Near Infrared Quantum Cutting of Tb3+-Yb3+ Co-Doped CeF3 Nanophosphors.

In this paper, Tb3+-Yb3+ Co-doped CeF3 nanophosphors were synthesized using the microwave-assisted heating hydrothermal method (M-H). The excitation and emission spectra of the samples at room temperature show that the samples absorb ultraviolet light from 250 nm to 280 nm, and emit light at 300 nm. This corresponds to the transitions from 5D to 4F of Ce3+, 480 nm, 540 nm, 583 nm, 620 nm which correspond to the transitions from 5D4 to 7F6,5,4,3 of Tb3+, 973 nm which corresponds to the transitions from 2F5/2-2F7/2 of Yb3+. In the emission spectra, it is clear that the emission intensity of Ce3+ and Tb3+ decreases, and Yb3+ increases with increasing Yb3+. This suggests that energy transfer from Ce3+ to Yb3+, and Ce3+ to Tb3+ to Yb3+ may occur. In the near infrared emission area, it is noted that a distinct emission centered at 973 nm was observed under 260 nm excitation. This is due to transitions among the different Stark levels of 2FJ(J=5/2,7/2) Yb3+ ions. This also suggests an energy transfer from Ce3+ ions to Tb3+ and then to Yb3+. The energy transfers from Tb3+-Yb3+ Co-doped CeF3 nanophosphors, which lead to intense NIR emissions at 900-1050 nm, match the energy of Si band gaps of Si-based solar cells. Therefore, these kinds of materials are promising candidates for applications that require modifying if solar spectrums and enhancement of conversion efficiency of Si-based solar cells.

[Preparation of Tb3+, Yb3+ doped Y2O3 luminescent powders and near-infrared quantum cutting research].

Y2O3:Tb3+ and Y2O3:Tb3+, Yb3+ samples were prepared by co-precipitation method. The morphology, microstructure and fluorescence spectra at room temperature of samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and fluorescence spectrometer, The optimal process conditions of Y2O3:Tb3+ under different doping concentrations, annealing temperature, and pH value of the solution were obtained: Tb3+ concentration is 1.5%, annealing temperature is 1400 degrees C, an alkaline solution environment, and samples under 300 nm light excitation have the largest green light emission at 543 nm. The corresponding relation of Tb3+ ion level structure and transition properties and experimental spectra were analyzed in detail, and we explained the influence mechanism of process conditions and the fluorescence quenching process mainly effects luminous intensity of samples. The energy transfer from sensitizing ions Tb3+ to active ion Yb3+ was confirmed, it made the sample have considerable emitting light in the near-infrared region; the authors described the process of cooperation conversion luminescence between the two ions from the level transition angle, and also analyzed the system of fluorescence quenching process. Test results showed that the near infrared quantum cutting can effectively improve the luminous efficiency of doped ions, and will have broad application prospects in the silicon solar cells and other fields.