Effect of shell layers on luminescence of colloidal CdSe/Zn(0.5)Cd(0.5)Se/ZnSe/ZnS core/multishell quantum dots

Colloidal CdSe/Zn(0.5)Cd(0.5)Se/ZnSe/ZnS core/multishell quantum dots (QDs) were synthesized by using the well developed successive ion layer adsorption and reaction (SILAR) technique. The UV-vis and PL spectra, TEM, X-ray diffraction and Raman measurement were performed to investigate the structure and optical properties of prepared QDs during the growth of shell layers, which indicated that the stress in CdSe core became stronger with the increasing shell thickness. Due to the gradual adjustment of the lattice parameters in the radial direction and the radial increase of the respective valence- and conduction-band offsets, the optical measurements show a significant enhancement in the photoluminescence quantum yield (QY) and an expedited radiative decay in QDs overcoated with thicker shell. The temperature-dependent optical spectra were measured, and the relation between the microstructure and the optical properties of these core/multishell quantum dots was discussed.