Recent Progress in Dye-Sensitized Solar Cells for Improving Efficiency: TiO₂ Nanotube Arrays in Active Layer

Figure 7

SEM images taken by Rho et al. of the freestanding TiO₂ films after ion milling of (a) 0, (b) 20, (c) 30, and (d) 90 minutes. Reprinted with permission from [45]. Copyright 2012, American Chemical Society.

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(b)

(c)

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