Increased hole injection in organic diodes by grafting of dipolar molecules on indium–tin oxide

We present the synthesis of an azobenzene derivative and its grafting by covalent bonding to an indium–tin oxide (ITO) anode, with the purpose of increasing hole injection in polymer organic diodes. The dipolar molecules form a monolayer and decrease the energy barrier for the injection of holes into the polymer. We observe a one to two orders of magnitude increase for the injected current at a given voltage between reference (unmodified) and grafted diodes made from poly-(9-vinylcarbazole) (PVK).