Discussion of Fill Factor: As shown in Fig. 3, the FF of the full-glass lens and cell B subunit is changed by less than 2% in the investigated range of cell-to-lens distances. The reason for this is the smaller grid finger spacing and thus lower series resistance of the cell B and the low chromatic aberration of the full-glass lens. The full-glass lens and cell A subunit, on the other hand, shows a dip in FF of nearly 4% absolute due to the higher grid finger spacing combined with the higher concentration of sunlight into a small area at a relative cell-tolens distance of zero resulting from the full-glass lens. The FF of the SoG Fresnel lens and cell B subunit shows the typical strong drops at ±2 mm relative cell-to-lens distance as a result of series resistance losses [12], [13].