Cooperative downconversion and near-infrared luminescence of Tb3+-Yb3+ codoped lanthanum borogermanate glasses

In the present paper, we investigate the near-infrared (NIR) luminescence of Tb3+-Yb3+ codoped lanthanum borogermanate (LBG) glasses under visible and ultraviolet light excitation. The results indicate that NIR quantum cutting occurs through cooperative energy transfer from Tb3+ to Yb3+ ions when only 4f (8) levels of Tb3+ ions are excited in the wavelength region of 300-490 nm. The highest quantum efficiency under the excitation (5) D (4) level of Tb3+ at 484 nm is 146%. Ultraviolet excitation that populates the charge transfer band (CTB) of Yb3+ near 270 nm does not result in quantum cutting as the fast nonradiative decay from CTB to (2) F (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.