Charge dynamics through pi-stacked arrays of conjugated molecules: effect of dynamic disorder in different transport/transfer regimes

We provide further computational evidence that the electronic coupling between pi-stacked molecules is strongly modulated by the thermal motions at room temperature, not only in supramolecular flexible systems (like DNA) but also in molecular crystals. The effect of this modulation on the charge dynamics is different for different transfer/transport mechanisms and depends on the modulation timescale. In the case of charge transfer (CT) between a donor and an acceptor, the effect of electronic coupling fluctuations introduces a corrective term in the expression of the rate constant (different for adiabatic and non-adiabatic CT). For the transport in molecular crystals, this fluctuation can be the limiting factor for the charge mobility. Although the fluctuation of the electronic coupling is similar in magnitude for all systems containing molecular pi-stacking, its importance for the charge dynamics increases with the decrease of the reorganization energy.