Preparation method of conductive film based on PEDOT: PSS and silver nanowires

Abstract

The invention belongs to the field of conductive films, and discloses a preparation method of a conductive film based on PEDOT: PSS and silver nanowires, and the preparation method specifically comprises the following steps: after carrying out surface hydroxylation treatment on the silver nanowires AgNWs, under the action of a silane coupling agent 3-(trimethoxymethylsilyl) propyl methacrylate TMSPMA, mixing the silver nanowires AgNWs with PEDOT: PSS to prepare a PEDOT: PSS / AgNWs base solution; the preparation method comprises the following steps: adjusting the pH value of a base solution to be nearly neutral through sodium citrate, then mixing the base solution with a PEA emulsion, carrying out spin coating to form a film, and finally, carrying out ultrafast laser treatment to improve the conductivity so as to obtain the conductive film based on PEDOT: PSS and silver nanowires. The conductive film provided by the invention has high conductivity (gt; 1200 S / cm), good stability and excellent mechanical properties, and is suitable for a flexible electronic device and stable work in a certain humidity environment.

Description

Technical Field

[0001] The present invention belongs to the field of conductive films, and particularly relates to a method for preparing a conductive film based on PEDOT:PSS and silver nanowires. Background Art

[0002] In recent years, with the rapid development of flexible electronic devices, the demand for high-performance conductive films has been increasing. Although traditional indium tin oxide (ITO) films have excellent electrical conductivity and light transmittance, their high brittleness, high cost and scarcity of indium resources limit their application in flexible devices.

[0003] Therefore, researchers have been committed to developing new conductive materials. Among them, poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) has become a research hotspot due to its good electrical conductivity, solution coating ability, excellent thermal stability, flexibility and solution processability. However, the electrical conductivity of pure PEDOT:PSS films is still insufficient to meet the requirements of some high-performance devices. Silver nanowires (AgNWs) are regarded as ideal alternative materials due to their high electrical conductivity, excellent mechanical flexibility and light transmittance. However, problems such as uneven resistance distribution caused by rough surfaces, easy oxidation and high interfacial contact resistance still need to be solved. Therefore, combining PEDOT:PSS with AgNWs to construct a synergistic conductive network has become an effective strategy to improve the comprehensive performance of the film. When PEDOT:PSS is incorporated into the AgNWs network, PEDOT:PSS forms a continuous conductive path by filling the gaps between silver nanowires, thus significantly improving the overall electrical conductivity of the network. At the same time, the flexibility and tunability of PEDOT:PSS make the film surface more uniform and smooth, effectively reducing the poor contact and interfacial defects between nanowires, and further improving the performance of the film. The combination of this composite material not only endows the silver nanowire network with excellent electrical conductivity characteristics, but also gives it better mechanical stability and surface quality, making it more suitable for the application of various electronic devices. In recent years, much work has been done on the research of transparent conductive films of PEDOT:PSS and AgNWs: The academic paper "Zhao Y, Zhang S, Yu T, et al. Ultra-conformal skinelectrodes with synergistically enhanced conductivity for long-time and low-motion artifact epidermal electrophysiology[J]. Nature Communications, 2021,12(1): 4880." proposed that by adding surfactants and ionic compounds, a thin, uniform, continuous, and conductive PEDOT:PSS layer was prepared on the top layer of graphene by taking advantage of the synergistic effect of improved PEDOT molecular packing and underlying graphene charge transfer. The optimized dry electrode of the PEDOT:PSS transferred CVD graphene film (PTG) exhibited a total thickness of ~100 nm, a sheet resistance of ~24 Ω / sq (4142 S / cm), high optical transparency, and sufficient skin electro-mechanical electrical stability.

[0004] The academic paper "Chen S, Song L, Tao Z, et al. Neutral-pH PEDOT: PSS as over-coating layer for stable silver nanowire flexible transparent conductivefilms[J]. Organic Electronics, 2014, 15(12): 3654-3659." proposed a multi-step preparation of AgNWs / PEDOT:PSS transparent conductive electrodes using neutralized PEDOT:PSS (guanidine as the neutralizing agent) as an over-coating layer. However, the conductivity of the neutralized PEDOT:PSS was relatively low (about 60% lower compared to the original), and the resulting AgNWs hybrid film showed poor uniformity and high surface roughness.

