Promising thermoelectric properties and anisotropic electrical and thermal transport of monolayer SnTe

Abstract

Motivated by the recent experimental synthesis of atomic-thick SnTe [Liu et al., Science 353(6296), 274 2016] exhibiting a layered orthorhombic phase similar to SnSe, we carried out systematic investigations on its electronic, thermoelectric, and phonon transport properties based on a combination of density functional theory and Boltzmann transport theory. Our results indicate that the monolayer is dynamically stable with a band gap of 1.05 eV. A considerable figure of merit (ZT) is predicted to be 2.9 for n-type doping and 2.2 for p-type doping along the armchair direction at a moderate carrier concentration of 1020 cm−3. The electronic band structure and the Fermi surface with multi-valleys lead to band convergence and anisotropic transport behavior. The synergistic optimization of Seebeck coefficient and electrical conductivity is achieved in anisotropic monolayer SnTe, due to the independence of carrier relaxation time and directional effective mass. A maximum power factor of 37 mW/(mK2) can be achieved for the n-type SnTe monolayer along the armchair direction, almost two times as high as that in the zigzag direction. However, the anisotropy of intrinsic lattice thermal conductivity is relatively low and strong phonon anharmonicity is found due to the coexistence of weak bonding and resonant bonding.

XTe (X = Ge, Sn, Pb) Monolayers: Promising Thermoelectric Materials with Ultralow Lattice Thermal Conductivity and High-power Factor

“…[36] The variation of S against  is basically the same for the electron and hole doping. The smaller electron effective mass causes a higher electron mobility than that of holes in the XTe monolayers, [20] which leads to smaller σ/e of electrons than that of holes at the same ||. Similar to σ/e, PF/e of p-type XTe monolayers is much higher than its n-type counterpart.…”

“…[26] A vacuum length of 20 Å is adopted to eliminate the interactions between neighboring layers. [27] ab initio molecular dynamics (AIMD) simulations [28] were performed by using the canonical ensemble (NVT) [29] at 900 K. [20] We compute the second-order (harmonic) interatomic force constants (IFCs) using the Phononpy package [30] and the third-order (anharmonic) IFCs using the thirdorder.py code. [31] 5×5×1 supercells and 4×4×1 supercells with 3×3×1 k-mesh are adopted for the calculations of second-order harmonic and third-order anharmonic IFCs, respectively.…”

“…S3 and S4 in the supplemental materials show two types of Sn-Te bonding coexist, one is strong bonding (resonant bonding) and the other is weak bonding. [20] Fig. 2(a) demonstrates the phonon dispersion relation of XTe monolayers.…”

“…[19] The calculated high ZT of monolayer SnTe show that it has better intrinsic thermoelectric behaviors than its bulk counterpart. [20] Motivated by the excellent thermoelectric performance of 2D materials, we systematically and comparatively studied the intrinsic thermoelectric properties of XTe monolayers, by combing the first-principles calculation and the Boltzmann transport theory. Our results show that XTe monolayers has higher ZT, compared with their bulk counterparts, which suggests that reducing the dimensions of bulk XTe is efficient to achieve better thermoelectric efficiency.…”

Remarkable High Thermoelectric Conversion Efficiency Materials of BeMF3 (M = Al, Y)

“…Ali et al. [ 18 ] found the p‐type power factor of KCaF 3 is larger at the properly charge carries, which lead the ZT of 0.7 at 800 K. Many other thermoelectric materials with higher ZT (>2) have also been reported, such as the full‐Heusler materials Ba 2 BiAu( ZT max = 5), [ 19 ] the half‐Heusler compound BCaGa( ZT max = 7.38), [ 20 ] the oxide monolayer La 2 Ti 2 O 7 ( ZT max = 2.5), [ 21 ] the monolayer SnSe and SnTe compounds( ZT max = 2.3 and 3.27), [ 22,23 ] ternary sulfur compound AgBi 3 S 5 ( ZT max = 2.24). [ 24 ]…”