上转换发光材料由于低的发光效率, 限制了其在太阳电池中的实际应用。为解决此问题, 采用溶剂热法制备了LiYF4∶Er3+/Yb3+上转换发光颗粒, 在LiYF4基质中引入Na+来打破Er3+周围晶体场的对称性, 增强其发光性能。研究了Na+掺杂对LiYF4∶Er3+/Yb3+的结构、形貌及其发光的影响。结果表明: 掺杂的Na+可以裁剪Er3+周围的晶体场, 当Na+摩尔分数为15%时, 得到了较大的发光增强, 绿光和红光发射分别获得4.2倍和2.9倍的增强。Er3+周围晶体场对称性的降低和材料中OH基团的减少是其发光增强的主要原因。

The applications of the upconversion (UC) phosphors in solar cells are still constrained because of their relatively low luminescence efficiency. In this work, LiYF4∶Er3+/Yb3+ co-doped with different concentrations of Na+ was prepared by a simple and green hydrothermal procedure. The co-doping of Na+ was proposed to enhance UC luminescence of LiYF4∶Er3+/Yb3+ microcrystals. The influence of Na+ on the crystal structure, morphology and luminescence of LiYF4∶Er3+/Yb3+ was investigated. The results indicate that the co-doping of Na+ can tailor the local crystal field around Er3+. Compared with LiYF4∶Er3+/Yb3+, the green and red emission intensities of LiYF4∶Er3+/Yb3+ co-doped with 15% Na+ are enhanced by about 4.2 and 2.9 times, respectively. The distortion of the local symmetry and the reduction of OH groups are confirmed to be the origin of the improvement.