Quantum cutting and up-conversion investigations in Pr3 +/Yb3 + co-doped oxyfluoro-tellurite glasses

•Transparent new Pr3 +/Yb3 + co-doped oxyfluoro-tellurite (TZYN) glasses.•Energy transfer from Pr3 + to Yb3 + via cross relaxation processes•Energy transfer efficiency of 66% for TZYNPrYb10 glass.•Total quantum efficiency (ηT) in the visible of 166% for TZYNPrYb10 glass.

In this work we have investigated quantum cutting, up-conversion and downconversion processes in new Pr3+/Yb3+ co-doped transparent oxyfluoro-tellurite glasses with chemical composition TeO2-ZnO-YF3-NaF-0.5Pr2O3-xYb2O3 (x = 0.25, 0.5, 0.75 and 1.0 mol%). In the down-conversion process, Pr3 +-Yb3 + co-doped samples present emission in the visible (Pr3+: 3P0 → 3F2 transition, 640 nm) and in the infrared (Yb3+: 2F5/2 → 2F7/2, 980 nm) spectral regions upon excitation at 440 nm. The luminescence decay time of the emitting levels were obtained in co-doped samples as a function of Yb3+ concentration and the results confirmed the occurrence of energy transfer from Pr3+ to Yb3+ via a combination of two different cross relaxation processes: (1) Pr3+: 3P0 → 1G4 to Yb3+: 2F7/2 → 2F5/2 and (2) Pr3+: 1D2 → 3F4 to Yb3+: 2F7/2 → 2F5/2. Furthermore due to the reverse-energy transfer mechanism from Yb3+2F5/2 level to- Pr3+1G4 level, luminescence intensity quenching was observed for the 2F5/2 → 2F7/2 transition at 980 nm, for Yb3+ concentrations higher than 0.5 mol%. The energy transfer efficiency was estimated from the intensity ratios and decay times associated to the 3P0 → 3F2 transition, and it reached 66% for a glass co-doped with 0.5Pr3+ and 1.0Yb3+ (mol%). The results indicate that these glasses are potential candidates for manipulation of the solar spectrum, via up-conversion and downconversion processes, in order to increase the absorption efficiency of currently used c-Si photovoltaic solar cells.