A novel and functional single-layer sheet of ZnSe.

The recently synthesized freestanding four-atom-thick double-layer sheet of ZnSe holds great promise as an ultraflexible and transparent photoelectrode material for solar water splitting. In this work, we report theoretical studies on a novel three-atom-thick single-layer sheet of ZnSe that demonstrates a strong quantum confinement effect by exhibiting a large enhancement of the band gap (2.0 eV) relative to the zinc blende (ZB) bulk phase. Theoretical optical absorbance shows that the largest absorption of this ultrathin single-layer sheet of ZnSe occurs at a wavelength similar to its four-atom-thick double-layer counterpart, suggesting a comparable behavior on incident photon-to-current conversion efficiency for solar water splitting, among a wealth of potential applications. The results presented herein for ZnSe may be generalized to other group II-VI analogues.