  Defects in low-bandgap polymer based photodetectors play a critical role in
determining switching characteristics in the near infra-red spectral-regime
relevant to communication wavelength. We carry out detailed studies of the
bandwidth limiting factors of the long-live transient photocurrent at different
incident wavelength as a function of temperature, light pulse width, bias
voltage. The results indicate that dominant transport mechanism of the
photogenerated carriers is limited by recombination at low temperature and
detrapping rate at high temperature. A general trend of a slower response of
photocarriers originating from the band-tail region is observed.
