Eu3+, Tb3+ doping induced tunable luminescence of Cs2AgInCl6 double perovskite nanocrystals and its mechanism

Incorporation of lanthanide ions (Ln3+) can remarkably enhance the structural stability and optical properties of lead-free perovskite NCs. Herein, we have established the relationship between the intrinsic emission of Cs2AgInCl6 host and the Ln3+ by Eu3+, Tb3+ doping in Cs2AgInCl6 NCs, realizing tunable luminescence of NCs in the visible region. Experimental studies and density functional theory (DFT) calculations analysis show that Eu3+ and Tb3+ occupy the sites of In3+ in Cs2AgInCl6, the defect formation energy for Cs2AgInCl6:Ln3+ is larger than the pristine Cs2AgInCl6, resulting in a more stable cubic double perovskite structure. The optical band gap increases with the increase in Ln3+ doping percentage. Turning excitation from 250 nm to 300 nm, the broad self-trapped excitons (STEs) emission is more remarkable, and the narrow Ln3+ emission is less notable. The emitted color can be adjusted from white to red and to green light by altering the doping concentration of Eu3+ or Tb3+ and excitation wavelength. This work promotes the design and optoelectronic application of desired lead-free perovskites.