Work function engineering of graphene oxide via covalent functionalization for organic field-effect transistors

•A method to produce work-function-tuned graphene based on the nucleophilic substitution of the epoxy groups on graphene oxide was reported.•The property of the graphene oxide is controlled dramatically, which results in the apparent work functions in a broad range between 3.73 eV and 5.1 eV.•We also demonstrated organic field effect transistors incorporating the functionalized graphene nanosheet interlayers.