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CN111446382B - Electroluminescent device, preparation method thereof and display device - Google Patents

Electroluminescent device, preparation method thereof and display device Download PDF

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Publication number
CN111446382B
CN111446382B CN202010257280.XA CN202010257280A CN111446382B CN 111446382 B CN111446382 B CN 111446382B CN 202010257280 A CN202010257280 A CN 202010257280A CN 111446382 B CN111446382 B CN 111446382B
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metal nanowire
electroluminescent device
coating
nanowires
top electrode
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CN111446382A (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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
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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 steps of: coating the metal nanowire solution on the substrate; drying the metal nanowire solution to form a metal nanowire film; and carrying out ultraviolet irradiation on the metal nanowire film. Therefore, the top electrode of the electroluminescent device is completely formed by the metal nano wire, the surface resistance of the whole top electrode is very small, the electroluminescent device prepared by the method is simple and convenient to manufacture, and the production and manufacturing cost of a display device comprising 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 thereof and a display device.
Background
Electroluminescent devices such as Organic Light Emitting Diodes (OLEDs) have the advantages of self luminescence, fast reaction, wide viewing angle, high brightness, light and thin, and quantum dot light emitting diodes (QLEDs) have the advantages of high light color purity, high light quantum efficiency, easy adjustment of light emission color, long service life, and the like, and are two main directions of research of display devices at present.
Electroluminescent devices are used in the display field, which are typically laminated structures comprising at least a substrate, a cathode, a light emitting layer and an anode, and further comprising a carrier transport layer for hole and electron transport, etc.
In order to enable the electroluminescent device to emit light, it is generally required that at least one electrode (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 light from the bottom; when the top electrode is a transparent conductive electrode, the electroluminescent device generally emits light from the top; when the bottom electrode and the top electrode are transparent conductive electrodes, the electroluminescent device is generally double-sided light emitting.
The transparent conductive electrode generally adopts Ag or MgAg (magnesium silver) alloy as the electrode, but the Ag or MgAg (magnesium silver) alloy electrode is generally semitransparent and cannot meet the requirements of high light transmittance and low surface resistance.
The transparent conductive electrode commonly used at present is transparent conductive oxide, generally doped indium oxide such as ITO, which is arranged on a glass substrate, and has better visible light transmittance within a certain thickness range.
However, ITO coatings have many disadvantages in application. In particular, the ITO coating is typically formed on the glass substrate using magnetron sputtering, and when the ITO coating is disposed on the functional layer of the electroluminescent device, high-speed particles, which are energy-intensive, are liable to cause serious damage to the functional layer. This means that ITO can be used only as a transparent bottom electrode provided on a glass substrate, and cannot be used as a top electrode provided on a functional layer. In addition, ITO coatings are brittle or subject to cracking, are also acid and alkali sensitive, and do not meet future requirements for flexibility characteristics.
In order to overcome the problems of ITO, a layer of nano metal wire (such as silver nano wire) network is embedded on the transparent conductive oxide electrode to form a film, so that the surface resistance of the transparent electrode can be further reduced on the basis of keeping the visible light transmittance.
Alternatively, nanowires are embedded in a transparent polymer material (e.g., PMMA) to produce a nanowire composite electrode. For example, "High-Performance Transparent Quantum Dot Light-Emitting Diode with Patchable Transparent Electrodes" by Sunho Kim et al, discloses a technique for embedding silver nanowires (AgNWs) into PMMA.
However, the above manufacturing process is very complicated, the cost is greatly increased, and the conductivity of the nanowire (e.g., silver nanowire) is not fully utilized, so that it is needed to provide an electroluminescent device with a nanowire electrode having a smaller area resistance and being more transparent.
Disclosure of Invention
Aiming at the technical problems, the application provides 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 steps of:
coating the metal nanowire solution on the second functional layer;
drying the metal nanowire solution to form a metal nanowire film;
and carrying out ultraviolet irradiation on the metal nanowire film.
