The role of intermolecular interactions on the optical and charge-transferproperties of conjugated polymers

We investigate by means of quantum-chemical calculations the influence of i ntermolecular interactions on the properties of conjugated chains. We first focus on the optical absorption and emission of clusters formed by identic al poly(paraphenylene vinylene), PPV, oligomers; we address the role played by the relaxation effects in the lowest excited state as well as the numbe r and relative orientations of the interacting units. Several strategies ar e suggested that can be developed to avoid a substantial decrease in lumine scence quantum yield in the solid state. In a second part, we illustrate by means of a simple theoretical model that charge or energy transfer can tak e place at the interface between two different PPV derivatives, depending o n the nature of the substituents grafted on the PPV backbone.