High quantum efficiency far red emission from double perovskite structured CaLaMgMO6:Mn4+ (M = Nb, Ta) phosphor for UV-based light emitting diodes application

High quantum efficiencies CaLaMgM1-xO6:xMn4+ (M = Nb, Ta; 0 < x ≤ 0.006) phosphors are prepared by a solid-state reaction method, and their crystal structure and luminescence property are investigated. The excitation spectra of CaLaMgM1-xO6:Mn4+ revealed two excitation bands at 250-450 nm and 450-600 nm corresponding to 4A2 → 4T1 and 4A2 → 4T2 transition of Mn4+ ions respectively, and emission spectra cover from 650 to 800 nm with the strongest emission peak at 710 nm owing to the 4E → 4A2 transition of Mn4+ ions. The optimal Mn4+ doping concentrations for both of CaLaMgNbO6 and CaLaMgTaO6 host are determined to be 0.004 mol. The PL intensity and quantum efficiencies of the entitled phosphors excited under related UV light are investigated and compared with that of K2TiF6:Mn4+, Y2O3:Eu3+, CaAlSiN3:Eu2+ phosphors. Finally, a bright red LED was fabricated by using a 365 nm UV chip with the as-prepared CaLaMgNbO6:Mn4+ phosphor.