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 comprises at least one of spray coating, blade coating, wire bar coating, brush coating, roll bar coating, screen printing, gravure printing, relief printing, spin coating printing, 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/mL.
Further, 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.
The application also provides an electroluminescent device, which is 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 50Ω/≡.
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 through multiple coating, at least one group of adjacent metal nanowire films are different in metal nanowire type.
The application also provides a display device comprising the electroluminescent device.
The beneficial effects are that:
1. the top electrode of the electroluminescent device is formed by coating the metal nanowire solution for a plurality of times and irradiating ultraviolet light after each coating, so that the contact between the metal nanowire 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 adopting the metal nanowire coating mode greatly reduces the starting voltage of the device, improves the luminous 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 coated on a functional layer; the metal nanowires are directly arranged on the functional layer to form the top electrode of 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 substrate 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 through 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 requirements on the film flatness of the functional layer;
7. the display device is simple and convenient to manufacture, good in repeatability, suitable for large-scale mass production, and capable of reducing the production and manufacturing cost of the electroluminescent device.
Drawings
FIG. 1 is a flow chart of a method of fabricating an electroluminescent device according to an embodiment of the present application;
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 an ultraviolet light irradiated metal nanowire film in yet 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 in conjunction with the implementation manners 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 can 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 will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Furthermore, unless expressly stated to the contrary, the words "comprise" and the words "comprising" when used in this specification mean the presence of stated features, regions, integers, steps, operations, elements, and/or components, but does not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. Accordingly, the above phraseology is to be understood as meaning to include the stated elements, 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 embodiment.
Definition of the definition
The following definitions apply to some aspects described in relation to some embodiments of the invention, which definitions are likewise extended herein.
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 a plurality of objects.
As used herein, the term "adjacent" refers to near or abutting. 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.
The term "connected," as used herein, refers to operatively coupled or linked. 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 "inner," "outer," "top," "bottom," "front," "back," "rear," "upper," "lower," "vertical," "lateral," "above … …," and "below … …" refer to the orientation of a set of objects relative to one another first, e.g., according to the drawings, but do not require a particular orientation of the objects during manufacture or use.
As used herein, the term "nano-scale" or "nm-scale" 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. Nanoscale objects may have any of a wide variety of shapes and may 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. Generally, metal nanowires have a lateral dimension in the nanometer range (e.g., a cross-sectional dimension in the form of a diameter, width, or width or diameter representing an average value across orthogonal directions).
As shown in fig. 1, the preparation method of the electroluminescent device in an embodiment of the present application 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 materials.
The flexible substrate includes a polymer film including one or more of polyethylene terephthalate (PET), polyethylene terephthalate (PEN), polyetheretherketone (PEEK), polystyrene (PS), polyethersulfone (PES), polycarbonate (PC), polyarylate (PAT), polyarylate (PAR), polyimide (PI), polyvinylchloride (PV), polyethylene (PE), polyvinylpyrrolidone (PVP), and textile fibers.
Step S2: and forming a bottom electrode, a first functional layer, an electroluminescent layer and a second functional layer on the substrate in sequence.
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, or can be a metal nanowire network structure electrode, 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-shaped structure in which the metal nanowires are stacked and arranged, the first functional layer can be filled in the gaps of the metal nanowires, and even the first functional layer and the bottom electrode form an integrated structure.
In this embodiment, the first functional layer and the second functional layer determine specific structures according to 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) -polystyrene sulfonic acid (PEDOT: PSS), copper phthalocyanine (CuPc), 2,3,5, 6-tetrafluoro-7, 7', 8' -tetracyanoquinone-dimethane (F4-TCNQ), 2,3,6,7,10, 11-hexacyano-1, 4,5,8,9, 12-Hexaazabenzophenanthrene (HATCN), poly (perfluoroethylene-perfluoroether sulfonic acid) (PFFSA) -doped Polythiophene (PTT), transition metal oxide, metal chalcogenide, preferably, the transition metal oxide includes MoO 3 、VO 2 、WO 3 、CrO 3 One or more of CuO, metal chalcogenide compound including MoS 2 、MoSe 2 、WS 2 、WSe 2 One or more of CuS, although the exemplary embodiments of the present application are not limited thereto.
