Theory of electrical rectification in a molecular monolayer - art. no. 085405

The current-voltage characteristics in Langmuir-Blodgett monolayers of gamm a -hexadecylquinolinium tricyanoquinodimethanide (C(16)H(33)Q-3CNQ) sandwic hed between Al or Au electrodes is calculated, combining ab initio and self -consistent tight-binding techniques. The rectification current depends not only on the position of the LUMO and HOMO relative to the Fermi levels of: the electrodes as in the Aviram-Ratner mechanism, but also on the profile o f the electrostatic potential which is extremely sensitive to where the ele ctroactive part of the molecule lies in the monolayer. This second effect c an produce rectification in the direction opposite to the Aviram-Ratner pre diction.