Chem. Sci., 2026, Advance Article DOI: 10.1039/D6SC03324E, Review Article Liangchen Qian, Bohong Chang, Danpeng Gao, Bo Li, Zonglong Zhu This review summarizes how ion migration, interfacial reactions, and stress/strain govern degradation in single- and multi-junction perovskite solar cells. Chemistry-to-function strategies for stable interfaces are discussed.