The material of the hole transport layer may be selected from organic materials having hole transport capability, including but not limited to one or more of 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 (carbazole-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, moS 2 、MoSe 2 、WS 2 、WSe 2 In CuSOne or more, but the exemplary embodiments of the present application are not limited thereto.
The material of the electron transport layer comprises, but is not limited to, a transport layer film composed of nano particles, and the material of the electron transport layer is selected from ZnO and TiO 2 、SnO 2 、Ta 2 O 3 、InSnO、Alq 3 、Ca、Ba、CsF、LiF、CsCO 3 But the exemplary embodiments of the present application are not limited thereto. Preferably, the electron transport material is a metal doped ZnO nanoparticle, e.g. Mg, al, li, W, ti, ni, sn, mgO, al 2 O 3 、Li 2 O、W 2 O 3 、TiO 2 、NiO、SnO 2 And (3) equally doped ZnO nano particles.
In an embodiment of the present application, the electroluminescent layer comprises a quantum dot luminescent material or an organic luminescent material. For example, the quantum dot light emitting material includes at least one of red light quantum dot, green light quantum dot and blue light quantum dot, and can be at least one of II-VIA group compound, IV-VIA group compound, III-VA group compound and I-VIA group compound. Preferably, the quantum dots are one or more of CdS, cdSe, cdSeS, cdZnSeS, cdS/ZnS, cdSe/CdS/ZnS, inP, inP/ZnS or ZnSe/ZnS, but the exemplary embodiments of the application are not limited thereto. In addition, the composition form of the quantum dot is not limited, and may be doped or undoped quantum dot.
In the electroluminescent device, the manner of forming each layer includes, but is not limited to, inkjet printing, spray coating, spin coating, printing, knife coating, dip-coating, dipping, roll coating, slit printing, and the like.
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 contains the metal nanowire, and the number of coating times is, for example, 1 to 10 times, and when the number of coating times is a plurality of times, the metal nanowire solution is coated in a sequential stacking manner. As shown in fig. 2, each application 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, so that the metal nanowire solution is uniformly spread on the second functional layer, and the formed top electrode has better flatness.
Step S32: and drying the metal nanowire solution to form a metal nanowire film.
The organic solvent in the metal nanowire solution is volatilized to leave the metal nanowires on the second functional layer to form a metal nanowire film, and the drying method comprises, but is not limited to, normal pressure air drying, vacuum drying or thermal drying.
Step S33: and carrying out ultraviolet irradiation on the metal nanowire film.
Ultraviolet irradiation is performed on the dried metal nanowire film, 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 by ultraviolet light, so that the metal nanowire film 11 is combined with the substrate 10 more tightly.
The step S33 may further include the steps of:
step S34: and annealing the metal nanowire film.
The annealing treatment in the embodiment of the application is to slowly heat the metal nanowire film to a certain temperature, keep the metal nanowire film for enough time and then cool the metal nanowire film at a proper 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 control temperature of the annealing treatment can be 70-200 ℃, the treatment time can be 1-30 minutes, and the annealing process parameters can be selected according to actual needs, so that the application is not limited.
According to the preparation method of the electroluminescent device, the metal nanowire solution is coated for a plurality of times, and after each coating, drying and ultraviolet irradiation are carried out to form the top electrode, so that the formed top electrode is more tightly combined with the second functional layer, ohmic contact between the top electrode and the second functional layer is improved, overlap joint between the metal nanowires in the top electrode is more optimized, and the conductivity of the top electrode is excellent.
