Miscibility-Driven Morphology Tuning as the Critical Role for Designing Efficient Nonfused Ring Electron Acceptors

A clear understanding of the structure-performance relationship is important for promoting the evolution of designing efficient nonfused ring electron acceptors (NFREAs). Inspired by the above intention, herein, a side-by-side study is carried out based on three newly developed NFREAs by regulating rigid conjugation and flexible side chains, yielding PhNT-4Cl, PhNC-4Cl, and PhNP-4Cl. It is unveiled that reduced miscibility by extending rigid conjugation can help to form nanofiber features, thus allowing high crystallinity, and a hindered overaggregation tendency by increasing steric hindrance of flexible side chain can help to form suitable domain sizes, thus avoiding severe charge recombination. As a result, PhNC-4Cl with cyclopentadithiophene building block and branched alkyl side chains achieves a good balance in the earlier two aspects, thus enabling a higher efficiency of 14.01% with both higher photocurrent and fill factor, relative to PhNT-4Cl (6.95%) and PhNP-4Cl (6.31%). This work points out the critical role of miscibility-driven morphology tuning on the device performance, thus guiding the molecular design toward efficient NFREAs. Three nonfused ring electron acceptors (PhNT-4Cl, PhNC-4Cl, and PhNP-4Cl) are reported, in which PhNC-4Cl-based device achieves a champion efficiency of 14.01%. The work proves the importance of miscibility tuning in optimizing the device performance.image (c) 2023 WILEY-VCH GmbH