Controlling the growth behavior of organic semiconductors (OSCs) is essential because it determines their optoelectronic properties. In order to accomplish this, graphene templates with electronic-state tunability are used to affect the growth of OSCs by controlling the van der Waals interaction between OSC ad-molecules and graphene. However, in many graphene-molecule systems, the charge transfer between an ad-molecule and a graphene template causes another important interaction. This charge-transfer-induced interaction is never considered in the growth scheme of OSCs. Here, the effects of charge transfer on the formation of graphene-OSC heterostructures are investigated, using fullerene (C60) as a model compound. By in situ electrical doping of a graphene template to suppress the charge transfer between C60 ad-molecules and graphene, the layer-by-layer growth of a C60 film on graphene can be achieved. Under this condition, the graphene-C60 interface is free of Fermi-level pinning; thus, barristors fabricated on the graphene-C60 interface show a nearly ideal Schottky-Mott limit with efficient modulation of the charge-injection barrier. Moreover, the optimized C60 film exhibits a high field-effect electron mobility of 2.5 cm2 V-1 s-1. These results provide an efficient route to engineering highly efficient optoelectronic graphene-OSC hybrid material applications.
Keywords: charge transfer; graphene; growth template; organic electronics; organic semiconductors.
© 2020 The Authors. Published by WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.