Fabrication of high-performance SnSe thermoelectric thin films with preferred crystallographic orientation

Abstract

SnSe2 has been of great interest as the n-type semiconductor exhibits high thermoelectric (TE) performance. Because material's thermoelectric properties are highly anisotropic, controlling the crystallographic orientation in the microstructure is one of the key factors for enhancing the TE performance. However, reports of SnSe2 with preferred crystallographic orientation have been limited due to the difficulty in fabrication. As a solution for this challenge, in this study, we report solution-processed fabrication of textured SnSe2 thin films. Following heat treatment optimization, the thin films possessed exceptionally strong crystallographic orientation order in the a–b plane, as demonstrated with x-ray diffraction analyses. Moreover, controlled defect formation through processing conditions realizes high electron concentrations of an order of ∼1020 cm−3. In particular, we demonstrate that the microstructure of the SnSe2 thin films determined their electronic transport properties, where the electron mobility increases with stronger crystallographic orientation. Finally, the thin film with the optimal structure exhibits the enhanced thermoelectric power factor of 3.69 μW cm−1 K−2. Our findings will offer a way to enhance the thermoelectric and electronic properties of highly anisotropic materials.