UC Santa Barbara

Simultaneous ion and electron conduction is a critical property of many material systems and is essential for applications ranging from fuel cells to batteries to bioelectronics. Conjugated polymers are uniquely suited to support both ionic and electronic transport because organic synthesis and molecular design strategies can be readily implemented to tailor their ionic, electronic, and structural properties. However, the molecular scale interactions that dictate simultaneous ionic and electronic transport are not well understood. This work aims to probe the fundamental physical phenomenon that effect electronic and ionic transport in mixed ion and electron conducting conjugated polymers. A controlled ion gated transistor model system is first developed and employed to probe the role of the ion distribution in conjugated polymers on the mechanism of electron transport on the nanometer crystalline scale. To further probe the role of interactions on the molecular scale, an electrochemical doping framework is used to change the charge density of counterions to electronic charges in conjugated polymers, which reveals the inter-relation between ion-electron Coulomb interactions, structure, and electronic mobility. Finally, the macroscopic ionic and electronic transport in a bulk conjugated polymeric mixed conductor is investigated, and the mechanism of transport is characterized via investigation of the nanoscale structure.