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Metal Grid Contact Design for Four-Terminal Tandem Solar Cells

Sofia SE, Sahraei N, Mailoa JP, Buonassisi T, Peters IM (2017)

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Publication Type: Journal article

Publication year: 2017

Journal

Book Volume: 7

Pages Range: 934-940

Article Number: 7893768

Journal Issue: 3

DOI: 10.1109/JPHOTOV.2017.2686651

Abstract

Flat-panel tandem solar cells have demonstrated the potential to exceed the efficiencies of their single-junction constituents. However, robust design rules for tandem solar cells are currently lacking, slowing the development of cost-effective implementations of this technology. A double-junction solar cell with four-terminal (4T) architecture stacks two electrically independent subcells and avoids current-matching losses, resulting in two main advantages over the conventional integrated two-terminal (2T) architecture: a higher energy yield and a loosened constraint on material bandgap combinations. Because both subcells are contacted independently in a 4T tandem, multiple stacked semitransparent contacts are needed, causing optical and series resistance losses. Moreover, for stationary flat-panel tandems, contacts need to be optimized for a varying direction of incident sunlight. In this study, we develop a framework for optimizing metal grid contacts for 4T tandem solar cells and quantify the electrical and optical loss associated with these contacts. We also explore the range of conditions for which it is beneficial to align metal grid contact fingers. We find that, for most applications, the front and back contacts of the top cell should be aligned, resulting in a decrease in energy yield loss between 5% and 15%, while aligning the bottom cell contacts is not beneficial and may even reduce total energy yield. Finally, we show that for nonideally matched subcell pairings, the contacts loss in a 4T tandem is not enough to counter the yield benefit of 4T over 2T tandems, while the contact loss may make the yield for more ideally matched subcells be comparable for 2T and 4T devices.

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How to cite

APA:

Sofia, S.E., Sahraei, N., Mailoa, J.P., Buonassisi, T., & Peters, I.M. (2017). Metal Grid Contact Design for Four-Terminal Tandem Solar Cells. IEEE Journal of Photovoltaics, 7(3), 934-940. https://doi.org/10.1109/JPHOTOV.2017.2686651

MLA:

Sofia, Sarah E., et al. "Metal Grid Contact Design for Four-Terminal Tandem Solar Cells." IEEE Journal of Photovoltaics 7.3 (2017): 934-940.

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