Synergistic Control of Radiative Decay and Exciton Splitting Dynamics for Efficient Organic Solar Cells Processed by Non‐Halogenated Solvent

ABSTRACT The commercialization of organic solar cells (OSCs) is strongly essential by the use of non‐halogenated solvents, which unfortunately suffers from inferior photovoltaic performance. To raise the efficiency, expanding the donor/acceptor interfacial distance can elevate charge transfer (CT) state energy and enhance CT/local excitation (LE) hybridization to boost the radiative decay dynamics ( k r ) and further upgrade open‐circuit voltage ( V oc ). However, this morphological modulation inadvertently induces excessive phase separation, which impairs exciton dissociation and subsequently reduces short‐circuit current density ( J sc ). Herein, we rationally designed a novel trimer, T‐IOI, as the third component to tackle this circumstance, where the ameliorated miscibility with the acceptor phase can impede large crystalline aggregate clusters with the assist of steric hindrance effect. Moreover, its extended and folded configuration broadens donor/acceptor interfaces, which can elevate CT energy, strengthen CT/LE hybridization and further raise k r metric. Consequently, the photovoltaic performance of the corresponding small‐area (0.06 cm 2 ) device is significantly enhanced from 18.8% to 20.5% upon optimal incorporation ratio of T‐IOI. Furthermore, large‐area devices (1 cm 2 ) are successfully fabricated with a remarkable PCE of 19.0%, which not only surpasses that of the binary control device (15.6%) but also maintains excellent reproducibility alongside accelerated operational stability (T 80 : 830 h).