Interlevel transitions in core–shell nanodots with dielectric environment

The interlevels absorption in spherical CdSe/ZnS and ZnS/CdSe core–shell nanodots is theoretically investigated taking into account the dielectric environment effect. By considering the joint action of the quantum confinement and polarization charges, the influence of the nanosystem geometry upon the energy spectrum and oscillator strength associated to interlevel transitions is studied. We found that: (1) the low dielectric constant environments significantly blueshift the energy levels; (2) the transition matrix elements and oscillator strengths considerably vary with the core–shell radius ratio; (3) the peak position of the interlevels optical absorption is greatly affected by changing of the shell thickness, but for some geometries the absorption spectrum also becomes sensitive to the environment dielectric properties. The possibility of tuning the resonant energies by using the combined effect of the spatial confinement and dielectric mismatch between the dot and the surrounding medium can be useful in the optoelectronic devices applications.

► Effects of the geometry and the dielectric environment on the core–shell QDs optical properties are investigated.
► The interlevel transition energies are strongly dependent on the core/shell radius ratio.
► In inverted core–shell nanodots the dielectric mismatch blue-shifts the absorption coefficient peak.