Dual-modal optical temperature sensing based on Sb³⁺/Mn²⁺ co-doped Cs₂NaYCl₆ double perovskites

Optical temperature sensing based on luminescence intensity ratio shows significant potential in achieving accurate temperature detection. In this work, Sb³⁺/Mn²⁺ co-doped Cs₂NaYCl₆ double perovskites were synthesised via a hydrothermal method. Introducing Sb³⁺ ions to the host significantly enhances the radiative recombination of self-trapped excitons (STEs), resulting in a broad blue emission. The co-doping of Mn²⁺ ions to the composition leads to a tunable dual-emission in the spectra, originating from the energy transfer between the STEs and Mn²⁺ ions. The dependence of the dual-emission on temperature is employed for optical temperature sensing. The maximum relative sensitivity, optimal thermal resolution, and optimal thermal repeatability are determined as 1.40 % K⁻¹, 0.002 K and 99.3% at 250 K, respectively. The results indicate that the synthesised Cs₂NaYCl₆: Sb³⁺/Mn²⁺ double perovskites are promising candidates for high-sensitivity optical thermometers.