Fusion or non-fusion of quasi-two-dimensional fused perylene diimide acceptors: the importance of molecular geometry for fullerene-free organic solar cells

Two small molecular electron acceptors (BT–FPDI and fBT–FPDI) with quasi-2D FPDI units were designed and synthesized for efficient fullerene-free organic solar cells (OSCs), and provide a new insight into the regulation of the molecular geometry.