The National Renewable Energy Laboratory (NREL) has a long history of building solar cells that capture light from the sun at record-setting efficiencies. But the sun is not the only light source from which photovoltaics can capture energy. Hot objects emit light, too—generally at longer, lower-energy wavelengths—and thermophotovoltaics (TPVs) are photovoltaic cells that are optimized to capture that light.
