Learning from oxide perovskites for defect engineering in halide perovskite photovoltaics

The exceptional functional diversity of perovskites arises from a flexible octahedral architecture that tolerates chemical substitution, lattice distortion, nonstoichiometry, and structural imperfections. In oxide perovskites, this flexibility has been used to engineer oxygen vacancies, cation valence states, and extended structural defects, converting local imperfections into controllable pathways for ion transport, surface reactivity, symmetry breaking, and charge flow. Halide perovskites inherit related structural adaptability, but their soft metal-halide lattices make defect evolution a major challenge for device stability. This perspective proposes that the value of the oxide–halide comparison lies not in directly transferring oxide defect chemistry to halides, but in using oxide perovskites as a structural reference for linking lattice distortion, defect formation, ion motion, chemical activity, and phase evolution. More broadly, this comparison motivates defect engineering as a route to control how defects form, migrate, react, order, and transform, thereby improving the stability and functionality of halide perovskite optoelectronic devices.