Overcoming the conductivity limit of insulator through tunneling-current junction welding: Ag@PVP core–shell nanowire for high-performance transparent electrode

Abstract

Core–shell structure can endow silver nanowire (AgNW) with excellent stability. However, its application is greatly hindered by non-industrial preparation process and bad dispersity of the present passivation shell layer. Polymer shell material can solve these problems but no researchers have adopted because apart from removing the polymer, there is no method which can overcome the conductivity limit of the insulating polymer at present. Herein, inspired by the tunnel effect of scanning tunneling microscope, we report a tunneling-current junction welding strategy which can preserve the polymer and overcome its conductivity limit simultaneously: (1) the key point for overcoming the conductivity limit is controlling the polymer thickness to generate tunneling current; (2) because the junction resistance is much higher than the nanowire resistance and Joule heat mainly accumulates on the inside of the junction, fixed-point junction welding can be realized to merely remove polymer on the inside of the junction to fuse AgNWs and the polymer in other places can be preserved. Based on this strategy and a welding law refined by us, silver@polyvinylpyrrolidone core–shell (Ag@PVP) nanowire film is welded and the results demonstrate that this strategy is effective. Ag@PVP film exhibits good stability and high opto-electrical performance, indicating that PVP shell layer greatly improves the stability of AgNW but hardly affects its opto-electrical performance. Finally, an optoelectronic device employing the Ag@PVP film as the electrode is fabricated and shows efficiencies comparable to those of an optoelectronic device on indium tin oxide.