Scientists at the National Renewable Energy Laboratory (NREL) and the Swiss Center for Electronics and Microtechnology (CSEM) have jointly reached a record conversion efficiency of 29.8%, setting a new world record for converting non-concentrated sunlight into electricity using a dual-junction III-V/Si solar cell.
The newly certified record conversion efficiency was set using NREL's top cell made of gallium indium phosphide and CSEM's bottom cell made of crystalline silicon using silicon heterojunction technology. The two cells were made separately and then stacked by NREL.
‘It's a record within this mechanically stacked category,’ says David Young, a senior researcher at NREL. ‘The performance of the dual-junction device exceeded the theoretical limit of 29.4 percent for crystalline silicon solar cells.’
Young, along with NREL's Stephanie Essig, Myles Steiner, John Geisz, Scott Ward, Tom Moriarty, Vincenzo LaSalvia and Pauls Stradins, co-authored a paper detailing the steps that were taken to break the previous record. The paper has been submitted for publication in the IEEE Journal of Photovoltaics.
‘CSEM partnered with the NREL scientists with the objective to demonstrate that 30 percent efficient tandem cells can be realized using silicon heterojunction bottom cells, thanks to the combination with high-performance top cells, such as those developed by NREL,’ says Matthieu Despeisse, manager of crystalline silicon activities at CSEM.
The companies attribute their success to the new design for the dual-junction solar cell and CSEM's contributions. What's more, these results indicate that greater efficiency can be achieved in the future by the combination of NREL and CSEM cells.
The research funding came from the Department of Energy's Office of Energy Efficiency and Renewable Energy SunShot Initiative and from the Swiss Confederation and the Nano-Tera.ch initiative.