CN115547574A

CN115547574A - Silver nanowire-sodium gluconate composite transparent conductive film and preparation method and application thereof

Info

Publication number: CN115547574A
Application number: CN202211189387.0A
Authority: CN
Inventors: 陈月花; 张舫搏; 张新稳; 王杨程
Original assignee: Nanjing University of Posts and Telecommunications
Current assignee: Nanjing University of Posts and Telecommunications
Priority date: 2022-09-28
Filing date: 2022-09-28
Publication date: 2022-12-30

Abstract

The invention discloses a silver nanowire-sodium gluconate composite transparent conductive film and a preparation method and application thereof, wherein the preparation method comprises the following steps: preparing silver nanowire suspension and sodium gluconate solution; cleaning the substrate, and performing hydrophilic treatment to obtain a pretreated substrate; firstly, coating a silver nanowire suspension on a pretreated substrate, and then heating and curing to form a silver nanowire film; and then coating a sodium gluconate solution on the silver nanowire film, and then heating and curing to form the silver nanowire-sodium gluconate composite transparent conductive film. By adopting the method, the sodium gluconate material can be utilized, so that the metal nanowire transparent conductive film can obtain a flat film surface and excellent mechanical stability, oxidation resistance, high temperature resistance and other properties under the premise of keeping good photoelectric properties, and has important application prospect and value in the field of low-cost large-scale flexible wearable optoelectronic devices.

Description

Silver nanowire-sodium gluconate composite transparent conductive film and preparation method and application thereof

Technical Field

The invention belongs to the technical field of optoelectronic devices, and particularly relates to a silver nanowire-sodium gluconate composite transparent conductive film as well as a preparation method and application thereof.

Background

The flexible transparent electrode is a key part for manufacturing flexible optoelectronic devices such as flexible touch screens, displays, solar cells and smart windows. In addition to high conductivity and optical transmittance, flexible electrodes require long-term mechanical stability to achieve reliable performance. Indium Tin Oxide (ITO) is commonly used as a transparent conductive electrode, but its brittleness limits its application in flexible devices. Researchers have extensively explored several alternative materials, including metal nanowires, carbon nanotubes, graphene, and conductive polymers.

Of these candidate materials, silver nanowires (AgNWs) are of particular interest because of their high conductivity, flexibility, ease of synthesis, and solution processability. Silver nanowire films with low sheet resistance and high transmittance can be currently prepared by a solution coating method. However, the adhesion of the coated silver nanowires to common polymer substrates is poor, which results in delamination of the silver nanowire electrodes during repeated mechanical deformation. Various coating layers made of metal oxide, graphene or polymer have been introduced on the silver nanowire thin film to inhibit delamination of the nanowires and reduce surface roughness of the electrode, but these coating layers generally cause a reduction in optical transmittance of the electrode. In addition, silver nanowires are embedded in a surface layer of a polymer such as Polydimethylsiloxane (PDMS) or Polyimide (PI), but such an electrode is obtained by curing a prepolymer, and thus this method is not easily extended to other conventional polymers. The high surface roughness and poor thermal stability of silver nanowire films are also key issues to be solved for their use in optoelectronic devices. Therefore, it is necessary to develop a silver nanowire thin film having high adhesion, mechanical stability and thermal stability with low surface roughness directly on a flexible polymer substrate without sacrificing its photoelectric properties.

Disclosure of Invention

The technical problem to be solved is as follows: aiming at the technical problems, the invention provides the silver nanowire-sodium gluconate composite transparent conductive film and the preparation method and application thereof.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

in a first aspect, the invention provides a preparation method of a silver nanowire-sodium gluconate composite transparent conductive film, which comprises the following steps:

step 1, preparation of silver nanowire solution

Mixing silver nanowire dispersion liquid serving as precursor solution with a solvent A to obtain a silver nanowire (AgNWs) solution, wherein the concentration of AgNWs in the AgNWs solution is 1-5 mg/mL, and the solvent A is absolute ethyl alcohol, isopropanol or deionized water;

