High efficiency white emission in Na3Ba2Ca(PO4)3:Eu2+, Mn2+ phosphors for urban ecological lighting

The white-light-emitting devices (WLEDs) for urban ecological lighting remain the challenge. The current urban lighting system destroys the growth habits of plants and leads to inhibition of plant growth, reduced branching, smaller leaf area and reduced total dry weight due to excessive blue light. In this work, a series of blue-green and red dual-emission Na3Ba2Ca(PO4)3:Eu2+, Mn2+ phosphors have been successfully synthesized by the high-temperature solid-state reaction method. The crystal structure, the occupancy of the dopant ions and the luminescence characteristics were carefully investigated. The excitation and emission spectra as well as the decay lifetime confirm the effective energy transfer from Eu2+ to Mn2+, which leads to a tunable luminescence with greatly reduced blue emission. Especially, the optimal Na3Ba2Ca(PO4)3:0.02Eu2+, 0.11Mn2+ phosphor demonstrates a high internal quantum yield of 99.7%. At 150 °C, the luminescence intensity of Na3Ba2Ca(PO4)3:0.02Eu2+, 0.11Mn2+ can maintain 64.5% of room temperature intensity. In addition, the WLED device fabricated with Na3Ba2Ca(PO4)3:Eu2+, Mn2+ phosphor shows white light emission with CIE coordinates of (0.3800, 0.3852), rendering index (Ra) of 65.4 and correlated color temperature (CCT) of 3640 K. These results confirm that the Na3Ba2Ca(PO4)3:Eu2+, Mn2+ phosphor can be applied as a white light source in the urban ecological field.