Two different solar energy cell techniques from Israel

The Economist : Israel, with poor access to fossil fuels and a highly educated population, is growing its solar-power industry.Shining sunlight onto silicon is the most direct way of turning it into electricity—the light knocks electrons free from the silicon atoms—but it is also the most expensive. Two small companies based in Jerusalem are trying, in different ways, to make solar energy cheaper.The physicists and chemists at GreenSun Energy , led by Renata Reisfeld , think the way is to use less silicon. In their designs the solar cell uses only 20% of the silicon of existing solar cells.Around the corner, Jonathan Goldstein of 3GSolar hopes to get rid of silicon altogether. 3G’s “dye-sensitized” solar cells use titanium dioxide (more familiar as a pigment used in white paints) and complicated dye molecules that contain a metal called ruthenium. When one of the dye molecules is hit by light of sufficient energy, an electron is knocked out of it and absorbed by the titanium dioxide, before being passed out of the cell to do useful work.