Brazilians joke that theirs is the country of the future—and always will be. Likewise, solar power has always been the ultimate green technology of the future. But maybe the sun is finally rising. The photovoltaic market, though small, has been growing briskly: by more than 60 percent in 2004. Plastering your roof with solar cells now runs as little as 20 cents per kilowatt-hour over the system's estimated lifetime, which is approaching what most households pay for electricity.
One especially promising technology that emerged in the 1990s was to make solar cells from plastic spiked with nanometer-scale crystals. Even those composite devices, though, were restricted to absorbing visible light. This year a group led by Edward H. Sargent at the University of Toronto coaxed them to absorb infrared light as well. A concoction of lead sulfide particles a few nanometers in size can absorb wavelengths as long as two microns. Thus able to harvest a wider swath of the solar spectrum, inexpensive plastic cells could rival the performance of pricey silicon ones.