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Abstract Central unit engineering in non‐fullerene acceptors (NFAs) plays a pivotal role in regulating molecular stacking, and further greatly affects the power conversion efficiency (PCE) of organic solar cells (OSCs). A high‐efficiency NFA of CS4 is developed in this work, with a sulfur‐bridged and chlorinated phenyl group on the central unit as a molecular stacking regulator. Detailed analyses reveal that CS4 exhibits tighter molecular packing, more balanced charge mobility, superior phase separation, and reduced energetic disorder compared to its counterpart, CH3. As a result, a notable efficiency of 18.57% is observed in the D18:CS4‐based binary OSC, much higher than 17.81% for that of CH3. Moreover, D18:CS4:BTP‐eC9‐based ternary device renders a champion PCE of 20.16%. D18:CS4 and ternary devices exhibit enhanced stability over D18:CH3. Under the pressure of 65 °C, T 80 lifetimes are 1200 h for D18:CS4 and 2500 h for D18:CS4:BTP‐eC9‐based ternary device. Under continuous light illumination, T 80 reaches 550 and 710 h, respectively. This study demonstrates an effective strategy to boost high‐performance OSCs through precise design of central molecular stacking regulator.
Liu et al. (Mon,) studied this question.