A Transparent, Smooth, Thermally Robust, Conductive Polyimide for Flexible Electronics

In this work, a thermally and mechanically robust, smooth transparent conductor composed of silver nanowires embedded in a colorless polyimide substrate is introduced. The polyimide is exceptionally chemically, mechanically, and thermally stable. While silver nanowire networks tend not to be thermally stable to high temperatures, the addition of a titania coating on the nanowires dramatically increases their thermal stability. This allows for the polyimide to be thermally imidized at 360 °C with the silver nanowires in place, creating a smooth (<1 nm root mean square roughness), conductive surface. These transparent conducting substrate-cum-electrodes exhibit a conductivity ratio figure of merit of 272, significantly outperforming commercially available indium-tin-oxide (ITO)-coated plastics. The conductive polymide is subjected to various mechanical tests and is used as a substrate for a thermally deposited, flexible, organic light-emitting diode, which shows improved device performance compared to a control device made on ITO coated glass.