Impact of shell thickness on exciton and biexciton binding energies of a ZnSe/ZnS core–shell quantum dot

Impact of shell structure on the exciton and biexciton binding energies has been studied in a ZnSe/ZnS core–shell quantum dot using Wentzel–Kramers–Brillouin (WKB) approximation. For excitons, the binding is caused by the Coulombic as well as the confinement potentials while biexciton binding energy is determined by taking into account the exchange and correlation effects. The exciton binding energy was found to increase initially with increasing shell thickness which reaches saturation at larger shell thickness. On the other hand, the biexciton binding energy exhibits a crossover from the bonding to antibonding state with increasing shell thickness for smaller core radius of the quantum dot.