Van der Waals-Zeeman Colloquium

Thursday, 8 April 2010, 16:00

Carrier Multiplication is more efficient in bulk than in quantum dots

Prof. Mischa Bonn
FOM Institute for Atomic and Molecular Physics

The possibility to generate, in semiconductors, multiple charge carriers per photon (carrier multiplication, CM) is of significant interest for future solar cells. CM is known to occur in bulk semiconductors, but has been thought to be enhanced significantly in nanocrystalline materials. We employ time-resolved TeraHertz spectroscopy to quantify directly and with picosecond time resolution the CM efficiency in several materials. Remarkably, for a given photon energy, CM occurs more efficiently in bulk materials than in nanocrystals of the same materials. We elucidate the underlying physics and discuss the consequences of our findings for solar energy conversion.