Photoluminescence in rare-earth based halide double perovskite Cs2NaRECl6 (RE = Ce, Eu, Y, Lu) microcrystals

Lead-free halide double perovskites (DPs) with superior photoelectric performance are of great importance in perovskites materials family. In this paper, a series of rare-earth (RE) based Cs2NaRECl6 (RE = Y, Ce–Nd, Sm–Gd, Dy–Lu) DPs microcrystals (MCs) were prepared by convenient hydrothermal method. Cs2NaCeCl6 and Cs2NaEuCl6 MCs exhibit typical UV emission from the 5d→4f transition of Ce3+ and orange-red emission from characteristic 5D1 → 7F0, 5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3, 5D0 → 7F4 transitions of Eu3+, respectively. The blue light emissions of Cs2NaYCl6 (300–650 nm) and Cs2NaLuCl6 (300–550 nm) are from the respective self-trapped exciton states (STEs). In addition, the bandgap and partial density of state (PDOS) of Cs2NaRECl6 (RE = Ce, Eu, Y, Lu) were calculated based on density functional theory (DFT) to have a further insight into the optical properties of the RE-DPs. The as-prepared RE based DPs have potential applications in advanced lighting, displaying and anti-counterfeiting, etc.