Lanthanide-doped Cs2NaYCl6 double perovskites with thermally enhanced luminescence for high-sensitivity temperature sensing

Lanthanide-doped double perovskites have emerged as promising candidates for remote optical thermometry owing to their exceptional photoluminescence properties. However, pronounced luminescence quenching at elevated temperatures remain a critical bottleneck for application in high-precision temperature measurements. Herein, we report Yb 3+ /Ho 3+ -doped Cs 2 NaYCl 6 double perovskites synthesized via a solid-phase synthesis method, exhibiting thermally enhanced upconversion luminescence (UCL) and controllable color conversion. By tailoring the lanthanide doping concentration and temperature, the emission color gradually transitions from green to orange. Remarkably, this pattern remains consistent over a wide temperature range of 303–573 K, delivering a maximum relative sensitivity of 1.34% K −1 at 303 K. These features enable thermometers based on fluorescence intensity ratio (FIR) with excellent stability, high sensitivity and visualization capability. More importantly, the system simultaneously realizes thermochromic upconversion switch, opening an opportunity for multifunctional optical devices in sensing, imaging, and smart photonics.