Thermal conductivity and enhanced thermoelectric performance of SnTe bilayer

Tin chalcogenides (SnS, SnSe, and SnTe) are the emerging key thermoelectric (TE) materials with low toxicity and eco-friendly nature, which could serve as an alternative to the toxic lead-based alloys. The Sn-based alloys are also found to have improved TE properties upon the reduction of their dimensionality. The structural optimization, molecular dynamics and phonon transport calculations predicted the tilted AA + s stacked two-dimensional (2D) SnTe bilayer as the energetically stable structure. The deformation potential theory was used to evaluate the carrier mobility and relaxation time, which are found to be relatively high due to the high 2D elastic modulus, low deformation potential constant and moderate effective masses. The SnTe bilayer shows a high Seebeck coefficient (> 400 mu V K-1), high electrical conductivity and significantly low lattice thermal conductivity (< 1.91 W m(-1) K-1). The as high TE figure of merit (ZT) values as 3.48 (4.61) along the armchair (zigzag) direction, are predicted for the SnTe bilayer within a practically attainable carrier concentration range of the order 10(12)-10(13) cm(-2). These ZT values are greatly enhanced as compared to the bulk as well as monolayer SnTe and other 2D compounds.