Enhanced luminescence via Li+ doping from a Sm3+/Eu3+ Co-doped cerium oxide phosphor

The Sm3+/Eu3+/Li+ co-doped cerium oxide phosphor has been synthesized through co-precipitation and hydro thermal method. The structure and phase of these crystals have been characterized by X-ray diffraction, and it turned out to be the cubic fluorite cerium oxide structure. The spectroscopic investigations of the synthesized phosphors reveal that the Sm3+-doped phosphor emits visible radiation in the red regions upon excitation with 365 nm. However, the addition of Eu3+ to the Sm3+-doped phosphor decrease the magnetic-dipole transitions of Sm3+, and then it emit an intense red emission corresponding to the characteristic transitions of Eu3+. It is also found that the presence of Li+ in the Sm3+/Eu3+ co-doped cerium oxide phosphor obviously enhance the emission intensity of Eu3+, whereas the increase of Sm3+ emission intensity is not obvious. A plausible mechanism of Li+ for that luminescence enhancement of Eu3+ is suggested based on experimental studies. There may be a energy transfer from the excited 5d state of Ce3+ to the F-4(7/2) of Sm3+ ions, and the F-4(7/2) of Sm3+ ions further relaxed to the (4)G(S/2) level by nonradiative relaxation. The two times enhancement in the electric-dipole transitions of Eu3+ is found, and thus Sm3+/Eu3+/Li+ co-doped cerium oxide phosphor may be provided with a potential application for the high efficient dye-sensitized solar cell.