Two polymers: fullerene bulk heterojunction solar cells: [(1) poly[ 2-methoxy-5-(3,7-dimethyloctyloxy)]-1,4-phenylenevinylene (MDMO-PPV): methanofullerene phenyl-C(61)-butyric-acid-methyl-ester ([60]PCBM) and (11) poly(3-hexylthiophene-2,5-diyl), highly regioregular (P3HT): [60]PCBM] were studied. Indium tin oxide (ITO) and/or poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) were/was used as transparent electrode, and lithium fluoride (LiF) was used as buffer layer for aluminium cathode. The role of ITO and PEDOT:PSS on the current-tension characteristics, on open circuit voltage V(OC) and on density of short-circuit current J(SC) was investigated for the two polymers:PCBM blend solar cells as deposited and after 40 days ageing. (C) 2009 Elsevier B.V. All rights reserved.