethersulfone (PES), Polycarbonate (PC), Polyarylate (PAT), Polyarylate (PAR), Polyimide (PI), polyvinyl chloride (PV), Polyethylene (PE), polyvinylpyrrolidone (PVP), textile fibers.
Step S2: and sequentially forming a bottom electrode, a first functional layer, an electroluminescent layer and a second functional layer on the substrate.
In this embodiment, the bottom electrode may be an opaque conductive electrode or a transparent conductive electrode, which is not limited in this application. For example, the bottom electrode can be a magnesium aluminum electrode or an ITO electrode, and can also be an electrode with a metal nanowire network structure, so that the transmittance and the conductivity of the bottom electrode are further improved. When the first functional layer is formed on the bottom electrode, a large number of gaps exist in the network structure formed by stacking and arranging the metal nanowires, the first functional layer can be filled into the gaps of the metal nanowires, and even the first functional layer and the bottom electrode form an integral structure.
In this embodiment, the first functional layer and the second functional layer have specific structures according to the properties of the bottom electrode, for example, when the bottom electrode is an anode, the first functional layer may include a hole injection layer and a hole transport layer, and the second functional layer includes an electron transport layer; when the bottom electrode is a cathode, the first functional layer may include an electron transport layer, and the second functional layer may include a hole transport layer.
The material of the hole injection layer includes, but is not limited to, one or more of poly (3, 4-ethylenedioxythiophene) -polystyrenesulfonic acid (PEDOT: PSS), copper phthalocyanine (CuPc), 2,3,5, 6-tetrafluoro-7, 7',8,8' -tetracyanoquino-dimethane (F4-TCNQ), 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-Hexaazatriphenylene (HATCN), Polythienothiophene (PTT) doped with poly (perfluoroethylene-perfluoroether sulfonic acid) (PFFSA), transition metal oxide, metal chalcogenide compound, preferably, the transition metal oxide includes MoO3、VO2、WO3、CrO3One or more of CuO, metal-sulfur compound including MoS2、MoSe2、WS2、WSe2CuS, but exemplary of the present applicationThe embodiments are not limited thereto.
The material of the hole transport layer may be selected from organic materials having hole transport ability, including but not limited to 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), doped graphene, undoped graphene, C60. The hole transport layer may also be selected from inorganic materials with hole transport capabilities including, but not limited to, doped or undoped MoOx, VOx, WOx, CrOx, CuO, MoS2、MoSe2、WS2、WSe2And CuS, but exemplary embodiments of the present application are not limited thereto.
The material of the electron transport layer includes, but is not limited to, a transport layer film composed of nanoparticles, and the material of the electron transport layer is selected from ZnO and TiO2、SnO2、Ta2O3、InSnO、Alq3、Ca、Ba、CsF、LiF、CsCO3Preferably, the electron transport material is a metal-doped ZnO nanoparticle, such as Mg, Al, L i, W, Ti, Ni, Sn, MgO, Al2O3、Li2O、W2O3、TiO2、NiO、SnO2Etc. doped ZnO nanoparticles.
In the embodiments, the electroluminescent layer includes a quantum dot light emitting material or an organic light emitting material. For example, the quantum dot light-emitting material comprises at least one of red light quantum dots, green light quantum dots and blue light quantum dots, and can be at least one of II-VIA group compounds, IV-VIA group compounds, III-VA group compounds and I-VIA group compounds. Preferably, the quantum dots are one or more of CdS, CdSe, CdSeS, CdSZnSeS, CdS/ZnS, CdSe/CdS/ZnS, InP/ZnS, or ZnSe/ZnS, but the exemplary embodiments of the present application are not limited thereto. In addition, the composition form of the quantum dots is not limited, and may be doped or undoped quantum dots.
In the electroluminescent device, the manner of forming each layer includes, but is not limited to, inkjet printing, spray coating, spin coating, printing, doctor blading, dip coating, dipping, roll coating, slit printing, and the like, and the present application is not limited thereto.
Step S3: and coating the metal nanowire solution on the second functional layer in a mode of coating for a plurality of times to form a top electrode.
The metal nanowire solution of the present embodiment includes metal nanowires, the number of coating times is, for example, 1 to 10, and when the number of coating times is multiple, the metal nanowire solution is coated in a sequential stacking manner. As shown in fig. 2, each coating of the metal nanowire solution includes the steps of:
step S31: and coating the metal nanowire solution on the second functional layer.
And coating the metal nanowire solution on the second functional layer to uniformly spread the metal nanowire solution on the second functional layer, so that the formed top electrode has better smoothness.
