We present the synthesis of an azobenzene derivative and its grafting by covalent bonding to an indium-fin 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). (C) 2003 Elsevier Science B.V. All rights reserved.