Signal-to-Noise Ratio Optimization for Planar Multijunction Thermal Converters

We investigate a comprehensive design guideline for optimizing the signal-to- noise ratio (SNR) of planar multijunction thermal converters (MJTCs). Optimizing the leg-length of the thermocouple using a shunted copper patch facilitates an increase in the sensitivity to more than twice that of a conventional thermocouple when the device fulfills the thermal impedance matching condition. The SNR does not depend on the thermocouple number or the leg cross-section at a fixed total cross-sectional area. Finally, during thermocouple material selection, different combinations of three thermophysical parameters, the Seebeck coefficient, electrical resistivity, and thermal conductivity that provide the same figure of merit would lead to different values of the SNR. For improving the SNR, increasing the Seebeck coefficient is the most desirable approach. The reduction of thermal conductivity is desirable for short leg-lengths, whereas increasing the electrical resistivity is better for long leg-lengths. The findings provide a useful guide to designing optimal planar MJTCs by maximizing the SNR.