  We study the dynamics of photo-induced charge carriers in realistic models of
LaVO3 and YTiO3 polar heterostructures. It is shown that two types of impact
ionization processes contribute to the carrier multiplication in these strongly
correlated multi-orbital systems: The first mechanism involves local spin state
transitions, while the second mechanism involves the scattering of high kinetic
energy carriers. Both processes act on the 10 fs timescale and play an
important role in the harvesting of high energy photons in solar cell
applications. As a consequence, the optimal gap size for Mott solar cells is
substantially smaller than for semiconductor devices.