[0005] The academic paper "Jin W Y, Ginting R T, Ko K J, et al. Ultra-smooth, fully solution-processed large-area transparent conducting electrodes for organic devices[J]. Scientific reports, 2016, 6(1): 36475." proposed the combination of embedded AgNWs metal grid and PEDOT:PSS conductive polymer in the polymer substrate to achieve high transparency (transmittance at 550 nm wavelength ~ 90%), low roughness (root mean square roughness ~ 1 nm), and high flexibility (bending radius ~ 1 mm). However, it did not solve the corrosion of embedded AgNWs caused by the acidity and hygroscopicity of PEDOT:PSS, resulting in poor stability of the fabricated thin film.

[0006] Although some progress has been made in the modification research on the mechanical and electrical properties of PEDOT:PSS / AgNWs flexible thin films, there are still the following deficiencies: 1. Since the PSS chains in PEDOT:PSS contain unstable sulfonic acid groups (-SO 3 H), these groups will undergo dissociation reactions in water, releasing hydrogen ions (H + ), resulting in the acidity of the PEDOT:PSS solution. In an acidic environment, silver nanowires are prone to oxidation reactions, generating silver oxides (such as Ag 2 O), thereby increasing the resistance of silver nanowires and reducing the overall conductivity of the composite thin film.

[0007] 2. In the composite system of PEDOT:PSS and silver nanowires (AgNWs), the binding between the two is poor. As a hydrophilic conductive polymer, the sulfonic acid groups (-SO 3 - ) of PEDOT:PSS are difficult to form a stable interface with the inert metal surface of AgNWs, resulting in a decrease in charge transfer efficiency and easy delamination under mechanical stress.

[0008] 3. The conductivity of PEDOT:PSS thin films prepared from the PEDOT:PSS stock solution is usually low, mainly because the presence of the PSS insulating phase restricts the transport of charge carriers. When PEDOT:PSS is combined with AgNWs, PEDOT:PSS fills the voids in the AgNWs network. However, due to its low conductivity, the transport of charge carriers in the PEDOT:PSS region is severely restricted, thus affecting the overall electrical conductivity of the composite thin film. To improve the conductivity of PEDOT:PSS thin films, additives (such as dimethyl sulfoxide DMSO or ethylene glycol EG) are usually added to the stock solution, or the thin film is post-treated with strong acids (such as sulfuric acid) and ionic solutions. However, these methods may cause certain damage to the stability and adhesion of AgNWs and the stability of the substrate, limiting their application in flexible electronic devices.

[0009] 4. When the PEDOT:PSS material is exposed to air, the sulfonic acid groups (-SO 3 H) in the PSS groups are highly hydrophilic and easily form hydrogen bonds with water molecules, giving the material a strong water absorption capacity. This water absorption property causes PEDOT:PSS to swell and even partially decompose in a humid environment, thereby leading to the degradation of device performance and limiting its stability during long-term use. Summary of the Invention

[0010] To solve the above technical problems, the present invention provides a method for preparing a conductive thin film based on PEDOT:PSS and silver nanowires. The acidity of PEDOT:PSS is neutralized by sodium citrate to promote the dispersion of silver nanowires. 3-(Trimethoxysilyl)propyl methacrylate (TMSPMA), a silane coupling agent, is used to bridge AgNWs and PEDOT:PSS to achieve efficient charge transport and interface strengthening, and ultrafast laser treatment is employed to enhance the overall conductivity. At the same time, by adding a PEA network, excessive swelling of PSS due to water absorption and detachment from the substrate are prevented, enabling the conductive thin film to operate in a certain humidity environment.

