NREL, CSEM set new efficiency record for dual-junction solar cell

Today the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) and the Swiss Center for Electronics and Microtechnology (CSEM) announced a new world record for a dual-junction solar PV cell without concentrated sunlight.

A joint efforts of the two institutions has produced a 29.8% efficient PV III-V/Si PV cell, using a top cell made of gallium indium phosphide and a bottom cell of crystalline silicon. The two layers were independently produced with NREL making the top cell and CSEM the bottom cell, and the two layers were mechanically bonded by NREL.

NREL notes that the The performance of the cell exceeds the theorertical limit of 29.4% for crystalline silicon PV cells, which dominate the global market.

NREL Senior Researcher David Young and his team had predicted that they could reach this efficiency using gallium indium phosphide and silicon layers in an academic paper, and a subsequent paper written by co-author Stephanie Essig attracted the attention of CSEM.

NREL notes that a new design for the PV cell and the work of CSEM were “key” for setting the new record, and the organization predicts that even greater efficiencies can be reached with combinations of NREL and CSEM cells.

Due to their higher cost, production of multi-junction cells is limited. Triple-junction cells have seen some deployment in concetrating photovoltaic (CPV) applications, and a number of high-efficiency PV makers including Panasonic and Silevo are producing multi-junction cells on a commercial scale which utilize crystalline silicon and amorphous silicon layers. To date dual-junction cells have not been widely deployed.

Funding for the work that went into the dual-junction cell was provided by the DOE’s SunShot Initiative, as well as from the Swiss Federation and the Nano-tera.ch initiative.