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Identification of embedded nanotwins at c-Si/a-Si:H interface limiting the performance of high-efficiency silicon heterojunction solar cells

Nature Energy volume 6, pages 194–202 (2021)Cite this article

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Abstract

The interface of high-quality crystalline silicon/hydrogenated amorphous silicon (c-Si/a-Si:H) is indispensable for achieving the ideal conversion efficiency of Si heterojunction solar cells. Therefore, it is extremely desirable to characterize and control the interface at the atomic scale. Here, we employ spherical aberration-corrected transmission electron microscopy to investigate the atomic structure of the c-Si/a-Si:H interface in high-efficiency Si heterojunction solar cells. Their structural evolution during in situ annealing is visualized at the atomic scale. High-density embedded nanotwins, detrimental to the device performance, are identified in the thin epitaxial layer between c-Si and a-Si:H. The nucleation and formation of these nanotwins are revealed via ex situ and in situ high-resolution transmission electron microscopy. Si heterojunction solar cells with low-density nanotwins are fabricated by introducing an ultra-thin intrinsic a-Si:H buffer layer and show better performance, indicating that the strategy to restrain embedded nanotwins can further enhance the conversion efficiency of Si heterojunction solar cells.

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Fig. 1: c-Si/a-Si:H interface structure characteristics of SHJ solar cell.
Fig. 2: Electronic structure characteristics of nanotwin configurations.
Fig. 3: c-Si/a-Si:H interface structures at different stages during cell preparation.
Fig. 4: HRTEM images showing structural evolution of c-Si/a-Si:H interface under heating.
Fig. 5: The characteristics of two groups of SHJ solar cells with and without the i* layer.
Fig. 6: The effect of surface configuration of Si wafer on formation of nanotwin.

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All data generated or analysed during this study are included in the published article and its Supplementary Information. Source data are provided with this paper.

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Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (no. 11774016, 61922005, 11874314 and 62034001), Beijing Great Wall Scholars Program, Beijing Academic Outstanding Young Scientists Projects (BJJWZYJH01201910005018) and Australian Research Council. We thank Y. Zhang, M. Yang and C. Yu for device fabrication and SHJ cell process development, X. Chen for theoretical calculations and Y. Qin for SEM characterization from Carl Zeiss.

Author information

Author notes

  1. These authors contributed equally: Xianlin Qu, Yongcai He, Minghao Qu.

Authors and Affiliations

  1. Beijing Key Lab of Microstructure and Properties of Solids, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, China

    Xianlin Qu, Yongcai He, Tianyu Ruan, Feihong Chu, Zilong Zheng, Hui Yan, Lihua Wang, Yongzhe Zhang & Kun Zheng

  2. Hanergy Chengdu Research and Development Center, Chengdu, China

    Minghao Qu, Xiaoning Ru & Xixiang Xu

  3. School of Science, Jiangsu University, Zhenjiang, China

    Yabin Ma & Yuanping Chen

  4. School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales, Australia

    Xiaojing Hao & Ziv Hameiri

  5. Centre for Future Materials, University of Southern Queensland, Springfield, Queensland, Australia

    Zhi-Gang Chen

  6. School of Mechanical and Mining Engineering, University of Queensland, St Lucia, Queensland, Australia

    Zhi-Gang Chen

  7. School of Chemical Engineering and Australian Institute for Bioengineering and Nanotechnology, University of Queensland, St Lucia, Queensland, Australia

    Lianzhou Wang

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Contributions

X.Q. prepared the TEM sample and executed aberration-corrected HRTEM and HAADF-STEM. Y.H., M.Q. and T.R. fabricated the devices and carried out photovoltaic characterization. F.C. and Z.Z. carried out theoretical calculations. Y.M and Y.C. assisted with the theoretical calculations. X.R. assisted in the fabrication of devices. X.Q., Y.Z. and K.Z. analysed the experimental results and wrote the manuscript. X.X., H.Y. and Lihua Wang made helpful comments on the manuscript. X.H., Z.H., Z.-G.C. and Lianzhou Wang guided the PCE loss analysis and provided constructive suggestions. K.Z. and Y.Z. led the entire project. All authors read the manuscript and contributed to the discussion of the results.

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Correspondence to Yongzhe Zhang or Kun Zheng.

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Peer review information Nature Energy thanks Urs Aeberhard, Kristopher Davis and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Information

Supplementary Figs. 1–13, Table 1 and references.

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Source Data Fig. 1

An efficiency of 24.85% is certified by the Institute for Solar Energy Research in Hamelin with a total area of 244.5 cm2 measured under standard test conditions.

Source Data Fig. 5

Source data of Fig. 5d.

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Qu, X., He, Y., Qu, M. et al. Identification of embedded nanotwins at c-Si/a-Si:H interface limiting the performance of high-efficiency silicon heterojunction solar cells. Nat Energy 6, 194–202 (2021). https://doi.org/10.1038/s41560-020-00768-4

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