Step S32: and drying the metal nanowire solution to form the metal nanowire film.
And volatilizing the organic solvent in the metal nanowire solution to enable the metal nanowires to be left on the second functional layer to form the metal nanowire film, wherein the drying method comprises but is not limited to atmospheric air drying, vacuum drying or thermal drying.
Step S33: and irradiating the metal nanowire film with ultraviolet light.
The dried metal nanowire film is irradiated with ultraviolet light, as shown in fig. 3, the metal nanowire solution on the substrate 10 is dried to form a metal nanowire film 11, and the metal nanowire film 11 is irradiated with ultraviolet light, so that the metal nanowire film 11 and the substrate 10 are combined more tightly.
The method of the embodiment of the present application may further include, after step S33:
step S34: and annealing the metal nanowire film.
The annealing treatment in the embodiment of the present application is to slowly heat the metal nanowire film to a certain temperature, maintain the temperature for a sufficient time, and then cool the metal nanowire film at a suitable speed, so as to further promote the volatilization of the organic solvent in the metal nanowire film, and improve the conductivity and the light transmittance of the top electrode. The annealing temperature may be controlled to 70-200 ℃, the treatment time may be 1-30 minutes, and the parameters of the annealing process are selected according to actual needs, which is not limited in this application.
According to the preparation method of the electroluminescent device, the metal nanowire solution is coated for a plurality of times, drying and ultraviolet irradiation are carried out after each coating to form the top electrode, so that the formed top electrode is combined with the second functional layer more tightly, ohmic contact between the top electrode and the second functional layer is improved, overlapping between the metal nanowires in the top electrode is optimized, and the conductivity of the top electrode is excellent.
It should be noted that the ultraviolet wavelength, the irradiation intensity, and the irradiation duration of the embodiment of the present application may be designed by referring to conventional use conditions according to actual needs, for example, the wavelength of the irradiated ultraviolet light may be 200 to 400nm, the irradiation intensity may be 10 to 200mW, the irradiation duration may be 1 to 300s, or the same time may be irradiated in a stroboscopic mode, which is not limited in the present application.
In a specific embodiment of the application, the metal nanowire solution comprises metal nanowires and an organic solvent, wherein the metal nanowires are uniformly dispersed in the organic solvent to form the metal nanowire solution, specifically, the metal nanowires comprise ligands, and the ligands help the metal nanowires to be directly dispersed in the organic solvent, further, the concentration of the metal nanowire solution may be less than 10mg/m L, for example, the concentration of the metal nanowire solution may be, for example, 1mg/m L, 3mg/m L, 5mg/m L, 7mg/m L, 8mg/m L, 9mg/m L, or 10mg/m L, the metal nanowires are uniformly dispersed on the substrate by using the low-concentration metal nanowire solution, and after multiple coatings, the metal nanowires of the top electrode are lapped to form a grid structure, so that a good conductive path can be formed between the metal nanowires.
In the method for manufacturing an electroluminescent device according to another embodiment of the present application, the coating method includes at least one of spraying, blade coating, wire bar coating, brush coating, roller bar coating, screen printing, gravure printing, relief printing, spin coating, and inkjet printing, and may be a single method or a combination of multiple methods, and the orientation method and the coating method may be selected in different manners according to actual use conditions and use scenarios. For example, the top electrode of one embodiment is formed by brushing a solution of metal nanowires. The spreading range of the metal nanowires can be controlled by the brushing mode, and in addition, the metal nanowires can be arranged in a certain trend in the brushing direction in the brushing process. Specifically, the top electrode is made of a metal nanowire solution, which includes a metal nanowire and a volatile solvent, for example, the metal nanowire is a silver nanowire (AgNWs), and the volatile solvent is ethanol. The silver nanowire solution is coated on the substrate in a brushing mode, and due to the fact that ethanol has strong volatility, the ethanol is quickly volatilized along with the brushing process, and silver nanowires are deposited, stacked and attached to the substrate.
In yet another embodiment of the present application, the organic solvent may be selected from at least one of methyl ethyl ketone, acetone, methyl isobutyl ketone, acetylacetone, ethyl acetate, methyl acetate, isopropyl acetate, butyl acetate, methanol, ethanol, isopropanol, butanol, isobutanol, diacetone alcohol, toluene, and xylene, which will be rapidly volatilized after drying the metal nanowire solution, leaving the silver nanowires only on the second functional layer.
