2019/07/20 by Mohammad Rafiee Diznab, Diznab, Mohammad Rafiee, Iraj Maleki Shahrivar +7
Engineering · Materials Science · #2D Materials and Applications #Advanced Thermoelectric Materials and Devices #Chalcogenide Semiconductor Thin Films #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci)
paper · pdf · doi:10.48550/arxiv.1907.08830
openalex publication_date 2019/07/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
An efficient approach to improve the thermoelectric performance of materials is to converge their electronic bands, which is known as band engineering. In this regard, lots of effort have been made to further improve the thermoelectric efficiency of bulk and exfoliated monolayers of Bi2Te3 and Sb2Te3. However, ultra-high band degeneracy and thus significant improvement of power factor have not been yet realized in these materials. Using first-principles methods, we demonstrate that the valley degeneracy of Bi2Te3 and Sb2Te3 can be largely improved upon substitution of the middle layer Te atoms with the more electronegative S or Se atoms. Our detailed analysis reveals that in this family of materials two out of four possible valence band valleys merely depend on the electronegativity of the middle layer chalcogen atoms, which makes the independent modulation of the valleys position feasible. As such, band alignment of Bi2Te3 and Sb2Te3 largely improves upon substitution of the middle layer Te atoms with more electronegative, yet chemically similar, S and Se ones. A superior valence band alignment is attained in Sb2Te2Se monolayers where the three out of four possible valleys are well-aligned, resulting in a giant band degeneracy of 18 that holds the record among all thermoelectric materials.