Achieving high efficiency and well-kept ductility in ternary all-polymer organic photovoltaic blends thanks to two well miscible donors

All-polymer solar cells (APSCs) are one of the most promising types of application-oriented photovoltaic technologies because they are operationally and mechanically stable; however, their low power conversion efficiency (PCE) restricts the core competitiveness against other types of solar cells. Besides, poor insight of mechanical performance, such as ductility, has been revealed for cutting-edge APSCs. Herein, we chose two well miscible polymer donors, PM6 and J71, and achieved a PCE of 16.52% for APSCs in a ternary blend with PY-IT and 15.74% for air-processed devices. The improvement is enabled by effective energy transfer, tuned crystallinity, and improved phase separation, which resulted in faster charge transfer and more balanced charge transport, suppressed exciton recombination, and more efficient charge extraction. Furthermore, the good miscibility between two donors enabled the target to have well-maintained film morphology without damaging the initial nanoscale network, bringing comparable film ductility. Last, the inner structure-property relationship of photovoltaic and morphological parameters, and film ductility was illustrated by a correlation study.