Microwave welding of silver nanowires for highly transparent conductive electrodes

Silver nanowires (Ag NWs) can be used in future conductive transparent electrodes to replace indium tin oxide (ITO) thin films. Welding between Ag NWs is required to achieve lower electrical resistance, and an appropriate heating mechanism. In this study, microwave-assisted welding was introduced in order to simultaneously improve the transmittance and electrical conductivity of Ag NWs, through a simple, selective, and rapid process. This method includes only two steps. First, Ag NWs dispersed in a solvent were coated onto polymer substrates by spin coating. The Ag NW-coated substrates were exposed to microwave radiation. Next, the resulting optical transmittances and electrical conductivities are compared between the samples. Ag NWs electrode showed high electrical conductivity with a low sheet resistance of 20 Ω sq⁻¹ at 87% transmittance (at 550 nm). Bending tests were also performed to examine the suitability of the welded Ag NWs for flexible substrates. We found that the transmittance and conductivity were preserved after repeated bending tests. Consequently, the sheet resistance was reduced by 40% using microwave heating, and these welded Ag NWs had good mechanical strength even after bending. These highly flexible and transparent electrodes can be mounted onto non-planar surfaces for use in various future flexible electronics.