Temperature effects on the absorption properties in II–VI semiconductor core–shell nanocrystals

By using Varshni's law, we have determined the temperature effects in the effective dielectric function of II–VI semiconductor nanocrystals distribution of type I. For each temperature, we have also used an extended Maxwell–Garnett theory to determine the effective dielectric function. We have taken into account the confinement of charge carriers by considering appropriate dielectric function for the cores in the distribution. For the shells, we have considered dielectric function similar to that in bulk semiconductors. Besides, the effects of (i) the cores sizes and (ii) the volume fraction of the distribution are investigated in the real and imaginary parts of the effective dielectric function. By increasing the temperature from 50 K to 300 K, we have found a red shift of the core resonant peaks as a consequence of its shrinkage bandgap along with a decreasing of its peak intensities and an increasing of its peak FWHM. Also, by increasing the core sizes, we have obtained a red shift of its resonant peak, while a decreasing of their sizes induces a blue shift, similar to that observed in other low-dimensional systems. Finally, by increasing the volume fraction, the intensities of the resonant peaks are higher and they are slightly red-shifted.

► We simulate optical properties of II–VI core–shell nanocrystals using an extended Maxwell–Garnett theory.
► Temperature and size effects are compared in order to determine the more dominant one on the resonant peaks and intensities.
► Finite potential confinement is used to evaluate the exciton energy in effective mass approximation. Also, size distribution is investigated through different values of volume factors.