| Abstract Scope |
Ho-based lead-free double perovskite microcrystals (MCs), Cs2NaHo1-xYbxCl6, were synthesized and demonstrated to be the most promising optical temperature sensing materials by understanding the concentration-dependent upconversion (UC) luminescence mechanisms. By optimizing the dopant concentration, a dominant emission shifting from red to green was successfully achieved in an activator-rich system. During this process, the red to green emission intensity ratio (R/G) can be changed from 12.5 to 0.14. We clarified that the cross-relaxation (CR) process between activator and the energy transfer process between Yb3+ and Ho3+ are the key mechanisms of UC luminescence intensity and R/G ratio variation. Moreover, the intensity of red and green UC emission shows strong dependence on temperature, resulted from the competition between CR and energy transfer in the emission levels. The multicolor UC luminescence quantitative modeling mentioned here is crucial for understanding the concentration-dependence UC luminescence characteristics and to optimize the design of the Ho-based thermometer. |