Strong multi-mode upconversion luminescence of YbVO4: Er3+ phosphors for multimode optical thermometry

This study explored the multi-mode upconversion luminescence in YbVO 4 : Er 3+ under a 980 nm laser. The optimal doping concentration of Er 3+ ions in YbVO 4 : Er 3+ is 0.02. The phosphor exhibits green (527 nm, 2 H 11/2 → 4 I 15/2 and 553 nm, 4 S 3/2 → 4 I 15/2 ), red (654 nm, 4 F 9/2 → 4 I 15/2 ) and near-infrared emissions (803 nm, 4 I 9/2 → 4 I 15/2 ). A multi-mode temperature sensor of YbVO 4 : Er 3+ was developed, featuring three temperature sensing modes based on the luminescent intensity ratio (LIR) of 2 H 11/2 / 4 S 3/2 thermally coupled level, as well as the LIR of 2 H 11/2 / 4 F 9/2 and 4 S 3/2 / 4 I 9/2 non-thermally coupled levels. Corresponding maximum relative sensitivities were determined to be 1.21 % K −1 at 298 K, 0.93 % K −1 at 298 K, and 0.33 % K −1 at 473 K, respectively. The phosphor demonstrates notable temperature sensitivity, highlighting its potential in optical temperature sensing. This study introduces an innovative platform for crafting multi-mode self-reference optical temperature sensors, presenting substantial advancements in the field.