step 2, preparation of sodium gluconate solution

Mixing a sodium gluconate material with a solvent B, oscillating the mixture in an ultrasonic cleaning machine for 1-2 hours to fully dissolve the sodium gluconate material to obtain a sodium gluconate solution, wherein the concentration of the sodium gluconate solution is 25-50 mg/mL, and the solvent B is absolute ethyl alcohol and deionized water in a volume ratio of 1: 1-1: 3 a mixed solvent;

step 3, pretreatment of the transparent substrate

Cleaning the substrate, and treating for 5min by using an ultraviolet ozone cleaning instrument (UV/ozone) to enhance the surface hydrophilicity of the substrate to obtain a pretreated substrate;

step 4, preparing the silver nanowire-sodium gluconate composite film

Firstly, coating AgNWs solution on a pretreated substrate, curing for 10-20 min at 100-130 ℃ to form an AgNWs film, then coating sodium gluconate solution on the AgNWs film, and curing for 10-15 min at 80-100 ℃ to form the silver nanowire-sodium gluconate composite transparent conductive film.

Preferably, in step 3, the substrate is glass, polyethylene Terephthalate (PET), polyimide (PI), or Polyethylene Naphthalate (PEN).

Preferably, the specific steps of cleaning the substrate in step 3 are as follows: and ultrasonically cleaning the substrate for 20-30 min by respectively using a detergent, deionized water, ethanol and acetone in sequence.

Preferably, the coating mode in the step 4 is blade coating, meyer bar blade coating, slit coating, spray coating or spin coating.

In a second aspect, the invention provides a silver nanowire-sodium gluconate composite transparent conductive film, which is prepared by the preparation method of the first aspect.

In a third aspect, the invention provides an application of the silver nanowire-sodium gluconate composite transparent conductive film of the second aspect in preparing a flexible transparent electrode.

Has the advantages that: 1) According to the invention, a sodium gluconate material is coated on the surface of the silver nanowire film as a protective layer by a solution method, so that the silver nanowire film with low surface roughness, high viscosity, mechanical stability and thermal stability is directly formed on the flexible polymer substrate under the condition of not sacrificing the photoelectric property of the silver nanowire film, and the silver nanowire film is greatly improved in multiple properties;

2) The sodium gluconate material adopted by the invention is an environment-friendly pollution-free material, the preparation process of the modified nanowire electrode is simple, and the modified nanowire electrode has certain help to reduce pollution in industrial production and is suitable for industrial production.

Drawings

FIG. 1 is a photograph of different electrodes, wherein (a) is AgNWs/PET electrode and (b) is AgNWs/sodium gluconate/PET electrode;

FIG. 2 shows the square resistance of AgNWs and AgNWs/sodium gluconate composite film;

FIG. 3 shows the transmittance of AgNWs and AgNWs/sodium gluconate composite films;

fig. 4 is an Atomic Force Microscope (AFM) image of AgNWs and AgNWs/sodium gluconate composite film and corresponding 3D image thereof, wherein (a) is the Atomic Force Microscope (AFM) image of AgNWs, (b) is the Atomic Force Microscope (AFM) image of AgNWs/sodium gluconate composite film, (c) is the 3D image of AgNWs, and (D) is the 3D image of AgNWs/sodium gluconate composite film;

FIG. 5 is a graph showing the resistance change after bending the AgNWs film and the AgNWs/sodium gluconate composite film 10000 times under the condition of a bending radius of 2 mm;

FIG. 6 is a graph showing the variation of sheet resistance of AgNWs and AgNWs/sodium gluconate composite films before and after 50 tape stripping cycles;

FIG. 7 is a graph of the change in sheet resistance of an original AgNWs electrode and a composite electrode heat treated at different temperatures for 60 s;

fig. 8 is a schematic diagram of a structure of a flexible green fluorescent OLED device prepared by using an AgNWs/sodium gluconate composite film and a luminance-voltage curve, where (a) is the schematic diagram of the structure of the flexible green fluorescent OLED device and (b) is the luminance-voltage curve.

