Femtosecond transient absorption study of oriented poly (9,9-dioctylfluorene) film: Hot carriers, excitons, and charged polarons - art. no. 193201

We present a transient absorption spectroscopy study of oriented poly (9,9- dioctylfluorene) film. By comparing the spectral features and dynamics at d ifferent wavelengths using different probe polarizations, we conclude that three species are generated after the photoexcitation: hot carriers, excito ns, and charged polarons. The charged polaron spectrum is measured with the probe beam polarized perpendicular to the polymer chains, and two bands ar e recognized. In addition, a new band in mid-IR regime is observed that dec ays faster than excitons, and whose peak shifts in time. This feature is as signed to hot carriers.