Eco-by-design soft hybrid phosphors for lighting applications – Eco-Phos

Rare-earth elements represent a series of element mainly corresponding to the gradual filling of the 4f sub-shell and thereby present exceptional magnetic and luminescent properties. Although these elements are quite abundant in the earth’s crust, their use on large scale like for lighting applications raises some concerns about their supplies. This is the case for Europium and Terbium widely used as red and green emitters respectively in inorganic phosphors for the design of fluoro-compact lamp (FCL) or light emitting diode (LED). If nothing is done, the supply for these elements will become rapidly problematic, their price will increase and these elements will finally deserve the designation of "rare-earths".
Hence, it appears necessary to change the paradigm and include the recycling problematic at the beginning of the design of new materials for the two major technologies of the market namely FCL and LED. It is the goal of the Eco-phos project: the design of new emissive materials for lighting application by i) optimizing the brightness to reduce the quantities of rare-earths and ii) taking into account the recycling problematic from the design. To that end, we propose to use lanthanide complexes as emitters rather than oxides materials to optimize incident light absorption and consequently the brightness at a given wavelength (280 nm for the FLC and 350 for the LED). We have shown that a simple adsorption of these complexes in mesoporous materials highly exalts their luminescence properties and that a simple washing allows us to recover the starting luminescent complexes at the end of use. The EcoPhos consortium merges together skills in coordination chemistry and spectroscopy, modeling, material sciences and advanced surfaces characterization to study and understand the interactions between the complex and the support at the origin of the luminescence exaltation phenomena. More generally, Eco-phos proposes to study the emission of complexes in a confined media, a relatively unexplored field of research. The presence of an industrial partner will also give the opportunity to produce real prototypes (FCL and LED) based on the new hybrid materials. These prototypes are proofs of concept of very high TRL (7) and will allow the determination of the lighting efficiencies in real conditions using cutting edge radiometric and photometrical characterization equipment. This very ambitious objective requires the optimization of the coating formulation of the hybrid materials in order to prepare uniform thin films with good optical quality. Such issues are crucial for industrial applications but are almost never discussed in academic laboratories. Finally, the recycling of these materials after the formulation step and prototype realization will a posteriori validate the proposed eco-by-design approach. In conclusion, Eco-Phos is an ambitious project that simultaneously addresses challenging scientific issues while preparing high TRL prototype based on new eco-by-design luminescent materials.