Ultra-narrow-band Blue-Emitting K2SrBa(PO4)2:Eu2+ Phosphor with Superior Efficiency and Thermal Stability

Abstract The design of phosphors simultaneously having excellent quantum efficiency, ultra-narrow emission band and zero thermal quenching is yet a big challenge. Herein, we report a blue-emitting K2SrBa(PO4)2:xEu2+ phosphor with ultra-narrow emission peaked at 425 nm with a full width at half maximum (FWHM) of 37 nm (2088 cm-1), high color purity (0.93), together with superior thermal stability and quantum efficiency. This phosphor displays an external quantum efficiency (EQE) of 75.3%, exceeding those of blue phosphors reported thus far. It also has excellent thermal stability showing near zero thermal quenching up to 300 °C, retaining 102%, 100% and 96% of its initial integrated emission intensity at 75, 200 and 300 °C, respectively. Rietveld refinements and density functional theory (DFT) calculations reveal that the Eu2+ ions preferentially occupy the Sr/Ba sites, rather than the K sites, of the host structure, contributing to the superior photoluminescence properties. The as-developed phosphors can be potentially applied in the phosphor-converted white light emitting diodes (pc-WLEDs) for applications such as high-power lighting and backlight display.