BaBiO3: A potential absorber for all-oxide photovoltaics

BaBiO₃ is presented as a potential absorber for all-oxide solar cells. Thin-films of BaBiO₃ were deposited by pulsed laser deposition. As-deposited thin-films were amorphous, but a rapid thermal anneal at 600 °C for 10 min yields polycrystalline thin-films. X-ray photoelectron spectroscopy measurements show that deposited films have Barium in Ba⁺² state and bismuth in both Bi⁺³ and Bi⁺⁵ state. UV–Vis spectrophotometer (UV–Vis) shows that BaBiO₃ films have direct and indirect bandgap (E_g) of 2.25 eV and 2.02 eV respectively, while ultraviolet photoelectron spectroscopy (UPS) shows that valence band maxima (E_V), conduction band minima (E_C) and work-function (ϕ) of BaBiO₃ is at 5.82 eV, 3.8 eV and 4.22 eV respectively. BaBiO₃ thin-film devices with a FTO/c-TiO₂/BaBiO₃/Au structure show rectifying current–voltage characteristics in dark. Under illumination, a photo response with a J_light/J_dark ratio of 1.75 is observed.