Exciton dissociation at donor-acceptor polymer heterojunctions: Quantum nonadiabatic dynamics and effective-mode analysis

摘要

The quantum-dynamical mechanism of photoinduced subpicosecond exciton dissociation and the concomitant formation of a charge-separated state at a semiconducting polymer heterojunction is elucidated.The analysis is based upon a two-state vibronic coupling Hamiltonian including an explicit 24-mode representation of a phonon bath comprising high-frequency (C=C stretch) and low-frequency (torsional) modes.The initial relaxation behavior is characterized by coherent oscillations,along with the decay through an extended nonadiabatic couphng region.This region is located in the vicinity of a conical intersection hypersurface.A central ingredient of the analysis is a novel effective mode representation,which highlights the role of the low-frequency modes in the nonadiabatic dynamics.Quantum dynamical simulations were carried out using the multiconfiguration time-dependent Hartree method.