17.5% Efficiency of Polythiophene‐based Solar Cell Enabled by Trialkylsilyl‐thienothiophene‐grafted Acceptor

ABSTRACT Despite significant progress in the power conversion efficiency (PCE) of polythiophene‐based organic solar cells (PT‐OSCs), their suboptimal blend morphology remains challenging to overcome when paired with prevailing non‐fullerene acceptors (NFAs). Herein, a new trialkylsilyl‐thieothiophene grafted NFA, named Y‐TTsi, is proposed, featuring a distinctly twisted backbone conformation, a high dipole moment, and well‐defined “face‐on” packing. Leveraging the trialkylsilyl‐thienothiophene grafted pendant, Y‐TTsi was introduced into the classical PT‐OSCs system (PTVT‐T:Y6‐BO‐4Cl) as the third component to fine‐tune intermolecular interactions. It is found that synergetic yet opposite intermolecular interactions of Y‐TTsi with the PTVT‐T polymer donor and Y6‐BO‐4Cl acceptor effectively reassemble miscibility strength, molecular aggregation, and film crystallinity. Benefiting from the improved exciton dissociation and charge transfer, the resultant PTVT‐T:Y6‐BO‐4Cl: Y‐TTsi‐based ternary PT‐OSCs afford a decent PCE of 17.5% with a short‐circuit current density of 27.78 mA/cm 2 , open‐circuit voltage of 0.803 V, and fill factor of 0.786. More importantly, the incorporation of Y‐TTsi resulted in reduced energy loss in the resultant ternary device by simultaneously mitigating both radiative and non‐radiative recombination. This study highlights not only the newly designed trialkylsilyl‐thienothiophene grafted NFA but also its effects on refining intermolecular interactions in the PT‐OSCs system toward minimized energy loss and ideal blend morphology.