Enhanced crystal network and charge transfer of non-fused ring electron acceptors via interchain interaction for efficient and stable organic solar cells

Abstract

Non-fused ring electron acceptors (NFREAs) are regarded as alternative materials for low-cost organic solar cells (OSCs), but their power conversion efficiencies (PCEs) lag behind those of their fused ring counterparts. Herein, we designed and synthesized three NFREAs of FIOTT-4F, HIOTT-4F, and MIOTT-4F with fluorine atoms, hydrogen atoms, and methyl groups on the rigid aromatic side chains, respectively, among which FIOTT-4F with fluorinated aromatic side chains shows the best photovoltaic properties. The interchain interactions orchestrated by F atoms on FIOTT-4F lead to the formation of a compact, well-ordered three-dimensional (3D) charge transport network and improved compatibility with the polymer donor D18, resulting in rapid charge generation and transfer. Consequently, the D18:FIOTT-4F-based OSC gives a champion PCE of 17.5%, the highest value reported for NFREAs-based cells to date. Furthermore, the device exhibits superior photostability: over 80% of the initial PCE is preserved after 200 h 1-sun illumination. This research offers an original example addressing the “efficiency-cost-stability” triangle, thus paving the way to the commercialization of OSCs.