The present application further provides an electroluminescent device, as shown in fig. 4, the electroluminescent device 100 includes a substrate 106, a bottom electrode 105, a first functional layer 104, an electroluminescent layer 103, a second functional layer 102, and a top electrode 101, the first functional layer 104 is disposed on the bottom electrode 105; an electroluminescent layer 103 is disposed on the first functional layer 104; the second functional layer 102 is disposed on the electroluminescent layer 103; the top electrode 101 is disposed on the second functional layer 102; wherein the top electrode 101 comprises a metal nanowire. The metal nanowires in the top electrode 101 are stacked and overlapped with each other, so that the top electrode has good conductivity and light transmittance.
In another embodiment of the present application, the top electrode 101 may be formed directly on the second functional layer 102, and when the electrode is formed by metal nanowires, the metal nanowires are embedded into the substrate to form a composite electrode, and then the composite electrode is applied to the electroluminescent device. In the application, the top electrode 101 containing the metal nanowires is directly arranged on the second functional layer 102 to form the top electrode 101 with the metal nanowire stacking arrangement structure, the top electrode 101 is completely composed of the metal nanowires, such as silver nanowires (AgNWs), the surface resistance of the whole top electrode 101 is very small, and the conductivity is enhanced; secondly, no base material is mixed in the top electrode 101, and the transmittance of the top electrode 101 is improved; in addition, compared with the prior art that ITO is sputtered by magnetron sputtering, the metal nanowire of the present embodiment is directly formed on the second functional layer 102 of the electroluminescent device 100 without damaging the second functional layer 102; in addition, the top electrode 101 with the metal nanowire network structure has no excessive requirement on the film flatness of the second functional layer 102; finally, the top electrode 101 is simple in manufacturing process, and the manufacturing cost of the electroluminescent device 100 is reduced.
In an embodiment of the present application, the substrate 106 and the bottom electrode 105 may be both made of flexible materials, and the top electrode 101 is a metal nanowire network structure and also a flexible structure, and the cooperation of the three can realize flexible display, that is, by combining the top electrode 101 of the metal nanowire network structure in the present embodiment with the flexible substrate 106 and the bottom electrode 105, the electroluminescent device 100 can emit light in a bending manner, and an application scenario of the electroluminescent device is expanded.
In another embodiment of the present application, the light transmittance of the top electrode in the electroluminescent device is 50% to 99.9%, and when the bottom electrode is also a transparent electrode, the electroluminescent device can be used in an electronic device for displaying a scene transparently to view an image on the other side of the electronic device, for example, the electroluminescent device can be used as an electrode device for displaying a device on a showcase, which is elegant and practical. Specifically, when the bottom electrode is a transparent conductive electrode ITO and the top electrode is a transparent metal nanowire electrode, the electroluminescent device of the present application can emit light on both sides, and further can achieve transparent display, that is, in a case where the electroluminescent device is capable of self-luminescence, an image behind the electroluminescent device can be seen through the electroluminescent device, and the electroluminescent device is transparent to a viewer.
In another embodiment of the present application, the sheet resistance of the top electrode is less than 50 Ω/□, so that the top electrode can be ensured to have good conductivity on the second functional layer.
In yet another embodiment of the present application, the metal nanowires in the top electrode of the electroluminescent device include, but are not limited to, at least one of gold nanowires, silver nanowires, copper nanowires, iron nanowires, cobalt nanowires, nickel nanowires. The metal nanowires in the metal nanowire solution coated for many times can be the same in kind or different in kind. Preferably, when the metal nanowire solution is coated on the second functional layer by multiple coating, the metal nanowires of at least one group of adjacent metal nanowire films are different in kind.
In the embodiment, the top electrode is completely composed of metal nanowires, such as silver nanowires (AgNWs), the surface resistance of the whole top electrode is very small, and the conductivity is enhanced; secondly, no base material is mixed in the top electrode 101, and the transmittance of the top electrode is improved; meanwhile, the metal nanowires are directly formed on the hole injection layer of the electroluminescent device in a brush coating mode, so that the hole injection layer cannot be damaged; in addition, the top electrode of the network structure formed by stacking and distributing the metal nanowires has no excessive requirement on the film smoothness of the hole injection layer; and finally, the manufacturing process of the top electrode is simple and convenient, and the production and manufacturing cost of the electroluminescent device is reduced.
Note that the structure of the electroluminescent device is not limited in this application. The electroluminescent device may be of a positive type structure; the metal nanowire array can also be of an inverted structure, and the network structure formed by stacking and arranging the metal nanowires in the top electrode is applicable to the application.
