Abstract
There is an urgent need to develop phosphors with high quantum efficiencies (QEs) since white light-emitting diodes (WLEDs) have emerged as a new generation of illumination materials. Utilizing energy transfer to improve the absorption of activators and adjust the emission colors of samples is one effective strategy. Here, color-tunable phosphors of the form CaAl4O7:Ce,Tb were synthesized aiming at efficient energy transfer from Ce3+ to Tb3+. Since Tb3+ can be suitably sensitized by Ce3+, the co-doped phosphors can be effectively excited by near-ultraviolet (NUV) light. The internal QE of CaAl4O7:0.04Ce,0.04Tb under 350 nm excitation is as high as 92.55%, and the external QE is 71.02%. A WLED fabricated from BAM:Eu2+, CaAl4O7:0.04Ce,0.04Tb, and CaAlSiN3:Eu2+ with a 365 nm LED chip exhibited a correlated color temperature (CCT) of 4706 K and a color rendering index (CRI, Ra) of 81.44. The energy transfer mechanism and thermal stability of the phosphor were also investigated. The results provide an effective approach for developing highly efficient green-emitting phosphors for NUV WLEDs.
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