Non‐covalent Intramolecular Interactions Induced High‐Performance Terpolymer Donors

Abstract Ternary polymerization are demonstrated as a feasible and successful method of optimizing absorption, energy level, and crystallinity by maintaining the excellent properties of a polymer matrix. However, the third unit inevitably interrupts the periodic sequence distribution of the ordering packing of conjugated backbones, and thus balancing the trade‐off between the advantages of the third component and the disruption caused by the nonperiodic sequence distribution remains a great challenge. Herein, two terpolymer donors L1 and L2 are developed by introducing diethyl‐5,5′“‐dibromo‐4,4′”‐bis(2‐ethylhexyl)‐[2,2′:5′,2′'‐terthiophene]‐3′,4′‐dicarboxylate (DDT) unit as the third component. Owing to the electron‐deficient ability and S···O non‐covalent intramolecular interactions of DDT, terpolymers L1 and L2 displays deeper energy levels, enhanced molecular rigidity, and planarity than PM6. After blending with L8‐BO, the L1‐based polymer solar cells exhibit well miscibility with L8‐BO, leading to a more well‐defined nanofibrous morphology, face‐on orientation, and a slight energy loss in the blend films. As a result, the optimized L1:L8‐BO‐based device achieves a record power conversion efficiency (PCE) as high as 18.75%. This work provides a feasible strategy to develop high‐performance polymer donors via utilizing S···O non‐covalent intramolecular interactions to improve the planarity of polymer donors.