First-principles and device-level investigation of physical and photovoltaic properties of lead-free JAgO ₃ (J = Nb, Ta) oxide perovskites

In the modern era, the search for stable and lead-free perovskite materials is essential for sustainable photovoltaic and optoelectronic technologies. This work presents a combined first-principles and device-level investigation of the oxide perovskites JAgO 3 (J = Nb, Ta). Density functional theory (DFT) calculations confirm that both compounds are structurally, thermodynamically, mechanically, and dynamically stable, with indirect band gaps of 1.396 eV for NbAgO 3 and 1.690 eV for TaAgO 3 . Their electronic structures are characterized by O- 2p -dominated valence bands and Nb/Ta- d -derived conduction bands, indicating strong metal oxygen hybridization and favorable band-edge alignment. Optical results show strong absorption in the visible region, with NbAgO 3 exhibiting superior absorption behavior. Device-level SCAPS-1D simulations using the Al/FTO/SnS 2 /JAgO 3 /Ni architecture demonstrate that NbAgO 3 delivers a significantly higher photovoltaic performance, achieving a power conversion efficiency of 24.13%, compared to 15.53% for TaAgO 3 under optimized conditions. These findings identify NbAgO 3 as a highly promising lead-free oxide perovskite absorber for next-generation solar cells, while TaAgO 3 remains a viable but less efficient alternative.