The Diversity of Electron‐Transport Behaviors of Molecular Junctions: Correlation with the Electron‐Transport Pathway

We report the electron-transport behaviors of a number of molecular junctions composed of π-conjugated molecular wires. From calculations performed by using density functional theory (DFT) combined with the non-equilibrium Green's function (NEGF) method, we found that the length-conductivity relations are diverse, depending on the particular molecular structures. The results reveal that the conductance-length dependence follows an exponential law for many conjugated molecules with a single channel, such as oligothiophene, oligopyrrole and oligophenylene. Therefore, a quantitative relation between the energy gap (E g ) ∞ of the molecular wire and the attenuation factor β can be defined. However, when the molecular wires have multichannels, the decay of conductance does not follow the exponential relation. For example, the conductance of porphyrin-based oligomers and fused thiophene decays almost linearly. The diversity of electron-transport behaviors of molecular junctions is directly dominated by the electron-transport pathway.