Bi-based double perovskites(Formula presented)and(Formula presented): Candidate materials for p-type transparent conducting applications with wide/ultra-wide band gaps

Developing high-performance p-type transparent conducting oxides (TCOs) is challenging due to large hole effective masses and limited mobility in oxides. Using first-principles density functional theory calculations, we show Bi-based double perovskites Ba₂NbBiO₆ and Ba₂TaBiO₆ are promising candidate materials for p-type transparent semiconductors. Ba₂NbBiO₆ possesses a wide band gap (WBG) while Ba₂TaBiO₆ has an ultra-wide band gap (UWBG). Strong Bi-6s/O-2p hybridization at the valence band maximum enhances dispersion, yielding low hole effective masses (0.34–0.39 m₀ (PBE), 0.46–1.1 m₀ (HSE06)). Both exhibit WBG to UWBG (2.04–2.59 eV (PBE), 3.08–3.68 eV (HSE06)), suppressing visible-light absorption. Idealized 30 nm thin films show high visible transparency, meeting fundamental optical requirements for TCO materials. Favorable electronic/optical properties are complemented by mechanical ductility (Pugh ratios above the threshold) and indications of structural stability with moderate Young's moduli, suggesting potential compatibility with thin-film deposition. Our results identify these perovskites as promising candidate systems for next-generation p-type wide- to ultra-wide-band-gap transparent conductors, highlighting Bi-based double-perovskite engineering for exploring high-transparency, mechanically stable p-type oxides.