Polarization Properties Orientation Coupling Regulates Molecular Packing and Device Performance Beyond Dipole Moment Strength in Organic Solar Cells

ABSTRACT Strong interactions between large dipole moment additives and host materials have been widely used to modulate molecular packing in organic solar cells (OSCs), while most studies focuses on dipole moment magnitude instead of the polarization properties orientation. Here, we challenge this oversimplified view by demonstrating that the polarization properties orientation—determined by both dipole orientation and polarizability anisotropy, rather than dipole magnitude alone – is the important factor. To quantify this, we introduce the “polarization properties orientation coupling degree” ( P ), which quantifies the matching of dipole orientation and polarizability distribution between additives and acceptors. Employing 1,4‐diiodobenzene (DIB) and 1,3,5‐triiodobenzene (TIB) as additives in the PM6:Y6 system with identical dipole moment magnitude but different orientation, we find that TIB exhibits a much higher p value (1.455 vs. 0.191), resulting in stronger intermolecular interactions. Consequently, TIB induces the formation of S‐type and S′‐type dimers of Y6, which optimizes exciton and charge transport behavior, boosting the performance from 17.53% to 18.08%. Furthermore, this principle is validated in high‐performance systems of PM6:L8‐BO (19.33%) and PM6:BTP‐eC9 (19.23%), and shows significant advantages in large‐area fabrication and reproducibility. This study highlights the significant role of polarization properties orientation, offering rational design strategy for high‐performance OSCs.