Environment-Assisted Quantum Photo-Protection in Interacting Multi-Exciton Transfer Complexes

Abstract

Transport of excitons through transfer networks is a unique example where the interplay between quantum coherence and environment-induced dephasing leads to nontrivial effects. One exciting example is the environment-assisted quantum transport, (ENAQT), where, counter intuitively, the environment interrupts quantum transport in a way that enhances the transfer efficiency. Here we show that the interplay between dephasing and quantum coherence can lead to an additional function in exciton transport -photo-protection, that is the reduction of current upon increased excitation. We start by demonstrating that even under weak coupling conditions, weak excitations can lead to multiple-exciton generation, thus going beyond the common single-exciton approximation. We then consider the transport of two excitons, and show that a interplay between dephasing and exciton-exciton interactions leads to a reduction in current, i.e.to photo-protection. The effect may be related to actual photo-protection observed in photosynthetic systems.

Environment assisted and environment hampered efficiency at maximum power in a molecular photo cell

“…In this case the efficiency drops substantially (becoming roughly inversely proportional to the dephasing rate 41 ). It is worthwhile to point out that the width of the ENAQT regime is controlled by the rate of injection of electrons at the D-LUMO level, which in our system is determined by the resultant of radiative (γ pht ) and non-radiative (γ phn ) transfer rates 42 .…”