First-principle study on the conductance of benzene-based molecules with various bonding characteristics

Electron transport through benzene-based molecule is the fundamental issue of the electrical properties of graphene and other conjugated pi-systems. To improve the device performance of conjugated pi-systems, we designed a series of benzene models and analyzed the effect of bonding environments on the molecular conductance of benzene. By combing density functional theory and the non-equilibrium Green's function method, it is found that the conductance of isolated benzene in a saturated sp(3) carbon chain is a little higher than that in a conjugated sp(2) oligophenyl chain, due to its lower attenuation with increasing unit number. The intermolecular d-p-pi coupling acts as an important positive factor favoring to improve the conductance, whereas the d-p-sigma decoupling is a negative factor to reduce the conductance. In conjugated pi-systems, the intramolecular pi-pi conjugation has enhanced by the increasing unit number, which is another positive factor contributing to the high conductivity with long molecular length. These analyses not only help to enrich our knowledge about electron transport through conjugated pi-systems, but also guide the design of graphene-based electronic devices.