Small molecule acceptors with a ladder-like core for high-performance organic solar cells with low non-radiative energy losses

Abstract

Three new low-cost A₁–D–A₂–D–A₁ type small molecule acceptors BT-IC4F, BT2F-IC4F and BTOR-IC4F have been designed and synthesized for high-performance organic solar cells (OSCs). In BT2F-IC4F and BTOR-IC4F, intramolecular noncovalent interactions are adopted to construct ladder-like planar molecular backbones. For BTOR-IC4F, the introduction of two alkoxyl chains at the 5,6-positions of the central benzothiadiazole unit can markedly improve the solubility, lift the lowest unoccupied molecular orbital level, and optimize the morphology of the active layer. As expected, PBDB-T:BTOR-IC4F based OSCs achieve a power conversion efficiency (PCE) of 11.48%, which is higher than those of devices based on PBDB-T:BT-IC4F (9.83%) and PBDB-T:BT2F-IC4F (8.45%). Meanwhile, the solar cells based on BTOR-IC4F demonstrate a low non-radiative energy loss of 0.28 eV.