Evaluating Crystalline Silicon Solar Cells at Low Light Intensities Using Intensity-Dependent Analysis of I-V Parameters

This paper discusses the influence of different solar cell loss mechanisms at low light intensities and presents a simple method for the analysis of solar cell performance under various illumination intensities below 1 sun. Suns-PL and Suns -V-oc are used to measure the intensity-dependent pseudo I-V curves of symmetric test structures and of finished silicon solar cells in an intensity range between 1 sun and 10(-3) suns. The solar cell parameters from the pseudo I-V curves are compared with the parameters evaluated by intensity-dependent measurements of the whole I-V curve. The pseudo efficiency and pseudo fill factor are found to be in good agreement with the real values at low intensities as the influence of the series resistance vanishes. Based on this finding, we compare the passivation quality of silicon dioxide and silicon nitride in combination with emitter windows on test structures. Above 0.1 suns, both passivation layers show similar performance. Below 0.1 suns, the pseudo fill factors and pseudo efficiencies of the silicon nitride passivated sample are strongly reduced compared with the samplewith silicon dioxide. The open-circuit voltage starts differing below 0.01 suns.