Theoretical Prediction of Thermoelectric Performance for Layered MSX (M = In, Tl; X = Cl, Br) Materials with the Inclusion of Multiple Carrier Scattering Mechanisms

Based on first principles, the electronic structure and thermoelectric (TE) transport properties of MSX (M = In, Tl; X = Cl, Br) monolayers are investigated systematically. The combination of high Grüneisen parameters and short phonon relaxation times in these materials significantly impedes phonon propagation, resulting in suppressed lattice thermal conductivity of 0.32–1.05 Wm–1 K–1. When multicarrier scattering is considered, the thermoelectric performance of MSX monolayers shows significant anisotropy, with distinct transport behavior along the x- and y-directions. Specifically, at 300 K, the optimal ZT values along the x(y) direction are 0.02 (0.48), 0.04 (1.02), 0.07 (1.22), and 0.07 (1.60) for InSCl, InSBr, TlSCl, and TlSBr, respectively, which are superior to those previously reported for thermoelectric materials. The above results suggest that these MSX monolayers are promising two-dimensional (2D) candidate thermoelectric materials.