Recent Advances in n-Type Thermoelectric Nanocomposites

Organic/inorganic thermoelectric nanocomposites (TENCs) have seized great attention because they integrate the advantages of inorganic (i.e., high electrical conductivity) and organic (i.e., low thermal conductivity and mechanical flexibility) components. Major barriers that obstruct the development of this field are the lack of n-type TE materials and their relatively low performance, leaving the construction of TE devices difficult to realize. This review article is therefore focused on recent advances on n-type TENCs that primarily comprise carbon nanotube (CNT) and inorganic nanocrystal (NC)-based hybrids. CNT-based n-type TENCs are fabricated mainly by transforming the p-type CNT to n-type with organic dopants or by blending CNTs with n-type semiconducting polymers. NC-based n-type TENCs are typically obtained by blending semiconductor nanocrystals or metallic nanostructures with polymers. Additionally, the fabrication and thermoelectric performance of 2D layered superlattice structures are also reviewed. Finally, an outlook of n-type TENCs is given with a perspective for their possible future improvements.