Charge-transfer and energy-transfer processes in π-conjugated oligomers and polymers: A molecular picture

The first calculations on polyenes and the attention given to the issues of bond length alternation and ordering of the lowest singlet excited state served as impetus for the description of the electronic structure of π-conjugated materials. Initially, the goal of most calculations was to determine the nature of the (unrelaxed) excited states playing a role in the second-order and third-order molecular polarizabilities. Later on, the relaxation effects in the excited states and impact of intermolecular interactions drew significant interest. These and other related works point to the increased significance of the dynamic processes taking place in π-conjugated materials, such as charge transport, charge recombination, exciton formation, exciton diffusion, or exciton dissociation.