Interfacial physics and electrostatic loss engineering in bandgap-engineered BaZrS3 chalcogenide solar cells: insights from numerical simulations

We present a comprehensive SCAPS-1D study of BaZrS₃-based chalcogenide-perovskite photovoltaics, combining bandgap engineering, parasitic-resistance analysis, ion-migration modelling, and tandem-cell design. By employing site-specific alloying strategies, the native bandgap of 1.71 eV was successfully reduced to 1.48 eV in Ba(Zr,Sn)S₃, 1.35 eV in BaZr(S,Se)₃, and 1.26 eV in (Ba,Ca)ZrS₃—effectively extending the absorption edge to 983 nm in the Ca-alloyed variant. Device-level simulations identified parasitic resistances as key loss mechanisms, with series resistance reducing the fill factor by up to 15%, and low shunt resistance causing open-circuit voltage drops of 50–100 mV. Pronounced J–V hysteresis was reproduced via fixed interfacial ionic charge modelling in SCAPS-1D, with forward scan PCE of 18.36% in pristine BaZrS₃ dropping to 3.70% in the reverse scan. Additionally, two-terminal tandem architectures integrating BaZrS₃ as the top cell with alloyed bottom cells demonstrated promising performance, with matched short-circuit current densities of 14.80, 10.08, and 13.72 mA/cm² for Ca-, Sn-, and Se-alloyed devices, respectively. Power conversion efficiencies of 28.4, 23.4, and 27.4 were achieved, affirming the potential of bandgap engineering, interface control, and spectral filtering to drive BaZrS₃ photovoltaics toward their theoretical performance limits.