Low-temperature nanowelding ultrathin silver nanowire sandwiched between polydopamine-functionalized graphene and conjugated polymer for highly stable and flexible transparent electrodes

Nanowelding of metal nanowires into large interconnected and adherent conductive networks has an important role in the applications of flexible electronics. Several strategies have been developed to reduce inter-nanowire contact resistance. However, these techniques either require high temperature annealing or high force pressing process. Furthermore, the as prepared metal nanowire networks have poor substrate adhesion and stability. Here, we report an efficient chemical engineering approach to construct robust flexible silver nanowires (AgNW) transparent electrodes at a low temperature. Ultrathin AgNW with a diameter ∼20 nm were sandwiched between a novel adhesion layer polydopamine-functionalized graphene (PFG) and over coating layer poly (3,4-ethylenedioxythiophene)(PEDOT). Capillary force as well as multi interfacial interactions between PFG sheets and conjugated PEDOT macromolecules induced an efficient welding of AgNW at nanoscale and low temperature. Abundant catechol functional groups on both sides of nature-inspired PFG sheets not only enhanced the adhesion force between AgNW networks and substrates but also improved the interfacial interactions in adjacent graphene sheets and that between graphene sheets and PEDOT chains, leading to an efficient load transfer during bending, stretching and scratching. The transparent electrodes maintain its excellent conductivity even after 500 cyclic bends. In addition, the robust flexible AgNW electrodes exhibit long-term stability with a low surface roughness (Rrms ∼ 5 nm). The welding mechanism and nature-inspired architecture strategy are expected to generic for other supercapacitor, battery electrodes and useful to construct next-generation high performance flexible and wearable optoelectronics.