A six-junction solar cell designed at the U.S. National Renewable Energy Laboratory (NREL) achieved a record Researchers John Geisz (left) and Ryan France fabricated a solar cell that is nearly 50% efficient. Source: Dennis Schroeder, NREL47.1% efficiency under 143 suns concentration. Under one sun illumination, a variation of the structure achieved a conversion efficiency of 39.2%, which is also a new record.

The six junctions of the device were engineered with different alloys of III–V semiconductors, each harnessing light from a different region of the solar spectrum. The 140 layers in total were assembled to realize nearly optimal bandgaps for the junctions.

The researchers believe the new photovoltaic design could provide a pathway for producing solar cells with even higher efficiencies that are ideally suited for use in concentrated solar power devices. A power system featuring a smaller number of the super high efficiency cells than currently deployed for this application and paired with concentrating mirrors could prove a viable means of generating cost-competitive solar power.

The next goal is to reach efficiencies surpassing 50%, which means developing technology to reduce series resistance in the solar cell.