Performance degradation due to outdoor exposure and seasonal variation in amorphous silicon photovoltaic modules

Thin-film silicon (Si) related photovoltaic (PV) modules suffer performance deterioration owing to outdoor exposure. We investigate the performance degradation and seasonal variation of hydrogenated amorphous Si (a-Si:H) related PV modules. The normalized maximum power (PMAX) of the single- and multi-junction modules tested herein decreased greatly and then stabilized after ~3 or 4 years of outdoor exposure. In summer (August 2016 and 2017), the PMAX of all a-Si:H related PV modules increased by 2.0%-3.8% over the PMAX in winter (December 2015 and 2016). In addition, the a-Si:H related PV modules show higher performance ratio (PR) in summer and lower in winter. These results are due to thermal annealing and light induced degradation effects in a-Si:H related PV modules. The a-Si:H related PV modules' PR two months after outdoor installation is lower than that before installation, which is explained by initial light exposure induced degradation.