III-V-on-Si Tandem Solar Cells

Kaitlyn VanSant received a bachelor's degree in Astronomy-Physics from Whitman College, a master's degree in Physics from Portland State University, and a PhD in Materials Science from Colorado School of Mines. Her PhD research focused on the design, fabrication, and characterization of 3- and 4-terminal III-V-on-Si tandem solar cells. She is also interested in photovoltaic failure and degradation modes at both the cell and module level. She is currently a NASA Postdoc Program Fellow conducting perovskite solar cell research for space applications, as part of a collaboration between NASA's Glenn Research Center and NREL. Emily Warren received her BS in Chemical Engineering from Cornell University, then studied Engineering for Sustainable Development at Cambridge before completing her PhD in Chemical Engineering at Caltech in 2013. She is a staff scientist at NREL. Her research interests include high- efficiency tandem photovoltaics, semiconductor growth and processing, and new architectures for solar fuel generation. Adele Tamboli received her PhD in Materials from the University of California, Santa Barbara in 2009, followed by postdoctoral research in Applied Physics at the California Institute of Technology. She currently works in the Materials Science Center at the National Renewable Energy Laboratory in Golden, Colorado and holds a joint appointment at the Colorado School of Mines. Her research focuses on improved device architectures for multijunction solar cells, including three- and four-terminal, III-V/Si tandems. She also has an active research program in the discovery and development of new semiconductor materials for energy applications. III-V-on-Si solar cells have demonstrated efficiencies exceeding 35%. Tandem cells are traditionally designed with two terminals, requiring current-matched subcells connected in series. They can, however, be designed with additional terminals to avoid current matching constraints. This article discusses the advantages and disadvantages of III-V-on-Si cells operated in the two-terminal, three-terminal, and four-terminal configurations. Future research priorities are addressed, with an emphasis on assessing tandem operation in the field (or in space), to identify the optimal cell and interconnection designs.