Gary Zaiats, Diana Yanover, Roman Vaxenburg, Arthur Shapiro, Aron Safran, Inbal Hesseg, Aldona Sashchiuk, Efrat Lifshitz
December 16, 2014
The present work describes the structural and optical characterization of PbSe and PbSe/CdSe colloidal quantum dots (CQDs), the latter being produced by cation exchange of Pb 2+ for Cd 2+ ions. The cation exchange occurs on preferred crystallographic facets and results in either non-concentric CdSe shells or Pb x Cd 1 –x Se alloyed-shell layers. The obtained heterostuctures are referred to as PbSe/CdSe “thin shell” CQDs. The parent PbSe CQDs are limited to relatively small diameters of 3–4 nm, with absorption edge between 1.0 and 1.3 eV. The steady-state and time-resolved photoluminescence spectra recorded at various temperatures reveal the following properties of the PbSe/CdSe CQDs: (1) the photoluminescence intensity of air-free CQDs is maintained upon their exposure to oxygen; (2) the band-edge exciton lifetime is extended by about a factor of two relative to the parent PbSe CQDs. The experimental results and the effective mass-based calculations suggest the formation of alloyed shells and highlight a pronounced effect of core displacement from the CQD center on the heterostructure optical properties.