Photophysics of phenylenevinylene polymers

We report steady-state and transient optical characterization of phenylenevinylene polymers and extract a picture of the photoexcitations and dynamics which may apply more generally to nondegenerate ground-state conjugated polymers. The most common excitation pathway involves formation of nonemissive interchain excitons, unless the polymer chains are separated so that intrachain excitons responsible for photoluminescence are formed preferentially. Oxidation defects can be introduced thermally or photochemically and lead to charge transfer quenching of intrachain excitons whose dynamics can be understood quantitatively. We have identified the defect site, quantified concentrations at which it becomes problematic and shown that we can essentially eliminate it with improved synthesis. The maximum electroluminescence efficiency is not simply related to the photoluminescence quantum yield ΦPL and might be several times higher than ΦPL/4 which we estimate to be only 4% for our material.