Design of dual-mode optical thermometry using Sb3+/Mn2+ codoped Cs2NaLuCl6 double perovskite

Abstract

Wide band emission has aroused widespread focus in various fields such as display, plant lighting, and solar cells due to its spectral continuity. Here, a series of Sb³⁺/Mn²⁺ doped Cs₂NaLuCl₆ double perovskites with wide blue and red emissions were synthesized through a precipitation method. Enhanced self-trapped exciton (STE) emission and red emission of Mn²⁺ ion are achieved by doping Sb³⁺ ion to construct energy transfer channels. The temperature dependent fluorescence spectra exhibit that the emission intensity at 418 K remains 66.4% of that at 298 K in Cs₂NaLuCl₆: 1% Sb³⁺, 10% Mn²⁺ microcrystal. Importantly, the full-width at half-maximum (FWHM) of STE and Mn²⁺ ion emissions show obvious broadening as the temperature increases, which is attributed to the enhanced electron-phonon interaction. The optical temperature sensing method based on FWHM of STE and Mn²⁺ emissions is designed, the corresponding maximum relative sensitivity (S_r) values are 0.14% at 298 K and 0.61% at 448 K, respectively. Furthermore, due to the fluorescence intensity ratio (FIR) between STE and Mn²⁺ ion is highly temperature-dependent, the temperature sensing based on FIR technique is investigated. The maximum S_r values reach 1.31% K⁻¹ at 448 K under 317 nm excitation. The minimum temperature resolution (δT) is calculated as 0.26 K at 448 K. The dual-mode temperature measurement methods based on FWHM and FIR can achieve more accurate remote temperature measurement. These results indicate the microcrystal has potential application in the fields of optical temperature thermometry.