[0011] To solve the above problems, the present invention adopts the following technical solutions: A method for preparing a conductive thin film based on PEDOT:PSS and silver nanowires, characterized in that: after surface hydroxylation treatment of AgNWs, under the action of the silane coupling agent TMSPMA, it is mixed with PEDOT:PSS to obtain a PEDOT:PSS / AgNWs base liquid; after adjusting the pH of the base liquid with sodium citrate, it is mixed with a PEA emulsion and spin-coated into a film, and finally the conductivity is improved by laser treatment to obtain a conductive thin film based on PEDOT:PSS and silver nanowires. The specific steps are as follows: Step 1. Surface hydroxylation treatment of silver nanowires Disperse 8 - 10 mg of AgNWs in 10 mL of nitric acid solution with a concentration of 0.01 - 0.03 M, stir at 25 °C for 5 - 8 min to form silver oxide Ag 2 O on some areas of the AgNWs surface. Centrifuge to remove the supernatant, wash with deionized water, and then disperse the precipitate in 10 mL of deionized water. Dropwise add 0.1 M - 0.2 M sodium hydroxide solution until the pH reaches 8 - 9, and ultrasonically treat at 45 - 55 °C for 10 - 15 min to promote the hydrolysis of Ag 2 O to generate surface hydroxyl groups OH - . After centrifuging again and removing the supernatant, wash with deionized water to thoroughly remove the residual Ag + . Disperse the obtained precipitate in 10 mL of deionized water to obtain a hydroxylated AgNWs dispersion; Step 2: Prepare the PEDOT:PSS / AgNWs base solution Dissolve 400 - 450 μL of silane coupling agent TMSPMA in 10 mL of a mixture of ethanol and water with a volume ratio of 8 - 9:1, add acetic acid to adjust the pH to 4.5 - 5.2, and stir to allow it to hydrolyze fully to generate Si - OH active groups to obtain a coupling agent hydrolysis solution; Mix the coupling agent hydrolysis solution with the hydroxylated AgNWs dispersion in Step 1. Under nitrogen protection, stir and react at 30 °C - 40 °C for 80 - 100 min, then centrifuge to remove the supernatant, wash more than 3 times with a mixed solution of ethanol and water with a volume ratio of 4:1 to thoroughly remove the unreacted silver ions and TMSPMA. Subsequently, disperse the precipitate in 3 - 5 mL of deionized water containing 0.05 wt% sodium dodecylbenzenesulfonate SDBS (the introduction of SDBS can prevent electrostatic repulsion during subsequent PEDOT:PSS coating) to obtain a TMSPMA - AgNWs dispersion; Pump 2 mL of the TMSPMA - AgNWs dispersion and 10 - 15 mL of a 1 wt% PEDOT:PSS solution into the flow channel through a microfluidic device at a total flow rate of 0.2 mL / min according to the volume ratio for mixing; after mixing, stir in the dark at 25 °C under nitrogen protection for 40 - 60 min to enable the other end of TMSPMA to achieve interfacial bonding with PEDOT:PSS through hydrogen bonding to prepare the PEDOT:PSS / AgNWs base solution; Step 3: Adjust the pH and increase the dispersibility of AgNWs While stirring, add 0.05 M sodium citrate solution to the PEDOT:PSS / AgNWs base solution prepared in Step 2 to adjust the pH to 6.0 - 6.3, and continue stirring at room temperature for 30 - 60 minutes; Step 4: Synthesis of PEA emulsion 72 g of ethyl acrylate (EA) and 17.1 - 20 μL of TMSPMA were mixed and ultrasonically treated for 5 - 10 min to remove dissolved oxygen. The resulting mixture was added to a round-bottom flask, and 0.4 - 0.45 g of sodium dodecyl sulfate (SDS), 0.015 - 0.02 g of ammonium persulfate (APS), and 168 - 200 g of distilled water were added. Nitrogen was purged into the mixture and stirred at a speed of 300 rpm for 10 - 15 min, and then the round-bottom flask was sealed with a septum plug; A syringe needle connected to the balloon was inserted into the septum plug to balance the additional pressure generated by the heat release during polymerization. The round-bottom flask was placed in an oil bath at 65 - 70 °C and stirred in a magnetic stirrer at 300 rpm for 8 - 10 h to obtain a PEA emulsion; The prepared PEA emulsion was stored at room temperature in a plastic tank made of high-density polyethylene; Step 5, Preparation and Post-treatment of the Film Take 10 mL of the PEDOT:PSS / AgNWs base solution after adjusting the pH in Step 3, and add 3.5 - 4 g of the PEA emulsion prepared in Step 4 thereto. After stirring evenly, it was degassed under vacuum to obtain a composite solution; The glass substrate was cleaned with oxygen plasma, and then the composite solution was spin-coated on the surface of the substrate and cured gradiently; The substrate with the formed film was subjected to ultrafast laser treatment on the processing table of an ultrafast laser, and after taking it out, it was put into an oven and cured at 80 - 100 °C to obtain a conductive film based on PEDOT:PSS and silver nanowires.

[0012] Preferably, in Step 5, the gradient curing is completed by drying in ventilation at 25 - 30 °C for 1 - 1.5 h, vacuum drying at 60 - 70 °C for 30 - 50 min, and annealing at 100 - 130 °C for 10 - 20 min.

[0013] Preferably, in Step 5, the parameters of the ultrafast laser treatment are set as follows: laser power 8.5 W - 9.5 W, line scanning speed 950 mm / s - 1150 mm / s, filling pitch 32 μm - 37 μm. Ultrafast laser treatment shows unique advantages compared with continuous laser in the processing of PEDOT:PSS films. Its ultrashort pulse (10 -15 ~10 -12 seconds) realizes non-thermal-dominated localized processing through the nonlinear absorption effect, significantly suppressing the influence of heat diffusion on the material, thereby avoiding the excessive carbonization of the PSS insulating phase or the degradation of the PEDOT conductive phase caused by heat accumulation in continuous laser, and retaining the conductivity and mechanical flexibility of the film to the greatest extent. This characteristic enables the ultrafast laser to achieve precise patterning with micron-level or even sub-micron resolution on the surface of PEDOT:PSS (such as the preparation of electrode microstructures), while avoiding common thermal stress cracks or edge ablation defects in continuous laser treatment, and is particularly suitable for local doping regulation and high-resolution device integration of transparent conductive films (such as flexible electronics, biosensors).

