Organic semiconducting materials are of increasing technological significance. Among the most promising applications are thin-film organic photovoltaic devices, which can be fabricated by low-cost, solution processing methods. A large number of different materials have been prepared in an effort to enhance the performance of these devices. The �push-pull� strategy is a widely used approach for optimizing oligomeric and polymeric materials, particularly those with small band gaps. By choosing appropriate electron-rich donor and electron-deficient acceptor monomers, the energy gaps of these polymers can be tuned.There has been an increased interest in investigating the effects of monomer sequence on macromolecular materials. However, studies of sequence effects�changing the order of donor and acceptor�on fully conjugated oligomers and polymers are rare. Indeed, the vast majority of donor/acceptor copolymers and co-oligomers have a simple alternating or random structure. Recently, however, we reported that HOMO-LUMO gap depended on sequence even for oligomers consisting of electronically similar alkoxy and unsubstituted phenylene-vinylenes. We have now extended these studies to include monomers with greater acceptor characteristics. In the figure below the difference in absorption wavelengths for a series of trimeric oligomers is presented (A = benzothiadiazole; D = 2,5-alkoxy-substituted phenyl units; connection through vinylene linkers). We have also noted sequence-based differences in intermolecular packing, which have profound implications for charge carrier mobility in device applications.

Sequence effects on electronic properties of benzothiadiazole-phenylene-vinylene oligomers

246th National Meeting (2013)

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