Two-layer organic photovoltaic cells have been fabricated using a triphenylene ether as a hole transporting material, and perylene derivatives as electron transporting materials. Three devices were studied and showed external quantum efficiencies of around 3%. These results are interpreted in the context of electrochemical measurements that provide the ionization potential and electron affinity. Furthermore, the high-exciton diffusion lengths and absorption coefficients contribute to the high-observed photocurrents. The organic/organic interface was found to be the main origin of the photocurrent generation. However, the photovoltaic parameters were found to be dependent also on the ITO/organic interface. In particular, we show that ITO treatments with argon plasma and UV-ozone modify the open-circuit voltage. (C) 2004 Elsevier B.V. All rights reserved.