[0014] The conductive thin film of the present invention is prepared from AgNWs, PEDOT:PSS, sodium citrate, TMSPMA, and polyethyl acrylate PEA. By introducing the silane coupling agent TMSPMA, a stable "silver-silane-PEDOT:PSS" bridging structure is constructed. By adding sodium citrate, the pH of the solution can be adjusted to near neutrality, and a complexation reaction occurs with the silver ions on the surface of the silver nanowires, effectively inhibiting the oxidation of silver ions and the corrosion of the nanowires. Sodium citrate also promotes the uniform dispersion of silver nanowires in the PEDOT:PSS aqueous solution through electrostatic repulsion and steric hindrance. In addition, the hydrophobic elastic network of the PEA emulsion further locks the PEDOT:PSS chains, preventing PEDOT:PSS from failing due to water absorption and swelling. The film is treated with ultrafast laser, which significantly improves the conductivity of the film by selectively removing part of the PSS insulating layer and increasing the oxidation degree of PEDOT. The conductive thin film provided by the present invention has a high conductivity (>1200 S / cm), good stability (the conductivity retention rate is >65% in a high-humidity environment), and excellent mechanical properties (the conductivity decreases by <10% when the bending radius <5 mm), and is suitable for stable operation in flexible electronic devices and an environment with a certain humidity. The beneficial effects of the present invention are specifically reflected in: 1. Introducing sodium citrate into the PEDOT:PSS emulsion can protect AgNWs from corrosion in the water environment through a multi-level cooperative mechanism, and its mechanism of action strictly follows the principles of electrochemistry and surface chemistry: First, as a pH buffer, sodium citrate neutralizes the inherent acidity (pH 2-3) of PEDOT:PSS, raises the pH of the system to near neutrality, and inhibits the oxidation reaction of silver by reducing the H + concentration; Second, the citrate ion (C 6 H 5 O 7 3- ) forms a stable complex ([Ag(C + H 6 H 5 O 7 )] 2- ) with the dissolved Ag + through the multidentate coordination ability of three carboxyl groups (-COO-) and one hydroxyl group (-OH), reduces the free Ag 2 concentration through complexation equilibrium, and inhibits the continuous progress of the corrosion reaction; Finally, the citrate ion forms a dense and extremely thin molecular layer on the surface of AgNWs through physical adsorption and chemical coordination. The tunneling resistance is slightly enhanced, but the steric hindrance effect of the citrate ion makes the AgNWs more evenly dispersed, forming a denser conductive network; and this layer effectively blocks the direct contact of H 2 O / O -Erosive ions such as these form a dual physicochemical barrier. This three-level protection mechanism significantly reduces the corrosion current density of silver, providing a theoretical basis and process guarantee for the stability of the AgNWs-PEDOT:PSS composite system in aqueous processing.

[0015] 2. As Figure 1 shown, the silane coupling agent TMSPMA achieves uniform dispersion and stable composite of AgNWs in the PEDOT:PSS aqueous solution through a two-step cooperative mechanism: First, its inorganic end (trimethoxysilyl group -Si-OCH 3 3) hydrolyzes to form silanol (-Si-OH), which condenses with the pre-treated hydroxyl groups (-OH) on the surface of AgNWs to form covalent bonds (Ag-O-Si), endowing AgNWs with hydrophilicity to inhibit agglomeration caused by van der Waals forces; Subsequently, the organic end (methacryloyloxy group) dynamically cross-links with the sulfonic acid groups (-SO 3 3H) in PEDOT:PSS through hydrogen bonds, and at the same time its hydrophobic segments (acrylate) are compatible with the hydrophobic regions of PEDOT, thus significantly enhancing the interfacial binding; Finally, the synergistic effect of covalent bonds and hydrogen bonds combined with the steric hindrance effect of silane segments enables AgNWs to form a sterically stable dispersion system in PEDOT:PSS, providing a controllable strategy for the interface engineering of high-performance flexible conductive composites.

