Molecular monolayer modification of the cathode in organic light-emitting diodes

Abstract

The effects of alkanethiol self-assembled monolayers (SAMs) attached to the gold cathode of organic light-emitting diodes made by soft contact lamination are investigated. In spite of reported work function lowering by alkanethiol SAMs, the results from this work showed that their primary effect in carrier transport is to act as a thin insulating layer, causing current reduction. At the same time, the luminescence efficiency was enhanced because the SAMs reduce exciton quenching by the metal cathode. A two-order-of-magnitude enhancement at light emission onset was observed for a hexadecanethiol modified device. (c) 2006 American Institute of Physics.