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

Abstract

The present invention discloses a silver nanowire-sodium gluconate composite transparent conductive film and its preparation method and application, comprising the following steps: preparing a silver nanowire suspension and a sodium gluconate solution; cleaning a substrate and subjecting it to hydrophilic treatment to obtain a pretreated substrate; coating the pretreated substrate with the silver nanowire suspension and then heat-curing it to form a silver nanowire film; and then coating the silver nanowire film with a sodium gluconate solution and then heat-curing it to form a silver nanowire-sodium gluconate composite transparent conductive film. This method, utilizing sodium gluconate as a material, allows a metal nanowire transparent conductive film to be produced while maintaining good optoelectronic properties while also achieving a flat film surface, excellent mechanical stability, antioxidant properties, and high-temperature resistance. This method has significant application prospects and value in the field of low-cost, large-scale flexible wearable optoelectronic devices.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic devices, and in particular relates to a silver nanowire-sodium gluconate composite transparent conductive film and a preparation method and application thereof. Background Art

[0002] Flexible transparent electrodes are key components in the fabrication of flexible optoelectronic devices, such as flexible touchscreens, displays, solar cells, and smart windows. In addition to high electrical conductivity and optical transmittance, flexible electrodes require long-term mechanical stability for 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.

[0003] Among these candidate materials, silver nanowires (AgNWs) have attracted particular interest due to their high conductivity, flexibility, ease of synthesis, and solution processability. Currently, AgNW films with low sheet resistance and high transmittance can be prepared via solution coating. However, the coated AgNWs exhibit poor adhesion to common polymer substrates, leading to delamination of AgNW electrodes during repeated mechanical deformation. Various capping layers made of metal oxides, graphene, or polymers have been introduced onto AgNW films to inhibit delamination and reduce surface roughness, but these capping layers typically result in reduced optical transmittance. Alternatively, AgNWs have been embedded in surface layers of polymers such as polydimethylsiloxane (PDMS) or polyimide (PI), but these electrodes are obtained by curing prepolymers, making this approach difficult to extend to other conventional polymers. The high surface roughness and poor thermal stability of AgNW films are also key challenges that need to be addressed for their use in optoelectronic devices. Therefore, it is necessary to develop a highly adhesive, mechanically stable, and thermally stable silver nanowire film with low surface roughness directly on a flexible polymer substrate without sacrificing its optoelectronic properties. Summary of the Invention

[0004] Technical problem to be solved: In response to the above technical problems, the present invention provides a silver nanowire-sodium gluconate composite transparent conductive film and its preparation method and application, using sodium gluconate material and an environmentally friendly process to achieve the preparation of a high-quality flexible transparent electrode.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] In a first aspect, the present invention provides a method for preparing a silver nanowire-sodium gluconate composite transparent conductive film, comprising the following steps:

[0007] Step 1, preparation of silver nanowire solution

[0008] A silver nanowire dispersion is used as a precursor solution and mixed with solvent A to obtain a silver nanowire (AgNWs) solution, wherein the concentration of AgNWs in the AgNWs solution is 1 to 5 mg / mL, and the solvent A is anhydrous ethanol, isopropyl alcohol or deionized water;

[0009] Step 2, preparation of sodium gluconate solution

[0010] Mixing the sodium gluconate material with solvent B, and shaking in an ultrasonic cleaning machine for 1 to 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 to 50 mg / mL, and the solvent B is a mixture of anhydrous ethanol and deionized water in a volume ratio of 1:1 to 1:3;

[0011] Step 3: Transparent substrate pretreatment

[0012] The substrate was cleaned and treated with an ultraviolet ozone cleaner (UV / ozone) for 5 minutes to enhance its surface hydrophilicity, thereby obtaining a pretreated substrate.

[0013] Step 4: Preparation of silver nanowire-sodium gluconate composite film

[0014] First, an AgNWs solution is coated on a pretreated substrate and cured at 100-130°C for 10-20 min to form an AgNWs film. Then, a sodium gluconate solution is coated on the AgNWs film and cured at 80-100°C for 10-15 min to form a silver nanowire-sodium gluconate composite transparent conductive film.

[0015] Preferably, in step 3, the substrate is glass, polyethylene terephthalate (PET), polyimide (PI) or polyethylene naphthalate (PEN).

[0016] Preferably, the specific steps of cleaning the substrate in step 3 are: ultrasonically cleaning the substrate with detergent, deionized water, ethanol and acetone respectively for 20-30 minutes.

[0017] Preferably, the coating method in step 4 is doctor blade coating, Meyer rod coating, slit coating, spray coating or spin coating.

[0018] In a second aspect, the present invention provides a silver nanowire-sodium gluconate composite transparent conductive film, which is prepared by the preparation method described in the first aspect.

