Surface passivation has been widely employed to suppress non-radiative charge recombination and prevent interfacial charge accumulation in perovskite photovoltaics. In this report, carbazole modified with ammonium iodide connected via alkyl chains of different lengths (i.e., ethyl, butyl, and hexyl chains) is used to form passivation layers on formamidinium lead triiodide FAPbI3-based perovskite films to improve operational stability. Owing to the strong hydrophobicity of the carbazole moiety, it is observed that the perovskite films with a carbazole passivation layer retain their initial properties even after direct contact with a water droplet for 100 s. In addition, carbazole treatment reduces the rate of trap-assisted recombination at the surface and grain boundaries of the perovskite layer. Furthermore, it accelerates interfacial hole transfer from the perovskite to the charge transport layer. As a result, devices treated with carbazole hexylammonium iodide achieve a power conversion efficiency (PCE) of up to 24.3% during quasi-steady-state (QSS) measurements with extraordinary long-term operational stability under conditions of the ISOS-L-1 protocol, maintaining 95% of their initial efficiency after 1000 h.|Surface passivation reduces non-radiative charge recombination and interfacial charge accumulation in perovskite photovoltaics. Carbazole, functionalized with ammonium iodide and alkyl chains, forms hydrophobic passivation layers on FAPbI3 perovskite films, improving stability and efficiency. This approach minimizes trap-assisted recombination and enhances hole transfer, achieving 24.8% PCE and maintaining 95% of its initial efficiency after 1000 h under the ISOS-L1 protocol. image