Dynamics of dissipative multiple exciton generation in semiconductor nanostructures

The population dynamics of single exciton and biexciton states in a simple model of a spherical semiconductor nanostructure is modeled numerically in the presence of Coulomb coupling between single and two exciton states and a dissipation channel in order to study the transient biexciton population that occurs in an optically excited semiconductor nanocrystal. The results show that the system evolution strongly changes if the dissipation is included. In a certain range of parameters, the growth of the exciton number (multiple exciton generation process) is fast (on picosecond time scale) and the following decay (Auger process) is much slower (hundreds of picoseconds). In some cases, the maximum occupation of the biexciton state increases when dissipation is included. The dynamics of an ensemble of nanostructures with a certain size dispersion is studied by averaging over the energy of the biexciton state which can be different for each single nanostructure. The validity of Markov and secular approximation is also verified.