Indium-tin oxide anodes modified by self-assembly for light-emitting diodes based on blue-emitting polyfluorenes

We present the electro-optical properties of light-emitting diodes (LEDs) based on two blue-emitting polyfluorenes, with aluminum cathodes and having indium-tin oxide (ITO) anodes modified by self-assembled monolayers (SAM) of benzenesulphenyl chloride derivatives. The modification of ITO surface was confirmed by contact angle measurements. Electroabsorption measurements were used to assess the modification of ITO work function upon SAM formation. We find that the use of a benzenesulphenyl chloride derivative containing a nitro group is as effective at improving LEDs characteristics as the use of a hole-injection layer of well known PEDOT:PSS.