White light emitting diode by using α- Ca₂ P₂ O₇: Eu²⁺, Mn²⁺ phosphor

The α- Ca2 P2 O7: Eu2+, Mn2+ phosphors show two emission bands peaking at around 416 (blue) and 600 nm (orange), originating from the allowed f-d transition of Eu2+ and the forbidden T14 - A16 transition of Mn2+, respectively, under near ultraviolet (UV) excitation at 400 nm. Spectroscopy and fluorescence lifetime measurements demonstrate that energy transfer from Eu2+ to Mn2+ performs with transfer efficiency as high as 65% for Mn2+ concentration of 12 mol %. The authors have fabricated a white light emitting diode (LED) through the integration of GaN near-UV chip and two phosphor blends (α- Ca2 P2 O7: Eu2+, Mn2+ blue-orange phosphor and Ba2 Si O4: Eu2+ green phosphor) into a single package. The white LED shows color rendering index of 78, luminescent efficiency of 9 lmW, and low color point variation against forward-bias currents.