[0019] In a third aspect, the present invention provides an application of the silver nanowire-sodium gluconate composite transparent conductive film described in the second aspect in the preparation of a flexible transparent electrode.

[0020] Beneficial Effects: 1) The present invention uses a solution method to coat sodium gluconate material on the surface of a silver nanowire film as a protective layer. This method develops a silver nanowire film with low surface roughness, high viscosity, mechanical stability, and thermal stability directly on a flexible polymer substrate without sacrificing its photoelectric properties, significantly improving multiple performance aspects of the silver nanowire film.

[0021] 2) The sodium gluconate material used in the present invention is an environmentally friendly and pollution-free material. The preparation process of the modified nanowire electrode is simple, which helps to reduce pollution in industrial production and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Photos of different electrodes, where (a) is the AgNWs / PET electrode and (b) is the AgNWs / sodium gluconate / PET electrode;

[0023] Figure 2 is the sheet resistance of AgNWs and AgNWs / sodium gluconate composite films;

[0024] Figure 3 is the transmittance of AgNWs and AgNWs / sodium gluconate composite films;

[0025] Figure 4 Atomic force microscope (AFM) images of AgNWs and AgNWs / sodium gluconate composite films and their corresponding 3D images, where (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;

[0026] Figure 5 The comparison of the square resistance changes of AgNWs film and AgNWs / sodium gluconate composite film after bending 10,000 times at a bending radius of 2 mm.

[0027] Figure 6 The change curves of the sheet resistance of AgNWs and AgNWs / sodium gluconate composite films before and after 50 tape peeling cycles;

[0028] Figure 7 The sheet resistance changes of the original AgNWs electrode and the composite electrode after heat treatment at different temperatures for 60s;

[0029] Figure 8 Schematic diagram of the structure and brightness-voltage curve of the flexible green fluorescent OLED device prepared using AgNWs / sodium gluconate composite film, where (a) is the schematic diagram of the structure of the flexible green fluorescent OLED device and (b) is the brightness-voltage curve. DETAILED DESCRIPTION

[0030] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments:

[0031] The substrate used is glass, polyethylene terephthalate (PET), polyimide (PI) or polyethylene naphthalate (PEN), etc.

[0032] Example 1

[0033] A method for preparing a silver nanowire-sodium gluconate composite transparent conductive film comprises the following steps:

[0034] 1) Preparation of silver nanowire solution and sodium gluconate solution:

[0035] Using AgNWs solution as the precursor solution, isopropyl alcohol was added to dilute the silver nanowire dispersion to obtain silver nanowire ink (AgNWs solution). The AgNWs concentration was 3 mg / mL.

[0036] Sodium gluconate was fully dissolved by ultrasonication after being mixed with solvent B. The concentration of the sodium gluconate solution was 50 mg / mL. The solvent B was obtained by mixing anhydrous ethanol and deionized water in a volume ratio of 1:1.

[0037] 2) Pretreatment of PET transparent film substrate:

[0038] The PET film (thickness of 125 μm) was ultrasonically cleaned with detergent, deionized water, ethanol, and acetone for 30 min, and then surface treated with a UV / ozone cleaner at a power of 45 W for 5 min to obtain the pretreated substrate.

[0039] 3) Preparation of AgNWs / sodium gluconate composite transparent conductive film:

[0040] A layer of silver nanowire solution was spin-coated on the pretreated substrate at 2000 rpm for 30 s using a spin coater and cured at 130 °C for 15 min to form an AgNWs film;

[0041] Then, a layer of sodium gluconate was spin-coated on the AgNWs film at 2000 rpm for 30 s and cured at 80°C for 10 min to obtain an AgNWs / sodium gluconate composite film.

[0042] Example 2

[0043] The AgNWs / sodium gluconate composite conductive film prepared in Example 1 was used as an example for performance characterization and application.

[0044] Figure 1 (b) is a photo of the AgNWs / sodium gluconate conductive film, which is different from the original AgNWs conductive film ( Figure 1 The sheet resistance and transmittance of the conductive film were tested, and the results were as follows: Figure 2-Figure 3 As shown in the figure, the coating of sodium gluconate has almost no effect on the photoelectric properties of the AgNWs conductive film. When the transmittance of the composite conductive film in the visible light range exceeds 90%, the sheet resistance is within 30 Ω / sq.

[0045] Figure 4 Atomic force microscope (AFM) images of conductive films, original silver nanowire films ( Figure 4 (a) has a high surface roughness (Rq = 28.7nm), which can easily cause short circuits in organic optoelectronic thin film devices and is not suitable for organic optoelectronic thin film devices. The AgNWs / sodium gluconate composite conductive film ( Figure 4 The middle (b) has a flat surface with a root mean square roughness Rq of 5.9 nm, which is suitable for organic optoelectronic thin film devices. Figure 4 The corresponding three-dimensional surface morphology images shown in (c) and (d) can more intuitively show the surface morphology of the conductive film.

