A Versatile Bridging Molecule Managed the Buried SnO₂/Perovskite Interface for Efficient and Stable Perovskite Solar Cells

Buried interface in perovskite solar cells (PSCs) is a critical determination for the performance and stability because it dominates the crystallization of the perovskite layer, non-radiative recombination, and ion migration at the interfaces. Herein, a novel versatile modifier, potassium sucrose octasulfate (K₈SOS) which is rich in sulfonic groups and potassium ions, is introduced for bridging the buried perovskite and SnO₂ interface, to improve the interfacial states and further the device performance. It is found that K₈SOS serves as a bridge that can not only passivate defects in perovskite and SnO₂ through multi-site strengthening chemical binding, thus effectively inhibiting non-radiation recombination and suppressing ion migration, but also can optimize the surface state of SnO₂ layer, improve the crystallization of perovskite absorber, thus ultimately achieving a gratifying efficiency of 25.32% with negligible hysteresis. What's more, the optimized device delivers admirable stability sustaining over 90% of initial power conversion efficiency after being aged under continuous 85 °C heating stress with 40 ± 5% RH humidity for ≈600 and ≈1200 h under continuous 1-sun illumination, respectively.