Robert F. Service
Efficiency versus cost. It's a trade-off that bedevils makers of solar cells. Cells made from crystalline silicon are good at absorbing photons and converting them to electricity. But they cost a lot. In contrast, noncrystalline cells made with amorphous silicon are much cheaper--but only about half as efficient as their crystalline counterparts. Now researchers think that they can trade in this devilish trade-off. At a conference last month in Arlington, Virginia, scientists were energized by a report that an ultrathin film--a mixture of copper, indium, gallium, and selenium--has been made into prototype cells that convert nearly 18% of incoming photons to electricity, a performance approaching that of the best crystalline silicon cells. If researchers can overcome nagging manufacturing and marketing problems, new devices could produce power for less than $0.50 per watt.
