Non-rare-earth dual green and red-emitting Mn-doped ZnAl2O4 phosphors for potential application in plan-growth LEDs

Non-rare-earth dual green and red-emitting Mn-doped ZnAl2O4 phosphors were successfully synthesized by a co-precipitation method. XRD and XPS spectra reveal that Mn ions in two valence states Mn2+ and Mn4+ are co-existed in the ZnAl2O4 host lattice. The ZnAl2O4:(Mn2+, Mn4+) phosphors exhibit two intense emission bands in the green and red spectral regions, peaking at 510 and 679 nm. It is demonstrated that the PL intensity ratio of green emission and red emission (I-Green/I-red) can simply be controlled by adjusting the annealing temperature and found to vary from 2.78 to 0.48 when increasing the temperature from 1200 to 1400 degrees C. A prototype red-emitting LED was fabricated using a 310-nm UV LED combined with the ZnAl2O4:0.5% (Mn2+, Mn4+) phosphor. The CIE color coordinates are x = 0.5643 and y = 0.2798, while the red-emitting LED is driven by 60 mA current. The quantum efficiency (QE) of the ZnAl2O4:0.5%Mn phosphor is estimated to be about 27.3%. To the best of our knowledge, this is the first time that the QE of Mn-doped ZnAl2O4 phosphor is reported. (C) 2020 Elsevier B.V. All rights reserved.