Optical and photoconductive properties of cerium-doped crystalline solids

The importance of donor- and acceptor-like charge transfer processes in the luminescence properties of rare earth doped crystalline solids have become increasingly evident in recent years. As an example, we present optical studies, including photoconductive spectroscopy, of cerium-doped hosts that exhibit drastically different luminescence efficiencies. The differences are demonstrated to be due to the location of the defect electronic levels with respect to the host bands. Small, but crucial, differences in the relative position of the lowest cerium 5-d level can result either in complete quenching of the emission or in luminescence with quantum efficiencies close to unity.