Stability, optoelectronic and thermal properties of two-dimensional Janus α -Te 2 S.

Motivated by recent progress in the two-dimensional (2D) materials of group VI elements and their experimental fabrication, we have investigated the stability, optoelectronic and thermal properties of Janus α -Te 2 S monolayer using first-principles calculations. The phonon dispersion and MD simulations confirm its dynamical and thermal stability. The moderate band gap (∼1.5 eV), ultrahigh carrier mobility (∼10 3 cm 2 V -1 s -1 ), small exciton binding energy (0.26 eV), broad optical absorption range and charge carrier separation ability due to potential difference (Δ V  = 1.07 eV) on two surfaces of Janus α -Te 2 S monolayer makes it a promising candidate for solar energy conversion. We propose various type-II heterostructures consisting of Janus α -Te 2 S and other transition metal dichalcogenides for solar cell applications. The calculated power conversion efficiencies of the proposed heterostructures, i.e. α -Te 2 S/T-PdS 2 , α -Te 2 S/BP and α -Te 2 S/H-MoS 2 are ∼21%, ∼19% and 18%, respectively. Also, the ultralow value of lattice thermal conductivity (1.16 W m -1 K -1 ) of Janus α -Te 2 S makes it a promising material for the fabrication of next-generation thermal energy conversion devices.