Reactive reconstruction and embedded passivation of heterointerfaces for intrinsically stable perovskite photovoltaics

Heterointerface degradation under operational stress represents a critical limitation to perovskite solar cell longevity. Here, we demonstrate contrasting aging behaviors between bulky anionic and cationic passivators at heterointerfaces, wherein anionic species induce lattice expansion under thermal stress. To address the thermal instability of conventional passivators, we synthesized cesium pyridine-3-carboxylate, which triggers reactive surface reconstruction, suppresses ion migration, and enhances interfacial charge transfer. Devices using this passivation strategy achieved certified power conversion efficiencies of 27.28% with exceptional operational stability. Unencapsulated devices retained 87% of their initial efficiency after 4092 hours of maximum power point tracking under the ISOS-L-1 protocol, while encapsulated devices maintained 80% of their initial efficiency after 3566 hours at 85°C under the ISOS-L-2 protocol. These findings establish rational design principles for stabilizing perovskite heterointerfaces and advancing device durability.