Waterproof Narrow-Band Fluoride Red Phosphor K₂TiF₆:Mn⁴⁺ via Facile Superhydrophobic Surface Modification

Abstract

With unique and efficient narrow-band red emission and broadband blue light absorption characteristics, Mn-activated fluoride red phosphors have gained increasing attention in warm white LEDs (WLEDs) and liquid crystal display (LCD) backlighting applications, whereas the intrinsic hygroscopic nature of these phosphors have inevitably limited their practical applications. Herein, a waterproof narrow-band fluoride phosphor KTiF:Mn (KTF) has been demonstrated via a facile superhydrophobic surface-modification strategy. With the use of superhydrophobic surface modification with octadecyltrimethoxysilane (ODTMS) on KTF surfaces, the moisture-resistance performance and thermal stability of the phosphor KTF can be significantly improved. Meanwhile, the absorption, and quantum efficiency did not show obvious changes. The surface-modification processes and mechanism, as well as moisture-resistance performances and luminescence properties, of the phosphors have been carefully investigated. It was found that the luminous efficiency (LE) of the modified KTF was maintained at 83.9% or 84.3% after being dispersed in water for 2 h or aged at high temperature (85 °C) and high humidity (85%) atmosphere (HTHH) for 240 h, respectively. The WLEDs fabricated with modified KTF phosphor showed excellent color rendition with lower color temperature (2736 K), higher color rendering index (CRI, Ra = 87.3, R9 = 80.6), and high luminous efficiency (LE = 100.6 lm/W) at 300 mA. These results indicate that hydrophobic silane coupling agent (SCA) surface modification was a promising strategy for enhancing moisture resistance of humidity-sensitive phosphors, exhibiting great potential for practical applications.

Next‐Generation Narrow‐Band Green‐Emitting RbLi(Li3SiO4)2:Eu2+ Phosphor for Backlight Display Application

“…Figure S8 (Supporting Information) shows the PL spectra, integrated emission intensities, and the corresponding digital photographs of the pristine RLSO:Eu 2+ and the samples exposed to 80% RH, 80 °C environment for different times. The emission intensity dropped to 13% of that of pristine sample after 1 h. These results indicate that the chemical stability of RLSO:Eu 2+ needs to be further improved, which can be achieved by the surface coating and modification techniques as elaborated in other systems …”

A Reverse Strategy to Restore the Moisture‐deteriorated Luminescence Properties and Improve the Humidity Resistance of Mn4+‐doped Fluoride Phosphors

“…However, the thermal stability of K 2 SiF 6 : Mn 4 + -OA phosphor was limited to 200°C, because of the decomposition reaction and thermal instability of OA layer. Zhang et al [23] modified K 2 TiF 6 : Mn 4 + surfaces by using super-hydrophobic surface with Octadecyltrimethoxysilane (OD). The luminescence intensity of OD-K 2 TiF 6 : Mn 4 + maintained 95.7% of the original intensity of K 2 TiF 6 : Mn 4 + .…”

Narrow‐Band Red‐Emitting Phosphor K2SiF6:Mn4+: HF‐Free Synthesis, Surface Modification, and Application for Warm White LEDs

“…85–1382) and space group O 5 h‐Fm3 m. The FTIR spectra was used to characterize the functional groups on the surface of coated KSFM‐1 phosphor, as shown in Figure b. The bands at 2924 cm −1 were attributed to the C−H group vibration of ODTMS . The KSFM‐1 without modification had very strong absorption peaks at 3443 and 1640 cm −1 , which were on account of the O−H stretching and H−O‐H bending of undissociated water molecules .…”