Reduced non-radiative charge recombination enables organic photovoltaic cell approaching 19% efficiency

Reducing non-radiative charge recombination is of critical importance to achieving high-performance organic photovoltaic (OPV) cells. The correlation between the exciton behaviors and non-radiative charge recombination is rarely studied. In this work, we achieved an increase in the exciton diffusion length (LD) in the acceptor phase via introducing HDO-4Cl to the PBDB-TF:eC9-based system. Compared with the eC9-based film, the exciton LD in the HDO-4Cl:eC9-based film is increased from 12.2 to 16.3 nm. The enlarged exciton LD can obviously decrease the non-radiative charge recombination and increase the efficiency of photon utilization in the PBDB-TF:eC9-based OPV cell. Finally, we not only obtained an outstanding power conversion efficiency (PCE) of 18.86% but also demonstrated the correlations between the non-radiative energy loss and exciton behaviors. The results show that regulating the exciton behaviors is an effective way to reduce the non-radiative energy loss and realize high-efficiency OPV cells.