Single-layer honeycomb sheets of zinc selenide and beyond with superior electronic and optical properties

The freestanding four-atom-thick double-layer honeycomb sheets of zinc chalcogenides which were synthesized recently are outstanding two-dimensional (2D) materials for next-generation ultrathin optoelectronic nanodevice. In this work, we report a theoretical study on two different single-layer honeycomb sheets of MX (M = Zn, Cd; X = Se, S). The two kinds of single-layer sheets of MX would be thought by cutting along the zinc blende (ZB) bulk as well as wurtzite (WZ) bulk. By using state-of-the-art calculations based upon quasiparticle GW and Bethe–Salpeter equation (BSE), the single-layer sheets of MX possess wide band gaps and are capable of being used as photocatalysts for solar water splitting. The optical absorbance demonstrates that the single-layer sheets of CdSe and CdS have substantial absorption within the visible light region, and the optical absorption of the single-layer sheets of ZnSe can be easily modulated via strains. Furthermore, the electronic transport properties of the single-layer sheets of MX are investigated through the nonequilibrium Green's function (NEGF) method combined with density functional theory (DFT). It is anticipated that these novel freestanding single-layer honeycomb sheets of MX would be great candidates for abundant potential applications in energy storage and conversion.