Here's how to make a solar cell from silicon : take one solid block of doped silicon, saw it into thin wafers, layer said semiconductors beneath a panel of transparent glass, connect them to a metal electrode that can channel away the electrons knocked loose by incoming photons and turn it into a photovoltaic device. That process has at least two flaws: such silicon is very expensive, as much as $300,000 for a wafer, and sawing it turns as much as half of that very expensive silicon into wasted grit. [More]