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
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Work by: Chien et al. (Nanotechnology 21 (2010) 134020 (5pp))
http://iopscience.iop.org/0957-4484/21/13/134020/pdf/0957-4484_21_1...
As an alternative to ITO, CNT/Al is used as anode. The sheet resistance of CNT layer was: 100 Ohm/sq with transmission ~60%. it goes up to 500 Ohm/sq for ~90% transmission. Device structure was: Al/Lif/organic layer/PEDOT-PSS/CNT (Al)
I had an impression that top emission means emission from cathode side. Anyway, I was trying to understand why was the effort on emission from CNT side. Is it due to increase extraction efficiency? Authors didnt mention anything about it. Differnece of refractive indices (ITO ~2.0, glass ~1.52, air 1.0, organic layer ~ 1.7) between organic and ITO is significant. I dont know refractive index of CNT. But I found this article: Nanotechnology 18 (2007) 265706 (5pp), (http://iopscience.iop.org/0957-4484/18/26/265706/pdf?ejredirect=.io...). I assume that refractive index of CNT ~1.1. (not sure, anybody knows about this?). If so, there is less refractive index difference between air and CNT. may be it should help to increase the external efficiency. CNT can also scatter the light. that would also further enhance, I assume.
Any comments from anybody??