A Chlorinated Donor Polymer Achieving High-Performance Organic Solar Cells with a Wide Range of Polymer Molecular Weight

In the field of non-fullerene organic solar cells (OSCs), compared to the rapid development of non-fullerene acceptors, the progress of high-performance donor polymers is relatively slow. The property and performance of donor polymers in OSCs are often sensitive to the molecular weight of the polymers. In this study, a chlorinated donor polymer named D18-Cl is reported, which can achieve high performance with a wide range of polymer molecular weight. The devices based on D18-Cl show a higher open-circuit voltage (V_OC) due to the slightly deeper energy levels and an outstanding short-circuit current density (J_SC) owing to the appropriate long periods of blend films and less ([6,6]-phenyl-C71-butyric acid methyl ester) (PC₇₁BM) in mixed domains, leading to the higher efficiency of 17.97% than those of the D18-based devices (17.21%). Meanwhile, D18-Cl can achieve high efficiencies (17.30–17.97%) when its number-averaged molecular weight (M_n) is ranged from 45 to 72 kDa. In contrast, the D18-based devices only exhibit relatively high efficiencies in a narrow M_n range of ≈70 kDa. Such property and performance make D18-Cl a promising donor polymer for scale-up and low-cost production.