Semiconductor material with three energy bands could be used to make solar cells with efficiencies of around 45 percent, compared with 25 percent for conventional cells that use a single semiconductor and 39 percent for cells with layers of mixed semiconductors.
The researchers found that introducing a few atoms of oxygen into a zinc-manganese-tellurium (ZnMnTe) alloy splits the compound semiconductor's conduction band into two parts. Similarly, adding nitrogen to a semiconductor such as gallium arsenide phosphide will also give a multi-band semiconductor.
LBNL has licensed the technology to RoseStreet Labs, a startup in Phoenix, AZ, which plans to commercialize solar cells made from these multi-band semiconductors. Because it's an entirely new technology, though, it's hard to say when such a solar cell will be available, Walukiewicz says.