Regulating Molecular Packing and Orientation of Nonfused Ring Electron Acceptors for Organic Solar Cells with a High Figure‐of‐Merit

Developing photovoltaic materials well balancing efficiency, stability, and cost is highly required for organic solar cells (OSCs) moving toward commercial applications. With such intention, two nonfused ring electron acceptors (NFREAs), 3TT11‐4F and 3TT46‐4F, with large steric hindrance substituents and linear/branched alkyl side chains are designed. The change of alkyl side chains from branched to linear leads to tighter π–π stacking and uniform molecular orientation for 3TT11‐4F, as revealed in single‐crystal structure, which further boosts the charge transport and regulates the aggregation property. Thus, a better efficiency of 15.02% is achieved in 3TT11‐4F‐based OSC with significantly improved photocurrent, relative to 3TT46‐4F‐based one (13.79%). Besides, the two NFREAs also enable good device stability with over 70% initial efficiencies maintained after 800 h illumination. Considering the low synthetic complexity, a high industrial figure‐of‐merit value of 16.34% is achieved for 3TT11‐4F‐based OSC, superior to some typical counterparts. The work provides a good reference for material design with an outstanding figure‐of‐merit.