We have investigated how bulk photoconductivity influences the photovoltaic parameters of zincphthalocyanine-fullerene ZnPc/C60 p-n heterojunction solar cells. The results indicate that the photocurrent action spectrum of a cell depends strongly on
the photoconductivity and spectral characteristics of each component material. We therefore propose a model that simulates the action spectra of the short-circuit photocurrent in the molecular organic solar cells, and our model is based on the assumption that the photocurrent action spectrum depends on the bulk layer photoconductivity.