Strong near-infrared upconversion luminescence of the Er³⁺/Y³⁺ co-doped YbVO₄ phosphor for multimode optical...

This study explored the enhancement of near-infrared emissions in YbVO₄: Er³⁺ through Y³⁺ ion doping under a 980 nm laser excitation. The phosphor exhibits weak green emissions at 527 nm (²H_11/2 → ⁴I_15/2) and 553 nm (⁴S_3/2 → ⁴I_15/2), red emissions at 654 nm (⁴F_9/2 → ⁴I_15/2), and a strong near-infrared emission at 803 nm (⁴I_9/2 → ⁴I_15/2). Optimal doping concentration of Y³⁺ ion in YbVO₄: 0.02 Er³⁺ was determined to be 0.1, resulting in a 7.6-fold enhancement of near-infrared luminescence. This enhancement is attributed to defect bands facilitating energy transfer from green and red levels to the near-infrared levels. Furthermore, a multi-mode temperature sensor based on YbVO₄: Er³⁺/Y³⁺ was developed, offering four distinct temperature sensing modes: TCEL of ²H_11/2/⁴S_3/2, NTCEL of ²H_11/2/⁴F_9/2 and ⁴S_3/2/⁴F_9/2, and single luminescence emission intensity of ⁴I_9/2 energy level. The sensor demonstrates maximum relative sensitivities of 1.17 % K^-1 at 298 K, 0.66 % K^-1 at 298 K, 0.41 % K^-1 at 298 K and 1.29 % K^-1 at 673 K. YbVO₄: Er³⁺/Y³⁺ phosphor exhibits high temperature sensitivity, showcasing significant potential for optical temperature sensing applications.