Detailed Description

The invention is described in detail below with reference to the following figures and specific examples:

the substrate is glass, polyethylene Terephthalate (PET), polyimide (PI), polyethylene Naphthalate (PEN), etc.;

example 1

A preparation method of a silver nanowire-sodium gluconate composite transparent conductive film comprises the following steps:

1) Preparing a silver nanowire solution and a sodium gluconate solution:

taking the AgNWs solution as a precursor solution, and adding isopropanol to dilute the silver nanowire dispersion solution to finally obtain silver nanowire ink (AgNWs solution); wherein the AgNWs concentration is 3 mg/mL;

mixing sodium gluconate and a solvent B, and then carrying out ultrasonic dissolution sufficiently, wherein the concentration of a sodium gluconate solution is 50 mg/mL, and the solvent B is prepared by mixing absolute ethyl alcohol and deionized water according to a volume ratio of 1:1 are mixed to obtain the product.

2) And (3) pretreating the PET transparent film substrate:

ultrasonically cleaning a PET film (the thickness is 125 mu m) with a detergent, deionized water, ethanol and acetone for 30 min respectively, and then carrying out surface treatment on the surface of the PET film for 5min at the power of 45W by using an ultraviolet ozone cleaning instrument UV/ozone to obtain a pretreated substrate;

3) And preparing the AgNWs/sodium gluconate composite transparent conductive film:

spin-coating a layer of silver nanowire solution on the pretreated substrate by using a spin-coating instrument at 2000rpm 30s, and curing at 130 ℃ for 15 min to form an AgNWs film;

and spin-coating a layer of sodium gluconate on the AgNWs film at the speed of 2000rpm 30s, and curing at the temperature of 80 ℃ for 10min to obtain the AgNWs/sodium gluconate composite film.

Example 2

The AgNWs/sodium gluconate composite conductive film prepared in example 1 is taken as an example for performance characterization and application.

Fig. 1 (b) is a photograph of an AgNWs/sodium gluconate conductive film, which exhibits a high transmittance as the original AgNWs conductive film (shown in fig. 1 (a)). The sheet resistance and the transmittance of the conductive film are tested, and as shown in fig. 2-3, the coating of the sodium gluconate hardly affects the photoelectric performance of the AgNWs conductive film, and the sheet resistance is within 30 Ω/sq when the transmittance of the composite conductive film in the visible light range exceeds 90%.

Fig. 4 is an Atomic Force Microscope (AFM) image of a conductive thin film, where an original silver nanowire thin film (fig. 4 (a)) has a high surface roughness (Rq =28.7 nm), which is likely to cause a short circuit of an organic optoelectronic thin film device, and is not suitable for the organic optoelectronic thin film device, and an AgNWs/sodium gluconate composite conductive thin film (fig. 4 (b)) has a flat surface with a root-mean-square roughness Rq of 5.9nm, which is suitable for the organic optoelectronic thin film device. The surface topography of the conductive film is more visually revealed in the corresponding three-dimensional surface topography maps shown in fig. 4 (c) and (d).

And testing the mechanical stability of the conductive film, namely testing the change of sheet resistance after the AgNWs film and the AgNWs/sodium gluconate composite film are bent for a certain number of times under the condition that the bending radius is 2 mm. Specifically, as shown in fig. 5, after 4000 times of bending, the sheet resistance of the AgNWs film starts to increase significantly, and the sheet resistance continues to increase along with the increase of the bending times, while the sheet resistance of the AgNWs/sodium gluconate composite film only slightly changes after 10000 times of bending tests, and the AgNWs/sodium gluconate composite film shows excellent mechanical stability.

The four conductive films were tested for adhesion to the substrate using 3M Scotch tape, as shown in fig. 6, and the original AgNWs electrode lost conductivity after 2 tape tests. The AgNWs/sodium gluconate composite film keeps the conductivity in the process of repeatedly sticking and peeling the adhesive tape for 50 times.

