Energy transfer and downconversion near-infrared material of Tb 3+ and Yb 3+ doped Ca 5 (BO 3 ) 3 F

Yb 3+ and Tb 3+ singly doped and Tb 3+ –Yb 3+ co-doped Ca 5 (BO 3 ) 3 F 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 Yb 3+ ion are located around 1000 nm, matching well with the optimal response of Si-based solar cells. Tb 3+ can be a sensitizer for Yb 3+ in the host. The energy transfer from Tb 3+ to Yb 3+ was investigated, the energy transfer mechanism was proposed as cooperative energy transfer. Tb 3+ concentration dependent quantum efficiency was calculated and the maximum efficiency approached 115.5%.