Effect of interface layer on the cooling performance of a single thermoelement

The resultant thermoelectric (TE) figure of merit Z, the coefficient of performance (COP), the heat pumping capacity per unit area (Qc/S) were derived analytically as functions of l0, ρc, κc and sc for a single thermoelement (STE) by taking into account the interface layers, where l0 is a length of a TE material, ρc the electrical interface resistivity, κc the thermal interface conductivity and sc the ratio of the Seebeck coefficient of an interface layer to that of a TE material. As a result, it was first revealed that the increase in Z0T of a TE material is not necessarily reflected in the increase in ZT of an STE as long as the interface layers are present. The COP and Qc/S are lowered remarkably for sc = 0 and κc ⩽ 104 W/m2 K. However, it was clarified that even for low values of κc, the COP and Qc/S return to the original high values (obtained for κc ⩾ 105 W/m2 K) at sc = 0.45 and 0.90, respectively. The definite criterion of sc whether or not the boundary Seebeck coefficient has an effect on the enhancement of the cooling performance was indicated quantitatively for an STE with interface layers.