On the improvement of the electroluminescent signal of organic light emitting diodes by the presence of an ultra-thin metal layer at the interface organic/ITO

The electroluminescent (EL) signal of organic light emitting diodes (OLEDs) based on simple "hole transporting layer/electron transporting layer" (HTL/ETL) structures has been studied as a function of the anode/HTL interface, the anode being an indium tin oxide (ITO) film. It is shown that the electroluminescent (EL) signal increases when a metal ultra-thin layer is introduced between the anode and the HTL. Experimental results show that the work function value of the metal is only one of the factors which allow improving the EL signal via better hole injection efficiency. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim