Efficiency of a Sandwiched Thermoelectric Material with a Graded Interlayer and Temperature-Dependent Properties

This paper investigates the energy conversion efficiency for a sandwiched thermoelectric (TE) material with a graded interlayer and temperature-dependent properties. The graded interlayer can be modeled as a composite of the two homogeneous end material members to achieve continuously varying composition and properties, thus eliminating the electrical contact resistance at the interfaces of segmented TE materials. The temperature distribution and efficiency are obtained by a semianalytical recurrence relation and a simple iteration technique. In the numerical examples, we consider a sandwiched TE element consisting of nanostructured Bi2Te3 at the cold-end side, nanostructured PbTe at the hot-end side, and a graded interlayer of Bi2Te3-PbTe composite. The numerical results show that the peak efficiency of the sandwiched TE material with no contact resistance is higher than that of segmented Bi2Te3/PbTe with contact resistance at the sharp interface between Bi2Te3 and PbTe. The peak efficiency of the sandwiched material is also influenced by the location of and gradation profile in the graded interlayer. Finally, it is found that temperature dependence of properties decreases the efficiencies of Bi2Te3 and PbTe.