Eco-friendly compound Cu₂SnS₃ shows promise as a thermoelectric material

Thermoelectric materials provide an alternative way to efficiently use and waste energy by converting heat into electricity. These materials have many scientific and industrial applications such as in the aerospace, manufacturing, and automotive industries.

Cu₂SnS₃ has attracted attention of researchers because it is eco-friendly and made of earth-abundant elements — and at the same time shows promising thermoelectric characteristics because they well satisfy the phonon-glass electron-crystal concept.

The energy conversion efficiency of a thermoelectric material depends on many factors such as its Seebeck coefficient, electrical conductivity, and thermal conductivity. Deng et al. studied the properties of a series of Cu_2+xSn_1-xS₃ materials, revealing the previously unknown underlying mechanisms for the compound’s high thermoelectric performance. The authors investigated the material‘s band structure and electrical transports and analyzed the relationship between the composition, defect chemistry and transport properties.

They discovered that the compound’s large density-of-states effective mass, high Seebeck coefficient, and high mobility under high carrier concentration all originated from the existence of multiple bands near the edge of the valence band. They also learned, perhaps unexpectedly, that the different crystal structures in the polymorphic Cu_2+xSn_1-xS₃ has little effect on electrical transports.

“Our results agree well with scenarios observed in most Cu-based Chalcogenides where the cations do not significantly affect the band structure near Fermi energy; instead it is the anion sublattice that constitutes the conductive network,” author Pengfei Qiu said.

The authors expect this research to help understand the electrical transport mechanism of Cu₂SnS₃-based thermoelectric compounds. They believe the next step is to investigate and optimize the thermal transport properties of the compound to acquire higher thermoelectric performance.

Source: “Thermoelectric properties of non-stoichiometric Cu_2+xSn_1-xS₃ compounds,” by Tingting Deng, Pengfei Qiu, Qingfeng Song, Hongyi Chen, Tian-Ran Wei, Lili Xi, Xun Shi, and Lidong Chen, Journal of Applied Physics (2019). The article can be accessed at https://doi.org/10.1063/1.5115195 .