Potential-induced degradation of n-type crystalline Si photovoltaic modules in practical outdoor systems

Potential-induced degradation (PID) of full-size photovoltaic (PV) modules based on n-type monocrystalline Si solar cells was observed in practical outdoor PV systems in the short term. The maximum power output of the module decreased by about 14% after 12 days of outdoor exposure with application of about -115V. In contrast, no degradation was observed after +115 V application in the outdoor system. These results indicate that the PID of the n-type Si PV module is easily induced by applying a lower negative potential that does not induce the PID of p-type Si PV modules in outdoor systems. Results suggest that water on the top of the modules during/after a rain, which increases the leakage current between the Al frame and the Si solar cells, is the predominant factor causing the PID of n-type Si PV modules exposed outdoors, rather than temperature and humidity. (c) 2018 The Japan Society of Applied Physics.