▎ 摘　　要

Understanding of the growth properties of organic thin film (OTF) on graphene surface is beneficial to develop high-performance organic electronic devices based on OTF and graphene electrodes. In this work, we investigated the growth behaviors of pentacene on the poly(methyl methacrylate) (PMMA)assisted wet-transfer graphene substrates. Especially, the influence of PMMA residues and graphene wrinkles on the initial nucleation behavior and subsequent aggregation of pentacene were studied in detail. Pentacene adopts standing-up geometry on the as-transferred graphene substrates. The molecules prefer to initially reside beside graphene wrinkles where the density of PMMA residues is found to be larger than the flat regions of graphene and then the subsequent deposited pentacene was packed face-to-face and developed into one-dimensional fiberlike domains with a fiber length of few micrometers. Controlled experiments and detailed surface analysis of graphene reveal that the hydroxyl groups of polymer residues are responsible for the standing-up geometry of pentacene on PMMA graphene. This emphasizes the importance to prepare clean graphene surface for layer-by-layer growth of pentacene with a lying-down geometry. Unfortunately, the complete removal of PMMA using acetone is not possible. Higher temperature may partially remove PMMA residue, but the decomposed radicals especially the hydroxyl radical induce standing-up geometry of pentacene, resulting in the coexistence of standing-up and lying-down molecular geometry for pentacene film deposited onto annealed graphene substrates.