Optical transitions in charged CdSe quantum dots

Using a many-body approach based on single-particle pseudopotential wave functions, we calculate the dependence of the optical transitions in CdSe nanocrystals on the presence of “spectator” electrons or holes. We find that (i) as a result of the different localization of the electron and hole wave functions, the absorption lines shift by as much as $22\mathrm{meV}/\mathrm{unit}\mathrm{}\mathrm{charge}$ when electrons or holes are loaded into the quantum dot. (ii) The lowest emission line is significantly red shifted with respect to the lowest allowed absorption line. (iii) Trapping of a “spectator” hole in a surface state is predicted to lead to dramatic changes in the absorption spectrum, including the appearance of new transitions.