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Sensitizing rare earth ions in optical materials : a challenge with high potential impact

Francesco Enrichi

Vendredi 8 septembre

11h — Site Sophia

The spectroscopic properties of rare earth ions (RE3+), which are characterized by specific narrow photoluminescence emissions and long luminescence lifetimes, make them suitable for many optical applications. Their use is well established in phosphors for lighting and light-emitting devices, light amplifiers, lasers, spectral conversion layers (up- and down-conversion), and optical biomarkers. However, major limitations are related to their small absorption cross section and limited absorption spectral bandwidth, which reduce their effective implementation and use. Therefore, a significant field of research is devoted to the development of sensitizing strategies, from the synthesis of organic ligands for rare earth complexes, to the coupling with other rare earth ions (like in Tb-Yb or Yb-Er codoped systems) or with semiconductor or metal nanoaggregates that act as energy-transfer centers.

This seminar will be focused on the sensitizing process of rare earth ions, highlighting how the photoluminescence characterization techniques can deepen the understanding of the physics of the interaction. As an example, I will illustrate the advantages that can be provided by silicon or silver nanoaggregates for a broadband enhancement of the efficiency of Er3+ ions for optical amplification. Moreover, I will present the increasing of quantum cutting efficiency by proper optimization of Tb3+/Yb3+-codoping in down-converting glasses and glass-ceramics for spectral conversion in solar cells and the possibilities of further improvements by the introduction of Ag nanoaggregates in the system.

These and other examples will be discussed, with a focus on the high potential impact of this field of investigation, suggesting perspectives for future research developments.