A ratiometric optical thermometer with dual-color emission based on Eu2+-doped CsCu2I3 microcrystals

With the increasing demand for non-contact fluorescence intensity ratio-based optical thermometry, novel phosphor materials with high-efficiency, dual-emitting centers, and differentiable temperature sensitivity are highly desired. In this work, rare earth Eu2+ ions were incorporated into CsCu2I3 microcrystals by solid–state reaction. Under a single UV excitation, the as-synthesized samples exhibit two emissions: 452 nm blue emission from the 5d→4f transition of Eu2+ and 582 nm yellow emission from self-trapped exciton emission of CsCu2I3. The photoluminescence quantum yield reaches to 50%. The dual-band emission of Eu2+-doped CsCu2I3 shows different temperature responses in the range of 260–360 K. Based on fluorescence intensity ratio technology, the maximum absolute sensitivity and relative sensitivity are 0.091 K–1 (at 360 K) and 2.60%/K (at 260 K), respectively. These results suggest that Eu2+-doped CsCu2I3 could be a good candidate for highly sensitive optical thermometer.