[0016] 3. Using ultrafast laser to treat the AgNWs / PEDOT:PSS composite conductive film, the increase in the conductivity of PEDOT:PSS is attributed to the fact that laser treatment increases the oxidation degree of PEDOT and reduces the content of PSS. Compared with traditional solvent addition and post-treatment methods, ultrafast laser treatment of the film is a green, pollution-free, and low-cost treatment method. Compared with continuous laser, ultrafast laser pulses have the advantages of short action time, high peak power, and low heat generation. When processing materials, ultrafast laser does not bring heat to the surrounding materials. Ultrafast laser can selectively process the PEDOT:PSS film to form electrode patterns. Selecting an appropriate power, ultrafast laser can selectively remove the PEDOT:PSS film without damaging the surrounding PEDOT:PSS film or substrate. Since no solvents are added, both cost is saved and the adhesion and flexibility of the film are increased.

[0017] 4. As Figure 2As shown, in the dry PEDOT:PSS / PEA / AgNWs film, PSS presents as a glassy polymer, while PEDOT behaves as a crystalline polymer, and PEA has rubber-like properties. When the PEDOT:PSS / AgNWs base liquid is mixed with the PEA emulsion, as the water evaporates, the TMSPMA silyl groups condense into siloxane bonds, and the siloxane bonds crosslink the PEA chains. The emulsion particles gradually fuse to form a continuous solid structure, which contains two main domains: the PEDOT:PSS domain and the PEA domain, and the characteristic sizes of these two domains are approximately in the micron range. The PSS chains remain continuous in the film and are not crosslinked. The PEDOT nanocrystals are embedded in the PSS and between the silver nanowires, and their sizes are much smaller than the emulsion particles. This structure enables the PEDOT nanocrystals to form a percolation network for electron transport in the film prepared from the mixed emulsion. This network is not disturbed by the hydrophobic and rubbery PEA chains, thus endowing the film with high conductivity. In addition, the presence of the PEA network effectively prevents the over-expansion of PSS, avoids the detachment of PSS from the substrate, and ensures the stability of the film in a certain humidity environment. Description of the Drawings

[0018] Figure 1 Schematic diagram of the interfacial enhancement mechanism of TMSPMA bridging PEDOT:PSS and silver nanowires.

[0019] Figure 2 Schematic diagram of the mechanism for improving the stability of the PEA-chain-fixed PEDOT:PSSD film in a certain humidity environment.

[0020] Figure 3 Variation of the film resistance with the placement time of the AgNWs film, AgNWs / PEDOT:PSS film, and AgNWs / PEDOT:PSS / PEA film when placed at a temperature of 85°C and a humidity of 30%.

[0021] Figure 4 Variation of the film resistance with the placement time of the AgNWs film, AgNWs / PEDOT:PSS film, and AgNWs / PEDOT:PSS / PEA film when placed at a temperature of 25°C and a humidity of 85%. Detailed Implementation Modes

[0022] The embodiments of the present invention will be described in detail below in conjunction with the drawings and embodiments. The following embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given. However, the protection scope of the present invention is not limited to the following embodiments.

[0023] The PEDOT:PSS used in the following embodiments was purchased from Shanghai Macklin Biochemical Co., Ltd. (containing 0.5 wt% PSS); The silver nanowires (AgNWs) used in the following examples were purchased from Shanghai Macklin Biochemical Co., Ltd. (diameter 90 nm, length 20 - 60 μm); The sodium citrate used in the following examples was purchased from Shanghai Macklin Biochemical Co., Ltd. (AR 99%); The ethyl acrylate used in the following examples was purchased from Shanghai Macklin Biochemical Co., Ltd. (AR 99%); The 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) used in the following examples was purchased from Sigma-Aldrich (AR 98%); The sodium dodecylbenzenesulfonate (SDBS) used in the following examples was purchased from Sigma Aldrich.

[0024] The sodium dodecyl sulfate (SDS) used in the following examples was purchased from Shanghai Macklin Biochemical Co., Ltd. (AR≥99%); The ammonium persulfate (APS) used in the following examples was purchased from Shanghai Macklin Biochemical Co., Ltd. (AR 98.5%).

[0025] Example 1

[0026] This example prepared a conductive film based on PEDOT:PSS and silver nanowires according to the following steps: Step 1. Hydroxylation treatment of the silver nanowire surface Disperse 10 mg of silver nanowires (AgNWs) in 10 mL of 0.02 M nitric acid (HNO 3 ) solution, place it in a 25°C constant temperature water bath and stir for 6 minutes to form silver oxide Ag 2 O on part of the surface of AgNWs. Then centrifuge at 8000 rpm for 10 minutes, remove the supernatant, wash it 6 times repeatedly with deionized water, and then disperse the precipitate in 10 mL of deionized water. Subsequently, slowly add 0.1 M sodium hydroxide solution to adjust the pH to 8 - 9, and ultrasonically treat it at 50°C for 10 min to promote the hydrolysis of Ag 2 O to generate OH - . Centrifuge again at 8000 rpm, remove the supernatant, wash it 5 times with deionized water, and disperse the obtained precipitate in 10 mL of deionized water to obtain a hydroxylated AgNWs dispersion.

