From device physics to system performance: multiscale evaluation of Ba₂AgBiBr₆ lead-free perovskite solar cells

Lead-free double-perovskite photovoltaic devices are gaining traction as environmentally preferable substitutes for lead-containing halide solar cells. This work conducts an extensive numerical assessment of the barium-based double-perovskite Ba₂AgBiBr₆ using SCAPS-1D, aiming to refine the device stack and elevate photovoltaic parameters. Six candidate electron transport layers (ETLs), such as CdS, SnS₂, WS₂, PCBM, TiO₂, and C₆₀, were systematically paired with nine candidate hole transport layers (HTLs), such as MoTe₂, CuI, Cu₂Te, MoS₂, CBTS, CFTS, Spiro-MeOTAD, PEDOT:PSS, and P₃HT, producing 54 distinct device permutations for parametric screening. Additionally, three front metal contacts (Al, Ag, Cu) and nine back metal contacts (Cu, Fe, C, Au, W, Ni, Pd, Pt, Se) were examined to evaluate contact influence on performance. The best-performing solar cell used CdS as ETL and MoTe₂ as HTL, achieving a power conversion efficiency (PCE) of 24.42%, with open-circuit voltage (V _OC) = 0.6 V, short-circuit current density (J _SC) = 49.58 mA cm^-2, and fill factor (FF) = 82%. Device-level results were ported into PVsyst to assess module behavior under realistic operating conditions. For a 72-cell module layout, the CdS-based module produced a P _MPP of 509.85 W among the tested ETL variants. The joint SCAPS-1D with PVsyst methodology thus provides a pragmatic route for translating cell-scale optimizations into module-scale energy predictions.