Candidate contact layer for SnTe-based thermoelectric device

Abstract

SnTe-based thermoelectric materials have demonstrated significant improvements in performance and are considered a promising, less-toxic alternative to PbTe. However, a substantial gap persists between experimental device efficiencies and those predicted from material performance metrics, primarily due to extra resistance in the contact layers. To fully realize the potential of SnTe thermoelectrics at the device level, it is critical to develop contact layers that ensure strong interfacial bonding, high thermal stability, and low electrical contact resistance. Although Ni is the most commonly used contact material for SnTe devices, it exhibits significant interdiffusion with SnTe, which can degrade interfacial integrity and ultimately lead to long-term device failure. Here, a reliable contact layer for SnTe through ther-modynamic analysis of the SnTe-Ni₃Te₂ phase diagram is identified, Ni_5.75SnTe₅ selected as a promising candidate. A single-leg thermoelectric device based on Sn_0.96Bi_0.04Te_0.98Se_0.02 with Ni_5.75SnTe₅ as a contact layer is fabricated, achieving a contact resistivity of approximately 3.7 µΩ cm². This contact layer selection strategy shows great promise for application to other thermoelectric materials.