[0027] Step 2. Preparation of the PEDOT:PSS / AgNWs base liquid Dissolve 400 μL of the silane coupling agent TMSPMA in a mixed solvent of 9 mL of ethanol and 1 mL of water, add 0.1 M acetic acid to adjust the pH to 4.8, and stir for 120 minutes to fully hydrolyze it to generate Si-OH active groups, obtaining a coupling agent hydrolysis solution.

[0028] Mix the hydrolyzed coupling agent solution with the hydroxylated AgNWs dispersion prepared in Step 1, and under nitrogen protection, stir at 40 °C for 90 minutes to complete the grafting reaction. After the reaction, centrifuge at 10,000 rpm for 15 minutes, remove the supernatant, wash 5 times with a mixed solution of ethanol and water with a volume ratio of 4:1 to remove unreacted silver ions and TMSPMA, and finally disperse the precipitate in 5 mL of deionized water containing 0.05 wt% SDBS to obtain a TMSPMA-AgNWs dispersion.

[0029] Pump 2 mL of the TMSPMA-AgNWs dispersion and 13 mL of a 1 wt% PEDOT:PSS solution into the flow channel through a microfluidic device at a total flow rate of 0.2 mL / min according to the volume ratio for mixing; after mixing, stir under nitrogen protection at 25 °C in the dark for 60 min to prepare a PEDOT:PSS / AgNWs base solution.

[0030] Step 3: pH adjustment and improvement of AgNWs dispersibility While stirring, add 0.05 M sodium citrate solution to the PEDOT:PSS / AgNWs base solution prepared in Step 2 to adjust the pH to 6, and continue stirring at room temperature for 60 minutes.

[0031] Step 4: PEA emulsion synthesis Mix 72 g of EA and 17.1 μL of TMSPMA and ultrasonically treat for 5 min to remove dissolved oxygen. Add the resulting mixture to a 500 mL round-bottom flask, add 0.415 g of SDS, 0.016 g of APS, and 168 g of distilled water, purge the mixture with nitrogen and stir at a speed of 300 rpm for 10 min, then seal the round-bottom flask with a septum plug. Insert a syringe needle connected to a balloon into the septum plug to balance the additional pressure generated by the exotherm during polymerization. Place the round-bottom flask in an oil bath at 65 °C and stir in a magnetic stirrer at 300 rpm for 8 h to prepare a PEA emulsion. Store the prepared PEA emulsion in a plastic jar made of high-density polyethylene (VWR, 16125-810) at room temperature.

[0032] Step 5: Preparation and post-treatment of the film Take 10 mL of the PEDOT:PSS / AgNWs base solution after adjusting the pH in Step 3, and add 3.5 g of the PEA emulsion prepared in Step 4 thereto. After continuously stirring for 2 hours, perform vacuum degassing to form a composite solution. Clean the glass substrate with 100 W oxygen plasma for 5 minutes to enhance the surface activity. Subsequently, spin-coat the composite solution on the substrate surface at a speed of 3000 rpm for 30 seconds to form a coating with a wet film thickness of approximately 200 nm. The coating is cured by drying in ventilation at 25°C for 1 hour, vacuum drying at 60°C for 30 minutes, and annealing at 120°C for 15 minutes in sequence. Perform ultrafast laser treatment on the substrate with the formed thin film on the processing table of an ultrafast laser. After taking it out, put it into an oven and cure it at 80°C for 30 minutes to obtain a conductive thin film based on PEDOT:PSS and silver nanowires.

[0033] Regulate the parameters of the ultrafast laser treatment and test the sheet resistance of the obtained conductive thin films under different parameters: 1. Set the filling pitch to 15 microns and the line scanning speed to 1350 mm / s. Regulate the laser powers to 0 W, 8 W, 8.5 W, 9 W, 9.5 W, 10 W, and 11 W respectively. The sheet resistance values of the obtained thin films are shown in Table 1. It can be seen that when the laser processing improves the conductivity of the thin film, the processing power must be within a suitable range. Too high or too low power cannot achieve the ideal effect. When the laser power is 9 W, the sheet resistance value of the thin film is the lowest and the deviation range is the smallest.

