Cyanoporphyrins have been included into the active layer of bulk heterojunction poly (3-hexylthiophene) (P3HT): [6,6]-phenyl-C-61 butyric acid methyl ester (PCBM) solar cells. The amount of porphyrin, P3HT and PCBM were systematically varied and the characteristics of the devices from the corresponding active layers were recorded. The spectral responses of the devices showed that the addition of the porphyrin to the active layer broadened the absorption efficiency of the device and led to a porphyrin contribution to the photocurrent of the solar cell. The porphyrin molecules did not contribute to the photocurrent unless both P3HT and PCBM were present in the active layer. In most cases, the porphyrin was unable to contribute to the photocurrent after the devices had been annealed, suggesting changes to the morphology of the active layer. (c) 2006 Elsevier B.V. All rights reserved.