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.