Upconversion Luminescence and Temperature Sensing Properties of Layered BiOCl: Er3+ under 1550 nm Excitation

The sensitivity of optical temperature sensing based on the conventional rare-earth ion doped upconversion (UC) materials is limited by the energy gap between thermally coupled levels (TCLs) of rare-earth ions. Therefore, it is of great theoretical and technical interest to explore UC luminescent materials for optical temperature sensing with ultra-sensitive temperature characteristic. In this work, the UC luminescence properties and temperature sensing characteristics were studied for Er3+ single-doped BiOCl excited by 1550 nm laser. Under near-infrared (NIR) excitation, BiOCl:Er3+ exhibits strong red emission at 670 nm, weak green emissions at 525 and 542 nm, extremely weak violet emission at 406 nm, and near-infrared emission at 983 nm. Red and green emissions of the UC system exhibit strong temperature dependence, and in the temperature range of 300 563 K, the maximum absolute sensitivity (S-A) obtained by employing the non-thermally coupled levels (NTCLs, F-4(9/2)/S-4(3/2)) is 95.3x10(-3) K-1, which is 21 times more than that obtained by employing the thermally coupled levels (TCLs,H-2(11/2)/S-4(3/2)), and the maximum relative sensitivity (S-R) is as high as 1.19% K-1. The results show that the intense red UC luminescence and temperature sensing with ultra-high sensitivity in BiOCl:Er3+ under 1550 nm excitation may have potential application prospect in display and optical temperature sensing.