Exploring elpasolite double perovskites Ba2XIO6 (X = Au and Ag) for non-toxic and stable photovoltaics: numerical optimization and device analysis

Abstract

This work presents a comprehensive numerical investigation of lead-free double perovskites Ba₂XIO₆ (X = Au and Ag) as promising absorber materials for stable, non-toxic photovoltaic devices. By employing one-dimensional device simulations, we first optimized key absorber parameters, including doping concentration and defect density, to maximize power conversion efficiency. Under standard AM 1.5G illumination and optimized absorber conditions, the simulated Ba₂AuIO₆ and Ba₂AgIO₆ devices achieved 14.14% and 11.23% efficiency, respectively. Temperature-dependent performance analysis revealed that both materials maintained operational stability up to 340 K, with negligible efficiency roll-off (<5%) owing to low intrinsic recombination rates. Equivalent-circuit modelling of series and shunt resistances quantified parasitic loss mechanisms, while voltage-profiling and Mott–Schottky analyses elucidated interfacial charge accumulation and built-in potential variations. Spectral response measurements indicated an extended absorption edge for Ba₂AuIO₆ (bandgap ≈ 2.00 eV) compared with Ba₂AgIO₆ (bandgap ≈ 2.26 eV), resulting in a 15% higher photogenerated current density. The lower bandgap of Ba₂AuIO₆ not only broadened its absorption into the red-near infrared region but also elevated its short-circuit current, thereby leading to superior efficiency. Collectively, these findings demonstrated that Ba₂AuIO₆ possessed favourable optoelectronic properties, thermal robustness, and minimal parasitic losses, outperforming its Ag-based analogue, underscoring the potential of elpasolite double perovskites in high-performance, eco-friendly solar energy conversion.