Unraveling the Failure Modes of Molecular Diodes:The Importance of the Monolayer Formation Protocol and Anchoring Groupto Minimize Leakage Currents

The failure modes of molecular junctions have been only sporadically investigated, but they are important to understand so they can be prevented and molecular junctions can be optimized. Although it is commonly accepted that the performance and electrical characteristics of molecular tunneling junctions depend strongly on the supramolecular structure of the molecules inside the junctions, how sensitive molecular junctions are to small supramolecular changes and the factors that cause disorder are poorly understood for most types of molecular junctions. This paper shows that the performance of a large-area molecular diode depends on the choice of the anchoring group and solvent used for the formation of the self-assembled monolayer (SAM) in which both affect the surface coverage and the occurrence of disordered SAM domains. As a result, the rectification ratio was reduced by more than a factor of 10 across a series of molecular diodes, containing a diphenylacetylene backbone and a ferrocenyl terminus. The ...