The full-glass lens and cell subunit showed a constant FF in the investigated range of cell-to-lens distances, whereas the SoG Fresnel lens and cell subunit showed significant variation of the FF between 84% and 78%. This is the primary cause for the drop in efficiency and is due to the chromatic aberration effects of the SoG Fresnel lens. The chromatic aberration causes different current generation profiles in the four subcells, which results in lateral current flows. The lateral current flows lead to power losses due to the series resistances of the solar cell’s sheet layers. The full-glass lens was designed to reduce chromatic aberration, and thus, the amount of lateral current flows and series resistances losses are decreased.