Effect of intrinsic oxygen vacancy on the electronic structure of β-Bi ₂O ₃: First-principles calculations

Oxygen vacancy is an intrinsic defect in metal oxides, which has a great effect on the electronic structures and physical properties. The influence of the intrinsic oxygen vacancy on the crystal and electronic structures of β-Bi ₂O ₃ has been studied. Results show that the vacancy is preferred to occupy the tetrahedral O3 (8c) site. It makes β-Bi ₂O ₃ lose I23 symmetry and leads to flat band structure. The quadrivalence post-transition ions M ⁴⁺ (M = S, Se, or Te) doping can keep I23 symmetry by forming MO ₄ units, and can result in dispersive valence bands and energy levels in the band gaps. These characters are beneficial for the mobility of the photogenerated carriers.