The application also provides a display device, which comprises the electroluminescent device, wherein the display device comprises but is not limited to a mobile phone, a computer, a vehicle-mounted display, an AR display, a VR display, a smart watch, a flexible display screen, a flexible display panel and the like, and the electroluminescent device can be a Q L ED device, an O L ED device, a P L ED device, a Micro-L ED device or a Mini-L ED device.
Electroluminescent device structures according to some exemplary embodiments of the present application are described in more detail below; however, the exemplary embodiments of the present application are not limited thereto.
Example 1
Fabrication of transparent Q L ED device:
s1, providing a glass substrate with an ITO conductive layer;
s2, coating a hole injection layer PEDOT on the glass substrate with the ITO conductive layer: PSS;
s3, forming a hole injection layer PEDOT: coating a hole transport layer TFB on the PSS;
s4, coating a red CdSe/ZnS quantum dot layer on the hole transport layer TFB;
s5, coating a ZnO electron transport layer on the red CdSe/ZnS quantum dot layer;
s6, brushing a metal nanowire solution on the ZnO electron transport layer for the first time, wherein the concentration of the metal nanowire solution is 5mg/m L;
s7, drying the metal nanowire solution to form a first metal nanowire film;
s8, carrying out UV irradiation on the first metal nanowire film for 30 seconds;
s9, brushing the metal nanowire solution on the first metal nanowire film for the second time, and sequentially preparing a second metal nanowire film, a third metal nanowire film and a fourth metal nanowire film on the first metal nanowire film according to the same brushing method to form the top electrode with the square resistance of 12 omega/□.
Finally, a red CdSe/ZnS quantum dot Q L ED device is prepared, the red CdSe/ZnS quantum dot Q L ED device is electrified, the starting voltage is 1.8V, the obtained light emission is uniform, the voltage is adjusted until the light emission brightness of the red CdSe/ZnS quantum dot Q L ED device is kept bright and unchanged, the maximum current efficiency and the maximum external quantum efficiency of the ITO side and the AgNWs side of the red CdSe/ZnS quantum dot Q L ED device are measured respectively, the maximum current efficiency of the ITO side is measured to be 5.75cd/A, the maximum external quantum efficiency is measured to be 8.94%, the maximum current efficiency of the AgNWs side is 4.79cd/A, the maximum external quantum efficiency is 7.29%, the total maximum current efficiency of the red CdSe/ZnS quantum dot Q L ED device is 10.54cd/A, and the total maximum external quantum efficiency is 16.23%.
Example 2
Fabrication of transparent Q L ED device:
s1, providing a top emission pixel substrate with an ITO/Ag/ITO conductive layer, wherein the pixel size is 32x120 mu m;
s2, printing PEDOT on the pixel substrate: PSS, and drying and annealing treatment are carried out;
s3, printing the TFB on the pixel substrate, and carrying out drying and annealing treatment;
s4, printing red light CdSe/ZnS quantum dots on the pixel substrate, and drying and annealing;
s5, printing a ZnO electron transport layer on the red CdSe/ZnS quantum dot layer, and drying and annealing;
s6, brushing a metal nanowire solution on the ZnO electron transport layer for the first time, wherein the concentration of the metal nanowire solution is 5mg/m L;
s7, drying the metal nanowire solution to form a first metal nanowire film;
s8, carrying out UV irradiation on the first metal nanowire film for 30 seconds;
s9, brushing the metal nanowire solution on the first metal nanowire film for the second time, and sequentially preparing a second metal nanowire film, a third metal nanowire film and a fourth metal nanowire film on the first metal nanowire film according to the same brushing method to form the top electrode with the square resistance of 12 omega/□.
And finally, preparing a red quantum dot Q L ED device, electrifying the red CdSe/ZnS quantum dot Q L ED device, wherein the starting voltage is 2.2V, the external quantum efficiency is 4.63 percent, the current efficiency is 2.93cd/A, and the luminescence is uniform.
Example 3
Fabrication of transparent Q L ED device:
s1, providing a glass substrate with an ITO conductive layer;
s2, coating a hole injection layer PEDOT on the glass substrate with the ITO conductive layer: PSS;
s3, forming a hole injection layer PEDOT: coating a hole transport layer TFB on the PSS;
s4, coating a red CdSe/ZnS quantum dot layer on the hole transport layer TFB;
s5, coating a ZnO electron transport layer on the red CdSe/ZnS quantum dot layer;
s6, brushing a metal nanowire solution on the ZnO electron transport layer for the first time, wherein the concentration of the metal nanowire solution is 5mg/m L;
s7, drying the metal nanowire solution to form a first metal nanowire film;
s8, brushing the metal nanowire solution on the first metal nanowire film for the second time, and sequentially preparing a second metal nanowire film and a third metal nanowire film on the first metal nanowire film according to the same brushing method to form a top electrode with the sheet resistance of 15 omega/□.
