Scanning IQE-measurement for accurate current determination on very large area solar cells

We developed a setup to measure the quantum efficiency and integral reflectance for large area solar cells where the cell is scanned underneath a 2×2 cm² illuminated area defined by a mask. Measurements with 90 wavelengths between 300 and 1200 nm on 12.5 × 12.5 cm² solar cells are obtained in less than 15 minutes with very low noise due to the good signal-to-bias ratio. A self-consistent scaling procedure based on the analysis of the internal quantum efficiency is used to account for scaling errors due to the electrical measurement and stray light. This analysis also provides data which enable the calculation of the current loss in the emitter of the solar cell. A method is introduced to identify the bias light level at which the small signal quantum efficiency coincides with the integral large signal response eliminating the need to take the complete quantum efficiency for many bias levels.