<p>Inorganic–organic hybrid lead halide perovskites are promising materials for photovoltaic applications but face challenges related to toxicity and stability. To address these issues, research has focused on “perovskite-inspired” alternatives that retain the advantages of lead-based perovskites. Bismuth (Bi³⁺)-based materials, with electronic structures resembling lead (Pb²⁺), have emerged as potential light absorbers, despite suboptimal efficiencies. This study explores CsBiSI₂ as an absorber layer in quaternary chalcohalide perovskite solar cells using SCAPS-1D simulations. Results highlight the critical influence of donor doping density on efficiency and impedance variations, surpassing the impact of acceptor density. Interface defect density significantly affects charge carrier dynamics, particularly at the electron transport layer and perovskite interface. Electrical and impedance analyses underscore these dynamics, offering insights into optimizing material interfaces for stability and efficiency. This research advances the development of environmentally friendly, stable, and efficient inorganic solar cells, paving the way for improved photovoltaic technologies.</p> Graphical Abstract <p></p>