This Special Issue Reprint is focused on recent developments and achievements in the design and application of new advanced materials for active coatings with a special emphasis on the surface engineering and functionalization of protective, sensitive, and selective coatings for energy conversion and storage. It includes papers authored by scientists from around the world. A variety of materials and coatings, like oxide-based coatings, functional polymers, and composites, are designed, characterized, and discussed in relation to their potential applications in photovoltaic and sensing devices. As a whole, the Special Issue shows a diverse range of methods, techniques, and innovative approaches that are commonly used in order to produce materials and coatings with improved and new functionalities.