Multiscale Perspectives on Perovskite Instability: From Atomistic Deformation to Device Degradation in Perovskite Solar Cells

ABSTRACT This review elucidates where the operational instability of perovskite‐based optoelectronic devices originates from by comprehensively exploring degradation phenomena from atomistic interactions to device scale. At thermodynamic equilibrium, the intrinsic stability of halide perovskites is reasonably good when considering the balance of intramolecular Asite covalent bonds, intermolecular A–X hydrogen bonds, and mixed ionic–covalent B–X bonding. Under operation, however, photoexcited or injected carriers become localized via trapping at surface and ionic defects and/or polaron formation in the soft Pb–halide framework, which induce Coulombic force to distort the crystal lattice and change atom‐to‐atom distances. Such effects lower ion migration barriers, enhance lattice distortion, and accelerate atmospheric reactions with ambient species, leading to quick degradation of perovskite crystals. In terms of device‐level stability, holerich conditions and interfacial charge accumulation in heterostructured architectures are identified as particularly detrimental, directly linking carrier localization to device‐level degradation. Based on these insights, we discuss composition engineering toward favorable large‐polaron formation, defect passivation to suppress trap‐assisted localization, and interfacial engineering within the heterostructured device. At the end, we propose advanced operation protocols that effectively relieve charge accumulation as key routes to realize durable perovskite optoelectronic devices.