Non-fullerene acceptors for large-open-circuit-voltage and high-efficiency organic solar cells

The development of fused ring-based non-fullerene acceptors has established a great competitiveness of solution-processed organic solar cells (OSCs) beyond other emerging solar photovoltaics. In this review, we highlight the recent progresses in non-fullerene OSCs that have shown high power conversion efficiencies along with large open-circuit voltages because of the low energy loss. By tailoring the molecular structures of non-fullerene acceptors, energy-level alignments between non-fullerene acceptors and the paired donors can be optimized, together with a complementary absorption covering a broad range of solar spectrum. Nanoscale morphological structure can be tuned by thermal annealing and solvent additive treatments to improve exciton dissociation and charge extraction. All these appealing features lead to a better photovoltaic performance of non-fullerene OSCs than that of fullerene counterparts, which is critically important for potential applications in economically efficient building-integrated photovoltaics.