Ultrahigh-Energy-Transfer Efficiency and Efficient Mn<sup>2+</sup> Red Emission Realized by Structural Confinement in Ca<sub>9</sub>LiMn(PO<sub>4</sub>)<sub>7</sub>:Eu<sup>2+</sup>,Tb<sup>3+</sup> Phosphor
Xinguo Zhang, Jiabao Luo, Zishan Sun, Weiying Zhou, Zhan‐Chao Wu, Jilin Zhang
Abstract
Structural confinement on Eu2+–Mn2+ optical centers is an effective strategy to boost Mn2+ red emission. On the basis of the Ca9LiMn(PO4)7 (CLMP) host with a compact Eu2+–Mn2+ distance of ∼3.5 Å, a pure and intense Mn2+ red emission without seeing Eu2+ emission is realized, indicating that an ultrahigh energy transfer (ET) could be induced by a structural confinement effect. It is found that the Mn2+ emission intensity and quantum efficiency could be further improved by a Tb3+ bridging effect, which offers extra energy levels to reduce the energetic mismatch between the excited states of Eu2+ and Mn2+. The optimal sample CLMP:0.02Eu2+,0.90Tb3+ shows a promising performance in terms of high color purity (93.9%), high quantum efficiency (QE = 51.2%), and good thermal stability (70% of the room-temperature value at 373 K). All of the results demonstrate that CLMP:Eu2+,Tb3+ phosphor is a promising red-light-emitting-diode phosphor, and the structural confinement effect should be developed as a general strategy to enhance the ET efficiency for a pure and efficient emission.