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Efficient kesterite solar cells with high open-circuit voltage for applications in powering distributed devices

Nature Energy volume 2, pages 884–890 (2017)Cite this article

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Abstract

Simultaneously achieving high voltage and high efficiency in thin-film solar cells is of paramount importance for real-world applications. While solar cells fabricated from the Earth-abundant kesterite absorber Cu2ZnSn(S x Se1−x )4 provide an attractive, non-toxic, energy harvesting solution, their utilization has been constrained by relatively low open-circuit voltages that limit efficiency. Increasing the sulfur content to widen the bandgap boosts the voltage, but usually at the expense of efficiency. Here, we report important progress on this fundamental problem by fabricating solar cells with high sulfur content that exhibit efficiencies up to 11.89% with open-circuit voltages as high as 670 mV. In a multistep process, fully functional solar cells are separated from their growth substrate, and a high-work-function back contact is subsequently deposited. With this approach, we fabricated a series-connected device that produces 5.7 V under 1 Sun illumination and ~2 V under low lighting conditions, below 10−3 Suns.

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Fig. 1: Back-contact engineering steps.
Fig. 2: Performance of exfoliated devices.
Fig. 3: Performance of the best exfoliated devices.
Fig. 4: Low-light performance parameters.
Fig. 5: Nine-cell series-connected device performance.
Fig. 6: Exfoliated device stability.

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Acknowledgements

We wish to acknowledge S. Singh who assisted with back-contact depositions and ICP analysis. We also wish to thank M. Hopstaken and M. Saccomanno for assistance with secondary-ion mass spectrometry analysis of our devices. We also acknowledge O. Gunawan for his help in masking procedures and various aspects of the electrical measurements, D. B. Farmer for his help in the design of the ultraslow cooling experiments for the humidity-controlled air anneals, and G. Tulevski for his technical assistance. Work supported by the US Department of Energy under award DE-EE0006334 (full statement in Supplementary Information).

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  1. Priscilla D. Antunez

    Present address: Argonne National Laboratory, Argonne, IL, USA

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  1. IBM T.J. Watson Research Center, PO Box 218, Yorktown Heights, NY, USA

    Priscilla D. Antunez, Douglas M. Bishop, Yu Luo & Richard Haight

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  1. Priscilla D. Antunez
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Contributions

P.D.A. developed the high sulfur anneals, designed experiments for the ultra-slow anneal under controlled humidity and optimized the exfoliation process to allow for higher yield during the nine device exfoliation. D.M.B. carried out device characterization and analysis, devised and carried out air-anneal and slow-cooling protocols and light-intensity measurements. Y.L. optimized and carried out the ink-based CZTSSe depositions. R.H. supervised the entire project, developed the back-contact mask and carried out device characterization including electronic structure measurements, band lineups and band bending. All authors carried out characterization of pre-exfoliated devices.

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Correspondence to Richard Haight.

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Supplementary Tables 1–3, Supplementary Figures 1–4

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Antunez, P.D., Bishop, D.M., Luo, Y. et al. Efficient kesterite solar cells with high open-circuit voltage for applications in powering distributed devices. Nat Energy 2, 884–890 (2017). https://doi.org/10.1038/s41560-017-0028-5

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