Universal Scaling of the Charge Transport in Large-Area Molecular Junctions

Charge transport through alkanes and para-phenylene oligomers is investigated in large-area molecular junctions. The molecules are self-assembled in a monolayer and contacted with a top electrode consisting of poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulfonic acid) (PEDOT:PSS). The complete set of J(V,T) characteristics of both saturated and π-conjugated molecules can be described quantitatively by a single equation with only two fit parameters. The derived parameters, in combination with a variation of the bulk conductivity of PEDOT:PSS, demonstrate that the absolute junction resistance is factorized with that of PEDOT:PSS. The temperature and bias dependence of charge transport in large-area molecular junctions containing different molecules is investigated. The transport exhibits universal scaling, quantitatively described by a single equation with two fit parameters. The scaling shows that PEDOT:PSS exhibits a dominant role in the electrical transport in these kinds of junctions. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.