Establishing phase diagram for the band engineering in p-type PbTe/SnTe from elementary electronic structure understanding

Band engineering is an important mechanism to increase the thermopower of thermoelectric materials by reconstructing the band structure near Fermi level. PbTe and SnTe are the most representative systems in which band engineering were achieved by various dopants. Starting with the elementary understanding of the band structures, we established the phase diagram for the band engineering in p-type PbTe/SnTe by constructing an s-p bonding model. We show that the effects of band tuning are mainly determined by an inherent parameter of doping element: the s orbital energy level. With the phase diagram, all the related experimental observations can be consistently explained, moreover, undiscovered effective dopants become foreseeable. Our study discovers an applicable criteria to pick up proper dopants from the periodic table directly, and the analytical method can be adopted to more thermoelectric materials.