Energy harvesting and conversion mechanisms for intrinsic upconverted mechano-persistent luminescence in CaZnOS

We interpreted the mechanisms of energy harvesting and conversion for intrinsic upconverted mechano-persistent luminescence in CaZnOS through a native point defects study. We found that vacancy defects such as Zn and O vacancies, as well as Schottky pair defects, act as energy harvesting centers; they are very readily formed and very active. They are found to be extra deep electron or hole trap levels near the valence or conduction band edges, respectively. This leads to a coupling and exchange effect to continuously collect and transport host charges along a path via localized states to deep recombination levels. The initiating energy barrier is small and can be overcome by ambient thermal stimulation or quantum tunneling. Native activators such as V2+O, V2+ZnO, and V2+CaZnOS function as energy conversion centers to transfer energy into photon emissions. This gives a solid theoretical reference for developing upconverted mechano-persistent luminescence.