Cooperative near-infrared quantum cutting in Tb3+, Yb3+ codoped polyborates La0.99-xYbxBaB9O16:Tb0.01

The experimental identification of cooperative energy transfer from Tb3+ to Yb3+ has been presented by the photoluminescence properties of La0.99-xYbxBaB9O16:Tb-0.01 and the mean decay lifetime curves of the D-5(4) emission of Tb3+. Near-infrared quantum cutting involving the F-2(5/2)-> F-2(7/2) emission of Yb3+ (about 960-1040 nm) is achieved upon the excitation of D-5(4) energy level of Tb3+ at 481 nm. Yb3+ concentration dependent quantum efficiency is calculated and the maximum efficiency approaches 152.5%. Because the energy of Yb3+ transition (about 960-1040 nm) is matched well with the band gap of crystalline Si, the phosphors could be applied potentially in silicon-based solar cells.