Aggregation of non-fullerene acceptors in organic solar cells

Organic solar cells (OSCs) employing non-fullerene acceptors (NFAs) have drawn significant research attention in recent years. Molecular stacking and aggregation of electron donors and acceptors within the photoactive layer is vitally important for light absorption and the photon-to-electricity conversion process. Herein, we present the versatile molecular stacking of the state-of-the-art NFAs, as well as the affecting factors including the chemical structures of NFAs and physical processing conditions. We highlight in particular experimental approaches to regulate molecular stacking and aggregation and summarize the influences of these features on optoelectronic and photovoltaic properties of NFA-based OSCs, which provide crucial guidance for further development of high performance OSCs.