Coherent Real-Space Charge Transport Across a Donor–Acceptor Interface Mediated by Vibronic Couplings

There is growing experimental and theoretical evidence that vibronic couplings, couplings between electronic and nuclear degrees of freedom, play a fundamental role for ultrafast excited state dynamics in organic donor–acceptor hybrids. While vibronic coupling has been shown to support charge separation at donor–acceptor interfaces, so far little is known about its role for the real-space transport of charges in such systems. Here, we theoretically study charge transport in thiophene:fullerene stacks using time-dependent density functional tight-binding theory combined with Ehrenfest molecular dynamics for open systems. Our results reveal coherent oscillations of the charge density between neighboring donor sites, persisting for about 200 fs and promoting charge transport within the polymer stacks. At the donor–acceptor interface, vibronic wave packets are launched, propagating coherently over distances of more than 3 nm into the acceptor region. This supports earlier experimental observations of long-ran...