Correlation between spatially resolved solar cell efficiency and carrier lifetime of multicrystalline silicon

The correlation between the spatially resolved carrier lifetime of multicrystalline silicon and the spatially resolved monochromatic solar cell efficiency is investigated by means of microwave-detected photoconductance decay (MW-PCD) measurements and illuminated lock-in thermography (ILIT). Local monochromatic solar cell efficiencies are determined from ILIT measurements under short-circuit conditions and at the maximum power point of the cell. The resulting efficiency images are compared with efficiency images obtained from MW-PCD lifetime images of unprocessed neighbouring wafers using PC1D simulations. We observe a qualitative correlation between the measured and the simulated efficiency images. Areas with reduced efficiency are found in the same locations using both methods. However, the dynamic range in the monochromatic efficiency is larger for the images obtained from ILIT measurements. Possible explanations for this difference are a change in carrier lifetime during cell processing and varying lifetimes on microscopic scales, leading to averaging faults in the lifetime images.