Mitigating phosphonic acid-perovskite interfacial degradation via molecular engineering for ultra-stable solar cells

• A novel triphenylamine-based phosphonic acid (1PA-TPD) enables robust covalent anchoring to ITO, overcoming the weak hydrogen bonding of conventional PA-SAMs. • The optimized mixed SAM system (60 wt% 1PA-TPD + 40 wt% EtCz3EPA) effectively suppresses interfacial degradation between PA-SAMs and perovskites. • The molecular engineering strategy simultaneously enhances substrate binding, inhibits interfacial reactions, improves crystallinity, and passivates defects. • This approach paves the way for ultra-stable perovskite solar cells meeting stringent operational standards.