A novel red phosphor Cs2NaGaF6:Mn4+ with ultra-strong zero-phonon lines and long wavelength phonon sidebands for high-quality WLEDs. Issue 17 (4th April 2023)

• Record Type: Journal Article
• Authors: Liao, Zhijian; Li, Yan; Zuo, Jiaxing; Chen, Guang; Liang, Heng; Wu, Shihao; Peng, Jiaqing; Ye, Xinyu
• Is Part Of: Dalton transactions. Volume 52:Issue 17(2023)
• Page Start: 5587
• Page End: 5596
• Publication Date: 2023-04-04
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d2dt03890k
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The novel Cs2 NaGaF6 :Mn 4+ fluoride red phosphor has ultra-strong zero-phonon lines and long-wavelength phonon sidebands with large x chromaticity coordinate, which enables high lumen efficiency and wide color gamut for WLEDs. Abstract : For high-efficiency lighting and wide color gamut backlight display, high-quality narrow-band red phosphors for WLEDs are still in high demand. Herein, a novel red-emitting fluoride phosphor Cs2 NaGaF6 :Mn 4+ was successfully synthesized by a simple two-step co-precipitation method and exhibits ultra-intense zero-phonon lines (ZPLs) and long wavelength phonon sidebands under 468 nm blue light irradiation. The ZPL emission peak of Cs2 NaGaF6 :Mn 4+ was located at 627 nm, which is much stronger than its υ6 vibration peak, more matchable with the eye-sensitive region of humans, and beneficial for obtaining higher luminous efficiency of WLEDs. Interestingly, the υ6 vibration peak of this red phosphor is at 636.5 nm, which is larger than that of the common fluoride phosphor A2 BF6 :Mn 4+ (usually at about 630 nm, represented by K2 SiF6 :Mn 4+ ) at about 6.5 nm. Thanks to the longer wavelength of the υ6 vibration peak, the chromaticity coordinates (0.7026, 0.2910) with a larger x -coordinate value were realized, leading to a potentially wider color gamut of WLEDs. In addition, this phosphor has high thermal stability and its emission intensity at 423 K remains 93.7% of the initial intensity at room temperature. The lumen efficiency of WLED1 packaged with a mixture of Cs2 NaGaF6 :Mn 4+ and YAG:Ce 3+ on the InGaN blue chip is 115.7 lm W −1 with the color temperature ( T c ) = 3390 K and the colour rendering index ( R a ) = 92.5 under 20 mA driving current. The chromaticity coordinates of WLED2 packaged with Cs2 NaGaF6 :Mn 4+ and β-SiAlON:Eu 2+ on the InGaN blue chip are (0.3149, 0.3262) and the calculated color gamut is up to 118.4% (NTSC). These results indicate that Cs2 NaGaF6 :Mn 4+ red phosphors have promising applications in the high-quality lighting and display fields.