Evaluation of bis-dicyanovinyl short-chain conjugated systems as donor materials for organic solar cells

Three conjugated compounds based on carbazole, cyclopentadithiophene and dithienopyrrole substituted by branched alkyl chains have been synthesized by the Knoevenagel condensation of malonodinitrile with the appropriate dicarboxaldehyde. Electronic properties of the target compounds have been analyzed in solution by UV–vis absorption spectroscopy and cyclic voltammetry and their potentialities as a donor material in donor–acceptor heterojunction solar cells have been evaluated in bilayer devices involving both solution processed or vacuum deposited donor layers and thermally evaporated fullerene C60 as an acceptor.