Goldschmidt, J.C.J.C.GoldschmidtFischer, S.S.FischerSteinkemper, H.H.SteinkemperHerter, B.B.HerterWolf, S.S.WolfHallermann, F.F.HallermannPlessen, G. vonG. vonPlessenJohnson, J.J.JohnsonAhrens, B.B.AhrensMiclea, P.-T.P.-T.MicleaSchweizer, S.S.Schweizer2022-03-042022-03-042015https://publica.fraunhofer.de/handle/publica/24004010.1002/9783527665662.ch92-s2.0-85028033199Owing to the discrete band-gap energy of the employed semiconductor material, solar cells generally do not utilize sub-band-gap photons. This chapter investigates up-converter materials based on lanthanides. The trivalent lanthanide ions have a rich energy spectrum from the near infrared (NIR) to the ultra violet spectral region which makes them prominent for many optical applications, like spectral conversion. Trivalent erbium (Er3+) shows conveniently spaced energy levels for up-conversion (UC) of photons around 1520 nm. The chapter describes the potential of transparent erbium-doped fluorozirconate (FZ) glasses as attractive UC systems. Another material is trivalent erbium doped hexagonal sodium yttrium fluoride. Both materials are very suitable up-converters that show high UC quantum yield and emission/absorption characteristics that match the spectral characteristics of silicon solar cells. The UC efficiencies are simulated on the basis of a rate equation model.enSolarzellen - Entwicklung und CharakterisierungFarbstoffOrganische und Neuartige SolarzellenPhotonenmanagementupconversion620621621697697book article