Noncovalent Interaction‐Engineered Ordered Self‐Assembled Molecules Enable Efficient and Stable Organic Photovoltaics

ABSTRACT Highly ordered and uniform self‐assembled molecules (SAMs) play an essential role in advancing organic solar cells (OSCs). Here we report a non‐covalent‐interaction‐mediated molecular engineering strategy in which 2,5‐dibromothiophene‐3,4‐dicarboxylic acid (DTDA) is employed to establish specific S···N non‐covalent interactions within carbazole phosphonate‐based SAMs. This strategy effectively regulates intermolecular packing and suppresses agglomeration‐induced defects, yielding highly uniform and structurally ordered interfacial film. The optimized SAMs serve as an effective interfacial template that directs the crystallization kinetics and molecular ordering of the overlying active layer, thereby promoting a favorable vertical phase separation. The resulting interfacial and bulk structural improvements synergistically enhance charge generation, transport, and collection. As a result, single‐junction OSCs achieve a power conversion efficiency (PCE) of 20.08% with an exceptionally high fill factor of 80.01%. In addition to efficiency enhancement, the devices exhibit improved operational photostability, retaining 90% of their initial PCE after 880 h of continuous illumination under maximum power point tracking. Importantly, the generality of this interfacial design is demonstrated by its successful application in perovskite‐organic tandem solar cells (TSCs), delivering a champion PCE of 26.42%.