Luminescence properties and high energy transfer of Ca9MgNa (PO4)7: Eu2+, Mn2+ blue-red dual emission phosphor for plant growth LEDs

Abstract

The Ca9MgNa(PO4)7: Eu2+, Mn2+ (CMNPO: Eu2+, Mn2+) phosphors were successfully prepared via high-temperature solid-phase method. Under near ultraviolet light (n-UV) excitation, CMNPO: Eu2+, Mn2+ phosphor exhibits blue and red double emissions centered at 419 nm and 642 nm due to Eu2+: 5d → 4f transition and Mn2+: 4T1(4G) → 6A1(6S) transition, respectively, which match well with the chlorophyll a and b absorption spectrum required for plant growth. The energy transfer (ET) efficiency between Eu2+ and Mn2+ ions was analyzed and is as high as 90.0%. Besides, the luminescence mechanism and ET process of the phosphors were explained according to the simple energy level diagram of Eu2+ and Mn2+ ions. In addition, it was also found that the phosphor has good thermal stability (the luminescence intensity maintains 77.4% at 423 K). Finally, a LED device was packaged with the obtained phosphor Ca9MgNa(PO4)7: 0.03Eu2+, 0.23Mn2+ and a commercial 365 nm n-UV chip, and the corresponding color rendering index Ra and the correlated color temperature (CCT) is 83.6 and 1842 K, respectively. The results show that the optimized phosphor has good application potential in plant cultivation LEDs.