Improvement in Conductivity and Mechanical Stability of a AgNW-Based Transparent Conductive Film by Using Ag Ionic Ink

Transparent conductive films (TCFs) based on silver nanowires (AgNWs) have become popular in flexible electronics. However, the high junction resistance between AgNWs and the poor attaching stability of AgNWs to the substrate greatly hinder their industrial application. In this study, a welding strategy is proposed to address these two major challenges simultaneously encountered with AgNW-based TCFs. This is achieved by trapping a thermally reducible silver ionic ink into gaps of the AgNW-based TCF and following low-temperature as well as intense pulse light (IPL) treatment. During the curing process, the ink decomposes into metallic silver to weld the wire junction and adjacent wire ends, thus improving the conductivity of the TCF significantly. More importantly, the subsequent IPL treatment would endow the decomposed Ag with excellent adhesion to the poly(ethylene terephthalate) (PET) substrate through mechanical locking and chemical interaction effects. Therefore, the mechanical stability of the TCF is fundamentally enhanced through robust connection between AgNWs and the substrate via the metallic silver. After being welded using ionic ink, the conductivity of AgNW-based TCFs is enhanced by up to 58% with negligible changes in transparency. Moreover, the welded TCFs exhibit good stability compared with an as-coated AgNW-based TCF even after undergoing rigorous tests, including 10,000 bending cycles and 100 tape peeling tests. Finally, such a strategy is successfully applied to enhance the properties of a flexible transparent heater, verifying its feasibility in flexible electronics.