Spectrum upconversion and downconversion in (Tm~(3+),Yb~(3+)) and (Tb~(3+) ,Yb~(3+)) co-doped fluorosilicate glass

摘要

We investigated the upconversion and downconversion luminescence in (Tm~(3+),Yb~(3+)) and (Tb~(3+),Yb~(3+)) co-doped lithium-lanthanum-aluminosilicate oxyfluoride glass. Upon excitation at 980 nm, where crystalline CdTe solar cells no longer absorb, the sub-bandgap photons can be converted to the higher-energy ones via upconversion. In addition, under excitation between 470 nm and 490 nm, one blue photon might be split up to two near-infrared ones via downconversion. The downconversion luminescence matches the spectral response of crystalline Si solar cell well. We observed much more intense upconversion luminescence from (Tm~(3+), Yb~(3+)) codoped glass than that from (Tb~(3+), Yb~(3+)) codoped glass under the same 980 nm excitation conditions. Our results indicate that the sequential energy transfer from Yb~(3+) ions to Tm~(3+) ions is much more efficient than the cooperative energy transfer from Yb~(3+) ions to Tb~(3+) ions.