It should be noted that, according to the embodiment of the present application, the ultraviolet wavelength, the irradiation intensity and the irradiation duration may be designed in a collocation manner according to actual needs with reference to conventional use conditions, for example, the irradiation ultraviolet wavelength may be 200-400 nm, the irradiation intensity may be 10-200 mW, the irradiation duration may be 1-300 s, or the same irradiation time may be performed by using a strobe mode, which is not limited in this application.
In one embodiment of the present application, a metal nanowire solution includes a metal nanowire and an organic solvent; the metal nanowires are uniformly dispersed in the organic solvent to form a metal nanowire solution, which can be specifically: the metal nanowires include ligands that facilitate the direct dispersion of the metal nanowires in an organic solvent. Further, the concentration of the metal nanowire solution can be less than 10mg/mL, for example, the concentration of the metal nanowire solution can be 1mg/mL, 3mg/mL, 5mg/mL, 7mg/mL, 8mg/mL, 9mg/mL or 10mg/mL, the metal nanowire solution with low concentration is adopted to uniformly disperse the metal nanowire on the substrate, and after multiple coating, 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 the electroluminescent device according to another embodiment of the present application, the coating method includes at least one of spraying, blade coating, wire rod coating, brush coating, roller coating, screen printing, gravure printing, relief printing, spin coating printing, and ink jet printing, and may be a single mode or a combination of modes, and may be an orientation mode and a coating method of different modes according to actual use conditions and use situations. For example, the top electrode of one embodiment is formed by brushing a metal nanowire solution. The brushing mode can control the spreading range of the metal nanowires, and in addition, the metal nanowires can be distributed in a certain trend in the brushing direction in the brushing process. Specifically, the top electrode is made from a metal nanowire solution comprising metal nanowires and a volatile solvent, for example, silver nanowires (AgNWs), the volatile solvent being ethanol. The silver nanowire solution is coated on the substrate in a brushing mode, and as ethanol has strong volatility, the ethanol volatilizes rapidly along with the brushing process, and the silver nanowires are deposited and stacked and attached on the substrate.
In yet another embodiment of the present application, the organic solvent may be at least one selected from the group consisting of methyl ethyl ketone, acetone, methyl isobutyl ketone, acetyl acetone, ethyl acetate, methyl acetate, isopropyl acetate, butyl acetate, methanol, ethanol, isopropyl alcohol, butanol, isobutanol, diacetone alcohol, toluene, xylene, which will quickly volatilize after drying the metal nanowire solution, leaving only the silver nanowires on the second functional layer.
The application also 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, where the first functional layer 104 is disposed on the bottom electrode 105; an electroluminescent layer 103 is disposed on the first functional layer 104; a second functional layer 102 is arranged on the electroluminescent layer 103; a top electrode 101 is disposed on the second functional layer 102; wherein the top electrode 101 comprises metal nanowires. The metal nanowires in the top electrode 101 are stacked and overlapped with each other, so that the top electrode has good conductive performance and light transmission performance.
In another embodiment of the present application, the preparation method of the top electrode 101 may be directly formed on the second functional layer 102, and when the electrode is prepared by using the metal nanowire, the metal nanowire is 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 a metal nanowire stacking arrangement structure, the top electrode 101 is completely formed by 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 ITO in the prior art through the magnetron sputtering method, the metal nanowire in the embodiment is directly formed on the second functional layer 102 of the electroluminescent device 100, so that the second functional layer 102 is not damaged; in addition, the top electrode 101 with the metal nanowire network structure has no excessive requirements on the film flatness of the second functional layer 102; finally, the manufacturing process of the top electrode 101 is simple, 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 made of flexible materials, the top electrode 101 is of a metal nanowire network structure, and is also of a flexible structure, and the three may be matched to realize flexible display, that is, by combining the top electrode 101 of the metal nanowire network structure in the embodiment with the flexible substrate 106 and the bottom electrode 105, the electroluminescent device 100 may be made to bend and emit light, and the 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% -99.9%, and when the bottom electrode is also a transparent electrode, the electroluminescent device may be used in an electronic device for transparent display of a scene, so as to view an image on the other side of the electronic device, for example, the electroluminescent device may be used as an electrode device for displaying a device on a showcase, which is attractive and 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 can realize two-sided light emission, and further can realize transparent display, namely, when the electroluminescent device can self-emit light, an image at the rear side of the electroluminescent device can be seen through the electroluminescent device, and the electroluminescent device is transparent for a viewer.
