Nanoscale and Real-Time Nuclear–Electronic Dynamics Simulation Study of Charge Transfer at the Donor–Acceptor Interface in Organic Photovoltaics

Charge-transfer (CT) processes in donor–acceptor interfaces of organic photovoltaics have been challenging targets for computational chemistry owing to their nanoscale and ultrafast nature. Herein, we report real-time nuclear–electronic dynamics simulations of CT processes in a nanometer-scale donor–acceptor interface model composed of a donor poly(3-hexylthiophene-2,5-diyl) crystal and an acceptor [6,6]-phenyl-C₆₁-butyric acid methyl ester aggregate. The simulations were realized using our original reduced-scaling computational technique, namely, patchwork-approximation-based Ehrenfest dynamics. The results illustrated the CT pathway with atomic resolution, thereby rationalizing the observed excitation-energy dependence of the quantity of CT. Further, nuclear motion, which is affected by the electronic dynamics, was observed to play a significant role in the CT process by modulating molecular orbital energies. The present study suggests that microscopic CT processes strongly depend on local structures of disordered donor–acceptor interfaces as well as coupling between nuclear and electronic dynamics.