Researchers from multiple China-based institutions have reported a perovskite stabilization strategy. The study describes a 3D/3D bilayer structure that combines a formamidinium-based perovskite absorber with an ultrathin ~5 nm CsPbI₃ capping layer deposited through vapor-phase co-evaporation. Structural analysis showed that lattice matching at the interface stabilized the photoactive cubic phase under ambient conditions. The inorganic capping layer reduced interfacial strain, suppressed phase transitions during aging, and limited ion migration under heat and illumination. In inverted device architectures, certified power conversion efficiency exceeded 27% for small-area cells, while larger-area devices achieved efficiencies close to 25%. Operational stability testing showed that the devices retained over 94% of their initial performance after more than 1,100 hours of continuous operation.