Investigations of optoelectronic properties of novel ZnO monolayers: A first-principles study

The development of non-toxic and low-cost two-dimensional materials has received considerable interest for applications in cutting-edge technologies. In this study, we report the devising of two types of ZnO monolayers for optoelectronic applications using the first-principles approach. These ZnO monolayers are originated from the zinc-blende (zb) and 5–5 phases of ZnO and are found to exhibit equivalent energetic stability as their bulk counterparts. The ZnO monolayer derived from zb-phase (ZnO(zb)) exhibits a narrow bandgap of magnitude 0.142 eV determined with Tran-Blaha modified Becke Johnson (TB-mBJ) exchange potential, whereas the monolayer derived from 5 to 5 phase (ZnO(5–5)) exhibits a relatively larger energy gap of magnitude 2.150 eV. The optical absorption in these monolayers approaches as high as 31.05 × 104 cm−1 for single-layered ZnO(zb) and 55.98 × 104 cm−1 for ZnO(5–5) monolayer. Further analysis of optical spectra demonstrated relatively weak reflectance of incident light by these monolayers and are found of transparent nature over a wide range of the solar spectrum. Overall, they demonstrate interesting electronic and optical features and are believed to find suitable applications in optoelectronic devices.