Two different solder alloys, Sn-37Pb and Sn-4Ag-0.5Cu, were used to joint p- and n-type bismuth telluride-based thermoelements with copper. SnTe and Pb1-xSnxTe were identified to be the major interfacial compounds for the Sn-Ag-Cu and Sn-Pb soldered junctions, respectively. The contact resistivity measured is around 10(-4) to 10(-5) Omega cm(2), which depends on both the thickness and composition of interfacial compounds. The study shall lead to the effective strategy for choosing appropriate solder alloy systems to improve the contact property of bismuth telluride-based thermoelectric coolers. (c) 2007 The Electrochemical Society.