Presented by Shane Ardo, University of California Irvine
When
Understanding, and moving beyond, band bending to perform useful work with light
Monday, March 10, Noon (Eastern Time)
Professor Shane Ardo (ardo@uci.edu)
Departments of Chemistry, Materials Science & Engineering, Chemical & Biomolecular Engineering
Director of Ensembles of Photosynthetic Nanoreactors (EPN) DOE Energy Frontier Research Center
University of California Irvine, Irvine, CA 92697, USA
It is widely known that semiconductor-based solar energy conversion could power our planet. This is because highly-crystalline inorganic semiconductors are unrivaled in their ability to separate photogenerated charged species — an effective approach leverages a phenomenon known as “band bending.” But details to justify why band bending results in photoinduced charge separation are more complicated than standard band diagrams suggest.
During my talk I will present exemplary systems and thought experiments that each suggest photoinduced charge separation can be driven by more than just band bending. To help visualize these effects, I will show plots rooted in fundamental chemical physics that depict the spatial dependence of not just bands, but also free energy, force, flux, force constant, and rate. In each case, photoinduced charge separation results from the influence of nonequilibrium species concentrations and kinetic descriptors, such as diffusion coefficients or rate coefficients. I will also clarify that effective charge separation alone does not guarantee high-efficiency operation, and that photogenerated free energy is also essential. While bandgap energy can be an important predictor of photogenerated free energy, semiconductor optical properties and reaction kinetics are actually more important. Together this information indicates that specificity of interfacial chemical reactions alone is sufficient to result in efficient solar energy conversion.
I hope that my talk provides researchers with a better appreciation of approaches that result in effective photoinduced charge separation, serving as a guide for the rational, hypothesis-driven design of next-generation ways to perform useful work with light.
Bio:
Prof. Shane Ardo, Ph.D.
Professor of Chemistry, Chemical & Biomolecular Engineering, Materials Science & Engineering
Director of Ensembles of Photosynthetic Nanoreactors (EPN), a U.S. DOE Energy Frontier Research Center
University of California Irvine, Irvine, California, USA
Shane obtained a B.S. Degree in Mathematics, with a concentration in Computer Programming, from Towson University. He subsequently worked as a software engineer, community college instructor, and high school teacher, and also tried out for a professional indoor soccer team. Shane then obtained an M.S. Degree in Nutrition from the University of Maryland, College Park, and M.A. and Ph.D. Degrees in Photo-Physical Inorganic Chemistry from the Johns Hopkins University. He was also a U.S. Department of Energy (DOE) EERE Postdoctoral Research Awardee at the California Institute of Technology.
Shane has been a faculty member at the University of California Irvine since 2013 and is currently a full Professor in the Department of Chemistry, holding courtesy joint appointments in the Departments of Chemical & Biomolecular Engineering and Materials Science & Engineering. Shane oversees the Ardo Group (chem.uci.edu/~ardo), a diverse team of innovators and educators that are allies for change. Their research spans solar energy conversion, carbon capture, and clean water, with specific expertise in photochemistry, electrochemistry, membranes, and ionics. Shane is the Director of Ensembles of Photosynthetic Nanoreactors (EPN, photosynthesis.uci.edu) – a U.S. DOE Energy Frontier Research Center founded in 2022 – is a member of the Liquid Sunlight Alliance (LiSA, www.liquidsunlightalliance.org) – a U.S. DOE Energy Innovation Hub founded in 2020 – and is the lead for broadening participation in the Center for Interfacial Ionics (CI2, ionics.uoregon.edu) – a U.S. National Science Foundation (NSF) Center for Chemical Innovation founded in 2022. Shane is also a recipient of a U.S. DOE Early Career Research Award and two Beall Innovation Awards, and was named one of five inaugural Moore Inventor Fellows, a Sloan Research Fellow, a Cottrell Scholar, a Kavli Fellow, a Scialog Fellow, and a UCI Faculty Innovation Fellow.