Effect of C<sub>60</sub> on the Photovoltaic Properties of Polypyrrole-C<sub>60</sub> Heterojunctions

Abstract

We report here a series of polypyrrole/C60-H3PO4 two-layer photovoltaic cells fabricated by varying the C60 ratio with regard to polypyrrole. It is found that a slight amount of C60 can remarkably improve photovoltaic properties by four orders of magnitude; with C60 ratio the open-circuit voltage and short-circuit current increase, and at higher C60 ratio the photovoltaic working threshold is lowered too, the cell can even work efficiently in dark, more approaching the efficiency under strong illumination. The optimized device yields 1.2 V open-circuit voltage and 14 μA/cm2 short-circuit current, and a power conversion efficiency 0.01%. Our results show that polypyrrole is a potentially good material for photovoltaic cells. The effect of C60 in combination with polypyrrole is discussed.