Optimizing Aggregation of A‐D‐A‐Type Acceptors via an Organic‐Metal Complex for High‐Performance Organic Solar Cells

ABSTRACT Although M‐series small‐molecule acceptors (SMAs) with an A‐D‐A‐type architecture offer lower synthetic complexity than current state‐of‐the‐art counterparts, their relatively modest power conversion efficiencies (PCEs) have hindered their development in organic solar cells (OSCs). To further enhance the photovoltaic performance of M‐series acceptors, an accessible organic‐metal complex, Platinum(II) acetylacetonate (Pt(acac) 2 ), is introduced as a solid additive to manipulate the self‐assembly of the representative acceptor M36 toward an optimal blend morphology with the polymer donor PM6. The incorporation of Pt(acac) 2 optimizes the film‐formation process of M36, affording improved molecular ordering and increased J ‐aggregation, both of which benefit exciton diffusion and dissociation. The PM6:M36 active layer processed with Pt(acac) 2 generates a favorable microstructure featuring well‐defined phase separation and a gradient vertical composition distribution. These morphological features facilitate efficient charge transport and collection while suppressing charge recombination. Consequently, the resulting PM6:M36 devices achieve a PCE of up to 19.0% with excellent operational stability, representing the highest efficiency among reported A‐D‐A‐type SMA‐based OSCs. Notably, the general applicability of this Pt(acac) 2 additive strategy is further verified in Y‐series systems, delivering outstanding PCEs exceeding 20%. This work provides a facile strategy to boost OSC performance and highlights the great potential of M‐series acceptors for practical applications.