Effect of the Molecular Configuration of Perylene Diimide Acceptors on Charge Transfer and Device Performance

Three perylene diimide (PDI)-based small molecules, T2-SePDI2, T3B-SePDI3, and T4B-SePDI4, with different molecular configurations are synthesized. Due to a large steric hindrance, the molecular configuration of T3B-SePDI3 is the most distorted, followed by T4B-SePDI4, while T2-SePDI2 shows the smallest steric hindrance. Inverted bulk heterojunction solar cells based on T3B-SePDI3 and PBDB-T show the highest power conversion efficiency (PCE) of 5.82% with an open-circuit voltage of 0.98 V, a high short-circuit current density of 10.52 mA/cm 2, and a fill factor of 56.31%. The PCEs of the T2-SePDI2 - and T4B-SePDI4- based devices are 4.10% and 5.10%, respectively. The results demonstrate that the molecular configuration of the PDI-based small molecule acceptor is critical and that increasing the steric hindrance is helpful in suppressing aggregation and improving device performance.