Optical spectroscopy of metastable states in persistent phosphors

Groep: Lumilab

Promotor: prof. dr. Philippe Smet, dr. Jonas Joos

Supervision: David Van der Heggen, Dirk Poelman

Persistent phosphors are luminescent materials that possess the ability to store energy inside them. Room temperature is typically sufficient to slowly release the stored energy, giving rise to the well-known “glow-in-the-dark” effect. The mechanism behind this energy storage is an electron transfer from the luminescent ion to a so-called trapping defect. The current state-of-the-art phosphors operate at only 1.6% of their maximal capacity so there is still a lot of room for improvement. Nevertheless, during the past two decades of research, only moderate improvements on these materials’ storage capacity have been achieved.

Recently our group has been able to identify the mechanism that limits the performance of these phosphors. The culprits are optically active trapping defects that absorb the excitation light which leads to an increased emptying of filled traps. This mechanism is known as optically stimulated luminescence by excitation light and is clearly an unwanted effect.

The goal of this thesis is to identify the chemical nature and optical signature of these unwanted defects. This will be accomplished by combining several optical characterization techniques such as diffuse reflectance, optically stimulated luminescence and thermoluminescence. To this end, new state-of-the-art equipment such as a high performance spectrophotometer and a high power OPO laser are available. The information collected during optical characterization can be used as input to synthesize our own, optimized persistent phosphors in-house. 

The results from this thesis should allow to accelerate further improvements of the persistent phosphors’ performance. Such a targeted approach is bound to be more successful than the current trial-and-error approach and promises that more demanding applications such as theranostics or glow-in-the-dark road markings are finally within reach!

Optical spectroscopy of metastable states in persistent phosphors

Opmerkingen:

  • Dit thesisonderwerp kan ook opgenomen worden in het kader van de Educatieve Master Fysica en Sterrenkunde.
  • Aan dit onderwerp is geen mobiliteitsaspect verbonden. Er kan met de promotoren wel overlegd worden over gerelateerde stage-activiteiten en/of vakken aan andere universiteiten.