Harnessing the Dual‐Mode Luminescence of Er/Yb Co‐Doped SrLaLiTeO6 Double Perovskite Phosphors for Remarkably Wide Range Temperature Sensing and NIR pc‐LEDs

Abstract The ever‐increasing demand for efficient and economic photonic materials has hastened the quest for robust, multifunctional phosphors. Herein, a dual‐mode luminescent SrLaLiTeO 6 :Er 3+ , Yb 3+ double perovskite phosphor whose concentration‐dependent up and down‐conversion luminescence are investigated and underlying mechanisms are discussed. Temperature‐dependent up‐conversion luminescence of 2 H 11/2 → 4 I 15/2 transition exhibits negative thermal quenching, owing to the thermalization process from the 4 S 3/2 level. Temperature dependent Raman analysis confirms a decrease in the phonon lifetime from 0.43 to 0.28 ps indicating an increased number of phonon decay channels, which explains the rapid thermal quenching of up‐conversion emission at elevated temperatures. The diverse thermal quenching of the thermally coupled levels contributes to the exceptionally high relative sensitivity of 4.49 %K −1 at 140 K. A maximum sensitivity, S r of 0.84 %K −1 (698 K) is obtained from the Raman‐PL intensity ratio (RPIR) of the band (719 cm −1 ) and the 986 nm emission band ( 4 I 11/2 → 4 I 15/2 ) of Er 3+ . Hence, by employing multi‐mode temperature sensing techniques a single phosphor can be used for optical thermometry for a broad temperature range from 90 to 698 K. In addition, the Near Infra‐Red (NIR)‐II emission of Er 3+ corresponding to 4 I 13/2 → 4 I 15/2 transition shows excellent thermal stability, maintaining 72% of the room temperature intensity at 500 K.