Highly Moisture-Stable and Enhanced Luminescence-Efficient Mn<sup>4+</sup>-Activated Red-Emitting Fluoride Phosphors via a Bi-hydrogen-Bond Organic Coating
Chang Chen, Wanggui Ye, Chuandong Zuo, Yingkui Li, Zicheng Wen, Liwei Guo, Yongge Cao, Chaoyang Ma
Abstract
A facile and eco-friendly ethanol-thermal method has been developed to improve the moisture resistance and luminescence efficiency of Mn 4+ -activated fluoride phosphors using oleylamine (OAm) as an organic coating layer. The luminescence efficiency of K 2 SiF 6:Mn 4+ phosphors was significantly enhanced after coating with the internal quantum efficiency increasing from 86.2 to 94.2%. Additionally, after being soaked in deionized water, the luminescence intensity of KSFM@OAm remained at 85.2% of its initial value, while that of non-coated KSFM decreased to 15.4%. This is due to the formation of a complete and uniform OAm coating layer that isolates KSFM crystals from humidity in the environment by forming bi-hydrogen bonds (−N–H···F) between −NH 2 in OAm and fluorine-terminal groups in KSFM. White light-emitting devices fabricated with commercial Y 3 Al 5 O 12:Ce 3+ and OAm-coated KSFM exhibit bright white light with an excellent correlated-color temperature (CCT = 4546 K), color rendering index (Ra = 89.7 and R9 = 85), luminous efficiency (LE = 155.1 lm/W), and color stability (Δ E = 6.1 × 10 –3 ), indicating that OAm-coated KSFM may be a promising red phosphor for WLEDs.