The role of top interface layer in bipolar resistive switching (BRS) behaviors of Al/PEDOT:PSS/Al memory devices was investigated via comparison with the Au/PEDOT:PSS/Al system. The IeV characteristic curves of device with a PEDOT:PSS layer sandwiched between two Al electrodes displayed bipolar resistive switching characteristics, while the device with Au top electrode showed a permanent breakdown in forming process. HRTEM and in-situ XPS observation demonstrated that the Al top electrode reacted with oxygen and sulfur of PSS chain and produced Al-O-S layers, whereas Au top electrode did not reacted to form these types of interfacial layers. These results have confirmed the critical role of Al top electrode with the strong reactivity with a PEDOT: PSS organic layer in the bipolar resistive switching behaviors, which seems to closely related with the presence of electron trap sites at the interface between the top electrode and organic active layer. (C) 2011 Elsevier B. V. All rights reserved.