For decades, scientists have sought to improve the efficiency of solar power technology. Today, silicon cells generally convert less than 15 percent of the sun's energy into electricity, according to Keith Emery, a research engineer with the National Renewable Energy Laboratory (NREL). But a new kind of photovoltaic (PV) cell promises to be even more efficient. Conceived and designed at NREL, Boeing-Spectrolab is now manufacturing record-breaking PV cells that can convert more than 40 percent of the solar radiation striking them into electricity. The magic is in their "multijunction" design: each of three layers harnesses a different range of the solar spectrum. "I have no doubt the efficiency will continue to go up," Emery says. Right now these PV cells are only viable for large-scale operations, but the improvements may eventually trickle down to residential applications and help lower PV electricity costs.