Enhanced luminescence and afterglow by heat-treatment in reducing atmosphere to synthesize the Gd3Al2Ga3O12: Ce3+ persistent phosphor for AC-LEDs

Yellow-emitting persistent phosphor Gd3Al2Ga3O12:Ce3+ (GAGG:Ce3+) was synthesized by two-step solid-state reactions. The phase evolution, luminescence, persistent luminescence, and thermal stabilities of GAGG:Ce3+ sintered in an O2 atmosphere and annealed in a CO reducing atmosphere at different temperatures were investigated. Comparing with the samples sintered only in O2, the samples annealed in CO show higher luminescence and afterglow and better thermal stability. Under 445 nm excitation, the luminescence and afterglow of GAGG:Ce3+ are similar with each other, displaying a broad yellow emission with a peak around 545 nm. By optimizing the sintering process, the internal quantum efficiency can reach as high as 71.3%. The time τ80 is about 15 ms, which is much longer than 0.4 ms required for alternating current (AC)-LEDs. These results indicate the promising application of the GAGG:Ce3+ persistent phosphor for reducing flicker from AC-LEDs.