Bright Walker (Kyung Hee Uni.): "Stable Organic Radical Ions for Charge Transport and Charge Storage"

Bright Walker is an Associate Professor of Chemistry at Kyung Hee University in South Korea, where he researches conjugated organic molecules and hybrid semiconducting materials. The goal of his research team is to develop innovative new materials for applications in batteries, solar cells, transistors, light-emitting transistors and unique types of semiconducting devices. Bright holds a B.Sc. in Chemistry from the University of California at Berkeley (2003) as well as a Ph.D. in Chemistry from the University of California at Santa Barbara (2012). He worked as a Research Scientist and Research Professor at Ulsan National University of Science and Technology, (UNIST), South Korea (2012-2018).  Prior to working with semiconducting devices, Bright worked for several years in the setting of a start-up company, synthesizing and characterizing commodity polymers.

Abstract: Charge carrier generation, motion and recombination underpin the operation of most organic semiconducting devices such as organic light emitting diodes, solar cells and transistors. These charge carriers usually take the form of organic radical cations (RCs) and radical anions (RAs) for holes and electrons, respectively.  In semiconducting devices, RCs and RAs often exist as transient states and are prone to degradation and side reactions. Our research group has endeavored to identify and isolate conjugated organic molecules that form stable RC and RA states. Further, we have investigated their use for charge storage applications in the form of redox flow batteries (RFBs), which offer an excellent solution to the need for energy storage infrastructure. Specifically, we explore the use of organic semiconducting moieties, including the 3,4-ethylenedioxythiophene (EDOT) moiety, phenoxathiin and benzothioxanthene imidide as radical ion storing active molecules in RFBs. By judiciously designing molecules with solubility in polar electrolyte solutions, stable radical ion states and blocked degradation mechanisms, we demonstrate RFBs with outstanding voltage and energy density.