A comparison of degradation in three amorphous silicon PV module technologies

Three commercial amorphous silicon modules manufactured by monolithic integration and consisting of three technology types were analysed in this study. These modules were deployed outdoors for 14 months and underwent degradation. All three modules experienced the typical light-induced degradation (LID) described by the Staebler–Wronski effect, and this was followed by further degradation. A 14 W single junction amorphous silicon module degraded by about 45% of the initial measured maximum power output (PMAX) at the end of the study. A maximum of 30% of this has been attributed to LID and the further 15% to cell mismatch and cell degradation. The other two modules, a 64 W triple junction amorphous silicon module, and a 68 W flexible triple junction amorphous silicon module, exhibited LID followed by seasonal variation in the degraded PMAX. The 64 W module showed a maximum degradation in PMAX of about 22%. This is approximately 4% more than the manufacturer allowed for the initial LID. However, the seasonal variation in PMAX seems to be centred around the manufacturer’s rating (±4%). The 68 W flexible module has shown a maximum decrease in PMAX of about 27%. This decrease is about 17% greater than the manufacturer allowed for the initial LID.