Novel concepts and nanostructured materials for thermionic-based solar and thermal energy converters

Thermal and concentrated solar solid-state converters are devices with no moving parts,corresponding to long lifetimes, limited necessity of maintenance, and scalability. Among thesolid-state converters, the thermionic-based devices are attracting an increasing interest in thespecific growing sector of energy conversion performed at high-temperature.During the last 10 years, hybrid thermionic-based concepts, conceived to cover operatingtemperatures up to 2000◦C, have been intensively developed. In this review, thethermionic-thermoelectric, photon-enhanced thermionic emission, thermionic-photovoltaicenergy converters are extensively discussed. The design and development processes as well asthe tailoring of the properties of nanostructured materials performed by the authors arecomprehensively described and compared with the advances achieved by the internationalscientific community.