"Spicy world of NanoScience" since 2007
A simple device structure (PEDOT-PSS//(PPV + electrolyte)//graphene) emitted yellow light.
Important note is graphene was used as cathode and graphene can be printed.
Although sheen resistance of grpahene was very high (5 k ohm per sq vs. 20 ohm per sq for ITO).
Published in ACSNano. http://pubs.acs.org/doi/pdfplus/10.1021/nn9018569