Design a novel red to near-infrared persistent phosphors of CaMgGe2O6: Mn2+, Sm3+ based on vacuum referred binding energy diagram

In this work, we designed and successfully synthesized a novel germanate-based Persistent luminescence (PersL) phosphor host, CaMgGe2O6, via a solid-state reaction. And we constructed an empirical energy level scheme of the CaMgGe2O6: Ln2+/Ln3+ phosphors according to Dorenbos model. Then we successfully theoretical predicting the choice of the optimal codopant of the CaMgGe2O6: Mn2+ phosphors by this empirical energy level scheme. As a result, after co-doping with Sm3+, the PersL intensity is increased to 16 times and the time duration are effectively improved to 52 times due to the high concentration of new traps. And the CaMgGe2O6: Mn2+,Sm3+ shows a red to near-infrared long persistent emission located at 675 nm, which can sustain about 60 minutes above the recognizable intensity level (≥0.32 mcd/m2), and the persistence duration of samples was three times that of the red commercial phosphor Y2O2S: Eu3+. The experimental results coincide well with the theoretical predictions. These results demonstrate that the strategy concepts of this work is feasible for the design of the Persistent luminescence materials. Moreover, a possible afterglow mechanism is studied and discussed with the assistance of thermoluminescence (TL) curves.