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Supercharging the silicon solar cell

Researchers at MIT have shown that single-layer silicon solar cells could convert up to 35% of the energy in sunlight to useful electricity, a boost from the current efficiency ceiling of 29% (Nature 2019, DOI: 10.1038/s41586-019-1339-4). The trick, they say, involves finding the right combination of materials to allow them to exploit a phenomenon predicted about 40 years ago. Semiconductors like silicon excel at converting some, but not all, wavelengths of light to electricity. The range of wavelengths a semiconductor can use to generate electricity depends on an inherent electrical property of the material, called the band gap. When these materials absorb wavelengths of light that pack more energy than those in that specific range, the energy gets lost as heat. Solar cells could run more efficiently and put out more electricity if researchers could expand that range of wavelengths. To do so, researchers led by Marc Baldo, an electrical