Fig. 5 shows the external quantum efficiency (EQE) of a CIGS solar cell with and without ARC applied. Similar to there flectance shown in Fig. 4, EQE seems to be effective mainly for wavelengths < 1000 nm. While there flectance is measured on a complete device, the EQE is only measured on an area of _2–3 mm². This may account for slight differences observed for the effectiveness of the ARC when comparing reflectance and EQE.