Fast response of organic photodetectors utilizing multilayered metal-phthalocyanine thin films

Multilayered photodetectors have been fabricated by using metal phthalocyanines as hole and electron transporting layers. From the dark and photocurrent density and applied voltage characteristics, the open-circuit voltage and short-circuit current density for the 5 periods of multilayered photodetector are about 0.3 V and 0.2 mA cm(-2), respectively. The photoresponse, irradiating pulsed light with the wavelength of 640 nm, has also been measured. The photogenerated excitons dissociate to free holes and electrons by relatively rapid charge transfer across closely stacked organic layer interfaces. The 3 dB bandwidth,of the device has been improved by applying a reverse bias field to the device and by decreasing the individual photo-absorbing layers while keeping the total layer thickness constant. A cutoff frequency of 1 MHz has been obtained for 5 periods of multilayered titanyl phthalocyanine/fluorinated zinc phthalocyanine photodetector by applying a reverse bias voltage of -5 V.