Mapping Ions and Polarons in Organic Mixed Conductors at The Nanoscale

Organic mixed ionic-electronic conductors have emerged as promising materials for an array of devices that leverage mixed conductivity, including bioelectronics, biosensors, and neuromorphic computing. One challenge of understanding structure-function relationships in OMIECs is the heterogeneous nature of these materials at the nanoscale, which impacts both ionic and electronic transport processes. To uncover nanoscale structure-property relationships, our group has developed ways to image ion and polaron distributions with ~10 nm spatial resolution using photoinduced force microscopy (PiFM). We correlate these measurements with nanoscale stiffness mapping to directly relate local crystallinity to local ion and polaron concentrations. Our images show that ions and polarons preferentially reside in the crystalline regions of organic mixed conductors, consistent with previous bulk studies.