High-Purity Narrow-Band Green Light KAl11O17: Eu2+, Mn2+ Phosphor Prepared Based on Energy Transfer Effect

A narrow-band green-emitting phosphor KAl 11 O 17 (KAO): Eu 2+ , Mn 2+ , was synthesized via a high-temperature solid-state reaction to evaluate its potential for use in high-quality backlight displays. Structural refinement reveals that Eu 2+ and Mn 2+ ions preferentially occupy distinct crystallographic sites: Eu 2+ resides at K + sites in the conductive layer, whereas Mn 2+ substitutes for tetrahedral Al 3+ sites within the spinel block. This spatial separation facilitates efficient energy transfer (ET) from Eu 2+ to Mn 2+ . Spectroscopic analysis of the optimally doped composition, KAO: 0.07Eu 2+ , 0.04Mn 2+ , indicates that the ET proceeds predominantly via a dipole - quadrupole ( d - q ) mechanism. The resulting phosphor exhibits bright green emission centered at 510 nm with an exceptionally narrow full width at half maximum (FWHM) of 8.13 nm, a high color purity of 98%, and an internal quantum efficiency (IQE) of 65.41%. Moreover, the material demonstrates excellent thermal stability, retaining 93.11% of its initial luminescence intensity at 423 K, corresponding to a thermal activation energy of 0.2917 eV. To demonstrate its practical utility, a white LED device was fabricated by combining the optimized green phosphor (KAO: 0.07Eu 2+ , 0.04Mn 2+ ) with a blue phosphor (BaMgAl 10 O 17 (BAM): Eu 2+ ), a red phosphor (Ca 9 KMn(PO 4 ) 7 : Eu 2+ ), and a 365 nm near-ultraviolet chip. The resulting device achieves a wide color-gamut covering 107.8% of the NTSC standard. Collectively, these results demonstrate that precise control of site occupancy and energy transfer enables the design of green phosphors that simultaneously exhibit narrow-band emission, high color purity, and robust thermal stability-properties that are essential for wide color-gamut WLED backlight displays.