RESUMEN
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 Cs2NaGaF6:Mn4+ 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 Cs2NaGaF6:Mn4+ 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 A2BF6:Mn4+ (usually at about 630 nm, represented by K2SiF6:Mn4+) 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 Cs2NaGaF6:Mn4+ and YAG:Ce3+ on the InGaN blue chip is 115.7 lm W-1 with the color temperature (Tc) = 3390 K and the colour rendering index (Ra) = 92.5 under 20 mA driving current. The chromaticity coordinates of WLED2 packaged with Cs2NaGaF6:Mn4+ and ß-SiAlON:Eu2+ 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 Cs2NaGaF6:Mn4+ red phosphors have promising applications in the high-quality lighting and display fields.
RESUMEN
Phosphor-converted light-emitting diodes (pc-LEDs) have important applications in security surveillance and food testing. However, developing new broadband near-infrared phosphors remains an important issue. Herein, the high-temperature solid-state reaction method was applied to synthesize a new type of Cr3+ doped Mg2Al4Si5O18 broadband NIR phosphor which matches a blue LED chip. It exhibits a broadband near-infrared (NIR) phosphor emission with a focus of 856 nm and a full width at half maximum >200 nm after excitation at 453 nm. The optimum concentration of Cr3+ was established to contain 2 mol%. At 398 K, the luminescence intensity is 45.2% of that at 298 K. The power output of NIR pc-LEDs fabricated by incorporating a 450 nm chip and the Mg2Al4Si5O18:0.02 Cr3+ phosphor is 19.69 mW at 300 mA current. Finally, the developed NIR pc-LED shows significant potential for use in night-vision imaging.