Bandgap Tailoring via Si Doping in Inverse-Garnet Mg₃Y₂Ge₃O₁₂:Ce³⁺ Persistent Phosphor Potentially Applicable in AC-LED

Abstract

The state-of-the-art alternating-current light-emitting diode (AC-LED) technique suffers from adverse lighting flicker during each AC cycle. Aiming to compensate the dimming time of AC-LED, herein, we report a novel Mg3Y2(Ge1-xSix)3O12:Ce(3+) inverse-garnet persistent phosphor whose afterglow is efficiently activated by blue light with persistent luminescence in millisecond range. It is experimentally demonstrated that Si doping tailors the host bandgap, so that both the electron charging and detrapping in the persistent luminescence process are optimized. To explore the origin of the millisecond afterglow, we performed a series of thermoluminescence analyses, revealing three types of continuously distributed traps in the host. Finally, an AC-LED prototype device was fabricated, which exhibits the warm white emission with a reduced percent flicker of 71.7%. These results demonstrate that the newly developed persistent phosphor might be a promising candidate applicable in low flickering AC-LED which has advantages of cheaper price, longer lifetime, and higher energy utilization efficiency.

Lu2CaMg2(Si1−xGex)3O12:Ce3+solid-solution phosphors: bandgap engineering for blue-light activated afterglow applicable to AC-LED

“…[42][43][44] Therefore, it is reasonable to postulate that the trap type in LCMSGO belongs to different kinds of Ge-related defect species, e.g., V Ge -Ce 3+ -V O defect clusters. 17,18,30 It is worth noting that there is an evident signal enhancement at g = 1.951 after irradiation. Considering the g-value of the lightenhanced EPR signal that is smaller than the g-value of a free electron (g freeÀion = 2.0023), this signal is readily assigned to the presence of trapped electrons.…”

“…As for the TL intensity decline in LCMGO, it is probably caused by the severe electron retrapping, i.e., the thermally released electrons from the trap do not combine with the emission centers but go back to the traps. 14,30 With the Ge content increase, the TL peak maximum shifts toward low temperatures, indicating the shallower average trap depths. There are two possibilities that would result in this phenomenon: one is that for the trap with a fixed energy location in the bandgap, its depth is reduced when the CB bottom decreases; and the other is that the CB bottom goes downward, while the trap energy position goes upward.…”

Tuning the Energy Transfer Efficiency between Ce3+ and Ln3+ Ions (Ln=Tm, Sm, Tb, Dy) by Controlling the Crystal Phase of NaYF4 Nanocrystals

“…However, in hexagonal NaYF 4 , the environment around Y 3+ site is trigonal prismatic with equatorials (nine‐fold coordination) . This difference in the coordination number and environment result in different crystal field effects on the 5d levels of Ce 3+ ions . As a result, the 5d levels of Ce 3+ split differently for the two phases.…”

Warm white light emitting from single composition SrGa12O19:Dy3+ phosphors for AC‐LED

“…In practical use conditions, the alternating current (AC) grid supply must be converted into DC by certain methods, including transformer systems and switching systems . About 30% unwanted electric power consumption causes energy waste when the AC in switching into direct current . The transformer also generates a large number of heat, and excessive heat can degrade the organic resins and the phosphors embedded on the LED chip and seriously damage the electric circuit.…”

“…The threshold of human blinking fusion is usually between 60 Hz (16.7 ms) and 90 Hz (11.1 ms). Therefore, the LED flicker frequencies should be above this range . An AC‐LED generates flicker at frequencies of 120 Hz (8.3 ms) in North America and 100 Hz (10 ms) in Europe and in China .…”