Cyclically Dynamic Defect Management Enables High‐efficiency Sn─Pb Perovskite Photovoltaics with Enhanced Photostability and Fatigue Resistance

Narrow-bandgap mixed Sn-Pb perovskite solar cells (PSCs) have showcased great promise to approach the Shockley-Queisser limit. Despite continuously proven elevated power conversion efficiencies (PCEs), the practical application and commercial use of Sn-Pb PSCs are hindered by poor photostability and anti-fatigue performance. These issues arise from multiple intrinsic imperfections formed during crystallization and light-triggered defects generated during device operation under intermittent illumination. Herein, we introduced a novel "dynamic defect management" (DDM) strategy that mitigated photodegradation of Sn-Pb perovskites and significantly enhanced the device lifespan. The strong coordination between metallocene intercalation and metal cations (Pb²⁺/Sn²⁺) within the perovskite lattice effectively passivated the crystallographic defects, reduced the defect densities by 34.5% and suppressed the non-radiative recombination. Furthermore, the metallocene and corresponding cation could function as a redox pair, offering a dynamic and continuous healing mechanism to restore the light-induced defects in a cyclical manner. Additionally, the metallocene interlayer itself acted as a shield against the ultraviolet radiation during the light aging process. Consequently, we achieved decent PCEs up to 23.59% for the mixed Sn-Pb PSCs modified with DDM strategy, 14.7% higher than that of the reference devices, accompanied by enhanced photostability which witnessed a 7-fold enhancement compared to the pristine device under MPP operation tracking and remarkable anti-fatigue performance, retaining 83% of the original PCE after 22 accelerated fatigue test cycles (12/12 h UV light/dark cycle).