During his Nobel Lecture at Stockholm University in Sweden, Alan Heeger pulled out a personal digital assistant and held it up so the crowd could marvel at its brilliant display screen. Heeger shared the 2000 Nobel Prize in chemistry for the materials that made this screen possible: electrically conductive plastics. What he didn’t hold up, though, was an application of those same new materials that could have a far greater impact. Instead of conducting electricity and emitting light, as they do in flat-panel displays, these same plastics can be made to run the reverse process, absorbing light and producing electricity. If they work, they could fulfill the dream of many energy researchers: inexpensive solar cells.
Such materials could change the face of solar power because plastic is cheap, and cheap would be a rather novel and welcome way to describe solar technology. The advantages of solar power are obvious: every minute, the sun pounds the surface of the earth with more energy than the entire world consumes in a year-a potential source of virtually unlimited, clean and free electricity. But until recently the high cost of the materials used in solar cells has relegated the technology to powering satellites, high-tech backwoods cabins and communications towers beyond the reach of power lines. Solar cells made from materials like electrically conductive plastics could finally make solar power affordable for far broader uses. Moreover, says Heeger, the chemistry behind these plastics is rather simple, so they could be fairly easy-and cheap-to manufacture.
Conventional solar cells cost so much because most are made from the same relatively expensive silicon semiconductors used in computer microchips. Recently, manufacturers have found ways of making solar cells using ultrathin films of silicon; consequently, solar power is getting cheaper and consumption is increasing. More than 200,000 homes in the United States now derive at least some of their power from solar cells; the technology is already paying its way in places like California, where energy is expensive and governments are willing to subsidize solar power to make it competitive with fossil fuels.
But switching to thin-film silicon may not bring about the drastic cost reductions solar cells need to effectively compete with coal-, oil- and natural-gas-generated electricity across the globe. Despite nearly quadrupling in sales over the last five years, solar still accounts for only .04 percent of worldwide power generation. What is needed to accelerate the penetration of solar power is even cheaper materials. And an increasing number of companies are looking to electrically conductive plastics and other novel organic materials as the solution.
Researchers developing these new-age materials for solar cells are sensitive to failed promises about solar power and caution that organic solar cells could be a decade or more from the market. At the same time, they are clearly excited about recent advances in the materials which, if sustained, could deliver the performance and affordability that will render solar power ubiquitous. “If the performance of organic solar cells was as good as conventional ones, it would be pretty darn interesting,” says Princeton University electronics expert Steven Forrest. “That could be a huge market.”