Designing Polychromatic Luminescence in Mn-Doped CsNaLuCl Double Perovskite Crystals via Energy Transfer Engineering for Optical Thermometry and X-ray Imaging.

Metal halide double perovskites with splendid optical features have been considerably investigated for optoelectronic applications. Herein, a series of Mn-doped CsNaLuCl double perovskite crystals were prepared. Via adopting the density functional theory calculation, the effect of Mn doping on the electronic structure of the CsNaLuCl compound was discussed. It was found that the CsNaLuCl crystal can emit intense blue light from the host self-trapped exciton (STE) emission. Excited by 320 nm, the STE and Mn emissions were simultaneously observed in the resulting crystals. Owing to the efficient energy transfer from the STE to Mn, polychromatic luminescence was observed in final products. Moreover, taking advantage of the various responses of the emission intensities of the STE and Mn to temperature, the thermometric characteristics of resulting crystals were investigated, and their maximum relative sensitivity is 0.99% K, which is hardly impacted by Mn content. Furthermore, the prepared crystals exhibit good X-ray radioluminescence properties, with a low detection limitation of 0.99 μGy s. Additionally, utilizing the designed crystal, flexible X-ray imaging with a high resolution of 20 lp mm that can be operated in a high-temperature environment was realized. These results indicated that the Mn-doped CsNaLuCl double perovskite crystals are suitable for optical thermometry and X-ray imaging.