Theoretical calculations of the optoelectronic properties of a penta-graphene monolayer: study of many-body effects

Based on density functional theory (DFT), the GW approximation and Bethe–Salpeter equation (BSE), we performed a theoretical calculation to study the electronic and optical properties of penta-graphene (PG) monolayers. Our findings reveal that PG behaves as a semiconductor with an indirect band gap of 2.27 eV at the DFT-GGA level. By incorporating the GW approximation based on many-body perturbation theory, we observed an increase in the band gap, resulting in a quasi-direct band gap of 4.53 eV. Furthermore, we employed the G₀W₀-RPA and G₀W₀-BSE approximations to compute the optical spectra of the monolayer in the absence and in the presence of electron–hole interaction, respectively. The results indicate that the inclusion of electron–hole interactions leads to a red-shift of the absorption spectrum towards lower energies compared to the spectrum obtained from the G₀W₀-RPA approximation. Notably, the optical absorption spectra are predominantly governed by the first bound exciton, characterized by a significant binding energy of 2.07 eV. Our results suggest that the PG monolayer, with its wider band gap and enhanced excitonic effects, is potentially a suitable candidate for the design and fabrication of optoelectronic components.