Synergistic Modulation via Linking Site Relocation and Fluorination for High‐Performance Organic Solar Cells †

Comprehensive Summary End group modification is an effective strategy to modulate the energy levels, molecular packing and intermolecular interactions of small molecule acceptors (SMAs) in organic solar cells (OSCs). However, conventional end group linking site in giant molecule acceptors (GMAs) based on SMA subunits often occupies halogen substitution sites of end group, limiting further modification of GMAs and the improvement of their power conversion efficiency (PCE). Here, we developed a serious of GMAs, G‐5H6H, G‐5F6H and G‐5F6F, by shifting the linking site to the 4‐position of the 1,1‐dicyanomethylene‐3‐indanone (IC) unit in the SMAs, enabling stepwise halogenation at the 5‐ and 6‐positions. Due to the di‐fluorination of inner IC end group, G‐5F6F shows enhanced planarity and intramolecular charge transfer effect, resulting in the red‐shifted absorption and highly ordered molecular packing. As a result, the OSCs based on D18:G‐5F6F achieve the highest PCE of 18.29%. Furthermore, incorporating G‐5F6F as the second acceptor into the D18:BTP‐eC9 based OSCs has resulted in a remarkable PCE of 19.52% and enhanced device stability. This work demonstrates a synergistic molecular design strategy integrating linking site relocation and fluorination for high‐performance OSCs based on GMAs.