Understanding Ion Injection and Transport in Mixed Ionic/Electronic Conductors

Thesis (Ph.D.)--University of Washington, 2019Materials with the ability to conduct both ionic and electronic charge have found a number of new applications recently with real potential to change the world. Each of these applications has its own design requirements, however all of these rely on the ability of the polymer to conduct ions throughout the bulk of the film. In order to expand these capabilities, deeper understanding of what affects ion injection and transport is required. Specifically, the role of the electrolyte, polymer, and processing conditions all play a role. Here we specifically isolate these effects to develop a deeper understanding of what factors control ion injection and transport in conjugated polymer mixed electronic/ionic conductors. Specifically, we show that larger, more polarizable anions are able to enter hydrophobic polymers films at a lower potential, to a greater extent, and faster. Next, we investigate the role of the polymer side-chain and find that polar side chains enhance ion uptake. Additionally, we show the polymer morphology affects performance in different ways than it does in dry films, suggesting the need for new design rules. Finally, we show in certain cases the charge compensation process is cation dependent as well. Together these studies help develop our understanding of ion injection into semiconducting polymers