Using an exotic form of silicon could substantially improve
the efficiency of solar cells, according to computer simulations by researchers
at the University of California, Davis, and in Hungary. The work was published
Jan. 25 in the journal Physical Review Letters.
Solar cells are based on the photoelectric effect: a photon,
or particle of light, hits a silicon crystal and generates a negatively charged
electron and a positively charged hole. Collecting those electron-hole pairs
generates electric current.
Conventional solar cells generate one electron-hole pair per
incoming photon, and have a theoretical maximum efficiency of 33 percent. One
exciting new route to improved efficiency is to generate more than one
electron-hole pair per photon, said Giulia Galli, professor of chemistry at UC
Davis and co-author of the paper.