Bright and Persistent Green Emitting MgGa2O4:Mn2+ for Phosphor Converted White Light Emitting Diodes

Abstract

Narrow band green emitting phosphors have got widespread attention due to their application in white light emitting diodes (WLEDs) backlight displays. The commercial backlight displays are having a broad band green phosphor which limits their performance. In this work, bright, narrow and thermally stable green emitting MgGa2O4:Mn2+ (MGO-Mn) has been synthesized Time-resolved emission spectroscopy suggested that Mn2+ ions are distributed at both Mg2+ and Ga3+ sites in MGO spinel which resulted in high internal quantum efficiency of 63%. The colour purity of the MGO-Mn (76.4%) superseded that of commercial green phosphor β-SiAlON:Eu2+ (59.12%). Doping induced creation of oxygen vacancy impart MGO-Mn with excellent persistent luminescence with time duration of more than 900 sec on 1 min charging with 270 nm UV light and persistence radioluminescence of more than 6000 sec when charged with X-rays for 1 min. Finally, tunable white LEDs (cool and neutral white LED) are fabricated by combining the RGB mixture of the green phosphor with commercial red and blue phosphor along with a 280 nm UV LED chip. This work also provides importance of different annealing atmosphere on the photoluminescence and persistence luminescence of the MGO-Mn phosphor.