Performance of amorphous and microcrystalline silicon pin solar cells under variable light intensity

We have studied the solar cell behaviour under variable light intensity (VLI) of a standard a-Si:H pin solar cell with a wide band gap a-SiC:H emitter layer, and microcrystalline (μc)-Si:H solar cells of different degrees of crystallinity, using experiments in conjunction with detailed electrical-optical modelling. Both experiments and modelling reveal that whereas the fill factor (FF) of the a-Si:H pin cell decreases with increasing light intensity, starting from a low applied light bias, that of the μc-Si:H cells increases with light intensity over a major part of this range. This fact enables one to attain the maximum of the open-circuit voltage - fill factor product (V_oc x FF) at 1 to 2 suns intensity for the latter case; however this is not achieved for the a-Si:H cell. Using modelling we try to understand this difference in behaviour of the FF under VLI for the two types of cells. We also predict under what conditions it would be possible to shift the (V_oc x FF) _max for the a-Si:H cell towards one sun intensity.