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.

This work highlights a novel double-perovskite red phosphor Gd2ZnTiO6:Mn4+for UV-based warm white LEDs.

The commercially dominant phosphor-converted illumination white light-emitting-diode (w-LED) generally suffers from red deficiency and poor thermal stability of organic encapsulants, resulting in cool white light, luminous degradation and chromatic aberration for the embedded YAG:Ce 3+ phosphors after long-term working. Aiming to solve these problems, herein, a chromaticity-tunable robust phosphor-in-glass (PiG) inorganic color converter was successfully fabricated by co-sintering the YAG:Ce 3+ ,Mn 2+ ,Si 4+ phosphor particles and the innovatively-designed TeO 2 -B 2 O 3 -ZnO-Na 2 O-Al 2 O 3 low-melting precursor glass. At first, the spectrally-modified YAG:Ce 3+ ,Mn 2+ ,Si 4+ phosphor was prepared by doping Mn 2+ as the red emitters and doping Si 4+ as the charge compensators through a solid-state reaction route. Then, the YAG:Ce 3+ ,Mn 2+ ,Si 4+ powder was incorporated 2 into the specifically prepared precursor glass to form the PiG composite at 550 °C. Owing to the density and the refractive index matches for the phosphor particles and the glass matrix, the particles dispersion in PiG is quite homogeneous and the adverse light-scattering is depressed. The high-power warm w-LED was constructed by coupling a PiG plate with the InGaN blue chip. Remarkably, the chromaticity coordinate of such w-LED can be well tuned to follow along the Planckian locus with the correlated color temperature evolving from cool white (5541 K) to warm white (3050 K) and a color rendering index around 70, under a driving current of 350 mA.Moreover, the PiG-based warm w-LED presents much superior thermal stability to the traditional phosphor-in-silicone (PiS)-based one. This work highlights the practical applications of the PiG luminescent material in the long-lifetime high-power warm w-LED.

Currently, the development of efficient red-emitting persistent phosphor is still an ongoing challenge. Herein, a novel red-emitting LPL phosphor Ca3Ti2O7:Pr(3+) is successfully prepared by a high-temperature solid-state method. XRD Rietveld refinement analyses demonstrate the high phase purity of the sample which crystallizes in an orthorhombic Ccm21 space group with lattice parameters of a = 5.7702(5) Å, b = 19.4829(7) Å, and c = 5.1214(2) Å. Electronic structure of the host matrix is analyzed by the first-principle calculation using CASTEP code. The calculation results show that Ca3Ti2O7 has a direct band gap with CB and VB mainly composed of the Ti-3d and O-2p states, respectively. On the basis of the DR spectrum, the band gap is determined to be 3.6 eV. It is demonstrated that the 612 nm red-emitting persistent luminescence of Ca3Ti2O7:Pr(3+) can be either activated by Ti(4+)-O(2-) → Ti(3+)-O(-) host absorption and Pr(3+)-O-Ti(4+) → Pr(4+)-O-Ti(3+) IVCT in the UV region, or Pr(3+):(3)H4 → (3)PJ transition in the blue region. The red afterglow can last for ∼ 5 min observed by the naked eyes in the dark after ceasing the irradiation source. On the basis of the TL analyses, the trap is found exponentially distributed in the host with the depth of 0.69-0.92 eV. Finally, a possible LPL mechanism for Ca3Ti2O7:Pr(3+) is proposed.

Persistent luminescence (PersL) has long commanded the curiosity of researchers owing to the complicated and profound physics behind it. In this work, the PersL mechanism in a new kind of persistent garnet phosphors, Lu 2 CaMg 2 (Si 1Àx Ge x ) 3 O 12 :Ce 3+ , is studied from the new perspective of a ''solid-solution'' scheme. Different from the conventional study in pursuit of long PersL, we focus on manipulation of afterglow to the millisecond range and tentatively demonstrate its potential to compensate the flickering of the alternating current driven LED (AC-LED) in every AC cycle. Evidently, the tailored host bandgap favors efficient electron charging and facilitates electron detrapping, as well as redeploying trap distribution, which results in a blue light activated afterglow in the millisecond time range, and subsequently a reduced percent flicker of 64.1% for the AC-LED. This investigation is the first attempt to establish the design guidelines for new PersL materials with an adjustable millisecond ranged afterglow, and, hopefully, it paves a pathway to the development of burgeoning low-flickering AC-LED technology.

Inorganic perovskite CsPbBr3−xIx(x= 0–3) QDs with tunable emission wavelength, narrow emission band and high quantum yields were synthesized. The fabricated CsPbBrI2QD-modified WLEDs show excellent performance in luminous efficacy, CCT and CRI, which are quite stable at an operational current as high as 350 mA.

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