Efficient energy transfer from band excitation to Nd3+ in β-La2S3:Nd, Ce

Efficient energy transfer from optically excited conduction band states to 4f Nd states via 5d Ce states in semiconducting La2S3:Nd, Ce is reported. The quantum efficiencies of the transfers Ce to Nd and band states to Nd are 0.7 and 0.3 respectively. Measurements of absorption, fluorescence and photoconductivity prove the strong coupling between band states and Ce 5d states as well as Ce 5d states and Nd 4f states. At 300 K, the fluorescence lifetimes of single doped samples are tau(1%Nd) = 70 μs, tau(10%Nd) = 8 μs due to Nd cross relaxation and tau(1%Ce) = 35 ns. For co-doped crystals (10% Nd, 1% Ce) the Nd3+ fluorescence is unaffected, whereas the Ce3+ fluorescence is absent. (author)