All-Vacuum-Deposited Bifacial Cu₂ZnSnSe₄ Photovoltaic Cells with Sputtered Cd-Free Buffer Layer

Figure 2

(a–d) SEM top views of the 1-cycle, 2-cycle, 3-cycle, and 4-cycle specimens, respectively; (e–h) cross-sectional views of the 1-cycle, 2-cycle, 3-cycle, and 4-cycle specimens, respectively; (i–l) AFM measurements of the 1-cycle, 2-cycle, 3-cycle, and 4-cycle specimens, respectively.

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