Coordination‐Induced Morphology Control With Non‐Volatile Ferric Acetylacetonate for Efficient Organic Solar Cells

The nanoscale morphology of the active layer, particularly the molecular packing distance and crystallinity of the donor and acceptor materials, is pivotal for the performance of organic solar cells (OSCs). Moving beyond conventional volatile additives, non‐volatile ferric acetylacetonate (Fe(acac) 3 ) is innovatively introduced as a coordination‐assisted morphology regulator in this work. It functions by coordinating‐induced molecular assembly rather than conventional electronic doping, enabling precise control over the bulk heterojunction morphology in OSCs. We systematically investigate the physicochemical mechanism by which Fe(acac) 3 modulates crystallization kinetics and final nanostructure through intermolecular interactions with the polymer donor. Comprehensive characterizations confirm that an optimal concentration of Fe(acac) 3 acts as a “molecular‐scale template” and “crystallization modulator” that successfully decreases the π–π stacking distance, enhances the crystal coherence length, and facilitates the formation of an ideal interpenetrating network. Consequently, champion devices achieve a power conversion efficiency (PCE) of 20.60% with increased short‐circuit current density ( J SC ) and fill factor (FF), significantly outperforming the control device. This work provides a novel, stable, and mechanistically insightful doping strategy for active layer morphology control and offers profound understanding of the role of metal complexes in organic semiconductor blends.