In another embodiment of the present application, the sheet resistance of the top electrode is less than 50Ω/≡, so that the top electrode can be well ensured to have good conductive performance 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 types of metal nanowires in the multi-coated metal nanowire solution can be the same or different. Preferably, when the metal nanowire solution is coated on the second functional layer through multiple coating, at least one group of adjacent metal nanowire films are different in metal nanowire type.
In this embodiment, the top electrode is entirely composed of metal nanowires, such as silver nanowires (AgNWs), and the overall top electrode has very low sheet resistance, enhancing conductivity; 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 brushing mode, so that the hole injection layer is not damaged; in addition, the top electrode of the network-shaped structure with the stacked arrangement of the metal nanowires has no excessive requirements on the film flatness of the air injection layer; finally, the manufacturing process of the top electrode is simple and convenient, and the production and manufacturing cost of the electroluminescent device is reduced.
It should be noted that the structure of the electroluminescent device is not limited in this application. The electroluminescent device may be of a front-mounted structure; the structure can also be an inverted structure, and the network structure of stacking and arranging the metal nanowires in the top electrode is applicable.
The application also provides a display device, including above-mentioned electroluminescent device, display device includes but is not limited to cell-phone, computer, on-vehicle display, AR display, VR display, intelligent wrist-watch, flexible display panel scheduling device, and the electroluminescent device of this application can be QLED device, OLED device, PLED device, micro-LED device or Mini-LED device. The display device of the application can be a top-light-emitting display device, a bottom-light-emitting display device or a transparent display 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
Manufacturing a transparent QLED device:
s1, providing a glass substrate with an ITO conductive layer;
s2, coating a hole injection layer PEDOT on a glass substrate with an ITO conductive layer: PSS;
s3, at the hole injection layer PEDOT: coating a hole transport layer TFB on the PSS;
s4, coating a red light 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/mL;
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;
and S9, brushing a 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 a top electrode with the square resistance of 12 omega/≡.
Finally, a red quantum dot QLED device is manufactured, the red CdSe/ZnS quantum dot QLED device is electrified, the starting voltage is 1.8V, the obtained luminescence is uniform, the voltage is regulated until the luminescence brightness of the red CdSe/ZnS quantum dot QLED 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 QLED device are respectively measured, the maximum current efficiency of the ITO side is measured to be 5.75cd/A, and the maximum external quantum efficiency is measured to be 8.94%; the maximum current efficiency on 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 QLED device is 10.54cd/A, and the total maximum external quantum efficiency is 16.23%.
Example 2
Manufacturing a transparent QLED 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, drying and annealing;
s3, printing a TFB on the pixel substrate, and drying and annealing;
s4, printing red 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/mL;
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;
and S9, brushing a 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 a top electrode with the square resistance of 12 omega/≡.
Finally, the red quantum dot QLED device is manufactured, the red CdSe/ZnS quantum dot QLED device is electrified, the starting voltage is 2.2V, the external quantum efficiency is 4.63%, the current efficiency is 2.93cd/A, and the light emission is uniform.
Example 3
Manufacturing a transparent QLED device:
s1, providing a glass substrate with an ITO conductive layer;
s2, coating a hole injection layer PEDOT on a glass substrate with an ITO conductive layer: PSS;
s3, at the hole injection layer PEDOT: coating a hole transport layer TFB on the PSS;
s4, coating a red light 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/mL;
s7, drying the metal nanowire solution to form a first metal nanowire film;
and S8, brushing a 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 square resistance of 15 omega/≡.
