Infrared-Active Heterostructured Nanocrystals with Ultra long Carrier Lifetimes

We present the synthesis of composite PbSe/CdSe/ CdS nanocrystals with two distinct geometries: core/shell/shell structures and tetrapods. These novel nanostructures exhibit extremely long carrier decay times up to 20 mu s that are combined with high emission efficiencies in the infrared. The increase in carrier lifetimes is attributed to the reduction of the electron-hole overlap as a result of delocalization of the electron wave function into the outer CdS shell or arms. The ultralong carrier lifetimes and controlled geometry render these nanocrystals attractive for a variety of applications from lasing to photocatalysis and photovoltaics.