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Elemental de-mixing-induced epitaxial kesterite/CdS interface enabling 13%-efficiency kesterite solar cells

Abstract

The conversion efficiency of kesterite solar cells has been stagnated at 12.6% since 2013. In contrast to chalcopyrite solar cells, the performance of kesterite solar cells is seriously limited by heterojunction interface recombination. Here we demonstrate kesterite/CdS heterojunction is constructed on a Zn-poor surface due to the dissolution of Zn2+ during chemical bath deposition. The occupation of Cd2+ on the Zn site and re-deposition of Zn2+ into CdS creates a defective and lattice-mismatched interface. Low-temperature annealing of the kesterite/CdS junction drives migration of Cd2+ from absorber back to CdS and Zn2+ from absorber bulk to surface, achieving a gradient composition and reconstructing an epitaxial interface. This greatly reduces interface recombination and improves device open-circuit voltage and fill factor. We achieve certified 12.96% efficiency small-area (0.11 cm2) and certified 11.7% efficiency large-area (1.1 cm2) kesterite devices. The findings are expected to advance the development of kesterite solar cells.

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Fig. 1: Fabrication procedure and photovoltaic performance.
Fig. 2: The characteristics of ACZTSSe and CISSe solar cells.
Fig. 3: The heterojunction interfaces.
Fig. 4: Surface and interface elements migration.
Fig. 5: Large-area device and stability.

Data availability

All data supporting the findings of this study are available within the paper and Supplementary Information files. Source data are provided with this paper.

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Acknowledgements

H.X. and W.Y. acknowledge the funding from the National Key Research and Development Program of China (grant number 2019YFE0118100) and the National Natural Science Foundation of China (grant number 22075150). Q.M. acknowledges funding from the National Natural Science Foundation of China (number U2002216 and number 51972332). S.C. acknowledges funding from the National Natural Science Foundation of China (grant number 12174060) and the Shanghai Academic/Technology Research Leader (grant number 19XD1421300). R.G. acknowledges the support from the Molecular Analysis Facility, a National Nanotechnology Coordinated Infrastructure site at the University of Washington, which is supported, in part, by the National Science Foundation (NNCI-1542101), the University of Washington, the Molecular Engineering & Sciences Institute, the Clean Energy Institute and the National Institutes of Health. We thank X. Sha and T. Qiu of Zeiss for preparing TEM lamellae by cryo-FIB and TEM characterization. We acknowledge D.S. Ginger for useful discussion and comments.

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Authors and Affiliations

Authors

Contributions

H.X. conceived the idea. H.X. and Y.G. designed the project and co-wrote the manuscript. Y.G. and Q.Z. fabricated and characterized the devices; B.L. fabricated and characterized the CISSe solar cells; S.W. and S.C. performed first-principles calculations and analysis of interface structure and electronic structure. B.D. and L.L performed M-TPV, M-TPC and CV-DLCP analysis; C.X. and Q.D. performed SEM measurement and discussed the TEM data; E.J. and R.G. performed GDOES measurements and analysed the data; Y.Z. provided important assistance in device fabrication. H.X. and W.Y. supervised the research at NJUPT; Q.M. supervised the research at CAS; S.C. supervised the research at Fudan University. All authors discussed and analysed the results.

Corresponding authors

Correspondence to Shiyou Chen, Qingbo Meng or Hao Xin.

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Nature Energy thanks Edgardo Saucedo and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary information

Supplementary Information

Supplementary Figs. 1–21, Notes 1–8 and Tables 1–7.

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Source data

Source Data Fig. 1

Unprocessed JV and EQE data, statistical device data, integrated JSC from EQE, derivative of EQE versus wavelength.

Source Data Fig. 2

Unprocessed TPV, TPC, Raman, CV and DLCP data and temperature-dependent VOC data.

Source Data Fig. 3

Unprocessed EDX line scan profile data.

Source Data Fig. 4

Unprocessed XPS and JV data, element content change with CBD time.

Source Data Fig. 5

Unprocessed JV, EQE data and device stability data.

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Gong, Y., Zhu, Q., Li, B. et al. Elemental de-mixing-induced epitaxial kesterite/CdS interface enabling 13%-efficiency kesterite solar cells. Nat Energy 7, 966–977 (2022). https://doi.org/10.1038/s41560-022-01132-4

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