Degradation and fault diagnosis of photovoltaic cells using impedance spectroscopy

Impedance spectroscopy is widely employed to evaluate electrochemical devices, and our group has been proposing its use as a novel diagnosis tool for photovoltaic modules. In this study, photovoltaic cells are subjected to several types of failure and degradation that frequently occur in polycrystalline photovoltaic cells, such as mechanical stress, interconnect ribbon disconnection, and potential-induced degradation. The impedance characteristics of these cells are measured as Nyquist plots, in addition to the current-voltage (I-V) characteristics to compare the characteristics among the failure modes and demonstrate the applicability of impedance spectroscopy as a potential photovoltaic module diagnosis tool. The equivalent circuit parameters, with and without failure and degradation, are obtained from the impedance characteristics and compared. The influence of bias voltage and temperature on the impedance characteristics are investigated prior to failure and degradation. The application of mechanical stress decreases the parallel resistance and moves the right edge of the Nyquist plot further inside the exact semicircle, while interconnection ribbon disconnection also decreases the parallel resistance and increases the series resistance, and potential-induced degradation decreases both the parallel resistance and capacitance. •Impedance spectroscopy was applied to photovoltaic cells with failures.•The influences of DC bias voltage and temperature were investigated.•Nyquist plots of the cells were measured and compared with the IV curves.