Dual-Mode Optical Thermometers Based on the Thermal-Stable Perovskite Nanocrystals Embedded in Robust Metal Halide Salts

Photothermal sensing is crucial for the creation of smart integrated devices. All-inorganic metal halide perovskites with the formula CsPbX₃ (X═Cl, Br, I) have excellent photo-physical performance, offering exciting opportunities for flexible electronics. Hence, a supersaturated precipitation strategy is proposed for the preparation of salt-shelled metal halide solids. The well-designed CsPbX₃@MX (M═K, Cs) products exhibit bright narrow visible emissions and favorable thermal stability up to 195 °C. Co-doping with Ni²⁺ and Mn²⁺ ions, the CsPbCl₃@KCl products have realized dual-mode thermometry. Utilizing the blue emission from the CsPbCl₃ host and the red emission from the Mn²⁺ ion, a fluorescence intensity ratio technique is obtained to monitor the temperature of good stability and repeatability. Based on the regular fluorescence decay of Mn²⁺ ions with rising temperature, the lifetime of Mn²⁺ ions can also be used for temperature sensing. It is believed that such stable metal halides with dual-mode thermometry will provide a new sight for optical thermometers and, more importantly, will unleash the possibility of a broad variety of applications in lightweight and integrated functional devices.