Stability and thermoelectric performance of the two-dimensional rare-earth compounds RTeCl ( R=La,Pr,Nd )

Thermoelectric conversion technology is increasingly important for sustainable energy, particularly in transforming waste heat into electricity. In this study, we explore the thermoelectric properties of three novel two-dimensional materials, monolayer RTeCl (with R=La,Pr,Nd), using density-functional theory and semiclassical Boltzmann transport theory. These materials are stable and can be easily exfoliated from bulk structures due to their low cleavage energy. Notably, monolayer RTeCl materials have high power factors ($(2.04--4.48)×{}{10}⁴{{0.2em}{0ex}}{{μ}}W{{0.2em}{0ex}}{m}^{{-}1}{{0.2em}{0ex}}{K}^{{-}2}$), attributed to multiple valleys in their valence-band maximum. Their complex crystal structures and the presence of two heavy elements contribute to an ultralow lattice thermal conductivity ($(2.42--4.58){{0.2em}{0ex}}W{{0.2em}{0ex}}{m}^{{-}1}{{0.2em}{0ex}}{K}^{{-}1}$) at room temperature. Impressively, the figure of merit ($ZT$) values of monolayer $RTeCl$ range from 0.4 to 1.2 at 300 K. Across the temperature range of 300 to 700 K, the average $ZT$ value and thermoelectric conversion efficiency reach $1.32--2.75$ and $15.3%--22.6%$, respectively. Our results indicate that monolayer $RTeCl$ is a promising candidate for nanoelectronics and low-dimensional thermoelectric devices, offering a new avenue for high-performance thermoelectric materials.