First-principles study on bilayer SnP 3 as a promising thermoelectric material.

The bilayer SnP 3 is recently predicted to exfoliate from its bulk phase, and motivated by the transition of the metal-to-semiconductor when the bulk SnP 3 is converted to the bilayer, we study the thermoelectric performance of the bilayer SnP 3 using first-principles combined with Boltzmann transport theory and deformation potential theory. The results indicate that the bilayer SnP 3 is an indirect band gap semiconductor and possesses high carrier mobility. The high carrier mobility results in a large Seebeck coefficient observed in both n- and p-doped bilayer SnP 3 , which is helpful for acquiring a high figure of merit ( ZT ). Moreover, by analyzing the phonon spectrum, relaxation time, and joint density of states, we found that strong phonon scattering makes the phonon thermal conductivity extremely low (∼0.8 W m -1 K -1 at room temperature). Together with a high power factor and a low phonon thermal conductivity, the maximum ZT value can reach up to 3.8 for p-type doping at a reasonable carrier concentration, which is not only superior to that of the monolayer SnP 3 , but also that of the excellent thermoelectric material SnSe. Our results shed light on the fact that bilayer SnP 3 is a promising thermoelectric material with a better performance than its monolayer phase.