Structural effects on mechanical and optoelectronic properties of S-doped graphyne

The graphyne family represents a versatile class of carbon-based materials, encompassing both semiconductors and semimetals with promising potential for technological applications. In this work, we analyze the influence of structural changes on the mechanical, electronic, and optical properties of sulfur-doped graphyne (S-GY), a recently synthesized carbon-based material composed of five-membered rings connected by acetylenic linkers. The S-GY monolayer is an indirect band-gap semiconductor with a gap of ∼1.3 eV. Furthermore, sulfur incorporation along with the resulting structural modifications breaks the electron-hole symmetry typically observed in pristine graphyne phases. Its thermodynamic stability is confirmed by phonon dispersion and ab initio molecular dynamics simulations, while the elastic response reveals pronounced anisotropy. The optical absorption spectrum indicates the presence of bound excitons, with a binding energy of 460 meV for the ground-state exciton, while the estimated maximum power-conversion efficiency of ∼22% highlights S-GY as a promising alkynyl carbon material for next-generation photovoltaic technologies.