Developing a high-performance donor polymer is critical for achieving efficient non-fullerene organic solar cells (OSCs). Currently, most high-efficiency OSCs are based on a donor polymer named PM6, unfortunately, whose performance is highly sensitive to its molecular weight and thus has significant batch-to-batch variations. Here we report a donor polymer (named PM1) based on a random ternary polymerization strategy that enables highly efficient non-fullerene OSCs with efficiencies reaching 17.6%. Importantly, the PM1 polymer exhibits excellent batch-to-batch reproducibility. By including 20% of a weak electron-withdrawing thiophene-thiazolothiazole (TTz) into the PM6 polymer backbone, the resulting polymer (PM1) can maintain the positive effects (such as downshifted energy level and reduced miscibility) while minimize the negative ones (including reduced temperature-dependent aggregation property). With higher performance and greater synthesis reproducibility, the PM1 polymer has the promise to become the work-horse material for the non-fullerene OSC community.

Here we demonstrate efficient all-polymer solar cells (all-PSCs) based on a polymer acceptor named PFBDT-IDTIC. By combining PFBDT-IDTIC with a fluorinated donor polymer (PM6), a high power conversion efficiency of 10.3% can be achieved, which is the highest value reported to date for single-junction all-PSCs. This performance can be attributed to its good absorption property (absorption coefficient: 2.74 × 10 5 cm −1 ) and high electron mobility of PFBDT-IDTIC. It is also found that the choice of donor polymer has major impacts on the performance of the cell. By replacing PBDB-T with its fluorinated counterpart, PM6, the V OC , J SC , and FF of the devices were all improved, which can be attributed to the deeper HOMO level of PM6 and more crystalline and pure domains of the active layer blends. Our study provides a promising polymer acceptor for all-PSCs and also shows that selecting a matching donor polymer is important in achieving the optimal all-PSC performance.