C-Shape or S-Shape? The Molecular Geometry Control of Fused-Ring Nonfullerene Acceptors for Lower Energy Loss in Organic Solar Cells
Yuanqing Bai, Ling Hong, Yuejia Dou, Shengtian Zhu, Haoran Tang, Denghui Liu, Yunhao Cao, Jingwen Chen, Shihao Chen, Lin Shao, Zhengwei Hu, Ding Tang, Kai Zhang, Shi‐Jian Su, Chunchen Liu, Fei Huang
Abstract
To elucidate the pivotal influence of molecular geometry in fused-ring nonfullerene acceptors (FRNFAs) on material properties and device performance of organic solar cells (OSCs), we designed and synthesized two isomeric molecules C–F and S–F, featuring C-shaped and S-shaped geometries with the acceptor–donor–acceptor conjugated framework. The alteration in geometries demonstrated negligible effects on the optical and electrochemical properties. Significantly, single crystal X-ray crystallography analyses uncovered that C–F exhibited a wave network packing, while S–F favored a linear brick packing with the intermolecular packing of end groups, different from the previously reported three-dimensional (3D) stacking network of C-shaped Y series FRNFAs. Despite the absence of 3D network packing, OSCs utilizing C–F demonstrated a remarkable power conversion efficiency of 17.0%, with lower voltage loss compared to the devices based on S–F. This study further underscores the essential role of the C-shaped geometry in FRNFAs, providing valuable insights for future molecular design for high-performance OSCs.