Roles of Long-Range Hopping, Quantum Nuclear Effect, and Exciton Delocalization in Exciton Transport in Organic Semiconductors: A Multiscale Study

Excitation energy transport in organic materials is of significance for determining the efficiency of light-harvesting systems. With the improved material preparation and device fabrication, the experimentally measured exciton diffusion length has increased rapidly in recent years and far exceeds the typical values found in synthetic organic systems on the order of 10 nm, calling for better understanding and evaluation of the intrinsic exciton diffusion property. We investigate the energy transport at three different levels, ranging from the semiclassical Marcus theory, to the quantum nuclear tunneling-mediated hopping, and eventually to the time-dependent exciton diffusion in organic semiconductors. All the calculations are based on first-principles evaluated molecular parameters. We find that the nuclear quantum effect can strongly enhance the exciton diffusion length by orders of magnitude. Both long-range energy transfer and exciton delocalization effects can also be identified.