Thermoelectric Properties of CrS_2–xTe_x (x: 0, 1, 2) Dichalcogenides Monolayers: First-Principles Study

Abstract

In this study, we conducted first-principles calculations interfaced with Boltzmann transport theory to examine the carrier-dependent thermoelectric properties of CrS2–x Te x (x: 0, 1, 2) dichalcogenides monolayers. We conducted a systematic analysis of the structural, phonon band structures, elastic properties, electronic structures, and thermoelectric properties, of electron (e) and hole (h) doped CrS2–x Te x (x: 0, 1, 2) dichalcogenides monolayers. The studied 2D TMDCs exhibit structural stability, as indicated by the negative formation energy. Additionally, the phonon band structures indicate no negative frequencies along any wave vector, confirming the dynamic stability of the CrS2–x Te x monolayers. CrS2 and CrTe2 monolayers are semiconductors with direct bandgaps of 1.01 and 0.67 eV, respectively. A Janus CrSTe monolayer has a smaller bandgap of 0.21 eV. Temperatures range between 300 and 500 K, and concentrations of e(h) doped in the range of 1.0 × 1018–1.0 × 1020 cm–3 are used to compute the thermoelectric transport coefficients. The low lattice thermal conductivity is predicted for the studied compounds, among which Janus CrSTe and CrTe2 have the minimum value of κlat ≈ 1 W/mK @ 700 K. The figure-of-merit ZT projected value at the optimal e(h) doping concentration for the CrS2 monolayer is as high as 0.07 (0.09) at 500 K. Our findings demonstrate how to design improved thermoelectric materials suitable for various thermoelectric devices.