Electrons Staying Hot

摘要

A silicon photovoltatic cell can produce a voltage because once electrons are photoexcited, the voltage bias created by the interface of positive and negative silicon (a p-n junction) draws these electrons in only one direction. Gabor et al. (p. 648, published online 6 October; see the Perspective by Basko) found that single- and double-layer graphene in a p-n junction generated a voltage not through the photovoltaic effect, but through a competing mechanism, whereby the excited electrons in graphene remained hotter than the rest of device, driving a photothermoelectric effect.