Figure 3

Transmission data of both (a) plano-convex and (b) ball lenses before (black) and after (red) the etching; (c) I–V curves and (d) efficiency enhancements of a 3J cell using two-stage BK7 optics before and after the etching.

Transmission data of both (a) plano-convex and (b) ball lenses before (black) and after (red) the etching; (c) I–V curves and (d) efficiency enhancements of a 3J cell using two-stage BK7 optics before and after the etching.