Fine-Tuning Intra/Inter-Molecular Interaction via Ternary Copolymerization Strategy to Obtain Efficient Polymer Donors

Incorporating a third component through ternary copolymerization strategy has proven to be a promising and effective approach for further improving the device performance of polymer donors. However, terpolymer donors typically exhibit negative effects on molecular stacking and weaken charge transport due to the irregular distribution of the polymer skeleton. Herein, two terpolymers PBBQ-5 (5% ff-Qx) and PBBQ-10 (10% ff-Qx) are developed by introducing the difluoro-2-(3-hexyldecyloxy) quinoxaline (ff-Qx) to the main chain of PM6. The introduction of ff-Qx unit not only enables the terpolymers to possess N···S noncovalent intramolecular interactions that contribute to enlarge molecular planarity and enhance intramolecular interaction but also can fine-tuning electrostatic potential (ESP) values of the related polymers, thereby regulate intermolecular interactions with acceptor by electrostatic force. After blending with L8-BO, the PBBQ-5:L8-BO-based blend film exhibits appreciated miscibility, desirable phase separation sizes, and more ordered molecular packing than the analogs. Consequently, an impressive power conversion efficiency (PCE) as high as 19.54% is realized in PBBQ-5-based devices, which set a new record for Qx-based polymer solar cells. The work emphasizes the drawbacks of terpolymers and provides a new pathway for developing high-performance polymer donors by optimizing intra/inter-molecular interaction.