The spectral transmission curves (hemispherical transmittance at near-normal incidence) of the two lenses are shown in Fig. 2 together with the external quantum efficiency (EQE) of cell A. The transmission of the Fresnel lens was measured on a test sample consisting of glass and silicone with a thickness comparable with the lens but without a lens structure. The reason for this is that the used measurement setup measures only the hemispherical transmission, which would lead to misleading results for the Fresnel lens. The transmission of the full-glass lens was measured directly.