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Phosphor-converted white light-emitting diodes (WLEDs) have received significant attention; however, the leaked light from their blue InGaN chips has an undesirable effect on human health. Hence, it is necessary to develop red, green, and blue-emitting phosphors, which can be excited by an NUV chip instead of a blue chip. Herein, green-emitting ZnO:Cu2+ phosphors have been successfully synthesized by a simple and facile thermal diffusion method. The obtained powder shows a broad emission band peaking at 525 nm and a strong absorption peak at 377 nm. The ZnO:5%Cu2+ phosphor annealed at 800 °C in 2 hours revealed a lifetime of 0.57 ms, an activation energy of 0.212 eV, and the highest emission intensity with (x, y) CIE colour coordinates (0.3130, 0.5253). A WLED prototype has been fabricated by coating the ZnO:5%Cu2+ phosphor on an NUV 375 nm LED chip, where this coated phosphor shows a high quantum efficiency (QE) of 56.6%. This is, so far, the highest reported QE value for ZnO-based phosphors. These results suggest that the ZnO:Cu2+ phosphor could be an excellent candidate for NUV-pumped phosphor-converted WLED applications. [ABSTRACT FROM AUTHOR]

• A novel Mn4+-doped Li 2 MgSn 2 O 6 phosphor with excellent color purity of 99.9% and good quantum efficiency of 44.5% • Strong red emissions peaking at 659 nm, achieved under excitation at 323 and 480 nm • Optimal Li 2 MgSn 2 O 6 :0.3%Mn4+ phosphor annealed at 1000 °C with particle size of 1.0 μm, 0.176 ms lifetime, and 0.335 eV activation energy • A prototype of NUV-pumped phytochrome-boosted plant growth LED using Li 2 MgSn 2 O 6 :0.3%Mn4+ phosphor In this study, a novel red-emitting Mn4+ doped Li 2 MgSn 2 O 6 (Li 2 MgSn 2 O 6 :Mn4+) phosphors were successfully synthesized using a simple solid-state reaction method. XRD patterns indicated the replacement of Mn4+ ions with Sn4+ ions in the [SnO 6 ] octahedrons site of the Li 2 MgSn 2 O 6 lattice, and XPS spectra confirmed the Mn4+ oxidation state. Excited at 323 nm and 480 nm, the phosphors exhibited a strong red emission band peaking at 659 nm, attributed to the 2E → 4A 2 transition of Mn4+ ions. Notably, the highest PL intensity was found in the Li 2 MgSn 2 O 6 :0.3%Mn4+ sample annealed at 1000 °C. These phosphors, with a particle size of 1.0 μm, possess a long lifetime of 0.176 ms, high activation energy of 0.335 eV, excellent color purity of 99.9%, and good internal and external quantum efficiency of 44.5% and 24.1%, respectively. Furthermore, an LED coated with Li 2 MgSn 2 O 6 :0.3%Mn4+ phosphor on a 365 nm NUV LED chip showed strong emission matching the absorption spectrum of the red phytochrome. Therefore, these results indicated that the synthesized Li 2 MgSn 2 O 6 :Mn4+ phosphors could be used as red-emitting materials for plant growth LED applications. [Display omitted] [ABSTRACT FROM AUTHOR]