Waterproof Alkyl Phosphate Coated Fluoride Phosphors for Optoelectronic Materials

Abstract

A facile approach for coating red fluoride phosphors with a moisture-resistant alkyl phosphate layer with a thickness of 50-100 nm is reported. K2 SiF6 :Mn(4+) particles were prepared by co-precipitation and then coated by esterification of P2 O5 with alcohols (methanol, ethanol, and isopropanol). This route was adopted to encapsulate the prepared phosphors using transition-metal ions as cross-linkers between the alkyl phosphate moieties. The coated phosphor particles exhibited a high water tolerance and retained approximately 87 % of their initial external quantum efficiency after aging under high-humidity (85 %) and high-temperature (85 °C) conditions for one month. Warm white-light-emitting diodes that consisted of blue InGaN chips, the prepared K2 SiF6 :Mn(4+) phosphors, and either yellow Y3 Al5 O12 :Ce(3+) phosphors or green β-SiAlON: Eu(2+) phosphors showed excellent color rendition.

Optical performance of Mn4+in a new hexa-coordinated fluorozirconate complex of Cs2ZrF6

“…This is a typical property of Mn 4+ activated fluoride red phosphor, and the red emissions originate from the spin-forbidden 2 E g → 4 A 2g transition. 19,20 Close inspection of the tips on this spectrum, we can find that it is composed of five strong peaks, which are attributable the anti-stokes ν 4 , ν 6 and stokes ν 6 , ν 4 and ν 3 vibronic emissions respectively, and the ZPL emission is hardly observed. 14 Therefore, the properties of wide blue-excitation and sharp red-emission for the as-prepared Cs 2 Fig.…”

“…In this kind of WLED, although the YAG phosphor can effectively absorbs blue light excited from GaN chip, 4,5 the possessed white light exhibits high correlated colour temperature (CCT, T c > 6000 K) and low colour rendering index (CRI, R a < 80) properties because of the absence of red light components, resulting in the white light cold and hard to be used in indoor illumination. 6,7 In order to obtain warm white light, considerable efforts have been devoted to constructing different kinds of red phosphor, typically Bi 3+ doped yttrium- 2+ . Although these materials exhibit fascinating luminescence properties, the harsh preparation process and broad emission band limit their further application in WLEDs.…”

Co-Precipitation Synthesis and Optical Properties of Mn4+-Doped Hexafluoroaluminate w-LED Phosphors

“…The deep red color of the 600–640 nm Mn 4+ emission is particularly favorable for extending the color gamut of displays, and KSF is already widely applied in displays. In lighting, large-scale application is still limited, partly hampered by issues related to thermal and chemical stability and saturation at high pump powers [14,16]. …”

Comparative analysis on the photoluminescence properties of Cs2BF6:Mn4+ (B = Ge, Si, Zr, Ti) red phosphors for WLEDs

“…The Mn 4+ ‐activated fluoride phosphors have been attracted more and more attentions recently . Mn 4+ is a transition metal ion with 3d 3 external electronic structure.…”