Giant suppression of Auger electron cooling in charged nanocrystals

This letter presents a detailed study of the electron relaxation lifetimes from the excited p-like state into the ground s-like state via Auger cooling in positively and negatively charged CdSe nanocrystals, where the dependence of Auger cooling rates on size, temperature and carrier-carrier interaction effects is investigated. A nearly two-orders-of-magnitude reduction of Auger rates is found in small nanocrystals populated by two electrons and one hole at room temperature. This effect increases with decreasing temperature leading to a total lifetime increase of up to 4 orders of magnitude for T ∼ 10 K. Such a giant suppression of Auger cooling rates appears to be a general property of semiconductor nanocrystals. A similar reduction of Auger rates at room T is found in negatively charged PbSe nanocrystals as well.