Abstract: As environmentally friendly compounds, lead-free perovskites have gained widespread application in the fabrication of solar cells in recent years. Among these, rudorffites such as AgBiI₄ are considered as promising candidates owing to their favorable band structure and exceptional stability. However, the formation of Ag vacancies during the synthetic process poses a significant challenge, severely hindering carrier transport properties. To address this issue, we propose an Ag management strategy utilizing aliphatic ammonium, which serves multiple purposes: it enhances the solubility of AgI in the precursor solution, mitigates phase separation caused by stoichiometric mismatches during AgBiI₄ film formation, and effectively passivates Ag defects. The butylamine hydroiodide modified AgBiI₄ solar cells achieved a champion power conversion efficiency of 1.97%, representing a 26% enhancement over the control device.