Photoluminescence Imaging at Uniform Excess Carrier Density Using Adaptive Nonuniform Excitation

Photoluminescence imaging is a fast and powerful technique to extract information about the nonuniformity of the recombination properties of silicon wafers and solar cells. In conventional photoluminescence imaging, where a uniform illumination is used, lateral carrier flows within the sample lead to smeared and quantitatively inaccurate results. In this study, a modified photoluminescence imaging setup, based on an adjustable spatially nonuniform excitation light source, is presented. With this setup, a laterally uniform excess carrier concentration is achieved across samples with nonuniform recombination properties by adaptively adjusting the light intensity at each position across the sample. Uniform photoluminescence images are obtained and the sample nonuniformity is extracted from the nonuniform excitation image that is applied. Without the presence of lateral carrier flows, carrier smearing effects are largely suppressed. Meanwhile, photoluminescence imaging-based quantitative analysis methods, such as carrier lifetime images, metastable defect imaging, etc., will greatly benefit from the fact that the sample is at a uniform excess carrier density.