To date, rare earths [9] and dyes [5] are the twomain active species to be considered
as down-converters for Si-based solar cells. In this work, we will focus on rare earths. The first down-converters incorporating lanthanide ions in solar cells were CaF2:Eu(III) single crystals [10] and organically modified silicate composite phosphor films doped with europium(III) [11]