▎ 摘　　要

We present a first-principles many-body Green's function method (GW approximation and Bethe-Salpeter equation) of the electronic and optical properties of recently predicted hydrogen-graphene-fluorine janus graphene. Significant self-energy corrections, of more than 50%, to the Kohn-Sham bandgap from the local density approximation (LDA) calculations are found. Moreover, the optical absorption spectrum of this janus graphene is dominated by enhanced excitonic effects with formation of a bound exciton with considerable binding energy. The reduced spatial separation of excited electrons and holes gives rise to extremely short radiative lifetimes, preventing condensation.