Everybody loves the idea of photovoltaic solar cells: endless clean electricity generated directly from sunlight. The problem lies in the messy reality of making the technology work well. For instance, says Boston College physicist Michael J. Naughton, the cells’ two functions—capturing light and making energy—pull the optimum design for a solar panel in opposite directions. “‘Photo’ wants it thick,” Naughton says, “but ‘voltaic’ wants it thin.” So Naughton and other like-minded scientists are rethinking the fundamental elements of solar cells. They aim to rewrite the rule book and finally make solar energy cost-competitive with coal and natural gas.
The limitations of current-generation solar cells are painfully clear. Although experimental cells have reached efficiencies greater than 40 percent, most silicon-based commercial designs struggle to get past about 20 percent. The lower the efficiency, the more cells it takes to generate a given amount of electricity. That in turn makes photovoltaics bulky and expensive. As a result, the United States had just 800 megawatts of grid-connected solar photovoltaic power in 2008, and solar accounted for less than a tenth of one percent of all energy consumed in the country.
