Chiral Steric Effect for Improved Phase Transition and Exciton Dynamics in Efficient and Stable All‐Polymer Solar Cells

Abstract Chiral materials exhibit distinctive properties that improve the performance of organic solar cells (OSCs). In this study, chiral PM6 is integrated into PM6:PY‐IT blends to fabricate chiral quasi‐binary OSCs (cOSCs). The produced devices displayed an increased short‐circuit current and fill factor, achieving a peak efficiency of 16.60% compared to 15.96% for the standard PM6:PY‐IT cell. Additionally, the incorporation of chiral PM6 significantly enhanced the thermal stability, with the cOSCs retaining over 80% of their initial efficiency after 1000 h of operation. The steric effect of chiral PM6 altered the molecular packing, thereby improving the overall crystallinity. The optimized nanoscale domain morphology resulted in a more effective blend film, leading to superior device performance. Moreover, the chirality‐induced orbital angular momentum increased the ratio of triplet states, which is a key factor for increasing the photocurrent in OSCs. The delocalization of electron wavefunctions is driven by chiral steric effects, and it diminished the Coulomb attraction between the interfacial electron–hole pairs, which enhanced the efficient charge generation. This study provides valuable insights into the role of chirality in optimizing both the performance and stability of OSCs.