Dark Ionic Liquid for Flexible Optoelectronics

Abstract

Owing to a wide visual angle, few aberrations, and great depth of focus, flexible optoelectronics have become one subject of intense investigation for rescue equipment and endoscopy tools. Ionic liquids are rising as a kind of fluidic "semiconductor" with advantages of high flexibility and self-healing. However, challenges in the molecular design of photoresponsive ionic liquids impede the exploration of ionic liquids as intrinsic flexible liquid optoelectronics. This work demonstrated an imidazole-based ionic liquid covalently linked with a polypyrrole oligomer by alkyl chains. Such an ionic liquid has wide absorption from the visible light range to the near-infrared light range. The imidazole moiety acts as an electrical conductor which is thermally responsive. On the other hand, the polypyrrole segment serving as a light antenna is able to convert light energy to thermal heat. The alkyl linker tailors the energy transfer between polypyrrole and an imidazole cation. Negligible molecular aggregation and phase separation are attributed to the preservation of the fluidic nature at room temperature. This photoresponsive ionic liquid is successfully exploited as a flexible light detector that is adaptable to special sensing tests in bending states.