Owing
to its low cost and admirable luminescent characteristics
for use in warm white-light-emitting diode (w-LED) applications, the
non-rare-earth Mn4+-activated red phosphor has emerged
as a potent competitor of commercial Eu2+-doped nitrides
in recent years. In this work, the novel red-emitting phosphor BaMgAl10–2x
O17:xMn4+,xMg2+ is successfully
synthesized, which exhibits bright and narrow-band luminescence peaking
at 660 nm with a full width at half-maximum of merely ∼30 nm
upon blue light excitation. The unique structural feature of BMA,
i.e., alternating arrangements of Mn4+-doped MgAl10O16/undoped BaO layers in the z direction
and Mn4+-doped [AlO6]/undoped [AlO4] groups in the x–y plane, favors efficient
Mn4+ luminescence by reducing nonradiative energy loss
channels. Unlike previously reported hosts, BMA accommodates Mg2+ in the lattice without destabilizing the crystal structure.
Remarkably, partitioning Mg2+ in the host not only greatly
enhances Mn4+ luminescence by 1.84-fold but also retards
the concentration quenching effect induced by Mn4+ dipole–dipole
interactions owing to the reduced number of Mn4+–Mn4+–O2– pairs. Spectroscopy demonstrates
that the luminescence of optimized BMA:0.02Mn4+,0.02Mg2+ exhibits a high color purity of 98.3%, good color stability
against heat, and excellent resistance to thermal impact. When incorporating
BMA:0.02Mn4+,0.02Mg2+ and YAG:Ce3+ phosphors into an oxide glass matrix at various ratios and then
coupling the phosphor-in-glass color converters using a blue chip,
the chromaticity parameters of the fabricated w-LED are well-tuned,
with the correlated color temperature decreasing from 6608 to 3622
K and the color rendering index increasing from 68.4 to 86.0, meeting
the requirements for in-door lighting use.
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.
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