High performance red/deep-red emitting phosphors for white LEDs

Abstract

Highly efficient oxide-based red line emitters are still a bottleneck for smart white LEDs. In the present investigation, sequences of narrow band red emitting phosphors were synthesized via the conventional solid-state technique. The X-ray diffraction studies revealed that the as-synthesized phosphors were crystallized in the trigonal phase with the space group I4₁/a (88). Under 395 nm excitation, NaSrGd(MoO₄)₃:Eu³⁺ phosphors showed sharp red emission at about 616 nm because of the ⁵D₀ → ⁷F₂ transition (ED transition). Moreover, the internal quantum efficiency (IQE) was found to be 82%, and the thermal stability study showed that the NaSrGd_0.5Eu_0.5(MoO₄)₃ phosphor retains the emission intensity of about 71.5% of its initial room temperature intensity at 423 K. The red LEDs were designed for the NaSrGd_0.5Eu_0.5(MoO₄)₃ red phosphors with the NUV LED chip. White LED was also fabricated by conjugating the blue LED with yellow dye + red phosphor and the LED showed CCT (6823 K), CRI (74%), and CIE (0.306, 0.331). The Sm³⁺ and Eu³⁺ co-doped deep red phosphor was synthesized and studied in plant growth. The LED emission of Sm³⁺ and Eu³⁺ co-doped phosphor completely covers the absorption spectrum of Phytochrome Pr. All of these consequences revealed that the as-synthesized phosphor could be an efficient red emitting phosphor for warm white LEDs with application in plant growth research.