Laser enhanced gettering of silicon substrates

Daniel CHEN, Matthew EDWARDS, Stuart WENHAM, Malcolm ABBOTT, Brett HALLAM

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Front. Energy ›› 2017, Vol. 11 ›› Issue (1) : 23-31. DOI: 10.1007/s11708-016-0441-7
RESEARCH ARTICLE

Laser enhanced gettering of silicon substrates

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Abstract

One challenge to the use of lightly-doped, high efficiency emitters on multicrystalline silicon wafers is the poor gettering efficiency of the diffusion processes used to fabricate them. With the photovoltaic industry highly reliant on heavily doped phosphorus diffusions as a source of gettering, the transition to selective emitter structures would require new alternative methods of impurity extraction. In this paper, a novel laser based method for gettering is investigated for its impact on commercially available silicon wafers used in the manufacturing of solar cells. Direct comparisons between laser enhanced gettering (LasEG) and lightly-doped emitter diffusion gettering demonstrate a 45% absolute improvement in bulk minority carrier lifetime when using the laser process. Although grain boundaries can be effective gettering sites in multicrystalline wafers, laser processing can substantially improve the performance of both grain boundary sites and intra-grain regions. This improvement is correlated with a factor of 6 further decrease in interstitial iron concentrations. The removal of such impurities from multicrystalline wafers using the laser process can result in intra-grain enhancements in implied open-circuit voltage of up to 40 mV. In instances where specific dopant profiles are required for a diffusion on one surface of a solar cell, and the diffusion process does not enable effective gettering, LasEG may enable improved gettering during the diffusion process.

Keywords

gettering / multicystaline / silicon / impurities / laser doping

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Daniel CHEN, Matthew EDWARDS, Stuart WENHAM, Malcolm ABBOTT, Brett HALLAM. Laser enhanced gettering of silicon substrates. Front. Energy, 2017, 11(1): 23‒31 https://doi.org/10.1007/s11708-016-0441-7

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Acknowledgments

This program was supported by the Australian Government through the Australian Renewable Energy Agency (ARENA) 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.

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2016 Higher Education Press and Springer-Verlag Berlin Heidelberg
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