The Controllable Synthesis Of High Aspect Ratio Silver Nanowires And Its Application In Network-based Flexible Electrode

The market of transparent electrodes is growing fast because of the rapid development of mobile intelligent devices. Currently, tin-doped indium oxide?ITO? occupies most of the market share of transparent electrode material. The brittle ceramic of ITO makes it friable and not suitable for flexible electrodes, while the indium element as a rare element, results in the market shortage and price volatility. Therefore, the next generation of transparent electrode material attracted widespread attention. Candidate materials include conductive polymers, metal mesh, carbon nanotubes, graphene and metal nanowires. Wherein the metal nanowires, especially silver nanowires?Ag NWs? has comprehensive advantages in performance.The basis and prerequisite of the preparation of Ag NWs transparent electrode is the synthesis of high aspect ratio Ag NWs. However, the current synthesis method still has many defects and deficiencies such as complicated process, poor dispersion, low production and small aspect ratio, which limit its application. In our work, we study the controlled synthesis of Ag NWs with high aspect ratio, and the preparation of high-performance flexible electrode of Ag NWs network stripes. The main contents are as follow:1. The synthesis of Ag NWs with high aspect ratio?up to 1000 or more? using polyol synthesis method.First, in the early stage of synthesis, we investigated the influence of the solvent ethylene glycol, growth inhibitors polyvinylpyrrolidone?pvp?, ionic additives Cu Cl₂, and the solvent content of oxygen reduction to the reduction of seed crystal and growth of nanowire. Secondly, in the late stage of synthesis, the residual nanoparticles are washed repeatedly away to improve the purity of the ink nanowires. Finally, using wash of alcohol solution, the polyvinylpyrrolidone?pvp? coating on the surface of the nanowires was removed. As a result, the conductivity of Ag nanowires was improved greatly.2. Optimization of the ink of Ag NWsEthanol solution is the most common dispersant of Ag nanowire. However, the low boiling point and flammability of ethanol has led to a great security risk in large area coating for film formation. After experiment exploration and reference of methods in the literature, we select water, which is cheap and stable, as a new dispersant. An appropriate amount of a surfactant PTFE surfactant?Zonyl @ FSO? and binder poly methyl propyl cellulose?HPMC? were added to improve the coating effect of the ink which was affected by the strongly polar of water.However, the introductions of additives can cause organic residues on nanowire surface, which increases the resistance of the film greatly. Therefore, a reduction treatment of the film is made to reduce its resistance.3. The preparation of dual functional transparent film for proximity and pressure sensingUsing optimizing ink of Ag NWs, we prepared a transparent, flexible electrode with Ag NWs network stripes as the row and column electrodes and measured its optical, electrical and mechanical properties. The excellent multi-point spatial resolution performance because of independent pixel capacitances makes the electrode able to make accurate identification of both the position of the approaching object and the size of the pressure quickly, stably and repeatedly.These advantages makes our electrode have a good prospect in the field of smart phones, robots.