OPTICAL AND PHOTOCONDUCTIVE PROPERTIES OF CERIUM-DOPED CRYSTALLINE SOLIDS

The importance of donor- and acceptor-like charge transfer processes i n the luminescence properties of rare earth doped crystalline solids h ave become increasingly evident in recent years. As an example, we pre sent optical studies, including photoconductive spectroscopy, of ceriu m-doped hosts that exhibit drastically different luminescence efficien cies. The differences are demonstrated to be due to the location of th e 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 l uminescence with quantum efficiencies close to unity.