In Operando Characterization of Organic Mixed Ion-Electron Conducting Materials

Organic mixed ion-electron conducting materials (OMIECs) bridge the gap between rigid electronics and soft biological systems as they transduce ionic and electronic signals while exhibiting similar mechanical properties as soft tissue. These materials generally operate in a complex environment, including an electrolyte containing positively and negatively charged ions. Thereby, the material characteristics of OMIECs during operation can differ strongly from their ex-situ properties, which markedly calls for in-operando characterization to study their behavior. Here, we apply several in-operando characterization techniques to state-of-the-art OMIECs and uncover previously undetected ion-backbone interactions. Through in-operando Fourier-transformed infra-red (FT-IR) spectroscopy, we find these ion-backbone interactions are crucially important to explain OECT characteristics as they govern the formation of multiply charged species. We find that the same interactions instigate changes in the film morphology, whereby the choice of electrolyte dictates the nature of the changes. Our results provide insight into the electrochemical doping mechanism of these polymers and uncover structure-property relations governing their device functions. These insights enable targeted optimization of both polymer structure and employed electrolyte, as well as provide an instrument for possible new applications.