Exploring the optoelectronic properties of calcium vanadate semiconductors: A combined experimental and DFT study

Metal vanadates garner significant interest because of their exceptional potential for use in diverse practical applications, which stems from their unique framework structures, bond strength heterogeneities, and strong O²⁻–V⁵⁺ charge-transfer bands. However, their optoelectronic properties have not yet been sufficiently explored. In this study, we synthesized three high-purity calcium vanadate compounds (CaV₂O₆, Ca₂V₂O₇, and Ca₃V₂O₈) and comprehensively investigated their optoelectronic properties via first-principles calculations and experimental characterizations. CaV₂O₆, Ca₂V₂O₇, and Ca₃V₂O₈ are indirect band gap semiconductors with band gaps of 2.5–3.4 eV. A comparative analysis between density functional theory (DFT) and DFT + U (local Coulomb interaction, U) calculations revealed that standard DFT was sufficient to accurately describe the lattice parameters and band gaps of these vanadates. Further luminescence studies revealed significant photo- and electro-luminescence properties within the visible light spectrum. Notably, the luminescence intensity of CaV₂O₆ exhibited a remarkable 10-fold enhancement under a modest pressure of only 0.88 GPa, underscoring its exceptional potential for use in pressure-tunable optical applications. These findings provide deeper insight into the electronic structures and optical behaviors of vanadates and highlight their potential as strong candidates for application in phosphor materials and optoelectronic devices.