Down-shifting in Ce3+- Tb3+ co-doped phosphate glasses for solar cells application

Abstract

The Down-Shifting (DS) of UV photons into the visible range has been attracting much attention for lighting appliances and solar cells. This work reported the DS luminescence in Ce³⁺-Tb³⁺ co-doped phosphate glasses. Photoluminescence and decay curves were measured and analysed. According to the emission spectra, it was noticed a decrease in emission of the Ce³⁺ peak intensity and an increase of the Tb³⁺ visible emission intensity when the Tb³⁺ concentration is enlarged, indicating an energy transfer process from Ce³⁺ to Tb³⁺. Moreover, it was observed that the blue emission of Tb³⁺ decreases, while the green emission enhances by gradually increasing Tb³⁺ concentration. According to the decay curves of Tb³⁺, this result can be explained by cross-relaxation between Tb³⁺ ions. The experimental temporal evolution of the green emission of Tb³⁺ ions obtained under excitation of the Ce³⁺ ions at 280 nm is well simulated using a proposed model. In this way, the dynamics of the processes involved is perfectly understood and can be applied for solar cell applications. Therefore, the samples were placed over a solar cell and excited with UV excitation. In this excitation range, the silicon solar cell is not efficient, but the Ce³⁺ ions absorb this energy and transfer to the Tb³⁺ ions, which produce an intense visible emission. This emission is detected by the solar cell and produces photocurrent. In summary, the use of co-doped phosphate glass could enhance the current in a solar cell in the UV region.