Composition-dependent contact resistivity in an n-type Mg3SbxBi2−x thermoelectric single leg

Abstract

In the current thermoelectric research framework, the material used to assemble a module is selected simply based on its transport properties while assuming that thermoelectric junction contact resistivity values are nearly constant for a specific material matrix, which raises concerns regarding incorrect material selection and thus deficient device performance. Here, by analyzing the thermoelectric performance of a series of Mg3.2SbxBi1.99−xTe0.01-based compounds, as well as their electrical contact resistivity across the Fe/Mg3.2SbxBi1.99−xTe0.01/Fe interface, we show that the contact resistivity in the n-type Mg3.2SbxBi2−x thermoelectric single leg is composition-dependent and then demonstrate that the high contact resistivity of a junction based on a material with even the highest figure of merit (zT) may considerably restrict performance at the device level. To overcome this dilemma, a multi-layered single leg design is proposed and investigated with the goal to reduce contact resistivity and thus maximize the conversion efficiency of thermoelectric devices.