Mixed conductors, i.e., materials that have the ability to conduct electricity using both electrons and ions, have many potential applications. One of the most appealing areas on which these materials can have an impact is the interface between living matter, whose physiology operates via ion fluxes, and electronics, which operate by moving electrons. The goal of this research project is to provide an in-depth understanding of how the molecular structure of these materials and their processing conditions affect their ability to operate as transducers of ionic signals into electronic signals. Better knowledge of these materials could impact many areas of society, from the management of energy to human health. In addition to these broader benefits, educating students in this emerging area contributes to producing a trained workforce ready to develop materials and devices for the marketplace. Outreach efforts associated with this project involve a local high school with a large Latino population.
Beyond organic electronic conductors, organic mixed conductors are a promising category of materials with potential applications in many areas, such as electrochemical cells and bioelectronics. Compared to the conventional conjugated polymers, mixed conductors have the added complexity of containing an ion-conducting phase. The interplay of the transport of the ion conducting and the electron conducting phase is at the heart of the operation of these materials. This project aims to establish the structure-property relationships in mixed conductors and to develop an in-depth understanding of how mixed conductors work. Specifically, the morphology of poly(3,4-ethylenedioxythiophene) (PEDOT)-based blends is widely tunable by changing the partner of PEDOT in the blend or by processing. The electrical characterization and modeling of the response of organic electrochemical transistors (OECT) allow the measurement of carrier mobility and the degree of entanglement of the ion conducting and electron conducting phase. Charge modulation spectroscopy is used to study the polaronic or bipolaronic nature of the carriers. Structural characterization, based on X-ray scattering and electron microscopy, is carried out to understand how morphology affects the functionality of mixed conductors. The project also plans to study new materials that integrate the ionic conduction functionality and the electronic conduction functionality in a single molecule.
