Distribution of multiexciton generation rates in CdSe and InAs nanocrystals

The distribution of rates of multiexciton generation following photon absorption is calculated for semiconductor nanocrystals (NCs). The rates of biexciton generation are calculated using Fermi's golden rule with all relevant Coulomb matrix elements, taking into account proper selection rules within a screened semiempirical pseudopotential approach. In CdSe and InAs NCs, we find a broad distribution of biexciton generation rates depending strongly on the exciton energy and size of the NC. Multiexciton generation becomes inefficientfor NCs exceeding 3 nm in diameter in the photon energy range of 2-3 times the band gap.