In this study, we report a theoretical investigations on the structural, optoelectronic and photovoltaic properties of a series of conjugated organic molecules containing thieno[2,3-b]thiophene, with different substituents. The DFT calculations were performed by using the quantum chemical methods using B3LYP [1] level with 6-31G(d) [2] basis set for all atoms. All calculations were realized by Gaussian 09 [3] program supported by GaussView 5.0.8 interface. Moreover, the optoelectronic properties (HOMO, LUMO, Egap…) were determined from the fully optimized structures. The absorption properties (λmax, Etr, OS) of these molecules are obtained by TD-B3LYP/6-31G(d) method [4].The studied oligomers can be subdivided in three categories; the first one constitutes by synthetized oligomers [5] but is characterized with the highest energy band values. Thanks to the effect of structural modifications in there chemical structures in the second and the third categories, the energy gap values have known a dramatic decrease. We conclude that these conjugated materials, especially of the third categories, are good candidates for bulk heterojunctions in organic solar cells applications.
