Impact of Contacting Geometries When Measuring Fill Factors of Solar Cell Current–Voltage Characteristics

We analyze the influence of a variety of different contacting geometries on the fill factor (FF) of solar cell I-V measurements. For this analysis, we compare a wide variety of modeled and measured FFs of Si solar cells. We consistently find large FF differences between individual contacting geometries. These differences amount to up to 3%abs for high busbar resistivities of up to 40 Ω/m. We analyze the contacting geometries for their sensitivity on uncontrolled variations of the contacting resistances. In this analysis, we find that using triplet rather than tandem configurations and using a larger number of test probes reduces the impact of varying contacting resistances to below 0.02%abs. We propose a contacting geometry that we consider to be suitable for calibrated I-V measurements. This contacting scheme is a configuration with a total of five triplets consisting of two current probes and one sense probe. The sense probe is positioned to measure the average busbar potential between the current probes. This is the optimal contacting geometry in terms of a low sensitivity to the busbar resistivity and variations of contacting resistances. In addition, this geometry does not impose unnecessarily large mechanical stress to the cell under measurement.