Defect passivation on cast-mono crystalline screen-printed cells

Abstract

Cast-mono crystalline silicon wafers contain crystallographic defects, which can severely impact the electrical performance of solar cells. This paper demonstrates that applying hydrogenation processes at moderate temperatures to finished screen print cells can passivate dislocation clusters within the cast-mono crystalline silicon wafers far better than the hydrogenation received during standard commercial firing conditions. Efficiency enhancements of up to 2% absolute are demonstrated on wafers with high dislocation densities. The impact of illumination to manipulate the charge state of hydrogen during annealing is investigated and found to not be significant on the wafers used in this study. This finding is contrary to a previous study on similar wafers that concluded increased H⁻ or H⁰ from laser illumination was responsible for the further passivation of positively charged dangling bonds within the dislocation clusters.

Keywords

silicon solar cell / dislocation / cast-mono / laser / hydrogen passivation

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Acknowledgments

This program has been supported by the Australian Government through the Australian Renewable Energy Agency (ARENA), the Australian Research Council (ARC) and the Australian Centre for Advanced Photovoltaics (ACAP). The views expressed herein are not necessarily the views of the Australian Government, and the Australian Government does not accept responsibility for any information or advice contained herein. The authors would also like to thank the commercial partners of the ARENA 1-060 project, and the UK Institution of Engineering and Technology (IET) for their funding support for this work through the A.F. Harvey Engineering Prize.

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