Theory of tunneling and electron transport through single molecules of polyaniline

Polyaniline is a linear organic polymer used often in battery devices, films, and organic electrodes, and it exhibits a dramatic increase in conductivity due to electrochemical oxidation or acidic treatment. The polymer chain has different bonding configurations depending on the oxidation state -- they include leucoemeraldine, emeraldine, and pernigraniline bases and their salts. Most forms are semiconducting and electron transport through these forms as single molecules is expected to occur via a tunneling mechanism. We have computed the complex bandstructure (which include imaginary k-vectors to allow for tunneling) of the semiconducting forms to gain insight into the expected length dependence of the electron tunneling current ($\sim $e$^{-\beta L})$ and the energy dependence of the decay parameter $\beta $. Model calculations of the I-V curves for metal/single-molecule/metal molecular electronics geometries will be discussed (the metal is gold). The electron transport calculations use DFT Green's function scattering methods.