Frequency response and equivalent circuit of organic photodetectors based on zinc phthalocyanine and the fullerene derivative organic solar cell

Abstract The photodetection properties and the equivalent circuit of organic photodetectors (OPDs) based on zinc phthalocyanine (ZnPc) and fullerene derivative (C 60 ) solar cells are discussed. The CuI layer is very effective to enhance the responsivity and the bandwidth of the OPDs. The obtained responsivity is 29 mA/W, and the bandwidth is 300 kHz, which is restricted by the modulation bandwidth of the illuminating laser. The complex impedance of the OPD is measured, and two types of equivalent circuit are discussed. The simple equivalent circuit is composed of a series resistance and a parallel circuit of a resistance and a capacitance, and it approximately describes the measured complex impedance. The precise equivalent circuit is composed of a series resistance and two parallel circuits of resistance and capacitance, describing the ZnPc and the C 60 separately, and it describes the measured complex impedance very well. The frequency response is simulated by using the equivalent circuits, and the simulated bandwidth is almost the same as the measured bandwidth.