Conjugated polymers at the verge of strongly correlated systems and 1D semiconductors

We review the solid state physics approach to electronic and optical properties of conducting polymers also with attempts to bring together languages of the solid state theory for polymers and the quantum chemistry of oligomers. We consider polymers as generic one-dimensional semiconductors with features of strongly correlated electronic systems. Our model combines the long range electron–hole Coulomb attraction with a specific effect of strong intra-monomer electronic correlations, which results in effective intra-monomer electron–hole repulsion. We explain, exploit and organize various experimental and numerical findings. For example we connect such different questions as shallow singlet and deep triplet excitons in phenylenes, A g –B u exciton levels crossing in polyenes, common 1/ N energy dependencies in oligomers.