Infrared-active heterostructured nanocrystals with ultralong carrier lifetimes

Abstract

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 micros 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.