Chalcogen-Fused Perylene Diimides-Based Nonfullerene Acceptors for High-Performance Organic Solar Cells: Insight into the Effect of O, S, and Se

Three perylene diimide (PDI) tetramers annulated by oxygen (O), sulfur (S), and selenium (Se), named as SF-4PDI-O, SF-4PDI-S, and SF-4PDI-Se, are designed, synthesized, and paired with polymeric donor PDBT-T1 to construct organic solar cells. The heteroatoms' effects on photoelectric properties, chemical geometry, charge transport, active-layer morphology, and photovoltaic performance are investigated in detail. These PDI acceptors exhibit a similar absorption profile, whereas the highest occupied molecular orbitals and lowest unoccupied molecular orbitals are simultaneously upshifted when heteroatoms are altered from O and S to Se due to the gradually weakening electronegativity. Alongside PDBT-T1, SF-4PDI-O achieves an outstanding power conversion efficiency of 8.904% with a high fill factor of 0.706, outcompeting its S-annulated and Se-annulated counterparts. The superiority of the PDBT-T1:SF-4PDI-O system lies in its stronger crystallinity, more balanced hole and electron mobilities, and weaker bimolecular recombination, coupled with more efficient charge transfer and collection. These results shed light on the invention of high-performance PDI acceptors by oxygen-decorated methodology.