For a precise prediction of the energy yield of amorphous (a-Si) and amorphous-microcrystalline tandem (a-Si/μc-Si) silicon-based thin film photovoltaic modules it is important to know their low (<15W/m²) and weak (15-100W/m²) light behavior. The weak light efficiency of silicon based thin film and mono-crystalline silicon (c-Si) solar cells show a different dependence from irradiation. Both have a decreasing efficiency with decreasing irradiation. Thin film solar cells based on a-Si or a-Si/μc-Si show at higher irradiation (>100W/m²) lower efficiency than c-Si solar cells. Our work will show that at lower irradiation (<15W/m²) the efficiency of a-Si and a-Si/μc-Si is higher than the efficiency of c-Si, this kind of irradiation appears every morning and evening. Also we show that the decrease in efficiency at lower irradiation compared to the labeled efficiency at standard test conditions is for thin film silicon modules lower than for c-Si modules.