Thermally Enhanced Upconversion Luminescence in Sc2Mo3O12:Yb/Er Thin Film Toward Versatile and High-Sensitivity Luminescent Temperature Sensing
Thermal quenching in lanthanide-based optical sensors severely limits performance at elevated temperatures. Negative thermal expansion (NTE) hosts have shown promise in bulk systems, but their potential in thin-film architectures for integrated photonics remains unexplored. This work demonstrates a Yb3+/Er3+ co-doped Sc2Mo3O12 thin film that leverages anisotropic NTE dynamics to achieve a 42-fold thermal enhancement in green upconversion luminescence from 300 to 560 K. In situ thermodiffraction and time-resolved spectroscopy reveal a dual mechanism: lattice contraction along the a- and c-axes reduces the cell volume by 11.3 Å3, amplifying Förster-type energy transfer (kET ∝ R−6) from Yb3+ to Er3+, and symmetry-breaking distortions suppress nonradiative 2H11/2 → 4F9/2 relaxations, extending Er3+ lifetimes by 358%. The strain-engineered crystal field enables multi-modal thermometry with record sensitivities: a relative sensitivity (Sr) of 4.33% K−1 at 300 K, and maximum Sr = 1.28% K−1 through lifetime-based sensing, outperforming conventional Boltzmann-limited approaches. The sub-200 nm thickness and SiO2/Si compatibility position this platform for on-chip integration, addressing unmet needs in high-resolution thermal mapping for quantum devices, aerospace diagnostics, and wearable sensors. This work deciphers the interplay between NTE and luminescence at the atomic scale and establishes a universal strategy to design anti-thermal-quenching thin films for extreme-environment photonics.