In this paper, the stability of small-molecule organic solar cells based on copper phthalocyanine (CuPc) and fullerene (C(60)) is investigated. The use of silver instead of aluminum as the metal electrode in these solar cells, with smaller grain size and grain boundaries as well as with more uniform grain size distribution in the film, results in significant improvement in the lifetime of the devices. The substantial role of silver in the protection of the cells against permeation of oxygen and/or water molecules into the organic thin films is confirmed. Substitution of a thin buffer layer (70 angstrom) of bathophenanthroline (Bphen) for bathocuproine (BCP), sandwiched between C(60) and the cathode, makes considerable progress in the lifetime of the device. (C) 2011 Elsevier B.V. All rights reserved.