Cationic Water-Soluble Conjugated Polyelectrolytes/Graphene Oxide Nanocomposites as Efficient Green Hole Injection Layers in Organic Light Emitting Diodes

The current research presents using a nanocomposite comprising of a cationic conjugated polyelectrolyte (CPE), poly­[(2,5-bis­(2-(<i>N</i>,<i>N</i>-diethylammonium bromide)­ethoxy)-1,4-phenylene)-<i>alt</i>-1,4-phenylene] or (PPPNEt₂·HBr), with graphene oxide (GO) as a new hole injection layer (HIL) for organic light emitting diodes. It is demonstrated that using the designed ionically functionalized water-soluble conjugated polymers instead of polyethylene dioxythiophene:polystyrenesulfonate (PEDOT:PSS) is a promising approach to overcome the strong acidic nature of PEDOT:PSS besides excluding its nonconductive PSS part. As the other aspiration of this work, we introduce a good partner for dissolving and spin-casting of GO as a simple and economic technique to use the hole conductive and electron blocking nature of GO in the hole injection portion of assembled devices. Using this new binary blend showed enhanced charge carrier mobility, good electroluminescence, and <i>J</i>–<i>V</i> characteristics in comparison with conventional devices. Such improvement is interpreted with induced ion space charge of HIL at the interface and resulting electric field screening effect due to ion migration