Control of hot carrier thermalization in type-II quantum wells: a route to practical hot carrier solar cells

Hot carrier distributions generated by the absorption of high-energy photons typically etherealize rapidly via various phonon-mediated relaxation processes. In this paper, it is shown that type-II quantum wells (QWs) exhibit stable non-equilibrium carrier distributions, which can be manipulated and stabilized independent of the photonic dispersion of the constituent materials. Moreover, it will be shown that the reduced overlap between electron and hole wave functions in type-II QWs, which inhibit radioactive recombination, play a critical role in hot carrier thermalization in these systems. Current-voltage characteristics from analogous MQW p-i-n structures show enhanced hot carrier photocurrent extraction with increasing optical excitation power. Specifically, upon increased photo-excitation the elevated thermal energy in the carrier distribution results in the tunneling of hot electrons from the QW and increased photo carrier collection.