Optical properties and dynamics of molecular excitons in oligothiophenes

CW absorption and emission spectra as well as time-resolved photoemission dynamics have been employed to detect the evolution of the first excited electronic states and the associated spectroscopical changes in passing from the isolated molecules to the aggregated state in thiophene oligomers. To this end a novel form of inclusion compound in PHTP in which the molecules are electronically decoupled in the solid state has been studied, thus avoiding the complications associated with the change in conformation occurring upon dissolution. The experimental data are interpreted in terms of the molecular exciton model.