Designing polymeric mixed ionic/electronic conductors for organic electrochemical transistors

Organic electrochemical transistors (OECTs) have gained considerable interest for applications in bioelectronics, power electronics, circuits and neuromorphic computing. Their defining characteristic is the bulk-modulation of channel conductance owing to the facile penetration of ions into the (semi)conducting polymeric channel. For this reason, their device scaling relies on film thickness, and often relaxes the stringent demands of clean and controlled interfaces required in traditional FETs. Despite recent progress and a rapidly expanding library of new materials, the understanding of stability and transport/coupling of ionic and electronic carriers remain largely unexplored. We highlight recent synthetic and processing approaches used to tailor device properties and stability, as well as new device concepts enabled by such advances. Our understanding of critical processes in electrochemical devices further requires us to study these materials in device-relevant conditions, considering the effects of ions and solvent on microstructure and transport. To this end, we report on recent efforts using operando scattering and spectroscopy to build a more device-relevant picture of structure-transport relations.