S9, annealing the top electrode at 100 ℃ for 10 minutes.
Finally, a red CdSe/ZnS quantum dot Q L ED device is prepared, the red CdSe/ZnS quantum dot Q L ED device is electrified, the starting voltage is 1.8V, the obtained light emission is uniform, the voltage is adjusted until the light emission brightness of the red CdSe/ZnS quantum dot Q L ED device is kept bright and unchanged, the maximum current efficiency and the maximum external quantum efficiency of the ITO side and the AgNWs side of the red CdSe/ZnS quantum dot Q L ED device are measured respectively, the maximum current efficiency and the maximum external quantum efficiency of the ITO side are measured to be 2.15cd/A and 3.31%, the maximum current efficiency of the AgNWs side is 1.95cd/A and 2.93%, the total maximum current efficiency of the red CdSe/ZnS quantum dot Q L ED device is 4.1cd/A, and the total maximum external quantum efficiency is 6.24%.
According to the invention, the silver nanowires (AgNWs) are directly formed on the zinc oxide electronic transmission layer, the top electrode is completely composed of the silver nanowires, the surface resistance of the whole top electrode is very small, the conductivity of the electroluminescent device is enhanced, the manufacturing process is greatly simplified, and the manufacturing cost of the Q L ED device is reduced.
Compared with the existing ITO sputtering mode, the silver nanowires (AgNWs) are formed on the zinc oxide electron transport layer in a brush coating and UV light irradiation mode, and the zinc oxide electron transport layer is basically not damaged.
Although the present disclosure has been described and illustrated in greater detail by the inventors, it should be understood that modifications and/or alterations to the above-described embodiments, or equivalent substitutions, will be apparent to those skilled in the art without departing from the spirit of the disclosure, and that no limitations to the present disclosure are intended or should be inferred therefrom.

Claims (10)

1. A method for manufacturing an electroluminescent device, comprising the steps of:
providing a substrate;
sequentially forming a bottom electrode, a first functional layer, an electroluminescent layer and a second functional layer on the substrate;
coating the metal nanowire solution on the second functional layer in a mode of coating for a plurality of times to form a top electrode; each coating comprises the following steps:
coating the metal nanowire solution on the second functional layer;
drying the metal nanowire solution to form a metal nanowire film;
and irradiating the metal nanowire film with ultraviolet light.
2. The method of claim 1, wherein the drying the metal nanowire solution comprises vacuum drying or thermal drying.
3. The method of claim 1, wherein the coating is wet coating;
preferably, the coating method includes at least one of spray coating, blade coating, wire bar coating, brush coating, roller bar coating, screen printing, gravure printing, relief printing, spin coating printing, and inkjet printing.
4. The method of claim 1, wherein the metal nanowire solution comprises metal nanowires and an organic solvent;
preferably, the concentration of the metal nanowire solution is not more than 10mg/m L.
5. The method of claim 4, wherein the organic solvent comprises at least one of methyl ethyl ketone, acetone, methyl isobutyl ketone, acetylacetone, ethyl acetate, methyl acetate, isopropyl acetate, butyl acetate, methanol, ethanol, isopropanol, butanol, isobutanol, diacetone alcohol, toluene, and xylene.
6. An electroluminescent device produced by the method for producing an electroluminescent device according to any one of claims 1 to 5.
7. The electroluminescent device of claim 6, wherein the top electrode has a light transmittance of 50% to 99.9%.
8. An electroluminescent device as claimed in claim 6, characterized in that the sheet resistance of the top electrode is less than 50 Ω/□.
9. The electroluminescent device of claim 6, wherein the metal nanowires comprise at least one of gold nanowires, silver nanowires, copper nanowires, iron nanowires, cobalt nanowires, and nickel nanowires.
10. A display device comprising an electroluminescent device as claimed in any one of claims 6 to 9.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104303238A (en) * 2012-04-26 2015-01-21 国立大学法人大阪大学 Transparent conductive ink, and method for producing transparent conductive pattern
CN110265564A (en) * 2019-05-09 2019-09-20 南方科技大学 Quantum dot light-emitting diode, preparation method thereof and display screen

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104303238A (en) * 2012-04-26 2015-01-21 国立大学法人大阪大学 Transparent conductive ink, and method for producing transparent conductive pattern
CN110265564A (en) * 2019-05-09 2019-09-20 南方科技大学 Quantum dot light-emitting diode, preparation method thereof and display screen

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