Thiogallate phosphor for white LEDs with water-resistance and green light-emitting capability

The application of sulfide phosphor in the field of phosphor-converted white light-emitting diodes (pc-WLEDs) and wide-gamut displays has been limited by its poor water resistance. Herein, a water-resistant green emission phosphor, LiGaS2:Eu2+ (LGSE), has been developed using a chalcogenometallate LiGaS2 (LGS) as the luminescent host. First-principles calculation was utilized to identify the electronic structure of LGS and the optimal site for the Eu2+ dopant. Upon stimulation by 450 nm light, the LGSE phosphor exhibits a brilliant green emission with a photoluminescence emission (PL) maximum at 544 nm and a quantum efficiency of 55.3%. The exceptional luminance characteristics of this green-emitting phosphor were revealed by diffuse reflection spectra, steady-state PL spectra, and temperature-dependent PL measurements. The LGSE phosphor retains at least 94% of its initial emission even after 20 days of water immersion. The integration of LGSE with a commercial red-emitting K2SiF6:Mn4+ phosphor on a 450 nm blue LED chip produced a warm white light LED device, in which the color rendering index was Ra = 80.3 and CCT = 5128 K. This development represents a significant advancement in the field of water-resistant sulfide phosphors.