Impurity states and photoionization cross section in CdSe/ZnS core-shell nanodots with dielectric confinement

► Electric field effect on the impurity states in core-shell quantum dots is studied. ► Electron cloud of the on-edge impurity is strongly distorted by the electric field. ► A pronounced redshift of the donor energy under low dielectric environment is found. ► Dielectric mismatch causes an increase of the photoionization cross-section. ► Photoionization cross-section depends on the donor position and electric field.