We examined the film morphologies and transistor properties of hetero-molecular bilayer consisting of N, N’- dioctyl-3, 4, 9, 10-perylenedicarboximide (PTCDI-C 8 ) and quaterrylene. First, the structure and carrier conduction of PTCDI-C 8 films were studied, followed by an analysis of the carrier accumulation process in a PTCDI-C 8 /quaterrylene hetero-bilayer transistor. Based on the displacement current measurement (DCM), we stress the potential of the hetero-bilayer for tuning carrier accumulation like carrier doping techniques in field-effect transistors.