Exciton radiative recombination in spherical CdS/CdSe/CdS quantum-well nanostructures

Photoluminescence (PL) and lifetimes of colloidal CdS/CdSe/CdS (core/well/shell) quantum-well (QW) nanostructures are investigated for different well thicknesses in the temperature range of 77-300 K. When the temperature increases, the PL intensity decreases continuously and PL peak shifts to lower energy side. The PL lifetimes for the 1-3 monolayer (ML) CdSe QWs increase with temperature and radiative recombination dominates the decay processes. The radiative lifetimes basically increase linearly with temperature, which indicates the existence of free two-dimensional excitons. For the 4 ML CdSe QW sample, the lifetime does not increase with temperature, showing more nonradiative processes due to more defect formation within the thicker QWs. (c) 2005 American Institute of Physics.