Unsymmetrically Chlorinated Non‐Fused Electron Acceptor Leads to High‐Efficiency and Stable Organic Solar Cells

Abstract Searching the cost‐effective organic semiconductors is strongly needed in order to facilitate the practice of organic solar cells (OSCs), yet to be fulfilled. Herein, we have succeeded in developing two non‐fused ring electron acceptors (NFREAs), leading to the highest efficiency of 16.2 % for the NFREA derived OSCs. These OSCs exhibit the superior operational stabilities under one sun equivalent illumination without ultraviolet (UV) filtration. It is revealed that the modulation of halogen substituents on aromatic side chains, as the new structural tool to tune the intermolecular interaction and optoelectronic properties of acceptors, not only promotes the interlocked tic‐tac‐toe frame of three‐dimensional stacks in solid, but also improves charge dynamics of acceptors to enable high‐performance and stable OSCs.