Garry Rumbles National Renewable Energy Laboratory
Laboratory Fellow in the Chemistry and Nanoscience Center
“Tracking mobile charges using microwave absorption”
Abstract: Understanding how to create separated charges in organic systems has been a topic of great interest for many decades, prompted mainly by our desire to understand natural photosynthesis and thereby be able to mimic it in artificial systems. The organic photovoltaic effect is one such example that spawned many investigations in molecular synthesis, materials characterization, device construction, device optimization, and the multiple levels of theoretical understanding. While using device performance to create a connection of understanding to the many components of the system is possible, it is a process that can be fraught with complexities, difficulties and misdirection.
Flash photolysis, time-resolved microwave conductivity (fp-TRMC) is a sensitive spectroscopic tool that provides an electrode-less method of selectively detecting the free carriers in these systems and, indeed, in even simpler systems. This presentation will describe the evolution of the technique at NREL using a number of specific examples to advertise a wide range of capabilities: (i) Carriers in conjugated polymers that are neat, lightly doped or blended with electron acceptors will form one study. (ii) Carriers generated in isolated, polymer-wrapped single-walled carbon nanotubes that a separated in a low dielectric solvent. (iii) Carriers in colloidal quantum dots in solution and thin films and, if time permits, (iv) a recent study of the effects of grain size in methyl ammonium lead halide perovskite films.
Bio: Prof. Garry Rumbles is a Laboratory Fellow in the Chemistry and Nanoscience Center at the National Renewable Energy Laboratory (NREL) in Golden, Colorado and holds affiliated faculty positions in the Departments of Chemistry at University of Colorado Boulder, Colorado State University and Imperial College London. He is also the Associate Director for research of the Renewable and Sustainable Energy Institute (RASEI), a joint institute between CU-Boulder and NREL. Prior to joining NREL in 2000, he was a member of physical chemistry faculty at Imperial College. His current research interests are in solar energy with a focus on the basic science of solar photoconversion processes and photoinduced electron transfer processes in polymerbased nanostructured interfaces. His primary research expertise lies in photochemistry and laser spectroscopy with a special interest in the photophysics of conjugated polymers. He has published over 200 articles, and is a Fellow of the Royal Society of Chemistry (UK).