In contrast to crystalline silicon solar modules the parameters of the I-V-curve cannot directly be extracted by one measured I-V-curve for amorphous solar modules. Especially the parasitical series and shunt resistance are not comparable to the slope in the short circuit respectively to the open circuit region of the I-V-curve. This work will show the behaviour of the I-V-curve of aSi:H solar modules and the influence of the single curve parameters. The influence of the separate parameters of aSi:H solar cells is more difficult to understand than for crystalline silicon. So a parameter study shows the influence of the parameters to the I-V-curve. A recombination current allows a more sufficient description of the recombination paths under illumination. The so called Merten-Model is sufficient to describe the curves behaviour. But to understand the degradation mechanism a more detailed model is needed. Thereto a second diode in the model allows a more exhaustive study of the degradation mechanism, especially the Staebler-Wronski-Effect. (C) 2013 Elsevier Ltd. All rights reserved.