Luminescence properties and the thermal quenching mechanism of Mn doped ZnGeO long persistent phosphors.

Cation doped ZnGeO materials have been intensively explored owing to their excellent performance in photocatalysts, optoelectronic devices and white light-emitting diodes. However, the luminescence process and thermal quenching arising during the optical excitation of these materials are yet to be clarified. The pure and 2% Mn doped ZnGeO phosphors were prepared via the high temperature solid state reaction. The phosphors were characterized by X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, photoluminescence spectroscopy, X-ray photoelectron spectroscopy and afterglow decay curves. The thermal stability and quenching of Mn luminescence were explained by the temperature dependence of photoluminescence spectroscopy and the configuration coordinate diagram. The thermal quenching of Mn luminescence is mainly due to the delocalization of excited electrons from the excited state to the ionized state. Two kinds of origination of the O 1s peak were revealed by X-ray photoelectron spectroscopy. A model is constructed to interpret all the photoluminescence and long persistent luminescence of the Mn doped ZnGeO. This may contribute to the understanding and optimization of luminescence properties for other Mn doped inorganic phosphors.