Visible to infrared energy conversion in Pr3+–Yb3+ co-doped fluoroindate glasses

• Good optical quality fluoroindate glasses have been prepared containing Pr3+ and Yb3+.
• Potential application in c-Si solar cells with the conversion of visible light into infrared light.
• Frequency conversion was studied and down-conversion and down shifting processes could be well identified.

Processes involving visible to infrared energy conversion are presented for Pr3+–Yb3+ co-doped fluoroindate glasses. The emission in the visible and infrared regions, the luminescence decay time of the Pr3+:3P0 → 3H4 (482 nm), Pr3+:1D2 → 3H6 (800 nm), Yb3+:2F5/2 → 2F7/2 (1044 nm) transitions and the photoluminescence excitation spectra were measured in Pr3+ samples and in Pr3+–Yb3+ samples as a function of the Yb3+ concentration. In addition, energy transfer efficiencies were estimated from Pr3+:3P0 and Pr3+:1D2 levels to Yb3+:2F7/2 level. Down-Conversion (DC) emission is observed due to a combination of two different processes: 1-a one-step cross relaxation (Pr3+:3P0 → 1G4; Yb3+:2F7/2 → 2F5/2) resulting in one photon emitted by Pr3+ (1G4 → 3H5) and one photon emitted by Yb3+ (2F7/2 → 2F5/2); 2-a resonant two-step first order energy transfer, where the first part of energy is transferred to Yb3+ neighbor through cross relaxation (Pr3+:3P0 → 1G4; Yb3+:2F7/2 → 2F5/2) followed by a second energy transfer step (Pr3+:1G4 → 3H4; Yb3+:2F7/2 → 2F5/2). A third process leading to one IR photon emission to each visible photon absorbed involves cross relaxation energy transfer (Pr3+:1D2 → 3F4; Yb3+:2F7/2 → 2F5/2).