Optimization of the Thermoelectric Properties of SnSe₂ Using First-Principles Calculations

Abstract

We present a first-principles framework to study the electronic properties of SnSe2, a potentially good layered thermoelectric material. We use density functional theory and solutions of the Boltzmann transport equation under relaxation time approximation including electron–phonon and ionized impurity interactions to calculate the thermoelectric power factor where electron–phonon scattering is computed using the PERTUBO package, and the modified Brooks-Herring approach is used to model the ionized impurity scattering. We study the temperature-dependent transport properties at different carrier concentrations with and without the inclusion of van der Waals interactions. The inclusion of van der Waals interactions increases the electron–phonon scattering, but the total relaxation time is mostly dominated by ionized impurity scattering at high concentration levels. We first validate our theory by comparing the results to available experimental data and then optimize the thermoelectric performance of SnSe2 as a function of temperature and carrier concentration. The optimized power factor times temperature happens at a carrier concentration of 4 × 1019 cm–3 and reaches the maximum value of 0.49 W m–1 K–1 at 523 K in the in-plane direction and 0.185 W m–1 K–1 at 700 K in the cross-plane direction. Finally, the lattice thermal conductivity is evaluated using Callaway’s model. Our optimized model shows the highest ZT value of 1.1 at 950 K originating in the ultralow thermal conductivity across the SnSe2 layers.

The thermoelectric properties of CdBr, CdI, and Janus Cd2BrI monolayers with low lattice thermal conductivity

“…At 600 K, the maximum zT values are 1.54, 3.03, and 1.71 for the p-type doping CdBr, Cd 2 BrI and CdI monolayers, respectively. Particularly, the zT value of p-type doped Janus Cd 2 BrI at 600K is higher than that of PtO 2 ( zT = 1.04 at 700 K) 67 and SnSe 2 ( zT = 1.1 at 900 K), 68 making it a promising material for application in medium temperature TE devices such as thermal insulators and low power thermoelectric refrigerators.…”

Electrostatic modulation of thermoelectric transport properties of 2H-MoTe2

“…Using a similar approach, recently we have reproduced the thermoelectric transport properties of MoSe 2 50 and SnSe 2 . 51…”

“…Using a similar approach, recently we have reproduced the thermoelectric transport properties of MoSe 2 50 and SnSe 2 . 51 In the case of phonons, we performed first-principles calculations by using the Vienna ab initio simulation (VASP), [52][53][54][55] SCAN-rVV10 XC potential to calculate the harmonic and anharmonic interatomic force constants using a 4 Â 4 Â 2 supercell. The thermal conductivity of naturally occurring isotopic and hypothetical isotopically pure MoTe 2 bulk was then calculated on a converged q-space grid 16 Â 16 Â 4 by iteratively solving the phonon Boltzmann transport equation as implemented in the Sheng-BTE package.…”

The interplay of chemical bonding and thermoelectric properties in doped cubic GeTe

“…Here, we have adopted an energy-dependent relaxation time approximation including electron–phonon scattering and ionized impurity scattering. This first-principles-based framework combining electron–phonon scattering and ionized impurity scattering has proven successful in previous studies of materials such as SnSe 2 , 73 MoSe 2 , 74 and MoTe 2 . 75 Through this approach, we aim to enhance the accuracy of our predictions and provide a more comprehensive understanding of the thermoelectric behavior of GeTe.…”