Abstract:
Organic semiconducting polymers present a versatile platform for energy conversion and storage and sensing devices due to tunable optical and transport gaps, compatibility with electrolytes, and scalability via solution processing. The Center for Soft Photoelectrochemical Systems (SPECS) is an Energy Frontier Research Center that focuses on understanding the fundamental factors that control charge and matter transport processes that underpin energy conversion and storage technologies across spatiotemporal scales in scalable, durable, π-conjugated polymer materials. Within SPECS, we aim to establish design rules for robust photocathode systems that elucidate key structure–property relationships related to charge transport, charge transfer, and operational durability.
As part of our efforts, SPECS is providing significant advances in revealing the nature of polarons in semiconducting polymers as a function of the varying chemical environment of the polymer–electrolyte interphase, a longer length scale description than discrete interfaces due to polymer swelling and dynamics in the presence of an electrolyte. The interphase stores charge with long lifetimes due to Coulombic interactions between polarons and supporting counterions and solvent from the electrolyte, where physicochemical variables such as the dielectric field, chain (chromophore) structure, interactions of polarons with counterions of varying hardness and valency, and polymer microstructure each can impact the nature and transport of polarons. In photocathodes, the local nanoenvironment ultimately controls the production of solar fuels from sunlight.
Our initial device employs a bulk heterojunction (BHJ) strategy, combining PTB7-Th (hole transport) and N2200 (electron transport) polymers, deposited on passivated ITO and capped with a hydrogen evolution reaction (HER) catalyst (e.g., Pt or RuO₂), all immersed in an acidic electrolyte. Insights from optoelectronic analogs guided our focus toward enhancing chemical and mechanical interfacial stability and enabling selective charge extraction.
Efforts that will be described in this talk include multiple spectroelectrochemical methods and theoretical efforts to reveal the impact of electrochemical doping and ultimately serve as signatures to drive charge transfer reactions such as solar fuel production. Other highlights will include opportunities to functionalize various interfaces to increase rates of hydrogen evolution.
Bio:
Prof. Erin L. Ratcliff is a Full Professor in the School of Materials Science and Engineering and the School of Chemistry and Biochemistry at the Georgia Institute of Technology and holds a joint appointment at the National Renewable Energy Laboratory. She earned a B.A. in Chemistry, Mathematics, and Statistics in 2003 from St. Olaf College in Northfield, MN and a PhD in Physical Chemistry from Iowa State University in 2007. After completing a postdoc at the University of Arizona (2007 – 2009), she served as a Research Scientist and Research Professor in the Department of Chemistry and Biochemistry (2009 – 2014). She was previously an Assistant and Associate Professor in the Department of Materials Science and Engineering and the Department of Chemical and Environmental Engineering at the University of Arizona (2014 – 2024). She joined the faculty at Georgia Tech in 2024.
Her group “Laboratory for Interface Science for Printable Electronic Materials” uses a combination of electrochemistry, spectroscopies, microscopies, and synchrotron-based techniques to understand fundamental structure-property relationships of next-generation materials for energy conversion and storage and biosensing. Materials of interest include metal halide perovskites, π-conjugated materials, colloidal quantum dots, and metal oxides. Current research is focused on mechanisms of electron transfer and transport across interfaces, including semiconductor/electrolyte interfaces and durability of printable electronic materials.
Prof. Ratliff was also the Director of the funded Energy Frontier Research Center (EFRC) entitled “Center for Soft PhotoElectroChemical Systems (SPECS)” and is currently the Associate Director of Scientific Continuity for SPECS. She has received several awards for her research and teaching, including the 2023 Da Vinci Fellow and the 2022 College of Engineering Researcher of the Year award at UArizona, The Ten at Ten People of Energy Frontier Research Centers DOE Basic Energy Sciences award in 2019, and Senior Summer Faculty Research Fellow at the Naval Research Laboratory (2020, 2021, and 2024). Her research program has been funded by the Department of Energy Basic Energy Sciences, the Solar Energy Technology Office, Office of Naval Research, National Science Foundation, and the Nano Bio Materials Consortium.