Investigation of solar cell degradation using electrochemical impedance spectroscopy

The performance of solar cells reduces annually due to various unavoidable phenomena of thermal cycling, damp heat, UV exposure, and mechanical stress, etc. Generally, I-V characteristic is used to check the performance of the solar cell, but the minor stress conditions mentioned above are difficult to characterize by I-V measurement. Impedance spectroscopy is a widely used method in fuel cell and a battery that can be used to detect minor degradation in the solar cell by analyzing the change in equivalent circuit parameters. In this work, commercially available polycrystalline silicon solar cell is investigated under the condition of hotspot, mechanical stress, and disconnection of interconnection ribbon and then characterized by impedance measurement, Fourier transform (Bode plot) as well as I-V characteristic. The results show noteworthy decrease in parallel resistance (Rp) which is clearly visible in Nyquist plot in compare to the I-V characteristic. The Rp decreases in EIS from 283.60 to 234.80 Ω for mechanical stress test, from 273.0 to 187.10 Ω for hotspot and from 352.80 to 345.20 Ω for disconnection of interconnection ribbon test. The results confirm potential application of impedance measurement for solar cell characterization due to noteworthy change in equivalent circuit parameters after test conditions.