Photon controlled electron juggling between lanthanides in compounds

► Different techniques and results on electron transfer are collected and reviewed in one paper. ► The relation between electron binding energy diagrams and electron transfer processes between lanthanides and host bands is demonstrated. ► Electron tunneling between different lanthanides is evidenced by afterglow and/or fading phenomena. ► Electron delocalization processes from states within the conduction band are studied by optical stimulated luminescence.