Highly Efficient Lead-Free (Bi,Ce)-Codoped Cs2Ag0.4Na0.6InCl6 Double Perovskites for White Light-Emitting Diodes

Lead-free double perovskite phosphors are promising alternatives to lead halide perovskites for wide uses in optoelectronic applications, but suffer from a low quantum efficiency. Here, we propose to enhance the quantum efficiency of orange-emitting Cs2Ag0.4Na0.6InCl6:Bi via a codoping strategy. The internal quantum efficiency of Cs2Ag0.4Na0.6InCl6:1% Bi phosphor was increased from 89.9% to the record 98.4 and 98.6% by codoping with 1% Ni and 1% Ce, respectively. High-level density functional theory calculations have revealed that the enhanced efficiency is ascribed to the formation of shallow trap states by codoping with Ce, while codoping with Mn can create delocalized deep traps that decrease the quantum efficiency. By applying the (Bi,Ce)-codoped sample together with a blue BaMgAl10O17:Eu2+ phosphor, a white light-emitting diode with an excellent color rendering index of 95.7 and a correlated color temperature of 4430 K has been demonstrated. The developed Cs2Ag0.4Na0.6InCl6:Bi,Ce phosphor shows a great potential as down-conversion luminescent material in solid-state lighting for general illumination.