Concentration dependence of photovoltaic properties of photodiodes based on polymer–fullerene blends

Photovoltaic properties of photodiodes based on the blends of poly[2-methoxy-5-(2′-ethylhexoxy-1,4-phenylenevinylene) (MEH-PPV) and fullerene (C60) are investigated. The experimental results show that the open-circuit voltage (Voc) declines with the increasing concentration of C60. A big variation of ∼400 mV in the Voc for the devices with the concentration of 0% and 50% indicates the electron affinity potential of C60 can strongly influence the resulting Voc. At the bias of −1.5 V, the photosensitivity of the device with the concentration of 50% is 55.6 mA/W under the illumination intensity of 16.7 mW/cm2 and its photogain sharply rises by two orders of magnitude than that of the undoped MEH-PPV device.