Energy transfer and downconversion near-infrared material of Tb3+ and Yb3+ doped Ca5(BO3)3F

Yb3+ and Tb3+ singly doped and Tb3+-Yb3+ co-doped Ca5(BO3)3F phosphors were prepared by a solid state reaction method. The luminescence emission and excitation spectra as well as the luminescence decay curves were investigated. The emission bands of Yb3+ ion are located around 1000 nm, matching well with the optimal response of Si-based solar cells. Tb3+ can be a sensitizer for Yb3+ in the host. The energy transfer from Tb3+ to Yb3+ was investigated, the energy transfer mechanism was proposed as cooperative energy transfer. Tb3+ concentration dependent quantum efficiency was calculated and the maximum efficiency approached 115.5%.