Abstract

Incorporation of self-assembled monolayers (SAMs) in (semi-)conducting organic diodes is an attractive way to study fundamental processes in organic electronics. We have incorporated SAMs in organic diodes with the general structure metal/SAM/polymer/metal, on which two research directions are based.

The first direction is based on tuning the injection barriers for holes and electrons into the semiconducting polymer through the formation of dipoles on the metal surface. Metal work functions of gold and silver are varied over 1.4 and 1.7 eV, respectively, by using the dipole moment of theSAM. Applying these modified electrodes, the hole current in a polymer LED can be tuned by more than 6 order of magnitude. Suppression of the hole current enabled us to measure the electron current in a polymer/polymer blend photovoltaic cell.¹

The second direction relies on the formation of metal-insulator-metal (MIM) diodes consisting of alkanedithiol (C8, C10, C12, C14) sandwiched between Au and the organic conductor topped with Au. We demonstrate a technology, using conventional photolithography, for the facile and highly reproducible fabrication of large-area molecular electronic MIM diodes based on SAMs of alkane dithiols with a non-reactive organic top electrode topped with gold to complete the crossbar circuit . This simple technology to fabricate molecular devices will pave the way for molecular electronics.

1. Adv. Mater., 17, 621–625 (2005).

2. Nature, 441, 69–72 (2006).