Department of Chemistry, National Taiwan University , Taipei 106, Taiwan.
Centre for Science at Extreme Conditions and School of Chemistry, University of Edinburgh , King's Buildings, Mayfield Road, EH9 3JZ Edinburgh, U.K.
J Am Chem Soc. 2017 Aug 30;139(34):11766-11770. doi: 10.1021/jacs.7b04338. Epub 2017 Aug 16.
Optimizing properties of phosphors for use in white-light-emitting diodes (WLEDs) is an important materials challenge. Most phosphors have a low level of lattice disorder due to mismatch between the host and activator cations. Here we show that deliberate introduction of high levels of cation disorder leads to significant improvements in quantum efficiency, stability to thermal quenching, and emission lifetime in Sr(CaBa)SiN:Eu (x = 0-1.5) phosphors. Replacing Sr by a (CaBa) mixture with the same average radius increases cation size variance, resulting in photoluminescence emission increases of 20-26% for the x = 1.5 sample relative to the x = 0 parent across the 25-200 °C range that spans WLED working temperatures. Cation disorder suppresses nonradiative processes through disruption of lattice vibrations and creates deep traps that release electrons to compensate for thermal quenching. Introduction of high levels of cation disorder may thus be a very useful general approach for improving the efficiency of luminescent materials.
优化用于白光发光二极管 (WLED) 的荧光粉性能是一项重要的材料挑战。由于主体和激活剂阳离子之间的不匹配，大多数荧光粉的晶格无序程度较低。在这里，我们表明，故意引入高水平的阳离子无序会导致 Sr(CaBa)SiN:Eu (x = 0-1.5) 荧光粉的量子效率、热猝灭稳定性和发射寿命得到显著提高。用具有相同平均半径的 (CaBa) 混合物代替 Sr 会增加阳离子尺寸方差，导致 x = 1.5 样品的光致发光发射相对于 25-200°C 范围内跨越 WLED 工作温度的 x = 0 母体增加 20-26%。阳离子无序通过破坏晶格振动抑制非辐射过程，并产生深陷阱，释放电子以补偿热猝灭。因此，引入高水平的阳离子无序可能是提高发光材料效率的一种非常有用的通用方法。
