Highly Efficient Green PhosphorCa4La(PO4)3O:Eu2+,Tb3+for white LEDs

Abstract

Although the green light emission of Tb3+ ions is able to be effectively improved by utilizing the energy transfer from Eu2+ to Tb3+ ions, obtaining phosphors with high quantum efficiency still remains as a big problem. Here, we achieved a novel type of apatite structure Ca4La(PO4)3O (CLPO) containing Eu2+ and Tb3+ ions. The CLPO:Eu2+ is capable of effectively excited by the near-ultraviolet light and emits blue light at about 460 nm. The energy transfer from the Eu2+ to Tb3+ ions in CLPO:Eu2+,Tb3+ can be readily constructed by utilizing the energy transfer from the Eu2+ to Tb3+ ions. The optimized phosphor CLPO:0.02Eu2+,0.7Tb3+ has a great internal quantum efficiency of 96.6% and an external quantum efficiency of 64.7%. CLPO:0.02Eu2+,0.7Tb3+, commercially available blue and red phosphors were coupled with a 365 nm chip package to form the WLEDs, presenting a nice Ra value (89.9) and a correlated color temperature (3808 K). Our work points out the avenue to realize novel and efficient green phosphors by selecting suitable hosts and constructing efficient energy transfer.