Luminescent enhancement and multi-mode optical thermometry of erbium doped halide Cs2(Na/Ag)BiCl6 microcrystals

Lanthanum-doped double halide perovskite has attracted increasing interest due to its distinctive up-conversion and near-infrared (NIR) luminous characteristics. Here, erbium ion (Er3+) doped Cs2(Na/Ag)BiCl6 microcrystals (MCs) were synthesized and proved to be one of the most prospective candidates for optical thermometry. The enhancement of both white light from self-trapped exciton emission and NIR emission from Er3+ ion of Cs2AgBiCl6 microcrystals is caused by lattice distortion due to Na+ ion doping. Fluorescence intensity ratio and lifetime methods provide self-referenced and sensitive thermometry under 405 and/or 980 nm laser excitation at the temperatures from 80 to 480 K. Besides, the maximum values of relative and absolute sensitivity of 3.62%/K and 27%/K can be achieved in the low to high temperature range under 980 and 405 nm laser co-excitation. Through the experimental analysis, Er3+ doped Cs2(Na/Ag)BiCl6 double perovskite is considered to be an ideal self-calibrating thermometric material due to its good long-term stability and multi-mode function of excitation and detection.