S9, annealing the top electrode at 100 ℃ for 10 minutes.
Finally, a red quantum dot QLED device is manufactured, the red CdSe/ZnS quantum dot QLED device is electrified, the starting voltage is 1.8V, the obtained luminescence is uniform, the voltage is regulated until the luminescence brightness of the red CdSe/ZnS quantum dot QLED 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 QLED device are respectively measured, the maximum current efficiency of the ITO side is measured to be 2.15cd/A, and the maximum external quantum efficiency is measured to be 3.31%; the maximum current efficiency on the AgNWs side is 1.95cd/A, the maximum external quantum efficiency is 2.93%, the total maximum current efficiency of the red CdSe/ZnS quantum dot QLED device is 4.1cd/A, and the total maximum external quantum efficiency is 6.24%.
As can be seen from the above, in the embodiment of the application, the top electrode is formed by brushing silver nanowires (AgNWs), and the finally prepared quantum dot QLED can be lightened, and when the bottom electrode is ITO, the maximum light-emitting current efficiency and the maximum external quantum efficiency of the silver nanowires (AgNWs) side and the ITO side are substantially the same. The QLED device has uniform light emission and high external quantum efficiency, and unlike the conventional method that silver nanowires (AgNWs) are embedded into PI or PMMA to manufacture a composite electrode, the method directly forms the silver nanowires (AgNWs) on the zinc oxide electron transport layer, the top electrode is completely formed by 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 QLED device is reduced.
Compared with the current ITO sputtering mode, the silver nanowires (AgNWs) are formed on the zinc oxide electron transport layer by brushing and UV light irradiation, and basically do not damage the zinc oxide electron transport layer.
While the present disclosure has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims.

Claims (12)

1. A method of 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 steps of:
coating the metal nanowire solution on the second functional layer;
drying the metal nanowire solution to form a metal nanowire film;
carrying out ultraviolet irradiation on the metal nanowire film, wherein the irradiation time is 30-300 seconds;
annealing the metal nanowire film;
the substrate and the bottom electrode are made of flexible materials, and the top electrode is of a metal nanowire network structure, and the substrate, the bottom electrode and the metal nanowire network structure are matched to realize flexible display.
2. The method of manufacturing an electroluminescent device according to claim 1, wherein the manner of drying the metal nanowire solution comprises vacuum drying or thermal drying.
3. The method for manufacturing an electroluminescent device according to claim 1, wherein the coating is wet coating.
4. A method of manufacturing an electroluminescent device as claimed in claim 3, characterized in that the coating method comprises at least one of spraying, blade coating, wire bar coating, brush coating, roll bar coating, screen printing, gravure printing, relief printing, spin coating printing, inkjet printing.
5. The method of manufacturing an electroluminescent device according to claim 1, wherein the metal nanowire solution comprises metal nanowires and an organic solvent.
6. The method of manufacturing an electroluminescent device according to claim 5, wherein the concentration of the metal nanowire solution is not more than 10mg/mL.
7. The method for manufacturing an electroluminescent device according to claim 5 or 6, 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.
8. An electroluminescent device, characterized in that it is produced by the method for producing an electroluminescent device according to any one of claims 1 to 7.
9. The electroluminescent device of claim 8, wherein the top electrode has a light transmittance of 50% to 99.9%.
10. The electroluminescent device of claim 8, wherein the top electrode has a sheet resistance of less than 50Ω/≡.
11. The electroluminescent device of claim 8, wherein the metal nanowires comprise at least one of gold nanowires, silver nanowires, copper nanowires, iron nanowires, cobalt nanowires, nickel nanowires.
12. A display device comprising an electroluminescent device as claimed in any one of claims 8 to 11.
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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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