The properties of interest of functional materials are strongly correlated to their intimate structure down to the nanometre scale. Designing novel, more efficient materials requires a control over their structure and chemistry at the very same scale. One of the challenges of the 21st century is to tailor energy conversion materials enabling a more efficient harvesting of the energy of the Sun. Thermoelectric power generation is a well-known effect through which thermal energy (heat) is directly converted into electricity without any intermediate working fluid or any moving parts. These materials are generally highly doped, nanostructured materials. Although very promising, the structure – activity relationship in this class of materials is still really unclear, due to a lack of nano-scale characterisation. I aim here to get trained on several analytical techniques, including dual beam Scanning Electron Microscope/Focused-Ion-Beam, Atom Probe Tomography (APT), and various declinations of Transmission Electron Microscopy. I will also acquire a better understanding on the functioning of the laser-assisted APT, which will enable me to start a collaborative work to correct the intrinsic aberrations of the technique. Drawing on the experience of the host group in conducting a complete materials science study, I will improve my skills in this field, and acquire methods, protocols and knowledge enabling me to solve materials science problems. This training will permit to perform at the same time an in-depth study of the multi-scale characterisation of the structure and chemistry of these materials, aiming to improve the design and efficiency of thermoelectric devices.