Single‐Mode Excited Thermally‐Responsive Multicolor Emissions of High Entropy Upconversion Perovskite Halides for Anticounterfeiting

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This work presents a novel and highly secure anticounterfeiting strategy based on high entropy upconversion perovskite halides with thermally responsive multicolor emissions excited by a single laser. The perovskite halides are doped with rare earth cations and oxygen anions simultaneously and form the high entropy crystal structure by using a solid‐state reaction method. The color‐shifting emissions stem from luminescent kinetics transformation from energy transfer upconversion at low temperature to excited state absorption at high temperature. The multicolor emissions can also be trigged by the 975 nm laser heating effect. The results indicate the great potential of the high entropy upconversion perovskites for anticounterfeiting applications with a convenient recognition method.