Exploring Lead‐Free <scp>Ca₃BiCl₃</scp>‐Based Perovskite Solar Cells: A Computational Comparison of Charge Transport Layers With <scp>DFT</scp> and <scp>SCAPS</scp>‐<scp>1D</scp>

Calcium bismuth chloride (Ca₃BiCl₃), an accessible and nontoxic chemical, exhibits considerable promise as a photovoltaic absorber material. This research investigates the structural, optical, and electrical properties of Ca₃BiCl₃ utilizing the CASTEP module in the context of density functional theory (DFT). To enhance the photovoltaic efficacy of Ca₃BiCl₃-based solar cells (SCs), two hole transport layers (HTLs), Spiro-OMeTAD and P3HT, and two electron transport layers (ETLs), C₆₀ and WS₂, were investigated. The Solar Cell Capacitance Simulator (SCAPS-1D) was utilized to undertake a comprehensive numerical analysis of Ca₃BiCl₃ SCs, employing essential semiconductor equations such as Poisson's equation, the carrier continuity equations, and the drift-diffusion model. A comprehensive parameter analysis was performed, including factors such as layer thickness, doping density, temperature, carrier production and recombination rates, defect densities at the interfaces and the bulk material, quantum efficiency, and series vs. shunt resistance. After optimizing the ETL and HTL settings, a maximum power conversion efficiency (PCE) of 27.54% was attained using WS₂ as the ETL and P3HT as the HTL. This arrangement produced a short-circuit current density (J_SC) of 23.393 mA/cm², an open-circuit voltage (V_OC) of 1.313 V, and a fill factor (FF) of 89.64%. The results highlight the significant potential of Ca₃BiCl₃ as an effective absorber material, especially in conjunction with WS₂ and P3HT, for the progression of high-efficiency perovskite heterostructure SCs.