Up-scalable ITO-free organic light emitting diodes based on embedded inkjet-printed copper grids

We report on ITO-free OLEDS with a transparent hybrid Cu nanoparticle grid/PEDOT:PSS electrode processed in ambient conditions. An experimentally based methodology was implemented, where studies on alternative PEDOT:PSS derivatives and Cu grid design were performed, to gradually increase the efficiency of lab scale ITO-free OLEDs. To further increase electrode performance, inkjet-printed (IJP) Cu-grids are embedded to flatten the electrode, reduce leakage current and enhance homogeneity and efficiency. Finally, embedded Cu based ITO-free OLEDs showed current and power efficiencies comparable to reference ITO-based OLEDs. Methods to manufacture large area flat embedded IJP Cu-electrodes on glass and flexible substrates are presented and upscaling prospects of the proposed ITO-free electrode are discussed.