Effect of excitation duration on phosphorescence decay and analysis of its mechanisms

The decay time of phosphorescence is often used to measure temperature since it is considered to be unaffected by factors other than temperature. However, in recent years, many factors have been found to affect the decay of phosphorescences, such as oxygen concentration and excitation light energy. In this study, the effect of excitation duration on the decay of phosphorescence was investigated. The commonly used phosphor Mg4FGeO6:Mn4+ was used, and its phosphorescence decay in different wavelength bands with different excitation duration was analyzed. A phenomenon of exponential change of the decay time with the excitation duration was observed. With the increase of excitation duration, a saturation phenomenon of the decay time was also observed. We discuss the decay behavior with different wavelength bands and propose a model to explain the measured data. Combined with the averaged spectrum data, we found that the distribution of excited triplet states electrons is affected by the excitation time, which affects the decay process. The multi-decay process, triplet-triplet absorption inside the coating, and excitation of dark triplet states are all discussed as potential causes. The current study validates the effect of excitation duration on phosphorescence decay experimentally and provides three possible reasons. Understanding the mechanisms underlying how excitation duration affects phosphorescence will aid in the advancement of phosphor thermometry.