The thermal stability of the conductive film was measured by heating the conductive film on a hot stage at various temperatures for 60 seconds (from 120 ℃ to 400 ℃) and measuring the change in sheet resistance. As shown in fig. 7 in particular, the sheet resistance of the original AgNWs started to increase sharply after heating at 200 ℃ and failed completely at 220 ℃. The poor thermal stability of the original AgNWs is due to the nanoscale size effect, and AgNWs tends to melt at relatively lower temperatures than bulk silver. In contrast, the AgNWs/sodium gluconate composite film has better thermal stability, and the sheet resistance value is slightly changed when the temperature is increased to 400 ℃.

Respectively preparing a flexible green fluorescent OLED device by utilizing a commercial ITO conductive thin film (glass substrate) and an AgNWs/sodium gluconate composite thin film (PET substrate), wherein the flexible OLED device based on the AgNWs/sodium gluconate composite thin film is shown as a part (a) in fig. 8, and as can be seen from a part (b) in fig. 8, the flexible OLED device based on the AgNWs/sodium gluconate composite thin film has the maximum brightness equivalent to that of a rigid ITO-based device; under the same condition, compared with a device (2.5 cd/A) based on a commercial rigid ITO electrode, the device based on the AgNWs/sodium gluconate flexible composite electrode has higher maximum current efficiency (4.2 cd/A).

In summary, according to the silver nanowire-sodium gluconate composite transparent conductive film and the preparation method and application thereof, the sodium gluconate material is coated on the surface of the silver nanowire film as the protective layer by a solution method, so that the mechanical stability, the thermal stability and the surface flatness of the silver nanowire film are greatly improved on the basis of keeping the original photoelectric property of the silver nanowire film, the silver nanowire film is greatly improved in multiple properties, and the silver nanowire film is suitable for industrial production.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A preparation method of a silver nanowire-sodium gluconate composite transparent conductive film is characterized by comprising the following steps:

step 1, preparing a silver nanowire solution: mixing a silver nanowire dispersion liquid serving as a precursor solution with a solvent A to obtain a silver nanowire solution, wherein the concentration of silver nanowires in the silver nanowire solution is 1-5 mg/mL, and the solvent A is absolute ethyl alcohol, isopropanol or deionized water;

step 2, preparation of sodium gluconate solution: mixing a sodium gluconate material with a solvent B, oscillating for 1-2 hours in an ultrasonic cleaning machine, and fully dissolving the sodium gluconate material to obtain a sodium gluconate solution, wherein the concentration of the sodium gluconate solution is 25-50 mg/mL, and the solvent B is absolute ethyl alcohol and deionized water according to a volume ratio of 1: 1-1: 3 a mixed solvent;

step 3, pretreatment of the transparent substrate: cleaning the substrate, and treating for 5min by using an ultraviolet ozone cleaning instrument to enhance the surface hydrophilicity of the substrate to obtain a pretreated substrate;

step 4, preparing the silver nanowire/sodium gluconate composite film: firstly, coating the pretreated substrate obtained in the step 3 with a silver nanowire solution, curing for 10-20 min at 100-130 ℃ to form a silver nanowire film, then coating the silver nanowire film with a sodium gluconate solution, and curing for 10-15 min at 80-100 ℃ to form the silver nanowire-sodium gluconate composite transparent conductive film.

2. The preparation method of the silver nanowire-sodium gluconate composite transparent conductive film according to claim 1, characterized by comprising the following steps: in step 3, the substrate is glass, polyethylene terephthalate, polyimide or polyethylene naphthalate.

3. The preparation method of the silver nanowire-sodium gluconate composite transparent conductive film according to claim 1, characterized by comprising the following steps: in step 3, the specific steps of cleaning the substrate are as follows: and (3) ultrasonically cleaning the substrate for 20-30 min by respectively sequentially using a detergent, deionized water, ethanol and acetone.

4. The preparation method of the silver nanowire-sodium gluconate composite transparent conductive film according to claim 1, characterized by comprising the following steps: the coating mode in the step 4 is blade coating, meyer bar blade coating, slit coating, spray coating or spin coating.

5. A silver nanowire-sodium gluconate composite transparent conductive film is characterized in that: prepared by the preparation method of any one of claims 1 to 4.

6. The application of the silver nanowire-sodium gluconate composite transparent conductive film of claim 5 in preparing a flexible transparent electrode.