Linker Group Fluorination Boosts Photovoltaic Performance of Branch‐Connected Dimerized Acceptors

Abstract Branch‐connected dimerized acceptors can take full advantages of four end units in enhancing molecular packing comparing to that of terminal‐connected ones, thus potentially reaching the best balance between stability and power conversion efficiency (PCE) of organic solar cells (OSCs). Herein, two branch‐connected dimerized acceptors, namely D1 and D2, are developed by employing bithiophene and difluorinated bithiophene as linker groups, respectively. Induced by the fluorine atoms on linker group, D2 affords a larger molar extinction coefficient, more importantly, the optimized nanoscale film morphology and superior charge transport behavior comparing to D1. Consequently, D2‐based binary OSCs render a good PCE of 16.66%, outperforming that of 15.08% for D1‐based ones. This work highlights the great significance of linker group screening in designing high‐performance branch‐connected dimerized acceptors.