Single- and Double-Layer Graphenes as Ultrabarriers for Fluorescent Polymer Films

Graphene offers great potential for electrodes in flexible organic optoelectronic devices. Moreover, it may function as a permeation barrier to protect a device from chemical degradation under ambient conditions. Here, we report on the chemical and structural stability of graphene in situ on a conjugated polymer film. Fluorescence and scanning force microscopies were used to probe the degradation kinetics of the fluorescent polymer protected from ambient by graphene. We demonstrate that defect-free single-layer graphene efficiently protects the polymer from oxygen and water in the ambient, reaching the technological requirements on ultrabarriers, but we also observe a growing number of individual permeable defects in the single-layer graphene resulting from photoinduced structural degradation of the graphene. In contrast, double-layer graphene remains free of permeable defects, which we attribute to the structural independence of the two single layers. This suggests that graphenes can function as both a transparent electrode and a barrier layer in future optoelectronic devices.