An outlook of rare-earth activated persistent luminescence mechanisms

By studying energy transfer and persistent energy transfer properties in Eu, Mn co-doped calcium aluminate CaAl2O4, it was found that traditional persistent luminescence mechanisms had difficulty in explaining persistent energy transfer property between Eu2+ and Mn2+ ions. Based on this question, a mechanism was suggested in which vibrational energy levels were considered as a Morse potential, and trap centers were distinguished into barriers and wells. Then, this phenomenon was explained by allowing energy transfer and persistent energy transfer could have different preference to different vibrational energy levels. Properties of trap centers were also discussed by using the concept of Madelung energy.