IV-curves with short circuit current of 1.2 A for modules M1, M2, M4 and M7 at their first day in operation outdoors (blue) and after operation between 12 and 18 months (red). The different open circuit voltages of first and respective last day are almost solely due to different temperatures at the two days. For the later dates the measured fill factor (FF) and the fill factor corrected for the different temperature and different open circuit voltage are given (the latter one in brackets).