Excellent Quantum Efficiency and Superior Color Purity Red-Emitting CaAl₁₂O₁₉–CaAl₄O₇–MgAl₂O₄:Mn⁴⁺ Phosphors for Plant Growth and High Color Rendering Index White Light-Emitting Diode Applications

This work reports an excellent quantum efficiency and superior color purity CaAl12O19–CaAl4O7–MgAl2O4:Mn4+ (CCM:Mn4+) red-emitting phosphor. This phosphor can be excited by a broad excitation band ranging from 300 to 500 nm, and it generates an intense broadband red emission peaking at 656 nm. The CCM:0.5%Mn4+ phosphor-possessed superior color purity of 100%, a long lifetime of 0.49 ms, and high activation energy of 0.286 eV. Four different prototypes of plant growth light-emitting diodes (LEDs) with high quantum efficiencies of 81.8, 72.1, 67.2, and 61.1% were fabricated by coating the optimized CCM:0.5%Mn4+ phosphors onto UV (365 nm), NUV (395 nm), violet (410), and blue (460 nm) LED chips, respectively. The 81.8% and 72.1% QE values are the highest values reported for the 365 nm UV-pumped and 395 nm NUV-pumped LEDs based on Mn4+-doped oxide phosphors. Furthermore, a white LED with a high color rendering index (CRI) of 90, correlated color temperature (CCT) of 2416 K, and luminous efficacy of radiation (LER) of 216 lm/W was realized using a blue LED chip and a mixture of CCM:0.5%Mn4+ and commercial YAG:Ce3+ phosphors. Our results demonstrate great potential for using CCM:Mn4+ phosphors for plant growth LEDs and white light-emitting diode (WLED) applications