[0046] To test the mechanical stability of the conductive film, the AgNWs film and the AgNWs / sodium gluconate composite film were bent a certain number of times with a bending radius of 2 mm to test the change in square resistance. Figure 5 As shown in the figure, after 4000 bends, the sheet resistance of the AgNWs film begins to increase significantly, and the sheet resistance continues to increase with the increase in the number of bends. However, the sheet resistance of the AgNWs / sodium gluconate composite film only changes slightly after 10,000 bends, showing excellent mechanical stability.

[0047] 3M Scotch tape was used to test the adhesion of four conductive films to the substrate, such as Figure 6 As shown in the figure, the original AgNWs electrode lost its conductivity after 2 tape tests, while the AgNWs / sodium gluconate composite film maintained its conductivity during 50 tape-stripping cycles.

[0048] To determine the thermal stability of the conductive film, heat the conductive film on a hot plate at different temperatures for 60 seconds (from 120°C to 400°C) and measure the change in square resistance. Figure 7 As shown in Figure 2, the square resistance of pristine AgNWs begins to increase dramatically after heating at 200°C and completely fails at 220°C. The poor thermal stability of pristine AgNWs is due to nanoscale size effects; compared to bulk silver, AgNWs tend to melt at relatively low temperatures. In contrast, the AgNWs / sodium gluconate composite film exhibits much better thermal stability, with only a slight change in square resistance when heated to 400°C.

[0049] Flexible green fluorescent OLED devices were prepared using commercial ITO conductive film (glass substrate) and AgNWs / sodium gluconate composite film (PET substrate), respectively. Figure 8 As shown in (a), from Figure 8 As can be seen in (b), the flexible OLED device based on AgNWs / sodium gluconate composite film has a maximum brightness comparable to that of the rigid ITO-based device; under the same conditions, the device based on the AgNWs / sodium gluconate flexible composite electrode has a higher maximum current efficiency (4.2 cd / A) than the device based on the commercial rigid ITO electrode (2.5 cd / A).

[0050] In summary, the present invention provides a silver nanowire-sodium gluconate composite transparent conductive film, its preparation method, and application. Sodium gluconate is coated on the surface of the silver nanowire film as a protective layer by a solution method. While maintaining its original photoelectric properties, the mechanical stability, thermal stability, and surface smoothness of the silver nanowire film are greatly improved, thereby significantly improving the silver nanowire film in multiple performance aspects and making it suitable for industrial production.

[0051] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a silver nanowire-sodium gluconate composite transparent conductive film, characterized in that: The following steps are involved: Step 1, preparation of a silver nanowire solution: using a silver nanowire dispersion as a precursor solution, mixing it with solvent A to obtain a silver nanowire solution, wherein the concentration of the silver nanowires in the silver nanowire solution is 1 to 5 mg / mL, and the solvent A is anhydrous ethanol, isopropyl alcohol or deionized water; Step 2, preparation of a sodium gluconate solution: mixing a sodium gluconate material with a solvent B, and oscillating in an ultrasonic cleaning machine for 1 to 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 to 50 mg / mL, and the solvent B is a mixture of anhydrous ethanol and deionized water in a volume ratio of 1:1 to 1:3; Step 3, pretreatment of the transparent substrate: cleaning the substrate and treating it with an ultraviolet ozone cleaner for 5 minutes to enhance its surface hydrophilicity, thereby obtaining a pretreated substrate; Step 4, preparation of silver nanowire / sodium gluconate composite film: first, apply a silver nanowire solution on the pretreated substrate obtained in step 3, and cure it at 100-130°C for 10-20 min to form a silver nanowire film, then apply a sodium gluconate solution on the silver nanowire film, and cure it at 80-100°C for 10-15 min to form a silver nanowire-sodium gluconate composite transparent conductive film.

2. The method for preparing the silver nanowire-sodium gluconate composite transparent conductive film according to claim 1, wherein: In step 3, the substrate is glass, polyethylene terephthalate, polyimide or polyethylene naphthalate.

3. The method for preparing the silver nanowire-sodium gluconate composite transparent conductive film according to claim 1, wherein: In step 3, the specific steps of cleaning the substrate are: ultrasonically cleaning the substrate with detergent, deionized water, ethanol and acetone in sequence for 20-30 minutes.

4. The method for preparing the silver nanowire-sodium gluconate composite transparent conductive film according to claim 1, wherein: The coating method in step 4 is doctor blade coating, Meyer rod coating, slit coating, spray coating or spin coating.

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

6. Use of the silver nanowire-sodium gluconate composite transparent conductive film according to claim 5 in the preparation of a flexible transparent electrode.

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