Abstract
Two-dimensional thermoelectric materials with a figure of merit ZT, which is greater than 2.0 at room temperature, would be highly desirable in energy conversion since the efficiency is competitive to conventional energy conversion techniques. Here, we propose that the indium triphosphide (InP₃) monolayer offers an extraordinary ZT of 2.2 at 300 K by using quantum calculations within the ballistic thermal transport region. A remarkably low and isotropic phononic thermal conductivity is founded, which is due to flat lattice vibration modes. This low thermal conductivity takes a major responsibility to the impressively high ZT. Moreover, a large ZT that is greater than 1.5 can be maintained, even if a 1% mechanic extension is applied on the lattice. These results suggest that the InP₃ monolayer is a promising candidate for low dimensional thermoelectric applications.