Enhancement and Tuning of Optical Properties of CdTe/CdS Core/Shell Quantum Dots by Tuning Shell Thickness

Abstract The high luminescent CdTe/CdS core/shell quantum dots in a stable, aqueous medium have been synthesized and their structural and optical properties of CdTe/CdS core/shell quantum dots have been scrutinized. The results indicate that by changing the shell thicknesses of 10 and 16 nm, the emission spectra of CdTe/CdS structures can span from 530 nm to 560 nm and the wavelength tunability is achieved. Moreover, the 10 nm shell thickness for CdS yields a high photoluminescence quantum yield of 32%, an average fluorescence lifetime of 18.4 ns, and a nonradiative decay rate of 0.3×108 s-1. An enhancement in the optical nonlinearities has been observed for CdTe/CdS core/shell quantum dot with a shell thickness of 10 nm compared to CdTe quantum dot and CdTe/CdS core/shell quantum dot with the thickness of 16 nm. This can be explained by the core surface passivation, decreasing of the surface trap density, and increased quantum confinement effects. Our results represent a valuable step towards the development of random lasers, optical limiters, and high-performance optoelectronic applications.