Designing band engineering for thermoelectrics starting from the periodic table of elements

Band engineering is an important experimental approach to increase the thermopower of thermoelectric materials, whereas the underlying mechanism has been barely clarified. In PbTe and SnTe, the effective dopants for band engineering, such as Sr, Mn, Cd, and Eu, seem to be randomly distributed on the periodic table. By constructing an analysis model from density functional calculations, the varied experimental observations are arranged into a unified phase diagram as a function of a single variable: the s orbital energy level. Consequently, several neglected effective dopants in previous studies are naturally identified. The analysis method is further applied to GeTe and GeSe, and two kinds of band engineering are theoretically suggested. In this study, the proposed method for electronic structure analysis enables us to design the band engineering directly from the periodic table, which we hope will encourage and accelerate more experimental and theoretical research studies in the thermoelectric field. (C) 2018 Elsevier Ltd. All rights reserved.