Graphene Ink as a Conductive Templating Interlayer for Enhanced Charge Transport of C₆₀-Based Devices

We demonstrate conductive templating interlayers of graphene ink, integrating the electronic and chemical properties of graphene in a solution-based process relevant for scalable manufacturing. Thin films of graphene ink are coated onto ITO, following thermal annealing, to form a percolating network used as interlayer. We employ a benchmark n-type semiconductor, C₆₀, to study the interface of the active layer/interlayer. On bare ITO, C₆₀ molecules form films of homogeneously distributed grains; with a graphene interlayer, a preferential orientation of C₆₀ molecules is observed in the individual graphene plates. This leads to crystal growth favoring enhanced charge transport. We fabricate devices to characterize the electron injection and the effect of graphene on the device performance. We observe a significant increase in the current density with the interlayer. Current densities as high as ∼1 mA/cm² and ∼70 mA/cm² are realized for C₆₀ deposited with the substrate at 25 °C and 150 °C, respectively.