Luminescence and energy transfer in Eu2+ and Mn2+ Co-doped Ca2 P2 O7 for white light-emitting diodes

Eu2+ and Mn2+ co-doped α - and Β -Ca2 P2 O7 are prepared by solid-state reaction. An orange emission band originating from the T4 1 (G4) - A6 1 (S6) transition of Mn2+ is observed in both phases upon UV excitation through energy transfer from Eu2+ to Mn2+. Photoluminescence and energy transfer in α -Ca2 P2 O7: Eu2+, Mn2+ are investigated as a function of Mn2+ concentrations. The energy transfer rates are calculated based on the analysis of the luminescence dynamical process as well as fluorescence lifetime measurements. The intensity ratios of the orange to blue band as a function of Mn2+ concentrations are also calculated and the results are in good agreement with that obtained directly from emission spectra. A white light emitting diode (LED) fabricated through the integration of a GaN near-UV chip and two phosphor blends (α -Ca2 P2 O7: Eu2+, Mn2+ blue-orange phosphor and Ba2 SiO4: Eu2+ green phosphor) into a single package shows a warm white light of 3797 K correlated color temperature, a good color rendering index (CRI) of 84, and a luminescent efficiency of 11 lm/W with color coordinates of x=0.39, y=0.40. Moreover, the CRI can be improved to 94 by using blue Ca2 (PO4) 3 Cl: Eu2+ phosphor added to the two phosphor blends.