Research on light-emitting diodes has considerably progressed over the years, so they are expected to possess excellent color rendition and high luminescent intensity. Cuboid-based red-nitride phosphors are highly promising because they are characterized by a narrow-band emission property, low energy waste, and excellent thermal stability. However, existing nitride phosphors have limited color diversity because of the lack of other anions. A new series of cuboid-based oxide phosphors called alkali lithosilicates is attracting considerable research attention because of these phosphors’ narrow-band emission and color-tunable properties. In this review, we demonstrate for the first time the features of nitride cuboid-based phosphors from a new perspective. The new perspective is then used to elucidate the color-control mechanism of the oxide cuboid-based phosphors. Finally, we propose a perspective about extending the color from the limit of current cuboid-based oxide phosphors. Our results can serve as a new reference for discovering new phosphors and controlling their luminescent color for practical applications.

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Narrowband green phosphors with high quantum efficiency are required for backlighting white light-emitting diode (WLED) devices. Materials from the A[Li3SiO4]4:Eu 2+ family have recently been proposed as having superior properties to industry-standard β-SiAlON green phosphors. Here we show that a cheap, easily synthesized host NaK2Li[Li3SiO4]4 (NKLLSO) doped with a mixture of Eu 2+ and Eu 3+ is an outstanding narrowband green phosphor, with an external quantum efficiency of 51% and superb thermal stability (97.1% of room temperature performance at 150 o C). Structural studies reveal that green emission occurs from two Eu 2+ sites, while Eu 3+ introduces a high concentration of vacancies that may suppress quenching from energy transfer between Eu 2+ sites. A WLED package constructed using our NKLLSO phosphor shows extremely high color vividness, competitive with a β-SiAlON comparator. This work will stimulate further research on efficient green phosphors for practical WLED devices.

The systematic substitution of Ba in the Sr site of Sr­[Mg2Al2N4]:Eu2+ generates a deep-red-emitting phosphor with enhanced thermal luminescence properties. Gas pressure sintering (GPS) of all-nitride starting materials in Molybdenum (Mo) crucibles yields pure-phase red-orange-colored phosphors. Peaks in the synchrotron X-ray diffraction (SXRD) data show a systematic shift toward smaller angles due to the introduction of the larger Ba cation in the same crystal structure. The photoluminescence property reveals that Ba substitution shifts the original emission wavelength of Sr­[Mg2Al2N4]:Eu2+ (625 nm) toward ∼690 nm for Ba­[Mg2Al2N4]:Eu2+. Thermal stability measurement of Sr1–x Ba x [Mg2Al2N4] indicates a systematic increase in stability from x = 0 to x = 1. X-ray absorption near-edge spectroscopy (XANES) results demonstrate the coexistence of Eu2+ and Eu3+. The red-shift and the enhanced thermal stability reveals that the distance of the emitting 5d level to the conduction band of Ba­[Mg2Al2N4]:Eu2+ is large. The ionic size mismatch of Eu occupying a Ba site reduces the symmetry, thereby further splitting the degenerate emitting 5d level and lowering the energy of the emitting center. The development of deep-red phosphors emitting at 670–690 nm (x = 0.8–1.0) offers possible candidates for plant lighting applications.