Quasi-particle energies and optical excitations of novel porous graphene phases from first-principles many-body calculations

Abstract

Using ab-initio density functional theory, the HSE06 functional, the quasi-particle G0W0 method and Bethe–Salpeter equation calculations, we systematically explore the electronic and optical properties of two recently proposed systems, namely hydrogenated porous graphene (HPG) and biphenyl carbon (BPC). Our results indicate that both structures have a direct band gap at the K-point. The HSE06 and G0W0 gave remarkably larger band gaps than the PBE functional for BPC and HPG, while they cannot open the band gap in graphene. The optical properties and excitonic effects of these materials are investigated in independent-quasiparticle (G0W0+RPA) and including excitonic effects (G0W0+BSE). The formation of first exciton peaks at 1.14 and 3.65 with binding energy of and 0.06 and 1.35eV was observed for BPC and HPG nanostructures, respectively. It is found that the optical conductivity for the BPC system in the 570–750nm range is larger than the graphene one. The enhanced optical conductivity can be useful in designing photonic and optoelectronic devices such as solar cells and light-emitters. The first absorption peak of HPG is located in UV-A range which can be used in the UV-absorbing devices.