Precisely Modulating Oxygen Vacancies Via Heterovalent Ions Substitution in Spinel-Structured Phosphor for Versatile...

Rare-earth ions doped phosphors have attracted great research interests owing to their versatile applications in optoelectronic fields. The phosphors often created atom vacancies because of the heterovalent substitution and different ion radii. However, how to previously modulate the defect concentration and position in ions doped phosphor is still a great challenge and significantly important for facilitating the optical applications. Herein, the accurate modulation of oxygen vacancies in spinel-like ZnGa₂O₄ phosphors is demonstrated via Eu³⁺ doping for advanced temperature sensing and optical information encryption applications. The experimental results and first-principle calculations confirmed that more Eu³⁺ ions introduced into the lattice of ZnGa₂O₄ can lead to the generation of high concentration of oxygen vacancies as well as much deeper and wider deficient states in its electronic bandgap, which therefore endow great potential for afterglow emission. The distinct luminescence quenching between Eu³⁺ and oxygen vacancies at high temperatures verified outstanding luminescence intensity ratio modeled temperature sensing performance with maximum relative sensitivity (S_r) value of 5.96% K^-1 (@360 K) for ZnGa₂O₄:0.02Eu³⁺ sample. Moreover, by virtue of the fantastic thermal-induced afterglow luminescence, the dynamic optimal information encryption and anti-counterfeiting over the ZnGa₂O₄:Eu³⁺ phosphor have been also achieved.