Propeller-like acceptors with difluoride perylene diimides for organic solar cells

Perylene diimide (PDI) is one of most intensively studied non-fullerene small molecule acceptors (SMAs). By fluorination on the conjugated backbone, a new PDI with difluoride substitution on adjacent bay positions of PDI is prepared. Then, four propeller-like SMAs are obtained by linking four PDIs with an aromatic core, wherein the molecular geometry is modulated by ring fusion of the aromatic core. Further study reveals that fluorination is helpful to enhance the absorption intensity, and thus promote the current density in organic solar cells. In addition, the ring-fused strategy is able to suppress the distortion and rotation of relevant molecules. Therefore, these four acceptors exhibit significantly diversity of photovoltaic performance, wherein the acceptor FPDIF4-DTC consisting of a fused core and fluoro-substituted PDIs shows a best efficiency of 5.1%. This result implies that fluorination on PDI conjugated backbone is a successful way to construct promising SMAs.