Ji, W., Zhao, Y., Fahad, H. M., Bullock, J., Allen, T., Lien, D.-H., De Wolf, S., Javey, A., "Dip Coating Passivation of Crystalline Silicon by Lewis Acids", ACS Nano, 2019, 13 (3), pp 3723–3729
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.