SOLAR cells could become much more efficient with the discovery of a way to make a single photon liberate two electrons instead of one. Most solar cells are made of sheets of semiconductor. A photon hitting the material knocks just one electron out of the crystal structure, allowing a current to flow. If the photon has more energy than is required to do this, the excess is lost as heat.
But when a high-energy photon hits a semiconductor nanocrystal, the extra energy kicks out more electrons. “You absorb the same number of photons but can produce double the number of…
