Thermoelectric materials are specifically engineered to have large electronic entropies. The thermoelectric effect relies on charge carriers exhibiting large entropies, as the driving force to establish a gradient in electrical potential is driven by the entropy associated with the charge carriers. In the thermoelectric literature, the term band structure engineering refers to the manipulation of material structure and chemistry to achieve a high density of states near the Fermi level. More specifically, thermoelectric materials are intentionally doped to exhibit only partially filled bands at the Fermi level, resulting in high electronic entropies. Instead of engineering band filling, one may also engineer the shape of the band structure itself via introduction of nanostructures or quantum wells to the materials.