The discovery of iron-based superconductors marks an important turning point in solid-state physics. The superconducting transition temperature (Tc) of these compounds is among the highest known. FeSe is one of the simplest ones but nevertheless presents a rich phase diagram. Although stoichiometric FeSe is not superconducting, it can display superconductivity under pressure, strain, partial substitution of Se with isovalent elements like Te or aliovalent elements like S, and even under electron doping. In the latter case, it develops high-Tc phases whose nature remains a subject of intense debate. My thesis work is positioned within this debate. It focuses on the study of thin films of FeSe0.45Te0.55, with a Tc= 14.5 K, before and after electron doping (obtained through hydrogen intercalation).