ASSIGNMENT OF THE PICOSECOND PHOTOINDUCED ABSORPTION IN PHENYLENE VINYLENE POLYMERS

We report results of time-resolved photoinduced absorption experiments on oriented poly(2-methoxy-1,4-phenylene vinylene) films using probe energies from 0.2 to 2.3 eV. We observe two photoinduced absorption bands centered near 0.5 and 1.5 eV which form within our time resolution (< 1 ps) and decay with a fast (ps) and a slow (ns) component. The relaxation dynamics for the two bands are identical, indicating they are from the same excited species. On the basis of the spectra, the dynamics, and the pump intensity and polarization dependences, we conclude that these absorption features are due to bound polaron pairs and not to singlet or triplet excitons as previously suggested.