Perovskite solar cells recycle photons

Inorganic-organic perovskite solar cells are very efficient in part because the charge carriers exhibit very long path lengths. Pazos-Outón et al. show that photon recycling, as seen previously in highly efficient gallium arsenide solar cells, contributes to this effect (see the Perspective by Yablonovitch). In most solar cells, the recombination of photogenerated charge carriers (electrons and holes) wastes all of the energy. In these lead tri-iodide cells, recombination emits a photon that can be reabsorbed and create more charge carriers.

Science, this issue p. 1430; see also p. 1401