Principal Investigator Moungi Bawendi
In recent years multiexcitons in NCs have become interesting for a key role they could play in light harvesting. In a conventional solar cell with a single active layer, photons with energy higher than the bandgap create a single electron-hole pair and any excess energy is lost to heat by rapid relaxation via phonon emission. However, if those initial highly energetic charge carriers are able to relax instead by collision with valence electrons to create additional e-h pairs a large part of the otherwise wasted energy could be recouped. The process, known as carrier multiplication, is very inefficient in the bulk, but recent experimental studies by other researchers have shown evidence for very efficient, ultrafast multiplication in a variety of semiconductor nanocrystal materials including PbX (X=S,Se,Te), InAs, Si and CdSe.