Intrachain charge generation and recombination in alkoxy-substituted poly-(p-phenylenevinylene) films

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Abstract
The role of intrachain processes in ultrafast charge photogeneration has been investigated in solid state for two dialkoxy PPV derivatives, characterized by an open-chain and a closed-chain substitution, respectively. In spite of the different strength of the intermolecular interaction induced by the chemical structure of substituents, similar relaxation dynamics are observed in the first few ps. Two main relaxation pathways are individuated. Upon excitation, single-photon absorption processes generate singlet excitons, whose relaxation dynamics is initially governed by intrachain diffusion. Two-step absorption processes are responsible for generation of high-energy excited states, which decay towards intrachain charge-transfer states on a time scale faster then our temporal resolution. Ultrafast charge recombination is then observed in the first hundreds of fs.