First-principles calculations of the optical response of single-layer and bilayer armchair graphene nanoribbons

Electronic and optical properties of single-layer bilayer armchair graphene nanoribbons are investigated using a first-principles method. Increased nanoribbon width reduces the band gap causes red shift in photon absorption energy. The 3 n + 2 family has smallest gaps lowest onset energy among three families considered due to high π -conjugation indicated by exciton wavefunctions. We also compare α β alignments with their counterparts. extra layer energy, difference between alignment configuration is more significant than that single layer. Our calculations indicate depend on details atomic structures, including width, edge number layers. These characteristics expected be important design optoelectronic devices.