Ca9La(PO4)7:Eu2+,Mn2+: an emission-tunable phosphor through efficient energy transfer for white light-emitting diodes

We have synthesized a series of single-composition emission-tunable Ca9La(PO4)(7):Eu2+,Mn2+ (CLP:Eu2+,Mn2+) phosphors by solid state reactions. Through an effective resonance-type energy transfer, the CLP:Eu2+,Mn2+ phosphors exhibit a systematically varied hues from green, yellow, and eventually to red and the relative intensity of green and red emissions can be tuned by adjusting the concentration of Mn2+, respectively. The energy transfer from Eu2+ to Mn2+ in CLP:Eu2+,Mn2+ has been studied and demonstrated to be a resonant type via a dipole-quadrupole mechanism based on the decay lifetime data and the energy transfer critical distance was estimated to be 11.36 angstrom by using the spectral overlap methods. A warm white light emitting diode (WLED) with CIE chromaticity coordinates of (0.35, 0.31), superior color-rendering index (Ra) of 91.5 and lower correlated color temperature (CCT) of 4,496 K was fabricated by combining a 365 nm UV-InGaN chip and a phosphor blend of yellow-emitting (Ca0.98Eu0.005Mn0.015)(9)La(PO4)(7) and blue-emitting BaMgAl10O17:Eu2+. (C) 2010 Optical Society of America