2011 William Spitzer Lecture
Mork Family Department of Chemical Engineering and Materials Science

"New Photonic Material Designs for Solar Energy Conversion"

Professor Harry Atwater
California Institute of Technology

Abstract
Solar energy is currently enjoying substantial growth and investment, owing to worldwide sensitivity to energy security and climate change, and this has spurred basic research on light-matter interactions relevant to solar energy. Professor Atwater will describe approaches to control of light-matter interactions leading to enhanced light-trapping and absorption, as well as increased open circuit voltage and enhanced quantum efficiency in solar photovoltaic structures. Conventionally, photovoltaic cells have a physical thickness comparable to their "optical thickness" for full light absorption and photocarrier current collection. Solar cell design and material synthesis considerations are strongly dictated by this simple "optical thickness" requirement. Dramatically reducing the absorber layer thickness or volume confers several fundamental and practical benefits, including increased open circuit voltage and conversion efficiency, and also expansion of the scope and quality of absorber materials that are suitable for photovoltaics. He will describe light absorption in thin film and wire array solar cells that demonstrate enhanced absorption compared with conventional photovoltaic cells, and limits to enhanced absorption will be explored. Plasmonics and metamaterials design can also be exploited advantageously in photovoltaics. He will describe design approaches using metallic nanostructures to enhance the radiative emission rate and hence also the photovoltaic material quantum efficiency relative to conventional light-trapping structures. Finally, future design metamaterials for broadband resonant absorption and spectrum-splitting will be discussed.

Biography
Harry Atwater is currently the Howard Hughes Professor and Professor of Applied Physics and Materials Science at the California Institute of Technology. His research interests center around photovoltaics, renewable energy, plasmonics, and metamaterials. Atwater and his group have been active in photovoltaics research for more than 20 years. He received his S.B. (1981), S.M. (1983), and Ph.D. (1987) in Electrical Engineering from the Massachusetts Institute of echnology. He is an early pioneer in surface plasmon photonics; he gave the name to the field of plasmonics in 2001. Professor Atwater currently serves as Director of DOE Energy Frontier Research Center on Light-Matter Interactions in Solar Energy Conversion and was recently named as Director of the Resnick nstitute for Science, Energy and Sustainability.