In
recent years, thermoelectric (TE) devices have been used in
several refrigeration applications and have gained attention for energy
generation. To continue the development of devices with higher efficiency,
it is necessary not only to characterize their materials but also
to optimize device parameters (e.g., thermal contacts). One attempt
to increase the efficiency at the device level consists of the replacement
of the typical ceramic layers in TE modules by metallic plates, which
have higher thermal conductivity. However, this alternative device
design requires the use of a very thin electrical insulating layer
between the metallic strips that connect the TE legs and the outer
external layers, which introduces an additional thermal resistance.
Impedance spectroscopy has been proved to be useful to achieve a detailed
characterization of TE modules, being even capable to determine the
internal thermal contact resistances of the device. For this reason,
we use here the impedance method to analyze the device physics of
these TE modules with outer metallic plates. We show for the first
time that the impedance technique is able to quantify the thermal
contact resistances between the metallic strips and the outer layers,
which is very challenging for other techniques. Finally, we discuss
from our analysis the prospects of using TE modules with external
metallic plates.