This scanning electron microscopy (SEM) image shows a side-view of nanowires which have been coated with a transparent and conductive oxide. The sunlight comes in from top, which is why the top contact must be transparent for light. The substrate is used for the bottom contact. This image relates to a paper that appeared in Jan. 17, 2013, issue of Science Express, published by AAAS. The paper, by Jesper Wallentin at Lund University in Lund, Sweden, and colleagues was titled, "InP Nanowire Array Solar Cells Achieving 13.8% Efficiency by Exceeding the Ray Optics Limit."