Two-dimensional Janus antimony chalcohalides for efficient energy conversion applications

Abstract

Specific functionalities at the nanoscale can emerge from the broken inversion symmetry in two-dimensional (2D) Janus monolayers. In this work, we employed the first-principles theory to systematically investigate novel 2D Janus SbYZ (Y = S and Se and Z = Cl, Br, and I) monolayers and study their applications in various energy conversion fields such as piezoelectric, thermoelectric, photovoltaic solar cell, and photocatalytic water splitting. The positive phonon spectra and ab initio molecular dynamics (AIMD) simulation plots suggest that these monolayers are dynamically and thermally stable. Our findings demonstrate that these monolayers have extremely low lattice thermal conductivity and excellent electronic transport properties. The computed thermoelectric performances (ZT) of the monolayers range from 0.15 to 1.66 at 800 K. The inspection of the piezoelectric stress and strain coefficients demonstrates strong out-of-plane piezoelectricity. These monolayers also exhibit characteristics such as semiconductor nature, high carrier mobility, and visible light absorption. The proposed heterostructures of these monolayers show high power conversion efficiencies, up to 19% in the case of SbSeBr/AsTeI heterostructures. We have demonstrated the photocatalytic properties of Janus SbSI and SbSeBr monolayers, as the band alignments of these monolayers are appropriate for photocatalytic water splitting. The HER process can occur without an external potential in pH 0 medium for SbSeBr monolayer. The high solar-to-hydrogen (STH) conversion efficiency (up to 18%) and relatively larger electron–hole recombination rates (1.02 ns and 1.80 ns for the Janus SbSI and SbSeBr monolayers, respectively) demonstrated via NAMD simulations indicated that these monolayers are potential materials for efficient photocatalytic water splitting. Our study suggests that these monolayers have the potential for various energy conversion applications.