Polymer solar cells based on regioregular poly(3-hexylthiophene) (P3HT) and ([6,6]-phenylC61-butyric acid methyl ester) (PCBM) were fabricated with two different architectures (normal and inverse). Normal cells using indium tin oxide (ITO) as anode and Al as cathode were fabricated on polyester foils and illuminated from substrate side. Inverse cells using Ti as cathode and ultrathin An layer as anode were illuminated from the top side covered by a transparent Au contact. Both An layer and PET/ITO show comparable transmission in the spectral range where P3HT absorbs. Inverse cells showed comparable device parameters to normal cell (open circuit voltage 550 mV, short circuit current 6.25 mA/cm(2), fill factor 0.33 and white light power conversion efficiency 1.12%). (C) 2004 Elsevier B.V. All rights reserved.