Picosecond photophysics of luminescent conducting polymers from excitons to polaron pairs

We present a study of picosecond(ps) time-resolved photo-modulation(PM) spectroscopy of DOOPPV in solution, pristine, photo oxidized and C60-doped DOOPPV films, and thin films of P3BT. We find that the photophysics of pristine luminescent polymers is determined by excitons, which in the singlet manifold are characterized by a PM spectrum consisting of two photoinduced absorption(PA) bands and a stimulated emission band. Excitons in the triplet manifold, on the contrary, can be identified by a PM spectrum consisting of a single PA band. After photo-oxidation or doping, a new type of photo-excitations is produced — intrachain polaron pairs, characterized by a broad PA band and much slower recombination dynamics compared to that of singlet excitons