2D materials as building blocks for solar energy conversion
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Wednesday, September 16, 2015 - 1:30pm to 3:00pm
Dr. Scott Warren, Departments of Chemistry & Applied Physical Sciences, University of North Carolina at Chapel Hill
Converting sunlight into electrical or chemical energy is a profound challenge, with progress closely linked to improvements in semiconductor design. Two dimensional semiconductors could provide many advantages, with tunable band gaps, high mobility, and no intrinsic surface states. Here we describe our development of black phosphorus—an elemental form of phosphorus—as a new quantum-confined 2D material. We have invented a new method to measure the band gap and have made the first direct measurements of this important parameter, finding that it can be tuned from 0.3 eV in bulk black phosphorus to 2.3 eV in a monolayer. This degree of tunability—which far exceeds other 2D materials and most quantum dots—opens opportunities to use this material for solar energy conversion, particularly in pan-chromatic multijunction solar cells. To that end, I will present two exciting developments from our laboratory: (1) a demonstration of how band gap engineering can be used in 2D black phosphorus to enhance solar-to-chemical energy conversion and (2) a discussion of how 2D black phosphorus can be re-assembled into an electrically conductive 3D material while remaining largely quantum-confined. Our experimental observations and the design rules that they illuminate should open a rich playground for innovative materials research, located squarely at the intersection of 2D materials and solar energy.
Scott Warren earned his Ph.D. in 2007 with work on the self-assembly of fuel cell electrodes in the groups of Uli Wiesner and Frank DiSalvo at Cornell University. He was a post-doctoral fellow with Michael Graetzel at EPFL, Switzerland, from 2007 to 2010. During that time, he directed a European consortium on solar-driven water splitting and was a visiting researcher at the Technion-Israel Institute of Technology with Avner Rothschild. Scott returned to the U.S. in 2011, working on nanoparticle electronics at Northwestern University with Bartosz Grzybowski. He has been an assistant professor in the departments of chemistry and applied physical sciences at UNC Chapel Hill since 2013, where he examines the unique properties of 2D materials for solar energy conversion, energy storage, and energy efficiency.