Remarkable intrinsic ZT in the 2D PtX2(X = O, S, Se, Te) monolayers at room temperature

Abstract

Two-dimensional (2D) thermoelectric (TE) materials which have the figure of merit ZT that is greater than 1.0 at room temperature would be highly desirable in energy conversion. Here, we study the thermoelectric properties of the 2D PtX2 (X = O, S, Se, Te) monolayers by using first-principles calculations within the ballistic transport region. The 2D PtX2 monolayers have nearly degenerated valleys in conduction bands, and also a very flat curvature around the extrema in both the conduction and valance bands near the Fermi level, which enhance the power factor. Moreover, as compared to many other 2D semiconductors, the 2D PtX2 monolayers possess a lower lattice thermal conductivity, which ranges from 0.207 WK−1m−1 to 0.643 WK−1m−1. These excellent electronic and thermal properties lead to the impressive ZT of 1.65 (PtTe2), 1.42 (PtS2), 0.94 (PtO2) and 0.84 (PtSe2) at 300 K, respectively. Moreover, large ZT of 1.29 (PtS2) and 1.02 (PtTe2) can still be achieved upon applying a 1% tensile strain on the lattice. These results indicate that the 2D PtX2 monolayers are promising TE materials for room temperature applications.