Band-gap engineering and giant anisotropic conduction in 2D carbon allotrope nanoribbons

We investigate the electronic structure and quantum transport of OPG-Z carbon nanoribbons using first-principles density functional theory (DFT) and non-equilibrium Green’s function (NEGF) methods. We find that cutting the OPG-Z lattice along different directions produces ribbon families with dramatically different behavior. One ribbon (armchair-PO motif) is essentially metallic, whereas others are semiconducting with giant electronic anisotropy: band gaps range from ~ 0.07 to 0.53 eV depending on the edge motif. This leads to highly direction-dependent conduction, with the metallic ribbon exhibiting orders-of-magnitude higher low-bias conductance than the narrow-gap ribbons. Transport simulations show that semiconducting OPG-Z nanoribbons require threshold biases comparable to their bandgap (~ 0.1–0.5 V) before significant current flows, whereas the metallic ribbon conducts readily at zero bias. Analysis of structure–property trends reveals that subtle changes in the fused pentagon–octagon edge motifs tune the effective bandgap and carrier transport. These pronounced anisotropic transport properties combined with the robust stability of the carbon lattice suggest OPG-Z nanoribbons as promising building blocks for future nanoelectronic and directional transport devices, such as anisotropic field-effect transistors and current rectifiers.