The Frenkel-Holstein model in the Born-Oppenheimer regime is used to interpret temperature-dependent photoluminescence spectra of solutions made with the poly(p-phenylene vinylene) derivative MEH-PPV. Using our recently developed structural optimization method and assuming only intrachain electronic coupling, we predict the structure of emissive MEH-PPV chromophores in terms of a mean torsional angle ϕ0 and its static fluctuations σϕ, assuming no cis–trans defects. This allows us to fully account for the observed changes in spectra, and the chromophore structures obtained are consistent with the known phase transition at 180 K between a “red” and “blue” phase.
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