Studies of long-lived photogenerated carriers in low band gap polymer photodiodes

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.