Nanoparticles show promise as an ingredient in solar cells, where they could absorb light and generate electrons. But photovoltaic devices made from nanoparticles are still far less efficient than conventional silicon cells. This is partly because some of the liberated electrons never reach an electrode. Now researchers at the University of Notre Dame in Indiana have doubled the efficiency with which these cells convert ultraviolet light to electricity. They deposited single-walled carbon nanotubes on an electrode to form a scaffold for electron-generating titanium dioxide particles. A carbon nanotube (cylindrical object, left) collects an electron (shown in pink) and provides a more direct route from the nanoparticles (round objects) to the electrode (right). The cells convert ultraviolet light to electrons more efficiently than commercial silicon cells, but they do not yet work with visible light.