Excitations and optical properties of phenylene based polymers

A complex picture of phenylene-based polymers is developed which unifies features of band and molecular exciton models. It incorporates major experimental finding in direct and photoinduced optical absorption, stimulated photoemission and photoconductivity. We give new assignments for the most disputed features and identify new ones as edge states. We confirm a low binding energy for the principle emitting exciton and show that it dominates also in the fundamental absorption. Contradictions in the current modeling state-of-art are displayed and discussed.