Quantum modeling of electron-hole dissociation at the donor-acceptor interface in an organic solar cell
- il y a 6 heures
- 2 min de lecture
Publication in Physical Review Applied!
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. |
Fig. 1: (a) Schematic representation of the modeled system and potential energy mapping. The vertical rectangles in donor material schematically represent the polymer chains. (b) Potential energy of holes in the middle of the chains as a function of position x, and schematic representation of the processes considered in the model.
Ref : N. Cavassilas, F. Michelini, M. Bescond, "Nonequilibrium quantum modeling of electron-hole dissociation at the donor-acceptor interface in an organic solar cell," Phys. Rev. Appl. 25, 054041 (2026).