Charge carrier recombination and voltage losses in organic solar cells

The power conversion efficiency (PCE) of organic solar cells (OSCs) has surpassed 20%, driven by the rapid advancement of non-fullerene acceptor materials, which have enhanced solar harvesting quantum efficiency and short-circuit current density. However, the performance of OSCs still lags behind that of traditional inorganic and perovskite solar cells, primarily due to significant voltage losses caused by the fast recombination of charge carriers. These voltage losses can be classified into radiative and non-radiative components, which are further linked to the decay dynamics of singlet excitons, triplet excitons, and charge transfer state excitons. This review provides a comprehensive overview of experimental observations and theoretical studies on voltage losses in OSCs, as well as the underlying charge carrier dynamics. Additionally, it discusses strategies to mitigate voltage losses and highlights promising approaches to further enhance the performance of OSCs.