Chemical bond-dependent degradation behavior in perovskites

The commercial development of halide perovskites is fundamentally hindered by intrinsic stability. Numerous efforts have been made to improve the stability; however, the role of different chemical bonds in governing their degradation remains poorly understood. In particular, the relative stability and failure thresholds of different chemical bonds and cation–lattice coulombic interactions between the [PbI₆]⁴⁻ octahedral framework and A-site cations (A⁺–BX₆⁴⁻ coulombic interactions) within perovskites under various aging environments have yet to be systematically quantified or elucidated. Here, the bond-dependent degradation of formamidinium lead iodide (FAPbI₃) materials is elucidated under LED illumination, UV radiation and thermal stress. Comprehensive in situ and ex situ characterization studies reveal that the perovskite degradation initiates from the breaking of lead–halide bonds and the disruption of A⁺–BX₆⁴⁻ coulombic interactions, which serve as the primary degradation sites and ultimately limit the intrinsic stability of the lattice. In contrast, the covalent bonds within A-site cations remain comparatively stable against these stress-induced degradations. Based on these insights, an intrinsic bond-engineering strategy through B-site doping is developed to strengthen the inorganic framework and suppress the perovskite degradation. The resultant B site-doped FAPbI₃ single crystals exhibit superior structural stability under environmental stress. This research provides a clearer and more systematic elucidation of perovskite degradation pathways and kinetic behavior from a novel perspective of bond stability, offering a rational framework for designing intrinsically stable perovskite optoelectronic materials.