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

Abstract

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:0.04Ce³⁺ is proposed to optimize the PersL intensity. The τ₈₀ value (the time when the PersL intensity reaches 80% of its initial value) of BYAGSO:0.04Ce³⁺,0.01Bi³⁺ 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:0.04Ce³⁺,0.01Bi³⁺ and the commercial red PersL phosphor Sr_0.75Ca_0.25S: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.