Influence of the wavelength of incident light on shunt conductance and fill factor in amorphous silicon solar cells

A variety of a-Si solar cells (n-i-m and n-i-p structures) were prepared by the method of sputtering. The photoconductive shunt resistance was obtained from the light I-V characteristics in far reverse bias, and the influence of this parameter on the fill factor (FF) was studied. Correlations were sought between FF's, diffusion lengths, collection widths, and the hydrogen concentration in the i-layer. The FF's were found to vary with the wavelengths of the light under which an I-V curve was measured, and for certain cells with poorer overall FF's, lower values were obtained in both the red and the blue portions of the spectrum. The decreased values at the ends of the spectrum were ascribed to recombination of the photogenerated carriers at both the front and the back contacts to the i-layer.