Effect of Defect States on the Upconversion Emission Properties in KLu2F7 Nanocrystalline

The influence of the introduction of Li+ ions on the upconversion (UC) properties of KLu2F7:Yb3+, Er3+ nanocrystalline has been investigated in detail. It is found that the UC emission intensity of 10 mol% Li+ ions doped KLu2F7:Yb3+, Er3+ nanocrystalline is enhanced about 13 times in comparison with that of Li+-free sample. Under the excitation of 980 nm laser diode (LD), a significant improvement of the green to red emission ratio (GRR) in the 10 mol% Li+-doped sample is observed by increasing pump power density. Li+ ions could occupy the cationic sites or the interstitial sites in the KLu2F7 host matrix, which probably eliminate the defect states via the charge compensation and tailor of the crystal field, leading to the promotion of the UC emission efficiency. Thus, the introduction of Li+ ions provides new opportunities for enhancing the scope of applications of Yb3+, Er3+ doped KLu2F7 nanocrystalline ranging from infrared solar cells to volumetric multiplexed bio-probe.