Parasitic oscillation in the low-frequency noise characterization of solar cells

International audienceThe analysis of low-frequency noise in solar cells is a very useful tool for defect characterization or understanding of fluctuation mechanisms in photodiodes. This type of noise characterization can however be limited by the presence of an undesired peak in the frequency spectra, caused by an oscillation in the measured current. It is shown in this work that this phenomenon originates in the interaction between the noise measurement system and the test structures of the solar cells, which usually introduce a high parasitic capacitance. Through experimental measurements, the link between the center frequency of the peak and the sensitivity of the noise measurement amplifier, as well as the solar cell surface area were explored. Finally, it is shown that, for characterization purposes, the oscillation peak could be pushed to higher frequencies by measuring smaller area cells or attenuated by choosing electrode shapes that enhance the device series resistance