A Zero-Thermal-Quenching Blue Phosphor for Sustainable and Human-Centric WLED Lighting

The worldwide popularization of white-light-emitting diode (WLED) lighting brings about chronic blue-light exposure, which has severe negative impacts on human health and circadian rhythm. The blue-light hazard can be readily minimized by developing violet LED chip (λem ≈ 400 nm)-pumped sustainable and human-centric WLED lighting. However, the development of sustainable healthy lighting is stringently restricted because few blue phosphors can be efficiently pumped by violet LED chips. Herein, we report a novel Na3KMg7(PO4)6:Eu2+ blue phosphor with high quantum efficiency (>90%) and color purity (95.4%), which can efficiently convert violet light to blue emission. A crystal-site engineering approach and density functional theory (DFT) prove that the narrow-band (FWHM = 41 nm) emission of the Na3KMg7(PO4)6:Eu2+ phosphor originates from the accommodation of Eu2+ dopants in the Na(2) site. More importantly, the Na3KMg7(PO4)6:Eu2+ phosphor shows zero-thermal-quenching luminescence due to a large band gap (>6 eV). By depositing the commercial Sr2Si5N8:Eu2+ red phosphor, β-SiAlON:Eu2+ green phosphor, and as-synthesized Na3KMg7(PO4)6:Eu2+ blue phosphor on a 400 nm violet LED chip, the prototypical WLED can emit full-spectrum warm white light (Ra = 94.3) with significantly diminished blue-light intensity. The outstanding Na3KMg7(PO4)6:Eu2+ blue phosphor reported here can speed up the industrialization of human-centric WLED lighting.