Enhancing Photovoltaic Performances of Naphthalene‐Based Unfused‐Ring Electron Acceptors upon Regioisomerization.

Isomeric effects play a crucial role in regulating electronic properties, molecular packing, and device performance of organic semiconductors. Herein, a series of unfused‐ring electron acceptor (UREA) regioisomers (NOF‐1, NOF‐2, and NOF‐3), which are constructed using 2,6‐α‐, 1,5‐β‐, and 3,7‐β‐type naphthalene cores, are successfully synthesized and characterized. The regioisomeric effects on geometries, photophysics, electrical properties, molecular packing behaviors, charge transport properties, blend film morphologies, and photovoltaic performance are systematically studied. As a result, the PBDB‐T:NOF‐3‐based device delivers a power conversion efficiency (PCE) of 11.58% due to its more balanced charge mobility, efficient exciton dissociation, less charge recombination, and favorable film morphology. These findings encourage further attention to the regioisomeric effects to design high‐performance UREAs. [ABSTRACT FROM AUTHOR]