Cooperative downconversion and near infrared luminescence of Tm3+/Yb3+ codoped Calcium Scandate phosphor

An efficient near infrared (NIR) quantum cutting in CaSc2O4: Tm3+/Yb3+ phosphor has been demonstrated by the visible and NIR spectra properties as well as the decay curves of Tm3+:1G4 level. Upon excitation of Tm3+:1G4 level with a blue photon at 466 nm, Yb3+:2F5/2 level can emit two NIR photons around 1000 nm through cooperative energy transfer (ET) from Tm3+ to Yb3+ with the maximum energy transfer efficiency is 71%, and highest theoretical quantum efficiency reaches 171%, close to the limit of 200%. Because the energy of Yb3+ transition is matched well with band gap of crystalline silicon, the excellent downconversion luminescence property indicates that CaSc2O4:Tm3+/Yb3+ is a promising oxide material for increasing the conversion efficiency of crystalline silicon solar cells.