Negative differential resistance and hysteresis in graphene-based organic light-emitting devices

Here, we report the experimental observation of negative differential resistance (NDR) and hysteresis phenomena in graphene-based OLEDs and their effects on device performance. Our results reveal that the NDR and hysteresis mainly originate from the poly(methyl methacrylate) residue resting on graphene. We further demonstrate that current annealing is a facile and effective technique to remove the polymeric residue and eliminate the NDR, leading to the dramatically enhanced luminous efficiency from 30.9 to 41.6 cd A^-1, and to 89.2 cd A^-1 when equipped with a high index half-ball lens. The demonstrated pretreatment process of graphene establishes a new path for the construction of a wide variety of high performance optoelectronic devices.