Luminescence decay evaluation of long-afterglow phosphors

In the current study, the phosphorescence decays of the long-afterglow materials of SrAl2O4:Eu, Dy, Sr4Al14O25:Eu, Dy, Sr2MgSi2O7:Eu, Dy, and ZnS:Cu, Co have been measured over long time (15 h to 16 h). The evaluation methods of luminescence decay are analyzed and summarized. The existing formulas are in accordance with the experimental decay data in the initial fast decay stage. However, the deviation is much larger and the accuracy is much lower in the slow decay stage. Therefore, the existing formulas cannot be used to accurately describe the luminescence decay of the samples with much longer afterglow time (>80 min). Moreover, certain formulas do not match the actual decay situation of long-afterglow luminescence. We suggest our solutions for this problem.