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Open Access Publications from the University of California

Dip Coating Passivation of Crystalline Silicon by Lewis Acids.

  • Author(s): Ji, Wenbo
  • Zhao, Yingbo
  • Fahad, Hossain M
  • Bullock, James
  • Allen, Thomas
  • Lien, Der-Hsien
  • De Wolf, Stefaan
  • Javey, Ali
  • et al.

The reduction of carrier recombination processes by surface passivation is vital for highly efficient crystalline silicon (c-Si) solar cells and bulk wafer metrological characterization. Herein, we report a dip coating passivation of silicon surfaces in ambient air and temperature with Nafion, achieving a champion effective carrier lifetime of 12 ms on high resistivity n-type c-Si, which is comparable to state-of-the-art passivation methods. Nafion is a nonreactive polymer with strong Lewis acidity, thus leading to the formation of a large density of fixed charges at silicon surface, 1-2 orders of magnitude higher than what is achievable with conventional thin-film passivation layers. Notably, Nafion passivates the c-Si surface only by the fixed charges without chemical modification of dangling bonds, which is fundamentally different from the common practice of combining chemical with field-effect passivation. This dip coating process is simple and robust, without the need for complex equipment or parameter optimization as there is no chemical reaction involved.

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