National Lab, Partner Jointly Set New Solar Cell Efficiency Record

Scientists at the U.S. Department of Energy National Renewable Energy Laboratory (NREL) and at the Swiss Center for Electronics and Microtechnology (CSEM) said they have jointly set a new record for converting non-concentrated (1-sun) sunlight into electricity using a dual-junction III-V/Si solar cell.

The newly certified record conversion efficiency of 29.8 percent was set using a top cell made of gallium indium phosphide developed by NREL, and a bottom cell made of crystalline silicon developed by CSEM using silicon heterojunction technology. The two cells were made separately and then stacked by NREL. The record was published in “Solar cell efficiency tables.”

“It’s a record within this mechanically stacked category,” David Young, a senior researcher at NREL, said in a statement. “The performance of the dual-junction device exceeded the theoretical limit of 29.4 percent for crystalline silicon solar cells.”

Young is co-author of a paper, “Realization of GaInP/Si dual-junction solar cells with 29.8 percent one-sun efficiency,” which details the steps taken to break the previous record. The paper’s co-authors from NREL are Stephanie Essig, Myles Steiner, John Geisz, Scott Ward, Tom Moriarty, Vincenzo LaSalvia, and Pauls Stradins.

According to NREL, Essig attracted interest from CSEM in March when she presented a paper, “Progress Towards a 30 percent Efficient GaInP/Si Tandem Solar Cell,” to the 5th International Conference on Silicon Photovoltaics in Germany.

“We believe that the silicon heterojunction technology is today the most efficient silicon technology for application in tandem solar cells,” Christophe Ballif, head of PV activities at CSEM, said in a statement.

Matthieu Despeisse, manager of crystalline silicon activities at CSEM said the organization partnered with NREL with the objective of demonstrating that 30 percent efficient tandem cells can be realized using silicon heterojunction bottom cells, due to the combination with high performance top cells, such as those developed by NREL.

The first collaboration results indicate that even greater efficiency can be achieved by the combination of NREL and CSEM cells, NREL said.

Lead image: Stack of solar cells. Credit: Shutterstock.

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