Growth of organic semiconductor thin films on a two-dimensional template is affected by its properties and is not well understood. This growth process dictates a thin film's final morphology and crystal structure and is controlled by the interactions between ad-molecules and the template. Here, we report that the template's charge density determines the tuning of such interactions. We observe the dependence of pentacene nucleation on charge carrier density ng in graphene under an applied electric field and contact-doping and then deduce that the interaction energy EA between the ad-molecule and the graphene is related linearly to ng. This tunability of EA allows control of the pentacene crystals growth. We exploit these findings to demonstrate that graphene, in which ng is controlled, can be used to template pentacene thin films for improved optoelectronic properties, such as electrical conductivity and exciton diffusion length.
Keywords: Graphene; charge carrier density; growth template; organic semiconductors.