He is the manager of the High Efficiency Crystalline Photovoltaics Group at the National Renewable Energy Laboratory (NREL). His interests at NREL have been in the development of next-generation multi-junction high-efficiency solar cells for concentrator systems and the transfer of this technology to industry. One of his early focuses after joining the group was to adapt the GaInP/GaAs multi-junction cell technology for concentrator operation, developing the first monolithic two-terminal solar cell to have a verified efficiency with more than 30%. More recently, he has studied novel semiconductor materials for photovoltaics, such as GaInNAs for potential application in a 1-eV-bandgap device on conventional GaAs or Ge substrates, as well as developing concepts for junctions suitable for fabrication on Si. His current work centers on development of future generations of lattice-mismatched multi-junction cell structures for ultrahigh-efficiency operation under concentration. He received his bachelor’s in physics from Princeton University and his doctorate in applied physics from Stanford University. He joined NREL in 1990.
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