Synergistically Regulating the Conjugation Length and Side Chain on Oligothiophene-Based Fully Nonfused Ring Electron Acceptors for Efficient Organic Solar Cells

Fully nonfused ring electron acceptors (FNEAs) have become a research hotspot due to their simple skeletons and reduced synthetic complexity. In this work, with the assistance of a noncovalent conformational lock, we synthesized four FNEAs based on an oligothiophene unit via synergistically regulating the conjugation length and side-chain engineering, which could effectively tune the molecular conformations, absorption spectra, energy levels, intermolecular interactions, and miscibility with polymer. The blend film PBDB-T:4TO-in forms clear bicontinuous interpenetrating networks and more clear phase separation feature due to the balance between crystallization and miscibility. Hence, PBDB-T:4TO-in devices achieved the highest PCE of 10.38%, while an enhanced power conversion efficiency of 11.63% was obtained with the polymer donor replaced by JD40. Overall, this work provides an effective route for oligothiophene-based FNEA design through fine-tuning the molecular skeleton.