Abstract The effect of lateral variations in material properties on the I−V characteristic of semicrystalline silicon solar cells is studied by means of numerical simulation. Individual crystallites are described with the aid of a one-diode model; the effective I−V characteristic of the cell under illumination is analyzed in terms of a two-diode model using curve fitting. A wide distribution of diffusion lengths of the minority charge carriers is found to worsen the I−V characteristic. This is reflected in increased values of the effective series resistance and second-diode saturation current. The study shows that the effects of intrinsic inhomogeneities cannot be separated in a straightforward manner from those of recombination in space-charge regions.