Multi-Layer Metallization Structure Development for Highly Efficient Polycrystalline SnSe Thermoelectric Devices

Abstract

Abstract:Recently, SnSe material with an outstanding high ZT (Figure of merit) of 2.6 has attracted much attention due to its strong applicability for highly efficient thermoelectric devices. Many studies following the first journal publication have been focused on SnSe materials, not on thermoelectric devices. Particularly, to realize highly efficient intermediate-temperature (600~1000 K) thermoelectric modules with this promising thermoelectric material, a more thermally and electrically reliable interface bonding technology needs to be developed so that the modules can stably perform their power generation in this temperature range. In this work, we demonstrate several approaches to develop metallization layers on SnSe thermoelectric legs. The single-layer metallization shows limitations in their electrical contact resistances and elemental diffusions. The Ag/Co/Ti multi-layer metallization results in lowering their electrical contact resistances, in addition to providing more robust interfaces. Moreover, it is found to maintain the interfacial characteristics without any significant degradation, even after heat treatment at 723 K for 20 h. These results can be effectively applied in the fabrication of thermoelectric devices or modules that are made of the SnSe thermoelectric materials.

Thermoelectric power generation: from new materials to devices

“…This study resolves the thermal conductivity discrepancy between single and poly-crystalline SnSe, and attains a ZT approximately 2.5 for polycrystalline SnSe which nearly matches the recordhigh value of the single crystals. We believe SnSe might revolutionize thermoelectric power generation technology if its device can be demonstrated, but to date such reports are few and will be discussed later [93,94].…”

Modelling a Segmented Skutterudite-Based Thermoelectric Generator to Achieve Maximum Conversion Efficiency

“…To avoid having a mismatch at the interface during expansion, the thermal coefficient of the diffusion layer should be similar to that of the TE material and the electrode. Bilayer metallization [54] and multilayer metallization [55] prove effective in lowering electrical contact resistance, providing thermal coefficient matching, and serve as a good diffusion barrier.…”

Nanostructured Thermoelectric Chalcogenides

“…Their election is guided by the need to use inert chemical materials at high temperature against typical compounds in many thermoelectric materials, such as Sn, Pb, Te, and Se. This is the reason we chose thermocouples made of a niobium and chromel combination, ensuring that the Nb wires are in contact with the sample [27,33], which allows us to reach temperatures near up to 950 K without reactions between samples and thermocouples.…”

“…Numerous different explanations have been proposed for such values, as surface oxidation, exact stoichiometry, porosity, morphology, and crystal defects of the samples. Thermoelectric devices made of this material have not been described yet despite the fact that SnSe presents one of the highest figures of merit, and only a few attempts proving the interface bonding properties for high-temperature modules have been reported [32,33].…”