Abstract
We explore the thermoelectric and phonon transport properties of two-dimensional monochalcogenides (SnSe, SnS, GeSe, and GeS) using density functional theory combined with Boltzmann transport theory. We studied the electronic structures, Seebeck coefficients, electrical conductivities, lattice thermal conductivities, and figures of merit of these two-dimensional materials, which showed that the thermoelectric performance of monolayer of these compounds is improved in comparison compared to their bulk phases. High figures of merit (ZT) are predicted for SnSe (ZT = 2.63, 2.46), SnS (ZT = 1.75, 1.88), GeSe (ZT = 1.99, 1.73), and GeS (ZT = 1.85, 1.29) at 700 K along armchair and zigzag directions, respectively. Phonon dispersion calculations confirm the dynamical stability of these compounds. The calculated lattice thermal conductivities are low while the electrical conductivities and Seebeck coefficients are high. Thus, the properties of the monolayers show high potential toward thermoelectric applications.
Highlights
Renewable energy is a very important field due to the insufficiency of natural energy source and global warming[1]
A large Seebeck coefficient, large electrical conductivity, and low thermal conductivity are needed for high thermoelectric performance, but a low amount of charge carrier is required to improve the Seebeck coefficient, which reduces the electrical conductivity[6]
Zhao et al recently reported that bulk SnSe is a very good thermoelectric material with a ZT of 2.6 at 973 K17
Summary
Renewable energy is a very important field due to the insufficiency of natural energy source and global warming[1]. Zhao et al recently reported that bulk SnSe is a very good thermoelectric material with a ZT of 2.6 at 973 K17. We studied two-dimensional SnSe, SnS, GeSe, and GeS materials for thermoelectric applications. Monolayers of these materials have already been experimentally synthesized, and they have band gaps less than 2 eV26–29. They have been recently reported to have low lattice thermal conductivity as well[30], which is a requirement for efficient thermoelectric materials. Group IV–VI compounds in bulk form have very good thermoelectric efficiency and a www.nature.com/scientificreports/
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