Designing High-Performance Nonfused Ring Electron Acceptors via Synergistically Adjusting Side Chains and Electron-Withdrawing End-Groups.

Three nonfused ring electron acceptors, Hexyl-0F , Isopropyl-0F , and Isopropyl-2F , are designed and synthesized. Unlike Hexyl-0F , Isopropyl-0F with two sterically hindered 2,4,6-triisopropyl-phenyl groups is highly soluble, which provides a good opportunity for solution processability. Compared with Isopropyl-0F , Isopropyl-2F with fluorinated end-groups exhibits red-shifted absorption. Due to these synergistic adjustment, Isopropyl-2F -based devices displayed a high power conversion efficiency of 12.55%, higher than that of Isopropyl-0F (9.49%). The result demonstrates that the introduction of large steric substituents in the π-bridge units and electron-withdrawing end-groups plays a positive role in the construction of high-efficiency nonfused ring electron acceptors.