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Simultaneously enhanced far-red luminescence and thermal stability in Ca3Al4ZnO10:Mn4+ phosphor via Mg2+ doping for plant growth lighting
摘要： Non-rare-earth-based Ca3Al4ZnO10:Mn4+,Mg2+ (CAZO:Mn4+,Mg2+) phosphors with admirable luminescence performance and great potential as far-red light source for plant growth light-emitting diodes (LEDs) were reported in this paper. The concentration-dependent optical properties of the as-prepared phosphors were investigated in detail. Under ultraviolet-light excitation at 358 nm, the composition-optimized CAZO:0.4%Mn4+,14%Mg2+ phosphor showed an intense broad far-red emission band in the 625-830 nm wavelength range with a maximum at 714 nm, which was due to the 2Eg→4A2g transition of Mn4+ ions. The luminescence intensity of the CAZO:0.4%Mn4+,14%Mg2+ phosphor was about 1.82 times higher than that of CAZO:0.4%Mn4+ phosphor, and the corresponding mechanism for the luminescence enhancement via Mg2+ doping was studied. Amazingly, the internal quantum efficiency of the CAZO:0.4%Mn4+ phosphor was increased from 31 to 60% after co-doping 14 mol% Mg2+. The CAZO:0.4%Mn4+,14%Mg2+ phosphor also showed enhanced thermal stability compared with the CAZO:0.4%Mn4+ counterpart. It was found that, for CAZO:0.4%Mn4+,14%Mg2+ phosphor, the emission intensity at 423 K (150 oC) was about 51% of that at 303 K (30 oC), while the corresponding activation energy was determined to be 0.245 eV.
关键词： thermal stability,plant growth,phytochrome,far-red emissions,LEDs.,Mn4+ ions
更新于2025-09-23 15:22:29
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Novel efficient deep-red-emitting Ca2LuTaO6:Mn4+ double-perovskite phosphors for plant growth LEDs
摘要： Deep-red-emitting phosphors are important for fabricating light-emitting diodes (LEDs) toward applications in plant growth lighting. Herein, we reported on novel efficient deep-red-emitting Mn4+-activated Ca2LuTaO6 (CLT) double-perovskite phosphors. A series of CLT:xMn4+ (x = 0.1, 0.2, 0.4, 0.6, 0.8, and 1.0 mol%) samples were prepared by the conventional high-temperature solid-state reaction technique, and they were characterized by using X-ray diffraction (XRD), field-emission scanning electron microscope (FE-SEM), elemental mapping, photoluminescence excitation and emission, decay curves, CIE chromaticity coordinates, internal quantum efficiency (IQE), and temperature-dependent emission spectra. The CLT host crystallized in a monoclinic structure with space group of P21/n, and it contained an octahedral site of TaO6 for Mn4+ doping. Impressively, under 351 ultraviolet light excitation these CLT:xMn4+ phosphors exhibited bright deep-red emissions around 682 nm with CIE chromaticity coordinates of (0.7272, 0.2728) and full width at half maximum (FWHM) of 25 nm. Notably, the optimal CLT:0.2%Mn4+ sample possessed an IQE of 37% and good resistance to thermal quenching (I423 K/I303K = 47%). Considering the emission spectrum of CLT:0.2%Mn4+ deep-red-emitting phosphors matched well with the absorption spectrum of phytochrome PFR, the as-prepared CLT:0.2%Mn4+ phosphors showed great potential in plant growth LEDs.
关键词： Deep-red emissions,Phosphors,Luminescence,Double-perovskite,Mn4+,Plant growth lighting
更新于2025-09-19 17:13:59
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A New Co-Substitution Strategy as a Model to Study a Rare-Earth-Free Spinel-Type Phosphor with Red Emissions and Its Application in Light-Emitting Diodes
摘要： The substitution of metal sites in Mg2TiO4 substrate leads to charge imbalance that will be closely related to a variety of changes including lattice structure, cell distortion, and photophysical properties. Herein, the co-substitution strategy of [Ga3+?Ga3+] for [Mg2+?Ti4+] and Sn4+ for Ti4+ achieves for the first time the novel Mg3Ga2SnO8 (MGS):xMn4+ (x = 0?3%) phosphors with efficient red emissions. In terms of X-ray powder diffraction (XRD) and Rietveld refinement analysis, MGS:Mn4+ possesses a structure isotypic of Mg2TiO4 in the cubic space group Fd3?m (227). There are two types of octahedra for Mn4+ ions in this structure, where Ga3+ ions completely occupy a group of octahedral sites and Mg2+/Sn4+ has been randomly distributed over another group of octahedral sites. A strong excitation band in the broad spectral range (220?550 nm) has been identified, thus facilitating the commercial uses for blue LED chips excitation. An intense red emission band at 680 nm has been observed due to the characteristic 2Eg?4A2g transition of Mn4+ ions. A concentration quenching effect occurs when the Mn4+ content exceeds 1.5%, and the quenching mechanism is demonstrated to be dipole?quadrupole interactions. Temperature-dependent luminescence measurements support its good thermal stability, and the corresponding activation energy Ea is determined to be 0.2552 eV. The possible luminous mechanism of the Mn4+ ion is explained by the Tanabe?Sugano energy level diagram. The crystal field strength and the Racah parameters together with the nephelauxetic ratio are also determined for Mn4+ in the MGS lattice. High color rendition warm white-light-emitting diodes (WLEDs) based on the optimal phosphor MGS:1.5%Mn4+,1.5%Li+ possess a color rendering index and color temperature of 85.6 and 3658 K, respectively. Its feasibility for application in solid-state white lighting has been verified.
关键词： Co-substitution strategy,Light-emitting diodes,Red emissions,Spinel-type phosphor,Rare-earth-free
更新于2025-09-12 10:27:22