Correlation between Luminescence Quantum Efficiency and Structural Properties of Vanadate Phosphors with Chained, Dimerized, and Isolated VO₄ Tetrahedra

The internal luminescence quantum efficiency and color properties of AVO3 (A: Li, Na, K, Rb, and Cs), M2V2O7 (M: Mg, Ca, Sr, Ba, and Zn), and M3V2O8 (M: Mg, Ca, Sr, Ba, and Zn) have been investigated. These vanadate phosphors exhibited broadband emission from 400 nm to over 800 nm due to the one-electron charge transfer transition in the VO4 tetrahedra, and the color of the luminescent materials ranged from green to yellow-orange via white, corresponding to 0.277 < x < 0.494 and 0.389 < y < 0.488 on the CIE chromaticity diagram. We found that the luminescence quantum efficiency of the vanadate phosphors with VO4 tetrahedra was strongly enhanced by the strong interaction between V ions and the weak interaction between V and A(M) ions in the crystal structures. We hypothesize that the long exciton diffusion lifetime induced by these structural features enhanced luminescence, leading to high quantum efficiency.