▎ 摘　　要

The electronic and optical properties of a new type of hydrogenated graphene in the C4H phase have been studied using the first-principles many-body Green's function method (GW approximation and Bethe-Salpeter equation). It demonstrates that strong charge-transfer excitonic effects dominate the optical properties of C4H. The binding energy of the first exciton, which turns out to be strongly localized, is as large as 1.67 eV. The spatial separation of exited electrons and holes makes C4H a candidate for the realization of excitonic Bose-Einstein condensate. Dark state provides a traveling path for the bound excitons. As the situation in graphane with H vacancies, changing H coverage changes the electronic and optical properties and the associated applications.