Electronic, thermoelectric, and optical properties of defective armchair graphene nanoribbons under transverse electric fields

Abstract We present a comprehensive study on the electronic, thermoelectric, and optical properties of armchair graphene nanoribbons (AGNRs) with a ribbon of width M = 15 dimer lines, incorporating divacancy defects at distinct positions. Using the tight-binding approximation combined with atomistic Green’s function formalism and the gradient approximation, we systematically analyze the role of defect positioning and external transverse electric fields on the material’s behavior. Our findings reveal that both the presence and the location of divacancies (DVs) significantly modulate the electronic band structure, leading to marked changes in thermoelectric and optical responses. Specifically, for DV = 7–8, the appearance of a divacancy induces two distinct peaks in the Seebeck coefficient curve, indicating an enhancement in the thermoelectric conversion efficiency of the material relative to pristine AGNRs. Moreover, the maximum value of the Seebeck coefficient is also approximately 6.55 times higher than that of a graphene monolayer. In addition, under an external electric field, with an applied potential of 0.4 V in the DV = 7–8 model, the optical absorption of the material increases sharply at an energy of 1.68 eV, corresponding to a wavelength of 738 nm, which lies in the red to near-infrared region.