White light emitting diode by using α-Ca_2P_2O_7:Eu~(2+), Mn~(2+) phosphor

摘要

The α-Ca_2P_2O_7: Eu~(2+), Mn~(2+) phosphors show two emission bands peaking at around 416 (blue) and 600 nm (orange), originating from the allowed f-d transition of Eu~(2+) and the forbidden ~4T_1-~6A_1 transition of Mn~(2+), respectively, under near ultraviolet (UV) excitation at 400 nm. Spectroscopy and fluorescence lifetime measurements demonstrate that energy transfer from Eu~(2+) to Mn~(2+) performs with transfer efficiency as high as 65% for Mn~(2+) 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-Ca_2P_2O_7: Eu~(2+), Mn~(2+) blue-orange phosphor and Ba_2SiO_4: Eu~(2+) green phosphor) into a single package. The white LED shows color rendering index of 78, luminescent efficiency of 9 lm/W, and low color point variation against forward-bias currents.