Quinoxaline-based non-fullerene guest acceptor enables ternary organic solar cells achieving 18.9% efficiency via reducing energy loss and regulating morphology

Designing appropriate third component is considered as a valid and facile approach to improve the devices photovoltaic performance of organic solar cells. Here, a novel quinoxaline central core based non-fullerene acceptor named BQ was successfully synthesized. The excellent electron-withdrawing capacity of quinoxaline core enables BQ to possess an obviously upshift lowest unoccupied molecular orbital (LUMO) energy level, resulting in an extremely high open-circuit voltage (VOC) of 0.959 V blended with polymer donor D18. When incorporating BQ as the guest acceptor to prepare ternary organic solar cells (TOSCs) in D18:N3 host system, an improved VOC of 0.846 V with reduced non-radiative recombination energy loss of 0.236 eV and an excellent fill factor of 79.95% were obtained. Encouragingly, the cascade-like model TOSCs achieved an excellent power conversion efficiency of 18.9%, which could be attributed to the complementary absorption, fast exciton diffusion and dissociation, efficient carries transport and collection, appropriate phase separation and the low energy loss. This work demonstrates that incorporating a quinoxaline-based guest acceptor is a feasible strategy to achieve high-performance TOSCs.