Near-infrared Quantum Cutting for Solar Cells in Ce3+-Yb3+ Co-Doped CaF2 Nanoparticles.

A series of Ce3+-Yb3+ co-doped CaF2 nanoparticles were prepared by a hydrothermal synthesis method. The structure, morphology, photoluminescence properties, and fluorescence dynamics were studied systemically. Under the excitation of the 5d level of Ce3+, an efficient energy transfer from Ce3+ to Yb3+ occurred, and the efficient near-infrared emission at 900-1050 nm matching to the energy of Si band gap of Si-based solar cells was observed. The lifetime of Ce3+ decreased, and the inner quantum efficiency increased with increasing Yb3+ concentration. The quantum efficiency dependent on Yb3+ concentration was calculated, and the maximum efficiency approached 186%. As a down-conversion luminescent convertor, this kind of material can be used in front of Si-based solar cells to reduce thermalization loss and enhance conversion efficiency of solar cells.