Synergistically Regulating\nthe Conjugation Length\nand Side Chain on Oligothiophene-Based Fully Nonfused Ring Electron\nAcceptors for Efficient Organic Solar Cells

Fully nonfused ring electron acceptors\n(FNEAs) have become\na research\nhotspot due to their simple skeletons and reduced synthetic complexity.\nIn this work, with the assistance of a noncovalent conformational\nlock, we synthesized four FNEAs based on an oligothiophene unit via\nsynergistically regulating the conjugation length and side-chain engineering,\nwhich could effectively tune the molecular conformations, absorption\nspectra, energy levels, intermolecular interactions, and miscibility\nwith polymer. The blend film PBDB-T:<b>4TO</b>-<i>in</i> forms clear bicontinuous interpenetrating networks and more clear\nphase separation feature due to the balance between crystallization\nand miscibility. Hence, PBDB-T:<b>4TO</b>-<i>in</i> devices achieved the highest PCE of 10.38%, while an enhanced power\nconversion efficiency of 11.63% was obtained with the polymer donor\nreplaced by JD40. Overall, this work provides an effective route for\noligothiophene-based FNEA design through fine-tuning the molecular\nskeleton.