LAUSR

Lead halide perovskites attract tremendous research attention due to excellent optoelectronic properties. However, realizing efficient near ultraviolet (NUV) luminescence with these materials is still a big challenge. Herein, a novel rare-earth perovskite cesium thulium chloride (CsTmCl3 ) with high crystallinity has been synthesized via a simple hot-injection method. The obtained CsTmCl3 microcrystals have a size distribution of around 1-5 µm, and demonstrate a highly efficient NUV emission at 337 nm with a full width at half maximum (FWHM) of 68 nm. The determined band gap of CsTmCl3 microcrystals is ≈3.92 eV, which is supported by theoretical calculations. Moreover, a high photoluminescence quantum yield (PLQY) of up to 12% in NUV region has been achieved in such a lead-free perovskite. The findings suggest that CsTmCl3 perovskite microcrystal is a promising low-toxic material for applications in NUV optoelectronic devices.