CELLO Analysis of Solar Cells with Silicon Oxide/Silicon Nitride Rear Side Passivation: Parasitic Shunting, Surface Recombination, and Series Resistance as Rear Side Influences

120 μm thick multicrystalline Si solar cells with SiO/SiN stack rear-side passivation and Al point contacts are locally characterized using the CELLO technique. By combining different standard measurement modes—e.g. using different laser wavelengths, variation of global illumination intensity, and by measuring at different points along the I-V curve—effects due to parasitic shunting can be separated from other rear side effects like inhomogeneous surface passivation (i.e. due to stack or contacts) or series resistance. An increased series resistance at the rear side is found to improve the rear surface recombination behavior and thus induces a boost in the photocurrent response as an unexpected seemingly positive side effect. As a consequence the series resistance distribution of the rear side has to be taken into account for the correct interpretation of photocurrent data measured using light with long wavelengths.