Optimizing the thermoelectric performance of low-temperature SnSe compounds by electronic structure design

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2015-01, Vol.3 (25), p.13365-1337
• Main Authors: Hong, A. J, Li, L, Zhu, H. X, Yan, Z. B, Liu, J.-M, Ren, Z. F
• Format: Article
• Language: English
• Subjects: charge transport; defects; materials and chemistry by design; MATERIALS SCIENCE; mechanical behavior; optics; phonons; solar (photovoltaic); solar (thermal); solid state lighting; spin dynamics; synthesis (novel materials); synthesis (scalable processing); synthesis (self-assembly); thermal conductivity; thermoelectric
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/c5ta01703c

Recently, the SnSe compound was reported to have a peak thermoelectric figure-of-merit ( ZT ) of ∼2.62 at 923 K, but the ZT values at temperatures below 750 K are relatively low. In this work, the electronic structures of SnSe are calculated using the density functional theory, and the electro- and thermo-transport properties upon carrier density are evaluated by the semi-classic Boltzmann transport theory, revealing that the calculated ZT values along the a - and c -axes below 675 K are in agreement with reported values, but that along the b -axis can be as high as 2.57 by optimizing the carrier concentration to n ∼ 3.6 × 10 19 cm −3 . It is suggested that a mixed ionic-covalent bonding and heavy-light band overlapping near the valence band are the reasons for the higher thermoelectric performance. Figure-of-merit factor ZT depending on hope-carrier density for single and polycrystal SnSe compounds at T = 675 K.