[0034] Table 1

[0035] 2. When setting the power of the ultrafast laser treatment to 9 W and the filling pitch to 15 microns, regulate the laser line scanning speeds to 650 mm / s, 850 mm / s, 1050 mm / s, 1250 mm / s, and 1450 mm / s respectively. The sheet resistance values of the obtained thin films are shown in Table 2. It can be seen that when the laser line scanning speed is 1050 mm / s, the sheet resistance value of the thin film is the lowest.

[0036] Table 2

[0037] 3. When setting the power of the ultrafast laser treatment to 9 W and the line scanning speed to 1050 mm / s, regulate the laser filling pitches to 15 μm, 25 μm, 35 μm, 5 μm, 45 μm, and 55 μm respectively. The sheet resistance values of the obtained thin films are shown in Table 3. It can be seen that when the laser filling pitch is 35 μm, the sheet resistance value of the thin film is the lowest.

[0038] Table 3

[0039] The thin film obtained under the conditions of the parameters of ultrafast laser treatment (power 9 W, line scanning speed 1050 mm / s, filling pitch 35 μm) is denoted as AgNWs / PEDOT:PSS / PEA thin film.

[0040] For comparison, the following thin films were also prepared in this example: AgNWs thin film: 10 mg of AgNWs was dispersed in isopropanol and stirred evenly at room temperature to obtain a dispersion with a concentration of 0.5 mg / mL; 10 mL of the dispersion was spin-coated (2000 rpm, 30 s) on the surface of a plasma-treated glass substrate and annealed at 150 °C for 20 minutes to obtain the AgNWs thin film.

[0041] AgNWs / PEDOT:PSS thin film: The silver nanowire dispersion (concentration 2 mg / mL) was mixed with the PEDOT:PSS aqueous solution at a volume ratio of 1:7.5, and 2 wt% of dimethyl sulfoxide (DMSO) was added as a conductive enhancer, and magnetically stirred for 2 hours to obtain a homogeneous mixture. The spin-coating method was used to spin-coat on the surface of the plasma-treated glass substrate at a speed of 2500 rpm for 30 s to form a wet film with a thickness of about 80 nm. Subsequently, it was pre-dried on a hot plate at 120 °C for 10 minutes, and then transferred to a vacuum oven and annealed at 150 °C for 30 minutes to form an effective overlapping network of silver nanowires to obtain the AgNWs / PEDOT:PSS thin film.

[0042] The AgNWs thin film, AgNWs / PEDOT:PSS thin film, and AgNWS / PEDOT:PSS / PEA thin film were placed at a temperature of 85 °C and a humidity of 30%. The relative change rate of the film resistance with the change of the placement time is as Figure 3 shown. In the figure, R 0 is the initial resistance, and R is the resistance after placement. It can be seen from the figure that after 40 days, the change rate of the sheet resistance of the AgNWs thin film and the AgNWs / PEDOT:PSS / PEA thin film did not show much change. In contrast, the resistance of the AgNWs / PEDOT:PSS thin film at high temperature increased by more than 90 times compared with its initial value, because a large amount of H + was generated by PEDOT:PSS under high temperature conditions, corroding the silver nanowires and resulting in poor conductivity. The AgNWs / PEDOT:PSS / PEA thin film of this example significantly improved the high temperature stability due to the addition of sodium citrate.

[0043] The AgNWs thin film, AgNWs / PEDOT:PSS thin film, and AgNWs / PEDOT:PSS / PEA thin film were placed at a temperature of 25 °C and a humidity of 85%. The relative change rate of the film resistance with the change of the placement time is as Figure 4 shown. In the figure, R 0R0 is the initial resistance, and R is the resistance after placement. It can be seen from the figure that after 40 days, the change rates of the sheet resistances of the AgNWs thin film and the AgNWs / PEDOT:PSS thin film have very large changes. In contrast, the sheet resistance of the AgNWs / PEDOT:PSS / PEA thin film only increases by 3 times compared to its initial value under high humidity conditions, indicating that the thin film manufactured in this embodiment can conduct electricity stably under a certain humidity.

[0044] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a conductive film based on PEDOT:PSS and silver nanowires, characterized in that: After surface hydroxylation treatment of silver nanowires AgNWs, the silver nanowires AgNWs were mixed with PEDOT:PSS under the action of silane coupling agent 3-(trimethoxymethylsilyl)propyl methacrylate TMSPMA to prepare PEDOT:PSS / AgNWs base liquid; the base liquid was adjusted in pH by sodium citrate, mixed with PEA emulsion and spin-coated into a film, and finally the conductivity was improved by laser treatment to obtain a conductive film based on PEDOT:PSS and silver nanowires.

