Vignetting in Luminescence Imaging of Solar Cells

We present a paper about vignetting in the context of luminescence imaging of solar cells and wafers. The physical phenomenon vignetting and its contributions are reviewed. A simple model to simulate vignetting and a method of measuring the vignette by the variation of aperture are introduced. The simulated and the measured results are compared showing good agreement with less than 2.1% deviation. For the investigated luminescence setup, it is shown that vignetting can cause an intensity decrease of up to 20% toward the image corners for wide opened apertures. To quantify the correction quality, a correction quality factor is adopted from a recent publication and applied to the suggested method. Additionally, the correction quality is quantified by investigating the linear correlation between luminescence intensity and charge carrier product measured via photoconductance on a suitably prepared sample. The correlation coefficient increases from R2 = 0.92 to R2 = 0.95 after the correction.