A novel sulfide phosphor, BaNaAlS3:Eu2+, discovered via particle swarm optimization

A novel quaternary sulfide phosphor, BaNaAlS3:Eu2+, was discovered emitting a cyan light that peaks at around 495 nm with a full width half maximum (FWHM) of 50 nm, and its utility for LED applications was suggested. The exact composition of the phosphor was identified via particle swarm optimization (PSO) in terms of the PL intensity. The PSO-nominated composition resulted in the optimal crystallinity and the highest PL intensity. Density functional theory (DFT) calculations also supported the experimentally measured band gap for the PSO-nominated BaNaAlS3:Eu2+ in a Pnma structure. Neither the typical concentration quenching behavior nor the typical decay-rate dependence on the probe wavelength was detected via time-resolved photoluminescence (TRPL) measurement. The absence of these typical decay traits was evident based on a relatively inactive rate of inter-activator energy transfer compared with that of other well-known Eu2+-activated phosphors.