2. The preparation method according to claim 1, characterized in that: The steps include: Step 1: Surface hydroxylation of silver nanowires 8-10 mg of AgNWs were dispersed in 10 mL of 0.01-0.03 M nitric acid solution and stirred at 25 °C for 5-8 min to generate silver oxide Ag2O on the surface of AgNWs. The supernatant was removed by centrifugation and washed with deionized water. The precipitate was then dispersed in 10 mL of deionized water and 0.1 M-0.2 M sodium hydroxide solution was added dropwise to pH 8-9. Ultrasonic treatment was performed at 45-55 °C for 10-15 min to promote the hydrolysis of Ag2O to generate surface hydroxyl groups OH - , centrifuged again and removed the supernatant, then washed with deionized water, and the resulting precipitate was dispersed in 10 mL of deionized water to obtain a hydroxylated AgNWs dispersion; Step 2: Preparation of PEDOT:PSS / AgNWs base solution Dissolve 400-450 μL of silane coupling agent TMSPMA in 10 mL of a mixture of ethanol and water in a volume ratio of 8-9:1, add acetic acid to adjust the pH to 4.5-5.2, stir to fully hydrolyze, generate Si-OH active groups, and obtain a coupling agent hydrolyzate; The coupling agent hydrolyzate is mixed with the hydroxylated AgNWs dispersion in step 1, and reacted at 30°C-40°C for 80-100 min under nitrogen protection, and then centrifuged to remove the supernatant, and washed more than 3 times with a mixture of ethanol and water in a volume ratio of 4:1 to completely remove unreacted silver ions and TMSPMA, and then the precipitate is dispersed in 3-5 mL of deionized water containing 0.05 wt% sodium dodecylbenzene sulfonate SDBS to obtain a TMSPMA-AgNWs dispersion; 2 mL of TMSPMA-AgNWs dispersion and 10-15 mL of 1 wt% PEDOT:PSS solution were mixed by pumping into the flow channel at a total flow rate of 0.2 mL / min according to the volume ratio through a microfluidic device; after the mixing was completed, the mixture was stirred at 25°C in the dark for 40-60 min under nitrogen protection to allow the other end of TMSPMA to achieve interfacial bonding with PEDOT:PSS through hydrogen bonding to obtain PEDOT:PSS / AgNWs base liquid; Step 3: pH adjustment and increase of AgNWs dispersion Add 0.05 M sodium citrate solution to the PEDOT:PSS / AgNWs base solution prepared in step 2 while stirring to adjust the pH to 6.0-6.3, and continue stirring at room temperature for 30-60 minutes; Step 4: Synthesis of PEA emulsion 72 g of ethyl acrylate EA and 17.1-20 μL of TMSPMA were mixed and ultrasonically treated for 5-10 min to remove dissolved oxygen, the resulting mixture was added to a round-bottom flask, and 0.4-0.45 g of sodium dodecyl sulfate SDS, 0.015-0.02 g of ammonium persulfate APS and 168-200 g of distilled water were added, nitrogen was flushed into the mixture and stirred at 300 rpm for 10-15 min, and then the round-bottom flask was sealed with a septum plug; a syringe needle connected to the balloon was inserted into the septum plug to balance the additional pressure of the heat released during the polymerization process, the round-bottom flask was placed in an oil bath at 65-70 ° C, and stirred in a magnetic stirrer at 300 rpm for 8-10 hours to obtain a PEA emulsion; the prepared PEA emulsion was stored in a plastic jar made of high-density polyethylene at room temperature; Step 5: Film preparation and post-processing Take 10 mL of the PEDOT:PSS / AgNWs base liquid after adjusting the pH in step 3, and add 3.5-4 g of the PEA emulsion prepared in step 4 thereto, stir evenly and perform vacuum degassing to obtain a composite liquid; use oxygen plasma to clean the glass substrate, then spin-coat the composite liquid on the surface of the substrate and gradient solidify it; perform ultrafast laser treatment on the substrate with the thin film formed on the processing table of an ultrafast laser, take it out and put it into an oven at 80-100°C for curing, so as to obtain a conductive film based on PEDOT:PSS and silver nanowires.

3. The preparation method according to claim 2, characterized in that: In step 5, the gradient curing is completed by successively performing ventilation drying at 25-30° C. for 1-1.5 hours, vacuum drying at 60-70° C. for 30-50 minutes, and annealing at 100-130° C. for 10-20 minutes.

4. The preparation method according to claim 2, characterized in that: In step 5, the parameters of the ultrafast laser processing are set as follows: laser power 8.5W~9.5W, line scanning speed 950mm / s~1150mm / s, and filling spacing 32μm~37μm.

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