Theoretical Study of Long-Range Electron Transport in Molecular Junctions

A study of long-range electron transport through a series of molecular junctions comprised of π-conjugated molecules is presented. A theoretical model is built by using a quantum chemistry based Landauer theory combined with Green’s function formalism and the D’Amato−Pastawski model to describe the electronic conduction in the presence of incoherent scattering effects. Effects of incoherent transport on the total conductance under the nonbiased, stationary, and nondissipative conditions are investigated. Calculation results with the Newns−Anderson approximation show that the distance dependence of electron conduction through molecular wires smoothly interpolates the transition of the dominant transporting mechanism from coherent tunneling with the exponential decay in short distance to incoherent tunneling associated with sequential hopping with weak distance dependence.