Efficient dual-mode emissions of high-concentration erbium ions doped lead-free halide double perovskite single crystals

Lead-free halide double perovskites have attracted great attention due to the intriguing optoelectronic properties. However, the related researches mainly focus on their down-shifting (DS) luminescence process,while the up-conversion (UC) luminescence process is still rarely studied. Herein, Er3+ ions doped Cs2Ag0.6Na0.4InCl6:0.3%Bi double perovskite single crystals were prepared by an improved hydrothermal method, and the efficient UC and DS emission of Er3+ ions were realized by high-level doping concentration of Er3+ ions. Interesting, the UC green emission of Er3+ ions can be all obtained under 808,980 and 1540 nm excitation, and the optimal photoluminescence quantum yield (PLQY) is 0.17%. To be emphasized, it is the UC luminescence of rare earth ions doped semiconductor materials, which is more advantages in the application of optoelectronic devices than the UC luminescence of rare earth ions doped insulator materials (e.g, NaYF4). Moreover, with the increase of Er3+ ions doping concentration, the DS luminescence color can be controlled from yellow to green. And the near-infrared (NIR) light with the peak at 1540 nm is simultaneously emitted, and the highest PLQY reaches 38.36%, which is suitable for optical communication. Notably, the NIR light (1540 nm) can be also obtained under 808 and 980 nm excitation, which has positive significance for biological applications. This work demonstrates that rare earth ions doping has the potential to impart new functions to double perovskites.