This numerical study addresses the challenge of transmission losses in BaZrS3-based chalcogenide perovskite solar cells by implementing targeted bandgap engineering to optimize optoelectronic performance. Specifically, site-specific alloying at the A-, B-, and X-sites—yielding (Ba0.98Ca0.02)ZrS3 ( \({E}_{g}=1.26\) eV), Ba(Zr0.875Sn0.125)S3 ( \({E}_{g}=1.48\) eV), and BaZr(S0.80Se0.20)3 ( \({E}_{g}=1.35\) eV)—reduced the native bandgap of 1.71 eV and delivered power conversion efficiencies of 23.47%, 22.90%, and 23.94%, respectively (compared to 18.43% for pristine BaZrS3), owing to enhanced light absorption and carrier collection. Numerical simulations then probed device behaviour over a temperature range of 300 to 400 K, revealing that increasing temperature led to an ∼ 8% decrease in open-circuit voltage—attributable to elevated intrinsic carrier concentrations and recombination rates—while short-circuit current density increased by ∼ 5% due to thermally-assisted carrier generation. Impedance spectroscopy (Nyquist and Bode analyses) indicated that transport resistance decreased by ∼ 15% and relaxation time shortened by ∼ 20% at 400 K, reflecting improved charge transport dynamics; concurrently, capacitance–voltage and conductance-voltage profiling confirmed temperature-induced modifications in depletion width and carrier mobility. These findings elucidate the interplay between bandgap-engineered material properties and thermal effects on charge-carrier dynamics and recombination mechanisms, offering critical insights for designing thermally stable, high-performance BaZrS3-derived photovoltaic technologies suitable for diverse environmental conditions.
