This work is dedicated to the elaboration and structural and optical characterization of a LaCoO3 selective layer for solar thermal collectors. LaCoO3 is a thermochromic material capable (similar to VO2 that is currently used for this application) of preventing overheating of the collector. Samples were prepared using two types of sputtering reactors—a rotary confocal sputtering reactor and an in-line semi-industrial reactor, allowing us to produce samples with areas of 1–2 cm2 and 21.0 × 29.7 cm2, respectively. The samples possess overall stoichiometry, with the La/Co ratio being equal to 1. However, TEM cross-sectional evaluations reveal that the structure of as-deposited films issued from the semi-industrial reactor corresponds to La/Co multilayers. Deposited at room temperature, metallic LaCo films should be annealed in air at 600 °C in order to crystallize and/or oxidize the perovskite structure. All films were characterized using, among other techniques, XRD, HRTEM, FTIR, and an IR camera. A strong correlation between the distribution of the elements (i.e., the presence or absence of the La/Co multilayers) and optical properties and a strong dependence of the latter on thickness and annealing conditions were ascertained. Nevertheless, for both types of reactors, good values of emissivity change, reaching as high as Δɛ = 64%, were obtained.