Journal
JOURNAL OF ALLOYS AND COMPOUNDS
Volume 644, Issue -, Pages 615-620Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jallcom.2015.04.175
Keywords
SnSe; Electronic structure; Thermoelectric property; Single crystalline
Categories
Funding
- National Natural Science Foundation of China [51371076, U1204112]
- Program for Innovative Research Team (in Science and Technology) in the University of Henan Province [13IRTSTHN017]
- Foundation of Henan Educational Committee [14A140016, 14A430029, 14B140003]
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The highest thermoelectric figure of merit (ZT) value of 2.6 has been experimentally determined in p-type single crystalline SnSe. In this work, we propose possible method to further enhance the thermoelectric performance of SnSe by comparing different thermoelectric performances of p- and n-type SnSe using the first-principles method and the semiclassical Boltzmann theory. There are relatively stronger intra-layer interactions between Sn and Se atoms for the layered single crystalline SnSe. The Sop and s electrons near the Fermi level are pushed away along the a-direction because of the anti-bonding interaction between Sn and Se atoms. The pushed away electrons would hinder holes transport in the a-direction. This leads to the lowest electrical conductivity and ZT value along the a-direction for the p-type single crystalline SnSe. For n-type SnSe, the Sn p and Se p electrons are primarily distributed along the a-direction near the Fermi level. This would lead to high electrical conductivity and large Seebeck coefficient simultaneously in the a-direction. Combined with its ultralow thermal conductivity in the a-direction, the ZT value (similar to 3.1 at 770 K by a rough estimation) of n-type SnSe along the a-direction is probably much higher than that of p-type one. The peak values of If of the p-type SnSe correspond to different carrier concentrations along the a- and b-directions. This is one reason for the low experimental peak ZT value of 0.6 for the p-type polycrystalline SnSe at 750 K. For the n-type SnSe, the I can attain their peak values almost at the same carrier concentration along the a-, b-, and c-directions. This suggests that the power factor value of n-type polycrystalline SnSe would be much higher than that of p-type one at 770 K. (C) 2015 Elsevier B.V. All rights reserved.
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