Chemical vapor deposition changes the quality of a surface without using extreme temperatures or solvents that might cause damage. When Barr’s team at MIT figured out how to use the process to make solar cells, he says, they went to an office supply store and loaded up on stuff to test it on: “Saran Wrap, copy paper, tissue paper, almost anything you can imagine,” he says. Barr maintains the technique could be adapted for mass production. Because it relies on abundant organic molecules, rather than heavy metals or rare elements, it could be cheap, too. Right now, Barr’s solar cells convert only about 2 percent of the energy in light into electric power, compared with 10 percent to 20 percent for conventional photovoltaic panels, though he thinks he can eventually raise the efficiency to 10 percent.