Optimized silver nanowire networks for transparent smart devices

Çakır, Onuralp
In the realm of transparent conductors, transparent conducting oxides have been chief among all materials. Specifically, indium tin oxide (ITO) has reigned for a long time, seen use in many applications. However, the scarcity of indium in the Earth’s crust and the innate brittleness of ITO arising from its oxide nature necessitates development of alternatives. Throughout the years, materials such as graphene, carbon nanotubes (CNTs), conductive polymers, metal meshes and metallic nanowires have been proposed as alternatives. Among metallic nanowires, silver nanowire (Ag NW) networks emerged as the strongest candidate to replace ITO. One aspect that needs to be resolved, though, is the junction resistance between two nanowires. The problem stems from the polyvinyl pyrrolidone (PVP) capping agent surrounding Ag NWs. Many researchers tried to tackle this issue by welding the nanowires together using a variety of ways. Some works were concerned with cleaning the nanowires’ surface. Yet in all the works, the Ag NWs used had widely different properties such as length, diameter, PVP thickness, and network deposition methods. In this thesis, treatments with different aims, taken from the literature, were developed in-house and later applied to the same batch of Ag NWs. The realization of the effects of all reported treatments on one type of nanowires was facilitated by this approach. The two most effective methods were combined in reaching a sheet resistance of 11.4 Ω/sq, optical transmittance of 90%, and optical figure of merit (FoM) of 305. The optimized Ag NW network was first used as a current collector layer in a transparent liquid-solid interface triboelectric nanogenerator (TENG). The TENG exploited the electrification between incident water droplets and the PDMS overcoat on the Ag NWs. The generated electrical output was utilized in sensing the pH and chemical concentration of the water droplets. The device was also used as a switch to activate an Ag NW-based thin film heater. Secondly, the Ag NWs were implemented in electrochromic devices (ECDs) as the transparent conductors. WO3, WOx, and NiO nanoparticles were used as the electrochromic layers. WOx films provided high optical contrast and coloration efficiency. These findings display the versatility of Ag NWs in state-of-the-art applications.
Citation Formats
O. Çakır, “Optimized silver nanowire networks for transparent smart devices,” M.S. - Master of Science, Middle East Technical University, 2023.