Highly efficient green phosphor Ca₄La(PO₄)₃O:Eu²⁺,Tb³⁺ for white LEDs

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