Xiang Guotao, Ma Yan, Liu Wen, Jiang Sha, Luo Xiaobing, Li Li, Zhou Xianju, Gu Zhiwei, Wang Jiapeng, Luo Yongshi, Zhang Jiahua
Department of Mathematics and Physics, Chongqing University of Posts and Telecommunications , 2 Chongwen Road, Chongqing 400065, People's Republic of China.
State Key Laboratory of Luminescence and Applications, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences , 3888 Eastern South Lake Road, Changchun 130033, People's Republic of China.
Inorg Chem. 2017 Aug 7;56(15):9194-9199. doi: 10.1021/acs.inorgchem.7b01236. Epub 2017 Jul 12.
The monochromaticity improvement of green upconversion (UC) in LuO:Yb/Ho powders has been successfully realized by tridoping Eu. The integral area ratio of green emission to red emission of Ho increases 4.3 times with increasing Eu doping concentration from 0 to 20 mol %. The energy transfer (ET) mechanism in the Yb/Ho/Eu tridoping system has been investigated carefully by visible and near-infrared (NIR) emission spectra along with the decay curves, revealing the existence of ET from the HoF/S level tothe EuD level and ET from the HoI level to the EuF level. In addition, the population routes of the red-emitting HoF level in the Yb/Ho codoped system under 980 nm wavelength excitation have also been explored. The ET process from the YbF level to the HoI level and the cross-relaxation process between two nearby Ho ions in the F/S level and I level, respectively, have been demonstrated to be the dominant approaches for populating the HoF level. The multiphonon relaxation process originating from the HoF/S level is useless to populate the HoF level. As the energy level gap between the HoI level and HoI level matches well with that between EuF level and EuF level, the energy of the HoI level can be easily transferred to the EuF level by an approximate resonant ET process, resulting in a serious decrease in the red UC emission intensity. Since this ET process is more efficient than the ET from the HoF/S level to the EuD level as well as the ET from the HoI level to the EuF level, the integral area ratio of green emission to red emission of Ho has been improved significantly.
通过三掺杂铕，成功实现了LuO:Yb/Ho粉末中绿色上转换（UC）的单色性改善。随着铕掺杂浓度从0增加到20 mol%，Ho的绿色发射与红色发射的积分面积比增加了4.3倍。通过可见和近红外（NIR）发射光谱以及衰减曲线，仔细研究了Yb/Ho/Eu三掺杂体系中的能量转移（ET）机制，揭示了从HoF/S能级到EuD能级以及从HoI能级到EuF能级的ET的存在。此外，还探索了在980 nm波长激发下Yb/Ho共掺杂体系中红色发射HoF能级的布居途径。已证明从YbF能级到HoI能级的ET过程以及在F/S能级和I能级中两个相邻Ho离子之间的交叉弛豫过程分别是布居HoF能级的主要途径。源自HoF/S能级的多声子弛豫过程对布居HoF能级无用。由于HoI能级与HoI能级之间的能级间隙与EuF能级与EuF能级之间的能级间隙匹配良好，HoI能级的能量可以通过近似共振ET过程轻松转移到EuF能级，导致红色UC发射强度严重降低。由于该ET过程比从HoF/S能级到EuD能级以及从HoI能级到EuF能级的ET更有效，Ho的绿色发射与红色发射的积分面积比得到了显著提高。
