Spatially Resolved Absorptance of Silicon Wafers From Photoluminescence Imaging

The absorptance of a silicon solar cell determines the upper limit of its short-circuit current and, thus, its efficiency. Traditional methods used to determine the absorptance require contact to the sample or are affected by parasitic absorption. This paper demonstrates that through the combination of the spectral response of photoluminescence with photoluminescence imaging, the contactless determination of spatially resolved absorptance is possible. The demonstrated method is based on the comparison of two photoluminescence images, each acquired using different excitation wavelengths (808 and 1060 nm). Thus, the relative absorptance between these specific wavelengths is determined. Experimental verification of the method is performed with passivated monocrystalline silicon wafers of varying absorptances. The demonstration of spatially resolved extraction of absorptance is then performed with a multicrystalline silicon wafer with a strong lateral variation in absorptance at 1060 nm.