On the basis of a combined experimental-theoretical investigation, we proposed that the enhanced diffusivity along those P3HT one-dimensional stacks stems from a transient delocalization of the energy carriers . That is, the excitonic density of states (EDOS) in these fibers comprises states that spatially extend over a few polymer chains and are thermally accessible at room temperature from the localized states sitting at the bottom of the EDOS; these extended states can then be transiently populated during the exciton lifespan, kicking energy transport along the stacking direction. A similar mechanism has been proposed in the context of charge transport in molecular semiconductors . Here, we show that this transient delocalization mechanism is remarkably sensitive to the interplay between the amount of onchain exciton delocalization and the spatial range of excitonic interactions along the fibers.