1 research outputs found
To Luminesce or to Change Valence? Insight into the Wavelength Dependency of the Reversible Valence Switching of Europium in Sr<sub>3</sub>SiO<sub>5</sub>
A good control over the valence state of dopants in luminescent
materials or phosphors is important for the development of highly
efficient phosphors for white light-emitting diodes (LEDs). Detailed
spectroscopic studies allow us to reveal optically induced charge
transfer processes and elucidate the underlying mechanisms in phosphors
with additional functionalities such as photochromism or persistent
luminescence. However, the spectroscopic study of the valence switching
of europium has scarcely been reported. Here, we report on the Sr3SiO5:Eu phosphor, in which photo-reduction (Eu3+ → Eu2+) and photo- or thermal-oxidation
(Eu2+ → Eu3+) reactions are demonstrated.
The variation of the illumination wavelength influences the efficiency
of both the photo-reduction/oxidation and the accompanying dynamic
process, especially when the two opposite reactions occur simultaneously.
Temperature-dependent annealing indicates a large trap depth for the
electron trapped by Eu3+. The good stability of Eu2+ obtained by photo-reduction and the repeatability of the
Eu2+/Eu3+ valence switching are confirmed as
well. Furthermore, the application of optical information storage
is demonstrated based on this phosphor. The results of this work may
not only improve the understanding of Eu2+/Eu3+ valence change during illumination but also allow the development
of new functional luminescent materials