Huang Xinyang, Xiong Liang, Yu Lin, Gao Xiaohui, Qiu Xiaoqing
Institute of Research on the Functional Materials, Jiangxi University of Finance and Economy, Nanchang Jiangxi 330013, P. R. China.
College of Chemistry and Chemical Engineering, Central South University, Changsha, Hunan 410083, P. R. China.
Inorg Chem. 2020 Jun 1;59(11):7752-7760. doi: 10.1021/acs.inorgchem.0c00799. Epub 2020 May 20.
Concentration quenching of upconversion (UC) luminescence (UCL) is a common phenomenon in rare-earth-doped materials that seriously restricts the concentration of the activator and sensitizer and withholds their UC emissions and quantum yields. In particular, it remains a tremendous challenge to develop one novel strategy based on the introduction of trivalent bismuth (Bi) ions to exceed the typical thulium (Tm) ion concentration and reach high-efficiency UC under low illumination. In this work, the Tm accommodation capacity can be increased from 2.0 to 8.0 mol % in NaYbF:Tm materials with the assistance of Bi ions, which maintains strong UC emissions with large absolute UC quantum yields under low illumination. Specifically, the total upconversion quantum yield (UCQY) of the as-obtained Na(TmYbBi)F (8Tm60Yb32Bi) sample can reach as high as 1.45% upon continuous-wave (CW) laser excitation at 40 W cm. Strikingly, the total UCQY still remains at a high level (0.41%) even though the CW power density decreases to 1.5 W cm. Moreover, the intrinsic mechanism of the breakthrough in the threshold of concentration quenching of UCL by Bi ions was also fully explored. These advances in enhancing UC emissions and UCQYs under a low pump power density offer exciting opportunities for important photonic applications.
上转换（UC）发光（UCL）的浓度猝灭是稀土掺杂材料中的常见现象，严重限制了激活剂和敏化剂的浓度，并抑制了它们的UC发射和量子产率。特别是，基于引入三价铋（Bi）离子来突破典型的铥（Tm）离子浓度限制并在低光照下实现高效UC，仍然是一个巨大的挑战。在这项工作中，在Bi离子的辅助下，NaYbF:Tm材料中的Tm容纳量可从2.0摩尔％提高到8.0摩尔％，该材料在低光照下保持强烈的UC发射和高绝对UC量子产率。具体而言，所制备的Na(TmYbBi)F（8Tm60Yb32Bi）样品在40 W cm的连续波（CW）激光激发下，其总上转换量子产率（UCQY）可高达1.45％。令人惊讶的是，即使CW功率密度降至1.5 W cm，总UCQY仍保持在较高水平（0.41％）。此外，还充分探索了Bi离子突破UCL浓度猝灭阈值的内在机制。这些在低泵浦功率密度下增强UC发射和UCQY的进展为重要的光子应用提供了令人兴奋的机会。
