Ammonium Hexafluoroaluminate Mediated Charge Compensation in Nickel Oxide and Interface Regulation for Heat‐Resilient Perovskite Solar Cells ^†

Comprehensive Summary Thermal instability originating from the buried interface, particularly the conductivity‐stability paradox characteristic of nickel oxide hole transport layers, severely impedes the commercialization of inverted perovskite solar cells (PSCs). Herein, we introduce ammonium hexafluoroaluminate (AHA) as a multifunctional interfacial layer to reconcile this contradiction and regulate the buried perovskite interface. We elucidate a charge compensation mechanism wherein AlF 6 3– anions coordinate with surface Ni 2+ via F – ions while NH 4 + cations fill nickel vacancies. These processes collectively promote Ni 3+ generation, thereby enhancing conductivity without inducing parasitic reactions. Simultaneously, AHA modulates perovskite crystallization through Lewis acid‐base and hydrogen bonding interactions, yielding high‐quality films with mitigated strain and favorable energy alignment. Consequently, inverted PSCs incorporating AHA achieve a champion power conversion efficiency of 26.07%. Furthermore, the devices demonstrate exceptional thermal resilience by retaining 90.8% of their initial efficiency after 1100 h of aging at 85 °C under the ISOS‐D‐2I protocol.