Band Gaps and Optical Spectra of Fluorinated and Hydrogenated Graphenes*

Two-dimensional (2D) materials derived from graphene by attachment of hydrogen and halogens have attracted considerable interest over the past few years because of their potential applications (e.g., in electronic devices or sensing)[1]. Here, we consider the effect of electron-electron and electron-hole correlation on the electronic/optical properties of materials under study. Large difference between the experimental optical gap and the electronic band gap from many-body GW theory for fluorographene CF, fluorographite, and graphane CH is explained by unusual large binding energies of excitons obtained by solution of Bethe-Salpeter equation (BSE}[2,3]. Fluorographane C₂FH is found as material with the widest electronic gap (~10 eV) and a largest binding energy of exciton (~3 eV) in the class of currently known 2D materials [4]. Finally, we show the importance of careful computational setup for reliable usage of many-body methods.

[1] Karlicky F., Datta KKR., Otyepka M., Zboril R., ACS Nano 7 (2013) 6434
[2] Karlicky F., Otyepka M., J. Chem. Theory Comput. 9 (2013) 4155
[3] Karlicky F., Otyepka M., Ann. Phys. 526 (2014) 408
[4] Karlicky F., Turon J., Carbon 135 (2018) 134