We study the dynamics of photoinduced charge carriers in semirealistic models of ${\mathrm{LaVO}}_3$ and ${\mathrm{YTiO}}_3$ polar heterostructures. It is shown that two types of impact ionization processes contribute to the carrier multiplication in these strongly correlated multiorbital 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.

• Received 25 January 2019
• Revised 22 July 2019

DOI:https://doi.org/10.1103/PhysRevB.100.075147