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Recycling of silicon solar panels through a salt-etching approach

Abstract

The production and use of silicon (Si) solar panels is soaring during the transition to a carbon-neutral energy system. To mitigate their environmental footprints, there is an urgent need to develop an efficient recycling method to handle end-of-life Si solar panels. Here we report a simple salt-etching approach to recycle Ag and Si from end-of-life Si solar panels without using toxic mineral acids and generating secondary pollution. The etching process is enabled by the high corrosivity of molten hydroxide that spontaneously reacts with SiNx, SiO2, Al2O3 and Al at the surface of Si wafers through the top-down direction, thereby directly separating Ag from Si wafers. The etching process takes only 180 s to recover >99.0% of Ag and >98.0% of Si from end-of-life Si solar panels. In addition, Cu, Pb, Sn and Al in Si solar panels are also recovered through a combined oxidation, alkaline leaching and electrodeposition approach. Overall, this study presents a viable approach for sustainable management of end-of-life Si solar panels, paving the way to a circular economy.

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Fig. 1: Schematic diagram of the recycling of an EoL PV panel and the recycled products.
Fig. 2: Characterization of four types of Si cells, Ag wires and Si wafers before and after salt etching.
Fig. 3: Thermodynamic analysis and mechanistic schematics of salt-etching processes.
Fig. 4: Recycling of Cu, Pb and Sn from solder strips through oxidation, alkaline leaching and electrochemical deposition.
Fig. 5: Environmental impacts of four scenarios on the recycling of Ag and Si from EOL Al-BSF Si cells.

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Data availability

The data that support the findings detailed in this study are available in the article and Supplementary Information or from the corresponding authors upon reasonable request.

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Acknowledgements

We thank the Fundamental Research Funds for the Central Universities (2042023kf0214), the starting funding from Wuhan University, the National Natural Science Foundation of China (number U22B2071) and the Postdoctoral Science Foundation of China (number 2022M722437). We also thank M. Ruan of the School of Power and Mechanical Engineering, Wuhan University, for the support for the SEM test.

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Authors and Affiliations

Authors

Contributions

H.Y. conceived the idea; S.G., H.Y. and D.W. designed the experiments; S.G. conducted the experiments, analysed the data and wrote the paper; D.W. ang H.Y. supervised the project; J.Q. and X.C. organized the data and figures; Y.G., X.Q. and F.P. conducted the electrolysis; H.S. conducted the modelling of heat conduction of c-Si cells in the molten salt; and L.G. conducted the distillation experiment. All authors discussed the results of this work.

Corresponding authors

Correspondence to Dihua Wang or Huayi Yin.

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Nature Sustainability thanks Zhenfeng Bian, Rong Deng 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 and 2: Solar cell development. Figs. 3–6: Solar cell dismantling. Figs. 7–46: Si and Ag recycling. Figs. 47–54: Solder recycling. Fig. 55: LCA analysis; Tables 1 and 2: Current recycling method. Tables 3–5: Material characterization. Tables 6–19: LCA analysis.

Reporting Summary

Supplementary Video 1

Salt etching of an Al-BSF Si cell.

Supplementary Video 2

Salt etching of a PERC-I Si cell.

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Gao, S., Chen, X., Qu, J. et al. Recycling of silicon solar panels through a salt-etching approach. Nat Sustain 7, 920–930 (2024). https://doi.org/10.1038/s41893-024-01360-4

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