Bos, Adrie JJ

Dorenbos, Pieter

Poelman, Dirk

Smet, Philippe

Van den Eeckhout, Koen

English

Ghent University Academic Bibliography

Probing trap depths in persistent luminescent CaAl2O4:Eu,Nd Koen Van den Eeckhouta, Adrie J.J. Bosb, Pieter Dorenbosb, Dirk Poelmana, Philippe F. Smeta  a LumiLab, Dept. of Solid State Sciences, Ghent University, Gent, Belgium b Delft University of Technology, Faculty of Applied Sciences, Delft, The Netherlands koen.vandeneeckhout@ugent.be  Persistent luminescent materials continue emitting light for minutes or hours after the excitation has ended. Research into this class of phosphors has seen a dramatic increase during the past decade, due to their importance in safety and emergency signage, dials and displays, luminous paint, and more recently also in vivo biomedical imaging [1]. The development of new and brighter afterglow phosphors is, unfortunately, hampered by a lack of understanding of the underlying mechanisms [2]. Most authors agree that excited electrons can escape from the luminescent centers and subsequently get caught at so-called ‘traps’, long-living energy states in the band gap of the host material. However, the nature of these traps and the kinetics of the (de)trapping are subject of an ongoing debate.   We have evaluated the emission intensity of persistent luminescent CaAl2O4:Eu,Nd during charging and during afterglow decay (at various excitation intensities) and measured the thermoluminescence at various heating rates, after various delay times (time between end of excitation and start of readout) and after excitation at different sample temperatures. We found that a single discrete trap level and first-order kinetics are unable to describe the TL glow curves. Evidence is found for a continuous distribution of traps. The relevance of these results for the afterglow mechanism is discussed.           [1] T. Maldiney et al., JACS 133 (2011) 11810-11815 [2] K. Van den Eeckhout et al., Materials 3 (2010) 2536-2566  Fig.1: Thermoluminescent glow curves  of CaAl2O4:Eu,Nd for various  excitation intensities. 

Probing trap depths in persistent luminescent CaAl2O4:Eu,Nd

https://biblio.ugent.be/publication/2133870/file/2914821

Probing trap depths in persistent luminescent CaAl2O4:Eu,Nd

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Ghent University Academic Bibliography