Abstract

We investigate the determination of non-adiabatic couplings between localized excitations (LEs) and charge-transfer (CT) excitations based on many-body Green’s functions theory in the GW approximation with the Bethe–Salpeter equation (GW-BSE). Using a small molecule dimer system, we first study the influence of different diabatization methods, as well as different model choices within GW-BSE, such as the self-energy models or different levels of self-consistency, and find that these choices affect the LE-CT couplings only minimally. We then consider a large-scale low-donor morphology formed from rubrene and fullerene and evaluate the LE-CT couplings based on coupled GW-BSE-molecular mechanics calculations. For these disordered systems of bulky molecules, we observe differences in the couplings based on the Edmiston–Ruedenberg compared to the more approximate Generalize Mulliken–Hush and Fragment Charge Difference diabatization formalisms. In a kinetic model for the conversion between LE and CT states, these differences affect the details of state populations in an intermediate timescale but not the final populations.