▎ 摘　　要

Recent advances in flexible perovskite solar cells (PSCs) have attracted considerable attention owing to their great potential for bendable and wearable electronic devices. In particular, developing high-quality low-temperature processed electron transport layers (ETLs) plays a pivotal role in realizing highly efficient flexible PSCs. Herein, we develop a facile strategy to fabricate graphene quantum dot/SnO2 composites (G@SnO2) as effective ETLs. Systematic optimization and investigation reveal that SnO2 blended with graphene quantum dots with ca. 5 nm diameter (G5@SnO2) has higher electron mobility, better film coverage and better energy level alignment compared to pristine SnO2, leading to promoted charge transfer and suppressed charge recombination. PSCs based on G5@SnO2 demonstrate superior photovoltaic performance with a champion power conversion efficiency (PCE) of 19.6% and average PCE of 19.0%. Amazingly, the G5@SnO2 based flexible PSCs obtain a best PCE and stabilized PCE of 17.7% and 17.2%, respectively, comparable to the highest PCEs recorded for flexible devices. Moreover, our flexible PSCs demonstrate outstanding mechanical durability, retaining over 91% of the initial PCE value after 500 bending cycles with a bending radius of 7 mm.