Realizing thermal and moisture stability in the K2Ge1-Ti F6:Mn4+ red phosphors with high efficiency for WLEDs

An Al3+-incorporated Ca2LuNbO6:Mn4+ oxide phosphor with dramatic deep-red and far-red emission bands

“…Compared to traditional lighting, pc-LEDs offer advantages such as low energy consumption, long fluorescence lifetime, and spectral customization. 3–5…”

Highly Moisture-Stable and Enhanced Luminescence-Efficient Mn4+-Activated Red-Emitting Fluoride Phosphors via a Bi-hydrogen-Bond Organic Coating

“…Various strategies have been reported to improve the moisture resistance of Mn 4+activated fluoride phosphors and can be roughly classified into organic coating, inorganic heterogeneous/homogeneous coating, surface deactivation and cation substitution, etc. 13,15,16 Various inorganic compounds, such as TiO 2 , 17 Al 2 O 3 , 17,18 CaF 2 , 19,20 and SrF 2 21 have been used to form a heterogeneous protective layer to improve moisture resistance for fluoride phosphors but at the expense of sacrificing the luminescence efficiency generally due to surface defects and nonradiative decay probability induced by the differences of physicochemical properties between inner phosphors and the coating layer. 14 Moreover, an inorganic coating generally needs a gas-phase deposition technique or highly toxic HF as solvent to form an inorganic layer on the surface of phosphors, and synthesis processes are complex, polluting, and unsafe.…”

“…Therefore, it is necessary to improve the moisture resistance of Mn 4+ -activated fluoride phosphors. Various strategies have been reported to improve the moisture resistance of Mn 4+ -activated fluoride phosphors and can be roughly classified into organic coating, inorganic heterogeneous/homogeneous coating, surface deactivation and cation substitution, etc. ,, Various inorganic compounds, such as TiO 2 , Al 2 O 3 , , CaF 2 , , and SrF 2 have been used to form a heterogeneous protective layer to improve moisture resistance for fluoride phosphors but at the expense of sacrificing the luminescence efficiency generally due to surface defects and nonradiative decay probability induced by the differences of physicochemical properties between inner phosphors and the coating layer . Moreover, an inorganic coating generally needs a gas-phase deposition technique or highly toxic HF as solvent to form an inorganic layer on the surface of phosphors, and synthesis processes are complex, polluting, and unsafe. , An inorganic homogeneous coating and surface deactivation were developed to construct a Mn 4+ -free or Mn 4+ -rare A 2 XF 6 fluoride matrix shell on the surface of phosphors to isolate the [MnF 6 ] 2– clusters from water and enhance the moisture resistance. − Due to the same physicochemical properties between inner phosphors and protective layers, a homogeneous coating and surface deactivation would not scarify the luminescence efficiency .…”