Efficient and Stable Tin Perovskite Solar Cells by Pyridine‐Functionalized Fullerene with Reduced Interfacial Energy Loss

Abstract In tin perovskite solar cells (PSCs), fullerene (C 60 ) and fullerene derivative [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) are commonly utilized electron transport materials. However, the energetic disorder, inadequate passivation, and energy level mismatch of C 60 and PCBM limit the improvement of power conversion efficiency (PCE) and lifespan of tin PSCs. In this work, a multifunctional interface manipulation strategy is developed by introducing a pyridine‐functionalized fullerene derivative, fullerene‐n‐butyl‐pyridine (C 60 ‐BPy), into the interface between the tin perovskite and the electron transport layer (ETL) to improve the photovoltaic performance and stability of tin PSCs. The C 60 ‐BPy can strongly anchor on the perovskite surface via coordination interactions between the pyridine moiety and the Sn 2+ ion, which not only reinforces the passivation of the trap‐state within the tin perovskite film, but also regulates the interface energy level alignment to reduce non‐radiative recombination. Moreover, the improved interface binding and carrier transport properties of C 60 ‐BPy contribute to superior device stability. The resulting devices have achieved the highest PCE of 14.14% with negligible hysteresis, and are maintained over 95% of their initial PCE under continuous one‐sun illumination for 1000 h.