C3H2 : A wide-band-gap semiconductor with strong optical absorption

Using first-principles calculations, we predict a new type of partially hydrogenated graphene system, C₃H₂ , which turns out to be a semiconductor with a band gap of 3.56 eV. The bands are rather flat at the band edges and thus lead to a large density of states, which further results in strong optical absorption between the valence band and the conduction band. Particularly, it shows strong optical absorption at about 4.5 eV for the light polarized along the lines connecting the nearest unhydrogenated carbon atoms. Thus, the predicted C₃H₂ system may have potential applications for a polarizer as well as other high-efficiency optical devices in the near ultraviolet region.