OPTICAL-EXCITATIONS OF POLY-3-ALKYLTHIOPHENE FILMS AND SOLUTIONS

We report a comparative study of the optical properties and photoexcitations of solid-state and solution samples of poly-3-alkylthiophenes. The pi-electron delocalization and backbone conformational properties are investigated by resonant and preresonant Raman scattering. Photoexcited electronic states are studied by cw photomodulation spectroscopy. The intensity and chopper-frequency dependence of the photoinduced electronic bands indicate two different photoexcitation pathways. An interchain mechanism takes place in the solid while in solution a weak solvent-polymer charge transfer is proposed.