Visible TADF and NIR Quenching Emission of Chromium Activated Zirconium-Halide Perovskite Toward Ultra-High-Sensitive Ratiometric Fluorescent Thermometer

With the development of science and technology, the measurement of temperature is receiving more and more attention. However, ratiometric fluorescent thermometers based on thermally coupled energy levels remain challenging because of their low relative sensitivity (Sr). In this work, chromium activated zirconium-halide perovskite Cs2ZrCl6 microcrystals are successfully synthesized via a simple co-precipitation method at room temperature. Interestingly, the host Cs2ZrCl6 exhibits reverse thermal quenching due to its thermal-activated delayed fluorescence (TADF) behavior, while the Cr3+ dopant shows normal thermal quenching. Leveraging the difference in their temperature-dependent luminescent properties, a ratiometric fluorescent thermometer is ingeniously developed, whose Sr reaches a maximum of 4.23% K-1. Besides, the as-synthesized thermometer is demonstrated for mobile phone remote temperature measurement. This finding offers a new approach for the design of high-sensitivity ratiometric fluorescent temperature sensors. The Cs2ZrCl6:Cr3+ microcrystals are synthesized via a room temperature co-precipitation method with a record-breaking photoluminescence quantum yield of 68.87%. The host Cs2ZrCl6 with thermal-activated delayed fluorescence property and the Cr3+ dopant with thermal quenching exhibit opposite temperature response, which can be ingeniously designed to serve as a high-sensitivity ratiometric fluorescent thermometer with a maximum relative sensitivity (Sr) of 4.23% K-1 at 170 K. image