Electron transfer channels in luminescent materials

Electron transfer processes underlie the functional behaviour of many lanthanide-based compounds. Recently, a long-standing debate was settled via a combination of high-resolution X-ray spectroscopy and optical spectroscopy, substantiating that a reversible electron transfer between Eu2+ and Dy3+ is responsible for the persistent luminescence (long afterglow) of several aluminate and silicate crystals. However important, this discovery does not answer all questions on persistent luminescence and electron transfer between metal dopants in general. A significant hurdle that is yet to be taken is explaining how the charge is transported between the (photo)redox partners. It has been speculated that it can move through the host crystal’s conduction band, be directly transferred between the lanthanides, or that a mobile intrinsic defect is involved. This experiment