Strain-resilient electrical functionality in thin-film metal electrodes using two-dimensional interlayers

Abstract

Flexible electrodes that allow electrical conductance to be maintained during mechanical deformation are required for the development of wearable electronics. However, flexible electrodes based on metal thin films on elastomeric substrates can suffer from complete and unexpected electrical disconnection after the onset of mechanical fracture across the metal. Here we show that the strain-resilient electrical performance of thin-film metal electrodes under multimodal deformation can be enhanced by using a two-dimensional interlayer. Insertion of atomically thin interlayers—graphene, molybdenum disulfide or hexagonal boron nitride—induces continuous in-plane crack deflection in thin-film metal electrodes. This leads to unique electrical characteristics (termed electrical ductility) in which electrical resistance gradually increases with strain, creating extended regions of stable resistance. Our two-dimensional interlayer electrodes can maintain a low electrical resistance beyond a strain at which conventional metal electrodes would completely disconnect. We use the approach to create a flexible electroluminescent light-emitting device with an augmented strain-resilient electrical functionality and an early damage diagnosis capability. Insertion of an atomically thin interlayer, such as graphene, between a metal thin film and a substrate can be used to create flexible electrodes with electrical performance that changes only gradually with strain and is resistant to abrupt mechanical failure.