Nanofluorides for Environmentally Benign Lighting and Energy Conversion in Solar Cells

Energy-saving lighting and the conversion of sunlight into electric energy by solar cells are both topics that are receiving a constantly growing interest both in their respective scientific communities as well as in society due to rising environmental awareness and the seek for a responsible handling of energy. Interestingly for both, lighting and solar cells, lanthanide fluorides as photonic materials are of high importance. Fluoride materials as photonic materials provide some distinct advantages compared to other materials because of their outstanding properties such as very low phonon frequencies, high refractive index, high thermal stability and sometimes tunable crystal phases and related photo physical properties. Lanthanide ions doped into fluoride host materials display low probabilities for multiphonon relaxation resulting in long lifetimes of their excited states and high luminescence quantum efficiencies. Such properties are needed for example for quantum-cutting phosphors for improved compact fluorescent lamps or solar cells. The spectral region of sunlight, not directly available for a classical solar, cell can also be made accessible by up-converting phosphors which today also rely on fluoridic phosphors – desirably on nanosized – materials.