Understanding the role of entropy and electron delocalization in triggering spontaneous charge separation at organic donor-acceptor interfaces

Understanding the dissociation of excitons in organic semiconductors is essential for improving the performance of next-generation photovoltaic devices. Here, we used a multiscale approach that combines a tight-binding model parameterized by DFT calculations, and kinetic Monte Carlo simulation to model the charge separation (CS) dynamics at an organic donor–acceptor interface. The model allows us to understand how entropy and electron delocalization can facilitate the enthalpy-uphill CS. Effects from a small band bending, and the arrangement of molecules near the interface on the CS dynamics are studied. These findings highlight the role of molecular-scale design in optimizing organic materials for photovoltaic applications.