In this paper, the optical and photo-induced electron transfer properties of a new conjugated molecule, 4,7-bis{5'-[4",4"-NN-diphenylamino-styryl]thiphen-2'-yl} -benzo[1,2,5-thiadiazole] (simplified as TPA-th-TPA), were investigated. Using TPA-th-TPA as a photoactive layer, organic solar cells with three different architectures were fabricated by spin-coating method. The photosensitive layers of these architectures comprise pure TPA-th-TPA layer, heterojunction of bi-layered TPA-th-TPA and C-60, and bulk-heterojunction of TPA-th-TPA and [6, 6]-phenyl C-61-butyric acid methyl ester (PCBM) blend. Furthermore, towards the bulk-heterojunction devices, the effect of the cathode materials (Mg, Ca, LiF/Al, Ba) on the performance of the devices was studied. The power conversion efficiency reached 0.26% for the device based on the blend of TPA-th-TPA and PCBM with Ba/Al as the cathode. (c) 2005 Elsevier B.V. All rights reserved.