Blue-light activated green emitting BaY2Al2Ga2SiO12:Ce3+,Bi3+: efficient persistent luminescence phosphors for AC-LEDs

The advent of alternating current light-emitting diodes (AC-LEDs) based on persistent luminescence (PersL) phosphors is a major breakthrough in terms of long service lifetime, reduced production cost, and high energy utilization efficiency. However, the efficiency of the current PersL based AC-LEDs for flicker reduction in each AC cycle needs to be improved. To address this issue, herein, we develop a series of green-emitting persistent luminescence (PersL) phosphors BaY2Al2Ga2SiO12:Ce3+,Bi3+ (BYAGSO:Ce3+,Bi3+) via a defect engineering approach, whose PersL can be efficiently activated by blue-light. A strategy that introduces bismuth with multivalent states into BYAGSO:0.04Ce(3+) is proposed to optimize the PersL intensity. The tau(80) value (the time when the PersL intensity reaches 80% of its initial value) of BYAGSO:0.04Ce(3+),0.01Bi(3+) is about 30 ms, which demonstrates its effectiveness in minimizing flicker from AC-LEDs. Meanwhile, with the aid of excitation temperature-dependent and fading thermoluminescence (TL) experiments, the trapping levels related to Bi3+ in BYAGSO:Ce3+,Bi3+ are also investigated through the initial rise method. Furthermore, we fabricate an AC-LED device using the phosphor BYAGSO:0.04Ce(3+),0.01Bi(3+) and the commercial red PersL phosphor Sr0.75Ca0.25S:Eu2+ (SCS:Eu2+) with an InGaN blue-emitting chip, which shows warm-white emission with a reduced percent flicker of 47.06%. These results demonstrate that the BYAGSO:Ce3+,Bi3+ phosphor might be a promising candidate for low-flicker AC-LEDs.

Automated summary

We have developed a series of green-emitting persistent luminescence (PersL) phosphors BaY2Al2Ga2SiO12:Ce3+,Bi3+ (BYAGSO:Ce3+,Bi3+) via a defect engineering approach, which can be efficiently activated by blue-light and effectively reduce flicker in AC-LEDs. By investigating the trapping levels related to Bi3+ in BYAGSO:Ce3+,Bi3+ and fabricating an AC-LED device with low flicker, we demonstrate that the BYAGSO:Ce3+,Bi3+ phosphor is a promising candidate for low-flicker AC-LEDs.