Size and shell effects on cdse quantum dots in binary ligand system

We synthesized various-sized CdSe quantum dots (QDs) capped with a binary ligand system using oleic acid (OA) and trioctylphosphine (TOP), as well as high-quality CdSe/CdS core/shell structured QDs using Cd-oleate and TOP as shell precursors. The energy of the fluorescence (FL) peak for the CdSe QDs shifted from 2.475 to 2.064 eV with increasing growth time, which resulted in increasing the size of QDs. Upon an increase in the size of QDs, the electron and hole level energies decreased due to the quantum confinement effect. The full width at half maximum (FWHM) of the FL peaks for the CdSe QDs decreased with increasing growth time because of the Se-rich surface and low OA molar ratio. In particular, the FWHM of FL peaks from the CdSe/CdS core/shell-structured QDs is smaller than that of the CdSe core QDs owing to the improved size uniformity resulting from slow continuous shell deposition and high reaction temperature. An enhanced light absorption capacity was also observed for the CdSe/CdS core/shell structure QDs.