Thermally enhanced upconversion luminescence in Sc2Mo3O12:Yb/Er thin film toward versatile and high-sensitivity luminescent temperature sensing

Thermal quenching, a pervasive challenge in luminescent materials, severely limits the performance of lanthanide-based optical sensors at elevated temperatures. While negative thermal expansion (NTE) hosts have shown promise in bulk systems for countering this effect, their potential in thin-film architectures, critically for integrated photonics and miniaturized sensing, remains unexplored. Here, we demonstrate a Yb 3+ /Er 3+ co-doped Sc 2 Mo 3 O 12 thin film that leverages anisotropic NTE dynamics to achieve 42-fold thermal enhancement in green upconversion luminescence from 300 to 560 K. In situ thermodiffraction and time-resolved spectroscopy reveal a dual mechanism: (1) lattice contraction along the a - and c -axes reduces the cell volume of Sc 2 Mo 3 O 12 by 11.3 Å 3 , thereby amplifying Förster-type energy transfer ( k ET ∝ R −6 ) from Yb 3+ to Er 3+ , and (2) symmetry-breaking distortions suppress nonradiative 2 H 11/2 → 4 F 9/2 relaxations, extending Er 3+ lifetimes by 358%. Crucially, the film’s strain-engineered crystal field enables multi-modal thermometry with record sensitivities: a relative sensitivity ( S r ) of 4.33% K −1 at 300 K, and maximum S r = 1.28% K −1 through lifetime-based sensing, which outperforms conventional Boltzmann-limited approaches. The sub-200 nm thickness and SiO 2 /Si compatibility further 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 not only deciphers the interplay between NTE and luminescence at the atomic scale but also establishes a universal strategy to design anti-thermal-quenching thin films for extreme-environment photonics.