Indium-Based Octahedra Coordinating Pb–I Termini for Stable Perovskites

Halide perovskite degradation initiates at surfaces/interfaces, where defect accumulation disrupts octahedral connectivity and triggers structural collapse. Herein, we design an indium-based octahedral motifs, i.e., (PMA)4InCl7 (PIC) (PMA=phenylmethylammonium) featuring disordered octahedra and (PMA)4NaInCl8 (PNIC) with ordered octahedral frameworks, as robust coordination agent to bind Pb-I termini at the surface/interface. Distinct from the isolated cluster of PIC, PNIC forms a coherent inorganic framework at Pb-I termini, enabling coherent interfacial coupling with the 3D perovskite via octahedral-level coupling between In(Na)-Cl and Pb-I units. This rigid octahedral coupling immobilizes formamidinium cations and Pb–I octahedra at the surface/interface, suppressing structural freedom. Moreover, this coupling facilitates the relaxation of interfacial structural imperfections while simultaneously establishing favorable band alignment, together governing enhanced carrier transport dynamics. As a result, the resulting perovskite solar cells deliver an efficiency of 27.29% (certified 26.84%), with the minimodules reaching 24% (certified 23.54%). Moreover, these devices demonstrate significant operational stability, retaining over 98% of their initial efficiency after 3,000 h of maximum power point tracking. Halide perovskites degrade at surfaces where defects break octahedral connectivity and destabilize the structure. Wen et al. design indium-based octahedral compounds that bind lead-iodide, forming rigid interfaces that enhance stability and carrier transport for efficient, durable solar cells.