Band Gaps and Optical Spectra from Single- and Double-Layer   Fluorographene to Graphite Fluoride: Many-Body Effects and Excitonic States
  We compare first-principle band gaps and optical absorption spectra of single- and double-layer fluorographene with bulk graphite fluoride. The electronic properties are calculated using the many-body GW approximation and the optical spectra using the Bethe-Salpeter equation (BSE). The inclusion of electron-hole interactions is crucial for predicting low energy excitonic absorption peaks. The position of the first exciton peak is identical in single-, double- and multilayer fluorographene, which may indicate that the onset of the absorption spectra does not differ in these materials. 
Franti\v{s}ek Karlick\'y and Michal Otyepka
cond-mat.mtrl-sci