Near infrared quantum cutting by cooperative energy transfer from Tb3+ to Yb3+ in YPO4

Near infrared quantum cutting by cooperative energy transfer from Tb3+ to Yb3+ was investigated by photoluminescence measurements on (YbxY1−x)PO4 (x = 0, 0.05, 0.1, 0.15) doped with 1 % Tb3+. Under the excitation of 473 and 486 nm continuous wave lasers, we found that one Tb3+ ion absorbed one blue photon with the transition from 5D4 to 7F5 (λ ~ 544 nm) and cooperatively transfer energy to Yb3+ ions, which is followed by the emission of two photons (λ ~ 980 nm). Application of cooperative energy transfer has prospects for increasing the energy efficiency of crystalline Si solar cells by photon doubling of the high energy part of the solar spectrum.