|
Rapidly expanding solar cell technology currently relies on expensive photovoltaic materials such as silicon or cadmium telluride, which is why their production, installation and maintenance costs are still high. Troy Townsend, an assistant professor of chemistry at St. Mary's College in St. Mary's City, Maryland, says less efficient but much cheaper inorganic materials could be used to create paintable solar cells. To make up for the low efficiency, this less expensive material may be used to cover large surfaces, such as the roofs of entire communities. "Typically, silicon solar cells are between 16 and 18 percent efficient," Townsend said. "There have been some commercially available cadmium telluride solar cells, from First Solar, that have gotten up to 20 percent. Our devices right now are between 5 and 12 percent." The photovoltaic material can be synthesized by mixing nanocrystals with organic solvents.The resulting substance "can be printed, sprayed or spin-coated to make an entire device fully solution-processed," Townsend said. Once deposited on a suitable surface, such as glass, the photosensitive layers have to be heated, together with an agent. Instead of commonly used highly toxic substances, Townsend discovered that it can be done with nontoxic salts. Individual cells can be connected in series or parallel to build up either voltage or current. | 
