Electronic quality factor for thermoelectrics

Abstract

Development of thermoelectrics usually involves trial-and-error investigations, including time-consuming synthesis and measurements. Here, we identify the electronic quality factor B_E for determining the maximum thermoelectric power factor, which can be conveniently estimated by a single measurement of Seebeck coefficient and electrical conductivity of only one sample, not necessarily optimized, at an arbitrary temperature. We demonstrate that thousands of experimental measurements in dozens of materials can all be described by a universal curve and a single material parameter B_E for each class of materials. Furthermore, any deviation in B_E with temperature or doping indicated new effects such as band convergence or additional scattering. This makes B_E a powerful tool for evaluating and guiding the development of thermoelectrics. We demonstrate the power of B_E to show both p-type GeTe alloys and n-type Mg₃SbBi alloys as highly competitive materials, at near room temperature, to state-of-the-art Bi₂Te₃ alloys used in nearly all commercial applications.