Cooperative downconversion and near-infrared luminescence of Tb~(3+)-Yb~(3+) codoped lanthanum borogermanate glasses

摘要

In the present paper, we investigate the near-infrared (NIR) luminescence of Tb~(3+)-Yb~(3+) codoped lanthanum borogermanate (LBG) glasses under visible and ultraviolet light excitation. The results indicate that NIR quantum cutting occurs through cooperative energy transfer from Tb~(3+) to Yb~(3+) ions when only 4 f~8 levels of Tb~(3+) ions are excited in the wavelength region of 300-490 nm. The highest quantum efficiency under the excitation ~5D_4 level of Tb~(3+) at 484 nm is 146%. Ultraviolet excitation that populates the charge transfer band (CTB) of Yb~(3+) near 270 nm does not result in quantum cutting as the fast nonradiative decay from CTB to ~2F_(5/2) level dominates. These materials are expected to be used as a converting layer for silicon solar cells to enhance their efficiency by splitting each high-energy photon into two NIR photons.