Optical and electronic properties of the SrAl2O4:Eu2+‐Dy3+ phosphor were investigated to analyze the mechanisms of its strong and long persistent luminescence. From the temperature dependence of photocurrent excitation spectra, the relative energy locations between the 5d levels of Eu2+ in two different sites and the conduction band were estimated. While most of the 5d levels of Eu2+ at the Sr site with weak crystal field are located within the conduction band, only the 5d levels of Eu2+ above 3.1 eV (400 nm) at the Sr site with strong crystal field are located within the conduction band. Based on the analysis of electron transfer from some electron traps, we assume that some electrons are transferred by a quantum tunnelling path. In addition, the persistent luminescence performance is good by the excitation of the usual blue LED (450 nm), composing white LEDs for the general illumination. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
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Ueda et al. (2012) studied this question.