Synthesis and optical properties of Bi3+/Yb3+ co-doped transparent oxyfluoride glass–ceramics

Abstract The Bi3+/Yb3+ co-doped transparent oxyfluoride glass–ceramics had been synthesized successfully. The formation of nanocrystals was studied using X-ray diffraction and scanning electron microscopy. The structure of fluoride nanocrystals indicates that the main phase in the oxyfluoride glass–ceramics is CaF2 nanocrystal sized at 25 nm by thermal treatment at 600 °C for 8 h. The metal ion Bi3+ has been shown to be an efficient broadband sensitizer for Yb3+ ion in oxyfluoride glass–ceramics. Under the ultraviolet excitation, an intense near-infrared emission of Yb3+:2F5/2→2F7/2 around 1 µm was observed, due to the cooperative energy transfer from one Bi3+ to two Yb3+ ions. Yb3+ concentration-dependent quantum efficiency was evaluated and the maximum efficiency approached 170.1%. The oxyfluoride glass–ceramics are promising for practical application to enhance the energy conversion efficiency of crystalline Si solar cells via spectrum modification.