Numerical Modeling and Performance Optimization of an FTO/SnO ₂ /Cs ₂ AgBiBr ₆ /NiO/Pt Double Perovskite Solar Cell Using SCAPS‐1D

ABSTRACT Cs 2 AgBiBr 6 is a lead‐free double perovskite material with a 3D crystal structure, characterized by a long carrier lifetime, low effective mass, excellent thermal stability, and minimal toxicity. Despite these advantages, Cs 2 AgBiBr 6 ‐based solar cells still face significant challenges, primarily due to their wide indirect bandgap, which limits power conversion efficiency. In this study, the performance of double perovskite solar cells (DPSCs) based on a Cs 2 AgBiBr 6 absorber was systematically investigated using the 1D Solar Cell Capacitance Simulator (SCAPS‐1D). Tin(IV) oxide (SnO 2 ) and nickel oxide (NiO) were employed as the electron transport layer (ETL) and hole transport layer (HTL), respectively. The effects of key device parameters including absorber layer thickness, defect density, doping concentration, operating temperature, and parasitic resistances were thoroughly analyzed. After optimization, the proposed device achieved excellent photovoltaic performance, with a power conversion efficiency (PCE) of 23.29%, a short‐circuit current density (Jsc) of 22.03 mA/cm 2 , a fill factor (FF) of 86.31%, and an open‐circuit voltage (Voc) of 1.23 V. These results provide valuable insights and suggest promising strategies for the development of efficient, environmentally friendly, and stable Cs 2 AgBiBr 6 ‐based perovskite solar cells.