Enhanced thermally stable performance of Pr³⁺-doped vanadate phosphor by inhibiting the intervalence charge transfer...

Praseodymium (Pr³⁺) ion and the transition metal vanadium (V⁵⁺) ion with d⁰ electronic configuration can form an intervalence charge transfer (IVCT) band, which can function both as a compensatory channel for its red emission and as a quenching channel, thus affecting the luminescence thermal stability of the phosphors. Research studies reveal that the emission of Pr³⁺ in the YVO₄ matrix can be quenched by the IVCT mechanism, thereby limiting the application of phosphors. As such, the present contribution is based on the solid solution replacement strategy to inhibit the constitutent of the IVCT quenching channel and thus improve thermal stability. Therefore, phosphonium (P⁵⁺) with a valence state matching V⁵⁺ and a similar ion radius was selected for the V/P substitution. It lacks a d⁰ electron configuration, preventing the formation of an IVCT band with Pr³⁺ and thereby inhibiting the construction of the quenching channels to enhance thermal stability. While the empirical formula of IVCT indicates a decrease in the IVCT energy level from 3.32438 to 3.06251 eV upon the introduction of P⁵⁺, the PLE spectra demonstrate a sharp reduction in IVCT intensity, i.e., weakening of the quenching channel. The thermal stability of the phosphors at different excitation locations was enhanced with the rise of P⁵⁺ concentration. When excited at the ³P₂ level, the Y_0.995PO₄:0.5%Pr³⁺ phosphor demonstrated highly stable red emission from 303 to 523 K, with a luminescence integrated intensity ranging from 95.5% to 105.3% compared to that at 303 K. This research provides a novel approach for inhibiting the IVCT quenching channel and broadens the commercial value of YVO₄:Pr³⁺ phosphor for various applications.