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 cm2) and mini-module (19.44 cm2), 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.