Scientists at the US Department of Energy’s National Renewable Energy Laboratory (NREL), the U.S. Department of Energy’s primary national laboratory for renewable energy and energy-efficiency research and development, have set a world record in solar cell efficiency with a photovoltaic device that converts 40.8 percent of the light that hits it into electricity. According to NREL, this is the highest confirmed efficiency of any photovoltaic device to date.
The inverted metamorphic triple-junction solar cell was designed, fabricated and independently measured at NREL. The 40.8 percent efficiency was measured under concentrated light of 326 suns. One sun is about the amount of light that typically hits earth on a sunny day. The new cell is a natural candidate for the space satellite market and for terrestrial concentrated photovoltaic arrays, which use lenses or mirrors to focus sunlight onto the solar cells.
The new solar cell differs significantly from the previous record holder, which also was based on an NREL design. The new device is extremely thin and light and represents a new class of solar cells with advantages in performance, design, operation and cost.
NREL’s Mark Wanlass invented the original inverted cell, which recently won a R&D 100 award. His design was modified by a team that further optimized the junction energies by making the middle and bottom junctions metamorphic. Metamorphic junctions are lattice mismatched, which means their atoms don’t line up. The material properties of the mismatched semiconductors allows for greater potential conversion of sunlight.