Novel near-ultraviolet-excited and thermally-stable blue-emitting phosphor for healthy WLED lighting

The widespread popularity of white light-emitting diodes (WLED) lighting results in a chronic exposure to blue light, which has negative impacts on human biological functions, emotions and health. As an alternative strategy, integrating near-ultraviolet (n-UV) LED chips with high-efficiency (high quantum efficiency, chemical and thermal stability) tricolor phosphors, can easily achieve high-quality white light and diminish the so-called "blue-light hazard". However, few blue-emitting phosphors can meet the aforementioned requirements. Herein, we report a novel n-UV excited bright blue-emitting CsBaB9O15:2%Eu2+ phosphor with high internal quantum efficiency (IQE = 68.8%) and outstanding thermal stability (94.2%@ 150 °C, 84%@ 250 °C). Impressively, this phosphor exhibits excellent chromaticity stability (Δx = 0.002, Δy = 0.012; 3.6 × 10−3 ≤ ΔE ≤ 8.1 × 10−3) from 25 to 150 °C. These remarkable thermal stability are mainly ascribed to the large band gap of host (Eg = 5.85 eV), which effectively suppresses the thermal ionization pathway of the dominant 440 nm emission in the CsBaB9O15:2%Eu2+ phosphor. A WLED device was fabricated by combining commercial phosphor Sr2Si5N8:Eu2+, green phosphor (Sr, Ba)2SiO4:Eu2+ and as-synthesized blue phosphor with a 380 nm n-UV LED chip, which exhibits high color-rendering index (CRI = 90) and low correlated color temperature (CCT = 3301 K). These results demonstrate that the outstanding CsBaB9O15:Eu2+ blue phosphor could be a candidate for next-generation healthy WLED lighting.