Nanowire crystals are used as the solar cells. The image (left) shows a SEM (Scaning Electron Microscope) image of GaAs nanowire crystal grown on a Silicon substrate. A TEM (Transmission Electron Microscope) image (middle) shows a single nanowire. Further zooming in on the crystal structure, using STEM (Scanning Transmission Electron Microscope) imaging, shows the actual atomic columns (right). Credit:  Niels Bohr Institute
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