Failure Mechanism of Flexible Transparent Conductor Materials under High Current

Flexible transparent conductors (FTCs) are key components of flexible photonic devices. However, their reliability under a high electrical current has not been sufficiently studied, which limits their practical applications. In this work, we investigated the failure processes of various FTCs under electrical current and proposed the underlying failure mechanism. For all tested FTCs composed of different materials, the failure was initiated at hot spots due to accumulated Joule heat, followed by the propagation of cracks perpendicular to the current and finally the electric spark discharge of accumulated charges beside the cracks. Consequently, the failed FTCs exhibit a distinctive morphology with a penetrating main crack perpendicular to the current and river-like minor cracks on both sides of the main crack. When comparing their reliability, Au film FTCs demonstrated relatively good performance, with a failure current of 0.34 A at 25 °C and 1.52 A at −196 °C for samples with a sheet resistance of 20.28 Ω/sq. The revealed mechanism provides critical insights into the design and protection of emerging FTCs.