A universal strategy via polymerizing non-fullerene small molecule acceptors enables efficient all-polymer solar cells with >1 year excellent thermal stability

Abstract Record-holding polymer solar cells (PSCs) composed of polymer donors and Y-series non-fullerene small molecule acceptors have reached the efficiency threshold for commercialization, but this type of PSCs is often difficult to work continuously and stably at high temperatures close to 100 °C, limiting its outdoor application. Therefore, in this work, we tried to boost the thermal stability of PSCs based on Y-series acceptors Y5-F-Br by polymerizing Y5-F-Br obtaining PFA1, and establish a precise correlation between the molecular structure and device thermal stability. Consequently, the excellent film stability based on long-chain acceptor PFA1 effectively suppressed the thermally induced phase separation of PTzBI-oF:PFA1 blend film at high temperatures, resulting in over 98% thermal stability at 100 °C for over 1 year in the nitrogen-filled glovebox. Furthermore, the use of long-chain acceptor for improving thermal stability was also confirmed in other two commonly used PSCs, suggesting that polymerizing non-fullerene small molecule acceptors is an effective and universal strategy to boost the thermal stability of PSCs.