Organic photovoltaics (OPVs) offer a potential route for large-scale solar energy development due to the ability to make light-weight devices with mechanical flexibility from low-cost materials and solution-based processing.  Despite a steady increase in the power conversion efficiencies (PCEs) that have been achieved by OPVs in recent years (~5-12%), these materials still lag behind inorganic counterparts.  The fundamental difference between organic and inorganic photovoltaics is the creation of strongly-bound electron-hole pairs, or excitons, in OPVs upon light absorption due to the low dielectric constants of organic semiconductors. Exciton dissociation occurs almost exclusively at the interface of the donor and acceptor materials, thus diffusion to this interface before exciton decay is often a limiting factor in OPV efficiencies. To achieve small exciton diffusion lengths (~10 nm) and optimum absorption thicknesses (~100-200 nm), an ideal OPV would have vertically-aligned, nanometer-scale channels of donor and acceptor materials throughout the active layer.  Block copolymers offer a solution since these materials self-assemble into well-ordered, nanometer-scale morphologies as a result of the inherent incompatibility of covalently-tethered polymer segments.  Furthermore, the covalent bond between donor and acceptor blocks can enhance the long-term stability of block copolymer OPVs. With this in mind, a pair of novel p-type oligiothiophene-functionalized norbornene monomers has been synthesized, characterized and polymerized through ring-opening metathesis polymerization. Polymerization of this type has been shown to afford well-ordered block copolymers, allowing for the potential to synthesize copolymers containing both p-type and n-type moieties for use in photovoltaic cells. Herein will be presented the synthesis, characterization, photophysical and electrochemical properties of these p-type monomers and resulting polymers.

Polynorbornene derivatives with oligothiophene side chains: p-Type materials for use in semiconducting block copolymers

247th National Meeting (2014)

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