Electron Transport Investigation of Thiophene Oligomers Based Molecular Wires

We investigate the electron conductance of thiophene oligomers based molecular wires using the first principles method, which is based on the density functional theory and nonequilibrium Green´s function. The molecular wires are built by bridging various thiophene oligomers (dimers, tetramers and hexamers with different inter-ring torsional angles) between two gold electrodes via terminal groups S and CN. The projected energy levels, energy gaps, transmission functions and current-voltage characteristics of the molecular wires are calculated and analyzed. Results show that the molecular wires with the planar structures of thiophene oligomers have larger electron transmission functions, hence better electronic conductance than those with twist structures. The conductance of molecular wires decreases when the chain length of the thiophene oligomer increases. The terminal groups between the oligomer and the electrode has nontrivial effects on the conductance of the wires. The results could provide a qualitative guidance for design molecular electronic wires.