First-Principles Calculations of Thermoelectric Properties of IV–VI Chalcogenides 2D Materials

Abstract

A first-principles study using density functional theory and Boltzmann transport theory has been performed to evaluate the thermoelectric (TE) properties of a series of single-layer 2D materials. The compounds studied are SnSe, SnS, GeS, GeSe, SnSe2, and SnS2, all of which belong to the IV-VI chalcogenides family. The first four compounds have orthorhombic crystal structures, and the last two have hexagonal crystal structures. Solving a semi-empirical Boltzmann transport model through the BoltzTraP software, we compute the electrical properties, including Seebeck coefficient, electrical conductivity, power factor, and the electronic thermal conductivity, at three doping levels corresponding to 300 K carrier concentrations of 10 . The spin orbit coupling effect on these properties is evaluated and is found not to influence the results significantly. First-principles lattice dynamics combined with the iterative solution of phonon Boltzmann transport equations are used to compute the lattice thermal conductivity of these materials. It is found that these materials have narrow band gaps in the range of 0.75-1.58 eV. Based on the highest values of figure-of-merit ZT of all the materials studied, we notice that the best TE material at the temperature range studied here (300-800 K) is SnSe.

Raman Spectra of Bulk and Few-Layer GeSe From First-Principles Calculations

“…forms by an in-plane vibration along the armchair direction, indicating an intrinsic ferroelectric vibration mode in one layer of bulk GeSe, which agrees with previous experiment work (Zhao et al, 2018). Monolayer GeSe has been predicted a member of ferrovalley materials with plenty of fantastic physical properties (Morales-Ferreiro et al, 2017;Shen et al, 2018;Liu et al, 2021). Thus, it is necessary to investigate the Raman spectrum dependence of fewlayer.…”

Thermoelectric and lattice dynamics properties of layered MX (M = Sn, Pb; X = S, Te) compounds

“…In specific, γ-phase of SnTe was observed to be the most stable structure at the mono-and bi-layered limit [39,40]. Similar to previous studies [35,41,42], a temperature range from 300 K to 700 K has been adopted. A significantly high TE efficiency is predicted in these group IV-VI compounds as they are found to have low lattice thermal conductivity.…”

Thermal conductivity and enhanced thermoelectric performance of SnTe bilayer

“…The predicted ZT peaks are 3.48, 2.27, 1.48 along the armchair and 4.61, 3.41, 3.86 along the zigzag directions at 700K, 500K and 300K, respectively are predicted. These values are significantly higher than those of bulk SnTe, 48 other 2D group IV MLs 15,16,21,38 and SnSe bilayer 20 as compiled in Table 2. The high values of ZT suggest AA + s stacked SnTe bilayer as a promising material for TE device applications and fabrications.…”

“…(3). Normally adopted value of relaxation time (𝜏) is in the order of 10 -14 s within the constant relaxation time approximation, 7,[38][39][40] but the actual value of 𝜏 of a specific material may vary depending upon its physical property. 15,20,21,28 Here the relaxation time (𝜏) is evaluated using the relation:…”