Imaging Techniques for Quantitative Silicon Material and Solar Cell Analysis

We present an overview of imaging techniques for analyzing different loss mechanisms in solar cells. The bulk and surface recombination, optical, series resistance, and shunt losses are investigated in more detail. It is shown that a detailed spatially resolved analysis of these loss channels is possible by combining different evaluation methods. Photoluminescence imaging is used to analyze carrier recombination in the material volume and the surfaces. Bulk recombination is investigated on wafer level by an analysis, which is able to investigate the impact of bulk lifetime and impurity concentration on cell efficiency. Variations in the production conditions of multicrystalline silicon serve as an example. Surface recombination is investigated on a cell precursor level, and the importance of detecting surface defects in cell processes featuring dielectric rear-side passivation is highlighted. For analyzing optical, series resistance, and shunt losses on final cells, a combination of photoluminescence imaging, dark lock-in thermography, and spectrally resolved light-beam-induced current is proposed. As an example, a detailed analysis of two solar cells is presented, allowing the assessment of the local and global impact of each loss mechanism on cell efficiency.