Donor–Acceptor Interaction Optimized Film‐Forming Processes Lead to Efficient Organic Solar Cells and Modules Fabricated with Non‐Halogenated Solvents

While the transition from halogenated to eco‐friendly processing solvents is vital for the industrialization of organic solar cells (OSCs), obtaining ideal morphology of active layer during green fabrication of the device remains a challenge. To address this issue, the famous polymer donor of PM6 is chemically modified through the introduction of 20% chlorinated dithiazole (Tz2Cl) segment into the mainchain. It is found that, the obtained terpolymer, PM6‐ClTz20, shows the improved solubility in the non‐halogenated solvent of m ‐xylene. More importantly, Tz2Cl units induce the enlarged electrostatic potential difference between PM6‐ClTz20 and the acceptor BTP‐eC9, giving donor–acceptor electrostatic attraction. This prolongs the nucleation and crystal growth time of donor and acceptor in m ‐xylene solution, endowing the blend film with fine phase‐separated domains and bigger crystal size. Consequently, the PM6‐ClTz20:BTP‐eC9 binary system yields outstanding power conversion efficiencies (PCEs) of 19.04% and 16.71% for the small‐area device (0.0476 cm 2 ) and mini‐module (19.44 cm 2 ), respectively. This work clarifies the key role of donor–acceptor interaction in regulating the film‐forming process and optimizing blend morphology, providing a feasible route to sustainable and scalable OSCs.