Experimental and theoretical study of parallel models for thermoelectric properties of double-layer thermoelectric thin films

Currently, the measurement and prediction of the electrical transport performance of thermoelectric double-layer membranes is often based on the theory of parallel modelling, however, the conditions for the use of parallel modelling lack theoretical and experimental support and validation. In this paper, the Seebeck coefficients of Cu/Si and Ag/Si bilayers under applied temperature difference are obtained by using finite element theory simulations with the help of COMSOL Multiphysics software and compared with the parallel model. The effects of whether the ends of the bilayer are plated with a metal Pt layer or not, and the insertion of a high-resistance/low-resistance/insulation interface between the bilayers on the Seebeck coefficient measurements of the bilayer are investigated. It is found that when there is no Pt at the hot and cold ends, the potentials on the Si and Cu sides at the high-resistance and electrically insulating interfaces are uniformly distributed along the direction of the temperature gradient, respectively, and the measured Seebeck coefficients are the same as the value of the material itself, respectively, and the thermal potentials on the Cu side at the low-resistance interfaces vary uniformly with the probe spacing L, while the Si side shows a non-uniform variation. With Pt, the thermal potentials on the Cu and Si sides are uniformly distributed along the direction of the temperature gradient, and the measured values on both Si and Cu sides are the same as the Cu Seebeck coefficients, regardless of the insulating/high-resistance/low-resistance interface. Si/Ag and Bi/Ag bilayers were experimentally investigated. In the absence of Pt, the absolute value of the Seebeck coefficient on the Si side of Si/Ag bilayers decreased with decreasing temperature, but the absolute value of the Seebeck coefficient on the Ag side increased with decreasing temperature. In the presence of Pt, the Seebeck coefficients are the same on both sides of the Bi/Ag bilayer membrane.