Effect of inhomogeneous broadening on time-resolved photoluminescence in CaAlSiN_3:Eu^2+

The decay behavior of CaAlSiN(3):Eu(2+) was monitored as a function of the detection wavelength on the Eu(2+) emission band for various Eu(2+) concentrations from 0.0005 to 0.05. The decay at the higher-energy side was faster and less linear than the lower-energy side decay for all Eu(2+) concentrations. This was due to an inhomogeneous broadening induced by the random distribution of Al and Si ions at a crystallographic site in the CaAlSiN(3) structure and to the successive site-to-site energy transfer. This phenomenon caused a redshift of the Eu(2+) emission band as the Eu(2+) concentration increased.