Electron-hole pairs in organic photovoltaics are known to dissociate efficiently despite a Coulomb binding energy that exceeds thermal energy, a behavior that remains only partially understood. While previous studies have highlighted the role of electron-phonon interactions and nonequilibrium effects, a clear and physically transparent picture of the dissociation mechanism is still lacking. In this work, we investigate this problem using a two-dimensional quantum transport model based on the nonequilibrium Green’s function formalism, treating the donor-acceptor interface as an open system. Rather than aiming at a material-specific description, our approach is designed to identify the key mechanisms governing charge separation. We show that increasing electron-phonon coupling leads to a strong enhancement of the dissociation probability, reaching values close to 90%. This behavior is explained by the broadening of quantum states, which promotes interpolymer chain hybridization and induces a transition from hopping to quasiband transport. Most importantly, we demonstrate that these effects give rise to a ratchetlike mechanism at the interface, combining phonon-assisted transitions and carrier delocalization, which enables directional transport and suppresses recombination. This Markovian mechanism, which arises from the interplay between the Coulomb potential profile and vibrational energies, provides a unified and physically transparent explanation for efficient exciton dissociation, even under equilibrium phonon conditions.

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• Photovoltaic absorbers
• Organic semiconductors
• Polymer networks
• Solar cells
• Nonequilibrium Green's function